• Journal of the Korean Solar Energy Society
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• v.36 no.3
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• pp.9-16
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• 2016

This paper discusses a refined model for investigating the micro-mechanical behavior of beam-like structures, which are composed of various elastic moduli and complex geometries varying through the cross-section directions and are also periodically-repeated and heterogeneous along the axial direction. Following the previous work (Lee and Yu, 2011), the original three-dimensional static problem is first formulated in a unified and compact form using the concept of decomposition of the rotation tensor. Taking advantage of the smallness of the cross-sectional dimension-to-length parameter and the micro-to-macro heterogeneity, while also performing homogenization along the dimensional reduction simultaneously, the variational asymptotic method is rigorously used to construct a total energy function, which is asymptotically correct up to the second order. Furthermore, through the transformation procedure based on the pure kinematic relations and the linearized equilibrium equations, a generalized Timoshenko model is systematically established. For the purpose of dealing with realistic and complex geometries and constituent materials at the microscopic level, this present approach is incorporated into a commercial analysis package. A few examples available in literature are used to demonstrate the consistency and efficiency of this proposed model, especially for the structures, in which the effects of transverse shear deformations are significant.

• Journal of the Korea Society of Computer and Information
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• v.21 no.8
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• pp.77-84
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• 2016

In general statistical analysis, we need to make a normal assumption. If this assumption is not satisfied, we cannot expect a good result of statistical data analysis. Most of statistical methods processing the outlier and noise also need to the assumption. But the assumption is not satisfied in big data because of its large volume and heterogeneity. So we propose a methodology based on box-plot and data smoothing for controling outlier and noise in big data analysis. The proposed methodology is not dependent upon the normal assumption. In addition, we select patent documents as target domain of big data because patent big data analysis is a important issue in management of technology. We analyze patent documents using big data learning methods for technology analysis. The collected patent data from patent databases on the world are preprocessed and analyzed by text mining and statistics. But the most researches about patent big data analysis did not consider the outlier and noise problem. This problem decreases the accuracy of prediction and increases the variance of parameter estimation. In this paper, we check the existence of the outlier and noise in patent big data. To know whether the outlier is or not in the patent big data, we use box-plot and smoothing visualization. We use the patent documents related to three dimensional printing technology to illustrate how the proposed methodology can be used for finding the existence of noise in the searched patent big data.

• Nuclear Engineering and Technology
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• v.42 no.1
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• pp.9-16
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• 2010

Experimental examinations for evaluating fracutres were conducted by using transparent replicas of a single fracture in order to obtain the fracture data to contribute to the methodlogy on how to improve the definitaion of representative parameter values used for a parallel plate fracture model. Quantitative aperture distribution and quantitative tracer concentration data at each point in time were obtained by measuring the attenuation of transmitted light through the fracture in high spatial resolution. the representative aperture values evaluated from the multiple different measurement methods, such as arithmetic mean of aperture distribution measured by the optical method, transport aperture evaluated from the tracer test, and average aperture evaluated from the fracture void volume measurement converged to a unique value that indicates the accuracy of this experimental study. The aperture data was employed for verifying the numerical simulation under the assuption of Local Cubic Law and showed that the calculated flow rate through the fracture is 10%-100% larger than hydraulic test results. The quantitative tracer concentration data is also very valuable for validating existing numerical code for advection dispersion transport in-plane heterogeneous fractures.

• Tuberculosis and Respiratory Diseases
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• v.87 no.1
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• pp.91-99
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• 2024

Background: Tuberculous pleural effusion (TPE) and parapneumonic effusion (PPE) are often difficult to differentiate owing to the overlapping clinical features. Observational studies demonstrate that the ratio of lactate dehydrogenase to adenosine deaminase (LDH/ADA) is lower in TPE compared to PPE, but integrated analysis is warranted. Methods: We conducted a systematic review to evaluate the diagnostic accuracy of the LDH/ADA ratio in differentiating TPE and PPE. We explored the PubMed and Scopus databases for studies evaluating the LDH/ADA ratio in differentiating TPE and PPE. Results: From a yield of 110 studies, five were included for systematic review. The cutoff value for the LDH/ADA ratio in TPE ranged from <14.2 to <25. The studies demonstrated high heterogeneity, precluding meta-analysis. Quality Assessment of Diagnostic Accuracy Studies Tool 2 assessment revealed a high risk of bias in terms of patient selection and index test. Conclusion: LDH/ADA ratio is a potentially useful parameter to differentiate between TPE and PPE. Based on the limited data, we recommend an LDH/ADA ratio cutoff value of <15 in differentiating TPE and PPE. However, more rigorous studies are needed to further validate this recommendation.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.6
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• pp.2437-2445
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• 2013

The objective of this study is finding the relationship between interstate highway accident frequencies and geometrics using Random Parameter Negative Binomial model. Even though it is impossible to take account of the same design criteria to the all segments or corridors on the road in reality, previous research estimated the fixed value of coefficients without considering each segment's characteristic. The drawback of the traditional negative binomial is not to explain the integrated variations in terms of time and the distinct characters specific segment has. This results in under-estimation of the standard error which inflates the t-value and finally, affects the modeling estimation. Therefore, this study tries to find the relationship of accident frequencies with the heterogeneous geometrics using 9-years and 7-interstate highway data in Washington State area. 16-types of geometrics are used to derive the model which is compared with the traditional negative binomial Model to understand which Model is more suitable. In addition, by calculating marginal effect and elasticity, heterogeneous variables' effect to the accidents are estimated. Hopefully, this study will help to estiblish the future policy of geometrics.

• Economic and Environmental Geology
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• v.33 no.6
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• pp.505-517
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• 2000

This study was undertaken to provide a drinking water quality on the basis of physicochemical properties. In this study, the 25 samples of supply waters of the Taejon area were sampled twice (February and August in 1999). Hydrochemistry of the supply water belongs to the $Ca^{2＋}$-${HCO_3}^{-1}$ type, whereas the supply water was characterized by the relatively significant enrichment of ${Ca}^{2+}$, ${Na}^{2+}$, ${K}^{2+}$, ${Cl}^{2+}$ ions and heavy metals compared to the original water from the Daecheong lake. Generally, the supply water has a mean values for $10.7^{\circ}C$ of temperature, 6.86 of pH, -12 mV of Eh, 88 ${\mu}S$/cm of EC and 70.379 mg/l of TDS in February, whereas the waters of the same sites in August are a slightly high temperature ($26.1^{\circ}C$), TDS (78.069 mg/l) and extremely high EC (442 ${\mu}S$/cm) value. These values are similar with physicochemical properties of the original lake water depending on the seasonal differences. Results of speciation calculation indicate that potentially toxic ions might exist mainly in the forms of free metal (${Cu}^{2+}$ or ${Zn}^{2+}$) and a small amount of ${CO_3}^{2-}$and ${OH}^{-}$in the supply water. The water seemed to be in equilibrium with kaolinite field of the normal stability diagrams for the natural water. Based on enrichment parameter of the supply water normalized by original lake water composition, the average value of those parameter can be calculated with nearly 1.00, but the those values for Cu＋Zn possible source of decrepit pipe lines are 126.75 in February and 115.63 in August samples. The parameter values varied with sampling sites, however, do not exceed by chemistry of drinking water standard. Solid compounds remained on the membrane filter papers after filtration are adhered to pale yellow or yellowish brown colored dissolved solids and precipitates, which are coated by 0.02 to 0.35 mm thick per 500 ml with colloidal particles of about 1 to 2${\mu}m$ size. The particles are mainly Fe-Cu-Zn compounds and partly detected to Mn and Pb.

• The Korean Journal of Ecology
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• v.27 no.2
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• pp.99-106
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• 2004

We developed the estimation model for the vegetation developmental processes on the severely burned slope areas after forest fire in the east coastal region, Korea. And we calculated the vegetation indices as a useful parameter for the development of land management technique in the burned area and suggested the changes of the vegetation indices after forest fire. In order to estimate the woody standing biomass in the burned area, allometric equations of the 17 woody species regenerated by sprouter were investigated. According to the our results, twenty year after forest fire need for the development to the normal forest formed by 4 stratum structure, tree, sub-tree, shrub and herb layer. The height of top vegetation layer, basal area and standing biomass of woody species show a tendency to increase linearly, and the ground vegetation coverage and litter layer show a tendency to increase logarithmically after forest fire. Among vegetation indices, Ive and Ivcd show a tendency to increase logarithmically, and Hcl and Hcdl show a tendency to increase linearly after forest fire. The spatial variation of the most vegetation factors was observed in the developmental stages less than the first 5 years which were estimated secondary disaster by soil erosion after forest fire. Among vegetation indices, Ivc and Ivcd were the good indices for the representation of the spatial heterogeneity in the earlier developmental stages, and Hcl and Hcdl were the useful indices for the long-term estimation of the vegetation development after forest fire.

• Journal of Labour Economics
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• v.25 no.3
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• pp.1-34
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• 2002

This paper investigates the effects of hours reduction on growth, investment, and consumption as well as employment. We adopt the basic framework of the indivisibility of labor developed by Hansen (1985) and Rogerson (1988) and extend it by allowing heterogeneity of workers in productive efficiency. On the basis of monthly panel data constructed from Economically Active Population Surveys and Household Income and Expenditure Surveys, we estimate the value of productive efficiency parameter of newly hired workers relative to existing workers by considering differences between the two groups in unobservable as well as observable worker characteristics. Numerical simulation of steady states demonstrates that reduction of statutory weekly hours from 44 to 40 leads to a rise in employees by 4.9 percent. However, GNP, investment, and consumption are all reduced by 2.03 percent, which is attributed to reduction in the amount of effective labor input, which in turn comes from reduction of actual average hours and productivity differences between exiting and newly hired workers.

• The Korean Journal of Applied Statistics
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• v.24 no.3
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• pp.485-494
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• 2011

When the observations can take only the non-negative integer values, it is called the count data such as the numbers of car accidents, earthquakes, or insurance coverage. In general, the Poisson regression model has been used to model these count data; however, this model has a weakness in that it is restricted by the equality of the mean and the variance. On the other hand, the count data often tend to be too dispersed to allow the use of the Poisson model in practice because the variance of data is significantly larger than its mean due to heterogeneity within groups. When overdispersion is not taken into account, it is expected that the resulting parameter estimates or standard errors will be inefficient. Since coverage is the main issue for insurance, some accidents may not be covered by insurance, and the number covered by insurance may be zero. This paper considers the zero-inflated model for the count data including many zeros. The performance of this model has been investigated by using of real data with overdispersion and many zeros. The results indicate that the Zero-Inflated Negative Binomial Regression Model performs the best for model evaluation.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.15 no.3
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• pp.207-221
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• 2020

This study conducted a meta-analysis on the effects of innovation, risk-taking, and enterprising on entrepreneurship. From 2013 to 2020, 392 papers, which were judged as quantitative research from doctoral and master thesis, and academic journals published in Korea were selected as research subjects. 28 duplicates of thesis and thesis are excluded. A total of 52 papers were finally selected, excluding 312 papers that were insufficient to be used as research data because there were no statistical values such as correlation coefficients. For the 52 selected papers, the homogeneity of the variables was first verified. As a result of the homogeneity test, the innovativeness, risk-taking, initiative, and entrepreneurship education all showed great effects on heterogeneity, and the average effect size was analyzed by random effect model. The average effect size analyzed was 0.38 ~ 0.49, and all four variables showed moderate average effect size. As a result of analyzing the average effect size by forest plot, all showed proper results. From the results of funnel plot analysis of entrepreneurship education, published errors were confirmed asymmetric. Research data on entrepreneurship education shows that it cannot represent the whole. It is a structural equation model with entrepreneurship and entrepreneurial intention as a parameter. Iinnovation and risk-taking have an impact on entrepreneurship by taking entrepreneurship education as a parameter. Initiative had an effect on the entrepreneurial intention a business, regardless of entrepreneurship education. In a number of studies, university entrepreneurship education has had an impact on the entrepreneurial intention. It should be changed to entrepreneurship education that combines theory and practice. Entrepreneurship education should be transformed into continuous and field-oriented education.