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1.
The internal dynamics of a hospital represent a complex non-linear structure. Planning and management of bed capacities must be evaluated within an environment of uncertainty, variability and limited resources. A common approach is to plan and manage capacities based on simple deterministic spreadsheet calculations. This paper demonstrates that these calculations typically do not provide the appropriate information and result in underestimating true bed requirements. More sophisticated, flexible and necessarily detailed capacity models are needed. The development and use of such a simulation model is presented in this paper. The modelling work, in conjunction with a major UK NHS Trust, considers various types of patient flows, at the individual patient level, and resulting bed needs over time. The consequence of changes in capacity planning policies and management of existing capacities can be readily examined. The work has highlighted the need for evaluating hospital bed capacities in light of both bed occupancies and refused admission rates. The relationship between occupancy and refusals is complex and often overlooked by hospital managers. 相似文献
2.
I T Vieira P R Harper A K Shahani V De Senna 《The Journal of the Operational Research Society》2003,54(7):713-722
Mother-to-child transmission (MTCT) of HIV is the most significant source of HIV infection in children below the age of 15 years. In 2000 alone, about 600 000 new infections occurred, the vast majority from mothers living in developing countries who were not aware of their HIV-positive status. To date, at least 4.3 million children have died from AIDS. In this paper, we discuss the development of an operational model that can be used to evaluate intervention options for the prevention of MTCT of HIV. The problem was approached by defining suitable pregnancy risk groups, prevention options and the required model outputs to evaluate different intervention strategies. The method chosen to approach the problem was a discrete-event, three-phase simulation, built in Visual Basic, with a stochastic semi-Markov structure. The developed model takes individual pregnant women through each stage of their pregnancy, labour and birth. Different intervention strategies may be modelled at any time, including short-course antiretroviral drugs and cessation of breastfeeding. The model is demonstrated with data from Botswana, which has one of the highest HIV-infection rates in the world. 相似文献
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5.
Dr. Dayton G. Kizzire Dr. Valerie García-Negrón Dr. David P. Harper Dr. David J. Keffer 《ChemistryOpen》2022,11(2):e202100220
Carbonized lignin has been proposed as a sustainable and domestic source of activated, amorphous, graphitic, and nanostructured carbon for many industrial applications as the structure can be tuned through processing conditions. However, the inherent variability of lignin and its complex physicochemical structure resulting from feedstock and pulping selection make the Process-Structure-Property-Performance (PSPP) relationships hard to define. In this work, radial distribution functions (RDFs) from synchrotron X-ray and neutron scattering of lignin-based carbon composites (LBCCs) are investigated using the Hierarchical Decomposition of the Radial Distribution Function (HDRDF) modelling method to characterize the local atomic environment and develop quantitative PSPP relationships. PSPP relationships for LBCCs defined by this work include crystallite size dependence on lignin feedstock as well as increasing crystalline volume fraction, nanoscale composite density, and crystallite size with increasing reduction temperature. 相似文献
6.
Harper JK Strohmeier M Grant DM 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2007,189(1):20-31
The (1)H-(13)C solid-state NMR heteronuclear correlation (HETCOR) experiment is demonstrated to provide shift assignments in certain powders that have two or more structurally independent molecules in the unit cell (i.e. multiple molecules per asymmetric unit). Although this class of solids is often difficult to characterize using other methods, HETCOR provides both the conventional assignment of shifts to molecular positions and associates many resonances with specific molecules in the asymmetric unit. Such assignments facilitate conformational characterization of the individual molecules of the asymmetric unit and the first such characterization solely from solid-state NMR data is described. HETCOR offers advantages in sensitivity over prior methods that assign resonances in the asymmetric unit by (13)C-(13)C correlations and therefore allows shorter average analysis times in natural abundance materials. The (1)H-(13)C analysis is demonstrated first on materials with known shift assignments from INADEQUATE data (santonin and Ca(OAc)(2) phase I) to verify the technique and subsequently is extended to a pair of unknown solids: (+)-catechin and Ca(OAc)(2) phase II. Sufficient sensitivity and resolution is achieved in the spectra to provide assignments to one of the specific molecules of the asymmetric unit at over 54% of the sites. 相似文献
7.
Ground state rotation and quartic distortion constants were obtained for 11B2D6 from the analysis of high resolution (~0.05 cm?1) Fourier transform infrared spectra. The bands studied comprised the ν17, ν18 type A, and ν14, ν9 + ν15 type C bands of 11B2H6 and the ν16, ν17, ν18 type A, ν8 type B, and ν14 type C bands of 11B2D6. In the case of 11B2H6, the authors' ground state data were combined with those of Lafferty et al. obtained from a previous study (J. Mol. Spectrosc.33, 345–367 (1970)) at comparable resolution of the ν16 type A and ν8 type B fundamentals. Information on the ground state rotational energy manifold of 11B2H6 was accumulated up to J = 23, Ka = 18, and of 11B2D6 up to J = 32, Ka = 22. This permitted rather precise determination of the distortion constants ΔJ0, ΔJK0, ΔK0, although δJ0 and δK0 proved to be too small (< 10?7 cm?1) and were constrained to values calculated from the force field. Sets of upper state parameters were determined for all vibrational levels studied. Although these appear to be essentially unperturbed globally, several localized perturbations were observed and identified. 相似文献
8.
Feuillade C Meredith RW Chotiros NP Clay CS 《The Journal of the Acoustical Society of America》2002,112(6):2702-2712
During August 1998, a bottom scattering tank experiment was performed at the Applied Research Laboratory, University of Texas to measure wideband acoustic reverberation from multiple objects (e.g., cobbles and pebbles) placed on a sediment simulation of the sea floor. In preparation for processing and analyzing the experimental data, time domain scattering measurements made with stainless steel and glass balls suspended in the water column were used to calibrate the sonar transceiver system by deconvolving the theoretical impulse response for steel and glass spheres, obtained via the Faran elastic sphere scattering model, from the scattered time signals. It is the analysis of these calibration measurements which forms the subject of this paper. Results show the critical importance of accurate input-output system calibrations for time domain sound scattering research, and successfully demonstrate a time domain method for accurately calibrating the complete sonar transceiver function, i.e., both the amplitude and time dependence, using a known reference target. The work has implications for boundary and volume scattering applications. 相似文献
9.
OR methods and tools are being increasingly applied within the health services domain to support objective decision-making for the effective and efficient provision of resources. Healthcare modelling, however, is beset with many challenges and this paper examines a number of issues that define the primary challenges faced by the modeller in this field. It is fair to say that their resolution determines the likely success or failure of healthcare modelling in general. Working with a number of participating health service organizations, a proposed framework towards successful implementation has evolved and is presented in this paper 相似文献
10.
Zen Harper 《Complex Analysis and Operator Theory》2009,3(1):113-146
We ask when convolution operators with scalar- or operator-valued kernel functions map between weighted L2 spaces of Hilbert space-valued functions. For a certain class of decreasing weights, including negative powers (t + a)−m for example, we solve the one-weight problem completely by using Laplace transforms and Bergman-type spaces of vector-valued
analytic functions. For a much more general class of decreasing weights, we solve the one-weight problem for all positive
real kernels (also for Lp(w) with p > 1), by results on Steklov operators which generalise the weighted Hardy inequality. When the kernel function is a strongly
continuous semigroup of bounded linear Hilbert space operators, which arises from input–output maps of certain linear systems,
then the most obvious sufficient condition for boundedness, obtained by taking norm signs inside the integrals, is also necessary
in many cases, but not in general.
Submitted: July 15, 2007.,Revised: November 19, 2007.,Accepted: December 14, 2007. 相似文献