• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.11
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• pp.2597-2615
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• 2013

This paper proposes a dynamic downlink load control scheme that jointly employs dynamic load threshold management and virtual coverage management schemes to reduce the degree of performance degradation due to traffic overload in two-tier femtocell networks. With the proposed scheme, the downlink load in a serving macrocell is controlled with a load threshold which is adjusted dynamically depending on the varying downlink load conditions of neighboring macrocells. In addition, traffic overloading is alleviated by virtually adjusting the coverage of the overloaded serving macrocell, based on the adjusted load threshold of the serving macrocell. Simulation results show that the proposed scheme improves the performance of two-tier femtocell networks in terms of the outage probability and sum throughput. This improvement is significantly increased with appropriate values of load thresholds and with an intermediate-level adjustment of the virtual coverage area (i.e., handover hysteresis margin: HOM). Furthermore, the proposed scheme outperforms both a previously proposed load control scheme with a static load threshold and the LTE system without a HOM adjustment.

• 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 Information Processing Systems
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• v.12 no.4
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• pp.661-680
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• 2016

The vehicle license plate recognition (VLPR) system analyzes and monitors the speed of vehicles, theft of vehicles, the violation of traffic rules, illegal parking, etc., on the motorway. The VLPR consists of three major parts: license plate detection (LPD), license plate character segmentation (LPCS), and license plate character recognition (LPCR). This paper presents an efficient method for the LPCS and LPCR of Korean vehicle license plates (LPs). LP tilt adjustment is a very important process in LPCS. Radon transformation is used to correct the tilt adjustment of LP. The global threshold segmentation method is used for segmented LP characters from two different types of Korean LPs, which are a single row LP (SRLP) and double row LP (DRLP). The cross-correlation matching method is used for LPCR. Our experimental results show that the proposed methods for LPCS and LPCR can be easily implemented, and they achieved 99.35% and 99.85% segmentation and recognition accuracy rates, respectively for Korean LPs.

• The Journal of the Acoustical Society of Korea
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• v.29 no.1
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• pp.62-68
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• 2010

This paper proposes a new masking threshold adjustment strategy to improve the performance for speech signals in low bit-rate audio coding. After determining formant regions, the masking threshold is adjusted by using the energy ratio of each sub-band to the average energy of each formant. More quantization noises are added to the bands that have relatively large energy, but less distortion is allowed in spectral valley regions by allocating more bits, which reflects the concept of perceptual weighting widely used in speech coding. From the results of objective speech quality measure, we verified that the proposed method improves quality for the speech input signals compared to the conventional one.

• The KIPS Transactions:PartC
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• v.10C no.4
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• pp.455-462
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• 2003

Techniques for the reduction of SRTS jitter and pointer adjustment jitter are studied. To reduce the stuffing jitter several methods have been proposed, such as bit leaking, stuff threshold modulation and sigma delta modulation. The characteristics of jitter generated in SRTS and pointer adjustment systen implementing these reduction techniques is analyzed with computer simulation. The results show that ms jitter value decreases to less than 50% as compared to a conventional pointer adjustment system. The amplitude of SRTS jitter using new techniques decreases or Increases dependent on system parameter.

• Transactions of the Korean Society of Automotive Engineers
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• v.7 no.7
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• pp.32-41
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• 1999

In this study, a new knocking control algorithm was developed using the knock threshold value auto-correction algorithm. This algorithm uses the Fast Fourier Transform9FFT) method by measuring cylinder block vibration signals of a 1498 cc four-cylinder spark ignition engine. The experimental results show the proposed knock control algorithm provides improved performance compared to existing methods. The results also show that the proposed FFT algorithm provides real-time adjustment of the knock threshold value.

• Environmental and Resource Economics Review
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• v.22 no.2
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• pp.393-410
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• 2013

We employ a threshold vector error correction models (TVECM) to investigate the nonlinear dynamic adjustment of gasoline prices in Korea. We consider 10 regional gasoline markets including Seoul, Busan, Daegu, Incheon, Kwangju, Daejeon, Ulsan, Kangwon, Chungbuk, Jeonbuk and construct 9 price differences against Seoul. We use the bootstrap procedure suggested by Hansen (1999) and generalized by Lo and Zivot (2001) to show that three-regime TVECM is suitable for our analysis. Results indicate the gasoline price adjustment processes are nonlinear. Our estimation shows that Seoul-Daejeon, Seoul-Daegu and Seoul-Ulsan have bigger transaction costs than other market pairs and thus gasoline prices of these three regional markets are lower than that of Seoul. Gasoline prices of the other 6 regional markets are close to Seoul's price. One interesting finding is that the transaction costs are not proportional to geographical distances. This implies that transportation costs are not the main factor of the transaction costs. The transaction costs may depends on the competition intensity of gasoline markets in supply side.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.5
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• pp.2651-2673
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• 2019

In order to detect Denial of Service (DoS) attacks, victim-side detection methods are used popularly such as static threshold-based method and machine learning-based method. However, as DoS attacking methods become more sophisticated, these methods reveal some natural disadvantages such as the late detection and the difficulty of tracing back attackers. Recently, in order to mitigate these drawbacks, source-side DoS detection methods have been researched. But, the source-side DoS detection methods have limitations if the volume of attack traffic is relatively very small and it is blended into legitimate traffic. Especially, with the subtle attack traffic, DoS detection methods may suffer from high false positive, considering legitimate traffic as attack traffic. In this paper, we propose an effective source-side DoS detection method with traffic seasonality aware adaptive threshold. The threshold of detecting DoS attack is adjusted adaptively to the fluctuated legitimate traffic in order to detect subtle attack traffic. Moreover, by understanding the seasonality of legitimate traffic, the threshold can be updated more carefully even though subtle attack happens and it helps to achieve low false positive. The extensive evaluation with the real traffic logs presents that the proposed method achieves very high detection rate over 90% with low false positive rate down to 5%.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.8
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• pp.1848-1853
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• 2003

Stuff threshold modulation(STM) technique is analyzed as method for reducing pointer adjustment jitter. The method for jitter reduction is described, and simulation results are presented to illustrate rms jitter performance. The results show that rms jitter value decrease to less than 50％ as compared to a conventional pointer adjustment system.

• 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.