• Journal of Electrical Engineering and information Science
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• v.3 no.3
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• pp.385-390
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• 1998

In this paper, the oscillator strengths of both the heavy-hole and the light-hole excitons in GaAs-A\ulcornerGa\ulcornerAs and In\ulcornerGa\ulcornerAs-InP quantum wells with the effect of a magnetic field applied along the growth axis are studied. The calculation is carried out usig a variational approach, based on a simple trial exction wave function. The exciton oscillator strengths are found to decrease with increasing well width and to increase with the applied magnetic fields which lead to additional quantum confinement for moderately wide well sizes. Also, the oscillator strengths for the heavy-hole exciton are found to be large than those of the light-hole exciton in these quantum well structures.

• The Journal of Industrial Distribution & Business
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• v.4 no.2
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• pp.21-30
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• 2013

Purpose - The objectives of this study are to find the strengths, weaknesses, opportunities, and threats related to the national innovation system of Iran (using a SWOT analysis) and to extract some strategic recommendations to modify the innovation policies of Iran. Research design, data, and methodology - This study used a literature review and field study. In the first phase, the author studied library resources and articles, and browsed through Internet information about the subject. The second phase was a field research investigation through designed questionnaires and interviews with more than 100 policymakers, officials, executives, and others related to the national innovation system in 2011. Results - In this research study, strategic recommendations were extracted through a SWOT model for improvements to the innovation policies of Iran. Conclusions - The findings of this study show the role of strengths, weaknesses, opportunities, and threats in the national innovation system of Iran and suggest strategic recommendations for its modification.

• International Journal of Concrete Structures and Materials
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• v.5 no.2
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• pp.87-96
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• 2011

Many studies have been performed on steel fiber-reinforced normal/high-strength concrete (SFRC, SFRHC) for years, which is to improve some of the weak material properties of concrete. Most of equations for material strengths of SFRHC, however, were proposed based on relatively limited test results. In this research, therefore, the material test results of SFR(H)C were extensively collected from literature, and material tests have conducted on SFR(H)C; compressive strength tests, splitting tensile tests, and modulus of rupture tests. Based on the extensive test data obtained from previous studies and this research, a database of SFR(H)C material strengths has been established, and improved equations for material strengths of SFR(H)C were also proposed. Test results showed that both the splitting tensile strength and the modulus of rupture of SFR(H)C increased as the volume fraction of steel fiber increased, while the effect of the steel fiber volume fraction on the compressive strength of SFR(H)C were not clearly observed. The proposed equations for the splitting tensile strength and the modulus of rupture of SFR(H)C showed better results than the previous equations examined in this study in terms of not only accuracy but also safety/reliability.

• Structural Engineering and Mechanics
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• v.34 no.1
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• pp.15-38
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• 2010

In order to predict the shear strengths of reinforced concrete beams, many deterministic models have been developed based on rules of mechanics and on experimental test results. While the constant and variable angle truss models are known to provide reliable bases and to give reasonable predictions for the shear strengths of members with shear reinforcement, in the case of members without shear reinforcement, even advanced models with complicated procedures may show lack of accuracy or lead to fairly different predictions from other similar models. For this reason, many research efforts have been made for more accurate predictions, which resulted in important recent publications. This paper develops probabilistic shear strength models for reinforced concrete beams without shear reinforcement based on deterministic shear strength models, understanding of shear transfer mechanisms and influential parameters, and experimental test results reported in the literature. Using a Bayesian parameter estimation method, the biases of base deterministic models are identified as algebraic functions of input parameters and the errors of the developed models remaining after the bias-correction are quantified in a stochastic manner. The proposed probabilistic models predict the shear strengths with improved accuracy and help incorporate the model uncertainties into vulnerability estimations and risk-quantified designs.

• Korean Journal of Mineralogy and Petrology
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• v.33 no.3
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• pp.273-291
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• 2020

The strength characteristics of the three orthogonal splitting planes, known as rift, grain and hardway planes in granite quarries, were examined. R, G and H specimens were obtained from the block samples of Jurassic granites in Geochang and Hapcheon areas. The directions of the long axes of these three specimens are perpendicular to each of the three planes. First, The chart, showing the scaling characteristics of three graphs related to the uniaxial compressive strengths of R, G and H specimens, were made. The graphs for the three specimens, along with the increase of strength, are arranged in the order of H < G < R. The angles of inclination of the graphs for the three specimens, suggesting the degree of uniformity of the texture within the specimen, were compared. The above angles for H specimens(θ^H, 24.0°~37.3°) are the lowest among the three specimens. Second, the scaling characteristics related to the three graphs of RG, GH and RH specimens, representing a combination of the mean compressive strengths of the two specimens, were derived. These three graphs, taking the various N-shaped forms, are arranged in the order of GH < RH < RG. Third, the correlation chart between the strength difference(Δσ_t) and the angle of inclination(θ) was made. The above two parameters show the correlation of the exponential function with an exponent(λ) of -0.003. In both granites, the angle of inclination(θ^RH) of the RH-graph is the lowest. Fourth, the six types of charts, showing the correlations among the three kinds of compressive strengths for the three specimens and the five parameters for the two sets of microcracks aligned parallel to the compressive load applied to each specimen, were made. From these charts for Geochang and Hapcheon granites, the mean value(0.877) of the correlation coefficients(R²) for total density(Lt), along with the frequency(N, 0.872) and density(ρ, 0.874), is the highest. In addition, the mean values(0.829) of correlation coefficients associated with the mean compressive strengths are more higher than the minimum(0.768) and maximum(0.804) compression strengths of three specimens. Fifth, the distributional characteristics of the Brazilian tensile strengths measured in directions parallel to the above two sets of microcracks in the three specimens from Geochang granite were derived. From the related chart, the three graphs for these tensile strengths corresponding to the R, G and H specimens show an order of H(R1+G1) < G(R2+H1) < R(R1+G1). The order of arrangement of the three graphs for the tensile strengths and that for the compressive strengths are mutually consistent. Therefore, the compressive strengths of the three specimens are proportional to the three types of tensile strengths. Sixth, the values of correlation coefficients, among the three tensile strengths corresponding to each cumulative number(N=1~10) from the above three graphs and the five parameters corresponding to each graph, were derived. The mean values of correlation coefficients for each parameter from the 10 correlation charts increase in the order of density(0.763) < total length(0.817) < frequency(0.839) < mean length(Lm, 0.901) ≤ median length(Lmed, 0.903). Seventh, the correlation charts among the compressive strengths and tensile strengths for the three specimens were made. The above correlation charts were divided into nine types based on the three kinds of compressive strengths and the five groups(A~E) of tensile strengths. From the related charts, as the tensile strength increases with the mean and maximum compressive strengths excluding the minimum compressive strength, the value of correlation coefficient increases rapidly.

• Journal of information and communication convergence engineering
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• v.9 no.6
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• pp.676-682
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• 2011

Sybil attack can disrupt proper operations of wireless sensor network by forging its sensor node to multiple identities. To protect the sensor network from such an attack, a number of countermeasure methods based on RSSI (Received Signal Strength Indicator) and LQI (Link Quality Indicator) have been proposed. However, previous works on the Sybil attack detection do not consider the fact that Sybil nodes can change their RSSI and LQI strength for their malicious purposes. In this paper, we present a Sybil attack detection method based on a transmission power range. Our proposed method initially measures range of RSSI and LQI from sensor nodes, and then set the minimum, maximum and average RSSI and LQI strength value. After initialization, monitoring nodes request that each sensor node transmits data with different transmission power strengths. If the value measured by monitoring node is out of the range in transmission power strengths, the node is considered as a malicious node.

• The Korean Journal of Elementary Counseling
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• v.11 no.2
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• pp.193-217
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• 2012

The purpose of this study was to investigate and suggest directions and assignments of elementary school counseling based on positive psychology. For this purpose, the goal, contents, techniques and effects of counseling based on positive psychology were examined. Based on this review, the suggested implications for directions and assignments of elementary school counseling as follows; In connection with the directions of elementary school counseling, first, it was suggested that problem-focused counseling approaches centered a small number of problem children should be changed to strength based counseling approaches facilitating all children's whole development, happiness and well-being. Second, it was suggested that continuous and systematic counseling helps should be served to all children so that they can aware, experience and use their character strengths in their all lives at the inside and outside of their school. In connection with the assignments of elementary school counseling, first, increasing children's understanding on happiness, developing counseling programs for enhancing happiness and verifying their effects were discussed. Second, developing effective applying plans of positive counseling techniques and verifying their effects were discussed. Finally, making researches on our children's character strengths and interventions for developing their character strengths were discussed.

• Journal of the Korea Concrete Institute
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• v.26 no.4
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• pp.449-456
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• 2014

Material properties of geopolymer, whose the reaction is very complicated, have been influenced by chemical compositions and particle size distributions of fly ash, concentrations and types of alkali-activators and curing conditions such as temperatures and time. In this research, experiments with several variables such as curing temperatures, preset prior to the high temperature curing and high temperatures have been conducted in order to evaluate to investigate effects on the compressive strengths of geopolymer caused by curing condition. Experiment results were evaluated with compressive strengths and micro-structures such as SEM and MIP of geopolymer pastes. As a result, as higher curing temperature or longer preset time were applied to the pastes, higher compressive strengths were observed. However, compressive strengths of geopolymer pastes declined due to increases in macropores (>50 nm) under high temperatures elapsed after 24 hours. In this sense, it can be considered that strengths and microstructures of geopolymers depends on curing temperature and time.

• Journal of the Korean Academy of Pediatric Dentistry
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• v.25 no.2
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• pp.277-284
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• 1998

For the purpose of comparing the shear bond strengths of pit and fissure sealants, and finding out the more efficient method of tooth surface treatment when the etched surface is contaminaed by saliva or moisture, an experiment was performed on 3 types of pit and fissure sealants. 120 extracted human molars were divided into 3 groups, each of which was composed of 40 specimens sealed with Helioseal, Teethmate-F and Fuji III respectively. And each groups was again divided into 4 subgroups according to tooth surface treatment. The shear bond strengths of each groups and subgroup was measured and statistically analyzed. The results obtained were as follows : 1. Shear bond strengths of nonfluoridated resin sealant, Helioseal were shown to be higher than those of fluoridated resin sealant, Teethmate-F, but, not significantly different. 2. Shear bond strengths of GI sealant, Fuji III were to be markedly lower than those of two resin sealants. 3. When there is moisture contamination, applying primer under sealant(Group IV) results in a significantly stronger bond strength of sealant to enamel than when using sealant alone(Group II) in case of all sealants. 4. When there is no moisture contamination, using primer under sealant (Group III) results in bond strength equivalent to bond strength on using sealant alone (Group I). 5. Based on the results above, it was demonstrated that the bond of sealant to tooth surface is greatly affected by saliva contamination and that the complete tooth isolation method should be fully emphasized. The application of primer is recommended when performing sealant under the environment very susceptible to saliva contamination.

• The Journal of the Korea Contents Association
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• v.16 no.12
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• pp.530-538
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• 2016

This study was to examine the effectiveness of Strengths-Focused Group Program in Korea by using method of Meta-analysis. For the purpose of the study, master's theses, doctoral dissertations, and journal articles published in Korea up to August, 2016 were systematically reviewed. As a result, a total of 25 studies were eligible for the inclusion criteria. The mean effect sizes and test for homogeneity of effect size(Q-statistic) were analyzed by using Comprehensive Meta-Analysis software 2.0. The main findings of the study were as follows. First, the average effect sizes for Strengths-Focused Group Program were ES=1.400 of Psychological Wellbeing, ES= 1.104 of School Adjustment, ES= 0.908 of Self-Esteem. Second, the moderate variables of the effect size for Strengths-Focused Group Program was 'age' of ' a characteristic of the program', and 'the major of group leader'. Based on the study results, the research and practice implications were discussed.