• Proceedings of the Korean Operations and Management Science Society Conference
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• 2002.05a
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• pp.306-311
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• 2002

This paper propose a personalized defection detection and prevention procedure based on the observation that potential defectors have tendency to take a couple of months or weeks. For this purpose, possible states of customer behavior are determined from past behavior data using SOM (Self-Organizing Map). For the evaluation of the proposed procedure, a case study has been conducted for a Korean online game site. The result demonstestes that the proposed procedure can assist defection prevention effectively and detect potential defectors without deterioration of prediction accuracy comparison to prediction by MLP. Our procedure can be applied to various service industries that can capture fluent customer behavior data such as telecommunications, internet access services, and content services, too.

• Nuclear Engineering and Technology
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• v.32 no.6
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• pp.595-604
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• 2000

Flow-Accelerated Corrosion Behavior of SA106 Gr.C steel in room temperature alkaline solution simulating the CANDU primary water condition was studied using Rotating Cylinder Electrode. Systems of RCE were set up and electrochemical parameters were applied at various rotating speeds. Corrosion current density decreased up to pH 10.4 then it increased rapidly at higher pH. This is due to the increasing tendency of cathodic and anodic exchange half-cell current. Corrosion potential shifted slightly upward with rotating velocity. Passive film was formed from pH 9.8 by the mechanism of step oxidation and the subsequent precipitation of ferrous species into hydroxyl compound. Above pH 10.4, the film formation process was active and the film became stable. Corrosion current density showed increment in pH 6.98 with the rotating velocity, while it soon saturated from 1000 rpm above pH 9.8. This seems that activation process which represents formation of passive film on the bare metal surface controls the entire corrosion process

• Computers and Concrete
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• v.20 no.4
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• pp.503-509
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• 2017

In this study, fire-damaged concrete was investigated by a nonlinear resonance vibration (NRV) technique, in order to evaluate its residual material properties. For the experiments, five cubic concrete specimens were prepared and four of them were damaged at different temperatures using a furnace. With a thermal insulator wrapped at the sides of specimen, thermal gradation was applied to the samples. According to the peak temperatures and depths of the samples, nonlinearity parameters were calculated with the NRV technique before the tendency of the parameters was evaluated. In addition, compressive strength and dynamic elastic modulus were measured for each sample and a comparison with the nonlinearity parameter was carried out. Through the experimental results, the possibility of the NRV technique as a method for evaluating residual material properties was evaluated.

• International journal of advanced smart convergence
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• v.8 no.2
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• pp.1-7
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• 2019

Drones will evolve from military to personal or social purposes. How can people socially interact with a drone that is familiar to them? This study explored the social proximity of human drone interaction with safety glass wall between participants and drone. The experiment results showed that drone's altitude, size and gender factor did not significantly affect social proxemics as to what extent participants got closer to hovering drones by the limitation of the distance from the safety wall. However, it shows a tendency that participants more closely approached an eye-level drone compared with an overhead drone, and females tended to approach more closely males. This study consequently demonstrated that most participants are nearly ready to allow a near field operation of social drone under safe conditions.

• Polymer(Korea)
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• v.38 no.2
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• pp.199-204
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• 2014

To prepare acrylic pressure sensitive adhesives (PSAs), quaternary copolymer syrups were photopolymerized from 2-ethylhexyl acrylate and 2-hydroxyethyl acrylate as default constituents and isobornyl acrylate and tetrahydrofurfuryl acrylate (THFA) as variable constituents. After polymerization, 1,6-hexanediol diacrylate and photoinitiator were added and then crosslinked by UV-irradiation to prepare the PSAs. The characteristics of the syrup such as viscosity, molecular weight, and solid content were investigated. As increasing THFA contents, the relationship between molecular weight and solid content of the syrup was reciprocal. Also, the relationship between peel strength and surface energy of the PSAs showed the same tendency. All the PSA samples showed high transmittance (more than 92%), low haze (less than 1.0%) and low color-difference (less than 1.0).

• The Korean Journal of Nuclear Medicine
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• v.18 no.1
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• pp.55-62
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• 1984

For an effective solid-phase labelling of protein with $^{125}I$, studies on the immobilization of lactoperoxidase(LPO) on the inner wall of polystyrene tubes were carried out. Labelling of bovine serum albumin(BSA) and insulin was also practiced using the LPO immobilized tubes. The immobilized enzyme of about $2.5{\mu}g/tube$ was sufficient for small scale labelling since the results of radio-paper chromatography of the labelling mixture of insulin indicated that the yields were sufficiently high(80%) even in the reactions conducted at room temperature for 60 sec. The results of the Sephadex column chromatography indicated that the labelled products were not contaminated with $LPO-^{125}I$, and the radiochemical purity of the products was more than 90%. In considering the general trend that the $^{125}I$ labelled protein obtained by using LPO maintains its intactness better than those obtained by using chloramine-T, together with the tendency of yield enhancing with increase of reactants-concentration, the LPO immobilized tube method is estimated to be one of the simple methods of labelling. The product might be applicable without further purification.

• Journal of Positioning, Navigation, and Timing
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• v.9 no.3
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• pp.285-292
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• 2020

This paper introduces a new computational efficient Dilution of Precision (DOP)-based landmark exclusion method while ensuring the safety of the LiDAR-based navigation system that uses an innovation-based Nearest-Neighbor (NN) Data Association (DA) process. The NN DA process finds a correct landmark association hypothesis among all potential landmark permutations using Kalman filter innovation vectors. This makes the computational load increases exponentially as the number of landmarks increases. In this paper, we thus exclude landmarks by introducing DOP that quantifies the geometric distribution of landmarks as a way to minimize the loss of integrity performance that can occur by reducing landmarks. The number of landmarks to be excluded is set as the maximum number that can satisfy the integrity risk requirement. For the verification of the method, we developed a simulator that can analyze integrity risk according to the landmark number and its geometric distribution. Based on the simulation, we analyzed the relationship between DOP and integrity risk of the DA process by excluding each landmark. The results showed a tendency to minimize the loss of integrity performance when excluding landmarks with poor DOP. The developed method opens the possibility of assuring the safety risk of the Lidar-based navigation system in real-time applications by reducing a substantial amount of computational load.

• BMB Reports
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• v.31 no.2
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• pp.177-182
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• 1998

A pool of cis-acting hammerhead ribozymes randomized in their substrate recognition sequences was constructed. A variety of active cis-acting ribozymes which had various structures of stems I and III was selected from the pool by in vitro selection. The selected ribozymes were cloned and sequenced. The relationship between the cleavage efficiency and base-pairing in stems I and III of the selected ribozymes was investigated. The ribozymes with the smaller difference in folding energies between the active conformation and the stable but inactive conformation showed a tendency to have the better cleavage efficiency. The optimum length of stem I was 5 or 6 bases while the longer stem III, in general, appeared to be required for efficient cleavage. The specificity of the ribozyme reaction is discussed in terms of the length of stems I and III.

• Journal of the Korean Society of Industry Convergence
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• v.18 no.4
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• pp.216-223
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• 2015

Recently Manipulation capability is important for a robot. Interaction between a robot hand and objects can be properly controlled only is suitable sensors are available. Recently the tendency is to create robot hands more compact and high integrated sensors system, in order to increase the grasping capability and in order to reduce cabling through the finger, the palm and the arm. As a matter of fact, miniaturization and cabling harness represents a significant limitation to the design of small sized embedded sensor. Ongoing work is focusing on a flexible manipulation system, which consists of a dual flexible multi-fingered hand-arm system, and a dual active vision system.

• Journal of Korea Foundry Society
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• v.39 no.5
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• pp.87-93
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• 2019

The effects of mold materials on the microstructure and tensile properties were investigated to develop a mass production technique of aluminum alloy parts with excellent mechanical properties using a lost foam casting method. The microstructures of the plate-shaped cast alloy showed a tendency to be finer in proportion to the thickness of the plate, and a remarkably fine structure was obtained by applying a steel chill or a ball as a mold material compared to general sand. When a steel ball was used, it was observed that the larger the ball, the finer the cast structure and the better the tensile properties. The microstructure and tensile properties of the cast parts with complex shapes were greatly affected by the gating system, but the positive effects of the steel chill and the steel ball as a mold material were clear.