Process parameter dependencies of continuous and pulsed laser modes on surface polishing of additive manufactured aluminium AlSi10Mg parts

Laser powder bed fusion is a well-established 3D printing technique for metal alloys, but exhibits a poor surface quality. Laser polishing provides the possibility of a fast contact-free and fully-automatable surface treatment. This paper deals with the experimental investigation of laser polishing of laser powder bed fusion parts made of aluminium AlSi10Mg. Laser polishing is done with a 4 kW solid state disc laser in combination with a multi-axis system and a one dimensional scanner optic. The laser is operated at continuous and pulsed operation mode. The parameter study reveals a high dependency of the achievable roughness on the laser beam intensity, the track and pulse overlap, the energy density and the number of polishing passes and polishing directions. Pulsed laser polishing mode with up to four passes from different directions revealed the lowest surface roughness of 0.14 μm Ra. With respect to the initial average surface roughness of Ra = 8.03 μm a reduction of the surface roughness of greater than 98 % could be achieved. Polishing with continuous laser radiation at one polishing pass resulted in Ra = 0.23 μm at an area rate of 20 cm²/min. Laser polishing using four passes achieved a further improvement up to Ra = 0.14 μm.     

Power MOSFET quality and robustness enhancement with a new QBD characterization performed at probe–die–wafer level

The quality of the gate oxide is a central parameter for power MOSFET devices dedicated to automotive applications. Reliability is systematically evaluated through electrical tests. The purpose of this study is to apply the Q_BD test directly at probe–die–wafer level and to correlate its results with reliability test conclusions. In other words, this new kind of Q_BD test is a monitor of power MOSFET robustness which helps identify extrinsic failures and the process steps responsible. In summary, it is an accurate and fast measurement method of identifying weakened parts and enhancing device quality.     

Cell-Based Optimization of Covalent Reversible Ketoamide Inhibitors Bridging the Unprimed to the Primed Site of the Proteasome β5 Subunit

The ubiquitin-proteasome system (UPS) is an established therapeutic target for approved drugs to treat selected hematologic malignancies. While drug discovery targeting the UPS focuses on irreversibly binding epoxyketones and slowly-reversibly binding boronates, optimization of novel covalent-reversibly binding warheads remains largely unattended. We previously reported α-ketoamides to be a promising reversible lead motif, yet the cytotoxic activity required further optimization. This work focuses on the lead optimization of phenoxy-substituted α-ketoamides combining the structure-activity relationships from the primed and the non-primed site of the proteasome β5 subunit. Our optimization strategy is accompanied by molecular modeling, suggesting occupation of P1′ by a 3-phenoxy group to increase β5 inhibition and cytotoxic activity in leukemia cell lines. Key compounds were further profiled for time-dependent inhibition of cellular substrate conversion. Furthermore, the α-ketoamide lead structure 27 does not affect escape response behavior in Danio rerio embryos, in contrast to bortezomib, which suggests increased target specificity.     

Poly(vinyl alcohol) functionalization with aldehydes in organic solvents: Shining properties of poly(vinyl acetals)

Poly(vinyl alcohol) has been functionalized with aldehydes in tetrahydrofuran (THF) with a good control of the grafting. A wide library of poly(vinyl acetals) could be obtained in order to study some structure/property correlations. The influence of the aldehyde nature on the functionalization rates has been studied, in particular for optical properties by measurement of the shininess for further applications in the cosmetic field. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40677.     

A computationally efficient approach for hidden-Markov model-augmented fingerprint-based positioning

This paper presents a computationally efficient approach for mobile subscriber position estimation in wireless networks. A method of data scaling assisted by timing adjust is introduced in fingerprint-based location estimation under a framework which allows for minimising computational cost. The proposed method maintains a comparable level of accuracy to the traditional case where no data scaling is used and is evaluated in a simulated environment under varying channel conditions. The proposed scheme is studied when it is augmented by a hidden-Markov model to match the internal parameters to the channel conditions that present, thus minimising computational cost while maximising accuracy. Furthermore, the timing adjust quantity, available in modern wireless signalling messages, is shown to be able to further reduce computational cost and increase accuracy when available. The results may be seen as a significant step towards integrating advanced position-based modelling with power-sensitive mobile devices.     

Automatic analysis of human posture equilibrium using empirical mode decomposition

The present study proposes a new approach for the assessment of the human balance control. This approach is based on the decomposition of the center of pressure displacement using empirical mode decomposition (EMD) that provides an effective time-frequency analysis of non-stationary signals. Twenty-eight healthy subjects performed quiet standing in four conditions—feet apart/together with respect to eyes open/closed—while recording the stabilometric signals in the anteroposterior (AP) and mediolateral (ML) directions. The EMD method decomposes each stabilometric signal into several subsignals called intrinsic mode functions (IMFs). Stabilogram-diffusion analysis technique is applied to generate the diffusion curve of each IMF signal. Each diffusion curve is modeled as a second-order system and provides representative features, such as the gain parameter. Analysis of the gain parameter shows the major effect of visual input and feet conditions on the strategy to control/stabilize the balance. Significant differences were found between young and elderly, and between women and men. In addition, the impact of feet position seems to be higher in ML direction than in AP direction.