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排序方式: 共有404条查询结果,搜索用时 15 毫秒
71.
This paper describes an equation discovery approach based on machine leamng using LAGdtAMGE as an equation discovery tool,with two sources of input,a dataset and model presented in context-free gammar.The approach is searching a large range of potential equations by a specific model.The parameters of the equation are fitted to find the best equations.The The experiments are illustratedwith commodity prices from the London Metal Exchange for the period of January-October 2009.The outputs of the experiments are a large number of equations;same of the equations display that the predicted rakes are following the market trends in perfect patterns. 相似文献
72.
Hemantha Kumar Yeddu Amer MalikJohn Ågren Gustav AmbergAnnika Borgenstam 《Acta Materialia》2012,60(4):1538-1547
In the present work a 3-D elastoplastic phase-field (PF) model is developed, based on the PF microelasticity theory proposed by A.G. Khachaturyan and by including plastic deformation as well as anisotropic elastic properties, for modeling the martensitic transformation (MT) by using the finite-element method. PF simulations in 3D are performed by considering different cases of MT occurring in an elastic material, with and without dilatation, and in an elastic perfectly plastic material with dilatation having isotropic as well as anisotropic elastic properties. As input data for the simulations the thermodynamic parameters corresponding to an Fe-0.3%C alloy as well as the physical parameters corresponding to steels acquired from experimental results are considered. The simulation results clearly show autocatalysis and morphological mirror image formation, which are some of the typical characteristics of a martensitic microstructure. The results indicate that elastic strain energy, anisotropic elastic properties, plasticity and the external clamping conditions affect MT as well as the microstructure. 相似文献
73.
Safaa El-din H. Etaiw Said A. Amer Mohamed M. El-bendary 《Journal of Materials Science》2010,45(5):1307-1314
The self-assembly of K3[Cu(CN)4] and unidentate pyridine bases (L): pyridine (py), 3-methyl pyridine (3-mpy), and 2,4,6-trimethyl pyridine (tmpy) in the
presence of Me3SnCl affords new coordination polymers (CPs) CuCN·0.5(py)] (1), [CuCN·0.5(3-mpy)] (2), and [CuCN·0.5(tmpy)] (3). The syntheses are achieved in H2O/acetonitrile media at room temperature. The structure of the CP 3 was characterized by X-ray single crystal analysis. It is crystallized as orthorhombic in the space group Pnma, a = 9.1065 (3) ?, b = 8.6669 (3) ?, and c = 12.1998 (5) ? and Z = 8. The CPs 1, 2 were investigated by IR, mass, Uv–visible, and 1H-NMR spectra, as well as TGA. The CPs 1–3 are 2D-polymers consisting of 1D-(CuCN)
n
chain structure while the ligands alternate on both sides of the chain with associated copper atom coordination number of
three. Hydrogen bonds play an essential role for developing 2D-network structure. These CPs exhibit strong fluorescent emissions
in the solid state. 相似文献
74.
Fabrega J Tantra R Amer A Stolpe B Tomkins J Fry T Lead JR Tyler CR Galloway TS 《Environmental science & technology》2012,46(2):1128-1135
We studied the effects of ZnO nanoparticles [ZnO NPs, primary particle size 35 ± 10 nm (circular diameter, TEM)], bulk [160 ± 81 nm (circular diameter, TEM)], and Zn ions (from ZnCl(2)) on mortality, growth, and reproductive endpoints in the sediment dwelling marine amphipod Corophium volutator over a complete lifecycle (100 days). ZnO NPs were characterized by size, aggregation, morphology, dissolution, and surface properties. ZnO NPs underwent aggregation and partial dissolution in the seawater exposure medium, resulting in a size distribution that ranged in size from discrete nanoparticles to the largest aggregate of several micrometers. Exposure via water to all forms of zinc in the range of 0.2-1.0 mg L(-1) delayed growth and affected the reproductive outcome of the exposed populations. STEM-EDX analysis was used to characterize insoluble zinc precipitates (sphaerites) of high sulfur content, which accumulated in the hepatopancreas following exposures. The elemental composition of the sphaerites did not differ for ZnO NP, Zn(2+), and bulk ZnO exposed organisms. These results provide an illustration of the comparable toxicity of Zn in bulk, soluble, and nanoscale forms on critical lifecycle parameters in a sediment dwelling organism. 相似文献
75.
H. A. Amer H. M. A. El-Hindi ElS. T. Awad A. M. Nour M. A. Abd ElMinem 《Molecular nutrition & food research》1991,35(2):203-208
A total of thirty laying hens divided into 3 equal groups was used. The 1st group served as control and was fed a basal ration. The 2nd and 3rd groups received L-Dopa and reserpine, respectively. The goal of the study was devoted to determine the effects of these additives on the rate of egg production, weights of eggs and yolks as well as yolk proteins and their amino acid pattern. In the reserpine-treated hens the rate of egg production was increased whereas in the L-Dopa-treated group, the weights of eggs and yolks, food intake as well as the amino acids aspartate, glutamate, glycine, alanine and methionine were significantly increased. The levels of tyrosine and histidine were decreased in both treatments while methionine was decreased by reserpine only. The addition of dopamine antagonist to a ration containing lysine and leucine in concentrations of 0.55% and 0.9% did not influence their levels in eggs. The increment of methionine, aspartate, glutamate and glycine by the dopamine agonist and their decrease by antagonist revealed that these amino acids are excitatory neurotransmitters in brain. 相似文献
76.
77.
A prototype of a hybrid solar dryer was developed for drying of tomato. It consists of a flat-plate concentrating collector, heat storage with auxiliary heating unit, and drying unit. It has a loading capacity of 20 kg of fresh half-cut tomato. The dryer was tested in different weather and operating conditions. The performance of the dryer was compared with an open sun-drying method. Drying performance was evaluated in terms of drying rate, color, ascorbic acid, lycopene, and total flavonoids. Tomato halves were pretreated with UV radiation, acetic acid, citric acid, ascorbic acid, sodium metabisulphite, and sodium chloride. Sodium metabisulphite (8 g L?1) was found to be effective to prevent the microbial growth at lower temperature (45°C). 相似文献
78.
Yubiao Sun Li Wang Wael A. Amer Haojie Yu Jing Ji Liang Huang Jie Shan Rongbai Tong 《Journal of Inorganic and Organometallic Polymers and Materials》2013,23(2):270-285
Recent decades have witnessed the explosive emergence of metal organic frameworks (MOFs) as functional ultrahigh surface area materials. Categorized as an intriguing class of hybrid materials, MOFs exhibit infinite crystalline lattices with inorganic vertices and molecular-scale organic linkers. Fortunately, the large internal surface areas and overall pore volumes, adjustable pore sizes, ultralow densities, and tunable framework–adsorbate interaction by ligand functionalization and metal choice, enable MOFs to be promising materials for wide applications. In particular, these remarkable properties render MOFs potential hydrogen storage materials. By virtue of their exceptionally high surface areas, unparalleled tenability and structural diversity, MOFs have become a hotspot of research within the scientific community. This paper reviews the different methods used for the synthesis of MOFs, the relationship between structural features and hydrogen adsorption, the strategies for hydrogen uptake improvement as well as the molecular simulation. 相似文献
79.
In this article, we propose an opportunistic transmission protocol for cooperative communication systems with L relay nodes under the influence of fading channels. Unlike the protocols previously known in the literature, and given the fact that direct single-link communication outperforms multilink cooperative communication in terms of throughput for same channel conditions, we adopt the channel conditions of the direct link as a main criterion to use whether the direct link in the transmission or the indirect cooperative link. Different performance metrics are derived to demonstrate the performance of the proposed protocol along with a switching combining with a preferable link scheme. These metrics include the bit error rate (BER), outage probability, signal to interference noise ratio (SNR) gain, average throughput and the sum SNR–throughput product (SSTP). The latter performance metric is introduced to compare the maximum achievable throughput as well as the SNR range at a given quality of service (QoS). Our results show that the proposed opportunistic protocol improves the throughput as compared to the conventional cooperative communication systems for the whole range of average SNR. On the other hand, it improves the coverage range as compared to the direct link communication. 相似文献
80.
Recycling of plastic poses several concerns to manufacturers. The most important concern is the unpredictable of their mechanical properties (modulus of elasticity, tensile strength and ductility). Olive solid waste, an abundant material usually thrown into land causing harms to environment was mixed with HDPE plastic and used as a filling material. The mixture was fed to a house made extruder operating at different speed and temperature. Two carbon particle sizes range (less than 150 µm and 180–250 µm) were used. The effect of carbon contents from 0 to 10% wt/wt and operating conditions were tested on the mechanical properties of the recycled HDPE plastic. It was found that up to 5% wt/wt carbon of less than 150 µm resulted in a noticeable improvement of modulus of elasticity and tensile strength. The optimum value of modulus at carbon particle size 180–250 µm was found at 2.5 olive solid carbon content. Increasing screw speed was found to increase tensile modulus and strength of used plastic. This was related to melt viscosity and reduction in particle size. An increase in processing temperature was found to improve tensile properties up to certain point where degradation of polymeric matrix begins to occur and therefore tensile properties deteriorate. 相似文献