bluuebunny/crossref_metadata_2025 huggingface dataset:
The Experience of 2 Independent Schools With In‐Person Learning During the COVID‐19 Pandemic
Authors: Gillespie Darria L. , Meyers Lauren A. , Lachmann Michael , Redd Stephen C. , Zenilman Jonathan M.
Published: March 2021

BACKGROUND

In 2020, US schools closed due to SARS‐CoV‐2 but their role in transmission was unknown. In fall 2020, national guidance for reopening omitted testing or screening recommendations. We report the experience of 2 large independent K‐12 schools (School‐A and School‐B) that implemented an array of SARS‐CoV‐2 mitigation strategies that included periodic universal testing.

METHODS

SARS‐CoV‐2 was identified through periodic universal PCR testing, self‐reporting of tests conducted outside school, and contact tracing. Schools implemented behavioral and structural mitigation measures, including mandatory masks, classroom disinfecting, and social distancing.

RESULTS

Over the fall semester, School‐A identified 112 cases in 2320 students and staff; School‐B identified 25 cases (2.0%) in 1400 students and staff. Most cases were asymptomatic and none required hospitalization. Of 69 traceable introductions, 63 (91%) were not associated with school‐based transmission, 59 cases (54%) occurred in the 2 weeks post‐thanksgiving. In 6/7 clusters, clear noncompliance with mitigation protocols was found. The largest outbreak had 28 identified cases and was traced to an off‐campus party. There was no transmission from students to staff.

CONCLUSIONS

Although school‐age children can contract and transmit SARS‐CoV‐2, rates of COVID‐19 infection related to in‐person education were significantly lower than those in the surrounding community. However, social activities among students outside of school undermined those measures and should be discouraged, perhaps with behavioral contracts, to ensure the safety of school communities. In addition, introduction risks were highest following extended school breaks. These risks may be mitigated with voluntary quarantines and surveillance testing prior to reopening.
Breastfeeding patterns and effects of minimal supplementation on breastfeeding exclusivity and duration in term infants: A prospective sub‐study of a randomised controlled trial
Authors: Bond Diana M , Shand Antonia W , Gordon Adrienne , Bentley Jason P , Phipps Hala , Nassar Natasha
Published: March 2021

Aim

Despite international recommendations, less than one‐third of Australian women exclusively breastfeed for 6 months. The aims of this study were to prospectively determine rates and factors associated with the type and duration of breastfeeding in the first year and examine the effect of minimal supplementation.

Methods

We conducted a sub‐study of a randomised controlled trial in Sydney, Australia, which included 635 women with uncomplicated term births who intended to breastfeed. Data were collected daily for 56 days, and then at 2, 6 and 12 months post‐partum.

Results

Breastfeeding outcomes were evaluated for 553 (87%), 480 (76%) and 392 (62%) women at 2, 6 and 12 months. Exclusive breastfeeding was 81% at 2 months and 8% at 6 months. Partial breastfeeding was 75% at 6 months and 54% at 12 months. Factors associated with breastfeeding cessation included caesarean birth, low milk supply, problems latching, increased time to breastfeed, use of formula >7 days in the first 2 months, return to work and early introduction of solids. Breast pain in the first week was associated with a 10% decrease in exclusive breastfeeding. Cracked nipples and no previous breastfeeding experience were associated with supplementation of ≤7 days but had no effect on long‐term breastfeeding duration.

Conclusions

Exclusive breastfeeding declined significantly between 2 and 6 months post‐partum. Early intervention and education to prolong breastfeeding duration should include strategies to manage breast pain and nipple damage to minimise prolonged supplementation. Consistent guidelines about introduction of complementary foods, improved maternity leave and workplace incentives could be effective in prolonging breastfeeding.
Sleep‐related monitoring on awakening mediates the relationship between insomnia‐related interpretive bias and insomnia symptoms using the insomnia ambiguity paradigm
Authors: Akram Umair , Bickle Eleanor , Howell Carley , Ozhan Vildan , Williamson Jessica , Du Rocher Andrew
Published: March 2021

A number of studies have examined and confirmed the presence of a sleep‐related interpretive bias amongst poor sleepers and individuals with insomnia using an insomnia ambiguity task. This study explored possible mechanisms underlying the relationship between interpretive bias and insomnia using the insomnia ambiguity task. More importantly, the possible mediating role of sleep‐associated monitoring, sleep preoccupation, sleep anticipatory anxiety and generalized anxiety was also examined. A total of N = 176 participants were stratified into normal sleepers and those displaying insomnia symptoms. Participants completed an online version of the insomnia ambiguity task and questionnaire measures pertaining to sleep and anxiety. Data concerning task response time and time of testing were also collected. Individuals in the insomnia symptom group presented significantly higher sleep‐related interpretive bias scores compared to normal sleepers. When sleepiness, sleep‐associated monitoring, sleep preoccupation, sleep anticipatory anxiety and generalized anxiety were controlled for, only monitoring on awakening predicted sleep‐related interpretive bias. Multiple mediation modelling demonstrated that sleep‐associated monitoring on awakening mediated the relationship between interpretive bias and insomnia symptoms. The current outcomes are consistent with previous research, supporting the notion that insomnia is characterized by a disorder‐consistent interpretive bias. Furthermore, monitoring for insomnia‐consistent cues on awakening appears to mediate group differences in interpretive bias.
TPCA‐1 negatively regulates inflammation mediated by NF‐κB pathway in mouse chronic periodontitis model
Authors: Wang Bo , Bai Shizhu , Wang Jiang , Ren Nan , Xie Rui , Cheng Geng , Yu Yan
Published: March 2021

The dysregulation of immune system plays a crucial function in periodontitis development. Pro‐inflammatory cytokines are thought to be critical for the generation and development of periodontitis. The enhanced activity of osteoclasts contributes to periodontitis pathogenesis. Nuclear factor‐κB (NF‐κB) signaling pathway directly enhances osteoclast differentiation and maturation. 2‐[(aminocarbonyl)amino]‐5‐(4‐fluorophenyl)‐3‐thiophenecarboxamide (TPCA‐1) is a IκB kinases (IKK) inhibitor. This research aimed to investigate whether TPCA‐1 had influence on the pathogenesis of chronic periodontitis. Mouse chronic periodontitis was induced by an in vivo ligature‐induced periodontitis model. TPCA‐1 was intravenously injected into mice after chronic periodontitis induction. Bone marrow‐derived macrophages were cultured in macrophage colony‐stimulating factor (M‐CSF)‐conditioned media with receptor activator of nuclear factor‐kappa B ligand (RANKL) induce in vitro osteoclast differentiation. Western blot was used to analyze protein levels and mRNA levels were analyzed through qRT‐PCR. TPCA‐1 promoted osteoclastogenesis and osteoclast‐related gene expression in vitro. The production of pro‐inflammatory cytokines in osteoclasts induced by lipopolysaccharides was inhibited by TPCA‐1 in vitro. In vitro TPCA‐1 treatment inhibited Aggregatibacter actinomycetemcomitans (A.a)‐induced expression of pro‐inflammatory cytokines and NF‐κB signal activation in osteoclasts. The induction of chronic periodontitis was inhibited by the absence of IKKb in mice. This research demonstrates that the treatment of TPCA‐1 negatively regulates inflammation response and inhibits the osteoclastogenesis through the inactivation of NF‐κB pathway in mouse chronic periodontitis model.
Post‐traumatic stress as a determinant of quality of life in pediatric solid‐organ transplant recipients
Authors: Hind Tatsuma , Lui Samantha , Moon Erin , Broad Katherine , Lang Samantha , Schreiber Richard A. , Armstrong Kathryn , Blydt‐Hansen Tom D.
Published: March 2021

Living with end‐stage organ failure is associated with an accumulation of traumatic medical events, and despite recovery after solid‐organ transplantation (SOT), many children continue to exhibit lower quality of life (QOL). Few studies have examined the relationship between post‐traumatic stress disorder (PTSD) and QOL among pediatric SOT recipients. We conducted a retrospective, cross‐sectional review of 61 pediatric SOT recipients (12 heart, 30 kidney, and 19 liver) to evaluate the association of PTSD with self‐reported QOL. PTSD was measured by the Child Trauma Screening Questionnaire (CTSQ), and QOL was measured using the PedsQL and PedsQL Transplant Module (PedsQL‐TM) surveys. Demographics, baseline, and contemporaneous factors were tested for independent association. SOT recipients were 15.2 (12.1–17.6) years old at survey completion. Median CTSQ score was 2 (1–3), highest in kidney recipients, and 13% were identified as high risk for PTSD. Median PedsQL score was 83 (70–91) and significantly associated with the CTSQ score (r = −.68, p < .001). Median PedsQL Transplant Module score was 89 (83–95) and similarly associated with the CTSQ score (r = −.64, p < .001). Age at time of surveys and presence of any disability were also independently associated with PedsQL and PedsQL‐TM, respectively. When adjusted for Emotional Functioning, CTSQ remained associated with PedsQL subscores (r = −.65, p < .001). Trauma symptoms are a major modifiable risk factor for lower self‐perceived QOL and represent a potentially important target for post‐transplant rehabilitation. Additional research is needed to understand the root contributors to PTSD and potential treatments in this population.
Supply Chain Carbon Footprinting and Climate Change Disclosures of Global Firms
Authors: Blanco Christian C.
Published: March 2021

The content of climate change disclosures of large, global companies evolved from 2007 to 2016. Within that window, the same set of firms started measuring and disclosing their supply chain carbon emissions. Does carbon footprinting influence the nature and content of a firm's disclosure on the climate change risks that are expected to affect its business? We explore this question using more than 10,925 climate change disclosures collected by the CDP (formerly the Carbon Disclosure Project) from 2,003 firms worldwide. We use singular value decomposition and text similarity scores to quantitatively examine the content of the CDP disclosures from 2007 to 2016. Using fixed effects and dynamic panel models, we find that measuring supply chain carbon emissions (Scope 3) explains a substantial shift in the content and nature of the disclosures. We find no evidence that measuring and disclosing direct emissions (Scope 1) are associated with substantial changes in the content of the disclosures. One explanation for this is that most of the climate change‐related risks are in the supply chain, not within the company boundaries of large, global firms. Our results show the importance of encouraging firms to voluntarily measure their supply chain carbon emissions if they are not yet aware of their contribution and exposure to climate change. Our work shows that firms’ response to climate change is dynamic, and it may take a decade to detect these shifts.
Managing exploration persistency in ambidextrous organizations
Authors: Shibata Tomoatsu , Baba Yasunori , Suzuki Jun
Published: March 2021

The concept of ambidextrous organization, which is allowing exploration and exploitation to coexist within an organization, has attracted considerable interest and is useful in understanding the corporate transformation process. We aim to advance the framework of ambidextrous organization by incorporating the aspect of exploration persistency. Our in‐depth case study revealed the contrasting persistence of exploration for new technology and new business between Fujifilm and Kodak through analysis of patent data from 1982 to 2012. Also, we discuss how the degree of exploration persistency is influenced by the effects of exploitation and knowledge accumulation within ambidextrous organization. In this paper, exploration persistency is defined as the degree to which an organization continues exploration in a consistent direction along a particular path and the amount of resources the organization applies to or invests in the exploration activity until the organization realizes that it is headed in the wrong direction. We examine the different fates of Fujifilm and Kodak through the lens of exploration persistency.
R&D employment effects of financial slack generated by R&D tax exemption: The importance of firm‐level contingencies
Authors: Teirlinck Peter , Spithoven André , Bruneel Johan
Published: March 2021

This paper focuses on R&D employment effects due to financial slack generated by an R&D tax exemption scheme in Belgium. The tax exemption is granted without firm‐level requirements, which facilitates testing firm‐level contingencies on the influence of the generated financial slack. We find that R&D employment effects increase with the level of the R&D tax exemption related to financial slack resources and that this positive relation is more outspoken for older firms and for firms with an intermediate share of R&D tax exemptions in the overall mix of R&D policy support. No effects are found for firm size and its R&D intensity. These findings suggest targeting the R&D tax exemption support according to firm characteristics to obtain longer term R&D employment effects. The focus on R&D employment adds to the literature on the evaluation of R&D policies which is largely oriented toward R&D expenditure and innovation outputs.
The symbiotic tensions of the regulatory–carceral state: The case of cannabis legalization
Authors: Aaronson Ely , Rothschild‐Elyassi Gil
Published: March 2021

Recent scholarship has emphasized the need to develop a polymorphic conceptualization of the regulatory state. This article contributes to this theory‐building project by outlining a research agenda for exploring the symbiotic interactions and tensions between the regulatory and carceral morphs of the state. Using the case study of cannabis legalization reforms in the United States, we argue that the legitimation deficits of the carceral state stimulate the proliferation of new regulatory frameworks for governing social problems that were traditionally handled by the criminal justice system. We demonstrate how the polymorphic approach illuminates the ways in which the regulatory and carceral morphs of the state compete for influence over shared policy domains, but also complement and reinforce one another. Thus, rather than precipitating the demise of the carceral state, cannabis legalization reforms sustain a bifurcated governance structure perpetuating long‐standing patterns of using drug law as a means for racialized social control.
The chemical compound ‘Heatin’ stimulates hypocotyl elongation and interferes with the Arabidopsis NIT1‐subfamily of nitrilases
Authors: van der Woude Lennard , Piotrowski Markus , Klaasse Gruson , Paulus Judith K. , Krahn Daniel , Ninck Sabrina , Kaschani Farnusch , Kaiser Markus , Novák Ondřej , Ljung Karin , Bulder Suzanne , van Verk Marcel , Snoek Basten L. , Fiers Martijn , Martin Nathaniel I. , van der Hoorn Renier A. L. , Robert Stéphanie , Smeekens Sjef , van Zanten Martijn
Published: March 2021

Temperature passively affects biological processes involved in plant growth. Therefore, it is challenging to study the dedicated temperature signalling pathways that orchestrate thermomorphogenesis, a suite of elongation growth‐based adaptations that enhance leaf‐cooling capacity. We screened a chemical library for compounds that restored hypocotyl elongation in the pif4‐2–deficient mutant background at warm temperature conditions in Arabidopsis thaliana to identify modulators of thermomorphogenesis. The small aromatic compound ‘Heatin’, containing 1‐iminomethyl‐2‐naphthol as a pharmacophore, was selected as an enhancer of elongation growth. We show that ARABIDOPSIS ALDEHYDE OXIDASES redundantly contribute to Heatin‐mediated hypocotyl elongation. Following a chemical proteomics approach, the members of the NITRILASE1‐subfamily of auxin biosynthesis enzymes were identified among the molecular targets of Heatin. Our data reveal that nitrilases are involved in promotion of hypocotyl elongation in response to high temperature and Heatin‐mediated hypocotyl elongation requires the NITRILASE1‐subfamily members, NIT1 and NIT2. Heatin inhibits NIT1‐subfamily enzymatic activity in vitro and the application of Heatin accordingly results in the accumulation of NIT1‐subfamily substrate indole‐3‐acetonitrile in vivo. However, levels of the NIT1‐subfamily product, bioactive auxin (indole‐3‐acetic acid), were also significantly increased. It is likely that the stimulation of hypocotyl elongation by Heatin might be independent of its observed interaction with NITRILASE1‐subfamily members. However, nitrilases may contribute to the Heatin response by stimulating indole‐3‐acetic acid biosynthesis in an indirect way. Heatin and its functional analogues present novel chemical entities for studying auxin biology.
Reviewer Acknowledgements
Authors: Oscar William
Published: March 2021

International Journal of Contemporary Education (IJCE) would like to acknowledge the following reviewers for their assistance with peer review of manuscripts for this issue. Many authors, regardless of whether IJCE publishes their work, appreciate the helpful feedback provided by the reviewers. Their comments and suggestions were of great help to the authors in improving the quality of their papers. Each of the reviewers listed below returned at least one review for this issue.Reviewers for Volume 4, Number 1 Aurora Q. Pestano, University of San Jose Recoletos, PhilippinesAziz Moummou, Ministry of Education, MoroccoBlessing Dwumah Manu, Jiangsu University, GhanaBožić-Lenard Dragana, University of Osijek Croatia, CroatiaBruna Gabriela Augusto Marçal Vieira, CEFET-MG, BrazilDina Radeljas, Mohawk Valley Community College, USAEdward Bolden, Case Western Reserve University, USAFederica Cornali, University of Turin, ItalyGiuseppe Maugeri, Ca' Foscari University, ItalyGraziano Serragiotto, Ca' Foscari University of Venice, ItalyInaad M Sayer, University of Human Development, IraqLi Li, Bath Spa University, UKMakrina Nina Zafiri, Aristotle University of Thessaloniki, GreeceMatthew Schatt, University of Florida, USANilgün Tosun, Trakya University, TurkeyRaymond Aaron Younis, ACU Australia, AustraliaTeresa Pozo-Rico, University of Alicante, SpainVassiliki Pliogou, Metropolitan College of Thessaloniki, GreeceVassilios Papadimitriou, University of Thessaly, Greece William OscarEditorial AssistantInternational Journal of Contemporary Education------------------------------------------------------------Redfame Publishing9450 SW Gemini Dr. #99416Beaverton, OR 97008, USATel: 1-503-828-0536 ext. 509Fax: 1-503-828-0537E-mail 1: ijce@redfame.comE-mail 2: ijce@redfame.orgURL: http://ijce.redfame.com
The Impact of Various Modeling Decisions on Flow Field Predictions in a Centrifugal Compressor
Authors: Gooding William J. , Meier Matthew A. , Key Nicole L.
Published: March 2021

Computational tools have become increasingly important in design and research applications in recent years due to increasing computational resources. In most cases, model geometry and flow physics are simplified to reduce the complexity of the computational model. While this was necessary historically, modern computational tools are capable of including realistic features such as fillets, surface roughness, and heat transfer. This work presents extensive and systematic numerical results from a simulation of a centrifugal compressor stage for an aero-engine application. Numerical results are compared to detailed experimental data to investigate the effect of various modeling decisions, including turbulence models, on the predicted aerodynamics developing through the diffuser passage. Roughness and the inclusion of fillets significantly impact the flow development, especially with the shear-stress transport (SST) turbulence model. This approach leads to the conclusion that the BSL-EARSM model is best able to predict the experimentally determined diffuser flow profiles and overall performance trends with the inclusion of the previously mentioned model features. Additionally, misleading conclusions can be reached if modeling decisions are based on merely matching overall performance values. Finally, frozen rotor simulations are used to roughly approximate the impact of unsteadiness on the flow field. The results show a significant impact and also that the inclusion of approximate unsteady effects tends to further improve the predictive capability of the computational models that were considered.
Enhancing the Power of Expert Systems Through Interprocess Communication
Authors: Murren Brian T. , Crapo Andrew W.
Published: March 2021

Today many excellent software packages are available both within GE and commercially. The challenge of the future is to integrate suites of these diverse packages to provide the best solution for a given application’s requirements. This paper will describe how the GEN-X expert system shell has been enhanced to execute as a cooperative program using a client-server model in multiprocessing environments that support this concept, i.e. Windows, UNIX, etc. Consistent with the GEN-X philosophy of providing ease of use, the knowledge base developer is shielded from the details of the implementation. The communication facilities allow commands and data to be exchanged with other processes by supporting multiple protocols and transport mechanisms. The initial Unix implementation used GDE, a protocol similar to Microsoft’s DDE under Windows (Microsoft, 1990). This paper describes how the addition of interprocess communication facilities to GEN-X allows powerful tools such as hypermedia managers to be integrated into an expert system application.
Effective Utilization of Design Geometry for Numerical Analysis Applications
Authors: Loule Jeffery M.
Published: March 2021

In many instances, companies are using design automation software from different software suppliers to perform their design and analysis functions. Selection of the software applications were probably based on “Best in class” and organizational requirements many years before the need to move analysis on to the critical design path was not even imaginable. The advances in technology in only the last few years has made the leveraging of design geometry for analysis possible. It would be impractical to throw away the legacy system in order to integrate the design and analysis function. Therefore, it is important to have the technologies and software applications which can efficiently use geometric data from the design application in the analysis application. This paper will discuss some of the issues with using design geometry and ways to address the issues.

The paper discusses some of the “real life” issues of trying to use geometry created from design systems for analysis applications. It proposes a multi-step approach to efficiently utilize design geometry for analysis applications. The paper will discusses the advantage and disadvantages of proprietary versus international data exchange standards. It will also identify the necessary functionality to modify geometry within the analysis application. To illustrate the productivity of this approach, the paper will go through the process of modifying design geometry of a hand held video camera for a finite element mesh.
Design of an AutoCAD Tablet Menu for Machine Design
Authors: Ezz Ali Abou , Al-Medfa Othman , Hamed Mostafa
Published: March 2021

Many computer packages are commercially available to design an object. AutoCAD is one of these packages which is commonly used in educational institutions to produce and modify technical drawings using personal computers. A customized Menu is developed to control the AutoCAD drawing editor through a digitizer tablet buttons. Tablet menu assigns AutoCAD commands to different locations of the digitizer tablet surface which is divided into four rectangular areas containing different sets of macros. Each macro contains a series of AutoCAD commands and parameters put together to perform an identified task.

Tablet area one consists of 200 boxes used for blocks library applications. Over 54 block drawings of different mechanical drawings are established, when user clicks the digitizer at one of these boxes location, a selected mechanical item is inserted from the library onto the current drawing with suitable scale factors. The user can assemble mechanical components of different elements from this library within a short time and with little effort.
Effect of Index Variation Form of an Epicyclic Gear Reducer Teeth on Turbo-Generator Set Vibrations
Authors: Rakhit A. K.
Published: March 2021

The index variation form of gear teeth is an important parameter that needs to be considered in analyzing vibrations of gear transmissions. Tests carried out showed the ring gear teeth index variation forms of an epicyclic reducer significantly influenced the vibrations of turbo-generator sets. The proper selection of this form combined with allowable index variation of ring gear teeth resulted in acceptable turbo-generator set vibrations.
Pitting Resistance and Bending Strength of Bevel and Hypoid Gear Teeth
Authors: Höhn B.-R. , Winter H. , Michaelis K. , Vollhüter F.
Published: March 2021

Bevel and hypoid gears are widely used for gears with crossed axis. The influence of a pinion offset on the load carrying capacity — pitting resistance and bending strength — is introduced in a different way in commonly used calculation methods. Load carrying and measurement investigations on the influence of pinion offset on pitting resistance and bending strength are reported. Tests show an increasing bending strength and decreasing maximum tooth root stresses with increasing pinion offset. Also a slight increase of pitting resistance and a slight decrease of the Hertzian pressure was evaluated. The load carrying calculation results for bevel gears without pinion offset, DIN 3991, is in good agreement with test results. The bending strength of hypoid gears calculated according to Niemann/Winter, is greater than that experimentally measured. For pitting resistance, however, the calculation is less than the measured results.
Dynamics of a Truck Gearbox
Authors: Perret-Liaudet J. , Sabot J.
Published: March 2021

This work is concerned with numerous numerical simulations of the overall dynamic behaviour of a parallel helical gear transmission. These results are compared to vibratory measurements made with a simplified gearbox test rig.

The dynamic modeling of the elastic components of the gear transmission (gears, shafts, bearings, housing) is realized using the finite element method. Fluctuated gear mesh stiffness is introduced owing to stiffness matrix which describes the elastic coupling between the pinion and the wheel. The kinematic transmission error is introduced as a vibratory excitation source. The equations of motion are established in a truncated modal base deduced from the average characteristics of the structure. A new computing method, called “Spectral Method”, is used for analytical study of a simplified gearbox whose housing is a simple rectangular plate.

The numerical results allows us to conclude on the dominent phenomenon of the overall dynamic behaviour of the gear transmission. They exhibit in particular the main characteristics of the transfer between the static transmission error and the vibratory response of the gearbox.

A series of vibration measurements made on a gearbox close to that used for the numerical simulations, has confirmed this characteristics.
Dynamics of a Split Torque Helicopter Transmission
Authors: Rashidi Majid , Krantz Timothy L.
Published: March 2021

A high reduction ratio split torque gear train has been proposed as an alternative to a planetary configuration for the final stage of a helicopter transmission. A split torque design allows a high ratio of power-to-weight for the transmission. The design studied in this work includes a pivoting beam that acts to balance thrust loads produced by the helical gear meshes in each of two parallel power paths. When the thrust loads are balanced, the torque is split evenly. A mathematical model was developed to study the dynamics of the system. The effects of time varying gear mesh stiffness, static transmission errors, and flexible bearing supports are included in the model. The model was demonstrated with a test case. Results show that although the gearbox has a symmetric configuration, the simulated dynamic behavior of the first and second compound gears are not the same. Also, results show that shaft location and mesh stiffness tuning are significant design parameters that influence the motions of the system.
The Optimum Modification of Tooth Profile for a Pair of Spur Gears to Make its Rotational Vibration Equal Zero
Authors: Cai Yurong , Hayashi Teru
Published: March 2021

This paper develops an optimum modification method of tooth profile for a pair of spur gears to make its rotational vibration become zero by using an exact vibration model. By minimizing the equivalent exciting force, which includes the effects of the static load, time-varying stiffness, and relative tooth profile error, each optimum modification curve for each gear pair with different designed contact ratios can be obtained. The magnitude and the shape of the optimum modification curve depend upon the value of the designed contact ratio ε strongly. Especially, the concave modification curve is obtained in case of ε ≤ 1.1. The effect of the optimum modification on eliminating the vibration, is verified by the numerical calculation using an exact equation of vibration. A parameter study is presented to investigate the effect of running condition.
Computational Issues Associated With Gear Rattle Analysis: Part II — Evaluation Criteria for Numerical Algorithms
Authors: Barlow R. C. , Padmanabhan C. , Singh Rajendra
Published: March 2021

The main focus of this study is to establish evaluation criteria for direct time domain integration algorithms used to solve gear rattle type problems. Such criteria may be used to identify specific numerical problems encountered. The ultimate goal obviously is to find reasonably accurate and reliable methods of solution for such physical systems. Six case studies of increasing complexity, linear to highly non-linear, are solved using well known algorithms. The solutions to the linear model are verified by using analytical results. Non-linear model solutions as yielded by different algorithms are compared qualitatively and quantitatively. Several non-linear simulation models have been validated by comparing predictions with experimental data and results available in the literature.
Design and Construction of a Machine to Evaluate the Forces in Roller Chain Drives
Authors: Conwell James C. , Johnson Glen E. , Peterson S. W.
Published: March 2021

In this article, a brief history of chain drives is presented, and the design and construction of a machine to investigate chain drive force phenomena is discussed. The new test machine allows the measurement of the impact force between a roller and the sprocket during “seating” and it can also be used to measure the forces that exist in the link sides plates during normal operation (including start-up and shut down conditions). Data can be obtained for a wide range of chain loads and speeds. Two companion papers (“Experimental Investigation of the Impact Force that Occurs When a Roller Seats on the Sprocket During Normal Operation of a Roller Chain Drive” and “Experimental Investigation of the Forces in a Link Side Plate During Normal Operation of a Roller Chain Drive”, both presented at this conference) describe experiments that have been completed with this test machine.
Experimental Investigation of the Forces in a Link Side Plate During Normal Operation of a Roller Chain Drive
Authors: Conwell James C. , Johnson Glen E. , Peterson S. W.
Published: March 2021

The fluctuation in the tension of a chain link during normal operation is very likely the root cause of chain stretch and fatigue in roller chain drives. In this paper we present the results from a recent experimental investigation of this tension variation phenomenon. The experimental procedure is described, and data are presented for a wide range of initial tensions, transmitted loads, and chain speeds.

At low speeds, the data give reasonable agreement with previously published theoretical models for quasi-static load distribution. However, at higher speeds (where inertia effects are more significant) the experimental results indicate that quasi-static models do not provide an adequate explanation. The differences are noted and discussed. An empirical equation for “tight side” chain tension is presented in terms of torque transmitted, sprocket pitch radius, mass per unit length of chain, and linear chain speed. This paper is accompanied by companion papers that describe the design and construction of the test machine and the measurement of the impact force as a roller seats on the sprocket.
Synthesis and Experimental Validation of Dynamic Parts-Orienting Devices
Authors: Han Inhwan , Gilmore B. J. , Ogot M. M.
Published: March 2021

Part orientation is an important aspect of factory automation. The parts-orienters presented by this paper are flexible to handle a variety of parts, passive (cost effective) and high-speed (i.e., include significant inertial effects). This paper presents a dynamic synthesis approach of gravity fed parts-orienters. In general, previous works were constrained by their quasi-static analyses. This research demonstrates the synthesis for dynamic parts-orienters based on the mechanics of the system using a simulation package as a design tool. The dynamic effects considered by this work include friction, inertial forces, impact with friction and contact/no-contact (changing kinematic constraints). The passive part orientation systems, which are developed by dynamic system synthesis in the presence of friction and impact, succeed in aligning a part into a specified orientation and through experiment are shown to be valid. This paper presents and experimentally validates a synthesis approach for dynamic mechanical systems with changing kinematic constraints. The experimental validation uses high speed video.
A Blackboard Architecture to Support Case-Based Reasoning in Mechanical Design
Authors: Bardsz Theodore , Zeid Ibrahim
Published: March 2021

One of the most significant issues in applying case-based reasoning (CBR) to mechanical design is to integrate previously unrelated design plans towards the solution of a new design problem. The total design solution (the design plan structure) can be composed of both retrieved and dynamically generated design plans. The retrieved design plans must be mapped to fit the new design context, and the entire design plan structure must be evaluated. An architecture utilizing opportunistic problem solving in a blackboard environment is used to map and evaluate the design plan structure effectively and successfuly. The architecture has several assets when integrated into a CBR environment. First, the maximum amount of information related to the design is generated before any of the mapping problems are addressed. Second, mapping is preformed as just another action toward the evaluation of the design plan. Lastly, the architecture supports the inclusion of memory elements from the knowledge base in the design plan structure. The architecture is implemented using the GBB system. The architecture is part of a newly developed CBR System called DEJAVU. The paper describes DEJAVU and the architecture. An example is also included to illustrate the use of DEJAVU to solve engineering design problems.
Representing Geometric Viariations in Complex Structural Assemblies on CAD Systems
Authors: Shalon Dari , Gossard David , Ulrich Karl , Fitzpatrick David
Published: March 2021

In previous airplane programs, Boeing identified interferences and misalignments between airplane parts as the two largest causes of engineering changes. Boeing is currently designing the 777 with a state-of-the-art solid modeling system. While the system is capable of detecting interferences and misalignments between ideally-sized and ideally-located solid models, it cannot model the effects of variation in the size, shape and location of parts and tools. This paper presents an initial, novel framework for modeling these variations called Indexed Pre-Assembly with Variation (IPAV).

The main points made in this paper are:

• Variations in both parts and tools should be modeled in exactly the same way.

• Mating features of parts and tools can be represented in the solid models with local index-point coordinate systems.

• Linking the mating index-point coordinate systems enables the positioning of the solid models in an assembly.

• The order in which the index-point coordinate systems are linked corresponds to the planned assembly sequence.

• The effects of size, shape and location variations on an assembly can be modeled by manipulating the index-point coordinate systems within the individual solid models.

The academic literature on tolerancing and existing software tools for tolerance analysis are reviewed. A survey of Boeing engineers is presented which led to the development of the Indexed Pre-Assembly with Variation method. A case study involving an actual assembly problem at Boeing is analyzed with IPAV. The paper also discusses the benefits of simulating variation at the design stage and proposes an implementation plan to integrate IPAV into a generic airplane development schedule. Lastly, the applicability of IPAV to other industries is evaluated and areas for further research are identified.
A Single-DOF Multi-Function Prosthetic Hand Mechanism With an Automatically Variable Speed Transmission
Authors: Guo Gongliang , Qian Xikang , Gruver Willim A.
Published: March 2021

This research concerns the design of a new three-fingered anthropomorphic hand mechanism for prosthetic and robotic applications. Based on the configuration and flexion/extension features of human hands, we develop a three-jointed finger mechanism using a gear-constrained planar five-bar linkage with a single degree of freedom (DOF). From an operational study of human hands, we also propose a multi-functional palm mechanism using a cam-groove submechanism. The hand can perform grasping, holding and pinching operations. To achieve the automatic shape adaptability of a human hand, a selfadaptable submechanism was designed within the palm based on the lever principle. An automatically variable speed transmission with selfadaptability was developed for this hand to achieve optimal flexing speed and optimal fingertip forces. This paper describes the mechanical structure and operational principles of this new prosthetic device.
On the Kinematics of the UPS Wrist for Real Time Control
Authors: Lee Jason J. , Chang Sun-Lai
Published: March 2021

A parallel structure is used in the design of the UPS wrist to allow for a large payload, high speed, high repeatability, and a large workspace. Because of the inherent design and machining difficulties involved with spherical mechanisms, a spatial mechanism has been adopted. In creating such a 3-DOF spatial mechanism, many practical design problems are unavoidable, and direct analysis of the mechanism becomes extremely difficult. In this paper, we discuss the concept of using an equivalent mechanism to simplify the kinematic analysis. By using this method, we have derived a closed-form solution for the inverse kinematics, as well as a formulation for the forward kinematics. We have also developed a numerical algorithm for the forward kinematics, and a methodology for implementing the results of the analysis. The results of this study have enabled real time control and force control to become feasible for the UPS wrist.
A Drift-Free Navigation System for a Mobile Robotic Vehicle Operating on Unstructured Terrain
Authors: Sreenivasan S. V. , Waldron Kenneth J.
Published: March 2021

The orientation and the angular rates of the body of a robotic vehicle are required for guidance and control of the vehicle. In the current robotic systems these quantities are obtained by the use of inertial sensing systems. Inertial sensing systems involve drift errors which can be significant even after the vehicle has traversed only short distances on the terrain. A different approach is suggested here which guarantees accurate, drift-free sensing of the angular position and rates of the vehicle body. A camera system consisting of two cameras in fixed relationship to one another is made to continuously track two stationary objects. The camera system is mounted on the vehicle body through an actuated three degree of freedom joint. The angular positions and rates of these joints can be used to evaluate the angular positions and rates of the vehicle body. An approximate estimate of the position of the vehicle on the terrain can also be obtained from the sensing system. This can serve as primary system for estimating the vehicle position, or as a backup to a more accurate scheme for obtaining the position of the vehicle on the terrain.
Grashof Type Rotatability Criteria of Spherical Five-Bar Linkages
Authors: Kohli Dilip , Khonji Ardie
Published: March 2021

In this paper rotatability criteria of spherical five bar linkages are analytically derived. First an equivalent linkage in which sum of any two link lengths is less than π is found and then rotatability criteria of spherical 5 bar linkage are developed for this linkage. The rotatability criteria developed in this paper are stated as follows:

The two input angles are completely revolvable if and only if in the equivalent linkage the sum of the longest and the two shortest links is less than the sum of the remaining two links and there is one and only one long link between each pair of noninput angles (long link being any link excluding the shortest links). It is also shown that an angle θ included by two links αi and αj is completely revolvable if and only if the sum of the longest link and shorter of αj and αj is less than or equal to the sum of the remaining three links.
Development of Commercial Quality Software for Mechanisms Design Education
Authors: Timmins Steven J.
Published: March 2021

Development of high quality technical software in a university environment has been a persistent problem since the introduction of educational software to institutions of higher learning. Design software presents a number of special considerations. It differs significantly from other types of educational software in that it requires a free-form creative environment rather than a question-and-answer format or even a detailed analysis of a fixed set of specified problems. Ideally, the student should be able to explore a wide range of realistic problems and develop both optimal and non-optimal solutions using a variety of mechanisms. This paper outlines the differences between truly “commercial quality” software and that developed for use at the local campus and explores the difficulties involved in producing such a product.

Users drastically underestimate the amount of manpower and funding required to develop software packages on a par with widely available applications such as AutoCAD, WordPerfect, or Lotus 1-2-3. Similarly, design education software developed at universities for national distribution represent thousands of man-hours of development and may be the work of a single individual or a team of programmers led by a faculty member.
On Flexible Pin Shafts and Clearance Interaction for the Dynamic Response of Planar Mechanisms
Authors: DeRong Wu
Published: March 2021

The dynamic equations of planar mechanisms with flexible pin shafts and clearance connections is developed here using Lagrangian formulation. The general flexible-connection planar mechanism can be described by a damped, circulatory, gyroscopic system. Quite often, damping and circulatory forces are small, one may regards them as the perturbations. Indeed, a perturbation method for obtaining the eigensolution and dynamic response is presented by regarding the undamped, non-circulatory, gyroscopic system as the unperturbed system.

The procedure may be used to investigate the fundamental nature of dynamic interaction between the elastic deflection of pin shafts and clearance connections. A major objective of this paper, in addition to the development of the analytical technique, was to obtain some insight into the phenomenon at flexible-connection, so that these effects may be included during the designing of mechanisms.
Object Norms: A Class of Coordinate and Metric Independent Norms for Displacements
Authors: Kazerounian Kazem , Rastegar Jahangir
Published: March 2021

Defining a “norm” that quantifies a measure of “distance” for rigid body displacement in plane or space, is essential to many problems in kinematics, dynamics and control of mechanical and manufacturing systems. The norm is an abstraction of our usual concept of the length. The mapping between different generalized coordinate systems used in the analysis or control of systems may also be derived from this norm. All such norms currently used in different analysis are highly sensitive to 1) coordinate systems defined, and 2) metrics defined.

A new class of norms is proposed to quantify the distance in the space. These norms are independent of the coordinate systems or metrics used. Its applications indesign, precision manipulation and control, computational kinematics and dynamics, assembly and part mating in manufacturing, space kinematics and dynamics, shape optimization and motion planning are explored.
Torsional and Translational Vibrations of a Drive Shaft System With a Cardan Joint
Authors: Routson Richard L. , Starkey John M. , Wang Peishuh , Davies Patricia
Published: March 2021

A drive-shaft system was designed and built for studying the effects of a Cardan joint on torsional and translational shaft vibrations. The design of the system is described, and the results of a modal test are included. The system was also used to test the validity of a new optical torsional vibrometer. Measurements on the system indicate that (1) clearances significantly effect the torsional resonances, (2) second order responses due to the parametric variations in the Cardan joint dominate the response, and (3) the optical probe system shows promise as a non-contacting torsional and translational vibrometer.
A Model of the Human Spine: Forward and Inverse Kinematics
Authors: Agrawal Sunil Kumar , Li Siyan , Desmier Glen
Published: March 2021

The human spine is a sophisticated mechanism consisting of 24 vertebrae which are arranged in a series-chain between the pelvis and the skull. By careful articulation of these vertebrae, a human being achieves fine motion of the skull. The spine can be modeled as a series-chain with 24 rigid links, the vertebrae, where each vertebra has three degrees-of-freedom relative to an adjacent vertebra. From the studies in the literature, the vertebral geometry and the range of motion between adjacent vertebrae are well-known. The objectives of this paper are to present a kinematic model of the spine using the available data in the literature and an algorithm to compute the inter vertebral joint angles given the position and orientation of the skull. This algorithm is based on the observation that the backbone can be described analytically by a space curve which is used to find the joint solutions..