910 research outputs found
Performance and non-destructive evaluation methods of airborne radome and stealth structures
No full textIn the past few years, great effort has been devoted to the fabrication of highly efficient, broadband radome and stealth (R&S) structures for distinct control, guidance, surveillance and communication applications for airborne platforms. The evaluation of non-planar aircraft R&S structures in terms of their electromagnetic performance and structural damage is still a very challenging task. In this article, distinct measurement techniques are discussed for the electromagnetic performance and non-destructive evaluation (NDE) of R&S structures. This paper deals with an overview of the transmission line method and free space measurement based microwave measurement techniques for the electromagnetic performance evaluation of R&S structures. In addition, various conventional as well as advanced methods, such as millimetre and terahertz wave based imaging techniques with great potential for NDE of load bearing R&S structures, are also discussed in detail. A glimpse of in situ NDE techniques with corresponding experimental setup for R&S structures is also presented. The basic concepts, measurement ranges and their instrumentation, measurement method of different R&S structures and some miscellaneous topics are discussed in detail. Some of the challenges and issues pertaining to the measurement of curved R&S structures are also presented. This study also lists various mathematical models and analytical techniques for the electromagnetic performance evaluation and NDE of R&S structures. The research directions described in this study may be of interest to the scientific community in the aerospace sectors.
Recent advances in thin and broadband layered microwave absorbing and shielding structures for commercial and defense applications
No full textThe development of cost-effective, lightweight, wideband microwave absorbing and shielding (MA&S) structures with exotic electromagnetic and mechanical properties is a complex task for academia and industry. The microwave absorption and shielding properties of materials can be significantly improved by the application of layered structures. In this article, an attempt is made to critically analyze and understand the current state of layered MA&S structures and their development directions. This article presents a critical and systematic review of the design and implementation of advanced and diversified layered MA&S structures such as nanocomposite, honeycomb, pyramidal, metamaterial and plasma structures. The objective of this article is to assist in the material and geometry selection process for the development of layered MA&S structures. The theory and operating principle of layered MA&S structures is briefly sketched with attention paid to the electromagnetic mixing models and optimization strategies. This article aims to address various issues associated with such a rapidly expanding field. This article also offers a perspective on the experimental efforts towards the development of efficient layered MA&S structures. This article will be helpful for academicians and scientists dealing with the design and development of electromagnetic structures for distinct practical electromagnetic applications.
Microwave absorption properties of FSS-impacted composites as a broadband microwave absorber
No full textThe development of a cost-effective microwave absorber with wide bandwidth corresponding to reflection loss (RL) <= -10 dB is still a very challenging task. A sugarcane bagasse-based agricultural waste composite has been analyzed for its elemental contents. The combination of elements is suitable for its possible usage as a cost-effective microwave absorbing material. Therefore, this composite has been subjected to morphological and electromagnetic studies to analyze its microwave absorbing behavior. The frequency dependent complex dielectric permittivity and complex magnetic permeability values were obtained using a transmission/reflection waveguide approach in the X-band. Furthermore, the effect of the Minkowski loop frequency selective surface (FSS) was studied over the absorption capability of the composite. It was found that the application of FSS leads to a reduction in thickness up to 2.9 mm and an enhancement in absorption bandwidth up to 3.6 GHz. The FSS patterned composite shows a remarkable performance with peak RL of -28.4 dB at 10.7 GHz and absorption bandwidth of 3.6 GHz.
Sweetners perception of polyols
No full textThis Dissertation / Report is the outcome of investigation carried out by the creator(s) / author(s) at the department/division of Central Food Technological Research Institute (CFTRI), Mysore mentioned below in this page
Ovarian Clear Cell Adenofibroma of Low Malignant Potential developing into Clear Cell Adenocarcinoma
No full textOvarian clear cell adenofibroma is uncommon, and borderline clear cell adenofibroma (low malignant potential) is extremely rare. Borderline clear cell adenofibromas may represent the precursor lesion of clear cell adenocarcinoma of the ovary, but this has not been established. We present a case of a woman in her mid-fifties with a clear cell adenofibroma ranging from benign to borderline to frankly invasive. While some clear cell adenocarcinomas are thought to arise from endometriosis, this range of findings supports the theory that some ovarian clear cell adenocarcinomas originate from borderline tumors.Peer reviewe
Scoping study of research trends on Nili Ravi buffalo applying scientometric analysis and network visualization
No full textThe study elucidates scientometric analysis of published scientific communications on Nili Ravi buffalo in journal(s) for having an appraisal of status-quo of the research and scientific activities. Metadata of 383 articles retrieved from Scopus were analysed to identify the most productive author(s), institution(s) vis-a-vis countries and to ascertain their collaboration trends. Keyword based analysis was performed to provide an overview of the strength areas of research on Nili Ravi for better comprehension. The results revealed that the research efforts on Nili Ravi were discernible after the year 2005. All except 1.30% articles have been an outcome of the collaborative authorship. There were only few productive authors with ≥10 records, but others contributed on the subject occasionally. Nearly 90% of the articles have been contributed by Pakistan and its' authors have worked in close collaboration with scientists from United Kingdom, United States of America, China, Canada, and South Korea. They also have conjoint symbiosis on academic/research endavours on Nili Ravi with experts from Austria, Netherlands, India, Germany, Italy, and Australia. Twelve leading institutions contributed to ≥10 articles. Publication outcome of the Animal Sciences Institute, National Agricultural Research Centre, Islamabad, Pakistan; Pir Mehr Ali Shah Arid Agriculture University, Rawalpindi, Pakistan; University of Gujrat, Gujrat, Pakistan and Semen Production Unit, Qadirabad, Sahiwal, Pakistan has higher Relative Citation Impact (RCI), making it obvious that their publication(s) have wider acceptance amongst scientific populace. Most productive vis-à-vis impactful journals publishing articles on Nili Ravi have also been identified
Massive Cellular Angiofibroma of the Vulva
No full textCellular angiofibromas of the vulva are uncommon, and usually small and circumscribed. A massive cellular angiofibroma extending into the pelvis is described.Peer reviewe
Development of Metamaterials Based Electromagnetic Structures
No full textMetamaterials (MM) are artificial or synthetic structures which possess unique properties such as negative permittivity (ε), permeability (µ), and refractive index, etc. The unique and useful properties of MM are offered by the shape, size, and arrangements of the unit cell, rather than the composition of the material. Conventional absorbers having larger thickness resulting in bulky, expensive, and narrow bandwidth that are replaced by the MM based absorbers (MMA). By considering the disadvantage of the conventional absorbers, in this thesis, MM based absorbers and low radar cross-section (RCS) antennas have been investigated. First of all, in this thesis, two distinct MM-based absorbers are designed, simulated, and measured in the range of 2 to 18 GHz. The first MMA is a hybrid structure that comprises of a cross-loaded split ring. The other proposed structure comprises eight sectors loaded circle inside the square. The first MMA show the reflection coefficient (RC) is less than -10 dB from 8.5 to 16 GHz for the hybrid structure, which covers 7.5 GHz bandwidth. The other proposed structure exhibits the four RC resonant peaks of -25.9 dB, -18.9 dB, -16.1 dB, and -21.3 dB are noticed at 4.4 GHz, 6.0 GHz, 14.1 GHz, and 16.0 GHz, respectively. To evaluate the optimized values of the distinct dimensions the parametric studies have been performed on both the structures. Further, an effort has been made to determine the angular stability and polarization sensitivity of the proposed structures. The frequency-dependent EM properties of both structures are also demonstrated in this chapter. Further, the surface current, electric (E) field, and magnetic (H) field distributions are also found. Finally, the proposed prototypes have been fabricated to evaluate the measured results. The free-space microwave measurement setup is used for the performance evaluation of the fabricated prototypes.
Next, an efficient tunable absorber based on an active frequency selective surfaces (AFSS) utilizing p-i-n diode is presented. Initially, the AFSS has been designed, simulated, and analyzed using the CST studio. Further, the design of the active absorber which is based on AFSS is also presented. Another study is executed on AFSS loaded absorber with diode and without diode, to know its effect on the absorption characteristics. A single-layered, tunable, wideband AFSS based absorber is presented, which demonstrates the tunability in the range of 9.2 GHz to 11.2 GHz. To obtain the tunability AFSS loaded absorber with different values of resistance has been evaluated. The normalized impedance, surface current, E field, and H field distributions are also presented. Finally, the proposed prototype has been fabricated to evaluate the measured result.
Further, two low RCS antennas are developed, which are based on MM techniques. The first one is MM inspired antenna and the second one is flexible MM-based superstrate coupled MPA, which enhances the gain along with RCS reduction (RCSR) of the MPA. The proposed MM impinged MPA it can be concluded that the structure provides RCSR, without affecting the other radiation properties and volume of the antenna. The reflection coefficient bandwidth of the second proposed MPA is the 800MHz, though the RCS bandwidth of the primary antenna is 1.7 GHz and the RCS bandwidth of the proposed antenna is 8.1 GHz. The increment in gain is observed in the proposed antenna. It can be observed that the maximum gain attained by the primary antenna is equal to 6.6 dB, whereas the maximum gain of the proposed antenna is equal to 7.2 dB. To evaluate the optimized values of the distinct dimensions, parametric studies have been performed on both the structures. Finally, the proposed prototypes have been fabricated to evaluate the measured results. The performance evaluation of the fabricated antennas has been carried out using a microwave measurement setup. A good agreement has been observed between the simulated and measured results of all the prototypes
Ghana's labor market (1987-92)
No full textUsing the household survey and other data sources, the authors analyze returns to education and other aspects of Ghana's labor market profile from 1987 to 1991. The labor force grew slower than the population did between 1980 and 1990, but the supply of labor is expected to increase as the population of youth is expected to grow faster from 1990 to 2000. And labor force participation rates for 26- to 45-year-olds have been increasing rapidly. Over time, the average labor force participation rates of women have become equal to men's; that of children younger than 15 has remained unchanged at 38 percent. More than half of Ghana's child laborers are employed in agriculture. The formal sector's share of employment is on the decline, while the private informal sector's share has increased, especially in urban areas. Over time, the informal sector (in which most workers have a primary education or less) has absorbed more labor than the formal sector (in which most workers have middle or secondary schooling). Unemployment is pervasive in urban areas, and is less visible in rural areas. Labor productivity may not have increased and is possibly declining. Between 1987 and 1992, there was reverse migration, with many people moving from urban to rural areas, mostly for family reasons. Employment-related migration has also been on the increase. As is true elsewhere, the level of education affects participation in the labor force. Literacy rates for women are lower than those for men, which is one reason men dominate the private formal sector. The rate of return to education increases with higher education and work experience. The return for each additional year of schooling rangesfrom 4 percent to 6 percent in Ghana, quite high for a Sub-Saharan African country. Private and social returns to education are greater for primary than for secondary or postsecondary education.Public Health Promotion,Health Economics&Finance,Health Monitoring&Evaluation,Labor Policies,Environmental Economics&Policies,Health Monitoring&Evaluation,Environmental Economics&Policies,Health Economics&Finance,Labor Standards,Poverty Assessment
The value of intra-household survey data for age-based nutritional targeting
No full textThe object of this paper has been, first to develop a framework for upper-limit indicator targeting, and to illustrate it for age based targeting of nutrition interventions using data from the Philippines. Second, the authors provide quantitative estimates of the value of individual level information and of knowledge of the intra-household allocation of calories. For the sample, age proved to be a good indicator of undernutrition. However, this was not the case with household level calorie adequacy which rendered age less useful as a targeting instrument, at an often considerable calorie cost. Food sharing, on the other hand, truly rendered age less helpful as a targeting instrument because of within-household leakage. The authors conclude that the design of nutrition interventions can be very susceptible to the level of aggregation of available information. This is consistent with findings that while poverty or undernutrition rankings of groups defined on household level characteristics were not sensitive to the level of aggregation, the rankings of groups defined on individual characteristics were very sensitive. Perhaps the costs of collection of these intra-household data outweigh the benefits, but the experiments in this paper begin to answer questions about the costs of not collecting them.Poverty Lines,Youth and Governance,Science Education,Scientific Research&Science Parks,Health Monitoring&Evaluation
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