• Journal of Korean Elementary Science Education
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• v.33 no.4
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• pp.607-619
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• 2014

The purpose of this study is to investigate the degree of concept understanding on the stratum for elementary school students. For this objective, questions on the stratum concept were developed, and concept survey was conducted for random sampling of $5^{th}$ and $6^{th}$ grade 536 students. As a result, students chosen correct answers of the average 57.4% for 16 questions. Below the average rate of correct answers in each domain were 1 question in the definition of the stratum, 3 questions in formation of the stratum, and 4 questions in features of the stratum. Especially, the percentage of correct answers were appeared in lowly that the difference between the visible side and non visible side on the stratum, the definition and formation process of a fault and the main cause of the stratum's exposure. Also, between the residence, grade, and gender of students, there were significant differences in 2 questions, 7 questions, and 1 questions, respectively. Therefore, many elementary school students do not have high understanding about the stratum concept. Through the results of this study, it can be contributed to find an efficient ways as a basic data for modify misconceptions of the stratum to the scientific concept.

• Journal of Pharmaceutical Investigation
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• v.23 no.3
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• pp.1-8
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• 1993

A simple and quick method based on the transient diffusion theory for predicting the steady state rate of penetration of a drug after transdermal drug administration was proposed. The amount of drug entering the stratum corneum was determined by 20 strippings with an adhesive tape. From the profile of the amount of drug as a function of the number of strippings, the quantity of drug on the surface of stratum corneum was extrapolated. Based on the amounts of drug entering the stratum corneum during two time intervals $(t_1\;and\;t_2)$ within 1 hour after the application, the diffusion and partition coefficient were determined. Once the diffusion coefficient of the drug in the stratum corneum and the partition coefficient (stratum corneum/vehicle) were determined from the present approach, the steady-state flux of penetration across the stratum corneum was calculated. The steady-state rates of penetration of ascorbic acid and estradiol across hairless mouse skin were evaluated from this approach and compared with those obtained from ill vitro penetration experiment using excised hairless mouse skin. The data confirmed that the proposed method can predict the steady-state rate of penetration of these drugs across the stratum corneum.

• Geomechanics and Engineering
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• v.2 no.1
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• pp.29-44
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• 2010

Vertical vibration tests were conducted using model footings of different size and mass resting on the surface of finite sand layer with different height to width ratios which was underlain by either rigid concrete base, under both dry and saturated condition. The effect of saturation on the damping ratio of finite sand stratum underlain by a rigid base has been verified and compared with the results obtained for the case of finite dry sand stratum underlain by the rigid base. Comparison of results of the experimental study showed that the damping in both the cases is less than 10%. The damping ratio obtained for finite saturated sand stratum is marginally lower than that obtained on finite dry sand stratum at H/B ratio of 0.5. The difference between the two cases becomes significant when the H/B ratio increases to 3.0, indicating the significant influence of soil moisture on damping ratio of foundation- soil system with increase in the thickness of the finite sand stratum. Comparison of the predicted damping ratio for a homogeneous sand stratum with the experimental damping ratio obtained corresponding to the height to width ratio of 3.0 of the finite sand stratum underlain by the rigid concrete base indicates a significant reduction in damping ratio of the foundation-soil system for both the cases.

• Communications for Statistical Applications and Methods
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• v.11 no.2
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• pp.297-311
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• 2004

In the sample survey for a highly skewed population, stratum jumpers often occur. Stratum jumpers are units having large discrepancies between a stratification variable and a study variable. We propose two models for stratum jumpers: a multiplicative model and a random replacement model. We also consider the modification of the L-H stratification algorithm such that we apply the previous models to L-H algorithm in determination of the sample sizes and the stratum boundaries. We evaluate the performances of the new stratification algorithms using real data. The result shows that L-H algorithm for the random replacement model outperforms other algorithms since the estimator has the least coefficient of variation.

• Communications for Statistical Applications and Methods
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• v.20 no.5
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• pp.367-376
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• 2013

Cut-off sampling is widely used for a highly skewed population like a business survey by discarding a part of the population (the take-nothing stratum). In this paper, we suggest a new composite estimator of the take-nothing stratum total obtained by use of the survey results of the take-nothing stratum and a take-some sub-stratum (a part of take-some stratum) for a more accurate estimate of the population total. Small simulation studies are conducted to compare the performances of known estimators and the new composite estimator suggested in this study. In addition, we use briquette consumption survey data for real data analysis.

• Journal of the Korean Society of Clothing and Textiles
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• v.10 no.3
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• pp.1-8
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• 1986

The purpose of this study was to investigate the characteristics of human epidermal stratum corneum as protein model soils for detergency test. The stratum corneum was collected by scraping of the skin and purified with solvent. The results obtained were as follows: 1. Purified stratum corneum contained $92.38\%$ of crude protein. 2. In the amino acid compositions, contents of glycine, glutamic acid and serine were high and methionine and cystine were low. They were similar to fibrous $\alpha$-keratin consisted of stratum corneum. Whereas the content of polar amino acids was decreased, that of nonpolar amino acids was increased after enzyme hydrolysis. 3. The hydrolysis of stratum corneum with enzyme increased muck at initial reaction time and levelled off in 4$\~$6 hours. The hydrolysis with enzyme was improved effectively at its optimum temperature and pH. 4. The hydrolysis of stratum corneum with enzyme increased by the addition of surfactants. The order of compatibility with enzyme was in the order of Triton X-100>AOS>LAS.

• Survey Research
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• v.5 no.1
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• pp.93-101
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• 2004

In business survey, cut-off sampling is usual, The contribution from cut-off part of the population is at least small in comparison with the remaining population. In this case, part of the target population is excluded from the selection and parameter estimations are only based on Take-all and Take-some stratum. It may be tempting not to use resources on enterprises that contribute little to the overall results of the survey. And this reduces the response burden for these small enterprises. But, the size of cut-off stratum has been increased as a way to manage reduced budgets. This leads to additional bias. In this study, the population have been separated as three stratum, cut -off, take-some, take-all, and we will estimate cut-off part using auxiliary variable.

• The Korean Journal of Applied Statistics
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• v.20 no.3
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• pp.515-530
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• 2007

Stratum-specific likelihood ratio, which is ratio of the sensitivity to 1-the specificity in each stratum of the test, could be biased if the sensitivity and specificity of diagnostic test are affected by verification bias. Therefore, the optimal cutoff point determined by biased stratum-specific likelihood ratios is incorrect. In this study, we derived adjusted stratum-specific likelihood ratios using the adjusted sensitivity and specificity, and obtained the adjusted optimal cutoff point. The influence of the verification bias on the optimal cutoff point was described through the relation between adjusted and unadjusted stratum-specific likelihood ratios.

• Journal of the Korea Fashion and Costume Design Association
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• v.19 no.2
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• pp.101-115
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• 2017

This study classified social stratum variables of adults in their 20s to 50s by subjective and objective measurements and classified leisure activities into groups to examine the conspicuous consumption of leisure apparel. A total of 365 adults in their 20s to 50s living in Daegu and the Kyungbuk area were selected considering their jobs and residences. SPSS PC+ 20.0 was used to analyze the data with frequency analysis, factor analysis, reliability examination, cluster analysis, ANOVA, Duncan-test, Scheffe-test, and ${\chi}^2-test$. The results of this study are shown as follows. First, 'Jogging/Walking' was found to be the most favorable activity in the examination of leisure sports activities among the participants and showed a difference in gender. Second, leisure activities were pastime-culture activity, sports activities, static activity, volunteering, and relaxing, and these activities were grouped into non-participant, active and passive leisure activities. Conspicuous consumption of leisure apparel was classified into personality oriented, luxury goods-oriented, and other people-oriented. Third, there was a significant difference in the sub-factors of the conspicuous consumption of leisure apparel (personality oriented, luxury goods-oriented, other people-oriented) according to the sub-factors of subjective stratum(economic power, social position, level of consumption, cultural level and overall stratum consciousness). Fourth, there was significance in the objective social stratum variable by the types of leisure activities. Significant differences were found in personality orientation, luxury goods-oriented, and other people-oriented in conspicuous consumption of leisure apparel by the types of leisure activities. Finally, there were significant differences in economic power, level of consumption, cultural level of subjective social stratum by gender, sports activities and volunteering in leisure activities, as well as other people-oriented conspicuous consumption of leisure apparel. This study also found significant differences in economic power, level of consumption and cultural level of social stratum by age, as well as other people-oriented conspicuous consumption of leisure apparel.

• The Korean Journal of Applied Statistics
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• v.22 no.6
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• pp.1277-1287
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• 2009

For stratifying skewed populations, the Lavall$\acute{e}$e-Hidiroglou(LH) algorithm is often considered to have a take-all stratum with the largest units and some take-some strata with the middle-size and small units. Related to its iterative nature have been reported some numerical difficulties such as the dependency of the ultimate stratum boundaries to a choice of initial boundaries and the slow convergence to locally-optimum boundaries. The geometric stratification has been recently proposed to provide initial boundaries that can avoid such numerical difficulties in implementing the LH algorithm. Since the geometric stratification does not pursuit the optimization but the equalization of the stratum CVs, the corresponding stratum boundaries may not be (near) optimal. This paper revisits these issues concerning convergence and near-optimality of optimal stratification algorithms using artificial numerical examples. We also discuss the formation of the strata and the sample allocation under the optimization process and some aspects related to discontinuity arisen from the finiteness of both population and sample as well.