• Bulletin of the Korean Chemical Society
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• 제24권7호
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• pp.993-998
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• 2003

In the aminolysis of phenacyl bromides ($YC_6H_4COCH_2Br$) with benzylamines ($XC_6H_4CH_2NH_2$) in acetonitrile, the Bronsted βx (βnuc) values observed are rather low ( βX = 0.69-0.73). These values are similar to those (βx $^~_=$ 0.7) for other aminolysis reactions of phenacyl compounds with anilines and pyridines, but are much smaller than those ( βx = 1.1-2.5) for the aminolysis of esters with benzylamines which are believed to proceed stepwise with rate-limiting expulsion of the leaving group. The relative constancy of the βx values (βx $^~_=$ 0.7) irrespective of the amine, leaving group and solvent can be accounted for by a bridged type transition state in the rate-limiting expulsion of the leaving group. Thus the aminolysis of phenacyl derivatives are proposed to proceed stepwise through a zwitterionic tetrahedral intermediate ($T^{\pm}$), with rate-limiting expulsion of the leaving group from $T^{\pm}$. In the transition state, the amine is bridged between the carbonyl and α-carbons, which leads to negligible effect of amine on the leaving group expulsion rate.

• 한국물환경학회지
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• 제27권1호
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• pp.54-60
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• 2011

To evaluate the feasibility of electrodialysis for copper removal from industrial wastewater, the effect of operating parameters on the removal of copper was experimentally estimated. The limiting current density (LCD) linearly increased with the copper concentration and the flow rate. The time when the copper concentration of diluate reaches to 3 mg/L was linearly proportional to initial concentration of diluate, and the concentration of concentrate did not affect the removal rate. Increase in the flow rate gave a positive effect on the removal rate and became insignificant at flow rates greater than 2.4 L/min. The removal rate increased with the applied voltage. From the operation of the electrodialysis module used in this research, the flow rate of 2.4 L/min and the voltage corresponding to the 80~90% of LCD were found be the optimum operating condition for the copper removal from highly concentrated copper solutions.

• 한국안전학회지
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• 제15권4호
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• pp.95-100
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• 2000

This study was performed in Hartmann type dust explosion apparatus in order to research the dust explosion characteristics of hydroxypropyl methyl cellulose(HPMC): minimum explosive limit, minimum ignition energy, limiting oxygen concentration, maximum explosion pressure, rate of pressure rise, etc. The samples of HPMC dust were distributed into 120-140 mesh, 170-230 mesh and 325 under, and the gap distance of the discharge electrode was setted up at 5mm. The experimental results were obtained as follows: (1) The minimum explosive limit for HPMC dust was founded at 180g/㎥. the minimum ignition energy at 9.8mJ and the limiting oxygen concentration at 12%. (2) The maximum explosion pressure of HPMC dust was $8.1kg/cm^2\;{\cdot}\;$abs at the concentration of $500g/m^3$ and the maximum rate of pressure rise was 203.98 bar/sec at the concentration of $480g/m^3$ for 325 under.

• Asian-Australasian Journal of Animal Sciences
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• 제19권9호
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• pp.1361-1368
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• 2006

Amino acid imbalances refer to the deleterious effects that occur when a second-limiting amino acid or mixture of amino acid lacking a particular limiting amino acid is supplemented in diets marginal in one or more indispensable amino acids. In spite of variation in the conditions that have been used to induce amino acid imbalances, such as protein level in the diet, the extent of difference in total nitrogen content between basal and imbalanced diets, and kinds of amino acids used as imbalancing agents, the conspicuous common features of amino acid imbalances have been a decreased concentration of the limiting amino acid in blood, depression of feed intake and weight gain, and increased dietary content of the limiting amino acid needed to correct the imbalances. There is strong evidence that a decrease in the concentration of a limiting amino acid detected in the anterior prepyriform cortex of the brain is followed by behavioral effects, especially a decrease in feed intake. This might be due to the competition between the limiting amino acid and the amino acids in the imbalancing mixture for transport from blood into brain. One of the biochemical responses of animals fed amino acid imbalanced diets is a rapid decrease in the concentration of the limiting amino acid, which are due in part to an increase in catabolism of the limiting amino acid by the increased activities of enzymes involved in the catabolism of the amino acid. Practically, specific amino acid imbalances could be induced in swine and poultry diets that have been supplemented with lysine, methionine, tryptophan when threonine, isoleucine, valine, etc. are potentially third- or fourth-limiting in diets. In these cases supplementation of the limiting amino acid could be beneficial in preventing the decrease of feed intake that could otherwise occur as a result of amino acid imbalance.

• Journal of Microbiology and Biotechnology
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• 제18권4호
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• pp.704-710
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• 2008

Glutamate availability in the argF-argR-proB${\Delta}$ strain of Corynebacterium glutamicum was increased by addition of glutamate to the cell or inactivation of the phosphoenolpyruvate carboxykinase activity and simultaneous overexpression of the pyruvate carboxylase activity to assess its effect on L-ornithine production. When glutamate was increased in an L-ornithine-producing strain, the production of L-ornithine was not changed. This unexpected result indicated that the intracellular concentration and supply of glutamate is not a rate-limiting step for the L-ornithine production in an L-ornithine-producing strain of C. glutamicum. In contrast, overexpression of the L-ornithine biosynthesis genes (argCJBD) resulted in approximately 30% increase of L-ornithine production, from 12.73 to 16.49 mg/g (dry cell weight). These results implied that downstream reactions converting glutamate to L-ornithine, but not the availability of glutamate, is the rate-limiting step for elevating L-ornithine production in the argF-argR-proB${\Delta}$ strain of C. glutamicum.

• Bulletin of the Korean Chemical Society
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• 제32권10호
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• pp.3743-3747
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• 2011

Kinetic studies on the reactions of Y-S-aryl phenyl phosphonochloridothioates with X-pyridines have been carried out in MeCN at $55.0^{\circ}C$. The Hammett and Bronsted plots for substituent X variations in the nucleophiles are biphasic concave upwards with a break point at X = H. The Hammett plots for substituent Y variations in the substrates are biphasic concave upwards with a break point at Y = H, and the sign of ${\rho}_Y$ is changed from unusual negative (${\rho}_Y$ < 0) with the weaker electrophiles to positive (${\rho}_Y$ > 0) with the stronger electrophiles. The stepwise mechanism is proposed on the basis of the ${\rho}_X$, ${\beta}_X$, and ${\rho}_{XY}$ values as follows: a ratelimiting leaving group departure from the intermediate involving a frontside attack and product-like TS for the stronger nucleophiles and weaker electrophiles; a rate-limiting leaving group departure from the intermediate involving a backside attack and product-like TS for the weaker nucleophiles and electrophiles; a rate-limiting bond formation involving a frontside attack for the stronger nucleophiles and electrophiles; a rate-limiting bond formation involving a backside attack for the weaker nucleophiles and stronger electrophiles. The substituent effects of X and Y on the pyridinolysis mechanisms of $R_1R_2P$(=S)Cl-type substrates are discussed.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 A
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• pp.37-40
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• 1996

Cable-In-Conduit Conductor(CICC) is widely accepted as an advanced superconductor configuration for large scale applications such as tokamak fusion reactors, MAGLEV (MAGnetic LEVitation), and SMES (Superconducting Magnetic Energy Storage). The stability of CICC cooled with supercritical helium can be very high if it is operated below a certain limiting current. This limiting current can be determined by Stekly type heat balance equation. The stability characteristic of CICC for AC operation is more complicated than that of DC because there are additional instability sources which are associated with local flux change. Ramp-rate limitation is a phenomenon discovered during US-DPC (United States-Demonstration Poloidal Coil) program, which showed apparent quench current degradation associated with high dB/dt. This paper describes recent experimental investigation results on the ramp-rate limitation and discusses current imbalance, induced current, current redistribution due to local quench of the strand in the cable.

• Asian-Australasian Journal of Animal Sciences
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• 제32권4호
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• pp.519-526
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• 2019

Objective: We determined the risk factors limiting first service conception (FSC) rate in dairy cows and their economic impact. Methods: Data were collected from 790 lactations regarding cow parity, peri- and postpartum disorders, body condition score (BCS), reproductive performance, and expenses associated with reproductive management (treatment, culling, and others). Initially, we identified the risk factors limiting FSC rate in dairy cows. Various biological and environmental factors, such as herd, cow parity, BCS at 1 month postpartum and first artificial insemination (AI), resumption of cyclicity within 1 month of calving, year, AI season, insemination at detected estrus or timed AI, peri- and postpartum disorders, and calving to first AI interval, were evaluated. Next, we evaluated the economic impact of the success or failure of FSC by comparing the expense associated with reproductive management until conception between cows that did or did not conceive at their first service. Results: Cows with BCS <3.0 had a lower probability of conceiving at first insemination (odds ratio [OR] = 0.64, p<0.05) than cows with $BCS{\geq}3.0$. Cows inseminated during summer were less likely to conceive (OR = 0.44, p<0.001) than cows inseminated during spring. Cows with peri- or postpartum disorders were less likely to conceive (OR = 0.55, p<0.001) than cows without disorders. Survival curves generated using MedCalc showed an 81 day extension in the mean interval between calving and conception in cows that failed to conceive over those that did conceive at first insemination. Cows failing conceive required additional expenditure on reproductive treatment ($55.40) and other management ($567.00) than cows that conceived at first insemination. Conclusion: Lower BCS, hot weather at first insemination, and peri- and postpartum disorders are risk factors limiting FSC, which result in an economic loss of $622.40 per dairy cow.

• Journal of Biosystems Engineering
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• 제15권2호
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• pp.110-122
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• 1990

This study was undertaken to develop the feed rate control system for the head feed thresher by making use of the microprocessor and to evaluate the response of the system to a various threshing conditions. The control unit was composed of one-board microcomputer. The speed of the wet-paddy feeding chain was controlled by dc moter with PI controller. It was used the adaptive control method to maintain the constant feed rate regardless of the fed rice varieties. The sliding type potentiometer was used as the feed rate sensor, which was attached on the sheaf-holding apparatus. The mathematical models of the system components were derived and computer simulation was developed for investigating the parameters affecting on control performance and for estimating the response of the system. A one-board microcomputer-based feed rate control system developed in this study was properly functioned and assessed as adequate for the feed rate control system of the head feed thresher. Based on the simulation for the bundle feed, it was anticipated that the lower setting value of the cylinder speed(RL) is to be set higher than the limiting operational speed. In addition, the higher setting value of the cylinder speed(RH) is to be set lower than the limiting cylinder speed for threshing. The computer simulation for the continuous spread feed showed that the lower the setting value of straw layer thickness(LL) was set, the shorter the correction time. However, if too low LL may be established, the feed rate could not reach to its desired rate.

• Communications for Statistical Applications and Methods
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• 제3권1호
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• pp.243-255
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• 1996

The number of neutron signals from a neutral particle beam(NPB) at the detector, without any errors, obeys Poisson distribution, Under two assumptions that NPB scattering distribution and aiming errors have a circular Gaussian distribution respectively, an exact probability distribution of signals becomes a Poisson-power function distribution. In this paper, we show that the error rate in simple hypothesis testing for the limiting Poisson-power function distribution is not zero. That is, the limit of ${\alpha}+{\beta}$ is zero when Poisson parameter$\kappa\rightarro\infty$, but this limit is not zero (i.e., $\rho\ell$>0)for the Poisson-power function distribution. We also give optimal decision algorithms for a specified error rate.