A Practical Guide to Statistical Tests in the Biomedical Field: From Parametric to Nonparametric, Where and How?

Healthcare decisions are based on scientific evidence obtained from medical studies by gathering data and analyzing it to obtain the best results. When analyzing data, biostatistics is a powerful tool, but healthcare professionals lack knowledge in this field. This lack of knowledge can manifest itself in situations such as choosing the wrong statistical test for the right situation or applying a statistical test without checking its assumptions, leading to inaccurate results and misleading conclusions. With the help of this “narrative review”, the aim is to bring biostatistics closer to healthcare professionals by answering certain questions: how to describe the distribution of data? how to assess the normality of data? how to transform data? and how to choose between nonparametric and parametric tests? Through this work, our hope is that the reader will be able to choose the right test for the right situation, in order to obtain the most accurate results.

Parametric resonance of axially functionally graded pipes conveying pulsating fluid

Based on the generalized Hamilton's principle,the nonlinear governing equation of an axially functionally graded(AFG)pipe is established.The non-trivial equilibrium configuration is superposed by the modal functions of a simply supported beam.Via the direct multi-scale method,the response and stability boundary to the pulsating fluid velocity are solved analytically and verified by the differential quadrature element method(DQEM).The influence of Young's modulus gradient on the parametric resonance is investigated in the subcritical and supercritical regions.In general,the pipe in the supercritical region is more sensitive to the pulsating excitation.The nonlinearity changes from hard to soft,and the non-trivial equilibrium configuration introduces more frequency components to the vibration.Besides,the increasing Young's modulus gradient improves the critical pulsating flow velocity of the parametric resonance,and further enhances the stability of the system.In addition,when the temperature increases along the axial direction,reducing the gradient parameter can enhance the response asymmetry.This work further complements the theoretical analysis of pipes conveying pulsating fluid.

Enhanced picosecond terahertz wave generation based on cascade effects in a terahertz parametric generator

Enhanced terahertz wave generation via a Stokes cascade process has been demonstrated using picosecond pulse pumped terahertz parametric generation at 1 kHz repetition rate.Clear cascade saturation of terahertz output was observed,and the corresponding cascade-Stokes spectra were analyzed.The maximum terahertz wave average power was 22μW under a pump power of 30 W,whereas the maximum power conversion efficiency was 8×10^(-7)under a pump power of 21 W.The THz power fluctuation was measured to be about 1%in 20 min.This THz parametric source with a relatively stable output is suitable for a variety of practical applications.

Parametric instability in the pure-quartic nonlinear Schrödinger equation

We study the nonlinear stage of modulation instability(MI)in the non-intergrable pure-quartic nonlinear Schrödinger equation where the fourth-order dispersion is modulated periodically.Using the three-mode truncation,we reveal the complex recurrence of parametric resonance(PR)breathers,where each recurrence is associated with two oscillation periods(PR period and internal oscillation period).The nonlinear stage of parametric instability admits the maximum energy exchange between the spectrum sidebands and central mode occurring outside the MI gain band.

Harmonic balance simulation of the influence of component uniformity and reliability on the performance of a Josephson traveling wave parametric amplifier

A Josephson traveling wave parametric amplifier(JTWPA),which is a quantum-limited amplifier with high gain and large bandwidth,is the core device of large-scale measurement and control systems for quantum computing.A typical JTWPA consists of thousands of Josephson junctions connected in series to form a transmission line and hundreds of shunt LC resonators periodically loaded along the line for phase matching.Because the variation of these capacitors and inductors can be detrimental to their high-frequency characteristics,the fabrication of a JTWPA typically necessitates precise processing equipment.To guide the fabrication process and further improve the design for manufacturability,it is necessary to understand how each electronic component affects the amplifier.In this paper,we use the harmonic balance method to conduct a comprehensive study on the impact of nonuniformity and fabrication yield of the electronic components on the performance of a JTWPA.The results provide insightful and scientific guidance for device design and fabrication processes.

Modularized and Parametric Modeling Technology for Finite Element Simulations of Underground Engineering under Complicated Geological Conditions

The surrounding geological conditions and supporting structures of underground engineering are often updated during construction,and these updates require repeated numerical modeling.To improve the numerical modeling efficiency of underground engineering,a modularized and parametric modeling cloud server is developed by using Python codes.The basic framework of the cloud server is as follows:input the modeling parameters into the web platform,implement Rhino software and FLAC3D software to model and run simulations in the cloud server,and return the simulation results to the web platform.The modeling program can automatically generate instructions that can run the modeling process in Rhino based on the input modeling parameters.The main modules of the modeling program include modeling the 3D geological structures,the underground engineering structures,and the supporting structures as well as meshing the geometric models.In particular,various cross-sections of underground caverns are crafted as parametricmodules in themodeling program.Themodularized and parametric modeling program is used for a finite element simulation of the underground powerhouse of the Shuangjiangkou Hydropower Station.This complicatedmodel is rapidly generated for the simulation,and the simulation results are reasonable.Thus,this modularized and parametric modeling program is applicable for three-dimensional finite element simulations and analyses.

Meta-Auto-Decoder:a Meta-Learning-Based Reduced Order Model for Solving Parametric Partial Differential Equations

Many important problems in science and engineering require solving the so-called parametric partial differential equations(PDEs),i.e.,PDEs with different physical parameters,boundary conditions,shapes of computational domains,etc.Typical reduced order modeling techniques accelerate the solution of the parametric PDEs by projecting them onto a linear trial manifold constructed in the ofline stage.These methods often need a predefined mesh as well as a series of precomputed solution snapshots,and may struggle to balance between the efficiency and accuracy due to the limitation of the linear ansatz.Utilizing the nonlinear representation of neural networks(NNs),we propose the Meta-Auto-Decoder(MAD)to construct a nonlinear trial manifold,whose best possible performance is measured theoretically by the decoder width.Based on the meta-learning concept,the trial manifold can be learned in a mesh-free and unsupervised way during the pre-training stage.Fast adaptation to new(possibly heterogeneous)PDE parameters is enabled by searching on this trial manifold,and optionally fine-tuning the trial manifold at the same time.Extensive numerical experiments show that the MAD method exhibits a faster convergence speed without losing the accuracy than other deep learning-based methods.

Research on Urban Building Parametric Modelling Method Based on CityEngine

With the advancement of technology and the development of cities,urban planning and management methods are also constantly improving.From paper-based assignments to modern digitization,new technologies have enabled more efficient design and management for cities.3D modeling can used to simulate the urban environment,which can assist in urban planning and management.However,large-scale modeling cannot be achieved through existing modeling methods,and there are still some shortcomings in the maintenance of the model.Therefore,this article proposes a Computer Generated Architecture(CGA)parametric 3D modeling method based on CityEngine.Research on expanding and customizing modeling rules to create indoor and outdoor modeling rule templates for buildings and methods for generating urban 3D models have been carried out.The results have shown that the completed model can be displayed on different platforms thanks to parameterized modeling.The model can be modified easily and directly applied to the analysis and decision-making of urban planning schemes.

Generation of tunable high-order Laguerre– Gaussian petal-like modes from a mid-infrared optical vortex parametric oscillator

High-order Laguerre–Gaussian(LG)petal-like beams have become a topic of significant interest due to their potential application in next-generation optical trapping,quantum optics,and materials processing technologies.In this work,we demonstrate the generation of high-order LG beams with petal-like spatial profiles and tunable orbital angular momentum(OAM)in the mid-infrared wavelength region.These beams are generated using idler-resonant optical parametric oscillation(OPO)in a KTiOAsO_(4)(KTA)crystal.By adjusting the length of the resonant cavity,the OAM of the mid-infrared idler field can be tuned and we demonstrate tuning in the range of 0 to10.When using a maximum pump energy of 20.2 mJ,the maximum output energy of high-order modes LG_(0.45),LG_(0.48),and LG_(0.410) were 0.8,0.53,and 0.46 mJ,respectively.The means by which high-order LG modes with petal-like spatial profiles and tunable OAM were generated from the OPO is theoretically modeled by examining the spatial overlap efficiency of the beam waists of the pump and resonant idler fields within the center of the KTA crystal.The methodology presented in this work offers a simple and flexible method to wavelength-convert laser emission and generate high-order LG modes.

基于Creo Parametric的新型防堵装置运动仿真

结合被动式防堵装置和动力驱动式防堵装置的优缺点,开发了一种新型的滑板压秆旋切式防堵装置,并分析了该防堵装置的结构和工作原理。同时,采用Creo Parametric软件建立了三维几何模型,并通过Creo Parametric软件的机构模块对关键部件进行了干涉和运动仿真分析。通过分析确保该装置各部件之间不存在干涉,并得到其关键部件旋切平面刀端点的速度、速度X方向分量、速度Y方向分量及加速度、加速度X方向分量和加速度Y方向分量随时间的变化规律,旨在为滑板压秆旋切式防堵装置的结构优化提供科学依据。

基于Creo Parametric的包装机曲柄滑块机构的优化设计

在Creo Parametric中,通过骨架模型,创建了偏置曲柄滑块机构模型,并对曲柄滑块机构进行了运动分析,应用Creo Parametric的行为建模功能,将滑块行程、最小压力角作为约束,对曲柄与连杆的长度进行了优化设计。该方法简单、实用性强,具有很大的推广价值,为曲柄滑块机构的设计提供了新的思路。

基于Creo Parametric软件平台的混合式建模方法研究

计算机辅助工业设计在设计流程中的应用越来越广泛。通过对参数化建模和自由式建模的对比研究,指出了这两种方法各自的弊端,提出基于Creo Parametric软件平台的混合式建模办法。以电吹风产品模型构建的案例来说明混合式建模方法的工作流程,并通过模型分析验证了这种方法的可行性。

Development of Parametric Design System Based on AutoCAD Automation

This paper discusses the method of how to develop the parametric design system. It presents an idea and a method of developing AutoCAD R14 with the help of VB, AutoLISP and DantaBase system on the base of AntoCAD Automation technology. Therefore, the question of how to integrate the user's interface, data (DataBase) management and parameter transformation can be solved properly.

基于Creo Parametric的易拉罐外形尺寸的优化设计

结合实例应用Creo Parametric的行为建模功能,对易拉罐的外形尺寸进行了优化设计。在Creo Paramet-ric中以易拉罐外形尺寸为设计变量,以易拉罐容积为约束条件,以易拉罐金属用量最小为设计目标,进行了优化设计。该方法操作简便、优化结果可靠、推广性强。为易拉罐及其他包装容器的优化设计提供了新的思路。

基于Creo Parametric的风机叶片建模方法研究

由于风机叶片在三维软件中直接建模的复杂度,探讨了一种较快捷创建风机叶片的建模方法。利用NACA软件生成叶片翼型截面离散点坐标,并将结果导入Creo Parametric软件。通过混合等命令,将多段翼型截面曲线生成光滑的叶片曲面模型,并对生成的实体表面进行了曲面分析与检查。最后利用Flow Simulation等软件,对叶片进行了流体仿真及模态分析,得出了叶片压力最大值在叶片的设计承受范围内,且叶片一阶固有频率远大于风机转动时的频率,叶片发生共振的可能性很小的结论,很好的证明了叶片建模方法的可行性和实用性。通过这种建模方法,将很大程度减少叶片在设计时的工作强度与难度,提高设计人员的设计效率。

Ince-Strutt Stability Charts for Ship Parametric Roll Resonance in Irregular Waves

Ince-Strutt stability chart of ship parametric roll resonance in irregular waves is conducted and utilized for the exploration of the parametric roll resonance in irregular waves. Ship parametric roll resonance will lead to large amplitude roll motion and even wreck. Firstly, the equation describing the parametric roll resonance in irregular waves is derived according to Grim’s effective theory and the corresponding Ince-Strutt stability charts are obtained. Secondly, the differences of stability charts for the parametric roll resonance in irregular and regular waves are compared. Thirdly, wave phases and peak periods are taken into consideration to obtain a more realistic sea condition. The influence of random wave phases should be taken into consideration when the analyzed points are located near the instability boundary. Stability charts for different wave peak periods are various. Stability charts are helpful for the parameter determination in design stage to better adapt to sailing condition. Last, ship variables are analyzed according to stability charts by a statistical approach. The increase of the metacentric height will help improve ship stability.

Nonparametric estimations of the sea state bias for a radar altimeter

To estimate the sea state bias（SSB） for radar altimeter, two nonparametric models, including a Nadaraya-Watson（NW） kernel estimator and a local linear regression（LLR） estimator, are studied based on the Jason-2 altimeter data. Selecting from different combinations of the Gaussian kernel function, spherical Epanechnikov kernel function, a fixed bandwidth and a local adjustable bandwidth, it is observed that the LLR method with the spherical Epanechnikov kernel function and the local adjustable bandwidth is the optimal nonparametric model for the SSB estimation. The comparisons between the nonparametric and parametric models are conducted and the results show that the nonparametric model performs relatively better at high-latitudes of the Northern Hemisphere. This method has been applied to the HY-2A altimeter as well and the same conclusion can be obtained.

AN APPROACH TO FEATURE-BASED PARAMETRIC DESIGN FOR DIE AND MOULD

An approach to feature-based parametric design for die and mould is proposed in this paper.The assembly relationship and parts of the die and mould are described by feature.The dependent relationship of features is described by parent-child operator structure.The feature shape and location can be modified by design parameters.An expert system is used for deriving a geometry of the features which satisfies the given constraints.This approach provides a more natural and convenient method of representing a parametric model of the die and mould.

RESEARCH OF THE PARAMETRIC ASSEMBLY METHOD

The parametric part assembly generation method is presented. Based on the parametric part generated by means of constructive-element, through interactively inputting the relationships of the location and the assembly, and by compiling operations like movement and rotation, the assembly drawing is created so as to implement the occurrence of the parameterizations of the assembly and the part drawing. The data structure of the assembly part and the key technologies of hidden line removal in the implementation of assembly process, etc. , are described in detail.

Suppression strategy for parametrically excited lateral vibration of mass-loaded string

This paper discusses a simple way to suppress the parametrically excited lateral vibration of a mass-loaded string. Supposing that the mass at the lower end of the string is subjected to a vertical harmonic excitation and neglecting the higher order vibration modes, the equation of motion for the mass-loaded string can be represented by a Mathieus equation with cubic nonlinearity. According to the theory of the Mathieus equation, in the mass-loaded string system, when the vertical vibration frequency of the mass approaches twice the natural frequency of the string lateral vibration, once the vertical vibration amplitude of the mass exceeds a critical value, the parametric resonance will occur in the string. To avoid the parametric resonance, a vibration absorber, composed of a thin beam and two mass blocks attached at both sides of the beam symmetrically, is proposed to install with the mass to reduce its vertical vibration, and ultimately suppress the lateral vibration of the string. Such a suppression strategy is finally validated by experiments.