• Journal of the Microelectronics and Packaging Society
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• v.29 no.2
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• pp.43-48
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• 2022

Effect of temperature/humidity (T/H) treatment conditions on the peel strength of screen-printed Ag/polyimide (PI) structures was evaluated by peeling PI films in 90° peel test. Initial peel strength was 25.99±1.47 gf/mm, and then decreased to 6.05±0.54 gf/mm after 500 h at 85℃/85% relative humidity T/H condition. And, the peeled locus was changed from Ag/PI interface to shallow cohesive inside PI near interface. X-ray photoelectron spectroscopy analysis on the peeled surfaces showed that the long-term moisture penetration into the Ag/PI interface during T/H treatment led to hydrolytic degradation of PI to form weak boundary layer inside PI near Ag/PI interface, which are responsible for large decrease in peel strength.

• Environmental and Resource Economics Review
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• v.31 no.3
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• pp.393-417
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• 2022

Using hourly SMP data from 2016 to 2020, this paper measures the weekly realized volatility and investigates the main force of its determinants. To this end, we extend the Bayesian variable selection by incorporating the regime-switching model which identifies important variables among a large number of predictors by regimes. We find that the increase in coal and nuclear generation, as well as solar power, reinforce the SMP volatility in both high volatility and low volatility regime. In contrast the increase in gas generation and gas price decrease SMP volatility when SMP volatility is high. These results suggest that the expansion of renewable energy according to 2050 Carbon Neutrality or energy transition policies increases SMP volatility but the increase in the gas generation or reduction of coal generation might offset its impact.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.192-192
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• 2022

하천유량은 기저유량과 직접유량으로 구성되어 있으며 기저유량은 갈수기 하천유량의 대부분을 차지하므로 직접유출과 기저유출의 분리는 중요하다. 또한, T-N, T-P는 기저유출에 영향을 많이 받는 수질 항목으로 기저유출과 직접유출에 의한 오염부하량을 정확히 분석해야한다. 따라서, 기저유출의 오염부하량 산정을 위해 기존의 WAPLE 2의 단점을 개선한 WAPLE 3가 개발되었으며, WAPLE 3는 유량 곡선의 하강부 변곡점에 붙는 특성을 가지고 있는 Baseflow filter program(BFlow) pass 1값을 사용하여 기저유량을 분리해 기저유출 오염부하량을 산정한다. WAPLE 3는 하천유량 중 기저유출을 어느 정도 분리하는지 결정하는 filter parameter 값을 Nathan과 McMahon가 제시한 최적값인 0.925를 사용하였다. 그러나 지형과 강우량 등에 따라 하천 유량에서의 기저유출 비율은 달라지기 때문에 이러한 한계점을 극복하기 위해 WAPLE 4를 개발하였다. WAPLE 4는 filter parameter 값을 사용자가 변경할 수 있게 개발하여 강우에 의한 유량변동 특정이 고려된 기저유량 및 오염부하를 산정하여 결과에 대한 정확도를 높였다. 또한, WAPLE 4는 강우시 오염부하량 산정에 탁월한 Numeric Integration(NI) 방법을 사용하여 직접유량, 기저유량의 오염부하량 및 유량가중평균농도(FWMC) 산정이 가능하도록 하였다. 본 연구의 결과는 오염총량제 및 기저유량 관리를 통한 유량 관련 정책 수립 시 기초자료로 활용될 수 있을 것으로 판단된다.

• Korean Journal of Construction Engineering and Management
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• v.16 no.4
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• pp.89-97
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• 2015

This paper analyzes the duration of the construction document (CD) phase of 42 large public building projects delivered by the total solution service of Public Procurement Services in Korea from 2009 to 2014. The quality of construction documents significantly affects the quality of construction and facility management. Thus, securing appropriate time for the CD phase during project planning is important for the quality of a project. Currently, the duration of the CD phase is planned based on the construction costs of a project following a notice of the Ministry of Land, Infrastructure and Transport. However, our analysis results showed that the correlation between the actual duration of the CD phase and construction costs is very weak. The actual CD phase takes 1.33-1.79 times longer than the planned duration. The practitioners who were interviewed, were already aware that the correlation between the duration of the CD phase and the construction costs is weak. They identified the complexity of the project, the extent of the design changes, project type, client characteristics, and others as more influential factors on the CD phase than the construction costs. To improve the quality of CDs, a new guideline for determining an adequate CD phase duration should be studied and developed.

• Journal of the Korean Institute of Landscape Architecture
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• v.44 no.5
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• pp.81-91
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• 2016

The study shows solutions of long-term unexecuted urban park and activation plans to facilitate the business promotion of Private Park Developers. This study conducted a feasibility analysis to determine if the business of a special case is applicable. The result of this study is as follows about three long-term unexecuted urban parks in Gwangju Metropolitan City's City Park. First, the three long-term unexecuted urban parks in Gwangju Metropolitan City's City Park are the forest type Neighborhood Parks. Businesses of a special case's park developing cost(average 0.4%) have a relatively low percentage. It is most affected by Land Compensation(average 33.8%) and building construction expenses(average 59.1%). Second, long-term unexecuted urban parks' Land Compensation and building construction expenses seed capital are excessive. The Bongsan Park balance floor space index is 179 percent; a reasonable profit floor space index is 220 percent. The Mareuk Park balance floor space index is 351 percent; a reasonable profit floor space index is 420 percent. The Jungoe Park balance floor space index is 327 percent; a reasonable profit floor space index is 400 percent. Third, to facilitate the business of special cases in deliberating, Bongsan Park should change its second class general residential area. Jungoe Park must change the quasi-residential area and semi-residential area. Mareuk Park must change the general commercial area. In this way, the feasibility of promoting private park projects will be improved.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.40 no.4
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• pp.261-273
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• 2022

This study aims to predict the land use demand of Seongnam-city using system dynamics and to simulate the effect of changes in family structure and land use density adjustment policy on land use demand. This study attempted to construct causal loop diagrams and an analysis model. The changes in land use demand over time were predicted through simulation results. As a result of the analysis, as of 2035, an additional supply of 2.08 km² for residential land and 1.36 km² for commercial land is required. Additionally, the current supply area of industrial land can meet the demand. Three policy experiments were conducted by changing the variable values in the basic model. In the first policy experiment, it was found that when the number of household members decreased sharply compared to the basic model, up to 7.99 km² of additional residential land were required. In the second policy experiment, if the apartment floor area ratio was raised from 200% to 300%, it was possible to meet the demand for residential land with the current supply area of Seongnam-city. In the third policy experiment, it was found that even if the average number of floors in the commercial area was raised from four to five and the building-to-land ratio in the commercial area was raised from 80% to 85%, the demand for commercial land exceeded the supply area of the commercial area in Seongnam-city. This study is meaningful in that it proposes a new analytical model for land use demand prediction using system dynamics, and empirically analyzes the model by applying the actual urban planning status and statistics of Seongnam-city.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.44 no.4
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• pp.567-575
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• 2024

The government and local governments are utilizing regulations, policies, and various project management techniques at each project stage to effectively and systematically manage public construction projects. However, the increase in construction costs continues to occur. In order to solve these problems, this study attempted to collect cases of existing public construction projects and analyze historical data. And it would like to derive the impact factor of increased construction costs. Based on the results, a plan was proposed to prevent the causes of increase and minimize in construction costs. The main reasons for the increase in costs were the occurrence of civil petition, differences between design documents and site conditions, and changes due to requests from the owner and changes in the business plan. And to solve these problems, this study proposed improvement for each cause from an institutional perspective, along with interview with experts and project owners. The results of this study are significant in improving the process of existing public construction process and presenting key inspection and review items for each major inspection stage in order to solve problem resulting from the analysis of the performance of public construction projects.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.7
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• pp.739-747
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• 2007

Dual-mode bandpass filter was designed by using periodic stepped impedance ring resonator with step perturbation. The periodic stepped impedance ring resonator has the effects of size reduction and $2^{nd}$ harmonic suppression by changing characteristic impedance ratio. The perturbation for dual-mode generation was also easily controlled by characteristic impedance ratio, and the variation of dual-mode resonant frequencies and attenuation pole frequencies were analyzed by the effect of step perturbation. Chip capacitors were used for input/output coupling, and the variation of center frequency by the coupling capacitance and step perturbation was also considered. From the results, two types of 2 GHz dual-mode bandpass filter were fabricated in size of $14{\times}14mm^2$, those have different attenuation poles and bandwidths. The measured results of proposed bandpass filters showed a good agreement with the calculated estimations, and those have insertion loss of 2.52, 0.52 dB and 3 dB bandwidth of 4.03, 15.02 %, respectively.

• 대한공업교육학회지
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• v.33 no.2
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• pp.120-136
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• 2008

Using the tangible programming tools, which combines physical objects (e.g. robot) and educational programming language, may help to encourage learners' creative thinking as well as to enhance problem solving ability. That is, learners can have opportunities to simulate problem solving processes through the physical objects, such as robots. Therefore, they can minimize an fixation about problem solving process. These experience is effective to induce creative thinking that is useful to find new solutions and change environment actively. Therefore, we developed a robot based programming teaching and learning curriculum and implemented it in college level introductory programming courses. The result shows that the robot based programming learning has a positive effect in all three factors of learners' creative problem solving potential, especially in a cognitive factor. The cognitive factor includes general problem solving abilities as well as factors that explain creativity, such as divergent thinking, problem recognition, problem representation. These result means that the developed robot based programming teaching and learning curriculum give positive effect to creative problem solving abilities.

• Journal of Internet of Things and Convergence
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• v.6 no.3
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• pp.75-80
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• 2020

Recently, the size of the IoT sensor has been decreased and the collecting direction of the IoT sensor for acquiring the data have been changed from 2D to 3D. It makes sensor structure complex. In the fabrication of the complex structure, 3D printing technology has more useful than traditional manufacturing technologies. Among 3D printing technologies, FDM (fused deposition modeling) is a candidate technology to fabricate a small IoT sensor because the price of the machine and the material is cheap. In the FDM process, a 3D shape is made by depositing the melted filament. Recently, the patent of FDM technology is expired and cheat machines are developed based on the open-source. In the FDM process, mechanical properties of a fabricated part is affected by a lots of factors such as the kind of material and process parameters. Among them, infill is affecting the mechanical properties and the production lead time as well. In this work, a new method to optimize the FDM process with the consideration of mechanical property and production lead time was proposed. To verify the method, the fabrications were performed with the different infill rates. The results of tensile tests were analyzed to verify the proposed method.