Thermoelectrics generating electricity from waste heat is a step closer

first_img Citation: Thermoelectrics generating electricity from waste heat is a step closer (2011, May 6) retrieved 18 August 2019 from https://phys.org/news/2011-05-thermoelectrics-electricity-closer.html A thermoelectric material consists of alternating n-type and p-type semiconductors that together convert heat into electricity. In theory the heat could be sourced from any process that generates heat, but at present the materials are too inefficient to provide a commercially feasible way of generating electricity from waste heat, such as that produced in car exhausts. The most common thermoelectric p-type material in use is based on lead telluride (PbTe) and devices based on this material have been used in satellites, with heat sourced from radioisotopes, and in niche markets on Earth, where the heat is generated by burning fuels such as gas. The efficiency of the thermoelectric material is expressed as a “thermoelectric figure of merit,” ZT, which is a dimensionless figure derived from several factors including the electrical conductivity and thermal conductivity. The figure of merit needs to be over 1.5 for the material to be capable of generating useful amounts of electricity in commercial applications. PbTe thermoelectric materials are capable of withstanding high temperatures, but their figures of merit are around 0.8, which makes them suitable only for niche markets such as satellites. Now physicists from the California Institute of Technology and the Chinese Academy of Sciences have modified the amount of tellurium in the PbTe alloy and added selenium and sodium to produce a material with a figure of merit of 1.8 at 850K, which lead author Dr. Jeffrey Snyder described as “extraordinary.” In previous research Snyder and colleagues had achieved a ZT of 1.5 by doping PbTe with thallium and 1.4 by using sodium. Adding selenium to the mix improved the electrical conductivity while also reducing the thermal conductivity. The selenium increases the number of “degenerate valleys” in the electronic band structure of the material, and this boosts the electrical conductivity and raises the ZT figure. Known thermoelectrics have a typical valley degeneracy of less than six, but the number for the new material is 12 or greater.Dr. Snyder said he thought a figure of merit of 1.8 was the highest ever to be reproduced in independent laboratories. He also suggested that doping other thermoelectrics in the same way should improve their performance.Dr. Snyder said the team is now working on creating a promising n-type material and in improving the p-type material’s effectiveness at higher temperatures. The paper is published in Nature. Image credit: Nature, doi:10.1038/nature09996. (PhysOrg.com) — Scientists in China and the US have modified a common thermoelectric material to vastly improve its thermoelectric properties. The development could lead to new devices capable of converting waste heat into useful amounts of electricity. Explore further © 2010 PhysOrg.com More information: Convergence of electronic bands for high performance bulk thermoelectrics, Nature 473, 66–69 (05 May 2011) doi:10.1038/nature09996AbstractThermoelectric generators, which directly convert heat into electricity, have long been relegated to use in space-based or other niche applications, but are now being actively considered for a variety of practical waste heat recovery systems—such as the conversion of car exhaust heat into electricity. Although these devices can be very reliable and compact, the thermoelectric materials themselves are relatively inefficient: to facilitate widespread application, it will be desirable to identify or develop materials that have an intensive thermoelectric materials figure of merit, zT, above 1.5 (ref. 1). Many different concepts have been used in the search for new materials with high thermoelectric efficiency, such as the use of nanostructuring to reduce phonon thermal conductivity2, 3, 4, which has led to the investigation of a variety of complex material systems5. In this vein, it is well known6, 7 that a high valley degeneracy (typically ≤6 for known thermoelectrics) in the electronic bands is conducive to high zT, and this in turn has stimulated attempts to engineer such degeneracy by adopting low-dimensional nanostructures8, 9, 10. Here we demonstrate that it is possible to direct the convergence of many valleys in a bulk material by tuning the doping and composition. By this route, we achieve a convergence of at least 12 valleys in doped PbTe1 − xSex alloys, leading to an extraordinary zT value of 1.8 at about 850 kelvin. Band engineering to converge the valence (or conduction) bands to achieve high valley degeneracy should be a general strategy in the search for and improvement of bulk thermoelectric materials, because it simultaneously leads to a high Seebeck coefficient and high electrical conductivity. Promising new material that could improve gas mileage This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.last_img read more

Microsoft offers 20000 payouts for Kinect apps

first_img More information: www.microsoft.com/bizspark/kinectacceleratorblogs.msdn.com/b/kinectforwind … ding-the-future.aspx The 10 top company applications, chosen by Microsoft after a competitive screening process, will have three months next year to deliver. The plan calls for work to begin March and continue through May in Seattle. Each Kinect Accelerator participant gets an Xbox development, the Windows Kinect SDK, plus office space.Microsoft’s idea is characteristically targeted toward more business. Just as its ecosystem of outside developers and technology partners helped build apps through the years for Windows and its digital dashboard, an ecosystem beyond Redmond can help grow Kinect and related Microsoft products.Microsoft says it just wants to help companies explore. “We have seen many interesting uses of the technology in the short time Kinect has been in market so we are excited to see new ideas and which companies will apply.”What the project gives to Microsoft is the advantage of more and more businesses leveraging Kinect for Xbox or Windows. What it offers participants is a unique chance not only to bag some money but work alongside key Microsoft staffers. Mentors for the Kinect Accelerator include entrepreneurs and venture capitalists in the industry as well as staffers from Microsoft Studios, Xbox, Microsoft Research and other Microsoft units.What types of apps will make the Microsoft people salivate? The answer, according to Microsoft, goes something like ‘Surprise Us.’ Suggested areas include retail, education, healthcare and art installations to name a few. According to the project’s criteria list, it can be any Kinect-enabled application on Windows or Xbox that can be a commercial business.Ten companies will be chosen to take part and they can be startups or already established. No prior experience developing with the Kinect is required but the business concept needs to leverage Kinect capabilities. The application has to apply to the Xbox 360 as well as other platforms.Microsoft will stage an Investor Demo Day where each participant will present to angel investors, venture capitalists, Microsoft executives. Microsoft’s Kinect is a motion-sensing input device that was launched as a controller-free gaming device so that kids and adults could play their living room games without having to clutch a controller. Visionaries in and outside of Redmond, however, easily see possibilities outside gaming that leverage new types of computing experiences. Kinect’s future beyond gaming also is seen in hospital operating rooms, classrooms and in business. Microsoft Kinect makes moves on computers (PhysOrg.com) — Microsoft has launched a project where it will give 10 companies $20,000 each for making the best use of Kinect on Windows or the Xbox. The project is Microsoft’s strategic push for extending creative and engaging application prototypes outside gaming environments. Applications are being accepted now through January 25th, 2012. The Kinect Accelerator is to be an on-site, Seattle-based incubator project. Explore furtherlast_img read more

Research shows copepods use pheromones to find mates

first_img Citation: Research shows copepods use pheromones to find mates (2014, January 28) retrieved 18 August 2019 from https://phys.org/news/2014-01-copepods-pheromones.html (Phys.org) —Copepods are tiny crustaceans, only millimeters long. Distributed sparsely in sea and fresh water, hundreds of body lengths may separate them. Oceanographer Laurent Seuront and biological physicist H. Eugene Stanley wanted to know how these small creatures find mates, as it would be unlikely for them to bump into each other accidently. In a study published in the Proceedings of the National Academy of Sciences, they determined that copepods change their movement patterns in response to pheromones produced by the opposite sex. One cubic meter of water may contain only a few copepods. As distances between individuals are very great, they cannot wait for chance encounters and must actively pursue potential mates in order for their species to survive. Because the strategy for locating mates must work over long distances, relative to the animals’ size, hydromechanical signals would not be effective, as such signals decay quickly. Therefore, it is likely that copepods use pheromones to find each other. Biologists already know that female copepods leave chemical trails, which males follow. However, previous experiments examining male trail-following behavior studied copepods in still water, in a laboratory environment. Copepods often live in turbulent environments, at the ocean’s surface and in estuaries, and Seuront and Stanley wanted to see how turbulence would affect the crustaceans’ responses to chemical signals.The researchers studied two copepod species found in the northern hemisphere: Temora longicornis, which lives in coastal waters, and Eurytemora affinis, which lives in estuaries. They placed male and females of both species in coastal or estuarial water that simulated their natural environments. Before placing the subjects in the water, Seuront and Stanley conditioned the water by placing various concentrations of copepods of the opposite sex in it and allowing them to remain there for 24 hours.Seuront and Stanley found that conditioning the water affected how the subjects moved. As the concentration of opposite sex copepods used to condition the water increased, movements became less random. Eventually, when the density was high enough, subjects began displaying movements associated with intense search strategies that depend on focusing on cues. These movements suggested that the copepods were reacting to pheromones released in the water during conditioning.Females and non-virgin males of both species displayed this change in movement pattern. However, virgin T. longicornis and E. affinis males did not show any response to female-conditioned water. This suggests that females have an innate response to male pheromones, while the male response to female pheromones is learned. The researchers think that as males gain mating experience, they learn how the pheromone field created by females can help them locate mates. Explore further Open wide: Zebrafish fool fast food Journal information: Proceedings of the National Academy of Sciencescenter_img Copepod. Credit: Uwe Kils/Wikipedia This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. © 2014 Phys.org More information: Anomalous diffusion and multifractality enhance mating encounters in the ocean, Laurent Seuront, PNAS, DOI: 10.1073/pnas.1322363111AbstractFor millimeter-scale aquatic crustaceans such as copepods, ensuring reproductive success is a challenge as potential mates are often separated by hundreds of body lengths in a 3D environment. At the evolutionary scale, this led to the development of remote sensing abilities and behavioral strategies to locate, to track, and to capture a mate. Chemoreception plays a crucial role in increasing mate encounter rates through pheromone clouds and pheromone trails that can be followed over many body lengths. Empirical evidence of trail following behavior is, however, limited to laboratory experiments conducted in still water. An important open question concerns what happens in the turbulent waters of the surface ocean. We propose that copepods experience, and hence react to, a bulk-phase water pheromone concentration. Here we investigate the mating behavior of two key copepod species, Temora longicornis and Eurytemora affinis, to assess the role of background pheromone concentration and the relative roles played by males and females in mating encounters. We find that both males and females react to background pheromone concentration and exhibit both innate and acquired components in their mating strategies. The emerging swimming behaviors have stochastic properties that depend on pheromone concentration, sex, and species, are related to the level of reproductive experience of the individual tested, and significantly diverge from both the Lévy and Brownian models identified in predators searching for low- and high-density prey. Our results are consistent with an adaptation to increase mate encounter rates and hence to optimize reproductive fitness and success.last_img read more

Researchers find greenhouse gas emissions from shale gas similar to that for

center_img (Phys.org) —A team of researchers with the Joint Institute for Strategic Energy Analysis, in the U.S. has found that greenhouse gas (GHG) emissions that occur during the lifecycle of shale gas when used as an energy source is roughly equal to that which occurs during the life cycle of conventional natural gas. In their paper published in Proceedings of the National Academy of Sciences, the team describes how they used a meta-analytical procedure they call harmonization to arrive at estimates for emissions of GHG due to extraction and use of shale gas. More information: Harmonization of initial estimates of shale gas life cycle greenhouse gas emissions for electric power generation, Garvin A. Heath, PNAS, DOI: 10.1073/pnas.1309334111AbstractRecent technological advances in the recovery of unconventional natural gas, particularly shale gas, have served to dramatically increase domestic production and reserve estimates for the United States and internationally. This trend has led to lowered prices and increased scrutiny on production practices. Questions have been raised as to how greenhouse gas (GHG) emissions from the life cycle of shale gas production and use compares with that of conventionally produced natural gas or other fuel sources such as coal. Recent literature has come to different conclusions on this point, largely due to differing assumptions, comparison baselines, and system boundaries. Through a meta-analytical procedure we call harmonization, we develop robust, analytically consistent, and updated comparisons of estimates of life cycle GHG emissions for electricity produced from shale gas, conventionally produced natural gas, and coal. On a per-unit electrical output basis, harmonization reveals that median estimates of GHG emissions from shale gas-generated electricity are similar to those for conventional natural gas, with both approximately half that of the central tendency of coal. Sensitivity analysis on the harmonized estimates indicates that assumptions regarding liquids unloading and estimated ultimate recovery (EUR) of wells have the greatest influence on life cycle GHG emissions, whereby shale gas life cycle GHG emissions could approach the range of best-performing coal-fired generation under certain scenarios. Despite clarification of published estimates through harmonization, these initial assessments should be confirmed through methane emissions measurements at components and in the atmosphere and through better characterization of EUR and practices. Citation: Researchers find greenhouse gas emissions from shale gas similar to that for conventional natural gas (2014, July 22) retrieved 18 August 2019 from https://phys.org/news/2014-07-greenhouse-gas-emissions-shale-similar.html Derrick and platform of drilling gas wells in Marcellus Shale – Pennsylvania. Credit: Wikipedia/ CC BY-SA 3.0last_img read more

Functional biological compass linked to light receptor protein

first_img More information: Cryptochrome 2 mediates directional magnetoreception in cockroaches. PNAS 2016 ; published ahead of print January 25, 2016, DOI: 10.1073/pnas.1518622113AbstractThe ability to perceive geomagnetic fields (GMFs) represents a fascinating biological phenomenon. Studies on transgenic flies have provided evidence that photosensitive Cryptochromes (Cry) are involved in the response to magnetic fields (MFs). However, none of the studies tackled the problem of whether the Cry-dependent magnetosensitivity is coupled to the sole MF presence or to the direction of MF vector. In this study, we used gene silencing and a directional MF to show that mammalian-like Cry2 is necessary for a genuine directional response to periodic rotations of the GMF vector in two insect species. Longer wavelengths of light required higher photon fluxes for a detectable behavioral response, and a sharp detection border was present in the cyan/green spectral region. Both observations are consistent with involvement of the FADox, FAD•− and FADH– redox forms of flavin. The response was lost upon covering the eyes, demonstrating that the signal is perceived in the eye region. Immunohistochemical staining detected Cry2 in the hemispherical layer of laminal glia cells underneath the retina. Together, these findings identified the eye-localized Cry2 as an indispensable component and a likely photoreceptor of the directional GMF response. Our study is thus a clear step forward in deciphering the in vivo effects of GMF and supports the interaction of underlying mechanism with the visual system. © 2016 Phys.org (Phys.org)—Many animals including birds and insects have been observed to perceive geomagnetic fields. Past studies have demonstrated that cryptochrome/photolyase family (CPF) light receptor proteins are involved in animal behavioral responses to the presence of geomagnetic fields, but so far, no studies have determined whether these proteins are linked with the direction of the magnetic field vector. Explore further This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. Monarch butterflies reveal a novel way in which animals sense the Earth’s magnetic fieldcenter_img Recently, an international collaborative of researchers explored the possibility that CPF proteins provide directional magnetosensitivity in cockroaches. By combining behavioral and genetic approaches, they demonstrated the first evidence that animal-type cryptochrome (Cry2) proteins are sensitive to the direction of geomagnetic fields in two cockroach species. They’ve published their results in the Proceedings of the National Academy of Sciences.In addition to their role in the detection of magnetic fields, Cryptochromes are also important in the regulation of the circadian cycle in many species, though they are likely not involved in the detection of light in mammals. At the outset of the research, the scientists developed an assay involving the American cockroach, Periplaneta americana, but when they realized that the species only expressed animal-type Cry2, they added Blatella germanica roaches, which express both Cry1 and Cry2.During resting cycles, around noon, roaches generally display minimal behavior. But when the direction of the horizontal magnetic vector of the geomagnetic field is rotated periodically, the animals become more active, changing their resting positions more frequently. This magnetically induced restlessness (MIR) was one observational basis the researchers used in the experiment.Observing no MIR when the roaches were in complete darkness, the researchers determined that photosensitive processes are involved with magnetosensitivity in P. americana roaches. To test the theory, they injected the roaches with double-stranded Cry2 RNA that significantly reduced the expression of Cry2, which completely abolished MIR behavior. While proving that MIR was not an endogenous activity of the roaches, this also knocked out their circadian rhythms. Other roaches tested in conditions of constant light developed arhythmic circadian cycles but did not demonstrate a loss of magnetoreception, proving the separation of geomagnetic field sensing and the circadian cycle. Thus, the researchers were able to associate the perception of geomagnetic fields with photoreception, separate from the circadian regulation.They tested seven wavelengths of light under different intensities to determine the conditions under which the animals could detect magnetic fields. They found that the magnetoreception depends on light from UV wavelengths to cyan/green 505 nm. Then they attempted to localize the site of magnetoreception by painting the compound eyes of the animals with black enamel. These roaches stopped expressing MIR behaviors altogether, strongly suggesting that Cry2 within the compound eyes is responsible for magnetoreception. The authors write, “Taken together, the results of our study establish the role of a mammalian-type Cry in light-dependent magnetoreception in two insect species phylogenetically distant to Drosophila. More important, our study delivers original evidence that the Cry2 protein is involved in the detection of geomagnetic field vector direction at natural intensities, which is a crucial feature of a biological receptor providing genuine compass bearings.” Journal information: Proceedings of the National Academy of Sciences Citation: Functional biological compass linked to light receptor protein (2016, February 4) retrieved 18 August 2019 from https://phys.org/news/2016-02-functional-biological-compass-linked-receptor.html Close up of a cockroach. Credit: Wikipedia/public domainlast_img read more

Quantum filter has 20000 Josephson junctions

first_img A small, inexpensive high frequency comb signal generator © 2016 Phys.org (Phys.org)—A team of researchers at CSIRO Manufacturing, in Australia has created several test quantum filters with arrays having as many as 20,000 Josephson junctions. In their paper published in Superconductor Science and Technology, the team describes their filters, how they were constructed, tuned and tested and several applications that they believe may benefit from their use. Explore further This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. More information: E E Mitchell et al. 2D SQIF arrays using 20 000 YBCO highJosephson junctions, Superconductor Science and Technology (2016). DOI: 10.1088/0953-2048/29/6/06LT01AbstractSuperconducting quantum interference filters (SQIFs) have been created using two dimensional arrays of YBCO step-edge Josephson junctions connected together in series and parallel configurations via superconducting loops with a range of loop areas and loop inductances. A SQIF response, as evidenced by a single large anti-peak at zero applied flux, is reported at 77 K for step-edge junction arrays with the junction number N = 1 000 up to 20 000. The SQIF sensitivity (slope of peak) increased linearly with N up to a maximum of 1530 V T−1. Array parameters related to geometry and average junction characteristics are investigated in order to understand and improve the SQIF performance in high temperature superconducting arrays. Initial investigations also focus on the effect of the SQUID inductance factor on the SQIF sensitivity by varying both the mean critical current and the mean inductance of the loops in the array. The RF response to a 30 MHz signal is demonstrated. The devices are a type of superconducting quantum interference filter, which work due to the use of arrays of superconducting interference devices—loops of superconductive material that is separated by Josephson junctions . Their purpose is to detect very small magnetic fields. In this new effort the researchers employed as many as 20,000 Josephson junctions in a single array which meant they were connected together in a series and in a parallel configuration all using loops. Josephson junctions in this context were devices made from two superconductive metals separated by a very thin insulator—current flowed via tunneling and it could be made to oscillate.The Josephson junctions were constructed with loop areas of different sizes, by adding in step-like bits on top of a magnesium-oxide base. They were then covered in a very thin layer of YBCO and then an even thinner layer of gold. The process was finished by etching to fashion the loops. The team describes their study of several parameters that were related to the geometry of the arrays and characteristics of the junctions under different conditions. They noted also that they focused mainly on the impact the inductance factor had on sensitivity, varying the current and inductance in the loops to fine tune their sensitivity. In testing their filters, the researchers found that they were able to detect a magnetic field as faint as 1 μT, which was several orders of magnitude better than devices currently in use. They also report that they were able to identify electromagnetic radiation at multiple frequencies. They suggest similar filters might be used in future magnetometers which are commonly used in geology studies. They add that they could also be used with analog to digital converters, in amplifier applications and as antennas. One restraining factor is that the devices can only be operated at extremely low temperatures. Citation: Quantum filter has 20,000 Josephson junctions (2016, May 3) retrieved 18 August 2019 from https://phys.org/news/2016-05-quantum-filter-josephson-junctions.html Journal information: Superconductor Science and Technologylast_img read more

Study identifies optimum human handthrowing techniques

first_img Explore further This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. Error propagation in throwing depends on the trajectory of the projectile. Underarm=ω0(ϕ)>0; overarm=ω0(ϕ)<0. (a) For a given target, there are generally multiple ways to strike it exactly; the solid red and green trajectories are two examples using an overarm and underarm style, respectively. The lightly shaded bands shows how uniformly distributed errors in position and velocity propagate; the overarm throw is more accurate. (b) The curve of launch parameters (ϕ,ω0(ϕ)) given by equation (2.4) that exactly strike the target. (c) Deviations away from this curve leads to an error (δxh)2 as a function of ϕ and ω. Error amplification is quantified by the maximal curvature of the valley of this surface. Credit: Royal Society Open Science (2017). DOI: 10.1098/rsos.170136 More information: M. Venkadesan et al. Optimal strategies for throwing accurately, Royal Society Open Science (2017). DOI: 10.1098/rsos.170136AbstractThe accuracy of throwing in games and sports is governed by how errors in planning and initial conditions are propagated by the dynamics of the projectile. In the simplest setting, the projectile path is typically described by a deterministic parabolic trajectory which has the potential to amplify noisy launch conditions. By analysing how parabolic trajectories propagate errors, we show how to devise optimal strategies for a throwing task demanding accuracy. Our calculations explain observed speed–accuracy trade-offs, preferred throwing style of overarm versus underarm, and strategies for games such as dart throwing, despite having left out most biological complexities. As our criteria for optimal performance depend on the target location, shape and the level of uncertainty in planning, they also naturally suggest an iterative scheme to learn throwing strategies by trial and error.Press release Journal information: Royal Society Open Science Humans have two basic ways of throwing—overhand or underhand. The approach used can impact accuracy, the researchers note, but there are other factors at play, as well. One example is throwing a basketball through a basketball net. During play, the action is fast, and there are other players attempting to steal the ball, so there are few if any attempts at underhand throwing. But, the researchers note, underhand throwing (aka granny style) when attempting to make free throws, can be more effective for players who practice the technique. The advantage, they note, is the way in which the ball approaches the target—when it comes in from just above the rimmed net, the target cross-section is relatively large, which means there is a better chance of the ball making it through the hoop than a ball that comes in at more of an angle. But the player has to have good control—sending the ball too high reduces the advantage, and sending it too low of course, removes all chances of success.The same science is at play in other throwing activities, they note, whether it is cricket, darts or tossing a waded paper at the waste can. Slower arcs, they found, result in better results. Faster throws cause an object to arrive at the target more quickly, but are generally less accurate. But there are exceptions to the success rule—such as when trying to toss accurately while at the same time attempting to prevent another player from hitting the object, such as in cricket or baseball.The researchers came to their conclusions by applying physics calculations to real-world throwing data, such as from studies of volunteers throwing paper wads into wastebaskets. They note also that accurate throwing is strictly human—monkeys throw things, they acknowledge, such as feces, but despite reports at zoos, they are very inaccurate.center_img Citation: Study identifies optimum human hand-throwing techniques (2017, April 26) retrieved 18 August 2019 from https://phys.org/news/2017-04-optimum-human-hand-throwing-techniques.html (Phys.org)—A pair of researchers with Harvard and Yale Universities has conducted a study of optimal human throwing techniques and found which work best under which conditions. In their paper published in the journal Royal Society Open Science, Madhusudhan Venkadesan and Lakshminarayanan Mahadevan describe how they combined physics with observed results to learn which techniques work best in which situations. Young baseball pitchers advised not to ignore shoulder pain © 2017 Phys.orglast_img read more

12316