Design considerations for an automotive magnetorheological brake

In this paper, design considerations for building an automotive magnetorheological (MR) brake are discussed. The proposed brake consists of multiple rotating disks immersed in a MR fluid and an enclosed electromagnet. When current is applied to the electromagnet, the MR fluid solidifies as its yield stress varies as a function of the magnetic field applied. This controllable yield stress produces shear friction on the rotating disks, generating the braking torque. In this work, practical design criteria such as material selection, sealing, working surface area, viscous torque generation, applied current density, and MR fluid selection are considered to select a basic automotive MR brake configuration. Then, a finite element analysis is performed to analyze the resulting magnetic circuit and heat distribution within the MR brake configuration. This is followed by a multidisciplinary design optimization (MDO) procedure to obtain optimal design parameters that can generate the maximum braking torque in the brake. A prototype MR brake is then built and tested and the experimental results show a good correlation with the finite element simulation predictions. However, the braking torque generated is still far less than that of a conventional hydraulic brake, which indicates that a radical change in the basic brake configuration is required to build a feasible automotive MR brake.     

A Practical Space-Code Correlator Receiver for DSP Based Software Radio Implementation in CDMA2000

Development of practical algorithms for beamforming in 3G CDMA systems and their software radio implementations are still a challenging task, which will facilitate upgrading of traditional base stations into smart antenna capable 3G base stations. In this paper, we propose a practical space-code correlator (SCC) receiver structure for its software radio implementation a DSP. SCC’s advantage comes from the fact that it doesn’t require any training sequence or learning parameter as in other algorithms (LMS or CM). DSP implementations of the SCC are performed using Texas Instruments C67xx family platforms. In the simulations, reverse link base band signal format of CDMA2000 is used and the effects of different array topologies (uniform linear array-ULA or uniform circular array-UCA) are considered. The implementation results regarding beamforming accuracy, weight vector computation time (execution time), search resolution effect on DOA estimation accuracy, DSP resource utilization, and received SINR are presented. The results show that DSP based SCC beamformer can estimate weight vectors within less than 10 ms with DOA search resolution of 2° especially when C6713 DSP is used. With faster DSPs and larger search resolutions, execution time could be significantly reduced as well. It provides comparable SINR performance with LMS and CM algorithms.

Poly(lactide)/cellulose nanocrystal nanocomposites by high-shear mixing

There is currently considerable interest in developing stiff, strong, tough, and heat resistant poly(lactide) (PLA) based materials with improved melt elasticity in response to the increasing demand for sustainable plastics. However, simultaneous optimization of stiffness, strength, and toughness is a challenge for any material, and commercial PLA is well-known to be inherently brittle and temperature-sensitive and to show poor melt elasticity. In this study, we report that high-shear mixing with cellulose nanocrystals (CNC) leads to significant improvements in the toughness, heat resistance, and melt elasticity of PLA while further enhancing its already outstanding room temperature stiffness and strength. This is evidenced by (i) one-fold increase in the elastic modulus (6.48 GPa), (ii) 43% increase in the tensile strength (87.1 MPa), (iii) one-fold increase in the strain at break (∼6%), (iv) two-fold increase in the impact strength (44.2 kJ/m²), (v) 113-fold increase in the storage modulus at 90°C (787.8 MPa), and (vi) 10³-fold increase in the melt elasticity at 190°C and 1 rad/s (∼10⁵ Pa) via the addition of 30 wt% CNC. It is hence possible to produce industrially viable, stiff, strong, tough, and heat resistant green materials with improved melt elasticity through high-shear mixing.     

Kinetically Stable Oxide Overlayers on Mo3P Nanoparticles Enabling Lithium–Air Batteries with Low Overpotentials and Long Cycle Life

The main drawbacks of today's state-of-the-art lithium–air (Li–air) batteries are their low energy efficiency and limited cycle life due to the lack of earth-abundant cathode catalysts that can drive both oxygen reduction and evolution reactions (ORR and OER) at high rates at thermodynamic potentials. Here, inexpensive trimolybdenum phosphide (Mo₃P) nanoparticles with an exceptional activity—ORR and OER current densities of 7.21 and 6.85 mA cm⁻² at 2.0 and 4.2 V versus Li/Li⁺, respectively—in an oxygen-saturated non-aqueous electrolyte are reported. The Tafel plots indicate remarkably low charge transfer resistance—Tafel slopes of 35 and 38 mV dec⁻¹ for ORR and OER, respectively—resulting in the lowest ORR overpotential of 4.0 mV and OER overpotential of 5.1 mV reported to date. Using this catalyst, a Li–air battery cell with low discharge and charge overpotentials of 80 and 270 mV, respectively, and high energy efficiency of 90.2% in the first cycle is demonstrated. A long cycle life of 1200 is also achieved for this cell. Density functional theory calculations of ORR and OER on Mo₃P (110) reveal that an oxide overlayer formed on the surface gives rise to the observed high ORR and OER electrocatalytic activity and small discharge/charge overpotentials.     

Glass Forming Ability and Magnetic Properties of Fe36Ni36B19.2Si4.8Nb4−x M x (M=Cu, Zr, Ti, Y, Pt) Bulk Glassy Alloys Fabricated by Suction Casting

In this study, the effects of Cu, Zr, Ti, Y, Pt substitution for Nb additions on the stability and magnetic properties of Fe-Ni-based bulk metallic glass (BMG) alloys fabricated by the suction casting method are investigated. The saturation magnetization (J _s) and coercivity (H _c) for as-cast Fe₃₆Ni₃₆B_19.2Si_4.8Nb_4?x M _x (M=Cu, Ti) BMG alloys were in the range of 0.51 T–0.55 T and 76–779 A/m, respectively. Differential scanning calorimetry curves show that the Fe₃₆Ni₃₆B_19.2Si_4.8Nb_4?x M _x (M=Cu, Ti) bulk metallic glasses have a supercooled liquid region for Cu at 44 K and for Ti at 39 K.     

Phase Identification of La-Doped Hard Magnetic Barium Ferrite Using Artificial Neural Network

A model based on an artificial neural network (ANN) was designed for the simulation and estimation of 2 theta and intensity values obtained by X-Ray Diffraction (XRD) of pure and La-doped barium ferrite powders which have been synthesized in ammonium nitrate melt. Its performance is evaluated by the influences of different La content, sintering temperature, Fe/Ba ratio, and washed in HCl (or not washed in HCl) samples. The XRD patterns of samples estimated by the ANN agree well with the experimental values, indicating that the model is reliable and adequate.     

Runtime data‐based characterization and torque estimation of switched reluctance motors

High‐performance control of a switched reluctance (SR) motor strictly requires an accurate nonlinear motor model as well as an appropriate control strategy. Since recent modeling methods are either complex or not accurate enough, this paper focuses on overcoming such drawdacks. An experimental method is proposed to collect useful data for modeling a 6/4 SR motor at running condition. Nonlinear modeling is done by an algorithm, which also enables simple static torque computation. The algorithm presents not only the static torque data but also an estimator model for instantaneous torque estimation during real‐time operation, which is very important for most torque control strategies. The nonlinear model is experimantally tested, and its accuracy verified. © 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Influence of Plasma Spray Parameters on Formation and Morphology of ZrO2–8 wt% Y2O3 Deposits

Spray prints of thermal spray coatings were created on glass slides for air-plasma-sprayed 8-wt%-yttria-partially-stabilized zirconia (YSZ) deposits. The spray parameters such as carrier gas flow rate, standoff distance, and torch power were systematically changed to investigate the influence of these parameters on the YSZ deposit characteristics. The deposit properties such as deposition efficiency (DE), substrate coverage, deposit thickness, and roughness were measured. The deposits sprayed with a 3.5–4.0 L/min carrier gas flow rate at an 80 mm standoff distance exhibited higher values of DE within the range of studied process parameters. The DE increased as much as 25% by varying the carrier gas flow rate from 2.0 to 4.0 L/min. The deposits sprayed at a higher standoff distance and low torch power gave poor deposit characteristics. The deposit characteristics were compared with the in-flight particle parameters and revealed that the deposit characteristics strongly depended on the in-flight particle temperature. Using the in-flight particle properties, the flattening ratio and the splat thickness were calculated. The average size of particles adhering to the substrate was found to drastically change with a change of process conditions, being much less than the average size of the starting powder.     

Sterols stabilize the ripple phase structure in dihexadecylphosphatidylcholine

The presence of various sterols in mixtures with dihexadecylphosphatidylcholine (DHPC) was studied using static X-ray diffraction of temperature equilibrated samples, and real-time X-ray diffraction of samples undergoing temperature scans. It was found that these sterols eliminate the interdigitation of the alkyl chains in the DHPC sub-gel and gel-state bilayers while stabilizing the ripple gel-state at the expense of the gel-state bilayer phase. The ripple-ripple phase transition previously observed for dipalmitoylphosphatidylcholine in the presence of low molar concentrations of sterols (Wolfe et al. (1992) Phys. Rev. Lett. 68, 1085-1088) was also observed for similar DHPC-sterol mixtures. In addition, we show the first evidence that the presence of 5 alpha-cholestane-3 beta,5,6 beta-triol will cause the lipid mixtures to continue to adopt a ripple mesophase structure even after the DHPC alkyl chain becomes disordered.