Static Plane Research Articles

Effects of manufacturing micro-structure on vibration of FFF 3D printing plates: Material characterisation, numerical analysis and experimental study

This paper presents the effects of manufacturing micro-structure on the elastic properties of FFF (fused filament fabrication) 3D printing material and the vibration characteristics of FFF 3D printing plates. According to the results of scanning electron microscopy, three different material directions are defined to describe the orthotropy of FFF 3D printing material including fibre direction, intra-layer direction, and inter-layer direction. Then, the constitutive model of the orthotropic elastic 3D printing material is established based on static experimental results and plane stress rotation formula. Static experimental results (totally 27 kinds of specimens) show that the largest difference of Young’s moduli in different material directions is 1104.684 MPa which is even larger than the Young’s modulus in the intra-layer direction. Finite element models of FFF 3D printing plates with six different printing directions (α-0°, α- 90°, β-0°, β-90°, λ-0°, λ-90°) and three different layer thicknesses (0.2 mm, 0.25 mm, 0.3 mm) are built and their natural frequencies are determined. Simulation results show that the largest difference of the natural frequencies among plates with different printing directions are 10.645 Hz, 39.588 Hz, 66.710 Hz, 123.780 Hz, and 185.720 Hz when the mode of the plates changes from one to five. Meanwhile, these differences are relative large when compared with the first five out-of-plane natural frequencies of these plates. Additionally, vibration experiments of FFF 3D printing plates are carried out to verify the validity of the simulation process and all the relative errors of the natural frequencies between simulation and the experimental results are found to be very small. Therefore, the accuracy of the finite element models is good enough and one can confirm that the effects of manufacturing micro-structure on the vibration characteristics are significant.

Smartphone Inclinometry Is a Valid and Reliable Tool for Measuring Frontal Plane Tibial Alignment in Healthy and Osteoarthritic Knees.

Frontal plane knee alignment plays an integral role in tibiofemoral knee osteoarthritis development and progression. Accessible methods for obtaining direct or indirect measures of knee alignment may help inform clinical decision making when specialized equipment is unavailable. The present study evaluated the concurrent validity, as well as intersession (within-rater) and interrater (within-session) reliability of smartphone inclinometry for measuring static frontal plane tibial alignment-a known proxy of frontal plane knee alignment. Twenty healthy individuals and 38 patients with knee osteoarthritis were measured for frontal plane tibial alignment by a pair of raters using smartphone inclinometry, manual inclinometry, and 3-dimensional motion capture simultaneously. Healthy participants were measured on 2 separate days. Bland-Altman analysis, supplemented with intraclass correlation coefficient (ICC)(2,k), was used to assess concurrent validity. ICC(2,k), SEM, and minimum detectable change with 95% confidence limits (MDC95) were used to assess measurement reliability. Compared against motion capture, smartphone inclinometry measured frontal plane tibial alignment with a mean difference of 0.7 and 1.1 degrees (biased toward varus) for healthy participants and participants with knee osteoarthritis, respectively (ICC[2,k]≥0.87). Smartphone inclinometry measurements demonstrated adequate intersession (within-rater) relative (ICC[2,k]=0.91) and absolute (SEM=0.7 degrees; MDC95=1.8 degrees) reliability, which outperformed manual inclinometry (ICC[2,k]=0.85; SEM=1.0 degrees; MDC95=2.6 degrees). Interrater (within-session) reliability of smartphone inclinometry was acceptable in both cohorts (ICC[2,k]=0.93; SEM=0.4 degrees to 1.2 degrees; MDC95=1.2 degrees to 3.2 degrees). Smartphone inclinometry is sufficiently valid and reliable for measuring frontal plane tibial alignment in healthy individuals and patients with medial tibiofemoral knee osteoarthritis. Smartphones are readily accessible by clinicians and researchers. Our assessment of measurement validity and reliability supports the use of smartphone inclinometry as a clinically available tool to measure frontal plane tibial alignment without medical imaging or specialized equipment.

Aortic and mitral flow quantification using dynamic valve tracking and machine learning: Prospective study assessing static and dynamic plane repeatability, variability and agreement.

BackgroundBlood flow is a crucial measurement in the assessment of heart valve disease. Time-resolved flow using magnetic resonance imaging (4 D flow MRI) can provide a comprehensive assessment of heart valve hemodynamics but it relies in manual plane analysis. In this study, we aimed to demonstrate the feasibility of automate the detection and tracking of aortic and mitral valve planes to assess blood flow from 4 D flow MRI.MethodsIn this prospective study, a total of n = 106 subjects were enrolled: 19 patients with mitral disease, 65 aortic disease patients and 22 healthy controls. Machine learning was employed to detect aortic and mitral location and motion in a cine three-chamber plane and a perpendicular projection was co-registered to the 4 D flow MRI dataset to quantify flow volume, regurgitant fraction, and a peak velocity. Static and dynamic plane association and agreement were evaluated. Intra- and inter-observer, and scan-rescan reproducibility were also assessed.ResultsAortic regurgitant fraction was elevated in aortic valve disease patients as compared with controls and mitral valve disease patients (p < 0.05). Similarly, mitral regurgitant fraction was higher in mitral valve patients (p < 0.05). Both aortic and mitral total flow were high in aortic patients. Static and dynamic were good (r > 0.6, p < 0.005) for aortic total flow and peak velocity, and mitral peak velocity and regurgitant fraction. All measurements showed good inter- and intra-observer, and scan-rescan reproducibility.ConclusionWe demonstrated that aortic and mitral hemodynamics can efficiently be quantified from 4 D flow MRI using assisted valve detection with machine learning.

CUANDO LA LÍNEA DE TIERRA ES UNA LÍNEA DE AGUA. VENECIA

Desde los orígenes la arquitectura está ligada al plano de tierra firme, estático, en el que se funda y sobre el que se soporta. Venecia, sin embargo, ha desarrollado elementos arquitectónicos y espacios habitables endémicos, distintivos, que se originan como respuesta a la continua variación topológica entre el plano de tierra y el plano de agua que sostiene su actividad urbana. Se acomete la descripción de los proyectos contemporáneos que con más solvencia han sabido integrar como parte de su estructura espacial la variabilidad de la cota cero que impone la oscilación de los niveles acuáticos a los que cotidianamente está sometida la ciudad.

Classification of non-conformally flat static plane symmetric perfect fluid solutions via proper conformal vector fields in f(T) gravity

The aim of this paper is to classify non-conformally flat static plane symmetric (SPS) perfect fluid solutions via proper conformal vector fields (CVFs) in [Formula: see text] gravity. For this purpose, first we explore some SPS perfect fluid solutions of the Einstein field equations (EFEs) in [Formula: see text] gravity. Second, we utilize these solutions to find proper CVFs. In this study, we found 16 cases. A detailed study of each case reveals that in three of these cases, the space-times admit proper CVFs whereas in the rest of the cases, either the space-times become conformally flat or they admit proper homothetic vector fields (HVFs) or Killing vector fields (KVFs). The dimension of CVFs for non-conformally flat space-times in [Formula: see text] gravity is four, five or six.

A large-range autofocus microwave photonic radar based on adaptive spatial filtering along the range direction

A large-range autofocus microwave photonic radar based on adaptive spatial filtering along the range direction is proposed to achieve high-resolution imaging of the target at any distance. By firstly estimating the target distance and then adaptively adjusting the coverage of the spatial filter, the targets at any distance can be filtered out and their high-resolution images can be achieved. Besides, the sampling rate of the back-end ADC can be as low as hundreds of megahertz, leading to low computation load. Comparing to the present microwave photonic radars, new radar structure and work flow are proposed to achieve high-resolution imaging of the targets at any distance. The range window is not limited and the computation load is low, which is hard to realize by the present microwave photonic radars. Experimentally, a K-band (18–26 GHz) autofocus radar is established, the large-range autofocus ability is verified by autofocusing and high-resolution imaging for a static metallic plane at the equivalent distances of 790 m, 3.97 km and 8.11 km, respectively. Imaging for a flying UAV also indicates the system’s high-resolution imaging ability for the moving target. The proposed system enhances the capabilities of microwave photonic radars and has the potential to be applied in non-cooperative target identification.

Modeling and experimental validation on temperature diffusion mechanism in high-speed bone milling

• High-speed bone milling heat is mainly caused by the friction effect between the bone chip and the cutter tooth. • Cutting edge temperature is determined by the equivalent static plane heat source. • The bone material temperature distribution is obtained according to the constant temperature moving heat source. • The thermal damage factors could be calculated based on the temperature diffusion mechanism model in bone milling. In orthopedic surgery, thermal damage of bone affects the accuracy of the prosthesis fixation and delays the postoperative recovery time. In order to avoid thermal damage in high-speed bone machining, it is necessary to establish an effective relationship among machining parameters, tool parameters, and temperature distribution of bone materials. Based on the characteristics of bone material and high-speed processing, this study proposes a novel temperature diffusion mechanism model (TDMM) in high-speed bone milling. According to the model, heat during high-speed bone milling is mainly generated by the friction effect between the bone chip and the cutter tooth. Then the cutting edge temperature of the milling cutter is determined by the equivalent static heat source, and cutting edge is regarded as a moving heat source with constant temperature. Under the action of the moving heat source, the bone material temperature distribution was determined. Moreover, the degree of thermal damage of bone materials under different machining and tool parameters was evaluated. Next, a high-speed bone milling experiment platform was established, in order to obtain accurate cutting edge temperature and bone material temperature. According to a large number of experimental measurements, the theoretical prediction temperature values of the cutting edge and bone materials were found to be within the reasonable error range of experimental measurements. The proposed model was proved to reasonably predict the temperature of the cutting edge and bone materials in high-speed bone milling. Experimental results indicate that the processing methods, tool diameter, cooling method, and cutting layer have a noteworthy impact on bone material distribution in bone milling. Spray cooling method can reduce the bone material temperature significantly. And the bone material temperature outside the cutting layer can be greatly lower than that in the cutting layer. This study also indicates that according to the TDMM, it is convenient for surgeons to select the appropriate machining parameters, and for engineers to optimize tool design.

Hip Load Moments and Muscular Activity During Lifting

The load on the hip joint during lifting was studied. Healthy subjects lifted a 12.8 kg box from floor to table level with straight and flexed knees in four different ways. The loading moment of force about the bilateral hip axis was calculated by means of a computerized static sagittal plane model. The highest load moment, 124 Nm, occurred initially in the straight knee lift and the compressive joint reaction force was 2.7 times body-weight. The lowest load moment, 82 Nm, occurred in the flexed knee lift with the burden moved close to the trunk, the compressive force was 3.2 X bw. The load moment was also discussed in relation to the strength capability. The EMG levels of seven different hip muscles were normalized and expressed as a percentage of the recorded level of each muscle group during an isometric maximum voluntary contraction. The initial activity in the hamstrings was higher in the straight knee lift compared to flexed knees. The gluteus maximus was activated to a moderate level.

A note on classification of static plane symmetric perfect fluid space-times via proper conformal vector fields in f(G) theory of gravity

In the [Formula: see text] theory of gravity, we classify static plane symmetric perfect fluid space-times via proper conformal vector fields (CVFs) using algebraic and direct integration approaches. During this classification, we found eight cases. Studying each case in detail, we found that the dimensions of CVFs are 4, 5, 6 or 15. In the cases when the space-time admits 15 independent CVFs it becomes conformally flat.

A theoretical computational model of a plate in hypersonic flow

A theoretical model of an elastic panel in hypersonic flow is derived to be used for design and analysis. The nonlinear von Kármán plate equations are coupled with 1st order Piston Theory and linearized at the nonlinear steady-state deformation due to static pressure differential and thermal loads. Eigenvalue analysis is applied to determine the system’s stability, natural frequencies and mode shapes. Numerically time marching the equations provides transient response prediction which can be used to estimate limit cycle oscillation amplitude, frequency and time to onset. The model’s predictive capability is assessed by comparison to an experiment conducted at a free stream flow of Mach 6. Good agreement is shown between the theoretical and experimental natural frequencies and mode shapes of the fluid–structure system. Stability analysis is performed using linear and nonlinear methods to plot stability, flutter and buckling zones on a free stream static pressure vs temperature differential plane.

A study of energy conditions in static plane symmetric space–times via homothetic symmetries

The aim of this study is twofold. First, we use a new approach to study the homothetic vector fields (HVFs) of static plane symmetric space–times by an algorithm which we have developed using the Maple platform. The interesting feature of this algorithm is that it provides the most general form of metrics admitting HVFs as compared to those obtained in an earlier study where direct integration techniques were used. Second, the obtained metrics are used in Einstein’s field equations to compute the energy–momentum tensor and it is shown how the parameters involved in the obtained space–time metrics are associated with certain important energy conditions.

Homothetic matter collineations of static plane symmetric spacetimes

In this paper, we present a complete classification of static plane symmetric spacetimes via their homothetic symmetries of the energy–momentum tensor, known as homothetic matter collineations (HMCs). The HMC equations for these spacetimes are derived and then solved by considering the degeneracy and non-degeneracy of the energy–momentum tensor. In the former case, we have obtained 6, 11 and infinite number of HMCs, while in the latter case, the solution of HMC equations yields 6-, 7-, 8-, 10- and 11-dimensional algebra of HMCs. The obtained HMCs generate some differential constraints involving the components of the energy–momentum tensor. Some examples of static plane symmetric spacetime metrics satisfying these constraints are provided and the physical interpretations of these metrics are discussed.

Dynamic focal plane estimation for dental panoramic radiography.

The digital panoramic radiography is widely used in dental clinics and provides the anatomical information of the intraoral structure along the predefined arc-shaped path. Since the intraoral structure varies depending on the patient, however, it is nearly impossible to design a common and static focal path or plane fitted to the dentition of all patients. In response, we introduce an imaging algorithm for digital panoramic radiography that can provide a focused panoramic radiographic image for all patients, by automatically estimating the best focal plane for each patient. The aim of this study is to improve the image quality of dental panoramic radiography based on a three-dimensional (3D) dynamic focal plane. The plane is newly introduced to represent the arbitrary 3D intraoral structure of each patient. The proposed algorithm consists of three steps: preprocessing, focal plane estimation, and image reconstruction. We first perform preprocessing to improve the accuracy of focal plane estimation. The 3D dynamic focal plane is then estimated by adjusting the position of the image plane so that object boundaries in the neighboring projection data are aligned or focused on the plane. Finally, a panoramic radiographic image is reconstructed using the estimated dynamic focal plane. The proposed algorithm is evaluated using a numerical phantom dataset and four clinical human datasets. In order to examine the image quality improvement owing to the proposed algorithm, we generate panoramic radiographic images based on a conventional static focal plane and estimated 3D dynamic focal planes, respectively. Experimental results show that the image quality is dramatically improved for all datasets using the 3D dynamic focal planes that are estimated from the proposed algorithm. We propose an imaging algorithm for digital panoramic radiography that provides improved image quality by estimating dynamic focal planes fitted to each individual patient's intraoral structure.

Analysis of Einstein Field Equations of Static Plane Symmetric Space-Time in General Relativity via Lie Approach

In this study, Einstein field equations of static plane symmetric space-time is discussed by means of Lie approach. Lie point symmetries are computed for the considered equations. Moreover, one dimensional conjugacy classes for symmetry algebra are reported. Additionally, similarity variables are derived which are further utilized to find the solutions for parameters $A$ and $B$ of the considered space-time. Both linearly independent and dependent relationships between the unknown parameters $A$ and $B$ are observed for different cases. At the end, some well-known solutions are presented.

Reproducibility of fetal lung-to-head ratio in left diaphragmatic hernia across the North American Fetal Therapy Network (NAFTNet).

To determine the antenatal sonographic lung area measurement method in left congenital diaphragmatic hernia (CDH) with the highest interrater agreement among North American Fetal Therapy Network (NAFTNet) centers within and outside the fetoscopic tracheal occlusion (FETO) consortium and in comparison with a European "expert" reviewer (ER). Nineteen members from nine FETO consortium centers and 29 reviewers from 17 non-FETO centers reviewed ultrasound clips of the chest from 13 fetuses with isolated left CDH and were asked to select a static plane for lung area measurement using anteroposterior (AP), longest, and trace methods. Interrater agreement in lung area measurements was determined using intraclass correlation coefficient (ICC). Bland-Altman analysis was used to evaluate mean difference (bias) between NAFTNet reviewers and ER. Among FETO centers, agreement was highest using trace (ICC 0.94; 95% CI, 0.83-0.98), followed by longest (ICC 0.89; 95% CI, 0.75-0.97) and lowest for A-P (ICC 0.83; 95% CI, 0.67-0.94). Similar trends were noted in non-FETO centers. When compared with ER, bias was lowest for trace: 14±38mm2 and 19±36mm2 for FETO and non-FETO centers, respectively. The trace method demonstrated the highest interrater agreement and lowest bias for lung area estimation in left CDH across NAFTNet.

Dust static plane symmetric solutions and their conformal vector fields in f(R) theory of gravity

We first find the dust solutions of static plane symmetric spacetimes in the theory of f(R) gravity. Then using the direct integration technique on the solutions obtained, we deduce the conformal vector fields. This is performed in the context of f(R) theory of gravity. There exist six cases. Out of these, in five cases the spacetimes become conformally flat and admit 15 conformal vector fields, whereas in the sixth case, conformal vector fields become Killing vector fields.

Simultaneous motion monitoring and truth-in-delivery analysis imaging framework for MR-guided radiotherapy

Intrafraction motion (i.e. motion occurring during a treatment session) can play a pivotal role in the success of abdominal and thoracic radiation therapy. Hybrid magnetic resonance-guided radiotherapy (MR-gRT) systems have the potential to control for intrafraction motion. Recently, we introduced an MRI sequence capable of acquiring real-time cine imaging in two orthogonal planes (SOPI). We extend SOPI here to permit dynamic updating of slice positions in one-plane while keeping the other plane position fixed. In this implementation, cine images from the static plane are used for motion monitoring and as image navigators to sort stepped images in the other plane, producing dynamic 4D image volumes for use in dose reconstruction. A custom 3D-printed target, designed to mimic the pancreas and duodenum and filled with radiochromic FXG gel, was interfaced to the dynamic motion phantom. 4D-SOPI was acquired in a dynamic motion phantom driven by an actual patient respiratory waveform displaying amplitude/frequency variations and drifting and in a healthy volunteer. Unique 4D-MRI epochs were reconstructed from a time series of phantom motion. Dose from a static 4 cm × 15 cm field was calculated on each 4D respiratory phase bin and epoch image, scaled by the time spent in each bin, and then rigidly accumulated. The phantom was then positioned on an Elekta MR-Linac and irradiated while moving. Following irradiation, actual dose deposited to the FXG gel was determined by applying a R1 versus dose calibration curve to R1 maps of the phantom. The 4D-SOPI cine images produced a respiratory motion navigator that was highly correlated with the actual phantom motion (CC = 0.9981). The mean difference between the accumulated and measured dose inside the target was 4.4% of the maximum prescribed dose. These initial results demonstrate that 4D-SOPI is a promising imaging framework enabling simultaneous real-time motion monitoring and truth-in-delivery analysis for integrated MR-gRT systems.

Single-shot phase retrieval based on axial phase diversity

A single-shot phase-retrieval algorithm based on axial phase diversity using a distorted phase grating is proposed. In this proposed scheme, an image array corresponding to different defocus distances of the object is formed on the fixed and static detector plane and is recorded simultaneously with one camera shot. After the recorded image array is split into separated sub-images, an iterative phase-retrieval algorithm is applied to retrieve the complex amplitude of the object. Compared with the method of multiple recordings, the proposed scheme has the advantages of fast data acquisition and a corresponding high temporal resolution, making it very suitable for high-speed phase imaging or pulsed laser beam diagnosis. Computer simulations are performed to verify the feasibility of the proposed scheme.

Frontal Plane Tibiofemoral Alignment is Strongly Related to Compartmental Knee Joint Contact Forces and Muscle Control Strategies During Stair Ascent.

Static frontal plane tibiofemoral alignment is an important factor in dynamic knee alignment and knee adduction moments (KAMs). However, little is known about the relationship between alignment and compartment contact forces or muscle control strategies. The purpose of this study was to estimate medial (MCF) and lateral (LCF) compartment knee joint contact forces and muscle forces during stair ascent using a musculoskeletal model implementing subject-specific knee alignments. Kinematic and kinetic data from 20 healthy individuals with radiographically confirmed varus or valgus knee alignments were simulated using alignment specific models to predict MCFs and LCFs. Muscle forces were determined using static optimization. Independent samples t-tests compared contact and muscle forces between groups during weight acceptance and during pushoff. The varus group exhibited increased weight acceptance peak MCFs, while the valgus group exhibited increased pushoff peak LCFs. The varus group utilized increased vasti muscle forces during weight acceptance and adductor forces during pushoff. The valgus group utilized increased abductor forces during pushoff. The alignment-dependent contact forces provide evidence of the significance of frontal plane knee alignment in healthy individuals, which may be important in considering future knee joint health. The differing muscle control strategies between alignments detail-specific neuromuscular responses to control frontal plane knee loads.

Conformal Collineations of the Ricci and Energy–Momentum Tensors in Static Plane Symmetric Space–Times

We provide a complete classification of static plane symmetric space–times according to conformal Ricci collineations (CRCs) and conformal matter collineations (CMCs) in both the degenerate and nondegenerate cases. In the case of a nondegenerate Ricci tensor, we find a general form of the vector field generating CRCs in terms of unknown functions of t and x subject to some integrability conditions. We then solve the integrability conditions in different cases depending upon the nature of the Ricci tensor and conclude that the static plane symmetric space–times have a 7-, 10- or 15-dimensional Lie algebra of CRCs. Moreover, we find that these space–times admit an infinite number of CRCs if the Ricci tensor is degenerate. We use a similar procedure to study CMCs in the case of a degenerate or nondegenerate matter tensor. We obtain the exact form of some static plane symmetric space–time metrics that admit nontrivial CRCs and CMCs. Finally, we present some physical applications of our obtained results by considering a perfect fluid as a source of the energy–momentum tensor.