bluuebunny/crossref_metadata_2025 huggingface dataset:
Contrasting Cloud Forest Restoration Potential Between Plantations of Different Exotic Tree Species
Authors: Thijs Koen W. , Aerts Raf , Van de Moortele Pieter , Musila Winfred , Gulinck Hubert , Muys Bart
Published: April 2014

The role of exotic tree plantations for biodiversity conservation is contested. Such plantations nevertheless offer various ecosystem service benefits, which include carbon storage and facilitation of indigenous tree species regeneration. To assess forest restoration potential in tropical exotic tree plantations, we assessed native cloud forest tree regeneration in 166 plots in ca. 50‐year‐old plantations of five timber species that are widely used in tropical plantations (Pinus patula, Eucalyptus saligna, Cupressus lusitanica, Grevillea robusta and Acacia mearnsii). Differences in species abundance, diversity and composition were compared among plantations, and between plantations and disturbed and undisturbed indigenous Afromontane cloud forest (southeast Kenya) relicts after controlling for environmental variation between plots (i.e. altitude, distance to indigenous forest, soil depth, slope, aspect) and for environmental and stand structural variation (i.e. dominant tree height and basal area). Regenerating trees were mostly early‐successional species. Indigenous tree species regeneration was significantly higher in Grevillea plantations, where the seedling community also included late‐successional tree species. Regeneration under Eucalyptus was particularly poor. Acacia had a strong invasive nature, reducing its potential role and usefulness in indigenous forest restoration. Our study underlined that exotic tree plantations have differential effects on native tree species regeneration, with high potential for Grevillea plantations and low potential for invasive exotic species.
Building Taxon Substitution Guidelines on a Biological Control Foundation
Authors: Aslan Clare E. , Aslan Austin , Croll Don , Tershy Bernie , Zavaleta Erika
Published: April 2014

When a species becomes extinct, its ecological functions are lost as well. Taxon substitution is a controversial approach to restoring such functions via introduction of non‐native species known to serve similar functions elsewhere. Due to the possibility of nontarget effects from such introductions, taxon substitution has been proposed and implemented in only a few systems, but these attempts have successfully restored functions. As a conservation tool, taxon substitution bears similarity to biological control, wherein species are also introduced for their ecological function with consideration of potential nontarget effects. To improve both the safety and efficacy of taxon substitution, regulatory bodies that currently issue guidelines for biological control can do the same for taxon substitution. Indeed, many biological control guidelines would apply well to taxon substitution. We examine the standard practices followed by biological control programs and propose corresponding taxon substitution guidelines. Integration of taxon substitution into the existing national and international environmental management conversation will improve the tool and has the potential to enhance conservation efforts across a wide diversity of systems if appropriate and stringent precautions are taken.
Aggression and prosocial behaviors in social conflicts mediating the influence of cold social intelligence and affective empathy on children's social preference
Authors: Carreras M. R. , Braza P. , Muñoz J. M. , Braza F. , Azurmendi A. , Pascual‐Sagastizabal E. , Cardas J. , Sánchez‐Martín J. R.
Published: April 2014

This study proposes a model in which aggressive and prosocial behaviors exhibited in social conflicts mediate the influence of empathy and social intelligence to children's social preference by same‐sex peers. Data were obtained from kindergarten to the end of the first grade. The sample yielded 117 Spanish children (64 girls and 53 boys) with a mean age of 62.8 months (SD = 3.3) at the beginning of the study. For boys, affective empathy contributed to boys’ social preference through a decrease in physical aggression as responses to social conflict. For girls, affective empathy had an indirect effect on girls’ preference by increasing assistance to others in their conflicts. No mediating effect in the contribution of social intelligence on girls’ social preference was detected. Our results suggest that, only for girls, cold social intelligence can promote both indirect aggression (coercive strategic that do not leave social preference, at least at these ages) and behaviors that lead social preference (such as prosocial behaviors).
Inference of Seasonal Long‐memory Time Series with Measurement Error
Authors: Tsai Henghsiu , Rachinger Heiko , Lin Edward M.H.
Published: April 2014

We consider the Whittle likelihood estimation of seasonal autoregressive fractionally integrated moving‐average models in the presence of an additional measurement error and show that the spectral maximum Whittle likelihood estimator is asymptotically normal. We illustrate by simulation that ignoring measurement errors may result in incorrect inference. Hence, it is pertinent to test for the presence of measurement errors, which we do by developing a likelihood ratio (LR) test within the framework of Whittle likelihood. We derive the non‐standard asymptotic null distribution of this LR test and the limiting distribution of LR test under a sequence of local alternatives. Because in practice, we do not know the order of the seasonal autoregressive fractionally integrated moving‐average model, we consider three modifications of the LR test that takes model uncertainty into account. We study the finite sample properties of the size and the power of the LR test and its modifications. The efficacy of the proposed approach is illustrated by a real‐life example.
50th Anniversary Article: The Origin and Management of Residual Stress in Heat‐treatable Aluminium Alloys
Authors: Robinson J. S. , Tanner D. A. , Truman C. E.
Published: April 2014

The presence of macroscopic residual stresses in heat‐treatable aluminium alloys can give rise to machining distortion, dimensional instability and increased susceptibility to in‐service fatigue and stress corrosion cracking. This paper presents and reviews details about the residual stress magnitudes and distributions introduced into wrought aluminium alloys by the thermal operations associated with heat treatment. Experimental measurement data and the results of finite element analysis are presented and discussed. The available technologies by which residual stresses in aluminium alloys can be relieved are reviewed. The limitations of these techniques are described, and recommendations are made as to selecting the most appropriate technique to manage residual stresses. Opportunities for the future optimisation of these techniques are also presented.
Decision Theory with Resource‐Bounded Agents
Authors: Halpern Joseph Y. , Pass Rafael , Seeman Lior
Published: April 2014

There have been two major lines of research aimed at capturing resource‐bounded players in game theory. The first, initiated by Rubinstein (), charges an agent for doing costly computation; the second, initiated by Neyman (), does not charge for computation, but limits the computation that agents can do, typically by modeling agents as finite automata. We review recent work on applying both approaches in the context of decision theory. For the first approach, we take the objects of choice in a decision problem to be Turing machines, and charge players for the “complexity” of the Turing machine chosen (e.g., its running time). This approach can be used to explain well‐known phenomena likefirst‐impression‐matters biases(i.e., people tend to put more weight on evidence they hear early on) andbelief polarization(two people with different prior beliefs, hearing the same evidence, can end up with diametrically opposed conclusions) as the outcomes of quite rational decisions. For the second approach, we model people as finite automata, and provide a simple algorithm that, on a problem that captures a number of settings of interest, provably performs optimally as the number of states in the automaton increases.
Biological Significance of the Importin‐β Family‐Dependent Nucleocytoplasmic Transport Pathways
Authors: Kimura Makoto , Imamoto Naoko
Published: April 2014

Importin‐β family proteins (Imp‐βs) are nucleocytoplasmic transport receptors (NTRs) that import and export proteins and RNAs through the nuclear pores. The family consists of 14–20 members depending on the biological species, and each member transports a specific group of cargoes. Thus, the Imp‐βs mediate multiple, parallel transport pathways that can be regulated separately. In fact, the spatiotemporally differential expressions and the functional regulations of Imp‐βs have been reported. Additionally, the biological significance of each pathway has been characterized by linking the function of a member of Imp‐βs to a cellular consequence. Connecting these concepts, the regulation of the transport pathways conceivably induces alterations in the cellular physiological states. However, few studies have linked the regulation of an importin‐β family NTR to an induced cellular response and the corresponding cargoes, despite the significance of this linkage in comprehending the biological relevance of the transport pathways. This review of recent reports on the regulation and biological functions of the Imp‐βs highlights the significance of the transport pathways in physiological contexts and points out the possibility that the identification of yet unknown specific cargoes will reinforce the importance of transport regulation.
Residual plasma in red blood cells and transfusion‐related acute lung injury
Authors: Weber Litchia L. , Roberts Laura D. , Sweeney Joseph D.
Published: April 2014

Background

Transfusion‐related acute lung injury (TRALI) is the most common cause of death from blood transfusion and red blood cells (RBCs) now account for approximately 50% of these fatalities. RBCs from female donors have been implicated in large series and HLA Class II antibodies to cognate recipient antigens identified in small series and case reports. The absolute volume of residual plasma in these RBCs is unknown.

Study Design and Methods

Two confirmed cases of RBC‐associated TRALI in which the implicated donors had Class II antibodies were investigated, and the antibody strength against recipient cognate antigens was assessed using a fluorescent bead assay. RBCs in additive solution (AS) were studied on Day 42 of liquid storage to calculate residual anticoagulated plasma.

Results

Both RBC units were stored in AS‐1 and were from female donors who had anti‐HLA Class II antibodies of high strength against cognate antigens in the recipients. Anti‐DR4 was identified in both cases. Nineteen AS‐1 RBC units manufactured from whole blood donations using a hard spin had a mean (±1SD) residual plasma content of 38 ± 8 mL, and 26 AS‐3 RBC units manufactured using a soft spin had 66 ± 13 mL (p < 0.01).

Conclusion

RBCs continue to be manufactured from female donors of unknown or even known anti‐HLA status. The residual plasma content of these RBCs may approach 100 mL. A combination of a high‐strength antibody and large residual plasma volume could explain severe or even fatal RBC‐associated TRALI.
Can Export Restrictions be Disciplined Through the World Trade Organisation?
Authors: Cardwell Ryan , Kerr William A.
Published: April 2014

A number of major agricultural exporting countries responded to high food prices from 2007 to 2011 by imposing export restrictions on agricultural commodities in efforts to constrain domestic food price inflation. These restrictions reduced the volume of internationally traded food and exacerbated international price spikes. Net food‐importing countries were faced with growing import bills, and non‐governmental organisations that target food security scaled‐back programme commitments and appealed for increased funding. There have subsequently been a chorus of calls for the development of a formal international framework that could discipline the use of agricultural export restrictions; the agreements of the World Trade Organisation (WTO) have been targeted as possible fora for such disciplines. We present a framework in which the efficacy of such disciplines can be analysed and conclude that constraints on agricultural export restrictions are not likely to be effective within the WTO's Dispute Settlement Understanding for two reasons. First, the timelines for dispute settlement in the WTO are too long to be useful in disputes about export restrictions during periods of high food prices. Second, the withdrawal of tariff concessions, or trade retaliation, that could be authorised in such cases would not be a credible response for many complainant countries.
PALLIATIVE RADIATION THERAPY OUTCOMES FOR CATS WITH ORAL SQUAMOUS CELL CARCINOMA (1999–2005)
Authors: Sabhlok Aarti , Ayl Rodney
Published: April 2014

Squamous cell carcinoma (SCC) accounts for approximately 10% of all feline tumors. The purpose of this retrospective study was to describe outcomes for a group of cats with oral SCC that were treated with palliative radiation therapy. Fifty‐four cats met the inclusion criteria of nonresectable, oral SCC treated with coarse fractionated megavoltage (MeV) radiation therapy. Radiation therapy for all cats was delivered with a 6 MeV linear accelerator. Total radiation doses of 24 Gray to 40 Gray were administered in three to four fractions, once‐per‐week over 4 to 5 weeks. Concurrent chemotherapy protocols varied and were administered at the discretion of the clinician and client. Forty‐nine patients completed the planned treatment protocols. Overall mean and median survival times for cats completing the planned treatment protocols were 127 and 92 days (n = 49). Mean and median survival times of cats receiving palliative radiation therapy alone were 157 and 113 days (n = 12). Mean and median survival times of patients receiving both radiation therapy and chemotherapy were 116 and 80 days (n = 37). Patients with sublingual tumors had a median survival time of 135 days (n = 15), compared to mandibular tumors that had a median survival time of 80 days (n = 26). For the majority of patients that completed the planned treatment protocol (65%), owners reported a subjectively improved quality of life. Findings from this uncontrolled study supported the use of palliative radiation therapy for cats with nonresectable oral squamous cell carcinoma.
OPTIMIZED CANINE DENTAL COMPUTED TOMOGRAPHIC PROTOCOL IN MEDIUM‐SIZED MESATICEPAHLIC DOGS
Authors: Esmans Maya C. , Soukup Jason W. , Schwarz Tobias
Published: April 2014

The purpose of this study was to develop an optimized imaging protocol for canine dental imaging using single‐detector row CT and multidetector row CT. Two medium‐sized mesaticephalic cadaver dog heads were scanned using varying slice thickness, sequential vs. helical scanning mode, sequential CT table increment, pitch, image reconstruction algorithm, and an additional moderate edge enhancement filter. For each series, two reviewers scored dental roots as not visible (score: 0), partially visible (score: 1) or completely visible (score: 2). Sharpness of the dento‐alveolar margin was scored as blurry (score: 0), sharp (score: 1) or very sharp (score: 2). Consensus reader scores were compared among CT protocols. For single‐detector row CT, complete visualization of all tooth roots was only achieved with 1 mm slice thickness and image interval sequential or helical series (pitch of 1 or 2) using a high‐frequency image reconstruction algorithm with or without additional edge enhancement. For four‐detector row CT, complete visibility of all tooth roots was recorded in all series. For single‐detector row CT, all medium frequency algorithm series yielded blurry margin scores and all other series yielded sharp margin scores. For four‐detector row CT, sequential and helical 0.5 mm thickness images yielded very sharp dento‐alveolar margin scores, whereas the 1 mm series yielded only sharp margin scores. Authors concluded that the optimal dental imaging protocol was a sequential mode 1 mm slice thickness and interval with a high‐frequency image reconstruction algorithm and an additional moderate edge enhancement filter.
MAGNETIC RESONANCE IMAGING CHARACTERISTICS IN FOUR DOGS WITH CENTRAL NERVOUS SYSTEM NEOSPOROSIS
Authors: Parzefall Birgit , Driver Colin J. , Benigni Livia , Davies Emma
Published: April 2014

Neosporosis is a polysystemic disease that can affect dogs of any age and can cause inflammation of the central nervous system. Antemortem diagnosis can be challenging, as clinical and conventional laboratory test findings are often nonspecific. A previous report described cerebellar lesions in brain MRI studies of seven dogs and proposed that these may be characteristic for central nervous system Neosporosis. The purpose of this retrospective study was to describe MRI characteristics in another group of dogs with confirmed central nervous system neosporosis and compare them with the previous report. The hospital's database was searched for dogs with confirmed central nervous system neosporosis and four observers recorded findings from each dog's MRI studies. A total of four dogs met inclusion criteria. Neurologic examination was indicative of a forebrain and cerebellar lesion in dog 2 and multifocal central nervous system disease in dogs 1, 3, and 4. Magnetic resonance imaging showed mild bilateral and symmetrical cerebellar atrophy in three of four dogs (dogs 2, 3, 4), intramedullary spinal cord changes in two dogs (dogs 3, 4) and a mesencephalic and metencephalic lesion in one dog (dog 2). Multifocal brain lesions were recognized in two dogs (dogs 1, 4) and were present in the thalamus, lentiform nucleus, centrum semiovale, internal capsule, brainstem and cortical gray matter of the frontal, parietal or temporal lobe. Findings indicated that central nervous system neosporosis may be characterized by multifocal MRI lesions as well as cerebellar involvement in dogs.
On a conjecture of Rudin on squares in arithmetic progressions
Authors: González-Jiménez Enrique , Xarles Xavier
Published: April 2014

Let $Q(N;q,a)$ be the number of squares in the arithmetic progression $qn+a$, for $n=0$,$1,\ldots,N-1$, and let $Q(N)$ be the maximum of $Q(N;q,a)$ over all non-trivial arithmetic progressions $qn + a$. Rudin’s conjecture claims that $Q(N)=O(\sqrt{N})$, and in its stronger form that $Q(N)=Q(N;24,1)$ if $N\ge 6$. We prove the conjecture above for $6\le N\le 52$. We even prove that the arithmetic progression $24n+1$ is the only one, up to equivalence, that contains $Q(N)$ squares for the values of $N$ such that $Q(N)$ increases, for $7\le N\le 52$ ($N=8,13,16,23,27,36,41$ and $52$).

Supplementary materials are available with this article.
Eye-Tracking Data Predict Importance of Product Features and Saliency of Size Change
Authors: Du Ping , MacDonald Erin F.
Published: April 2014

Features, or visible product attributes, are indispensable product components that influence customer evaluations of functionality, usability, symbolic impressions, and other qualities. Two basic components of features are visual appearance and size. This work tests whether or not eye-tracking data can (1) predict the relative importances between features, with respect to their visual design, in overall customer preference and (2) identify how much a feature must change in size in order to be noticeable by the viewer. The results demonstrate that feature importance is significantly correlated with a variety of gaze data. Results also show that there are significant differences in fixation time and count for noticeable versus unnoticeable size changes. Statistical models of gaze data can predict feature importance and saliency of size change.
Probabilistic Force Prediction in Cold Sheet Rolling by Bayesian Inference
Authors: Nelson Andrew W. , Malik Arif S. , Wendel John C. , Zipf Mark E.
Published: April 2014

A primary factor in manufacturing high-quality cold-rolled sheet is the ability to accurately predict the required rolling force. Rolling force directly influences roll-stack deflections, which correlate to strip thickness profile and flatness. Accurate rolling force predictions enable assignment of efficient pass schedules and appropriate flatness actuator set-points, thereby reducing rolling time, improving quality, and reducing scrap. Traditionally, force predictions in cold rolling have employed deterministic, two-dimensional analytical models such as those proposed by Roberts and Bland and Ford. These simplified methods are prone to inaccuracy, however, because of several uncertain, yet influential, model parameters that cannot be established deterministically under diverse cold rolling conditions. Typical uncertain model parameters include the material's strength coefficient, strain-hardening exponent, strain-rate dependency, and the roll-bite friction characteristics at low and high mill speeds. Conventionally, such parameters are evaluated deterministically by comparing force predictions to force measurements and employing a best-fit regression approach. In this work, Bayesian inference is applied to identify posterior probability distributions of the uncertain parameters in rolling force models. The aim is to incorporate Bayesian inference into rolling force prediction for cold rolling mills to create a probabilistic modeling approach that learns as new data are added. The rolling data are based on stainless steel types 301 and 304, rolled on a 10-in. wide, 4-high production cold mill. Force data were collected by observing load-cell measurements at steady rolling speeds for four coils. Several studies are performed in this work to investigate the probabilistic learning capability of the Bayesian inference approach. These include studies to examine learning from repeated rolling passes, from passes of diverse coils, and by assuming uniform prior probabilities when changing materials. It is concluded that the Bayesian updating approach is useful for improving rolling force probability estimates as evidence is introduced in the form of additional rolling data. Evaluation of learning behavior implies that data from sequential groups of coils having similar gauge and material is important for practical implementation of Bayesian updating in cold rolling.
A Hybrid Compressible–Incompressible Computational Fluid Dynamics Method for Richtmyer–Meshkov Mixing
Authors: Oggian Tommaso , Drikakis Dimitris , Youngs David L. , Williams Robin J. R.
Published: April 2014

This paper presents a hybrid compressible–incompressible approach for simulating the Richtmyer–Meshkov instability (RMI) and associated mixing. The proposed numerical approach aims to circumvent the numerical deficiencies of compressible methods at low Mach (LM) numbers, when the flow has become essentially incompressible. A compressible flow solver is used at the initial stage of the interaction of the shock wave with the fluids interface and the development of the RMI. When the flow becomes sufficiently incompressible, based on a Mach number prescribed threshold, the simulation is carried out using an incompressible flow solver. Both the compressible and incompressible solvers use Godunov-type methods and high-resolution numerical reconstruction schemes for computing the fluxes at the cell interfaces. The accuracy of the model is assessed by using results for a two-dimensional (2D) single-mode RMI.
Numerical Study of Purely Viscous Non-Newtonian Flow in an Abdominal Aortic Aneurysm
Authors: Marrero Victor L. , Tichy John A. , Sahni Onkar , Jansen Kenneth E.
Published: April 2014

It is well known that blood has non-Newtonian properties, but it is generally accepted that blood behaves as a Newtonian fluid at shear rates above 100 s−1. However, in transient conditions, there are times and locations where the shear rate is well below 100 s−1, and it is reasonable to infer that non-Newtonian effects could become important. In this study, purely viscous non-Newtonian (generalized Newtonian) properties of blood are incorporated into the simulation-based framework for cardiovascular surgery planning developed by Taylor et al. (1999, “Predictive Medicine: Computational Techniques in Therapeutic Decision Making,” Comput. Aided Surg., 4, pp. 231–247; 1998, “Finite Element Modeling of Blood Flow in Arteries,” Comput. Methods Appl. Mech. Eng., 158, pp. 155–196). Equations describing blood flow are solved in a patient-based abdominal aortic aneurysm model under steady and physiological flow conditions. Direct numerical simulation (DNS) is used, and the complex flow is found to be constantly transitioning between laminar and turbulent in both the spatial and temporal sense. It is found for the case simulated that using the non-Newtonian viscosity modifies the solution in subtle ways that yield a mesh-independent solution with fewer degrees of freedom than the Newtonian counterpart. It appears that in regions of separated flow, the lower shear rate produces higher viscosity with the non-Newtonian model, which reduces the associated resolution needs. When considering the real case of pulsatile flow, high shear layers lead to greater unsteadiness in the Newtonian case relative to the non-Newtonian case. This, in turn, results in a tendency for the non-Newtonian model to need fewer computational resources even though it has to perform additional calculations for the viscosity. It is also shown that both viscosity models predict comparable wall shear stress distribution. This work suggests that the use of a non-Newtonian viscosity models may be attractive to solve cardiovascular flows since it can provide simulation results that are presumably physically more realistic with at least comparable computational effort for a given level of accuracy.
Computing Numerical Solutions of Delayed Fractional Differential Equations With Time Varying Coefficients
Authors: Suresh Deshmukh Venkatesh
Published: April 2014

Fractional differential equations with time varying coefficients and delay are encountered in the analysis of models of metal cutting processes such as milling and drilling with viscoelastic damping elements. Viscoelastic damping is modeled as a fractional derivative. In the present paper, delayed fractional differential equations with bounded time varying coefficients in four different forms are analyzed using series solution and Chebyshev spectral collocation. A fractional differential equation with a known exact solution is then solved by the methodology presented in the paper. The agreement between the two is found to be excellent in terms of point-wise error in the trajectories. Solutions to the described fractional differential equations are computed next in state space and second order forms.
Strongly Nonlinear Subharmonic Resonance and Chaotic Motion of Axially Moving Thin Plate in Magnetic Field
Authors: Yuda Hu , Peng Hu , Jinzhi Zhang
Published: April 2014

In this paper, the nonlinear vibration and chaotic motion of the axially moving current-conducting thin plate under external harmonic force in magnetic field is studied. Improved multiple-scale method is employed to derive the strongly nonlinear subharmonic resonance bifurcation-response equation of the strip thin plate in transverse magnetic field. By using the singularity theory, the corresponding transition variety and bifurcation, which contain two parameters of the universal unfolding for this nonlinear system, are obtained. Numerical simulations are carried out to plot the bifurcation diagrams, corresponding maximum Lyapunov exponent diagrams, and dynamical response diagrams with respect to the bifurcation parameters such as magnetic induction intensity, axial tension, external load, external excited frequency, and axial speed. The influences of different bifurcation parameters on period motion, period times motion, and chaotic motion behaviors of subharmonic resonance system are analyzed. The results show that the complex dynamic behaviors of resonance system can be controlled by changing the corresponding parameters.
Comprehensive Online Control Strategies for Plastic Injection Molding Process
Authors: Seo Jaho , Khajepour Amir , Huissoon Jan P.
Published: April 2014

This study proposes an effective thermal control for plastic injection molding (polymer: Santoprene 8211-45 with density of 790 kg/m3, injection pressure: 1400 psi (9,652,660 Pa)) in a laminated die. For this purpose, a comprehensive control strategy is provided to cover various themes. First, a new method for determining the optimal sensor locations as a prerequisite step for modeling and controller design is introduced. Second, system identification through offline and online training with finite element analysis and neural network techniques are used to develop an accurate model by incorporating uncertain dynamics of the laminated die. Third, an additive feedforward control by adding direct adaptive inverse control to self-adaptive PID is developed for temperature control of cavity wall (cavity size: 52.9 × 32.07 × 16.03 mm). A verification of designed controller's performance demonstrates that the proposed strategy provides accurate online temperature tracking and faster response under thermal dynamics with various cycle-times in the injection mold process.
Amputee Subject Testing Protocol, Results, and Analysis of a Powered Transtibial Prosthetic Device
Authors: Sun Jinming , Fritz Jessica M. , Del Toro David R. , Voglewede Philip A.
Published: April 2014

A powered ankle-foot prothesis and its control system were previously designed and built. To evaluate this prosthesis, amputee subject testing was performed. The testing results are analyzed and compared between the powered prosthesis, passive prosthesis, and able-bodied gait. Qualitative comparison showed the prosthesis achieved the design objectives. During stance phase, active ankle moment was generated in the powered prosthesis before push-off to help the amputee walk more naturally. During swing phase, the powered prosthesis was able to move to natural position to achieve foot clearance. However, the prosthesis is slightly under powered compared with the able-bodied ankle.
Output-Feedback Stabilization for a Special Class of Stochastic Nonlinear Time-Delay System With More General Growth Conditions
Authors: Guo Long-Chuan , Liu Jian-Wei , Zuo Xin , Liang Hua-Qing
Published: April 2014

This paper focuses on a special class of stochastic nonlinear time-delay system with more weak conditions in which the drift and diffusion vectors depend on all the states, including the unmeasurable states for the first time. By introducing a high-gain observer, finding the maximum value interval of high-gain for the desired performance and choosing an appropriate Lyapunov-Krasoviskii function, an output-feedback controller is designed to ensure the equilibrium at the origin of the closed-loop system is globally asymptotically stable in probability and the output can be almost regulated to the origin surely. A practice example of mechanical movement system is provided to demonstrate the efficiency of the output-feedback controller.
Formation Control Protocols for Nonlinear Dynamical Systems Via Hybrid Stabilization of Sets
Authors: Haddad Wassim M. , Nersesov Sergey G. , Hui Qing , Ghasemi Masood
Published: April 2014

In this paper, we develop a hybrid control framework for addressing multiagent formation control protocols for general nonlinear dynamical systems using hybrid stabilization of sets. The proposed framework develops a novel class of fixed-order, energy-based hybrid controllers as a means for achieving cooperative control formations, which can include flocking, cyclic pursuit, rendezvous, and consensus control of multiagent systems. These dynamic controllers combine a logical switching architecture with the continuous system dynamics to guarantee that a system generalized energy function whose zero level set characterizes a specified system formation is strictly decreasing across switchings. The proposed approach addresses general nonlinear dynamical systems and is not limited to systems involving single and double integrator dynamics for consensus and formation control or unicycle models for cyclic pursuit. Finally, several numerical examples involving flocking, rendezvous, consensus, and circular formation protocols for standard system formation models are provided to demonstrate the efficacy of the proposed approach.
Thermal Analysis and Experimental Validation of Laminar Heat Transfer and Pressure Drop in Serpentine Channel Heat Sinks for Electronic Cooling
Authors: Hao Xiaohong , Peng Bei , Xie Gongnan , Chen Yi
Published: April 2014

In this paper, a thermal resistance network analytical model is proposed to investigate the thermal resistance and pressure drop in serpentine channel heat sinks with 180 deg bends. The total thermal resistance is obtained using a thermal resistance network model based on the equivalent thermal circuit method. Pressure drop is derived considering straight channel and bend loss because the bends interrupt the hydrodynamic boundary periodically. Considering the effects of laminar flow development and redevelopment, the bend loss coefficient is obtained as a function of the Reynolds number, aspect ratios, widths of fins, and turn clearances, through a three-regime correlation. The model is then experimentally validated by measuring the temperature and pressure characteristics of heat sinks with different Reynolds numbers and different geometric parameters. Finally, the temperature-rise and pressure distribution of the thermal fluid with Reynolds numbers of 500, 1000, and 1500 are examined utilizing this model.
Using a Statistically Calibrated Biphasic Finite Element Model of the Human Knee Joint to Identify Robust Designs for a Meniscal Substitute
Authors: Leatherman Erin R. , Guo Hongqiang , Gilbert Susannah L. , Hutchinson Ian D. , Maher Suzanne A. , Santner Thomas J.
Published: April 2014

This paper describes a methodology for selecting a set of biomechanical engineering design variables to optimize the performance of an engineered meniscal substitute when implanted in a population of subjects whose characteristics can be specified stochastically. For the meniscal design problem where engineering variables include aspects of meniscal geometry and meniscal material properties, this method shows that meniscal designs having simultaneously large radial modulus and large circumferential modulus provide both low mean peak contact stress and small variability in peak contact stress when used in the specified subject population. The method also shows that the mean peak contact stress is relatively insensitive to meniscal permeability, so the permeability used in the manufacture of a meniscal substitute can be selected on the basis of manufacturing ease or cost. This is a multiple objective problem with the mean peak contact stress over the population of subjects and its variability both desired to be small. The problem is solved by using a predictor of the mean peak contact stress across the tibial plateau that was developed from experimentally measured peak contact stresses from two modalities. The first experimental modality provided computed peak contact stresses using a finite element computational simulator of the dynamic tibial contact stress during axial dynamic loading. A small number of meniscal designs with specified subject environmental inputs were selected to make computational runs and to provide training data for the predictor developed below. The second experimental modality consisted of measured peak contact stress from a set of cadaver knees. The cadaver measurements were used to bias-correct and calibrate the simulator output. Because the finite element simulator is expensive to evaluate, a rapidly computable (calibrated) Kriging predictor was used to explore extensively the contact stresses for a wide range of meniscal engineering inputs and subject variables. The predicted values were used to determine the Pareto optimal set of engineering inputs to minimize peak contact stresses in the targeted population of subjects.
Simultaneous Wake- and Vortex-Induced Vibrations of a Cylinder With Two Degrees of Freedom in Each Direction
Authors: Chaplin J. R. , Batten W. M. J.
Published: April 2014

The flow-induced vibration of one cylinder in the wake of another is the subject of continuing interest in connection with interactions between vertical tension risers in deep water. When one riser is downstream of another, it is likely to be subject to wake-induced and vortex-induced excitations at different frequencies simultaneously. Both are complex mechanisms, and it is reasonable to assume that they interact. To begin to understand this complicated process, it is desirable that any modeling should incorporate some features of a multidegree-of-freedom structural response. With this aim, this paper describes experiments in which one cylinder was free to undergo simultaneous wake- and vortex-induced vibrations downstream of a similar but stationary cylinder in a steady flow. The downstream cylinder was mounted on an elastic system that had two natural frequencies in both the in-line and cross-flow directions. Mass ratios were almost the same in all four modes. Measurements are presented of simultaneous wake- and vortex-induced vibrations for cylinder separations of 5 and 10 diameters in the in-line direction, and up to 4 diameters transversely. At a reduced velocity of 83 (based on the cylinder's lower submerged natural frequency) and a separation of 5 diameters, excursions of wake-induced vibrations peaked at almost 5 diameters, when the downstream cylinder was near the edge of the upstream cylinder's wake.
Observer Design for Axial Flow Compressor
Authors: Gao Xuejun , Huang Tingwen , Huang Yu , Liu Jun , Xiao MingQing
Published: April 2014

Flow disturbance is the main cause which leads to the instability occurred in aero-engines, and it is an infinite-dimensional quantity that is impossible for a direct online measurement in reality. The unstable flow not only results in a drastic pressure reduction but also can damage to engine's components during the compressor operations. In this paper, we construct a local state observer which can deliver the full information of the flow disturbance by only sensing on an arbitrarily small area at the duct entrance in terms of averaging the flow disturbance, which provides a practical approach for real applications. The proposed observer makes possible in applications by using a feedback control to stabilize the system. The convergent gain is obtained through the approach of operator spectrum theory. Numerical simulations are provided to illustrate the effectiveness of the proposed observer by showing typical types of flow situations for aero-engine compressors.
Interdisciplinary cantilever physics: Elasticity of carrot, celery, and plasticware
Authors: Pestka Kenneth A.
Published: April 2014

This article presents several simple cantilever-based experiments using common household items (celery, carrot, and a plastic spoon) that are appropriate for introductory undergraduate laboratories or independent student projects. By applying Hooke's law and Euler beam theory, students are able to determine Young's modulus, fracture stress, yield stress, strain energy, and sound speed of these apparently disparate materials. In addition, a cellular foam elastic model is introduced—applicable to biologic materials as well as an essential component in the development of advanced engineering composites—that provides a mechanism to determine Young's modulus of the cell wall material found in celery and carrot. These experiments are designed to promote exploration of the similarities and differences between common inorganic and organic materials, fill a void in the typical undergraduate curriculum, and provide a foundation for more advanced material science pursuits within biology, botany, and food science as well as physics and engineering.
A collection of homework problems about the application of electricity and magnetism to medicine and biology
Authors: Roth Bradley J. , Hobbie Russell K.
Published: April 2014

This article contains a collection of homework problems to help students learn how concepts from electricity and magnetism can be applied to topics in medicine and biology. The problems are at a level typical of an undergraduate electricity and magnetism class, covering topics such as nerve electrophysiology, transcranial magnetic stimulation, and magnetic resonance imaging. The goal of these problems is to train biology and medical students to use quantitative methods, and also to introduce physics and engineering students to biological phenomena.
Ultrasound imaging as an undergraduate physics laboratory exercise
Authors: Stiles Timothy A.
Published: April 2014

Ultrasound imaging provides an interesting and accessible example of the intersection between biology, medicine, and physics. This article provides a review of the physics and technology currently available and discusses two recent methods that have expanded the diagnostic capabilities of ultrasound imaging. We also describe two undergraduate physics laboratory exercises involving ultrasound imaging.
Electrical interactions in the cell: Asymmetric screening in a watery “antiverse”
Authors: Doerr T. P. , Yu Yi-Kuo
Published: April 2014

The problem of electrostatics in biomolecular systems presents an excellent opportunity for cross-disciplinary science and a context in which fundamental physics is called for to answer complex questions. Due to the large density in biological cells of charged biomacromolecules such as protein factors and DNA, it is challenging to understand quantitatively the electric forces in these systems. Two questions are especially puzzling. First, how is it that such a dense system of charged molecules does not simply aggregate in random and non-functional ways? Second, since some mechanism apparently prevents such aggregation, how is it that binding of biomolecules still occurs so reliably? Recognizing the role of water as a universal solvent in living systems is key to understanding these questions. We present a simplified physical model in which water is regarded as a medium of high dielectric constant that nevertheless exhibits the key features essential for answering the two questions presented. The answer to the first question lies in the strong screening ability of water, which reduces the energy scale of the electrostatic interactions. Furthermore, our model reveals the existence of asymmetric screening, a pronounced asymmetry between the screening for a system with like charges and that for a system with opposite charges, and this provides an answer to the second question.
Mean-field master equation formalism for biofilament growth
Authors: Michaels Thomas C. T. , Knowles Tuomas P. J.
Published: April 2014

Nucleated polymerization is a general one-dimensional growth process that is commonly encountered as the mechanism of formation of protein filaments of fundamental importance to normal and aberrant biology. We discuss a mean-field description of this process. We formulate the problem in terms of a master equation and discuss approaches to reduce the infinite-dimensional master equation to a finite-dimensional system by considering the moments of the length distribution. We then present example solutions of the moment equations in several cases of practical importance.
Modeling discrete-variable stochastic dynamics: Ecological populations, gene networks, and a nanotube ion channel
Authors: Hilborn Robert C.
Published: April 2014

Many complex systems in both the physical and life sciences can be modeled as interacting elements with discrete-value variables. In most of these systems, stochasticity plays an important role. This paper examines an ecological population dynamics model, a simple model of a gene regulatory network, and a model for the conductance of a nanotube ion channel. The interplay of discrete-value variables, stochasticity, and nonlinear dynamics produces fascinating phenomena that are important in many areas of physics and biology.
Introductory physics in biological context: An approach to improve introductory physics for life science students
Authors: Crouch Catherine H. , Heller Kenneth
Published: April 2014

We describe restructuring the introductory physics for life science students (IPLS) course to better support these students in using physics to understand their chosen fields. Our courses teach physics using biologically rich contexts. Specifically, we use examples in which fundamental physics contributes significantly to understanding a biological system to make explicit the value of physics to the life sciences. This requires selecting the course content to reflect the topics most relevant to biology while maintaining the fundamental disciplinary structure of physics. In addition to stressing the importance of the fundamental principles of physics, an important goal is developing students' quantitative and problem solving skills. Our guiding pedagogical framework is the cognitive apprenticeship model, in which learning occurs most effectively when students can articulate why what they are learning matters to them. In this article, we describe our courses, summarize initial assessment data, and identify needs for future research.
Toward better physics labs for future biologists
Authors: Moore K. , Giannini J. , Losert W.
Published: April 2014

We have developed a set of laboratories and hands on activities to accompany a new two-semester interdisciplinary physics course that has been developed and tested in two small test classes at the University of Maryland, College Park (UMD) in 2012–2013. We have designed the laboratories to be taken accompanying a reformed course in the student's second year, with calculus, biology, and chemistry as prerequisites. These prerequisites permit the laboratories to include significant content on physics relevant to cellular scales, from chemical interactions to random motion and charge screening in fluids. We also introduce students to research-grade equipment and modern physics analysis tools in contexts relevant to biology while maintaining the pedagogically valuable open-ended laboratory structure of reformed laboratories. Preliminary student response results from these two classes are discussed.
Entropy and spontaneity in an introductory physics course for life science students
Authors: Geller Benjamin D. , Dreyfus Benjamin W. , Gouvea Julia , Sawtelle Vashti , Turpen Chandra , Redish Edward F.
Published: April 2014

Life science students develop a variety of resources for thinking about entropy and spontaneity in their biology, chemistry, and introductory physics courses. Helping students to develop a deeper and more coherent conceptual framework for organizing these varied ideas means attending carefully to the ways in which students interact with different disciplinary descriptions and to the ways in which these descriptions may be in tension. Canonical introductory physics treatments of the second law of thermodynamics, while useful in some contexts, may not be the most productive ones in authentic biological or chemical contexts. We draw on case-study interviews with introductory physics for life science students to argue that an approach to the second law of thermodynamics that emphasizes the interplay of energy and entropy in determining spontaneity (one that involves a central role for free energy) is one that draws on students' resources from biology and chemistry in particularly effective ways. We see the positioning of entropic arguments alongside energetic arguments in the determination of spontaneity as an important step toward making our life science students' biology, chemistry, and physics experiences more coherent.