共查询到20条相似文献，搜索用时 765 毫秒
1.
A. K. Shukla 《Resonance》2011,16(12):1294-1302
The intensity of solar radiation in the Earth’s direction from the Sun is approximately 1.361 kW/m2, a number also called the ‘solar constant’. Accordingly, it is estimated that the power Earth receives is about 96 billion
kilowatts from the Sun each second. If this colossal and unlimited energy could be more fully utilized, our dependence on
fast dwindling fossil cache will be drastically reduced. Solar energy is available in various forms such as direct solar radiation,
wind, wave power, rain (in the form of hydropower), photosynthesis and ocean thermal gradients. Among these, the direct conversion
of sunlight into electricity is clean and attractive. This article highlights various routes to directly harness electricity
from sunlight. 相似文献
2.
Ravi Mosurkal 《Resonance》2001,6(10):76-86
The dream of generating electricity from sunlight in large scale at low cost may not be that far from reality in this century.
Rapidly emerging solar energy technology using low cost dye sensitized photovoltaic cells on plastics would be a real boost
for the third world countries. Though the conventional silicon solar cells are efficient in converting solar energy into electricity
until now, the non conventional solar cells based on molecular photosensitization by colored materials in wide band gap semiconductors
is a fast growing field of basic scientific and industrial research. Present state-of-the-art cells using molecular dyes shows
energy conversion efficiencies of 10–11%. In this article, we present the concept of dye-sensitized photovoltaic (DSPV) cell
and the progress in current research. The important contributions of molecular dyes that are used as photosensitizers in these
photovoltaic or solar cells are also described. 相似文献
3.
With rising standards of living, the per capita energy consumption is increasing rapidly all over the world. The limited reserves of fossil fuels may be exhausted by the middle of the next century. This crisis situation has forced technologists to turn to alternate sources of energy, like wind energy, ocean thermal energy and solar energy. All the above forms of energy are indirectly derived from solar energy. In this article a short account of the amount of solar radiation reaching the earth, its spectral distribution and its interaction with the earth’s atmosphere is presented. A brief discussion is given on hydro-power, wind-power and ocean thermal energy conversion as indirect techniques of utilization of solar energy. Solar energy can also be directly converted into heat and electricity. Techniques for such direct conversion, with special reference to photovoltaic generation of electricity, are also described in this article. 相似文献
4.
The elusive neutrinos have periodically yielded their secrets to man and at each such juncture major advances have been achieved
in our understanding of the sub-atomic phenomena. These particles also carry invaluable information about the centre of the
Sun where energy is generated through nuclear fusion. In Part I of this article, history of the discovery of neutrinos is
traced, their properties and types are described. Also, the Standard Model which forms the basis of the structure of matter
and of which massless neutrinos are an integral part, is described. The role of neutrinos in solar energy generation and the
great ‘solar neutrino puzzle’ and its solution will be described later in the series. 相似文献
5.
Sheela K. Ramasesha 《Resonance》2013,18(5):440-457
The global warming issues were discussed in Part 1 of this series of articles. This part describes the different solar energy technologies that are available for generating electricity to meet our daily power requirement. The article focuses on different kinds of materials that can be used to make the photovoltaic cells. The most common photovoltaic cells are made with monocrystalline or polycrystalline silicon. The next generation photovoltaic cells are thin film based. The high efficiency multijunction and concentrated solar cell technologies are also introduced in this article. The concept of power generation using solar thermal energy is explained. In the Indian scenario, there are about 250–300 sunny days in most parts of the country. A brief summary of the solar sector achievements in the country is given. 相似文献
6.
The technological revolution that has finally permeated K-12 education has direct implications for modern teacher educators
whose “Hippocratic oath” is to best prepare future teachers for twenty-first-century classrooms. The goal of this article
is to suggest that the heart of sound technological implementation is to encourage students to use whatever tools are available
to explain the mathematical relations that underlie what they observe on the screen. We suggest ways in which Mishra and Koehler’s
construct of Technological Pedagogical Content Knowledge may be customized to provide a framework for guiding prospective
teachers’ efforts to develop and assess lesson plans that use technology in novel and effective ways. Data are presented in
the form of two contrasting case studies to illustrate the differing degrees to which prospective mathematics teachers leveraged
technology to teach themselves and their future students to explain the mathematics behind various topics. 相似文献
7.
Electromagnetic radiation is all around us, and essential for the survival of all lifeforms. It provides valuable information
about the physical world around us, feeds us by providing energy to plants, allows us to maintain human metabolism, and cures
us of various diseases. This article deals with the various properties of electromagnetic radiation, its sources and detectors,
its nature, and its uses. A brief discussion on the absorption spectrum of the Earth’s atmosphere and the atmospheric windows,
and celestial objects seen through optical and radio telescopes is also provided. 相似文献
8.
Conversion of sunlight to electricity with high conversion eficiencies at low cost is possible with emerging photovoltaic technologies. Organic–inorganic halide perovskite, a newcomer in the solar cell industry has proved its potential for increasing efficiency rapidly from 3.8% in 2009 to 22.1% in 2016. High efficiency, fiexibility, and cell architecture of the emerging hybrid halide perovskite have caught the attention of researchers and technologists in the field. This article focuses on the emergence, properties, and current research status of hybrid perovskite solar cells. 相似文献
9.
B. V. Sreekantan 《Resonance》2005,10(12):42-51
Cosmic rays are very high energy particles arriving from the depths of space and incident on the earth’s atmosphere at all
places and at all times. The energy of these particles extends over 12 decades from around 109 ev to 1021 ev and mercifully for the survival of life, the intensity falls by atleast 22 decades from about 100 particles/cm2/s to 1 particle/1000 km2 year. Cosmic ray research led to the discovery of many of the fundamental particles of nature in the 30’s, 40’s and 50’s
of this century and ushered in the era of ‘elementary particle physics’ at man-made accelerators. Even 86 years after the
discovery, the sources of these particles and the mechanism of acceleration continue to remain a mystery. 相似文献
10.
D. C. V. Mallik 《Resonance》2009,14(11):1032-1039
The Kodaikanal Observatory was established during the closing years of the 19th century to carry out scientific observations
of the Sun. John Evershed, an established amateur solar observer, came to Kodaikanal in 1907 as the Chief Assistant to the
Director and became the director of the observatory 4 years later. In 1909, he discovered the phenomenon of radial motion
of gases in sun spots, the earliest successful observation of velocity fields due to a complex magnetohydrodynamicalprocess
in actionin a celestial setting. Through Evershed’s work Kodaikanal became known as one of the premier solar observatories
in the world. 相似文献
11.
T. Padmanabhan 《Resonance》2008,13(4):312-318
The gravitational field of a massive, spherical, body like the Sun is described in general relativity by a solution to Einstein’s
equations called the Schwarzschild soution. Here is an elementary persepective on this solution, which — though far from a
rigourous derivation — raises intriguing questions.
T Padmanabhan works at IUCAA, Pune and is interested in all areas of theoretical physics, especially those which have something
to do with gravity.
This is based on an article originally published by the author in Physics Education, Vol. 23, No.1, p.47, 2006. 相似文献
12.
Harnessing sunlight for the production of electrical energy is an engrossing prospect. The crucial concept underlying the success of solar power stations is energy storage and its retrieval on demand which can be most effectively achieved with storage batteries. This article highlights the chemistry of existing and emerging battery technologies. 相似文献
13.
Sheela K. Ramasesha 《Resonance》2013,18(8):756-770
Wind energy, like solar energy, is a renewable form of energy that can be used to generate electricity using wind turbines. There are different kinds of wind turbines and a detailed discussion of each of these is given in the article. A brief introduction to the wind energy usage in India is also given. 相似文献
14.
T. P. Radhakrishnan 《Resonance》1998,3(12):4-12
The concept of individual molecules functioning as active devices has been around for a few decades. The active device size
has continuously decreased during this century, starting with meter-sized vacuum valve tubes of the early 1930’s and 40’s,
through millimeter-sized transistors in the 1960’s to micrometer-sized integrated circuits in the 1970’s and 80’s. Thus the
molecular scale devices represent the logical evolution to nanoscale devices expected towards the end of this century and
the beginning of the next. This article presents some examples to provide a glimpse of the activity in this area.
An erratum to this article is available at . 相似文献
15.
Georgia Liarakou Costas Gavrilakis Eleni Flouri 《Journal of Science Education and Technology》2009,18(2):120-129
Investigating knowledge, perceptions as well as attitudes of public that concern various aspects of environmental issues is
of high importance for Environmental Education. An integrated understanding of these parameters can properly support the planning
of Environmental Education curriculum and relevant educational materials. In this survey we investigated knowledge and attitudes
of secondary school teachers in Greece towards renewable energy sources, particularly wind and solar energy systems. A questionnaire
with both open and close questions was used as the main methodological instrument. Findings revealed that although teachers
were informed about renewable energy sources and well disposed towards these sources, they hardly expressed clear positions
regarding several issues about wind and solar energy technologies and farms. Moreover such themes are limited integrated in
teaching either as extra curricular educational programs or through the curriculum. These findings cannot confirm that teachers
could influence students’ opinion towards renewable energy systems. Thus, authorities should invest more in Environmental
Education and relevant Teachers' Education. 相似文献
16.
Leena Rao 《Resonance》2007,12(8):65-75
This article deals with various ‘supported’ acid catalysts developed as alternatives for the conventional ones in organic
synthesis. They have advantages such as producing less toxic waste and using less energy. 相似文献
17.
This article in two parts presents a brief overview of the Sun’s mysteries revealed from space observations, using recent
solar spacecrafts: Yohkoh, SOHO, TRACE and RHESSI. 相似文献
18.
G. Kallianpur 《Resonance》1999,4(1):32-35
In this article I will be concerned only with what I think are Wiener’s most important contributions to probability theory.
In the concluding section of this essay, I mention some of my personal reminiscences about him.
An erratum to this article is available at . 相似文献
19.
Manoj K. Harbola 《Resonance》2008,13(2):134-171
In this article we discuss how the concept of quantum of energy came into being from the analysis of black-body spectrum.
We start our discussion with the work of Wien who discovered the general form of black-body spectrum and on the basis of his
discovery proposed a formula to obtain power radiated from a black body as a function of its temperature and the frequency
of radiation. We then focus on the work of Planck who modified Wien’s formula to bring it in close agreement with the experimental
results. However, the real greatness of Planck is displayed in his interpretation of the modified formula that led him to
introduce the revolutionary concept of the quantum of energy. How Planck arrived at this conclusion is described in detail.
We conclude the article with a discussion of the generalization of the concept of quanta by Einstein to propose quantization
of radiation as well as of mechanical vibrations.
Manoj K. Harbola is a professor of physics at the Indian Institute of Technology, Kanpur. His area of research is in the field
of electronic structure of matter and he has contributed significantly to fundamental aspects of density functional theory
and applied it to study atoms, molecules, clusters and solids. 相似文献
20.
Solar energy is a natural resource which can be harnessed to provide clean electricity for hydrogen production systems. However, this technology is not widely used because of control issues, particularly for hydrogen refuelling stations. At present, direct or DC-DC converter couplings are the most common system configurations for hydrogen refuelling stations. However, these system configurations are costly and suffer from gas shortage at hydrogen refuelling stations. Furthermore, the hydrogen produced by such system configurations varies considerably depending on the levels of solar radiation. In order to address these issues, a new system configuration is proposed, incorporating the feedback signal of the storage level in the control system. The photo- voltaic （PV） system, electrolyzer, and storage tank are integrated with a fuzzy logic controller （FLC） to determine the backup current compensation for electrolyzer operation in order to obtain the minimum power required for hydrogen production. The proposed FLC is constructed with three input variables which are the PV current, hydrogen storage level, and the battery state of charge. The rules-based fuzzy inference process is based on the proposed configuration which combines the advantages of direct and DC-DC converter coupling configurations. The simulation results show that the proposed configuration offers better adapta- bility to variable radiation conditions compared to other methods. This gives a more promising option for ensuring the adequacy of hydrogen supply at hydrogen refuelling stations. 相似文献