• Journal of the Korean Chemical Society
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• v.38 no.12
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• pp.880-884
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• 1994

An indirect spectrophotometric method, presumably heretofore unmentioned, for the rapid determination of COD in the presence of chloride of high concentration is described. The alkaline sample is refluxed to react with a definite amount of permanganate, present in excess. A photometric measurement at 535 nm for the extent of the fading of the permanganate color after refluxing completes the procedure. The optimum conditions which give the absorbance-concentration plot the maximum linearity and slope in the range of 0∼5 ppm COD are as follows: reflux at $100\circC$ for 10 min in the presence of 0.15 mM permanganate and 0.2% NaOH with a sample size of 5 ml. An overall running time was less than 15 min. The t-test reveals that the proposed method is not significantly different from the official method.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.338-338
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• 2012

사파이어 ($Al_2O_3$)는 높은 밴드갭 에너지 (~19.5 eV)를 가진 물질로서 우수한 내마모성, 강도, 전기 절연성 및 안정한 화학적 특성을 갖고 발광다이오드 기판, 보석재료 등 각종 산업 및 기술적 분야에서 널리 사용되고 있다. 특히, 플립칩 발광다이오드 구조의 경우 광추출효율을 향상시키기 위해 높은 투과도를 갖는 사파이어 기판이 요구되어 왔으며, 지금까지 건식/습식식각방법을 이용한 사파이어 표면에 마이크로 크기의 심한 거칠기 또는 요철이 형성된 나노크기의 격자구조를 형성시키는 연구가 진행되어 오고 있다. 그 중, 나노 크기의 격자구조는 공기에서 반도체 기판까지 선형적인 유효굴절률 분포를 갖기 때문에 표면에서 생기는 Fresnel 반사 손실을 줄일 수 있다. 이러한 구조를 형성하기 위해서는 식각 마스크가 필요한데, 형성 방법으로 레이저 간섭 리소그래피, 전자빔 리소그래피, 나노임프린트 리소그래피 등이 있으나, 비싼 가격과 복잡한 공정 절차 등의 단점을 지니고 있다. 따라서 본 연구에서는 식각 마스크 패턴을 위해, 보다 저렴하고 간단한 실리카 나노구 및 열적응집 금 나노 입자를 이용하였다. 양면 폴리싱 c-plane 사파이어 기판을 사용하였고, 단일 층의 주기적인 실리카 나노구를 기판 표면에 스핀코팅에 의해 도포한 후 유도결합플라즈마 식각 장비를 이용하여 식각하여 주기적인 패턴을 갖는 렌즈모양의 격자구조를 형성하였다. 그리고 주기적으로 형성된 격자 위에 열 증착기를 이용하여 금 박막을 증착한 후 급속열적어닐닝(rapid thermal annealing)을 이용하여 열처리함으로써 비주기적인 금 나노입자를 형성시켰다. 형성된 금 나노패턴을 이용하여 동일한 조건으로 식각함으로써 광대역 및 전방향성 높은 투과도를 갖는 원뿔 모양의 사파이어 나노구조를 제작하였다. 제작된 샘플의 패턴 및 식각 형상은 전자현미경을 사용하여 관찰하였으며, UV-vis-NIR 분광광도계 (spectrophotometer)를 사용하여 투과율을 측정하였다. 렌즈 모양 표면 위에 원뿔모양의 나노구조를 갖는 사파이어 기판은 일반적인 사파이어 기판보다 향상된 투과율 특성을 보였다.

• Korean Journal of Construction Engineering and Management
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• v.10 no.4
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• pp.14-25
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• 2009

Development work of apartment houses is a complex medium-and long-term project requiring grand resources and work force. Since in combination inner and outer project variables relate to project output, uncertainties caused by not only a given site condition but also politic, economy and social sectors are generated during the project. These risks influence output of the project as important factors, and ultimately as management variables in priority giving an effect on earnings and the financial structure of enterprises they should be manageable with the risk reduction plan. In this point of view, this study focused on development work of apartment houses among construction project. Risky factors were deduced, analyzed and evaluated based on Value Engineering from planning to designing to executing to maintaining. Eventually, this study showed the foundation guaranteeing competitive power of public and private construction sectors.

• Informatization Policy
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• v.20 no.4
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• pp.23-50
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• 2013

The main purpose of this study is to empirically examine and to develop the optimal model about an influential relationship between the types of source-based trust and knowledge sharing of local government officials. Procedural and distributive justice-based calculative trust in organization, cognition-based trust in organization, cognition-based trust in supervisor, cognition-based trust in coworkers, and emotion-based trust in coworkers were set up as independent variables of this research model, and sharing of tacit knowledge and explicit knowledge based on the knowledge content as dependent variables. The research results shows that the suitability of each model has approximate value to the required level, and that emotion-based trust in coworkers significantly affects knowledge sharing for both the individual and integrated factors in hypothetical influential relationship. This study is expected to help to enable knowledge sharing in various situations by dividing the concepts of trust that affect knowledge sharing into a few types, and deriving the influential model of knowledge sharing by types.

• Korean Journal of Construction Engineering and Management
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• v.12 no.6
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• pp.31-41
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• 2011

Since the cases of time extension have continuously transpired in the public construction project, the potential of economical loss and claims is increasing because the concerned parties such as an owner or a contractor have not properly performed their own responsibility for time extension. One of the main reasons is that the present planning and scheduling do not support the method to apportion the proper responsibility to the right party. This problem has repeatedly led to time extension and made it difficult for the concerned parties to perform the responsibility for time extension. In order to overcome this problem, a framework of delay administration is required as the method to apportion the proper responsibility to the right party. To solve this problem, this paper aimed to develop the conceptual model and prototype system as the practical method to administrate delay causation. Furthermore, the verification result for the reliability and applicability throughout the case studies on real construction projects shows that the conceptual model and prototype system developed would help efficiently to administrate the delay causation.

• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.5
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• pp.773-786
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• 2018

In this paper, viscosity features of sealant (bentonite-cement slurry), which is used for umbrella arch method in tunnel, were studied. The sealant must secure optimal strength and capacity for the waterproof and stabilization of borehole as well as to satisfy groutability. In this study, the variation of viscosity was measured with different mixing processes. With an increase of initial mixing period with water and bentonite mixture, the required time for the rapid increase of viscosity of the sealant is shorten. With increase of mixing period, the possibility of swelling of bentonite will increases and this can lead increase of the viscosity of the mixture. In addition, the behaviors of sealant vary with a drastic increase of the viscosity: thixotropy and rheopexy. Furthermore, the bentonite/water mixing period influences on the bleeding features of the sealant. Further study is required to introduce the guideline, which can be applicable in the field in the aspect of required capacity of the sealants and mixing processes of the ingredients.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.7
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• pp.673-682
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• 2017

As the culture of making things based on "do-it-yourself" (DIY) activity is increasingly promoted, the use of recent digital technologies and tools, including the 3D printer, have become widespread. However, the use of computerized numerical control (CNC) engraving machine is considered difficult because of the complicated procedures and specialized knowledge required for its operation. Therefore, this study aims to resolve the issue that limits the usability of the CNC engraving machine. This paper presents a novel CNC engraving machine system for non-experts based on human-centered design. First, the size and type of the workpiece and tool are reduced. Second, computer-aided process planning (CAPP) steps such as tool path generation, workpiece clamping, and corresponding coordinate system are automated by compromising productivity and efficiency. As a result, a CNC engraving machine system that can be easily used by non-experts was developed. This development has great significance in that it opens up the possibility of using the CNC engraving machine for a wider range of DIY activities.

• Korean Journal of Construction Engineering and Management
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• v.3 no.2 s.10
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• pp.114-120
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• 2002

Traditional bidding process and activities in public construction area has many problems in terms of the transparency and fairness of administration. And, it causes many expenses to suppliers. As part of the efforts to solve these problems, some public institutions developed the electronic bidding systems. But these systems have still problems in diverse aspects. Therefore, the purpose of this study is to analyze current bidding systems through literature survey, Questionnaire, contentment estimation and IDEF method to compare the result of the analysis with the developed electronic bidding systems and to suggest the improvement for the coming bidding systems. According to the survey, under present bidding system big problem is inconvenience of conducting process. Nearly all users of current electronic bidding systems were contented. When public institutions are planning new electronic bidding systems, standardization, security, law and bidding system consolidation must be applied. This study proposes an improved bidding system and described the effects through the improvements.

• Korean Journal of Construction Engineering and Management
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• v.16 no.6
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• pp.73-83
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• 2015

Construction management firms in Korea have mainly focused on the key management areas of time, cost, quality and safety management in line with a rapid change of construction industry recently. However, a risk management is considered comparatively less important found from our research on an investment by the firms for training, system establishment. This has been identified that the construction management firms have taken an approach of dealing with risks with their experience, insight rather than managing risks with a systemized principles or proper tools. Therefore, the current system for risk management was identified by analyzing risk factors and work process in this research and systemized process for risk management of the identified risk factors was suggested. This research is expected to be a basis on establishing standard gudiance for risk management and risk management tools.

• Journal of the Society of Disaster Information
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• v.9 no.1
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• pp.50-55
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• 2013

Self-Prevention Plan Review Report and Review Standards Process Safety Management(PSM), Safety Management System(SMS), including the contents of the safety management system audit standards, notices and guidelines on the screening form and were analyzed. Were expected through the interview and screening personnel in the screening process to identify problems prior research so that it can be reflected in the. Also divided into methods such as document review and on-site implementation status of the review written Emergency Preparedness Plan depending on the item proposed. Toxic Chemicals Control Act(TCCA) Self-Prevention Plan Review Regulations. However, the substantial approval process, and do not enable the system performance lacked Self-Prevention Plan Review. Review half configuration to enhance the professionalism and efficiency of the work of this research was performed.