Insertion loss (IL) of finite sound barriers of different contours - An introduction to geometrical solutions in 3-D space

2021 ◽  
Vol 263 (6) ◽  
pp. 164-174
Author(s):  
Giora Rosenhouse
Keyword(s):  
Insertion Loss ◽  
Vector Analysis ◽  
Control Points ◽  
Noise Sources ◽  
3D Space ◽  
Sound Barriers ◽  
Environmental Acoustics ◽  
And Control ◽  
Rectangular Barrier

The design of finite sound barriers noise sources and control points requires calculations beyond those that are used when the Maekawa formula is applied, since the problem involves polygon sd barriers located in various possible orientations in 3D space. We present here some means that are linked to basic mathematical geometrical tools. Those means are relatively simple, as compared to the physical formulation of the relevant diffraction solutions for sound barriers (e.g. Rosenhouse, 2019, 2020). Such calculations can apply algebraic, trigonometric or vector analysis and their combinations to define the geometries of barrier IL. This approach includes the location of the sources and control points, which are essential as data for finding IL and other issues of environmental acoustics. We will show solutions including results of IL for a common rectangular barrier, as compared to IL of a barrier with a sloped top and side, among other possibilities.

From NURBS to C-NURBS: I — C-NURBS Curves and Their Properties

1999 ◽  
Author(s):  
Manhong Wen ◽  
Kwun-Lon Ting
Keyword(s):  
Shape Control ◽  
Free Form ◽  
Control Points ◽  
Degree Elevation ◽  
Nurbs Curve ◽  
3D Space ◽  
Cad Cam ◽  
Form Model ◽  
And Control ◽  
The Given

Abstract This paper develops a new free-form model, called c-NURBS, which is a general model of NURBS. A c-NURBS curve or surface is the projection of a 6D B-spline curve from a 6D homogeneous space H6 into a 3D space R3. The construction procedure of a c-NURBS curve or surface is that using cubic curves or bicubic patches repeatedly and piecewisely interpolates the given control points. The distinct properties of c-NURBS include independent weight modification, super-convexity, strong c-convex hull, and hidden degrees and control points. These properties greatly enhance the shape control and modification capability. All techniques developed for NURBS, such as the de Boor-Cox algorithm, knot insertion, and degree elevation and reduction, can be applied to c-NURBS. The implementation of c-NURBS requires little improvement on the CAD/CAM systems based on NURBS.

scholarly journals Fully Automatic Cell Segmentation with Fourier Descriptors

2021 ◽  
Author(s):  
Dominik Hirling ◽  
Peter Horvath
Keyword(s):  
Neural Networks ◽  
Convolutional Neural Networks ◽  
Fundamental Problem ◽  
Cell Segmentation ◽  
Fourier Descriptors ◽  
Control Points ◽  
Coefficient Vector ◽  
Fully Automatic ◽  
High Level ◽  
And Control

Cell segmentation is a fundamental problem in biology for which convolutional neural networks yield the best results nowadays. In this paper, we present HarmonicNet, a network, which is a modification of the popular StarDist and SplineDist architectures. While StarDist and SplineDist describe an object by the lengths of equiangular rays and control points respectively, our network utilizes Fourier descriptors, predicting a coefficient vector for every pixel on the image, which implicitly define the resulting segmentation. We evaluate our model on three different datasets, and show that Fourier descriptors can achieve a high level of accuracy with a small number of coefficients. HarmonicNet is also capable of accurately segmenting objects that are not star-shaped, a case where StarDist performs suboptimally according to our experiments.

Critical Control Points of Street-Vended Foods in the Dominican Republic

1988 ◽  
Vol 51 (5) ◽  
pp. 373-383 ◽  
Author(s):  
FRANK L. BRYAN ◽  
SILVIA C. MICHANIE ◽  
PERSIA ALVAREZ ◽  
AURELIO PANIAGUA
Keyword(s):  
Dominican Republic ◽  
Prevention And Control ◽  
Preventive Measures ◽  
Control Points ◽  
Street Vending ◽  
Ambient Temperatures ◽  
Critical Control Points ◽  
Rice Samples ◽  
And Control ◽  
Time Periodic

Hazard analyses were conducted at four street-vending stands in the Dominican Republic. Temperatures of foods were measured during cooking, display (holding), and reheating (when done). Samples were taken at each step of the operation and at 5 to 6-h intervals during display. Foods usually attained temperatures that exceeded 90°C at the geometric center during cooking and reheating. At three of the stands, foods (e.g., fish, chickens, pork pieces) were fried and held until sold. Leftovers were held overnight at ambient temperatures in the home of the vendor or in a locked compartment of the stand. They were usually reheated early in the morning and displayed until sold. During the interval of holding, aerobic mesophilic counts progressively increased with time from about 103 after cooking to between 105 to 109/g. The higher counts were usually associated with holding overnight. Escherichia coli (in water, milk and cheese samples), Bacillus cereus (in bean and rice samples), and Clostridium perfringens (in meat, chicken and bean samples) were isolated, but usually in numbers less than 103/g. At the other stand, foods (e.g. beans, rice, meat and chicken) were cooked just before serving as complete meals. There were no leftovers. This operation was less hazardous, although there were many sanitary deficiencies. Recommendations for prevention and control of microbial hazards (mainly reducing holding time, periodic reheating and requesting reheating just before purchasing) are given. The need and suggestions for implementing educational activities to alert and inform those concerned about hazards and preventive measures are presented.

scholarly journals Smooth 3D Path Planning by Means of Multiobjective Optimization for Fixed-Wing UAVs

Electronics ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 51 ◽  
Author(s):  
Franklin Samaniego ◽  
Javier Sanchis ◽  
Sergio Garcia-Nieto ◽  
Raul Simarro
Keyword(s):  
Path Planning ◽  
Multiobjective Optimization ◽  
Unmanned Aerial Vehicles ◽  
Design Methodology ◽  
Optimization Problem ◽  
Three Dimensional ◽  
Control Points ◽  
3D Space ◽  
Single Solution ◽  
Constant Altitude

Demand for 3D planning and guidance algorithms is increasing due, in part, to the increase in unmanned vehicle-based applications. Traditionally, two-dimensional (2D) trajectory planning algorithms address the problem by using the approach of maintaining a constant altitude. Addressing the problem of path planning in a three-dimensional (3D) space implies more complex scenarios where maintaining altitude is not a valid approach. The work presented here implements an architecture for the generation of 3D flight paths for fixed-wing unmanned aerial vehicles (UAVs). The aim is to determine the feasible flight path by minimizing the turning effort, starting from a set of control points in 3D space, including the initial and final point. The trajectory generated takes into account the rotation and elevation constraints of the UAV. From the defined control points and the movement constraints of the UAV, a path is generated that combines the union of the control points by means of a set of rectilinear segments and spherical curves. However, this design methodology means that the problem does not have a single solution; in other words, there are infinite solutions for the generation of the final path. For this reason, a multiobjective optimization problem (MOP) is proposed with the aim of independently maximizing each of the turning radii of the path. Finally, to produce a complete results visualization of the MOP and the final 3D trajectory, the architecture was implemented in a simulation with Matlab/Simulink/flightGear.

scholarly journals Noise Source Identification of a Ring-Plate Cycloid Reducer Based on Coherence Analysis

2013 ◽  
Vol 2013 ◽  
pp. 1-5
Author(s):  
Bing Yang ◽  
Yan Liu
Keyword(s):  
High Performance ◽  
High Reliability ◽  
Coherence Analysis ◽  
Noise Sources ◽  
Ring Plate ◽  
Speed Reducer ◽  
Noise Test ◽  
Analysis System ◽  
And Control ◽  
Plate Type

A ring-plate-type cycloid speed reducer is one of the most important reducers owing to its low volume, compactness, smooth and high performance, and high reliability. The vibration and noise tests of the reducer prototype are completed using the HEAD acoustics multichannel noise test and analysis system. The characteristics of the vibration and noise are obtained based on coherence analysis and the noise sources are identified. The conclusions provide the bases for further noise research and control of the ring-plate-type cycloid reducer.

Redundancy utilization for obstacle avoidance of planar robot manipulators

1997 ◽  
Vol 211 (6) ◽  
pp. 463-475 ◽  
Author(s):  
U Sezgin ◽  
L D Seneviratne ◽  
S W E Earles
Keyword(s):  
Obstacle Avoidance ◽  
Computer Simulations ◽  
Redundant Manipulators ◽  
Control Points ◽  
Kinematic Redundancy ◽  
End Effector ◽  
Revolute Joints ◽  
Planar Robot ◽  
And Control ◽  
Configuration Control

Two obstacle avoidance criteria are developed, utilizing the kinematic redundancy of serial redundant manipulators having revolute joints and tracking pre-determined end effector paths. The first criterion is based on the instantaneous distances between certain selected points along the manipulator, called configuration control points (CCP), and the vertices of the obstacles. The optimized joint configurations are obtained by maximizing these distances. Thus, the links of the manipulator are configured away from the obstacles. The second criterion uses a different approach, and is based on Voronoi boundaries representing the equidistant paths between two obstacles. The optimized joint configurations are obtained by minimizing the distances between the CCP and control points selected on the Voronoi boundaries. The validities of the criteria are demonstrated through computer simulations.

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