• Journal of the Institute of Electronics and Information Engineers
• /
• v.49 no.9
• /
• pp.225-234
• /
• 2012

In Wireless Sensor Networks (WSNs) where deployed sensors are not stationary, the most important demand of is to design a cost effective and reliable network. This paper proposes an energy aware network construction and routing scheme, which is based on the hierarchical approach to distribute the task in some sensors in order to prolong the network lifetime. It aims to make even the energy consumption on constitute nodes. With the node hierarchy, the sink initiates the construction by electing gateway nodes in the network and the elected gateway nodes participate to form logical clusters by electing a cluster head in each cluster. Then, the cluster heads aggregate data from the sensing sensors and transmit the data to the sink through the gateway. Our simulation result illustrates that the proposed scheme provides a basement to reduce the source of energy dissipation in network construction, and as well as in data routing.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.11 no.2
• /
• pp.253-261
• /
• 1987

Thermoacoustic oscillation of an air column induced by heated wires is investigated analytically and experimentally. Acoustic power generation from a single heater wire is estimated based on the result of heat transfer analysis and expressed in terms of the efficiency factor indicating the conversion efficiency from heat to acoustic energy. It is shown that the efficiency factor becomes maximum when the wire radius is the order of the coustic boundary layer thickness and the flow velocity is close to the thermal diffusion velocity. Onset condition of the column oscillation is obtained by equating the acoustic power generation at the heater to the power loss due to thermoviscous dissipation at the tube wall and the convection and radiationloss at the open ends of the tube. In estimating the acoustic power generation, the heater is treated as a stretched single wire by correcting the flow velocity to take into account the interactions between adjacent heater wires. Experiment is performed by using a spiral heater of 1mm diameter in an air column of 37mm diameter. The heat input to drive the oscillation is measured and compared with the theoretical prediction. A good agreement is found between the theory and experiment, which is regarded as a substantial verification of the present analysis.

• Journal of The Korean Astronomical Society
• /
• v.43 no.2
• /
• pp.25-39
• /
• 2010

We perform kinetic simulations of diffusive shock acceleration (DSA) in Type Ia supernova remnants (SNRs) expanding into a uniform interstellar medium (ISM). Bohm-like diffusion due to self-excited $Alfv\acute{e}n$ waves is assumed, and simple models for $Alfv\acute{e}nic$ drift and dissipation are adopted. Phenomenological models for thermal leakage injection are considered as well. We find that the preshock gas temperature is the primary parameter that governs the cosmic ray (CR) acceleration efficiency and energy spectrum, while the CR injection rate is a secondary parameter. For SNRs in the warm ISM of $T_0\lesssim10^5K$, if the injection fraction is $\xi\gtrsim10^{-4}K$, the DSA is efficient enough to convert more than 20% of the SN explosion energy into CRs and the accelerated CR spectrum exhibits a concave curvature flattening to $E^{-1.6}$, which is characteristic of CR modified shocks. Such a flat source spectrum near the knee energy, however, may not be reconciled with the CR spectrum observed at Earth. On the other hand, SNRs in the hot ISM of$T_{0}\approx10^{6}K$ with a small injection fraction, $\xi$<$10^{-4}$, are inefficient accelerators with less than 10% of the explosion energy getting converted to CRs. Also the shock structure is almost test-particle like and the ensuing CR spectrum can be steeper than $E^{-2}$. With amplified magnetic field strength of order of $30{\mu}G$ $Alfv\acute{e}n$ waves generated by the streaming instability may drift upstream fast enough to make the modified test-particle power-law as steep as $E^{-2.3}$, which is more consistent with the observed CR spectrum.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.7 no.3
• /
• pp.17-22
• /
• 2003

This paper presents an experimental investigation of a reversible colloidal seismic damper, which is statically loaded, The porous matrix is composed from silica gel (labyrinth or central-cavity architecture), coated by organo-silicones substances, in order to achieve a hydrophobic surface. Water is considered as associated lyophobic liquid. Reversible colloidal damper static test rig and the measuring technique of the static hysteresis are described. Influence of the pare and particle diameters, particle architecture and length of the grafted molecule upon the reversible colloidal damper hysteresis is investigated, for distinctive types and mixtures of porous matrices, Variation of the reversible colloidal damper dissipated energy and efficiency with temperature, pressure, is illustrated.

• Proceedings of the IEEK Conference
• /
• 2004.06b
• /
• pp.549-552
• /
• 2004

The thesis describes the design of 12bit digital-to-analog converter (DAC) which shows the conversion rate of 500MHz and the power supply of 3.3V with 0.35${\mu}m$ CMOS 1-poly 4-metal process for advanced wireless transceiver of high speed and high resolution. The proposed DAC employes segmented structure which consists of 6bit MSB, 3bit mSB, 3bit LSB for area efficiency Also, using a optimized aspect ratio of process and new triple diagonal symmetric centroid sequence for high yield and high linearity. The proposed 12bit current mode DAC was employs new deglitch circuit for the decrement of the glitch energy. Simulation results show the conversion rate of 500MHz, and the power dissipation of 85mW at single 3.3V supply voltage. Both DNL and INL are found to be smaller than ${\pm}0.65LSB/{\pm}0.8LSB$.

• JSTS:Journal of Semiconductor Technology and Science
• /
• v.17 no.2
• /
• pp.302-317
• /
• 2017

This paper proposes a new full adder design based on pass-transistor logic that offers ultra-low power dissipation and superior variability together with low transistor count. The pass-transistor logic allows device count reduction through direct logic realization, and thus leads to reduction in the node capacitances as well as short-circuit currents due to the absence of supply rails. Optimum transistor sizing alleviates the adverse effects of process variations on performance metrics. The design is subjected to a comparative analysis against existing designs based on Monte Carlo simulations in a SPICE environment, using the 22-nm CMOS Predictive Technology Model (PTM). The proposed ULP adder offers 38% improvement in power in comparison to the best performing conventional designs. The trade-off in delay to achieve this power saving is estimated through the power-delay product (PDP), which is found to be competitive to conventional values. It also offers upto 79% improvement in variability in comparison to conventional designs, and provides suitable scalability in supply voltage to meet future demands of energy-efficiency in portable applications.

• JSTS:Journal of Semiconductor Technology and Science
• /
• v.15 no.1
• /
• pp.77-84
• /
• 2015

This paper presents the design of a low-power, low area 256-radix 16-bit crossbar switch employing a 2D Hyper-X network topology. The Hyper-X crossbar switch realizes the high radix of 256 by hierarchically combining a set of 4-radix sub-switches and applies three modifications to the basic Hyper-X topology in order to mitigate the adverse scaling of power consumption and propagation delay with the increasing radix. For instance, by restricting the directions in which signals can be routed, by restricting the ports to which signals can be connected, and by replacing the column-wise routes with diagonal routes, the fanout of each circuit node can be substantially reduced from 256 to 4~8. The proposed 256-radix, 16-bit crossbar switch is designed in a 65 nm CMOS and occupies the total area of $0.93{\times}1.25mm^2$. The simulated worst-case delay and power dissipation are 641 ps and 13.01 W when operating at a 1.2 V supply and 1 GHz frequency. In comparison with the state-of-the-art designs, the proposed crossbar switch design achieves the best energy-delay efficiency of $2.203cycle/ns{\cdot}fJ{\cdot}{\lambda}2$.

• Journal of Korea Technical Association of The Pulp and Paper Industry
• /
• v.30 no.2
• /
• pp.40-46
• /
• 1998

This study was aimed to investigate any improvement of dewatering and energy saving on the papermaking process when the various types of fillers were used, i.e., clay, talc and grounded calcium carbonate (GCC). Cationic polyelectrolyte and alum coagulants neutralized the surface charge of the filler particles and the filler particles were coagulated. The rates of dewatering and drying were investigated. The results indicated that clay tended to intense anion, while talc and GCC tended to anion trend nearly to neutrality. Clay and talc added with EPI-DMA, P-DADMAC and alum respectively as optimum levels showed a significant efficiency on the dewatering and the turbidity dissipation. However, the turbidity and dewatering rate of GCC decreased, when GCC was added with EPI-DMA and P-DADMAC respectively Drying rate of clay was increased when coagulant added. However drying rates of talc and GCC were not affected by coagulant, while the apprarent drying time of talc and GCC in the absence of any coagulant was shorter than the clay in the presence of a coagulant. The result confirmed that talc or GCC was more efficient than clay on the dewatering and drying, which is consistent with a general knowledge in the collodal science.

• Smart Structures and Systems
• /
• v.4 no.5
• /
• pp.685-696
• /
• 2008

This paper deals with the numerical model of a bracing-friction damper system and its deployment using the optimal slip load distribution for the seismic retrofitting of a damaged building. The Slotted Bolted Connection (SBC) type friction damper system was tested to investigate its energy dissipation characteristic. Test results coincided with the numerical ones using the conventional model of a bracing-friction damper system. The placement of this device was numerically explored to apply it to the assumed damaged-building and to evaluate its efficiency. It was found by distributing the slip load that minimizes the given performance indicies based on structural response. Numerical results for the damaged building retrofitted with this slip load distribution showed that the seismic design of the bracing-friction damper system under consideration is effective for the structural response reduction.

• Journal of Korea Foundry Society
• /
• v.38 no.3
• /
• pp.60-65
• /
• 2018

In the present study, the characteristics of Mg inverter cases for hybrid cars are investigated. Concerns over the use of lightweight materials to reduce energy use and to mitigate emission problems are inevitable in the twenty-first century. Magnesium is a promising material for the manufacturing of lightweight parts. Several cases for thermal cooling channels have been designed and simulated, and the effects of materials and coatings on the thermal cooling efficiency have been discussed. The effects of the coating thickness on heat extraction in an Mg inverter housing case using the PEO (plasma electrolyte oxidation) coating method were also discussed. In order to produce an inverter case by the diecasting process, the filling sequence and cooling behavior during the diecasting process were simulated. The optimized process conditions from the simulation result were then used in a trial diecasting experiment.