bluuebunny/crossref_metadata_2025 huggingface dataset:
Microphase Separation of Block Copolymer Thin Films
Authors: Zhang Jilin , Yu Xinhong , Yang Ping , Peng Juan , Luo Chunxia , Huang Weihuan , Han Yanchun
Published: January 2010

Today, high‐ordered micro‐ and nano‐patterned surfaces are widely used in many areas, such as in the preparation of super‐thin dielectric films, photonic crystals, antireflective films, super‐non‐wetting surfaces, bio‐compatible surfaces and microelectric devices. Considering the critical fabrication conditions and the irreducible high cost of the photolithography technique in patterning nano‐scale structures (<100 nm), the development of other micro‐ and nano‐patterning techniques that can be used to fabricate long‐range ordered features – especially nanoscale arrays – is a promising subject in surface science. In contrast to the traditional photolithography patterning technique, block copolymers can spontaneously phase separate into arrays of periodic patterns with length‐scales of 10–50 nm, which provides an efficient pathway to pattern nanoscale features. Today, preparing long‐range ordered arrays by block copolymer microphase separation is one of the most promising techniques for the fabrication of nanoscale arrays, not only being a simple process but also having a lower cost than traditional methods. In this feature article, we first summarize the many techniques developed to induce ordering in the microphase separation of the block copolymer thin films. Then, evolution, order–order transitions and reversible switching microdomains are considered, since they are very important in the ordered engineering of microphase separation of the block copolymer thin films. Finally, the outlook of this research area will be given.

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A new classification system for muscle and nerve preservation in DIEP flap breast reconstruction
Authors: Lee Bernard T. , Chen Chen , Nguyen Minh‐Doan , Lin Samuel J. , Tobias Adam M.
Published: January 2010

The main advantage of deep inferior epigastric perforator (DIEP) flap breast reconstruction is muscle preservation. Perforating vessels, however, display anatomic variability and intraoperative decisions must balance flap perfusion with muscle or nerve sacrifice. Studies that aggregate DIEP flap reconstruction may not accurately reflect the degree of rectus preservation. At Beth Israel Deaconess Medical Center from 2004–2009, 446 DIEP flaps were performed for breast reconstruction. Flaps were divided into three categories: DIEP‐1, no muscle or nerve sacrifice (126 flaps); DIEP‐2, segmental nerve sacrifice and minimal muscle sacrifice (244 flaps); DIEP‐3, perforator harvest from both the medial and lateral row, segmental nerve sacrifice and central muscle sacrifice (76 flaps). Although the rate of abdominal bulge was similar among groups, fat necrosis was significantly higher in DIEP‐1 when compared with DIEP‐3 flaps (19.8% vs. 9.2%, P = 0.049). We describe a DIEP flap classification system and operative techniques to minimize muscle and nerve sacrifice. © 2010 Wiley‐Liss, Inc. Microsurgery, 2010.
Ten‐digit replantation with seven years follow‐up: A case report
Authors: Cong Haibo , Sui Haiming , Wang Chenlin , Wang Zhumin , Yang Qingmin , Wang Buxing
Published: January 2010

In this report, we present a case of successful replantation of 10‐digit complete amputation and results of postoperative rehabilitation in 7 years follow‐up. The rehabilitation program included psychotherapy, physical therapy, sensory re‐education, and measurements. At the 7 years postoperatively, the static two‐point discriminations of replanted digits ranged from 4 to 11 mm. Grasping powers ranged from 69 to 81 lb, and pinching powers ranged from 13 to 19 lb. The patient returned to the previous employment. Our experience has demonstrated that systemic postoperative rehabilitation and measurements could achieve satisfactory recovery of the sensory and motor functions of multiple‐digit replantation. © 2010 Wiley‐Liss, Inc. Microsurgery 30:405–409, 2010.
Equitable bandwidth allocation in content distribution networks
Authors: Luss Hanan
Published: January 2010

Applications for content distribution over networks, such as Video‐on‐Demand (VOD), are expected to grow significantly over time. Effective bandwidth allocation schemes that can be repeatedly executed must be deployed since new programs are often installed at various servers while other are deleted. We present a model for bandwidth allocation in a content distribution network that consists of multiple trees, where the root of each tree has a server that broadcasts multiple programs throughout the tree. Each network link has limited capacity and may be used by one or more of these trees. The model is formulated as an equitable resource allocation problem with a lexicographic maximin objective function that attempts to provide equitable service performance for all requested programs at the various nodes. The constraints include link capacity constraints and tree‐like ordering constraints imposed on each of the programs. We present an algorithm that provides an equitable solution in polynomial time for certain performance functions. At each iteration, the algorithm solves single‐link maximin optimization problems while relaxing the ordering constraints. The algorithm selects a bottleneck link, fixes various variables at their lexicographic optimal solution while enforcing the ordering constraints, and proceeds with the next iteration. © 2010 Wiley Periodicals, Inc. Naval Research Logistics, 2010
FLEXMG: A new library of multigrid preconditioners for a spectral/finite element incompressible flow solver
Authors: Rasquin M. , Deconinck H. , Degrez G.
Published: January 2010

A new library called FLEXMG has been developed for a spectral/finite element incompressible flow solver called SFELES. FLEXMG allows the use of various types of iterative solvers preconditioned by algebraic multigrid methods. Two families of algebraic multigrid preconditioners have been implemented, namely smooth aggregation‐type and non‐nested finite element‐type. Unlike pure gridless multigrid, both of these families use the information contained in the initial fine mesh. A hierarchy of coarse meshes is also needed for the non‐nested finite element‐type multigrid so that our approaches can be considered as hybrid. Our aggregation‐type multigrid is smoothed with either a constant or a linear least‐square fitting function, whereas the non‐nested finite element‐type multigrid is already smooth by construction. All these multigrid preconditioners are tested as stand‐alone solvers or coupled with a GMRES method. After analyzing the accuracy of the solutions obtained with our solvers on a typical test case in fluid mechanics, their performance in terms of convergence rate, computational speed and memory consumption is compared with the performance of a direct sparse LU solver as a reference. Finally, the importance of using smooth interpolation operators is also underlined in the study. Copyright © 2010 John Wiley & Sons, Ltd.
Dual‐grid‐based tree/cotree decomposition of higher‐order interpolatoryH(∇∧, Ω) basis
Authors: Beig Davood Ansari Oghol , Leong Mook‐Seng
Published: January 2010

This work extends the zeroth‐order tree/cotree (TC) decomposition method into higher order (HO) interpolatory elements and develops the constraints operator required for the elimination of spurious solutions for general HOspectralbasis. Earlier methods explicitly enforce the divergence condition that requires a mixed finite element (FE) formulation with bothH1andH(∇∧) expansions and involves repeated solutions of thePoissonequation. A recent approach, which avoids the mixed formulation and the Poisson problem, uses TC decomposition of edgeDoFover the primal graph and construction of integration and gradient matrices. The approach is easily applied toHO hierarchicalelements but becomes quite complex for HO spectral elements. In the presence of internal DoF, it is difficult to utilize the primal graph for an explicit decomposition of the spectral DoF. In contrast, this work utilizes thedualgrid, resulting in an explicit decomposition of DoF and construction of constraint equations from a fixed element matrix. Thus, mixed formulation and the Poisson problems are avoided while eliminating the need for evaluation of integration and gradient matrices. The proposed constraints matrix is element‐geometry independent and possesses an explicit sparsity formulation reducing the need for dynamic memory allocation. Numerical examples are included for verification. Copyright © 2010 John Wiley & Sons, Ltd.
High potential of thin (<1 µm) a‐Si: H/µc‐Si:H tandem solar cells
Authors: Schicho S. , Hrunski D. , van Aubel R. , Gordijn A.
Published: January 2010

Silicon based thin tandem solar cells were fabricated by plasma enhanced chemical vapor deposition (PECVD) in a 30 × 30 cm2 reactor. The layer thicknesses of the amorphous top cells and the microcrystalline bottom cells were significantly reduced compared to standard tandem cells that are optimized for high efficiency (typically with a total absorber layer thickness from 1.5 to 3 µm). The individual absorber layer thicknesses of the top and bottom cells were chosen so that the generated current densities are similar to each other. With such thin cells, having a total absorber layer thickness varying from 0.5 to 1.5 µm, initial efficiencies of 8.6–10.7% were achieved. The effects of thickness variations of both absorber layers on the device properties have been separately investigated. With the help of quantum efficiency (QE) measurements, we could demonstrate that by reducing the bottom cell thickness the top cell current density increased which is addressed to back‐reflected light. Due to a very thin a‐Si:H top cell, the thin tandem cells show a much lower degradation rate under continuous illumination at open circuit conditions compared to standard tandem and a‐Si:H single junction cells. We demonstrate that thin tandem cells of around 550 nm show better stabilized efficiencies than a‐Si:H and µc‐Si:H single junction cells of comparable thickness. The results show the high potential of thin a‐Si/µc‐Si tandem cells for cost‐effective photovoltaics. Copyright © 2010 John Wiley & Sons, Ltd.
Positive adjustment to breast cancer: development of a disease‐specific measure and comparison of women diagnosed from 2 weeks to 5 years
Authors: Boot Julia S. , Holcombe Christopher , Salmon Peter
Published: January 2010

Objective: Many women describe ‘positive adjustment’ as a consequence of having breast cancer. It is unclear whether positive experiences reflect the absence of anxiety and depression or are part of a separate process of adjustment. Existing measures are not specific to breast cancer and may lack validity. Our aims were as follows: (1) to develop a valid questionnaire to measure positive adjustment after breast cancer; (2) to clarify whether it measures aspects distinct from anxiety and depression and (3) to suggest when positive adjustment typically emerges.

Methods: A new measure, the Positive Adjustment Questionnaire (PAQ), was developed and completed by 156 women with breast cancer, allocated to three groups: 2–4 weeks; 6 months–2 years and 2–5 years post‐diagnosis. Other questionnaires were used to assess anxiety and depression and test the validity of the PAQ.

Results: Principal components analysis of the PAQ identified four domains of positive adjustment; Fulfilment, Re‐evaluation, New ways of living and Valuing Life. Women questioned 2–5 years after diagnosis reported more fulfilment, re‐evaluation of life and new ways of living than those asked shortly after diagnosis. Differences in these aspects of positive adjustment remained after controlling for anxiety and depression.

Conclusions: This study (1) provides a measure specific to positive adjustment following breast cancer; (2) suggests that positive adjustment is different from anxiety and depression and (3) indicates that positive adjustment is seen in women assessed 2–5 years after diagnosis. Psychological therapies that promote positive adjustment could enhance existing interventions that focus on reducing anxiety and depression. Copyright © 2010 John Wiley & Sons, Ltd.
Theoretical analysis and experimental results on the modulated photocarrier grating technique
Authors: Schmidt J. A. , Budini N. , Ventosinos F. , Longeaud C.
Published: January 2010

We present a complete theoretical analysis of the modulated photocarrier grating method (MPG). Our calculations show that the response of the sample will be not only a photocurrent modulated with the frequency f of the illumination, but also a response in dc and with frequency 2f. In order to put to test our calculations, we implement experimentally the MPG technique and we apply it to a hydrogenated amorphous silicon sample. We verify the existence of a response at frequency 2f, and we measure the relative intensity of this signal – which compares well with the result of our theoretical calculation. We also show that under certain conditions the density of states (DOS) at the quasi‐Fermi level for the majority carriers is related to the ratio of the MPG and modulated photoconductivity (MPC) signals. We present a simple formula that allows estimating the DOS as a function of energy by changing the temperature and the generation rate.
a‐Si:H temperature sensor integrated in a thin film heater
Authors: Caputo D. , de Cesare G. , Nascetti A. , Scipinotti R.
Published: January 2010

In this work we present an hydrogenated amorphous silicon (a‐Si:H) temperature sensor integrated in a thin film heater to perform biomolecular treatments. The system is fabricated on a microscope glass slide and includes a PolyDiMethylSiloxane (PDMS) chamber to confine the solution containing the sample and to avoid its evaporation. The heater is a 200 nm‐thick titanium/tungsten sputtered film with a serpentine shaped geometry that has been designed by a finite element simulator in order to obtain a spatial‐uniform temperature distribution. A uniformity better than 3% has been achieved over the surface of the structure. The temperature sensor is a n‐type/intrinsic/p‐type a‐Si:H stacked structure deposited by plasma enhanced chemical vapor deposition. The top and bottom contacts of the diode are made by the same metal utilized to fabricate the heater. The characterization of the sensor response has been performed both under forward and reverse bias condition. In reverse bias condition, at fixed voltage, the current–temperature curve exhibits an exponential behavior. In forward bias condition, at constant bias current, the voltage across the diode is linearly dependent on the temperature in the range 30–90 °C. In particular, using a constant bias current of 10 nA, a sensitivity around −3.3 mV/°C has been achieved.
A fully integrated optical detector with a‐Si:H based color photodiodes
Authors: Watty Krystian , Merfort Christian , Seibel Konstantin , Schöler Lars , Böhm Markus
Published: January 2010

The fabrication of an electrophoresis separation microchip with monolithic integrated excitation light source and variospectral photodiodes for absorption detection is presented in this paper. Microchip based separation techniques are essential elements in the development of fully integrated micro‐total analysis systems (µ‐TAS). An integrated microfluidic device, like an application specific lab‐on‐microchip (ALM) (Seibel et al., in: MRS Spring Meeting, San Francisco, USA, 20051), includes all components, necessary to perform a chemical analysis on chip and it can be used as a stand‐alone unit directly at the point of sampling. Variospectral diodes based on hydrogenated amorphous silicon (a‐Si:H) technology allow for advanced optical detection schemes, because the spectral sensitivity of the devices can be tailored to fit the emission of specific fluorescent markers. Important features of a‐Si:H variospectral photodiodes are a high dynamic range, a bias‐tunable spectral sensitivity and a very good linearity for the separation of mixed color signals.

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Principle of ALM device
Structural models of a‐Si:H with a low defect concentration: A first‐principles molecular dynamics study
Authors: Jarolimek K. , de Wijs G. A. , de Groot R. A. , Zeman M.
Published: January 2010

We present a theoretical study of hydrogenated amorphous silicon (a‐Si:H) with a device quality hydrogen concentration of 11 at%. We used a first principle, parameters‐free method. The interaction between the atoms was treated quantum mechanically within the density functional theory approximation. Amorphous structures were prepared by cooling from the liquid phase. When using a cooling rate of 0.02 K/fs defect‐free structures were prepared. All silicon atoms were fourfold coordinated and there were no defect states in the band gap. The calculated short range order showed a good agreement with available neutron scattering measurements. We further calculated the formation energy of dangling bonds (DBs; threefold coordinated Si atom) in all three charge states (negative, neutral, and positive) as a function of the Fermi energy. Interestingly, the DB correlation energies can have both positive and negative values.
In situ measurements of surface (photo)voltage of roll‐to‐roll deposited thin film silicon solar cells
Authors: Van Aken Bas B. , Bakker Klaas J. , Heijna Maurits C. R. , Reid Dennis , Baikie Iain , Soppe Wim J.
Published: January 2010

The Kelvin probe is a non‐contact, non‐destructive vibrating capacitor device that measures the work function difference between a conducting sample and a vibrating tip. This contribution focuses on inline monitoring of the surface (photo)voltage of deposited silicon layers. We apply a custom‐built in situ Kelvin probe, operated in a roll‐to‐roll PECVD system, located immediately after the plasma zones to enable direct feedback to the controlling system of the plasma deposition. The surface photovoltage of nip thin film Si solar cells increases with increasing Voc. The results imply that inline, contactless measurements of the open‐circuit voltage are possible and that thus monitoring the doped layer quality during roll‐to‐roll production is feasible.
Investigation of crystalline orientation factor in microcrystalline silicon thin film deposition
Authors: Saito Kimihiko , Kondo Michio
Published: January 2010

Crystalline orientation factors in microcrystalline silicon (µc‐Si) deposition are investigated by the triode‐plasma enhanced chemical vapor deposition (PECVD) method and conventional diode‐PECVD with optical emission spectroscopy (OES). The existence of more important factors for the orientation than the ion and the [H]/[SiHx] ratio on the growing surface is suggested from the SiH4 flow rate and the mesh‐electrode gap dependence of the orientation and the crystallinity in triode‐PECVD. Improvement of the crystallinity and the independent orientation of the following film on the seed‐layer offer the deposition radicals to act a key role for the crystalline growth direction. The oligomerized‐silane radical (probably dimeric radical) is proposed as an orientation factor by the relation of SiH* emission intensity on the deposition rate and the orientation.
The study of structural changes of amorphous Ge2Sb2Te5 films after annealing by optical absorption spectroscopy
Authors: Gotoh Tamihiro , Kawarai Kenta
Published: January 2010

Optical absorption spectra of post‐annealed Ge2Sb2Te5 films were measured in the photon energy range from 0.5 to 3.5 eV. Optical absorption edge and Urbach slope parameter changed slightly with increase in annealing temperature and then abrupt changes occurred at around crystallization temperature. The band gaps of amorphous and cubic Ge2Sb2Te5 are 0.74 and 0.54 eV, respectively. The spectroscopic method is demonstrated to be suitable for evaluation of structural disorder and crystalline composition in phase‐change materials.
Medium‐range order in a‐Si:H films prepared from hydrogen diluted silane
Authors: Vavrunkova Veronika , van Elzakker Gijs , Zeman Miro , Sutta Pavol
Published: January 2010

A systematic and detailed analysis of the influence of hydrogen (H2) dilution of silane (SiH4) on the structural properties of thin hydrogenated silicon (Si:H) films was carried out. The Si:H films were prepared by plasma enhanced chemical vapour deposition method at different H2 to SiH4 flow ratios (R) ranging from R = 0 to 40. A detailed structural analysis was carried out by X‐ray diffraction (XRD). In order to suppress the XRD intensity from the substrate, Si:H films were deposited onto a [100]‐oriented single‐crystalline silicon substrate and XRD was carried out with a thin‐film attachment. The XRD analysis demonstrated that the first diffraction peak in the Si:H films corresponded to the signal from silicon hydride (Si4H) ordered domains having tetragonal lattice structure. The full width of half maximum (FWHM) of the peak was decreasing with increasing H2 dilution, and remained nearly constant for R ≥ 20. The FWHM values confirmed that the Si:H films grown at R ≥ 20 are more ordered than films deposited at lower R. This trend was confirmed by the Raman spectroscopy from the analysis of the shift of the Raman amorphous peak.
Modulated surface textures using zinc‐oxide films for solar cells applications
Authors: Isabella Olindo , Moll Folkert , Krč Janez , Zeman Miro
Published: January 2010

We present modulated surface textures on glass substrates for improved light trapping in thin‐film silicon solar cells. The surface morphology, the roughness spectral distribution, and the scattering properties of the modulated surface‐textured substrates were characterized. We deposited solar cells on the modulated surface‐textured substrates and observed enhancement in the performance compared to a solar cell deposited on textured ZnO:Al (reference) substrates.
Growth of stable amorphous silicon films by gas‐flow‐controlled RF plasma‐enhanced chemical vapor deposition
Authors: Niikura Chisato , Matsuda Akihisa
Published: January 2010

We proposed a multi‐hollow discharge‐based plasma‐enhanced chemical vapor deposition (PECVD) technique with gas‐flow control for preparation of highly stable a‐Si:H films at high rates. The conditions for multi‐hollow plasma production have been optimized under radio‐frequency (RF) and low pressure conditions. The effectiveness of the gas‐flow control has been confirmed. As a result, a‐Si:H films with a SiH2 density of 0 at.% were successfully obtained at a relatively high growth rate of 0.27 nm/s by the novel technique, even under RF conditions. Further optimization of electrode configuration and deposition conditions would improve the growth rate of a‐Si:H films with high stability against light soaking.
Properties of interfaces in amorphous/crystalline silicon heterojunctions
Authors: Olibet Sara , Vallat‐Sauvain Evelyne , Fesquet Luc , Monachon Christian , Hessler‐Wyser Aïcha , Damon‐Lacoste Jérôme , De Wolf Stefaan , Ballif Christophe
Published: January 2010

To study recombination at the amorphous/crystalline Si (a‐Si:H/c‐Si) heterointerface, the amphoteric nature of silicon (Si) dangling bonds is taken into account. Modeling interface recombination measured on various test structures provides insight into the microscopic passivation mechanisms, yielding an excellent interface defect density reduction by intrinsic a‐Si:H and tunable field‐effect passivation by doped layers. The potential of this model's applicability to recombination at other Si heterointerfaces is demonstrated. Solar cell properties of a‐Si:H/c‐Si heterojunctions are in good accordance with the microscopic interface properties revealed by modeling, that are, e.g., slight asymmetries in the neutral capture cross‐sections and band offsets. The importance of atomically abrupt interfaces and the difficulties to obtain them on pyramidally textured c‐Si is studied in combination with transmission electron microscopy.
Optimization of the in situ series connection of amorphous silicon solar modules on glass and foil substrates
Authors: Merz Rainer , Kistner Jens , Bouattour Mohamed Ali , Schubert Markus B.
Published: January 2010

Thin film solar cell technology allows for integrated monolithic series connection. During manufacturing of the cells, patterning steps in between the layer depositions form cell stripes and form the monolithic series connection between the front contact of one cell and the back contact of the adjacent one. The in situ series connection (ISSC) technology is not patterning in between the layer depositions but during the depositions. The patterning during layer deposition offers a couple of advantages over common laser scribing techniques. The in situ patterning does not break the vacuum or workflow to establish the monolithic series connection. The non‐thermal patterning enables the use of any flexible or rigid substrate like glass plates or polyethylene naphthalate (PEN) foil. We present the optimization of the wire pattering for plasma enhanced chemical vapor deposition and sputtering of highly conductive front contact material with three times improved shunt protection for an optimized production yield. Evaluating the interconnection losses of the ISSC projects interconnection losses down to 7% with optimized patterning. First amorphous silicon (aSi)‐based ISSC modules exhibit a total interconnection loss F = 15% on PEN foil. Moreover, for the first time we report on the successful implementation of the ISSC of aSi cells on rigid glass substrates.
Metastability in multicomponent oxide transistors
Authors: Jackson Warren B. , Hoffman Randy , Yeh Bao , Emery Tim , Koch Tim , McConica C. , Kwon Ohseung
Published: January 2010

Results of an investigation of bias stress metastability of multicomponent, zinc–indium and zinc–tin oxides, transistors are investigated. The bias stress as a function of various dielectrics, passivation layers, and illumination conditions indicate that for negative gate bias stressing defects often are created in the semiconductor, probably near or at the surface, particularly if the devices are unpassivated. Oxygen vacancy formation is a likely candidate. For many dielectrics, the positive gate bias metastability appears to be dominated by charge trapping within the insulator. For zinc–tin oxide devices, the kinetics of the metastability follows a stretched exponential behavior with a power law dependence on gate voltage. Correcting for the observed Meyer–Neldel behavior, the activation energy of τ is about 1.2 eV for defect generation and the disorder energy from β is about 0.06 eV. By using passivation, the best gate dielectrics and annealing protocols, we have reduced the bias stress metastability to about 0.1 V for a 25,000 s stress at 22 °C.
Structure and properties of silver doped SnSe2 and Ge2Sb2Te5 thin films prepared by pulsed laser deposition
Authors: Popescu M. , Velea A. , Sava F. , Lőrinczi A. , Tomescu A. , Simion C. , Matei E. , Socol G. , Mihailescu I. N. , Andonie A. , Stamatin I.
Published: January 2010

Amorphous thin films of SnSe2 and Ge2Sb2Te5 doped by different amount of silver (0.1, 0.2, 0.5 and 1 Ag atoms per formula unit) have been prepared by pulsed laser deposition (PLD) starting from solid polycrystalline targets. The films were investigated by X‐ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The good gas sensing properties for CO, as well as the sensitivity for CH4 and NO of the Ag doped SnSe2 films have been demonstrated in the composition SnSe2Ag0.2. The structural effect of silver introduced in Ge2Sb2Te5 matrix has been investigated. The freshly deposited thin films doped by various amount of Ag develop three phases: an amorphous one, and two crystalline phases consisting of a major fcc cubic phase of AgSbTe2 and a minor cubic phase of composition Ag2Te.
Relation of nanoscale and macroscopic properties of mixed‐phase silicon thin films
Authors: Fejfar A. , Vetushka A. , Kalusová V. , Čertík O. , Ledinský M. , Rezek B. , Stuchlík J. , Kočka J.
Published: January 2010

Scanning probe methods (SPMs) such as conductive atomic force microscopy (C‐AFM) can be used to probe the structure and local conductivity of the mixed phase silicon thin films with nanometer resolution. Effective medium approximations (EMAs) were used to relate the nanoscale properties with effective macroscopic properties for the dark conductivity measured with coplanar contacts. Comparison of the percolation threshold predicted by diffferent EMAs show partial correlation of the structure, with resistive amorphous phase coating the conductive grains. In sandwich structures (such as solar cells) the local fields may play important role: concentration of both optical and electrical internal fields to the tips of spherically capped conical microcrystalline grains. Adaptive higher‐order polynomial finite‐element methods (FEMs) were used to calculate the internal field distributions in the C‐AFM. The calculated values agree with the experimental C‐AFM, providing the first quantitative description of the relation of the nanoscale and macroscopic properties of the mixed phase Si films.
Chemical etching and surface oxidation studies of cadmium zinc telluride radiation detectors
Authors: Özsan M. E. , Sellin P. J. , Veeramani P. , Hinder S. J. , Monnier M. L. T. , Prekas G. , Lohstroh A. , Baker M. A.
Published: January 2010

CdZnTe (CZT) is commonly used as a radiation detector material and the surface properties are important as they influence detector performance. The surface chemistry is generally controlled through chemical etching and oxidation processes. In this paper, X‐ray photoelectron spectroscopy (XPS) is employed to investigate changes in the surface composition of single‐crystal Cd0.95Zn0.05Te samples after exposure to bromine in methanol (BM) chemical etching treatments and subsequent oxidation in air or 30% H2O2. BM treatment of CZT is found to result in a graded Te‐rich surface layer which increases in thickness as a function of BM concentration. Room‐temperature air oxidation of 0.2% BM‐treated CZT follows a logarithmic rate law. BM‐treated CZT exposed to 30% H2O2 for 30 s shows a linear increase in the TeO2 oxide thickness with increasing BM concentration up to a BM concentration of 1.5%. Above 2% BM concentration, the Te enrichment in the CZT surface region has reached saturation and is effectively pure Te. Copyright © 2010 John Wiley & Sons, Ltd.
X‐ray photoelectron spectroscopy study of the interaction of ultra‐thin alumina films on NiAl alloys with NaCl solutions
Authors: Bennour Inès , Maurice Vincent , Marcus Philippe
Published: January 2010

We report a XPS study of the reactivity in 0.5 M NaCl aqueous solution of NiAl(100) surfaces covered by ultra‐thin aluminium oxide films grown by thermal oxidation of the alloy at 900 °C. Detailed analysis of the film thickness, the oxide stoichiometry and the alloy composition below the oxide was performed to characterize the drastic modifications induced by chloride exposure. Chloride entry in the oxide was observed by AR‐XPS that revealed the existence of two chemical states of chlorides, one associated to aluminium oxide, the other one to aluminium hydroxide. The film modifications were initiated in the inner part and characterized by the formation of chloride‐containing hydroxide species. The growth of these species spread later to the entire film, accompanied by a marked thickening of the modified alumina layer by selective oxidation of the alloy. Longer immersion times (>20 h) led to the formation of mixed nickel–aluminium chloride‐containing hydroxide species, indicating the loss of corrosion protection. Copyright © 2010 John Wiley & Sons, Ltd.
Intelligent cognition‐based systems approach to multiple‐criteria computerized essay assessment
Authors: Cheng Shu‐Ling
Published: January 2010

With the advance of computational techniques, computerized assessment becomes increasingly popular due to the advantages of consistency, efficiency and labour‐saving. In computerized assessment, it evaluates the subject's performance based on the experts' assessment criteria and also criteria preferences, thus indicating an effort to implement expert assessment policy. The key element of developing the computerized assessment system is to measure the complexity of an expert's cognitive structures containing assessment criteria and criteria preferences. To achieve this goal, we present an intelligent cognition‐based systems approach which includes three integrated parts to build the computerized assessment model. It first utilizes text‐mining techniques to automatically around important meaning themes that frame as assessment criteria. Human experts' criteria preferences are then derived from the pre‐assessed essays by applying a multiple‐criteria decision analysis. Meanwhile, the optimal parameter set for the assessment system is determined using the genetic algorithm. To demonstrate its effectiveness, the essays of university students majoring in information management are empirically evaluated by the proposed method. The results show that the proposed method can not only effectively model expert cognitive structure but also report high classification accuracy under different assessment settings. Copyright © 2010 John Wiley & Sons, Ltd.
Verification support for ARINC‐653‐based avionics software
Authors: de la Cámara Pedro , Castro J. Raúl , Gallardo María del Mar , Merino Pedro
Published: January 2010

Software model checking consists in applying the most powerful results in formal verification research to programming languages such as
C. One general technique to implement this approach is producing a reduced model of the software in order to employ existing and efficient tools, such as
SPIN. This paper focusses on the application of this approach to the avionics software constructed on top of the Application Executive Software (APEX) Interface, which is widely employed by manufacturers in the avionics industry. It presents a method to automatically extract PROMELA models from the C source code. In order to close the extracted model during verification, we built a reusable APEX‐specific environment. This APEX environment models the execution engine (i.e. an APEX compliant real‐time operating system) that implements APEX services. In particular, it explains how to deal with aspects such as real‐time and APEX scheduling. Time is modelled in such a way that the we save time and memory by avoiding the analysis of irrelevant steps. This model of time and the construction of a deterministic scheduler guarantees the scalability of our approach. The paper also presents a tool that can verify realistic applications, and that has been used as a novel testing method to ensure the correctness of our APEX environment. This testing method uses SPIN to execute official APEX test cases. Copyright © 2010 John Wiley & Sons, Ltd.
Validation of volume measurements for fetal echocardiography using four‐dimensional ultrasound imaging and spatiotemporal image correlation
Authors: Uittenbogaard L. B. , Haak M. C. , Peters R. J. H. , van Couwelaar G. M. , Van Vugt J. M. G.
Published: January 2010

Objectives

To assess the accuracy and reliability of four‐dimensional (4D) ultrasound imaging using spatiotemporal image correlation (STIC) employing three different techniques to measure volumes in vitro.

Methods

Customized miniature balloons attached to a pump system were used to mimic fetal cardiac chambers. After the balloon model had been immersed in a bath filled with viscous gel, 4D datasets were acquired and three methods were used for volume analysis: three dimensional (3D) slice method, Virtual Organ Computer‐aided AnaLysis (VOCAL™) and VOCAL combined with inversion mode. Accuracy and measurement error were measured as the difference between the volume measurements and the actual volumes. Intraobserver reliability was assessed by computing coefficients of variation (CV) and intraclass correlation (ICC).

Results

Measurement of 76 different volumes, ranging from 0.30 to 4.95 mL, resulted in a total of 912 measurements. The 3D slice method had a mean error of −3.3%, the inversion method underestimated the volumes with a mean error of −6.1%, and VOCAL had a mean error of −2.9%. The 3D slice method had the best agreement (95% limits of agreement (LOA), −11.2 to 4.7%), followed by VOCAL (95% LOA, −14.1 to 8.3%); the inversion mode demonstrated the worst agreement (95% LOA, −21.4 to 9.2%). All three methods were reliable with CV < 10% and ICC > 0.95.

Conclusions

4D ultrasonography with STIC is a feasible and accurate method for calculating volumes of 0.30 mL upwards. In an in‐vitro model the 3D slice method proved accurate, was the least time consuming, had the best reliability and had the smallest LOA. This method may prove useful when applied to in‐vivo investigations. Copyright © 2010 ISUOG. Published by John Wiley & Sons, Ltd.
Quantitative three‐dimensional power Doppler angiography: a flow‐free phantom experiment to evaluate the relationship between color gain, depth and signal artifact
Authors: Martins W. P. , Raine‐Fenning N. J. , Ferriani R. A. , Nastri C. O.
Published: January 2010

Objectives

To evaluate the presence of false flow three‐dimensional (3D) power Doppler signals in ‘flow‐free’ models.

Methods

3D power Doppler datasets were acquired from three different flow‐free phantoms (muscle, air and water) with two different transducers and Virtual Organ Computer‐aided AnaLysis was used to generate a sphere that was serially applied through the 3D dataset. The vascularization flow index was used to compare artifactual signals at different depths (from 0 to 6 cm) within the different phantoms and at different gain and pulse repetition frequency (PRF) settings.

Results

Artifactual Doppler signals were seen in all phantoms despite these being flow‐free. The pattern was very similar and the degree of artifact appeared to be dependent on the gain and distance from the transducer. False signals were more evident in the far field and increased as the gain was increased, with false signals first appearing with a gain of 1 dB in the air and muscle phantoms. False signals were seen at a lower gain with the water phantom (−15 dB) and these were associated with vertical lines of Doppler artifact that were related to PRF, and disappeared when reflections were attenuated.

Conclusions

Artifactual Doppler signals are seen in flow‐free phantoms and are related to the gain settings and the distance from the transducer. In the in‐vivo situation, the lowest gain settings that allow the detection of blood flow and adequate definition of vessel architecture should be used, which invariably means using a setting near or below the middle of the range available. Additionally, observers should be aware of vertical lines when evaluating cystic or liquid‐containing structures. Copyright © 2010 ISUOG. Published by John Wiley & Sons, Ltd.
Three‐dimensional ultrasound of the pelvic floor 2 days after first delivery: influence of constitutional and obstetric factors
Authors: Falkert A. , Endress E. , Weigl M. , Seelbach‐Göbel B.
Published: January 2010

Objectives

Morphological changes of the pelvic floor during pregnancy and delivery can be visualized by three‐dimensional (3D) perineal ultrasound. The aim of this study was to compare biometric measurements of the levator ani muscle according to maternal constitutional factors, delivery mode and size of the baby immediately after the first delivery.

Methods

In this prospective observational study, 130 primiparae were recruited (all of them Caucasians with singleton pregnancy and cephalic presentation). A 3D perineal ultrasound scan was performed on the second day after delivery with standardized settings. Volumes were obtained at rest and on Valsalva maneuver, and biometric measurements of the levator hiatus were determined in the axial plane. Different obstetric and constitutional parameters were obtained from our clinical files.

Results

All biometric measurements of the levator hiatus were significantly greater in the vaginal delivery group than in the Cesarean section group (P < 0.001), whereas subgroup analysis within the vaginal (spontaneous vs. operative vaginal) and Cesarean (primary vs. secondary) delivery groups did not show statistically significant differences. There was no demonstrable influence of maternal constitutional factors (age, body mass index (BMI)) or different obstetric parameters (length of second stage of labor, episiotomy, maternal injuries) on levator hiatus size postpartum, even in subgroups that delivered vaginally. Women with de novo postpartum stress incontinence showed a significantly higher mean levator hiatus transverse diameter and larger hiatal area on Valsalva maneuver (P < 0.05). There was also a positive but very weak correlation between the newborn's head circumference and hiatal dimensions at Valsalva maneuver (P < 0.05).

Conclusions

Pelvic floor imaging by 3D ultrasound is easily accessible even on the first days after delivery and can provide useful information on morphological changes of the levator ani muscle. In our study, women with vaginal or operative vaginal delivery had a significantly larger hiatal area and transverse diameter than women who delivered by Cesarean section. Maternal constitutional factors (BMI, age) and duration of second stage of labor had no influence on the biometric measurements of hiatal area, whereas weight and head circumference of the baby showed a positive correlation with area of the levator hiatus. Copyright © 2010 ISUOG. Published by John Wiley & Sons, Ltd.
Jointly multi‐user detection and channel estimation with genetic algorithm
Authors: Ciriaco Fernando , Abrão Taufik , de Toledo Antonio Fischer , Jeszensky Paul Jean E.
Published: January 2010

This work aims at proposing the use of the evolutionary computation methodology in order to jointly solve the multi‐user channel estimation (MuChE) and detection problems at its maximum‐likelihood, both related to the direct sequence code division multiple access (DS/CDMA). The effectiveness of the proposed heuristic approach is proven by comparing performance and complexity merit figures with that obtained by traditional methods found in literature. Simulation results considering genetic algorithm (GA) applied to multipath, DS/CDMA and MuChE and multi‐user detection (MuD) show that the proposed genetic algorithm multi‐user channel estimation (GAMuChE) yields a normalized mean square error estimation (nMSE) inferior to 11%, under slowly varying multipath fading channels, large range of Doppler frequencies and medium system load, it exhibits lower complexity when compared to both maximum likelihood multi‐user channel estimation (MLMuChE) and gradient descent method (GrdDsc). A near‐optimum multi‐user detector (MuD) based on the genetic algorithm (GAMuD), also proposed in this work, provides a significant reduction in the computational complexity when compared to the optimum multi‐user detector (OMuD). In addition, the complexity of the GAMuChE and GAMuD algorithms were (jointly) analyzed in terms of number of operations necessary to reach the convergence, and compared to other jointly MuChE and MuD strategies. The joint GAMuChE–GAMuD scheme can be regarded as a promising alternative for implementing third‐generation (3G) and fourth‐generation (4G) wireless systems in the near future. Copyright © 2010 John Wiley & Sons, Ltd.
Synchronization challenges in media access coordination for vehicularad hocnetworks
Authors: Blum Jeremy J. , Natarajan Rajesh , Eskandarian Azim
Published: January 2010

Vehicularad hocnetworks (VANETs) can support a wide range of future cooperative safety and efficiency applications. However, the node density and high demand for wireless media in these networks can lead to theTimeslot Boundary Synchronization Problem, in which increased transmission collisions occur due to back‐off timer synchronization. This paper proposes an enhancement to the wireless access in vehicular environments (WAVE) communications architecture to address this problem, called RAndom Propagation Initiation Delay for the Distributed Coordination Function (RAPID DCF). The effectiveness of RAPID DCF is evaluated through simulations of both single‐hop and multi‐hop emergency messages. In these simulations, RAPID DCF was able to improve message delivery rates by as much as 35% and reduce multi‐hop message latency by as much as 18%. Copyright © 2010 John Wiley & Sons, Ltd.
A Stackelberg game for resource allocation in multiuser cooperative transmission networks
Authors: Cong Li , Zhao Liqiang , Yang Kun , Zhang Hailin , Zhang Guopeng
Published: January 2010

In this paper, we consider the problem of stimulating cooperation and resource allocation in cooperative transmission networks. We formulate this problem as a sellers' market competition where a relay is willing to share its resource with multiple users. We use a Stackelberg game to jointly consider the benefits of the relay and the users. Firstly, the relay determines the price of relaying according to the user demand. Secondly, the users purchase the optimal amount of resources to maximize their utilities. Although the Nash equilibrium, i.e., the solution of the game, can be obtained in a centralized manner, we develop a distributed algorithm to search the Nash equilibrium, which is more applicable in practical systems. Also, the convergence conditions of the algorithm are analyzed. Simulation results show, by using the distributed algorithm, the relay and the users could determine what price should ask for and how much bandwidth should buy, respectively. Copyright © 2010 John Wiley & Sons, Ltd.
Power control for delay constrained multi‐channel communications using outdated CSI
Authors: Li Xiaochen , Cao Fengming , Dong Xihua , Wu Dapeng
Published: January 2010

In this paper, we study the power allocation scheme for a single user, multi‐channel system, e.g., orthogonal frequency‐division multiplexing (OFDM) systems, under time‐variant wireless fading channels. We assume the receiver feeds back perfectly estimated channel state information (CSI) to the transmitter after a processing delay. The objective of the power allocation is to maximize throughput subject to quality‐of‐service (QoS) constraint. The QoS measure of our consideration is a triplet of data rate, delay, and delay bound violation probability. A two‐step sub‐optimal power allocation scheme is proposed to address the impact of outdated CSI. In the first step, the total transmission power that can be used within one block is determined according to the summation of the channel gains of all the channels. In the second step, the total transmission power is allocated among all the channels. The proposed power control scheme is less sensitive to the feedback delay. Compared to the optimal power allocation scheme designed for the perfect CSI scenario, it has lower computational complexity while achieving comparable capacity. Copyright © 2010 John Wiley & Sons, Ltd.
Efficient multiplicity calculation for algebraic soft‐decision decoding of Reed—Solomon codes
Authors: An Jianping , Jiang Tao , Li Xiangming , Li Anxin , Kayama Hidetoshi
Published: January 2010

Soft‐decision decoding of Reed—Solomon (RS) codes consists of three key steps: multiplicity calculation, bivariate interpolation, and factorization. In this work, we investigate the first step, with the aim of reducing the complexity of multiplicity calculation. It is observed that the objective value of multiplicity calculation in Koetter and Vardy's (KV) algorithm can be expressed as an increasing function of independent parameter. Based on this fact, we propose to use bisection or golden section methods in multiplicity calculation. Simulation study demonstrates that our proposed approach can significantly reduce the computational complexity of RS codes decoding. Copyright © 2010 John Wiley & Sons, Ltd.