• Journal of the Korean Ceramic Society
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• v.13 no.2
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• pp.31-38
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• 1976

Korean tremoitic talc, wollastonite and clay have been used to develop a wall tile body to appropriate to the fast firing process. Some of ceramic properties of the raw materials were investigated by X-ray diffraction, thermal analysis and chemical analysis. The body compositions were formulated from the range of 35~75% tremolitic talc, 0~30% wollastonite and 25~35% plastic clay. Thermal gravity analysis and thermal expansion were tested for each of unfired bodies to study the correlation between thermal dehydration and linear shrinkage during the firing procedure. Linear shrinkage and water absorption of the fired bodies at the various temperature were taken as a measures for determining the proper firing range of the bodies. Increasing the content of wollastonite and firing temperature, the thermal expansion of the fired body showed the gradual decrease, and the thermal expansion curves showed a tendency to straighten. These observations may be resulted from the fact that the amounts of diopside and anorthite formed were gradually increased and those of quartz relatively decreased. The optimum compositions of the wall tile bodies for fast firing are 30% clay, 10~20% wollastonite and 50~60% tremolitic talc.

• Journal of Institute of Control, Robotics and Systems
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• v.17 no.2
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• pp.149-156
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• 2011

This paper reveals a distance estimation algorithm based on multi-code ultrasonic and wireless sensor network. For measuring the distances among the sensor nodes, each ultrasonic transmitter transmits multi-code ultrasonic signal simultaneously. Receivers use cross correlation method to separate the coded signals. The information of measured distances is broadcasted to each sensor node by wireless sensor network. The wireless sensor network measures the distance among the sensor nodes using the received signal strength of the broadcasting. The multi-code ultrasonic have a limitation of measurable distance. And the received signal strength is affected from an environment. This paper measures a distance using ultrasonic and a received signal strength in short range. These measured data are applied to the least square estimation algorithm. By the expansion of the fitting curve, a distance measurement in long range using the received signal strength is compensated. The coupled system reduce the error to an acceptable level.

• International Journal of Highway Engineering
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• v.17 no.4
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• pp.135-141
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• 2015

PURPOSES: This study has been conducted to determine a homogeneous segment and integration to improve the efficiency of short-term traffic count. We have also attempted to reduce the traffic monitoring budget. METHODS: Based on the statistical approach, a homogeneous segment in the same road section is determined. Statistical analysis using t-test, mean difference, and correlation coefficient are carried out for 10-year-long (2004-2013) short-term count traffic data and the MAPE of fresh data (2014) are evaluated. The correlation coefficient represents a trend in traffic count, while the mean difference and t-score represent an average traffic count. RESULTS : The statistical analysis suggests that the number of target segments varies with the criteria. The correlation coefficient of more than 30% of the adjacent segment is higher than 0.8. A mean difference of 36.2% and t-score of 19.5% for adjacent segments are below 20% and 2.8, respectively. According to the effectiveness analysis, the integration criteria of the mean difference have a higher effect as compared to the t-score criteria. Thus, the mean difference represents a traffic volume similarity. CONCLUSIONS : The integration of 47 road segments from 882 adjacent road segments indicate 8.87% of MAPE, which is within an acceptable range. It can reduce the traffic monitoring budget and increase the count to improve an accuracy of traffic volume estimation.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.2
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• pp.1240-1252
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• 2015

The purpose of this study was to investigate feeding difficulty and its influencing factors of elders with dementia in long-term care facilities. Participants were 158 elders with dementia residing in three nursing facilities. Data were collected from Aug. 18 to Sep. 12 in 2014. The feeding difficulty in dementia scale, Korean version-Activities of Daily Living and Mini-Mental State Exam-Korean version were used as instruments. Data were analyzed using descriptive statistics, t-test, ANOVA, Pearson correlation and stepwise multiple regression by SPSS 17.0. Mean feeding difficulty score was $0.62{\pm}0.43$(range of 0-2). The highest feeding difficulty item was "patient require close supervision while feeding". The variables influencing the feeding difficulty was ADL(${\beta}=.312$), cognitive function(${\beta}=-.172$) which explained about 20.0% of total variance. The results suggest the need of developing feeding difficulty coping strategy according to dietary behavior phase, In addition, the development and testing the educational program for caregivers to help feeding difficulty of the elders with dementia in long-term facility are recommended.

• Wind and Structures
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• v.34 no.5
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• pp.421-435
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• 2022

To investigate the non-Gaussian properties of fluctuating wind pressures and the error margin of extreme wind loads on a long-span curved roof with matching and mismatching ratios of turbulence integral scales to depth (L_u^x/D), a series of synchronized pressure tests on the rigid model of the complex curved roof were conducted. The regions of Gaussian distribution and non-Gaussian distribution were identified by two criteria, which were based on the cumulative probabilities of higher-order statistical moments (skewness and kurtosis coefficients, S_k and K_u) and spatial correlation of fluctuating wind pressures, respectively. Then the characteristics of fluctuating wind-loads in the non-Gaussian region were analyzed in detail in order to understand the effects of turbulence integral-scale. Results showed that the fluctuating pressures with obvious negative-skewness appear in the area near the leading edge, which is categorized as the non-Gaussian region by both two identification criteria. Comparing with those in the wind field with matching L_u^x/D, the range of non-Gaussian region almost unchanged with a smaller L_u^x/D, while the non-Gaussian features become more evident, leading to higher values of S_k, Ku and peak factor. On contrary, the values of fluctuating pressures become lower in the wind field with a smaller L_u^x/D, eventually resulting in underestimation of extreme wind loads. Hence, the matching relationship of turbulence integral scale to depth should be carefully considered as estimating the extreme wind loads of long-span roof by wind tunnel tests.

• Journal of the Korean earth science society
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• v.23 no.7
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• pp.587-596
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• 2002

A super ensemble model was developed for the seasonal prediction of regional precipitation in Korea using the lag correlated large scale predictors, based on the empirical orthogonal function (EOF) analysis and multiple linear regression model. The predictability of this model was also evaluated by cross-validation. Correlation between the predicted and the observed value obtained from the super ensemble model showed 0.73 in spring, 0.61 in summer, 0.69 in autumn and 0.75 in winter. The predictability of categorical forecasting was also evaluated based on the three classes such as above normal, near normal and below normal that are clearly defined in terms of a priori specified by threshold values. Categorical forecasting by the super ensemble model has a hit rate with a range from 0.42 to 0.74 in seasonal precipitation.

• Journal of Korean Neurosurgical Society
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• v.40 no.3
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• pp.148-153
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• 2006

Objective : The authors conducted this study to present the long-term treatment outcomes [minimum 2 years] of Gamma knife radiosurgery[GKS] for trigeminal neuralgia[TN] and to demonstrate the correlation of treatment outcomes and the anatomical characteristics of TN. Methods : From 1997 to 2003, 44 consecutive patients suffering from medically intractable pain underwent GKS for TN. A single 4mm collimator was used with a median maximum dose of 80Gy [range $75{\sim}80Gy$] prescribed to the root entry zone of the trigeminal nerve. Median follow up duration was 30 months [range $24{\sim}78\;months$]. Anatomical measurements of trigeminal nerve in magnetic resonance images during GKS planning were correlated with clinical outcome. Results : Twenty-two patients [50%] achieved an excellent outcome [BNI grade I & II], 20 patients [45.5%] a good outcome [grade IIIa & IIIb], and only 2 patients [4.5%] a poor outcome [grade IV & V]. Eleven patients [25.0%] experienced pain recurrence after initial pain relief. Smaller volume of trigeminal nerve area irradiated more than 40Gy was significantly correlated with excellent outcome in both univariate and multivariate analyses respectively [P=0.033 and 0.040]. Conclusion : Anatomical considerations during the planning of GKS would be helpful for predicting clinical outcome in TN.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.3
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• pp.33-40
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• 2010

Multizeros(multiple order zeros) optical beams which belong to the Laguerre-Gaussian beams, have rotational phase and conically-shaped amplitude structures around multizeros points in their phase and amplitude profiles, respectively. Especially, they have their own characteristics that the multizero points do not vanish over free-space propagation. Therefore, they are expected to be adequate for the applications of long-range optical measurement by using their multizero points as optical markers for the deformation sensing. In this paper, fundamental properties of multizeros optical beams for long-range optical measurement applications are investigated and clarified. In particular, the mathematical investigations are described on the characteristics of multizeoros optical beams such as (1) separation of a multizero into isolated single order zeros, (2) topological charge of zeros distribution which are induced by superposing them. And also the outline of a fundamental experiment and its result are explained briefly.

• Korea-Australia Rheology Journal
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• v.19 no.2
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• pp.51-59
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• 2007

A polyelectrolyte chain confined in a slit nanochannel exhibits a structural transition from the one in free space. In this paper, the effect of the long-range electrostatic interactions between the xanthan polyelectrolyte and the slit wall on the confined xanthan conformation is investigated via the Brownian dynamics simulation. A neutral and two negatively charged surfaces of polydimethylsiloxane (PDMS) and glass are combined to make four kinds of slit channels with different charge characteristics: i) neutral-neutral, ii) glass-glass, iii) neutral-PDMS and iv) neutral-glass walls. Their walls are characterized by uniform surface charge densities determined from experimental data of zeta potential. Both the nonmonotonic chain size variation and the loss of long-range bond vector correlation, previously observed under confinement in the PDMS-PDMS slit, are also found in the neutral slit, demonstrating the nonelectrostatic origin of such crossover behaviors. As expected, the effect of wall charges is negligible at sufficiently high medium ionic strength of 100mM but it becomes significant in the opposite limit of 0.01mM. In the latter case, the high charge density of glass walls strengthens the effective confinement of a negatively charged polyelectrolyte and produces a xanthan structure comparable to that confined in a much narrower neutral slit. The obtained structural data suggest the possibility of controlling the structure of confined polyelectrolytes by the modification of surface charge characteristics of micro/nanofluidic devices in combination with the adjustment of the medium ionic strength.

• Proceedings of the KAIS Fall Conference
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• 2006.05a
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• pp.294-297
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• 2006

Measurement of network traffic have shown that the self-similarity is a ubiquitous phenomenon spanning across diverse network environments. In previous work, we have explored the feasibility of exploiting the long-range correlation structure in a self-similar traffic for the congestion control. we show that a multiple time scale TCP endows the underlying feedback control with proactivity by bridging the uncertainty gap associated with reactive controls which is exacerbated by the high delay-bandwidth product in broadband wide area networks. Third, we investigate the influence of the three traffic control dimensions-tracking ability, connection duration, and fairness-on performance.