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.

Nonparametric estimation for derivatives of compound distribution

Zhimin Zhang,Chaolin Liu 한국통계학회 2015 Journal of the Korean Statistical Society Vol.44 No.3

The compound random variableNj =1 Xj and its distribution have many applications in actuarial science. In this paper, we consider estimation of the derivative functionals of the compound distribution when the underlying density f of Xj is unknown. The estimator is constructed by Fourier inversion and kernel method. An order bound for the bias and asymptotic expression for the variance are given, and the asymptotic normality and uniform consistency are also discussed. Some simulation studies are presented to illustrate the performance of the estimator under finite sample setting.

Spinal Tuberculosis: Always Understand, Often Prevent, Sometime Cure

Zhimin Pan,Zujue Cheng,Jeffrey C. Wang,Wei Zhang,Min Dai,Bin Zhang 대한척추신경외과학회 2021 Neurospine Vol.18 No.3

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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.

RECOVERY TYPE A POSTERIORI ERROR ESTIMATES IN FINITE ELEMENT METHODS

Zhang, Zhimin,Yan, Ningning 한국전산응용수학회 2001 The Korean journal of computational & applied math Vol.8 No.2

This is a survey article on finite element a posteriori error estimates with an emphasize on gradient recovery type error estimators. As an example, the error estimator based on the ZZ patch recovery technique will be discussed in some detail. AMS Mathematics Subject Classification : 65N30, 65N15

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

Xi Zhang,Zhongwei Zhang,Bocheng Bao,Han Bao,Zhimin Wu,Kaiwen Yao,Jing Wu 전력전자학회 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 itsuitable for the power supplies used in various portable electronic devices. However, considering the effect of the outer voltageloop, the stable range of the duty-cycle is significantly diminished in CC controlled buck converters. To investigate the stabilityeffect of the outer voltage loop on buck converters, a CC controlled buck converter with a proportion-integral (PI) compensatoris taken as an example, and its second-order discrete-time model is established. Based on this model, the instability caused by theduty-cycle is discussed with consideration of the outer voltage loop. Then the dynamical effects of the feedback gain of the PIcompensator and the equivalent series resistance (ESR) of the output capacitor on the CC controlled buck converter with a PIcompensator are studied. Furthermore, the design-oriented closed-loop stability criterion is derived. Finally, PSIM simulationsand experimental results are supplied to verify the theoretical analyses.

Performance analysis and experimental verification of hydraulic driven axial flow pumps

Zhiting Tong,Ye Yuan,Chao Zhang,Zhimin Zhang,Yue Zhang 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.6

To investigate axial flow pumps’ performance characteristics, NUMECA software is selected to perform numerical simulation at four rotating speeds (1380, 1840, 2300, and 2530 r/min) based on the Spalart-Allmaras turbulence model. The relationship curves of flowhead and flow-pump efficiency, static pressure distribution on blade surfaces, velocity variation near the hub, and total pressure distribution at different blade heights are obtained. Results indicate that with the improvement of the rotating speed, the curves of the head and the efficiency rise and shift to the right, the pressure difference on both sides of the blade ascends, and the moment acting on the blade induced by the water flow also increases, resulting in higher head. At the rated speed of 2300 r/min, the pressure difference between the pressure side and the suction side at low flowrates increases, the minimum pressure is lower, and the anticavitation performance decreases, whereas the velocity distribution near the hub is the same at different flowrates. Moreover, the velocity is lower near the hub’s leading edge, and no influence is observed. To guarantee the reliability and comparability, experimental data are contrasted with the simulated results at the speed of 2182 r/min. At the near design condition (Q = 534.4-567 m 3 /h), the relative deviation of efficiency and head is less than 4.5 %, which is a small gap. These conclusions provide valuable reference for axial flow pumps to operate under variable speed conditions.

A Comparative Study on Physiological Activities of Lager and Ale Brewing Yeasts under Different Gravity Conditions

Zhimin Yu,Mou-Ming Zhao,Huiping Li,Hai-Feng Zhao,Qingli Zhang,Chunyan Wan,Huipin Li 한국생물공학회 2012 Biotechnology and Bioprocess Engineering Vol.17 No.4

High gravity (HG) or very high gravity (VHG)brewing has become popular in modern breweries due to its economic and product quality advantages. However,there are the negative impacts such as the fermentation performance of brewer’s yeast in HG or VHG wort, which are closely related to changes in cell physiological activity. In the present study, 3 kinds of worts, with different gravities, were used to examine the systematic effects on fermentation performance and physiological activity of lager yeast FBY009505 (Saccharomyces pastorianus) and ale yeast FBY0099 (Saccharomyces cerevisiae), as well as the resulting beer flavor. Results showed that the responses of FBY009505 and FBY0099 to the HG or VHG worts were similar. The specific fermentation rate and viability of cropped yeast of FBY009505 and FBY0099 were decreased with increasing wort gravity. The increased wort gravity resulted in the increase of energy charge and the decrease of α-glucosides transport rate and glycolytic enzyme activities. Moreover, the environmental stresses in the HG or VHG wort showed a higher inhibitory activity against α-glucoside transport than glycolytic enzymes. The content of intracellular trehalose and glycerol of FBY009505 and FBY0099 increased with the increase in wort gravity. The results from this study provided a potential means to systematically understand the physiology of brewer’s yeast under HG or VHG conditions. High gravity (HG) or very high gravity (VHG)brewing has become popular in modern breweries due to its economic and product quality advantages. However,there are the negative impacts such as the fermentation performance of brewer’s yeast in HG or VHG wort, which are closely related to changes in cell physiological activity. In the present study, 3 kinds of worts, with different gravities, were used to examine the systematic effects on fermentation performance and physiological activity of lager yeast FBY009505 (Saccharomyces pastorianus) and ale yeast FBY0099 (Saccharomyces cerevisiae), as well as the resulting beer flavor. Results showed that the responses of FBY009505 and FBY0099 to the HG or VHG worts were similar. The specific fermentation rate and viability of cropped yeast of FBY009505 and FBY0099 were decreased with increasing wort gravity. The increased wort gravity resulted in the increase of energy charge and the decrease of α-glucosides transport rate and glycolytic enzyme activities. Moreover, the environmental stresses in the HG or VHG wort showed a higher inhibitory activity against α-glucoside transport than glycolytic enzymes. The content of intracellular trehalose and glycerol of FBY009505 and FBY0099 increased with the increase in wort gravity. The results from this study provided a potential means to systematically understand the physiology of brewer’s yeast under HG or VHG conditions.

3D printed MXene (Ti2AlN)/polycaprolactone composite scaffolds for in situ maxillofacial bone defect repair

Zhimin Xu,Yingxin Zhang,Huanyan Dai,Yu Wang,Yujie Ma,Shuang Tan,Bing Han 한국공업화학회 2022 Journal of Industrial and Engineering Chemistry Vol.114 No.-

Obtaining a safe and reliable scaffold that can be rapidly fabricated and used for clinical bone defect repairhas always been a challenge. In this study, polycaprolactone (PCL) composite scaffolds with various MXene(Ti2AlN) contents were prepared using 3D printing technology. The effects of different contents of Ti2AlNon the mechanical properties, hydrophilicity, cytocompatibility, and osteogenic differentiation abilitywere systematically studied and analysed. In vitro experiments showed that scaffolds containing 5%Ti2AlN (PCL@5#Ti2AlN) obtained the best cell adhesion and proliferation ability and significantly upregulatedthe alkaline phosphatase (ALP) level. In vivo experiments of tibial defect repair in rats showed thatthe PCL scaffold containing 5% Ti2AlN (PCL@5#Ti2AlN) could significantly promote the formation of newbone, and the experimental results of rabbit maxillofacial bone defect repair further proved that thePCL@5#Ti2AlN scaffold could effectively promote the repair of bone defects. Transcriptome analysis indicatedthat Ti2AlN may promote osteogenic differentiation by the Wnt/b-catenin signaling pathway andcalcium-binding proteins. These findings suggest that Ti2AlN/PCL composite scaffolds with improvedin situ bone repair ability represent an intelligent strategy for bone defect repair.

Light Metals and Alloys : THE EFFECT OF SILVER ON AGING RESPONSE OF Al - Mg - Li - Zr ALLOYS

Zhang siqi,Shen Jian,Liang Ying,Lu Bin,Yin Zhimin 대한금속재료학회 ( 구 대한금속학회 ) 1995 Advanced Material and Processing Vol.3 No.-