• International Journal of Aeronautical and Space Sciences
• /
• 제3권2호
• /
• pp.82-87
• /
• 2002

Aerodynamic analysis of NACA wings moving with a constant speed over guideways are performed using an indirect boundary element method (potential-based panel method). An integral equation is obtained by applying Green's theorem on all surfaces of the fluid domain. The surfaces over the wing and the guideways are discretized as rectangular panel elements. Constant strength singularities are distributed over the panel elements. The viscous shear layer behind the wing is represented by constant strength dipoles. The unknown strengths of potentials are determined by inverting the aerodynamic influence coefficient matrices constructed by using the no penetration conditions on the surfaces and the Kutta condition at the trailing edge of the wing. The aerodynamic characteristics for the wings flying over nonplanar ground surfaces are investigated for several ground heights.

• 한국원자력학회:학술대회논문집
• /
• 한국원자력학회 1996년도 춘계학술발표회논문집(3)
• /
• pp.111-116
• /
• 1996

IGSCC(Intergranular stress corrosion cracking) behaviors of Alloy 600 were studied by the electrchemical ten methods of controlling specimens electrode potentials in the active-passive transition region of anodic polarization curve. Anodic polarization and static potential tests of stressed C-ring type MA Alloy 600 were carried out in 10% NaOH at 300 $^{\circ}C$ for 7days. It was confirmed that IGSCC of Alloy 600 was accellerated by maintaining the specimen potential in the susceptible active-passive transition region of anodic polarization curve. An intergranular crack was initiated on the surface area of C-ring specimens where protective oxide layer was broken down. And the depth of the crack growth was about 100 ${\mu}$m during the testing periods.

• 전자공학회논문지D
• /
• 제36D권4호
• /
• pp.70-76
• /
• 1999

Punchthroush 원통형 접합의 항복전압에 대한 해석적 모델을 에피층의 두께와 nonpunchthrough 원통형 접합의 항복시 임계공핍영역폭이 함수로 제안하였다. 이 해석적 모델에서의 모든 거리변수와 전계 및 전위식을 정규화된 형태로 사용하므로써 항복전압을 소자의 물리적 parameter에 관계없이 쉽게 결정할 수 있게 하였다. 제안된 모델의 계산결과를 2차원 소자 Simulation Program인 MEDICI를 사용하여 얻은 결과와 비교하여 매우 잘 일치함을 보였다.

• 생약학회지
• /
• 제17권1호
• /
• pp.1-6
• /
• 1986

A cardiac principle of Aconiti tuber, higenamine was analyzed with a differential pluse voltammetry employing a glassy carbon electrode. The peak potentials for the oxidation of higenamine were varied depending on the pH of the media. Higenamine at the concentration of $5.4{\times}10^{-7}M$ (0.146ppm) was easily determined using a pH 7.0 phosphate buffer. The amounts of higenamine in the crude Aconiti tuber and tablets containing A. tuber were determined by a standard addition method after extracting with methanol, partitioning with a mixture of $H_2O$ and $CHCl_3$, and freeze-drying the aqueous layer.

• 한국초전도ㆍ저온공학회논문지
• /
• 제17권4호
• /
• pp.1-7
• /
• 2015

This paper addresses technical problems of thermal contact conductance or resistance which inevitably occurs in most cryogenic engineering systems. The main focus of this paper is to examine what kind of physical factors primarily influences the thermal contact resistance and to suggest how it can be minimized. It is a good practical rule that the contact surface must have sub-micron roughness level with no oxide layer and be thinly covered by indium, gold, or Apiezon-N grease for securing sufficient direct contact area. The higher contact pressure, the lower the thermal contact resistance. The general description of this technique has been widely perceived and reasonable engineering results have been achieved in most applications. However, the detailed view of employing these techniques and their relative efficacies to reduce thermal contact resistances need to be thoroughly reviewed. We should consider specific thermal contact conditions, examine the engineering requirements, and execute each method with precautions to fulfil their maximum potentials.

• 대한기계학회논문집A
• /
• 제21권2호
• /
• pp.232-244
• /
• 1997

In this paper weight function theory is extended to the determination of the stress intensity factors for the mode I in elliptic crack. For the calculation of the fundamental fields Poisson's theorem and Ferrers's method were employed. Fundamental fields are constructed by single layer potentials with surface density of crack harmonic fundamental polynimials. Crack harmonic fundamental polynimials up to order four were given explicitly. As an example of the application of the weight function theory the stress intensity factors along crack tips in nearly penny-shaped elliptic crack are calculated.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2011년도 제40회 동계학술대회 초록집
• /
• pp.11-11
• /
• 2011

In this talk, I will discuss roles of pseudo vector and scalar potential in changing physical properties of graphene systems. First, graphene under small uniaxial strain is shown to be described by the generalized Weyl's Hamiltonian with inclusion of pseudo vector and scalar potential simultaneously [1]. Thus, strained graphene is predicted to exhibit velocity anisotropy as well as work function enhancement without any gap. Second, if homogeneous strains with different strengths are applied to each layer of bilayer graphene, transverse electric fields across the two layers can be generated without any external electronic sources, thereby opening an energy gap [2]. This phenomenon is made possible by generation of inequivalent pseudo scalar potentials in the two graphene layers. Third, when very tiny lateral interlayer shift occurs in bilayer graphene, the Fermi surfaces of the system are shown to undergo Lifshitz transition [3]. We will show that this unexpected hypersensitive electronic topological transition is caused by a unique interplay between the effective non-Abelian vector potential generated by sliding motions and Berry's phases associated with massless Dirac electrons.

• Smart Structures and Systems
• /
• 제1권3호
• /
• pp.309-324
• /
• 2005

This paper presents an efficient and accurate coupled beam model for piezoelectric bimorphs based on improved first-order shear deformation theory (FSDT). The model combines the equivalent single layer approach for the mechanical displacements and a layerwise modeling for the electric potential. General electric field function is proposed to reasonably approximate the through-the-thickness distribution of the applied and induced electric potentials. Layerwise defined shear correction factor (k) accounting for nonlinear shear strain distribution is introduced into both the shear stress resultant and the electric displacement integration. Analytical solutions for free vibrations and forced response under electromechanical loads are obtained for the simply supported piezoelectric bimorphs with series or parallel arrangement, and the numerical results for various length-to-thickness ratios are compared with the exact two-dimensional piezoelasticity solution. Excellent predictions with low error estimates of local and global responses as well as the modal frequencies are observed.

• Macromolecular Research
• /
• 제16권1호
• /
• pp.51-56
• /
• 2008

Spherical micelles of poly(styrene-b-isoprene) (SI) diblock copolymers in selective solvents have been reported to pack onto either face-centered cubic (fcc) or body-centered cubic (bcc) lattices. The selection rule for fcc and bcc lattices has been understood in terms of the intermicellar potentials, and they have been quantified using the ratio of the corona layer thickness to the core radius, $L/R_c$, as suggested by McConnell and Gast. In order to test the validity of the McConnell-Gast criterion, this study compared the $L/R_c$ values from various solutions i.e. nine SI copolymers in several different selective solvents. The McConnell-Gast criterion was not found to be a determining factor, even though it could explain the fcc/bcc selection qualitatively. From the phase diagrams, the transition between fcc and bcc phases was also considered as a function of concentration and temperature, and their physical mechanisms are discussed based on the recent mean-field calculation reported by Grason.

• Journal of Welding and Joining
• /
• 제29권5호
• /
• pp.90-94
• /
• 2011

Ag metallic particles from nano-scale to submicron-scale are combined with organic solvent to provide fine circuits and interconnection. Ink-jet printing with Ag nano particle inks demonstrated the potentials of the new printed electronics technology. The bonding at the interface between the Ag wiring layer and the various substrates is very important. In this study, the details of interfaces in Ag wiring are investigated primarily by microstructure observation. By adjusting the materials and sintering conditions, nicely formed interfaces between Ag wiring and Cu, Au or organic substrates are achieved. In contrast, transmission electron microscope (TEM) image clearly shows interface debonding between Ag wiring and Sn substrate. Sn oxides are formed on the surface of the Sn plating. The formation of these is a root cause of the interface debonding.