bluuebunny/crossref_metadata_2025 huggingface dataset:
Ion transport through nanoslits dominated by the effective surface charge
Authors: Schoch Reto B. , Renaud Philippe
Published: July 2005

A model showing the importance of the parameters characterizing ion transport through geometrically defined nanoslits filled with electrolyte is presented. A conductance plateau (in log-log scale) at low salt concentrations in the nanometer-sized apertures was both modeled and measured. This is due to the dominance of the effective surface charge density in the nanoslits inducing an excess of mobile counterions to maintain electroneutrality. The nanoslit conductance could be regulated at low salt concentrations by pH adjustment and by an external voltage applied on the chip. This effect can be exploited for ionic flow regulation in nanofluidic devices.
Generation of megawatt-power terahertz pulses by noncollinear difference-frequency mixing in GaAs
Authors: Tochitsky S. Ya. , Ralph J. E. , Sung C. , Joshi C.
Published: July 2005

Terahertz pulses with a peak power of ∼2MW were generated in a noncollinear phase-matched GaAs crystal at room temperature. Efficient difference-frequency generation was achieved using 250-ps CO2 laser pulses for which the surface damage threshold increased in comparison with standard 200-ns pulses. Tunable CO2 lasers in combination with this technique should yield a source in the 0.1–3.0-THz range.
Fe-silicide nanostructures on Si(111)-3×3-Ag
Authors: Vanormelingen K. , Paredis K. , Vantomme A.
Published: July 2005

Scanning tunneling microscopy was used to investigate the influence of Ag-induced surface reconstructions on the formation of low-dimensional Fe-Si structures. The deposition of 1Å Fe (i.e., 1.1 monolayer) at 300°C on the 3×1-Ag, the 3×3-Ag, and the 7×7 reconstructions of the Si(111) surface results in the self-assembly of small islands. For both Ag-induced reconstructions, these islands are significantly larger compared to those formed on the Si(111)-7×7 surface due to an increased surface diffusion. Moreover, on the 3×3 structure, these nanodots are well separated and in between, the initial reconstruction remains unchanged. In the presence of surface steps, these islands preferentially nucleate at the lower step edge, which can be used to grow long continuous nanowires for higher Fe coverage and vicinal surfaces. Furthermore, from the phenomena such as step retraction and island/hole combinations, it is concluded that these nanostructures consist of Fe-silicide.
Magnetic anisotropy of epitaxial MgO∕Fe∕MgO films studied by network analyzer ferromagnetic resonance
Authors: Counil G. , Kim Joo-Von , Devolder T. , Crozat P. , Chappert C. , Cebollada A.
Published: July 2005

The dynamic magnetic properties of MgO∕Fe epitaxial thin films are investigated through a network analyzer ferromagnetic resonance in the 0–26-GHz range. The high-frequency response is measured for applied in-plane magnetic fields comparable to the fourfold magnetocrystalline anisotropy of the film, resulting in large-angle in-plane quasistatic motion of the magnetization. We show that the variation of the resonance frequency with both the amplitude and the direction of the external field is in good agreement with the ferromagnetic resonance equations, allowing precise determination of the anisotropy.
A new scheme for determining the intramolecular seven-membered ring N–H⋯OC hydrogen-bonding energies of glycine and alanine peptides
Authors: Wang Chang-Sheng , Zhang Yan , Gao Kun , Yang Zhong-Zhi
Published: July 2005

In this paper a new scheme was proposed to calculate the intramolecular hydrogen-bonding energies in peptides and was applied to calculate the intramolecular seven-membered ring N–H⋯OC hydrogen-bonding energies of the glycine and alanine peptides. The density-functional theory B3LYP∕6-31G(d) and B3LYP∕6-311G(d,p) methods and the second-order Møller-Plesset perturbation theory MP2∕6-31G(d) method were used to calculate the optimal geometries and frequencies of glycine and alanine peptides and related structures. MP2∕6-311++G(d,p), MP2∕6-311++G(3df,2p), and MP2/aug-cc-pVTZ methods were then used to evaluate the single-point energies. It was found that the B3LYP∕6-31G(d), MP2∕6-31G(d), and B3LYP∕6-311G(d,p) methods yield almost similar structural parameters for the conformers of the glycine and alanine dipeptides. MP2/aug-cc-pVTZ predicts that the intramolecular seven-membered ring N–H⋯OC hydrogen-bonding strength has a value of 5.54kcal∕mol in glycine dipeptide and 5.73 and 5.19kcal∕mol in alanine dipeptides, while the steric repulsive interactions of the seven-membered ring conformers are 4.13kcal∕mol in glycine dipeptide and 6.62 and 3.71kcal∕mol in alanine dipeptides. It was also found that MP2∕6-311++G(3df,2p) gives as accurate intramolecular N–H⋯OC hydrogen-bonding energies and steric repulsive interactions as the much more costly MP2/aug-cc-pVTZ does.
Prediction of ceramic stereolithography resin sensitivity from theory and measurement of diffusive photon transport
Authors: Wu K. C. , Seefeldt K. F. , Solomon M. J. , Halloran J. W.
Published: July 2005

A general, quantitative relationship between the photon-transport mean free path (l*) and resin sensitivity (DP) in multiple-scattering alumina/monomer suspensions formulated for ceramic stereolithography is presented and experimentally demonstrated. A Mie-theory-based computational method with structure factor contributions to determine l* was developed. Planar-source diffuse transmittance experiments were performed on monodisperse and bimodal polystyrene/water and alumina/monomer systems to validate this computational tool. The experimental data support the application of this l* calculation method to concentrated suspensions composed of nonaggregating particles of moderately aspherical shape and log-normal size distribution. The values of DP are shown to be approximately five times that of l* in the tested ceramic stereolithography suspensions.
Fabrication and optical characterization of hexagonal photonic crystal microcavities in InP-based membranes containing InAs∕InP quantum dots
Authors: Dalacu Dan , Frédérick Simon , Bogdanov Alexei , Poole Philip J. , Aers Geof C. , Williams Robin L. , McCutcheon Murray W. , Young Jeff F.
Published: July 2005

Hexagonal photonic crystal microcavities with missing-hole defects were fabricated in suspended InP membranes. Embedded InAs quantum dots were utilized as broadband emitters to characterize the modes of the cavities. Photoluminescence emission consists of two orthogonally polarized peaks corresponding to the two dipole modes of the hexagonal defect cavity of reduced symmetry. The emission wavelength ranges from 745 to 840 meV, depending on the crystal structure, and quality factors are up to 850. Finite-difference time-domain simulations reproduce the cavity mode energies and the quality factor dependence on the crystal structure, but predict quality factors systematically lower. The experimental quality factors and mode splittings are associated with a slight ellipticity of the lattice holes.
Avalanche-driven fractal flux distributions in NbN superconducting films
Authors: Rudnev I. A. , Shantsev D. V. , Johansen T. H. , Primenko A. E.
Published: July 2005

Flux distributions in thin superconducting NbN films placed in a perpendicular magnetic field have been studied using magneto-optical imaging. Below 5.5K the flux penetrates in the form of abrupt avalanches resulting in dendritic structures. Magnetization curves in this regime exhibit extremely noisy behavior. Stability is restored both above a threshold temperature T* and applied field H*, where H* is smaller for increasing field than during descent. The dendrite size and morphology are strongly T dependent, and fractal analysis of the first dendrites entering into a virgin film shows that dendrites formed at higher T have larger fractal dimension.
Z-contrast imaging of AlN exclusion layers in GaN field-effect transistors
Authors: Wallis D. J. , Balmer R. S. , Keir A. M. , Martin T.
Published: July 2005

The structural characteristics of AlN exclusion layers used to enhance the electron mobility in GaN-based field-effect transistor structures are investigated using scanning transmission electron microscopy. It is shown that a peak in electron mobility is achieved for an AlN exclusion layer with a nominal thickness of 2.3 nm, although significant compositional grading at the interfaces appears to be present. For longer growth times (i.e., 30 s), a transition to three-dimensional growth occurs, roughening the GaN/AlN/AlGaN interfaces. This roughening is likely to be associated with scattering of carriers in the two-dimensional electron gas (2DEG) consistent with an observed increase in 2DEG sheet resistivity.
Gigantic enhancement of magnetochiral effect in photonic crystals
Authors: Sawada Kei , Nagaosa Naoto
Published: July 2005

We theoretically propose a method to enhance dramatically a magnetochiral (MC) effect by using the photonic crystals composed of a multiferroic material. The MC effect, the directional birefringence even for unpolarized light, is so small that it has been difficult to observe experimentally. Two kinds of periodic structures are investigated: (a) a multilayer and (b) a stripe composed of a magnetochiral material and air. In both cases, the difference in reflectivity between different magnetization directions is enhanced by a factor of hundreds compared with a bulk material.
Segregation of nearest-neighbor donor-pair defects to Si∕SiO2 interfaces
Authors: Kim Yong-Sung , Chang K. J.
Published: July 2005

We perform first-principles density-functional calculations to study the stability of donor-pair defects at Si∕SiO2 interfaces. For P dopants, individual dopant atoms energetically favor Si lattice sites in the interface region, as compared to bulk Si. When dopant atoms aggregate to the interface region at very high dopant concentrations, dopant segregation occurs in form of electrically deactivating nearest-neighbor donor pairs that comprise two threefold coordinated dopant atoms. Our defect model explains both the redistribution and deactivation of dopant atoms observed at Si∕SiO2 interfaces.
Src-like adaptor protein down-regulates T cell receptor (TCR)–CD3 expression by targeting TCRζ for degradation
Authors: Myers Margaret D. , Dragone Leonard L. , Weiss Arthur
Published: July 2005

Src-like adaptor protein (SLAP) down-regulates expression of the T cell receptor (TCR)–CD3 complex during a specific stage of thymocyte development when the TCR repertoire is selected. Consequently, SLAP−/− thymocytes display alterations in thymocyte development. Here, we have studied the mechanism of SLAP function. We demonstrate that SLAP-deficient thymocytes have increased TCRζ chain expression as a result of a defect in TCRζ degradation. Failure to degrade TCRζ leads to an increased pool of fully assembled TCR–CD3 complexes that are capable of recycling back to the cell surface. We also provide evidence that SLAP functions in a pathway that requires the phosphorylated TCRζ chain and the Src family kinase Lck, but not ZAP-70 (ζ-associated protein of 70 kD). These studies reveal a unique mechanism by which SLAP contributes to the regulation of TCR expression during a distinct stage of thymocyte development.
Lethal giant larvae proteins interact with the exocyst complex and are involved in polarized exocytosis
Authors: Zhang Xiaoyu , Wang Puyue , Gangar Akanksha , Zhang Jian , Brennwald Patrick , TerBush Daniel , Guo Wei
Published: July 2005

The tumor suppressor lethal giant larvae (Lgl) plays a critical role in epithelial cell polarization. However, the molecular mechanism by which Lgl carries out its functions is unclear. In this study, we report that the yeast Lgl proteins Sro7p and Sro77p directly interact with Exo84p, which is a component of the exocyst complex that is essential for targeting vesicles to specific sites of the plasma membrane for exocytosis, and that this interaction is important for post-Golgi secretion. Genetic analyses demonstrate a molecular pathway from Rab and Rho GTPases through the exocyst and Lgl to SNAREs, which mediate membrane fusion. We also found that overexpression of Lgl and t-SNARE proteins not only improves exocytosis but also rescues polarity defects in exocyst mutants. We propose that, although Lgl is broadly distributed in the cells, its localized interaction with the exocyst and kinetic activation are important for the establishment and reenforcement of cell polarity.
The nuclear pore complex–associated protein, Mlp2p, binds to the yeast spindle pole body and promotes its efficient assembly
Authors: Niepel Mario , Strambio-de-Castillia Caterina , Fasolo Joseph , Chait Brian T. , Rout Michael P.
Published: July 2005

The two yeast proteins Mlp1p and Mlp2p (homologues of the vertebrate protein Tpr) are filamentous proteins attached to the nuclear face of nuclear pore complexes. Here we perform a proteomic analysis, which reveals that the two Mlps have strikingly different interacting partners, testifying to their different roles within the cell. We find that Mlp2p binds directly to Spc110p, Spc42p, and Spc29p, which are three core components of the spindle pole body (SPB), the nuclear envelope–associated yeast spindle organizer. We further show that SPB function is compromised in mlp2 mutants. Cells lacking Mlp2p form significantly smaller SPBs, accumulate aberrant SPB component-containing structures inside the nucleus, and have stochastic failures of cell division. In addition, depletion of Mlp2p is synthetically lethal with mutants impaired in SPB assembly. Based on these data, we propose that Mlp2p links the SPB to the peripheral Mlp assembly, and that this linkage is required for efficient incorporation of components into the SPB.
A critical role for the programmed death ligand 1 in fetomaternal tolerance
Authors: Guleria Indira , Khosroshahi Arezou , Ansari Mohammed Javeed , Habicht Antje , Azuma Miyuki , Yagita Hideo , Noelle Randolph J. , Coyle Anthony , Mellor Andrew L. , Khoury Samia J. , Sayegh Mohamed H.
Published: July 2005

Fetal survival during gestation implies that tolerance mechanisms suppress the maternal immune response to paternally inherited alloantigens. Here we show that the inhibitory T cell costimulatory molecule, programmed death ligand 1 (PDL1), has an important role in conferring fetomaternal tolerance in an allogeneic pregnancy model. Blockade of PDL1 signaling during murine pregnancy resulted in increased rejection rates of allogeneic concepti but not syngeneic concepti. Fetal rejection was T cell– but not B cell–dependent because PDL1-specific antibody treatment caused fetal rejection in B cell–deficient but not in RAG-1–deficient females. Blockade of PDL1 also resulted in a significant increase in the frequency of IFN-γ–producing lymphocytes in response to alloantigen in an ELISPOT assay and higher IFN-γ levels in placental homogenates by ELISA. Finally, PDL1-deficient females exhibited decreased allogeneic fetal survival rates as compared with littermate and heterozygote controls and showed evidence of expansion of T helper type 1 immune responses in vivo. These results provide the first evidence that PDL1 is involved in fetomaternal tolerance.
Inborn errors of immunity to infection
Authors: Casanova Jean-Laurent , Abel Laurent
Published: July 2005

The immune system's function is to protect against microorganisms, but infection is nonetheless the most frequent cause of death in human history. Until the last century, life expectancy was only ∼25 years. Recent increases in human life span primarily reflect the development of hygiene, vaccines, and anti-infectious drugs, rather than the adjustment of our immune system to coevolving microbes by natural selection. We argue here that most individuals retain a natural vulnerability to infectious diseases, reflecting a great diversity of inborn errors of immunity.
Attitudes towards low‐allergen food in food allergic consumers
Authors: Miles Susan , Bolhaar Suzanne , González‐Mancebo Eloina , Hafner Christine , Hoffmann‐Sommergruber Karin , Fernández‐Rivas Montserrat , Knulst André
Published: July 2005

Purpose

The aim was to look at food‐allergic consumers’ preferences concerning the development of low‐allergen food.

Design/methodology/approach

A questionnaire was designed to measure attitudes towards low‐allergen food. Data were collected from 20 food‐allergic consumers in Austria, Spain and The Netherlands respectively between April and May 2002 using interviewer‐assisted questionnaire methodology.

Findings

The results suggested that food‐allergic consumers are interested in having low‐allergen food available, with 70‐95 per cent wanting it produced. A total of 89 per cent identified a number of benefits to themselves, including being able to resume eating the food to which they were allergic, and being able to eat all food with no worries, no symptoms and no need to check labels. Fewer disadvantages were mentioned, with 53 per cent identifying no disadvantages. Factors that would encourage or discourage purchase of low‐allergen food were also identified with price, quality (particularly taste) and safety being important. Whilst acceptance of low‐allergen food produced using genetic modification was reasonably high (55‐85 per cent), in general participants would prefer this food to be produced through conventional means.

Research limitations/implications

Further research is required with a larger sample, where cross‐cultural statistical comparisons can be made. Originality/value This study provides new information about acceptability of low‐allergen food which is of use for the food industry when developing such food, benefiting both the industry and food‐allergic consumers.
The remarkable role of nutrition in learning and behaviour
Authors: Dani Jennifer , Burrill Courtney , Demmig‐Adams Barbara
Published: July 2005

Purpose

The purpose of this review is to examine the effect of nutrition on mental functions of children and adolescents.

Design/methodology/approach

The approach taken is to evaluate published research on key dietary factors, including recent, rigorously designed supplementation studies.

Findings

The result of this analysis is that nutrition has potent effects on brain function. It is concluded that protein, iron, iodine, and the consumption of breakfast all impact on a child’s learning capability and behaviour. Moreover, recent research has identified additional, potent roles of micronutrients, such as essential fatty acids, minerals, and vitamins, in the prevention of learning and behavioural disorders. Among the latter, this review focuses particularly on attention deficit hyperactivity disorder.

Research limitations/implications

While several controlled supplementation trials with supplementation are now available, the limitation of the present analysis is that more large‐scale trials are needed before final conclusions can be reached.

Practical implications

The practical implication of this review for health‐care providers, nutritionists, teachers, and parents at this time is that enough promising evidence has be accumulated to warrant a recommendation to include adequate levels of minerals, vitamins, essential fatty acids, and other nutrients in children’s diets to improve learning and behaviour.

Originality/value

This review is unique in its comprehensive nature and provides a synopsis of the power of diet in influencing learning and behavior for professionals and parents.
Organic‐mineral content of the main Brazilian cereals and legumes
Authors: Lúcia Valente Mesquita Vera , de Lourdes Reis Giada Maria
Published: July 2005

Purpose

In Brazil there is a lack of food composition data and the nutrition professionals frequently need to consult compiled tables of international reference. It is known that the extrapolation of international food data to the regional level is not accurate and requires caution because it may result in nutritional problems. Thus, the purpose of this work was to determine and compare the organic‐mineral content of the main Brazilian cereals and legumes with those of the available reference in this country.

Design/methodology/approach

The chemical composition of the samples was examined according to AOAC methods. The energy value for each sample was calculated using the specific Atwater energy factors.

Findings

The moisture as well as lipids and ash content were found to accord with the consulted bibliography for most of the samples. The protein values were the same as those found by some authors and different from others.

Originality/value

The results obtained showed the need for elaborating a Brazilian food composition table able to better reproduce the real nutritive value of food produced in this country.
Human resource management practice and institutional constraints The case of Mozambique
Authors: Webster Edward , Wood Geoffrey
Published: July 2005

Purpose

This article aims to explore the nature of contemporary HRM practice in Mozambique, and the extent to which “best practice” HRM strategies are likely to emerge, given present institutional realities.

Design/methodology/approach

The research was based on an extensive survey of Mozambican employers concentrated in the major urban centres of the country.

Findings

The survey revealed little evidence of innovation or of leading edge practices, other than in a small minority of firms. It is concluded that the diffusion of higher value added managerial strategies is only likely to take place in a more supportive institutional context.

Practical implications

The failure of innovative HRM techniques to diffuse across the economy, despite heightened external pressures, highlights organizational inertia, including the continued reliance of many firms on low‐paid and low‐skilled workers, and on autocratic paternalism. It remains uncertain whether a more “high value” added path is viable in a context of cut‐throat competition from abroad.

Originality/value

The Mozambique experience underscores the importance of an institutional context which encourages firms to buy into mutually advantageous sets of rules governing fair play and limits the rewards accruing to bad practice. Whilst the more efficient enforcement of legislation may encourage the broader adoption of “high road” practices, their sustainability is, at least in part, contingent on the diffusion and reconstitution of supportive conventions; regrettably, this makes it extremely difficult to depart from the low value added path.
Ten years of European works councils in Ireland: testing the regulatory capacity of soft‐style EU directives
Authors: O’Hagan Emer
Published: July 2005

Purpose

The European Works Council (EWC) Directive reflects a shift to a softer style of governance which has been adopted by the EU in recent years. This article sets out to explore how successful this soft style governance is when implemented at the national level.

Design/methodology/approach

The paper introduces the literature on the subject and shows that two main theses have been developed to date; one which favours the softer mechanism of governance and one which is critical of it. Two propositions are developed from the literature. The article explores them by examining them in light of the manner in which the Directive has bedded down in the Irish context. It does this through a micro and macro analysis of material available on the EWC in Ireland and a series of interviews. Ireland is regarded as a suitable arena in which to explore these propositions.

Findings

The article finds that the EWC Directive was implemented in Ireland in a manner which was deemed suitable for its smooth integration into the Irish context. However, the transposition’s flexible nature is such that it is unclear that it has made any significant contribution to Ireland’s system of industrial relations. It is suggested that the EU may not yet have developed a form of governance suitable for a disparate, expanding community.

Originality/value

The paper provides a micro‐analysis of how the EWC Directive has been transposed in one Member State (Ireland). It combines this with a macro‐analysis which enables us to compare the Irish transposition with other Member States. This approach indicates that the Directive has been applied in a very heterogeneous style throughout the Member States, which tends to reproduce indigenous industrial relations systems rather than reform or challenge them.
Effects of HRM on client satisfaction in nursing and care for the elderly
Authors: Ott Marlies , van Dijk Han
Published: July 2005

Purpose

HRM is supposed to increase job satisfaction. But does it also increase client satisfaction? Sets out to discuss this issue.

Design/methodology/approach

The unit of analysis is the home. Using data from a benchmark study among Dutch homes for elderly care, 154 homes were scored on three groups of indicators: HRM activities as experienced by employees, employee satisfaction, and client satisfaction. Scores were based on interviews with 3,542 patients and surveys of 12,193 employees.

Findings

HRM does affect job and client satisfaction. Correlations between HRM and client satisfaction were generally rather low. Employees’ satisfaction with their organisation is a better predictor of client satisfaction than job satisfaction. Job‐related training showed no relation with job satisfaction, but a clear relation with client satisfaction, while leadership style of their manager had a significant relation with job satisfaction, and a more limited one with client satisfaction. Regular performance reviews are important for job satisfaction and client satisfaction. Employee and client satisfaction can also conflict: more regular schedules increase employee satisfaction, but decrease client satisfaction.

Research limitations/implications

To decide on best practices the correlations found need to be explained. For instance, why do performance reviews correlate with employee satisfaction and with client satisfaction about employee expertise?

Practical implications

These results confirm the importance of the leadership style of line managers. Helping middle management to develop a supportive and transparent leadership style can improve employee satisfaction. The HRM activity most relevant for client satisfaction seems to be job‐related training.

Originality/value

The paper is unique in combining data on employee and client satisfaction. It is of interest both to HRM researchers and to health‐care management.
Improving strategic thinking: a multilevel approach
Authors: Bonn Ingrid
Published: July 2005

Purpose

Following a multilevel approach, the purpose of this paper is to develop a framework of strategic thinking, which integrates the micro‐domain's focus on individuals and groups with the macro‐domain's focus on organisations.

Design/methodology/approach

The paper first defines strategic thinking, outlines its elements and examines some of the conceptual issues surrounding the construct, especially those concerning levels of analysis. The following questions are addressed. What are the characteristics of an individual strategic thinker? What are the dynamics that take place within groups and how do they influence strategic thinking? What are the contributions of the organisational context to strategic thinking?

Findings

Strategic thinking at the individual level is discussed in terms of diversity in representational systems. Strategic thinking at the group level looks at heterogeneity and conflict. Strategic thinking within the organisational context examines middle management involvement, the role of organisational structure, and reward and compensation systems.

Practical implications

The paper may help senior managers to develop practical interventions for improving strategic thinking in their organisations. This includes the design of appropriate selection, recruitment and development strategies as well as paying attention to group and organisational level factors that create the enabling conditions for the individual characteristics associated with strategic thinking to be utilised.

Originality/value

The paper outlines a theoretical framework of strategic thinking that integrates previous fragmented research from a number of areas and disciplines into a more comprehensive theory of strategic thinking. It represents an important antecedent to strategic decision making and may provide a key to a better understanding of organisational change phenomena and, ultimately, organisational performance and survival.
Leaders lost in transformation
Authors: Emiliani M.L. , Stec D.J.
Published: July 2005

Purpose

To examine why most Lean transformations achieve only modest favorable results, despite years of effort.

Design/methodology/approach

Comparative/evaluative discussion of efforts made by senior managers to implement the Lean management system, with commentary on a published example.

Findings

Presents common obstacles and identifies common implementation errors that must be avoided in order to realize the full benefits of the Lean management system.

Research limitations/implications

Illustrates the ease by which Lean transformation efforts can lead to less desirable outcomes when senior managers fail to fully grasp the implicit and explicit aspects of both task and behavioral elements of a new management system.

Practical implications

Provides specific suggestions that will enable senior managers and organizations to achieve improved outcomes.

Originality/value

Identifies numerous common errors made by senior managers, the rationale for why the errors have occurred, and suggests improvements for implementing the Lean management system.
Establishment of energy management tools for facilities managers in the tropical region
Authors: Haji‐Sapar Majid , Eang Lee Siew
Published: July 2005

Purpose

To establish national energy performance benchmarks and an energy efficiency classification system for commercial office buildings from whole building to sub‐systems level for building professionals including facility managers.

Design/methodology/approach

Issuing of survey form and questionnaires to 16 building owners before field interview. Building physical data and systems nameplate, quantities and types were verified on site. The past 24 months electricity consumption bills were also collected from building owners. Physical environmental conditions and short‐term power measurement on building systems were done to determine the level of energy consumption and performance.

Research limitations/implications

The classification and benchmarking methodology developed is useful for the regions to establish their own database and tools.

Practical implications

The building energy performance assessment and auditing methodology are useful to both building owner/manager and energy services companies (ESCOs) in carrying out systematic assessment and analysis on building energy characteristics. The benchmark system established will also serve as a reference to building professionals to adopt a more holistic approach in designing an energy efficient building. Useful also for building owners who are considering carrying out retrofitting works on their existing building or systems.

Originality/value

The study provides detailed whole building and systems benchmarks for Singapore. The results provide an objective evaluation system of commercial office building energy performance.
Modelling water closet demand in shopping centres
Authors: Wong L.T. , Yau C.L.
Published: July 2005

Purpose

To quantify water closet (WC) provisions in shopping malls in order to help building professionals to determine effective sanitary designs at certain service standards in terms of the user's probable waiting time.

Design/methodology/approach

The proposed WC provision takes account of the probable waiting time corresponding to certain demand patterns of shopping malls. The probable waiting time for a WC and the failure rate of the closet in providing immediate service to the users at various WC provision levels described by a simple queuing process are evaluated by the Monte Carlo simulations. Model parameters such as the maximum waiting time expected by the users, the frequency distributions of the time between user arrivals and the service time at sanitary facilities were determined from a survey of a large shopping mall in Hong Kong.

Findings

The suitable provision of WCs was determined by the user's acceptable waiting time, and compared with those provision levels determined by the limiting failure rate of providing immediate service.

Research limitations/implications

The model parameters are not exhaustive, with assumptions made for the queuing process of washroom users and have only been determined from a recent survey in Hong Kong, which perhaps will limit the model's usefulness elsewhere.

Practical implications

A useful source of reference in planning the sanitary facilities of shopping malls for various user demands. The methodology can be used in a modified form for most building types.

Originality/value

This paper proposes mathematical expressions for WC provision in shopping malls and presents a template to determine the required model parameters. The model offers practical help to professionals involved in planning, designing and managing the sanitary facilities of shopping malls.
Optimal reliability allocation under uncertain conditions, with application to hybrid electric vehicle design
Authors: Allella Flavio , Chiodo Elio , Lauria Davide
Published: July 2005

Purpose

The purpose of this paper is the investigation of the main aspects of optimal reliability allocation with respect to the design of hybrid electric vehicles. In particular, with reference to the hybrid electric vehicle propulsion system, the problem of data uncertainty, due to a scarce knowledge of the components' reliabilities, is taken into account. This problem is crucial for new technology systems and it is faced with a Bayesian approach: components' reliabilities are considered as random variables, characterised in the paper by negative log‐gamma distributions.

Design/methodology/approach

The main aspects of optimal reliability allocation with the design of hybrid electric vehicles are presented, pointing out the opportunity of a reliability evaluation in the planning stage.

Findings

The topic of a series hybrid vehicle reliability is addressed, nevertheless results can be easily extended to the parallel configuration. In particular, the opportunity of a reliability evaluation of the propulsion system in the design stage is highlighted, mainly when new technology components are involved.

Originality/value

The value of the paper consists in the methodology allowing to express the system reliability uncertainty as a function of component uncertain data. Then, as far as concern the practical implications, the optimal allocation of the components' reliabilities can be efficiently performed, in order to minimise the system total cost respecting a prefixed value of the system reliability. In the final part of the paper, a numerical application, related to a series hybrid electric vehicle propulsion system, is presented to show the feasibility of the approach.
Lossy three‐phase transmission line transient analysis by Park approach
Authors: Leva Sonia , Paolo Morando Adriano
Published: July 2005

Purpose

To provide a unified analytical tool, based on Park transformation, for the theoretical and practical analysis of a lossy three‐phase transmission line.

Design/methodology/approach

The results obtained in the study of TEM waves propagation in two‐wire line can be extended to a symmetric m‐wire line by employing the modal analysis. This approach relates the dynamic of m‐wire guided field to the propagation of m modal voltages and currents acting on m single‐wire decoupled transverse electromagnetic (TEM) lines. In the symmetric three‐phase system case, the modal analysis includes, as a particular case for m=3, the symmetric component theory. In previous papers, the authors applied the Park transformation to study the wave propagation of (TEM) three‐phase symmetrical lines. The formulation proposed and tested considers the lossless TEM wave propagation of a three‐phase line without consideration to the dissipations phenomena present in the line itself. Taking into account the obtained results, the extension of the developed approach to the lossy three‐phase transmission line transient analysis is very useful on both theoretical and practical points of view.

Findings

The symmetrical three‐phase line Park model for the lossy transmission line transient analysis, regarded as vector formulation of the line modal analysis, has been presented. The proposed examples highlight how, thanks to the Park model, the dynamic analysis of the three‐phase line in distorted and unsymmetrical systems becomes an integral part of the more general and well‐established power electric system dynamic theory.

Originality/value

The three‐phase transmission line transient analysis presented in this paper emphasizes the conceptual contents, specific to the Park approach. Furthermore, it gives some results very important for the practical analysis of a lossy three‐phase transmission line.
Scalar and vector potentials' coupling on nonmatching grids for the simulation of an electromagnetic brake
Authors: Flemisch Bernd , Wohlmuth Barbara , Rapetti Francesca , Maday Yvon
Published: July 2005

Purpose

We present a method for the simulation of the dynamical behavior of a coupled magneto‐mechanical system given in terms of a conductor moving through an electromagnetic field.

Design/methodology/approach

For the magnetic part, we consider a model based on an electric vector and a magnetic scalar potential, whereas the mechanical part is modelled by the equation of a rigid body motion. A weak coupling is employed: at each time step the resulting forces are calculated yielding the new displacement of the conductor.

Findings

Numerical results are given for the simulation of an electromagnetic brake with axisymmetric geometry. They indicate that the proposed method is especially well suited for eddy current problems involving moving conductors.

Research limitations/implications

Further research should be undertaken toward the application of the proposed method to real 3D problems.

Originality/value

The spatial discretization of the problem relies on the use of two independent triangulations to approximate the two involved potentials. Whereas the scalar magnetic potential is discretized by means of nodal H1‐conforming finite elements on a grid covering the global computational domain, the vector electric potential is approximated by Hcurl‐conforming edge elements on another grid only covering the conductor. The coupling between the two grids is accomplished via the mortar finite element method. At each time step, only the coupling matrix has to be reassembled, all other involved matrices remain the same. Moreover, no remeshing is necessary when the conductor changes its position. The paper should be valuable for any researcher interested in the numerical simulation of eddy current problems.
Experimental design method applied to a multiphysical model
Authors: Vivier S. , Hecquet M. , Ait‐Hammouda A. , Brochet P.
Published: July 2005

Purpose

The aim of this paper is to use an analytical multi‐physical model – electromagnetic, mechanic and acoustic – in order to predict the electromagnetic noise of a permanent magnet synchronous machine.

Design/methodology/approach

The aim of this work is to develop and use an analytical multi‐physical model – electromagnetic, mechanic and acoustic – of a synchronous machine with permanent magnets. The complete model is coded in order to predict acoustic noise. A study of sensitivity is presented in order to deduce the influential – or significant – factors on the noise. For that, the technique of the experimental designs is used. More particularly, the modeling of the noise will be achieved due to the new “trellis” designs.

Findings

Three models are presented: electromagnetic, mechanical of vibration and acoustic. For each of them, comparisons with finite element method and experiments have been made. Several response surfaces are given; they represent the noise according to influential factors, with respect to different speeds of the machine. These surfaces are useful to deduce the parts of the design space to avoid.

Originality/value

Different multi‐physical aspects are considered: electromagnetic, mechanic and acoustic phenomena are taken into account due to a single analytical model. The experimental design method is the privileged tool used to make the complex relationships between the main variables appear.
Genetic optimisation of radial eddy current couplings
Authors: Canova A. , Freschi F. , Gruosso G. , Vusini B.
Published: July 2005

Purpose

The purpose of this paper is to obtain a fully analytical model of an eddy current coupler and to use it in a multi‐objective optimisation algorithm.

Design/methodology/approach

Analytical expressions of device performances are adopted in the objective function and are obtained from a closed solution of the field problem. The optimisation has been carried out by considering both the torque and the momentum of inertia of the object. Two different structures have been considered.

Findings

A fully analytical expression of the torque has been obtained for two different geometrical configurations. The optimisation procedure has been used to compare these structures and it is possible to observe that the DSPM performances are better than the SSPM ones.

Research limitations/implications

To obtain a closed form of the torque function, the non‐linearities of the iron have been neglected. Nevertheless, in the optimisation procedure has been limited the magnetic flux density in the iron core to a feasible value in the linear part of the ferromagnetic characteristic. The thermal effects have been neglected.

Pratical implications

In the industry, eddy current couplers can be used as transmission, dampers and brakes. The use of objective functions (OFs) in a closed formulation allows to perform a light optimisation from the point of view of the time computation and to drastically increase the development efficiency.

Originality/value

In this paper, a model for computing the electromagnetic behaviour of eddy current couplers is presented. The optimisation of both the torque and the inertia momentum allows to obtain good static and dynamic performances.
System optimization by multiobjective genetic algorithms and analysis of the coupling between variables, constraints and objectives
Authors: Régnier J. , Sareni B. , Roboam X.
Published: July 2005

Purpose

This paper presents a methodology based on Multiobjective Genetic Algorithms (MOGAs) for the design of electrical engineering systems. MOGAs allow one to optimize multiple heterogeneous criteria in complex systems, but also simplify couplings and sensitivity analysis by determining the evolution of design variables along the Pareto‐optimal front.

Design/methodology/approach

To illustrate the use of MOGAs in electrical engineering, the optimal design of an electromechanical system has been investigated. A rather simplified case study dealing with the optimal dimensioning of an inverter – permanent magnet motor – reducer – load association is carried out to demonstrate the interest of the approach. The purpose is to simultaneously minimize two objectives: the global losses and the mass of the system. The system model is described by analytical model and we use the MOGA called NSGA‐II.

Findings

From the extraction of Pareto‐optimal solutions, MOGAs facilitate the investigation of parametric sensitivity and the analysis of couplings in the system. Through a simple but typical academic problem dealing with the optimal dimensioning of a inverter – permanent magnet motor – reducer – load association, it has been shown that this multiobjectivea posterioriapproach could offer interesting outlooks in the global optimization and design of complex heterogeneous systems. The final choice between all Pareto‐optimal configurations can bea posterioridone in relation to other issues which have not been considered in the optimization process. In this paper, we illustrate this point by considering the cogging torque for the final decision.

Originality/value

We have proposed an original quantitative methodology based on correlation coefficients to characterize the system interactions.
LORETA‐contracting algorithm for solving EEG source distribution problems
Authors: Ma Xinshan , Guan Xin
Published: July 2005

Purpose

The electroencephalography (EEG) source tomography in bio‐electromagnetics is to estimate current dipole sources inside the brain from the measured electric potential distribution on the scalp surface. A traditional algorithm is the low‐resolution electromagnetic tomography algorithm (LORETA). In order to obtain high‐resolution tomography, the LORETA‐contracting algorithm is proposed.

Design/methodology/approach

The relation between the dipolar current source J at the nodes in source region and the potential U at the observed points on the scalp surface can be expressed as a matrix equation U=KJ after discretization. K is a coefficient matrix. Usually its simultaneous equation is an under‐determined system. The LORETA approach is to find out min‖BWJ‖2, under constraint U=KJ where B is the discrete Laplacian operator matrix, W is a weighting diagonal matrix. Its solution is J=(WBTBW)−1KT{K(WBTBW)−1KT}+U where {}+ denotes the Moore‐Penrose pseudo‐inverse matrix. The improvement on this approach is to establish an iterative program to repeat LORETA and reduce the number of unknown J quantities in the step i+1 by contracting the source region excluding some extreme little quantities of J given in the step i. The simultaneous equations will gradually turn to a properly determined system or to an over‐determined system. Finally, its solution can be obtained by using the least square method.

Findings

Repeating to make the low‐resolution tomography by contracting the source region, we can get a high‐resolution tomography easily.

Research limitations/implications

The LORETA‐contracting algorithm is based on the assumption that the dipolar current sources inside the brain are sparse and concentrated based on the physiological study of the brain activity.

Originality/value

It is new to repeat LORETA combined with the contracting technique. This algorithm can be developed to solve EEG problems of realistic head models.
Optimisation in electromagnetics with the space‐mapping technique
Authors: Echeverría D. , Lahaye D. , Encica L. , Hemker P.W.
Published: July 2005

Purpose

Optimisation in electromagnetics, based on finite element models, is often very time‐consuming. In this paper, we present the space‐mapping (SM) technique which aims at speeding up such procedures by exploiting auxiliary models that are less accurate but much cheaper to compute.

Design/methodology/approach

The key element in this technique is the SM function. Its purpose is to relate the two models. The SM function, combined with the low accuracy model, makes a surrogate model that can be optimised more efficiently.

Findings

By two examples we show that the SM technique is effective. Further we show how the choice of the low accuracy model can influence the acceleration process. On one hand, taking into account more essential features of the problem helps speeding up the whole procedure. On the other hand, extremely simple auxiliary models can already yield a significant acceleration.

Research limitations/implications

Obtaining the low accuracy model is not always straightforward. Some research could be done in this direction. The SM technique can also be applied iteratively, i.e. the auxiliary model is optimised aided by a coarser one. Thus, the generation of hierarchies of models seems to be a promising venue for the SM technique.

Originality/value

Optimisation in electromagnetics, based on finite element models, is often very time‐consuming. The results given show that the SM technique is effective for speeding up such procedures.