• Korean journal of applied entomology
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• v.24 no.4 s.65
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• pp.231-238
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• 1986

Molecular orbital theoretical study on the stability of conformations and chemical reactivity of 0,0-diethylphenylphosphate derivatives were carried out by EHT and CNDO/2 molecular orbital calculation method. The results shown that the dipole moment(${\mu}$) and total energies of the ${\theta}=90^{\circ}$ conformer were ${\mu}=3.185D\;&\;E_t=-162.6479(au)$ and also that of the ${\theta}=0^{\circ}$ conformer were ${\mu}=5.596D\;&\;E_t=-162.4013(au)$, respectively. Therefore, the values of ${\mu}\;&\;E_t$ of the ${\theta}=90^{\circ}$ conformer were much smaller than that of the ${\theta}=0^{\circ}$ conformer. The form with angle of rotation ${\theta}=90^{\circ}$ of phenyl ring was shown to be most stable and this was interpreted in terms of electrostatic and steric effect. 0,0-diethylphenylphosphate derivatives are predicted to increase both charge and orbital controlled $SN_2$ reactivity of the electron withdrawing substituent reduces the HOMO & LUMO energy, while the electron withdrawing substituent due to increase in positive charge of phosphorus atom of phosphate molecule.

• Journal of Life Science
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• v.33 no.10
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• pp.842-850
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• 2023

Pyrrolnitrin, pyrrolomycin, and pyoluteorin are functional halogenated phenylpyrrole derivatives (HPDs) derived from microorganisms with diverse antimicrobial activities. Pyrrolnitrin is a secondary metabolite produced from L-tryptophan through four-step reactions in Pseudomonas fluorescens, Burkholderia cepacia, Serratia plymuthica, etc. It is currently used for the treatment of superficial dermatophytic fungal infections, has high antagonistic activities against soil-borne and foliar fungal infections, and has many industrial applications. Since pyrrolnitrin is easily decomposed by light, it is difficult to widely use it outdoors. As an alternative, fludioxonil, a synthetically produced non-systemic surface fungicide that is structurally similar and has excellent light stability, has been commercialized for seed and foliar treatment of plants. However, due to its high toxicity to aquatic organisms and adverse effects in human cell lines, many countries have established maximum residue levels and strictly control its levels. Pyrrolomycin and pyoluteorin, which have antibiotic/antibiofilm activity against Gram-positive bacteria and high anti-oomycete activity against the plant pathogen Pythium ultimum, respectively, were isolated and identified from microorganisms. This review summarizes the biosynthesis and production of natural pyrrolnitrin derived from bacteria and the characteristics of synthetic fludioxonil and other natural phenylpyrrole derivatives among the HPDs. We expect that a plethora of highly effective, novel HPDs that are safe for humans and environments will be developed through the generation of an HPD library by microbial biosynthesis and chemical synthesis.

• Bulletin of the Society of Naval Architects of Korea
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• v.21 no.1
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• pp.3-12
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• 1984

Up to now, it has been common to treat the maneuvering motion of a ship as a 3-degree-freedom motion i.e. surge, sway and yaw on the sea surface, for the simplicity and mathematical calculation, and it is quite acceptable in the practical point of view. Meanwhile, considering the maneuverability of a ship under the special conditions such as in irregular waves, in wind or at high speed with small GM value, it is required that roll effect must be considered in the equation of ship motion. In this paper the author tried to build up the 4-degree-freedom motion equation by adding roll. And then, applying the M.M.G.'s mathematical model and with captive model test results the roll-coupled hydrodynamic derivatives were found. With these the author could make some simulating program for turning and zig-zag steering. Through the computer simulations, the effect of roll to the ship maneuver became clear. The effect of the wind force to the maneuverability was also found. Followings are such items that was found. 1) When roll is coupled in the maneuvering motion, the directional stability becomes worse and the turning diameter becomes smaller as roll becomes smaller as roll becomes larger. 2) When maneuver a ship in the wind, the roll becomes severe and the directional stability becomes worse. 3) When a ship turns to the starboard side, the wind blowing from 90 degree direction to starboard causes the largest roll and the largest turning diameter, and the wind from other direction doesn't change the turning diameter. 4) When a ship is travelling with a constant speed with rudder amidship, if steady wind blows from one direction, the ship turns toward that wind. This phenomenon is observed in the actual seaways.

• Journal of Electrochemical Science and Technology
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• v.6 no.3
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• pp.106-110
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• 2015

This study investigates Cu(II) complexes of cyclam, propylene cross-bridged cyclam (PCB-cyclam), and propylene cross-bridged cyclam diacetate (PCB-TE2A) as homogeneous electrocatalysts for CO₂ reduction in comparison with Ni(II)-cyclam. It is found that Cu(II)-cyclam can catalyze CO₂ reduction at the potential close to its thermodynamic value (0.75 V vs. Ag/AgCl) in tris-HCl buffer (pH 8.45) on a glassy carbon electrode. Cu(II)-cyclam, however, suffers from severe demetalation due to the insufficient stability of Cu(I)-cyclam. Cu(II)-PCB-cyclam and Cu(II)-PCB-TE2A are revealed to exhibit much less demetalation behavior, but poor CO₂ reduction activities as well. The inferior electrocatalytic ability of Cu(II)-PCB-cyclam is ascribed to its redox potential that is too high for CO₂ reduction, and that of Cu(II)-PCB-TE2A to the steric hindrance preventing facile contact with CO₂ molecules. This study suggests that in addition to the redox potential and chemical stability, the stereochemical aspect has to be considered in designing efficient electrocatalysts for CO₂ reduction.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.5
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• pp.34-40
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• 2005

Most analyses and researches on Micro Aerial Vehicle(MAV) have focused upon propulsion, automatic control, aerodynamic configuration in low Reynolds number region, and miniaturization of telemetric parts. In the present study, a structural concept for MAV is designed by using the composite material suitable for light flight structures. In order to study the load path and stress state of the MAV, the load and structural analyses are simultaneously performed by the aeroelasticity module of MSC/NASTRAN. The stability derivatives of the MAV are obtained for three symmetric, two antisymmetric, and four unsymmetric maneuvering conditions. Although the aerodynamic theory in MSC/NASTRAN could not be proper for MAV analysis, it provides an traditional and effective tool for trim and load analyses and may be corrected with the results by more accurate theory or test. The results show that the inertial load due to payloads has a more effect on stress rather than the aerodynamic load.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.9
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• pp.88-93
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• 2003

This Paper described the simulation program development for helicopter. In the design of flight control system to accomplish some special missions like UAV, it is important to minimize the execution time obtaining a linear model from nonlinear model that is used for design of controller. The first step for this kind of purpose is to complete a nonlinear model that contains full dynamic characteristics. The second step is to get the trim values that are obtained from the nonlinear model by solving an algebraic equation. And then stability and control derivatives are derived through hovering to forward flight by numerical perturbation that will be used for linear model for a specified flight condition. The software program(HeliSim) is developed by using MATLAB GUI and will provide easy modeling procedure. The suggested method in this paper is much more simpler than any other method like a fully scale helicopter model. The advantage of our suggested method will reduce the computational time due to simple formula to extract a linear model from nonlinear model that will be beneficially used for flight control system of unmanned helicopter by some reduction of computational load.

• Wind and Structures
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• v.29 no.6
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• pp.417-430
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• 2019

To study the wake influence of an upstream bridge on the wind-resistance performance of a downstream bridge, two adjacent long-span cable-stayed bridges are taken as examples. Based on wind tunnel tests, the static aerodynamic coefficients and the dynamic response of the downstream bridge are measured in the wake of the upstream one. Considering different horizontal and vertical distances, the flutter derivatives of the downstream bridge at different angles of attack are extracted by Computational Fluid Dynamics (CFD) simulations and discussed, and the change in critical flutter state is further studied. The results show that a train passing through the downstream bridge could significantly increase the lift coefficient of the bridge which has the same direction with the gravity of the train, leading to possible vertical deformation and vibration. In the wake of the upstream bridge, the change in lift coefficient of the downstream bridge is reduced, but the dynamic response seems to be strong. The effect of aerodynamic interference on flutter stability is related to the horizontal and vertical distances between the two adjacent bridges as well as the attack angle of incoming flow. At large angles of attack, the aerodynamic condition around the downstream girder which may drive the bridge to torsional flutter instability is weakened by the wake of the upstream bridge, and the critical flutter wind speed increases at this situation.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.9 no.2
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• pp.111-119
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• 1976

Discoloration of canned boiled oyster namely greening, yellowing and browning often occur separately or associatively in the storage of the product. Greening is mainly caused by the appearance of chlorophyll and its derivatives on the surface around the digestive diverticula of the oyster and yellowing by dispersion of carotenoid. Browning reactions by sugar amino condensation or enzymatic action, tyrosinase, also cause an undesirable color development. In this paper, the stability and the changes in distributional or partitional ratio of chlorophyll and carotenoid pigment of meat vs viscera in raw and canned oyster during six month storage in order to measure the dispersion rate of both pigments between meat and viscera, and to evaluate the feasibility of discoloration of oyster meat. The development of brownish pigment and the toss of free tyrosine in oyster were also determined to compare the readiness of color development. In addition the influence of processing and storage conditions to the dispersion rate and the tendency of discoloration, and finally the effect of inhibitor were discussed. The results showed that greening or yellowing was initiated by the dispersion of chlorophyll or carotenoids from viscera to the meat of oyster, and the dispersion rate of carotenoid was much higher than the chlorophyll's, so that, yellowing appeared a leading reaction of discoloration. The dispersion rate was obviously fastened by raising the temperature in the process of sterilization and storage. Consequently, the low temperature storage could largely retard the occurance of yellowing or greening of oyster meat. The pH control of canned oyster did not seem to affect the dispersion of pigment but significantly did on the stability of the piqments. Browning by the reaction of sugar-amino condensation and enzymatic oxidation of tyrosine was positively detected in canned oyster meat. The development of brownish color was influenced rather by the storage temperature than the heating process. Addition of sodium sulfite in can or treating the boiled oyster with sulfite solution prior to filling seemed possibly inhibit the color development particularly in cold-storaged oyster meat.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.33 no.3
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• pp.194-200
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• 2020

Perylene bisimide derivatives are developed for red organic phosphor because of their advantages, such as excellent luminous efficiency and high thermal stability. Despite these advantages, they have poor solubility characteristics in organic solvents and short emission wavelength as red organic phosphor for hybrid light-emitting diodes (LEDs). In this study, we prepared terrylene bisimide using a coupling reaction and swallow-tail imide group, which has excellent solubility. The structures and properties of swallow-tail terrylene bisimide (9C) were analyzed using ¹H-nuclear magnetic resonance (¹H-NMR), Fourier-transform infrared (FT-IR), UV/Vis spectroscopy, and thermal gravimetric analysis (TGA). The maximum absorption wavelength of (9C) in the UV/Vis spectrum was 647 nm, and the maximum emission wavelength was 676 nm. In the TGA, (9C) demonstrated good thermal stability with less than 5 wt% weight loss up to 415℃. In the solubility test, (9C) has a good solubility of more than 5 wt% in chloroform and dichloromethane. When the compounds (9C) were mixed with PMMA (polymethly methacrylate), the films showed peaks at 680 nm in the PL spectra. The results verify the suitability of (9C) as a red organic phosphor for hybrid LEDs.

• Applied Chemistry for Engineering
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• v.16 no.6
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• pp.790-793
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• 2005

Recently, the interest in the extension of human life and personal health has been increased. Accordingly, many researchers in a pharmacy and a medical world have been making efforts to improve the sustained drug release property and the stability of drug release property in a body. Many biological researches have demonstrated that chitosan derivatives are effective, safe absorption enhancers that can improve the delivery efficiency of drug and vaccine, and they are suitable for controlled drug release because they have good stability, bio-compatibility, and biodegradability. In this study the experiment was performed in vivo by utilizing chitosan nanoparticles as a biopolymer to control drug delivery rate at an optimal temperature, pH, and concentration. It was observed that nanoparticles containing insulin could effectively control the blood glucose at a low level.