• Clean Technology
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• v.5 no.2
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• pp.25-35
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• 1999

Behavior of permeate flux decline was examined through the hollow fiber membrane in ultrafiltration system for Si colloidal solution. Flux decline with time was due to the growth of Si cake deposited on the membrane surface and the pore blocking by Si particles for the hollow fiber membrane. At the pseudo steady state of operation, the permeate flux of dead-end flow was 60 % to that of the cross flow. The ratio of permeate flux to the pure water flux, $J/J_w$, decreased with increasing the trans-membrane pressure, from 64.2 % for $0.5kg_f/cm^2$ to 45.7 % for $2.0kg_f/cm^2$. When the feed flow rate was 3 L/min, the pore blocking model was dominant at the initial period of filtration and was followed by the cake filtration model. And with increasing the feed flow rate from 1 L/min to 3 L/min, $R_c$ was $1.79{\times}10^{12}{\sim}2.34{\times}10^{12}m^{-1}$ which was the about 40 % decreased value to that of the 1 L/min while $R_p$ was not changed and was $1.71{\times}10^{12}m^{-1}$ approximately.

• Membrane Journal
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• v.16 no.4
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• pp.303-312
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• 2006

The asymmetric hybrid membranes of polyethersulfone (PES) and $ZrO_2$ nanoparticles were prepared via new one-step procedure combining simultaneously the phase-inversion method and the sol-gel technique. The optimum contents of $Zr(PrO)_4\;and\;HNO_3$ catalyst were determined by the adsorption experiments of phosphate anion onto the resulting hybrid membranes. The maximum adsorption of phosphate anion is obtained at the conditions of 0.15 mL $Zr(PrO)_4$ addition per 1 mL PES and 30 mL $HNO_3$ addition per 1 mL $Zr(PrO)_4$. Variation of morphology, performance and incorporated $ZrO_2$ amount of the resulting hybrid membranes were discussed and determined using SEM, pure water flux, TGA, ICP, XRD and contact angle measurements. Increasing $Zr(PrO)_4$ addition into casting solution, pure water flux is increased and $ZrO_2$ amount in the hybrid membrane is maximized at the conditions 0.15 mL $Zr(PrO)_4$ addition per 1 mL PES. The prephosphatation of PES-$ZrO_2$ hybrid membrane was studied to modify the surface characteristics of membrane. Ultrafiltration of bovine serum albumin (BSA) solution was performed in a dead-end cell using both a bare (non-phosphated) and a phosphated hybrid membrane. It is revealed that both the permeate flux and BSA rejection were increased as about 40% by prephosphatation of hybrid membrane. These results may be explained on the basis of the increase of membrane hydrophilicity, which was determined from contact angle measurements.

• Economic and Environmental Geology
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• v.52 no.1
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• pp.37-48
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• 2019

In geological $CO_2$ sequestration, the behavior of $CO_2$ within a reservoir can be characterized as two-phase flow in a porous media. For two phase flow, these processes include drainage, when a wetting fluid is displaced by a non-wetting fluid and imbibition, when a non-wetting fluid is displaced by a wetting fluid. In $CO_2$ sequestration, an understanding of drainage and imbibition processes and the resulting NW phase residual trapping are of critical importance to evaluate the impacts and efficiencies of these displacement process. This study aimed to observe migration and residual trapping of immiscible fluids in porous media via cyclic injection of drainage-imbibition. For this purpose, cyclic injection experiments by applying n-hexane and deionized water used as proxy fluid of $scCO_2$ and pore water were conducted in the two dimensional micromodel. The images from experiment were used to estimate the saturation and observed distribution of n-hexane and deionized water over the course drainage-imbibition cycles. Experimental results showed that n-hexane and deionized water are trapped by wettability, capillarity, dead end zone, entrapment and bypassing during $1^{st}$ drainage-imbibition cycle. Also, as cyclic injection proceeds, the flow path is simplified around the main flow path in the micromodel, and the saturation of injection fluid converges to remain constant. Experimental observation results can be used to predict the migration and distribution of $CO_2$ and pore water by reservoir environmental conditions and drainage-imbibition cycles.

• Journal of The Korean Association For Science Education
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• v.42 no.4
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• pp.383-396
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• 2022

In this study, pre-service chemistry teachers' questions in their teaching practices were analyzed considering the context of discourse. Five pre-service teachers participated in the study. Their questions were analyzed by considering various data including class videos, interviews, and teaching-learning materials. Their questions were classified into relevant question, affective question, dead-end question, rhetorical question, and structuring question. Each question was also classified into appropriate question and convenient question by the aspect of proper responses of students. The analyses of the results indicate the differences in the frequencies of several types of questions depending on the content of the lessons. After using convenient questions, pre-service teachers proceeded to prepared classes as they rather than prompted students' responses. The affective questions were rarely used. The dead-end questions were found to be used for promoting interaction with students. The rhetorical questions were used for various purposes such as arousing students' attention or promoting their thinking. Practical implications were discussed based on the results.

• The Korean Journal of Malacology
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• v.31 no.4
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• pp.267-272
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• 2015

This study was conducted in order to elucidate the dissemination mechanism of P. olseni using field and laboratory experiments. For this purpose, we quantified the level of P. olseni infection in buried (healthy) and surfaced (gapped) R. philippinarum from a clam bed on Wi-do Island on the west coast of Korea. In addition, the levels of internal and released P. olseni cells from artificially infected (and later dead) R. philippinarum were monitored for 8 days using the RFTM-2 M NaOH lysis method. Our results indicate that P. olseni cells in buried R. philippinarum was $2,655,625{\pm}1,536,936cells/clam$; the level in gapped R. philippinarum was considerably lower, $28,203{\pm}24,889cells/clam$ (p < 0.05). In the laboratory experiment, the P. olseni cells remained in the host tissue 2 days after death was approximately 50% lower than the level of infection measured in living clams. The level dropped to 20% 4 days after death and to 1.5% 6 days after death; eight days after death, P. olseni cells were undetectable since the R. philippinarum flesh had completely decomposed. The level of released cells on the day of death was only 0.05% of the internal level in live R. philippinarum; however, the level increased to 2.3% 5 days after death then gradually decreased and no released cells were detected 8 days after death. Therefore, our laboratory experiment suggest that the low level of P. olseni infection observed in gapped R. philippinarum at Wi-do Island could be caused by lysis of the most of P. olseni cells during the decomposition of dead R. philippinarum tissues. Until the end of decomposition of R. philippinarum, 6.68% of the total amount of P. olseni was released within 8 days. Our study showed that the amount of P. olseni cells from dead host is a considerably higher level than naturally released from healthy R. philippinarum, suggesting that death of the host plays an important role in the dissemination of P. olseni.

• The KIPS Transactions:PartA
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• v.18A no.3
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• pp.109-114
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• 2011

We describe a technique for automatically proving compiler optimizations sound, meaning that their transformations are always semantics-preserving. As is well known, IR (Intermediate Representation) optimization is an important step in a compiler backend. But unfortunately, it is difficult to detect and debug the IR optimization errors for compiler developers. So, we introduce a C level error check system for detecting the correctness of these IR transformation techniques. In our system, we first create an IR-to-C converter to translate IR to C code before and after each compiler optimization phase, respectively, since our technique is based on the Memory Comparison-based Clone(MeCC) detector which is a tool of detecting semantic equivalency in C level. MeCC accepts only C codes as its input and it uses a path-sensitive semantic-based static analyzer to estimate the memory states at exit point of each procedure, and compares memory states to determine whether the procedures are equal or not. But MeCC cannot guarantee two semantic-equivalency codes always have 100% similarity or two codes with different semantics does not get the result of 100% similarity. To increase the reliability of the results, we describe a technique which comprises how to generate C codes in IR-to-C transformation phase and how to send the optimization information to MeCC to avoid the occurrence of these unexpected problems. Our methodology is illustrated by three familiar optimizations, dead code elimination, instruction scheduling and common sub-expression elimination and our experimental results show that the C level error check system is highly reliable.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.23 no.2
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• pp.178-185
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• 2014

This paper describes a fabrication multiplexing sensor probe that employs a fiber Bragg grating(FBG) based on multiple measurements to determine the blade deflection of a wind power generator the reliability analysis of this probe is also presented. To diminish the temperature sensitivity of the FBG sensor, we form multiple CFRPs onto the upper and lower layers of the FBG and package it with an epoxy resin. As a result, the depth of the CFRP is 1mm, and the temperature sensitivity is $2.39pm/^{\circ}C$. We construct a sensor network utilizing the fabricated sensor with a blade beam model. As the number of pendulums is increased on the fore-end of the beam, the strain value is measured. The strain variation is calculated from the measurement of the load on the blade beam model by monitoring the strain of the FBG sensor. When the linear equation is applied, the strain error is 0.4% and when the finite difference method is used, the tip deflection error is 3.3%. The displacement error derived from the strain value of the FBG sensor is 4.39%. The calculated result between the measured value of the dead-end of the beam and the strain is less than 2.46% tip distortion error. Therefore, our proposed multiplexing sensor probe is a low-cost and high-reliability solution for a commercial wind power generator.

• Journal of Korean Society on Water Environment
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• v.25 no.2
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• pp.306-310
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• 2009

Packed-bed reactor for removing ammonia was tested at different loading rates. Nitrifiers for ammonia removing was encapsulated in gel media which consisted of polyethlene glycol, alginate and activated carbon. The removal efficiency was nearly 100% when ammonia loading was $12g/m^3/hr$, and the maximum elimination capacity (EC) achieved on this study was $18g/m^3/hr$. The initial microbial portion of nitrifiers in the media was about 82% and it was increased to more than 90% at the end of the operation. Short-term shock loading test was carried out to survey the stability of the media. The inlet loading rates were varied from 2 to $20g/m^3/hr$. The packed-bed reactor overcame the shock loading i.e. removal efficiency recovered rapidly from about 80% to almost 100% within 6 hrs. The results of Live/Dead cell test showed that nitrifiers maintained there activity in the encapsulated media during the test and also against ammonia shock load.

• Korean Journal of Adult Nursing
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• v.22 no.6
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• pp.663-675
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• 2010

Purpose: The purpose of this study was to explore the life experiences of patients with a severe Chronic Obstructive Pulmonary Disease (COPD). Methods: The data were collected through in-depth interviews of six patients suffering from severe COPD. The interviewed data were audio-recorded and transcribed verbatim and checked for accuracy. The Giorgi method of phenomenology was used for analyzing data. Results: Eight themes forming the, units of meaning, were: Repeated and Unpredictable Suffering of Dyspnea, Confidence Loss/Exhaustion Life due to non-efficient breathing, Gradually Deprived Liberty, Absolute Being to Sustaining my life, Source of Burden but Significant Person I am in the Family, Endless Tug-of-War-Capability/Endeavor to Breath, Longing for my Life, and Dead-end of breathing. Conclusion: The study results provide an in-depth understanding of life experiences of patients suffering from severe COPD. The findings will be useful to nurses caring for this population.

• Journal of Institute of Control, Robotics and Systems
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• v.19 no.8
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• pp.702-708
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• 2013

Underwater TRN (Underwater Terrain Referenced Navigation) estimates an underwater vehicle state by measuring a distance between the vehicle and undersea terrain, and comparing it with the known terrain database. TRN belongs to absolute navigation methods, which are used to compensate a drift error of dead reckoning measurements such as IMU (Inertial Measurement Unit) or DVL (Doppler Velocity Log). However, underwater TRN is different to other absolute methods such as USBL (Ultra-Short Baseline) and LBL (Long Baseline), because TRN is independent of the external environment. As a magnetic-field-based navigation, TRN is a kind of geophysical navigation. This paper develops an EKF (Extended Kalman Filter) formulation for underwater TRN. A filter propagation part is composed by an inertial navigation system, and a filter update is executed with echo-sounder measurement. For large-initial-error cases, an adaptive EKF approach is also presented, to keep the filter be stable. At the end, simulation studies are given to verify the performance of the proposed TRN filter. With simplified sensor and terrain database models, the simulation results show that the underwater TRN could support conventional underwater navigation methods.