• Resources Recycling
• /
• v.19 no.6
• /
• pp.43-50
• /
• 2010

The crisis of energy gives rise to the growing concerns over continuing uncertainty in the energy market. Under these circumstances, there are also increasing interests on coals. In particular, Low Rank Coal (LRC) is receiving gradual attentions from green industry. But due to is high moisture content range from 30 - 60%, drying process has to be preceded before being utilized as power plant. In this study drying kinetics of LRC is induced by using a fixed-bed reactor. The drying kinetics was evaluated in from of the particle size, the inlet gas temperature, the drying time, the gas velocity, and the LID ratio. The consideration of the reynold's number was taken for correction of gas velocity, particle size and LID was taken for correction of reactor diameter, packing height of coal. As being seen as characteristic of drying coal, it can be found that fixed-bed reactor can contributed to active drying of free water. In this sense, it could be considered that phase boundary reaction is appropriate mechanism.

• Korean Journal of Soil Science and Fertilizer
• /
• v.38 no.5
• /
• pp.238-246
• /
• 2005

We conducted this investigation to observe competitive adsorption phenomena among the heavy metals onto the available sorption sites of soil particle surfaces in sandy clay loam and clay soil collected from Nonsan city, Chungnam and Yoosung, Daejeon in Korea, respectively. Polluted and contaminated soils can often contain more than one heavy metal species, resulting in competition for available sorption sites among heavy metals in soils due to complex competitive ion exchange and specific sorption mechanism. And the adsorption characteristics of the heavy metals were reported that the selectivity for the sorption sites was closely related with electropotential and electro negativity carried by the heavy metals. The heavy metals were treated as single, binary and ternary systems as bulk solution phase. Adsorption in multi-element system was different from single-element system as Cr, Pb and Cd. The adsorption isotherms showed the adsorption was increased with increasing equilibrium concentrations. For binary and ternary systems, the amount of adsorption at the same equilibrium concentration was influenced by the concentration of individual ionic species and valence carried by the respective heavy metal. Also we found that the adsorption isotherms of Cd and Pb selected in this experiment were closely related with electronegativity and ionic potential regardless number of heavy metals in solution, while the adsorption of Cr carried higher valance and lower electro negativity than Cd and Pb was higher than those of Cd and Pb, indicating that adsorption of Cr was influenced by ionic potential than by electronegativity. Therefore adsorption in multi-element system could be influenced by electronegativity and ionic potential and valance for the same valance metals and different valance, respectively. But it still needs further investigation with respect to ionic strength and activity in multi-element system to verify sorption characteristics and reaction processes of Cr, especially for ternary system in soils.

• Radiation Oncology Journal
• /
• v.4 no.2
• /
• pp.115-128
• /
• 1986

Hyperthermia can enhance the radiation effect as a synergistic reaction in combined X-ray irradiation and hyperthermia; hyperthermia sensitize radioresistant S-phase cells and inhibit cellular recovery from sublethal damage. We fabricated 100 watts, 2450 MHz microwave applicator for hyperthermia and planned the method and condition of heating and measured the temperature by using Agar phantom as a preliminary test. For biological examination, 102 rats were divided into 4 groups as hyperthermia, X-ray irradiation (6Gy-15Gy), combined X-ray and hyperthermia, and normal control groups. Microscopic examination of the rectum and bladder was done and the results were as followings: 1. The microwave generator with 100 watts, 2450MHz magnetron could be heating up to $40^{\circ}{\sim}50^{\circ}C$ for one hour in living tissue. 2. The thermal distribution in tissue equivalent phantom with microwave can be maintained at $40^{\circ}{\sim}44^{\circ}C$ in area of 3cm in depth and 2-10cm in diameter. 3. In Hyperthermia alone group, there was submucosal edema of the rectum but no histologic change in the urinary bladder was seen. 4. The minimal necrosis of the mucosa was appeared in the rectum and bladder after 15 days of 6 Gy and 8 Gy irradiation respectively. The minimal necrosis of the muscle layer of rectum and bladder was appeared after 15 days of 8Gy and 60days of 10Gy irradiation respectively. 5. In combined group of radiation and hyperthermia, thermal enhancement ratio (calculated at necrosis of mucosa and muscle layer) of rectum and bladder was 1.0, and it suggest that there is no change of tolerance dose of normal rectum and bladder.

• Korean Journal of Materials Research
• /
• v.6 no.8
• /
• pp.779-785
• /
• 1996

Thin $700^{\circ}C$films were formed through layer inversion of Co/Nb bilayer during rapid thermal annealing(RTA). The Nb interlayer seems to effectively prevent over-consumption of Si and to control the silicidation reaction by forming Co-Nb intermetallic compounds and removing the native oxide formed on Si substrate which interferes the uniform Co-Si interaction. The final layer structure of the Co/Nb bilayer after $700^{\circ}C$ RTA was found to be ${Nb}_{2}{O}_{3}$/${Co}_{2}$Si.CoSi/${NbCo}_{x}$/Nb(O, C)/${CoSi}_{2}$/ Si. The layer inversion and the formation of a stable CoSi, phase occurred above $700^{\circ}C$, and the Nb silicides were not found at any annealing temperature. These may be due to the formation of very stable Co-Nb intermetallic compounds and Nb oxides which limit the moving of Co and Si.

• Journal of Preventive Medicine and Public Health
• /
• v.35 no.4
• /
• pp.282-286
• /
• 2002

Objectives : The level of 4-hydroxyproline (4-Hyp) in human urine was measured using high performance liquid chromatography (HPLC) with a fluorescence detector. This method is useful for medical examinations and investigating the radicals induced by physical, chemical, mental stresses. This method is superior to many published several methods in terms of its low cost and ability to analyze many samples. Methods : The urine from workers in a tire manufacturing company (22 male pre- and post-shift workers) and 18 office-workers as controls were analyzed. Data concerning age, the cumulative drinking amount and the cumulative smoking amount was collected with a questionnaire. The optimum applied amount of dansyl-Cl, the optimum reaction temperature and time, the recoveries and the optimum pH of the eluent and buffer were determined.4-Hyp from human urine was derivatized with dansyl-Cl (dimethylamino-naphthalene-1-sulfonyl chloride) after removing the a-amino acid by a treatment with phthalic dicarboxaldehyde (OPA) and cleaned with Bond Elut C18 column. The 4-Hyp derivatives were separated on a reversed phase column by gradient elution with a phosphate buffer (5 mmol, pH 8.0) and acetonitrile, and detected by fluorescence measurements at 340 nm (excitation) and 538 nm (emission). Results : The detection limit for the urinary free 4-Hyp was $0.364{\mu}mol/l$. The recovery rate of 4-Hyp was 99.7%, and the effective pH of the phosphate buffer and borate buffer were 3.0 and 8.0, respectively. From statistical analysis, age, drinking and smoking did not affect the urinary free 4-Hyp in both the controls and workers. The range of urinary 4-Hyp in the controls, pre-shift, and post-shift workers were 0.33-16.44, N.D-49.06, and $0.32-56.27{\mu}mol/l$. From the pared-sample t-test, the urinary 4-Hyp levels in post-shift workers ($11.82{\pm}6.73\;nmmol/mg\;Cre$) were 2-fold higher than in pre-shift workers ($5.36{\pm}5.53\;nmol;/mg\;Cre$) and controls ($4.91{\pm}4.89\;nmol;/mg\;Cre$). Conclusions : This method was developed with high sensitivity, accuracy, and precision. The present method was effectively applied to analyze the urinary free 4-Hyp in both controls and workers.

• Journal of Life Science
• /
• v.18 no.4
• /
• pp.537-541
• /
• 2008

White adipose tissue is now recognized as an important endocrine organ which secretes various signal factors and proteins termed 'adipokine'. Haptoglobin (Hp), which has been known as an acute phase protein, belongs to the adipokine. However, the function of Hp in adipose tissue remains unclear. To verify the role of Hp in preadipocytes, in this study, 3T3-L1 preadipocyte cells were stably transfected with human Hp gene and Hp-overexpressing cells were made. The Hp had no effect on cell growth of preadipocytes. By RT-PCR and Western blot analysis, the Hp inhibited gene expression of IL-6 and COX-2 and enhanced HO-1 synthesis in preadipocytes. Moreover, invasion assay showed the Hp suppressed migration of monocytes to preadipocytes. These findings suggest that the Hp may inhibit an inflammatory reaction in adipose tissue by regulating the expressions of pro-inflammatory and anti-inflammatory mediators, and by repressing monocytes/macrophages infiltration.

• Journal of Food Hygiene and Safety
• /
• v.33 no.2
• /
• pp.118-123
• /
• 2018

The objective of this study was to develop a sensitive method for the identification and determination of nitrovin in fishery products by using a solid-phase extraction (SPE), as performed with a liquid chromatography-tandem mass spectrometry (LC-MS/MS). The samples were extracted with a mixture of acetonitrile and water, and were then defatted with acetonitrile saturated hexane, after which further clean-up was accomplished with SPE on the hydrophilic-lipophilic balance (HLB) cartridges. The analytes were subsequently ionized in the positive mode of an electrospray ionization (ESI), and where thereby detected in a process of multiple reaction monitoring (MRM). The linearity (expressed as correlation coefficients) of the matrix calibration curves was > 0.985. The limit of the quantification for the nitrovin was measured at 0.001 mg/kg. The accuracy (expressed as average recovery) was noted between 72.1 and 122%. The precision (expressed as coefficient variation) was noted from 2.9 to 16.9%. According to the CODEX CAC/GL-71 guideline accuracy, precision, linearity, and limit of detection were determined in three matrices (which were flatfish, eel and shrimp). The proposed method was suitable for analyzing the associated nitrovin residues. This application and result can also be a factor to contribute to the non-detection drugs management in fishery products.

• Resources Recycling
• /
• v.13 no.5
• /
• pp.45-50
• /
• 2004

To investigate the characteristics of phases formed in iron carbides, super iron carbide was synthesized from hematite fines with $CO-H_2$ gas mixture after reduction under $H_2$ gas at $600^{\circ}C$. Before carburization, the surface of iron powder reduced was pre-treated in the atmosphere of 0.05 vol% $NH_3$-Ar. The synthesized iron carbides were comprehensively explored by C/S analyzer(Low C/S determinator), M$\"{o}$ssbauer spectroscopy, X-ray diffraction patterns(XRD), scanning electron microscopy(SEM), transmission electron microscopy(TEM), and Raman spectroscopy at various reaction time of 5, 10, 15, 20, 25, 30, and 35 min, respectively. By adding a small amount of $NH_3$ gas, the super iron carbides containing 10 wt% carbon were synthesized, and its addition stabilized iron carbides. It was found that the $NH_3$ treatment played a major role in the formation of iron carbide without decomposition($Fe_3C{\to}$3Fe+C) of iron carbides and precipitation of free carbon. It also succeed to synthesize super iron carbide, $Fe_5C_2$, as a stable single phase without involving Fe and $Fe_3C$ phases.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2004.07b
• /
• pp.838-841
• /
• 2004

[ $B_2O_3$ ] added $Ba(Mg_{1/3}Nb_{2/3})O_3$ (BBMN) ceramics were not sintered below $900^{\circ}C$. However, when CuO was added to the BBMN ceramic, it was sintered even at $850^{\circ}C$. The amount of the $Ba_2B_2O_5$ second phase decreased with the addition of CuO. Therefore, the CuO additive is considered to react with the $B_2O_3$ inhibiting the reaction between $B_2O_3$ and BaO. Moreover, it is suggested that the solid solution of CuO and $B_2O_3$ might be responsible for the decrease of the sintering temperature of the specimens. A dense microstructure without pores was developed with the addition of a small amount of CuO. However, a porous microstructure with large pores was formed when a large amount of CuO was added. The bulk density the dielectric constant $({\varepsilon}_r)$ and the Q-value increased with the addition of CuO but they decreased when a large amount of CuO was added. The variations of those properties are closely related to the variation of the microstructure. The excellent microwave dielectric properties of Qxf=21500 GHz, ${\varepsilon}_r=31$ and temperature coefficient of resonance frequency$({\tau}_f)=21.3\;ppm/^{\circ}C$ were obtained for the $Ba(Mg_{1/3}Nb_{2/3})O_3+2.0\;mol%B_2O_3+10.0$ mol%CuO ceramic sintered at $875^{\circ}C$ for 2h.

• Bulletin of the Korean Chemical Society
• /
• v.21 no.11
• /
• pp.1125-1132
• /
• 2000

The pH effect of the precursor solution on the preparation of $LiCoO_2$ by a solution phase reaction containing malonic acid was carried out. Layered $LiCoO_2$ powders were obtained with the precursors prepared at the different pHs (4, 7, and 9) and heat-treated at $700^{\circ}C(LiCoO_2-700)$ or $850^{\circ}C(LiCoO_2-850)$ in air. pHs of the media for precursor synthesis affects the charge/discharge and electrochemical properties of the $LiCoO_2electrodes.$ Upon irrespective of pH of the precursor media, X-ray diffraction spectra recorded for $LiCoO_2-850$ powder showed higher peak intensity ratio of I(003)/I(104) than that of $LiCoO_2-700$, since the better crystallization of the former crystallized better. However, $LiCoO_2$ synthesized at pH 4 displayed an abnormal higher intensity ratio of I(003)/I(104) than those synthesized at pH 7 and 9. The surface morphology of the $LiCoO_2-850$ powders was rougher and more irregular than that of $LiCoO_2-700$ made from the precursor synthesized at pH 7 and 9. The $LiCoO_2electrodes$ prepared with the precursors synthesized at pH 7 and 9 showed a better electrochemical and charge/discharge characteristics. From the AC impedance spectroscopic experiments for the electrode made from the precursor prepared in pH 7, the chemical diffusivity of Li ions (DLi+) in $Li0.58CoO_2determined$ was 2.7 ${\times}$10-8 $cm^2s-1$. A cell composed of the $LiCoO_2-700$ cathode prepared in pH 7 with Lithium metal anode reveals an initial discharge specific capacity of 119.8 mAhg-1 at a current density of 10.0 mAg-1 between 3.5 V and 4.3 V. The full-cell composed with $LiCoO_2-700$ cathode prepared in pH 7 and the Mesocarbon Pitch-based Carbon Fiber (MPCF) anode separated by a Cellgard 2400 membrane showed a good cycleability. In addition, it was operated over 100 charge/discharge cycles and displayed an average reversible capacity of nearly 130 mAhg-1.