• Journal of the Korean Institute of Intelligent Systems
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• v.19 no.5
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• pp.615-621
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• 2009

TFT-LCD image consists of ununiform background, random noises and target defect signal components. Defects in TFT-LCD have some intensity variations compared to background region. It is sometimes difficult for human inspectors to figure out. In this paper, we propose multi-level threshold scheme for detection of the real defect using probability density function with Parzen Window. The experimental results show that the proposed algorithms produce promising results and can be applied to automated inspection systems for finding defects in the TFT-LCD image.

• 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 Electrical and Electronic Material Engineers
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• v.36 no.3
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• pp.255-260
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• 2023

In order to spread LED lighting, LED lighting technology directly driven by alternating current (AC) commercial power has recently been introduced. Since current does not flow at a voltage lower than the threshold voltage of the LED, a non-conductive section occurs in the current waveform, and the higher the threshold voltage of the LED, the more discontinuous current waveforms are generated. In this paper, multi-LED modules are connected in series so that the threshold voltage can be adjusted according to the number of LED modules. A small number of LED modules are driven at a low instantaneous rectified voltage, and a large number of LED modules are driven at a high instantaneous rectified voltage to lengthen the overall lighting time of AC-LED lighting, thereby minimizing the luminance deviation of AC-LED lighting. In addition, the load current flowing through the LED module is adjusted to be the same as the design current even at the maximum rectified voltage higher than the design voltage, so that the light brightness of the LED module is kept constant. Therefore, even if the rectified voltage applied to the LED module changes, the AC-LED lighting in which the light brightness is constant and the luminance deviation is minimal has been realized.

• Elastomers and Composites
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• v.52 no.4
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• pp.272-279
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• 2017

The heterocoagulation of latex is a simple and useful method to fabricate various polymer nanocomposites in which a precise control of the colloid stability is essential. In this work, a multi-layered graphenes (MLGs)/poly(styrene-co-butyl acrylate) (P(S-co-BA)) nanocomposite having an excellent dispersion of MLGs was prepared via the sudden heating heterocoagulation process. The P(S-co-BA) component was obtained by emulsion polymerization. This process can effectively shorten the process and particles growth steps. The colloid stability of these dispersions was controlled by factors such as ionic charge, temperature, and reaction times. The influence of these factors on heterocoagulation was evaluated and the properties of the nanocomposites were investigated. The conductivity of the MLGs/P(S-co-BA) nanocomposites increased from -11.53 to -5.70 S/cm for an increase in MLG content from 0.01 to 5 wt%. Moreover, percolation threshold was observed in the case of 0.01 wt% MLGs.

• International Journal of CAD/CAM
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• v.6 no.1
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• pp.81-87
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• 2006

This paper describes a method for extracting surfaces from multi-material CT (Computed Tomography) data. Most contouring methods such as Marching Cubes algorithm assume that CT data are composed of only two materials. Some extended methods such as [3, 6] can extract surfaces from the multi-material (non-manifold) implicit representation. However, these methods are not directly applicable to CT data that are composed of three or more materials. There are two major problems that arise from fundamentals of CT. The first problem is that we have to use n(n-1)/2 threshold values for CT data contains n materials and select appropriately one threshold value for each boundary area. The second is that we cannot reconstruct only from CT data in which area three or more materials are adjacent each other. In this paper, we propose a method to solve the problems by using image analysis and demonstrate the effectiveness of the method with application examples construct polygon models from CT data of machine parts.

• Journal of the Korean Data and Information Science Society
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• v.26 no.1
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• pp.255-260
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• 2015

Among many optimal threshold criteria from ROC curve, the closest-to-(0,1) and amended closest-to-(0,1) criteria are considered. An ROC curve that passes close to the (0,1) point indicates that two models are well classified. In this case, the ROC curve is located far from the (1,0) point. Hence we propose two criteria: the farthest-to-(1,0) and amended farthest-to-(1,0) criteria. These criteria are found to have a relationship with the KolmogorovSmirnov statistic as well as some optimal threshold criteria. Moreover, we derive that a definition for the proposed criteria with more than two dimensions and with relations to multi-dimensional optimal threshold criteria.

• International Journal of Naval Architecture and Ocean Engineering
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• v.13 no.1
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• pp.187-193
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• 2021

In order to solve the problem of false terrains caused by environmental interferences and tunneling effect in the conventional multi-beam seafloor terrain detection, this paper proposed a seafloor topography detection method based on fast two-dimensional (2D) Censored Mean Level Detector-statistics Constant False Alarm Rate (CMLD-CFAR) method. The proposed method uses s cross-sliding window. The target occlusion phenomenon that occurs in multi-target environments can be eliminated by censoring some of the large cells of the reference cells, while the remaining reference cells are used to calculate the local threshold. The conventional 2D CMLD-CFAR methods need to estimate the background clutter power level for every pixel, thus increasing the computational burden significantly. In order to overcome this limitation, the proposed method uses a fast algorithm to select the Regions of Interest (ROI) based on a global threshold, while the rest pixels are distinguished as clutter directly. The proposed method is verified by experiments with real multi-beam data. The results show that the proposed method can effectively solve the problem of false terrain in a multi-beam terrain survey and achieve a high detection accuracy.

• Journal of IKEEE
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• v.8 no.1 s.14
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• pp.33-38
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• 2004

A multi-valued logic(MVL) pass gate is an important element to configure multi-valued logic. In this paper, we designed the Quaternary MIN(QMIN)/negated MIN(QNMIN) gate, the Quaternary MAX(QMAX)/negated MAX(QNMAX) gate using double pass-transistor logic(DPL) with neuron $MOS({\nu}MOS)$ threshold gate. DPL is improved the gate speed without increasing the input capacitance. It has a symmetrical arrangement and double-transmission characteristics. The threshold gates composed by ${\nu}MOS$ down literal circuit(DLC). The proposed gates get the valued to realize various multi threshold voltages. In this paper, these circuits are used 3V power supply voltage and parameter of 0.35um N-Well 2-poly 4-metal CMOS technology, and also represented HSPICE simulation results.

• Korean Journal of Remote Sensing
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• v.19 no.6
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• pp.465-478
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• 2003

This paper presents two methods for automatic estimation of threshold values in unsupervised change detection of multi-temporal remote sensing images. The proposed methods consist of two analytical steps. The first step is to compute the parameters of a 3-component Gaussian mixture model from difference or ratio images. The second step is to determine a threshold value using Bayesian rule for minimum error. The first method which is an extended version of Bruzzone and Prieto' method (2000) is to apply an Expectation-Maximization algorithm for estimation of the parameters of the Gaussian mixture model. The second method is based on an iterative thresholding algorithm that successively employs thresholding and estimation of the model parameters. The effectiveness and applicability of the methods proposed here were illustrated by two experiments and one case study including the synthetic data sets and KOMPSAT-1 EOC images. The experiments demonstrate that the proposed methods can effectively estimate the model parameters and the threshold value determined shows the minimum overall error.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.7
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• pp.3524-3542
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• 2017

In a single-source and multi-relay amplify-forward (AF) cooperative network, the outage probability and the power allocation are two key factors to influence the performance of an entire system. In this paper, an optimized AF relay selection by an exclusive method and near optimal power allocation (NOPA) is proposed for both good outage probability and power efficiency. Given the same power at the source and the relay nodes, a threshold for selecting the relay nodes is deduced and employed to minimize the average outage probability. It mainly excludes the relay nodes with much higher thresholds over the aforementioned threshold and thus the remainders of the relay nodes participate in cooperative forwarding efficiently. So the proposed scheme can improve the utility of the resources in the cooperative multi-relay system, as well as reduce the computational complexity. In addition, based on the proposed scheme, a NOPA is also suggested to approach sub-optimal power efficiency with low complexity. Simulation results show that the proposed scheme obtains about 2.1dB and 5.8dB performance gain at outage probability of $10^{-4}$, when compared with the all-relay-forward (6 participated relays) and the single-relay-forward schemes. Furthermore, it obtains the minimum outage probability among all selective relay schemes with the same number of the relays. Meanwhile, it approaches closely to the optimal exhaustive scheme, thus reduce much complexity. Moreover, the proposed NOPA scheme achieves better outage probability than those of the equal power allocation schemes. Therefore, the proposed scheme can obtain good outage probability, low computational complexity and high power efficiency, which makes it pragmatic efficiently in the single-source and multi-relay AF based cooperative networks.