bluuebunny/crossref_metadata_2025 huggingface dataset:
Shatter cones and planar deformation features confirm Santa Marta in Piauí State, Brazil, as an impact structure
Authors: de Oliveira Grace Juliana Gonçalves , Vasconcelos Marcos Alberto Rodrigues , Crósta Alvaro Penteado , Reimold Wolf Uwe , Góes Ana Maria , Kowitz Astrid
Published: October 2014

A total of 184 confirmed impact structures are known on Earth to date, as registered by the Earth Impact Database. The discovery of new impact structures has progressed in recent years at a rather low rate of about two structures per year. Here, we introduce the discovery of the approximately 10 km diameter Santa Marta impact structure in Piauí State in northeastern Brazil. Santa Marta is a moderately sized complex crater structure, with a raised rim and an off‐center, approximately 3.2 km wide central elevated area interpreted to coincide with the central uplift of the impact structure. The Santa Marta structure was first recognized in remote sensing imagery and, later, by distinct gravity and magnetic anomalies. Here, we provide results obtained during the first detailed ground survey. The Bouguer anomaly map shows a transition from a positive to a negative anomaly within the structure along a NE–SW trend, which may be associated with the basement signature and in parts with the signature developed after the crater was formed. Macroscopic evidence for impact in the form of shatter cones has been found in situ at the base around the central elevated plateau, and also in the interior of fractured conglomerate boulders occurring on the floor of the surrounding annular basin. Planar deformation features (PDFs) are abundant in sandstones of the central elevated plateau and at scattered locations in the inner part of the ring syncline. Together, shatter cones and PDFs provide definitive shock evidence that confirms the impact origin of Santa Marta. Crystallographic orientations of PDFs occurring in multiple sets in quartz grains are indicative of peak shock pressures of 20–25 GPa in the rocks exposed at present in the interior of the crater. In contrast to recent studies that have used additional, and sometimes highly controversial, alleged shock recognition features, Santa Marta was identified based on well‐understood, traditional shock evidence.
Trade‐offs and utility of alternative RADseq methods: Reply to Puritz et al.
Authors: Andrews Kimberly R. , Hohenlohe Paul A. , Miller Michael R. , Hand Brian K. , Seeb James E. , Luikart Gordon
Published: October 2014

Puritz et al. provide a review of several RADseq methodological approaches in response to our ‘Population Genomic Data Analysis’ workshop (Sept 2013) review (Andrews & Luikart 2014). We agree with Puritz et al. on the importance for researchers to thoroughly understand RADseq library preparation and data analysis when choosing an approach for answering their research questions. Some of us are currently using multiple RADseq protocols, and we agree that the different methods may offer advantages in different cases. Our workshop review did not intend to provide a thorough review of RADseq because the workshop covered a broad range of topics within the field of population genomics. Similarly, neither the response of Puritz et al. nor our comments here provide sufficient space to thoroughly review RADseq. Nonetheless, here we address some key points that we find unclear or potentially misleading in their evaluation of techniques.
Hive‐stored pollen of honey bees: many lines of evidence are consistent with pollen preservation, not nutrient conversion
Authors: Anderson Kirk E. , Carroll Mark J. , Sheehan Tim , Mott Brendon M. , Maes Patrick , Corby‐Harris Vanessa
Published: October 2014

Honey bee hives are filled with stored pollen, honey, plant resins and wax, all antimicrobial to differing degrees. Stored pollen is the nutritionally rich currency used for colony growth and consists of 40–50% simple sugars. Many studies speculate that prior to consumption by bees, stored pollen undergoes long‐term nutrient conversion, becoming more nutritious ‘bee bread’ as microbes predigest the pollen. We quantified both structural and functional aspects associated with this hypothesis using behavioural assays, bacterial plate counts, microscopy and 454 amplicon sequencing of the 16S rRNA gene from both newly collected and hive‐stored pollen. We found that bees preferentially consume fresh pollen stored for <3 days. Newly collected pollen contained few bacteria, values which decreased significantly as pollen were stored >96 h. The estimated microbe to pollen grain surface area ratio was 1:1 000 000 indicating a negligible effect of microbial metabolism on hive‐stored pollen. Consistent with these findings, hive‐stored pollen grains did not appear compromised according to microscopy. Based on year round 454 amplicon sequencing, bacterial communities of newly collected and hive‐stored pollen did not differ, indicating the lack of an emergent microbial community co‐evolved to digest stored pollen. In accord with previous culturing and 16S cloning, acid resistant and osmotolerant bacteria like Lactobacillus kunkeei were found in greatest abundance in stored pollen, consistent with the harsh character of this microenvironment. We conclude that stored pollen is not evolved for microbially mediated nutrient conversion, but is a preservative environment due primarily to added honey, nectar, bee secretions and properties of pollen itself.
Identifying the Modal Parameters of a Structure from Ambient Vibration Data via the Stationary Wavelet Packet
Authors: Su W. C. , Huang C. S. , Chen C. H. , Liu C. Y. , Huang H. C. , Le Q. T.
Published: October 2014

Ambient vibration tests are conducted widely to estimate the modal parameters of a structure. The work proposes an efficient wavelet‐based approach to determine the modal parameters of a structure from its ambient vibration responses. The proposed approach integrates the time series autoregressive (AR) model with the stationary wavelet packet transform. In addition to providing a richer decomposition and allowing for an improved time–frequency localization of signals over that of the discrete wavelet transform, the stationary wavelet packet transform also has significantly higher computational efficiency than the wavelet packet transform in terms of decomposing time‐shifted signals because the former has a time‐invariance property. The correlation matrices needed in determining the coefficient matrices in an AR model are established in subspaces expanded by stationary wavelet packets. The formulation for estimating the correlation matrices is shown for the first time. Because different subspaces contain signals with different frequency subbands, the fine filtering property enhances the ability of the proposed approach to identify not only the modes with strong modal interference, but also many modes from the responses of very few measured degrees of freedom. The proposed approach is validated by processing the numerically simulated responses of a seven‐floor shear building, which has closely spaced modes, with considering the effects of noise and incomplete measurements. Furthermore, the present approach is employed to process the velocity responses of an eight‐storey steel frame subjected to white noise input in a shaking table test and ambient vibration responses of a cable‐stayed bridge.
Whole genome/exome sequencing in mood and psychotic disorders
Authors: Kato Tadafumi
Published: October 2014

Recent developments in DNA sequencing technologies have allowed for genetic studies using whole genome or exome analysis, and these have been applied in the study of mood and psychotic disorders, including bipolar disorder, depression, schizophrenia, and schizoaffective disorder. In this review, the current situation, recent findings, methodological problems, and future directions of whole genome/exome analysis studies of these disorders are summarized. Whole genome/exome studies of bipolar disorder have included pedigree analysis and case–control studies, demonstrating the role of previously implicated pathways, such as calcium signaling, cyclic adenosine monophosphate response element binding protein (CREB) signaling, and potassium channels. Extensive analysis of trio families and case–control studies showed that de novo mutations play a role in the genetic architecture of schizophrenia and indicated that mutations in several molecular pathways, including chromatin regulation, activity‐regulated cytoskeleton, post‐synaptic density, N‐methyl‐D‐aspartate receptor, and targets of fragile X mental retardation protein, are associated with this disorder. Depression is a heterogeneous group of diseases and studies using exome analysis have been conducted to identify rare mutations causing Mendelian diseases that accompany depression. In the near future, clarification of the genetic architecture of bipolar disorder and schizophrenia is expected. Identification of causative mutations using these new technologies will facilitate neurobiological studies of these disorders.
N4‐Methylation of Cytosine Drastically Favors the Formation of (6‐4) Photoproducts in a TCG Context
Authors: Douki Thierry , Meador Jarah A. , Bérard Izabel , Wack Aude
Published: October 2014

Methylation of cytosine is a common biological process both in prokaryotic and eukaryotic cells. In addition to 5‐methylcytosine (5mC), some bacterial species contain in their genome N4‐methylcytosine (N4mC). Methylation at C5 has been shown to enhance the formation of pyrimidine dimeric photoproducts but nothing is known of the effect of N4 methylation on UV‐induced DNA damage. In the present work, we compared the yield and the nature of bipyrimidine photoproducts induced in a series of trinucleotides exhibiting a TXG sequence where X is either T, C, 5mC or N4mC. HPLC associated to tandem mass spectrometry was used to quantify cyclobutane pyrimidine dimers (CPD), (6‐4) photoproducts (64PP) and their Dewar valence isomer. Methylation at position N4 was found to drastically increase the reactivity of C upon exposure to both UVC and UVB and to favor the formation of 64PP. In contrast methylation at C5 increased the yield of CPD at the expense of 64PP. In addition, enhancement of photoreactivity by C5 methylation was much higher in the UVB than in the UVC range. These results show the drastic effect of the methylation site on the photochemistry of cytosine.
The Human Right to Sanitation: A Critique on the Absence of Environmental Considerations
Authors: Feris Loretta
Published: October 2014

As approximately 2.6 billion people are without access to basic sanitation, the recognition of a human right to sanitation represents an important development in international human rights law. The right, derived from Article 11 (the right to an adequate living) of the International Covenant on Economic, Social and Cultural Rights, has been framed as the human right to safe drinking water and sanitation. However, what has been largely absent in both the emergence of the right to sanitation in various international law instruments, as well as the conceptualization of it over the last decade, is a consideration of the impact of inadequate sanitation on the natural environment and the associated infringement of environmental rights. This article problematizes the scant acknowledgement of environmental considerations in the framing of the right to sanitation and argues that a multifaceted approach to the right to sanitation must integrate environmental concerns.
Participation and Political Equality in Direct Democracy: Educative Effect or Social Bias
Authors: Fatke Matthias
Published: October 2014

This paper analyses the moderating effect of direct democracy on the relationship between socioeconomic status and electoral participation. A sceptical position holds that direct democracy increases social bias in the electorate as issues are too complex and demanding. Participatory democrats in contrast invoke an educative effect of direct democratic institutions, thus decreasing social bias within the electorate. To test both arguments we use data from the Swiss cantons and estimate cross‐level interactions of socioeconomic and direct democracy variables on electoral participation. First differences between effects in the least and most direct democratic cantons are not statistically significant. This result may be seen as relief for sceptics as well as dampener for proponents of direct democracy.
Synchrotron X‐ray computed laminography of the three‐dimensional anatomy of tomato leaves
Authors: Verboven Pieter , Herremans Els , Helfen Lukas , Ho Quang T. , Abera Metadel , Baumbach Tilo , Wevers Martine , Nicolaï Bart M.
Published: October 2014

Synchrotron radiation computed laminography (SR‐CL) is presented as an imaging method for analyzing the three‐dimensional (3D) anatomy of leaves. The SR‐CL method was used to provide 3D images of 1‐mm² samples of intact leaves at a pixel resolution of 750 nm. The method allowed visualization and quantitative analysis of palisade and spongy mesophyll cells, and showed local venation patterns, aspects of xylem vascular structure and stomata. The method failed to image subcellular organelles such as chloroplasts. We constructed 3D computer models of leaves that can provide a basis for calculating gas exchange, light penetration and water and solute transport. The leaf anatomy of two different tomato genotypes grown in saturating light conditions was compared by 3D analysis. Differences were found in calculated values of tissue porosity, cell number density, cell area to volume ratio and cell volume and cell shape distributions of palisade and spongy cell layers. In contrast, the exposed cell area to leaf area ratio in mesophyll, a descriptor that correlates to the maximum rate of photosynthesis in saturated light conditions, was no different between spongy and palisade cells or between genotypes. The use of 3D image processing avoids many of the limitations of anatomical analysis with two‐dimensional sections.
Hydroxyethyl starch and granulocyte transfusions: considerations of utility and toxicity profile for patients and donors
Authors: Ambruso Daniel R.
Published: October 2014

Hydroxyethyl starch (hetastarch) is a synthetic glucose compound with extensive clinical use as a volume expander. Because of its red blood cell–sedimenting properties, hetastarch plays a major role in preparation of granulocyte products. Recent concerns have been raised about the use of hetastarch in critically ill patients for the development of renal injury and other severe adverse events. In contrast, granulocyte donors receive much less of this compound during collection procedures, and over many years, minimal toxicity has been documented in these individuals. Furthermore, granulocyte products contain very little hetastarch, and ill effects on renal function have not been associated with their administration. This review assesses available information about the toxicity profile of hetastarch in critically ill patients requiring a volume expander as well as granulocyte donors and recipients. Because of the lack of toxicity in these latter two groups, hetastarch should be available for preparation of granulocyte products and their administration.
Computation of the Flow Over a Sphere at Re = 3700: A Comparison of Uniform and Turbulent Inflow Conditions
Authors: Bazilevs Y. , Yan J. , de Stadler M. , Sarkar S.
Published: October 2014

A highly resolved computation of the flow past a sphere at Reynolds number Re = 3700 using a finite element method (FEM)-based residual-based variational multiscale (RBVMS) formulation is performed. Both uniform and turbulent inflow conditions are considered with the uniform flow case validated against a previous direct numerical simulation (DNS) study. We find that, as a result of adding free-stream turbulence of moderate intensity, the drag force on the sphere is increased, the length of the recirculation bubble is reduced dramatically, and the near-wake turbulence is significantly more energetic than in case of uniform inflow. In the case of uniform inflow, we find that the solution exhibits low temporal frequency modes, which necessitate long-time simulations to obtain high-fidelity statistical averages. Subjecting the sphere to turbulent inflow removes the low-frequency modes from the solution and enables shorter-time simulations to achieve converged flow statistics.
Flow Boiling Dynamics of Water and Nanofluids in a Single Microchannel at Different Heat Fluxes
Authors: Edel Zachary , Mukherjee Abhijit
Published: October 2014

The preferable cooling solution for micro-electronic systems could be forced flow boiling in micro heat exchangers. Nanoparticle deposition affects nucleate boiling via alteration of surface roughness, capillary wicking, wettability, and nucleation site density. In this study, flow boiling was investigated using water and nanofluids in a single rectangular microchannel at different heat fluxes. The observed change in flow regime transition revealed the effect of nanoparticles on the onset of nucleate boiling (ONB) and the onset of bubble elongation (OBE). The addition of nanoparticles was found to stabilize bubble nucleation and growth and increase heat transfer in the thin film regions.
Effect of Pore to Throat Size Ratio on Interfacial Heat Transfer Coefficient of Porous Media
Authors: Ozgumus Turkuler , Mobedi Moghtada
Published: October 2014

In this study, the effects of pore to throat size ratio on the interfacial heat transfer coefficient for a periodic porous media containing inline array of rectangular rods are investigated, numerically. The continuity, Navier–Stokes, and energy equations are solved for the representative elementary volume (REV) of the porous media to obtain the microscopic velocity and temperature distributions in the voids between the rods. Based on the obtained microscopic temperature distributions, the interfacial convective heat transfer coefficients and the corresponding Nusselt numbers are computed. The study is performed for pore to throat size ratios between 1.63 and 7.46, porosities from 0.7 to 0.9, and Reynolds numbers between 1 and 100. It is found that in addition to porosity and Reynolds number, the parameter of pore to throat size ratio plays an important role on the heat transfer in porous media. For the low values of pore to throat size ratios (i.e., β = 1.63), Nusselt number increases with porosity while for the high values of pore to throat size ratios (i.e., β = 7.46), the opposite behavior is observed. Based on the obtained numerical results, a correlation for the determination of Nusselt number in terms of porosity, pore to throat size ratio, Reynolds and Prandtl numbers is proposed.
Influence of the Sweep Stacking on the Performance of an Axial Fan
Authors: Nazmi Ilikan Ayhan , Ayder Erkan
Published: October 2014

In modern turbomachinery blade design, nonradial stacking of the profiles is often assumed to be one of the ways to improve the performance of a machine. Instead of stacking the profiles radially, the stacking line is changed by several modifications such as sweep, dihedral, lean, or a combination of these. Nonradial stacking influences secondary flows that have effects on the aerodynamic parameters such as efficiency, pressure rise, blade loading, and stall margin. However, many of the studies in literature are limited by the comparison of two or three cases. This situation leads to conflicting results because a modification may cause a positive effect in one study while in another one, the same modification may have a negative effect. In this study, a modified free vortex axial fan (named as base fan (BF) for this study) is designed first and the profiles of the blades are stacked radially by joining the centroids of the profiles. Second, 45 deg, 30 deg forward sweep (FS) and backward sweep (BS) modifications are applied. The effects of these modifications on aerodynamic performance of the fans are investigated by means of numerical calculations. The results show that FS and BS do not significantly affect the overall performance of the fan at the design flowrate in spite of the occurring modifications of the local blade pressure distribution. However, at low flowrates, FS and BS have positive and negative effects on the fan performance, respectively.
Multiscale Mass-Spring Model for High-Rate Compression of Vertically Aligned Carbon Nanotube Foams
Authors: Thevamaran Ramathasan , Fraternali Fernando , Daraio Chiara
Published: October 2014

We present a one-dimensional, multiscale mass-spring model to describe the response of vertically aligned carbon nanotube (VACNT) foams subjected to uniaxial, high-rate compressive deformations. The model uses mesoscopic dissipative spring elements composed of a lower level chain of asymmetric, bilateral, bistable elastic springs to describe the experimentally observed deformation-dependent stress–strain responses. The model shows an excellent agreement with the experimental response of VACNT foams undergoing finite deformations and enables in situ identification of the constitutive parameters at the smaller lengthscales. We apply the model to two cases of VACNT foams impacted at 1.75 ms−1 and 4.44 ms−1 and describe their dynamic response.
A Closed-Form Solution for Selecting Maximum Critically Damped Actuator Impedance Parameters
Authors: Paine Nicholas , Sentis Luis
Published: October 2014

This paper introduces a simple and effective method for selecting the maximum feedback gains in PD-type controllers applied to actuators where feedback delay and derivative signal filtering are present. The method provides the maximum feedback parameters that satisfy a phase margin criteria, producing a closed-loop system with high stability and a dynamic response with near-minimum settling time. Our approach is unique in that it simultaneously possesses: (1) a model of real-world performance-limiting factors (i.e., filtering and delay), (2) the ability to meet performance and stability criteria, and (3) the simplicity of a single closed-form expression. A central focus of our approach is the characterization of system stability through exhaustive searches of the feedback parameter space. Using this search-based method, we locate a set of maximum feedback parameters based on a phase margin criteria. We then fit continuous equations to this data and obtain a closed-form expression which matches the sampled data to within 2–4% error for the majority of the parameter space. We apply our feedback parameter selection method to two real-world actuators with widely differing system properties and show that our method successfully produces the maximum achievable nonoscillating impedance response.
Modal Analysis of Double-Helical Planetary Gears With Numerical and Analytical Approach
Authors: Sheng Zhaohua , Tang Jinyuan , Chen Siyu , Hu Zehua
Published: October 2014

The vibration modal properties of double-helical planetary gear (DHPG) system with three-dimensional motion are investigated with a combined use of numerical and analytical approach in this paper. The lumped-parameter model of the DHPG considering stiffness coupled between the left gear and the right gear is developed. Load-sharing with journal bearings is accepted in this planetary gear system, so that four stiffness coefficients can be applied to describe the dynamic behavior between the planet gear and the carrier. The model has three planar degrees of freedom for the carrier and an added axial degree of freedom for all gears, considering the effect of axial dynamic forces. The vibration equations are obtained according to Lagrange equation. A modal type distribution map is plotted initially to simplify modal classification. With the application of this modal type distribution map, all vibration modes are categorized distinctly into three essentially different types of modes including planet mode (PM), rotational-axial mode (RAM), and planer-translational mode (PTM). Unique characteristics of these vibration modes, such as, eigenvalue number, multiplicity of natural frequencies and deflection relations, are deduced and proved analytically. For each type of vibration modes, the reduced-order eigenvalue problems are derived.
Compound Control Strategy Based on Active Disturbance Rejection for Selected Catalytic Reduction systems
Authors: Ning Jinbiao , Yan Fengjun
Published: October 2014

Urea-based selected catalytic reduction (SCR) systems are effective ways in diesel engine after-treatment systems to meet increasingly stringent emission regulations. To achieve high NOx reduction efficiency and low NH3 slip, the control of the SCR system becomes more challenging, especially in transient operating conditions with model uncertainties. To effectively address this issue, this paper proposed a compound control strategy with a switching mechanism between an active disturbance rejection (ADR) controller and a zero-input controller. The ADR controller estimates and rejects the total (internal and external) disturbances from the SCR system when the exhaust gas temperature is high and its variation is small. The zero-input controller is used to lower ammonia surface coverage ratio to avoid high ammonia slip when exhaust gas temperature suddenly rises. The proposed control strategy is validated through a high-fidelity GT-Power simulation for a light-duty diesel engine over steady states and federal test procedure (FTP-75) test cycle. Its effectiveness is demonstrated especially in rapidly transient conditions with model uncertainties.
MEMS-Based Conjugate Surfaces Flexure Hinge
Authors: Verotti Matteo , Crescenzi Rocco , Balucani Marco , Belfiore Nicola P.
Published: October 2014

This paper presents a new concept flexure hinge for MEMS applications and reveals how to design, construct, and experimentally test. This hinge combines a curved beam, as a flexible element, and a pair of conjugate surfaces, whose contact depends on load conditions. The geometry is conceived in such a way that minimum stress conditions are maintained within the flexible beam. A comparison of the new design with the other kind of revolute and flexible joints is presented. Then, the static behavior of the hinge is analyzed by means of a theoretical approach, based on continuum mechanics, and the results are compared to those obtained by means of finite element analysis (FEA) simulation. A silicon hinge prototype is also presented and the construction process, based on single step lithography and reactive ion etching (RIE) technology, is discussed. Finally, a crucial in–SEM experiment is performed and the experimental results are interpreted through the theoretical models.
A Novel Bioreactor for Mechanobiological Studies of Engineered Heart Valve Tissue Formation Under Pulmonary Arterial Physiological Flow Conditions
Authors: Ramaswamy Sharan , Boronyak Steven M. , Le Trung , Holmes Andrew , Sotiropoulos Fotis , Sacks Michael S.
Published: October 2014

The ability to replicate physiological hemodynamic conditions during in vitro tissue development has been recognized as an important aspect in the development and in vitro assessment of engineered heart valve tissues. Moreover, we have demonstrated that studies aiming to understand mechanical conditioning require separation of the major heart valve deformation loading modes: flow, stretch, and flexure (FSF) (Sacks et al., 2009, "Bioengineering Challenges for Heart Valve Tissue Engineering," Annu. Rev. Biomed. Eng., 11(1), pp. 289–313). To achieve these goals in a novel bioreactor design, we utilized a cylindrical conduit configuration for the conditioning chamber to allow for higher fluid velocities, translating to higher shear stresses on the in situ tissue specimens while retaining laminar flow conditions. Moving boundary computational fluid dynamic (CFD) simulations were performed to predict the flow field under combined cyclic flexure and steady flow (cyclic-flex-flow) states using various combinations of flow rate, and media viscosity. The device was successfully constructed and tested for incubator housing, gas exchange, and sterility. In addition, we performed a pilot experiment using biodegradable polymer scaffolds seeded with bone marrow derived stem cells (BMSCs) at a seeding density of 5 × 106 cells/cm2. The constructs were subjected to combined cyclic flexure (1 Hz frequency) and steady flow (Re = 1376; flow rate of 1.06 l/min (LPM); shear stress in the range of 0–9 dynes/cm2) for 2 weeks to permit physiological shear stress conditions. Assays revealed significantly (P < 0.05) higher amounts of collagen (2051 ± 256 μg/g) at the end of 2 weeks in comparison to similar experiments previously conducted in our laboratory but performed at subphysiological levels of shear stress (<2 dynes/cm2; Engelmayr et al., 2006, "Cyclic Flexure and Laminar Flow Synergistically Accelerate Mesenchymal Stem Cell-Mediated Engineered Tissue Formation: Implications for Engineered Heart Valve Tissues," Biomaterials, 27(36), pp. 6083–6095). The implications of this novel design are that fully coupled or decoupled physiological flow, flexure, and stretch modes of engineered tissue conditioning investigations can be readily accomplished with the inclusion of this device in experimental protocols on engineered heart valve tissue formation.
Prediction of In Vivo Knee Joint Kinematics Using a Combined Dual Fluoroscopy Imaging and Statistical Shape Modeling Technique
Authors: Li Jing-Sheng , Tsai Tsung-Yuan , Wang Shaobai , Li Pingyue , Kwon Young-Min , Freiberg Andrew , Rubash Harry E. , Li Guoan
Published: October 2014

Using computed tomography (CT) or magnetic resonance (MR) images to construct 3D knee models has been widely used in biomedical engineering research. Statistical shape modeling (SSM) method is an alternative way to provide a fast, cost-efficient, and subject-specific knee modeling technique. This study was aimed to evaluate the feasibility of using a combined dual-fluoroscopic imaging system (DFIS) and SSM method to investigate in vivo knee kinematics. Three subjects were studied during a treadmill walking. The data were compared with the kinematics obtained using a CT-based modeling technique. Geometric root-mean-square (RMS) errors between the knee models constructed using the SSM and CT-based modeling techniques were 1.16 mm and 1.40 mm for the femur and tibia, respectively. For the kinematics of the knee during the treadmill gait, the SSM model can predict the knee kinematics with RMS errors within 3.3 deg for rotation and within 2.4 mm for translation throughout the stance phase of the gait cycle compared with those obtained using the CT-based knee models. The data indicated that the combined DFIS and SSM technique could be used for quick evaluation of knee joint kinematics.
Characterization of the Behavior of Confined Laminar Round Jets
Authors: Tyler Landfried D. , Jana Anirban , Kimber Mark
Published: October 2014

In this work, the Navier–Stokes equations are solved for a laminar, round jet in a large confinement. The flow is characterized as a function of the enclosure-to-jet diameter ratio, in the range 40–100, and the Reynolds numbers at jet inlet in the range 32–65. Results for jet decay and half width suggest that near the jet inlet the flow is identical to a free jet but eventually deviates away from the jet inlet. We develop a set of correlations including the jet centerline velocity and the jet half width, and features of the transition regions in the flow field.
Modeling and Experimental Study of a Wire Clamp for Wire Bonding
Authors: Wang Fuliang , Fan Dengke
Published: October 2014

A wire clamp is used to grip a gold wire with in 1–2 ms during thermosonic wire bonding. Modern wire bonders require faster and larger opening wire clamps. In order to simplify the design process and find the key parameters affecting the opening of wire clamps, a model analysis based on energy conservation was developed. The relation between geometric parameters and the amplification ratio was obtained. A finite element (FE) model was also developed in order to calculate the amplification ratio and natural frequency. Experiments were carried out in order to confirm the results of these models. Model studies show that the arm length was the major factor affecting the opening of the wire clamp.
Effect of Electromagnetic Actuation on Contact Loss in a Hertzian Contact Oscillator
Authors: Bichri Amine , Belhaq Mohamed , Perret-Liaudet Joël
Published: October 2014

The effect of electromagnetic actuation (EMA) on the dynamic of a single-sided Hertzian contact forced oscillator is studied near primary and secondary resonances. Emphasis is put on the case where two symmetric EMAs are introduced, such that one is driven by a DC actuation and the other is actuated by AC actuation with a fast frequency. An averaging technique and a perturbation analysis are performed to obtain the frequency response of the system. It is shown that for appropriate values of AC, forced Hertzian contact systems are more likely to remain operating in the linear regime without the loss of contact near certain resonances.
Identification and Validation of a Low Cycle Fatigue Damage Model for Al 7075-T6 Alloy
Authors: Masih Saeed , Mashayekhi Mohammad , Torabian Noushin
Published: October 2014

In this paper, the behavior of 7075-T6 aluminum alloy under low cycle fatigue (LCF) loading is experimentally and numerically investigated using continuum damage mechanics (CDM). An experimental procedure is established to identify the damage parameters for Al 7075-T6. A damage-coupled explicit finite element code is developed using the experimentally extracted damage parameters to study the material behavior under LCF loading. Moreover, fractographic examinations are conducted to identify the fatigue crack initiation locations and propagation mechanisms. The model is employed for life-time assessment of stringer-skin connection of a fuselage and the results are compared with the data available in the literature.
Model Validation for Identification of Damage Dynamics
Authors: Madden Ryan J. , Sawicki Jerzy T. , Pesch Alexander H.
Published: October 2014

Robust control techniques have allowed engineers to create more descriptive models by including uncertainty in the form of additive noise and plant perturbations. As a result, the complete model set is robust to any discrepancies between the mathematical model and actual system. Experimental unfalsification of the model set leads to the guarantee that the model and uncertainties are able to recreate all experimental data points. In this work, such a robust control relevant model validation technique is applied to structural health monitoring in order to (1) detect the presence of damage and (2) identify the damage dynamics when used in conjunction with model-based identification. Additionally, the robust control relevant model validation technique allows for a novel quality measure of the identified damage dynamics. Feasibility of the method is demonstrated experimentally on a rotordynamic crack detection test rig with the detection and identification of a change in structure. Further insight is gained from application of the method to seeded damage on a rotor levitated on active magnetic bearings (AMBs) in the form of a local reduction in stiffness.
An Integrator Backstepping Position Control of Electro-Hydraulic Servo System Based on Particle Swarm Optimization
Authors: Assegu Ermiyas , Roozbahani Hamid , Handroos Heikki
Published: October 2014

This paper presents a position control of a single rod electro-hydraulic actuator based on an integrator backstepping approach and tuned controller gain parameters by using a Particle Swarm Optimization (PSO). The aim of this paper is to develop optimal Back Stepping Controller (BSC) architecture on a nonlinear Electro Hydraulic Servo System (EHSS) of asymmetric cylinder to improve the position control performance. The influences of getting the parameters on the control law are analyzed in order to establish some rules of optimization. This can be determined automatically and intelligently by minimizing Integral Square Error (ISE). The proposed controller is simulated and then implemented to the experimental test bed to track the desired signal and test the limits of its performance. The simulation and experimental results are given to demonstrate the effectiveness of the proposed controller.
A Novel Three-Parameter Tuning Method for Seismic Simulation Shaking Table
Authors: Mao He , Luan Qiangli , Chen Zhangwei
Published: October 2014

Three-parameter control strategy, which incorporates signals of displacement, velocity and acceleration coming from the tested subject, has become a major technology in servo control for seismic simulation shaking table. The three-parameter control strategy allows the system to broaden its response bandwidth and increase its damping property. Normally, trial and error method is used to determine the proper value of each parameter, so the tested system can exhibit favorable frequency response performances. Whereas it can be very labor-intensive to find the optimal parameter values during the parameter trial and error process which also has a certain possibility to fail. To solve this problem, a novel rapid parameter tuning method of three-parameter control strategy has been proposed to consume less time in calculation, but realize the optimal response characteristics at the same time. The servo controller for seismic simulation shaking table is usually made up of three-parameter feedback, feed forward links and signal generator. By deducing the transfer function for each feedback and feed forward link the values of three parameters for the servo controller can be tuned efficiently. Simulation and experiment results have shown the control results of the novel and traditional three-parameter control methods to be virtually identical, proving the feasibility and validity of this novel parameter tuning method proposed in this study. Moreover, this method is proven to have a wide application in different tested system with different vibration characteristics, and it won’t bereave the system of its initial stability.
An Adaptive Robust Control for Displacement-Controlled End-Effectors
Authors: Busquets Enrique , Ivantysynova Monika
Published: October 2014

Cascade linear control strategies with output feedback have been studied at the Maha Fluid Power Research Center to demonstrate robust control for displacement-controlled rotary actuation. These strategies have been mainly investigated for closed-loop actuator control where the operator specifies the actuator position to close the loop. This paper presents an extension of the work developed for this kind of actuation by introducing a non-linear control strategy for open-loop applications (i.e. the operator closes the loop via a joystick). The test bench, a 1.5 ton hydraulically-operated end-effector with a range of motion of 270° is utilized to validate the obtained control law. The proposed control scheme, an adaptive robust control (ARC) law, ensures system stability and robustness for a wide range of motion while eliminating the linear controller approach limitations. Furthermore, changes in the plant behavior are taken into account through online parameter adaptation. To emphasize on the advantages of ARC, a deterministic robust control (DRC) law has been derived from the ARC. Results show that the advantages of online parameter adaptation lead to a dramatic increase on the actuator position accuracy. In addition, the ARC results are compared to the cascade controller developed by Grabbel in 2004.
Simulation of Water Hydraulic Control System of Francis Turbine
Authors: Walczak Pawel , Sobczyk Andrzej
Published: October 2014

In the modern world continually grows ecological consciousness of societies. We are looking for new and develop the already known methods of energy generation from renewable sources. Designing of simulation models using newest software (i.e. Simulation X) of existing system and on their base building new allow in an easy and fast way to demonstrate their advantages but also find areas that need to be improve. Based on previous experiences and virtual tests [12] finally was managed to create model of Francis turbine control system using water hydraulic elements. This article presents of the system consisting of three connected and interacting subsystems: hydraulic model of the guide apparatus control system, three-dimensional model of guide apparatus and model of water flow through the system of guide apparatus - turbine.
Electric Motor Based Hydraulic Pump Emulator in Real-Time HIL-Simulation: Finding the Optimum Emulator Electric Motor
Authors: Heikkinen Jani E. , Minav Tatiana A. , Handroos Heikki M. , Tapia Juan A.
Published: October 2014

Hardware-in-the-loop (HIL) setups are widely used in research, since they allow us fast and accurate testing under realistic conditions and easy repeatability. In this paper a HIL-setup is used to emulate the behavior of a hydraulic pump with an electric motor/generator. The setup contained a real-time simulator (RTS), two electric motors and two frequency converters. A real-time simulator was used for simulating the hydraulic and mechanical parts of the hydraulic machine. In previous study, it was shown that a virtual model of a hydraulic machine in a HIL setup can be used for testing by emulating the hydraulic pump with an electric motor. As the built setup did not fulfill requirements, new components for this kind of HIL setup are needed to be chosen carefully: optimized for data transfer speed, low latency and suitable refresh rates. In this research an attempt to find the optimum electric motor parameters, for the emulation purpose of a hydraulic pump was made. The parameters should be chosen based on refresh rate of the motor and initial analysis to narrow down the choices.
Hardware-in-the-Loop Testing of a Novel Blended Hydraulic Hybrid Transmission
Authors: Sprengel Michael , Ivantysynova Monika
Published: October 2014

Hydraulic hybrid transmissions have demonstrated considerable potential in improving the fuel economy of on-road and off-highway vehicles. The authors have previously proposed a novel hydraulic hybrid transmission architecture termed the Blended Hybrid with benefits in efficiency and performance over existing systems. Recently an optimally controlled simulation study found that a blended hybrid power split transmission consumed 16% less energy than an equivalent series hybrid power split transmission over the US standard Urban Dynamometer Driving Schedule. To further explore this novel architecture the authors constructed a hardware-in-the-loop transmission test rig. In this paper the authors detail the construction, control, and measurements results of the blended hybrid on this test rig.
Experimental Analysis of Heat Losses in Different Types of Hydraulic Accumulators
Authors: Juhala Jyri , Kajaste Jyrki , Pietola Matti
Published: October 2014

Even though an accumulator seems to be an ideal energy storage component, it also has some disadvantages. Further energy losses in form of heat transfer from gas to walls of the accumulator and to surroundings is a well-known problem. Especially the fast filling of the accumulator is nearly adiabatic process where the temperature of gas increases significantly. A part of this stored energy escapes from gas through the walls of the accumulator to the environment in form of heat reducing the energy efficiency. Several methods for improving the energy efficiency of the accumulator can be found in the literature. However, the previous studies made by the authors have concentrated to piston type accumulator but the knowledge of differences in performance characteristics of different type of accumulators is also important. The aim of this study is to compare different type of accumulator; piston, bladder and diaphragm type. The results of this study consist of experimental measurements of different types of hydraulic accumulators. The results demonstrate that the membrane inside the bladder type accumulator acts as a thermal insulator between the gas and the hydraulic fluid resulting to smaller thermal losses whereas in diaphragm and piston type accumulators the membrane is not protecting the nitrogen from heat losses.
Material Combinations for the Piston-Cylinder Interface of Axial Piston Machines: A Simulation Study
Authors: Mizell Daniel , Ivantysynova Monika
Published: October 2014

Axial-piston pumps and motors which operate at high pressures (above 380 bar) typically incorporate a copper-alloy bushing paired with a steel piston. Manufacturers have a desire to eliminate such nonferrous heavy metals from their designs to reduce manufacturing complexity and cost. This paper explores possible alternatives to this material combination at high pressures. Simulations incorporating thermal and elastic material properties are computed using a Fluid Structure Thermal Interaction (FSTI) model. The results of simulation reveal how material properties interact to affect fluid film thickness and pressure generation during pump operation. An understanding of these phenomena points the way toward the selection of novel material combinations to improve the behavior of the piston/cylinder interface.
Capabilities and Challenges of CFD in Multiphase Simulation of Hydraulic Tanks
Authors: Vollmer Thees , Untch Johannes
Published: October 2014

A major purpose of hydraulic tanks is the segregation of air, which can be supported by different design measures. To improve these measures CFD multiphase simulation can be used, as it is capable to assess the air flow within the oil. The different possibilities of CFD simulation are presented. Here single-phase flow models, simplified multiphase models as well as full multiphase flow models are discussed and evaluated. An example of each presented method is given and the results are compared. Last the capabilities of validating the simulations on a test bench are briefly discussed.
Multistep Aztec profiles by grayscale electron beam lithography for angle-resolved microspectrometer applications
Authors: Zhang Sichao , Shao Jinhai , Liu Jianpeng , Xu Chen , Ma Yaqi , Chen Yifang , Taksatorn Nit , Sun Yan
Published: October 2014

In this paper, grayscale electron beam lithography is applied to generate multistep Aztec profiles (MAPs) for angle-resolved spectral applications such as microspectrometers. Monte Carlo simulations taking into consideration the proximity effect are carried out to calculate the spatial dose distributions for desired profiles, using actual dissolution rates measured on the same resist. The MAPs in PMMA resist with step heights from 50 to 200 nm and step widths from 0.1 to 5 μm are achieved by high-resolution electron beam lithography, and high-resolution scanning electron microscopy and atomic force microscopy are used to characterize the quality of the MAPs. Angle-resolved spectra of the reflectance are obtained using a finite-difference time-domain simulator and by experimental measurements. A distinct angle selection of the wavelengths is demonstrated, though the high surface roughness measured on the deeper steps may cause broadening of the spectral peaks. Initial investigations into the origin of the surface roughness are carried out, and further improvements are discussed.
Application of cluster-plus-glue-atom model to barrierless Cu–Ni–Ti and Cu–Ni–Ta films
Authors: Li Xiaona , Ding Jianxin , Wang Miao , Chu Jinn P. , Dong Chuang
Published: October 2014

To improve the thermal stability of copper and avoid its diffusion into surrounding dielectrics or interfacial reactions with them, the authors applied the cluster-plus-glue-atom model to investigate barrierless Cu–Ni–M (M = Ti or Ta) seed layers. The dissolution of the third element (Ti or Ta) in the Cu lattice with the aid of Ni significantly improved the thermal stability of the Cu seed layer. The appropriate M/Ni (M = Ti or Ta) ratio was selected to obtain a low resistivity: the resistivity was as low as 2.5 μΩ cm for the (Ti1.5/13.5Ni12/13.5)0.3Cu99.7 film and 2.8 μΩ cm for the (Ta1.1/13.1Ni12/13.1)0.4Cu99.6 film after annealing at 500 °C for 1 h. After annealing at 500 °C for 40 h, the two films remained stable without forming a Cu3Si compound. The authors confirmed that the range of applications of the cluster-plus-glue-atom model could be extended. Therefore, a third element M with negative enthalpies of mixing with both Cu and Ni could be selected, under the premise that the mixing enthalpy of M–Ni is more negative than that of M–Cu.