• Journal of Microbiology and Biotechnology
• /
• v.18 no.9
• /
• pp.1522-1528
• /
• 2008

The morphogenetic behavior of a tropical marine Yarrowia lipolytica strain on hydrophobic substrates was studied. Media containing coconut oil or palm kernel oil (rich in lauric and myristic acids) prepared in distilled water or seawater at a neutral pH supported 95% of the cells to undergo a transition from the yeast form to the mycelium form. With potassium laurate, 51 % of the cells were in the mycelium form, whereas with myristate, 32% were in the mycelium form. However, combinations of these two fatty acids in proportions that are present in coconut oil or palm kernel oil enhanced the mycelium formation to 65%. The culture also produced extracellular lipases during the morphogenetic change. The yeast cells were found to attach to the large droplets of the hydrophobic substrates during the transition, while the mycelia were associated with the aqueous phase. The alkane-grown yeast partitioned more efficiently in the hydrophobic phases when compared with the coconut oil-grown mycelia. A fatty acid analysis of the mycelial form revealed the presence of lauric acid in addition to the long-chain saturated and unsaturated fatty acids observed in the yeast form. The mycelia underwent a rapid transition to the yeast form with n-dodecane, a medium-chain aliphatic hydrocarbon. Thus, the fungus displayed a differential behavior towards the two types of saturated hydrophobic substrates.

• Journal of Pharmaceutical Investigation
• /
• v.41 no.6
• /
• pp.371-376
• /
• 2011

The objective of this work was to investigate the existence of new crystal forms of tulobuterol which is used to prevent morning asthma attacks by ${\beta}_2$ agonist and the transformation of crystal forms. Three crystal forms of tulobuterol have been isolated by recrystallization and Form 2 was transformed to Form 4 at 52% RH and 95% RH and these four crystal forms are characterized by differential scanning calorimetry (DSC), powder X-ray diffractometry (PXRD) and thermogravimetric analysis (TG). The DSC and PXRD patterns of four crystal forms of tulobuterol were different respectively. The dissolution patterns of these three crystal forms of tulobuterol were studied and they showed significant differences in the dissolution rate. After storage of 2 months at 0% RH (silica gel, $20^{\circ}C$), 52% RH (saturated solution of $Na_2Cr_2O_7{\cdot}2H_2O/20^{\circ}C$) and 95% RH (saturated solution of $Na_2HPO_4/20^{\circ}C$), Form 1 and Form 3 were not transformed. But Form 2 was transformed to Form 4 at 52% RH and 95% RH.

• Communications of the Korean Mathematical Society
• /
• v.11 no.2
• /
• pp.407-413
• /
• 1996

The $(\alpha, \beta)$-metric is a Finsler metric which is constructed from a Riemannian metric $\alpha$ and a differential 1-form $\Beta$; it has been sometimes treat in theoretical physics. In particular, the projective flatness of Finsler space with a metric $L^2 = 2\alpha\beta$ is considered in detail.

• 전기의세계
• /
• v.27 no.2
• /
• pp.53-63
• /
• 1978

The problem of optimally controlling a time-delay control system to a function as the final target is inverstigated. Necessary conditions are presented in the form of Pontryagin's maximum principle, and it is further shown that they are also sufficient for linear systems with a convex cost functional. Several examples are given to illustrate the results.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.30 no.3
• /
• pp.8-16
• /
• 2002

The implicit formulation of rotor dynamics for helicopter flight simulation has been derived and and presented. The generalized vector kinematics regarding the relative motion between coordinates were expressed as a unified matrix operation and applied to get the inertial velocities and accelerations at arbitaty rotor blade span position. Based on these results the rotor aeromechanic equations for flapping dynamics, lead-lag dynamics and torque dynamics were formulated as an implicit form. Spatial integration methods of rotor dynamic equations along blade span and the expanded applicability of the present implicit formulations for arbitrary hings geometry and hinge sequences have been investigated. Time integration methods for present DAE(Differential Algebraic Equation) to calculate dynamic response calculation are recommenaded as future works.

• BMB Reports
• /
• v.35 no.4
• /
• pp.364-370
• /
• 2002

The effect of sodium n-dodecyl sulphate (SDS) on hemoglobin autoxidation was studied in the presence of a 100mM phosphate buffer (pH 7.0) by different methods. These included spectorphotometry, fluorescence technique, cyclic voltametry, differential scanning calorimetry, and densitometry. Spectroscopic studies showed that SDS concentrations up to 1 mM increased deoxy-, decreases oxy-, and had no significant effect on the met- conformation of hemoglobin. Therefore, a SDS concentration up to 1 mM increased the deoxy form of hemoglobin as the folded, compact state and decreases the oxy conformation. The turbidity measurements and differential scanning calorimetry techniques indicated a more stable conformation for hemoglobin in the presence of SDS up to 1mM. Electrochemical studies also confirmed a more difficult oxidation under these conditions. The induction of the deoxy form in the presence of SDS was confirmed by densitometry techniques. The compact structure of deoxyhemoglobin blocks the formation of met-conformation in low SDS concentrations.

• Structural Engineering and Mechanics
• /
• v.54 no.4
• /
• pp.793-807
• /
• 2015

Constructing the influence lines of forces of statically indeterminate structures is a traditional issue in structural engineering and mechanics. However, the existing kinematic method for establishing these force influence lines is an indirect or mixed approach by combining the force method with the theorem of reciprocal displacements, which is yet inconsistent with the kinematic method for statically determinate structure. This paper proposes the direct kinematic method in conjunction with the load-displacement differential relation for exactly constructing influence lines of reaction and internal forces of indeterminate structures. Firstly, through applying the principle of virtual displacement, the formula for influence lines of reaction and internal forces of indeterminate structure via direct kinematic method is derived based on the released structure. Then, a computational approach with a clear concept and unified procedure as well as wide applicability based on the load-displacement differential relation of beam is suggested to achieve conveniently the closed-form expression of force influence lines, and exactly draw them. Finally, three representative examples for constructing force influence lines of statically indeterminate beams and frame illustrate the superiority of the proposed method.

• Structural Engineering and Mechanics
• /
• v.86 no.1
• /
• pp.49-68
• /
• 2023

This study investigates the static and dynamic structural analysis of symmetrical and asymmetrical coupled shear walls using the continuous and modified transfer matrix methods by idealizing the coupled shear wall as a three-field CTB-type replacement beam. The coupled shear wall is modeled as a continuous structure consisting of the parallel coupling of a Timoshenko beam in tension (with axial extensibility in the shear walls) and a shear beam (replacing the beam coupling effect between the shear walls). The variational method using the Hamilton principle is used to obtain the coupled differential equations and the boundary conditions associated with the model. Using the continuous method, closed-form analytical solutions to the differential equation for the coupled shear wall with uniform properties along the height are derived and a numerical solution using the modified transfer matrix is proposed to overcome the difficulty of coupled shear walls with non-uniform properties along height. The computational advantage of the modified transfer matrix method compared to the classical method is shown. The results of the numerical examples and the parametric analysis show that the proposed analytical and numerical model and method is accurate, reliable and involves reduced processing time for generalized static and dynamic structural analysis of coupled shear walls at a preliminary stage and can used as a verification method in the final stage of the project.

• Structural Engineering and Mechanics
• /
• v.72 no.2
• /
• pp.229-244
• /
• 2019

Weak form integral equations are developed to investigate the flapwise bending vibration of the rotating beams. Rayleigh and Eringen nonlocal elasticity theories are used to investigate the rotatory inertia and Size-dependency effects on the flapwise bending vibration of the rotating cantilever beams, respectively. Through repetitive integrations, the governing partial differential equations are converted into weak form integral equations. The novelty of the presented approach is the approximation of the mode shape function by a power series which converts the equations into solvable one. Substitution of the power series into weak form integral equations results in a system of linear algebraic equations. The natural frequencies are determined by calculation of the non-trivial solution for resulting system of equations. Accuracy of the proposed method is verified through several numerical examples, in which the influence of the geometry properties, rotatory inertia, rotational speed, taper ratio and size-dependency are investigated on the natural frequencies of the rotating beam. Application of the weak form integral equations has made the solution simpler and shorter in the mathematical process. Presented relations can be used to obtain a close-form solution for quick calculation of the first five natural frequencies of the beams with flapwise vibration and non-local effects. The analysis results are compared with those obtained from other available published references.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2017.05a
• /
• pp.547-553
• /
• 2017

Thermal analysis of three energetic materials used in pyroelectric device was performed using Differential Scanning Calorimetry (DSC). The theoretical method for extracting the reaction rate equation of energetic materials using DSC experimental data is proposed and the reaction rate extraction is performed. The results of the DSC were analyzed by the conversion method such as Friedman. Activation energy and frequency factor according to mass fraction were extracted to complete the reaction rate equation. The extracted reaction rate equation has a form that represents the entire chemical reaction process, not the assumption that the chemical reaction process of the high energy material is a main step in several stages. It has considerable advantages in terms of theoretical and accuracy as compared with the chemical reaction rate form extracted through conventional thermal analysis experiments. Using the derived reaction rate equation, we predicted the performance change of three energetic materials operating on actual storage condition over 20 years.