SIZE-DEPENDENT OPTICAL PROPERTIES OF COPPER NANOPARTICLE OVER A WIDE RANGE OF WAVELENGTHS: AN ELECTROMAGNETIC SIMULATION STUDY

In this article, we modulate the optical absorption, scattering, extinction, transmission and field intensities of an ellipsoid copper nanoparticle by tuning its dimension. The finite-difference time-domain (FDTD) method is employed for this electromagnetic simulation study and a comparative investigation has been carried out. In the investigation it is found that Cu nanoparticle with 20 nm size exhibiting the optical absorption at the resonant wavelength ~530 nm. This plasmon peak is shifted to ~550 nm when the particle size is increased to 40 nm. In addition to shifting, the enhancement of the plasmon peak is also observed. This nonlinear enhancement arises due to the size dependent property of the surface plasmon resonance (SPR). For smaller nanoparticle, the scattering is found to be negligible as compared to the larger particle. The scattering becomes dominant as the particle size increases beyond 28 nm. The scattering cross-sections of all the particle decreases at the longer wavelength. All the structures exhibit a strong transmission minimum at a wavelength close to 590 nm in the visible spectrum. However, above 600 nm high transmission is observed. The electric field intensity is also enhanced from 5.15 (V/m)2 to 16.9 (V/m)2 as the particle size increases from 20 nm to 40 nm. We strongly believe that this research could provide an overall idea about the importance of particle size variation while fabricating Cu based solar energy harvesting systems, plasmonics photovoltaic devices etc

Fatigue Performance Assessment of Refurbished Orthotropic Deck for a Signature Bridge under Simulated Site-Specific Loading

After a comprehensive study of the site specific loading, it was decided to replace the 45 year old distressed concrete filled steel grid deck at the upper level of the signature suspension bridge with a steel orthotropic deck that is integral with the floor system and the stiffening truss. In view of the high volume of truck traffic on the deck, and the concerns of increased possibility of fatigue cracking from a large number of welded connections in the orthotropic deck, the design and fabrication of the replacement orthotropic deck details needed to be verified for infinite fatigue life, i.e., 75 years\u27 service life without any fatigue cracking under site specific loading.A full size prototype of a quarter of the deck between the panel points of the stiffening truss, and including one floor beam and two stringers was fatigue tested in at the ATLSS Engineering Research Center, Lehigh University. This study, identified as Phase 1 and reported by Alapati (2012), demonstrated that the proposed replacement deck design did not meet the fatigue design requirements of 75 years\u27 service life. The prototype exhibited premature fatigue cracking of the intermediate subfloor beam-to-rib weld at the cutout termination, and the internal bulkhead plate-to-rib welds at the intermediate subfloor beam. Based on these findings, it was recommended to reduce the stresses at the critical details below their respective constant amplitude fatigue thresholds (CAFT) for achieving a 75 years\u27 service life under site specific loading. Accordingly, deck design was revised where the cutout for the ribs at the intermediate subfloor beams was enlarged at the rib termination, and the thickness of the subfloor beam web was increased from 5/8 in. (16 mm) to 7/8 in. (22 mm). In addition, the number of subfloor beams between the floor beams was also increased from four to five, which reduced the spacing between the subfloor beams from 12 ft. 41/2 in. (1.257 m) to 8 ft. 3 in (2.515 m). The thickness of the full depth bulkhead plates inside the ribs was increased from 5/16 in. (8 mm) to 5/8 in. (16 mm). The welded connection between the bulk-head plate and the rib over the top 7 in. (175 mm) critically stressed region was fabricated as a complete joint penetration weld, which ensured adequate penetration at the weld root and increased the fatigue resistance of this cruciform detail.The fatigue performance of the refurbished deck was evaluated by full size prototype testing of the modified Phase 1 specimen, where the intermediate floor beam was replaced to incorporate the improved design. Similar to the Phase 1 testing, the test setup simulated the global boundary conditions including the supporting floor framing. The deck was fatigue tested using four stationary overhead hydraulic actuators positioned centrally in the transverse direction. In the longitudinal directions the actuators were positioned in concentric and eccentric configuration about the intermediate subfloor beam and were loaded in paired sequence simulating the passage of the tandem axle of an AASHTO fatigue truck across the intermediate subfloor beam. Three additional under deck actuators were used to simulate continuity boundary conditions. The deck was tested for 5 million cycles at a load level of 3.45×HS15 (=3×0.75×HS20 or the HL-93 fatigue truck) including impact, which was considered equivalent to 75 years\u27 service life under site specific loading. The deck was instrumented to evaluate its response, with majority of the instrumentation concentrated around the critical welded details in the intermediate subfloor beam.No fatigue cracking was found in the deck upon completion of the testing. The Phase 2 study verified that the refurbished deck would provide a 75 years\u27 service life under site specific loading. With the design improvements, the stresses at the fatigue critical details reduced significantly compared to the original deck tested in Phase 1. The measured stress ranges at all details except at the cutout edge were at or below the constant amplitude fatigue threshold (CAFT) of their respective detail categories. 3D Finite Element analyses of the deck were performed to understand the complex behavior of the deck under localized and moving wheel loads, and to verify the measured response under static and dynamic loading conditions. Multi-level submodel analyses were performed to assess the fatigue performance of the critical connection details, and to assess the fatigue strength of the rib-to-subfloor beam and rib-to-bulkhead plate weld connection at the cutout termination using local stress based approaches. The hot spot stress obtained at the rib-to-subfloor beam and the rib-to-bulkhead plate weld toes were compared against the FAT 100 curve as per IIW recommendations. The notch stress approach used by Roy and Fisher (2005) for assessing constant amplitude fatigue threshold (CAFT) of welded connections was also implemented to predict the fatigue performance of the rib-to-subfloor beam connection detail

Atomistic simulations of driven alloys: a study of effective temperature models for low and high temperature applications

Immiscible alloys under severe plastic deformation (SPD) or irradiation form non-equilibrium microstructures at steady-state with microstructural features of a characteristic length scale that are stable over prolonged processing times. Such alloys have been termed ‘driven alloys’ as these steady-state microstructures are formed and stabilized as a consequence of the dynamical competition between the applied extrinsic driving force that tends to homogenize the microstructure and the thermodynamic driving force restoring its phase-separated equilibrium state. In recent years, non-equilibrium processing of immiscible alloys by SPD or ion-beam mixing have attracted significant interest as they enable the synthesis of novel nano-composite alloys with desirable properties such as enhanced mechanical strength, high electrical/thermal conductivity, creep resistance and radiation tolerance. Nonetheless, some major roadblocks must be overcome before the promise of these alloys can be realized. Currently, there is no general theoretical framework that can predict the microstructures formed under driven conditions. Furthermore, the present understanding of the mechanisms underlying microstructural evolution in driven alloys is still rather limited. One approach to rationalize the novel microstructure that evolves in driven alloys has been the effective temperature model (ETM) which posits that the non-equilibrium phases formed during processing will correspond to the equilibrium phase at a different, typically higher, effective temperature different from the ambient one. The underlying intuition behind this model is that the extrinsic forcing via irradiation or SPD represents an entropy-like contribution to the free energy of the system. Thus, to a first approximation, the evolution of driven alloys will be determined by the relative magnitudes, captured in the forcing intensity parameter, of the chemical diffusivities corresponding to ballistic mixing and vacancy-mediated thermal diffusion (typically accelerated by the excess vacancies produced by the forcing mechanism). In this work, the validity of such ETM’s is investigated using atomistic simulations of two different alloy systems. Firstly, molecular dynamics simulations are used to study the phase evolution during low-temperature shear deformation of highly immiscible alloys (Ω=2 eV/atom). Key findings from this work that support the ETM concept are: (i) a two-phase microstructure evolves at steady-state despite the absence of thermal diffusion and significant co-deformation of the two phases; (ii) the observed steady-state supersaturation varies with the precipitate size reminiscent of Gibbs-Thomson-like behavior; (iii) the effective temperature scales with the shear modulus of the alloy, thereby supporting the proposal of a modified ETM (METM) for low-temperature SPD of immiscible alloys. The simulations are also shown to agree very well on a semiquantitative basis with experimental studies, providing new insights in understanding phase stability in real alloys, as well as elucidating the mechanisms underlying microstructural evolution during low-temperature SPD. The second part of the thesis employs kinetic Monte Carlo (KMC) simulations to investigate the evolution of moderately immiscible alloys (Ω=0.33 eV/atom) during irradiation at elevated temperatures. The effective temperature of these systems is shown to scale with the forcing intensity parameter as predicted by the ETM. Furthermore, it is shown that when the system is in the compositional patterning regime, defined by the presence of clusters of characteristic size distribution, the system follows an inverse Gibbs-Thomson relation upon increasing the nominal composition of the alloy, i.e. the steady-state solubility increases with increasing cluster size

Knee Injuries: correlation of MRI with arthroscopic findings

Introduction: Knee injuries are common among active adults. Achieving a correct clinical diagnosis is often difficult in acute presentations. Knee arthroscopy is considered the gold standard in diagnosing post-traumatic intra-articular lesions, but it is an invasive procedure requiring a certain degree of expertise. Magnetic Resonance Imaging (MRI) is a non-invasive, sensitive diagnostic tool for knee injuries. This study aims to correlate the findings of MRI with arthroscopy of the knee. Method: This Prospective Observational Study was done at Shree Birendra Hospital, Kathmandu, Nepal from 13 Feb 2016 to 13 Jun 2016. The sensitivity, specificity, and accuracy of MRI findings in ligamentous, meniscal, and osteochondral injuries of the knee were analyzed using arthroscopic findings as standard. Result: Fifty-two patients (35 male and 17 female), mean age 35.4 years were included in the study. The accuracy of MRI for anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), medial meniscus, lateral meniscus, and chondral lesions of the knee were 94%, 100%, 92%, 86%, and 86% respectively. Conclusion: The MRI is accurate (86-94%) in diagnosing Meniscal and Ligamentous injuries of the knee. It has poor sensitivity (22%) for chondral lesions

Policy mixes for incumbency: the destructive recreation of renewable energy, shale gas 'fracking,' and nuclear power in the United Kingdom

The notion of a ‘policy mix’ can describe interactions across a wide range of innovation policies, including ‘motors for creation’ as well as for ‘destruction’. This paper focuses on the United Kingdom’s (UK) ‘new policy direction’ that has weakened support for renewables and energy efficiency schemes while strengthening promotion of nuclear power and hydraulic fracturing for natural gas (‘fracking’). The paper argues that a ‘policy apparatus for incumbency’ is emerging which strengthens key regimebased technologies while arguably damaging emerging niche innovations. Basing the discussion around the three technology-based cases of renewable energy and efficiency, fracking, and nuclear power, this paper refers to this process as “destructive recreation”. Our study raises questions over the extent to which policymaking in the energy field is not so much driven by stated aims around sustainability transitions, as by other policy drivers. It investigates different ‘strategies of incumbency’ including ‘securitization’, ‘masking’, ‘reinvention’, and ‘capture.’ It suggests that analytical frameworks should extend beyond the particular sectors in focus, with notions of what counts as a relevant ‘policy maker’ correspondingly also expanded, in order to explore a wider range of nodes and critical junctures as entry points for understanding how relations of incumbency are forged and reproduced

دراسة كيفية اتخاذ قرارات التناقص في العطاءات لدى مقاولي قطاع غزة

Decision-making in construction industry is a very complex task due to uncertainty about many factors influencing the outcomes of the selected choice. Bidding decisions by contractors is one of the most critical decisions which can be made by contractors. In an attempt to uncover the underlying factors that characterize the two different but sequential decisions which are bid/no bid and markup size decisions, a questionnaire survey was conducted among 77 general contractors in Gaza Strip-Palestine regarding this issue. This research was able to identify 94 factors characterizing the bidding decision making process. The factors were categorized under three main categorize which are "Firms related factors", "project related factors" and "market conditions demand and strategic considerations" which are further divided into 16 groups. Characteristics of contractors, factors affecting bid/no bid and markup size decisions, and policies and practice of contractors are reported. The results indicate that some factors are considered very important for bid/no bid and markup size decisions. Other factors are found to have considerable importance for one decision but not for another. The study reveals that bid/no bid decision are greatly influenced by some factors, such as "current financial capability of the client", "project size", "financial status of the company", 'the donor of the project" and "terms of payment" are identified as the top five important factors. "Allowed project duration being enough", "the political environment, security situation and the cargo crossing point situation", "terms of payments", "stability of exchange rate in the country" and "the amount of changes expected throughout the execution of the project" are the highest ranked factors affecting markup size decision. One of the striking findings of this research was the distinct difference in approach of varying sizes of contractors regarding this issue. The contractors were classified into small and medium size contractors according to their annual sales. Some factors were considered high by both types of contractors for bid/no bid decision, such as "project size", "the current financial capability of the client", "the donor of the project" and "financial status of the company" and some were ranked high by one type but not by another. In markup size decision some of the factors which were found to be important by both types of contractors are "allowed project duration being enough", "the political environment, security situation and the cargo crossing point situation", "terms of payment" and " the amount of changes expected throughout the execution of the project"

Design flood estimation in ungauged catchments : quantile regression technique and probabilistic rational method compared

Estimation of design floods in ungauged catchments is frequently required in hydrological practice and is of great economic significance. The most commonly adopted methods for this task include the Probabilistic Rational Method, the U.S. Soil Conservation Service Method, the Index Flood Method and the U. S. Geological Survey Quantile Regression Technique. The Probabilistic Rational Method has been recommended in the Australian Rainfall and Runoff for general use in south-east Australia (I. E. Aust., 1997). The central component of this technique is a dimensionless runoff coefficient which in the ARR is assumed to vary smoothly over geographical space, an assumption that may not be satisfied in many cases because two nearby catchments though are likely to share similar climatic characteristics but may exhibit quite different physical characteristics

Three-dimensional modified Korteweg-de Vries equation in a magnetised relativistic plasma with positron beam and vortex-like electron distribution

The nonlinear features of Ion Acoustic (IA) waves are studied in a fully relativistic three-dimensional (3-D) plasma system with consideration of effect of both positron beam and trapped electrons. We consider a set of 3-D magnetised hydrodynamic equations with pressure expansion for our plasma model along with kinetic Vlasov equation for electrons. Applying the perturbative expansion technique, a Modified Korteweg-de Vries (m-KdV)-like equation is derived, exhibiting the evolution of small amplitude IA waves in plasma. The modified coefficient of nonlinear term in K-dV equation has arrived due to impact of vortex-like distribution of electrons. An analytical and numerical investigation of the nonlinear evolution equations is exhibited with external magnetic field effects, the time derivative pressure expansion as well as other parameters like relativistic effect, mass variation, beam velocity and temperature effect have been taken into consideration. The presence of vortex like trapped electron distribution and positron beam governs the influence of soliton structure quite significantly. The present result should help us to understand the experiments that involve particle trapping and also the salient features of astrophysical environment like ionospheric plasma together with situations in plasma describing the electrostatic solitary structures usually seen in antimatter-related environment in interplanetary region