• Membrane and Water Treatment
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• 제5권3호
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• pp.183-195
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• 2014

The efficiency of two metal ions (cadmium, zinc) removal from aqueous solutions by ultrafiltration (UF) and Polymer Enhanced Ultrafiltration (PEUF) processes were investigated in this work. The UF and PEUF studies were carried out using an ultrafiltration tangential cell system equipped with 5.000 MWCO regenerated cellulose. A water-soluble polymer: the polyacrylic acid (PAA) was used as complexant for PEUF experiments. The effects of transmembrane pressure, pH, metal ions and loading ratio on permeate fluxes and metal ions removals were evaluated. In UF process, permeate fluxes increase linearly with increasing pH for different transmembrane pressure, which may be the consequence of the formation of soluble metal hydroxyl complexes in the aqueous phase. In PEUF process, above pH 5.0, the Cd(II) retention reaches a plateau at 90% and Zn(II) at 80% for L = 5. Also, cadmium retention at different L is greater than zinc retention at pH varying from 5.0 to 9.0. In a mixture solution, cadmium retention is higher than zinc for different loading ratio, this is due to interactions between carboxylic groups of PAA and metal ions and more important with cadmium ions.

• Magazine of the Korea Concrete Institute
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• 제10권6호
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• pp.313-323
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• 1998

Fluidity retention of concrete used high range water reducing AE agent(HWAE) is varied according to main component, dosage amount and dosing method of HWAE. The type and substitution ratio of mineral admixture also have influence on the fluidity retention of concrete used HWAE. In this study, for the purpose of improving the fluidity retention in concrete used HWAE. 3 types of HWAE and ground granulated blast furnace slag(SG) are used in cement paste, mortar and concrete varing dosage amount and dosing time of HWAE and substitution ratio of SG respectively. According to using the HWAE of naphthalene sulfonates and SG, the fluidity retention of mortar and concrete is improved remarkably. And after 30 min, dosing method of HWAE is very effective in improving the fluidity retension and strength of concrete regardless of type of HWAE.

• KSBB Journal
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• 제7권3호
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• pp.179-185
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• 1992

An anion-charged membrane was used for selective retention of coenzyme NAD(H) in reactor without any chemical modification. The membrane could reject permeation of NAD (H) (80.9%) but not reject permeation of product. The retention ratio was enhanced in the presence of albumin and Tris-maleate buffer. A bioreactor equipped with a membrane, NTR 7410 was constructed and used in the repeated batch production of sorbitol. NADH-dependent sorbitol dehydrogenase from sheep liver was used for the production of sorbitol from fructose. The coenzyme oxidized was regenerated with alcohol dehydrogenase. 47g/L sorbitol was produced for 198 hr with a substrate conversion ratio of 70%. The retention ratio was almost maintained throughout the entire reaction.

• Membrane and Water Treatment
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• 제8권4호
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• pp.337-353
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• 2017

Membrane fouling at different solids retention times (SRT) (7, 12 and 20 days) was studied under well-controlled conditions in a laboratory-scale aerobic submerged membrane bioreactor under constant biomass concentration using a synthetic high strength wastewater. An increase in SRT was found to improve membrane performance and this correlated to changes in the total production of bound extracellular polymeric substances (EPS), and the composition and properties of bound EPS using X-ray photoelectron spectroscopy (XPS) and Fourier transform-infrared spectroscopy (FTIR) and floc sizes. A larger amount of total bound EPS was found at the lowest SRT (7 days) tested but the ratio of proteins (PN) to carbohydrates (CH) in bound EPS increased with an increase in SRT. Similarly, the quantity of soluble microbial products (SMP) decreased with an increase in SRT and the SMP PN/CH ratio increased with an increase in SRT. SMP concentrations positively correlated to the percentage of membrane pore blocking resistance. The quantity of total bound EPS and total SMP positively corresponded to the membrane fouling rate, while the PN/CH ratio in the bound EPS and SMP negatively correlated to the membrane fouling rate. The results show that both the quantity and composition of bound EPS and SMP and floc sizes are important in controlling membrane fouling.

• Journal of Gastric Cancer
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• 제21권3호
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• pp.298-307
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• 2021

Purpose: Delayed gastric emptying usually manifests as gastric food retention. This study aimed to evaluate the incidence of gastric food retention after distal gastrectomy with gastrojejunostomy in gastric cancer patients and identify the risk factors for its development. Materials and Methods: We retrospectively enrolled 245 patients who underwent distal gastrectomy with gastrojejunostomy for gastric cancer at Boramae Medical Center between March 2017 and December 2019. We analyzed the presence of gastric food residue via computed tomography (CT) scans at 3 and 12 months postoperatively and analyzed the risk factors that may influence the development of gastric food retention. Results: CT scans were performed on 235 patients at 3 months and on 217 patients at 12 months postoperatively. In the group that received closure of Petersen's space, the incidence of gastric food retention was significantly low as per the 3- and 12-month postoperative follow-up CT scans (P=0.028 and 0.003, respectively). In addition, hypertension was related to gastric food retention as per the 12-month postoperative follow-up CT scans (P=0.011). No other factors were related to the development of gastric food retention. In the multivariate analysis, non-closure of Petersen's space (hazard ratio [HR], 2.54; 95% confidence interval [CI], 1.20-5.38; P=0.010) was the only significant risk factor for gastric food retention at 3 months postoperatively, while non-closure of Petersen's space (HR, 2.81; 95% CI, 1.40-5.64; P=0.004) and hypertension (HR, 2.30; 95% CI, 1.14-4.63; P=0.020) were both significant risk factors for gastric food retention at 12 months postoperatively. Conclusions: Closure of Petersen's space has an effect on decrease the incidence of gastric food retention after distal gastrectomy with gastrojejunostomy in gastric cancer patients.

• Journal of the Korea Institute of Information and Communication Engineering
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• 제9권3호
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• pp.609-615
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• 2005

The effects of Zr/Ti concentration ratio in PLZT (10/y/z) thin films prepared by sol-gel method are investigated for the NVFRAM application. As Ti amount of Zr/Ti concentration ratio increases, the dielectric constants at 10 kHz decrease from 550 to 400, while the loss tangents increase from 0.028 to 0.053 and the leakage current densities at 170 kV/cm decrease from $1.64\times10^{-6}$ to $1.26\times10^{-7}\;A/cm^2$. In the results of hysteresis loops measured at $\pm170kV/cm$, the remanent polarization and the coercive field increase from 6.62 to $12.86{\mu}C/cm^2$ and from 32.15 to 56.45 kV/cm, respectively, according to the change from 40/60 to 0/100 in Zr/Ti concentration ratio. Fatigue and retention properties also improve much as the Zr/Ti concentration ratio change from 40/60 to 0/100. After applying $10^9$ square pulses with $\pm5V$, the remanent polarization of the PLZT (10/40/60) thin film decreases $50\%$ from the initial state while that of the PLZT (10/0/100) thin film decreases $28\%$. In the results of retention measurements of 10s s, the remanent polarization of the PLZT (10/0/100) thin film dec.eases only $10\%$ from the initial state, while that of the PLZT (10/40/60) thin film decreases $40\%$.

• Journal of the Korean Society for Precision Engineering
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• 제31권12호
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• pp.1171-1176
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• 2014

Oil retention experiments were conducted and the performance was characterized for electrochemically etched stainless steels. The 304 stainless steels were electrochemically etched in dilute Aqua Regia to form porous structures. The structures were also hierarchical, which provides very large area for oils to adhere. Also the structures had deep valleys, which act as reservoir and are able to resist against oil-detaching forces. Several commercial oils were dispensed to characterize oil retention properties via rotating disk experiment method. The results showed that the etched surfaces have superior oil retention performance in every conditions. Also the retention enhancement ratio went particularly higher as the environments became more severe. This surface modification technique could be applied to other steel products for pretreatments of various kinds of coatings.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• 제8권1호
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• pp.151-165
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• 1996

Relation between condensate retention and heat transfer performance is studied for condensation of CFC-11 on horizontal integral-fin tubes. Eight tubes with trapezoidally shaped integral fin density from 738fpm to 1654fpm and 10, 30 grooves are tested. The liquid retention angles are measured by the height gauge, and each tube is tested under static(non-condensing) condition (CFC-11, water) and under dynamic(condensing) condition (CFC-11). The analytical model predicts the amount of liquid retention on a horizontal integral-fin tubes within＋10 percent over most of the data. Average retention angle increases as both surface tension-to-density ratio($\sigma/\rho$) and fin density(fpm) increase, The tube having a fin density of 1299~1654fpm has the best heat transfer performance. The amount of surface flooding must keep below of 40 percent for best heat transfer performance at condensation. The tube having low number of fin density must be used for fluids having high values of $\sigma/\rho$(water, (TEX)$NH_3$, ect.) and the tube having high number of fin density must be used for the fluid having low values of $\sigma/\rho$(R-11, R-22, etc.)

• Geomechanics and Engineering
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• 제25권2호
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• pp.75-87
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• 2021

Because the hydraulic/mechanical behaviour of unsaturated soil is more complicated than that of saturated soil, one of the most important issues in modelling unsaturated soil is to properly couple its stress-strain relationship with its water retention characteristics. Based on the results of a series of tests, the stress-strain relationship and the changes in suction and saturation of unsaturated completely decomposed granite (CDG, also called Masado) vary substantially under different loading/hydraulic conditions. To precisely model the hydraulic/mechanical behaviour of unsaturated Masado, in this study, the superloading concept was firstly introduced into an existing saturated/unsaturated constitutive model to consider the structural influences. Then a water retention curve (WRC) model considering the volumetric change in the soil, in which the skeleton and scanning curves of the water retention characteristics were assumed to shift in parallel in accordance with the change in the void ratio, was proposed. The proposed WRC model was incorporated into the constitutive model, and the validity of the newly proposed model was verified using the results of tests conducted on unsaturated Masado, including water retention, oedometer and triaxial tests. The accuracy of the proposed model in describing the stress-strain relationship and the variations in suction and saturation of unsaturated Masado is satisfactory.

• Journal of Korean Society for Atmospheric Environment
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• 제14권2호
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• pp.107-116
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• 1998

Coal gasification fuel has generally a lower calorific values than natural gas and also contains ammonia which is a main source of fuel NOx. Such a fuel is in need of the advanced technologies for the NOx reduction with higher combustion efficiency. Therefore fuel staged combustion was investigated for the fuel NOx control using a bench scale gas combustoi for the fuel NOx control. Parametric screening studies were performed with the variation of air ratio, retention length and reburning fuel. The NOx reduction efficiency was increased with an increase of total air ratio having optimum reburning air ratio differently, The Increased retention length of the reburning zone was preferable for NOx reduction. Hydrocarbonic reburning fuels like propane and butane were more effective for the NOx reduction efficiency than hydrogen fuel. The NOx concentration at exit was linearly increased according to the fuel-N the fuel.