bluuebunny/crossref_metadata_2025 huggingface dataset:
Unexplained Dyspnea and Cardiopulmonary Exercise Testing: Rationale for a Dyspnea Clinic
Authors: Nair Pooja , Christle Jeffrey W , Verdonk Constance , Cauwenberghs Nicholas , Blumberg Yair , Sasportas Laura S , Zamanian Roham , Ashley Euan , Kuznetsova Tatiana , Myers Jonathan , Haddad Francois , Amsallem Myriam
Published: November 2021

Objective

To describe the experience of a tertiary-care center in the management of patients with unexplained dyspnea referred for cardiopulmonary exercise testing (CPX).

Methods

All consecutive adults with unexplained dyspnea who underwent CPX at a single tertiary referral center over a ten-year period were included from a prospective registry. We collected data on final diagnosis, routine labs and diagnostic testing including stress/resting echocardiography performed within 6 months of CPX.

Results

From 2008 to 2019, 156 patients with unexplained dyspnea were referred for CPX with no prior history of cardiovascular disease, lung disease or neuromuscular disease. A 4-fold increase in referrals was noted during this time period. Analysis of diagnostic work-up revealed marked heterogeneity, particularly according to the specialty of the referring physician. Among the 134 patients who achieved an adequate level of exertion during CPX, 24 (17.9%) and 30 (22.4%) patients had an abnormal age-predicted peak VO2 of < 80% according to Wasserman’s and FRIEND equations respectively. Further analysis revealed 22.5% of patients had a VE/VCO2 slope > 34, suggesting ventilatory inefficiency. Subgroup analysis of 108 patients with complete left ventricular (LV) diastology revealed 13% of patients with a final diagnosis of unexplained dyspnea after CPX were found to have underlying diastolic dysfunction.

Conclusions

Our study illustrates an increase in CPX referrals for unexplained dyspnea and associated heterogeneity in diagnostic testing in this population. There is a need for an integrated dyspnea clinic to standardize workflow and facilitate early diagnosis for these patients.
An appraisal of Australia's approach to promoting urban sustainability
Authors: Martek Igor , Edwards David J. , Seaton Stewart , Jones David
Published: November 2021

Purpose

Much rhetoric exists on the urgency of transitioning from current practices to a more sustainable society. However, because this imperative is guided by strong ideological overtones, weaknesses and failures in the transition effort attract inadequate scrutiny. This paper reviews Australia's progress with sustainability in an urban domain and identifies key issues hindering the sustainability transition effort.

Design/methodology/approach

Research on urban sustainability is ubiquitous but this weight of publications tends to emphasize technical, operational or prescriptive themes. This research uses an interpretivist philosophical lens and inductive reasoning to manually analyse pertinent literature sourced from the Scopus and Web of Science data-bases. Specifically, this study assembles outcome and evaluative assessments pertaining to Australia's urban sustainability efforts to identify both the progress achieved and residual structural impediments.

Findings

Emergent findings illustrate that Australia's urban sustainability goals, as expressed by the Paris Accord, have not been met. Obstruction can be attributed to over-ambitious objectives combined with weak federal leadership, under-resourced local government, over-reliance on superficial rating systems and an ineffective regulatory regime. Elite “green branding” by image conscious corporations are insufficient to offset the general disinterest of the unincentivized majority of building owners and developers.

Originality/value

This paper cogently summarizes Australia's urban sustainability status, along with complexity of the challenges it faces to meet targets set.
Interplay among blockchain technology adoption strategy, e-supply chain management diffusion, entrepreneurial orientation and human resources information system in banking
Authors: Adel Heba Mohamed , Younis Raghda Abulsaoud Ahmed
Published: November 2021

Purpose

To empirically study the direct and mediating relationships between blockchain technology adoption strategy (BCTAS), electronic supply chain management diffusion (eSCMD), entrepreneurial orientation (EO) and human resources information system (HRIS) in Egyptian banks. This paper aims to connect the dots and show the relationships linking these related constructs after the emergence of this breakthrough blockchain technology.

Design/methodology/approach

The authors have undertaken a thematic review of relevant multidisciplinary business management literature and then developed a conceptual model. This model was examined through adopting a mixed-methods approach, through which 300 quantitative questionnaires were filled by information technology (IT) staff at 12 banks in Egypt utilising a snowball sample. Besides, 20 qualitative interviews were carried out with international and Egyptian blockchain experts for exploratory and explanatory purposes. The suggested hypotheses were tested using structural equation modelling.

Findings

The results revealed that EO affects positively and significantly BCTAS and HRIS. BCTAS affects positively and significantly both HRIS and eSCMD. Concerning the linkage between external/supply chain and internal/organisational information diffusion, HRIS has a positive and significant effect on eSCMD. The direct EO–eSCMD relationship is not supported. Yet, indirectly, BCTAS mediates significantly EO–eSCMD and EO–HRIS relationships. Further, HRIS mediates significantly the indirect BCTAS–eSCMD relationship.

Practical implications

The findings of this research shed light on the benefits and challenges of adopting BCTAS within emerging markets in general and Egyptian banking in specific, which can support an effective and efficient decision-making process undertaken by strategic and functional banking managers with EO in similar emerging economies.

Originality/value

Conceptually and empirically, it is the first article that investigated direct and mediating EO–BCTAS–HRIS–eSCMD relationships in a promising banking industry of an emerging market. It solved an interdisciplinary research puzzle by piecing together the relevant contemporary literature on production, operations and SC management, entrepreneurship, HR management and strategic technology adoption.
Sources for advertising and marketing history at the McCracken Research Library, Buffalo Bill Center of the West
Authors: Witkowski Terrence H.
Published: November 2021

Purpose

This paper aims to describe written and visual data sources useful for researching the history of advertising and marketing that are held in the collections of the McCracken Research Library at the Buffalo Bill Center of the West in Cody, Wyoming.

Design/methodology/approach

Knowledge of the McCracken collections has been acquired over several years of online searches and subsequent data analyses, communications with Library staff and from a personal visit to Cody in September 2021.

Findings

Several digital collections are surveyed. The Roy Marcot Firearms Advertisement Collection visually documents industry practices and also speaks to larger issues in American gun culture. The Winchester Publications provide insights via company magazines into product and management strategies, hardware retailing and visual merchandising tactics during the 1920s. The Schuyler, Hartley and Graham archive of business correspondence illustrate business-to-business marketing from the nineteenth through the early 20th century. The Buffalo Bill Collection reveals how the culturally important Wild West shows were promoted and experienced.

Originality/value

This paper familiarizes advertising and marketing historians with the primary sources in the McCracken Research Library and suggests some potential areas for study.
Linking empowerment, engagement, communication and organizational health: moderated mediation model
Authors: Singh Anupama
Published: November 2021

Purpose

This paper aims to examine the factors that mediate and moderate the relationship between psychological empowerment and organizational health. Specifically, work engagement is posited to mediate the relationship between psychological empowerment and organizational health and organizational communication to moderate the relationship between psychological empowerment and work engagement.

Design/methodology/approach

Data were collected from 524 scientists belonging to 10 laboratories of CSIR – an Indian R&D organization. For statistical analysis of moderated-mediation model, hierarchical multiple regression and process macro for SPSS was used.

Findings

Results revealed that work engagement was found to mediate the positive relationship between psychological empowerment and organizational health and organizational communication moderated the influence of psychological empowerment on work engagement. Results of moderated-mediation revealed that mediation of work engagement was moderated by organizational communication such that at higher levels of communication, the mediating effect of work engagement became stronger.

Originality/value

This study extends the understanding of the organizational health concept by studying the mediating effect of work engagement being moderated by organizational communication and its subsequent impact on organizational health.
Gender detransition: a case study
Authors: Marchiano Lisa
Published: November 2021

Within the last decade, there has been a sharp global rise in the number of young people identifying as transgender. More recently, there appears to be an increase in the numbers of young people detransitioning or returning to identifying with their natal sex after pursuing medical transition. A case is presented of a young woman who pursued a gender transition and returned to identifying as female after almost two years on testosterone. The author considers and critiques the affirmative model of care for gender dysphoric youth in light of this case.
Machine perfusion organ preservation: Highlights from the American Transplant Congress 2021
Authors: Pavan‐Guimaraes Juliana , Zarrinpar Ali , Beduschi Thiago , Atkinson Carl , Martins Paulo N.
Published: November 2021

The American Transplant Congress 2021 was a virtual meeting and occurred between June 4 and June 9 through an online platform. We highlighted abstracts discussing machine perfusion preservation, a hot topic that may become the gold standard of organ preservation in the future. A total of 33 abstracts on organ machine preservation (3 for heart, 4 for lungs, 18 for liver, and 8 for kidneys) were presented at the meeting. We selected 23 abstracts that showed advances including new approaches to organ preservation, promising treatments and biomarkers, cellular therapy, and novel research areas. Here, we summarize the new developments concerning machine perfusion in both experimental and clinical studies.
Peripheral corneal thickness and associated factors – results from the population‐based German Gutenberg Health Study
Authors: Fieß Achim , Marx‐Groß Susanne , Wasielica‐Poslednik Joanna , Nagler Markus , Schmidtmann Irene , Wild Philipp S. , Münzel Thomas , Beutel Manfred E. , Lackner Karl J. , Pfeiffer Norbert , Schuster Alexander K.
Published: November 2021

Purpose

Changes in peripheral corneal thickness are described in various corneal diseases such as corneal ectasia. However, few data exist describing the increase in corneal thickness from central to peripheral and reporting the normal distribution of corneal thickness in rings around the corneal centre. The aim of this study was to report these cornea characteristics and investigate associated factors in a population‐based setting.

Methods

The Gutenberg Health Study is a prospective, population‐based study examining participants in a 5‐year follow‐up (age range 40–80 years) using Scheimpflug imaging. Corneal thickness was assessed in each participant at the apex, as well as in the corneal centre (thinnest corneal thickness) and in rings with 2, 4, 6, 8 and 10 mm diameter around the corneal centre, and the increase in corneal thickness towards the periphery. The relationship between corneal thickness at these locations and possible associated factors was determined using linear regression models. For this purpose, general and ocular parameters were included.

Results

A total of 9729 participants were included in the present analysis (4874 women, age 59.2 ± 10.8 years). Multivariable analysis showed a correlation between the increase in corneal thickness in the circles from 0 to 10 mm (diameter) and the following parameters: age (B = −0.24 µm per year, p < 0.001); body height (B = −0.04 µm, p = 0.005); smoking (B = −0.72 µm, p < 0.001); spherical equivalent (B = −0.70 µm per dioptre, p < 0.001); white‐to‐white distance (B = −0.75 µm/mm, p < 0.001); mean corneal radius (B = −3.61 µm/mm, p < 0.001); intraocular pressure (B = −0.12 µm/mmHg, p < 0.001); glaucoma (B = −1.94 µm, p < 0.001); and pseudophakia (B = 0.89 µm, p < 0.001).

Conclusion

The results of the present study suggest that several general and ocular parameters are associated with peripheral corneal thickness. In the context of diagnosing glaucoma, a smaller increase in corneal thickness towards the periphery might be a new additional marker.
Epithelioid hemangioma involving large arteries in the skin
Authors: Markidan Janina , Hardy Naomi , Kallen Michael , Ma Linglei
Published: November 2021

Epithelioid hemangioma (EH) is a benign vascular lesion, typically consisting of small vascular channels lined by epithelioid endothelial cells and associated with a dense lymphocytic infiltrate with eosinophils. Here, we report a rare case of EH involving large arteries. The patient presented with a 9‐month history of an asymptomatic nodule on the forehead, which was thought to be an epidermal inclusion cyst. Skin biopsy revealed large arteries with clusters of epithelioid cells in the vascular walls and lumen. Scattered eosinophils were noted in the walls. Adjacent areas showed groups of small‐caliber vessels lined by prominent endothelial cells and associated with a dense lymphoid infiltrate with eosinophils. No significant cytologic atypia was noted. Given the presence of the classic small‐vessel involvement, along with CD31 reactivity for the epithelioid cells in the large vessels, the findings are classified as EH involving large arteries, which is an uncommon subtype. There have only been a handful of such cases reported in the literature.
IFN‐γ‐induced PD‐L1 expression on human melanocytes is impaired in vitiligo
Authors: Willemsen Marcella , Krebbers Gabrielle , Tjin Esther P. M. , Willemsen Karin J. , Louis Alesha , Konijn Veronique A. L. , Narayan Vidhya S. , Post Nicoline F. , Bakker Walbert J. , Melief Cornelis J. M. , Bekkenk Marcel W. , Luiten Rosalie M.
Published: November 2021

Mounting evidence shows that the PD‐1/PD‐L1 axis is involved in tumor immune evasion. This is demonstrated by anti‐PD‐1 antibodies that can reverse tumor‐associated PD‐L1 to functionally suppress anti‐tumor T‐cell responses. Since type I and II interferons are key regulators of PD‐L1 expression in melanoma cells and IFN‐γ‐producing CD8+ T cells and IFN‐α‐producing dendritic cells are abundant in vitiligo skin, we aimed to study the role of PD‐1/PD‐L1 signalling in melanocyte destruction in vitiligo. Moreover, impaired PD‐1/PD‐L1 function is observed in a variety of autoimmune diseases. It is, therefore, hypothesized that manipulating PD‐1/PD‐L1 signalling might have therapeutic potential in vitiligo. The PD‐1+ T cells were abundantly present in situ in perilesional vitiligo skin, but expression of PD‐L1 was limited and confined exclusively to dermal T cells. More specifically, neither melanocytes nor other epidermal skin cells expressed PD‐L1. Exposure to IFN‐γ, but also type I interferons, increased PD‐L1 expression in primary melanocytes and fibroblasts, derived from healthy donors. Primary human keratinocytes only showed increased PD‐L1 expression upon stimulation with IFN‐γ. More interestingly, melanocytes derived from non‐lesional vitiligo skin showed no PD‐L1 upregulation upon IFN‐γ exposure, while other skin cells displayed significant PD‐L1 expression after exposure. In a vitiligo skin explant model, incubation of non‐lesional vitiligo skin with activated (IFN‐γ‐producing) T cells from vitiligo lesions was previously described to induce melanocyte apoptosis. Although PD‐L1 expression was induced in epidermal cells in these explants, this induction was completely absent in melanocytes. The lack of PD‐L1 upregulation by melanocytes in the presence of IFN‐γ‐producing T cells shows that melanocytes lack protection against T‐cell attack during vitiligo pathogenesis. Manipulating PD‐1/PD‐L1 signalling may, therefore, be a therapeutic option for vitiligo patients.
Origen’s Theological System in On First Principles
Authors: Fernández Samuel
Published: November 2021

This article aims to reconsider Origen’s theological system in the light of his treatise On First Principles. Was Origen a systematic thinker? If so, what kind of systematicity characterised his theology? Since the reception of the treatise was marked by theological quarrels, it is not possible to isolate its theology from the problems related to the transmission of the text. Therefore, the first part of the article tackles the text of On First Principles (I). The second part studies the structure, addressees and aim of the treatise; the paper then moves on to a discussion of the nature of Origen’s systematic thinking, and an analysis of the pre‐existence of the soul to disclose the theological rationale lying behind On First Principles (II). Finally, the article outlines the theology of the treatise with a special focus on the two main features of Origen’s systematic thinking: its aspiration to reach coherence and comprehensiveness. To grasp the deep consistency of Origen’s thought, it is necessary to contemplate the history of salvation as a whole (III).
Understanding innovation policy governance: A disaggregated approach
Authors: Zhang Xiaoke
Published: November 2021

This article presents a disaggregated approach to understanding innovation policy governance. It first develops a conceptual framework for differentiating innovation policy domains in terms of the complexity of governance problems and for describing governance approaches and outcomes. The article then advances a theoretical explanation of divergent governance patterns by granting causal primacy to the interplay between government structures and interactive arrangements. It contends that these socio‐political institutions interact differently to structure the resolution of governance problems and thus generate divergent patterns of innovation policy governance. The article illustrates the empirical relevance of its theoretical framework and explanation through a comparative analysis of innovation policy governance in four East Asian economies.
Local implementation evaluation of a suicide prevention predictive model at a large VA health care system
Authors: du Pont Alta , Stanley Ian H. , Pruitt Larry D. , Reger Mark A.
Published: November 2021

Background

The Veterans Health Administration (VHA) implemented REACH VET, which analyzes health records to identify veterans at statistically elevated risk for suicide and other adverse outcomes compared to other veterans in VHA. This project evaluated REACH VET program implementation at a large VA health care system by examining program fidelity and treatment engagement, receipt of suicide prevention interventions, and suicide‐related behaviors in the 6 months following identification.

Methods

Over a 12‐month period, 218 unique cases were identified by REACH VET within a local VA system. Data were extracted from the VA’s electronic medical records.

Results

Protocol adherence for required clinical and administrative steps was 94% and above. After identification, 88% received outpatient mental health treatment, 21% had a psychiatric hospitalization, and 83% engaged in Safety Planning around the time of identification or in the following six months. Twenty‐six percent of cases were identified by another existing method for identifying high‐risk veterans. Five percent had a medically documented suicide attempt, and none were known to die by suicide in the following 6 months.

Conclusions

Local evaluation suggested high protocol fidelity and high engagement in mental health and suicide prevention services following identification among veterans who remained at elevated risk in the 6 months that followed.
Characterization of the novel HLA‐DQA1*05:01:07 allele by sequencing‐based typing
Authors: Blandin Lucie , Ralazamahaleo Mamy , Guidicelli Gwendaline , Rouzaire Paul , Lemal Richard
Published: November 2021

HLA‐DQA1*05:01:07 differs from HLA‐DQA1*05:01:01:02 by one nucleotide substitution in codon 58 in exon 2.
Tensile and Fracture Characterization of PVC Foam Cores
Authors: Viana Gilmer M. , Carlsson Leif A.
Published: November 2021

Mechanical behavior in tension and fracture toughness of cross-linked PVC foams have been characterized. Young’s modulus, yield strength and fracture toughness data were compared to micro-structural relations derived for open and closed-cell foams. The failure process and stress strain response were indicative of brittle material behavior.
Dynamic Failure Mechanisms in 3D Cellular Woven Composite Systems
Authors: Baucom Jared N. , Zikry Mohammed A. , Qiu Yiping
Published: November 2021

The role of porosity on failure resistance of 3-D woven fiber reinforced epoxy panels under dynamic loading condition is investigated. Incident and residual velocities are measured to determine the energy absorption by the target. Material behavior segregates by porosity, and the more highly porous samples absorb a greater amount of specific energy. The reason for this may be due to the deflection of matrix cracks by pores or due to the greater flexibility of the fibers to absorb energy through tensile straining. Although porosity is generally an undesirable property in textile composites, the induction of porosity may result in reduced panel weight without degradation of ballistic performance, which is a clear advantage for weight minimization.
Methods and Tools for the Design of Mechatronic Products Concepts and Examples From the University of Darmstadt
Authors: Anderl Reiner , Kleiner Sven
Published: November 2021

This paper describes the academic program of Mechanical and Process Engineering at Darmstadt University of Technology in Germany. The faculty is offering courses in general mechanical engineering, mechatronics as well as paper science and technology and chemical engineering. A closer look will be provided on design methodologies on one hand and computer aided methods and tools on the other hand in order to show the importance of teaching these specific classes. As a consequence of efficient curriculum structure of the faculty, two examples will be used to illustrate the results of project and research work in cooperation between the Department of Computer Integrated Design and students.
Dispatching of Coordinated Proximity Sensors for Object Surveillance
Authors: Naish Michael D. , Croft Elizabeth A. , Benhabib Beno
Published: November 2021

This paper presents a method of selecting and positioning groups of sensors in a coordinated manner for the surveillance of a maneuvering object The object trajectory is discretized into a number of demand instants (data acquisition times) to which groups of sensors are assigned, respectively. Heuristic rules are used to evaluate the suitability of each sensor for servicing (observing) a demand instant, determine the composition of the sensor group, and, in the case of dynamic sensors, specify the position of each sensor with respect to the object This approach aims to improve the quality of the surveillance data in three ways: (1) the assigned sensors are maneuvered into “optimal” sensing positions, (2) the uncertainty of the measured data is mitigated through sensor fusion, and (3) the poses of the unassigned sensors are adjusted to ensure that sensing-system can react to object maneuvers. Simulations with proximity sensors demonstrate the advantages of dispatching dynamic sensors over similar static-sensor systems.
Time-Optimal Path Planning and Control Using Neural Networks and a Genetic Algorithm
Authors: Chaiyaratana Nachol , Zalzala Ali M. S.
Published: November 2021

This paper presents the use of neural networks and a genetic algorithm in time-optimal control of a closed-loop 3-dof robotic system. Extended Kohonen networks which contain an additional lattice of output neurons are used in conjunction with PID controllers in position control to minimise command tracking errors. The results indicate that the extended Kohonen network controller is more efficient than the trajectory preshaping scheme reported in early literature. Subsequently, a multi-objective genetic algorithm (MOGA) is used to solve an optimisation problem related to time-optimal control. This problem involves the selection of actuator torque limits and an end-effector path subject to time-optimality and tracking error constraints. Two chromosome coding schemes are explored in the investigation: Gray and integer-based coding schemes. The results suggest that the integer-based chromosome is more suitable at representing the decision variables. As a result of using both neural networks and a genetic algorithm in this application, an idea of a hybridisation between a neural network and a genetic algorithm at the task level for use in a control system is also effectively demonstrated.
Preemptive Control of Multiply Actuated Processes: Application to Moisture Content Control in Paper Manufacturing Using Surrogate Measurements
Authors: Li Perry Y. , Bjegovic Petar J. , Ramaswamy Shri
Published: November 2021

Many manufacturing processes involve the successive processing of the substrate at multiple station on a transport medium, with the hope that at the end of the process, the product has the desired property. Paper manufacturing is an example in which over 90% of the water from pulp is sequentially removed through gravity, vacuum dewatering, pressing, and thermal drying. The consistency and uniformity of the moisture content at the end of process is important for paper quality. Current strategy for the control of moisture content uses a feedback sensor at the end of the process to adjust the dryers. This introduces a long deadtime and causes excessive use of the dryers, which translate to limitations in performance, robustness and inefficient energy usage. In this paper, we investigate a new control approach in which in-process moisture contents are estimated using air-flow as surrogate measurements, and the pressure settings in the multiple vacuum dewatering boxes are adjusted according to the surrogate measurements. A preemptive control algorithm is developed which has the ability to decouple and eliminate the effects of the disturbances that occur upstream in the process from downstream. Robustness analysis and simulation studies suggest that as long as the surrogate measurements are accurate, the proposed control scheme will be robust and accurate.
State-Space Modeling and Control of Acoustic Systems
Authors: Kashani Reza , Mohammad Asim S.
Published: November 2021

Synthesis and analysis of model-based controllers for an acoustic system require the state-space formulation of the system. The use of modal data, i.e. resonant frequencies, model damping ratios, and mode shapes, in constructing state-space model of an aoucstic system is described in this paper. Moreover, a simple, low-order feedback controller for adding damping to and/or cancelling offending noise in an acoustic system is introduced. State-space modeling, as well as the effectiveness of the proposed feedback controller are demonstrated through numerical and experimental, illustrative examples.
Experience With Sliding Mode Control of a Pneumatic Cartesian Robot
Authors: Surgenor Brian W. , Xia Yang
Published: November 2021

This paper outlines experience with a 3 axis pneumatic Cartesian robot that was constructed from commercially available valves and cylinders. Experiments demonstrate that a linear PVA controller is suitable for step tracking applications. However, acceptable performance was achieved only after extensive trial and error tuning of the controller gains. Preliminary gain estimates were obtained for PVA with a Linear Quadratic (LQ) design and a linear model of the robot. Sliding Mode Control (SLM) was found to be superior to PVA in that it provided acceptable performance with minimal tuning effort. The relay nature of SLM was also found to provide a measure of friction compensation. Preliminary results for SLM as applied to circle tracking are presented.
Identification of a Driver Steering Model, and Model Uncertainty, From Driving Simulator Data
Authors: Chen Liang-Kuang , Ulsoy A. Galip
Published: November 2021

Driver steering models have been extensively studied. However, driver model uncertainty has received relatively little attention. For active safety systems that function while the driver is still in the control loop, such uncertainty can affect overall system performance significantly. In this paper, an approach to obtain both the driver model and its uncertainty from driving simulator data is presented. The structured uncertainty is used to represent the driver’s time-varying behavior, and the unstructured uncertainty is used to account for unmodeled dynamics. The uncertainty models can be used to represent both the uncertainty within one driver and the uncertainty across multiple drivers. The results show that the unstructured uncertainty is significant, probably due to randomness in driver behavior. The structured uncertainty suggests that an estimation and adaptation scheme might be applicable for the design of controllers for active safety systems.
Tube Bending Process: Part I — Theory
Authors: Lieh Junghsen , Li Wei Jie
Published: November 2021

This paper contains two parts, Part-I is focused on simulation of nonlinear springback problems. In part II, a fuzzy control law is implemented in order to compensate the nonlinearity and uncertainty in tube bending. By combining elasticity and plasticity theories, a mathematical model for predicting springback is established and Simpson’s integration rule is adopted. The discrepancy between theoretical and experimental results is used to examine the accuracy of established model.
Path Planning for Motion Control of Hexapod Machines
Authors: Ji Zhiming , Li Zhenqun
Published: November 2021

The dramatic departure in structure of the hexapod machine tools from the traditional five-axis machines leads to the question: can the planning and control methods for the traditional CNC machines be used for the hexapod machine tools? We studied several tool motion characteristics, such as Jocabian matrices, path tracking errors and the extra degree of freedom (e-DOF), and found that the traditional five-axis planning methods cannot take into consideration of the kinematics performance variation and the e-DOF in a hexapod. A kinematics-based tool path planning scheme for the hexapods is therefore proposed. It combines the traditional tool path planning with the kinematic condition optimization. The optimization is a two-step process. First a high accuracy zone of the workspace is identified globally for the placement of the part. Then a set of 5-DOF tool paths is generated and extended to a set of 6-DOF tool paths based on the local planning of e-DOF. Finally the relationship between the e-DOF and the stiffness of the Hexapods, another factor in the use of e-DOF, are discussed.
Time Delay-Free Nonlinear Bilateral Teleoperation With Model-Based Predictive Display
Authors: Parra-Vega Vicente
Published: November 2021

Robotic teleoperation is a difficult task because of the inherent difficulty to model and control time-delay nonlinear models. In order to handle tractable models, typically there have been two ways to tackle this problem: i) The first approach is to assume that the system is fast enough and thus the time delay can be neglected, in this way time-delay-free differential equations are obtained such that the controller is time-delay-free. This approach needs further formal study to validate this assumption, and so far there is neither strict nor rigorous result that support this claim, when considering the full nonlinear telerobotic dyanmics. ii) In the second approach, the time delay is considered explicitly, however typically nonlinear dynamics is neglected and then linear models are used to derive time-delay-based control systems. The second approach ignores that the robots are nonlinear systems with strong nonlinear inertial couplings, and therefore controllers based on linear time-delay models render low performance. In this paper, the teleoperation of robots is modeled, including nonlinear dynamics in the continuous domain, without any time delay, and model-based nonlinear continuous second order sliding mode controllers are proposed which guarantee finite-time convergence. Thus, this approach attempts to propose a scheme for the second approach outlined above. The teleoperation system provides force reflection to the human operator, and a kinematic-based predictive display yields visual stimuli while the master robot yields kinesthetic feedback to the operator to allow planning better desired trajectories, including contact forces, in contrast to other predictive displays that have been proposed in the literature. Therefore, the theoretical foundations of finite-time convergent telecontrol system and its advantages are discussed.
Optimized Driving Force Control of a Planar Micro-Robot Using Friction Drive Mechanism
Authors: Ferreira Antoine , Fontaine Jean-Guy
Published: November 2021

This paper presents a new generation of compliant piezoelectric microconveyers for microobjects based on the cooperation of arrayed direct-drive standing wave ultrasonic actuators. A method using an equivalent electromechanical circuit is proposed for estimating and analysing the optimum driving force. On the basis of the proposed method, the friction drive optimization of the micro-robot is performed through the implementation of an electromagnetic field-based preload controller. Preliminary experiments were also performed in order to demonstrate the proposed control method.
Rolling Contact Dynamics and Optimal Feedforward Control for the Modular Distributed Manipulator
Authors: Bedillion Mark , Messner William , Choset Howie
Published: November 2021

The Modular Distributed Manipulator System (MDMS) is an array of actuators that is capable of manipulating objects in the plane [1]. This paper derives equations of motion for the coupled dynamics of the MDMS actuators and objects riding upon it, and it derives feedforward control strategies for this multi-input, three-output system. Unlike previous work in which traction forces were generated using viscous friction caused by sliding contact between the manipulated object and the actuators, this paper considers traction forces generated by no-slip rolling contact. This approach allows more precise manipulation, because object positions and orientations and their time derivatives can be determined by wheel encoder information. The dynamic equations account for the electromechanical dynamics of each actuator and the coupling between them and the translational and rotational dynamics of the manipulated object. This paper then presents two different feedforward control strategies based on minimizing the sum of the squares of the inputs or minimizing the total system power.
Visualization and Computation of the Flow of a Highly Shear-Thinning Liquid Past the Axisymmetric Contraction-Expansion: Application to Blood Flow Through Stenotic Vessels
Authors: Quintella Erick F. , Mendes Paulo R. Souza , Azevedo Luis F. A. , Naccache Mônica F.
Published: November 2021

Stenosis is a constriction or narrowing of a duct or passage. This word is often used to refer to constrictions that occur in blood vessels, especially arteries. A stenotic vessel generally causes blood flow stagnation and hence formation of thrombus, which may be rather harmful to the human physiology. In this work we perform flow visualization experiments and finite-volume computation to study the flow of an yield-stress (or highly shear-thinning) liquid through a tube in the neighborhood of an axisymmetric constriction. The rheology of the liquid was chosen to be close to the one of blood with 55% hematocrit Reynolds and Yield number values characteristic to different arteries have been studied, as well as different levels of constriction. Results for a Newtonian liquid were also obtained, for comparison purposes. Numerical solutions of the mass and momentum balance equations were obtained. In these solutions it was assumed that the materials behave like a Generalized Newtonian Liquid with a biviscosity function, which mimics closely the Herschel-Bulkley equation but allows deformation below the yield stress limit.

Among other findings, it has been observed that the non-Newtonian rheology causes a significant change in the flow pattern in the neighborhood of the stenosis. Because the conditions for thrombus formation are directly related to the flow pattern, studies of the flow through stenotic vessels that assume a Newtonian rheology may lead to erroneous conclusions.
A Study of the NOx Emission in a Regenerative Industrial Furnace
Authors: Jiang Qing , Zhang Chao
Published: November 2021

A study of the nitrogen oxides (NOx) emission and combustion process in a gas-fired regenerative, high temperature, low emission industrial furnace has been carried out numerically. The effect of two additives, methanol (CH3OH) and hydrogen peroxide (H2O2), to fuel on the NOx emission has been studied. A moment closure method with the assumed β probability density function (PDF) for mixture fraction is used in the present work to model the turbulent non-premixed combustion process in the furnace. The combustion model is based on the assumption of instantaneous full chemical equilibrium. The results showed that CH3OH is effective in the reduction of NOx in a regenerative industrial furnace. However, H2O2 has no significant effect on the NOx emission.
Effects of Initial Diameter on Burning of Nonane Droplets in a Non-Buoyant and Buoyant Ambience: Burning Rate, Soot Formation and Flame Structure
Authors: Bae J. H. , Avedisian C. T.
Published: November 2021

The results from nonane droplet combustion experiments conducted at 1g and μg are analyzed and compared in the following aspects: the burning rate, soot formation, flame structure. By varying the initial droplet diameter, we observe and discuss the effect of Do on droplet burning. The μg experiments were performed in a drop tower and a drag shield was used to create a low buoyant environment All experiments were fiber-supported and used the same experimental instruments. The droplet size between 0.40 to 0.95mm was examined in the experiments.

Results showed that droplet burning is nonlinear in both a buoyant and a non-buoyant environment for the initial droplet diameters examined. Soot formation, which is influenced by Do may strongly affect the droplet burning process in both environments. The large droplet produces more soot and bums slowly whereas the small droplet bums fast because there is less soot.
Using Amorphous Material Properties in Scattering-Mediated Acoustic Mismatch Model for Predicting Thermal Boundary Resistance
Authors: Devpura Amit , Prasher Ravi S. , Phelan Patrick
Published: November 2021

Solid-solid thermal boundary resistance (Rb) plays an important role in determining the heat flow between materials. The acoustic mismatch model (AMM) and the diffuse mismatch model (DMM), work pretty well in describing and predicting the thermal energy transport at solid-solid interface at very low temperatures (in the range of few Kelvin). At moderate cryogenic temperatures they do not perform that well, and the reason may be attributed to the dominance of scattering in determining Rb. Scattering mediated acoustic mismatch model (SMAMM) was developed on this principle. Though SMAMM works well, it has some fundamental problems. SMAMM’s assumption of U-processes, for amorphous layer formed between materials, is physically unexplainable. It also assumes unrealistically small scattering time. We propose a modified version of SMAMM called Amorphous SMAMM, which takes into account amorphous material properties for the interstitial layer formed, to find the scattering time to be used in SMAMM. This model performs better than all the models in the range of 25 to 60 K in predicting Rb. Above this temperature, original SMAMM performs better, but Amorphous SMAMM always performs better than the AMM. Amorphous SMAMM does not run into any physical problems with the assumptions made, hence the results have a better physical significance than SMAMM’s.
Comparison Between Thermal Conductive Models for Moving Heat Sources in Material Processing
Authors: Bianco Nicola , Manca Oronzio , Nardini Sergio
Published: November 2021

A comparison between two quasi-steady state models describing a three dimensional conductive thermal field inside a brick-type solid under a moving laser heat source with a Gaussian profile is carried out. One of the two model has been simplified by neglecting the thermal diffusion along the direction of the motion. This model is suitable for high values of the Peclet number. The thermophysical properties of the solid are temperature dependent and radiative and convective heat losses, the latter due to an impinging gas jet on the upper surface, have been taken into account. The comparison has been made in terms of temperature profiles, maximum temperature ratios and temperature fields. The differences between the two models are around 35% for Reynolds numbers greater than 10000 and for Pe = 0.1. The influence of the width of the solid is weak for Reynolds number greater than 10000. Relative errors are less than 5% for Pe ≥ 1 and they are negligible for Pe ≥ 5 for all the parameter ranges considered in this paper.
Predictions of Carbon Fluxes During a Low Pressure Carburizing Treatment
Authors: Jacquet Philippe , Rousse Daniel R. , Ibarra Clemente C.
Published: November 2021

This paper presents the qualitative assessment of a novel device developed for the regulation of carburizing processes in industrial vacuum furnaces. The proposed device involves a U-shaped thin wall iron tube: the outside surface of the tube is exposed to the carburizing atmosphere simultaneously with the workload, while the decarburizing gas mixture (here H2 + H2O) is circulated inside the tube. The outflow of decarburizing mixture is then continuously analyzed and eventually permits to determine the carbon potential and the transfer coefficient at the interface between the carburizing atmosphere and the workloads. To assess the principle, the probe has been used to compare the carburizing powers of different gases (propane, methane, ethylene, and acetylene) for a specific set of parameters. The results reported here, compared with microhardness and micrographies of the samples, indicate that the probe can indeed be used to carry out this task.
On the Design of Continuum Thermal Transport Systems With Applications to Solidification Processes
Authors: Zabaras Nicholas J.
Published: November 2021

A general class of design problems is examined in thermal transport systems. We mainly address inverse problems with overspecified coupled boundary conditions in one part of the boundary and unknown thermal conditions in another part of the boundary. The methods of choice for the solution of the above inverse problems are functional optimization methods using appropriately defined continuum sensitivity and adjoint problems. Conjugate gradient techniques, preconditioning and regularization are considered within an innovative object-oriented finite element framework.

Our particular interest for examining such inverse transport systems arises from the desire to address the design of directional solidification processes that lead to desired microstructures. As the main application of this paper, we will address the calculation of the mold/furnace heat flux conditions such that a desired solidification state (growth rate and temperature gradient) is achieved at the freezing interface. Changes in growth rate and thermal gradient at the freezing interface are known to alter the relative importance of thermal/mass transport and interfacial energy effects, and the magnitude of this partitioning of available driving forces dictates the formation of specific microstructures.
Intensity and Uniformity of Gallium Nitride Deposition in Sublimation Sandwich Growth
Authors: Wu B. , Zhang H.
Published: November 2021

Gallium Nitride (GaN) bulk crystal growth is a challenging process due to its high melting temperature, low sublimation/decomposition temperature, very high equilibrium nitrogen vapor pressure, and low solubility. A GaN bulk crystal can be grown from the vapor phase by either evaporation of the gallium (Ga) metal or sublimation of GaN powder in an ammonia (NH3) atmosphere in a temperature-controlled growth furnace. The Sublimation Sandwich Technique (SST) is one of the techniques which utilizes reaction of gallium vapors with ammonia. Not only a high growth rate (up to 1mm/h) but also the intensity and uniformity of the deposition can be achieved and controlled through changing temperatures on the source, and the substrate, and the distance between them. A GaN growth model using SST has been developed to investigate the effects of the incoming velocity, source temperature, temperature difference, and the gap width on the growth cell during the growth process.
Characterization of Ceramic Components Exposed in Industrial Gas Turbines
Authors: Ferber M. K. , Lin H.-T.
Published: November 2021

This paper provides a review of recent studies undertaken to examine the mechanical and thermal stability of silicon nitride ceramic components that are currently being considered for use in gas turbine applications. Specific components examined included a bowed ceramic nozzle evaluated in an engine test stand, ceramic vanes exposed in two field tests, and an air-cooled vane that is currently under development. Scanning electron microscopy was used to elucidate the changes in the microstructures arising from the environmental effects. The recession of the airfoils resulting from the volatilization of the normally protective silica layer was also measured. The stability of the intergranular phases was evaluated using x-ray diffraction. The surface strength was measured using a miniature biaxial test specimen, which was prepared by diamond core drilling.
Investigation and Analysis of Structural Cracking in Transit Car Trucks
Authors: Janiszewski John A. , Chrismer Steven M. , Pearson John B.
Published: November 2021

This paper describes an investigation into the causes of cracking of transit car truck side frames on the PATCO system. The investigation included inspection of the PATCO fleet, laboratory examination of a sample from a failed truck, field-testing of an instrumented truck, measurement of residual stresses in the truck, and engineering analysis of the resulting data. It was concluded that the observed cracks were slowly propagating due to fatigue from low-level stresses induced by lateral and vertical loading from routine curving forces and other vehicle-track interactions. The side frames with fatigue cracks can be repaired by welding without the need for postweld stress relief and the lifetime of those that do not have cracks at present can be extended by preventive measures. The combination of preventive measures and repairs should enable the trucks to serve for the balance of the PATCO fleet lifetime without the need to purchase replacement trucks. Continued surveillance of the trucks in the area of concern will be necessary.