Growth-dependent refractive index nonlinearity and mean microstructural properties of codeposited composite gadolinia silica films

Codeposited gadolinia silica composite films have been probed for their growth-dependent optical and microstructural properties using phase-modulated spectroscopic ellipsometry and scanning probe microscopy. The mean refractive indices were computed using an effective ellipsometric multilayer modeling approach. Most of the composite films have shown growth-induced nonlinear refractive indices to some extent. However, the mean optical properties have depicted interesting trends in the microstructural evolutions. Gadolinia silica composite films in the composition ratio ranging from 90:10 to 70:30 have depicted superior optical as well as morphological properties. Unlike conventional oxide films, these composite films displayed microstructural, spectral refractive index, and bandgap supremacy over the pure films. Such an observation cannot be explained by the empirical Moss law. Atomic force microscopy also revealed a superior morphology in the composite films. The autocorrelation and height-height correlation functional analysis have distinctly supported such superior microstructural features in the composite films, which justifies the supremacy of the optical properties. Such an observation has opened up possibilities to utilize such composite films toward deep-and extreme-ultraviolet spectral regions of the electromagnetic spectrum.     

CAE FOR THE MANUFACTURING ENGINEER: THE ROLE OF PROCESS SIMULATION IN CONCURRENT ENGINEERING

As America refocuses its attention on the factory, design and manufacturing engineers must work together closely to design the appropriate products, and matching production process in a team effort. By building off the designer's CAE tools that predict product performance, the manufacturing engineer is today able to simulate the proposed production process. Process simulations for the following manufacturing processes are available or being developed:

▪Forging, ▪Machining, ▪Injection Molding, ▪Die Casting, ▪Investment Casting, ▪Metal Forming, ▪Heat Treating, ▪Assembly Tolerancing

By utilizing the same 3-D solid model and finite element modeling tools used by the designer, coupled to powerful analysis simulation tools to predict the transient nonlinear heat transfer and plastic material flow found in many manufacturing processes, the manufacturing engineer is able to explore alternative processing plans, evaluate trade-offs and even influence the design to produce superior products.

Process simulation brings a science to support the manufacturing engineers experience for reduced lead time, lower cost, increase product quality and better understanding of the process. The next step will be to directly link the process simulation to an expert system.

This paper describes the current state of technology in the area of manufacturing process computer simulation for a number of manufacturing operations and suggests how these tools can be used “up-front” and lead to concurrent engineering.     

Trends in aerospace forgings in the 1990s

In the 1990s, forgings require computer-aided design and manufacturing, process modeling, cleaner forging materials, better control of forging and related processes, and closer cooperation between supplier and customer. Forgers will have to employ more sophisticated forging and sensing and control equipment to better meet the demands of close tolerances and increasingly difficult-to-forge materials. Customers will continue to place higher emphasis on quality that remains consistently high. This article examines trends in aerospace forgings that will affect forgers, equipment and materials suppliers in the 1990s. Most of these trends are virtually certain to occur; indeed, some have already begun. What is less certain is the degree to which these trends will occur, and the rapidity of their occurrence.     

PVC membrane selective electrode for determination of cadmium(II) ion in chocolate samples

Benzil bis（carbohydrazone） （BBC） is prepared and explored as new NN Schiff’s base, which plays the role of an excellent ion carrier in the construction of a Cd（II） ion membrane sensor. The tris（2-ethylhexyl） phosphate best performance corresponds to a membrane composition of 30%poly （vinyl chloride）, 65%（TEHP）, 3.5%BBC and 1.5%tetradodecyl-ammoniumtetrakis（4-chlorophenyl） borate （ETH 500）. This sensor shows very good selectivity and sensitivity towards cadmium ion over a wide variety of cations, including alkali, alkaline earth, transition and heavy metal ions. The effect of membrane composition, selectivity, pH and influence of additive on the response properties of electrode were investigated. The response mechanism was discussed in the view of UV-spectroscopy. The electrode exhibits a Nernstian behavior （with slope of 29.7 mV per decade） over a very wide concentration range from 1.0×10^-1 to 1.0×10^-8 mol·L^-1 with a detection limit of 3.2×10^-8 mol·L^-1. It shows rela-tively fast response time in whole concentration range （〈8 s） and can be used for at least 10 weeks in the pH range of 2.0-9.0. The proposed sensor is successfully used for the determination of cadmium in different chocolate sam-ples and as indicator electrode in titration with ethylene diamine tetraacetate （EDTA）.     

Observation and analysis of self-organized surface grain structures in silica films under nonepitaxial growth mode

Silica films under present reactive electron beam deposition conditions have depicted a novel self-organized surface grain structures when probed through atomic force microscopy, 2D fast Fourier transform and glancing incidence X-ray diffraction techniques. The formation of such ordered surface grain structures is observed to be strongly correlated to the nucleation and growth process of the silica films. However, the nature of the substrate (amorphous or crystalline) and multilayer geometries have influenced the shapes, sizes and abundances in the grain structures and the ordering. The strain mediation of such ordered structures when buried under polycrystalline layers like Gd₂O₃ have shown to influence both the grain size as well as roughness. A variety of grain structure evolutions and morphological changes in silica layers were noticed in different multilayer geometries. It is, hence, inferred that by appropriately using combinations of these materials, it is possible to have a control over the multilayer morphology and grain structures, which is a very relevant factor in developing precision ultraviolet laser coatings.     

Mechanical issues in laser and abrasive water jet cutting

In forging and other metal-working industries, lasers and abrasive water jets are being applied to cut a variety of metal products to improve productivity and reduce costs. As described in the following, both the processes have their unique cutting capabilities and characteristics. Before selecting one, however, users must be aware of how each technique influences the end product as well as its performance (e.g., high-cycle fatigue life). For this article, we examined the mechanics of these two cutting processes by studying their effects on Ti-6Al-4Vand A286 steel.     

Numerical investigation of thermal performance of extended surfaces for a novel heat exchanger

The present paper provides a thorough numerical study of variation in geometrical parameters that affect the performance of the novel finned‐tube type heat exchanger design. The finite volume method was employed to discretize and solve the governing partial differential equations of heat conduction. A wide range of constant convective heat transfer coefficient (5 < h < 200 W/m² K) is chosen to reduce the computational time and power, which covers thermal applications of latent thermal energy storage, refrigeration & air‐conditioning, etc. The effects of the ratio of fin spacing of fins to the outer diameter of the tube (0.1 ≤ δ* ≤ 8), the material of fins (copper and stainless steel) and the ratio of fin thickness to the outer diameter of the tube (0.0333 ≤ t* ≤ 0.4) on the performance parameters namely efficiency (η) and effectiveness (ε) of the fins were studied. Temperature contours for a wide range of geometries were depicted. The maximum effectiveness of copper fins is 304.62, whereas that for steel fin is 219.33 with the optimum dimensionless fin thickness reported to be t* = 0.1666. Furthermore, the maximum overall efficiencies of fins were 99.98% and 99.62% for copper and steel fins, respectively.