다중경로 페이딩채널에서 가상가지기법을 적용한 16-QAM 시스템의 MRC 다이버시티 성능 해석

김태영,고봉진,박승엽 국립7개대학공동논문집간행위원회 2003 공업기술연구 Vol.3 No.-

In this paper, the error rate performance of MRC diversity for 16-QAM which have high bandwidth efficiency has been analyzed in consideration of correlated Nakagami-Fading and cochannel interference in mobile communication channel. Conventional analysis of MRC diversity technique in correlated Nakagami-Fading is complicated since the instantaneous SNR's are correlated and fading parameter's are not necessarily equal. Therefore, virtual branche technique was introduced. From the results, an increase of physical branch number provides the performance improvement of about 5~11[dB] when diversity technique applied to obtain error rate of 10-3. Also, an increase of correlation coefficient degrade error performance. When the influence of cochannel interference was considered, the error performance of 16-QAM remarkably degraded.

전기화학법에 의해 형성된 Ti 양극산화피막의 특성

김태영,손원우,권태엽,강인규,김교한 大韓齒科器材學會 2002 대한치과재료학회지 Vol.29 No.3

The effects of electrolyte concentration and current density on the behaviour of volt-time curve of the anodizing, morphology, roughness, crystallinity and composition of the oxide layer were studied. Microstructural morphology, crystallinity, composition and surface roughness of oxide layer were analyzed by observed by scanning electron microscopy(SEM) and X-ray diffractometry(XRD), Energy-dispersive spectrometer(EDS), Electron Probe Micro Analyzer(EPMA)and roughness tester, respectively. The results of this study showed that the voltage incresed as the anodizing time increase. The growth of the oxide film developed a barrier layer to a pore-like layer with an increasing of current density, arising a spark discharge. On the morphology of anodic oxide layer the number and size of porosity was increased by increasing anodizing time at a constant concentration of electrolyte. The size of porosity and the roughness of the anodic oxide layer were increased by the increasing of concentration of electrolyte. The anodic oxide layer obtained in the conditions of this experiment was identified as anatase. The crystallinity of oxide layer was decreased by increasing the concentration of electrolyte at constant current density, and increased by the increasing current density at constant electrolyte concentration. In the EPMA analysis of anodic oxide layer, the concentration of phosphorous was increasing the electrolyte concentration and increasing the final voltage at constant electrolyte concentration, The ratio of O/Ti of the oxide layer obtained in this experiment was near 2 confirming this oxide layer was TiO₂

상아질 접착제의 적용이 법랑질 접착에 미치는 영향

권태엽,권용훈,김교한,송근배 大韓齒科器材學會 2003 대한치과재료학회지 Vol.30 No.2

The objective of this study was to evaluate the effect of various enamel surface treatments on the bond strength of a composite resin to enamel (n=15). Ground bovine enamel specimens were divided into seven groups. A composite resin (Z250. 3M) was bonded to the specimens using different enamel surface treatments. Four groups examined the effect of application of all-in-one adhesives (Prompt L-Pop (POP), One-Up Bond F (ONE)) with respect to static priming (SP) or dynamic priming (DP). The other two examined use of the POP and ONE after phosphoric acid etching (PE). And the control group provided bond strength of the composite resin to phosphoric acid etched enamel with a resin bonding system (Single bond, SB, 3M). Shear bond strengths for the specimens were measured after 24 hours storage in water at 37 ℃. Effects of various surface treatments on enamel were examined by SEM. Dynamic priming resulted in higher enamel bond strengths than static priming and the best bond strengths were obtained when the enamel was etched with phosphoric acid. SEM analysis showed that depth of etching was related to the bond strengths measured. The enamel etch pattern after static priming showed little retentive surfaces. After dynamic priming, the enamel rod structure has become apparent in the shallow etch. SEM view showed that the resin tags and resin penetration were related to the bond strengths measured. SEM showed minimal resin penetration into enamel following static priming. After application of adhesives to phosphoric acid etched enamel, SEM showed more extended tags that are reflective of the deeper etch pattern.

휴대폰용 외관프레임의 전해 디버링 특성 평가

신태희,백승엽,이은상 한국공작기계학회 2009 한국공작기계학회 춘계학술대회논문집 Vol.2009 No.-

For the graceful design and durability, cellular phone frame is been changing from the external to internal. Most of external frames are made by aluminium alloy, because that is required to be light and cheap while that should be hard. Due to the mass product using injection molding method or die casting method, these external frames have a lot of burrs. Moreover, microscopic burrs affect for parts badly, how that makes electric jamming. In addition, microscopic burrs could injure workers or users. In this paper, for the removal of microscopic burrs on the cellular phone external frame, electrochemical deburring is conducted and electrochemical conditions are researched.

실험적 동소성 전 간이식후 이식간의 초기 간 기능 예측 지표에 관한 연구 : 조직검사를 통한 보존 손상정도와 혈청 젖산, 혈중 암모니아 및 동맥혈 pH의 변화 Analysis of preservation injury seen in protocol biopsy, change of plasma lactate, ammonia and arterial pH

권태원,이승규,공경엽 울산대학교 의과대학 1996 울산의대학술지 Vol.5 No.1

One of the most dramatic advances in the field of liver diseases in the twentieth century is the successful transplantation of the human liver, now on a worldwide scale. With the developments of new surgical techniques, transplantation immunology, and the capability to prevent and to control infections, it has been developed and become an acceptable therapy for patients with irreversible fiver diseases. After transplantation, it is of paramount importance to predict the function of allograft, which affects the result of transplantation and patient's survival. After transplantation, the first two or three days are always characterized by a marked elevation of transaminase levels and hepatocellular failure. Poor early graft function(PEGF) has a clinical spectrum characterized by varying degrees of coma and renal failure associated with lactic acidosis, persistent coagulopathy, poor bile production and marked elevations of ALT and AST. The occurrence of PEGF is unpredictable : its most severe form, requiring retransplantation and termed primary nonfunction(PNF), is seen following approximately 10 % of transplant procedures. Possible etiologic factors include liver disease in the donor, technical errors, ischemic injury, and immunologic damage. Ischemic injury is inherent in the process of organ retrieval, storage, and implantation and is considered as the main factor to contribute to PEGF. Protocol biopsies of liver allografts obtained during backtable preparation and 1 to 2 hours after revascularization in the recipients have detailed the sequential histologic events that occur after reperfusion. Once the liver is revascularized, quick assessment of its quality from metabolic studies is far more practical than a postperfusion biopsy. The purpose of this experiment is to observe whether protocol biopsy of allografts(during backtable procedure and 2 hours after revascularization), serum 1actate, serum ammonia and arterial pH would be used as the indicators of initial graft function after canine orthotopic whole liver transplantation. The experiment consisted of ten cases of orthotopic whole liver transplantation in mongrel dogs using venovenous bypass. The arterial blood were taken as just after anesthesia, anhepatic period, 15 minutes, 2 hours, and 6 hours after reperfusion in recipients. Protocol biopsies of allograft were taken at backtable preparation and 2 hours after reperfusion. We grouped the recipients according to the result of survival time(group A ;short survival time group, B ; long survival time group) and according to the degree of preservation injury(group C ; histologically no preservation injury group, D ; histologically preservation injury group). And we analysed the change of parameters (serum lactate, ammonia, ALT, AST, arterial pH, histologic finding) between group A and B and between group C and D. To evaluate the statistical significance, we used the SAS program and IBM - PC. In conclusion, we found out that preservation injury seen in protocol biopsy would be one of the indicators to predict the initial function of allograft and the pattern of change of serum lactate and blood ammonia are another possible indicators. And we also found out that immediate correction of metabolic acidosis which usually happens just after reperfusion would be related to the result of transplantation.

금합금의 프라이머 처리가 교정용 브라켓의 접착에 미치는 영향

류동범,권태엽,권용훈,김교한 大韓齒科器材學會 2003 대한치과재료학회지 Vol.30 No.3

The purpose of this study was to compare the bonding strength and the interfacial micromorphology of two surface modification of gold alloys in direct bonding of orthodontic brackets. Flat tab of cast gold alloys (n= 120) were subjected to either of two surface treatments: 1.50㎛ aluminum oxide sandblasting, and 2. sandblasting plus adhesive primer for noble metal. Orthodontic brackets (RMO Co.) were bonded directly with Superbond C&B (Sun Medical Co. Ltd.), or Transbond XT (3M Unitek), or Ortho One (Bisco). All specimens were stored in distilled water at 37℃ for 24 hours, and then the tensile bond strength testing was performed in a Instron test machine. Bond failure sites were classified by a modified Adhesive Remnant Index (ARI) system. The results showed that sandblasting plus adhesive primer for noble metal produced stronger bonds to gold alloy than sandblasting only in all cases (Superbond C&B, Transbond XT, Ortho One). Superbond provided significantly stronger bonds to gold alloy than the others. Bond failure of Superbond to sandblast only and sandblast plus adhesive primer for noble metal to gold alloy occurred at the bracket/adhesives interface, whereas bond failure of the others occurred at the gold/adhesive interface. The clinical implications of these findings are discussed.

임플란트 보철물에서 임시 접착용 시멘트의 인장결합강도 비교

서경숙,권태엽,권용훈,김교한 大韓齒科器材學會 2003 대한치과재료학회지 Vol.30 No.4

The major disadvantage of cement-retained implant-supported superstructure is difficulty of retrievability. Sometimes, it is recommended that proetheses be provisionally cemented to implant abutment in order to ebaluate occlusion, screw loosening and tissue reaction. The retention of the provisional luting cementedusually employed in this case is considered to be important. This study compared tensile bond strength of gold crowns cemented to machined titanium implant abutments with three provisional luting cements. Also the effect of petrolatum and thermocycling on tensile bond stength were evaluated. Tensile bond strength of provisional luting cement were as follows with the decreasing order of Eugenol (13.06±1.544 kgf), Temp-Bond (9.41±0.737 kgf), Cavex (8.04±0.974 kgf), and Temp-bond with petrolatum (5.28±0.800 kgf). The addition of petrolatum in Temp-bond decreased tensile bond strength significantly (p<0.01). After thermocycling of 1,500 cycles, the tensile bond strengths of the cements were decreased with the order of Nogenol (10.87±3.031 kgf), Temp-Bond (8.1±0.667 kgf), Cavex (7.33±1.103 kgf), Temp-bond with petrolatum (4.88±1.348 kgf). The mocycling decreased the bond strength of Temp-Bond significantly, with no effects no other cements (p<0.01).

Vital Bleaching이 법랑질 접착에 미치는 영향

김종해,권태엽,권용훈,김교한 大韓齒科器材學會 2003 대한치과재료학회지 Vol.30 No.4

The objective of this in vitro study was to evaluate the effect of bleaching on the composite to enamel bond and surface hardness change. Extracted human premolars were treated with 35% hydrogen peroxide (Sigma Chemical Co, USA) for 1hr/day at 0, 3, 6 and 9 day respectively. For the obsrvation of surface mophology alteration due to the treatment with hydogen peroxide, a SEM (S-4300, Hitachi, Japan) was used. The specimens were ground flat using serial SiC papers and ground ultra-finely using a 0.1㎛ diamond compound paste. To measure the microhardness, five non-carious premolars were ground using SiC papers and ten indentations were made on the surfacd with Vickers hardness tester (FM-7 FUTURE-TEC Inc., Japan). To evaluate shear bond strength, composite was bonded with One Up Bond-F, Prompt L-Pop, AQ Bond to the non-bleached and bleached enamel surface of sixty non-carious premolars. The bonding procedure is postponed for 1 week after bleaching and shear bond strength was measured. All specimens with a SEM. Bleaching created some enamel porosity but the teeth showed nonsignificant morphological chonge as bleaching time increased from SEM analysis. Most microhardness change occured on the first day of bleaching. Bleaching with 35% hydrogen peroxide did not result in significant change in the shear bond strength of composite resin to enamel. In the shear bond strength test, the fractured surfaces of specimens showed mixed adhesive and cohesive failure behavior.

난소절제후 Estrogen을 투여한 흰쥐 대동맥에서 Protein Kinase C-α와 Fas 발현의 변화

이왕수,이상엽,안지현,송영빈,김학진,이광재,유재격,김상욱,김태호,김치정,류왕성 중앙대학교 의과대학 의과학연구소 2001 中央醫大誌 Vol.26 No.3

Estrogen is believed to decrease coronary artery disease. Protein kinase C-α(PKCα)appear to be important in signal conduction pathways. Estrogen treatment increases catalytic activity of PKCα,and activation of PKCαcan modulate estrogen receptor levels and responsiveness. And it was reported that activation of PKC can protect cells from apoptosis induced by Fas ligation. But the beneficial effect of estrogen on PKCαwas not clearly demonstrated. The objective of this study was to evaluate the role of PKCαafter ovariectomy and estrogen therapy in rat aorta. The results were summarized as below: 1. The significant pathological changes were not observed in the rat aorta irrelevant to ovariectomy and estrogen therapy. 2. The expression of Fas was decreased in the aorta of estrogen-treated rats than that of ovariectomized rats without estrogen therapy. 3. Increased expression of PKCαwas more marked in the aprta of estrogen-treated rats than that of ovariectomized rat without estrogen therapy. In conclusion,PKCαmay be important in signal conduation pathway on the effect of estrogen. Activation of PKCαby estrogen reduced Fas expression, suggesting that PKCαactivation may play a role in protection against atherasclerosis. Further studies are needed to elucidate the role of PKCαafter estrogen therapy.

Nitinol 형상기억합금 전해가공의 전해액 영향분석

김백겸,신태희,백승엽,이은상 한국공작기계학회 2008 한국공작기계학회 춘계학술대회논문집 Vol.2008 No.-

Electro-chemical Machining, the anodic dissolution process is able to achieve wanted a sharp shape and high quality surface without contact with workpiece and low heat effect using electrochemical reaction between anode and cathode. In hence this process useful to apply micro structure. A shape memory alloy for micro-structure and micro industrial technique, Nitinol is composed of approximately 55% Nikel and 45% Titanium by weight. This material is able to function as to transform specific shape from a certain deformation when the alloy is heated. Therefore Nitinol is used for several industries such as a medical industry, a aerospace, electrical application on a part of micro structure. In this paper, effect of electrolyte is studied on electrochemical machining for Nitinol shape memory alloy, copper is used for electrode, diameter and depth are measured as a extent of processing using optical microscope.