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Laser interference fabrication of large-area functional periodic structure surface

Lei WANG, Zi-Han WANG, Yan-Hao YU, Hong-Bo SUN

《机械工程前沿（英文）》 2018年 第13卷 第4期   页码 493-503 doi: 10.1007/s11465-018-0507-9

摘要：

Functional periodic structures have attracted significant interest due to their natural capabilities in regulating surface energy, surface effective refractive index, and diffraction. Several technologies are used for the fabrication of these functional structures. The laser interference technique in particular has received attention because of its simplicity, low cost, and high-efficiency fabrication of large-area, micro/nanometer-scale, and periodically patterned structures in air conditions. Here, we reviewed the work on laser interference fabrication of large-area functional periodic structures for antireflection, self-cleaning, and superhydrophobicity based on our past and current research. For the common cases, four-beam interference and multi-exposure of two-beam interference were emphasized for their setup, structure diversity, and various applications for antireflection, self-cleaning, and superhydrophobicity. The relations between multi-beam interference and multi-exposure of two-beam interference were compared theoretically and experimentally. Nanostructures as a template for growing nanocrystals were also shown to present future possible applications in surface chemical control. Perspectives on future directions and applications for laser interference were presented.

关键词： laser interference     four-beam interference     multi-exposure of two-beam interference     additive fabrication    

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Cellulose aerogels decorated with multi-walled carbon nanotubes: preparation, characterization, and applicationfor electromagnetic interference shielding

Jian LI,Caichao WAN

《农业科学与工程前沿（英文）》 2015年 第2卷 第4期   页码 341-346 doi: 10.15302/J-FASE-2015082

摘要： Electromagnetic wave pollution has attracted extensive attention because of its ability to affect the operation of electronic machinery and endanger human health. In this work, the environmentally-friendly hybrid aerogels consisting of cellulose and multi-walled carbon nanotubes (MWCNTs) were fabricated. The aerogels have a low bulk density of 58.17 mg·cm . The incorporation of MWCNTs leads to an improvement in the thermal stability. In addition, the aerogels show a high electromagnetic interference (EMI) value of 19.4 dB. Meanwhile, the absorption-dominant shielding mechanism helps a lot to reduce secondary radiation, which is beneficial to develop novel eco-friendly EMI shielding materials.

关键词： cellulose aerogels     carbon nanotubes     electromagnetic interference shielding     composites    

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Aerodynamic interference effects and mitigation measures on vortex-induced vibrations of two adjacent

Xiaoliang MENG, Ledong ZHU, Zhenshan GUO

《结构与土木工程前沿（英文）》 2011年 第5卷 第4期   页码 510-517 doi: 10.1007/s11709-011-0129-3

摘要： By examining the two neighboring Haihe Bridges with semi- and full-closed bridge decks, the aerodynamic interference between the two decks on the vortex-induced vibration (VIV) and the corresponding aerodynamic mitigation measures are investigated via a series of wind tunnel tests with a spring-suspended sectional model aided with computational fluid dynamics (CFD) method. The results show that the VIV responses of both bridges can be significantly affected by the aerodynamic interference and that the extent of the influence varies with the shapes of the windward and leeward decks. The VIV amplitudes of the windward bridge are often fairly close to those of the single bridge. However, those of the leeward bridge are magnified substantially by aerodynamic interference if the same structural and aerodynamic configurations are adopted for the two bridges. Otherwise, the VIV responses are not significantly increased and may even be reduced by the aerodynamic interference if different configurations are employed for the two bridges. Furthermore, an effective combined measure of adding wind barriers and sharpening the wind fairing noses of the two box decks is presented for mitigating both the vertical and torsional VIV responses of the windward and leeward bridges.

关键词： separated parallel decks     vortex-induced vibration     aerodynamic interference     aerodynamic mitigation measure     semi-closed box deck     full-closed box deck    

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Adaptive robust beamformer formulti-pair two-way relay networks with imperfect channel state information

Jin WANG,Feng SHU,Ri-qing CHEN,Yu-di CUI,Yu CHEN,Jun LI

《信息与电子工程前沿（英文）》 2016年 第17卷 第3期   页码 265-280 doi: 10.1631/FITEE.1500134

摘要： In wideband multi-pair two-way relay networks, the performance of beamforming at a relay station (RS) is intimately related to the accuracy of the channel state information (CSI) available. The accuracy of CSI is determined by Doppler spread, delay between beamforming and channel estimation, and density of pilot symbols, including transmit power of pilot symbols. The coefficient of the Gaussian-Markov CSI error model is modeled as a function of CSI delay, Doppler spread, and signal-to-noise ratio, and can be estimated in real time. In accordance with the real-time estimated coefficients of the error model, an adaptive robust maximum signal-to-interferenceand- noise ratio (Max-SINR) plus maximum signal-to-leakage-and-noise ratio (Max-SLNR) beamformer at an RS is proposed to track the variation of the CSI error. From simulation results and analysis, it is shown that: compared to existing non-adaptive beamformers, the proposed adaptive beamformer is more robust and performs much better in the sense of bit error rate (BER); with increase in the density of transmit pilot symbols, its BER and sum-rate performances tend to those of the beamformer of Max-SINR plus Max-SLNR with ideal CSI.

关键词： Multi-pair two-way relay     Adaptive robust beamformer     Channel state information (CSI)     Maximum signal-to-interference-and-noise ratio (Max-SINR)     Maximum signal-to-leakage-and-noise ratio (Max-SLNR)    

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Proposing two new methods to decrease lateral-torsional buckling in reduced beam section connections

Samira EBRAHIMI; Nasrin BAKHSHAYESH EGHBALI; Mohammad Mehdi AHMADI

《结构与土木工程前沿（英文）》 2022年 第16卷 第12期   页码 1581-1598 doi: 10.1007/s11709-022-0886-1

摘要： Reduced web section (RWS) connections can prevent lateral-torsional buckling and web local buckling experienced by reduced beam section (RBS) connections. In RWS connections, removing a large portion of web can result in shear demand intolerance induced to plastic hinge region. The present study aims to resolve the problems of RBS and RWS connections by proposing two new connections: (1) RBS with stiffener (RBS-ST) and (2) RBS with reduced web (RW-RBS) connections. In the first connection (RBS-ST), a series of stiffeners is connected to the beam in the reduced flange region, while the second connection (RW-RBS) considers both a reduction in flanges and a reduction in web. Five beam-to-column joints with three different connections, including RBS, RBS-ST, and RW-RBS connections were considered and simulated in ABAQUS. According to the results, RBS-ST and RW-RBS connections can decrease or even eliminate lateral-torsional buckling and web local buckling in RBS connection. It is important to note that RW-RBS connection is more effective in long beams with smaller shear demands in the plastic hinge region. Moreover, results showed that RBS and RW-RBS connections experienced strength degradation at 4% to 5% drift, while no strength degradation was observed in RBS-ST connection until 8% drift.

关键词： RBS     RBS-ST     RW-RBS     lateral-torsional buckling     cyclic performance    

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Processing parameter optimization of fiber laser beam welding using an ensemble of metamodels and MOABC

《机械工程前沿（英文）》 2022年 第17卷 第4期 doi: 10.1007/s11465-022-0703-5

摘要： In fiber laser beam welding (LBW), the selection of optimal processing parameters is challenging and plays a key role in improving the bead geometry and welding quality. This study proposes a multi-objective optimization framework by combining an ensemble of metamodels (EMs) with the multi-objective artificial bee colony algorithm (MOABC) to identify the optimal welding parameters. An inverse proportional weighting method that considers the leave-one-out prediction error is presented to construct EM, which incorporates the competitive strengths of three metamodels. EM constructs the correlation between processing parameters (laser power, welding speed, and distance defocus) and bead geometries (bead width, depth of penetration, neck width, and neck depth) with average errors of 10.95%, 7.04%, 7.63%, and 8.62%, respectively. On the basis of EM, MOABC is employed to approximate the Pareto front, and verification experiments show that the relative errors are less than 14.67%. Furthermore, the main effect and the interaction effect of processing parameters on bead geometries are studied. Results demonstrate that the proposed EM-MOABC is effective in guiding actual fiber LBW applications.

关键词： laser beam welding     parameter optimization     metamodel     multi-objective    

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Scaled boundary finite element method with exact defining curves for two-dimensional linear multi-field

Jaroon RUNGAMORNRAT, Chung Nguyen VAN

《结构与土木工程前沿（英文）》 2019年 第13卷 第1期   页码 201-214 doi: 10.1007/s11709-018-0488-0

摘要： This paper presents an efficient and accurate numerical technique based upon the scaled boundary finite element method for the analysis of two-dimensional, linear, second-order, boundary value problems with a domain completely described by a circular defining curve. The scaled boundary finite element formulation is established in a general framework allowing single-field and multi-field problems, bounded and unbounded bodies, distributed body source, and general boundary conditions to be treated in a unified fashion. The conventional polar coordinates together with a properly selected scaling center are utilized to achieve the exact description of the circular defining curve, exact geometry of the domain, and exact spatial differential operators. Standard finite element shape functions are employed in the discretization of both trial and test functions in the circumferential direction and the resulting eigenproblem is solved by a selected efficient algorithm. The computational performance of the implemented procedure is then fully investigated for various scenarios to demonstrate the accuracy in comparison with standard linear elements.

关键词： multi-field problems     defining curve     exact geometry     general boundary conditions     SBFEM    

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Semi-analytical approach for free vibration analysis of cracked beams resting on two-parameter elastic

null

《机械工程前沿（英文）》 2014年 第9卷 第2期   页码 191-202 doi: 10.1007/s11465-014-0293-y

摘要：

In present study, free vibration of cracked beams resting on two-parameter elastic foundation with elastically restrained ends is considered. Euler-Bernoulli beam hypothesis has been applied and translational and rotational elastic springs in each end considered as support. The crack is modeled as a mass-less rotational spring which divides beam into two segments. After governing the equations of motion, the differential transform method (DTM) has been served to determine dimensionless frequencies and normalized mode shapes. DTM is a semi-analytical approach based on Taylor expansion series that converts differential equations to recursive algebraic equations. The DTM results for the natural frequencies in special cases are in very good agreement with results reported by well-known references. Also, the DTM procedure yields rapid convergence beside high accuracy without any frequency missing. Comprehensive studies to analyze the effects of crack location, crack severity, parameters of elastic foundation and boundary conditions on dimensionless frequencies as well as effects of elastic boundary conditions on cracked beams mode shapes are carried out and some problems handled for first time in this paper. Since this paper deals with general problem, the derived formulation has capability for analyzing free vibration of cracked beam with every boundary condition.

关键词： free vibration     cracked beam     elastic foundation     restrained ends     differential transform method    

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Solar photocatalytic decomposition of two azo dyes on multi-walled carbon nanotubes (MWCNTs)/TiO 2 composites

Huilong WANG, Shuqin LIU, Hui WANG, Wenfeng JIANG,

《环境科学与工程前沿（英文）》 2010年 第4卷 第3期   页码 311-320 doi: 10.1007/s11783-010-0237-7

摘要： Multi-walled carbon nanotubes (MWCNTs)/TiO composite photocatalysts with high photoactivity were prepared by sol-gel process and further characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FT-IR), and UV-vis absorption spectra. Compared to pure TiO, the combination of MWCNTs with titania could cause a significant absorption shift toward the visible region. The photocatalytic performances of the MWCNTs/TiO composite catalysts were evaluated for the decomposition of Reactive light yellow K-6G (K-6G) and Mordant black 7 (MB 7) azo dyes solution under solar light irradiation. The results showed that the addition of MWCNTs enhanced the adsorption and photocatalytic activity of TiO for the degradation of azo dyes K-6G and MB 7. The effect of MWCNTs content, catalyst dosage, pH, and initial dye concentration were examined as operational parameters. The kinetics of photocatalytic degradation of two dyes was found to follow a pseudo-first-order rate law. The photocatalyst was used for seven cycles with photocatalytic degradation efficiency still higher than 98%. A plausible mechanism is also proposed and discussed on the basis of experimental results.

关键词： sol-gel     multi-walled carbon nanotubes (MWCNTs)/TiO2 composite     photocatalysis     azo dye     solar irradiation    

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Elastoplastic frictional contact problem study on interference fits of compressor

ZHANG Hongwu, WU Changhua, LIAO Aihua

《能源前沿（英文）》 2008年 第2卷 第3期   页码 313-319 doi: 10.1007/s11708-008-0026-1

摘要： The FE parametric quadratic programming (PQP) method developed from the parametric variational principle (PVP) was used for the analysis of the stress distribution of the 3D elastoplastic frictional contact of an impeller-shaft sleeve-shaft. A locomotive-type turbocharger compressor with 24 blades under combined centrifugal and interference-fit loading was considered in the numerical analysis. The solution of elastoplastic frictional contact problems belongs to unspecified boundary problems where the interaction between two kinds of nonlinearities should occur. To save time in the numerical computation, a multi-substructure technique was adopted in the structural modeling. The effect of fit tolerance, wall thickness of the shaft sleeve, and rotational speed on the contact stress was discussed in detail in the numerical computation. To decrease the difficulty of the assembly process and ensure the safety of the working state, the amount of interference between the shaft sleeve and shaft by press-fitting should be controlled strictly to avoid the rapid increase of contact stress. The numerical results show that the algorithm has high accuracy and good convergence. The study can be referred to in deciding the proper fit tolerance and improving the design and manufacturing technology of compressor impellers.

关键词： computation     thickness     interference-fit     interference     unspecified    

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有固相析出的多效两段蒸发系统模型与过程模拟

李玲,阮奇

《中国工程科学》 2008年 第10卷 第10期   页码 54-60

摘要：

建立了带有冷凝水闪蒸的有固相析出的多效两段蒸发系统的常规设计数学模型，模型将系统的相平衡关系用回归式表达，使模型可以用计算机编程求解，避免了手工计算结合查相图的烦琐的计算过程；利用矩阵方程具有结构清晰和高度模块化的特点，将系统的物料衡算和热量衡算方程组写成矩阵方程的形式，只要保留或舍弃矩阵方程中的相关块矩阵，模型就能代表没有冷凝水闪蒸或没有固相析出的多效两段蒸发系统常规设计模型；采用迭代法结合矩阵法来求解模型，算例表明，冷凝水闪蒸对多效两段蒸发系统是有效的节能措施，算法收敛速度快、收敛稳定性好。

关键词： 固相析出     多效两段蒸发数学模型     冷凝水闪蒸    

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Long-term exposure to air pollution and cerebrovascular disease: findings from Beijing Health Management

《环境科学与工程前沿（英文）》 2023年 第17卷 第7期 doi: 10.1007/s11783-023-1684-2

摘要：

● This study explored the long-term association by double robust additive models.

关键词： Air pollution     Cerebrovascular disease     Incidence     Long-term exposure     Doubly robust additive model    

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Construction and identification of lentiviral RNA interference vector of rat leptin receptor gene

Zhengjuan LIU, Jie BIAN, Yuchuan WANG, Yongli ZHAO, Dong YAN, Xiaoxia WANG

《医学前沿（英文）》 2009年 第3卷 第1期   页码 57-60 doi: 10.1007/s11684-009-0003-z

摘要： Leptin resistance is a main mechanism of acquired childhood obesity, and the suppression of long form of leptin receptor (OBRb) gene expression in diet-induced obese rats indicates that the down-regulation of OBRb gene expression plays a pivotal role in the mechanism of leptin resistance. The aim of the present study was to construct the lentiviral RNA interference (RNAi) vector of rat OBRb gene and evaluate the effects of siRNA on silencing OBRb gene expression. The target sequence of siRNA-OBRb was designed, and the complementary DNA containing both sense and antisense oligonucleotides was synthesized. After phosphorylation and annealing, these double-stranded DNA was cloned to pRNA-lentivector-VGFP to construct pRNA-Lenti-OBRb-VGFP recombinants with U6-containing promoter, target sequence and Poly III terminator. Then, the products were confirmed by electrophoresis and sequencing analysis, and the effects of RNAi on reducing gene expression were further confirmed by real-time polymerase chain reaction in transfected rat glioma cells expressing OBRb. The target sequence of siRNA-OBRb was successfully cloned to pRNA-lentivector-VGFP, and the RNAi protocol specifically reduced the expression of OBRb mRNA by approximately 80% compared with controls in transfected rat glioma cells. The successful construction of rat lentivirus vectors expressing OBRb-specific shRNA may be useful for further investigation .

关键词： receptors     leptin     RNA interference     lentivirus vector    

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面向5G多波束MIMO系统应用的基于先进LTCC封装的39 GHz双信道收发机芯片组 Aticle

余益明, 陈志林, 赵晨曦, 刘辉华, 吴韵秋, 尹文言, 康凯

《工程（英文）》 2023年 第22卷 第3期   页码 125-140 doi: 10.1016/j.eng.2022.04.023

摘要：

本文介绍了一种用于5G多输入多输出（MIMO）应用的39 GHz收发机前端芯片组。每个芯片包括两个可变增益变频信道，可以支持两个同时独立的波束。该芯片还集成了一个本地振荡器链和数字模块，用于多芯片的扩展和增益状态控制。为了提高射频性能，针对前端系统中的关键构建模块提出了几种电路级改进技术。此外，还开发了先进的低温共烧陶瓷工艺，用于封装39 GHz双信道收发机芯片组，实现了低封装损耗和两个发射（TX）/接收（RX）信道之间的高隔离。通过进行芯片级和系统封装（SIP）级的测量，展示了收发机芯片组的性能。测量特性表明，TX SIP 提供11 dB 的最大增益和10 dBm饱和输出功率，而RX SIP实现52 dB的最大增益，5.4 dB噪声系数和7.2 dBm输出1 dB压缩点。收发机的单信道通信链路测试显示，对于64 次正交幅度调制（QAM），误差矢量幅度（EVM）为3.72%，频谱效率为3.25 位⋅s−1⋅ Hz−1。对于1 m距离内的256-QAM 调制，EVM为3.76%，频谱效率为3.9 位⋅s−1⋅Hz−1。在该芯片组的基础上，还开发了39 GHz的多波束原型，用于执行5G毫米波应用的MIMO操作。用于单流和双流传输的空中通信链路表明，多波束原型可以覆盖5~150 m的距离，具有相当的吞吐量。

关键词： 5G     多波束     多输入多输出     毫米波     收发机     无线通信    

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多径环境下脉冲超宽带系统的传输性能分析

林迪,沙学军,吴宣利,张乃通

《中国工程科学》 2009年 第11卷 第2期   页码 75-81

摘要：

为分析多径环境下脉冲超宽带跳时多址系统的传输性能，通过研究IEEE802.4.53a工作组给出的多 径信道参考模型，提出了一个同时存在符号间干扰、符号内多径干扰和多用户干扰的跳时超宽带系统相干解 调的性能分析模型，分别得到了符号内多径干扰、符号间干扰和多用户干扰的方差，且推导得到了系统的误 比特率计算公式，并用计算机仿真验证了公式的有效性。通过计算相邻多径的平均间隔，论证了符号内脉冲 自身多径的干扰是不可忽略的。在不同的信道环境下，以一定误码率要求作为衡量标准，比较了单用户系统 中仅考虑符号间干扰和同时考虑符号内多径干扰及符号间干扰的用户最高传输速率，并分析了多用户系统 中接入不同用户数时对应的平均传输速率的上限。

关键词： 超宽带     符号内多径干扰     符号间干扰     多用户干扰     传输性能分析模型    

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标题 作者 时间 类型 操作

Laser interference fabrication of large-area functional periodic structure surface

Lei WANG, Zi-Han WANG, Yan-Hao YU, Hong-Bo SUN

期刊论文

Cellulose aerogels decorated with multi-walled carbon nanotubes: preparation, characterization, and applicationfor electromagnetic interference shielding

Jian LI,Caichao WAN

期刊论文

Aerodynamic interference effects and mitigation measures on vortex-induced vibrations of two adjacent

Xiaoliang MENG, Ledong ZHU, Zhenshan GUO

期刊论文

Adaptive robust beamformer formulti-pair two-way relay networks with imperfect channel state information

Jin WANG,Feng SHU,Ri-qing CHEN,Yu-di CUI,Yu CHEN,Jun LI

期刊论文

Proposing two new methods to decrease lateral-torsional buckling in reduced beam section connections

Samira EBRAHIMI; Nasrin BAKHSHAYESH EGHBALI; Mohammad Mehdi AHMADI

期刊论文

Processing parameter optimization of fiber laser beam welding using an ensemble of metamodels and MOABC

期刊论文

Scaled boundary finite element method with exact defining curves for two-dimensional linear multi-field

Jaroon RUNGAMORNRAT, Chung Nguyen VAN

期刊论文

Semi-analytical approach for free vibration analysis of cracked beams resting on two-parameter elastic

null

期刊论文

Solar photocatalytic decomposition of two azo dyes on multi-walled carbon nanotubes (MWCNTs)/TiO 2 composites

Huilong WANG, Shuqin LIU, Hui WANG, Wenfeng JIANG,

期刊论文

Elastoplastic frictional contact problem study on interference fits of compressor

ZHANG Hongwu, WU Changhua, LIAO Aihua

期刊论文

有固相析出的多效两段蒸发系统模型与过程模拟

李玲,阮奇

期刊论文

Long-term exposure to air pollution and cerebrovascular disease: findings from Beijing Health Management

期刊论文

Construction and identification of lentiviral RNA interference vector of rat leptin receptor gene

Zhengjuan LIU, Jie BIAN, Yuchuan WANG, Yongli ZHAO, Dong YAN, Xiaoxia WANG

期刊论文

面向5G多波束MIMO系统应用的基于先进LTCC封装的39 GHz双信道收发机芯片组

余益明, 陈志林, 赵晨曦, 刘辉华, 吴韵秋, 尹文言, 康凯

期刊论文

多径环境下脉冲超宽带系统的传输性能分析

林迪,沙学军,吴宣利,张乃通

期刊论文