Dynamics of Quadriceps Muscles during Isometric Contractions: Velocity-Encoded Phase Contrast MRI Study

Objective: To quantify the spatial heterogeneity of displacement during voluntary isometric contraction within and between the different compartments of the quadriceps. Methods: The thigh muscles of seven subjects were imaged on an MRI scanner while performing isometric knee extensions at 40% maximal voluntary contraction. A gated velocity-encoded phase contrast MRI sequence in axial orientations yielded tissue velocity-encoded dynamic images of the four different compartments of the thigh muscles (vastus lateralis (VL), vastus medialis (VM), vastus intermedius (VI), and rectus femoris (RF)) at three longitudinal locations of the proximal–distal length: 17.5% (proximal), 50% (middle), and 77.5% (distal). The displacement, which is the time integration of the measured velocity, was calculated along the three orthogonal axes using a tracking algorithm. Results: The displacement of the muscle tissues was clearly nonuniform within each axial section as well as between the three axial locations. The ensemble average of the magnitude of the total displacement as a synthetic vector of the X, Y, and Z displacements was significantly larger in the VM at the middle location (p < 0.01), and in the VI at the distal location than in the other three muscles. The ensemble average of Z-axis displacement, which was almost aligned with the line of action, was significantly larger in VI than in the other three muscles in all three locations. Displacements of more than 20 mm were observed around the central aponeuroses, such as those between VI and the other surrounding muscles. Conclusions: These results imply that the quadriceps muscles act as one functional unit in normal force generation through the central aponeuroses despite complex behavior in each of the muscles, each of which possesses different physiological characteristics and architectures.

Syn-shearing deformation mechanisms of minerals in partially molten metapelites

We investigated an experimentally sheared (γ = 15, γ ̇ = 3 x 10-4s-1, 300 MPa, 750°C) quartz-muscovite aggregate to understand the deformation of parent and new crystals in partially molten rocks. The SEM and EBSD analyses along the longitudinal axial section of the cylindrical sample suggest that quartz and muscovite melted partially and later produced K-feldspar, ilmenite, biotite, mullite, and cordierite. Quartz grains became finer, and muscovite was almost entirely consumed in the process. With increasing , melt and crystal fractions decreased and increased, respectively. Amongst the new minerals, K-feldspar grains (highest area fraction and coarsest) nucleated first, whereas cordierite and mullite grains, finest and least in number, respectively, nucleated last. Fine grain size, weak CPOs, low intragranular deformation, and equant shapes suggest both initial and new minerals deformed dominantly by melt-assisted grain boundary sliding, which is further substantiated by higher misorientations between adjacent grains of quartz, K-feldspar, and ilmenite.

Comparison of two types of fixation for proximal tibial epiphysiodesis: An experimental study in a rabbit model

Objectives: In this study, we describe a novel hemiepiphysiodesis technique to prevent implant-related perichondrial ring injury in a rabbit model. Materials and methods: Proximal tibial epiphyseal plates of a total of 16 white New Zealand rabbits were used for this animal model. The subjects were divided into three equal groups as follows: Group 1 (Kirschner wire [K-wire]/cerclage), Group 2 (8-plate) right-hind legs, Group 3 (Control) left hind legs. Using anteroposterior radiography, the medial slope angle (MSA), articular line-diaphyseal angle (ALDA), and the angle between screws of 8-plate in lateral X-ray tibial slope angle (TSA) were measured. The radiographs were taken early postoperative (Day 1) and on sacrification day (Week 8). The histological evaluation of the perichondrial ring was made on a 7-mm axial section that stained with Safranin O/fast green at X10 magnification. Results: In both K-wire and 8-plate groups, the early postoperative ALDA and TSA were greater than the sacrification ALDA and TSA (p=0.028 and p<0.001, respectively). The early postoperative MSA was lower than the sacrification MSA in groups, (p<0.001). The MSA in the control group was lower than the K-wire and 8-plate groups (p<0.001 and p=0.009; respectively). The perichondrial ring thickness of the K-wire group was greater than the 8-plate group in histological evaluation (p<0.001). Conclusion: Both of the K-wire and 8-plate groups showed similar angulation effects in the proximal tibia, although histologically less damage to the perichondrial ring was observed in the K-wire group, compared to the 8-plate group.

Numerical investigation of the radial cold rolling process of the grooves

The radial cold rolling process is widely used in industry due to the advantages of chip removing processing. In this study, circular complex profiles were formed by cold-rolling with radial feed, using a patented device with two roller-tools. By achieving several numerical simulations of the radial rolling process, the study aimed to establish the influence that the maximum set force and the diameter of the workpiece have on the productivity of the process and the quality of the formed trapezoidal and metric grooves. The numerical simulations were performed with ABAQUS/Explicit software and by using a previously validated finite element model. The penetration curve of the roller-tools in the material was introduced in the simulation as an analytical function and was determined based on experimental researches. To express the dependency of the penetration curve coefficients on other rolling conditions, a multivariable analysis using a design of experiments technique was performed. The parameters that result from numerical simulations and were analyzed in this study are the profile forming time, the maximum radial force, the distribution of the equivalent strains in the axial section of the profiles, and the profile dimensions. The conclusions that were drawn from the analysis of the results regarding the influence of the set maximum force and the workpiece diameter on the analyzed parameters of the numerical simulations, together with the definition of efficient process criteria, allowed also the identification of the optimal conditions of the rolling process.

Numerical Investigation on Propagation Characteristics of Inlet Total-Pressure Distortion in a Centrifugal Compressor

The propagation characteristics of inlet total-pressure distortion in a centrifugal compressor are investigated by full-annulus unsteady three-dimensional numerical simulation. The inlet distortions considered in the paper are the total-pressure distortions covering a 60-deg sector (60deg distortion) and three 20-deg sectors (3*20deg distortion), respectively. One is the classical distortion form, and the other is to simulate the downstream flow of the axial section of a centrifugal-axial combined compressor. By analyzing the distributions of flow parameters, the propagation of the total-pressure distortion in the centrifugal compressor is interpreted. The results show that, with the distortion propagating to the downstream, the low-pressure region produces a phase deviation along the streamwise direction relative to the opposite direction of impeller rotation direction, and the range of distortion region is reduced. Additionally, the propagation of the inlet distortion makes the three-dimensional characteristics of airflow more complex. The flow angle increases with different amplitudes along the direction of blade height corresponding to the distorted sector. The distortion region affects the location of blades which are in a low-pressure area, and the intensity of the distortion affects the increase of the flow angle. The distortion region causes more local relative flow losses, especially near the leading edge of blade suction surface.

Hob cutter shaping for internal straight thread

Резьба используется во многих механизмах и достаточно часто для разъемных соединений деталей судовых машин. Для повышения долговечности внутренней цилиндрической резьбы и производительности процесса ее нарезания предлагается новая методика «профилирования червячной фрезы для нарезания внутренней цилиндрической резьбы методом огибания. В данной статье приведено аналитическое определение сопряженных профилей цилиндрической внутренней резьбы и инструмента. Рассматривается метод профильных нормалей для профилирования червячной фрезы при нарезании внутренней резьбы способом огибания, основанный на применении теории матриц. Червячная фреза в осевом сечении имеет конкретный криволинейный профиль, для его получения необходимо знать расчетные зависимости торцового профиля резьбы, и уравнения ее винтовой поверхности и осевого профиля. Для возможности образования витков резьбы необходимы определенные зависимости скорости резанья фрезы и резьбы, а для формирования внутренней резьбы - ее поверхность должна набегать на зубья червячной фрезы. Эти задачи решены с помощью разработанной системы уравнений для изготовления фрез при нарезании внутренней цилиндрической резьбы способом огибания методом профильных нормалей. Расчетный механизм профилирования инструмента - фрезы для нарезания цилиндрических внутренних резьб – может применяться для формообразования конических внутренних резьб. Threads are used in many mechanisms and frequently in detached connections of marine engines elements. The new technique of hob cutter shaping for internal straight thread is proposed in order to increase durability of the internal cylindrical thread and to improve its cutting performance process. The article gives analytical definition of conjugate profiles of internal straight thread and of a tool. It also deals with the method of profile normals for shaping hob cutter whilst cutting the internal thread by enveloping. The method applies the matrix theory. There is some curved profile in the hob cutter axial section. In order to obtain that profile, it is necessary to know the calculated dependence of a thread transverse profile and its helical surface and axial profile equation. Special dependences of thread speed range and cutting are required to produce turns of the thread. To form internal thread – its surface is to slide on cutter teeth. All the mentioned tasks can be solved by the system of equations for cutters manufacture with cutting internal straight thread applying enveloping with the method of profiles normals. The calculation mechanism for shaping the tool – the hob cutter for internal straight threads – can be used for making internal taper threads.

Worm addendum thickness and gear curvature interference for enveloping cylindrical worm drive with arc-toothed worm

The purpose of this paper is to provide the calculation methods on worm addendum thickness and curvature interference limit line, and find the feasible value range of the technological crossing angle to avoiding addendum sharpening and curvature interference for enveloping cylindrical worm drive with arc-toothed worm. In accordance with the features of the proposed worm, the mathematical models of cutting and working are established. Based on this, the tooth profile geometry of the worm in its axial section and the worm addendum thickness are obtained by geometric analysis and calculation, and then, the feasible value range of the technological crossing angle is given. In virtue of vector rotation and elimination method, the nonlinear equation with one variable for solving the interference limit line is determined. In the process of solving nonlinear equation, the method of geometric construction is used to judge the existence of solutions and provide an initial value for the subsequent iterative calculation. The numerical example results show that with the increases of the technological crossing angle, the interference limit line is close to the boundary line of the conjugate region of the worm pair, and the hazard of curvature interference evident increases. Generally, a smaller value of the technological crossing angle within its available value range can completely avoid the occurrence of the curvature interference.

Effect of an axial-radial plate reactor modifications on a mega methanol plant production

Axial-radial flow plate reactors have been recently considered as efficient and practical types of reactors for methanol synthesis. Generally, an axial–radial reactor (AR) consists of two main parts namely the axial section and the radial section and the vast majority of the feed enters the radial section. Moreover, the structure of AR has a space above the axial part, which can add an adiabatic bed in the system. In this study, the performance of two novels AR configurations is investigated to improve the effectiveness of the axial–radial plate reactor. In the first configuration, the optimum length of the adiabatic bed is calculated and the adiabatic bed is located above the axial section inside the AR and is named IAAR. Therefore, in IAAR the feed of the axial section just enters the adiabatic bed and warms up. On the other configuration, the adiabatic bed with the optimum length is placed outside the reactor and is named OAAR. Therefore, in OAAR the total feed passes through the adiabatic bed, highly warms up, then cools to the optimum temperature in a heat exchanger, and finally enters AR. Two-dimensional mathematical modeling via orthogonal collocation on the finite element method is developed to compare the performance of two configurations. The results show that the maximum proportion of methanol produces in IAAR, which is approximately 3.8% higher than that produced in conventional AR due to utilizing an adiabatic bed inside the AR and superior gas distribution in the process. Momentum, mass, and heat equations are calculated and molar flow rates, mole fractions and temperatures are depicted along the radius and the length of the three configurations.

Understanding deformation behavior of lower crustal rocks from experimentally deformed metapelitic aggregate: an EBSD-based approach

&lt;p&gt;Partial melting of metapelites at high-P and high-T conditions typical of lower crustal levels is a well-known phenomenon. Its role in strain localization &amp;#173;&amp;#8211; both at micro- and regional scale &amp;#8211; and subsequent rheological weakening of rocks have been widely investigated. Previous researchers have also explored the influence of such melt networks on the variation of the dominant phases' active deformation processes &amp;#8211; especially quartz &amp;#8211; over the entire range of tectono-thermal evolution of the rock. However, mechanisms driving the deformation of the phases crystallized in-situ from the melt has so far been largely overlooked.&lt;/p&gt;&lt;p&gt;In this work, we focus on the deformation behavior of the in-situ crystallized phases with increasing shear strain. In that pursuit, we took a quartz-muscovite mixture (dry) that was initially cold pressed at 200 MPa, followed by hot pressing at 160 MPa and 580 &amp;#176;C to obtain an analogue of pelite. The cylindrical sample was then experimentally deformed in a Patterson-type apparatus under a finite shear strain (&amp;#947;) of 15.0 at 750 &amp;#176;C, a confining pressure of 300 MPa, and constant shear strain rate ( 3 &amp;#215; 10&lt;sup&gt;-4&lt;/sup&gt;s&lt;sup&gt;-1&lt;/sup&gt;). Subsequently, a longitudinal axial section was cut and was examined using electron backscattered diffraction (EBSD).&lt;/p&gt;&lt;p&gt;The initial minerals, quartz (Qtz) and muscovite (Ms), underwent deformation and reacted to produce K-Feldspar (Kfs), Mullite (Mul), Cordierite (Crd), Ilmenite (Ilm), and Biotite (Bt). The Qtz grains show limited evidence of dynamic recrystallization. Ms, on the other hand, exhibit strong crystal preferred orientations (CPO). The J-Indices of both Qtz and Ms increase with shear strain (from the center to the edge of the cylinder). Among the reaction products, Kfs (maximum in volume) show weak CPO throughout, similar to Qtz. The maxima of [001] plot near parallel to the shear direction in the pole figures for all values of &amp;#947;. The rest of the phases show strong CPOs. The J-Index of Crd and Mul increase with shear strain, whereas that of Ms and Kfs increase till &amp;#947; = 7 and fall at higher strains. Neighbor-pair misorientation axes for Crd, Ilm, and Kfs, corresponding to the high-angle boundaries (HAGBs), are randomly oriented, implying &amp;#8216;rigid grain rotation,&amp;#8217; which could also be responsible for the lower [001] pole figure intensities. Overall, with increasing shear strain, the number of HAGBs decreases. The corresponding misorientation axes exhibit stronger preferred alignment, probably signifying restricted rotation with progressive melt crystallization. Although the area-equivalent diameters for all the melt-crystallized phases are nearly close (RMS: 1.5 &amp;#8211; 2 &amp;#181;m), the Kfs CPOs are considerably weaker than the rest. This possibly affirms the dominance of fluid/melt in triggering diffusion creep and grain boundary sliding over grain size.&lt;/p&gt;