• 태양에너지
• /
• 제8권1호
• /
• pp.49-56
• /
• 1988

Thermally treated Korean ilmenite was characterized and used for water splitting to obtain hydrogen by photo-catalytic reaction. Experiments on specific surface area, X-ray diffraction and EDS showed that the formation of FeO, $Fe_2O_3$ and $TiO_2$ ilmenite crystal surface increased the specific surface area with maximum value, phase change of $TiO_2$ at $600^{\circ}C$ and hetrogeneity. The hydrogen evolved in caustic soda solution on these ilmenites indicated that there was a maximum yield point at about $600^{\circ}C$. This point was explained with the change of the surface area due to sintering of newly formed FeO, $Fe_2O_3$ and $TiO_2$, as well as crystal phase change of anatase to rutile at $600^{\circ}C$. Produced hydrogen increased also as the concentration of caustic soda, but become constant at the near 1N solution.

• Communications for Statistical Applications and Methods
• /
• 제6권3호
• /
• pp.801-812
• /
• 1999

Change-point hazard rate models arise for example in applying "burn-in" techniques to screen defective items and in studing times until undesirable side effects occur in clinical trials. Sometimes in screening defectives it might be sensible to model two stages of burn-in. In a clinical trial there might be an initial hazard rate for a side effect which after a period of time changes to an intermediate hazard rate before settling into a long term hazard rate. In this paper we consider the multiple change points hazard rate model. The classical approach's asymptotics can be poor for the small to all moderate sample sizes often encountered in practice. We propose a Bayesian approach avoiding asymptotics to provide more reliable inference conditional only upon the data actually observed. The Bayesian models can be fitted using simulation methods. Model comparison is made using recently developed Bayesian model selection criteria. The above methodology is applied to a generated data and to a generated data and the Lawless(1982) failure times of electrical insulation.

• Nuclear Engineering and Technology
• /
• 제56권3호
• /
• pp.772-784
• /
• 2024

The hexagonal nodal code RENUS has been enhanced to handle irregularly deformed hexagonal assemblies. The underlying RENUS methods involving triangle-based polynomial expansion nodal (T-PEN) and corner point balance (CPB) were extended in a way to use line and surface integrals of polynomials in a deformed hexagonal geometry. The nodal calculation is accelerated by the coarse mesh finite difference (CMFD) formulation extended to unstructured geometry. The accuracy of the unstructured nodal solution was evaluated for a group of 2D SFR core problems in which the assembly corner points are arbitrarily displaced. The RENUS results for the change in nuclear characteristics resulting from fuel deformation were compared with those of the reference McCARD Monte Carlo code. It turned out that the two solutions agree within 18 pcm in reactivity change and 0.46% in assembly power distribution change. These results demonstrate that the proposed unstructured nodal method can accurately model heterogeneous thermal expansion in hexagonal fueled cores.

• 디지털산업정보학회논문지
• /
• 제6권1호
• /
• pp.13-22
• /
• 2010

In this paper, we propose a management system for positioning and indicating the surveyed control point using RFID and UMPC. This system is composed of digital control point, management system and application. The digital control point transmits information of the surveyed control point and the management system receives the data from the digital control points and manages the scattered digital control points. The system offers three services for managing the surveyed control point. The first service is control point monitoring service for identifying the change of location, locating the missing control point and the second service is control point search service notifying selected control point to user, and the third service is control point land management service for editing the control point information in the land. Therefore, this system makes it easy for administrators to access the control point information of the scattered surveyed control point through the country and enhances the managing efficiency.

• Communications for Statistical Applications and Methods
• /
• 제7권3호
• /
• pp.789-798
• /
• 2000

The mean residual function is the expected remaining life of an item at age x. The problem of trend change in the mean residual life is great interest in the reliability and survival analysis. In this paper, we develop a family of test statistics for testing whether or not the mean residual life changes its trend. The asymptotic normality of the test statistics is established. Monte Carlo simulations are conducted to study the performance of our test statistics.

• 한국통계학회:학술대회논문집
• /
• 한국통계학회 2005년도 추계 학술발표회 논문집
• /
• pp.43-48
• /
• 2005

We consider the problem of testing for parameter changes in time series models based on a cusum test. Although the test procedure is well-established for the mean and variance in time series models, a general parameter case has not been discussed in the literature. Therefore, here we develop a cusum test for parameter change in a more general framework. As an example, we consider the change of the parameters in an RCA(1) model and that of the autocovariances of a linear process. We also consider the variance change test for unstable models with unit roots and GARCH models.

• Archives of Plastic Surgery
• /
• 제42권4호
• /
• pp.419-423
• /
• 2015

Background Orthognathic surgery is required in 25% to 35% of patients with a cleft lip and palate, for whom functional recovery and aesthetic improvement after surgery are important. The aim of this study was to examine maxillary and mandibular changes, along with concomitant soft tissue changes, in cleft patients who underwent LeFort I osteotomy and sagittal split ramus osteotomy (two-jaw surgery). Methods Twenty-eight cleft patients who underwent two-jaw surgery between August 2008 and November 2013 were included. Cephalometric analysis was conducted before and after surgery. Preoperative and postoperative measurements of the bone and soft tissue were compared. Results The mean horizontal advancement of the maxilla (point A) was 6.12 mm, while that of the mandible (point B) was -5.19 mm. The mean point A-nasion-point B angle was $-4.1^{\circ}$ before surgery, and increased to $2.5^{\circ}$ after surgery. The mean nasolabial angle was $72.7^{\circ}$ before surgery, and increased to $88.7^{\circ}$ after surgery. The mean minimal distance between Rickett's E-line and the upper lip was 6.52 mm before surgery and 1.81 mm after surgery. The ratio of soft tissue change to bone change was 0.55 between point A and point A' and 0.93 between point B and point B'. Conclusions Patients with cleft lip and palate who underwent two-jaw surgery showed optimal soft tissue changes. The position of the soft tissue (point A') was shifted by a distance equal to 55% of the change in the maxillary bone. Therefore, bone surgery without soft tissue correction can achieve good aesthetic results.

• 조명전기설비학회논문지
• /
• 제22권1호
• /
• pp.50-57
• /
• 2008

철도 정거장 구내에서는 본선으로부터 측선으로 진로를 바꾸기 위하여, 즉 다른 선로로 분기하기 위하여 분기지점에 설치한 궤도설비를 분기기라 하며, 분기기의 방향을 전환시키는 장치를 선로전환기라 하는데, 이 장치에 문제가 발생하면 심각한 상황이 초래될 수 있다. 이 장치에는 정밀한 기기와 센서가 설치되어 사용되는데, 장애가 많이 발생하며 열차 탈선이라는 극한의 상황까지 이를 수 있다. 본 논문에서는 사용중인 안전장치들을 장애와 사고를 정밀 분석하고 이를 대체할 수 있는 장치를 개발하였다. 이 장치는 낙뢰에 의한 과전압의 영향을 받지 않도록 설계되어서 열차운행이 원활하게 된다.

• 대한화학회지
• /
• 제40권1호
• /
• pp.81-86
• /
• 1996

반도체를 보호하기 위하여 사용하는 반도체 성형 재료로, 현재 주로 사용되고 있는 Epoxy Molding Compound(EMI)의 주성분인 올소 크레졸 노볼락 에폭시 수지의 특성과 성형 재료의 관계를 조사하기 위하여 올소 크레졸 노볼락 에폭시 수지의 분자량과 깊은 관련이 있는 수지의 연화점 변화에 따른 EMC의 물성변화를 살펴보았다. 사용된 epoxy 수지의 연화점은 각각 65.1$^{\circ}C$, 72.2$^{\circ}C$, 83.0$^{\circ}C$ 인 3종을 사용하였으며 연화점 변화에 따른 EMC의 물성변화를 살펴보기 위하여 기계적 물성으로 굴곡 강도와 굴곡탄성율을, 열적 특성 변화를 관찰하기 위하여 열팽창 계수와 열전도도 그리고 유리 전이온도를 각각 측정하였다. 그리고 성형 특성과의 관계를 살펴보기 위하여 스피랄 플로우(Spiral Flow)를 측정하였다, 연화점이 증가함에 따라 굴곡 탄성율과 유리상에서의 열팽창 계수(${\alpha}_1$), 그리고 열전도도는 거의 변화가 없었으나 유리전이온도는 연화점 증가에 따라 증가함을, 스피랄 플로우는 연화점 증가에 따라 감소함을 보여주었다. 이는 에폭시 수지의 분자량이 증가함에 따라 가교밀도가 증가하는 현상에 기인한다고 판단된다. 고무상에서의 여팽창 계수(${\alpha}_2$)와 굴곡강도의 경우는 전이점을 보여주고 있는데, 이는 수지점도 증가에 따른 충전제의 분산성에 기인한 것으로 판단된다.

• 한국치위생학회지
• /
• 제7권4호
• /
• pp.395-403
• /
• 2007

The purpose of this study is to investigate the main factors that affect turnover of Dental Hygienists so that it leads to preventing high turnover and long-term service in their position. Data were obtained from 112 dental hygienists who are currently working for dental clinics from September 17th 2007 to October 16th 2007 via questionnaires. For this study, the demographic factors and unique characteristics of Dental Hygienists are considered as well as all the variables of statistic. The results derived from using SPSS 11.0 are as follows: 1. The average of job related factors is 2.55 point, the average of job satisfaction is 2.59 point, the average of salary related factor is 2.24 point and the average of changing their occupation is 2.85 point. 2. The difference between the factors related to age and changing their occupation shows the highest level on job related factors.(pM0.033) in the age between 26 and 30. 3. Dental Hygienists who are in their occupation for 6years to 9 years answer that salary would be the main reason to change their jobs. 4. For married dental hygienists, salary related factor is the main reason to make them change their occupation.(pM0.002)