Variable-Geometry Extrusion Die Synthesis and Morphometric Analysis Via Planar, Shape-Changing Rigid-Body Mechanisms

The presented work advances the kinematic synthesis methodology for planar, shape-changing rigid-body mechanisms. This methodology approximates a set of profile curves that represent the desired shapes with a single chain comprised of rigid links connected by revolute or prismatic joints. Two applications of the shape-changing chains are investigated. The first one is variable-geometry dies for polymer extrusion. The exit orifice of an extrusion die defines the cross-sectional shape of the extruded products. A die that alters its orifice shape during extrusion is capable of extruding products of varying cross section, which benefits the extrusion process by reducing the material waste and time cost. The second application is morphometric analysis. Morphometrics is the quantitative analysis for comparing a set of geometric representations of biological forms, including shape and size. Current forms of morphometrics require analyzing numerous variables. Rigid-body shape-change theory can be used as an alternate approach to analyzing morphometric problems. The primary advantage of the presented approach is that a modest number of physical parameters describes the shape and size change among a set of curves. The presented work addresses the constraints arising in the two applications and improves the methodology in the following aspects. First, new types of design profiles are implemented to accommodate the need in moveable die designs. Second, in order to reduce or eliminate the use of revolute joints in die designs which create leak path, the manner in which segments are connected can be specified a priori as either fused or by revolute joints. Third, algorithms for assembling the chain with revolute joints and aligning it with the target profiles while satisfying endpoint constraints for different types of profiles are presented. Fourth, a strategy for approximating profiles containing sharp corners or high-curvature regions is presented. Fifth, a new type of segments is introduced to address growth factor for morphometric applications. Other contributions of the presented work include a new algorithm for randomly generating an initial segment matrix, eliminating segments from the chain during optimization process, an alternate approach to determining matching error, shifting endpoint locations for closed profiles, and animating the morphing chain. The rigid-body shape-change methodology was applied to several die design and morphometric problems, and the results proved the capability of the presented technique in the applications investigated

Improving techniques for center of mass estimation using statically equivalent serial chain modeling

Any system composed of rigid bodies connected by revolute, spherical, and/or universal joints defines a Statically Equivalent Serial Chain (SESC). The SESC is a virtual serial chain that terminates at the center of mass (CoM) of the original system. The SESC is defined by the individual link masses, the CoM location of each mass, the distance between the joints, and the relative joint axis orientations. The joint angles of the SESC change corresponding to the movement of the original system, thereby keeping its terminus pointing at the CoM location of the original system for any configuration. A SESC may be generated experimentally without any knowledge of the individual link masses, the CoM location of each mass, and the distance between the joints. The data that is needed includes the relative orientations between joint axes, the current joint values, and the CoM of the entire articulated system. In most cases, the SESC can be derived with only partial CoM information collected for each configuration. An example of this is collecting the x and y values of the CoM in a horizontal plane while not knowing its height or z value. The resulting SESC is able to generate the location of the CoM for an arbitrary configuration given the joint angles. Necessary conditions are generated on the minimum number of data points needed to generate a SESC. The minimum number needed depends on the number of links of the original system, the dimension of the CoM data collected for each configuration, and a measure of the degree of redundancy in the columns of the matrix associated with the initial SESC modeling.This thesis presents four developments toward recognizing the SESC as a practical modeling technique. First, modifications to a matrix necessary in computing the SESC model are proposed. The modifications are required due to redundant columns that arise in the matrix as part of the modelling process. Second, a SESC is developed via experimentation for a spatial articulated rigid-body system. The SESC was derived from planar CoM data and joint readings, and generated predictions of the spatial CoM with acceptable accuracy. Third, problems of generating a SESC experimentally are presented and a possible remedy is proposed. If only partial dimensions of the CoM are measured during data collecting, and the CoM locations of one or more bodies in the system cannot be changed with respect to the unmeasured direction, then the SESC derived experimentally cannot predict the system\u27s CoM location in the unmeasured direction. A potential remedy for this problem is that the stationary body has a similar mass distribution (identical or symmetric) to a second body in the system, and both bodies are the outer most links in their branches. For this case, the SESC modeling for the full CoM estimation would not be impacted. This observation is particularly useful in studies including human or humanoid subjects, because these subjects are likely to keep one foot on the ground when they keep static balance and the two feet are (roughly) symmetric bodies. Fourth, with the goal of understanding the quantity of data required before the experimentally-constructed SESC obtains acceptable accuracy, an investigation of the error of the experimental SESC versus the number of data readings collected in the presence of errors in joint readings and CoM data is conducted. A general form of the function for estimating the error of the experimental SESC is propose

Improving techniques for center of mass estimation using statically equivalent serial chain modeling

Any system composed of rigid bodies connected by revolute, spherical, and/or universal joints defines a Statically Equivalent Serial Chain (SESC). The SESC is a virtual serial chain that terminates at the center of mass (CoM) of the original system. The SESC is defined by the individual link masses, the CoM location of each mass, the distance between the joints, and the relative joint axis orientations. The joint angles of the SESC change corresponding to the movement of the original system, thereby keeping its terminus pointing at the CoM location of the original system for any configuration. A SESC may be generated experimentally without any knowledge of the individual link masses, the CoM location of each mass, and the distance between the joints. The data that is needed includes the relative orientations between joint axes, the current joint values, and the CoM of the entire articulated system. In most cases, the SESC can be derived with only partial CoM information collected for each configuration. An example of this is collecting the x and y values of the CoM in a horizontal plane while not knowing its height or z value. The resulting SESC is able to generate the location of the CoM for an arbitrary configuration given the joint angles. Necessary conditions are generated on the minimum number of data points needed to generate a SESC. The minimum number needed depends on the number of links of the original system, the dimension of the CoM data collected for each configuration, and a measure of the degree of redundancy in the columns of the matrix associated with the initial SESC modeling.This thesis presents four developments toward recognizing the SESC as a practical modeling technique. First, modifications to a matrix necessary in computing the SESC model are proposed. The modifications are required due to redundant columns that arise in the matrix as part of the modelling process. Second, a SESC is developed via experimentation for a spatial articulated rigid-body system. The SESC was derived from planar CoM data and joint readings, and generated predictions of the spatial CoM with acceptable accuracy. Third, problems of generating a SESC experimentally are presented and a possible remedy is proposed. If only partial dimensions of the CoM are measured during data collecting, and the CoM locations of one or more bodies in the system cannot be changed with respect to the unmeasured direction, then the SESC derived experimentally cannot predict the system\u27s CoM location in the unmeasured direction. A potential remedy for this problem is that the stationary body has a similar mass distribution (identical or symmetric) to a second body in the system, and both bodies are the outer most links in their branches. For this case, the SESC modeling for the full CoM estimation would not be impacted. This observation is particularly useful in studies including human or humanoid subjects, because these subjects are likely to keep one foot on the ground when they keep static balance and the two feet are (roughly) symmetric bodies. Fourth, with the goal of understanding the quantity of data required before the experimentally-constructed SESC obtains acceptable accuracy, an investigation of the error of the experimental SESC versus the number of data readings collected in the presence of errors in joint readings and CoM data is conducted. A general form of the function for estimating the error of the experimental SESC is propose

Improving Techniques in Statically Equivalent Serial Chain Modeling for Center of Mass Estimation

Any articulated system of rigid bodies defines a statically equivalent serial chain (SESC). The SESC is a virtual chain that terminates at the center of mass (CoM) of the original system of bodies. An SESC may be generated experimentally without knowing the mass, CoM, or length of each link in the system given that its joint angles and overall CoM may be measured. This paper presents three developments toward recognizing the SESC as a practical modeling technique. Two of the three developments improve utilizing the technique in practical applications where the arrangement of the joints impacts the derivation of the SESC. The final development provides insight into the number of poses needed to create a usable SESC in the presence of data collection errors. First, modifications to a matrix necessary in computing the SESC are proposed, followed by the experimental validation of SESC modeling. Second, the problem of generating an SESC experimentally when the system of bodies includes a mass fixed in the ground frame are presented and a remedy is proposed for humanoid-like systems. Third, an investigation of the error of the experimental SESC versus the number of data readings collected in the presence of errors in joint readings and CoM data is conducted. By conducting the method on three different systems with various levels of data error, a general form of the function for estimating the error of the experimental SESC is proposed

Superchirality induced enhanced circular dichroism spectroscopy via multi-beam superposition

Circular dichroism (CD) spectroscopy is a typical technique to detect the chirality of an object. Due to the mismatch between light wavelength and the size of molecules, CD signal generally tends to be very weak in natural materials. In this work, we demonstrate the generation of superchiral field in free space through multi-beam superposition, without plasmonic/dielectric substrate that required in traditional methods. Through a systematic study of the superposition effect of up to six beams of light, we found that even achiral light fields can obtain optical chirality through superposition, and circularly polarized light fields can most effectively enhance the optical chirality density in the interference field. Generally, a maximal superchiral factor equivalent to the number of superposed beams can be achieved through optimizing the orientation of the illumination. However, when the number of superposed beams is more than three, the initial phase of superposed beams would play a significant role in determining the characteristics of the interference field, which must be carefully treated in modulating both the shape and the optical chiral density of the synthesized subwavelength chiral hotspot. Furthermore, we demonstrate that this technique is suitable to combine optical tweezers and CD spectroscopy. Based on three-beam superposition configuration, we explore the optical force and CD effects from single chiral nanoparticle, which are introduced into the optical standing wave formed by a flat mirror. It is found out that the nanoparticle can be stably trapped by the superchiral hotspot and gives rise to 2.92-fold enhancement of CD signal. This work may serve as a guideline for establishing applications in chirality sorting, chiral imaging, and CD spectroscopy

MXene Hollow Spheres Supported by a C–Co Exoskeleton Grow MWCNTs for Efficient Microwave Absorption

Highlights A hollow core–shell structure was constructed with C–Co as the exoskeleton to support the MXene and multiwalled carbon nanotubes (MWCNTs) endoskeleton, with MWCNTs growing toward the center of the sphere. A reflection loss of − 70.70 dB and an effective absorption bandwidth of 5.67 GHz were obtained when the thickness was only 2.04 mm. The powder filler ratio was only 15 wt%. The unique hollow core–shell structure enhanced multiple reflection and scattering losses

Telomere dysfunction promotes small vessel vasculitis via the LL37-NETs-dependent mechanism

Background: Small vessel vasculitis (SVV) is a group of systemic autoimmune diseases that are mediated by neutrophil extracellular traps (NETs) in response to cathelicidin LL37, an aging molecular marker, which could be induced by telomere dysfunction. Therefore, in this study, we evaluated the hypothesis that telomere dysfunction in neutrophils may promote SVV via an LL37-NETs-dependent mechanism. Methods: We contrasted the release of neutrophil NETs from mice with telomere dysfunction, mice with DNA damage and wide-type mice. Neutrophil telomere length, the expression of LL37, and the formation of NETs were measured in SVV patients and healthy controls (HCs). The co-expression of gamma H2AX, LL37, and NETs were detected in SVV patients to evaluate the association of the immune aging of neutrophils and pro-inflammatory conditions. LL37 inhibitor was used to verify its key role in NETs release in SVV patients and DNA damage mice. Results: We found that NETs were over-induced by telomere dysfunction and DNA damage in mice, which may be associated with a marked increase in LL37. For patients with SVV, telomeres in neutrophils were significantly shortened, which was also associated with higher levels of LL37 and NETs. Inhibition of LL37 reduced the NETs released from neutrophils. Conclusions: Taken together, the results of these studies suggest that dysfunction of telomeres may promote SVV through the mechanism of LL37-dependent NETs. Thus, targeting the LL37-NETs may be a novel therapy for SVV.Funding Agencies|National Basic Research Program of ChinaNational Basic Research Program of China [2012CB517603]; National Natural Science Foundation of ChinaNational Natural Science Foundation of China [81470938, 81200546, 81300619]; Zhejiang Science and Technology Department [LQ19H050005, 2012C13G2010133]</p

Whole-Genome Analysis of an Extensive Drug-Resistant Acinetobacter Baumannii ST195 Isolate from a Recipient After DCD Renal Transplantation in China

Background/Aims: Infection with Acinetobacter baumannii was emerging as one of the leading causes of mortality after donation after cardiac death transpalantion. Methods: We reported a case of a recipient who underwent DCD renal transplantation and later got infected by A.baumannii. Etests were done to verify the susceptibility test results in clinic. Whole-genome analysis was applied to investigate the resistant mechanism at gene level. Results: The pathogen was isolated from his draining liquid the day after the surgery, and susceptibility test reavealed that it was sensitive to tigecycline. However, the isolate obtained from the draining liquid became tigecycline-resistant after fifteen-day administration of tigecycline. The Susceptibility tests showed that the pathogen recovered from tigecycline resistance and became intermediated to tigecycline. Whole-Genome analysis revealed the genetic level change leading to tigecycline resistance and we identified the location of mutation by comparing the whole genome sequence of the isolates. Three loci were figured out which may contribute to drug resistance, including genes encoding HTH domain protein, MFS transporter and AdeS. Conclusion: Understanding the genetic characteristics associated with drug resistance mechanism and antimicrobial profiles of pathogen is important in controlling infection outbreak and preventing serious complications and gives a new insight into the development of antimicrobial agents