• Journal of Korea Society of Digital Industry and Information Management
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• v.13 no.3
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• pp.11-17
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• 2017

The aerial support air sculptures currently exhibited in indoor spaces are similar to simple ad balloons, using multiple rope strands. Users now want more advanced unfixed sculptures, and hope these will develop into buoyant sculptures that can maintain the attitudes that users want on their own. This study investigated an attitude control system for unfixed levitation sculptures that can levitate with no rope and continuously maintain a certain attitude at a height specified by the user. To facilitate levitation, the exterior part of the sculpture was made of lightweight fibers, and the interior part was filled with helium gas. The controller was composed of a microprocessor of the dsPIC30F line from microchip, gyro, acceleration, and earth magnetic field sensors, and a highly efficient brushless DC (BLDC) electric motor. The attitude and position control system requires scheduling considering the trajectories of the sculpture and the control system, because the roles of the overall components are more important than those of a single controller. Furthermore, the system was designed like a fusion system that is expanded and controlled as a total controller, because it is interconnected with various sensors. The attitude control system of buoyant sculptures was implemented in this study, such that it can actively cope with the position, direction, stopping, and time aspects. The system performance was then evaluated.

• Transactions of the Korean Society of Automotive Engineers
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• v.1 no.3
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• pp.1-11
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• 1993

An experimental study was carried out to evaluate the characteristics of transient performance of carburettered gasoline engine under rapid accelerating transient driving conditions. In order to evaluate the characteristics of transient performance quantitatively, the concept of dead time $t_d$ response delay time $t_r$ are introduced. Performance parameters such as air mass fiowrate Gat, engine speed N, manifold boost pressure Pb, and output torque T are measured simultaneously during the rapid opening of the throttle valve by the stepping motor. During the rapid opening of the throttle valve, air mass fiowrate Gat is increased immediately without delay time, but response of engine revolution N, and output torque T are delayed. Therefore hesitation, and stumble phenomena are occurred. Dead time $t_d$ and response delay time $t_r$ of engine revolution N, which is extremely delayed comparing to other performance parameters, are respectively 0.2-0.3sec., 3.0-4.6sec., and dead time rate $t_d/{\Delta}t$ and response delay time rate $t_r/{\Delta}t$ are linearly increased with the throttle valve opening rate ${\theta}$ during the acceleration from 12 degree to 20 degree at 1250rpm.

• Journal of the korean Society of Automotive Engineers
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• v.8 no.4
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• pp.24-35
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• 1986

현재 주요 가스상물질은 미국의 경우 규제전보다 일산화탄소가 96%, 탄화수소 96%, 질소산화물 76%가 개선되어 어느정도 안정단계에 들어 갔다고 볼 수 있다. 그러나, 입자상물질규제는 디이 젤자동차의 증가와 더불어 1986-1994기간동안 대폭적으로 강화되고 있다. 그러나 자동차 배출 가스중에는 수백가지의 화학물질이 존재하고 인체에 유독한 물질은 규제물질외에도 엄청나게 많다. 따라서 1977년 8월에 개정된 미국의 대기정정법(CAA, clean air act)에는 "신규 제작자동 차나 엔진에 사용되는 어떠한 방지장치, 시스템 또는 부품도 공중보건, 복지 및 안전에 부당한 위험을 일으키거나 일으키는 요인이 될 수 없다"(참조, CAA 202 (a) 및 CFR 86.084-5)고 규 정하고 있다. 이에 따라 미국환경청에서는 회람 등을 통하여 가능한 독성물질에 대하여 경우에 따라 측정할 것을 요구하고 있다. 국내 환경보전법에도 자동차연료첨가제 사용할 때 현저하게 유해한 물질이 배출된다고 인정하는 때에는 그 사용을 규제할 수 있게 되어있고 새로 제정될 자동차 배출가스 시험검사방법 및 절차에 관한 규정에 이에 관한 사항을 추가할 움직임이 있다. 물론 미규제물질의 규제하는 인체에 대한 피해정도나 측정방법 등의 여러 가지 문제가 수반되나 장기적인 국민보건과 환경보전 측면에서 신중하게 다루어져야 되리라 봐서 여러 가지 오염물질의 현황이나 분석방법 등에 대하여 기술코자 한다.여 기술코자 한다.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2001.11a
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• pp.230-236
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• 2001

We developed a built-in sensor bearing to measure the rotor motion of a rolling piston type compressor for the air conditioner. Because of needs for the high efficiency and long life span of compressor, and the usage of alternative refrigerants, the operating condition of the compressor becomes more severe. The accurate measurement of the rotor motion of the compressor can contribute greatly to the design and analysis of the hydrodynamic bearing. However, it is difficult to measure accurately the shaft behavior of small compressor because of the small space for the sensor mount, high temperature and pressure of compressor, oil mixed with refrigerant, and electromagnetic noise of the motor. To overcome these difficulties, we develop the cylindrical capacitive sensor that is built in the hydrodynamic bearing and calibrate the built-in sensor bearing indirectly through measuring the oil relative permittivity. We measured the rotor motion as well as suction and discharge pressures in various conditions. The several experimental results show that the developed built-in sensor bearing can measure the rotor motion not only in steady state but also in transient state.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.1
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• pp.54-62
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• 2015

This paper describes the design and fabrication of an electronically rotated Tactical Air Navigation(TACAN) antenna using parasitic elements and PIN diode switches. We used parasitic elements arranged in a circular array and PIN diode switches to electronically rotate the antenna instead of employing a mechanically rotated antenna using motor. The antenna's physical characteristics and design features to generate the cardioid pattern and nine-lobe pattern including bearing information are described and simulated. The measured result shows a very good agreement with simulation and meets the specification of MIL-STD-291C.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.9 no.1
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• pp.33-42
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• 1997

The reciprocating compressors are widely used in industrial fields for its simplicity in principle and high efficiency. But the design of it requires rigorous experiments due to its high dependence on many design parameters. In this work, a mathematical model is developed so that we can analyze the gas-solid interaction during the whole working processes of a reciprocating compressor. The governing equations, which represent the fluid-solid interaction, was derived from the unsteady Bernoulli's equation with the assumption of quasi-steady working process. The valve itself was assumed to be a one degree of freedom spring-mass-damper system. A simple thermodynamic relation, the ideal gas state equation, was used to give it an external force term assuming that the refrigerant behaves like an ideal gas. It was suggested to use a motor of higher driving frequency to enhance the performance of the reciprocating compressor without causing a faster failure of the valve.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.21 no.6
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• pp.333-339
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• 2009

The objective of this study is to predict optimal intermediate pressure of a 2-stage compression heat pump system using river water. To determine the maximum performance of the 2-stage compression heat pump system, the experimental evaluations on the 2-stage compression cycle were carried out under various operating conditions. Electronic expansion valves were applied to control intermediate pressure and superheat. Based on the experimental data, an empirical correlation for predicting optimal intermediate pressure which considering cycle operating parameters was developed. The present correlation was verified by comparing the predicted data with the measured data. The predictions showed a good agreement with the measured data within a relative deviation of ${\pm}4%$ at various operating conditions.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.25 no.10
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• pp.529-533
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• 2013

Heat-recovery ventilators are being adopted in most newly built apartment houses for energy reduction and indoor environment improvement. In winter, however, the dew condensation resulting from the difference between the indoor and outdoor temperatures may reduce the ventilator's performance and threaten the health of indoor residents. This study analyzes the occurrence of dew condensation according to the ventilator's operational conditions and the changes of temperature and products. The experimental results show that condensations is formed at $26^{\circ}C$ and 60%R.H, which is an unfavorable climatic condition, and when the damper is not closed tightly. Therefore it is important to ensure damper performance to prevent back flow.

• Journal of Korean Society for Atmospheric Environment
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• v.22 no.3
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• pp.383-391
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• 2006

In Korea, the major source of serious air pollution is motor vehicles. Air pollution from vehicles has been annually increased. Then the government will try to control the vehicle emission by applying the effective emission management policy for the manufactured and in-used car. It is necessary to correctly calculate the emission factor for successful propulsion of the vehicle emission control policy. In this study, correlation analysis of exhaust emissions from vehicles between CVS-75 mode and Korea mode was conducted. A total of 25 light-duty buses were tested on the chassis dynamometer system in order to measure CO, HC, NOx PM and fuel efficiency (F.E.). For the test modes, 10 different Korea modes and CVS-75 mode were used. As the result of correlation analysis between those modes, most of the correlation coefficients were higher than 0.90. On the basis of high correlation between those modes, correction factors by driving conditions were estimated. Through the results of this study, we obtained essential basic data to correct difference from those modes.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.5
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• pp.432-438
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• 2003

This paper describes a modified Roebuck compression device as a potential compression device of a rotating cryogenic refrigeration system in superconducting machine such as generator or motor. The conventional cryogen transfer method from stationary refrigeration system to rotating system can be eliminated by an on-board cryogenic refrigeration system that utilizes well-designed multi-stage modified Roebuck compression device. This paper shows basic thermodynamic analysis of modified Roebuck compression device and its application for compressing neon at 77 K with substantial pressure ratio when the rotor diameter is 0.8 m with rotating speed of 3600 rpm. The device does not require any moving part in rotating frame, but two separate thermal reservoirs to convert thermal energy into mechanical compression work. The high temperature thermal reservoir is atmospheric environment at 300 K and the low temperature thermal reservoir is assumed as a liquid nitrogen bath at 77 K. The concept of the compression device in this paper demonstrates its usefulness of generating high-pressure neon at 77 K for rotating J-T neon refrigeration cycle of superconducting rotor.