Theory and analysis of electrode size optimization for capacitive microfabricated ultrasonic transducers

Cataloged from PDF version of article.Theoretical analysis and computer simulations of capacitive microfabricated ultrasonic transducers indicate that device performance can be optimized through judicious patterning of electrodes. The conceptual basis of the analysis is that electrostatic force should be applied only where it is most effective, such as at the center of a circular membrane. If breakdown mechanisms are ignored, an infinitesimally small electrode with an infinite bias voltage results in the optimal transducer, A more realistic design example compares the 3-dB bandwidths of a fully metalized transducer and a partially metalized transducer, each tuned with a lossless Butterworth network. It is found that the bandwidth of the optimally metalized device is twice that of the fully metalized device

Optimasi Desain Rangka Sepeda Berbahan Baku Komposit Berbasis Metode Anova

Pada dasarnya kriteria frame yang baik adalah memilki kekuatan dan kekakuan yang tinggi tetapi ringan dan mempunyai ketahanan terhadap korosi. Berdasarkan kriteria tersebut digunakanlah material komposit, dimana dapat diperoleh kriteria yang lebih baik dibandingkan dengan frame baja atau alumunium, Frame dapat dibuat lebih kuat dan ringan, tetapi yang lebih penting, desainer dapat mengontrol karakteristik pengendalian dan tidak dibatasi oleh penggunaan metal. Adapun tujuan dilakukan penelitian ini adalah menganalisa kondisi optimum desain rangka sepeda dengan metode Taguchi dan analisis ANOVA. Berdasarkan hasil analisis pengolahan data dengan kondisi desain optimum yg memberikan Tegangan Von Mises (MPa) yang besar adalah : A2 B2 C3 atau yang dilakukan perhitungan dengan kondisi desain menggunakan Seat Tube Angle sebesar 72o, dengan pergeseran Head Tube 0.2 mm dan beban pengendara sebesar 90 kg. Analisis perhitungan dengan ANOVA untuk mengetahui pengaruh masing-masing faktor terhadap perhitungan Tegangan Maksimum pada sepeda berbahan komposit, yaitu : Faktor A (Seat Tube Angle) sebesar 85% memiliki pengaruh yang sangat besar, dibandingkan dengan faktor C (Beban Pengendara) sebesar 10%, selanjutnya untuk faktor B (Pergeseran Head Tube) memiliki pengaruh 1%

Surface micromachined capacitive ultrasonic transducers

Cataloged from PDF version of article.The current state of a novel technology, surface microfabricated ultrasonic transducers, is reported. Experiments demonstrating both air and water transmission are presented. Air-coupled longitudinal wave transmission through aluminum is demonstrated, implying a 110 dB dynamic range for transducers at 2.3 MHz in air. Water transmission experiments from 1 to 20 MHz are performed, with a measured 60 dB SNR at 3 MHz. A theoretical model is proposed that agrees well with observed transducer behavior. Most significantly, the model is used to demonstrate that microfabricated ultrasonic transducers constitute an attractive alternative to piezoelectric transducers in many applications

Cu-Mn and Cu-Ce supported over agro-based carbons: characteristics and NOx adsorption study

As there is an urgent need for cheaper and sustainable resources for selective catalytic reduction catalyst, this study determined the potential, in terms of the catalyst characteristics and NOx adsorption, of coconut shell (CSAC) and palm kernel shell activated carbons (PSAC) to be used as precursors for the catalyst in a low-temperature flue gas denitrification system. The carbons were impregnated with bimetallic catalysts –copper-manganese (Cu-Mn) and copper-cerium (Cu-Ce) – before calcined at low temperature. The produced coconut shell catalysts (CuMn/CS and CuCe/CS) and palm kernel shell catalysts (CuMn/PS and CuCe/PS) were then characterized using a nitrogen adsorption-desorption test, Fourier-Transform infra-red, x-ray fluorescence, x-ray diffraction and hydrogen temperature-programmed reduction. The removal of NOx was also studied for all catalysts in a fixed-bed reactor. It was found that CuMn/CS gave the highest NOx removal. CuMn/CS had high pore volume, good Cu-Mn crystallinity, highmetal loading and dispersion, high copper reduction activity at the operating temperature, and rich in ketone and amine surface functional groups. It is then concluded that the coconut shell has the potential to be developed as a good SCR catalyst via impregnation with Cu-Mn

Strength Characteristics of Mortar Containing Different Sizes Glass Powder

A greater portion of nonrecyclable waste glass is accumulated on landfills creating a serious environmental problem. Recent studies have been carried out to utilize the waste glass in construction as partial replacement of cement. This paper investigates the fineness properties of four sizes glass particles and strength characteristics of mortar in which cement is partially replaced with glass powder in the replacement level with 10%, 20%, 30% and 40%. Mortar cubes containing with varying particle sizes in the ranges of 212 μm, 75 μm, 63-38 μm and lower than 38 μm and in a water to cement ratio 0f 0.50 and 0.45 have been prepared. Room temperature and relative humidity have been maintained 32ºC and 90% respectively during the curing process. Replacement of 10% cement with glass powder reveals the higher compressive strength at 28days than other levels of replacement. The reduction in compressive strength increases with the level of cement replacement

Genetic Diversity among Nigeria Maiwa Type of Pearl Millet Germplasm

Characterization of pearl millet germplasm is imperative for categorization of germplasm and identification of the desirable genotypes for introgression into breeding programs. The available pearl millet genetic resources from Nigeria, and especially photoperiodsensitive materials or stay-green traits, have so far been exploited only to a limited extent. The present study was undertaken for initial morphological and phonological characterization of unexploited ‘maiwa’ or stay-green pearl millet accession in geographical gaps of Nigeria, to ensure high precision in future genotyping and phenotyping. The germplasm displayed considerable variability for Downy mildew severity,,days to 50 % flowering, plant height, panicle length and grain weight. There was no significant differences to striga infestation since there was no experience of striga emergence, suggesting resistance

Association of Blood Lead (Pb) and Plasma Homocysteine: A Cross Sectional Survey in Karachi, Pakistan

Background: High blood lead (Pb) and hyperhomocysteinemia have been found to be associated with cardiovascular disease (CVD). Mean blood Pb and mean plasma homocysteine levels have been reported to be high in Pakistani population. The objective of the present study was to assess the relationship of blood Pb to the risk of hyperhomocysteinemia in a low income urban population of Karachi, Pakistan. Methodology/Principal Findings: In a cross sectional survey, 872 healthy adults (355 males, 517 females, age 18-60 years) were recruited from a low income urban population of Karachi. Fasting venous blood was obtained and assessed for blood Pb and plasma/serum homocysteine, folate, pyridoxal phosphate (PLP, a coenzymic form of vitamin B6) and vitamin B12. The study population had median (IQR) blood Pb of 10.82 microg/dL (8.29-13.60). Prevalence of high blood Pb (levels\u3e10 microg/dL) was higher in males compared to females (62.5% males vs 56% females, p value=0.05). Mean+/-SD/median (IQR) value of plasma homocysteine was significantly higher in the highest quartile of blood Pb compared to the lowest quartile 16.13+/-11.2 micromol/L vs 13.28+/-9.7micromol/L/13.15 (10.33-17.81) micromol/L vs 11.09 (8.65 14.31) micromol/L (p valu

Sustainable Nanopozzolan Modified Cement: Characterizations and Morphology of Calcium Silicate Hydrate during Hydration

There are environmental and sustainable benefits of partially replacing cement with industrial by-products or synthetic materials in cement based products. Since microstructural behaviours of cement based products are the crucial parameters that govern their sustainability and durability, this study investigates the microstructural comparison between two different types of cement replacements as nanopozzolan modified cement (NPMC) in cement based product by focusing on the evidence of pozzolanic reactivity in corroboration with physical and mechanical properties. Characterization and morphology techniques using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), energy-dispersive X-ray spectroscopy (EDS), and scanning electron microscopy (SEM) were carried out to assess the pozzolanic reactivity of cement paste modified with the combination of nano- and micro silica as NPMC in comparison to unmodified cement paste (UCP) of 0.5 water to cement ratio (w/c). Results were then substantiated with compressive strength (CS) results as mechanical property. Results of this study showed clear evidence of pozzolanicity for all samples with varying reactivity with NPMC being the most reactive