bluuebunny/crossref_metadata_2025 huggingface dataset:
Viscosity and Non‐Newtonian Features of Thickened Fluids Used for Dysphagia Therapy
Authors: O’Leary Mark , Hanson Ben , Smith Christina
Published: July 2010

Abstract:  Thickening agents based primarily on granulated maize starch are widely used in the care of patients with swallowing difficulties, increasing viscosity of consumed fluids. This slows bolus flow during swallowing, allowing airway protection to be more properly engaged. Thickened fluids have been shown to exhibit time‐varying behavior and are non‐Newtonian, complicating assessment of fluid thickness, potentially compromising efficacy of therapy. This work aimed to quantify the flow properties of fluids produced with commercial thickeners at shear rates representative of slow tipping in a beaker to fast swallowing. Results were presented as indices calculated using a power‐law model representing apparent viscosity (consistency index) and non‐Newtonian nature of flow (flow behavior index). Immediately following mixing, 3 fluid thicknesses showed distinct consistency indices and decreasing flow behavior index with increasing thickener concentration. An increase in consistency index over 30 min was observed, but only for samples that were repeatedly sheared during acquisition. Three‐hour measurements showed changes in consistency index across fluids with the largest being a 25% rise from initial value. This may have implications for efficacy of treatment, as fluids are not always consumed immediately upon mixing. Flow behavior indices were comparable across thickeners exhibiting similar rises over time. The indices were a more complete method of quantifying flow properties compared with single viscosity measurements, allowing an increased depth of analysis. The non‐Newtonian nature of fluids perhaps renders them particularly suitable for use as dysphagia therapies, and such analysis may allow the possibility of altering these properties to optimize therapeutic efficacy to be explored.

Practical Application: Effective treatment of swallowing disorders relies upon the appropriate choice and subsequent reproduction of drinks thickened to one of a number of predetermined levels. Currently there are no agreed methods of measuring the thickness of these drinks in use and the specifications are subjective, relying on descriptions such as “syrup” thick. This research aims to further understanding of the flow properties of thickened drinks and bring a quantified measure of thickness closer to being a practical reality.
Effects of Theabrownin from Pu‐erh Tea on the Metabolism of Serum Lipids in Rats: Mechanism of Action
Authors: Gong Jiashun , Peng Chunxiu , Chen Ting , Gao Bin , Zhou Hongjie
Published: July 2010

Abstract:  Theabrownin (TB), one of the main bioactive components in pu‐erh tea, has a significant blood lipid‐lowering effect in hyperlipidemic rats. Therefore, it was hypothesized that TB would regulate the activity of key enzymes involved in lipid metabolism and accelerate the catabolism of exogenous cholesterol in rats fed a high fat diet. A total of 90 Sprague–Dawley rats were randomly divided into a normal control group (Group I), a high fat diet group (Group II), and high‐fat diet plus TB group (Group III). A total of 10 rats were selected from each group and killed at 15, 30, or 45 d after starting the study for analysis. After feeding 45 d, the contents of TC, TG, and LDL‐C levels in Group II were increased by 54.9%, 93.1%, and 134.3% compared with those in Group III, respectively, and the content of HDL‐C in Group II was decreased by 55.7%. These effects were inhibited in the rats in Group III, which exhibited no significant differences in these levels compared with Group I, indicating that TB can prevent hyperlipidemia in rats fed a high fat diet. TB enhanced the activity of hepatic lipase and hormone‐sensitive triglyceride lipase (HSL) and increased the HSL mRNA expression in liver tissue and epididymis tissue. The HL activity in serum of Group III was increased by 147.6% compared with that in Group II. The content of cholesterol and bile acid in the feces of rats was increased by 21.11‐ and 4.08‐fold by TB. It suggested that TB could promote the transformation and excretion of dietary cholesterol of rats in vivo.
Characterization and Stability Analysis of Zinc Oxide Nanoencapsulated Conjugated Linoleic Acid
Authors: Choy Jin‐Ho , Shin Jiwon , Lim Seung‐Yong , Oh Jae‐Min , Oh Mi‐Hwa , Oh Sangsuk
Published: July 2010

Abstract:  Nanoencapsulation technology has a diverse range of applications, including drug‐delivery systems (DDS) and cosmetic and chemical carriers, because it can deliver various bio‐ and organic‐molecules and improve their stabilities. Conjugated linoleic acid (CLA) has health benefits, including being an anticancer agent, but it decreases flavor due to volatiles from oxidation. To improve the stability of CLA for food applications, nanoencapsulated CLA was synthesized for use in zinc basic salt (ZBS) and characterized by powder X‐ray diffractometry, thermogravimetric analysis (TGA), elemental CHN analysis, inductively coupled plasma (ICP) analysis, UV/VIS spectroscopy, and FTIR spectroscopy. The thermal stability of nanoencapsulated CLA at 180 °C, a temperature similar to that used in cooking, was analyzed by gas chromatography. The gallery height of nanoencapsulated CLA was determined to be approximately 26 Å through powder X‐ray diffractometry; therefore, the CLA molecules were closely packed with zig‐zag form between the intracrystalline spaces of nano particles. Elemental CHN analysis and ICP data determined the chemical composition of nanoencapsulated CLA to be Zn4.86(OH)8.78(CLA)0.94. By TGA, it was determined about 45% (wt/wt) of weight loss corresponded to CLA, which is good agreement with the 42.13% (wt/wt) determined from high‐performance liquid chromatography (HPLC) and elemental CHN analysis. UV/VIS spectroscopy and Fourier‐transformed infrared (FTIR) spectroscopy showed encapsulated CLA maintained a conjugated diene structure, supporting the presence of CLA. Nanoencapsulation improved the thermal stability of CLA by about 25%, compared to pristine CLA.

Practical Application: This system can be used for protection of encapsulated negatively‐charged food ingredients from thermal processing.
Characterization of Biogenic Amines and Factors Influencing Their Formation in Traditional Chinese Sausages
Authors: Lu Shiling , Xu Xinglian , Shu Ruihua , Zhou Guanghong , Meng Yong , Sun Yongming , Chen Yanping , Wang Peng
Published: July 2010

Abstract:  Biogenic amines in 42 traditional Chinese sausage samples obtained from different regions were determined by HPLC. The result showed that cadaverine was the major amine, followed by tyramine and putrescine. A total of 4 groups of samples were identified on the basis of total amines by cluster analysis. Group A included samples showing low amine contents (76.5 to 220 mg/kg) and accounted for 28.5% of the sausages examined. Group B included samples with moderate amine contents (220 to 600 mg/kg) and accounted for 45.2%. Group C included 11.9% of the samples showing high total biogenic amines contents (600 to 1000 mg/kg) and group D contained 14.28% of the samples showing very high levels of biogenic amines (higher than 1000 mg/kg). High correlation coefficients were found between the total counts of Enterobacteria and concentrations of total biogenic amines (r = 0.73). Sanitary quality of raw materials and the specific flora are import factors influencing biogenic amines formation in traditional Chinese sausages.

Practical Application: Biogenic amines are considered potentially harmful substances to human health worldwide and are usually found in fermented sausage.Traditional Chinese sausage is one form of spontaneously fermented sausage and manufactured in small‐scale plants following spontaneous fermentation. Little information, however, exists on the traditional Chinese sausage.
Sibling Relationships During the Transition to Adulthood
Authors: Conger Katherine Jewsbury , Little Wendy M.
Published: July 2010

Abstract— Recent research has shed new light on individual development during the early adulthood years, yet few investigators have examined sibling relationships during this stage of life. These relationships undergo transformations as individuals enter adult roles and orient their lives toward friends and romantic partners and establish independence from parents and siblings. This article examines major life events and role transitions, such as leaving home, completing school, obtaining employment, getting married, and having children, that influence individuals and their sibling relationships. In addition, it considers how sibling relationships may affect individuals during the transition to adulthood and calls attention to the importance of family and cultural contexts in shaping these relationships. The article concludes with suggestions for future research on sibling relationships during early adulthood and beyond.
Sex Differences in Attachment Emerge in Middle Childhood: An Evolutionary Hypothesis
Authors: Del Giudice Marco , Belsky Jay
Published: July 2010

Abstract— J. Bowlby’s (1969/1982) theory of attachment, focused as it was on the survival function of attachment behaviors that the ethology of the time emphasized, led to the expectation that there would be no sex differences in patterns of attachment. Modern evolutionary thinking, however, building on insights of life history theory, parental investment theory, and sexual selection, yields an alternative prediction—that adaptive sex differences in attachment should emerge in middle childhood and be present in adults, consistent with sexual differentiation of reproductive strategies. This article reviews the theoretical basis of this expectation, including the recent proposal that a hormonally driven reorganization of attachment occurs at the beginning of middle childhood. Available data and various methodological issues involved in empirically testing the proposed model are discussed. It argues that life history theory offers a powerful organizing principle for understanding the emergence of individual differences, providing developmental researchers with exciting opportunities for empirical discovery and theoretical synthesis.
Learning to Eat in an Obesogenic Environment: A Developmental Systems Perspective on Childhood Obesity
Authors: Birch Leann L. , Anzman Stephanie L.
Published: July 2010

Abstract— Currently, children are developing in an obesity‐promoting, or obesogenic, environment, which has emerged within the past 3 decades. This rapid change provides a rare opportunity to investigate the phenotypic outcomes that result from the expression of human genetic predispositions in a new environment. Unfortunately, the environmental changes that have occurred are associated with epidemic obesity rates in all age groups. Using a developmental perspective, this article argues that this probabilistic outcome is not predetermined, however. The article also provides examples of learning paradigms—familiarization and associative and observational learning—that present opportunities for parents and caregivers to restructure children’s environments in early life, increasing the likelihood of healthy weight‐status outcomes in the context of the current obesogenic environment.
From Poverty to Food Insecurity and Child Overweight: A Family Stress Approach
Authors: McCurdy Karen , Gorman Kathleen S. , Metallinos‐Katsaras Elizabeth
Published: July 2010

Abstract—Food insecurity and child overweight represent major public health problems in the United States, especially for children living in poverty. Recent research has greatly expanded our knowledge regarding the antecedents of these health concerns, yet the causal mechanisms connecting poverty to food insecurity and to child overweight remain unclear. This article reviews the research through the perspective of family stress theory and proposes a developmental model to explain how poverty and its related economic stress affect specific parental resources and behaviors that, in turn, may account for food insecurity and overweight in young children. It proposes maternal depression and family food behaviors—such as the acquisition, provision, and distribution of food in the household—as key mediators linking poverty to food insecurity and child overweight.
Frequency Response Characteristics of Parametrically Excited System
Authors: Han Qinkai , Wang Jianjun , Li Qihan
Published: July 2010

The frequency response characteristic of a general time-invariant system has been extensively analyzed in literature. However, it has not gained sufficient attentions in the parametrically excited system. In fact, due to the parametric excitation, the frequency response of time-periodic system differs distinctly from that of the time-invariant system. Utilizing Sylvester’s theorem and Fourier series expansion method, commonly used in the spectral decomposition for matrix, the frequency response functions (FRFs) of a single-degree-of-freedom (SDOF) parametrically excited system are derived briefly in the paper. The external resonant condition for the system is obtained by analyzing the specific expressions of FRFs. Then, a spur-gear-pair with periodically time-varying mesh stiffness is selected as an example to simulate the frequency response characteristics of parametric system. The effects of parametric stability, periodic mesh stiffness parameters (mesh frequency and contact ratio), and damping are considered in the simulation. It is shown from both theoretical and simulation results that the frequency response of parametric system has the following properties: there are multiple FRFs even for a SDOF periodic system as the forced response contains many frequency components and each FRF is corresponding to a certain response spectrum; the system has multiple external resonances. Besides the resonance caused by the external driving frequency equals to the natural frequency, the system will also be external resonant if external frequency meets the combination of natural frequency and parametric frequency. When the system is in external resonant state, the dominant frequency component in the response is the natural frequency; damping makes the peak values of FRFs drop evidently while it has almost no impact on the FRFs in nonresonant regions.
Vibration Analysis of Composite Beams With End Effects via the Formal Asymptotic Method
Authors: Kim Jun-Sik , Wang K. W.
Published: July 2010

Vibration analysis of composite beams is carried out by using a finite element-based formal asymptotic expansion method. The formulation begins with three-dimensional (3D) equilibrium equations in which cross-sectional coordinates are scaled by the characteristic length of the beam. Microscopic two-dimensional and macroscopic one-dimensional (1D) equations obtained via the asymptotic expansion method are discretized by applying a conventional finite element method. Boundary conditions associated with macroscopic 1D equations are considered to investigate the end effect. It is then described how one could form and solve the eigenvalue problems derived from the asymptotic method beyond the classical approximation. The results obtained are compared with those of 3D finite element method and those available in the literature for composite beams with solid cross section and thin-walled cross section.
Structure-Borne Sound Characterization of Coupled Structures—Part II: Feasibility Study
Authors: Pavić Goran , Elliott Andrew S.
Published: July 2010

A novel method has been outlined in the first part of this paper aimed at characterization of structure-borne sound transmission from a vibration source coupled via resilient mounts to a receiver. It can deliver the source mobility and its free velocity, together with the mobility of the receiver to which the source is connected, without decoupling the two structures. The only condition which has to be fulfilled is the conservation of coupling forces and moments across the mounts. In this part of the paper the method is examined from the feasibility point of view. A benchmark test is used as a validation reference for the method, where the properties of the resilient mounts are required and are assumed as known but not completely certain. The feasibility of the principal method is tested by virtual experiment involving two built-up plates resiliently connected at several points. The comparison of the benchmark and the principal method is used to illustrate the benefits of the latter given a small error in the supposedly known mount properties.
Simulations and Experiments of a Nonlinear Aircraft Braking System With Physical Dispersion
Authors: Chevillot Fabrice , Sinou Jean-Jacques , Hardouin Nicolas , Jezequel Louis
Published: July 2010

This paper deals with the simulation of nonlinear vibration induced by friction in an aircraft braking system. Experimental tests reveal that in similar experimental conditions the mechanism can generate vibrations of various amplitudes. The aim of this study is to simulate the behavior of the brake by taking into account the dispersion of parameters, which produce the variability of the response. A nonlinear model of the brake is presented. The time-history response is obtained by integration of the full set of nonlinear dynamic equations. Based on experimental results, the dispersions of the coefficient of friction and of the damping configuration are introduced. Monte Carlo simulations are performed and show a very good agreement with the experimental results.
An Active Acoustic Metamaterial With Tunable Effective Density
Authors: Baz Amr M.
Published: July 2010

Extensive efforts are being exerted to develop various types of acoustic metamaterials to effectively control the flow of acoustical energy through these materials. However, all these efforts are focused on passive metamaterials with fixed material properties. In this paper, the emphasis is placed on the development of a class of one-dimensional acoustic metamaterials with tunable effective densities in an attempt to enable the adaptation to varying external environment. More importantly, the active metamaterials can be tailored to have increasing or decreasing variation of the material properties along and across the material volume. With such unique capabilities, physically realizable acoustic cloaks can be achieved and objects treated with these active metamaterials can become acoustically invisible. The theoretical analysis of this class of active acoustic metamaterials is presented and the theoretical predictions are determined for an array of fluid cavities separated by piezoelectric boundaries. These boundaries control the stiffness of the individual cavity and in turn its dynamical density. Various control strategies are considered to achieve different spectral and spatial control of the density of this class of acoustic metamaterials. A natural extension of this work is to include active control capabilities to tailor the bulk modulus distribution of the metamaterial in order to build practical configurations of acoustic cloaks.
Effect of Pasternak Foundation on Axisymmetric Vibration of Polar Orthotropic Annular Plates of Varying Thickness
Authors: Sharma Seema , Gupta U. S. , Lal R.
Published: July 2010

Free axisymmetric vibrations of polar orthotropic annular plates of variable thickness resting on a Pasternak-type elastic foundation have been studied based on the classical plate theory. Hamilton’s energy principle has been used to derive the governing differential equation of motion. Frequency equations for an annular plate for two different combinations of edge conditions have been obtained employing Chebyshev collocation technique. Numerical results thus obtained have been presented in the form of tables and graphs. The effect of foundation parameter and thickness variation together with various plate parameters such as rigidity ratio, radius ratio, and taper parameter on natural frequencies has been investigated for the first three modes of vibration. Mode shapes for specified plates have been presented. A close agreement of results with those available in the literature shows the versatility of the present technique.
Transient Behavior of Crossflow Heat Exchangers Due To Sinusoidal Excitation
Authors: Mishra Manish , Das P. K. , Sarangi Sunil
Published: July 2010

Transient temperature response of crossflow heat exchangers with both fluids unmixed and finite wall capacitance is investigated numerically for sinusoidal excitation provided in hot fluid inlet temperature. The effect of two-dimensional longitudinal conduction in separating sheet and the axial dispersion in fluids has also been considered on the thermal performance of the heat exchanger. The present method has good accuracy and simplicity. An attempt has also been made to study the performance of the sinusoidal excitation in the graphical form.
Transient Thermal Analyses of Midwall Cooling and External Cooling Methods for a Gun Barrel
Authors: Mishra Avanish , Hameed Amer , Lawton Bryan
Published: July 2010

Liquid cooling methods are often used for thermal management of a large caliber gun barrel. In this work, transient thermal analyses of midwall-cooled and externally cooled gun barrels were performed. At first, a novel simulation scheme was developed for the computation of the gun barrel temperature history (temperature variation over time), and its experimental validation was performed. In the computational scheme an internal ballistics code, GUNTEMP8.EXE, was developed to simulate the total heat transfer per cycle for the given ammunition parameters. Subsequently, a finite element (FE) model of the barrel was developed in ANSYS 11.0. Heat transfer to the barrel was approximated by an exponentially decaying heat flux. The FE model was solved to compute for barrel temperature history. Simulations were performed for a burst of 9 cycles, and the results were found to agree with the experimental measurements. Subsequently, the simulation scheme was extended to analyze a burst of 40 cycles at 10 shots per minute (spm). Three cases were investigated as follows: (1) a naturally cooled gun barrel, (2) a gun barrel with midwall cooling channels, and (3) an externally cooled gun barrel. Natural cooling was found insufficient to prevent cook-off, whereas midwall and external cooling methods were found to eliminate any possibility of it. In the context of a self-propelled howitzer, a midwall-cooled gun barrel connected to an engine cooling system was also analyzed.
Experimental Study on Heat Transfer and Pressure Drop of Recuperative Heat Exchangers Using Carbon Foam
Authors: Lin Y. R. , Du J. H. , Wu W. , Chow L. C. , Notardonato W.
Published: July 2010

This work focuses on the development of high-effectiveness recuperative heat exchangers using solid and corrugated carbon foam blocks. Characterization tests were conducted on heat transfer and pressure drop for a single carbon foam block with different sizes. Results show that carbon foam can be an effective medium for heat transfer enhancement, and a short length in the flow direction yields a high heat transfer coefficient. The corrugation can enhance heat transfer and reduce pressure drop at the same time. A recuperative heat exchanger with carbon foam, which consists of separate blocks of carbon foams packed between thin sheets of stainless steel, was designed. The hot and cold flow paths were arranged in counterflow in the recuperator. The heat exchanger was designed in a modular manner so that it can be scaled up for a larger heat transfer requirement or a higher overall effectiveness. The anisotropic property of carbon foam was exploited to achieve higher effectiveness for one pair of foam blocks. Experiments with four pairs of carbon foams were conducted to evaluate the performance of carbon foam used in the recuperative heat exchanger. Measurements were made for both solid and corrugated foams for comparison. With four pairs of carbon foam blocks, an overall effectiveness εtotal greater than 80% was achieved. This paper demonstrates an approach to reach an effectiveness εtotal of 98% by placing many pairs of carbon foams in series.
A Novel Approach to Low Profile Heat Sink Design
Authors: Stafford Jason , Walsh Ed , Egan Vanessa , Walsh Pat , Muzychka Yuri S.
Published: July 2010

This paper discusses the importance of developing cooling solutions for low profile devices. This is addressed with an experimental and theoretical study on forced convection cooling solution designs that could be implemented into such devices. Conventional finned and corresponding finless designs of equal exterior dimensions are considered for three different heat sink profiles ranging from 1 mm to 4 mm in combination with a commercially available radial blower. The results show that forced convection heat transfer rates can be enhanced by up to 55% using finless designs at low profiles with relatively small footprint areas. Overall, this paper provides optimization and geometry selection criteria, which are relevant to designers of low profile cooling solutions.
Experimental and Numerical Investigation of Heat Transfer Characteristics of Inline and Staggered Arrays of Impinging Jets
Authors: Xing Yunfei , Spring Sebastian , Weigand Bernhard
Published: July 2010

A combined experimental and numerical investigation of the heat transfer characteristics within an array of impinging jets has been conducted. The experiments were carried out in a perspex model using a transient liquid crystal method. Local jet temperatures were measured at several positions on the impingement plate to account for an exact evaluation of the heat transfer coefficient. The effects of the variation in different impingement patterns, jet-to-plate spacing, crossflow schemes, and jet Reynolds number on the distribution of the local Nusselt number and the related pressure loss were investigated experimentally. In addition to the measurements, a numerical investigation was conducted. The motivation was to evaluate whether computational fluid dynamics (CFD) can be used as an engineering design tool in the optimization of multijet impingement configurations. This required, as a first step, a validation of the numerical results. For the present configuration, this was achieved assessing the degree of accuracy to which the measured heat transfer rates could be computed. The overall agreement was very good and even local heat transfer coefficients were predicted at high accuracy. The numerical investigation showed that state-of-the-art CFD codes can be used as suitable means in the thermal design process of such configurations.
Harvesting Nanoscale Thermal Radiation Using Pyroelectric Materials
Authors: Fang Jin , Frederich Hugo , Pilon Laurent
Published: July 2010

Pyroelectric energy conversion offers a way to convert waste heat directly into electricity. It makes use of the pyroelectric effect to create a flow of charge to or from the surface of a material as a result of heating or cooling. However, an existing pyroelectric energy converter can only operate at low frequencies due to a relatively small convective heat transfer rate between the pyroelectric materials and the working fluid. On the other hand, energy transfer by thermal radiation between two semi-infinite solids is nearly instantaneous and can be enhanced by several orders of magnitude from the conventional Stefan–Boltzmann law as the gap separating them becomes smaller than Wien’s displacement wavelength. This paper explores a novel way to harvest waste heat by combining pyroelectric energy conversion and nanoscale thermal radiation. A new device was investigated numerically by accurately modeling nanoscale radiative heat transfer between a pyroelectric element and hot and cold plates. Silica absorbing layers on top of every surface were used to further increase the net radiative heat fluxes. Temperature oscillations with time and performances of the pyroelectric converter were predicted at various frequencies. The device using 60/40 porous poly(vinylidene fluoride–trifluoroethylene) achieved a 0.2% efficiency and a 0.84 mW/cm2 electrical power output for the cold and hot sources at 273 K and 388 K, respectively. Better performances could be achieved with 0.9Pb(Mg1/3Nb2/3)–0.1PbTiO3 (0.9PMN-PT), namely, an efficiency of 1.3% and a power output of 6.5 mW/cm2 between the cold and hot sources at 283 K and 383 K, respectively. These results are compared with alternative technologies, and suggestions are made to further improve the device.
Nanofluid Convection in Microtubes
Authors: Lee Joohyun , Gharagozloo Patricia E. , Kolade Babajide , Eaton John K. , Goodson Kenneth E.
Published: July 2010

While there has been much previous research on the thermal conductivity and convection performance of nanofluids, these data are rarely reported together with effective viscosity data that govern the relevance for heat exchanger applications. We report here the effective convection coefficient and viscosity in microtubes (D=0.5 mm) along with stationary thermal conductivity measurements for nanofluids based on spherical particles (Al2O3, ZnO, and CuO) and carbon nanotubes. Sample data include an effective convection coefficient increase of 5% for 3 vol %Al2O3/DI water nanofluid, 13.3% for 4 vol % CuO/DI water nanofluid, and 11.6% for 0.2 vol % Carbon nanotube(CNT)/DI water nanofluid. When considered together with our viscosity measurement on the same fluids, we find that the only the CNT-based nanofluids are promising for microfluidic heat exchangers.
The Analyses of Dynamic Stability at Milling Machine Tools
Authors: Pop Petru A.
Published: July 2010

The paper has presented a study about dynamic stability of universal precision milling machine, using four side-milling cutters. These cutters with three edges and inserts have different geometrical parameters, constant and variable pitch angle. For study of milling cutting process has used a dynamic installation, ensured the acquisition of vibrations and cutting forces from three axes of milling machine. The installation is making by milling machine (FUS 22-modified), dynamometer with 16 strain gages, electronic bridge circuit, accelerometer and computer. The calculus and interpretation of dynamic tests have done by MATLAB Program, being recorded approx. 500 tests. For each side milling cutter has plotted stability diagrams, which established the dynamic performances of milling machine and given the solutions of improving process. The side-milling cutters with variable pitch angle had enhancement the dynamic stability of milling process, by suppressing the amplitude of vibrations and cutting forces.
Bifurcation and Stability of the Periodic Motion of a Rotor Bearing System With Pedestal Looseness and Rub-Impact
Authors: Liu Changli , Zhang Xiuli , Cui Li , Xie Pengru , Zheng Jianrong
Published: July 2010

A rotor bearing system usually has various faults that could simultaneously exist (e.g., rub-impact, pedestal looseness etc), but, in the past, individual fault has been mostly modeled and analyzed separately. In this paper, the dynamic model of rotor bearing system with rub-impact and pedestal looseness is formulated. Continuation-shooting method for the periodic solution of nonlinear non-autonomous system is used to obtain the bifurcation and stability of the periodic motion of the rotor-bearing system. The effect of the unbalance and rotor/stator clearance on the bifurcation and stability of the periodic motion of the rotor bearing system are analyzed respectively. It has been observed that the periodic motion of the system lose stability by Hopf and doubling bifurcation respectively under the small and large unbalance; the system with coupling faults has the same way of losing stability as the system with rub-impact only. The Hopf bifurcation set is broadened with the rotor/stator clearance decreases. The results of the paper may provide theory references to fault diagnoses, vibration control and security operating of the rotor system.
The Use of Interference Diagrams to Avoid Impeller Resonance: An Application to IGV Design
Authors: Ferioli Marco
Published: July 2010

Interference diagrams can be used to avoid the potential excitation of a particular mode of vibration for centrifugal compressor impellers, thus reducing the risk of fatigue failures. Such diagrams are an excellent tool to combine information on impeller natural frequencies and mode shapes, excitation sources and operating speed of the machine on the same graph. Once the impeller design has been finalized in terms of aerodynamic performance, structural assessments and therefore geometry, Finite Element Analysis can be used to predict its natural frequencies and mode shapes (i.e. nodal diameters). Results can therefore be shown on a chart, together with the operating speed range of the machine. The need to plot on a single diagram this whole set of data arises from the mathematical evidence to consider the frequency of vibration together with the mode shape and the shape of the exciting force, while analyzing resonances. Typical Campbell diagrams are unable to provide this information at a glance. A common source of excitation for the first impeller of centrifugal compressors is the IGV set. Inlet Guide Vanes produce an exciting frequency that is directly proportional to the number of vanes N, where N represents also the shape of the excitation. The interference diagram can therefore be used: • to design and optimize the IGV for a new machine; • to choose between two different designs; • to evaluate the impact of a new IGV for the impeller of an existing compressor. A case study will be introduced, in order to show the application of interference diagrams to avoid potentially dangerous resonances between an IGV set and the first impeller during the re-design phase for a centrifugal compressor already in operation.
Thermal Effects on Geometrically Nonlinear Vibrations of Rectangular Plates With Fixed Ends
Authors: Amabili M. , Carra S.
Published: July 2010

Large-amplitude vibrations of rectangular plates subjected to harmonic excitation and thermal loads are investigated. The von Ka´rma´n nonlinear strain-displacement relationships are used to describe the geometric nonlinearity and the effect of thermal loads are included. Calculations are performed for a AISI 304 stainless-steel thin plate which has been tested experimentally. The plate is fixed to a AISI 410 stainless-steel frame which has a different coefficient of thermal expansion. Both calculations and experiments show a very large effect of temperature changes of the order of one degree Celsius on the nonlinear results.
Computer Modeling of Impressed Current Cathodic Protection (ICCP) System Anodes
Authors: Peratta Cristina , Peratta Andres , Baynham John , Adey Robert
Published: July 2010

Computer modeling is now widely used to predict how effective cathodic protection (CP) systems are at protecting structures and maritime vessels. There are two types of CP systems based on either sacrificial anodes or impressed anodes (ICCP) or some combination of the two types. Impressed anodes are often referred to as “active” systems as they can respond to changes in the protection requirements as they are connected to some form of control system. Typically in computer models ICCP anodes are controlled by specifying the current they output in response to the potential measured at a reference electrode. In this paper an alternative approach has been investigated where the model also includes the power supply as well as the associated cables etc connecting to the anodes. This enables us to more accurately model situations where any number of anodes are connected to a single power supply, anode/reference electrode (RE) failure scenarios, non symmetric anode layouts, localized damage to coatings and situations where there are significant appendages to the vessel which change the current requirements. The paper will describe the technical approach to the modeling and present examples of modeling of a commercial FPSO vessel. (Floating, Production, Storage and Offloading vessels are used in the Oil & Gas industry typically as part of deepwater developments) The benefits of the proposed approach compared with the conventional approach will be presented and the results critically analyzed.
Hybrid Control Scheme of Coordinated Motion and Active Vibration Suppression for Free-Floating Space Flexible Manipulator With Parameter Uncertainty
Authors: Hong Zhaobin , Li Chen
Published: July 2010

The dynamic control and vibration suppression problems of free-floating space flexible manipulator are studied. The Variable Structure Control (VSC) law alone, which is designed to track the desired trajectories of base’s attitude and joint angles, does not guarantee the stability of the flexible mode dynamics of the flexible link. In order to actively suppress the flexible vibration, a hybrid trajectory for the VSC is generated using the virtual control force concept. Based on the hybrid trajectory, the hybrid control scheme is proposed to eliminate the flexible vibration while the robustness of VSC developed for coordinated motion is maintained. In particular, it doesn’t require measuring the position, velocity nor acceleration of the base in the controller design. Simulation result confirms that the proposed hybrid control scheme can dominates the trajectory tracking of coordinated motion and actively suppress the vibration in the presence of parameter uncertainty.
Influence of Modal Coupling on the Nonlinear Dynamics of Augusti’s Model
Authors: Gonc¸alves Paulo B. , Orlando Diego , Rega Giuseppe , Lenci Stefano
Published: July 2010

The non-linear behavior and stability under static and dynamic loads of an inverted spatial pendulum with rotational springs in two perpendicular planes, called Augusti’s model, is analyzed in this paper. This 2DOF lumped-parameter system is an archetypal model of modal interaction in stability theory representing a large class of structural problems. When the system displays coincident buckling loads, several post-buckling paths emerge from the bifurcation point (critical load) along the fundamental path. This leads to a complex potential energy surface. Herein, we aim to investigate the influence of nonlinear modal interactions on the dynamic behavior of Augusti’s model. Coupled/uncoupled dynamic responses, bifurcations, escape from the pre-buckling potential well, stability and space–time-varying displacements, attractor-manifold-basin phase portraits are numerically evaluated with the aim of enlightening the system complex response. The investigation of basins evolution due to variation of system parameters leads to the determination of erosion profiles and integrity measures which enlighten the loss of safety of the structure due to penetration of eroding fractal tongues into the safe basin.
Computational Prediction of Electric Fields in Shallow Water Testing Environment
Authors: Wimmer Stephanie A. , DeGiorgi Virginia G. , Hogan Elizabeth A.
Published: July 2010

There has been an increased need for understanding of how ship’s cathodic protection systems work in shallow water environment. This is a result of the evolving role of the US Navy. The existing cathodic protection system design process relies on experimental processes. This paper investigates a proposed modification to a deep water experimental facility to allow for measurements of electrical fields, a pertinent design measurement, in shallow water conditions. The modifications involve the insertion of a false bottom in the existing deep water tank. The work presented here are a series of computational studies that establish that the insertion of a false bottom would provide an electric field environment that is equivalent to shallow water for the depths considered.
General Steady Turning of a Benchmark Bicycle Model
Authors: Peterson Dale L. , Hubbard Mont
Published: July 2010

We analyze general steady turns of a benchmark bicycle model in the case of nonzero applied steer torque. In a general steady turn, the lean and steer angles are constant, the velocity of the bicycle must ensure moment balance about the contact line, and some torque must be applied to maintain the constant steer angle. We identify two boundaries in lean–steer plane: first, the region of kinematic feasibility, and second, the region where steady turns are feasible. In the region of feasible steady turns, we present level curves of these steady turning velocities and steer torques. Additionally, we present level curves of mechanical trail in the lean–steer plane.
Energy Losses of Impacts With Friction
Authors: Pfeiffer Friedrich
Published: July 2010

Many machine and mechanism processes are accompanied by impacts with friction. They arise by short-time contacts between two or more bodies, and they generate energy losses mainly due to friction in tangential contact directions. During the last two decades a couple of impact models based on the theory of rigid body contact were established connected with the names of Moreau, Fremond and Glocker, which all work quite satifactorily with respect to practical applications, although some examples indicate deviations requiring more investigations with respect to the impact models and the type of examples considered. We shall focus on Glocker’s model, for which some experimental verifications are available by Beitelschmidt. A missing link are energy considerations, which are available, but nevertheless do not provide us with a complete information for all possible cases. The paper tries to fill a bit this gap by founding the investigations on a combined phenomenological and theoretical basis.
Effect of Weight on the Experimental Modal Analysis of Slender Cantilever Beams
Authors: Virgin Lawrence , Holland David
Published: July 2010

It is relatively well known that axial loads tend to influence lateral stiffness and hence natural frequencies of slender structural components. Tensile forces tend to increase the lateral stiffness and compressive forces tend to reduce lateral stiffness, bringing with it the possibility of buckling. In many practical situations this is a negligible effect. But for very slender structures it can be important, including the effect of self-weight. This paper will focus attention on a form of double cantilever beam system, i.e., two cantilevers sharing a common hub. A differential axial load can be applied to this system via orientation in a gravitational field. We shall neglect the effect of gravity when the beams are in their horizontal orientation from a limited theoretical standpoint. It is of course present in the experiments but the cantilevers are much stiffer in one direction than the other, and the beams are clamped with their stiffer resistance in the vertical direction. The focus of the current paper is on the natural frequencies and mode shapes of a two-beam system from an experimental modal analysis perspective.
Multibody System for Virtual Prototyping
Authors: Chang Kevin , Johnson Christopher
Published: July 2010

The Ground Systems (GS) business unit of BAE Systems Inc. develops and manufactures major ground combat vehicles for military. Because the development of ground-based combat vehicles is a complex process, it requires the coordinated effort of multiple engineering disciplines that include human factor engineering (HFE), product design, as well as modeling and simulation (M&S), to perform design analysis and to predict vehicle performance. In order to increase engineering efficiency and to reduce product development costs, GS has developed a virtual prototyping technology. Using this technology, it enables GS to perform vehicle design and requirement validation in a virtual environment prior to expensive and time consuming hardware prototyping. This technology also enables GS customers to be more involved in the product development cycle and makes the product development process more customer-centric. The development of this virtual environment requires integration of various technologies, including multibody dynamics, 3D computer graphics, networking, modeling and simulation, and the human-machine interface design. This paper describes how multibody system simulations are used in this virtual environment to support GS vehicle design in the areas of crew visibility studies, crew station design, vehicle interference checking, and electrical power management simulation.
Development and Validation of Geometry-Based Compliant Contact Models
Authors: Luo Lianzhen , Nahon Meyer
Published: July 2010

Simulations are often used to evaluate space manipulator tasks that involve contact with the environment. In this paper, we present two compliant contact models for polyhedral contacting objects. These models explicitly consider the distinction between true contact geometry and interference geometry. To account for the energy dissipated during impact, a damping force is included in the two models. Model validation is then performed in three ways: against analytical models, against experimental data, and against FEM models.
Optimized Simulation Method and Experimental Verification on Dynamic Analysis of a Light Truck Frame
Authors: Gao Feng , Xiong Yonghua , Tian Lei , Du Farong , Xu Guoyan
Published: July 2010

The three-dimensional geometric model of the fringe-beam frame had been built based on the frame structure of a light truck. In order to optimize the frame structure, the finite element model of the frame and the suspension system were set up. Considering the influence of suspension on frame dynamic performance, the modal properties of the frame model was analyzed in the commercial analysis program ANSYS, using two different methods. Based on the experiments, it was verified that combining MPC184 elements and spring elements Combin14 is a better way to simulate suspension compared to using spring finite elements only. Furthermore, the combined simulation results coincide with experimental modal analysis results, which were conducted thereafter. Subsequently, the frame stress-strain distribution rules and dynamics response were calculated under the random road spectrum excitation, and the frame dynamic parameters were obtained. This study provides some theoretical bases for frame structure improvement, and proposes an optimum method to simulate suspension. The results have direct significance in ensuring the stability, comfort and reliability of a light truck frame.
Dynamics of Coupled Bubble Oscillators With Delay
Authors: Rand Richard H. , Heckman Christoffer R.
Published: July 2010

We investigate the stability of the in-phase mode in a system of two delay-coupled bubble oscillators. The bubble oscillator model is based on a 1956 paper by Keller and Kolodner. Delay coupling is due to the time it takes for a signal to travel from one bubble to another through the liquid medium that surrounds them. Using techniques from the theory of delay-differential equations as well as the method of averaging, we show that the equilibrium of the in-phase mode can be made unstable if the delay is long enough and if the coupling strength is large enough, resulting in a Hopf bifurcation. This work is motivated by medical applications involving noninvasive localized drug delivery via microbubbles.
Ellipsoidal Approximations of Invariant Sets in Stabilization Problem for a Wheeled Robot Following a Curvilinear Path
Authors: Pesterev Alexander V. , Rapoport Lev B.
Published: July 2010

A stabilization problem for a wheeled robot following a curvilinear target path is studied. In [1], a method for constructing invariant ellipsoids—quadratic approximations of the attraction domains for the target trajectory under a given control law—was developed. A basic result of that study is a theorem by means of which construction of the invariant ellipsoids reduces to solving a system of linear matrix inequalities (LMIs) and checking a scalar inequality. This paper is a sequel to work [1] and is devoted to practical implementation of the results obtained in that paper. It is discussed how to select the parameters in terms of which the theorem is formulated. An algorithm is developed that, for a given value of maximal deviation from the target trajectory, constructs an invariant ellipsoid of as large volume as possible.