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71.
The development of a novel, low power optical sensing platform based on light emitting diodes (LEDs) is described. The sensor is constructed from a pair of LEDs fused together at an angle where one LED functions as the light source and the other LED is reverse biased to function as a light detector. Sensor function is based on the level of light received by the detector diode, which varies with the reflectance of the interface between the device and its environment, or the chemochromic membrane that covers the device. A simple microprocessor circuit is used to measure the time taken for the photon-induced current to discharge the detector LED from an initial 5 V (logic 1) to 1.7 V (logic zero). This sensing device has been successfully used for colour and colour-based pH measurements and offers extremely high sensitivity, enabling detection down to the sub micro molar level of dyes. 相似文献
72.
We present numerical methods for obtaining the stationary distribution of states for multi-server retrial queues with Markovian
arrival process, phase type service time distribution with two states and finite buffer; and moments of the waiting time.
The methods are direct extensions of the ones for the single server retrial queues earlier developed by the authors. The queue
is modelled as a level dependent Markov process and the generator for the process is approximated with one which is spacially
homogeneous above some levelN. The levelN is chosen such that the probability associated with the homogeneous part of the approximated system is bounded by a small
tolerance and the generator is eventually truncated above that level. Solutions are obtained by efficient application of block
Gaussian elimination. 相似文献
73.
A sensor with potential for the development of a “chemical barcode” for real-time monitoring of fish freshness is described. This on-package sensor contains a pH sensitive dye, bromocresol green, that responds through visible colour change to basic volatile spoilage compounds, such as trimethylamine (TMA), ammonia (NH3) and dimethylamine (DMA) collectively known as Total Volatile Basic Nitrogen (TVB-N). The sensor characteristics were studied as well as its response with standard ammonia gas. Trials on cod and under-utilised species have verified that the sensor response correlates with bacterial growth patterns in fish samples thus enabling the “real-time” monitoring of spoilage in various fish species. The sensor response can be interrogated with a simple, inexpensive reflectance colorimeter that we have developed based on two light emitting diodes (LEDs) and a photodetector. 相似文献
74.
Thomas R. Boussie Gary M. Diamond Christopher Goh Keith A. Hall Anne M. LaPointe Margarete K. Leclerc Vince Murphy James A. W. Shoemaker Howard Turner Robert K. Rosen James C. Stevens Francesca Alfano Vincenzo Busico Roberta Cipullo Giovanni Talarico 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2006,118(20):3356-3361
75.
Phil Diamond Anthony Klemm Peter Kloeden Aleksej Pokrovskii 《Journal of statistical physics》1996,84(3-4):713-733
Computer simulations of dynamical systems arediscretizations, where the finite space of machine arithmetic replaces continuum state spaces. So any trajectory of a discretized dynamical system is eventually periodic. Consequently, the dynamics of such computations are essentially determined by the cycles of the discretized map. This paper examines the statistical properties of the event that two trajectories generate the same cycle. Under the assumption that the original system has a Sinai-Ruelle-Bowen invariant measure, the statistics of the computed mapping are shown to be very close to those generated by a class of random graphs. Theoretical properties of this model successfully predict the outcome of computational experiments with the implemented dynamical systems. 相似文献
76.
Summary Semihyperbolic dynamical systems generated by Lipschitz mappings are investigated. A special form of robustness of topological entropy under perturbations of a Semihyperbolic mapping is discussed, and weakened forms of persistence and of structural stability are considered. Proofs are based on the concept of bi-shadowing, which is a stronger version of the shadowing lemma. 相似文献
77.
Anderson and Putnam showed that the cohomology of a substitution tiling space may be computed by collaring tiles to obtain a substitution which ``forces its border.' One can then represent the tiling space as an inverse limit of an inflation and substitution map on a cellular complex formed from the collared tiles; the cohomology of the tiling space is computed as the direct limit of the homomorphism induced by inflation and substitution on the cohomology of the complex. For one-dimensional substitution tiling spaces, we describe a modification of the Anderson-Putnam complex on collared tiles that allows for easier computation and provides a means of identifying certain special features of the tiling space with particular elements of the cohomology.
78.
Stephens FS Deleplanque MA Lee IY Macchiavelli AO Ward D Fallon P Cromaz M Clark RM Descovich M Diamond RM Rodriguez-Vieitez E 《Physical review letters》2005,94(4):042501
We have developed a new method to study the order-to-chaos transition in rotational nuclei. Correlations between successive gamma rays are used to determine the average complexity of the intermediate levels and thereby the ratio of the interaction potential between levels to the level spacing. The measured ratios, 0.15 to 1.5, span the range from nearly fully ordered to nearly fully chaotic. 相似文献
79.
Svensson CE Macchiavelli AO Juodagalvis A Poves A Ragnarsson I Aberg S Appelbe DE Austin RA Baktash C Ball GC Carpenter MP Caurier E Clark RM Cromaz M Deleplanque MA Diamond RM Fallon P Furlotti M Galindo-Uribarri A Janssens RV Lane GJ Lee IY Lipoglavsek M Nowacki F Paul SD Radford DC 《Physical review letters》2000,85(13):2693-2696
A superdeformed rotational band has been identified in 36Ar, linked to known low-spin states, and observed to its high-spin termination at Ipi = 16(+). Cranked Nilsson-Strutinsky and spherical shell model calculations assign the band to a configuration in which four pf-shell orbitals are occupied, leading to a low-spin deformation beta(2) approximately 0.45. Two major shells are active for both protons and neutrons, yet the valence space remains small enough to be confronted with the shell model. This band thus provides an ideal case to study the microscopic structure of collective rotational motion. 相似文献
80.
E. A. Henry M. J. Brinkman C. W. Beausang J. A. Becker N. Roy A. Kuhnert S. W. Yates J. A. Cizewski R. M. Diamond M. A. Deleplanque F. S. Stephens J. E. Draper W. H. Kelly R. J. McDonald J. Burde W. Korten E. Rubel Y. A. Akovali 《Zeitschrift für Physik A Hadrons and Nuclei》1990,336(3):361-362
By analyzing the thick target yield curve of resonant (p,γ) reactions on23Na and26Mg for various target temperatures within a Monte Carlo approach, we are able to define the Debye and Einstein temperature of the target material in the surface region. The obtained surface temperatures are noticeably higher than the respective calorimetric values. 相似文献