• Geomechanics and Engineering
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• v.30 no.2
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• pp.153-167
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• 2022

This study proposes a method to analyze the distribution of coal porosity disturbances after the excavation of ultra-large-diameter water jet boreholes using a coal wetting and softening model. The high-pressure jet is regarded as a short-term high-pressure water injection process. The water injection range is the coal softening range. The time when the reference point of the borehole wall is shocked by the high-pressure water column is equivalent to the time of high-pressure water injection of the coal wall. The influence of roadway excavation with support and borehole diameter on the ultra-large-diameter jet drilling excavation is also studied. The coal core around the borehole is used to measure the gas permeability for determining the porosity disturbance distribution of the coal in the sampling plane to verify the correctness of the simulation results. Results show that the excavation borehole is beneficial to the expansion of the roadway excavation disturbance, and the expansion distance of the roadway excavation disturbance has a quadratic relationship with the borehole diameter. Wetting and softening of the coal around the borehole wall will promote the uniform distribution of the overall porosity disturbance and reduce the amplitude of disturbance fluctuations.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.05a
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• pp.349-352
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• 2001

In this paper, novel device structure in order to realize ultra fast and ultra small silicon devices are investigated using ultra-high vacuum chemical vapor deposition(UHVCVD) and Excimer Laser Annealing (ELA) for ultra pn junction formation. Based on these fundamental technologies for the deep sub-micron device, high speed and low power devices can be fabricated. These junction formation technologies based on damage-free process for replacing of low energy ion implantation involve solid phase diffusion and vapor phase diffusion. As a result, ultra shallow junction depths by ELA are analyzed to 10~20 nm for arsenic dosage (2$\times$10$^{14}$ $\textrm{cm}^2$), excimer laser source(λ=248nm) is KrF, and sheet resistances are measured to 1k$\Omega$/$\square$ at junction depth of 15nm.

• Journal of the Semiconductor & Display Technology
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• v.20 no.4
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• pp.29-37
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• 2021

A 7 nm technology node using extreme ultraviolet lithography with a wavelength of 13.5 nm has been recently developed and applied to the semiconductor manufacturing process. Furthermore, the development of sub-3 nm technology nodes continues to be required. In this study, design factors of an electrostatic deflector for an ultra-miniaturized microcolumn system that can realize an electron wavelength of below 1.23 nm with an acceleration voltage of above 1 eV were investigated using a three-dimensional simulator. Particularly, the optimal design of the electrostatic octupole floating deflector was derived by optimizing the design elements and improving the driving method of the 1 keV low energy ultra-miniaturized microcolumn deflector. As a result, the entire wide field of view greater than 330 ㎛ at a working distance of 4 mm was realized with an ultra-high-resolution electron beam spot smaller than 10 nm. The results of this study are expected to be a basis technology for realizing a wafer-scale multi-array microcolumn system, which is expected to innovatively improve the throughput per unit time, which is the biggest drawback of electron beam lithography.

• Journal of the Korean Ceramic Society
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• v.49 no.4
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• pp.308-317
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• 2012

Reactive processing, such as reactive hot pressing (RHP) and reactive spark plasma sintering (R-SPS), is effective densification method to prepare $ZrB_2$-based ultra high temperature ceramics (UHTCs). The present paper reviewed some typical reactive processing of $ZrB_2$-based UHTCs. All the reactions from the starting materials in the reactive processing are thermodynamically favorable, which generate enough energy and driving force for the densification of the final products under a relatively low temperature. Besides, compared with non-reactive processing, anisotropic $ZrB_2$ grains, such as $ZrB_2$ platelets, can only be obtained in the reactive processing, resulting in an improvement of the mechanical properties.

• Structural Engineering and Mechanics
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• v.48 no.6
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• pp.791-807
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• 2013

Ultra High Performance Cementitious Composites with compressive strength 200MPa (UHPCC-200) is proposed for the structural design of super high hybrid wind turbine tower to gain durability, ductility and high strength design objectives. The minimal wall thickness is analyzed using basic bending and compression theory and is modified by a toque influence coefficient. Two cases of wall thickness combination of middle and bottom segment including varied ratio and constant ratio are considered within typical wall thickness dimension. Using nonlinear finite element analysis, the effects of wall thickness combinations with varied and constant ratio and prestress on the structural stress and lateral displacement are calculated and analyzed. The design limitation of the segmental wall thickness combinations is recommended.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.04a
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• pp.265-268
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• 1999

In this study, we manufactured the ultra-high strength concrete using mineral admixture which is easily workable. From the test results of compressive strength, It is concluded that the proper replacement ratio of silica fume should not exceed to 10% and the replacement of slag is more effective that the replacement of fly ash to gain very high compressive strength. Thermal stress analysis is conducted to find the way of controlling the thermal crack of ultra-high strength concrete. As results of thermal stress analysis, it was found that reducing placing temperature of concrete(pre-cooling) is effective to reduce thermal crack and placing concrete in high air temperature is more effective than placing concrete in low air temperature.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.25-28
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• 2006

This study investigated pre-mixed cement combined with ordinary portland cement, BF and SF, in order to manufacture cement binder, which is possible to produce 150MPa ultra high strength concrete. The BF used in this study reduces and control hydration heat. It can also improve concrete fluidity, while AP increases hydration product and accelerates reaction of BF. SF has micro filler effect and makes pozzolanic reaction. It also fabricates high density internal organization. This developed pre-mixed cement can reduce hydration heat and increase hydration product. It is possible to fabricate high density organization and to secure homogeneity. The mock-up test of ultra high strength concrete showed excellent dispersibility and workability and indicated compressive strength more than 150MPa at 28 days.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.395-398
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• 2005

In recent years, the applications of high-strength concrete have increased, and high-strength concrete has now been used in many parts of the world. The growth has been possible as a. result of recent developments in material technology and a demand for higher-strength concrete in Korea. In this study, we have an object to produce the ultra-high strength concrete(Super-Con) of over 100MPa with low price materials. First, the binders for Super-Con should be selected by the tests; setting time of paste, flow value and strength of mortar. From the test results, the binders are blended with ordinary portland cement, pulverized portland cement and silica fume. Fundamentally the compressive strength, frost resistance and chloride resistance are investigated.

• Proceedings of the IEEK Conference
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• 2003.11b
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• pp.45-48
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• 2003

We can easily buy network system for high performance micro-processor, progress computer architecture is caused of high bandwidth and low delay time. Coupling PC-based commodity technology with distributed computing methodologies provides an important advance in the development of single-user dedicated systems. Lately Network is joined PC or workstation by computers of high performance and low cost. Than it make intensive that Cluster system is resembled supercomputer. Unix, Linux, BSD, NT(Windows series) can use Cluster system OS(operating system). I'm chosen linux gain low cost, high performance and open technical documentation. This paper is benchmark performance of Beowulf clustering by UltraSPARC-1K(64bit-RISC processor). Benchmark tools use MPI(Message Passing Interface) and NetPIPE. Beowulf is a class of experimental parallel workstations developed to evaluate and characterize the design space of this new operating point in price-performance.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2018.05a
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• pp.275-276
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• 2018

Ultra high performance concrete(UHPC) represents high early age autogenous shrinkage strain due to its low water-to-binder ratio(W/B) and high fineness admixture usage. It has been reported that fiber can control restrained tensile stress and crack. The purpose of the present study is, therefore, to investigate the autogenous shrinkage as well as mechanical properties including compressive strength, flexural strength and modulus of elasticity on the UHPC with fiber type and pre-mix of binder.