bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of Volute Curvature on Performance of a Low Specific-Speed Centrifugal Pump at Design and Off-Design Conditions
Authors: Alemi Hamed , Nourbakhsh Seyyed Ahmad , Raisee Mehrdad , Najafi Amir Farhad
Published: October 2014

The effects of the volute geometry on the head, efficiency, and radial force of a low specific-speed centrifugal pump were investigated focusing on off-design conditions. This paper is divided into three parts. In the first part, the three-dimensional flow inside the pump with rectangular volute was simulated using three well-known turbulence models. Simulation results were compared with the available experimental data, and an acceptable agreement was obtained. In the second part, two volute design methods, namely, the constant velocity and the constant angular momentum were investigated. Obtained results showed that in general the constant velocity method gives more satisfactory performance. In the third part, three volutes with different cross section and diffuser shape were designed. In general, it was found that circular cross section volute with radial diffuser provides higher head and efficiency. Moreover, the minimum radial force occurs at higher flowrate in circular volute geometry comparing to rectangular cross section volute.
Calculation of Flow Instability Inception in High Speed Axial Compressors Based on an Eigenvalue Theory
Authors: Liu Xiaohua , Zhou Yanpei , Sun Xiaofeng , Sun Dakun
Published: October 2014

This paper applies a theoretical model developed recently to calculate the flow instability inception point in axial high speed compressors system with tip clearance. After the mean flow field is computed by 3D steady computational fluid dynamics (CFD) simulation, a body force approach, which is a function of flow field data and comprises of one inviscid part and the other viscid part, is taken to duplicate the physical sources of flow turning and loss. Further by applying appropriate boundary conditions and spectral collocation method, a group of homogeneous equations will yield from which the stability equation can be derived. The singular value decomposition (SVD) method is adopted over a series of fine grid points in frequency domain, and the onset point of flow instability can be judged by the imaginary part of the resultant eigenvalue. The first assessment is to check the applicability of the present model on calculating the stall margin of one single stage transonic compressors at 85% rotational speed. The reasonable prediction accuracy validates that this model can provide an unambiguous judgment on stall inception without numerous requirements of empirical relations of loss and deviation angle. It could possibly be employed to check overcomputed stall margin during the design phase of new high speed compressors. The following validation case is conducted to study the nontrivial role of tip clearance in rotating stall, and a parameter study is performed to investigate the effects of end wall body force coefficient on stall onset point calculation. It is verified that the present model could qualitatively predict the reduced stall margin by assuming a simplified body force model which represents the response of a large tip clearance on the unsteady flow field.
Influence of Radial Flux Inflow Profile on Pressure Drop of Perforated Horizontal Wellbore
Authors: Abdulwahid M. A. , Niranjan Kumar I. N. , Dakhil S. F.
Published: October 2014

In this study, the authors have attempted to present five different profiles for a uniform radial influx through a perforated wellbore. The total pressure drop is not only frictional, accelerational and gravitational pressure drops, but also by the inflow pressure drop that is caused by the inflow through the perforation. The inflow through the wellbore model affects the shear stress due to the wall friction. The influence of inflow depends on the flow regime present in the wellbore. Numerical simulations were performed using ansys fluent 14-cfx, where the governing equations of mass and momentum were solved simultaneously, using the two equations of a standard k–ε turbulence model. The results proved that the behavior of wall shear stress followed the shape of the radial inflow, i.e., the shear stress increased with the increase of radial flow and decreased with the decrease of radial flow. It was found that the fluid influx has increased the apparent friction factor along the horizontal wellbore, but in some cases the influx is decreased.
Energy–Water–Food Nexus and Recommendations for Security
Authors: Wong Kaufui Vincent
Published: October 2014

The clean, renewable sources of energy are the wind, water, and the sun. Geothermal energy from the Earth is a good source of energy for electricity generation that has not been fully utilized. Sustainable energy sources must have “respect for environment” in the center of the 4-cornered diamond. Respect for the environment is very critical for the energy sources to be long lasting and thus sustainable. Respect for the environment needs to be the central philosophy of keeping the three components of the environment clean and healthy. These components—air, water and the land, overlap three of the four sources of clean energy. Mankind has to be responsible custodians of these three natural resources. One main cause of the energy–water nexus is that about 90% of the world's electricity is manufactured following the Rankine cycle for power generation, and water is used for the removal of heat from the condenser. The energy–water–food nexus arise in some parts of the world mainly because of the local climatic conditions. High population density involved mainly with agriculture and adverse climatic events (floods from melting glaciers owing to climate change) are the major factors that cause these energy–water–food nexus problems. Areas identified to have these energy–water–food problems include several parts of Saharan Africa, Sub-Saharan Africa, the Arabian Peninsula, Japan, and the Punjab.
Nonlinear Systems Analysis and Control of Variable Speed Wind Turbines for Multiregime Operation
Authors: Semrau Greg , Rimkus Sigitas , Das Tuhin
Published: October 2014

The key control problems associated with variable speed wind turbines are maximization of extracted energy when operating below the rated wind speed, and power and speed regulation when operating above the rated wind speed. In this paper, we develop a nonlinear systems framework to address these problems. The framework is used to visualize and analyze the equilibria of the wind turbine as its operating regimes and controllers change. For both below rated and above rated wind speeds, we adopt nonlinear controllers, analyze the stability property of the resulting equilibria, and establish the criterion for switching between control regimes. Further, the regions of attraction of the resulting equilibria are determined, and the existence of a common region of attraction, which allows stable switching between operating regimes, is shown. The control input maintains continuity at the point of switching. We next provide a method for blade pitch modulation to control rotor speed at high wind speeds. Through Lyapunov stability analysis, we prove stability of the equilibria in the presence of the two independently functioning torque- and pitch-control feedback loops. Simulation results are presented and the controller is compared with existing works from the literature.
Robust Reliable Control for Uncertain Vehicle Suspension Systems With Input Delays
Authors: Sakthivel R. , Arunkumar A. , Mathiyalagan K. , Selvi S.
Published: October 2014

Synthesis of control design is an essential part for vehicle suspension systems. This paper addresses the issue of robust reliable H∞ control for active vehicle suspension system with input delays and linear fractional uncertainties. By constructing an appropriate Lyapunov–Krasovskii functional, a set of sufficient conditions in terms of linear matrix inequalities (LMIs) are derived for ensuring the robust asymptotic stability of the active vehicle suspension system with a H∞ disturbance attenuation level γ. In particular, the uncertainty appears in the sprung mass, unsprung mass, damping and stiffness parameters are assumed in linear fractional transformation (LFT) formulations. More precisely, the designed controller is presented in terms of the solution of LMIs which can be easily checked by Matlab-LMI toolbox. Finally, a quarter-car suspension model is considered as an example to illustrate the effectiveness and applicability of the proposed control strategy.
Lattice Boltzmann Simulation of the Flow Field in Pump Intakes—A New Approach
Authors: Schneider Andreas , Conrad Daniel , Böhle Martin
Published: October 2014

In recent years, lattice Boltzmann methods (LBMs) have become popular for solving fluid flow problems of engineering interest. Reasons for this popularity are due to the advantages of this method, which are, for example, the simplicity to handle complex geometries and the high efficiency in calculating transient flows. For the operational reliability and efficiency of pumps and pump systems, the incoming flow conditions are crucial. Since the efficiency and reliability requirements of pumps are rising and must be guaranteed by the pump and plant manufacturer, the flow conditions in pump intakes need to be evaluated during plant design. Recent trends show that pump intakes are built more and more compact, what makes the flow in the intake even more complex and holds a higher risk for unacceptable pump inflow conditions. In this contribution, a numerical scheme for the simulation of pump intake flows based on a lattice Boltzmann-large eddy simulation (LES) approach is presented and the ability of the method to capture the flow phenomena in intake flows is analyzed. Special attention is turned to the potential of the numerical scheme to reproduce the transient vortex behavior of intake flows, which results in a very complex flow structure and is challenging to model numerically.
High-Order Solution of Viscoelastic Fluids Using the Discontinuous Galerkin Method
Authors: Mirzakhalili Ehsan , Nejat Amir
Published: October 2014

In this paper, the high-order solution of a viscoelastic fluid is investigated using the discontinuous Galerkin (DG) method. The Oldroyd-B model is used to describe the viscoelastic behavior of the fluid flow. The high-order accuracy of the applied DG method is verified for a Newtonian benchmark problem with an exact solution. Next, the same algorithm is utilized to solve the viscoelastic flow by separating the stress tensor into the stress due to the Newtonian solvent and the stress due to the solved viscoelastic polymers. The high-order accuracy of the solution for viscoelastic flow is demonstrated by solving the planar Poiseuille flow. Then, the planar contraction problem is simulated as a benchmark for the viscoelastic flow. The obtained results are in good agreement with the results in the literature for both creeping and inertial flow when high-order polynomials were used even on coarse meshes.
Elastic Theory of Nanomaterials Based on Surface-Energy Density
Authors: Chen Shaohua , Yao Yin
Published: October 2014

Recent investigations into surface-energy density of nanomaterials lead to a ripe chance to propose, within the framework of continuum mechanics, a new theory for nanomaterials based on surface-energy density. In contrast to the previous theories, the linearly elastic constitutive relationship that is usually adopted to describe the surface layer of nanomaterials is not invoked and the surface elastic constants are no longer needed in the new theory. Instead, a surface-induced traction to characterize the surface effect in nanomaterials is derived, which depends only on the Eulerian surface-energy density. By considering sample-size effects, residual surface strain, and external loading, an explicit expression for the Lagrangian surface-energy density is achieved and the relationship between the Eulerian surface-energy density and the Lagrangian surface-energy density yields a conclusion that only two material constants—the bulk surface-energy density and the surface-relaxation parameter—are needed in the new elastic theory. The new theory is further used to characterize the elastic properties of several fcc metallic nanofilms under biaxial tension, and the theoretical results agree very well with existing numerical results. Due to the nonlinear surface effect, nanomaterials may exhibit a nonlinearly elastic property though the inside of nanomaterials or the corresponding bulk one is linearly elastic. Moreover, it is found that externally applied loading should be responsible for the softening of the elastic modulus of a nanofilm. In contrast to the surface elastic constants required by existing theories, the bulk surface-energy density and the surface-relaxation parameter are much easy to obtain, which makes the new theory more convenient for practical applications.
Molecular Dynamics Simulation Study of Tool Wear in Vibration Assisted Nano-Impact-Machining by Loose Abrasives
Authors: James Sagil , Sundaram Murali M.
Published: October 2014

Vibration assisted nano-impact-machining by loose abrasives (VANILA) is a novel target specific nano-abrasive machining process wherein, nano-abrasives, injected in slurry between the workpiece and the vibrating atomic force microscope probe, impact the workpiece causing nanoscale material removal. In this study, a molecular dynamics (MD) based simulation approach is used to investigate the tool wear mechanism. The simulation results reveal that the tool wear is influenced by the impact velocity of the abrasive grains and the effective tool tip radius. It is seen that based on the process conditions, the wear process could happen through distinctive mechanisms such as atom-by-atom loss, plastic deformation, and brittle fracture. Experimental results show evidences of tool wear by aforementioned mechanisms in VANILA process.
A Batchelor Vortex Model for Mean Velocity of Turbulent Swirling Flow in a Macroscale Multi-Inlet Vortex Reactor
Authors: Liu Zhenping , Fox Rodney O. , Hill James C. , Olsen Michael G.
Published: October 2014

The velocity field in a macroscale multi-inlet vortex reactor (MIVR) used in “flash nanoprecipitation (FNP)” process for producing functional nanoparticles was investigated using stereoscopic particle image velocimetry (SPIV). Based on the experimental data, a simple model was proposed to describe the average velocity field within the reactor. In the model, the axial and azimuthal velocities could be well described by the combination of two coflowing Batchelor vortices. In this model, six dimensionless coefficients are identified by nonlinear curve fitting, and their dependence on Reynolds number can be linearly described. This simple model is able to accurately predict the mean velocity field within the confined turbulent swirling flow based purely on Reynolds number.
Damage Identification in Collocated Structural Systems Using Structural Markov Parameters
Authors: Bighamian Ramin , Mirdamadi Hamid Reza , Hahn Jin-Oh
Published: October 2014

This paper presents a novel approach to damage identification in a class of collocated multi-input multi-output structural systems. In the proposed approach, damage is identified via the structural Markov parameters obtained from a system identification procedure, which is in turn exploited to localize and quantify damage by evaluating relative changes occurring in the mass and stiffness matrices associated with the structural system. To this aim, an explicit relationship between structural Markov parameters versus mass and stiffness matrices is developed. The main strengths of the proposed approach are that it is capable of quantitatively identifying the occurrence of multiple damages associated with both mass and stiffness characteristics in the structural system, and it is computationally efficient in that it is solely based on the structural Markov parameters but does not necessitate costly calculations related to natural frequencies and mode shapes, making it highly attractive for structural damage detection and health monitoring applications. Numerical examples are provided to demonstrate the validity and effectiveness of the proposed approach.
Planar Flexible Hinges With Curvilinear-Axis Segments for Mechanisms of In-Plane and Out-of-Plane Operation
Authors: Lobontiu Nicolae
Published: October 2014

The new design class and related analytic compliance-matrix model of planar flexible hinges with curvilinear longitudinal axes is presented here. The proposed approach enhances and generalizes the existing design and modeling variants dedicated to straight-axis and circular-axis hinge configurations. In-plane and out-of-plane small-displacement compliances are derived for standalone curvilinear-axis hinges as well as for hinges that are formed by serially connecting several curvilinear- and straight-axis segments. The general algorithm is further utilized to derive the compliance model of symmetric hinges, which utilizes a reduced number of compliances defining half the hinge. To illustrate the modeling/design procedure, a new flexible hinge is introduced and studied whose half portion comprises a constant-thickness parabolic-axis segment and a straight-axis segment of elliptically varying thickness. The resulting analytical compliances are validated by finite element simulation (FEA). Two compliant mechanisms that incorporate the new hinge design are studied in terms of specific performance qualifiers.
Real-Time Dynamic Simulations of Large Road Vehicles Using Dense, Sparse, and Parallelization Techniques
Authors: Hidalgo Andrés F. , García de Jalón Javier
Published: October 2014

This article presents three multibody formulations with improved efficiency in order to achieve real-time simulations for the forward dynamic of two real-life road vehicles. The bigger is a semitrailer truck with 40 degrees of freedom (DOF). Two topological and semirecursive formulations are used as well as a global formulation based on the use of Euler parameters and flexible joints. The first semirecursive formulation carries out a double velocity transformation and the integration is done by means of the explicit fourth order Runge–Kutta method. The second semirecursive formulation and the global one use a penalty scheme at position level and orthogonal projections at velocity and acceleration levels. In both cases the integrator was the implicit Hilbert–Huges–Taylor (HHT) method. The double velocity transformation method involves the coordinate partitioning of the constraint Jacobian matrix which leads to the costly solution of a redundant but consistent with the constraints linear system of equations. The choice of a unique set of independent coordinates may not be valid for a complete simulation and additional repartitioning would be required. Based on previous experience and as the examples show in this article, a careful initial choice of the independent coordinates can remain valid for complete simulations involving common maneuvers. This represents a numerical advantage for dense matrix methods and can be further exploited if sparse matrix techniques are employed. This has been the case for both of the vehicles used, reaching real-time simulations even with the semitrailer truck. The implicit semirecursive formulation involves the numerical evaluation of the stiffness and damping matrices, which hamper obtaining real-time simulations. For the semitrailer truck, this computation represents the 76% of the total simulation time. The numerical computation of these matrices is carried out by columns and its algorithm is straightforwardly parallelizable. Using a quad-core processor and with a simple and efficient OpenMP implementation, it has been possible to achieve a speedup of 3.25 reducing the simulation times under the real-time limit. The sparse matrices of Euler parameters formulation show very different sparsity degrees, difference that grows with the size of the multibody model. This poses a challenge to sparse matrix implementations in order to be able to efficiently perform matrix operations without increasing fillings or handling zero entries. This has been successfully accomplished using a new sparse matrix representation. This one is not a feature of general purpose sparse software, requiring at some stages the implementation of our own algorithms. Reductions in time of three orders of magnitude have led to real-time simulations even with the semitrailer truck.
Mistuned Response Prediction of Dual Flow-Path Integrally Bladed Rotors With Geometric Mistuning
Authors: Beck Joseph A. , Brown Jeffrey M. , Kaszynski Alexander A. , Slater Joseph C. , Cross Charles J.
Published: October 2014

The geometric mistuning problem is investigated for dual flow-path integrally bladed rotors (DFIBRs) by outlining two methods that explicitly account for blade geometry surface deviations. The methods result in reduced-order models (ROMs) that are a reduced form of a parent Craig–Bampton component mode synthesis (CB-CMS) model. This is accomplished by performing a secondary modal analysis on different degrees of freedom (DOF) of the parent model. The DFIBR is formulated in cyclic symmetry coordinates with a tuned disk and ring and blades with small geometric deviations. The first method performs an eigen-analysis on the constraint DOF that provides a truncated set of interface modes, while the second method includes the disk and ring fixed interface normal mode in the eigen-analysis to yield a truncated set of ancillary modes. Utilization of tuned modes have the benefit of being solved in cyclic symmetry coordinates and only need to be calculated once, which offers significant computational savings for subsequent mistuning studies. Each geometric mistuning method relies upon the use of geometrically mistuned blade modes in the component mode framework to provide an accurate ROM. Forced response results are compared to both the full finite element model (FEM) solutions and a traditional frequency-based approach outlined in a previous effort. It is shown that the models provide highly accurate results with a significant reduction in solution time compared to the full FEM and parent ROM.
Turbulent Drag Reduction by Biopolymers in Large Scale Pipes
Authors: Campolo Marina , Simeoni Mattia , Lapasin Romano , Soldati Alfredo
Published: October 2014

In this work, we describe drag reduction experiments performed in a large diameter pipe (i.d. 100 mm) using a semirigid biopolymer Xanthan Gum (XG). The objective is to build a self-consistent data base which can be used for validation purposes. To aim this, we ran a series of tests measuring friction factor at different XG concentrations (0.01, 0.05, 0.075, 0.1, and 0.2% w/w XG) and at different values of Reynolds number (from 758 to 297,000). For each concentration, we obtain also the rheological characterization of the test fluid. Our data is in excellent agreement with data collected in a different industrial scale test rig. The data is used to validate design equations available from the literature. Our data compare well with data gathered in small scale rigs and scaled up using empirically based design equations and with data collected for pipes having other than round cross section. Our data confirm the validity of a design equation inferred from direct numerical simulation (DNS) which was recently proposed to predict the friction factor. We show that scaling procedures based on this last equation can assist the design of piping systems in which polymer drag reduction can be exploited in a cost effective way.
Numerical Simulation of Particle Transport and Deposition in the Pulmonary Vasculature
Authors: Sohrabi Salman , Zheng Junda , Finol Ender A. , Liu Yaling
Published: October 2014

To quantify the transport and adhesion of drug particles in a complex vascular environment, computational fluid particle dynamics (CFPD) simulations of blood flow and drug particulate were conducted in three different geometries representing the human lung vasculature for steady and pulsatile flow conditions. A fully developed flow profile was assumed as the inlet velocity, and a lumped mathematical model was used for the calculation of the outlet pressure boundary condition. A receptor–ligand model was used to simulate the particle binding probability. The results indicate that bigger particles have lower deposition fraction due to less chance of successful binding. Realistic unsteady flow significantly accelerates the binding activity over a wide range of particle sizes and also improves the particle deposition fraction in bifurcation regions when comparing with steady flow condition. Furthermore, surface imperfections and geometrical complexity coupled with the pulsatility effect can enhance fluid mixing and accordingly particle binding efficiency. The particle binding density at bifurcation regions increases with generation order and drug carriers are washed away faster in steady flow. Thus, when studying drug delivery mechanism in vitro and in vivo, it is important to take into account blood flow pulsatility in realistic geometry. Moreover, tissues close to bifurcations are more susceptible to deterioration due to higher uptake.
Localized Structures in Indented Shells: A Numerical Investigation
Authors: Nasto Alice , Reis Pedro M.
Published: October 2014

We present results from a numerical investigation of the localization of deformation in thin elastomeric spherical shells loaded by differently shaped indenters. Beyond a critical indentation, the deformation of the shell ceases to be axisymmetric and sharp structures of localized curvature form, referred to as “s-cones,” for “shell-cones.” We perform a series of numerical experiments to systematically explore the parameter space. We find that the localization process is independent of the radius of the shell. The ratio of the radius of the shell to its thickness, however, is an important parameter in the localization process. Throughout, we find that the maximum principal strains remain below 6%, even at the s-cones. As a result, using either a linear elastic (LE) or hyperelastic constitutive description yields nearly indistinguishable results. Friction between the indenter and the shell is also shown to play an important role in localization. Tuning this frictional contact can suppress localization and increase the load-bearing capacity of the shell under indentation.
Adaptive Fuzzy Sliding Mode Control of MEMS Gyroscope Sensor Using Fuzzy Switching Approach
Authors: Fei Juntao , Xin Mingyuan
Published: October 2014

In this paper, an adaptive fuzzy sliding mode control strategy, which combines the merits of sliding mode control and adaptive fuzzy control, is proposed to control the MEMS gyroscope in the presence of model uncertainties and external disturbances. The adaptive fuzzy systems are employed to approximate both the equivalent control term and the sliding mode controller. Then the switching control becomes continuous and the chattering phenomena can be attenuated. The adaptation laws based on the Lyapunov analysis can adaptively adjust the fuzzy rules to guarantee the asymptotical stability of the adaptive fuzzy closed-loop control system. Numerical simulations are investigated to verify the effectiveness of the proposed adaptive fuzzy control schemes.
Optimization of Inertial Sensor-Based Motion Capturing for Magnetically Distorted Field Applications
Authors: Schiefer Christoph , Ellegast Rolf P. , Hermanns Ingo , Kraus Thomas , Ochsmann Elke , Larue Christian , Plamondon André
Published: October 2014

Inertial measurement units (IMU) are gaining increasing importance for human motion tracking in a large variety of applications. IMUs consist of gyroscopes, accelerometers, and magnetometers which provide angular rate, acceleration, and magnetic field information, respectively. In scenarios with a permanently distorted magnetic field, orientation estimation algorithms revert to using only angular rate and acceleration information. The result is an increasing drift error of the heading information. This article describes a method to compensate the orientation drift of IMUs using angular rate and acceleration readings in a quaternion-based algorithm. Zero points (ZP) were introduced, which provide additional heading and gyroscope bias information and were combined with bidirectional orientation computation. The necessary frequency of ZPs to achieve an acceptable error level is derived in this article. In a laboratory environment the method and the effect of varying interval length between ZPs was evaluated. Eight subjects were equipped with seven IMUs at trunk, head and upper extremities. They performed a predefined course of box handling for 40 min at different motion speeds and ranges of motion. The orientation estimation was compared to an optical motion tracking system. The resulting mean root mean squared error (RMSE) of all measurements ranged from 1.7 deg to 7.6 deg (roll and pitch) and from 3.5 deg to 15.0 deg (heading) depending on the measured segment, at a mean interval-length of 1.1 min between two ZPs without magnetometer usage. The 95% limits of agreement (LOA) ranged in best case from −2.9 deg to 3.6 deg at the hip roll angle and in worst case from −19.3 deg to 18.9 deg at the forearm heading angle. This study demonstrates that combining ZPs and bidirectional computation can reduce orientation error of IMUs in environments with magnetic field distortion.
Enhanced Individual Trabecular Repair and Its Mechanical Implications in Parathyroid Hormone and Alendronate Treated Rat Tibial Bone
Authors: Altman Allison R. , de Bakker Chantal M. J. , Tseng Wei-Ju , Chandra Abhishek , Qin Ling , Sherry Liu X.
Published: October 2014

Combined parathyroid hormone (PTH) and bisphosphonate (alendronate—ALN) therapy has recently been shown to increase bone volume fraction and plate-like trabecular structure beyond either monotherapy. To identify the mechanism through which plate-like structure was enhanced, we used in vivo microcomputed tomography (μCT) of the proximal tibia metaphysis and individual trabecular dynamics (ITD) analysis to quantify connectivity repair (incidences of rod connection and plate perforation filling) and deterioration (incidences of rod disconnection and plate perforation). Three-month-old female, intact rats were scanned before and after a 12 day treatment period of vehicle (Veh, n = 5), ALN (n = 6), PTH (n = 6), and combined (PTH+ALN, n = 6) therapy. Additionally, we used computational simulation and finite element (FE) analysis to delineate the contributions of connectivity repair or trabecular thickening to trabecular bone stiffness. Our results showed that the combined therapy group had greater connectivity repair (5.8 ± 0.5% connected rods and 2.0 ± 0.3% filled plates) beyond that of the Veh group, resulting in the greatest net gain in connectivity. For all treatment groups, increases in bone volume due to thickening (5–31%) were far greater than those due to connectivity repair (2–3%). Newly formed bone contributing only to trabecular thickening caused a 10%, 41%, and 69% increase in stiffness in the ALN, PTH, and PTH+ALN groups, respectively. Moreover, newly formed bone that led to connectivity repair resulted in an additional improvement in stiffness, with the highest in PTH+ALN (by an additional 12%), which was significantly greater than either PTH (5.6%) or ALN (4.5%). An efficiency ratio was calculated as the mean percent increase in stiffness divided by mean percent increase in BV for either thickening or connectivity repair in each treatment. For all treatments, the efficiency ratio of connectivity repair (ALN: 2.9; PTH: 3.4; PTH+ALN: 4.4) was higher than that due to thickening (ALN: 2.0; PTH: 1.7; PTH+ALN: 2.2), suggesting connectivity repair required less new bone formation to induce larger gains in stiffness. We conclude that through rod connection and plate perforation filling PTH+ALN combination therapy improved bone stiffness in a more efficient and effective manner than either monotherapy.
Trabecular Bone Loss at a Distant Skeletal Site Following Noninvasive Knee Injury in Mice
Authors: Christiansen Blaine A. , Emami Armaun J. , Fyhrie David P. , Satkunananthan Patrick B. , Hardisty Michael R.
Published: October 2014

Traumatic injuries can have systemic consequences, as the early inflammatory response after trauma can lead to tissue destruction at sites not affected by the initial injury. This systemic catabolism may occur in the skeleton following traumatic injuries such as anterior cruciate ligament (ACL) rupture. However, bone loss following injury at distant, unrelated skeletal sites has not yet been established. In the current study, we utilized a mouse knee injury model to determine whether acute knee injury causes a mechanically significant trabecular bone loss at a distant, unrelated skeletal site (L5 vertebral body). Knee injury was noninvasively induced using either high-speed (HS; 500 mm/s) or low-speed (LS; 1 mm/s) tibial compression overload. HS injury creates an ACL rupture by midsubstance tear, while LS injury creates an ACL rupture with an associated avulsion bone fracture. At 10 days post-injury, vertebral trabecular bone structure was quantified using high-resolution microcomputed tomography (μCT), and differences in mechanical properties were determined using finite element modeling (FEM) and compressive mechanical testing. We hypothesized that knee injury would initiate a loss of trabecular bone structure and strength at the L5 vertebral body. Consistent with our hypothesis, we found significant decreases in trabecular bone volume fraction (BV/TV) and trabecular number at the L5 vertebral body in LS injured mice compared to sham (−8.8% and −5.0%, respectively), while HS injured mice exhibited a similar, but lower magnitude response (−5.1% and −2.5%, respectively). Contrary to our hypothesis, this decrease in trabecular bone structure did not translate to a significant deficit in compressive stiffness or ultimate load of the full trabecular body assessed by mechanical testing or FEM. However, we were able to detect significant decreases in compressive stiffness in both HS and LS injured specimens when FE models were loaded directly through the trabecular bone region (−9.9% and −8.1%, and 3, respectively). This finding may be particularly important for osteoporotic fracture risk, as damage within vertebral bodies has been shown to initiate within the trabecular bone compartment. Altogether, these data point to a systemic trabecular bone loss as a consequence of fracture or traumatic musculoskeletal injury, which may be an underlying mechanism contributing to increased risk of refracture following an initial injury. This finding may have consequences for treatment of acute musculoskeletal injuries and the prevention of future bone fragility.
Application of the Subequation Method to Some Differential Equations of Time-Fractional Order
Authors: Bekir Ahmet , Aksoy Esin
Published: October 2014

The main goal of this paper is to develop subequation method for solving nonlinear evolution equations of time-fractional order. We use the subequation method to calculate the exact solutions of the time-fractional Burgers, Sharma–Tasso–Olver, and Fisher's equations. Consequently, we establish some new exact solutions for these equations.
Specific Features of Dynamic Behavior of Stationary and Rotating Single/Coaxial Cylindrical Shells Interacting With the Axial and Rotational Fluid Flows
Authors: Bochkarev Sergey A. , Matveenko Valery P.
Published: October 2014

The paper is concerned with the finite element analysis of hydroelastic stability of stationary or rotating elastic single and coaxial cylindrical shells subjected to compressible fluid flows having axial and tangential velocity components. The behavior of the flowing and rotating fluid is described in the framework of the potential theory. Consideration of elastic shells is based on the classical shell model. The results of the numerical analysis of shell stability for various boundary conditions, geometrical dimensions and different sizes of the annular gap between the outer and inner shells are discussed. It has been found that single and coaxial shells interacting with the combined fluid flows show qualitative differences in the dynamic behavior.
Pulsation Energy in the Suction Manifold of a Reciprocating Compressor as a Measure for Parameter Sensitivity
Authors: Bilal Nasir , Adams Douglas E.
Published: October 2014

Gas pulsations in a compressor suction manifold radiate noise and reduce the efficiency of the compressor. The objective of this paper is to identify and quantify the effects of modeling assumptions and uncertainties in input parameters on the pulsation model output predictions and to estimate the sensitivity of the model to changes in the input design parameters. A unique method of sensitivity analysis is presented that uses the total pulsation energy in the suction manifold of a compressor as a measure of gas pulsations. This method is used to determine the sensitivity of the gas pulsations in the suction manifold to input design parameters. First, the gas pulsations in the suction manifold are calculated using linear acoustic theory. Second, the effects of varying several different design parameters of the suction manifold on gas pulsations are analyzed, and the three most important parameters are selected. Next, energy due to gas pulsations in the suction manifold due to these design parameter variations is calculated. Suction manifold radius was identified as the most critical parameter, followed by width and depth. The optimized values of manifold radius resulted in an overall reduction of up to 24% in the gas pulsation energy compared to the pulsation energy at the nominal design parameter values in the suction manifold.
Experimental Implementation of Opposed Shape Memory Alloy Wires for Actuator Control
Authors: Kolansky Jeremy , Tarazaga Pablo , Ohanian, O. John
Published: October 2014

Shape memory alloys (SMAs) are capable linear actuators. This research demonstrates the capabilities of SMA wires for the control of a pivot actuator. The wires impart opposing forces to control the motion of the pivot, and their deformation lengths are used to control the angle of rotation. The performance of the actuator is demonstrated through the tracking of a trajectory. Several effects that are important to the behavior of the actuator are also investigated. These are the block force generation of SMA wires for various temperatures and cooling strategies, and the open-loop response of the system.
Experimental Investigation of Air Flow Through a Perforated Tile in a Raised Floor Data Center
Authors: Arghode Vaibhav K. , Joshi Yogendra
Published: October 2014

Raised floor data centers supply cold air from a pressurized plenum to the server racks through perforated floor tiles. Hence, the design of an efficient air delivery scheme requires better understanding of the flow features, through and above the perforated tiles. Different tiles with circular pores in a staggered arrangement and with the same thickness are considered. Tile sheet porosities of 23% and 40%, air flow rates of 0.56 m3/s (1177 CFM) and 0.83 m3/s (1766 CFM), and pore sizes of 3.18 mm (1/8 in.) and 6.35 mm (1/4 in.) are investigated. Tiles with 38.1 mm (1.5 in.) region blocked along the edges is compared to the base case with 12.7 mm (0.5 in.) blocked edges. Width reduced to 0.46 m (1.5 ft) from standard width of 0.61 m (2 ft) is also examined. Reduced tile width is used to simulate 0.91 m (3 ft) cold aisle instead of standard 1.22 m (4 ft) cold aisle, with potential to save floor space. A case where the rack is recessed by 76.2 mm (3 in.) from the tile edge is also included in the investigation, as there is a possibility of having racks nonadjacent to the tile edges. Particle image velocimetry (PIV) technique is used to characterize the flow field emerging from a perforated tile and entering the adjacent rack. Experiments suggest that lower tile porosity significantly increases cold air bypass from the top, possibly due to higher air jet momentum above the tile, as compared to a tile with higher porosity. For the air flow rates investigated here, the flow field was nearly identical and influence of flow rate was nondistinguishable. The influence of pore size was non-negligible, even when the porosity and flow rate for the two cases were same. Larger blockage of the tile edges resulted in higher cold air bypass from the top. Reduction in the tile width showed improved air delivery to the rack with considerably reduced cold air bypass. Recessing the rack did not affect the flow field significantly.
A New Approach to Determine Ligament Strain Using Polydimethylsiloxane Strain Gauges: Exemplary Measurements of the Anterolateral Ligament
Authors: Zens Martin , Ruhhammer Johannes , Goldschmidtboeing Frank , Woias Peter , Feucht Matthias J. , Mayr Herrmann O. , Niemeyer Philipp
Published: October 2014

A thorough understanding of ligament strains and behavior is necessary to create biomechanical models, comprehend trauma mechanisms, and surgically reconstruct those ligaments in a manner that restores a physiological performance. Measurement techniques and sensors are needed to conduct this data with high accuracy in an in vitro environment. In this work, we present a novel sensor device that is capable of continuously recording ligament strains with high resolution. The sensor principle of this biocompatible strain gauge may be used for in vitro measurements and can easily be applied to any ligament in the human body. The recently rediscovered anterolateral ligament (ALL) of the knee joint was chosen to display the capability of this novel sensor system. Three cadaver knees were tested to successfully demonstrate the concept of the sensor device and display first results regarding the elongation of the ALL during flexion/extension of the knee.
Numerical Analysis of Laminar-Drag-Reducing Grooves
Authors: Mohammadi A. , Floryan J. M.
Published: October 2014

The performance of grooves capable of reducing shear drag in laminar channel flow driven by a pressure gradient has been analyzed numerically. Only grooves with shapes that are easy to manufacture have been considered. Four classes of grooves have been studied: triangular grooves, trapezoidal grooves, rectangular grooves, and circular-segment grooves. Two types of groove placements have been considered: grooves that are cut into the surface (they can be created using material removal techniques) and grooves that are deposited on the surface (they can be created using material deposition techniques). It has been shown that the best performance is achieved when the grooves are aligned with the flow direction and are symmetric. For each class of grooves, there exists an optimal groove spacing, which results in the largest drag reduction. The largest drag reduction results from the use of trapezoidal grooves and the smallest results from the use of triangular grooves for the range of parameters considered in this work. Placing the same grooves on both walls increases the drag reduction by up to four times when comparing with grooves on one wall only. The predictions remain valid for any Reynolds number as long as the flow remains laminar.
Short-Term Bone Formation is Greatest Within High Strain Regions of the Human Distal Radius: A Prospective Pilot Study
Authors: Bhatia Varun A. , Brent Edwards W. , Johnson Joshua E. , Troy Karen L.
Published: October 2014

Bone adaptation is understood to be driven by mechanical strains acting on the bone as a result of some mechanical stimuli. Although the strain/adaptation relation has been extensively researched using in vivo animal loading models, it has not been studied in humans, likely due to difficulties in quantifying bone strains and adaptation in living humans. Our purpose was to examine the relationship between bone strain and changes in bone mineral parameters at the local level. Serial computed tomography (CT) scans were used to calculate 14 week changes in bone mineral parameters at the distal radius for 23 women participating in a cyclic in vivo loading protocol (leaning onto the palm of the hand), and 12 women acting as controls. Strains were calculated at the distal radius during the task using validated finite element (FE) modeling techniques. Twelve subregions of interest were selected and analyzed to test the strain/adaptation relation at the local level. A positive relationship between mean energy equivalent strain and percent change in bone mineral density (BMD) (slope = 0.96%/1000 με, p < 0.05) was observed within experimental, but not control subjects. When subregion strains were grouped by quartile, significant slopes for quartile versus bone mineral content (BMC) (0.24%/quartile) and BMD (0.28%/quartile) were observed. Increases in BMC and BMD were greatest in the highest-strain quartile (energy equivalent strain > 539 με). The data demonstrate preliminary prospective evidence of a local strain/adaptation relationship within human bone. These methods are a first step toward facilitating the development of personalized exercise prescriptions for maintaining and improving bone health.
Electro Hydraulic Gas Exchange Valve Actuation of 4-Stroke Large Bore Diesel Engine
Authors: Herranen Mika , Huhtala Kalevi
Published: October 2014

After several years of study, a large bore diesel engine Electro-Hydraulic Valve Actuation (EHVA) system has reached a development point where the system has been successfully used for years in laboratory test engine environment too. During the evolution of the EHVA, insight of the hydraulic and control systems features has been cleared. This paper concludes main findings and results of EHVA research in Tampere University of Technology / IHA.

The hydraulic circuit effect to the power consumption of EHVA is clear. 3-way controlled actuator has advantages compared to 4-way controlled system. Direction control valve defines controllability of the system, and has source of the largest single component power loss. Hydraulic actuator design has also a fair effect to the overall power consumption when pressure force vs. required flow changes heavily, due to load forces. Mechanically, return spring design of the gas exchange valve has great effect to power consumption too.

Controller design is dependent on what kind of performance is required. The controller compensates lack of control valve bandwidth, and reacts to changing environmental variables. In this state, the Iterative Learning Controller (ILC) has proved the best choice. If gas exchange valve exact lift motion during the lift event is not important but variation between the strokes is kept in narrow range, a Model-Based Controller (MBC) is a strong option.
A Real Time Controlled Test Rig for High Bandwidth Force Control
Authors: Bertucci Alessandro , Mornacchi Andrea , Jacazio Giovanni , Sorli Massimo
Published: October 2014

This paper describes an electronically controlled active force control system developed to test the tail rotor actuator of a new medium size helicopter. As for all hydraulic force control systems, the critical control issue is to mitigate the disturbance generated by the actuator velocity. For this particular case, the problem was accrued by the high bandwidth of the tail rotor actuator. To define the optimum control algorithm a model based approach was followed, estimating, when unable to measure directly, mechanical and hydraulic model parameters with a dedicated experimental campaign. A controller was eventually developed able to cope with the severe dynamic disturbances by introducing velocity and acceleration compensation laws. The controller was then implemented in a high recursion rate real time machine interfacing with a servovalve controlling the flow to a hydraulic actuator provided with hydrostatic bearings to minimize the friction force. The actuator force was sensed by a load cell providing the feedback signal for the force servoloop. A critical feature of the control was the need to develop a dedicated complex filter for the velocity signal able to cancel out the signal noise while allowing to retain the correct real time information of the actuator velocity and maintain adequate stability margins.