• Title/Summary/Keyword: Mission Condition

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달착륙선 지상시험모델의 구조체 개발 (Development of a Structure for Lunar Lander Demonstrator)

  • 손택준;나경수;임재혁;김경원;황도순
    • 항공우주기술
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    • 제12권1호
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    • pp.213-220
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    • 2013
  • 국가우주개발계획에 따라 2020년 이후 한국형 달탐사선이 발사될 예정이다. 달탐사선은 무인 경량화모델로 달궤도선과 달착륙선 2종을 개발할 계획이다. 달탐사선의 구조체는 발사 및 궤도하중, 착륙하중을 견딜 수 있는 구조적 안정성과 탑재장비의 장착공간을 제공할 뿐만 아니라 발사체의 탑재능력을 고려하여 가볍게 설계되어야 한다. 이를 위해 달탐사선 구조체의 개발과 관련된 핵심기술의 선행개발이 요구된다. 특히, 달착륙선의 경우 착륙선이 달 지면에 안전하게 착륙할 수 있게 해주는 착륙장치의 개발기술이 필수적이다. 본 논문에서는 달착륙선 지상시험모델 구조체의 설계, 제작, 시험을 포함한 개발내용을 다룬다.

해양작업지원선(PSV)의 기본설계 및 저항추진 성능 향상을 위한 선형개선 방안 연구 (A Study on the Basic Design for Platform Support Vessel (PSV) and Hull Form Development for Enhancement of Resistance & Propulsion Performance)

  • 염종길;강국진;이영연;이춘주;옥군도
    • 대한조선학회논문집
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    • 제55권3호
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    • pp.196-204
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    • 2018
  • Present paper shows the basic design procedure for platform support vessel operating in open sea, and hull form development process. General design concept considering the operating mission, operating sea condition and shipping freight, etc. is explained shortly. For the hull form design, the initial hull form was designed based on the reference PSVs. The resistance and propulsion test results for the initial hull form with twin Azimuth thruster were analyzed and a few items for improvement were derived. At the next stage, main parameters including Length, Cp-curve, Cb, Lcb, etc. were changed totally for the hull form improvement. Furthermore, 3 different bulbous bows for the fore-body design to reduce the wave resistance and after-body design to reduce the residual resistance were carried out. The best hull form among the 3 fore-bodies with same after-body was selected through the comparison of wave resistance calculation results. Twin ducted Azimuth thruster with the smaller propeller diameter than the former were adapted to increase the propulsive efficiency. The final hull form with the twin Azimuth thruster was evaluated to satisfy more than the target design speed 14 knots in sea condition with sea margin 15% at the 5,000kW BHP through the model test in KRISO.

광대역 무선송신장치의 RF 반사손실을 이용한 안테나 자체고장진단 방법 (Built-In-Test Methods to use RF returnloss for fault Diagnosis of the Wideband Transmitter Antenna)

  • 정원희
    • 한국항공우주학회지
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    • 제45권5호
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    • pp.409-416
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    • 2017
  • 공중의 비행체에 필요한 정보를 전달하는 광대역 송신시스템은 근거리에서 동시에 운용될 수 있도록 다수의 부채널 주파수를 확보하고 있다. 취약한 외부환경에 노출되는 송신기의 경우, 시스템의 신뢰성을 높이기 위하여 안테나를 포함하여 다른 내부의 하위 구성품들의 자체고장진단을 할 수 있도록 설계되어야 한다. 안테나 자체고장진단은 보통의 경우 안테나 반사세기를 기준으로 판정 내리는데, 증폭단과 안테나가 긴 길이의 케이블로 연결될 경우는 안테나 반사세기가 주파수마다 많은 차이가 발생된다. 본 논문에서는 증폭단과 안테나의 연결에 사용되는 케이블 길이에 따라 안테나 반사세기가 주기성을 갖는 현상을 이론적으로 살펴보고, 반사세기 반복주기를 기반으로 점검주파수 범위설정, 다수 주파수 설정 점검 등을 이용하여 효과적인 안테나 고장진단 방법에 대하여 제시한다.

EDF 모델링을 이용한 저궤도위성 다중 출력 컨버터 설계 및 검증 (Low-earth orbiting satellite multi-output converter design and verification by using EDF modeling)

  • 윤석택;양정환
    • 한국위성정보통신학회논문지
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    • 제7권2호
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    • pp.76-79
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    • 2012
  • 위성의 전력 시스템은 전력의 생산, 변환 및 분배를 담당하는 주요한 시스템으로, 임무 수명뿐 아니라 임무 횟수, 시기 등의 설계에 사용된다. 이중 전력의 변환을 담당하는 변압기의 부하와 입력 조건에 따라 안정화 설계가 이루어 져야 하지만, 실지 궤도상에서 Test 및 check-out을 진행할 수 없는 특성으로 다양한 입출 조건 변화에 대한 성능 및 안전성을 확인하기위한 방법이 요구된다. 일반적으로 위성 컨버터는 다양한 부하 조건에 따라 설계되므로, 부피 및 설계의 효율성을 위해 다중 출력 및 여러 개의 stage를 거쳐서 전력 변환이 이루어지게 된다. 하지만, 이로 인해 분석에 많은 어려움을 지니게 되어 직관적인 회로의 파악은 쉽지 않게 된다. 또한 일반적인 분석으로는 모든 상태 방적식의 해를 구하기 쉽지 않아서 실제 운용 시에 가해질 수 있는 소자에 대한 영향성에 대한 분석이 힘들 수 있게 된다. EDF model은 fundamental 주파수 분석을 통해 모든 소자에 대한 분석이 가능한 방법이며 multi-stage의 경우에도 입력 모델링으로 한꺼번에 1st stage와 2nd stage의 분석이 가능한 방법이다. 본 논문에서는 EDF 방법을 통한 modeling과 시뮬레이션 modeling을 비교하여 적용의 타당성을 분석하고, 이를 통해 제어기를 설계하여 multi-stage 컨버터의 직관적인 회로 분석이 가능함을 확인 하였다.

Design of Regional Coverage Low Earth Orbit (LEO) Constellation with Optimal Inclination

  • Shin, Jinyoung;Park, Sang-Young;Son, Jihae;Song, Sung-Chan
    • Journal of Astronomy and Space Sciences
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    • 제38권4호
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    • pp.217-227
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    • 2021
  • In this study, we describe an analytical process for designing a low Earth orbit constellation for discontinuous regional coverage, to be used for a surveillance and reconnaissance space mission. The objective of this study was to configure a satellite constellation that targeted multiple areas near the Korean Peninsula. The constellation design forms part of a discontinuous regional coverage problem with a minimum revisit time. We first introduced an optimal inclination search algorithm to calculate the orbital inclination that maximizes the geometrical coverage of single or multiple ground targets. The common ground track (CGT) constellation pattern with a repeating period of one nodal day was then used to construct the rest of the orbital elements of the constellation. Combining these results, we present an analytical design process that users can directly apply to their own situation. For Seoul, for example, 39.0° was determined as the optimal orbital inclination, and the maximum and average revisit times were 58.1 min and 27.9 min for a 20-satellite constellation, and 42.5 min and 19.7 min for a 30-satellite CGT constellation, respectively. This study also compares the revisit times of the proposed method with those of a traditional Walker-Delta constellation under three inclination conditions: optimal inclination, restricted inclination by launch trajectories from the Korean Peninsula, and inclination for the sun-synchronous orbit. A comparison showed that the CGT constellation had the shortest revisit times with a non-optimal inclination condition. The results of this analysis can serve as a reference for determining the appropriate constellation pattern for a given inclination condition.

Near-Infrared Imaging Spectroscopic Survey in Space

  • Jeong, Woong-Seob;Park, Sung-Joon;Moon, Bongkon;Lee, Dae-Hee;Park, Won-Kee;Lee, Duk-Hang;Ko, Kyeongyeon;Pyo, Jeonghyun;Kim, Il-Joong;Park, Youngsik;Nam, Ukwon;Kim, Minjin;Ko, Jongwan;Song, Yong-Seon;Im, Myungshin;Lee, Hyung Mok;Lee, Jeong-Eun;Shin, Goo-Hwan;Chae, Jangsoo;Matsumoto, Toshio
    • 천문학회보
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    • 제40권1호
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    • pp.54.3-54.3
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    • 2015
  • To probe the star formation in local and early Universe, the NISS with a capability of imaging spectroscopy in the near-infrared is being developed by KASI. The main scientific targets are nearby galaxies, galaxy clusters, star-forming regions and low background regions. The off-axis optical design of the NISS with 15cm aperture was optimized to obtain a wide field of view (FoV) of $2deg.{\times}2deg.$ as well as a wide spectral coverage from 0.9 to $3.8{\mu}m$. The opto-mechanical structure was designed to be safe enough to endure in both the launching condition and the space environment. The dewar will operate $1k{\times}1k$ infrared sensor at 80K stage. The NISS will be launched in 2017 and explore the large areal near-infrared sky up to $200deg.^2$ in order to get both spatial and spectral information for astronomical objects. As an extension of the NISS, KASI is planning to participate in a new small space mission together with NASA. The promising candidate, SPHEREx (Spectro-Photometer for the History of the Universe Epoch of Reionization, and Ices Explorer) is an all-sky survey satellite designed to reveal the origin of the Universe and water in the planetary systems and to explore the evolution of galaxies. Though the survey concept is similar to that of the NISS, the SPHEREx will perform the first near-infrared all-sky imaging spectroscopic survey with the wider spectral range from 0.7 to $5{\mu}m$ and the wider FoV of $3.5deg.{\times}7deg.$ Here, we report the current status of the NISS and introduce new mission for the near-infrared imaging spectroscopic survey.

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4차산업혁명 시대, 대학경영의 효율적 제고를 위한 전략적 접근 - 서비스 경영이론의 적용을 중심으로 - (A Strategic Approach to Enhancing University Management in the Era of Industry Revolution 4.0 - Application of Service Operations Management Theory -)

  • 정상철;오세구
    • 서비스연구
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    • 제10권4호
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    • pp.21-41
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    • 2020
  • 4차 산업혁명이 빠른 속도로 전개됨에 따라 대학이 생존하기 위한 조건으로 대학에 주어진 본질적 사명을 시스템 이론의 관점에서 재조명할 필요가 있다. 본 연구에서는 대학을 고등교육 서비스를 통해 고부가가치를 창출하는 5차 서비스 산업으로 규정하고, 경영학을 기반으로 한 다학제적(Multidisciplinary) 관점의 접근을 시도하되 특히 서비스 운영관리이론에 기초하여 이를 재조명함으로써 대학경영의 과학적 합리화를 위해 다양한 대학관계자에게 새롭고 참신한 시각을 제공하려고 시도하였다. 이를 위해 대학의 본질적 사명인 교육, 연구, 봉사를 제대로 수행하기 위한 교육조직, 연구조직, 봉사조직, 그리고 이들에 대한 지원조직의 성격을 분류하고 이들에 맞는 경영행위를 수행하기 위한 개념과 기법을 탐색하는 것이 본 연구의 일차적 목적이다. 또한, 학문적·실무적 관점에서 대학을 고등교육 서비스를 통해 고부가가치를 창출하는 5차 서비스 산업으로 규정한 뒤 경영학적 관점에서 새로운 접근을 시도하되 보다 구체적으로는 서비스 경영이론, 특히 서비스 운영관리이론에 기초하여 대학 행정을 재조명함으로써 대학경영의 과학적 합리화를 위한 새로운 관점과 수단을 제공하는 것, 나아가 대학 총장을 CEO의 관점에서 바라보는 최근의 한 경향을 반영하여 이를 학문적으로 체계화시켜보려는 것이 본 연구의 구체적인 목적이다. 이를 통해 새로운 환경변화에 대응할 수 있는 체계적이고 과학적인 대학경영조직의 이상형을 모색해보고자 하였다.

미용사의 직무만족도와 직업관 (Beauty Shop Workers' Views of Job)

  • 오애자;남철현
    • 한국학교ㆍ지역보건교육학회지
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    • 제2권1호
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    • pp.67-84
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    • 2001
  • This study was conducted to examine beauty shop workers' views of job. Data were collected from the workers in Seoul, Daegu, Pohang, Junjoo, and Kimhae from June 1, 2000 to August 31, 2000. The results of this study are summarized as follows. 1. According to general characteristics of the subjects, 28,7% of them was female; 94.2% 'specialized in hair'; 46.4% 'below twenty nine years old'; 47.1% 'married'; 59.7% 'highschool graduate'; 33.9% 'worked for below three years'; 28.5% 'monthly income of five hundred thousand to nine hundred ninety thousand won'; 62.3% 'working for above twelve hours a day' ; 41.0% 'above five workers' ; 40.6% 'working in city'. 2. 54.8% of the respondents thought that they were in good health. 76.3% of them smoked and 54.8% drank. 62.8% of them did not exercise and 78.7% was under stress. 61.5% responded that they chose the job because of its possibility of professional vocation. 91.0% of them obtained the beauty skill from beauty schools. 3. Among the factors which influenced job satisfaction, 'stable job and life security' was highest(43.9%), while 'interest in the job and amount of pay' was lowest(3.2%). 'Personal ability and use of originality' was 19.4% and 'harmonious relationship with fellow workers' was 18.1%. 'Job environment' was 7.1% and 'harmonious relationship with higher workers' was 4.5%. 4. The level workers' view of job was $113.8{\pm}17.3$ points on the basis of 150 points. On the basis of 75 points, each item showed it points in order of self-development($22.3{\pm}3.8$), service for customers($20.1{\pm}3.1$), vocational mission($15.6{\pm}3.1$), harmony with the others($18.9{\pm}3.5$), working environment($18.6{\pm}3.6$), and working condition($14.3{\pm}5.1$). 5. Among the reasons why they considered leaving the job, 24.0% of them considered it because they could not free time, while 15.4% considered it because undesirable living environment or long distance from home. 15.0% thought it because they could not receive proper treatment as much as they worked and 12.8% thought they overworked. 6. When they move into new working places, they consider such factors as good working environment(24.1%), good place to open their own beauty shops(16.7%), good beauty shop to learn beauty skill(15.6%), chance to have job training(9.5%), and close place from home(9.0%). 7. 40.6% of the respondents wanted to leave the job, while 32.3% of them did not want to leave the job. The intention of leaving the displayed significant difference in the variables of age, working period, monthly income, marital status, the number of workers, location of the shop, rank, and reason of selecting the job. 8. According to the results of a regression analysis of factors which influenced job satisfaction, it was affected significantly by intention of leaving job, the number of workers, health condition, level of stress, and monthly income. The beauty shop workers showed low satisfaction level with working environment, working condition, and working mission, They considered leaving the job because of lack of free time, overwork, poor working environment, improper treatment, etc. Therefore, related professionals and organizations must device adequate measures in order to make them work with pride as creators of beauty.

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데이터 마이닝 기법을 활용한 군용 항공기 비행 예측모형 및 비행규칙 도출 연구 (A Study on the Development of Flight Prediction Model and Rules for Military Aircraft Using Data Mining Techniques)

  • 유경열;문영주;정대율
    • 한국정보시스템학회지:정보시스템연구
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    • 제31권3호
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    • pp.177-195
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    • 2022
  • Purpose This paper aims to prepare a full operational readiness by establishing an optimal flight plan considering the weather conditions in order to effectively perform the mission and operation of military aircraft. This paper suggests a flight prediction model and rules by analyzing the correlation between flight implementation and cancellation according to weather conditions by using big data collected from historical flight information of military aircraft supplied by Korean manufacturers and meteorological information from the Korea Meteorological Administration. In addition, by deriving flight rules according to weather information, it was possible to discover an efficient flight schedule establishment method in consideration of weather information. Design/methodology/approach This study is an analytic study using data mining techniques based on flight historical data of 44,558 flights of military aircraft accumulated by the Republic of Korea Air Force for a total of 36 months from January 2013 to December 2015 and meteorological information provided by the Korea Meteorological Administration. Four steps were taken to develop optimal flight prediction models and to derive rules for flight implementation and cancellation. First, a total of 10 independent variables and one dependent variable were used to develop the optimal model for flight implementation according to weather condition. Second, optimal flight prediction models were derived using algorithms such as logistics regression, Adaboost, KNN, Random forest and LightGBM, which are data mining techniques. Third, we collected the opinions of military aircraft pilots who have more than 25 years experience and evaluated importance level about independent variables using Python heatmap to develop flight implementation and cancellation rules according to weather conditions. Finally, the decision tree model was constructed, and the flight rules were derived to see how the weather conditions at each airport affect the implementation and cancellation of the flight. Findings Based on historical flight information of military aircraft and weather information of flight zone. We developed flight prediction model using data mining techniques. As a result of optimal flight prediction model development for each airbase, it was confirmed that the LightGBM algorithm had the best prediction rate in terms of recall rate. Each flight rules were checked according to the weather condition, and it was confirmed that precipitation, humidity, and the total cloud had a significant effect on flight cancellation. Whereas, the effect of visibility was found to be relatively insignificant. When a flight schedule was established, the rules will provide some insight to decide flight training more systematically and effectively.

건강가정사의 직무 및 근무환경 인식 (Certified Healthy Family Specialists' Job and Working Conditions from the Insiders' Perspective)

  • 성미애;진미정;이재림;최새은
    • 한국생활과학회지
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    • 제21권3호
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    • pp.453-468
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    • 2012
  • The number of Healthy Family Support Centers has dramatically increased during the past eight years since the Framework Act on Healthy Families was enacted. This phenomenal growth is largely credited to Certified Healthy Family Specialists (CHFSs). Despite their contributions, the job and working conditions of the CHFSs have rarely been explored from the insiders' perspective. In this study, we aim to delineate CHFSs' job and working conditions from their own narratives in order to improve an understanding of CHFSs' profession and work environment. We conducted in-depth interviews with nine CHFSs and a focus-group interview with five CHFSs. Our findings revealed that CHFSs took pride in their professions, internalized their professional mission of enhancing family strengths, and highlighted CHFSs' unique professional role in comparison to other human services professionals. In conclusion, CHFSs showed a strong professional identity consisting of rich professional knowledge, solid career goals, and integrated socio-political values. Contrary to the positive perception of the CHFSs' job, CHFSs expressed challenges in their working conditions in terms of small-scale organizations at local Healthy Family Support Centers, a heavy workload, hierarchical relationships with local government officers, and the unsatisfactory payroll and promotion system. This study contributes to a better understanding of CHFSs' job and their working conditions and provides insights on how to enhance professionalism among CHFSs and their work environment. As for policy implications, we suggest advancing qualifications for CHFSs, improving professional training programs for current CHFSs, and expanding small-scale organizations.