Geometry of Sailmaking

1981 ◽  
Author(s):  
Ted Andresen
Keyword(s):  
Integral Method ◽  
Current Practice ◽  
Aerodynamic Force ◽  
Pragmatic Approach ◽  
Cross Sectional ◽  
Geodesic Paths ◽  
Two Parameters ◽  
Sectional Shape

The aerodynamic force developed by a sail depends on the sail's shape. The horizontal cross-sectional shape is of particular importance in determining sail performance. Two parameters for describing the shape are presented and three methods of measuring the shape are outlined. The current practice of using edge rounding and broadseaming is de­scribed and four solutions to the problem of creating faster shapes are presented. First, the pragmatic approach which uses an interative search for the fastest edge round and broadseam pattern is examined. Three other approaches that model the sail as a mathematical surface and use geometry to compute the patterns are presented. Here the sail is treated as a stack of horizontal arcs with precisely defined shapes. In one method, a path excess equation is used to calculate the luff round for a mainsail. Another approach plots the geodesic paths on the sail's surface and computes the seam­by-seam broadseaming. Lastly, an integral method is employed to find the broadseaming for a sail based on the Penguin mainsail. Measurements of the sail made by this method are presented and discussed.

On the cross-sectional shape of the cellulose crystallites in the tunicate Halocynthia papillosa

1990 ◽  
Vol 48 (3) ◽  
pp. 566-567
Author(s):  
J.-F. Revol ◽  
Y. Van Daele ◽  
F. Gaill
Keyword(s):  
Contrast Imaging ◽  
Animal Kingdom ◽  
Bright Field ◽  
Field Mode ◽  
Cross Sectional ◽  
Ultrathin Sections ◽  
The Cross ◽  
Sectional Shape ◽  
Valonia Ventricosa ◽  
C Nmr

The only form of cellulose which could unequivocally be ascribed to the animal kingdom is the tunicin that occurs in the tests of the tunicates. Recently, high-resolution solid-state l3C NMR revealed that tunicin belongs to the Iβ form of cellulose as opposed to the Iα form found in Valonia and bacterial celluloses. The high perfection of the tunicin crystallites led us to study its crosssectional shape and to compare it with the shape of those in Valonia ventricosa (V.v.), the goal being to relate the cross-section of cellulose crystallites with the two allomorphs Iα and Iβ.In the present work the source of tunicin was the test of the ascidian Halocvnthia papillosa (H.p.). Diffraction contrast imaging in the bright field mode was applied on ultrathin sections of the V.v. cell wall and H.p. test with cellulose crystallites perpendicular to the plane of the sections. The electron microscope, a Philips 400T, was operated at 120 kV in a low intensity beam condition.

Automated 3D measurement of fiber cross section morphology in handsheets

2012 ◽  
Vol 27 (2) ◽  
pp. 264-269 ◽  
Author(s):  
Christian Lorbach ◽  
Ulrich Hirn ◽  
Johannes Kritzinger ◽  
Wolfgang Bauer
Keyword(s):  
Image Analysis ◽  
Cross Section ◽  
Cross Sections ◽  
Image Plane ◽  
3D Measurement ◽  
Cross Sectional ◽  
Fiber Cross Section ◽  
Fiber Wall ◽  
Sectional Shape ◽  
Cross Section Geometry

Abstract We present a method for 3D measurement of fiber cross sectional morphology from handsheets. An automated procedure is used to acquire 3D datasets of fiber cross sectional images using an automated microtome and light microscopy. The fiber cross section geometry is extracted using digital image analysis. Simple sample preparation and highly automated image acquisition and image analysis are providing an efficient tool to analyze large samples. It is demonstrated that if fibers are tilted towards the image plane the images of fiber cross sections are always larger than the true fiber cross section geometry. In our analysis the tilting angles of the fibers to the image plane are measured. The resulting fiber cross sectional images are distorted to compensate the error due to fiber tilt, restoring the true fiber cross sectional shape. We use an approximated correction, the paper provides error estimates of the approximation. Measurement results for fiber wall thickness, fiber coarseness and fiber collapse are presented for one hardwood and one softwood pulp.

Study of Correctly Expanded Sonic Jet with Air Tabs

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Arun Prasad R ◽  
Thanigaiarasu S ◽  
Sembaruthi M ◽  
Rathakrishnan E
Keyword(s):  
Numerical Study ◽  
Cross Sectional ◽  
Potential Core ◽  
Convergent Nozzle ◽  
Jet Mixing ◽  
Pressure Profiles ◽  
Constant Diameter ◽  
Sonic Jet ◽  
Sectional Shape ◽  
Length Reduction

AbstractThe present numerical study is to understand the effect of air tabs located at the exit of a convergent nozzle on the spreading and mixing characteristics of correctly expanded sonic primary jet. Air tabs used in this study are two secondary jets issuing from constant diameter tubes located diametrically opposite at the periphery of the primary nozzle exit, normal to the primary jet. Two air tabs of Mach numbers 1.0 to 1.4, in steps of 0.1 are considered in this study. The mixing modification caused by air tabs are analysed by considering the mixing of uncontrolled (free) primary jet as a reference. Substantial enhancement in jet mixing is achieved with Mach 1.4 air tabs, which results in 80 % potential core length reduction. The total pressure profiles taken on the plane (YZ) normal to the primary jet axis, at various locations along the primary jet centreline revealed the modification of the jet cross sectional shape by air tabs. The stream-wise vortices and bifurcation of the primary jet caused by air tabs are found to be the mechanism behind the enhanced jet mixing.

Experimental investigation and optimization on field shaper structure parameters in magnetic pulse welding

2021 ◽  
pp. 095440542110148
Author(s):  
Yingzi Chen ◽  
Zhiyuan Yang ◽  
Wenxiong Peng ◽  
Huaiqing Zhang
Keyword(s):  
Magnetic Field ◽  
High Speed ◽  
Light Metal ◽  
Magnetic Pulse ◽  
Cross Sectional ◽  
Magnetic Pulse Welding ◽  
Pulse Welding ◽  
Sectional Shape ◽  
Welding System ◽  
The Magnetic Field

Magnetic pulse welding is a high-speed welding technology, which is suitable for welding light metal materials. In the magnetic pulse welding system, the field shaper can increase the service life of the coil and contribute to concentrating the magnetic field in the welding area. Therefore, optimizing the structure of the field shaper can effectively improve the efficiency of the system. This paper analyzed the influence of cross-sectional shape and inner angle of the field shaper on the ability of concentrating magnetic field via COMSOL software. The structural strength of various field shapers was also analyzed in ABAQUS. Simulation results show that the inner edge of the field shaper directly affects the deformation and welding effect of the tube. So, a new shape of field shaper was proposed and the experimental results prove that the new field shaper has better performance than the conventional field shaper.

scholarly journals Postoperative opioids and risk of respiratory depression – A cross-sectional evaluation of routines for administration and monitoring in a tertiary hospital

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Karoline Kolås Andersen ◽  
Gunnvald Kvarstein
Keyword(s):  
Respiratory Depression ◽  
Patient Monitoring ◽  
Current Practice ◽  
Tertiary Hospital ◽  
University Hospital ◽  
Post Anesthesia Care Unit ◽  
Cross Sectional ◽  
Routes Of Administration ◽  
Surgical Ward ◽  
Cross Sectional Design

AbstractObjectivesOpioids are the most potent analgesics in the treatment of postoperative pain. Respiratory depression is, however, a serious side effect. The aims of this study were to evaluate current practice and routines for post-operative administration of opioids in a Norwegian university hospital and to evaluate whether the clinical safeguards adequately protected patients’ safety regarding risk of respiratory depression.MethodsThe study had a retrospective cross-sectional design and included 200 patients, treated with opioids postoperatively. The patients were treated in a post-anesthesia care unit (PACU) before transferal to a surgical ward. Relevant data such as opioid dosages, routes of administration, sedation and respiratory function, routines for patient monitoring, and numbers of patients with opioid induced respiratory depression was collected.ResultsTwo patients (1%) developed respiratory depression that needed naloxone to reverse the effect, and 32 patients (16%) had a respiratory rate (RR) <10/min, which may have been caused by opioids. In the PACU, the patient’s RR was evaluated on a routine base, but after transferal to a surgical ward RR documented in only 7% of the patients.ConclusionsThe lack of routines for patient monitoring, especially RR, represented a risk of not detecting opioid induced respiratory depression.

Blast Wave Shaping by Altering Cross‐Sectional Shape

2021 ◽  
Author(s):  
Kelly Williams ◽  
Martin J. Langenderfer ◽  
Gayla Olbricht ◽  
Catherine E. Johnson
Keyword(s):  
Blast Wave ◽  
Cross Sectional ◽  
Sectional Shape

scholarly journals A Cross-sectional Survey of the North American Skull Base Society: Current Practice Patterns of Vestibular Schwannoma Evaluation and Management in North America

2017 ◽  
Vol 79 (03) ◽  
pp. 289-296 ◽  
Author(s):  
Jamie Van Gompel ◽  
R. Wiet ◽  
Nicole Tombers ◽  
Anand Devaiah ◽  
Devyani Lal ◽  
...  
Keyword(s):  
North America ◽  
Skull Base ◽  
Vestibular Schwannoma ◽  
North American ◽  
Management Practices ◽  
Current Practice ◽  
Cross Sectional Survey ◽  
Cross Sectional ◽  
Number Of Patients ◽  
Wide Range

Background Very few studies have examined vestibular schwannoma (VS) management trends across centers and between providers. The objective of this study is to examine current practice trends, variance in treatment philosophies, and nuanced or controversial aspects of VS care across North America. Methods This is a cross-sectional survey of North American Skull Base Society (NASBS) members who report regular involvement in VS care. Results A total of 57 completed surveys were returned. Most respondents claimed to have over 20 years of experience and the majority reported working in an academic practice with an affiliated otolaryngology and/or neurosurgery residency program. Sixty-three percent of respondents claimed to evaluate VS patients in clinic with both an otolaryngologist and neurosurgeon involved. Eighty-six percent of respondents claimed to operate on VS with both an otolaryngologist and neurosurgeon involved, while only 18% of neurosurgeons and 9% of otolaryngologists performed surgery alone. There was a wide range in the number of cases evaluated at each center annually. Similarly, there was wide variation in the number of patients treated with microsurgery and radiation at each center. Additional details regarding management preferences for microsurgery, stereotactic radiosurgery, stereotactic radiotherapy, and conservative observation are presented. Conclusion VS management practices vary between providers and centers. Overall, most centers employ a multidisciplinary approach to management with collaboration between otolaryngology and neurosurgery. Overall, survey responses concur with previous studies suggesting a shift toward conservatism in management.

Numerical simulation of strain rate effect on the inelastic behavior of metal matrix composites

2017 ◽  
Vol 24 (2) ◽  
pp. 279-288
Author(s):  
Qiang Chen ◽  
Zhi Zhai ◽  
Xiaojun Zhu ◽  
Caibin Xu ◽  
Xuefeng Chen
Keyword(s):  
Strain Rate ◽  
Metal Matrix Composites ◽  
Metal Matrix ◽  
Plastic Region ◽  
Micromechanical Model ◽  
Matrix Composites ◽  
Cross Sectional ◽  
Axis Orientation ◽  
Array Pattern ◽  
Sectional Shape

AbstractThe primary goal of this paper is to investigate the combined effects of strain rate and microscopic parameters (fiber off-axis orientation, array pattern and cross-sectional shape) on the mechanical behavior of metal matrix composites (MMCs). To this end, a rate-dependent micromechanical model by the combination of finite-volume theory and Bodner-Partom viscoplastic model is developed to analyze the inelastic response of MMCs. In the simulations, the fibers are modeled as linearly elastic while the metal matrix exhibits viscoplasticity. The macroscopic stress-strain response, local stress and strain fields are obtained simultaneously. An acceptable agreement has been found between the model’s prediction and finite-element results, which demonstrates the good predictive capabilities of the proposed method. It is concluded that the composite response is strongly affected by strain rate, fiber array pattern and cross-sectional shape in the elastic-plastic region but to a lesser extent in the elastic region. Furthermore, the clustering array provides stiffer response than random and square ones; the square fiber predicts stiffer response than circular and elliptical ones. However, increasing the strain rate will weaken the influence of clustering array and square fibers.

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