bluuebunny/crossref_metadata_2025 huggingface dataset:
Molecular investigation of genetic assimilation during the rapid adaptive radiations of East African cichlid fishes
Authors: Gunter Helen M. , Schneider Ralf F. , Karner Immanuel , Sturmbauer Christian , Meyer Axel
Published: November 2017

Adaptive radiations are characterized by adaptive diversification intertwined with rapid speciation within a lineage resulting in many ecologically specialized, phenotypically diverse species. It has been proposed that adaptive radiations can originate from ancestral lineages with pronounced phenotypic plasticity in adaptive traits, facilitating ecologically driven phenotypic diversification that is ultimately fixed through genetic assimilation of gene regulatory regions. This study aimed to investigate how phenotypic plasticity is reflected in gene expression patterns in the trophic apparatus of several lineages of East African cichlid fishes, and whether the observed patterns support genetic assimilation. This investigation used a split brood experimental design to compare adaptive plasticity in species from within and outside of adaptive radiations. The plastic response was induced in the crushing pharyngeal jaws through feeding individuals either a hard or soft diet. We find that nonradiating, basal lineages show higher levels of adaptive morphological plasticity than the derived, radiated lineages, suggesting that these differences have become partially genetically fixed during the formation of the adaptive radiations. Two candidate genes that may have undergone genetic assimilation,gifandalas1,were identified, in addition to alterations in the wiring ofLPJpatterning networks. Taken together, our results suggest that genetic assimilation may have dampened the inducibility of plasticity related genes during the adaptive radiations of East African cichlids, flattening the reaction norms and canalizing their feeding phenotypes, driving adaptation to progressively more narrow ecological niches.
WRINKLED1 and ACYL‐COA:DIACYLGLYCEROL ACYLTRANSFERASE1 regulate tocochromanol metabolism in Arabidopsis
Authors: Pellaud Sébastien , Bory Alexandre , Chabert Valentin , Romanens Joëlle , Chaisse‐Leal Laurie , Doan Anh Vu , Frey Lucas , Gust Andrea , Fromm Katharina M. , Mène‐Saffrané Laurent
Published: November 2017

Photosynthetic organisms such as plants, algae and some cyanobacteria synthesize tocochromanols, a group of compounds that encompasses tocopherols and tocotrienols and that exhibits vitamin E activity in animals. While most vitamin E biosynthetic genes have been identified in plant genomes, regulatory genes controlling tocopherol accumulation are currently unknown.

We isolated by forward genetics Arabidopsis enhanced vitamin E (eve) mutants that overaccumulate the classic tocopherols and plastochromanol‐8, and a tocochromanol unknown in this species. We mapped eve1 and eve4, and identified the unknown Arabidopsis tocochromanol by using a combination of analytical tools. In addition, we determined its biosynthetic pathway with a series of tocochromanol biosynthetic mutants and transgenic lines.

eve1 and eve4 are two seed lipid mutants affecting the WRINKLED1 (WRI1) and ACYL‐COA:DIACYLGLYCEROL ACYLTRANSFERASE1 (DGAT1) genes, respectively. The unknown tocochromanol is 11′‐12′ γ‐tocomonoenol, whose biosynthesis is VITAMIN E 1 (VTE1) ‐ and VTE2‐dependent and is initiated by the condensation of homogentisate (HGA) and tetrahydrogeranylgeranyl pyrophosphate.

This study identifies the first two regulatory genes, WRI1 and DGAT1, that control the synthesis of all tocochromanol forms in seeds, and shows the existence of a metabolic trade‐off between lipid and tocochromanol metabolisms. Moreover, it shows that Arabidopsis possesses a tocomonoenol biosynthetic pathway that competes with tocopherol synthesis.
Geographic variation in forest composition and precipitation predict the synchrony of forest insect outbreaks
Authors: Haynes Kyle J. , Liebhold Andrew M. , Bjørnstad Ottar N. , Allstadt Andrew J. , Morin Randall S.
Published: November 2017

Evaluating the causes of spatial synchrony in population dynamics in nature is notoriously difficult due to a lack of data and appropriate statistical methods. Here, we use a recently developed method, a multivariate extension of the local indicators of spatial autocorrelation statistic, to map geographic variation in the synchrony of gypsy moth outbreaks. Regression analyses indicated that local synchrony of gypsy moth defoliation increased with the local synchrony of precipitation and the proportion of host tree density composed of oaks, especially those in the Lobatae (red oak) section. This may be the first study that demonstrates a relationship between defoliator population synchrony and host tree composition. More broadly, this study contributes to a small body of recent work that illustrates how mapping hotspots of unusually high or low synchrony facilitates an improved understanding of factors influencing spatially synchronous population dynamics generally, and triggers of pest insect outbreaks, more specifically.
Resolving biological impacts of multiple heat waves: interaction of hot and recovery days
Authors: Ma Chun‐Sen , Wang Lin , Zhang Wei , Rudolf Volker H. W.
Published: November 2017

Heat waves are increasing with global warming and have more dramatic biological effects on organisms in natural and agricultural ecosystems than mean temperature increase. However, predicting the impact of future heat waves on organisms and ecosystems is challenging because we still have a limited understanding of how the different components that characterize heat waves interact. Here we take an experimental approach to examine the individual and combine consequences of two important features that characterize heat waves: duration of successive hot days and recovery days between two hot spells. Specifically we exposed individuals of a global agricultural pest, the aphid Sitobion avenae to different heat wave scenarios by factorially manipulating the number of extreme hot days versus normal days and altered which period individuals experienced first in their life cycle. We found that effects of heat waves were driven by a delicate balance of damage during hot periods versus repair during normal periods. Increasing the duration of hot days in heat waves had a negative effect on various demographic rates and life‐time fitness of individuals, but magnitude of this effect was typically contingent on the temporal clustering of hot periods. Importantly, this interaction effect indicates that changes in the temporal distribution of extreme hot versus normal days can strongly alter the performance of organisms and dynamics of populations even when the total number of hot days during a given period remains unchanged. Together, these results emphasize the importance of accounting for the temporal distribution and quantitative patterns of extreme temperature events for predicting their consequences of natural and agricultural ecosystems.
Evaluation and development of flood‐tolerant soybean cultivars
Authors: Wu Chengjun , Zeng Ailan , Chen Pengyin , Hummer Wade , Mokua Jane , Shannon J. Grover , Nguyen Henry T.
Published: November 2017

Soybean (Glycine max [L.] Merr.) cultivars are generally sensitive to flooding stress. The plant growth is severely affected and grain yield is largely reduced in the flooded field. It is important to develop flood‐tolerant soybean cultivars for grain production in regions of heavy rainfalls worldwide. In this study, a total of 722 soybean genotypes were evaluated for flooding tolerance at R1 stages (first flower at any node) in the 5‐year flooding screening tests. Differential soybean genotypes exhibited diverse responses to flooding stress with that plant foliar damage score (FDS) and plant survival rate (PSR) ranged from 1.9 to 8.8 and 3.4% to 81.7%, respectively (p < .0001). Based on our standard of flooding evaluation, most genotypes were sensitive to flooding with 6.0 of average FDS and 38.7% of PSR. Fifty‐two soybean genotypes showed flooding tolerance and 11 genotypes were with consistent flooding tolerance during 4‐ to 5‐year continual evaluations. In the meantime, six genotypes were identified with consistent high sensitivity to flooding. The group analysis showed that genotypes from different sources had distinguishable responses to flooding stress (p < .0001). The interacting analysis of year and flooding tolerance indicated that FDS and PSR means were significantly different among 5 years due to weather temperature and flooding treatment time influences of each year (p < .0001). Furthermore, five breeding lines with high‐yielding and flood‐tolerant traits were developed using selected consistent flood‐tolerant and high‐yielding genotypes through conventional breeding approach.
Development of a molecular marker for self‐compatible S4′ haplotype in sweet cherry (Prunus avium L.) using high‐resolution melting
Authors: Muñoz‐Espinoza Claudia , Espinosa Evelyn , Bascuñán Roberto , Tapia Sebastián , Meneses Claudio , Almeida Andréa Miyasaka
Published: November 2017

Sweet cherry (Prunus avium L.) has stylar gametophytic self‐incompatibility, which is controlled by the multi‐allelic S‐locus and encompasses the highly polymorphic genes for the S‐ribonuclease (S‐RNase) and S‐haplotype‐specific F‐box (SFB), which are female and male determinants, respectively. The self‐compatible mutant SFB4′ corresponds to an allele variant of SFB4 and presents a frameshift mutation. Even though male‐determinant molecular markers can discriminate between SFB4 and SFB4′ alleles, the methods required are laborious, time‐consuming and expensive, and not suitable for massive analysis and integration into breeding programmes. Our aim was to develop molecular markers for the evaluation of self‐compatibility alleles in sweet cherry, that could be used as a high‐throughput screening strategy to identify SFB4 and SFB4′ alleles, based on a marker for male determinacy. Our results were consistent using primers flanking the mutation responsible for the SFB4′ allele. We designed a specific molecular marker and confirmed it in sweet cherry commercial varieties. This new molecular marker is feasible for self‐compatibility alleles in the male determinant in sweet cherry‐assisted breeding programs.
The Cancer Risk Associated with Residential Exposure to Soil Containing Radioactive Coal Combustion Residuals
Authors: Towle Kevin M. , Jacobs Neva F. B. , Keenan James J. , Monnot Andrew D.
Published: November 2017

Coal combustion residuals (CCRs) are composed of various constituents, including radioactive materials. The objective of this study was to utilize methodology on radionuclide risk assessment from the Environmental Protection Agency (EPA) to estimate the potential cancer risks associated with residential exposure to CCR‐containing soil. We evaluated potential radionuclide exposure via soil ingestion, inhalation of soil particulates, and external exposure to ionizing radiation using published CCR radioactivity values for 232Th, 228Ra, 238U, and 226Ra from the Appalachia, Illinois, and Powder River coal basins. Mean and upper‐bound cancer risks were estimated individually for each radionuclide, exposure pathway, and coal basin. For each radionuclide at each coal basin, external exposure to ionizing radiation contributed the greatest to the overall risk estimate, followed by incidental ingestion of soil and inhalation of soil particulates. The mean cancer risks by route of exposure were 2.01 × 10−6 (ingestion), 6.80 × 10−9 (inhalation), and 3.66 × 10−5 (external), while the upper bound cancer risks were 3.70 × 10−6 (ingestion), 1.18 × 10−8 (inhalation), and 6.15 × 10−5 (external), using summed radionuclide‐specific data from all locations. The upper bound cancer risk from all routes of exposure was 6.52 × 10−5. These estimated cancer risks were within the EPA's acceptable cancer risk range of 1 × 10−6 to 1 × 10−4. If the CCR radioactivity values used in this analysis are generally representative of CCR waste streams, then our findings suggest that CCRs would not be expected to pose a significant radiological risk to residents living in areas where contact with CCR‐containing soils might occur.
Risk Assessment of Human Toxoplasmosis Associated with the Consumption of Pork Meat in Italy
Authors: Condoleo Roberto , Rinaldi Laura , Sette Stefania , Mezher Ziad
Published: November 2017

Toxoplasmosis is a cosmopolitan disease and has a broad range of hosts, including humans and several wild and domestic animals. The human infection is mostly acquired through the consumption of contaminated food and pork meat has been recognized as one of the major sources of transmission. There are, however, certain fundamental differences between countries; therefore, the present study specifically aims to evaluate the exposure of the Italian population to Toxoplasma gondii through the ingestion of several types of pork meat products habitually consumed in Italy and to estimate the annual number of human infections within two subgroups of the population. A quantitative risk assessment model was built for this reason and was enriched with new elements in comparison to other similar risk assessments in order to enhance its accuracy. Sensitivity analysis and two alternative scenarios were implemented to identify the factors that have the highest impact on risk and to simulate different plausible conditions, respectively. The estimated overall average number of new infections per year among adults is 12,513 and 92 for pregnant women. The baseline model showed that almost all these infections are associated with the consumption of fresh meat cuts and preparations (mean risk of infection varied between 4.5 × 10−5 and 5.5 × 10−5) and only a small percentage is due to fermented sausages/salami. On the contrary, salt‐cured meat products seem to pose minor risk but further investigations are needed to clarify still unclear aspects. Among all the considered variables, cooking temperature and bradyzoites’ concentration in muscle impacted most the risk.
Poverty is a Public Bad: Panel Evidence From Subjective Well‐Being Data
Authors: Welsch Heinz , Biermann Philipp
Published: November 2017

Previous research has found that subjective well‐being (SWB) is lower for individuals classified as being in poverty. We extend the poverty‐SWB literature by focusing on aggregate poverty. Using panel data for 39,239 individuals living in Germany from 2005–2013, we show that people's SWB is negatively correlated with the regional (state‐level) poverty ratio while controlling for individual poverty status and poverty intensity. This suggests that poverty is a public bad. The negative relationship between aggregate poverty and SWB is more salient in the upper segments of the income distribution and is robust to controlling for the rate of unemployment and per capita GDP. The character of poverty as a public bad suggests that poverty alleviation is a matter not only of distributive justice, but of allocative efficiency.
Improving wellbeing in patients undergoing dialysis: Can meditation help?
Authors: Bennett Paul N , Ngo Trey , Kalife Christine , Schiller Brigitte
Published: November 2017

Coping with the stress and anxiety caused by end stage kidney disease (ESKD) symptoms, treatment, restrictions, and social, financial and family stressors, consumes many afflicted with kidney disease. Meditation has been shown to decrease anxiety and stress, and improve wellbeing and quality of life of people with chronic disease. However, the clinical uptake of meditation is low in the ESKD dialysis population. This review describes what meditation and mindful meditation are and how they have been used for people with ESKD. Further research, using active control conditions and larger sample size, is required to identify effective meditation interventions that can improve the wellbeing of our patients and their ability to cope with the demands of ESKD.
First Encounters: Repair Sequences in Cross‐Signing
Authors: Byun Kang‐Suk , de Vos Connie , Bradford Anastasia , Zeshan Ulrike , Levinson Stephen C.
Published: November 2017

Most human communication is between people who speak or sign the same languages. Nevertheless, communication is to some extent possible where there is no language in common, as every tourist knows. How this works is of some theoretical interest (Levinson, ). A nice arena to explore this capacity is when deaf signers of different languages meet for the first time and are able to use the iconic affordances of sign to begin communication. Here we focus on other‐initiated repair (OIR), that is, where one signer makes clear he or she does not understand, thus initiating repair of the prior conversational turn. OIR sequences are typically of a three‐turn structure (Schegloff ), including the problem source turn (T−1), the initiation of repair (T0), and the turn offering a problem solution (T+1). These sequences seem to have a universal structure (Dingemanse et al. 2013). We find that in most cases where such OIR occur, the signer of the troublesome turn (T−1) foresees potential difficulty and marks the utterance with “try markers” (Moerman, ; Sacks & Schegloff, ) which pause to invite recognition. The signers use repetition, gestural holds, prosodic lengthening, and eyegaze at the addressee as such try‐markers. Moreover, when T−1 is try‐marked this allows for faster response times of T+1 with respect to T0. This finding suggests that signers in these “first encounter” situations actively anticipate potential trouble and, through try‐marking, mobilize and facilitate OIRs. The suggestion is that heightened meta‐linguistic awareness can be utilized to deal with these problems at the limits of our communicational ability.
Full-Annulus Simulation of Nonsynchronous Blade Vibration Excitation of an Axial Compressor
Authors: Espinal Daniel , Im Hong-Sik , Zha Ge-Cheng
Published: November 2017

A high speed 1–1/2 axial compressor stage is simulated in this paper using an unsteady Reynolds-averaged Navier–Stokes (URANS) solver for a full-annulus configuration to capture its nonsynchronous vibration (NSV) flow excitation with rigid blades. A third-order weighted essentially nonoscillatory scheme for the inviscid flux and a second-order central differencing for the viscous terms are used to resolve nonlinear unsteady fluid flows. A fully conservative rotor/stator sliding boundary condition (BC) is employed with multiple-processor capability for rotor/stator sliding interface that accurately captures unsteady wake propagation between the rotor and stator blades while conserving fluxes across the rotor/stator interfaces. The predicted dominant frequencies using the blade tip response signals are not harmonic to the engine order, which is the NSV excitation. The simulation is based on a rotor blade with a 1.1% tip-chord clearance. Comparison with the previous 1/7 annulus simulations show that the time-shifted phase-lag BCs used in the 1/7 annulus are accurate. For most of the blades, the NSV excitation frequency is 6.2% lower than the measurement in the rig test, although some blades displayed slightly different NSV excitation frequencies. The simulation confirms that the NSV is a full annulus phenomenon. The instability of the circumferential traveling vortices in the vicinity of the rotor tip due to the strong interaction of incoming flow is the main cause of the NSV excitation. This instability is present in all blades of the rotor annulus. For circumferentially averaged parameters like total pressure ratio, NSV is observed to have an effect on the radial profile, particularly at radial locations above 70% span. A design with a lower loading of the upper blade span and a higher loading of the midblade spans is recommended to mitigate or remove NSV.
Experimental and Numerical Studies of the Excess Pore Pressure Field Surrounding an Advancing Spudcan Footing
Authors: Yi Jiang Tao , Li Yu Ping , Li Yi Wei , Yang Yu , Liu Yong
Published: November 2017

The rapid jack-in process of spudcan footing tends to generate substantial build-up of excess pore pressure below the spudcan underside. An intimate knowledge of the excess pore pressure concentration is thus of significance for understanding both the short-term and long-term mechanical behavior of spudcan. As yet there is a dearth of information in this area. This paper presents a comprehensive research to explore the pattern and magnitude of the excess pore pressure field surrounding an advancing spudcan. Both centrifuge experiments and effective-stress large deformation finite element analyses (LDFEAs) were involved, while the former served mainly to benchmark the latter and the latter provided a complete information database of the excess pore pressure. The bulb-shaped excess pore pressure concentration zone was identified below the spudcan underside. Sizes of pressure bulbs as well as the magnitudes of excess pore pressures inside them bore close relationship to the penetration depths and soil's properties. The results of parametric study led to the development of a simple yet useful approach to estimate the spudcan-penetration-induced excess pore pressure in soil without carrying out the complicated computation. Necessary charts and tables were provided to facilitate its usage. It is expected that the development of such an approach can aid the practicing engineer to obtain a quick and rough estimate of excess pore pressure generated in the midst of the jack-up spudcan penetration and prepare for its short-term and long-term implications.
Lubrication and Thermal Failure Mechanism Analysis in High-Speed Angular Contact Ball Bearing
Authors: Yunlong Wang , Wenzhong Wang , Yulong Li , Ziqiang Zhao
Published: November 2017

Lubrication analysis of rolling bearing is often conducted with assumed operating conditions, which does not consider the effect of internal dynamics of rolling bearing. In this paper, the effects of the applied load and bearing rotational speed on the lubrication performance in an angular contact ball bearing are conducted, which combines the bearing dynamic analysis and thermo-elastohydrodynamic lubrication (TEHL) analysis. First, the internal motions and contact forces are obtained from the developed bearing dynamic model, and then were integrated into the TEHL model to investigate the lubrication performance of the bearing. The results show that the rotational speed and external load has significant effects on film thickness, temperature, and power loss; if the improper axial load is applied for certain bearing speed, the lubrication performance will deteriorate and thermal failure may occur; there exists critical load or speed to keep good lubrication performance and avoid thermal failure; the skidding contributes to the thermal failure and bad lubrication performance.
The Effect of Spur Gear Tribo-Dynamic Response on Pitting Crack Nucleation
Authors: Li Sheng , Anisetti Anusha
Published: November 2017

This study investigates the role of the tribo-dynamic behavior in the contact fatigue crack nucleation for spur gears. To describe this fatigue phenomenon, a six-degree-of-freedom (DOF) lumped parameter dynamics formulation is coupled with a set of mixed elastohydrodynamic lubrication (EHL) governing equations. The former provides the dynamic tooth force to the EHL analysis, and the latter yields the gear mesh damping as well as the friction excitations that are required in the gear dynamics simulation. The converged tribo-dynamic surface normal pressure and tangential shear are then used to determine the multi-axial stress fields using the potential theory based closed-form stress formulation for half space. Lastly, the stress means and amplitudes are implemented in a multi-axial fatigue criterion to assess the fatigue damage.
Case Study Validation of Common Torsional Rotordynamic Practices for Integrally Geared Compressors
Authors: Kumar Dhruv , Moeller Michael
Published: November 2017

Drivetrains for turbomachinery used in plant operations generally consist of a centrifugal compressor driven by turbines or electric motors, and may include intermediate speed reducing gearboxes. Each of these drivetrain components require accurate torsional modelling to ensure safe operation. Shaft modelling assumptions for these component sections can significantly alter the location of predicted torsional criticals and responses. One essential modelling assumption is the calculation of effective torsional stiffness in stepped shafts. Industry accepted methods include shaft penetration, the 45 degree rule and FEA approaches. A comparison of the three methods and the torsional impacts on a case study are presented.
Optimal Collision-Free Path Planning for an Autonomous Multi-Wheeled Combat Vehicle
Authors: Mohamed Amr , El-Gindy Moustafa , Ren Jing , Lang Haoxiang
Published: November 2017

This paper presents an optimal collision-free path planning algorithm of an autonomous multi-wheeled combat vehicle using optimal control theory and artificial potential field function (APF). The optimal path of the autonomous vehicle between a given starting and goal points is generated by an optimal path planning algorithm. The cost function of the path planning is solved together with vehicle dynamics equations to satisfy the vehicle dynamics constraints and the boundary conditions. For this purpose, a simplified four-axle bicycle model of the actual vehicle considering the vehicle body lateral and yaw dynamics while neglecting roll dynamics is used. The obstacle avoidance technique is mathematically modeled based on the proposed sigmoid function as the artificial potential field method. This potential function is assigned to each obstacle as a repulsive potential field. The inclusion of these potential fields results in a new APF which controls the steering angle of the autonomous vehicle to reach the goal point. A full nonlinear multi-wheeled combat vehicle model in TruckSim software is used for validation. This is done by importing the generated optimal path data from the introduced optimal path planning MATLAB algorithm and comparing lateral acceleration, yaw rate and curvature at different speeds (9 km/h, 28 km/h) for both simplified and TruckSim vehicle model. The simulation results show that the obtained optimal path for the autonomous multi-wheeled combat vehicle satisfies all vehicle dynamics constraints and successfully validated with TruckSim vehicle model.
Vibration Characteristics of Friction Plate of a 6-Speed Planetary Gear Train Base on Multi-Body Dynamic Model
Authors: Su Tinghui , Cao Zheng , Shao Yimin , Wang Liming , Li Hongwu , Cheng Yan , Xu Jin
Published: November 2017

As braking components, friction plates are key components in automobile transmissions. Due to tough working conditions, i.e. high speed, high friction, fracture and plastic deformation are easily observed in friction plates. However, most of previous studies mainly focused on the chemical analysis of the fracture friction plate, the researches on impact damage have rarely published in the listed literature. In order to investigate the impact damage for friction plate, a dynamic model for a friction plate of a 6-speed planetary gear train is established based on multi-body theory. The dynamic model of planetary gear transmission mechanism is constructed. The rotating speed of the inner hub is obtained. Furthermore, the contact force between the friction plate and the inner hub is calculated. The relationship between the vibration characteristics of the friction plate and operation conditions are studied.
Study on the Pitch Error in the Initial Stage of Gear Rolling Process
Authors: Ma Ziyong , Luo Yuanxin , Wang Yongqin
Published: November 2017

Gear rolling process is a state-of-the-art technology on track for the future due to the productivity, high material unitization rate and high profile qualities. The pitch error has been one of main concern to fabricate high precision gears. The initial stage is to divide the angular position of teeth, and it has significant impact to pitch error of the formed gear as well as fatigue life of the rolling tools. This paper is aimed to study the two geometrical requirements of dividing teeth in the initial stage that are the phase difference of rolling tools and the contact ratio. The contact ratio is modeled with consideration of the geometric of the forming tool, bite depth, size of the workpiece, etc. A speed-controlled forced synchronization system is proposed for forming large module gear and the rolling experiments demonstrates its effectiveness. Finally, some discussions and conclusions are given.
Innovative Structural Topology Optimization Approach for Rotordynamics Components Using Innovative Materials and New Manufacturing Techniques
Authors: Boccini Enrico , Meli Enrico , Rindi Andrea , Corbò Simone , Iurisci Giuseppe
Published: November 2017

Topology optimization is an innovative strategy applied in the turbomachinery field with the aim of substantially improving the performances of turbomachinery components in terms of weights, stress levels and rotation speed, with a very remarkable economic impact. Being very flexible, topology optimization allows to manage the structures topology, significantly improving material distribution within a given design space for a given set of loads and boundary conditions. In this paper, the authors, in cooperation with General Electric Nuovo Pignone, develop a new concept design of a turbine disk and the optimized component is compared to the benchmark, in order to verify the achieved improvements. Special attention is paid to the use of innovative materials with lattice structures, characterized by complex three-dimensional geometries. Thanks to advanced technologies, as additive manufacturing, it is now possible to effectively exploit topology optimization to develop new components featured by complex structures. The developed prototypes will be manufactured and tested in the near future together with the industrial partners.
Structure Sensitivity Analysis and Dynamic Performance Optimization of Marine Gearbox
Authors: Lin Tengjiao , Xie Daokun , Tan Ziran , Liu Bo
Published: November 2017

The aim of this paper is to investigate the influence of structure parameters on the vibration characteristics and improve the dynamic performance of marine gearbox. A finite element model was established to solve the dynamic response by using modal superposition method. Based on the theory of multi-objective optimization design, the structure sensitivity analysis model of marine gearbox was established, which takes the structure parameters of the housing as design variables. The modal and response sensitivity was obtained by using the optimal gradient method. According to the results of sensitivity analysis, a modal and response optimization model of marine gearbox was established. The objective was to avoid natural frequencies from the excitation frequencies and minimize the root mean square of vibration acceleration of the evaluating points on the surface of housing. Then the modal optimization and response optimization of gearbox were carried out by using zero-order and first-order optimization method. The results indicate that the dynamic optimization of the gearbox can be achieved. After optimization, the amplitude of vibration acceleration of the evaluating points on the housing surface has been reduced and the resonance of marine gearbox can be avoided.
Elastic Energy Absorption of Origami-Based Corrugations
Authors: Tolman Sean S. , Magleby Spencer P. , Howell Larry L.
Published: November 2017

The mechanical properties of origami tessellations may provide innovative new designs for energy absorbing applications. The elastic energy absorbing properties of a particular tesselation, the Miura-ori, is investigated. Analytical models for the kinematics and force-deflection of a unit cell based on two different modes of elastic energy absorption are derived. The force-deflection model is developed based on the application of compliant mechanism theory and virtual work analysis. The models are verified through comparison with published results for similar models, analysis using commercial kinematics software and comparison to physical testing. Physical prototypes are used to determine values stiffness terms. The analytical models are used to explore the effects of the key geometrical parameters of the tessellation. This work lays a foundation for the use of origami-based corrugations in elastic energy absorption applications.
Multiple Model Predictive Control for Solid Oxide Fuel Cells
Authors: Pan Lei , Xue Yali , Sun Li , Li Donghai , Wu Zhenlong
Published: November 2017

It is difficult to control the output voltage of the Solid Oxide Fuel Cells (SOFCs) because of the system nonlinearity, load disturbance and various constraints on the actuators and the fuel utilization rate. To overcome these difficulties, this paper proposed a multiple model predictive control scheme. The nonlinearity is addressed by using multiple models that are linearized at different operating conditions. The disturbance is accommodated by directly sending the load current information to the optimizer. And the constraints are naturally handled by formulating a constrained optimization problem. The simulation results show the effectiveness of the proposed strategy.
Relative Navigation of Non-Cooperative Space Target Based on Multiple Cooperative Space Robots
Authors: Hong Yao , Simon Dan
Published: November 2017

It is difficult for a space robot to perform autonomous relative navigation of a non-cooperative space target using only a single line-of-sight measurement. To solve this problem, a decentralized-centralized relative navigation method based on multiple space robots in a leader-follower formation is proposed. All the leader and follower robots observe the same space target and combine their estimates to obtain an improved estimate of the target motion. The relative navigation filter of each leader and follower robot is independently implemented based on non-dimensional invariant sets of Hill-Clohessy-Wiltshire (HCW) equations. The invariant sets of relative motion between the follower and leader space robots are known due to their mutual cooperation, and are used in this research as state equality constraints to improve the estimate of the target motion. Numerical simulations show the feasibility of the proposed method, and the results indicate that the constrained state estimation accuracy of the space target is improved compared to unconstrained state estimation.
The Experimental Study on a Bistable Piezoelectric-Electromagnetic Combined Vibration Energy Harvester
Authors: Yao Ming Hui , Liu Peng Fei , Zhang Wei , Cao Dong Xing
Published: November 2017

This paper presents an experimental investigation on the bistable piezoelectric electromagnetic combined energy harvester based on vibration. The end of the piezoelectric cantilever beam has a tip magnet. The opposite of the piezoelectric cantilever beam has a coil, a spring and a magnet. The power generation efficiency and dynamic behaviors for three different kinds of the piezoelectric cantilever beam structures are experimentally studied, such as the conventional piezoelectric cantilever beam, the bistable piezoelectric cantilever beam introduced spring and magnet, and the bistable piezoelectric cantilever beam introduced spring, magnet and coil. Experimental results show that the introduction of the spring and magnet improves the maximum output voltage and broaden the effective frequency bandwidth. The power generation efficiency of the system is improved by adding the coil. Complicated nonlinear dynamic behaviors occur in the system, when the spring and the magnet are introduced. These nonlinear dynamic behaviors broaden the effective frequency bandwidth.
The Accurate Analysis of Magnetic Force of Bi-Stable Piezoelectric Cantilever Energy Harvester
Authors: Zhang Yu-Yang , Leng Yong-Gang , Fan Sheng-Bo
Published: November 2017

In the study of nonlinear bi-stable piezoelectric cantilever energy harvesting system, the accuracy of magnetic force’s calculation on which the potential function and dynamics of the system depend is essential to predict the output response and energy harvesting effect. In this paper, we built a shape function to calculate the trace of the end of the beam with the integral of the entire cantilever beam’s slope, and the magnetic force is consequently derived from the achieved magnets’ real-time position and posture using the magnetizing currents method. With the comprehensive consideration of axial magnetic force and lateral magnetic force, the change of both resultant magnetic force’s value and direction are achieved. The simulation results demonstrate that when the displacement of the magnet at the end of the beam is large enough, the axial and lateral magnetic forces change turn from repulsion to attraction, which leads to a large veer of the direction of resultant magnetic force across two quadrants. And the relationship between magnetic force and interval between two magnets is also achieved. The calculation results of this work are nicely consistent with experimental data. So, the accuracy of this calculation method has been proved to be much higher than the existing calculation method.
Aerodynamic Automobile Shape Optimization by Incorporating Reverse Shape Design Method With CFD Analysis
Authors: Song Kisun , Choo Kyung Hak , Kim Jung-Hyun , Mavris Dimitri N.
Published: November 2017

In modern automotive industry market, there have been a lot of state-of-art methodologies to perform a conceptual design of a car; functional methods and 3D scanning technology are widely used. Naturally, the issues frequently boiled down to a trade-off decision making problem between quality and cost. Besides, to incorporate the design method with advanced optimization methodologies such as design-of-experiments (DOE), surrogate modeling, how efficiently a method can morph or recreate a vehicle’s shape is crucial. This paper accomplishes an aerodynamic design optimization of rear shape of a sedan by incorporating a reverse shape design method (RSDM) with the aforementioned methodologies based on CFD analysis for aerodynamic drag reduction. RSDM reversely recovers a 3D geometry of a car from several 2D schematics. The backbone boundary lines of 2D schematic are identified and regressed by appropriate interpolation function and a 3D shape is yielded by a series of simple arithmetic calculations without losing the detail geometric features. Besides, RSDM can parametrize every geometric entity to efficiently manipulate the shape for application to design optimization studies. As the baseline, an Audi A6 is modeled by RSDM and explored through CFD analysis for model validation. Choosing six design variables around the rear shape, 77 design points are created to build neural networks. Finally, a significant amount of CD reduction is obtained and corresponding configuration is validated via CFD.
Measurement and Control Software for Transmission Error of Bevel Gear Pair
Authors: Wang Binghe , Tang Jie , Shi Zhaoyao
Published: November 2017

In order to measure the transmission error of bevel gear pair, a measurement method of transmission error based on the best mounting distance was introduced. The algorithm of adjustment of the best mounting distance was presented, and the single flank testing of bevel gear pair was carried out on this position. The evaluation of transmission error and frequency spectrum was described. Measurement and control software was developed including the function of data acquisition and processing and graphic display, optimizing search of best mounting distance and SPC statistical analysis. The class diagram, the sequence diagram, the test case diagram and the main interface of the software was designed. The experiment was carried out that the mounting distance on 130.0mm of pinion is the best mounting distance according to the value of the factor F 0.699. Under the best mounting distance, the total tangential composite deviation is 79.27μm. The method and the software mentioned in this paper can be used in measurement of the bevel gear pair or the face gear pair.
Design of a Real-Time Dynamic Test Bench for Testing and Developing a Novel Seamless Two-Speed Transmission for Electric Vehicles
Authors: Nguyen Truong Sinh , Song Jian , Fang Shengnan , Song Haijun , Tai Yuzhuo , Li Fei
Published: November 2017

Experiment on a test bench is one of the key points during the research and development of a transmission. This paper designs a new real-time dynamic test bench based on MATLAB/Simulink® for testing and developing a novel seamless two-speed automatic mechanical transmission (AMT) for electric vehicles (EVs). Structure of the transmission allowing seamless shifting between two gears is also proposed. According to the transmission structure and the real-time testing requirements, hardware components and software system of the test bench are designed. A real-time executable and flexible model of the EV that is more suitable for hardware-in-the-loop (HIL) simulation, is built to run on Simulink Real-Time platform. The EV model is combined with two induction motors adopting direct torque control (DTC) technique to emulate the dynamic driving conditions of the transmission on the test bench. Simulation and experimental results show that the test bench responds well to the real-time dynamic requirements and it is very useful for testing and developing the proposed transmission.
Nonlinear Oscillations of Hyperelastic Annular Membranes With Varying Density
Authors: Soares Renata M. , Gonçalves Paulo B.
Published: November 2017

This research presents the mathematical modeling for the nonlinear oscillations analysis of a pre-stretched hyperelastic annular membrane with varying density under finite deformations. The membrane material is assumed to be homogeneous, isotropic, and neo-Hookean and the variation of the membrane density in the radial direction is investigated. The membrane is first subjected to a uniform radial traction along its outer circumference and the stretched membrane is fixed along the outer boundary. Then the equations of motion of the pre-stretched membrane are derived. From the linearized equations of motion, the natural frequencies and mode shapes of the membrane are obtained analytically. The vibration modes are described by hypergeometric functions, which are used to approximate the nonlinear deformation field using the Galerkin method. The results are compared with the results evaluated for the same membrane using a nonlinear finite element formulation. The results show the influence of the stretching ratio and varying density on the linear and nonlinear oscillations of the membrane.
Self-Locking Origami Structures and Locking-Induced Piecewise Stiffness
Authors: Fang Hongbin , Chu Shih-Cheng A. , Wang K. W.
Published: November 2017

The folding motion of an origami structure can be stopped at a non-flat position when two of its facets bind together. Such facet-binding will induce self-locking so that the overall origami structure can stay at a pre-specified configuration without the help of additional locking devices or actuators. This research investigates the designs of self-locking origami structures and the locking-induced kinematical and mechanical properties. We show that incorporating multiple cells of the same type but with different geometry could significantly enrich the self-locking origami pattern design. Meanwhile, it offers remarkable programmability to the kinematical properties of the self-locking origami structures, including the number and position of locking points, and the deformation range. Self-locking will also affect the mechanical characteristics of the origami structures. Experiments and finite element simulations reveal that the structural stiffness will experience a sudden jump with the occurrence of self-locking, inducing a piecewise stiffness profile. The results of this research would provide design guidelines for developing self-locking origami structures and metamaterials with excellent kinematical and stiffness characteristics, with many potential engineering applications.
Electrostatically Actuated M/NEMS With Casimir Effect: Primary Resonance — Comparison Between Three Methods
Authors: Caruntu Dumitru I. , Beatriz Julio S. , Reyes Christian
Published: November 2017

This paper deals with electrostatically actuated micro- and nano-electromechanical systems (M/NEMS) cantilever resonator under electrostatic actuation. The model includes Casimir effect. Three different methods are used to investigate the primary resonance of the MEMS resonator. The first two methods are based on a Galerkin approach in which the initial value and boundary value problem, given by the partial differential equation (PDE) of motion and the initial and boundary conditions, is transformed into an initial value problem of one ordinary differential equation (ODE) or a system of ODEs depending on how many modes of vibrations are considered in the model. The first method used is the Method of Multiple Scales (MMS) which is an approximate analytical method used to solve the model using one mode of vibration. The second method referred to as Reduced Order Model (ROM) solves the model using two to five modes of vibration using numerical integration. The third method is different than the first two in the sense that the initial value and boundary value problem describing the MEMS resonator is transformed into a boundary value problem (BVP) by using finite differences tor time derivatives. For this Matlab built-in function bvp4c is used to solve the problem. This built-in function is used for two different versions of the same equation. One which involves Taylor expansions of the nonlinear terms, and the other which does not. Results between the methods are in agreement. Thus any of these methods can be used to accurately predict the behavior of the MEMS resonator. For the ROM, two equations are also used, one for Casimir and one for without. The influence of damping, Casimir, and voltage parameter are also shown.
A Method for the Optimal Design of Split Ring Dampers for Aviation Gears
Authors: Ye Hang , Wang Yanrong , Jiang Xianghua
Published: November 2017

In order to reduce the resonance of aviation bevel gears, designing frictional interfaces for gear systems is an important approach through dissipate vibration energy. One emerging technology uses ring dampers, which are ring-like substructures constrained to move inside a groove at the rim of the gear. Ring dampers are in contact with the rim of the gear due to centrifugal force, and they create nonlinear dissipation by relative motion between the ring and the gear.

The analysis of the dynamic response of nonlinear structures is commonly done by numerical integration of the equations of motion, which is computationally inefficient, especially for steady-state responses.

In this paper an efficient methodology to predict the effect of the ring damper based on energy method, predicting the dissipated energy by friction force, converting into equivalent damping and to identify the main design parameters affecting the damper performance is proposed. The approach is based on expressing the vibration energy dissipated by nonlinear forces per vibration cycle as equivalent nonlinear damping ratio. This method avoids computing the forced response of the gear with ring damper in the frequency domain, that can increase the efficiency of the ring damper design.

The methodology is applied to an aviation bevel gear. The effect of the principal design parameters of the ring damper is identified.