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신승재,이도영,나태흠,이창식,김태연,S.J. Shin,D.Y. Lee,T.H. Na,C.S. Lee,T.Y. Kim 한국전자통신연구원 2024 전자통신동향분석 Vol.39 No.2
The 3GPP (3rd Generation Partnership Project) mobile communication standard has emerged as a leading standard in the market over the past 20 years, driving continuous development in protocol stacks and libraries that support the standard within simulation software for communication network research. We summarize and analyze seven communication network simulators that support the 3GPP standard specifications related to core network technologies. Through comparisons, we aim to offer valuable insights for researchers and engineers engaged into research and development related to mobile communication networks based on 3GPP standards. Our findings can provide assistance for making informed decisions on simulator selection.
양전자방출단층촬영기의 표준 성능평가 방법 : GE AdvanceTM 에 적용한 예
김상은(S . E . Kim),이경한(K . H . Lee),이정림(J . R . Lee),최용(Y . Choi),신승애(S . A . Shin),김병태(B . T . Kim),최연성(Y . S . Choe) 대한핵의학회 1996 핵의학 분자영상 Vol.30 No.4
N/A A series of performance measurements of positron emission tomography (PET) were performed following the recommendations of the Computer and Instrumentation Council of the Society of Nuclear Medicine and the National Electrical Manufacturers Association. We investigated the performance of the General Electric AdvanceTM PET. The measurements include the basic intrinsic tests of spatial resolution, scatter fraction, sensitivity, and count rate losses and randoms. They also include the tests of the accuracy of corrections: count rate linearity correction, uniformity correction, scatter correction and attenuation correction. GE AdvanceTM PET has bismuth germanate oxide crystals (4.0mm transaxial × 8.lmm axial × 30.0mm radial) in 18 rings, which form 35 imaging planes spaced by 4.25mm. The system has retractable tungsten septa 1mm thick and 12cm long. Transaxial resolution was 4.92mm FWHM in 2D and 5.14mm FWHM in 3D at the center. Average axial resolution in 2D decreased from 3.91mm FWHM at the center to 6.49mm FWHM at R=20cm. Average scatter fraction of direct and cross slices was 9.57%. Dead-time losses of 50% corresponded to a radioactivity concentration of 4.86μCi/cc and a true count rate of 519 kcps in 2D. The accuracy of count rate linearity correction was 1.84% at the activity of 4.50μCi/cc. Non-uniformity was 2.06% in 2D and 2.93% in 3D. Remnant errors after scatter correction were 0.55% in 2D and 4.12% in 3D. The errors of attenuation correction were 6.21% (air), 0.20% (water), -6.32% (teflon) in 2D and 5.00% (air), 6.94% (water), 3.01% (teflon) in 3D. The results indicate the performance of GE AdvanceTM PET scanner to be well suited for clinical and research applications.
양전자방출단층촬영 ( PET ) 에서 회전 핀선원과 투과 및 방출 동시 영상 방법을 이용한 감쇠보정 방법 특성에 관한 고찰
김상은(S . E . Kim),이경한(K . H . Lee),이정림(J . R . Lee),최용(Y . Choi),지대윤(D . Y . Chi),신승애(S . A . Shin),김병태(B . T . Kim) 대한핵의학회 1995 핵의학 분자영상 Vol.29 No.4
N/A Attenuation correction is important in producing quantitative positron emission tomography (PET) images. Conventionally, photon attenuation effects are corrected using transmission measurements performed before tracer administration. The pre-injection transmission measurement approach may require a time delay between transmission and emission scans for the tracer studies requiring a long uptake period, about 45 minutes for F-18 deoxyglucose study. The time delay will limit patient throughput and increase the 1ikelihood of patient motion. A technique for performing simultaneous transmission and emission scans (T+E method) after the tracer injection has been validated. The T+E method substracts the emission counts contaminating the transmission measurements to produce accurate attenuation correction coefficients. This method has been evaluated in experiments using a cylindrical phantom filled with background water (5750 cc) containing 0.4 μCi/cc of F-18 fluoride ion and one insert cylinder (276 cc) containing 4.3 μCi/cc. GE AdvanceTM PET scanner and Ge-68 rotating pin sources for transmission scanning were used for this investigation. Post-injection transmission scan and emission scan were performed alternatively over time. The error in emission images corrected using post-injection transmission scan to emission images corrected using post-injection transmission scan to emission images corrected transmission scan was 2.6% at the concentration of 1.0 μCi/cc. No obvious differences in image quality and noise were apparent between the two images. The attenuation correction can be accomplished with post-injection transmission measurement using rotating pin sources and this method can significantly shorten the time between transmission and emission scans and thereby reduce the likelihood of patient motion and increase scanning throughput in PET.
$MgB_2$ 초전도체의 합성에 미치는 고에너지 밀링에 의한 초기 보론 분말의 특성
이지현,신승용,김찬중,박해웅,Lee, J.H.,Shin, S.Y.,Kim, C.J.,Park, H.W. 한국초전도학회 2007 Progress in superconductivity Vol.9 No.1
We characterized the highly refined boron precursor powders which were attrition milled for different milling times. $MgB_2$ powder precursor was formed from elemental crystalline Mg and amorphous B powder. The microstructure was investigated by SEM. SEM results indicate that the size of the milled powders was reduced with increasing milling time, which were varied from 0 to 8 hours. We also studied thermal behavior of the starting precursor by DSC as a function of milling time. The thermal behavior of the powder precursors was influenced by milling time. In order to determine the thermal events at DSC peaks, we annealed the milled powder mixture at $600^{\circ}C$ and $650^{\circ}C$ under protective gas and then analyzed the formation of $MgB_2$ by the XRD. We observed that superconducting $MgB_2$ phase was formed at lower temperature by the longer high energy milling. These results show that the high energy milling of the boron precursor powder can improve the reactivity for the formation of $MgB_2$.
어트리션 볼 밀링에 의한 보론 분말의 미세화 및 $MgB_2$의 초전도특성
이지현,신승용,전병혁,김찬중,박해웅,Lee, J.H.,Shin, S.Y.,Jun, B.H.,Kim, C.J.,Park, H.W. 한국초전도학회 2008 Progress in superconductivity Vol.10 No.1
We report refinement of crystalline boron by an attrition ball milling system and the superconducting properties of the $MgB_2$ pellets prepared from the refined boron. In this work, we have conducted the ball milling with only crystalline boron powder, in order to improve homogeneity and control the grain size of the $MgB_2$ that is formed from it. We observed that the crystalline responses in the ball-milled boron became broader and weaker when the ball-milling time was further increased. On the other hand, the $B_{2}O_{3}$ peak became stronger in the powders, resulting in an increase in the amount of MgO within the $MgB_2$ volume. The main reason for this is a greater oxygen uptake. From the perspective of the superconducting properties, however, the sample prepared from boron that was ball milled for 5 hours showed an improvement of critical current density ($J_c$), even with increased MgO phase, under an external magnetic field at 5 and 20 K.