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Single parameter model for cosmic scale photon redshift in a closed Universe 封闭宇宙中宇宙尺度光子红移的单参数模型
Pub Date : 2021-02-04 DOI: 10.21203/rs.3.rs-180626/v1
A. Steynberg
A successful single parameter model has been formulated to match the observations of photons from type 1a supernovae which were previously used to corroborate the standard 𝛬 cold dark matter model. The new single parameter model extrapolates all the way back to the cosmic background radiation (CMB) without requiring a separate model to describe inflation of the space dimensions after the Big Bang. The model for the redshift progression of a photon is: 1 + z =(frac{text{sin}left(frac{13.8}{T}right)pi /2}{text{sin}left(frac{t}{T}right)pi /2}) T is the fitted parameter and t is the time when the photon was emitted, both measured in billions of years from time zero in the Big Bang. The angle is expressed in radians. The number 13.8 should be updated if an improved estimate for the time elapsed since the Big Bang is found. The single parameter model assumes that spacetime forms a finite symmetrical manifold with positive curvature.
一个成功的单参数模型已经制定,以匹配先前用于证实标准𝛬冷暗物质模型的1a型超新星光子的观测结果。新的单参数模型可以一直外推到宇宙背景辐射(CMB),而不需要一个单独的模型来描述大爆炸后空间维度的膨胀。光子红移过程的模型是:1 + z = (frac{text{sin}left(frac{13.8}{T}right)pi /2}{text{sin}left(frac{t}{T}right)pi /2}) T是拟合参数,T是光子发射的时间,两者都是从大爆炸的时间零点开始以数十亿年为单位测量。角度用弧度表示。如果发现自大爆炸以来经过的时间的改进估计,则应该更新数字13.8。单参数模型假设时空形成一个有限对称的正曲率流形。
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引用次数: 0
The Marshall-Olkin Right Truncated Fréchet-Inverted Weibull Distribution: Its Properties and Applications Marshall-Olkin右截断fr&eacutecet -倒威布尔分布的性质及应用
Pub Date : 2021-01-27 DOI: 10.4236/OJMSI.2021.91005
Nora Nader, M. El-Damcese, B. El-Desouky
In this paper, a new probability distribution is proposed by using Marshall and Olkin transformation. Some of its properties such as moments, moment generating function, order statistics and reliability functions are derived. The method of maximum likelihood is used to estimate the model parameters. The graphs of the reliability function and hazard rate function are plotted by taken some values of the parameters. Three real life applications are introduced to compare the behaviour of the new distribution with other distributions.
本文利用Marshall和Olkin变换提出了一种新的概率分布。推导了其矩、矩生成函数、阶数统计量和可靠度函数等性质。采用极大似然法对模型参数进行估计。通过取一些参数的值,绘制了可靠性函数和危险率函数的曲线图。介绍了三个实际应用程序来比较新分布与其他分布的行为。
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引用次数: 1
Applying Graph Theory and Mathematical-Computational Modelling to Study a Neurophysiological Circuit 应用图论和数学计算模型研究神经生理回路
Pub Date : 2021-01-01 DOI: 10.4236/OJMSI.2021.92011
Camila de Andrade Kalil, M. C. Castro, Dilson Silva, C. Cortez
The aim of the present study is to contribute to the knowledge about the functioning of the neuronal circuits. We built a mathematical-computational model using graph theory for a complex neurophysiological circuit consisting of a reverberating neuronal circuit and a parallel neuronal circuit, which could be coupled. Implementing our model in C++ and applying neurophysiological values found in the literature, we studied the discharge pattern of the reverberant circuit and the parallel circuit separately for the same input signal pattern, examining the influence of the refractory period and the synaptic delay on the respective output signal patterns. Then, the same study was performed for the complete circuit, in which the two circuits were coupled, and the parallel circuit could then influence the functioning of the reverberant. The results showed that the refractory period played an important role in forming the pattern of the output spectrum of a reverberating circuit. The inhibitory action of the parallel circuit was able to regulate the reverberation frequency, suggesting that parallel circuits may be involved in the control of reverberation circuits related to motive activities underlying precision tasks and perhaps underlying neural work processes and immediate memories.
本研究的目的是促进对神经回路功能的认识。我们利用图论建立了一个由混响神经元回路和并行神经元回路组成的复杂神经生理回路的数学计算模型。在c++语言中实现我们的模型,并应用文献中发现的神经生理学值,我们分别研究了相同输入信号模式下混响回路和并行回路的放电模式,考察了不应期和突触延迟对各自输出信号模式的影响。然后,对完整电路进行了相同的研究,其中两个电路耦合,并联电路可以影响混响的功能。结果表明,不应期对混响电路输出谱图的形成起着重要作用。平行回路的抑制作用能够调节混响频率,这表明平行回路可能参与控制与精密任务动机活动相关的混响回路,也可能参与神经工作过程和即时记忆相关的混响回路。
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引用次数: 1
A Finite Element Model of Unsteady Cavitating Fluid Flow around a Hydrofoil 非定常空化流体绕水翼流动的有限元模型
Pub Date : 2021-01-01 DOI: 10.4236/ojmsi.2021.94027
C. Carbonel
The present study deals with the unsteady dynamics of cavitation around the NACA 0015 hydrofoil in a channel. A finite element model is proposed to solve the governing equations of momentum and mass conservation. Turbulent flows around the hydrofoil are described by the Prandtl-Kolmogorov model. The cavitation phenomenon is modeled through a mixture model in-volving liquid and vapor flows and the Zwart-Gerber-Belamri (ZGB) model is considered to evaluate the transport of the water vapor fraction. The variational finite element model formulation includes the mixing of the characteristic method and the finite element. Also, at the open sides of the channel flow, an open boundary condition is imposed. Numerical experiments are performed for cavitation numbers 0.8 and 0.4. The presented model predicts the essential features of unsteady cavitating flows, the generation of vapor cavities, the time-dependent oscillations of the variables and the presence of vortical flow structures associated to vapor volume concentrations during the shedding process.
本文研究了NACA 0015型水翼在通道内空化的非定常动力学。提出了求解动量守恒和质量守恒控制方程的有限元模型。水翼周围的湍流用Prandtl-Kolmogorov模型来描述。空化现象的模拟采用了液体和蒸汽混合流模型,并考虑了Zwart-Gerber-Belamri (ZGB)模型来评估水蒸气组分的输运。变分有限元模型公式包括特征法和有限元的混合。此外,在河道流动的开放侧,施加了一个开放的边界条件。对空化数0.8和0.4进行了数值实验。该模型预测了非定常空化流动的基本特征、汽腔的产生、变量的随时间振荡以及在脱落过程中与蒸汽体积浓度相关的涡流结构的存在。
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引用次数: 0
Modelling and Simulation of an Ohmic Heating Process 欧姆加热过程的建模与仿真
Pub Date : 2021-01-01 DOI: 10.4236/ojmsi.2021.91002
Hongwei Zhang, A. Mohamed, T. Breikin, M. Howarth
Ohmic Heating (OH) is one of the emerging thermal technologies used in food processing which can produce rapid and uniform heating with close to 100% energy transfer efficiency. Although mathematical modelling for OH processes has been studied by many researchers in recent years, systematic simulations of OH have not been developed for model-based control of the processes. In this paper, mathematical model for a Colinear Ohmic Heater is presented, analyzed, and studied based on the selected configuration. A numerical solution for the mathematical equations has been defined and proposed. MATLAB/Simulink model is hence developed and validated against the available data. Simulation results have shown that MATLAB/Simulink model can produce robust outputs at low computational costs with an accuracy of up to 99.6% in comparison to the analytical solution. This model can be used in further studies for analysis of the OH processes and development of advanced controllers.
欧姆加热(OH)是一种用于食品加工的新兴热技术,它可以产生快速均匀的加热,能量传递效率接近100%。尽管近年来许多研究人员已经研究了OH过程的数学建模,但还没有开发出基于模型的OH过程控制的系统模拟。本文根据所选结构,建立了共线欧姆加热器的数学模型,并进行了分析和研究。定义并提出了数学方程的数值解。因此,开发了MATLAB/Simulink模型,并根据现有数据进行了验证。仿真结果表明,与解析解相比,MATLAB/Simulink模型可以以较低的计算成本产生鲁棒输出,精度高达99.6%。该模型可用于进一步研究OH过程的分析和开发先进的控制器。
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引用次数: 3
Numerical Analysis of Thermal Convection in a CPU Chassis CPU机箱内热对流数值分析
Pub Date : 2021-01-01 DOI: 10.4236/OJMSI.2021.91003
M. Bangalee, M. M. Rahman, M. Ferdows, M. S. Islam
Flow distribution and the effects of different boundary conditions are achieved for a steady-state conjugate (Conduction & Convection) heat transfer process. A plate fin heat sink with horizontal fin orientation along with a computer chassis is numerically investigated and simulated using software ANSYS CFX. Fin orientation of a heat sink changes the direction of fluid flow inside the chassis. For predicting turbulence of the flow inside the domain, a two-equation based k-e turbulence model is chosen. The Reynolds number based on inflow velocity and geometry is found 4.2 × 103 that indicates that the flow is turbulent inside the chassis. To get proper thermal cooling, the optimum velocity ratio of inlet/outlet, dimension of inlet/outlet and different positions of outlet on the back sidewall of the chassis are predicted. Aspect velocity ratio between the inlet airflow and the outlet airflow has an effect on the steadiness of the flow. Mass flow rate depends on the dimension of the inlet/outlet. The horizontal fin orientation with 1:1.6 inlet-outlet airflow velocity ratio gives better thermal performance when outlet is located at the top corner of the chassis, near to the inner sidewall. Flow distribution and heat transfer characteristics are also analyzed to obtain the final model.
研究了稳态共轭(传导和对流)传热过程的流动分布和不同边界条件的影响。利用ANSYS CFX软件对一种水平翅片方向的平板翅片散热器进行了数值模拟研究。散热器翅片的方向改变了机箱内部流体的流动方向。为了预测区域内流动的湍流,选择了基于两方程的k-e湍流模型。基于来流速度和几何形状的雷诺数为4.2 × 103,表明底盘内部的流动是湍流的。为了获得合适的热冷却效果,对进风口的最佳速度比、进风口的尺寸以及出风口在底盘后侧壁上的不同位置进行了预测。进口气流与出口气流的展弦速比对气流的稳定性有影响。质量流量取决于进口/出口的尺寸。当出口位于底盘顶角,靠近内侧壁时,水平翅片的进、出口流速比为1:6 .6,散热性能较好。并对流动分布和换热特性进行了分析,得到了最终模型。
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引用次数: 0
Delayed Dynamics of SIR Model for COVID-19 COVID-19 SIR模型的延迟动力学
Pub Date : 2020-11-06 DOI: 10.21203/rs.3.rs-101284/v1
H. Ebraheem, Nizar J. Alkhateeb, H. Badran, A. Hajjiah, Ebraheem Sultan
BackgroundThe global spread of the COVID-19 pandemic has been one of the most challenging tasks the world has faced since the last pandemic outbreak of 1918. Early on countries felt the strength and persistence of the virus infections spreading with no means of estimating the dispersion rates. Officials in infected countries followed several guidelines set by the World Health Organization (WHO) to try and flatten the infection curve and maintain a low number of infectives. Nonetheless, the virus kept on spreading with impunity and all predictions of how containments or peak detections have been a fail so far. Therefore, a need for a more accurate model to predict the peaking of infections and help guide officials on what best to enact as a measure of public health safety from a multitude of choices outlined by the WHO. Earlier studies of compartmental model of Susceptible-Infected-Recovered (SIR) did not predict the peaking of a hot spots flairs of viral infections and a new model needed to provide a more realistic results to serve public officials battling the pandemic worldwideMethodsA new modified SIR model which incorporates appropriate delay parameters leading to a more precise prediction of COVID-19 real time data. The predictions of the new model are compared to real data obtained from four countries, namely Germany, Italy, Kuwait, and Oman. Two included delay periods for incubation and recovery within the SIR model produces a sensible and more accurate representation of the real time data. The reproductive number 𝑅0 is defined for the model for values of recovery time delay 𝜏2 of the infective case.ResultsIncorporating two delay periods that corresponds to the duration of the incubational and recovery periods measured for COVID-19 gives a more accurate prediction of the peak pandemic infections per geographical area. The parameter variations in the model 𝛽,𝛾,𝛼,𝜏1,𝑎𝑛𝑑 𝜏2 makeup different cases corresponding to different situations. The variations are estimated a priori based on what is being observed and collected data of an infected region to give officials better guidelines on what health policies should be enacted in the future.2 of 15ConclusionsThe empirical data provided by WHO show that the proposed new SIR model gives a better more accurate prediction of COVID-19 pandemic spreading curve. The model is shown to closely fit real time data for four countries. Simulation results are consistent with data and generated curves are well constrained. The parameters can be varied and adjusted for producing and/or reproduction of numbers within the range of each country
COVID-19大流行的全球传播是自1918年上次大流行爆发以来世界面临的最具挑战性的任务之一。早期,各国感到病毒感染传播的强度和持久性,无法估计传播速度。受感染国家的官员遵循了世界卫生组织(WHO)制定的几项指导方针,试图使感染曲线趋于平缓,并保持低感染人数。尽管如此,病毒仍在肆无忌惮地传播,到目前为止,所有关于控制措施或检测高峰的预测都是失败的。因此,需要一个更准确的模型来预测感染的高峰,并帮助指导官员从世界卫生组织概述的众多选择中制定最佳的公共卫生安全措施。早期对易感-感染-恢复(SIR)区室模型的研究不能预测病毒感染热点的峰值,需要一个新的模型来提供更现实的结果,以服务于全球抗击大流行的政府官员。方法一种新的改进SIR模型,该模型纳入了适当的延迟参数,可以更精确地预测COVID-19实时数据。新模型的预测结果与德国、意大利、科威特和阿曼四个国家的实际数据进行了比较。SIR模型中包含的两个潜伏期和恢复延迟期产生了对实时数据的合理和更准确的表示。传染病例的恢复时间延迟𝜏2的值定义模型的繁殖数𝑅0。结果结合与COVID-19的潜伏期和恢复期相对应的两个延迟期,可以更准确地预测每个地理区域的大流行感染高峰。模型中参数的变化,如:时延、、时延、𝜏1、𝑎𝑛𝑑𝜏2,对应不同的情况构成不同的情况。这些变化是根据观察到的情况和在受感染地区收集的数据进行先验估计的,以便为官员提供更好的指导方针,指导未来应该制定哪些卫生政策。WHO提供的实证数据表明,本文提出的新SIR模型能够更好、更准确地预测COVID-19大流行传播曲线。该模型与四个国家的实时数据非常吻合。仿真结果与数据一致,生成的曲线约束良好。这些参数可以改变和调整,以便在每个国家的范围内编制和(或)复制数字
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引用次数: 6
Bertalanffy-Pütter Models for the Growth of Tropical Trees and Stands 热带树木和林分生长的bertalanffy - p<e:2>模型
Pub Date : 2020-09-07 DOI: 10.4236/ojmsi.2020.84006
N. Brunner, M. Kühleitner
The Bertalanffy-Putter (BP) five-parameter growth model provides a versatile framework for the modeling of growth. Using data from a growth experiment in literature about the average size-at-age of 24 species of tropical trees over ten years in the same area, we identified their best-fit BP-model parameters. While different species had different best-fit exponent-pairs, there was a model with a good fit to 21 (87.5%) of the data (“Good fit” means a normalized root-mean-squared-error NRMSE below 2.5%. This threshold was the 95% quantile of the lognormal distribution that was fitted to the NRMSE values for the best-fit models for the data). In view of the sigmoidal character of this model despite the early stand we discuss whether the setting of the growth experiment may have impeded growth.
Bertalanffy-Putter (BP)五参数增长模型为增长建模提供了一个通用的框架。利用文献中关于同一地区24种热带树木10年平均年龄大小的生长实验数据,我们确定了它们最适合的bp模型参数。虽然不同物种有不同的最佳拟合指数对,但有一个模型对21(87.5%)的数据具有良好的拟合(“良好拟合”意味着标准化均方根误差NRMSE低于2.5%)。该阈值是对数正态分布的95%分位数,该分位数与数据的最佳拟合模型的NRMSE值相拟合)。鉴于该模型的s型特征,尽管早期立木,我们讨论了生长实验的设置是否可能阻碍了生长。
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引用次数: 0
Demand and Capacity Modelling in Healthcare Using Discrete Event Simulation 使用离散事件模拟的医疗保健需求和能力建模
Pub Date : 2020-09-07 DOI: 10.4236/ojmsi.2020.84007
Saurav Singla
The NHS is right now confronting huge pressures relating to demand and capacity in radiology. The purpose of this research has been to provide information about MRI usage, details of operational aspects of MRI services, and to ascertain the planning intentions of NHS radiology services to keep up and create MRI capacity. The report expands on using Discrete Event Simulation (DES) to inspect and plan the utilisation of NHS hospital resources for the radiology department to help a 24 hr service that is available to outpatients which will help with diminishing patient waiting time, better resource usage, understanding the capacity and demand. Consequently, this research examines to adjust staff and resources with the demand of the MRI. The research was investigated using DES in various scenarios to find which resources are inactive; patients are treated slowly. DES helped in discovering resource utilisation and outpatient throughout the system. It additionally helped in distinguishing the bottlenecks in patient flow. The DES simulation results demonstrated that time for the outpatient in the system is less and more outpatients have been treated too. There is a higher level of outpatient patients leaving the system under 120 minutes. The report uncovered an MRI report interpretation time. Reception room time and MRI waiting room time are decreased significantly. It additionally exhibited with an expanded outflow of outpatients, resources, for example, MRI capacity and radiographer utilisation expanded.
NHS目前正面临着与放射学需求和能力有关的巨大压力。本研究的目的是提供有关MRI使用的信息,MRI服务操作方面的细节,并确定NHS放射服务的规划意图,以保持和创造MRI能力。该报告扩展了使用离散事件模拟(DES)来检查和规划NHS放射科医院资源的利用情况,以帮助门诊患者提供24小时服务,这将有助于减少患者等待时间,更好地利用资源,了解容量和需求。因此,本研究探讨如何根据MRI的需求调整人员和资源。该研究使用DES在各种情况下进行调查,以找出哪些资源是不活跃的;病人治疗缓慢。DES帮助发现整个系统的资源利用率和门诊情况。它还有助于识别患者流中的瓶颈。DES仿真结果表明,系统内门诊病人的时间较少,门诊病人也较多。门诊病人在120分钟内离开系统的比例更高。报告发现MRI报告解释时间。接待室时间和核磁共振候诊时间明显减少。此外,它还表现出门诊病人、资源外流的扩大,例如,核磁共振成像能力和放射技师的利用扩大。
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引用次数: 5
Generalized Central Factorial Numbers with Odd Arguments 具有奇数参数的广义中心阶乘数
Pub Date : 2020-06-16 DOI: 10.4236/ojmsi.2020.83005
Youmna H. Zaid, F. Shiha, B. El-Desouky
In this paper, we consider r-generalization of the central factorial numbers with odd arguments of the first and second kind. Mainly, we obtain various identities and properties related to these numbers. Matrix representation and the relation between these numbers and Pascal matrix are given. Furthermore, the distributions of the signless r-central factorial numbers are derived. In addition, connections between these numbers and the Legendre-Stirling numbers are given.
在本文中,我们考虑了具有第一类和第二类奇自变量的中心阶乘数的r-推广。主要是,我们获得了与这些数字相关的各种恒等式和性质。给出了矩阵表示以及这些数字与Pascal矩阵之间的关系。此外,还导出了无符号r中心阶乘数的分布。此外,还给出了这些数与勒让德-斯特灵数之间的联系。
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引用次数: 1
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建模与仿真(英文)
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