• JSTS:Journal of Semiconductor Technology and Science
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• v.13 no.1
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• pp.28-33
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• 2013

Spin-torque oscillators (STO) is a new device that can be used as a tunable microwave source in various wireless devices. Spin-transfer torque effect in magnetic multilayered nanostructure can induce precession of magnetization when bias current and external magnetic field are properly applied, and a microwave signal is generated from that precession. We proposed a semi-empirical circuit-level model of an STO in previous work. In this paper, we present a refined STO model which gives more accuracy by considering physical phenomena in the calculation of effective field. Characteristics of the STO are expressed as functions of external magnetic field and bias current in Verilog-A HDL such that they can be simulated with circuit-level simulators such as Hspice. The simulation results are in good agreement with the experimental data.

• Transactions of the Korean Society of Automotive Engineers
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• v.16 no.2
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• pp.58-65
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• 2008

The finite element programs have been developed for structure, collision, flow, dynamics, heat transfer, acoustics, electromagnetism, MEMS (Micro Electro Mechanical Systems), and etc. These programs can be classified as either "package" program or "single purpose" program. Single purpose programs usually have convenient and powerful functions, but these programs have limited expandability to different fields of analysis. Therefore, the method to converter the analysis results of single purpose program to other programs is needed. In the research, multi-body data conversion methods of 1) finite element model and 2) solid model were created to convert fluid analysis result of CFD-ACE+ to ANSYS data structure. Automatic boundary condition algorithms were developed for blade, and finite element model was compared with solid model. It is expected that, by sealess data transfer, the Multi-body Data Conversion Program could reduce the development period of torque converters.

• Composites Research
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• v.23 no.6
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• pp.26-31
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• 2010

This research work contributes to a study for the procedure and methodology to assess the fatigue durability for a composite torque link for helicopter landing gear, which was newly developed and fabricated by the resin transfer moulding technique to interchange with metal component. The simulated load spectrum anticipated to be applied to the torque link during its operation life was generated using an advanced method of probabilistic random process, and the fatigue durability was evaluated by the residual strength degradation approach on the basis of material test data. The full scale fatigue test was performed and compared with the analysis results.

• The Journal of Advanced Prosthodontics
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• v.7 no.1
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• pp.62-68
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• 2015

PURPOSE. The purpose of this research was to evaluate the amount of reosseointegration after counter torquing (reverse torque) and transposing the installed implants at different times. MATERIALS AND METHODS. This study was done on ten tibiae of five cross-bred dogs. At the first day one implant was installed in each tibia. After one week half of the implants were randomly counter torqued (1WCT) and the other half were explanted and reimplanted in a new juxtaposition site (transposed)(1WT). At the same time three new implants were installed in each dog, one of them was considered as one week control (1WC) and remaining two as 8 week groups (8WCT&8WT). After eight weeks the 1WCT and 1WT implants were loosened by counter torque and the quantity of needed force for liberation was measured with the digital device (BGI). At the same time one implant was installed in each dog as eight week control (8WC) and the same protocol was repeated for 8 week groups after another 8 weeks. RESULTS. All implants were osseointegrated. Mean quantities of osseointegration in case groups indicated better amounts rather than control groups. CONCLUSION. Counter torque or transposition of the installed implants one week or eight weeks after the implantation did lead to osseointegration.

• Journal of Electrical Engineering and Technology
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• v.11 no.4
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• pp.801-809
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• 2016

The electrically excited synchronous generator (EESG) is applied in wind turbine systems recently. In an EESG control system, electrical torque is affected by stator flux and rotor current. So the control system is more complicated than that of the permanent-magnet synchronous generator (PMSG). Thus, the higher demanding of the control system is required especially in case of wind turbine mechanical resonance. In this paper, the mechanism of rotor speed resonant phenomenon is introduced from the viewpoint of mechanics firstly, and the characteristics of an effective damping torque are illustrated through system eigenvalues analysis. Considering the variables are tightly coupled, the four-order small signal equation for torque is derived considering stator and rotor control systems with regulators, and the bode plot of the closed loop transfer function is analyzed. According to the four-order mathematical equation, the stator flux, stator current, and electrical torque responses are derived by torque reference step and ramp in MATLAB from a pure mathematical deduction, which is identical with the responses in PSCAD/EMTDC simulation results. At last, the simulation studies are carried out in PSCAD software package to verify the resonant damping control strategy used in the EESG wind turbine system.

• Tribology and Lubricants
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• v.33 no.2
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• pp.71-78
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• 2017

The drag torque in the wet clutch system of a dual clutch transmission system is investigated because it is relatively high, up to 10 of the total output torque of the engine, even when the clutch is in the disengagement state with zero torque transfer. Drag torque results from the shear resistance of the DCTF between the friction pad and separator plate. To reduce the drag torque for ensuring fuel economy, the groove pattern of the wet clutch friction pad is designed to have a high flow rate through the pattern groove. In this study, four types of groove patterns on the friction pad are designed. The volume fraction of the DCTF (VOF) and hydrodynamic pressure developments in the gap between the friction pad and separator plate are computed to correlate with the computation of the drag torque. From the computational results, it is found that a high VOF and hydrodynamics increase the drag torque resulting from the shear resistance of the DCTF. Therefore, a patterned groove design should be used for increasing the flow rate to have more air parts in the gap to reduce the drag torque. In this study, ANSYS FLUENT is used to solve the flow analysis.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.12 no.2
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• pp.59-64
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• 2003

Continuously Variable Transmission (CVT) consists of a driving pulley and a driven pulley joined by rubber V-belt. Each pulley consists of a fixed flange and a movable flange. The main advantages of the U with V-belt, which has been Popular in Asia, are a simple mechanism less maintenance and low cost. One of the important factors which have an influence on the performance of the CVT is change of axial distance. Base on an experiment the effects of transfer torque and speed ratio of both driving pulley and driven pulley during the alteration of axial distance were studied.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1213-1218
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• 2007

The brake judder comes from non-uniformities in the tire/wheel assembly caused by mechanical effects such as a brake torque variation (BTV). A disc thickness variation (DTV) related with the kinematic behavior of the disc was investigated a main source of BTV. In this study, a dynamic model with brake corner assembly of full vehicle using MSC.ADAMS was correlated by experiment of judder phenomenon. Judder was generated and correlated systematically by judder experiment in chassis and brake dynamometer from variation in the thickness of the disc. Also it has been found a judder transfer path and variation of the braking pressure. Through analysis of transfer function and movement of subsystem caused by BTV generation, design parameters have been found. Based on the results obtained from parameter study of suspension module, the effective design process and developed model with brake corner assembly was suggested for vibration reduction of steering wheel caused by the judder phenomenon.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.342-352
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• 2003

Idle NVH characteristics are one of the most important aspects among the vehicle performances. Vehicle developers are devoted to improve vehicle interior noise and steering wheel and seat vibrations. In order to improve the idle quality, noise and vibration transfer path should be carefully evaluated. Also, effects of various components related to the idle performance should be confirmed. A general procedure for improving the idle qualify is described in detail. The relationship among cylinder pressure characteristics, crankshaft rotational speed variation, and vehicle vibrations is also investigated. Influences of drive shaft, torque converter, air conditioning system, vehicle structure including engine mount system, and idle control parameters on the vehicle idle quality are studied. Weak points of typical vehicles on the idle qualify are identified. Some of improvement measures are proposed and verified.

• Journal of Magnetics
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• v.15 no.4
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• pp.149-154
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• 2010

Synthetic antiferromagnets (SAFs) are used as free layer structures for various magnetic devices utilizing spintransfer torque (STT). Therefore, it is important to understand current-induced excitation of SAFs. By means of drift-diffusion and macrospin models, we studied the current-induced excitation of a SAF-free layer structure (NiFe/Ru/NiFe). The simulation results were compared with the previous experimental results [N. Smith et al., Phys. Rev. Lett. 101, 247205 (2008)]. We confirmed that a nonzero STT through the Ru layer is essential for explaining the experimental results.