• 대한조선학회논문집
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• 제53권5호
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• pp.343-352
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• 2016

In this study, a pre-swirl duct for the 180,000 DWT bulk carrier has been designed from a propulsion standpoint using CFD. The stern duct - designed by NMRI - was selected as the initial duct. The objective function is to minimize the value of delivered power in model scale. Design variables of the duct include duct angle, diameter, chord length, and vertical and horizontal displacements from the center. Design variables of the stators are blade number, arrangement angle, chord length, and pitch angle. A parametric design was carried out with the objective function obtained using CFD. Reynolds averaged Navier-Stokes equations have been solved; and the Reynolds stress model applied for the turbulent closure. A double body model is used for the treatment of free-surface. MRF and sliding mesh models have been applied to simulate the actuating propeller. A self-propulsion point has been obtained from the results of towing and self-propelled computations, i.e., form factor obtained from towing computation and towing forces obtained from self-propelled computations of two propeller rotating speeds. The reduction rate of the delivered power of the improved stern duct is 2.9%, whereas that of the initial stern duct is 1.3%. The pre-swirl duct with one inner stator in upper starboard and three outer stators in portside has been designed. The delivered power due to the designed pre-swirl duct is reduced by 5.8%.

• 한국항공운항학회지
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• 제23권1호
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• pp.103-112
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• 2015

In this study, a study was carried out to see what influence low-cost carrier's e-service quality has on low-cost carrier customers' perceived value and customer satisfaction and what impact the results have on customer loyalty based on the results of previous studies related to e-SERVQUAL, an e-SERVQUAL measurement model for general e-commerce. In addition, a survey of consumers who have experienced using low-cost carrier experience through web sites was conducted. For the analysis of the data collected, SPSS 18.0 was used to conduct frequency analysis, factor analysis, reliability analysis, correlation analysis, and regression analysis and thus to test a hypothesis. Research findings showed that perceived value and customer satisfaction are closely related to customer loyalty, and it was also observed that the reliability factor on the service provided on the web site acts as an important influencing factor for customer loyalty in the perceived value and security factors such as payment by credit cards and protection of personal information serve as important one in terms of customer satisfaction. This study has its limitation in that samples of users who have experienced low-cost carrier are concentrated on specific ages and professions. In the future, it is required to conduct further studies on whether difference is made on the importance of measurement factors related to e-service quality by gender, age group, occupation, and e-service quality.

• Journal of Periodontal and Implant Science
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• 제38권sup2호
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• pp.355-362
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• 2008

Purpose: The carrier for the delivery of bone morphogenetic proteins(BMPs) should also serve as a scaffold for new bone growth. In addition, predictable bone formation in terms of the volume and shape should be guaranteed. This study evaluated the ectopic bone formation of recombinant human BMP-2(rhBMP-2) using a micro macroporous biphasic calcium phosphate (MBCP: mixture of ${\beta}TCP$ and HA) block as a carrier in a rat subcutaneous assay model. Materials and Methods: Subcutaneous pockets were created on the back of 40 male Sprague-Dawley rats. In the pockets, rhBMP-2/MBCP and MBCP alone were implanted. The blocks were evaluated by histological and histometric parameters after a healing interval of 2 weeks (each 10 rats; MBCP and rhBMP-2/MBCP) or 8 weeks (each 10 rats; MBCP and rhBMP-2/MBCP). Results: The shape and volume of the block was maintained stable over the healing period. No histological bone forming activity was observed in the MBCP alone sites after 2 weeks and there was minimal new bone formation at 8 weeks. In the rhBMP-2/MBCP sites, new bone formation was evident in the macropores of the block. The new bone area at 8 weeks was greater than at 2 weeks. There was a further increase in the quantity of new bone with the more advanced stage of remodeling. Conclusions: A MBCP block could serve as a carrier system for predictable bone tissue engineering using rhBMPs.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.13-13
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• 2010

Switching an elementary excitation by injecting a single carrier would offer the exciting opportunity for the ultra-high data storage technologies. However, there has been no methodology available to investigate the interaction of low energy discrete carriers with nano-structures. In order to map out the spatial dependency of such single carrier level interactions, we developed a pulse-and-probe algorithm, combining with low temperature scanning tunneling microscopy. The new tool, which we call single carrier spectroscopy, allows us to track the interaction with the target macrostructure with tunneling carriers on a single carrier basis. Using this tool, we demonstrate that it is possible not only to locally write and erase individual bi-solitons, reliably and reversibly, but also to track of creation yields of single and multiple bi-solitons. Bi-solitons are pairs of solitons that are elementary out-of-phase excitations on anti-ferromagnetically ordered pseudo-spin system of Si dimers on Si(001)-c(42) surfaces. We found that at low energy tunneling the single bisoliton creation mechanism is not correlated with the number of carriers tunneling, but with the production of a potential hole under the tip. An electric field at the surface determines the density of the local charge density under the tip, and band-bending. However a rapid, dynamic change of a field produces a potential hole that can be filled by energetic carriers, and the amount of energy released during filling process is responsible for the creation of bi-solitons. Our model based on the field-induced local hole gives excellent explanation for bi-soliton yield behaviors. Scanning tunneling spectroscopy data supports the existence of such a potential hole. The mechanism also explains the site-dependency of bi-soliton yields, which is highest at the trough, not on the dimer rows. Our study demonstrates that we can manipulate not just single atoms and molecules, but also single pseudo-spin excitations as well.

• 한국방사선학회논문지
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• 제15권2호
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• pp.229-238
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• 2021

본 논문에서는 고에너지 엑스선(6 MV X선)을 조사한 갑상선의 소포세포막 모델에서 막의 두께차이, 고정전달자[VP-AN% (w/ w)]의 농도차이, OH-이온의 농도차이가 세포내부와 세포외부사이로 갑상선호르몬의 구성성분인 요오드이온의 농도차이로 발생하고 갑상선호르몬의 생성량에 영향을 미치는데 이러한 영향을 구명하기위해서 소포의 세포막을 통한 요오드의 선택적 투과전달 특성에 대하여 연구하였다. 이 실험에 사용한 세포막 모델은 피리딘 양이온을 고정전달자로 한 poly(4-vinylpyridine- co-acrylonitrile :VP-AN)분말을 인장강도의 강화용인 polysulfone과 결합시킨 불균질의 복합막을 사용하였다. 고정전달자[VP-AN% (w/ w)]의 농도차이(0~62 %)에서 36.5 ℃로 방사선을 조사한 소포의 고분자 막(세포막모델)은 형태학적 변화인 인장강도가 비 조사된 세포막모델보다 약 1.2 ~ 1.8배 정도 감소되었다. 방사선을 조사한 갑상선의 소포세포막모델 [2mole AN%(w/w)]에서 막의 두께차이, 고정전달자[VP-AN% (w/ w)]의 농도차이, OH-이온의 농도 차이로 발생하는 요오드이온의 선택적 투과플럭스는 비 조사된 세포막모델보다 막의 두께가 변화 할 때 각각 약 2.1 ~ 4.5배, 약 2.2 ~ 2.5배, 약 2.1 ~ 2.67배 정도 감소되었다. 결국 방사선조사로 인해서 갑상선의 소포세포막에서 요오드이온의 선택적 투과 전달기능이 비정상적으로 되어 세포장해가 발생하고 갑상선호르몬의 생성량 감소도 동반하게 되었다고 사료됐다.

• International Journal of Naval Architecture and Ocean Engineering
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• 제11권2호
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• pp.723-735
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• 2019

This paper employs computational tools to investigate the cause of resistance reductions in calm water and waves of the sharp bow form compared to the blunt bow in 66,000 DWT bulk carriers. A more slender shape at the fore-shoulder without a bulbous bow is a prominent feature of the sharp bow. The blunt bow incorporates a bulbous shape. A two-phase unsteady Reynolds averaged Navier-Stokes equations have been solved; and a realizable k-ε model has been applied for the turbulent closure. The free-surface is obtained by solving a VOF equation. The computational results have been validated with model tests carried out at a towing tank. The pressure component of resistance in the sharp bow is reduced by 8.9% in calm water, and 6.4-12.7% in regular head waves. The frictional components of resistance in the sharp and blunt bows are largely the same.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 춘계학술대회논문집
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• pp.1205-1205
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• 2003

Rotary compressors are one of the most important parts of air-conditioners in the industry This device usually has noise problems during the circulation process of the refrigerant and muffler is used for the noise reduction. The acoustic performance of the muffler depends on its shape and its hole locations on the upper surface. Therefore finding the optimum location of the muffler holes is a topic of increasing importance in the compressor industry. In this research the optimization of the muffler hole locations and the importance of the resonator cavity on the lower surface of the muffler in acoustic point of view is studied. At first, the topology optimization for the 2 hole muffler is performed based on a model without resonator cavity by using genetic algorithm. The 2 hole muffler's acoustic analysis and experiment results are matching, however, the optimized model's results are not. By adding the resonator cavity and also by changing the cavity shape, the acoustic analysis and experiment result comparison is Performed for different cavity shapes. The topology optimization of the revised model with cavity is carried out for noise reduction. Finally, the optimized design is produced and tested for validation.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2006년도 International Symposium on GPS/GNSS Vol.1
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• pp.535-540
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• 2006

The relationship between the observable noise model and the satellite elevation angle can be modeled quite well by an exponential function.[Jin, 1996] Noise size and dependence on the elevation angle are, however, different for each observation and receiver type. Therefore, the coefficient determination of this model is an issue, and various methods including PR-CP, single difference, and time difference have been suggested. The limitations of them are difficulty to model the carrier phase noise and to eliminate bias. To overcome these disadvantages for using Jin's model, we suggest zero baseline double difference (DD) and noise sorting algorithm. Data DD technique in zero baseline is useful to eliminate all the troublesome GPS biases, and the remaining error is the sum of GPS measurement noises from two satellites. These DD residuals for hours should be sorted by the combination of satellite elevation angles, and then variance value of the residual for each combination can be estimated. Using these values, we construct an over-determined linear equation whose solution is a set of noise variance for each satellite elevation angle. With 24hr Trimble 4000ssi data, we easily worked out the coefficients of the noise model not only for pseudorange but also for carrier phase. We estimated the standard deviation of the measurement DD using our model, and plotted 1 and 3 sigma lines for every epoch to verify the representation of the residual error. 63.3% of pseudorange residual and 65.9% of phase error did not exceed the 1 sigma lines. Additionally, 99.2% and 99.5% of them lied within 3sigma line. These figures prove that the Gaussian property of measurement noise, and that the suggested model by our algorithm corresponds to the observable noise information.

• 한국국방경영분석학회지
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• 제11권1호
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• pp.55-78
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• 1985

This thesis provides the implementation of a simulation model for a particular Local Area Network (LAN), employs carrier sense multiple access (CSMA) bus architecture, which implements functions of the Stock Point Logistics Integrated Communication Environment (SPLICE). First, specifications of the model are identified based on the given functional specification and operating system design. Then the approach taken for modeling and programming in GPSS is discussed. Finally, the program and results of the simulation run are provided.

• Spatial Information Research
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• 제15권2호
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• pp.111-121
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• 2007

GPS의 3차원 위치결정은 코드파와 반송파를 이용한다. 하지만 이동체에 대한 cm 수준의 정확도를 획득하기 위해서는 정확한 기지점의 성과를 이용한 GPS 반송파 상대측위, 즉 RTK-GPS 기법을 수행하여야 한다. 이 때 두 대의 수신기 사이의 거리가 증가할수록 기선장에 따른 오차가 증가하여 기준국과 사용자 수신기의 거리를 $10{\sim}20km$ 정도로 제한하고 있다. 따라서 사용자는 깊은 내륙, 연안 해역 등과 같은 기준국과 이동체의 이격이 수십 km로 증대되는 지역에서는 기준국 설치의 문제를 포함하고 있으며 독자적인 기준국을 설치하여야 하는 인력 및 장비의 부담을 가지게 된다. 이를 극복하기 위해 본 연구에서는 네트워크 기반의 GPS 반송파 상대측위 방식을 제안하였으며 GPS 네트워크 처리 프로그램인 DAUNet을 개발하였다. 기선장에 따른 오차보정량 산출을 위해 선형보간알고리즘 방식에 기반한 함수모델과 통계모델을 제시하였으며, 오차보정량의 보간은 면보정매개변수 방식을 제안하였다. 기존 단일기준국 방식은 기선장에 따른 오차를 소거하지 못하였지만 본 연구에서는 사용자 수신기와 평균 30km 떨어진 3대의 기준국을 이용하여 기선장에 따른 오차보정량을 소거 혹은 감소시킬 수 있었다. 따라서 사용자는 네트워크 기반의 GPS 반송파 상대측위 방식을 이용하여 이동체에 대한 10cm 이하 수준의 정확도를 획득할 수 있었다.