• Journal of the Korea Concrete Institute
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• v.18 no.6 s.96
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• pp.819-825
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• 2006

The objective of the present study is to verify the validity of a new truss model for evaluating the contribution by arch action to shear resistance in shear-critical reinforced concrete beams. The new truss model is based on the relationship between shear and bending moment in a beam subjected to combined shear and bending. The compatibility condition of the shear deformation that deviates from Bernoulli bending plane is formulated utilizing the smeared truss idealization with an inclined compression chord. The Modified Compression Filed Theory is employed to calculate the shear deformation of the web, and the relative axial displacements of the compression and the tension chord by the shear flow are also calculated. From this shear compatibility condition in a beam, the shear contribution by the arch action is numerically decoupled. Then the validity of the model is examined by applying the model to some selected test beams in literatures. On the basis of the analytical results, the contribution by the web to shear resistance can be constant and have an excellent linear correlation with the web reinforcement ratio. The present decoupling approach may provide a simple way for the assessment of the role of each parameter or mechanism that affects the ultimate shear behavior of reinforced concrete beams.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.1D
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• pp.51-63
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• 2011

This study suggests that prior to construction of the 2nd Changwon tunnel and implementation of the demanded free of charge on Changwon tunnel, it is recommended to improve the traffic facilities and management of the traffic condition in order to create an efficient road that will keep traffic flow to a minimum and maintain the facilities proper working order. It has been generally accepted that the 2nd Changwon tunnel is necessary to construct and open as soon as possible. This is due to the service level of current traffic volume in the Changwon tunnel pay toll road which have been so congested that the fees have increased causing a public complaint to be filed, demanding a early free of charge be implemented for the Changwon tunnel. Furthermore, the objective and impartial analysis of the traffic situation based on a simulation of the alternative and traffic congestion fees has been provided to make the early free of charge on toll road as soon as possible. Finally, careful attention should be paid to seek to make the early free of charge on toll road in order to minimize the damages both specified and unspecified that may arise the prompt settlement of construction repayments and security of minimum management fees should be given priority over other alternatives.

• Journal of the Korean GEO-environmental Society
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• v.21 no.3
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• pp.5-11
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• 2020

Recently, ground pits that have been occurring frequently in urban areas are hindering traffic flow and causing property damages and loss of human life, acting as factors that are threatening the safety of citizens. Therefore, sunken ground must be quickly restored and provisions must be made for additional damage but current domestic detailed standards regarding ground pits and accurate definitions regarding causes and measures to be taken for reoccurrences are lacking. Restoration methods of sunken ground include backfilling by reusing sunken soil or other fill material and paving the road and while this is the most often used method, this only prevents ground from sinking temporarily and can not serve as a fundamental solution. Also, additional ground pits can occur on ground that is reinforced using this method due to faulty backfill material or faulty hardening. This study used Eco-friendly High-Strength Material (EHSM) as restoration material that can be used in the restoration of underground cavities that have occurred due to ground subsidence to analyze the engineered characteristics of modified dredging clay and test pieces made from changed ratios of EHSM and weathered granite soil were uniaxial compression tests were conducted and freezing-thawing tests were conducted to study strength properties according to environmental changes of restoration material, and after tests were concluded by each level, uniaxial compression tests and dynamic elasticity tests were conducted for intensity analysis. Also, to evaluate strength characteristics of the restored ground, dynamic plate load tests were conducted to verify the improvement effectiveness of the restored ground.

• Journal of Biosystems Engineering
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• v.29 no.3
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• pp.267-274
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• 2004

Using geo-statistical method, yield data of different fields were analyzed to examine their field variability according to examining year, analysis method. Semivariogram and Kriged maps of geo-statistical analysis were used to examine their spatial dependence within a filed. The results obtained were as follows. 1) Descriptive statistical results of the yield showed that the yield and the difference of yield ranged from 100 to 946kg/10a and from 272 to 653kg/10a, respectively within a field. The coefficient of variation also ranged from 5.9 to 22.4 %. 2) More than 90% of yield data were placed between 350 to 850kg/10a. e results indicated that the gram mass flow sensor should have the measuring range from 0.34 to 0.82kg/s considering the yields when 4 rows head-feeding combine with 0.8 m/s of working speed was utilized. 3) A high spatial dependence was found within paddy field. The Q values ranged from 0.20 to 0.97, and the range of spatial dependence was from 6.9 to 53.3m. From this result, the rational sampling interval for yield investigation was estimated 6.9m. 4) Yields within a field between observation years showed considerable variability even if the field was evenly cultivated and managed. To apply precision agriculture in a paddy field, the field test should be continued to build a solid data-base including meteorological data, blight damage and insect damage.

• Review of Culture and Economy
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• v.17 no.2
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• pp.103-135
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• 2014

This research dwells on the new paradigm of policy making of some innovative nations in Korean content industry. Especially this paper did evaluation of governmental policy in recent 5 years (2008~2012) in the field of Korean content industry. According to this research, the program of policy in Korean content industry had been obsessed to passive enrichment focusing on some part of content industry. The whole process of policy, scheme of policy and working flow of policy were very constrained in order to encourage more measurable area like CT(culture technology). Thus, we need new strong policy in this new government launched in 2013. The apparent keyword should be 'management'. New activity of policy need to focus on encourage Korean content industry in the real site of field, not in bureaucratic office in remote site. This change reflecting real filed management system would be productive innovation for policy making and activity in Korea.

• Journal of Aerospace System Engineering
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• v.15 no.5
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• pp.33-42
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• 2021

Modern aircraft fighters improve the maneuverability and performance with the RSS (Relaxed Static Stability) concept and therefore these aircrafts are susceptible to abrupt pitch-up in the transonic and moderate Angle-of-Attack (AoA) flight region where the shock wave is formed and the mean aerodynamic center is moved forward during deceleration. Also, the modeling of the aircraft flying in this flight region is very difficult due to complex flow filed and unpredictable dynamic characteristics and the model-based control design technique does not fully cover this problem. In this paper, we analyzed the performance of the TPMC (Transonic Pitching Moment Compensation) control based on the model-based IDI (Incremental Dynamic Inversion) and the Hybrid IDI based on the model and sensor based IDI during the SDT (Slow Down Turn) in transonic region. As the result, the Hybrid IDI had quicker response and the same maximum g suppression performance and provided the predictable flying qualities compared to the TPMC control. The Hybrid IDI improved the performance of the Over-G protection controller in the transonic and moderate AoA region

• Journal of Korea Water Resources Association
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• v.52 no.2
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• pp.163-172
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• 2019

The linear and cross-sectional shapes of the natural river channel are subjected to continuous changes in time and space due to the interaction with the flow of water and sediment transport. This study aims to investigate the morphological characteristics and change patterns of river channel quantitatively for the middle reach of Nakdong River, which has undergone large scale riverbed dredging and construction work, as Four Major River Restoration Project. A series of bathymetry and near-river survey has been conducted to obtain the detailed terrain information for the study area. The properties related to the linear and cross-sectional characteristics of river channel have been calculated based on the filed survey data and analyzed with comparing the survey data obtained in 2012 for the project completion. Since there has not been enough time for meaningful terrain change to take place, it was not possible to extract special tendency in the degree and aspect of terrain change. However, it is necessary to make regular examinations to the patterns and degree of river channel change using the proposed methodology.

• Journal of Korea Water Resources Association
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• v.41 no.12
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• pp.1219-1230
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• 2008

Stream inflows induced by flood runoffs have a higher density than the ambient reservoir water because of a lower water temperature and elevated suspended sediment(SS) concentration. As the propagation of density currents that formed by density difference between inflow and ambient water affects reservoir water quality and ecosystem, an understanding of reservoir density current is essential for an optimization of filed monitoring, analysis and forecast of SS and nutrient transport, and their proper management and control. This study was aimed to quantify the characteristics of inflow density current including plunge depth($d_p$) and distance($X_p$), separation depth($d_s$), interflow thickness($h_i$), arrival time to dam($t_a$), reduction ratio(${\beta}$) of SS contained stream inflow for different flood magnitude in Daecheong Reservoir with a validated two-dimensional(2D) numerical model. 10 different flood scenarios corresponding to inflow densimetric Froude number($Fr_i$) range from 0.920 to 9.205 were set up based on the hydrograph obtained from June 13 to July 3, 2004. A fully developed stratification condition was assumed as an initial water temperature profile. Higher $Fr_i$(inertia-to-buoyancy ratio) resulted in a greater $d_p,\;X_p,\;d_s,\;h_i$, and faster propagation of interflow, while the effect of reservoir geometry on these characteristics was significant. The Hebbert equation that estimates $d_p$ assuming steady-state flow condition with triangular cross section substantially over-estimated the $d_p$ because it does not consider the spatial variation of reservoir geometry and water surface changes during flood events. The ${\beta}$ values between inflow and dam sites were decreased as $Fr_i$ increased, but reversed after $Fr_i$>9.0 because of turbulent mixing effect. The results provides a practical and effective prediction measures for reservoir operators to first capture the behavior of turbidity inflow.

• Journal of Intelligence and Information Systems
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• v.20 no.4
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• pp.121-139
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• 2014

Predicting corporate failure has been an important topic in accounting and finance. The costs associated with bankruptcy are high, so the accuracy of bankruptcy prediction is greatly important for financial institutions. Lots of researchers have dealt with the topic associated with bankruptcy prediction in the past three decades. The current research attempts to use ensemble models for improving the performance of bankruptcy prediction. Ensemble classification is to combine individually trained classifiers in order to gain more accurate prediction than individual models. Ensemble techniques are shown to be very useful for improving the generalization ability of the classifier. Bagging is the most commonly used methods for constructing ensemble classifiers. In bagging, the different training data subsets are randomly drawn with replacement from the original training dataset. Base classifiers are trained on the different bootstrap samples. Instance selection is to select critical instances while deleting and removing irrelevant and harmful instances from the original set. Instance selection and bagging are quite well known in data mining. However, few studies have dealt with the integration of instance selection and bagging. This study proposes an improved bagging ensemble based on instance selection using genetic algorithms (GA) for improving the performance of SVM. GA is an efficient optimization procedure based on the theory of natural selection and evolution. GA uses the idea of survival of the fittest by progressively accepting better solutions to the problems. GA searches by maintaining a population of solutions from which better solutions are created rather than making incremental changes to a single solution to the problem. The initial solution population is generated randomly and evolves into the next generation by genetic operators such as selection, crossover and mutation. The solutions coded by strings are evaluated by the fitness function. The proposed model consists of two phases: GA based Instance Selection and Instance based Bagging. In the first phase, GA is used to select optimal instance subset that is used as input data of bagging model. In this study, the chromosome is encoded as a form of binary string for the instance subset. In this phase, the population size was set to 100 while maximum number of generations was set to 150. We set the crossover rate and mutation rate to 0.7 and 0.1 respectively. We used the prediction accuracy of model as the fitness function of GA. SVM model is trained on training data set using the selected instance subset. The prediction accuracy of SVM model over test data set is used as fitness value in order to avoid overfitting. In the second phase, we used the optimal instance subset selected in the first phase as input data of bagging model. We used SVM model as base classifier for bagging ensemble. The majority voting scheme was used as a combining method in this study. This study applies the proposed model to the bankruptcy prediction problem using a real data set from Korean companies. The research data used in this study contains 1832 externally non-audited firms which filed for bankruptcy (916 cases) and non-bankruptcy (916 cases). Financial ratios categorized as stability, profitability, growth, activity and cash flow were investigated through literature review and basic statistical methods and we selected 8 financial ratios as the final input variables. We separated the whole data into three subsets as training, test and validation data set. In this study, we compared the proposed model with several comparative models including the simple individual SVM model, the simple bagging model and the instance selection based SVM model. The McNemar tests were used to examine whether the proposed model significantly outperforms the other models. The experimental results show that the proposed model outperforms the other models.

• Magazine of the Korean Society of Agricultural Engineers
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• v.24 no.2
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• pp.49-55
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• 1982

The purpose of this study is to classify the factors influenced on the damages of head works suffered from the storm flood occurred on July 22 1980 in both Musim and Bochong rivers and to find out an integral counter measures against the causes influenced on the disaster of head works in the engineering aspect of planning, design, construction and maintenance. In this survey, number of samples was taken 25 head Works, and the counter measures against the causes of their disasters summarized was as follows, 1. In the aspect of planning a. As the flood water level after the establishment of head works is more increased than the level before setting of head works owing to having more gentle slope of river bed between the head works than nature slope of river bed. Number of head works should be reduced for the appropriate annexation of them b. In the place where head works is established on the curved point of levee, the destruction of levee becomes severe by the strong deflective current. Therefore the setting of head works on the curved point should be kept off as long as possible and in case of unavoidable circumstances the construction method such as reinforced concrete wall or stone wall filed with concrete and anchored bank revetments should be considered. 2. In the aspect of design a. As scoring phenomena at up stream is serious around the weir Where the concentration of strong current is present in such a place, up stream apron having impermeability should be designed to resist and prevent scoring. b. As the length of apron and protected bed is too short to prevent scoring as down stream bed, the design length should be taken somewhat more than the calculated value, but in the case the calculated length becomes too long to be profitable, a device of water cushion should be considered. c. The structure of protected river bed should be improved to make stone mesh bags fixed to apron and to have vinyl mattress laid on river bed together with the improvement for increasing the stability of stone mesh bags and preventing the sucked sand from the river bed. d. As the shortage of cut-off length, especialy in case of the cutoffs conneting both shore sides of river makes the cause of destruction of embankment and weir body, the culculation of cut-off length should be taken enough length based on seepage length. 3. In the aspect of design and constructions a. The overturing destruction of weir by piping action was based on the jet water through cracks at the construction and expansion joints. therefore the expansion joint should be designed and constructed with the insertion of water proof plate and asphalt filling, and the construction joint, with concaved shape structure and steel reinforcement. b. As the wrong design and construction of the weep holes on apron will cause water piping and weir destruction, the design and construction of filter based on the rule of filter should be kept for weep holes. c. The wrong design and construction of bank revetment caused the severe destruction of levee and weir body resulting from scoring and impulse by strong current and formation of water route behind the revetment. Therefore bank revetment should be designod and constructed with stone wall filled with concrete and anchored, or reinforced concrete wall to prevent the formation of water flow route behind the wall and to resist against the scoring and impulse of strong stream. 4. In the aspect of maintenance When the damaged parts occurred at head works the authorities and farmers concerned should find and mend them as soon as possible with mutual cooperation, and on the other hand public citizen should be guided for good use of public property.