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排序方式: 共有498条查询结果,搜索用时 15 毫秒
491.
This paper presents a composite model in which two simulation approaches, discrete-event simulation (DES) and system dynamics (SD), are used together to address a major healthcare problem, the sexually transmitted infection Chlamydia. The paper continues an on-going discussion in the literature about the potential benefits of linking DES and SD. Previous researchers have argued that DES and SD are complementary approaches and many real-world problems would benefit from combining both methods. In this paper, a DES model of the hospital outpatient clinic which treats Chlamydia patients is combined with an SD model of the infection process in the community. These two models were developed in commercial software and linked in an automated fashion via an Excel interface. To our knowledge this is the first time such a composite model has been used in a healthcare setting. The model shows how the prevalence of Chlamydia at a community level affects (and is affected by) operational level decisions made in the hospital outpatient department. We discuss the additional benefits provided by the composite model over and above the benefits gained from the two individual models. 相似文献
492.
Frederico M. A. Silva Paulo B. Gonçalves Zenón J. G. N. del Prado 《Nonlinear dynamics》2011,66(3):303-333
Using Donnell non-linear shallow shell equations in terms of the displacements and the potential flow theory, this work presents
a qualitatively accurate low dimensional model to study the non-linear dynamic behavior and stability of a fluid-filled cylindrical
shell under lateral pressure and axial loading. First, the reduced order model is derived taking into account the influence
of the driven and companion modes. For this, a modal solution is obtained by a perturbation technique which satisfies exactly
the in-plane equilibrium equations and all boundary, continuity, and symmetry conditions. Finally, the equation of motion
in the transversal direction is discretized by the Galerkin method. The importance of each mode in the proposed modal expansion
is studied using the proper orthogonal decomposition. The quality of the proposed model is corroborated by studying the convergence
of frequency–amplitude relations, resonance curves, bifurcation diagrams, and time responses. The parametric analysis clarifies
the influence of the lateral and axial loads on the non-linear vibrations and stability of the liquid-filled shell. Finally,
the global response of the system is investigated in order to quantify the degree of safety of the shell in the presence of
external perturbations through the use of bifurcation diagrams and basins of attraction. This allows one to evaluate the safety
and dynamic integrity of the cylindrical shell in a dynamic environment. 相似文献
493.
Atalla El‐Taher Omer Kotlicki Paul Harper Sergei Turitsyn Jacob Scheuer 《Laser \u0026amp; Photonics Reviews》2014,8(3):436-442
In traditional communication systems the transmission medium is considered as a given characteristic of the channel, which does not depend on the properties of the transmitter and the receiver. Recent experimental demonstrations of the feasibility of extending the laser cavity over the whole communication link connecting the two parties, forming an ultra‐long fiber laser (UFL), have raised groundbreaking possibilities in communication and particularly in secure communications. Here, a 500 km long secure key distribution link based on Raman gain UFL is demonstrated. An error‐free distribution of a random key with an average rate of 100 bps between the users is demonstrated and the key is shown to be unrecoverable to an eavesdropper employing either time or frequency domain passive attacks. 相似文献
494.
495.
H.F. Chen X.C. Dong B.S. Zen K. Gao S.G. Yuan A. Panaye 《SAR and QSAR in environmental research》2013,24(4):251-264
An efficient virtual and rational drug design method is presented. It combines virtual bioactive compound generation with 3D-QSAR model and docking. Using this method, it is possible to generate a lot of highly diverse molecules and find virtual active lead compounds. The method was validated by the study of a set of anti-tumor drugs. With the constraints of pharmacophore obtained by DISCO implemented in SYBYL 6.8, 97 virtual bioactive compounds were generated, and their anti-tumor activities were predicted by CoMFA. Eight structures with high activity were selected and screened by the 3D-QSAR model. The most active generated structure was further investigated by modifying its structure in order to increase the activity. A comparative docking study with telomeric receptor was carried out, and the results showed that the generated structures could form more stable complexes with receptor than the reference compound selected from experimental data. This investigation showed that the proposed method was a feasible way for rational drug design with high screening efficiency. 相似文献
496.
Sun C Bojdys MJ Clarke SM Harper LD Jefferson A Castro MA Medina S 《Langmuir : the ACS journal of surfaces and colloids》2011,27(7):3626-3637
Differential scanning calorimetry (DSC) and X-ray powder diffraction (PXRD) have been used to determine the phase behavior of the binary mixtures of undecanoic acid (A) and undecylamine (B) in the bulk. In addition, we report DSC data that indicates very similar behavior for the solid monolayers of these materials adsorbed on the surface of graphite. The two species are found to form a series of stoichiometric complexes of the type AB, A(2)B, and A(3)B on the acid rich side of the phase diagram. Interestingly, no similar series of complexes is evident on the amine rich side. As a result of this complexation, the solid monolayers of the binary mixtures exhibit a very pronounced enhancement in stability relative to the pure adsorbates. 相似文献
497.
Alberto F. Garrido-Castro Yuta Hioki Yoshifumi Kusumoto Kyohei Hayashi Jeremy Griffin Kaid C. Harper Yu Kawamata Phil S. Baran 《Angewandte Chemie (International ed. in English)》2023,62(42):e202309157
A mild, scalable (kg) metal-free electrochemical decarboxylation of alkyl carboxylic acids to olefins is disclosed. Numerous applications are presented wherein this transformation can simplify alkene synthesis and provide alternative synthetic access to valuable olefins from simple carboxylic acid feedstocks. This robust method relies on alternating polarity to maintain the quality of the electrode surface and local pH, providing a deeper understanding of the Hofer-Moest process with unprecedented chemoselectivity. 相似文献
498.
Daniel C. Morris Adrian R. Morris Prof. William S. Price Assoc. Prof. Stuart W. Prescott Assoc. Prof. Jason B. Harper 《Chemphyschem》2023,24(11):e202300015
The self-diffusion coefficients of each of the components in mixtures containing pyridine and each of the homologous series 1-alkyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imides in acetonitrile were determined using NMR diffusometry (i. e., Pulsed Gradient Spin Echo). The nature of solvation was found to change significantly with the proportion of salt in the mixtures. Increased diffusion coefficients (when corrected for viscosity) for the molecular components were observed with increasing proportion of ionic liquid and with increasing alkyl chain length on the cation. Comparison of the molecular solvents suggests increased interactions in solution of the pyridine with other components of the mixture, consistent with the proposed interactions shown previously to drive changes in reaction kinetics. Discontinuities were seen in the diffusion data for each species in solution across different ionic liquids between the hexyl and octyl derivatives, suggesting a change in the structuring in solution as the alkyl chain on the cation changes and demonstrating the importance of such when considering homologous series. 相似文献