A normal section plane method for profile error analysis of five-axis machine tools based on the ideal tool flank milling surface

The existing studies on profile error analysis and machining accuracy measurement do not consider the impact of the theoretical errors on the machine tool accuracy measurement. Therefore, this study proposes an estimation method of the surface profile error based on the normal section plane, using the theoretical flank milled surface for comparison. This effectively improves the accuracy of profile error estimation. The theoretical flank milled surface is the surface machined by flank milling under ideal conditions. Hence, compared to the traditional analysis method based on the designed three-dimensional model of S-shaped test pieces, the calculated profile error of this method does not include theoretical errors, thereby eliminating the impact of theoretical errors on machine tool accuracy measurement and evaluation. First, an improved method for continuous parameterized dual spline interpolation was proposed. It simplifies the solution of the singular problem of the coefficient matrix of the spline basis function and obtains a continuous ideal machining tool axis trajectory surface with complete geometric characteristics. Next, a method for constructing the theoretical flank milled surface machined with a cylindrical milling tool using equidistant mapping characteristics was proposed; then, the differential transformation relationship at the cutting contact point of the curved surface under the influence of tool path errors was established. Furthermore, the normal section plane method based on the differentiation of the cutting contact point was proposed. The problem of solving the distance from a point to a surface is converted to the problem of solving the distance from a point to a curve in the normal section plane. This improves the accuracy of profile error estimation. The effectiveness of the method was verified by comparing the analysis results of the profile errors of a typical cylindrical surface with the point to surface and the point to curve methods.

New Method for Analysis of the Temporomandibular Joint Using Cone Beam Computed Tomography

Modern dentistry commonly uses a variety of imaging methods to support diagnosis and treatment. Among them, cone beam computed tomography (CBCT) is particularly useful in presenting head structures, such as the temporomandibular joint (TMJ). The determination of the morphology of the joint is an important part of the diagnosis as well as the monitoring of the treatment results. It can be accomplished by measurement of the TMJ gap width at three selected places, taken at a specific cross-section. This study presents a new approach to these measurements. First, the CBCT images are denoised using curvilinear methods, and the volume of interest is determined. Then, the orientation of the vertical cross-section plane is computed based on segmented axial sections of the TMJ head. Finally, the cross-section plane is used to determine the standardized locations, at which the width of the gap between condyle and fossa is measured. The elaborated method was tested on selected TMJ CBCT scans with satisfactory results. The proposed solution lays the basis for the development of an autonomous method of TMJ index identification.

The edge regions in tergites of the desert isopod Hemilepistus reaumuri: the transition from hard cuticle to flexible arthrodial membrane

The arthrodial membrane is a thin and flexible type of cuticle that inserts at the edge regions of neighbouring rigid skeletal elements creating a flexible connection. In the present study, we analyzed the structure, mineral composition, calcite organization and local stiffness and hardness of edge regions that form transitions to the arthrodial membranes in the tergites of the desert isopod Hemilepistus reaumuri. For the transitions to the arthrodial membrane, the results show an increase in the thickness of the epicuticle at cost of the distal exocuticle and a calcite layer, an increase in the ratio of phosphorus to calcium and a decrease in the local mechanical properties. The posterior edge region contains an unusually large stack of unidirectionally oriented parallel fibrils projecting to the lateral sides. At the edge, it turns down into a long ventral cuticle overlapping an anterior part of the neighbouring tergite. It forms a thin arched gap between the tergites that can help reducing water loss through the arthrodial membrane and protects the arthrodial membrane upon predation. A thick ventral ridge near the transition to the arthrodial membrane carrying bristles can prevent sand grains from access to the arthrodial membrane. From the dorsal cuticle to the transition to the arthrodial membrane, calcite units become larger and single crystalline turning their c-axes orientation perpendicular to the sagittal section plane. Comparison with edge regions of the beach isopod Tylos europaeus reveal common characteristics of the edge region, but also specific adaptations to the desert habitat of H. reaumuri.

Aerospace and Ergonomic Methods for Ear Anthropometry Supported by Bulgarian Research

Translation into English has recently been completed for excerpts on ear and craniofacial anthropometry from an innovative, unpublished Bulgarian-language doctoral thesis written in 1986 by a plastic surgeon, M. M. Madzharov, MD-PhD; MD-SC. Most remarkable among the many benefits of the translation was revelation of heretofore unavailable text descriptions for 49 dimensions. Of these, 43 explain the titles and abbreviations with summary statistical data on ear measurements for young adults that were published in 1989 in the English language. Especially valuable among these data were four new and unique, long-axial ear lengths, all measured from a common ear landmark. These could locate “station planes” for cross-section views of human ears, similar to those for 3-D coordinate systems in aircraft and spacecraft fuselage engineering. Examples explaining the concepts and values of such a new approach to ear anthropometry are herein introduced, described and illustrated, together with previously recommended improvements in ear anthropometry notation and illustration, a virtual Ear Primary View Plane, a section plane through the ear long axis, newly introduced “semi-width” measurements extending perpendicular to the aforementioned section plane, new concepts of “view depths,” which are measured perpendicularly from the Ear Primary View Plane toward ear surfaces and a previously described three-axis aircraft motion analogy for defining static ear orientation. These innovative approaches are advocated for adoption by future researchers, designers of related hardware, modelers and standards developers.

The Centriolar Adjunct–Appearance and Disassembly in Spermiogenesis and the Potential Impact on Fertility

During spermiogenesis, the proximal centriole forms a special microtubular structure: the centriolar adjunct. This structure appears at the spermatid stage, which is characterized by a condensed chromatin nucleus. We showed that the centriolar adjunct disappears completely in mature porcine spermatozoa. In humans, the centriolar adjunct remnants are present in a fraction of mature spermatids. For the first time, the structure of the centriolar adjunct in the cell, and its consequent impact on fertility, were examined. Ultrastructural analysis using transmission electron microscopy was performed on near 2000 spermatozoa per person, in two patients with idiopathic male sterility (IMS) and five healthy fertile donors. We measured the average length of the “proximal centriole + centriolar adjunct” complex in sections, where it had parallel orientation in the section plane, and found that it was significantly longer in the spermatozoa of IMS patients than in the spermatozoa of healthy donors. This difference was independent of chromatin condensation deficiency, which was also observed in the spermatozoa of IMS patients. We suggest that zygote arrest may be related to an incompletely disassembled centriolar adjunct in a mature spermatozoon. Therefore, centriolar adjunct length can be potentially used as a complementary criterion for the immaturity of spermatozoa in the diagnostics of IMS patients.

Section Plane Effects on Morphometric Values of Microcomputed Tomography

Objectives. Histomorphometry is the established gold standard for inspection of trabecular microstructures in biomaterial research. However, microcomputed tomography can provide images from the perspective of various section planes. The aim of the present study was to evaluate the effects of different section planes, which may cause bias in two-dimensional morphometry, on the morphometric values of microcomputed tomography. Methods. A socket preservation technique was performed on the extracted premolar area of 4 beagle dogs. After an 8-week healing period, a total of 16 specimens were obtained and analyzed with conventional histomorphometry and microtomographic morphometry. Using the original images of the histologic specimens for comparison, the most similar tomographic image was selected by trial and error. Then, the section plane was then moved with ±79 μm parallel offsets and rotated ±10° around the center from the occlusal view. The images were compared in terms of bone, graft, and noncalcified area, and the concordance correlation coefficient (CCC) was calculated. Results. There was a high CCC in the comparison between histomorphometric images and the most similar microtomographic images. However, the CCC value was low in the comparisons with both parallel movement and rotation. Our results demonstrate that the sectioning plane has a significant effect on measurements. Conclusion. Two-dimensional morphometric values for biomaterial research should be interpreted with caution, and the simultaneous use of complementary 3-dimensional tools is recommended.

Extraction of Rotational Surfaces and Generalized Cylinders from Point-Clouds Using Section Curves

In industrial facilities, there are various types of equipment composed of surfaces that have a high degree of freedom. Rotational surfaces and generalized cylinders are often used for equipment handling liquids and gases. In this paper, we propose methods for reconstructing rotational surfaces and generalized cylinders from noisy and incomplete point-clouds captured by a terrestrial laser scanner. In our method, we convert point-clouds into wireframe models and calculate the intersection points with section planes. Then, we extract ellipses from the intersection points on each section plane and reconstruct the rotational surfaces and generalized cylinders using the extracted ellipses. We also propose a method for subdividing a rotational surface into primitive surfaces. We evaluated our method using actual point-clouds of engineering facilities and confirmed that our method could successfully reconstruct rotational surfaces and generalized cylinders.

Modeling and analysis of variable-core groove for integral cutting tools

With good stiffness, the helical groove with variable-core radius has been widely used for end mills, drills and other integral cutting tools. However, ground by five-axis grinder, its machining process is high cost and time consuming. Thus, this paper reports a graphical analysis method to obtain the structure parameters and geometric shapes of variable-core grooves with the known wheel geometry and position before the practical machining. The wheel movement during the machining process is firstly decomposed into three simple motions and modeled as a translation matrix. Then, a family of wheel surfaces is calculated and the groove cross section line is deduced by splitting the surfaces with a cross section plane. Accordingly, the normal section line of the groove is expressed by a series of scattered points, which are the intersections of the normal section plane and the helical curves generated by the points on the groove cross section line which moves along the wheel trajectory. All the mathematic models are programed by Matlab and verified by experiment. Finally, the key parameters of the variable-core groove, including the rake angle, groove width on the cross and normal sections and the departure distance between the cross and normal groove section lines, are analyzed from the tool bit to the hilt.