• Journal of Advanced Marine Engineering and Technology
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• v.38 no.9
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• pp.1045-1050
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• 2014

$N_2O$(Nitrous Oxide) is known as the third major GHG(Green House Gas) following $CO_2$(Carbon Oxide) and $CH_4$(Methane). The GWP(Global Warming Potential) factor of $N_2O$ is 310 times as large as that of $CO_2$ because $N_2O$ in the atmosphere is very stable, and it becomes a source of secondary contamination after photo-degradation in the stratosphere. Investigation on the cause of the $N_2O$ formation have been continuously reported by several researchers on power sources with continuous combustion form, such as a boiler. However, in the diesel engine, research on $N_2O$ generation which has effected from fuel components has not been conducted. Therefore, in this research, author has investigated about $N_2O$ emission rates which was changed by nitrogen and sulfur concentration in fuel on the diesel engine. The test engine was a 4-stroke direct injection diesel engine with maximum output of 12 kW at 2600rpm, and operating condition of that was set up at a 75% load. Nitrogen and sulfur concentrations in fuel were raised by using six additives : nitrogen additives were Pyridine, Indole, Quinoline, Pyrrol and Propionitrile and sulfur additive was Di-tert-butyl-disulfide. In conclusion, diesel fuels containing nitrogen elements less than 0.5% did not affect $N_2O$ emissions in the all concentrations and kinds of the additive agent in the fuel. However, increasing of the sulfur additive in fuel increased $N_2O$ emission in exhaust gas.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.7
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• pp.929-933
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• 2010

Four-point bending tests were performed to investigate the interfacial adhesion of Cu-Cu bonding fabricated by thermo-compression process for three dimensional packaging. A pair of Cu-coated Si wafers was bonded under a pressure of 15 kN at $350^{\circ}C$ for 1 h, followed by post annealing at $350^{\circ}C$ for 1 h. The bonded wafers were diced into $30\;mm\;{\times}\;3\;mm$ pieces for the test. Each specimen had a $400-{\mu}m$-deep notch along the center. An optical inspection module was installed in the testing apparatus to observe crack initiation at the notch and crack propagation over the weak interface. The tests were performed under a fixed loading speed, and the corresponding load was measured. The measured interfacial adhesion energy of the Cu-to-Cu bonding was $9.75\;J/m^2$, and the delaminated interfaces were analyzed after the test. The surface analysis shows that the delamination occurred in the interface between $SiO_2$ and Ti.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.2
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• pp.171-179
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• 2013

The thermodynamic characteristics of a combined cycle applied with a topping cycle such as a trilateral cycle at relatively high temperatures and a bottoming cycle such as an organic Rankine cycle at relatively low temperatures have been theoretically investigated. This is an electric generation system used to recover the waste heat of the exhaust gas from a diesel engine used for the propulsion of a large ship. As a result, when the boundary temperature between the topping and the bottoming cycles increased, the system efficiencies of energy and exergy were simultaneously maximized because the total exergy destruction rate (${\sum}\dot{E}_d$) and exergy loss ($\dot{E}_{out2}$) decreased, respectively. In the case of a marine diesel engine, the waste heat recovery electric generation system can be utilized for additional propulsion power, and the propulsion efficiency was found to be improved by an average of 9.17 % according to the engine load variation, as compared to the case with only the base engine. In this case, the specific fuel consumption and specific $CO_2$ emission of the diesel engine were reduced by an average of 8.4% and 8.37%, respectively.

• Journal of the Korean Society for Nondestructive Testing
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• v.33 no.5
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• pp.443-451
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• 2013

Acoustic emission(AE) has emerged as a powerful nondestructive tool to detect any further growth or expansion of preexisting defects or to characterize failure mechanisms. Recently, this kind of technique, that is an in-situ monitoring of inside damages of materials or structures, becomes increasingly popular for monitoring the integrity of large structures like a huge wind turbine blade. In this study, the activities of AE signals generated from external artificial sources was evaluated and located by new developed signal mapping source location method and this test is conducted by 750 kW full-scale blade. And a new source location method was applied to assess the damage in the wind turbine blade during step-by-step static load test. In this static loading test, we have used a full scale blade of 100 kW in capacity. The results show that the acoustic emission activities give a good agreement with the stress distribution and damage location in the blade. Finally, the applicability of the new source location method was confirmed by comparison of the result of source location and experimental damage location.

• Korean Journal of Environmental Agriculture
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• v.26 no.1
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• pp.1-6
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• 2007

In view of energy supply, biogas can be seen as alternative fuel by substituting considerable amount of fossil fuel and may be utilized for heat and power production or for transport fuel production ($CH_4-enriched$ biogas). The aim of this research is to analyse the emission of $NO_x$ and CO from biogas fired combustion engine for electric power production. The result indicate a significant effect of biogas composition ($CH_4-CO_2$ ratio) and biogas flow rate on the air pollutants emission. The emission factors from this study were compared with those of U.S. EPA. Low $CH_4-CO_2$ ratio condition typically shows the lower $NO_x$ and CO emission than higher $CH_4-CO_2$ ratio condition. At normal $CH_4-CO_2$ ratio (7:3) emission factors of $NO_x$ and CO were 1.29 and 30.43 g/MMBtu, respectively. At low $CH_4-CO_2$, ratio (6:4) emission factors of $NO_x$ and CO were 0.646 and 60.86 g/MMBtu, respectively, It should be emphasized that the actual emission may vary considerably from these results due to operating conditions including torque load and engine speed.

• International Journal of Highway Engineering
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• v.3 no.4 s.10
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• pp.127-136
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• 2001

To increase the structural integrity of concrete box culvert good compaction by the dynamic compaction roller with bi9 capacity is as effective as good backfill materials. It is needed for effective compaction that a compaction roller closes to concrete structure with high frequency. However structural distress of the culvert could be occur due to the excessive earth pressure by great dynamic compaction load. To investigate the characteristics of Induced stress by compaction, a box culvert was constructed with changing cushion materials and compaction methods. Two types of cushion material such as tire rubber chip and EPS(Expanded Polystyrene) were used as cushion panels and they are set on the culverts before backfill construction. Laboratory test result of cushion material says that the value of dynamic elastic modulus of rubber is lesser than that of EPS. On the other hand, material damping of rubber material is greater than that of EPS. In most case, dynamic compaction rollers with 10.5 ton weights were used and vibration frequency was applied 30Hz for the great compaction energy. This paper presents the main results on the characteristics of dynamic earth pressures during compaction. The amounts of induced dynamic pressures$(\Delta\sigma\;h)$ by compaction are affected with construction condition such as compaction frequency, depth of pressure cell, distance between roller and the wall of culvert and roller direction. Based on the measured values dynamic lateral pressure on the culverts, it could be said that orthogonal direction of roller to the length of culvert is more effective to compaction efficiency than parallel direction.

• Journal of the Korea Concrete Institute
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• v.27 no.6
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• pp.615-623
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• 2015

The previous strut-and-tie models (STMs) to evaluate the shear strength of squat shear walls with aspect ratio less than 2.0 do not consider the axial load transfer of concrete strut and individual shear transfer contribution of horizontal and vertical shear reinforcing bars in the web. To overcome the limitation of the existing models, a simple STM was established based on the crack band theory of concrete fracture mechanics. The equivalent effective width of concrete strut having a stress relief strip was determined from the neutral axis depth and effective factor of concrete strength. The shear transfer mechanism of shear reinforcement at the extended crack band zone was calculated from an internally statically indeterminate truss system. The shear transfer capacity of concrete strut and shear reinforcement was then driven using the energy equilibrium in the stress relief strip and crack band zone. The shear strength predictions of squat shear walls evaluated from the current models are in better agreement with 150 test results than those determined from STMs proposed by Siao and Hwang et al. Furthermore, the proposed STM gives consistent agreement with the observed trend of the shear strength of shear walls against different parameters.

• Journal of the Korea Concrete Institute
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• v.24 no.5
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• pp.543-551
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• 2012

Road pavements in Korea generally show shorter service life than the predicted one. There are many reasons for this phenomenon including increased traffic load and other attacks from exposure conditions. In order to extend a service life and upgrade the pavement, a new multi-functional composite pavement system is being developed in Korea. This study is to investigate the performances of fiber-reinforced lean concrete for pavement base. This study considered mineral admixtures of fly ash and reject ash. The reject ash is defined as ash that does not meet the specifications for fly ash so that it cannot be used as a supplemental material for cement replacement. Due to the inherent property of lean concrete, compaction during the fabrication of specimens is a key factor. Therefore, this study suggests an appropriate compaction method. From the test results, the compressive strengths of the concrete satisfied the required limit of 5 MPa at 7 days. When a compaction roller was used to mimic actual field conditions, the strength development seemed to be influenced by the compaction energy rather than hydration of cement itself.

• Journal of the Korean Operations Research and Management Science Society
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• v.17 no.1
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• pp.117-117
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• 1992

Pubilc utility industries including the electric utility industry are facing a new stream of privatization com-petition with the private sector and deregulation. The necewssity to solve now and in the future power supply and demand problems has been increasing through the sophisticated generation expansion plan(GEP) approach con-sidering not only KEPCo's supply-side resources but also outside resources such as non-utility generation(NUG) demand-side management (DSM). Under the environmental situation in the current electric utility industry a new approach is needed to acquire multiple resources competitively. This study presents the development of a modified electric generation expansion analysis system(EGEAS) model with avoided cost based on the existing EGEAS model which is a dynamic program to develope an optimal generation expansion plan for the electric utility. We are trying to find optimal GEP in Korea's case using our modified model and observe the difference for the level of reliabilities such as the reserve margin(RM) loss of load probability(LOLP) and expected unserved energy percent(EUEP) between the existing EGEAS model and our model. In addition we are trying to calculate avoided cost for NUG resources which is a criterion to evaluate herem and test possibility of connection calculation of avoided cost with GEP implementation using our modified model. The results of our case study are as follows. First we were able to find that the generation expansion plan and reliability measures were largely influenced by capacity size and loading status of NUG resources, Second we were able to find that avoided cost which are criteria to evaluate NUG resources could be calculated by using our modified EGEAS model with avoided cost. We also note that avoided costs were calculated by our model in connection with generation expansion plans.

• Progress in Medical Physics
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• v.26 no.1
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• pp.18-27
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• 2015

Since a Compton camera has high detection sensitivity due to electronic collimation and a good energy resolution, it is a potential imaging system for nuclear medicine. In this study, we investigated the feasibility of a Compton camera for multi-tracer imaging and proposed a rotating Compton camera to satisfy Orlov's condition for 3D imaging. Two software phantoms of 140 and 511 keV radiation sources were used for Monte-Carlo simulation and then the simulation data were reconstructed by listmode ordered subset expectation maximization to evaluate the capability of multi-tracer imaging in a Compton camera. And the Compton camera rotating around the object was proposed and tested with different rotation angle steps for improving the limited coverage of the fixed conventional Compton camera over the field-of-view in terms of histogram of angles in spherical coordinates. The simulation data showed the separate 140 and 511 keV images from simultaneous multi-tracer detection in both 2D and 3D imaging and the number of valid projection lines on the conical surfaces was inversely proportional to the decrease of rotation angle. Considering computation load and proper number of projection lines on the conical surface, the rotation angle of 30 degree was sufficient for 3D imaging of the Compton camera in terms of 26 min of computation time and 5 million of detected event number and the increased detection time can be solved with multiple Compton camera system. The Compton camera proposed in this study can be effective system for multi-tracer imaging and is a potential system for development of various disease diagnosis and therapy approaches.