Enhanced piezoelectric energy harvester performance using magnetic force and thermal energy

One possible approach of improving the performance of energy harvesters is to use energy harvester with an external magnetic force to create a nonlinear coupling system. In this work, we report experimental results of a single piezoelectric cantilever beam (PCB) with tip mass or conventional piezoelectric energy harvester (CPEH), and the effect of applying an external magnetic force. The output voltage and power at optimal resistance was 7.62 V and 0.62 mW, respectively, at the resonance frequency of approximately 11 Hz of a CPEH. Also, the output voltage and average power at optimal resistance was 8.56 V and 0.44 mW, respectively, at resonance frequency of 7 Hz of a PCB with fixed opposing magnet. Furthermore, the output voltage and average power at optimal resistance was 13.31 V and 1.77 mW, respectively, at resonance frequency of 11 Hz of a PCB with opposing magnet attached at a second cantilever. In addition, comparison between the experimental results of all different configurations showed a reasonable enhancement of performance of energy harvester when an external magnetic force added over the main PCB. Finally, the performance of a multisource energy harvester with magnetic, thermal and mechanical sources is also presented in this study. In this case, it is demonstrated that increase in output voltage with temperature gradient under effect of magnetic force; the results of 2^nd and 3^rd model showed 44% and 99% enhancement of its original output voltage value at 1.2 °C and 2.7 °C temperature difference, respectively.     

An adaptive spatial–spectral total variation approach for Poisson noise removal in hyperspectral images

Poisson distributed noise, such as photon noise, is an important noise source in multi- and hyperspectral images. We propose a variational-based denoising approach that accounts the vectorial structure of a spectral image cube, as well as the Poisson distributed noise. For this aim, we extend an approach initially developed for monochromatic images, by a regularisation term, which is spectrally and spatially adaptive and preserves edges. In order to take the high computational complexity into account, we derive a split Bregman optimisation for the proposed model. The results show the advantages of the proposed approach compared with a marginal approach on synthetic and real data.     

Efficiently sampling nested Archimedean copulas

Efficient sampling algorithms for both Archimedean and nested Archimedean copulas are presented. First, efficient sampling algorithms for the nested Archimedean families of Ali-Mikhail-Haq, Frank, and Joe are introduced. Second, a general strategy how to build a nested Archimedean copula from a given Archimedean generator is presented. Sampling this copula involves sampling an exponentially tilted stable distribution. A fast rejection algorithm is developed for the more general class of tilted Archimedean generators. It is proven that this algorithm reduces the complexity of the standard rejection algorithm to logarithmic complexity. As an application it is shown that the fast rejection algorithm outperforms existing algorithms for sampling exponentially tilted stable distributions involved, e.g., in nested Clayton copulas. Third, with the additional help of randomization of generator parameters, explicit sampling algorithms for several nested Archimedean copulas based on different Archimedean families are found. Additional results include approximations and some dependence properties, such as Kendall’s tau and tail dependence parameters. The presented ideas may also apply in the more general context of sampling distributions given by their Laplace-Stieltjes transforms.     

Synthesis of poly(N‐isopropylacrylamide) under atmospheric pressure plasma conditions

This work is focused on obtaining and characterizing thin films of a certain thermosensitive polymer, i.e., poly(N‐isopropylacrylamide). To obtain such polymers dielectric barrier discharge plasma working at atmospheric pressure in plan–plan geometry was used. The plasma parameters were monitored during polymerization reaction by its electrical and optical signals. The obtained films were analyzed by different techniques such as X‐photoelectron spectroscopy, Fourier transform infrared spectroscopy, atomic force microscopy, contact angle, impedance spectroscopy measurements, and light interferometry for thickness measurements. Chemical analyses of obtained films showed that they sort well with the polymers obtained by other methods in literature. It has been proved that plasma polymerized films have a superhydrophilic character at room temperature, the measured contact angle being around 13°, the lower critical solution temperature was also identified at about 30–31°C. The films' thickness for a 10‐min duration deposition was 400 nm. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

The effect of Pd‐catalyst wettability on hydrogenation of nitrate to hydroxylamine

In the HPO process of the DSM, nitrate is reduced to hydroxylamine on Pd/C catalyst in a 5 M salt solution. Pd/C catalyst increases the interfacial area by a coalescence hindering effect. Nevertheless, mass transfer limitation is encountered and Pd/C catalyst in the liquid bulk is not just useless but even catalyses product decomposition. In this study, the more selective Pd/Al₂O₃ catalyst was silanised with trichloromethyl silane to reduce its wettability and enrich the catalyst at the gas–liquid interface. The silanization did not affect the catalyst activity. In a stirred tank reactor, significantly higher hydrogen absorption rates were achieved for a flat interface but the effect decreased at higher stirring speed.     

Epitaxial ferromagnetic samarium and samarium silicide synthesized on Si(001)

Samarium is deposited on Si(001) at various temperatures (room temperature to 400 °C), and the surface structure, interface reactivity, electron configuration, and magnetic properties are investigated by low-energy electron diffraction (LEED), X-ray photoelectron spectroscopy (XPS), and magneto-optical Kerr effect (MOKE), respectively. It is found that metal Sm is present on samples prepared at room temperature with an interface layer containing mostly Sm²⁺ and a lower amount of Sm³⁺. When samples are prepared at high temperature, much less Sm⁰ is found with an increasing amount of Sm²⁺. Freshly prepared Sm⁰ and SmSi₂ layers react strongly with oxygen from the residual gas, promoting formation of Sm₂O₃ at the expense of both metal Sm and SmSi₂. Room temperature ferromagnetism is observed for all prepared layers with a decrease of the saturation magnetisation when samples are prepared at high temperature. It is found that ferromagnetism implies mostly Sm³⁺ and Sm metal. In addition to these findings, this work proposes a new assignment of the Sm 3d chemically shifted components. Also, a noticeable variation of the XPS Sm 3d spin-orbit splitting is found as a function of the Sm ionization state.     

Attenuated effects of chitosan-capped gold nanoparticles on LPS-induced toxicity in laboratory rats

The impact of nanoparticles in medicine and biology has increased rapidly in recent years. Gold nanoparticles (AuNP) have advantageous properties such as chemical stability, high electron density and affinity to biomolecules. However, the effects of AuNP on human body after repeated administration are still unclear. Therefore, the purpose of the present study was to evaluate the effects of gold-11.68 nm (AuNP1, 9.8 μg) and gold-22.22 nm (AuNP2, 19.7 μg) nanoparticles capped with chitosan on brain and liver tissue reactivity in male Wistar rats exposed to lipopolysaccharide (LPS from Escherichia coli serotype 0111:B4, 250 μg) upon 8 daily sessions of intraperitoneal administration. Our results suggest that the smaller size of chitosan-capped AuNP shows the protective effects against LPS-induced toxicity, suggesting a very high potential for biomedical applications.     

Audio based solutions for detecting intruders in wild areas

This paper presents an overview of the work that has been done in the field of wildlife intruder detection using only acoustic sensors. The motivation of such an application is related to protection of large wildlife regions, such as forests, lakes, and other natural reservations. The sounds of interest are represented by humans, engines, birds and animals. In order to simulate various environmental situations, different types of noisy environments have been considered. Both low complexity and standard audio classification methods are presented. Standard audio classification methods prove to be more robust, but at an expense of significantly increased complexity. Since low complexity systems are more feasible for monitoring remote areas, the complexity issue is discussed and solutions are proposed.