• Journal of the Society of Naval Architects of Korea
• /
• v.55 no.1
• /
• pp.75-82
• /
• 2018

Wedge-shaped fins are generally used to provide sufficient forces and moments to control and maneuver a supercavitating vehicle. There are four fins placed along the girth of the vehicle, near he tail: two of the fins are horizontal and the other two fins are vertical. In a fully developed supercavitating flow condition, a part of the fin is in a cavity pocket and the other is exposed to water. In this paper, experimental investigations of hydrodynamic characteristics of the wedge-shaped fin models are presented. Experiments were conducted at a cavitation tunnel of the Chungnam National University. We first closely observed the typical formation of wake cavitation and measured lift and drag forces acting on two different test models. Next, using a special device for generating natural and artificial supercavities, we investigated hydrodynamic forces at different cavitation number conditions. This work provides a basis for interpreting the cavity stability and hydrodynamic characteristics of the wedge-shaped control fin for a supercavitating vehicle.

• Journal of the Society of Naval Architects of Korea
• /
• v.58 no.1
• /
• pp.24-31
• /
• 2021

In this study, we present experimental observations of artificial supercavitation generated by the injection of compressed air at multiple locations on the body. Experiments were conducted at a cavitation tunnel equipped with a special facility to remove injected air before returning to the test section. Artificial supercavitation, which is generated at a relatively low speed compared to natural supercavitation, is formed asymmetrically on the axis of the body due to the buoyancy effect. In order to accelerate the development of the supercavity and increase the area covering the body, an experimental device capable of additional injection from the body was designed and its performance was evaluated through the model test. The shapes of the supercavity generated by multi-injections of different combinations according to different flow speeds were analyzed using high-speed shadow images. The results show that multiple injections at suitable locations can effectively increase the length of the supercavity and consequently improve propulsion efficiency.

• Journal of the Society of Naval Architects of Korea
• /
• v.56 no.4
• /
• pp.327-334
• /
• 2019

Recently, there has been a growing interest in artificial supercavitation as a way to reduce friction drag of submerged vehicles. A cavitator plays an important role to generate the supercavity, so many studies have focused on the case of cavitator only. However, the body shape behind the cavitator affects the growth of the supercavity and this effect must be considered for evaluating the overall performance of the system. In this work, we conducted experimental investigation on artificial supercavitation generated by different combinations of the cavitator and body. We observed the supercavity pattern by using a high-speed camera and measured the pressure inside the cavity by using an absolute pressure transducer. We estimated the relation between the amount of injected air and the supercavity shape for different combinations. In summary, the disk type cavitator generates larger supercavity than that of the cone and ellipsoidal cavitators, but cavity development speed is relatively slower rather than the others. Furthermore, fore body angle plays an important role to generate the supercavity enveloping the entire body.

• Journal of the Society of Naval Architects of Korea
• /
• v.53 no.6
• /
• pp.465-472
• /
• 2016

A study was carried out to investigate typical features of natural supercavitation generated behind axisymmetric bodies such as disk and cone shaped cavitators. Main focuses of the study were to observe formation process of the supercavity and to measure drag forces acting on cavitators. Experiments were carried out at the cavitation tunnel of the Chungnam National University (CNU-CT), which has a capability to make sufficient flow speed for supercavitation experiments and to remove broken cavity bubbles coming back to the test section. Blockage effects on supercavity dimensions were evaluated and an effort was made to correlate tunnel experiments with unbounded flow. On the basis of experimental and numerical results, geometrical features of supercavities and characteristics of drag forces were examined and their relations were proposed.

• Journal of the Korean Institute of Traditional Landscape Architecture
• /
• v.33 no.4
• /
• pp.166-175
• /
• 2015

Nowadays, in the European countries, landscape is spoken of its importance as often as environment, by those who are engaged in such fields as politics, administration, research and civil society. In Korea, while recognizing such an international trend, academics and administrators have made a series of efforts to reflect landscape concept on a variety of policies. However, it is recognized that the effects of these policies have not been satisfactory. Under these circumstances, this paper aims to examine the complex values and multiple meanings in the landscape, which have been discussed by landscape experts in the European countries. Then, it aims to the explore the future direction of policy and research on the landscape to be pursued in Korea, where there is relatively less interest in the issues of landscape. It is argued that landscape should be approached and understood from a holistic perspective, because it is a very complex concept with multiple meanings that have been coined differently depending on the situation. All the academic fields, involved in the landscape research, should try in co-operation to develop the comprehensive approach rather than the inter- and multi-disciplinary approach to the landscape study. In Korea, moreover, it is also necessary in the legislation to recognize the fact that degradation and retreat in the quality of landscape would make a negative effect on the quality of human daily life. Natural and cultural heritages contained in the rural landscape are also now in danger of disappearing. These heritages, therefore, should become an important subject for research and policy on landscape before the countryside is completely evacuated after the aging population die out. To make this happen, it is very urgent that evaluation and classification of landscape character should be undertaken from the holistic perspective, which is equipped with a methodology overcoming as well as encompassing the boundaries of academic fields. It is also equally very urgent that education on landscape should be provided to the politicians, citizens and students as well as the officials dealing with landscape matters. Finally, government should strive to make the landscape concept penetrate deeply as well as widely into the spatial planning and legislation process while designing and implementing a comprehensive landscape policy at the national level.

• The Journal of Korean Philosophical History
• /
• no.50
• /
• pp.363-389
• /
• 2016

Any moral ideas get integrity upon their practices. Because in human society systems, morality have capability among human interactions, for it gives moral standards(good or bad/ right or wrong) to them. And when the society system is Korean, Koreans surely have developed unique styles of moral practice and moral education in their traditional ages. So reinterpretating and categorizing the moral tradition for taking advantage of it in contemporary context, make sense. In this study, Korean moral tradition is focused in its scope, as 'Confucian moral tradition in semi-modern era'. For convenience of study and the potentials of effective revision, Korean tradition have been resized. In Confucian moral tradition, semi-modern Korean moral ideas could be presented as ren(仁) and yi(義). Furthermore, ren and yi could be practiced with several moral virtues, like xiao(孝), di(弟), ci(慈), zhi(直) qin(勤) gian(儉). When compared with contemporary moral education idea systems, the traditional system can have affinity with the systems in moral ideas division('with-self morality', 'with-others morality', 'with-universe and transcendence morality'). And several fusion-style, integration-based education practices can be developed and applied at contemporary school moral education.

• Journal of Christian Education in Korea
• /
• v.63
• /
• pp.221-253
• /
• 2020

The purpose of this study is to define the key competency as Christian(in another word: Christian key competency) and to interpret the six key competencies of the 2015 revised curriculum in a Christian educational way. Also as an alternative to the key competencies model of the 2015 revised curriculum, this study aims to materialize the formation of a Christian key competencies model based on Christian faith. This study derived 'faith' from the key competencies as Christian throughout preceding research analysis. The 'faith' of the key competencies as Christian means the ability to know oneself, and to know the world and God within the knowledge of the Bible (knowledge of God) in the personal relationship with God, and also it is the ability to think, judge, and act with biblical values, Christian world view, and Christian self-identity. The key competency 'faith' could be the basis (standard) of motivation, attitude and the value of all competencies in cultivation and exercise. The model of Christian key competencies has the structure in which each six key competencies become to be cultivated based on the Christian key competency called "faith." Based on the structure, the six key competencies of the 2015 revised curriculum were interpreted and explained from the perspective of Christian education. In the self-management competency, self-identity can be correctly formed in relations with transcendent God. In aesthetic emotional competency, the empathic understanding of human beings comes from the understanding of the image of God, the supreme beauty, the source of beauty. About the community competency, human community is the source of God who created the universe, human and all of things. It is because a Christian community is a community within the relationship of Trinity God, Nature and others. Therefore regions, countries, and the world become one community. Communication competency first stem from good attitudes toward yourself and others with respectful mind. It comes from an understanding of Christian human beings. Also, there is a need of having a common language for communications. The common language is the Bible that given to us for our communicative companionship. Through the language of the Bible, God made us to know about God, human being and the creative world, and also made us to continue to communicate with God, others and the world. For having the knowledge-information processing competency, a standard of value for the processing and utilization of knowledge and information is required. The standard should be the basis of moral and ethical values for human respect. About creative thinking competency, the source of creativity is God who created the world. Human beings who have the image of God own creative potential. As well as, creativity has different expression forms depending on individual preferences and interests, and different approaches will be made depending on each individual's importance and achievement. Individual creativity can be found through education, and it can be embodied by converging knowledge, skills and experience.