• 산업경영시스템학회지
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• 제19권39호
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• pp.89-98
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• 1996

This paper is concerned with cost analysis model in free -replacement policy under the periodic maintenance policy The free-replacement policy with minimal repairable item is considered as follows; in a manufacturer's view point operating unit is periodically replaced, if a failure occurs between minimal repair and periodic maintenance time, unit is remained in a failure condition. Also unit undergoes minimal repair at failures in minimal-repair interval. Then total expected cost per unit time is calculated according to maintenance period Tin a viewpoint of consumer's. The expected costs are included repair cost and usage cost: operating, fixed, minimal repair and loss cost. Numerical example is shown in which failure time of item has beta distribution.

• Pediatric Gastroenterology, Hepatology & Nutrition
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• 제18권4호
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• pp.238-245
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• 2015

Purpose: The aim of this study was to evaluate bolus transit during esophageal swallow (ES) and gastroesophageal reflux (GER) events and to investigate the relationship between the characteristics of ES and GER events in a population of term and preterm newborns with symptoms of gastroesophageal reflux disease (GERD). Methods: The study population consisted of term and preterm newborns referred to combined multichannel intraluminal impedance (MII) and pH monitoring for GERD symptoms. The frequency and characteristics of ES and GER events were assessed by two independent investigators. Statistical significance was set at p<0.05. Results: Fifty-four newborns (23 preterm) were included in the analyses. Median bolus head advancing time corrected for esophageal length (BHATc) was shorter during mealtime than during the postprandial period (median, interquartile range): 0.20 (0.15-0.29) s/cm vs. 0.47 (0.39-0.64) s/cm, p<0.001. Median bolus presence time (BPT) was prolonged during mealtime: 4.71(3.49-6.27) s vs. 2.66 (1.82-3.73) s, p<0.001. Higher BHATc (p=0.03) and prolonged BPT (p<0.001) were observed in preterm newborns during the postprandial period. A significant positive correlation between BHATc and bolus clearance time was also observed (${\rho}=0.33$, p=0.016). Conclusion: The analysis of ES and GER events at the same time by MII provides useful information to better understand the physiopathology of GERD. In particular, the analysis of BHATc during the postprandial period could help clinicians identify newborns with prolonged esophageal clearance time due to impaired esophageal motility, which could allow for more accurate recommendations regarding further tests and treatment.

• Current Optics and Photonics
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• 제5권1호
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• pp.32-39
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• 2021

We propose a three-dimensional (3D) streaming system based on a lamina display that can convey field information in real-time by creating floating 3D images that can satisfy the accommodation cue. The proposed system is mainly composed of three parts, namely: a 3D vision camera unit to obtain and provide RGB and depth data in real-time, a 3D image engine unit to realize the 3D volume with a fast response time by using the RGB and depth data, and an optical floating unit to bring the implemented 3D image out of the system and consequently increase the sense of presence. Furthermore, we devise the streaming method required for implementing augmented reality (AR) images by using a multilayered image, and the proposed method for implementing AR 3D video in real-time non-face-to-face communication has been experimentally verified.

• 한국국방경영분석학회지
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• 제4권1호
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• pp.113-123
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• 1978

Consider a series system of two units, named 1 and 2, respectively. Two units are observed at the beginning of discrete time periods t=0,1,2, $cdots$ and classified as being in one of a countable number of states. Let (i, r) be a state of the system at time t, when the state of unit 1 is i and state of unit 2 is r at time t, Under some conditions, the opportunistic replacement policy that minimizes the expected total discounted cost or the average cost of maintenance is shown to be characterized by the control limits $i^{*}(r)$ (a function of r) and $r^{*}(i)$ (a function of i) : (a) in observed state (i, r), the optimal policy for unit 1 is to replace if $i{\ge}i^{*}(r)$ and no action otherwise; (b) in observed state (i, r), the optimal policy for unit 2 is to replace if $r{\ge}r^{*}(i)$ and no action otherwise. In addition, this paper also develops optimal policy in the finite time horizon case, where time horizon is fixed or a finite integer valued r.v. with known pmf.

• IEIE Transactions on Smart Processing and Computing
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• 제4권2호
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• pp.65-70
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• 2015

In this paper, we describe the world's first real-time ray-tracing chip architecture. Ray-tracing technology generates high-quality 3D graphics images better than current rasterization technology by providing four essential light effects: shadow, reflection, refraction and transmission. The real-time ray-tracing chip named RayChip includes a real-time ray-tracing graphics processing unit and an accelerating tree-building unit. An ARM Ltd. central processing unit (CPU) and other peripherals are also included to support all processes of 3D graphics applications. Using the accelerating tree-building unit named RayTree to minimize the CPU load, the chip uses a low-end CPU and decreases both silicon area and power consumption. The evaluation results with RayChip show appropriate performance to support real-time ray tracing in high-definition (HD) resolution, while the rendered images are scaled to full HD resolution. The chip also integrates the Linux operating system and the familiar OpenGL for Embedded Systems application programming interface for easy application development.

• Water Engineering Research
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• 제1권4호
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• pp.279-291
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• 2000

A mathematical model using dynamic programming approach is applied to an optimal unit commitment problem. In this study, the units are treated as stages instead of as state dimension, and the time dimension corresponds to the state dimension instead of stages. A considerable amount of computer time is saved as compared to the normal approach if there are many units in the basin. A case study on the Lower Colorado River Basin System is presented to demonstrate the capabilities of the optimal scheduling of hydropower units.

• Archives of Plastic Surgery
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• 제32권6호
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• pp.757-759
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• 2005

Acquired defects involving exposed bone on the forehead is challenging to reconstruct. Skin expansion provides an ideal thin flap for forehead aesthetic unit, but it takes long time and high cost, and many patients are dissatisfied at their figures. Free flap can provide enough tissue immediately, but it takes long time and has the risk of mismatches of color and texture. This report details our experiences with two patients who had soft tissue defect on their forehead that was covered with remnant forehead flap unit. This method uses one-unit-forehead island flap based on supratrochlear and supraorbital vessel. We obtained satisfactory results in terms of aesthetic and functional consideration.

• 전자공학회논문지T
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• 제36T권1호
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• pp.51-57
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• 1999

본 논문은 온도센서 RSD. Pt 100Ω의 감지신호가 Temperature Controller의 릴레이 출력을 발생시키고 PLC 입력접점으로 입력시켜 1Scan Time으로 연산된 PLC 출력을 접점 P030에 Interface Unit를 연결시키므로 부하를 구동시키는 개발장비인 Wired Logic Type Unit에 대해서 기술하였다. 현재 PLC 교육장에서 프로그램 되어진 PLC가 부하를 구동시킬 수 있는 국내의 교육 PLC Test Kit로는 PLC와 부하 사이에 Interface 과정이 무시된 상태에서 PLC의 교육을 하도록 되어있다. 개발 키 트는 이 점을 보안하기 위해서 각종 센서 중 전자에서 언급한 온도 센서 Pt 100Ω을 이용한 온도 제어기의 릴레이 출력이 PLC 입력으로 피드백 되었을 때, 연산된 PLC 출력접점에 WLTU를 삽입시켜 PC, PLC와 부하 사이에 실시간 시스템으로 구동 시킬 수 있는 설비로, PLC 사용의 핵심원리를 쉽게 이해하고 알아 볼 수 있었다. 부하 Interface Unit인 WLTU의 구성은 구동 부분인 유 접점, 무접점, 센서, 지시 등, A접점, B접점 부하인 Motor로 나누었다.

• 물과 미래
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• 제19권2호
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• pp.157-166
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• 1986

미측측 소하천 유역에 적용할만한 합성단위도를 찾아내기 위하여 대표유역의 관측자료로부터 각 소하천의 실측단위도를 유도하였다. 소하천 유역의 특성인자와 단위도의 특성치를 분석하여 Snyder, S.C.S, Nash, Clark에서 이용되는 식을 유도하였다. 이들 식을 이용하여 대표유역의 유역특성치로서 각 방법에 의한 합성단위도를 유도하고 이들 합성단위도와 실측단위도를 비교 분석한 결과 다음과 같은 특성을 발견하였다. Snyder 방법에 의한 첨두유량과 근사하였으나 첨두유량의 25,50,75%되는 단위도의 좌표만으로는 단위도의 형을 결정하기엔 미흡함이 남아있다. Clark 방법에 의하여 합성단위도를 정확하게 유도하기 위하여 그 유역의 시간-면적도의 기저장과 등유달시간면적을 정확하게 구할 수 있는 방법이 모색되어야 한다고 생각한다. Nash 방법에 의한 합성단위도의 첨두유량과 기저시간은 저장상수와 Gamma 함수인자만의 함수이기 때문에 정확한 저장상수와 Gamma 함수인자의 결정이 선행되어야만 신빙성있고 정도가 높은 단위도 유도가 가능하리라 판단된다. S.C.S 방법에서 첨두유량은 유역면적에 비례하고 첨두유량 발성시간에 반비례하기 때문에 첨두유량 발생이 빠른 소유역에서는 다소 큰 첨두유량 값을 갖음을 알았다.

• International Journal of Reliability and Applications
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• 제3권4호
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• pp.165-171
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• 2002

An optimization of the M/M/1 queue with impatient customers is studied. The impatient customer does not enter the system if his or her virtual waiting time exceeds the threshold K ＞ 0. After assigning three costs to the system, a cost proportional to the virtual waiting time, a penalty to each impatient customer, and also a penalty to each unit of the idle period of the server, we show that there exists a threshold K which minimizes the long-run average cost per unit time.