Dual gas jet-assisted fibre laser blind cutting of dry pine wood by statistical modelling

This paper presents a statistical analysis of the performance of an Ytterbium fibre laser utilising single and dual gas jets in a single pass to blind cut dry pine wood. Cutting wood with lasers is a multi-factor process and a proper combination of the parameters involved is needed to achieve high quality and optimum process efficiency. This study employs design of experiments and statistical modelling approach to investigate the significant process parameters along with their interactions. A high brightness, 1 kW IPG single mode Ytterbium-doped fibre laser was employed to produce blind cuts on samples of dry pine wood. The experiments were performed parallel to the direction of the wood fibre. The parameters investigated include laser power, focal plane position, traverse speed, gas pressure and single and dual gas jets. Results were compared using a number of process responses which define the efficiency of the cut in terms of kerf depth, mass removal and energy consumption as well as quality of the cut section considering the heat-affected zone, kerf width and roughness of the edge of the surface. It has been found that application of an additional gas jet produced a surface finish superior to the single jet.     

Jacobian Coordinates on Genus 2 Curves

This paper presents a new projective coordinate system and new explicit algorithms which together boost the speed of arithmetic in the divisor class group of genus 2 curves. The proposed formulas generalize the use of Jacobian coordinates on elliptic curves, and their application improves the speed of performing cryptographic scalar multiplications in Jacobians of genus 2 curves over prime fields by an approximate factor of 1.25x. For example, on a single core of an Intel Core i7-3770 (Ivy Bridge), we show that replacing the previous best formulas with our new set improves the cost of generic scalar multiplications from 239,000 to 192,000 cycles and drops the cost of specialized GLV-style scalar multiplications from 155,000 to 123,000 cycles.     

Wear behavior of as-deposited and oxidized ternary (Zr,Hf)N coatings

In the present study, the tribological performance of ternary (Zr,Hf)N coatings, whose Hf content was varied between 0 and 21 wt pct, has been systematically examined in the as-deposited and oxidized conditions. Coatings were applied on AISI D2 tool steel plates by arc physical vapor deposition (PVD). Oxidation was conducted at 400 °C for times up to 12 hours in air. Wear tests revealed pronounced improvement in the wear resistance with increasing Hf content in the as-deposited coatings. Oxidation for 12 hours yielded more than a fourfold increase in wear resistance. The beneficial effect of Hf on wear resistance decreased upon oxidation.     

Mechanical Properties and Corrosion Behavior of As-Cast Mg-Zn-Zr-(La) Magnesium Alloys

The effects of La content on the mechanical properties and corrosion behavior of as-cast Mg-Zn-Zr (ZK) magnesium alloys were investigated. The results showed that La addition to ZK60 alloy resulted in a considerable grain refinement and an increase in the volume fraction of second phases by formation of Mg-Zn-La ternary phase. The tensile tests were performed at both room and elevated temperatures. At room temperature, the yield and tensile strengths and elongation-to-fracture significantly increased with 0.2 wt.% La addition, then deteriorated slightly with increasing La additions above 0.2 wt.%. At 200 °C, the yield and tensile strengths continually improved and elongation-to-fracture decreased with increasing La content due to the presence of thermally stable Mg-Zn-La phase. Immersion and electrochemical corrosion tests revealed that the formation of Mg-Zn-La phases led to a higher amount of cathodic sites and preferential corrosion propagation, and thus a decrease in the corrosion resistance of ZK60 alloys.     

Ultrasound‐assisted bioscouring of cotton

In this study, the effects of ultrasound on the bioscouring of cotton by alkaline pectinase were examined. Conventional alkaline scouring was considered as the control treatment, and two different sources of ultrasound, an ultrasonic bath and an ultrasonic homogeniser, were tested, along with the enzymatic scouring process. Results indicated a clear increase in the efficiency of the enzymatic scouring process when the ultrasonic homogeniser was used: wettability time and wicking distance after ultrasonic homogeniser‐assisted bioscouring were much better than for enzymatic scouring without the use of ultrasound energy and almost the same as when conventional alkaline scouring was employed. Ultrasonic bath‐assisted enzymatic bioscouring gave slightly better results than enzymatic scouring without sonication. Reasons for the difference in efficacy of the ultrasound sources were postulated. Weight loss was increased by the use of ultrasonic equipment during enzymatic scouring. Fabric thickness and fabric strength was not significantly affected by the scouring processes. The environmental impact of the processes was also monitored by chemical oxygen demand measurement of the treatment liquors. Conventional alkaline scouring resulted in the highest environmental impact. Ultrasonic homogeniser‐assisted bioscouring also led to slightly higher chemical oxygen demand loads than other enzymatic processes owing to the more efficient removal of impurities.     

A Chemometric Approach to Assess the Frying Stability of Cottonseed Oil Blends During Deep-Frying Process: I. Polar and Polymeric Compound Analyses

The main goal of the present study was (i) to determine the formation of degradation products in cottonseed oil (CSO) blends during deep frying process by adsorption and high performance size exclusion chromatography techniques and (ii) to evaluate the impacts of food additives on total polar (TPC) and polymeric compound (PTAG) formation using a chemometric approach. In order to prepare the frying CSO blends; ascorbic palmitate, mixed tocopherols, dimethylpolysiloxane, lecithin and sesame oils were used as additives. To determine the real impacts of additives, a quarter-fraction factorial experimental design with two levels and five factors was used. The changes in TPC and PTAG data were carefully evaluated during 10 h of frying at 170 ± 5 °C with normal distribution (ND) graphs and analyzed using a one-way analysis of variance (ANOVA), followed by Tukey’s Post-hoc test (α = 0.05). The results indicated that the increasing values for TPC and PTAG during the frying processes for all blends, TPC and PTAG contents reached maximum levels of 16.37 and 6.01 % respectively, which are below the limit values stated by official authorities for the quality assessment of frying oils. The ANOVA test results were in good agreement with ND graphs and data indicated that the impact of mixed tocopherols was significant for TPC formation, meanwhile the impact of lecithin and ascorbic palmitate × dimethylpolysiloxane were significant for PTAG formation. Thus, the present study should be considered to be a very useful guide for developing new frying oil formulations based on CSO by using food additives.     

Stress-strain response of a cast 319-T6 aluminum under thermomechanical loading

The stress-strain behavior of cast 319-T6 aluminum-copper alloys with three different secondary dendrite arm spacings (SDASs) was studied at high temperatures and under thermomechanical deformation, exposing marked cyclic softening. A two state-variable unified inelastic constitutive model proposed earlier was modified to describe the stress-strain responses of these alloys by considering the variation of hardening and recovery functions of back-stress and drag stress. The SDAS was incorporated in the model as a length-scale parameter, and the material constants were determined systematically from experiments on a cast 319-T6 aluminum with small and large SDASs. The capabilities of the constitutive model were checked by the comparisons of simulations to experiments in the small-strain regime (<0.005). The results show that the model provides successful simulations for material response after thermal exposure at high temperature and cyclic transient stress-strain behavior. The causes of mechanical behaviors at the macro scale are discussed based on microstructural changes during thermal exposure.     

Swage casting of A380 alloy

Swage casting is a new casting technique which combines the advantages of squeeze, centrifugal and semi-solid casting methods. In this new casting method, components with one rotating axis can be produced on a swage casting machine from molten metal in a one-step operation. A shape like a “bomb-body” is chosen to demonstrate the advantages of this new method by using A380 Al–Si–Cu alloy. The same alloy is also cast with centrifugal and squeeze casting methods. In this study, the swage casting method and its features are briefly described. The final microstructures, mechanical properties and amount of porosity of the cast pieces produced by squeeze, centrifugal and swage casting methods are compared. Swage cast pieces showed a different composition of microstructure that consists of fine dendritic particles at the chill ends and a mixture of spherical and rosette shaped particles at the core. The swage cast pieces also have a slightly higher mechanical strength as indicated by tensile strength and Brinell hardness values.