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991.
Indoor body-area channel model for narrowband communications 总被引:1,自引:0,他引:1
Fort A. Desset C. Wambacq P. Biesen L.V. 《Microwaves, Antennas & Propagation, IET》2007,1(6):1197-1203
Using wireless sensors placed on a person to continuously monitor health information is a promising new application. At the same time, new low-power wireless standards such as Bluetooth and Zigbee have been proposed for short range, low data-rate communication matching the requirements of these bio-medical applications. However, there are currently few measurements or models describing propagation around the body. To address this problem, electromagnetic waves near the torso are measured and a statistical model is derived for communication in the 915 MHz and 2.45 GHz industrial, scientific and medical bands associated with Zigbee and Bluetooth. Measurement setup and statistical analysis are described. 相似文献
992.
The paper proposes a novel method of forecasting short-term electricity price based on a two-stage hybrid network of self-organised map (SOM) and support-vector machine (SVM). In the first stage, a SOM network is applied to cluster the input-data set into several subsets in an unsupervised manner. Then, a group of SVMs is used to fit the training data of each subset in the second stage in a supervised way. With the trained network, one can predict straightforwardly the next-day hourly electricity prices. To confirm its effectiveness, the proposed model has been trained and tested on the data of historical energy prices from the New England electricity market. 相似文献
993.
Jonathan P. Belnoue Giang D. Nguyen Alexander M. Korsunsky 《International Journal of Fracture》2007,144(1):53-60
This paper presents a new 1-D non-local damage-plasticity deformation model for ductile materials. It uses the thermodynamic
framework described in Houlsby and Puzrin (2000) and holds, nevertheless, some similarities with Lemaitre’s (1971) approach.
A 1D finite element (FE) model of a bar fixed at one end and loaded in tension at the other end is introduced. This simple
model demonstrates how the approach can be implemented within the finite element framework, and that it is capable of capturing
both the pre-peak hardening and post-peak softening (generally responsible for models instability) due to damage-induced stiffness
and strength reduction characteristic of ductile materials. It is also shown that the approach has further advantages of achieving
some degree of mesh independence, and of being able to capture deformation size effects. Finally, it is illustrated how the
model permits the calculation of essential work of rupture (EWR), i.e. the specific energy per unit cross-sectional area that
is needed to cause tensile failure of a specimen. 相似文献
994.
There are some foods that contain mutagenic or carcinogenic agents, some of which occur naturally and others that may be formed during preparation or cooking. Several foods such as legumes, also contain natural antimutagens and/or anticarcinogens. Lupine is one such legume that contains high amounts of protein (40%) and oils (14%). About 90 species of lupine have been reported throughout Mexico. However, the use of this crop as a source of food has been limited by the presence of antinutritional agents such as phenolic compounds (PC), carbohydrates (CH) and quinolizidinic alkaloids (Qas). It has also been suggested that consuming these compounds can affect human health and may even reduce the risk of disease. The objective of this work was to determine the effect of PC, CH and Qas, isolated and quantified from Lupinus campestris on the mutagenicity of 1-nitropyrene (1-NP) as a model mutagen and we used the Salmonella typhimurium tester strain YG1024 by the Kado microsuspension method. The results indicate that L. campestris seeds have 11 mg (+)catechin equivalent g(-1) seed coat; 120.3 mg g(-1) seeds and 2.13 mg g(-1) seeds of PC, CH and Qas, respectively. 1-NP mutagenicity was inhibited by 86% for PC, 76% for CH and 75% for Qas at concentrations of 200, 512 and 13.6 microg/tube, respectively. 相似文献
995.
R. Oliva A. L. Gemal A. W. N brega A. C. P. Araú jo 《Food Additives & Contaminants》2003,20(8):758-763
The structure of the recently introduced Brazilian government programme for monitoring pesticide residues in six major agricultural products is described. Residues found from the analysis of samples of tomatoes and strawberries are discussed in detail. The much greater frequency of detection of pesticide residues, many of which are not approved for use in Brazil, in produce being sold on the domestic market, as opposed to that produced for export, is of major concern. It is perceived that this new monitoring programme will become permanent and be used to underpin enforcement actions that will need to be taken to reduce the numbers of incidents of illegal residues occurring, particularly in fresh fruits and vegetables. 相似文献
996.
We consider the dynamics of a dark soliton in an elongated harmonically trapped Bose-Einstein condensate. A central question
concerns the behavior at finite temperatures, where dissipation arises due to the presence of a thermal cloud. We study this
problem using coupled Gross-Pitaevskii and N-body simulations, which include the mean field coupling between the condensate and thermal cloud. We find that the soliton
decays relatively quickly even at very low temperatures, with the decay rate increasing with rising temperature. 相似文献
997.
The polycrystalline samples of Dy
x
Bi1−x
FeO3 (x = 1, 0.8, 0.6, 0.4 and 0.2) were synthesized by standard solid state reaction technique. The samples synthesized were characterized
by X-ray diffraction (XRD) technique. Further the samples were characterized by infrared (IR) spectroscopic technique. The
dielectric measurements were carried out as a function of frequency in the range 100 Hz to 1 MHz at room temperature. Also
the dielectric measurements were carried out as a function of temperature at certain fixed frequencies. The ac and dc resistivity
measurements were carried out using two probe method. Also temperature dependence of ac and dc resistivity was noted. These
measurements suggest polaron conduction in the samples. Finally, the data from XRD, IR, dielectric measurements were correlated. 相似文献
998.
A phenomenological model is developed for describing the kinetics of the crystallite size refinement process of Cu powder
under mechanical treatment conditions. Based on the evidence that collisions represent the elementary events of energy transfer,
the rate of crystallite size decrease is related on a statistical basis to the amount of powder trapped at each collision,
to the number of collisions and to the collision energy. The mathematical approach allows for identifying the approximate
functional form of the kinetic curves obtained at largely different impact energies. The values of the apparent kinetic constants
and of the model parameters involved can be thus estimated by fitting the model curves to the experimental data. The results
obtained provide a deeper insight into the details of the crystallite size refinement process. 相似文献
999.
The equilibrium shape and dihedral angles at the solid–liquid–vapor tri-junctions of two-phase alloy small particles containing
a cusp-oriented interface were modeled as a function of phase fraction, surface energy and the interfacial energy. The calculation
was applied to different combinations of surface and/or interfacial energies to demonstrate the various possible particle
shapes and dihedral angles that result for two-phase particles. The dihedral angles at the tri-junction vary with the phase
fraction, due to the coupling between the relative amounts of each phase, interfacial energy relative to the two surface energies
and the equilibrium conditions at the tri-junction. These features can be used to find the ratio of the interfacial energy
to the surface energies of two-phase particles for any state of matter. 相似文献
1000.
Reaction models are proposed to quantify the hydration products and to determine the composition of C–S–H from alkali-activated
slags (AAS). Products of the slag hydration are first summarized from observations in literature. The main hydration products
include C–S–H, hydrotalcite, hydrogarnet, AFm phases (C4AH13 and C2ASH8) and ettringite. Then, three stoichiometric reaction models are established correlating the mineral composition of slag (the
glass part) with the hydration products. Using the proposed models, quantities of hydration products and composition of C–S–H
are determined. The models are validated with a number of experimental investigations reported in literature, yielding good
agreement, i.e., these models can successfully predict the hydration reaction of AAS. The models are furthermore applied to
calculate the retained water in the hydration products of AAS in different hydration states and a general hydration equation
of AAS is derived. As an illustration to one of the model applications, chemical shrinkage of the AAS cement paste in different
hydration states are predicted. The chemical shrinkage of AAS is shown to be remarkably higher than OPC. Furthermore, phase
distribution in the hardened AAS paste and the porosity are calculated. 相似文献