• Journal of the Korean Mathematical Society
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• v.44 no.2
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• pp.275-296
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• 2007

We study the self-duality operator on conic 4-manifolds. The self-duality operator can be identified as a regular singular operator in the sense of $Br\"{u}ning$ and Seeley, based on which we construct its parametrizations and closed extensions. We also compute the indexes.

• Journal of Radiation Protection and Research
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• v.15 no.2
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• pp.57-65
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• 1990

Newly developed LiF(Mg, Cu, Na, Si) thermoluminescence phosphors sealed in a plastic capsules (32mm dia., 0.9mm wall thickness) were used for in-phantom dosimetry of $^{60}Co$ $\gamma$-irradiation. The absorbed doses in water were determined by applying the general cavity theory to the absorbed dose in TLD cavity, which was computed from exposure. The absorbed doses at various sites in the water-phantom were measured by LiF(Mg, Cu, Na, Si) TLD and compared with doses obtained by the ionization method. Both results were consistent within the experimental fluctuation$({\pm}3%)$ Central axis percentage depth doses and phantom-air ratios measured by LiF(Mg. Cu, Na, Si) TLD showed good agreement with the published values[Br. J. Radiology, Suppl. 17(1983)].

• Bulletin of the Korean Chemical Society
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• v.31 no.5
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• pp.1349-1354
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• 2010

The geometries and isomerization of the alkylidene silylenoid $H_2C$ = SiLiF as well as its insertion reactions with R-H (R = F, OH, $NH_2$) have been systematically investigated at the B3LYP/6-311+$G^*$ level of theory. The potential barriers of the three insertion reactions are 97.5, 103.3, and 126.1 kJ/mol, respectively. Here, all the mechanisms of the three reactions are identical to each other, i.e., an intermediate has been formed first during the insertion reaction. Then, the intermediate could dissociate into the substituted silylene ($H_2C$ = SiHR) and LiF with a barrier corresponding to their respective dissociation energies. Correspondingly, the reaction energies for the three reactions are -36.4, -24.3, and 3.7 kJ/mol, respectively. Compared with the insertion reaction of $H_2C$ = Si: and R-H (R = F, OH and $NH_2$), the introduction of LiF makes the insertion reaction occur more easily. Furthermore, the effects of halogen (F, Cl, Br) substitution and inorganic salts employed on the reaction activity have also been discussed. As a result, the relative reactivity among the three insertion reactions should be as follows: H-F > H-OH > H-$NH_2$.

• Journal of Sericultural and Entomological Science
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• v.33 no.2
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• pp.87-92
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• 1991

The shrinkages and physical properties of silk yarn were studied on the effect of treatment concentration, time and temperature with various neutral salts. The degummed silk yarn was shrunk about 35 percent by highly concentrated solution of Ca(NO3)2 on conditions of S.G.(special gravity) 1.45 at 9$0^{\circ}C$ or S. G. 1.46 at 8$0^{\circ}C$. About 40 percent of silk yarn was contracted in length by the treatment of CaCl2 solution on conditions of S. G. 1.33 at 9$0^{\circ}C$ for 5 mins. or at 85$^{\circ}C$ for 10 mins. By treating the concentrated solution of LiBr the silk yarn showed about 40 percent of shrinkage on a conditions of S. G. 1.38, $25^{\circ}C$ 24hrs. The physical properties of salt-treated silk yarn could be significantly changed with shrinkage variations. There were some differences in shrinkages between different type of salts. However, it was observed that generally the tenacity was decreased and breaking elongation increased as the shrinkage increased. The bulkiness of salt-treated silk yarn was increased by 110 to 120 percent compared with untreated yarn.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.272-278
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• 2009

The characteristics of hybrid type absorption chiller are studied numerically to use a waste hot water effectively. In the case of the full load, the concentration and temperature of LiBr solution are increase about $11^{\circ}C$, 1.3% respectively at the single effect generator by hot water. As a result, the heat of the high temperature generator are decrease, so the energy can be saved. As the partial load decreased the consumption ratio of fuels are decreased and the reduction ratio of fuels are increased. The variation of COP with the inlet temperature of hot water is higher than that of the flow rate of hot water. The effect of mean temperature difference with solution and hot water of the generator are higher that of flow rate of hot water, it can effect on COP which is sensitive to heat of generator.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.109-114
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• 2008

A dynamic model has been developed to simulate dynamic operation of a real double-effect absorption chiller. Dynamic behavior of working fluids in main components was modeled in first-order nonlinear differential equations based on heat and mass balances. Mass transport mechanisms among the main components were modeled by valve throttling, 'U' tube overflow and solution sub-cooling. The nonlinear dynamic equations coupled with the subroutines to calculate thermodynamic properties of working fluids were solved by a numerical method. The dynamic performance of the model was compared with the test data of a commercial medium chiller. The model showed a good agreement with the test data except for the first 5,000 seconds during which different flow rates of the weak solution caused some discrepancy. It was found that the chiller dynamics is governed by the inlet temperatures of the cooling water and the chilled water when the heat input to the chiller is relatively constant.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.12
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• pp.781-788
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• 2008

A dynamic model has been developed to simulate dynamic operation of a real double-effect absorption chiller. Dynamic behavior of working fluids in main components was modeled in first-order nonlinear differential equations based on heat and mass balances. Mass transport mechanisms among the main components were modeled by valve throttling, 'U' tube overflow and solution sub-cooling. The nonlinear dynamic equations coupled with the subroutines to calculate thermodynamic properties of working fluids were solved by a numerical method. The dynamic performance of the model was compared with the test data of a commercial medium chiller. The model showed a good agreement with the test data except for the first 5,000 seconds during which different flow rates of the weak solution caused some discrepancy. It was found that the chiller dynamics is governed by the inlet temperatures of the cooling water and the chilled water when the heat input to the chiller is relatively constant.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.29 no.7
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• pp.373-384
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• 2017

The objective of this study was to determine the effect of refrigerant heat exchanger on the performance of type II absorption heat pump performance using numerical analysis. Two heat exchange installation methods were used: solution to refrigerant and waste hot water to refrigerant. These methods were compared to the standard model of hot water flow without using refrigerant heat exchanger. When waste hot waters were bypassed to refrigerant heat exchanger, COP was not affected. However, steam mass generation rates were increased compared to those of the standard model. When solutions were bypassed to the refrigerant heat exchanger, results were different depending on the place where the solution rejoined. COP and steam mass generation rates were lower compared to those when waste heat water was passed to refrigerant heat exchanger. Thus, it is possible to obtain higher steam mass generation rates by using waste water and installing refrigerant heat exchanger.

• Solar Energy
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• v.15 no.1
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• pp.29-38
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• 1995

This paper concerns the study of a two-stage binary absorption cycle employing the refrigerant/absorbent combinations of $LiBr/H_2O$ and $NH_3/H_2O$. This cycle consists of coupling two single-effect absorption cycles so that the first stage absorber and condenser produces heating water to evaporate refrigerant in the evaporator of the second stage. The effect of operating variables such as evaporator temperature, condenser and absorber temperature, and generator temperature on the coefficient of performance and temperature lift have been studied for two-stage binary absorption heat pump systems. It is found that this cycle has a large temperature lift at $105^{\circ}C$ of optimum generator temperature to obtain $50^{\circ}C$ of condenser temperature.

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.52-57
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• 2006

This study investigates the distribution stability of binary nanofluids where binary mixtures such as $NH_3/H_2O$ and $H_2O/LiBr$ solution are used as a base fluid. When a little amount of certain nanosized particles is added into a basefluid, the thermal conductivity of that mixture increases greatly. Such mixtures are named 'nanofluids' where nano-particles should be distributed stably and uniformly so the distribution stability of nanoparticles in nanofluids is one of the most important factors for nanofluid application. Therefore, binary nanofluids in which binary mixtures are applied as the basefluids are considered as working fluids. The kind and the concentration of nanoparticles, and the concentration of ammonia are considered as the key parameters. The objectives of this paper are to visualize the dispersed status of particles in binary nanofluids and to find the effect of key parameters on the distribution stability in the ammonia absorption system.