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Robotics technology is used widely in minimally invasive surgery (MIS) which provides high performance and accuracy. The most famous robot arm mechanisms, which are used in MIS, are tendon-driven mechanism (TDM), and concentric tube mechanism (CTM). Unfortunately, these mechanisms until now have some limitations, i.e. making friction with the tissue during extracting and retracting and strain limits, for TDM and CTM respectively. A new hybrid concentric tube-tendon driven mechanism (HCTDM) is proposed to overcome these limitations. HCTDM enables the end-effector to get close to and get away from the surgical area during the operation without harming the tissue and with more flexibility. In addition to that, the workspace increases as a result of this combination, too. This benefit serves MIS, especially endoscopic surgeries (ESs). We did an analytical study of this idea and got the forward kinematics. In the inverse kinematics, an intelligent approach which is called an adaptive neuro-fuzzy inference system (ANFIS) is used because the closed-form solution is more complicated for such these mechanisms. Finally, HCTDM is analyzed and evaluated by using a computer simulation. The simulation results show that the workspace becomes wider and has more dexterity than use TDM or CTM individually. Furthermore, various trajectories are used to test the mechanism and the kinematic analysis, which show the mechanism can follow and track the trajectories with maximum mean error 1.279, 0.7027, and [Formula: see text] for X, Y, and Z axes respectively.

Background:Persistent strength and biomechanical deviations remain after anterior cruciate ligament reconstruction (ACLR). Eccentric training may reduce these and associated reinjury or osteoarthritis risks.Hypothesis:For male patients who have undergone ACLR, eccentric training is more effective than concentric training at improving knee flexion angle and other biomechanical deviations, as well as strength and patient-reported outcomes, using a matched perceived exertion dose.Study Design:Randomized controlled trial; Level of evidence, 1.Methods:A total of 26 men, 10-16 weeks after hamstring tendon graft ACLR, were randomized to an eccentric training group or a concentric control group. Both groups trained 3 times a week for 8 weeks using the same isokinetic cycle ergometer in a matched studio environment. Exercise dose was matched in training frequency, time, progression, and intensity using a target rating of perceived exertion. Baseline and follow-up testing included questionnaires, dynamometer strength testing, and walk/run gait analysis.Results:Eccentric training increased knee (+2.1°; P = .022) and hip (+2.1°; P = .010) flexion angles more than concentric training but not more than the minimal clinically important difference of 3°. Very large asymmetries in baseline knee abduction moment (walk, −0.10 N·m/kg/m; run, −0.54 N·m/kg/m) had not changed in either group by follow-up. Knee valgus angle effects were mixed. Tibial rotation angle increased in both groups, but concentric training was more effective at promoting symmetry ( P < .001). Both groups had similar increases in affected limb quadriceps strength and knee flexion moments during walk/run gait (by 20% to 33%). Hamstring strength increased in the eccentric group (+15.4%) but not the concentric group. Eccentric group limb forces were 33% to 70% higher than those of the concentric group, with a lower heart rate. Both groups had low pain scores throughout.Conclusion:For rehabilitation after ACLR, progressive eccentric cycle training was not more clinically effective than concentric training at a matched perceived intensity dose in male patients. This can guide exercise prescription for reducing gait and strength deviations of these patients.Registration:PACTR201602001449365 (Pan African Clinical Trials Registry), NHREC 4344 (South African).

In the development of telemanipulated surgical robots, a class of continuum robots known as concentric tube robots has drawn particular interest for clinical applications in which space is a major limitation. One such application is transnasal surgery, which is used to access surgical sites in the sinuses and at the skull base. Current techniques for performing these procedures require surgeons to maneuver multiple rigid tools through the narrow confines of the nasal passages, leaving them with limited dexterity at the surgical site. In this article, we present a complete robotic system for transnasal surgery featuring concentric tube manipulators. It illustrates a bagging concept for sterility, and intraoperatively interchangeable instruments that work in conjunction with it, which were developed with operating room workflow compatibility in mind. The system also includes a new modular, portable surgeon console, a variable view-angle endoscope to facilitate surgical field visualization, and custom motor control electronics. Furthermore, we demonstrate elastic instability avoidance for the first time on a physical prototype in a geometrically accurate surgical scenario, which facilitates use of higher curvature tubes than could otherwise be used safely in this application. From a surgical application perspective, this article presents the first robotic approach to removing tumors growing behind the eyes in the orbital apex region, which has not been attempted previously with a surgical robot.

Understanding the material flow in friction stir welding (FSW) is one of the challenging aspects for producing defect free and quality welds. The material flow is majorly governed by the tool shoulder/pin geometries and process conditions. In the present study, concentric circles shoulder shape with various polygonal pin designs are selected, and their influence on material flow and mechanical properties in Al 6082 friction stir welds is addressed. Material flow is studied by inserting the markers before welding and subsequent analysis of deformed marker material by radiography and macrostructure after welding. The outcome shows the welds with square pin design facilitated a constant stable force, and hexagonal pin design facilitated a decreasing behavior of force with reference to welding length/time. The heat input is increasing from triangular pin to hexagonal pin and is maximum for welds with hexagonal pins (973 kJ/mm). Further, welds with hexagonal pins (TCC)HEX tool facilitated higher mechanical properties of strength (187 MPa) and average hardness (79 HV) at the stir zone.

A 3D analytical model is formulated for diffuse sound field transmission control through a smart hybrid double concentric sandwich circular cylindrical shell structure in presence of external and internal air gap mean flows. The multi-input multi-output sliding mode control is applied to enhance the sound transmission loss characteristics via direct control action of a uniform force piezoelectric actuator layer along with semi-active variation of the stiffness/damping characteristics of the electrorheological fluid core layer incorporated in a non-collocated configuration within the external or internal shell structure. Extensive numerical simulations examine the uncontrolled/controlled diffuse field sound transmission loss spectrums in a broad frequency range for single-wall and hybrid double-wall sandwich shells at selected external and air gap Mach numbers. The proposed smart hybrid active/semi-active double-wall configuration is demonstrated to provide satisfactory overall acoustic insulation control performance with much lower operative energy requirements. Limiting cases are considered, and validity of the formulation is verified against the available data.

The effect of cut-out parameters (shapes: square and circular; position: concentric/eccentric) on the dynamic deflection values of the curved/flat layered composite panel are verified experimentally with the higher-order finite element solutions first-time. The solutions are obtained using the linear finite element model in the framework of cubic-order displacement filed functions. The necessity of higher-order kinematic model is verified by comparing the experimental transient data by conducting the different test to show the accuracy of the finite element solution. Moreover, the theoretical finite element solutions are obtained using the own experimental elastic property data for the comparison (numerical and experimental) purpose. Finally, the critical behaviour of the proposed numerical model for the dynamic analysis of damaged composite structure is examined by solving different types of example by varying the design constraint parameter including the cut-out factors (shape, size, location and eccentricity). The inclusiveness of each parameter on the time-dependent deflections is expressed in details from the various example including the comparison.

This paper evaluates the crashworthiness performance of concentric structures with different numbers of tubes (i.e. one to five) and cross-sectional shapes (i.e. hexagon, octagon, decagon and circle) under the multiple loadings of θ = 0, 10, 20 and 30°. An experimentally validated finite element model generated in LS-DYNA is employed to calculate the crashworthiness parameters including the specific energy absorption, maximum crush force and crush force efficiency. A total of 20 concentric structures are analyzed to explore the effects of number of tubes and cross-sectional shapes on the crushing performance. A multi-criteria decision-making method known as TOPSIS is also used to compare and rank the concentric structures in terms of crushing performance. Based on the results, the hexagonal structure including two tubes and octagonal, decagonal and circular structures including three tubes demonstrate the best results among their corresponding cross-sectional shapes. These structures show 9, 39, 38 and 39% higher specific energy absorption compared to their corresponding single tubal cases, respectively. However, in comparison to single tubal cases, they generate 4, 57, 57 and 58% higher maximum crush force, respectively. As such, the values for the improvement of the crush force efficiency are 3, 26, 25 and 21%, respectively. Furthermore, the decagonal structure including three tubes provides the highest energy absorbing characteristics as compared with all the other structures studied in this research. Meanwhile, taking into account all the multiple loading conditions, this structure shows 50% higher specific energy absorption than the hexagonal structure including single tube (as the weakest structure).

Objectives: To provide detailed descriptions of contraction-induced morphometric changes in the extravelar segments of the levator veli palatini (LVP) muscle using 3-dimensional (3-D) magnetic resonance imaging (MRI). Design: Three-dimensional MRI data were acquired at rest and during “silent /i/” from 4 singers. During silent /i/, participants voluntarily sustained velar elevation while breathing orally for the entire scan time. Focusing on the extravelar segments, LVP length, angle of the muscle origin, and cross-sectional area (CSA), measurements were obtained and compared between tasks. Results: Three of the 4 participants exhibited the expected patterns of change following concentric contraction of the LVP muscle. Consistent changes from the resting to the contracted state included reductions in LVP length by 13.5% and angle of the muscle origin by 9.8%, as well as increases in CSAs by 22.1%, on average. Conclusions: This study presented high-resolution data of the LVP muscle behavior with the first in vivo 3-D measurements of the contracted LVP muscle, which can be useful for the validation of computational models that aim at describing biomechanical properties of the LVP muscle in future research. The active behavior of the extravelar LVP muscle also provides some insight on optimal LVP muscle geometry to consider during cleft palate repair.

The purpose of the study was to compare 2 techniques of arthrocentesis, to find out the efficacy of one over the other at various parameters, and to contribute to the scarce literature of these 2 techniques. Forty patients reported with a chief complaint of pain in temporomandibular joint (TMJ), clicking in TMJ, and restricted mouth opening were included in this study. Twenty patients were divided into 2 groups, all reporting with temporomandibular disorders. Group A was treated with 2-needle technique of arthrocentesis, while group B underwent concentric needle technique of arthrocentesis under local anesthesia with Ringer’s lactate solution. The operating time was found to be less in concentric needle technique (mean: 25.36 minutes) compared to 2-needle technique (mean: 42.82 minutes), and the difference was found to be statistically significant. Concentric needle technique proved to be a better alternative for TMJ arthrocentesis as it has quite a lot of advantages over 2-needle technique.

This study is aimed to establish a detailed chemical reactor network model based on the analysis of complex reaction flowfield structures in aeroengine combustors, so that the emissions of nitrogen oxides and carbon monoxide from advanced civil aeroengines can be predicted quickly and accurately. In this study, a low-emission concentric staged combustor with three axial swirlers is designed for civil aeroengines, and numerical simulations of the three-dimensional reaction flowfields of the combustor during four load phases of takeoff, climb, approach, and idle, are conducted. Based on the numerical results, a simple chemical reactor network model with seven perfectly stirred reactors and a detailed chemical reactor network model using up to 15 perfectly stirred reactors are established. Using the developed chemical reactor network models and the detailed JP10 chemical reaction mechanism—composed of 374 step elementary reactions and 82 species, the emission variations of nitrogen oxides and carbon monoxide are predicted and compared with those estimated using an empirical formula and with the numerical results as a function of the combustion load. Using a combined chemical reactor network–computational fluid dynamics analysis method, the variations of the formation path, the mechanism, and the amounts of nitrogen oxides in the combustor and in the perfectly stirred reactors, are analyzed as a function of the combustion load. In addition, the effects of fuel and air pilot-to-total ratio on nitrogen oxides emissions for the 100% load condition are also analyzed. It is found that at high loads, the production rate of the thermal NO is the highest, while at low loads, the production rate of the prompt NO is the highest. The nitrogen oxide is mainly produced in the pilot zone and the recirculation zone, while its production in the outer main stage zone is low. The results show that the NOx emissions predicted by the complex chemical reactor network model are most consistent with those elicited using the empirical formula.

In this research, different techniques of repair of deficient reinforced concrete columns are compared. These include carbon fiber–reinforced polymer sheets, steel jackets, and reinforced concrete jackets. The experimental investigation includes testing of 16 deficient columns of dimensions 150 × 150 × 800 mm subjected to concentric and eccentric loading up to failure. Two main variables are considered: the load eccentricity and the strengthening technique. The experimental results showed that the three strengthening techniques used in this research significantly improved the ultimate load carrying capacity in all cases of loading. Also, in the two cases of concentric loading and big eccentricity of 150 mm, carbon fiber–reinforced polymer wrapping achieved the highest ductility and absorbed energy capacity. In addition, strengthening with reinforced concrete jacket improved the initial stiffness and toughness. The cracking load, ultimate load, and ductility of the deficient columns after strengthening were experimentally recorded and compared. The results can help the structural engineer to consider the most efficient method of repair for such columns.

Here, we introduce and explore Scintillating Starbursts, a stimulus type made up of concentric star polygons that induce illusory scintillating rays or beams. We test experimentally which factors, such as contrast and number of vertices, modulate how observers experience this stimulus class. We explain how the illusion arises from the interplay of known visual processes, specifically central versus peripheral vision, and interpret the phenomenology evoked by these patterns. We discuss how Starbursts differ from similar and related visual illusions such as illusory contours, grid illusions such as the pincushion grid illusion as well as moiré patterns.

Pressure fluctuations that cause acoustic radiation from vessel models with concentric and eccentric blunt stenoses are investigated. Large eddy simulations of non-pulsatile flow condition are performed using OpenFOAM. Calculated amplitude and spatial-spectral distribution of acoustic pressures at the post-stenotic region are compared with previous experimental and theoretical results. It is found that increasing the Reynolds number does not change the location of the maximum root mean square wall pressure, but causes a general increase in the spectrum level, although the change in the shape of the spectrum is not significant. On the contrary, compared to the concentric model at the same Reynolds number, eccentricity leads to an increase both at the distance of the location of the maximum root mean square wall pressure from the stenosis exit and the spectrum level. This effect becomes more distinct when radial eccentricity of the stenosis increases. Both the flow rate and the eccentricity of the stenosis shape are evaluated to be clinically important parameters in diagnosing stenosis.

The vibration of functionally graded circular plates of variable thickness under a thermal environment is analyzed when the nodal lines are concentric circles by using the generalized differential quadrature method for the nonlinear temperature distribution in the thickness direction. The parabolic variation in thickness along the radial direction is controlled by a taper constant. The plate material is graded in the transverse direction and its mechanical properties are temperature-dependent. The thermal environment over the top and bottom surfaces of the plate is assumed to be uniform. Hamilton's principle has been used in obtaining the governing differential equations for thermo-elastic equilibrium and axisymmetric motion for such a plate model employing Kirchhoff plate theory. Numerical results for thermal displacements and natural frequencies of clamped and simply supported plates have been obtained using MATLAB. The effect of the taper constant, volume fraction index, and temperature difference on the vibration characteristics has been analyzed for the lowest three modes of vibration. A study in which the plate material has temperature-independent properties has also been performed. The accuracy of the present technique is verified by comparing the results with those available in the literature.

Temperature-sensitive magnetic fluid is a smart material for energy carrier. The most interesting aspect of temperature-sensitive magnetic fluid is that the thermal flow behavior is actively controlled by means of magnetic field. Based on the effect of the temperature-dependent magnetization, temperature-sensitive magnetic fluid can be utilized as an energy conversion system, which can automatically transfer the thermal energy. The advantage in the engineering application can be derived from the fact that there would be entirely no external energy consumption, with which large amount heat can be transported for a long distance without any external power consumption. Taking into account of the advantage, a magnetically-driven cooling device is newly designed for recovering of low- to high-temperature waste heat in the present study. The basic performance of the cooling device with concentric pipe structure is investigated experimentally and data gained in the device is examined in detail in view of magneto-hydrodynamics. In the present study, electromagnet is used as an external magnetic field for the purpose of investigating basic heat transfer characteristics of the present experimental device, so that the magnetic field can be continuously altered. However, it can be easily replaced to a permanent for the practical device without additional electrical energy. The results show that the binary temperature-sensitive magnetic fluid can be circulated freely with a high flow rate of 2.0 × 10−3 m3/min by imposing the magnetic field of 55.8 kA/m. It is found that the newly designed device can transfer thermal energy more than 250 W with overall system efficiency of 11.0% at air temperature of 623 K.

The mathematical model responsible for fully developed laminar transient flow formation between the gaps of two stationary concentric porous tubes due to the imposition of azimuthal pressure gradient (Dean flow) is solved semi-analytically. The tubes walls are porous so that a radial flow can be superimposed. The solution of the momentum and continuity equations are obtained semi-analytically by using the combination of Laplace transform technique and a Laplace inversion method called Riemann sum approximation method. The solutions for skin friction at [Formula: see text] (outer surface of the inner porous tube) and [Formula: see text] (inner surface of the outer porous tube) are presented. The impact of suction/injection parameter and the ratio of the radii of the tubes are examined for the velocity profile and skin friction. Results show that the velocity profile decreases with increase in suction/injection parameter for various values of time, [Formula: see text] and at large value of time, ([Formula: see text]), the velocity and the skin friction attain a steady state.

Background: One-repetition maximum (1RM) tests are time-consuming, and they might not always be logistically possible or warranted due to increased risk of injury when performed incorrectly or by novice athletes. Repetitions-to-failure tests are a widespread method of predicting the 1RM, but its accuracy may be compromised by several factors such as the type of exercise, sex, training history, and the number of repetitions completed in the test. Hypothesis: The touch-and-go bench press would provide a higher 1RM than the concentric-only bench press for both genders regardless of whether the 1RM was obtained by the direct or repetitions-to-failure method and the error in the 1RM prediction would be positively correlated with the number of repetitions performed to failure and negatively correlated with the 1RM strength and resistance training experience. Study Design: Cross-sectional study. Level of Evidence: Level 3. Methods: A total of 113 adults (87 men and 26 women) were tested on 2 sessions during the concentric-only and touch-and-go bench press. Each session consisted of an incremental loading test until reaching the 1RM load, followed by a repetitions-to-failure test. Results: The 1RM was higher for the touch-and-go bench press using both the direct (men, 7.80%; women, 7.62%) and repetitions-to-failure method (men, 8.29%; women, 7.49%). A significant, although small, correlation was observed between the error in the estimation of the 1RM and the number of repetitions performed ( r = 0.222; P < 0.01), 1RM strength ( r = −0.169; P = 0.01), and resistance training experience ( r = −0.136; P = 0.05). Conclusion: The repetitions-to-failure test is a valid method of predicting the 1RM during the concentric-only and touch-and-go bench press variants. However, the accuracy of the prediction could be compromised with weaker and less experienced individuals and if more than 10 repetitions are completed during the repetitions-to-failure test. Clinical Relevance: The repetitions-to-failure test does not require any sophisticated equipment and enables a widespread use in different training environments.

Background Advanced magnetic resonance imaging (MRI) is capable of identifying subtle effects of exercise. However, it is unclear whether it is sensitive enough to differentiate between different contractions. Purpose To compare the acute and delayed effects of concentric and eccentric exercise on quantitative MRI in hamstring muscles. Material and Methods Participants performed eccentric and concentric leg curls. Quantitative T2 and magnetization transfer ratio (MTR) maps were calculated in the hamstring complex before exercise, 30 minutes, 24 hours, 7 days, and 14 days after exercise. Results Compared to baseline, significant MTR reduction (-7.3%) and T2 elevation (72.2%) were observed in the semitendinosus muscle (ST) at 24 hours after eccentric exercise ( P = 0.04). Concentric contractions induced T2 elevation in the ST (20.8%) and biceps femoris (5.1%) muscles at 30 minutes after exercise ( P = 0.04) which normalized within 24 hours. Conclusions Longitudinal effects of concentric and eccentric exercise can be detected by both T2 and MTR, but T2 is more sensitive to subtle alterations.

This article deals with the structural behavior of a multi-bar system which maintains pole pieces in a concentric magnetic gear. Simplified analytic magnetic and mechanical models of the system are proposed in order to be integrated in a multi-criteria global optimization for the sizing of a magnetic gear in wind power applications. For this purpose, the reduction of the computation time is taken into account. The geometry of the support bar subsystem is defined and a Q bar structure is proposed. The magnetic study is based on Maxwell’s equations and subdomain method in order to determine variable radial and tangential magnetic loads. The mechanical study is based on a multibody model with different bars stiffnesses which are determined from a one-dimensional model. Variable radial and tangential magneto-mechanical pole pieces loads (magnetic load and weight) are also considered. An example of a magnetic gear with 172 pole pieces (i.e. 6-MW wind turbine) is proposed to analyze the mechanical behavior and also the computation time.

Knowledge of the power– and velocity–load relationships is a key factor to guide loads during resistance training and optimize sports performance. This study compares mean velocity–, peak velocity– and power–load relationships, and determines the load which elicits maximal power output in the military press and bench press. Fifty-seven healthy, active men were randomly assigned to a bench press (n = 28) or military press (n = 29) group. In separate test sessions, concentric-only or eccentric-concentric sequences of each exercise were performed in random order as incremental isoinertial load tests. Both mean velocity and peak velocity were highly related with the load lifted (% 1RM) in both bench press and military press (mean velocity: R2 = 0.94 and 0.95; peak velocity: R2 = 0.93 and 0.93, respectively). The loads maximizing mean power and peak power output were similar for the eccentric-concentric versus concentric sequences in bench press and military press. The loads maximizing mean power and peak power were between 54% and 57.5% 1RM for the bench press and 59.8%–63.1% 1RM for the military press. For the bench press, no significant differences were observed in mean power from 30% to 80% 1RM and peak power from 30% to 95% 1RM. For the military press, no significant differences were observed in mean power from 40% to 80% 1RM and peak power from 30% to 90%/95% 1RM. The close relationship detected between mean velocity or peak velocity and load means that the % 1RM can be estimated according to mean velocity and peak velocity. In both exercises, a broad range of relative intensities could be used at which power output is not significantly different than that at maximized power output (mean = 30%/40%–80% 1RM; peak = 30%–90%/95%). Mean velocity lower than approximately 0.33 m s−1 for bench press and 0.4 m s−1 for military press, as well as peak velocity lower than approximately 0.4 m s−1 for bench press and 0.5 m s−1 for military press do not optimize power output responses. The eccentric action was a determining factor for increasing power output only in bench press.

Grouted connections are structural joints formed by a cementitious grout cast between two concentric circular tubes. They are widely used in the offshore construction of oil and gas platforms, and for offshore wind turbines (monopiles and jackets). However, their application in offshore wind turbine installations can be critical due to the high bending moments coming from wind loading. Recently, it was found that grouted connections show limited performance in offshore wind turbine installations leading to settlements between the steel tubes and steel/grout debonding. Hence, structural health monitoring techniques for grouted connections are needed that ensure a safe and reliable operation of offshore wind turbines. This short communication describes the successful application of electromechanical impedance spectroscopy for damage detection in grouted connections.

Concentric tube robots offer the capability of follow-the-leader motion, which is desirable when navigating in cluttered environments, such as in minimally invasive surgery or in-situ inspections. The follow-the-leader capabilities identified in the existing literature, however, are limited to trajectories with piecewise constant-curvature segments or piecewise helical segments. A complete study of follow-the-leader kinematics is, therefore, relevant to determine the full potential of these robots, and clarify an open question. In this paper, a general analysis of follow-the-leader motion is presented, and a closed-form solution to the complete set of trajectories where follow-the-leader is possible under the assumption of no axial torsion of the tubes composing the robot is derived. For designs with constant-stiffness tubes, the precurvatures required are found to be either circumference arcs, helices, or deformed helices with exponentially varying curvature magnitude. The analysis developed also elucidates additional motions of interest, such as the combination of follow-the-leader motion in a robot segment with general maneuvers in another part. To determine the applicability of the assumption regarding the tubes’ torsion, the general equilibrium of the robot designs of interest is considered, and a closed-form solution to torsion in two-tube robots with helical precurvatures is derived. Criteria to select a desired torsional behavior are then extracted. This enables one to identify stable trajectories where follow-the-leader is possible, for potential application to minimally invasive surgery. An illustrative case study involving simulation and experiment is conceived using one of these trajectories, and the results are reported, showcasing the research.

This paper presents the results of fluid flow and convection heat transfer in concentric and eccentric annuli between two cylinders using a three-dimensional computational fluid dynamics model. Effects of rotational speed ( n = 0, 150, 300, and 400 rpm) and eccentricity (ε = 0, 0.15, 0.3, 0.45, and 0.6) on axial and tangential velocity distribution, pressure drop and forced convection heat transfer are investigated for radii ratios (η) of 0.2, 0.4, 0.6, and 0.8, Reynolds number 2.0 × 103–1.236 × 105, Taylor number 1.47 × 106–1.6 × 1010, and Prandtl number 3.71–6.94. The parameters cover many applications, including rotary heat exchangers, mixers, agitators, etc. Nusselt numbers and friction factors for stationary and rotated concentric and eccentric annuli are correlated with four dimensionless numbers. The results revealed that when the speed of the inner cylinder increases from 0 to 400 rpm, the friction factor increases by 7.7%–103% for concentric and 8.2%–148% for eccentric annuli, whereas Nusselt number enhances by 37%–333% for concentric and 44%–340% for eccentric annuli. The radius ratio has a substantial effect on the heat transfer and pressure drop in annuli. The eccentricity enhances the heat transfer up to 12%, whereas its effect on the friction factor is not monotonic as it depends on Reynolds number, radii ratios, and rotational speed.

In reinforced concrete elements strengthened with fiber-reinforced polymer sheets, premature debonding of the fiber-reinforced polymer from the concrete substrate occurs due to lack of anchorage, which reduces the efficiency of the retrofitting system. This article reviews several common anchor systems and describes the development, optimization, and testing of a steel tube anchor in retrofit of reinforced concrete structural elements using externally bonded fiber-reinforced polymer sheets suitable for application to improve resistance against extreme load conditions (e.g. blast, impact, or an earthquake). A detailed review of common anchor designs including the proposed tube anchor based on previous studies on flexure-dominated fiber-reinforced polymer-strengthened reinforced concrete shear walls is presented. In this study, finite element analysis is conducted to verify the observed behavior and better understand the deformation mechanisms of the tube anchor. Finite element modeling is then used to evaluate the influence of different design parameters on its performance and propose a design methodology that can be used to optimize the tube anchor design. To verify the performance of the optimized tube anchor, it is tested in an experimental program on the in-plane seismic strengthening of two shear-dominated squat walls strengthened using fiber-reinforced polymer sheets. Experimental results reveal that the optimized tube anchor performs well in preventing premature debonding and allows the fiber-reinforced polymer composite to achieve a higher level of strain when compared to an alternative anchor system. Finally, a set of design steps for the implementation of the tube anchor in fiber-reinforced polymer retrofit applications for reinforced concrete shear walls are presented.

Previously, fingertip capillary blood glucose measurements from the CONTOURA Radar Plot, a new method for capturing a distinct, single visualization of BGMS analytical performance, is a collection of concentric circles, each representing a particular magnitude of error. The center of the plot represents zero error (BGMS result is equivalent to reference result); as points are more distant from the center, the error increases, expressed in units of mg/dL or percentage for YSI values100 and ≥100 mg/dL, respectively. The position of the data point above or below the horizontal line bisecting the plot indicates whether the BGMS measurement error was positive (BGMS resultYSI result) or negative (BGMS resultYSI result). Points within the "15-15 Zone," representing ±15 mg/dL or ±15% error, satisfy ISO 15197:2013 accuracy criteria.The percentage of results within the 15-15 Zone ranged from 83.6% to 99.8% for the 6 BGMSs (99.6% for CN).Radar Plots provide a different method for visually comparing the analytical performance of multiple BGMSs. The tight clustering of data points at the center of the CN Radar Plot illustrates the analytical performance of CN compared with 5 other BGMSs.

For revolving components like compressor stages in aero-engine, it is critical to ensure that the overall concentric performance of the assembly is extremely excellent to satisfy the requirements of vibration-free and noise-free. However, in practical production, it is hard to meet the target requirement by manual adjustments; in virtual assembly, it is difficult to build an effective deviation propagation model with traditional methods. This article focuses on two points: one is the assembly technique of multistage rotational optimization and the other is the deviation propagation model for revolving components assembly. The revolution joint was introduced in the unified Jacobian–Torsor model to provide the rotary regulating effects. This modified model has advantages of being able to consider rotating optimization, geometric tolerance, and percentage contribution compared with other mathematical methods. General formulas for the n-stage components assembly were derived including the deviation propagation function and optimization destination expression. Comparisons between three assembly techniques and experiments were made to prove the suggested method was feasible and of high practicability. It can be integrated with computer-aided design systems to propose assistance for operators in assembling stage or redesign parts tolerances where FEs’ percentage contributions can be obtained in design preliminary stage.

The purpose of this study was to compare anthropometric and lower body power measurements between current professional and amateur male rugby union players. The present study also sought to determine which anthropometric and physical performance variables were predictive of playing standard. Thirty professional and 30 amateur RU players performed Wattbike 6 s maximal effort (WB6S) and countermovement (CMJ) and squat jump (SJ) assessments, anthropometric measures were also taken. Dependant variables recorded and analysed including: body mass, stature, Σ8 site skinfolds, WB6S absolute and relative peak power, CMJ and SJ average concentric force, jump height, peak velocity, time to peak force, rate of force development (RFD) and absolute and relative peak force and power. Professional players were heavier, taller and leaner than their amateur counterparts ( p

This study evaluates the effect of 3 months resistance and aerobic training on muscle strength and power in 17 male overweight and obese men. Subjects underwent either a resistance or aerobic training for a period of 3 months (three sessions per week). Peak isometric force, rate of force development, peak power and height of countermovement and squat jumps, reactive strength index, and mean power in the concentric phase of bench presses were all assessed prior to and after completing the training program. Results identified a significant increase of mean power during both countermovement bench presses at 30 kg (18.6%, p = .021), 40 kg (14.6%, p = .033), and 50 kg (13.1%, p = .042) and concentric-only bench presses at 30 kg (19.6%, p = .017) and 40 kg (13.9%, p = .037) after the resistance training. There was also a significant increase in the height of the jump (12.8%, p = .013), peak power (10.1%, p = .026), and peak velocity (9.7%, p = .037) during the countermovement jump and height of the jump (11.8%, p = .019), peak power (9.6%, p = .032), and peak velocity (9.5%, p = .040) during the squat jump. There were no significant changes in the reactive strength index, peak force, and the rate of force development after the resistance training. The aerobic group failed to show any significant improvements in these parameters. It may be concluded that 3 months of resistance training without caloric restriction enhances upper and lower body muscle power in overweight and obese men.

Muscle contractions can be categorized into isometric, isotonic (concentric and eccentric) and isokinetic contractions. The eccentric contractions are very effective for promoting muscle hypertrophy and produce larger forces when compared to the concentric or isometric contractions. Surface electromyography signals are widely used for analyzing muscle activities. These signals are nonstationary, nonlinear and exhibit self-similar multifractal behavior. The research on surface electromyography signals using multifractal analysis is not well established for concentric and eccentric contractions. In this study, an attempt has been made to analyze the concentric and eccentric contractions associated with biceps brachii muscles using surface electromyography signals and multifractal detrended moving average algorithm. Surface electromyography signals were recorded from 20 healthy individuals while performing a single curl exercise. The preprocessed signals were divided into concentric and eccentric cycles and in turn divided into phases based on range of motion: lower (0°–90°) and upper (>90°). The segments of surface electromyography signal were subjected to multifractal detrended moving average algorithm, and multifractal features such as strength of multifractality, peak exponent value, maximum exponent and exponent index were extracted in addition to conventional linear features such as root mean square and median frequency. The results show that surface electromyography signals exhibit multifractal behavior in both concentric and eccentric cycles. The mean strength of multifractality increased by 15% in eccentric contraction compared to concentric contraction. The lowest and highest exponent index values are observed in the upper concentric and lower eccentric contractions, respectively. The multifractal features are observed to be helpful in differentiating surface electromyography signals along the range of motion as compared to root mean square and median frequency. It appears that these multifractal features extracted from the concentric and eccentric contractions can be useful in the assessment of surface electromyography signals in sports medicine and training and also in rehabilitation programs.

Image analysis of a fiber cross-section can provide direct measurements for cotton maturity. Effective segmentation of fiber contours in a cross-sectional image is paramount for accurate fiber geometrical measurements. In a wide-field microscopic image, the adhesion, breakage, and ambiguity (low contrast or noise) of fiber contours make the segmentation rather challenging. This paper presents a new approach for contour segmentation that takes advantage of the shape features of the triple concentric contours, called the coupled-contour model (CCM), of a cross-section, and a CCM-based algorithm developed to locate, split, merge, and refine fiber contours based on the established rules concerning contour features. For a wide-field microscopic image (12 megapixels), this CCM-based algorithm could detect >500 fiber cross-sections with a recall rate of 93.53% and a precision rate of 98.13%, and reduced the errors in maturity measurements by 50%.

The aim of this study was to determine the effects of using an electrical heating garment during a 30-min recovery period after a standardized swimming warm-up on subsequent swimming performance and upper body power output. On two occasions, eight male and four female elite competitive swimmers completed a standardized swimming warm-up, followed by a 30-min passive recovery period before completing maximal plyometric press-ups and a 50-m freestyle swim. Plyometric press-ups determined starting strength, peak force and peak concentric power. During the recovery period, participants wore tracksuit bottoms and (1) a standard tracksuit top (CON) or (2) jacket with integrated electric heating elements (HEAT). The overall results demonstrated a trend of a relevant (>0.4%) improvement in the 50-m freestyle performance of 0.83% ( p = 0.06) in HEAT versus CON. In male participants, performance in the 50-m freestyle significantly improved by 1.01% (CON 25.18 ± 0.5 s vs HEAT 24.93 ± 0.4 s; p

Pupillary contagion—responding to pupil size observed in other people with changes in one’s own pupil—has been found in adults and suggests that arousal and other internal states could be transferred across individuals using a subtle physiological cue. Examining this phenomenon developmentally gives insight into its origins and underlying mechanisms, such as whether it is an automatic adaptation already present in infancy. In the current study, 6- and 9-month-olds viewed schematic depictions of eyes with smaller and larger pupils—pairs of concentric circles with smaller and larger black centers—while their own pupil sizes were recorded. Control stimuli were comparable squares. For both age groups, infants’ pupil size was greater when they viewed large-center circles than when they viewed small-center circles, and no differences were found for large-center compared with small-center squares. The findings suggest that infants are sensitive and responsive to subtle cues to other people’s internal states, a mechanism that would be beneficial for early social development.

Background: Isokinetic dynamometry is a useful tool to objectively assess muscle strength of children and adults in athletic and rehabilitative settings. This study examined test-retest reliability of isokinetic knee strength measurements in children aged 8 to 10 years and defined limits for the minimum difference (MD) in strength that indicates a clinically important change. Hypothesis: Isokinetic knee strength measurements (using the Biodex System 4) in children will provide reliable results. Study Design: Descriptive laboratory study. Methods: In 22 healthy children, 5 maximal concentric (CON) knee extensor (KE) and knee flexor (KF) contractions at 2 angular velocities (60 deg/s and 180 deg/s) and 5 maximal eccentric (ECC) KE/KF contractions at 60 deg/s were assessed 7 days apart. The intraclass correlation coefficient (ICC2.1) was used to examine relative reliability, and the MD was calculated on the basis of standard error of measurement. Results: ICCs for CON KE/KF peak torque measurements were fair to excellent (range, 0.49-0.81). The MD% values for CON KE and KF ranged from 31% to 37% at 60 deg/s and from 34% to 39% at 180 deg/s. ICCs in the ECC mode were good (range, 0.60-0.70), but associated MD% values were high (>50%). There was no systematic error for CON KE/KF and ECC KE strength measurements at 60 deg/s, but systematic error was found for all other measurements. Conclusion: The dynamometer provides a reliable analysis of isokinetic CON knee strength measurements at 60 deg/s in children aged 8 to 10 years. Measurements at 180 deg/s and in the ECC mode were not reliable, indicating a need for more familiarization prior to testing. Clinical Relevance: The MD values may help clinicians to determine whether a change in knee strength is due to error or intervention.

The optical performance of the off-axis three-mirror imaging system can be greatly improved using freeform surfaces. This article focuses on the polishing of the primary mirror and tertiary mirror in an off-axis three-mirror imaging system. The primary mirror and tertiary mirror are fabricated on one monolithic substrate and described by non-uniform rational B-spline–based freeform surfaces. The separated and integrated polishing strategies are presented for polishing the two mirrors on the four-axis computer numerical control polishing platform. A tool path generation approach is proposed for polishing of the non-uniform rational B-spline–based freeform surface. Three kinds of the tool paths are given for ultra-precision polishing of the primary mirror and tertiary mirror with the freeform surfaces. The concentric circle path and the approximately concentric circle path are generated for polishing two mirrors separately, while the spiral path is calculated for integrated polishing of two mirrors simultaneously. The polishing tool posture along the planned tool paths is also analyzed. The ultra-precision polishing experiments of the primary mirror and tertiary mirror on the four-axis computer numerical control polishing platform are performed to verify the proposed approach for tool path generation.

Background: Isotonic exercise is commonly adopted for shoulder rehabilitation, but the efficacy of isokinetic exercise for rehabilitation has not been evaluated. Purpose: To evaluate the efficacy of isotonic and isokinetic external shoulder rotation exercises. Study Design: Controlled laboratory study. Methods: Using surface electromyography (EMG) and the Biodex system, we investigated the EMG amplitude of the infraspinatus (IS), total work (tWK), and EMG(IS)/tWK ratio and examined the relative IS and posterior deltoid (PD) contributions to all exercises. A total of 24 healthy participants without musculoskeletal injuries were included. Participants performed isotonic external shoulder rotation at 10%, 20%, 30%, 40%, and 50% of the maximum voluntary isometric contraction (MVIC) as well as isokinetic external shoulder rotation at angular velocities of 60, 120, 180, 240, and 300 deg/s. Levels of intensity were classified from 1 to 5: level 1 corresponded to 10% of the MVIC and a 300-deg/s angular velocity; level 2 corresponded to 20% MVIC and 240 deg/s; level 3 corresponded to 30% MVIC and 180 deg/s; level 4 corresponded to 40% MVIC and 120 deg/s; and level 5 corresponded to 50% MVIC and 60 deg/s. Normalized IS and tWK amplitudes were calculated for each exercise. Results: During isotonic exercise, the EMG(IS)/tWK ratio significantly decreased from level 5 to 3, 2, and 1; from level 4 to 2 and 1; and from level 3 to 1. During isokinetic exercise, the EMG(IS)/tWK ratio at level 3 was greater than that at all other levels except level 1. Statistical differences were found between isotonic and isokinetic modes at levels 1, 2, and 3. The IS/PD activation ratios were not significantly different between exercise modes at any level. Conclusion: Isokinetic resistance may provide more effective stimulation of the IS muscle compared with isotonic resistance. Clinical Relevance: Isokinetic exercise needs to be considered as a method of rehabilitation that effectively increases infraspinatus muscle activity.

This paper presents the development of performance based plastic design (PBPD) method to design steel concentric braced frames (SCBFs). The design base shear is obtained based on energy-work balance equation using preselected target drift and yield mechanism. Also, the energy-work balance can be applied to estimate seismic demands, herein called the energy spectrum method. PBPD method was originally developed to design SCBFs. The results were too conservative. For further improvement, this paper presents some modifications such as C2-Factor method and P-delta effect in energy-work balance equation to give a better estimate of design base shear. For validity, three baselines frames (3, 6, 9-story) are designed according to AISC 2005 seismic provisions (Baseline frames). Then, the frames are designed based on the Original PBPD method (Original PBPD method). Finally, they are designed based on modifications applied on PBPD method (Modified PBPD frames). These frames are subjected to extensive inelastic pushover and time-history analyses. The Results show that the Modified PBPD frames meet all the intended performance objectives in terms of yield mechanisms and target drifts whereas the Baseline frames show very poor response due to premature brace fractures leading to unacceptably large drifts and instability. Also, Modified PBPD frames show that the structures having 20%–25% weight less than the Original PBPD can meet the performance objectives. Moreover, the drift demands obtained from energy spectrum method significantly correspond with the results of time history analyses.

The tangentially injected swirling tube flow has broad applications in various engineering fields. In the textile industry, the vortex spinning technology, which produces short-staple yarns by means of a tangentially injected swirling airflow, is of great prospect in view of its spinning speed and yarn structure. In this paper, the vortex spinning nozzle is abstracted into a model of concentric tubes of different lengths with tangential injectors. A computational fluid dynamics model is presented to study the effects of some structural parameters on the swirling flow generated in this tube system. The particle image velocimetry (PIV) technique is adopted to measure the flow field. Due to the difficulty in duplicating the Mach number, Reynolds numbers are matched between the tube model and prototype in the PIV experiment. Despite the discrepancy between the velocity values provided by the numerical simulation and experiment due to the compressibility effects not being reproduced in the PIV measurement, a comparative analysis concludes that qualitatively matched results on the flow pattern and effects of the structural parameters are obtained by the numerical simulation and PIV measurement.

This study compared the biomechanical characteristics of the heavy sprint-style sled pull and squat. Six experienced male strongman athletes performed sled pulls and squats at 70% of their 1RM squat. Significant kinematic and kinetic differences were observed between the sled pull start and squat at the start of the concentric phase and at maximum knee extension. The first stride of the heavy sled pull demonstrated significantly (p

During the last decades, great progress has been made in the research and application of high strength concrete (HSC). Due to its high strength, low dilation and brittle nature, substantial more transverse reinforcement is needed for HSC columns to obtain ductile behavior, especially for columns with large axial load ratio and/or located in seismic zones. In this paper, a novel HSC concrete column with double high-strength stirrups is proposed, which features two concentric transverse stirrups. The concrete in the cross section are divided into three parts under different confinement level, namely unconfined concrete, singly and doubly confined concrete. This structural form possesses many advantages over traditional HSC with single stirrup and steel-concrete composite columns, including enhanced strength and ductility, easy to construction and easy to connection with RC beams. Three demonstrative circular HSC columns with double spirals were prepared and tested under concentric axial compression. A current stress-strain model for steel confined HSC was modified and found suitable to predict the behavior of present HSC column with double spirals. A parametric study was then conducted to investigate the influence of several key parameters on load-strain response of HSC column with double spirals, including concrete strength, transverse reinforcement ratio, yield strength of transverse reinforcement and center to center diameter of inner spiral.

This study quantified systematic and intraindividual variability among three repetitions of concentric isokinetic knee extension and flexion tests to determine velocity-related differences in peak torque (PT) and mean power (MP) in healthy elderly (HE) versus sarcopenic and malnourished elderly (SME). In total, 107 HE ( n = 54 men, n = 53 women) and 261 SME ( n = 101 men, n = 160 women) performed three maximal concentric isokinetic knee extension and flexion repetitions at 60°·s−1 and 180°·s−1. PT for Repetition 3 was lower than Repetitions 1 and 2, while MP for Repetition 1 was lower than Repetitions 2 and 3 in SME. Intraindividual variability among repetitions was correlated with strength, but not age, and was greater in SME, during knee flexion, and at 180°·s−1. Velocity-related decreases in PT from 60°·s−1 to 180°·s−1 were more pronounced in SME. In summary, (a) the repetition with the highest PT value may be the best indicator of maximal strength, while the average may indicate strength maintenance in SME; (b) intraindividual variability among repetitions reflects functional decrements from HE to SME; and (c) decreases in PT from 60°·s−1 to 180°·s−1 may reflect greater losses of fast-twitch (type II) fiber function.

This paper presents an experimental study that was undertaken to investigate the effects of key parameters on the compressive behavior of fiber reinforced polymer (FRP)-concrete-steel composite columns that were manufactured with S-Glass FRP tubes. A total of 24 hollow and concrete-filled double-skin tubular columns (DSTCs), two concrete-filled FRP tubes (CFFTs), and six CFFTs with inner voids (H-CFFTs) were prepared and tested. The parameters examined included the inner steel tube diameter, influence of concrete-filling the inner steel tube, and the loading pattern. The results indicate that concrete-filling the inner steel tubes of DSTCs results in an increase in the compressive strength of confined concrete in DSTCs, compared to that of the companion specimens with hollow inner steel tubes. It was observed that cyclically loaded DSTCs exhibited slightly higher strength and strain enhancements compared to their monotonically loaded counterparts. The results also indicate that H-CFFTs perform significantly worse than DSTCs and CFFTs and their performance further degrades with an increase in the diameter of inner void. Comparison of the results from DSTCs and CFFTs indicate that both hollow and concrete-filled DSTCs exhibit improved compressive behavior compared to those of the companion CFFTs.

For semi-active shock and vibration mitigation systems using magnetorheological energy absorbers, fail-safe performance is of particular significance if electric power is lost. At the same time, the minimization of the field-off damping force of the magnetorheological energy absorbers at high speed is also important because the damping force due to the viscous damping force at high speed becomes too excessive, and thus, the controllable dynamic range is rapidly reduced. In this article, a fail-safe magnetorheological energy absorber with dual concentric annular valves and an inner-set permanent magnet is proposed to decrease the field-off damping force while keeping an appropriate dynamic range for improving shock and vibration mitigation performance. In the magnetorheological energy absorber, the dual concentric annular valves are configured so as to decrease the baseline damping force, and magnetic activation methods using the electromagnetic coil winding and the permanent magnet are used to maintain appropriate magnetic intensity in these concentric annular valves. An initial field-on damping force is produced by the magnetic field bias generated from the inner-set permanent magnet in consideration of the failure of the electric power supply. The initial field-on damping force of the magnetorheological energy absorbers can be increased (or decreased) by applying positive (or negative) current to the electromagnetic coil winding, and thus, bidirectional controllable damping performance could be realized. After establishing the analytical damping force model of the magnetorheological energy absorber using a Bingham-plastic nonlinear fluid model, its working principle and magnetic properties are analytically validated and analyzed via electromagnetic finite element analysis. The performance of the magnetorheological energy absorber is also theoretically compared with that of a conventional magnetorheological energy absorber with a single valve with the constraint of an identical volume under different excitation velocities.

The purpose was to examine the acute effect of pre-exercise static stretching on barbell power and velocity during the bench press exercise. Forty male high school athletes performed 1 repetition maximum (1 RM) testing and were divided into either a static stretching (SS), or a no stretching (NS) protocol. Subjects performed 1 set of 3 repetitions of the bench press with 50% 1 RM as a warm-up. SS then performed a series of stretching exercises for the involved muscles. After completing either the bench press warm-up or the stretching protocol, subjects executed one bench press repetition at 85% 1 RM. After 24 hours, the groups switched protocols. Concentric mean barbell power and velocity were measured during the 85% lift. Stretching resulted in significantly lower mean power (NS=366.6±115.7 W, SS=282.7±111.4W) and mean velocity (NS=0.413±0.103 m×s−1, SS=0.302±0.086 m·s−1) when compared to NS. Static stretching has an acute detrimental effect on muscular performance.

The purpose of this study was to examine the effects of graduated compression sleeves on muscle performance during high-intensity exercise. Twenty-four resistance trained men were randomly assigned to one of two groups: compression sleeve (GCS, n=11) or placebo sleeve (GPS, n=13). Participants performed 4 sets of 10 unilateral maximal eccentric/concentric elbow flexion repetitions on an isokinetic dynamometer at 120°s−1 with 1 min of inter-set rest. Average torque, work and power were measured during concentric and eccentric actions. ANOVA revealed no significant interactions or main effects for group for any variable. However, values decreased significantly across sets for average torque (1st = 46.55 ± 11.11 Nm to 4th = 36.75 ± 8.78 Nm), average work (1st = 78.83 ± 18.49 J to 4th = 53.26 ± 10.04 J) and average power (1st = 52.3 ± 12.03 W to 4th = 32.59 ± 8.82 W). Therefore, the use of a graduated compression sleeve appears not enhance isokinetic elbow flexion muscle performance.

The combustion performance of inverse diffusion and partially premixed flames was optimized by employing concentric elliptical ports with variable relative angular orientation, co-swirling, and cross-flow opposing jets of different inclination angles. The flexible and favorably active control of combustion was pronounced by changing the nozzle relative angular orientation. The optimum angular shift was found to be 20° where the flame length was shortened by 39% from the case of 0° and the NOx levels were reduced to about 0.51 g/kg of fuel for the inverse partially premixed flames. At such optimum angular shift, the minimum CO and NOx emissions respectively decreased to 17.1 and 1.52 g/kg of fuel for the inverse diffusion flames. The elliptical jets increased the size of the swirling flow recirculation zone by about 28%. Increasing the inner aspect ratio consistently increased the combustion efficiency, where the CO emissions reach minimum values of 12.3 and 6.22 g/kg of fuel respectively for the inverse diffusion and partially premixed flames. The correspondingly minimum NOx emissions were thus 0.89 and 0.51 g/kg of fuel at a cross-flow momentum flux ratio of 2.0. Splitting the opposing cross-flow air jets by increasing their inclination angle above 0° duplicated the stagnation zone vortical impact to enrich the average turbulent energy at the major axis tips. The inclination angle of 15° was the optimum at no swirl while increasing the outer swirl angle shifted the optimum inclination angle to 25°. The inner/outer co-swirl of 45°/60° thus provided a minimum CO emission of 11.1 g/kg of fuel for the inverse diffusion flame and 2.65 g/kg of fuel for the inverse partially premixed flame.

An experimental study was performed to investigate the flow characteristics of single, double, and triple eccentric butterfly valves and concentric inclined disc butterfly valves. Valve flow coefficients, relative valve flow coefficients, and valve loss coefficients are compared between each type of butterfly valve in detail. These coefficient curves are quite different from those of conventional butterfly valves. Finally, the triple eccentric butterfly valve is recommended for use in flow rate or pressure controls, while single or double eccentric butterfly valves are better used in on–off regulation of large flow rates.

Objective: To analyse treatment effects of eccentric vs. concentric graded exercise in chronic tennis elbow. Design: Randomized controlled trial. Setting: Primary care in Uppsala County, Sweden. Subjects: A total of 120 subjects with tennis elbow lasting more than three months were recruited from primary care and by advertisement. Intervention: Eccentric ( n = 60) or concentric exercise ( n = 60), by lowering or lifting a weight, at home daily, for three months with gradually increasing load. Main measures: Pain during muscle contraction and muscle elongation, as well as strength, was assessed at baseline and after one, two, three, six, and 12 months. Function and quality of life was assessed at baseline and after three, six and 12 months. Results: The eccentric exercise group had faster regression of pain, with an average of 10% higher responder rate at all levels of pain reduction, both during muscle contraction and elongation, ( p < 0.0001 and p = 0.006, respectively). Significant differences were found in Cox’s analysis from two months onwards (HR 0.78, 95% confidence interval (CI) 0.63–0.96, p < 0.02). This represents an absolute pain reduction of 10% in the eccentric vs. the concentric group and a number-needed-to-treat of 10. The eccentric group also had a greater increase of muscle strength than the concentric ( p < 0.02). The differences persisted throughout the follow-up period. There were no significant differences between the groups regarding function or quality of life measures. Conclusion: Eccentric graded exercise reduced pain and increased muscle strength in chronic tennis elbow more effectively than concentric graded exercise.

In this article, a systematic dimensional analysis and similitude study for the three-dimensional rotating flow within the narrow spacing (usually of the order of 100 µm) of multiple concentric discs is presented. An engineering application of this flow configuration is the Tesla disc turbine, and the dimensional analysis leads to proper scaling laws for such machines. Using the Buckingham Pi theorem, the list of non-dimensional numbers necessary for describing the incompressible flow through the concentric discs has been formulated and physical interpretation of the non-dimensional numbers has been provided. The complete criteria for achieving geometric, kinematic and dynamic similarity between a model and the prototype have been established. Computational fluid dynamics (CFD) solutions have been obtained for various geometries, fluid properties and flow conditions to demonstrate the validity of the similitude criteria developed. The CFD results show that, when the present similitude criteria are fulfilled, the values of all non-dimensional output parameters such as the power and pressure-drop coefficients remain unchanged for various combinations of input variables. What is more striking is that the three-dimensional variations of non-dimensional z component of velocity Uz (whose non-zero values are computed by the CFD solver even though the only physical boundary condition applied is [Formula: see text] at the inlet and on disc surfaces) are superposed on one another for all models and the prototype. Systematic methods for arriving at simplified conservation equations are discussed and it is shown how the corresponding list of non-dimensional numbers and similitude criteria evolve with such simplification of the conservation equations.

This rotary engine comprises a cylindrical chamber inside a casing wherein there is a concentric rotatable power shaft and a rotatable asymmetric main wheel mounted eccentrically enough as such to avoid contact with the wall of cylindrical chamber. In addition, two bars traversing the main wheel radially further have a wiping contact with the cylindrical chamber wherein one bar is fixed with power shaft and other bar is hinged with said power shaft. A combustion process is in detonation phase within a demarcated combustion chamber whereby the combustion chamber rotatably travels from a bottom dead volume to a top dead volume, and hence, a power, generated during this path of rotational travel, is subsequently available for delivery at the concentric power shaft.

Objective: To investigate the effects of high-velocity resistance training on muscle function, muscle properties, and physical performance in patients with hip osteoarthritis by comparison with those of low-velocity resistance training. Design: Single-blind randomized controlled trial. Setting: Home-based exercise programmes. Subjects: A total of 46 women with hip osteoarthritis were randomly assigned to the high-velocity ( n = 23) or low-velocity ( n = 23) training group. Interventions: Both groups underwent an eight-week daily home-based resistance training programme using an elastic band. Exercises involved hip abduction, extension, and flexion and knee extension. Participants in the high-velocity group performed the concentric phase of each repetition as rapidly as possible and returned to the initial position eccentrically in 3 s. Participants in the low-velocity group performed both the concentric and eccentric phases in 3 s. Main measures: The following outcome measures were evaluated: isometric muscle strength, muscle power, muscle thickness, muscle echo intensity, maximum walking speed, Timed Up and Go test, 3-minute walking test, Harris Hip Score, and hip pain. Results: Decreases in the time for performing the Timed Up and Go test (mean changes: high-velocity group −0.46 s, low-velocity group −0.23 s) and echo intensity of the gluteus maximus (mean changes: high-velocity group −6.8, low-velocity group −1.0) were significantly greater in the high-velocity group than in the low-velocity group. No significant difference was observed in changes of other outcome measures between the groups. Conclusion: This study revealed that high-velocity training for patients with hip osteoarthritis has partially a greater effect on muscle properties and physical performance than low-velocity training.