• Journal of the Korean Institute of Telematics and Electronics D
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• v.34D no.11
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• pp.90-100
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• 1997

In this paper, we propose a new optical thresold generator as a key-stream genrator for stream cipher systems. The random key-bit stream is generated by a digital generator that is composed of LFSRs and nonlinear ligics. Digital implementatin of a key-stream generator requires large memory to implement programmable tapping points. This memory problem may be overcome easily by using the proposed optical system which has the proberty of 2D parallel processing.To implement hte threshold generator optically, we use conventional twisted nematic type SLMs (LCDs). This proposed system is based on the shadow casting technique for the AND operation between taps and sregister stages. It is also based on the proposed PMRS method for modulo 2 addition. The proposed PMRS method uses the property of light's polarization on LCD and can be implemented optically using one LCD and some mirrors. One of the major advantages of the proosed system is that there is no limitation of the number of the progarmmable tapping points. Therefore, the proposed system can be applied for the 2D encryption system which processes large amounts of data such as 2D images. We verify the proposed system with some simulation.

• The Journal of Advanced Prosthodontics
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• v.14 no.3
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• pp.133-142
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• 2022

PURPOSE. A large number of studies have suggested the practicability and predictability of immediate implant function, but few studies have reported marginal bone level changes during sequential loading periods. The purpose of this study was to evaluate the marginal bone remodeling of immediately loaded self-tapping implants both at each time point and during each loading period between two time points. MATERIALS AND METHODS. The patients included in this retrospective study were treated with immediately loaded NobelSpeedy Replace implants between August 2008 and July 2009. Differences in the marginal bone level (MBL) at each time point and the marginal bone level change (ΔMBL) between two time points were analyzed with Bonferroni correction (P < .05). RESULTS. Overall, 24 patients (mean age, 47.3 ± 12.8 years) with 42 immediately loaded implants and a median follow-up of 6.5 years (IQR, 67.8 months) were included. The cumulative survival rate after 10 - 12 years was 95.2%. Continuous but slow marginal bone loss was observed during long-term follow-up. MBL at both 7.5 years and 11 years was significantly lower than that at loading, 6 months, 2 years and 4 years (P < .05). No bone loss difference was found in any period before 4 years of follow up (P > .05). The loading period of 4 years to 7.5 years showed the largest ΔMBL compared to those of other time periods (P < .05). CONCLUSION. Slight bone loss occurred continuously, and more radical changes of marginal bone can be observed during the period of 4-7.5 years. Thus, long-term effective follow-up of immediately loaded implants is needed.

• Investigative Magnetic Resonance Imaging
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• v.3 no.1
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• pp.41-46
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• 1999

Purpose : To investigate the difference of total activation in visual area, motor area, and cerebellum according to the stimulation paradigm. Materials and Methods : Functional MR imaging was performed in 5 healthy volunteers with visual and motor activity using EPI technique. LED and Checker-Board stimulation were performed for visual activity. Thumb motion and Finger Tapping were performed for motor and cerebellum activity. Stimulus timing was 60sec. off, 120sec. on, 60sec. off. Data processing was carried out by using the cross-correlation method for each pixel. Each pixel was then selected and assumed activated if the correlation coefficient was equal or larger than a threshold value. Time course data was obtained by calculating the total activation which was defined as the number of activated pixel x averaged pixel intensity. Results : In the case of visual activity with LED stimulation, we found increased total activity of more than 100% compared with Checker-Board stimulation. In the case of motor area and cerebellum with Finger tapping stimulation, we found increased total activity of more than 10% and 150%, respectively compared with Thumb motion stimulation.

• KIEAE Journal
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• v.3 no.4
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• pp.23-31
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• 2003

From 1998, the number of household who live in apartment house outnumber that of household live in detached dwelling by 0.3% in Korea. As walls and floors are shared with neighbourhood in apartment houses, percent complaints to the impact noise from the upper floor was so high that it represents an important factor in apartment indoor noise. And the rate is closely correlate with children's running, playing and jumping. In this study, comparisons of standard impact source, such as Tapping Machine and Bang Machine, with real life impact sources were made in order to investigate acoustical characteristics between them. Also reproducibility tests for impact sound sources were carried out.

• Environmental Analysis Health and Toxicology
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• v.28
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• pp.15.1-15.8
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• 2013

Objectives The aim of this study was to determine the association between low-level mercury exposure and neurobehavioral functions in adults living in coastal regions of Korea. Methods We selected 172 adults aged 20-65 years living in a city in the coastal region of Korea. A sociodemographic survey was conducted, mercury levels in the blood, urine, and hair were measured, and the associations according to computerized neurobehavioral tests were determined using univariate analysis. After adjustment for associated variables, a multivariate linear regression analysis was performed. Results The geometric mean mercury levels in the blood, urine, and hair were $5.41{\mu}g/L$ (range, $0.00-15.84{\mu}g/L$), $1.17{\mu}g/g$-creatinine (range, $0.00-32.86{\mu}g/g$-creatinine), and 1.37 mg/kg (range, 0.42-6.56 mg/kg), respectively. Variables that were associated with simple reaction time according to the neurobehavioral test results were age and urine mercury level. Variables associated with choice reaction time were the recent use of Korean traditional medicine and urine mercury level. Variables associated with the right-hand finger tapping speed test were age, gender, smoking behavior, education level, monthly household income, and urine mercury level. Variables associated with the left-hand finger tapping speed test were age, gender, education level, and urine mercury level. After adjustment for associated variables, there was no significant association between urine mercury level and simple reaction time (${\beta}=25.96$; p =0.47), choice reaction time (${\beta}=50.37$; p =0.32), or the number of left-hand finger taps (${\beta}=-1.54$; p =0.21). However, urine mercury level was significantly associated with the number of right-hand finger taps (${\beta}=-3.86$; p =0.01). Conclusions We found no evidence that low-level mercury exposure in adults is associated with deficits in neurobehavioral functions. A longer follow-up study is required to confirm this conclusion.

• Journal of Computational Design and Engineering
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• v.3 no.3
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• pp.266-273
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• 2016

Optimization of hole-making operations in manufacturing industry plays a vital role. Tool travel and tool switch planning are the two major issues in hole-making operations. Many industrial applications such as moulds, dies, engine block, automotive parts etc. requires machining of large number of holes. Large number of machining operations like drilling, enlargement or tapping/reaming are required to achieve the final size of individual hole, which gives rise to number of possible sequences to complete hole-making operations on the part depending upon the location of hole and tool sequence to be followed. It is necessary to find the optimal sequence of operations which minimizes the total processing cost of hole-making operations. In this work, therefore an attempt is made to reduce the total processing cost of hole-making operations by applying relatively new optimization algorithms known as shuffled frog leaping algorithm and proposed modified shuffled frog leaping algorithm for the determination of optimal sequence of hole-making operations. An industrial application example of ejector plate of injection mould is considered in this work to demonstrate the proposed approach. The obtained results by the shuffled frog leaping algorithm and proposed modified shuffled frog leaping algorithm are compared with each other. It is seen from the obtained results that the results of proposed modified shuffled frog leaping algorithm are superior to those obtained using shuffled frog leaping algorithm.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.5
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• pp.1194-1200
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• 2014

One of problems in car navigation systems is that a number of inputs are required for a directions search. This may even causes a car accident due to poor concentration while driving. In order to solve the issue we design and implement a safe and easy-to-use car navigation system which allows a driver to look up directions with just a single tap. Our smartphone app creates an NFC tag by deriving location information from a text, voice, GPS, and so on. The driver can then get the directions by just tapping a phone or card with the Tag on the navigation system. We show the feasibility and effectiveness of our system by comparing our implementation with the existing car navigation systems.

• Proceedings of the Korea Contents Association Conference
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• 2007.11a
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• pp.687-690
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• 2007

The environment of digital broadcast which represents as multi-channel and multimedia provides more crisis and pressure to newspapermen called as an uncrowned monarch in region of the press. The circulation of newspaper is declining dramatically and newspaper companies are turning their attention into digital broadcast in order to survive. Furthermore, besides of Chosun, Jung-Ang and Dong-A which are the three major newspapers in S. Korea, local newspaper companies are suffering from severe financial difficulties. However it could be an opportunity for digital broadcasters who undergo the lack of contents whether they are qualitative or quantitative. For the purpose of this study, it is to present a number of strategic approach in order that local newspapers outlast in the competitive digital broadcasting marketplace. Beyond the localism it intends to discuss about tapping into valuable newspaper contents as on-line journalism.

• Korean Journal of Materials Research
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• v.27 no.12
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• pp.705-709
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• 2017

The electronic and optical characteristics of molybdenum disulphide ($MoS_2$) film significantly vary with its thickness, and thus a rapid and accurate estimation of the number of $MoS_2$ layers is critical in practical applications as well as in basic researches. Various existing methods are currently available for the thickness measurement, but each has drawbacks. Transmission electron microscopy allows actual counting of the $MoS_2$ layers, but is very complicated and requires destructive processing of the sample to the point where it will no longer be useable after characterization. Atomic force microscopy, particularly when operated in the tapping mode, is likewise time-consuming and suffers from certain anomalies caused by an improperly chosen set point, that is, free amplitude in air for the cantilever. Raman spectroscopy is a quick characterization method for identifying one to a few layers, but the laser irradiation causes structural degradation of the $MoS_2$. Optical microscopy works only when $MoS_2$ is on a silicon substrate covered with $SiO_2$ of 100~300 nm thickness. The last two optical methods are commonly limited in resolution to the micrometer range due to the diffraction limits of light. We report here a method of measuring the distribution of the number of $MoS_2$ layers using a low voltage field emission electron microscope with acceleration voltages no greater than 1 kV. We found a linear relationship between the FESEM contrast and the number of $MoS_2$ layers. This method can be used to characterize $MoS_2$ samples at nanometer-level spatial resolution, which is below the limits of other methods.

• Journal of Computational Design and Engineering
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• v.3 no.4
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• pp.337-348
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• 2016

An experimental approach is presented for the measurement of wear that is common in the threading of cold-forged steel. In this work, the first objective is to measure wear on various types of roll taps manufactured to tapping holes in microalloyed HR45 steel. Different geometries and levels of wear are tested and measured. Taking their geometry as the critical factor, the types of forming tap with the least wear and the best performance are identified. Abrasive wear was observed on the forming lobes. A higher number of lobes in the chamber zone and around the nominal diameter meant a more uniform load distribution and a more gradual forming process. A second objective is to identify the most accurate data-mining technique for the prediction of form-tap wear. Different data-mining techniques are tested to select the most accurate one: from standard versions such as Multilayer Perceptrons, Support Vector Machines and Regression Trees to the most recent ones such as Rotation Forest ensembles and Iterated Bagging ensembles. The best results were obtained with ensembles of Rotation Forest with unpruned Regression Trees as base regressors that reduced the RMS error of the best-tested baseline technique for the lower length output by 33%, and Additive Regression with unpruned M5P as base regressors that reduced the RMS errors of the linear fit for the upper and total lengths by 25% and 39%, respectively. However, the lower length was statistically more difficult to model in Additive Regression than in Rotation Forest. Rotation Forest with unpruned Regression Trees as base regressors therefore appeared to be the most suitable regressor for the modeling of this industrial problem.