bluuebunny/crossref_metadata_2025 huggingface dataset:
Unraveling plant strategies in tidal marshes by investigating plant traits and environmental conditions
Authors: Schulte Ostermann Tilla , Heuner Maike , Fuchs Elmar , Temmerman Stijn , Schoutens Ken , Bouma Tjeerd J. , Minden Vanessa
Published: April 2021

Aims

Tidal marsh vegetation along estuaries is exposed to strong environmental gradients that determine which species — enabled through specific traits — can establish and persist. With these ecosystems under anthropogenic pressure, in‐depth knowledge on the conservation of remaining tidal wetlands and restoration potentials is needed. In this study we elaborate the habitat conditions in the natural vegetation of the Elbe estuary and analyze: (a) which abiotic factors drive species composition; and (b) which species traits are key to the plants’ strategies in this specific ecotone.

Location

Three sites in the Elbe estuary (river kilometer 671–703).

Methods

We collected data on soil nutrients, inundation period and wave height and sampled traits of the 17 most abundant plant species, which we analyzed by RLQ (three‐table analysis, including environment variables [R], species abundance [L] and a species traits table [Q]).

Results

We detected a strong ˈwave–disturbance–inundation gradientˈ, which separated sparsely vegetated low‐lying plots receiving high wave impact and exposed to long inundation periods, from high‐lying plots showing dense vegetation and aerated soils. Close to the shore, plants showed low organ density and high investment into rhizomes, with a correlation of 0.72 between mass fraction of rhizome and phosphorus content of rhizome tissue. On higher elevations, plants strongly expressed traits relating to competition, like high allocation to stem biomass. Further, we found species with high leaf chlorophyll content showing low specific leaf area values and a negative correlation with the nutrient gradient.

Conclusion

The results of our study are particularly relevant for restoration measures in order to re‐establish healthy marsh vegetation. However, changes in the environmental conditions, for instance stronger wave energies by a higher shipping frequency in the river channel and sea level rise may trigger changes in species composition through plant trait adaptations, for example by demanding a stem flexibility beyond what would be structurally feasible.
HEXOKINASE1 signalling promotes shoot branching and interacts with cytokinin and strigolactone pathways
Authors: Barbier Francois F. , Cao Da , Fichtner Franziska , Weiste Christoph , Perez‐Garcia Maria‐Dolores , Caradeuc Mathieu , Le Gourrierec José , Sakr Soulaiman , Beveridge Christine A.
Published: April 2021

Plant architecture is controlled by several endogenous signals including hormones and sugars. However, only little information is known about the nature and roles of the sugar signalling pathways in this process. Here we test whether the sugar signalling pathway mediated by HEXOKINASE1 (HXK1) is involved in the control of shoot branching.

To test the involvement of HXK1 in shoot branching and in the hormonal network controlling this process, we modulated the HXK1 pathway using physiological and genetic approaches in rose, pea and arabidopsis.

Mannose‐induced HXK signalling triggered bud outgrowth in rose and pea. In arabidopsis, both HXK1 deficiency and defoliation led to decreased shoot branching and conferred hypersensitivity to auxin. Complementation of the HXK1 knockout mutant gin2 with a catalytically inactive HXK1, restored shoot branching to the wild‐type level. HXK1‐deficient plants displayed decreased cytokinin levels and increased expression of MAX2, which is required for strigolactone signalling. The branching phenotype of HXK1‐deficient plants could be partly restored by cytokinin treatment and strigolactone deficiency could override the negative impact of HXK1 deficiency on shoot branching.

Our observations demonstrate that HXK1 signalling contributes to the regulation of shoot branching and interacts with hormones to modulate plant architecture.
The MdMYB16/MdMYB1‐miR7125‐MdCCR module regulates the homeostasis between anthocyanin and lignin biosynthesis during light induction in apple
Authors: Hu Yujing , Cheng Hao , Zhang Yan , Zhang Jie , Niu Shuqing , Wang Xingsui , Li Wenjing , Zhang Jie , Yao Yuncong
Published: April 2021

Light induces anthocyanin accumulation and hence decides the coloration of apple fruit. It also plays a key role in regulating the biosynthesis of other secondary metabolites. However, the crosstalk between anthocyanin and lignin metabolism during light induction, which affects the edible quality and visual quality of apple fruit, respectively, have rarely been characterized.

In this study, we identified and functionally elucidated the roles of miR7125 and its target, cinnamoyl‐coenzyme A reductase gene (CCR), in regulating the homeostasis between anthocyanin and lignin biosynthesis during light induction. Overexpressing miR7125 or inhibiting CCR transiently in apple fruit promoted anthocyanin biosynthesis but reduced lignin production under light‐induced conditions. Consistently, opposite results were observed under the background of repressed miR7125 or overexpressed CCR.

We found that the repressor MdMYB16 and the activator MdMYB1 bound to the miR7125 promoter. Transient repression of MdMYB16 upregulated miR7125 expression significantly, accompanied by decreased levels of MdCCR transcript, resulting in a reduction in the lignin biosynthesis and an increase in anthocyanin accumulation. However, transient overexpression of MdMYB16 produced the opposite effects to MdMYB16‐RNAi.

The results reveal a novel mechanism by which the MdMYB16/MdMYB1‐miR7125‐MdCCR module collaboratively regulates homeostasis between anthocyanin and lignin biosynthesis under light induction in apple.
Temporal and sociocultural effects of human colonisation on native biodiversity: filtering and rates of adaptation
Authors: Amiot Christophe , Ji Weihong , Ellis Erle C. , Anderson Michael G.
Published: April 2021

Modern human societies have negatively impacted native species richness and their adaptive capacity on every continent, in clearly contrasting ways. We propose a general model to explain how the sequence, duration and type of colonising society alter native species richness patterns through changes in evolutionary pressures. These changes cause different ‘filtering effects' on native species, while simultaneously altering the capacity of surviving species to adapt to further anthropogenic pressures. This framework may better explain the observed native species extinction rates and extirpation legacies following human colonisation events, as well as better predict future patterns of human impact on biodiversity.
Assessment of the association between cytomegalovirus DNAemia and subsequent acute graft‐versus‐host disease in allogeneic peripheral blood stem cell transplantation: A multicenter study from the Spanish hematopoietic transplantation and cell therapy group
Authors: Bueno Felipe , Solano Carlos , Vázquez Lourdes , Giménez Estela , de la Cámara Rafael , Albert Eliseo , Rovira Montserrat , Espigado Ildefonso , Martín Calvo Carmen , López‐Jiménez Javier , Suárez‐Lledó María , Chinea Anabella , Esquirol Albert , Pérez Ariadna , Bermúdez Aránzazu , Saldaña Raquel , Heras Inmaculada , González‐Huerta Ana Julia , Torrado Tamara , Batlle Montserrat , Jiménez Santiago , Vallejo Carlos , Barba Pere , Cuesta María Ángeles , Duarte Rafael , Piñana José Luis , Navarro David ,   Spanish Group of Hematopoietic Transplantation, Cell Therapy (GETH)
Published: April 2021

The potential role of active CMV infection in promoting acute Graft‐versus‐Host Disease (aGvHD) in allogeneic hematopoietic stem cell transplantation (allo‐HSCT) remains a matter of debate. We further addressed this issue conducting a retrospective, observational, multicenter study of 632 patients subjected to allogeneic peripheral blood HSCT at 20 Spanish centers. Monitoring of CMV DNA load in plasma or whole blood was performed by real‐time PCR assays. Cumulative incidence of CMV DNAemia was 48.9% (95% CI, 45%‐52.9%), of any grade aGvHD, 45.6; 95% (CI, 41.3%‐50.1%), and of grade II‐IV aGvHD, 30.7 (95% CI, 24.9%‐36.4%). Overall, development of CMV DNAemia at any level resulted in an increased risk of subsequent all grade (HR, 1.38; 95% CI, 1.08 ‐ 1.76; P = .009) or grade II‐IV (HR, 1.58; 95% CI, 1.22 ‐ 2.06; P = .001) aGvHD. The increased risk of aGvHD linked to prior occurrence of CMV DNAemia was similar to the above when only clinically significant episodes were considered for the analyses (HR for all grade aGvHD, 1.48; 95% CI, 1.13 ‐ 1.91; P = .041, and HR for grade II‐IV aGvHD, 1.53; 95% CI. 1.13‐1.81; P = .04). The CMV DNA doubling time in blood was comparable overall in episodes of CMV DNAemia whether followed by aGvHD or not. Whether CMV replication is a surrogate risk marker of aGvHD or it is causally involved is an important question to be addressed in future experimental research.
LA ADQUISICIÓN O SUMINISTRO DE BIENES Y SERVICIOS DE CARACTERÍSTICAS TÉCNICAS UNIFORMES Y DE COMÚN UTILIZACIÓN A TRAVÉS DE SUBASTA INVERSA
Authors: Chaves Villada Jaime Eduardo
Published: April 2021

El presente artículo busca demostrar el desbordamiento de la potestad reglamentaria del Gobierno nacional en el ámbito de la contratación estatal, específicamente a partir de las disposiciones establecidas en el Decreto 2474 del 2008 en lo que concierne a la adquisición y suministro de bienes y servicios de características técnicas uniformes y de común utilización bajo el procedimiento de subasta inversa, frente a los criterios de selección objetiva desarrollados en la Ley 1150 expedida en el año 2007.
COMENTARIO BIBLIOGRÁFICO. "Los daños colectivos" de Lidia Garrido Cordobera
Authors: Stiglitz Gabriel , Rusconi Dante
Published: April 2021

Ed. Pontificia Universidad Javeriana - Facultad de Ciencias Jurídicas. Colección Internacional Nº 10. Bogotá. (2009).
Performance of Existing Methods in Baselining Demand Response From Commercial Building HVAC Fans
Authors: Lei Shunbo , Mathieu Johanna L. , Jain Rishee K.
Published: April 2021

Commercial buildings generally have large thermal inertia and thus can provide services to power grids (e.g., demand response (DR)) by modulating their heating, ventilation, and air conditioning (HVAC) systems. Shifting consumption on timescales of minutes to an hour can be accomplished through temperature setpoint adjustments that affect HVAC fan consumption. Estimating the counterfactual baseline power consumption of HVAC fans is challenging but is critical for assessing the capacity and participation of DR from HVAC fans in grid-interactive efficient buildings (GEBs). DR baseline methods have been developed for whole-building power profiles. This study evaluates those methods on total HVAC fan power profiles, which have different characteristics than whole-building power profiles. Specifically, we assess averaging methods (e.g., Y-day average, HighXofY, and MidXofY, with and without additive adjustments), which are the most commonly used in practice, and a least squares-based linear interpolation method recently developed for baselining HVAC fan power. We use empirical submetering data from HVAC fans in three University of Michigan buildings in our assessment. We find that the linear interpolation method has a low bias and by far the highest accuracy, indicating that it is potentially the most effective existing baseline method for quantifying the effects of short-term load shifting of HVAC fans. Overall, our results provide new insights on the applicability of existing DR baseline methods to baselining fan power and enable the more widespread contribution of GEBs to DR and other grid services.
Rigidity Regulation Approach for Geometric Tolerance Optimization in End Milling of Thin-Walled Components
Authors: Agarwal Ankit , Desai K. A.
Published: April 2021

This article presents a novel approach to optimize geometric tolerances (flatness and cylindricity) by manipulating the rigidity among finishing and roughing cutting sequences during end milling of thin-walled components. The proposed approach considers the design configuration of the thin-walled component as an input and aims to determine semi-finished geometry such that the geometric tolerance parameters are optimized while performing a finish cutting sequence. The objective is accomplished by combining mechanistic force model, finite element (FE) analysis-based workpiece deflection model, and particle swarm optimization (PSO) technique to determine optimal disposition of material along the length of component thereby regulating rigidity. The algorithm has been validated by determining the rigidity-regulated semi-finished geometries for thin-walled components having straight, concave, and convex configurations. The outcomes of the proposed algorithm are substantiated further by conducting a set of end milling experiments for each of these cases. The results of the proposed strategy are compared with a traditional approach considering no change in the rigidity of component along length of the cut. It is demonstrated that the proposed approach can effectively optimize geometric tolerances for thin-walled components during end milling operation.
Dexterity Analysis Based on Jacobian and Performance Optimization for Multi-Segment Continuum Robots
Authors: Wang Jiao , Lau Henry Y. K.
Published: April 2021

This paper focuses on the performance analysis of multi-segment continuum robots, including reachable workspace and dexterity performance. Since excellent dexterity is an important feature of continuum robots, two local indices inspired by separating robotic Jacobian matrix, namely axiality and angularity dexterity, are introduced to explore the dexterity. Then, a Monte Carlo Method is adopted to simulate the distribution of local dexterity over the workspace. On this basis, the corresponding global indices in axiality and angularity are defined to assess global dexterity performance. To investigate the optimal kinematic performance, an objective function related to the segment lengths is designed under the consideration of reachable workspace and dexterity performance. Finally, Particle Swarm Optimization (PSO) algorithm is used to solve this optimization problem successfully. The optimal length distributions for two-segment and three-segment continuum robots are discovered. Most importantly, it is found that our method can also apply to general multi-segment continuum robots.
A Methodology for Incorporating Multiple Goals in Automated Abstract Design
Authors: Bohren J. S. , Nevill G. E.
Published: April 2021

This paper deals principally with two important issues of design automation, the use of abstract design problem solving to guide detail design in top down refinement models, and the incorporation of multiple requirements in design. An iterative, incremental methodology involving generation and selection of abstract decompositions and of abstract operators defining design moves is described. Multiple requirements are handled by organizing relevant evaluation, generation and choice knowledge around individual requirements and providing each requirement with the capability to determine when it has a contribution to make, what that contribution should be, and how it interacts with other requirements. The methodology has been implemented as part of the MOSAIC project and is illustrated by examples of the automated preliminary design of mechanical structures.
Comparing Fuzzy and Probability Calculus for Representing Imprecision in Preliminary Engineering Design
Authors: Wood K. L. , Antonsson E. K. , Beck J. L.
Published: April 2021

A technique to perform design calculations on imprecise representations of parameters using the calculus of fuzzy sets has been previously developed [17]. An analogous approach to representing and manipulating uncertainty in choosing among alternatives (imprecision) using probability calculus is presented and compared with the fuzzy calculus technique. We find that the fuzzy calculus is well suited to representing and manipulating the imprecision aspect of uncertainty, and probability is best used to represent stochastic uncertainty.
Tolerance Representation Scheme in Solid Model: Part II
Authors: Roy U. , Mantooth K. , Pollard M. D. , Liu C. R.
Published: April 2021

Tolerance representation in a CAD data structure demands a user interactive environment which enables the user to input the tolerance information in both the unevaluated (CSG) and in the evaluated (B-Rep) databases [4]. This requires an effective linking mechanism between the CSG and the B-Rep data models at each stage of the object development. This has been achieved through the development of a reference face list. Tolerance information has been attached with this face list as “constraint nodes,” which are formed and updated after each “set operation.” Several functions have also been developed to retrieve essential information from the data structure in order to answer various queries.
Representation of Tolerance Information in Solid Models
Authors: Bernstein N. S. , Preiss K.
Published: April 2021

A set of tolerance constraints in solid models is represented as a constraint network over the degrees of freedom of the shape elements of the body. This approach is referred to as the constraint propagation approach to the representation of tolerance information. An evaluation of the resultant constraint network provides both an analysis of a specific dimension and tolerance scheme and figures of merit regarding the combinatorial and geometric/numeric computational complexity of a set of engineering spatial constraints. This paper discusses the representation needed to achieve that evaluation. The inherent computational complexity of spatial designs can then be explicitly evaluated and controlled. For many practical cases, semantic integrity and other evaluations may be conducted in low polynomial time, in the number of tolerance constraints. The representation is applicable also to assemblies.
Generative Process Planning of Prismatic Parts by Feature Relaxation
Authors: Mantyla M. , Opas J. , Puhakka J.
Published: April 2021

Feature-based product models have recently been proposed as a basis for generative process planning systems for mechanical applications. In this approach, the part is broken into a set of manufacturing features which are associated with various kinds of technological information useful for process planning.

A fundamental problem of this approach is the fact that a given part usually has several interpretations as features. Ideally, all these interpretations should be taken into account in the process planner in order to achieve globally optimal plans. Hence, any planner that starts from a fixed collection of features created by feature recognition or by user input has already committed itself to a limited view of the part, and cannot take into account manufacturing opportunities corresponding with the other views.

As a solution to this problem of premature commitment, we propose the use of what we call relaxed feature models. In this approach, features can be reinterpreted by the process planner to take into account manufacturing possibilities from a wider range than what any particular selection would make possible. As an example of the benefits of this approach, we describe the manufacturability analysis component of our experimental generative process planner for 3-axis milling operations of prismatic parts.
The Reduced Calculation of Volumetric Properties of Sweep-Generated Solids
Authors: Al-Daccak M. J. , Angeles J.
Published: April 2021

Due to its ease of implementation, the sweep generation of solid models is a widely accepted technique in dealing with complex shapes occurring in mechanical elements such as turbine blades and bevel gears. A key issue in the geometric and mechanical analyses of such elements is the accurate and economic computation of their volumetric properties, namely, their volume, centroid coordinates and inertia tensor. A method is proposed here for the computation of these properties for sweep-generated solids based only on their 2D generating contour and their sweeping parameters. Thus, the direct 3D calculations of the volumetric properties of such solids are reduced to simple 2D calculations. Comparisons of numerical results are presented, which show that the volumetric properties of sweep-generated solids can be effectively performed in a computationally reduced fashion which, additionally, enhances the accuracy of the computed values.
Identification and Minimization of Deviations of Real Gear Tooth Surfaces
Authors: Litvin F. L. , Zhang Y. , Kieffer J. , Handschuh R. F.
Published: April 2021

The authors propose an approach that uses coordinate measurements of the real surface to: (i) determine the real applied machine-tool settings, (ii) determine the deviations of the real surface from the theoretical one, (iii) minimize the deviations by correction of the machine-tool settings, and (iv) represent the real surface analytically in the same Gaussian coordinates as the theoretical one.
An Interactive Graphics Application for Computer Aided Development of Inspection Programs for Coordinate Measurement Machines
Authors: Atkins N. W. , Derby S.
Published: April 2021

The development of an interactive computer graphics application at RPI, sponsored by Pratt & Whitney, to create inspection programs for coordinate measurement machines using complete product definitions, is one step in evaluating the virtue of the PDDI/GMAP endeavor. One of the key factors in computer integrated manufacturing is the need to provide a database for the complete representation of product definition data. The PDDI/GMAP project, sponsored by the United States Air Force, is one of several efforts currently defining environments and neutral data formats for product data definition. The virtue of this data format can only be measured by the success of applications developed to work within this environment.
Using Fine-Grained Parallel Simulation for Design
Authors: Oh J. S. , Ulrich K. T.
Published: April 2021

One of the most imposing handicaps for designers is the lack of versatile engineering tools for rapid simulation of materials. Simulations must run fast enough to grant engineers immediate feedback on their design changes. Conventional methods of simulating mechanical behaviors are slow and require significant expertise. We propose an alternative we call Fine-Grained Parallel Simulation (FGPS). FGPS uses thousands of processors to compute finite element behavior in parallel. The advantage of this approach is that modeling assumptions can be made at a physical particle level rather than at a macroscopic continuum mechanics level, and that within certain bounds the resulting simulation runs in constant time, independent of the size of the problem. We have prototyped this scheme using the Connection Machine, a massively parallel computer containing up to 65,536 processors, and we are laying the groundwork for the development of a special purpose machine with hundreds of thousands of processors. Our initial results indicate that simulation can be performed significantly faster using FGPS than with conventional supercomputers, although there is need for additional research.
Design Quality and Reliability Through Technology Readiness
Authors: Fox J.
Published: April 2021

This paper discusses the relationship between the growth of reliability in the early stages of a product delivery process and Technology Readiness, and describes the importance of ‘ready’ technologies if product launch schedules are to be achieved. Technology Readiness itself is defined and the enablers for it are identified.

A process which has been developed is described, and some proposals for tracking and managing progress are made.

Finally, the importance of critical design parameters both in the development of technologies and in understanding technology capabilities are described fully.
Determination of the Minimum Evidence Set in Expert Systems Using Boolean Methods
Authors: Liu P. , Siddall J. N.
Published: April 2021

A new method is proposed for rapidly solving expert system applications using Boolean algebra formulations. The method consists of two algorithms, applied after the conventional hierarchical type rules have been converted to Boolean expressions. The first algorithm automatically reduces the expressions to the equivalent of only two levels in a logic network, eliminating all intermediate conclusions, and also minimizes the number of inputs per rule. This algorithm has general application in the condensation of rule systems, and makes possible the use of high speed bit matching in specific solutions. The second algorithm operates on the reduced rule set so that, in a given application, a rapid solution is achieved using the fewest possible items of evidence, or user inputs. It is believed that these algorithms will be particularly useful in applications where high speed solutions are important.
Robot Path Planning via Simulated Annealing: A Near Real Time Approach
Authors: Sandgren E. , Venkataraman S.
Published: April 2021

An efficient procedure for near optimal robot path planning in a two dimensional workplace is presented. Obstacles are represented as a series of rectangular regions which allows collision detection to be performed by an operation similar to clipping in computer graphics. The feasible design space is approximated by a discrete set of robot arm and gripper positions. A control sequence of the angular position of each link is determined. A set of intermediate link positions are generated and grouped into stages. A dynamic programming problem is formulated to locate the best state within each stage which minimizes the overall path length. A simulated annealing solution procedure is implemented in order to locate a reasonable solution in the minimum amount of time. Several examples are presented involving a three link planar manipulator. Extensions to three dimensional robot path planning and real time control in a dynamically changing workplace are discussed.
Design of Keratorefractive Surgical Procedures: Radial Keratotomy
Authors: Bryant M. R. , Velinsky S. A.
Published: April 2021

By surgically incising a patient’s cornea, an ophthalmologist can reduce or eliminate the patient’s myopia (nearsightedness). Although one such keratorefractive procedure, known as radial keratotomy, is a common practice among some ophthalmologists, there is presently no comprehensive or universally accepted method that a surgeon can use to determine how to perform the operation to exactly eliminate a patient’s refractive error. In this paper, a general methodology for designing radial keratotomy procedures that determines the optimal incision geometry on a patient-by-patient basis is presented. This approach is based on coupling a transversely isotropic finite element model of the human cornea to an optical model of the entire eye. Two objective functions are considered, and each one is shown to possess monotonicity properties that specify a constraint bound solution, obtained by directly solving the constraint equations. Consequently, the resulting incision geometry in each formulation not only eliminates the myopic error but yields the global minimum of the objective function.
Algebraic Acceleration of Finite Element Optimization; Four Modeling Errors in a Weldment Design
Authors: Sheppard S. D. , Wilde D. J. , Hsu Y.-L.
Published: April 2021

A method is proposed for incorporating finite element stress analysis into the constraints of an optimization model. To reduce the number of computationally intensive finite element analyses, the more accurate FEA plate model is approximated by an algebraic beam model having an adjustable factor whose value is determined by comparing FEA stresses with the corresponding beam theory predictions. This factor compensates both for the inaccuracies of beam theory and the effect of stress concentration. The algebraic form is retained to permit application of powerful optimization techniques not applicable directly to finite element models. The optimization problem is thus reduced to the determination of the single factor by linear interpolation. When tested on Keith’s well-known welded cantilever problem, the method needs only three FEAs. Keith’s model is also shown to suffer from four errors, of which three are remedied here. Because of special problem structure, the resulting design is correct for three of the four design variables, but the length of the weld cannot be determined without a better weld stress model.
Automatic Finite Element Mesh Generation Over Domains Comprised of Military Connected, Intersecting, Rigid Body-Movable Subdomains
Authors: Yang H. , Hoeltzel D. A.
Published: April 2021

A novel approach for the automatic generation and refinement of finite element meshes over nonconvex domains subdivided by multiply connected, rigid body-movable subdomains has been developed. The basis of this method relies on 1) the automatic insertion of nodes on the digitized boundaries and within the interiors of movable subdomains 2) the generation of superelement meshes, using the nodes which have been inserted on the subdomains, 3) determination of the points of intersection between adjacent subdomains following their rigid body movement, 3) ensuring the satisfaction of both interelement connectivity and compatability across subdomain boundaries which undergo rigid body movement along with the subdomains, and 4) the interactive refinement of userselectable subdomains using quadrilaterization for global refinement and triangularization for local refinement.

The creation of a finite element mesh for an acetabular cup inserted in a human pelvis, which is representative of a mesh generated over complex, two-dimensional, multiply connected subdomains, as employed in an orthopedic total hip replacement, serves as a realistic application of this approach and demonstrates its utility for expeditiously performing finite element-based, parametric design optimization studies.
3D Finite Element Analysis of Rolling Mill Bearings
Authors: Yuanke L. , Guanwei C. , Jun Y. , Qigui Z. , Caiyun Z.
Published: April 2021

The analysis and computation on stress and load-distribution state of rolling bearings via finite element method is one of the major studies on rolling bearings. This finite element analysis is much more complicated than that of common structures because of the contact problems existed in it and most of them can not be treated as plane prolems. This paper not only discusses the basic method of 3D contact finite element analysis and its solving technique in terms of the characteristics of four-row taper roller bearings attached to cold-rolling-mill work rolls, but also presents a simplified analytical model and computing results. The load-distribution curve under different working conditions is illustrated too in this paper.
Application of a Decomposition Technique for Treating a Shape Optimization Problem
Authors: Bremicker M. , Eschenauer H.
Published: April 2021

The range of application of structural optimization methods can be considerably enlarged by using decomposition techniques. In this paper a novel procedure is introduced to deal with such problems more efficiently. The mechanical structure resp. system is divided into several subsystems splitting up the design variables, objective functions, and constraints accordingly. The boundary state quantities of the subsystems and the global (i.e. subsystem overlapping) functions are approximated by a sensitivity analysis of the entire system using suitable approximation concepts. It is thus possible to optimize the subsystems independently. Variables, objective functions and constraints can be chosen arbitrarily; all coupling information is obtained from the sensitivity analysis by means of global information. The application of this technique is demonstrated by a two-dimensional shape optimization problem.
Using the Generalized Reduced Gradient Method to Handle Equality Constraints Directly in a Multilevel Optimization
Authors: Renaud J. E. , Gabriele G. A.
Published: April 2021

In recent years there have been several multilevel optimization algorithms proposed and implemented in design studies. Equality constraints are often imposed between levels in the optimization to maintain system and subsystem variable continuity. In most implementation studies these equality constraints are handled indirectly. This paper describes the utility of the Generalized Reduced Gradient (GRG) method for handling these equality constraints directly in a multilevel optimization. Two engineering design examples illustrate the methods effectiveness when incorporated in a multilevel linear decomposition scheme based on the Sobieski algorithm.
Parameter Sensitivity Analysis of a Large-Scale System With Several Components Interacting in Series
Authors: Torab H.
Published: April 2021

Parameter sensitivity for large-scale systems that include several components which interface in series is presented. Large-scale systems can be divided into components or sub-systems to avoid excessive calculations in determining their optimum design. Model Coordination Method of Decomposition (MCMD) is one of the most commonly used methods to solve large-scale engineering optimization problems. In the Model Coordination Method of Decomposition, the vector of coordinating variables can be partitioned into two sub-vectors for systems with several components interacting in series. The first sub-vector consists of those variables that are common among all or most of the elements. The other sub-vector consists of those variables that are common between only two components that are in series. This study focuses on a parameter sensitivity analysis for this special case using MCMD.
Extremal Behavior of One Parameter Families of Optimal Design Models
Authors: Rao J. R. J. , Papalambros P. Y.
Published: April 2021

Optimal design models contain parameters that are considered fixed during the optimization process. When these parameters change values, the mathematical properties of the model and the physical behavior of the underlying engineering system may change drastically. This article examines how large changes in one parameter affect the optimal solution and the type of singularities that may be encountered. The theory presented extends parametric optimization beyond the usual sensitivity analysis, and can be used as a modeling tool or as a rigorous treatment of related problems, such as multi-level decomposition. The algorithmic implementation and numerical examples are presented in a sequel article.
Optimal Design of Mechanical Components With Sizing, Configurational and Topological Consideration
Authors: Sandgren E. , Lee H. , El-Sayed M.
Published: April 2021

A methodology for the optimal design of structural mechanical components with sizing, configurational and topological consideration is presented. The optimization involves the minimization of structural weight subject to stress and deflection constraints. A finite element code with internally generated design sensitivities and general element connectivities is implemented in order to solve for the stresses and deflections in the structure. Beam elements with various crossectional configurations are considered. The generalized reduced gradient method is applied to solve the constrained nonlinear programming problem. A hierarchical design optimization approach is taken with topological issues considered at the upper level and geometric and crossectional issues considered at the lower level. An example involving the design of an automotive seat frame structure is presented to demonstrate the approach.
Robot Path Planning and Obstacle Avoidance: A Design Optimization Approach
Authors: Sandgren E. , Venkataraman S.
Published: April 2021

A design optimization approach to robot path planning in a two dimensional workplace is presented. Obstacles are represented as a series of rectangular regions and collision detection is performed by an operation similar to clipping in computer graphics. The feasible design space is approximated by a discrete set of robot arm and gripper positions. Control is applied directly through the angular motion of each link. Feasible positions which are located between the initial and final robot link positions are grouped into stages. A dynamic programming algorithm is applied to locate the best state within each stage which minimizes the overall path length. An example is presented involving a three link planar manipulator. Extensions to three dimensional robot path planning and real time control in a dynamically changing workplace are discussed.
A Dual-Purpose KBES for Preliminary Structural Design
Authors: Hart P. K. , Rodriguez J.
Published: April 2021

A prototype expert system for automatic preliminary shape synthesis is being developed. The purpose of this system is to generate preliminary designs which can be used either for basic engineering or as an initial solution in an optimization scheme. The developed prototype intends to emulate the conceptual-design/preliminary-redesign phases in the design process. Both phases have been modularized and developed under adequate computational shells. Modules requiring heuristic support are implemented in a LISP/KEE™ environment, the ones being computer-intensive are in C subroutines. Heuristics are applied in the initial design phase to produce an adequate definition of the geometric domain. For the redesign phase, a set of options were programmed into the inference mechanism. These rules focus on molding the geometric domain. Rules for the inference mechanism, and common databases were elaborated. The two-dimensional problems of a fillet in a tension bar, and a connecting link are used to illustrate the system. This is part of an ongoing project at the Center for Computer Aids for Industrial Productivity (CAIP) in New Jersey.
A Two Dimensional Rule-Based Shape Synthesis Method
Authors: Russell D. M. , Manoochehri S. P.
Published: April 2021

The objective of this study is to form two-dimensional structural/mechanical parts under general loading and restraint conditions. The designs created are of minimum weight with the stresses throughout the parts as close to the allowable limit as possible. The study uses a thresholding approach with minimal designer intervention for generating optimal configurations. The process begins with the user creating an initial design which encompasses all the specified loads and restraints. Finite element techniques are employed to discretize the part geometry. Then a set of heuristics are utilized for shape modification, by removing elements from the finite element model. A Bi-Directional Thresholding technique, BDT, is developed that determines which elements ought to be removed. After BDT is performed element connectivity is checked and maintained. A two-step connectivity check algorithm is implemented which locates and resolves major (complete) as well as minor (partial) losses in connectivity. This procedure, unlike most common shape optimization methods, is capable of quickly making very large changes in the geometry of the part. It is able to create holes in the geometry, where none existed in the initial shape, in order to produce a better design.
Multiobjective Optimization Dealing With Uncertainty
Authors: Mohandas S. U. , Sandgren E.
Published: April 2021

An algorithm to handle uncertainty in a multiobjective design optimization problem is developed. The procedure is applied to three examples where objective functions in each of them compete against each other. The uncertainty in the description of objective functions is modeled by using fuzzy goals and the terms of natural language. Multiobjective function is formulated as a fuzzy set. The minimization is carried out using a combination of the Complex Box method and a technique of ranking of fuzzy sets.
Application of Generalized Newton-Euler Equations and Recursive Projection Methods to Dynamics of Deformable Multibody Systems
Authors: Wehage R. A. , Shabana A. A.
Published: April 2021

A general symbolic-based method is presented for solving equations of motion for open-loop kinematic chains consisting of interconnected rigid and deformable bodies. The method utilizes matrix partitioning, recursive projection based on optimal block U-L factorization and generalized Newton-Euler equations to obtain an order n solution for the constrained equations of motion. Kinematic relationships between the absolute reference, joint and elastic coordinates are used with the generalized Newton-Euler equations for deformable bodies to obtain a large, loosely coupled system of equations. Taking advantage of the inertia matrix structure associated with elastic coordinates yields a recursive solution algorithm whose dimension is independent of the elastic degrees of freedom. The above solution techniques applied to this system of equations yield a much smaller operations count and can more effectively exploit vectorization and parallel processing. The algorithms presented in this paper are illustrated with the aid of cylindrical joints which are easily extended to revolute, prismatic, rigid and other joint types.
A Dynamics Workstation
Authors: Wu J. K. , Fogle M. A. , Wang J. Y. , Lu J. K.
Published: April 2021

The engineer’s modeling capability is the weakest link in the chain that supports the simulation of dynamic mechanical systems, due to the fact that engineers are forced to define mechanical system models in a way they are not familiar with. Advanced developments in computer techniques, computer graphics, and recursive computational algorithms for mechanical systems make the high speed dynamic simulation and graphic animation of mechanical systems feasible. But without a practical, useful modeling tool, the engineer has difficulty in using these advanced techniques.

The Dynamics Workstation is a modeling tool developed to help the engineer define mechanical system models in a natural, practical way. The engineer can communicate with the workstation naturally and interactively, define the model in formats that meet the needs for both high speed dynamic simulation and conventional dynamic analysis, define and assemble the model body by body using a relative coordinate system, visualize the configuration of the model, carry out simple joint exercises to detect the errors of the model in the early design stage, graphically lock and unlock joints, and adjust the system configuration even after initial assembly. The workstation automatically generates the mechanical system model based on the engineer’s interactive input data. The model design system strengthens the engineer’s modeling capability; it not only improves the design quality, but also boosts productivity.
Solution of Multibody Dynamics Using Natural Factors and Iterative Refinement: Part II — Closed Kinematic Loops
Authors: Wehage R. A.
Published: April 2021

A symbolic algorithm exploiting natural factors of generalized inertia matrices and iterative refinement to compute the dynamics of open kinematic-loop systems was developed in Part I of this paper. The general equations of motion for open and closed loop systems were derived in an earlier paper (Wehage, 1988) and it was shown that algorithms for open loop dynamics could be used to solve closed loop problems by cutting the secondary joints. In this paper it is shown that secondary joint forces can be obtained either from a dynamic force balance or from constraint surface deformations. Closed kinematic loops create additional numerical problems and require substantially more computational overhead. Therefore the iterative refinement algorithm developed in Part I is extended to address some of these problems. Exploitation of iterative refinement and computer architecture can substantially improve overall algorithm performance.
An Optimal Design of Composite Robot Arms
Authors: Sung C. K. , Shyl S. S.
Published: April 2021

A design methodology considering the issue of manufacturability, in particular, is presented for synthesizing high-performance articulating robotic systems fabricated with optimally-tailored composite laminates. By optimally specifying the types of fiber, matrix, stacking sequence, fiber volume fraction, fiber layups, etc., the synthesized composite material may possess significantly superior characteristics such as high damping, high stiffness, high strength and low mass.

In accordance with the design requirements, the minimum deflection during articulating motion or the fast settling time after the power stopped, the design objectives and constraint conditions were specified. As an illustrative example, a two-link robot manipulator fabricated with aforementioned composite laminates is employed for demonstrating the proposed design methodology.
Hydrodynamic Lubrication of Pocket Bearings and Effect of Contouring the Inner and Outer Regions, and Optimum Design Data
Authors: Bagci C. , McClure C. J. , Rajavenkateswaran S. K.
Published: April 2021

The article investigates pocket bearings with contoured profiles of exponential forms on both surfaces inside and outside of the step boundary forming hydro-dynamic action surfaces, and develops optimum design data yielding efficient slider bearings with small pockets with higher load capacities than conventional pocket bearings. In the case of a pocket bearings, in addition to the Reynolds equation used for the regions inside and outside the pocket, the continuity equation along the pocket boundary is satisfied to form the complete model of the bearing. The optimum design data includes dimensionless load-, flow-, temperature rise-, power loss-, stiffness-, and the coefficient of friction factors. Incompressible lubricant with temperature dependent viscosity is considered. Detailed study of conventional pocket bearings with planar surfaces is included. Some optimum exponential pocket bearings yield up to 561 percent increase in load capacity as compared to the conventional tapered bearings.
Direct Kinematics and Dynamics of a Planar Three-DOF Parallel Manipulator
Authors: Ma O. , Angeles J.
Published: April 2021

In this paper, the direct kinematics and dynamics, as applied to a three degree-of-freedom planar parallel manipulator, are studied. In the direct displacement problem, the method of virtual removal of kinematic constraints and a technique of four-bar linkage-performance evaluation are applied, so that the problem can be solved efficiently. Moreover, branches of solution may also be controlled in the numerical procedure without involving additional computations. In the dynamics formulation, the natural orthogonal complement is applied, which leads to the algorithmic-oriented equations of motion involving only independent generalized coordinates. A new and simple method is introduced to calculate the natural orthogonal complement and the joint-velocity Jacobian matrices. A fully solved numerical example of direct kinematics and dynamics is included.
A Manipulator Jacobian Based Modified Newton-Raphson Algorithm (JMNR) for Robot Inverse Kinematics
Authors: Singh V. K. , Gupta K. C.
Published: April 2021

This paper deals with the formulation of a manipulator Jacobian based Newton-Raphson algorithm for robot inverse kinematics. A strict descent feature has been incorporated into the algorithm to make it robust. Previous studies with Newton-Raphson type matrix iteration have produced an overdetermined system of linear equations which relates small changes in the joint variables. Dealing with these extra equations led to computational inefficiency. Previous manipulator Jacobian based predictor-corrector algorithms for inverse kinematics avoided this inefficiency, but these required either a variable time step or a small fixed time step; also special attention was required to start these algorithms. Motivated by the advantages of these two methods, this paper presents a robust manipulator Jacobian based Newton-Raphson algorithm for robot inverse kinematics.
Synthesis of
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C-enriched amino acids with
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C-depleted insoluble organic matter in a formose-type reaction in the early solar system
Authors: Furukawa Yoshihiro , Iwasa Yoshinari , Chikaraishi Yoshito
Published: April 2021

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C-enriched organic compounds were formed more widely in the early solar system by ammonia-involved formose-type reaction.