bluuebunny/crossref_metadata_2025 huggingface dataset:
(Re)thinking (re)connection: Young people, “natures” and the water–energy–food nexus in São Paulo State, Brazil
Authors: Kraftl Peter , Balestieri Jose Antonio Perrella , Campos Arminda Eugenia Marques , Coles Benjamin , Hadfield‐Hill Sophie , Horton John , Soares Paulo Valladares , Vilanova Mateus Ricardo Nogueira , Walker Catherine , Zara Cristana
Published: November 2018

This paper critically analyses pervasive contemporary discourses that call for children and young people to be “reconnected” with nature and natural resources. Simultaneously, it reflects on emerging forms of nexus thinking and policy that seek to identify and govern connections between diverse sectors, and especially water, energy and food. Both of these fields of scholarship are concerned with connections, of different kinds, and at different spatial scales. Based on a large‐scale, mixed‐method research project in São Paulo State, Brazil, this paper explores how these rather different literatures could be combined in order to (re)think notions of (re)connection that operate across different spatial, political and material registers. Through research with Brazilian professionals and young people about their experiences of, and learning about, the water–energy–food nexus, the paper makes several substantive contributions to scholarship on childhood, youth, environmental education and nexus thinking. Centrally, it is argued that, rather than dispense with them, there are manifold possibilities for expanding and complicating notions of (re)connection, which rely on a more nuanced analysis of the logistical, technical, social and political contexts in which nexuses are constituted. Thus, our work flips dominant forms of nexus thinking by privileging a “bottom‐up” analysis of (especially) young people's everyday, embodied engagements with water, food and energy. Our resultant findings indicated that young people are “connected” with natures and with the water–energy–food nexus, in both fairly conventional ways and in ways that significantly extend beyond contemporary discourses about childhoods–natures (and particularly in articulating the importance of care and community). Consequently, the nexus approach that is advocated in this paper could enable more nuanced, politically aware conceptualisations of (re)connection, both within and beyond scholarship on childhoods–natures and nexus thinking.
A definitive method for distinguishing cultivated onion from its weedy mimic, Asphodelus fistulosus, at multiple developmental stages
Authors: Ughade B R , Khilare V C , Sangale D M , Korhale G A , Ingle P , Tathe A E , Patil R , Khedkar G D
Published: November 2018

The onion, Allium cepa, is an important vegetable crop around the world. Globally, India ranks second in onion production, but yields are often much lower than in many other onion producing countries. This study reports on one major contributing factor to low onion yields in India: the presence of a weedy mimic that is morphologically similar to onion until the onset of flowering. We used morphological and molecular methods to identify this mimic as Asphodelus fistulosus, an exotic weed not previously reported in India. Our study indicated that molecular markers derived from the rbcL and/or matK chloroplast genes in a DNA barcoding approach allow accurate identification of this weed using any tissue and even at early developmental stages. Our results also showed that visual examination of seed lots coupled with DNA barcoding analysis of samples of 5–10 individual seeds can be used to confirm identification. The ability to easily identify contaminating material before and during cultivation can allow farmers to minimise production losses and prevent further spreading of this weed.
Hydrophobic zinc-tellurite glass system as self-cleaning vehicle: Interplay amid SiO2 and TeO2
Authors: Mazlan Siti Nur Nazhirah , Arifin Ramli , Ghoshal Sib Krishna
Published: November 2018

Cost-effective, environmental amiable and maintenance free glasses with improved hydrophobic activity are needed for diverse industrial applications. Pollutant and dirt depositions on glasses that cause the visual obscurity and damages of the cultural heritages require inhibition. The underlying mechanism of hydrophobic interactions assisted self-cleaning traits of glass is poorly understood. It has been shown that excellent hydrophobic glass with water contact angle (WCA) above 90o and very low surface wettability can be achieved by controlling the surface roughness (SR), where liquid droplets remain perfectly spherical on such surfaces (literally without touching) before being self-cleaned (rolls off). Moreover, selection and optimization of constituent materials composition as well as the preparation technique play a significant role towards such success. Most of the previous attempts for the self-cleaning glass preparation were made via coating strategy on glass surface. Yet, preparation of super-hydrophobic glass surfaces with self-cleaning attributes remains an open challenge. Driven by this idea, we prepared a new glass system of composition (80 x) TeO2-20ZnO-(x)SiO2 (x = 0, 0.03, 0.06, 0.09 and 0.12 mol%) by melt-quenching method, where the proportions of SiO2 and TeO2 were interplayed. As-prepared samples (thin pellet without coating) were characterized using atomic force microscopy (AFM) and video contact angle (VCA) measurements. The effects of SiO2 concentration on the glass SR, surface energy and hydrophobic properties were evaluated. Glass 0.06 mol% of SiO2 revealed the optimal WCA of 112.39º and SR of 7.806 nm. It was established that a trade-off between SiO2 and TeO2 contents in the studied glasses could produce super-hydrophobic surface (WCA over 90º), leading to great opportunities for diverse self-cleaning applications.
A robust vector autoregressive model for forecasting economic growth in Malaysia
Authors: Khamis Azme , Abdul Razak Nur Azreen , Abdullah Mohd Asrul Affendi
Published: November 2018

Economic indicator measures how solid or strong an economy of a country is. Basically, economic growth can be measured by using the economic indicators as they give an account of the quality or shortcoming of an economy. Vector Auto-regressive (VAR) method is commonly useful in forecasting the economic growth involving a bounteous of economic indicators. However, problems arise when its parameters are estimated using least square method which is very sensitive to the outliers existence. Thus, the aim of this study is to propose the best method in dealing with the outliers data so that the forecasting result is not biased. Data used in this study are the economic indicators monthly basis starting from January 1998 to January 2016. Two methods are considered, which are filtering technique via least median square (LMS), least trimmed square (LTS), least quartile difference (LQD) and imputation technique via mean and median. Using the mean absolute percentage error (MAPE) as the forecasting performance measure, this study concludes that Robust VAR with LQD filtering is a more appropriate model compare to others model.
The effect of A. Fumigatus SK1 and trichoderma sp. on the biogas production from cow manure
Authors: Zulkifli Zulfah , Rasit Nazaitulshila , Umor Noor Azrimi , Ismail Shahrul
Published: November 2018

Lignocellulosic material consists of lignin, cellulose and hemicellulose. Converting lignocellulosic biomass such as cow manure (CM) into value-added products provides a potential alternative. Hydrolysis of cellulose and hemicellulose is a limiting step during Anaerobic Digestion (AD) of lignocellulosic biomass. Lignin in lignocellulosic biomass is the barrier for hydrolysis, thus limits the biogas production. In this study, the effect of A.Fumigatus SK1 and Trichoderma sp. on enzymatic pre-treatment of CM was investigated with respect to the biogas production. Three set of anaerobic digestion assays were carried out, with a working volume of 500 mL at 35 ± 2°C and 120 rpm. The first set of fermentation contained untreated CM. The second set of fermentation involved addition of A.Fumigatus SK1, and the last set contained Trichoderma sp. Several analysis were conducted to determine the biomethane potential (BMP), anaerobic biodegradability, reducing sugars concentration and lignin removal of CM before and after pre-treatment. Result showed that, among both evaluated pre-treatment methods, CM treated with Trichoderma sp. gave the highest methane potential with 0.023 LCH4-STP g VS-1 compared to CM treated with A.Fumigatus SK1(0.011 LCH4-STP g VS-1). A good correlation have been found in this study between lignin removal and reducing sugar produced where, the total lignin removal after treated with Trichoderma sp. was 60% followed by 43% after treated with A.Fumigatus SK1.The reducing sugar produced after pre-treated with Trichoderma sp. and A.Fumigatus SK1 was about 9.59 and 4.91 μmol glucose, respectively. These results collectively suggested that CM treated with Trichoderma sp. could be a better pre-treatment method for the higher methane production in anaerobic mono-digestion process.
Combustion characteristics of palm pressed fibres biochar and sub-bituminous Malaysian coal
Authors: Aliyu Aminu Safana , Abdullah Nurhayati , Sulaiman Fauziah , Umar Sadik
Published: November 2018

In this research, the combustion properties of coal and biochar were investigated and compared to identify the potentiality of biochar for coal replacement application. Biochar is derived from the pyrolysis of palm pressed fibre (PPF) at 400 oC. Thermogravimetric analysis (TGA) was used to study the combustion profiles of the materials. The biochar and coal were combusted via thermogravimetric analysis from ambient temperature to 800 oC at 10 oCmin-1 of heating rate. From the results, biochar showed the high calorific value of 27.30 MJkg-1compared to that of coal 26.21 MJkg-1. Furthermore, biochar comprised the greater content of carbon and fixed carbon. Although, during combustion, coal releases high heat of 0.052 W than biochar which gave 0.049 W. This reveals that the biochar produced from PPF can be a perfect competitor against coal for heat generation. This finding could assist in promoting the application of biomass as an alternative to fossil fuel.
A preliminary study of identification halal gelatin using Quartz Crystal Microbalance (QCM) sensor
Authors: Pradini Diwasasri , Juwono Hendro , Madurani Kartika Anoraga , Kurniawan Fredy
Published: November 2018

Gelatin has been widely used as an additive in pharmaceutical, cosmetic, and food industry. The similar physical appearance between bovine and porcine gelatin causes an issue for some communities like a Muslim due to awareness of halal food. A Muslim community consider porcine gelatin is non-halal material which must be avoided. So there is a demand to distinguish and labeling the origin source of the gelatin in any products. In turn, it lead to development of  a method to identify the source of gelatin. In this study, performance of a modified Quartz Crystal Microbalance (QCM) sensor to identify halal gelatin has been investigated. A QCM sensor was modified by depositing polyaniline/nickel compound on the surface of gold electrode QCM carried out by Layer by Layer (LbL) deposition technique. Bovine and porcine gelatin were measured in demineralized water at pH 9. This modified QCM sensor shows good frequency response to distinguish bovine and porcine gelatin. The measurements gave a negative frequency shifts for bovine gelatin and a positive frequency shifts for porcine gelatin. The modified QCM sensor also worked well in the real sample. This indicates that a modified QCM sensor is very useful and effective technique to distinguish bovine gelatin (halal) from porcine gelatin (non-halal).
Numerical Analysis of an Instrumented Turbine Blade Cascade
Authors: Ubald Bryn N. , Tucker Paul G. , Cui Jiahuan , Watson Rob , Shahpar Shahrokh
Published: November 2018

The measurement accuracy of the temperature/pressure probe mounted at the leading edge of a turbine/compressor blade is crucial for estimating the fuel consumption of a turbo-fan engine. Apart from the measurement error itself, the probe also introduces extra losses. This again would compromise the measurement accuracy of the overall engine efficiency. This paper utilizes high-fidelity numerical analysis to understand the complex flow around the probe and quantify the loss sources due to the interaction between the blade and its instrumentation. With the inclusion of leading-edge probes, three-dimensional flow phenomena develop, with some flow features acting in a similar manner to a jet in cross flow. The separated flow formed at the leading edge of the probe blocks a large area of the probe bleedhole, which is one of the reasons why the probe accuracy can be sensitive to Mach and Reynolds numbers. The addition of 4% free-stream turbulence is shown to have a marginal impact on the jet trajectory originated from the probe bleedhole. However, a slight reduction is observed in the size of the separation bubble formed at the leading edge of the probe, preceding the two bleedhole exits. The free-stream turbulence also has a significant impact on the size of the separation bubble near the trailing edge of the blade. With the addition of the free-stream turbulence, the loss observed within the trailing edge wake is reduced. More than 50% of the losses at the cascade exit are generated by the leading-edge probe. A breakdown of the dissipation terms from the mean flow kinetic energy equation demonstrates that the Reynolds stresses are the key terms in dissipating the counter-rotating vortex pairs with the viscous stresses responsible for the boundary layer.
Experimental Measurements and Numerical Computation of Nano Heat Transfer Enhancement Inside a Porous Material
Authors: Saghir M. Z. , Welsford C. , Thanapathy P. , Bayomy A. M. , Delisle C.
Published: November 2018

The rapid rate of improvement in electronic devices has led to an increased demand for effective cooling techniques. The purpose of this study is to investigate the heat transfer characteristics of an aluminum metallic foam for use with an Intel core i7 processor. The metal foams used have a porosity of 0.91 and different permeabilities ranging from 10 pores per inch (PPI) to 40 PPI. The flow rate at the entrance of the porous cavity varied from 0.22 USGPM to 0.1 USGPM. The fluid consists of water with aluminum nanoparticles having a concentration from 0.1% to 0.5%. The heat fluxes applied at the bottom of the porous test cell vary from 13.25 W/cm2 to 8.34 W/cm2. It has been observed that nanofluid and forced convection improves heat extraction. These observations lead to the conclusion that heat enhancement is possible with nanofluid and it is enhanced further in the presence of a high flow rate. However, it was detected experimentally, verified numerically, and agreed upon by different researchers that higher heat extraction is found for a nanofluid concentration of 0.2%. This observation is independent of the porous permeability or applied heat flux. It has also been shown that heat enhancement in the presence of nanofluid is evident, when experimental results were compared to water.
Behavior of Thin Elastic Circular Rings With Large Deformations Under Nonuniform Loads
Authors: Azzuni E. , Guzey S.
Published: November 2018

Thin elastic circular rings under uniform pressure have been extensively studied by many researchers. Both the deflection and buckling behavior of rings were considered in these studies, but most have focused on the small deformations analysis approach. Even though the use of the small deformations assumption helps find the deflections of the ring prior to reaching the buckling load, it does not accurately capture the behavior of the ring after buckling. The in-plane large deformations analysis of thin elastic circular rings under nonuniform pressure explored in this paper expands on previous work and investigates varying pressure profiles. The pressure profiles studied here can be described by p=p01+qcosnθ. The large deformations assumption allows for the investigating of buckling loads as well as post-buckling behavior. Nonuniform normal pressure acting on a thin elastic circular ring results in a behavior that is described by a second-order ordinary differential equation (ODE) of the Duffing type, which is solved here through a numerical approach.
Is More Less? Benefits and Costs of High-Variety Production in Nonassembled Manufacturing
Authors: Laureijs Rianne E. , Fuchs Erica R. H. , Whitefoot Kate S.
Published: November 2018

While many studies have characterized the costs of product variety in assembly production, there is little research detailing the sources and costs of increased product variety on a nonassembled (fabrication) production line, despite nonassembled products accounting for over 50% of U.S. manufacturing. Our research examines the production-level costs, benefits, and margins associated with producing a variety of nonassembled products, and how design attributes affect these outcomes. We propose a theoretical framework of nonassembled product variety, identifying five general design attributes of nonassembled products that influence product-variety outcomes, and identify potential sources of variety costs and benefits. We then conduct a case study of a plant that produces a large variety of unique products in a single year. We develop a new process-based cost modeling (PBCM) technique to capture the impacts of product variety. Leveraging design of experiments (DOE), we model fourteen representative products, altering the mix of products to focus on each design attribute. In our case study, which has relatively large lot sizes, less customized designs, and less flexible equipment, we find that cost increases related to changeovers between product designs are small relative to cost benefits derived from sharing equipment and labor. We provide a framework illustrating how these results generalize to other contexts, which shows that changeover costs will dominate sharing benefits in environments with more customized designs, produced in smaller lot sizes, and processed on flexible equipment.
Combined Level-Set-XFEM-Density Topology Optimization of Four-Dimensional Printed Structures Undergoing Large Deformation
Authors: Geiss Markus J. , Boddeti Narasimha , Weeger Oliver , Maute Kurt , Dunn Martin L.
Published: November 2018

Advancement of additive manufacturing is driving a need for design tools that exploit the increasing fabrication freedom. Multimaterial, three-dimensional (3D) printing allows for the fabrication of components from multiple materials with different thermal, mechanical, and “active” behavior that can be spatially arranged in 3D with a resolution on the order of tens of microns. This can be exploited to incorporate shape changing features into additively manufactured structures. 3D printing with a downstream shape change in response to an external stimulus such as temperature, humidity, or light is referred to as four-dimensional (4D) printing. In this paper, a design methodology to determine the material layout of 4D printed materials with internal, programmable strains is introduced to create active structures that undergo large deformation and assume a desired target displacement upon heat activation. A level set (LS) approach together with the extended finite element method (XFEM) is combined with density-based topology optimization to describe the evolving multimaterial design problem in the optimization process. A finite deformation hyperelastic thermomechanical model is used together with an higher-order XFEM scheme to accurately predict the behavior of nonlinear slender structures during the design evolution. Examples are presented to demonstrate the unique capabilities of the proposed framework. Numerical predictions of optimized shape-changing structures are compared to 4D printed physical specimen and good agreement is achieved. Overall, a systematic design approach for creating 4D printed active structures with geometrically nonlinear behavior is presented which yields nonintuitive material layouts and geometries to achieve target deformations of various complexities.
Model-Based Reliability Analysis With Both Model Uncertainty and Parameter Uncertainty
Authors: Xi Zhimin
Published: November 2018

Model-based reliability analysis may not be practically useful if reliability estimation contains uncontrollable errors. This paper addresses potential reliability estimation errors from model bias together with model parameters. Given three representative scenarios, reliability analysis strategies with representative methods are proposed. The pros and cons of these strategies are discussed and demonstrated using a tank storage problem based on the finite element model with different fidelity levels. It is found in this paper that the confidence-based reliability analysis considering epistemic uncertainty modeling for both model bias and model parameters can make reliability estimation errors controllable with less conservativeness compared to the direct reliability modeling using the Bayesian approach.
Generation of Tool-Life-Prolonging and Chatter-Free Efficient Toolpath for Five-Axis Milling of Freeform Surfaces
Authors: Wang Jiarui , Luo Ming , Xu Ke , Tang Kai
Published: November 2018

Short tool service life is always a major concern when milling hard materials, such as Ni-based superalloy. In the current research of tool life optimization in multi-axis machining of freeform surfaces, the focus is mostly on choosing suitable cutting parameters and better application of coolant. In this paper, aiming at averaging the tool wear on the entire cutting edge and hence prolonging the tool service life, we report a study on how to generate a multilayer toolpath with a varying tool lead angle for multi-axis milling of an arbitrary freeform surface from an initial raw stock. The generated toolpath is guaranteed to be free of chatter, which is well known for its detrimental effect on the cutting edge. In this study, we first experimentally construct the chatter stability lobe diagram, which reveals the relationship between the lead angle and the cutting depth. With the chatter stability lobe diagram as the major constraint, we then generate the machining toolpath by selecting a proper pair of the best lead angle and cutting depth along the toolpath. While the proposed algorithm currently is restricted to the iso-planar type of toolpath, it can be adapted to other types of milling. The physical cutting experiments performed by us have convincingly confirmed the advantage of the proposed machining strategy as compared to the conventional constant lead angle and constant cutting depth strategy—in our tests the maximum wear on the cutting edge is reduced by as much as 39%.
Solution of the Phase Change Stefan Problem With Time-Dependent Heat Flux Using Perturbation Method
Authors: Parhizi Mohammad , Jain Ankur
Published: November 2018

Theoretical understanding of phase change heat transfer problems is of much interest for multiple engineering applications. Exact solutions for phase change heat transfer problems are often not available, and approximate analytical methods are needed to be used. This paper presents a solution for a one-dimensional (1D) phase change problem with time-dependent heat flux boundary condition using the perturbation method. Two different expressions for propagation of the phase change front are derived. For the special case of constant heat flux, the present solution is shown to offer key advantages over past papers. Specifically, the present solution results in greater accuracy and does not diverge at large times unlike past results. The theoretical result is used for understanding the nature of phase change propagation for linear and periodic heat flux boundary conditions. In addition to improving the theoretical understanding of phase change heat transfer problems, these results may contribute toward design of phase change based thermal management for a variety of engineering applications, such as cooling of Li-ion batteries.
Effect of Slot Jet Temperature on Impingement Heat Transfer Over a Heated Circular Cylinder
Authors: Pachpute Sharad , Premachandran B.
Published: November 2018

In this paper, heat transfer and effectiveness of a turbulent slot jet impinging over a heated circular cylinder have been investigated numerically by varying the ratio of jet temperature to the ambient temperature, Θj = Tj/Tamp, from 0.7 to 1.2. In all cases, the ambient temperature (Tamb) is assumed to be constant (300 K). The Reynolds number defined based on the average nozzle exit velocity, the diameter of the cylindrical target (D), and properties at the nozzle exit temperature, ReD=ρVD/μ is varied from 6000 to 20,000. The ratio of cylinder diameter to the slot width, D/S = 5.5, 8.5, and 17 are considered and the nondimensional distance from the nozzle exit to the cylinder, H/S is varied in the range of 2 ≤ H/S ≤ 12. The v′2¯−f turbulence model was used for numerical simulations. Numerical results reveal that the local Nusselt number is found to be higher at the stagnation point in the case of cold jet impingement at Θj = 0.7. The local heat transfer at the rear side of the cylinder is 8–18% less as compared to that of Θj = 1.0 for ReD = 6000. The local effectiveness calculated over a circular cylinder strongly depends on H/S and D/S. Based on the parametric study, a correlation has been provided for the local effectiveness at the stagnation point.
Simplified Approach to Solution of Mixed Boundary Value Problems on Homogeneous Circular Domain in Elasticity
Authors: Singh Gaurav , Bhandakkar Tanmay K.
Published: November 2018

This work proposes a novel strategy to render mixed boundary conditions on circular linear elastic homogeneous domain to displacement-based condition all along the surface. With Michell solution as the starting point, the boundary conditions and extent of the domain are used to associate the appropriate type and number of terms in the Airy stress function. Using the orthogonality of sine and cosine functions, the modified boundary conditions lead to a system of linear equations for the unknown coefficients in the Airy stress function. Solution of the system of linear equations provides the Airy stress function and subsequently stresses and displacement. The effectiveness of the present approach in terms of ease of implementation, accuracy, and versatility to model variants of circular domain is demonstrated through excellent comparison of the solution of following problems: (i) annulus with mixed boundary conditions on outer radius and prescribed traction on the inner radius, (ii) cavity surface with mixed boundary conditions in an infinite plane subjected to far-field uniaxial loading, and (iii) circular disc constrained on part of the surface and subjected to uniform pressure on rest of the surface.
Significance of Lorentz Force and Thermoelectric on the Flow of 29 nm CuO–Water Nanofluid on an Upper Horizontal Surface of a Paraboloid of Revolution
Authors: Animasaun I. L. , Mahanthesh B. , Jagun A. O. , Bankole T. D. , Sivaraj R. , Shah Nehad Ali , Saleem S.
Published: November 2018

Combination of electric and magnetic forces on charged molecules of flowing fluid in the presence of a significant electromagnetic fields on surfaces with a nonuniform thickness (as in the case of upper pointed surface of an aircraft and bonnet of a car which are examples of upper horizontal surfaces of a paraboloid of revolution—uhspr) is inevitable. In this study, the influence of imposed magnetic field and Hall effects on the flow of 29 nm CuO–water nanofluid over such object is presented. Suitable similarity variables were employed to nondimensionalize and parameterize the dimensional governing equation. The numerical solutions of the corresponding boundary value problem were obtained using Runge–Kutta fourth-order integration scheme along with shooting technique. The domain of cross-flow velocity can be highly suppressed when the magnitude of imposed magnetic strength and that of Hall parameter are large. A significant increase in the cross-flow velocity gradient near an upper horizontal surface of the paraboloid of revolution is guaranteed with an increase in the Hall parameter. Enhancement of temperature distribution across the flow is apparent due to an increase in the volume fraction.
A Computationally Efficient Computer-Aided Design Strategy for Iterative Combat Helmet Design and Analysis
Authors: Saunders Robert , Moser Alex , Matic Peter
Published: November 2018

Assessing combat helmet ballistic performance is a costly endeavor using either an experimental or a computational process. Experimental assessment requires many iterations and helmets to acquire a sufficient data set. To circumvent this, computational simulation is incorporated into the design process to supplement a few experiments. However, due to the complex constitutive response of the helmet (anisotropic elasticity, plasticity, damage initiation and evolution, and failure), it is computationally costly to run many ballistic impact simulations. The goal of this work is to develop a computer-aided design (cad) software to rapidly analyze combat helmets undergoing a ballistic impact. The software considers a representative mix of potential threats, helmet geometry modifications and additions, brain functional anatomy, and injury considerations. The resulting software demonstrates that a given helmet can be analyzed in a matter of minutes on a standard desktop computer and parametric studies can be completed in a matter of hours. The results of the cad software show how helmet design parameters such as helmet shell materials, geometry, and ceramic appliques all affect helmet ballistic performance.
Effect of Nonuniform Flexibility on Hydrodynamic Performance of Pitching Propulsors
Authors: Zeyghami Samane , Moored Keith W.
Published: November 2018

Many aquatic animals propel themselves efficiently through the water by oscillating flexible fins. These fins are, however, not homogeneously flexible, but instead their flexural stiffness varies along their chord and span. Here, we develop a simple model of these functionally graded materials where the chordwise flexibility of the foil is modeled by one or two torsional springs along the chord line. The torsional spring structural model is then strongly coupled to a boundary element fluid model to simulate the fluid–structure interactions. We show that the effective flexibility of the combined fluid–structure system scales with the ratio of the added mass forces acting on the passive portion of the foil and the elastic forces defined by the torsional spring hinge. Importantly, by considering this new scaling of the effective flexibility, the propulsive performance is then detailed for a foil with a flexible hinge that is actively pitching about its leading edge. The scaling allows for the resonance frequency of the fluid–structure system and the bending pattern of the propulsor to be independently varied by altering the effective flexibility and the location of a single torsional spring along the chord, respectively. It is shown that increasing the flexion ratio, by moving the spring away from the leading edge, leads to enhanced propulsive efficiency, but compromises the thrust production. Proper combination of two flexible hinges, however, can result in a gain in both the thrust production and propulsive efficiency.
Apex Height Control of a Two-Mass Robot Hopping on a Viscoelastic Foundation With Inertia
Authors: Allafi Amer , Mathis Frank B. , Mukherjee Ranjan
Published: November 2018

A majority of the results in the literature on hopping robots assume the ground to be rigid. Hopping on a foundation that can be modeled as a mass-spring-damper system poses challenges due to undesired vibration of the additional degree-of-freedom and dissipation due to impact and viscous damping. A hybrid control strategy is developed to converge the maximum jumping height of the center-of-mass of a two-link prismatic-joint robot to a desired value. The hybrid control strategy uses backstepping in continuous time and integral control in discrete time to control the internal degree-of-freedom and the total energy. Simulation results are presented to demonstrate the efficacy of the controller.
Learning Based Speed Control of Soft Robotic Fish
Authors: Rajendran Sunil Kumar , Zhang Feitian
Published: November 2018

Bioinspired robotics takes advantage of biological systems in nature for morphology, action and perception to build advanced robots of compelling performance and wide application. This paper focuses on the design, modeling and control of a bioinspired robotic fish. The design utilizes a recently-developed artificial muscle named super coiled polymer for actuation and a soft material (silicone rubber) for building the robot body. The paper proposes a learning based speed control design approach for bioinspired robotic fish using model-free reinforcement learning. Based on a mathematically tractable dynamic model derived by approximating the robotic fish with a three-link robot, speed control simulation is conducted to demonstrate and validate the control design method. Exampled with a three-link reduced-order dynamic system, the proposed learning based control design approach is applicable to many and various complicated bioinspired robotic systems.
Dynamic Modeling and Computed Torque Control of Flexure Jointed TVC Systems
Authors: Aydogan Ahmet , Rogers Eric , Hasturk Ozgur
Published: November 2018

Thrust Vector Control (TVC) is one means of controlling air vehicles to follow a desired flight path where, in particular, those that are flexure jointed are currently the most commonly used. Often, dynamic modeling of such systems is for the case where a universal gimbal joint is present, which neglects uncertainties in the dynamics, such as vertical motion of the pivot point of nozzle and misalignment. This paper gives early results on a new approach to dynamic modeling of TVC systems that includes one more degree of freedom compared to previously reported models and also enables the flexure jointed structure to move along vertical direction on the flight axis. A Computed Torque Control Law (CTCL) is then designed for the new resulting model with the potential for higher tracking accuracy and lower feedback gains. A simulation based case study is given to demonstrate the new design.
Experimental Study of NMP Sample and Hold Input Using an Inverted Pendulum
Authors: Wang Yingxu , Zhu Guoming G. , Mukherjee Ranjan
Published: November 2018

Early research showed that a zero-order hold is able to convert a continuous-time non-minimum-phase (NMP) system to a discrete-time minimum-phase (MP) system with a sufficiently large sampling period. However the resulting sample period is often too large to adequately cover the original NMP system dynamics and hence not suitable for control application to take advantage of a discrete-time MP system. This problem was solved using different sample and hold inputs (SHI) to reduce the sampling period significantly for MP discrete-time system. Three SHIs were studied analytically and they are square pulse, forward triangle and backward triangle SHIs. To validate the finding experimentally, a dual-loop linear quadratic regulator (LQR) control configuration is designed for the Quanser single inverted pendulum (SIP) system, where the SIP system is stabilized using the Quanser continuous-time LQR (the first loop) and an additional discrete-time LQR (the second loop) with the proposed SHIs to reduce the cart oscillation. The experimental results show more than 75% reduction of the steady-state cart displacement variance over the single-loop Quanser controller and hence demonstrated the effectiveness of the proposed SHI.
Design Optimization of RML Glove for Improved Grasp Performance
Authors: Vanteddu Teja , Sebastian Bijo , Ben-Tzvi Pinhas
Published: November 2018

This paper describes the design optimization of the RML Glove in order to improve its grasp performance. The existing design is limited to grasping objects of large diameter (> 110mm) due to its inability in attaining high bending angles. For an exoskeleton glove to be effective in its use as an assistive and rehabilitation device for Activities of Daily Living (ADL), it should be able to interact with objects over a wide range of sizes. Motivated by these limitations, the kinematics of the existing linkage mechanism was analyzed in detail and the design variables were identified. Two different cost functions were formulated and compared in their ability to yield optimal values for the design variables. The optimal set of design variables was chosen based on the grasp angles achieved and the resulting mechanism was simulated in CAD for feasibility testing. An exoskeleton mechanism corresponding to the index finger was manufactured with the chosen design variables and detailed experimental validation was performed to illustrate the improvement in grasp performance over the existing design. The paper ends with a summary of the experimental results and directions for future research.
Comparison of Individual-Electrode State of Health Estimation Methods for Lithium Ion Battery
Authors: Lee Suhak , Siegel Jason B. , Stefanopoulou Anna G. , Lee Jang-Woo , Lee Tae-Kyung
Published: November 2018

It is essential to understand the state-of-health (SOH) of the individual electrode to avoid accelerating degradation of Li-ion battery. Electrode SOH can be quantified based on estimating the capacity and the utilization range of each electrode. Here, we introduce two methods: i) voltage fitting (VF) and ii) peak alignment (PA), and compare their ability to estimate the electrode SOH parameters. Both methods assume the half-cell open-circuit potentials (OCPs) are invariant functions of the stoichio-metric states with the cell aging, which can make the accuracy of the electrode parameter estimation vulnerable to degradation that would cause changes in the half-cell OCP curves. This hypothesis is verified experimentally by applying the two methods to aged cells cycled at high temperature. A discernible misalignment of the peaks is observed in the differential voltage curve from the VF method indicating the estimation result is incorrect, even though it reconstructs the OCV with the small error and estimates the cell capacity accurately. Therefore, it is seen that the lower voltage error and the accurate cell capacity estimate do not necessarily promise a better estimation accuracy for the electrode SOH parameters.
Proportional Power Sharing Consensus in Distributed Generators
Authors: Aalipour Farzad , Das Tuhin
Published: November 2018

In this study, the problem of proportional power sharing consensus in a DC microgrid (MG) consisting of distributed generators (DGs) is discussed. Presently, MGs face challenges involving the intermittent nature of DGs and load power fluctuations. To address these challenges, three different control schemes are proposed. The first consensus-based control algorithm is introduced to address proportional power sharing in the presence of variations in the DGs rate, i.e., power capacity. Secondly, in regards to load power fluctuations, a control scheme is designed to enable the DGs to compute their individual proportional power share in a distributed manner. Eventually, a comprehensive real-time control approach is developed through which the DGs cooperatively maintain the required power load and achieve the updated proportional share simultaneously. To demonstrate the effectiveness of the proposed approaches simulations results for a simple network of DGs are presented.
Experimental Bifurcation Diagram of Furuta Pendulum
Authors: Vizi Mate B. , Stepan Gabor
Published: November 2018

The Furuta pendulum is a two degree of freedom mechanical system that serves as an excellent and simple device to check control strategies applied for strongly nonlinear mechanical structures. Stability results related to certain stationary motions of the Furuta pendulum are compared to experimental observations, and conclusions are obtained regarding some essential mechanical phenomena that are present in the experimental rig, but still not properly described in the standard mathematical model of the pendulum. The results call the attention for the importance of the identification of the Coulomb friction in the structure, which effect the control strategies to be implemented.
A Novel Non-Raster Scan Method for AFM Imaging
Authors: Nikooienejad Nastaran , Maroufi Mohammad , Moheimani S. O. Reza
Published: November 2018

We report a new non-raster scan method based on a rosette pattern for high-speed atomic force microscopy (AFM). In this method, the lateral axes of the scanner are driven by the sum of two sinusoids with identical amplitudes and different frequencies. We formulate the problem so as to generate the rosette pattern and calculate scan parameters and resolution. To achieve high performance tracking, a controller is designed based on the internal model principle. The controller includes the dynamic modes of the reference signals and higher harmonics to cope with the system nonlinearities. We conduct an experiment employing the proposed method and a two degree of freedom microelectromechanical system nanopositioner to scan a circular-shaped area with a diameter of 6μm in 0.2 sec. The steady state tracking error is less than 4.48nm, i.e. only 9% of the selected resolution. AFM scanning is performed in contact mode constant height and high quality images are obtained.
Control Design With Inverse Feedback Shaper for Quadcopter With Suspended Load
Authors: Bušek Jaroslav , Kuře Matěj , Hromčík Martin , Vyhlídal Tomáš
Published: November 2018

A control design and numerical study is presented for the problem of maneuvering a quadcopter with suspended load. An inverse shaper with a distributed time delay is applied to the feedback path in order to pre-compensate the oscillatory mode of the two-body system. As the first step, the mode to be targeted by the inverse shaper is determined, which is neither the oscillatory mode of the overall system dynamics, nor the oscillatory mode of the suspended load. Next, the established cascade control scheme for UAVs with slave PD pitch angle controller and master PID velocity controller is adopted and supplemented by the inverse shaper tuned to the isolated flexible mode. The numerical and simulation based analysis reveals the key design aspects and dynamics features — due to including the inverse shaper with time delays, the closed loop system becomes infinite dimensional. As the main result, the positive effects of including the inverse shaper in the loop feedback are demonstrated. First of all, the oscillatory mode is well compensated when excited by both the set-point and disturbance changes. Besides, it is shown that the mode compensation is preserved even when reaching the saturation limits at the control actions.
Second Law Modeling and Robust Control for Thermal-Fluid Systems
Authors: Nash Austin L. , Jain Neera
Published: November 2018

In this paper we present a dynamic model formulation for thermal-fluid systems that enables direct minimization of dissipative and frictional losses, otherwise known as entropy generation. While analysis based upon the second law of thermodynamics has long been used for optimizing steady-state design of thermodynamic systems, transient performance and efficiency have largely been overlooked. Across a range of sectors, from power generation to microelectronics, answering the question of how to control a system to minimize these transient losses is becoming increasingly important. Unfortunately, thermodynamic expressions for entropy generation are typically highly nonlinear and not easily amenable to control synthesis and design. Here we derive a control-oriented dynamic model of a notional thermal-fluid system with entropy generation rate as part of the dynamic state vector. The proposed model formulation technique is generalizable to a wide range of energy conversion systems and, importantly, enables the synthesis of model-based state feedback controllers which can in turn optimize transient system performance to minimize irreversibilities due to energy conversion and transport in real-time. To illustrate the utility of the formulation, we design a state feedback H∞ controller to minimize the total entropy generation rate of the notional system in the presence of pulsed, episodic load disturbances.
Optimization of Mode Switching Timing Control for a Lean-Burn Gasoline Engine With a Prototype Passive SCR System
Authors: Strange Dakota , Chen Pingen , Prikhodko Vitaly Y. , Parks James E.
Published: November 2018

Passive selective catalytic reduction (SCR) has emerged as a promising NOx reduction technology for highly-efficient lean-burn gasoline engines to meet stringent NOx emission regulation in a cost-effective manner. In this study, a prototype passive SCR which includes an upstream three-way catalyst (TWC) with added NOx storage component, and a downstream urealess SCR catalyst, was investigated. Engine experiments were conducted to investigate and quantify the dynamic NOx storage/release behaviors as well as dynamic NH3 generation behavior on the new TWC with added NOx storage component. Then, the lean/rich mode-switching timing control was optimized to minimize the fuel penalty associated with passive SCR operation. Simulation results show that, compared to the baseline mode-switching timing control, the optimized control can reduce the passive SCR-related fuel penalty by 6.7%. Such an optimized mode-switching timing control strategy is rather instrumental in realizing significant fuel efficiency benefits for lean-burn gasoline engines coupled with cost-effective passive SCR systems.
A Traveling Wave Model Guided Robotic Fish Design Using Double Slot-Crank Mechanism
Authors: Zuo Wenyu , Chen Zheng
Published: November 2018

In this paper, we present a novel multi-joint robotic fish design using a double-slot crank mechanism. The double slot crank (DSC) is a DC motor driven mechanism, which can convert the rotation to oscillation in two axes. This mechanism can be applied to designing a multi-joint robotic fish by using one DC motor to simulate two-joint robotic fish or cooperating with one servo motor to make a three-joint robotic fish. The slot crank enabled multi-joint design is guided by an idea traveling wave model, which can mimic the traveling wave along the fish body to optimize the propulsion efficiency as well as maneuvering capabilities. After multiple tests, the slot crank mechanism has been proven that it is an efficient propulsion mechanism for robotic fish. The DSC mechanism can achieve good performance on mimicking the real fish swimming and boosting the swimming speed. The DSC mechanism also represents good potential in imitating the real fish locomotion. It is expected to improve the power efficiency of the multi-joint robotic fish. The robotic fish with DSC enabled tail can achieve 20 cm/sec forward speed and 23.6 degree/sec turning speed with less than 8 w power consumption.