• Journal of the Korea institute for structural maintenance and inspection
• /
• v.21 no.6
• /
• pp.106-112
• /
• 2017

This paper presents a mathematical model derived from the upper-bound theorem of concrete plasticity to rationally evaluate the shear friction strength of concrete interfaces with a construction joint. The upper limit of the shear friction strength was formulated from the limit state of concrete crushing failure on the strut-and-tie action along the construction joints to avoid overestimating the shear transfer capacity of a transverse reinforcement with a high clamping force. The present model approach proposed that the cohesion and coefficient of friction of concrete can be set to be $0.27(f_{ck})^{0.65}$ and 0.95, respectively, for rough construction joints and $0.11(f_{ck})^{0.65}$ and 0.64, respectively, for smooth ones, where $f_{ck}$ is the compressive strength of concrete. From the comparisons with 155 data compiled from the available literature, the proposed model gave lower values of standard deviation and coefficient of variation of the ratios between predictions and experiments than AASHTO and fib 2010 equations, indicating that the proposed model has consistent trends with test results, unlike the significant underestimation results of such code equations in evaluating the shear friction strength.

• Korean Journal of Food Science and Technology
• /
• v.34 no.2
• /
• pp.186-193
• /
• 2002

This study was conducted to enhance the protein quality of wheat flour extrudates with the addition of fish sauce by-products and dried biji. The experimental design was used to determine the optimum ratio of each ingredient. The compositional and functional properties of test extrudate were measured, and these values were applied to the mathematical models. A canonical form and trace plot showed that the influence of each ingredient on the mixture final product. Protein content of extrudate was increased by the addition of the dried biji, and bending failure stress of extrudate became hardened due to interaction effects between dried biji and pacific sand lance sauce by-product. Also, the addition of dried biji decreased ash and salt contents. An optimum formulation was obtained as 15.83 : 44.17 : 40% with numerical and 15.74 : 44.26 : 26.40% with graphical method (pacific sand lance sauce by-product : dried biji : wheat flour). Based on the growth performance, feed conversion efficiency was slightly lower than control group, but the protein content in feed extrudate increased to a large extent compared to that mixed with wet biji.

• Korean Journal of Construction Engineering and Management
• /
• v.11 no.4
• /
• pp.22-31
• /
• 2010

Because the estimated cost at early stage has great influence on decisions of project owner, the importance of early cost estimation is increasing. However, it depends on experience and knowledge of the estimator mainly due to shortage of information. Those tendency developed into case-based reasoning(CBR) method which solves new problems by adapting previous solution to similar past problems. The performance of CBR model is affected by attribute weight, so that its accurate determination is necessary. Previous research utilizes mathematical method or subjective judgement of estimator. In order to improve the problem of previous research, this suggests CBR schematic cost estimation method using genetic algorithm to determine attribute weight. The cost model employs nearest neighbor retrieval for selecting past case. And it estimates the cost of new cases based on cost information of extracted cases. As the result of validation for 17 testing cases, 3.57% of error rate is calculated. This rate is superior to accuracy rate proposed by AACE and the method to determine attribute weight using multiple regression analysis and feature counting. The CBR cost estimation method improve the accuracy by introducing genetic algorithm for attribute weight. Moreover, this makes user understand the problem-solving process easier than other artificial intelligence method, and find solution within short time through case retrieval algorithm.

• Journal of The Korean Association For Science Education
• /
• v.24 no.5
• /
• pp.814-824
• /
• 2004

This article presents the effects of estimation activities related to speed and density on students' concept-understanding, answer-prediction, and answer-calculation in problem solving procedure with quantitative and qualitative methods. Participants were one hundred and ninety two seventh graders from one coeducational school in Seoul. Half of them participated in the estimation activities and the other half did in the measurement activities. Discussions of three students during estimation activities on density and their post-interviews were tape-recorded. Pre- and post-assessment scores were analyzed for the whole classes, and students' discussions and interviews served this research as evidences for the case analysis. Results of scores indicated that students in the estimation activities were significantly better than those in the measurement activities for predicting answers, but not for understanding concepts. Analysis of the cases revealed that estimation activity helped them to understand the relations of mass, volume and density, empirically, which enhanced their prediction ability. Furthermore, the ability could help a student with low calculation ability to comprehend the calculation problems. Thus, it is concluded that estimation activities could influence students' empirical learning on quantitative concepts, which enhanced their prediction ability.

• Journal of The Korean Association For Science Education
• /
• v.36 no.4
• /
• pp.607-616
• /
• 2016

In the 2009 revised science curriculum, comprehensive verbs such as 'know (38%)' and 'understand (46%)' are used in more than 80% of the achievement standard. Many readers, such as teachers, textbook makers, etc. have difficulties in interpreting the meaning of achievement standard sentences with these comprehensive verbs. On the other hand, 'Trends in International Mathematics and Science Study (TIMSS)' uses more various and specific verbs to express the cognitive domain. In this study, we analyzed the 2009 revised science curriculum achievement standard focusing on the TIMSS cognitive domain assessment framework. We divided achievement standard to 228 sentences and three teachers analyzed the meaning of verbs in achievement standard. There were two main results of this study. First, the verb 'Know' was analyzed into different kinds of meanings, such as 'Describe (27%)', 'Recall/Recognize (25%)' and 'Relate (17%)', etc; and the verb 'Understand' was analyzed into 'Explain (37%)', 'Relate (27%)' and 'Describe (21%)', etc. Second, there appeared to have a disagreement among the three analysts during the process of interpreting the achievement standards when the level and scope of the contents of each grade is not clear. This study concludes that there's a need for continuous discussion on the use of verbs in achievement standard to promote clearer expressions for better understanding.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.34 no.10B
• /
• pp.1050-1061
• /
• 2009

The Tactical Internet(TI) managed by Infantry Brigades is used for the purpose of sharing information of Command Control and Situation Awareness. When there are more than two destinations to transmit data in the TI system, a multicasting is utilized based on pre-defined multicast groups. However even in the case when a source node needs to send some messages like weathercast and attack alarm etc to only a part of Battalion or Brigades in a specific geographical region (destination region), the current TI multicasting protocol is designed to transmit the messages to the pre-defined group or all of the Battalion/Brigade nodes, resulting in inefficiency in terms of end-to-end delay and overhead. In this paper, we propose more efficient protocol for such cases, named as "Tactical Internet Geocasting (TIG)". The proposed scheme firstly checks whether the destination region belongs to one Battalion region or more than two Battalion regions using location information, and then performs a greedy forwarding from the source node to the destination region, followed by a local flooding inside of the destination region. With performance analysis and simulations using NS-2, TIG is compared to the current TI multicasting protocol (i.e., Simplified MDP) and the LBM (Location-based Multicast). The simulation results show that the proposed TIG is more efficient than both in terms of delay and network overhead.

• Journal of Korea Water Resources Association
• /
• v.31 no.6
• /
• pp.779-793
• /
• 1998

In this study, for the purpose of water supply planning, we propose a sophisticated multi-period mixed integer programming model that can coordinate the behavior of multi-reservoir operation, minimizing unnecessary spill. It can simulate the system with operating rules which are self- generated by the optimization engine in the algorithm. It is an optimization model in structure, but it indeed simulates the coordinating behavior of multi-reservoir operation. It minimizes the water shortfalls in demand requirements, maintaining flood reserve volume, minimizing unnecessary spill, maximizing hydropower generation release, keeping water storage levels high for efficient hydroelectric turbine operation. This optimization model is a large scale mixed integer programming problem that consists of 3.920 integer variables and 68.658 by 132.384 node-arc incidence matrix for 28 years of data. In order to handle the enormous amount of data generated by a big mathematical model, the utilization of DBMS (data base management system)seems to be inevitable. It has been tested with the Han River multi-reservoir system in Korea, which consists of 2 large multipurpose dams and 3 hydroelectric dams. We demonstrated successfully that there is a good chance of saving substantial amount of water should it be put to use in real time with a good inflow forecasting system.

• Journal of KIISE:Computing Practices and Letters
• /
• v.7 no.2
• /
• pp.151-164
• /
• 2001

Java, used as the most representative object-oriented language, isil becoming the popular language for Internet/Intranet based program development. Moreover, it is used for development language in a variety of areas such as component based development language. In the view of reuse and maintenance of developed program, quality evaluation of program is becoming a more important issue. So, metrics measurement for quality evaluation of program that is developed at present including existing Java application is necessary. However, it is necessary that whether existing object-oriented software metrics is suitable on Java program is to be validated So, in this paper, we build an automated metrics measurement system that needs to validate on object-oriented software metrics and wish to support metrics measurement that is to determine it. The purpose of this system is to support a precise quality evaluation tool. In this system, we apply the metrics classified by Briand. Briand classified the metrics by formalizing mathematically them to verify feasibility of existing object-oriented software metrics. Using the proposed system, we can make comparison and analysis of validation on existing object-oriented metrics by calculating quantitative information more rapidly from Java source program. If there is any problem in feasibility of the metrics, we can establish a suitable metrics on Java program by considering reiJ,1forcement of the existing metrics or proposing new metrics.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.17 no.2
• /
• pp.119-129
• /
• 2004

A three dimensional (3D) method of analysis is presented for determining the free vibration frequencies and mode shapes of thick, circular and annular plates with nonlinear thickness variation along the radial direction. Unlike conventional plate theories, which are mathematically two dimensional (2D), the present method is based upon the 3D dynamic equations of elasticity. Displacement components u/sub s/, u/sub z/, and u/sub θ/ in the radial, thickness, and circumferential directions, respectively, are taken to be sinusoidal in time, periodic in θ, and algebraic polynomials in the s and z directions. Potential (strain) and kinetic energies of the plates are formulated, and the Ritz method is used to solve the eigenvalue problem thus yielding upper bound values of the frequencies by minimizing the frequencies. As the degree of the polynomials is increased, frequencies converge to the exact values. Convergence to four digit exactitude is demonstrated for the first five frequencies of the plates. Numerical results we presented for completely free, annular and circular plates with uniform linear, and quadratic variations in thickness. Comparisons are also made between results obtained from the present 3D and previously published thin plate (2D) data.

• Hwankyungkyoyuk
• /
• v.6 no.1
• /
• pp.199-209
• /
• 1994

To investigate the trends in environmental education research of foreign countries, the paper published in the Journal of Environmental Education from 1984 to 1992 were analyzed. Major results of this study are as follows: 1. Total number of the paper analyzed was 178 and the average numbers of paper published per year were similar. 2. Researchers' majors were various. 3. The major targets of the researches in environmental education were school students. 4. Questionnaire was used in many researches and the main area of researches was strategy for environmental education. 5. Major type of research was survey and the main area of researches was strategy for environmental education. 6. The affective domain was highly concerned in environmental education researches.