• Elastomers and Composites
• /
• v.42 no.1
• /
• pp.20-31
• /
• 2007

Material characteristics and lifetime evaluation are very important in design procedure to assure the safety and reliability of the rubber components. In this paper, the NBR compound was prepared by sulfur-cure system, and was used in predicting the lifetime of rubber gasket made by the compound. The accelerated material aging was investigated at different temperatures at 120, 140 and $160^{\circ}C$ and aging time from 3 hours to 600 hours at 5, 6, 7 vol %. of $H_2SO_4$ concentrations The rubber strips were placed in acid solution using pyrex g1ass tube. Both ends of pyrex g1ass tube were sealed to avoid evaporation of solution during heating at given time. The material test and accelerated acid-heat aging test were carried out to predict the useful life of NBR rubber gasket for a fuel cell stack. In order to investigate the effects of acid-heat aging on the properties of the NBR, tensile strength, elongation at break, hardness and crosslink-density were measured. The tensile strength decreases as the $H_2SO_4$ concentrations and temperature increase. Results were evaluated using Arrhenius equation.

• Journal of the Korean Geotechnical Society
• /
• v.27 no.1
• /
• pp.77-86
• /
• 2011

The advanced geotechnical information has been required to determine the accurate design parameters for complex construction. However, the Standard Penetration Test (SPT), which has low reliability, has been used to estimate the subsurface condition in the field. The objective of this paper is development and application of the Static-Dynamic penetrometer, which detects the resistances in soft clay, sand and rock. The energy losses according to the rod connection methods (perfect or non-perfect connection, and number rods) are experimentally evaluated. The reflection and transmission ratios are used to investigate the energy loss by a simulation. The static-dynamic cone penetrometer, in which the accelerometers and strain gauges are installed on the cone tip and the rod head, is used to estimate the energy loss during penetration by impacts. The experimental and simulation studies show that the transferred energy through rods with non-perfect connection dramatically decreases. Furthermore, the transferred energy on the rod head is not the same as that on the cone tip. This study demonstrates that the energy loss should be evaluated on the cone tip.

• Journal of the Korean BIBLIA Society for library and Information Science
• /
• v.31 no.1
• /
• pp.193-212
• /
• 2020

In Korea, the term 'public library service population' is applied in various situations without academic discourse. This study analyzed concepts and applications of the term with literary reviews and case studies in United States, Australia, Japan, and Korea. And also this study redefined concepts and suggested new measurements of 'design population' and 'service population.' The former is the population who lives in area where public library can serve, and only demographic characteristics can be identified. It can be calculated based on the population of administrative district. In case of urban areas with a population of more than 100,000, it can be calculated the population within a radius of 2km from library. In areas with a population of less than 100,000 it can be calculated based on the population of Eup, Myeon, and Dong. In both cases the estimated population up to the library's opening year is added. Service population is used for the planning, evaluating, and promoting library services, and it can be defined as the actual users or estimated population determined by the input resources of the public libraries. It can be calculated by the number of enrolled members, or service participants, or target populations according to the size of input resources. The advantages of the proposal in this study are enabling efficient facility placement or resource inputs in public libraries and enhancing reliability of measuring output versus input. In addition, this study proposed to delete for paragraph 1 of Article 3 of the Library Act to avoid confusion.

• Korean Journal of Construction Engineering and Management
• /
• v.16 no.6
• /
• pp.124-135
• /
• 2015

As many countries have been raising awareness of environmental issues, greater efforts for eco-friendly construction have been made in both governmental and private sectors. However, assessment circumstances for building energy performance and green building standard of legislation are still based on two dimension and handwork. This takes time, cost and labor, and makes assessment inaccurate and inefficient. Therefore, this study suggests methods to improve eco-friendly construction permission process and to automatize open BIM-based assessment of Energy Performance Index (EPI) among several eco-friendly construction certification standards. First, it analyzes the relations between assessment criteria and IFC data, and provides solutions to problems and limitations. Second, it applies the solutions to assessment program in order to automatize open BIM-based assessment for EPI. The eco-friendly construction permission process with these solutions applied will reduce time, cost, and labor by simplifying and automatizing the tasks. Also, the simplified process of design revision will improve not only productivity and efficiency but also accuracy and reliability.

• Korean Journal of Construction Engineering and Management
• /
• v.10 no.5
• /
• pp.123-134
• /
• 2009

Since 1970s, urethane waterproofing method is broadly used in rooftops, underground spaces, and sports stadium for its outstanding ultraviolet blockage, watertightness, and elasticity. However, development of slippage-resistance and endurance, improvement of function considering convenience and visually pleasing of users, urethane waterproofing method is necessary, since rooftops and underground spaces have slippage and external force risks. Therefore, many improved waterproofing methods are being developed and, recently, embo-thane waterproofing method, which applies embo-spray coating system, has been developed. This paper explains exposure, nonexposure, and floor-material of embo-thane waterproofing method, and then perform experimental study for comparison with urethane waterproofing method about tensile strength, coefficient of expansion, performance of bond, anti-abrasion, and slippage-resistance. In addition, the performance index was presented for the superiority of embo-thane waterproofing method compared to urethane by setting up evaluation criteria considering not only physical performance but also design side of embo-thane waterproofing method, and Value Analysis applying AHP. Also for an assessment considering uncertain result, Monte Carlo Simulation Method was used to operate reliability analysis through statistic approach method.

• Journal of Bio-Environment Control
• /
• v.21 no.4
• /
• pp.459-465
• /
• 2012

This study analyzed the effect of semi-rigid rafter-purlin cross-linking connection and driven steel pipe base on the static behavior of plastic greenhouse (PG). To promote the time and cost efficiency of the assembly process, each cross-linking connections of space arch type grid that consists of rafter and purlin is linked with steel-wire buckles, and each end of the rafters was driven directly to the ground to support the PG structure. However, in the design process, cross-linking connections and bases are idealized by being categorized as fully rigid or frictionless pinned, which does not appropriately reflect actual conditions. This study takes a full-scale loading test of PG and analyzes the effect of member cross-linking connections and driven steel pipe base on the behavior of a structure. The analysis provided a basis for determining the rigidity factor of member cross-linking nodes needed for finite element analysis, and the reliability of the result regarding the static behavior of PG.

• Journal of the Korea Convergence Society
• /
• v.11 no.9
• /
• pp.261-266
• /
• 2020

The purpose of the Convergence study is to analyze the impact of students' satisfaction and educational performance through research on overall educational service quality factors for beauty academies. The subjects of the study were conducted from March 29 to April 12, 2020 for those in their 10s and 40s attending beauty academies in Seoul, Gyeonggi-do and Incheon, and 377 surveys were analyzed and used for research. Multiple regression analysis was performed using the SPSSWIN 21.0 program for research purposes. As a result of the study, the higher the level of empathy, reliability, responsiveness, type, and certainty of educational service quality, the higher the satisfaction level of the class. The higher the satisfaction level, the higher the educational performance. Based on these research results, measures to improve the quality of education services that can enhance the satisfaction and educational performance of beauty academies should be improved by diversifying educational methods and contents and enhancing the quality of education and service expertise. The expertise of education should be strengthened to improve competitiveness. Therefore, follow-up research is needed to develop various programs to enhance future course satisfaction and educational performance and to develop education methods to enhance the quality of beauty education services.

• Journal of the Microelectronics and Packaging Society
• /
• v.19 no.2
• /
• pp.7-15
• /
• 2012

Semiconductor packages are increasingly moving toward miniaturization, lighter and multi-functions for mobile application, which requires highly integrated multi-stack package. To meet the industrial demand, the package and silicon chip become thinner, and ultra-thin packages will show serious reliability problems such as warpage, crack and other failures. These problems are mainly caused by the mismatch of various package materials and geometric dimensions. In this study we perform the numerical analysis of the warpage deformation and thermal stress of 4-layer stacked FBGA package after EMC molding and reflow process, respectively. After EMC molding and reflow process, the package exhibits the different warpage characteristics due to the temperature-dependent material properties. Key material properties which affect the warpage of package are investigated such as the elastic moduli and CTEs of EMC and PCB. It is found that CTE of EMC material is the dominant factor which controls the warpage. The results of RSM optimization of the material properties demonstrate that warpage can be reduced by $28{\mu}m$. As the silicon die becomes thinner, the maximum stress of each die is increased. In particular, the stress of the top die is substantially increased at the outer edge of the die. This stress concentration will lead to the failure of the package. Therefore, proper selection of package material and structural design are essential for the ultra-thin die packages.

• Journal of Intelligence and Information Systems
• /
• v.8 no.2
• /
• pp.205-227
• /
• 2002

Our study is focused on a multiple-agent system to provide efficient collaborative work by automating the conference calling process with the help of intelligent agents. Automating the meeting scheduling requires a careful consideration of the individual official schedule as well as the privacy and personal preferences. Therefore, the automation of conference calling needs the distributed processing task where a separate calendar management process is associated for increasing the reliability and inherent parallelism. This paper describes in detail the design and implementation issues of a multiple-agent system for conference calling that allows the convener and participants to minimize their efforts in creating a meeting. Our system is based on the client-sewer model. In the sewer side, a scheduling agent, a negotiating agent, a personal information managing agent, a group information managing agent, a session managing agent, and a coordinating agent are operating. In the client side, an interface agent, a media agent, and a collaborating agent are operating. Agents use a standardized knowledge manipulation language to communicate amongst themselves. Communicating through a standardized knowledge manipulation language allows the system to overcome heterogeneity which is one of the most important problems in communication among agents for distributed collaborative computing. The agents of our system propose the dates on which as many participants as possible are available to attend the conference using the forward chaining algorithm and the back propagation network algorithm.

• Journal of KIISE:Computer Systems and Theory
• /
• v.32 no.7
• /
• pp.377-392
• /
• 2005

A lot of studies to measure and analyze the system performance have been done in areas such as system modeling, performance measurement, monitoring, and performance prediction since the advent of a computer system. Studies on a framework to unify the performance related areas have rarely been performed although many studies in the various areas have been done, however. In the case of TMO(Time-Triggered Message-Triggered Object), a real-time programming model, it hardly provides tools and frameworks on the performance except a simple run-time monitor. So it is difficult to analyze the performance of the real-time system and the process based on TMO. Thus, in this paper, we propose a framework for the dynamic analysis of the real-time system based on TMO, TDAF(TMO based Dynamic Analysis Framework). TDAF treats all the processes for the performance measurement and analysis, and Provides developers with more reliable information systematically combining a load model, a performance model, and a reporting model. To support this framework, we propose a load model which is extended by applying TMO model to the conventional one, and we provide the load calculation algorithm to compute the load of TMO objects. Additionally, based on TMO model, we propose performance algorithms which implement the conceptual performance metrics, and we present the reporting model and algorithms which can derive the period and deadline for the real-time processes based on the load and performance value. In last, we perform some experiments to validate the reliability of the load calculation algorithm, and provide the experimental result.