Microwave dielectric properties of glass-Bi₂Ti₂O7 ceramic composites

Sang Ok Yoon,Kwan Soo Kim,Sang Heung Shim,Yun Han Kim,Shin Kim 한양대학교 세라믹연구소 2008 Journal of Ceramic Processing Research Vol.9 No.1

The microwave dielectric properties of glass-Bi₂Ti₂O7 ceramic composites were investigated. Using bismuth-zinc borosilicate (BZBS) glass and TiO₂, glass-Bi₂Ti₂O7 composites were prepared by liquid phase sintering. The linear shrinkage exhibited a two-stage sintering behavior; viscous flow of the liquid phase and then crystallization. The crystalline phases of Bi₂Ti₄O₁₁and Bi₂Ti₂O7 were observed at 700 and 900oC, respectively. The dielectric constant (εr) and the quality factor (Q×f0) were affected by the formation of crystalline phases as well as the density. For the specimen sintered at 900oC, the dielectric constant, the quality factor and the temperature coefficient of the resonant frequency (τf) was respectively 56.4, 518 GHz (105 at 4.898 GHz), and +119 ppm/K. The microwave dielectric properties of glass-Bi₂Ti₂O7 ceramic composites were investigated. Using bismuth-zinc borosilicate (BZBS) glass and TiO₂, glass-Bi₂Ti₂O7 composites were prepared by liquid phase sintering. The linear shrinkage exhibited a two-stage sintering behavior; viscous flow of the liquid phase and then crystallization. The crystalline phases of Bi₂Ti₄O₁₁and Bi₂Ti₂O7 were observed at 700 and 900oC, respectively. The dielectric constant (εr) and the quality factor (Q×f0) were affected by the formation of crystalline phases as well as the density. For the specimen sintered at 900oC, the dielectric constant, the quality factor and the temperature coefficient of the resonant frequency (τf) was respectively 56.4, 518 GHz (105 at 4.898 GHz), and +119 ppm/K.

Mono-dehalogenation of gem-Dihalocyclopropanes Using Tetracarbonylhydridoferrate

Shim, Sang-Chul,Lee, Seung-Yub,Lee, Dong-Yub,Choi, Heung-Jin Korean Chemical Society 1994 Bulletin of the Korean Chemical Society Vol.15 No.10

Tetracarbonylhydridoferrate, $HFe(CO)^-_4$, generated by the reaction of $Fe(CO)_5$ with alkaline solution, is a good reducing agent for mono-dehalogenation of gem-dihalocyclopropanes. It also acts as a good reducing catalyst under phase transfer reaction conditions. 1,1-Dibromo-2-phenylcyclopropane and 1,1-dichloro-2-phenylcyclopropane were reduced to the corresponding mono-dehalogenated products in excellent yields. Thermodynamically stable trans-l-bromo-2-phenyl cyclopropane was formed as the major product over the cis-isomer, trans/cis=3/2. The 1-bromo-2-phenyl cyclopropane radical intermediate was formed by single electron transfer from $HFe(CO)^-_4$. Dissociation of bromide anion, followed abstraction of hydrogen radical from alcoholic solvent would lead to the formation of the stable trans-isomer. The further mechanistic aspects were discussed.

Microwave dielectric properties of lead borosilicate glass-Al₂O₃ composites

Sang Ok Yoon,Kwan Soo Kim,Sang Heung Shim,Yun Han Kim,Shin Kim 한양대학교 세라믹연구소 2008 Journal of Ceramic Processing Research Vol.9 No.2

A lead borosilicate (PBS) glass-Al₂O₃ composite was prepared and its microwave dielectric properties were investigated. Although the anorthite-type phase was observed above 800oC, this phase might have crystallized from the PBS glass because the PBS glass originally contained the constituents of the anorthite phase and a one-stage sintering behavior was conducted. The densification behavior was suggested to occur through a non-reactive liquid phase sintering. The dielectric constant (εr), the quality factor (Q×f0), and the temperature coefficient of the resonant frequency (τf) of the 50 vol% PBS glass-Al₂O₃ composite sintered at 900oC were 9.26, 4 941 GHz, and −38 ppm/K, respectively. A lead borosilicate (PBS) glass-Al₂O₃ composite was prepared and its microwave dielectric properties were investigated. Although the anorthite-type phase was observed above 800oC, this phase might have crystallized from the PBS glass because the PBS glass originally contained the constituents of the anorthite phase and a one-stage sintering behavior was conducted. The densification behavior was suggested to occur through a non-reactive liquid phase sintering. The dielectric constant (εr), the quality factor (Q×f0), and the temperature coefficient of the resonant frequency (τf) of the 50 vol% PBS glass-Al₂O₃ composite sintered at 900oC were 9.26, 4 941 GHz, and −38 ppm/K, respectively.

Recurrent thrombosis after endovascular treatment for malignant superior vena cava syndrome

( Sang Ho Lee ),( Sun Young Kim ),( Heung Tae Kim ),( Chang Woo Shim ),( Ho Seok Chi ),( Hye In Lee ),( Do Il Choi ),( Hyun Bum Kim ),( In Jun Lee ) 대한내과학회 2015 대한내과학회 추계학술대회 Vol.2015 No.1

Endovascular treatment (EVT) including angioplasty and stenting is an effective treatment for superior vena cava (SVC) syndrome. Recurrence of SVC syndrome is mainly caused by tumor progression and occurs in around 20% after EVT, but sometimes venous thrombosis within stent accounts for recurrence of SVC syndrome. Anticoagulation after EVT is still a controversial issue. In our case, a 73 year-old man with SVC syndrome caused by mediastinal lymph node metastasis from non-small cell lung cancer underwent EVT followed by anticoagulation with low molecular weight heparin (LMWH), but symptomatic progression due to in-stent thrombosis necessitated the second procedure after two weeks. A total of 4 sessions of EVT and anticoagulation with LMWH, warfarin and rivaroxaban did not induce durable resolution of in-stent thrombosis. The 4th EVT was done with stent -graft, but computed tomography after the last procedure revealed remained thrombus in SVC and newly developed pulmonary thromboembolism during warfarinization. Our case suggests refractory in-stent thrombosis could develop despite of anticoagulation after EVT for SVC syndrome.

Carbonylation of Protected or Non-protected 2-Bromobenzaldehyde Catalyzed by Cobalt Carbonyl

Sang Chul Shim,Dong Yup Lee,Heung Jin Choi,Chil Hoon Doh,Keun Tai Huh Korean Chemical Society 1994 Bulletin of the Korean Chemical Society Vol.15 No.9

The cobalt catalyzed carbonylation of bromobenzene having protected aldehyde group gives the corresponding ester in good yields, but 2-bromobenzaldehyde gives 3-alkoxyphthalide in the noticeable yield instead of alkyl 2-formylbenzoates.

A Kinetic Study of the Fe(Ⅲ)-Catalyzed Aquation of Bis(malonato)Diaquochromate(Ⅲ) Ion

Shim, Jeong-Ae,Moon, Jung-Dae,Park, Heung-Jae,Choi, Sung-Nak Korean Chemical Society 1990 Bulletin of the Korean Chemical Society Vol.11 No.4

The bis(malonato)diaquochromate(III) ion, $Cr(C_3H_2O_4)_2^-$ in acidic solution hydrolyzes to give $Cr(C_3H_2O_4)^{+}.$ This reaction is catalyzed by ferric ion and the rate law for this cation catalyzed-aquation in a $HClO_4/NaClO_4$ medium, $I = 1.00 M, is-d[Cr(C_3H_2O_4)_2^-]/dt = ({\kappa}_1[Fe^{3+}] + {\kappa}_2[H^+])[Cr(C_3H_2O_4)_2^-]$ where ${\kappa}_1(25^{\circ}C) = 4.72×10^{-5} M^{-1}sec^{-1} ({\Delta}H^{\neq} = 22.5 Kcal/mol, {\Delta}S^{\neq} = - 2.58 eu) and {\kappa}_2(25^{\circ}C) = 4.75{\times}10^{-5} M^{-1}sec^{-1} ({\Delta}H^{\neq} = 21.2 Kcal/mol, {\Delta}S^{\neq} = - 7.13 eu).$ Rapid preequilibrium association of basic Cr-bound oxygen with $Fe^{3+},$ followed by rate-determining ring opening, is proposed to account for the ${\kappa}_1,$ hydrolysis pathway.

골다공증을 동반한 70세 이상 고령의 고관절부 골절에서 시행한 무시멘트 양극성 반치환술

황성관 ( Sung Kwan Hwang ),심영준 ( Young Jun Shim ),양재형 ( Jea Heung Yang ),강동현 ( Dong Hyon Kang ) 대한고관절학회 2008 Hip and Pelvis Vol.20 No.2

목적: 골다공증을 동반한 70세 이상 고령 환자에서 대퇴 경부 및 전자간부 골절 치료로 무시멘트 대퇴 주대를 이용한 양극성 반치환술의 단기 추시 결과를 임상적 및 방사선학적으로 확인 하고자 하였다. 대상 및 방법: 1997년 7월부터 2006년 5월까지 대퇴 경부와 전자간부 골절로 무시멘트 대퇴 주대를 이용한 양극성 고관절 반치환술을 시행 받은 환자 중 진단 당시의 연령이 70세 이상이고 골다공증이 동반된 환자로 2년치상 추시가 가능하였던 83명 (84예)을 대상으로 하였다. 임상평가는 최종 추시 Harris 고관절 점수와 Koval의 분류에 의한 수상전 및 최종 추시 보행상태를 분석하였으며, 단순 방사선 사진을 통해 방사선학적 평가를 하였다. 결과: 환자의 평균 추시기간은 31.4개월이었다. 수술시간은 평균 35분이었고, 술 후 보행 보조기 사용을 포함한 보행시까지의 기간은 평균 6일이었다. 최종 추시시 Harris 고관절 평균점수는 82.7점 이었으며, Koval에 의한 보행 능력정도는 수상전 보행능력으로 회복 25명(30.1%), 수상전보다 1단계 감소 56명(67.5%) 2단계 감소 2명(2.4%)로 나타났으며, 방사선학적 평가상 최종 추시시 1예(1.2%)에서 피질골 과성장이 관찰되었으며, 전예에서 대퇴주대의 안정 삽입을 보였다. 결론: 고령 고관절 주위 골절 환자에서 무시멘트 대퇴주대를 이용한 양극성 고관술 반치환술의 2년이상 단기 추시 결과 임상적 및 방사선학적으로 만족스러운 결과를 얻을 수 있었다. Purpose: This study evaluated the effectiveness of bipolar hemiarthroplasty with a cementless femoral stem for hip fractures in patients older than 70 years with osteoporosis. Materials and Methods: This study examined 84 hips with osteoporosis that are available to follow up of more than 2 years, between July 1997 and May 2006. The clinical evaluation was carried out using the Koval classification before the fracture and at the last follow-up, and the Harris hip score at the last follow up. The radiological evaluation was carried out using the plain radiographs. Results: The average follow up period was 31.4 months. The Koval classification was as follows: recovery to the condition before the fracture in 25 cases (30.1%), degradation by 1 class in 56 cases (67.5%) and degradation by 2 classes in 2 cases (2.4%). The Harris hip score was 82.7 points at the last follow-up. One case (1.2%) showed cortical hypertrophy and all cases showed stable insertion of the femoral stem. Conclusion: Bipolar hemiarthroplasty with a cementless femoral stem is effective and satisfactory, both clinically and radiologically, for the treatment of elderly patients with fractures around the hip.

IP 망을 통한 비디오 전송에 효율적인 조건적 ARQ 기반의 오류 제어 기법

심상우(Sang-woo Shim),서광덕(Kwang-deok Seo),정순흥(Soon-heung Jung),배성준(Seong-jun Bae) 한국방송·미디어공학회 2010 한국방송공학회 학술발표대회 논문집 Vol.2010 No.7

본 논문에서는 패킷 오류가 발생하는 IP 망을 통해 비디오 전송 서비스를 제공하기 위한 조건적 ARQ 기반의 오류 제어기법을 제안한다. IP 망에서 패킷 손실이 발생하면 수신 단말은 서버에게 손실된 패킷의 재전송을 요청할 수 있다. 그러나 망 상황과 접속 단말 개수를 고려하지 않고 무조건적인 재전송을 요청 할 경우 손실된 패킷이 복호화에 필요한 시점까지 도착 할 것인지가 보장되지 않을 뿐더러, 오히려 불필요한 재전송 요청에 의해 망에서의 트래픽 량을 가중시킬 수 있다. 따라서 망 상황을 고려하여 손실된 패킷이 재전송에 의해 적절한 시간 내에 도착이 가능한지를 판단하여 조건적으로 ARQ를 요청하는 기술이 요구된다. 본 논문에서는 기존의 RFC 문서에서 권고하는 재전송 관련 메카니즘들을 효과적으로 활용하여 표준기술 기반의 조건적 ARQ 오류제어 기법을 제안한다. 제안된 기법에서는 단말에서 추정된 망 상황을 기반으로 조건적으로 재전송 요청 여부를 결정하고, 더 나아가서 유효한 재전송 요청 시점을 결정하여 보다 효율적인 ARQ 가 적용될 수 있도록 한다. 제안된 조건적 ARQ 기반의 오류 제어 기법의 성능을 검증하기 위하여 패킷 손실 네트워크 환경을 NIST-Net을 활용하여 구축하며 실험 결과를 통해 제안된 기법의 우수한 오류 강인 성능을 확인한다.

태양광 변동성을 고려한 연간 시간별 전력수요 예측방안 연구

손흥구(Heung-Gu Son),심현보(Hyun-Bo Shim),허성일(Sung-il Hur),박희준(Hee-Jun Park),김현수(Hyunsu Kim),문정민(Jung-Min Mun),이수민(Su-Min Lee),최용옥(Yongok Choi),김창식(Chang-Sik Kim) 대한전기학회 2023 대한전기학회 학술대회 논문집 Vol.2023 No.7

Densification and Dielectric Properties of Glass/Ceramic Composites Sintered with Various Borosilicate Glass

Yoon, Sang Ok,Kim, Kwan Soo,Kim, Shin,Shim, Sang Heung,Park, Jong Guk Trans Tech Publications, Ltd. 2007 Materials science forum Vol.544 No.-

<P>Al2O3 and TiO2 were sintered with three types (lead, zinc, bismuth) of borosilicate glass. Their microwave dielectric properties and sintering behavior were investigated as functions of glass type, glass addition (10~50 vol%) and sintering temperature (600~950°C for 2 hrs). Sintering characteristics were well described in terms of softening temperature, second phase, and excessive liquid. In particular, Bi2O3 addition to the glass enhanced reaction with Al2O3 and TiO2 to form liquid phase and second phase. In terms of dielectric properties glass/Al2O3 composites for application to substrates while glass/TiO2 composites for filters were shown to be appropriate.</P>