On a perturbed Sparre Andersen risk model with dividend barrier and dependence

Zhimin Zhang,Xiu Wu,Hu Yang 한국통계학회 2014 Journal of the Korean Statistical Society Vol.43 No.4

In this paper, we consider a Sparre Andersen risk model perturbed by a Brownian motion,where the inter-claim time and individual claim size follow some bivariate distribution. Assume that a barrier dividend strategy is applied to the surplus process, so that dividendsare paid out whenever the surplus level attains a barrier b. Integral equations and integrodifferentialequations satisfied by the Gerber–Shiu discounted penalty functions and theexpected discounted dividend payments are derived, and solutions are also given for somespecial cases.

Asymmetric reduction of chloroacetophenones to produce chiral alcohols with microorganisms

Zhimin Ou,Jianping Wu,Lirong Yang,Peilin Cen 한국화학공학회 2008 Korean Journal of Chemical Engineering Vol.25 No.1

Four strains of yeast with reduction activity of chloroacetophenones were screened, in which Saccharomyces cerevisiae B5 showed best reduction activity and stereoselectivity. High optical purity (R)-2'-chloro-1-phenylethanol can be obtained with Saccharomyces cerevisiae B5 as biocatalyst. The influence of several co-substrates on the enantiometric excess (ee%) and yield of (R)-2'-chloro-1-phenylethanol was evaluated. 5% (v/v) ethanol is optimal cosubstrate for (R)-2'-chloro-1-phenylethanol formation. The optimal bioconversion conditions of 2'-chloroacetophenone catalyzed by Saccharomyces cerevisiae B5 are as follows: pH 8.0, 25 oC and 24 h. The yield and the enantiometric excess of (R)-2'-chloro-1-phenylethanol can both reach more than 99% with 10.75 g/l Saccharomyces cerevisiae B5 (the cell dry weight) and 1 g/l 2'-chloroacetophenone used in the biotransformation.

Human Glutathione S-Transferase P1 Suppresses MEKK1-mediated Apoptosis by Regulating MEKK1 Kinase Activity in HEK293 Cells

Zhimin Yin,Xin Zhao,Yumei Fan,Jiayin Shen,Yifan Wu 한국분자세포생물학회 2006 Molecules and cells Vol.21 No.3

A Novel Multi-scale 3D Area Morphological Filtering Method for Airborne LiDAR Building Extraction

Cao Zhimin,Wu Yun 보안공학연구지원센터 2016 International Journal of Smart Home Vol.10 No.6

Automatic building extraction is one of the most important issues in the fields of geoscience and remote sensing. In this letter, by introducing the idea of area morphology to the analysis of 3-D point clouds, a novel approach for automatic building extraction from airborne LiDAR data was proposed. At first, single scale area opening and area closing operator was used to produce normalized point clouds. With the normalized point clouds as input, multi-scale area morphology was employed to obtain connected regions, and then tree points were removed by PCA based local structural analyzing technique. Finally, building regions were extracted by analyzing geometry properties of the obtained connected regions without tree points. Experiments for different terrains were conducted. And the corresponding experimental results are very promising.

An efficient method for the compressive behavior of FRP-confined concrete cylinders

Xinglang Fan,Zhimin Wu,Yufei Wu,Jianjun Zheng 사단법인 한국계산역학회 2013 Computers and Concrete, An International Journal Vol.12 No.4

Fiber reinforced polymer (FRP) jackets have been widely used as an effective tool for the strengthening and rehabilitation of concrete structures, especially damaged concrete columns. Therefore, a clear understanding of the compressive behavior of FRP-confined concrete is essential. The objective of this paper is to develop a simple efficient method for predicting the compressive strength, the axial strain at the peak stress, and the stress-strain relationship of FRP-confined concrete. In this method, a compressive strength model is established based on Jefferson’s failure surface. With the proposed strength model, the strength of FRP-confined concrete can be estimated more precisely. The axial strain at the peak stress is then evaluated using a damage-based formula. Finally, a modified stress-strain relationship is derived based on Lam and Teng’s model. The validity of the proposed compressive strength and strain models and the modified stress-strain relationship is verified with a wide range of experimental results collected from the research literature and obtained from the self-conducted test. It can be concluded that, as a competitive alternative, the proposed method can be used to predict the compressive behavior of FRP-confined concrete with reasonable accuracy.

Seismic rehabilitation of substandard RC columns with partially deteriorated concrete using CFRP composites

Dongxu Hou,Zhimin Wu,Jianjun Zheng,Yao Cui 사단법인 한국계산역학회 2015 Computers and Concrete, An International Journal Vol.15 No.1

Many existing reinforced concrete (RC) columns in structures tend to become substandard RC ones due to updated standards or environmental changes. These substandard columns may alter the behaviors of the whole structure and therefore are in urgent need of seismic retrofitting. Owing to their superior advantages, carbon fiber reinforced polymer (CFRP) composites are widely used to retrofit RC columns. The applications mainly focus on various substandard RC columns, but few deals with substandard columns with deteriorated concrete, especially damaged by earthquake. The purpose of this paper is to investigate the seismic behaviors of CFRP reinforced partially deteriorated RC columns and to evaluate the effect of CFRP sheets on them. Six flexure-dominant columns were tested under a constant axial load and transverse cyclic displacements. It is found that the seismic behaviors of partially deteriorated columns can be recovered by wrapping CFRP sheets on them. Numerical analysis is then conducted using finite element methods and verified with experimental results. The effects of the axial load ratio, the ratio of the thickness of CFRP sheet to the column diameter, and the slenderness ratio on the seismic behaviors of CFRP reinforced RC columns are evaluated. Finally, a method is proposed to determine the required thickness of CFRP sheet.

Network Traffic Anomaly Detection Based on N-ARMA Model

Pingping Gu,Shijing Zhang,Zhimin Huang,Qingfeng Wu 보안공학연구지원센터 2016 International Journal of Database Theory and Appli Vol.9 No.11

With the rapid development of the Internet and the continuous expanding of the data network, little potential anomaly can seriously affect the normal operation of the network, and even lead to huge economic losses. In order to be more accurate and efficient in the traffic detection, in this paper, we propose an N-ARMA based traffic anomaly detection model. We also conduct extensive experiments to verify the higher accurate ratio and recall ratio of our model by comparing with other traffic anomaly detection methods.

Active monitoring of pipeline tapered thread connection based on time reversal using piezoceramic transducers

Xiaobin Hong,Gangbing Song,Jiaobiao Ruan,Zhimin Zhang,Sidong Wu,Guixiong Liu 국제구조공학회 2016 Smart Structures and Systems, An International Jou Vol.18 No.4

The monitoring of structural integrity of pipeline tapered thread connections is of great significance in terms of safe operation in the industry. In order to detect effectively the loosening degree of tapered thread connection, an active sensing method using piezoceramic transducers was developed based on time reversal technique in this paper. As the piezoeramic transducers can be either as actuators or sensors to generate or detect stress waves, the energy transmission for tapered thread connection was analyzed. Subsequently, the detection principle for tapered thread connection based on time reversal was introduced. Finally, the inherent relationship between the contact area and tightness degree of tapered thread connection for the pipe structural model was investigated. Seven different contact area scenarios were tested. Each scenario was created by loosening connectors ranging from 3 turns to 4.5 turns in the right tapered threads when the contact area in the left tapered threads were 4.5 turns. The experiments were separately conducted with a highly noisy environment and various excitation signal amplitudes. The results show the focused peaks based on time reversal have the monotonously rising trend with the increase of the contact areas of tapered threads within an acceptable monitoring resolution for metal pipes. Compared with the energy method, the proposed time reversal based method to monitor tapered threads loosening demonstrates to be more robust in rejecting noise in Structural Health Monitoring (SHM) applications.

A 5.6 kW 11.7 kW per kg Four-Phase Interleaved Buck Converter for the Unmanned Aerial Vehicle

Cheng Xu-Feng,Peng Zhenzhen,Yang Yulong,Liang Zhimin,Wu Chaofeng,Shao Zhiwei,Wang Dianlong 대한전기학회 2022 Journal of Electrical Engineering & Technology Vol.17 No.2

This paper proposed a 5.6 kW 11.7 kW/kg four-phase interleaved buck converter (FPIBC) for the unmanned aerial vehicle (UAV) low-voltage power system. The UAV mainly concerns the lightweight strategy and the power density of the DC-DC converter. We proposed a comprehensive lightweight strategy with the characteristics of reduced inductor current ripples, small size of fi lter inductors and capacitors, and high output power. The output current ripples are reduced by using interleaved modulation strategy and integrated CLC fi lters cascaded to the input side and output side respectively. In addition, the aluminum based printed circuit board (PCB) is used with SMD power transistors to obtain better heat dissipation capability without fans. With abovementioned methods, the designed DC-DC converter has a power of 5.6 kW @ 0.48 kg, the powerto-weight ratio is improved to be 11.7 kW/kg, and the power density is 3 W/cm 3 . The effi ciency of this DC-DC converter is up to 95.8%.

Design-Oriented Stability of Outer Voltage Loop in Capacitor Current Controlled Buck Converters

Zhang, Xi,Zhang, Zhongwei,Bao, Bocheng,Bao, Han,Wu, Zhimin,Yao, Kaiwen,Wu, Jing The Korean Institute of Power Electronics 2019 JOURNAL OF POWER ELECTRONICS Vol.19 No.4

Due to the inherent feedforward of load current, capacitor current (CC) control shows a fast transient response that makes it suitable for the power supplies used in various portable electronic devices. However, considering the effect of the outer voltage loop, the stable range of the duty-cycle is significantly diminished in CC controlled buck converters. To investigate the stability effect of the outer voltage loop on buck converters, a CC controlled buck converter with a proportion-integral (PI) compensator is taken as an example, and its second-order discrete-time model is established. Based on this model, the instability caused by the duty-cycle is discussed with consideration of the outer voltage loop. Then the dynamical effects of the feedback gain of the PI compensator and the equivalent series resistance (ESR) of the output capacitor on the CC controlled buck converter with a PI compensator are studied. Furthermore, the design-oriented closed-loop stability criterion is derived. Finally, PSIM simulations and experimental results are supplied to verify the theoretical analyses.