• Journal of information and communication convergence engineering
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• v.8 no.6
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• pp.655-659
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• 2010

In the conventional PNC scheme, the relay node requires simultaneous transmission of two source nodes with strict power control and carrier-phase matching between two received symbols. However, this pre-equalization process at source nodes is not practical in fading channels. In this letter, we propose a novel physical-layer network coding (PNC) scheme with log-likelihood ratio (LLR) conversion for fading channels, which utilizes not pre-equalizer at transmitters (source nodes) but joint detector at receiver (relay node). The proposed PNC requires only channel side information at the receiver (CSIR), which is far more practical assumption in fading channels. In addition, the proposed PNC scheme can use the conventional modulation scheme like M-QAM regardless of modulation order, while the conventional PNC scheme requires reconfiguration of modulation scheme at the source nodes for detection of the received signal at relay node. We consider the combination of the proposed PNC and channel coding, and find that the proposed PNC scheme is easily combined the linear channel codes such as turbo codes, LDPC, and convolutional codes.

• ETRI Journal
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• v.37 no.4
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• pp.717-726
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• 2015

In this paper, we study an asymmetric two-way relaying network where two source nodes intend to exchange information with the help of multiple relay nodes. A hybrid time-division broadcast relaying scheme with joint relay selection (RS) and power allocation (PA) is proposed to realize energy-efficient transmission. Our scheme is based on the asymmetric level of the two source nodes' target signal-to-noise ratio indexes to minimize the total power consumed by the relay nodes. An optimization model with joint RS and PA is studied here to guarantee hybrid relaying transmissions. Next, with the aid of our proposed intelligent optimization algorithm, which combines a genetic algorithm and a simulated annealing algorithm, the formulated optimization model can be effectively solved. Theoretical analyses and numerical results verify that our proposed hybrid relaying scheme can substantially reduce the total power consumption of relays under a traffic asymmetric scenario; meanwhile, the proposed intelligent optimization algorithm can eventually converge to a better solution.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.7B
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• pp.706-718
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• 2002

In bluetooth system, there are two kinds of interference. One is the frequency static interference, for example 802.11 direct sequence, the interferer uses fixed frequency band. Another is frequency dynamic interference, for example other piconets or 802.11 frequency hopping, the interferer uses dynamic frequency channel and cant be estimated. In this paper we introduce a novel solution of hybrid method of Listen-Before-Talk (LBT) and Adaptive Frequency Hopping (AFH) to address the coexistence of bluetooth and Direct Sequence of wireless local area network (WLAN). Before any bluetooth packet transmission, in the turn around time of the current slot, both the sender and receiver sense the channel whether there is any transmission going on or not. If the channel is busy, packet transmission is withdrawn until another chance. This is the LBT in Bluetooth. Because of asymmetry sense ability of WLAN and bluetooth, AFH is introduced to combat the left front-edge packet collisions. In monitor period of AFH, LBT is performed to label the channels with static interference. Then, all the labeled noisy channels are not used in the followed bluetooth frequency hopping. In this way, both the frequency dynamic and frequency static interference are effectively mitigated. We evaluate the solution through packet collision analysis and a detail realistic simulation with IP traffic. It turns out that the hybrid method can combat both the frequency dynamic and frequency static interference. The packet collision analysis shows it almost doubles the maximal system aggregate throughput. The realistic simulation shows it has the least packet loss.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.10a
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• pp.186-189
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• 2008

The flex plate, an automotive part which mounts to the automotive engine to transfer torque to transmission, should have considerable hardness and shape accuracy. As a way to produce the flex plate, the hot press forming technology which takes advantages of high formability at elevated temperature, enhanced strength and shape stability was introduced. Therefore, as one of major process parameters the heat treatment condition should be determined to obtain appropriate hardness in the range of manufacturer's specifications. In this study, two heat treatments, austempering and quenching and tempering (QT), were compared as feasible conditions fur the hot press forming of high-carbon tool steel and the hardness and toughness after heat treatments were evaluated. The study showed that both heat treatments resulted in improved hardness but only quenching and tempering showed practicable range of toughness.

• Journal of Chest Surgery
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• v.13 no.3
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• pp.301-305
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• 1980

Myasthenia gravis is a disorder that affects neuromuscular transmission in a way that is still poorly understood. some think that myasthenia gravis results from a reduction of available acetylcholine receptors in neuromuscular junctions, consequent to some form of autoimmune injury. Surgical interest in this disease was first aroused in 1939 when Blalock observed that some patients with thymic tumors and myasthenia gravis improved following thymectomy. This report represents two cases of myasthenia gravis. The 14-year-old girl was admitted to Korea Universtiy Hospital with chief complaintment of bilateral ptosis, diplopia, swallowing difficulty, and mastication difficulty, which were relieved by administration of edrophonium (Tensilon) chloride, given intravenously. Myasthenica gravis was confirmed and thymectomy was given. After thymectomy, symptoms were relieved but the administration of neostigmine was contijued to be needed till following 3 months. After that period, she was free from this symptoms without anticholinesterase drugs. Second case is 57 year old male who has the symptoms of diplopia, bilatreal ptosis, walking disturbance, and speech difficulty. He had thymectomy too but in thymic tissue, malignant thymoma was included. He has subjective improvement only, with no major reduction of medication requirements after thymectomy.

• Journal of the Korean Professional Engineers Association
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• v.30 no.4
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• pp.18-29
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• 1997

The telecommunications industry pro-grossed as old media, but new media is going into a new era of multi-media in the 21st century. In the latter half of 1970s we saw a boom of new media as a post-telephone era began. As the machines grew to the world level(standard), facsimiles, minitels of France and word processors of Japan were developed. Today some 15 years since the advent of new media era, the progress of technology is astonishing. Advancement of technology is seen in V and U letters attached to semiconductor chips, astonishing capability advancement of light emitting lasers and photo-diodes, etc and additionally technology advancement in large capacitized light disks. Thus these technologies have made possible transmitting a broad band network and a mobile communication and digitalized broadcasting. Increased capacity of every terminal, e.g, "letters $.$ voice $.$ still and mov-ing pictures" are essential for new media simultaneous and two -way transmission.

• Journal of Korea Multimedia Society
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• v.19 no.12
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• pp.1992-1999
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• 2016

In layered communication architecture, each layer is designed to service its own functions to higher layer while getting serviced by lower layer. Usually layered architectures are not optimized in a total view of whole services and functions. So cross layer design pursues performance enhancements by optimizing in various ways. In LTE, MAC layer uses HARQ mechanism and RLC layer uses ARQ mechanism for retransmission. According to the 3GPP 36.331 specification, two layers' cooperation may not happen in an optimized way. This paper suggests an adaptive MAC layer approach which RLC layer's function might be initiated in MAC layer in advance to utilize MAC layer's idling wasting time for RLC layer's next decision. This adaptive ARQ method in MAC layer speeds up the next retransmission and reduces the overall transmission time. Emulation shows the improved performance in total retransmission time and retransmission success ratio. In wireless shadow area, the retransmission occurs frequently. Our approach has strong points in this poor wireless condition.

• Journal of KSNVE
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• v.9 no.3
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• pp.517-524
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• 1999

Mathematical formulas for multi-dimensional isolation analysis via vibrational power transmission can be derived in a rather simple form when the wave effects of the isolators are completely neglected. With increase of frequency range of interest, however, the wave effects play a very important role and hence cannot be neglected. The formulas get involved accordingly. In this study, a method of equivalent stiffness modeling of the isolators to include the wave effects is proposed in such a way that not only the complexity of the mathematical expressions but also that of experiments of necessity can be reduced. This method is illustratively applied to a two-dimensional vibration isolation system with nonrigid source and base structures.

• Proceedings of the KIEE Conference
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• 2004.04a
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• pp.247-249
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• 2004

Electric systems can be classified into two classes on the basis of the location of its energy source. One system is to be connected with its outside energy source. Obviously, these electric system is limited of its motion range and impossible to operate in the situation without a way to find an energy source nearby. another is to posses the energy source within it. These electric systems are free of motion range limit while their using is limited by the life of source. These limits can be tided over by using passive-type RF communication. RF-ID is a system that Is possible to interchange electricity and data by Radio Frequency to locate and identify various objects including a man.

• Proceedings of the KIEE Conference
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• 2002.07d
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• pp.2540-2542
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• 2002

In recent years, it is a worldwide trend that many power utilities focus their attention to employ up-to-date communication technology to the automation of their power plants and distribution systems. Automation Systems in Korea was installed using twisted pair cable(TPC), power line carrier(PLC), coaxial cable(CA), wireless network(wireless data, TRS and PCS). Among the communication media only Satellite Communication guarantees the reliable communication in case of emergency such as a flood, a heavy snow and an earthquake. It can integrate two-way satellite systems to existent nationwide SCADA controlling points of electric power transmission & distribution system that enables real time remote monitoring and controlling automatically. This paper presents some of design efforts for the satellite communication network as the media of Automation Systems.