• KIEAE Journal
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• v.7 no.5
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• pp.3-11
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• 2007

Nowadays, housing density in a city is getting higher, and this trend is expected to continue in the future. Therefore, Skyscraper is considered as future alternative architecture beyond symbolic meaning in aspect of demand and supply of urban land. However, skyscrapers which were newly built in Korea have many problems such as consumption of enormous amounts of energy, destruction of natural environment, and traffic jam. And from now on, environment-friendly development of skyscraper is urgently needed. However, plans or evaluation standards, which take account of the environment-friendly aspect of skyscraper, leave much to be desired. And especially it is hard to find environment-friendly skyscrapers. Therefore, this study aims to find realistic alternative solutions of environment-friendly skyscraper through analysis of the works of Ken Yeang who has been known as bio-climatic architect and tried to apply environment-friendly plans to skyscraper.

• Laser Solutions
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• v.11 no.2
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• pp.33-38
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• 2008

Laser micromachining has increasingly been adopted in various advanced industries where the high-precision machining of large-area, high-density and multi-layered components is in a strong demand. To effectively meet the requirements, the laser micromachining process must be carefully monitored. In order to facilitate the development of a new laser micromachining process and/or a new system, we have fabricated a UV laser micromachining platform that is equipped with optical modules for monitoring the process online. They include a laser power stabilizing module, a module for laser-induced breakdown spectroscopy, and an auto-focusing module.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 1997.11a
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• pp.610-616
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• 1997

One of the notable changes in Korean Industry in 1990's was globalization. Many of Korea plants have been built In the foreign countries and many of foreign plants have been build in Korea. And it is believed that many foreign insurance companies will begin their business in Korea soon, as Korea will open their insurance market to them. While sprinkler system plays very important role in total fire protection system, Korean sprinkler system design has not been studied in depth. Thus, it is not easy to convince the performance of Korean sprinkler system and compare it to NFPA 13, Standard for the Installation of Sprinkler System. Design guideline from both system will be listed and compared in detail. Fire water demand from both system will be reviewed to evaluate its adequacy. Water spray density and actuation time will be estimated, too.

• Proceedings of the KIEE Conference
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• summer
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• pp.424-426
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• 2004

As power demand increases gradually, the call for underground transmission system increases. But it is very difficult and high in cost to construct new ducts and/or tunnels for power cables in metropolitan areas. HTS (High Temperature Superconducting) cable has the several useful characteristics such as increased power density, stronger fields and/or reduced losses. Therefore HTS cable can allow more power to be moved in existing ducts, which means very large economical and environmental benefits. In these days, companies world-wide have conducted researches on HTS cable. A development project for a 22.9kV class HTS cable is proceeding at a research center and university in Korea. In this paper, we investigate the expected price of HTS cable to have a merit in viewpoint of economic aspect. First, life-cycle cost of conventional cable is calculated and based on this, the expected price of HTS cable is evaluated, which HTS cable is competitive against conventional cable.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.6
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• pp.2893-2907
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• 2019

Wireless mobile communication systems in subway tunnels have been widely researched these years, due to increased demand for the communication applications. As a result, an accurate model is essential to effectively evaluate the communication system performance. Thus, a neoteric three-dimensional (3D) geometry-based stochastic model (GBSM) is proposed for the massive multiple-input multiple-output (MIMO) fading channels in tunnel environment. Furthermore, the statistical properties of the channel such as space-time correlation, amplitude and phase probability density are analyzed and compared with those of the traditional two-dimensional (2D) model by numerical simulations. Finally, the ergodic capacity is investigated based on the proposed model. Numerical results show that the proposed model can describe the channel in tunnels more practically.

• Electronics and Telecommunications Trends
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• v.36 no.3
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• pp.23-33
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• 2021

Two main technologies of III-V/Si laser diode for optical communication, direct epitaxial growth, and wafer bonding were studied. Until now, the wafer bonding has been vigorously studied and seems promising for the ideal III-V/Si laser. However, the wafer bonding process is still complicated and has a limit of mass production. The development of a concise and innovative integration method for silicon photonics is urgent. In the future, the demand for high-speed data processing and energy saving, as well as ultra-high density integration, will increase. Therefore, the study for the hetero-junction, which is that the III-V compound semiconductor is directly grown on Si semiconductor can overcome the current limitations and may be the goal for the ideal III-V/Si laser diode.

• International Journal of High-Rise Buildings
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• v.12 no.1
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• pp.11-18
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• 2023

The urbanity of high-rise buildings does not simply reference their physical characteristics but also encompasses their impact on the overall urban environment and the daily lives of citizens. This involves the economic benefits, social development, urban culture and public activities that high-rise buildings bring to a city. High-rise buildings are an important aspect of urban development and play a crucial role in providing public services in high-density urban habitats. However, to ensure that their contribution to the city is positive, it is essential to take into account their impact on surrounding buildings and the built environment. This paper analyzes their urban attributes and value system and summarizes their current development status. In short, as the demand for public services continues to evolve, it is necessary for high-rise buildings to keep up with these changes by continuously enhancing their urbanity.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2022.04a
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• pp.111-112
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• 2022

Lightweight aggregate is a porous material that has a lower density than natural aggregate and is a lightweight construction material. Lightweight Aggregate has a suitable purpose because it is effective in reducing the heavy unit mass in high-rise buildings. However, since lightweight aggregate has weak strength and high water absorption compared to natural aggregate, it is difficult to control the quality of concrete. Although lightweight aggregate has disadvantages such as high water absorption, it is expected that the demand for lightweight aggregate concrete will continue to use in the future because the advantage of being able to reduce the weight of concrete is greater. In this study, we conducted an experimantal study on the compressive strength property of cement matrix according to the type of lightweight aggregate.

• Journal of Powder Materials
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• v.30 no.6
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• pp.528-535
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• 2023

Since their initial development in 2012, triboelectric nanogenerators (TENGs) have gained popularity worldwide as a desired option for harnessing energy. The urgent demand for TENGs is attributed to their novel structural design, low cost, and use of large-scale materials. The output performance of a TENG depends on the surface charge density of the friction layers. Several recycled and biowaste materials have been explored as friction layers to enhance the output performance of TENGs. Natural and oceanic biomaterials have also been investigated as alternatives for improving the performance of TENG devices. Moreover, structural innovations have been made in TENGs to develop highly efficient devices. This review summarizes the recent developments in recycling and biowaste materials for TENG devices. The potential of natural and oceanic biowaste materials is also discussed. Finally, future outlooks for the structural developments in TENG devices are presented.

• Journal of the Korean Society of Industry Convergence
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• v.27 no.2_2
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• pp.325-332
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• 2024

Contemporary power systems demand efficient and sustainable technologies. Single-phase induction motors, while widely used, face efficiency challenges due to inherent rotor losses. Proposed solutions include the Line-start Permanent Magnet Synchronous Motor (LSPMSM), leveraging permanent magnets for enhanced energy density but facing demagnetization and cost issues. Alternatively, the Line-start Synchronous Reluctance Motor (LSRM) operates as a hybrid motor without permanent magnets, reducing rotor losses and potentially improving efficiency. This paper focuses on designing an LSRM rotor for air conditioner compressors, analyzing start-up characteristics and efficiency through finite element analysis. A comparative study with single-phase induction motors provides insights for future motor technology selection, balancing efficiency and other requirements.