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The cable routing problem in offshore wind farms consists in designing a transportation network to transfer the electricity generated by wind turbines to a central hub (substation) which is connected to shore. The submarine electrical cables are expensive, comprising about 5% of the total capital expenditure (CAPEX) of an offshore wind farm (BVG Associates, 2019). For this reason, the optimization of cable routing has been investigated in literature, with the objective of finding the cable routing of minimum cost (Bauer & Lysgaard, 2015). One important constraint for the cable routing problem is that cable crossings are forbidden, due to the increased installation costs and difficult maintenance. Another constraint is that the routing must avoid all obstacles in the wind farm sea area. These obstacles may be due to unsuitable seabed conditions, to ship wrecks, and to regulations, such as fishing corridors and natural reserves. Cables must not cross any of these areas for the routing solution to be feasible. Acable routing allows only one electrical cable to exit from each turbine, and multiple cables to enter turbines and the substation. Each sub-tree leaving the substation is denoted a rootbranch. A property of cable routing solution is related to how many turbines are present in each root-branch. If the number of turbines in each root-branch is the same or differs at most by one, we denote the solution balanced. While literature mainly has focused on the general unbalanced cable routing problem, in industry the wind farm developers favor balanced cable routing solutions. As the solutions to the balanced problem are a subset of the solutions to the unbalanced formulation, unbalanced solutions may be cheaper than balanced. The drawbacks of the unbalanced routing are related to the additional electrical equipment cost that needs to be installed in the offshore substation. In particular, the cost of installing a spare Offshore Transformer Module (OTM) on the substation is about 5M€ (Walling & Ruddy, 2005), depending on its rating. In the case of a balanced cable routing, a single type of transformer is needed as spare in case of failures (online spare), since the transformer share the same electrical loads and can substitute any of the transformers in case of failure. For the unbalanced case instead, different transformer ratings and different spares would be needed, making this option less attractive in the industry. The contributions of this work are:• Wedevelop a matheuristic that uses different neighborhoods to optimize the cable routing problem, for both balanced and unbalanced networks. • We present a technique to handle obstacles in the cable routing based on a visibility graph. • We quantify the difference between balanced and unbalanced cable routing on a set of realistic wind farm instances, taking into account the additional OTM costs.

This paper characterizes the actual science performance of the James Webb Space Telescope (JWST), as determined from the six month commissioning period. We summarize the performance of the spacecraft, telescope, science instruments, and ground system, with an emphasis on differences from pre-launch expectations. Commissioning has made clear that JWST is fully capable of achieving the discoveries for which it was built. Moreover, almost across the board, the science performance of JWST is better than expected; in most cases, JWST will go deeper faster than expected. The telescope and instrument suite have demonstrated the sensitivity, stability, image quality, and spectral range that are necessary to transform our understanding of the cosmos through observations spanning from near-earth asteroids to the most distant galaxies., Comment: 5th version as accepted to PASP; 31 pages, 18 figures; https://iopscience.iop.org/article/10.1088/1538-3873/acb293

The multi-commodity network flow problem (MCNF) consists in routing a set of commodities through a capacitated network at minimum cost and is relevant for routing containers in liner shipping networks. As commodity transit times are often a critical factor, the literature has introduced hard limits on commodity transit times. In practical contexts, however, these hard limits may fail to provide sufficient flexibility since routes with even tiny delays would be discarded. Motivated by a major liner shipping operator, we study an MCNF generalization where transit time restrictions are modeled as soft constraints, in which delays are discouraged using penalty functions of transit time. Similarly, early commodity arrivals can receive a discount in cost. We derive properties that distinguish this model from other MCNF variants and adapt a column generation procedure to efficiently solve it. Extensive numerical experiments conducted on realistic liner shipping instances reveal that the explicit consideration of penalty functions can lead to significant cost reductions compared to hard transit time deadlines. Moreover, the penalties can be used to steer the flow towards slower or faster configurations, resulting in a potential increase in operational costs, which generates a trade-off that we quantify under varying penalty functions., Transportation Research Part E: Logistics and Transportation Review, 150, ISSN:1366-5545

In global liner shipping networks, a large share of transported cargo is transshipped at least once between container vessels, and the total transportation time of these containers depends on how well the corresponding services are synchronized. We propose a problem formulation that integrates service scheduling into the liner shipping network design problem. Furthermore, the model incorporates many industry-relevant modeling aspects: it allows for leg-based sailing speed optimization, it is not limited to simple or butterfly-type services, and it accounts for service-level requirements such as cargo transit time limits. The classic liner shipping network design problem is already a hard problem, and to solve the extended version, we propose a column-generation matheuristic that uses advanced linear programming techniques. The proposed method solves LINER-LIB instances of up to 114 ports and, if applied to the classic liner shipping network design problem, finds new best solutions to all instances, outperforming existing methods reported in the literature. Additionally, we analyze the relevance of scheduling for liner shipping network design. The results indicate that neglecting scheduling and approximating transshipments instead may result in the design of liner shipping networks that underestimate cargo transit times and their implications.

This paper introduces the transit time constrained fixed charge multi-commodity network design problem. Transit times are origin-to-destination time limits for the commodities, which appear for example in transport systems with perishable goods. We discuss how to model the problem and present three different formulations of it. The first formulation is an exponential size path formulation, which we solve with a branch-and-price algorithm. Several speed up techniques from the literature on fixed charge multi-commodity network design problems are implemented, such as lifted cover inequalities and the recently proposed deep dual-optimal inequalities. In an extensive set of computational experiments, we show that these inequalities significantly improve the performance of the algorithm. The other two formulations are of polynomial size: one uses path indices and the other uses time indices. While the branch-and-price algorithm outperforms solving the compact formulations with a general-purpose mixed-integer programming solver, the study of compact models helps better understand the problem, and we can use them as benchmarks. A detailed sensitivity analysis of the branch-and-price algorithm shows that longer transit times and an increased ratio of fixed charge to flow cost increase the difficulty of solving the problem whereas the arc capacity has less impact. We further discuss in-depth implementational details.

We consider a strategic infrastructure and tanker fleet sizing problem in the liquefied natural gas business. The goal is to minimize long-term on-shore infrastructure and tanker investment cost combined with interrelated expected cost for operating the tanker fleet. A non-linear arc-based model and an exact solution method based on a set-partitioning formulation are developed. The latter approach allows very fast solution times. Computational results for a case study with a liner shipping company are presented, including an extensive sensitivity analysis to account for limited predictability of key parameter values, to analyze the solutions’ robustness and to derive basic decision rules.

Despite a precisely established plan, disruptions are a reality in liner shipping. They are caused by unforeseen factors such as weather, port congestion, low terminal productivity, crane breakdowns etc. Disruptions vary in magnitude. Smaller disruptions, such as the temporary stop of a crane operations due to fog, often impacts only a single vessel. In contrast, the closure of a hub terminal as Algeciras for two days due to rough weather in Gibraltar Straits has severe ripple effects that spread across the entire network. Recovery actions for such major events require rescheduling of multiple vessels, as well as cargo re-routing. Maersk, in cooperation with the Technical University of Denmark, is working on a decision support tool aimed at recovering operations after disruptions of different sizes in near real time. The tool uses an integrated approach that jointly optimizes vessel schedules and cargo routes. The objective is to minimize (a) operational cost, mainly vessel related such as fuel and port stays, and (b) impact on cargo delivery dates. The outcome is "cargo-friendly" revised vessel schedules that recovers operations within a fixed time horizon. The practical considerations and mathematical formulation of the model(s) will be presented together with preliminary computational results.

Global container liner shipping networks are composed of services and each service represents a roundtrip that connects a set of ports following a published schedule. The majority of services is operated at a weekly frequency, and each port on a service is visited at the same time each week. Commonly, all vessels deployed on a service are of the same capacity. Liner services are connected through common port calls that allow liner network operators to move cargo from one service to another. The movement of containers between services is called transshipment and enables large liner shipping companies to transport containers between almost any possible pair of ports around the globe. Current state-of-the-art models and methods (e.g. Karsten et al., 2017) for liner shipping network design problems only determine the routes and sailing speeds for individual services, but approximate transshipment times by a constant. In practice, the transshipment time between two services depends on how well the schedules of the individual services are synchronized. In the network of the world’s largest overseas cargo carrier, around half of all transported containers are transshipped, and the transshipment times may significantly affect the total transit time of containers between their origin and destination port.

Den moderne økonomi er afhængig af billig og pålidelig godstransport over hele kloden. Transportved hjælp af containerskibe udgør et vigtigt element i den globale forsyningskæde. Containerskibeforbinder lande og kontinenter over lange afstande med forholdsvis lave transportomkostninger.Store containerskibsrederier (linierederier) kontrollerer flere hundrede containerskibe dertypisk sejler på faster ruter. En enkelt rute deles typisk mellem adskillige containerskibe så hverhavn på ruten modtager et besøg af et containerskib fra den pågældende rute en gang omugen. De enkelte ruter er forbundet via havne, hvor containere kan lastes, losses, men ogsåomlastes mellem skibe. Kombinationen af containerskibsruter og havne danner et komplicerettransportnetværk der muliggør transport af containere mellem de fleste større havne i verden.I denne afhandling præsenterer vi matematiske modellerings- og optimeringsværktøjer, derhjælper beslutningstagere inden for containerskibssejlads til at finde løsninger på kompleksebeslutningsproblemer. Beslutningsproblemerne vi adresserer indebærer spørgsmål som: Hvilkehavne skal være omfattet af transportnetværket? Hvordan skal hver rute udformes for at opnået godt forbundet og omkostningseffektivt netværk? Hvordan skal havnebesøg planlægges ogsynkroniseres mellem ruterne for at give den mest økonomiske og hurtigste transport? På hvilkenrute skal containere transporteres, hvis der findes flere muligheder? Artiklerne i denne afhandlingbidrager til forskning indenfor operationsanalyse med anvendelse i maritim optimering.Nærmere bestemt fremlægger de to første artikler modeller og løsningsmetoder til design ogre-planlægning af store netværk indenfor containerskibsfart.Artiklerne kombinerer og udvider modelleringsegenskaberne væsentligt i forhold til tidligerebidrag og mindsker afstanden mellem akademiske prototyper og de reelle problemstillinger somlinierederier står overfor. Resultaterne, opnået ved at løse modellerne, kaster lys over tidligereuudforskede problemer. De udviklede løsningsalgoritmer kan ikke kun håndtere den øgede kompleksiteti modellerne, men også forbedre løsningskvaliteten sammenlignet med eksisterendemetoder foreslået i litteraturen. Den tredje artikel omhandler en problemstilling indenfor dimensioneringaf infrastruktur og tankerflåde som et led i en industriel casestudie med et stortlinjerederi. Casestudiet er motiveret af de seneste ændringer i miljøbestemmelser, som i væsentliggrad kan ændre forudsætningerne for containerskibsfart i fremtiden. Artiklen omhandler oprettelsenaf en forsyningskæde der leverer flydende naturgas til en række havne langs en vigtig ruteindenfor containerskibsfart. Artiklen analyserer samspillet mellem langsigtede investeringer ogdriftsomkostninger. Simple beslutningsregler uddrages i artiklen og det undersøges hvor robustede foreslåede forsyningskæder er i forhold til ændringer i forudsætningerne for modellen. The modern economy relies on cheap and reliable transportation of goods all around the globe. Liner shipping networks represent an important link in the global supply chain, as they connect countries and continents over long distances at comparatively low transportation costs. In largeliner shipping networks, several hundred container vessels operate more than a hundred shipping routes. The individual routes are linked through ports, where containers can be loaded, unloaded but also be transshipped between shipping routes. The resulting networks constitute inherently complex systems. In this thesis we present mathematical modeling and optimization tools that help decision makers in the liner shipping industry to find solutions to complex decision problems. The decision problems we address involve questions like: Which ports shall be covered by the network? How shall each single shipping route be designed to achieve a well-connected but cost-efficient network? How shall port calls be scheduled and synchronized between shipping routes to offer the most economical and fastest transportation between ports? On which route shall containers be transported, if multiple options exist? The articles in this thesis contribute to the field of Operations Research with application in maritime optimization. More particularly, the first two articles present models and solution methods to (re-)design and (re-)schedule large liner shipping networks. The articles combine and substantially extend modeling features of previous contributions and narrow the gap to the economic and operational reality of liner shipping. The results obtained from solving the models shed light on previously unexamined issues. The developed solution algorithms cannot only handle the increased complexity inherent to the models, but improve over existing methods proposed in the literature. The third article addresses a strategic infrastructure and tanker fleet sizing problem as part of an industrial case study with a large liner shipping company. The case study is motivated by recent changes in environmental regulations that may substantially change the way liner vessels are operated in the future. The article addresses the establishment of a large-scale liquefied natural gas supply chain along a major trade lane. It analyzes the interaction between long-term investment and operational costs, derives basic decision rules and evaluates the robustness of the solutions.

On March 10 to March 12, 2015, the National Institute of Neurological Disorders and Stroke and the Tuberous Sclerosis Alliance sponsored a workshop in Bethesda, Maryland, to assess progress and new opportunities for research in tuberous sclerosis complex with the goal of updating the 2003 Research Plan for Tuberous Sclerosis (http://www.ninds.nih.gov/about_ninds/plans/tscler_research_plan.htm). In addition to the National Institute of Neurological Disorders and Stroke and Tuberous Sclerosis Alliance, participants in the strategic planning effort and workshop included representatives from six other Institutes of the National Institutes of Health, the Department of Defense Tuberous Sclerosis Complex Research Program, and a broad cross-section of basic scientists and clinicians with expertise in tuberous sclerosis complex along with representatives from the pharmaceutical industry. Here we summarize the outcomes from the extensive premeeting deliberations and final workshop recommendations, including (1) progress in the field since publication of the initial 2003 research plan for tuberous sclerosis complex, (2) the key gaps, needs, and challenges that hinder progress in tuberous sclerosis complex research, and (3) a new set of research priorities along with specific recommendations for addressing the major challenges in each priority area. The new research plan is organized around both short-term and long-term goals with the expectation that progress toward specific objectives can be achieved within a five to ten year time frame.

Isobenzofurans (IBF)s have seen widespread use in the synthesis of both natural products and polycyclic aromatic hydrocarbons. There are few examples that have two IBF entities linked in a fused aromatic ring system. Here we present the synthesis and characterization of a bis(IBF), 2,7-di(tert-butyl)pyreno[4,5-c:9,10-c']difuran. Reaction with bis(maleimide) dienophiles gives pyrenophanes. The solid-state structures of the bis(IBF) and two cyclophanes are discussed.

Pt/4H-SiC Schottky photodiodes have been fabricated with the device areas up to 1 cm/sup 2/. The I-V characteristics and photoresponse spectra have been measured and analyzed. For a 5 mm/spl times/5 mm area device leakage current lower than 10/sup -15/ A at zero bias and 1.2/spl times/10/sup -14/ A at -1 V have been established. The quantum efficiency is over 30% from 240 to 320 nm. The specific detectivity, D/sup */, has been calculated from the directly measured leakage current and quantum efficiency are shown to be higher than 10/sup 15/ cmHz/sup 1/2//W from 210 to 350 nm with a peak D/sup */ of 3.6/spl times/10/sup 15/ cmHz/sup 1/2//W at 300 nm.

All life forms depend ultimately upon sunlight to create the energy ‘currency’ required for the functions of living. Green plants can make that conversion directly but the rest of us would perish without access to foods derived, directly or indirectly, from plants. We also require their fibre which we use for clothing, building and other purposes. However, plants, just as humans and animals, are attacked by pathogens that cause a myriad of symptoms that can lead to reduced yields, lower quality products and diminished nutritional value. Plant pathogens share many features with their human and animal counterparts. Some pathogens - whether of humans, animals, or plants - have nimble genomes or the ability to pirate genes from other organisms via mobile elements. Some have developed the ability to cross kingdoms in their host ranges. Many others share virulence factors, such as the type III secretion system (T3SS) or mechanisms for sensing population density, that work equally well in all kingdoms. Certain pathogens of hosts in all kingdoms rely upon insect vectors and use similar mechanisms to ensure dispersal (and sometimes survival) in this way. Plant-pathogen interactions have more direct consequence for humans when the microbes are human pathogens such as Escherichia coli 0157:H7 and Salmonella spp., which can contaminate fresh produce or when they produce metabolites, such as mycotoxins, which are harmful when consumed. Finally, national biosecurity concerns and the need for prevention, preparedness and forensic capabilities cross all kingdom barriers. Thus, our communities that focus on one of these kingdoms have much to learn from one another and a complete and balanced ‘One Health’ initiative must be tripartite, embracing the essential components of healthy plants, healthy animals and healthy people.

Two-dimensional microshutter arrays are being developed at NASA Goddard Space Flight Center (GSFC) for the Next Generation Space Telescope (NGST) for use in the near-infrared region. Functioning as focal plane object selection devices, the microshutter arrays are 2-D programmable masks with high efficiency and high contrast. The NGST environment requires cryogenic operation at 45 K. Arrays are close-packed silicon nitride membranes with a unit cell size of 100x100 micrometer. Individual shutters are patterned with a torsion flexure permitting shutters to open 90 degrees with minimized mechanical stress concentration. The mechanical shutter arrays are fabricated with MEMS technologies. The processing includes a RIE front-etch to form shutters out of the nitride membrane, an anisotropic back-etch for wafer thinning, and a deep RIE (DRIE) back-etch down to the nitride shutter membrane to form frames and to relieve the shutters from the silicon substrate. A layer of magnetic material is deposited onto each shutter. Onto the side-wall of the support structure a metal layer is deposited that acts as a vertical hold electrode. Shutters are rotated into the support structure by means of an external magnet that is swept across the shutter array for opening. Addressing is performed through a scheme using row and column address lines on each chip and external addressing electronics.

We report on the design, fabrication and characterization of a back-illuminated voltage bias selectable dual-band AlGaN UV photodetector. The photodetector can separate UVA and W-B band radiation by bias switching a two terminal n-p-n homojunction structure that is fabricated in the same pixel. When a forward bias is applied between the top and bottom electrodes, the detector can sense UV-A and reject W-B band radiation. Alternatively, under reverse bias, the photodetector can sense UV-B and reject UV-A band radiation.

Using conventional photolithography, Al 0.35 Ga 0.65 N pin diodes have been fabricated that exhibit extremely low reverse bias leakage currents. Macroscopic I-V measurements from a statistical population of 64, 120 μm diameter, circular diodes gives a mean leakage current of 0.96 fA with a standard deviation of 0.90 fA at -0.5 V bias.

Pt/n-type GaN Schottky photodiodes with large active areas which exhibit low leakage currents are fabricated. Reverse bias leakage currents of 2.7 nA for a 1 cm2 diode and 14 pA for a 0.25 cm2 diode both at −0.5 V bias are reported. External quantum efficiency measurements between the spectral range 50 to 500 nm gave a peak responsivity of 77.5 mA/W at 320 nm for a 0.25 cm2 diode, corresponding to a spectral detectivity, D*=1.5×1014 cmHz1/2W−1.

Tactical service scheduling and operational cargo allocation are two interdependent problems in liner shipping. The schedules and sailing speeds of individual liner shipping services and the synchronization among all services determine the transit times of containers through a liner shipping network. On the other hand, the market demand in terms of container volume and expected transit times between origin and destination ports drive the schedule design of liner shipping services. We present a graph-based model and a branch-and-price algorithm to solve the combined problem. The goal is to minimize the difference between fuel consumption costs and revenues from transporting containers under consideration of transit time limits. Fuel consumption is modeled as a function of both speed and payload. Results are presented for 12 liner shipping networks and emphasize the importance of explicitly modeling schedules in large networks; transshipment times and thus transit times may be severely miscalculated otherwise. The results further show that neglecting payload in the fuel consumption function can result in suboptimal service schedules and cargo routing decisions.