• Korean Journal of Crystallography
• /
• v.4 no.2
• /
• pp.54-62
• /
• 1993

The crystal shnture of dehydrated fully Cd2+-exchanged zeolite A evacuated at 2 × 10-6 Torr and 650℃ (a:12.189(2) A) and of its iodine sorption corrplex (a:12.168(2)A) have been netsmlmn by single uystal x-ray diffraction techliques in the cubic space group hkTn at 21(1)℃. The strutures were refined to final error indices, Ri:0.057 and R2 =0.063 with 186 reflections and Rl:0.082 and R2:0.085 with 181 reflections, respectively, for which 1>3σ(In both structure, six lie at two distinguished threefold axes of unit cell ten the crystal structure of an iodine sorption complex of Cd6-A four Cd2+ ions are recessed 0.69(1) A into the large cavity to complex each with from the (111) plane of 0(3), whereas two Cd2+ ions recessed 0.68(1) A into the sodalite unit Awximately 4.0 l3ions per nit cell are sorbed. Each bridge between a Cd2+ ion and 8-ring oxygens ((I-I-I)= 117(1) ˚ and 0(1)-I(1)-I(2)=172(1)). The near linear I-I-0 angle and its interatomic distance (I-0=3.57(3) A) are indicative of a weak charge transfer interacticn between the frarrework oxygen and iodine. The existence of In3 inside the large cavity indicates that the If ions and H ions may be produced by reaction of In vapor with water molecules which maybe associated with Cd2+ ions in partially dehydrated Cd6-A In3- ions may be produced by the combination of I- and I2.

• Nuclear Engineering and Technology
• /
• v.28 no.1
• /
• pp.1-16
• /
• 1996

In an effort to determine the combined effects of major parameters of heat exchanger tubes on the nucleate pool boiling heat transfer in the scaled in-containment refueling water storage tank (IRWST), a total of 1,966 data for q'quot; versus ${\Delta}T$ has been obtained using various combinations of tube diameters, surface roughness, and tube orientations. The experimental results show that (1) increased surface roughness enhances heat transfer for both horizontal and vertical tubes, (2) the two heat transfer mechanisms, i.e.,enhanced heat transfer for both horizontal and vertical tubes, (2) the two heat transfer mechanisms, i.e., enhanced heat transfer due to liquid agitation by bubbles generated and reduced heat transfer by the formation of large vapor slugs and bubble coalescence are different in two regions of low heat fluxes (q'quot; $\leq$50kW/$m^2)$ and high heat fluxes (q'quot; $\geq$50kW/$m^2)$ depending on the orientation of tubes and the degree of surface roughness, and (3) the heat transfer rate decreases as the tube diameter is increased for both horizontal and vertical tubes, but the effect of tube diameter on the nucleate pool boiling heat transfer for vertical tubes is greater than that for horizontal tubes. Two empirical heat transfer correlations for q'quot;, one for horizontal tubes and the other for vertical tubes, are obtained in terms of surface roughness $({\varepsilon})$ and tube diameter (D). In addition, a simple empirical correlation for nucleate pool boiling heat transfer coefficient $(h_b)$ is obtained as a function of heat flux (q'quot;) only.ucleate pool boiling heat transfer coefficient $(h_b)$ is obtained as a function of heat flux (q'quot;) only.

• Korean Journal of Food Science and Technology
• /
• v.27 no.3
• /
• pp.358-364
• /
• 1995

In order to determine the moisture content level for safe storage of wild vegetables, drying characteristics and water vapor sorption characteristics of four vegetables, i.e., zucchini slice, sweet potato stem, taro stem, and platycodon, were investigated. The drying curves of these vegetables were consisted of three characteristic stages which were the initial settling down period, the constant drying rate period, and the falling drying rate period. And the falling rate period of the vegetables showed 2 or 3 parts of falling rate. All of the falling rate curves of the vegetables showed upwardly convex shape which is known as a characteristic pattern for the drying of fibrous food materials. The critical moisture contents of the vegetables were $8.29{\sim}9.75,\;10.40{\sim}15.08,\;9.51{\sim}14.52\;and\;3.29{\sim}3.56g\;H_2O/g$ dry solids for zucchini slice, sweet potato stem, taro stem, and platycodon, respectively. Activation energy values of drying rate during falling rate period were 2.30, 2.11, 4.97, and 2.80 kcal/mol for zucchini slice, sweet potato stem, taro stem, and platycodon respectively. The BET monolayer moisture contents of the vegetables were $10.05{\sim}13.59,\;9.49{\sim}12.69,\;9.50{\sim}16.48\;and\;5.01{\sim}5.44g\;H_2O/g$ dry solids for zucchini slice, sweet potato stem, taro stem, and platycodon, respectively. And these values were found to be very compatible with the values of the critical moisture content. Consequently, it was found that the moisture of these vegetables should be removed below the BET monolayer moisture content or below the critical moisture content for the long term storage.

• Atmosphere
• /
• v.29 no.5
• /
• pp.511-523
• /
• 2019

A new Korean Meteorological Administration (KMA) airborne measurement platform has been established for regular observations for scientific purpose over South Korea since late 2017. CRDS G-2401m analyzer mounted on the King Air 350HW was used to continuous measurement of CO₂, CH₄ and CO mole fraction. The total uncertainty of measurements was estimated to be 0.07 ppm for CO₂, 0.5 ppb for CH₄, and 4.2 ppb for CO by combination of instrument precision, repeatability test simulated in-flight condition and water vapor correction uncertainty. The airborne vertical profile measurements were performed at a regional Global Atmosphere Watch (GAW) Anmyeon-do (AMY) station that belongs to the Total Carbon Column Observing Network (TCCON) and provides concurrent observations to the Greenhouse Gases Observing Satellite (GOSAT) overpasses. The vertical profile of CO₂ shows clear altitude gradient, while the CH₄ shows non-homogenous pattern in the free troposphere over Anmyeon-do. Vertically averaged CO₂ at the altitude between 1.5 and 8.0km are lower than AMY surface background value about 7 ppm but higher than that observed in free troposphere of western pacific region about 4 ppm, respectively. CH₄ shows lower level than those from ground GAW stations, comparable with flask airborne data that was taken in the western pacific region. Furthermore, this study shows that the combination of CH₄ distribution in free troposphere and trajectory analysis, taking account of convective mixing, is a useful tool in investigating CH₄ transport processes from tropical region to Korean region in winter season.

• Applied Biological Chemistry
• /
• v.21 no.3
• /
• pp.144-149
• /
• 1978

Fermented soy sauce was dehydrated by spray drying to form powder, and moisture sorption properties of powdered soy sauce with or without cover of the flexible films were examined on different relative humidity by using saturated salt solutions at $30^{\circ}$. The results obtained were summarized as follows: The equilibrium moisture content of spray-dried soy sauce containing 18.3% moisture was determined to 52% by graphical interpolation method, and E.M.C. of powdered soy sauce covered with plastic films decreased at low relative humidity whereas sharply increased curves were seen at high relative humidity. The rate constant of moisture adsortion K for the power covered with films were $66.2{\times}10^{-5}\;to\;225{\times}10^{-5}/hr$., and K' became greater when film having higher water vapor transmission rate was used. The shelf-life of powdered soy sauce covered with Al. foil/P.E. film by Brown formula at the accelerated condition of $38^{\circ}$, 92% R. H. was the longest period, 164 days compared with any other films used, and the shortest period, 18 days in P.V.C. film.

• Journal of Korean Society of Environmental Engineers
• /
• v.28 no.3
• /
• pp.249-256
• /
• 2006

Catalytic combustion of toluene was investigated on the Cu-Mn oxide catalysts prepared by the impregnation(Imp) and the deposition-precipitation(DP) methods. The mixing of copper and manganese has been found to enhance the activity of catalysts. It is then found that catalytic efficiency of the Cu-Mn oxide catalyst prepared by the DP method on combustion of toluene is much higher than that of the Cu-Mn oxide catalyst prepared by Imp method with the same chemical composition. The catalyst prepared by the deposition-precipitation method observed no change of toluene conversion at time on stream during 10 days and at the addition of water vapor. On the basis of catalyst characterization data, it has been suggested that the catalysts prepared by the DP method showed uniform distribution and smaller particle size on the surface of catalyst and then enhanced reduction capability of catalysts. Therefore, we think that the DP method leads on progressive capacity of catalyst and promotes stability of catalyst. It was also presumed that catalytic conversion of toluene on the Cu-Mn oxide catalyst depends on redox reaction and $Cu_{1.5}Mn_{1.5}O_4$ spinel phase acts as the major active sites of catalyst.

• Korean Journal of Food Science and Technology
• /
• v.37 no.1
• /
• pp.30-37
• /
• 2005

To mass-produce useful biopolymer films, chitosan/gelatin blend films were prepared by solution casting method. Effects of mixing ratio, tensile strength (TS), elongation (E) at break, total color difference (${\Dalta}E$), opacity, water vapor permeability (WVP), oxygen permeability (OP), and thermal properties on chitosan/gelatin blend films properties were investigated. TS, E, ${\Dalta}E$, opacity, WVP, and OP values were 58.24-22.01 MPa, 13.11-24.67%, 1.86-17.45, 0.3104-1.2161 nmO.D./${\mu}m$, $1.6875-1.7225ng{\cdot}m/m^{2}{\cdot}s{\cdot}Pa$, and $2.2380{\times}10^{-7}-2.2975{\times}10^{-7}\;mL{\cdot}{\mu}m/m^{2}{\cdot}s{\cdot}Pa$, respectively. TS of blend films decreased, while E, ${\Dalta}E$, and opacity increased with increasing chitosan content. WVP of blend films did not show any significant relationship with mixing ratio and thickness of blend films. Miscibility of films was examined over entire composition range by thermogravimetric analyzer (TGA) and dynamic mechanical analyzer (DMA). TGA results showed gelatin is more thermally stable than chitosan and some interactions among functional groups of two biopolymers. Glass transition temperature $(T_{2})$ of films as determined by DMA decreased with increasing content of chitosan in the blend. Results of thermal analysis indicate high miscibility among polymer components in the blend.

• Korean Journal of Food Science and Technology
• /
• v.37 no.1
• /
• pp.142-146
• /
• 2005

Soy protein isolate (SPI) film was laminated with corn zein or wheat gluten to improve functional properties. Both SPI/corn zein-laminated film (Film B) and SPI/wheat gluten-laminated film (Film C) showed increased tensile strength by 150%, compared to control (Film A). Film C showed significant 253% increase in percentage elongation. Water vapor permeability (WVP) of Films B and C decreased slightly compared to Film A. Solubility values of Films B and C were lower than that of Film A. Hunter color values of Films A and C were not significantly different, while Film B showed yellowness due to presence of corn zein. These results suggest SPI/wheat gluten-laminated film is suitable as packaging material.

• Food Science and Preservation
• /
• v.8 no.1
• /
• pp.47-53
• /
• 2001

In order to investigate the effect of two type of ceramic film(15% SiO$_2$ incorporated LDPE, 10% zeolite incorporated LDPE), perforated film and LDPE film on freshness of shiitake mushroom, weight loss, surface color and marketability of mushroom were measured during MA storage at 5 $\^{C}$ and 20$\^{C}$. The effect of packaging films on weight loss and marketability index of shiitake mushroom at 20$\^{C}$ was negligible due to its rapid physiological changes. However, the effect of packaging films on surface color of shiitake mushroom was significant at 20$\^{C}$ storage, but not at 5$\^{C}$ storage. During MA storage of shiitake mushroon, discoloration were reduced effectively by ceramic films and weight loss were by LDPE film, but they had little difference between packaging 51ms. However, there were significant differences among the packaging films in marketability of mushroom induced by water vapor inside package and accelerate its spoilage and browning. Ceramic film(15% SiO$_2$ incorporated LDPE) showed best result to maintain marketability of shiitake mushroom and zeolite incorporated film, perforated film, LDPE film in order.

• Korean Chemical Engineering Research
• /
• v.49 no.6
• /
• pp.857-864
• /
• 2011

Oxy-fuel combustion with many advantages such as high combustion efficiency, low flue gas flow rate and low NOx emission has emerged as a promising CCS technology for coal combustion facilities. In this study, the effects of the direct sulfation reaction on $SO_2$ removal efficiency were evaluated in a drop tube furnace under typical oxy-fuel combustion conditions represented by high concentrations of $CO_2$ and $SO_2$ formed by gas recirculation to control furnace combustion temperature. The effects of the operating parameters including the reaction temperature, $CO_2$ concentration, $SO_2$ concentration, Ca/S ratio and humidity on $SO_2$ removal efficiency were investigated experimentally. $SO_2$ removal efficiency increased with reaction temperature up to 1,200 due to promoted calcination of limestone reagent particles. And $SO_2$ removal efficiency increased with $SO_2$ concentrations and the humidity of the bulk gas. The increase of $SO_2$ removal efficiency with $CO_2$ concentrations showed that $SO_2$ removal by limestone was mainly done by the direct sulfation reaction under oxy-fuel combustion conditions. From the impact assessment of operation parameters, it was shown that these parameters have an effects on the desulfurization reaction by the order of the Ca/S ratio > residence time > $O_2$ concentration > reaction temperature > $SO_2$ concentration > $CO_2$ concentration > water vapor. The semi-empirical model equation for to evaluate the effect of the operating parameters on the performance of in-furnace desulfurization for oxy-fuel combustion was established.