检索结果-南通市图书馆

On a New Hybrid Estimator for the Central Mean Space

在线全文

学校读者我要写书评

暂无评论

Journal of Systems Science & Complexity 2017年第1期30卷 111-121页

作者： xia qi DONG Yuexiao Department of Statistical Science Temple University USA.

Existing estimators of the central mean space are known to have uneven performances across different types of link functions. By combining the strength of the ordinary least squares and the principal Hessian directions, the authors propose a new hybrid estimator that successfully recovers the central mean space for a wide range of link functions. Based on the new hybrid estimator, the authors further study the order determination procedure and the marginal coordinate test. The superior performance of the hybrid estimator over existing methods is demonstrated in extensive simulation studies.

关键词： Marginal coordinate test order determination ordinary least squares principal Hessiandirections sufficient dimension reduction.

Buckling optimization of curvilinear fiber-reinforced composite structures using a parametric level set method

在线全文

学校读者我要写书评

暂无评论

Frontiers of Mechanical Engineering 2024年第1期19卷 149-160页

作者： Ye TIAN Tielin SHI qi xia State Key Laboratory of Intelligent Manufacturing Equipment and Technology Huazhong University of Science and TechnologyWuhan 430074China

Owing to their excellent performance and large design space,curvilinear fiber-reinforced composite structures have gained considerable attention in engineering fields such as aerospace and *** addition to the stiffness and strength of such structures,their stability also needs to be taken into account in the *** study proposes a level-set-based optimization framework for maximizing the buckling load of curvilinear fiber-reinforced composite *** the proposed method,the contours of the level set function are used to represent fiber *** a composite laminate with a certain number of layers,one level set function is defined by radial basis functions and expansion coefficients for each ***,the fiber angle at an arbitrary point is the tangent orientation of the contour through this *** the finite element of buckling,the stiffness and geometry matrices of an element are related to the fiber angle at the element *** study considers the parallelism constraint for fiber *** the sensitivity calculation of the objective and constraint functions,the method of moving asymptotes is utilized to iteratively update all the expansion coefficients regarded as design *** numerical examples under different boundary conditions are given to validate the proposed *** show that the optimized curved fiber paths tend to be parallel and equidistant regardless of whether the composite laminates contain holes or ***,the buckling resistance of the final design is significantly improved.

关键词： buckling optimization curvilinear fiber composite structure level set method manufacturing constraint

Filters for manufacturability in design optimization of variable stiffness composites

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2021年第4期34卷 153-159页

作者： Ye TIAN Yuhang HUO Tielin SHI qi xia State Key Laboratory of Digital Manufacturing Equipment and Technology Huazhong University of Science and TechnologyWuhan 430074China State Key Laboratory of Structural Analysis for Industrial Equipment Dalian University of TechnologyDalian 116024China

In the design optimization of variable stiffness composites,manufacturing constraints imposed by the automated fiber placement technology must be *** the present paper,two filters are proposed to address this issue,and they are incorporated into the Shepard interpolation-based design optimization framework developed in our previous *** fiber angle arrangement of a composite is represented by a continuous function that interpolates fiber angles at scattered design *** filters are appointed for each design point to deal with two typical manufacturing constraints,i.e.,fiber curvature and gap/*** each design point,the sensitivity is first filtered in a rectangular region around this point,and by this means the fiber curvature is controlled;then in another rectangular region around this design point,the filtered sensitivities are averaged,and the result is used to update the corresponding design *** numerical examples are investigated,and the results show that the proposed method is effective.

关键词： Composite laminates Design optimization Fiber angle Filter Manufacturing constraints

Photometric investigation and orbital period analyses of the W UMa binaries FP Lyn, FV CVn and V354 UMa

在线全文

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2019年第7期19卷 103-114页

作者： Raul Michel qi-qi xia Jesus Higuera1 Observatorio Astronomico Nacional Instituto de AstronomíaUniversidad Nacional Autońoma de MéxicoApartado Postal 877EnsenadaB.C.22830Mexico Shandong Provincial Key Laboratory of Optical Astronomy and Solar-Terrestrial Environment Institute of Space SciencesShandong UniversityWeihai 264209China

New light curves and photometric solutions of FP Lyn,FV CVn and V354 UMa are *** found that these three systems are W-subtype shallow contact *** addition,it is obvious that the light curves of FP Lyn and V354 UMa are ***,a hot spot was added on the primary star of FP Lyn and a dark spot was added on the secondary star of V354 *** the same time,we added a third light to the photometric solution of FP Lyn for the final *** obtained mass ratios and fill-out factors are q = 1.153 and f = 13.4% for FP Lyn,q = 1.075 and f = 4.6% for FV CVn,and q = 3.623 and f = 10.7% for V354 UMa *** investigations of orbital period for these three systems indicate that the periods are *** Lyn and V354 UMa were discovered to have secularly increasing components with rates of dp/dt = 4.19 ×10^-7 dyr^-1 and dp/dt = 7.70 ×10^-7 dyr^-1 respectively,which are feasibly caused by conservative mass transfer from the less massive component to the more massive *** addition,some variable components were discovered for FV CVn,including a rate of dp/dt =-1.13 ×10^-6 dyr^-1 accompanied by a cyclic oscillation with amplitude and period of 0.0069 d and 10.65 yr *** most likely explanation for the long-term decrease is angular momentum *** existence of an additional star is the most plausible explanation for the periodic variation.

关键词： stars:binaries:close stars:binaries:eclipsing stars:individual (FP Lyn, FV CVn and V354 UMa)

A Parameter-Free Approach to Determine the Lagrange Multiplier in the Level Set Method by Using the BESO

在线全文

学校读者我要写书评

暂无评论

Computer Modeling in Engineering & Sciences 2021年第7期128卷 283-295页

作者： Zihao Zong Tielin Shi qi xia The State Key Laboratory of Digital Manufacturing Equipment and Technology Huazhong University of Science and TechnologyWuhanChina

A parameter-free approach is proposed to determine the Lagrange multiplier for the constraint of material volume in the level set *** is inspired by the procedure of determining the threshold of sensitivity number in the BESO *** first computes the difference between the volume of current design and the upper bound of ***,the Lagrange multiplier is regarded as the threshold of sensitivity number to remove the redundant *** examples proved that this approach is effective to constrain the *** importantly,there is no parameter in the proposed approach,which makes it convenient to *** addition,the convergence is stable,and there is no big oscillation.

关键词： Lagrange multiplier threshold of sensitivity BESO method level set method topology optimization

An M-VCUT level set-based data-driven model of microstructures and optimization of two-scale structures

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Frontiers of Mechanical Engineering 2024年第4期19卷 73-86页

作者： Minjie SHAO Tielin SHI qi xia State Key Laboratory of Intelligent Manufacturing Equipment and Technology Huazhong University of Science and TechnologyWuhan 430074China

The optimization of two-scale structures can adapt to the different needs of materials in various regions by reasonably arranging different microstructures at the macro scale,thereby considerably improving structural ***,a multiple variable cutting(M-VCUT)level set-based data-driven model of microstructures is presented,and a method based on this model is proposed for the optimal design of two-scale *** geometry of the microstructure is described using the M-VCUT level set method,and the effective mechanical properties of microstructures are computed by the homogenization ***,a database of microstructures containing their geometric and mechanical parameters is *** two sets of parameters are adopted as input and output datasets,and a mapping relationship between the two datasets is established to build the data-driven model of *** the optimization of two-scale structures,the data-driven model is used for macroscale finite element and sensitivity *** efficiency of the analysis and optimization of two-scale structures is improved because the computational costs of invoking such a data-driven model are much smaller than those of homogenization.

关键词： two-scale structure structural optimization M-VCUT level set homogenization radial basis function data-driven

A Pulsar Wind Nebula Origin of the Ultra-high-energy Source 1LHAASO J1929+1846

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2023年第10期23卷 218-223页

作者： qi xia Lian-Cheng Zhou Jun Fang Department of Astronomy Yunnan UniversityKunming 650091China

1LHAASO J1929+1846 is one of the ultra-high-energy(UHE,E>0.1 PeV)sources in the first catalog ofγ-ray sources detected by the Large High Altitude Air Shower *** has been detected fluxes at 3 TeV for2.48±0.11×10^(-13)TeV^(-1)cm^(-2)s^(-1)with the Water Cherenkov Detector Array and at 50 TeV for0.64±0.06×10^(-16)TeV^(-1)cm^(-2)s^(-1)with the Kilometer Squared Array,but the origin of its UHE emission remains *** pulsar wind nebula(PWN)G54.1+0.3,which is powered by the pulsar PSR 1930+1852with a period of 136 ms and it is detected within a 0°.29 region around the centroid of 1LHAASO J1929+*** explore whether G54.1+0.3 is capable of producing the UHE radiation of 1LHAASO J1929+***,the data with Fermi Large Area Telescope for the PWN is analyzed to obtain the GeV ***,the multiband nonthermal fluxes for the nebula are investigated based on a one-zone time-dependent *** the model,we assume the spin-down energy of the pulsar is persistently injected into particles(electrons and positrons)and magnetic field in the PWN,and these high-energy particles produce multiband non-thermal radiation from radio toγ-rays via synchrotron radiation and inverse Compton *** reproduce the spectral energy distribution of PWN G54.1+0.3 with reasonable *** result indicates that the UHEγ-ray source 1LHAASO J1929+1846possibly originates from PWN G54.1+0.3.

关键词： radiation mechanisms:non-thermal ISM:supernova remnants gamma-rays:stars

Sensitivity Analysis of a Bioinspired Refractive Index Based Gas Sensor

在线全文

学校读者我要写书评

暂无评论

Journal of Bionic Engineering 2011年第3期8卷 323-334页

作者： Yang Gao qi xia Guanglan Liao Tielin Shi Wuhan National Laboratory for Optoelectronic Wuhan 430074 P. R. Chinao State Key Laboratory of Digital Manufacturing Equipment and Technology Huazhong University of Science and Technology Wuhan 430074 P. R. China

It was found out that the change of refractive index of ambient gas can lead to obvious change of the color of Morpho butterfly＇s wing. Such phenomenon has been employed as a sensing principle for detecting gas. In the present study, Rigorous Coupled-Wave Analysis （RCWA） was described briefly, and the partial derivative of optical reflection efficiency with respect to the refractive index of ambient gas, i.e., sensitivity of the sensor, was derived based on RCWA. A bioinspired grating model was constructed by mimicking the nanostructure on the ground scale of Morpho didius butterfly＇s wing. The analytical sensitivity was verified and the effect of the grating shape on the reflection spectra and its sensitivity were discussed. The results show that by tuning shape parameters of the grating, we can obtain desired reflection spectra and sensitivity, which can be applied to the design of the bioinspired refractive index based gas sensor.

关键词： bioinspired gas sensor sensitivity diffraction gratings refractive index subwavelength structures

The relationship between farm size and fertilizer use efficiency:Evidence from China

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Integrative Agriculture 2022年第1期21卷 273-281页

作者： ZHU Wei qi Li-xia WANG Rui-mei College of Economics and Management China Agricultural UniversityBeijing 100083P.R.China School of Public Administration North China University of Water Resources and Electric PowerZhengzhou 450045P.R.China

Low fertilizer use efficiency is commonly found in China’s agriculture sector. It is critical to understand the drivers of fertilizer use in order to increase fertilizer use efficiency(FUE). The purpose of this paper is to investigate the relationship between farm size and FUE based on farm-level data in China. The results suggest a positive farm size–FUE relationship. The estimated elasticities of farm size for rice, maize, wheat–maize, and rice–maize are similar, and the average elasticity of farm size is around 0.2. Statistically, a 1% increase in farm size is associated with a 0.2%increase in FUE. The positive effect of farm size on FUE is not due to the increase in yield, but the reduction in fertilizer use while keeping yield largely unchanged. The findings suggest that promoting the expansion of farm size may increase FUE, and thus reduce environmental pollution caused by fertilizer overuse.

关键词： farm size farm scale fertilizer use efficiency positive relationship