• Journal of the Korean Institute of Gas
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• v.27 no.3
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• pp.1-10
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• 2023

Due to the development of the industrial revolution, regulations on exhaust emissions have been continuously strengthened to reduce the rapidly increasing greenhouse gas emissions. The use of environmentally friendly fuels is essential to meet these regulations. Hydrogen has been attracting attention as a future environmentally friendly fuel, but due to its material properties, it faces significant challenges in handling and storage. As an alternative, ammonia has been proposed. Ammonia can be easily liquefied at room temperature compared to hydrogen and has a high energy density. In order to examine the applicability of ammonia as an engine fuel, experiments were conducted to investigate the effects of changes in combustion control parameters in a direct injection ammonia combustion engine. The experiments were conducted by varying two variables: spark timing and excessive air ratio. Observations were made on combustion stability and the trends of exhaust emissions such as nitrogen oxides and unburned ammonia under the conditions of an engine speed of 1,500 rpm and medium to high loads (brake torque of 200 Nm). By optimizing the combustion control parameters, conditions for stable combustion even when using ammonia as the sole fuel were identified, and plans are underway to apply strategies for future expansion of the operating range.

• Journal of Information Technology Applications and Management
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• v.10 no.1
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• pp.111-125
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• 2003

This paper proposes a product data model that can express and enforce integrity constraints on product structure during engineering changes (ECs). The model adopts and extends an active object-oriented database model in order to Integrate IC data and their integrity constraints. Tightly integrated with product structure, It will enable designers to maintain and exchange consistent EC data throughout the product life cycle. In order to properly support operations for ECs, the model provides the data, operations, and Event-Condition-Action rules for nested ECs and simultaneous EC applications to multiple options. in addition, the EC objects proposed In the model integrate the data and Integrity constraints into a unified repository. This repository enables designers to access all EC data and integrity constraints through the product structure and relationships between EC objects. This paper also describes a prototype product data management system based on the proposed model In order to demonstrate its effectiveness.

• Proceedings of the Korea Information Processing Society Conference
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• 2007.11a
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• pp.399-402
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• 2007

다양하게 개발되는 정보시스템은 지속가능경영을 위한 서비스 인프라로 그 중요성이 날로 높아지고 있다. 이에 따라 새롭게 개발된 시스템을 얼마나 신속하게 전파하고 공유하여 조직 경쟁력을 향상시킬 것인가가 생존의 기본 조건이 된 것이다. 그러나, 전파 및 공유 도구로서의 콘텐츠 수준은 단순한 매뉴얼 또는 Help 메뉴 형태로 획일적으로 제공되어 단기간 내 조직 확산에는 한계가 있다. 이를 해결하기 위해 콘텐츠의 활용도를 극대화 할 수 있는 새로운 콘텐츠 개발 요구 정의 방법이 제시되어야 할 필요가 있다. 본 논문에서는 개발된 정보 시스템의 조직 전개를 위해 필요한 콘텐츠를 개발함에 있어 업계에 널리 활용되고 있는 스토리 기반 또는 전통적 콘텐츠 개발 방법의 한계를 극복하기 위하여 요구분석 시 Blue Ocean 전략과 6 Sigma 방법론을 결합한 시스템 개발 BORE Process를 콘텐츠 개발에 적합하게 변경한 Value innovative Requirements Engineering for Contents 프로세스로 제안하고, 콘텐츠 개발에 적용한 후, 그 결과의 유효성을 입증하기 위하여 공인된 기관의 콘텐츠 평가 결과를 제시한다.

• Korean Journal of Culture and Social Issue
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• v.20 no.3
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• pp.205-233
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• 2014

This study aims to identify work conflicts in Korean socio-cultural context by applying grounded theory. Survey has been conducted through in-depth interviews with 11 different employees from various occupational categories. Data collected from the survey were then analyzed based on the grounded theory of Strauss and Corbin (1998), thus resulted in a paradigm model consisting of 31 categories, 63 subcategories, and 100 concepts by open coding. Axial coding was then conducted and the results were as follows. The causal condition was the 'character of an opponent'. Contextual conditions which affect the causal condition were 'situational characteristics', 'character of an opponent', 'character of oneself', and their 'mutuality'. 'Negative feeling' was the central phenomena of work conflict and action/interaction strategies were verified to be 'avoidance', 'expression', 'effort toward solving problems' and 'increasing conflict'. Intervening conditions were 'interrelation', 'intervention', and 'group/task characteristics'. The consequences were organized as 'conflict continuance', 'personnel change' and 'positive effect'. Through selective coding, 'managing with the conflict' was derived as core-category and three different types of management were classified. Ultimately, this study shows how employees work in Korea experience the work conflicts and what kinds of socio-cultural factors have influence on the work conflicts, which can supplement previous inadequate empirical research. Also, this study can provide implications and suggestions as a fundamental integrated model for the future empirical research on work conflicts.

• Journal of Korean Society of Transportation
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• v.20 no.2
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• pp.93-104
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• 2002

The purpose of this study was to develop a improved high-order continuum model among macroscopic traffic flow models. This study was mainly performed for uninterrupted flow. In the first step, the proposed model described traffic flow at dropped lane. (no exits) It was possible to describe the traffic flow during short-term considering lane change. The proposed model was based on Payne's model. Our model was newly applied to uninterrupted traffic flow in consideration of geometry condition and driver behavior. It is possible to establish efficient control strategies, simulation and assess the effects of geometric improvements using this model. This model was simulated with field data for the actual adaption. The results of the model tests, traffic volume and density is suitably represented. we think that the results in the article can be led to predicting the situation in the near future.

• Journal of Korean Society for Quality Management
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• v.33 no.3
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• pp.156-160
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• 2005

We consider practical experimental design strategies and analysis to find out whether a modified method give better results than the standard method. The most practical design strategy is for experimenter to make r successive runs under the current standard method and then, change the standard method to a modified method to make another r successive runs under a modified method. To test a statistically significant difference between the population mean of the standard method and a modified method, additional recent data for sufficient number of consecutive responses under the standard method is needed to construct external reference distribution(Box, et al., 1968). Upon those informations unavailable, the practical design strategy is to run the experiment by split plot designs. In this paper, two types of split plot designs are proposed and how to determine efficiently the number of repetition within a given method and replication of those two methods are discussed based on results of the level of significance ${\alpha}$= 0.05 and the power being at least 0.9 at the detectable difference of ${\mu}_2-{\mu}_1=1.5{\times}{\sigma}$.

• School Mathematics
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• v.13 no.1
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• pp.175-187
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• 2011

The purpose of this study is to develop and utilize various kinds of mathematics teaching materials for gifted class in elementary school by utilizing polyominoes and a what-if-not strategy. Blokus is used to let students understand the characteristics of polyominoes, and omok is utilized to let them grasp interior point. Thus, the activities that utilized the new materials, blokus and omok, are developed to teach Pick's theorem. Besides, recreation activities were additionally prepared to provide education in an easy, intriguing and creative manner. The findings of the study is as follows: First, each of the materials was utilized in a different manner when the students engaged in basic and enrichment learning. Second, the mathematically gifted students were able to discover Pick's theorem in the course of utilizing the materials that contained recreational elements. Third, the students were taught to foster their problem-solving skills about area, girth and interior point by making use of the materials that were designed to be linked to each other. Fourth, existing programs were just designed to attain particular objects, to be conducted at a fixed time and to cater to particular graders. Fifth, when the students made problems by making use of the what if (not) strategy and the materials, they responded in diverse ways and were able to apply them.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.21 no.3
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• pp.115-121
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• 2021

Human's landing strategies have been explained through lower extremity kinetics in various conditions. However, how lower extremity kinetics respond when the two conditions between a load and landing height are combined is not yet understood. To achieve the purpose of this study, a total of 20 men and women were subjected to drop landing according to a load(No load, 10%, 20%, 30% of the body weight) at various landing heights(0.3 m, 0.4 m, 0.5 m). As a result of the study, the main effect of a load was not statistically significant in all variables. But increasing of the landing heights showed more flexion angle which was statistically significant in knee joint. In addition, as the landing height increased, the medial-lateral, anterior-posterior, vertical force, and loading rate increased, while time to peak vertical force decreased which was statistically significant. Thus, humans can successfully perform the landing motion even if the load is changed at various heights. However, it reacted more sensitively to the change in landing height than that load condition. The landing height can be prepared for recognition and shock absorption through visual information, but the weight level is difficult for the body to perceive and explains why it is more difficult to apply it to the landing strategy mechanism for shock absorption.

• The KIPS Transactions:PartB
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• v.14B no.4
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• pp.287-294
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• 2007

Many classification algorithms for real world data suffer from a data class imbalance problem. To solve this problem, various methods have been proposed such as altering the training balance and designing better sampling strategies. The previous methods are not satisfy in the distribution of the input data and the constraint. In this paper, we propose a focused sampling method which is more superior than previous methods. To solve the problem, we must select some useful data set from all training sets. To get useful data set, the proposed method devide the region according to scores which are computed based on the distribution of SOM over the input data. The scores are sorted in ascending order. They represent the distribution or the input data, which may in turn represent the characteristics or the whole data. A new training dataset is obtained by eliminating unuseful data which are located in the region between an upper bound and a lower bound. The proposed method gives a better or at least similar performance compare to classification accuracy of previous approaches. Besides, it also gives several benefits : ratio reduction of class imbalance; size reduction of training sets; prevention of over-fitting. The proposed method has been tested with kNN classifier. An experimental result in ecoli data set shows that this method achieves the precision up to 2.27 times than the other methods.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.4
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• pp.711-717
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• 2017

Startability and harmful emissions are the main issues in diesel engine development under cold conditions. The characteristics of combustion with multiple injection were investigated under cold start conditions. For quantitative analysis, the in-chamber pressure profile was measured and combustion visualization using direct imaging was accomplished. With multiple injection, the peak in-chamber pressure and heat release rate were increased compared to single injection. In addition, the period of flame luminosity detection was shortened using multiple injection. Combustion by main injection was improved with an increase in heat released by pilot combustion when the pilot injection quantity was increased. Finally, an increase in injection pressure also showed the possibility of combustion improvement. On the other hand, an increase of in the pilot injection quantity and injection pressure can cause an increase in harmful emissions, such as HC and CO due to wall wetting. Therefore, more sensitive calibration will be needed when applying a multiple injection strategy under cold start conditions.