Freezing-induced splashing during impact of molten metal droplets with high Weber numbers

The impact of molten tin droplets (0.6 mm diameter) on solid surfaces was observed for a range of impact velocities (10–30 m/s), substrate temperatures (25–200 °C) and substrate materials (stainless steel, aluminum and glass). The substrate was mounted on the rim of a rotating flywheel and the collision of single droplets with the moving substrate was photographed. Droplet impact Reynolds number ranged from 2.2 × 10⁴ to 6.5 × 10⁴ and Weber number from 8.0 × 10² to 7.2 × 10³. On a hot surface there was no splashing and droplets spread to form disk-like splats with smooth edges. Solidification around the edges of droplets spreading on cold surfaces created a solid rim that obstructed flow and triggered splashing. An analytical model was developed to predict the transition temperature at which splashing disappeared by assuming that the thickness of the solid layer had to equal that of the splat in the time the droplet spread to its maximum extent in order to obstruct liquid flow. The model predicted the transition temperature for aluminum and stainless steel surfaces, assuming that thermal contact resistance between the droplet and substrate varied between 10⁻⁶ and 10⁻⁷ m² K/W. The model also predicted that tin droplets would not splash on glass surfaces maintained at or above room temperature, and this was confirmed by experiments.     

A simple and versatile overcurrent protection circuit for power MOSFETs

This paper proposes an overcurrent protection (OCP) circuit for power MOSFETs employed in low voltage power converters. The proposed configuration requires only discrete components with a gate driver IC and uses the voltage drop across the device for overcurrent detection. It can operate independently in cycle-by-cycle shutdown and multiple cycle shutdown modes. In coordination with a micro-controller based driver IC input signal generator and controller, the proposed OCP circuit can also operate in a single cycle latch-up and hiccup OCP modes. The performance of the proposed scheme is evaluated experimentally at both, hard and soft fault conditions. By experimentation, it is shown that the proposed circuit can operate in various protection modes and capable of protecting a MOSFET in both, hard and soft fault conditions.     

Plasma Etch Processes for Embedded FRAM Integration

We describe the etch processes used for integration of embedded ferroelectric random access memory (FRAM) within a standard CMOS logic flow. The ferroelectric module is inserted following front-end contact formation and prior to backend integration using only two additional mask levels: capacitor pattern and bi-level via pattern. The single-mask stack etch process employs a TiAlN hardmask to define Ir/IrO_x/PZT/IrO_x/Ir capacitors. Protective sidewalls can be formed using an etchback process. The bi-level via etch and subsequent metal fill processes complete the FRAM module formation. Functional 4 MB arrays embedded with 5 levels of Cu/FSG integration have been demonstrated.     

A design approach for myoelectric arm with hand and wrist motions using single actuator

This paper relates to the development of prosthetic myoelectric hand that performs many functions of real human hand like opening and closing of fingers and wrist rotation. This dual movement of prosthetic hand is controlled by a single DC motor. Below-elbow amputee persons with missing limbs can append this prosthetic hand with the available stump and can do some of the hand operations with multiple degrees of freedom by voluntary activation of muscles using electromyogram (EMG) electrodes. To rehabilitate such a person, facilities like opening, closing, grasping, and lifting objects of different weight with variable grip force are available like natural hand. The main design consideration includes degrees of freedom, number of actuators, power of actuators, reliability, electronic control, light weight, economic viability, wrist rotation, variable grip force pattern, and ease of attachment with limb. Use of electromagnetic clutches along with the coupling logic of DC motor and microcontroller based on grip force generation and wrist rotation based on EMG signals imparts a new function to the device. It will be useful for both robotic and prosthetic industry.     

Grafting of polyaniline onto the radiation crosslinked chitosan

In this paper we report the chemical grafting of polyaniline onto the radiation crosslinked chitosan. Chitosan is crosslinked using 8 MeV electron beam and Co⁶⁰ γ-ray in the presence of CCl₄ as sensitizer. The so-obtained crosslinked chitosan is grafted with polyaniline (PANI) chemically using ammonium peroxy disulphate (APS) as an initiator. Grafted polymer is characterized by dissolution, swelling, UV–vis–NIR spectroscopy, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis, DC conductivity and nanoindentation studies. From the dissolution studies, grafting of PANI onto the crosslinked chitosan is confirmed. From the weight of films before and after grafting, grafting percentage is calculated. Grafting percentage increases as the monomer concentration increases and decreases with increase in crosslinking. This may be due to the decrease in the penetration of monomer onto the chitosan matrix with increase in crosslinking density. This is verified from SEM (cross-sectional view) of blend. UV–vis–NIR spectrum shows absorption peaks of PANI. Electrical property of grafted polymer is improved after doping with 1 M HCl. The change in volume conductivity is from 10⁻¹¹ to 10⁻⁵ S/cm and surface conductivity from 10⁻¹⁰ to 10⁻² S/cm. From TGA it is observed that grafted polymer and doped polymer are thermally stable.     

Dielectric properties of electron irradiated PbZrO<Subscript>3</Subscript> thin films

The present paper deals with the study of the effects of electron (8 MeV) irradiation on the dielectric and ferroelectric properties of PbZrO₃ thin films grown by sol-gel technique. The films were (0.62 μm thick) subjected to electron irradiation using Microtron accelerator (delivered dose 80, 100, 120 kGy). The films were well crystallized prior to and after electron irradiation. However, local amorphization was observed after irradiation. There is an appreciable change in the dielectric constant after irradiation with different delivered doses. The dielectric loss showed significant frequency dispersion for both unirradiated and electron irradiated films. T _c was found to shift towards higher temperature with increasing delivered dose. The effect of radiation induced increase of ɛ′(T) is related to an internal bias field, which is caused by radiation induced charges trapped at grain boundaries. The double butterfly loop is retained even after electron irradiation to the different delivered doses. The broader hysteresis loop seems to be related to radiation induced charges causing an enhanced space charge polarization. Radiation-induced oxygen vacancies do not change the general shape of the AFE hysteresis loop but they increase P _s of the hysteresis at the electric field forced AFE to FE phase transition. We attribute the changes in the dielectric properties to the structural defects such as oxygen vacancies and radiation induced charges. The shift in T _C, increase in dielectric constant, broader hysteresis loop, and increase in P _r can be related to radiation induced charges causing space charge polarization. Double butterfly and hysteresis loops were retained indicative of AFE nature of the films.     

Synthesis of nanocrystalline Ni0.5Zn0.5Fe2O4 ferrite and study of its magnetic behavior at different temperatures

Ni_0.5Zn_0.5Fe₂O₄ ferrite nanocrystals with average diameter in the range of 1–2 nm have been synthesized by reverse microemulsion. X-ray diffraction (XRD), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM) are used to characterize the structural, morphological and magnetic properties. X-ray analysis showed that the nanocrystals possess cubic spinel structure. The absence of hysteresis, negligible remanence and coercivity at 300 K indicate the superparamagnetic character and single domain in the nanocrystalline Ni_0.5Zn_0.5Fe₂O₄ ferrite materials. The nanocrystalline Ni_0.5Zn_0.5Fe₂O₄ ferrite were annealed at 600 °C. As a result of heat treatment the average particle size increases from 2 nm to 5 nm and the corresponding magnetization values have increased to 21.69 emu/g at 300 K. However, at low temperature of 100 K, the annealed samples show hysteresis loop which is the characteristic of a superparamagnetic to ferromagnetic transition. In addition, a comparative study of the magnetic properties of Ni_0.5Zn_0.5Fe₂O₄ ferrite nanocrystals obtained from reverse microemulsion has been carried out with those obtained from the general chemical co-precipitation route.     

Automated Plant Leaf Disease Detection and Classification Using Fuzzy Based Function Network

Wireless Personal Communications - In recent years, the applications of the computer vision concepts and information communication technology has been observed in number of applications including...