• Journal of applied mathematics & informatics
• /
• v.27 no.1_2
• /
• pp.259-266
• /
• 2009

We consider an M/G/1 feedback retrial queue with Bernoulli schedule in which after being served each customer either joins the retrial group again or departs the system permanently. Using the supplementary variable method, we obtain the joint generating function of the numbers of customers in two groups.

• Proceedings of the Korean Nuclear Society Conference
• /
• 1996.05a
• /
• pp.137-141
• /
• 1996

A new general high order consistent nodal method for solving the 3-D multigroup neutron kinetic equations in (x-y-z) geometry has been derived by expending the flux in a multiple polynomial series for the space variables by without the quadratic fit approximations of the transverse leakage and for the time variable and using a weighted-integral technique. The derived equation set is consistent mathematically, and therefore, we can expect very accurate solutions and less computing time since we can use coarse meshes in time variable as well as in spatial variables and the solution would converge exactly in fine mesh limit.

• Communications of the Korean Mathematical Society
• /
• v.39 no.1
• /
• pp.247-257
• /
• 2024

We use the structure of skew braces to enhance the biquandle counting invariant for virtual knots and links for finite biquandles defined from skew braces. We introduce two new invariants: a single-variable polynomial using skew brace ideals and a two-variable polynomial using the skew brace group structures. We provide examples to show that the new invariants are not determined by the counting invariant and hence are proper enhancements.

• Water Engineering Research
• /
• v.1 no.4
• /
• pp.293-298
• /
• 2000

Optimal values of $\alpha$ characterizing the linear dispersion property in the modified Boussinesq equations are determined by minimizing the combined relative errors of the phase and group velocities. The value of $\alpha$ is fixed in previous studies, whereas it is varying in the present study. The phase and group velocities are calculated by using variable $\alpha$ and compared to those of the linear Stokes wave theory and previous studies. It is found that the present study produces the best match to the linear Stokes theory.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.10 no.2
• /
• pp.159-165
• /
• 2010

The Multi-code (Mc) modulation has been developed for high-speed data transmission over the wireless environments, but it suffers two critical problems due to the limited resource of Orthogonal Codes (OC) and high Peak-Average Power Ratio (PAPR). In this paper, we propose a novel modulation technique called AOCG [1] (Advanced Orthogonal Code Group)-OFDM (Orthogonal Frequency Division Multiplexing) to solve the above problems and obtain the variable high bit rates which can be controlled by the four parameters depending on the quality of services (QoS) required by users.

• Journal of Families and Better Life
• /
• v.20 no.1
• /
• pp.115-124
• /
• 2002

The purpose of this study is to examine the social competence of children with reference to day care center's structural, process variables and demographic variables. The subjects were 156 children who attend day care center, aged from 3 to 5 years and 9 teachers in Seoul or the province of KyungkiDo. Data were gathered via the structured Questionnaires distributed to the teachers to rate children's social competence and their own job satisfaction. And two observers rated teacher-child interaction in day care center The major findings are as follows The variables predicting children's social competence were child's sex, age, period of attendance in day care center, teacher's job satisfaction, and group size. Especially this study suggests that teachers who are highly satisfied with their job and small group size influence children's social competence positively.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
• /
• v.27 no.1
• /
• pp.37-45
• /
• 2001

The errors in orthognathic surgery can occur during the preoperative preparations including the model surgery, but till now there's been some lack of reserches about them. So we wanted to verify the accuracies in measurements used in model surgery. We compared the accuracy of measurements by vernier calipers, which has been the main measurement tool for conventional model surgery, and that by height gauge, which is recently claimed to be more accurate, with 3 dimensional coordinate analyzer. We could have following results and have a plan to use them for the invention of new model surgery techniques. 1. The measurement errors in Group 1, which mean the difference between "the measurements by 3-D analyzer"and "the measurements by height gauge", were small enough with the range of $0.1{\sim}0.2mm$ in all planes. 2. The mean error in Group 2, which is the differences between the measurements of 3-D analyzer and those of vernier calipers, was 1.1mm. 3. The measurement errors in Group 2 were variable according to the factors including the differences of individuality and expertness of each measurers. But in case of Group 1, they were small and not variable by the expertness. 4. The measurements were more accurate at the points in anterior teeth than in molar teeth in Group 1 and 2. 5. The errors after model surgery increased remarkably, compared with those before surgery in Group 2. And the situation was different in Group 1 in that errors decreased after surgery. According to these results, it assumed that the measurements with height gauge during the model surgery for orthognathic surgery are accurate enough and can be maintained, regardless of complexity of models, individuality, or expertness of measurers.

• Fashion & Textile Research Journal
• /
• v.11 no.3
• /
• pp.390-398
• /
• 2009

The research purposes are (1) to identify male market segmentation based on fashion involvement, (2) to compare purchase intention of clothing items and store attribute evaluation at two different retail formats, department store and internet shopping mall, and (3) to compare the influence of store attributes on intention to purchase fashion products at two retail formats among segments. The data are collected from 275 male consumers through internet research institute. The major results of this study are as follows. First, the dimensions of fashion involvement are identified into external involvement and internal involvement. Male respondents present high mean scores on external involvement items, emphasizing social roles of clothing. Two involvement factors generate three market segments: high involvement group(32.4%), external involvement group(44%), and low involvement group(23.6%). Second, high involvement group shows higher mean scores on purchase intention of seven clothing items than low involvement group. Third, department store attributes are identified into four factors, product assortment, quality per price, service, and symbolic image, while internet shopping mall includes assortment & convenience, quality per price, and symbolic image. High involvement group again presents higher mean scores on each retail attribute factor than low involvement group. Finally, quality per price is the most significant variable to explain the purchase intention at department store among three market segment, whereas assortment & convenience and quality per price are important predictors to increase purchase intention at internet shopping mall. However, relative importance of each attribute variable is different among three involvement groups.

• Journal of the Korean Regional Science Association
• /
• v.32 no.4
• /
• pp.3-18
• /
• 2016

National research and development(R&D) project plays an important role in the economic growth of a country as well as a company. This article aim to examine the development of the performance evaluation framework for assessing the contribution of national research and development(R&D) program to productivity growth. The main idea of this paper begins with the employment of between-group analysis for evaluating the returns to R&D. The method of this study is based on the comparison of productivity growth between different groups with time series data, not cross-sectional approach with one period. In these regards, backward effect and forward effect are operationally defined as a measurement for contributions of R&D in this study. The results of analysis gives that the outcomes of between-group analysis shows the lower performance of R&D compared to the within-group analysis. while the difference was not especially evident with the case of operating profit variable, but sales variable.

• Korean Journal of Applied Biomechanics
• /
• v.28 no.4
• /
• pp.213-218
• /
• 2018

Objective: The purpose of this study was to examine the effect of the core muscle strength enhancement of the elderly on 8 weeks training using the core exercise equipment for the elderly on the ability to control the whole-body center of mass in posture stabilization. Method: 16 females (10 exercise group, 6 control group) participated in this study. Exercise group took part in the core strength training program for 8 weeks with total of 16 repetitions (2 repetitions per week) using a training device. External perturbation during standing as pulling force applied at the pelvic level in the anterior direction was provided to the subject. In a UCM model, the controller selects within the space of elemental variables a subspace (a manifold, UCM) corresponding to a value of a performance variable that needs to be stabilized. In the present study, we were interested in how movements of the individual segment center of mass (elemental variables) affect the whole-body center of mass (the performance variable) during balance control. Results: At the variance of task-irrelevant space, there was significant $test^*$ group interactions ($F_{1,16}=7.482$, p<.05). However, there were no significant main effect of the test ($F_{1,16}=.899$, p>.05) and group ($F_{1,16}=1.039$, p>.05). At the variance of task-relevant space, there was significant $test^*$ group interactions ($F_{1,16}=7.382$, p<.05). However, there were no significant main effect of the test ($F_{1,16}=.754$, p>.05) and group ($F_{1,16}=1.106$, p>.05). Conclusion: The results of this study showed that the 8 weeks training through the core training equipment for the elderly showed a significant decrease in the $Vcm_{TIR}$ and $Vcm_{TR}$. This result indicates that the core strength training affects the trunk stiffness control strategy to maintain balance in the standing position by minimizing total variability of individual segment CMs.