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Integrated Acoustic Analysis of Payload Fairing Using an FE-SEA Hybrid Method
안병현,이수갑 한국항공우주학회 2023 International Journal of Aeronautical and Space Sc Vol.24 No.1
To ensure the stability of the launch vehicle payload, we developed an integrated acoustic analysis method. The integrated process involved three key steps: first, the acoustic load was derived by extracting the inputs required for the empirical model through numerical analysis, the results of which were in agreement with the experimental results. Second, depending on the frequency bands, the acoustic load on the fairing was calculated by performing a finite element analysis and statistical energy analysis for low and high frequencies, respectively. Third, we optimized the design parameters of a Helmholtz resonator using the particle swarm optimization algorithm and modeled the various shapes of an acoustic blanket. The internal acoustic load specification of the fairing was satisfied, and the results were noted to be consistent with the experiment results. The proposed method can be adopted in the launch vehicle development phase.
회전형 변압기를 이용한 비동기 AC-DC 하이브리드 계통연계 시스템
안병현,박재덕,채준수,김태훈,박태식 한국조명.전기설비학회 2023 조명·전기설비학회논문지 Vol.37 No.2
Recently, research on large-scale power grid interconnection and AC-DC hybrid power gird has been issued to improve supply reliability and flexibility. The conventional power grid interconnection method is HVDC. HVDC for asynchronous AC grid interconnection has advantage of high transmission efficiency over long distances and low short-circuit current, but it has disadvantages of harmonic generation, high investment cost, and low scalability. Therefore, to solve these problems, several studies have been conducted. In particular, a variable frequency transformer(VFT) for power grid interconnection has been proposed. Asynchronous power grid interconnection using VFT has the advantages of low harmonic generation, simple control, and high scalability. In this paper, we propose a new method for interconnection two AC systems and one DC system. The proposed method has economic feasibility and convenience of control. In order to verify the performance of asynchronous power grid interconnection, simulation through Matlab Simulink was performed.
안병현,서병로 충남대학교 의과대학 지역사회의학연구소 1990 충남의대잡지 Vol.17 No.2
A new glaucoma drainage implant, silicone tube attached to an expanded polytetrafluoroethylene (e-PTFE) membrane, was used in patients with recalcitrant glaucomas. Aqueous was shunted via the silicone tube to reservoir which was formed under the posterior Tenon's capsule by an oval piece of e-PTFE memberane, (Japan Gore-tex Inc., Tokyo) was 0.1mm thick, malleable and foldable. Therefore, the e-PTFE membrane of the implant could be introduced through a small incision of a quadrant conjunctiva in folded form and then spreaded over the sclera. The implant had been placed in 18 eyes of 17 patients with one or more unsuccessful glaucoma filtration surgeries including three neovascular glaucoma (NVG) patients. After follow-up of peroids ranging between seven and 18 months (mean: 10 months), 15 of the 18 eyes (83%) had controlled intraocular pressure (IOP) using 20 mmHg as normal. Three patients were not on any glaucoma medication. Seven patients required one β-blocker. Five patients were on one β-blocker and pilocarpine or a small dose of acetazolamide on their final visits. Three eyes with an unsuccessful surgery had an IOP over 25 mmHg in spite of maximum tolerated medical therapy. A postequatorial filtration bleb was found in each operated eye following removal of 5-0 cat-gut threaded through the silicone tube for the prevention of aqueous overdrainage. Postoperative complications included hyphema and fibrinous aqueous in the eyes with NVG(17%), prolonged shallow chamber(22%), obstruction of the silicone tube in the anterior chamber(6%), and choroidal datachment(6%) silicone tube in the anterior chamber (6%), and choroidal detachment(6%). The required conjuctival incision for the installation of the e-PTFE drainage implant was less than 90° and the overall surgical procedures seemed to be simple.
안병현 한국고무학회 2023 엘라스토머 및 콤포지트 Vol.58 No.1
Aromatic diamine containing ortho catenation and methyl group was synthesized from 4-methyl catechol and 4-nitrobenzoyl chloride. Subsequently, a poly(amic acid) was prepared by reacting 4-methyl-1,2-phenylene bis(4- aminobenzoate) with 4,4'-hexafluoroisopropylidenediphthalic anhydride (6FDA). The resulting poly(amic acid) was transformed into a polyimide through chemical imidization. The polyimide formed was soluble in N-methyl-2-pyrrolidone (NMP) and could be cast into a flexible, transparent film. Furthermore, the polyimide exhibited a 5% weight loss at 380 ℃ in the nitrogen atmosphere.