Thermoelectric Energy Harvesting from Transient Ambient Temperature Gradients

We examine a thermoelectric harvester that converts electrical energy from the naturally occurring temperature difference between ambient air and large thermal storage capacitors such as building walls or the soil. For maximum power output, the harvester design is implemented in two steps: source matching of the thermal and electrical interfaces to the energy source (system level) followed by load matching of the generator to these interfaces (subsystem level). Therefore, we measure thermal source properties such as the temperature difference, the air velocity, and the cutoff frequency in two application scenarios (road tunnel and office building). We extend a stationary model of the harvester into the time domain to account for transient behavior of the source. Based on the model and the source measurements, we perform the source and load matching. The resulting harvester consists of a pin fin heat sink with a thermal resistance of 6.2?K/W and a cutoff frequency 2.5?times greater than that of the source, a thermoelectric generator, and a DC/DC step-up converter starting at a total temperature difference of only ??T?=?1.2?K. In a final road tunnel field test, this optimized harvester converts 70?mJ of electrical energy per day without any direct solar irradiation. The energy provided by the harvester enables 415?data transmissions from a wireless sensor node per day.     

Teleoperated 3-D Force Feedback From the Nanoscale With an Atomic Force Microscope

In this study, 3-D experimental teleoperated force feedback during contact with nanoscale surfaces is demonstrated using an atomic force microscope (AFM) on the slave side and a haptic device on the master side. To achieve 3-D force feedback, coupling between one of the horizontal forces and the vertical force is a crucial bottleneck. To solve this coupling issue, a novel force decoupling algorithm is proposed. This algorithm uses local surface slopes, an empirical friction force model, and the haptic device motion angle projected onto the surface to estimate the friction value during experiments. With this estimation, it is possible to decouple the three orthogonal forces acting on the tip of the AFM cantilever. Moreover, using an adaptive observer, parameters of the friction model can be changed online, removing the necessity to calibrate the friction model initially. Finally, a modified passivity-based bilateral control is used to reflect the scaled nanoscale forces to the master side and the operator. The performance of the system is demonstrated on experimental results for flat and non-flat, and hard and soft surfaces.      

Design of broadband microwave amplifiers with mixed-elements via reflectance data modeling

A practical method is introduced, to design single-stage broadband microwave amplifiers with mixed lumped and distributed elements via modeling the reflectance data obtained from lumped-element input and output matching network prototypes. The same transducer power gain level is obtained by using less number of lumped-elements in the mixed-element amplifier than that of the lumped-element amplifier prototype. A mixed-element amplifier design is presented, to exhibit the utilization of the method. It is expected that the method will be employed, to design microwave amplifiers for broadband communication systems.     

Influence of leather meal fertilizer on soil organic matter: A laboratory study

Leather meal fertilizer was mixed with a soil (Typic Xerorthent) and incubated in the laboratory for one year at room temperature. Soil samples were collected periodically and analyzed in order to follow the transformation of the organic matter as well as the availability of Cr and certain plant nutrients.The results obtained showed intense mineralization during the first 60–120 days of the incubation period. The amount of humic acids (HAs) separated from the alkaline extracts showed that the humification level increased markedly after the first 60 days of incubation and, as shown by IEF analysis, organic compounds similar to the soil humic substances were formed.Variations in the amount of available nutrients were observed; only the extractable Cr increased during the first period of mineralization.     

Effect of cesium salt of tungstophosphoric acid (Cs-TPA) on the properties of sulfonated polyether ether ketone (SPEEK) composite membranes for fuel cell applications

We have prepared composite membranes for fuel cell applications. Cesium salt of tungstophosphoric acid (Cs-TPA) particles was synthesized by aqueous solutions of tungstophosphoric acid and cesium hydroxide and, Cs-TPA particles and sulfonated (polyether ether ketone) (SPEEK) with two sulfonation degrees (DS), 60 and 70%have been used. We examined both the effects of Cs-TPA in SPEEK membranes as functions of sulfonation degrees of SPEEK and the content of Cs-TPA. The performance of the composite membranes was evaluated in terms of water uptake, ion exchange capacity, proton conductivity, chemical stability, hydrolytic stability, thermal stability and methanol permeability. The morphology of the membranes was investigated with SEM micrographs. Increasing sulfonation degree of SPEEK from 60 to 70 caused agglomeration of the Cs-TPA particles. The methanol permeability was reduced to 4.7 × 10⁻⁷ cm²/s for SPEEK (DS: 60%)/Cs-TPA membrane with 10 wt.% Cs-TPA concentration, and acceptable proton conductivity of 1.3 × 10⁻¹ S/cm was achieved at 80 °C under 100% RH. The weight loss at 900 °C increased with the addition of inorganic particles, as expected. The hydrolytic stability of the SPEEK/Cs-TPA based composite membranes was improved with the incorporation of the Cs-TPA particles into the matrix. We also noted that SPEEK60/Cs-TPA composite membranes were hydrolytically more stable than SPEEK70/Cs-TPA composite membranes. On the other hand, Methanol, water vapor, and hydrogen permeability values of SPEEK60 composite membranes were found to be lower than that of Nafion^®.     

Supported CoCl2 catalyst for NaBH4 dehydrogenation

In this paper, economically favorable, supported CoCl₂ catalysts were produced for NaBH₄ dehydrogenation. Among the used supports, diatomite and γ-Al₂O₃ supports show great stability with CoCl₂ and do not break up during experiments some of which lasts 3000 min. Slow and continuous hydrogen release throughout all of the experiments is observed. Furthermore, prepared catalyst could be used for 250 h uninterruptedly. XRF and Atomic Absorption Spectrometer (AAS) analysis prove that CoCl₂ could be permanently joined and distributed homogeneously on the support surface. In addition, kinetic investigations of the dehydrogenation reaction fit zero order kinetic for low temperatures while it obeys the first order at high temperature. Computation of activation energy results 132 kJ/mol for low and 78 kJ/mol for high temperature regions.     

Temperature dependence of electrical conductivity in double-wall and multi-wall carbon nanotube/polyester nanocomposites

The aim of this study is to investigate temperature dependence of electrical conductivity of carbon nanotube (CNT)/polyester nanocomposites from room temperature to 77 K using four-point probe test method. To produce nanocomposites, various types and amounts of CNTs (0.1, 0.3 and 0.5 wt.%) were dispersed via 3-roll mill technique within a specially formulized resin blend of thermoset polyesters. CNTs used in the study include multi walled carbon nanotubes (MWCNT) and double-walled carbon nanotubes (DWCNT) with and without amine functional groups (–NH₂). It was observed that the incorporation of carbon nanotubes into resin blend yields electrically percolating networks and electrical conductivity of the resulting nanocomposites increases with increasing amount of nanotubes. However, nanocomposites containing amino functionalized carbon nanotubes exhibit relatively lower electrical conductivity compared to those with non-functionalized carbon nanotubes. To get better interpretation of the mechanism leading to conductive network via CNTs with and without amine functional groups, the experimental results were fitted to fluctuation-induced tunneling through the barriers between the metallic regions model. It was found that the results are in good agreement with prediction of proposed model.     

Monodisperse Pd nanoparticles assembled on reduced graphene oxide-Fe3O4 nanocomposites as electrocatalysts for borohydride fuel cells

5 nm palladium nanoparticles (Pd NPs) are synthesized and assembled on reduced graphene oxide-iron oxide nanocomposite (rGO-Fe₃O₄) to be used in oxygen reduction reaction (ORR) and borohydride oxidation reaction (BOR) studies in alkaline media. The structure and morphology of the resulting Pd/rGO-Fe₃O₄ hybrid material are evaluated by X-ray diffraction (XRD), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDS) analyses. The electrochemical behavior of Pd/rGO-Fe₃O₄ hybrid material for the ORR and BOR is investigated by voltammetry with rotating disk and rotating ring disk electrode and electrochemical impedance spectroscopy, enabling evaluation of the number of exchanged electrons, Tafel slope, exchange current density and activation energy. The results reveal that ORR at Pd/rGO-Fe₃O₄ proceeds as a 2-electron process with Tafel slope of 0.133 V dec^?1, while BOR proceeds as a 5.6-electron process with Tafel slope of 0.350 V dec^?1 and exchange current density of 1.38 mA cm^?2. The BOR activation energy was found to be 12.4 kJ mol^?1. Overall, this study demonstrates the good efficiency of Pd/rGO-Fe₃O₄ hybrid material for BOR.     

Regional and structural analysis of the manufacturing industry in Turkey

The geography of the manufacturing industry has been changing due to technological development, flexible production and reducing transportation costs regarding the new specialization and distribution process in the world. While manufacturing production has been moving from developed countries to the relatively less developed ones, which have become the emerging economies over the last two decades, the concentration of these activities within the countries has always received the attention of researchers. On the other hand, not only the geographical shift but also structural shifts have increasingly been an important phenomenon of the twenty-first century. It is known that the level of technology and innovation makes a significant contribution to regional economic development. Determinants of manufacturing agglomerations have created a wide literature based on different empirical studies. Moreover the structural changes of industry need to be investigated regarding the spatial agglomerations. The aim of this paper is to explore how the factors of manufacturing agglomerations have differentiated due to the technological level across the country. Furthermore, we assume that the agglomeration mechanism is likely to vary across the space. Therefore, we have run both global and local regression models based on the employment data of the 81 NUTS III level regions (provinces) of Turkey in 2012. The results point out that the factors of agglomerations are different in the east and west provinces, while GWR has significantly improved global results.