Performance analysis and optimization of AMGA for the large‐scale virtual screening

This paper addresses performance issues on ARDA Metadata Grid Application (AMGA) and presents new techniques to improve the throughput of AMGA for the WISDOM environment. The first issue is a performance degradation problem when AMGA is used as a metadata service for task retrieval in the WISDOM environment. To deal with the issue, a new AMGA operation designed to reduce the communication overhead required to retrieve a task from AMGA is proposed. According to a performance study conducted with the new operation, the throughput of task retrieval using the proposed operation can be as much as 70 times higher than the throughput when using the existing AMGA operations. The second issue is an AMGA throughput issue in large‐scale grid‐enabled applications such as WISDOM, where it is not uncommon that thousands of jobs running on grid nodes access the AGMA service simultaneously. To address this issue, integration of a load‐balancing technique and a DB connection pool technique into the AMGA are proposed. Test results demonstrate that the performance can be improved linearly in proportion to the number of AMGA servers set up for load balancing; the performance improvement continues until the performance limit of the backend database system is reached. Copyright © 2009 John Wiley & Sons, Ltd.     

Aero‐structural dynamics of a flexible hub connection for load reduction on two‐bladed wind turbines

In this study, an innovative concept for load reduction on the two‐bladed Skywind 3.4 MW prototype is presented. The load reduction system consists of a flexible coupling between the hub mount, carrying the drive train components including the hub assembly, and a nacelle carrier supported by the yaw bearing. This paper intends to assess the impact of introducing a flexible hub connection on the system dynamics and the aero‐elastic response to aerodynamic load imbalances. In order to limit the rotational joint motion, a cardanic spring‐damper element is introduced between the hub mount and the nacelle carrier flange, which affects the system response and the loads. A parameter variation of the stiffness and damping of the connecting spring‐damper element has been performed in the multi‐body simulation solver Simpack. A deterministic, vertically sheared wind field is applied to induce a periodic aerodynamic imbalance on the rotor. The aero‐structural load reduction mechanisms of the coupled system are thereby identified. It is shown that the fatigue loads on the blades and the turbine support structure are reduced significantly. For a very low structural coupling, however, the corresponding rotational deflections of the hub mount exceed the design limit of operation. The analysis of the interaction between the hub mount motion and the blade aerodynamics in a transient inflow environment indicates a reduction of the angle of attack amplitudes and the corresponding fluctuations of the blade loading. Hence, it can be concluded that load reduction is achieved by a combination of reduced structural coupling and a mitigation of aerodynamic load imbalances. Copyright © 2016 John Wiley & Sons, Ltd.     

Truncated branch-and-bound,schedule-construction,and schedule-improvement procedures for resource-constrained project scheduling

We present heuristic procedures for approximately solving large project scheduling problems with general temporal and resource constraints. In particular, we propose several truncated branch-and-bound techniques, priority-rule methods, and schedule-improvement procedures of types tabu search and genetic algorithm. A detailed experimental performance analysis compares the different heuristics devised and shows that large problem instances with up to 1000 activities and several resources can efficiently be solved with sufficient accuracy.

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Received: July 26, 2000 / Accepted: May 15, 2001     

Bending stiffness loss of paperboard at conversion — predicting the bending ability of paperboard

The ability of paperboard to resist bending has been investigated. Paperboard is often bent in converting and packaging machines. The paperboard is bent over rolls and thus formed to certain curvatures. If the roll diameter is small the paperboard will be highly curved. This means that high tensile stresses occur on the convex side and high compression stresses on the concave side. If these stresses are too high the paperboard will be damaged by fractures and wrinkles on the surfaces. The bending stiffness of the board will also be reduced. The importance of certain parameters, such as roll diameter, angle of wrap, board thickness, board compression strength and others, have been investigated. In this study seven qualities of paperboard were investigated. It has been shown that the bending force–bending angle curve can be used to obtain information about the ability of different board qualities to be bent to certain curvatures without being damaged. © 1998 John Wiley & Sons, Ltd.     

Microstructure‐ and Theory‐Based Modeling and Simulation of Batteries and Fuel Cells

The quality of digitalized design and development processes for advanced electrochemical technologies depends crucially on the accuracy of available models and the level of details at which simulations can be performed. In this article, an overview is given over recent advances in developing coupled models of transport and electrochemistry and simulation tools to investigate and modify very detailed processes in batteries and fuel cells, two of the decisive electrochemical technologies for future energy markets.     

Axial Magnetic Fields,Axial Force,and Losses in the Stator Core and Clamping Structure of a Synchronous Generator with Axially Displaced Stator

Axial displacement of the stator in a synchronous machine gives rise to axial magnetic field both at the ends and deep inside the stator. The axial magnetic field causes losses. This article contains results from two studies with an axially displaced stator. In the first study, axial magnetic leakage fields in the ends of a small synchronous generator at load and no load were measured and simulated. In the second study, axial force and iron losses at no load were calculated with non-linear materials and a three-dimensional, time-stepped finite element method. For some machines with vertical shafts, the sum of iron losses and thrust bearing losses can be reduced if the rotor is lowered or the stator raised, whichever is best.     

Renewable energy research 1995–2009: a case study of wind power research in EU, Spain, Germany and Denmark

The paper reports the developments and citation patterns over three time periods of research on Renewable Energy generation and Wind Power 1995–2011 in EU, Spain, Germany and Denmark. Analyses are based on Web of Science and incorporate journal articles as well as conference proceeding papers. Scientometric indicators include publication collaboration ratios, top-player distribution as well as citedness and correspondence analyses of citing publications, relative citation impact, distributions of top-cited as well as top-citing institutions and publication sources and cluster analysis of citing title terms to map knowledge export areas. Findings show an increase in citation impact for Renewable Energy and Wind Power research albeit hampered by scarcely cited conference papers. Although EU maintains its global top position in producing Renewable Energy and Wind Power research the developments of EU and German world shares as well as citation impact are negative during the most recent 7 year period. During the same time the citation impact of Spain and Denmark increase and place both nations among the top-ranking countries in Wind Power research. Spain is the only EU country that increases its world production share from 2000. China is currently ranked three after EU and USA in research output, however with a very low citation impact. Spain, Denmark and Germany each demonstrates distinct collaboration patterns and publication source and citation distribution profiles. More than half the citations to EU Wind Power research are EU-self citations. An expected intensified EU collaboration in the Wind Energy field does not come about. The most productive research institutions in Denmark and Spain are also the most cited ones.     

Morphology of PZT-PMN Films Grown from Airflow

Lead zirconate titanate-lead magnesium niobate (PZT-PMN) films with thicknesses in the range 5 to 200 μm were fabricated by deposition from airflow at room temperature. Precursor powders of PZT and PMN were mixed in a ball mill and entrained in an airflow generated by a commercial jet-mill (Micron-Master 02-506). Films were grown at a rate of 1 μm/minute onto the Ni and tungsten carbide substrates exposed to the air-powder mixture. Unfired, poled PZT-PMN films provided an audio acoustic response and form translucent 20–30 μm thick layers. Full density of the air-flow deposited materials has been achieved at temperatures 450°C lower than that typical for ball milled bulk PZT-PMN ceramics. After sintering for 2 hours at 850°C PZT-PMN ceramics with relative density of 99.5%, ? ～ 2170, tan δ ～ 0.009 @1 kHz and acceptable piezoelectric properties was obtained. Films sintered 2 hours at 1000°C showed remnant polarization P _r = 26 μC/cm², P _s = 36 μC/cm² @95 kV/cm, and 50 Hz ac electric breakdown field as high as 120–170 kV/cm. Unusual grain morphology governs improved sinterability and enhanced properties of ferroelectric ceramics. Optical and AFM micrographs revealed needle-like grains preferentially oriented parallel to the air-powder stream. As-deposited films were found to be very non-uniform across the thickness: glass-like and with tensile strain on the contact surface. This strain is released and film microcrystalline structure becomes uniform in annealed film.