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- 2018
- Solar Photovoltaic (SPV)
- Fuzzy Logic Control (FLC)
- MATLAB/Simulink
- Simulation
- Variable Step Size Incremental Conductance (VSS InC)
- Maximum Power Point Tracking (MPPT)
- Electrical Engineering and Automation
- Cochin University College of Engineering
- T.K.M College of Engineering
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Key-Hole Type Quadrupole Lens Test for Advanced Operation of a Microcolumn
摘要： An electron lens is an important part of a microcolumn for focusing electron beam on a sample plane. In this study, we introduced a new type electron lens with a key-hole type quadrupole electrode to improve the microcolumn for advanced operation. And, we analyzed electron beam characteristics of the electron lens using a 3-D simulation analysis.
关键词： Electron beam size,Quadrupole lens,Einzel lens,Microcolumn
更新于2025-09-23 15:22:29
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On the predictive modelling of machined surface topography in abrasive air jet polishing of quartz glass
摘要： Abrasive Air Jet Polishing (AAJP) process can be considered as one of the most promising ultra-high-precision finishing methods of quartz glass products due to the superior machined surface integrity, and the high machining feasibility for free-form surfaces. Although many academic and engineering efforts have been paid so far to AAJP process from the theoretical, numerical and experimental aspects, most of the available studies have considered neither (i) the stochastic nature of the abrasive sizes nor (ii) the elastic springback after the impacting abrasives bounced back from the workpiece surface. To fill this gap, this paper proposes the predictive model of the machined surface topography in the AAJP process of quartz glass. A series of experimental trials are performed as well which to a large extent proved the model feasibility and accuracy, and, more importantly, the necessity to consider the normally-distributed abrasive sizes, the stochastic abrasive distribution within the spray airflow, and the elastic workpiece deformation recovery after the AAJP process. Both the experimental and theoretical results also conclude that the small-sized abrasives and the low jet airflow pressure were more effective to achieve the smooth surfaces. The proposed model in this work is expected to be not only helpful to provide the theoretical foundation to study more in-depth mechanism of the AAJP process of brittle materials, but also meaningful to guide the industrial manufacturing in terms of machining parameter optimisation and machined surface quality prediction.
关键词： Elastic springback,Stochastic abrasive size,Plastic deformation,Machined surface topography,Abrasive air jet polishing
更新于2025-09-23 15:22:29
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Significance of Micro and Nano PZT Particles on Dielectric and Piezoelectric Properties of PZT-PVDF Composites
摘要： PZT-PVDF composites were prepared using different particle size of PZT and a hot press apparatus has been used for making samples. The structural and compositional analysis of the composite sample was done by using Scanning Electron Microscope (SEM) and Energy Dispersive Analysis of X-rays (EDAX) respectively. The grain size of the ball milled PZT powder was analyzed using powder X-Ray Diffraction (XRD). The samples were poled at a fixed temperature for about an hour under different poling fields. The dielectric constant (εr) and the piezoelectric properties like piezoelectric strain coefficient (d33) and voltage coefficient (g33) of composite have been analyzed.
关键词： composite,ferroelectric materials,dielectric constant,strain coefficient,voltage coefficient,particle size,lead zirconate titanate
更新于2025-09-23 15:22:29
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Surface structural alteration of multi-walled carbon nanotubes decorated by nickel nanoparticles based on laser ablation/chemical reduction methods to enhance hydrogen storage properties
摘要： The catalytic effect of nickel is addressed to decorate the multi-walled carbon nanotubes for the purpose of hydrogen storage. The hydrogen sorption/desorption are investigated using the volumetric technique. Nickel nanoparticles are distributed on the surface of nanotubes using the laser ablation/chemical reduction treatments. The hydrogen uptake is elevated at higher nickel population up to a certain value and then experiences a significant drop for larger nickel content. The laser treatment is accompanied by the induced pores around nanotubes. This gives rise to the creation of the larger pores at higher laser doses leading to decrease the hydrogen trapping. Despite the pore size distribution strongly alters during both synthesis methods, however the abundance of small pore size in laser treatments is relatively higher than the that of the other technique. In comparison, the laser ablation demonstrates a relatively smaller desorption temperature against chemical one, mainly owing to the formation of larger pore size/volume. Generally, the hydrogen trapping efficiently takes place in the laser treated samples against chemical reduction method. The highest value of hydrogen storage ~1% (0.6% weight) is corresponding to 12.3% (13% weight) of nickel loading via the laser ablation (chemical reduction).
关键词： Hydrogen uptake,Nickel nanoparticles,Laser ablation,Chemical reduction,Pore size
更新于2025-09-23 15:22:29
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A 10-year record of aerosol optical properties and radiative forcing over three environmentally distinct AERONET sites in Kenya, East Africa
摘要： In the framework of Aerosol Robotic Network (AERONET), the aerosol optical, microphysical and radiative properties were investigated over three sites (CRPSM_Malindi, Nairobi, and ICIPE_Mbita) in Kenya, East Africa (EA) during 2006-2015. The annual mean (±σ) aerosol optical depth at 440 nm (AOD440) was found high at Mbita (0.27±0.09) followed by Malindi (0.26±0.07), and low at Nairobi (0.19±0.04). Whereas, the seasonal mean AOD440 noticed high (low) values during the local dry (wet) seasons. The aerosol optical properties: AOD, single scattering albedo (SSA), asymmetry parameter (ASY), and complex aerosol refractive index (RI) exhibited significant temporal and spectral heterogeneities illustrating the complexity of aerosol types with an abundance of fine-mode aerosols during the local dry (JJA) season. Characterization of major aerosol types revealed the dominance of mixed-type followed by biomass burning aerosols. The aerosol volume size distribution revealed that the coarse- over fine-mode aerosols showed a significant contribution to the total volume particle concentration, especially at high (> 0.3) AOD440. Further, the aerosol columnar number size distribution (CSD) retrieved from the King’s inversion of spectral AOD exhibited a power law distribution affirming multiplicity of aerosol sources. The direct aerosol radiative forcing values simulated in the shortwave region using the Santa Barbara DISORT Atmospheric Radiative Transfer (SBDART) model showed good correlation (r=>0.85) with the AERONET derived ones at the top-of-atmosphere (TOA), bottom-of-atmosphere (BOA) and within the atmosphere (ATM). The annual mean (±σ) TOA, BOA, and ATM forcing values were found in the range from -8.10±3.75 to -13.23±4.87, -34.54±4.86 to -46.11±10.27, and 26.63±6.43 to 36.24±7.26 Wm-2, respectively, with an atmospheric heating rate (AHR) of 0.74±0.12–1.02±0.20 K day-1. The SBDART-derived DARF exhibited significant temporal heterogeneity with high (low) during the local dry (wet) seasons. Results derived from the present study forms a basis for regional climate change studies and could increase the accuracy of climate models over this unexplored region of Africa.
关键词： Aerosol radiative forcing,Aerosol optical depth,Size distribution,East Africa,AERONET,Single scattering albedo
更新于2025-09-23 15:22:29
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Elucidating Spray Dried Dispersion Dissolution Mechanisms with Focused Beam Reflectance Measurement: Contribution of Polymer Chemistry and Particle Properties to Performance
摘要： Amorphous spray dried dispersions (SDDs) are a key enabling technology for oral solid dosage formulations, used to improve dissolution behaviour and clinical exposure of poorly-soluble active pharmaceutical ingredients (APIs). Appropriate assessment of amorphous dissolution mechanisms is an ongoing challenge. Here we outline the novel application using Focused Beam Reflectance Measurement (FBRM) to analyse particle populations orthogonal to USP 2 dissolution. The relative impact of polymer substitution and particle attributes on 25% BMS-708163/HPMC-AS SDD dissolution was assessed. Dissolution mechanisms for SDDs were categorized into erosion versus disintegration. Beyond an initial mixing period, FBRM particle counts diminish slowly and particles are detectable until the point where API dissolution is complete. There is correlation between FBRM particle count decay rate, representing loss of SDD particles in the dissolution media, and UV dissolution rate, measuring dissolved API. For the SDD formulation examined, the degree of succinoyl substitution for HPMC-AS, SDD particle size and surface area all had an impact on dissolution. These data indicate the SDD displayed an erosion mechanism and that FBRM is capturing a rate-limiting step. From this screening tool, the mechanistic understanding and measured impact of polymer chemistry and particle properties can inform a risk-assessment and control strategy for this compound.
关键词： HPMC-AS,FBRM,SDD,substitution,dissolution-mechanism,amorphous,surface area,erosion,dispersion,particle-size
更新于2025-09-23 15:22:29
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Characterisation of AlN nano thin films prepared by PLD
摘要： Aluminium nitride (AlN) nano thin films have been prepared by pulsed laser deposition (PLD) in this paper. The microstructure and grain size of the nano thin films were characterised by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results showed that the PLD conditions such as laser fluence, ambient pressure and substrate temperature influence the thickness, morphology and grain size of the nano thin films obviously, i.e. the surface of the nano thin films becomes rough while the grain size increases with increasing the laser fluence, ambient pressure and substrate temperature. In addition, there exists a preferred orientation growth in the thin films.
关键词： microstructure,pulsed laser deposition (PLD),aluminium nitride,grain size,Nano thin films
更新于2025-09-23 15:22:29
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[IEEE 2018 China International SAR Symposium (CISS) - Shanghai (2018.10.10-2018.10.12)] 2018 China International SAR Symposium (CISS) - Compact Size Multi-Channel True Time Delay Moudle with High Accuracy
摘要： A 9-bit digital true time delay (TDD) and amplification module with high integration is proposed in this paper. The true time delay units, bi-directional amplifiers, serial-to-parallel converter and power pulse modulated circuits are integrated in a multi-chip module (MCM) with monolithic microwave integrated circuit (MMIC) and surface mount technology (SMT). Multi-layer microwave board is used to implement the routing of DC, control and RF signals. Moreover, in order to achieve better flatness of time delay, distributed amplifiers and high isolation cavity structures have been adopted. To calculate the spatial isolation of the cavity structures, electromagnetic simulation with microwave high frequency software has been utilized. For verification, a multi-channel TDD module has been designed, fabricated and measured. According to the measured results, the TDD module achieves the receive gain within 4.5 dB ± 0.8 dB, transmit power within 17dBm ± 1.0 dB, and high time-delay accuracy within ± 0.5 ps for 6.25 ps and ± 20 ps for 1600 ps, simultaneously.
关键词： high accuracy,compact size,multi-channel,true time delay
更新于2025-09-23 15:22:29
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[IEEE 2018 IEEE 13th Annual International Conference on Nano/Micro Engineered and Molecular Systems (NEMS) - Singapore, Singapore (2018.4.22-2018.4.26)] 2018 IEEE 13th Annual International Conference on Nano/Micro Engineered and Molecular Systems (NEMS) - Wafer-Scale Fabrication of V-Shaped Silicon Nano-Slit Arrays
摘要： This paper presents a strategy of fabricating v-shaped nano-slit arrays in silicon substrates at wafer scale, by using a three-step wet anisotropic etching method with the combination of a color-feed mechanism. Through careful mask design, nano-slits with various aspect ratios and sizes were obtained at wafer scale. The minimum feature size of the obtained nano-slits was 5 nm, which holds great potential in bio-molecule analysis such as DNA and protein detection and analysis.
关键词： uniformity,v-shaped nano-slit arrays,wet anisotropic etching,feature size
更新于2025-09-23 15:22:29
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Effects of Microsphere Size on the Mechanical Properties of Photonic Crystals
摘要： Photonic crystal (PC) thin films that are self-assembled from different-sized silica microspheres were prepared for studying mechanical properties via nanoindentation at the submicron scale. We found that the silica photonic crystals (PCs) possessed a face-centered cubic (FCC) microstructure and their elastic modulus and hardness were in the range of ~1.81–4.92 GPa and 0.008–0.033 GPa, respectively. The calculated results proved that there were size-dependent properties in the silica PCs, in that the elastic modulus and hardness increased as the diameter decreased from 538 nm to 326 nm. After studying the total work and plastic work in the progressive deformation of silica PCs during the nanoindentation tests, we developed a two-stage deformation model to explain how the microsphere size affects the mechanical properties of PC thin films. The phenomenon of 'smaller is stronger' is mainly due to the energy consumption, which combines the effects of microstructure collapse, microsphere slide, and reduced porosity during the whole loading and unloading process. In addition, the results of numerical simulation matched the experimental data and reflected the energy change rules of PCs during the indentation process. Furthermore, the study affords useful guidance for constructing high-performance films with proper design and potential application in next-generation PC materials.
关键词： photonic crystals,deformation mechanism,nanoindentation,size-dependent
更新于2025-09-23 15:22:29