• Journal of the Korean Society of Propulsion Engineers
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• v.22 no.2
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• pp.74-86
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• 2018

This paper presents the one-dimensional model of a hydrogen generator, where the alkali solution was supplied from the top to the dry aluminum powders. Hydrogen was produced as the solution moved downward and reacted with aluminum. The species conservation equations were considered for the hydrogen gas and alkali solution, while the energy conservation equation was applied to the gas-liquid-solid mixture as a single medium. The gas rising velocity and liquid penetration velocity were also included in the theoretical approach. The developed code was validated with the experimental data of the hydrogen production amount and collector pressure. Additionally, the model successfully predicted the various reactor properties, such as the concentrations, volume fractions, and temperatures, and is expected to help significantly in the design of a novel hydrogen generator.

• Journal of the Korea Institute of Building Construction
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• v.23 no.4
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• pp.429-440
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• 2023

This research investigates the deployment of waterproofing technologies in construction, with a specific focus on augmenting worker safety, work environment, and solve the difficulty of securing skilled workers. Implementing liquid waterproofing cement equipment resulted in a remarkable increase in adhesion performance by around 20%, coupled with a twofold acceleration in operational speed. The application of primer spraying apparatus led to a two-fold improvement in both penetration and adhesion performance, concurrently boosting the work speed by approximately the same factor. With urethane spraying equipment, the workload could be reduced to a third for the same layer thickness, adhesion performance enhanced by approximately 1.4 times, and workability improved by about 1.4 to 1.5 times. These findings suggest that such technological interventions can potentially enhance work efficiency, improve the quality of output, and mitigate safety accidents that are commonplace in manual operations. Furthermore, these advancements present promising solutions to the ongoing challenges of sourcing highly-competent workers in the industry.

• Geotechnical Engineering
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• v.10 no.4
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• pp.153-166
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• 1994

In this paper, the experimental study on the behavior of the dredged clay was performed by introducing the consolidation teat method using continuous loading. Also a new testing method was examined and the strength of the dredged clay using thin plate was evaluated. The rheological characteristics of the dredged clay are described by the gingham model. The static and rheologic thin plate penetration test is proposed for the shear strength testing method. It is found that both of testing methods are reasonable and have a practicability. Especially, the strength increases for a water content which is less than two times of liquid limit in case of silty soil and clayey soil. About plasticity index, the strength increases rapidly for a value less than 10 for silt, 5 for clay which a water content is normalized by plasticity index of silty soil rather than clayey soil.

• Journal of ILASS-Korea
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• v.20 no.2
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• pp.88-94
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• 2015

Recently, exhaust gas regulation has been gradually strengthened due to depletion of fossil fuels and environmental problem like a global warming. Due to this global problem, the demand for eco-friendly vehicle development is rapidly increasing. A clean diesel vehicle is considered as a realistic alternative. The common-rail fuel injection system, which is the key technology of the clean diesel vehicle, has adopted injection strategies such as high pressure injection, multiple injection for better atomization of the fuel. In addition, the emission regulations in the future is expected to be more stringent, which a conventional engine is difficult to deal with. One of the way for actively proceeding is the study of alternative fuels. Among them, the bio-diesel has been attracted as an alternative of diesel. So, in this study, spray characteristics of bio-diesel was analyzed in the common-rail fuel injection system with three injectors driven by different operating mechanism.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.53 no.9
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• pp.507-512
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• 2004

HTS (High Temperature Superconducting) Transformer has the several useful characteristics in the viewpoints of technical and economical. Especially, an HTS transformer replaces the copper wire coils in a conventional transformer with lower loss HTS wire. In addition, inexpensive, environmentally benign liquid nitrogen replaces the conventional oil as the electrical insulation (dielectric) and provides the necessary cooling for the HTS transformer Therefore, the Life-cycle cost of an HTS transformer is much more attractive than conventional because it is more energy efficient, lighter in weight, smaller in size, and environmentally compliant. HTS transformer can be the best way to replace with conventional transformer in the future. In these days, companies world-wide have conducted researches on HTS transformer. A development project for a 154kV HTS transformer is proceeding at a research center and university in Korea. In this paper, we investigate the expected price of HTS transformer to have a merit in viewpoint of economic aspect. First, life-cycle cost of conventional transformer is calculated and based on this, the expected price of HTS transformer is evaluated. which HTS transformer is competitive against conventional transformer.

• Journal of ILASS-Korea
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• v.4 no.1
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• pp.45-54
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• 1999

The spray characteristics of a direct injection multi-hole diesel nozzle having the 2-spring nozzle holder were investigated by using the image processing system and a PDPA(phase Bowler particle analyzer) system. The spray tip penetration, the spray angle, and the droplet diameter and velocity with the variation of the pump speed, injection quantity were measured. From, the experiments, we know that there are small droplets which are not to be detected with spray image around the leading edge of the spray. In order to represent the mean characteristics of the intermittent spray very well, it is very important to set the time windows accurately. From the measurements along the axis of the spray, close to the nozzle, the initially injected droplets are overtaken by droplets that follow them. And also there are the maximum axial mean velocity and SMD at the following part of the leading edge of the spray.

• Transactions of the Korean hydrogen and new energy society
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• v.25 no.6
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• pp.643-647
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• 2014

Two types of fuel supply method ar used in CNG vehicles. One is premixed ignition and the other is gas-jet ignition. In premixed ignition, the fuel is introduced with intake air so that homogeneous air-fuel mixture may form. The ignitability of this method depends on the global equivalence ratio. In gas-jet ignition, CNG is introduced directly into the engine combustion chamber. The overall mixture is stratified by retarded fuel injection. In this study, a visualization technique was employed to obtain fundamental properties regarding overall mixture formation of direct injected CNG fuel inside a constant volume chamber. Jet angles, penetrations and projected jet area with respect to ambient pressure are investigated. The penetration decreases apparently and the time reaching the CVC wall was delayed as the chamber pressure increases. This is caused by the higher inertia of the fluid elements that the injected fluid must accelerate and push aside. It is same to liquid fuel such as diesel and gasoline, but this phenomenon is far more prominent for the gaseous fuel.

• Journal of Welding and Joining
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• v.22 no.5
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• pp.65-72
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• 2004

The tendency and degree of hot cracking of high strength 5083, 6N01 and 7N01 Al alloy welds by using DCSP-GTAW through modified Varestraint test and autogenous butt welding were investigated. In hot cracking test, 6N01 alloy showed the highest susceptibility to hot cracking in the weld metal and HAZ. Cracking susceptibilities generally increased with increase of solidification temperature range of the base metal and bead penetration-to-width ratio of the weld metal. The cracks in welds of the alloys vertically formed to solid-liquid interface and propagated along with columnar grain boundaries. The fracture facets of cracks showed the typical morphology of solidification crack observed as dendritic structures. Especially, in 6N01 alloy, liquation cracks which were due to elements of Si, Fe and Mg also observed in HAZ near fusion boundary. In butt welding of different Al alloys, the bead crack was mainly occurred in the welds of 6N01, 7N01 and other Al alloys together with 6N01 or 7N01. In the butt welds of 7N01, it was found that the component of Cu had an effect on the higher susceptibility to the hot cracking.

• Magazine of the Korean Society of Agricultural Engineers
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• v.31 no.2
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• pp.43-53
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• 1989

In this research programs, a series test was conducted to show the effects of freeze/thaw process on the various soil properties. The tests were carried out taken from the west sea shore of Korean peninsular and the west sea shore of Scotland, and their results are as follows; 1. There was a positive total heave in a freezing run, although water may he expelled for the sample initially. The water flow must he reverse' from expulsion to intake. 2. The confining pressure had an overriding influence on the heave and frost penetration, a sudden change of the axial strain at failure with strain rate was observed occuring at a strain rate between 10-5 and 10-6, and the initial friction angle of frozen clay was appeared zero. 3. There was shown a significant decrease in liquid limit of soil which was subjected to freeze/thaw process for the initial value of about 20% because of soil particles aggregation. 4. The cyclic freeze/thaw caused a sinificant reduction in shear strength and its thixotropic regain. The frozen/thawed soil exibited negative strength regain, particularly at high freeze/thaw cycles. 5. The freezing temperature greatly influenced on the failure strength of soils and this. Trend was more pronounced the lower the freezing temperature and shown the ductile failure with indistinct peaks.

• Journal of Sensor Science and Technology
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• v.13 no.5
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• pp.378-382
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• 2004

A micromachined fluidic structure for the introduction of liquid samples into a chip-based sensor array composed of individually addressable polymeric microbeads has been developed. The structure consists of a separately attached cover glass, a single silicon chip having micromachined channels and microbead storage cavities, and a glass carver. In our sensor array, transduction occurs via colorimetric and fluorescence changes to receptors and indicator molecules that are covalently attached to termination sites on the polymeric microbeads. Data streams are acquired for each of the individual microbeads using a CCD. One of the key parts of the structure is a passive fluid introduction system driven only by capillary force. The velocity of penetration of a horizontal capillary for the device having a rectangular cross section has been derived, and it is quite similar to the Washburn Equation calculated for a pipe with a circular cross section having uniform radius. The test results show that this system is useful in a ${\mu}$-TAS and biomedical applications.