Addressing effective construction logistics through the lens of vehicle movements

Purpose – Construction logistics is an essential part of construction supply chain management (CSCM). However, limited attention has been paid to this issue in the New Zealand construction industry. The purpose of this paper is to contribute to the knowledge about what hampers efficiency in transporting construction materials and plants to a construction site. The intention is to gain detailed understanding of the practice and obstacles in efficient construction logistics and thus identify interventions to improve logistics efficiency, especially using the numbers of vehicle movements to the construction site as an indicator. Design/methodology/approach – A case study approach was adopted with on-site observations and interviews. Observations were performed during constructions on-site from the start of construction to “hand-over” to the building owner. A selection of construction suppliers and subcontractors involved in the studied project were interviewed. Findings – Data analysis suggested that cost-related factors affecting the construction logistics, both monetary and non-monetary factors were not measured and largely ignored, especially the possible environmental and/or social impact occurred by the truck movement. Factors in the service-related sector were insufficiently managed in the observed site. The main contribution to inefficient construction logistics are related to understanding and implementing CSCM. It is noticed that there is inadequate awareness of CSCM and logistics efficiency largely due to lack of commitment from the management level and skills at the operational level. Originality/value – Significant intrinsic and extrinsic interventions necessary to enhance construction logistics were acknowledged from the data analysis. These include both qualitative and quantitative data. These intrinsic and extrinsic interventions, such as implementing appropriate logistics tools that suits individual site and introducing traffic management costs, offer plausible explanations regarding how to improve the efficiency in construction logistics through optimising transportation movements to the construction site

Explosion mechanism of core-collapse supernovae: role of the Si/O interface

We present a simple criterion to predict the explodability of massive stars based on the density and entropy profiles before collapse. If a pronounced density jump is present near the Si/Si-O interface, the star will likely explode. We develop a quantitative criterion by using $\sim 1300$ 1D simulations where $\nu$-driven turbulence is included via time-dependent mixing-length theory. This criterion correctly identifies the outcome of the supernova more than $90 \%$ of the time. We also find no difference in how this criterion performs on two different sets of progenitors, evolved using two different stellar evolution codes: FRANEC and KEPLER. The explodability as a function of mass of the two sets of progenitors is very different, showing: (i) that uncertainties in the stellar evolution prescriptions influence the predictions of supernova explosions; (ii) the most important properties of the pre-collapse progenitor that influence the explodability are its density and entropy profiles. We highlight the importance that $\nu$-driven turbulence plays in the explosion by comparing our results to previous works.Comment: 20 pages, 12 figures, submitted to Ap

Size-Dependent Surface Plasmon Dynamics in Metal Nanoparticles

We study the effect of Coulomb correlations on the ultrafast optical dynamics of small metal particles. We demonstrate that a surface-induced dynamical screening of the electron-electron interactions leads to quasiparticle scattering with collective surface excitations. In noble-metal nanoparticles, it results in an interband resonant scattering of d-holes with surface plasmons. We show that this size-dependent many-body effect manifests itself in the differential absorption dynamics for frequencies close to the surface plasmon resonance. In particular, our self-consistent calculations reveal a strong frequency dependence of the relaxation, in agreement with recent femtosecond pump-probe experiments.Comment: 8 pages + 4 figures, final version accepted to PR

Spaceflight Payload Design, Flight Experience G-408

Worcester Polytechnic Institute\u27s first payload of spaceflight experiments flew aboard Columbia, STS-40, during June of 1991 and culminated eight years of work by students and faculty. The Get Away Special (GAS) payload was installed on the GAS bridge assembly at the aft end of the cargo bay behind the Spacelab Life Sciences (SLS-l) laboratory. The experiments were turned on by astronaut signal after reaching orbit and then functioned for 72 hours. Environmental and experimental measurements were recorded on three cassette tapes which, together with zeolite crystals grown on orbit, formed the basis of subsequent analyses. The experiments were developed over a number of years by undergraduate students meeting their project requirements for graduation. The experiments included zeolite crystal growth, fluid behavior, and microgravity acceleration measurement in addition to environmental data acquisition. Preparation also included structural design, thermal design, payload integration, and experiment control. All of the experiments functioned on orbit and the payload system performed within design estimates

Size-dependent Correlation Effects in Ultrafast Optical Dynamics of Metal Nanoparticles

We study the role of collective surface excitations in the electron relaxation in small metal particles. We show that the dynamically screened electron-electron interaction in a nanoparticle contains a size-dependent correction induced by the surface. This leads to new channels of quasiparticle scattering accompanied by the emission of surface collective excitations. We calculate the energy and temperature dependence of the corresponding rates, which depend strongly on the nanoparticle size. We show that the surface-plasmon-mediated scattering rate of a conduction electron increases with energy, in contrast to that mediated by a bulk plasmon. In noble-metal particles, we find that the dipole collective excitations (surface plasmons) mediate a resonant scattering of d-holes to the conduction band. We study the role of the latter effect in the ultrafast optical dynamics of small nanoparticles and show that, with decreasing nanoparticle size, it leads to a drastic change in the differential absorption lineshape and a strong frequency dependence of the relaxation near the surface plasmon resonance. The experimental implications of our results in ultrafast pump-probe spectroscopy are also discussed.Comment: 29 pages including 6 figure

Estimativa do balanço de energia utilizando o modelo de interação biosfera-atmosfera - CABLE.

O objetivo desse trabalho foi avaliar o desempenho do modelo CABLE (Csiro Atmosphere Biophisic Land Exchange) na estimativa do saldo de radiação, para três dias consecutivos acima da cultura da soja. Foram realizadas medições contínuas dos fluxos de massa e energia para um ciclo completo da cultura da soja durante o período de novembro de 2008 a abril de 2009, no município de Cruz Alta, RS, Brasil. Para simulação do saldo de radiação foi utilizado o modelo Biofísico de interação solo-planta-atmosfera ?CABLE?. Foram realizados quatro testes estatísticos para testar o modelo CABLE, o qual conseguiu reproduzir os valores dos dados observados dos componentes do balanço de energia durante os três dias analisados, obtendo índice de correlação ?r? e índice de concordância ?d? de 0,98 e 0,97, respectivamente