• Journal of the Korea Society for Simulation
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• v.28 no.4
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• pp.21-32
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• 2019

Inspired by the social behavior models of a bird flock or fish school, particle swarm optimization (PSO) is a popular metaheuristic optimization algorithm and has been widely used from solving a complex optimization problem to learning a artificial neural network. However, PSO is difficult to apply to many real-life optimization problems involving stochastic noise, since it is originated in a deterministic environment. To resolve this problem, this paper incorporates a resampling method called the uncertainty evaluation (UE) method into PSO. The UE method allows the particles to converge on the accurate optimal solution quickly in a noisy environment by selecting the particles' global best position correctly, one of the significant factors in the performance of PSO. The results of comparative experiments on several benchmark problems demonstrated the improved performance of the propose algorithm compared to the existing studies. In addition, the results of the case study emphasize the necessity of this work. The proposed algorithm is expected to be effectively applied to optimize complex systems through digital twins in the fourth industrial revolution.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.25 no.1
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• pp.27-35
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• 2015

Objectives: To investigate safety and health management, conditions in factories or facilities handling radiation-generating devices and radioactive isotopes were reviewed in terms of regulations of radiation safety control in Korea. Radiation exposure levels generated at those facilities were directly measured and evaluated for establishing an effective safety and health management plan. Methods: Government organizations with laws and systems of radiation safety and health were investigated and compared. There are three laws governing radiation-related employment such as occupational safety and health acts, nuclear safety acts, and medical service acts. We inspected 12 workplaces as research objects:four workplaces that manufacture and assemble semiconductor devices, three non-destructive inspection workplaces that perform inspections on radiation penetration, and five workplaces in textile and tire manufacturing. Monitoring of radiation exposure was performed through two methods. Spatial and surface monitoring using real-time radiation instruments was performed on each site handling radiation generating devices and radioactive isotopes in order to identify radiation leakage. Results: According to the occupational safety and health act, there is no legal obligation to measure ionizing radiation and set dose limits. This can cause confusion in the application of the laws, because the scopes and contents are different from each other. Surface dose rates in radiation generating devices such as implanters, thickness gages and accelerators, which were registered according to nuclear safety acts, using surveymeters, and seven of 36 facilities(19.4%) exceeded the international standards for surface radiation dose of $10{\mu}Sv/hr$. Conclusions: The results showed that occupational health and safety acts require a separate provision for measuring and assessing the radiation exposure of workers performing radiation work. Like noise, ionizing radiation will also periodically be controlled by including it in the object factors of work-environment measurement.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.16 no.4
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• pp.364-374
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• 2006

Natural ventilation technique could be the substitute for or the complement to the local exhaust ventilation system in the sense of protecting work environment. Moreover, it has many strong points ; almost no mechanical parts, no energy use and no noise. If applied appropriately, it could have the very high ventilation rate and save a lot of energy expense. But, it depends on the outdoor environment, especially temperature and wind speed/direction. Predicting the capacity of natural ventilation is not an easy job because it comes from both buoyancy and wind effect. Another problem is too much flow through the ventilator especially in winter time due to too much difference between indoor and outdoor temperature. Thus some ventilators in industries are sealed by door or plastic sheet, resulting in bad work environment. Various types of dampers are used to control the flow rate through ventilators. The capabilities of flow control by damper has not been estimated. In addition, it was not tested whether the damper could obstruct the flow through ventilator when fully opened. To answer these questions, 4 types of dampers were tested by using computational fluid dynamics. 10 different configurations includes no damper, full open and half open. Flow rates were estimated and airflow fields were analysed to clarify the before-mentioned questions. The dual type damper was the best choice for controling the capability of ventilator. In addition, the upward grill type damper was the best for not obstructing the air flow when fully opened.

• Current Industrial and Technological Trends in Aerospace
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• v.7 no.2
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• pp.95-105
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• 2009

Fuel cells are applied to the propulsion system of aircraft based on environmental-friendly characteristics with low noise and zero emission of CO2, currently many kinds of UAV and small manned aircraft equipped with fuel cells are being developed. Fuel cells for aircraft typically classified into PEMFC(Proton Exchange Membrane Fuel Cell) type and SOFC(Solid Oxide Fuel Cell) type and the system is developed to adapt missions and operational conditions of aircraft. For UAV, various types of aircraft mostly based on PEM fuel cell technology are investigated for military or commercial uses, and the stability and endurance of system will be improved. For small manned aircraft, many researches are carried out to substitute the propulsion system by fuel cell, also some developments for the higher performance of APU of large commercial aircraft to apply fuel cells are in progress. In the future, a fuel cell aircraft will be expected to improve the reliability and efficiency with higher power density.

• The Journal of the Korea institute of electronic communication sciences
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• v.7 no.5
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• pp.1067-1072
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• 2012

Recently, linear motors have been widely researched and have been increasingly used in various industrial applications. Especially, permanent magnet linear synchronous motors(PMLSMs) have been getting the spotlight in the transportation system. A PMLSM is structurally simple and has a lot of merits such as high speed, high thrust force, etc. However, in case of a long stator system which arranges armature to the full length of transportation lines, a PMLSM has some disadvantages such as the material cost increase and long manufacturing time. Hence, in order to overcome these problems, the PMLSM with stationary discontinuous armature structure and concentrated windings was proposed. However, this method occurs undesirable cogging force by outlet edge effect. The cogging force causes thrust force ripples and generates noise and vibration. Therefore, in this paper, we proposed installation method of auxiliary pole PMLSM with concentrated winding applying bifurcating in order to reduce cogging force by the outlet edge when the armature is placed in a discontinuous arrangement. Also, we have examined characteristics of outlet edge cogging force using 2-D finite element analysis(FEA).

• Journal of the Korean Society of Safety
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• v.33 no.2
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• pp.21-27
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• 2018

The expansion and stable operation of electric power facilities are important factors with development of industrial facilities in modern society. In high-voltage equipment such as GIS, the insulation characteristics may be deterioated by environment-friendly gas adaption and miniaturization. There is also the possibility of accidents due to insulation breakdown due to the deterioration of power facilities. Therefore, it is necessary to extend the diagnosis system to continuously monitor the danger signals of these power equipment and to prevent accidents. Most of the internal defects in the GIS system are conductive particles, floating electrode defects, protrusion defects, and the like. In this case, a partial discharge phenomenon is accompanied. These partial discharge signals occur irregularly and various noise signals are included in the field, so it is difficult to evaluate the reliability in the development of the diagnostic system. In this paper, a study was made on equipment capable of generating a partial discharge simulated signal that can be adjusted in size and frequency to be applied to a diagnostic device by electromagnetic wave detection method. The PD simulated pulse generator consists of a user interface module, a high-voltage charging module, a pulse forming circuit, a voltage sensor and an embedded controller. In order to simulate the partial discharge phenomenon similar to the actual GIS, a discharge cell was designed and fabricated. The application of the prototype pulse generator to the commercialized PD diagnosis module confirmed that it can be used to evaluate the performance of the diagnostic device. It can be used for the development of GIS diagnosis system and performance verification for reliability evaluation.

• Journal of Power System Engineering
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• v.12 no.3
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• pp.38-43
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• 2008

The usage of electric forklift truck is gradually increasing due to the convenience at conveying and arranging the materials in the industrial field. In this study, the author designed and suggested the optimum driving system and load tester which both of them are the most important part of the forklift truck. The planetary gear is chose to driving system because it makes big power even though the motor size is small. The gear teeth of planetary gear were designed and the designed planetary gear was tested considering the yield strength and the abrasion of gear teeth. The B-Type electric brake which consists of multiple plates and operates with non-magnetic type was connected with a single shaft in the driving system. So, it can be applied at the sudden braking situation which has the torque increment. And it has the compact size and excellent durability Load tester can give the various levels of load to the planetary gear of driving system in the electric forklift truck and it can also measure the levels of the load which were applied. Therefore, we can measure the noise, torque and perform the durability, vibration tests using load tester. It will be economical because many kinds of test can be performed using reasonable priced load tester The driving system of electric forklift truck which has sufficient competitive can be manufactured using our designed planetary gear reducer with reasonable price. The designed load tester can use for checking the performance of other reducers, as well.

• Journal of Korean Physical Therapy Science
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• v.7 no.1
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• pp.367-375
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• 2000

The purpose of this study is to announce the present condition, walking training, and adaptable training of a limb amputated patient. The study is a successful report of the limb amputated patient through the medical treatment of the physical therapy. A cause of the limb amputated patient, a truck driver, was that the patient was hit by a train when the driver alight from the truck. Then, the driver was surgical operated on left AK (Above Knee) amputation and left AE (Above Elbow) amputation by orthopedics at the Young Dong Severance Hospital on Dec.7, 1996. Two weeks after the operation (Dec., 22, 1996), the patient was trained at the Yonsei Medical Center Physical Therapy Hospital for the walking and temper adjust training. It was possible to do a flat surface walking and a slope surface walking without helping due to the patients optimistic personal character and motivation. However, the patient struggled to a dull surface walking and his weak endurance. the patient has several problems when the patient wears artificial legs and hands, fears on fall down, and mentally worries on noise when he walks. It is necessary to approach for this problems by many fields of the helpers, such as Rehabilitation medical doctor, physical therapist, occupational therpist, artificial limbs makers, psychologists, and etc. Therefore, in order for recovering from the amputated parts function after the surgical operation, more approved reports have to be for the amputated patients due to increasing traffic accidents, industrial disaster, cancer, diabetes, obstacles of the peripheral nervous system, and etc.

• Journal of Navigation and Port Research
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• v.28 no.10 s.96
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• pp.875-879
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• 2004

In this paper, sub-harmonic pumped(SHP) mixer using anti-parallel diode pair(APDP) is designed for 5 GHz band wireless communication system. Conventional mixers mix LO with RF, and obtain IF signal from the difference between LO and RF. As the frequency increase, LO signal requires higher LO power, better phase noise characteristics, more stable La. However, using APDP, the SHP mixer mixes the 2nd harmonics of LO signal. Therefore, the SHP mixer has an advantage that the LO signal frequency required for IF signal is reduced at half value of LO fundamental frequency. When LO power is 3 dBm, the conversion loss of manufactured SHP mixer is 12.83 dB. The isolation of LO/IF, 2LO/IF, RF/1F and LO/RF is 39.17 dB, 58 dB, 34 dB, and 67.9 dB. respectively. For this case, IP3 at input is 8 dBm.

• Fashion & Textile Research Journal
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• v.12 no.2
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• pp.203-213
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• 2010

This study examined the wearing conditions of working clothes of shipbuilding industry workers according to the working environmental factors and working process features. It was also investigated the relationship between the wearing sense of working clothes and the overall comfort according to work processes. In the working process of shipbuilding industry, the process of fitting, welding, grinding and painting were chosen by considering work environmental factors, disaster types, hazardous materials, work process features, working clothes and safety equipments of each work categorized. The workers of fitting process usually wore the standard working clothes, while more than 60% of the workers of welding, grinding and painting wore the specialized protective clothes. The hazardous work environmental factors such as noise, heavy dust, high temperature and noxious fumes affected to the workers of fitting, welding and grinding. However, the workers of painting were greatly damaged by organic solvent. The dissatisfaction with the wearing performance of working clothes was highly shown in the sweat absorbency, moisture permeability and body protection. In respect of the correlation between the overall comfort and the wearing sense of working clothes, the satisfaction was decreased in orders of movement comfort> sensual comfort> physiological comfort.