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Wireless piezoelectric strain sensing measurement using a frequency modulation technique
Yoon, Hwan-Sik,Kim, Se-hun,Kim, Min-Hyuck,Jung, Dongsoo,Kim, Joo-Hyung,Kim, Hyeon-Ju,Lee, Ho-Saeng Sage Science Press (UK) 2015 Journal of intelligent material systems and struct Vol. No.
<P>A simple wireless strain sensor using a frequency modulation technique is presented. The sensor employs a piezoelectric transducer that produces electric voltage as it is mechanically strained. When the piezoelectric sensor is connected to a single-transistor frequency modulation circuit, the sensor output voltage causes the modulation circuit frequency to shift. This modulated signal is then wirelessly transmitted to a remote station, where a demodulation circuit retrieves the buried strain measurement data in real time. Using this technique, a dynamic strain measurement is possible without any wire connection between the sensing point and the monitoring station. In order to demonstrate the performance of the wireless strain sensor and the measurement system, a wireless measurement of a vibrating cantilevered beam is experimentally conducted. This type of sensor has numerous applications in the strain or vibration measurement of moving or rotating structures such as turbo machinery.</P>
Yoon Hwan Kim(김윤환),Jang-Gun Oh(오장근),Hyang-Mi Shin(신향미),Young Saeng Kim(김영생) 대한두경부종양학회 2009 대한두경부 종양학회지 Vol.25 No.2
Dermoid cysts are benign neoplasm that is derived from both ectoderm and mesoderm. They may be found at various sites of the body, but are extremely rare to occur in the lower neck. We present the case of a 22-year old woman with a midline cystic mass anterior to the cervical trachea. The mass was excised under local anesthesia. Histopathologically the diagnosis was confirmed as a dermoid cyst.
강구에 의한 횡방향 충격을 받는 적층복합판의 충격 응답 거동
김문생(Moon-Saeng Kim),김남식(Nam-Shik Kim),박승법(Seung-Bum Park),백인환(In-Hwan Paik) 한국해양공학회 1993 韓國海洋工學會誌 Vol.7 No.2
본 연구는 강구에 의한 충격을 받는 유리/에폭시 적층복합판의 충격 응답 및 파동 전파 특성을 연구하는데 그 목적이 있다. 이를 위하여 고차전단변형이론에 기초한 동적 유한요소해석을 행하였으며, 저속 및 고속 충격 실험을 행하였다. 동적 유한요소해석으로 부터 접촉력의 변화와 강구의 반발 속도 그리고 충격에 의한 변형률 응답을 구하였다. 변형률 응답은 충격 실험의 결과와 비교하였다. 또한 고속 충격 실험의 결과로 부터 파동전파 속도를 계산하여 파동 전파 이론에 의한 결과와 비교 검토하였다.<br/> 그 결과, 충격 실험에서 구한 변형률 응답은 동적 유한요소해석에 의한 결과의 경향과 잘 일치하였으며, 충격 속도의 증가에 따른 최대접촉력의 증가율은 판의 크기가 클수록 증가하였다. 그리고 파동 전파 속도는 두 결과가 잘 일치하였으며, 접촉시간에 의한 영향으로 강구의 크기가 클 수록 빠르게 나타났다. The purpose of this paper is to analyze the impact response behaviors of glass/epoxy laminated composite plates subjected to the transversely impact of a steel ball. For this purpose, dynamic finite element analysis based on the higher-order shear defomation plate theory is used to compute the contact forces, rebound velocity of a steel ball, and dynamic strain response histories. And low-velocity and high-velocity impact experiments were conducted to compare the results and compute the wave propagation velocities.<br/> The results obtained from impact experiments are in good agreement with those of dynamic finite element analysis. Also the wave propagation velocities obtained from high-velocity impact experiments and wave propagation theory agree well, and wave velocities were higher in the smaller radius of steel ball.
Input Disturbance Estimation Using a General Structured Observer
Lee, Choong-Hwan,Shin, Min-Saeng,Kim, Hwan-Seong,Kim, Sang-Bong The Korean Society of Mechanical Engineers 2001 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.15 No.12
This paper presents the characteristics of a general structured observer and presents an estimation algorithm for a system with external disturbances which are added to the input of the system. By using a disturbance model, the general structured observer can estimate the states of the system is spite of disturbances, where the system is affected from external disturbances. Also, the general structured observer can include the function of a PI observer or high gain observer by properly adjusting the observer's gain matrices. The existence condition for the observer is derived, which can be checked by the system's observability condition and the pole-zero cancellation of the system's polynomial matrix. Through a numerical example, it is verified that the proposed observer is effective estimating the system and the input disturbance.
Chae, Ki-Hwan,Ju, Chang-Il,Lee, Seung-Myung,Kim, Byoung-Wook,Kim, Saeng-Youp,Kim, Hyeun-Sung The Korean Neurosurgical Society 2009 Journal of Korean neurosurgical society Vol.46 No.4
Objective : The purpose of this study was to evaluate the efficacy of a transforaminal suprapedicular approach, semi-rigid flexible curved probe, and 3-dimensional reconstruction computed tomography (3D-CT) with discogram in the endoscopic treatment of non-contained lumbar disc herniations. Methods : The subjects were 153 patients with difficult, non-contained lumbar disc herniations undergoing endoscopic treatment. The types of herniation were as follows : extraforaminal, 17 patients; foraminal, 21 patients; high grade migration, 59 patients; and high canal compromise, 56 patients. To overcome the difficulties in endoscopic treatment, the anatomic structures were analyzed by 3D reconstruction CT and the high grade disc was extracted using a semi-rigid flexible curved probe and a transforaminal suprapedicular approach. Results : The mean follow-up was 18.3 months. The mean visual analogue scale (VAS) of the patients prior to surgery was 9.48, and the mean postoperative VAS was 1.63. According to Macnab's criteria, 145 patients had excellent and good results, and thus satisfactory results were obtained in 94.77% cases. Conclusion : In a posterolateral endoscopic lumbar discectomy, the difficult, non-contained disc is considered to be the most important factor impeding the success of surgery. By applying a semi-rigid flexible curved probe and using a transforaminal suprapedicular approach, good surgical results can be obtained, even in high grade, non-contained disc herniations.