• Journal of Institute of Control, Robotics and Systems
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• v.14 no.3
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• pp.318-325
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• 2008

In this paper, a dynamic backoff adjustment method of IEEE 802.15.4 is proposed for time-critical sporadic data in a noisy factory environment. For this, a superframe of IEEE 802.15.4 is applied to a real-time mixed data (periodic data, sporadic data, and non real-time message) transmission in factory communication systems. To guarantee a channel access of real-time sporadic(non-periodic) data, a transmission method using the dynamic backoff is applied to wireless control networks. For the real-time property, different initial BE, CW parameters are used for the dynamic backoff adjustment method. The simulat-ion results show an enhancement of the real-time performance of sporadic emergency data. The proposed method provides the channel access of real-time sporadic data efficiently, and guarantee real-time transmission simultaneously within a limite-d timeframe.

• ETRI Journal
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• v.32 no.5
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• pp.823-826
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• 2010

This letter proposes a handover ranging power adjustment scheme to improve handover performance. Incorrect ranging power can degrade handover performance due to the increased handover latency; therefore, the proposed scheme exploits the uplink channel information to adjust the uplink handover ranging power. Simulation results demonstrate that the proposed scheme reduces call outage probability by 33% compared to that of the conventional scheme. It also improves the number of users who satisfy the system requirements for handover interruption time.

• Korean Journal of Organic Agriculture
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• v.26 no.4
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• pp.571-583
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• 2018

The purpose of this study is to explore the dynamic properties of causality and asymmetric price transmission in the distributional channel of the tomato market in Korea. Using the wholesale and retail price series of the tomato market, we obtain the following results. First, the price transmission mechanism reveals the causal relationship channeling from the wholesale price to the retail price. Second, we find an asymmetric price transmission from the analysis using the threshold partial adjustment model. The retail price responds strongly when the wholesale price increases. On the other hand, the retail price shows sluggish adjustment when the wholesale price decreases.

• Journal of Internet Computing and Services
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• v.10 no.3
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• pp.85-94
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• 2009

In this work we propose an energy-efficient transmission strategy for wireless sensor networks that operate in a strict energy-constrained environment. Our transmission algorithm consists of two components: a binary-decision based transmission and a channel-aware backoff adjustment. In the binary-decision based transmission, we obtain the optimum threshold for successful transmission via Markov decision process (MDP) formulation. A channel-aware backoff adjustment, the second component of our proposal, is introduced to favor sensor nodes seeing better channel in terms of transmission priority. Extensive simulations are performed to verify the performance of our proposal over fading wireless channels.

• ETRI Journal
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• v.37 no.5
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• pp.845-855
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• 2015

To enable the coexistence of Licensed Assisted Access (LAA) and Wi-Fi in 5 GHz unlicensed bands, a new channel access mechanism is proposed. Accounting for the fairness between LAA and Wi-Fi, the proposed mechanism finds the optimal transmission time ratio by adaptively adjusting the transmission durations for LAA and Wi-Fi. In addition, we propose a new analytical model for the distributed coordination function of IEEE 802.11 through some modifications of conventional analytical models for saturation and non-saturation loads. By computing the activity ratio of Wi-Fi, the proposed analytical model is able to control the time ratio between LAA and Wi-Fi, which is required for practical implementation of the proposed access mechanism. Through numerical simulations, the proposed channel access mechanism is compared with conventional methods in terms of throughput and utility.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.47 no.6
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• pp.28-39
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• 2010

The study aims at offering a solution to the problems of transmission delay and data throughput decrease as the number of contending On-Board Units (OBU) increases by applying CSMA medium access control protocol based upon IEEE 802.11p. In a competition-based medium, contention probability becomes high as OBU increases. In order to improve the performance of this medium access layer, the author proposes EDCA which a adaptive adjustment of the Contention Windows (CW) considering traffic density and data type. EDCA applies fixed values of Minimum Contention Window (CWmin) and Maximum Contention Window (CWmax) for each of four kinds of Access Categories (AC) for channel-specific service differentiation. EDCA does not guarantee the channel-specific features and network state whereas it guarantees inter-AC differentiation by classifying into traffic features. Thus it is not possible to actively respond to a contention caused by network congestion occurring in a short moment in channel. As a solution, CWminAS(CWmin Adaptation Scheme) and ACATICT(Adaptive Contention window Adjustment Technique based on Individual Class Traffic) are proposed as active CW control techniques. In previous researches, the contention probabilities for each value of AC were not examined or a single channel based AC value was considered. And the channel-specific demands of IEEE 802.11p and the corresponding contention probabilities were not reflected in the studies. The study considers the collision number of a previous service section and the current network congestion proposes a dynamic control technique ACCW(Adaptive Control of Contention windows in considering the WAVE situation) for CW of the next channel.

• Journal of the Korean Institute of Telematics and Electronics
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• v.24 no.3
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• pp.472-477
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• 1987

In order to prevent the short-channel effects due to threshold voltage adjustment implantation in conventional n+ doped silicon gate process, a new approach involving automatic doping of polycide by boron during source and drain implantation is introduced. P-MOSFET devece fabricated by theis approach shows improved short channel characteristics than conventional device with n+ doped gate. Some concerns of adopting this approach in CMOS technology are addressed togetheer with some suggestions.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1992.05a
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• pp.86-90
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• 1992

We have studied the characteristics of n-and p-channel FETs with submicron channel length fabricated by twin-well process. Threshold voltage variation and potential distribution with channel ion implantation conditions and impurity profile of n-and p-channel region wee simulated using SUPREM-II and MINIMOS 4.0 simulater, P-channel FET had buried-channel in the depth of 0.15 $\mu\textrm{m}$ from surface by counter-doped boron ion implantation for threshold voltage adjustment. As a result of device measurement, we have obtained good drain saturation characteristics for 3.3 [V] opreation, minimized short channel effect with threshold voltage shift below 0.2[V], high punchthrough and breakdown voltage above 10[V] and low subthreshold value.

• Journal of Industrial Technology
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• v.22 no.A
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• pp.219-228
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• 2002

The divided channel is not often used on the river and when the installation is for the controlling of the flow quantity. The determination of the channel size is not a easy task. Model tests are examined to confirm the variation of distribution rate by the method of the channel installation and the position of the structure and the adjustment of numerical simulation is executed by the comparing of the results. This study is to execute numerical model according to installation of divided channel by using AQUADYN program, the 2nd dimension numerical model, and HEC-RAS program, the 1st dimension numerical model, by the shape of divided channel. Also, it compares with difference by method about each case.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.34D no.8
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• pp.35-40
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• 1997

To suppress the short channel effects in nMOSFET with 0.1.mu.m channel length, we have fabricated and characterized the ISRC n MOSFET with several process condition. When the recess oxide thickness is 100nm and the channel dose for threshold voltge adjustment is 6*10$^{12}$ /c $m^{-2}$ , B $F_{2}$$^{+}$, the maximum transconductance at $V_{DS}$ =2.0V is 455mS/mm and the BIDL is kept within 67mV. By comparing the ISRC n MOSFET with the conventioanl SHDD (shallowly heavily dopped drain) nMOSFET, we verify the suppression of short channel effects ISRC structure.e.