Effect of High Temperature Storage on AC Characteristics of Polymer Tantalum Capacitors

Replacement of MnO2 with conductive polymers as cathode materials in chip tantalum capacitors allows for a substantial reduction of the equivalent series resistance (ESR), improvement of frequency characteristics, and elimination of the possibility of ignition during failures. One of the drawbacks of chip polymer tantalum capacitors (CPTCs) is a relatively poor long-term stability at high temperatures. In this work, variations of capacitance, dissipation factor, and ESR in different types of capacitors including automotive grade parts from three manufacturers have been monitored during storage at temperatures from 100°C to 175°C for up to 18,000 h. Results show that ESR is the most and capacitance the least sensitive to degradation parameter. Times to parametric failures have been simulated using a Weibull-Arrhenius model that allowed for assessments of activation energies of the degradation and prediction of times to failure at the use temperature. Degradation of CPTCs was explained by thermo-oxidative processes in conductive polymers that result in exponential increasing of the resistivity with time of ageing. This process starts after a certain incubation period that depends on packaging materials and design and corresponds to the time that is necessary to form delamination between the encapsulating molding compound and lead frame. The effectiveness of the existing qualification procedures to assure stable operation of CPTCs is discussed.

DISTRIBUTED DEEP LEARNING FRAMEWORK FOR SMART BUILDING TRANSDUCER NETWORK

This work is devoted to the development of a distributed framework based on deep learning for processing data from various sensors that are generated by transducer networks that are used in the field of smart buildings. The proposed framework allows you to process data that comes from sensors of various types to solve classification and regression problems. The framework architecture consists of several subnets: particular convolutional net that handle input from the same type of sensors, a single convolutional fusion net that processes multiple outputs of particular convolutional nets. Further, the result of a single convolutional fusion net is fed to the input of a recurrent net, which allows extracting meaningful features from time sequences. The result of the recurrent net opera- tion is fed to the output layer, which generates the framework output based on the type of problem being solved. For the experimental evaluation of the developed framework, two tasks were taken: the task of recognizing human actions and the task of identifying a person by movement. The dataset contained data from two sensors (accelerometer and gyroscope), which were collected from 9 users who performed 6 actions. A mobile device was used as the hardware platforms, as well as the Edison Compute Module hardware device. To compare the results of the work, variations of the proposed framework with different architectures were used, as well as third-party approaches based on various methods of machine learning, including support machines of vectors, a random forest, lim- ited Boltzmann machines, and so on. As a result, the proposed framework, on average, surpassed other algorithms by about 8% in three metrics in the task of recognizing human actions and turned out to be about 13% more efficient in the task of identifying a per- son by movement. We also measured the power consumption and operating time of the proposed framework and its analogues. It was found that the proposed framework consumes a moderate amount of energy, and the operating time can be estimated as acceptable.

Effect of High Temperature Storage on AC Characteristics of Polymer Tantalum Capacitors

Replacement of MnO2 with conductive polymers as cathode materials in chip tantalum capacitors allows for a substantial reduction of the equivalent series resistance (ESR), improvement of frequency characteristics, and elimination of the possibility of ignition during failures. One of the drawbacks of chip polymer tantalum capacitors (CPTCs) is a relatively poor long-term stability at high temperatures. In this work, variations of capacitance, dissipation factor, and ESR in different types of capacitors including automotive grade parts from three manufacturers have been monitored during storage at temperatures from 100 °C to 175 °C for up to 18,000 hours. Results show that ESR is the most and capacitance the least sensitive to degradation parameter. Times to parametric failures have been simulated using a Weibull-Arrhenius model that allowed for assessments of activation energies of the degradation and prediction of times to failure at the use temperature. Degradation of CPTCs was explained by thermo-oxidative processes in conductive polymers that result in exponential increasing of the resistivity with time of ageing. This process starts after a certain incubation period that depends on packaging materials and design and corresponds to the time that is necessary to form delamination between the encapsulating molding compound and lead frame. The effectiveness of the existing qualification procedures to assure stable operation of CPTCs is discussed.

The specifics of the ironic in the Marc-André Hamelin’s creativity on the example of “Variations on a Theme of Paganini”

Background. From the era of romanticism to the present day there is a stable interest of world-renowned virtuoso musicians to such kind of creativity as transcription, which makes it possible to speak not only as a performer, but also to express themselves in the composer’s perspective. Many prominent pianists of different eras have made a significant contribution to this branch of musical art, we need only recall the names of F. Liszt, K. Tausig G. von Bulow, F. Busoni, L. Godowsky, Vladimir Horowitz, Glenn Gould. Among artists of our time, it should be noted the Canadian piano virtuoso and composer Marc-Andre Hamelin, for which transcriptions are characterized by a harmonious combination of technical complications and modernization of the selected thematic material, which provides his music a wide audience. A striking confirmation of this are the thousands of views of his transcriptions on the channel in YouTube. Perhaps one of the secrets of such popularity is not only the actualization of the musical language of the original, but also The article is devoted to the specifics of the ironic, as one of the manifestations of the comic, in creative heritage of the world-famous Canadian pianist and composer Marc-André Hamelin On material Of “Variations on a Theme of Paganini”, which are the most illustrative example in this perspective, the features of the artist’s work with a quote thematic material. Identifies certain dominants of the composer’s style, among them: the destruction elected canons, their modification and approach to the aesthetics of the modern world perception through the use of the musical language of the XX–XXI centuries, as well as the desire for harmonious unification, combining styles of different eras within one work. Objectives. The object of research is a musical composition; its subject of research is the identification of the specifics of the irony in the composer’s style. The purpose of the article is to consider the trends of manifestation of irony and the stylistic orientations in the composer’s work of Hamelin, referring to the most indicative in this aspect of the work “Variations on a Theme of Paganini”. Methodology. Structural-functional and genre-style methods are applied in the consideration of the compositional and stylistic specificity of “Variations on a Theme of Paganini”. To identify the peculiarities of the composer’s work with quotations, the method of comparative analysis was used. The methodological basis consists of the concepts of postmodern citation put forward by such leading researchers and representatives of postmodernism as Umberto Eco and Sigmund Bauman. Presenting the main material. The figure of Niccolo Paganini, enveloped in a mysterious halo, attracted the attention of contemporaries and many artists of subsequent generations, and his creative heritage found a significant response in the musical environment. One of the most famous works of N. Paganini has a cycle “Twenty-four capris” for solo violin, among which the most frequently used for a variety of composer’s interpretations was the theme of Caprice No. 24. Interesting is the fact that it remains relevant, continuing even in the twenty-first century to attract attention. A striking example of this is the Hamelin’s “Variations on a Theme of Paganini” (2011). This work, written for solo piano, is a dedication to the American composer, pianist, conductor, teacher Yehud Weiner and his wife Susan Dewen-Weiner. In his interpretation of Caprice 24, the composer chooses a free interpretation of his figurative and substantial side. This is evidenced not only by the increase in the number of variations (14 instead of 11), but also many other aspects that appear at different levels of composition of the whole. It turns out the specificity of the composer’s work with the quote material, which permeates the whole work, the tendency to its ironic interpretation, as well as harmonious coexistence within the work of styles of different eras, their combination. Results. This work is one of the most striking embodiments of the ironic in the work of the Canadian artist. Here is typical for his style work with the used material quote, the basis of which – the destruction of the selected sample, bringing atypical for the original harmonic, melodic, rhythmic turns. Most often such “curvature” is used at the first posted quote topics. The composer tends to synthesize several styles within the framework of the work, this is often achieved by combining one of the styles of past eras with the styles of modernity, while not contrasting, isolating, contrasting them, but creating a melodic, tonal-harmonic and compositional integrity. Conclusion. Hamelin’s “Variations on a Theme of Paganini” represent a vivid manifestation of the ideas of postmodern worldview in music, which is based on the ironic attitude to the sample of the past.

Analysis of causes of delay in Indian construction projects and mitigation measures

Purpose Construction projects in India continue to suffer excessive delays. This paper aims to investigate the delay causes in India by project sector (transport, power, buildings and water) and carry out a comparative study of delay causes in design build (DB) projects with that of design bid build (DBB) projects along with mitigation measures. Design/methodology/approach A questionnaire survey was conducted among major clients, contractors and consultants in India. Importance Index was used for ranking of the delay causes. Projects were categorized based on the type, and causes of delay in each project type were identified. Projects were also categorized based on type of contract, and delay causes in DB and DBB projects were compared. Statistical analysis of responses by Cronbach’s alpha, one-way analysis of variance, Kruskal–Wallis tests was carried out with Statistical Package for Social Sciences. Semi-structured in-depth interviews were conducted with senior industry professionals to develop exhaustive mitigation measures. Findings The research findings indicate finance-related causes as the most critical causes of delay in Indian projects. Delay in settlement of claims, contractor’s financial difficulties, delay in payment for extra work/variations by owner, late payment from contractor to subcontractor or suppliers, variation orders/changes of scope by owner during construction and changes in design by owner were the highly ranked delay causes. The research found no significant difference in the delay causes in DB and DBB projects. Originality/value This is the first study wherein delay causes for various project types within a single country are identified. In addition, the study has identified and compared the delay causes in DB projects and DBB projects. Mitigation measures developed in this study will help professionals and project managers not just in India but other developing countries as well to alleviate delay causes and in improvement of project timelines.

Specific LTR-Retrotransposons Show Copy Number Variations between Wild and Cultivated Sunflowers

The relationship between variation of the repetitive component of the genome and domestication in plant species is not fully understood. In previous work, variations in the abundance and proximity to genes of long terminal repeats (LTR)-retrotransposons of sunflower (Helianthus annuus L.) were investigated by Illumina DNA sequencingtocompare cultivars and wild accessions. In this study, we annotated and characterized 22 specific retrotransposon families whose abundance varies between domesticated and wild genotypes. These families mostly belonged to the Chromovirus lineage of the Gypsy superfamily and were distributed overall chromosomes. They were also analyzed in respect to their proximity to genes. Genes close to retrotransposon were classified according to biochemical pathways, and differences between domesticated and wild genotypes are shown. These data suggest that structural variations related to retrotransposons might have occurred to produce phenotypic variation between wild and domesticated genotypes, possibly by affecting the expression of genes that lie close to inserted or deleted retrotransposons and belong to specific biochemical pathways as those involved in plant stress responses.

Eating Out

In Virginia Woolf’s The Years (1937), Eleanor Pargiter observes a lower-middle-class couple in a restaurant, enjoying their time off after work. Variations of this scene appear in many novels of the 1930s; the restaurants and teashops where London’s lower middle class spent their lunch breaks and evening outings became the settings in which their behaviour, their cultural preferences and even their dreams could be scrutinised. Eleanor concludes after watching the self-conscious couple that their performance is borrowed from the movies and illustrated magazines. This performance consisted of glamour and ‘nonchalance’ – modes incompatible with their working lives, but perfectly fitting in establishments that offered ordinary people atmospheres far removed from their mundane routines. Although Woolf does not identify it as such, the scene probably takes place in a Lyons Corner House – one of the four grand central London teashops that provided their patrons not only with affordable food, but also with a visual spectacle that could rival the glitter of the West End and the glamour of cinemas.

Calculation of Temperature in Fracture for Carbon Dioxide Fracturing

Summary Carbon dioxide (CO2) temperature-field models in the wellbore and fracture are proposed to calculate transitions of fluid-phase states and variations of the fluid thermal-physical parameters during CO2 fracturing. The models take two items into account in the formula of the specific enthalpy: the internal energy and the flow work. The flow work is usually ignored for conventional hydraulic fracturing. When computing the CO2 temperature at the bottom of the hole, we find a 3.8°C deviation (well depth of 2000 m, injection temperature: –20°C) if the effects of the flow-work variations on the fluid temperatures are ignored. The phase states of CO2 vary from liquid to the supercritical state, and the position of the phase-state transition moves from inside the wellbore to the fracture. The fluid temperatures in the wellbore and fracture drop rapidly, whereas the pressures rise gradually. The temperature differences between the fracture fluid and the matrix-leakoff zone are small, and the cooling-formation distance increases with time and the injection rate.

Options for Chemical Modification of Wastes from a Brazilian Hardwood Species and Potential Applications

Two pathways for chemical modification of wastes from an Amazon hardwood species named Cordia goeldiana were proposed in this work. Variations in reaction time (2 h or 0.5 h) and temperature (80 and 150 °C), besides reaction medium (mechanical stirring or pressurized closed system) were tested for alkali treatment. NaOH at 5% was kept for both conditions. Afterwards, bleaching with H2O2 and NaOH was performed, but reaction conditions were held constant for both pathways. In general, the mild alkali treatment resulted mainly in the removal of extractives and hemicelluloses from the raw sawdust. The onset temperature and crystalline index increased. On the other hand, the use of higher pressure and temperature in alkali treatment at closed system had a remarkable lignin removal and crystalline index increase without changing cellulose polymorphism as the main effects, but thermal stability became lower. Apart from mineral residues removal, bleaching had negligible effects on fiber properties, suggesting that this procedure could be avoided.

Non-contact characterization of printed resistors

In this work we demonstrate the use of a high resolution non-contact scanning microwave microscope for characterization of printed resistors. The resonant microwave probe operates at a frequency of 5.73 GHz and it is based on a dielectric resonator coupled to a gold-coated tungsten tip with radius of 200 μm protruding from a cavity wall. Direct print additive manufacturing was used to produce the resistive films. Non-contact measurements of the resonant frequency fr and quality factor Q of the resonant microwave probe at a standoff distance of 20 μm were performed. Quality factor images were obtained over a scan area of 160 μm × 1670 μm in steps of 10 μm. Measurements reveal that Q varies from 214 to 233 over the studied region. In this work, variations in Q are associated with non-uniformities on the resistor surface. The quality factor of the probe was also acquired as a function of the tip-sample distance and measured data was fitted to a polynomial equation. We converted Q images to sheet resistance images using the polynomial equation and the material resistivity (400 Ω/sq/mil). Using the proposed approach, we found that the average sheet resistance over the scan area is Rs = 1027 W/sq and that Rs variations up to 662 Ω/sq, due to non-uniformities in the resistor's thickness, were detected by the microwave microscope. The localized microwave characterization capability demonstrated by the non-contact microscope could be of interest for defect detection in printed microwave circuits.