• Electronics and Telecommunications Trends
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• v.11 no.4 s.42
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• pp.13-25
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• 1996

본 고에서는 ADSL(Asymmetric Digital Subscriber Lines) 서비스를 DMT(Digital Multichannel Transmitter) 시스템 모델에 관하여 고찰한다. CSA(Carrier Service Area) 구역에서 6Mb/s급의 다중반송파변조방식(multi-carrier modulation)을 전송방식으로 하는 ADSL-3급 서비스가 가능한 가입자 루프 및 전송신호 특성을 고려한 설계 요구 조건을 살펴보고, 이를 만족하는 DMT ADSL 시스템 모델, 등화기 구조 및 DMT ADSL시스템의 성능예측방법을 고찰함으로써 보다 나은 성능의 ADSL시스템 구현을 위한 설계방향을 제시하고자 한다.

• Proceedings of the IEEK Conference
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• 2002.06d
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• pp.351-354
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• 2002

DVR(Digital Video Recorder), a recently popular visual monitoring system, is required to support multi camera channel display(upto 16 channels) with various display modes in real-time. For such a multichannel display system, it is well known that tearing artifacts become more serious. Thus, one needs to design a display system for DVR so that it does not show tearing artifacts as much as possible, but keeps real-time display speed. In this paper, we present our efforts in designing and implementing a display system which rarely ever shows tearing artifacts, but without degradation of required real-time display speed, and which displays character information stably without blinking.

• Progress in Superconductivity and Cryogenics
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• v.22 no.4
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• pp.62-66
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• 2020

We fabricated superconducting quantum interference devices (SQUIDs) based on Nb Josephson junctions, and characterized the key parameters of the SQUIDs. The SQUIDs are double relaxation oscillation SQUIDs (DROSs) having larger flux-to-voltage transfer coefficient than the standard DC-SQUIDs. SQUID sensors were fabricated by using Nb junction technology consisted of a DC magnetron sputtering and a conventional photolithography process. In multichannel SQUID systems for whole-head magnetoencephalography measurement with a helmet-type SQUID array, we need about 336 SQUID sensors for each system. In this paper, we fabricated a few hundred SQUID sensors, measured the critical current, flux modulation voltage and decided if each tested SQUID can be used for the multichannel systems. As the criterion for the acceptance of the sensors, we chose the critical current and amplitude of the modulation voltage to be 8 ㎂ and 80 ㎶, respectively. The average critical current of the SQUIDs was 10.58 ㎂. The typical flux noise of the SQUIDs with input coil shorted was 2 μΦ0/√Hz at white region.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 1996.06a
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• pp.277-280
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• 1996

• Journal of Sensor Science and Technology
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• v.10 no.4
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• pp.239-249
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• 2001

LAPS is a device which is dependent on the bias potential between a pH sensitivity and alternating photocurrent. We implemented the multichannel LAPS device and the detection system which was able to effectively measure the sensor's output by a synchronized detection circuit and multiple methods. The implemented LAPS was structured the multiple sensing sites for analyzing a various components simultaneously. And the system included a time-division method using one pre-amplifier being able to detect the multichannel pH concentration preserving a high S/N ratio and a control part. System hardware consists of a pre-amplifier, digital unit and sensor unit, and software consists of a system program and PC program. As results, we verified the successful operations of system including an implemented pre-amplifier and signal processing units.

• Bulletin of the Korean Chemical Society
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• v.23 no.11
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• pp.1560-1567
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• 2002

The transformation devised by Lecomte and Ueda for the study of resonance structures in the multichannel quantum defect theory (MQDT) is used to analyze partial photofragmentation cross section formulas in MQDT analogous to Fano's resonance formula obtained in the previous work for the system involving two open and one closed channels. Detailed comparison of the MQDT results with the configuration mixing (CM) ones is made. Resonance structures and their geometrical relations in the MQDT formulation are revealed and classified by combining Lecomte and Ueda's theory with the geometrical method devised to study the coupling between background and resonance scatterings.

• Korean Journal of Optics and Photonics
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• v.8 no.1
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• pp.63-67
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• 1997

We have experimentally investigated the fiber four-wave mixing effect on equal spaced multichannel optical transmission system with dispersion shifted fiber. To reduce the fiber four-wave mixing effect, we set the polarization states of the adjacent channels to be orthogonal each other by using polarization controller. In this case, we can reduce the transmission power penalty by 1.5 dB compared with that of equal polarization states.

• Bulletin of the Korean Chemical Society
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• v.12 no.2
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• pp.228-238
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• 1991

Generalized multichannel quantum defect theory [C. H. Greene et al. Phys. Rev., A26, 2441 (1982)] is implemented to the vibrational predissociation of triatomic van der Waals molecules. As this is the first one of such an application, the dependences of the quantum defect parameters on energy and radius are examined carefully. Calculation shows that, in the physically important region, quantum defect parameters remain smoothly varying functions of energy for this system as in atomic applications, thus allowing us very coarse energy mesh calculations for the photodissociation spectra. The choice of adiabatic or diabatic potentials as reference potentials for the calculation of quantum defect parameters as done by Mies and Julienne [J. Chem. Phys., 80, 2526 (1984)] can not be used for this system. Physically motivated reference potentials that may be generally applicable to all kinds of systems are utilized instead. In principle, implementation can be done to any other predissociation processes with the same method.

• Journal of Communications and Networks
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• v.13 no.3
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• pp.221-231
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• 2011

A joint multipath routing algorithm and channel allocation and scheduling for wireless multihop and multichannel systems is discussed. In packet transmission, distribution of packets to multiroutes makes it possible to reduce the transmission cost of the channels. Cross-layer cooperation of routing, channel allocation, and scheduling is an effective method of packet distribution. As a framework for the cooperation, we propose a multiroute distance vector routing (MDVR) scheme. In the MDVR scheme, the routing table is logically placed in between the routing and link layers, and the table plays the role of a service access point between these two layers. To evaluate the performance of MDVR, simulation is performed in a multichannel, multihop environment. The simulation results show that the MDVR framework can be efficiently implemented in the form of a distributed routing algorithm. It is also shown that in MDVR, the system-wise channel efficiency is almost 25% higher than that in a conventional single-route routing approach.

• Journal of Communications and Networks
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• v.17 no.2
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• pp.172-183
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• 2015

To provide an efficient link maintenance approach, we propose a cross layer medium access control (LM-MAC) protocol for multichannel cognitive radio ad hoc networks. Link establishment and reliable transmission are two key problems for a perfect link maintenance mechanism. Since the cognitive user (CU) pairs have to reestablish their links each frame, in the proposed MAC protocol, three different access modes are designed to guarantee transmission efficiency in continuous frames. To enhance the transmission reliability, each CU will create a father spectrum list (FSL) after joining in the network. FSL is divided into three groups of sub-channels with different functions to compensate the packet loss caused by the primary users' appearance and the deep fading. Meanwhile, since the transmitter and the receiver will share the same FSL, periodical cooperative sensing is adopted to further optimize the former problem. Finally, compared with the existing opportunistic multichannel (OMC)-MAC protocol, the proposed LM-MAC protocol achieves better system performance in terms of saturation throughput, continuity and access delay.