• The Journal of the Korea institute of electronic communication sciences
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• v.15 no.3
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• pp.433-438
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• 2020

Nodes on a data communication path in a wireless network emit electro-magnetic waves whenever they transmit packets; thus, the path can be exposed and identified with capturing and analyzing a sequence of the signals emitted there. One of countermeasures against a malicious eavesdropper is to let certain nodes mimic the nodes on the data path in sending dummy packets. In this paper we propose a packet transfer protocol which establishes the shortest path between source-destination pair a time and restricts heavy generation of dummy packets. We verify the location-privacy of a node on the communication paths through simulation.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.10a
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• pp.531-534
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• 2010

In this paper, we introduce an efficient energy management using a notion of virtual energy system for shared solar-powered sensor network. Virtual energy system is an abstraction that allows sensor network applications on a node to reserve their own fractions of the shared solar cell and the shared rechargeable battery, hence achieving logically partition of a shared renewable power source with no change in design and implementation. Our results show that our design and implementation are reliable, lightweight and efficient, allowing proper isolation of energy consumption among applications.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.05a
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• pp.598-599
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• 2015

For the wireless mesh networks, efficient routing protocol is required to transmit data from source to destination node through multi-hop transmission. Multipath routing enable the stable data transmission even in the case of traffic congestion or unstable link. In this paper, we propose partial multipath routing which does not make a full multipath but partial for some parts of unstable links. This partial multipath routing reduce the number of nodes for routing and minimized the required power.

• Journal of Communications and Networks
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• v.10 no.2
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• pp.186-193
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• 2008

A two-hop multiple-input multiple-output (MIMO) relay network which comprises a multiple antenna source, an amplify-and-forward MIMO relay and many potential users are studied in this paper. Consider the achievable sum rate as the performance metric, a joint design method for the processing units of the BS and relay node is proposed. The optimal structures are given, which decompose the multiuser MIMO relay channel into several parallel single-input single-output relay channels. With these structures, the signal-to-noise ratio at the destination users is derived; and the power allocation is proved to be a convex problem. We also show that high sum rate can be achieved by pairing each link according to its magnitude. The sum rate of three broadcast strategies, time division multiple access (TDMA) to the strongest user, dirty paper coding (DPC), and beamforming (BF) are investigated. The sum rate bounds of these strategies and the sum capacity (achieved by DPC) gain over TDMA and BF are given. With these results, it can be easily obtained that how far away TDMA and BF are from being optimal in terms of the achievable sum rate.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.361-361
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• 2010

노광을 통해 형성되는 패턴 단위를 Shot이라 부르며, 이때 노광되는 각 Shot은 Wafer상에 이전 Layer에서 형성되어 있는 Shot 위에 정확히 중첩되어 형성 시켜야하며, 노광된 Shot이 중첩되어야 할 이전 Layer의 Shot에 대해 얼마만큼의 위치적 오차를 가지고 형성 되었는가 하는 것은 중첩위치오차 (Overlay Alignment Error)로 계측 된다. 이렇게 계측된 중첩위치오차는 현재 진행된 Lot에 대한 재 공정 필요 여부를 결정하거나 다음 Lot 공정을 진행할 때 각 Shot를 이전 Layer Shot에 정확히 중첩시키기 위해 얼마만큼의 위치 보정이 필요한지를 결정하는데 사용된다. 이처럼 Device Node의 Shrink로 인해 엄격한 허용도를 만족시키기 위해서는 Overlay 측정 정확도의 향상이 매우 중요해 지고 있다. 본 논문에서는 Halogen Lamp 대비 Led의 Light Intensity 부분에 대해 중점적으로 실험 하였으며, RBG Type의 Led는 Halogen Lamp Wavelength (광대역) 400nm ~ 800nm가 모두 포함된 White Light Source에서 특정한 단일파장대역 600nm ~ 650nm (가시광선 Led 영역)에서 계측하는 Layer에 대해 적용 가능성을 제시하였다.

• JSTS:Journal of Semiconductor Technology and Science
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• v.8 no.1
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• pp.11-20
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• 2008

The structure of 2-bit/cell flash memory device was characterized for sub-50 nm non-volatile memory (NVM) technology. The memory cell has spacer-type storage nodes on both sidewalls in a recessed channel region, and is erased (or programmed) by using band-to-band tunneling hot-hole injection (or channel hot-electron injection). It was shown that counter channel doping near the bottom of the recessed channel is very important and can improve the $V_{th}$ margin for 2-bit/cell operation by ${\sim}2.5$ times. By controlling doping profiles of the channel doping and the counter channel doping in the recessed channel region, we could obtain the $V_{th}$ margin more than ${\sim}1.5V$. For a bit-programmed cell, reasonable bit-erasing characteristics were shown with the bias and stress pulse time condition for 2-bit/cell operation. The length effect of the spacer-type storage node is also characterized. Device which has the charge storage length of 40 nm shown better ${\Delta}V_{th}$ and $V_{th}$ margin for 2-bit/cell than those of the device with the length of 84 nm at a fixed recess depth of 100 nm. It was shown that peak of trapped charge density was observed near ${\sim}10nm$ below the source/drain junction.

• Journal of Power System Engineering
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• v.3 no.2
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• pp.26-33
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• 1999

Pressure pulsation Inside the discharge and suction cavity of rotary and scroll compressor are often a major source of objectionable noise and vibration. The key factor of these noise and vibration is due to the cavity resonance. It is not only necessary to understanding the characteristics of pulsation in order to reduce the excitation force of gas to the cavity but also to verifying the phenomena of cavity resonance. For the purpose of these understandings, measurement and simulation of cavity resonance can lead to a better understandings how they occur and be very important to identify the ways to reduce the noise efficiently. In this paper, modeling of the cavity(internal acoustics inside the shell) is discussed and simulated using FEM. Results from the simulation are compared with those measurement in experiments. In describing of cavity mode by experiments, it is very important to specify the exact conditions under which they are measured. Finally, this paper shows the one example of reduced cavity resonance in the compressor.

• Publications of The Korean Astronomical Society
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• v.19 no.1
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• pp.77-81
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• 2004

A high performance computing cluster for astronomical computations has been built at Korea Astronomy Observatory. The 64 node cluster interconnected with Gigabit Ethernet is composed of 128 Intel Xeon processors, 160 GB memory, 6 TB global storage space, and an LTO (Linear Tape-Open) tape library. The cluster was installed and has been managed with the Open Source Cluster Application Resource (OSCAR) framework. Its performance for parallel computations was measured with a three-dimensional hydrodynamic code and showed quite a good scalability as the number of computational cells increases. The cluster has already been utilized for several computational research projects, some of which resulted in a few publications, even though its full operation time is less than one year. As a major resource of the $K^*Grid$ testbed, the cluster has been used for Grid computations, too.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.12A
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• pp.1160-1170
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• 2010

Existing multipath routing mechanism has much overhead to maintain the state of nodes on the multipath route and does not guarantees completely disjoint multipath construction from source to destination. In this paper, we propose an Explicit Disjoint Multipath (EDM) routing algorithm to enhance energy efficiency through removing the flooding mechanism for route discovery process, minimizing the number of nodes participating in route update and balancing the traffic load for entire network. EDM constructs logical pipelines which can create disjoint multipaths in logical way. Then it physically performs anchor node based geographic routing along the logical pipeline in order to build multipath to the destination. EDM can provide the distribution effect of traffic load over the network, help to balance the energy consumption and therefore extend the network lifetime.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.12A
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• pp.1122-1127
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• 2010

In this paper, we propose a relay-based DF cooperative communication scheme using repetitive transmission algorithm for wireless LAN environments on D-STBC. Additional transmission diversity gain can be obtained by repetitive transmission algorithm. However, in comparison with conventional schemes, data rate is decreased in half. We consider data modulation constellation twice higher than conventional schemes. Further, system complexity is decreased and performance degradation is minimized because repetitive transmission algorithm is adapted between source and relay node. We show the uncoded BER performance of the proposed algorithm over HiperLAN/2 Rayleigh fading channel.