• Korea journal of population studies
• /
• v.31 no.1
• /
• pp.99-125
• /
• 2008

This article aimed to clear that the systematic bias according to the length of work time exists between estimated work time by self-reported questions used mainly in measuring and calculating the length of work time because of strong points of easy in measuring and so on and diary work time by time-diary method used because of the strong point that can measure more accurate lifetime by recording various activities of respondents during 24 hours in the stream. As the result that analyze the data from Lifetime Use Survey in 2004, the result like the contradiction came that the tendency of overstating work time is rising according as estimated work time increases via estimated work time, whereas the tendency of understating work time is rising according as diary work time increases via diary work time. The reason that the opposite results come despite the data from the same survey is that random errors act in the opposite directions by regression to the mean. Therefore, we cannot emphasize that a man working long hours tends to exaggerate his work hours by the result via estimated work time. That is, the fact that the systematic bias by the increase of work time does not exist is confirmed, and therefore, it is also impossible to raise questions about the accuracy of the data through estimated work time by self-reported questions from the evidence of the existence of that bias.

• Journal of Sericultural and Entomological Science
• /
• v.8
• /
• pp.27-34
• /
• 1968

상수의 엽면적은 상엽의 수획량 즉 수량과 높은 상관관계가 있고 그의 간이측정법은 매우 의의 깊은 일이므로 상전에서 생체대로 엽면적을 측정할 수 있도록 간이측정법을 고안하였다. 우리나리 상수의 주요품종인 개량서반, 일지뢰, 노상 그리고 수원 제4호의 4개품종을 재료로 절위별로, 지조별로 엽면적과 엽장, 최대엽폭과의 관계를 조사 실험하였으며 공시 엽수는 개량서반 741문, 일지뢰 853문, 노상 507문, 수원제4호 441문, 도합 2,542문이었다. 5개열엽으로 엽형이 비슷한 개량서반과 일지뢰의 2개품종의 엽면적은 (엽장$\times$최대엽폭)$\times$0,643, 단엽인 노상과 수원제4호의 2개품종의 엽면적은 (엽장$\times$최대엽폭)$\times$0,735에 의해서 구할 수 있음을 알았다. 즉 개량서반과 일지뢰는 엽장에 최대엽폭을 곱한 적에 계수 0.634를 곱함으로써 전처리엽에서 planimeter에 의한 엽면적과 높은 상관관계를 보였고 이때의 상관계수의 평균을 개량서반에 있어서는 r=0.931, 일지뢰에 있어서는 r=0.960이었다. 노상과 수원상4호는 엽장에 최대엽폭을 곱한 적에 계수 0.735를 곱함으로써 전처리엽에서 planimeter에 의한 엽면적과 또한 높은 상관관계를 보였고 이때의 상관계수의 평균을 개량서반에 있어서는 r=0.931, 일지뢰에 있어서는 r=0.960이었다. 노상과 수원상 4호는 엽장에 최대엽폭을 곱한 적에 계수 0.735를 곱함으로써 전처리엽에서 planimeter에 의한 엽면적과 또한 높은 상관관계를 보였고 이 때의 상관계수 r의 평균을 노상에 있어서는 r=0.999, 수원상 4호에 있어서는 r=0.996이었다. 이 방법에 의하면 시간과 노력을 크게 절감시킬 수 있을 뿐만 아니라 생체대로 쉽게 엽면적을 구할 수 있는 이점이 있다.

• International Journal of Highway Engineering
• /
• v.12 no.1
• /
• pp.21-27
• /
• 2010

Management of driver hours of service (HOS) for commercial vehicle operators has been a continual safety challenge. One of the more critical issues to government and motor carriers is fatigue and fatigue-related accidents. To reduce truck drivers’fatigue-related accident risk in other countries, the government issued the HOS regulations. However, korea government does not have any HOS regulations. The objective of this research gives the clues that korea should have the HOS regulation to reduce truck drivers’fatigue-related accident risk. This study examines the HOS regulation over other countries and conducts relative accident risk analysis using the real data from 3 freight companies. The data set includes 231 accident involved drivers and 462 non-accident drivers. Therefore, the size of the total data set is 693 drivers. One of the most important aspects of early studies of safety and HOS was the need to characterize continuous driving by using the notion of "survival". Subsequent research used a data replication scheme and logistic regression to capture the survival effect. This study uses time-dependent logistic regression. The test of significance between parameters indicates that the first three hours are almost the same risk. In the 10th hour of driving, the risk was more than 2.2times that in the baseline first hour. In conclusion, as driving time goes on, the crash risk increases.

• Korean Journal of Human Ecology
• /
• v.18 no.1
• /
• pp.113-122
• /
• 2009

This study aimed to examine the urban families and rural families in tenns of life styles on Saturday-with-no-school. The subjects were the 386 parents whose children were in the first or second grade in rural or urban area. The instruments of analysis were time diary method and parents' stress scale developed by Kim & Kang(l997). The main results were as follows: First, in comparison with urban children, rural children spent more time in viewing TV and playing computer but spend less time in sleeping. field trip and cleaning on Saturday-with-no-school. Second, the difference of child-rearing time between mothers and fathers was less marked in urban area than in rural area. Rural fathers spent more time in watching TV or playing computer, while rural mothers spent more time in feeding and bathing of their children, helping their children do homework, and total child-rearing. Third, unlike urban parents, rural parents ddid not have much parenting stress on Saturday-with-no-school. These results show that there is a need to focus on rural parents in the preparation for introduction of 5 days-school-week system.

• The Korean Journal of Air & Space Law and Policy
• /
• v.20 no.2
• /
• pp.253-276
• /
• 2005

A pilot logbook is an essential data for proving pilot's flight experience. the reason for maintaining this information is to fulfill the requirement for pilot certificates, manage internationally shared career placement. this study focuses on the instrument flight related items among other flight time items which are included in a pilot logbook. By comparing the way of flight time logging among Korean Aviation Law, Federal Aviation Regulation and Joint Aviation Requirements, this study concludes intensively how to define items for flight time, to amend the definition and to apply the policy in Korea with respect to the pilot logbook.

• Communications of Mathematical Education
• /
• v.16
• /
• pp.93-108
• /
• 2003

본 논문은 테크날러지가 주 도구인 기하수업시간에 학생들이 수학적 개념을 이해하는데 테크날러지가 어떠한 역할을 하는지 조사하였다. 본 연구를 위한 수업은 이미 진행되오던 형태의 수업이 아니라 교사도 학생들에게도 모두 새로운 형태의 수업이었고 GSP와 웹사이트를 이용하여 수업이 진행되었다. 자료 수집은 개인 면담, 교실 관찰, 과제 분석 및 일지작성을 통해서 이루어졌고 분석 지속적 비교분석법을 이용하였다. 학생들은 GSP를 이용하여 개념을 이해하려고 하기보다는 자신이 이해한 개념을 확인하는데 GSP를 이용하였고 일단 이렇게 이해되고 확인된 것에 대해 확장하는데 GSP에 많이 의존하였다. 특히, 학생들의 정의적 및 기능적 측면을 고려해야 할 필요성을 일깨워 주었다.

• Computational Structural Engineering
• /
• v.11 no.1
• /
• pp.205-216
• /
• 1998

A solution method is presented to solve the eigenvalue problem arising in the dynamic analysis of nonclassicary damped structural systems with multiple eigenvalues. The proposed method is obtained by applying the modified Newton-Raphson technique and the orthonormal condition of the eigenvectors to the linear eigenproblem through matrix augmentation of the quadratic eigenvalue problem. In the iteration methods such as the inverse iteration method and the subspace iteration method, singularity may be occurred during the factorizing process when the shift value is close to an eigenvalue of the system. However, even though the shift value is an eigenvalue of the system, the proposed method provides nonsingularity, and that is analytically proved. Since the modified Newton-Raphson technique is adopted to the proposed method, initial values are need. Because the Lanczos method effectively produces better initial values than other methods, the results of the Lanczos method are taken as the initial values of the proposed method. Two numerical examples are presented to demonstrate the effectiveness of the proposed method and the results are compared with those of the well-known subspace iteration method and the Lanczos method.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2011.08a
• /
• pp.351-352
• /
• 2011

그래핀(Graphene)은 2차원 평면구조의 $sp^2$ 탄소 결합으로 이루어진 물질이다. 일반적으로 그래핀은 탄소 원자 한층 정도의 얇은 두께를 가지면서 강철의 100배 이상 높은 강도, 다이아몬드보다 2배 이상 뛰어난 열 전도성, 그리고 규소보다 100배 이상 빠른 전자이동도 등의 매우 우수한 특성을 지닌다. 그래핀을 합성하거나 얻는 방법에는, 기계적 박리법(Micro mechanical exfoliation), 산화흑연(graphite oxide)을 이용한 reduced graphene oxide(RGO)방법과 탄화 규소(SiC)를 이용한 epitaxial growth 방법 등이 있지만, 대 면적화가 어렵거나 구조적 결함이 큰 문제점이 있다. 반면, 탄화수소(hydrocarbon)를 탄소 공급원으로 하는 열화학 기상 증착법(Thermal chemical vapor deposition, TCVD)은 구조적 결함이 상대적으로 적으면서 대 면적화가 가능하다는 이점 때문에 최근 가장 많이 이용되고 있는 방법이다. TCVD를 이용, 니켈, 몰리브덴, 금, 코발트 등의 금속에서 그래핀 합성연구가 보고되었지만, 대부분 수 층(fewlayer)의 그래핀이 합성되었다. 하지만, 구리 촉매를 이용하는 것이 단층 그래핀 합성에 매우 효율적이라는 연구결과가 보고되었다. 구리의 경우, 낮은 탄소융해도(solubility of carbon) 때문에 표면에서 self limiting 과정을 통하여 단층 그래핀이 합성된다. 그러나 단층 그래핀 일지라도 면저항(sheet resistance)이 매우 높고, 이론적 계산값에 비해 전자이동도(electron mobility)가 낮게 측정된다. 이러한 원인은 구조적 결함에서 기인된 것으로써 산업으로의 응용을 어렵게 만들기 때문에 양질의 단층 그래핀 합성연구는 필수적이다[1,2]. 본 연구에서는 TCVD를 이용하여 구리 포일(25 ${\mu}m$, Alfa Aeser) 위에 메탄가스를 탄소공급원으로 하여 수소를 함께 주입하고, 메탄가스의 양과 합성시간, 열처리 시간을 조절하면서 균일한 단층 그래핀을 합성하였다. 합성된 그래핀을 $SiO_2$ (300 nm)기판위에 전사(transfer)후 라만 분광법(raman spectroscopy)과 광학 현미경(optical microscope)을 통하여 분석하였다. 그 결과, 열처리 시간이 증가할수록 촉매로 사용된 구리 포일의 grain size가 커짐을 확인하였으며, 구리 포일 위에 합성된 그래핀의 grain size는, 구리 포일의 grain size에 의존하여 커짐을 확인하였다. 또한 동일한 grain 내의 그래핀은 균일한 층으로 합성되었다. 이는 기계적 박리법, RGO 방법, epitaxial growth 방법으로 얻은 그래핀과 비교하여 매우 뛰어난 결정성을 지님이 확인되었다. 본 연구를 통하여 면적이 넓으면서도 결정성이 매우 뛰어난 양질의 단층 그래핀 합성 방법을 확립하였다.

• Journal of Agricultural Extension & Community Development
• /
• v.12 no.2
• /
• pp.137-150
• /
• 2005

Although the rate of women farmer's participation in agricultural activities have been increased upto 52.7 % as of year 2003, Korean society has not fully recognized their roles in rural society. According to the agricultural basic law, most of rural women were engaged in agriculture as full time job, however, only about 11% of them could have supporting evidence of themselves as farmer having legal right. If women farmers faced some unexpected things such as a traffic accident, insurance company would not reward them as farmers unless they provide written proof of their job as farm worker or farm owner. Based on lawyer's legal advice, the authors developed a diary called "Saenghwalilji", a daily diary based on their time use and bookkeeping to prove the fact of their contribution to income generation of the farm. After examination of the diary, 18 persons out of 29 volunteers kept two types of dairy for the period of two weeks, and they reported it was very useful. Finally the better one of two was selected after reflecting the suggestions from the respondents. The "Saenghwalilji", will be very useful proof of women farmer's contribution to income, at the same time improving their farm management through better use of daily life time.

• Journal of Radiation Protection and Research
• /
• v.38 no.2
• /
• pp.52-59
• /
• 2013

The internal contamination screening method using gross beta measurement was performed for radioisotope workers. 24 h and spot urine samples from workers of medical isotope production facilities were collected and measured. Most of the results were similar with the background level of gross beta activity except for a specific worker. Gross beta activity was slightly increased in several hours after finishing work. And the environmental factor of production facilities causing internal contamination were estimated based on screening results. The additional detailed internal dose assessment must be followed after the screening for protection of workers. Moreover, a procedure was established to apply a simple internal contamination assessment for radiation workers.