• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.29 no.2 s.233
• /
• pp.239-246
• /
• 2005

A rotor dynamic analysis is implemented to confirm the vibration stability of the high speed centrifugal chiller coupled with gear system. As the rotating speed of the centrifugal chiller under investigation is increased up to 17605rpm at the pinion rotating part, the bearing instability is getting higher and, furthermore, the rotor-bearing system might experience a few critical speed which lead to system failure due to the excessive vibration. In this study, considering the loading capacity and stability conditions, offset journal bearings are adopted for the pinion rotating system and general cylindrical bearings are used for motor part. From the modal analysis, the system is found to be stable as the critical damping ratio which shows the damping characteristics of the system are positive over all operating ranges, and in addition, the synchronous rotating frequency does not come across with any whirl natural frequency. From these results the authors confirm the vibration stability of the rotor-bearing system suggested in this study.

• Journal of Arbitration Studies
• /
• v.17 no.1
• /
• pp.137-155
• /
• 2007

Since China joined the WTO, the trade between Korea and China has continued to grow by leaps and bounds, making both nations become mutually important trading partners to each other. The volume of trades with China showed a rapid upward trend with an average annual increase rate of 20% and the resultant dispute is also rising. Thus, this study was aimed to make some suggestions and come up with ways of responding claims by surveying Korean trading firms which have experience in making transactions with China to investigate the current status and the actual condition of their occurrence. As a result of this study, firstly, the main cause of such dispute was shown to be the failure to perform the agreement. Secondly, there were malty verbal agreements and due to a deterioration of trust in Chinese firms, the method of a letter of credit was adopted by many Korean firms. Thirdly, the payment and credit appeared to be most important in transactions with China. A credit inquiry is a must in future transactions with China. Fourthly, the indirect cause of the occurrence of trade claims was the difference in commercial practices and as for the way of settling disputes, the agreement through negotiations between the parties involved was the most. Fifthly, small and medium firms should make more of their credit and English proficiency than large ones do.

• Steel and Composite Structures
• /
• v.20 no.4
• /
• pp.913-930
• /
• 2016

It is common practice to use Reduced Web Beam Sections (RWBS) in steel moment resisting frames. Perforation of beam web in these members may cause stress and strain concentration around the opening area and facilitate ductile fracture under cyclic loading. This paper presents a numerical study on the cyclic fracture of these structural components. The considered connections are configured as T-shaped assemblies with beams of elongated circular perforations. The failure of specimens under Ultra Low Cycle Fatigue (ULCF) condition is simulated using Cyclic Void Growth Model (CVGM) which is a micromechanics based fracture model. In each model, CVGM fracture index is calculated based on the stress and strain time histories and then models with different opening configurations are compared based on the calculated fracture index. In addition to the global models, sub-models with refined mesh are used to evaluate fracture index around the beam to column weldment. Modeling techniques are validated using data from previous experiments. Results show that as the perforation size increases, opening corners experience greater fracture index. This is while as the opening size increases the maximum observed fracture index at the connection welds decreases. However, the initiation of fracture at connection welds occurs at lower drift angles compared to opening corners. Finally, a probabilistic framework is applied to CVGM in order to account for the uncertainties existing in the prediction of ductile fracture and results are discussed.

• Journal of the Society of Disaster Information
• /
• v.3 no.2
• /
• pp.147-169
• /
• 2007

This study investigates the reinforcing effects of the Multi-bar Spring nails with respect to the conventional Soil-nails in artificial slopes. Based on wide experience related to design and construction, soil nails have been widely applied to reinforce slope in the world. Multi-bar spring nails are one of the improved soil nailing methods. These method maximizes bending, shearing, pull-out resistance for those multi-nails, not unit nail, that are inserted in the borehole using special spacer at regular intervals. In addition, because cutting plane is confined effect resulting from a pressured plate at the end of the nails with compression spring equipment, slope stability is secured using MS-nailing method. Analyzing bending, pull-out, shearing condition of MS-nail, it was examined throughly elastic region, load transfer capacity, reinforcing effect on cutting plate of MS-nails. In addition, Pilot and laboratory tests, numerical analysis were carried out to verify the superiority of MS-nailing method. In case, MS nailing method is applied to reinforce artificial slope, it was analyzed that bending, pull-out, shearing resistance was increased more than existing nailing method was applied. In this study, it was shown that surface failure was more or less prevented using MS-nailing method, confining effect on cutting plane using spring stuck to flexible equipment.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.13 no.1
• /
• pp.1-9
• /
• 2009

As a result of the study on a number of the works, published in Russia, the methodical aspects of experimental improvement on working capacity of LRE (Liquid Rocket Engine) are reviewed. In the article, on the basis of the experience of Russia and USA, the special features of experimental improvement on working capacity of LRE and the methods of its rational implementation formulated. The organizational and technical solutions of experimental improvement on working capacity of LRE for achieving the required level of the reliability and decreasing the material expenditures are presented in the article. These suggested solutions can be used for the development of LRE.

• The Transactions of the Korean Institute of Electrical Engineers A
• /
• v.54 no.9
• /
• pp.449-456
• /
• 2005

The preventive diagnostic technique prevents transformers from power failure through giving alarm and observing transformers in service. And it helps to establish the plan for optimum maintenance of the transformer as well as to find location or cause of fault using accumulated data. Data detection and experience of the preventive diagnostic system need to establish the preventive diagnostic algorithm regarding interrelationship between detected data and deterioration of equipment. Therefore in-depth analysis about the preventive diagnosis system is required. KEPCO has adopted the preventive diagnostic system at nine 345kV substations since 1997. Techniques for component sensors of the preventive diagnosis system were settled but diagnosis algorithm, diagnostic criteria and practical use of accumulated data are not yet established. This paper, to build up the base of preventive diagnostic algorithm for the Power transformer. investigated the preventive diagnostic criteria for the power transformer.

• Journal of Korea Game Society
• /
• v.5 no.2
• /
• pp.3-9
• /
• 2005

Interactive real-time 3D enables users to explore virtual three dimensional environments and also experience contents in an absorbing fashion. Unlike other media, Interactive real-time 3D users take an active role in the process of "real-time fashion" where action and reaction occur instantly in a digital 3D structure. Once the components and origins of interactive real-time 3D is made, it is possible making principles of the beauty that help decide success or failure of real-time 3D in two way system. Substantial real-time 3D has not yet passed 10 years so it was unable to make sufficient precedents of fundamental artistic value based upon the credibility of the media. The goal is to explain the new form of design in relation to general principles of arts at the same time to understand the technical definition better. Concepts of historical documentation are explained with an example of categorization of recent video game and recent technology. This thesis concludes with rough forecast on the future interactive real time 3D. Since the medium began relatively recently and is developing in the rapid pace, recent analyses, though clear forecast is difficult, tend to investigate potential directions to some level the field allows.

• Korean System Dynamics Review
• /
• v.16 no.2
• /
• pp.5-32
• /
• 2015

Last year, a disastrous accident happened on the sea. Car ferry Se-wol which was on its way from In-cheon to Je-ju sank in the middle of the western sea. 304 passengers were drowned at the sea in the accident. There were no passengers who were waiting on board ship rescued in the accident. This study is to review the pattern of decision making in the middle of saving a life, right after Se-wol was about to sink. The starting point of this study is decision making on the rescue by rescue corps with no expert knowledge at the initial stage. When it comes to saving victims, there was no expert on rescue on the sea. Failure in rescue at Se-wol disaster lets us find a vicious circle of positive feedback loop. Experts with no experience act like well-qualified persons. Unqualified persons(leaders) have no expertise. Those who pretend to be expert occupy the important post in the hierarchy. It means we could not accumulate expertise of know-how in rescue division. That's why a vicious circle of positive feedback is formed in areas of disasters. It is necessary to train experts in Government Organizations to weaken the vicious circle of positive feedback.

• Journal of the Korean Society of Industry Convergence
• /
• v.15 no.1
• /
• pp.13-19
• /
• 2012

Due to a low stiffness of cranktrain and a failure experience from a history within short development time, a viscous torsional vibration damper was applied in order to reduce the torsional vibration and keep the high reliability for the durability of cranktrain system in the direct injection diesel engine. As an improvement of the crankshaft stiffness by increasing the diameter of main and pin journal, a rubber type damper could be considered. In this study, the control factors of rubber damper, the moment of inertia ring, stiffness of damper and damping coefficient of ring, were investigated by DFSS method through the analysis work and the measurement in the real engine condition.

• Journal of Technology Innovation
• /
• v.12 no.2
• /
• pp.99-126
• /
• 2004

Japan's economic clusters are characterized by their high level of diversity. In essence, Japanese economic clusters are not limited to single industries; they comprise numerous manufacturing industries and firms which cluster in specific heterogeneous economic zones, vice political boundaries. Japanese manufacturing sectors are showing an increased level of diversity, resulting in the spread of experience and knowledge among clusters, and sustained growth at the point of industrial structural transformation. Japan's Ministry of Education, Culture, Sports, Science and Technology (MEXT) proposed the creation of intellectual clusters for the purpose of promoting research and development(R&D) activities resulting in the stimulation and development of new technologies. The Ministry of Economy Trade and Industry (METI) is also proposing the industrial cluster plan with the aim to promote the local rebirth and revitalization of the Japanese industrial sector. This paper proposes a methodological analysis which will result in the integration of the two policies currently implemented by the Japanese government. If the current policies are not coordinated and integrated, artificial firms and sectors will continue to hamper innovation and discourage competitiveness, which will ultimately result in Japan's loss of economic opportunities within Asia. In the worst case, failure to act on current economic deficiencies illuminated in this paper could cost Japan its position as an Asian economic leader.