• Asian-Australasian Journal of Animal Sciences
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• v.1 no.2
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• pp.73-79
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• 1988

Experiments were conducted to determine whether supplemental cobalt (Co) or nickel (Ni) would prevent the signs of zinc (Zn) deficiency in chicks fed a high calcium (1.5%) corn-soybean diet and to examine the difference in $^{65}Zn$ absorption rates between inbred Ancona and crossbred New Hampshire X Single Comb White Leghorn chicks. In the initial experiment, the supplementation of 27 ppm Ni, 27 ppm Co or 54 ppm Co to a basal diet increased weight gain and reduced feather defects; 54 ppm Ni tended to increase weight gain but did not reduce feather defects. In further experiments, chicks fed the diet supplemented with 54 ppm Co usually showed increased weight gain and reduced feather defects; however, chicks fed a diet supplemented with 54 ppm Ni less frequently showed these effects. In another test, Ancona chicks fed a diet supplemented with 30 ppm Zn (except during a $^{65}Zn$ absorption study period) showed lower weight gain, more feather defects and less $^{65}Zn$ absorption than did New Hampshire X Leghorn cross chicks. Similar results were achieved with two strains of chicks fed the basal and 54 ppm Ni, 54 ppm Co or 60 ppm Zn supplemented diets. The sparing effects of Co on Zn which were commonly observed and the lesser effect of Ni or Zn were shown to be, at least in part, the result of increased availability of dietary Zn. That Ancona chicks required more Zn than New Hampshire cross chicks for the development of feathers and for growth is partly the result of decreased Zn absorption from the type of diets fed.

• Journal of architectural history
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• v.20 no.1
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• pp.23-39
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• 2011

The Sungnyemun roofing tiles were twice disassembled for maintenance work, in 1963 and 1997, and modern tiles were applied in 1997. However, besides differing in visual appearance, the modern tiles had distinctly different physical properties. A study has been carried out on 22 different tiles, including original Sungnyemun tiles, modern tiles applied during maintenance, traditional tiles made by tile-makers, and others, to examine their physical properties, such as bending strength, frost resistance, absorption, whole-rock magnetic susceptibility, chromaticity, differential thermal analysis, and other characteristics. Since the method of making modern tiles involves compressing clay in a vacuum, modern tiles showed relatively greater bending strength and specific gravity, while Sungnyemun tiles and those made by tile-makers, in comparison, demonstrated less bending strength and specific gravity owing to their production method of 'treading,' in which clay is mixed by having someone tread upon it repeatedly. Over time, the absorption rate of the original tile used for Sungyemun gradually decreased from 21% to 14.7%; traditional tiles from tile-makers showed absorption rates of 17%, while the absorption rate of modern tiles was just 1%, which is significantly low. As for frost resistance, Sungnyemun tiles and traditional tiles from tile-makers showed cracking and exfoliation after being subjected to testing 4 or 5 times, while slight cracking was seen on the surface for modern tiles after 1ngy, or 3 times. In other words, no significant difference from influence by frost was found. According to the results of differential thermal analysis, the plastic temperature was shown to have been no less than 1, $on^{\circ}C$ for all types of tile, and cristobalite was measuredthrough XRD analysis from a Sungnyemun female tile applied during maintenance in 1963, which appeared to have been plasticized at between $1,200^{\circ}C{\sim}1,300^{\circ}C$. Based on these research results on the physical properties of tiles from the Sungnyemun roof, a fundamental production method for tiles to be applied in the restoration of Sungnyemun has been identified.

• Journal of the Korean Wood Science and Technology
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• v.47 no.3
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• pp.290-298
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• 2019

The sound absorption coefficient and transmission loss of several types of rice hull mats with varying apparent densities and thicknesses are estimated in this paper using the transfer function and matrix methods, respectively, to evaluate the possibility of using rice hull as an acoustic construction material. The mean sound absorption rates of 10-cm-thick rice hull mats with target densities of $0.10g/cm^3$, $0.12g/cm^3$, and $0.14g/cm^3$ were 0.91, 0.92, and 0.95, respectively, while those of the 1-cm-thick plywood attached to the back of the rice hulls were 0.90, 0.92, and 0.92, respectively. The means of the sound transmission loss of the 10 cm-thick rice hull mats with the target densities of $0.10g/cm^3$, $0.12g/cm^3$, and $0.14g/cm^3$ were 7.66 dB, 10.49 dB, and 14.14 dB, respectively, while those of the 1 cm-thick plywood attached to the back of the rice hulls were 33.34 dB, 36.72 dB, and 38.95 dB, respectively. In conclusion, a rice hull mat could be used as acoustic construction materials because of its high sound absorption coefficient and sound transmission loss.

• Composites Research
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• v.37 no.2
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• pp.126-131
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• 2024

The moisture absorption rate and structural strength changes of oven-cured composite skin based on closed molds were studied. Moisture absorption was performed on specimens with and without filler applied. The specimens were exposed to moisture for up to 231 days. Tensile and compression tests were conducted with and without filler application. As a result of the test, the moisture absorption rates of the tensile and compressive specimens without filler were 2.4 and 0.3% higher, respectively, than those with the filler applied. The tensile and compressive strengths of the specimen without filler applied were average 305 MPa and 139 MPa, respectively, and the tensile and compressive strengths of the specimen with filler applied were 313 MPa and 166 MPa, respectively, appeared high.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.22 no.12
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• pp.852-858
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• 2010

In an absorption chiller, solution is circulated by a solution pump with an inverter to vary flow rate depending on operating conditions. For optimal operation, the solution level in the high temperature generator should be kept constant. However, a sensor for measuring continuous level is not available because of varying solution concentration. Instead, level switches are used and hence feedforward control associated with limit checking is a common practice. In the study, inverter frequencies are estimated from a dynamic simulation model and pump performance. Designed frequencies are compared with those implemented in real chillers. It was found that the frequencies used in real chillers are larger than those needed in circulation flow rates. It was intended to prevent system shut-off caused by dry-out. However, it is necessary to minimize the excessive frequency setting in order to reduce frequent pump stops and the range of solution level for continuous pump operation.

• Journal of Pharmaceutical Investigation
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• v.23 no.2
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• pp.103-110
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• 1993

Microcapsules(Mc) of cephalexin (CEPH), using Eudragit RS, RL, L, S and polyethylene glycol 1540, were evaluated biopharmaceutically. The area under the curve of CEPH-Eudragit RS/RL Mc administered orally once was larger than that of cephalexin powder twice every 6 hrs. Controlledrelease effectiveness and the absorption rate effectiveness, two important parameters of Vallner's method, of CEPH-Eudragit RS/RL Mc indicate that these Mc can be good sustained-release preparations. And a simple pharmacokinetic model is introduced which allows the gastric emptying and intestinal-transit rates of a drug itself and a solid-state drug contained in Mc. Decreasing $K_r$, without change in $K_a$, showed that the rate-limiting step of absorption moved from absorption step to releasestep.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.10 no.6
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• pp.784-794
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• 1998

The present study has been directed at developing thermal models to investigate the dynamic behavior of a solar cooling system including an absorption chiller, solar collectors, a hot water storage tank, a fan coil unit, and the air-conditioned space. The operation of the system was simulated for 8 hours in two different operation modes. In the mode 1, the system operated without any capacity control.0 the mode 2, an auxiliary boiler supplied heat to the generator if hot water temperature became lower than a certain value. Moreover, the mass flow rate of hot water to the generator was controlled by comparing the instantaneous room air temperature with the design value. The variation of temperature and concentration in the system components and that of heat transfer rates in the system were obtained for both modes of operation. It was found that the room temperature was maintained near the desired value in the mode 2 by supplying auxiliary heat or controlling the mass flow rate of hot water, while the deviation of room temperature was quite great in the mode 2.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.12
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• pp.817-821
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• 2017

As a ZnO varistor is subjected to electrical and environmental stresses, it degrades gradually, which may result in power interruption by short circuit. This study investigates changes in the electrical characteristics of ZnO varistors due to deterioration owing to energy absorption, and determines the optimal parameters for on-line diagnosis of the varistor. Two types of varistors were used for an accelerated aging experiment involving the application of the $8/20{\mu}s$ standard lightning impulse current. The electrical characteristics in terms of the reference voltage, total leakage current, resistive leakage current, and third-harmonic component of the total leakage current were measured, and their change rates were analyzed. The results revealed that the total leakage current increased slightly with an increase in the varistor absorbed energy, while the resistive leakage current and the third-harmonic component increased apparently. Therefore, the third-harmonic component of the total leakage current was proposed as the optimal parameter for on-line monitoring of ZnO varistor conditions.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.967-972
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• 2009

A dynamic model has been developed to investigate the operability of a single and double-effect solar energy assisted parallel type absorption chiller. In the study, main components and fluid transport mechanism were modeled. And solar radiation and the solar collector also were also modeled along with its control design. The model was run for the single mode with solar energy supply only and the solar/gas driving double effect mode. From the simulation results, it was found that the present configuration of the chiller is not capable of regulating solution flow rates according to variable solar energy input. And the issues of the excessive circulation flowrate and the mismatch between available solar power and cooling load discourages the use of the single mode, but the dual use of gas and solar power is recommendable in view of controllability and enhanced COP.

• Computers and Concrete
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• v.19 no.2
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• pp.121-126
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• 2017

This paper presents the effect of aggregate type on high temperature resistance of self-compacting mortars (SCM) produced with normal and lightweight aggregates like expanded perlite and pumice. Silica fume (SF) and fly ash (FA) were used as mineral additives. Totally 13 different mixtures were designed according to the aggregate rates. Mini slump flow, mini V-funnel and viscometer tests were carried out on the fresh mortar. On the other hand, bulk density, porosity, water absorption and high temperature tests were made on the hardened SCM. After being heated to temperatures of 300, 600 and $900^{\circ}C$, respectively, the tensile strength in bending and compressive strength of mortars determined. As a result of the experiments, the increase in the use of lightweight aggregate increased total water absorption and porosity of mortars. It is observed that, the increment in the usage of lightweight aggregate decreased tensile strength in bending and compressive strengths of mortar specimens exposed to high temperatures but the usage of up to 10% expanded perlite in mortar increased the compressive strength of specimens exposed to $300^{\circ}C$.