Search

Copyright of Grundwasser is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper provides an overview of the recent definition, technologies and current trends regarding 3D fabrics. In this paper a definition of 3D fabrics, including spacer fabrics, is given and the recent technologies regarding weaving, braiding, weft and warp knitting and tailored fiber placement are presented. Furthermore, an overview of the latest developments in 3D fabrics at the Institut für Textiltechnik of RWTH Aachen University is presented including: large circular 3D knitting, braided and woven structures for medical purposes, newest testing methods and equipment for spacer fabrics, multiaxial fabrics for composites, warp knitted spacer fabrics for space and construction applications, ceramic matrix composite 3D braiding and 4D textiles. [ABSTRACT FROM AUTHOR]

With the deployment of the TetraSpar demonstrator, a significant cost-reduction is realized in the field of offshore floating wind turbines. The TetraSpar floating wind turbine foundation brings a milestone that emphasizes on a modular and fully industrialized foundation that consists of main components already widely available in the current wind energy supply chain. In an effort to provide an open approach to the development of the concept, this paper aims at giving a description of the design in order to enable an educated discussion of different design philosophies and their influence on material usage and production times. The description of the different subcomponents of the system should allow any entity to build a model for comparison and/or benchmarking any of their own findings against this concept. It is the authors’ expectation that this open approach to technological discussion is paramount to obtaining continued cost-reduction in the area of floating offshore wind—for this concept and others.

Zirconium is an ideal material for nuclear reactors due to its low absorption cross-section for thermal neutrons, whereas the typically contained hafnium with strong neutron-absorption is very harmful for zirconium as a fuel cladding material. This paper provides an overview of the processes for nuclear grade zirconium production with emphasis on the methods of Zr–Hf separation. The separation processes are roughly classified into hydro- and pyrometallurgical routes. The known pyrometallurgical Zr–Hf separation methods are discussed based on the following reaction features: redox characteristics, volatility, electrochemical properties and molten salt–metal equilibrium. In the present paper, the available Zr–Hf separation technologies are compared. The advantages and disadvantages as well as future directions of research and development for nuclear grade zirconium production are discussed. [ABSTRACT FROM AUTHOR]

Carbon dioxide (CO 2) and methane (CH 4) constitute biogas that is formed from landfill and anaerobic digestion processes. Furthermore, raw biogas consists of minor quantities of hydrogen sulfide (H 2 S), hydrogen (H 2), ammonia (NH 3), carbon monoxide (CO), nitrogen (N 2), and oxygen (O 2). As a renewable energy, biogas can be obtained and upgraded to produce biomethane for injection into the natural gas grid or applied as fuel in-vehicle, for on-site heat, and for steam/electricity generation in the industry. Different technologies are thus applied for the removal of such components, converting biogas to biomethane. Bottom ash (BA) upgrading and alkaline with regeneration (AwR) are two other novel technologies that mineralize carbon not only to remove CO 2 but also store it from biogas using waste from municipal solid waste incinerators containing calcium. This research reviews the most widespread technologies and recent studies on the removal of CO 2 , as well as studies several parameters, merits, and demerits of these methods. [Display omitted] • Recent advances in biogas upgradation methods in different views are compared. • The BA upgrading and AwR are regarded as environmentally-friendly techniques. • Technology selection can be considered by the specific conditions and strategies. • Captured carbon from biogas can be used to produce chemical materials. [ABSTRACT FROM AUTHOR]

Computing a distance map (distance transform) is an operation that converts a two-dimensional (2-D) image consisting of black and white pixels to an image where each pixel has a value or a pair of coordinates that represents the distance to or location of the nearest black pixel. It is a basic operation in image processing and computer vision fields, and is used for expanding, shrinking, thinning, segmentation, clustering, computing shape, object reconstruction, etc. This paper examines the possibility of implementing the problem of finding a distance map for an image efficiently using an optical bus. The computational model considered is the linear array with a reconfigurable pipelined bus system (LARPBS), which has been introduced recently based on current electronic and optical technologies. It is shown that the problem for an n x n image can be implemented in O(log n log log n) bus cycles deterministically or in O(log n) bus cycles with high probability on an LARPBS with [n.sup.2] processors. By high probability, we mean a probability of [greater than or equal to] (1 - [n.sup.-[alpha]]) for any constant [alpha] [greater than or equal to] 1. We also show that the problem can be solved in O(log log n) bus cycles deterministically or in O(1) bus cycles with high probability on an LARPBS with [n.sup.3] processors. Scalability of the algorithms is also discussed briefly. The same problem can be solved using an LARPBS of P < n processors in O(([n.sup.2]/P)log n log log n) time deterministically or in O(([n.sup.2]/P) log n) time with high probability for any practical machine size of P. For processor arrays with practical sizes, a bus cycle is roughly the time of an arithmetic operation. Hence, the algorithm compares favorably to the best known parallel algorithms for the same problem in the literature. Index Terms--Distance map, Euclidean distance transform (ETD), image analysis, parallel algorithm, reconfigurable optical bus, time complexity.

The system of equations that govern kinematically redundant robotic manipulators is commonly solved by finding the singular value decomposition (SVD) of the corresponding Jacobian matrix. This can require a considerable amount of time to compute, thus a parallel SVD algorithm reducing execution time is sought. The approach employed here lends itself to parallelization by using Givens rotations and information from previous decompositions. The key contribution of this research is the presentation and implementation of parallel SVD algorithms to compute the SVD for a set of Jacobians that represent various different joint failure scenarios. Results from implementation of the algorithm on a MasPar MP-1, an IBM SP2, and the PASM prototype parallel computers are compared. Specific issues considered for each implementation include: how data is mapped to the processing elements, the effect that increasing the number of processing elements has on execution time, the type of parallel architecture used, and trade-offs between modes of parallelism. KEY WORDS: IBM SP2; redundant manipulator; MasPar MP-1; robotic controls; singular value decomposition.

This paper describes a neural network model for the reactive behavioral navigation of a mobile robot. From the information received through the sensors the robot can elicit one of several behaviors (e.g., stop, avoid, stroll, wall following), through a competitive neural network. The robot is able to develop a control strategy depending on sensor information and learning operation. Reinforcement learning improves the navigation of the robot by adapting the eligibility of the behaviors and determining the linear and angular robot velocities. Index Terms--Adaptive behavior, learning control, mobile robots, neural networks, obstacle avoidance, robot navigation.

Alerting systems and related decision-making automation are widely used to enhance the safety and capability of controlled processes across many applications. Traditional alerting systems use physical metrics such as temperature, distance between vehicles, or time-to-impact as bases for making alerting decisions. Threshold values on these metrics are typically derived using an iterative process to ensure the achievement of desired performance goals, defined by higher-level metrics such as false alarm, safety, or success probabilities. We generalize this problem and develop two state spaces, one representing physical metrics and one representing performance metrics. A traditional alerting system operates completely within the physical space, using decision thresholds that have been developed offline during the design process by examining how the physical threshold translates across to the performance state space. The physical metrics thus act as an indirect means to control the performance of the system. We propose an alternate approach that enables the system to operate online in the performance space. Alerting decisions are based directly on the computed values of metrics such as false alarm probability rather than on surrogate physical metrics. These two design approaches are then contrasted in case studies of recently-developed alerting systems. Index Terms--Alarm systems, algorithms, decision support systems, threshold logic.

SUE inspection is a novel usability evaluation method for hypermedia, which falls into the category of inspection methods. Its primary goal is to favor a Systematic Usability Evaluation (hence the acronym SUE), for supplying hypermedia usability inspectors with a structured flow of activities, allowing them to obtain more reliable, comparable, and cost-effective evaluation results. This is obtained especially thanks to the use of evaluation patterns, called Abstract Tasks, which describe in details the activities that evaluators must carry out during inspection. Abstract Tasks helps share and transfer evaluation know-how among different evaluators, thus making it easier to learn the SUE inspection method by newcomers. A further notable advantage provided by the SUE inspection over other existent approaches is that it focuses on navigation and information structures, making evident some problems that other "surface-oriented" approaches might not reveal. This paper describes the SUE inspection for hypermedia. It also reports on a validation experiment, involving 28 evaluators, that has shown the major effectiveness and efficiency of the SUE inspection for hypermedia, with respect to traditional heuristic evaluation techniques. Index Terms--Evaluation methods, hypermedia, usability.

Recently, several general optimization algorithms based on the demon algorithm from statistical physics have been developed and tested on a few traveling salesman problems with encouraging results. In this paper, we conduct an extensive computational study of 11 annealing-based heuristics for the traveling salesman problem. We code versions of simulated annealing, threshold accepting, record-to-record travel and eight heuristics based on the demon algorithm. We apply each heuristic to 29 traveling salesman problems taken from a well-known online library, compare the results with respect to accuracy and running time and provide insights and suggestions for future work. Index Terms--Demon algorithm, heuristics, traveling saleman problem.

Humans interact with their environments in many ways, and that interaction has become the focus of ever-greater interest as technology empowers the physical environment with new sensor and computer-based intelligence. This paper describes four different types of coupling between the human and environment, where "coupling" here refers to two-way interactions which are sufficiently tight that causality between human and environment is obscure and even arbitrary. These are not four mutually exclusive categories, but rather four ways of characterizing the relationship between the human and environment. Some generalizations of these relationships are discussed, along with hints on how we might improve our designs of intelligent technology, especially the interfaces to human users. Index Terms--Decision-aid, ecological interface, human-machine interface, human-machine system design, impedance, manual control.

Information seeking is fundamentally a situated cognitive activity where user's cognitive capabilities and limitations, the work domain and task context, and the content and form of medium, influence the process. We used questionnaire responses, field studies of real-world professionals, and cognitive modeling techniques to collect data about the complex information-seeking process under real conditions, to develop a knowledge base for principled design, and to create a cognitive model of information seeking in a corporate environment. We describe the design and evaluation of task-based personalized search form interfaces based on the cognitive model. Results show that search forms personalized for the individual searcher improve performance over those interfaces that are mismatched to searcher's characteristics. Further, findings show that information source selection is critical in enhancing the effectiveness of information retrieval in real-world electronic information systems. Index Terms--Cognitive modeling, information retrieval, user interfaces.

Users at different levels of domain experience have very different needs. For example, a system designed to assist domain novices may frustrate experts and vice-versa. This is one of several challenges specific to building decision support systems for experience-centered domains. Examples of experience-centered domains include medical diagnosis [37], chess [15], [16], as well as most professional design or planning tasks [24]. A second challenge in working with complex experience-centered domains is that it is hard for nonexperts to understand the domain in order to model it. In this paper we present DAISY, the Design Aid for Intelligent Support SYstems. It is a software design methodology for constructing decision support systems in complex, experience-based domains. DAISY address the specialized challenges of these domains by augmenting existing cognitive engineering methodologies. In particular, DAISY provides a method for identifying the specialized needs of users within a specific range of domain experience. Thus, it can help software designers to understand, "What does the domain expert need?" or "What does a trained novice need?" To help system designers manage the complexity of modeling unfamiliar experience-centered domains, it provides a tool called a Time/Activity matrix. To illustrate each of DAISY's steps, we will used the development of a decision support system, Fox. Fox assists expert military planners by rapidly generating alternative plans. This is a cognitively difficult, time critical task with life and death consequences. Index Terms--Cognitive engineering, decision support, experience-centered design, task analysis.

A matrix is described for studying the transverse magnetic (TM) modes of slab waveguides with arbitrary index profiles. Numerical results indicate that the method's efficiency is good.

In this work we propose and implement a new variant of the well-known write invalidate protocol called "Y-invalidate." Whereas the former protocol required that every copy of a page be invalidated every time that page is updated, our variant invalidates a copy of a page at process A only at the next synchronization point which is relevant to A and or if the copy was modified by the owner's process after the page was copied to A. We thus avoid invalidating copies of pages that were modified but never read after modification, and avoid, of course, the associated overhead. Y-Invalidate is basically a weak-consistency protocol. Its main advantage is that it implements weak consistency without the need to "merge" copies of a page that were updated in different machines. To the best of our knowledge, this is the first variant of weak consistency protocols which does not "merge" multiple copies of pages. Unlike other variants of weak consistency, Y-invalidate supports implicit synchronization points in the program by invalidating copies of shared memory pages that are referenced by while-loops. In this way, Y-invalidate approximates strict consistency. The Y-invalidate protocol was implemented in the ParC system, which is a powerful parallel extension of the C language. The ParC compiler was modified to detect some of the implicit synchronization points in the source code. Experimental results show significant improvement compared to both the traditional write-invalidate protocol and weak consistency. KEY WORDS: Parallel; DSM; strict consistency; loose consistency; write invalidate.

Companies eager to improve sales would probably deliver a custom product to each buyer, if they could. Every customer would receive a product with only the functions and features requested. [...]

Green's functions are used to enable derivation of expressions for electrical admittance of an aperiodic one-dimensional acoustic grating with matched boundaries. By contrast, the classical [delta]-function model only provides the radiation conductance.

Time division multiplexing (TDM) is the most common technical basis for the costly backhaul facilities used by wireless service providers to connect base stations and mobile switching centers to transport-level traffic. Asynchrnous transfer mode (ATM) has significant advantages, particularly in the ability to integrate voice and data transmission, consolidate facilities and offer fast provisioning, but adds management complexity. A non-disruptive approach to ATM services management for wireless equipment is presented. The wireless element management system (EMS) acts as a control point and represents ATM services as virtual clouds within each of several market domains. It uses mature technology, provides guaranteed quality of service (QoS) and may be outsourced to a separate business unit or outsider provider as needed.

Carrier networks are combining SONET with SDH and optical networking (ON) interfaces to support phenomenal growth in bandwidth demand. Hybrid network elements combine data and optical transports to rapidly deliver bandwidth and service enhancements, and management tools do not always keep pace with the complexity of such solutions. Simplistic approaches used by traditional optical and data network management systems do not work because many capabilities now cross technologies. A hybrid management approach offers enough flexibility to eliminate traditional barriers between data and transport. Hybrid management platforms will use CORBA standards and run management software packages that can be distributed over a variety of hardware systems using standard information models and protocols.

Operations cost models comparing trunk operations cost of present method of operations (PMO) tandem networks and future method of operations (FMO) packet-based networks are presented and analyzed in detail. Each model accounts for network and service architectures, operations processes and OSS efficiency and consists of a set of parameters that can be readily adjusted to reflect customer-specific benchmarks. Applying the models to several realistic applications reveals that voice trunk provisioning and maintenance costs can be reduced substantially by combining ATM switched virtual channel technology with a distributed voice gateway network architecture.

Abstract: We performed a consistent comparison of state-of-the-art and advanced electricity and hydrogen production technologies with CO2 capture using coal and natural gas, inspired by the large number of studies, of which the results can in fact not be compared due to specific assumptions made. After literature review, a standardisation and selection exercise has been performed to get figures on conversion efficiency, energy production costs and CO2 avoidance costs of different technologies, the main parameters for comparison. On the short term, electricity can be produced with 85–90% CO2 capture by means of NGCC and PC with chemical absorption and IGCC with physical absorption at 4.7–6.9€ct/kWh, assuming a coal and natural gas price of 1.7 and 4.7€/GJ. CO2 avoidance costs are between 15 and 50€/t CO2 for IGCC and NGCC, respectively. On the longer term, both improvements in existing conversion and capture technologies are foreseen as well as new power cycles integrating advanced turbines, fuel cells and novel (high-temperature) separation technologies. Electricity production costs might be reduced to 4.5–5.3€ct/kWh with advanced technologies. However, no clear ranking can be made due to large uncertainties pertaining to investment and O&M costs. Hydrogen production is more attractive for low-cost CO2 capture than electricity production. Costs of large-scale hydrogen production by means of steam methane reforming and coal gasification with CO2 capture from the shifted syngas are estimated at 9.5 and 7€/GJ, respectively. Advanced autothermal reforming and coal gasification deploying ion transport membranes might further reduce production costs to 8.1 and 6.4€/GJ. Membrane reformers enable small-scale hydrogen production at nearly 17€/GJ with relatively low-cost CO2 capture. [Copyright &y& Elsevier]

Many people mistakenly assume that faster hardware and faster networking technologies (ATM, FDDI, Fast Ethernet, or switching technology), rather than comprehensive network capacity planning, are the solutions to performance bottlenecks. […]

AVAR needs three great software packages: one for accounting, one for sales tracking, and one for customer support," says Doug Nicholas, CEO of Software Marketing Group (Des Moines, Iowa), maker […]

If the manufacturers have their way, 1995 will be the Year of Asynchronous Transfer Mode, or ATM. Most VARs have not entered this area yet, and although ATM products and […]