• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.34 no.4
• /
• pp.47-52
• /
• 2006

Using the equivalent ARMA model representation of the mixed random errors, we propose Klaman filter design methods for aided INS(Inertial Navigation System) which contains the gyroscope mixed random errors. At first step, considering the characteristic of indirect feedback Kalman filter used in the aided INS, we perform the time difference of equivalent ARMA model. Next, according to the order of the time differenced ARMA model, we achieve the state space conversion of that by two methods. If the order of AR part is greater than MA part, we use controllable or observable canonical form. Otherwise, we establish the state apace equation via the method that several step ahead predicts are included in the state variable, where we can derive high and low order models depending on the variable which is compensated from gyroscope output. At final step, we include the state space equation of gyroscope mixed random errors into aided INS Kalman filter model. Through the simulation, we show that both the high and low order filter models proposed give less navigation errors compared to the conventional filter which assume the mixed random errors as white noise.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.20 no.3
• /
• pp.625-639
• /
• 2018

This study is about the reinforcing type of reinforcement method which is reinforced in tunnel portal of tunnel with bad ground condition. Generally, it is known that the horizontal reinforcement method is more effective than the conventional reinforcement method. However, as a limitation of the tunnel construction technology, it is being constructed by the superposition reinforcement method. In recent years, high-strength large-diameter steel pipes and horizontally oriented longitudes (L = 30.0~50.0 m) construction technology have been developed. Therefore, it is required to study reinforcement method of tunnel portal reinforcement method. Therefore, 3-D numerical analysis (Midas GTS NX 3D) was performed by setting the reinforcement method (No reinforcement type, overlap reinforcement type and horizontal reinforcement type) and ground condition as parameters. As a result, it was considered that the reinforcement effect was the largest as the horizontal reinforcement type of the reinforcement method was the smallest in the displacement and the support material stress. Based on the results of the numerical analysis, horizontal steel pipe grouting was applied to the actual tunnel site. The displacement of the tunnel portal and the stress of the support material occurred within the allowable values and were considered to ensure sufficient stability.

• The Korean Journal of Applied Statistics
• /
• v.35 no.1
• /
• pp.131-146
• /
• 2022

Logit models are commonly used to predicting and classifying categorical response variables. Most Bayesian approaches to logit models are implemented based on the Metropolis-Hastings algorithm. However, the algorithm has disadvantages of slow convergence and difficulty in ensuring adequacy for the proposal distribution. Therefore, we use auxiliary mixture sampler proposed by Frühwirth-Schnatter and Frühwirth (2007) to estimate logit models. This method introduces two sequences of auxiliary latent variables to make logit models satisfy normality and linearity. As a result, the method leads that logit model can be easily implemented by Gibbs sampling. We applied the proposed method to diabetes data from the Community Health Survey (2020) of the Korea Disease Control and Prevention Agency and compared performance with Metropolis-Hastings algorithm. In addition, we showed that the logit model using auxiliary mixture sampling has a great classification performance comparable to that of the machine learning models.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.19 no.5
• /
• pp.167-175
• /
• 2018

Load transfer experiments have been carried out to evaluate the performance of the anchorage and it has been stated that the specimens were manufactured and tested according to ETAG 013. On the other hand, the amount of spiral reinforcement and auxiliary reinforcement exceeded the amount specified in ETAG 013. In this study, the load transfer test method and the criteria specified in ETAG 013 were considered and the PT anchorage system was applied to manufacture specimens with high strength concrete and a high tensile prestressing strand. A load transfer test according to ETAG 013 was performed to evaluate the performance of the circular anchorage. As a result, it was confirmed that ETAG 013 is a very strict specification that does not satisfy the performance of an anchorage unless the specimens of an appropriate size and spiral reinforcement are used. To assess the stability of the specimens, increasing the size of the specimen by 15%, rather than increasing the amount of auxiliary reinforcement, is considered to be the correct method in accordance with ETAG 013.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2015.08a
• /
• pp.239.1-239.1
• /
• 2015

1차원 탄소나노재료이며 한 겹의 흑연을 말아 놓은 형태인 단일벽 탄소나노튜브(Single-walled carbon nanotubes, SWNTs)는 감긴 형태에 따라 반도체성, 금속성 성질을 나타내는 특이성과 우수한 기계적 성질을 지니고 있어 광범위한 분야로 응용이 기대되어왔다. 이러한 SWNTs의 응용가능성을 실현시키기 위해서는 보다 경제적, 산업적인 면에서 손쉬운 합성방법의 개발이 필요한 실정이다. SWNTs의 합성 방법들로는 아크방전법과 레이저 증발법, 그리고 열화학기상증착법(Thermal chemical vapor deposition, TCVD) 등이 이용되었다. 이 중 TCVD법은 대면적의 균일한 CNTs를 합성할 수 있다는 장점이 있다. 그러나 탄화수소가스를 효율적으로 분해하기 위하여 $800^{\circ}C$ 이상의 고온 공정이 요구되며, 이는 경제적, 산업적인 면에서 사용이 제한적이다. 따라서 저결함, 고수율의 SWNTs를 저온합성 할 수 있는 공정의 개발이 지속적으로 필요하다. 본 연구에서는, TCVD법을 이용하여 에틸렌 원료가스로 SWNTs의 저온합성 가능성을 확인하였다. 합성을 위한 기판과 촉매로는 실리콘 산화막 기판(SiO2/Si wafer)에 철 나노입자를 지닌 ferritin을 스핀코팅 후 산화하여 이용하였다. 저온합성 공정의 변수로는 합성온도와 원료가스인 에틸렌의 분율을 설정하여, 변수가 SWNTs의 결정성과 수율에 미치는 영향을 고찰하였다. 합성된 SWNTs의 분석의 용이함과 손지기(Chirality)의 제어를 위하여 나노 다공성 물질인 제올라이트(Zeolite)를 보조 기판으로 사용하였다. 실험결과 에틸렌 원료가스로 합성한 SWNTs는 $700^{\circ}C$ 부근의 저온에서도 합성이 가능함을 확인하였다. 또한 에틸렌 원료가스의 분율과 합성시간의 정밀한 제어를 통해 SWNTs의 합성온도를 더욱 감소시키는 것도 가능할 것으로 예상된다.

• Proceedings of the KIEE Conference
• /
• summer
• /
• pp.731-733
• /
• 2004

제약급전계획은 중앙급전발전기 및 중앙급전부하의 급전값을 산정하기 위해 각 급전주기마다 해당급전주기에 대하여 전력거래소가 예측한 비중앙급전발전기 및 비중앙급전부하에 대한 자료를 기초로 제약요소를 고려하여 작성하는 급전계획이다. 이 급전계획은 실제발전기와 부하의 출력 및 전력소비를 결정하므로 전력수급 조건, 발전기제약, 전력망제약, 보조서비스제약 등을 고려하여 전력의 시장거래가치를 최대화하도록 해야 한다. 본 논문에서는 제약급전을 결정함에 있어 선형계획법의 적용방법을 제시하고, 해의 수렴 개선을 위해 결정변수 및 제약조건의 수를 줄일 수 있는 방법을 제시한다.

• Proceedings of the Korea Association of Information Systems Conference
• /
• 1998.10a
• /
• pp.56-63
• /
• 1998

정보화사회가 도래함에 따라 교육분야에서도 다양한 교수와 학습활동을 실현할 수 있는 방법으로 컴퓨터의 활용이 중요성을 지니게 되었는데 그 중 중요한 방법 중의 하나가 강의실 수업의 연장으로써, 보조학습수단으로써 인터넷 서비스 중 웹(WWW)상의 교사 홈페 이지를 이용한 학습은 전통적 교수-학습 형태에서 볼 수 있었던 폐해를 극복하고 정보화시 대가 요구하는 창조적이고 능동적인 인간성을 길러내는데 일조하게 될 인터넷에 올려진 교 사 홈페이지를 이용한 교수-학습시스템인 것이다. 본 연구의 목적은 현재 몇몇 학교에서 실 시하고 있는 인터넷을 통한 교사 홈페이지를 이용한 교수-학습시스템의 구체적인 성과를 알아보고, 이에 영향을 미치는 요인들과의 관계를 밝혀 교사 홈페이지를 이용한 교수-학습 시스템의 좀 더 적극적으로 활용되었으면 하는 것이다. 시스템활용의 편이성과 시스템의 활 용도 그리고 학생의 학습 태도 등을 성과변수로 설정하고 학생의 시스템 활용능력과 교사의 홈페이지 구성내용 그리고 학교측의 지원 등을 주요 요인으로 설정하여 설문조사를 통하여 분석한 결과, 설정된 성과인 시스템활용의 편이성과 시스템의 활용도 그리고 학생의 학습 태도에는 긍정적인 측면을 나타냈고 이들에 영향을 미치는 요인들로는 공히 학생의 시스템 활용능력과 학교측의 지원으로 나타난 바, 이러한 시스템의 도입은 상당히 긍정적이며 앞으 로도 다각적인 연구의 필요가 충분히 있다.

• Survey Research
• /
• v.5 no.1
• /
• pp.93-101
• /
• 2004

In business survey, cut-off sampling is usual, The contribution from cut-off part of the population is at least small in comparison with the remaining population. In this case, part of the target population is excluded from the selection and parameter estimations are only based on Take-all and Take-some stratum. It may be tempting not to use resources on enterprises that contribute little to the overall results of the survey. And this reduces the response burden for these small enterprises. But, the size of cut-off stratum has been increased as a way to manage reduced budgets. This leads to additional bias. In this study, the population have been separated as three stratum, cut -off, take-some, take-all, and we will estimate cut-off part using auxiliary variable.

• Survey Research
• /
• v.9 no.2
• /
• pp.151-166
• /
• 2008

This paper deals with the use of the separate ratio estimator in the survey of cultivated land area. As a kind of repeated survey conducted every year, this survey estimates the total cultivated land area by using the separate ratio estimator. When using the separate ratio estimation in the survey, we may face with some practical problems such as (i) changing population size over time, (ii) auxiliary variables taken zero values in some strata and (iii) changing stratification criteria due to sample redesign. In this paper, after investigating practical problems occurred in the survey we presented some adjusted separate ratio estimators to tackle such problems.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.34 no.7
• /
• pp.821-827
• /
• 2010

This paper proposes a density method based topology optimization of a perpendicular magnetic recording system design in which the saturation effect is taken into account. During the topology optimization process in magnetic fields, the magnetic reluctivity is updated in accordance with the changes in element density determined by a sensitivity analysis. The magnetic reluctivity is determined from a B-H curve and is used to represent nonlinear material property, i.e., the saturation effect. The sensitivity for a generalized response functional is formulated using the adjoint variable method in which the nonlinear property is taken into account and the objective function is set such that the magnetic energy in the media is maximized. Effects due to the nonlinear property can be observed from a numerical study in which the linear and the nonlinear topology optimization results are compared.