6,975 research outputs found
Fundamentals of PV Efficiency Interpreted by a Two-Level Model
Elementary physics of photovoltaic energy conversion in a two-level atomic PV
is considered. We explain the conditions for which the Carnot efficiency is
reached and how it can be exceeded! The loss mechanisms - thermalization, angle
entropy, and below-bandgap transmission - explain the gap between Carnot
efficiency and the Shockley-Queisser limit. Wide varieties of techniques
developed to reduce these losses (e.g., solar concentrators, solar-thermal,
tandem cells, etc.) are reinterpreted by using a two level model. Remarkably,
the simple model appears to capture the essence of PV operation and reproduce
the key results and important insights that are known to the experts through
complex derivations.Comment: 7 pages, 6 figure
Management and Complications of Arnold Chiari Hydrocephalus at Tertiary Health Care Center
Objective: to investigate the role of CT and MRI in diagnosis of Arnold chiari malformation of hydrocephalus and its treatment with VP shunt along with complications.
Study Design: Prospective study
Place and duration: Department of Neurosurgery, DG Khan Medical College from May 4, 2018 to May 4, 2019.
Methodology: Fifty patients of congenital hydrocephalus who were not treated previously were selected. Detailed history about disease and clinical examination of patients was performed. Follow ups were done at neurosurgery OPD. SPSS software for data analysis was used and mean ± SD, frequency and percentages were calculated for variables. P value ≤0.05 was considered as significant.
Results: Treatment in case of congenital hydrocephalus as VP shunt, intra-aneurysmal coiling, excision of meningomyelocele with VP shunt and suboccipital craniectomy + upper cervical laminectomy (scucl) were observed as 10%, 6%, 8% and 8% respectively. Twelve percent of patients were not treated.
Conclusion: CT and MRI are the main diagnostic tools for diagnosis of Arnold chiari malformation and VP shunt is the treatment of choice. Among complications of VP shunt infection of shunt and shunt block are the main complications
Response of Gaussian-modulated guided wave in aluminum: An analytical, numerical, and experimental study
The application of guided-wave ultrasonic testing in structural health monitoring has been widely accepted. Comprehensive experimental works have been performed in the past but their validation with possible analytical and numerical solutions still requires serious efforts. In this paper, behavior and detection of the Gaussian-modulated sinusoidal guided-wave pulse traveling in an aluminum plate are presented. An analytical solution is derived for sensing guided wave at a given distance from the actuator. This solution can predict the primary wave modes separately. Numerical analysis is also carried out in COMSOL® Multiphysics software. An experimental setup comprising piezoelectric transducers is used for the validation. Comparison of experimental results with those obtained from analytical and numerical solutions shows close agreement
A Short Review on the Development of Salt Tolerant Cultivars in Rice
Rice is staple food for half of the world. With a population of almost 9.6 billion by the year 2050, there is a dire need of developing techniques to improve the crop plants, not only in terms of better yield but also to withstand harsh environmental conditions and stresses like drought, temperature, flood and salinity. Salinity is second to drought stress and hence it is very important to develop crops tolerant to salinity stress. This review discusses the mechanisms of salt tolerance and the recent developments in understanding the complex tolerance phenomena. One way to address the salinity issue is to develop tolerant rice varieties using conventional and modern breeding techniques for which screening the rice germplasm for the varieties with desired traits is critical. Conventional methods to develop tolerant rice varieties are discussed along with modern biotechnology techniques are also discussed. Quantitative Trait Loci (QTL) and Marker Assisted Selection (MAS) are promising techniques. In addition to these modern techniques, some recent developments in the fields of transgenic plants, haploid breeding and Somaclonal variations have also been discussed. The limited knowledge about molecular and genetic mechanisms to tolerate abiotic stresses, however is a barrier to efficiently develop tolerant cultivars. A combination of conventional and modern biotechnology techniques could possibly open up the new ways
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