28,313 research outputs found

    Collaboration in Truck Appointment System in Container Terminals

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    Due to the continual increase of the global containerized trade, many container terminals face the problem of high demands that their current resource capacity cannot afford. The consequences of such situation are not only the long queues of trucks at the entrance gates and storage yards but also the large turnaround times of trucks. In response, Truck Appointment Systems (TAS) were introduced to schedule truck arrivals in order to alleviate the terminal rush hours, however, the mandatory appointments developed by TASs have a negative impact on the operations as well as resources of the trucking companies. In recent literature, this issue was considered by introducing collaborative TAS in which the trucking companies as well as the container terminals collaborate to set the truck appointments. This work elaborates on the difference between traditional and collaborative TAS and demonstrates how collaborative TAS can improve the performance of the container terminal and reduce the cost of the trucking companies.&nbsp

    Aquaculture, employment, poverty, food security and well-being in Bangladesh: A comparative study

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    Comparison of CDMS [100] and [111] oriented germanium detectors

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    The Cryogenic Dark Matter Search (CDMS) utilizes large mass, 3" diameter Ă—\times 1" thick target masses as particle detectors. The target is instrumented with both phonon and ionization sensors and comparison of energy in each channel provides event-by-event classification of electron and nuclear recoils. Fiducial volume is determined by the ability to obtain good phonon and ionization signal at a particular location. Due to electronic band structure in germanium, electron mass is described by an anisotropic tensor with heavy mass aligned along the symmetry axis defined by the [111] Miller index (L valley), resulting in large lateral component to the transport. The spatial distribution of electrons varies significantly for detectors which have their longitudinal axis orientations described by either the [100] or [111] Miller indices. Electric fields with large fringing component at high detector radius also affect the spatial distribution of electrons and holes. Both effects are studied in a 3 dimensional Monte Carlo and the impact on fiducial volume is discussed.Comment: Low Temperature Detector 14 conference proceedings to be published in the Journal of Low Temperature Physic

    EFFECTS OF LOG POSITION IN THE STEM AND CUTTING WIDTH ON SIZE DISTRIBUTION OF BLACK SPRUCE CHIPS PRODUCED BY A CHIPPER-CANTER

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    Fifteen stems of black spruce (Picea mariana (Mill.) B.S.P.) coming from the Abitibi-TĂ©miscamingue region, were cross-cut into three sections: bottom, middle, and top logs. Logs were fragmented producing three faces with a chipper-canter using three cutting widths (CW) of 12.7, 19.1, and 25.4 mm. Chip dimensions were assessed by thickness, width, and length (Domtar and Williams classifications). Knot characteristics [total knot number (TKN) and area (TKA)] were assessed in the three cant faces. Growth ring attributes [earlywood density, latewood density (LWD), ring density, earlywood proportion, ring width and rings per mm (R/mm)], mechanical properties (shear, splitting, modulus of elasticity (MOE) and modulus of rupture in bending), and basic density were evaluated on samples obtained within each CW area. The results showed that most of these wood attributes were affected by the log position in the stem and/or CW. The weighted mean chip thickness (WCT) and chip size distributions were significantly affected by the log position and CW. WCT increased as CW increased. WCT variation with height could be principally associated to the number and size of knots within the stem. However, the presence of higher taper in the bottom logs produced thicker chips. Multiple linear regressions showed that CW, TKN, LWD, and TKA were significant predictors of WCT. Moreover, chip thickness distribution was affected primarily by TKA, cutting height and LWD, while the width and length distribution was mainly affected by R/mm, TKN and MOE. Chip size variation is to some point determined by knot characteristics, bending properties, growth ring width, and wood density of the raw material. These results showed the potential benefits of classifying logs in woodyards and better controlling the raw material attributes in sawmills. If the CW is combined with the knowledge of the raw material, chip dimensions can be adjusted using other fragmentation parameters to increase chip size uniformity

    Reflectionless Potentials and PT Symmetry

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    Large families of Hamiltonians that are non-Hermitian in the conventional sense have been found to have all eigenvalues real, a fact attributed to an unbroken PT symmetry. The corresponding quantum theories possess an unconventional scalar product. The eigenvalues are determined by differential equations with boundary conditions imposed in wedges in the complex plane. For a special class of such systems, it is possible to impose the PT-symmetric boundary conditions on the real axis, which lies on the edges of the wedges. The PT-symmetric spectrum can then be obtained by imposing the more transparent requirement that the potential be reflectionless.Comment: 4 Page

    Evolution of an elliptical bubble in an accelerating extensional flow

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    Mathematical models that describe the dynamical behavior of a thin gas bubble embedded in a glass fiber during a fiber drawing process have been discussed and analyzed. The starting point for the mathematical modeling was the equations presented in [1] for a glass fiber with a hole undergoing extensional flow. These equations were reconsidered here with the additional reduction that the hole, i.e. the gas bubble, was thin as compared to the radius of the fiber and of finite extent. The primary model considered was one in which the mass of the gas inside the bubble was fixed. This fixed-mass model involved equations for the axial velocity and fiber radius, and equations for the radius of the bubble and the gas pressure inside the bubble. The model equations assumed that the temperature of the furnace of the drawing tower was known. The governing equations of the bubble are hyperbolic and predict that the bubble cannot extend beyond the limiting characteristics specified by the ends of the initial bubble shape. An analysis of pinch-off was performed, and it was found that pinch-off can occur, depending on the parameters of the model, due to surface tension when the bubble radius is small. In order to determine the evolution of a bubble, a numerical method of solution was presented. The method was used to study the evolution of two different initial bubble shapes, one convex and the other non-convex. Both initial bubble shapes had fore-aft symmetry, and it was found that the bubbles stretched and elongated severely during the drawing process. For the convex shape, fore-aft symmetry was lost in the middle of the drawing process, but the symmetry was re-gained by the end of the drawing tower. A small amount of pinch-off was observed at each end for this case, so that the final bubble length was slightly shorter than its theoretical maximum length. For the non-convex initial shape, pinch-off occurred in the middle of the bubble resulting in two bubbles by the end of the fiber draw. The two bubbles had different final pressures and did not have fore-aft symmetry. An extension of the fixed-mass model was considered in which the gas in the bubble was allowed to diffuse into the surrounding glass. The governing equations for this leaky-mass model were developed and manipulated into a form suitable for a numerical treatment
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