• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.9 no.2
• /
• pp.112-121
• /
• 1997

This study is focused on the development and selection of optimal cool tube system to maximize its thermal performance. Cool tube is devised to reduce the heating and cooling load of building by preheating or refreshing of intake air. Finite volume method was adopted to solve the conduction problem between the cool tube and earth. We examine the cool tube system for two operating periods, a short term(12 hours) and a long term(3 months). The results of short term operations reveal that condensation significantly influences and raises the exit air temperature. For long term operations, optimum conditions of cool tube system are obtained with variations of flow-rate, depth, length and diameter of cool tube.

• Proceedings of the KIEE Conference
• /
• 2008.11a
• /
• pp.150-152
• /
• 2008

It is necessary to improve the time efficiency in the high power testing station because tests are mainly performed by high-priced equipment. Minimizing a human error through building the database of relevant standards is possible to expect reliable tests. And also, application program that is properly customized for the certain laboratory's power system will help test engineer to easily analyze the phenomenon that is happened in short-circuit and load switching tests. This paper introduces the several functions of the application program that is developed in order to realize these requirements.

• Journal of Korean Society for Atmospheric Environment
• /
• v.14 no.5
• /
• pp.397-410
• /
• 1998

Tracer experiments were performed 4 times in December 1992 on the relatively flat terrain and nearby building area adjacent to the Taedok Science Town in Korea. Each experiment was continued for relatively short period of 1 or 2 hours with intermittent release of SF6 up to 2.07g/s at 10m height. Movement of tracer plume was tracked by a continuous tracer analyzer installed on an air monitoring van. Simulation with INPUFF was carried out to analyze and predict experiments. Measured profiles of tracer plume were narrow and sharp while predicted profiles by INPUFF were broad and slowly varied. Tracer plumes were detected at a short distance of 0.5 to 2.2 km mainly due to intermittent release and high value of lower detectable limit. Various experimental conditions were tested by INPUFF simulation in order to find desirable conditions. Higher wind speed and less variable wind direction could yield longer distance of plume tracking only when the lower detectable limit was sufficiently low. Distance of plume tracking was long and did not much depend on the lower detectable limit in stable atmospheric conditions.

• Journal of the Korea Society of Computer and Information
• /
• v.23 no.7
• /
• pp.1-10
• /
• 2018

In this paper, we propose the principles and design details of Automatic cable assembly test system and show its utility. Testing the cable assembly is required periodically or non-periodically in the system that the cable assembly performance is quite important like military equipment. There are several weaknesses when humans test the cable assembly manually. It not only takes much time but also could happen human error. To improve these disadvantages, I developed Automatic cable assembly test system. The system can be implemented by building switching control system that connect and disconnect the cable assembly and measuring devices. Through the result of the cable assembly test with this test system, we show this system makes test time short and improves of test reliability as compared with manual test.

• Proceedings of the KIEE Conference
• /
• 2002.11b
• /
• pp.234-236
• /
• 2002

The Co-Gen System which maximize energy efficiency was installed at the industrial plants at the initial stage. However Small Scale Co-Gen System was expanded even to the general end-users such as housing and building owing to ESCO business recently. For this SSC, inter-connected operation to the utility is desirable due to voltage and frequency fluctuation following to unbalance between power output and load. Then voltage unbalance with utility system, frequency, increase of short circuit capacity, reclosing, and ALTS etc. should be fully considered for the inter-connected operation. Voltage variation, protection coordination, Co-Generators single running, and short circuit capacity should also be solved. To research the method and solve the problems through the field test and application, we study individual customers Co-Gen System as a case study.

• Korean System Dynamics Review
• /
• v.1 no.2
• /
• pp.33-60
• /
• 2000

This study aims to conceptually identify the circular causal-relationship which is structured between downsizing and technological innovation in organization. First, through the literature review concerning downsizing and (technological) innovations, we have outlined the conceptual building blocks and research boundaries in this field. Second, we used system thinking method to accomplish our research purpose. The research findings are as follows. First, the promotion of financial resources by downsizing have trade-off relations that have negative of effects in short terms, but positive effects in long time. Second, workforce reduction by downsizing usually has negative influence on employees. Third, capital reduction by downsizing generates not only the climates of cost-cut but also the fact that although the climates may increase economic performance in short terms, it may interrupt technological innovations in long terms. In conclusion, this theses suggests that the relationship of downsizing and technological innovations have complex causal and feedback structures. Therefore, the results of this thesis propose that the argument or practices of downsizing with partial emphasis is very dangerous. Finally some limitations are also discussed.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.9 no.4
• /
• pp.517-526
• /
• 1997

This study is focused on the development and selection of the optimal cool tube system to maximize its thermal performance. Cool tube is devised to reduce the heating and cooling load of building by preheating or refreshing of intake air with buried pipes. Finite volume method is adopted to solve the conduction problem between the cool tube and earth. We examine the cool tube system for two operating periods, a short term(12 hours) and a long term(3 months). The results of short term operations reveal that condensation significantly influences and raises the exit air temperature. For long term operations, optimum conditions of cool tube system are obtained with variations of flow-rate, depth, length and diameter of cool tube.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.5 no.2
• /
• pp.428-439
• /
• 2011

The main challenge in building efficient broadcast systems is to encrypt messages with short ciphertexts. In this paper, we present a new construction based on the identity. Our construction contains the desirable features, such as constant size ciphertexts and private keys, short public keys and not fixing the total number of possible users in the setup. In addition, the proposed scheme achieves the full security which is stronger than the selective-identity security. Furthermore we show that the proof of security does not rely on the random oracles. To the best our knowledge, it is the first efficient scheme that is full security and achieves constant size ciphertexts and private keys which solve the trade-off between the ciphertext size and the private key size.

• Earthquakes and Structures
• /
• v.17 no.3
• /
• pp.283-295
• /
• 2019

During the seismic performance assessment of existing buildings, staircases are generally not taken into account as structural members but as dead load. Staircases, as secondary structural members, not only serve for connecting successive floors but also provide considerable amount of strength and stiffness to the building which can modify its seismic behaviour considerably. In this parametric study, the influence of staircases on the seismic response of substandard RC frame buildings which differ in number of storey and span, presence of staircase and its position has been examined. Modal Analyses and bi-directional Non-Linear Time History Analyses (NLTHA) were conducted to compare several engineering demand parameters (EDPs) such as inter-storey drift ratio (ISDR), floor accelerations, modal properties, member shear forces and plastic hinge distribution. Additionally, short column effect, variation in shear forces of columns that are attached to the staircase slab, failure and deformation in staircase models have also been investigated. As the staircase was considered in the analytical model, a different damage pattern can be developed especially in the structural components close to staircase.

• International Journal of Highway Engineering
• /
• v.18 no.3
• /
• pp.109-114
• /
• 2016

PURPOSES : The demand for extending national highways is increasing, but traffic monitoring is hindered because of resource limitations. Hence, this study classified highway segments into 5 types to improve the efficiency of short-term traffic count planning. METHODS : The traffic volume trends of 880 highway segments were classified through R-squared and linear regression analyses; the steadiness of traffic volume trends was evaluated through coefficient of variance (COV), and the normality of the data were determined through the Shapiro-Wilk W-test. RESULTS : Of the 880 segments, 574 segments had relatively low COV and were classified as type 1 segments, and 123 and 64 segments with increasing and decreasing traffic volume trends were classified as type 2 and type 3 segments, respectively; 80 segments that failed the normality test were classified as type 4, and the remaining 39 were classified as type 5 segments. CONCLUSIONS : A theoretical basis for biennial count planning was established. Biennial count is recommended for types 1~4 because their mean absolute percentage errors (MAPEs) are approximately 10%. For type 5 (MAPE =19.26%), the conventional annual count can be continued. The results of this analysis can reduce the traffic monitoring budget.