• Transactions of Materials Processing
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• v.13 no.7
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• pp.570-579
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• 2004

정상상태 압연공정의 오일러리안 공정해석 모델에 관한 연구들을 종합 정리하였다 본 연구의 유한요소해석 모델은 집합조직의 발전에 따른 이방성과 미세기공의 성장에 따른 기계적 성질의 열성화를 평형방정식에 직접 결합하였다 따라서 집합조직의 발전 및 기공률의 변화를 예측하고 동시에 이방성과 기계적성질의 열성화를 해석에 반영할 수 있다. 더불어 오일러리안 해석에서 형상예측을 위하여 자유곡면 수정법과 유선추적법을 유한요소해석 모델에 결합하였다 본 연구의 공정해석 모델을 평판 압연, 클래드압연, 삼차원 사각단면봉의 압연 및 형상압연에 적용하여 집합 조기의 발전, R-값, 항복곡면, 결함성장 등의 기계적성질의 변화 예측과 클래드 압연시에 이중재 접촉면 형상, 배불림, 형상압연 시의 단면변화 등의 형상변화 예측을 보여주었다.

• Journal of the KSME
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• v.19 no.2
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• pp.98-105
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• 1979

이상의 고압중스트레인 측정실험으로부터 다음과 같은 결론을 얻었다. (1) 고압중에서 스트레인을 측정할 경우, 압력효과스트레인이 생기므로 스트레인의 지시치를 보정할 필요가 있다. (2) 고압 효과스트레인은 같은 종류의 게이지에 있어서도 흩어짐이 있으나 흩어짐의 폭은 압력효과스트 레인의 값보다 작다. 특히 300 기압이상에서는 브릿지의 평형을 취해가지고 측정하며는 이 흩 어짐은 한결 작아진다. (3) 고압수중에서 측정 할 경우, 대후론, 시리콘고무, 이중피복선을 도선 으로 하여 사용하고, 게이지의 부분은 시리콘고무코우팅을 되도록 두껍게 하며는 3,000 기압 정 도까지의 수압중에서도 절연저하를 초래하지 안고, 스트레인측정을 할 수가 있다. (4) 상기의 절연방법은 도선인출부에도 적용할 수 있다. (5) 원통형 하우징 모형의 내외면의 스트레인를 측 정한 결과, 유한요소법해석결과의 타당성을 확인 할 수가 있었다. 본실험은 1974년도 일본통산 성공업기술원에서 위탁받아 동지종합연구소에서, [대식도 원읍조작해저석유굴삭장치의 개발]에 관한 연구성과의 일부와 Waterloo 대학의 G.S. Kular 교수연구실의 연구결과임을 밝혔다.

• Journal of Radiation Protection and Research
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• v.14 no.2
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• pp.23-29
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• 1989

A Lucas cell was established and calibrated by using the double layer tube standard radon source. The calibration factors were 0.031$\pm$0.002 (pCi/l)/(cph/Cell) at room temperature, and 0.029$\pm$0.001 (pCi/l)/(cph/Cell) at $50^{\circ}C$. Radon and its daughters concentrations were measured in a room air for the demonstrating purpose. The concentrations of 222 Rn, $^{218}Po,\;224\;Pb,\;and\;^{214}Bi$ were 0.87, 0.53, 0.35 and 0.26 pCi/l. The total eqilibrium factor was around 0.40 and the WL is $3.33{\times}10^{-3}$, resulting in 30 mrem/yr at this place.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.10 no.3
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• pp.199-205
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• 2017

In a small cell base station used in densely populated areas, a dual polarized multiple antenna(MIMO) is mainly used to increase the cell capacity. This paper demonstrates a dual-polarization antenna with high cross-polarization discrimination(XPD) that can improve the capacity of a small cell using a dual polarization multiple antenna (MIMO). By using the symmetric structure and differential feeding, high XPD in all directions is achieved. In addition, a very similar radiation pattern is observed between each polarization. Because of high XPD and similar radiation pattern in all directions, proposed antenna is well adopted for small-cell multiple-input multiple-output(MIMO) system. Experimental results shows that the proposed antenna has a bandwidth of 180 MHz (2.51~2.7 GHz), a maximum gain of 4.5 dBi (3.5~4.5 dBi), and a half-power beam width of 85 degrees. In addition, average XPD of 26.4 dB in all directions, more than 13.8 dB increase than previous dual-polarization antennas which use single emitter by using different feeding or selectively use polarization through switching.

• Journal of Nutrition and Health
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• v.54 no.6
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• pp.573-583
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• 2021

Energy requirement is defined as energy expenditure in an energy equilibrium state. The doubly labeled water (DLW) method is considered the gold standard for measuring total energy expenditure (TEE). In 2002, the Institute of Medicine (IOM) of the National Academies established dietary reference intakes (DRIs) for Americans and Canadians, and the equations for estimated energy requirement (EER) were developed by using pooled data from studies that had applied the DLW method. Since 2005, these equations have been used for establishing EER in the DRI for Koreans. These equations based on age group include the physical activity (PA) coefficient determined by the PA level (PAL; sedentary, low active, active and very active) as well as body weight and height. The PAL values of Koreans calculated using the DLW method and PA diaries were determined to fall in the low active category (1.40~1.59). Therefore, the PA coefficient corresponding to 'low active' was applied to the EER equations. In recent years, with increasing number of people regularly engaging in various physical activities in Korea, EER is now separately presented for people with 'active' and 'very active' PALs. In the future, like the United States and Japan, Korea needs to expand the DLW research for developing EER predictive equations for Koreans. In addition, standardized guidelines should be prepared to accurately evaluate the PAL using the physical activity diary and the new PA classification table for Koreans.

• Journal of Korean Society of Transportation
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• v.27 no.6
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• pp.147-156
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• 2009

We present a methodology for modeling and solving the transit frequency design problem with variable demand. The problem is described as a bi-level model based on a non-cooperative Stackelberg game. The upper-level operator problem is formulated as a non-linear optimization model to minimize net cost, which includes operating cost, travel cost and revenue, with fleet size and frequency constraints. The lower-level user problem is formulated as a capacity-constrained stochastic user equilibrium assignment model with variable demand, considering transfer delay between transit lines. An efficient algorithm is also presented for solving the proposed model. The upper-level model is solved by a gradient projection method, and the lower-level model is solved by an existing iterative balancing method. An application of the proposed model and algorithm is presented using a small test network. The results of this application show that the proposed algorithm converges well to an optimal point. The methodology of this study is expected to contribute to form a theoretical basis for diagnosing the problems of current transit systems and for improving its operational efficiency to increase the demand as well as the level of service.

• The Transactions of the Korea Information Processing Society
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• v.7 no.11
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• pp.3479-3489
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• 2000

Most of the study on fairness control method for Distributed-Queue Dual-Bus(DQDB) have been performed under specific load types such as equal probability load types or symmetric load types. On Web-based internet enviroments client-server load types are more practical traffic patlerns than specrfic load types. In this paper, an effiective fairness control method to distribute DQDR network bandwidth fairly to all stations under a client-server load is proposed. In order to implement a dynamic bandwidth timing capabihty needed to distribute the bandwidth fairty at heavy loads, the proposed method uses two pararnetexs, one is an access hrnit to legulate each station's packet transmission and the other is the number of extra emply slots that are yielded to downstream stations. In point of implementation this mechanism is simpler and easier than Bandwidth Tuning Mechanism(BTM) that uses an intermediate pattern and an adptation function. Simulation results show that it outperforms othen mecharusms.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.14 no.6
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• pp.117-124
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• 2015

In this paper, a new kind of wideband, low-loss composite right/left-handed (CRLH) transmission line (TL) and a Wilkinson power divider are presented. The TL is composed of a parallel meander inductor and a series cutting capacitor based on coplanar waveguide (CPW) structure. The power divider is designed by substituting the CRLH-TL into the conventional transmission line. The experiment results show that the TL has a good agreement with the desired results, exhibiting the return losses under 12 dB from 8.4 GHz to 34.4 GHz. The operating frequencies of the power divider are 12.05 GHz to 13.15 GHz and 16.50 GHz to 19.30 GHz, respectively. The 20 dB bandwidths are 8.9 % and 17.9 %, respectively. Typical experimental measurements are conducted and compared with the simulated results.

• Journal of Korean Society of Transportation
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• v.19 no.1
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• pp.89-99
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• 2001

The conventional studies on equilibrium network design problem(ENDP) with fixed travel demand models assume that the future OD travel demand might not be changed even if the structure and the capacity of the network are improved. But this fixed demand assumption may loose its validity in the long-range network design because OD travel demand actually shifts with the network service level. Thus, it is desirable to involve the variable travel demand which is determined endogenously in the model in the optimal network design. In this paper a hi-level model formulation and solution procedure for ENDP with variable travel demand are presented. Firstly It is considered how to measure the net user benefits to be derived from the improved in link capacities, and the equilibrium network design problem considered here is to maximize the increase of net user benefit which results from a set of lift capacity enhancements within the budget constraints, while the OD travel demands and link travel times are obtained by solving the lower level network equilibrium problem with variable demand. And secondly sensitivity analysis is carried out to find the links to which the network equilibrium flow pattern is the most sensitive. Finally numerical example with simple network is carried out to test the validity of the model.

• Aerospace Engineering and Technology
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• v.13 no.2
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• pp.160-166
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• 2014

The shutoff valve of a Liquid Rocket Engines (LRE) controls the flow of propellant between turbo-pump and combustion devices of LRE using pilot pressure and spring force. The shutoff valve is closed when the pilot pressure is removed from the diaphragm type actuator. During designing process of life cycle is when should be analyzed according to the characteristics of forces with respect to the opening and closing of diaphragm actuator. A valve has been designed to adjust the control pressure which is required to open a poppet and to determine the working fluid pressure at which a valve starts to close. During flow capacity test under room temperature as a part of life cycle tests, the leakage in diaphragm was occurred due to the leakage of sheet welding sections. The operating cycle of the diaphragm type actuator is about 61 times with 22 MPa of pilot pressure.