• International Journal of Automotive Technology
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• v.8 no.2
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• pp.127-135
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• 2007

The objective of this study is to analyze the effect of velocity and vorticity on stratified mixture formation in the visualization engine. In order to investigate spray behavior, the pray velocity is obtained through the cross-correlation PIV method, a useful optical diagnostics technology and the vorticity calculated from the spray velocity component. These results elucidated the relationship between vorticity and entropy, which play an important role in the diffusion process for the early injection case and the stratification process for the late injection case. In addition, we quantified the homogeneous diffusion ate of spray using entropy analysis based on Boltzmann's statistical thermodynamics. Using these methods, we discovered that the homogeneous mixture distribution is more effective as a momentum dissipation of surrounding air than that of the spray concentration with a change in the injection timing. We found that the homogenous diffusion rate increased as the injection timing moved to the early intake stroke process, and BTDC $60^{\circ}$ was the most efficient injection timing for the stratified mixture formation during the compression stroke.

• Korean Journal of Applied Biomechanics
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• v.13 no.2
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• pp.139-160
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• 2003

The purpose of this study was to suggest the guideline for scientific and quantitative skill acquisition methods of badminton smashing so that the novice could learn the motions of badminton smashing efficiently. The subject participated consisted of total 6 middle school students of the stilled(3) and the unskilled(3). The cinematographical experimental & Analysis equipments used in the study were composed of two Model D-5100 Video Cameras, a control point, a synchronization timer and Kwon3d motion analysis system. The conclusions obtained were as follows, 1. It was necessary for the unskilled to learn the smashing impact phase in situation of max. velocity of COG in order to minimize the timing loss phase. 2. Particularly. The power from segments of Power Zone must participate in utilization in sequence of order of trunk-upper arm- forearm-hand-racket segment in both the skilled and the unskilled.. 3. Therefore it was necessary for the unskilled to do smashing practice for cumulated sum of absolute & relative velocity transfer into shuttle cock after adjusting anterior-posterior tilting angle and max timing, in sequence of segment recruited.

• Journal of Positioning, Navigation, and Timing
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• v.13 no.2
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• pp.131-136
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• 2024

This paper deal with a method for calculating the continuity of Korea Augmentation Satellite System (KASS), which was completed in Korea in December 2023, and a plan to respond in the event that a continuity hazard situation occurs during operation. For this purpose, the International Civil Aviation Organization (ICAO) Satellite Based Augmentation System (SBAS) continuity standards, Wide Area Augmentation System (WAAS), and European Geostationary Navigation Overlay Service (EGNOS) continuity cases are examined in this paper. According to the measures recommended by the ICAO, when the number of continuity risks exceeds a certain level and the level drops drastically, various mitigation operations by country are implemented. Through this, if KASS does not meet ICAO continuity standards in the future, such measures can be referred to. In addition, this paper computes the short-term KASS continuity during the test broadcast period. Although continuity does not meet the ICAO standards, although this test period is too short, further meaningful analysis in the future is required. Additionally, this paper carried out an analysis of the timing and period to systematically calculate the meaningful value of continuity.

• Journal of Positioning, Navigation, and Timing
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• v.11 no.4
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• pp.341-349
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• 2022

When designing a new RNSS signal, the performance analysis for the legacy signal providing the same service, is required to determine the performance requirements. However, there are few studies on the secured service (SS) signal performance analysis, and the waveform is the only published information on the signal design component of the SS signal. Therefore, in this paper, we introduce several figures-of-merit (FoMs) that can be used for performance analysis in terms of the waveform. And then, we calculate the FoMs, such as autocorrelation main peak to secondary peak ratio (AMSR), spectral efficiency, Gabor bandwidth, multipath error, and jamming resistance quality factor, for the existing SS signals and discuss the analysis results. Finally, we conclude that the superior waveform for each FoM is different, and that the consideration of the trade-off relationship between the FoMs is required for waveform design.

• Korean Journal of Construction Engineering and Management
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• v.10 no.3
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• pp.62-71
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• 2009

The purpose of this study is to analyze of profitability accordance to the different sales timing in apartment housing development projects. The adapted research method about public apartment hosing development projects by a private construction company is concentrated on the middle and large scale housing. The methodology for analysis of profitability through the change of timing for sales is analysed. According to this methodology, the difference of profitability by different timing of first sales is compared and analyzed. The results of this study are as followed 1)The major factors to affect the profitability for apartment housing development project consist of the timing of sales, the method of payment and the rate of sales. 2) The case study was carried out and then the profitability is analyzed the profitability for the three of cases is got worse when the sale after construction especially on the time of construction progress rate 80% is carried out.

• Journal of Positioning, Navigation, and Timing
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• v.12 no.4
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• pp.369-377
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• 2023

This paper presents the analysis results of navigation performance of Korea Augmentation Satellite System (KASS) test signals. Performance analysis was performed with Global Positioning System (GPS) and Satellite Based Augmentation System (SBAS) signals received from 7 KASS reference stations. And the performances were analyzed in terms of the signal strength, statistics for each SBAS message, coverage of ionospheric correction, accuracy, integrity, continuity, and availability. In addition, the navigation solutions provided by commercial receiver was analyzed and the performance experienced by general users was presented. Lastly, directions for further improvement of the KASS system were addressed. These performance analysis results can be used to confirm the feasibility of utilizing KASS in user applications.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.3
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• pp.221-228
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• 2013

An experimental study was carried out to investigate the effects of the injection timing on the spray and combustion characteristics in a spray-guided direct-injection spark-ignition (DISI) engine under lean stratified operation. An in-cylinder pressure analysis, exhaust emissions measurement, and visualization of the spray and combustion were employed in this study. The combustion in a stratified DISI engine was found to have both lean premixed and diffusion controlled flame combustion characteristics. The injection timing condition corresponding to the stratified mixture characteristics was verified to be a dominant factor for these flame characteristics. For the early injection timing, a non-luminous blue flame and low combustion efficiency were observed as a result of the lean homogeneous mixture formation. On the other hand, a luminous sooting flame was shown at the late injection timing because of an under-mixed mixture formation. In addition, the smoke emission and incomplete combustion products were increased at the late injection timing as a result of the increased locally rich area. On the other hand, the NOx emissions decreased and IMEP increased as the injection timing retarded. The combustion phasing produced by the injection timing was verified as the reason for this observation.

• Journal of Korean Society for Quality Management
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• v.36 no.3
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• pp.76-86
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• 2008

This paper examines when a consumer in existent telecommunication 2G applies to new telecommunication service 3G from the viewpoint of an option pricing theory. To improve telecommunication quality of service, the consumer applies to 3G. The application means an exchange of 2G for 3G with extra costs such as searching and conversion costs. Since the option to exchange is a right that the consumer can exercise or not, application to 3G is deemed an exercise of the option to exchange at most suitable value of the option. The timing to exercise the option depends on the extra costs and the additional communication benefit from new telecommunication quality of service. These affect an optimal timing to apply to 3G. The optimal applying or switching timing to 3G is when an economic value of the option to exchange is equal to an economic value of the extra costs plus the additional telecommunication quality from new telecommunication service. The option analysis used in this paper is applicable to various industries.

• Journal of KIISE:Computer Systems and Theory
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• v.27 no.2
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• pp.216-226
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• 2000

This paper presents a new method to synthesize timed asynchronous circuits directly from the specification without generating a state graph. The synthesis procedure begins with a deterministic signal transition graph specification with timing constraints. First, a timing analysis extracts the timed concurrency and timed causality relations between any two signal transitions. Then, a hazard-free implementation under the timing constraints is synthesized by constructing a precedence graph and finding paths in the graph. The major result of this work is that the method does not suffer from the state explosion problem, achieves significant reductions in synthesis time, and generates circuits that have nearly the same area as compared to previous methods.

• International Journal of Automotive Technology
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• v.8 no.6
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• pp.697-704
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• 2007

Recently, a variable valve timing system has been widely adopted in internal combustion engine in order to improve the fuel economy and torque at low engine speed. In addition, it is known that varying valve timing according to the various engine operations could reduce exhaust gas, especially NOx, because of residual gas by valve overlap. In this study, to improve the low exhaust gas and fuel economy at part load condition, the residual gas and back flow of exhaust gas due to valve overlap were calculated computationally. Moreover, the characteristics of engine performances and NOx formations were investigated with the experiment of combination of intake and exhaust valve timing condition. Under these various valve operating conditions, the effects of both the positive valve overlap and negative valve overlap(valve underlap) were examined simultaneously. Finally, the characteristics of cyclic THC emission were analyzed by using Fast Response FID(FR-FID) in the cylinder, intake port and exhaust port positions. Besides, the effect of the different gradients of the valve timing change on engine performance was investigated and an optimum control strategy was suggested.