Search results

The purpose of this paper is to illustrate the new technical demands and reliability challenges to printed circuit board (PCB) designs, materials and processes when the transmission frequency increases from Sub-6 GHz in previous generations to millimeter (mm) wave in fifth-generation (5G) communication technology.

The approach involves theoretical analysis and actual case study by various characterization techniques, such as a stereo microscope, metallographic microscope, scanning electron microscope, energy dispersive spectroscopy, focused ion beam, high-frequency structure simulator, stripline resonator and mechanical test.

To meet PCB signal integrity demands in mm-wave frequency bands, the improving proposals on copper profile, resin system, reinforcement fabric, filler, electromagnetic interference-reducing design, transmission line as well as via layout, surface treatment, drilling, desmear, laminating and electroplating were discussed. And the failure causes and effects of typical reliability issues, including complex permittivity fluctuation at different frequencies or environments, weakening of peel strength, conductive anodic filament, crack on microvias, the effect of solder joint void on signal transmission performance and soldering anomalies at ball grid array location on high-speed PCBs, were demonstrated.

The PCB reliability problem is the leading factor to cause failures of PCB assemblies concluded from statistical results on the failure cases sent to our laboratory. The PCB reliability level is very essential to guarantee the reliability of the entire equipment. In this paper, the summarized technical demands and reliability issues that are rarely reported in existing articles were discussed systematically with new perspectives, which will be very critical to identify potential reliability risks for PCB in 5G mm-wave applications and implement targeted improvements.

The objective of this paper is to perform infrared (IR) face recognition efficiently with convolutional neural networks (CNNs). The proposed model in this paper has several advantages such as the automatic feature extraction using convolutional and pooling layers and the ability to distinguish between faces without visual details.

A model which comprises five convolutional layers in addition to five max-pooling layers is introduced for the recognition of IR faces.

The experimental results and analysis reveal high recognition rates of IR faces with the proposed model.

A designed CNN model is presented for IR face recognition. Both the feature extraction and classification tasks are incorporated into this model. The problems of low contrast and absence of details in IR images are overcome with the proposed model. The recognition accuracy reaches 100% in experiments on the Terravic Facial IR Database (TFIRDB).

Databases New STN databases. In conjunction with the opening of an STN service centre in Japan, STN introduced a new English‐language file on the STN network: JICST‐E (JICST File on Science, Technology and Medicine in Japan). The database contains English citations and abstracts and covers the literature published in Japan on all fields of science, technology and medicine. References are drawn from approximately 4,500 journals and other serials as well as conference proceedings and technical reports. The file contains over 400,000 citations from 1985. Updates will increase this number by 16,000 citations each month.

A description is given of the English Electric ‘Thesaurofacet’, a faceted classification and thesaurus covering engineering and related scientific, technical, and management subjects. A novel feature of the system is the integration of the classification schedules and thesaurus. Each term appears both in the thesaurus and in the schedules. In the schedules the term is displayed in the most appropriate facet and hierarchy: the thesaurus supplements this information by indicating alternative hierarchies and other relationships which cut across the classified arrangement. The thesaurus also controls word forms and synonyms and acts as the alphabetical index to the class numbers. The resulting tool is multipurpose, as easily applicable to shelf arrangement and conventional classified card catalogues as to co‐ordinate indexing and computerized retrieval systems. The reasons are given for modifying certain traditional facet techniques, including the choice of traditional disciplines for main classes, the lack of a ‘built‐in’ preferred order, and the me, in certain instances, of enumeration rather than synthesis to express multi‐term concepts. Methods of application of the Thesaurofacet in pre‐coordinate and post‐coordinate systems are discussed and a brief account is given of the techniques employed in its compilation.

This is a follow‐up study of a multimedia program developed as a student project by high school pupils. The initial study sought to determine what learners would gain from constructing multimedia programs for their peers. “Multimax” is a multimeter skills fixation simulation. The students who designed it acquired subject skills, multimedia authoring and teamwork skills that would benefit them in the context of lifelong learning. To investigate the usefulness of the product this follow‐up seeks to determine what the peers of the design team learnt when using the program. A formal, summative and dynamic evaluation of the program was designed and executed to determine its suitability for teaching multimeter skills to university engineering students. Both empirical and interpretive evaluation methods were used in a way to answer evaluation questions using both the quantitative and qualitative paradigms. It may be concluded that the objectives and outcomes of the learning opportunity are successfully reached. A number of content errors are a matter for concern, while the technical implementation requires a great deal of reconstruction.

The purpose of this paper is to know-how the university libraries are managing online databases, especially from the Maharashtra state of India. The focus is to study the difficulties and challenges faced by the university librarians.

In this descriptive research, survey of 15 university libraries was conducted. Seven universities are subscribing online databases apart from databases accessible under national consortia. A comprehensive questionnaire comprised of 16 sections and total 47 questions was designed for data collection. Personal contacts helped to a great extent to get back the questionnaire.

The study revealed that the university librarians are trying to cope up with the management of electronic resources. Major challenges are unawareness about the life cycle of electronic resources, lack of standard procedures, collection development and preservation policies, failed to conduct user information need surveys, negotiation skills, competencies of staff and so on.

The scope of the present research was to study the current practices of management of online databases subscribed by the university libraries in Maharashtra. Other types of electronic resources were not considered in the present study. It was found that out of 15 universities only seven universities subscribe the online databases apart from the databases provided by UGC-INFONET. Therefore, the data from these seven libraries were considered for analysis.

This study will provide the guidelines for managing online databases in academic libraries.

Very few studies are conducted to study the management of online databases by university librariesin India.

Transporting hydrogen through natural gas pipelines in blended compositions has been proven to be a highly feasible solution in the short term. However, under hydrogen-rich environments, steel structures are prone to hydrogen-induced damage (HID). Additionally, uncertainties in various parameters can significantly impact the performance evaluation of hydrogen pipelines. Efficient reliability and sensitivity analyses of medium- to high-strength steel pipelines considering HID have become a challenge. Therefore, the primary aim of this study is to address this issue.

This study first establishes reliability analysis models for medium- to high-strength steels, represented by X65 and X80. In these models, the effect of HID is expressed by reduced stress, and its statistical parameters are calculated. Then, a highly efficient enhanced first order reliability method (FORM) is proposed for pipeline reliability analysis. This method overcomes the oscillation and convergence issues of traditional FORM when dealing with certain problems and can compute negative reliability indices. The proposed reliability analysis method is applied to solve the constructed reliability models. Finally, a reliability sensitivity analysis is conducted on the models to identify the key variables affecting the reliability of medium- to high-strength steel pipelines under HID.

First, two reliability analysis examples are used to validate the effectiveness of the proposed enhanced FORM. Then, using this method to solve the constructed reliability models for X65 and X80 steel pipelines under HID reveals that, for both types of steel, the reliability indices decrease significantly when considering HID compared to cases without HID. The decline is more pronounced for X80 steel than for X65 steel. As internal pressure increases, the reliability of both steels drops sharply, showing a concave parabolic trend. Moreover, the reliability sensitivity analysis shows that at a pressure of 10 MPa, for both X80 and X65, internal pressure, pipeline wall thickness and model error are the top three factors influencing reliability. As internal pressure increases, its influence becomes stronger, while the impact of other variables diminishes. Notably, for X80 steel, the presence of hydrogen amplifies the effect of internal pressure on pipeline reliability compared to when HID is not considered, but for X65, this trend is reversed.

Given the urgent need for safety evaluation studies on hydrogen transport through natural gas pipelines, this research provides new insights by constructing reliability models for X65 and X80 pipeline steels under HID and introducing an enhanced FORM method. The results of the reliability and sensitivity analyses of the models offer valuable insights and serve as a reference for engineering design.

As a clean and renewable energy source, wind energy will become one of the main sources of new energy supply in the future. Relying on the stable and strong wind resources at sea, wind energy has great potential to become the primary energy. As a critical part of the wind turbine, the gearbox of a wind turbine often bears a large external load. Especially at sea, due to the effects of ocean corrosion, waves and wind, the burden of the wind turbine gearbox is greater, which brings great challenges to its reliability analysis. This study aims to systematically review the reliability research in wind turbine gearboxes and guide future research directions and challenges.

This study systematically reviews some design requirements and reliability analysis methods for wind turbine gearboxes. Then, it summarizes previous studies on wind load uncertainty modeling methods, including the processing of wind measurement data and the summary of three different classifications of random wind speed prediction models. Finally, existing reliability analysis studies on two major parts of the gearbox are described and summarized.

First, the basic knowledge of wind turbine gearboxes and their reliability analysis is introduced. The requirements and reliability analysis methods of wind turbine gearboxes are explained. Then, the processing methods of wind measurement data and three different random wind speed prediction models are described in detail. Furthermore, existing reliability analysis studies on two common parts of wind turbine gearboxes, gears and bearings, are summarized and classified, including a summary of bearing failure modes. Finally, three possible future research directions for wind turbine gearbox reliability analysis are discussed, namely, reliability research under the influence of multiple factors on gears, damage indicators of bearing failure modes and quantitative evaluation criteria for the overall dynamic characteristics of offshore wind turbine gearboxes and a summary is also given.

This paper aims to systematically introduce the relevant contents of wind turbine gearboxes and their reliability analysis. The contents of wind speed data processing, predictive modeling and reliability analysis of major components are also comprehensively reviewed, including the classification and principle introduction of these contents.

The use of the Web by academic researchers is discipline‐dependent and highly variable. It is increasingly central for sharing information, disseminating results and publicising research projects. This pilot study seeks to identify the subjects that have the most impact on the Web, and look for national differences in online subject visibility. The highest impact sites were from computing, but there were major national differences in the impact of engineering and technology sites. Another difference was that Taiwan had more high impact non‐academic sites hosted by universities. As a pilot study, the classification process itself was also investigated and the problems of applying subject classification to academic Web sites discussed. The study draws out a number of issues in this regard, having no simple solutions and point to the need to interpret the results with caution.

New Officers for 1988/89 ‐ CCA administration for the coming two years will be in the hands of the following office‐bearers: