DISTANCE APPROXIMATIONS FOR ROUTING MANUAL PICKERS IN A WAREHOUSE

This paper evaluates and compares strategies for routing a manual picker through a simple warehouse. It expands on previous work, in which optimization algorithms were developed, by deriving equations which relate route length to warehouse attributes. Several rules of thumb are derived for selection of order picking strategies and optimization of warehouse shape.     

Modeling the diffusion-adsorption kinetics of 1-methylcyclopropene (1-MCP) in apple fruit and non-target materials in storage rooms

The purpose of this research was to model the kinetics of adsorption of 1-methylcyclopropene (1-MCP) in apple fruit and non-target solid materials found in apple storage rooms. The process was described by Fick’s second law of diffusion of the gas through the pores of the material coupled with adsorption kinetics of the gas on the material’s binding sites. A finite element formulation of the model, describing the diffusion and adsorption mechanisms separately, was first developed. The values of the relevant parameters were estimated based on headspace measurements of the decrease of 1-MCP in jars containing the different materials. The headspace concentration of 1-MCP was measured using gas chromatography. Apple fruit (Golden Delicious and Jonagold) and the following bin construction materials were investigated: high density polyethylene (HDPE), oak, poplar wood and card lining. The range in the magnitude of the diffusion coefficient, adsorption coefficient, and concentration of active sites in the various solids was 10,000-, 8-, and 30-fold, respectively.     

Pressure effect of growing with electron beam-induced deposition with tungsten hexafluoride and tetraethylorthosilicate precursor

Electron beam-induced deposition (EBID) provides a simple way to fabricate submicron- or nanometer-scale structures from various elements in a scanning electron microscope (SEM). The growth rate and shape of the deposits are influenced by many factors. We have studied the growth rate and morphology of EBID-deposited nanostructures as a function of the tungsten hexafluoride (WF6) and tetraethylorthosilicate (TEOS) precursor gas pressure and growth time, and we have used Monte Carlo simulations to model the growth of tungsten and silicon oxide to elucidate the mechanisms involved in the EBID growth. The lateral radius of the deposit decreases with increasing pressure because of the enhanced vertical growth rate which limits competing lateral broadening produced by secondary and forward-scattered electrons. The morphology difference between the conical SiO(x) and the cylindrical W nanopillars is related to the difference in interaction volume between the two materials. A key parameter is the residence time of the precursor gas molecules. This is an exponential function of the surface temperature; it changes during nanopillar growth and is a function of the nanopillar material and the beam conditions.     

Building the Connection Between Housing Needs and Metropolitan Planning in Sydney,Australia

The theme of a more compact city has been a central feature of planning policy for Sydney's development over the last two decades. Urban consolidation, in the form of attached dwellings in medium- and high-density configurations, has become the predominant form of new residential development since the early 1990s. One of the largely untested claims for this policy is that it provides more housing choice for an increasingly diverse population and that simply building larger amounts of smaller housing in high-density concentrations will be sufficient to meet that demand. As a result, planning for higher density housing has been undertaken with little explicit recognition of the housing sub-markets higher density housing caters for or their specific spatial characteristics within the city. These issues are examined by an analysis of the socio-economic characteristics of areas with high concentrations of attached housing. These data are processed by factor analysis to identify and locate the range of sub-markets within attached housing and additional small area data used to fill out the market profiling. The results reveal that a range of specific housing needs are met by this form of housing with discriminative characteristics in certain locations. In other words, higher density housing is associated with a range of locationally specific and spatially distinctive sub-markets. These findings are particularly relevant and timely as a new metropolitan strategy is in preparation for Sydney where an estimated 60–70 per cent of new dwelling provision in the next 30 years will take place within existing suburbs through higher density redevelopment. Planning for such development must take into account the local markets for such accommodation which have very different characteristics in different parts of the city.     

Computer Applications in Intelligent Compaction

The term “intelligent compaction” is now heard so often one might believe that the method used for documenting and controlling the quality of hot-mix asphalt pavement has evolved to a state of total commercial and engineering acceptance. In fact, today’s most-used process for determining the density of an asphalt mat uses 1960’s technology. Now, however, the responsibility for quality control (QC) of the paving and compaction process has largely been given to the contractor. This shift in responsibility comes at a time when the construction industry as a whole is faced with the worst labor shortage in history, limiting the number of qualified QC technicians and equipment operators. Recently, researchers introduced a patented system that, when mounted on a vibratory asphalt compactor, can render an asphalt density reading (in pounds per cubic foot) every 1?s in real time. This paper briefly describes the system and details the essential contributions made by computer hardware and software to a successful onboard asphalt density measuring system.     

In situ probing of the growth and morphology in electron-beam-induced deposited nanostructures

Three series of nanofiber structures were grown via electron-beam-induced deposition as a function of beam energy (1, 5 and 20?keV) using a W(CO)(6) precursor. At each beam energy a time series ranging from 0.5 to 128?s was performed and the sample current during each growth was monitored versus growth time. The subsequent current traces have been correlated to the nanostructure morphology. For the 1 and 5?keV beam energy, two distinct lateral growth regimes were observed. Initially there is a rapid base broadening consistent with the electron beam interaction region. Secondly, a lateral 'platelet' type growth was observed. At 20?keV beam energy, there is an initial rapid broadening: however, no 'platelet' growth is observed. For each beam energy, the measured current trace is correlated to the observed growth regimes.     

Bearing Response of Skirted Foundation on Nonhomogeneous Soil

Circular skirted offshore foundations on nonhomogeneous soil have been studied numerically, analytically, and physically, with the offshore sediment simulated as a cohesive soil with strength increasing linearly with depth. In the numerical analysis, the h-adaptive FEM is adopted to provide an optimal mesh, in which a strain-superconvergent patch recovery error estimator and mesh refinement with subdivision concept are used. This paper presents two main studies of circular skirted foundations on nonhomogeneous soil, consisting of a bearing-capacity study and a large penetration study. The bearing capacity of the foundations is studied with the degree of nonhomogeneity (kD∕suo) of soil up to 30, different skirt roughness and skirt depth up to five times the foundation diameter (i.e., Df∕D = 5), using an h-adaptive FEM and extended upper-bound method. The bearing-capacity values and soil flow mechanisms are discussed. In the foundation large penetration study, circular skirted foundations penetrating into normally consolidated and overconsolidated soils are tested physically in the centrifuge and analyzed numerically using the h-adaptive remeshing and interpolation technique with small strain method for soil large deformation analysis. The load-displacement responses from centrifuge test data and finite-element results are compared.     

Ultrasensitive detection and characterization of posttranslational modifications using surface-enhanced Raman spectroscopy

Posttranslational modification (PTM) of proteins is likely to be the most common mechanism of altering the expression of genetic information. It is essential to characterize PTMs to establish a complete understanding of the activities of proteins. Here, we present a sensitive detection method using surface-enhanced Raman spectroscopy (SERS) that can detect PTMs from as little as zeptomoles of peptide. We demonstrate, using model peptides, the ability of SERS to detect a variety of protein modifications, such as acetylation, trimethylation, phosphorylation, and ubiquitination. In addition, we show the capability to obtain positional information for modifications such as trimethylation and phosphorylation using SERS and wavelet decomposition data analysis techniques. We further show that it is possible to apply SERS to detect PTMs from biological samples such as histones. We envision that this detection method might be a valuable technique that is complementary to mass spectrometry in obtaining orthogonal chemical and modification-specific information from biological samples at sensitive levels.     

Large Deformation Finite-Element Analysis of Submarine Landslide Interaction with Embedded Pipelines

Submarine landslides represent one of the most significant geohazards on the continental slope in respect of the risk they pose to infrastructure such as deep water pipelines. A numerical approach, based on the finite-element method but using remeshing, was established in this paper to simulate large flow deformation of debris from a landslide and to quantify the loads and displacements imposed on pipelines embedded in the seabed. A simple two-dimensional elastic perfectly plastic soil model with plane strain conditions was employed in this analysis. The pipeline was restrained by a set of springs so that the load on the pipeline built up to a stable value, representing the limiting load at which the debris flowed over the pipeline. A parametric study was undertaken by varying the pipeline embedment and the relative strengths of the debris and seabed. The analysis results show that the various combinations of soil strength and embedment depth lead to different debris-pipeline movement patterns and consequently lead to rather different magnitudes of the loads imposed on pipelines. The pipeline is subjected to the largest load (an equivalent pressure of 11.5 times debris strength) from the landslide when it rests on the weakest seabed. The pressure is proportional to the debris material strength but varies inversely with the seabed strength for partially embedded pipelines. For all strength combinations, there is a critical embedment depth beyond which the force on the pipeline reduces to a very small magnitude.