• Journal of Korea Water Resources Association
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• v.37 no.3
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• pp.219-231
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• 2004

The use of air diffuser system to ameliorate the reservoir by breaking stratification is now widespread. This study focuses on the hydrodynamic behavior of bubble plumes, which is the major mechanism of destratification and their combined effect of adjacent plumes on destratification efficiency. By introducing 2-phase Computational Fluid Dynamics(CFD) technique, we could suggest the optimal diffuser spacing having optimal destratification efficiency by simply analyzing the complex destratification procedures varying with the seasonal stratification intensity and bubble flow rate. Lab experiments were also carried out to verify CFD model in thermally stratified fresh water which quite differs from former researches using salts. This study showed that the mixing efficiency strongly depends on the spacing of neighboring plumes. When diffuser spacing is lower than 1.5 times the depth, the combined effect is stronger; as Plume Number(PN) is increased, the efficiency is strongly affected by spacing. If the distance is shorter than the depth of water, the efficiency increases linearly in proportion to PN. Otherwise, the efficiency increases non-linearly. These findings suggest that the combined effect should be more quantitatively taken into consideration for design and operation of air-diffuser destratification system, and recommend that the optimal destratification efficiency will be when plume number is 1000 and the spacing between neighboring diffusers is 1.5 times the depth.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.3
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• pp.1053-1058
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• 2010

Infinite element approach has been widely used to analysis soil-structure interaction, in which the soil domain is treated as infinite domain. However, most of the developed infinite element has been formulated in the frequency domain rather than the time domain to include the frequency contents of the earthquake or vibration wave. Due to that, those approaches have a critical limitation which is restricted to the linear elastic analysis. To main objective of this research is to develop the infinite element in the time domain to cooperate the inelastic soil and structure behavior. Developed infinite element is verified with the results of finite element analysis modeled in large domain. The nonlinear analysis also conducted to demonstrate the application of developed infinite element. Hence, based on above-mentioned statements, it can be concluded that the propose approach would assist for structure-seismic design.

• Pediatric Gastroenterology, Hepatology & Nutrition
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• v.12 no.2
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• pp.163-170
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• 2009

Purpose: Intussusception is the most common cause of intestinal obstruction in young children. Although intussusceptions are easily treated, some intussusceptions with or without a pathologic lead point (PLP) often recur. In this study, we analyzed the clinical characteristics and prognosis of recurrent intussusceptions (RI), the frequency of the PLP, and correlation between RI with PLP. Methods: The medical records of 144 patients, among 590 patients with intussusceptions who had been admitted to the Department of Pediatrics and Pediatric Surgery of Dankook University Hospital between May 1994 and June 2009 were reviewed retrospectively. Results: The overall recurrence rate of intussusceptions in this study was 9.2%. The mean interval between the initial occurrence and the first recurrent attack was 130${\pm}$175 days (range, 12 hours to 3 years). There was no statistically significant difference in the recurrence rate among patients who underwent air, barium, and manual reduction (p=0.131). Eighty-seven cases (92.6%) of RI had a successful reduction by the use of non-operative techniques. A PLP was present in 18 patients (3.0%). The most common PLP was intestinal lymphoid hyperplasia, followed by Meckel's diverticulum, duplication cyst, intestinal polyp, and adenomyoma. The mean number of intussusceptions was 4.7${\pm}$1.9 in 7 patients with PLP, which was significantly higher than (2.4${\pm}$0.9) patients without a PLP (p=0.023). The mean duration of recurrences was 17.4${\pm}$19.8 months (range, 2 days to 72 months). Conclusion: A careful search for a PLP should be performed to prevent recurrence of intussusception, especially when intussusception has recurred more than three times.

• Journal of the Korean Society of Propulsion Engineers
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• v.26 no.3
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• pp.10-21
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• 2022

The propellant tank, which is a space launch vehicle structure, must have structural integrity as various static and dynamic loads are applied during ground transportation, launch standby, take-off and flight processes. Because of these characteristics, the propellant tank cylinder, the structural object of this study, has a thin thickness, so buckling due to compressive load is considered important in the cylinder design. However, the existing buckling design standards such as NASA and Europe are fairly conservative and do not reflect the latest design and manufacturing technologies. In this study, nonlinear buckling analysis is performed using various analysis models that reflect initial defects, and a method for establishing new buckling design standards for cylinder structures is presented. In conclusion, it was confirmed that an effective lightweight design of the cylinder structure for common bulkhead propulsion tank could be realized.

• Journal of Biomedical Engineering Research
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• v.25 no.2
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• pp.89-95
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• 2004

Intensity-modulated radiation therapy (IMRT) often uses small beam segments. The heterogeneity effect is well known for relatively large field sizes used in the conventional radiation treatments. However, this effect is not known in small fields such as the beamlets used in IMRT. There are many factors that can cause errors in the small field i.e. electronic disequilibrium and multiple electron scattering. This study prepared geometrically regular heterogeneous phantoms, and compared the measurements with the calculations using the Convolution/Superposition algorithm and Monte Carlo method for small beams. This study used the BEAM00/EGS4 code to simulate the head of a Varian 2300C/D. The commissioning of a 6MV photon beam were performed from two points of view, the beam profiles and depth doses. The calculated voxel size was 1${\times}$1${\times}$2$\textrm{cm}^2$ with field sizes of 1${\times}$1$\textrm{cm}^2$, 2${\times}$2$\textrm{cm}^2$, and 5${\times}$5$\textrm{cm}^2$. The XiOTM TPS (Treatment Planning System) was used for the calculation using the Convolution/Superposition algorithm. The 6MV photon beam was irradiated to homogeneous (water equivalent) and heterogeneous phantoms (water equivalent ＋ air cavity, water equivalent ＋ bone equivalent). The beam profiles were well matched within :t1 mm and the depth doses were within ${\pm}$2%. In conclusion, the dose calculations of the Convolution/Superposition and Monte Carlo simulations showed good agreement with the film measurements in the small field.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.12
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• pp.1877-1885
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• 2004

The purpose of this study is to show pressure distribution of the bearing girder in large vessel engine and to consider finite elements analysis using the pressure distribution. Various kinds of the exciting forces act on a bearing girder. And at the same time, it is necessary to consider the contact between a crankshaft and a bearing girder because a bearing girder supports a crankshaft. However it is to need the computer resource with much time if we apply the contact element to a complex solid model and perform a repeated analysis. Thus we have accomplished a contact analysis in the simplistic finite element model of the bearing girder. After that we take a pressure distribution, and apply this to actual finite element model and accomplish finite element analysis. The result of stresses and strains has been produced using superposition method. The concept of superposition method is to find the resultant deflection of several loads acting on a member as the sum of contributions of individual loads. The results were compared with measured results and were verified to be accurate. Resulting analyzed strain favorably coincides with measured strain. The experiment result justifies this paper method.

• Korean Journal of Optics and Photonics
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• v.14 no.4
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• pp.377-382
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• 2003

We propose a new optical watermarking method, which can protect the copyright of digital data, using a binary phase hologram and a Mach-Zehnder interferometer. Using a simulated annealing algorithm, the binary phase hologram of the mark image to be hidden is designed. We obtained a watermarked image by linearly superposing the hologram, which is the watermark, in the original image. The extraction processing of the mark image from the watermarked image is achieved by placing the phase-modulated watermarked image on a LCD in one path and the phase-modulated original image on another LCD in the other path in the Mach-Zehnder interferometer. The mark image was obtained by inverse Fourier transforming the phase modulated interference intensity. We confirmed that the proposed method is robust for the cropped images through computer simulation, and we implemented it optically using LCDs which are phase modulation devices.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.11
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• pp.91-98
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• 2004

TFLIM(Transverse Flux Linear Induction Motor), making its closed magnetic path with the direction of the traveling field orthogonal, had been developed to decrease an edge effect of the general induction motor. To control the levitation force and the thrust force on the secondary part of TFLIM independently, the various methodologies have been presented. When we try to achieve the independent control using only the multi-phase inputs assigned in the stator coils as an approach, in which condition we can minimize the coupling effect between two forces\ulcorner In this paper, we show the qualitative influence of a slip frequency, an ac magnitude, a dc offset superposed in the ac power, and a major parameter of TFLIM on the couple through the computer simulation. And to realize the independent motions between levitation and thrust motion without any auxiliary means fur isolation of the secondary part of TFLIM, the decouple compensator is suggested, including the experimental results.

• 한국HCI학회:학술대회논문집
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• 2006.02a
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• pp.1361-1366
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• 2006

본 논문에서는 제약되지 않은 카메라에서 얻어진 회전과 크기 변화를 가진 영상들을 특징 기반의 보로노이 거리 매칭 방법을 이용하여 고속으로 합성 하는 기법에 관해 기술한다. 기존의 특징점 기반 매칭 기법들이 사람의 개입에 의해 영상을 정합하거나, 크기나 회전 변화를 고려하지 않은 형태의 영상들을 처리하는 것과 달리 회전이나 크기변화요소가 포함된 입력영상들을 사람의 개입이 없이 자동으로 정확한 중첩영역을 빠르게 검색하는 방법을 제안한다. 제안된 방법은 우선 영상내의 특징 점들의 위상 정보와 특징 점들 사이의 거리 정보를 가지는 보로노이 거리 정합법을 통해 대응점을 구하고, 찾아진 대응 쌍들을 이용하여 2차원 투영의 초기 변환행렬을 구한다. 다음으로 비선형 이승오차 최적화 알고리즘을 이용하여 최적의 변환 행렬을 구한 후, 마지막으로 구해진 변환 행렬을 이용하여 영상을 합성한다. 실험결과를 통해 본 논문에서 제안한 방법의 효율성을 보인다.

• Journal of the Korea Computer Industry Society
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• v.8 no.3
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• pp.167-172
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• 2007

Generally, In a application program the core part for parallel processing is a loop. therefore in this paper, loop interchange parallel compiler is proposed. this is a procedure for the automatic conversion of a loop interchange. According to execution to the outside CDOALL statements of cedar fortran, loop interchange is more effectively method the extracting parallelism in order to parallel processing in iterations. This method will be expected to effectively execution result with mixed into linear conversion and go far toward solving the effectively implementation of the non-unimodular nested loop.