Xem 1-20 trên 217 kết quả Activation energy
  • A look on energy, renewable energies, energy storage and synthetic fuels, hybrid architecture, fuel cells, hydrogen as a vector of energy of the future.The Earth resources are quite limited in quantity Many challenges to mankind in 21st century: development, health, water, food, demography, education, energy.In physics, energy (Ancient Greek: ἐνέργεια energeia "activity, operation"[1]) is a quantity that is often understood as the ability a physical system has to produce changes on another physical system.

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  • AT THE transition to the new millennium the future of nuclear energy looks brighter. Nuclear power plants worldwide have operated safely. Applications for extension of reactor operating licenses in the U.S. are in place and construction is continuing abroad. Uses of isotopes and radiation in applications to medicine, research, and industry continue to assure human benefit. Research and development are active in the areas of controlled fusion, accelerator uses, isotope separation, space exploration, and excess weapons material disposition.

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  • In relation to studies and understanding of broad energy and pollution management issues, the U.S. National Academies have had an on-going program of cooperation with the Chinese Academies (Chinese Academy of Sciences and Chinese Academy of Engineering) for a number of years. Joint study activities date to the late 1990s and led to the publication in 2000 of Cooperation in the Energy Futures of China and the United States. This volume was the first examination of the broad energy questions facing both nations at the turn of the new millennium. ...

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  • A reaction happens need the energy to vibrate the molecules and the reactant concentration enough. The energy here is often provided by heat. However, in living system, high temperature may harm the biological structure Truly that the concentration in living system is very low. So living organisms solve these problems by using enzyme

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  • Although the vast majority of earthquakes that occur in the world each year have natural causes, some of these earthquakes and a number of lesser magnitude seismic events are related to human activities and are called “induced seismic events” or “induced earthquakes.” Induced seismic activity has been documented since at least the 1920s and has been attributed to a range of human activities including the impoundment of large reservoirs behind dams, controlled explosions related to mining or construction, and underground nuclear tests.

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  • Abstract Man is an omnivore and originally met energy requirements by hunting and gathering. Man evolved in an environment of feast and famine: there were periods with either a positive or negative energy balance. As an introduction to human energetics, this book on energy balance in motion starts with a chapter on animal energetics. How do animals survive and reproduce in an environment with a variable food supply? The examples on animal energetics illustrate how animals grow, reproduce and survive periods of starvation.

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  • The hypothalamic neuropeptides modulate physiological activity via G pro-tein-coupled receptors (GPCRs). Galanin-like peptide (GALP) is a 60 amino acid neuropeptide that was originally isolated from porcine hypo-thalamus using a binding assay for galanin receptors, which belong to the GPCR family.

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  • Fujishima and Honda (1972) demonstrated the potential of titanium dioxide (TiO2) semiconductor materials to split water into hydrogen and oxygen in a photo-electrochemical cell. Their work triggered the development of semiconductor photocatalysis for a wide range of environmental and energy applications. One of the most significant scientific and commercial advances to date has been the development of visible light active (VLA) TiO2 photocatalytic materials. In this review, a background on TiO2 structure, properties and electronic properties in photocatalysis is presented.

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  • Lecture Biology - Chapter 6 provides knowledge of energy, enzymes, and metabolism. In this chapter, students will be able to understand: What physical principles underlie biological energy transformations? What is the role of ATP in biochemical energetics? What are enzymes? How do enzymes work? How do enzymes work?

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  • Recent experiences from carrying out Design for Assembly (DFA) and Design for Manufacture (DFM) product studies in industry have reinforced the authors’ belief that consideration of manufacturing problems at the design stage is the major means available for improving product quality, reducing manufacturing costs and increasing productivity. In the second edition, as well as providing further information to help select processes for components and the joining of components, we have included data on assembly process selection and costing.

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  • Recycling of plastic materials is now an important field in the plastics industry, not just an activity born under environmental pressure. The recycling processes include industrial operations in which secondary materials are reprocessed and/or monomers recovered for further polymerization; such processes are termed secondary and tertiary recycling.

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  • Manufacturing is a vital activity for a society from a strategic point of view. It has a long history in human civilizations and gives a society a definite edge over its competitors. A manufacturing system can be viewed as an arrangement of tasks and processes, properly put together, to transform a selected group of raw materials and semi-finished products to a set of finished products. Historically, manufacturing activities have grown over centuries and their evolution can be divided into three stages....

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  • Over the past decade, there has been a prolific increase in the research, development and commercialisation of Wireless Sensor Networks (WSNs) and their associated technologies (see Figure 1). This rise has been a result of a number of contributing factors, including continued miniaturisation (leading towards an era of truly ‘pervasive’ and ‘invisible’ computing); low-power circuits, devices and computation (for example, the ultra-low-power sleep states now found in microcontrollers); and efficient short-range communication (such as ZigBee and Bluetooth).

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  • The municipal and industrial activities of the man affects human health, leads to degradation of the environment and even degradation of the objects built by himself or his predecessors. The pollutants are emitted to the atmosphere with off-gases from industry, power stations, residential heating systems and vehicles, some additional emissions come from the natural sources as volcanoes as well. Fossil fuels, which include coal, natural gas, petroleum, shale oil and bitumen are the main source of heat, electrical energy and are the basic duels for the engines of the transport vehicles....

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  • This book focuses on the very important and diverse field of vibration analysis and control.

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  • Introduction: A sustainable energy future with a stable global climate is central to the present worldwide debate on climate change due to the emissions of carbon dioxide (CO2), which is the main greenhouse gas (GHG) from human activities.

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  • Wastes are materials generated as a result of numerous anthropic activities and should be disposed to prevent environmental pollution which aff ects human health and contributes ecosystem degradation. Most of the environmental problems, which we are dealing with, are a result of improper management of wastes. In particular, fresh water resources are under serious stress throughout the globe. Water supply and water quality degradation are global concerns.

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  • This book is a compilation of some selected articles devoted to the analysis and control of vibrations. Vibrations are a phenomenon found in many engineering systems; their harmful effects are translated into low performance, noise, energy misspend, discomfort and system breakdown, among others. These are the reasons why, in the last years, researchers have made great efforts in seeking ways to eliminate them totally or partially.

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  • This book is based on recent research work conducted by the authors dealing with the design and development of active and passive microwave components, integrated circuits and systems. It is divided into seven parts. In the first part comprising the first two chapters, alternative concepts and equations for multiport network analysis and characterization are provided. A thru-only de-embedding technique for accurate on-wafer characterization is introduced.

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  • Vibrations are extremely important in all areas of human activities, for all sciences, technologies and industrial applications. Sometimes these vibrations are harmless, often they can be noticed as noise or cause wear. Vibrations, if they are not desired, can be dangerous. But sensibly organized and controlled vibrations may be pleasant (think of all kinds of music) or vitally imp

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