Hypothesis testing by simulation of a medical study model using the expected net benefits criteria

Introduction: This work investigates whether to conduct a medical study from the point of view of the expected net benefit taking into account statistical power, time and cost. The hypothesis of this paper is that the expected net benefit is equal to zero. Methods: Information were obtained from a pilot medical study that investigates the effects of two diagnostic modalities, magnetic resonance imaging (MRI) and computerized axial tomography scanner (CT), on patients with acute stroke. Statistical procedure was applied for planning and contrasting equivalence, non-inferiority and inequality hypotheses of the study for the effectiveness, health benefits and costs. A statistical simulation model was applied to test the hypothesis that conducting the study would or not result in overall net benefits. If the null hypothesis not rejected, no benefits would occurred and therefore the two arms-patterns of diagnostic and treatment are of equal net benefits. If the null hypothesis is rejected, net benefits would occur if patients are diagnosed with the more favourable diagnostic modality. Results: For any hypothesis design, the expected net benefits are in the range of 366 to 1796 per patient at 80% of statistical power if conducting the study. The power depends on the monetary value available for a unit of health improvement. Conclusion: The statistical simulations suggest that diagnosing patients with CT will provide more favourable health outcomes showing statistically significant expected net benefits in comparison with MRI.

On the Simulation Hypothesis and Its Implications

This paper reports on the potential use of video games as well as gaming engines in the domain of physics and artificial intelligence. Unreal Engine 4 (UE4) [1] is used to render the history of the universe back in time to the quantum gravity era and then standard cosmology is assumed for its evolution until the appearance of life that was a simplified model of human-like evolution is rendered. The results of the simulations have a potential implication on the origin of life and matter and favorite the simulation hypothesis of the universe.

Arrhenius relationship and two-step scheme in AF hyperdynamics simulation of diffusion of Mg/Zn interface

The accelerating factor （AF） method is a simple and appropriate way to investigate the atomic long-time deep diffusion at solid-solid interface. In the framework of AF hyperdynamics （HD） simulation, the relationship between the diffusion coefficient along the direction of z-axis which is normal to the Mg/Zn interface and temperature was investigated, and the AF＇s impact on the diffusion constant （D0） and activation energy （Q^＊） was studied. Then, two steps were taken to simulate the atomic diffusion process and the formation of new phases： one for acceleration and the other for equilibration. The results show that： the Arrhenius equation works well for the description of Dz with different accelerating factors; the AF has no effect on the diffusion constant Do in the case of no phase transition; and the relationship between Q＊ and Q conforms to Q^＊=Q/A. Then, the new Arrhenius equation for AFHD is successfully constructed as Dz=Doexp[-Q/（ART）]. Meanwhile, the authentic equilibrium conformations at any dynamic moment can only be reproduced by the equilibration simulation of the HD-simulated configurations. Key words： accelerating factor method; Arrhenius equation; two-steps scheme; Mg/Zn interface; hyperdynamic simulation

A Study of Eddy Viscosity Coefficient in Numerical Tidal Simulation

Based on the fluid motion equations, the physical meaning of eddy viscosity coefficient and the rationality of the Boussinesq hypothesis are discussed in this paper. The effect of the coefficient on numerical stability is analyzed briefly. A semi-enclosed rectangular sea area, with an orthogonal spur dike, is applied in a 2-D numerical model to study the effect of horizontal eddy viscosity coefficient (A(H)), The computed result shows that A(H) has little influence on the tidal level and averaged flow velocity, but has obvious influence on the intensity and the range of return flow around near the spur dike. Correspondingly, a wind-driven current pool and an annular current are applied in a 3-D numerical model respectively to study the effect of vertical eddy viscosity coefficient (A(V)). The computed result shows that the absolute value of A(V) is inversely proportional to that of horizontal velocity, and the vertical gradient value of A(V) determines the vertical distribution of horizontal velocity, The distribution form of A(V) is theoretically recommended as a parabolic type, of which the maximum value appears at 0.5 H.

Simulation of Spark Source Wavelet Under Multibubble Motion

Marine spark sources are widely used in high-resolution marine seismic surveys.The characteristic of a wavelet is a critical part in seismic exploration;thus,the formation and numerical simulation of spark source wavelets should be explored.In studies on spark source excitation,the acoustic field generated by the interaction between bubbles constitutes the near-field wavelet of a source.Therefore,this interaction should be revealed by studying complex multibubble motion laws.In this study,actual discharge conditions were combined to derive the multibubble equation of motion.Energy conservation,ideal gas equation,and environmental factors in the discharge of spark source wavelets were studied,and the simulation method of an ocean spark source wavelet was established.The accuracy of the simulation calculation method was verified through a comparison of indoor-measured signals using three electrodes and the spark source wavelet obtained in the field.Results revealed that the accuracy of the model is related to the number of electrodes.The fewer the number of electrodes used,the lower will be the model's accuracy.This finding is attributed to the statistical hypothesis factor introduced to eliminate the coupling term of the interaction of the multibubble motion equation.This study presents a method for analyzing the wavelet characteristics of an indoor-simulated spark source wavelet.

A New Parallel Algorithm for Simulation of Spin-Glass Systems on Scales of Space-Time Periods of an External Field

We study the statistical properties of an ensemble of disordered 1D spatial spin-chains (SSCs) of certain length in the external field. On nodes of spin-chain lattice the recurrent equations and corresponding inequal-ity conditions are obtained for calculation of local minimum of a classical Hamiltonian. Using these equa-tions for simulation of a model of 1D spin-glass an original high-performance parallel algorithm is developed. Distributions of different parameters of unperturbed spin-glass are calculated. It is analytically proved and shown by numerical calculations that the distribution of the spin-spin interaction constant in the Heisenberg nearest-neighboring Hamiltonian model as opposed to the widely used Gauss-Edwards-Anderson distribu-tion satisfies the Lévy alpha-stable distribution law which does not have variance. We have studied critical properties of spin-glass depending on the external field amplitude and have shown that even at weak external fields in the system strong frustrations arise. It is shown that frustrations have a fractal character, they are self-similar and do not disappear at decreasing of calculations area scale. After averaging over the fractal structures the mean values of polarizations of the spin-glass on the scales of external field's space-time peri-ods are obtained. Similarly, Edwards-Anderson’s ordering parameter depending on the external field ampli-tude is calculated. It is shown that the mean values of polarizations and the ordering parameter depending on the external field demonstrate phase transitions of first-order.

Inverted Simulations Demonstrating Strong Ecological Fallacies in Cohort Studies

We start with a description of the statistical inferential framework and the duality between observed data and the true state of nature that underlies it. We demonstrate here that the usual testing of dueling hypotheses and the acceptance of one and the rejection of the other is a framework which can often be faulty when such inferences are applied to individual subjects. This follows from noting that the statistical inferential framework is predominantly based on conclusions drawn for aggregates and noting that what is true in the aggregate frequently does not hold for individuals, an ecological fallacy. Such a fallacy is usually seen as problematic when each data record represents aggregate statistics for counties or districts and not data for individuals. Here we demonstrate strong ecological fallacies even when using subject data. Inverted simulations, of trials rightly sized to detect meaningful differences, yielding a statistically significant p-value of 0.000001 （1 in a million） and associated with clinically meaningful differences between a hypothetical new therapy and a standard therapy, had a proportion of instances of subjects with standard therapy effect better than new therapy effects close to 30%. A ―winner take all‖ choice between two hypotheses may not be supported by statistically significant differences based on stochastic data. We also argue the incorrectness across many individuals of other summaries such as correlations, density estimates, standard deviations and predictions based on machine learning models. Despite artifacts we support the use of prospective clinical trials and careful unbiased model building as necessary first steps. In health care, high touch personalized care based on patient level data will remain relevant even as we adopt more high tech data-intensive personalized therapeutic strategies based on aggregates.

Quantum Realities and Observer-Dependent Universes: An Advanced Observer Model

This paper presents a novel observer model that integrates quantum mechanics, relativity, idealism, and the simulation hypothesis to explain the quantum nature of the universe. The model posits a central server transmitting multi-media frames to create observer-dependent realities. Key aspects include deriving frame rates, defining quantum reality, and establishing hierarchical observer structures. The model’s impact on quantum information theory and philosophical interpretations of reality are examined, with detailed discussions on information loss and recursive frame transmission in the appendices.

Generation of spatial atmospheric turbulence field in aircraft motion simulation based on refined similarity hypothesis

It is necessary to build turbulence model to study the response of aircraft to atmospheric turbulence for high resolution earth observation. The conventional method is on the basis of Dryden’s model with the assumption that individual patches are Gaussian. In this paper,based on Kraichnan’s refined similarity idea,a new 1D atmospheric turbulence model is set up by introducing the energy transfer rate as an intermittency disturbance to a Gaussian process. Our results show that the turbulent fields generated by our new method exhibit an anomalous scaling described by the She-Leveque (SL) formula,which is now well accepted for homogenous and isotropic turbulence.

我国煤与瓦斯突出机理70年发展历程与展望

煤与瓦斯突出灾害的有效防治一直是我国煤矿安全生产面临的挑战性难题,其前提和基础是对煤与瓦斯突出机理的深入研究。全面阐述我国近70年来在煤与瓦斯突出机理研究领域所开展的工作和取得的成绩,其研究过程分别经历了积极探索阶段(1955—1977年)、理论奠定阶段(1978—2002年)、快速发展阶段(2003—2015年)和稳定发展阶段(2016年至今);基于文献计量学方法和科学知识图谱分析,探讨了突出机理的研究热点和前沿趋势。分别从理论假说、物理模拟、数值模拟3个方面系统总结了我国煤与瓦斯突出机理研究进展:理论假说方面,在综合作用假说的基础上,针对我国煤矿实际情况形成了以流变假说、球壳失稳理论、力学作用假说等为代表的新观点和新理论,奠定了突出理论研究基础;物理模拟方面,围绕突出主控因素、多物理场演化、能量转化与失稳条件、地质构造与构造煤、两相流致灾机制等方面进行了大量的试验研究,基本掌握了突出的发动条件、发展过程、演化规律及影响因素;数值模拟方面,主要开展了突出煤层、地质构造和突出两相流等方面的模拟研究,然而由于突出过程和影响因素的复杂性,仍无法实现突出全过程的模拟分析。目前,已初步形成了具有我国特色的煤与瓦斯突出理论体系,但时有发生的突出事故表明突出防治形势依然严峻。结合研究现状和发展趋势,认为应进一步研究突出全过程、全要素、全时空耦合演化过程,分析含瓦斯煤多尺度流变行为,探索煤层储能与动态释放过程,揭示复合与次生灾害成灾机制,形成煤与瓦斯突出耦合演化机理、力学模型、能量模型和灾变模型;在此基础上针对典型突出场景,开展复杂地层下突出物理模拟试验和全过程数值模拟反演,实现突出危险的实时监测和连续预警。

极小样本两独立定量资料假设检验方法比较

目的 探索极小样本两独立定量资料假设检验方法的表现性能。方法 使用蒙特卡洛方法产生不同均数差、分布和样本量的数据,分别使用t检验、Wilcoxon秩和检验和Bootstrap法进行假设检验,并估计每种情形下的统计效率。结果 当样本量极小时,Wilcoxon秩和检验的统计效率极低。当数据呈偏态分布时,Bootstrap置信区间法容易犯Ⅱ类错误。当均数差较大时,该法仍有较高的统计效率。不论数据是否服从正态分布,当样本量极小时,t检验的表现优于Wilcoxon秩和检验。结论 根据本模拟研究结果,当数据服从正态分布时,建议使用t检验对极小样本进行统计推断。当数据不服从正态分布时,建议使用Bootstrap置信区间法对极小样本进行统计推断。

基于小样本利用神经网络组合评价软件质量

分析用于软件质量评价的神经网络在训练时只有小样本的原因,及由此导致的网络泛化能力差和泛化能力无法定量估算等问题,提出输出一致假设,用“分析评价结果和表决结果”作为解决问题的途径,以已经训练出对小样本准确率高且未过拟合的少量相对合格网络为前提,依据蒙特卡洛模拟方法生成的大量随机数,采用表决成功率(VSR)和评价相同率均值(SR)反推出泛化能力最优的网络组合,用t分布定量估算最优网络组合泛化能力。实例结果表明,该方法基于小样本,能够挑选出对新软件项目泛化能力较强的最优网络组合,为从软件度量直接评价软件综合质量的工作和集成学习提供新思路。

康德与元宇宙

康德对现象界/物自身的区分中隐藏着元宇宙的哲学奥秘。基于兰顿和查尔默斯对康德先验观念论的认知结构实在论(ESR)解读,现象界关乎事物的关系性质,物自身关乎事物的内在性质。这意味着,实在的关系性质或元宇宙的物理学结构是可知的,而其内在性质或元-宇宙的物理学结构是不可知的。“元宇宙→现实世界→元-宇宙→本体世界”的模拟链条连接了元宇宙与物自身。对认知结构实在论的“平原景观”和“山地景观”的区分,为我们理解康德与元宇宙提供了一个实现双向阐释的全新视角:元宇宙的模拟假说契合于认知结构实在论者的口号“一切源于结构,结构源于X”,而这里的“X”正是康德的物自身。最后我们回应了一些重要的批评意见。

Gaussian Sum PHD Filtering Algorithm for Nonlinear Non-Gaussian Models

A new multi-target filtering algorithm, termed as the Gaussian sum probability hypothesis density （GSPHD） filter, is proposed for nonlinear non-Gaussian tracking models. Provided that the initial prior intensity of the states is Gaussian or can be identified as a Gaussian sum, the analytical results of the algorithm show that the posterior intensity at any subsequent time step remains a Gaussian sum under the assumption that the state noise, the measurement noise, target spawn intensity, new target birth intensity, target survival probability, and detection probability are all Gaussian sums. The analysis also shows that the existing Gaussian mixture probability hypothesis density （GMPHD） filter, which is unsuitable for handling the non-Gaussian noise cases, is no more than a special case of the proposed algorithm, which fills the shortage of incapability of treating non-Gaussian noise. The multi-target tracking simulation results verify the effectiveness of the proposed GSPHD.

1966年以来华北地区一系列七级大震破裂过程的数值模拟

用非连续变形分析方法 (DDA +FEM)数值模拟 ,在华北地区各地块相互制约的块体系统环境中 ,地块边界断层上发生 196 6年邢台地震、196 9年渤海地震、1975年海城地震、1976年唐山地震等不同类型破裂模式大震的破裂过程 .数值模拟结果给出每个大震释放的主应力场 ,最大剪应力变化等值线图 ,地震前后位移变化矢量图 ,发震断层滑移随时间变化以及走滑错距和应力降等震源参数 .这些结果与地震的震源机制 ,用地震波资料研究得到的震源参数 ,宏观等震线 ,地表观测的水平位移矢量图基本一致 .其中 196 9年渤海地震正交破裂模式的结果与宏观等震线及小震分布图像更接近 .1976年唐山地震复杂震源模式与该震早期余震分布图像更相符 .表明用DDA +FEM方法进行数值模拟研究 ,能较好地模拟地震破裂过程 .

空空导弹系统仿真模型验证平台

文章介绍了空空导弹系统仿真模型验证平台。该平台基于CLIMB方案,将不同数据资源分为五个等级。利用等级高的数据库对产生等级低的数据库资源的模型进行验证。平台集成了工程上用于仿真模型有效性评估的统计检验方法。平台验证方法完备且具有良好的开放性,易于扩充。最后用实例说明平台的工作界面。

考虑天气不确定性的光伏电站置信容量评估

光伏发电由于具有间歇性和波动性,一般认为只有能量价值而没有容量价值,但在光伏电站并网后电力系统的发电可靠性会有所提升,这表明光伏发电也具有一定的容量价值,如何衡量其置信容量是大规模光伏电站接入电网时需要考虑的问题之一。文中提出了一种评估光伏电站置信容量的计算方法。首先,根据1年中天气情况建立考虑不同天气概率、最大辐射强度、云遮蔽以及温度波动的年光伏电站输出功率波动模型;其次,采用了基于序贯蒙特卡洛仿真的电力系统发电可靠性计算方法,在此基础上应用弦截法进行光伏电站置信容量的迭代求解,并将数理统计中的检验2个大子样均值相等——u检验的假设检验方法引入到迭代求解的收敛性判据之中;最后,应用可靠性标准算例的仿真计算,证明了所述方法的正确性和有效性。

关于仿真可信性的度量

仿真可信性研究的主要方法是将仿真试验结果与实物试验结果进行静态和动态一致性检验。该文通过讨论一致性检验的置信度 ,给出了置信度与弃真概率和采伪概率的关系。并说明要选择恰当的显著性水平 ,以保证检验的置信度具有合理性。

基线资料均衡性检验存在的问题与探讨

目的选择恰当的均衡性检验方法,探讨均衡性检验的必要性。方法采用Monte Carlo模拟比较假设检验和标准化差异检验基线资料均衡性的能力。结果随机化研究中,大样本情况下出现不均衡的可能性很小;而在样本量相对较小的情况下,很难保证基线资料的均衡性。结论标准化差异是一种有效的均衡性检验方法。非随机化研究中,均衡性检验必不可少;随机化研究中,样本相对较小情况下也需要作均衡性检验。

汉语简单否定陈述句理解的心理模拟过程

采用自定步速阅读的方法,从体验认知的角度探索了汉语简单否定句的动态理解过程。以具有对立谓词的汉语陈述性的肯定句和否定句为实验句,以与否定句的两种状态相对应的图片为实验图片,并构成句子-图片匹配/不匹配两种匹配状态。研究结果表明,实验1在以250ms为间隔时间的条件下,肯定句和否定句的理解有显著的匹配效应;实验2以750ms为间隔时间,则未表现出匹配效应,而实验3以1500ms为间隔时间,肯定句和否定句的理解又表现出显著的匹配效应。实验结果证明,具有对立谓词的简单的汉语否定句理解的心理模拟过程,并不像两步模拟假设所设想的那样遵循着先模拟被否定状态再模拟实际状态的顺序,而是在理解的初期就完成了对事件的实际状态的模拟。