• Journal of the Institute of Convergence Signal Processing
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• v.10 no.1
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• pp.49-59
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• 2009

In this paper a watermarking algorithm is proposed to optimize the capacity of the digital watermark insertion in an experimental threshold using the characteristics of human visual system(HVS), adaptive scale factors, and weight functions based on discrete wavelet transform. After the original image is decomposed by a 3-level discrete wavelet transform, the watermarks for capacity optimization are inserted into all subbands except the baseband, by applying the important coefficients from the experimental threshold in the wavelet region. The adaptive scale factors and weight functions based on HVS are considered for the capacity optimization of the digital watermark insertion in order to enhance the robustness and invisibility. The watermarks are consisted of gaussian random sequences and detected by correlation. The experimental results showed that this algorithm can preserve a fine image quality against various attacks such as the JPEG lossy compression, noise addition, cropping, blurring, sharpening, linear and non-linear filtering, etc.

• Physical Therapy Korea
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• v.27 no.2
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• pp.102-110
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• 2020

Background: There is an opinion that improper postures of the head and cervical spine are associated with temporomandibular joint (TMJ) disorders (TMDs). Objects: The aim of this study was to investigate the proportions among the cervical kyphotic angle, physical symptoms including the pain intensity level of the TMJ, and severity of TMD disability in patients diagnosed with TMD. Methods: Sixty-two subjects participated in the study. The evaluation tools included measurements of the cervical kyphotic angle based on the Ishihara index, pressure pain threshold (PPT) on the TMJ, maximal mouth opening (MMO) without pain, current pain intensity level of the TMJ measured using the Quadruple Visual Analogue Scale (QVAS), Korean TMD (KTMD) disability index, KTMD Symptom Frequency/Intensity Scales (SFS/SIS), and Korean Headache Impact Test-6. Correlation analysis was conducted to investigate the correlations between the cervical kyphotic angle and parameters related to TMJ symptoms. Results: Variables that were significantly correlated with the cervical kyphotic angle were the PPT around the TMJ (r = 0.259, p < 0.05), current pain intensity level of the TMJ based on the QVAS (r = -0.601, p< 0.01), and usual pain intensity level based on the SIS (r = -0.379, p < 0.01). The level of TMD functional disability was significantly correlated with the degree of headache (r = 0.551, p < 0.01), level of PPT of the TMJ (r = -0.383, p < 0.01), pain-free MMO (r = -0.515, p < 0.01), pain intensity level of the TMJ based on the QVAS (r = 0.393, p < 0.01), TMD symptom frequency (r = 0.739, p < 0.01), usual pain intensity of the TMJ (r = 0.624, p < 0.01), and most severe pain intensity of the TMJ (r = 0.757, p < 0.01). Conclusion: There is a positive correlation between the cervical kyphotic angle and PPT and a negative correlation between the current and usual pain intensity levels of the TMJ. The cervical kyphotic angle was a predictor of the pain level, tenderness threshold, and intensity of pain in the TMJ.

• Korean journal of applied entomology
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• v.47 no.4
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• pp.407-411
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• 2008

This study was conducted to estimate the economic injury level (EIL) and economic threshold (ET) of the green peach aphid, Myzus persicae, on Chinese cabbage (Brassica campestris var). The changes of biomass of Chinese cabbage and M. persicae density were investigated after introduction of M. persicae at different density (0, 2, 5, 10, 15, and 20 per plant; inoculated at 10d after planting). The densities of M. persicae largely increased from the above initial densities to 0, 92.3, 177.4, 406.9, 440.4, and 471.3 aphids per plant at 18d after the initial inoculation, respectively. The biomass of Chinese cabbage significantly decreased with increasing the initial inoculated density of M. persicae: 602.0, 264.2, 262.0, 109.3, 151.0, and 67.3 g in above plots with different initial densities, respectively. The relationship between cumulative aphid days (CAD) and yield loss (%) of Chinese cabbage was well described by a nonlinear logistic equation. Using the estimated equation, EIL of M. persicae on Chinese cabbage was estimated 25 CAD per plant based on the yield loss 13%, which take into account of an empirical gain threshold 5% and marketable rate 92% of spring Chinese cabbage. Also, ET was calculated at 80% of EIL: 20 aphids per plant. Until a more elaborate EIL-model is developed, the present result may be useful for M. persicae management at early growth stage of Chinese cabbage.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.8
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• pp.17-22
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• 2007

In this paper, we propose a threshold estimation algorithm for a noncoherent IR-UWB receiver using 1-bit sampler. The proposed method reduces the hardware complexity by using the information of binary data resulted from 1-bit sampler instead of measuring the energy level of a received signal. Besides, mathematical modeling shows that the performances are similar to those of theoretically optimal threshold in terms of bit error rate. Computer simulations based on the IEEE 802.15.4a channel model also demonstrate the superiority of the proposed algorithm.

• Journal of Communications and Networks
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• v.10 no.2
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• pp.213-220
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• 2008

This paper analyzes a broadcasting technique for wireless multi-hop sensor networks that uses a form of cooperative diversity called opportunistic large arrays (OLAs). We propose a method for autonomous scheduling of the nodes, which limits the nodes that relay and saves as much as 32% of the transmit energy compared to other broadcast approaches, without requiring global positioning system (GPS), individual node addressing, or inter-node interaction. This energy-saving is a result of cross-layer interaction, in the sense that the medium access control (MAC) and routing functions are partially executed in the physical (PHY) layer. Our proposed method is called OLA with a transmission threshold (OLA-T), where a node compares its received power to a threshold to decide if it should forward. We also investigate OLA with variable threshold (OLA-VT), which optimizes the thresholds as a function of level. OLA-T and OLA-VT are compared with OLA broadcasting without a transmission threshold, each in their minimum energy configuration, using an analytical method under the orthogonal and continuum assumptions. The trade-off between the number of OLA levels (or hops) required to achieve successful network broadcast and transmission energy saved is investigated. The results based on the analytical assumptions are confirmed with Monte Carlo simulations.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.4
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• pp.77-85
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• 1999

By assuming a linearly graded depletion edge approximation in the intrinsic MOS region and by taking into account the mobility variation dependent on both lateral and vertical fields, a physics-based analytical model for a short-channel(n-channel) MOSFET is suggested. Derived expressions for the threshold voltage and the drain current of typical MOSFET is structures could be used in a unified manner for all operating range. The threshold voltage was calculated by changing following variables : channel length, drain-source voltage, source-substrate voltage, p-substrate doping level, and oxide thickness. It is shown that the threshold voltage decreases almost exponentially as the channel length decreases. In addition, the short-channel threshold voltage roll-off, the channel length modulation and the electron mobility degradation can be derived within a satisfactory accuracy.

• Progress in Medical Physics
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• v.7 no.2
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• pp.79-90
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• 1996

In this paper, we present an automatic threshold decision method to detect the contour of the a 2-D echocarodiogram by using the Bayes estimator for the boundary-like region. The boundary-like region is constructed from the conduction coefficient of the heat anisotro-pic diffusion method which enforces the blurred image during the preprocessing step. For the boundary-like region, we used the Bayes estimator to select an optimal threshold level. From this threshold value, the contour of the echocardigrams can be detected automatically Finally by overlapping the estimated contour to the original echocardiogram, we can obtain the contour enforced ultrasound echocardiogram.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05b
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• pp.245-248
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• 2005

It should be noted that the critical chloride threshold level is not considered to be a unique value for all conditions. This value is dependent on concrete mixture proportions, cement type and constituents, presence of admixtures, environmental factors, steel reinforcement surface. conditions, and other factors. In this study, the accelerated corrosion test for reinforcing steel was conducted by electrochemical and cyclic wet and dry seawater method, respectively and during the test, corrosion monitoring by half cell potential method was carried out to estimate the chloride corrosion threshold value when corrosion for reinforcing steel in concrete was perceived. For this purpose, lollypop and right hexahedron test specimens were made for 31.4$\%$, 41.5$\%$ and 49.7$\%$ of w/c, respectively and then the accelerated corrosion test for reinforcing steel was executed. It was observed from the test that the time to initiation of corrosion was found to be different with water-cement ratio and accelerated corrosion test method, respectively and the chloride corrosion threshold value was found to range from 0.91 to 1.43 kg/$m^{3}$.

• Journal of the Korean Institute of Intelligent Systems
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• v.17 no.4
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• pp.443-450
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• 2007

In this paper, we propose a novel threshold selection method based on statistical information on gray-levels of given images and interval-valued fuzzy sets. In the proposed threshold selection method, the interval-valued fuzzy set is used to represent more definitely the relationship between a pixel and its belonging region, that is, the object and the background. Also the statistical information on gray-level is used to determine the rules and partitions of interval-valued fuzzy sets. To show the validity of the proposed method, we compared the performance of the proposed with those of conventional methods such as Otsu's method, Huang and Wang's method applied to 5 test images with various types of histograms.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.15 no.12
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• pp.4617-4632
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• 2021

IEEE 802.11ax is a protocol being developed for high-density Wireless Local Area Networks (WLAN). Several algorithms have been proposed to improve the level of spatial reuse applied in IEEE 802.11ax. However, these algorithms are tentative and do not specify how to select the transmit power and carrier sense threshold in practice; It is unclear when and why the tuned parameters lead to better network performance. In this paper, we restricted the scale of transmit power tuning to prevent the case of backfire in which spatial reuse will result in transmission failure. If the restrictions cannot be satisfied, spatial reuse will be abandoned. This is why we named the proposed scheme as Arbitration based Spatial Reuse (ASR). We quantified the network performance after spatial reuse, and formulate a corresponding maximum problem whose solution is the optimal carrier sense threshold and transmit power. We verified our theoretical analysis by simulation and compared it with previous studies, and the results show that ASR improves the throughput up to 8.6% compared with 802.11ax. ASR can avoid failure of spatial reuse, while the spatial reuse failure rate of existing schemes can up to 36%. To use the ASR scheme in practice, we investigate the relation between the optimal carrier sense threshold and transmit power. Based on the relations got from ASR, the proposed Relation based Spatial Reuse (RSR) scheme can get a satisfactory performance by using only the interference perceived and the previously found relations.