• Title/Summary/Keyword: Carrier

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On the Carrier Spacing for Mobile Multimedia Systems

  • Hong Een-Kee;Yun Sang-Hyuck;Kim Jeong-Geun
    • Journal of Communications and Networks
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    • v.8 no.2
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    • pp.182-186
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    • 2006
  • Previous approaches to sizing the carrier spacing for voice-oriented cellular systems have been based on the outage requirement. However, such a design paradigm needs to be changed as the performance of most upcoming cellular systems employing adaptive modulation and coding (AMC) techniques is more sensitive to throughput than outage. In this paper, we propose a novel approach to determining the carrier spacing which is based on a throughput criterion. The proposed method reflects well the characteristics of throughput-sensitive cellular systems that transport multimedia traffic. Numerical results show that our approach requires less carrier spacing, thus leading to more efficient spectrum utilization.

Terahertz Oscillations in p-Type Quantum-Well Oscillators

  • Cao, J.C.;Li, A.Z.
    • Journal of Korean Vacuum Science & Technology
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    • v.6 no.1
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    • pp.43-45
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    • 2002
  • We have theoretically investigated steady-state carrier transport and current self-oscillation in negative-effective-mass (NEM) p$\^$+/pp$\^$+/diodes. The current self-oscillation here is a result of the formation and traveling of electric field domains in the p base having a NEM. The dependence of self-oscillating frequency on the applied dc voltage is obtained by detailed numerical simulations. In the calculations, we have considered the scatterings by carrier-impurity, carrier-acoustic phonon, carrier-polar-phonon, and carrier-nonpolar-phonon-hole interactions . This kind of NEM oscillator allows us to reach a current oscillation with terahertz frequency, thus it may be used as a broadband source of terahertz radiation.

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The Proposal of Efficient Hit Prevention Technique according to the Frequency Hopping Pattern in Orthogonal Multi-Carrier FH/CDMA System (직교 멀티캐리어 FH/CDMA 시스템에서 주파수 도약 패턴에 따른 효율적인 충돌 방지 기법 제안)

  • 이문승
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.6 no.2
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    • pp.141-150
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    • 2002
  • In this paper, we composed orthogonal multi carrier FH/CDMA system using frequency hopping sequence. Considering hit possibilities by delayed other user's signals we searched the optimal number of user access carrier slots not to influence on performance deterioration with the variation of number of carrier slots according to the number of user access carrier slots. A]io, we evaluated the BER performance improvement due to TCM and Concatenated coding technique by computer simulation.

Optimization of input carrier powers considering satellite link environment in the multi-level SCPC systems (Multi-level SCPC 시스템에서 링크환경을 고려한 중계기 입력반송파 전력의 최적화)

  • 김병균;최형진
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.21 no.5
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    • pp.1240-1255
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    • 1996
  • This paper suggests power optimization technique in multi-level SCPC system as a method for efficient utilization of limited satellite power. The power optimization is realized by optimal assignment of satellite input carrier powers considering interference and noise generated in up-link and down-link. The Fletcher-Powell algorithm searching minimum(or maximum) point using gradient information is used to detemine the optimal input carrier powers. To apply Flectcher-Powell algorithm mathematical descriptions and their partial derivatives to interference and nose are presented. Because a target, which should be optimized, is satellite input carrier power, amplitude of each carrier group will be assumed to be an independent variable. The performance criterion for optimal power assignmentis classified into 4 categories with respect to CNR of destination receiver earth station to meet the requirement for various satellite link environment. Simulation results for two-level, four-level and six-level SCPC system are presented.

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The Present Status of Pumps Installed in the Large Merchant Ships (대형 상선에서의 펌프사용 현황)

  • Kim, You-Taek;Nam, Chung-Do;Lee, Young-Ho
    • The KSFM Journal of Fluid Machinery
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    • v.4 no.4 s.13
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    • pp.43-52
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    • 2001
  • Pumps arre used extensively for transporting fluid in many ships. However, the present state of pumps used in the large merchant ships has not been studied. In this paper, we have reported the general description of the operating pumps according to the different ship types(Bulk, Container, Car-Carrier, Tanker, LNG). Moreover, the pump total powers are compared with the main engine Normal Continuous Rating power and the pump total weights are also compared with the ship deadweight.

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Analysis of success rate of GPS carrier phase ambiguity resolution in Korea peninsula

  • Soo, Son-Ji;In, Jee-Gyu
    • 제어로봇시스템학회:학술대회논문집
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    • 2001.10a
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    • pp.114.1-114
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    • 2001
  • GPS Receiver gives pseudorange Doppler and integrated carrier phase for measurements to compute navigation information. Thought the integrated carrier phase can be transfer to the equal domain as pseudorange by multiplying the wave length of the received signal, in order to get position information from the carrier phase measurements the integer ambiguity should be resolved. And differencing technique is generally used to eliminate the common error terms of the integrated carrier phase measurements between robber and server. In short baseline double-differencing operation has effect on elimination the common biases for both stations and thus ambiguity resolution are to be reliable. But the baseline increases, the integer ambiguity resolution is hardly, due to the correlated common error is increase ...

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A Study on the Effect of Device Degradation Induced by Hot-Carrier to Analog Circuits (Hot-Carrier에 의한 소자 외쇠화가 아날로그 회로에 미치는 영향)

  • 류동렬;박종태;김봉렬
    • Journal of the Korean Institute of Telematics and Electronics A
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    • v.31A no.12
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    • pp.91-99
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    • 1994
  • We used CMOS current mirror and differenial amplifier to find out how the degradation of each devices in circuit affect total circuit performance. The devices in circuit wer degraded by hot-carrier generated during circuit operation and total circuit performance were changed according to the change of each device parameters. To examine the circuit performance phenomena of current mirror, we analyzed three diffent kinds of current mirrors and made correlation model between circuit performance and stressed device parameters, and compare hot-carrier immunity of these circuits. Also we analyzed how the performance of differential amplifier degraded from the initial value after hot-carrier stress incircuit operations.

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A Study on the Thermal Design of the Cryogenic LNG Carrier (초저온 LNG선의 열설계에 관한 연구)

  • 김용모;고상철;천병일;김경근
    • Journal of Advanced Marine Engineering and Technology
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    • v.17 no.4
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    • pp.1-10
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    • 1993
  • This paper introduces the outline of hull structure to the sorts of LNG carrier briefly. Especially, explains in detail for the insulation system of Moss Rosenberg Verft spherical tank type LNG carrier. It is not easy task to calculate exactly the temperature distribution of hull because of very complicated structure of hull. Therefore, in this paper by the adequate modeling of the Moss Rosengerg spherical tank type LNG carrier, a program is developed which calculate the temperature distribution of every hull and estimate the heat influx from every hull and output the BOR according to the variation of atmospheric conditions on boyage.

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A Study on the Computation of Hull Temperature Distribution and Boil off Ratio of MRV Type LNG Carrier (MRV형 LNG선의 선체온도분포 및 증발률 산정에 관한 연구)

  • 천병일;김용모;김경근
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.18 no.4
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    • pp.986-996
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    • 1994
  • Insulation system of LNG carrier has made important roles such as maintaining a proper Boil off Ratio(BOR) for the cargo and avoiding the excessive low temperature of the adjacent inner hull beyond the permissible limit. At the same time, safety and economy of the LNG transportation by the ship are connected with the performance of the insulation system. Also, thermal insulation system of LNG carrier is one of the most advanced technique with the structure analysis of tank, welding and assembling. In this study a computer program is developed to calculate the hull temperature distribution and BOR, which are important factors in thermal design for the Moss Rosenberg Verft spherical tank type LNG carrier. Detailed results for hhull temperature distribution close to LNG tank, BOR and the thickness effect of insulation material are reported in this paper in the range of standare design sea condition.

MOSFET Characteristics and Hot-Carrier Reliability with Sidewall Spacer and Post Gate Oxidation (Sidewall Spacer와 Post Gate Oxidation에 따른 MOSFET 특성 및 Hot Carrier 신뢰성 연구)

  • 이상희;장성근;이선길;김선순;최준기;김용해;한대희;김형덕
    • Proceedings of the IEEK Conference
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    • 1999.06a
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    • pp.243-246
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    • 1999
  • We studied the MOSFET characteristics and the hot-carrier reliability with the sidewall spacer composition and the post gate oxidation thickness in 0.20${\mu}{\textrm}{m}$ gate length transistor. The MOSFET with NO(Nitride+Oxide) sidewall spacer exhibits the large degradation of hot-carrier lifetime because there is no buffering oxide against nitride stress. When the post gate oxidation is skipped, the hot-carrier lifetime is improved, but GIDL (Gate Induced Drain Leakage) current is also increased.

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