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Effect of the Friction Characteristics of Sliding Contacts on Electrical Signal Transmission
Jang, Ho,Park, Hyung Kyu Korean Tribology Society 2001 KSTLE International Journal Vol.2 No.1
A resin bonded copper-graphite brush was investigated to evaluate the characteristics electrical signal transmission through a sliding contact as a function of the relative amount of graphite and copper in the brush. Particular attention was given to the correlation between electrical signal fluctuation and tribological properties in an electrical sliding contact system. A ring-on-block type tribotester was used for this experiment and the ring was made from pure copper. Results showed that a copper-graphite brush at a particular composition range exhibited the most stable frictional behavior with a minimum voltage drop. The amount of voltage drop at the friction interface was affected by the surface roughness, transfer film formation at the friction interface, and the real area of contact. Microscopic observations and the surface analysis showed a good agreement with the results from this experiment. The results also indicated that the electrical signal flunctuation was directly associated with the oscillation of the coefficient of friction during sliding by nanoscale variation of contacts at the friction interface.
Cooperative Underwater Vehicle-Manipulator Operation Using Redundant Resolution Method
Jangho Bae,Yecheol Moon,Eugene Park,Jongwon Kim,Sangrok Jin,TaeWon Seo 한국정밀공학회 2022 International Journal of Precision Engineering and Vol.23 No.9
This paper presents a cooperative manipulation method for a dual-arm underwater vehicle-manipulator system (UVMS). The objective task is handle valve turning, which is a common underwater task. We propose a manipulation method that includes the concept of grasping a fixed structure such as a pipeline. While grasping a fixed structure and a handle valve, the entire system can be considered a parallel manipulator. Because of the kinematic properties of the system, the load for turning the handle valve can be distributed between the vehicle and the dual-arm manipulator, which means the vehicle can help with the operation of the manipulator. In addition, external disturbances such as oceanic currents can be efficiently compensated by using the proposed cooperative method due to the properties of the system. The kinematics and dynamics of the system were analyzed. The cooperative manipulation method was developed by modifying and adjusting redundancy resolution method with theory of a parallel manipulator. To prove the superiority of the method, a dual-arm UVMS was designed and fabricated. The advantages of the proposed cooperative method were validated through simulations and experiments.
A Structural Model of Stress, Motivation, and Academic Performance in Medical Students
Jangho Park,정석훈,Hoyoung An,Seungjin Park,Chul Lee,Seong Yoon Kim,이재담,Ki-Soo Kim 대한신경정신의학회 2012 PSYCHIATRY INVESTIGATION Vol.9 No.2
Objective The purpose of the present study was 1) to identify factors that may influence academic stress in medical students and 2) to investigate the causal relationships among these variables with path analysis. Methods One hundred sixty medical students participated in the present study. Psychological parameters were assessed with the Medical Stress Scale, Minnesota Multiphasic Personality Inventory, Hamilton Depression Scale, Beck Depression Inventory, and Academic Motivation Scale. Linear regression and path analysis were used to examine the relationships among variables. ResultsaaSignificant correlations were noted between several factors and Medical Stress scores. Specifically, Hamilton Depression Scale scores (β=0.26, p=0.03) and amotivation (β=0.20, p=0.01) and extrinsically identified regulation (β=0.27, p<0.01) response categories on the Academic Motivation Scale had independent and significant influences on Medical Stress Scale scores. A path analysis model indicated that stress, motivation, and academic performance formed a triangular feedback loop. Moreover, depression was associated with both stress and motivation, and personality was associated with motivation. Conclusion The triangular feedback-loop structure in the present study indicated that actions that promote motivation benefit from interventions against stress and depression. Moreover, stress management increases motivation in students. Therefore, strategies designed to reduce academic pressures in medical students should consider these factors. Additional studies should focus on the relationship between motivation and depression.
Study on Impact-Ionization MOS for 1T-DRAM Operation
Jangho Jung(정장호),Hamin Park(박하민) 대한전자공학회 2023 대한전자공학회 학술대회 Vol.2023 No.11
In this paper, we implemented and analyzed the impact-ionization MOS (I-MOS) for 1T-DRAM using TCAD simulation. Based on a TCAD model with reliability ensured through calibration, we demonstrated the feasibility of 1T-DRAM operation through I-MOS parameter optimization and additional Boron doping in the channel region to induce the hysteresis. Furthermore, we analyzed the drain current variation and memory window through a region-specific impact ionization and charge transport analysis of the I-MOS device.