• 한국산업융합학회 논문집
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• 제21권3호
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• pp.141-147
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• 2018

In a time when product development cycles are getting shorter and shorter, many companies are making efforts to develop products with high reliability in a short period of time, accelerated life test is widely used as a method to quickly evaluate reliability. Accelerated life test reduces the test life or the life of the product from the observed data by shortening the lifetime of the product or abruptly lowering the performance under the worse condition than the actual condition in order to shorten the test cost or the test time. In this paper, BL3640A-06P+RB35, DC12V model, which is used in the support device of an automatic rotation type digital signage, which display various information such as textures and images on a display screen in a public place or a commercial space, BLDC motors were subjected to a constant stress test and at the rotational speed of 1rpm, $180^{\circ}$ rotation and reverse rotation under actual use conditions, the stress was imposed on the rotating speed of 2rpm and the weight of the actual installed product from 22.2kgf to 10kgf were installed. The lifetime of the actual use environment condition is 23,545 hours and the rotation speed is accelerated. The life time of the acceleration condition with the additional weight is 1,380 hours. The acceleration factor is calculated as 17.06, the one year guarantee test day is 235 days to 14 days, of the period from 470 days to 28 days, and the third year from 704 days to 42 days. The test date of the BLDC motor was tested on the shortened test date, and the rotational speed and the current value were measured. It is found that there is no defect even if it operates as the test date corresponding to the specified one year warranty period and the 3 year accelerated life test which is experimented. Using the statistical technique of the regression analysis the expected time for the motor to defect to #4 samples was 20 years.

• 한국자동차공학회논문집
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• 제7권8호
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• pp.7-16
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• 1999

To maintain thereasonable temperature in the engines is very important to keep the steady combustion state of engine and to prevent increasing of oil consumption , deteriorating of lubricant, shortening of the life time of engine and decreasing of material strength. The method of energy balance for divided elements of radiator and engine-oil cooler is considered to analyse the performance of radiator and engine-oil cooler. The data obtained by engine test and vehicle cooling tunnel test are applied to program for calculation of radiator outlet temperature. As a result, data obtained by numerical analysis agree well with those by experiments. And thus, it is concluded that this simulation program is available in developing the cooling system for a new car.

• 한국의류산업학회지
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• 제6권6호
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• pp.699-706
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• 2004

In today's fashion industry, directions for new products and high value added of fashion goods, product changes according to cycles, the shortening of life cycles, added value, planned obsolescence, and presentation is focused on fashion trends that will be selected by many consumers at the point of selling time. Therefore fashion information poses great importance and its weight is growing bigger everyday. Fashion information recognized to be important is reflected practically in the prediction of fashion changes in the fashion industry; especially, it is the first stage of the merchandising process that is the course of new product development. Presently, with some differences according to the size and specialized area of a firm, domestic fashion menufacturers obtain information from sales data of competing brands and their own, market information, consumer information based on primary data, shared fashion trend information given by domestic fashion information providing companies. Firms can not produce differentiated images and product concepts using such shared information. Although the types, importance and reflection of used information vary according to merchandising processes, all experts engaging in the merchandising of fashion products use the same shared information.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1999년도 추계학술대회 논문집
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• pp.155-158
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• 1999

Because the traditional filters have many demerits, multi-step electric oil filter have manufactured the efficiency of insulating oil to improve. Therefore, the function of oil filter to improve based on my experience and know-how about my job. Through this study have obtained many merits. The efficiency of insulating oil is improved. The waste oil reused in repair works of the damaged transformer. Multi-step filter is shortening the working time and safety. it is handy for use and movement. This study lengthen the expected life span of filter. The improvement of oil filter bring about elevation of productivity.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 춘계 학술발표회 제16권1호
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• pp.636-639
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• 2004

Reinforced concrete structures have been used for a long time. However, corrosion problem in reinforcing steel is inevitable, which results in the degradation of performance and the shortening of the life of structures. To overcome such problems, FRP(Fiber Reinforced Polymer) rebars have been developed. Due to their corrosion resistance and their superior mechanical properties, FRP rebars are increasingly applied to concrete structures in other countries. To obtain the composite action between FRP rebars and concrete, sufficient bond between two materials must be secured. But, the behavior of FRP rebars is different from that of steel rebars. Therefore, it is necessary to understand and develop the proper bond mechanism of FRP rebars to use them in concrete structures. This paper presents analytical results to investigate the bond-slip relationship between FRP rebars and concrete based on pull out tests.

• 전기학회논문지
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• 제64권4호
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• pp.616-622
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• 2015

A microgrid which is composed of distributed generation systems, energy storage systems and loads is operated in the grid-connected mode and in the islanded mode. Especially, in the islanded mode, a microgrid should maintain frequency in the allowed range. The frequency is decided by a balance between power supply and power demand. In general, the frequency is controlled by using battery energy storage systems (BESSs) in the microgrid. Especially, droop control is applied to controlling BESSs in the microgrid. Meanwhile, over-charging and deep-discharging of BESS in operation and control cause life-shortening of batteries. In this paper, a fuzzy droop control is proposed to change droop gains adaptively by considering state of charge (SOC) of BESSs to improve the life cycle of the battery. The proposed fuzzy droop control adjusts droop gains based on SOC of BESSs in real time. In other to show the performance of the proposed fuzzy droop control, simulation based on Matlab/Simulink is performed. In addition, comparison of the convention droop control and the proposed fuzzy droop control is also performed.

• The Korean Journal of Physiology and Pharmacology
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• 제23권6호
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• pp.483-491
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• 2019

Cordycepin exerts neuroprotective effects against excitotoxic neuronal death. However, its direct electrophysiological evidence in Alzheimer's disease (AD) remains unclear. This study aimed to explore the electrophysiological mechanisms underlying the protective effect of cordycepin against the excitotoxic neuronal insult in AD using whole-cell patch clamp techniques. ${\beta}$-Amyloid ($A{\beta}$) and ibotenic acid (IBO)-induced injury model in cultured hippocampal neurons was used for the purpose. The results revealed that cordycepin significantly delayed $A{\beta}$ + IBO-induced excessive neuronal membrane depolarization. It increased the onset time/latency, extended the duration, and reduced the slope in both slow and rapid depolarization. Additionally, cordycepin reversed the neuronal hyperactivity in $A{\beta}$ + IBO-induced evoked action potential (AP) firing, including increase in repetitive firing frequency, shortening of evoked AP latency, decrease in the amplitude of fast afterhyperpolarization, and increase in membrane depolarization. Further, the suppressive effect of cordycepin against $A{\beta}$ + IBO-induced excessive neuronal membrane depolarization and neuronal hyperactivity was blocked by DPCPX (8-cyclopentyl-1,3-dipropylxanthine, an adenosine $A_1$ receptor-specific blocker). Collectively, these results revealed the suppressive effect of cordycepin against the $A{\beta}$ + IBO-induced excitotoxic neuronal insult by attenuating excessive neuronal activity and membrane depolarization, and the mechanism through the activation of $A_1R$ is strongly recommended, thus highlighting the therapeutic potential of cordycepin in AD.

• 열처리공학회지
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• 제22권4호
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• pp.228-233
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• 2009

In order to predict the temperature distribution of stainless steel strip in Bright Annealing (BA) furnace, we performed the analysis of heat transfer and fluid flow using STAR-CCM+. The analysis model included unsteady fluid flow, heat transfer with radiation and moving grid. Two kinds of radiative properties, emissivity and reflectivity, were applied to the stainless steel strip, one is constant and the other is variable with time. As we call, the BA furnaces of stainless steel strip have two different types, muffle and no-muffle. The using of muffle type has been faced with some problems such as rising in material price and shortening of life cycle, etc. So the development of no-muffle type BA furnace is very important in order to save energy cost, lower environmental load and increase the productivity. The designed (or expected) temperature of stainless steel strip coming out of BA furnace was about $1065^{\circ}C$ while the environment temperature maintains around $1100^{\circ}C$. The result of our calculation was very close (or similar) to design temperature, and the application of radiative properties variable with time produced more accurate result than applying constant ones.

• 한국인터넷방송통신학회논문지
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• 제17권1호
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• pp.153-158
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• 2017

광범위한 공사현장에서 드론 운용 시 효율적인 데이터의 수집을 위해 대표적인 노드를 선정하여 방문하는 랑데부 포인트를 사용한다. 랑데부 포인트는 선정된 노드와 그 주변의 노드들에 데이터 전송이 증가하여 에너지 소모가 집중될 수 있으며 이는 네트워크 수명의 단축을 유발할 수 있다. 따라서 장시간의 공사기간을 고려할 때 랑데부 포인트를 효과적으로 교체하여 네트워크 수명을 장시간 유지하는 것이 중요하다. 본 논문에서는 센서의 에너지 잔량에 따라 랑데부 포인트를 교체해가며 드론을 통해 효율적으로 데이터를 수집하는 방법을 제안한다. 또한 제안 기법은 드론과의 상대거리도 반영하여 지리적으로 가까운 랑데부 포인트를 선정함으로써 드론의 이동 거리를 줄일 수 있다. 또한 시뮬레이션을 통해 제안 기법이 기존의 기법들에 비해 네트워크의 수명을 늘리고 드론의 비행 거리를 줄일 수 있다는 것을 확인하였다.

• 국제초고층학회논문집
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• 제1권1호
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• pp.37-51
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• 2012

New generation of tall and complex buildings systems are now introduced that are reflective of the latest development in materials, design, sustainability, construction, and IT technologies. While the complexity in design is being overcome by the availability and advances in structural analysis tools and readily advanced software, the design of these buildings are still reliant on minimum code requirements that yet to be validated in full scale. The involvement of the author in the design and construction planning of Burj Khalifa since its inception until its completion prompted the author to conceptually develop an extensive survey and real-time structural health monitoring program to validate all the fundamental assumptions mad for the design and construction planning of the tower. The Burj Khalifa Project is the tallest structure ever built by man; the tower is 828 meters tall and comprises of 162 floors above grade and 3 basement levels. Early integration of aerodynamic shaping and wind engineering played a major role in the architectural massing and design of this multi-use tower, where mitigating and taming the dynamic wind effects was one of the most important design criteria established at the onset of the project design. Understanding the structural and foundation system behaviors of the tower are the key fundamental drivers for the development and execution of a state-of-the-art survey and structural health monitoring (SHM) programs. Therefore, the focus of this paper is to discuss the execution of the survey and real-time structural health monitoring programs to confirm the structural behavioral response of the tower during construction stage and during its service life; the monitoring programs included 1) monitoring the tower's foundation system, 2) monitoring the foundation settlement, 3) measuring the strains of the tower vertical elements, 4) measuring the wall and column vertical shortening due to elastic, shrinkage and creep effects, 5) measuring the lateral displacement of the tower under its own gravity loads (including asymmetrical effects) resulting from immediate elastic and long term creep effects, 6) measuring the building lateral movements and dynamic characteristic in real time during construction, 7) measuring the building displacements, accelerations, dynamic characteristics, and structural behavior in real time under building permanent conditions, 8) and monitoring the Pinnacle dynamic behavior and fatigue characteristics. This extensive SHM program has resulted in extensive insight into the structural response of the tower, allowed control the construction process, allowed for the evaluation of the structural response in effective and immediate manner and it allowed for immediate correlation between the measured and the predicted behavior. The survey and SHM programs developed for Burj Khalifa will with no doubt pioneer the use of new survey techniques and the execution of new SHM program concepts as part of the fundamental design of building structures. Moreover, this survey and SHM programs will be benchmarked as a model for the development of future generation of SHM programs for all critical and essential facilities, however, but with much improved devices and technologies, which are now being considered by the author for another tall and complex building development, that is presently under construction.