• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.915-920
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• 2001

This study was performed to investigate the behavior of vapor phase of fuel mixtures with different piston bowl shapes(F, B, and R-type) in a optically accessible engine. The images of liquid and vapor phases were captured in the motoring engine using exciplex fluorescence method. Fuel was injected into atmospheric nitrogen to prevent quenching phenomenon by oxygen. Injection pressure is 5.1MPa. Two dimensional spray fluorescence image of vapor phases was acquired to analyze spray behaviors and fuel distribution inside of cylinder. Four injection timings were set at BTDC $90^{\circ},\;80^{\circ},\;70^{\circ},\;and\;60^{\circ}$. With a fuel injection timing of BTDC $90^{\circ}$, fuel-rich mixture level in the center region was highest in a B-type piston. With a fuel injection timing of BTDC $60^{\circ}$, R-type piston was best. R-type piston shape was suitable under enhanced swirl ratio and late injection condition and B-type piston shape was right in a weak swirl ratio. It was found that the piston bowl shape affected the mixture stratification inside of cylinder.

• 감성과학
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• 제23권1호
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• pp.57-68
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• 2020

This research investigates how digital design agencies and client companies incorporate design thinking-a human-centered approach to solving difficult problems-into their website development processes. Based on a literature review on the design-thinking-driven web development process, multiple case studies of award-winning website projects were performed by in-depth interviews with key practitioners. Through analyses of these cases, their user-centered approaches for website innovation were identified according to the following four phases: web planning (discovery and defining phases) and web design and development (development and delivery phases). Moreover, distinct approaches of design thinking practices were identified according to two website types: a brand promotion website with a killer brand storytelling approach; and a service channel website with a strategic UI/UX-driven approach. Next, the key success drivers of these website projects were suggested in light of the typical themes of design thinking (i.e., human centeredness, research based, context awareness, and collaboration). Some practical limitations were also found in adopting the design-thinking-driven web development process, such as limited research methods and tools, and insufficient prototyping and experimentation. Along with these limitations, it was also discovered that current digital design agencies still face the following challenges in adopting the design-thinking-driven web development process: building a long-term, playful partnership with clients; leveraging decision-makers' design thinking awareness; and coping with limited resources (design thinking practitioners, budgets, and schedules).

• Journal of electromagnetic engineering and science
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• 제7권4호
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• pp.169-174
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• 2007

This paper presents a method of superimposing the rotation phases over the pilot and data symbols in order to reduce the peak-to-average power ratio(PAPR) in orthogonal frequency division multiplexing(OFDM). The phases of the rotation vector are added to those of the pilot symbols and those of the data symbols by interlaying them between any two pilot symbols. The receiver restores the data symbols by utilizing the channel estimation of the pilot symbols. Therefore, the bandwidth efficiency is improved by not using the subcarriers that are assigned for the reduction of the PAPR. Also, the enormous increase of the bit error rate which would be caused by incorrectly receiving the side information, i.e. the phases of the rotation vector, is prevented. The simulation results of the bit error rate performance for the BPSK are given using the COST-207 channel model.

• 한국자동차공학회논문집
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• 제10권2호
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• pp.23-30
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• 2002

This present study experimentally investigates the behavior of liquid and vapor phase of fuel mixtures with changing the in-cylinder air motion in an optically accessible engine. The conventional MPI/DOHC engine was modified to gasoline direct injection engine with swirl motion. The images of liquid and vapor phases were captured in the motoring operation condition using exciplex fluorescence method. Two dimensional spray fluorescence images of liquid and vapor phases were acquired to analyze spray behaviors and fuel distribution inside of cylinder respectively, In early injection timings $(BTDC\;270^{\circ},\;180^{\circ})$, tumble flow transported most of vapor phase to the lower region and the both sides of cylinder, so vapor phase didn't become uniform distribution up to the half of the compression stroke. In the case of swirl flow, the fuel mixture was confined near the swirl origin in upper region of cylinder. In late injection timings $(BTDC\;90^{\circ})$, tumble flow transported vapor phase to the intake valve and swirl flow to the exhaust valve.

• International Journal of Aeronautical and Space Sciences
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• 제14권3호
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• pp.282-295
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• 2013

In order to communicate with a ground station, the tracking profile design problem for a directional antenna system is considered. Because the motions of the gimbal angles in the antenna system affect the image quality, the main object is to minimize the motion of the gimbal angles during the satellite's imaging phase. For this goal, parameter optimization problems in the imaging and maneuver phases are formulated separately in the body-frame, and solved sequentially. Also, several mechanical constraints, such as the limitation of the gimbal angle and rate, are considered in the problems. The tracking profiles of the gimbal angles in the maneuver phases are designed with N-th order polynomials, to continuously connect the tracking profiles between two imaging phases. The results confirm that if the vector trace of the desired antenna-pointing vector is within the antenna's beam-width angle, motions of the gimbal angles are not required in the corresponding imaging phase. Also, through numerical examples, it is shown that motion of the gimbal angles in the imaging phase can be minimized by the proposed design process.

• Journal of the Optical Society of Korea
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• 제14권3호
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• pp.209-214
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• 2010

The Raman shift of water vapor is 3657 $cm^{-1}$, and this Raman signal can be easily separated from other Raman signals or elastic signals. However, it is difficult to make simultaneous Raman measurements on the three phases of water, namely, ice water, liquid water, and water vapor. This is because we must consider the overlap between their Raman spectra. Therefore, very few groups have attempted to make Raman simultaneous measurements even on two elements (water vapor and liquid water, or water vapor and ice water). We have made an effort to find three characteristic Raman wavelengths that correspond to the three phases of water after measuring full Raman spectra of water on particular days that are rainy, snowy or clear. Finally, we have found that the 401-nm, 404-nm, and 408-nm wavelengths are the most characteristic Raman wavelengths that are representative of the water phases when we are using the 355-nm laser wavelength for making measurements.

• 한국한의학연구원논문집
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• 제9권2호
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• pp.17-27
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• 2003

Eumyang-ohaeng[陰陽五行-Eumyang and five phases], as a standing rule that establishes the theory of Oriental medicine and origin of the oriental philosophy, it provides the perspective of the oriental medicine's outlook of the world. Without knowing the Eumyang-ohaeng, we cannot discuss Oriental medicine, nor can we understand the oriental way of thinking. Time and Space is what the human being created in order to explain the existence and change of matters. There is a common denominator between this universal concept of time and space and the theory of Eumyang-ohaeng. Consequently this paper investigates how characteristics of Eumyang-ohaeng and that of time and space matches Eumyang represents all matter and its characteristic, by comparison with each other space, and Ohaeng shows the change of matter with time gradually and sequancely. But this separation is only a separation by words, they really melt into one like two sides of a coin is actually just one coin. After all the theory of Eumyang-ohaeng is a theory that leads us to realize time and space, matter and power are all just one. So consequently, despite the difference in mass or size or longevity of matters, Eumyang-ohaeng pulls all matter into one body. It's why Eumyang-ohaeng is defined as the unified theory of time and space.

• 조명전기설비학회논문지
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• 제28권7호
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• pp.41-47
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• 2014

The on-line partial discharge (PD) in stator windings of air-cooled gas turbine (GT) generator (119.2MVA, 13.8kV) is measured and analyzed in this paper. This generator was designed by global vacuum pressure impregnation (VPI). The generator failed two times at top bar (16T) of phase B in the stator slot. Six epoxy-mica capacitors were installed in three phases of GT generator. On-line PD test was performed on GT generator using turbine generator analyzer (TGA). TGA showed that the normalized quantity number (NQN) and the PD magnitude($Q_m$) were high in phase B. Internal discharges were generated in phases A, B and C. The trend analysis of NQN and $Q_m$ value are obtained in order to monitor the insulation condition in GT generator stator windings. Phases A and C were in good condition. But phase B had deteriorated significantly

• 한국운동역학회지
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• 제28권2호
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• pp.79-85
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• 2018

Objective: This study aimed to create a strategic training method to enhance optimal athletic ability using information from 1H to 10H rhythmic units. Method: Top three world class athletes and three national winners of 110-m hurdle finals from the 2010 Daegu International Athletics Competition and 2017 National Athletics Championship, respectively, were selected. To analyze the kinematic variables, Dartfish 9.0 was used for two-dimensional analysis. Results: Regarding the interval time from the start to the finish line, the national athletes took less time during the pure acceleration phase (start to 1H) than the foreign athletes. The horizontal velocity increase was slower after 1H; the national athletes showed a lack of ability to accelerate at the interval phases. Moreover, the hurdle clearance time between phases was longer in the national athletes than in the foreign athletes and lacked consistency. Conclusion: The national athletes lacked the ability to accelerate at the transition, maximum rhythm, rhythm maintenance, and re-acceleration phases and showed a longer hurdle clearance time. If technical improvements and strategic training methods using rhythmic units are applied for hurdling motions, the national athlete's hurdling abilities, performance, and consistency could improve.

• Corrosion Science and Technology
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• 제20권6호
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• pp.466-474
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• 2021

A wet type scrubber for merchant vessel uses super austenitic stainless steels with pitting resistance equivalent number (PREN) of 40 or higher for operation in a harsh corrosive environment. However, it is expensive due to a high nickel content. Thus, electrochemical behavior and cavitation erosion characteristics of UNS S32750 as an alternative material were investigated. Microstructure analysis revealed fractions of ferritic and austenitic phases of 48% and 52%, respectively, confirming the existence of ferritic matrix and austenitic island. Potentiodynamic polarization test revealed damage at the interface of the two phases because of galvanic corrosion due to different chemical compositions of ferritic and austenitic phases. After a cavitation test, a compressive residual stress was formed on the material surface due to impact pressure of cavity. Surface hardness was improved by water cavitation peening effect. Hardness value was the highest at 30 ㎛ amplitude. Scanning electron microscopy revealed wave patterns due to plastic deformation caused by impact pressure of the cavity. The depth of surface damage increased with amplitude. Cavitation test revealed larger damage caused by erosion in the ferritic phase due to brittle fracture derived from different strain rate sensitivity index of FCC and BCC structures.