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항공기 실측 진동 데이터를 이용한 환경시험 규격 생성 연구
김충현,송기혁 한국군사과학기술학회 2021 한국군사과학기술학회지 Vol.24 No.3
Developers generally use test standards suggested by military standards such as MIL-STD-810G when performing vibration tests in the materiel development. However, according to MIL-STD-810G, it is recommended to test by tailoring the test standard suitable for the developed materiel, and it is specified to apply the suggested test standard only when there is difficulty in tailoring. In addition, the test standards presented by MIL-STD-810G are standards created under operating conditions different from the actual operating environment of each developed materiel, so the test according to this standard may be excessive or understated. Therefore, the developer must create an appropriate vibration test standard for the developed materiel as similar to the operating conditions as possible. In this paper, the procedure for creating the functional test standard and durability test standard suitable for the operating environment of the equipment to be mounted on the propeller aircraft under development is described, and the created standard is introduced.
김충현,안효석,정태형,Kim, Chung-Hyeon,An, Hyo-Seok,Jeong, Tae-Hyeong 대한기계학회 2001 大韓機械學會論文集A Vol.25 No.11
Wear characteristics of Nylon and acetal pinions against steel gears for different pitch line velocities was studied with a power circulating gear test rig under unlubricated condition. Specific wear rate was measured as a function of tooth number, module, tooth width and total revolution. The worn tooth surfaces were examined with a profile projector. The Nylon pinion showed lower specific wear rate than the acetal pinion. However, the Nylon pinion was fractured at high tooth loads, whereas the acetal pinion exhibited a steady wear behavior. The wear characteristics of Nylon pinion varied significantly with the Pitch line velocity. Wear occurred most severely at the tooth tip and the region immediately below the pitch line of pinion. The dominant wear mechanisms were adhesion and abrasion.
김충현,안효석,정태형,Kim, Chung-Hyeon,An, Hyo-Seok,Jeong, Tae-Hyeong 대한기계학회 2000 大韓機械學會論文集A Vol.24 No.3
Nylon, Polyacetal and PTFE were studied to gain a better understanding of their tribological behavior. Wear tests were conducted with reciprocating motion under dry sliding conditions. Friction coefficient and specific wear rate were measured as a function of sliding distance. The worn surfaces were examined with a Scanning Electron Microscope(SEM). Polyacetal showed lowest specific wear rates and PTFE exhibited lowest friction coefficient. The dominant wear mechanism found were adhesion and abrasion.
전산화단층촬영 및 초음파촬영을 이용한 방광암의 병기결정
김충현 대한영상의학회 1987 대한영상의학회지 Vol.23 No.5
Accurate staging of bladder cancer is the important factor affecting its management and prognosis. Clinical staging of bladder cancer consists of cystoscopic biopsy and vimanual examination during anesthesia, but this is crude and has a high rate of error. More recently, computed tomography and ultrasonography have been new means for the noninvasive staging of bladder cancer. CT is shown to be fairly accurate in demonstrating extramural tumor extension, but it tends to overstage and cannot differentiate between mucosal and muscular involvement because of its limited tissue specificity. However, US may be able to differentiate between mucosal and muscular involvement because of its high tissue specificity, and can easily provide information about involvement because of its high tissue specificity, and can easily provide information aout involvement of prostate or seminal vesicles. RESULTS : 1. Overall accuracy of CT staging in bladder cancer was77%. 2. In 15 cases of CT stage B or less cancer, 14 were correct, but it was impossible to differentiate between stage O & A, B1 or B2. 3. In 7 cases of CT stage C cancers, 3 were correct, and in 4 cases of CT stage D cancers, 3 were correct. 4. Overall accuracy of US staging in bladder cancer was 69%. 5. In 8 cases of US stage B2 or less cancers, 5 were correct, and it was possivle to differentiate batween stage O & A, B1 or B2. 6. In 3 cases of US stage C cancers, 2 were correct, and in 2 cases of US stageD cancers, 2 were correct. As a result, authors considered US as a valuable addition to CT in staging of bladder cancer.
A Micro Tribotester for MEMS Elements
김충현,안효석 한국생산제조학회 2006 한국생산제조학회지 Vol.15 No.4
A computer-controlled micro tribotester has been developed to investigate the friction and wear characteristics of thin coatings, which can be applied to silicon-based materials. In the developed system, a step motor gives a reciprocating movement and an electromagnet applies a load between a ball and a plate specimen. Test results confirmed that the application of load in the range of 0.03 ~ 1.8N and with a sliding speed of 4.44 ~ 7.70mm/s was successfully accomplished. Advantages of the developed micro tribotester are: (1) realization of micro load and displacement applicable to microelectromechanical systems(MEMS) using DC motor and electromagnet (2) continuously variable load and reciprocating speed; and (3) high reliability, which allows for unattended use for long periods.
김충현,서홍석,이형우,김진년 韓國食品流通學會 2018 한국식품유통학회 학술대회 Vol.- No.하계
As the National Statistical Office replaced the beef statistics with beef traceability data from September 2017, it is necessary to develop an economic model of Hanwoo based on the data. This study developed an advanced supply-demand model of Hanwoo by utilizing endogenous advantages of the data. The model was constructed by using a mixture of cohort factor method and econometric method. We estimated cohort factors, such as mortality, slaughter, and sex ratio at birth, and attempted to build a stable model using the cohort factors. On the other hand, the econometric methods were used because the farm household’s intention to breed and slaughter as well as the intension of consumption are determined by various economic factors. The model developed in this study is expected to be useful as a tool to forecast the Hanwoo market and establish the preemptive supply and demand policies.