• Computers and Concrete
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• v.24 no.4
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• pp.379-397
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• 2019

Steel-concrete composite beams are widely employed in constructions and their performance at the serviceability stage is of concern among practitioners and design regulations. In this context, an accurate evaluation of long-term deflections via various rheological concrete models is needed. In this work, the performance and predict capability of some concrete creep and shrinkage models ACI, CEB, B3, FIB and GL2000 are ascertained, and compared by using statistical bias indicators. Ten steel-concrete composite beams with existing experimental and numerical results are then modeled for this purpose. The proposed modeling technique uses the finite element method, where the concrete slab and steel beam are modeled with shell finite elements. Concrete is considered as an aging viscoelastic material and cracking is treated with the common smeared approach. The results show that when the experimental ultimate shrinkage strain is used for calibration, all studied rheological models predict nearly similar deflections, which agree with the experimental data. In contrast, significance differences are encountered for some models, when none calibration is made prior to. A value between twenty and thirty times the cracking strain is recommended for the ultimate tensile strain in the tension stiffening model. Also, increasing the relative humidity and decreasing the ambient temperature can lead to a substantial reduction of slab cracking for beams under negative flexure. Finally, there is not a unique rheological model that clearly excels in all scenarios.

• Journal of National Security and Military Science
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• s.3
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• pp.73-120
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• 2005

Today's world is generation of Transformation. The Term "Transformation" is widely used in many nations and international organizations such as U.S. and NATO to describe the course of change undertaken by militaries to respond to the new and emerging security environment. Transformation involves all elements of the defense enterprise including Operational Environment, Operational Concepts, Doctrine, Structure and Technologies, within a supportive Cultures context. An Operational Environment is defined as "a composite of conditions, circumstances, and influences that affect the employment of military forces and bear on the decisions of the unit commander." The context for developing future military concept and capability lies essentially within the anticipated boundaries of the operational environment in a collective sense. The joint operational environment is essential to the nation's defense. It describes volatile, complex, and dangerous environment in which the military personnel. organizations, and material will operate. Implications coming forth from joint Operational Environment are but a starting point - many others exist. More and better Implications will come forth as people think about massages of Operational Environment, experiment its characteristics, learn to deal with its threats and scenarios, apply their experience and judgement, and then consider what is required of Korean military doctrine, organizations, training and education, material development, and leadership for operations in the joint Operational Environment.

• School Mathematics
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• v.16 no.4
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• pp.783-802
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• 2014

The purpose of this study was to explore in detail students' understanding of fraction as quotient. A total of 158 sixth graders in 6 elementary schools were surveyed by 8 tasks in relation to fraction as quotient. As a result, students used various partitioning strategies to solve the given sharing tasks such as partitioning the singleton unit, the composite unit, or the whole unit of the dividend. They also used incorrect partitioning strategies that were not appropriate to the given context. Students' partitioning strategies and performance of fraction as quotient varied depending on the given contexts and models. This study suggests that students should have rich experience to partition various units and reinterpret the context based on the singleton unit of the dividend.

• Journal of Computing Science and Engineering
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• v.6 no.2
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• pp.89-104
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• 2012

In dynamic Web service environments, the performance of the Internet is unpredictable; the reliability and effectiveness of remote Web services are also unclear. Therefore, it can hardly be guaranteed that the quality of Web service (QoWS) attributes of Web services do not fluctuate with the dynamic Web service environments. When a composite service is planned in the context of dynamic service environments, there is another aspect which has not been taken into account by existing works, namely, concurrency - the fact that multiple requests to a composite service may arrive at the same time. Considering the dynamics of Web service environments and concurrency of requests, we propose in this paper a service selection scheme which adopts top-k dominating queries to generate a composition solution rather than only select the best composition solution for a given request. The experimental results have investigated the efficiency and effectiveness of our approach and shown that it outperforms baseline and traditional methods for service selection.

• Journal of Power Electronics
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• v.14 no.2
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• pp.369-382
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• 2014

A growing dynamic electrical demand has created an increasing interest in utilizing nonconventional energy sources like Photovoltaic (PV), wind power, etc. In this context, this paper focuses on the design and development of a composite power controller (CPC) in the decoupled double synchronous reference frame (DDSRF) combining the advantages of direct power control (DPC) and voltage oriented control (VOC) for a PV sourced grid connected inverter. In addition, a controller with the inherent active filter configuration is tested with nonlinear and unbalanced loads at the point of common coupling in both grid connected and autonomous modes of operation. Furthermore, the loss and reactive power compensation due to a non-fundamental component is also incorporated in the design, and the developed DDSRF model subsequently allows independent active and reactive power control. The proposed developed model of the controller is also implemented using MATLAB-Simulink-ISE and a Xilinx system generator which evaluate both the simulated and experimental setups. The simulation and experimental results confirm the validity of the developed model. Further, simulation results for the DPC are also presented and compared with the proposed CPC to further bring out the salient features of the proposed work.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.10a
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• pp.265-268
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• 2002

In this work, the blend system of epoxy and PMR-15 polyimide is investigated in terms of the cure behaviors and thermal stabilities. The cure behaviors are studied in DSC measurements and thermal stabilities are also carried out by TGA analysis. DDM (4, 4'-diamino diphenyl methane) is used as curing agent for EP and the content of PMR-15 is varied within 0, 5, 10, 35, and 20 phr to neat EP. As a result, the cure activation energy ($E_a$) is increased at 10 phr of PMR-15, compared with that of neat EP. From the TGA results of EP/PMR-15 blend system, the thermal stabilities based in the initial decomposed temperature (IDT) and integral procedural decomposition temperature (IPDT) are increased with increasing the PMR-15 content. The fracture toughness, measured in the context of critical stress intensity factor ($K_{IC}$) and critical strain energy release rate ($G_{IC}$), shows a similar behavior with $E_a$. This result is probably due to the crosslinking developed by the interactions between intermolecules in the polymer chains.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.10a
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• pp.269-272
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• 2002

UV curing technology becomes important in various sectors of applications due to the high efficiency, environmental protection, and saving of energy. The effect of different proportion of vinylester (VE) and unsaturated polyester (UP) for VE/UP blend system was investigated in context of mechanical properties. The compositions of VE/UP blend were varied within 0:100, 20:80, 40:60, 60:40, 80:20, and 100:0 by weight percent. 1 wt% 1-hydroxy-cyclohexyl-phenyl-ketone was used as photoinitiator. The used intensity of UV light was in the range of $40~70 mW/\textrm{cm}^2$. The flexural strength of vinylester was not sensitive to the intensity of UV light. But the unsaturated polyester was very sensitive to the intensity of UV light. The flexural strength of vinylester was always superior to that of unsaturated polyester. The addition of the vinylester increased the flexural strength of blend system.

• Steel and Composite Structures
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• v.25 no.4
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• pp.403-413
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• 2017

The fabric braided braking hose that delivers the driver's braking force to brake cylinder undergoes the large deformation cyclic motion according to the steering and bump/rebound motions of vehicle. The cyclic large deformation of braking hose may give rise to two critical problems: the interference with other adjacent vehicle parts and the micro cracking stemming from the fatigue damage accumulation. Hence, both the hose deformation and the fatigue damage become the critical issue in the design of braking hose. In this context, this paper introduces a multi-objective optimization method for minimizing the both quantities. The total length of hose and the helix angles of fabric braided composite layers are chosen for the design variables, and the maximum hose deformation and the critical fatigue life cycle are defined by the individual single objective functions. The trade-off between two single objective functions is made by introducing the weighting factors. The proposed optimization method is validated and the improvement of initial hose design is examined through the benchmark simulation. Furthermore, the dependence of optimum solutions on the weighting factors is also investigated.

• Proceedings of the Korea Contents Association Conference
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• 2005.11a
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• pp.539-542
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• 2005

In the ubiquitous computing environment, service providers should able to deliver their services to various devices, such as PDA Smart Phone, Telematics devices. For this, W3C announced 'Composite Capabilities/Preference Profile (CC/PP) Standard' for delivery-context description. But at present, only a small number of mobile phone supports the CC/PP standard, most of contents servers do not support the CC/PP profiles. In this paper, a rule-based CC/PP profiling method in ubiquitous environment is developed. A rule-based profiles are generated by analyzing request headers which are received from various ubiquitous devices. Service providers can use these profiles to provide optimized services to the various devices which have different capabilities.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.9
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• pp.1687-1693
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• 2007

Advances in technologies of networking, chip integration, and embedded system have enabled sensor networks applicable to a wide range of areas. Sharing some common characteristics, sensor networks are thus diversified in features depending on their applications. An intelligent and digital home can be one area to establish a particular feature of sensor network. This paper proposes a composite sensor and control network, and discusses its applying to the next generation intelligent and digital home. Development results of the network and a test-bed as a virtual test environment are also presented. The proposed network can not only be efficiently applying to achieve new home intelligences but also provide a sound solution to maintenance and operations of home network or devices.