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Static analysis of ultra-thin beams based on a semi-continuum model

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Acta Mechanica Sinica 2011年第5期27卷 713-719页

作者： cheng Li Zhi-Jun Zheng Ji-Lin Yu c.w. lim cAS Key Laboratory of Mechanical Behaviorand Design of Materials University of Science and Technology of China230027 Hefei China Department of Building and construction City University of Hong KongTat Chee Avenue KowloonHong Kong SAR China

A linear semi-continuum model with discrete atomic layers in the thickness direction was developed to investigate the bending behaviors of ultra-thin beams with nanoscale *** theoretical results show that the deflection of an ultra-thin beam may be enhanced or reduced due to different relaxation *** the relaxation coefficient is greater/less than one,the deflection of micro/nano-scale structures is enhanced/reduced in comparison with macro-scale ***,two opposite types of size-dependent behaviors are observed and they are mainly caused by the relaxation *** with the classical continuum model,exact nonlocal stress model and finite element model （FEM） verify the validity of the present semi-continuum *** particular,an explanation is proposed in the debate whether the bending stiffness of a micro/nano-scale beam should be greater or weaker as compared with the macro-scale *** characteristics of bending stiffness are proved to be associated with the relaxation coefficients.

关键词： Bending stiffness · MEMS/NEMS · Relaxation coefficient · Semi-continuum model · Size-dependence

A Discussion on the Physics and Truth of Nanoscales for Vibration of Nanobeams based Nonlocal Elastic Stress Field Theory

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A Discussion on the Physics and Truth of Nanoscales for Vibr...

弹性圆柱壳在轴向冲击载荷和温度耦合作用下的屈曲

第十二届全国非线性振动暨第九届全国非线性动力学和运动稳定性学术会议

作者： c.w. lim Department of Building and construction City University of Hong Kong

Two critical but overlooked issues in the physics of nonlocal elastic stress field theory for nanobeams are discussed: (i) why does the presence of increasing nonlocal effects induce reduced nanostructural stiffness in many, but not consistently for all, cases of study, ie. increasing static deflection, decreasing natural frequency and decreasing buckling load, in virtually all previously published works in this subject (a total of 51 papers known since 2003) although intuition in physics tells otherwise? and (ii) the intriguing conclusion that nanoscale effects are missing in the solutions in many exemplary cases of study for bending of nanobeams. Applying the nonlocal elasticity field theory in nanomechanics and an exact variational principal approach, the exact equilibrium conditions, domain governing differential equation and boundary conditions for vibration of nanobeams are derived for the first time. These new equations and conditions involve essential higher-order terms which are missing in virtually all nonlocal models and analyses in previously published works in statics and dynamics of nonlocal nano-structures. Such negligence of higher-order terms in these works results in misleading nanoscale effects which predicts completely incorrect, reverse trends with respect to what the conclusion of this paper tells. Effectively, for the first time this paper not only discovers the truth of nanoscale, as far as nonlocal elastic stress modelling for nanostructures is concerned, on equilibrium conditions, governing differential equation and boundary conditions but also reveals further the true basic vibration responses for nanobeams with various boundary conditions. It also concludes that the widely accepted equilibrium conditions of nonlocal nanostructures currently are in fact not in equilibrium, but they can be made perfect should the nonlocal bending moment be replaced by an equivalent nonlocal bending moment. The conclusions above are substantiated by other ap

关键词：非局部弹性应力场屈曲载荷纳米结构动力学分析

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计算力学学报 2010年第5期27卷 759-763页

作者：褚洪杰徐新生 c.w.lim 马建青大连理工大学工程力学系工业装备结构分析国家重点实验室大连116024 香港城市大学建筑系

通过引入哈密顿体系,将临界载荷和临界温度及它们所对应的屈曲模态归结为辛体系下的广义本征值和本征解问题。根据辛本征解的正交性和完备性,给出了全部的且独立存在的屈曲模态。数值结果表明,在轴向冲击载荷和温度耦合作用下,弹性圆柱... 详细信息

通过引入哈密顿体系,将临界载荷和临界温度及它们所对应的屈曲模态归结为辛体系下的广义本征值和本征解问题。根据辛本征解的正交性和完备性,给出了全部的且独立存在的屈曲模态。数值结果表明,在轴向冲击载荷和温度耦合作用下,弹性圆柱壳的屈曲呈现出复杂的模式,温度直接影响冲击临界载荷的大小。随着温度的增加,冲击临界荷载降低,最后,文中给出各种条件下的屈曲模态。

关键词：哈密顿体系动态屈曲圆柱壳轴向冲击温度

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轴向冲击下柱形壳局部和整体动力屈曲

钢结构(中英文) 2009年第7期 86-86页

作者： c.w. lim

对轴向受压冲击荷载下,柱形壳局部和整体屈曲进行研究。引进哈密尔顿系统,通过哈密尔顿二元方程,采用4对对偶变量,对系统中的基础问题进行数学描述,并归纳为临界荷载的特征值和特征解问题。通过各自的阶数对屈曲模式进行描述,将其分为两... 详细信息

对轴向受压冲击荷载下,柱形壳局部和整体屈曲进行研究。引进哈密尔顿系统,通过哈密尔顿二元方程,采用4对对偶变量,对系统中的基础问题进行数学描述,并归纳为临界荷载的特征值和特征解问题。通过各自的阶数对屈曲模式进行描述,将其分为两类:短波或局部屈曲以及长波或整体屈曲,得到解析与数值的解决方案并给出了一些规则。

关键词：轴向冲击屈曲模式柱形壳动力屈曲整体屈曲哈密尔顿系统局部屈曲纵向波

Single-cell and spatial omics:exploring hypothalamic heterogeneity

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Neural Regeneration Research 2025年第6期20卷 1525-1540页

作者： Muhammad Junaid Eun Jeong Lee Su Bin lim Department of Biochemistry&Molecular Biology Ajou University School of MedicineSuwonSouth Korea Department of Biomedical Sciences Graduate School of Ajou UniversitySuwonSouth Korea Department of Brain Science Ajou University School of MedicineSuwonSouth Korea

Elucidating the complex dynamic cellular organization in the hypothalamus is critical for understanding its role in coordinating fundamental body functions. Over the past decade, single-cell and spatial omics technologies have significantly evolved, overcoming initial technical challenges in capturing and analyzing individual cells. These high-throughput omics technologies now offer a remarkable opportunity to comprehend the complex spatiotemporal patterns of transcriptional diversity and cell-type characteristics across the entire hypothalamus. current single-cell and single-nucleus RNA sequencing methods comprehensively quantify gene expression by exploring distinct phenotypes across various subregions of the hypothalamus. However, single-cell/single-nucleus RNA sequencing requires isolating the cell/nuclei from the tissue, potentially resulting in the loss of spatial information concerning neuronal networks. Spatial transcriptomics methods, by bypassing the cell dissociation, can elucidate the intricate spatial organization of neural networks through their imaging and sequencing technologies. In this review, we highlight the applicative value of single-cell and spatial transcriptomics in exploring the complex molecular-genetic diversity of hypothalamic cell types, driven by recent high-throughput achievements.

关键词： cellular diversity hypothalamus multi-omics single-cell transcriptomics spatial transcriptomics

Stress analysis of anisotropic thick laminates in cylindrical bending using a semi-analytical approach

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2007年第11期8卷 1740-1745页

作者： LU chao-feng lim c.w. XU Feng Department of civil Engineering Zhejiang University Hangzhou 310027 China） Department of Building and construction City University of Hong Kong Kowloon Hong Kong China Zhejiang Tiandi Environmental Protection Engineering co. Ltd. Hangzhou 310012 China

Semi-analytical elasticity solutions for bending of angle-ply laminates in cylindrical bending are presented using the state-space-based differential quadrature method (SSDQM). Partial differential state equation is derived from the basic equations of elasticity based on the state space concept. Then, the differential quadrature (DQ) technique is introduced to discretize the longitu- dinal domain of the plate so that a series of ordinary differential state equations are obtained at the discrete points. Meanwhile, the edge constrained conditions are handled directly using the stress and displacement components without the Saint-Venant principle. The thickness domain is solved analytically based on the state space formalism along with the continuity conditions at interfaces. The present method is validated by comparing the results to the exact solutions of Pagano’s problem. Numerical results for fully clamped thick laminates are presented, and the influences of ply angle on stress distributions are discussed.

关键词： Semi-analytical elasticity solution State-space-based differential quadrature method (SSDQM) Angle-ply laminates cylindrical bending

comprehensive molecular characterization to predict immunotherapy response in advanced biliary tract cancer:a phase II trial of pembrolizumab

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Oncology Research 2025年第1期33卷 57-65页

作者： RYUL KIM JOO KYUNG PARK MINSUK KwON MINAE AN JUNG YONG HONG JOON OH PARK SUNG HEE lim SEUNG TAE KIM Division of Hematology-Oncology Department of MedicineSamsung Medical CenterSungkyunkwan University School of MedicineSeoulKorea Division of Gastroenterology Department of MedicineSamsung Medical CenterSungkyunkwan University School of MedicineSeoulKorea Department of Hematology-Oncology Ajou University School of MedicineSuwon-siGyeonggi-doKorea Samsung Advanced Institute of Health Science and Technology Sungkyunkwan University School of MedicineSeoulKorea

Background:Immune checkpoint inhibitors(IcIs)are effective in a subset of patients with metastatic solid ***,the patients who would benefit most from IcIs in biliary tract cancer(BTc)are still *** and methods:we molecularly characterized tissues and blood from 32 patients with metastatic BTc treated with the IcI pembrolizumab as second-line ***:All patients had microsatellite stable(MSS)type *** of the 32 patients achieved partial response(PR),with an objective response rate(ORR)of 9.4%(95%confidence interval[cI],2.0–25.2)and nine showed stable disease(SD),exhibiting a disease control rate(DcR)of 37.5%(95%cI,21.1–56.3).For the 31 patients who had access to PD-1 ligand 1(PD-L1)combined positive score(cPS)testing(cut-off value≥1%),the ORR was not different between those who had PD-L1-positive(PD-L1+;1/11,9.1%)and PDL1-(2/20,10.0%)tumors(p=1.000).The tumor mutational burden(TMB)of PD-L1+BTc.w.s comparable to that of PD-L1-BTc(p=0.630).TMB and any exonic somatic mutations were also not predictive of pembrolizumab *** analysis of blood and tumor samples demonstrated a relatively high natural killer(NK)cell proportion in the peripheral blood before pembrolizumab treatment in patients who achieved tumor ***,the tumors of these patients presented high enrichment scores for NK cells,antitumor cytokines,and Th1 signatures,and a low enrichment score for cancer-associated ***:This study shows the molecular characteristics associated with the efficacy of pembrolizumab in BTc of the MSS type.

关键词： Pembrolizumab whole-exome sequencing whole-transcriptome sequencing Biliary tract cancer

Is a nanorod (or nanotube) with a lower Young’s modulus stiffer? Is not Young’s modulus a stiffness indicator?

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Science china(Physics,Mechanics & Astronomy) 2010年第4期53卷 712-724页

作者： lim c. w. Department of Building and construction City University of Hong Kong

It has been a known fact in classical mechanics of materials that Young’s modulus is an indicator of material stiffness and materials with a higher Young’s modulus are stiffer. At the nanoscale, within the scope and under specific circumstances described in this paper, however, a nanorod (or a nanotube) with a smaller Young’s modulus (smaller stress-strain rate) is stiffer. In such a scenario, Young’s modulus is not a stiffness indicator for nanostructures. Furthermore, the nonlocal stress-strain rate is dependent on types of load, boundary conditions and location. This is likely to be one of the many possible reasons why numerous experiments in the past obtained significantly varying values of Young’s modulus for a seemingly identical nanotube, i.e. because the types of loading and/or boundary conditions in the experiments were different, as well as at which point the property was measured. Based on the nonlocal elasticity theory and within the scope of material and geometric linearity, this paper reports the strange and hitherto unrealized effect that a nanorod (or a nanotube) with a lower Young’s modulus (smaller stress-strain rate) indicates smaller extension in tensile analysis. Similarly, it is also predicted that a nanorod (or a nanotube) with a lower Young’s modulus results in smaller bending deflection, higher critical buckling load, higher free vibration frequency and higher wave propagation velocity, which are at all consequences of a stiffer nanostructure.

关键词： nanorod nanotube nonlocal stress nonlocal elasticity stiffness tensile Young’s modulus

On the truth of nanoscale for nanobeams based on nonlocal elastic stress field theory:equilibrium,governing equation and static deflection

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Applied Mathematics and Mechanics(English Edition) 2010年第1期31卷 37-54页

作者： c. w. lim Department of Building and construction City University of Hong Kong

This paper has successfully addressed three critical but overlooked issues in nonlocal elastic stress field theory for nanobeams：（i） why does the presence of increasing nonlocal effects induce reduced nanostructural stiffness in many, but not consistently for all, cases of study, i.e., increasing static deflection, decreasing natural frequency and decreasing buckling load, although physical intuition according to the nonlocal elasticity field theory first established by Eringen tells otherwise？（ii） the intriguing conclusion that nanoscale effects are missing in the solutions in many exemplary cases of study, e.g., bending deflection of a cantilever nanobeam with a point load at its tip; and （iii） the non-existence of additional higher-order boundary conditions for a higher-order governing differential equation. Applying the nonlocal elasticity field theory in nanomechanics and an exact variational principal approach, we derive the new equilibrium conditions, do- main governing differential equation and boundary conditions for bending of nanobeams. These equations and conditions involve essential higher-order differential terms which are opposite in sign with respect to the previously studies in the statics and dynamics of nonlocal nano-structures. The difference in higher-order terms results in reverse trends of nanoscale effects with respect to the conclusion of this paper. Effectively, this paper reports new equilibrium conditions, governing differential equation and boundary condi- tions and the true basic static responses for bending of nanobeams. It is also concluded that the widely accepted equilibrium conditions of nonlocal nanostructures are in fact not in equilibrium, but they can be made perfect should the nonlocal bending moment be replaced by an effective nonlocal bending moment. These conclusions are substantiated, in a general sense, by other approaches in nanostructural models such as strain gradient theory, modified couple stress models and experim

关键词： bending effective nonlocal bending moment nanobeam nanomechanics,nanoscale nonlocal elastic stress strain gradient