Papers by Jeffrey Vipperman
Journal of Biomechanical …, 2008
Proportional, integral, and derivative (PID) controllers have proven to be robust in controlling ... more Proportional, integral, and derivative (PID) controllers have proven to be robust in controlling many applications, and remain the most widely used control system architecture. The purpose of this work was to use this architecture for designing and tuning two PID controllers. The first was used to control the physiologic arterial circumferential wall stress (CWS) and the second to control the physiologic arterial shear stress (SS) imposed on intact vascular segments that were implanted into an ex vivo vascular perfusion system (EVPS). In order to most accurately control the stresses imposed onto vascular segments perfused ex vivo, analytical models were derived to calculate the CWS and SS. The mid-vein-wall CWS was calculated using the classical Lame solution for thick-walled cylinders in combination with the intraluminal pressure and outer diameter measurements. Similarly, the SS was calculated using the Hagen-Poiseuille equation in combination with the flow rate and outer diameter measurements. Performance of each controller was assessed by calculating the root mean square of the error (RMSE) between the desired and measured process variables. The performance experiments were repeated ten times (N=10) and an average RMSE was reported for each controller. RMSE standard deviations were calculated to demonstrate the reproducibility of the results. Sterile methods were utilized for making blood gas and temperature measurements in order to maintain physiologic levels within the EVPS. Physiologic blood gases (pH, pO(2), and pCO(2)) and temperature within the EVPS were very stable and controlled manually. Blood gas and temperature levels were recorded hourly for several (N=9) 24 h perfusion experiments. RMSE values for CWS control (0.427+/-0.027 KPa) indicated that the system was able to generate a physiologic CWS wave form within 0.5% error of the peak desired CWS over each cardiac cycle. RMSE values for SS control (0.005+/-0.0007 dynescm(2)) indicated that the system was able to generate a physiologic SS wave form within 0.3% error of the peak desired SS over each cardiac cycle. Physiologic pH, pO(2), pCO(2), and temperature levels were precisely maintained within the EVPS. The built-in capabilities and overall performance of the EVPS described in this study provide us with a novel tool for measuring molecular responses of intact vascular segments exposed to precisely simulated arterial biomechanical conditions.
Journal of biomechanical …, 2009
Numerical algorithms for subspace system identification (N4SID) are a powerful tool for generatin... more Numerical algorithms for subspace system identification (N4SID) are a powerful tool for generating the state space (SS) representation of any system. The purpose of this work was to use N4SID to generate SS models of the flowrate and pressure generation within an ex vivo vascular perfusion system (EVPS). Accurate SS models were generated and converted to transfer functions (TFs) to be used for proportional integral and derivative (PID) controller design. By prescribing the pressure and flowrate inputs to the pumping components within the EVPS and measuring the resulting pressure and flowrate in the system,_four TFs were estimated;_two for a flowrate controller (H(RP,f) and H(RPP,f)) and two for a pressure controller (H(RP,p) and H(RPP,p)). In each controller,_one TF represents a roller pump (H(RP,f) and H(RP,p)),_and the other represents a roller pump and piston in series (H(RPP,f) and H(RPP,p)). Experiments to generate the four TFs were repeated five times (N=5) from which average TFs were calculated. The average model fits, computed as the percentage of the output variation (to_the_prescribed_inputs) reproduced by the model, were 94.93+/-1.05% for H(RP,p), 81.29+/-0.20% for H(RPP,p), 94.45+/-0.73% for H(RP,f), and 77.12+/-0.36% for H(RPP,f). The simulated step, impulse, and frequency responses indicate that the EVPS is a stable system and can respond to signals containing power of up to 70_Hz.
Advances in Bioengineering, 2004
ABSTRACT Failure of veins employed as arterial bypass grafts via intimal hyperplasia (IH) often o... more ABSTRACT Failure of veins employed as arterial bypass grafts via intimal hyperplasia (IH) often occurs within 5 years after implantation, requiring re-operation in 60% of all cases1 . IH is characterized by de-adhesion, followed by migration of medial and adventitial smooth muscle cells (SMCs) and myofibroblasts into the intima, where they demonstrate uncontrolled proliferation. It is thought that this process may be induced by the abrupt exposure of the veins to the dynamic mechanical environment of the arterial circulation2 . Veins are much thinner walled and more distensible than arteries. Therefore, the SMCs within the vein wall are exposed to significantly higher levels of stress and strain than they are accustomed2 . The tissue responds to this perceived injury by thickening, which is thought to be an attempt to return the stress and strain to venous levels. However, when this response is uncontrolled it can over-compensate, leading to stenosis instead of the desired thickening or “arterialization” of the vein segment. Cellular de-adhesion, which refers to a change from a state of stronger adherence to a state of weaker adherence, is involved in the earliest response and therefore was the focus of this study. While there are many important proteins involved in the regulation of cellular adhesion, we focus our attention here to matricellular proteins, which function as adaptors and modulators of cell-matrix interactions3,4 , and intracellular adhesion proteins, which have been shown to localize to cellular focal adhesion sites5,6 . Tenascin-C (TN-C), thrombospondin-1,2 (TSP), and secreted protein acidic and rich in cysteine (SPARC) are matricellular proteins that exhibit highly regulated expression during development and cellular injury7 . Mitogen inducible gene 2 (Mig-2) and integrin linked kinase (ILK) are intracellular proteins involved in cellular shape modulation5 and integrin-mediated signal transduction8 , respectively. It is well known that many intracellular and extracellular matrix proteins are regulated by mechanical stress9,10 . The purpose of this work was to explore the hypothesis that intact vein segments exposed to arterial hemodynamics will alter their expression of TN-C, TSP, SPARC, Mig-2 and ILK within 24 hours. This may induce a modulation of the level of cell adhesion, which could contribute to IH.
Journal of Vibration and Acoustics, 2006
... Jesse B. Bisnette, Adam K. Smith, Jeffrey S. Vipperman, Daniel D. Budny. Abstract. ... One re... more ... Jesse B. Bisnette, Adam K. Smith, Jeffrey S. Vipperman, Daniel D. Budny. Abstract. ... One recent report uses active electronics to tune a passive speaker, which serves as an acoustic absorber similar in action to a Helmholtz resonator . ...
Journal of Vibration and Acoustics, 1999
... Research Engineer, [email protected] Research Engineer Assistant Professor, Member AIAA §... more ... Research Engineer, [email protected] Research Engineer Assistant Professor, Member AIAA §Assistant Research Professor, Member AIAA Copyright c 1998 by the American Institute of Aeronau-tics and Astronautics, Inc. ... (1996), and Balas et al. (1995). ...
Applied Physics Letters, 2014
ABSTRACT Acoustic metamaterials have attracted much attention in recent years. Acoustic cloaks, w... more ABSTRACT Acoustic metamaterials have attracted much attention in recent years. Acoustic cloaks, which make objects invisible to acoustic waves, are the most common use for acoustic metamaterials. In this paper, acoustic cloaks with arbitrary shapes are presented based on transformation acoustics. This method interprets the compression and dilation of space as appropriate properties of materials. The derived properties of the cloak with irregular shapes are highly inhomogeneous and anisotropic, much more complex than the annulus cloaks. The materials for this kind of cloak are impossible to find in nature, and difficult to fabricate with artificial materials. In order to overcome this difficulty, layered structure with isotropic materials is adopted to approximate the required properties of the cloak. Numerical simulations of cloaks of arbitrary shape are performed to validate the design.
Journal of Vibration and Acoustics, 2003
ABSTRACT
Volume 14: Vibration, Acoustics and Wave Propagation, 2013
ABSTRACT The assumption of one dimensional acoustic propagation breaks down at very low frequenci... more ABSTRACT The assumption of one dimensional acoustic propagation breaks down at very low frequencies for large sized mufflers. Finite element analysis is the preferred method for predicting the performance of mufflers when three dimensional acoustics are present. In this study three performance metrics were measured in field tests, and then the results of the FEA simulations were compared to the field measurements. There were three muffler models considered in this study. For the purpose of protecting intellectual property they will be referred to as muffler models A, B, and C. A is the smallest muffler model, C is the largest, and B is the mid-size model.Good agreement is found between the field measurements and the FEA simulations. A method for increasing the accuracy of noise reduction and insertion loss predictions for realistic environments is also presented.
36th Structures, Structural Dynamics and Materials Conference, 1995
Adaptive Structures Forum, 1996
PLoS ONE, 2014
Human exposure to blast waves without any fragment impacts can still result in primary blast-indu... more Human exposure to blast waves without any fragment impacts can still result in primary blast-induced traumatic brain injury (bTBI). To investigate the mechanical response of human brain to primary blast waves and to identify the injury mechanisms of bTBI, a three-dimensional finite element head model consisting of the scalp, skull, cerebrospinal fluid, nasal cavity, and brain was developed from the imaging data set of a human female. The finite element head model was partially validated and was subjected to the blast waves of five blast intensities from the anterior, right lateral, and posterior directions at a stand-off distance of one meter from the detonation center. Simulation results show that the blast wave directly transmits into the head and causes a pressure wave propagating through the brain tissue. Intracranial pressure (ICP) is predicted to have the highest magnitude from a posterior blast wave in comparison with a blast wave from any of the other two directions with same blast intensity. The brain model predicts higher positive pressure at the site proximal to blast wave than that at the distal site. The intracranial pressure wave invariably travels into the posterior fossa and vertebral column, causing high pressures in these regions. The severities of cerebral contusions at different cerebral locations are estimated using an ICP based injury criterion. Von Mises stress prevails in the cortex with a much higher magnitude than in the internal parenchyma. According to an axonal injury criterion based on von Mises stress, axonal injury is not predicted to be a cause of primary brain injury from blasts.
Volume 9: Mechanical Systems and Control, Parts A, B, and C, 2007
ABSTRACT
ASME 2008 Summer Bioengineering Conference, Parts A and B, 2008
ABSTRACT Joint motion simulators (JMS’s) have been developed for many applications enabling the r... more ABSTRACT Joint motion simulators (JMS’s) have been developed for many applications enabling the repeatable testing of prostheses, scientific investigations of joint mechanics and the study of surgical procedures.[1–4] Although Morrey has reported that radial head implants have lower post-operative satisfaction than other joint implants[5] and Dunning has examined several issues with radial heads, many problems remain.[6] It is therefore beneficial to develop a simulator capable of evaluating radial head implants. A robust simulator can also provide the ability to test soft tissue strains at the elbow and compare control schemes that may elucidate the body’s means of controlling multiaxial multimuscle systems.
Volume 9: Mechanical Systems and Control, Parts A, B, and C, 2007
The many muscles crossing the elbow joint allow for its motions to be created from different comb... more The many muscles crossing the elbow joint allow for its motions to be created from different combinations of muscular activations. Muscles are strictly contractile elements and the joints they surround rely on varying loads from opposing antagonists for stability and movement. In designing ...
Journal of Medical Devices, 2009
The Allegheny General Hospital (AGH) elbow simulator was designed to be a closed-loop physiologic... more The Allegheny General Hospital (AGH) elbow simulator was designed to be a closed-loop physiologic simulator actuating movement in cadaveric elbow specimens via servoelectric motors that attach to the tendons of the biceps, brachialis, triceps, and pronator teres muscles. A physiologic ...
ASME 2007 Summer Bioengineering Conference, 2007
ABSTRACT Motion analysis is an important tool for biomechanical studies and its accuracy and reli... more ABSTRACT Motion analysis is an important tool for biomechanical studies and its accuracy and reliability for large-volume applications, such as gait labs, is well-established. Previous work has offered a comparison of commercially available systems.[1] No work to date has quantified the error in position of a given tracking marker caused by its removal from the view of one or more cameras, either by obstruction or by the data being removed during the image reconstruction process. This issue is critical to the tracking of extremely fine movements such as the travel of the radial head on the capitellum during elbow motion. Due to anatomical constraints, markers must frequently be placed a distance away from the body of interest and must be smaller than those conventionally used in gross motion analysis. The nature of the motion may not permit all cameras to view all markers all of the time. For example, a specimen may itself obstruct a camera’s view during certain motions.
Volume 2: Theory and Fundamental Research; Aerospace Heat Transfer; Gas Turbine Heat Transfer; Computational Heat Transfer, 2009
ABSTRACT
Volume 6: Emerging Technologies: Alternative Energy Systems; Energy Systems: Analysis, Thermodynamics and Sustainability, 2009
ABSTRACT
Volume 8: Energy Systems: Analysis, Thermodynamics and Sustainability; Sustainable Products and Processes, 2008
From the time mechanical refrigeration was first introduced, its use has significantly increased.... more From the time mechanical refrigeration was first introduced, its use has significantly increased. In general, cooling is achieved with vapor compression machines that use specific refrigerants (blends of hydrogen, carbon, fluorine and chlorine in various mixing ratios) that can be tailored to create cooling at any required temperature level. Each refrigerant exhibits a specific global warming potential and ozone depletion potential in the atmosphere by absorbing infrared radiation and breaking down of ozone molecules. Since the adverse effects of those substances have been discovered, the field of refrigeration has been moving away from conventional refrigerants, and searching for better alternatives. Thermoacoustic refrigeration is such an alternative that can provide cooling to essentially any required temperature level without using any environmentally harmful substances. It is presently a niche technology that can be expanded into a broader market, primarily if the sizing problem can be solved. Currently, the most efficient thermoacoustic refrigerators are used in industrial settings. This work explores the possibility of decreasing the footprint of these refrigerators by utilizing a coiled resonator. A CFD analysis has been developed and first results in regard to coiled resonators are shown and discussed.
Volume 9: Mechanical Systems and Control, Parts A, B, and C, 2007
ABSTRACT
Uploads
Papers by Jeffrey Vipperman