Exact and heuristic approaches for the ship-to-shore problem

After a natural disaster such as a hurricane or flooding, the navy can help by bringing supplies, clearing roads, and evacuating victims. If destinations cannot be reached over land, resources can be transported using smaller ships and helicopters, called connectors. To start aid on land as soon as possible this must be done efficiently. In the ship-to-shore problem, trips with their accompanying resources are determined while minimising the makespan. Limited (un)loading capacities, heterogeneous connector characteristics and constraints posed by priority of the resources and grouping of the resources (resource sets) all require that the connector trips are carefully coordinated. Despite the criticality of this coordination, existing literature does not consider resource sets and has only developed heuristics. We provide a formulation that incorporates resource sets and develop (i) an exact branch-and-price algorithm and (ii) a tailored greedy heuristic that can provide upper bounds. We find that 84% of our 98 practical instances terminate within an hour in on average 80 s. Our greedy heuristic can find optimal solutions in two-thirds of these instances, mostly for instances that are very constrained in terms of the delivery order of resources. When improvements are found by the branch-and-price algorithm, the average gap with the makespan of the greedy solution is 40% and, in most cases, these improvements are obtained within three minutes. For the 20 artificial instances, the greedy heuristic has consistent performance on the different types of instances. For these artificial instances improvements of on average 35% are found in reasonable time.</p

Scanning-helium-ion-beam lithography with hydrogen silsesquioxane resist

A scanning-helium-ion-beam microscope is now commercially available. This microscope can be used to perform lithography similar to, but of potentially higher resolution than, scanning electron-beam lithography. This article describes the control of this microscope for lithography via beam steering/blanking electronics and evaluates the high-resolution performance of scanning helium-ion-beam lithography. The authors found that sub-10 nm-half-pitch patterning is feasible. They also measured a point-spread function that indicates a reduction in the micrometer-range proximity effect typical in electron-beam lithography.National Science Foundation (U.S.). Graduate Research Fellowship Progra

National Institute of Standards and Technology - Texas instruments industrial collaboratory testbed.

A portion of the mission of the NIST Manufacturing Engineering Laboratory (MEL) is to improve and advance length metrology in aid of U.S. Industry. This responsibility is found within the Precision Engineering Division (PED). The successful development of a ''Collaborator'' for TelePresence Microscopy provides an important new tool to promote technology transfer in the area of length metrology and measurement technology. NIST and Texas Instruments under the auspices of the National Automated Manufacturing Testbed (NAMT) and in collaboration with the University of Illinois are developing a microscopy collaborator testbed to demonstrate the value of telepresence microscopy within a large distributed manufacturing facility such as Texas Instruments and between organizations such as NET, Texas Instruments and Universities. Telepresence Microscopy is an application of the state-of-the-art Internet based technology to long-distance scientific endeavors. Long distance can refer to across the country or from one site within a company to another. Telepresence is currently being applied to electron microscopy in several locations where unique analytical facilities (such as those at NIST) can be utilized via Internet connection. Potentially this can provide tremendous savings to a company where asset sharing can now be rapidly and effectively accessed or remote unique facilities can be utilized without the requirement of expensive and time consuming travel. This methodology is not limited to electron microscopy, but its power is currently exemplified by its application to that form of microscopy

Automated Transmission-Mode Scanning Electron Microscopy (tSEM) for Large Volume Analysis at Nanoscale Resolution

Transmission-mode scanning electron microscopy (tSEM) on a field emission SEM platform was developed for efficient and cost-effective imaging of circuit-scale volumes from brain at nanoscale resolution. Image area was maximized while optimizing the resolution and dynamic range necessary for discriminating key subcellular structures, such as small axonal, dendritic and glial processes, synapses, smooth endoplasmic reticulum, vesicles, microtubules, polyribosomes, and endosomes which are critical for neuronal function. Individual image fields from the tSEM system were up to 4,295 µm2 (65.54 µm per side) at 2 nm pixel size, contrasting with image fields from a modern transmission electron microscope (TEM) system, which were only 66.59 µm2 (8.160 µm per side) at the same pixel size. The tSEM produced outstanding images and had reduced distortion and drift relative to TEM. Automated stage and scan control in tSEM easily provided unattended serial section imaging and montaging. Lens and scan properties on both TEM and SEM platforms revealed no significant nonlinear distortions within a central field of ~100 µm2 and produced near-perfect image registration across serial sections using the computational elastic alignment tool in Fiji/TrakEM2 software, and reliable geometric measurements from RECONSTRUCT™ or Fiji/TrakEM2 software. Axial resolution limits the analysis of small structures contained within a section (~45 nm). Since this new tSEM is non-destructive, objects within a section can be explored at finer axial resolution in TEM tomography with current methods. Future development of tSEM tomography promises thinner axial resolution producing nearly isotropic voxels and should provide within-section analyses of structures without changing platforms. Brain was the test system given our interest in synaptic connectivity and plasticity; however, the new tSEM system is readily applicable to other biological systems.This study was funded by United States National Institutes of Health (http://www.nih.gov; grant numbers NS021184, NS074644, and MH095980 to KMH) and Texas Emerging Technologies Fund (http://governor.state.tx.us/ecodev/etf/). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Biological Sciences, School o