bluuebunny/crossref_metadata_2025 huggingface dataset:
3D Bioprinting with UVA1 Radiation and Photoinitiator Irgacure 2959: Can the ASTM Standard L929 Cells Predict Human Stem Cell Cytotoxicity?
Authors: Godar Dianne E. , Gurunathan Chandra , Ilev Ilko
Published: September 2018

3D bioprinting often involves human mesenchymal stem cells (hMSC) that are differentiated into the desired cells to replace body parts like ears. Scaffolds of crosslinked hydrogels offer structural support during differentiation. Different photoinitiators are used to make free radicals that photocrosslink these hydrogels; the more penetrating ultraviolet A1 (UVA1) (340–400 nm) wavelengths can be used because Irgacure 2959 only absorbs in the UV (100–400 nm) region. We questioned if the L929 mouse fibroblast cells used in the American Society for Testing Materials standard cytotoxicity assays (F895&F813) can predict the viability of hMSC after exposure to UVA1 radiation alone and in combination with Irgacure 2959 (0.05–0.5% w/v usual range). We exposed both cell types to a high dose of LED UVA1 (370 ± 5 nm; 788 kJ m−2) and side by side to increasing UVA1 doses from a glass‐filtered black light source combined with either 0.05% (w/v) or 0.5% (w/v) of Irgacure 2959 and monitored their viabilities using flow cytometry. We found UVA1 radiation alone killed ~50% of the hMSC cells compared to ~8% of the L929 cells and significantly more hMSC than L929 died after UVA1 with Irgacure 2959. Thus, L929 cannot be used to accurately predict the viability of hMSC after these specific 3D bioprinting conditions.
Frequency of occurrence of polymorphic light eruption in patients treated with photohardening and patients treated with phototherapy for other diseases
Authors: Gruber‐Wackernagel Alexandra , Hofer Angelika , Legat Franz , Wolf Peter
Published: September 2018

Background

Medical phototherapy can lead to the manifestation of polymorphic light eruption (PLE), though little is known about the frequency of such events.

Aims

The aim of this Austrian single center study was to retrospectively investigate over a 4‐year time period the frequency of PLE in patients prone to the condition and patients with other diseases under phototherapy (mainly narrow‐band and broad‐band UVB).

Materials and Methods

The data for analysis were obtained from the electronic health and patient record database and patient files of the Photodermatology Unit, Department of Dermatology, Medical University of Graz, Austria.

Results

PLE occurred in 24.3% (18/74) of PLE patients but only 0.7% (3/421) of psoriasis patients under phototherapy (chi‐square; P < 0.0001). PLE also occurred in 1.2% (3/257) of patients with atopic eczema, 0.8% (1/118) with prurigo, 3.5% (4/115, P = 0.0206) with parapsoriasis en plaques/mycosis fungoides, 7.4% (2/27, P = 0.0013) with granuloma anulare, 14.3% (1/7, P = 0.0002) with scleroderma, and 16.7% (1/6, P < 0.0001 vs. psoriasis) with pityriasis lichenoides chronica or pityriasis lichenoides eruptiva et varioliformis acuta.

Discussion and Conclusion

These results are helpful for treatment allocation and risk estimation of PLE occurrence with regard to obtaining informed consent not only from PLE‐prone patients but also from patients with other skin disorders commonly treated by phototherapy.
Generation, characterization, perniciousness, removal and reutilization of solids in aquaculture water: a review from the whole process perspective
Authors: Bao Weijun , Zhu Songming , Jin Guang , Ye Zhangying
Published: September 2018

The generation of solids by aquaculture activities has led to many problems in animal welfare, environmental quality, water treatment effects and public health, such as gill and intestinal damage, water eutrophication, system components blockages and antibiotics transfers through the food chain to human; thus, effective solid wastes management is very important. The purpose of this review is to summarize the sources, characterization methods, harmfulness, removal technologies and reutilization of solids in aquaculture water, including (i) different sources of solids, such as uneaten feed, feces and debris; (ii) solids characterization based on the general parameters, particle size distribution and chemical composition; (iii) the toxicity and detriment of solids to cultured species, the environment, aquaculture system components and human health; (iv) Solids removal, effluents solids thickening and source control techniques for better solids management; and (v) various methods for the reutilization of aquacultural solid wastes for resource value‐adding. In addition to these five specific objectives, the merits and drawbacks of each method or technology and future research priorities are discussed. The present review provides an understanding of the role played by solids in aquaculture water and provides guidance for aquacultural solid wastes precision management, aquaculture practices and technological developments. Thus, solids management can be carried out based on this guidance to improve animal welfare and the stability of water treatment systems, reduce harm to the environment and public health, and enable the development of aquaculture in a sustainable way.
Attention as a means of self‐dissolution and reformation
Authors: Carpenter Amber D.
Published: September 2018

Buddhist ethics generally favour attention over action, and mental cultivation as the means of ethical transformation. Buddhaghosa’s treatment ofsamādhi– meditation – in thePath of Purification(Visuddhimagga) exemplifies this view that practices of attention are morally transforming. His detailed discussion of which forms of attentional exercises are transformative to whom reveal that edifying attention is directed to impersonal reality rather than persons – even when the Buddha is our object of attention. In successful meditation, we do not just recognise reality and ourselves as devoid of essence; we experience it as such – and in the experiencing, become so ourselves.
Responsibilities, Caring Practices and Agriculture: Farmers’ Perspectives on Recruitment and Employer–Employee Relationships
Authors: Stenbacka Susanne
Published: September 2018

With Swedish agriculture as its point of departure, this paper seeks to explore farmers’ recruiting practices and employer–employee relationships. Taking on the employer’s role means becoming subject both to formal statutory obligations and to regulations on wages, security and other aspects of working conditions. This article focuses on the more informal aspects of acting as an employer. The results show that recruiting, interacting and engaging with employees involve multiple responsibilities towards individuals and society alike. The practices of care identified are thus both private and public in nature, and exist within a framework of norms and ethical principles, a ‘moral economy’. The farmers’ strategies and decisions are understood as merged into negotiations regarding their identity, tradition, role in society and position in a global industry. Caring practices are embedded in farming practices and the focus on recruitment and employers’ experience adds to a multifaceted understanding of caring practices in which male farmers’ caring practices, too, become visible.
Ferritin testing to characterize and address iron deficiency in young donors
Authors: Vassallo Ralph R. , Bravo Marjorie D. , Kamel Hany
Published: September 2018

BACKGROUND

Iron deficiency is observed in blood donors who meet hemoglobin requirements for donation. Frequent donation results in negative iron balance, and teenage donors may thus be at risk for adverse health consequences.

STUDY DESIGN AND METHODS

Blood Systems implemented ferritin testing on all successful 16‐ to 18‐year‐old (teen) donations. Low ferritin (LF) was defined as less than 20 ng/mL in females and less than 30 ng/mL in males. Donors with LF were deferred from red blood cell (RBC) donations (12 months for females, and 6 for males) and counseled to take low‐dose iron for 60 days. A ferritin value less than 26 ng/mL indicated iron‐deficient erythropoiesis and less than 12 ng/mL absent iron stores.

RESULTS

Over 16 months, 110,417 teen donations were tested and represented 10.5% of all successful donations. The rate of absent iron stores was 9.0% (1.9% male; 15.9% female) and of iron‐deficient erythropoiesis, 31.9% (12.4% male; 50.6% female). The rate of LF deferrals was 26.9% (16.7% male; 36.6% female). The proportion of LF donors decreased with increasing predonation hemoglobin and rose with increasing RBC donations in the prior 24 months. Seasonality in LF deferrals and the RBC contribution from teen donors was observed.

CONCLUSIONS

Ferritin testing of teen donors identified individuals with LF who might benefit from risk mitigation. LF is more common in teenage female than male donors and those with RBC donations in the prior 24 months. An appreciable number of new/lapsed donors presented with LF, however. These data may be useful in guiding future risk mitigation efforts.
Stability of anti‐A blood group titers among blood group B renal transplant candidates
Authors: Jacob Reuben P. , Dean Christina L. , Krummey Scott M. , Goodman Abigail L. , Roback John D. , Gebel Howard M. , Bray Robert A. , Sullivan Harold C.
Published: September 2018

BACKGROUND

As deceased donor kidney allocation is based in part on blood type compatibility, group B candidates are disadvantaged due to their disproportionate representation on the wait list compared to the group B donor pool. To mitigate this discrepancy, group B candidates can receive group A2 or A2B donor kidneys if their anti‐A titers are below a predetermined cutoff. Currently, eligibility is reverified quarterly to UNet based on individual center protocols, which can vary due to a lack of set guidelines for monitoring ABO titers in these patients. Our goal was to assess the stability of anti‐A titers in blood group B renal transplant candidates over time to provide data that could aid in the development of standardized ABO titer protocols.

STUDY DESIGN AND METHODS

Titers performed between January 2011 and December 2015 were assessed for 191 group B patients with two or more documented titers.

RESULTS

Fifty patients (26%) were ineligible, as the first titer exceeded the cutoff of 8. Of the remaining 141 patients, 19 (13%) became ineligible as the second titer exceeded 8. Thirty‐nine patients (28%) had no change in titer between samples, while 71 (50%) had a titer change that never exceeded 8. Only 12 patients (8.5% of total) experienced a titer change that affected eligibility after the second test.

CONCLUSION

Although patients experience some variability in anti‐A titers over time, in most cases, stability did not affect candidate eligibility. Our results indicate that regular testing beyond the second titer may be unnecessary and represent test overutilization.
Genetic variant in the β2‐adrenergic receptor (Arg16Gly) influences fat‐free mass, muscle strength and motor unit behaviour in young men
Authors: Jenkins Nathaniel D. M. , Colquhoun Ryan J. , Tomko Patrick M. , Gradnigo Trey , Magrini Mitchel A. , Muddle Tyler W. D. , Fleming Sydnie , Ferrell Matthew , El‐Sohemy Ahmed
Published: September 2018

New Findings

What is the central question of this study?

Does a common genetic variant in the β2‐adrenergic receptor (β2‐AR) have effects on skeletal muscle function in young, healthy men?

What is the main finding and its importance?

This study provides preliminary evidence that β2‐AR Arg16Gly genotype has a significant effect on fat‐free mass, muscle strength and motor unit behaviour in recreationally trained men. These data might have important clinical and exercise‐related implications. For example, β2‐AR (rs1042713) genotype might influence the responsiveness of skeletal muscle to clinical or exercise‐based interventions or β‐AR agonist treatment.

This study explored whether the β2‐adrenergic receptor (β2‐AR) single nucleotide polymorphism at amino acid 16 (Arg16Gly) has functional effects on skeletal muscle mass, torque production and motor unit behaviour in young, healthy men. Twenty‐eight recreationally active men (mean ± SD 23.1 ± 1.3 years of age) were genotyped for Arg16Gly polymorphisms of β2‐AR as arginine homozygous (ArgArg; n = 5), glycine homozygous (GlyGly; n = 11) or arginine–glycine heterozygous (ArgGly; n = 12). The participants then completed body composition testing, assessments of leg extensor size and echo intensity, and evoked and voluntary isometric leg‐extension muscle actions. During the evoked muscle actions, peak twitch torque, peak rate of torque development and peak relaxation rate were assessed. During the voluntary muscle actions, maximal voluntary isometric (MVIC) strength was assessed, and surface EMG signals were obtained during submaximal isometric muscle actions and later decomposed to examine motor unit firing behaviour. Fat‐free mass and MVIC strength were greater (P = 0.004, d = 1.74 and P = 0.026, d = 1.10, respectively) in those expressing the GlyGly versus ArgArg allele. The slope of the mean firing rate versus recruitment threshold relationship was more negative in the GlyGly than the ArgArg allele carriers (P = 0.012, d = 1.68) at 50% MVIC, but was less negative in GlyGly and ArgGly versus ArgArg allele carriers (P = 0.013 and 0.016, respectively; d = 1.34 and 1.20, respectively) at 70% MVIC. These data provide preliminary evidence that β2‐AR Arg16Gly genotype has a significant effect on fat‐free mass, muscle strength and motor unit behaviour in humans.
A New Technique to Predict In Situ Stress Increment Due to Biowaste Slurry Injection Into a Sandstone Formation
Authors: Kholy Sherif M. , Almetwally Ahmed G. , Mohamed Ibrahim M. , Loloi Mehdi , Abou-Sayed Ahmed , Abou-Sayed Omar
Published: September 2018

Underground injection of slurry in cycles with shut-in periods allows fracture closure and pressure dissipation which in turn prevents pressure accumulation and injection pressure increase from batch to batch. However, in many cases, the accumulation of solids on the fracture faces slows down the leak off which can delay the fracture closure up to several days. The objective in this study is to develop a new predictive method to monitor the stress increment evolution when well shut-in time between injection batches is not sufficient to allow fracture closure. The new technique predicts the fracture closure pressure from the instantaneous shut-in pressure (ISIP) and the injection formation petrophysical/mechanical properties including porosity, permeability, overburden stress, formation pore pressure, Young's modulus, and Poisson's ratio. Actual injection pressure data from a biosolids injector have been used to validate the new predictive technique. During the early well life, the match between the predicted fracture closure pressure values and those obtained from the G-function analysis was excellent, with an absolute error of less than 1%. In later injection batches, the predicted stress increment profile shows a clear trend consistent with the mechanisms of slurry injection and stress shadow analysis. Furthermore, the work shows that the injection operational parameters such as injection flow rate, injected volume per batch, and the volumetric solids concentration have strong impact on the predicted maximum disposal capacity which is reached when the injection zone in situ stress equalizes the upper barrier stress.
Heat Transfer Models of Moving Packed-Bed Particle-to-sCO2 Heat Exchangers
Authors: Albrecht Kevin J. , Ho Clifford K.
Published: September 2018

Particle-based concentrating solar power (CSP) plants have been proposed to increase operating temperature for integration with higher efficiency power cycles using supercritical carbon dioxide (sCO2). The majority of research to date has focused on the development of high-efficiency and high-temperature particle solar thermal receivers. However, system realization will require the design of a particle/sCO2 heat exchanger as well for delivering thermal energy to the power-cycle working fluid. Recent work has identified moving packed-bed heat exchangers as low-cost alternatives to fluidized-bed heat exchangers, which require additional pumps to fluidize the particles and recuperators to capture the lost heat. However, the reduced heat transfer between the particles and the walls of moving packed-bed heat exchangers, compared to fluidized beds, causes concern with adequately sizing components to meet the thermal duty. Models of moving packed-bed heat exchangers are not currently capable of exploring the design trade-offs in particle size, operating temperature, and residence time. The present work provides a predictive numerical model based on literature correlations capable of designing moving packed-bed heat exchangers as well as investigating the effects of particle size, operating temperature, and particle velocity (residence time). Furthermore, the development of a reliable design tool for moving packed-bed heat exchangers must be validated by predicting experimental results in the operating regime of interest. An experimental system is designed to provide the data necessary for model validation and/or to identify where deficiencies or new constitutive relations are needed.
A Review on Different Design Modifications Employed in Inclined Solar Still for Enhancing the Productivity
Authors: Kabeel A. E. , Muthu Manokar A. , Sathyamurthy Ravishankar , Prince Winston D. , El-Agouz S. A. , Chamkha Ali J.
Published: September 2018

The current challenge of human society is to meet the large demand of freshwater, which is depleting at a faster rate due to a rapid rise in human population and fast urbanization. Solar still is the economical way to obtain fresh water since it solely requires the energy from the sun alone for its operation, which is abundantly and freely available in nature. The major constraint in conventional solar still (CSS) is to maintain a large surface area of water with a minimum water depth. The best solution for the above constraint is to prefer inclined solar still (ISS) in which the surface area of water is large with a minimum water depth. In order to improvise the performance and efficiency of ISS, numerous works have been incorporated by increasing the free surface area of water. The distillate yield collected from the passive ISS was found as 1000–8100 mL/m2 whereas active ISS produced the distillate yield of 1045–9000 mL/day. In this review, an attempt is made to analyze the present status of different designs in ISS to motivate further research in ISS technology for meeting the demand of fresh water.
On Void Shape and Distribution Effects on Void Coalescence
Authors: Barrioz Pierre-Olivier , Hure Jérémy , Tanguy Benoît
Published: September 2018

Void coalescence is known to be the last microscopic event of ductile fracture in metal alloys and corresponds to the localization of plastic flow in between voids. Limit-analysis has been used to provide coalescence criteria that have been subsequently recast into effective macroscopic yield criteria, leading to models for porous materials valid for high porosities. Such coalescence models have remained up to now restricted to cubic or hexagonal lattices of spheroidal voids. Based on the limit-analysis kinematic approach, a methodology is first proposed to get upper-bound estimates of coalescence stress for arbitrary void shapes and lattices. Semi-analytical coalescence criteria are derived for elliptic cylinder voids in elliptic cylinder unit cells for an isotropic matrix material, and validated through comparisons to numerical limit-analysis simulations. The physical application of these criteria for realistic void shapes and lattices is finally assessed numerically.
Tunable Adhesion of a Bio-Inspired Micropillar Arrayed Surface Actuated by a Magnetic Field
Authors: Li Xingji , Peng Zhilong , Yang Yazheng , Chen Shaohua
Published: September 2018

Bio-inspired functional surfaces attract many research interests due to the promising applications. In this paper, tunable adhesion of a bio-inspired micropillar arrayed surface actuated by a magnetic field is investigated theoretically in order to disclose the mechanical mechanism of changeable adhesion and the influencing factors. Each polydimethylsiloxane (PDMS) micropillar reinforced by uniformly distributed magnetic particles is assumed to be a cantilever beam. The beam's large elastic deformation is obtained under an externally magnetic field. Specially, the rotation angle of the pillar's end is predicted, which shows an essential effect on the changeable adhesion of the micropillar arrayed surface. The larger the strength of the applied magnetic field, the larger the rotation angle of the pillar's end will be, yielding a decreasing adhesion force of the micropillar arrayed surface. The difference of adhesion force tuned by the applied magnetic field can be a few orders of magnitude, which leads to controllable adhesion of such a micropillar arrayed surface. Influences of each pillar's cross section shape, size, intervals between neighboring pillars, and the distribution pattern on the adhesion force are further analyzed. The theoretical predictions are qualitatively well consistent with the experimental measurements. The present theoretical results should be helpful not only for the understanding of mechanical mechanism of tunable adhesion of micropillar arrayed surface under a magnetic field but also for further precise and optimal design of such an adhesion-controllable bio-inspired surface in future practical applications.
A Computational Model for the Dynamics of Cerebrospinal Fluid in the Spinal Subarachnoid Space
Authors: Toro Eleuterio F. , Thornber Ben , Zhang Qinghui , Scoz Alessia , Contarino Christian
Published: September 2018

Global models for the dynamics of coupled fluid compartments of the central nervous system (CNS) require simplified representations of the individual components which are both accurate and computationally efficient. This paper presents a one-dimensional model for computing the flow of cerebrospinal fluid (CSF) within the spinal subarachnoid space (SSAS) under the simplifying assumption that it consists of two coaxial tubes representing the spinal cord and the dura. A rigorous analysis of the first-order nonlinear system demonstrates that the system is elliptic-hyperbolic, and hence ill-posed, for some values of parameters, being hyperbolic otherwise. In addition, the system cannot be written in conservation-law form, and thus, an appropriate numerical approach is required, namely the path conservative approach. The designed computational algorithm is shown to be second-order accurate in both space and time, capable of handling strongly nonlinear discontinuities, and a method of coupling it with an unsteady inflow condition is presented. Such an approach is sufficiently rapid to be integrated into a global, closed-loop model for computing the dynamics of coupled fluid compartments of the CNS.
Modified Collision Energy, a New Chemical Model in the DSMC Algorithm
Authors: Zakeri Ramin , Kamali-Moghadam Ramin , Mani Mahmoud
Published: September 2018

A new chemical model in the direct simulation Monte Carlo (DSMC) algorithm, entitled modified collision energy (MCE), has been developed for simulation of reactive rarefied flows without some limitations of the conventional macroscopic models. Determination of correct values of the experimental parameters for computing the Arrhenius reaction rate is a serious challenge in some macroscopic chemical reaction models such as total collision energy (TCE) and general collision energy (GCE). A slight variation of these constant parameters in the Arrhenius relation could lead to significant change in the results. On the other hand, these experimental parameters have been extracted empirically only for limit number of gases and so they cannot be used for simulation of chemical reactions in various types of gases. Since some of these constants have been determined experimentally by several studies, they have been reported by different values in different references. The proposed MCE model in the present study is a reliable method to properly determine values of these parameters for all types of gases with the intrinsic properties of the particles and without need of any experimental data. Extraction of the constant parameters has been carried out using the analytical method or numerical quantum kinetics (QK) or modified quantum kinetics (MQK) models. The proposed MCE method has been evaluated in four test cases, including assessment of the reaction rate in equilibrium and nonequilibrium conditions, studying of the rarefied flow along the stagnation line, and investigation of the hypersonic gas flow over the axial symmetry blunt nose. The results show that the proposed method has desirable accuracy without use of any experimental parameters. The MCE method can also be used to calibrate the macroscopic reactive models such as the TCE and GCE.
A New Approach to Delay or Prevent Frost Formation in Membranes
Authors: Navid Pooya , Niroomand Shirin , Simonson Carey J.
Published: September 2018

Saturation of the water vapor is essential to form frost inside a permeable membrane. The main goal of this paper is to develop a numerical model that can predict temperature and humidity inside a membrane in order to show the location and time of saturation. This numerical model for heat and mass transfer is developed to show that frost formation may be prevented or delayed by controlling the moisture transfer through the membrane, which is the new approach in this paper. The idea is to simultaneously dry and cool air to avoid saturation conditions and thereby eliminate condensation and frosting in the membrane. Results show that saturation usually occurs on side of the membrane with the highest temperature and humidity. The numerical model is verified with experimental data and used to show that moisture transfer through the membrane can delay or prevent frost formation.
Energy Efficiency State Identification Based on Continuous Wavelet Transform—Fast Independent Component Analysis
Authors: Cai Yun , Shi Xinhua , Shao Hua , Yuan Jianjian
Published: September 2018

In metal cutting operations, energy efficiency can have significant consequences for the environment and for sustainable development (such as ever-increasing demand for cost saving and quality improvements), particularly when the processes are practiced on a very large scale. The energy efficiency state is a cutting process condition that coexists with other conditions such as cutter state, workpiece quality state, or machine tool state. It must be monitored by operators to avoid system failure of low energy efficiency state, on-line energy efficiency state monitoring is becoming more and more important in intelligent manufacturing and green manufacturing. The idea of energy efficiency state identification is proposed and the monitoring strategy of energy efficiency state is established for this subject. A combined application method of continuous wavelet transform (CWT) and fast independent component analysis (FICA) is proposed for feature extraction of low or high energy efficiency state. The feature of energy efficiency state is extracted by CWT on the premise of determining the state of high and low energy efficiency based on modeling of energy efficiency state and experiment data. The feature signal is reconstructed by FICA and the reconstruction signal is verified by short time Fourier transform (STFT). The feature tracing of cutting system is carried out. It is illustrated that the feature of energy efficiency state can be extracted and the different energy efficiency states also can be identified for milling processes. The proposed method will be helpful for energy efficiency state monitoring.
An Adaptive Geometry Transformation and Repair Method for Hybrid Manufacturing
Authors: Praniewicz Maxwell , Kurfess Thomas , Saldana Christopher
Published: September 2018

Hybrid manufacturing has become particularly attractive for refurbishing of high-value freeform components. Components may experience unique geometric distortions and/or wear-driven material loss in service, which require the use of part-specific, adaptive repair strategies. The current work presents an integrated adaptive geometry transformation method for additive/subtractive hybrid manufacturing based on rigid and nonrigid registrations of parent region material and geometric interpolation of the repair region material. In this approach, rigid registration of nominal part geometry to actual part geometry is accomplished using iterative alignment of profiles in the parent material. Nonrigid registration is used to morph nominal part geometry to actual part geometry by transformation of the profile mean line. Adaptive additive and subtractive tool paths are then used to add material based on constant stock margin requirements, as well as to produce blend repairs with smooth transition between parent and repair regions. A range of part deformation conditions due to profile twist and length changes are evaluated for the case of a compressor blade/airfoil geometry. Accuracy of the resulting adaptive geometry transformation method were quantified by (1) surface comparisons of actual and transformed nominal geometry and (2) blend region surface accuracy. Performance of the adaptive repair strategy relative to a naïve strategy is evaluated by the consideration of material efficiency and process cycle time. It is shown that the adaptive repair strategy resulted in an increase in material efficiency by 42.2% and a decrease in process time by 17.8%, depending on the initial deformation imposed on the part geometry.
A Novel Region-Division-Based Tolerance Design Method for a Large Number of Discrete Elements Distributed on a Large Surface
Authors: Sa Guodong , Liu Zhenyu , Qiu Chan , Tan Jianrong
Published: September 2018

The array structure is widely used in precise electronic products such as large phased array antennas and large optical telescopes, the main components of which are a large surface base and a large number of high-precision discrete elements mounted on the surface base. The geometric error of discrete elements is inevitable in the manufacturing process and will seriously degrade the product performance. To deal with the tolerance design of discrete elements, a region-division-based tolerance design method is proposed in this paper. The whole array was divided into several regions by our method and the tolerance of discrete elements was correlated with the region importance on the performance. The method specifically includes the following steps: first, the sensitivity of the product performance to geometric errors was analyzed and the statistical relationship between the performance and geometric errors was established. Then, based on the sensitivity matrix, the regional division scheme was developed, and the corresponding tolerance was optimized according to the established relationship function. Finally, the optimal tolerance was selected among the multiple solutions to achieve the best performance. Taking a large phased array as an example, a simulation experiment was performed to verify the effectiveness of the proposed method.
Regularization-Free Strain Mapping in Three Dimensions, With Application to Cardiac Ultrasound
Authors: Boyle John J. , Soepriatna Arvin , Damen Frederick , Rowe Roger A. , Pless Robert B. , Kovacs Attila , Goergen Craig J. , Thomopoulos Stavros , Genin Guy M.
Published: September 2018

Quantifying dynamic strain fields from time-resolved volumetric medical imaging and microscopy stacks is a pressing need for radiology and mechanobiology. A critical limitation of all existing techniques is regularization: because these volumetric images are inherently noisy, the current strain mapping techniques must impose either displacement regularization and smoothing that sacrifices spatial resolution, or material property assumptions that presuppose a material model, as in hyperelastic warping. Here, we present, validate, and apply the first three-dimensional (3D) method for estimating mechanical strain directly from raw 3D image stacks without either regularization or assumptions about material behavior. We apply the method to high-frequency ultrasound images of mouse hearts to diagnose myocardial infarction. We also apply the method to present the first ever in vivo quantification of elevated strain fields in the heart wall associated with the insertion of the chordae tendinae. The method shows promise for broad application to dynamic medical imaging modalities, including high-frequency ultrasound, tagged magnetic resonance imaging, and confocal fluorescence microscopy.
Multiple Dynamic Response Patterns of Flexible Multibody Systems With Random Uncertain Parameters
Authors: Wang Zhe , Tian Qiang , Hu Haiyan
Published: September 2018

The mechanisms with uncertain parameters may exhibit multiple dynamic response patterns. As a single surrogate model can hardly describe all the dynamic response patterns of mechanism dynamics, a new computation methodology is proposed to study multiple dynamic response patterns of a flexible multibody system with uncertain random parameters. The flexible multibody system of concern is modeled by using a unified mesh of the absolute nodal coordinate formulation (ANCF). The polynomial chaos (PC) expansion with collocation methods is used to generate the surrogate model for the flexible multibody system with random parameters. Several subsurrogate models are used to describe multiple dynamic response patterns of the system dynamics. By the motivation of the data mining, the Dirichlet process mixture model (DPMM) is used to determine the dynamic response patterns and project the collocation points into different patterns. The uncertain differential algebraic equations (DAEs) for the flexible multibody system are directly transformed into the uncertain nonlinear algebraic equations by using the generalized-alpha algorithm. Then, the PC expansion is further used to transform the uncertain nonlinear algebraic equations into several sets of nonlinear algebraic equations with deterministic collocation points. Finally, two numerical examples are presented to validate the proposed methodology. The first confirms the effectiveness of the proposed methodology, and the second one shows the effectiveness of the proposed computation methodology in multiple dynamic response patterns study of a complicated spatial flexible multibody system with uncertain random parameters.
Design and Kinematic Analysis of a Novel Hybrid Kinematic Mechanism With Seven-Degrees-of-Freedom and Variable Topology for Operation in Space
Authors: He Jun , Gao Feng , Sun Qiao
Published: September 2018

We propose a novel hybrid robot with seven degrees-of-freedom (DOF) and variable topology for operation in space. Design specifications of the space robot are presented for the type synthesis of hybrid mechanisms. Based on GF set theory, three design rules are given, thus providing the design method of the 7DOF hybrid space robot mechanism. Twenty-four combinations of the hybrid robotic mechanisms are obtained. The final synthesized configuration for the design of the space robot has a 3DOF parallel module and a 4DOF serial module with four revolute (RRRR) joints. The parallel module consists of a limb with universal-prismatic (UP) joints and two limbs with universal-prismatic-spherical (UPS) joints. The topology of the hybrid robot can be changed, and it will become an RPRR four-bar mechanism when it is folded for launch. The closed-form solution for the inverse displacement model is developed, and then the forward displacement equations are also obtained. After that, the Jacobian matrix is derived from the displacement model; the Jacobian matrix will analyze the singularity and workspace. We find that there are four singularities of mechanisms. The dexterous workspace of the hybrid robot is a good match for the grapple operation in space. An experiment with the prototype shows the present hybrid robot can grapple to a satellite-rocket docking ring and therefore validates the kinematic equations.
Modeling Large Deflections of Initially Curved Beams in Compliant Mechanisms Using Chained Beam Constraint Model
Authors: Chen Guimin , Ma Fulei , Hao Guangbo , Zhu Weidong
Published: September 2018

Understanding and analyzing large and nonlinear deflections are the major challenges of designing compliant mechanisms. Initially, curved beams can offer potential advantages to designers of compliant mechanisms and provide useful alternatives to initially straight beams. However, the literature on analysis and design using such beams is rather limited. This paper presents a general and accurate method for modeling large planar deflections of initially curved beams of uniform cross section, which can be easily adapted to curved beams of various shapes. This method discretizes a curved beam into a few elements and models each element as a circular-arc beam using the beam constraint model (BCM), which is termed as the chained BCM (CBCM). Two different discretization schemes are provided for the method, among which the equal discretization is suitable for circular-arc beams and the unequal discretization is for curved beams of other shapes. Compliant mechanisms utilizing initially curved beams of circular-arc, cosine and parabola shapes are modeled to demonstrate the effectiveness of CBCM for initially curved beams of various shapes. The method is also accurate enough to capture the relevant nonlinear load-deflection characteristics.
Origami Kaleidocycle-Inspired Symmetric Multistable Compliant Mechanisms
Authors: Zhang Hongchuan , Zhu Benliang , Zhang Xianmin
Published: September 2018

Compliant kaleidocycles can be widely used in a variety of applications, including deployable structures, origami structures, and metamorphic robots, due to their unique features of continuous rotatability and multistability. Inspired by origami kaleidocycles, a type of symmetric multistable compliant mechanism with an arbitrary number of units is presented and analyzed in this paper. First, the basic dimension constraints are developed based on mobility analysis using screw theory. Second, the kinematic relationships of the actual rotation angle are obtained. Third, a method to determine the number of stabilities and the position of stable states, including the solution for the parameterized boundaries of stable regions, is developed. Finally, experimental platforms are established, and the validity of the proposed multistable mechanisms is verified.
Prediction of Surface Wear of Involute Gears Based on a Modified Fractal Method
Authors: Li G. , Wang Z. H. , Zhu W. D.
Published: September 2018

A new wear prediction method of tooth surfaces of involute gears based on a real tooth surface model and a modified fractal method is developed. The real tooth surface model of an involute gear pair is introduced, and microgeometry feature detection of tooth surfaces is achieved by monitoring variations of normal vectors of each discrete data point of the real tooth surface model. To predict wear progression of tooth surfaces of a gear pair, an abrasive wear analysis model and the modified fractal method are used to analyze contact performance and its changes with accumulation of surface wear. The abrasive wear analysis model can analyze wear depths of gear tooth surfaces with sliding distances, local contact pressure, and directions of wear progression based on Archard's model. The modified fractal method is proposed to calculate instantaneous contact stiffness and estimate elastic and plastic deformation regions based on an asperity contact model. Microgeometry features of tooth surface asperities can be described as the basis of an asperity contact model and allow tooth contact analysis of real tooth surface models with their local microgeometry feature changes due to plastic deformations. Feasibility and effectiveness of this wear prediction method were verified by comparing predicted results of gear surface wear progression with gear wear test results.
Adapted Motor-Assisted Elliptical for Rehabilitation of Children With Physical Disabilities
Authors: Burnfield Judith M. , Buster Thad W. , Pfeifer Chase M. , Irons Sonya L. , Cesar Guilherme M. , Nelson Carl A.
Published: September 2018

Many children with physical disabilities experience difficulty using traditional exercise equipment for gait rehabilitation and fitness training, and the clinician resources required to deliver intensive overground or treadmill-based therapies are infrequently available in most clinics, hospitals, and school settings. This work describes design and testing of a comprehensive set of modifications that enabled children to use a commercially available robotic exercise device (i.e., Intelligently Controlled Assistive Rehabilitation Elliptical (ICARE)) initially developed to address walking and fitness goals of adults with physical disabilities and chronic conditions. Fifteen children (3–11 years old) concurrently enrolled in physical therapy due to varied neurologic conditions were recruited with their parent(s) to evaluate the safety, comfort, and usability of the adult ICARE and pediatric-modified ICARE. After children tried each device, feedback was recorded. To assess feasibility, each child then participated in up to ten sessions (two to five sessions per week; average session length: 38 min, range 21–66 min) using the pediatric-modified ICARE. Parents, on average, perceived that the pediatric-modified ICARE was significantly safer, more comfortable and usable than the adult ICARE. Children's perceptions of the pediatric-modified ICARE were similar, although not statistically significant. Children used the prototype device during 133 sessions for over 3800 min and more than 162,000 cycles. In conclusion, this study demonstrated the feasibility of using the pediatric-modified ICARE with children as young as 3 years old as an adjunct to ongoing therapy.
Utilization of Cable Guide Channels for Compact Articulation Within a Dexterous Three Degrees-of-Freedom Surgical Wrist Design
Authors: Podolsky Dale J. , Diller Eric , Fisher David M. , Wong Riff Karen W. , Looi Thomas , Drake James M. , Forrest Christopher R.
Published: September 2018

Pin-jointed wrist mechanisms provide compact articulation for surgical robotic applications, but are difficult to miniaturize at scales suitable for small body cavity surgery. Solid surface cable guide channels, which eliminate the need for pulleys and reduce overall length to facilitate miniaturization, were developed within a three-degree-of-freedom cable-driven pin-jointed wrist mechanism. A prototype was 3D printed in steel at 5 mm diameter. Friction generated by the guide channels was experimentally tested to determine increases in cable tension during constant cable velocity conditions. Cable tension increased exponentially from 0 to 37% when the wrist pitched from 0 deg to 90 deg. The shape of the guide channel groove and angle, where the cable exits the channel impacts the magnitude of cable tension. A spring tensioning and cam actuation mechanism were developed to account for changing cable circuit path lengths during wrist pitch. This work shows that pulley-free cable wrist mechanisms can facilitate miniaturization below current feasible sizes while retaining compact articulation at the expense of increases in friction under constant cable velocity conditions.
Real-Time Tuning of Delayed Resonator-Based Absorbers for Spectral and Spatial Variations
Authors: Jenkins Ryan , Olgac Nejat
Published: September 2018

This paper offers two interlinked contributions in the field of vibration absorption. The first involves an active tuning of an absorber for spectral and spatial variations. The second contribution is a set of generalized design guidelines for such absorber operations. “Spectral” tuning handles time-varying excitation frequencies, while “spatial” tuning treats the real-time variations in the desired location of suppression. Both objectives, however, must be achieved using active control and without physically altering the system components to ensure practicality. Spatial tuning is inspired by the concept of “noncollocated vibration absorption,” for which the absorber location is different from the point of suppression. This concept is relatively under-developed in the literature, mainly because it requires the use of part of the primary structure (PS) as the extended absorber—a delicate operation. Within this investigation, we employ the delayed resonator (DR)-based absorber, a hybrid concept with passive and active elements, to satisfy both tuning objectives. The presence of active control in the absorber necessitates an intriguing stability investigation of a time-delayed dynamics. For this subtask, we follow the well-established methods of frequency sweeping and D-subdivision. Example cases are also presented to corroborate our findings.
Resonant Ultrasound Spectroscopy: Sensitivity Analysis for Isotropic Materials and Anisotropic Materials With Cubic Symmetry
Authors: Farzbod Farhad , Scott-Emuakpor Onome E.
Published: September 2018

Resonant ultrasound spectroscopy (RUS) is an experimental method to measure elastic and anelastic properties of materials. The RUS experiment is conducted by exciting a specimen with a simple geometry and measuring resonant frequencies. From the resonant behaviors, both elastic and anelastic properties of the sample material can be extracted. This paper investigates the sensitivities of measured resonant frequencies to changes in elastic constants for an isotropic material and anisotropic material with cubic symmetry. Also under investigation is whether different specimen geometries increase the sensitivity of RUS; in other words, a path for optimizing the reliability of RUS data is explored.
Li-Ion Battery Pack Thermal Management: Liquid Versus Air Cooling
Authors: Han Taeyoung , Khalighi Bahram , Yen Erik C. , Kaushik Shailendra
Published: September 2018

The Li-ion battery operation life is strongly dependent on the operating temperature and the temperature variation that occurs within each individual cell. Liquid-cooling is very effective in removing substantial amounts of heat with relatively low flow rates. On the other hand, air-cooling is simpler, lighter, and easier to maintain. However, for achieving similar cooling performance, a much higher volumetric air flow rate is required due to its lower heat capacity. This paper describes the fundamental differences between air-cooling and liquid-cooling applications in terms of basic flow and heat transfer parameters for Li-ion battery packs in terms of QITD (inlet temperature difference). For air-cooling concepts with high QITD, one must focus on heat transfer devices with relatively high heat transfer coefficients (100–150 W/m2/K) at air flow rates of 300–400 m3/h, low flow induced noise, and low-pressure drops. This can be achieved by using turbulators, such as delta winglets. The results show that the design concepts based on delta winglets can achieve QITD of greater than 150 W/K.
Analysis
of Thermal Characteristic of Spur/Helical Gear
Transmission
Authors: Li Wei , Zhai Pengfei , Ding Lei
Published: September 2018

Gear drives are widely used in mechanical driving devices, and the heating problem of gear has been paid much attention. The tooth surface temperature field of spur/helical gear is compared and thermal characteristic of spur/helical gear is studied in this paper. The calculation formula of frictional heat flux and convective heat transfer coefficient, which considers different surfaces of gear tooth, is derived. The frictional heat flux of the helical gear is different from that of the spur gear, and the calculation method is different. The finite element parametric model for thermal analysis is built and it realizes the automatic parametric modeling, loading, and generation of temperature field by ANSYS parametric design language (APDL) program. The influence of different parameters on gear temperature rise is analyzed and the distribution of the three-dimensional (3D) temperature field of spur/helical is obtained. The simulation analysis and experiment are compared to validate the accuracy of thermal analysis results. The research result reveals the distribution law of the 3D temperature field of spur/helical gear transmission at different working parameters. It provides theoretical guidance for gear antiscuffing capability and gear optimization design.