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The knowledge of the electrical properties of materials is inevitable in surface technologies, such as microtechnology, corrosion, etc. Concerning the surface phenomena, the work function represents the main property. It was developed by Lord Kelvin and it corresponds to the contact potential difference between two surfaces of materials. In this project, the data acquisition of Kelvin Probe System (KPS) was performed after sequential tests in electronic computing and physical fields in order to acquire the work function of conductor and semiconductor materials. This system has revealed the great importance of controlling the support voltage Vb calculating the capacitor applied to the Metal-Insulator-Semiconductor (MIS) structure in order to measure the surface potential of the semiconductors. Some problems were solved during the assembly of the system and the pertinent frequency of 50 Hz was suitably adjusted. However, the conversion of current-voltage was not carried out in KPS due to the insensitivity of the amplifiers on hand. To understand this difficulty in signal experimental study, we have used a calculation by a Fortran code. The latter has confirmed that the signal of Kelvin probe is a very weak amplitude of the order of pico-volts. Because of the available measuring devices whose sensitivity is much lower than the signal itself, on the other hand, these results justify the experimental steps. [ABSTRACT FROM AUTHOR]

This paper reports the effect of Fe incorporation on structural and electro-optical properties of ZnO thin films prepared by spin coating techniques. The Fe/Zn nominal volume ratio was 7 % in the solution. X-ray diffraction patterns of the films showed that doped incorporation leads to substantial changes in the structural characteristics of ZnO films. All the films have polycrystalline structure, with a preferential growth along the ZnO (002) plane. The crystallite size was calculated using a well-known Scherrer’s formula and found to be in the range of 22-17 nm. The highest average optical transmittance value in the visible region was belonging to the Fe doped ZnO film. The results of the Raman scattering confirmed the observations of XRD and UV-Vis analysis techniques by the appearance of these occupancies at Zn+2 sites. These results are explained theoretically and are compared with those reported by other workers. The results of Hall measurement of ZnO and ZnO:Fe thin films reveal a high electron concentration around 1016 cm–3 and low mobility 2.6 cm2/Vs. All as-grown samples show ambiguous carrier conductivity type (p-type and ntype) in the automatic Van der Pauw Hall measurement. A similar result has been observed in Li-doped ZnO and in As-doped ZnO films by other groups before. However, by characterizing our samples whit XPS, we have demonstrated that the ambiguous carrier type n in intended our ZnO films is not intrinsic behavior of the samples. It is due to the persistent photoconductivity effect in ZnO. [ABSTRACT FROM AUTHOR]

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The development of an effective strategy for the inspection and monitoring of the nation's critical bridges has become necessary due to aging, increased traffic loads, changing environmental conditions, and advanced deterioration. This article presents the development of a probabilistic mechanistic modeling approach supported by durability monitoring to obtain improved predictions of service life of concrete bridge decks exposed to chlorides. The application and benefits of this approach are illustrated on a case study of a reinforced concrete barrier wall of a highway bridge monitored over 10 years. It is demonstrated that service life predictions using probabilistic models calibrated with selected monitored field data can provide more reliable assessments of the probabilities of reinforcement corrosion and corrosion-induced damage compared to using deterministic models based on standard data from the literature. Such calibrated probabilistic models can help decision makers optimize intervention strategies as to how and when to repair or rehabilitate a given structure, thus improving its life cycle performance, extending its service life and reducing its life cycle cost. [ABSTRACT FROM AUTHOR]

This paper presents a system for the maintenance management of aging highway bridges that integrates two different approaches for deterioration modeling. Probabilistic state-based/time-based models are used to predict the macro-response of bridge components for network level analysis, while reliability-based mechanistic models are used to predict the micro-response of bridge components for project level analysis. Probabilistic state-based/time-based models are developed using qualitative performance indicators (condition ratings) that are determined through visual inspections to identify the overall condition of damaged components in a bridge network. Reliability-based mechanistic models are developed using quantitative performance indicators (physical parameters) that are determined through detailed condition surveys, analytical assessments, and empirical investigations to identify the extent and severity of specific deterioration mechanisms for safety critical structures and/or highly damaged components. The condition rating data obtained from the Ministére des Transports du Québec database and the condition assessment of the Dickson Bridge in Montreal, Canada were used to demonstrate the two approaches for predicting the deterioration of concrete bridge decks at the two levels of management of the integrated system. [ABSTRACT FROM AUTHOR]

The construction of new bridges and the maintenance and renewal of aging highway bridge network using ultra high performance concrete can lead to the construction of long life bridges that will require minimum maintenance resulting in low life cycle costs. Ultra high performance concrete (UHPC) is a newly developed concrete material that provides very high strength and very low permeability to aggressive agents such as chlorides from de-icing salts or seawater. Ultra high performance concrete could enable major improvements over conventional high performance concrete (HPC) bridges in terms of structural efficiency, durability, and cost-effectiveness over the long term. A simplified design approach of concrete slab on UHPC girders bridge using the Canadian Highway Bridge Design code and the current recommendations for UHPC design is proposed. An illustrative example demonstrates that the use of UHPC in precast-prestressed concrete girders yields a more efficient design of the superstructure where considerable reduction in the number of girders and girder size when compared to conventional HPC girders bridge with the same span length. Hence, UHPC results in a significant reduction in concrete volume and then weight of the superstructure, which in turn leads to significant reduction in the dead load on the substructure, especially for the case of aging bridges, thus improving their performance. La construction de nouveaux ponts ainsi que l’entretien et la réfection du réseau vieillissant des ponts autoroutiers par l’utilisation de béton à très haute performance, peut conduire à la construction de ponts à longue durée de vie qui demanderont un minimum d’entretien, permettant ainsi de faibles coûts du cycle de vie. Le béton à ultra haute performance (BUHP) est un nouveau béton qui fournit une très grande résistance et une très faible perméabilité aux agents chimiques tels que les chlorures provenant des sels de déglaçage et de l’eau de mer. Le BUHP pourrait permettre de grandes améliorations par rapport aux ponts conventionnels en béton haute performance en termes d’efficacité structurale, de durabilité et de rentabilité à long terme. L’article propose une approche simplifiée de conception des dalles de béton sur les ponts à poutres en UHPC en utilisant le Code canadien sur le calcul des ponts routiers et les recommandations courantes sur la conception des ouvrages en BUHP. Selon un exemple présenté, l’utilisation des BUHP dans les ponts en poutres de béton précontraint permet une conception plus efficace de la superstructure, permettant une réduction importante du nombre et de la taille des poutres par rapport aux ponts à poutres conventionnels en béton haute performance de la même portée. Ainsi, les résultats de l’utilisation des BUHP engendrent une réduction importante du volume de béton et, ainsi, du poids de la superstructure. Ceci résulte en une réduction importante de la charge permanente sur l’infrastructure, particulièrement dans le cas des ponts vieillissants, améliorant ainsi leur performance. [ABSTRACT FROM AUTHOR]

This article proposes a methodology for predicting the time to onset of corrosion of reinforcing steel in concrete bridge decks while incorporating parameter uncertainty. It is based on the integration of artificial neural network (ANN), case-based reasoning (CBR), mechanistic model, and Monte Carlo simulation (MCS). A probabilistic mechanistic model is used to generate the distribution of the time to corrosion initiation based on statistical models of the governing parameters obtained from field data. The proposed ANN and CBR models act as universal functional mapping tools to approximate the relationship between the input and output of the mechanistic model. These tools are integrated with the MCS technique to generate the distribution of the corrosion initiation time using the distributions of the governing parameters. The proposed methodology is applied to predict the time to corrosion initiation of the top reinforcing steel in the concrete deck of the Dickson Bridge in Montreal. This study demonstrates the feasibility, adequate reliability, and computational efficiency of the proposed integrated ANN-MCS and CBR-MCS approaches for preliminary project-level and also network-level analyses. [ABSTRACT FROM AUTHOR]

In general, state-of-the-art bridge management systems have adopted Markov-chain models to predict the future condition of bridge elements and networks in different environments when various maintenance actions are implemented. However, the categories used to describe the various possible environments for a bridge element are neither accurately defined nor explicitly linked to the external factors affecting the element deterioration. In this paper, a new approach is proposed to provide transportation agencies with an effective decision support tool to identify the categories that best define the environmental and operational conditions specific to their bridge structures. This approach is based on genetic algorithms to determine the combinations of deterioration parameters that best fit each environmental category. The proposed approach is applied to develop Markovian deterioration models for concrete bridge decks using actual data obtained from the Ministére des Transports du Québec. This application illustrates the ability of the proposed approach to correlate the definition of environmental categories to parameters, such as highway class, region, average daily traffic, and percentage of truck traffic, in an accurate and efficient manner. [ABSTRACT FROM AUTHOR]

Building maintenance management involves decision making under multiple objectives and uncertainty, in addition to budgetary constraints. This article presents the development of a multiobjective and stochastic optimization system for maintenance management of roofing systems that integrates stochastic condition-assessment and performance-prediction models with a multiobjective optimization approach. The maintenance optimization includes determination of the optimal allocation of funds and prioritization of roofs for maintenance, repair, and replacement that simultaneously satisfy the following conflicting objectives: (1) minimization of maintenance and repair costs, (2) maximization of network performance, and (3) minimization of risk of failure. A product model of the roof system is used to provide the data framework for collecting and processing data. Compromise programming is used to solve this multiobjective optimization problem and provides building managers an effective decision support system that identifies the optimal projects for repair and replacement while it achieves a satisfactory tradeoff between the conflicting objectives. [ABSTRACT FROM AUTHOR]

Studies the bus bar structure that minimizes wiring inductance in high power IGBT inverter. Role of wiring inductance in limiting the use of inverter; Application of the bus bar technology; Testing of two wiring structures; Techniques that permits low wiring inductance so that no snubber circuits are needed.

Conventional precast I-girder bridge systems are widely used in North America for short and medium spans, up to 45 m. Spliced standard precast I-girder segments made continuous by longitudinal posttensioning have been used for spans of up to 75 m, making them far more competitive with the steel plate girder and concrete box girder alternatives. The span and/or girder spacing capabilities of the standard I-sections of Nebraska University, Florida, American Association of State Highway and Transportation Officials-Precast/Prestressed Concrete Institute (AASHTO-PCI), and Canadian Prestressed Concrete Institute (CPCI) are determined for both spliced posttensioned and conventional pretensioned girder systems. This investigation shows that the Florida and Nebraska University I-sections are the most efficient girders for spliced posttensioned and conventional pretensioned bridges, respectively. Using a nonlinear optimization program, the optimum girder shape is found to be a bulb-tee for spliced posttensioned girders and a quasi-symmetrical I-section for conventional pretensioned girders. A new set of five I-sections that achieve a balanced efficiency for both spliced posttensioned and conventional pretensioned bridge girder systems are proposed. Three examples of alternative preliminary bridge designs using both the existing standard and the newly proposed I-sections illustrate the practicality of the presented results. [ABSTRACT FROM AUTHOR]