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Fiber-reinforced composite post removal using guided endodontics: a case report
Cho Changgi,Jo Hyo Jin,하정홍 대한치과보존학회 2021 Restorative Dentistry & Endodontics Vol.46 No.4
Although several techniques have been proposed to remove fiber-reinforced composite (FRC) post, no safe and efficient technique has been established. Recently, a guided endodontics technique has been introduced in cases of pulp canal obliteration. This study describes 2 cases of FRC post removal from maxillary anterior teeth using this guided endodontics technique with a dental operating microscope. Optically scanned data set from plaster cast model was superimposed with the data set of cone-beam computed tomography. By implant planning software, the path of a guide drill was selected. Based on them, a customized stent was fabricated and utilized to remove the FRC post. Employing guided endodontics, the FRC post was removed quickly and safely with minimizing the loss of the remaining tooth structure. The guided endodontics was a useful option for FRC post removal.
이단압축을 이용한 이산화탄소 사이클의 냉방성능에 관한 연구
조홍현(Honghyun Cho),류창기(Changgi Ryu),김용찬(Yongchan Kim),조성욱(Sungwook Cho) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5
To improve of the cooling performance of a CO₂ cycle, a CO₂ air-conditioner using two-stage compression cycle was tested with a variation of compressor frequency ratio. The cycle options include a basic cycle, a cycle with an intercooler, a cycle with an IHX(internal heat exchanger), and a cycle with an intercooler and IHX. The results show that the cycles with the intercooler, IHX, and intercooler and IHX improved the cooling performance significantly at all frequency ratios. The cycle with the intercooler, the cycle with the IHX and the cycle with the intercooler and IHX improved the cooling COP by 7, 12, and 15% over the basic CO₂ cycle.
Hu Jin,Changgi Cho,Nah-Oak Song,Dan Keun Sung IEEE 2011 IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS Vol.10 No.2
<P>Orthogonal frequency division multiple access (OFDMA) systems, such as IEEE 802.16e/m and 3GPP Long Term Evolution (LTE), require significantly large signaling overhead for delivering small-sized delay-sensitive traffic such as voice over IP (VoIP) service. It may result in a significant decrease in the spectral efficiency. In order to overcome this drawback, recently, a persistent scheduling scheme has been standardized in standard bodies. In order to reduce the signaling overhead, the modulation and coding scheme (MCS) is set to be fixed during a burst period for the persistent scheduling procedure and an incomplete transmission, if it occurs, is recovered by a hybrid automatic repeat request (HARQ) scheme. In this paper, considering the HARQ retransmissions, we propose a rate selection scheme for the persistent scheduling satisfying given quality of service (QoS) requirements. In our proposed rate selection scheme, we consider two important factors which were not considered in previous HARQ-related work: time-correlations of the wireless channel in the HARQ retransmissions and the resource usage of signaling overhead. Numerical results show that the proposed rate selection scheme can efficiently enhance the utilization of radio resources compared to the conventional schemes.</P>