Bi-layered materials are a reduced weight derivative of the sandwich structure and are comprised of one thin skin face reinforced by a thick layer of low density material. Bi-layered materials are characterized by high flexural stiffness and are a viable alternative to conventional sandwich materials in applications where the functional requirements can be met without the second face sheet of the sandwich. For structural applications bi-layered materials are required to have oil canning and buckling resistance. This work addresses the buckling of shallow bi-layered arches using numerical and analytical approaches. A numerical, finite element model is developed to simulate the buckling phenomenon and the results were compared with known experimental data. An analytical model was developed using the energy method analysis and the buckling load was predicted from the minimum energy criterion. Comparison of the numerical and analytical results yielded fairly good agreement. An imperfection analysis conducted by means of the numerical model indicated that the load carrying capacity of bi-layered structures is reduced by up to 40% due to the presence of material and geometric imperfections. A parametric study conducted using the analytical model has been described to setup design guidelines for shallow bi-layered arches. It was found that the use of bi-layered structures can result in weight reduction of around 70% when compared with equivalent single layered structure.

The laminar-to-turbulent transition process in swept-wing boundary layers is often dominated by an inflectional instability arising from crossflow. It is now known that freestream turbulence and surface roughness are two of the key disturbance sources in the crossflow instability problem. Recent experimental findings have suggested that freestream turbulence of low intensity (less than 0.2%) may have a larger influence on crossflow instability than was previously thought. The present work involves experimental measurement of stationary and traveling crossflow mode amplitudes in freestream turbulence levels between 0.02% and 0.2%. A 1.83 m chord, 45-degree swept-wing model is used in the Klebanoff-Saric Wind Tunnel to perform these experiments. The turbulence intensity and length scales are documented. Although a significant amount of research on the role of turbulence has been completed at higher turbulence levels, comparatively little has been done at the low levels of the present experiments, which more closely reflect the flight environment. It is found that growth of the traveling crossflow mode is highly dependent on small changes to the freestream turbulence. Additionally, previously studied attenuation of saturated stationary disturbance amplitudes is observed at these low turbulence levels. The extent of laminar flow is also observed to decrease in moderate freestream turbulence.

In this study, it was nanoimprint focused on the anti-adhesion technique between the grating structure silicon molds below 200nm half-pitch and polymer materials (H-PDMS). The nano-groove structure molds with different depths and widths were made by FIB. During the process of molding by soft-lithography, an anti-adhesion layer needed being plated between the silicon and PDMS mold, which was in order to get completely formed H-PDMS soft mold and prevent defective mold caused by the adhesion problem on the surface. There were three kinds of method of plating anti-adhesion layer which were the liquid immersion, vapor deposition, and fluorine doped DLC film. The PFOTCS was used as mold releasing agent in the methods of liquid immersion and vapor deposition, and the contact angle was measured to realize the ability of anti-adhesion. In the method of fluorine doped DLC film, in addition to measuring the anti-adhesion ability for each sample through contact angle with water, the AFM was also applied to measure the degree of adhesion on the surface for each film. And the contact angles with water between each film were also compared. The methods of plating anti-adhesion film with lower degree of adhesion on the surface could be acquired and discussed by means of the above-mentioned ways to fabricate the molds with good formability

Bi-layered materials are a reduced weight derivative of the sandwich structure and are comprised of one thin skin face reinforced by a thick layer of low density material. Bi-layered materials are characterized by high flexural stiffness and are a viable alternative to conventional sandwich materials in applications where the functional requirements can be met without the second face sheet of the sandwich. For structural applications bi-layered materials are required to have oil canning and buckling resistance. This work addresses the buckling of shallow bi-layered arches using numerical and analytical approaches. A numerical, finite element model is developed to simulate the buckling phenomenon and the results were compared with known experimental data. An analytical model was developed using the energy method analysis and the buckling load was predicted from the minimum energy criterion. Comparison of the numerical and analytical results yielded fairly good agreement. An imperfection analysis conducted by means of the numerical model indicated that the load carrying capacity of bi-layered structures is reduced by up to 40% due to the presence of material and geometric imperfections. A parametric study conducted using the analytical model has been described to setup design guidelines for shallow bi-layered arches. It was found that the use of bi-layered structures can result in weight reduction of around 70% when compared with equivalent single layered structure.

Abstract The behaviors of the TaNx barrier layer that placed between the Cu metal and GaAs have been studied by using X-ray diffraction, X-ray photoelectron spectroscopy and scanning electron microscopy. The TaNx and Cu films were deposited on GaAs sequentially with RF magnetron sputter. With a 250 nm thick TaNx barrier layer, the Cu metal can be impeded from reacting with GaAs substrate at 575¢Jannealed for one hour. Within an As or Ga overpressure environment condition, the failure temperature still occurred below 600¢J. The failure of TaNx diffusion barrier layer for preventing the reaction of the Cu and GaAs was originated for the dissociation of the GaAs itself at 580¢J. The outgoing As atoms increased the deterioration speed of the TaNx film and reduced its blocking ability.

Abstract This study focuses on analyzing depth distributions of d18O and changes in mixed layer thickness in the South China Sea (SCS). The oxygen isotopic compositions of the samples collected were determined using the Epstein-Mayeda (1953). The overall precision of the d18OSMOW measurements is +0.1‰. Our data suggest that depth changes of average d18OSMOW of seawater in the SCS as follows: the average d18OSMOW values for the surface (0-100m) is 0.02‰; subsurface (100-400m) is 0.2‰; intermediate (400-1500m) is ¡V0.03‰ and deep waters (>1500m) is ¡V0.06‰. The effect of monsoon on the mixed layer in the SCS water is evident as the increases in the mixed layer is always coincident with the northeast monsoon in winter. Furthermore, the d18OSMOW values are correlated linearly with the mixed layer thickness. In other words, the lower d18OSMOW values of seawater are, the less the thickness of mixed layer is.

The work of this thesis includes molecular beam epitaxy (MBE) and optical study of strained InGaAs and InGaAlAs multiple quamtum well (MQW) structures. Two strained layer structures suitable for devices applications have been designed, grown, and investigated. The first one is a 0.98-

Thesis (M.S. in Meteorology and Oceanography)--Naval Postgraduate School, September 1990. / Thesis Advisor(s): Shaw, W.J. Second Reader: Nuss, W.A. "September 1990." Description based on title screen as viewed on December 29, 2009. DTIC Identifier(s): Marine atmospheres, marginal ice zones, geostropic wind, atmospheric boundary layer, stratus clouds, cumulus clouds, stratocumulus clouds, wind velocity, temperature inversion, air ice interactions. Author(s) subject terms: Marginal ice zone. Includes bibliographical references (p. 45-46). Also available in print.

Thesis (Ph. D.)--University of Washington, 2001. / Vita. Includes bibliographical references (p. 125-136).

Thesis (Ph. D.)--University of Washington, 2002. / Vita. Includes bibliographical references (leaves 184-197).