• Journal of Convergence for Information Technology
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• v.7 no.5
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• pp.53-58
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• 2017

In the age of oil exhaustion, low cost, semi-transparent solar cell, the dye-sensitized solar cell (DSC) has attracted significant attention since 1991 of $Gr{\ddot{a}}tzel$ report. To enhance the light-harvest capability of the photoelectric electrode, and efficiency of photoelectric transformation of the DSC, scattering layer of various structure have been proposed to photoelectric electrode materials. The scattering center of scattering layer needs the large titanium dioxide nanoparticles of 250 - 300 nm in diameter. In this study, the large sized $TiO_2$ nanocyrstals of around 300 nm were synthesized using the modified sol-gel process. According to the analysis of XRD and TEM, the synthesized $TiO_2$ nanoparticles exhibit single crystals of anatase phase. The optical transmittance of the synthesized titanium dioxide film prepared by spin coating is around 50% at 550 nm. It is suitable for scattering layer as a scattering center, and expected to enhance the efficiency of photoelectric transformation of the DSC.

• Korean Journal of Food Science and Technology
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• v.51 no.4
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• pp.404-409
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• 2019

This study was performed to determine the optimum conditions for the production of gaseous chlorine dioxide ($ClO_2$) from aqueous $ClO_2$ (HCl+$NaClO_2$). When 1 N HCl was reacted with various concentrations of $NaClO_2$ (50,000-500,000 mg/mL), the highest concentration (695 mg/L) of gaseous $ClO_2$ was obtained from the aqueous $ClO_2$ containing $100,000{\mu}g/mL$ $NaClO_2$. Next, the effects of relative humidity (RH; 43, 85, and 100%) and temperature (4, 12, and $25^{\circ}C$) on the production of gaseous $ClO_2$ were investigated. It was observed that the concentration of gaseous $ClO_2$ was increased as RH was decreased, or the temperature was increased. Finally, it was confirmed that the amount of gaseous $ClO_2$ was highly correlated ($R^2=0.9546-0.9992$) with the volume of aqueous $ClO_2$. The results of this study provide useful information for designing a sanitization program using gaseous $ClO_2$ under various environmental conditions.

• Journal of Korea Society of Industrial Information Systems
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• v.23 no.2
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• pp.29-39
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• 2018

In this paper, we discuss a discrete-time queueing system with dyadic server control policy that combines workload control and multiple vacations. Customers arrive at the system with Bernoulli arrival process. If there is no customer to serve in the system, an idle single server spends a vacation of discrete random variable V and returns. The server repeats the vacation until the total service time of waiting customers exceeds the predetermined workload threshold D. In this paper, we derived the steady-state workload distribution of a discrete-time queueing system which is operating under a more realistic and flexible server control policy. Mean workload is also derived as a performance measure. The results are basis for the analysis of system performance measures such as queue lengths, waiting time, and sojourn time.

• Journal of the Korea Society of Computer and Information
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• v.12 no.1 s.45
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• pp.17-24
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• 2007

Critical practicality problems are cause to search the presentation and contents according to user request and purpose in previous internet system. Recently, there are a lot of researches about dynamic adaptable ontology based system. We designed ontology based educational system which uses discrete probability and user profile. This system provided advanced usability of contents by ontology and dynamic adaptive model based on discrete probability distribution function and user profile in ontology educational systems. This models represents application domain to weighted direction graph of dynamic adaptive objects and modeling user actions using dynamically approach method structured on discrete probability function. Proposed probability analysis can use that presenting potential attribute to user actions that are tracing search actions of user in ontology structure. This approach methods can allocate dynamically appropriate profiles to user.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.23 no.1
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• pp.84-89
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• 2019

JPEG is a most widely used standard image compression technology. This research introduces the JPEG image compression algorithm and describes each step in the compression and decompression. Image compression is the application of data compression on digital images. The DCT (discrete cosine transform) is a technique for converting a time domain to a frequency domain. First, the image is divided into 8 by 8 pixel blocks. Second, working from top to bottom left to right, the DCT is applied to each block. Third, each block is compressed through quantization. Fourth, the matrix of compressed blocks that make up the image is stored in a greatly reduced amount of space. Finally if desired, the image is reconstructed through decompression, a process using IDCT (inverse discrete cosine transform). The purpose of this research is to review all the processes of image compression / decompression using the discrete cosine transform method.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.15 no.2
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• pp.89-94
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• 2022

In this paper, a discrete-time loop filter(DLF) phase-locked loop with a Frequency Fluctuation Converting Circuit(FFCC) has been proposed. Discrete-time loop filter can improve spur characteristic by connecting the charge pump and voltage oscillator discretely unlike a conventional continuous-time loop filter. The proposed PLL is designed to operate stably by the internal negative feedback loop including the SSC acting as a negative feedback to the discrete-time loop filter of the external negative feedback loop. In addition, the phase noise is further improved by reducing the magnitude of the loop filter output voltage variation through the FFCC. Therefore, the magnitude of jitter has been reduced by 1/3 compared to the conventional structure. The proposed phase locked loop has been simulated with Hspice using the 1.8V 180nm CMOS process.

• The KIPS Transactions:PartB
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• v.10B no.6
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• pp.639-646
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• 2003

This paper proposes a neural network model for extracting optical illusions produced by a sequence of discontinuous dot stimuli. The proposed model is based on visual cell's characters founded by visual information processing path. This study approaches on the basis of physiological observation of the perceptual phenomena that some simple ways of discrete dots are perceived as a continuous virtual contour rather than as separate dots. This paper presents the implementation of the optical illusions from discrete dot stimuli that are composed of virtual polygons from 6 to 10 dots. This experimental data are similar to those of Smith & Vos's physiological experiments. The proposed model shows that it can extract continuous illusion contours from discrete dot stimuli successfully.

• Journal of KIISE:Information Networking
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• v.29 no.4
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• pp.346-351
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• 2002

We improve a new probabilistic public key cryptosystem, in which the one wav function was defined only on the discrete logarithmic functions, proposed by Okamoto and Uchiyama. The plaintexts are calculated from the modular product of two these functions, one of which has a fixed value depending on a given public key. The improvement is achieved by a well-chosen public key assuming an unit element 1 as the fixed function value. Because it is possible to reduce the number of operations at the decryption. Also the concrete method for a public key of our improved scheme is suggested.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2022.06a
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• pp.150-154
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• 2022

The Automatic Ship Identification System(AIS) is importantly used to evaluate the trajectory of ships and the possibility of collision between ships. However, it is difficult to provide real-time information due to the limitation of the transmission intervals. Most of the studies to improve this are conducted based on ideal data, so there is a problem that it is hard to respond to the actual situation. Therefore, in this paper, we propose a discrete Kalman filter-based method that reflects the turning angle according to the type of trajectory, to provide real-time position information on real-time data. In addition, the accuracy evaluation of the proposed algorithm is conducted through experiments using actual data.

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.2
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• pp.100-106
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• 2014

Lower control arm (LCA) is a part of chassis in automotive. Performances of LCA such as stiffness, durability and permanent displacement must be considered in design optimization. However it is hard to consider different performances at once in optimization because these are measured by different commercial tools like Radioss, Abaqus, etc. In this paper, firstly, we construct the integrated design automation system for LCA based on Matlab including Hypermesh, Radioss and Abaqus. Secondly, Akaike information criterion (AIC) is used for assessment of reliability of LCA. It can find the best estimated distribution of performance from limited and discrete stochastic information and then obtains the reliability from the distribution. Finally, we consider tolerances of design variables and variation of elastic modulus and achieve the target reliability by carrying out reliability-based design optimization (RBDO) with the integrated system.