• Proceedings of the Korean Reliability Society Conference
• /
• 2004.07a
• /
• pp.167-175
• /
• 2004

A nonparametric procedure is proposed to test the exponentiality against the hypothesis that one life distribution has a greater residual life times than the other life distribution. Such a hypothesis turns out to be equivalent to the one that one failure rate is greater than the other and so the proposed test works as a competitor to more IFR tests by Kochar (1979, 1981) and Cheng (1985). Our test statistic utilizes the U-statistics theory and a large sample nonpara metric test is established. The power of the proposed test is discussed by calculating the Pitman asymptotic relative efficiencies against several alter native hypotheses. A numerical example is presented to exemplify the proposed test.

• Journal of Korean Society of Industrial and Systems Engineering
• /
• v.26 no.1
• /
• pp.79-84
• /
• 2003

종래의 연구들은 주로 시간이 경과함에 따라 수리비용과 고장시간 간격이 고정된 상태에서 최적교환시각(T)을 구하는 조건을 발견하는데 중점을 두었으나, 대부분의 시스템은 시간이 경과할수록 고장시간간격이 좁아지고 수리비용은 증가하는 것이 일반적이다. 본 논문에서는 위의 두 조건을 만족하는 보다 현실적인 모델을 구축하였으며, 또 일정시간 내에 2개의 시스템이 존재할 때 어느 조건 하에서 시스템이 확률적으로 우월한가를 분석하는 연구를 수행하였다. 즉, 시스템은 시간이 경과함에 따라 확률 P［N=k］로서 완전수리를, 1-P［N=k］로서 소수리를 행하는 모델을 고려하였다. 여기서 N은 연속된 완전수리 사이의 소수리의 수를 나타낸다. 또한 초기고장에 있어서 수리에 의해 새로운 시스템이 되는 확률이 높고, 고장횟수가 증가함에 따라 완전수리가 행해지는 확률이 낮아지는, 보다 현실에 가까운 모델을 구축하였다. 모델을 일반화하기 위해 수리비용은 확률변수로 가정하였다.

• Proceedings of the KSRS Conference
• /
• 2000.04a
• /
• pp.79-84
• /
• 2000

해양 영역에 대한 SAR(Synthetic Aperture Radar) 자료는 좋은 해상도로 기상조건이나 주야에 상관없이 wind vector를 구할 수 있는 장점이 있다. 해안지역의 scatterometer 자료는 육지의 영향으로 인하여 정확한 자료를 얻을 수 없지만, SAR자료를 이용하면, Scatterometer에 비해 좋은 해상도로 해안지역의 wind vector 추출이 가능하다. 본 연구에서는 SAR 자료로부터 풍속을 추출할 수 있는 CMOD_4와 CMOD_IFR2 알고리즘을 사용하였다. 이 알고리즘들은 정확한 sigma-naught 값과, 풍향, 그리고 local incidence angle을 입력변수로 요구한다. CMOD 알고리즘들은 ERS-1/2와 같이 C-band, VV-polarization을 위해 개발된 알고리즘이므로, C-band, HH-polarization을 가진 RADARSAT 자료에 바로 적용할 수가 없다. 이것을 해결하기 위해 본 연구에서는 두 CMOD 알고리즘을 몇 가지 polarization ratio와 같이 적용하여 보았다. 각 연구지역에 해당하는 자료에는 제주도 주변의 Fine mode 자료, 서해안과 제주도 근해의 Standard mode 자료, 그리고 동해안 지역의 ScanSAR 자료 등이다. 여러 가지 Polarization ratio와 CMOD 알고리즘의 조합, 그리고 2-DFFT로부터 추출된 풍향으로부터 각 연구지역의 풍속은 가까운 기상관측소 및, 부이의 관측값과 비교하였다. 그 결과 Fine mode 자료로부터 추출된 풍속은 실제 관측 값보다 항상 상당히 높게 나타났지만, Standard mode 나 ScanSAR 자료로부터 추출된 풍속은 현지 기상관측소 관측 값과 잘 일치한다.

• International Journal of Reliability and Applications
• /
• v.2 no.2
• /
• pp.81-97
• /
• 2001

Lifetesting problems have been the subject of investigations for over three decades. Most suggested approaches are markedly different from those used in the related but wider goodness of fit problems. In the current investigation, it is demonstrated that a goodness of fit approach is possible in many lifetesting problems and that It results in simpler procedures that are asymptotically equivalent or better than standard ones. They may also have superior finite sample behavior. Several perennial classes are addressed here. The class of increasing failure rate (IFR) and the class of new better than used (NBU) are addressed first. In addition, we provide testing for a newer and practical class of new better than used in convex ordering (NBUC) due to Cao and Wang (1991). Other classes can be developed similarly and this point is illustrated with the classes of new better than used in expectation (NBUE) and harmonic new better than used in expectation (HNBUE).

• Journal of the Korean Society for Aviation and Aeronautics
• /
• v.26 no.4
• /
• pp.129-141
• /
• 2018

In this paper, two different flight training devices were constructed to verify the effectiveness of a pilot training system based on a Virtual Reality Head Mount Display. VFR Flight Procedure and IFR Flight Procedure were conducted by high level pilots with Commercial Pilot Licence. Flight data and pilot's visual data for each flight procedure were extracted, compared and analyzed with two training systems. Finally, the effectiveness of the training systems based on the VR HMD was demonstrated by assessing the given mission and the flight results.

• Management & Information Systems Review
• /
• v.34 no.5
• /
• pp.213-231
• /
• 2015

In this paper, I examine whether the listed companies in Korea tend to manage operating cash flows upward via classification shifting after the adoption of K-IFRS. As proxies for cash flow management, I derive a measure of abnormal operating cash flows borrowing from Lee(2012). Alternative proxies include a series of categorical variables designed to identify the types of classification shifting of interest and dividend payments among others, in the statement of cash flows. Higher level of estimated abnormal operating cash flows, and the classification of interest/dividend payments in non-operating activity sections are considered to indicate the managerial intention to maximize reported operating cash flows. I consider several potential incentives to manage operating cash flows, which include financial distress, the credit rating proximity to investment/non-investment cutoff threshold, avoidance of negative or decreasing operating cash flows relative to previous period and so forth. In a series of empirical analyses, I do not find evidence in support of the opportunistic classification shifting explanation, inconsistent with several previous literature in Korea. In contrast, I observe negative associations between the CFO management proxies and selected incentives, which suggest that the classification is likely to represent above average cash flow performance rather than opportunistic motives exercised to maximize reported operating cash flows. I reckon that this observation is, in part, driven by the K-IFRS requirement to maintain temporal consistency in classifying interest and dividend receipts/payments in cash flow statement.

• The Korean Journal of Air & Space Law and Policy
• /
• v.18
• /
• pp.363-384
• /
• 2003

The Military Airbase Law has designated imaginary surface, restricting the height of structure above the imaginary surface. The purpose of establishment of imaginary surface is to promote safety of aircraft operation. However, given the fact that the land is limited, the Military Airbase Law does not set up outer horizontal surface such that the reduced imaginary surface would undermine the safety of aircraft operations with respect to IFR (Instrument Flight Rules) procedures. The fact that some areas which IFR procedures require are not designated as imaginary surface results in no imposition of height restriction on such area. With regard to aviation safety, this article deals with issue of height restriction on area which is beyond the imaginary surface area. This article also examines the establishment of the imaginary surface in the Military Airbase Law, and conducts case study of imaginary surface systems in other country. Based upon this discussion, the current problems posed in the Military Airbase Law will be discussed. To resolve these problems, it is necessary to establish height restriction zone beyond the current imaginary surface area. The provisions of ICAO, FAA and other counties in relation with this issue are referred as well. As a result, many different proposals are suggested, and it is concluded as the most effective proposal that, in certain zone beyond the imaginary surface area, an aeronautic study should be required for the purpose of ensuring aviation safety before a permit of construction higher than prescribed height is issued.

• The Journal of the Korea Contents Association
• /
• v.19 no.11
• /
• pp.365-374
• /
• 2019

Loss of Control in Flight(LOC-I) due to aircraft upset attitude has the highest air accident rate, and International Aviation Institute such as ICAO and FAA recommended flight crew to operate aircraft safely through UPRT(Upset Prevention & Recovery Training) program. ICAO has selected Loss of Control(LOC) as key safety indicator, and recommended to respond using TEM(Threat and Error Management). However there are not much specific treats and errors classified for UPRT programs using real TEM based on evidences. This study intends to consider the importance of UPRT through the introduction of UPRT and accident analysis using TEM. Typical upset accidents were classified to common threats as IFR, inadequate training, Automation surprise, and inexperienced copilots. The common errors were cross-check, speed and altitude deviation, callouts, communication, thrust and stall action fail. The undesired aircraft states were inadequate automation mode, Deviation of speed and vertical, stall, and crash. These suggest areas to improve UPRT.

• Management & Information Systems Review
• /
• v.35 no.4
• /
• pp.37-56
• /
• 2016

This study investigates how adapting of K-IFRS effects NI and OCI affecting of credit rating on changing of the period and variable by using samples of around adapting of K-IFRS. First of all, after adapting of K-IFRS(2011-2013), it was noticeable that how NI affecting after adapting of K-IFRS(2007-2010) had been increased more than that of before affecting of K-IFRS. However, there was not a single difference in affecting OCI on credit rating comparing to the past of adapting of K-IFRS. Second, it seemed like NI affected more after adapting of K-IFRS(2011-2013). The first year of K-IFRS had bigger incremental effect than after adapting of K-IFRS. However, after adapting of K-IFRS, OCI affecting on credit rating had no ncremental effect. Third, it seemed like NI in the first year affected more than OCI on credit rating. After adapting(2012-2013) of K-IFRS, it seemed like NI and OCI do not affect on credit rating. To interpret this, NI and OCI affected the first year of adapting of K-IFRS; therefore, adapting of K-IFRS affected without affecting financial ratio on adapting credit rating. As the time goes on, it can be expected that adapting K-IFRS became stable; therefore, extra incremental effect will not be seen comparing to the early adaption. The implication of this study is when information users use credit rating, they have to concern of affecting of K-IFRS. This is because NI in financial ratio is affecting on credit rating.

• Korean Journal of Construction Engineering and Management
• /
• v.15 no.2
• /
• pp.104-111
• /
• 2014

Due to the structure of advanced installment sales of houses which is a construction industrial structure unique to Korea and the Project Financing (PF) project structure that includes construction companies' debt guarantee agreements, the changes in accounting methods resulting from the introduction of K-IFRSs are expected to act in a direction to deteriorate construction businesses' financial statements. Therefore, K-IFRSs are an important issue that can seriously affect the entire domestic construction industry and construction businesses are conceiving strategies to respond to the introduction of K-IFRSs. From this viewpoint, this study was intended to empirically analyze the effect of the introduction of K-IFRSs on construction businesses utilizing financial data applied with the K-IFRSs recently announced. In the analysis, the EDFs were calculated by business using the existing accounting standards GAAP and using K-IFRSs and the results were compared with each other. The results of the analysis indicated that most construction businesses were adversely affected by the introduction of K-IFRSs. It is also considered that businesses with relatively good financial statements under the existing accounting standards GAAP would be affected more by the introduction of K-IFRSs than other businesses. In addition, the introduction of K-IFRSs is expected to have larger effects on large construction businesses that have been providing debt guarantees for PF projects than on small or medium sized construction businesses.