• International Journal of Air-Conditioning and Refrigeration
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• v.14 no.4
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• pp.131-137
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• 2006

The absorber in which heat and mass transfer phenomena occur simultaneously is one of the most critical components in the absorption system. It has the most significant influence on the performance and the size of the absorption system. During the absorption process, heat and mass transfer resistances exist in both liquid and vapor regions, so that the heat transfer mode should be carefully selected to reduce them. The objective of this paper is to review the previous papers analysing mathematical models of simultaneous heat and mass transfer phenomena during the absorption process. The most conventional working fluids ($H_2O$LiBr and $NH_3/H_2O$) are considered and the most common absorption modes (falling film and bubble mode) are dealt with in this review.

• Journal of Industrial Technology
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• v.41 no.1
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• pp.15-20
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• 2021

This work proposes a simple method to use the added absorption per person values to predict the expected values of the acoustical conditions in occupied classrooms. This method is based on the effects of the values of added absorption per person on the unoccupied total absorption values of the classrooms and on other room acoustical parameters. The total sound absorption in an unoccupied classroom can be calculated from measured reverberation times in the classroom. The expected occupied absorption can be calculated using equation which was obtained in a previous study (Choi, 2017) by fitting a linear regression line to a plot of total occupied absorption versus the corresponding unoccupied total absorption values measured in 12 university classrooms. The ratios of occupied-to-unoccupied sound absorption are used to predict increments in the values of acoustical parameters that result when occupants are added to the rooms.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.48 no.3
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• pp.30-36
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• 2016

This study was conducted to investigate the influence of the changes in handsheet structure by beating, wet pressing and the addition of wood flour spacer on the water absorption and the moisture absorption properties. The higher beating treatment of BKP resulted in the denser structure of handsheet samples, which leaded to the lower water and moisture absorption. The wet pressing showed the similar effects by reducing the bulk of handsheets. In case of the handsheet samples with similar bulk structure made of different beaten pulps, the severer beating treatment increased the water absorption and the moisture absorption. The addition of the wood flour spacer resulted in the higher bulk following the higher water and moisture adsorption. Since the water and the moisture absorption properties of paper products could greatly affect on not only the product quality but also the process runnability, the control of the water response of paper product has been considered as very important technology. The results of this study might be useful for control of water and moisture absorption properties of paper products.

• Journal of the Korean Society of Safety
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• v.18 no.4
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• pp.92-97
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• 2003

The purpose of this study is heavy metal absorption of recycled PET(poly ethylene terephatalate) NWF(non woven faric). The results of test are summarized as follows; Heavy metal abworption rates in Ni ions were higher then Zn and Cu ions, whereas heavy metal absorption rates by sulfonation times were not different. The heavy metal absorption times have a higher tendency from 60 min to 120 min. There were significant negative correlations among the amount used CSA(Chloro Sulfuric Acid) and the amount of absorption Zn(r = -0.33784, p < 0.05), Cu(r = -0.61177, p < 0.01) ions, whereas correlations between heavy metal absorption rates and sulfonation times were not significant. There were significant positive correlations among the amount of absorption Zn ions and the amount of absorption Ni(r = 96475, p < 0.014), Cu(r = 0.51614, p < 0.01) ions, likewise the positive correlations between the amount of absorption N ions and the amount of absorption Cu(r = 0.54766) ions were significant(p < 0.01).

• Korean Journal of Materials Research
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• v.27 no.8
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• pp.451-458
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• 2017

The service life of coal gangue concrete(CGC) strongly depends on the capillary water absorption, this water absorption is susceptible to freeze-thaw cycles. In this paper, the cumulative water absorption and sorptivity were obtained to study the effects of 0, 0.5, 1.0, and 1.5 % steel fiber volume fraction added on the water absorption of CGC. Sorptivity and freeze-thaw tests were conducted, and the capillary water absorption was evaluated by the rate of water absorption(sorptivity). Three prediction models for the initial sorptivity of steel fiber reinforced coal gangue concrete(SFRCGC) under freeze-thaw cycles were established to evaluate the capillary water absorption of SFRCGC. Results showed that, without freeze-thaw cycles, the water absorption of CGC decreased when steel fiber at 1.0 % volume fraction was added, however, the water absorption increased with the addition of 0.5 or 1.5 % steel fibers. Once the SFRCGC specimens were exposed to freeze-thaw cycles, the water absorption of SFRCGC significantly increased, and 1.0 % steel fiber in volume fraction added to CGC caused the lowest water absorption, except for the case of the sample without steel fibers added. The CGC with steel fiber at 1.0 % volume fraction performed better. The SFRCGC has a strong response to freeze-thaw cycles. Results also showed that the linear function prediction model is practical in the field of engineering because of its simple form and a relatively high precision. Although the polynomial prediction model presents the highest computation precision among the three models, the complicated form and too many coefficients make it impractical for engineering applications.

• Advances in aircraft and spacecraft science
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• v.5 no.4
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• pp.499-513
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• 2018

One of the major problems in glass fiber reinforced epoxy (GFRE) composite pipes is the durability under water absorption. This condition is generally recognized to cause degradations in strength and mechanical properties. Therefore, there is a need for an intelligent system for detecting the absorption rate and computing the mass of water absorption (M%) as a function of absorption time (t). The present work represents a new non-destructive evaluation (NDE) technique for detecting the water absorption rate by evaluating the dielectric properties of glass fiber and epoxy resin composite pipes subjected to internal hydrostatic pressure at room temperature. The variation in the dielectric signatures is employed to design an electrical capacitance sensor (ECS) with high sensitivity to detect such defects. ECS consists of twelve electrodes mounted on the outer surface of the pipe. Radius-electrode ratio is defined as the ratio of inner and outer radius of pipe. A finite element (FE) simulation model is developed to measure the capacitance values and node potential distribution of ECS electrodes on the basis of water absorption rate in the pipe material as a function of absorption time. The arrangements for positioning12-electrode sensor parameters such as capacitance, capacitance change and change rate of capacitance are analyzed by ANSYS and MATLAB to plot the mass of water absorption curve against absorption time (t). An analytical model based on a Fickian diffusion model is conducted to predict the saturation level of water absorption ($M_S$) from the obtained mass of water absorption curve. The FE results are in excellent agreement with the analytical results and experimental results available in the literature, thus, validating the accuracy and reliability of the proposed expert system.

• Journal of Environmental Science International
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• v.20 no.4
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• pp.501-509
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• 2011

Unlike many laboratory-scale studies on absorption of organic compounds (VOCs), limited pilot-scale studies have been reported. Accordingly, the present study was carried out to examine operation parameters for the effective control of a hydrophilic VOC (methyl ethyl ketone, MEK) by applying a circular pilot-scale packed-absorption system (inside diameter 37 cm ${\times}$ height 167 cm). The absorption efficiencies of MEK were investigated for three major operation parameters: input concentration, water flow rate, and ratio of gas flow-rate to washing water amount (water-to-gas ratio). The experimental set-up comprised of the flow control system, generation system, recirculation system, packed-absorption system, and outlet system. For three MEK input concentrations (300, 350, and 750 ppm), absorption efficiencies approached near 95% and then, decreased gradually as the operation time increased, thereby suggesting a non-steady state condition. Under these conditions, higher absorption efficiencies were shown for lower input concentration conditions, which were consistent with those of laboratory-scale studies. However, a steady state condition occurred for two input concentration conditions (100 and 200 ppm), and the difference in absorption efficiencies between these two conditions were insignificant. As supported by an established gas-liquid absorption theory, a higher water flow rate exhibited a greater absorption efficiency. Moreover, as same with the laboratory-scale studies, the absorption efficiencies increased as water-to-gas ratios increased. Meanwhile, regardless of water flow rates or water-to-gas ratios, as the operation time of the absorption became longer, the pH of water increased, but the elevation extent was not substantial (maximum pH difference, 1.1).

• The Korean Journal of Food And Nutrition
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• v.15 no.1
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• pp.7-11
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• 2002

This study was performed to estimate fille zinc absorption, excretion, and balance of preschool children in Pohang and to evaluate the relationship zinc absorption and related variables. To determine the zinc absorption and excretion, duplicate food samples, pooled faces and urine samples were collected for 3 consecutive days in 21 preschool children. The mean fecal and urine excretions were 7.03mg/day and 0.16mg/day far the boys and 5.87mg/day and 0.15mg/day for the girls. Analyzed daily mean zinc intake was 10.45mg/day for the boys and 7.80mg/day for the girls. The mean ,apparent absorption rate and balance were 29.7% and 3.25mg for the boys and 23.3%, 1.78mg for the girls. Although the mean apparent absorption rate and balance of boys tended to be higher, there was no significant difference between boys and girls. In this study, subjects showed the positive balance except one. Fecal zinc loss reflected dietary zinc (p < 0.01), but urinary zinc loss was unaffected by zinc intake. There was a positive relationship between zinc apparent absorption and zinc balance (p<0.01). These results show that the zinc absorption and balance were favorable.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.683-686
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• 2007

This paper investigates acoustical characteristics of open-type ceilings using 1:25 scale model. The field survey in the existing 15 halls was carried out to figure out the ceiling structure. The components of the open-type ceiling were mainly steel truss structures, duct, catwalk and finishing surfaces. In order to investigate the absorption characteristics of the equipped ceiling, the absorption coefficient measurements were made using 1:25 reverberation chamber based on ISO 354. Results showed that the absorption coefficient of the empty ceiling structure (6m-height) with 50%-perforated covering plate was 0.2-0.3 at above 500 Hz. When steel structure was added inside the empty ceiling, absorption coefficient increased by 0.16 at 250-1kHz. Adding catwalk did not increase the absorption, but adding duct increased the absorption at 1-2kHz. NRC of the equipped ceiling was 0.39, and the absorption characteristics were mainly found at high frequencies. In addition, the opening size of the covering plate did not change the absorption coefficient of the equipped ceiling meaningfully.

• Journal of the Korean Wood Science and Technology
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• v.18 no.2
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• pp.36-48
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• 1990

This experiment was carried out to improve the quality of high absorbent polymer which has excellent absorptivity and water retention compared to pulp and absorption sheet, through absorption characteristics-absorptive power, water retention, absorption rate, gel strength, pH, particle size, and moisture content. - of six polymers, namely, anionic polyacrylamide, cationic polyacrylamide, polyacrylic, acid polyvinyle alcohol 500, and 1500, and a-cellulose. and to examine the possibility of substitution of amide groups for carboxyl group and/or hydroxyl group which were commercial high absorbent polymer by comparing the absorption characteristics of the polymers. Polyacrylamide has high absorptive power and water retention, but has low gel strength and poor absorption rate. The rest of polymers were similiar to ${\alpha}$-cellulose in every respect. Thus, polyacrylamides could be replaced with polyacrylic acid and polyvinyl alcohol which are presently a high absorbent polymers. In comparing the absorption characteristics and the absorptive power of the polymers-anionic polyacrylamide, cationic polyacrylamide, polyacrylic acid, polyvinyle alcohol. a-cellulose-the absorptive power was in inverse proportion to the gel strength and absorption rates, affected by the particle size and pH change.