• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.7B
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• pp.578-585
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• 2012

Location tracking system through GPS and Wi-Fi is available at no additional cost in an environment of IEEE 802.11-based wireless network. It is useful for many applications in outdoor environment. However, a previous systems used for general device to tag. It is unsuitable for power aware location tracking system because general devices is more expensive and non-optimized for tracking. The hand-off method of IEEE 802.11 standard is not enough considering power consumption. This thesis analyzes the previous location tracking systems and proposes power aware system. First, we designed and implemented tag to optimize location tracking. Next, we propose low-power hand-off method and low-power behavior model in implemented tag. The proposed hand-off method resolve power problem by using the location information and behavior model minimize power consumption of tag through power-saving mode and the concept of duty cycle. To evaluating proposed methods and system performance, we perform simulations and experiments in real environment. And then, we calculate tag's power consumption based on the actual measured current consumption of each operation. In a simulation result, the proposed behavior model and hand-off method reduced about 98%, 59% than the standard's hand-off and default behavior model.

• Journal of Chest Surgery
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• v.50 no.2
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• pp.105-109
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• 2017

Coronary arterial involvement in Takayasu arteritis (TA) is not uncommon. Herein, we describe a case of TA with celiac trunk and superior mesenteric artery occlusion combined with coronary artery disease. Bilateral huge internal thoracic arteries (ITAs) and the inferior mesenteric artery provided the major visceral collateral circulation. After percutaneous intervention to the right coronary artery, off-pump coronary artery bypass grafting for the left coronary territory was done using a right ITA graft and its large side branch because of its relatively minor contribution to the visceral collateral circulation.

• The KSFM Journal of Fluid Machinery
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• v.2 no.3 s.4
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• pp.45-51
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• 1999

Centrifugal fans are widely used and the noise generated by these machines causes one of the most serious problems. In general, the centrifugal fan noise is often dominated by tones at BPF(blade passage frequency) and its higher harmonics. This is a consequence of the strong interaction between the flow discharged from the impeller and the cutoff in the casing. However, only a few researches have been carried out on predicting the noise due to the difficulty in obtaining detailed information about the flow field and casing effects on noise radiation. The objective of this study is to develop a prediction method for the unsteady flow field and the acoustic pressure field of a centrifugal fan and to calculate the effects of rotating velocity, flow rate, cut-off distance and the number of blades and its effects on the noise of the fan. We assume that the impeller rotates with a constant angular velocity and the flow field around the impeller is incompressible and inviscid. So, a discrete vortex method (DVM) is used to model the centrifugal fan and to calculate the flow field. The force of each element on the blade is calculated with the unsteady Bernoulli equation. Lowson's method is used to predict the acoustic source. The cut-off distance is the most important factor effecting the noise generation. Acoustic pressure is proportional to 2.8, which shows the same scaling index as the experimental result. In this paper, the cut-off distance is found to be the dominant parameter offecting the acoustic pressure.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.17 no.5
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• pp.103-109
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• 2017

In this paper, the advancement in IT technology is not only inducing the multi-functionality of simple products but also changing even the lifestyle, that is, the pattern of consumers' daily life. The actual paradigm for the conversion from off-line to on-line is at the level of threatening the ecology of off-line. In this study, the diversified advancement method of off-line is in functional relationship with the increase in sales revenue and profits not only through the visit of consumers to the sales outlets for the simple purpose of making purchase but also through the application of augmented realities such as 3-dimensional sense in space and sense in reality, which are entertainment experience factors. Therefore, the improvement in the enhancement of sales revenues by applying augmented reality to off-line department store was researched in this study.

• The Journal of the Acoustical Society of Korea
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• v.11 no.4
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• pp.5-13
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• 1992

The vibration of a vehicle, which is caused by and transmitted from the engine, has significant effect on the ride comfort and the dynamic characteristics of the engine mount system has direct influence on the vibration and noise of the vehicle. This paper examines the body shake caused by the engine excitation force on engine key-off of a jeep by experiment and computer simulation using a general purpose mechanical system program, DADS. The computer simulation model consists of the engine, body including frame, and front and rear axles and each axle has right and left tires. The force element between body and suspension is modeled as a combination of suspension spring and damper, and the unsprung mass has roll and pitch motion. The body shake obtained from experiment was compared with the result of computer simulation. Parametric study of the body shake on engine key-off is performed with changing the stiffness of engine mount rubber, the engine mount installation angle and position of engine mounts by using the verified computer simulation model.

• Journal of the Korean Society of Industry Convergence
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• v.24 no.6_2
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• pp.773-779
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• 2021

CNG, which has recently been attracting attention as an alternative fuel in the transportation field to reduce emissions caused by global warming, is natural gas with abundant reserves and mainly composed of methane. Being in a gaseous state, natural gas requires the compression and liquefaction processes for transportation. Until now, general shut-off valves for liquid and gas piping have been developed in Korea, but there are few studies on shut-off valves for high pressures of about 200 bar. Currently, research on the flow analysis of valves is being actively conducted around the world. However, there are relatively many studies on large valves such as low-pressure valves or shipbuilding and marine, and the safety factor through structural analysis to check the structural integrity of the valve is checked at the design stage. Since it is necessary to have a fast response speed while minimizing pressure and speed loss due to flow change, basic research was conducted on the flow analysis of the valve to secure design data, and the numerical analysis was performed on high-pressure automatic shut-off valves applied to CNG refueling stations. After securing the basic valve shape through reverse engineering for advanced products, we compared the valve flow coefficient Cv coefficient with advanced products. As a result, it was found that the reverse engineering model was at the level of about 60%. However, we compared the Cv coefficient by modifying the reverse engineering model, and the result showed that it was improved to about 96%.

• Journal of Korean Foot and Ankle Society
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• v.7 no.2
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• pp.238-249
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• 2003

Purpose: To report the clinical result of the intraarticular calcaneus fracture after open reduction and internal fixation with plate by lateral approach. Materials and Methods: Thirty-six calcaneal fractures of 33 patients(29 men and 4 women) were treated by open reduction and internal fixation using an lateral approach from March, 1997 to May, 2002 and were followed more than one year. The autogenous iliac bone graft was done in 2 cases but the others didn't. Radiographically B?hler angle and Gissane angle on simple lateral radiograph were measured and in the 15 cases, the step-off(gap) of posterior facet joint on post-operative CT images were followed. The Salama method was used for evaluation of clinical results. Results: According to Sanders classification, 19 cases of the 36 cases were classified as type II. Type III fracture were found in 12 cases and type IV in 5 cases. The following results were obtained: twenty-two cases(61.1%) out of 36 cases were estimated as good or excellent. The good results or more were obtained in 15 cases(78.9%) in type II and 7 cases(58.3%) in type ill, but no case in type IV. B?hler angles were improved from preoperative average 1.6?to postoperative average 23.4?, Gissane angle was improved from preoperative 107.2?to postoperative 122.8?, respectively. Among 36 cases, Computed tomography was carried out in 15 cases. The postoperative step-off (gap) of posterior facet joint on computed tomography was filled with cancellous bone. Satifactory results was obtained in 7 cases with 2mm gap or less and in 6 cases of 2-5mm. There were no satifactory results in 2 cases with 5mm gap or more. Conclusion: Open reduction and internal fixation for intra-articular fracture of calcaneus was thought to be a good treatment modality. It is thought that the lateral approach is one of the good one for surgical treatment, and that accurate reduction of the posterior facet, acceptable recovery of B?hler angle are more important to obtain best results.

• Magazine of the Korean Society of Agricultural Engineers
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• v.26 no.4
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• pp.52-65
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• 1984

In general precise estimation of hourly of daily distribution of the long-term run-off should be very important in a design of source of irrigation. However, there have not been a satisfying method for forecasting of stationar'y long-term run-off in Korea. Solving this problem, this study introduces unit-hydrograph method frequently used in short-term run-off analysis into the long-term run-off analysis, of which model basin was selected to be Sumgin-river catchment area. In the estimation of effective rainfall, conventional method neglects the Soil moisture condition of catchment area, but in this study, the initial discharge (qb) occurred just before rising phase of the hydrograph was selected as the index of a basin soil moisture condition and then introduced as 3rd variable in the analysis of the reationship between cumulative rainfall and cumulative loss of rainfall, which built a new type of separation method of effective rainfall. In next step, in order to normalize significant potential error included in hydrological data, especially in vast catchment area, Snyder's correlation method was applied. A key to solution in this study is multiple correlation method or multiple regressional analysis, which is primarily based on the method of least squres and which is solved by the form of systems of linear equations. And for verification of the change of characteristics of unit hydrograph according to the variation of a various kind of hydrological charateristics (for example, precipitation, tree cover, soil condition, etc),seasonal unit hydrograph models of dry season(autumn, winter), semi-dry season (spring), rainy season (summer) were made respectively. The results obtained in this study were summarized as follows; 1.During the test period of 1966-1971, effective rainfall was estimated for the total 114 run-off hydrograph. From this estimation results, relative error of estimation to the ovservation value was 6%, -which is mush smaller than 12% of the error of conventional method. 2.During the test period, daily distribution of long-term run-off discharge was estimated by the unit hydrograph model. From this estimation results, relative error of estimation by the application of standard unit hydrograph model was 12%. When estimating by each seasonal unit bydrograph model, the relative error was 14% during dry season 10% during semi-dry season and 7% during rainy season, which is much smaller than 37% of conventional method. Summing up the analysis results obtained above, it is convinced that qb-index method of this study for the estimation of effective rainfall be preciser than any other method developed before. Because even recently no method has been developed for the estimation of daily distribution of long-term run-off dicharge, therefore estimation value by unit hydrograph model was only compared with that due to kaziyama method which estimates monthly run-off discharge. However this method due to this study turns out to have high accuracy. If specially mentioned from the results of this study, there is no need to use each seasonal unit hydrograph model separately except the case of semi-dry season. The author hopes to analyze the latter case in future sudies.

• Fire Science and Engineering
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• v.25 no.3
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• pp.1-7
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• 2011

This paper studied analysis of deflagration rapid propagation of burning through only a few second and fire cause into the Busan indoor shooting range. We carried out combustion experiment of sound-absorbing materials extensively used, to analyze propagation path of burning in indoor shooting range. From the experimental results, general sound-absorbing materials were rapid burned simultaneously with ignition and in case of attached gunpowder residue, they were burning about tripled by comparison with general sound-absorbing materials. The incombustibility sound-absorbing materials had all gone out simultaneously with ignition, but they were burning similar to general type materials in case of attached gunpowder residues. In order to analysis of the cause of fire, we calculated kinetic energy of bounced off bullet, from result, if the bounced off bullet impacted gunpowder residues, the gunpowder residues were possible to ignite by the bullet.

• Journal of the Korean Society of Food Culture
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• v.19 no.6
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• pp.678-690
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• 2004

This study was implemented to offer materials for the activation of On-line food shopping mall though census about purchasing food. A percentage of people who had accessed to On-line food shopping mall was 53.8%, and who had an experience of purchasing food at the On-line sopping mali was 18.9%. The number of food purchasing in On-line food market is $1{\sim}3$ times(67.7%). It is general that an amount of food purchase is less than 100,000 wons. And the health assistant food is the most interesting item followed by Meet, Special products like a laver and mushroom, and an anchovy. in purchasing food at On-line market, customer thought that the confidence and the freshness of food are important because customer can't choose a product directly. In the future of food purchase using On-line shopping mall, 38.1% of people show their intend of purchasing at the mall. People who had experience of food purchase though the Internet have more positive view about repurchase than ones had not.