bluuebunny/crossref_metadata_2025 huggingface dataset:
Physiological and molecular attributes contribute to high night temperature tolerance in cereals
Authors: Schaarschmidt Stephanie , Lawas Lovely Mae F. , Kopka Joachim , Jagadish S. V. Krishna , Zuther Ellen
Published: March 2021

Asymmetric warming resulting in a faster increase in night compared to day temperatures affects crop yields negatively. Physiological characterization and agronomic findings have been complemented more recently by molecular biology approaches including transcriptomic, proteomic, metabolomic and lipidomic investigations in crops exposed to high night temperature (HNT) conditions. Nevertheless, the understanding of the underlying mechanisms causing yield decline under HNT is still limited. The discovery of significant differences between HNT‐tolerant and HNT‐sensitive cultivars is one of the main research directions to secure continuous food supply under the challenge of increasing climate change. With this review, we provide a summary of current knowledge on the physiological and molecular basis of contrasting HNT tolerance in rice and wheat cultivars. Requirements for HNT tolerance and the special adaptation strategies of the HNT‐tolerant rice cultivar Nagina‐22 (N22) are discussed. Putative metabolite markers for HNT tolerance useful for marker‐assisted breeding are suggested, together with future research directions aimed at improving food security under HNT conditions.
Source:sink imbalance detected with leaf‐ and canopy‐level spectroscopy in a field‐grown crop
Authors: Burnett Angela C. , Serbin Shawn P. , Rogers Alistair
Published: March 2021

The finely tuned balance between sources and sinks determines plant resource partitioning and regulates growth and development. Understanding and measuring metabolic indicators of source or sink limitation forms a vital part of global efforts to increase crop yield for future food security. We measured metabolic profiles of Cucurbita pepo (zucchini) grown in the field under carbon sink limitation and control conditions. We demonstrate that these profiles can be measured non‐destructively using hyperspectral reflectance at both leaf and canopy scales. Total non‐structural carbohydrates (TNC) increased 82% in sink‐limited plants; leaf mass per unit area (LMA) increased 38% and free amino acids increased 22%. Partial least‐squares regression (PLSR) models link these measured functional traits with reflectance data, enabling high‐throughput estimation of traits comprising the sink limitation response. Leaf‐ and canopy‐scale models for TNC had R2 values of 0.93 and 0.64 and %RMSE of 13 and 38%, respectively. For LMA, R2 values were 0.91 and 0.60 and %RMSE 7 and 14%; for free amino acids, R2 was 0.53 and 0.21 with %RMSE 20 and 26%. Remote sensing can enable accurate, rapid detection of sink limitation in the field at the leaf and canopy scale, greatly expanding our ability to understand and measure metabolic responses to stress.
What you don't know might hurt me: Keeping secrets in interpersonal relationships
Authors: Bedrov Alisa , Leary Mark R.
Published: March 2021

Despite being an inherently interpersonal phenomenon, secrecy has rarely been studied within specific relationships. This study examines how the secret‐keeper's relationship with the target relates to concealment among undergraduates (n = 292) and MTurk workers (n = 249). Participants rated keeping a personal secret as more detrimental to well‐being when it involved greater concealment difficulty, rumination, and negative affect. For MTurk workers, this burden was compounded when the information was directly relevant to the target. Across both samples, participants in higher quality relationships kept their secrets to avoid shame or relationship damage and perceived less distance from the target. These results demonstrate that the motivations for and consequences of keeping secrets vary with the specific relationships in which they are kept.
Robust Bilevel Resource Recovery Planning
Authors: Xiong Jie , Wang Shuming , Ng Tsan Sheng
Published: March 2021

In this study, we consider a resource recovery planning problem under a public–private partnership. The local authority's problem is to determine the waste sorting scheme, and also a cost‐sharing budget, to minimize her expected payout, subject to a requirement of economic feasibility of the private operator. Given the budget and sorting scheme, the private operator's problem is to site and operate resource recovery facilities, and his goal is to maximize his expected total profits. A salient feature of the problem is that the feedstock condition (composition and volume) is uncertain, but can be influenced by the sorting‐at‐source scheme implemented. This feature drives the interactions of the public and private partners. We develop a bilevel resource recovery planning model in the framework of distributionally robust optimization, where a decision‐dependent ambiguity set is defined to model the influence of sorting schemes on the feedstock uncertainty. We perform the model analysis on the cost‐share ratio, which suggests the importance of sorting investment in achieving the sustainable resource recovery. Computationally, we show that the solutions of the bilevel problem can be obtained by solving one instance of a mixed‐integer linear program that does not induce any additional integer variable. Our proposed optimization framework provides a useful decision‐analysis tool for effectively utilizing and balancing the instruments of sorting and facility installation investments for resource recovery planning under feedstock ambiguity. For instance, the computational experiments with partial real data in the Singapore context justify several important insights: (i) the suitable sorting scheme implementation serves as a cost‐effective instrument that could significantly enhance the utility of the cost sharing; (ii) the sorting dependency of feedstock condition is critical in affecting the private operator's recovery performance; and (iii) the robust planning is effective in hedging against ambiguously poor feedstock condition. These findings should deserve attentions of both public and private sectors in current waste management practice.
The Value of Supply Chain Disruption Duration Information
Authors: Mehrotra Mili , Schmidt William
Published: March 2021

Companies that experience a disruption in their supply chain often face a difficult decision—either accept the information that they have regarding the duration of the disruption, or invest in collecting better information. This choice is not clear since better information may not be attainable, and if it is attainable, it may not improve operational decision‐making. In light of this dilemma, we collaborate with a multinational division of a Fortune 500 manufacturing firm to develop stochastic linear programming models that quantify the value of disruption duration information. Our models allow us to examine characteristics of the disrupted part that may be associated with the value of better information. We focus on characteristics that are knowable at the outset of the disruption, as those can help the firm decide whether to invest in collecting better information. Using our research partner's supply chain and production data, we find that the value of information can vary materially—from < 1% to over 99% of the cost of the disruption, underscoring the value of identifying disruptions that are sensitive to information quality. To address this, we use the company's data to identify several part‐related characteristics that influence the value of disruption duration information. These findings can help managers to identify parts in their own supply chains whose impact in a disruption is sensitive to different levels of duration information, and allow them to make informed decisions on whether or not to gather better information when a disruption strikes.
An Economic Analysis of Agricultural Support Prices in Developing Economies
Authors: Guda Harish , Dawande Milind , Janakiraman Ganesh , Rajapakshe Tharanga
Published: March 2021

The goals of the guaranteed support price (GSP) scheme, adopted by several developing countries to support their farmers and the underprivileged population, are threefold: (a) as a supply‐side incentive, to ensure high output from the farmers, (b) as a demand‐side provisioning tool, to subsidize the consumption needs of the poor, and (c) to maintain an adequate amount of foodgrains as reserve stock, to mitigate the adverse effects of yield uncertainty (food security). We offer analytically supported insights on the fundamental aspects of this scheme by analyzing a Stackelberg game between a homogenous population of small farmers and a social planner. We model the strategic behavior of the farmers and the consuming population (Above‐ and Below‐Poverty‐Line consumers), and compare the equilibrium outcome with that under the direct benefit transfer (DBT) scheme, where the social planner simply distributes the budget among the BPL consumers. The comparison of the social planner's surplus depends on the marginal value from maintaining a reserve stock (i.e., the significance of food security). If this value is high, then the surplus under the GSP scheme strictly dominates that under DBT; otherwise, the surplus is identical. The comparison of the production by the farmers depends on two economic forces—the poorness of the BPL consumers and yield uncertainty. If the poorness is extreme, then the two schemes lead to identical production. If yield uncertainty is dominant, then DBT is ineffective in improving production while the GSP scheme can induce a strictly higher production by strategically choosing the reserve stock.
Integrating genomics in population models to forecast translocation success
Authors: Seaborn Travis , Andrews Kimberly R. , Applestein Cara V. , Breech Tyler M. , Garrett Molly J. , Zaiats Andrii , Caughlin T. Trevor
Published: March 2021

Whole‐genome sequencing is revolutionizing our understanding of organismal biology, including adaptations likely to influence demographic performance in different environments. Excitement over the potential of genomics to inform population dynamics has prompted multiple conservation applications, including genomics‐based decision‐making for translocation efforts. Despite interest in applying genomics to improve translocations, there is a critical research gap: we lack an understanding of how genomic differences translate into population dynamics in the real world. We review how genomics and genetics data could be used to inform organismal performance, including examples of how adaptive and neutral loci have been quantified in a translocation context, and future applications. Next, we discuss three main drivers of population dynamics: demographic structure, spatial barriers to movement, and introgression, and their consequences for translocations informed by genomic data. Finally, we provide a practical guide to different types of models, including size‐structured and spatial models, that could be modified to include genomics data. We then propose a framework to improve translocation success by repeatedly developing, selecting, and validating forecasting models. By integrating lab‐based and field‐collected data with model‐driven research, our iterative framework could address long‐standing challenges in restoration ecology, such as when selecting locally adapted genotypes will aid translocation of plants and animals.
Continuous renal replacement therapy in patients treated with extracorporeal membrane oxygenation
Authors: Selewski David T. , Wille Keith M.
Published: March 2021

Extracorporeal membrane oxygenation (ECMO) is a life‐saving therapy utilized for patients with severe life‐threatening cardiorespiratory failure. Patients treated with ECMO are among the most severely ill encountered in critical care and are at high‐risk of developing multiple organ dysfunction, including acute kidney injury (AKI) and fluid overload. Continuous renal replacement therapy (CRRT) is increasingly utilized inpatients on ECMO to manage AKI and treat fluid overload. The indications for renal replacement therapy for patients on ECMO are similar to those of other critically ill populations; however, there is wide practice variation in how renal supportive therapies are utilized during ECMO. For patients requiring both CRRT and ECMO, CRRT may be connected directly to the ECMO circuit, or CRRT and ECMO may be performed independently. This review will summarize current knowledge of the epidemiology of AKI, indications and timing of CRRT, delivery of CRRT, and the outcomes of patients requiring CRRT with ECMO.
Focused methane migration formed pipe structures in permeable sandstones: Insights from uncrewed aerial vehicle‐based digital outcrop analysis in Varna, Bulgaria
Authors: BÖttner Christoph , Callow Ben J. , Schramm Bettina , Gross Felix , Geersen Jacob , Schmidt Mark , Vasilev Atanas , Petsinski Petar , Berndt Christian
Published: March 2021

Focused fluid flow shapes the evolution of marine sedimentary basins by transferring fluids and pressure across geological formations. Vertical fluid conduits may form where localized overpressure breaches a cap rock (permeability barrier) and thereby transports overpressured fluids towards shallower reservoirs or the surface. Field outcrops of an Eocene fluid flow system at Pobiti Kamani and Beloslav Quarry (ca 15 km west of Varna, Bulgaria) reveal large carbonate‐cemented conduits, which formed in highly permeable, unconsolidated, marine sands of the northern Tethys Margin. An uncrewed aerial vehicle with an RGB sensor camera produces ortho‐rectified image mosaics, digital elevation models and point clouds of the two kilometre‐scale outcrop areas. Based on these data, geological field observations and petrological analysis of rock/core samples, fractures and vertical fluid conduits were mapped and analyzed with centimetre accuracy. The results show that both outcrops comprise several hundred carbonate‐cemented fluid conduits (pipes), oriented perpendicular to bedding, and at least seven bedding‐parallel calcite cemented interbeds which differ from the hosting sand formation only by their increased amount of cementation. The observations show that carbonate precipitation likely initiated around areas of focused fluid flow, where methane entered the formation from the underlying fractured subsurface. These first carbonates formed the outer walls of the pipes and continued to grow inward, leading to self‐sustaining and self‐reinforcing focused fluid flow. The results, supported by literature‐based carbon and oxygen isotope analyses of the carbonates, indicate that ambient seawater and advected fresh/brackish water were involved in the carbonate precipitation by microbial methane oxidation. Similar structures may also form in modern settings where focused fluid flow advects fluids into overlying sand‐dominated formations, which has wide implications for the understanding of how focusing of fluids works in sedimentary basins with broad consequences for the migration of water, oil and gas.
Utility of high‐frequency ultrasound in assessing cutaneous edema in venous ulcer patients
Authors: Pragasam Shakthi , Kumari Rashmi , Munisamy Malathi , Mohan Thappa Devinder
Published: March 2021

Background

High‐frequency ultrasound (HFUS) using a 20 MHz probe is a non‐invasive assessment tool. Its utility in dermatology for diagnosis of disease or for monitoring of treatment response in various dermatological conditions is still being explored. Edema secondary to venous hypertension is the main pathogenic factor in the development of venous leg ulcers. However, there is no objective method for assessment of degree of edema. In this study, we explore the utility of high‐frequency ultrasound in assessing cutaneous edema and for monitoring its improvement with compression therapy among patients with venous ulcer.

Materials and Methods

Twenty patients with venous ulcer were enrolled in the study. Measurement of cutaneous edema was done at baseline and after 2 weeks of compression therapy in all patients. The 3 levels of measurement were dorsum of foot (low site, L1), 4 cm proximal to the medial malleolus (middle site, L2), and the medial aspect of the calf between the medial malleolus and the knee (upper site, L3).

Results

Baseline subepidermal low echogenic band (SLEB) measurements were 2.46 ± 0.69 mm, 2.94 ± 0.65 mm, and 2.66 ± 0.64 mm at L1, L2, and L3, respectively. There was a significant reduction in SLEB measurement after compression therapy ( p values 0.008, 0.002, and 0.003 at L1, L2, and L3, respectively). The mean percentage reduction in SLEB at level of medial malleolus (mid level ‐ 29.61 ± 12.24) was higher than the other 2 sites (L1‐22.45 ± 15.83 and L3 were 27.57 ± 12.34).

Conclusion

Cutaneous ultrasound aids in accurate assessment of level and severity of edema. Hence, it can be utilized in trials to objectively assess the adequacy of treatment for patients with venous insufficiency.
Introduction of glucan synthase into the cytosol in wheat endosperm causes massive maltose accumulation and represses starch synthesis
Authors: Schreier Tina B. , Fahy Brendan , David Laure C. , Siddiqui Hamad , Castells‐Graells Roger , Smith Alison M.
Published: March 2021

We expressed a bacterial glucan synthase (Agrobacterium GlgA) in the cytosol of developing endosperm cells in wheat grains, to discover whether it could generate a glucan from cytosolic ADP‐glucose. Transgenic lines had high glucan synthase activity during grain filling, but did not accumulate glucan. Instead, grains accumulated very high concentrations of maltose. They had large volumes during development due to high water content, and very shrivelled grains at maturity. Starch synthesis was severely reduced. We propose that cytosolic glucan synthesized by the glucan synthase was immediately hydrolysed to maltose by cytosolic β‐amylase(s). Maltose accumulation resulted in a high osmotic potential in developing grain, drawing in excess water that stretched the seed coat and pericarp. Loss of water during grain maturation then led to shrinkage when the grains matured. Maltose accumulation is likely to account for the reduced starch synthesis in transgenic grains, through signalling and toxic effects. Using bioinformatics, we identify an isoform of β‐amylase likely to be responsible for maltose accumulation. Removal of this isoform through identification of TILLING mutants or genome editing, combined with co‐expression of heterologous glucan synthase and a glucan branching enzyme, may in future enable elevated yields of carbohydrate through simultaneous accumulation of starch and cytosolic glucan.
Analysis of Shroud and Disk Heat Transfer in Aero-Engine Compressor Rotors
Authors: Jackson Richard W. , Tang Hui , Scobie James A. , Pountney Oliver J. , Sangan Carl M. , Owen J. Michael , Lock Gary D.
Published: March 2021

Heat transfer within the rotating compressor cavity of an aero-engine is predominantly governed by buoyancy, which can be characterized by the Grashof number. Unsteady and unstable buoyancy-induced flow structures influence the temperatures and stresses in the compressor rotors, and these affect the radial growth of the disks. In addition, the heat transfer from the disks and shroud increases the temperature of the throughflow of cooling air. This paper contains two connected parts. First, a heat transfer correlation for the shroud of a rotating cavity was determined from steady-state heat flux measurements collected in the bath compressor-cavity rig at engine-simulated conditions. The Nusselt numbers were based on the cavity air temperature adjacent to the shroud, which was predicted using the Owen–Tang buoyancy model. Heat transfer from the shroud was consistent with free convection from a horizontal plate in a gravitational field. Maximum likelihood estimation was used with a Rayleigh–Bénard equation to correlate the shroud Nusselt number with the local Grashof number. Second, an energy balance was used to calculate the enthalpy rise of the axial throughflow from the measured disk and shroud heat fluxes. Disk fluxes were derived from radial distributions of measured steady-state disk temperatures using a Bayesian model and the equations for a circular fin. The calculated throughflow temperature rise was consistent with direct thermocouple measurements. The complex, three-dimensional flow near the cavity entrance can result in enthalpy exchange penetrating upstream in the throughflow, and rotationally induced flow can create upstream axial flow in the outer part of the annulus.
Workflow-Based Design and Evaluation of a Device for CBCT-Guided Biopsy
Authors: Pfeil A. , Barbé L. , Geiskopf F. , Cazzato R. L. , Renaud P.
Published: March 2021

Biopsies for personalized cancer care can be performed with cone beam computed tomography (CBCT) guidance, but manual needle manipulation remains an issue due to X-ray exposure to physicians. Modern CBCT scanners integrate today real-time imaging and software assistance for needle planning. In this paper, these available features are exploited to design a novel device offering an intermediate level of assistance between simple passive mechanical devices of limited efficiency, and advanced robotic devices requiring adapted procedure workflows. Our resulting system is built to limit its impact on the current manual practice. It is patient-mounted and provides remote control of needle orientation and insertion. A multilayer phantom is specifically developed to reproduce interactions between the needle and soft abdominal tissues. It is used to experimentally evaluate the device added value by comparing assisted versus manual needle insertions. The device is shown to help reducing X-ray exposure by a factor 4, without impacting the accuracy obtained manually.
A Knowledge Based Automatic Pipe Routing System
Authors: Jain D. , Chatterjee M. , Unemori A. , Thangam N.
Published: March 2021

The pipe routing problem, wherein layout of one or more pipes has to be decided in a 3-dimensional space while satisfying several different types of constraints, has attracted significant attention recently. This paper describes a knowledge-based automated pipe routing system which generates practical routes that meet several diverse criteria. The system employs intelligent search (with embedded design constraints) upon a compact representation of the free space in a facility, thus avoiding expensive interference checks and adjustments that must be performed in some of the other systems.
A Graphic Simulator for the Study of Robotic Tracking and Catching Operations
Authors: Côte Jean , Gosselin Clément , Laurendeau Denis
Published: March 2021

This paper presents a real time robot simulator running on a Silicon Graphics Personal IRIS workstation. In addition to the simulator, we introduce a new approach to compute the inverse kinematic functions whose domain of solution is not limited to the manipulator’s workspace. Using this approach, every point in the Cartesian space leads to a real solution when used as data for the inverse kinematic problem. The solution gives the minimum distance between the end-effector and the prescribed point in the Cartesian space. The proposed inverse kinematic functions are of great interest for tracking, approach and catching operations where the object to be reached or tracked by the manipulator is inside or outside the robot’s workspace. With the simulator, we can easily build any kind of manipulator and describe it using the Hartenberg-Denavit convention.
Simulation of Large and Complex Structures With Multiple Contacts and Wear
Authors: Bagepalli B. S. , Dinc S. , Jlidi B. , Imam I. , Barnes J. , Slocum C.
Published: March 2021

This paper deals with the simulation methodology of large and complex structures with multiple contacts and wear. The methodology developed is used to evaluate the dynamics and wear of gas turbine combustors. A unified approach of representing multiple rigid/elastic bodies with numerous contacts is developed. Representation is made, too, of the changing nature of these contacts — both geometric and material. The entire methodology is implemented in a generic and easy-to-use simulation code which serves as a useful generic design/analysis evaluation tool MAP (Mechanism Analysis Program). Appropriate analytical models for inter-material constitutive laws — both incremental (contact friction, pressure, damping, etc.) and cumulative (wear theories) — are incorporated in the tool.

As applications of this approach, dynamic simulations of two different gas turbine combustor designs are run, and comparisons are made with real systems. Excellent correlations have been obtained, both with respect to laboratory test (accelerometer) data, and wear patterns at various contacts and junctions on field samples.
Using Automatic Feature Recognition to Interface CAD to CAPP
Authors: Wang Eric
Published: March 2021

Interfacing CAD to CAPP (computer-aided process planning) is crucial to the eventual success of a fully-automated computer-integrated manufacturing (CIM) environment. Current CAD and CAPP systems are separated by a “semantic gap” that represents a fundamental difference in the ways in which they represent information. This semantic gap makes the interfacing of CAD to CAPP a non-trivial task.

This paper argues that automatic feature recognition is an indispensable technique in interfacing CAD to CAPP. It then surveys the current literature on automatic feature recognition methods and systems, and analyzes their suitability as CAD/CAPP interfaces. It also describes a relatively recent automatic feature recognition method based on volumetric decomposition, using Kim’s alternating sum of volumes with partitioning (ASVP) algorithm. The paper’s main theses are: (1) that most previous automatic feature recognition approaches are ultimately based on pattern-matching; (2) that pattern-matching approaches are unlikely to scale up to the real world; and (3) that volumetric decomposition is an alternative to pattern-matching that avoids its shortcomings. The paper concludes that automatic feature recognition by volumetric decomposition is a promising approach to the interfacing of CAD to CAPP.
Vehicle Occupant Crash Simulation Using SuperCrash
Authors: Huang Shyh-Chour , Jair Joy Yir-Shyuan
Published: March 2021

The objective of this paper is to investigate the effect of restraining belt systems in restricting occupant motion during a crash-victim environment.

The study is conducted using a pc-based computer simulator — SuperCrash. In the study, the dynamic response of a passenger seated in back seat is simulated during a frontal impact environment.
A Study of a Sharp 90 Degree Curved Flow
Authors: Kim R. H.
Published: March 2021

An investigation of air flow along a 90 degree elbow-like tube is conducted to determine the velocity and temperature distributions of the flow. The tube has a sharp 90 degree turn with a radius of curvature of almost zero. The flow is assumed to be a steady two-dimensional turbulent flow satisfying the ideal gas relation. The flow will be analyzed using a finite difference technique with the K-ε turbulence model, and the algebraic stress model (ASM). The FLUENT code was used to determine the parameter distributions in the passage. There are certain conditions for which the K-ε model does not describe the fluid phenomenon properly. For these conditions, an alternative turbulence model, the ASM with or without QUICK was employed. FLUENT has these models among its features. The results are compared with the result computed by using elementary one-dimensional theory including the kinetic energy loss along the passage of the sharp 90 degree curved tube.
Numerical Modeling of Flame Lift-Off Phenomenon in a Combustion Chamber With Three Cylinder Methane Fuel Injector
Authors: Mohieldin T. O. , Chaturvedi S. K.
Published: March 2021

This work summarizes results for a three cylinder fuel injector that has been adopted as a model for investigating combustion phenomenon in the 8-Foot High Temperature Tunnel (HTT) at NASA Langley Research Center. The primary objective here is to understand the flame lift-off phenomenon in the three cylinder fuel injector geometry in two-dimensions. Three chemistry models, namely fast chemistry, one-step kinetics and two-step kinetics are employed in conjunction with a computational fluid dynamics code to analyze the flame structure and flame lift-off characteristics downstream of the fuel injector.

Effects of fuel jet velocity and chemistry model on the flame lift-off phenomenon from the injector surface are analyzed by considering simultaneously the combined convection (outside the cylinders) and conduction (inside the cylinders). Results indicate that as the fuel jet velocity is increased, the flame is transformed from a wrap around configuration to a clearly lifted flame configuration. Of the three chemistry models considered in the present study, only the two-step chemistry model predicts a clearly lifted flame. The ability of the CFD code to predict lifted flame is important since a slightly lifted but stable flame is of paramount importance to the operation of the combustor.
Combustion Flowfield Prediction for CVD Diamond Synthesis
Authors: Dong Mingchun , Lilley David G.
Published: March 2021

A computer code has been developed to simulate the combustion flowfield of an axisymmetric jet flame impinging normally on to a flat plate. Premixed oxygen and acetylene emerges from the jet nozzle, and complexities include turbulence and high temperature chemical kinetics. In CVD diamond synthesis, parameters of interest include the fuel-oxygen ratio and the distance from the heat nozzle to the surface. Combustion flow field predictions are given for acetylene and oxygen flames (all fuel rich), axisymmetric-vertical impingement on an adiabatic surface to show the effects of varying the nozzle-substrate separation distance, nozzle size, overall equivalence ratio and flow rate on the flowfield and substrate temperature. These have been shown to have dramatic effects on the rate of diamond growth on the surface.
An Analytical Interpretation of High Strain Rate Material Behavior During Early Time Plastic Deformation in the Taylor Impact Test
Authors: Jones S. E. , Maudlin Paul J. , Gillis Peter P. , Foster Joseph C.
Published: March 2021

Using information from experiments and continuum mechanics code calculations, an analytical stress/strain-rate relation is developed. This relation is valid during the early time plastic deformation phase of the Taylor impact test. The results show good correlation between experiment and the continuum code predictions.
Constitutive Modeling of Composite Laminates With Progressive Ply Cracking
Authors: Hahn H. T. , Kiusalaas J. , Burns B. P. , Bogetti T. A.
Published: March 2021

A computational procedure is proposed to determine effective constitutive relations for composite laminates with progressive cracking. The procedure is based on the assumption that the effective stiffness of a cracked ply in a laminate can be determined by analyzing the cracked ply by itself independent of the rest of the laminate. A polynomial failure criterion is used to predict ply cracking using effective ply stresses. The procedure provides a full set of effective laminate stiffnesses as well as crack densities in constituent plies.
Stability Considerations of Primary Loadings of a Stepladder
Authors: Collins David , Kaplan Mitchell P. , Czerwinski James
Published: March 2021

The effects of certain loadings on a stepladder are investigated using finite element analysis. The ladder considered is a light-duty six-foot aluminum stepladder with the user standing on the fourth step. The loading results from the user’s weight and from his exerting a horizontal force against a fixed object to his right. The analyses show that as long as all four feet of the ladder are constrained not to move on the floor, structural deflections and stresses are acceptable. However, if the right two feet are allowed to move, a moderate push can result in sudden collapse of the ladder.

Further analyses demonstrate that torsional compliances within the structure, which also allow tolerance for an irregular floor, are the major structural participants in this instability, and that the rigidity and strength of the entire structure can be substantially increased by the stiffening of certain substructural components.
Integrating Concurrent Engineering and FEA Into Engineering Technology Programs
Authors: Kitto Kathleen L.
Published: March 2021

Strategies involved in concurrent engineering are being integrated into the engineering technology programs at Western Washington University Because finite element analysis (FEA) is an integral part of concurrent engineering, it too has been added to the curriculum Students explore such topics as design for manufacturability, lifetime ownership factors, world class manufacturing, building in quality and time-to-market, even in their first engineering technology course. Students are first introduced to FEA in basic mechanics courses. Then they take a more complete FEA project course in the senior year In that course, students use FEA to model components, and verify their models in the laboratory.

This paper describes the concurrent engineering integration efforts at Western Washington University and includes course outlines and laboratory examples Examples from student projects are given. The paper also addresses the issues complicating the integration of analysis and simultaneous engineering into engineering technology programs.
Global Local Finite Element Method (GLFEM) in Gear Tooth Stress Analysis
Authors: Moriwaki I. , Fukuda T. , Watabe Y. , Saito K.
Published: March 2021

The present study is concerned with an application of the Global Local Finite Element Method (GLFEM) to a gear tooth stress analysis. The GLFEM is a numerical analysis technique which combines finite element solutions and classical analytical ones on the basis of the energy principle. In this method, the classical analytical solutions give an almost exact stress field to the elements in which the stress varies very rapidly and/or the stress concentration is found. A fine subdivision, therefore, is not required.

In the application of the conventional finite element method to the gear tooth stress analysis, the fine subdivision is required especially at the positions near tooth bottom and the load applied point. Hence, only two dimensional analysis is available for common use. Furthermore, in order to determine an exact location of a critical section on which a fillet stress is maximum, we must use complicated procedures, e.g. an iteration of subdivision for searching the maximum nodal stress.

In the present paper, the GLFEM is applied to the gear tooth stress analysis to show that even the rough subdivision enables us to make the precise three dimensional analysis. It also guarantees an easy determination of the critical section. Thus, we show the effective future of the GLFEM to the gear tooth stress analysis.
Computer Simulation of Torsional Waves in a Single Gear Transmission
Authors: Mioduchowski A. , Nadolski W.
Published: March 2021

The theory of one dimensional torsional elastic waves is used for the dynamical analysis of a discrete-continuous model of a single gear transmission. The method allows for the calculation of results either as functions of time or as functions of location. These results can be put together into a 3D time-space display offering an interesting tool in simulation of torsional waves in a single gear transmission.
A General Formula for Determining the Normal to the Path of Contact in Parallel-Axis Gearing
Authors: Chen Chih-Hsin , Wang Yuri , Colbourne John R.
Published: March 2021

A formula is derived for determining the normal to the path of contact in parallel-axis gearing. The formula can be used to predict the onset of undercutting or interference in non-involute profiles.
The Influence of Flank Deviations on the Vibration of a Helical Gear Pair Transmitting Light Load
Authors: Umezawa Kiyohiko , Houjoh Haruo , Matsumura Shigeki
Published: March 2021

This paper introduces a simulator which can depict the rotational vibration of a helical pair having any kind of deviations transmitting light load. Under light load condition the contact pattern does not extend to full length of ideal contact tooth surface. Under this condition, the determination of the contact pattern sometimes become very sensitive to the numerical calculation error. In the worst cases, calculation leap into endless loop. The developed simulator was improved robuster.

This paper firstly derives how we can obtain the relationship between the deflection and the load distribution of single pair of mating teeth. Secondary, the determination method of multi tooth pair load sharing is introduced. Afterwards, the simulation is experimentally verified with various kinds of tooth flank deviations.

Through this study, an easy design method to realize a low vibration helical gear is suggested.
Tooth Surface Fatigue of AISI9310 Steel Spur Gears
Authors: Kotorii H.
Published: March 2021

With a JIS 0 class Spur Gears of AISI9310 steel, module 4, presure angle 25 degree tooth profile, the numbers of pinion teeth 21 / gear teeth 29 carburized and tooth surface hardness HRc 59, the relationships of the load and the service life (S-N) diagram were investigated by running test on the power-circulated type gear tester.

MIL-L-23699 equivalent synthetic oil at 50° C were fed at a ratio of 0.8 l/min and circumferential velocity of 8.8 m/sec.

Also the running performance of the gears, variation of tooth profile errors, affairs of damage, etc. were examined.

Types of tooth surface fatigue mere scoring, spalling, or micropitting.

A durability limit of Hertz-stress was assumed to be around 2GPa at the load cycle of 108.
A General Method for Computing the Distance Between Two Moving Objects Using Optimization Techniques
Authors: Ma Ou , Nahon Meyer
Published: March 2021

Presented in this paper is a general method used to find the distance between two moving objects. This distance is defined as the length of the shortest path from one object to the other. The objects are assumed to be composed of arbitrary quadratic surface segments. The distance problem is formulated as a quadratic programming problem with linear and/or quadratic constraints, which is solved by efficient and robust quadratic programming techniques. Attention is focused on implementation in order to achieve computational efficiency for real-time applications. Computing tests show that the computational speed of this method is of linear order in terms of the total number of bounding surfaces of the two objects. It is also shown that, with a minor modification, this method can be used to calculate the interference between objects. A corresponding general software code has been implemented, and will be used for kinematics and dynamics modelling and simulation of space manipulators including situations with transient topologies, contact of environment, and capture/release of payloads.
Design of Machine Tool Spindle for Minimum Workpiece Cylindricity Error
Authors: Li John , Musukula Vijayachander , Trabia Mohamed B.
Published: March 2021

The design of machine tool spindle for minimum cylindricity error is presented. The shape of the spindle portion between the bearings, usually cylindrical, is reconfigured to increase the spindle rigidity. Two methods of reconfiguration are presented. In the first method, the spindle is reshaped as a smooth body of revolution. In the second method, the spindle is reshaped as a stepped shaft. Effects of bearings rigidity and fatigue stresses are also considered.
Design of an Aircraft Tire: A Study in Modeling Uncertainty
Authors: Vadde S. , Swadi S. , Bhattacharya N. , Mistree F. , Allen J. K.
Published: March 2021

During the early stages of project initiation, the information available to a designer may be uncertain (imprecise or stochastic). In response to this need, two extensions of the crisp compromise Decision Support Problem using fuzzy set theory and Bayesian statistics are developed to model uncertainty in design problems. The fuzzy compromise DSP is used to model imprecise information and the Bayesian compromise DSP is used to model stochastic information. The design of an aircraft tire is used as an illustrative example.
Modeling and Dynamic Analysis of the Suspension System of a Front Loaded Washing Machine
Authors: Türkay O. S. , Sümer I. T. , Tuğcu A. K.
Published: March 2021

A non-linear time invariant dynamic model of the suspension system of a front-loaded washing machine has been formulated, programmed for simulation, and assessed experimentally A drum mounted in a tub which is hung to the cabinet by three linear helical springs and supported by two dry-friction dampers rotates together with an eccentric laundry mass. The displacement responses due to centrifugal excitation have been obtained for the spin-dry cycle ranging from 0rpm to 650rpm until steady-state has been reached The comparison of simulation and experimental results has demonstrated the validity of the model by predicting the steady-state and transient peak-to-peak vertical and horizontal amplitudes within 5% and 11% errors, respectively The mechanical performance and the “striking” and “stepping” phenomena can be assessed for prototype design purpose by undertaking a parametric investigation to the end of optimizing the design.
Direct Position Analysis of the 4-6 Stewart Platforms
Authors: Chen Ning-Xin , Song Shin-Min
Published: March 2021

Although Stewart platforms have been applied in the designs of aricraft and vehicle simulators and parallel robots in many years, their closed-form solution of direct (forward) position analysis has not been completely solved. Up to the present time, only the relatively simple Stewart platforms have been analyzed. Examples are the octahedral Stewart and the 4-4 Stewart platforms, in which two pairs of both upper and lower joint centers are coincident. The former results in in an eighth degree polynomial and the latter results in an eighth and a twelfth degree polynomials for different cases. The single unknown variable is in the form of square of a tan-half-angle. This paper further extends the direct position analysis to a more genearl case of the Stewart platform, the 4-6 Stewart platforms, in which two pairs of upper joint centers of adjacent limbs are coincident. The result is a sixteenth degree polynomial in the square of a tan-half-angle, which indicates that a maximum of 32 configurations may be obtained. It is also shown that the previously derived solutions of 4-4 and and 3-6 Stewart platforms can be easily deduced from the sixteenth degree polynomial by setting some geometric parameters be equal to 1 or 0.
A Finite Element Formulation for the Dynamic Analysis of Machine Components Fabricated From Composite Materials
Authors: Semos A. , Chassapis C.
Published: March 2021

In this paper finite element procedures are presented for analyzing the elastic-dynamic behavior of mechanical components fabricated from fiber-reinforced composite materials. An arbitrarily laminated composite plate element is created which allows the analysis of components that are moving in three dimensional space. The five D.O.F. per node static model of S. C. Panda and R. Natarajan is used as a basis for the derivation of the dynamic model. The elemental equations of motion are derived from Hamilton’s Principle. The formulation considers the total kinetic and strain energies of the moving element, together with the work due to bending, caused by the transversely acting external forces, as well as that due to the foreshortening of the element, caused by axially applied loads.
Instability and Chaos in Quadruped Gallop
Authors: Nanua Prabjot , Waldron Kenneth J.
Published: March 2021

A dynamic model for the two dimensional quadruped has been developed. The main body is modelled as a rigid bar and each leg consists of a constant stiffness spring, a viscous damper and a force actuator. Based on symmetry principles, a controller has been devised that will enable the quadruped to gallop at constant speed. The controller consists of two parts: an energy controller which will apply the required amount of force through the legs, and the speed controller that will control the forward speed by appropriately placing the legs. It will be shown that the body pitch need not be explicitly controlled. The stability of this controller will be examined using Poincare maps. Stable systems show either periodic or quasi-periodic response. This system also exhibits chaotic behavior and chaotic response leads to instability. The stability of the system with changes in the initial conditions, as well as variations in the system parameters, will also be examined. It will be shown that the system is stable for a range of leg stiffnesses. Outside this range, the system shows chaotic behavior.
Transmission Error Analysis of a Parallel Symmetric Geared Linkage Mechanism
Authors: Yang Ji-Hou
Published: March 2021

Many machine systms consist of parallel symmetric mechanisms, but-the unsymmetric force transmission between two sides may often happen, due to the dimentional errors of mechanism and the clearences in the kinematic pairs. This makes a machine of low efficiency and bad power transmission capacity.

In this work, as a model of a punch press, a parallel symmetric geared crank and slider mechanism is analyzed about the unsymmetric input torque and the reactions in the kinematic pairs between two sides due to the errors of input angle and radius of crank. The behavior of journal clearences during the force transmitting process are also considered.

The analyzed results are well suit to the experimental results and hence have actual use to the design and manufacturing of machine.
Evaluation Criteria for Conceptual Designs of Deployable-Foldable Truss Structures
Authors: Warnaar Dirk B.
Published: March 2021

Techniques for the creative design of deployable-foldable truss structures have recently been developed to result in the generation of all possible designs for some given general characteristics of the structure [1–4]. This article discusses the development of evaluation criteria for these designs, so that the process of selection and enumeration of desirable candidates can be facilitated. To accommodate the evaluation of large numbers of conceptual designs, special attention is given to the development of criteria that are suitable for implementation in automated procedures for the design selection. Examples are provided that demonstrate the use of these criteria in a design selection process.
Automated Cam-Mechanism Synthesis and Analysis
Authors: Eventoff Arnold T.
Published: March 2021

An automated computer-based method for deriving the shape of machine elements such as cams is described for complex mechanisms. Traditional cam synthesis concentrates on follower motion; the method described here enables complete control of the required output motion. Output motion is defined for any constant or variable camshaft velocity. The process is not limited by the degrees of freedom, follower shape, follower suspension, or complexity of the mechanism linking followers to output points.

The method includes a velocity analysis to predict cam shape, pressure angle, and relative velocity of the follower with respect to the cam. This analysis allows immediate visual inspection and further dynamic and wear analyses. Cam-follower contact stress is readily calculated for an entire cycle of motion during the synthesis process.

An example consisting of a five-bar linkage displaced by three cams is synthesized using the methodology. The general method described facilitates development of mechanisms previously not feasible using conventional methods. Servomotor command displacement profiles required for complex systems can also be derived using this method.