ZrO₂(m)-Al₂O₃ZrO₂(t)-Al₂O₃ 세라믹스의 제조와 물리적 특성

박재성,박주태,박정량,Park, Jae-Sung,Park, Ju-Tae,Park, Jung-Rang 한국조명전기설비학회 2010 조명·전기설비학회논문지 Vol.24 No.4

The effects of the addition of either monoclinic $ZrO_2(ZrO_2(m))$ or tetragonal $ZrO_2(ZrO_2(t))$ containing 5.35[wt%] $Y_2O_3$ on the physical properties and electrical conductivity of $Al_2O_3$ were investigated. The addition of $ZrO_2$(m) and $ZrO_2$(t) increased sintered density of $Al_2O_3$. The Vickers hardness also increased as addition of $ZrO_2$(t) increased going through a maximum at 20[wt%] and the hardness of the specimens was found to be dependent on the sintered density. The addition of $ZrO_2$(t) improved the hardness of $Al_2O_3-ZrO_2$ systems and the $ZrO_2$(m) addition showed the better effect on the thermal shock property of $Al_2O_3-ZrO_2$ systems than that of the $ZrO_2$(t) addition. Above 15[wt%] addition of $ZrO_2$(t), the electrical conductivity is gradually increased with increasing applied voltage but not effects by addition of $ZrO_2$(m). 단사정 $ZrO_2(ZrO_2(m))$ 또는 $Y_2O_3$를 5.35[wt%] 첨가한 정방정 $ZrO_2(ZrO_2(t))$를 $Al_2O_3$에 첨가하여 물리적 및 전기전도도의 영향을 연구하였다. $ZrO_2$(m)과 $ZrO_2$(t)의 첨가는 $Al_2O_3$의 소결밀도를 증가시켰다. $ZrO_2$(t)의 첨가함에 따라 비커스 경도 또한 증가했으며, 그 량이 20[wt%]에서 최대가 되었다. 시편의 경도는 소결 밀도에 의존함을 알 수 있었다. $Al_2O_3-ZrO_2$계의 경도는 $ZrO_2$(t)의 첨가에 의해 개선되었고, $ZrO_2$(m)의 첨가가 $ZrO_2$(t)의 첨가보다 $Al_2O_3-ZrO_2$계의 열충격 특성에는 더 많은 영향을 받음을 알 수 있었다. 15[wt%] 이상의 $ZrO_2$(t) 첨가에서 인가전압이 증가 함에 따라 점차로 전기전도도가 증가 하였으나, $ZrO_2$(m)의 첨가에서는 영향이 없었다.

눈모음부족형 외사시에서 근경사부착술을 이용한 단안 외직근 후전술의 효과

박재성,이수정,노영배,최희영,Jae Sung Park,Soo Jung Lee,Young Bae Roh,Hee Young Choi 대한안과학회 2007 대한안과학회지 Vol.48 No.8

Purpose: To evaluate the efficacy of monocular slanted lateral rectus (LR) muscle recession for exotropia with convergence insufficiency. Methods: Twenty five patients with exotropia greater at near than at versus far distance by ≥10 prism diopters (PD), were divided into two groups: 15 patients who underwent monocular slanted LR recession (study group), and 10 patients who underwent monocular standard LR recession (control group). In the study group, the lower horn of the LR was recessed according to near deviation, the upper horn was recessed according to distance deviation. In the control group, monocular LR was recessed according to distance deviation. The postoperative ocular alignment at distance and near, and the difference between them, were measured and compared retrospectively. The criteria for successful outcome were postoperative residual deviation at near and distance, and the difference of 8 PD or less between the two. Results: The mean distance deviation showed a significant postoperative reduction in both groups (P<0.001, P<0.001). The mean near deviation showed a significant postoperative reduction in both groups (P<0.001, P<0.001). The mean difference between near and distance deviation showed a significant postoperative reduction only in the study group (P<0.001, P=0.175). Successful outcome was obtained in 13 our of 15 (86.7%) patients in the study group, in 2 out of 10 (20%) patients in the control group. None of the study patients had postoperative diplopia. Conclusions: Monocular slanted lateral rectus recession is effective in reducing both distant and near exodeviation and in collapsing the difference between distance and near deviation them at postoperative 4 months.

협력 게임 이론을 이용한 대역폭 할당 기법의 성능 비교

박재성,임유진,Park, Jae-Sung,Lim, Yu-Jin 한국정보처리학회 2011 정보처리학회논문지 C : 정보통신,정보보안 Vol.18 No.2

게임 이론은 다수의 사용자에게 공유 자원을 효율적이고 공정하게 분배할 수 있는 이론적 기반을 제공하므로 이를 대역폭 할당에 이용하려는 연구가 활발히 진행되어 왔다. 그러나 게임 이론에 의한 대역폭 할당 기법들은 적용한 게임 기법들에 따라 동일 조건에서 할당하는 대역폭이 달라진다. 그러나 현재까지 네트워크 분야에서는 게임 이론의 수학적 근거만을 차용하고 있으며 이들이 대역폭 할당 문제에 적용될 때 각 기법 별 특성에 대한 정량적 비교 분석은 이루어지고 있지 않다. 이에 따라 본 논문에서는 다수의 노드가 대역폭을 공유하는 경우 파산(Bankruptcy) 게임 이론과 협상(Bargaining) 게임 이론을 이용하여 송신 노드의 입력율에 따른 각 노드 별 대역폭 할당 기법들의 특성을 비교 분석하고 이에 따른 향후 연구 방향을 제시한다. Since the game theory provides a theoretical ground to distribute a shared resource between demanding users in a fair and efficient manner, it has been used for the bandwidth allocation problem in a network. However, the bandwidth allocation schemes with different game theory assign different amount of bandwidth in the same operational environments. However, only the mathematical framework is adopted when a bandwidth allocation scheme is devised without quantitatively comparing the results when they applied to the bandwidth allocation problem. Thus, in this paper, we compare the characteristics of the bandwidth allocation schemes using the bankrupt game theory and the bargaining game theory when they applied to the situation where nodes are competing for the bandwidth in a network. Based on the numerical results, we suggest the future research direction.

간헐외사시에서 수술 당일 편위각과 수술 결과의 관계

박재성,전종배,최희영,Jae Sung Park,Jong Bae Jeon,Hee Young Choi,Ph,D 대한안과학회 2007 대한안과학회지 Vol.48 No.8

Purpose: We assessed the relationship between the surgical outcome of intermittent exotropia and initial postoperative alignment by checking it on the first postoperative day or the day of strabismus surgery. Methods: Seventy-three patients with intermittent exotropia underwent bilateral lateral rectus recession or unilateral medial rectus resection and lateral rectus recession. Thirty-two patients had their postoperative alignment checked on the day of surgery, and forty-one patients were checked on the first postoperative day. Success was defined as sustained alignment six months postoperatively from esotropia 10PD to exotropia 10PD. Overcorrection was defined as esotropia greater than 11PD, and undercorrection was exotropia greater than 11PD. We assessed the relationship between the alignment on the day of surgery or on the first postoperative day and also at six months postoperatively, as well as the success rate according to the initial postoperative alignment. Results: There was a statistically significant relationship between alignments on the day of surgery or on the first postoperative day and those at six months postoperatively (p<0.001, p<0.001). The deviation on the first postoperative day had a greater correlation coefficient compared to the deviation on the day of the operation (Pearson correlation coefficient=0.704, and 0.593, respectively). The alignment of overcorrection ranged from 11~20PD on the day of surgery, and on the first postoperative day it produced a relatively high success rate (p=0.016, p=0.035). There was no statistically significant difference in the success rate between the two types of surgery (p=0.832). Conclusions: The alignment on the day of surgery showed a high correlation to the outcome on the sixth postoperative month in intermittent exotropia patients. The initial postoperative overcorrection of 11 to 20PD on the day of surgery and on the first postoperative day resulted in the best long-term outcomes.

임신 중 발생한 보크트-고야나기-하라다 병에 합병된 긴장성 동공 1예

박재성,박준모,이지은,엄부섭,Jae Sung Park,Jun Mo Park,Ji Eun Lee,Boo Sup Oum 대한안과학회 2007 대한안과학회지 Vol.48 No.11

Purpose: We report a case of bilateral tonic pupils and decreased corneal sensitivity in a patient with Vogt-Koyanagi-Harada (VKH) disease during pregnancy. Case summary: A 33-year-old Korean woman in the sixth month of pregnancy presented with visual impairment in both eyes. Her best corrected visual acuity was 0.2 in the right eye and 0.125 in the left. Slit-lamp examination revealed cells in the anterior chamber and serous retinal detachments in both eyes. The patient was treated with topical corticosteroid in both eyes and posterior subtenon injection of triamcinolone acetonide in the left eye. The serous retinal detachment resolved completely at 2 months in the left eye and at 3 months in the right. As pigmentation of the retina developed, VKH disease was confirmed. The patient complained of photophobia, and both pupils were found to be enlarged to 8 mm without dilation. Light reflex was absent and near reflex was suppressed and slow. After instillation of 0.125% pilocarpine, the pupils were constricted to 3.5 mm and were diagnosed as tonic pupils. Though the patient`s corrected visual acuity improved to 0.8 in the right eye and 1.0 in the left at 6 months, her pupils remained unchanged. Corneal sensitivity was decreased. Conclusions: Tonic pupils may be complicated with VKH disease even during pregnancy. We recommend examinations of the pupils and corneal sensitivity in patients with VKH disease, especially those complaining of photophobia.

WLAN Mesh 망을 위한 라우팅 기법의 성능 분석

박재성,임유진,안상현,Park, Jae-Sung,Lim, Yu-Jin,Ahn, Sang-Hyun 한국정보처리학회 2007 정보처리학회논문지 C : 정보통신,정보보안 Vol.14 No.5

무선 LAN(WLAN) 기반 mesh 망은 유선 엑세스 망의 단점을 보완하기 위한 대안으로 많은 주목을 받고 있으나 성공적인 상업화를 위해서는 성능, 보안, 관리 등 기술적인 이슈들을 해결해야 한다. 특히 단말과 유선망 사이의 데이터 교환을 위한 효율적인 경로 선정 문제는 WLAN mesh 망의 신뢰성과 안전성에 많은 영향을 미치므로 효과적인 라우팅 기법의 개발은 선결해야 될 중요한 문제이다. WLAN mesh 망은 포설되는 환경과 단말의 이동성 등에 의해 다양한 특징을 가지므로 reactive 라우팅 기법 혹은 proactive 라우팅 기법 하나만을 이용하는 것은 모든 mesh 망 환경에 적합하지 않다. 따라서 망 환경 변화에 따른 동적인 라우팅 기법 개발이 필요하며 이론 위해서는 망과 단말의 특성이 각 라우팅 기법의 성능에 미치는 영향이 종합적으로 파악되어야 한다. 그러나 현재까지 제안된 라우팅 기법들의 성능 평가에 관한 연구는 제한된 환경에서 모의 실험을 통한 정량적 평가에 머물고 있다. 이에 따라 본 논문에서는 망의 크기, 송신 단말의 밀도, 단말의 이동성, 망 형상 변화 주기론 모두 고려하여 reactive 기법인 AODV와 proactive 기법인 DSDV의 수학적 성능 분석 모델을 제시한다. 제안된 분석 모델은 변화하는 mesh 망 환경에 적응성 있는 라우팅 기법 개발에 이용될 것으로 기대된다. Mesh networks using WLAN technology have been paid attention as a key wireless access technology. However, many technical issues still exist for its successful deployment. One of those issues is the routing problem that addresses the path setup through a WLAN mesh network for the data exchanges between a station and a wired network. Since the characteristics of a WLAN mesh network can be very dynamic, the use of single routing protocol would not fit for all environments whether it is reactive or proactive. Therefore, it is required to develop an adaptive routing protocol that modifies itself according to the changes in the network parameters. As a logical first step for the development, an analytical model considering all the dynamic features of a WLAN mesh network is required to evaluate the performance of a reactive and a proactive routing scheme. In this paper, we propose an analytical model that makes us scrutinize the impact of the network and station parameters on the performance of each routing protocol. Our model includes the size of a mesh network, the density of stations, mobility of stations. and the duration of network topology change. We applied our model to the AODV that is a representative reactive routing protocol and DSDV that is a representative proactive routing protocol to analyze the tradeoff between AODV and DSDV in dynamic network environments. Our model is expected to help developing an adaptive routing protocol for a WLAN mesh network.

무선랜 환경에서 IPTV 서비스 품질 향상을 위한 AP 선택 기법

박재성,임유진,Park, Jae-Sung,Lim, Yu-Jin 한국정보처리학회 2011 정보처리학회논문지 C : 정보통신,정보보안 Vol.18 No.4

무선랜 환경에서 사용자 데이터 수신율은 RSS (received signal strength) 뿐만 아니라 AP (access point)의 채널 경합 수준에 의하여 결정된다. 그러나 현재 사용자 단말은 AP로부터의 RSS를 기반으로 접속할 AP를 선정하므로 IPTV 서비스의 최소한의 요구사항을 보장할 수 없다. 따라서 본 논문에서는 기존의 IEEE 802.11 표준에 대한 수정없이 무선랜 환경에서 IPTV 서비스 요구사항을 만족시킬 수 있는 효율적인 AP 선택 기법을 제안한다. 사용자 단말은 주변 AP들의 채널 경합 수준과 현재 진행중인 IPTV 서비스의 품질을 모니터링 함으로써, 서비스 품질이 일정이하로 떨어지면 AP 부하정도가 가장 작은 AP로 재접속함으로써 IPTV 서비스의 최소한의 요구사항을 제공하도록 하였다. In a WLAN, the data reception rate of a user station depends not only on the received signal strength (RSS) from an AP (Access Point) but also on the contention level of the AP. However, since only the RSSs measured at the physical layer have been used for a station to select an AP to associate with, the station may not satisfy the minimum quality requirements necessary for a seamless IPTV service. Thus, in this paper, we propose an AP selection method to support quality requirements of the IPTV service in a wireless LAN without modifying the IEEE 802.11 standard. A user station keeps monitoring a contention level of APs around it and a quality of an ongoing IPTV service. If the quality deteriorates below a threshold, the station reassociates with another AP having the least load so that the ongoing IPTV program is played without disruption.

휴대용콘의 선단저항값을 이용한 모래의 상대밀도 및 내부마찰각 추정

박재성,손영환,노수각,봉태호,Park, Jae-Sung,Son, Young-Hwan,Noh, Soo-Kack,Bong, Tae-Ho 한국농공학회 2012 한국농공학회논문집 Vol.54 No.4

Sand is one of the essential materials used for social infrastructure construction such as embankment, landfill and backfill. It was known that mechanical properties and shear strength of sand are closely related to relative density. Therefore it is very important to determine accurate relative density. In this study, Portable Cone Penetration Tester (PCPT) was used to estimate the relative density and the internal friction angle of sand. PCPT cone-tip resistance ($q_c$) was measured changing the relative density of the two soil samples.Standard sand (JMJ) and Busan sand (BS). Also, a direct shear test was performed to investigate relationship between relative density and internal friction angle. The size and shape of soil particles were confirmed by using Scanning Electron Microscope (SEM). As a result, the log value of $q_c$ was linearly correlated with relative density and internal friction angle. In particular, the internal friction angle of BS sample was greater than that of JMJ, which was due to difference of the shape and mean size of particles. This result shows that it is important to determine the shape and size of particles as well as relative density to define mechanical property of sand. Through this study, it can be more effectively and conveniently to investigate relative density and shear strength of sand by using PCPT in situ.

무선 메쉬 망의 서비스 품질 향상을 위한 확률적 부하 분담 기법

박재성,임유진,안상현,Park, Jae-Sung,Lim, Yu-Jin,Ahn, Sang-Hyun 한국정보처리학회 2008 정보처리학회논문지 C : 정보통신,정보보안 Vol.15 No.5

무선 메쉬망 (Wireless Mesh Network: WMN)에서 트래픽은 IGW (Internet Gateway)를 통해 유선망과 교환되므로 트래픽은 IGW로 집중되어 병목지점이 된다. 따라서 다수의 채널과 다수의 인터페이스를 이용하여 증대된 WMN의 전체 용량을 다수의 IGW를 통해 균등하게 분산시키는 것은 WMN의 안정적인 운영을 위해 필요하다. 이에 따라 본 논문에서는 무선 메쉬 망의 부하를 다수의 IGW에 분산시켜 망의 안정성과 서비스 품질 향상을 위한 확률적 부하 분담 기법을 제안한다. 제안 기법은 혼잡한 IGW의 부하를 망 내 IGW들의 혼잡 정도에 따라 다수의 IGW에 분산시킨다. 또한 IGW와 거리가 가까울수록 집중되는 트래픽 양은 증가하므로 급격하게 과도한 트래픽이 새로운 IGW에 집중되는 것을 방지하기 위해, 제안기법은 혼잡한 IGW와 인터넷 접속을 위해 이를 사용하고 있는 MR (Mesh Router) 사이의 거리 정보에 따라 접속 IGW의 변경 여부를 결정한다. NS-2를 이용한 모의 실험을 통해 제안기법은 최소 혼잡 IGW를 이용한 기법에 비해 IGW의 혼잡 발생시 이를 해결하기 위한 망 안정화 시간과 망 내 패킷 손실율 측면에서 우수하다는 것을 검증하였다. As the use of Internet and information communication technology is being generalized, the SSL protocol is essential in Internet because the important data should be transferred securely. While the SSL protocol is designed to defend from active attack such as message forgery and message alteration, the cipher suite setting can be easily modified. If the attacker draw on a malfunction of the client system and modify the cipher suite setting to the symmetric key algorithm which has short key length, he should eavesdrop and cryptanalysis the encrypt data. In this paper, we examine the domestic web site whether they generate the security session in the symmetric key algorithm which has short key length and propose the solution of the cipher suite setting problem.

미국(美國)의 의료과오실태에 관한 분석(分析)

박재성,Park, J.S. 대한예방의학회 1978 Journal of Preventive Medicine and Public Health Vol.11 No.1