First-principles investigations of structural, mechanical, electronic and optical properties of U_3Si_2-type AlSc_2Si_2 under high pressure

The structural, elastic, electronic and optical properties for U3Si2-type AlSc2Si2 compound under pressure were systematically investigated by using the first-principles calculations. The values of elastic constants and elastic moduli indicate that AlSc2Si2 keeps mechanical stability under high pressure. The mechanical properties of AISc2Si2 are compared with those of Al3Sc. The results indicate that AlSc2Si2 is harder than AI3Sc. Anisotropic constant AU and 3D curved surface of elastic moduli predict that AISc2Si2 is obviously anisotropic under pressure. The electronic structure of AlSc2Si2 exhibits metallic character and the metallicity decreases with the elevated pressure. In addition, optical properties as a function of pressure were calculated and analyzed. The present work provides theoretical support for further experimental work and industrial applications.

Electronic,optical,and mechanical properties of BN,AlN,and InN with zinc-blende structure under pressure

In this work, the electronic, optical, and mechanical properties of BN, AlN, and InN under the action of pressure are calculated. For each of these compounds, the energy band structure, band gaps（E^L_g, E~Γ_g, E^X_g）, refractive index（n）,dielectric constants（ε_∞, ε_0）, elastic constants（C_11, C_12, C_44）, and relevant parameters such as bulk（B_u）, shear（S_h）, and Young＇s（Y_0） moduli are studied, and other important parameters such as bond-stretching（α）, bond-bending（β） force constant, internal-strain parameter（ζ）, effective charges（e~＊_T, Z~＊）, anisotropy factor（I_s）, Poisson＇s ratio（P_o）, Cauchy ratio（C_a）, the ductility index（μ_D）, and linear compressibility（C0_） are also calculated. The effects of pressure on all studied properties are investigated. Our results are in good agreement with the available experimental and theoretical data for BN,AlN, and InN.

Study of the Electronic Structure and Optical Properties of Rare Earth Luminescent Materials

Rare earth luminescent materials have attracted significant attention due to their wide-ranging applications in the field of optoelectronics. This study aims to delve into the electronic structure and optical properties of rare earth luminescent materials, with the goal of uncovering their importance in luminescence mechanisms and applications. Through theoretical calculations and experimental methods, we conducted in-depth analyses on materials composed of various rare earth elements. Regarding electronic structure, we utilized computational techniques such as density functional theory to investigate the band structure, valence state distribution, and electronic density of states of rare earth luminescent materials. The results indicate that the electronic structural differences among different rare earth elements notably influence their luminescence performance, providing crucial clues for explaining the luminescence mechanism. In terms of optical properties, we systematically examined the material’s optical behaviors through fluorescence spectroscopy, absorption spectroscopy, and other experimental approaches. We found that rare earth luminescent materials exhibit distinct absorption and emission characteristics at different wavelengths, closely related to the transition processes of their electronic energy levels. Furthermore, we studied the influence of varying doping concentrations and impurities on the material’s optical properties. Experimental outcomes reveal that appropriate doping can effectively regulate the emission intensity and wavelength, offering greater possibilities for material applications. In summary, this study comprehensively analyzed the electronic structure and optical properties of rare earth luminescent materials, providing deep insights into understanding their luminescence mechanisms and potential value in optoelectronic applications. In the future, these research findings will serve as crucial references for the technological advancement in fields such as LEDs, lasers, and bioimaging.

Impact of doping and hydrostatic pressure on structural, electronic, optical, and mechanical properties of novel double halide perovskite Cs_(2)LiGaBr_(6)

The emergence of lead-free halide double perovskites exhibiting bandgaps within the visible spectrum represents a substantial advancement in engineering environmentally benign perovskite solar cells.In this work,we investigated the structural,optical,electronic,and mechanical properties of Cs-based lead-free Cs2LiGaBr6 double halide perovskites with Mn and Cr doping under hydrostatic pressure ranging from 2 to 80 GPa using density functional theory(DFT).The introduction of dopants consistently alters the lattice parameters because of the mismatch in atomic radii,whereas increasing the pressure leads to a reduction in these constants.All the studied Cs2LiGaBr6 compounds exhibited direct band gaps,which increased slightly with doping.This is attributed to the modulation of electronic states by dopant-related defect levels.The bandgap variation under pressure is primarily attributed to changes in the quantum confinement effects induced by compressive strain.Analysis of the density of states and optical properties revealed enhanced absorption in the visible spectrum for the doped compositions,and in the UV spectrum under pressure.The study of mechanical stability confirms the ductile nature of both the doped and pristine compounds under pressure,underscoring their suitability for thin film production.This study contributes to the understanding of sustainable alternatives for perovskite optoelectronic applications,emphasizing Cs2LiGaBr6’s potential under diverse conditions and dopant influences.

Electronic, optical, and mechanical properties of Cu_2ZnSnS_4 with four crystal structures

The structural, electronic, optical, and mechanical properties of Cu2ZnSnS4 with four crystal structures are calculated using the density functional theory. No significant difference is observed between the calculated optical and mechanical properties of the considered four crystal structures. The calculated results are in agree- ment with available reported experimental data. According to the calculated results, the fundamental band gap of Cu2ZnSnS4 is mainly determined by the bandwidth of the isolated conduction band. The effective-mass of carriers of Cu2ZnSnS4 are very small, especially the effective-mass of electrons on the bottom of the conduction band of zincblende-derived Cu2ZnSnS4. Using the calculated elastic constants matrix, the Born stability criteria is shown to be satisfied, and the high B/G ratio indicates that Cu2ZnSnS4 is prone to ductile behavior.

Reform and Reconstitution of Core Courses in Mechanical and Electronic Engineering Under the Background of New Engineering

With the arrival of the intelligence era of Industry 4.0,social development has shown complex and diversified characteristics,gradually forming an innovation ecological environment constructed by vertical interaction of multi-layer innovation systems and horizontal collaboration of multiple organizations and departments,which has posed extremely challenging requirements for higher engineering education to cultivate engineering talents with comprehensive engineering qualities who can solve complex engineering problems.However,practical engineering problems may involve a complex knowledge chain of interdisciplinary and multi-disciplinary cross-coupling.Therefore,higher engineering education needs to form a new interdisciplinary and multi-disciplinary integrated engineering innovation talent training system.Based on the characteristics of the mechanical and electronic engineering major,we will reshape and reconstruct the core courses of the mechanical and electronic engineering major.Two core courses are formed:Drive and Measurement and Control I and Drive and Measurement and Control II,with information flow and energy flow as the main lines,following up with the comprehensive practical curriculum system based on the unity of knowledge and practice and ability-oriented thinking,supporting teaching objectives,promoting students’individual development,and providing guidelines for relevant curriculum reforms.

3D-printed optical-electronic integrated devices

The monolithic incorporation of electrical and optical components is critically important for achieving high-speed on-chip signal processing, but yet hard to satisfy the explosive growth in the demands on bandwidth and information density. Three-dimensional(3D) circuits, which are desirable for their improved performance in data handling, are ideal candidates to simultaneously promise high-capacity computing with improved speed and energy efficiency. In such highly integrated circuits, however, the selective electrical modulation of light signals is still difficult to achieve owing to the lack of controllable integration of microscale optical functional devices and modulation units. In this work, we demonstrate an electrically modulated microlaser module on a 3D-integrated microsystem composed of a dye-doped polymeric microcavity and an underneath microscale electrical heating circuit. The lasing mode was modulated based on electrical heating-assisted thermo-optic response of the polymeric matrices, which were further fabricated into coupled microdisks, yielding wavelength-tunable single-mode microlasers with selective electrical modulation. On this basis, a prototype of electrically controlled microlaser module with reduced signal crosstalk was achieved. The results will provide a useful enlightenment for the rational design of novel tunable optical devices with more complicated functionalities under far-field regulation, paving the way for the on-chip optoelectronic integration.

Silicon photonics for telecom and data‐com applications

In recent decades,silicon photonics has attracted much attention in telecom and data-com areas.Constituted of high refractive-index contrast waveguides on silicon-on-insulator(SOI),a variety of integrated photonic passive and active devices have been implemented supported by excellent optical properties of silicon in the mid-infrared spectrum.The main advantage of the silicon photonics is the ability to use complementary metal oxide semiconductor(CMOS)process-compatible fabrication technologies,resulting in high-volume production at low cost.On the other hand,explosively growing traffic in the telecom,data center and high-performance computer demands the data flow to have high speed,wide bandwidth,low cost,and high energy-efficiency,as well as the photonics and electronics to be integrated for ultra-fast data transfer in networks.In practical applications,silicon photonics started with optical interconnect transceivers in the data-com first,and has been now extended to innovative applications such as multi-port optical switches in the telecom network node and integrated optical phased arrays(OPAs)in light detection and ranging(LiDAR).This paper overviews the progresses of silicon photonics from four points reflecting the recent advances mentioned above.CMOS-based silicon photonic platform technologies,applications to optical transceiver in the data-com network,applications to multi-port optical switches in the telecom network and applications to OPA in LiDAR system.

GKPA-联合全局与关键区域的光学-SAR中分辨率遥感影像场景分类

遥感影像场景分类是自然灾害检测和城市功能规划等实际应用的基础,因此研究遥感影像场景分类具有重要意义。基于深度学习的方法由于其强大的特征提取能力已经成为遥感影像场景分类领域最常用的方法,此类方法强烈依赖数据集的质量。现阶段场景分类领域的数据集大多为高分辨率的光学影像,易于提取有效的语义特征。在面对中分辨率场景时,影像中细节信息更匮乏,有效特征不够显著,场景分类具有更大难度,相较于高分辨率场景分类精度不够理想。在此情况下,利用其他模态的数据如合成孔径雷达(SAR)提供互补特征可以有效改善场景分类精度。考虑到以上现状,本文构建光学-SAR遥感影像场景分类数据集(OS-RSISC),基于此数据集进一步提出了一个联合全局与关键区域的感知注意力双模态场景分类框架(GKPA-RSSC)。实验结果显示GKPA-RSSC相较于对比方法具有最高的分类精度,总体精度达81.97%。光学-SAR数据与单模态数据的对比试验结果突显双模态数据的优势,进而验证了本文提出的光学-SAR场景分类数据集的重要意义。

Energy Transfer from Ce^3＋ to Eu^2＋ in LiSrBO3 and Its Potential Application in UV-LED-Based White LEDs

Ce3＋/Eu2＋ codoped LiSrBO3 phosphor is synthesized, and its luminescent characteristics are investigated. LiSrBO3：Ce3＋,Eu2＋ phosphor exhibits varied hues from blue to white and eventually to yellow by resonance-type energy transfer from Ce3＋ ion to Eu2＋ ion and tuning the relative proportion of Ce3＋/Eu2＋ properly. Energy transfer mechanism in LiSrBOa：Ce3＋, Eu2＋ phosphor is dominated by the dipole-dipole interaction, and the critical distance of the energy transfer is estimated to be about 2 nm by both spectral overlap and concentration quenching methods. Under UV radiation, white light is generated by coupling 436 and 565nm emission bands attributed to Ce3＋ and Eu2＋ radiations, respectively.

First principles investigation of protactinium-based oxide-perovskites for flexible opto electronic devices

The structural,elastic,mechanical,electronic,and optical properties of KPaO_3 and RbPaO_3 compounds are investigated from first-principles calculations by using the WIEN2 k code in the frame of local density approximation（LDA） and generalized gradient approximation（GGA）.The calculated ground state quantities,such as lattice constant（α_0）,ground state energy（E）,bulk modulus（S）,and their pressure derivative（B_p） are in reasonable agreement with the present analytical and previous theoretical results and available experimental data.Based on several elastic and mechanical parameters,the structural stability,hardness,stiffness and the brittle and ductile behaviors are discussed,which reveal that protactiniumbased oxide series of perovskites is mechanically stable and possesses weak resistance to shear deformation compared with resistance to unidirectional compression while flexible and covalent behaviors are dominated in them.The analysis of band profile through Trans-Blaha modified Becke-Johnson（TB-mBJ） potential highlights the underestimation of bandgap with traditional density functional theory（DFT） approximation.Specific contribution of electronic states is investigated by means of total and partial density of states and it can be evaluated that both compounds are（Γ-Γ） direct bandgap semiconductors.All fundamental optical properties are analyzed while attention is paid to absorption and reflection spectra to explore extensive absorptions and reflections of these compounds in high frequency regions.The present method represents an influential approach to calculating the whole set of elastic,mechanical,and opto-electronic parameters,which would conduce to the understanding of various physical phenomena and empower the device engineers to implement these materials in flexible opto-electronic applications.

Cryptanalysis and Improvement of Quantum Secret Sharing Protocol between Multiparty and Multiparty with Single Photons and Unitary Transformations

In a recent paper [Yan F L et al. Chin.Phys.Lett. 25（2008）1187], a quantum secret sharing the protocol between multiparty and multiparty with single photons and unitary transformations was presented. We analyze the security of the protocol and find that a dishonest participant can eavesdrop the key by using a special attack. Finally, we give a description of this strategy and put forward an improved version of this protocol which can stand against this kind of attack.

新工科理念下学科交叉机械电子工程人才培养模式探索

围绕新时代国家科技发展对复合型人才的需求,基于拥有的学科资源和学科特色,文中提出了新工科理念下的机械化、信息化和智能化三化融合的学科交叉人才培养体系,详细介绍了“三化融合”的人才培养目标及人才培养模式。实践证明,“三化融合”的机械电子工程专业教学创新人才培养模式可以有效提升复合型人才培养的质量。

基于积分滑模的电子机械制动系统ABS控制

为解决传统制动系统逻辑门限控制存在逻辑复杂且难以充分利用路面附着的问题,以及ABS存在的非线性、不确定性问题,提出了一种基于路面识别的ABS控制策略应用在电子机械制动系统。首先,通过Simulink建立1/4车辆制动模型;其次,分析附着系数在不同路面存在的差异性以及附着系数和车轮角减速度的变化规律,设计了一种高效且准确的路面识别算法来估算当前路面的最佳滑移率;最后,设计了基于积分滑模控制的ABS控制策略跟踪最佳滑移率。仿真结果表明:路面识别算法识别响应快、识别准确度高;所设计的ABS控制策略能够稳定跟踪最佳滑移率,对不同路面工况具有较强的适应性。与基于逻辑门限控制的传统制动系统相比,在单路面条件下制动时间减少了11.89%,制动距离缩短了12.7%;在变路面条件下制动时间减少了17.8%,制动距离缩短了19.9%。

一种光机电一体化增量式光电编码器设计

为解决现有轴柄式控制增量编码器损耗高、寿命短、抗振动能力差、可靠性低等问题,介绍一种光机电一体化的增量式光电编码器设计方案,包括32内花瓣轴套和可伸缩滚珠定位、Z型遮光盘设计和红外光敏OC开路输出电路等创新设计。通过精密结构设计和材料选择,实现了高精度32档位电信号转换。采用三维建模和有限元分析进行了结构可靠性验证。通过与国外同类产品的技术指标对比,验证数据和所达到的环境适应能力。本研究在性能、结构和成本等方面皆有优势,应用前景广阔。

大口径热不敏星敏感器光机设计与分析

为满足大口径长焦距星敏感器的需求,对一种大口径热不敏星敏感器进行光机设计,根据指标要求,对热不敏系统进行光机热集成分析。使用MSC.Patran软件对主次镜结构施加温度载荷,计算出主次镜结构的热弹性变形,先利用MSC.Nastran软件计算热变形后节点的刚体位移,再利用Sigft光机接口软件分析得到变形后主次镜表面的Zernike多项式系数。将结果导入Zemax中,预判镜片面型变化以及刚体位移对弥散斑、光轴漂移量及波像差的影响。最后通过在20℃±5℃的温度范围内装调测试验证了系统性能满足指标要求以及光机热集成分析的准确性,提供了一套准确快捷的光机热集成分析流程。

农机农艺融合的高效割胶技术优化设计与应用

割胶是橡胶树收获胶乳的重要途径,便携式机械化割胶是实现产业升级和节本增效的途径之一。为进一步提高机械割胶效果,根据采胶生理特殊性、割胶工况复杂多变性、橡胶树收获物胶乳黏弹特性、橡胶树生长差异性、割胶形式多样性等农机农艺融合问题对割胶机械的设计需求,优化设计便携式电动割胶装备的切割刀片、电子调速器、导向器等零部件。优化结果表明:采用刃高≥10 mm的刀片割胶,可以轻松切断旧胶线;电子调速器在电机转速为3 201~8 459 r/min区间调速时,灵敏度高,单次割胶轨迹连续平稳;导向器形状从“L”型优化为“T”型,减少旧胶线对割胶机械的干预。优化后的技术,提高便携式割胶机械对割胶农艺的适应性,降低操作技术难度和单株割胶时间,胶工更容易快速掌握。

高压下三元层状氮化物M_(2)AlN(M=Ti,Zr)的结构、力学、电子及光学性质的第一性原理研究

本文采用基于密度泛函理论的第一性原理计算方法,优化了三元层状氮化物M_(2)AlN(M=Ti,Zr)的几何结构,研究了高压下三元层状氮化物M_(2)AlN(M=Ti,Zr)的结构、力学、电子及光学性质。结构和力学性质研究表明,Ti_(2)AlN的压缩性优于Zr_(2)AlN,弹性常数证实了高压下的力学稳定性。延展性和弹性各向异性随着压力的增加而增强,Zr_(2)AlN对压力更加敏感。电子性质研究表明,两种三元层状氮化物均表现为金属性,共价性随着压力的增加而增强。Ti_(2)AlN和Zr_(2)AlN的多晶体和不同轴上的静态介电函数ε_(1)(0)以及静态折射率n(0)表明光学性质存在较低的各向异性,两种三层状氮化物都表现出较强的光吸收能力和反射率。本文的理论研究阐述了高压下三元层状氮化物Ti_(2)AlN和Zr 2AlN的相关性质,为今后的实验研究提供了比较可靠的理论依据。

Sr_(2)ReNbO_(6)双钙钛矿电子结构及性质的第一性原理研究

基于密度泛函理论(DFT),采用Perdew–Burke–Ernzerhof交换关联势的PBEsol–GGA泛函优化Sr_(2)ReNbO_(6)(Re=La,Gd,Lu)双钙钛矿晶体的结构,获得最低能量的稳定结构。以优化的结构为模型,计算Sr_(2)ReNbO_(6)(Re=La,Gd,Lu)晶体的能带结构和态密度(DOS)、复介电函数ε(ω)、折射率n(ω)、反射率R(ω)及消光系数k(ω)等光学特性指标,分析入射光子能量对材料光学特性的影响;计算Sr_(2)ReNbO_(6)(Re=La,Gd,Lu)晶体的弹性常数Cij,并由Cij进一步获得杨氏模量(Y)、体积模量(B)、剪切模量(G)和泊松比(χ)等机械特性指标,分析晶体结构对材料机械特性的影响。结果表明:优化双钙钛矿晶体结构获得的晶格常数与现有的实验值吻合较好;Sr_(2)ReNbO_(6)(Re=La,Gd,Lu)材料的能带结构呈现半导体特性,其中立方结构的Sr_(2)LaNbO_(6)带隙宽度为3.12 eV,且为直接带隙,而单斜结构的Sr_(2)GdNbO_(6)和Sr_(2)LuNbO_(6)为间接带隙,带隙宽度分别为3.25,3.29 eV;Sr_(2)ReNbO_(6)(Re=La,Gd,Lu)的最大反射率R(ω)分别为32.8%,29.3%,33.0%,在紫外区域存在较大的吸收系数;Sr_(2)ReNbO_(6)(Re=La,Gd,Lu)的泊松比χ分别为0.27,0.28,0.27,均位于0.25附近,该系列材料的原子更倾向于以离子键的形式结合,表现出一定的柔韧性。