• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.11
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• pp.1047-1054
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• 2013

In this paper, we propose a dual-mode mixer to have multi-band radar signal receiver to be compact. The proposed mixer using a anti-parallel diode is operated as a fundamental mixer or sub-harmonic mixer with respect to a control voltage. A fundamental mixer with a control voltage show a conversion loss of -10 dB, 1dB compression point of 2 dBm at X-band. On the other hand, it is performed as a sub-harmonic mixer with a conversion loss of -10 dB, 1 dB compression point of 2 dBm at K-band.

• Korean Journal of Materials Research
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• v.24 no.5
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• pp.249-254
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• 2014

Due to their unique properties, tungsten borides are good candidates for the industrial applications where certain features such as high hardness, chemical inertness, resistance to high temperatures, thermal shock and corrosion. In this study, conditions were investigated for producing tungsten boride powder from tungsten oxide($WO_3$) by self-propagating high-temperature synthesis (SHS) followed by HCl leaching techniques. In the first stage of the study, the exothermicity of the $WO_3$-Mg reaction was investigated by computer simulation. Based on the simulation experimental study was conducted and the SHS products consisting of borides and other compounds were obtained starting with different initial molar ratios of $WO_3$, Mg and $B_2O_3$. It was found that $WO_3$, Mg and $B_2O_3$ reaction system produced high combustion temperature and radical reaction so that diffusion between W and B was not properly occurred. Addition of NaCl and replacement of $B_2O_3$ with B successfully solved the diffusion problem. From the optimum condition tungsten boride($W_2B$ and WB) powders which has 0.1~0.9 um particle size were synthesized.

• Journal of Nutrition and Health
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• v.39 no.3
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• pp.264-273
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• 2006

Elevated maternal plasma homocysteine concentrations have been associated with adverse pregnancy outcomes. Serum homocysteine levels may be affected by the MTHFR genotypes and the nutritional status of B vitamins including vitamin $B_2,\;B_6$, folate and vitamin $B_{12}$. We investigated whether postnatal growth measurements were influenced by maternal MTHFR genotypes and their mid-pregnancy serum vitamin B and homocysteine levels. In 130 pregnant women of 24-28 wks of gestation, the MTHFR genotypes, serum B vitamins and homocysteine concentrations were analyzed. Physical growth status was assessed in their offsprings by measuring height, weight, and head and chest circumferences from birth up to 24 months. Serum homocysteine levels were higher in the subjects with T/T genotype than those with the C/T or C/C. Heights and head and chest circumferences of offsprings from the T/T mothers were significantly lower than those from the C/C or C/T mothers only when the serum homocysteine levels were above the median. The mean height of offsprings from the T/T mothers was significantly lower than those from the C/C and C/T mothers. The mean weight and head circumferences of offsprings born from the mothers whose mid-term pregnancy PLP levels were in the lowest quartile was significantly lower than those from mothers in the highest quartile. Heights and head circumferences of offsprings from the T/T mothers were significantly lower than those from the C/C or C/T mothers only when the serum FAD levels were in the lowest quartile. These results suggest that postnatal growth up to 24 months may be influenced by the maternal C677T MTHFR genotypes, and mid-pregnancy serum homocysteine and vitamin B status.

• The Journal of the Korean Society for Microbiology
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• v.34 no.6
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• pp.573-582
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• 1999

Cytokines are hormone-like proteins which mediate and regulate inflammatory and immune responses. The purpose of this study was to investigate the effect of lipopolysaccharide (LPS), Staphylococcus enterotoxin B (SEB), and Mycoplasma lysates on regulation of IL-6 and IL-8 production by human nasal fibroblasts. Primary cultured cells were incubated with LPS ($1.0\;{\mu}g/ml$) from E.coli, SEB ($1.0\;{\mu}g/ml$) from S.aureus, or Mycoplasma lysates (M.pneumoniae, Mp; M. fermentans, Mf; M. hominis, Mh, each $1.0\;{\mu}g/ml$). The culture supernatants were collected at 2, 6, and 24 hr and assessed for IL-6 and IL-8 production by enzyme-linked immunosorbent assay. The production of IL-6 in the culture supernatant was downregulated by LPS, SEB, or Mycoplasma lysates. But IL-6 was upregulated by mixed exposure with Mp+LPS (2 hr), Mp+LPS+SEB (24 hr), Mf+LPS (24 hr), Mf+LPS+SEB (2 hr), Mh+LPS (24 hr), Mh+SEB (24 hr), or Mh+LPS+SEB (24 hr). The production of IL-8 in the culture supernatant was similar to that of IL-6 by same stimulants. But IL-8 was upregulated by mixed exposure with Mf+LPS+SEB (2 hr), Mh+LPS (24 hr), Mh+ SEB (24 hr), or Mh+LPS+SEB (24 hr). These studies show that costimulation of LPS or SEB with Mycoplasma whole cell lysates upregulates the production of IL-6 and IL-8.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.3
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• pp.311-319
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• 1999

The thermal conductivity ${\lambda}_b$, thermal diffusivity ${\alpha}_b$ of the thin black paint layer sprayed on solid surface and absorptivity a for laser beam are measured by applying a non-contact measurement method of the thermophysical properties of solids. The values of a=0.67, ${\lambda}_b=1.45W/mK$ and ${\alpha}_b=1.24{\times}10^{-6}m^2/s$ are obtained for the sprayed lay~ thickness $z_b{\fallingdotseq}40\;{\mu}m$. Furthermore, for the $z_b{\fallingdotseq}24\;{\mu}m$ thick layers which arc formed by rubbing with a glass rod after spraying, the values of a=0.73, ${\lambda}_b=1.85W/mK$. and ${\alpha}_b=1.09{\times}10^{-6}m^2/s$ are obtained. It is also shown that the present thermal diffusivity ${\alpha}_b$ for $z_b{\fallingdotseq}40\;{\mu}m$ Is about 30~80% larger than those obtained by Araki et al. for the thicker layer $z_b{\fallingdotseq}150{\sim}248\;{\mu}m$. This method could be applied to the measurement of thermophysical properties of thin layer on solids.

• Journal of the Korean Society of Food Culture
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• v.10 no.3
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• pp.133-137
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• 1995

The objectives of this study were to determine the chemical composition of persimmon pickles and microorganisms associated with the manufacture of persimmon pickles. Moisture content was 80.04% and sugar content was 13.72%, but crude ash content was 4.26% which meant some of sodium chloride in soaking solution were permeated into fresh persimmon. Soluble tannin and total vitamin C contents were decreased from 635.45 mg% and 34.53 mg% to 81.04 mg% and 23.76 mg%, respectively. Free sugars contained in persimmon pickles were glucose, fructose and sucrose, 17 kinds of free amino acids were detected including glutamic acid (24.97 mg%), aspartic acid (24.02 mg%) and leucine (22.33 mg%). Microorganisms asociated with the manufacture of persimmon pickles were identified as Bacillus subtilis, B. cereus, B. pumilus, B. thuringiensis, Candida glabrata, C. guilliermondi and Hansenula cnomala, especially C. glabrata was the strain which caused the swelling of vacuum packages of persimmon pickles in retail stores.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.5A
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• pp.490-496
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• 2007

This paper describes the design and implementation of an integrated LTCC front-end module for the IEEE802.11a WLAN applications by performing the behavioral-level simulation using measurement-based behavioral model. To meet the IEEE802.11a WLAN standard, a system transmitting 1024 symbols through 64-QAM process at the rate of 54Mbps should be implemented and nonlinear properties are confirmed by simulations of ACPR and EVM in this circumstance. The right offsets of ACPR which are 30MHz, 20MHz, and 11MHz distant from the center frequency of 5.8GHz are 49.36dBc, 36.90dBc, and 24.58dBc, respectively. The left offsets are 50.14dBc, 30.04dBc, and 28.85dBc, respectively and EVM is 2.94%. The size of the module implemented with LTCC five-layer substrates is $13.4mm{\times}14.2mm$. The measured characteristics of the transmitter show P1dB of 16.2dBm and power gain of 16.73dB. Those of the receiver exhibit the small signal gain of 16.24dB and noise figure of 7.83dB.

• The Plant Pathology Journal
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• v.24 no.2
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• pp.159-163
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• 2008

Accurate identification of pine wood nematode, Bursaphelenchus xylophilus is a prerequisite to diagnose the pine wilt disease. However, a fungivorous nematode, B. mucronatus is highly similar to B. xylophilus and it is difficult to differentiate these two species by morphological features. A molecular diagnosis method, ITSRFLP was applied for the identification of B. xylophilus and B. mucronatus from Korea. Genomic DNA was extracted from a single individual nematode and ITS DNA was amplified by PCR. The size of PCR product was approximately 900bp and the sequence data were obtained after cloning. Amplified ITS was digested by 5 different restriction enzymes (Rsa I, Hae III, Msp I, Hinf I, and Alu I) and provided a discriminatory profile for B. xylophilus and B. mucronatus. Besides, B. mucro- natus was determined to have 2 different genotypes, East Asian type and European type also clearly separated by Rsa I and Hae III digestion. European type of B. mucronatus is recently collected from Pinus koraiensis and has not been reported before. ITS sequnce data were analyzed by Restriction Mapper program and the result supported ITS-RFLP pattern. These data indicated that PCRRFLP method is an accurate and simple way for identification of Bursaphelenchus species.

• Bulletin of the Korean Chemical Society
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• v.24 no.2
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• pp.189-192
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• 2003

The reaction of 4-(2-methylaziridin-1-yl)-3-ureidobenzotrifluorides 4 with triphenylphosphine, carbon tetrachloride, and triethylamine (Appel's condition) led to the corresponding carbodiimides 5, which underwent intramolecular cycloaddition reaction with aziridine under the reaction condition to give the benzimidazolefused heterocycles, 2,3-dihydro-1H-imidazo[1,2-a]benzimidazoles 8 and 12,13-dihydro-5H-benzimidazo[2,3-b] [1,3]benzodiazepines 9.

• Bulletin of the Korean Chemical Society
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• v.33 no.9
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• pp.2861-2866
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• 2012

Results of the comparisons of various density functional theory (DFT) methods with different basis sets for predicting the molecular geometry of TPOP24N-Oxide macrocycle, an oxoporphyrin N-oxide, are reported in this paper. DFT methods, including M06-2X, B3LYP, LSDA, B3PW91, PBEPBE, and BPV86, are examined. Different basis sets, such as 6-$31G^*$, 6-31+G (d, p), 6-311+G (d, p), and 6-311++G (d, p), are also considered. The M06-2X/6-$31G^*$ level is superior to all other density functional methods used in predicting the geometry of TPOP24N-Oxide. The geometries of regioisomeric chlorin N-oxide and oxoporphyrin N-oxide are reported using M06-2X/6-$31G^*$ method. The geometry effects of oxoporphyrin and chlorin N-oxide regioisomers are increased ${\beta}-{\beta}$ bond lengths by N-oxidation because the bond overlap index due to charge transfers is decreased. In N-oxidation ring (II, III), angles that include ${\beta}-{\beta}$ bond length increase as the bond overlap index of ${\beta}-{\beta}$ bond is decreased by N-oxidation. The potential energy surfaces of chlorin N-oxide and oxoporphyrin N-oxide are explored by M06-2X/6-$31G^*$, and single-point calculations are performed at levels up to M06-2X/6-311++G (d, p). Total and relative energies are then calculated. The results indicate that chlorin 24 N-oxides are more stable than chlorin 22 N-oxides in chlorin N-oxide regioisomers. Moreover, TPOP24N-Oxide is less stable than TPOP22N-Oxide.