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안효근,선철 한국항공우주학회 2015 한국항공우주학회 학술발표회 논문집 Vol.2015 No.11
초음속 비행체를 개발하는데 있어 공력가열의 측정과 해석은 중요한 업무 중의 하나이다. 부정확한 공력가열 예측으로 열구조 설계를 수행했다면 비행체의 안정적 비행을 보장하기가 어렵다. 공력가열 해석오차가 크면 비행체의 구조는 최적설계가 되지 못하여 구조적으로 불안정해지거나, 혹은 과도 설계가 되어 성능 미달의 비행체가 될 수 있다. 또한, 공력가열 현상은 공력특성과 달리 지상시험을 통하여 비행 상황을 재현하기가 어려우므로, 전적으로 시뮬레이션에 의존하고 있다. 공력가열 시뮬레이션 결과의 타당성은 비행시험을 통하여 검증한다. 비행시험시 열유속을 측정하고, 해석결과와 비교, 분석하여 시뮬레이션 툴의 업그레이드 연구를 수행하고 있다. 본 논문에서는 비행체의 재질에 따라 변하는 열유속 측정의 불확실성에 대해 연구하였고, 그 원인에 대해 분석하였다. In development of supersonic vehicle, aerodynamic heating is one of important parameters. If the structure of a vehicle were designed with inaccurate aerodynamic heating data, stable flight of the vehicle couldn’t be assured. Inaccuracy of aerodynamic heating causes under- or over-design for vehicle structure, and it will affect the vehicle performance. Also, because ground test for aerodynamic heating for flight condition is not possible, simulation or calculation is the only method to know the heating environment during flight. The calculated heating data are being validated through flight test. In flight test, aerodynamic heating rates are measured using heatflux sensor, and compared with calculated values. The comparison of heating rates is using in upgrade of simulation tool. In this study, uncertainty of measured heating rate is investigated, and its reason is analyzed.
안효근,이은주,이미재,An Hyo-Keun,Lee Eun-Joo,Lee Mi-Jae 대한방사선사협회 2004 대한방사선사협회지 Vol.30 No.1
Purpose : To assess the mammographic findings of male breast disease. Materials and methods : Between Jan 1997 and May 2004, mammograms were obtained in 89 patients with male breast disease. Mammograms were retrospectively reviewed and correlated with med
자원이 제약된 유비쿼터스 장치의 보안을 위한 초경량 LEA 128비트 블록 암호화 아키텍처
안효근,강수동,Kanda Guard,류광기 국제차세대융합기술학회 2022 차세대융합기술학회논문지 Vol.6 No.1
초경량 LEA 128비트 블록 암호화 아키텍처는 자원이 제약된 유비쿼터스 장치에 보안성을 높일 방법으 로, 국가보안기술연구소에서 개발되고 국제표준화기구와 국제전기기술위원회에서 암호 분야 국제 표준으로 제정된 보안 알고리즘인 128비트 Lightweight Encryption Algorithm 알고리즘을 하드웨어 환경에서 설계하여 내부 레지 스터 재사용, 리소스 공유를 통해 LEA 암호화/복호화 모듈을 저 면적으로 구현하였다. Xilinx ISE 14.7 Virtex-5 를 이용하여 합성한 결과, 최대 주파수는 190.88MHz를 달성했으며 최대 128Mbps의 처리 속도를 가진다. 또한, 301개의 Flip-Flop, 1151개의 Look-Up-Table, 485개의 슬라이스로 구현되어 128비트 LEA 알고리즘을 저면적으 로 구현된 하드웨어 디자인을 제시한다. In this paper, we present an efficient hardware design of the 128-bit Lightweight Encryption Algorithm. LEA is a security algorithm developed by the National Security Technology Institute and established as an international standard for cryptography in the International Organization for Standardization and International Electrotechnical Commission for use in a hardware environment. The proposed architecture is based on internal register reuse and resource sharing to lower the LEA encryption/decryption crypto core’s area. The maximum frequency is 190.88MHz and has throughput of 128Mbps. In addition, 301 Flip-Flops, 1151 Look-Up-Tables, and 485 Slices are utilized to present a low-area 128-bit LEA hardware design.
위장관계의 위석, CBD역류, 식도정맥류의 원인과 방사선학적 소견
안효근(Hyo Keun Ahn),송호석(Ho Seok Song),이충모(Chung Mo Lee),최승극(Seung Keug Choi),이신호(Shin Ho Lee) 대한영상의학기술학회 2005 대한영상의학기술학회 논문지 Vol.2005 No.1
This study is intended to examine the causes, symptoms and treatment method of the bezoar, common bile duct(CBD) reflux, and Esophageal Varix which are frequently observed in UGI and then to briefly describe the form of lesion and an inspection method. 1. Cause and radiologic findings of bezoar Bezoar is a hard indigestible mass of material found in the stomachs of humans. In particular, it can be frequently observed in patients who have achalasia, the basal motor abnormality with pooling by many causes. It also can be easily formed in stomachs because foods are not digested andremains in stomachs when the anastomosis is narrow after the subtotal gastrectomy. 2. Cause and radiologic findings of CBD reflux Patients with CBD reflux have mostly diseases in the past CBD. Its causes include 1) a tumefaction of ampula of vater, 2) vater underaction, 3) inflammation of pancreatic cancer, and 4) the barium caused by the underaction in Endoscopic retrograde cholangiopancreatography(ERCP) after the subtotal gastrectomy or in UGI after ERCP or EST. 3. Cause and radiologic findings of esophageal varices Most causes of esophageal varices are the portal hypertension. It is mainly related to the increase of portal venous pressure by the obstruction of portal vein or thrombosis of splenic vein in liver cirrhosis patients.
( Mi Young Kim ),( Myung Hyun Cho ),( Ji Hyun Kim ),( Yo Han Ahn ),( Hyun Jin Choi ),( Il Soo Ha ),( Hae Il Cheong ),( Hee Gyung Kang ) 대한신장학회 2018 Kidney Research and Clinical Practice Vol.37 No.4
Background: Nephrotic syndrome (NS) is the most common glomerulopathy in children. Acute kidney injury (AKI) is a common complication of NS, caused by severe intravascular volume depletion, acute tubular necrosis, interstitial nephritis, or progression of NS. However, the incidence and risk factors of childhood-onset NS in Korea are unclear. Therefore, we studied the incidence, causes, and risk factors of AKI in hospitalized Korean patients with childhoodonset NS. Methods: We conducted a retrospective review of patients with childhood-onset NS who were admitted to our center from January 2015 to July 2017. Patients with decreased renal function or hereditary/secondary NS, as well as those admitted for management of other conditions unrelated to NS, were excluded. Results: During the study period, 65 patients with idiopathic, childhood-onset NS were hospitalized 90 times for management of NS or its complications. Of these 90 cases, 29 met the Kidney Disease Improving Global Outcomes criteria for AKI (32.2%). They developed AKI in association with infection (n = 12), NS aggravation (n = 11), dehydration (n = 3), and intravenous methylprednisolone administration (n = 3). Age ≥ 9 years at admission and combined use of cyclosporine and renin-angiotensin system inhibitors were risk factors for AKI. Conclusion: AKI occurred in one-third of the total hospitalizations related to childhood-onset NS, owing to infection, aggravation of NS, dehydration, and possibly high-dose methylprednisolone treatment. Age at admission and use of nephrotoxic agents were associated with AKI. As the AKI incidence is high, AKI should be considered during management of high-risk patients.