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The leakage of shield tunnels built in confined aquifers of silt or fine sand may result in the erosion of soil. Due to the loss of ground support, significant distortions of the tunnel structure may arise. As an initial insight into the mechanisms driving disaster chains, the erosion morphology of silt or fine sand under converging flow should be made clear first. In this study, a series of laboratory tests were performed to investigate the erosion morphology of fine sand under converging flow and its spatiotemporal evolution. Notably, for consistency with practical engineering, the initial effective stress of the soil was also considered. The initial results indicated that the erosion process may involve the soil arching effect due to the presence of soil effective stress. On this basis, tests with two leakage points were conducted. It was found that successively opening the two leakage points may lead to a larger erosion area of superposition when compared with the case of simultaneously opening two leakage points. [ABSTRACT FROM AUTHOR]

In order to improve machining efficiency and quality of aero-engine blisks, a novel multi-spindle 5-axis machine tool is developed under the inspiration of the blisk structure. The proposed machine contains 8 spindles, which are arranged radially along the blisk and simultaneously participate in machining. The actuator of the machine contains three rotation axes and two translation axes, which can realize 5-axis CNC machining. Based on the unified kinematics model, the mechanism is analyzed in terms of forward and inverse kinematics, singularity, and flexible workspace. Meanwhile, the structural parameters of the machine are optimized according to the flexibility index to improve the kinematic performance of the mechanism. Theoretical and experimental results show that the machine tool has a more compact structure, fewer moving axes, and better kinematics performance, compared with the traditional multi-spindle modular machine tool. Therefore, the machine has significant advantages in processing efficiency and has great application potential in large batch machining of the blisk. [ABSTRACT FROM AUTHOR]

The coronavirus disease 2019 (COVID‐19) pandemic has greatly stressed the global community, exposing vulnerabilities in the supply chains for disinfection materials, personal protective equipment, and medical resources worldwide. Disinfection methods based on cold atmospheric plasma (CAP) technologies offer an intriguing solution to many of these challenges because they are easily deployable and do not require resource‐constrained consumables or reagents needed for conventional decontamination practices. CAP technologies have shown great promise for a wide range of medical applications from wound healing and cancer treatment to sterilization methods to mitigate airborne and fomite transfer of viruses. This review engages the broader community of scientists and engineers that wish to help the medical community with the ongoing COVID‐19 pandemic by establishing methods to utilize broadly applicable CAP technologies. [ABSTRACT FROM AUTHOR]

The climate change on the Tibetan Plateau (TP) exhibits a north-south dipole trend during the Holocene. However, it is unclear whether regional differences exist in the variations and driving mechanisms of dust storm activities across the entire TP, and whether these mechanisms align with those found in monsoonal northern China. Here, we present a high-resolution Holocene record of dust storms from an undisturbed lake in the research gap area of the TP, and compile previously published records from other TP regions. Our findings indicate that the dust storm activity increased from the early Holocene to the late Holocene, peaking after 5 cal ka BP. Importantly, our comparison with other dust storm records reveals a unified intensification of dust storm activity across the entire TP during the late Holocene, a pattern distinctly different from the north-south dipole trend of precipitation variation. Moreover, this unified pattern of dust storm intensification across the TP cannot be explained by the decreasing intensity of the East Asian winter monsoon (EAWM) during the Holocene. The observations suggested a limited role for precipitation and EAWM in modulating TP dust storms on the millennial timescale during this period. By contrast, the increases in dust storms on the TP after 5 cal ka BP correlates well to the southward shift of the westerly jet driven by the North Atlantic Oscillation (NAO). As the NAO transitioned to a negative phase during the late Holocene, a meandering westerly jet shifted southward to the interior of the TP, intensifying wind intensity and leading to dust storm outbreaks. • Holocene dust storm record in the crucial research gap area of the Tibetan Plateau (82 characters). • A spatial consistency in Holocene dust storm changes over the entire Tibetan Plateau (84 characters). • Low frequency of dust storm activity during the early and middle Holocene (73 characters). • Southward shift of the westerly drove dust storm outbreaks during the late Holocene (83 characters). [ABSTRACT FROM AUTHOR]

Contact calculation is of great importance in predicting the material removal (MR) of flexible grinding process (FGP). The contact is mostly considered approximately constant in the existing MR models, while the situations that contact varies a lot after FGP are ignored. Therefore, a novel model is proposed in this paper to take those situations into consideration. Firstly, the nonconstant-contact situation is introduced. Then, an equivalent method is developed to convert the nonconstant-contact grinding process into the accumulation of several quasi-constant-contact grinding processes. Based on the equivalent method, a MR model is established, and the procedure to obtain the model parameters by the finite element analysis (FEA) is introduced. In the end, the equivalent method and the MR model are tested by a series experiments of different process parameters. Results show that the proposed MR model can predict the material removal effectively for the nonconstant-contact situations. [ABSTRACT FROM AUTHOR]

[Display omitted] As the fourth state of matter, plasma's unique properties and interactions with other states of matter offer many promising opportunities for investigation and discovery. In particular, cold atmospheric plasma (CAP), operating at atmospheric pressure and room temperature, has remarkable potential for biomedical applications through various delivery methods. These biomedical applications include sterilization, wound healing, blood coagulation, oral/dental diseases treatment, cancer therapy, and immunotherapy. Effective delivery of plasma constituents is critical to its efficacy for these applications. Therefore, this review presents the key research activities related to CAP delivery (including direct CAP delivery, delivery of plasma-activated media, biomedical device-assisted plasma delivery, and CAP delivery with other therapeutics) and needs for future research. This review will be of great interest for understanding the current state-of-the-art of biomedical applications of plasma medicine while also giving researchers from a broad range of communities insight into research efforts that would benefit from their contributions. Such communities include biomedicine, physics, biochemistry, material science, nanotechnology, and medical device manufacturing. [ABSTRACT FROM AUTHOR]

The sculptured surface has been widely used in aerospace and machinery manufacturing industries. CNC machining of sculptured surfaces is an important research area, and computation efficiency improvements are considered critical topics in this field. This paper presents a highly efficient method to generate smooth tool paths by establishing a mathematical model to describe the relationship between the relative curvature of sculptured surface and the machining strip width in five-axis machining. The method is improved from the middle-point error control method (MPECM) and the feasible tool position surface method (FTPSM), by changing the objective from the complete optimization for each drive point to the drive points' interpolation. The drive point with the narrowest machining strip width and some sample points is selected to interpolate the remaining points. Both theoretical analysis and test examples show the correctness of the proposed method. Under the same condition, compared with the MPECM and the FTPSM, the computing time of the new method decreases to 10% at least. Besides, the fluctuation of the tool path is reduced. The machining examples verified the superiority of the proposed method. [ABSTRACT FROM AUTHOR]

Trichomes are differentiated epidermal cells and can be found on above ground organs of nearly all land plants. Results from previous studies show that trichomes play important roles against a wide range of both biotic and abiotic stresses. By examining differences between parental genotypes of available populations, we identified a population of recombinant inbred lines showing clear segregation for trichome density and length. Assessing the F8 lines of the population growing in the field detected a major locus on chromosome arm 4BL. This locus was detected based the assessments of either fully expanded third leaves or flag leaves after anthesis. Based on the position of the QTL, an SSR marker was used to identify heterozygous plants at this locus from F5 lines derived from the same cross for the F8 population. Three pairs of near isogenic lines targeting this locus were obtained from these heterozygous plants. Difference in trichome length between the two lines with opposite alleles for each of these NIL pairs were similar to that between the two parental genotypes for the mapping populations, confirming that this single locus is mainly responsible for the trichome characteristics measured in this study. The allele with long and dense trichome is dominant as this characteristic was shown by the heterozygous individuals at this marker locus. Apart from the targeted locus, NIL pairs have highly homogeneous genetic backgrounds. Thus, the NILs could be invaluable in understanding the relationship between trichome density and resistance or tolerance to various biotic and abiotic stresses. [ABSTRACT FROM AUTHOR]

The lower Yangtze is one of the regions of origin of rice agriculture but it is unclear if environmental change drove the transition from hunting-gathering to agriculture. Long-term and continuous lacustrine records of anthropogenic fire are a more effective means of addressing this problem than the fragmentary terrestrial records available for the lower Yangtze region. We constructed a Holocene fire history revealed by records of black carbon content (BCC) and grain size of the sediments of Lake Nanyi in the lower Yangtze. Our results show the following: 1) Peaks in fire activity occurred during ∼8400–6500 (fire peak P1) and ∼ 1100–0 cal BP (fire peak P2), while weaker fire activity occurred during ∼6500–1100 cal BP (S2). 2) This temporal pattern of fire activity, with a double peak (P1-S2-P2), was asynchronous from east to west across the lower Yangtze. The warm and humid climate would not have caused intense fires and the reduction of forest during ∼8400–6500 and ∼ 1100–0 cal BP. Therefore, we suggest that anthropogenic ignitions, corresponding to pronounced population fluctuations after 8400 cal BP, dominated the regional fire activity. Combined with archaeological evidence, the inverse relationship between the agricultural and population levels and fire intensity during the mid-Holocene suggests that fire intensity at this time was the result of the diversity of landscape types associated with prehistoric subsistence patterns, rather than the magnitude of anthropogenic activity. Combined with sea level, rainfall and archaeological evidence, we propose a mechanism whereby asynchronous water-level rise during ∼8400–6500 cal BP forced the migration of humans to the foothills where they often used fire to modify the landscape as part of a broad-spectrum subsistence pattern. Whereas, water-level fall after 6500 cal BP expanded the area of open ground for human settlement, and in this less diverse landscape, less use was made of fire in agricultural subsistence. Overall, our study reveals how regional water-level, driven by sea-level rise and extreme rainfall, delayed the transition from hunting-gathering to agriculture in the lower Yangtze region. • The Holocene fire history representing the lower Yangtze area is reconstructed. • Paleofire in the lower Yangtze area peaked during ∼8400-6500 cal BP and 1100-0 cal BP. • Increased burning of forests by human-induced fire peaks in the lower Yangtze area. • Prehistoric subsistence regimes dominated the burning strategy in the lower Yangtze area. • Rising water level delayed the emergence of prehistoric agriculture in the lower Yangtze area. [ABSTRACT FROM AUTHOR]

Cold atmospheric plasma (CAP) has become a topical research area due to its diverse applications in agriculture, medicine, environment, materials, energy, nanotechnology, and other fields. Plasmas in contact with liquids form marked sensitivity patterns at the interface depending on controlling parameters, including gas species, driving current, gas flow rate, gap length, and electrolyte conductivity. This review overviews basic aspects of plasmas inducing self-organization including computational and experimental studies and potential applications of such plasmas-treated liquids in agriculture and medicine. Representative experimental evidence of self-organized pattern (SOP) in diverse types of plasma discharges is reviewed. Generation and transport of reactive species in SOP plasma and SOP plasma interacting with liquids are introduced and discussed from their potential applications in agriculture and medicine. [ABSTRACT FROM AUTHOR]

As a result of the recently increasing demands on high-performance machining technology in the aero-engine industry, the near-net shape forming technique can be suitable for many integrated impellers. However, the previous forming deformation can raise serious problems for the secondary NC machining of non-formed area, which is mostly applicable for leading/trailing edge (LE/TE) and its adjacent area. It is even worse that non-designed shape and dimension of LE/TE may be responsible for the deteriorated aerodynamic performance and subsequent high in-service cost, especially when its radius is small. Based on previous efforts, this paper presents a 5-axis adaptive machining framework for the LE/TE of near-net-shape integrated impeller. On-machine measurement (OMM) with a touch-trigger probe is utilized to digitalize the impeller. The distribution and uncertainty of sampling points are taken into account with data processing. Through the comparison between the measured and nominal geometric parameters, the impeller profile can be reconstructed sequentially on each tandem cascade. Among this, the camber line deformation emphasizes the functional significance of design intent and the thickness distribution conforms the processed data at most degree. Utilizing the ability to remove small allowance and the low continuous grinding force, the 5-axis CNC grinding with electroplated cubic boron nitride (CBN) wheel is carried out. Moreover, typical examples are used to demonstrate the effectiveness and superiority of this strategy. [ABSTRACT FROM AUTHOR]

The Tibetan Empire, the only united regime in Tibetan history, existed between 618 and 877 CE, when Tibet was a unified world power, contesting control of Central Asia with the Tang Empire and the Abbasid Caliphate. Before its collapse in the 9th century, this was the world's highest elevation empire, ruling a vast territory that extended well beyond the Tibetan Plateau. However, factors leading to the rapid decline of this powerful highland empire remain elusive. Here we use a highly resolved lake sediment record from the western Tibetan Plateau to demonstrate that pronounced fluctuations in the climate regime between the 7th and 9th centuries played a key role in the fragmentation of the Tibetan Empire. Specifically, we demonstrate that a nearly complete shift from planktonic to benthic diatom life strategy signified markedly drier conditions and lower lake-levels. The height of the empire's power (ca. 600–800 CE) coincided with two centuries of uncharacteristically warm and humid conditions, whereas the empire's collapse (ca. 800–877 CE) co-occurred with an abrupt onset of severe drought conditions that were clearly registered in the paleolimnological records. Severe drought conditions combined with decreased social resilience might have led to rapid declines in crop production, which fostered a surge in domestic conflicts and expediated the final collapse of the Tibetan Empire. Although religious and political factors are commonly cited to explain the fall of this formidable great power, our paleoenvironmental analyses underscore that harsh environmental factors might have hastened the cultural decline of this highland region. • Paleolimnological data from a rare freshwater lake in the western Tibetan Plateau. • Abrupt collapse of the Tibetan Empire around 9th century linked to severe drought. • Rise and fall of empire linked to marked climate shifts between 7th and 9th centuries. • These changes were detrimental to the political unity of the Tibetan Plateau. • Diatoms closely tracked changes in lake level. [ABSTRACT FROM AUTHOR]

Cold atmospheric plasmas are currently gaining increasing attention for cancer therapy. However, very limited studies regarding the interaction mechanisms between plasma species and tissues are available. We report the interaction of plasma produced species ( and ) with gap junction by employing reactive molecular dynamics simulations. Our results indicate and radicals can chemically react with N-terminal of gap junction resulting in its structural damage. There are two breaking mechanisms being identified: C-N peptide bonds and C-C bonds can be damaged by and radicals, respectively. Our findings could be particularly important for understanding the plasma-generated reactive species triggering bystander effect based on gap junction intercellular communication. [ABSTRACT FROM AUTHOR]

The finite element method (FEM) and scratch sliding test were combined to investigate the tribological behaviors of Chromium Aluminum Silicon Nitride (CrAlSiN) coatings with various Si contents. The tribological behavior was evaluated through sliding tests using a conventional ball-on-disc wear apparatus. It was found that the coefficient of friction (COF) of CrAlSiN was lower than CrAlN coating and it reached a minimum value of 0.56 for CrAlSi3.7N. Energy-dispersive Scanning Electron Microscopy (SEM) with X-ray spectroscopy (EDX) was employed to reveal the compositions of wear debris formed during the scratch sliding experiments. As a reasonable approximation, a static condition was applied, and the scratch behavior was modeled by a sphere indenter scratching on a thin coating coated on a thick substrate. A three-dimensional finite element model was constructed with the help of the ABAQUS to describe the mechanical response during scratch. [ABSTRACT FROM AUTHOR]

In five-axis machining, multipoint tool orientation has the merit of getting a wider strip width. However, large computing time restricts its application. In this paper, for machining free-form surfaces by toroidal tools, a highly efficient and convergent multipoint tool orientation optimization method is proposed. The method is improved from Middle Point Error Control Method (MPECM), by changing the objective from the maximum strip width to multipoint tool orientation. H-function is defined, and the consistency between multipoint tool orientation and H-function's zero is demonstrated. Based on that, the seeking for optimal tool orientation is equivalent to the computation of H-function's zero. Under the same conditions, compared with MPECM and mechanical equilibrium method (MEM), the computing time of the proposed method decreases to 5% at least. Convergence is ensured by the analysis of the existence of multipoint tool orientation. In the end, the proposed method is validated in machining a mold surface and an aero-engine blade. [ABSTRACT FROM AUTHOR]

Cold atmospheric plasma (CAP) was shown to affect cells not only directly, but also indirectly by means of plasma pre-treated solution. This study investigated a new application of CAP generated in deionized (DI) water for the cancer therapy. In our experiments, the CAP solution was generated in DI water using helium as carrier gas. We report on the effects of this plasma solution in breast (MDA-MD-231) and gastric (NCI-N87) cancer cells. The results revealed that apoptosis efficiency was dependent on the plasma exposure time and on the levels of reactive oxygen and nitrogen species (ROS and RNS). The plasma solution that resulted from 30-min treatment of DI water had the most significant effect in the rate of apoptosis. [ABSTRACT FROM AUTHOR]

The cutter posture optimization in five-axis machining is of importance for machining efficiency and quality. In order to achieve a cutter posture with wide strip width, this paper proposes a mechanical equilibrium-based method. When the defined middle point on the cutter is fixed, two contact points are needed and obtained for seeking an equilibrium state of the cutter. After initially positioned on the desired surface, the cutter is firstly stressed by the gravity, then impact on the desired surface. The process repeats until the cutter is in an equilibrium state. The uplift of the cutter is also optimized to avoid excess that caused by the shift of the actual middle point on the error distribution curve. In the implementation, the proposed method distinctly increases the strip width compared with two existing methods. [ABSTRACT FROM AUTHOR]

This paper presents a method to reduce the fluctuation of machining strip width by modifying tool position. When the machining strip width varies rapidly within a tool path, the fluctuation of cutting force brings negative influence on the workpiece and cutter. Furthermore, as the tool path interval is always defined conservatively to avoid undercut, the machined strips of adjacent tool paths have unnecessary amount of overlap. Rapid changing machining strip width usually creates too much overlap at some location, which causes repeated cutting. A method is proposed to modify tool position and reduce the fluctuation of machining strip width. Besides, tilt angle smoothness along the tool path is also taken into account. The computation result of a blade surface verified the validity of the proposed method. [ABSTRACT FROM AUTHOR]

The multi-point tool positioning algorithms produce much larger machining strip width than the single-point algorithms and apparently reduce the actual machining time. This paper presents a tool positioning algorithm for multi-point machining of sculptured surface, which is excellent at dealing with both of concave and convex surfaces. The proposed method is based on the middle-point error control (MPEC) method, which means the connection point between cutter and surface corresponds to the middle point of error distribution curve. Usually, only one cut contact (CC) point can be obtained with this method. Thus, the proposed method improved the MPEC method for achieving two CC points. At first, the shape of error distribution curve is investigated, and its asymmetry is evaluated. Secondly, the error distribution curve becomes symmetrical after the cutter is rotated with a roll angle, and the cutter is separated with surface at the same time. Finally, the minimum tilt angle is found, and two CC points are obtained without gouging. Machining experiment is conducted to verify the proposed method, and the result reveals that the machining strip width is increased apparently and the tool position is almost unchanged after the adjustment with proposed method. Simulation, measurement, and analysis are also given in the part of the experiment. [ABSTRACT FROM AUTHOR]

• Presents an indirect evaluation of the equivalent notch root radius of the surface profile——the arch-height & chord-length formula. • No single direct index of surface profile can determine the fatigue strength, but the indirect indexes, the notch bottom radius and the stress concentration factor can be used. • The surface notch roots radius ρ is the key to the stress concentration coefficient. Using the arch-height & chord-length formula, the linear fitting goodness of the stress concentration coefficient and the fatigue strength reaches 0.9. Considering the current controversy about the key indicators of surface roughness, this paper presents an indirect evaluation of the equivalent notch root radius of the surface profile. Using this method, the influence of surface roughness on fatigue strength on GH4169 is studied. Various sets of specimens with different fabrication conditions are machined to get a wide range of surface roughness. Vacuum annealing treatment is conducted on some of the specimens to eliminate the effect of residual stresses. Different classical formulae for stress concentration factor based on the notch root radius of the surface profile are used and the fatigue life reduction factor for various surface roughness values is presented. The results show that no single direct index of surface profile can determine the fatigue strength, but the indirect indexes, the notch bottom radius and the stress concentration factor can be used. The surface notch roots radius ρ is the key to the stress concentration coefficient. Using the arch-height & chord - length formula proposed in this paper to evaluate ρ , the linear fitting goodness of the stress concentration coefficient and the fatigue strength reaches 0.9. [ABSTRACT FROM AUTHOR]

Blade is the core component of aero-engine, and its manufacturing capability improvement has always been the focus of aviation manufacturing industry. With the high-efficiency machining of multi-spindle machine tool, this paper proposes a synchronous polishing method based on the cluster grouping of actual blade profile. Firstly, the multi-spindle machining system, flexible polishing with determined path, and synchronous polishing process cycle are analyzed in detail. Secondly, the allowable difference within group is determined by the relationship of polishing compression and surface roughness/removal. Then, the distribution of grouping mark points is determined by the profile differences of sampled blades. Thirdly, the consistency of each two blade profiles is expressed as the vector difference of measurement data, and the grouping result can be established with the Ray-Turi index. Finally, a typical blade is used to demonstrate the effectiveness and efficiency. After multi-spindle synchronous polishing, the average synchronous polishing cycle time is 3.14 times less than single-spindle machine tool, the profile error and its difference are less than 0.0685 mm and 0.048 mm, the surface roughness can satisfy Ra ≤ 0.4 μ m , which can meet the design requirement of aero-engine blade. [ABSTRACT FROM AUTHOR]

Abstract: This paper investigates the in situ tensile cracks propagating behavior of composite coatings on the aluminized steel generated using the plasma electrolytic oxidation (PEO) technique. Cross-sectional micrographs and elemental compositions were investigated by scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS). The composite coatings were shown to consist of Fe–Al, Al and Al2O3 layers. The cracks propagating behavior was observed in real-time in situ SEM tensile test. In tensile process, the cracks were temporarily stopped when cracks propagated from Fe–Al layer to Al layer. The critical crack opening displacement δ c was introduced to quantitatively describe the resistance of the Al layer. There was a functional relation among the thickness ratio , the δ c of composite coatings and tensile cracks’ spacing. The δ c increased with the increasing of the thickness ratio (). The high δ c value means high fracture resistance. Therefore, a control of the thickness ratio was concerned as a key to improve the toughness and strength of the aluminized steel. [Copyright &y& Elsevier]

A six-axis machining configuration is proposed to improve the surface quality and finishing efficiency of an aeroengine blisk. It flexibly enlarges the accessible interference-free space of the tool for finishing the full-shape surface, including the blade body, root, and hub surfaces. An error model for tool contact posture with respect to the kinematic axis errors is established, revealing the relationship between the kinematic deviation of the axes and resultant profile error. An improved Sobol method is applied for error sensitivity analysis to identify crucial error terms based on the quasi-Monte Carlo algorithm. In particular, an efficient error sensitivity index is proposed by combining a unified objective function to identify crucial error terms, followed by the simulations and cutting experiments for validation. As a result, the blade profile error was successfully suppressed by approximately 40 % in most. This work provides a fundamental framework for elevating the multi-axis machining accuracy of aeroengine blisk. • A six-axis machine tool has been proposed to achieve the full-shape-surface grinding on the blisk. • A constrained error sensitivity index model was proposed to compensate for key error terms. • Sensitivity analysis was conducted using an improved Sobol method incorporated quasi-Monte-Carlo algorithm. • The effectiveness of error sensitivity analysis and corresponding tool-path-based compensation were verified. [ABSTRACT FROM AUTHOR]

• A statistical sampling method was proposed for mass-produced blades measurement. • The statistics confidence region estimation is used to get the minimum sample size. • The correlation analysis is used to determinate the sampling distribution. • The proposed method can reduce the CMM measurement workload significantly. The complex geometry and inevitable manufacturing errors of aero-engine blade profile bring difficulties to high-efficiency and high-accuracy measurement. Usually, blade profile is measured by coordinate measuring machine (CMM) in mass production. Since the measurement time and cost increase proportionally as the increase of sampling points, it is essential to study a sampling method that can answer two basically different sampling problems: how many blades need to be sampled from mass production, and how many points need to be measured for a blade. This paper calculates the sample size for statistical analysis with sufficient confidence and accuracy. The correlation analysis for profile deviations of cross sections (e.g. rotation parameters) and cross-sectional points (e.g. point to point normal distances) is conducted, and the proposed method is carried out through traversing the neighboring Spearman rank correlation coefficient and noting low correlations between each other. The studied cases of two real blades indicated that the proposed statistical sampling method can improve measurement efficiency and ensure the measurement accuracy of mass-produced blades. [ABSTRACT FROM AUTHOR]

The fatigue life of aerospace components depends greatly on the mechanical properties of the finished surface layer. However, no independent strength test of this layer has been reported because of the lack of suitable samples. Therefore, a direct method of assessing the surface tensile strength using film samples with thicknesses of approximately 40 μm is proposed in this paper. The immediate objective of this research is to demonstrate the fundamentals of surface strength testing and prove the feasibility of preparing films by tracking the evolution of the surface integrity. The test results show that layer‐by‐layer grinding and polishing is a feasible method for preparing film samples with sufficient area, controllable thickness, and well‐maintained surface integrity. During the preparation of the film samples, the roughness and micro‐hardness of the test side (the side kept unprepared for testing) are protected, and those of the processed side (the side that is ground and polished) are controlled. The residual stress on both sides is released to zero. The film specimens exhibit regular fracture behaviour in the tensile tests, and their stress–strain curves can be explained as weighted averages of the stress–strain functions of multiple layers. [ABSTRACT FROM AUTHOR]

This article discusses the use of cold atmospheric plasma (CAP) as a potential treatment for chordomas, a type of skull base tumor that is difficult to treat. CAP is a room temperature gas that has been shown to have anti-tumor effects in various types of cancer. The study found that CAP exposure decreased the survival of chordoma cells in vitro. Further research is needed to understand the mechanism of cell death and how to increase the sensitivity of chordoma cells to CAP. [Extracted from the article]

Front Cover: Cold atmospheric plasma generated in deionized water has potential to be non invasively delivered, combined with other drugs or used as standalone drug and injected into tumors. Further details can be found in the article by Zhitong Cheng et al. on page 1151. [ABSTRACT FROM AUTHOR]

The aero-engine blade is typically a thin-walled part with poor rigidity and a complex structure. This causes aero-engine blades to be susceptible to flutter and deformation during the machining processing, leading to the dimensional and positional accuracy outside the stipulated tolerance values. With the aim of improving the machining precision of the blades, the conventional blade processing methods were analysed in this study. Based on the analysis, a novel deformation control method named reverse segment machining method was proposed. Additionally, a stress-free auxiliary fixture was designed to improve the stiffness of thin-walled parts. Finally, an experiment was conducted to study the effectiveness of the developed reverse segment method and the stress-free auxiliary fixture in comparison to the forward machining methods. The results show that they can significantly improve machining precision. [ABSTRACT FROM AUTHOR]

This article presents a resistor-array-tuning-based hybrid adaptive digital delay compensated rectifier for wireless power transfer systems. A no-crossing problem and nonlinearity problem for conventional delay-compensations are analyzed. In order to enhance the robustness of digital control, the on-delay and off-delay are compensated with different compensation schemes. The on-delay is compensated with a comparator-offset-adjusted technique, while the off-delay is compensated with a pulsewidth modulation (PWM)-based technique to guarantee falling zero-voltage crossing and adjust off-delay time linearly. Compared with the previous works, the delay time is adjusted by tuning the voltage drop across resistor arrays instead of changing the injected offset current of push–pull comparator so as to improve the power conversion efficiency (PCE) and loop stability. Implemented in a 0.18- $\mu$ m BCD process with a total area of 0.446 mm $^{2}$ , the rectifier delivered a maximum output power of 54.5 mW. With a 13.56 MHz ac input voltage in the range of 2.5 and 3.3 V, the measurement results show the peak VCR of 96.1 $\%$ and peak PCE of 93.1 $\%$ for the load resistance of 2 k $\Omega$ and 500 $\Omega$ , respectively. [ABSTRACT FROM AUTHOR]

Due to their potential benefits, cold atmospheric plasmas (CAPs), as biotechnological tools, have been used for various purposes, especially in medical and agricultural applications. The main effect of CAP is associated with reactive oxygen and nitrogen species (RONS). In order to deliver these RONS to the target, direct or indirect treatment approaches have been employed. The indirect method is put into practice via plasma-activated water (PAW). Despite many studies being available in the field, the permeation mechanisms of RONS into water at the molecular level still remain elusive. Here, we performed molecular dynamics simulations to study the permeation of RONS from vacuum into the water interface and bulk. The calculated free energy profiles unravel the most favourable accumulation positions of RONS. Our results, therefore, provide fundamental insights into PAW and RONS chemistry to increase the efficiency of PAW in biological applications. [ABSTRACT FROM AUTHOR]

Cold atmospheric plasma (CAP) is a unique form of physical plasma that has shown great potential for cancer therapy. CAP uses ionized gas to induce lethal oxidative stress on cancer cells; however, the efficacy of CAP therapy continues to be improved. Here, we report an injectable hydrogel-mediated approach to enhance the anti-tumor efficacy of CAP by regulating the phosphorylation of eIF2α. We discovered that reactive oxygen and nitrogen species (ROS/RNS), two main anti-tumor components in CAP, can lead to lethal oxidative stress on tumor cells. Elevated oxidative stress subsequently induces eIF2α phosphorylation, a pathognomonic marker of immunogenic cell death (ICD). Trehalose, a natural disaccharide sugar, can further enhance CAP-induced ICD by elevating the phosphorylation of eIF2α. Moreover, injectable hydrogel-mediated delivery of CAP/trehalose treatment promoted dendritic cell (DC) maturation, initiating tumor-specific T-cell mediated anti-tumor immune responses. The combination therapy also supported the polarization of tumor-associated macrophages to an M1-like phenotype, reversing the immunosuppressive tumor microenvironment and promoting tumor antigen presentation to T cells. In combination with immune checkpoint inhibitors (i.e., anti-programmed cell death protein 1 antibody, aPD1), CAP/trehalose therapy further inhibited tumor growth. Importantly, our findings also indicated that this hydrogel-mediated local combination therapy engaged the host systemic innate and adaptive immune systems to impair the growth of distant tumors. [ABSTRACT FROM AUTHOR]

In this work, honeycomb-like SiO x coating was successfully prepared on steel surface by atmospheric pressure low temperature plasma jet. The surface morphology, corrosion resistance and stability of the coating were systematically analyzed. In addition, the growth mechanism of the coating was discussed. The analysis revealed that the coatings were primarily composed of Si-O-Si and Si-OH groups, with a minor presence of Si-CH 3 moieties. The coating obtained after two deposition cycles exhibits the highest level of uniformity and density, with minimal porosity and superior corrosion resistance. The increase in deposition cycles led to particle aggregation, augmented particle dimensions and porosity, which adversely affected the coating's performance. The dense SiO x coating resulted in a significant reduction in the corrosion current density of the alloy steel, and showed no significant corrosion defects when exposed to the crude oil simulant in 25 °C. The coating simultaneously enhanced the hydrophilicity and oil transfer of the steel surface. Finally, the coating exhibited self-cleaning properties, stability and high potential for safeguarding steel pipes against low-viscosity crude oil contamination. This study provides a general surface modification method for the preparation of corrosion-resistant coatings on metal surfaces under mild conditions. [ABSTRACT FROM AUTHOR]

In the present paper, the strength and interfacial properties of square-wave joints under tension are analyzed. By using the bilinear cohesive zone model, three main factors in practice, including geometric parameters, preexisting defects and mismatches, are considered. It is found that the strength and fracture toughness of the joints can be improved by proper adjustment of geometric parameters of the joint. What is more, the length of defect has a great influence on the mechanical properties of the adhesive joints, different from the defect's location. Compacting adherends tightly during glue consolidation, making the bonding part as symmetrical as possible and introducing some protuberances on square-wave plug are found to be helpful to improve the joints' mechanical behavior. The findings should be useful for the design of square-wave joints and the assessment of mechanical properties of adhesive joints in practical and potential applications. [ABSTRACT FROM AUTHOR]

A novel method for the in situ visualization and profilometry of a plasma-facing surface is demonstrated using a long-distance microscope. The technique provides valuable in situ monitoring of the microscopic temporal and morphological evolution of a material surface subject to plasma–surface interactions, such as ion-induced sputter erosion. Focus variation of image stacks enables height surface profilometry, which allows a depth of field beyond the limits associated with high magnification. As a demonstration of this capability, the erosion of a volumetrically featured aluminum foam is quantified during ion-bombardment in a low-temperature argon plasma where the electron temperature is ∼7 eV and the plasma is biased relative to the target surface such that ions impinge at ∼300 eV. Three-dimensional height maps are reconstructed from the images captured with a long-distance microscope with an x–y resolution of 3 × 3 μm2 and a focus-variation resolution based on the motor step-size of 20 μm. The time-resolved height maps show a total surface recession of 730 μm and significant ligament thinning over the course of 330 min of plasma exposure. This technique can be used for developing plasma-facing components for a wide range of plasma devices for applications such as propulsion, manufacturing, hypersonics, and fusion. [ABSTRACT FROM AUTHOR]

This systematic and meta-analytic review aimed to investigate the effects of Tai Chi Chuan (TCC) on the cognitive function of the elderly with cognitive impairment and to analyze the moderators of these effects. We searched eight electronic databases for randomized controlled trials on the effects of TCC on cognitive function, published up to June 14, 2020. The PEDro scale was used to evaluate the methodological quality of the included literature. Stata14.0 software was used for meta-analysis, subgroup analysis, and publication bias testing. A total of 19 studies and 1,970 samples were included. The methodological quality of the included literature was fair to good, and there was no publication bias. Overall, the research shows that the effect of TCC on the elderly with cognitive impairment is statistically significant (SMD = 0.31, p < 0.0001). Five of the cognitive function subdomains were significant moderators [Q (5) = 15.66, p = 0.008 ], and the effect size (ES) was the largest for global cognitive function (SMD = 0.41), followed by executive function (SMD = 0.33), memory (SMD = 0.31), and verbal fluency (SMD = 0.27). Regarding the exercise prescription variables, results were significantly moderated by the length of exercise training [Q (2) = 6.00, p = 0.05 ], with ESs largest for moderate length (SMD = 0.41), followed by short length (SMD = 0.40) and long length (SMD = 0.29). However, the results were not moderated by session time or frequency. TCC can improve multiple cognitive functions of the elderly with cognitive impairment. The intervention effects are moderated by exercise length, but not by exercise session time and frequency. [ABSTRACT FROM AUTHOR]

• The model of an actuator bonded to a homogeneous half plane with an arbitrarily varying graded coating is analyzed. • The model functions effectively to explore the interfacial behavior of a graded coating with various graded laws. • The interfacial response can be tuned by the inhomogeneity parameter, the variation law and the adhesive interlayer. In the present paper, the model of a piezoelectric actuator bonded to an inhomogeneous substrate, which is composed of a homogeneous half plane and an arbitrarily varying graded coating, is established. Based on the fundamental solution of the inhomogeneous substrate, the governing integro-differential equation of the model is investigated and numerically solved. The interfacial shear stress and the transverse stress in the actuator are comprehensively analyzed. It is found that the interfacial response of the actuator/substrate system can be modified by tuning inhomogeneity parameter and variation law of the graded coating, material and geometric parameters of the adhesive interlayer, etc. A graded coating abiding by an exponential law corresponds to a more reliable interface and a more durable actuator, compared with a linear one. The results should be very helpful to design various film/substrate structures and choose proper graded coating in real applications. [ABSTRACT FROM AUTHOR]

Phase change materials (PCMs) are gaining increasing attention and becoming popular in the thermal energy storage field. Microcapsules enhance thermal and mechanical performance of PCMs used in thermal energy storage by increasing the heat transfer area and preventing the leakage of melting materials. Nowadays, a large number of studies about PCM microcapsules have been published to elaborate their benefits in energy systems. In this paper, a comprehensive review has been carried out on PCM microcapsules for thermal energy storage. Five aspects have been discussed in this review: classification of PCMs, encapsulation shell materials, microencapsulation techniques, PCM microcapsules' characterizations, and thermal applications. This review aims to help the researchers from various fields better understand PCM microcapsules and provide critical guidance for utilizing this technology for future thermal energy storage. [ABSTRACT FROM AUTHOR]

Phase change materials (PCMs) are gaining increasing attention and becoming popular in the thermal energy storage field. Microcapsules enhance thermal and mechanical performance of PCMs used in thermal energy storage by increasing the heat transfer area and preventing the leakage of melting materials. Nowadays, a large number of studies about PCM microcapsules have been published to elaborate their benefits in energy systems. In this paper, a comprehensive review has been carried out on PCM microcapsules for thermal energy storage. Five aspects have been discussed in this review: classification of PCMs, encapsulation shell materials, microencapsulation techniques, PCM microcapsules' characterizations, and thermal applications. This review aims to help the researchers from various fields better understand PCM microcapsules and provide critical guidance for utilizing this technology for future thermal energy storage. [ABSTRACT FROM AUTHOR]

Despite the promise of immune checkpoint blockade (ICB) for cancer treatment, challenges associated with this therapy still exist, including low response rates and severe side effects in patients. Here, we report a hydrogel-mediated combination therapy for enhanced ICB therapy. Specifically, cold atmospheric plasma (CAP), an ionized gas consisting of therapeutically effective reactive oxygen species (ROS) and reactive nitrogen species (RNS), can effectively induce cancer immunogenic cell death, releasing tumor-associated antigens in situ and initiating anti-tumor immune responses, which, therefore, can synergistically augment the efficacy of immune checkpoint inhibitors. To minimize the systemic toxicity of immune checkpoint inhibitors and improve the tissue penetration of CAP, an injectable Pluronic hydrogel was employed as a delivery method. Our results show that major long-lived ROS and RNS in CAP can be effectively persevered in Pluronic hydrogel and remain efficacious in inducing cancer immunogenic cell death after intratumoral injection. Our findings suggest that local hydrogel-mediated combination of CAP and ICB treatment can evoke both strong innate and adaptive, local and systemic anti-tumor immune responses, thereby inhibiting both tumor growth and potential metastatic spread. [ABSTRACT FROM AUTHOR]

Highlights • A new frictional contact model of an arbitrarily oriented substrate loaded by a rigid flat indenter is investigated in the paper, in which a spatially varying friction coefficient is included. • The proposed model functions effectively to explore the contact stress field as well as stress singularity near contact ends. • The contact behavior is significantly influenced by the friction coefficient, inhomogeneity parameter as well as gradient orientation angle of the graded substrate. Abstract A new frictional contact model of an arbitrarily oriented substrate loaded by a rigid flat indenter is proposed in the present paper, in which a spatially varying friction coefficient is considered. With the aid of Fourier integral transformation, the governing equation is obtained and solved semi-analytically. The surface contact stress field, the moment applied to make the indenter move vertically to the substrate's top surface, as well as the nominal friction coefficient are investigated comprehensively. It is found that the contact behavior can be well improved by choosing proper friction coefficient, inhomogeneity parameter as well as gradient orientation angle. The new finding of the present paper should be helpful to access the surface wear resistance and design various inhomogeneous composites. Graphical abstract Image, graphical abstract [ABSTRACT FROM AUTHOR]

Abstract Cold atmospheric plasma (CAP) is an emerging biomedical technique that shows great potential for cancer treatment. On the other hand, magnetic nanoparticles open up a wide field of possible applications in medicine. Here we seek to develop a novel dual cancer therapeutic method by integrating promising CAP and iron oxide-based magnetic nanoparticles (MNPs), and evaluate its underlying mechanism for targeted lung cancer treatment. For this purpose, the synergistic effects of CAP and iron oxide-based MNPs on cellular bioactivity, epidermal growth factor receptor (EGFR) expression, and EGFR downstream signaling pathways were investigated. Results showed that the effectiveness of CAP and iron oxide-based MNPs for synergistic strongly killed activity against lung cancer cells, and significantly inhibited cell proliferation via reduction of viability and induction of apoptosis. Importantly, CAP combining with iron oxide-based MNPs induced EGFR downregulation while CAP inhibited lung cancer cells via depressing pERK and pAKT. Translation of these findings to an in vivo setting demonstrates that CAP combining iron oxide-based MNPs is effective at preventing xenograft tumors. Thus, the integration of CAP and iron oxide-based MNPs provides a promising tool for the development of a new cancer treatment strategy. Graphical abstract fx1 [ABSTRACT FROM AUTHOR]

Aluminum alloy AA 6061-T651 and 5A06-H112 rolled plates were successfully welded by friction stir welding (FSW) at three rotation speeds of 600, 900, and 1200 rpm with two transverse speeds of 100 and 150 mm/min. Mechanical properties and strain field evolution of FSW AA 6061-AA 5A06 were characterized by the uniaxial tension and digital image correlation (DIC) tests. Furthermore, the hardness distribution map of whole cross section was obtained via the nanoindentation method with 700 indents. Both DIC and nanoindentation results reveal that the heat-affected zone (HAZ) of AA 6061 alloy is the softest area in the weldment, and the fracture happens in this region. The microstructure evolution characterized by electron-backscatter diffraction (EBSD) indicates that the continuous dynamic recrystallization is the primary grain structure evolution in the stirring zone, and the grain refinement helps improve the mechanical properties. Analyses of the micro- and macrofeatures of the fracture surfaces via scanning electron microscopy (SEM) and optical microscope suggest that the increasing of heat input could enlarge the size of HAZ and reduce the slant angle of HAZ and thus lead the fracture angle to decrease and cause the dimples change from inclined ones to normal ones. [ABSTRACT FROM AUTHOR]

Avoiding significant fluctuations of tool orientation is an important problem in five-axis machining. The dramatic change of tool orientation may greatly increase the angular acceleration of machine rotary axes, produce larger nonlinear machining errors and gouging, reduce the feed rate of machine rotary axes, etc. In this paper, we propose a tool orientation smoothing method based on machine rotary axes for five-axis machining with ball end cutters to reduce fluctuations of tool orientation in the machine coordinate system (MCS). The core idea of the proposed method is to directly smooth machine rotary angles in the machine coordinate system for the smooth variation of tool orientation. First of all, we establish the relationship between the design variables of tool position and machine rotary angles. Then, we define an objective function of tool orientation smoothing based on machine rotary angles. In order to solve the above objective function, we also develop a simplified algorithm to obtain the minimum sum of squares of compound angular accelerations. Finally, a blade surface is used as a test example, and tool paths are generated by the Sturz and proposed methods, respectively. Comparison and analysis results show that the proposed method can improve the kinematics performance of five-axis machine tool, as well as surface machining quality and efficiency. [ABSTRACT FROM AUTHOR]

Selective and sensitive determination of L -cysteine (L -Cys) plays an important role in clinical diagnoses and regulation of L -Cys level. However, glutathione (GSH) interferes greatly with the L -Cys detection due to their similar electrochemically active functional sulfhydryl groups and the high abundance of GSH in biological samples. Herein, Ni 2 P nanocrystallines anchored on black phosphorus nanosheets (Ni 2 P @ BPNSs) electrocatalysts were prepared by an in-situ solvothermal method using BPNSs as phosphorus sources and substrate. The electrochemical behaviors of Ni 2 P @ BPNSs with different Ni 2 P contents were studied for L -Cys determination. The experimental and DFT calculation results reveal the extraordinary electrocatalytic and selective sensing mechanism of Ni 2 P @ BPNSs toward L -Cys is attributed to the high selective adsorption and electrocatalytic activity of Ni active sites, and BPNSs matrix. The electrochemical sensor displays low detection limit (2 nM), more negative oxidation potential (+0.30 V), extremely broad linear range (0.02 −1000 μM), excellent sensitivity (396.00 μA mM−1 cm−2), and extraordinary selectivity. The sensor has been practically applied in detection of L -Cys concentrations in serum and urine samples. This work opens the avenues for the engineering design of metal atoms decorated BP materials in biosensors with enhanced sensing performance by adjusting the properties of materials, allowing for more selective and sensitive analyte detection. [Display omitted] • 2D Ni 2 P nanocrystallines anchored BP nanosheet is fabricated through solvothermal method. • The Ni 2 P @ BPNSs hybrids exhibit extraordinary selective electrocatalytic activity to cysteine. • The Ni 2 P @ BPNSs show low overpotential, wide linear range and low LOD for cysteine detection. • The sensor is successfully applied to detect cysteine in various biological samples. • The electrocatalytic and selective sensing mechanism were clarified. [ABSTRACT FROM AUTHOR]

The improvement of the ignition and combustion performance of aerospace engines under extreme conditions such as high altitude, low temperature, low pressure, and high speed is a research topic of broad and current interest. Plasma technology has attracted increasing attention due to its significant potential in improving ignition and combustion performance. Scientists and engineers have conducted numerous investigations and experiments on the use of plasma technology in aerospace engines, especially in aviation gas turbine engines, driving the research and applications of plasma-assisted ignition (PAI) and plasma-assisted combustion (PAC). The aim of this comprehensive review paper is to summarize and discuss the developments and applications of PAI and PAC in the fields of aerospace engines during the last ten years, including ignition, lean blow-out, combustion efficiency, emission, outlet temperature distribution quality, combustion stability, and fuel distribution. This review paper mainly focuses on experimental research progress. We also introduce new applications of PAI and PAC in novel aerospace engines and discuss the prospects for its practical implementation. [ABSTRACT FROM AUTHOR]

The Non-Uniform Rational B-spline (NURBS) surface not only has the characteristics of the rational Bézier surface, but also has changeable knot vectors and weights, which can express the quadric surface accurately. In this paper, we investigated new bounds of the first- and second-order partial derivatives of NURBS surfaces. A pilot study was performed using inequality theorems and degree reduction of B-spline basis functions. Theoretical analysis provides simple forms of the new bounds. Numerical examples are performed to illustrate that our method has sharper bounds than the existing ones. [ABSTRACT FROM AUTHOR]