Schmelzen und Behandeln von Metallen und Legierungen im Vakuum

The growing demands for better quality of metallic materials can only be met by the application of vacuum during the production of these metals and alloys and their field of application.     

Step response analysis of phosphoric acid fuel cell (PAFC) cathode through a transient model

Transient state response analysis of phosphoric acid fuel cell (PAFC) cathode is important to understand various competitive processes like diffusion, reaction and product back diffusion occurring at various layers of the composite cathode. A two-dimensional unsteady state model for simulating PAFC cathode is developed as an extension of the previously developed steady-state model [S. Roy Choudhury, M.B. Deshmukh, R. Rengaswamy, A two-dimensional steady-state model for phosphoric acid fuel cells (PAFC), J. Power sources 112 (2002) 137–152]. The transient model is solved to study the impact of various parameters such as Tafel slope, diffusivity etc on the step response of the fuel cell. The effect of partial pressure variation in bulk gas for large sized PAFC cathode is also analysed. Trend analysis based on the model output is also experimentally verified using a small unit cell setup. The effect of various parameters on the settling time of the cathode, as revealed in this study, suggests possible development of a diagnostic tool employing such transient model.     

Barrier properties of poly(vinyl alcohol) membranes containing carbon nanotubes or activated carbon

Carbon nanotube addition has been shown to improve the mechanical properties of some polymers. Because of their unique adsorptive properties, carbon nanotubes may also improve the barrier performance of polymers used in contaminant containment. This study compares the barrier performance of poly(vinyl alcohol) (PVA) membranes containing single-walled carbon nanotubes (SWCNTs) to that for PVA containing powdered activated carbon (PAC). Raw and surface-functionalized versions of each sorbent were tested for their abilities to adsorb 1,2,4-trichlorobenzene and Cu(2+), representing the important hydrophobic organic and heavy metal contaminant classes, as they diffused across the PVA. In both cases, PAC (for 1,2,4-trichlorobenzene) and functionalized PAC (for Cu(2+)) outperformed SWCNTs on a per mass basis by trapping more of the contaminants within the barrier membrane. Kinetics of sorption are important in evaluating barrier properties, and poor performance of SWCNT-containing membranes as 1,2,4-TCB barriers is attributed to kinetic limitations.     

Effect of Cerium Doping on Microstructure and Dielectric Properties of BaTiO3 Ceramics

A solid state reaction method was used to synthesize barium titanate (BT) and barium cerium titanate (BCT) ceramics at sintering temperature of 1473 K for 4 h. The effect of cerium (Ce) on the structure, microstructure and dielectric properties of BCT was investigated. The scanning electron microscopy (SEM) investigations revealed that the grain size increases with increasing Ce content. The X-ray diffraction (XRD) patterns showed mostly the BT phase, where the lattice parameter decreased with the addition of Ce. The temperature dependence of dielectric constant showed decrease in the phase transition temperature with higher Ce content. The dielectric constant decreased slightly with increasing frequency. The direct current (dc) density-voltage characteristics of the ceramics showed ohmic behavior for both the BT and BCT. As the temperature increased, the dc resistivity of the ceramics decreased. The activation energy increased with increasing Ce content.     

Organic and Inorganic Blocking Layers for Solution‐Processed Colloidal PbSe Nanocrystal Infrared Photodetectors

A PbSe solution‐processed nanocrystal‐based infrared photodetector incorporating carrier blocking layers is demonstrated, and significant reduction of dark current is achieved. Detectivity values close to 10¹² Jones are achieved by using poly[(9,9′‐dioctylfluorenyl‐2,7‐diyl)‐co‐(4,4′‐(N‐(4‐sec‐butyl))diphenylamine)] (TFB) and ZnO nanocrystals (NC) as the electron blocker and hole blocker, respectively. An improvement in lifetime is also observed in the devices with the ZnO NCs hole blocking layer.     

BeWell: Sensing Sleep,Physical Activities and Social Interactions to Promote Wellbeing

Smartphone sensing and persuasive feedback design is enabling a new generation of wellbeing apps capable of automatically monitoring multiple aspects of physical and mental health. In this article, we present BeWell+ the next generation of the BeWell smartphone wellbeing app, which monitors user behavior along three health dimensions, namely sleep, physical activity, and social interaction. BeWell promotes improved behavioral patterns via feedback rendered as an ambient display on the smartphone’s wallpaper. With BeWell+, we introduce new mechanisms to address key limitations of the original BeWell app; specifically, (1) community adaptive wellbeing feedback, which generalizes to diverse user communities (e.g., elderly, children) by promoting better behavior yet remains realistic to the user’s lifestyle; and, (2) wellbeing adaptive energy allocation, which prioritizes monitoring fidelity and feedback responsiveness on specific health dimensions (e.g., sleep) where the user needs additional help. We evaluate BeWell+ with a 27 person, 19 day field trial. Our findings show that not only can BeWell+ operate successfully on consumer smartphones; but also users understand feedback and respond by taking steps towards leading healthier lifestyles.     

Investigation on Sodium Benzoate Release from Poly(Butylene Adipate‐Co‐Terephthalate)/Organoclay/Sodium Benzoate Based Nanocomposite Film and Their Antimicrobial Activity

Polymeric nanocomposites embedded with nontoxic antimicrobial agents have recently gained potential industrial significance, mainly for their applicability to preserve food quality and ensure safety. In this study, a poly(butylene adipate‐co‐terephthalate) (PBAT)/organoclay (CMMT) based nanocomposite film doped with sodium benzoate (SB) as antimicrobial agent was prepared by a solution mixing process. A homogenous dispersion of organoclay (cetyltrimethylammonium‐modified montmorillonite [CMMT]) in PBAT matrix was observed by X‐ray diffraction and transmission electron microscopy. PBAT/CMMT nanocomposite film showed higher barrier properties against water and methanol vapor compared to the PBAT film. The release of SB from PBAT and its nanocomposite film was measured and the relevant data were fitted to the Weibull model. The higher values of Weibull's shape factor and scale parameter as corroborated by experimental findings indicated faster rate of SB release from PBAT/CMMT/SB nanocomposite film, when compared to the pristine PBAT film. Bacterial inhibition studies were accomplished against 2 food pathogenic bacteria, Bacillus subtilis and Staphylococcus aureus, by determining the zone of inhibition and corresponding growth profiles. Both bacterial inhibition studies and growth profiles established that PBAT/CMMT/SB demonstrated better antimicrobial activity than PBAT/SB film. Therefore, PBAT/CMMT/SB nanocomposite film can be used for food packaging application as it showed good barrier properties and antimicrobial activity against food pathogenic bacteria.     

Axial ratio bandwidth improvement of compact planar monopole antenna with dual-band and dual-sense

A small size, dual-band and dual-sense monopole antenna is proposed to improve the axial ratio bandwidth (ARBW). The proposed antenna is considered on a low-cost lossy FR4 substrate with parasitic strips (PSs) and partial ground plane of half guided wavelength dimensions. The dimension of the antenna in terms of wavelength is $\mathbf{0.27}{\mathit{\lambda }}_{\mathbf{0}}\mathit{\times }\mathbf{0.29}{\mathit{\lambda }}_{\mathbf{0}}\mathit{\times }\mathbf{0.02}{\mathit{\lambda }}_{\mathbf{0}}$, where ${\mathit{\lambda }}_{\mathbf{0}}$ is the wavelength at the lowest resonant frequency. The circularly polarized (CP) mode is created for strong orthogonal electric fields ${\mathit{E}}_{\mathit{X}}$ and ${\mathit{E}}_{\mathit{Y}}$. The obtained phase difference (PD) between two electric fields ${\mathit{E}}_{\mathit{X}}$ and ${\mathit{E}}_{\mathit{Y}}$ is varied from ${\mathbf{86}}^{°}$ to ${\mathbf{96}}^{°}$ under ARBW. The achieved ARBW is 3.68–3.8 GHz, 4.84–12.58 GHz, and impedance bandwidth (IBW) is 3.51–3.82 GHz and 4.28–15 GHz. The applications of the proposed antenna are International Telecommunication Union (ITU) for 5G, C-band IEEE 802.11a wireless local area network (WLAN) at 5 GHz (5.15–5.825 GHz) and X-band wireless systems.     

Metabolism and pharmacokinetics of 1-(2''-trimethylacetoxyethyl)-2-ethyl-3-hydroxypyridin-4-one (CP117) in the rat

A modified endoscopic technique for anterior cruciate ligament (ACL) reconstruction using an autologous patellar tendon graft is described using the early results for 120 patients. A special technique using an oscillating hollow saw allows for the rapid and standardized harvest of cylindrical bone plugs, ensuring safe and adequate femoral press-fit fixation. The complications encountered included one fracture of a bone back on plugging in as well as two cases with revision procedures for interference screw fixation due to insufficient femoral anchorage. Within the framework of a prospective study, all 120 patients underwent a control arthroscopy after the first postoperative year showing viable and mechanically stable grafts in 64 (53.3%) of the patients. In 44 patients (36.7%), viable though somewhat lax grafts were found, whereas the remaining 12 patients (10%) only showed insufficient tissue residues. All of these cases were the result of a ventral misplacement of the femoral insertion site representing the primary complication of transtibial technique. The results of the control arthroscopies showed a highly significant correlation with the clinical results for the IKDC score obtained in a follow-up after an average 29 (18 to 36) months. The results for stability according to the IKDC rating scale showed a normal or near-normal knee function in 76.7%. With regard to the subjective results in the IKDC rating scale, 83.3% of the patients (n = 100) assessed their knee function as normal or almost normal. The location and positioning of the femoral and tibial tunnel were evaluated in an exact radiographic evaluation showing an "ideal position" of the graft in only 94 cases (78.3%). Statistically, a significant correlation of stability with the femoral fixation site could be shown.     

Phonon dispersion relations and densities of states in La2CuO4 and La2NiO4

Rigid-ion model calculations of phonon dispersion relations, densities of states and partial densities of states of the highT _c superconductor La₂CuO₄ and its isostructural compound La₂NiO₄ have been carried out both in the tetragonal and orthorhombic phases of La₂CuO₄ and the tetragonal phase of La₂NiO₄. The calculations are in fair agreement with reported experiments. The computed phonon dispersion in the tetragonal phase of La₂CuO₄ reproduces the soft mode behaviour for the lowest Σ₄ TO branch which is found to harden in the orthorhombic phase, consistent with experimental data.