Search

While numerous studies have revealed the impact of different bullying behaviors, such as victimization and perpetration, on the psychological development of adolescents, the exploration of the correlates of positive/negative bystander behaviors and their potential underlying mechanisms remains scarce in China. The present study aims to compare the relationships between mental health and positive versus negative bystander behavior and to clarify whether self-efficacy and coping styles mediate the relationships between mental health and bullying dynamics. The current study was conducted on 11,734 students from 18 secondary schools in Suzhou, China (Meanage = 15.00, SDage = 1.47; 53.8% boys). The information on bullying victimization, perpetration, positive/negative bystander behaviors, as well as self-efficacy, coping styles and mental health variables (including depression, anxiety, sleep disturbance, suicide risk), were collected. Negative bystander behavior was positively associated with mental health problems, while positive bystander behavior was negatively associated with these factors. Also, further analysis showed that coping styles and self-efficacy mediated the relationship between different bullying behaviors and mental health outcomes. The results highlighted the comparison of the correlates of positive and negative bystander behaviors, which were comparably crucial to those of victims and perpetrators for prevention and intervention efforts. Promoting adaptive coping styles and self-efficacy to buffer the deleterious psychological consequences of bullying behavior in adolescents was also important. [ABSTRACT FROM AUTHOR]

The corrosion of reinforced concrete (RC) is one of the most serious durability problems in civil engineering structures, and the corrosion detection of internal reinforcements is an important basis for structural durability assessment. In this paper, the appropriate frequency required to cause excitation signals in the specimen is first analyzed by means of frequency dispersion curves. Subsequently, the effectiveness of five damage indexes (DIs) is discussed using random corrosion in finite elements. Finally, guided ultrasonic wave (GUW) tests are conducted on reinforcement and RC specimens at different corrosion degrees, and the test results are verified using a theoretical corrosion model. The results show that the larger the covered thickness is at the same frequency, the higher the modal order of the GUW in the frequency dispersion curve is, and the smaller the group velocity is. The SAD is the most sensitive to the corrosion state of the reinforcement compared with the other DIs, and it shows a linear increasing trend with the increase in the corrosion degree of the reinforcement. The SAD values of the RC specimens showed a three-stage change with the increase in the corrosion time, and the time until the appearance of corrosion cracks was increased with the increase in the covered thickness. It can be seen that increasing the covered thickness is an effective method to delay the time until the appearance of corrosion cracks in RC specimens. [ABSTRACT FROM AUTHOR]

Objective. Proposing a novel arterial cannulation technique for acute DeBakey type I aortic dissection with severe aortic arch and branch involvement to enhance CPB effectiveness and reduce organ malperfusion complications. Methods. The technique involves retrograde insertion of an arterial perfusion tube into the aortic arch through the left common carotid artery. Extracorporeal circulation is established, and total aortic arch replacement with deep hypothermic systemic circulation and a frozen elephant trunk stent placement are performed to restore lower body perfusion. Results. Six patients with severe aortic arch and branch involvement underwent the new arterial cannulation technique. All patients had smooth postoperative recoveries without significant complications. Conclusion. The novel arterial cannulation technique shows promise in managing acute DeBakey type I aortic dissection with extensive vascular involvement, reducing complications, and enhancing patient outcomes. Further validation with a larger patient cohort is needed to confirm its effectiveness and safety. If successful, this technique could become a valuable addition to treatment strategies for improved outcomes. [ABSTRACT FROM AUTHOR]

A metal-free carbon catalyst is a kind of oxygen reduction catalyst with great prospects. It is an important material with potential to replace the traditional Pt catalyst. In this paper, a kind of irregular and ultra-thin carbon nanosheet (K180M-300-900) with high catalytic activity was synthesized by hydrothermal calcination using okra as a biomass and NH4Cl as an N source. The prepared nitrogen-doped metal-free catalyst with high pyridine-N and graphitic-N provides an extremely large number of active sites and has certain lattice defects. Ultra-thin carbon nanosheets promote sufficient contact between the catalyst and electrolyte, promote the diffusion of oxygen, and result in a faster transfer rate of electrons. The initial potential and half-slope potential of K180M-300-900 are 0.99 V and 0.82 V, respectively, which are comparable to those of 20% Pt/C. In addition, the stability and methanol tolerance of this catalyst (K180M-300-900) are better than 20% Pt/C, so it has great development potential and application value. This result provides a new method to prepare metal-free carbon materials that will take the place of traditional Pt catalysts. [ABSTRACT FROM AUTHOR]

In blockchain networks, transactions can be transmitted through channels. The existing transmission methods depend on their routing information. If a node randomly chooses a channel to transmit a transaction, the transmission may be aborted due to insufficient funds (also called balance) or a low transmission rate. To increase the success rate and reduce transmission delay across all transactions, this work proposes a transaction transmission model for blockchain channels based on non-cooperative game theory. Channel balance, channel states, and transmission probability are fully considered. This work then presents an optimized channel transaction transmission algorithm. First, channel balances are analyzed and suitable channels are selected if their balance is sufficient. Second, a Nash equilibrium point is found by using an iterative sub-gradient method and its related channels are then used to transmit transactions. The proposed method is compared with two state-of-the-art approaches: SilentWhispers and SpeedyMurmurs. Experimental results show that the proposed method improves transmission success rate, reduces transmission delay, and effectively decreases transmission overhead in comparison with its two competitive peers. [ABSTRACT FROM AUTHOR]

Current 3D target detection methods used in the field of autonomous driving generally have low real-time performance and insufficient target context feature to detect dynamic multi-target accurately. In order to solve these problems, a dynamic multi-target detection algorithm of voxel point cloud fusion based on PointRCNN is proposed, which adopts a two-stage detection structure. The first stage directly processes the point cloud to extract key point features and divides voxel space. A novel submanifold sparse convolution is used to extract voxel features. Then key point features and voxel features of the point cloud are merged to generate pre-selection boxes. In the second stage, reference points are set based on the voxel features. The features of key points around reference points are merged for the second time to achieve optimized detection boxes. Finally, for the problem of inconsistent confidence, a mandatory consistency loss function is proposed to improve the accuracy of the detection box. The proposed algorithm was compared with other algorithms in three different datasets, and further tested on a self-made dataset from an actual vehicle platform. Results showed that the proposed algorithm had higher accuracy, better robustness, stronger generalization ability for dynamic multi-target detection. [ABSTRACT FROM AUTHOR]

During major epidemics, monitoring vaccine quality can ensure the public health and social stability. Considering that social media has become an important way for the public to obtain external information during the epidemic. We developed a dual regulatory system of vaccine quality with the government in the leading role and the participation of We Media, and constructed a four-party evolutionary game model (government regulatory agency, We Media, vaccine industry groups, and the public) and analyzed the stability of each game player's strategy choice. The system's possible equilibrium points are identified using Lyapunov's first law. Then the game trajectory between stakeholders is simulated by MATLAB, the effects of initial intention and parameters on the evolution process and results are analyzed. The results show that to ensure the quality and safety of vaccines and stabilize network public opinion during epidemics, the government should invest in an effective supervision mechanism. By strengthening responsibility, increasing penalties, and reducing supervision costs, the probability of vaccine industry groups providing high-quality vaccines is effectively enhanced. Restricting the behavior of We Media and supervising vaccine industry groups to reduce speculation reduces the cost of government supervision and improves its efficiency. [ABSTRACT FROM AUTHOR]

Ultrasonic motors are typically driven by the dry friction force between the rotor and the stator; the friction pairs' high friction coefficient and low wear rate are two essential elements for improving the operational stability with longer service life. In this research article, high-precision microgroove arrays were manufactured on the surfaces of the stator and rotor of the TRUSM60 ultrasonic motor using laser machining. Dry friction and wear tests between the stator and the rotor were carried out with pin-on-disc using HSR-2M high-speed reciprocating friction and wear tester to determine the tribological properties of the ultrasonic motor. According to a different distribution of microgrooves on the two contact surfaces, the influence of smooth surface, single-sided texture, and double-sided texture on the friction pair's friction performance were discussed. The results show that the textured surface can substantially increase the coefficient of friction of the contact surface and reduce the rate of wear. The one-sided textured phosphor bronze surface with a microgroove width of 200μm and an area ratio of 20% had the highest coefficient of friction of 0.334 and a friction increase rate of 36.3%. Similarly, the single-sided textured Polyimide surface attained the highest friction coefficient of 0.355 and friction increase rate of 44.9% when the groove width is 150μm and the area ratio is 30%. A higher friction coefficient of the double-sided texture can be obtained through reasonable parameter configuration than the single-sided texture. The included angle of 0° between the two textured surfaces produced the highest friction coefficient of 0.368 and the wear rate of the phosphor bronze and polyimide surfaces were 2.01 × 10−4 mm3/N-m and 1.949 × 10−3 mm3/N-m, respectively. The result provides an essential benchmark for enhancing the tribological performance of ultrasonic motors and increasing the output torque. [ABSTRACT FROM AUTHOR]

Nowadays, it is still challenging for the blind image quality assessment (BIQA) to accurately predict quality scores of distorted images, since distorted images have rich content information and complex distortions. To solve these problems, a content perception and distortion inference network for BIQA is proposed, which divides IQA task into content perception and distortion inference processes. Since humans try to understand image content before perceiving quality scores, a content feature extractor is designed to explore content information in an image to deal with the content variation problem. To handle the distortion diversity problem, a distortion feature extractor is proposed to capture distortion features in images. Because extracted content features and distortion ones have different characteristics, attention‐based fusion blocks to fuse multi‐scale content features and distortion ones as guidance to selectively enhance important features based on calculated weight scores are proposed. With fused features, a quality prediction module is designed to regress multi‐scale features to quality scores. Experiments are performed on six public IQA datasets, including LIVE, CSIQ, TID2013, LIVEC, KonIQ‐10k, and SPAQ. Experimental results show that the proposed method can effectively predict quality scores for both synthetically and authentically distorted images than its peers, including the state‐of‐the‐art methods. [ABSTRACT FROM AUTHOR]

In recent years, We Media's chaotic behavior has emerged one after another. How to properly supervise We Media and effectively manage its violations has become an urgent problem in the process of national governance system and governance capacity building. From the three aspects of opportunity, motivation, and control methods, this paper analyzes the relevant stakeholders and their relationships in the process of We Media information dissemination. It constructs a tripartite evolutionary game model of government, We Media, and public participation, which focuses on the analysis of the equilibrium point of the game model and carries out simulation experiments to explore the influence of government responsibility constraints on the evolution results. The research results show that government regulation plays an important role in restricting We Media's information release. When the government's willingness to regulate increases, We Media will be punished more if it violates rules. In order to reduce the cost of punishment and other factors, We Media will reduce the willingness to violate the rules. After the occurrence of social hot events, the public is more willing to be guided by positive information from We Media, prompting the government to choose strict supervision strategies, effectively reducing the violations of We Media and achieving the Pareto optimum. According to the research results, this paper puts forward reasonable countermeasures to realize the comprehensive governance pattern of noncompliance of We Media and correct guidance of public emotional cognitive behavior under responsibility constraints. The research results provide theoretical support and decision-making basis for We Media information management and control. [ABSTRACT FROM AUTHOR]

To enhance the friction and wear resistance of GCr15/PTFE sliding contact surfaces, the synergistic lubrication effect of micro-textures and solid lubricants were studied in this paper. Micro-textures were processed on GCr15 samples by Nd:YAG laser, which were filled with MoS2. Tribological performance tests were carried out on a Rtec-MFT 5000 tester. Tribological properties were optimal with the textures density of 20% and depth of 9 µm. A continuous composite solid lubricating film was formed by PTFE and MoS2. As load increases, friction coefficient of the sample shows a rapid decline and then stabilizes. With the increase of reciprocating frequency, friction curve of the sample shows a trend of slight fluctuation. When frequency is 2.7 Hz, friction coefficient is the lowest. Tribological properties of PTFE/GCr15 contact surfaces could be significantly optimized by micro-textures and MoS2, which performs favorable prospect of engineering application such as guide rails, bearings, machinery seal, etc. [ABSTRACT FROM AUTHOR]

In the last ten years, cloud services provided many applications in various areas. Most of them are hosted in a heterogeneous distributed large-scale cloud computing environment and face inherent uncertainty, unreliability, and malicious attacks that trouble both service users and providers. To solve the problems of malicious attacks (including solo and collusion deception ones) in a public cloud computing environment, we for the first time propose a double-blind anonymous evaluation-based trust model. Based on it, cloud service providers and users are anonymously matched according to user requirements. It can be used to effectively handle some malicious attacks that intend to distort trust evaluations. Providers may secretly hide gain-sharing information into service results and send the results to users to ask for higher trust evaluations than their deserved ones. This paper proposes to adopt checking nodes to help detect such behavior. It then conducts gain–loss analysis for providers who intend to perform provider–user collusion deception. The proposed trust model can be used to effectively help one recognize collusion deception behavior and allow policy-makers to set suitable loss to punish malicious providers. Consequently, provider-initiated collusion deception behavior can be greatly discouraged in public cloud computing systems. Simulation results show that the proposed method outperform two updated methods, i.e., one based on fail-stop signature and another based on fuzzy mathematics in terms of malicious node detection ratio and speed. [ABSTRACT FROM AUTHOR]

A two-dimensional numerical model considering recoil pressure and Hertz-Knudsen ablation rate was established on the foundation of the laser remelting model to investigate the influence of laser processing parameters on crater feature and melted zone, and it was verified through experiments. The temperature and flow velocity distribution of the molten pool during the formation of the crater were analyzed. The results showed that the ablation velocity could be considered under a higher laser peak power density or higher pulse width due to the metal evaporation caused by heat accumulation. The depth and diameter of the crater were significantly affected by laser peak power density and laser pulse duration. Simultaneously, the height of the edge bulge decreased with the increase in pulse duration after 1.5 ms, and the growth rate of central depth was more rapid than that of edge bulge height with the increase of laser peak power density. In the texture with the same depth, a larger melted zone could be obtained with a longer laser duration than the higher peak power density. [ABSTRACT FROM AUTHOR]

A cloud computing paradigm has quickly developed and been applied widely for more than ten years. In a cloud data center, cloud service providers offer many kinds of cloud services, such as virtual machines (VMs), to users. How to achieve the optimized allocation of VMs for users to satisfy the requirements of both users and providers is an important problem. To make full use of VMs for providers and ensure low makespan of user tasks, we formulate an optimal allocation model of VMs and develop an improved differential evolution (IDE) method to solve this optimization problem, given a batch of user tasks. We compare the proposed method with several existing methods, such as round-robin (RR), min–min, and differential evolution. The experimental results show that it can more efficiently decrease the cost of cloud service providers while achieving lower makespan of user tasks than its three peers. Note to Practitioners—VM allocation is one of the challenging problems in cloud computing systems, especially when user task makespan and cost of cloud service providers have to be considered together. We propose an IDE approach to solve this problem. To show its performance, this article compares the commonly used methods, i.e., RR and min–min, as well as the classic differential evolution method. A cloud simulation platform called CloudSim is used to test these methods. The experimental results show that the proposed one can well outperform its compared ones, and its VM allocation results can achieve the highest satisfaction of both users and providers. The proposed method can be readily applicable to industrial cloud computing systems. [ABSTRACT FROM AUTHOR]

This article aims to investigate tribological properties of a surface modified by laser texturing under full oil lubrication as well as the effect of laser texturing on the abrasion resistance properties. Laser texturing was carried out to fabricate a spherical bulge texture on the surface of GCr15 bearing steel using an SPI fiber laser. Rriction and wear tests were performed to simulate the actual situation of sliding friction under full oil lubrication. Mechanical properties of the micro bulge and substrate region were detected and analyzed using an optical microscope, microhardness tester, and residual stress detector. Friction and wear tests showed that under full oil lubrication, the friction coefficient (FC) of bulge-textured samples is positively correlated with texture density. Compared with a smooth sample, the FC of the sample with 50.2% texture density decreased by 64.4%. The sample with 28.2% texture density had a minimal wear volume (1.35 × 108 μm3), which was diminished by 87.6% versus the smooth sample. The microstructure of the heat-affected zone is transformed into austenite by a large amount of heat and finally became acicular martensite when cooled. The microhardness of the bulge was increased to 419 and 331% of that of the substrate in vertical and radial directions, respectively. In addition, the surface of the micro bulge mainly revealed 20–35 MPa of residual tensile stress. The research proved that the surface wear resistance and antifriction effect of the sliding friction pair can be greatly improved by laser texturing, which shows favorable prospects for engineering applications such as bearings, guide rails, and mold formation. [ABSTRACT FROM AUTHOR]

Loess material requires improvement before being used as a filler for the bottom layer of the subgrade bed and substructure of a high-speed railway. Currently, cement and lime are often used to improve loess in engineering. However, whether improved loess material and the solution of key problems of the different types of improved loess can meet the long-term dynamic stability requirements of the bottom layer of a high-speed railway subgrade needs further study. Dynamic triaxial tests on cement-improved (CI) and lime-improved (LI) loess specimens were conducted to study the cyclic shear strain threshold and critical dynamic stress and to evaluate the long-term dynamic stability of CI and LI loess as fillers for the bottom layer of a subgrade bed. The results showed that the two improved loess materials can meet the long-term dynamic stability requirements when used as the bottom layer of a high-speed railway subgrade. After comprehensive consideration, 5% cement or 6% lime is recommended, with the CI soil prioritised. Compared with the critical dynamic stress method, the dynamic shear strain evaluation method is a more systematic and comprehensive method for evaluating the long-term dynamic stability of roadbeds. The research results can provide a technical reference for subgrade filler selection and subgrade design in a loess area. [ABSTRACT FROM AUTHOR]

Cloud computing has become an important scientific computing and commercial application paradigm. Many computing resources and data exist in clouds, and face various trust issues. Malicious providers may provide poor services to users, while malicious users may give good providers unfaithful trust evaluations. Hence, it is important to detect these malicious nodes that can be providers and users. Current studies on trust management do not sufficiently address the issues of minimizing trust management overhead and maximizing the ability to detect malicious nodes. This paper proposes a new trust model and related algorithm to decrease trust management overhead and improve malicious node detection ability based on domain partition. Partitioning nodes into domains is helpful for decreasing the overhead of trust management in terms of trust storage and computation. Domain and cross-domain sliding-windows are proposed and utilized to store the most recent trust values. Then, an algorithm is designed to compute domain and cross-domain trust values for nodes, and a filter procedure is adopted to remove malicious trust evaluations and malicious nodes from a domain. Simulation results show that the proposed model and algorithm outperform two updated methods, i.e., one based on fuzzy mathematics and another based on authenticated trust and reputation calculation and management, in terms of speed and accuracy of trust computation and malicious node detection. [ABSTRACT FROM PUBLISHER]

Purpose This paper aims to find out the tribological performance and self-lubricating mechanism of the laser-textured surface filled with solid lubricant in rolling friction pair.Design/methodology/approach The textures on the surfaces of GCr15 bearing steel were produced by acousto-optic Q diode-pumped yttrium aluminum garnet laser with the technology of “single pulse one time, repeating at intervals” and filled with composite solid lubricant. The tribology tests were conducted on the MMW-1A universal friction and wear testing machine.Findings It was found that the solid-lubricated micro-textured surface can reduce the friction coefficient effectively. The MoS2/PI composite solid lubricant works better than the single MoS2 solid lubricant, and the ratio of PI/MoS2 + PI at 20 per cent is the best recipe. The friction coefficient of the sample surfaces decreases first and then increases with the increase in texture densities, and a texture density of 19.6 per cent has the best effect on friction reduction. The friction coefficient of the textured surfaces gradually decreases with the increase in both rational speed and load. For the same texture density, the friction coefficient of textured surfaces decreases slightly with the increase in diameter. Furthermore, the mechanism of “rolling-extrusion-accumulation” occurred on the textured surface can collect the solid lubricant, thereby, improve the effect of lubricating and anti-friction.Originality/value The results of the experimental studies demonstrated the application prospect of laser surfaces texturing combined with solid lubricant in rolling friction pair. [ABSTRACT FROM AUTHOR]

This paper investigates several speedup techniques for a multiobjective integer linear program (ILP) used to obtain an optimal Petri net supervisor with a compressed structure for automated manufacturing systems (AMSs). An optimal supervisor can be obtained by forbidding all first-met bad markings and no legal markings of a plant net via place invariants. An iterative method to perform lexicographic multiobjective ILP is proposed to design such supervisor with a simple structure in terms of the numbers of control places and added arcs. Instead of a single ILP, several much smaller ILPs are formulated in the iterative method, and they can be solved much faster. To further reduce the ILP solution time, an efficient redundancy identification method is used. Finally, some AMS examples are provided to demonstrate the proposed speedup techniques and approaches. [ABSTRACT FROM PUBLISHER]

The correspondence between five precipitation products, including CMORPH, GPCP-2, TRMM 3B43, GPCC, and ITPCAS, and ground-based measurements of precipitation were evaluated on annual, seasonal, and monthly scales during 2000–2014 in the Qinling-Daba Mountains over China, which is a significant area with vital value of climate and hydrology. Performances of the precipitation products in the relatively arid/humid years were also analyzed. In general, ITPCAS data displayed the highest accuracy, GPCP-2 and CMORPH data showed relatively poor performance, and GPCC and TRMM 3B43 data were average at different temporal scales among the five precipitation products. The Pearson correlation coefficient of each station had minor fluctuations for the five precipitation products. A larger deviation was found at Wudu station, most likely due to the undulating terrain. The performances of the precipitation products from highest to least accuracy are as follows: ITPCAS > TRMM 3B43 > GPCC > GPCP-2 > CMORPH. Except for CMORPH (-20.76%), the percentage precipitation differences (PPDs) of the other four precipitation products fluctuated in the range of 10% during the relatively arid (2001) and humid (2011) years. In addition, all precipitation products and ground gauge observed precipitation did not show an obvious gradient with altitude, which is different from that in other mountainous areas and is perhaps due to complex terrain, lack of observation in high altitudes, and precipitation undercatch. In consideration of the significance of Qinling-Daba Mountains as the geographic and ecological dividing lines, the present study may provide a new perspective for hydrological, climatic, and ecological researches and practices in local and other mountainous areas. [ABSTRACT FROM AUTHOR]

The laser surface processing parameters and tribological properties of a textured surface filled with Gr-MoS-PI-carbon nanotube nanocomposite solid lubricant under oil lubrication were investigated. Micro-dimples were fabricated on GCr15-bearing steel material using Gaussian-shaped beam profile nanosecond semiconductor sound and light-pumped Nd:YAG laser machining equipment. Friction and wear tests were performed using MMW-1A testing machine with the flat-on-flat configuration under different conditions in air. The results show that micro-dimple morphology is affected strongly by the laser head to sample surface distance, pulse repetition frequency, and single pulse energy. Additionally, the textured surface filled with solid lubricant (TSL) exhibited an enhanced tribological performance as compared to the textured (T) and smooth (S) surfaces under dry friction condition. In the oil medium, the efficiency of the textured surface (TO) was 18%, while the textured surface filled with solid lubricant (TSO) was 22% as compared to the plateau smooth surface (SO). Furthermore, under different conditions of load and rotational speed, the solid-oil composite lubricating film effectively reduces the friction and wear on the surface of the sample. The research results identified that the good lubrication and anti-wear properties of the TSO sample were mainly attributed to the double-action lubrication system and synergistic lubricating effect generated by the composite solid lubricant and oil. [ABSTRACT FROM AUTHOR]

Motivated by the problem of simplifying the manual operation of the composition process, we propose an approach to automatically compose available Web services to fulfill user’s goal based on the assumption that there are a set of alternative Web services with similar functionality and different QoS properties. A formal model (i.e. semantic links matrix, SLM for short) is proposed to store semantic links values for the Web services with semantic relationship and QoS of Web services. The SLM provides a search place for a backward-search planning algorithm, at the same time; the QoS criteria make a rational and effective decision among a number of similar Web services. The function and some properties of the algorithm are analyzed. The approach can improve the correctness and flexibility for Web services composition and satisfy the local QoS attribute. [ABSTRACT FROM AUTHOR]