• Geomechanics and Engineering
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• v.29 no.4
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• pp.391-405
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• 2022

A newly proposed grouting simulation method, the sequential diffusion solidification method was introduced into the numerical simulation of combined bi-borehole grouting. The traditional, critical and difficult numerical problem for the temporal and spatial variation simulation of the slurry is solved. Thus, numerical simulation of grouting and blocking of flowing water in karst conduits is realized and the mechanism understanding of the combined bi-borehole technology is promoted. The sensitivity analysis of the influence factors of combined bi-borehole grouting was investigated. Through orthogonal experiment, the influences of proximal and distal slurry properties, the initial flow velocity of the conduit and the proximal and distal slurry injection rate on the blocking efficiency are compared. The velocity variation, pressure variation and slurry deposition phenomenon were monitored, and the flow field characteristics and slurry outflow behavior were analyzed. The interaction mechanism between the proximal and distal slurries in the combined bi-borehole grouting is revealed. The results show that, under the orthogonal experiment conditions, the slurry injection rate has the greatest impact on blocking. With a constant slurry injection rate, the blocking efficiency can be increased by more than 30% when using slurry with weak time-dependent viscosity behavior in the distal borehole and slurry with strong time-dependent viscosity behavior in the proximal borehole respectively. According to the results of numerical simulation, the grouting scheme of "intercept the flow from the proximal borehole by quick-setting slurry, and grout cement slurry from the distal borehole" is put forward and successfully applied to the water inflow treatment project of China Resources Cement (Pingnan) Limestone Mine.

• Composites Research
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• v.36 no.5
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• pp.361-368
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• 2023

Composite materials used in aircraft must be certified using approved materials to ensure the the airworthiness of the aircraft. Certification is carried out by verifying the physical properties and processes of the materials, and producing material and process specifications. The composite material certification system in ROK(Republic of Korea) has been established through the MOLIT(Ministry of Land, Infrastructure and Transport) pilot certification project for aircraft composite materials. Currently, the KIAST(Korea Institute of Aviation Safety Technology) operates and manages the certification and shared data system. This study identifies realm for improvement in the established certification system for aircraft composite materials based on empirical evidence and aims to propose measures for the certification and industrial promotion of domestically produced aircraft composite materials.

• Steel and Composite Structures
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• v.6 no.2
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• pp.159-182
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• 2006

Current fire design codes for determining the temperature within the structural elements that form part of a complete building are based on isolated member tests subjected to the standard fire. However, the standard time-temperature response bears little relation to real fires and doesn't include the effects of differing ventilation conditions or the influence of the thermal properties of compartment linings. The degree to which temperature uniformity is present in real compartments is not addressed and direct flame impingement may also have an influence, which is not considered. It is clear that the complex thermal environmental that occurs within a real building subject to a natural fire can only be addressed using realistic full-scale tests. To study global structural and thermal behaviour, a research project was conducted on the eight storey steel frame building at the Building Research Establishment's Cardington laboratory. The fire compartment was 11 m long by 7 m wide. A fire load of $40kg/m^2$ was applied together with 100% of the permanent actions and variable permanent actions and 56% of live actions. This paper summarises the experimental programme and presents the time-temperature development in the fire compartment and in the main supporting structural elements. Comparisons are also made between the test results and the temperatures predicted by the structural fire Eurocodes.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.28 no.10
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• pp.402-407
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• 2016

Ground-coupled heat pump systems have been widely used, as they are regarded as a renewable energy source and ensure a high annual efficiency. Among the system components, borehole heat exchangers (BHE) play an important role in decreasing the entering water temperature (EWT) to heat pumps in the cooling season, and consequently improve the COP. The optimal sizing of the BHEs is crucial for a successful project. Other than the existing sizing methods, a simulation-based design tool is more applicable for modern complex geothermal systems, and it may also be useful since design and engineering works operate on the same platform. A simulation-based sizing method is proposed in this study using the well-known Duct STorage (DST) model in Trnsys. TRNOPT, the Trnsys optimization tool, is used to search for an optimal value of the length of BHEs under given ground loads and ground properties. The result shows that a maximum EWT of BHEs during a design period (10 years) successfully approaches the design EWT while providing an optimal BHE length. Compared to the existing design tool, very similar lengths are calculated by both methods with a small error of 1.07%.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.12
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• pp.1037-1044
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• 2014

In this study, we designed a drop test system considering lunar surface environment and tested landing gear of experimental lunar lander. The lunar lander would be landed at soil place for soft landing. When the lunar lander touches down, the acceleration of the lander is largely affected by mechanical characteristics of the lunar soil. Accordingly, a drop test using lunar soil is needed to verify the performance of the lunar landing gear. Because the lunar soil is not available generally, we developed a lunar simulant KAUMLS(Korea Aerospace University Mechanical Luna Simulant) based on mechanical properties of the lunar soil of NASA's LUNA PROJECT. In addition, drop tests on steel plate and dry sand are performed to evaluate impact characteristics by the surface environment.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.253.2-253.2
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• 2014

Micro hollow cathode discharges (MHCDs) are high-pressure, non-equilibrium discharges. Those MHCDs are useful to produce an excimer radiation. A major advantage of excimer sources is their high internal efficiency which may reach values up to 40% when operated under optimum conditions. To produce strong excimer radiation, the optimisation of the discharge conditions however needs a detailed knowledge of the properties of the discharge plasma itself. The electron density and temperature influence the excitation as well as plasma chemistry reactions and the gas temperature plays a major role as a significant energy loss process limiting efficiency of excimer radiation. Most of the recent spectroscopic investigations are focusing on the ultraviolet or vacuum ultraviolet range for direct detection of the excimer. In our experiments we have concentrated on investigating the micro hollow cathodes from the near UV to the near infrared (300~850 nm) to measure the basic plasma parameters using standard plasma diagnostic techniques such as stark broadening for electron density and the relative line intensity method for electron temperature. Finally, the neutral gas temperature was measured by means of the vibrational rotational structures of the second positive system of nitrogen.

• Journal of Biosystems Engineering
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• v.38 no.2
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• pp.103-112
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• 2013

Background: The Korean government launched a project in 2008, where the amount of rice used as raw ingredient in rice-based foods in 2012 was planned to increase up to 10% (470,000 ton) of the total rice production through developing various new rice-based processed foods and their commercial manufacturing technology. Among the four major rice-based processed foods, rice cakes and noodles need rice flour as their main raw ingredient. Technology in rice flour utilization and manufacturing is far behind than the technology pertinent to wheat flour in many subject areas. Purpose: This review aims to provide information on rice flour utilization and manufacturing with some fundamental subjects in the area of size reduction. Results: A variety of food items including bread, noodle, cake, cookie, muffin, pre-mix, beverage, vinegar, surimi, and artificial meat have found rice flour as their raw ingredient. Rice bread made out of 100% rice flour has been developed and is now sold in retail stores. Various noodle products made from rice flour are also on the market. Issues on product definition and labeling regulation about rice flour content of the products were explored. Generalized grinding equations available in the literature were seldom used in practice; instead, it has been a general practice to develop empirical equations from test milling data. Introductory remarks on three popular particle size measurement methods (sieving, Coulter counter, light diffraction) were explained. Mathematical expressions frequently used to describe particle size distribution and to correlate cumulative quantity of particles with particle size were represented. Milling methods used in producing rice flour were described along with their advantages and disadvantages. Because of their profound effect on functional properties of the rice flour, four rice flour milling equipments used at both laboratory experiments and commercial manufacturing plants were discussed.

• Nuclear Engineering and Technology
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• v.53 no.10
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• pp.3344-3351
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• 2021

The Rare Isotope Science Project was launched in 2011 in Korea toward constructing the Rare isotope Accelerator complex for ON line experiments (RAON). RAON will house several experimental systems, including the Muon Spin Rotation/Relaxation/Resonance (μSR) facility in High Energy Experimental Building B. This facility will use 600-MeV protons with a maximum current of 660 pμA and beam power of 400 kW. The key μSR features will facilitate projects related to condensed-matter and nuclear physics. Typical experiments require a few million surface muons fully spin-polarized opposite to their momentum for application to small samples. Here, we describe the design of a muon transport beam line for delivering the requisite muon numbers and the electromagnetic-component specifications in the μSR facility. We determine the beam-line configuration via beam-optics calculations and the transmission efficiency via single-particle tracking simulations. The electromagnet properties, including fringe field effects, are applied for each component in the calculations. The designed surface-muon beamline is 17.3 m long, consisting of 2 solenoids, 2 dipoles affording 70° deflection, 9 quadrupoles, and a Wien filter to eliminate contaminant positrons. The average incident-muon flux and spin rotation angle are estimated as 5.2 × 10⁶ μ⁺/s and 45°, respectively.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.1
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• pp.56.3-57
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• 2015

As of early 2015, more than 12,000 Near-Earth Objects (NEOs) have been catalogued by the Minor Planet Center, however their observational properties such as broadband colors and rotational periods are known only for a small fraction of the population. Thanks to time series observations with the KMTNet, orbits, optical sizes (and albedo), spin states and three dimensional shapes of asteroids and comets including NEOs will be systematically investigated and archived for the first time. Based on SDSS and BVRI colors, their approximate surface mineralogy will also be characterized. This so-called DEEP-South (Deep Ecliptic Patrol of the Southern Sky) project will provide a prompt solution to the demand from the scientific community to bridge the gaps in global sky coverage with a coordinated use of the network of ground-based telescopes in the southern hemisphere. We will soon finish implementing dedicated software subsystem consisted of automated observation scheduler and data pipeline for the sake of increased discovery rate, rapid follow-up, timely phase coverage, and efficient data analysis. We will give a brief introduction to test runs conducted at CTIO with the first KMTNet telescope in February and March 2015 and experimental data processing. Preliminary scientific results will also be presented.

• The Research Journal of the Costume Culture
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• v.9 no.4
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• pp.616-628
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• 2001

The purpose of this research is to create a polyester sample book that serves as a point of reference that exporters in the Taegu area can allude to when exporting to the U.S. By getting this project off the ground, we can expect to make a worthy contribution to the manufacture of high-quality, value-added fashion & textile goods. The research was conducted as follows. First, a study was carried out in the local market ensued by consumer surveys with regards to consumer attitude on man-made fibers, market researches, and interviews with experts, all in conjunction with the Color Association of the U.S. Also, a diverse array of fabric swatches were collected from Manhattans fabric wholesalers and then classified by color and fabric type fur the sample book. In short, this research found that man-made fibers have full marketability in the U.S. Thus, in order for Taegus synthetic textile firms to be successful in exporting to the US, it is essential that they come up with fabrics that have properties resembling natural fibers such as having a soft hand, natural sheen, smooth draping, and diverse textures as well as being in line with the current trends. In addition, it is also necessary to develop fabrications that are versatile and functional. Thus, by developing innovative fabrications, the synthetic textile business will turn toward the production of high-quality synthetics and will also provide a platfrom for strengthening the competitive edge of Koreas textile & fashion business.