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A Study on CFD Data Compression Using Hybrid Supercompact Wavelets
Hyungmin Kang,Dongho Lee,Dohyung Lee 대한기계학회 2003 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.17 No.11
A hybrid method with supercompact multiwavelets is suggested as an efficient and practical method to compress CFD dataset. Supercompact multiwavelets provide various advantages such as compact support and orthogonality in CFD data compression. The compactness is a crucial condition for approximated representation of CFD data to avoid unnecessary interaction between remotely spaced data across various singularities such as shock and vortices. But the supercompact multi wavelet method has to fit the CFD grid size to a product of integer and power of two. m×2^n. To resolve this problem, the hybrid method with combination of 3.2 and 1 dimensional version of wavelets is studied. With the hybrid method, any arbitrary size can be handled without any shrinkage or expansion of the original problem. The presented method allows high data compression ratio for fluid simulation data. Several numerical tests substantiate large data compression ratios for now field simulation successfully.
Kang Cho Ryok,Ahn Bin,Choe Young June,Lim So Yun,Kim Han Wool,Kang Hyun Mi,Park Ji Young,Lee Hyungmin,Lee Seungho,Jeong Sumin,Kwon Sunghee,Choi Eun Hwa 대한의학회 2024 Journal of Korean medical science Vol.39 No.21
Background: The Korea Expert Committee on Immunization Practices (KECIP) is a key advisory body the government to develop guidelines and provide technical advisory activities on immunization policies in Korea. A recent policy study, inspired by global best practices, aims to enhance KECIP's functionality for providing timely and transparent recommendations in the face of evolving vaccine science and emerging infectious diseases like COVID-19. Methods: This study reviewed the current status of KECIP and collected expert opinions through surveys and consultations. Among the 40 panel members who were surveyed, 19 responded to a questionnaire specifically designed to assess the potential areas of improvement within KECIP. Results: The majority of respondents favored maintaining the current member count and emphasized the need for a subcommittee. Opinions varied on issues such as the length of KECIP’s term, the representation of vaccine manufacturers’ perspectives, and the chairperson’s role. However, there was a consensus on the importance of expertise, transparency, and fair proceedings within the committee. Conclusion: This study underscores the pivotal role of KECIP in shaping national immunization policies, emphasizing the necessity for informed guidance amidst evolving vaccine science and emerging infectious diseases. Furthermore, it stressed the importance of enhancing KECIP’s capacity to effectively address evolving public health challenges and maintain successful immunization programs in South Korea.
Kang Dong Yoon,Kim Hyunah,Ko SooJeong,Kim HyungMin,Shinn Jiwon,Kang Min-Gyu,Byeon Sun-ju,Choi Jeong-Hee,Shin Soo-Yong,Kim Hun-Sung 대한의학회 2022 Journal of Korean medical science Vol.37 No.7
Background: The most important aspect of a retrospective cohort study is the operational definition (OP) of the disease. We developed a detailed OP for the detection of sodiumglucose cotransporter-2 inhibitors (SGLT2i) related to diabetic ketoacidosis (DKA). The OP was systemically verified and analyzed. Methods: All patients prescribed SGLT2i at four university hospitals were enrolled in this experiment. A DKA diagnostic algorithm was created and distributed to each hospital; subsequently, the number of SGLT2i-related DKAs was confirmed. Then, the algorithm functionality was verified through manual chart reviews by an endocrinologist using the same OP. Results: A total of 8,958 patients were initially prescribed SGLT2i. According to the algorithm, 0.18% (16/8,958) were confirmed to have SGLT2i-related DKA. However, based on manual chart reviews of these 16 cases, there was only one case of SGLT2i-related DKA (positive predictive value = 6.3%). Even after repeatedly narrowing the diagnosis range of the algorithm, the effect of a positive predictive value was insignificant (6.3–10.0%, P > 0.999). Conclusion: Owing to the nature of electronic medical record data, we could not create an algorithm that clearly differentiates SGLT2i-related DKA despite repeated attempts. In all retrospective studies, a portion of the samples should be randomly selected to confirm the accuracy of the OP through chart review. In retrospective cohort studies in which chart review is not possible, it will be difficult to guarantee the reliability of the results.
Hyungmin Kang,Yingmei Jin,Hyeokbin Kwon,Kyuhong Kim 한국항공우주학회 2017 International Journal of Aeronautical and Space Sc Vol.18 No.4
The characteristics of aerodynamic drag for Transonic Vehicle in Evacuated Tube was investigated using computational fluid dynamics. At first, parametric study on the system was performed according to the Mach number of the vehicle’s speed (Machv), evacuated pressure of the tube (Pret), and blockage ratio (BR) between the vehicle and tube via axisymmetric flow analysis; the Machv ranged from 0.3 to 1.0. The Pret was 100, 1,000 and 10,000 Pa and the BR was 0.1, 0.2, and 0.4. In the calculations, the aerodynamic drag of the vehicle was larger when the BR and the pressure became larger. Concerning the Machv, the drag coefficient (Cd) became the maximum when the Machv was near the Kantrowitz limit and decreased, which showed the typical transonic flow pattern. Then, three dimensional flow analysis was performed by changing the Machv from 0.3 to 1.0 and setting the BR and the Pret as 0.34 and 100 Pa, respectively by referring the Hyperloop Alpha documentation. From the calculations, the Cd from three dimensional flow simulations were somewhat larger than those of axisymmetric ones because of the eccentricity of the vehicle inside the tube. However, the pattern of Cd according to the Machv was compatible with that of axisymmetric ones.