Engineering

This paper presents the development process for a new variable frequency drive (VFD) system for large size compressor trains for natural gas and liquefied natural gas (LNG) applications. The paper covers the multiple steps of the product development process, from identification of applications requirements, definition of design 61 ELECTRIC SYSTEMS FOR HIGH POWER COMPRESSOR TRAINS IN OILAND GASAPPLICATIONS— SYSTEM DESIGN,VALIDATIONAPPROACH,AND PERFORMANCE

The use of fuel cell technology for urban transportation system in Europe and Australia is demonstrated through the projects CUTE, ECTOS and STEP. This paper gives an overview of these projects and respective characteristics. The department of Life Cycle Engineering of IKP, University of Stuttgart and PE Europe will perform a life cycle analysis of this new technology together with the needed infrastructure. This paper focuses on the LCA of the various forms of hydrogen supply.

A series of experiments with rotating, electromagnetically forced, turbulent flows were carried out at the Sapienza University of Rome to investigate the eddy–wave duality in flows with a β-effect and the electromagnetic force acting in the westward direction. When the β-effect is significant, i.e., as in planetary atmospheric and oceanic circulations, nonlinear eddy/wave interactions facilitate flow self-organization into zonal patterns in which Rossby waves and westward propagating cyclonic and anticyclonic eddies coexist. Upon time averaging, eddies disappear and the flow pattern transforms into a system of alternating zonal jets. What is the relationship between eddies, jets, and Rossby waves? To address this issue, we designed a laboratory experiment in which a westward zonal flow is produced by applying an electromagnetic small-scale forcing to a thin layer of a rotating fluid. In order to investigate different levels of flow zonality and a wider range of zonal modes, we varie...

The electronic transport and magnetotransport properties of Fe3O4/SiO2/Si heterostructures were investigated with a current source. Negative differential resistance is observed in Fe3O4/SiO2/p-Si heterostructures. The measurement circuit with four electrodes that I+ (I−) and V+ (V−) came into contact with the Fe3O4 (Si) layer introduces an in-plane transport into the heterostructures. By decreasing the temperature, the in-plane conductive channel switches from Fe3O4 to p-Si. However, the in-plane current is still carried by Fe3O4 in Fe3O4/SiO2/n-Si heterostructures. The formation of an accumulation layer in p-Si facilitates conductive channel switching (CCS), while the depletion layer in n-Si hampers the CCS. At 150 K, a magnetic-field-independent magnetoresistance (MR) in Fe3O4/SiO2/p-Si heterostructures manifests the conductive channel in the space charge region of p-Si. A positive MR generated from the increased electronic scattering in a trapezoidal space charge region reshaped ...

This study demonstrates the first synthesis of MXene‐derived ferroelectric crystals. Specifically, high‐aspect‐ratio potassium niobate (KNbO3) ferroelectric crystals is successfully synthesized using 2D Nb2C, MXene, and potassium hydroxide (KOH) as the niobium and potassium source, respectively. Material analysis confirms that a KNbO3 orthorhombic phase with Amm2 symmetry is obtained. Additionally, ferroelectricity in KNbO3 is confirmed using standard ferroelectric, dielectric, and piezoresponse force microscopy measurements. The KNbO3 crystals exhibit a saturated polarization of ≈21 µC cm−2, a remnant polarization of ≈17 µC cm−2, and a coercive field of ≈50 kV cm−1. This discovery illustrates that the 2D nature of MXenes can be exploited to grow ferroelectric crystals.

We report investigations of magnetoresistance (MR) in epitaxial and polycrystalline Fe3O4 films. MR in epitaxial Fe3O4 films exhibits a local maximum at TV and a large value of −20% at 60 K. Based on a 1D half infinite spin chain model, the fitting parameter, which depends on the volume fraction of electronic scattering boundaries, sharply increases below TV with the decreased temperature. We suppose that the twin boundaries formed below TV facilitate the increase in MR and can act as antiphase boundaries (APBs) where the magnetic moments across twin boundaries are coupled antiferromagnetically. Similar MR behavior in Fe3O4(100) and (111) epitaxial films manifests the independence of MR on the spatial distribution of APBs. The outline of normalized MR in the epitaxial films shows a distinct temperature dependence. The temperature dependence may result from the different electronic transport mechanisms in Fe3O4 films. In a polycrystalline Fe3O4 film, MR comes from the disordered dist...

The direct conversion of solar energy into fuels or feedstock is an attractive approach to address increasing demand of renewable energy sources. Photocatalytic systems relying on the direct photoexcitation of metals have been explored to this end, a strategy that exploits the decay of plasmonic resonances into hot carriers. An efficient hot carrier generation and collection requires, ideally, their generation to be enclosed within few tens of nanometers at the metal interface, but it is challenging to achieve this across the broadband solar spectrum. Here the authors demonstrate a new photocatalyst for hydrogen evolution based on metal epsilon-near-zero metamaterials. The authors have designed these to achieve broadband strong light confinement at the metal interface across the entire solar spectrum. Using electron energy loss spectroscopy, the authors prove that hot carriers are generated in a broadband fashion within 10 nm in this system. The resulting photocatalyst achieves a hy...

Transferrin is the major iron binding protein in human plasma. In black persons, the transferrin CD phenotype has been associated with alterations in certain markers of iron status. We studied vitamin C status in a Zimbabwean population according to transferrin phenotype because vitamin C metabolism is influenced by iron-driven oxidative stress. The study population consisted of 150 black African adults, 90 of whom were at risk of iron overload on the basis of high dietary iron content in the form of traditional beer. Transferrin phenotypes, indirect measures of iron status, and leukocyte ascorbic acid concentrations were determined. The in vitro rate of L-ascorbic acid depletion in sera from different transferrin phenotypes was investigated. The transferrin phenotype frequencies of transferrin CC and CD were 0.893 and 0.107, respectively. The iron status of transferrin CC and CD subjects was similar. After adjustment for traditional beer consumption, baseline leukocyte vitamin C co...