bluuebunny/crossref_metadata_2025 huggingface dataset:
Naturalizing Critical Thinking: Consequences for Education, Blueprint for Future Research in Cognitive Science
Authors: Pasquinelli Elena , Farina Mathieu , Bedel Audrey , Casati Roberto
Published: March 2021

While very popular in public discourse about education, critical thinking education is still a work in progress. Two key conditions for successfully addressing critical thinking education are lacking: (a) the availability of a clear, specific, and operational definition, and (b) a deeper understanding of the natural cognitive bases of critical thinking. We, therefore, propose a theoretical framework for critical thinking education, grounded on a cognitive approach. Starting from a restrictive characterization of critical thinking—defined as the capacity of evaluating the epistemic quality of information, and of calibrating one's confidence in relationship to it—we identify specific mechanisms subserving critical thinking that are present in early human development. We refer to these mechanisms as the natural building blocks of critical thinking. On this naturalistic ground, effective educational strategies can be envisaged that both harness the natural building blocks of critical thinking and help overcome its shortcomings.
Potato StMPK7 is a downstream component of StMKK1 and promotes resistance to the oomycete pathogen Phytophthora infestans
Authors: Zhang Houxiao , Li Fangfang , Li Zhenzhen , Cheng Jing , Chen Xiaokang , Wang Qinhu , Joosten Matthieu H.A.J. , Shan Weixing , Du Yu
Published: March 2021

A cascade formed by phosphorylation events of mitogen‐activated protein kinases (MAPKs) takes part in plant stress responses. However, the roles of these MAPKs in resistance of potato (Solanum tuberosum) against Phytophthora pathogens is not well studied. Our previous work showed that a Phytophthora infestans RXLR effector targets and stabilizes the negative regulator of MAPK kinase 1 of potato (StMKK1). Because in Arabidopsis thaliana the AtMPK4 is the downstream phosphorylation target of AtMKK1, we performed a phylogenetic analysis and found that potato StMPK4/6/7 are closely related and are orthologs of AtMPK4/5/11/12. Overexpression of StMPK4/7 enhances plant resistance to P. infestans and P. parasitica. Yeast two‐hybrid analysis revealed that StMPK7 interacts with StMKK1, and StMPK7 is phosphorylated on flg22 treatment and by expressing constitutively active StMKK1 (CA‐StMKK1), indicating that StMPK7 is a direct downstream signalling partner of StMKK1. Overexpression of StMPK7 in potato enhances potato resistance to P. infestans. Constitutively active StMPK7 (CA‐StMPK7; StMPK7D198G, E202A) was found to promote immunity to Phytophthora pathogens and to trigger host cell death when overexpressed in Nicotiana benthamiana leaves. Cell death triggered by CA‐StMPK7 is SGT1/RAR1‐dependent. Furthermore, cell death triggered by CA‐StMPK7 is suppressed on coexpression with the salicylate hydroxylase NahG, and StMPK7 activation promotes salicylic acid (SA)‐responsive gene expression. We conclude that potato StMPK7 is a downstream signalling component of the phosphorelay cascade involving StMKK1 and StMPK7 plays a role in immunity to Phytophthora pathogens via an SA‐dependent signalling pathway.
Regulatory electron transport pathways of photosynthesis in cyanobacteria and microalgae: Recent advances and biotechnological prospects
Authors: Nikkanen Lauri , Solymosi Daniel , Jokel Martina , Allahverdiyeva Yagut
Published: March 2021

Cyanobacteria and microalgae perform oxygenic photosynthesis where light energy is harnessed to split water into oxygen and protons. This process releases electrons that are used by the photosynthetic electron transport chain to form reducing equivalents that provide energy for the cell metabolism. Constant changes in environmental conditions, such as light availability, temperature, and access to nutrients, create the need to balance the photochemical reactions and the metabolic demands of the cell. Thus, cyanobacteria and microalgae evolved several auxiliary electron transport (AET) pathways to disperse the potentially harmful over‐supply of absorbed energy. AET pathways are comprised of electron sinks, e.g. flavodiiron proteins (FDPs) or other terminal oxidases, and pathways that recycle electrons around photosystem I, like NADPH‐dehydrogenase‐like complexes (NDH) or the ferredoxin‐plastoquinone reductase (FQR). Under controlled conditions the need for these AET pathways is decreased and AET can even be energetically wasteful. Therefore, redirecting photosynthetic reducing equivalents to biotechnologically useful reactions, catalyzed by i.e. innate hydrogenases or heterologous enzymes, offers novel possibilities to apply photosynthesis research.
An EPA for better Bedside Teaching
Authors: van Dam Marjel , Ramani Subha , ten Cate Olle
Published: March 2021

Background

Bedside teaching (BST), a time‐honoured tradition of clinical teaching which integrates theoretical knowledge and clinical practice, has declined steeply over the last decade. Moreover, many clinician teachers today are not specifically trained in and/or comfortable in delivering effective BST. Resucitating this valuable educational format may require a new approach to preparing teachers and setting the stage for effective BST. Framing BST as an entrustable professional activity (EPA) for teachers may be one strategy to enhance its application and quality.

Methods

We aimed to redefine, describe essential features and effective practices for high‐quality BST, based on clinical teacher participant perspectives through a focus group discussion and open‐ended questionnaires via e‐mail, supplemented by insights from literature.

Results

Based on data collected, we generated a definition of BST and a list of suggested strategies to optimise BST, for example, preparation, safe learning environment, flexible teaching and patient's benefits. A structured EPA description was created based on this definition.

Conclusion

Effective BST requires skilled clinical teachers who are comfortable and confident in this mode of teaching; framing BST as a teaching EPA could guide faculty development and clinical teacher certification.
Exploring the feasibility of using very short answer questions (VSAQs) in team‐based learning (TBL)
Authors: Millar Kate R. , Reid Michael D. , Rajalingam Preman , Canning Claire A. , Halse Omid , Low‐Beer Naomi , Sam Amir H.
Published: March 2021

Background

Team‐based learning (TBL) currently relies on single best answer questions (SBAQs) to provide immediate feedback. Very short answer questions (VSAQs) are a reliable and discriminatory alternative that encourage learners to use more authentic clinical reasoning strategies compared to SBAQs. However, the challenge of marking VSAQs has limited their integration into TBL; we therefore explored the feasibility of VSAQs within a TBL session.

Methods

An online platform was developed to allow immediate marking of VSAQs during the TBL sessions. As part of the readiness assurance process, students completed VSAQs and SBAQs, which were marked in real time.

Results

Instructors were able to mark all VSAQs during the individual readiness assurance test (iRAT), which facilitated the provision of immediate feedback during the team readiness assurance test (tRAT). The mean time to mark five VSAQs was 422 seconds (SD 73 seconds). For VSAQs, the number of attempts to reach the correct answer ranged from 1 to 38, compared to 1 to 4 for SBAQs. In total, 71.6% of students agreed that using VSAQs in TBL helped to emphasise group discussions.

Discussion

The wide range of attempts at, and students’ perspectives of VSAQs are suggestive of their positive impact on student discussion during TBL. We demonstrate how new technology allows VSAQs to be feasibly integrated into TBL with the potential to enrich group discussions.
A case of acute monocytic leukemia (AMoL or AML‐M5) in an adult FeLV/FIV‐positive cat
Authors: da Silva Serpa Priscila Beatriz , Messick Joanne B.
Published: March 2021

A 7‐year‐old castrated male domestic shorthair cat was presented for evaluation of decreased appetite and respiratory signs. A CBC run on presentation revealed severe nonregenerative anemia, thrombocytopenia, and leukocytosis characterized by a prominent population of blasts, having morphologic features suggestive of a monocytic lineage. The cat tested positive for FIV, FeLV,Mycoplasma haemominutum,and only mild abnormalities were identified on the chemistry panel. Bone marrow biopsies were obtained to investigate the bicytopenia and the possibility of a hematopoietic neoplasm. Although the bone marrow aspirate was nondiagnostic, the core biopsy was markedly hypercellular with a population of blasts, largely replacing the normal hematopoietic tissue. Immunohistochemical staining revealed that the blasts were CD3‐negative, Pax5‐negative, dimly CD18‐positive, and moderately positive for Iba1. These findings, in addition to the prominent monocytic differentiation seen in peripheral blood, supported a diagnosis of acute monocytic leukemia. Palliative antiviral and antibiotic treatment and blood transfusion were performed. The patient was discharged on his fourth day of hospitalization. However, 15 days following discharge, the cat was euthanized due to the worsening of his systemic signs. This report discusses the classifications of myeloid leukemias, implications of infectious diseases in the pathogenesis of neoplasia in cats, and the use of Iba1, a “pan‐monocytic/histiocytic” marker, in the diagnosis of acute leukemia.
Validation of the Implementation Climate Scale in Nursing
Authors: Ehrhart Mark G. , Shuman Clayton J. , Torres Elisa M. , Kath Lisa M. , Prentiss Andrea , Butler Eve , Aarons Gregory A.
Published: March 2021

Background

One critical factor in effective implementation of evidence‐based practices (EBPs) in nursing is an organizational context that facilitates and supports implementation efforts. Measuring implementation climate can add useful insights on the extent to which the organizational context supports EBP implementation.

Aims

This study cross‐validates and examines the psychometric properties of the Implementation Climate Scale (ICS), which measures nurses’ perceptions of their unit’s climate for EBP implementation.

Methods

This study analyzed ICS data from two cross‐sectional studies, including 203 nurses from California and 301 nurses from Florida. Analyses included evaluation of internal consistency, multilevel aggregation statistics, and confirmatory factor analyses.

Results

The 18‐item ICS demonstrated comparable psychometric properties to the original measure development paper in both samples. Confirmatory factor analyses provided support for the scale’s factor structure in both samples.

Linking Evidence to Practice

The ICS is a pragmatic measure that can be used to assess unit implementation climate in nursing contexts. Results from the ICS from nurses and nurse leaders can provide insights into implementation‐specific barriers and facilitators within the organizational context.
A Method to Design and Optimize Axial Flow Cyclones for Gas–Liquid Separation
Authors: Anderson Kyle , Zhang Xiang , Abbasi Bahman
Published: March 2021

This article provides a detailed design guide, optimization, and performance assessment for air–water separation of an axial flow cyclone. Axial flow cyclones (also known as swirl tube demisters, mist eliminators, or Austin–Write cyclones) have a range of applications in several different industries. This method of gas–liquid separation offers many benefits. Among these are high liquid separation efficiencies (near 99%) and an inline design that allows them to be more easily fitted into existing piping structures. Despite these benefits, there are several design parameters that have not been optimized for performance in wastewater purification applications. This research fills the gap in the literature by quantifying the effect of new design parameters on water collection efficiency, ηwater collection, and the air bypass efficiency, ηair bypass, defined as the ratio of the air mass flowrate exiting through the desired air outlet over the inlet air mass flowrate. A set of wide-ranging experiments were conducted to study the effects of gas–liquid flow rates, tube geometry, and relative injection angles to optimize the water collection and air bypass efficiencies. The water collection efficiency exceeded 99.8% when the liquid streamline came in direct contact with the water drainage exit. An empirical correlation was developed to predict the swirl pitch as a function of the above design parameters. Predictions from the correlation were within 10% of the experimental results. The correlation can be used to design highly efficient in-line gas–liquid separators.
Effect of Vessel Tortuosity on Stress Concentration at the Distal Stent–Vessel Interface: Possible Link With New Entry Formation Through Biomechanical Simulation
Authors: Tan Wei Ting , Liew Yih Miin , Mohamed Mokhtarudin Mohd Jamil , Pirola Selene , Wan Ab Naim Wan Naimah , Amry Hashim Shahrul , Xu Xiao Yun , Lim Einly
Published: March 2021

A computational approach is used to investigate potential risk factors for distal stent graft-induced new entry (dSINE) in aortic dissection (AD) patients. Patient-specific simulations were performed based on computed tomography images acquired from six AD patients (three dSINE and three non-dSINE) to analyze the correlation between anatomical characteristics and stress/strain distributions. Sensitivity analysis was carried out using idealized models to independently assess the effect of stent graft length, stent tortuosity and wedge apposition angle at the landing zone on key biomechanical variables. Mismatch of biomechanical properties between the stented and nonstented regions led to high stress at the distal stent graft–vessel interface in all patients, as well as shear strain in the neighboring region, which coincides with the location of tear formation. Stress was observed to increase with the increase of stent tortuosity (from 263 kPa at a tortuosity angle of 50 deg to 313 kPa at 30 deg). It was further amplified by stent graft landing at the inflection point of a curve. Malapposition of the stent graft led to an asymmetrical segment within the aorta, therefore changing the location and magnitude of the maximum von Mises stress substantially (up to +25.9% with a +25 deg change in the distal wedge apposition angle). In conclusion, stent tortuosity and wedge apposition angle serve as important risk predictors for dSINE formation in AD patients.
Research on Biomechanical Compatibility for the Artificial Anal Sphincter Based on Improved Actuator
Authors: Zan Peng , Ding Qiao , Yang Banghua , Zhang Guofu , Xue Yingjie , Zhao Yutong
Published: March 2021

Anal incontinence, also known as fecal incontinence, refers to the loss of the body's ability to accumulate and control the liquid, solid, and gas contents in the rectum, increasing the frequency of bowel movements. It is a symptom of defecation disorders. The artificial anal sphincter provides a new solution for clinical treatment. In this paper, in order to solve the problem of biomechanical compatibility of the actuator of the artificial anal sphincter system, the original actuator was improved. The model of the rectum and the actuator was constructed by ANSYS. The mechanical finite element analysis of the clamping mechanism was carried out by simulating sphincter behavior, and the displacement cloud diagram and stress cloud diagram of the clamping rectum were obtained. in vitro experiments were carried out using pig intestine to simulate the rectum, which verified the effectiveness of the actuator. The results of the experiment show that the successful rate of holding the rectum reached 96% under the condition of ensuring the normal blood supply to the rectum. It fully proves that the actuator has good biomechanical compatibility.
Fatigue Evaluation of API 12F Shop-Welded Tanks With a New Roof-to-Shell Junction Detail
Authors: Feng Heyi , Guzey Sukru
Published: March 2021

The American Petroleum Institute (API) provides a series of standards and specifications on storage tanks, in which the API 12F specification provides 12 tank designs that can be fabricated in the shop and transported to the field. The nominal capacity of the 12 API 12F tank designs ranges from 90 bbl (14.3 m3) to 1000 bbl (158.99 m3). The minimum required thickness and operational pressure levels that each tank case can sustain are given in Table 1 of the current 13th edition of API 12F (API, 2019, “API 12F Specification for Shop-Welded Tanks for Storage of Production Liquids,” 13th ed., API Publishing Services, Washington, DC, Standard No. API 12F). The objective of this study is to estimate the fatigue life of API 12F tanks under normal operation pressure cycles following the procedure presented in ASME VIII-2. The stored liquid product specific gravity is assumed to be 1.2 when the liquid height is half of the tank height, while the specific gravity is assumed to be 0.7 when the stored liquid height is 18 in. (460 mm). Meanwhile, a new roof–shell attachment detail is proposed in this study, the new rectangular cleanout junction detail presented in the 13th edition of API 12F is modeled, and various component thickness combinations are considered to investigate the effect of component thickness on fatigue life. The roof–shell joint (top junction) and shell–bottom plate (bottom junction) are studied by axisymmetric models under axisymmetric idealization as they are away from the cleanout junction, while the cleanout junction is studied by applying a submodeling technique. Stress classification is performed at each location of interest to obtain the stress components to calculate the stress range within each loading cycle that is needed to perform fatigue evaluation. The results and discussion about fatigue evaluation of API 12F tanks are presented in this report.
Synergetic Design Systems
Authors: Shah Jami J. , Urban Susan D. , Raghupathy Siva P. , Rogers Mary T.
Published: March 2021

The paper describes an experiment in creating a design environment comprising of a number of specialist design systems that co-operatively solve design problems, from conceptual layout to detailing The systems targeted were in-house programs, as well as, commercial products. The objective of the experiment was to demonstrate a synergetic design environment by providing an integrated approach to design data. In the first phase of the project, the systems were arranged sequentially, with unidierctional flow of data using file transfers. The second phase of the project, currently underway, is based on an integrated view of product data using semantic data modeling concepts with an object-oriented database as a communication tool. The database approach provides a greater degree of integration giving designers a more global view of design data and thus facilitating iterative design.
Numerical Flow Simulation in the Induction System of an Internal Combustion Engine
Authors: Ho S. Y. , Przekwas A. J.
Published: March 2021

An advanced computational fluid dynamics package, REFLEQS, has been adapted to calculate the flow in the induction system of an internal combustion engine. Results of complex flow fields in multi-valve engine intake/exhaust ports and cylinders, including moving valves and piston, are calculated. The body-fitted structured grids generated with partial differential equations method have been applied to represent complex engine components configuration such as engine intake/exhaust ports, ducts, valves and cylinders. An upwind scheme combined with SIMPLEC method is employed to solve the Navier-Stokes equations. Several 2D and 3D flows in engine ports/cylinders are simulated. Complex flow fields involve separated flows near the entry of cylinder head, vortices near the corner and behind the valves and the valve/stem generated swirling and tumbling flows. The present work aims at establishing a generalized computational environment for analyzing the physical mechanisms and design parameters controlling internal flows in automotive air/fuel induction systems.
Optimized Accelerating Parameters of Convergence for the Navier-Stokes Equations
Authors: AbdulNour Bashar S.
Published: March 2021

An over-relaxation procedure, that includes weighing factors, is applied to the steady, two-dimensional Navier-Stokes equations in order to reduce the computational time. The benefits obtained from this strategy are illustrated by the problem of viscous flow in the entrance region of an unconstricted and a constricted channel. The describing equations are expressed in terms of the stream function and vorticity. The convergence domain for the Successive Over-Relaxation method and the optimum values of the accelerating parameters, which consist of the over-relaxation and weighting factors for both the stream function and vorticity, are discussed. Numerical solutions are obtained for Reynolds numbers ranging from 20 to 2000. The computer time is reduced by as much as a factor of six using the optimum values of the accelerating parameters.
Natural Frequencies of Parallelogrammic Plates Using Characteristic Orthogonal Polynomials in Rayleigh-Ritz Method
Authors: Lee L. T. , Pon W. F.
Published: March 2021

Natural frequencies of parallelogrammic plates are obtained by employing a set of beam characteristic orthogonal polynomials in the Rayleigh-Ritz method. The orthogonal polynomials are generalted by using a Gram-Schmidt process, after the first member is constructed so as to satisfy all the boundary conditions of the corresponding beam problems accompanying the plate problems. The strain energy functional and kinetic energy functionals are transformed from Cartesian coordinate system to a skew coordinate system. The natural frequencies obtained by using the orthogonal polynomial functions are compared with those obtained by other methods with all four edges clamped boundary conditions and greet agreements are found between them. The natural frequencies for parallelogrammic plates with other boundary conditions, such as four edges simply supported, clamped-free and simply supported-free, are also obtained. This method is considered as a better and accurate comprehensive treatment for this type of problems.
Building Three-Dimensional Computer Graphics Surface Models for Anatomy Education
Authors: Alciatore David G. , Miranda Rick
Published: March 2021

This paper describes an approach to generating three-dimensional computer graphics images of gross anatomical structures. These images are used in an interactive teaching aid which is currently being developed by the Colorado State University Vesalius Project. Key steps in the generation of these images include acquisition of appropriate anatomical data, the generation of parallel cross-sectional contours, and the creating of rendered surface models of the anatomy by triangulating between these contours. The algorithms involved with these steps are described and several resulting images are presented here. The interactive Hypertext educational system being developed around these images is also briefly discussed.
Modeling and Animation of Mechanical Systems
Authors: Wen Li , Bahr Behman
Published: March 2021

This paper presents a general purpose method for mechanism modeling and animation using 2-D or 3-D computer graphics technique. A simulation system based on this method enables designers or management to evaluate the motion performance of mechanisms in effective, flexible and inexpensive ways. This method is particularly well suited for uses in small manufacturing companies and educational institutes because of a little required expense. Examples, from a simple mechanism to a complex robot, will be given in the paper to prove that this method can be applied to a variety of applications.
Design of a Teleprogrammable Space Robotic Workcell for Unstructured Environments
Authors: Haule D. D. , Noorhosseini S. M. , Malowany A. S.
Published: March 2021

Many studies for the preliminary definition of a space teleoperated robotic devices are recently completed or under development. One example of such devices is the Flight Telerobotic Servicer (FTS) developed by NASA. These studies will assist astronauts in many ot the on- and off-board tasks of assembly, maintenance, servicing and inspection of the Space Station. This paper makes an assessment of the role that teleprogramming may have in furthering the automation capabilities of these devices by extending their capacity for growth and evolution. Relevant system engineering design issues are identified for its programming. An outline of teleprogramming environments is given which comprises of task planning and interpretation, simulation, specialized modules known as system agents and world model manager (influencing teleoperator decisions at a remote worksite).

A Space Robotic Workcell (SRW) is a collection of robots, sensors, and other equipment grouped in a cooperative environment to perform various complex tasks in space. Due to their distributed nature, the control and programming of SRWs is often a difficult task, for which dedicated space environments have to be designed. There is clearly established need to perform intervention tasks remotely in hazardous environments by machines. Examples of this need that are highly relevant to our discussion are space safety applications, space exploration and underwater structure maintenance and repair. In this paper we focus on Space Robotics & Automation. We have discussed a detailed study of autonomy versus teleoperation for intervention robots making a case for task level teleprogramming as a new emerging field in Telerobotics. A rationale for teleprogramming and its techniques, Expert Systems, SRW Subsystem Agents, SRW Task Planner and SRW Plan (for growth and evolution) are also covered in this paper.
New Design of Production Type CNC Hobbing Machine and its Gear Cutting Performance
Authors: Yagishita H. , Iizuka T.
Published: March 2021

A production type CNC hobbing machnie (a maximum module to be cut of 4 mm and a maximum workpiece diameter of 150 mm) has been newly designed and manufactured based on the concept that a special attention is paied to a rigidity and a thermal deformation of the machine structure as well as a rotational transmission mechanism to enable high speed drive. A maximum speed of hob shaft is 1200 rpm and a table speed is possible up to 160 rpm due to a full spur gear drive. A CNC controller used is a common type for a hobbing machine which has a 32 bit CPU and five axes are numerically controlled.

By paying a special attention to a torsional rigidity and a dynamic synchronous error between a hob and table, some tests are carried out. The results are compared with those of a full mechanical drive (FMD) hobbing machine.

It is ascertained that by high accuracy gear cutting tests spur gears are generated with a sufficiently high accuracy although a correction of synchronous error between a hob and table is not applied at all by NC software. Also, in a production shop, it is demonstrated that a lot of helical gears for automobile can be manufactured with high-productivity and high-accuracy, that is : a machining cycle time per one gear is shortened by shortening a loading and unloading time of gear blank; a lead error is maintained within a small deviation in spite of high feed rate; and a measured value by over roll method is maintained within a permitted limit during a continuously long machining operation, for example, all day-long.
The Stress Intensity Factor and Stiffness for a Cracked Spur Gear Tooth
Authors: Daniewicz S. R. , Collins J. A. , Houser Donald R.
Published: March 2021

The stiffness of a spur gear tooth mesh controls load sharing in an operating gearset as well as vibratory properties which further dictate fatigue resistance and gear noise. A spur gear mesh consisting of a pinion with a single cracked tooth and an uncracked gear is considered. Expressions are presented which allow the determination of stress intensity factors for small through face width fatigue cracks in spur gear teeth. Predictions of tooth pair stiffness for a cracked pinion tooth and uncracked gear tooth pair are made using an analytical model. The model is based on elastic energy methods and fracture mechanics principles. The model employs a conformal mapping technique from elasticity theory, often denoted in spur gear applications as the complex potential method, in which a gear tooth is mapped onto an elastic half-plane.
Tooth Cutting Method of Face Gear by Using CNC-Hobbing Machine
Authors: Ishii Harumi , Nagata Shigeyoshi
Published: March 2021

At present, the research on a gear having special tooth profile a using CNC hobbing machine have been making progress. However, the method of tooth cutting with using CNC hobbing machine is not used the full for an inherent ability of itself.

From the aforementioned view point, we have tried to test cut a face gear which is used an inherent latent ability of the CNC hobbing machine.

The unipurpose device has been manufactured for the purpose of improving aforementioned defects of conventional tooth cutting method. Then we have used a fly tool instead of an unipurpose hob cutter.

In general, a helicon gear has been cut by unipurpose hob cutter, giving vertical feed with using general type hobbing machine.

In this way, not only the tooth roughness decreases, but also processing time increases for the tooth cutting because the size of cut has to be made very small due to heavy cutting resistance.

In our research, the unipurpose device is attached to the CNC hobbing machine. Then a fly tool already located on the final point of full depth, translates along the tangential direction of the gear from an appointed position in the radial direction.

In this way, we can expect the cutting resistance to be reduced during manufacture. Also the tooth roughness will be improved.
Experimental Investigation of Flowrate Irregularity in Rotary Gear Pumps
Authors: Mimmi G.
Published: March 2021

In a previous paper the author proposed a method to reduce the periodic variation in flow rate for an external gear pump.

To verify the experimental results, a series of experimental tests on a expressly realized gear pump, was carried out. The pump was equipped with relieving grooves milled into the side plates.

The tests were done on a closed piping specifically realized and equipped for measuring the instantaneous flow rate of the fluid through a wedge-shaped hot film probe.
Computerized Analysis of Gear Meshing Based on Coordinate Measurement Data
Authors: Kin Vadim
Published: March 2021

A mathematical model is proposed for the reconstruction of gear tooth surface features based on the manufacturing process deviations measured with the help of a gear inspection (or coordinate measurement) machine. The model is extended to facilitate the computer simulation of meshing between the measured year and a theoretical master gear, or between two measured gears. This would allow one to predict the transmission errors and bearing contact which are otherwise only possible to investigate using the combination of single-flank testing and a time-consuming work-in and examination procedure.

The developed model is applied to the determination of tooth-to-tooth transmission errors of parallel-axis gears and can also be utilized to determine bearing contact and contact stresses and be useful in tooth surface fatigue life calculations.
How to Ensure Precise Analysis of Gear Surfaces and Diagnosis of Changes During Operation
Authors: Mengen D. , Weck M.
Published: March 2021

Constantly rising demands on power transmitting components such as gears have lead to special efforts in gear production processes. Aiming to increase the transmission of power while simultaneously maintaining as little volume as possible, the influence of microgeometry as well as fine surface form and structure are especially increasing in significance. These factors play an important role for the operational safety, lifespan and noise emission of gears. Accordingly, it has become increasingly important to be able to dependably describe and register the microstructural characteristics of surfaces, so that knowledge concerning fatigue mechanisms can be abstracted from the surface topography. For this, the process of stereophotogrammetry in combination with an efficient PC-program can provide extremely exact and informative data.

When the surface of mechanical components undergoes changes caused by fatigue mechanisms during operation, both micro- and macrostructural changes take place. In order to facilitate smooth and undisturbed operations, it is of utmost importance to be able to register developments of the condition of strongly stressed components during operation. This way, preventive maintenance measures can be enacted in advance. For this purpose, an effective monitoring and diagnosis instrument was developed, based mainly on structure borne noise analysis. The new diagnostic equipment is described an examples for effective monitoring of gears are given.
Comparative Fatigue Resistance of Fiber Reinforced Nylon 6 Gears
Authors: Crippa Giuseppe , Davoli Piermaria
Published: March 2021

The fatigue-life diagrams of injection-molded nylon 6 gears with different reinforcements are presented for various lubrication modes (dry, grease, splash oil lubrication) and for different meshing combinations (plastic/plastic and steel/plastic gears).

Tests have been carried out with a properly designed back-to-back rig; results are compared with previous experiments, performed with unreinforced nylon 6 gears. Tested gears have been 232 (70 in unreinforced nylon and 162 in differently filled polyamides). More than 700·106 cycles have been totalised.

From test data, and from the “matrix” of gear/pinion material combination, the capabilities of differently reinforced nylon 6 gears for fatigue and wear resistance have been outlined. These capabilities are the basis for a proper material selection in plastic gear design.
Comparison of Analysis and Experiment for Gearbox Noise
Authors: Oswald Fred B. , Seybert A. F. , Wu T. W. , Atherton William
Published: March 2021

Low-contact-ratio spur gears were tested in the NASA gear-noise rig to study the noise radiated from the top of the gearbox. Experimental results were compared with a NASA acoustics code to validate the code for predicting transmission noise.

The analytical code is based on the boundary element method (BEM) which models the gearbox top as a plate in an infinite baffle. Narrow-band vibration spectra measured at 63 nodes on the gearbox top were used to produce input data for the BEM model. The BEM code predicted the total sound power based on this measured vibration.

The measured sound power was obtained from an acoustic intensity scan taken near the surface of the gearbox at the same 63 nodes used for vibration measurements. Analytical and experimental results were compared at four different speeds for sound power at each of the narrow-band frequencies over the range of 400 to 3200 Hz. Results are also compared for the sound power level at meshing frequency plus three sideband pairs and at selected gearbox resonant frequencies. The difference between predicted and measured sound power is typically less than 3 dB with the predicted value generally less than the measured value.
Structural Configuration Examples of an Integrated Optimal Design Process
Authors: Chirehdast Mehran , Gea Hae Chang , Kikuchi Noboru , Papalambros Panos Y.
Published: March 2021

Structural optimization procedures usually start from a given design topology and vary proportions or boundary shapes of the design to achieve optimality of an objective under various constraints. This article presents examples of the application of a novel approach for initiating formal structural optimization at an earlier stage, where the design topology is rigorously generated. A three-phase design process is used. In Phase I, an optimal initial topology is created by a homogenization method as a gray-scale image. In Phase II, the image is transformed to a realizable design using computer vision techniques. In Phase III, the design is parameterized and treated in detail by conventional size and shape optimization techniques. Fully-automated procedures for optimization of two-dimensional solid structures are outlined, and several practical design problems for this type of structures are solved using the proposed procedure, including a crane hook and a bicycle frame.
An Approach to Zero Setup Panel Bending
Authors: Sturges Robert H.
Published: March 2021

An opportunity is found to reduce setup time in sheet metal panel bending tasks by deliberately leaving gaps between a segmented punch to allow passage of a bent flange or to adjust the distance between articulated die sections for reentrant bends. The effects of this practice on part appearance and dimension is addressed to assure part quality. The gap/thickness ratio is found to be an indicator of part geometry and subjective quality. A zero setup punch and die set is described for four-bend parts.
The Development of Virtual Concurrent Engineering and its Application to Stamped Products
Authors: Schmitz J. , Desa S.
Published: March 2021

It is well-known that so-called Concurrent Engineering is a desirable alternative to the largely sequential methods which tend to dominate most product development methods. However, the proper implementation of a concurrent engineering method is still relatively rare. In order to facilitate the development of a reliable concurrent engineering product development method, we start with a careful definition of concurrent engineering and, after an extensive study of all of product development, we propose three criteria which ideal concurrent engineering must satisfy. However, for labor, time, and overall cost considerations, ideal concurrent engineering is infeasible. Instead, we propose a computer-based environment which, by being constructed in accordance with the three criteria, attempts to approach ideal concurrent engineering. The result is the Virtual Concurrent Engineering method and computer implementation environment. This product development method and computer-based implementation system provide the detailed, structured information and data needed to optimally balance the product with respect to the main product development parameters (e.g., manufacturing costs, assembly, reliability). This important information includes re-design suggestions to improve the existing design. The designer can directly apply these re-design suggestions for design optimization, or he can use the results as input into a more complex design optimization or design parameterization function of his own. To demonstrate Virtual Concurrent Engineering, we use it to refine earlier work done by the authors in the Design for Producibility of stamped products. We discuss, in some detail, the results of applying Design for Producibility to complex stampings, including process plans and product producibility computations.
The Effective Use and Implementation of Computer-Aids for Life-Cycle Product Design
Authors: Ishii K. , Hornberger L.
Published: March 2021

This paper describes the key elements of usage and implementation of AI-based tools in a real product design environment. In the past several years, the authors have developed several intelligent programs to empower mechanical engineers in the product design of personal computers. The programs focused on plastic material selection, snap fit design, design for assembly, design for service, and design for injection molding. Engineers used the tools initially as training tools and then attempted to use them for real design tasks. Some programs received long term acceptance and usage by designers, while others did not. The metrics for successful development of the AI-based tools do not coincide with successful implementation and usage. This paper briefly describes each of the programs, takes a critical look at their long term utility, and seeks to extract the metrics behind successful tools in practical product design.
A Methodology for Compliant Mechanisms Design: Part II — Shooting Method and Application
Authors: Her I. , Midha A. , Salamon B. A.
Published: March 2021

A major task envisioned in the design of compliant mechanisms entails analyzing a large-deflection elastica for its deformed configuration, while being subjected to given displacement and force boundary conditions. The accuracy and convergence behavior of a chain calculation method for predicting nonlinear deflections in beam structures is examined. Three shooting methods are implemented to reduce boundary condition closure errors. These methods are evaluated by considering two example problems in compliant mechanisms.
Using Exact Gradients in Mechanism Design
Authors: Mariappan J. , Krishnamurty S.
Published: March 2021

This paper presents a new approach for mechanism synthesis using exact gradients in optimization. Currently, finite difference methods or similar approximate techniques are used to evaluate the derivatives that are necessary for performing mechanism optimization using gradient-based methods. Typical mechanism synthesis problems involve highly nonlinear functional relationship, and the use of finite difference methods in such problems often leads to an excessive number of function evaluations, algorithm failures, and inaccurate results. Instead, an alternative approach using exact gradients will completely eliminate all of the above problems, and will result in a faster and efficient convergence. This paper also discusses the identification of an appropriate optimization method, namely, the generalized reduced gradient method for mechanisms synthesis based on its good convergence properties, reliability, intermediate feasibility, and efficiency. Numerical examples are included to illustrate the advantages of using exact gradients and the results are discussed.
Optimal Tolerance Allocation Over Multiple Manufacturing Alternatives
Authors: Cagan Jonathan , Kurfess Thomas R.
Published: March 2021

We introduce a methodology for concurrent design that considers the allocation of tolerances and manufacturing processes for minimum cost. Cost is approximated as a hyperbolic function over tolerance, and worst-case stack-up tolerance is assumed. Two simulated annealing techniques are introduced to solve the optimization problem. The first assumes independent, unordered, manufacturing processes and uses a Monte-Carlo simulation; the second assumes well known individual process cost functions which can be manipulated to create a single continuous function of cost versus tolerance with discontinuous derivatives solved with a continuous simulated annealing algorithm. An example utilizing a system of friction wheels over the manufacturing processes of turning, grinding, and saw cutting bar stock demonstrates excellent results.
A Symmetrical Coordinate Frame on the Hexagonal Grid for Computer Graphics and Vision
Authors: Her I.
Published: March 2021

This note is concerned with the hexagonal tessellation of picture elements used in computer graphics and computer vision systems. The purpose is to propose a symmetrical hexagonal coordinate frame to replace the existing oblique coordinate system. In the proposed symmetrical coordinate frame, spatial properties of the hexagonal grid such as distance functions are better represented.
Blending and Joining Using Cyclides
Authors: Srinivas Y. L. , Dutta Debasish
Published: March 2021

We consider the use of cyclides in geometric modeling. These are algebraic surfaces of degree four with interesting properties such as rational parametric forms and closure under offsets. The incorporation of cyclides as primitives in solid modellers will increase their geometric coverage. In this paper, we describe the cyclide and discuss two applications of its use in computer aided design — modeling blending surfaces and the automatic joining of pipes. Implemented examples are also included.
Boundary Surface Recovery From Skeleton Elements: Part I — Skeleton Curves
Authors: Gelston Sean M. , Dutta Debasish
Published: March 2021

Skeleton curves and surfaces have many applications in computer aided design and analysis. Construction of skeletons is an active area of research. We consider the inverse problem that of recovering boundary surfaces from given skeleton elements. The skeleton of any 3D object will, in general, consist of curves and surfaces. Therefore, any boundary reconstruction algorithm must systematically process the surfaces generated by the skeletal curves and the skeletal surfaces. In this paper (Part I) we present algorithms for reconstructing boundary surfaces corresponding to skeletal curves. Implemented examples are also included. In a companion paper (Part II) we consider skeletal elements that are surfaces.
Kinematic Evaluation of Robots for Assembly Tasks
Authors: Zussman Eyal , Shoham Moshe , Lenz Ehud
Published: March 2021

An automatic assembly planning program should be able to analyze the assembly kinematic constraints, generate possible motions and select the appropriate assembly machines. This paper develops an approach for evaluating a robot for assembly tasks and planning its motions. The kinematical characteristics of both the robot and the assembly tasks are described by infinitesimal screws. The possible motions of the assembled parts are represented by convex cone of screws derived from the geometrical constraints. The robot’s possible motions are represented by the Jacobian cone, which is a modification of the Jacobian matrix that provides a common mathematical basis for convex cones operations. The selection procedure of the robot is based on the intersection of its cone with the assembly cones which results in feasible assembly directions for the robot. Choosing the optimal assembly direction and the robot posture is obtained by minimizing a cost function subjected to the constraints of both the robot and the assembly. Several given examples demonstrate the evaluation procedure and the planning approach.
On the Direct Kinematics of General Spherical Three-Degree-of-Freedom Parallel Manipulators
Authors: Gosselin Clément M. , Sefrioui Jaouad , Richard Marc J.
Published: March 2021

In this paper, the direct kinematics of general spherical parallel three-degree-of-freedom manipulators is investigated. A polynomial of degree 8 is obtained to describe this problem and it is shown that this polynomial is minimal since 8 real solutions corresponding to actual configurations have been found for a given set of actuator coordinates and a given architecture. This result completes the study on the direct kinematics of spherical three-degre-of-freedom parallel manipulators undertaken by the authors in a previous paper. An example of an architecture and a set of actuator coordinates which lead to 8 real solutions is presented to illustrate the results.
Direct Kinematics of General Stewart Platforms
Authors: Dhingra Anoop , Kohli Dilip , Xu Yong-Xian
Published: March 2021

A formulation for solving the direct kinematics of the general Stewart platform consisting of six moving and six grounded spheric joints is presented. The homotopy method is used for solving the direct kinematics of the platform, and it is shown that there exist a maximum of 40 possible solutions to the direct kinematics problem. These 40 solutions can be obtained by tracking only 64 homotopy paths. It is also shown that there are a maximum of 24 solutions for the Stewart platform with four spheric joints, and there exist a maximum of 16 solutions to the direct kinematics of the Stewart platform with three moving and three grounded spheric joints thus confirming the correctness of 24th and 16th degree direct kinematics polynomials obtained by other researchers.
A Coulomb Friction Model for Spherical Joints
Authors: Gutkowski L. J. , Kinzel G. L.
Published: March 2021

A method is presented to develop the “force-constraint” equations enforced by a spherical joint with Coulomb friction. The spherical joint is assumed to behave instantaneously as a revolute joint. This instantaneous revolute will have an axis along the instant screw axis between the two links connected by the joint. The effective radius of the instantaneous revolute will be a function of joint loading and the coefficient of friction.