• Journal of the Korean Chemical Society
• /
• v.44 no.5
• /
• pp.403-409
• /
• 2000

The formation and dissociation rates of $Zn^{2+}$ Complexes with l,4,7,10-tetraaza-13,16-diox-acyclooctadecane-N,N',N",N'"-tetraacetic acid (1), 1,4,7,10-tetraaza-13,16- dioxacyclooctadecane-N,N',N",N'"-tetramethylacetic acid (2), and 1,4,7,10-tetraaza-13,16- dioxacyclooctadecane-N,N',N",N'"-tetrapropionic acid(3) have been measured by stopped-flow and conventional spectrophotometry. Observations were made at 25.0$\pm$0.1 $^{\circ}C$ and at an ionic strength of 0.10 M NaClO$_4$. The formation reactions of $Zn^{2+}$ ion with 1 and 2 took place by the rapid formation of an intermediate complex (ZnH$_3L^+$) in which the $Zn^{2+}$ ion is incompletely coor-dinated. This might then lead to be a final product in the rate-determining step.ln the pH range 4.76-5.76, the diprotonated (H2L2-) form is the kinetically active species despite of its low concentration. The stability con-stants (log$K_{(ZnH$_3$3$L^+$)}$) and specific water-assisted rate constants (koH) of intermediate complexes have been deter-mined from the kinetic data. The dissociation reactions of $Zn^{2+}$ complexes of 1,2, and 3 were investigated with $Cu^{2+}$ ions as a scavenger in acetate buffer. All complexes exhibit acid-independent and acid-catalyzed con-tributions. The effect of buffer and $Cu^{2+}$ concentration on the dissociation rate has also been investigated. The ligand effect on t dissociation rate of $Zn^{2+}$ complexes is discussed in terms of the side-pendant armsand the chelate ring sizes of the ligands.

• Food Science and Preservation
• /
• v.11 no.2
• /
• pp.195-200
• /
• 2004

Microbial lethal value and nutrient retention of sous vide processed spinach were evaluated with mathematical model prediction and experimental trial for different package sizes and pasteurization temperatures. The package size covers 500 g, 1 kg and 2 kg, while the pasteurization temperature includes 80, 90 and 97$^{\circ}C$. The basic process scheme consists of filling blanched spinach into barrier plastic film pouch, sealing under vacuum, pasteurization in hot water with over pressure and final cooling to 3$^{\circ}C$. Pasteurization condition was designed based on attainment of 6 decimal inactivation of Listeria monocytogenes at geometric center of the pouch package by heating cycle, which was determined by general method. Heat penetration property of the package and thermal destruction kinetics were combined to estimate the retention of ascorbic acid and chlorophyll. Smaller packages with shorter pasteurization time gave better nutrient retention, physical and chemical qualities. Larger package size was estimated and confirmed experimentally to give higher pasteurization value at center, lower ascorbic acid and chlorophyll contents caused by longer heat process time. Lower pasteurization temperature with longer process time was predicted to give lower pasteurization value at center and lower ascorbic acid, while chlorophyll content was affected little by the temperature. Experimental trial showed better retention of ascorbic acid and chlorophyll for smaller package and higher pasteurization temperature with shorter heating time. The beneficial effect of smaller package and higher pasteurization temperature was also observed in texture, color retention and drip production.

• Journal of the Korean Magnetics Society
• /
• v.22 no.3
• /
• pp.85-90
• /
• 2012

Oxidation of the $Nd_2Fe_{14}B$ compound crystal and its effect on the coercivity of the fine $Nd_2Fe_{14}B$ crystal particles were investigated. Oxidation kinetics of the $Nd_2Fe_{14}B$ compound crystal was investigated using an excessively grown $Nd_2Fe_{14}B$ grains in the $Nd_{15}Fe_{77}B_8$ alloy ingot. Oxidation of the $Nd_2Fe_{14}B$ compound crystal occurred by dissociation of the phase into multi-phase mixture of ${\alpha}$-Fe, $Fe_3B$, and Nd oxides. Oxidation rate of the $Nd_2Fe_{14}B$ compound crystal showed no dependence on the crystallographic direction. The oxidation reaction was modeled according to simple linear relationship. Activation energy for the oxidation of $Nd_2Fe_{14}B$ compound crystal was calculated to be approximately 26.8 kJ/mol. Fine $Nd_2Fe_{14}B$ crystal particles in near single domain size was prepared by ball milling of the HDDR-treated $Nd_{15}Fe_{77}B_8$ alloy, and these particles were used for investigating the effect of oxidation on the coercvity. The near single domain size $Nd_2Fe_{14}B$ crystal particles (${\fallingdotseq}0.3\;{\mu}m$) had high coercivity over 9 kOe. However, the coercivity was radically reduced as the temperature increased in air (<2 kOe at $200^{\circ}C$). This radical coercivity reduction was attributed to the soft magnetic phases, ${\alpha}$-Fe and $Fe_3B$, which were formed on the surface of the fine particles due to the oxidation.

• Journal of Veterinary Clinics
• /
• v.18 no.3
• /
• pp.195-200
• /
• 2001

Metabolism and phamacokinetics of albendazole have been studied in Korean native cattle after oral administration of 5 mg/kg of albendazole. As ABZ is known to be rapidly biotransformed to many metabolites in most animal species, it is very imperative to establish the analytical conditions for its metabolites. LC/MS methods for ABZSO and ABZS $O_2$met every requirement enough to study the metabolism of pharmacokinetics of albendazole in Korean native cattle. The parent drug (ABZ) was only measured at first two time points of 0.5 h and 1h, whereas two metabolites were consistently formed between 0.5 h to 48-72 h post-treatment. Formation kinetics for ABZSO and ABZS $O_2$were similar. Time to peak concentration (Tmax) of ABZ-SO appeared at 12h post-treatment of ABZ, faster than that of ABZS $O_2$at 24h. Cmax of ABZS $O_2$(1.05$\pm$0.05 ug/ml) was 1.09 times higher than that of ABZSO (0.96$\pm$0.15). Elimination half-life of ABZS $O_2$(4.2 h) was much shorter than ABZS $O_2$(7.0h) (p<0.005). ABZSO was detected until 48h post-administration but ABZS $O_2$was measurable even at 72h post-dosing. AU $C_{0longrightarrow{\infty}}$ of ABZSO was smaller than that of ABZS $O_2$. Regimen of ABZ is advised to take into consideration is metabolite profiles, especially that of ABZSO, an active metabolite.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2003.05a
• /
• pp.91-93
• /
• 2003

A comprehensive numerical study is carried out to investigate for the understanding of the flow evolution and flame development in a supersonic combustor with normal injection of ncumally injecting hydrogen in airsupersonic flows. The formulation treats the complete conservation equations of mass, momentum, energy, and species concentration for a multi-component chemically reacting system. For the numerical simulation of supersonic combustion, multi-species Navier-Stokes equations and detailed chemistry of H2-Air is considered. It also accommodates a finite-rate chemical kinetics mechanism of hydrogen-air combustion GRI-Mech. 2.11[1], which consists of nine species and twenty-five reaction steps. Turbulence closure is achieved by means of a k-two-equation model (2). The governing equations are spatially discretized using a finite-volume approach, and temporally integrated by means of a second-order accurate implicit scheme (3-5).The supersonic combustor consists of a flat channel of 10 cm height and a fuel-injection slit of 0.1 cm width located at 10 cm downstream of the inlet. A cavity of 5 cm height and 20 cm width is installed at 15 cm downstream of the injection slit. A total of 936160 grids are used for the main-combustor flow passage, and 159161 grids for the cavity. The grids are clustered in the flow direction near the fuel injector and cavity, as well as in the vertical direction near the bottom wall. The no-slip and adiabatic conditions are assumed throughout the entire wall boundary. As a specific example, the inflow Mach number is assumed to be 3, and the temperature and pressure are 600 K and 0.1 MPa, respectively. Gaseous hydrogen at a temperature of 151.5 K is injected normal to the wall from a choked injector.A series of calculations were carried out by varying the fuel injection pressure from 0.5 to 1.5MPa. This amounts to changing the fuel mass flow rate or the overall equivalence ratio for different operating regimes. Figure 1 shows the instantaneous temperature fields in the supersonic combustor at four different conditions. The dark blue region represents the hot burned gases. At the fuel injection pressure of 0.5 MPa, the flame is stably anchored, but the flow field exhibits a high-amplitude oscillation. At the fuel injection pressure of 1.0 MPa, the Mach reflection occurs ahead of the injector. The interaction between the incoming air and the injection flow becomes much more complex, and the fuel/air mixing is strongly enhanced. The Mach reflection oscillates and results in a strong fluctuation in the combustor wall pressure. At the fuel injection pressure of 1.5MPa, the flow inside the combustor becomes nearly choked and the Mach reflection is displaced forward. The leading shock wave moves slowly toward the inlet, and eventually causes the combustor-upstart due to the thermal choking. The cavity appears to play a secondary role in driving the flow unsteadiness, in spite of its influence on the fuel/air mixing and flame evolution. Further investigation is necessary on this issue. The present study features detailed resolution of the flow and flame dynamics in the combustor, which was not typically available in most of the previous works. In particular, the oscillatory flow characteristics are captured at a scale sufficient to identify the underlying physical mechanisms. Much of the flow unsteadiness is not related to the cavity, but rather to the intrinsic unsteadiness in the flowfield, as also shown experimentally by Ben-Yakar et al. [6], The interactions between the unsteady flow and flame evolution may cause a large excursion of flow oscillation. The work appears to be the first of its kind in the numerical study of combustion oscillations in a supersonic combustor, although a similar phenomenon was previously reported experimentally. A more comprehensive discussion will be given in the final paper presented at the colloquium.

• Tuberculosis and Respiratory Diseases
• /
• v.45 no.4
• /
• pp.835-845
• /
• 1998

Background: Silica-induced lung diseases is characterized by the accumulation of inflammatory cells at early stage and fibrosis in pulmonary parenchyma and interstitium at late stage. As a consequence of inflammation, silicosis is accompanied with the expansion of interstitial collagen and the formation of fibrotic nodule. In this process, several kinds of lung cells produce cytokines which can amplify and modulate pulmonary fibrosis. The alveolar macrophage is a potent source of proflammatory cytokines and growth factor. But in the process of silicotic inflammation and fibrosis, there are many changes of the kinetics in cytokine network. And the sources of cytokines in each phase are not well known. Method: 2.5 mg of silica was instillated into the lung of C57BL/6J mice. After intratracheal instillation of silica, the lungs were removed for imunohistochemical stain at 1, 2, 7 day, 2, 4, 8, 12 week, respectively. We investigated the expression of IL-1$\beta$, IL-6, TNF-$\alpha$ and TGF-$\beta$ in lung tissue. Results: 1) The expression of IL-6 increased from 1 day after exposure to 8 weeks in vascular endothelium. Also peribronchial area were stained for IL-6 from 7 days and reached the peak level for 4 weeks. 2) The IL-1 $\beta$ was expressed weakly at the alveolar and peribronchial area through 12 weeks. 3) The TNF-$\alpha$ expressed strongly at alveolar and bronchial epithelia during early stage and maintained for 12 weeks. 4) TGF-$\beta$ was expressed strongly at bronchial epithelia and peribronchial area after 1 week and the strongest at 8 weeks. Conclusion: The results above suggests IL-6, TNF-$\alpha$ appear to be a early inflammatory response in silica induced lung fibrosis and TGF-$\beta$ play a major role in the maintenance and modulation of fibrosis in lung tissue. And the regulation of TNF-$\alpha$ production will be a key role in modultion of silica-induced fibrosis.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.26 no.12
• /
• pp.605-619
• /
• 2014

This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering during 2013. It is intended to understand the status of current research in the areas of heating, cooling, ventilation, sanitation, and indoor environments of buildings and plant facilities. Conclusions are as follows. (1) The research works on the thermal and fluid engineering have been reviewed as groups of fluid machinery, pipes and relative parts including orifices, dampers and ducts, fuel cells and power plants, cooling and air-conditioning, heat and mass transfer, two phase flow, and the flow around buildings and structures. Research issues dealing with home appliances, flows around buildings, nuclear power plant, and manufacturing processes are newly added in thermal and fluid engineering research area. (2) Research works on heat transfer area have been reviewed in the categories of heat transfer characteristics, pool boiling and condensing heat transfer and industrial heat exchangers. Researches on heat transfer characteristics included the results for general analytical model for desiccant wheels, the effects of water absorption on the thermal conductivity of insulation materials, thermal properties of Octadecane/xGnP shape-stabilized phase change materials and $CO_2$ and $CO_2$-Hydrate mixture, effect of ground source heat pump system, the heat flux meter location for the performance test of a refrigerator vacuum insulation panel, a parallel flow evaporator for a heat pump dryer, the condensation risk assessment of vacuum multi-layer glass and triple glass, optimization of a forced convection type PCM refrigeration module, surface temperature sensor using fluorescent nanoporous thin film. In the area of pool boiling and condensing heat transfer, researches on ammonia inside horizontal smooth small tube, R1234yf on various enhanced surfaces, HFC32/HFC152a on a plain surface, spray cooling up to critical heat flux on a low-fin enhanced surface were actively carried out. In the area of industrial heat exchangers, researches on a fin tube type adsorber, the mass-transfer kinetics of a fin-tube-type adsorption bed, fin-and-tube heat exchangers having sine wave fins and oval tubes, louvered fin heat exchanger were performed. (3) In the field of refrigeration, studies are categorized into three groups namely refrigeration cycle, refrigerant and modeling and control. In the category of refrigeration cycle, studies were focused on the enhancement or optimization of experimental or commercial systems including a R410a VRF(Various Refrigerant Flow) heat pump, a R134a 2-stage screw heat pump and a R134a double-heat source automotive air-conditioner system. In the category of refrigerant, studies were carried out for the application of alternative refrigerants or refrigeration technologies including $CO_2$ water heaters, a R1234yf automotive air-conditioner, a R436b water cooler and a thermoelectric refrigerator. In the category of modeling and control, theoretical and experimental studies were carried out to predict the performance of various thermal and control systems including the long-term energy analysis of a geo-thermal heat pump system coupled to cast-in-place energy piles, the dynamic simulation of a water heater-coupled hybrid heat pump and the numerical simulation of an integral optimum regulating controller for a system heat pump. (4) In building mechanical system research fields, twenty one studies were conducted to achieve effective design of the mechanical systems, and also to maximize the energy efficiency of buildings. The topics of the studies included heating and cooling, HVAC system, ventilation, and renewable energies in the buildings. Proposed designs, performance tests using numerical methods and experiments provide useful information and key data which can improve the energy efficiency of the buildings. (5) The field of architectural environment is mostly focused on indoor environment and building energy. The main researches of indoor environment are related to infiltration, ventilation, leak flow and airtightness performance in residential building. The subjects of building energy are worked on energy saving, operation method and optimum operation of building energy systems. The remained studies are related to the special facility such as cleanroom, internet data center and biosafety laboratory. water supply and drain system, defining standard input variables of BIM (Building Information Modeling) for facility management system, estimating capability and providing operation guidelines of subway station as shelter for refuge and evaluation of pollutant emissions from furniture-like products.

• The Journal of Korean Academy of Prosthodontics
• /
• v.49 no.4
• /
• pp.333-340
• /
• 2011

Purpose: The aim of this study was to study the effect of hydroxyapatite (HA) coating crystallinity on the proliferation and differentiation of human osteosarcoma cells. Materials and methods: Surface roughness of the titanium disks increased by anodizing treatment and then HA was coated using ion beam-assisted deposition (IBAD). HA coating was crystallized by heat-treated at different temperature ($100^{\circ}C$, $300^{\circ}C$, $500^{\circ}C$, $800^{\circ}C$). According to the temperature, disks were divided into four groups (HA100, HA300, HA500, HA800). With the temperature, crystallinity of the HA coating was different. Anodized disks were used as control group. The physical properties of the disk surface were evaluated by surface roughness tests, XRD tests and SEM. The effect of the crystallinity of HA coating on HOS cells was studied in proliferation and differentiation. HOS cells were cultured on the disks and evaluated after 1, 3, 5, and 7 days. Growth and differentiation kinetics were subsequently investigated by evaluating cell proliferation and alkaline phosphatase activity. Results: Regardless of the heat-treated temperature, there is no difference on the surface roughness. Crystallinity of the HA was appeared in the groups of HA500, HA800. HOS cells proliferation, ALP activity were higher in HA500 and HA800 group than HA100 and HA300. Conclusion: Within the results of this limited study, heat treatment at $500^{\circ}C$ of HA coating produced by IBAD has shown greater effect on proliferation and differentiation of HOS cells. It is considered that further in vivo study will be necessary.

• Korean Chemical Engineering Research
• /
• v.48 no.2
• /
• pp.259-267
• /
• 2010

The catalytic wet oxidations of the wastewater containing azo dye Reactive Black 5(RB5) with heterogeneous catalyst of CuO have been carried out to investigate the effects of temperature($190{\sim}230^{\circ}C$) and catalyst concentration(0.00~0.20 g/l) on the removals of colour and total organic carbon TOC. The wastewater colour was measured with spectrophotometer, and the oxidation rate was estimated with TOC. About 90% of colour was removed during 120 min in thermal degradation of the RB5 wastewater at $230^{\circ}C$, while TOC was not removed at all. As increasing reaction temperature and catalyst concentration, the removal rates of colour and TOC increased in the catalytic wet oxidations of RB5 wastewater. The effects of catalyst were already considerable even at 0.01 g CuO/l, while the removal rates of colour and TOC increased negligibly with increasing the catalyst concentration above 0.05 g CuO/l. The initial destruction rates of the wastewater colour have shown the first-order kinetics with respect to the wastewater colour. TOC changes during catalytic wet oxidations have been well described with the global model, in which the easily degradable TOC was distinguished from non-degradable TOC of the wastewater. The impacts of reaction temperature on the destruction rate of the wastewater colour and TOC could be described with Arrhenius relationship. Activation energies of the colour removal reaction in thermal degradation, wet oxidation, and catalytic wet oxidation(0.20 g CuO/l) of the RB5 wastewater were 108.4, 78.3 and 74.1 kJ/mol, respectively. The selectivity of wastewater TOC into the non-degradable intermediates relative to the end products in the catalytic wet oxidations of RB5 wastewater was higher compared to that in phenol wet oxidations.

• Restorative Dentistry and Endodontics
• /
• v.24 no.2
• /
• pp.265-285
• /
• 1999

The purposes of this investigation were to observe the reaction kinetics of five commercial dual cured resin cements (Bistite, Dual, Scotchbond, Duolink and Duo) when cured under varying thicknesses of porcelain inlays by chemical or light activation and to evaluate the effect of the porcelain disc on the rate of polymerization of dual cured resin cement during light exposure by using thermal analysis. Thermogravimetric analysis(TGA) was used to evaluate the weight change as a function of temperature during a thermal program from $25{\sim}800^{\circ}C$ at rate of $10^{\circ}C$/min and to measure inorganic filler weight %. Differential scanning calorimetry(DSC) was used to evaluate the heat of cure(${\Delta}H$), maximum rate of heat output and peak heat flow time in dual cured resin cement systems when the polymerization reaction occured by chemical cure only or by light exposure through 0mm, 1mm, 2mm and 4mm thickness of porcelain discs. In 4mm thickness of porcelain disc, the exposure time was varied from 40s to 60s to investigate the effect of the exposure time on polymerization reaction. To investigate the effect on the setting of dual cured resin cements of absorption of polymerizing light by porcelain materials used as inlays and onlays, the change of the intensity of the light attenuated by 1mm, 2mm and 4mm thickness of porcelain discs was measured using curing radiometer. The results were as follows 1. The heat of cure of resin cements was 34~60J/gm and significant differences were observed between brands (P<0.001). Inverse relationship was present between the heat of reaction and filler weight % the heat of cure decreased with increasing filler content (R=-0.967). The heat of reaction by light cure was greater than by chemical cure in Bistite, Scotchbond and Duolink(P<0.05), but there was no statistically significant difference in Dual and Duo(P>0.05). 2. The polymerization rate of chemical cure and light cure of five commercially available dual cured resin cements was found to vary greatly with brand. Setting time based on peak heat flow time was shortest in Duo during chemical cure, and shortest in Dual during light cure. Cure speed by light exposure was 5~20 times faster than by chemical cure in dual cured resin cements. The dual cured resin cements differed markedly in the ratio of light and chemical activated catalysts. 3. The peak heat flow time increased by 1.51, 1.87, and 3.24 times as light cure was done through 1mm, 2mm and 4mm thick porcelain discs. Exposure times recommended by the manufacturers were insufficient to compensate for the attenuation of light by the 4mm thick porcelain disc. 4. A strong inverse relationship was observed between peak heat flow and peak time in chemical cure(R=0.951), and a strong positive correlations hip was observed between peak heat flow and the heat of cure in light cure(R=0.928). There was no correlationship present between filler weight % or heat of cure and peak time. 5. The thermal decomposition of resin cements occured primarily between $300^{\circ}C$ and $480^{\circ}C$ with maximum decomposition rates at $335^{\circ}C$ and $440^{\circ}C$.