A MODULAR-TYPE ATOMIC ABSORPTION INSTRUMENT WITH THE GRAPHITE FURNACE IN A GLOVE BOX FOR NUCLEAR APPLICATIONS

This article describes a glove box adaptation of an atomic absorption spectrometer with a graphite furnace as the atomization source. Unlike flame atomic absorption, in which the ground state atoms quickly diffuse out of the atom cell, graphite furnace atomic absorption, being a total consumption technique, offers the ability to de-solvate and atomize the entire sample solution in a more controlled environment. This significantly improves the sensitivity and provides superior detection limits with microliter sample volumes. An atomic absorption instrument was converted into separate modular units consisting of the source, atomizer, and detection system. In addition, these units were modified to enable their use in the glove box, allowing the analysis of nuclear samples. Proper optical alignment of the source, atomizer, and detector system was performed to allow the analysis of toxic samples.     

Modeling of diffusional limitations in styrene acrylonitrile random bulk copolymerization

Diffusional limitations (the gel, glass, and cage effects) are manifested in several bulk free radical homopolymerizations as well as in random copolymerizations. These are associated with decreases of several orders of magnitude of the rate constants of termination, propagation, and initiation (the initiator efficiency), respectively. These phenomena have been modeled earlier using the free volume theory for the diffusivities of primary radicals, macro‐radicals, and monomer molecules, and have been applied to homopolymerizations. In this study, a similar model is developed for random bulk copolymerizations. The parameters of the model are fitted using isothermal data on styrene acrylonitrile random copolymerization carried out in small ampoules. Thereafter, best‐fit global correlations have been developed for this system. This enables the model to be used for studying non‐isothermal copolymerizations, as well as for carrying out optimization of industrial reactors, where non‐isothermal conditions are a norm. POLYM. ENG. SCI., 55:2098–2110, 2015. © 2014 Society of Plastics Engineers     

Optimisation of Detergent Ingredients for Stain Removal Using Statistical Modelling

Artificially soiled test fabrics are widely used to study the cleaning performance of detergents formulations. In this study, artificial soiled cotton test fabrics were prepared in the laboratory using carbon black as a model soil. Design of experiments was used to optimise the concentration of detergent ingredients for stain removal. A multi‐factorial analysis of variance was used to model the effect of sodium dodecylbenzene sulfonate, nonylphenol ethoxylate, sodium silicate, sodium citrate and sodium carbonate as builders on soil removal. A colourimetric evaluation using the CIELAB system was used to measure soil removal. In general, performance increases with increasing concentration of surfactant, silicate and soda ash.     

Melting model for modular self wiping co-rotating twin screw extruders

A model for the melting process in a self wiping co-rotating twin screw extruder is described. Self-wiping co-rotating twin screw extruders are modular and starve fed. This leads to melting mechanisms that are different from single screw extruders. The melting process in the modular screw configurations generally occurs in specialized sections such as kneading disk blocks. The model, based on our previous experimental observations, considers the formation of two stratified layers of melt in contact with the hot barrel and solid pellets in contact with the relatively colder screw. In the kneading disk blocks, a part of the solid bed is blocked because of the relative stagger between successive disks. The model predicts both the location of melting and melting lengths in a screw configuration. Calculations for individual screw elements and kneading disc elements are presented first. Melting in a modular configuration of these elements is then considered. The effect of operating variables such as mass flow rate and screw speed on melting is then studied. The model is put in a dimensionless form and the effect of various dimensionless groups is discussed. We make a comparison to the experiment and agreement is good.     

Effects of Clinorotation on Growth and Chlorophyll Content of Rice Seeds

Microgravity, as a different environment, has been shown to affect plant growth and development (Sievers et al. 1996; Sack 1997). In the present study, effects of slow clinorotation (2 rpm) on growth and chlorophyll content in rice (variety: PRH-10) seedlings were investigated. Rice seeds were clinorotated continuously for 3, 5 and 7 days under ambient conditions. Root and shoot lengths and weights of rice seedlings were measured on the third, fifth and seventh day. Chlorophyll was extracted using N, N-Dimethylformamide (DMF). Absorption and fluorescence spectra of chlorophyll were recorded. Chlorophyll a, chlorophyll b and total chlorophyll contents were calculated from absorption spectra using Arnon’s method. Results showed an increase in root and shoot lengths in clinorotated samples. Similar results were obtained for root and shoot weights. Absorption spectra of chlorophyll showed no shift in the absorption peaks. Chlorophyll content was increased in clinorotated samples as compared to the controls. Interestingly, the difference between chlorophyll content in control and clinorotated samples decreased as the number of days of clinorotation increased. Chlorophyll a/b ratio was lowered in clinorotated samples as compared to the controls. These results suggest that slow clinorotation (2 rpm) affects plant growth and chlorophyll content in rice seedlings.     

Fluorimetric Nerve Gas Sensing Based on Pyrene Imines Incorporated into Films and Sub‐Micrometer Fibers

The chemical sensing of nerve gas agents has become an increasingly important goal due to the 1995 terrorist attack in a Tokyo subway as well as national security concerns in regard to world affairs. Chemical detection needs to be sensitive and selective while being facile, portable, and timely. In this paper, a sensing approach using a pyrene imine molecule is presented that is fluorimetric in response. The detection of a chloro‐Sarin surrogate is measured at 5 ppmv in less than 1 second and is highly selective towards halogenated organophosphates. The pyrene imine molecule is incorporated into polystyrene films as well as micrometer and sub‐micrometer fibers. Using both a direct drawing approach and electrospinning, micrometer and nanofibers can be easily manufactured. Applications for functional sensing micrometer and nanofibers are envisioned for optical devices and photonics in addition to solution and airflow sensing devices.     

Optimization of MIG Welding Parameters to Control the Angular Distortion in Fe410WA Steel

In the fabrication industry, metal inert gas (MIG) welding is a very important process and Fe410WA is the most commonly used material for the manufacturing of fabricated structures. During the preparation of butt welded joints, angular distortion is a major concern. Angular distortion can be minimized by optimizing the input parameters. In this paper, a study of the optimization of controllable input parameters such as current, voltage and gas flow rate by using the Taguchi method is performed. Butt welding samples were prepared by using three levels and three factors. An orthogonal array of nine trials is considered for the design of the experiment. After measuring the distortion angle, observed readings were verified by using analysis of variance (ANOVA) technique and it was found that the p-values were less than 0.05. Theoretical calculations were performed to optimize the process parameters to achieve the minimum distortion angle. A confirmation test was taken for validation purposes and to confirm the result.