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Variational-Auto-Encoder for tooth image generation
Guohua Zhu,Suk Chan Kim(김석찬) 한국통신학회 2021 한국통신학회 학술대회논문집 Vol.2021 No.6
Variational Autoencoder (VAE), as a kind of deep latent space generation model, has achieved great success in performance in recent years, especially in image generation. In this article, we expound on the application of VAE in tooth image generation. Variational-Auto-Encoder is a recently proposed excellent algorithm for data generation. We show that VAE also has a good generation effect in tooth image generation.
Nonlinear dynamic response of cable-suspended systems under swinging and heaving motion
Guohua Cao,Naige Wang,Lei Wang,Zhencai Zhu 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.7
In order to enhance the fidelity, convenient and flexibility of swinging motion, the structure of incompletely restrained cablesuspended system controlled by two drums was proposed, and the dynamic response of the system under swinging and heaving motion were investigated in this paper. The cables are spatially discretized using the assumed modes method and the system equations of motion are derived by Lagrange equations of the first kind. Based on geometric boundary conditions and linear complementary theory, the differential algebraic equations are transformed to a set of classical difference equations. Nonlinear dynamic behavior occurs under certain range of rotational velocity and frequency. The results show that asynchronous motion of suspension platform is easily caused imbalance for cable tension. Dynamic response of different swing frequencies were obtained via power frequency analysis, which could be used in the selection of the working frequency of the swing motion. The work will contribute to a better understanding of the swing frequency, cable tension and posture with dynamic characteristics of unilateral geometric and kinematic constraints in this system, and it is also useful to investigate the accuracy and reliability of instruments in future.
Weighing the Evidence of Dividend Initiations
Tianyu Zhu,Guohua Ma,Xu-Shen Zhou 사람과세계경영학회 2011 Global Business and Finance Review Vol.16 No.1
This paper analyzes post-event stock performance based on the strength and the weight of evidence of dividend initiations. The strength refers to how extreme the evidence is; the weight refers to how credible the evidence is. Griffin and Tversky’s (1992) experiments show that people are underconfident when presented with low strength and high weight information and overconfident with high strength and low weight information. This study shows that Griffin and Tversky’s results extend to dividend initiation as well. Portfolios with high strength and low weight overreact to dividend announcement, while portfolios with low strength and high weight underreact. The empirical results in this paper show that the strength-weight model can explain the underreaction-overreaction puzzle and suggests that psychological biases may impact stock performance.
CRASHWORTHINESS OPTIMIZATION OF TAPERED UD-CFRP TUBE ACCOUNTING FOR MULTIPLE LOADING PANGLES
Chen Yisong,Zhu Guohua,Wang Zhen 한국자동차공학회 2023 International journal of automotive technology Vol.24 No.4
Tapered composite energy-absorbing components have superior advantages in weight reduction and crashworthiness improvement subjected to oblique compressions compared to straight structures. This study investigated the crashworthiness characteristics of uni-directional carbon fiber reinforced plastic (UD-CFRP) tubes under various loading angles, and further provided the guidance on multi-objectives optimization for UD-CFRP tubes accounting for multiple loading cases. The crashworthiness characteristics of straight UD-CFRP tubes subjected to three compressive angles (0°, 10° and 20°) were firstly explored experimentally, and results indicated that energy-absorbing capacity of samples decreased with the loading angles increasing due to changes in deformation behaviors. The multi-layer finite element modes (FEMs) were developed and validated, and simulations found that internal energy (IE) of intra-CFRP layer and inter-cohesive layer, friction energy decreased with the increase in loading angles. Parametric studies indicated crashworthy performances of UD-CFRP samples under multiple loading angles can be further improved by adjusting the tapered angle or wall thickness. Consequently, the synthetic special energy absorption (SEAβ), synthetic peak crushing force (PCFβ) and mass of tapered tube were optimized accounting for three different loading groups. Compared to baseline sample, the SEAβ was improved by 14 %, while the PCFβ and mass were reduced by 30.2 % and 19 %, respectively.
Coupled bending and torsional vibration of a rotor system with nonlinear friction
Chunli Hua,Guohua Cao,Zhushi Rao,Na Ta,Zhencai Zhu 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.6
Unacceptable vibrations induced by the nonlinear friction in a rotor system seriously affect the health and reliability of the rotating machinery. To find out the basic excitation mechanism and characteristics of the vibrations, a coupled bending and torsional nonlinear dynamic model of rotor system with nonlinear friction is presented. The dynamic friction characteristic is described with a Stribeck curve, which generates nonlinear friction related to relative velocity. The motion equations of unbalance rotor system are established by the Lagrangian approach. Through numerical calculation, the coupled vibration characteristics of a rotor system under nonlinear friction are well investigated. The influence of main system parameters on the behaviors of the system is discussed. The bifurcation diagrams, waterfall plots, the times series, orbit trails, phase plane portraits and Poincaré maps are obtained to analyze dynamic characteristics of the rotor system and the results reveal multiform complex nonlinear dynamic responses of rotor system under rubbing. These analysis results of the present paper can effectively provide a theoretical reference for structural design of rotor systems and be used to diagnose selfexcited vibration faults in this kind of rotor systems. The present research could contribute to further understanding on the self-excited vibration and the bending and torsional coupling vibration of the rotor systems with Stribeck friction model.
A novel energy regeneration system for emulsion pump tests
Li Yilei,Zhu Zhencai,Chen Guoan,Cao Guohua 대한기계학회 2013 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.27 No.4
A novel energy regeneration system based on cylinders and a rectifier valve for emulsion pump tests is presented and studied. The overall structure and working principles of this system are introduced. Both simulation and experiments are carried out to investigate the energy regeneration feasibility and capability of this novel system. The simulation and experimental results validate that this system is able to save energy and satisfy the test requirement. The energy recovery coefficient and overall energy regeneration coefficient of the test bench are 0.785 and 0.214, respectively. Measures to improve these two coefficients are also given accordingly after analysis of power loss. This novel system brings a new method of energy regeneration for emulsion pump tests.
김하얀(Kim Ha Yan),주궈화(Guohua Zhu),김석찬(Suk Chan Kim) 한국통신학회 2021 한국통신학회 학술대회논문집 Vol.2021 No.11
본 논문은 RNN 의 한 종류인 LSTM 을 활용하여 주가를 예측했다. 데이터는 삼성전자의 2016 년 3 월부터 2021 년 3 월까지의 일별 주가 데이터를 사용했다. 학습된 모델은 실제 값의 경향성을 높은 정확도로 따라갔으나 딜레이가 확인되어 개선이 필요하다.