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Flexible Structure (flexible + structure)
Selected AbstractsAn educational tool for power electronics circuitsCOMPUTER APPLICATIONS IN ENGINEERING EDUCATION, Issue 1 2010Cetin Elmas Abstract In this study, an educational tool has been prepared for a shorter term and more economic education of power electronics circuits. In parallel with the improvements of semiconductor technology, the development of power electronics circuits has magnified the importance of either teorical or practical education of power electronics course. The education of power electronic circuits in laboratory is an agelong, costly piece of work. In this study, to overcome the mentioned negativities, a tool has been prepared for the education of power electronic circuits. The tool, which has been prepared on C++ Builder environment has a flexible structure and a graphical interface. It has enabled the analysis of working principles of the circuits and traceability of the system response by the help of graphics, under different conditions created by changing the values of circuit elements. © 2009 Wiley Periodicals, Inc. Comput Appl Eng Educ 18: 157,165, 2010; Published online in Wiley InterScience (www.interscience.wiley.com); DOI 10.1002/cae.20237 [source] An educational tool for controlling of SRMCOMPUTER APPLICATIONS IN ENGINEERING EDUCATION, Issue 4 2008Tuncay Yigit Abstract This article introduces an educational tool for a switched reluctance motor (SRM) drive system. It is prepared for undergraduate and graduate level students. Classical PI and Genetic PI controllers are used in SRM drive system. The Genetic PI controller was applied to the speed loop, replacing the classical PI controller. The tool software was implemented using C++ Builder on a PC. It has flexible structure and graphical interface. The students can be easily establishing a thorough understanding of both classical PI and genetic PI controller for a SRM drive system. The education tool allowed the student to interact with the SRM drive system and it is using controllers. Then it is responses on a dynamic and instantaneous basis under different operating conditions. © 2008 Wiley Periodicals, Inc. Comput Appl Eng Educ 16: 268,279, 2008; Published online in Wiley InterScience (www.interscience.wiley.com); DOI 10.1002/cae20148 [source] Learning with an active e-course in the Knowledge Grid environmentCONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 3 2006Hai Zhuge Abstract An active e-course is an open, self-representable and self-organizable media mechanism. Its kernel idea is to organize learning materials in a concept space rather than in a page space. The tailored content and flexible structure of the e-courses can be dynamically formed to cater for different learners with different backgrounds, capabilities and expectations, at different times and venues. The active e-course can also assess learners' learning performances and give appropriate suggestions to guide them in further learning. An authoring tool for constructing course ontology and a system prototype have been developed to support an active e-course, enabling a learner-centred, highly interactive and adaptive learning approach. The results of an empirical study show that the system can help enhance the effectiveness and efficiency of learning. Copyright © 2005 John Wiley & Sons, Ltd. [source] Robust active vibration suppression control with constraint on the control signal: application to flexible structuresEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 11 2003A. Forrai Abstract A unified mathematical framework, sustained by experimental results, is presented for robust controller design taking into account the constraint on the control signal. The design procedure is exemplified for an active vibration suppression control problem with applications to flexible structures. The considered experimental set-up is a three-storey flexible structure with an active mass driver placed on the last storey. First, the considered flexible structure is identified and the model's parametric uncertainties are deduced. Next, control constraints are presented for the robust control design problem, taking into account the restriction imposed on the control signal. Finally, the effectiveness of the control system is tested through experiments, when the input disturbance is assumed to be a sinusoidal one as well as a historical earthquake record (1940 El Centro record). Copyright © 2003 John Wiley & Sons, Ltd. [source] Experimental and theoretical simulations of seismic poundings between two adjacent structuresEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 4 2003K. T. Chau Abstract Shaking table tests have been carried out to investigate the pounding phenomenon between two steel towers of different natural frequencies and damping ratios, subject to different combinations of stand-off distance and seismic excitations. Both harmonic waves and ground motions of the 1940 El Centro earthquake are used as input. Subjected to sinusoidal excitations, poundings between the two towers could appear as either periodic or chaotic. For periodic poundings, impact normally occurs once within each excitation cycle or within every other excitation cycle. A type of periodic group poundings was also observed for the first time (i.e. a group of non-periodic poundings repeating themselves periodically). Chaotic motions develop when the difference of the natural frequency of the two towers become larger. Under sinusoidal excitations, the maximum relative impact velocity always develops at an excitation frequency between the natural frequencies of the two towers. Both analytical and numerical predictions of the relative impact velocity, the maximum stand-off distance, and the excitation frequency range for pounding occurrences were made and found to be comparable with the experimental observations in most of the cases. The stand-off distance attains a maximum when the excitation frequency is close to that of the more flexible tower. Pounding appears to amplify the response of the stiffer structure but suppress that of the more flexible structure; and this agrees qualitatively with previous shaking table tests and theoretical studies. Copyright © 2003 John Wiley & Sons, Ltd. [source] A Triphenylamine Dye Model for the Study of Intramolecular Energy Transfer and Charge Transfer in Dye-Sensitized Solar Cells,ADVANCED FUNCTIONAL MATERIALS, Issue 21 2008Haining Tian Abstract A novel dye (2TPA-R), containing two triphenylamine (TPA) units connected by a vinyl group and rhodanine-3-acetic acid as the electron acceptor, is designed and synthesized successfully to reveal the working principles of organic dye in dye-sensitized solar cells (DSSCs). 2TPA and TPA-R, which consist of two TPA units connected by vinyl and a TPA unit linked with rhodanine-3-acetic acid, respectively, are also synthesized as references to study the intramolecular energy transfer (EnT) and charge transfer (ICT) processes of 2TPA-R in CH2Cl2 solution and on a TiO2 surface. The results suggest that the intramolecular EnT and ICT processes show a positive effect on the performance of DSSCs. However, the flexible structure and less-adsorbed amount of dye on TiO2 may make it difficult to improve the efficiency of DSSCs. This study on intramolecular EnT and ICT processes acts as a guide for the design and synthesis of efficient organic dyes in the future. [source] Modelling of a snowpack in interaction with a flexible structure using a coupled Lagrangian-discrete approachINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 4 2003François Nicot Abstract The search to improve protective techniques against natural phenomena such as snow avalanches continues to use classic methods to calculate flexible structures. This paper deals with a new method for designing avalanche protection nets; this method is based on a coupled analysis of both the net structure and the snow mantel using a coupled Lagrangian-discrete approach. This has led to the development of computational software so that avalanche nets can be easily designed. This tool provides for the evolving forces acting on several parts of the net as a function of the snow situation. Copyright © 2003 John Wiley & Sons, Ltd. [source] Molecular structure, conformational analysis and charge distribution of pralidoxime: Ab initio and DFT studiesINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 3 2002Alexandre T. Castro Abstract A detailed structural study of pralidoxime (2-PAM), the main antidote against organophosphate intoxication, was performed using Hartree-Fock, Möller,Plesset (MP2), and density functional theory (Becke, Lee, Yang, and Paar [B3LYP]) methods. Rotational barriers, equilibrium geometries, and charge distributions were calculated, showing important differences between the two forms available in physiological conditions, namely with the oxime group protonated or unprotonated. For the protonated form, conjugation between the side chain and the pyridinium ring, although present, has little importance, resulting in a flexible structure. On the other hand, the unprotonated form has a more rigid structure and a smaller charge density on the oxime oxygen. Contrary to the common belief, those results strongly suggest that it may be the protonated form of 2-PAM, instead of the unprotonated form, that is responsible for the antidote activity of this compound. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002 [source] Synthesis of a New Hyperbranched Polyaminoester and Its Use as a Reactive Modifier in Anionic Curing of DGEBA ThermosetsMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 17 2010Mireia Morell Abstract The synthesis and characterization of a new hyperbranched PAE with a flexible structure and terminal hydroxyl groups is reported. The influence of PAE in the anionic curing of DGEBA with 1-methylimidazole was studied. The curing reaction was investigated by DSC and FT-IR. The covalent incorporation of the modifier in the matrix was proven. The addition of PAE to the formulation reduced the contraction on curing. The modified materials were more thermally degradable than neat DGEBA thermosets, which is advantageous from the point of view of their reworkability. Their Tgs were reduced by the flexibility introduced by the aliphatic structure of PAE. SEM microscopy on the fractured surface of cured samples revealed a homogeneous morphology and a possible effect of PAE as a toughness enhancer. [source] Riesz basis and stabilization for the flexible structure of a symmetric tree-shaped beam networkMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 3 2008Jun-Min Wang Abstract The stabilization of a symmetric tree-shaped network of Euler,Bernoulli beams described by a system of partial differential equations is considered. The boundary controllers are designed based on passivity principle. The eigenfrequencies are analysed in detail and the asymptotic expansion of eigenvalues are presented. It is shown that there is a set of generalized eigenfunctions for the closed-loop system, which forms a Riesz basis with parentheses for the energy state space. This concludes the spectrum-determined growth condition and the exponential stability of the closed-loop system. Copyright © 2007 John Wiley & Sons, Ltd. [source] Use of an innovative video feedback technique to enhance communication skills trainingMEDICAL EDUCATION, Issue 2 2004Debra L Roter Context, Despite growing interest in medical communication by certification bodies, significant methodological and logistic challenges are evident in experiential methods of instruction. Objective, There were three study objectives: 1) to explore the acceptability of an innovative video feedback programme to residents and faculty; 2) to evaluate a brief teaching intervention comprising the video feedback innovation when linked to a one-hour didactic and role-play teaching session on paediatric residents' communication with a simulated patient; and 3) to explore the impact of resident gender on communication change. Design, Pre/post comparison of residents' performance in videotaped interviews with simulated patients before and after the teaching intervention. Individually tailored feedback on targeted communication skills was facilitated by embedding the Roter Interaction Analysis System (RIAS) within a software platform that presents a fully coded interview with instant search and review features. Setting/participants, 28 first year residents in a large, urban, paediatric residency programme. Results, Communication changes following the teaching intervention were demonstrated through significant improvements in residents' performance with simulated patients pre and post teaching and feedback. Using paired t -tests, differences include: reduced verbal dominance; increased use of open-ended questions; increased use of empathy; and increased partnership building and problem solving for therapeutic regimen adherence. Female residents demonstrated greater communication change than males. Conclusions, The RIAS embedded CD-ROM provides a flexible structure for individually tailoring feedback of targeted communication skills that is effective in facilitating communication change as part of a very brief teaching intervention. [source] A nanoengine for gliding motilityMOLECULAR MICROBIOLOGY, Issue 1 2007Grant Jensen Summary The terminal organelle present in some mycoplasma species is a very large, complex, flexible structure involved in cell adherence, motility and cell division. In this issue of Molecular Microbiology, Hasselbring and Krause report on a mutant in which the terminal organelle is only weakly connected to the rest of the cell. ,Run-away' terminal organelles first stretch the cells, then break away and continue moving independently for more than half an hour. This remarkable observation proves that the ,nanoengine' driving motility is indeed associated with the terminal organelle, and opens up new opportunities for dissecting and understanding its mechanism. [source] Electromechanics of Cardiac Tissue: A Unified Approach to the Fully Coupled Excitation-Contraction ProblemPROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2009Serdar Göktepe This contribution is concerned with a new, unified finite element approach to the fully coupled problem of cardiac electromechanics. In contrast to the existing numerical approaches suggested in the literature; to the best of our knowledge, for the first time, we propose a fully implicit, purely finite-element-based approach to the coupled problem. The system of coupled algebraic equations obtained by simultaneous linearization of non-linear weighted residual terms is solved monolithically. The put forward modular algorithmic framework leads to an unconditionally stable and geometrically flexible structure that can readily be extended towards complex ionic models of cardiac electrophysiology. The performance of the proposed approach is illustrated by the coupled electromechanical analysis of a biventricular generic heart model. (© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Chaperone-like activities of different molecular forms of ,-casein.BIOPOLYMERS, Issue 8 2009Importance of polarity of N-terminal hydrophilic domain Abstract As a member of intrinsically unstructured protein family, ,-casein (,-CN) contains relatively high amount of prolyl residues, adopts noncompact and flexible structure and exhibits chaperone-like activity in vitro. Like many chaperones, native ,-CN does not contain cysteinyl residues and exhibits strong tendencies for self-association. The chaperone-like activities of three recombinant ,-CNs wild type (WT) ,-CN, C4 ,-CN (with cysteinyl residue in position 4) and C208 ,-CN (with cysteinyl residue in position 208), expressed and purified from E. coli, which, consequently, lack the phosphorylated residues, were examined and compared with that of native ,-CN using insulin and alcohol dehydrogenase as target/substrate proteins. The dimers (,-CND) of C4-,-CN and C208 ,-CN were also studied and their chaperone-like activities were compared with those of their monomeric forms. Lacking phosphorylation, WT ,-CN, C208 ,-CN, C4 ,-CN and C4 ,-CND exhibited significantly lower chaperone-like activities than native ,-CN. Dimerization of C208 ,-CN with two distal hydrophilic domains considerably improved its chaperone-like activity in comparison with its monomeric form. The obtained results demonstrate the significant role played by the polar contributions of phosphorylated residues and N-terminal hydrophilic domain as important functional elements in enhancing the chaperone-like activity of native ,-CN. © 2009 Wiley Periodicals, Inc. Biopolymers 91: 623,632, 2009. This article was originally published online as an accepted preprint. The "Published Online" date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com [source] Dimensional analysis of the earthquake-induced pounding between adjacent structuresEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 7 2009Elias Dimitrakopoulos Abstract In this paper the dynamic response of two and three pounding oscillators subjected to pulse-type excitations is revisited with dimensional analysis. Using Buckingham's ,-theorem the number of variables that govern the response of the system is reduced by three. When the response is presented in the dimensionless ,-terms remarkable order emerges. It is shown that regardless of the acceleration level and duration of the pulse all response spectra become self-similar and follow a single master curve. This is true despite the realization of finite duration contacts with increasing durations as the excitation level increases. All physically realizable contacts (impacts, continuous contacts, and detachments) are captured via a linear complementarity approach. The study confirms the existence of three spectral regions. The response of the most flexible among the two oscillators amplifies in the low range of the frequency spectrum (flexible structures); whereas, the response of the most stiff among the two oscillators amplifies at the upper range of the frequency spectrum (stiff structures). Most importantly, the study shows that pounding structures such as colliding buildings or interacting bridge segments may be most vulnerable for excitations with frequencies very different from their natural eigenfrequencies. Finally, by applying the concept of intermediate asymptotics, the study unveils that the dimensionless response of two pounding oscillators follows a scaling law with respect to the mass ratio, or in mathematical terms, that the response exhibits an incomplete self-similarity or self-similarity of the second kind with respect to the mass ratio. Copyright © 2008 John Wiley & Sons, Ltd. [source] Strengthening of moment-resisting frame structures against near-fault ground motion effectsEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 6 2004Babak Alavi Abstract Near-fault ground motions with forward directivity are characterized by a large pulse. This pulse-like motion may cause a highly non-uniform distribution of story ductility demands for code-compliant frame structures, with maximum demands that may considerably exceed the level of code expectations. Strengthening techniques for multi-story frame structures are explored with the objective of reducing maximum drift demands. One option is to modify the code-based SRSS distribution of story shear strength over the height by strengthening of the lower stories of the frame. The modified distribution reduces the maximum story ductility demand, particularly for weak and flexible structures. However, this strengthening technique is less effective for stiff structures, and is almost ineffective in cases in which the maximum demand occurs in the upper stories, i.e. strong and flexible structures. As an alternative, the benefits of strengthening frames with elastic and inelastic walls are evaluated. The effects of adding walls that are either fixed or hinged at the base are investigated. It is demonstrated that strengthening with hinged walls is very effective in reducing drift demands for structures with a wide range of periods and at various performance levels. Wall inelastic behavior only slightly reduces the benefits of strengthening with hinged walls.Copyright © 2004 John Wiley & Sons, Ltd. [source] Robust active vibration suppression control with constraint on the control signal: application to flexible structuresEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 11 2003A. Forrai Abstract A unified mathematical framework, sustained by experimental results, is presented for robust controller design taking into account the constraint on the control signal. The design procedure is exemplified for an active vibration suppression control problem with applications to flexible structures. The considered experimental set-up is a three-storey flexible structure with an active mass driver placed on the last storey. First, the considered flexible structure is identified and the model's parametric uncertainties are deduced. Next, control constraints are presented for the robust control design problem, taking into account the restriction imposed on the control signal. Finally, the effectiveness of the control system is tested through experiments, when the input disturbance is assumed to be a sinusoidal one as well as a historical earthquake record (1940 El Centro record). Copyright © 2003 John Wiley & Sons, Ltd. [source] Modelling of a snowpack in interaction with a flexible structure using a coupled Lagrangian-discrete approachINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 4 2003François Nicot Abstract The search to improve protective techniques against natural phenomena such as snow avalanches continues to use classic methods to calculate flexible structures. This paper deals with a new method for designing avalanche protection nets; this method is based on a coupled analysis of both the net structure and the snow mantel using a coupled Lagrangian-discrete approach. This has led to the development of computational software so that avalanche nets can be easily designed. This tool provides for the evolving forces acting on several parts of the net as a function of the snow situation. Copyright © 2003 John Wiley & Sons, Ltd. [source] Aeroelastic forces and dynamic response of long-span bridgesINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 6 2004Massimiliano Lazzari Abstract In this paper a time domain approach for predicting the non-linear dynamic response of long-span bridges is presented. In particular the method that leads to the formulation of aeroelastic and buffeting forces in the time domain is illustrated in detail, where a recursive algorithm for the memory term's integration is properly developed. Moreover in such an approach the forces' expressions, usually formulated according to quasi-static theory, have been substituted by expressions including the frequency-dependent characteristics. Such expressions of aeroelastic and buffeting forces are made explicit in the time domain by means of the convolution integral that involves the impulse functions and the structural motion or the fluctuating velocities. A finite element model (FEM) has been developed within the framework of geometrically non linear analysis, by using 3-d degenerated finite element. The proposed procedure can be used to analyze both the flutter instability phenomenon and buffeting response. Moreover, working in the geometrically non-linearity range, it verifies the possibility of strongly flexible structures of actively resisting the wind loading. Copyright © 2004 John Wiley & Sons, Ltd. [source] A viscous vortex particle method for deforming bodies with application to biolocomotionINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 12 2009Li Jeany Zhang Abstract Bio-inspired mechanics of locomotion generally consist of the interaction of flexible structures with the surrounding fluid to generate propulsive forces. In this work, we extend, for the first time, the viscous vortex particle method (VVPM) to continuously deforming two-dimensional bodies. The VVPM is a high-fidelity Navier,Stokes computational method that captures the fluid motion through evolution of vorticity-bearing computational particles. The kinematics of the deforming body surface are accounted for via a surface integral in the Biot,Savart velocity. The spurious slip velocity in each time step is removed by computing an equivalent vortex sheet and allowing it to flux to adjacent particles; hence, no-slip boundary conditions are enforced. Particles of both uniform and variable size are utilized, and their relative merits are considered. The placement of this method in the larger class of immersed boundary methods is explored. Validation of the method is carried out on the problem of a periodically deforming circular cylinder immersed in a stagnant fluid, for which an analytical solution exists when the deformations are small. We show that the computed vorticity and velocity of this motion are both in excellent agreement with the analytical solution. Finally, we explore the fluid dynamics of a simple fish-like shape undergoing undulatory motion when immersed in a uniform free stream, to demonstrate the application of the method to investigations of biomorphic locomotion. Copyright © 2008 John Wiley & Sons, Ltd. [source] Manoeuvring and vibration reduction of a flexible spacecraft integrating optimal sliding mode controller and distributed piezoelectric sensors/actuatorsINTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 6 2007Qinglei Hu Abstract This investigation is to apply optimal sliding mode (OSM) control theory and distributed piezoelectric sensor/actuator technology to vibration control of a flexible spacecraft. An approximate analytical dynamic model of a slewing flexible spacecraft with surface-bonded piezoelectric sensors/actuators is developed using Hamilton's principle with discretization by assumed model method. To satisfy pointing requirements and simultaneously suppress vibration, two separate control loops are adopted. The first uses the piezoceramics as sensors and actuators to actively suppress certain flexible modes by designing a positive position feedback (PPF) compensators that add damping to the flexible structures in certain critical modes in the inner feedback loop; then a second feedback loop is designed using OSM control to slew the spacecraft. The OSM controller minimizes the expected value of a quadratic objective function consisting of only the states with the constraints that the error states always remain on the intersection of sliding surfaces. The advantage in this method is that the vibration reduction and attitude control are achieved separately in the two separate feedback loops, allowing the pointing requirements and simultaneous vibrations suppression to be satisfied independently of one another. An additional attraction of the design method is that the selection of PPF gain is determined by introducing a cost function to be minimized by the feedback gains which are subject to the stability criterion at the same time, such that the feedback gains are selected in a more systematical way to avoid the arbitrary selecting of feedback gains. The proposed control strategy has been implemented on a flexible spacecraft, which is a hub with a cantilever flexible beam appendage and can undergo a single axis rotation. Both analytical and numerical results are presented to show the theoretical and practical merits of this approach. Copyright © 2006 John Wiley & Sons, Ltd. [source] Robustness analysis of flexible structures: practical algorithmsINTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 8 2003Gilles Ferreres Abstract When analysing the robustness properties of a flexible system, the classical solution, which consists of computing lower and upper bounds of the structured singular value (s.s.v.) at each point of a frequency gridding, appears unreliable. This paper describes two algorithms, based on the same technical result: the first one directly computes an upper bound of the maximal s.s.v. over a frequency interval, while the second one eliminates frequency intervals, inside which the s.s.v. is guaranteed to be below a given value. Various strategies are then proposed, which combine these two techniques, and also integrate methods for computing a lower bound of the s.s.v. The computational efficiency of the scheme is illustrated on a real-world application, namely a telescope mock-up which is significant of a high order flexible system. Copyright © 2003 John Wiley & Sons, Ltd. [source] The highly specialized vocal tract of the male Mongolian gazelle (Procapra gutturosa Pallas, 1777 , Mammalia, Bovidae)JOURNAL OF ANATOMY, Issue 5 2003R. Frey Abstract The entire head and neck of a wild adult male Mongolian gazelle (Procapra gutturosa) was dissected with special reference to its enlarged larynx. Two additional adult male specimens taken from the wild were analysed by computer tomography. The sternomandibularis, omohyoideus, thyrohyoideus and hyoepiglotticus muscles are particularly enlarged and improve laryngeal suspension and stabilization. The epiglottis is exceptionally large. A permanent laryngeal descent is associated with the evolution of an unpaired palatinal pharyngeal pouch. A certain momentary descent seems to occur during vocalization. The high lateral walls of the thyroid cartilage are ventrally connected by a broad keel. The large thyroarytenoid muscle is divided into two portions: a rostral ventricularis and a caudal vocalis muscle. A paired lateral laryngeal ventricle projects between these two muscles. The massive vocal fold is large and lacks any rostrally directed flexible structures. It is supported by a large cymbal-like fibroelastic pad. Vocal tract length was measured in the course of dissection and in computer tomographic images. Two representative spectrograms, one of an adult male and one of a juvenile, recorded in the natural habitat of the Mongolian gazelle are presented. In the spectrograms, the centre frequency of the lowest band is about 500 Hz in the adult male and about 790 Hz in the juvenile. The low pitch of the adult male's call is ascribed to the evolutionary mass increase and elongation of the vocal folds. In the habitat of P. gutturosa a call with a low pitch and, thus, with an almost homogeneous directivity around the head of the vocalizing animal may be optimally suited for multidirectional advertisement calls during the rut. The signal range of an adult male's call in its natural habitat can therefore be expected to be larger than the high-pitched call of a juvenile. [source] High-pressure processing effects on the mechanical, barrier and mass transfer properties of food packaging flexible structures: a critical reviewPACKAGING TECHNOLOGY AND SCIENCE, Issue 1 2004Cengiz Caner Abstract Food products can be high-pressure processed (HPP) either in bulk or prepackaged in flexible or semi-rigid packaging materials. In the latter case the packaging material is subjected, together with the food, to high-pressure treatment. A number of studies have been performed to quantify the effects of high-pressure processing on the physical and barrier properties of the packaging material, since the integrity of the package during and after processing is of paramount importance to the safety and quality of the food product. This article reviews the results of published research concerning the effect of HPP on packaging materials. Copyright © 2004 John Wiley & Sons, Ltd. [source] Biofilm streamers and drag of flexible structures in flowBIOTECHNOLOGY & BIOENGINEERING, Issue 3 2010Article first published online: 23 DEC 200 No abstract is available for this article. [source] Progress toward a biomimetic leaf: 4,000 h of hydrogen production by coating-stabilized nongrowing photosynthetic Rhodopseudomonas palustrisBIOTECHNOLOGY PROGRESS, Issue 4 2010Jimmy L. Gosse Abstract Intact cells are the most stable form of nature's photosynthetic machinery. Coating-immobilized microbes have the potential to revolutionize the design of photoabsorbers for conversion of sunlight into fuels. Multi-layer adhesive polymer coatings could spatially combine photoreactive bacteria and algae (complementary biological irradiance spectra) creating high surface area, thin, flexible structures optimized for light trapping, and production of hydrogen (H2) from water, lignin, pollutants, or waste organics. We report a model coating system which produced 2.08 ± 0.01 mmol H2 m,2 h,1 for 4,000 h with nongrowing Rhodopseudomonas palustris, a purple nonsulfur photosynthetic bacterium. This adhesive, flexible, nanoporous Rps. palustris latex coating produced 8.24 ± 0.03 mol H2 m,2 in an argon atmosphere when supplied with acetate and light. A simple low-pressure hydrogen production and trapping system was tested using a 100 cm2 coating. Rps. palustris CGA009 was combined in a bilayer coating with a carotenoid-less mutant of Rps. palustris (CrtI,) deficient in peripheral light harvesting (LH2) function. Cryogenic field emission gun scanning electron microscopy (cryo-FEG-SEM) and high-pressure freezing were used to visualize the microstructure of hydrated coatings. A light interaction and reactivity model was evaluated to predict optimal coating thickness for light absorption using the Kubelka-Munk theory (KMT) of reflectance and absorptance. A two-flux model predicted light saturation thickness with good agreement to observed H2 evolution rate. A combined materials and modeling approach could be used for guiding cellular engineering of light trapping and reactivity to enhance overall photosynthetic efficiency per meter square of sunlight incident on photocatalysts. © 2010 American Institute of Chemical Engineers Biotechnol. Prog., 2010 [source] | ||||||||||||||||||||||||||||||||||