Improved electrochemical performance of nitrocarburised stainless steel by hydrogenated amorphous carbon thin films for bone tissue engineering

In this study, hydrogenated amorphous carbon thin films, structurally similar to diamond‐like carbon (DLC), were deposited on the surface of untreated and plasma nitrocarburised (Nitrocarburizing‐treated) stainless steel medical implants using a plasma‐enhanced chemical vapour deposition method. The deposited DLC thin films on the nitrocarburising‐treated implants (CN+DLC) exhibited an appropriate adhesion to the substrates. The results clearly indicated that the applied DLC thin films showed excellent pitting and corrosion resistance with no considerable damage on the surface in comparison with the other samples. The CN+DLC thin films could be considered as an efficient approach for improving the biocompatibility and chemical inertness of metallic implants.Inspec keywords: tissue engineering, bone, biomedical materials, electrochemistry, amorphous state, carbon, hydrogen, thin films, plasma CVD, adhesion, corrosion resistance, surface hardeningOther keywords: electrochemical performance, plasma nitrocarburised stainless steel medical implants, hydrogenated amorphous carbon thin films, bone tissue engineering, plasma‐enhanced chemical vapour deposition method, adhesion, corrosion resistance, biocompatibility, chemical inertness, metallic implants, C:H     

Large-scale parallel lattice Boltzmann–cellular automaton model of two-dimensional dendritic growth

An extremely scalable lattice Boltzmann (LB)–cellular automaton (CA) model for simulations of two-dimensional (2D) dendritic solidification under forced convection is presented. The model incorporates effects of phase change, solute diffusion, melt convection, and heat transport. The LB model represents the diffusion, convection, and heat transfer phenomena. The dendrite growth is driven by a difference between actual and equilibrium liquid composition at the solid–liquid interface. The CA technique is deployed to track the new interface cells. The computer program was parallelized using the Message Passing Interface (MPI) technique. Parallel scaling of the algorithm was studied and major scalability bottlenecks were identified. Efficiency loss attributable to the high memory bandwidth requirement of the algorithm was observed when using multiple cores per processor. Parallel writing of the output variables of interest was implemented in the binary Hierarchical Data Format 5 (HDF5) to improve the output performance, and to simplify visualization. Calculations were carried out in single precision arithmetic without significant loss in accuracy, resulting in 50% reduction of memory and computational time requirements. The presented solidification model shows a very good scalability up to centimeter size domains, including more than ten million of dendrites.     

Effects of preweaning total plane of milk intake and weaning age on intake,growth performance,and blood metabolites of dairy calves

The objective of this study was to evaluate the effects of preweaning total plane of milk intake and weaning age on intake, growth performance, and blood metabolites of dairy calves. A total of 48 Holstein calves (40 ± 1.6 kg of body weight) were used in a 2 × 2 factorial arrangement with the factors of weaning age (d 60 vs. 75) and the total plane of milk intake (medium vs. high) during the preweaning period. Calves were assigned to 1 of 4 treatments: (1) calves fed medium plane of milk (MPM) intake and weaned on d 60 of age (MPM-60d, 4 L/d of milk from d 3 to 10, 6 L/d of milk from d 11 to 55, and 3 L/d of milk from d 56 to 60 of age; total milk intake = 317 L), (2) calves fed MPM intake and weaned on d 75 of age (MPM-75d, 4 L/d of milk from d 3 to 10 and 4.5 L/d of milk from d 11 to 70 of age followed by feeding 2.25 L/d of milk from d 71 to 75 of age; total milk intake = 313 L), (3) calves fed high plane of milk (HPM) intake and weaned on d 60 of age (HPM-60d, 4 L/d of milk from d 3 to 10, 6 L/d of milk from d 11 to 20, and 8.5 L/d of milk from d 21 to 55 followed by feeding 4.25 L/d of milk from d 56 to 60 of age; total milk intake = ～411 L); and (4) calves fed HPM intake and weaned on d 75 (HPM-75d, 4 L/d of milk from d 3 to 10, and 6 L/d of milk from d 11 to 70 of age followed by feeding 3 L/d of milk from d 71 to 75 of age; total milk intake = 407 L) with no milk refusals. All of the calves were monitored up to d 90 of age. Regardless of weaning age, starter feed intake and dry matter intake (% of body weight) were lower in calves fed HPM compared with those receiving MPM. A tendency for the plane of milk intake × weaning age interaction was observed for metabolizable energy intake with the highest value was recorded with the HPM-75d calves. The lowest efficiency of metabolizable energy intake and average feed efficiency was observed in HPM-60d calves throughout the experimental period as compared with the other groups. An interaction was found between the total plane of milk intake and weaning age regarding effects on total average daily gain, average daily gain/metabolizable energy intake, feed efficiency, final body weight, and plasma β-hydroxybutyrate levels with the highest values measured in HPM-75d calves. Weaning on d 75 versus d 60 improved wither height and hip width, which tended to increase body length at the end of the trial. The results suggest that calves fed high amounts of milk during their preweaning period benefit from extending the time of weaning from 60 to 75 d of age based on average daily gain, feed efficiency, and final body weight.     

A CMOS transconductor with 80-dB SFDR up to 10 MHz

A CMOS transconductor uses resistors at the input and an OTA in unity-gain feedback to achieve 80-dB spurious-free dynamic range (SFDR) for 3.6-V_pp differential inputs up to 10 MHz. The combination of resistors at the input and negative feedback around the operational transconductance amplifier (OTA) allows this transconductor to accommodate a differential input swing of 4 V with a 3.3-V supply. The total harmonic distortion (THD) of the transconductor is -77 dB at 10 MHz for a 3.6-V_pp differential input and third-order intermodulation spurs measure less than -79 dBe for 1.8-V_pp differential inputs at 1 MHz. The transconductance core dissipates 10.56 mW from a 3.3-V supply and occupies 0.4 mm² in a 0.35-μm CMOS process     

Synthesis of aluminum nanoparticles by electromagnetic levitational gas condensation method

A novel electromagnetic levitational gas condensation (ELGC) system was designed and manufactured for the synthesis of aluminum nanoparticles. Both liquid and membrane filtration systems were used for collecting the nanoparticles. Effects of induction coil design, input power and gas flow rate were investigated. It was found that the wet collection in toluene resulted in a smaller particle size than the dry collection on membrane filter. While using low argon flow rate, coarser particles were produced, high argon flow rate intensified the particle coalescence. The best argon flow rate for the synthesis of aluminum nanoparticles was found about 10-15 lit/min.     

Effects of oxide interface traps and transient enhanced diffusionon the process modeling of PMOS devices

We present a model which simulates the trapping of arsenic and boron dopants at the silicon-silicon dioxide interface, and demonstrate that this model gives significantly more accurate doping profiles for a wide range of PMOS devices, as characterized by the device Threshold Voltage. In addition, a newly-developed Transient Enhanced Diffusion (TED) model is applied for the first time to the process simulation of buried-channel PMOS devices, predicting an enhanced Short Channel Effect and Drain Induced Barrier Lowering (DIBL) effect. By using both these models, an excellent agreement is achieved between simulated and measured device characteristics for PMOS devices with gate lengths varying from 2 to 0.4 μm, over a wide range of bias conditions and operating temperatures     

Mechanistic investigation of aluminide coating formation by low-pressure chemical vapor deposition method on NiCoCrAlY coating in presence of nickel-ceria composite layer

In this study, a hybrid coating comprised of NiCoCrAlY fabricated by HVOF method, Ni–CeO₂ composite coated by electrodeposition, and aluminide coating applied by low pressure chemical vapor deposition (LPCVD) method are investigated. To elucidate the formation process of aluminide coating, the microstructure and properties of the applied coatings were examined by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and EDS analyses. It was concluded that the desired β-NiAl phases are uniformly created within a single step on the surface. Furthermore, with the extending of the coating duration from 2 to 4 h, the thickness of the aluminide coating was increased from 14 to 25 μm. The thickness values were increased even further in the presence of Ni–CeO₂ coating, where the growth mechanism was also changed. Within 4 h, a coating with a thickness of roughly 50 μm was obtained. Moreover, in the presence of Ni–CeO₂ coating, it was observed that the inward diffusion of aluminum was predominant at the beginning of the process, whereas with longer processing durations, the outward diffusion of the nickel becomes dominant instead.     

Design of a new squaring function for the Viterbi algorithm

An approximate squaring method has been developed for the Viterbi algorithm that is faster and more area efficient than conventional exact squaring methods and table look-up. Using Monte-Carlo simulations, it is shown here that the performance of the Viterbi algorithm is not degraded using this approximation. The circuit performance is verified by implementing a 7-b approximate squaring function in a 2-μm CMOS process. It operates at a maximum speed of 20 MHz, consumes 95 pW/Hz of power, and occupies an active area of 380 μm×650 μm     

Transient scattering of elastic waves by three dimensional non-axisymmetric dipping layers

Scattering of elastic plane waves by three dimensional non-axisymmetric multiple dipping layers embedded in an elastic half-space is investigated by using a boundary method. The dipping layer is subjected to incident Rayleigh waves and oblique incident SH, SV and P waves. For the steady state problem, spherical wave functions are used to express the unkown scattered field. These functions satisfy the equation of motion and radiation conditions at infinity but they do not satisfy the stress free boundary conditions on the surface of the half-space. The boundary and continuity conditions are imposed locally in the least-square sense at points on the layer interfaces and on the surface of the half-space. The transient response is constructed from the steady state solution by using Fourier synthesis. Numerical results are presented for both steady state and transient problems. Steady state problems include solutions for two non-axisymmetric dipping layers in the form of a prolate. Transient responses are presented for one and two dipping layer models subjected to incident wave signals in the shape of a Ricker wavelet. It is shown that change in azimuthal orientation of the incident wave may significantly change the surface response of the dipping layer. For the transient problem, response comparison of one and two dipping layers indicates that the addition of an extra layer may also completely change the response characteristics of the alluvium. In particular, the delay in arrival of much larger amplitude surface waves by two dipping layers in comparison with other geometrically compatible models demonstrates the importance of the detailed three dimensional modelling of layered irregularities.     

The effect of variable stator on performance of a highly loaded tandem axial flow compressor stage

Increasing the aerodynamic load on compressor blades helps to obtain a higher pressure ratio in lower rotational speeds.Considering the high aerodynamic load effects and structural concerns in the design process,it is possible to obtain higher pressure ratios compared to conventional compressors.However,it must be noted that imposing higher aerodynamic loads results in higher loss coefficients and deteriorates the overall performance.To avoid the loss increase,the boundary layer quality must be studied carefully over the blade suction surface.Employment of advanced shaped airfoils (like CDAs),slotted blades or other boundary layer control methods has helped the designers to use higher aerodynamic loads on compressor blades.Tandem cascade is a passive boundary layer control method,which is based on using the flow momentum to control the boundary layer on the suction surface and also to avoid the probable separation caused by higher aerodynamic loads.In fact,the front pressure side flow momentum helps to compensate the positive pressure gradient over the aft blade's suction side.Also,in comparison to the single blade stators,tandem variable stators have more degrees of freedom,and this issue increases the possibility of finding enhanced conditions in the compressor off-design performance.In the current study,a 3D design procedure for an axial flow tandem compressor stage has been applied to design a highly loaded stage.Following,this design is numerically investigated using a CFD code and the stage characteristic map is reported.Also,the effect of various stator stagger angles on the compressor performance and especially on the compressor surge margin has been discussed.To validate the CFD method,another known compressor stage is presented and its performance is numerically investigated and the results are compared with available experimental results.