• Proceedings of the Korean Information Science Society Conference
• /
• 2012.06d
• /
• pp.369-371
• /
• 2012

Wireless sensor networks have taken immense interest in healthcare systems in recent years. One example of it is in an in vivo sensor that is deployed in critical and sensitive healthcare applications like artificial retina, cardiac pacemaker, drug delivery, blood pressure, internal heat calculation, glucosemonitoring etc. In vivo sensor nodes exhibit temperature that may be very dangerous for human tissues. However, existing in vivo thermal aware routing approaches suffer from hotspot creation, delay, and computational complexity. These limitations motivate us toward an in vivo virtual backbone, a small subset of nodes, connected to all other nodes and involved in routing of all nodes, -based solution. A virtual backbone is lightweight and its fault-tolerant version allows in vivo sensor nodes to disconnect hotspot paths and to use alternative paths. We have formulated the problem as m-connected k-dominating set problem with minimum temperature cost in in vivo sensor network. This is a combinatorial optimization problem and we have been motivated to use evolutionary approach to solve the problem.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.10 no.2
• /
• pp.227-237
• /
• 1998

A numerical simulation has been carried out for the automotive air conditioning system. The purpose of this simulation is to present the methods for simulating car air conditioning components, systems and cool-down performance by computerized mathematical model and to analyze the performance of A/C system. In analyzing the heat exchanger(evaporator and condenser), the finite volume model which has a merit in predicting the temperature field in detail because it can consider partial variation of thermal property and heat transfer coefficient is used. In analyzing the compressor, the polytropic approach which regards the actual compression process as a reversible polytropic process is employed. In analyzing vehicle passenger compartment, the thermal network is employed to simulate the car cool down process. This A/C system program can be used for analyzing a component performance when a component is alternated or designed and for analyzing the engine cooling system when A/C system is operated.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2006.05a
• /
• pp.70-73
• /
• 2006

In the present study, the flow-softening behavior occurring during high temperature deformation of AZ31 Mg alloy was investigated. Flow softening of AZ31 Mg alloy was attributed to (1) thermal softening by deformation heating and (2) microstructural softening by dynamic recrystallization. Artificial neural networks method was used to derive the accurate amounts of thermal softening by deformation heating. A series of mechanical tests (High temperature compression and load relaxation tests) was conducted at various temperatures ($250^{\circ}C{\sim}500^{\circ}C$) and strain rates ($10^{-4}/s{\sim}100/s$) to formulate the recrystallization kinetics and grain size relation. The effect of DRX kinetics on microstructure evolution (fraction of recrystallization) was evaluated by the unified SRX/DRX (static recrystallization/dynamic recrystallization) approaches

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1993.05a
• /
• pp.59-62
• /
• 1993

This Paper studies on thermal oxidation of alumina filled epoxy network polymer used in Extra-High voltage application. The thermal oxidation of surface has investigated by yellow index variation and various electrical properties which are surface resistivity, tracking resistance and AC dielectric strength are estimated by yellow index.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.8 no.6
• /
• pp.553-563
• /
• 1984

Heat transfer modeling was performed in order to study a natural solar heating system. Simulation of the system was obtained by writing instantaneous energy balance equations for the various components. A thermal-network provided the means for systematically accounting for each of the energy balances. The resulting balances were solved using time varying inputs, such as solar gain and ambient temperature, and the initial temperatures of the components. Parametric heat transfer calculations were performed. Results are discussed which illustrate several effects, including variation of thermal capacity of the storage wall, installation of night insulation, installation of a thermally controlled fan between the sunspace and room, and variation of the width of the sunspace.

• Journal of Mechanical Science and Technology
• /
• v.18 no.2
• /
• pp.230-239
• /
• 2004

A compact model approach of a network of spring elements for elastic loading is presented for the thermal deformation analysis of BGA package assembly. High-sensitivity moire interferometry is applied to evaluate and calibrated the model quantitatively. Two ball grid array (BGA) package assemblies are employed for moire experiments. For a package assembly with a small global bending, the spring model can predict the boundary conditions of the critical solder ball excellently well. For a package assembly with a large global bending, however, the relative displacements determined by spring model agree well with that by experiment after accounting for the rigid-body rotation. The shear strain results of the FEM with the input from the calibrated compact spring model agree reasonably well with the experimental data. The results imply that the combined approach of the compact spring model and the local FE analysis is an effective way to predict strains and stresses and to determine solder damage of the critical solder ball.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1997.04a
• /
• pp.257-262
• /
• 1997

A compact measurement system is developed to measure in-process errors due to thermal deformation of a machine tool, this system is composed of a gauge, 5gap-sensors and a PC. The gauge is made of invar, which is a material that has a very low thermal expansion coefficient. A new neural network model is constructed to estimate thermally induced machine tool errors based on the measured data,the given data,that is a width of cut,a depth of cut, a feed rate, a spindel speed etc, and the calculated data. The detail of the model proposed is described in the paper together with the experimental methodologies using a proposed compact measurement system to examine the validity of the proposed approach.

• Structural Monitoring and Maintenance
• /
• v.3 no.2
• /
• pp.129-144
• /
• 2016

We present a methodology to validate with monitoring data finite element models of existing concrete dams: numerical analyses are performed to assess the structural response under the effects of seasonal loading conditions, represented by hydrostatic pressure on the upstream-downstream dam surfaces and thermal variations as recorded by a thermometers network. We show that the stiffness effect of the rock foundation and the surface degradation of concrete due to aging are crucial aspects to be accounted for a correct interpretation of the real behavior. This work summarizes some general procedures developed by this research group at Politecnico di Milano on traditional static monitoring systems and two significant case studies: a buttress gravity and an arch-gravity dam.

• Proceedings of the KIEE Conference
• /
• 2000.11b
• /
• pp.265-267
• /
• 2000

The RMU is a power apparatus which is used in loop network distribution system. This paper considers the development of the hybrid interrupter in RMU which adopts both rotating arc and thermal expansion technology. Because of the operating principle of this device, it has some merit, compared with other interrupter. In this research, the geometric construction of the interrupting techniques are given and experimental results of hybrid interrupter which is developed by new technology is introduced.

• Proceedings of the SAREK Conference
• /
• 2006.06a
• /
• pp.938-943
• /
• 2006

The primary purpose of a computer room of data center and associated infrastructure is to support the operation of critical IT equipment. Traditionally, most owners of large critical data centers have been more than willing to accept a reasonable amount of computer room worker discomfort if necessary to support critical IT systems. All electrical equipment produces heat, which must be removed to prevent the equipment temperature from rising to an unacceptable level. Most information technology equipment and other equipment found in a data center or network room is air-cooled. Sizing a cooling system requires an understanding of the amount of heat produced by the equipment contained in the enclosed space, along with the heat produced by the other heat sources typically encountered.