• Journal of Magnetics
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• v.19 no.4
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• pp.365-371
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• 2014

The aim of this study was to evaluate the utility of 3-D images by comparing and analyzing reconstructed 3-D images from fast spin echo images of MRI cholangiopancreatography (MRCP) images using maximum intensity projection (MIP) with the subtraction images derived from dynamic tests of magnetic resonance mammography. The study targeted 20 patients histologically diagnosed with pancreaticobiliary duct disease and 20 patients showing pancreaticobiliary duct diseases, where dynamic breast MR (magnetic resonance) images, fast spin echo imaged of pancreaticobiliary duct, and 3-D reconstitution images using a 1.5T MR scanner and 3.0T MR scanner were taken. As a result of the study, the signal-to-noise ratio in the subtracted breast image before and after administering the contrast agent and in the reconstructed 3-D breast image showed a high ratio in the reconstructed image of lesional tissue, relevant tissue, and fat tissue. However, no statistically meaningful differences were found in the contrast-to-noise ratio of the two images. In the case of the MRCP image, no differences were found in the ratios of the fast spin echo image and reconstructed 3-D image.

• Investigative Magnetic Resonance Imaging
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• v.1 no.1
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• pp.148-153
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• 1997

Purpose: To evaluate the diagnostic role of a three-dimensional MR cholangiopancreatography (MRCP) over endoscopic retrograde cholangio-pancreatography (ERCP) in various extrah-epatic biliary disease. Materials and Methods: MRCP and ERCP were performed in 45 consecutive patients with suspected extrahepatic biliary diseases. MRCP was obtained using a reverse fast imaging with a steady-state free precession (reverse FISP: PSIF) sequence, and then images were reconstructed by standard MIP algorithm. The predictability of biliary dilatation and level of obstruction of MRCP was evaluated using ERCP as a gold standard. The accuracy distinguishing malignant from benign lesions, and overall diagnostic accuracy were compared between MRCP and ERCP. Results: The sensitivity, specificity and accuracy of MRCP in predicting biliary dilatation were 94.6%, 75.0% and 91.1%, respectively. The level of obstruction was accurate in 87.0% with MRCP. The sensitivity, specificity and accuracy of MRCP and ERCP in distinguishing malignant from benign lesions were 76.2%, 87.5% and 82.2% and 71.4%, 83.3% and 77.8%, respectively. The overall diagnostic accuracy was 60.0% with MRCP and 55.6% with ERCP. Conclusion: 3D MRCP shows a good diagnostic value compared to that of ERCP, and can replace a ERCP.

• The KIPS Transactions:PartC
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• v.12C no.4 s.100
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• pp.481-488
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• 2005

The Mobile W provides an efficient and scalable mechanism for host mobility within the Internet. However, the mobility implies higher security risks than static operations in fixed networks. In this paper, the Mobile IP has been adapted to allow AAA protocol that supports authentication, authorization, and accounting(AAA) for security and collection for accounting information of network usage by mobile nodes(MNs). For this goal, we Propose the boundary tone overlapped network structure while solidifying the security for the authentication of an MN. That is, the Proposed scheme delivers the session keys at the wired link for MN's security instead of the wireless one, so that it provides a fast and seamless handoff mechanism. According to the analysis of modeling result, the proposed mechanism compared to the existing session key reuse method is up to about $40\%$ better in terms of normalized surcharge for the handoff failure rate that considers handoff total time.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.6B
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• pp.411-419
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• 2008

As the set of new mobile data networking service technologies, such as WiBro, mobile WiMAX and WCDMA-HSDPA, have been introduced in recent years, IP mobility management protocols which aim to provide seamless IP service over the mobile networking environment become one of the important building blocks for the successful mobile networks. IETF has introduced a basic mobility management protocol over IPv6 (MIPv6) and a set of enhanced protocols such as FMIPv6 and HMIPv6, followed by FHMIPv6, S-MIPv6 and HIMIPv6 which combine the benefits of the basic protocols. We have studied the impact of the various IP mobility management protocols over TCP sessions through extensive simulations with ns-2. Our simulation results show that TCP performance with the HIMIPv6 outperforms MIPv6, FMIPv6 and HMIPv6 over the various TCP protocols, due to its efficient combination of the hierarchical mobility management scheme of the HMIPv6, the predictive handover scheme of the FMIPv6 and the fast simulcasting scheme of the S-MIP.

• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.67-70
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• 2000

최근 들어, 인터넷의 폭넓은 보급과 급속한 대중화에 따라 네트워크를 통하여 음성을 전송하거나 저장하려는 시도가 많이 이루어지고 있다. 본 논문에서는 네트워크를 통한 멀티미디어 전송에서 음성부호화 표준으로 널리 상용되는 ITU-T G.723.1 dual-rate speech coder의 효율적인 다채널 구현을 위한 고속 알고리듬을 제안한다. 고속 알고리듬은 부호화 과정에서 많은 계산량을 차지하는 적응 코드북 검색과 고정 코드북 검색 과정에 적용된다. 적응 코드북 검색 과정에서는 지연과 이득을 동시에 찾는 기존의 방법 대신, 지연과 이득을 순차적으로 검색함으로써 계산량을 개선하였다. 전송률에 따라 다른 알고리듬을 사용하는 고정 코드북 검색 과정에서는 다음과 같은 고속 알고리듬을 제안한다. MP-MLQ(Multi-Pulse Maximum Likely Quantization) 방법을 사용하는 높은 전송률(6.3 kbit/s)인 경우, 펄스를 등 간격으로 검색함으로써 계산량을 줄였다. ACELP(Algebraic CELP) 방법을 사용하는 낮은 전송률(5.3 kbit/s)인 경우는 기존의 nested-loop 검색방법 대신, 펄스를 쌍으로 나누어 순차적으로 찾는 depth-first tree 검색 방법을 적용하여 계산량을 감소시켰다. 제안된 고속 알고리듬에 대해 주관적 음질 평가 방법을 수행한 결과, 제안된 방법이 기존의 방법에 비해 음질의 저하가 없음을 확인하였다. 고정 소수점 DSP인 TMS320C6201을 사용하여 고속 알고리듬을 구현한 결과, 높은 전송률의 경우에는 10.29 MIPS, 낮은 전송률의 경우에는 8.70 MIPS의 연산량으로 구현 가능함을 확인하였다.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.1
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• pp.67-72
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• 2004

AC servo system has been implemented to FA system and also depends on its quality. Recently with the development of power switching device and DSP which has peripheral devices to control AC servo system, the servo technology has met a new development opportunity. A DSP based AC servo system with a 3-phase PMSM is proposed. The newly produced DSP TMX320F2812-version C which has the performance of fast speed, 150MIPS, and rich peripheral interface is used. Also space vector pulse width modulation (SVPWM) and the digital PI control are implemented to the servo system

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.11
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• pp.2451-2456
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• 2010

As the recent development of mobile technology, users want to multi-service in anytime, anywhere, any terminal. To meet the needs of users, it causes a lot of expense that redesign of the entire network or expand the network of services areas. Therefore, IEEE, IETF is offering Handover technology between heterogeneous network. In this paper, the IEEE 802.21 MIH information server is based on the network. It proposes an improved handover that L3 layer to optimize the handover process use of FMIPv6 and executes simulation.

• The Journal of the Korea Contents Association
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• v.5 no.3
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• pp.237-242
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• 2005

In this paper, a fast handoff algorithm between PDSNs in 3GPPx network for a mobile node, is proposed. It introduces a method by which handoff can be performed without reestablishing PPP connection that may occur in the process of performing handoff between PDSNs. When the PDSN recognizes the mobile node moving into its coverage area, it can quickly establish a communication channel with the mobile node based on the already received subscriber information. As a result, handoff is performed without reestablishing PPP. Accordingly, handoff between PDSNs can be performed faster, removing time needed for establishing a PPP session with a terminal and for terminating a previously set up PPP session.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.1B
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• pp.1-9
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• 2009

In this paper, we propose an enhanced handoff support scheme based on network-based mobility management protocol, Proxy Mobile IPv6 (PMIPv6), which is actively standardized by the IETF NETLMM working group. By utilizing the dynamic virtual hierarchy network architecture between mobile access gateways (MAGs), the proposed scheme can support network scalability and reliability to wireless access network. In addition, we propose pre-authentication process based on the policy store (PS) to support a fast and seamless handoff. We evaluate the performance of the proposed scheme in terms of handoff delay and end-to-end delay thru computer simulation. Thru, various computer simulation results, we verified the superior performance of the proposed scheme by comparing with the results of other schemes.

• The KIPS Transactions:PartC
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• v.9C no.1
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• pp.97-106
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• 2002

In 3GPP2 standard, MIP is used and a PDSN performs the function of FA to support macro mobility. When a MS is roaming from a PDSN area to another, the mobility supported is called macro mobility, while it is called micro mobility when a MS is roaming from a RN area to another in a PDSN area. Since a PDSN performs the function of FA in 3GPP2 standard, it is possible to support mobility but its mechanism is actually for supporting macro mobility, not for micro mobility, thus it is weak in processing fast and seamless handoff to support micro mobility. In this paper, we suggest the seamless handoff algorithm barred on multicast group mechanism to support micro mobility. Depending on the moving direction and velocity of a MS, the suggested algorithm constructs a multicast group of RNs on the forecasted MS's moving path, and maximally delays RNs'joining to a multicast group to increase the network efficiency. Moreover, to resolve the buffer overhead problem of the existent multicast scheme, the algorithm suggests that each RN buffers data only after the forecasted handoff time. To prove deadlock freeness and liveness of the algorithm. we use state transition diagrams, a Petri-net modeling and its reachability tree. Then, we evaluate the performance by simulation.