The time dependence of the size distribution of arsenic precipitates during annealing for both large (~10nm) and small size (~4nm) regimes is investigated. A narrowing of the size distribution is observed in the small size regime. This improvement in size uniformity is in marked contrast to what is observed for larger precipitates, which coarsen with a widening distribution similar to that of classical Ostwald ripening. Inverse coarsening caused by an elastic interaction between small precipitates due to coherency strain is a possible mechanism for this interesting and potentially useful behavior.

Large-sized flat-panel displays have become increasingly important for use in computer monitors and televisions. This paper has considered the problem of automatic visual inspection of micro-defects including pinholes, scratches and particles in patterned thin film transistor-liquid crystal display (TFT-LCD) panel surfaces. For large-sized TFT-LCD panel inspection, high-resolution line scan is demanded. We propose a global one-dimensional (1-D) Fourier-based image reconstruction scheme that directly works on the 1-D line images instead of the traditional two-dimensional area images. The proposed method fully uses the inherent geometric structure of a TFT-LCD panel. It first eliminates the frequency components that represent the periodic pattern of a TFT-LCD line image in the 1-D Fourier spectrum and then back-transforms the 1-D Fourier-domain image to the 1-D spatial domain image using the inverse Fourier transform. The Fourier reconstruction process can effectively remove the patterned background and distinctly preserve local anomalies in the resulting 1-D image. Wavelet decomposition is further applied to remove uneven illumination in the filtered image so that defects can be easily segmented with simple statistical control limits. Experimental results on a number of micro-defects embedded in TFT-LCD panels show that the proposed method can reliably detect various ill-defined defects without designing and measuring the quantitative features of individual defect types.

Construction firms specializing in large commercial buildings often purchase large steel plates, cut them into pieces and then weld the pieces into H-beams and other construction components. We formalize the material ordering and cutting problem faced by this industry and propose a grouping genetic algorithm, called CPGEA, for efficiently controlling the relevant costs. We test the quality of CPGEA in various ways. Three sets of simulated problems with known optimal solutions are solved using CPGEA, and the gap between its solutions and optimal solutions is measured. The same problem sets are also solved with an expert system and a multi-start greedy heuristic. CPGEA solutions are found to be consistently lower cost than the competing methods. The difference in solution quality is most pronounced for difficult problems requiring multiple identical plates in the optimal solution. CPGEA is also tested using data from actual construction projects of a company faced with this problem. Since an optimal solution for the problems is not available, a lower bound is created. For the historical problems tested, the average percent difference between CPGEA solutions and the lower bound is 0.67%. To put this performance in context, the results of solving these problems with an expert system and using experienced engineers is also reported. Of these three methods, CPGEA achieves the best performance and the human experts the worst performance.

A challenge in neutron diffraction experiments is growing large (greater than 1 cubic millimeter) macromolecule crystals.In taking up this challenge we have used statistical experiment design techniques to quickly identify crystallization conditions under which the largest crystals grow.These techniques provide the maximum information for minimal experimental effort, allowing optimal screening of crystallization variables in a simple experimental matrix, using the minimum amount of sample.Analysis of the results quickly tells the investigator what conditions are the most important for the crystallization.These can then be used to maximize the crystallization results in terms of reducing crystal numbers and providing large crystals of suitable habit.We have used these techniques to grow large crystals of glucose isomerase.Glucose isomerase is an industrial enzyme used extensively in the food industry for the conversion of glucose to fructose.The aim of this study is the elucidation of the enzymatic mechanism at the molecular level.The accurate determination of hydrogen positions, which is critical for this, is a requirement that neutron diffraction is uniquely suited for.Preliminary neutron diffraction experiments with these crystals conducted at the Institute Laue-Langevin (Grenoble, France) reveal diffraction to beyond 2.5 Ǻ. Macromolecular crystal growth is a process involving many parameters, and statistical experimental design is naturally suited to this field.These techniques are sample independent and provide an experimental strategy to maximize crystal volume and habit for neutron diffraction studies.

Direct phase determination of surface in-plane reflection is realized for thin films on substrates by using substrate reflections as an intermediary to enhance the coherent interaction in resonant multiwave grazing incidence diffraction in thin films. The coupling of the in-plane diffracted waves at the interface between the thin film and the substrate is essential. The intensity variation due to this enhanced interaction/coupling becomes clearly visible, thus leading to unambiguous phase determination. This opens a different way for direct phase determination of surface reflections in thin films.

A detailed analysis of multiple diffraction data collected by the stereoscopic multibeam imaging technique from a tetragonal lysozyme crystal is reported. Calculations based on the dynamical theory are employed to account for diffraction profiles obtained with Bragg-angle scan in stereoscopic imaging and the conventional azimuthal scan in Renninger arrangement. The formation of a multibeam intensity profile and the relationship and mutual influence between the two scans are investigated. A simple practical method of quantitative estimation of the reflection phases of structure-factor multiplets from the experimental data obtained with two inversion-symmetry-related diffractions is proposed. The procedures for data handling and for distinguishing "partial" diffraction images from "full" diffraction images are also developed considering multibeam diffraction geometry and experimental conditions. These procedures thus provide a practical way of reconstructing diffraction profiles for experimental phase determination for macromolecular crystals.

Firms specializing in the construction of large commercial buildings and factories must often design and build steel structural components as a part of each project. Such firms must purchase large steel plates, cut them into pieces and then weld the pieces into H-beams and other construction components. The details of the order and the production operation are specified in the cutting plan. This dissertation focuses on solving this cutting plan generation problem with the goal of minimizing cost. Two solution approaches are proposed in this dissertation: a multi-expert system and an evolutionary algorithm. The expert system extends the field by relying on the knowledge of multiple experts. Furthermore, unlike traditional rule-base expert systems, this expert system (XS) uses procedural rules to capture and represent experts' knowledge. The second solution method, called CPGEA, involves development of an evolutionary algorithm based on Falkenauer's grouping genetic algorithm. A series of experiments is designed and performed to investigate the efficiency and effectiveness of the proposed approaches. Two types of data are used in the experiments. Historical data are real data provided by a construction company. Solutions developed manually and implemented are available. In addition, simulated data has been generated to more fully test the solution methods. Experiments are performed to optimize CPGEA parameters as well as to compare the approaches to each other, to known solutions and to theoretical bounds developed in this dissertation. Both approaches show excellent results in solving historical cases with an average cost 1% above the lower bound of the optimal solution. However, as revealed by experiments with simulated problems, the performance decreases in

Construction firms specializing in large commercial buildings must often design and build steel structural elements as a part of each project. Such firms must purchase large steel plates, cut them into pieces and then weld the pieces into H-beams and other construction components. We formalize the material ordering and cutting problem faced by this industry and propose an expert system for efficiently combining steel elements into plates to control relevant costs. This expert system is based on the procedural knowledge of multiple experts rather than on the rules of a single expert as is more common. We tested the expert system using data supplied by Lien-Kang Heavy Industrial Company, Ltd. (LK) as well as using simulated data with known optimal solutions. Comparison to LK's solutions indicates that the expert system solution is less costly in every historical project. Testing on 40 simulated projects reveals how problem parameters affect performance. The expert system has been embedded into a decision support system (DSS) that LK is currently using. The qualitative benefits of using this computerized system include a significant reduction in the time and effort required for generating a solution and increased report accuracy.

In this article, we report the magnetic properties of ultrathin (15–200 Å) NiFe and CoFe films deposited using ion beam deposition techniques. They are symmetrically sandwiched between Ta, Cu, or Ta/Cu under and capping layers. NiFe and CoFe films grown between Ta/Cu and Cu/Ta bilayers exhibit the smallest magnetic thickness loss of about 1 Å. This interfacial magnetic dead layer thickness, t0, is about 5 Å for Cu-sandwiched films and about 15 Å for Ta-sandwiched films. As the film thickness becomes thinner than 100 Å, the magnetic properties are found to be more sensitive to the choice of material and growth environment. CoFe films show an interfacial contribution, λi, about ten times larger than that for NiFe films. Among others, NiFe and CoFe films sandwiched by Ta/Cu and Cu/Ta bilayers exhibit the smallest values of λi. The magnetic anisotropy in Ta-sandwiched CoFe films appears to be predominantly magnetoelastic in nature.

Two sets of PtPdMn exchange biased films Ta 50 Å/CoFe 100 Å/PtPdMn (tAF) Å/Ta 50 Å, with PtPdMn thickness, tAF=350, 600 Å, were deposited on Si substrates by dc magnetron sputtering techniques. After magnetic annealing, these two sets of films exhibited values of exchange bias field, Hex=229 and 254 Oe, respectively. The PtPdMn layer was then thinned to various thicknesses from 600 down to 50 Å by ion beam etching. Hex does not retain its original value. It decreases with decreasing tAF and becomes zero at tAF∼75 Å. In addition, we have observed that the training effect or the anomalous hysteresis loss becomes more pronounced with decreasing tAF. This confirms that not only face-centered-tetragonal phase but, more critically, tAF plays role in determining exchange biasing and its thermal stability. The blocking temperature, TB, appears unaffected by the thinning of the PtPdMn layer, and no apparent change occurs in the local blocking temperature distribution, as suggested by the finite size effect.

Sputter deposited FeRhN films with unique microstructural characteristics are presented. They consist of fine α-Fe and γ-Fe4N grains with slightly expanded lattice parameters, which result in soft magnetic properties of the film. The significant amount of face-centered-cubic Fe4N phase gives rise to higher resistivity and therefore improved high frequency permeability than conventional FeRhN films.

IrMn exchange biased bottom spin-valve films of structure Ta/underlayer/IrMn/CoFe/Cu/CoFe/NiFe/Ta were prepared using ion beam deposition techniques. The exchange bias field exhibits strong underlayer thickness dependence. For the first time, a large exchange energy of 0.29 erg/cm(2) was measured in spin-valve films exchange biased by a disordered antiferromagnet, comparable to the values usually obtained in spin-valve films exchange biased by an ordered antiferromagnet.We have conducted a comparative study on both bottom and top exchange biased spin-valve and ferromagnetic/antiferromagnetic bilayer films. The results indicate that the exchange field obeys very well the inverse pinned layer thickness law over a thickness range from 200 Angstrom down to 10 Angstrom. The exchange energy for bottom spin-valve films is, however, a factor of two larger than that for top spin-valve films. When normalized, the exchange field exhibits the same temperature dependence for both bottom and top spin-valve films.The enhancement in exchange biasing is mainly attributed to an enhanced texture for fcc (111) crystallographic orientation of the IrMn layer in bottom spin-valve films.

The use of strain to direct the assembly of nanoparticle arrays in a semiconductor is investigated experimentally and theoretically. The process uses crystal strain produced by a surface structure and variations in layer composition to guide the formation of arsenic precipitates in a GaAs-based structure grown at low temperature by molecular beam epitaxy. Remarkable patterning effects, including the formation of single and double one-dimensional arrays with completely clear fields are achieved for particles in the 10-nm size regime at a depth of about 50-nm from the semiconductor surface. Experimental results on the time dependence of the strain patterning indicates that strain controls the late stage of the coarsening process, rather than the precipitate nucleation. Comparison of the observed particle distributions with theoretical calculations of the stress and strain distributions reveals that the precipitates form in regions of maximum strain energy, rather than near extremum points of hydrostatic stress or dilatation strain. It is therefore concluded that the patterning results from modulus differences between the particle and matrix materials rather than from other strain related effects. The results presented here should be useful for extending strain directed assembly to other materials systems and to other configurations of particles.

A narrowing of the size distribution of arsenic precipitates in nonstoichiometric GaAs-based compounds is observed during annealing for precipitates in the small size regime of a few nanometers. This improvement in size uniformity is in marked contrast to what is observed for larger precipitates, which coarsen with a widening distribution similar to that of classical Ostwald ripening. Inverse coarsening caused by an elastic interaction between small precipitates due to coherency strain is a possible mechanism for this interesting and potentially useful behavior.

A large value of giant magnetoresistance ΔR/R=9% with an exchange field Hex=350 Oe has been measured from simple NiFe/CoFe/Cu/CoFe/IrMn top spin-valve films prepared by ion beam deposition (IBD) techniques. The exchange biasing was greatly enhanced when a synthetic pinned layer, CoFe/Ru/CoFe, is used in the spin-valve structures. Apparent exchange field values in excess of 2000 Oe and ΔR/R values above 8% have been obtained in synthetic spin-valve films. These IBD spin-valve films show excellent thermal stability and they are suitable for the applications in high density magnetic recording heads.

Spin-valve (SV) films Si(100)/Ta30/NiFe50/CoFe20/Cu26/CoFe23/Ru7/CoFe20/IrMn50/Ta30 (in Å) exhibit a room temperature (RT) giant magnetoresitance (GMR) ratio of 8.5% with an effective exchange pinning field (Heex) of ∼1.3 kOe and an antiferromagnetic (AF) saturation field (Hs) of ∼6.0 kOe. The synthetic spin valve shows a GMR ratio of 5.0% at 150 °C with Heex>500 Oe, while a conventional spin valve [Si(100)/Ta50/NiFe50/CoFe20/Cu28/CoFe22/IrMn50/Ta50 in Å] has a GMR ratio of 5.0% with Hex<200 Oe. The synthetic sample also showed a superior thermal stability with a RT GMR value of 6.9% (compared to 6.1% for conventional sample) after an anneal at 250 °C for 10 h. Shielded narrow track synthetic SV readers demonstrated high amplitude, large dynamic range, and excellent magnetic stability, indicating extendibility for ultrahigh density read head applications.

The spatial distribution of arsenic precipitates formed in a nonstoichiometric AlGaAs/GaAs quantum well is examined for different annealing temperatures and times. Preferential precipitation in the GaAs layer of samples annealed at 600 °C is found to be much weaker than in samples annealed at 850 °C because of the reduced diffusion of arsenic at lower temperatures. Nevertheless, it is demonstrated that strong preferential precipitation is possible at low annealing temperatures, provided that the annealing time is sufficiently long. Limitations to the preferential precipitation process imposed by interface mixing and the decrease in gallium vacancy concentration during annealing are also examined.

An approach for the enantioselective synthesis of functionalized γ-lactones and its application to the syntheses of (−)-muricatacin 1a and 5-epi-(−)-muricatacin 1b is reported. A sequential oxidation of the intermediate 4 with m-chloroperoxybenzoic acid was conducted to realize the reaction mechanism.