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51.
Torben Larsen 《International Journal of Circuit Theory and Applications》1991,19(5):431-452
This paper gives a treatment of the theory of noise in general non-linear multiport systems by use of the Volterra series representation. Expressions for the response of a non-linear noisy (N + l)-port system with N signal input ports and one output port under excitation of noise and a deterministic signal at each input port are determined. Noise generated in the system itself is accounted for by equivalent random variable noise voltage or current generators. These internal noise generators are extracted from the system and applied at separate external ports. A noise-free equivalent of the noisy system is obtained with N signal input ports and Q – I input ports accounting for the systemgenerated noise. the Volterra series representation is used to describe the input-output response relation of the system. Once the Volterra transfer functions of the system are determined and cross-and autocorrelations of the noise generators are specified, it is possible to determine the noise performance of the system under arbitrary noise and deterministic signal excitation. the investigation leads to the determination of expressions for the equivalent average exchangeable output noise power density and the average output noise power flow from the system. Expressions for the noise power densitypand the noise power flow at the load of the non-linear system are determined. As an example of the theory an expression is derived for the effective input noise temperature of a non-linear system. 相似文献
52.
Yifang Wang Mohannad Mayyas Jiong Yang Jianbo Tang Mohammad B. Ghasemian Jialuo Han Aaron Elbourne Torben Daeneke Richard B. Kaner Kourosh Kalantar-Zadeh 《Advanced functional materials》2021,31(3):2005866
2D transition metal dichalcogenides (TMDs) play increasingly significant roles in research and future optoelectronics. However, the large-scale deposition of 2D TMDs remains challenging due to sparse nucleation and substrate dependency. Liquid metals can offer effective solutions to meet these challenges due to their reactive, non-polarized, and templating properties. Here, self-deposition of 2D molybdenum sulfide is shown by introducing a molybdenum precursor onto the surface of a eutectic alloy of gallium and indium (EGaIn). EGaIn serves as an ultra-smooth template and reducing agent for the precursor to form large-scale planar molybdenum sulfides, which is transferrable to any substrate. The molybdenum sulfides form spontaneously on the surface of EGaIn, which has a sufficient potential to drive the cathodic reactions of the deposition process. A highly crystalline 2H-MoS2 is obtained after a final annealing step. This work demonstrates a fundamentally new capability for the formation of large-scale 2D TMDs. 相似文献
53.
Mohammad B. Ghasemian Mohannad Mayyas Shuhada A. Idrus‐Saidi Muhammad A. Jamal Jiong Yang Sajjad S. Mofarah Esmaeil Adabifiroozjaei Jianbo Tang Nitu Syed Anthony P. O'Mullane Torben Daeneke Kourosh Kalantar‐Zadeh 《Advanced functional materials》2019,29(36)
Liquid metals offer unprecedented chemistry. Here it is shown that they can facilitate self‐limiting oxidation processes on their surfaces, which enables the growth of metal oxides that are atomically thin. This claim is exemplified by creating atomically thin hydrated MnO2 using a Galvanic replacement reaction between permanganate ions and a liquid gallium–indium alloy (EGaIn). The “liquid solution”–“liquid metal” process leads to the reduction of the permanganate ions, resulting in the formation of the oxide monolayer at the interface. It is presented that under mechanical agitation liquid metal droplets are established, and simultaneously, hydrated gallium oxides and manganese oxide sheets delaminate themselves from the interfacial boundaries. The produced nanosheets encapsulate a metallic core, which is found to consist of solid indium only, with the full migration of gallium out of the droplets. This process produces core/shell structures, where the shells are made of stacked atomically thin nanosheets. The obtained core/shell structures are found to be an efficient photocatalyst for the degradation of an organic dye under simulated solar irradiation. This study presents a new research direction toward the modification and functionalization of liquid metals through spontaneous interfacial redox reactions, which has implications for many applications beyond photocatalysis. 相似文献
54.
Sonication‐Assisted Synthesis of Gallium Oxide Suspensions Featuring Trap State Absorption: Test of Photochemistry
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Nitu Syed Ali Zavabeti Md Mohiuddin Baoyue Zhang Yichao Wang Robi S. Datta Paul Atkin Benjamin J. Carey Cheng Tan Joel van Embden Anthony S. R. Chesman Jian Zhen Ou Torben Daeneke Kourosh Kalantar‐zadeh 《Advanced functional materials》2017,27(43)
Gallium is a near room temperature liquid metal with extraordinary properties that partly originate from the self‐limiting oxide layer formed on its surface. Taking advantage of the surface gallium oxide (Ga2O3), this work introduces a novel technique to synthesize gallium oxide nanoflakes at high yield by harvesting the self‐limiting native surface oxide of gallium. The synthesis process follows a facile two‐step method comprising liquid gallium metal sonication in DI water and subsequent annealing. In order to explore the functionalities of the product, the obtained hexagonal α‐Ga2O3 nanoflakes are used as a photocatalytic material to decompose organic model dyes. Excellent photocatalytic activity is observed under solar light irradiation. To elucidate the origin of these enhanced catalytic properties, the electronic band structure of the synthesized α‐Ga2O3 is carefully assessed. Consequently, this excellent photocatalytic performance is associated with an energy bandgap reduction, due to the presence of trap states, which are located at ≈1.65 eV under the conduction band minimum. This work presents a novel route for synthesizing oxide nanostructures that can be extended to other low melting temperature metals and their alloys, with great prospects for scaling up and high yield synthesis. 相似文献
55.
Per Langholz Peter Andersen Torben Forskov Walther Schmidtsdorff 《Journal of the American Oil Chemists' Society》1989,66(8):1120-1123
Lipases catalyze the reesterification or hydrolysis of fats and oils and may show specificity towards certain fatty acids.
An immobilized lipase from the fungusMucor miehei shows specificity towards docosahexaenoic acid (DHA) (DHA being a poor substrate), whether the DHA is used as a free fatty
acid (FFA) as substrate in esterification with methanol, or fatty acid methyl ester (FAME) is used as a substrate for hydrolysis.
The specificity of the lipase fromM. miehei may be applied to concentrate DHA originating from a marine oil in either the FAME or the FFA fraction, which can be separated. 相似文献
56.
Trans fatty acids from hydrogenated vegetable and marine oils could be as hypercholesterolemic and atherogenic as saturated fatty
acids. Hence, it is important to know the fatty acid composition in major food contributors, e.g., margarines and shortenings.
In 1992 margarines were examined, and in 1995 brands covering the entire Danish market were examined. Significant amounts
oftrans-18∶1 were found only in hard margarines (mean: 4.2±2.8%) and shortenings (mean: 6.8 ±3.1%), whereas the semisoft and soft
margarines contained substantially lesstrans-18∶1 in 1995 than in 1992. Where marine oils had been used to a larger degree the meantrans-monoenoic content was about 15%, of which close to 50% was made up of long-chain (C20 and C22)trans fatty acids. A note-worthy decrease in the content oftrans-18∶1 had occurred for the semisoft margarines, from 9.8±6.1% in 1992 to 1.2±2.2% in 1995. Calculated from sales figures,
the supply oftrans-18∶1 plus saturated fatty acids from margarines had decreased over this three-year period by 1.4 g/day, which has been replaced
bycis monounsaturated and polyunsaturated fatty acids. 相似文献
57.
Torben Pätz Robert M. Kirby Tobias Preusser 《International Journal of Computer Vision》2013,103(2):190-212
We discuss an extension of the Ambrosio-Tortorelli approximation of the Mumford-Shah functional for the segmentation of images with uncertain gray values resulting from measurement errors and noise. Our approach yields a reliable precision estimate for the segmentation result, and it allows us to quantify the robustness of edges in noisy images and under gray value uncertainty. We develop an ansatz space for such images by identifying gray values with random variables. The use of these stochastic images in the minimization of energies of Ambrosio-Tortorelli type leads to stochastic partial differential equations for a stochastic smoothed version of the original image and a stochastic phase field for the edge set. For the discretization of these equations we utilize the generalized polynomial chaos expansion and the generalized spectral decomposition (GSD) method. In contrast to the simple classical sampling technique, this approach allows for an efficient determination of the stochastic properties of the output image and edge set by computations on an optimally small set of random variables. Also, we use an adaptive grid approach for the spatial dimensions to further improve the performance, and we extend an edge linking method for the classical Ambrosio-Tortorelli model for use with our stochastic model. The performance of the method is demonstrated on artificial data and a data set from a digital camera as well as real medical ultrasound data. A comparison of the intrusive GSD discretization with a stochastic collocation and a Monte Carlo sampling is shown. 相似文献
58.
Petersen FJ Wørts O Schaefer T Sojka PE 《Drug development and industrial pharmacy》2004,30(3):319-326
Atomization of aqueous polymer solutions is a key step in the formulation of several pharmaceutical products. Droplet size control is essential in order to produce pharmaceutical products with the desired properties. The purpose of this paper is to investigate design issues for an inside-out type of effervescent atomizer used to spray water and aqueous solutions of polyvinylpyrrolidone (Kollidon® K-30) and hydroxypropyl methylcellulose (Pharmacoat® 603). The atomizer was operated at air-to-liquid mass ratios of 0.1, 0.3, and 0.5 and a feed pressure of 1172 kPa. Fluid viscosities ranged from 1 to 47 mPa.s. The influence of several atomizer design features was considered, including exit orifice length-to-diameter ratio, exit orifice diameter, the total area of the air injection holes, the distance between the air injection point and the exit orifice, the diameter of the mixing chamber, and the orientation of both air and liquid flows. Droplet size distributions were shown to vary significantly with the atomizer's exit orifice diameter, air injector design, and air injector distance to the exit orifice. In all cases air-to-liquid mass ratio played a key role in the mean droplet size. The design of the atomizer was shown to have the most pronounced effect on the mean droplet size at the lowest air-to-liquid mass ratios. Optimization of the atomizer design is very important in order to obtain small droplet sizes in pharmaceutical processes where the amount of air/gas should be minimized, e.g., closed-cycle spray drying and agglomeration processes. 相似文献
59.
We present an extension of the random walker segmentation to images with uncertain gray values. Such gray-value uncertainty may result from noise or other imaging artifacts or more general from measurement errors in the image acquisition process. The purpose is to quantify the influence of the gray-value uncertainty onto the result when using random walker segmentation. In random walker segmentation, a weighted graph is built from the image, where the edge weights depend on the image gradient between the pixels. For given seed regions, the probability is evaluated for a random walk on this graph starting at a pixel to end in one of the seed regions. Here, we extend this method to images with uncertain gray values. To this end, we consider the pixel values to be random variables (RVs), thus introducing the notion of stochastic images. We end up with stochastic weights for the graph in random walker segmentation and a stochastic partial differential equation (PDE) that has to be solved. We discretize the RVs and the stochastic PDE by the method of generalized polynomial chaos, combining the recent developments in numerical methods for the discretization of stochastic PDEs and an interactive segmentation algorithm. The resulting algorithm allows for the detection of regions where the segmentation result is highly influenced by the uncertain pixel values. Thus, it gives a reliability estimate for the resulting segmentation, and it furthermore allows determining the probability density function of the segmented object volume. 相似文献
60.
Boll Torben Unocic Kinga A. Pint Bruce A. Mårtensson Anders Stiller Krystyna 《Oxidation of Metals》2017,88(3-4):469-479
Oxidation of Metals - It is widely accepted that the growth of protective α-Al2O3 scales on Ni-based alloys is governed by the inward diffusion of oxygen through the oxide grain boundaries... 相似文献