• Nuclear Engineering and Technology
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• v.19 no.2
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• pp.115-121
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• 1987

A high voltage stabilization system for the SNU 1.5MV Tandem Van do Graaff accelerator was set up and its operational characteristics were examined and optimized. The optimum parameters of beam transport system were experimentally determined, and under the proper condition the accelerated proton beam current of 350nA was obtained at the target chamber. Without the high voltage stabilization the observed magnitude of voltage fluctuation was $\Delta$V/ V=5.2$\times$10$^{-3}$ without ion beam and 7.2$\times$10$^{-3}$ with ion beam, respectively, and its apparent ripple frequency for voltage fluctuations was about 3Hz or less. Through the optimized operation of the high voltage stabilization system, the terminal voltage fluctuation was reduced to $\Delta$V/V=2.45$\times$10$^{-4}$ and the energy stability with $\Delta$E/E=2.44$\times$10$^{-4}$ was steadily maintained at the 247.3kV terminal voltage, and the stabilization factor was deduced to be 29.4.

• Fisheries and Aquatic Sciences
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• v.18 no.2
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• pp.131-135
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• 2015

Two new bitter-tasting cyclic peptides comprising six amino acids, namely gamakamide C and D, were isolated from cultured oysters Crassostrea gigas. Dimethylaminoazobenzene sulfonyl-amino acid analysis detected Val and Leu in gamakamide C and Ile and Leu in gamakamide D. The molecular formula of gamakamide C was determined as $C_{43}H_{60}N_{7}O_8S$ by high-resolution fast atom bombardment mass spectroscopy (HR FAB-MS) ($[M+H]^+m/z822.4200{\Delta}-2.4mmu$), and that of gamakamide D was determined as $C_{43}H_{62}N_7O_8S$ by HR FAB-MS ($[M+H]^+m/z836.4379{\Delta}-2.0mmu$). Comparison of amino acid analyses and fragment ions by MS/MS among gamakamide C, D, and E (known), the structures of gamakamide C and D were confirmed $as-{\small{L}}-Val-{\small{L}}-Met(SO)-{\small{L}}-NMe-Phe-{\small{L}}-Leu-{\small{D}}-Lys-{\small{L}}-Phe-$ and $-{\small{L}}-Ile-{\small{L}}-Met(SO)-{\small{L}}-NMe-Phe-{\small{L}}-Leu-{\small{D}}-Lys-{\small{L}}-Phe-$, respectively.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.46 no.1
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• pp.52-58
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• 2009

A low voltage, low power delta-sigma modulator is proposed for cardiac pacemaker applications. A cascade of delta-sigma modulator stages that employ a feedforward topology has been used to implement a high-resolution oversampling ADC under the low supply. An inverter-based switched-capacitor circuit technique is used for low-voltage operation and ultra-low power consumption. An experimental prototype of the proposed circuit has been implemented in a $0.35-{\mu}m$ CMOS process, and it achieves 61-dB SNDR, 63-dB SNR, and 65-dB DR for a 120-Hz signal bandwidth at 7.6-kHz sampling frequency. The power consumption is only 280 nW at 1-V power supply.

• Journal of the korean Society of Automotive Engineers
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• v.5 no.1
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• pp.32-44
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• 1983

In case of $K_{Imax}$ < $K_{Iscc}$, the corrosion fatigue of high strength steel in 0.1N $H_{2}$S $O_{4}$ solution and 3.5% salt water is as follows. 1. The fatigue life shortens in order of 3.5% salt water and 0.1N $H_{2}$S $o_{4}$ solution. 2. The fatigue crack growth rate in air is obtained as the following equation. (dc/dN)$_{atr}$=7.23*10$^{-6}$ (.DELTA. K)$^{2.23}$ 3. The corrosion fatigue crack growth rate in environment is divided into three regions, that is, First Region, Second Region and Third Region from the small cyclic stress intensity. 4. The formation rate of the active surface on metal is slower than the mechano-chemical reaction rate in First Region. The crack growth rate depends on time and the cyclic stress intensity and is expressed as the following equation. (dc/dN)$_{I}$=C(/DELTA. K)$^{\delta}$ 5. The formation rate of the active surface is faster than the mechano-chemical reaction rate in Second Region and the synergistic effect by stress and corrosion becomes slow. In case the fatigue load is large, we have the critical crack growth rate which is not related to the cyclic stress intensity. 6. The corrosion crack growth rate by the mechano-chemical reaction is the same in $H_{2}$S $O_{4}$ solution and salt water, so Hydrogen accelerates the crack growth. 7. The environment has no effect on the corrosion fatigue crack growth rate in Third Region. 8. In First Region and Second Region, dimple is observed on the fatigue fracture surface in 0.1N $H_{2}$S $O_{4}$ solution. 9. The striation is observed in any environment as in air in Third Region and its interval approximately coincide with the crack growth rate.ate.e.e.

• Bulletin of the Korean Chemical Society
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• v.31 no.4
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• pp.874-880
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• 2010

A series of 13- and 14-membered cyclic enkephalin analogs based on the moderately $\mu$ selective prototype compound Tyr-C[D-$A_2bu$-Gly-Phe-Leu] 8a were synthesized to investigate the structure-activity relationship. The modifications of sequence were mainly focused on two positions 3 and 5, critical for the selective recognition for $\mu$ and $\delta$ opioid receptors. The substitution of hydrophobic $Leu^5$ with hydrophilic $Asp^5$ derivatives led to Tyr-C[D-$A_2bu$-Gly-Phe-Asp(N-Me)] 7 and Tyr-C[D-Glu-Phe-gPhe-rAsp(O-Me)] 5, the peptides with a large affinity losses at both $\mu$ and $\delta$ receptors. The substitution of $Phe^3$ with $Gly^3$ led to Tyr-C[D-Glu-Gly-gPhe-rLeu] 3 and Tyr-C[D-Glu-Gly-gPhe-D-rLeu] 4, the peptides with large affinity losses at $\mu$ receptors, indicating the critical role of phenyl ring of $Phe^3$ for $\mu$ receptor affinities. One atom reduction of the ring size from 14-membered analogs Tyr-C[D-Glu-Phe-gPhe-(L and D)-rLeu] 6a, 6b to 13-membered analogs Tyr-C[D-Asp-Phe-gPhe-(L and D)-rLeu] 1, 2 reduced the affinity at both $\mu$ and $\delta$ receptors, but increased the potency in the nociceptive assay, indicating the ring constrain is attributed to high nociceptive potency of the analogs. For the influence of D- or L-chirality of $Leu^5$ on the receptor selectivity, regardless of chirality and ring size, all cyclic diastereomers displayed marked $\mu$ selectivity with low potencies at the $\delta$ receptor. The retro-inverso analogs display similar or more active at $\mu$ receptor, but less active at $\delta$ receptor than the parent analogs.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.205-210
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• 2001

Fatigue crack growth tests were carried out using high manganese cast steel under constant amplitude loading. Average crystal grain sizes of the material are $200{\mu}m$ and $1000{\mu}m$. For this material, ${\Delta}K_{th}$ is about $8MPa{\sqrt{m}}$ which is quiet large as compared to the general structural steels and the crack growth rate is lower than the general structural steels especilly in the low ${\Delta}K$ regsion. The reason of this behavior is crack closure due to fracture surface roughness and fretting oxide. The relationship between da/dN and the ${\Delta}K_{eq}$ was represented by narrow band regardless of the stress ratio.

• Journal of the Korean Society of Safety
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• v.7 no.2
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• pp.47-56
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• 1992

The retardation effect of fatigue crack propagation after cyclic overloading seems to be affected by strain hardening exponent. Namely, for the material with high values of n, the delay effect is found to be severe. We proposed a modified crack retardation equation which may apply the retardation of fatigue crack growth after a cyclic overloading, as (da/dN)'$_{cyc}$=($\mu$n＋λ)B $\Delta$ $K^{q}$ /[(1－ $R_{eff}$) $K_{cf}$ －$\Delta$K]. where, $R_{eff}$ is effective stress ratio [＝( $K_{min}$－K, os)/( $K_{max}$－ $K_{res}$)] The constants $\mu$＝－0.5 and λ＝0.6, and the values are found to be identical for materials such as aluminum (A 1060), steel (SS 34), brass ( $B_{s}$ SIB) and stainless steel (SUS 304) used in this investigation. (SUS 304) used in this investigation.ation.n.n.

• Journal of Korean Society of Forest Science
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• v.101 no.1
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• pp.121-129
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• 2012

The edge area with burn severity is known as significant factor that has great effects on the ecosystem recovery. However, there is little study on the edge area and its effects in the South Korea. Thus, this study aimed to analyze immediate responses of vegetation following forest fires due to combined effect of burn severity and edge-interior effect. Burn Severity (BS), or ${\Delta}NBR$ values were computed using satellite images of pre and post-forest fire in Samcheock areas. The burn forest was classified 231 $1-km^2$ girds and these grids were further reclassified into 4 groups by BS type (low BS and high BS areas) and forest areas (edge areas and interior areas). These four groups of grids including low BS-interior (group A), low BS-edge (group B), high BS-interior (group C) and high BS-edge (group D). Post-fire vegetation responses measured with (${\Delta}NDVI$) among four groups were then compared and tested by T-test. The results indicated that group C (${\Delta}NDVI$=0.047) and D (${\Delta}NDVI$ = 0.059) showed considerably greater vegetation regeneration than those of low BS areas including group A (${\Delta}NDVI$ = -0.039) and group B (${\Delta}NDVI$ = -0.036). It was also observed that edges areas showed greater vegetation regeneration than interior areas when BS is the same. Group B (${\Delta}NDVI$ = -0.036) showed greater (${\Delta}NDVI$) values than group A (${\Delta}NDVI$ = -0.039) in low BS condition. Similar relationship is observed between group C and group D in high BS condition. Thus adequate restoration practices for burned areas might need to pay close attention to interior areas with low BS to minimize the secondary damages and to rehabilitate the burned forests.

• Journal of the Korean Society of Food Science and Nutrition
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• v.34 no.8
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• pp.1202-1209
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• 2005

The purpose of this study was to observe the effects of high-carbohydrate (HC) diet, high-protein (HP) diet and high-fat (HF) diet with a normal diet (N) on diet-induced thermogenesis (DIT) in healthy Korean women. The four isoenergetic test meals consisted as follows: HC (75$ \% $ energy from carbohydrate, 10$ \% $ from protein and 15$ \% $ from fat), HP (10$ \% $ energy from carbohydrate, 75$ \% $ from protein and 15$ \% $ from fat) HF (15$ \% $ energy from carbohydrate, 10$ \% $ from protein and 75$ \% $ from fat) diet and N (65$ \% $ energy from carbohydrate, 15$ \% $ from protein and 20$ \% $ from fat) diet. Fasting and postprandial thermogenesis were measured after each test meals in eight subjects by indirect calorimetry for 3 hours. Fasting and postprandial serum glucose, insulin and triacylglycerol contents were also measured for 3 hours. DIT were 10.4$\pm$3.2 for HC, 12.7$\pm$0.5 for HP, 6.9$\pm$2.8 for HF and 8.7$\pm$4.8 for N diet as a percentage of the energy load. DIT of HP was greater than HF significantly, but had no differences with HC and N Integrated areas under the curves ($ \delta- $-AUC) of plasma glucose and insulin were significantly higher for HC compared to HP, HF and N diets. $ \delta$-AUC of plasma triacylglycerol was significantly higher for HF compared to the other test meals. In conclusion, intake of protein rich meal stimulates postprandial energy expenditure, but has no relation between DIT and insulin response, body composition.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.121-126
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• 2002

The railroad cars or the commercial vehicles are generally manufactured by the spot welding. Among various kinds of spot welded lap joints, multi-lap joints are one of popular joints in manufacturing their body structures. But, fatigue strength of these joints are lower than that of base metal due to high stress concentration at the nugget edge of the spot weld and are known to considerably be influenced by welding conditions as well as the mechanical and geometrical factors. Thus, it is necessary to establish a reasonable and systematic fatigue design criterion for spot welded multi-lap joints. In this paper, the $\Delta$P-N$_{f}$ curves has been rearranged in the $\Delta$$\sigma$-N$_{f}$ relation with the maximum stress at the nugget edge of spot welded multi-lap joints subjected to tensile shear load. Consequently, the fatigue data were evaluated in terms of fracture mechanics by plotting on the $\Delta$OP-N$_{f}$ curves. From the results obtained, both of them have been revealed to be applicable to fatigue design of spot welded multi-lap joints. However, the fracture mechanical approach is found to be more effective than the maximum stress approach in the range on N$_{f}$$\geq$2x10$^{5}$ . .