Influence of indenter shape on nanoindentation: an atomistic study

Lai, Chia-Wei,Chen, Chuin-Shan Techno-Press 2013 Interaction and multiscale mechanics Vol.6 No.3

The influence of indenter geometry on nanoindentation was studied using a static molecular dynamics simulation. Dislocation nucleation, dislocation locks, and dislocation movements during nanoindentation into Al (001) were studied. Spherical, rectangular, and Berkovich indenters were modeled to study the material behaviors and dislocation activities induced by their different shapes. We found that the elastic responses for the three cases agreed well with those predicted from elastic contact theory. Complicated stress fields were generated by the rectangular and Berkovich indenters, leading to a few uncommon nucleation and dislocation processes. The calculated mean critical resolved shear stresses for the Berkovich and rectangular indenters were lower than the theoretical strength. In the Berkovich indenter case, an amorphous region was observed directly below the indenter tip. In the rectangular indenter case, we observed that some dislocation loops nucleated on the plane. Furthermore, a prismatic loop originating from inside the material glided upward to create a mesa on the indenting surface. We observed an unusual softening phenomenon in the rectangular indenter case and proposed that heterogeneously nucleating dislocations are responsible for this.

Numerical Method with High Real-time Property Based on Shortest Path Algorithm for Optimal Control

Wei Liao,Xiaohui Wei,Jizhou Lai,Hao Sun 제어·로봇·시스템학회 2021 International Journal of Control, Automation, and Vol.19 No.6

A numerical method consisting of an off-line part and an on-line part for optimal control problems is proposed in this paper. In the off-line part, the state space is discretized into a Cartesian grid structure and then define a graph over all grid points by connecting two points if the Euclidean norm between them is closer than a positive number called adjacent radius, the minimum cost between them is estimated using difference method and stored in a matrix. After that the matrix is updated by a shortest path algorithm and a matrix holding the information of the shortest paths between any two grid points is generated. In the on-line part, the optimal control vector at each time step can be generated by reading data from the matrix according to the current state and target state and doing some simple calculations. Since there is no need to do a lot of calculation in the on-line part, this method can satisfy the real-time requirements in some engineering control problems. We prove that the solution of the proposed method converge to the analytical solution when the adjacent radius and the grid size tend to zero and the grid size tend is a higher order infinitesimal of the adjacent radius. At the end of this paper, some numerical examples are taken to illustrate the effectiveness of the proposed method.

Investigation of in-train stability and safety assessment for railway vehicles during braking

Lai Wei,Jing Zeng,Qunsheng Wang 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.4

In-train stability of railway vehicles has becoming a major concern for railway vehicles, which refers to the jackknifing behavior of couplers under large in-train forces. For the train to train rescue scenario, braking induced impacts from couplers can adversely affect the dynamic performance of the coupled train. It is indicated from field tests that in-train forces if combined with large rotational angles of couplers can produce vertical components, which will further lead to the interference of adjacent carbodies and structural damages. In this paper, the dynamic model of the train and coupler system is developed. The model verifications are conducted by comparing the calculated responses with the tested results. The safety indices are formulated on the basis of which the running safety of the coupled train is evaluated. The propelling test in the laboratory is conducted to reproduce the coupler jackknifing behavior. The quasi-static analysis and anti-jackknifing mechanism under compressing in-train forces are analysed. Parametric studies are then conducted to propose some limitations for the application of train to train rescue. It is indicated from numerical and testing results that the decrease of the braking deceleration or a limitation of the free rotational angle of couplers is beneficial to lower the amplitude of braking induced impacts.

Comments on Relationship between the High Fatty Liver Index and Risk of Fracture

Lai Shih-Wei,Liao Kuan-Fu 거트앤리버 소화기연관학회협의회 2023 Gut and Liver Vol.17 No.4

Safety and Efficacy of Ledipasvir/Sofosbuvir in a Genotype 1 HCV Infected Chinese Population: Results from a Phase 3, Clinical Trial

( Lai Wei ),( Qing Xie ),( Jin Lin Hou ),( Hong Tang ),( Qin Ning ),( Jun Cheng ),( Yuemin Nan ),( Lunli Zhang ),( Jun Li ),( Jianning Jiang ),( Megan Kim ),( Brian Mcnabb ),( Fangqiu Zhang ),( Gregor 대한간학회 2018 춘·추계 학술대회 (KASL) Vol.2018 No.1

Aims: Chronic hepatitis C virus (HCV) infection remains a major health threat in China, affecting at least 10 million people, with approximately 58% having genotype (GT) 1 infection. There is a critical need for simple, all oral, direct-acting antiviral regimens to treat GT1 HCV in this region. Treatment with ledipasvir (LDV)/sofosbuvir (SOF) results in high sustained virologic response rates 12 weeks after therapy (SVR12) in GT1 HCV infected patients in clinical trials and real-world settings. This study evaluated the efficacy and safety of LDV/SOF for 12 weeks in Chinese patients with chronic GT1 HCV infection. Methods: Treatment experienced and treatment naïve patients with chronic GT1 HCV infection with no cirrhosis or with compensated cirrhosis were eligible to enroll in a single-arm, openlabel trial to receive a fixed dosed combination of LDV/SOF 90/400 mg daily for 12 weeks. The primary efficacy endpoint was SVR12 using the CAP/CTM HCV 2.0 assay (LLOQ =15 IU/mL) and the primary safety endpoint was adverse events (AEs) leading to LDV/SOF discontinuation. Results: A total of 206 Chinese patients were enrolled and treated. Of these, 50% were male, 16% had compensated cirrhosis, 49% were treatment-experienced, 76% had IL28B CC genotype, and 100% had GT1b HCV infection. The mean (range) age and body mass index of enrolled subjects were 47 (21-72) years and 23 (14-34) kg/m2, respectively. The overall SVR12 rate is 100% (206/206). All 32 patients with cirrhosis (15 of whom were treatment-experienced), achieved SVR12. There were no discontinuations due to AEs. No serious or severe AEs were assessed by the investigator as related to study drug and there were no deaths. Conclusions: Treatment with the single tablet regimen of LDV/SOF for 12 weeks resulted in 100% SVR12 and was well tolerated in treatment experienced and treatment naïve GT1 HCVinfected Chinese patients with and without cirrhosis.

Oxidation Effect on the Break-Up of the Liquid Metal Jet

( Wei Hsiang Lai ),( Chia Chin Chen ) 한국액체미립화학회 2001 한국액체미립화학회 학술강연회 논문집 Vol.2001 No.-

Ethanol and Water Atomization of Like- and Unlike-Doublet Impinging Jets

( Wei Hsiang Lai ),( Shun Jie Yang ),( Wen Non Huang ) 한국액체미립화학회 2005 한국액체미립화학회 학술강연회 논문집 Vol.2005 No.-

The objective of the present study is to further investigate the general influence of the physical properties and environment effects on the mean drop size generated by like- and unlike-doublet impinging jets with 95% ethanol and purified water. The orifice of the injector element are 0.3, 0.5, and 0.7 mm in diameter, with depth-to-diameter ratio of 10, the impinging angle is set to be 60°, 90° and 120° respectively. In order to measure the mean drop size, the jet velocity is varied from 2 m/s to 30 m/s, the environment pressure is designated as 1, 2, 5 and 9 bar. Results show that in liquid shape mode, the larger impinging angle, the lower jet velocity threshold of mode transition is observed. Regarding the liquid film size, an empirical equation can be used to calculate the ψ angle, and the equation induced by Ibrahim et al.(1991) can figure out the film length by multiply a constant, which is related to the viscosity. The SMD of unlike-doublet impinging is highly influenced by the surface tension. High ambient pressure has no effect on film size, but it causes the liquid shape change mode in lower jet velocity.

Home Energy Management System for Interconnecting and Sensing of Electric Appliances

( Wei-ting Cho ),( Chin-feng Lai ),( Yueh-min Huang ),( Wei-tsong Lee ),( Sing-wei Huang ) 한국인터넷정보학회 2011 KSII Transactions on Internet and Information Syst Vol.5 No.7

Due to the variety of household electric devices and different power consumption habits of consumers at present, general home energy management (HEM) systems suffer from the lack of dynamic identification of various household appliances and a unidirectional information display. This study presented a set of intelligent interconnection network systems for electric appliances, which can measure the power consumption of household appliances through a current sensing device based on OSGi platform. The system establishes the characteristics and categories of related electric appliances, and searches the corresponding cluster data and eliminates noise for recognition functionality and error detection mechanism of electric appliances by applying the clustering algorithm. The system also integrates household appliance control network services so as to control them according to users` power consumption plans or through mobile devices, thus realizing a bidirectional monitoring service. When the system detects an abnormal operating state, it can automatically shut off electric appliances to avoid accidents. In practical tests, the system reached a recognition rate of 95%, and could successfully control general household appliances through the ZigBee network.

Efficient Cluster Radius and Transmission Ranges in Corona-based Wireless Sensor Networks

( Wei Kuang Lai ),( Chung-shuo Fan ),( Chin-shiuh Shieh ) 한국인터넷정보학회 2014 KSII Transactions on Internet and Information Syst Vol.8 No.4

In wireless sensor networks (WSNs), hierarchical clustering is an efficient approach for lower energy consumption and extended network lifetime. In cluster-based multi-hop communications, a cluster head (CH) closer to the sink is loaded heavier than those CHs farther away from the sink. In order to balance the energy consumption among CHs, we development a novel cluster-based routing protocol for corona-structured wireless sensor networks. Based on the relaying traffic of each CH conveys, adequate radius for each corona can be determined through nearly balanced energy depletion analysis, which leads to balanced energy consumption among CHs. Simulation results demonstrate that our clustering approach effectively improves the network lifetime, residual energy and reduces the number of CH rotations in comparison with the MLCRA protocols.

Particle Size and Loading Effects on Particle-Laden Flow with Mono-sized Droplets

( Wei Hsiang Lai ),( Wei Fu Lu ),( Keh Chin Chang ) 한국액체미립화학회 2010 한국액체미립화학회 학술강연회 논문집 Vol.2010 No.-

Turbulence modulation is an interaction between phases that occurs in multiphase flow, and turbulence intensity traditionally can be represented as an indicator of turbulence modulation. Many researchers paid attention on the subject, but no coincident conclusion can be proposed. A general cognition is that larger particles induced wake to enhance the fluid turbulence intensity and smaller particles suppressed the fluid turbulence intensity since the fluid eddy imparted energy to the smaller particle. Here, the authors orderly changed particle size of dispersed phase and mass loading ratio (LR) to study the change on fluid turbulence intensity. Mono-dispersed droplets with a narrow size distribution were used to load into a homogeneous turbulence to investigate the turbulence modulation. Particle Dynamic Analyzer (PDA) was used to measure the particle (droplets and tracers) dynamic information. The particle concentration effect can be significantly observed. After coupling particle concentration and particle wetting area (πd2), a linear relationship can be obtained and it represents the turbulence modulation dominated the dilute two-phase flow as our expectation.