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RNA interactomes and their diversified functionalities have recently benefited from critical methodological advances leading to a paradigm shift from a conventional conception on the regulatory roles of RNA in pathogenesis. However, the dynamic RNA interactomes in adenoma-carcinoma sequence of human CRC remain unexplored. The coexistence of adenoma, cancer, and normal tissues in colorectal cancer (CRC) patients provides an appropriate model to address this issue. Here, we adopted an RNA in situ conformation sequencing technology for mapping RNA-RNA interactions in CRC patients. We observed large-scale paired RNA counts and identified some unique RNA complexes including multiple partners RNAs, single partner RNAs, non-overlapping single partner RNAs. We focused on the antisense RNA OIP5-AS1 and found that OIP5-AS1 could sponge different miRNA to regulate the production of metabolites including pyruvate, alanine and lactic acid. Our findings provide novel perspectives in CRC pathogenesis and suggest metabolic reprogramming of pyruvate for the early diagnosis and treatment of CRC. [ABSTRACT FROM AUTHOR]

When earth pressure balance tunnel boring machines (EPB-TBMs) tunnelling in abrasive sandy ground, soil additives are critical for promoting excavation surface stability, reducing residual soil permeability, decreasing screw conveyor torque, avoiding mud cake siltation and preventing excessive tool wear. However, the existing studies mainly focus on the first four aspects. The influence mechanism of soil additives on cutting tool wear is still unclear due to the lack of reliable test methods. In the present study, a newly developed WHU-SAT tester (Soil Abrasion Tester developed by Wuhan University) was used to evaluate the influence of conditioning additives (foam additives and bentonite slurry) on soil abrasivity. Scraper wear in additive-conditioned sand has been compared with that in water-conditioned sand to reveal the mechanism of foam additive and bentonite slurry. The soil additive parameters (solution concentration and injection ratio) were optimized to reduce scraper wear in abrasive sandy ground. The results indicate that the mitigation effect of the foam additive on scraper wear is related to the lubrication of the active agent and the cushioning of the air bubbles. The optimized foam solution concentration and foam injection ratio for the quartz sand samples are FSC = [5%, 10%] and FIR = [22.5%, 25.0%], respectively. The aggravation in scraper wear caused by bentonite slurry is related to the improvement of particle gradation and the increase of sand cohesion. The bentonite slurry parameters should be selected to keep the water content of the conditioned sand away from the peak water content to decrease scraper wear. [ABSTRACT FROM AUTHOR]

The shear behaviour of natural joints generally exhibits anisotropy due to variations in morphological characteristics. The anisotropic shear behaviour of natural joints mainly determines the rock mass stability. It is improbable to sample a large number of natural joints with same surface morphologies in the field. In this study, 3D laser scanning and 3D engraving techniques were adopted to reconstruct natural joints in the laboratory. In the reconstruction process, a series of trial and error engraving tests were conducted due to the lack of engraving resolution evaluation and engraving parameter selection methods. Both 2D and 3D characterization methods were used to quantitatively assess the engraving resolution. A method was proposed to determine the interval path based on the cone angle of the cutter. A series of engraving tests were conducted to study the effect of the path interval on the engraving resolution and to verify the proposed method. The results indicated that the engraving path interval should not be too large (> 0.20 mm) or too small (< 0.10 mm), which could result in a strip between adjacent engraving paths or overengraving, respectively. The natural joints in the sandstone specimen could be successfully reconstructed when the optimal cutter radius and path interval were 0.40 and 0.10 mm, respectively. The root mean square error (RMSE) of the profile height between the original and reconstructed joints was less than 0.10 mm. The difference in the 3D roughness θ max ∗ / C + 1 between the original and engraved joints was less than 0.5. The methods proposed in this study can be employed to accurately assess the engraving resolution and to quickly determine reasonable engraving parameters. In this way, natural joints can be reconstructed with high engraving resolution. The anisotropic shear behaviour of natural joints can be suitably investigated in the laboratory. [ABSTRACT FROM AUTHOR]

Rockbursts have become one of the main engineering disasters in deep-buried tunnel, seriously threatening the safety of worker and equipment. To monitor microseismic (MS) events and predict rockburst, in the present study, a MS monitoring system was established in a deep-buried tunnel excavated by tunnel boring machine (TBM). Characteristics of MS events were studied and a prediction method for intense rockburst was proposed by analyzing the temporal–spatial distribution, source parameters, and failure mechanism. The results indicated that most of MS events occurred during the tunneling process and within 15 min after a tunneling cycle completed. The MS events mainly distributed within 15 m before and after the tunneling face, and within approximate 2.0 times of the tunnel diameter. The energy of these MS events mainly ranged from 30 to 100 kJ. The prediction method based on cumulative energy index of per day and cumulative apparent volume cannot predict intense rockburst accurately in the present study, the forecast accuracy less than 60%. The proposed prediction index based on the energy index of per MS event and the apparent volume of per MS event can effectively sharpen the forecast accuracy (> 85%). The failure mechanism of MS events was predominated by tensile failure. While as the rockburst segment transited from mild to intense, the percentage of MS events of mixed failure and shear failure increased, especially shear failure events. Highlights: The temporal and the spatial distribution characteristics of rockburst segment in a deep-buried tunnel were revealed. Microseismic event count, energy, energy index, apparent volume, failure mechanism, and the development process of mild, moderate, and intense rockburst segments were studied. A prediction index based on energy index and apparent volume of per microseismic event was proposed to forecast intense rockburst. [ABSTRACT FROM AUTHOR]

The Brazilian test is extensively used to indirectly measure the tensile strength of rock. However, the Brazilian tensile strength (BTS) does not always align with the direct tensile strength (DTS), resulting in a lack of consensus regarding the applicability of Brazilian test across diverse rock types. To evaluate the applicability of Brazilian test loading with various platens, the different numerical tensile tests based on the discrete element procedure PFC2D were conducted. The simulation results indicate that the discrepancy between the BTS and DTS of rock is heavily influenced by the rock's uniaxial compressive strength (UCS) to direct tensile strength (DTS) ratio. Specifically, the DTS/BTS ratio exhibits a strong negative correlation with the UCS/DTS. This negative correlation holds true across the usage of different loading platens in the Brazilian test. Moreover, the simulation results indicate that the process of crack initiation and propagation of specimens in Brazilian test is closely related to the relative relationship between the BTS and DTS. The UCS/DTS ratio of rock and the selection of the loading platen simultaneously affect the process of crack initiation and propagation. Specimens with a low UCS/DTS ratio tend to crack from the loading ends inward under concentrated end loading, such as flat platen and curved jaws. In this scenario, the BTS often underestimates the rock's tensile strength. If the UCS/DTS ratio of a specimen is sufficiently high, cracking does not originate from the end, but rather from discrete microcracks in the internal tensile stress zone. These microcracks then propagate towards the loading end, leading to failure. Under these conditions, the BTS typically overestimates the tensile strength. Utilizing platforms with a central angle of 20°can mitigate stress concentration at the loading end in Brazilian tests, prompting internal crack initiation. However, the resulting BTS is also more likely to overestimate the tensile strength. Therefore, selecting an appropriate loading platen based on the rock's UCS/DTS ratio is crucial to minimize the difference between the BTS and DTS. The proper range of UCS/DTS ratios of rock for the Brazilian test with flat platen, curved jaws and loading platforms are recommended as 10–15, 8–10 and 5–8, respectively. Highlights: The discrepancy between the direct tensile strength (DTS) and Brazilian tensile strength (BTS) of rock is closely related to its compression-tension ratio. The initiation and propagation of cracks during the Brazilian test are influenced by both the compression-tension ratio of rock and the chosen loading platen. The applicable range of compression-tension ratios for rock during Brazilian tests loading with different platens are proposed. [ABSTRACT FROM AUTHOR]

The macro-indentation test is widely used to evaluate rock mechanical properties. Due to the complex indentation process and the multi-peak force–penetration curve, many indentation indices are proposed to evaluate rock properties. It is critically important to assess these indices and select the proper index for certain usages (i.e., estimating rock strength, representing rock brittleness, and drillability). In the present study, indentation indices proposed in the previous studies were summarized first. To analyze statistical characteristic of the indentation indices (i.e., distribution characteristic and correlation), the indentation test was conducted on 47 granite specimens. 26 indentation indices were calculated from each force–penetration curve of the indentation test. The indentation indices are generally concentrated at the mean value, but these indices have different dispersion degree. The force indices and energy indices of the same large-scale fracture are highly correlated, while the force indices and modulus indices are little correlated. Most modulus indices are correlated with each other, while most dimensionless indices are independent of each other. For highly correlated indices, the index with small dispersion is the first choice for usage. Finally, proper indices are suggested for estimating rock strength and representing rock brittleness and drillability according to their distribution characteristics, correlations, and prediction accuracy. The minimal testing number to attain the required accuracy is also proposed for these selected indices. Highlights: The definition and application of the existing indentation indices are summarized. The indentation test is conducted on 47 granite specimens to evaluate the applicability of the indentation index. The distribution characteristics and correlations of the testing data of the indentation indices are studied. Proper indentation indices are suggested for estimating rock strength and representing rock brittleness and drillability. [ABSTRACT FROM AUTHOR]

The mechanical properties of rock, especially the uniaxial compressive strength (UCS), the elastic modulus (E), and the Brazilian tensile strength (BTS) are critically important for rock engineering. Since standard laboratory tests have some limitations, various indirect methods have been developed for estimating these mechanical properties, e.g., the indentation test. In the indentation test, an indenter is forced into the rock to obtain the load-displacement curve. Most estimation models of rock mechanical properties by indentation test are appropriate for fine-grained rock or soft rock, and there is little estimation model for coarse-grained rock and hard rock. Therefore, it is important to establish an estimation model appropriate for rock with large grain sizes and high strength. Since the specimen size may affect the test result, specimens with different sizes were tested first to study the specimen size effect. The result showed that both the specimen diameter and height affect the specimen failure pattern, the load-displacement curve, and the indentation indices. The proper specimen size is suggested using in the indentation test with a 7-mm diameter indenter. Then, 8 types of rock were prepared for indentation tests, uniaxial compression tests, and Brazilian tests. The UCS, BTS, and E all increase with indentation indices, e.g., the energy per unit (W) and the indentation modulus of the first peak (IM1). There are linear correlations between the UCS, E, BTS, and indentation indices (W and IM1) with high determination coefficients. [ABSTRACT FROM AUTHOR]

With the rapid development of urbanization and industrialization, electric power consumption continues to increase on a worldwide basis. Traditional overhead transmission lines cannot satisfy the requirements for modernization of power distribution systems. Cable tunnels with ultra-high-voltage and complex network have become the trend of urban power transmission lines for their advantages in flexibility, expandability, and convenient maintenance. Although cable tunnels have good adaptability in power transmission, their application is severely restricted by construction and inspection technologies. Especially for long-distance cross-river tunnels installed with 1000 kV equipment, there is still a lack of reliable solutions to deal with complex challenges encountered during the construction and inspection of ultra-high-voltage cable tunnels. In the present study, complexity features of the first underwater gas-insulated transmission line for 1000 kV power in the world, Sutong GIL Yangtze River Crossing Cable Tunnel, have been analyzed. Engineering challenges encountered during the construction and inspection of long-distance cable tunnel have been discussed. Key technologies including embankment deformation control, gas explosion prevention, synchronous transportation organization, dust-free equipment installation, and robot intelligent inspection have been developed. The application of these technologies has enabled the safe and efficient construction and inspection of a high-quality cross-river cable tunnel. [ABSTRACT FROM AUTHOR]

Acetylcholinesterase (AChE) is an essential serine hydrolase associated with neurodegenerative diseases and serves as a biomarker. In this work, a ratiometric fluorescence strategy for the sensitive assay of AChE activity is developed based on the decomposition of MnO2 by the enzymatic hydrolysis product and DNAzyme-mediated strand cleavage. The sensing system is termed as MnO2/DNAzyme. DNAzyme locked by H2 strands is inactive in the absence of AChE. The fluorescence emission of fluorescein amidite (FAM)-labeled DNA (DNA-F) at 518 nm is quenched by neutral red (NR) and the fluorescence of NR at 632 nm is simultaneously enhanced due to fluorescence resonance energy transfer (FRET). The presence of AChE triggers the hydrolysis of the substrate acetylcholine (ATCh) to enzymatic thiocholine (TCh), which reduces MnO2 nanowires to Mn2+ and releases the attached H1 strands into the solution. The H1 strands hybridize with H2 strands through the strand displacement reaction. Meanwhile, the activated DNAzyme cleaves the RNA nucleotide of the DNA-F signal probe to release FAM. The fluorescence of FAM at 518 nm is thus recovered, corresponding to a decrement of NR emission at 632 nm owing to the blocking of FRET. The fluorescence ratio of F518/F632 serves as a signal readout for the AChE assay within 5 × 10−4–10 U mL−1, with a limit of detection (LOD) of 2.7 × 10−4 U mL−1. The feasibility of this method was demonstrated by the measurement of AChE activity in human blood, which reveals its promising potential in clinical assays. [ABSTRACT FROM AUTHOR]

The novel strain TF-2, isolated from a contaminated site and identified as Burkholderia stabilis, is able to degrade chlorobenzene via assimilation (51%-89%) and co-metabolism (98%-100%) for 60–200 mg/L chlorobenzene. Whole-genome sequencing experiments of strain TF-2 were carried out to reveal its global metabolism. Notably, 19 aromatic hydrocarbon dioxygenase genes and a gene cluster related to chlorobenzene metabolism were discovered in this strain. Moreover, the complete genome of strain TF-2 is composed of three circular chromosomes and two plasmids. The total length is 8.83 Mb, containing 8,807 protein coding genes, 18 rRNA genes and 69 tRNAs genes. Additionally, it contains 209 carbohydrate-active-enzyme-encoding genes, of which mainly 33.0% distributed in glycosyl transferases, 24.8% in carbohydrate esterases and 21.1% in auxiliary activities. Finally, the degradation pathway of chlorobenzene in TF-2 was proposed. The annotated complete genome sequence of TF-2 will provide genetic insights into the degradation of chlorobenzenes. [ABSTRACT FROM AUTHOR]

Rockburst has become a main factor threatening the safe construction of deep-buried tunnels. To monitor microseismic (MS) event and comprehend evolution process of rockbursts, a MS monitoring system was established in a deep-buried tunnel excavated by drilling and blasting. The mechanisms of three typical rockburst cases were investigated through the analysis of the MS sequence and development process. The results showed that the MS sequence of first rockburst case was a main-aftershock type, corresponding to a strain rockburst that occurred in intact surrounding rocks. Most of the MS events were failure in tensile, with few MS events presenting mixed failure mode. For the second rockburst case, the MS sequence was a fore-main-aftershock type, corresponding to a strain-structural slip rockburst that occurred in surrounding rocks with a considerable number of small-scale structural planes. The MS events in tensile failure were predominated, and a few MS events were failure in mixed and shear. The MS sequence of the third rockburst case was a new type observed in the present study, i.e. main shock type, corresponding to a strain-structural slip rockburst. It occurred in high strength surrounding rocks with rigid structural planes, which easily induced collapse in the rockburst process. The MS events in tensile failure were predominated. The precursor phenomena of former two cases of the rockburst can be identified through the analysis of MS sequence and source parameters. While before the third rockburst case occurred, no or a few MS events were obtained. It is difficult to predict this type of rockburst based on source parameters. For this case, destress blasting method was adopted. The number of high-energy MS events decreased abruptly, and no intense rockbursts occurred. This method can effectively release the concentrated stress of the surrounding rocks and reduce the risk of rockbursts. The results of this study could provide guidance and reference for the early warning and prevention of rockbursts in deep-buried tunnels. • The temporal and spatial evolution process of microseismicity of three typical rockbursts were studied. • The evolution mechanism of three typical rockbursts was revealed. • Mitigation measures were adopted to reduce the risk of rockbursts. [ABSTRACT FROM AUTHOR]

The inherent intermittency of solar power due to diurnal and seasonal cycles has usually resulted in the need for alternative generation sources thereby increasing system operation costs. However, when solar power is spread over a large geographical area with significant time differences, the intermittency can be significantly reduced and also the electricity market balancing cost. The aim of this article is to address the fundamental scientific question on how the intermittency of solar power generation is affected by aggregation, which is of great interest in the wider power and energy community and would have profound impacts on the solar energy integration into the energy supply and Net-Zero Implementation. This article goes beyond the typical regional analysis by investigating solar power intermittency at 5 aggregation levels from a global perspective based on global 7 year hourly meteorological re-analysis data with a fine spatial resolution of 0.25 ∘ × 0.25 ∘ (∼ 28 km × 28 km) . In the proposed assessment framework, a coefficient of variation (CV) is used to quantify solar power intermittency and hence characterize the potential benefits of wide area solar power aggregation. A duration curve is used to characterize the intermittency in terms of power availability and a probability density function is further employed to investigate the dispersion and scaling behavior of CV at different aggregation levels. The findings indicate that the CV of solar power generation of 'Inner Mongolia' in China drops from 129.65 to 105.65% in the level of 'Asia' (by 24% decrease), to 56.11% in 'Asia-North_America' (by 73.54% decrease) and to the smallest 43.50% in 'Global' (by 86.15% decrease), nearly 3.5 times of that in 'Asia'; (b) the availability of solar power generation increases from 52.17% in Germany, to 73.30% in 'Europe_EU_plus', to 77.82% in 'Europe', to 98.59% in 'Europe-North_America' (80.60% in 'Europe-Africa', 96.90% in 'Europe-Asia'), to 100% in 'Global'. Finally, conclusions and recommendations are provided to support a Net-Zero strategy. [ABSTRACT FROM AUTHOR]

The estimation of soil abrasivity and cutting tool wear during soft ground tunneling is complicated and arduous work due to the lack of a generally accepted testing system. To date, geotechnical baseline reports (GBRs) and geotechnical data reports (GDRs) still cannot provide reliable soil abrasion indices for tool life prediction. This is considered a deficiency in the geotechnical investigation of shield-driven tunnel projects. In this study, the Multifunctional Shield Test System (MSTS) developed by the Key Laboratory of Safety for Geotechnical and Structural Engineering of Hubei Province at Wuhan University is presented. The MSTS was motivated by the need for a test platform with the ability to simulate undisturbed soil conditions and actual tool working environments to explore the mechanism of cutting tool wear, bentonite slurry penetration, and filter cake formation in various geomaterials with grain sizes including clay, silt, sand, and gravel (< 15 mm). Experimental studies on the effect of alloy hardness on cutting tool wear are conducted. The soil samples used in the tests are dense fine silty sand from the Sutong GIL Yangtze River Crossing Cable Tunnel. When the wear extent is plotted against the alloy hardness, an inverted S-shaped band bounded by the highest and lowest alloy hardnesses is formed. The sensitive hardness interval is HRC = [47, 52]. If the alloy hardness is higher than 52 HRC, the wear extent is relatively small. Since alloy hardness is negatively correlated with bending strength, using a cutting tool material with a hardness slightly higher than the upper limit of the sensitive hardness interval is optimal. Thus, an alloy with a hardness interval of HRC = [52, 63] is recommended for the dense fine silty sand ground at the Sutong GIL Yangtze River Crossing Cable Tunnel. [ABSTRACT FROM AUTHOR]

Zinc ion (Zn2+) is a necessary transition metal ion in the human body and plays a vital role in biological systems. Therefore, it is meaningful for rapid, sensitive, and specific detection of Zn2+. Herein, a "switch-on" fluorescence sensing platform for the detection of Zn2+ was successfully established. In this work, we report an optical nanoprobe with amino functional groups based on porphyrin metal-organic frameworks (PCN-NH2) through a simple treatment method. The modification of the salicylaldehyde (SA) through the C=N acts as a quencher of PCN-NH2 and the ligand of Zn2+ can effectively inhibit the fluorescence emission of PCN-NH2. The complex of porphyrin-based metal-organic framework and salicylaldehyde (PCN/SA) acts as the fluorescence sensing probe. The presence of Zn2+ results in the new emission peak at 448 nm due to the formation of a complex between Zn2+ and SA. The corresponding fluorescence signal changes were used to accurately detect the concentration of Zn2+. The fluorescence sensing platform shows advantages, including rapid response, high sensitivity, and excellent specificity with a linear detection range of Zn2+ between 0.1 and 250 μM, and a low detection limit (LOD) of 0.07 μM. And the feasibility of the method was verified for the quantification of Zn2+ in cell lysate, environmental water, and plasma. [ABSTRACT FROM AUTHOR]

In two-way time-of-arrival (TOA) systems, a user device (UD) obtains its position and timing information by round-trip communications to a number of anchor nodes (ANs) at known locations. Compared with the one-way TOA technique, the two-way TOA scheme is easy to implement and has higher localization and synchronization accuracy. Existing two-way TOA methods assume a stationary UD. This will cause uncompensated position and timing errors. In this article, we propose an optimal maximum likelihood (ML) based two-way TOA localization and synchronization method, namely TWLAS. Different from the existing methods, it takes the UD mobility into account to compensate the error caused by the UD motion. We analyze its estimation error and derive the Cramér-Rao lower bound (CRLB). We show that the conventional two-way TOA method is a special case of the TWLAS when the UD is stationary, and the TWLAS has high estimation accuracy than the conventional one-way TOA method. We also derive the estimation error in the case of deviated UD velocity information. Numerical result demonstrates that the estimation accuracy of the new TWLAS for a moving UD reaches CRLB, better than that of the conventional one-way TOA method, and the estimation error caused by the deviated UD velocity information is consistent with the theoretical analysis. [ABSTRACT FROM AUTHOR]

However, the value of crack closure stress ( I i SB cc sb ) and crack initiation stress ( I i SB ci sb ) will be clearly changed by small fluctuations of Poisson's ratio. If the stress level is higher than the crack damage stress ( I i SB cd sb ) but lower than peak strength ( I i SB f sb ), cracks will propagate continuously and coalescence to reach macroscopic failure. 6 Curves of lateral strain difference for a siliceous siltstone and b limestone Moving Point Regression Method (MPR) Eberhardt et al. ([4]) proposed a new method to obtain the crack closure stress ( I i SB cc sb ) and the crack initiation stress ( I i SB ci sb ). If the stress level is higher than crack initiation stress ( I i SB ci sb ) but lower than crack damage stress ( I i SB cd sb ), cracks randomly initiated but they will cease at a certain length without coalescence. [Extracted from the article]

• The temporal and spatial evolution process of microseismicity in a fault‑slip rockburst were studied. • The development process and evolution mechanism of the fault‑slip rockburst were revealed. • The mechanism of intermittent occurrence of the rockburst and mud gushing near the fault was discussed. An intense fault-slip rockburst occurred in a deep-buried tunnel excavated by tunnel boring machine (TBM). After the intense rockburst occurrence, moderate rockburst and mud gushing intermittently occurred several times, which resulted in the main beam of the TBM being buried and delaying construction schedule for several months. In the present study, microseismic (MS) monitoring and geological survey were carried out to investigate the evolution process and development mechanism of the rockbursts. The temporal and spatial evolution of MS activity, dynamic stress drop, and fracture mechanism were analyzed. The results indicated that prior to 2–4 days of the fault-slip rockburst, the number of MS event gradually decreased, while the energy level and dynamic stress drop gradually increased. Prior to one day of the fault-slip rockburst, the number of MS event with high energy sharply increased. During the development stage of the fault-slip rockburst, most of the MS events were failure in tensile and a few events were in mixed and shear failure. The main MS event of the fault-slip rockburst is in mixed failure, result from the dislocation of the fault. The energy accumulated near the fault was not released fully through the intense rockburst. After that, the energy intermittently released, i.e. moderate rockburst and mud gushing intermittently occurring several times. It was because that some hard rock layers were within the fault fracture zone. As the mud gushing occurred, the stress applied on the hard rocks was unloading and a moderate rockburst was prone to occur. As the moderate rockburst occurred, the path of mud gushing was opening, and a mud gushing tended to occur. The research results can be helpful for further research on fault-slip rockbursts and planning appropriate warning and mitigation methods. [ABSTRACT FROM AUTHOR]

Tunnel boring machine (TBM) is the preferred method in the construction of long-distance and deep-buried tunnel due to its advantages in safety and high efficiency. However, the TBM method is very sensitive to the condition of the surrounding rock. The strength and integrity characteristics of rock mass have great influence on the safe and efficient tunnelling. To provide a fast perception method for these characteristics during the TBM tunnelling process, an in-situ penetration testing system is proposed in the present study. The development and testing procedure of the system are elaborated. The system is applied to a TBM-excavated water conveyance tunnel to continuously perceive the strength and integrity characteristics of the surrounding rock. Firstly, the force-penetration (F-P) responses of the surrounding rock under penetration are qualitatively studied. Then, series of penetration indices are summarized to quantify the characteristics of the F-P responses. Finally, the quantitative relationships between the rock strength and the penetration indices are studied. The results indicate that the in-situ penetration testing system can perceive the rock mass strength and integrity characteristics qualitatively and quantitatively. On the qualitative aspect, the F-P responses can be categorized into four types (Type I to Type IV), which correspond to the level of rock mass strength and integrity. On the quantitative aspect, a single penetration index cannot represent the complete information of the F-P response. The descriptive classification of the rock mass strength (class I to III) is established through multiple penetration indices. The in-situ penetration testing system can be used as a method to quickly perceive the strength and integrity characteristics of the surrounding rock in TBM tunnelling. [ABSTRACT FROM AUTHOR]

Two main methods are commonly used in tunnel excavation, drilling and blasting (DB) and tunnel boring machine (TBM) tunnelling method. To better understand the differences and predict rockbursts, the characteristics of microseismic (MS) events in two parallel tunnels excavated by DB and TBM methods were compared, including temporal distribution, spatial distribution, and intensity distribution. The results indicated that the characteristics of MS events induced by two excavation methods had some differences. In the DB excavated tunnel, the number of MS events decreased exponentially as the time to a blasting cycle increased. The MS events predominantly occurred within 15 min to a blasting cycle. On the other hand, in the TBM excavated tunnel, the MS events primarily occurred while the TBM was working. Similarly, when a tunnelling cycle was completed, there was an exponential decrease in the number of MS events, which mainly occurred within 15 min. The distribution of MS events in relation to the tunnelling face exhibited similarities for both excavation methods, presenting a normal distribution. The range of the TBM excavation (approximately 2.3 times of tunnel diameter) was generally larger compared to the DB excavation (approximately a time of tunnel height). In terms of energy levels, both the DB and TBM excavations predominantly produced low-level energy MS events (less than 30 kJ). For moderate and high-level energy events, the percentage of TBM excavation induced events was higher than that of DB excavation induced. In the TBM excavation, surrounding rocks maintain good integrity and high bearing capacity, and a large tangential stress gradient is near the tunnelling face. It is more likely to induce a large rupture scale of seismic sources and lead to a more prolonged and widespread active period. On the other hand, the fracturing zone induced by the DB excavation reduces bearing capacity of surrounding rocks, and strain energy within surrounding rocks is released to a certain extent. The tangential stress gradient is relatively small, so it is associated with more localized and short-lived seismic activity in the DB excavated tunnel. [ABSTRACT FROM AUTHOR]

Fractional Frequency Transmission is a competitive technology for offshore wind power transmission. Modular Multilevel Matrix Converter (M3C) plays a key role in a Fractional Frequency Transmission System (FFTS) as the frequency changer. M3C is broadly considered as the AC–AC converter for the future with its attractive advantages in high voltage and high power applications. Due to the lack of a DC link, electrical quantities at different frequencies from two AC systems couple in M3C, resulting in a complex harmonic condition. Harmonics can lead to stability issues and its analysis is of great importance. This paper focuses on the harmonic analysis of M3C. The arm capacitor voltage ripples and the harmonic currents are analyzed at various frequencies. Major factors influencing the harmonics magnitude are discussed. Analysis is conducted on sub-module capacitance and arm inductance selection. A zero-sequence current mitigation controller for M3C is implemented and tested. It is found that for a FFTS, some current harmonics flow into AC systems even though the system is balanced, while the others circulate within the converter. The theoretical harmonic analysis is verified by simulations in Real Time Digital Simulator (RTDS) of a M3C system where each arm consists of forty sub-modules. [ABSTRACT FROM AUTHOR]

An exceptionally strong solvation effect of dimethyl sulfoxide (DMSO) on I2 is identified by the largest shift observed so far of the I2 Raman peak with respect to I2 vapor and by elongated I−I bond lengths in first‐principles molecular‐dynamics simulations. This effect together with strong binding by an RuO2 surface to I2 is found to invert the direction of the reaction I−+I2⇌I3− to the left‐hand side. Inspired by this finding, we prepared a Li–O2 battery with the Li/DMSO+LiI/RuO2 structure. The synergic action of DMSO and RuO2 on I2 is found to suppress the shuttle effect of the redox mediator (RM) by anchoring I2 molecules, the oxidation product of the RM. Significantly enhanced stability is demonstrated over 100 cycles at charging voltage below 3.65 V. [ABSTRACT FROM AUTHOR]

An exceptionally strong solvation effect of dimethyl sulfoxide (DMSO) on I2 is identified by the largest shift observed so far of the I2 Raman peak with respect to I2 vapor and by elongated I−I bond lengths in first‐principles molecular‐dynamics simulations. This effect together with strong binding by an RuO2 surface to I2 is found to invert the direction of the reaction I−+I2⇌I3− to the left‐hand side. Inspired by this finding, we prepared a Li–O2 battery with the Li/DMSO+LiI/RuO2 structure. The synergic action of DMSO and RuO2 on I2 is found to suppress the shuttle effect of the redox mediator (RM) by anchoring I2 molecules, the oxidation product of the RM. Significantly enhanced stability is demonstrated over 100 cycles at charging voltage below 3.65 V. [ABSTRACT FROM AUTHOR]

Damage to the blood-brain barrier (BBB) resulting from systemic inflammation caused by surgical trauma is associated with cognitive dysfunction, and individuals with hyperlipidemia are more sensitive to such impairment. The present study was designed to ascertain whether dexmedetomidine (Dex) treatment could reduce the incidence of cognitive dysfunction following surgery in a hyperlipidemia model. Hyperlipidemia was induced in Sprague-Dawley rats (male, 6–7 months old) by consuming a high-fat diet, and rats were divided into three groups (n=10 each) and underwent: exploratory laparotomy to introduce surgical trauma (surgery group), laparotomy and Dex treatment (surgery+Dex group), or sham surgery (sham group). Learning, memory and exploration behavior were assessed using the Morris water maze. Concentrations of tumor necrosis factor (TNF)-α and interleukin (IL)-1β, were determined by enzyme-linked immunosorbent assay. BBB permeability was assessed by Evans blue staining. Relative major facilitator superfamily domain-containing protein 2 (Mfsd2a) mRNA expression was determined by quantitative PCR. In the Morris water maze test, the time and distance ratio for the surgery group was significantly lower than those of the sham and surgery+Dex groups (P<0.05). In addition, the TNF-α concentrations in the sham and surgery+Dex groups were lower than that in the surgery group (P<0.05 on days 1 and 3). Evans Blue staining was increased in the surgery group on day 1 (P<0.01). Mfsd2a mRNA expression was higher in the sham and surgery+Dex groups compared with that noted in the surgery group (P<0.05). In conclusion, Dex treatment decreased the incidence of cognitive dysfunction following surgical trauma in a hyperlipidemia rat model. We demonstrated that Dex stabilized BBB integrity through increased Mfsd2a gene expression. [ABSTRACT FROM AUTHOR]

The investment cost of renewable energy systems for achieving net-zero energy buildings (ZEB/NZEB) is a vital factor concerned by most building owners, which raises a requirement for a new financial scheme specifically designed considering the level of ZEB. This study thus focuses on the design of reward-penalty mechanism for promoting the target of net-zero energy balance in each building design, enabling that a cost-effective design option for buildings where high integration of renewable energy systems can be expected. The benefits for building owners are formulated into three scenarios (S0, S1, and S2), in which the effectiveness of the proposed three functions were investigated. The results show that a higher cost is required by a lower level of ZEB whilst considerable bonuses can be realized by owners opting for higher levels of ZEB. In addition, the boundary of building energy consumption level as well as zero energy level is identified and provided for the proposed three reward-penalty functions. Based on the case study, the proposed reward-penalty functions were verified to be effective for a building energy consumption level between 0.8 and 2.0, with an error index lower than 7.0%. This study can provide an efficient yet effective approach for developing a financial scheme to further boost zero energy buildings. • A reward-penalty mechanism is proposed for the design of net-zero energy buildings. • Case studies are conducted on a PV-integrated single-family house. • Three scenarios are designed to study the effectiveness of the developed functions. • Application of the reward-penalty function for building owners is provided. [ABSTRACT FROM AUTHOR]

Splitting joints have been widely used to study the morphology characteristic and shear behavior of rock joints in the laboratory. There are some differences between the splitting joint and natural joint both in morphology characteristic and shear behavior. To quantitatively compare the differences, the present study used several splitting joints and natural joints to carry out the roughness analysis and direct shear test. Six profiles were extracted from each joint surface with a 30° interval to calculate the 2D roughness parameters (i.e., amplitude roughness parameter, average asperity inclination, root-mean-square of profile slope, and joint roughness coefficient). These parameters of the natural joints have a wide range and have obvious fluctuation. On the contrary, these parameters of the splitting red sandstone joints converge on a small range with tiny fluctuation, even calculated from different joint surfaces. The directional parameter (θ ⁎ max (C + 1)) was adopted to calculate the 3D roughness with a 5° interval. The directional parameter of the natural joints in range of 0° ∼ 360° forms a peanut, a prolate ellipse, or a gourd shape, presenting significant anisotropy. For the splitting joints, it forms a circle or a roughly circular shape, presenting insignificant anisotropy. The asperity heights of natural joints mainly present an irregular distribution, and they present an approximately normal distribution in few joints. For the splitting joints, the asperity heights generally obey a normal distribution. It indicates that there are huge differences between natural joint and splitting joint in morphology characteristic. To study the shear behavior, two types of joint were reconstructed for repeated test. The mechanical performance and failure characteristic of the splitting joint under different shear directions are similar. On the contrary, those of the natural joints under different shear directions are different, presenting obvious anisotropy. Based on the comparative analysis of the natural joints and the sandstone splitting joints in the present study, there is substantial difference between two types of joints both in morphology characteristic and shear behavior. The splitting joints cannot reproduce the characteristics of the natural joints well. • The difference in the morphological characteristic between the natural joint and splitting joint is compared quantitatively. • The difference in the shear behavior between the natural joint and splitting joint is analyzed in detail. • The mechanism of the shear behavior difference between two types of joints induced by the morphology difference is discussed. [ABSTRACT FROM AUTHOR]

This paper introduces significant performance enhancements to the ac filterless LCC HVDC by including fixed series capacitors at the primary side of a converter transformer. In terms of technical performance, 1) the amount of active power that can be transmitted is increased by more than 60% compared with ac filterless LCC HVDC, especially under severe unbalanced fault such as single-phase fault (most common fault in power systems); 2) the required voltage level of the controllable capacitor for Commutation Failure (CF) elimination is reduced by more than 70%, which leads to considerable reductions of the associated costs and losses. In terms of economic performance, due to the reduction of the required voltage from controllable capacitors (hence, the number of power electronic devices), the cost of the proposed converter station is lower than that of the ac filterless LCC HVDC. Theoretical analysis is presented to illustrate the performance enhancements and select the size of the series capacitor. Simulation results for various kinds of faults and cost analysis are presented to validate the technical and economic performances of the proposed method. Comparisons are made with ac filterless LCC HVDC. Finally, various practical issues and possible solutions are discussed. [ABSTRACT FROM AUTHOR]

• It is improper to determine the failure nature of macro-crack by using the proportion of micro-cracks (tensile ⧹ shear). • Moment tensor inversion can indicate the forces applied on failure sources and distinguish the nature of primary and secondary cracks. • The failure modes of secondary cracks are complicated, changing from shear to tensile as the cracks propagate. Cracking processes have been extensively studied in brittle rock and rock-like materials. For a better understanding of failure processes, moment tensor is used to distinguish the nature of primary cracks and secondary cracks in a single-flaw-contained specimen based on the bonded-particle model, which can indicate the force applying on the failure source. The results reveal that the primary cracks solely consist of micro-tensile cracks and the failure nature is tensile, while the secondary cracks are composed of both micro-shear cracks and micro-tensile cracks and the failure mechanisms are complicated. The failure mechanisms of acoustic emission (AE) events of the first part of secondary cracks, which initiate from the tips of the pre-existing flaw, are mainly "implosional" and "shear", implying that the unbalance forces applied on the failure source are predominately implosional and shear components after breakage. As the secondary cracks propagate farther, the failure nature of AE event changes to "tensile" mode finally. [ABSTRACT FROM AUTHOR]

Abstract In the first 3602 m tunnelling of TBM1 section at water conveyance tunnel of Lanzhou Water Source Construction Engineering, the lithology is composed of quartz diorite and quartz schist. 409 disc cutters and cutter rings are replaced in the TBM1 section, which is very high compared to other tunnel project. Based on data of disc cutter replacement at different installation locations, the consumption law and its reason are analyzed and the standard for disc cutter replacement is put forward. The disc cutter consumption and its influence on TBM tunnelling efficiency under different surrounding rock conditions are analyzed. Countermeasures of the control of tunnelling parameters, inspection and treatment of cutter and the daily management are proposed to reduce the cutter replacement. The consumption of the disc cutter was reduced to a certain degree after practice. Finally, suggestions for the optimization of the strength and toughness of the cutter ring, the secondary wear rule, and auto analysis system for the disc cutter management in the TBM cutter consumption are proposed. Related methods can provide reference for similar projects. [ABSTRACT FROM AUTHOR]

Highlights • Penalty cost is introduced for the design of net zero energy building (NZEB). • Three scenarios are conducted to study the impact of penalty cost on system design. • Case studies are conducted on the Hong Kong Zero Carbon Building. • The relationship between total cost (IPOC) and safety factor is investigated. Abstract It is well known that the high cost of installing renewable energy systems (RES) is still a barrier to overcome in the promotion of net-zero energy buildings (NZEB). The current practice in selecting the optimal RES system for NZEB basically involves a consideration of all possible design options, which is usually not a cost-effective process when compared with costs for no or for less RES in buildings. This study, therefore, introduces a penalty cost in the RES design process for NZEB, which aims to ensure that the cost-effective design option is the system which provides for a net-zero/positive energy building. The proposed penalty cost function is investigated in three scenarios (two scenarios with penalty costs and one scenario without a penalty cost) based on the Hong Kong Zero Carbon Building. It is found that the total cost of the building under a safety factor of 0.0 is increased by about 70% when a penalty cost is considered whilst it is reduced by 39% (for penalty cost 1) and 48.9% (for penalty cost 2) for the building under a safety factor of 1.0 (i.e., NZEB), respectively. In addition, three fitting formulas were derived for designers to better understand the relationship between the total cost and safety factor. The idea of developing a penalty cost mechanism provides a progressive perspective to assist the promotion of NZEB in terms of both governments as well as building designers/owners. [ABSTRACT FROM AUTHOR]

Abstract To better investigate hydraulic fracturing in tight reservoirs, interaction modes between a hydraulic fracture and a weak plane are studied with acoustic emission (AE) based on moment tensor under different differential stresses (Δσ) and approaching angles (β). Failure nature of hydraulic fracture is mainly tensile based on moment tensors except that the hydraulic fracture propagates into weak plane. At β = 30°, the hydraulic fracture is arrested by the weak plane. The failure nature of weak plane changes from 'Shear' (Δσ = 10, 7 and 5 MPa) to 'Tensile' (Δσ = 3 MPa). At β = 60°, the hydraulic fracture branches into weak plane as crossing, the nature of which is 'Shear' as differential stress decreases from 10 MPa to 5 MPa. At β = 90°, the hydraulic fracture crosses the weak plane perpendicularly. [ABSTRACT FROM AUTHOR]

Abstract The existence of micro cracks inside rocks influences the rock strength and deformation significantly and controls the presence of crack closure stage under compression. However typical discrete element method (DEM) fails to model the gradual crack closure behavior of rock due to insufficient consideration for pre-existing micro-cracks. The stress-strain curves simulated in previous DEM are usually linear in initial stage until numerous cracks are induced under stress. Thus a new method implemented in Discrete Element Method is proposed to model the crack closure behavior of rocks under uniaxial compression. The pre-existing micro-cracks inside the rock sample are created and opened by introducing two notional contact surfaces and giving a negative reference gap. These opened cracks are gradually closed under stress as the adjacent discs sustain sufficient relative movement (re-contact). Thus the gradual crack closure behavior of rock under compression is reproduced. The crack distribution respect to the crack orientation is described with the crack tensor analysis to consider the effect of crack density and anisotropy. Three factors including crack intensity, crack orientation and crack gap are discussed with parametric study to study their influence on the crack closure behavior. The effects of pre-existing cracks on the properties of rocks (such as rock strength, Young's modulus, crack closure stress levels) are also analyzed, and are in well agreement with observations by experiment. A little modification is made to previous calibration process to consider the crack closure stage of rock. Finally two types of rocks including limestone and granite are calibrated and compared to the experiment results. The simulated stress-strain curves match the curves of experiment, especially the initial crack closure segment perfectly, which validates the proposed method. [ABSTRACT FROM AUTHOR]

Different from conventional haze removal methods based on a single image, near-infrared imaging can provide two types of multimodal images: one is the near-infrared image and the other is the visible color image. These two images have different characteristics regarding color and visibility. The captured near-infrared image is haze-free, but it is grayscale, whereas the visible color image has colors, but it contains haze. There are serious discrepancies in terms of brightness and image structures between the near-infrared image and the visible color image. Due to this discrepancy, the direct use of the near-infrared image for haze removal causes a color distortion problem during near-infrared fusion. The key objective for the near-infrared fusion is therefore to remove the color distortion as well as the haze. To achieve this objective, this paper presents a new near-infrared fusion model that combines the proposed new color and depth regularizations with the conventional haze degradation model. The proposed color regularization sets the color range of the unknown haze-free image based on the combination of the two colors of the colorized near-infrared image and the captured visible color image. That is, the proposed color regularization can provide color information for the unknown haze-free color image. The new depth regularization enables the consecutively estimated depth maps not to be largely deviated, thereby transferring natural-looking colors and high visibility of the colorized near-infrared image into the preliminary dehazed version of the captured visible color image with color distortion and edge artifacts. Experimental results show that the proposed color and depth regularizations can help remove the color distortion and the haze simultaneously. The effectiveness of the proposed color regularization for the near-infrared fusion is verified by comparing it with other conventional regularizations. [ABSTRACT FROM AUTHOR]

This paper presents a further significant development to the developed flexible LCC HVDC system with controllable capacitors , which can provide ac voltage/reactive power control. The development involves the installations of fixed parallel capacitors at the valve side of converter transformer, which brings the following significant benefits: First, ac filter banks at the ac side of converter transformer are not needed as a better harmonic filtering performance can be achieved; second, significant reduction of the HVDC station land requirement (compared with traditional LCC HVDC), as the ac filters together with the switchgear can occupy over 50% of the HVDC station footprint; third, up to 50% reduction of the required voltage rating and more than 60% reduction of the capacitance of controllable capacitors for commutation failure elimination can be achieved while similar power system dynamic performance (ac voltage/reactive power control) compared with that in can be demonstrated. Detailed analyses are presented to illustrate the effective commutation process and superb harmonic filtering performance with the fixed parallel capacitors. Selections of the component values are presented. Simulation results in real-time digital simulator are presented to verify the effectiveness of commutation failure elimination, power system dynamic performance, harmonic filtering performance, and show voltage/current stress of the fixed parallel capacitors. [ABSTRACT FROM AUTHOR]

[Display omitted] • Automatic acquisition and analysis system for TBM muck is developed. • Rock–machine interaction is qualitatively and quantitatively analyzed. • Real-time perceptions of rock mass condition and TBM performance are realized. Tunnel boring machine (TBM) is frequently used in tunnel construction due to its advantages in safety, high efficiency, environmental friendliness. However, the tunnelling efficiency of a TBM heavily depends on the rock–machine interaction conditions. To realize the real-time perception of rock–machine interaction information during the TBM tunnelling, an automatic acquisition and analysis system for rock muck is developed. Firstly, a framework for using the system to perceive the rock mass and TBM conditions was constructed. Then the method to quantitatively evaluate the geometric properties of rock muck is elaborated. Finally, the system was applied to a TBM-excavated tunnel to verify the functions of rock muck in the real-time perception of rock–machine interaction information. The results show that the geometric properties of rock muck can indicate both the rock mass conditions and the TBM performance. In rock mass condition perception: Rock blocks trend to be large in size and elongated in shape as the uniaxial compressive strength (UCS) of the surrounding rock decrease. The blocks produced from a relatively intact rock mass trend to be small in size and round in shape. Larger or smaller blocks with flat planes are frequently produced when TBM drives in the jointed rock masses. In TBM performance perception: The TBM utilization can be estimated through the ratio of the number of images with muck to the total number of captured images. A high value of the field penetration index (FPI) corresponds to blocks with large sizes and elongated shapes (or small sizes and round shapes). Elongated blocks are produced when TBM drives at a low FPI. These results are significant for the safe and efficient TBM tunnelling. [ABSTRACT FROM AUTHOR]

The adverse impacts of commutation failure (CF) of a line-commutated converter (LCC)-based high-voltage direct current (HVdc) system on the connected ac system are becoming more serious for high-power ratings, for example, the development of ultra-HVdc systems. Aiming to solve the problem of CF particularly for higher power/current LCC HVdc systems, this paper proposes a new method, which utilizes a thyristor-based controllable capacitor (TBCC), to eliminate CFs. The topology of the proposed TBCC LCC HVdc and its operating principles are presented. Then, mathematical analysis is carried out for the selection of component parameters. To validate the performance of the proposed method, modified LCC-HVdc and capacitor-commutated converter (CCC)-based HVdc systems based on the modified CIGRE HVdc system are modeled in a real-time digital simulator. Simulation studies for zero impedance single-phase and three-phase faults are carried out, and comparisons are made with both LCC-HVdc and CCC-HVdc systems. Furthermore, voltage and current stress of the TBCC are investigated and power-loss calculations are presented. The results show that the proposed method is able to achieve CF elimination under the most serious faults while the increase of power losses due to the TBCC is small. [ABSTRACT FROM AUTHOR]

In this paper, we developed a direct way for the study of hydroquinone oxidation through in situ electrochemistry-combined nuclear magnetic resonance (EC-NMR). Electro-polymerization-induced nano-polyaniline film was utilized as the catalyst in the process of electrochemical oxidation of hydroquinone. In situ EC-NMR provides a powerful tool to probe products distribution and reaction rate, which could be useful to investigate electro-catalytic mechanism and evaluate the electro-catalytic capacity. To study the influence of both protic and aprotic media in the electrocatalytic process, we mixed water and dimethylsulfoxide to mimic possible real-life electrochemical environments. The proposed in situ EC-NMR is capable of quantitatively monitoring the generation of products under varied solvent composition and pH values. A positive effect to electro-catalysis capacity is observed when the concentration of DMSO or water is increased from the volume equivalent point, implying that there should be a competition between protic and aprotic media, which can be characterized by EC-NMR technique. [ABSTRACT FROM AUTHOR]

Cancer vaccines mostly aim to induce cytotoxic T lymphocytes (CTLs) against tumors. An appropriate adjuvant is of fundamental importance for inducing cellular immune response. Since the antigen in particulate form is substantially more immunogenic than soluble form antigen, it is beneficial to interact with antigen-presenting cells membrane to induce robust CD8+ T cell activation following vaccination. Based on previous research, we designed an adjuvant formulation by combining Astragalus saponins, cholesterol, and liposome to incorporate antigen into a particulate delivery system, so as to enhance cellular immune response. Meanwhile, angiogenesis contributes to tumor growth and metastasis, and basic fibroblast growth factor (bFGF) is involved in tumor angiogenesis. Therefore, using lipo-saponins adjuvant formulation and a human recombinant bFGF antigen protein, we tried to induce bFGF-specific CTL response to inhibit tumor angiogenesis to achieve antitumor activity. After five immunizations, the lipo-saponins/bFGF complex elicited robust antibody response and markedly higher amount of interferon-γ in BALB/c mice, resulting in superior antitumor activities. Decreased microvessel density in CD31 immunohistochemistry and the lysis of vascular endothelial cells by the T lymphocytes from the immunized mice indicated that the immunity inhibited the angiogenesis of tumors and further led to the inhibition of tumors. Our data suggest that the approach to construct adjuvant formulation between liposome and Astragalus saponins appeared highly desirable, and that Astragalus saponins may be utilized as a valuable additive for enhancing the effectiveness of vaccines and stimulating an appropriate immune response that can benefit tumor therapy. [ABSTRACT FROM AUTHOR]

To study the effects of the mixed ground conditions on the cutter force and failure pattern during the tunnel boring machine (TBM) excavation, rock cutting tests under wedge cutter are conducted both in the physical experiments and the bonded particle model (BPM) numerical simulations. The results of simulation are generally comparable with those of experiments under single cutter. It demonstrates that the softer bottom material causes more disperse stress distribution which leads to wider AE accumulated area and more rapid displacement change in the indentation direction. Further simulations are conducted under double cutters. Crack may propagate deeper into the specimen due to the weaker bottom material. When the inclination of the material interface changes, the failure pattern of the specimen becomes highly asymmetric and the forces of the two cutters are not equal any more. Frequent change of ground conditions causes high asymmetric cutter force distribution, frequent changing cutter force as well as high eccentric moments on the cutter head. [ABSTRACT FROM AUTHOR]

To better investigate the cracking processes under uniaxial compression, a numerical approach using bonded-particle model (BPM) was adopted to simulate the loading processes and AE events of limestone. To validate the model, a physical experiment with acoustic emission (AE) monitoring was performed. It revealed that the AE parameters in the BPM including crack number and AE event were generally comparable with the AE count and AE hit in the experiments. The b-value of AE does not accurately evaluate the degree of damage in rocks. But it can indicate the different states of damage during cracking processes. [ABSTRACT FROM AUTHOR]

Defining a sound shift operator for graph signals, similar to the shift operator in classical signal processing, is a crucial problem in graph signal processing (GSP), since almost all operations, such as filtering, transformation, prediction, are directly related to the graph shift operator. We define a set of energy-preserving shift operators that satisfy many properties similar to their counterparts in classical signal processing, but are different from the shift operators defined in the literature, such as the graph adjacency matrix and Laplacian matrix based shift operators, which modify the energy of a graph signal. We decouple the graph structure represented by eigengraphs and the eigenvalues of the adjacency matrix or the Laplacian matrix. We show that the adjacency matrix of a graph is indeed a linear shift invariant (LSI) graph filter with respect to the defined shift operator. We further define autocorrelation and cross-correlation functions of signals on the graph, enabling us to obtain the solution to the optimal filtering on graphs, i.e., the corresponding Wiener filtering on graphs and the efficient spectra analysis and frequency domain filtering in parallel with those in classical signal processing. This new shift operator based GSP framework enables the signal analysis along a correlation structure defined by a graph shift manifold as opposed to classical signal processing operating on the assumption of the correlation structure with a linear time shift manifold. Several illustrative simulations are presented to validate the performance of the designed optimal LSI filters. [ABSTRACT FROM PUBLISHER]

Near-infrared gray images captured along with corresponding visible color images have recently proven useful for image restoration and classification. This paper introduces a new coloring method to add colors to near-infrared gray images based on a contrast-preserving mapping model. A naive coloring method directly adds the colors from the visible color image to the near-infrared gray image. However, this method results in an unrealistic image because of the discrepancies in the brightness and image structure between the captured near-infrared gray image and the visible color image. To solve the discrepancy problem, first, we present a new contrast-preserving mapping model to create a new near-infrared gray image with a similar appearance in the luminance plane to the visible color image, while preserving the contrast and details of the captured near-infrared gray image. Then, we develop a method to derive realistic colors that can be added to the newly created near-infrared gray image based on the proposed contrast-preserving mapping model. Experimental results show that the proposed new method not only preserves the local contrast and details of the captured near-infrared gray image, but also transfers the realistic colors from the visible color image to the newly created near-infrared gray image. It is also shown that the proposed near-infrared coloring can be used effectively for noise and haze removal, as well as local contrast enhancement. [ABSTRACT FROM PUBLISHER]

As the instance system of information center networking (ICN), the named data networking (NDN) attracts more and more attention in academia. NDN changes the network service from "destination to destination" to "retrieving data of given names". NDN is more convenient for consumers to share data and it gets a substantial increase in the rate of repeated utilization of data. We focus on the forwarding of NDN routing nodes and propose a forwarding strategy based on historical access records called HRF, which can find out whether there is target data stored by the neighbor nodes in the local network, and then access the target data in the local network efficiently and rapidly. Through a series of typical scenarios, we validate the feasibility and effectiveness of the HRF. [ABSTRACT FROM AUTHOR]

• 3D laser scanning technology is used to reconstruct irregular cutting tool model. • Dimensionless parameters are proposed to quantify irregular cutting tool wear. • 3D quantitative method is developed to rationally evaluate tool wear failure. • Heterogeneous wear and eccentric wear are analyzed by 3D quantitative method. When shield TBM tunneling in abrasive sandy ground, excessive cutting tool wear resulting from untimely and inaccurate failure evaluation is prone to damage cutterhead structure and delay tunneling progress. Hence it is critical important for fast and accurate evaluation of tool wear failure. At present, caliper measurement method is used to qualify cutting tool wear in abrasive ground tunneling. The height reduction of cutter edge is considered as a common parameter to evaluate whether cutting tool is invalid. When it comes to irregular cutting tool, they will be unsuitable due to the complex surface topography. Especially when abrasive sand remains between the cutterhead and excavation face, severe secondary wear will occur on cutter body instead of cutter edge. There is still a lack of comprehensive methods and parameters for evaluating the wear failure of cutting tools. In the present study, the handheld 3D laser scanner has been applied to obtain the point cloud data of irregular cutting tool. The point cloud data has been imported into the Geomagic Control software for model reconstruction. Then, surface overlapped methodology has been utilized for the comparison of cutting tool models before and after wear to obtain the 3D wear nephogram. Cutter volume wear ratio (CVWR) and cutter height wear ratio (CHWR) have been proposed to quantity the wear failure of cutter edge and cutter body. A case study of ripper tooth and replaceable scraper at Sutong GIL Yangtze River Crossing Cable Tunnel has been conducted to set the threshold value of wear failure. The results indicate that the CVWR and CHWR are functional to identify the wear failure of irregular cutting tools. Compared with traditional caliper measurement method, 3D quantitative method allows a more rational and accurate evaluation of heterogeneous cutter edge wear and eccentric cutter body wear. [ABSTRACT FROM AUTHOR]

To investigate the acoustic emission characteristic of rock under different compressive loading rates, a numerical approach using the bonded-particle model (BPM) is adopted in the present study. It reveals that under uniaxial compressive test, the physical mechanism and distribution of AE events recorded by the BPM are generally consistent with the phenomena observed from the laboratory experiments. The total crack number, tensile crack number, shear crack number and AE event number increase as the loading rate increases. The increase of loading rates from 0.005 m/s to 0.6 m/s in the BPM does not have obvious influence on the distribution of AE events. [ABSTRACT FROM AUTHOR]

A comprehensive process of the control and protection against a DC fault in a voltage source converter (VSC) based high-voltage direct current (HVDC) system typically includes fault detection, fault isolation and system recovery. Regarding an offshore wind farm (OWF) integrated modular multilevel converter (MMC) based multi-terminal HVDC (MTDC) system with two control paradigms, i.e. master-slave control and droop control under DC faults, this paper presents the fault isolation, including the isolation of the faulted line section, with detailed control and protection sequence, which would be useful for practical engineering. The control and protection sequence at the system recovery/reconfiguration phase is comprehensively investigated, which includes: (1) when to start the recovery/reconfiguration control; (2) the sequence between deblocking the MMCs and reclosing the AC circuit breakers (AC CBs); and (3) the recovery sequence of each HVDC terminal. Based on the analysis of the system characteristics, a preferred recovery/reconfiguration scheme is proposed. Simulation results on the real-time digital simulator (RTDS) validate the proposed scheme and demonstrate the advantages through comparison with a different recovery sequence. The impact of transient and permanent DC faults on the system recovery/reconfiguration control is discussed. In addition, the recovery/reconfiguration control of the MTDC in radial and meshed topologies is compared and demonstrated. Based on the analytical and simulation studies, a general guideline on the recovery/reconfiguration control of MMC MTDC systems is proposed. [ABSTRACT FROM AUTHOR]

It is well known that traditional line-commutated converter (LCC) based high voltage direct current (HVDC) system is not able to control its reactive power and terminal AC voltages. This paper investigates the reactive power and AC voltage control at the inverter side of the LCC HVDC system with controllable capacitors. The system's ability of operating under negative extinction angle is utilized to achieve a wide range of reactive power control and, in particular, the ability of exporting reactive power. In connection with the inverter AC terminal voltage or reactive power control, among different control possibilities at the rectifier side, active power control is desirable since large variations of active power transfer is very unfavorable. Detailed theoretical analysis is carried out first to show the reactive power controllability, and the capacitor voltage level is selected based on the desired control range. In addition, a new extinction angle measurement approach is proposed for negative extinction angle measurements. The effectiveness of the reactive power/voltage control capability for the proposed system is validated through simulation results using Real-Time Digital Simulator (RTDS). To verify the effectiveness of the reactive power and voltage control, CCC HVDC and LCC HVDC with SVC are also set up in RTDS, and simulation comparisons are made. Furthermore, contribution to AC voltage control in power system using the proposed method is demonstrated through simulation results of the modified two-area four-machine AC power system. [ABSTRACT FROM AUTHOR]

• • The WHU-SAT tester has been developed to study scraper wear mechanism. • • The influence of soil parameters on scraper wear has been evaluated. • • The optimized solutions have been proposed to alleviate scraper wear. When shield TBM tunneling in abrasive sandy ground, scrapers are loaded with heavy forces resulting from the extrusion and friction processes of sand particles. Scraper wear reflected as displacement or desquamation is related to soil parameters. Due to the lack of reliable test methods, experimental studies on the influence of soil parameters on scraper wear are limited. In the present study, existing soil abrasion testers have been reviewed to discuss the advantages and deficiencies. An improved WHU-SAT soil abrasion tester has been developed to study the influence mechanism of soil parameters on scraper wear. Experimental studies have been conducted to evaluate the variation of scraper wear with quartz content, particle size, particle shape and water content. Two soil abrasion tests have been performed for each case. Scraper wear has been considered to be the average value. The results indicate that scraper wear increases with the increase of quartz content and the growth rate increases. It is related to the particle crushing and adhesion effect of limestone sand. As the average particle size increases, the extrusion and friction between the modeled scraper and the sand particles increases first and then decreases. Thus, scraper wear increases first and then decreases with the increase of average particle size. The trend is generally comparable to the corresponding changes in scraper wear with water content. As quartz balls collide with sand particles and destroy the microscopic friction system composed of scrapers and asperities, scraper wear decreases as the increase of roundness and the falling rate decreases. Optimized solutions such as soil abrasivity evaluation, tunnel alignment optimization and soil discharge improvement have been proposed to alleviate the influence of soil parameters on scraper wear. The present study promotes the rational estimation of sand abrasivity and scraper consumption during the feasibility study of abrasive sandy gournd tunneling using shield TBM. [ABSTRACT FROM AUTHOR]

This paper presents a novel hybrid converter configuration for conventional Line-Commutated Converter (LCC) HVDC technology aiming to eliminate commutation failures under serious faults. Dynamic series insertion of capacitors during commutation is utilized to increase the effective commutation voltage. The operating principles are presented followed by detailed mathematical analysis for both zero impedance single-phase and three-phase faults in order to select the required capacitor size and its voltage level. The performance of the proposed method is validated by simulation results in Real Time Digital Simulator (RTDS) and the results show that the proposed converter configuration is able to eliminate commutation failures under both fault cases. Consequently partial power transferring capability during single-phase fault and fast fault recovery from three-phase fault can be achieved. Further simulation results show that the harmonic content of inverter AC voltage and current are not significantly increased and the voltage stress of the thyristor valve is comparable to that of the original benchmark system. [ABSTRACT FROM PUBLISHER]

The modular multilevel converter (MMC) provides promising development for high-voltage direct current (HVDC) applications, including multiterminal HVDC (MTDC) and renewable energy integration. This paper, considering an offshore wind farm (OWF) integrated MMC MTDC system, investigates its start-up process with three main developments: 1) it further develops the mathematical model of MTDC with active networks and proposes a hierarchical start-up control scheme; 2) for the terminal which connects the OWF, it proposes a reduced dc voltage control scheme of mitigating the current surges with deblocking the converter at zero voltage difference on submodules (SMs) and proposes an overall sequential start-up control scheme for the offshore integrated MTDC; and 3) it analyzes and compares different start-up control schemes. To evaluate the proposed sequential start-up control scheme, an offshore MMC HVDC system is established on the RTDS. The simulation results verify effectiveness of the proposed scheme on the MMC MTDC system with two control paradigms, i.e., master–slave control and droop control, respectively. In comparison with different start-up control schemes, the superiority of the mitigation of voltage spikes and current surges are shown using the proposed scheme with less complexity and easier implementation. [ABSTRACT FROM PUBLISHER]