身份认同视角下马来西亚华人的汉语传承

基于身份认同理论,马来西亚华人坚持汉语文化传承有生存、文化、政治三个动因。从生存动因维度看,有利于马来西亚华人在特定职场竞争中具有显著优势,为新兴业态提供人才支持,赓续语言教育,拓展生存空间。从文化动因维度看,有利于强化马来西亚华人的身份认同意识,提升中华文化影响力,维系中华特色文化。从政治动因维度看,汉语是政治表达的有力工具,政治因素对汉语传承产生了深远影响。马来西亚华人汉语传承的动因,共同推动了马来西亚华人汉语传承工作的向前发展。

纳米流体的制备、稳定性及热物性研究进展

作为一类新型固液两相流体,纳米流体相比于基础流体,其导热系数、表面张力等热物性的优势已逐渐被认可。然而,纳米颗粒的高表面活性以及颗粒间的高吸引力使纳米颗粒极易团聚并沉淀,导致纳米流体的热物性优势被削弱,进而影响传热效果。因此,制备既具优良热物性又具较强稳定性的纳米流体成为将其规模化应用的前提。为此,本文对纳米流体的制备、稳定性与热物性进行了总结分析,归纳了通过磁力搅拌、调节基液pH、超声分散技术、颗粒表面改性技术及添加表面活性剂以促进颗粒的稳定分散的技术特点。通过分析各类参数对纳米流体热物性的影响,指出解决颗粒团聚与沉淀问题的有效研究方向,以期满足纳米流体实际应用的需求。

香蕉皮单宁提取物对大肠杆菌的抑菌机理探究

研究香蕉皮单宁对大肠杆菌的抑菌机理,为香蕉皮的高效利用以及新型食品生物抑菌剂的开发提供理论基础。采用二倍稀释涂布平板法测定香蕉皮单宁对大肠杆菌的最低抑菌浓度(MIC)。通过测定菌液中碱性磷酸酶(AKP)、核酸和葡萄糖等含量变化,反映菌体细胞壁完整性、细胞膜完整性、消耗糖量变化,以此为指标对抑菌机理做出初步分析。香蕉皮单宁对大肠杆菌的最低抑菌浓度(MIC)为2.5mg/m L。菌液中碱性磷酸酶(AKP)前后含量无明显变化;菌液中核酸存在明显差异,1MIC实验组是对照的两倍。香蕉皮单宁通过破坏细胞膜的完整性发挥抑菌作用。

热控制制度强化再生A356铝合金性能研究

文章考察了废铝制品制备再生A356铝合金过程中精炼除杂脱气、冷却制度及热处理条件对再生铝合金组织结构及力学性能的影响,研选了提升再生A356铝合金力学性能的关键工艺参数,结果表明:通过投加自制Ti-C_(2)Cl_(6)精炼剂,再生铝合金浇注后立即室温水淬骤冷,以及固溶+时效的热处理等步骤,可实现脱气除杂、晶粒细化和抑制β-Fe相生成目的,所得铸态再生A356铝合金抗拉强度由201 MPa大幅度提升至277 MPa,将有助于推动汽车用再生铝技术的高质量发展。

A356铝合金轮毂低压铸造数值模拟以及组织与力学性能

采用轻质铝合金构件是实现汽车轻量化的重要策略,轮毂作为典型车用铝合金零件,其成形质量与低压铸造工艺参数密切相关。本文采用ProCAST有限元软件对A356铝合金轮毂低压铸造过程进行模拟仿真,研究了浇注温度及保压时间对轮毂成形质量的影响。并利用优化参数对轮毂进行铸造,对其成形质量及组织性能进行分析;同时,对轮毂不同部位进行微观组织及力学性能分析;对轮辋部位进行拉伸性能测试。结果表明:在浇注温度为700℃、保压时间为80 s时,铝液充型平稳,凝固符合顺序凝固原则,其铸造缺陷产生的概率最低;轮毂由内至外晶粒尺寸逐渐减小,由轮毂中心部位的58μm减小至外轮缘的23μm;轮辋部位抗拉强度可达228 MPa,屈服强度为170 MPa,断后伸长率为6%。

遵义市校园足球发展现状、新理念及未来对策思考

近年,随着校园足球发展规模的逐渐壮大,如何确保高质量可持续发展成为开展校园足球亟待解决的重要问题。本文采用实地调研、专家访谈、文献资料等方法,展示了遵义市校园足球发展的现阶段成绩,分享了遵义市校园足球"体学兼优、集中管理和可持续发展"的新理念;同时,梳理了遵义市校园足球发展所遇到的突出问题,并提出"如何最大化利用现有资源以解决困顿"的对策建议,以期为遵义市乃至其他省域更好地开展校园足球提供借鉴与思考。

TiB_(2)/A356复合材料在NaCl溶液中的电化学腐蚀行为

采用动电位极化和电化学阻抗试验研究了不同颗粒含量原位自生TiB_(2)/A356复合材料在3.5%NaCl溶液中的腐蚀行为。结果表明:TiB_(2)颗粒的引入,可以提高A356合金的腐蚀电位,降低腐蚀速率,增强其耐蚀性;电荷转移电阻和腐蚀产物的扩散电阻共同决定腐蚀反应速率,进而决定合金耐腐蚀性能的高低。复合材料耐蚀性能的提高,一方面由于TiB_(2)颗粒的引入显著细化基体晶粒,使得合金表面氧化膜的生成速度加快、氧化膜的稳定性提高;另一方面沿晶界均匀分布的TiB_(2)颗粒阻断了晶界位置Si、Mg2Si与Al基体组成的腐蚀电偶的活化通道,降低合金的腐蚀速率,提高腐蚀抗力。随着颗粒含量的增多,复合材料的腐蚀敏感性降低,而且TiB_(2)颗粒团聚将削弱材料抗腐蚀性能。2%TiB_(2)/A356复合材料的耐蚀性最好。

Anomaly IoT Node Detection Based on Local Outlier Factor and Time Series

The heterogeneous nodes in the Internet of Things(IoT)are relatively weak in the computing power and storage capacity.Therefore,traditional algorithms of network security are not suitable for the IoT.Once these nodes alternate between normal behavior and anomaly behavior,it is difficult to identify and isolate them by the network system in a short time,thus the data transmission accuracy and the integrity of the network function will be affected negatively.Based on the characteristics of IoT,a lightweight local outlier factor detection method is used for node detection.In order to further determine whether the nodes are an anomaly or not,the varying behavior of those nodes in terms of time is considered in this research,and a time series method is used to make the system respond to the randomness and selectiveness of anomaly behavior nodes effectively in a short period of time.Simulation results show that the proposed method can improve the accuracy of the data transmitted by the network and achieve better performance.

Double interface modification promotes efficient Sb2Se3 solar cell by tailoring band alignment and light harvest

The band alignment at the front interfaces is crucial for the performance of Sb_(2)Se_(3) solar cell with superstrate configuration.Herein,a Sn O_(2)/Ti O_(2) thin film,demonstrated beneficial for carrier transport in Sb_(2)Se_(3) device by the first-principle calculation and experiment,is proposed to reduce the parasitic absorption caused by CdS and optimize the band alignment of Sb_(2)Se_(3) solar cell.Thanks to the desirable transmittance of SnO_(2)/TiO_(2) layer,the Sb_(2)Se_(3) solar cell with SnO_(2)/TiO_(2)/(CdS-38 nm) electron transport layer performances better than (CdS-70 nm)/Sb_(2)Se_(3) solar cell.The optimized band alignment,the reduced interface defects and the decreased current leakage of Sb_(2)Se_(3) solar cell enable the short-circuit current density,fill factor,open-circuit voltage and efficiency of the Sb_(2)Se_(3) solar cell increase by 26.7%,112%,33.1%and 250%respectively when comparing with TiO_(2)/Sb_(2)Se_(3) solar cell without modification.Finally,an easily prepared Sn O_(2)/Ti O_(2)/CdS ETL is successfully applied on Sb_(2)Se_(3) solar cell by the first time and contributes to the best efficiency of 7.0%in this work,which is remarkable for Sb_(2)Se_(3) solar cells free of hole transporting materials and toxic CdCl_(2) treatment.This work is expected to provide a valuable reference for future ETL design and band alignment for Sb_(2)Se_(3) solar cell and other optoelectronic devices.

Molecular dynamics simulation of atomic hydrogen diffusion in strained amorphous silica

Understanding hydrogen diffusion in amorphous SiO2(a-SiO2),especially under strain,is of prominent importance for improving the reliability of semiconducting devices,such as metal-oxide-semiconductor field effect transistors.In this work,the diffusion of hydrogen atom in a-SiO2 under strain is simulated by using molecular dynamics(MD)with the ReaxFF force field.A defect-free a-SiO2 atomic model,of which the local structure parameters accord well with the experimental results,is established.Strain is applied by using the uniaxial tensile method,and the values of maximum strain,ultimate strength,and Young's modulus of the a-SiO2 model under different tensile rates are calculated.The diffusion of hydrogen atom is simulated by MD with the ReaxFF,and its pathway is identified to be a series of hops among local energy minima.Moreover,the calculated diffusivity and activation energy show their dependence on strain.The diffusivity is substantially enhanced by the tensile strain at a low temperature(below 500 K),but reduced at a high temperature(above 500 K).The activation energy decreases as strain increases.Our research shows that the tensile strain can have an influence on hydrogen transportation in a-SiO2,which may be utilized to improve the reliability of semiconducting devices.

Ab initio calculations on oxygen vacancy defects in strained amorphous silica

The effects of uniaxial tensile strain on the structural and electronic properties of positively charged oxygen vacancy defects in amorphous silica(a-SiO2)are systematically investigated using ab-initio calculation based on density functional theory.Four types of positively charged oxygen vacancy defects,namely the dimer,unpuckered,and puckered four-fold(4×),and puckered five-fold(5×)configurations have been investigated.It is shown by the calculations that applying uniaxial tensile strain can lead to irreversible transitions of defect structures,which can be identified from the fluctuations of the curves of relative total energy versus strain.Driven by strain,a positively charged dimer configuration may relax into a puckered 5×configuration,and an unpuckered configuration may relax into either a puckered 4×configuration or a forward-oriented configuration.Accordingly,the Fermi contacts of the defects remarkably increase and the defect levels shift under strain.The Fermi contacts of the puckered configurations also increase under strain to the values close to that of Eα′center in a-SiO2.In addition,it is shown by the calculations that the relaxation channels of the puckered configurations after electron recombination are sensitive to strain,that is,those configurations are more likely to relax into a two-fold coordinated Si structure or to hold a puckered structure under strain,both of which may raise up the thermodynamic charge-state transition levels of the defects into Si band gap.As strain induces more puckered configurations with the transition levels in Si band gap,it may facilitate directly the development of oxide charge accumulation and indirectly that of interface charge accumulation by promoting proton generation under ionization radiation.This work sheds a light on understanding the strain effect on ionization damage at an atomic scale.

First-principles investigations of proton generation inα-quartz

Proton plays a key role in the interface-trap formation that is one of the primary reliability concerns, thus learning how it behaves is key to understand the radiation response of microelectronic devices. The first-principles calculations have been applied to explore the defects and their reactions associated with the proton release in a-quartz, the well-known crystalline isomer of amorphous silica. When a high concentration of molecular hydrogen （H2） is present, the proton generation can be enhanced by cracking the He molecules at the positively charged oxygen vacancies in dimer configuration. If the concentration of molecular hydrogen is low, the proton generation mainly depends on the proton dissociation of the doubly- hydrogenated defects. In particular, a fully passivated E~ center can dissociate to release a proton barrierlessly by structure relaxation once trapping a hole. This research provides a microscopic insight into the proton release in silicon dioxide, the critical step associated with the interface-trap formation under radiation in microelectronic devices.

Passivation and dissociation of P_(b)-type defects at a-SiO_(2)/Si interface

It is well known that in the process of thermal oxidation of silicon,there are P_(b)-type defects at amorphous silicon dioxide/silicon(a-SiO_(2)/Si)interface due to strain.These defects have a very important impact on the performance and reliability of semiconductor devices.In the process of passivation,hydrogen is usually used to inactivate P_(b)-type defects by the reaction P_(b)+H_(2)→P_(b)H+H.At the same time,P_(b)H centers dissociate according to the chemical reaction P_(b)H→P_(b)+H.Therefore,it is of great significance to study the balance of the passivation and dissociation.In this work,the reaction mechanisms of passivation and dissociation of the P_(b)-type defects are investigated by first-principles calculations.The reaction rates of the passivation and dissociation are calculated by the climbing image-nudged elastic band(CI-NEB)method and harmonic transition state theory(HTST).By coupling the rate equations of the passivation and dissociation reactions,the equilibrium density ratio of the saturated interfacial dangling bonds and interfacial defects(P_(b),P_(b)0,and P_(b)1)at different temperatures is calculated.

First-principles calculations of the hole-induced depassivation of SiO2/Si interface defects

The holes induced by ionizing radiation or carrier injection can depassivate saturated interface defects.The depassivation of these defects suggests that the deep levels associated with the defects are reactivated,affecting the performance of devices.This work simulates the depassivation reactions between holes and passivated amorphous-SiO_(2)/Si interface defects(HP_(b)+h→P_(b)+H^(+)).The climbing image nudged elastic band method is used to calculate the reaction curves and the barriers.In addition,the atomic charges of the initial and final structures are analyzed by the Bader charge method.It is shown that more than one hole is trapped by the defects,which is implied by the reduction in the total number of valence electrons on the active atoms.The results indicate that the depassivation of the defects by the holes actually occurs in three steps.In the first step,a hole is captured by the passivated defect,resulting in the stretching of the Si-H bond.In the second step,the defect captures one more hole,which may contribute to the breaking of the Si-H bond.The H atom is released as a proton and the Si atom is three-coordinated and positively charged.In the third step,an electron is captured by the Si atom,and the Si atom becomes neutral.In this step,a Pb-type defect is reactivated.

First-principles calculations of F-, Cl-, and N-related defects of amorphous SiO_(2) and their impacts on carrier trapping and proton release

The first-principles calculations based on density functional theory are performed to study F-,Cl-,and N-related defects of amorphous SiO_(2)(a-SiO_(2)) and their impacts on carrier trapping and proton release.The possible geometric configurations of the impurity-related defects,the formation energies,the hole or electron trapping of the neutral defects,and the mechanisms to suppress proton diffusion by doping N are investigated.It is demonstrated by the calculations that the impurity atoms can interact with the oxygen vacancies and result in impurity-related defects.The reactions can be utilized to saturate oxygen vacancies that will cause ionization damage to the semiconducting devices.Moreover,the calculated formation energy indicates that the F-or Cl-related oxygen vacancy defect is a deep hole trap,which can trap holes and prevent them from diffusing to the a-SiO_(2)/Si interface.However,three N-related defects,namely N(2)o-H,N(2)o=O,and N(3)o-Vo,tend to act as shallow hole traps to facilitate hole transportation during device operation.The N(2)o and N(3)o configurations can be negatively charged as deep electron traps during the oxide charge buildup after ionization radiation.In addition,the nudged elastic band(NEB) calculations show that four N-related defects,namely N(2)o,N(2)o-H,N(2)o=O,and N(3)o are capable of capturing protons and preventing them from diffusing to and de-passivating the interface.This research reveals the fundamental properties of the F-,Cl-,and N-related defects in amorphous silica and the details of the reactions of the carrier trapping and proton release.The findings help to understand the microscopic mechanisms that alleviate ionization damage of semiconducting devices by doping a-SiO_(2).

Structural,electronic,and magnetic properties of vanadium atom-adsorbed MoSe2 monolayer

Using the first-principles calculations, we study the structural, electronic, and magnetic properties of vanadium adsorbed MoSe_2 monolayer, and the magnetic couplings between the V adatoms at different adsorption concentrations. The calculations show that the V atom is chemically adsorbed on the MoSe_2 monolayer and prefers the location on the top of an Mo atom surrounded by three nearest-neighbor Se atoms. The interatomic electron transfer from the V to the nearestneighbor Se results in the polarized covalent bond with weak covalency, associated with the hybridizations of V with Se and Mo. The V adatom induces local impurity states in the middle of the band gap of pristine MoSe_2, and the peak of density of states right below the Fermi energy is associated with the V- dz^2 orbital. A single V adatom induces a magnetic moment of 5 μBthat mainly distributes on the V-3d and Mo-4d orbitals. The V adatom is in high-spin state, and its local magnetic moment is associated with the mid-gap impurity states that are mainly from the V-3d orbitals. In addition,the crystal field squashes a part of the V-4s electrons into the V-3d orbitals, which enhances the local magnetic moment.The magnetic ground states at different adsorption concentrations are calculated by generalized gradient approximations（GGA） and GGA＋U with enhanced electron localization. In addition, the exchange integrals between the nearest-neighbor V adatoms at different adsorption concentrations are calculated by fitting the first-principle total energies of ferromagnetic（FM） and antiferromagnetic（AFM） states to the Heisenberg model. The calculations with GGA show that there is a transition from ferromagnetic to antiferromagnetic ground state with increasing the distance between the V adatoms. We propose an exchange mechanism based on the on-site exchange on Mo and the hybridization between Mo and V, to explain the strong ferromagnetic coupling at a short distance between the V adatoms. However, the ferromagnetic exchange mechanism is sensitive to both the increased inter-adatom distance at low concentration and the enhanced electron localization by GGA＋U, which leads to antiferromagnetic ground state, where the antiferromagnetic superexchange is dominant.

基于二次枝晶间距的差压铸造A356铝合金疲劳寿命预测

差压铸件由于复杂的结构、凝固条件不均匀,其内部的二次枝晶间距分布存在较大差异,进而导致不同区域存在不同的性能。目前,产品设计阶段的有限元分析采用统一的材料疲劳性能模型,导致模拟与试验结果存在偏差。通过对差压铸件不同位置区域进行二次枝晶间距测量和材料疲劳试验,建立了差压铸造A356铝合金的疲劳寿命、应力和二次枝晶间距的定量关系式,得到了不同二次枝晶间距对应的S-N曲线。经过试验验证,该定量关系式的预测结果与试验结果符合较好,预测疲劳寿命的对数相对误差最大绝对值在2%以下。同时,还通过扫描电镜(SEM)对材料疲劳断口进行了观察,阐述了疲劳裂纹的萌生和扩展机制。

增强体含量对TiB_(2)/A356铝基复合材料组织与性能的影响

通过熔盐反应法成功合成了原位TiB_(2)/A356铝基复合材料,研究了不同增强体含量对复合材料组织与性能的影响。结果表明,随着TiB_(2)颗粒含量增加,复合材料的晶粒尺寸逐渐降低。复合材料的强度随着增强体含量的增加而升高,而伸长率则表现出逐渐降低的趋势。利用改进的剪切-滞后模型对复合材料的屈服强度进行了预测,结果表明,该模型较好地反映了TiB_(2)/A356铝基复合材料的强度变化。

Enhancing ferromagnetic coupling in CrXY(X=O,S,Se;Y=Cl,Br,I)monolayers by turning the covalent character of Cr-X bonds

On the basis of first-principles calculations,we investigate the electronic and magnetic properties of 1T phase chromium sulfide halide CrXY(X=O,S,Se;Y=Cl,Br,I)monolayers in CrCl_(2) structure with the P3m1 space group.Except for the CrOI monolayer,all CrXY monolayers are stable and ferromagnetic semiconductors.Our results show that the ferromagnetic coupling is dominated by the kinetic exchange between the empty e_(g)-orbital of Cr atoms and the p-orbital of anions under the three-fold rotational symmetry.In this context,the coupling strength allows for being greatly enhanced by turning the nature of Cr–X bonds,i.e.,increasing the covalent contribution of the bonds by minimizing the energy difference of the coupled orbitals.As we illustrate for the example of CrOY,the Curie temperature(T_(c))is nearly tripled by substituting O by S/Se ion,eventually reaching the highest Tc in CrSeI monolayer(334 K).The high stabilities and Curie temperature manifest these monolayer ferromagnetic materials feasible for synthesis and applicable to 2D spintronic devices.