Geometric Axis Research Articles

The Matlab code of the method based on the Full Range Factor for assessing the safety of masonry arches

In most masonry arches stresses are very low and, therefore, collapse does not occur because of material failure. As a consequence, the safety of arches should not be assessed by means of a safety factor based on material strength as for conventional structures. In 1969 Heyman was the first to state that the safety of masonry arches relies on their geometry and proposed a method for computing the so-called “geometrical factor of safety” based on the comparison between the shape of the thrust line and the profile of the arch. In this context, we have recently developed a method capable of computing the line of thrust closest to the geometrical axis and defining a safety factor based on the comparison between such a line of thrust and the profile of the arch, which we have denoted as “performance factor”. In this paper, that supplements the author ref. (Tempesta and Galassi, 2019 [41]), the Matlab code of our method is provided for unlimited and unrestricted use by researchers as well as academics for educational purposes.•The method (denoted as FRS Method) is inspired by the method proposed by Heyman in 1969•Unlike the original iterative method, the FRS Method computes the line of thrust using a one-step procedure, which is less time consuming and provides the exact solution•The original geometrical factor of safety is replaced by a performance factor, that characterizes the range of the equilibrium thrust lines within the profile of the arch effectively and the safety factor in a targeted way

Measurement of the Antenna Phase Center Position in Anechoic Chamber

An algorithm to measure in Anechoic Chamber (AC) the antenna Phase Center (PhC) position is presented. It is based on the assumption that the PhC belongs to the geometrical symmetry axis of the antenna under test. In particular, the algorithm is able to account for the possible presence of an unknown misalignment between such axis and the rotation axis of the turntable of the AC, thus extending the two point-approach available in the literature. The method has been validated through measurements on an X-band microstrip radar antenna.

Study on the three-dimensional orientation of the posterior facet of the subtalar joint using simulated weight-bearing CT.

The purpose of this study was to describe the normal 3D orientation and shape of the subtalar calcaneal posterior facet. This is not adequately described in current literature. In a supine position both feet of 20 healthy subjects were imaged in a simulated weight-bearing CT. A cylinder and plane were fitted to the posterior facet of the surface model. The orientation of both shapes was expressed by two angles in (1) the CT-based coordinate system with the axis of the foot aligned with the sagittal axis and (2) a coordinate system based on the geometric principal axes of the subject's calcaneus. The subtalar vertical angle was determined in the intersection in three different coronal planes of the cylinder. The cylinder's axis oriented from supero-postero-laterally to infero-antero-medially. The plane's normal directed supero-antero-medially in the CT-based coordinate system, and supero-antero-laterally in the other coordinate system. The subtalar vertical angle was significantly different (p < 0.001) between the three defined coronal planes and increased from anterior to posterior. The mean diameter of the fitted cylinder was 42.0 ± 7.7 mm and the root mean square error was 0.5 ± 0.1 mm. The posterior facet can be modelled as a segment of a cylinder with a supero-postero-lateral to infero-antero-medial orientation. The morphometry of the posterior facet in a healthy population serves as a reference in identifying abnormal subtalar joint morphology. More generally this study shows the need to include the full 3D morphology in assessing the orientation of the subtalar posterior facet. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 9999:1-8, 2018.

안도 다다오 지중 미술관의 건축 어휘 및 공간 구성적 특성

Purpose: Tadao Ando's architecture maximizes spatial experiences by his design solutions created in the relationship among surrounding nature, human, and architecture. The Chichu Art Museum is considered as one of his best masterpieces that concentrate Tadao Ando's design philosophy. This research focuses on the analysis of architectural characteristics and aesthetics of the Chichu Art Museum by examining how his common design languages are used and how differentiated characteristic enhances the value of the Chichu Art Museum. It will be a precedent research on the design guideline for museums and buildings made in the underground. Method: This research is to review precedent theses on Tadao Ando's design philosophy & theory and his museum projects, and to figure out the architectural design languages and characteristic of the Chichu Art Museum by visiting Tadao Ando's museums, studying various local materials, and interviewing with the museum staffs. Result: The Chichu Art Museum shows Tadao Ando's universal design languages such as a harmony with the surrounding nature, blending of western modern architecture and eastern traditional architecture, composition of spaces emphasizing geometrical axis and shape, marvelous spaces developed by the exposed concrete and light, and providing various spatial experiences created by phenomenological architectural concept. The distinctive feature is that it maximizes the harmony with surrounding nature by placing all spaces in the underground and blending into the earth. It creates dramatic scenes with contrast of light by incorporating natural light in the underground spaces including courtyards and exhibition halls. Moreover, it has a strong organic relationship between architecture and art works by specifically designing the optimized spaces for artists who use light as a crucial element in their works such as Walter de Maria, James Turrell, and Claude Monet.

A novel method for continuous formation of cord-like collagen gels to fabricate durable fibers in which collagen fibrils are longitudinally aligned.

We developed a continuous formation method of cord-like collagen gels comprising fibrils preferentially aligned along the geometrical axes (CCGs). Collagen (2.5%) dissolved in a sodium phosphate buffer containing 280 mM of sodium chloride was introduced into a stainless cylinder (length 52 mm, diameter 2.0 mm) warmed at 38°C at a linear velocity of 2.5 mm/s. This process caused collagen fibril alignments under acute fibril formation in the cylinder, resulting in continuous formation of CCGs. Fibril formation rate, shear rate, and shear duration were substantial factors for successful CCG formation. Outstanding advantages of this method over conventional wet spinning include the capacity of this technique to form aligned fibrils in the entire gels and to control the diameter of cord-like gels over 1 mm. The air-drying of CCGs which were crosslinked with 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide and N-hydroxy-succinimide produced dry collagen fibers with cross-sectional areas of 0.0123-0.135 mm2 . Upon the rewetting of the fibers, they failed at a stress of 54.5 ± 7.8 MPa, which is higher than the mean failure stress of anterior cruciate ligament tissue (13.3-37.8 MPa). These findings indicate that the CCG formation method enables the fabrication of collagen fibers which are potential components of collagen-based artificial tendons. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 1011-1023, 2019.

Articular-surface-based automatic anatomical coordinate systems for the knee bones

Increasing use of patient-specific surgical procedures in orthopaedics means that patient-specific anatomical coordinate systems (ACSs) need to be determined. For knee bones, automatic algorithms constructing ACSs exist and are assumed to be more reliable than manual methods, although both approaches are based on non-unique numerical reconstructions of true bone geometries. Furthermore, determining the best algorithms is difficult, as algorithms are evaluated on different datasets. Thus, in this study, we developed 3 algorithms, each with 3 variants, and compared them with 5 from the literature on a dataset comprising 24 lower-limb CT-scans. To evaluate algorithms’ sensitivity to the operator-dependent reconstruction procedure, the tibia, patella and femur of each CT-scan were each reconstructed once by three different operators.Our algorithms use principal inertia axis (PIA), cross-sectional area, surface normal orientations and curvature data to identify the bone region underneath articular surfaces (ASs). Then geometric primitives are fitted to ASs, and the ACSs are constructed from the geometric primitive points and/or axes. For each bone type, the algorithm displaying the least inter-operator variability is identified. The best femur algorithm fits a cylinder to posterior condyle ASs and a sphere to the femoral head, average axis deviations: 0.12°, position differences: 0.20 mm. The best patella algorithm identifies the AS PIAs, average axis deviations: 0.91°, position differences: 0.19 mm. The best tibia algorithm finds the ankle AS center and the 1st PIA of a layer around a plane fitted to condyle ASs, average axis deviations: 0.38°, position differences: 0.27 mm.

Elastic Pneumatic Cylinder for Vibration Suppression in Slip Bearings

Vibrations in machines and their effect on performance are analyzed. One of the main sources of vibrations in machine parts is the slip bearing, in which the shaft passes through a bush with some gap. Impact arises when that gap closes. The operation of vibroprotective systems based on an elastic shock absorber is considered. The influence of the rigidity of the elastic element on the performance of slip bearings is analyzed. An elastic pneumatic element of increased rigidity is proposed, in the form of a cylinder with limited radial deformation. This element is able to center the shaft relative to the geometric axis of the bearing under the action of a radial load, thanks to the difference in contact area of the external surface of the bearing housing and the surface of the elastic cylinder. A method is developed for increasing the contact of the elastic element (the pneumatic cylinder with limited radial deformation) and the surface through which the external load is transmitted, with specified bearing parameters: the cylinder length; and the excess gas pressure within the cylinder. The shaft is assumed to fit in the bearing without a gap and the cylinder casing is regarded as inextensible. The deformation and rigidity of the elastic pneumatic cylinder with limited radial deformation are found to depend on the cylinder length and the excess gas pressure within the cylinder cavity. The mathematical formulas obtained permit the determination and specification of the parameters of the pneumatic element (the cylinder length and the excess gas pressure within the cylinder) as a function of the slip bearing’s operating conditions.

Positions of Ocular Geometrical and Visual Axes in Brazilian, Chinese and Italian Populations

ABSTRACTPurpose: To identify the relative positions of geometrical and visual axes of the eye and present a method to locate the visual center when the geometrical axis is taken as a reference.Methods: Topography elevation data was collected using a Pentacam HR ® topographer from 2040 normal eyes of 1020 healthy participants in Brazil, China and Italy. A three-dimensional, rotation algorithm, a first-order Zernike polynomial fit and a nonlinear least-squares error function was used within an optimization function to locate the geometrical axis and the visual center of each eye.Results: The right eyes of participants were significantly more tilted than left eyes throughout the topography scanning process (p < 0.001). The visual centers were always located in the nasal-superior quadrant, although the visual centers of fellow eyes were not symmetrically located. Mean distances between the visual center and the geometrical center in right eyes were 0.8 ± 0.29 mm, 0.56 ± 0.18 mm and 0.91 ± 0.34 mm among Brazilian, Chinese and Italian participants, respectively, and located at angular positions of 38.7 ± 24.5°, 23.0 ± 29.8° and 23.1 ± 28.1° from the nasal side. However, in left eyes, mean distances were 0.76 ± 0.33 mm, 0.45 ± 0.12 mm and 0.75 ± 0.33 mm at polar angles from the nasal side of 59.3 ± 29.0°, 50.6 ± 44.5° and 61.8 ± 34.1°, respectively.Conclusions: Fellow eyes do not perform similarly during the fixation process, with right eyes tending to tilt more than left eyes, and the visual centers of the fellow eyes positioned differently relative to the geometrical centers.

Prestressed cold-formed steel beams: Concept and mechanical behaviour

An innovative concept, whereby the load-carrying capacity and serviceability performance of cold-formed steel beams are enhanced by utilising prestressing techniques, is presented. The prestressing force is applied by means of a high-strength steel cable, which is housed at a location eccentric to the strong geometric axis within the bottom hollow flange of the cold-formed steel beam, inducing initial stresses in the beam that are opposite in sign to those introduced during the subsequent loading stage. As a consequence, the development of local instabilities during loading is delayed and thus the capacity of the beam is enhanced. Furthermore, the pre-camber induced during prestressing, as well as the contribution of the cable to the bending stiffness of the system, decrease the overall vertical deflections of the beam. The conceptual development of prestressed cold-formed steel beams and a study investigating the potential benefits are presented. The mechanical behaviour of the proposed beams in both the prestressing and imposed loading stages is described in terms of analytical expressions, while failure criteria for the design of the cold-formed steel beam and the cable are also developed by employing interaction equations in conjunction with the Direct Strength Method. Geometrically and materially nonlinear finite element analysis with imperfections is employed to simulate the behaviour of the proposed beams. Sample numerical results are presented and compared with the developed analytical expressions and failure criteria, demonstrating the substantial enhancement in moment capacity and serviceability performance offered by these beams.

Geometry of the Large Magellanic Cloud using multiwavelength photometry of classical Cepheids

We determine the geometrical and viewing angle parameters of the Large Magellanic Cloud (LMC) using the Leavitt law based on a sample of more than $3500$ common classical Cepheids (FU and FO) in optical ($V,I$), near-infrared ($JHK_{s}$) and mid-infrared ($[3.6]~\mu$m and $[4.5]~\mu$m) photometric bands. Statistical reddening and distance modulus free from the effect of reddening to each of the individual Cepheids are obtained using the simultaneous multi-band fit to the apparent distance moduli from the analysis of the resulting Leavitt laws in these seven photometric bands. A reddening map of the LMC obtained from the analysis shows good agreement with the other maps available in the literature. Extinction free distance measurements along with the information of the equatorial coordinates $(\alpha,\delta)$ for individual stars are used to obtain the corresponding Cartesian coordinates with respect to the plane of the sky. By fitting a plane solution of the form $z=f(x,y)$ to the observed three dimensional distribution, the following viewing angle parameters of the LMC are obtained: inclination angle $i=25^{\circ}.110\pm 0^{\circ}.365$, position angle of line of nodes $\theta_{\text{lon}}=154^{\circ}.702\pm1^{\circ}.378$. On the other hand, modelling the observed three dimensional distribution of the Cepheids as a triaxial ellipsoid, the following values of the geometrical axes ratios of the LMC are obtained: $1.000\pm 0.003:1.151\pm0.003:1.890\pm 0.014$ with the viewing angle parameters: inclination angle of $i=11^{\circ}.920\pm 0^{\circ}.315$ with respect to the longest axis from the line of sight and position angle of line of nodes $\theta_{\rm lon} = 128^{\circ}.871\pm 0^{\circ}.569$. The position angles are measured eastwards from north.

The geometrical axis of the talocrural joint—Suggestions for a new measurement of the talocrural joint axis

BackgroundDespite intensive research there is no consensus about the talocrural joint axis. The aim of the present study is a new method to determinate the geometric rotational axis of the talocrural joint. MethodsWe analyzed 98 CT-scans of full cadaver Caucasian legs. We generated three-dimensional reconstruction models of the talus. A best fitting cone was orientated to the talar articular surface. The geometric rotational axis was defined to be the axis of this cone. ResultsThe geometric rotational axis of the talocrural joint is orientated from lateral–distal to medial–proximal (85.6°±10 compared to anatomical tibial axis in torsional plane), from posterior–distal to anterior–proximal (81.43°±44.35 compared to anatomical tibial axis in sagittal plane) and from posterior–medial to anterior–lateral (169.2°±5.91 compared to intermalleolar axis in axial plane). ConclusionsThe consideration of our results might be helpful for better understanding of ankle biomechanics.

Principles for the Construction of a Metrological Complex for Certification of High-Precision Optoelectronic Goniometers

The geometric diagram of a bench for determining the instrument errors of high-precision two-dimensional optoelectronic goniometers is considered. These errors are found by measuring the angles between known spatially fixed reference directions and comparing the values obtained to the sizes of these angles measured by means of autocollimators oriented to a special caliber (calibrating prism) that fixes the point of intersection of the geometric axes of the controlled goniometer. The caliber standard is in the form of a multifaceted prism with reflective surfaces the normals to which form the required geometric diagram in space.

GRAVITY MIXERS WITH VIBRATION ACTIVATOR IN CONSTRUCTION ENGINEERING

Vibration processes and corresponding machinery and equipment are widely used in construction, production of construction materials and other industries. Compaction, crushing, separation, piling, dosing and transportation of bulk materials are just several processes where it is expedient to use vibration. The article presents original designs of gravity (drum) mixers with vibration activators placed inside the mixing chamber. A vibration activator is installed in dead zones located along the geometrical axis of the mixing chamber where intensity of convective mixing is low. Methods of design of balanced eccentric vibration activators of precessing type are considered. Results of production tests with regard to the industrial design of the gravity vibration mixer are presented. Considerable attention is paid to measurement of the vibration level reflecting the quality of dynamic balancing of the vibration activator. Vibrational impact on the environment and maintenance personnel amounts to ~ 5 m/s2, corresponding to standard values for processing equipment as per GOST 22061-76.

Tradition and modernity in the designs and fabrics fashion gowns Islamic

The importance of the heritage of the Iraqi heavy symbolism and connotations where contacted habits rights and beliefs from antiquity to the present, in addition to being represented with data aesthetic it is an expression philosophical concepts associated implications incentives cultural aesthetic of the content of the intellectual including contents of semantics and symbols and the dimensions of the meanings Sayings , to turn form a legacy popularly moving window to communicate worth studying its details and search function on the character and identity and origins . Where have emerged in recent years, a phenomenon characterized by inventing new designs by modernist styles that have entered into technical system design and effectiveness to its full potential until it became one of the components of the foundation in the art of design. And here lies the importance of modernity being characterized by taking it more than knowledge domain in the various and diverse intellectual bases , and when he has designed fabrics presence of modernist trends in thought and planning. Where the first chapter discusses the problem of the research to answer the following question , Is it possible to achieve modernity symbols of heritage designs in fabrics and costumes gowns Islamic ? The aim of the research : know the design features of the vocabulary of the heritage of Iraq . , II : Trying to recruit vocabulary inherited the same meaning and significance in the designs of fabrics and fashion gowns Islamic . adopted the limits of search products Iraqi Fashion House . has dealt with the theoretical framework first topic : Attributes aesthetic elements and symbols in the legacy of Iraq , while the second modernity and technology design in fabrics and fashion gowns Islamic . , and Chapter III : measures since been identified research community , which amounted to (10) design parameter model , has reached the research sample (5) models sampled according to deliberate on the methods of application and selection criteria to achieve the goal of the research. research and reach to the most important results : 1-Adoption of designer configurations derived from the environment in which they live, characterized by simplicity in terms of the method of execution or distribution . 2 - to adopt forms of elements and vocabulary inherited style geometric axis are the complexity and simplification to represent the idea of ​​integration with functional purpose. The most important conclusions : . 1 - owning designer Iraqi aware and willing to express his ideas and requirements derived from the environment and cultural heritage , and thus creating a model expresses the identity of the community to emphasize its close connection to societ 2 - keep pace with scientific development and innovation of a new method to express the changes of modernity in the design formats . 3 - contributed to the means and the technical developments in the formulation of ideas and artistic concepts of modernity , which involved the design configuration of the fabrics in form and substance . Research has recommended an emphasis on experience on how to pick and use ways and means of art direction and layout , and proficiency that by the designer to achieve design plan , and the creation of technical staff specializes in the use of computers to carry out the variables of color and formality and repetitive in design processes on fabrics multifunctional . The proposals include research study vocabulary folklore and handicraft industries and employment in the areas of design and printed fabrics woven and knitting , and conduct a study to establish the foundations of a design to fabric designs in the light of modern developments.

Теоретичне дослідження руху робочих органів ширококолійного агрозасобу

The purpose. Elaboration of mathematical dependences determining acceptable limits of cross-section offsets of end-effectors of specialized wide-track agricultural machines, and justifying area of protected zone proceeding from absence of damageability of plants. Methods. Original positions of theoretical mechanics, theory of probability, creation of programs and calculations on PC. Results. New mathematical dependences determining acceptable limits of cross-section offsets of end-effectors, which are characterized by root-mean-square aberration of agrotechnical conditions according to damageability of plants in a row are developed. Such situation often occurs at general assessment of indexes of operation wide-track agricultural machines in track system of farming agriculture. Conclusions. At arrangement of end-effectors of cultivator for wide-track agricultural machines it is necessary to consider the factor of variance of their offsets. For the end-effectors which are outside concerning geometrical axis of a row and center of agricultural machine, the value of protection zone should be greater than for inner, under condition of uniform damage of plants in a row (approximately for 3 cm).

Preoperative Ultrasonographic Assessment of the Anterior Pelvic Plane for Personalized Total Hip Replacement.

Correct positioning of the acetabular component is a key factor in minimizing the risk of dislocation after total hip replacement (THR) surgery. A "safe" orientation of the cup is usually defined by 2 angles measured between its geometric axis and the anterior pelvic plane. However, in the current state-of-the-art approach to THR surgery, the intraoperative orientation of the anterior pelvic plane cannot be measured. Even less is known about the functional orientation of the pelvis, which determines the postoperative orientation of the cup during the patient's everyday activities. The aim of this article is to present an original approach to personalized THR surgery, in which the necessary measurements are done preoperatively without interfering with the surgical work flow, and the individual orientation of the cup is obtained without navigation using standard tools that are available in the operating room. To quantify the effect of the anatomic conditions on the final orientation of the cup, we measured the orientation of the anterior pelvic plane in 43 patients scheduled for THR using a newly developed noninvasive method based on ultrasonography and mobile devices. Our results confirm a large variability of the pelvic orientation in both supine and standing positions. We further show how this variability affects the final position of the cup and discuss its consequences for the patient. Finally, we explore a few practical solutions for individualized cup placement, including our own approach, which is based on tilting of the operating table. In this work, we show that the common guidelines used today for cup implantation can only be effectively applied to a small portion of the population. In most cases, it is crucial that the orientation of the cup is readjusted for the particular anatomy of the individual patient.

ОТ АКТИВНОГО ЛЕМЕХА К РЕЖУЩИМ АППАРАТАМ

The subject of the article relates to agricultural machinery, namely, to the working units of root harvesting machines and to cutting device of harvesting machines. In both the first and second designs, work is performed in an abrasive medium, which reduces their service life and increases energy costs. The devices are proposed, in which the work is carried out in the absence of abrasive friction in the working parts. The novelty of devices is marked by patents for invention. The effect is achieved by the special arrangement of the geometric axes of the joints of the links, which are designed on needle roller bearings, by the simplicity of structures, by reduction of energy costs for the drive of the working units, by reliability and durability.

Changes in echo-pulse instantaneous frequency when scanning the transducer

A theoretical model has been proposed that makes it possible to explain peculiarities in the frequency characteristics of echo signals at the output of a receiving transducer depending on the geometrical parameters of a reflecting spherical surface when the transducer axis is displaced with respect to the surface’s center of curvature, that is, during scanning. It has been demonstrated that both with and without displacement of the transducer’s geometrical axis with respect to the center of curvature of the reflecting surface, the type of changes in the temporal dependences of the instantaneous frequency of signals at the output of the receiving transducer essentially depends on the geometrical parameters of a wavefront reflected from the surface: the smaller the radius of wavefront curvature at the aperture of the receiving transducer, the stronger the changes of the instantaneous frequency in the echo pulse. It has also been shown that the larger the curvature of this surface, the stronger the changes in the frequency characteristics of the echo pulse as the transducer axis is displaced with respect to the center of curvature of the reflecting spherical surface.

Influence of electro-magneto-thermal environment on the wave propagation analysis of sandwich nano-beam based on nonlocal strain gradient theory and shear deformation theories

In this paper, the dispersion characteristics of elastic waves propagation in sandwich nano-beams with functionally graded (FG) face-sheets reinforced with carbon nanotubes (CNTs) is investigated based on various high order shear deformation beam theories (HOSDBTs) as well as nonlocal strain gradient theory (NSGT). In order to align CNTs as symmetric and asymmetric in top and bottom face-sheets with respect to neutral geometric axis of the sandwich nano-beam, various patterns are employed in this analysis. The sandwich nano-beam resting on Pasternak foundation is subjected to thermal, magnetic and electrical fields. In order to involve small scale parameter in governing equations, the NSGT is employed for this analysis. The governing equations of motion are derived using Hamilton\'s principle based on various HSDBTs. Then the governing equations are solved using analytical method. A detailed parametric study is conducted to study the effects of length scale parameter, different HSDBTs, the nonlocal parameter, various aligning of CNTs in thickness direction of face-sheets, different volume fraction of CNTs, foundation stiffness, applied voltage, magnetic intensity field and temperature change on the wave propagation characteristics of sandwich nano-beam. Also cut-off frequency and phase velocity are investigated in detail. According to results obtained, UU and VA patterns have the same cut-off frequency value but AV pattern has the lower value with respect to them.

Applying Spatial Orbit Motion to Accelerometer Sensitivity Measurement

For appropriate application of an accelerometer, it is required to measure both its geometric axis of sensitivity and transverse sensitivity. Besides single-axial vibration exciters and planar testing systems, a tri-axial vibration exciter with the ability of generating spatial orbit motion steps in the field of transducer calibration. The method of applying spatial orbit motion to accelerometer sensitivity measurement is investigated. Amplitudes and phases of the acceleration components for a tri-axial vibration exciter to compose a given spatial orbit is derived. The accelerometer output vector of a spatial spherical orbit that is composed of multiple rotated circular orbits is constructed. The over determined rectilinear equations of the accelerometer output vector are formulated to solve the accelerometer’s sensitivity by the least squares approach. The output vectors of the spatial spherical orbit are distributed on a sphere surface and the determined accelerometer sensitivity matches well with the spatial orbit motion and the measured accelerometer outputs.