Highly birefringent large negative dispersion-flattened photonic crystal fibre for broadband residual dispersion compensation

A triangular lattice photonic crystal fibre is presented in this paper for residual dispersion compensation. The fibre exhibits a flattened negative dispersion of ?992.01 ± 6.93 ps/(nm-km) over S+C+L wavelength bands and ?995.83 ± 0.42 ps/(nm-km) over C-band. The birefringence is about 4.4 × 10^?2 at the excitation wavelength of 1550 nm which is also very high. Full vector finite element method (FEM) with a perfectly matched absorbing layer (PML) boundary condition is applied to numerically investigate the guiding properties of this PCF. The fibre operates at fundamental mode only. All these properties endorse this fibre as a suitable candidate for compensating residual dispersion and polarization maintaining applications.     

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.     

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.     

High-yield synthesis of well-crystalline alpha-Fe2O3 nanoparticles: structural, optical and photocatalytic properties

In this paper, the high-yield facile synthesis, detailed characterization and photocatalytic application of alpha-Fe2O3 nanoparticles are reported. The synthesis was done via simple hydrothermal process by using aqueous mixtures of iron chloride, hexamethylenediamine and NH3 x H2O at 110 degrees C. The morphologies of the synthesized products were examined by using field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) which confirmed that the synthesized structures are almost spherical shaped nanoparticles with the average diameters of -35 +/- 5 nm, and are grown in high yield. The detailed structural characterizations and composition of the as-synthesized nanoparticles were investigated by using X-ray diffraction (XRD), high-resolution TEM (HRTEM), energy dispersive spectroscopy (EDS) attached with FESEM and Fourier transform infrared spectroscopy (FTIR) which substantiated that the as-synthesized nanoparticles are well crystalline and pure alpha-Fe2O3. The UV-Vis absorption spectrum of the synthesized nanoparticles demonstrated the existence of two optical band gaps which correspond to direct and indirect transitions, respectively. The as-synthesized alpha-Fe2O3 nanoparticles exhibit good photocatalytic properties on photocatalytic degradation of methylene blue.     

Safety assessment in plant layout design using indexing approach: implementing inherent safety perspective. Part 1 - guideword applicability and method description

Layout planning plays a key role in the inherent safety performance of process plants since this design feature controls the possibility of accidental chain-events and the magnitude of possible consequences. A lack of suitable methods to promote the effective implementation of inherent safety in layout design calls for the development of new techniques and methods. In the present paper, a safety assessment approach suitable for layout design in the critical early phase is proposed. The concept of inherent safety is implemented within this safety assessment; the approach is based on an integrated assessment of inherent safety guideword applicability within the constraints typically present in layout design. Application of these guidewords is evaluated along with unit hazards and control devices to quantitatively map the safety performance of different layout options. Moreover, the economic aspects related to safety and inherent safety are evaluated by the method. Specific sub-indices are developed within the integrated safety assessment system to analyze and quantify the hazard related to domino effects. The proposed approach is quick in application, auditable and shares a common framework applicable in other phases of the design lifecycle (e.g. process design). The present work is divided in two parts: Part 1 (current paper) presents the application of inherent safety guidelines in layout design and the index method for safety assessment; Part 2 (accompanying paper) describes the domino hazard sub-index and demonstrates the proposed approach with a case study, thus evidencing the introduction of inherent safety features in layout design.     

Architecture-dependent surface chemistry for Pt monolayers on carbon-supported Au

Pt monolayers were grown by surface-limited redox replacement (SLRR) on two types of Au nanostructures. The Au nanostructures were fabricated electrochemically on carbon fiber paper (CFP) by either potentiostatic deposition (PSD) or potential square wave deposition (PSWD). The morphology of the Au/CFP heterostructures, examined using scanning electron microscopy (SEM), was found to depend on the type of Au growth method employed. The properties of the Pt deposit, as studied using X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS), and cyclic voltammetry (CV), were found to depend strongly on the morphology of the support. Specifically, it was found that smaller Au morphologies led to a higher degree of cationicity in the resulting Pt deposit, with Pt(4+) and Pt(2+) species being identified using XPS and XAS. For fuel-cell catalysts, the resistance of ultrathin catalyst deposits to surface area loss through dissolution, poisoning, and agglomeration is critical. This study shows that an equivalent of two monolayers (ML) is the low-loading limit of Pt on Au. At 1 ML or below, the Pt film decreases in activity and durability very rapidly due to presence of cationic Pt.     

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.     

Contractors’ Views of the Potential Causes of Inconsistencies between Design and Construction in Saudi Arabia

The study identifies the causes of inconsistencies between the design and construction of large building projects. To achieve the study objectives, a questionnaire survey was carried out to collect information on potential causes of inconsistencies at the project design and construction interface. Responses from 27 contractors were analyzed. The results suggest that the involvement of designer as consultant, communication gap between constructor and designer, insufficient working drawing details, lack of coordination between parties, lack of human resources in design firm, lack of designer’s knowledge of available materials and equipment, and incomplete plans and specifications were considered as the most important causes of the project design and construction interface inconsistencies. On the other hand, project management as a professional service, weather conditions, nationalities of participants, involvement of the contractor in design conceptual phase, unforeseen problems, involvement of the contractor in design development phase, and government regulations were the least important causes of inconsistencies between professionals at the project design and construction interface in large building projects.     

Adsorption kinetics and enhanced oil recovery by silica nanoparticles in sandstone

This study addresses adsorption kinetics of silica nanoparticles on sandstone mineral surfaces and Enhanced oil recovery (EOR) by nanoparticles. It was shown that nanoparticle adsorption on quartz which is the major constituent of sandstone reservoirs was best described as second order process. Both rate and equilibrium adsorption increases with salinity. However, salinity reduces Intraparticle diffusion while enhancing film diffusion. Spontaneous imbibition with nanoparticles dispersed in low salinity water showed higher incremental recovery which may be due to increased structural disjoining pressure. This was supported by surface forces analysis based on particle size and zeta potential measurements of the nanofluids.