• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.880-883
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• 2000

Temperature generated in the workpiece during grinding process can cause thermal damages. Therefore it is important to understand surface temperature generated during grinding process. In this paper, a theoretical and experimental investigation were performed for the grinding temperature. Grinding experiments were performed in machining center using vitrified bonded CBN cup-type wheel. The surface temperature was measured using thermocouple and calculated through a model of the partition of energy between wheel and workpiece. The residual stress and hardness of ground surface were measured. The experimental results indicate that the surface temperature was in good agreement with theoretical ones. Residual stress and hardness of ground surface were more affected by the change of table speed than the depth of cut.

• Journal of Hydrogen and New Energy
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• v.8 no.3
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• pp.111-119
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• 1997

In this study, feasibility of expansion of BFL equivalence ratio are examined with change of injection location of hydrogen gas in intake pipe, coolant temperature, spark timing and amount of residual gas. As the results, BFL equivalence ratio is increased when injection location has some distance from intake valve. And it is decreased in accordance with increasing of coolant temperature and advance of spark timing. The amount of residual gas has little effect on BFL equivalence ratio.

• Smart Structures and Systems
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• v.4 no.2
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• pp.137-152
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• 2008

The work presented in this paper includes material characterisation and an investigation of suitability in seismic dampers for two commercially available NiTi-alloys, along with a numerical analysis of a new damper system employing composite NiTi-wires. Numerical simulations of the new damper system are conducted, using Brinson's one-dimensional constitutive model for shape memory alloys, with emphasis on the system's energy dissipation capabilities. The two alloys tested showed some unwanted residual strain at temperatures higher than $A_f$, possibly due to stress concentrations near inclusions in the material. These findings show that the alloys are not ideal, but may be employed in a seismic damper if precautions are made. The numerical investigations indicate that using composite NiTi-wires in a seismic damper enhances the energy dissipation capabilities for a wider working temperature range.

• Structural Engineering and Mechanics
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• v.60 no.5
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• pp.829-849
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• 2016

In this paper, experimental as well as numerical analysis of Glass Fiber Reinforced Polymer (GFRP) laminated composite has been presented under ballistic impact with varying projectile nose shapes (conical, ogival and spherical) and incidence velocities. The experimental impact tests on GFRP composite plate reinforced with woven glass fiber ($0^{\circ}/90^{\circ}$)s are performed by using pneumatic gun. A three dimensional finite element model is developed in AUTODYN hydro code to validate the experimental results and to study the ballistic perforation characteristic of the target with different parametric variations. The influence of projectile nose shapes, plate thickness and incidence velocity on the variation of residual velocity, ballistic limit, contact force-time histories, energy absorption, damage pattern and damage area in the composite target have been studied. The material characterization of GFRP composite is carried out as required for the progressive damage analysis of composite. The numerical results from the present FE model in terms of residual velocity, absorbed energy, damage pattern and damage area are having close agreement with the results from the experimental impact tests.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.9
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• pp.2105-2113
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• 1995

The compressive tests under impact conditions were performed to establish a design guide for impact damage tolerance. The composition of layup was selected for the real cases of composite aircraft structure. The energy level of visible of visible damage threshold was determined as 7 Joules. It was found that the normalized bending stiffnesses in the direction of closely fixed boundary affected the area of damage. Graphite/epoxy used in the tests exhibited 60% reduction in compression strength at the energy level of visible damage threshold. Wet-conditioned specimens represented 9% reduction in residual compressive strength in comparison with room temperature ambient specimens. In this study, a design factor of 2.1 was proposed for the low velocity impact damage.

• Journal of Hydrogen and New Energy
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• v.22 no.6
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• pp.794-799
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• 2011

In order to reduce the oil consumption for a 2 stroke free piston hydrogen fueled engine, the behaviors of residual lubricant oil of the cylinder wall surface were visualized and oil mass emitted into exhaust port was measured by using research engine with cross-head and eccentric crankshaft. As the results, it was shown that characteristics of residual lubricant oil such as oil thickness and distribution were remarkably different from a conventional 4 stroke engine. It was also analyzed that these tendencies relied on the configuration and installed position of the exhaust port, piston pin boss and so on.

• Journal of the Korean institute of surface engineering
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• v.36 no.1
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• pp.1-8
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• 2003

In general, the microstructure in thin films was known to evolve in similar manner according to the energy striking the condensing film at similar homologous temperature, Th for the materials of the same crystal structure. The fundamental factors affecting particle energy are a function of processing parameters such as working pressure, bias voltage, target/sputtering gas mass ratio, cathode shape, and substrate orientation. In this study, Al, Cu, Pt films of the same crystal structure of face centered cubic (FCC) have been prepared under various processing parameters. The influence of processing variables on the microstructures and residual stress states in the films has been studied.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2002.05a
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• pp.39-39
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• 2002

In order to improve wear and fatigue resistance of the structural materials, especially cold work roller for 304 stainless steel, an eco-super-finishing and surface hardening treatment using ultrasonic vibration energy was developed and applied to the SKD-ll roller. The eco-super-finishing machine was designed and fabricated by DesignMecha Co, by its own technology. It was observed that the surface roughness, hardness and residual stress were changed from $Ra{\;}={\;}O.25\mu\textrm{m}$, Hv=710 and ${\sigma}$={\;}+400{\;}MPa{\;}to{\;}Ra{\;}={\;}0.165\mu\textrm{m}$, Hv = 1200 and ${\sigma}=-610$ MPa after 20 KHz micro-cold forging, which means almost equal to the 300 % improvement of life-time.

• Journal of Institute of Control, Robotics and Systems
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• v.15 no.12
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• pp.1184-1191
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• 2009

Energy harvesting from environment can make the energy constrained systems such as sensor networks to sustain their lifetimes. However, environmental energy is highly variable with time, location, and other factors. Unlike the existing solutions, we solved this problem by allowing the sensor nodes with mobilizer to move in search of energy and recharge from remote energy station. In this paper we present and analyze a new harvesting aware framework for mobile sensor networks with remote energy station. The framework consists of energy model, motion control system and data transfer protocol. Among them, the objective of our data transfer protocol is to route a data packet geographically towards the target region and at the same time balance the residual energy and the link connectivity on nodes with energy harvesting. Our results along with simulation can be used for further studies and provide certain guideline for realistic development of such systems.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.1
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• pp.187-192
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• 2017

In dense deployments of sensor nodes in Wireless Sensor Networks, the MAC protocol has challenges to solve problems such as reducing delivery delay and reducing energy consumption. To solve these problems lots of protocols are suggested. This paper proposed a sensor nodes' residual energy based wake-up control mechanism, in which each node decides whether it wakes up or stays in sleep mode to save energy consumption by reducing unnecessary idle listening. The main idea of the wake-up control mechanism is to save node's energy consumption. The proposed wake-up control mechanism is based on the RI-MAC protocol, which is one of the receiver-initiated MAC protocols. A receiver node in the proposed mechanism periodically wakes up and broadcasts a beacon signal based on the energy status of the node. A receiver node also adjusts wake-up period based on the traffics. Results have shown that the proposed MAC protocol outperformed RI-MAC protocol in the terms of energy consumption.