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Clustering is an essential unsupervised technique when category information is not available. Although K-means and Max-min distance K-means clustering algorithms are widely used, they have some disadvantages such as dependence on the initial centers, sensitivity to outliers caused by using only distance as the clustering criterion. To overcome the problems, this paper proposes SMM-K-means algorithm which overcomes the dependence on the initial cluster centers and the initial number of clusters and the sensitivity to the outliers. First, the initial value K of the optimal cluster number is determined by the elbow method, and K-means is used for initial clustering. A new inter-cluster separation measure is then constructed based on the idea of q-nearest neighbors, which is constructed by comprehensive considering the separation between clusters and the distribution compactness of clusters themselves. Finally, the two sample points with highest degree of separation are brought into Max-min distance K-means algorithm as new initial centers for clustering. The definite determining method of cluster centers eliminates the complicated iterative calculation, and the construction of inter-cluster separation measure overcomes the sensitivity of clustering results to noise points and isolated points, and has good applicability and generalization. In addition, this algorithm is not limited by the shape and size of the clusters and has better flexibility. The experimental results show that the SMM-K-means algorithm has higher CH values, resulting in a better clustering effect and stability. [ABSTRACT FROM AUTHOR]

Thermoelectric devices that consist of N-and P-type TE legs in series have been well known and applied owing to the ability that could convert waste heat into electric energy. Among them, skutterudite materials have been frequently studied as the main object because they are environmentally friendly and inexpensive. In this study, N-type CoSb 3 -based materials were synthesized using a low-temperature synthesis method and spark plasma sintering. Those thermoelectric matrix that incorporated Indium (In) particles were prepared via manual grinding method. The thermoelectric properties, microstructures, and morphologies of the pure and In-doped Co 0.91 Ni 0.09 Sb 3 samples were systematically evaluated. A maximum power factor value of 3642.3 μW/mK2 was obtained at 723 K for a Co 0.91 Ni 0.09 Sb 3 /1 wt%In sample and the highest figure of merit value of 1.01 was attained for a Co 0.91 Ni 0.09 Sb 3 /2 wt%In sample. These results indicate that Indium particles as secondary phase can improve the thermoelectric performance of N-type CoSb 3 -based materials. [ABSTRACT FROM AUTHOR]

High-performance one-dimensional (1D) CdSxSe1−x nanostructures arrayed photodetectors exhibit broad spectrum (450–750 nm) selective detection from the near-ultraviolet to the near-infrared regime, which has a great deal of interest in broad spectral flexible optoelectronic devices. Here, we report the microstamp transfer technology to construct high-performance rigid (SiO2/Si) and flexible (polyethylene terephthalate) photodetectors with broad spectrum selective detection, which was based on arrayed 1D CdSxSe1−x nanostructures obtained via chemical vapor deposition in a dual-temperature zone tube furnace. Photoresponse measurements have demonstrated their superior spectral photoresponsivity (∼105 AW−1), extremely high on/off switching ratio (105), rapid response/recovery time between 10% and 90% of the maximum photocurrent (0.089/0.044, 0.044/0.044, 0.133/0.131, and 0.178/0.180 s), and excellent long-term environmental photostability. Furthermore, the as-prepared flexible arrayed photodetector displayed excellent folding endurance properties (after 2000 times, the photocurrent decreases less than 50%) and stable electrical properties (bending angle from 0° to 150°). The improvement nanoarray technology in this research can be exploited to lead to the design of high-performance flexible photodevices comprising other 1D or 2D alloy nanomaterials. [ABSTRACT FROM AUTHOR]

In this paper, we first proposed a statistical test for the detrended multiple moving average cross-correlation coefficient DMMC (s). The DMMC (s) mainly was used to analyze the correlation between the dependent variable y and other n independent variables x i . We proved that DMMC (s) approximately obeys the chi-square distribution. We studied the statistical properties of the DMMC (s) between normally distributed random sequences and power-law ARFIMA long memory random sequences. Furthermore, we discussed the influence of the cross-correlation among the target variable and independent variables on DMMC (s). Finally, we further study the application of DMMC (s) to China's stock markets and China carbon emission trading markets to investigate multiple cross-correlation. The empirical results show that there is a strong multiple correlation between China's Shanghai, Shenzhen and Hong Kong stock markets, while the correlation between China's carbon markets is not significant. This paper provides new ideas and theoretical support for exploring the correlation between multiple variables, which has implications for investors and policymakers. [ABSTRACT FROM AUTHOR]

Abuse of antibiotics in animal husbandry and medicine has led to severe environmental problems especially the risk of bacterial resistance. Different from common organic pollutants, antibiotics in wastewater could not be easily removed by biological treatment because of their poor biodegradability. Electrocatalysis including electrocatalytic oxidation and reduction has gained great attention for the removal of antibiotic contaminants in wastewater due to its advantages of high efficiency, simple operation, and thorough degradation. This review summarizes the common features and synthesis methods as well as research progress of electrode materials used in the electrocatalytic process for the treatment of antibiotics in the last five years. The removal mechanism and transformation pathways of antibiotics in the electrocatalytic oxidation and reduction processes are presented, especially to avoid the second pollution. Cost aspects in the electrocatalytic process are also discussed by considering practical applications and comparison with adsorption and photocatalysis process. Finally, several developing directions of electrocatalysis in the antibiotic wastewater treatment are proposed as a guidance for further research. [ABSTRACT FROM AUTHOR]

In the face of the batch, dynamic access data, or the flow of data that continuous changes over time, the traditional support vector machine algorithm cannot dynamically adjust the previous classification model. To overcome this shortcoming, the incremental support vector machine (ISVM) algorithm is proposed. However, many incremental support vector algorithms still have shortcomings such as low efficiency, memory limitation, and poor generalization. This paper puts forward the new ISVM algorithm, HDFC-ISVM ∗ algorithm, based on the high-dimensional distance and forgetting characteristics. This paper firstly proposes the original HDFC-ISVM algorithm that first learns the distribution characteristics of the samples according to the distance between the samples and the normative hyperplane. Then, it introduces the forgetting factor. In the incremental learning process, the classifier gradually accumulates the spatial distribution knowledge of samples, eliminates the samples that have no contributions to the classifier, and selectively forgets some useless samples according to the forgetting factor, which overcomes the shortcomings such as low efficiency and poor accuracy of some algorithms. But, the original HDFC-ISVM algorithm is sensitive to parameters, and different settings of the parameters have a great impact on the final classification accuracy of the algorithm. Therefore, on the basis of the original algorithm, an improved algorithm HDFC-ISVM ∗ based on the adjustments to the initialization strategy and updating rules of the forgetting factor is proposed. The initialization strategy and updating rules of the forgetting factor are adjusted to adapt datasets with different distributions in this improved algorithm. The rationality of the improved strategy about the forgetting factor is discussed theoretically. At the same time, the proposed algorithm has better classification accuracy, classification efficiency, and better generalization ability than other algorithms, which is verified by experiments. [ABSTRACT FROM AUTHOR]

Ladder resonant switched-capacitor converters (RSCCs) provide high step-up voltage gain, but the continuous regulation range is typically limited with an extremely wide switching frequency band. This article introduces a new full-range regulation method for step-up ladder RSCCs along with seven switching techniques. Each switching technique offers multiple possibilities for implementation. Furthermore, ladder RSCCs with the proposed switching techniques feature the merits of simple control, soft switching, and high efficiency. A comprehensive analysis of operation principle, voltage gain curves, device stress, active switch utilization, zero voltage switching range, output voltage ripple, and input current ripple is given for the proposed seven switching techniques. A 3X step-up Ladder RSCC prototype was built and tested to validate the theoretical results. [ABSTRACT FROM AUTHOR]

Adsorption desalination and cooling is a promising technology that has recently been investigated. In this study, a silica gel powder composite (SGPC) with nano-copper (NC) and polyvinyl pyrrolidone (PVP) was synthesized by mechanical grinding and melt blending for the first time. It can improve the thermal conductivity of silica gel powder (SGP) and the operation efficiency of the adsorption desalination and cooling system (ADCS). By measuring the curve of temperature variation to compare the four thermal conductivity enhancers (TCE), graphite powder (GP), carbon nanotubes (CNT), nano-alumina (NA) and NC, it was found that NC had the best thermal conductivity enhancement. The microstructure, adsorption and thermal properties of the SGPC samples were systematically characterized by scanning electron microscopy (SEM), thermogravimetric analyzer (TGA) and thermal constant analyzer. The results showed that the adsorption capacity of SGPC with NC content of 0–1.6 wt% was in the range of 0.29–0.33 g −1. The thermal conductivity of SGPC with NC content of 0.8wt%, 1.2 wt%, and 1.6 wt% was found to be improved by 114%, 156% and 185% compared to the parent SGP, and the thermal conductivity was effectively enhanced. Thus, the developed adsorbent has eximious water adsorbability and thermal conductivity and has good adsorption/desorption cycle stability, which is attractive for ADCS. [ABSTRACT FROM AUTHOR]

Evaluating the accuracy of the satellite and reanalysis precipitation products is very important for understanding their uncertainties and potential applications. However, because of underestimation existing in commonly used evaluation benchmark, gauge precipitation data, it is necessary to investigate the influence of systematic errors in gauge data on the performance evaluation of satellite and reanalysis precipitation datasets. Daily satellite-based IMERG and model-based ERA5-Land, together with gauge precipitation data, were collected with the period from 2005 to 2016 over China in this study. Daily corrections for precipitation biases from wind-induced undercatch, wetting loss, and trace error were made for gauge measurements. A set of metrics, including relative bias, Kling-Gupta efficiency, frequency bias, and critical success index, were used to evaluate and intercompare the performances of IMERG and ERA5-Land against original and bias-corrected gauge data in different locations, years, seasons, climatic zones, classes of precipitation events, and precipitation phases. The results have shown that: After removing the bias in gauge data, the relative biases of IMERG and ERA5-Land both significantly decline. The noticeable changes of their accuracy occur and vary with different locations, years, seasons, climatic zones, and precipitation phases. Furthermore, the frequency biases of IMERG and ERA5-Land rise in no precipitation events and decline in light, moderate, heavy, and extreme precipitation events. The detection capability of IMERG and ERA5-Land in no and light precipitation events is also obviously affected. Therefore, this study has demonstrated the significant influence of systematic gauge precipitation errors on the assessment of IMERG and ERA5-Land and reinforces the necessity to remove negative bias in gauge data before using it as the benchmark. [ABSTRACT FROM AUTHOR]

Multilevel resonant switched-capacitor converters (RSCCs) have drawn attention in large step-down voltage conversion but are hindered in a wide area of applications due to limited voltage regulation range. A new full-range regulation (FR) method for multilevel step-down RSCCs is proposed in this article. As an example of the proposed FR method, the fixed on-time modulation for modified Dickson RSCC is provided. In addition to full-range voltage regulation, the multilevel RSCCs with the proposed FR method feature complimentary driving signals, zero voltage switching turn-on for switches, zero current switching turn-off for diodes, even switch voltage stress, even diode voltage stress, high active switch utilization, high efficiency, and high power density. A modified Dickson RSCC prototype was built to validate the proposed FR method. The proposed FR method is further extended to series-parallel RSCCs and Fibonacci RSCCs. [ABSTRACT FROM AUTHOR]

Herein, the magnetic field facilitated electrocatalytic degradation of tetracycline is reported for the first time. A magnetic porous carbonized phthalonitrile resin electrocatalyst has been prepared through directly annealing phthalonitrile monomer, polyaniline coated barium ferrite and potassium hydroxide. The tetracycline degradation percentage (DP%) by such electrocatalyst is significantly increased up to 37.42% under magnetic field with the optimal pH value of 5.0 and bias voltage of 1.0 V (vs. SCE). The mechanism of this phenomenon is explained by the spin-selective electron removal process in the reaction between metal-oxygen species and tetracycline on the electrocatalyst. The comparison of degradation pathways for tetracycline with and without magnetic field confirms the improvement of tetracycline DP%. This work opens a new direction for the application of an external magnetic field in the electrocatalytic degradation of antibiotics in wastewater. [Display omitted] • A novel magnetic porous carbonized phthalonitrile resin was successfully prepared. • Magnetic field enhanced electrocatalytic degradation of tetracycline was observed. • Spin-selective electron removal process was proposed in tetracycline degradation. • Degradation pathways with/without magnetic field affirmed the boost of degradation. [ABSTRACT FROM AUTHOR]

The polymer nanocomposites with 3-dimensional (3D) nanofillers can form a 3D network and attain a uniform distribution of nanofillers, which benefits the transfer of charge carriers and phonons as well as the dispersion of stress at a very low loading of nanofillers. These polymer nanocomposites with high mechanical properties would have great potential for thermal and electrical conduction as well as electromagnetic interference (EMI) shielding. In this paper, the 3D epoxy nanocomposites are manufactured by stuffing epoxy resin into 3D p -phenylenediamine-aniline copolymer nanofibers@Cu foam (P-PANI@f-Cu) hybrid nanofillers that are constructed by electrophoretic deposition of phosphoric acid doped P-PANI copolymer nanofibers onto the surface of sodium hydroxide oxidized Cu foam. Benefiting from 3D continuous network of P-PANI@f-Cu hybrid nanofillers, the electrical conductivity and thermal conductivity of 3D P-PANI@f-Cu/epoxy nanocomposites with the P-PANI loading of 0.262 wt% could achieve 7.71 ± 0.04 S cm−1 and 5.4670 ± 0.0085 W m−1K−1, respectively, which are much better than that of pure epoxy (insulator and 0.2310 ± 0.0017 W m−1K−1, respectively) and epoxy composites filled with only Cu foam (4.46 ± 0.03 S cm−1 and 2.7907 ± 0.0057 W m−1K−1, respectively). Meanwhile, with a thickness of 1.8 mm, the average total EMI shielding effectiveness (SE T) of 3D P-PANI@f-Cu/epoxy nanocomposites in the X-band range reaches a high value of 66.14 dB, which is capable of effectively shielding the electromagnetic signal between Bluetooth earphone and smartphone in the practical application. Furthermore, the 3D P-PANI@f-Cu hybrid nanofillers can efficiently prevent the crack growth in the epoxy nanocomposites and improve their mechanical properties including hardness and elastic modulus. The 3D p -phenylenediamine-aniline copolymer nanofibers @Cu foam/epoxy nanocomposites possess the outstanding thermal conductivity, electrical conductivity, mechanical properties and electromagnetic shielding properties arising from the continuous porous network of 3D hybrid nanofillers and the synergistic interaction among 3D Cu skeleton, P-PANI nanofibers, and epoxy matrix, which can effectively shield the signal between Bluetooth earphone and smartphone in practical application. [Display omitted] • 3D p -phenylenediamine/aniline@Cu foam/epoxy nanocomposites are fabricated. • 3D P-PANI@f-Cu/epoxy nanocomposites exhibit outstanding EMI shielding performance. • P-PANI@f-Cu/epoxy could shield EM signal between Bluetooth earphone and smartphone. • 3D P-PANI@f-Cu/epoxy has excellent thermal conductivity and mechanical properties. [ABSTRACT FROM AUTHOR]

Based on the traditional detrended moving average cross-correlation analysis (DMCA) method and the detrended multiple cross-correlation analysis (DMC) method, we propose the detrended multiple moving average cross-correlation analysis method (DMMC) to quantify the correlation between non-stationary signals on different time scales. It will be the generalization of the correlation between pairwise time series and can be used to measure the multivariate correlation between the dependent variable y with the others i independent variable x. To validate the DMMC method, we determined the DMMC coefficient into numerical simulations on the standard Gaussian distribution, Lognormal distribution t distribution and ARFIMA long memory random sequences. Then we apply the proposed method to explore the multiple correlations between China's Shanghai, Shenzhen, and Hong Kong stock markets and analyze the dynamic time-varying characteristics of the correlation with the sliding window approach. The results show that DMMC is suitable to measure multiple cross-correlations. This new method can be further applied to multiple cross-correlation in different areas of knowledge, such as energy, meteorology, medicine, transportation, etc. • We proposed a new detrended multiple moving average cross-correlation coefficient. • We performed numerical simulations under different distributions. • The results are presented in a new map of colors. [ABSTRACT FROM AUTHOR]

Cu films were deposited on the silicon substrate at ground potential by bipolar pulse and conventional HiPIMS configurations in combination with different bias voltages. The fraction and energy of ion bombardment were tailored using different control strategies. The increasing deposition rate mechanism for bipolar pulse HiPIMS was discussed based on a phenomenological equilibrium analytical model. The morphology, structure, stress, electrical and mechanical properties of Cu films were investigated. Our results show that the positive pulse has a minor influence on the ionization rate of target materials in plasma, but it can effectively resist the ions back and drive them to arrive at the substrate during the deposition process. The deposition rate improves by ~ 55% for KP100 and KV100 samples than CHiPIMS. The positive reversed pulse in the whole pulse-off time benefits a compact microstructure, smooth surface morphology and minor residual tensile stress for Cu films due to the high energy of accelerating ions. Cu films prepared by BPH method exhibit good adhesion strength, electrical and tribological properties. When the kick voltage increases to 50 V with a constant kick pulse length, the critical load for the copper film reaches 10 N, and the COF is also the lowest. The high bias voltage causes a rising coefficient of friction, likely due to cavities on the film's surface. [ABSTRACT FROM AUTHOR]

SUMMARY: Rice (Oryza sativa L.) is a short‐day plant whose heading date is largely determined by photoperiod sensitivity (PS). Many parental lines used in hybrid rice breeding have weak PS, but their F1 progenies have strong PS and exhibit an undesirable transgressive late‐maturing phenotype. However, the genetic basis for this phenomenon is unclear. Therefore, effective methods are needed for selecting parents to create F1 hybrid varieties with the desired PS. In this study, we used bulked segregant analysis with F1 Ningyou 1179 (strong PS) and its F2 population, and through analyzing both parental haplotypes and PS data for 918 hybrid rice varieties, to identify the genetic basis of transgressive late maturation which is dependent on dominance complementation effects of Hd1, Ghd7, DTH8, and PRR37 from both parents rather than from a single parental genotype. We designed a molecular marker‐assisted selection system to identify the genotypes of Hd1, Ghd7, DTH8, and PRR37 in parental lines to predict PS in F1 plants prior to crossing. Furthermore, we used CRISPR/Cas9 technique to knock out Hd1 in Ning A (sterile line) and Ning B (maintainer line) and obtained an hd1‐NY material with weak PS while retaining the elite agronomic traits of NY. Our findings clarified the genetic basis of transgressive late maturation in hybrid rice and developed effective methods for parental selection and gene editing to facilitate the breeding of hybrid varieties with the desired PS for improving their adaptability. Significance Statement: We identified the genetic basis of transgressive late maturation in hybrid rice, which is dependent on dominance complementation effects of Hd1, Ghd7, DTH8, and PRR37 from both parents and developed effective methods for parental selection and gene editing to facilitate the breeding of hybrid varieties with the desired photoperiod sensitivity. Our study lays an important foundation for improving the breeding efficiency and latitude adaptability of hybrid rice. [ABSTRACT FROM AUTHOR]

Metal oxides were emerging as persulfate (PS) catalysts in advanced oxidation processes, facilitating the degradation of recalcitrant pollutants. A novel iron/manganese (Fe/Mn) binary oxide catalyst was synthesized using a straightforward ultrasound-hydrothermal method in this study. The successful preparation of the material was also verified by XRD, HRTEM, EF-TEM, STXM, FTIR and the adsorption properties of the material were characterized. The removal of tetrabromobisphenol A (TBBPA) by Fe/Mn binary oxide and PS system was systematically investigated by changing the reaction parameters including Fe/Mn ratio in the catalyst, PS dosages and solution pH. The results indicated that the degradation percentage of TBBPA increased with higher PS dosage and reached its maximum at a solution pH of 8.0 with Fe/Mn-1.0. The highest removal ratio of TBBPA could be reached up to 90.50%. Finally, the intermediate products were identified and the degradation pathways were proposed. Remarkably, a low metal leaching ratio at different solution pH values was revealed by the Fe/Mn binary oxide, demonstrating high stability. This study paves the way for a novel approach to the heterogeneous activation of persulfate using a low-cost, environmentally friendly, and high-performance catalyst for the degradation of persistent pollutants. [Display omitted] • Fe/Mn binary oxide is prepared for activating persulfate to degrade TBBPA. • Sulfate and hydroxyl radicals are reactive species for degradation mechanism. • Degradation pathways are speculated with several typical intermediates identified. • Fe/Mn binary oxide exhibits high catalytic efficiency and long-term stability. [ABSTRACT FROM AUTHOR]

Herein, we report the first example of controllable magnetoresistance in a semiconducting carbonized phthalonitrile resin. This special phenomenon is explained using the different ratios of graphite-like (sp2) and diamond-like (sp3) bonds and localization length (a0) as well as the density of states at the Fermi-level (N(EF)). [ABSTRACT FROM AUTHOR]

Key message: We clarify the influence of the genotypes of the heading date genes Hd1, Ghd7, DTH8, and PRR37 and their combinations on yield-related traits and the functional differences between different haplotypes. Heading date is a key agronomic trait in rice (Oryza sativa L.) that determines yield and adaptability to different latitudes. Heading date 1 (Hd1), Grain number, plant height, and heading date 7 (Ghd7), Days to heading on chromosome 8 (DTH8), and PSEUDO-RESPONSE REGULATOR 37 (PRR37) are core rice genes controlling photoperiod sensitivity, and these genes have many haplotypes in rice cultivars. However, the effects of different haplotypes at these genes on yield-related traits in diverse rice materials remain poorly characterized. In this study, we knocked out Hd1, Ghd7, DTH8, or PRR37, alone or together, in indica and japonica varieties and systematically investigated the agronomic traits of each knockout line. Ghd7 and PRR37 increased the number of spikelets and improved yield, and this effect was enhanced with the Ghd7 DTH8 or Ghd7 PRR37 combination, but Hd1 negatively affected yield. We also identified a new weak functional Ghd7 allele containing a mutation that interferes with splicing. Furthermore, we determined that the promotion or inhibition of heading date by different PRR37 haplotypes is related to PRR37 expression levels, day length, and the genetic background. For rice breeding, a combination of functional alleles of Ghd7 and DTH8 or Ghd7 and PRR37 in the hd1 background can be used to increase yield. Our study clarifies the effects of heading date genes on yield-related traits and the functional differences among their different haplotypes, providing valuable information to identify and exploit elite haplotypes for heading date genes to breed high-yielding rice varieties. [ABSTRACT FROM AUTHOR]

Magnetron sputtered TiNi thin films usually exhibit an amorphous structure and need a high substrate temperature (>450 °C) or a post-annealing treatment (>500 °C) to promote crystallization. However, these treatments could extremely limit the use of low melting point substrate materials. In this study, TiNi thin films were prepared by HiPIMS using different deposition parameters. The structure and phase transformation of TiNi films were investigated. Based on SEM, XRD, TEM, DSC and electrical resistivity analysis, results show that it is possible to deposit dense crystalline TiNi thin films at a low substrate temperature (230 °C). The crystallization mechanism was also discussed. Ions energy and substrate temperatures significantly affected the formation of crystalline structures. • Crystalline TiNi thin films were prepared by HiPIMS at a low substrate temperature (230 °C). • Microstructure and crystalline mechanism of TiNi thin films were investigated. • The substrate temperature and bias voltage play important roles on the formation of crystalline TiNi films. [ABSTRACT FROM AUTHOR]

Phase change energy storage is a new type of energy storage technology that can improve energy utilization and achieve high efficiency and energy savings. Phase change hysteresis affects the utilization effect of phase change energy storage, and the influencing factors are unknown. In this paper, a low-temperature eutectic phase change material, CaCl2·6H2O-MgCl2·6H2O, was selected as the research object, combined with the mechanism of phase change hysteresis characteristics, using a temperature acquisition instrument to draw the step cooling curve. A differential scanning calorimeter was used to measure the DSC (differential scanning calorimetry) curve, and the hysteresis characteristics of phase transformation were studied by factors, such as heat storage temperature, cooling temperature, and cooling rate. The experimental results show that when heating temperature increases by 30 °C, phase transition hysteresis decreases by about 3 °C. The cooling temperature decreased by 10 °C, and the phase transition hysteresis increased by 2.69 °C. This paper provides a new idea for optimizing the properties of phase change energy storage materials and provides a possibility for realizing the parametric control of phase change hysteresis factors. [ABSTRACT FROM AUTHOR]

• The plate responses to complicated elastic-plastic impacts are characterized. • The existing impact characterization diagram is examined for three contact types. • The extended impact characterization diagram is proposed. • The proposed diagram is robust in identifying the plate impact responses. • The proposed diagram is efficient in fast predicting the maximum impact force. This paper presents a study on the characterization of low-velocity and low-energy impact responses of elastic-plastic plate struck by elastic-plastic spherical impactor. The applicability of the existing impact characterization diagram is examined firstly by intensive finite element (FE) simulations for a wide range of complicated impact situations including all three types of contact: indentation, flattening and combined flattening and indentation. The limitations of the existing diagram are found in identifying the type of impact response and predicting the maximum impact force for complicated impact situations. The effects of elastic and plastic deformations of impactor on the identification and prediction by the existing diagram are analyzed. A new linear contact law is presented according to the piecewise linear characteristics of contact stiffness observed from the intensive FE results. An extended impact characterization diagram is then proposed to characterize low-velocity and low-energy impact responses of plate under complicated impact situations with arbitrary three contact types. The extended diagram is validated by the intensive FE simulations and experimental results. It is concluded that the extended impact characterization diagram can identify correctly the plate response type to complicated impacts and predict accurately the maximum impact force in a fast and simple way without the aid of FE models and experimental tests. [ABSTRACT FROM AUTHOR]

We propose a strategy to improve the TE performance of Bi 0.4 Sb 1.6 Te 3 (BST) using cold pressing and thermal annealing. This process has the advantages of low-cost, time saving, and suitable for large-scale preparation. The BST alloy exhibits exceptional TE performance, achieving a maximum ZT of ∼1.27 at 333 K. Furthermore, the fabricated TE module demonstrates a high output power density of 12.62 mW/cm2 with a temperature difference of 30 K, enabling direct utilization of human skin heat for powering electronic devices. [Display omitted] • Bi 0.4 Sb 1.6 Te 3 allay is prepared by a low-cost cold pressing and annealing method. • A optimal ZT value of ∼1.27 at 60 °C is achieved. • An ultra-high output power density of 12.62 mW/cm2 with a temperature difference of 30 K. • TEG can directly harvest heat from human skin to power electronic devices. • The TE module active cooling of human skin and achieve a cooling effect of ∼8.0 °C. Manufacturing low-cost, high-performance thermoelectric (TE) modules is essential for power generation and cooling. However, traditional fabrication methods (zone melting and hot pressing) are time-consuming and expensive, and the fabricated Bi 2 Te 3 -based materials have unsatisfied performance. Herein, Bi 0.4 Sb 1.6 Te 3 alloys with high TE properties were prepared using cold pressing and thermal annealing processes. This preparation process is simple, time saving, and suitable for large-scale promotion. The annealing process induces the formation of pores within the grain interface, which effectively scatters low-energy charge carriers and enhance the phonon scattering. Although the electrical properties is reduced, the improved Seebeck coefficient compensates for the deteriorated electrical properties. Meanwhile, the thermal conductivity is significantly reduced. Eventually, a peak ZT of ∼1.27 is achieved at 333 K. The TE modules assembled with our Bi 0.4 Sb 1.6 Te 3 alloy exhibit high output and cooling performance, with an output power density of 12.62 mW/cm2 with a temperature difference of 30 K. Furthermore, the TE module can be used for the active cooling of human skin and achieve a cooling effect of ∼8.0 °C. These results indicate that our samples are suitable for the preparation of commercially applicable TE modules and as power sources for next-generation wearable electronic devices. [ABSTRACT FROM AUTHOR]

With the reduction and depletion of shallow energy, the mining depth of coal around the world is increasing year by year, and the mining depth of some coal mines in China has reached kilometers. The main roadway near the goaf with the deep high static stress is very easy to be damaged after being disturbed by the mine earthquake. Taking the main roadway in the no. 1 mining area of Gaojiapu coal mine in Binchang mining area, Shaanxi Province, China, as the engineering background, the high-energy mine earthquake monitored by the on-site microseism is equivalently simulated through the dynamic module of FLAC3D, and the spatial-temporal rotation characteristics of the principal stress of roadway surrounding rock under the disturbance of mine earthquake are studied and analyzed and put forward corresponding prevention and control measures. Research shows early stage of mine earthquake disturbance, roadway roof is first affected, and the principal stress of the roof has the trend of deflection to the side of the goaf. In the middle stage of mine earthquake disturbance, the main body of roof principal stress deflects to the side of goaf, and the deflection range is large. In the later stage of mine earthquake disturbance, the principal stress directions in the surrounding rock reverse rotation, and the reverse rotation angle of the principal stress direction in the roof is the largest. Finally, the asymmetric distribution characteristics of principal stress rotation are verified by using the asymmetric deformation phenomenon on both sides of roadway surrounding rock. Based on the rotation characteristics of principal stress under the dual influence of mine earthquake disturbance and goaf, optimize the layout scheme and blasting parameters of blasting pressure relief holes. The transmission direction of principal stress can be changed by blasting pressure relief method; meanwhile, the transmission of principal stress can be blocked; through the comparison of microseismic activity law before and after pressure relief, pressure relief effect is good. The research results can provide a certain reference basis for coal mine roadway pressure relief and reducing disaster conditions. [ABSTRACT FROM AUTHOR]

With the reduction and depletion of shallow energy, the mining depth of coal around the world is increasing year by year, and the mining depth of some coal mines in China has reached kilometers. The main roadway near the goaf with the deep high static stress is very easy to be damaged after being disturbed by the mine earthquake. Taking the main roadway in the no. 1 mining area of Gaojiapu coal mine in Binchang mining area, Shaanxi Province, China, as the engineering background, the high-energy mine earthquake monitored by the on-site microseism is equivalently simulated through the dynamic module of FLAC3D, and the spatial-temporal rotation characteristics of the principal stress of roadway surrounding rock under the disturbance of mine earthquake are studied and analyzed and put forward corresponding prevention and control measures. Research shows early stage of mine earthquake disturbance, roadway roof is first affected, and the principal stress of the roof has the trend of deflection to the side of the goaf. In the middle stage of mine earthquake disturbance, the main body of roof principal stress deflects to the side of goaf, and the deflection range is large. In the later stage of mine earthquake disturbance, the principal stress directions in the surrounding rock reverse rotation, and the reverse rotation angle of the principal stress direction in the roof is the largest. Finally, the asymmetric distribution characteristics of principal stress rotation are verified by using the asymmetric deformation phenomenon on both sides of roadway surrounding rock. Based on the rotation characteristics of principal stress under the dual influence of mine earthquake disturbance and goaf, optimize the layout scheme and blasting parameters of blasting pressure relief holes. The transmission direction of principal stress can be changed by blasting pressure relief method; meanwhile, the transmission of principal stress can be blocked; through the comparison of microseismic activity law before and after pressure relief, pressure relief effect is good. The research results can provide a certain reference basis for coal mine roadway pressure relief and reducing disaster conditions. [ABSTRACT FROM AUTHOR]

With the reduction and depletion of shallow energy, the mining depth of coal around the world is increasing year by year, and the mining depth of some coal mines in China has reached kilometers. The main roadway near the goaf with the deep high static stress is very easy to be damaged after being disturbed by the mine earthquake. Taking the main roadway in the no. 1 mining area of Gaojiapu coal mine in Binchang mining area, Shaanxi Province, China, as the engineering background, the high-energy mine earthquake monitored by the on-site microseism is equivalently simulated through the dynamic module of FLAC3D, and the spatial-temporal rotation characteristics of the principal stress of roadway surrounding rock under the disturbance of mine earthquake are studied and analyzed and put forward corresponding prevention and control measures. Research shows early stage of mine earthquake disturbance, roadway roof is first affected, and the principal stress of the roof has the trend of deflection to the side of the goaf. In the middle stage of mine earthquake disturbance, the main body of roof principal stress deflects to the side of goaf, and the deflection range is large. In the later stage of mine earthquake disturbance, the principal stress directions in the surrounding rock reverse rotation, and the reverse rotation angle of the principal stress direction in the roof is the largest. Finally, the asymmetric distribution characteristics of principal stress rotation are verified by using the asymmetric deformation phenomenon on both sides of roadway surrounding rock. Based on the rotation characteristics of principal stress under the dual influence of mine earthquake disturbance and goaf, optimize the layout scheme and blasting parameters of blasting pressure relief holes. The transmission direction of principal stress can be changed by blasting pressure relief method; meanwhile, the transmission of principal stress can be blocked; through the comparison of microseismic activity law before and after pressure relief, pressure relief effect is good. The research results can provide a certain reference basis for coal mine roadway pressure relief and reducing disaster conditions. [ABSTRACT FROM AUTHOR]

• Numerical analysis of plastic yield behavior in early impact stage based on mesh-refined FE models. • Newly observed characteristics of dynamic stress responses in early impact stage. • Newly observed evolution modes of initial plastic zone and analysis of plastic yield mechanism. • Single-valued dependence of critical impact parameters on normalized impact velocity. • Newly proposed velocity criterion for quasi-static impact by considering the limitation of plastic yield. This paper investigates the plastic yield behavior during the supersonic, transonic and subsonic stages of impact. The frictionless impacts of a rigid sphere on an elastic-perfectly plastic half-space are simulated by the mesh-refined finite element (FE) models without the assumption of the rigid sphere moving at constant velocity. The dynamical characters of stress field and evolutions of the initial plastic zone are analyzed based on the simulations of a wide range of materials and impact velocities. The plastic yielding is found to occur at all the stages of impact. The present investigation shows that impact-induced waves and fast expansion of contact region have great influence on the high stress regions and the evolution modes of the initial plastic zone. A determination method for the stable yield inception is proposed to avoid the disturbances of the observed local unloading at the beginning of the main plastic zone. The critical parameters at the yield inception are extracted and their dependences upon the normalized impact velocity are analyzed. By considering the limitation of the plastic yield, a new velocity criterion is proposed to solve the critical impact parameters by the quasi-static impact theory. The present investigation shows that the impact with relative high impact velocity makes the plastic yielding shallower and reduces greatly the impact force and dynamic indentation required for yielding. [Display omitted] [ABSTRACT FROM AUTHOR]

• An experimental analysis is presented for the dynamic behavior of elastic visco-plastic beam under repeated impacts at different impact positions. • The effects of repeated impacts and impact positions on the sub-impact behaviors and wave propagations, high-frequency vibrations and long-term beam responses are analyzed. • Two influence modes of repeated impacts with the deterministic and random features are observed. • The couplings of sub-impacts, wave propagation and high-frequency vibrations make the repeated-impact behavior much more complicated. Repeated impact behaviors of an elastic visco-plastic steel beam struck by a hard sphere are experimentally examined in this paper. The interaction between impact bodies, behaviors of sub-impacts, wave propagations and dynamics of the beam are tested to get a better understanding into the mechanism of repeated impacts. At the four different impact locations on the beam, thirty repeated-mass-impact tests are conducted for each impact location under identical initial conditions except for the accumulated deformations. The effects of repeated impacts and impact location on the sub-impact behaviors, local contact deformations, wave propagations, high-frequency vibrations and long-term beam responses are analyzed. The sub-impact phenomenon is observed. The deterministic and random features of the influences of repeated impacts on the behaviors of sub-impacts are observed. The deterministic feature similar to the elastic shakedown phenomenon is found to occur for the first sub-impact behaviors, such as the kinetic coefficient of restitution, residual deformations and early wave propagations. The random feature is found to occur for the second sub-impact behaviors as well as the vibrational modes and long-term stress and displacement responses. The couplings of sub-impacts, wave propagation and high-frequency vibrations make the repeated impact behaviors of flexible structure much more complicated than single impact. [ABSTRACT FROM AUTHOR]

[Display omitted] • The magnetic amorphous carbon@manganese ferrite (C@MnFe 2 O 4) hybrid materials were fabricated. • C@MnFe 2 O 4 is an effective persulfate (PS) activator with high stability. • The total organic carbon mineralization in C@MnFe 2 O 4 activated PS system reached 50.1% • Possible degradation pathways of TBBPA in the C@MnFe 2 O 4 activated PS system were proposed. Tetrabromobisphenol A (TBBPA), a typical brominated flame retardant in industry, has been recognized as a toxic chemical and an endocrine disruptor. Hence, it's urgently required to remove it from aquatic environment. In this work, the magnetic amorphous carbon@manganese ferrite (C@MnFe 2 O 4) hybrid materials have been fabricated by hydrothermal method with high temperature annealing method to serve as catalyst for the activation of persulfate (PS) to degrade the TBBPA. The structure characterization results manifest that the synthesized MnFe 2 O 4 particles are evenly distributed on the surface of amorphous carbon in the C@MnFe 2 O 4 hybrid. The factors to affect the catalytic degradation of TBBPA by C@MnFe 2 O 4 hybrid/PS system including type of C@MnFe 2 O 4 hybrid materials, PS dosage, concentration of C@MnFe 2 O 4 and reaction time are investigated systematically. The results show that the highest removal ratio of TBBPA could reach 91.9% after treatment of 90 min by C@MnFe 2 O 4 hybrid/PS system. Furthermore, the C@MnFe 2 O 4 hybrid demonstrates a high stability and recyclability. The electron paramagnetic resonance (EPR) verifies that the introduction of C@MnFe 2 O 4 hybrid into PS system could facilitate the generation of ⋅OH and SO 4 ⋅- radicals for degradation of TBBPA. The degradation intermediates are detected and two possible degradation pathways are proposed. This work provides a new insight for the design and development of novel catalyst for the activation of PS to degrade organic pollutants. [ABSTRACT FROM AUTHOR]

With the rapid increase of the thermal power of electronic devices, phase change material(PCM) have shown great application prospects in the field of electronic thermal management. However, due to the irregular surface of the electronic device, PCM can only act on the back of the component or the outside of the package, which leads to the occurrence of heat transfer hysteresis. In order to reduce the heat transfer distance between the heat source and PCM, a new type of ER/SAT/DSP composite functional material with thermal control function was prepared in this paper to solve the key technical problem of fluid seamless packaging thermal control. The composite material is encapsulated in a fluid state and will no longer melt after solidification. Through thermophysical experiments and morphological characterization, the results show that when the mass fraction of PCM is 35%, the composite material has the best physical properties and application performance. And after 200 thermal cycles, the leakage rate is only 3.7%. Through the PTC thermal control experiment, the results show that the maximum temperature at different positions of the device for pouring the new composite was reduced by 7.4 °C and 8.1 °C, respectively, and the operation time corresponding to different temperatures was increased by 5.76 times, 5.80 times and 6.98 times, respectively. Therefore, the composite material shows a good thermal control ability for electronic components of any surface shape. [ABSTRACT FROM AUTHOR]

[Display omitted] • The hysteresis is due to the difference of primary nucleation mechanism during heating and cooling. • The PCH is related to the properties of the material itself and the experimental measurement conditions. • The hysteresis temperature is positively correlated with the heating/cooling rate. • The hysteresis effect is more obvious in an incomplete phase transition. • Numerical models of the hysteresis effect of complete and incomplete phase transition are summarized. As an efficient energy storage material, phase change material can be combined with lightweight buildings to reduce the energy consumption of the building envelopes effectively, while it is often accompanied by phase change hysteresis(PCH) and supercoiling (SC) phenomena during the phase transition. SC means that the nucleation does not solidify at the theoretical solidification temperature and needs to be nucleated at a lower temperature. PCH indicates the difference between the melting temperature and the solidification temperature of the phase change materials (PCMs). So far, a lot of research on SC has been done and there is still a lack of research on PCH. On the one hand, the PCH is proportional to the energy loss of the system, the latent heat of PCMs cannot be exploited if PCH is beyond the operating temperature range of the system. On the other hand, when PCMs are combined with building envelopes, the greater the hysteresis temperature, the better the thermal performance of the wall. It's vital to use the hysteresis temperature to improve the performance of the system. Especially, PCMs are equipped in building envelopes, the hysteresis phenomenon of incomplete phase transition will be more obvious because of large temperature fluctuation outside. The hysteresis effect of PCMs in building envelopes is discussed in this paper, the numerical simulation methods and experimental research of PCH are reviewed and analyzed from two aspects of complete and incomplete phase transition. It showed that the PCH should be considered when simulating the thermal behavior of PCMs in building envelopes. The results would be more accurate if two enthalpy-temperature curves (H(T) curve) are used to represent the melting and solidification process, respectively. In addition, the nucleation mechanism of PCH has not been discussed in previous articles and there is no explanation about whether the hysteresis phenomenon is caused by the properties of the material itself or is affected by experimental measurement conditions. Therefore, the related issues are discussed in this paper, it is considered that the PCH is not only related to the properties of the materials but also affected by the experimental measurement conditions. [ABSTRACT FROM AUTHOR]

The elastic deformation on indenter is inevitable and has significant influences on indentation measurements. From a systematic finite element analysis for the indentation of elastic-perfectly plastic half-space by elastic spherical indenter, the piecewise linear characteristics of post-yield deformation are observed. Linear contact constitutive equations depending on elastic deformation of the indenter are derived by curve-fitting approach. An explicit theoretical contact model is presented to predict real contact radius, contact force and deformations of both contacting bodies ranging from elastic to finite plastic deformations. The applicability of the model is verified numerically and experimentally by static indentations and low-to-moderate velocity impacts. • Elastic-plastic indentation by elastic indenter is systematically analyzed. • Deformation characteristics are significantly affected by the indenter elasticity. • Piecewise linear characteristics from elastic to finite plastic are observed. • Linear contact constitutive equations are derived by curve-fitting approach. • The model is applied to rigid indentations and low-to-moderate velocity impacts. [ABSTRACT FROM AUTHOR]

Deep high static loading roadway is extremely prone to rock burst under dynamic load disturbance. The "force-energy criterion" for the failure of surrounding rock in such deep roadways and the "energy criterion" for the rock burst was established by considering the stress and energy evolution characteristics of rock burst under this circumstance. Under the engineering background of the main roadway in No.1 mining area of Gaojiapu Coal Mine in Binchang Mining Area, Shaanxi Province, China, the partial stress field and distortion energy field of surrounding rock in the main roadway and the spatial-temporal evolution laws under dynamic load disturbance were simulated and analyzed by using a built-in dynamic module of FLAC3D. Results show that after the dynamic load disturbance, the partial stress and distortion energy are concentrated in the shallow part at two walls of the roadway in the early phase. With the continuous propagation of dynamic load stress wave, the partial stress and distortion energy are transferred to the deep part. The sudden high-energy release occurred in the peak zone of partial stress, leading to the plastic failure of coal and rock mass. Subsequently, the distortion energy was fully accumulated in the original plastic zone and transferred from shallow surrounding rocks to the deep surrounding rocks in the roadway, where the partial stress and distortion energy of coal and rock mass reached the yield conditions. Thus, the original plastic zone was sharply expanded, thereby forming a new plastic zone. The coal and rock mass experienced an approximately static failure when no residual energy (ΔU) was found in it. When ΔU > 0, the rock mass experienced dynamic failure, and ΔU was mainly the volume transformation energy, which is approximately one-half of the total elastic strain energy. ΔU was transformed into the initial kinetic energy of broken coal and rock mass. Thus, the coal and rock mass are burst out. In severe cases, this condition was manifested by the rock burst in the main roadway. An optimization scheme of prevention and control measures for rock burst was proposed on the basis of the above conclusions. The microseismic activity laws before and after the unloading were compared, and a good effect was achieved. The research results can lay a theoretical foundation for predicting and preventing rock bursts in coal mines by actively regulating the disaster-pregnant environment and mitigating the disaster-inducing conditions. [ABSTRACT FROM AUTHOR]