Synthesis Configuration Research Articles

Configuration synthesis and structural design of lower-mobility parallel external fixators based on corrective degree-of-freedom classification

Foot and ankle deformity remains a common presenting complaint in orthopedic surgery. External fixator is a key medical device to assist gradual correction. Its configuration selection has a significant influence on correction results. Among two external fixators currently used in clinic, conventional Ilizarov external fixator (IEF) has high use difficulty and low accuracy, whereas the single configuration of later hexapod external fixator (HEF) leads to inadequate adaptation to diverse deformity types in foot and ankle. To solve the above problems, this paper presents a novel parallel distraction apparatus (PDA). First, corrective degree-of-freedom (c-DOF) is defined to determine expected posture transformation of external fixator required by corrective manipulation. By summarizing and classifying c-DOF, predominant foot and ankle deformities with fewer correction requirements are divided into six types. Subsequently, six lower-mobility parallel mechanisms are introduced as the configurations of external fixators via the c-DOF based configuration synthesis approach. After performing reconfigurable structural design, PDA can respectively form six types of parallel external fixators for six deformity types. Finally, clinical case simulations are provided to verify the application potential and advantages of PDA.

Total Synthesis and Determination of the Absolute Configuration of Rakicidin C.

The absolute configuration of rakicidin C was predicted by comparison of optical rotation data and absolute configuration of APD-cyclic depsipeptides and further determined by total synthesis. The absolute configuration of five chiral centers was determined as 2R, 15R, 16R, 17S, and 19S. Our efficient route involves 19 longest linear steps with an overall yield of 1.49%.

Comparative analysis of three categories of four-DOFs exoskeleton mechanism based on relative movement offsets

PurposeThe purpose of this paper is to evaluate three categories of four-degrees of freedom (4-DOFs) upper limb rehabilitation exoskeleton mechanisms from the perspective of relative movement offsets between the upper limb and the exoskeleton, so as to provide reference for the selection of exoskeleton mechanism configurations.Design/methodology/approachAccording to the configuration synthesis and optimum principles of 4-DOFs upper limb exoskeleton mechanisms, three categories of exoskeletons compatible with upper limb were proposed. From the perspective of human exoskeleton closed chain, through reasonable decomposition and kinematic characteristics analysis of passive connective joints, the kinematic equations of three categories exoskeletons were established and inverse position solution method were addressed. Subsequently, three indexes, which can represent the relative movement offsets of human–exoskeleton were defined.FindingsBased on the presented position solution and evaluation indexes, the joint displacements and relative movement offsets of the three exoskeletons during eating movement were compared, on which the kinematic characteristics were investigated. The results indicated that the second category of exoskeleton was more suitable for upper limb rehabilitation than the other two categories.Originality/valueThis paper has a certain reference value for the selection of the 4-DOFs upper extremity rehabilitation exoskeleton mechanism configurations. The selected exoskeleton can ensure the safety and comfort of stroke patients with upper limb dyskinesia during rehabilitation training.

Module combination based configuration synthesis and kinematic analysis of generalized spherical parallel mechanism for ankle rehabilitation

In the previous rehabilitation robot research, the proposed ankle models for rehabilitation robot design have distinctions with the ankle bone structure. It leads to the unsatisfactory human-machine compatibility of the robots constructed based on the fitting onto the motion of these models. For this problem, 6 motion fitting models having higher similarities with ankle bone structure are proposed. For constructing a generalized spherical parallel mechanism (GSPM) with the same kinematic characteristics with these models, a module combination configuration synthesis method is presented. This method establishes the GSPM with partially decoupled characteristics by combining position and orientation modules. Firstly, this method constructs basic limbs/groups of 2 modules based on enumeration and screw theory. Secondly, a class of compact equivalent limbs and groups are constructed by equivalent replacement method based on basic limbs and groups. Thirdly, with the equivalent group being an example, the kinematics of 2 modules are analyzed based on the D-H method and their geometric characteristics, a module combination kinematic analysis method is summarized. Finally, 6 suitable GSPMs are established based on these methods.

Total Synthesis and Assignment of the Absolute Configuration of (+)-Omphalic Acid

Omphalane diterpenoids usually contain a cyclohexane-fused bicyclo[3.2.1]octane scaffold embedded with two continuous quaternary carbon centers, which pose considerable challenges to synthetic chemists. Herein, we reported the first total synthesis of omphalic acid with high stereochemical control, featuring an intermolecular Diels-Alder cycloaddition, ring reorganization through Criegee oxidative cleavage and programmed aldol condensations, conformationally controlled hydrogenation, and Pd-catalyzed carboxylation. The absolute configuration of omphalic acid was defined for the first time via the asymmetric total synthesis facilitated by a derivatization resolution protocol.

A configurative synthesis of evidence for fear in the criminal decision-making process

This paper reviews what previous research has found on the role of fear and other associated feelings in the criminal decision-making process, and the techniques that might plausibly amplify such emotions so as to reduce or disrupt intent. To this aim, we conduct a systematic review of the offender decision-making literature (23 studies), incorporating a qualitative synthesis of the role of fear in the criminal decision-making process. The results section is formed of six parts based on dominant themes identified in our eligible studies, namely evidence of fear in offender decision-making, the presumed sources of fear, variation in levels and/or the effect of fear across offenders, the specific role of fear across aspects of the crime process (before, during, after), the results of fear and offender fear management processes. We conclude with a discussion of the implication for crime prevention policies.

Configuration synthesis of nine-speed automatic transmissions based on structural decomposition

The configuration of nine-speed automatic transmission (AT) is one of the most important factors to determine its performance, and the pursuit of a better configuration of AT has always been the research focus. This paper proposes a new structural decomposition method, based on which the configuration synthesis of nine-speed AT with a cut-link is conducted by the combination of two independent planetary gear trains (PGT). Firstly, two different decomposition types are introduced, and the structure of nine-speed AT with four planetary gear sets (PGSs) and two degrees of freedom (DOF) is divided into two substructures with one-DOF. Secondly, all the topological graphs of substructures in the two decomposition types are obtained by screening in our atlas database. Thirdly, the layouts of shifting elements (SEs) are analyzed based on the lever method, and all the possible layouts of SEs are obtained. Finally, the substructures are combined according to the layouts of SEs to synthesize the configurations of nine-speed AT. As a result, 168 different configurations of AT are obtained including some classical and new configurations. Furthermore, the method can be extended to the synthesis of other multi-speed ATs.

Research on the Kinematic Compatibility of Position Solution of a Four-DOFs Mechanical Structure Mechanism

Upper extremity rehabilitation exoskeletons are the key devices for stroke patients with movement function disorders. Based on the configuration synthesis and optimum principles of 4-DOFs upper limb exoskeleton mechanisms, an exoskeleton mechanism compatible with upper limb were presented. When the exoskeleton was worn to the upper extremity, a kinematic chain with two closed loops was formed. Moreover, the kinematic equations of the chain were established and a position solution method was addressed. Based on the presented position solution, the kinematic characteristics during eating movement were investigate. The conclusion suggested that the exoskeleton was applied to the upper extremity rehabilitation and can be applied as main structural design parameters for the presented exoskeleton.

Synthesis method for planetary gear trains without using rotation graphs

The displacement graphs (d-graphs) are the final form of planetary gear trains (PGTs) synthesis. The existing configuration synthesis methods for the d-graphs of PGTs need rotation graphs (r-graphs) as the intermediate step and produce a large amount of isomorphic KCs. This paper proposes a method to obtain d-graphs directly from the geared graph. Meanwhile, a uniform isomorphism identification method suitable for parent graphs, geared graphs, and d-graphs is presented. Finally, a fully automatic method based on parent graphs is tested on synthesizing 1-DOF PGTs with up to nine links. Our synthesis results and those in the literature are comparatively analyzed, and the reasons for contradictory synthesis results are analyzed.

Learning with technology during emergencies: A systematic review of K‐12 education

AbstractEmergency situations that cause damage to educational buildings or require the closure of schools due to unsafe health, environmental, or political conditions can be an unwelcomed interruption to education. Indeed, the recent COVID‐19 pandemic created the largest disruption of education in history, affecting 94% of the world's student population. In emergencies, technology is often utilised as part of a crisis response protocol by continuing education using emergency remote education (ERE). The purpose of this study is to determine how technology has been used to continue K‐12 learning remotely during an emergency. This systematic review included an aggregated and configurative synthesis to examine extant empirical work over eleven years, from January 2010 to December 2020. Following a rigorous, PRISMA selection process, 60 articles were included in the final analysis from 48 countries. Grounded coding of the strategies used for learning revealed the following categories: communication, delivery systems, student ERE readiness, partnerships, promoting student learning and engagement, and resources. Grounded coding of the technologies revealed that types of technologies used were divided into two major categories: Internet‐based and non‐Internet based, with the majority using Internet‐based technologies. Practitioner notesWhat is already known about this topic The COVID‐19 pandemic has caused school closures across the globe and prevented in‐person school teaching. The rapid shift to distance education in schools can be conceptualised as ‘emergency remote education’ (ERE). Prior ERE research focused on bounded geographic locations where localised emergencies occurred. What this paper adds This provides the scholarly community with a unique systematic review of existing academic research on K‐12 ERE implementation in emergencies. This provides aggregated data and analysis on the past 11 years of the types of emergencies, participants, subject domain, technologies used, and location information. This provides findings of the types of remote teaching strategies involving technology used to continue K‐12 learning in emergency situations. This provides a set of recommendations on ERE for teachers, school leaders, policy makers, and funders. This provides researchers with a review of the field with identification of gaps and future research opportunities. Implications for practice and/or policy Recommendations regarding ERE are provided in this paper that will be of benefit to K‐12 teachers, school leaders policymakers, and funders in the continuing COVID‐19 pandemic and future emergencies. The research gaps highlighted in this paper, such as the lack of studies conducted in low and low middle‐income countries, are presented with suggestions for much needed future research. This can lead to changes in practice and policy.

Instant Center Identification of Single-Loop Multi-DOF Planar Linkage Using Virtual Link

Instant center is an important kinematic characteristic which can be used for velocity and singularity analysis, configuration synthesis and dynamics modeling of multi-degree of freedom (multi-DOF) planar linkage. The Aronhold–Kennedy theorem is famous for locating instant centers of four-bar planar linkage, but for single-loop multi-DOF linkages, it fails. Increasing with the number of the links of single-loop multi-DOF planar linkages, the lack of link relationship makes the identification of instant center become a recognized difficulty. This paper proposes a virtual link method to identify instant centers of single-loop multi-DOF planar linkage. First, three types of instant centers are redefined and the instant center identification process graph is introduced. Then, based on coupled loop chain characteristic and definition of instant center, two criteria are presented to convert single-loop multi-DOF planar linkage into a two-loop virtual linkage by adding the virtual links. Subsequently, the unchanged instant centers are identified in the virtual linkage and used to acquire all the instant centers of original single-loop multi-DOF planar linkage. As a result, the instant centers of single-loop five-bar, six-bar planar linkage with several prismatic joints are systematically researched for the first time. Finally, the validity of the proposed method is demonstrated using loop equations. It is a graphical and straightforward method and the application is wide up to single-loop multi-DOF N-bar (N ≥ 5) planar linkage.

Configuration Design of an Upper Limb Rehabilitation Robot with a Generalized Shoulder Joint

For stroke patients with upper limb motor dysfunction, rehabilitation training with the help of rehabilitation robots is a social development trend. Existing upper limb rehabilitation robots have difficulty fully fitting the complex motion of the human shoulder joint and have poor human–robot compatibility. In this paper, based on the anatomical structure of the human upper limb, an equivalent mechanism model of the human upper limb is established. The configuration synthesis of the upper limb rehabilitation mechanism was carried out, a variety of shoulder joint man–machine closed-chain Θs and shoulder elbow human–machine closed-chain Θse configuration combinations were synthesized, and the configuration model with compatibility and reduced moment conduction attenuation was selected from them. Two configurations, 2Pa1P3Ra and 5Ra1P, are proposed for the generalized shoulder joint mechanism of the robot. The closed-chain kinematic models of the two configurations are established, and the velocity Jacobian matrix is obtained. Motion performance analysis, condition reciprocal analysis and operability ellipsoid analysis of different configuration design schemes were carried out in different operation planes. The results show that in the normal upper limb posture of the human body, the 5Ra1P configuration of the shoulder joint has better kinematic performance. Finally, on this basis, an upper limb rehabilitation robot prototype with good human–computer compatibility is developed, and its moving space was verified.

Asymmetric Total Synthesis and Determination of the Absolute Configuration of (+)-Srilankenyne via Sequence-Sensitive Halogenations Guided by Conformational Analysis.

This first asymmetric total synthesis of (+)-srilankenyne (1), a halogenated C15 tetrahydropyran acetogenin isolated from Aplysia oculifera, features a sequence-sensitive process guided by conformational analysis to solve the challenging problem of introducing halogens. A competing semipinacol rearrangement during the installation of C(12)-bromide was suppressed by our A1,3 strain-controlled bromination protocol with support from X-ray crystallographic and computational studies. The C(10)-chloride was then placed by the Nakata chloromesylate-mediated chlorination.

Configuration synthesis of linear foldable over-constrained deployable unit based on screw theory

According to a description of the topology structure of deployable antennas, this work proposes the configuration synthesis method of over-constrained deployable units on the basis of screw theory and conducts example analyses on the basis of an analysis method and certain design steps. First, the basics of screw theory are introduced in detail, and an over-constrained deployable unit is represented by a screw. Second, through over-constraint analysis, the kinematic pair configurations of the mechanism under over-constraint have been established. Third, according to the general process of the deployable unit with common over-constraints proposed in this paper, the example is analyzed in detail. Finally, the model is verified according to the obtained configuration synthesis results. The cubic deployable unit mechanism is obtained through 3D printing, and the folding function is tested to verify the correctness of the theoretical analysis, which can provide theoretical reference for the mechanism design of large deployable units.

Configuration synthesis of variable stiffness mechanisms based on guide-bar mechanisms with length-adjustable links

A variable stiffness mechanism (VSM) is used to connect the principal motor and the load of a serial-configuration variable stiffness actuator (VSA) and can adjust the intrinsic stiffness of the VSA to improve the dynamic performance, energy efficiency, and safety of robotic systems. This paper presents a new configuration synthesis method to design VSMs based on guide-bar mechanisms through the addition of linear springs and the use of length-adjustable links. The springs are used to constrain the mechanism and generate compliant behaviour, and the length-adjustable links are used to adjust the transmission ratio and modulate the apparent stiffness. The conditions for designing VSMs with symmetrical stiffness characteristics, capable of low-power cost stiffness modulation and decoupled control of equilibrium position and stiffness, are also derived. By selecting different spring-constrained joints, length-adjustable links, initial angles of input joints, and length ranges of the adjustable links, twelve energy-efficient VSMs with different stiffness performance are constructed. In addition, the concept design of a VSA that can vary its stiffness from zero to infinity is presented; this design uses only one linear torsion spring without a preload.

Asymmetric Total Synthesis and Assignment of Absolute Configuration of Arbornamine.

The asymmetric total synthesis of arbornamine was accomplished in 13 steps, leading to the assignment of its absolute configuration. The key features of the strategy include construction of the C16 quaternary carbon center by a highly diastereoselective Grignard reagent addition to N-tert-butanesulfinylimine, sequential site-selective amidation and N-alkylation to form the C and E rings, and [Ni(COD)2]-mediated Michael addition to close the D ring.

Automated Controller and Sensor Configuration Synthesis Using Dimensional Analysis

Automated controller synthesis methods for cyber-physical systems (CPSs) often require precise knowledge of the system's state. Unfortunately, parts of the state may not be directly measurable, which limits the application of these methods. We present a design methodology for the co-design of software controllers and the required sensing capabilities. Our method leverages the knowledge of physical units in the model of a system to find ways of indirectly measuring parts of the system's state which cannot be measured directly. The method contains a search procedure which uses dimensional analysis to explore the space of physically well-typed expressions and it generates as an intermediate result possible sensor combinations. The integration between the physical and software design for CPS that we present make automated controller synthesis techniques more widely applicable. We have implemented our method and applied it to the design of robotic manipulators.

Topological invariant and definition method for detecting isomorphism in planar kinematic chains

Isomorphism identification is an essential step in mechanism configuration synthesis. Although various detection methods have been proposed, some of them can only effectively identify kinematic chains (KCs) within 10 links or complex programs that are needed to identify multilink KCs. In this study, a new isomorphism identification method is proposed based on the distance concept of graphs and the graph theory definition of isomorphism. In addition to two complex 21- and 28-link planar simple-joint KCs (PSKCs), the proposed algorithm is tested on the complete atlas of 8-link 1-DOF, 9-link 2-DOF, 10-link 1-DOF, 12-link 1-DOF, and 13-link 2-DOF PSKCs. The algorithm is also tested on 6-link 1-DOF and 7-link 1-DOF planetary gear trains (PGTs) to detect isomorphism. All results are in agreement with those of the existing literature. The method is fully automated via a computer program and has been verified to be reliable and efficient.

Correction to “Highly Convergent Total Synthesis and Assignment of Absolute Configuration of Majusculamide D, a Potent and Selective Cytotoxic Metabolite from Moorea sp.”

ADVERTISEMENT RETURN TO ISSUEPREVAddition/CorrectionNEXTORIGINAL ARTICLEThis notice is a correctionCorrection to “Highly Convergent Total Synthesis and Assignment of Absolute Configuration of Majusculamide D, a Potent and Selective Cytotoxic Metabolite from Moorea sp.”Eduardo J. E. Caro-DiazEduardo J. E. Caro-DiazMore by Eduardo J. E. Caro-Diaz, Frederick A. ValerioteFrederick A. ValerioteMore by Frederick A. Valeriote, and William H. Gerwick*William H. GerwickMore by William H. Gerwickhttp://orcid.org/0000-0003-1403-4458Cite this: Org. Lett. 2020, 22, 15, 6220Publication Date (Web):July 17, 2020Publication History Received7 July 2020Published online17 July 2020Published inissue 7 August 2020https://doi.org/10.1021/acs.orglett.0c02252Copyright © 2020 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views825Altmetric-Citations-LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (408 KB) Get e-Alerts Get e-Alerts

Synthesis and networking of tetrahedral deployable mechanism based on screw theory

Aiming at the synchronous motion of tetrahedral deployable unit, the kinematic pair is designed and the coupling motion branch is synthesized based on screw theory. The optimal deployable unit is determined by the application. According to the networking requirements, a networking mechanism composed of multiple units with coupling degree of freedom (DOF) is synthesized. The application of the screw theory in the configuration synthesis of deployable mechanism is realized in this paper. The mechanism is suitable for the deployable mechanism of satellite antenna reflector or other space surface deployable support mechanism, which has broad application prospects.