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Low-cost
Terms modified by Low-cost Selected AbstractsBuilding a Compact, Low-Cost, and Portable Peristaltic Sampling PumpGROUND WATER, Issue 6 2007William W. Woessner Hydrogeologic research often involves obtaining water quality samples in field settings without vehicle access. Such conditions often require the use of a sampling pump. Researchers at The University of Montana have been using a handheld peristaltic pump powered by a rechargeable variable-speed drill. This Montana Drill Pump (MDP) is highly portable and can be inexpensively built for about $225 to $295 (US). Over the last two decades, the pump has been used to sample and filter (as appropriate) surface water and ground water for analyses of general inorganic and organic chemistry, stable and radioactive isotopes, pathogens, and trace pharmaceuticals and to develop small-diameter wells and sample suction lysimeters. The MDP provides researchers and educators with an economical tool to pump water in classrooms, laboratories, and field settings. [source] A Facile, Low-Cost, and Scalable Method of Selective Etching of Semiconducting Single-Walled Carbon Nanotubes by a Gas ReactionADVANCED MATERIALS, Issue 7 2009Hongliang Zhang A facile, scalable, and low-cost gas-treatment method for selectively etching semiconductor single-walled carbon nanotubes (SWNTs) is developed. Using SO3 gas as the etchant at a temperature of 400 °C, semiconductor SWNTs can be selectively and efficiently removed, and after this gas treatment samples enriched with metallic SWNTs can be obtained. [source] Design of a Low-Cost, USB-Compatible, Otoscope Image-Capture System,THE LARYNGOSCOPE, Issue 12 2006Jon-Paul Pepper BS No abstract is available for this article. [source] The Financial Performance of Low-Cost and Full-Service Airlines in Times of CrisisCANADIAN JOURNAL OF ADMINISTRATIVE SCIENCES, Issue 1 2005Triant Flouris This paper examines the stock and accounting performance of three major airlines in the United States in the aftermath of the September 11, 2001, terrorist attacks. September 11 (9/11) resulted in dramatic changes in the airline industry and had significant implications for the economic gains and future prospects of most airlines. Our study focuses on the stock market's perception of the viability of low-cost versus full-service business models in the aftermath of 9/11. We choose Southwest Airlines as a typical low-cost airline and compare its accounting and stock performance to two full-service airlines, Continental and Northwest. We find that Southwest's performance was highly superior to that of Continental and Northwest and argue that Southwest's business model, in the eyes of investors, provides the firm with significantly more financial and operational flexibility than full-service airlines. Southwest's lower operating costs, consumer trust, product offering, corporate structure, workforce and work practices, as well as operational procedures are all factors that appear to contribute to Southwest's relative success. Résumé Cet article étudie la performance boursière et comptable de trois grands transporteurs aériens opérant aux États-Unis au lendemain des attentats du 11 septembre 2001. Ces événements ont entraîné des changements radicaux dans l'industrie du transport aérien et ont eu des répercussions considérables sur les gains économiques de la plupart des compagnies aériennes. Notre étude compare la viabilité des modèles d'entreprise à bas prix à celle des modèles traditionnels, au lendemain de l'attaque terroriste. Nous avons choisi Southwest Airlines comme l'exemple type de transporteur aérien pratiquant des bas prix et nous comparons sa comptabilité et le rendement de son action à ceux de deux transporteurs aériens à service complet, notamment Continental et Northwest. Nous constatons que le rendement de Southwest est de loin supérieur à celui de Continental et de Northwest. Nous montrons que, d'après les investisseurs, le modèle de gestion de Southwest lui donne beaucoup plus de flexibilité financière et opérationnelle que le modèle de gestion pratiqué par les transporteurs aériens traditionnels. La faiblesse de ses charges d'exploitation, la confiance des consommateurs, son offre de produits, sa structure d'organisation, son effectif, ses pratiques de travail, ainsi que ses méthodes opérationnelles sont autant d'éléments qui semblent contribuer au succès relatif de Southwest. [source] ChemInform Abstract: Highly Efficient Dynamic Kinetic Resolution of Secondary Aromatic Alcohols with Low-Cost and Easily Available Acid Resins as Racemization Catalysts.CHEMINFORM, Issue 32 2010Yongmei Cheng Abstract A combination of Novozym435 with an acidic polystyrene resin CD8604 affords a new and efficient dynamic kinetic resolution of acetophenones to give the corresponding benzylic alcohols with good to excellent enantioselectivities. [source] High-resolution estimation for time-variant MIMO channel sounding,EUROPEAN TRANSACTIONS ON TELECOMMUNICATIONS, Issue 7 2008Sofia Martinez Lopez A wideband vector channel sounder with 16 parallel RF chains is proposed for parameter estimation in an indoor channel. Low-cost and high-resolution are obtained by using a chirp probe signal, five-port receivers and the MUSIC algorithm. The system covers up to 500,MHz centred at 2.45,GHz. Experimental results show errors inferior to 1,ns in the time domain and of few degrees in the angular domain. Accurate results are found in static as well as in time-variant scenarios. Copyright © 2008 John Wiley & Sons, Ltd. [source] On-Line Control Architecture for Enabling Real-Time Traffic System OperationsCOMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 5 2004Srinivas Peeta Critical to their effectiveness are the control architectures that provide a blueprint for the efficient transmission and processing of large amounts of real-time data, and consistency-checking and fault tolerance mechanisms to ensure seamless automated functioning. However, the lack of low-cost, high-performance, and easy-to-build computing environments are key impediments to the widespread deployment of such architectures in the real-time traffic operations domain. This article proposes an Internet-based on-line control architecture that uses a Beowulf cluster as its computational backbone and provides an automated mechanism for real-time route guidance to drivers. To investigate this concept, the computationally intensive optimization modules are implemented on a low-cost 16-processor Beowulf cluster and a commercially available supercomputer, and the performance of these systems on representative computations is measured. The results highlight the effectiveness of the cluster in generating substantial computational performance scalability, and suggest that its performance is comparable to that of the more expensive supercomputer. [source] Improving Heart Failure Self-Management Support by Actively Engaging Out-of-Home Caregivers: Results of a Feasibility StudyCONGESTIVE HEART FAILURE, Issue 1 2008John D. Piette PhD The benefits of heart failure (HF) care management have been demonstrated, yet health systems are often unable to meet patients' needs for support between outpatient visits. Informal care provided by family or friends is a low-cost, and potentially effective, adjunct to care management services. The authors evaluated the feasibility of augmenting HF care management with weekly, automated assessment and behavior change calls to patients, feedback via the Internet to an out-of-home informal caregiver or CarePartner (CP), and faxes to the patient's health care team. The program included 52 HF patient-CP pairs participating for an average of 12 weeks. Patients completed 586 assessments (92% completion rate) and reported problems that might otherwise have gone unidentified. At follow-up, 75% had made changes in their self-care as a result of the intervention. The CP program may extend the impact of HF telemonitoring beyond what care management programs can realistically deliver. [source] Nanocrystalline transparent SnO2 -ZnO films fabricated at lower substrate temperature using a low-cost and simplified spray techniqueCRYSTAL RESEARCH AND TECHNOLOGY, Issue 3 2010K. Ravichandran Abstract Nanocrystalline and transparent conducting SnO2 - ZnO films were fabricated by employing an inexpensive, simplified spray technique using a perfume atomizer at relatively low substrate temperature (360±5 °C) compared with conventional spray method. The structural studies reveal that the SnO2 -ZnO films are polycrystalline in nature with preferential orientation along the (101) plane. The dislocation density is very low (1.48×1015lines/m2), indicating the good crystallinity of the films. The crystallite size of the films was found to be in the range of 26,34 nm. The optical transmittance in the visible range and the optical band gap are 85% and 3.6 eV respectively. The sheet resistance increases from 8.74 k,/, to 32.4 k,/, as the zinc concentration increases from 0 to 40 at.%. The films were found to have desirable figure of merit (1.63×10,2 (,/,),1), low temperature coefficient of resistance (,1.191/K) and good thermal stability. This simplified spray technique may be considered as a promising alternative to conventional spray for the massive production of economic SnO2 - ZnO films for solar cells, sensors and opto-electronic applications. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Customer Learning Processes, Strategy Selection, and Performance in Business-to-Business Service Firms,DECISION SCIENCES, Issue 2 2004Debra Zahay ABSTRACT Learning about customers takes place through relevant dialogues with those customers, also known as customer relationship management (CRM). As relationships develop, information about the customer is gathered in the firm's customer information systems (CIS): the content, processes, and assets associated with gathering and moving customer information throughout the firm. This research develops a measure of CIS management capabilities based on learning organization theory and measured by the ability to get, store, move, and use information throughout the business unit. This measure is then used to analyze customer learning processes and associated performance in the context of marketing strategic decision making. This study of 209 business services firms finds that generic marketing strategy positioning (low-cost and differentiation) and the marketing tactics of personalization and customization are related to CIS development. Customer information systems development in turn is associated with higher levels of customer-based performance, which in turn is associated with increased business growth. Since the strongest association with customer-based performance is strategy selection, the long-term benefits of the knowledge gained from the CIS may be in the ability to assist in measuring customer-based performance, rather than in the ability to immediately contribute to performance. Finally, for these firms, customization and personalization are not directly associated with performance and thus may not be necessary to support every firm's marketing strategy. [source] A polymeric master replication technology for mass fabrication of poly(dimethylsiloxane) microfluidic devicesELECTROPHORESIS, Issue 9 2005Hai-Fang Li Abstract A protocol of producing multiple polymeric masters from an original glass master mold has been developed, which enables the production of multiple poly(dimethylsiloxane) (PDMS)-based microfluidic devices in a low-cost and efficient manner. Standard wet-etching techniques were used to fabricate an original glass master with negative features, from which more than 50 polymethylmethacrylate (PMMA) positive replica masters were rapidly created using the thermal printing technique. The time to replicate each PMMA master was as short as 20 min. The PMMA replica masters have excellent structural features and could be used to cast PDMS devices for many times. An integration geometry designed for laser-induced fluorescence (LIF) detection, which contains normal deep microfluidic channels and a much deeper optical fiber channel, was successfully transferred into PDMS devices. The positive relief on seven PMMA replica masters is replicated with regard to the negative original glass master, with a depth average variation of 0.89% for 26 ,m deep microfluidic channels and 1.16% for the 90 ,m deep fiber channel. The imprinted positive relief in PMMA from master-to-master is reproducible with relative standard deviations (RSDs) of 1.06% for the maximum width and 0.46% for depth in terms of the separation channel. The PDMS devices fabricated from the PMMA replica masters were characterized and applied to the separation of a fluorescein isothiocyanate (FITC)-labeled epinephrine sample. [source] Joint compensation of IQ imbalance, frequency offset and phase noise in OFDM receivers,EUROPEAN TRANSACTIONS ON TELECOMMUNICATIONS, Issue 3 2004Jan Tubbax Zero-IF receivers are getting a lot of attention because of their potential to enable low-cost OFDM terminals. However, zero-IF receivers also introduce IQ imbalance which can have a huge impact on the performance. Rather than increasing component cost to decrease the IQ imbalance, an alternative is to tolerate the IQ imbalance and compensate for it digitally. Current solutions either require additional analog hardware or are based on digital algorithms that converge too slowly for bursty communication. Moreover, the impact of a frequency offset and phase noise on the IQ imbalance estimation/compensation problem is not considered. In this paper, we analyze the joint IQ imbalance/frequency offset/phase noise estimation and propose a low-cost, highly effective, all-digital mitigation scheme. For large IQ imbalance large frequency offsets and in the presence of phase noise our solution still results in an average implementation loss below 0.5,dB. It, therefore, enables the design of low-cost, lowcomplexity OFDM receivers. Copyright © 2004 AEI [source] Inkjet-Printed Single-Droplet Organic Transistors Based on Semiconductor Nanowires Embedded in Insulating PolymersADVANCED FUNCTIONAL MATERIALS, Issue 19 2010Jung Ah Lim Fabrication of organic field-effect transistors (OFETs) using a high-throughput printing process has garnered tremendous interest for realizing low-cost and large-area flexible electronic devices. Printing of organic semiconductors for active layer of transistor is one of the most critical steps for achieving this goal. The charge carrier transport behavior in this layer, dictated by the crystalline microstructure and molecular orientations of the organic semiconductor, determines the transistor performance. Here, it is demonstrated that an inkjet-printed single-droplet of a semiconducting/insulating polymer blend holds substantial promise as a means for implementing direct-write fabrication of organic transistors. Control of the solubility of the semiconducting component in a blend solution can yield an inkjet-printed single-droplet blend film characterized by a semiconductor nanowire network embedded in an insulating polymer matrix. The inkjet-printed blend films having this unique structure provide effective pathways for charge carrier transport through semiconductor nanowires, as well as significantly improve the on-off current ratio and the environmental stability of the printed transistors. [source] The Effects of Moisture in Low-Voltage Organic Field-Effect Transistors Gated with a Hydrous Solid ElectrolyteADVANCED FUNCTIONAL MATERIALS, Issue 16 2010Nikolai Kaihovirta Abstract The concept of using ion conducting membranes (50,150 ,m thick) for gating low-voltage (1 V) organic field-effect transistors (OFETs) is attractive due to its low-cost and large-area manufacturing capabilities. Furthermore, the membranes can be tailor-made to be ion conducting in any desired way or pattern. For the electrolyte gated OFETs in general, the key to low-voltage operation is the electrolyte "insulator" (the membrane) that provides a high effective capacitance due to ionic polarization within the insulator. Hydrous ion conducting membranes are easy to process and readily available. However, the role of the water in combination with the polymeric semiconductor has not yet been fully clarified. In this work electrical and optical techniques are utilized to carefully monitor the electrolyte/semiconductor interface in an ion conducting membrane based OFET. The main findings are that 1) moisture plays a major part in the transistor operation and careful control of both the ambient atmosphere and the potential differences between the electrodes are required for stable and consistent device behavior, 2) the obtained maximum effective capacitance (5 ,F cm,2) of the membrane suggests that the electric double layer is distributed over a broad region within the polyelectrolyte, and 3) electromodulation spectroscopy combined with current,voltage characteristics provide a method to determine the threshold gate voltage from an electrostatic field-effect doping to a region of (irreversible) electrochemical perturbation of the polymeric semiconductor. [source] Large-Area Nanoscale Patterning of Functional Materials by Nanomolding in CapillariesADVANCED FUNCTIONAL MATERIALS, Issue 15 2010Xuexin Duan Abstract Within the past years there has been much effort in developing and improving new techniques for the nanoscale patterning of functional materials used in promising applications like nano(opto)electronics. Here a high-resolution soft lithography technique,nanomolding in capillaries (NAMIC),is demonstrated. Composite PDMS stamps with sub-100,nm features are fabricated by nanoimprint lithography to yield nanomolds for NAMIC. NAMIC is used to pattern different functional materials such as fluorescent dyes, proteins, nanoparticles, thermoplastic polymers, and conductive polymers at the nanometer scale over large areas. These results show that NAMIC is a simple, versatile, low-cost, and high-throughput nanopatterning tool. [source] Enhanced Charge Transportation in Semiconducting Polymer/Insulating Polymer Composites: The Role of an Interpenetrating Bulk InterfaceADVANCED FUNCTIONAL MATERIALS, Issue 11 2010Guanghao Lu Abstract The charge transportation in poly(3-butylthiophene) (P3BT)/insulating polymer composites is studied both microscopically and macroscopically. The increased mobility of free charge carriers, in particular hole mobility, contributes to the enhanced electrical conductivity of this semiconductor/insulator composite. The conductivity origin of the composite, as revealed by conductive-atomic force microscopy (C-AFM), comes mainly from the P3BT network, whose carrier mobility has been improved as a result of reduced activation energy for charge transportation upon forming an interface with the insulating matrix. Both the huge interfacial area and interconnected conductive component are morphologically required for the enhanced electrical property of the composite. An increased size of the P3BT domains, which correspondingly reduces the interfacial area between the two components, ruins the enhancement. This study clarifies the mechanism of the higher electrical properties achieved in a semiconducting polymer upon blending with an insulating polymer, which will further promote the development of these low-cost, easily processable, and environmentally stable composites. [source] Controllable Shifts in Threshold Voltage of Top-Gate Polymer Field-Effect Transistors for Applications in Organic Nano Floating Gate MemoryADVANCED FUNCTIONAL MATERIALS, Issue 2 2010Kang-Jun Baeg Abstract Organic field-effect transistor (FET) memory is an emerging technology with the potential to realize light-weight, low-cost, flexible charge storage media. Here, solution-processed poly[9,9-dioctylfluorenyl-2,7-diyl]-co-(bithiophene)] (F8T2) nano floating gate memory (NFGM) with a top-gate/bottom-contact device configuration is reported. A reversible shift in the threshold voltage (VTh) and reliable memory characteristics was achieved by the incorporation of thin Au nanoparticles (NPs) as charge storage sites for negative charges (electrons) at the interface between polystyrene and cross-linked poly(4-vinylphenol). The F8T2 NFGM showed relatively high field-effect mobility (µFET) (0.02,cm2 V,1 s,1) for an amorphous semiconducting polymer with a large memory window (ca. 30,V), a high on/off ratio (more than 104) during writing and erasing with an operation voltage of 80,V of gate bias in a relatively short timescale (less than 1,s), and a retention time of a few hours. This top-gated polymer NFGM could be used as an organic transistor memory element for organic flash memory. [source] High Performance Carbon-Supported Core@Shell PdSn@Pt Electrocatalysts for Oxygen Reduction ReactionFUEL CELLS, Issue 4 2010W. Zhang Abstract In this report, a low-cost and high performance PdSn@Pt/C catalyst with core,shell structure is prepared by two-stage route. X-ray diffraction (XRD) and transmission electron microscopy (TEM) examinations show that the composite catalyst particles distribution is quite homogeneous and has a high surface area and the PdSn@Pt/C catalyst has an average diameter of ca. 5.6,nm. The oxygen reduction reaction (ORR) activity of PdSn@Pt/C was higher than commercial Pt/C catalyst. Catalytic activity is studied by cyclic voltammetry. High electrocatalytic activities could be attributed to the synergistic effect between Pt and PdSn. [source] Nanoscale Phase Separation and High Photovoltaic Efficiency in Solution-Processed, Small-Molecule Bulk Heterojunction Solar CellsADVANCED FUNCTIONAL MATERIALS, Issue 19 2009Bright Walker Abstract Research relating to organic solar cells based on solution-processed, bulk heterojunction (BHJ) films has been dominated by polymeric donor materials, as they typically have better film-forming characteristics and film morphology than their small-molecule counterparts. Despite these morphological advantages, semiconducting polymers suffer from synthetic reproducibility and difficult purification procedures, which hinder their commercial viability. Here, a non-polymeric, diketopyrrolopyrrole-based donor material that can be solution processed with a fullerene acceptor to produce good quality films is reported. Thermal annealing leads to suitable phase separation and material distribution so that highly effective BHJ morphologies are obtained. The frontier orbitals of the material are well aligned with those of the fullerene acceptor, allowing efficient electron transfer and suitable open-circuit voltages, leading to power conversion efficiencies of 4.4,±,0.4% under AM1.5G illumination (100,mW cm,2). Small molecules can therefore be solution processed to form high-quality BHJ films, which may be used for low-cost, flexible organic solar cells. [source] Battery Drivable Organic Single-Crystalline Transistors Based on Surface Grafting Ultrathin Polymer DielectricADVANCED FUNCTIONAL MATERIALS, Issue 18 2009Liqiang Li Abstract High-performance and battery drivable organic single-crystalline transistors with operational voltages,,,2.0,V are demonstrated using high-quality copper phthalocyanine (CuPc) single-crystalline nanoribbons and ultrathin polymer nanodielectrics. The ultrathin polymer nanodielectric is synthesized by grafting a ca. 10,nm poly(methyl methacrylate) (PMMA) brush on a silicon surface via surface-initiated atom-transfer radical polymerization (SI-ATRP). This surface-grafted nanodielectric exhibits a large capacitance, excellent insulating property, and good compatibility with organic semiconductors. The realization of a low operational voltage for battery driving at high performance, together with the merits of surface grafting of a nanodielectric, as well as the mechanical flexibility of the organic nanoribbon, suggests a bright future for use of these transistors in low-cost and flexible circuits. [source] High-Performance Single Crystal Organic Field-Effect Transistors Based on Two Dithiophene-Tetrathiafulvalene (DT-TTF) PolymorphsADVANCED MATERIALS, Issue 37 2010Raphael Pfattner Solution prepared single crystal organic field-effect transistors (OFETs) combine low-cost with high performance due to structural ordering of molecules. However, in organic crystals polymorphism is a known phenomenon, which can have a crucial influence on charge transport. Here, the performance of solution-prepared single crystal OFETs based on two different polymorphs of dithiophene-tetrathiafulvalene, which were investigated by confocal Raman spectroscopy and X-ray diffraction, are reported. OFET devices prepared using different configurations show that both polymorphs exhibited excellent device performance, although the ,-phase revealed charge carrier mobility between two and ten times higher in accordance to the closer stacking of the molecules. [source] Private Higher Education and Diversity: An Exploratory SurveyHIGHER EDUCATION QUARTERLY, Issue 4 2001Pedro Teixeira In this preliminary review, the authors analyse the effects of privatisation on diversity in higher education (HE) systems by exploring the consequences of the establishment of HE Institutions by non-public organisations. The rising importance of privatisation in Europe (Western and transitional economies), Latin America, and Southeast Asia is analysed. Then follows detailed examinations of private-sector HE in countries representative of all these geographical areas to determine how far privatisation has stimulated diversity. The preliminary results indicate that in each case the private sub-sector has promoted limited and partial diversification. In general, though, the more recent private establishments, created to satisfy increasing demand for HE, have nonetheless focused predominately on teaching, have undertaken little, or no, research and appear to be of lower quality than the older institutions. The private sub-sector is characterised mostly by its low-risk behaviour, and a concentration on low-cost and/or safer initiatives. Public authorities must share at least a partial responsibility for some of the negative side effects of the development of private higher education. [source] Solution Processing of Chalcogenide Semiconductors via Dimensional ReductionADVANCED MATERIALS, Issue 31 2009David B. Mitzi Abstract The quest to develop thin-film solution processing approaches that offer low-cost and preferably low-temperature deposition, while simultaneously providing quality semiconductor characteristics, has become an important thrust within the materials community. While inorganic compounds offer the potential for outstanding electronic properties relative to organic systems, the very nature of these materials rendering them good electronic materials,namely strong covalent bonding,also leads to poor solubility. This review presents a "dimensional reduction" approach to improving the solubility of metal chalcogenide semiconductors, which generally involves breaking the extended framework up into discrete metal chalcogenide anions separated by small and volatile cationic species. The resulting soluble precursor may be solution-processed into thin-film form and thermally decomposed to yield the desired semiconductor. Several applications of this principle to the solution deposition of high-performance active layers for transistors (channel mobility >10,cm2 V,1 s,1), solar cells (power conversion efficiency of as high as 12%), and fundamental materials study will be presented using hydrazine as the deposition solvent. [source] A Facile Synthesis Approach to C8 -Functionalized Magnetic Carbonaceous Polysaccharide Microspheres for the Highly Efficient and Rapid Enrichment of Peptides and Direct MALDI-TOF-MS AnalysisADVANCED MATERIALS, Issue 21 2009Hemei Chen Biocompatible C8 -functionalized magnetic carbonaceous polysaccharide microspheres are synthesized via a facile, low-cost, and large-scale route, and their use for the enrichment of peptides from protein digest mixtures is presented. The process of enrichment is very simple, quick, and efficient. Peptides loaded onto the C8 -functionalized magnetic carbonaceous polysaccharide microspheres can be directly analyzed by MALDI-TOF-MS without prior elution from the microspheres. [source] Controlled Deposition of Crystalline Organic Semiconductors for Field-Effect-Transistor ApplicationsADVANCED MATERIALS, Issue 12 2009Shuhong Liu Abstract The search for low-cost, large-area, flexible devices has led to a remarkable increase in the research and development of organic semiconductors, which serve as one of the most important components for organic field-effect transistors (OFETs). In the current review, we highlight deposition techniques that offer precise control over the location or in-plane orientation of organic semiconductors. We focus on various vapor- and solution-processing techniques for patterning organic single crystals in desired locations. Furthermore, the alignment of organic semiconductors via different methods relying on mechanical forces, alignment layers, epitaxial growth, and external magnetic and electric fields are surveyed. The advantages, limitations, and applications of these techniques in OFETs are also discussed. [source] Inexact information aided, low-cost, distributed genetic algorithms for aerodynamic shape optimizationINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 10-11 2003Marios K. Karakasis Abstract Despite its robustness, the design and optimization of aerodynamic shapes using genetic algorithms suffers from high computing cost requirements, due to excessive calls to Computational Fluid Dynamics tools for the evaluation of candidate solutions. To alleviate this problem, either the use of distributed genetic algorithms or the implementation of surrogate evaluation models have separately been proposed in the past. A distributed genetic algorithm relies on the handling of population subsets that evolve in a semi-isolated manner by regularly exchanging their best individuals. It is known that distributed schemes generally outperform single-population ones. On the other hand, the implementation of less costly surrogate evaluation tools, such as the autocatalytic radial basis function networks developed by the authors for the purpose of getting rid of most of the ,useless' exact evaluations, reduces considerably the computational cost. The aim of the present paper is to employ a surrogate evaluation model in the context of a distributed genetic algorithm and to demonstrate that the combination of both results in maximum economy in CPU cost. In addition, whenever a multiprocessor system is available, the gain is much more pronounced, since the new optimization method maximizes parallel efficiency. The proposed method is used to solve inverse design and optimization problems in aeronautics and turbomachinery. Copyright © 2003 John Wiley & Sons, Ltd. [source] Combinatorial Hierarchically Ordered 2D Architectures Self-assembled from Nanocrystal Building Blocks,ADVANCED MATERIALS, Issue 19 2008Xiangxing Xu A one-step, low-cost, and general nanocrystal self-assembly method that covers both the nanometer-scale superlattice and macroscale ordered patterns,that is, hierarchical architectures,is developed. This approach can generate various functional, compositional, and dimensional combinatorial architectures. It may give new opportunities in applications of catalysis, electronics, energy, magnetic devices, and bio-techniques. [source] Ceramic Matrix Composites: A Challenge in Space-Propulsion Technology ApplicationsINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 2 2005Stephan Schmidt Various technology programs in Europe are concerned, besides developing reliable and rugged, low-cost, throwaway equipment, with preparing for future reusable propulsion technologies. One of the key roles for realizing reusable engine components is the use of modern and innovative materials. One of the key technologies that concerns various engine manufacturers worldwide is the development of fiber-reinforced ceramics,CMCs (ceramic matrix composites). The advantages for the developers are obvious,the low specific weight, the high specific strength over a large temperature range, and their great damage tolerance compared with monolithic ceramics make this material class extremely interesting as a construction material. Over the past few years, the EADS-ST Company (formerly DASA) has, together with various partners, worked intensively on developing components for hypersonic engines and liquid rocket propulsion systems. In the year 2000, various hot-firing tests with subscale (scale 1:5) and full-scale nozzle extensions were conducted. In this year, a further decisive milestone was achieved in the sector of small thrusters, and long-term tests served to demonstrate the extraordinary stability of the C/SiC material. Besides developing and testing radiation-cooled nozzle components and small-thruster combustion chambers, EADS-ST worked on the preliminary development of actively cooled structures for future reusable propulsion systems. In order to get one step nearer to this objective, the development of a new fiber composite was commenced within the framework of a regionally sponsored program. The objective here is to create multidirectional (3D) textile structures combined with a cost-effective infiltration process. Besides material and process development, the project also encompasses the development of special metal/ceramic and ceramic/ceramic joining techniques as well as studying and verifying nondestructive investigation processes for the purpose of testing components. [source] Low-cost data communication network for rural telecom network managementINTERNATIONAL JOURNAL OF NETWORK MANAGEMENT, Issue 1 2008C. Jagadish The backbone networking infrastructure of rural telecom networks is often costly and is of limited bandwidth. The availability of connectivity such as DSL or leased lines is scarce. In order to keep operational costs low, these rural telecom networks are often kept unmanned and are managed from a centralized network management station (NMS). This often requires a low-cost, efficient and reliable data communication network (DCN) between the rural telecom equipment and the central NMS. The conventional DCN used for telecom management consists either of leased lines or Internet connectivity. These are often costly and not freely available in rural areas. We have developed a new DCN model, based on dial-up, which is easily available. Using mathematical models and measurements we show that this DCN meets the QoS requirements of a telecom network at an affordable cost. We have implemented this DCN in corDECT networks. This is in use in India and Tunisia, and is under implementation in other similar countries. Copyright © 2007 John Wiley & Sons, Ltd. [source] Primary Amine-Thioureas based on tert -Butyl Esters of Natural Amino Acids as Organocatalysts for the Michael ReactionADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 9 2009Christoforos Abstract A new class of primary amine-thioureas based on tert -butyl esters of (S)-,-amino acids and (1S,2S)-diphenylethylenediamine was synthesized and their activity as catalysts in Michael additions was evaluated. Derivatives based on di- tert -butyl aspartate and tert -butyl O - tert -butyl threoninate provided the product of the reaction between trans- ,-nitrostyrene and acetone in quantitative yield and high enantioselectivity (87,91% ee). All the thioureas based on tert -butyl esters of amino acids catalyzed the reaction of nitroolefins with acetophenone with high enantioselectivity (92,98% ee). Thus, low-cost, commercially available tert -butyl esters of natural amino acids are very important chiral building blocks for the construction of novel chiral thioureas able to catalyze asymmetric Michael additions with high enantioselectivity. [source] | |||||||||||||||||||||||||||||||||||||||||||||||||