• 제어로봇시스템학회논문지
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• 제2권3호
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• pp.220-228
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• 1996

This paper presents a extended stochastic Petri net (ESPN) model for CTN(Circulated Token with No duration) service in the data link layer of IEC/ISA fieldbus. It is assumed that a station on the fieldbus has a specified minimum token holding time, a finite capacity buffer, and one transmitter queue with the highest priority. The mean transmission (or service) time at a station and the mean token rotation time for the symmetric fieldbus system atr derived using the presented SPN model and the moment generating function. These performance measures are represented in terms of the minimum token holding time, the number of stations, the arrival rate of messages, and the mean length of messages. The presented performance measure are validated by computer simulations.

• International Journal of Aeronautical and Space Sciences
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• 제16권4호
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• pp.602-613
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• 2015

As one of the mission payloads to be verified through the cube satellite mission of Cube Laboratory for Space Technology Experimental Project (STEP Cube Lab), we developed a hinge driving separation nut-type holding and releasing mechanism. The mechanism offers advantages, such as a large holding capacity and negligible induced shock, although its activation principle is based on a nylon cable cutting mechanism triggered by a nichrome burn wire generally used for cube satellite applications for the purpose of holding and releasing onboard appendages owing to its simplicity and low cost. The basic characteristics of the mechanism have been measured through a release function test, static load test under qualification temperature limits, and shock measurement test. In addition, the structural safety and operational functionality of the mechanism module under launch and on-orbit environments have been successfully demonstrated through a vibration test and thermal vacuum test.

• 항공우주시스템공학회지
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• 제7권3호
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• pp.20-25
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• 2013

In case of cube satellite, it is difficult to realize the same performance as commercial satellite due to its highly restricted unit accommodation space. To maximize the performance of the cube satellite, design concept considering the multi-function of satellite is required. In this paper, mechanism design of cube satellite which is applicable for the holding and release of multi-deployable structures has been proposed and investigated. In addition, a switch mechanism design for the autonomous system operation just after the cube satellite separation from P-POD has also been proposed. The effectiveness of the mechanism design for holding and release of multi-deployable structures has been demonstrated by EM test of the holding and release mechanism.

• Smart Structures and Systems
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• 제24권1호
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• pp.141-155
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• 2019

This work evaluates the influence of negative stiffness on the performances of various vehicle suspension systems, and proposes a re-centering negative stiffness device (NSD). The re-centering NSD consists of a passive magnetic negative stiffness spring and a positioning shaft with a re-centering function. The former produces negative stiffness control forces, and the latter prevents the amplification of static spring deflection. The numerical simulations reveal that negative stiffness can improve the ride comfort of a vehicle without affecting its road holding abilities for either passive or semi-active suspension systems. In general, the improvement degree of ride comfort increases as negative stiffness increases. For passive suspension system, negative stiffness brings in negative stiffness feature in the control forces, which is helpful for the ride comfort of a vehicle. For semi-active suspensions, negative stiffness can alleviate the impact of clipped damping in semi-active dampers, and thus the ride comfort of a vehicle can be improved.

• 한국항공우주학회지
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• 제42권6호
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• pp.529-534
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• 2014

전개형 우주 구조물의 구속 및 분리를 위해 일반적으로 적용되는 폭발식 분리장치의 경우, 극초소형 위성으로 분류되는 큐브위성에는 적용불가가 설계요구조건으로 규정되어있다. 큐브위성의 제한된 장착 공간과 이로 인한 저충격 요구조건, 저가의 개발비 등의 요구조건으로부터 일반적으로 적용이 용이한 나일론선 열선절단방식이 적용되고 있다. 하지만 나일론선 적용에 따른 낮은 체결력과 복수 구조물의 구속/분리를 위해 복수의 체결부와 열선을 필요로 하는 등 시스템 복잡화 및 신뢰도 저하의 문제점이 존재한다. 본 연구에서는 상기의 문제점 해결을 위해 힌지 구동형 분리너트를 적용한 구속분리장치를 제안하였으며, 인증시험 온도범위에서의 분리장치 동작 기능시험, 정하중 시험, 충격레벨 측정시험을 통해 설계의 유효성을 입증하였다.

• KDI Journal of Economic Policy
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• 제14권3호
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• pp.49-72
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• 1992

본고(本稿)는 부동산, 특히 토지에 대한 보유과세가 강화되어야 한다는 주장들을 검토하여 토지보유과세(土地保有課稅)를 강화하는 것이 바람직한가, 그럴 경우 어느 정도의 세부담(稅負擔) 증가(增加)가 필요한가를 살펴봄으로써 세제개편(稅制改編)의 실천적인 지침을 도출하는 데에 그 목적이 있다. 빠른 지가상승(地價上昇)이 계속되는 상황에서는 보유과세가 가진 효과들이 나타나기 어려우므로, 토지개발(土地開發) 및 공급(供給)의 확대로 지가상승(地價上昇) 추세(趨勢)를 완화시키는 한편, 양도과세(讓渡課稅)의 기능을 제고(提高)하는 것이 우선적으로 추진되어야 할 과제이며, 토지보유과세(土地保有課稅)의 증가(增加)는 토지정책적(土地政策的) 목적(目的)에서보다는 지방세수(地方稅收)의 확대(擴大)와 같은 목적(目的)을 위해 지속적으로 추구해야 할 정책방향이다. 토지보유과세(土地保有課稅)는 조세저항 등의 부작용을 보아가면서 점진적으로 높여 가되 보다 '좋은' 조세의 특성을 가지도록 개편해 가야 할 것이다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2010년도 춘계학술대회 논문집
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• pp.1898-1903
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• 2010

The hold clamp which is for holding feeder distribution line in direct current can be lengthened its span of life by inserting insulators(EDPM rubber) through improving its function such as preventing damage from temperature change and electric corrosion. This paper reviews the development background, design, manufacture and performance assessment of the hold clamp inserting insulators to prevent circulating current.

• 한국안전학회지
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• 제12권2호
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• pp.80-86
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• 1997

In this paper, a temperature controller with monitor function is proposed for the electric furnace system. This controller includes holding and ramp control function, and the control program for the temperature process monitor of the electric furnace. For this purpose, the implementation and performance of auto tuning algorithms in a computer-based controller was studied in relation to the control of nonlinear electric furnace system which is characterized with large delay time. The control program for this controller programmed by c-language. To communicate a control and detection signals, between the controller and the electric furnace is implemented by the I/O data card. We apply the temperature controller to the practical electric furnace. As a result, the proposed controller shows the better status characteristic.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 추계학술대회 논문집
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• pp.900-903
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• 2014

Fly-wheel, Gimbal antenna, CMG, Spaceborne cyrocooler generate micro-vibration during their on-orbit operation as well as implementing their own function. To comply with the mission requirement of high resolution observation satellite, additional technical efforts have been required to isolate the micro-vibration derived from such payloads by applying the vibration isolator. In this study, we proposed a passive isolator using SMA mesh washer, which guarantees the structural safety of both micro-vibration disturbance source and itself under harsh launch vibration loads without an additional holding mechanism and the micro-vibration isolation performance on orbit environment. To verify the micro-vibration isolation performance of the proposed vibration isolator, we performed the micro-vibration isolation measurement test using the dedicated micro-vibration measurement device proposed in this study.

• 항공우주시스템공학회지
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• 제15권5호
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• pp.81-88
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• 2021

일반적으로 큐브위성용 전개형 태양전지판을 수납 및 전개시키기 위해 사용되는 구속분리장치는 비폭발식 나일론선 절단방식이 적용된다. 그러나 상기 방식은 태양전지판 수납 상태에서 큐브위성의 배터리 충전, PCB 및 탑재체의 전기적 점검 및 시험 등을 위한 접근 포트 연결 시 분리장치의 구속해제 및 재채결 작업이 반복적으로 요구된다. 따라서, 기존의 구속분리장치는 위성체 내부 접근을 위해서는 작업자의 번거로움 및 일관된 나일론선 체결작업 공정 유지의 어려움이 존재한다. 본 연구에서는 나일론 선 절단 없이 구속 핀 분리만으로 자유롭게 태양전지판 전개 및 수납이 가능한 Pin-puller형 태양전지판 구속분리장치를 제안하였으며, 기능 및 성능검증을 위한 분리장치의 전개시험 및 최대 분리하중 측정 시험을 통해 분리장치 설계의 유효성을 입증하였다.