Design and demonstration of direct UV-written small angle X couplers in silica-on-silicon for broadband operation

Experimental demonstration of small angle (0.8 degrees-5 degrees ) direct UV-written X couplers in silica-on-silicon is presented. Maximum and minimum coupling ratios of 95%(+/-0.8%) and 1.9% (+/-1%), respectively, were recorded. The structures also display very low polarization and wavelength dependence. A typical excess loss of 1.0 dB(+/-0.5 dB) was recorded. Device modeling using the beam propagation method and an analytical model showed good agreement with experimental results over a broad crossing angle and wavelength range.     

Wrinkle free plaited knitted fabrics without pre-heat setting

Wrinkle free fabric at low cost is always a desirable aesthetic property. Different type of resins/finishes and pre-heat setting prior to processing are applied to avoid wrinkles in woven and hosiery, respectively. Current study is proposed to produce wrinkle free circular plaited knitted fabric by the elimination of a pre-boarding step. In this achievement, yarn covering parameters and compatibility of yarns with knitting machines are examined. Sock samples were analyzed for improved physical appearance (wrinkles) after various processes (pre-tumbling, dyeing, bleaching, and washing). Yarn specifications (sheath yarn fineness, sheath yarn texture i.e. shrink/un-shrink, covering air-knots) impact on socks physical appearance were also analyzed. The results clearly showed that by decreasing number of yarn covering air knots and sheath yarn fineness leads to prevention of wrinkle formation. The results also prove to be supportive for cost effectiveness by eliminating the pre-setting stage.     

The impact of daylight saving time on electricity consumption: Evidence from southern Norway and Sweden

This paper examines the impact of daylight saving time (DST) on electricity consumption in southern Norway and Sweden. As DST was implemented in both the countries in 1980, we do not have a clear counterfactual in the form of a control period to identify the impact of DST directly with before and after or with and without analysis. This problem in the study is resolved by using “equivalent day normalization technique” to identify the impact of DST. The difference-in-difference (DID) average treatment effects model suggests an annual reduction of at least 1.0 percent in electricity consumption for both Norway and Sweden due to DST. The average annual electricity consumption reduction corresponding to DST effects equals 519 and 882 GWh for southern Norway and Sweden, resulting in an annual financial saving of 16.1 million Euros and 30.1 million Euros, respectively. The distribution of treatment effects across different hours of the day indicates a small but significant reduction in electricity consumption during the morning and a steep decline during the evening hours in both countries.     

Supply chain risk modelling and mitigation

In today’s global competitive environment, supply chains are more susceptible to vulnerability due to the increasing occurrence of internal and external risk events. In addition, the trend associated with lean management, which involves reducing inventory, leads to more dependency of supply chain partners on each other which exacerbates risk exposure of companies in the supply chain. This creates the need for more effective management of supply chain risks. In this research, a methodology based on Bow-Tie analysis and optimisation techniques is proposed to quantify and mitigate supply chain risks. The proposed methodology takes into consideration risk interconnections, and it identifies the best combination of mitigation strategies under budget constraints. A real case study from a high-end server manufacturing environment is presented. Results from the case study showed that the proposed methodology for risk modelling and mitigation can effectively be used to quantify the risks and achieve the required risk reduction at minimum cost while considering risk correlations.     

Clear-water scour at long skewed bridge piers

Abstract

The results of an experimental study on clear-water scour at long skewed rectangular piers under steady flows at threshold velocity are presented. The scour mechanisms due to skewness effects with a wide range of angle of attack, α, and two sizes of uniform cohesionless bed sediment (d₅₀ = 0.23 and d₅₀ = 0.80 mm) have been investigated in a 50-m-long, 1.5-m-wide, and 2.0-m-deep flume. Empirical relation to demonstrate the effects of skewness in terms of dimensionless variables, such as aspect ratio (L/b), the angle of attack (α), flow shallowness (y/B_α), sediment coarseness (B_α/d₅₀), the sediment gradation coefficient (σ_g), on scour depth is presented. The empirical relation is focused on predicting the angle of attack factor, K_α. The experimental data obtained in this study and data available from the literature were used to validate the predictions of existing methods and the accuracy of the proposed method. The proposed method gives reasonable scour depth predictions and was verified with statistical methods where the mean error was reduced from 53.6 to 18.1%.     

Hydrogen storage in liquid organic hydride: Selectivity of MCH dehydrogenation over monometallic and bimetallic Pt catalysts

Hydrogen storage for mobile and stationary applications is an expanding research topic. One of the more promising storage techniques relies on the reversibility, high selectivity, and high hydrogen density of liquid organic hydrides, in particular methylcyclohexane (MCH). Catalyst evaluation for MCH dehydrogenation to toluene is based on three catalytic parameters: activity, selectivity, and stability. Current catalysts, optimized for catalytic reforming, do not meet the targeted aromatic selectivity (+99%) for MCH dehydrogenation. Therefore, a range of Pt catalysts was prepared and compared with commercially available catalysts in a fixed-bed reactor under operating conditions suitable for mobile and stationary applications. The best overall performance was realized by a particular monometallic Pt catalyst. This catalyst showed superior activity, selectivity, and stability compared with other prepared and commercial catalysts. As an effort to further enhance the aromatic selectivity, this study identified the main side-reactions associated with MCH dehydrogenation, the effect of operating parameters on by-product yields, and the effect of catalyst deactivation on long-term selectivity.     

Natural Convection around Horizontal Tubes with Smooth,Rough, and Machined Surfaces

This study concerns natural convection around horizontal tubes with smooth, rough, and machined surfaces. The study is motivated by the need for understanding the machining effect or the use of a rough surface layer on the natural convection process. An experimental system is constructed that includes a thick wall metal tube equipped with thermocouples for measuring the surface temperature. A heating element is inserted inside the tube and is coupled with a power supply that can be adjusted to achieve surface temperatures of 60–160°C. The tube surface is machined at various depths of 1–3 mm. Also, four grades of sandpaper are used to cover the tube surface. An analysis of measured data is based on variations in the Nusselt number as a function of the Rayleigh number and surface condition. Results show that the measured data for the smooth tube are consistent with literature results. Although surface machining increases the heat transfer area, it lowers the heat transfer rate because of the low thermal conductivity of air, which replaces the removed metal in the machined grooves. Similarly, covering the tube surface with sandpaper reduces the rate of heat transfer from the tube surface because of contact resistance and the thermal resistance of the sandpaper. Data analysis that takes into consideration the above resistances, where the contact and sandpaper thermal resistances are eliminated, show enhancement of up to 30%. This implies that the direct roughening of a metal surface would enhance the heat transfer rate by 30%.     

Interface architecture determined electrocatalytic activity of Pt on vertically oriented TiO(2) nanotubes

The surface atomic structure and chemical state of Pt is consequential in a variety of surface-intensive devices. Herein we present the direct interrelationship between the growth scheme of Pt films, the resulting atomic and electronic structure of Pt species, and the consequent activity for methanol electro-oxidation in Pt/TiO(2) nanotube hybrid electrodes. X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) measurements were performed to relate the observed electrocatalytic activity to the oxidation state and the atomic structure of the deposited Pt species. The atomic structure as well as the oxidation state of the deposited Pt was found to depend on the pretreatment of the TiO(2) nanotube surfaces with electrodeposited Cu. Pt growth through Cu replacement increases Pt dispersion, and a separation of surface Pt atoms beyond a threshold distance from the TiO(2) substrate renders them metallic, rather than cationic. The increased dispersion and the metallic character of Pt results in strongly enhanced electrocatalytic activity toward methanol oxidation. This study points to a general phenomenon whereby the growth scheme and the substrate-to-surface-Pt distance dictates the chemical state of the surface Pt atoms, and thereby, the performance of Pt-based surface-intensive devices.