• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1963-1968
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• 2004

A collection efficiency of cyclone is influenced by cut-size and slope of grade efficiency curve. It has been recognized that the collection efficiency is improved when the cut-size is reduced. However, effects of the slope have never been studied so far. In this study, we analyze a relationship between slope of grade efficiency and collection efficiency in two-stage cyclones. In single stage cyclones, higher slope cyclones have high efficiency. On the contrary to single stage cyclone, collection efficiency of two-stage cyclone have the maximum value when the first cyclone has a lower slope and second cyclone is high.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.4
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• pp.321-328
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• 2008

In this paper, variable gain amplifier(VGA) with a gain slope controller has been proposed and verified by circuit simulations and measurements. The proposed VGA has a gain control, gain slope switch and variable gain range. The input source coupled pair with diode connected load is used for VGA gain stage. The gain slope controller with switch can control VGA gain slope. The proposed VGA is fabricated in $0.18{\mu}m$ CMOS process for multi -standard wireless receiver. The proposed two stage VGA consumes min. 2.0 mW to max. 2.6 mW in gain control range and gives input IP3 of -3.77 dBm and NF of 28.7 dB at 1.8 V power supply under -25 dBm, 1 MHz input. The proposed VGA has 37 dB(-16 dB $\sim$ 21 dB) variable gain range, and 8 dB gain range control per 0.3 V control voltage, and can provide variable gain, positive and negative gain slope control, and gain range control. This VGA characteristics provide design flexibility in multi-standard wireless receiver.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.946-956
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• 2008

Acoustic emission(AE) is low-energy seismic event associated with a sudden inelastic deformation such as the sudden movement of existing fractures, the generation of new fractures or the propagation of fractures. These events rapidly increase before major failure and happen within a given rock volume and radiate detectable seismic waves. Rock slopes are usually large in scale and there are many discontinuities in rock mass. AE waves are strongly attenuated when they propagate through joints. Thus we should resolve the attenuation problem to monitor large volume. In this study, we developed waveguide which is composed of two different materials, cement mortar and stainless steel rod. And several laboratory tests on developed waveguide are performed to obtain generalized AE parameters to predict the failure stage in rock slope. Comparing field data with experimental data in laboratory tests, failure stage of rock slope can be evaluated. To verify and optimize the developed monitoring method, we are now carrying out the field application at a rock slope.

• Structural Engineering and Mechanics
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• v.60 no.5
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• pp.809-828
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• 2016

In deep open pit mines, slope stability is very important. Particularly, increasing the depths increase the risks in mines having weak rock mass. Blasting operations in this type of open pits may have a negative impact on slope stability. Several or combination of methods can be used in order to enable better analysis in this type of deep open-pit mines. Numerical modeling is one of these options. Many complex problems can be integrated into numerical methods at the same time and analysis, solutions can be performed on a single model. Rock failure criterions and rock models are used in numerical modeling. Hoek-Brown and Mohr-Coulomb terms are the two most commonly used rock failure conditions. In this study, mine planning and discontinuity conditions of a lignite mine facing two big landslides previously, has been investigated. Moreover, the presence of some damage before starting the study was identified in surrounding structures. The primary research of this study is on slope study. In slope stability analysis, numerical modeling methods with Hoek-Brown and Mohr-Coulomb failure criterions were used separately. Preparing the input data to the numerical model, the outcomes of patented-blast vibration minimization method, developed by co-author was used. The analysis showed that, the model prepared by applying Hoek-Brown failure criterion, failed in the stage of 10. However, the model prepared by using Mohr-Coulomb failure criterion did not fail even in the stage 17. Examining the full research field, there has been ongoing production in this mine without any failure and damage to surface structures.

• Korean Journal of Materials Research
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• v.12 no.6
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• pp.482-487
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• 2002

A $TiO_2$ film for photocatalyst was prepared by anodic oxidation at 180V in acidic electrolyte and film formation mechanism was studied. The major part of anodic $TiO_2$ film consisted of anatase type structure and surface morphology exhibited a porous cell structure. The thickness growth rate of the oxide film with anodization time revealed two-stage slope corresponds to the surface morphology between anodic films. The growth of pores on cell structure and the growth rate of film with two-stage slope are related to the constant formation rate of the $TiO_2$ layer.

• Advances in concrete construction
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• v.10 no.2
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• pp.151-159
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• 2020

An experimental study on the stress-strain relation of PVC-CFRP confined reinforced concrete columns subjected to eccentric compression was carried out. Two parameters, such as the CFRP strips spacing and eccentricity of axial load, were considered. The experimental results showed that all specimens failed by compressive yield of longitudinal steel bar and rupture of CFRP strips. The bearing capacity of specimen decreases as the eccentricity or the CFRP strips spacing increases. The stress-strain relation of specimens undergoes two stages: parabolic and linear stages. In the parabolic stage, the slope of stress-strain curve decreases gradually as the eccentricity of axial loading increases while the CFRP strips spacing has little effect on the slope of stress-strain curve. For the linear stage, the slope of stress-strain curve decreases as the eccentricity of axial load or the CFRP strips spacing increases. A model for predicting the stress-strain relation of columns under eccentric compression is proposed and it agrees well with various test data.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.324-327
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• 2008

Two stage startup of high thrust liquid rocket engine can reduce the abrupt impulse to the vehicle and engine by changing oxidizer flow rate to the combustion chamber. Also it ensures stable ignition of combustion chamber against hard start and to prevent pump stall by the sudden supply of large mass flow rate. However high discharge pressure of oxidizer pump or temperature rise in gas generator may be a problem in applying the preliminary stage. To solve this problem, we analyzed the effect of the slope of oxidizer pump's head curve and the oxidizer mass flow rate to combustion chamber during preliminary stage using the rocket engine startup analysis code. A moderate slope(${\circleddash}{\sim}$-3) of head curve and 80% mass flow rate during preliminary stage can reduce the oxidizer pump discharge pressure by 15 to 20% comparing with the condition of ${\circleddash}$=-4.37 head curve and 70% mass flow rate. Also it can maintain the turbine inlet temperature rise within 50K from the nominal value.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.26 no.2
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• pp.47-59
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• 2023

This study investigated and analyzed the effects of vegetation on the roadside slopes at the expressway construction sites in order to evaluate the vegetation recovery regarding soil type and revegetation technique. We selected two study sites with an area of 1,000 m² located in the construction sites of the Korea Expressway Corporation, named Hwado-Yangpyeong Expressway Section 3 and Saemangeum-Jeonju Expressway Section 7. The revegetation was monitored in three plot groups (earth, soft rock, and hard rock slopes), and scored based on the guideline of the Ministry of Land, Transport and Maritime Affairs. The revegatation was generally lower in the Hwado-Yangpyeong site than that of the Saemangeum-Jeonju site. The field monitoring indicated that the revegetation varied with slope aspect and environmental characteristics between plots. the Saemangeum-Jeonju site showed a high overall evaluation score, but there was a slight difference in the score for each plot. This seems to be due to the differences in geographical conditions, construction methods, and site environment between two sites. This study can provide basic information to understand the short-term effects of revegetation techniques in the roadside slopes.

• Proceedings of the Korean Society for Rock Mechanics Conference
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• 2007.10a
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• pp.63-79
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• 2007

Several remedial works were attempted to stabilize the collapsed area of the inlet slopes of diversion tunnel, but prevention of any further movement was being only carried out at beginning stage by filling the area with aggregates and rock debris, after several cracks had been initiated and developed around the area. The extra specialty developed folding zone is consisted with highly weathered Greywacke and Black shale. The suggested solution is to improve the properties of the rock mass of failed area by choosing the optimum level of reinforcement through the increment of slope rock support design so as to control the movement of slopes during the re-excavation. The Bakun hydroelectric project includes the construction of a hydroelectric power plant with an installed capacity of 2,520MW and a power transmission system connecting to the existing transmission networks in Sarawak and Western Malaysia. The power station will consist of a 210m height Concrete Faced Rockfill Dam. During the construction of the dam and the power facilities the Balui River has to be diverted of the tunnels is 12m and the tunnel width is 16m at the portal area. This paper describes the stability analysis and design methods for the open cut rock slopes in the inlet area of the diversion tunnels. The geotechnical parameters employed in stability calculations were given as a function of four defined Rock Mass Type (RMT) which were based on RMR system from Bieniawski. The stability calculations procedure of the rock slopes are divided into two stages. In the first stage, it is calculated for the stability of each "global" slope without any rock support and shotcrete system. In the second stage, it is calculated for each "local" slope stability with berms and supported with rock bolts and shotcrete. The monitoring instrumentation was performed continuously and some of the design modification was carried out in order to increase the safety of failed area based on the unforeseen geological risks during the open cut excavation.

• Microbiology and Biotechnology Letters
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• v.6 no.3
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• pp.109-113
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• 1978

The process of milk clotting by enzymes was confirmed to be consisted of two distinct stages: an enzymic coagulation stage followed by a nonenzymic clotting stage. The endpoint of the enzymic stage was determined simply by measuring flow distance of milk-enzyme system in a regular test tube being laid down to five degree slope after the reaction. By measuring the time elapsed during the enzymic stage a new method of evaluating the power of milk clotting enzymes was proposed.