Segmented Electrodes for Piezoelectric Energy Harvesters

This letter studies the impact of electrode segmentation on energy harvesting with piezoelectrics. For cases where the load can be distributed, it is concluded that segmentation of electrodes helps to improve energy content by minimizing surface currents. Using a ribbon of polyvinylidene fluoride under tension as an example, we show that using a six segmented electrode improves energy content by a factor of 2.5. Power delivery remains almost constant except for an anomalous increase when the number of segments is made large. Models are developed to predict improvements in energy content and power delivery.

Capacity of Gaussian Channels With Energy Harvesting and Processing Cost

Energy harvesting sensor nodes are gaining popularity due to their ability to improve the network life time and are becoming a preferred choice supporting green communication. In this paper, we focus on communicating reliably over an additive white Gaussian noise channel using such an energy harvesting sensor node. An important part of this paper involves appropriate modeling of energy harvesting, as done via various practical architectures. Our main result is the characterization of the Shannon capacity of the communication system. The key technical challenge involves dealing with the dynamic (and stochastic) nature of the (quadratic) cost of the input to the channel. As a corollary, we find close connections between the capacity achieving energy management policies and the queueing theoretic throughput optimal policies.

Low-Cost Cloud-Based Design of Smart Rural Energy Device in Microgrid: Perspective India An Energy-On-Demand Service for Rural India

In this paper we present a combination of technologies to provide an Energy-on-Demand (EoD) service to enable low cost innovation suitable for microgrid networks. The system is designed around the low cost and simple Rural Energy Device (RED) Box which in combination with Short Message Service (SMS) communication methodology serves as an elementary proxy for Smart meters which are typically used in urban settings. Further, customer behavior and familiarity in using such devices based on mobile experience has been incorporated into the design philosophy. Customers are incentivized to interact with the system thus providing valuable behavioral and usage data to the Utility Service Provider (USP). Data that is collected over time can be used by the USP for analytics envisioned by using remote computing services known as cloud computing service. Cloud computing allows for a sharing of computational resources at the virtual level across several networks. The customer-system interaction is facilitated by a third party Telecom Service provider (TSP). The approximate cost of the RED Box is envisaged to be under USD 10 on production scale.

Achieving universal rural energy access in india: A low carbon pathway

India's energy challenges are three pronged: presence of majority energy poor lacking access to modern energy; need for expanding energy system to bridge this access gap as well as to meet the requirements of fast-growing economy; and the desire to partner with global economies in mitigating the threat of climate change. The presence of 364 million people without access to electricity and 726 million relying on biomass for cooking out of a total rural population of 809 million indicate the seriousness of challenge. In this paper, we discuss an innovative approach to address this challenge, which intends to take advantage of recent global developments and untapped capabilities possessed by India. Intention is to use climate change mitigation imperative as a stimulus and adopt a public-private-partnership-driven ‘business model' with innovative institutional, regulatory, financing, and delivery mechanisms. Some of the innovations are: creation of rural energy access authorities within the government system as leadership institutions; establishment of energy access funds to enable transitions from the regime of "investment/fuel subsidies" to "incentive-linked" delivery of energy services; integration of business principles to facilitate affordable and equitable energy sales and carbon trade; and treatment of entrepreneurs as implementation targets. This proposal targets 100% access to modern energy carriers by 2030 through a judicious mix of conventional and biomass energy systems with an investment of US$35 billion over 20 years. The estimated annual cost of universal energy access is about US$9 billion for a GHG mitigation potential of 213Tg CO2e at an abatement cost of US$41/tCO2e. It is a win-win situation for all stakeholders. Households benefit from modern energy carriers at affordable cost; entrepreneurs run profitable energy enterprises; carbon markets have access to CERs; the government has the satisfaction of securing energy access to rural people; and globally, there is a benefit of climate change mitigation.

Energy funneling and macromolecular conformational dynamics: a 2D Raman correlation study of PEG melting

Cascading energy landscapes through funneling has been postulated as a mechanistic route for achieving the lowest energy configuration of a macromolecular system (such as proteins and polymers). In particular, understanding the molecular mechanism for the melting and crystallization of polymers is a challenging fundamental question. The structural modifications that lead to the melting of poly(ethylene glycol) (PEG) are investigated here. Specific Raman bands corresponding to different configurations of the PEG chain have been identified, and the molecular structural dynamics of PEG melting have been addressed using a combination of Raman spectroscopy, 2D Raman correlation and density functional theory (DFT) calculations. The melting dynamics of PEG have been unambiguously explained along the C-O bond rotation coordinate.

Estimation of the 2.0(5) helix type i -> i hydrogen bond energy at Aib*-Oxa motif: an isodesmic approach

Bending at the valence angle N-C-alpha-C' (tau) is a known control feature for attenuating the stability of the rare intramolecular hydrogen bonded pseudo five-membered ring C-5 structures, the so called 2.0(5) helices, at Aib. The competitive 3(10)-helical structures still predominate over the C5 structures at Aib for most values of tau. However at Aib*, a mimic of Aib where the carbonyl 0 of Aib is replaced with an imidate N (in 5,6-dihydro-4H-1,3-oxazine = Oxa), in the peptidomimic Piv-Pro-Aib*-Oxa (1), the C(5)i structure is persistent in both crystals and in solution. Here we show that the i -> i hydrogen bond energy is a more determinant control for the relative stability of the C5 structure and estimate its value to be 18.5 +/- 0.7 kJ/mol at Aib* in 1, through the computational isodesmic reaction approach, using two independent sets of theoretical isodesmic reactions. (C) 2014 Elsevier Ltd. All rights reserved.

Effect of Input Source Energy on SASW Evaluation of Cement Concrete Pavement

A series of spectral analyses of surface waves (SASW) tests were conducted on a cement concrete pavement by dropping steel balls of four different values of diameter (D) varying between 25.4 and 76.2 mm. These tests were performed (1) by using different combinations of source to nearest receiver distance (S) and receiver spacing (X), and (2) for two different heights (H) of fall, namely, 0.25 and 0.50 m. The values of the maximum wavelength (lambda(max)) and minimum wavelength (lambda(min)) associated with the combined dispersion curve, corresponding to a particular combination of D and H, were noted to increase almost linearly with an increase in the magnitude of the input source energy (E). A continuous increase in strength and duration of the signals was noted to occur with an increase in the magnitude of D. Based on statistical analysis, two regression equations have been proposed to determine lambda(max) and lambda(min) for different values of source energy. It is concluded that the SASW technique is capable of producing nearly a unique dispersion curve irrespective of (1) diameters and heights of fall of the dropping masses used for producing the vibration, and (2) the spacing between different receivers. The results presented in this paper can be used to provide guidelines for deciding about the input source energy based on the required exploration zone of the pavement. (C) 2014 American Society of Civil Engineers.

Energy based approach for the evaluation of damage under partial slip and gross sliding condition

Three possible contact conditions may prevail at a contact interface depending on the magnitude of normal and tangential loads, that is, stick condition, partial slip condition or gross sliding condition. Numerical techniques have been used to evaluate the stress field under partial slip and gross sliding condition. Cattaneo and Mindlin approach has been adapted to model partial slip condition. Shear strain energy density and normalized strain energy release rate have been evaluated at the surface and in the subsurface region. It is apparent from the present study that the shear strain energy density gives a fair prediction for the nucleation of damage, whereas the propagation of the crack is controlled by normalized strain energy release rate. Further, it has been observed that the intensity of damage strongly depends on coefficient of friction and contact conditions prevailing at the contact interface. (C) 2014 Elsevier B.V. All rights reserved.

Consequences of Converting Graded to Action Potentials upon Neural Information Coding and Energy Efficiency

Information is encoded in neural circuits using both graded and action potentials, converting between them within single neurons and successive processing layers. This conversion is accompanied by information loss and a drop in energy efficiency. We investigate the biophysical causes of this loss of information and efficiency by comparing spiking neuron models, containing stochastic voltage-gated Na+ and K+ channels, with generator potential and graded potential models lacking voltage-gated Na+ channels. We identify three causes of information loss in the generator potential that are the by-product of action potential generation: (1) the voltage-gated Na+ channels necessary for action potential generation increase intrinsic noise and (2) introduce non-linearities, and (3) the finite duration of the action potential creates a `footprint' in the generator potential that obscures incoming signals. These three processes reduce information rates by similar to 50% in generator potentials, to similar to 3 times that of spike trains. Both generator potentials and graded potentials consume almost an order of magnitude less energy per second than spike trains. Because of the lower information rates of generator potentials they are substantially less energy efficient than graded potentials. However, both are an order of magnitude more efficient than spike trains due to the higher energy costs and low information content of spikes, emphasizing that there is a two-fold cost of converting analogue to digital; information loss and cost inflation.

Orbital phase resolved spectroscopy of GX 301-2 with MAXI

GX 301-2, a bright high-mass X-ray binary with an orbital period of 41.5 d, exhibits stable periodic orbital intensity modulations with a strong pre-periastron X-ray flare. Several models have been proposed to explain the accretion at different orbital phases, invoking accretion via stellar wind, equatorial disc, and accretion stream from the companion star. We present results from exhaustive orbital phase resolved spectroscopic measurements of GX 301-2 using data from the Gas Slit Camera onboard MAXI. Using spectroscopic analysis of the MAXI data with unprecedented orbital coverage for many orbits continuously, we have found a strong orbital dependence of the absorption column density and equivalent width of the iron emission line. A very large equivalent width of the iron line along with a small value of the column density in the orbital phase range 0.10-0.30 after the periastron passage indicates the presence of high density absorbing matter behind the neutron star in this orbital phase range. A low energy excess is also found in the spectrum at orbital phases around the pre-periastron X-ray flare. The orbital dependence of these parameters are then used to examine the various models about mode of accretion on to the neutron star in GX 301-2.

Determination of Internal Structures of Heterogeneous Nanocrystals Using Variable-Energy Photoemission Spectroscopy

This article describes the determination of the internal structure of heterogeneous nanoparticle systems including inverted core-shell (CdS core and CdSe shell) and alloyed (CdSeS) quantum dots using depth-resolved, variable-energy X-ray photoelectron spectroscopy (XPS). A unique feature of this work is the combination of photoelectron spectroscopy performed at lower X-ray energies (400-700 eV), to achieve surface sensitivity, with bulk sensitive measurements at high photon energies (>2000 eV), thereby providing detailed information about the whole nanoparticle structure with a great accuracy. The use of high photon energies furthermore allows us to investigate nanoparticles much larger than those studied thus far. This capability is a consequence of the much-increased mean free path of the photoelectron achieved at high excitation energies. Our results show that the actual structures of the synthesized nanoparticles are considerably different from the nominal, targeted structures, which can be post facto rationalized in terms of the reactivity of different constituents.

Propensity to Form Amyloid Fibrils Is Encoded as Excitations in the Free Energy Landscape of Monomeric Proteins

Protein aggregation, linked to many of diseases, is initiated when monomers access rogue conformations that are poised to form amyloid fibrils. We show, using simulations of src SH3 domain, that mechanical force enhances the population of the aggregation-prone (N*) states, which are rarely populated under force free native conditions but are encoded in the spectrum of native fluctuations. The folding phase diagrams of SH3 as a function of denaturant concentration (C]), mechanical force (f), and temperature exhibit an apparent two-state behavior, without revealing the presence of the elusive N* states. Interestingly, the phase boundaries separating the folded and unfolded states at all C] and f fall on a master curve, which can be quantitatively described using an analogy to superconductors in a magnetic field. The free energy profiles as a function of the molecular extension (R), which are accessible in pulling experiments, (R), reveal the presence of a native-like N* with a disordered solvent-exposed amino-terminal beta-strand. The structure of the N* state is identical with that found in Fyn SH3 by NMR dispersion experiments. We show that the timescale for fibril formation can be estimated from the population of the N* state, determined by the free energy gap separating the native structure and the N* state, a finding that can be used to assess fibril forming tendencies of proteins. The structures of the N* state are used to show that oligomer formation and likely route to fibrils occur by a domain-swap mechanism in SH3 domain. (C) 2014 Elsevier Ltd. All rights reserved.

Deformation of nanograined Ni-60Co alloy with low stacking fault energy

The evolution of deformation texture in a Ni-60Co alloy with low stacking fault energy and a grain size in the nanometre range has been investigated. The analyses of texture and microstructure suggest different mechanisms of deformation in nanocrystalline as compared to microcrystalline Ni-60Co alloy. In nanocrystalline material, the mechanism responsible for texture formation has been identified as partial slip, whereas in microcrystalline material, a characteristic texture forms due to twinning and shear banding.