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고온가압소결을 이용한 YSZ-TiC 세라믹스 복합체의 제조와 특성
최재형,최지영,김성원,Choi, Jae-Hyung,Choi, Ji-Young,Kim, Seongwon 한국분말재료학회 (*구 분말야금학회) 2021 한국분말재료학회지 (KPMI) Vol.28 No.5
Zirconia has excellent mechanical properties, such as high fracture toughness, wear resistance, and flexural strength, which make it a candidate for application in bead mills as milling media as well as a variety of components. In addition, enhanced mechanical properties can be attained by adding oxide or non-oxide dispersing particles to zirconia ceramics. In this study, the densification and mechanical properties of YSZ-TiC ceramic composites with different TiC contents and sintering temperatures are investigated. YSZ - x vol.% TiC (x=10, 20, 30) system is selected as compositions of interest. The mixed powders are sintered using hot pressing (HP) at different temperatures of 1300, 1400, and 1500℃. The densification behavior and mechanical properties of sintered ceramics, such as hardness and fracture toughness, are examined.
최재형,장민욱,이윤우,윤종진,Choi, Jae Hyung,Chang, Min Wook,Lee, Yoon-Woo,Yoon, Jong Jin 한국항공운항학회 2017 한국항공운항학회지 Vol.25 No.3
The Nose Landing Gear(NLG) of Rotary Wing Aircraft is an essential equipment in Landing System for pilot to perform a flight mission. It supports the fuselage at ground and absorbs the impact from the ground when landing, thereby, these functions sustain operational capability for pilot and crew. However, the A aircraft caused stick-slip behavior when it was stationed on the ground. Therefore, this paper summarizes pilot comment in operation which are classified by cause of occurrence and the troubleshooting process about each comment. It also describes design improvements which was derived from troubleshooting and suggests verification results of flight test.
급성 일산화탄소 중독 환자에서 발생한 양하지 말초 운동신경병증 1례
최재형 ( Jae Hyung Choi ),임훈 ( Hoon Lim ) 대한임상독성학회 2015 대한임상독성학회지 Vol.13 No.1
Carbon monoxide (CO) intoxication is a leading cause of severe neuropsychological impairments. Peripheral nerve injury has rarely been reported. Following are brief statements describing the motor peripheral neuropathy involved bilateral lower extremities of a patient who recovered following acute carbon monoxide poisoning. After inhalation of smoke from a fire, a 60-year-old woman experienced bilateral leg weakness without edema or injury. Neurological examination showed diplegia and deep tendon areflexia in lower limbs. There was no sensory deficit in lower extremities, and no cognitive disturbances were detected. Creatine kinase was normal. Electroneuromyogram patterns were compatible with the diagnosis of bilateral axonal injury. Clinical course after normobaric oxygen and rehabilitation therapy was marked by complete recovery of neurological disorders. Peripheral neuropathy is an unusual complication of CO intoxication. Motor peripheral neuropathy involvement of bilateral lower extremities is exceptional. Various mechanisms have been implicated, including nerve compression secondary to rhabdomyolysis, nerve ischemia due to hypoxia, and direct nerve toxicity of carbon monoxide. Prognosis is commonly excellent without sequelae. Emergency physicians should understand the possible-neurologic presentations of CO intoxication and make a proper decision regarding treatment.
최재형(Jae Hyung Choi),임현규(Hyun-Gyu Lim),윤종진(Jong Jin Yoon),강득수(Deuk Soo Kang) 한국항공우주학회 2017 韓國航空宇宙學會誌 Vol.45 No.4
한국형 기동헬기(KUH-1)에 적용된 휠 브레이크 조립체는 브레이크 계통 구성품으로 조종사의 임무 수행에 핵심적인 장비이다. 휠 브레이크 조립체는 항공기의 안전한 착륙성능을 만족시키기 위해 항공기 활주이동, 차동 제동 및 주기 제동 기능이 요구된다. 그러나 KUH-1 양산 운용 중에 타이어 스키드와 마모 현상이 발생하였으며, 해당 결함 발생 시 더이상 비행을 할 수 없기 때문에 항공기 가동률 저하에 큰 원인이 된다. 본 논문에서는 휠브레이크 조립체의 운용과정에서 발생한 결함사항의 발생 원인을 파악하고, 고장탐구 수행과정을 정리하였다. 또한, 고장탐구 내용을 바탕으로 도출한 설계개선 사항과 개선사항에 대한 비행시험 검증 결과를 함께 기술하였다. The KUH-1’s Wheel Brake Assembly which is Brake System is an essential component to perform flight mission for pilot. It has function of taxing, differential braking and parking to sustain landing capability. However, the skid and abrasion of tire were occurred in mass-produce operation. Also, if it is occurred on the ground, the flight can not be performed. In this case, the defect is a major cause of the decrease in the operation rate of aircraft. In this paper, the cause of the defect in flight was identified and the failure process was organized. Also, it describes design improvements which was derived from troubleshooting and suggests verification results of flight test.
회전익 항공기 안전 확보를 위한 주륜완충장치 결함 개선연구
최재형(Jae Hyung Choi),장민욱(Min Wook Chang),임현규(Hyun-Gyu Lim),이제석(Je Suk Lee) 한국항공우주학회 2017 韓國航空宇宙學會誌 Vol.45 No.6
회전익 항공기에 적용된 주륜완충장치는 착륙계통 장비로서 조종사의 임무 수행에 핵심적인 장비이다. 주륜완충장치는 항공기가 지상에 있을 때 동체를 지지해주며 착륙 시 지면으로부터 오는 충격을 흡수함으로서 조종사 및 병력의 작전 운용능력을 만족시킨다. 그러나 A 항공기 지상 계류 시 항공기의 비대칭 현상과 누유 현상이 발생되었다. 따라서 본 논문에서는 주륜완충장치의 운용 시 발생한 결함사항을 발생원인 별로 분류하고, 각 지적 사항에 대한 고장탐구 수행과정을 정리하였다. 또한, 고장탐구 내용을 바탕으로 도출한 설계개선 사항과 개선사항에 대한 검증 결과를 함께 기술하였다. The Main Landing Gear(MLG) of Rotary Wing Aircraft is an essential equipment in Landing System for pilot to perform a flight mission. It supports the fuselage at ground and absorbs the impact from the ground when landing, thereby, these functions sustain operational capability for pilot and crew. However, the A aircraft caused asymmetry and leakage hydraulic when it was stationed on the ground. Therefore, this paper summarizes pilot comments in operation which are classified by cause of occurrence and the troubleshooting process about each comment. It also describes design improvements which was derived from troubleshooting and suggests verification results of flight test.
신재생에너지가 연계된 구내 DC 배전망에서의 고조파와 잡음 특성
최재형(Jae-Hyung Choi),정범진(Bum-Jin Jung),최동진(Dong-Jin Choi),이재형(Jae-Hyung Lee),손성용(Sung-Yong Son) 대한전기학회 2010 대한전기학회 학술대회 논문집 Vol.2010 No.7
DC 배전은 디지털 부하가 많은 현대 구내 환경에서 AC배전 대비 전력 변환의 효율성과 운영의 신뢰성 등의 측면에서 최근 각광을 받고 있다. 보편적으로 DC 체계가 지속적으로 변화되는 AC 체계와 비교하여 더욱 안정적이고 좋은 환경을 가지고 있을 것으로 추정되며 새롭게 도입되는 신재생에너지 연계 운영의 측면에서 보다 좋은 통신 환경을 제시할 것으로 기대된다. 본 연구에서는 신재생에너지가 연계된 구내 DC 배전망에서 고조파와 잡음 특성을 측정함으로써, DC 배전망에서 전력 · 통신 융합 운영의 신뢰성과 고려사항을고찰하였다
Segmental Arterial Mediolysis으로 인한 신경색과 혈복강
최재형 ( Jae Hyung Choi ),조영순 ( Young Soon Cho ),김재우 ( Jae Woo Kim ),이정원 ( Jung Won Lee ),문형준 ( Hyung Jun Moon ) 대한응급의학회 2012 대한응급의학회지 Vol.23 No.6
This article reports a patient with both a renal infarction and acute intra-abdominal hemorrhage secondary to a rare vascular disease, segmental arterial mediolysis. The patient was a 37-year-old male who presented with acute right flank pain. Abdominal and pelvic computerized tomography (CT) showed a right renal infarction. After three days, the right flank pain had diminished but left flank pain began. Visceral angiography revealed a wedge shape perfusion defect at the mid pole of the left kidney, suggesting a left renal infarction but there were no definite perfusion defects at the right kidney. After ten days, the patient complained of abdominal pain and 2 episodes of syncope. Abdominal CT revealed active bleeding from the splenic artery and a large amount of hemoperitoneum. After emergency embolization, the patient`s were stabilized. After 28 days, his condition was improved and discharged without complications. The angiographic and laboratory findings were consistent with a diagnosis of segmental arterial mediolysis involving the renal and splenic artery. This is the first case report of clinical progression related to segmental arterial mediolysis requiring emergent coil embolization.