• Nuclear Engineering and Technology
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• v.38 no.4
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• pp.353-358
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• 2006

Alpha track analysis for the determination of the trace amount of alpha emitting nuclides in a very small particle was performed as an efficient and powerful technique during safeguard inspection. Metal particles with well-defined spherical shape, size and isotopic compositions as a reference material were used to correlate the number of tracks or track diameter with an isotopic composition eventually to identify the uranium enrichment in the environmental swipe samples. Slopes in the number of tracks versus the exposure time curve provide a simple insight into the uranium enrichment of an unknown particle. Low enriched uranium metal particles result in slopes still steeper than the depleted or natural uranium metal particles. In addition, a linear relationship between track diameter and particle size Is thought to be a useful first stage analytical tool as an efficient and convenient inspection guide. The significance of the simple linear model was also judged using the usual statistical tests.

• Proceedings of the KSR Conference
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• 2011.05a
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• pp.1214-1221
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• 2011

It is an well-known fact that dynamic properties should be considered in design and maintenance of civil structures undergoing dynamic force such as rail track. For designing of the rail tack structures, dynamic properties of track bed soil such as shear modulus (G) and damping coefficients(D) obtained in small to medium range of shear strain must be known. In general, small size sample of D=5 cm and H=10cm has been used mostly for test convenience. However, ratio of largest particle diameter of the soil to sample diameter is very important and affects to the values of dynamic soil properties in track bed. In this study, an RC/TS test apparatus was built and was run for testing a medium size soil sample that can handle with compacted soil sample up to 10 cm diameter and 20 cm height.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.375-381
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• 2011

The passage of railway vehicles generates mechanical vibrations and noises. This problem can be mitigated by the 'floating slab track' that isolating from infrastructures by installing vibration isolator in the concrete slab track. In the previous researches, adjacent floating slab tracks are connected by dowel bar system. It has been reported that many dowel bars with less diameter show better load transfer efficiency (LTE) compared to small number of dowel bars with larger diameter under the condition of the same dowel area. In this study, dowel system is further considered as a concrete anchorage system and the design strength of the dowel system was evaluated based on ACI code 318-08 Appendix D. The design strength of dowel system is then verified against failure load test of floating slab system.

• International Journal of Highway Engineering
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• v.20 no.1
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• pp.9-18
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• 2018

PURPOSES : In this research, the initiation and development of corrugation on a gravel road with certain wheel and boundary conditions were evaluated using a coupled discrete-element method (DEM) with multibody dynamics (MBD). METHODS : In this study, 665,534 particles with a 4-mm diameter were generated and compacted to build a circular roadbed track, with a depth and width of 42 mm and 50 mm, respectively. A single wheel with a 100-mm diameter, 40-mm width, and 0.157-kg mass was considered for the track. The single wheel was set to run slowly on the track with a speed of 2.5 rad/s so that the corrugation was gradually initiated and developed without losing contact between the wheel and the roadbed. Then, the shape of the track surface was monitored, and the movement of the particles in the roadbed was tracked at certain wheel-pass numbers to evaluate the overall corrugation initiation and development mechanism. RESULTS : Two types of corrugation, long wave-length and short wave-length, were observed in the circular track. It seems that the long wave-length corrugation was developed by the longitudinal movement of surface particles in the entire track, while the short wave-length corrugation was developed by shear deformation in a local section. Properties such as particle coefficients, track bulk density, and wheel mass, have significant effects on the initiation and development of long-wave corrugation. CONCLUSIONS : It was concluded that the coupled numerical method applied in this research could be effectively used to simulate the corrugation of a gravel road and to understand the mechanism that initiates and develops corrugation. To derive a comprehensive conclusion for the corrugation development under various conditions, the driver's acceleration and deceleration with various particle gradations and wheel-configuration models should be considered in the simulation.

• Journal of the Semiconductor & Display Technology
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• v.4 no.1 s.10
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• pp.35-41
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• 2005

An air levitation type wafer transfer system is composed of control and transfer track. Wafer transfer speed is mainly affected by air velocity of propulsion nozzle. In this study, the propulsion force coefficient was evaluated experimentally for the nozzle with 0.5mm, 0.8mm, and 1.0mm diameter. As a result, the propulsion force was largest in the smallest size of nozzle at same air velocity. The propulsion force coefficient of nozzle increases with reducing diameter of nozzle. This increment of propulsion force coefficient was enlarged remarkably at the 0.5mm diameter of nozzle.

• Proceedings of the KSR Conference
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• 2007.11a
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• pp.505-510
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• 2007

Concrete track will be constructed in Gyungbu High Speed Railway II(GHSR II) stage construction site from Daegu to Busan. Concrete track is supported by substructure consisting of the original ground and embankment and does not allow the settlement of track because of its structural type. The embankment is composed of rock and soil mixture and settlement is feasible. So management of settlement of embankment is key point in successful construction of the concrete track. Compaction management of mixed fill materials is important in minimizing the settlement of embankment. In this study, in order to assess the compaction characteristics of mixed fill materials, large laboratory compaction tests were conducted. Mixed fill materials were obtained from two construction sites in GHSR II construction site. Modeled mixed fill materials having different rock type, fine content, maximum particle diameter, and moisture contents were prepared. From the test results, compaction characteristics of mixed fill materials were analysed.

• Journal of Powder Materials
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• v.29 no.4
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• pp.314-319
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• 2022

The effect of the laser beam diameter on the microstructure and hardness of 17-4 PH stainless steel manufactured via the directed energy deposition process is investigated. The pore size and area fraction are much lower using a laser beam diameter of 1.0 mm compared with those observed using a laser beam diameter of 1.8 mm. Additionally, using a relatively larger beam diameter results in pores in the form of incomplete melting. Martensite and retained austenite are observed under both conditions. A smaller width of the weld track and overlapping area are observed in the sample fabricated with a 1.0 mm beam diameter. This difference appears to be mainly caused by the energy density based on the variation in the beam diameter. The sample prepared with a beam diameter of 1.0 mm had a higher hardness near the substrate than that prepared with a 1.8 mm beam diameter, which may be influenced by the degree of melt mixing between the 17-4 PH metal powder and carbon steel substrate.

• Journal of Radiation Protection and Research
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• v.9 no.2
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• pp.61-66
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• 1984

A study on the characteristics of ${\alpha}$-particle track on cellulose nitrate film was carried out with a particular emphasis on the dependence of track diameter upon chemical etching condition. The track diameters etched in KOH solution appeared to be, on average, three times larger than those etched in NaOH under the same etching condition. The relationship between the track diameters and both etching time and the energy of incident ${\alpha}$-particles was also investigated. It is shown that the particle fluence rate is fairly independent of etching time as far as the condition of irradiation remains unchanged.

• Nuclear Engineering and Technology
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• v.37 no.4
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• pp.395-400
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• 2005

An environmental radon monitoring system, comprising a radon-cup, an etching system, and a track counting system, was constructed. The radon cup is a cylindrical chamber with a radius of 2.2 cm and a height of 3.2 cm in combination with a CR-39 detector. Carbon is impregnated in the bodies of the detector chamber to avoid problem of an electrostatic charge. The optimized etching condition for the CR-39 exposed to a radon environment turned out to be a 6 N NaOH solution at 70^{\circ}$ over a 7hour period. The bulk etch rate under the optimized condition was $1.14{\pm}0.03\;{\mu}m\;h^{-1}$. The diameter of the tracks caused by radon and its progeny were found to be in the range of $10\~25\;{\mu}m$ under the optimized condition. The track images were observed with a track counting system, which consisted of an optical microscope, a color charged couple device (CCD) camera, and an image processor. The calibration factor of this system is obtained to be $0.105{\pm}0.006$ tracks $cm^2$ per Bq $m^{-3}$ d.

• Journal of the Korean Geotechnical Society
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• v.21 no.10
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• pp.73-83
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• 2005

Recently, foundation designs based on piled raft concept have been increasing, where the piles are required not to ensure the overall stability of the foundation but to act as settlement reducer. When a concrete track is constructed on soft ground, excessive settlements may occur, while it rarely has bearing capacity problems. In this case, the settlement of the concrete track may be effectively reduced by arranging a small number of small-diameter piles beneath the track. This paper presents the effect of pile installation on the reduction of concrete track's settlement. A 3D finite difference method was employed to model the piled concrete tracks. A parametric study was carried out to assess the effect of varying soil condition and pile arrangements. From the analysis results, it is verified that the effect of the pile installation is significant to effectively reduce the settlement of concrete track. Optimal number of pile rows and pile spacings was proposed for the economical design of a piled concrete track. The bearing mechanism of piles was also investigated by analyzing load sharing characteristics of pile according to soil conditions and pile arrangements.