반복적인 펄스레이저 조사에 의한 알루미늄 합금의 표면상태 변화분석

최성호,김정석,장경영,신완순,Choi, Sung-Ho,Kim, Chung-Seok,Jhang, Kyung-Young,Shin, Wan-Soon 한국군사과학기술학회 2011 한국군사과학기술학회지 Vol.14 No.5

The objective of this study is to investigate the thermal behavior on material surface and the variation in the surface morphology of aluminum 6061 alloy by the Nd:YAG pulsed-laser irradiation. First, we predicted the surface temperature variation during pulsed-laser irradiation by using the two dimensional finite element analysis. When the pulsed-laser of 133 mJ energy and 5 ns pulse duration is irradiated on the surface of aluminum alloy, the material surface is thought to be melting because the surface temperature rises steadily up to about $660^{\circ}C$ exceeding the melting point. Also, the experimental results show that the solidification microstructure has been developed clearly after surface melting. Second, the diameter of melted zone was analysed by finite element analysis and measured by OM(Optical Microscopy). It increased logarithmically with increase in the number of laser irradiation. In addition, AFM(Atomic Force Microscopy) measurement showed an increase in the average surface roughness during pulsed-laser irradiation.

단말기 보조금이 소비자 편익에 미치는 영향 분석

최성호,한성수,안지영,Choi, Sung-Ho,Han, Sung-Soo,Ahn, Ji-Young 한국통신학회 2005 韓國通信學會論文誌 Vol.30 No.10B

In the mobile telecommunication industry, the effects of handset subsidies are revealed as two aspects. There are the activation of service and handset market and the acceleration of related technology development in the desirable aspect. On the other hand, the rise in service rates and the squandering of the related resources in the undesirable one. There have been a lot of researches that disclose the desirable or undesirable factors through the qualitative methods. However, the quantitative studies are rare. In this study, we consider the positive, from the increase of demand, and negative, from the increase of service rates, effects on consumers' benefit attendant handset subsidies. Then, we quantitatively compared between the positive and negative effects and analyze the direct effects of consumers' benefit of handset subsidies, and figured out that the direct effect is not expected to be positive. 이동통신산업에서 단말기보조금의 효과는 이동통신서비스와 단말기 시장의 활성화와 관련 기술개발의 촉진 등과 같은 긍정적인 효과와 서비스 요금의 상승, 과도한 자원의 낭비, 유효경쟁에 미치는 악영향 등의 부정적인 효과를 동시에 가진다. 이러한 이유로 단말기보조금에 시행에 관한 수많은 논란이 계속되고 있고, 특히 새로운 형태의 이동통신서비스의 시작을 앞두고 있는 근래에는 단말기보조금의 재시행을 두고 그 논란이 더욱 증대되고 있다. 이를 반영하듯 그 동안 많은 연구들이 단말기보조금이 관련 산업 및 사회후생에 미치는 효과를 분석하여 왔다. 그러나 이러한 연구들의 대부분은 단말기보조금의 영향 요소를 파악하고 이에 대한 정성적인 분석에 중점을 두고 있었기 때문에 단말기보조금의 효과에 대한 정량적인 연구를 위한 노력은 지극히 부족한 실정이다. 본 연구에서는 단말기보조금 시행의 직접적인 영향을 받는 소비자 수요증가로 인한 정의 효과와 지급되는 보조금 보전을 위한 이용요금의 인상 등으로 인한 부의 효과를 계량적으로 비교함으로써 과연 단말기 보조금의 직접적인 효과가 소비자 편익에 어느 정도의 영향을 주고 있는지를 분석하여 현 단계에서 그 효과가 긍정적이라고 기대하기 어렵다는 결론을 얻었다.

다중 대역 전송 시스템을 위한 전치왜곡 알고리즘

최성호,이병환,이철수,정의림,Choi, Sung-Ho,Lee, Byung-Hwan,Lee, Chul-Soo,Jeong, Eui-Rim 한국정보통신학회 2012 한국정보통신학회논문지 Vol.16 No.1

본 논문에서는 다중 대역 전송 시스템에서 광대역 전력 증폭기의 선형화를 위한 새로운 전치왜곡 기법을 제안한다. 특히, 한 시스템에서 동시에 다중대역/다중모드 신호를 전송함에 있어 다중대역 신호가 하나의 전력 증폭기에 의해 증폭되어 전송되는 시스템을 고려한다. 상호 대역 간 비선형 왜곡을 포함한 비선형 특성을 보상하기 위하여, 본 논문에서는 다중 전치왜곡기 블록을 갖는 새로운 전치왜곡 구조를 제안하며, 다중 전치왜곡기의 계수를 동시에 갱신하는 적응 알고리즘을 제안한다. 제안하는 다중 대역 모델을 검증하기 위하여 상용 증폭기를 사용하여 증폭기 모델을 추출하였으며, 추출된 모델을 기반으로 제안한 알고리즘을 모의실험을 통해 검증하였다. 모의실험 결과는 제안 알고리즘이 효과적으로 다중 전치왜곡기의 계수를 구할 수 있으며, 다중 대역을 효과적으로 선형화 할 수 있음을 보여준다. New digital predistortion technique is proposed for power amplifier linearization in multi-band transmission systems. We consider a system where muli-band signals are combined and amplified by a single power amplifier (PA). In this system, the PA output is distorted by the nonlinear cross-products between different band signals as well as their own nonlinear self-products. To compensate these nonlinear effects, we propose a multiple PD structure. Each PD removes the nonlinear cross-products and self-products to mitigate the spectral regrowth for the corresponding band. Since the PD parameters for different bands are linked together, it is difficult to find the PD parameters separately. Thus, we propose an iterative method for finding the PD parameters jointly. For demonstration of the proposed method, multi-band characteristics of PA are extracted from a commercial power amplifier. Computer simulation was executed based on the PA parameters. The simulation results show that the proposed method can effectively linearize the PA and remove spectral regrowth at each signal band.

RF 전자기장 생체 영향 연구 문헌에서 노출량 메타분석을 위한 통계적 기법

최성호,김남,Choi, Sung-Ho,Kim, Nam 한국전자파학회 2003 한국전자파학회논문지 Vol.14 No.12

본 논문에서는 RF 전자기장을 사용한 동물 및 세포 실험에서 전자기장 노출량의 정확성을 평가할 수 있는 방법을 제안하였다. 이를 위해 전자파 흡수율(SAR)을 전자기장 노출량의 단위로 사용한 동물 및 세포 연구 논문과 휴대폰 및 PDA에 대한 전자파 흡수율 시험 성적서를 대상으로 출력 전력, 전력 밀도 등과 SAR의 상관 관계 및 회귀 관계를 분석하였다. 동물 실험의 경우 전력 밀도와 SAR이, 세포 실험의 경우 출력 전력이 duty factor를 고려한 SAR과 통계적으로 유의한 상관 관계를 보였다. 회귀분석에서의 노출 불확실성을 평가하기 위해 결정계수값을 분석하였다. 각각의 실험장치 및 방법에 대한 해석 또는 측정 기법의 분석 이전에 본 연구 방법을 실시하여 대상 연구군의 특성을 고찰한다면 보다 효율적인 전자기장노출신뢰성 평가를 실시할 수 있을 것으로 판단된다. This paper proposed the estimating method of electromagnetic dosimetric reliability at in-vivo and in-vitro experiments. For more accurate consequences of these researches, we have tried to find out any correlations among output power, power density and specific absorption rate(SAR) with the results of in-vivo, in-vitro tests and SAR reports of cellular phone and PDA. In the case of in-vivo tests, the power density has close statistical correlations with SAR value and in the event of in-vitro tests, the output power has considerable statistical correlations with SAR containing duty factor. We analysed the coefficient of determination to estimate the dosimeoic uncertainty. If we use this method before evaluating techniques of measurement and analysis at both in-vivo and in-vitro experiments, we will conduct more accurate reliability test.

성견 3급 분지부 병소에서 Dura mater와 $Guidor^{(R)}$사용후 치주조직 치유의 비교 연구

최성호,구현서,정현철,조규성,채중규,김종관,Choi, Seong-Ho,Koo, Hyun-Seo,Jung, Hyun-Chul,Cho, Kyoo-Sung,Chai, Jung-Kiu,Kim, Chong-Kwan 대한치주과학회 1997 Journal of Periodontal & Implant Science Vol.27 No.3

There are various treatment methods including barrier membranes in attaining periodontal regeneration and regaining the function of destructed periodontal tissues due to periodontal disease. Barrier membranes consist of non-Resorbable and resorbable types such as Dura mater and $Guidor^{(R)}$ used in the treatment of intrabony defects and classII furcation defects have been shown to be effectively increased the amount of new bone and cementum.In our study we used premolars with class III furcation defects created by removing the bone 4mm apically from CEJ in adult dogs and placed resorbable membrane Dura mater and $Guidor^{(R)}$ for the test group and flap operation was carried out for the control groups. The effect of membrane on junctional epithelium, alveloar bone, cementum, and gingival connective tisssue in the regeneration and healing potential of periodontal tissues was evaluated and healing results were evaluated histologically and histometrically 8 weeks following the surgical procedure. 1. In the clinical observation, there was no exposure of furcation defects in the control group, whereas slight membrane exposure was noted in the test group. 2. New bone was formed up to the level of the notch in the control group, whereas in the test group new bone formation was observed above the level of the notch. 3. New cementum was formed in both groups of the experiment. 4. The connective tissue observed between the new cementum and new bone in the test group were functionally orientated, compared to the irregular formation of connective tissues found in the control group. 5. Root resorption or ankylosis was not observed in any of the groups 6. The mean and median of the control group were 4.31% and 2.23% and for the Dura mater group were 27.85% and 15.57% respectively. There was no significant difference between Dura mater and the control group. 7. The mean and median of the control group were 4.31% and 2.23% and for the $Guidor^{(R)}$ group were 37.27% and 37.19% respectively. There was a significant difference in these two groups(P<O.05). 8. The mean and median of the Dura mater group were 27.85% and 15.57% and for the $Guidor^{(R)}$ were 37.27% and 37.19%. There was no significant difference between the two test groups. Thus, by using Dura mater and Guidor in classIII furcation defects, the predictable amount of periodontal ligament and alveolar bone regeneration may result.

성견 열개형 결손부에 DFDB이식과 Dura Mater막의 효과

최성호,김일영,김영희,서종진,정현철,조규성,채중규,Choi, Seong-Ho,Kim, Il-Young,Kim, Young-Hee,Suh, Jong-Jin,Jung, Hyun-Chul,Cho, Kyoo-Sung,Chai, Jung-Kiu 대한치주과학회 1998 Journal of Periodontal & Implant Science Vol.28 No.2

The present study invetigates the effects of root planing only(control group), DFDBA alone(test group 1) and combined use of DFDB and Dura mater(test group 2) in dehiscence defects in dogs. The results of 8weeks post-surgery by histological comparison between the three groups are as follows. 1. The contol group showed minimum regeneration of new cementum and new bone with limited migration of epitheilal cells, and healed by connective tissue attachment. 2. The test group 1 showed minimum regeneration of new cementum and new bone with limited migration of epitheilal cells, and healed by connective tissue attachment. 3. The test group 2 showed significant amount of the new cementum and new bone. 4. Both control and test groups healed without any observable root resorption and ankylosis. The above the results suggest that the use of resorbable Dura mater only does not improve the regeneration of new bone and periodontal ligament due to difficulties of space making, but the combined use with DFDB may be more effective.

성인성 치주질환에서 미노클린 국소송달제 효과에 대한 연구

최성호,현석주,구현서,서종진,조규성,채중규,김종관,Choi, Seong-Ho,Hyun, Suk-Ju,Koo, Hyun-Seo,Suh, Jong-Jin,Cho, Kyoo-Sung,Chai, Jung-Kui,Kim, Chong-Kwan 대한치주과학회 1998 Journal of Periodontal & Implant Science Vol.28 No.2

20 Subjects with clinical diagnosis of adult periodontitis with sites having average pocket depth of 4mm were selected for the study. After scaling and root planing of those sites, 30% minocycline-HCI contained in biodegradable device were inserted in one group, scaling and root planing was carried out in another group and the last group was without any periodontal treatment. the difference between the group was detemined by pocket dept, bleeding on prbing, attachment level, distribution of subgingval plaque bacteria. Conclusion was made for the comparisons between baseline and 4 week and the groups. 1. In analysis of pocket depth, there was significant sifference in scaling and root planing group only. 2. Both the scaling and root planing group and minocycline group showed significant decrease in bleeding on probing. 3. There was significant increase in the attachment level in scaling and root planing group, but no difference was foundbetween the groups. 4. There was significant decrease in the total number of subgingival bacteria in all groups and the number of motile bacteria decreased significantly in the minocycline group. These result indicate that insertion of Minocycline-HCI at the base of periodntal pocket was useful as an additional aid of mechanical trarment at the point of periodontal pocket, bleeding on probing, attachment level, microbial distribution.

수종의 조직 양화재에서 탄성 변형과 복원에 관한 연구

최성호,심준성,문홍석,정문규,Choi Sung-Ho,Shim June-Sung,Moon Hong-Seok,Chung Moon-Kyu 대한치과보철학회 2003 대한치과보철학회지 Vol.41 No.1

The dimensional stability of tissue conditioners characterizes the ability of the materials to yield accurate functional impressions of oral mucosa. This study evaluated the viscoelastic property and the linear dimensional changes with the factor of time and thickness of tissue conditioners ($COE-COMFORT^{TM}$, Visco-gel. $COE-SOFT^{TM}$, Soft-Liner). The thickness of these materials were changed (1.5mm, 3.0mm) and the percentage changes in dimension were measured at 1h, 12h, 24h, 36h, 3day, 7day after specimen preparation. From the results large differences appear between the various tissue conditioners. The results suggest that the period recommended for forming functional impression would be 2-3days after insertion in the mouth. in addition. it is important to select tissue conditioners suitable for functional impression because of the wide range of dimensional stability among the materials.

성견 열개형 수평 결손부에서 Calcium Sulfate 차단막이 치주조직 치유에 미치는 영향

최성호,조규성,문익상,채중규,김종관,Choi, Seong-Ho,Cho, Kyu-Sung,Moon, Ik-Sang,Chai, Jung-Kyu,Kim, Jong-Kwan 대한치주과학회 1997 Journal of Periodontal & Implant Science Vol.27 No.1

The present study investigates the effects of calcium sulfate graft on the periodontal healing in intrabony periodontal defects of dogs. Following the general anesthesia with 30mg/kg pentobarbital injected intravenously, the first premolar was extracted and full-thickness periodontal flap was elevated from the second premolar to the fourth premolar. The portion of premolars coronal to the alveolar crest was removed and mesial and distal roots were separated. Exposed root canals were sealed with Caviton and covered completely with flaps sutured. Following the healing period of 12 weeks, the surgical sited were uncovered and $4{\times}4mm$ intrabony defects were surgically created. Those defects with calcium sulfate graft following the root planing was designated as the test sites and those with flap surgery-only were designated as control sites. The animals were sacrificed after 8 weeks and the healing was histologically analyzed. The results were as follows. 1. No foreign body reaction or inflammation were observed in either groups. Calcium sulfate was completely resorbed in the test sites. 2. New cementum was observed coronal to the notch in both groups. Connective tissue fibers were oriented parallel to the root surface in the controls. Connective tissues were formed in large amount in the sites. 3. Test sites showed marked amount of new bone formation while the control sites showed minimal bone gain. 4. Root resorption was observed in coronal portions of th control Sites. The results suggest that calcium sulfate is a biocompatible graft material with a potential for new bone and cementum formation.

초극소저출생체중아와 극소저출생체중아의 미숙아망막병증 발생 빈도와 위험 인자에 관한 연구

최성호,함돈일.Sung Ho Choi. M.D.. Don Il Ham. M.D. 대한안과학회 2006 대한안과학회지 Vol.47 No.6

Purpose: To evaluate the risk factors and prevalence of retinopathy of prematurity (ROP) in extremely low birth weight (ELBW) infants and very low birth weight (VLBW) infants. Methods: All babies were screened for ROP at a postconceptional age of 31 weeks or at 4 weeks of chronological age. We divided the infants into two groups according to birth weight < 1000 g (ELBW) and 1000~1500 g (VLBW), to compare the incidence of ROP and photocoagulation, and to retrospectively evaluate the risk factors. Results: Three hundred eight consecutive infants were included in the data analysis. The incidences of ROP were 70.5% (79/112) in ELBW infants and 36.7% (72/196) in VLBW infants (p<0.0001). 31 of 79 ELBW infants (39.2%) and 17 of 72 VLBW infants (23.6%) had undergone photocoagulation (p<0.0001). Among the various risk factors, mechanical ventilat6ion (p=0.039) and surfactant (p<0.000) were the independent risk factors associated with ROP in all infant groups by logistic regression analysis. In the ELBW group, however, surfactant injection was the only factor independently associated with ROP (p=0.008). The use of surfactant, the only risk factor in ELBW infants, was attributed with the initiation of ROP. However, it did not act as an aggravating factor. Conclusions: ELBW was associated with a higher incidence of ROP and laser photocoagulation. The results of this study emphasize that more special attention is needed for immature infants when ventilators and surfactants are used.