Engineering Research Express

Stimulated emission depletion (STED) microscopy is one of the highly explored far field microscopic techniques capable of providing resolution down to few tenth of nanometers even in in situ environments. Optically engineered donut beam is the main element of a STED microscope. To accurately predict the resolution of a STED microscope, donut beam spatial profile needs to be properly measured at the focal plane of high numerical aperture objective. In this work, we measured donut profile by collecting Raman scattering from polymeric nanoparticles, and one photon luminescence (1PL), pure scattering, and up-conversion luminescence from gold nanoparticles. We found that donut profile obtained from Raman scattering, 1PL, and pure scattering can be fitted with a x ² function (normal profile); whereas donut obtained from up-conversion luminescence can be fitted with x ⁴ function (distorted profile). Calculation of STED point spread function for continuous wave excitation using normal donut profile shows full width half maximum width (i.e. resolution) of 60 nm but distorted donut profile, in comparison to excitation width of 250 nm, barely shows any improvement. This study shows that the measured focal plane intensity profile of donut beam is severely affected by inherent property of optical signal collected from nanoparticle.

The present research makes use of a braiding-cum-weaving technique for the fabrication and investigation of electricity-induced heating fabrics. Braided conductive yarns (BCYs) were produced using a Maypole braiding machine by introducing conductive copper filament as the core and polyester multifilament yarn as the sheath. A different number of polyester yarns, 6-, 10- and 16-end, were used to cover the copper core. Electrically heating fabrics (e-HFs) were fabricated by interweaving the BCYs through pick insertion in a plain-woven construction at 4-, 8- and 12-pick spacing. Various electro-mechanical tests were carried out on the BCYs and e-HFs. The mechanical performance of 16-end BCY was the most superior while 6-end BCY exhibited the poorest performance amongst the three BCY-types. The temperature profiles obtained via thermal mapping elucidate the difference in the heat-barrier effect of each of the BCYs. It also shows the presence of overlapping concentric (cylindrical) isotherms running along the axes of the BCYs. These isotherms have shown to significantly affect the temperature uniformity on the e-HF surface. Heating response under different variables—pick-spacing, time, voltage and input power, were evaluated, and direct correlations were found. A temperature of about 89.8 °C was attained at 5 V after 40 min of heating. For an input power of 3, 5 and 7 W, a maximum temperature of 40.5, 48.8 and 55.3 °C was measured for different e-HFs. Wash and sweat durability tests were also carried out to corroborate the utility of the e-HFs for day-to-day usage. These tests proved to have a minimal detrimental effect on the heating performance of the e-HFs establishing a good utilitarian quotient of such material for the purpose of wearable electronics and essentially, as active heating garments.

We proposed a relationship model between the exit velocity distribution and the shape of the extrusion profile. To verify the model, we designed multiple-extrusion ram differential extrusion and used the Arbitrary Lagrangian-Eulerian (ALE) method to simulate the natural bending deformation of the sheet metal. The die experimental test used a self-bending extrusion die for sheet metal was designed via a spline curve with inclination as the contour of the deflector chamber. The results showed that the standard arc profile was extruded when the exit velocity was linear, and the relative error between the predicted radius of curvature and the ALE simulation result was controlled within 5%. The relative error between the predicted value and the actual experimental result was 9.9%. Thus, this study can provide a reference for the design of self-bending extrusion dies.

We propose an interference based molecular transistor consisting of two side groups and a central molecule group. The proposed transistor incorporates a more realistic situation and utilizes three level interference model, a novel concept which yields better transistor performance. Analytical expression of the transmission is obtained using three site energy model and the transfer characteristic of the proposed molecular transistor is investigated. Two different transistor configurations are considered, namely the central molecule directly coupled to the gate lead and isolated by a gate dielectric. The closed form expression for the voltage at which the transistor turns OFF, an important design parameter, is also obtained. Then, performance comparison is done between the two proposed configurations by varying the coupling energy between the side group states and the leads. It is shown that the dielectric separated central molecule configuration has much lower subthreshold slope than present day MOSFETs and much higher ON/OFF current ratio than the four level interference based molecular transistor. Finally, the application of the obtained analytical expressions is demonstrated with an example of logic inverter design. This work may provide an analytical tool for designing, analyzing and improving the performance of interference based molecular transistors as well as guidelines for experimental research.

For recording bioelectrical signals using Instrumentation Amplifiers (INA), capacitive AC coupling of the differential inputs is necessary for two major reasons, providing DC electrical isolation of the subject to avoid hazards of tissue burn, and to block DC or very low frequency skin-electrode contact potentials. The latter, when met, allows high admissible differential gain of the INA, which in turn, is expected to give a desirable high Common Mode Rejection Ratio (CMRR). However, the use of conventional passive RC high pass filters at the input greatly reduces CMRR. This work intends to design an improved AC coupled input circuitry for INA giving high CMRR and high input impedance. A differential RC high-pass input circuit has been developed using an active element. It creates an effective high resistance for the common mode current but provides a low resistance path to input bias currents for normal operation of the INA. Between 1 Hz and 100 Hz, CMRR of the DC coupled INA (LT1167) was 115 dB, using a well matched traditional RC coupling, 55 to 95 dB, while it was 110 dB using the improved active AC coupled circuit. This improvement was practically demonstrated through Electrocardiogram measurements from a human subject. A novel active AC coupling circuitry has been proposed and developed giving high CMRR, very close to the maximum of an INA, which is non-varying within the frequency band of interest of Bioelectrical amplifiers. The developed input circuit will improve all bioelectrical measurements in the future.

This research reports the WEDM of heat treated Ti-6Al-4V by considering the pulse on/off duration, current, voltage and wire feed rate as machining parameters via Taguchi’s L ₂₅ array to assess the output responses i.e. material removal rate (MRR) and surface roughness (SR). It was observed that the material removal was significantly influenced with the change of wire feed rate at longer P-on (128 μs) and higher current (230 A). Lower wire feed rate (8 m min ⁻¹) and shorter P-off (51 μs) increased material removal more than that of higher wire feed rate (10 m min ⁻¹) with longer P-off (63 μs). Craters and globules of debris were viewed during all machining conditions on the machined surfaces. However, surface with maximum MRR (Trial 21, 59.021 mm ³ min ⁻¹) depicts droplets of molten materials, micro-cracks and micro-voids compared to deep and wide craters on the surface with minimum MRR (Trial 5, 2.973 mm ³ min ⁻¹) in SEM examination. The surface finish (1.301 μm) at lower value of P-on (112 μs) is always better than that at higher pulse-on-time (128 μs, 3.038 μm). Furthermore, the output responses were statistically investigated using analysis of variance (ANOVA) to evaluate the significant factors and contribution of each selected parameters.

The purpose of this study is to develop a disposable, inexpensive, and compact biosensor for rapid detection of ciprofloxacin (Cipro) in water. The electrochemical sensor used is a screen-printed electrode (SPE), and chronoamperometric (CA) method is used for detection of Cipro. Different concentrations of Cipro were tested for the response of the sensor, by the simple application of a droplet of Cipro at the working electrode of the SPE and measured the CA response for a particular applied voltage of 0.35 V versus Ag/AgCl. From the CA analysis and the linear regression analysis equation, we measured the sensitivity to be 0.031 μA μM ⁻¹. The limit of detection of the sensor was measured to be 0.33 μM, with a linear determination coefficient of .986, over a linear range of concentrations of Cipro (13.75 μM–135 μM).

In the present paper, we will report results about experimental study of brain functional connectivity performed by using a multichannel magnetoencephalographic system based on superconducting quantum interference devices. Such quantum devices exhibit magnetic field sensitivity high enough as to measure the extremely weak magnetic signals generated by the electrical neuronal activity. This powerful tool allows to study the temporal relation of spatially neurophysiological events, i.e. the functional connectivity, which recently captured attention in the field of brain function exploration. The paper reports system and sensors performance as well as data acquisition system and a detailed pipeline data analysis will be described. Brain connectivity measurements relative to parents of children with autism spectrum disorder will be shown, highlighting the preliminary results in topological metrics for different sub-items of autism-spectrum quotient test.

This paper reports a novel shadow mask aligner, which is capable of aligning planar with ∼1 μm alignment error as well as provision to compensate the wedge error by using movements of three precision linear actuators, spotted under optical microscope. The use of three points leveling also overcomes the common error of the upper assembly bending, which could occur with time after its continuous use. The reported wafer/mask holding mechanism is able to accommodate substrates of 3″ to 6″ diameter. The unique magnetic clamping mechanism after alignment has been successfully demonstrated. The fabricated system is useful for alignment of mask and wafer, as well as for other applications like nano-imprint and micro-contact printing lithography. In these cases, moulds/stamp is aligned with the patterned/un-patterned target substrate; to create complex 3D structures micro-assembly of independently fabricated 2D components by proper aligning and clamping.

Light weight thin alloys and composite materials have revolutionized aerospace, marine, electronics and construction industries. Based on their application and structural behaviour, plates are often designed in arbitrary shapes. This paper deals with free vibration analysis of simply supported plates with different geometries. The plates are modelled with a stiffener which is curvilinear in shape. To enable comparison of plates, three parameters viz., the area of plates, starting point of the stiffener and curvature of the stiffener were kept constant. The Finite Element model was developed for free vibration analysis using FEAST (Finite Element Analysis of Strctures). The geometries considered were circular, square, rectangular (with aspect ratio of 1.25, 1.50 and 1.75, respectively) and skew square (with 70 ^o, 76.67 ^o and 83.33 ^o skew angles, respectively). It was observed that the stiffness increased with the increase in aspect ratio of bare plates unlike the case of stiffened plates. In the case of stiffened plates, the stiffness increased with increase in aspect ratio up to 1.50 and thereafter decreased for the aspect ratio of 1.75. The bare and stiffened plates showed an increase in stiffness with increase in skewness of the geometry. Among the geometries considered, the stiffener was found to be most effective for the circular plate (110% increase in stiffness compared to bare plate) and least effective for the rectangular plate (50% increase in stiffness compared to bare plate) with 1.75 aspect ratio. The rectangular plate with aspect ratio 1.75 had the maximum overall stiffness and the circular plate had the minimum overall stiffness in the case of bare plates. In the case of stiffened plates, skew plates with 70 ^o skew angle had the maximum overall stiffness and the circular plate had the minimum overall stiffness.

Diesel exhaust emission soot (DEES) collected and coated on polyurethane foam (PUF). DEES coated foam (DEES-foam) was found hydrophobic and oleophilic in nature and can be used for oil-water separation. Kinetic study of oil sorption showed that the rate of sorption directly dependent on the viscosity of the oil. Petrol and engine oils were found fastest and slowest to absorb on DEES-foam, respectively. Pseudo-second order kinetic models fitted best to both oil and dye adsorption kinetic data. Maximum adsorption capacity for the adsorption of rhodamine B (RB) was found to be 17.7 g g ⁻¹. Langmuir isotherm was most appropriate to isotherm data of adsorption and R _L < 1 (Langmuir dimensionless constant) showed favorability of adsorption process. The adsorbed dye was successfully desorbed in ethanol and DEES was found reusable for multiple cycles.

The increasing rate of erosion due to the presence of excessive silt concentration in river water of the Himalayan region is adversely affecting the availability of most demanded hydropower in India. Many researchers investigated several methods to minimize the rate of erosion wear on hydro turbine blades, runners, pumps, guide vanes, valves, seats, etc. However, some of them are successful, some are not. The problem of silt erosion is encountered during the high flow monsoon period. Various techniques have been developed to rally suitable coatings like chemical vapor deposition technique, thermal spray technique, an electroplating technique, etc. Therefore, in this paper, an attempt has been made to provide an overview of suitable micro and nanocomposite coatings with the application of thermal spray high-velocity oxygen fuel deposition process to minimize the problem of erosion due to silt in hydropower plants.

This article deals with the analysis of buckling behavior of simply supported porous functionally graded (FG) sandwich nanoplates resting on a Kerr foundation. The material properties of the FG sandwich nanoplate considered to be dependent on temperature and graded continuously along the thickness direction. The analytical equations are obtained using Hamilton’s variational principle, by considering the strain energies due to the thermal loads, and higher order nonlocal strain gradient plate theory which captures the shear deformation influences needless of any shear correction factor. Power-law model is adopted to describe continuous variation of material properties of FG sandwich nanoplate. An accurate solution for nonlinear temperature variation across the sandwich nanoplate thickness of is employed taking into account the thermal conductivity, the inhomogeneity parameter and the sandwich schemes. The numerical results computed indicate the influence of volume fraction index, nonlocal parameter, length scale parameter, porosity coefficient, Kerr foundation and temperature difference on the buckling response.

Acoustic emission (AE) provide snumerous statistics regarding the fracture attitude of distinct materials. In this research AE investigation was handled on 14 numbers of tensile specimens built of aluminum 6061 strengthened by silicon carbide particles at which 100 KN. Universal testing machine is used for tensile testing. The AE parameters are refined from the specimens and only 60% of actual tensile strength parameters are considered for further analysis. Parameters like count, energy, duration, rise time and amplitude are used to characterize the fractures occurred on metal matrix composites due to the low matrix cavitations, particle cracking, interfacial debonding and the transition of mode from tensile to shear. The two individual artificial neural networks generated with the parameters rise angle and by theshear mode of rise angle. The ultimate strength is considered as the anticipated output by training it properly. The structure has the capable to predict the absolute fault up to 2.74% and 1.31%. The shear mode values which occurred at few cycles before the failure of the specimen as inputs are found to be better than the rise angle(RA) data entered, however the prediction exercise proved by the two trained artificial neural network(ANN) has proved its significances.

This paper highlights the tool life of Al ₂O ₃ reinforced thermoplastic composites for rapid tooling (RT) applications. The RT have been 3D printed with fused deposition modelling (FDM) by using recycled low-density polyethylene (LDPE) reinforced with double particle size (DPS) Al ₂O ₃ and high-density polyethylene (HDPE) reinforced with triple particle size (TPS) Al ₂O ₃. The tool life has been calculated in terms of weight loss of RT while milling operation. The study also reports effect of machining conditions on surface hardness, porosity, thermal stability and microstructure of RT as a case study. The results of study suggest that the machined zones prepared with RT are more thermally stable.

Self-powered photodetectors (PDs) are suitable for application in smart systems, image sensing and optical communications. Herein, a self-powered PD based on triple cation lead-halide perovskite (TCLP) is reported. We showed the effect of bromide concentration on the optical and structural properties of the TCLP films. Additionally, an environmental stability test was conducted and it was found that TCLP with 10% Br can remain stable for up to 128 days after exposure to ambient air. Using this material, a self-powered perovskite PD was fabricated and demonstrated an impressive performance with a responsivity of 0.52 A W ⁻¹, detectivity of 8.8 × 10 ¹² Jones, on/off ratio of 7.3 × 10 ⁵, and a rapid rise and decay time of 19 μs and 21 μs, respectively. This work offers a useful insight into the effects the fabrication method of the thin film plays in building low-cost, stable, and high-performance self-powered PDs for application in structural health monitoring, imaging, optical communication, and biomedical sensing.

In photovoltaic industry, silica crucible has an important influence on the quality of single crystal silicon. To obtain a silica glass crucible with large diameter, high uniformity, and low bubble content, two series of crucibles were prepared by the arc melting method, one with various melting parameters (initial power, melting power, and melting time) and crucible sizes, and the other with various quartz purities. The bubbles inside the crucible wall and pores on the inner surface were all measured using a polarised optical microscope and a portable microscope. The results show that all crucibles have a bubble aggregation area in their inner surface (0–0.4 mm), in which the density and size of bubbles are affected by melting time, melting power, and the distance between the crucible and the graphite electrode. The uniformity of the crucible decreases as the crucible diameter increases (16–28 inches), and the crucible is relatively stable when the initial power is below 400 kW. In final, a silica crucible with large size (diameter of 28 inches) and low bubble content on inner surface (∼50% reduction than that of traditional crucibles) was successfully prepared, which is of great value to the photovoltaic industry.

Nanomaterials have become crucial to develop new technologies in several practical applications fields. Until now nanostructures have been mostly associated with electromagnetism and optics. The aim of this letter is to extend the applicability of such structures also to other wave-based phenomena, such as thermodynamics. Here, in analogy to electric nanocircuits, we present the concept of thermal circuit nanoelements. The basic circuit elements, namely, resistors, capacitors and inductors, are evaluated in terms of electromagnetic (electric permittivity ε) and thermal (conductivity k and convection coefficient h) nanostructure properties. Coupled nanocircuits and parallel/series combinations are also developed. The multi-functional nanostructure can simultaneously control and manipulate both electromagnetic and thermal waves, paving the way to realize more complex electrical and thermal devices.

A novel configuration called negative axicon microsphere (NAMS) is proposed to generate ultralong light focusing. The key configurations of the engineered microsphere are investigated to optimize the figure-of-merit (FOM) of focusing beam. Through the fabricated NAMS with an original radius R of 11.5 μm, incident light at a wavelength λ of 405 nm can form a focused beam ∼52 λ away from its flat exit surface with the beam length of 120.4 λ. The ultralong focusing beam can be applied for remote laser nano-patterning etc with long depth-of-focus (DOF).

Wavefront Sensors (WFS) have now become core components in the fields of adaptive optics for astronomy, biomedical optics, or metrology of optical systems. However, none of the designs used or proposed so far seems to achieve simultaneously a high spatial resolution at the pupil of the tested optics and absolute measurement accuracy comparable to that attained by laser-interferometers. This paper presents a new WFS concept susceptible to achieving both previous goals. This device is named crossed-sine wavefront sensor and is based on a gradient transmission filter located near the image plane of the tested system. The theoretical principle of the sensor is fully described in a Fourier optics framework. Numerical simulations confirm that the achievable measurement accuracy can reach λ/80 RMS, which is significantly higher than achieved by other types of WFS. The crossed-sine WFS also offers the advantages of being quasi-achromatic and working on slightly extended, natural or artificial light sources.

The increasing rate of erosion due to the presence of excessive silt concentration in river water of the Himalayan region is adversely affecting the availability of most demanded hydropower in India. Many researchers investigated several methods to minimize the rate of erosion wear on hydro turbine blades, runners, pumps, guide vanes, valves, seats, etc. However, some of them are successful, some are not. The problem of silt erosion is encountered during the high flow monsoon period. Various techniques have been developed to rally suitable coatings like chemical vapor deposition technique, thermal spray technique, an electroplating technique, etc. Therefore, in this paper, an attempt has been made to provide an overview of suitable micro and nanocomposite coatings with the application of thermal spray high-velocity oxygen fuel deposition process to minimize the problem of erosion due to silt in hydropower plants.