Shell Cracking In Investment Casting with Laser Stereolithography Patterns

This paper presents an investigation of ceramic shell cracking during the burnout process in investment casting with internally webbed laser stereolithography patterns. We hypothesize that shell cracking will occur when the rupture temperature of the ceramic shell is lower than both the glass transition temperature of the pattern material and the web· link buckling temperature. The hypothesis is validated by our experimental observations which confirm the numerical predictions from our fillite element analysis. This provides a basis for design of the internal web geometry of a lithography pa.tternand evaluation ofthe burnolltprocesswithsuch a pattern. We show the shell cracking and web link buckling temperatures to be functiollsofthe pattern geometry (including the cross~sectional dimensions and span length of the web link) and the shell thickness.Mechanical Engineerin

Determination of O_2 (a¹Δg) and O_2 (b¹Σ^+g) yields in the reaction O + ClO → Cl + O_2 : Implications for photochemistry in the atmosphere of Venus

A discharge flow apparatus with chemiluminescence detector has been used to study the reaction O + ClO → Cl + O2^*, where O_2^* = O_2(a^¹Δ_g) or O_2(b^¹Σ^+g). The measured quantum yields for producing O-2(a6¹Δ-g) and O-2(b6¹Σ^+_g) in the above reaction are less than 2.5 × 10^(−2) and equal to (4.4 ± 1.1) × 10^(−4), respectively. The observed O_2(a^¹Δ_g) airglow of Venus cannot be explained in the context of standard photochemistry using our experimental results and those reported in recent literature. The possibility of an alternative source of O atoms derived from SO_2 photolysis in the mesosphere of Venus is suggested

Analysis of three-component aeromagnetic data

The numerical method of obtaining three field components from total field measurements, using double Fourier series expansion, is presented. The expressions for moments of the anomalous field components over a finite area are given. The magnitude and direction of the magnetization vector indicate that the vertical component of the magnetic field calculated from total field observations is more accurate at higher geomagnetic latitudes than at lower latitudes. The opposite is true for the horizontal components. The error in determining the magnetization vector directions are significantly large over most of the range of variation of declination and inclination of the vector, demonstrating the practical limitations of computing field components from total field data even under the best of conditions

Nymphaea kakaduensis (Nymphaeaceae), a new species from the northern portion of the Northern Territory, Australia

Nymphaea kakaduensis C. B. Hellq., A. Leu & M. L. Moody (Nymphaeaceae) is described from Kakadu National Park, Northern Territory. This new species is endemic to the “Top End” of the Northern Territory and was formerly included in N. violacea Lehm. The distinct floral form of N. kakaduensis of having generally smaller flowers with blunt-tipped petals and different coloration than N. violacea instigated a genetic study of taxa from the region. The cpDNA trnL (UAA) - trnF (GAA) intergenic spacer region was sequenced from samples from across northern Australia and a haplotype network analysis was conducted. Plants from populations that had the distinct floral form of N. kakaduensis are found to be genetically distinct from N. violacea in northern Australia sharing 4 SNPs and a notable 23 bp indel in the cpDNA intergenic spacer region to support the morphological attributes and species designation

Alternative iterative methods for nonexpansive mappings, rates of convergence and applications

Alternative iterative methods for a nonexpansive mapping in a Banach space are proposed and proved to be convergent to a common solution to a fixed point problem and a variational inequality. We give rates of asymptotic regularity for such iterations using proof-theoretic techniques. Some applications of the convergence results are presented

Increase of Heat Transfer to Reduce Build Time in Rapid Freeze Prototyping

Reduction of part build time in the Rapid Freeze Prototyping (RFP) process, which fabricates a 3D ice part layer-by-layer by depositing and freezing water droplets, has been achieved by increase of heat transfer. Three mechanisms have been experimentally investigated: 1) cooling the substrate, 2) use of forced convection, and 3) use of a chilling plate. Cooling the substrate is effective for parts of small heights but becomes ineffective with increase in part height. Forced convection produced desirable reduction in part build time but with the undesirable formation of frost on the built ice part. The use of chilling plate to increase heat conduction proved to be most effective. To ensure that the frozen ice from the deposited water can be easily removed from the chilling plate, various surface coats were investigated and the most effective surface coat was found to be a thin Teflon film. After incorporating the chilling plate we have successfully achieved 75% reduction in part build time.Mechanical Engineerin

Characteristics and Optimal Design of Variable Airgap Linear Force Motors

An analytical model for predicting the characteristics of variable airgap linear force motors is developed. the model takes into account magnetic losses including the leakage and fringing effects and the reluctance existing at the contacts between permanent magnets and pole pieces. the model is validated by comparing its predicted characteristics with the results obtained from experiments and a finite element program. with the use of the modelled characteristics, computer programs based on the method of constrained steepest descent with state equations are developed for automating and optimising the design of linear force motors. Numerical studies are made for both minimisation of weight and minimisation of power consumption

Spatial Description of the Distribution Cases of BTA Positive Pulmonary TB in Kota Kupang

Tuberculosis is one of the top 10 leading causes of death in the world. In 2017 an estimated 10.4 million people suffered from TB and 1.3 million people died of the disease. TB is a disease based on the region that has a spatial dependence (correlation between geographic regions), therefore its restraint must also consider the spatial distribution patterns of the case that can be learned through spatial analysis. The purpose of this research was to analyze spatially the distribution of BTA positive pulmonary TB cases based on population density, coverage of healthy houses, altitude, and the number of poor families in Kota Kupang 2018. The type of research used in this study was quantitative descriptive with Geographic Information System (GIS) approach. The sample in this study consisted of all new cases of BTA positive pulmonary TB in 2018 amounted to 451 cases.  Spatial analysis showed that the BTA positive pulmonary TB cases distributed to spread the subdistricts in Kota Kupang which was a region of low altitude (<150 masl) with the highest distribution in the areas with high population density, high coverage of the healthy house, and the high number of poor families. It calls for networking between the government and the community in the prevention of BTA positive pulmonary TB