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Fractals/Computer graphic techniques/workflow

Image processing or pipeline of 2D graphic or workflow

Graphics pipeline in wikipedia

Color Theory: Color_gradient =Stages=

Image processing stages:
 * colour calibration ( for all devices taking an active part of a colour-managed workflow)
 * preprocessing
 * processing ( capturing image = taking the photo, creating digital image )
 * postprocessing = editing a captured image = modification of the image: Graphic algorithms
 * postprocessing raw files

Film ( motion picture) production consists of five major stages:
 * Development: Ideas for the film are created, rights to existing intellectual properties are purchased, etc., and the screenplay is written. Financing for the project is sought and obtained.
 * Pre-production: Arrangements and preparations are made for the shoot, such as hiring cast and film crew, selecting locations and constructing sets.
 * Production: The raw footage and other elements of the film are recorded during the film shoot, including principal photography.
 * Post-production: The images, sound, and visual effects of the recorded film are edited and combined into a finished product.
 * Distribution: The completed film is distributed, marketed, and screened in cinemas and/or released to home video to be viewed.

=color spaces=

For correct results, different Color Spaces are needed for:
 * rendering,
 * display and printing
 * storage of images.

Rendering and compositing is best done in scene linear color space, which corresponds more closely to nature, and makes computations more physically accurate.

=2D pipeline=
 * choose algorithm
 * choose image size in pixels ( iWidth x iHeight = iX_Size x iY_Size)
 * choose plane viewport ( rectangle defined 4 corner points or center, radius and aspect ratio )
 * Choose plane transformation
 * creating empty array
 * Fil array
 * Save array as raw file
 * postprocessing (pl. Poprodukcja)

Another example, for each pixel of a image
 * take integer coordinate of memmory 1D array
 * compute integer coordinate of virtual 2D array
 * compute world coordinate of the pixel
 * compute value of representation function for this pixel
 * compute color of the pixel

Data structures
 * memmory 1D array
 * virtual 2D array

Files
 * raw files with data
 * raster image file with colors ( png, pgm, ... )
 * mixed file with both above informations ( like exr)

"use pro editing techniques by working non-destructively. This means, don’t edit on the original image layer. Instead, duplicate the layer for every type of edit you plan to do. This way, you can repeat the editing steps with a duplicate file at 16 bits." Chris Parker

Steps
 * clipping : covert object in world coordinate to object subset = = applaying world window to object
 * window to vieport mapping
 * rasterisation = (scan conversion) – Convert high level object descriptions to pixel colors in the frame buffer
 * display/ save

RAW
The raw graphic file
 * contains raw pixel data (numbers) in binary format
 * programs can save the raw iteration data for later colouring or other analysis.
 * because the file contains no image formatting information before reading/opening the file one needs informations about:
 * Image dimensions
 * pixel data format
 * Pixel scan order
 * Byte arrangement (little or big endian format)

stages of raw file processing

Actions:
 * reading: from the disc and save data to memory array
 * Colorize = convert raw data info of Pixel to Pixel color.
 * Exposure Value adjustment
 * White balance adjustment
 * Hue and tone adjustment
 * Highlight and shadow recovery
 * Vibrance and saturation adjustment
 * Cropping & Rotation
 * Noise reduction
 * Sharpening
 * Some of the actions that are preferred after conversion to jpg files are
 * Red-eye removal
 * Local touch up of cloning to erase unwanted object in frame
 * Adding of frame
 * Mixing with other output files, like changing the background.
 * saving

Convert and colorize, for each pixel do:

pgm[i] = raw[i]•m

 Examples of RAW Image processing

Example by Kyung-Hoe Huh
 * Raw image before processing
 * Binary image
 * Outline image
 * Skeletonized image after preprocessing
 * Composition image of raw and outline images
 * Composition image of raw and skeletonized image

Image Processing Over Time of A Raw Fractal by ImageJ

Tips
 * "the process of applying full-screen filters and effects to a camera’s image buffer before it is displayed to screen. It can drastically improve the visuals of your product with little setup time."

full HDR pipeline

 * HDR image
 * HLG or PQ transfer function
 * HDR monitor

HDR Content Production Workflow by EIZO:
 * checking the data from a shoot
 * VFX = Visual effects
 * compositing work
 * final color grading.

HDR to SDR pipeline
From HDR to tone mapped SDR
 * HDR image
 * Reinhard & Drago tone mapping
 * SDR display = SDR image tone mapped from HDR

full SDR pipeline

 * SDR image
 * gamma transfer function ( gamma correction)
 * SDR monitor ( SRGB)

color workflow
Rendering intent : color operations should be done with the use case in mind:
 * to either model human perception
 * or the physical behavior of light ( Physically Based Rendering PBR)
 * a linear version of RGB ( not sRGB)

Color space:
 * Images are stored on disk and passed to displays in sRGB, which is approximately perceptually uniform in intensity.
 * Shader math is done in linear RGB, which is physically uniform in intensity.
 * priniting is in CMYK

See also rendering styles:
 * Unbiased rendering = Photorealistic rendering
 * Non-photorealistic rendering
 * Artistic rendering
 * hyperrealistic rendering = Rendering styles that combine photorealism with non-photorealism

Examples

 * krita : color managed workflow
 * blender : blender : official color management and wikibooks
 * efi: fiery color imaging workflow
 * skia color menagment
 * Adobe

Correct procedure when working with graphics is to convert all gamma encoded media to linear intensities, perform any calculation/blending/averaging, and convert back to gamma encoding.

Rendering and compositing is best done in scene linear color space, which corresponds more closely to nature, and makes computations more physically accurate. ( Blender doc)

linear workflow
The Linear Workflow uses linear color space for rendering
 * "In the real world, the colors we perceive are all in linear color space. In order for the monitor to mimic the real world, it needs to also display in linear fashion. Due to the limitations of the monitor hardware and image optimization requirements, images are processed and saved with Gamma correction."
 * Due to limitations of old CRT monitor technology, images can only be displayed via gamma 2.2 color correction. Even though modern monitors can directly display linear images, gamma 2.2 has become something of a standard convention
 * There is no need to linearize floating point image formats such as .hdr and .exr (32 bit) which are already in gamma space 1.0.
 * When a camera snaps an image, an 8 bit image is saved for monitor compatibility and file optimization via sRGB Gamma 0.45 processing.

sRGB Image Gamma 0.45 + Monitor Gamma 2.2 = Final Display Gamma 1

Workflow in Unity3D
Unity3D
 * Linear color space workflow: linear color space rendering gives more precise results
 * Gamma color space workflow: gamma color space is the historically standard format = don't use it

Color buffers by Poimandres
( Open source developer collective ):
 * UnsignedByteType sRGB frame buffers ( = 8 bits per color channel) to store intermediate results. This is a trade-off between hardware support, efficiency and quality. With low precision sRGB buffers, colors will be clamped to [0.0, 1.0] and information loss will shift to the darker spectrum which leads to noticable banding in dark scenes.
 * linear results normally require at least 12 bits per color channel to prevent color degradation and banding. Linear, high precision HalfFloatType buffers don't have these issues and are the preferred option for HDR-like workflows on desktop devices.

Color Pipeline in CUVI
Krita (a GPU-accelerated library for Imaging and Computer Vision applications.)

Let's take a typical color pipeline and measure its performance on one of the entry level GPUs. Any color pipeline almost always starts with the Raw image. Before converting to RGB, you might want to do some processing on the raw which may include applying LUTs (look up tables), FPN (fixed point noise) removal and fixing white balance. Next comes demosaic/debayer followed by several further enhancement functions and a color space conversion into the desired format. This pipeline can perform in real-time on a decent entry level GPU on an 8k images and at over 100 FPS on a 2k image:

Desktop Publishing Workflow

 * GIMP provides top-notch color management features to ensure high-fidelity color reproduction across digital and printed media.
 * It is best used in workflows involving other free software such as Scribus, Inkscape, and SwatchBooker.

Krita color workflow
Krita has two systems dedicated to color management
 * lcms2, which deal with ICC profiles for keeping colors consistent over many interpretations of devices (screens, printers) by using a reference space. for connection with programs like : Gimp 2.9+, Inkscape, digiKam and Scribus
 * OCIO, which deal with LUT color management for manipulating the interpretation of said colors, for connection with programs like Blender and Natron

skia
Skia: The 2D Graphics Library

All the color spaces Skia works with describe themselves by how to transform colors from that color space to a common “connection” color space called XYZ D50.

And we can infer from that same description how to transform from that XYZ D50 space back to the original color space.

XYZ D50 is a color space represented in three dimensions like RGB, but the XYZ parts are not RGB-like at all, rather a linear remix of those channels. Y is closest to what you’d think of as brightness, but X and Z are a little more abstract. It’s kind of like YUV if you’re familiar with that. The “D50” part refers to the whitepoint of this space, around 5000 Kelvin.

All color managed drawing is divided into six parts:
 * three steps connecting the source colors to that XYZ D50 space
 * then three symmetric steps connecting back from XYZ D50 to the destination color space.

Some of these steps can annihilate with each other into no-ops, sometimes all the way to the entire process amounting to a no-op when the source space and destination space are the same.

Color management steps
 * unpremultiply if the source color is premultiplied – alpha is not involved in color management, and we need to divide it out if it’s multiplied in linearize the source color using the source color space’s transfer function
 * convert those unpremultiplied, linear source colors to XYZ D50 gamut by multiplying by a 3x3 matrix
 * convert those XYZ D50 colors to the destination gamut by multiplying by a 3x3 matrix
 * encode that color using the inverse of the destination color space’s transfer function
 * premultiply by alpha if the destination is premultiplied

Requirements for a color-managed workflow

 * Accurate device profiles obtained with source or output characterization software.
 * Correctly loaded video card LUTs (or monitor profiles that do not require LUT adjustments).
 * Color-managed applications that are configured to use a correct monitor profile and input/output profiles, with support for control over the rendering intent and black point compensation.

Calibration and profiling requires:
 * for input devices (scanner, camera, etc.) a color target which the profiling software will compare to the manufacturer-provided color values of the target.
 * or for output devices (monitor, printer, etc.) a reading with a specific device (spectrophotometer, colorimeter or spectrocolorimeter) of the color patch values and comparing the measured values against the values originally sent for output.

Monitor calibration and profiling
One of the critical elements in any color-managed workflow is the monitor, because, at one step or another, handling and making color adaptation through imaging software is required for most images, thus the ability of the monitor to present accurate colors is crucial.

Monitor color management consists of calibration and profiling. The first step, calibration, is done by adjusting the monitor controls and the output of the graphics card (via calibration curves) to match user-definable characteristics, such as brightness, white point and gamma. The calibration settings are stored in a  file. The second step, profiling (characterization), involves measuring the calibrated display's response and recording it in a color profile. The profile is stored in an  file ("ICC file"). For convenience, the calibration settings are usually stored together with the profile in the ICC file.

Note that  files are identical to   files - the difference is only in the name.

Seeing correct colors requires using a monitor profile-aware application, together with the same calibration used when profiling the monitor. Calibration alone does not yield accurate colors. If a monitor was calibrated before it was profiled, the profile will only yield correct colors when used on the monitor with the same calibration (the same monitor control adjustments and the same calibration curves loaded into the video card's lookup table). macOS has built-in support for loading calibration curves and installing a system-wide color profile. Windows 7 onward allows loading calibration curves, though this functionality must be enabled manually. Linux and older versions of Windows require using a standalone LUT loader.

Device profiles
ICC profiles are cross-platform and can thus be created on other operating systems and used under Linux. Monitor profiles, however, require some additional attention. Since a monitor profile depends both on the monitor itself and on the video card, a monitor profile should only be used with the same monitor and video card with which it was created. The monitor settings should not be adjusted after creating the profile. In addition, since most calibration software use LUT adjustments during calibration, the corresponding LUTs must be loaded every time the display server (X11, Wayland) is started (e.g. with every graphical login).

In the unlikely case of a colorimeter being unsupported by Linux, a profile created under Windows or macOS can be used under Linux.

Display-channel lookup tables
There are two approaches to loading display channel LUTs:

 * 1) Create a profile that does not modify video card LUTs and thus does not require LUTs be loaded later on. Ideally, this approach would rely on Display Data Channel (DDC)-capable monitors—the internal monitor settings of which are set via calibration software. Unfortunately, monitors capable of making these adjustments through Display Data Channel (DDC)) are not common and are generally expensive. There is only one calibration software on Linux that can interact with a Display Data Channel (DDC) monitor. For mainstream monitors, a couple of options exist:
 * 2) * BasICColor software, which works with most colorimeters on the market, allows one to adjust display output via the monitor interface, and then to choose a "Profile, do not calibrate" option. By doing this, one can create a profile that does not require video card LUT adjustments.
 * 3) * For EyeOne devices, EyeOne Match allows the user to calibrate to "Native" gamma and white point targets, which results in the LUT adjustment curves displayed after the calibration as a simple, linear 1:1 mapping (a straight line from corner to corner).
 * 4) * Both BasICColor and EyeOne Match do not presently run under Linux but they are capable of creating a profile that does not require LUT adjustments.
 * 5) Use an LUT loader to actually load the LUT adjustments contained within the profile prepared during calibration. According to the documentation, these loaders do not modify the video card LUT by itself, but achieve the same type of adjustment by modifying the X server gamma ramp. Loaders are available for Linux distributions that use X.org or XFree86—the two most popular X servers on Linux. Other X servers are not guaranteed to work with the currently available loaders. There are two LUT loaders available for Linux:
 * 6) * Xcalib is one such loader, and although it is a command-line utility, it is quite easy to use.
 * 7) * dispwin is a part of Argyll CMS.
 * 8) * If, for any reason, the LUT cannot be loaded, it is still recommended to go through the initial stages of calibration where a user is asked by calibration software to make some manual adjustments to the monitor, as this will often improve display linearity and also provide information on its color temperature. This is especially recommended for CRT monitors.

Color-managed applications
In ICC-aware applications, it is important to make sure the correct profiles are assigned to devices, mainly to the monitor and the printer. Some Linux applications can auto-detect the monitor profile, while others requires that it is specified manually.

Although there is no designated place to store device profiles on Linux,  has become the de facto standard.

Most applications running under WINE have not been fully tested for color accuracy. While 8-bits per pixel (bpp) programs can have some color resolution difficulties due to depth conversion errors, colors in higher-depth applications should be accurate, as long as those programs perform their gamut conversions based on the same monitor profile as that used for loading the LUT, granted that the corresponding LUT adjustments are loaded.

Hardware acceleration

 * OpenGl
 * Vulkan
 * SYCL
 * OpenCl
 * CUDA
 * HIP = Heterogeneous-compute Interface for Portability
 * OpenMP
 * OpenACC

=See also=
 * 3D pipeline
 * Category:Graphics_pipeline in commons

=References=
 * benq: how-photographers-incorporate-with-color-management-workflow
 * Basics of Image Processing — Vincent Mazet (Université de Strasbourg), 2020-2023 — CC BY-NC 4.0.
 * image-editor-effects by Alain Galvan
 * CCD ASTROPHOTOGRAPHY processing by Pedro Ré
 * colormanagement.org

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


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User talk:75.89.226.251

A page you created, Monopoly/The_Mega_Edition, has been deleted. This page was also deleted once before. Please stop creating this page - it was likely deleted because it does not cover a topic which fits with the rest of the book (this 'edition' of the game is not well known).--ЗAНИA talk 08:45, 5 July 2020 (UTC)

title: User talk:75.89.226.251


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Talk:Graph Theory/Definitions

Definitions
The definition of a graph is currently phrased as an ordered pair:

"A graph is an ordered pair $$G = (V, E)$$ where, [...]"

It would be better, I think, to define a graph as a set:

"A graph is a set $$G = \{V, E\} $$ of two sets, $$V$$ and $$E$$, where, [...]"

First, no ambiguity is introduced, since each the vertex set and the edge set contain distinct elements, and the vertex set may not be empty. Second, this is slightly more pure with respect to mathematics: Graphs are all about sets, so there's no inherent reason to muddle that. Finally, if we never use the ordering of the ordered pair, then there's no reason to introduce it in the first place.

What do you think? Josh5923 (discuss • contribs) 18:27, 5 July 2020 (UTC)

title: Talk:Graph Theory/Definitions


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User:Day2006

Dayton Ekstraal

title: User:Day2006


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User talk:217.181.21.105

No vandalism on pages. -- Tegel (discuss • contribs) 12:45, 6 July 2020 (UTC)

title: User talk:217.181.21.105


text: User talk:106.78.54.215

title: User talk:106.78.54.215


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Ada Programming/Platform/Portable builds

GPRbuild can be used to make portable builds.

Platform-independent code
Create a project for platform-independent code which is common to all supported platforms.

portable.gpr

Portable Main ("portable.adb"); Exec_Dir "bin"; Source_Dirs use ("src"); Portable;

Platform-specific code
For example, open portable-windows.gpr with GPS or GPRbuild to build a project for Windows.

portable-windows.gpr

Portable.Windows "portable.gpr" Languages ("Ada", "WinRes"); Source_Dirs ("windows", "resources"); Object_Dir "windows-obj"; Exec_Dir "bin"; Linker for Default_Switches ("Ada") use ("-lgdi32", "windows-obj/resources.o", "-mwindows"); Linker; Compiler Driver ("WinRes") "windres"; Default_Switches ("WinRes") ("--target=pe-x86-64"); Leading_Required_Switches ("WinRes") ("-i"); Object_File_Suffix ("WinRes") ".o"; Compiler; Naming Body_Suffix ("WinRes") ".rc"; Naming; Portable.Windows;


text: User talk:2409:4043:2381:6C1F:38F6:3B74:4D01:30B5


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OpenVOGEL/Free flight

=Free flight simulation in OpenVOGEL=

One of the most recent features developed in the OpenVOGEL suit is the free flight simulation module. This module combines the unsteady aeroelastic solver (which provides air loads for a given flow field) with the numerical integration of the rigid body equations of motion (in 6 degrees of freedom). It resembles in some aspects the aeroelastic module, but here the flow field is directly manipulated from the outcome of the equations (in the aeroelastic module, the variation of the flow field is a consequence of the repositioning if the shedding edges).

Coupling algorithm
The free flight simulation consists of an algorithm that couples the air loads and the motion. The air-loads are first computed using the instantaneous flow field at the beginning of each time step using the previous state. Based on these air loads, the motion is predicted (through numerical integration) for the next time step and the result is translated into a new flow field. The air loads are then recomputed in the new state and the motion is corrected in a cycle that is repeated until convergence is reached. Once the convergence criteria are met, the time is advanced by one step.

Equations of motion
If we attempt to write the equations of motion of a rigid body in an inertial reference frame, the inertial properties of the body become time dependent. So to reduce the complexity of the equations, the motion can better be described from the point of view of the body itself (a non inertial reference frame), where the inertia tensor is an invariant. Additionally, to avoid having the kinetic moment being coupled to the momentum, it is convenient to take the reference point for the moments as the center of gravity. Finally, to avoid a complex coupling of the angular velocities in the angular momentum equations, it is much simpler to align the axes with the main axes of inertia.

With all this said, the equations of motion for the rigid aircraft model including the external forces and gravity field can be written as follows :

$$\frac{dt}\bold{G} = \bold{F} + m\bold{g}$$

$$\frac{dt}\bold{H} = \bold{M}$$

Note that we have used Tenembaum's notation, in which the superscript R at the left of the differential operator means that the derivatives are taken with respect to the inertial reference frame (for the sake of simplicity, the earth in our case).

To convert the derivatives to the non inertial reference frame A (the moving aircraft), we use the reference frame transformation formula:

$$\frac{^{R}d}{dt}\bold{a} = \frac{^{A}d}{dt}\bold{a} + \bold{\omega} \times \bold{a}$$

where $$\bold{a}$$ is a generic vector.

The equations turn now to be:

$$\frac{dt}\bold{v} + \bold{\omega} \times \bold{v} = \frac{1}{m} \bold{F} + \bold{g}$$

$$II. \frac{dt}\bold{\omega} + \bold{\omega} \times II. \bold{\omega} = \bold{M}$$

Tenembaum would accurately write the angular velocity vector as $${^R}\bold{\omega}^A$$, however, to simplify the notation (and because we only have two reference frames here) we simply write $$\bold{\omega}$$ to refer to the angular velocity of the aircraft with respect to the earth. The matrix $$II$$ is the tensor of inertia, which for us is an identity matrix with $$I_{xx}$$, $$I_{yy}$$ and $$I_{zz}$$ in the main diagonal and 0's anywhere else.

In order to use the equations for numerical computations, it is necessary to write them in scalar form and to leave the derivatives alone at the left side:

Momentum $$\frac{dt}v_x = \frac{F_x}{m} + g_x - \omega_y v_z + \omega_z v_y$$ $$\frac{dt}v_y = \frac{F_y}{m} + g_y - \omega_z v_x + \omega_x v_z$$ $$\frac{dt}v_z = \frac{F_z}{m} + g_z - \omega_x v_y + \omega_y v_x$$ Angular momentum (Euler's equations) $$\frac{dt}\omega_x = \frac{1}{I_{xx}} [M_x + (I_{yy} - I_{zz}) \omega_y \omega_z]$$ $$\frac{dt}\omega_y = \frac{1}{I_{yy}} [M_y + (I_{zz} - I_{xx}) \omega_z \omega_x]$$ $$\frac{dt}\omega_z = \frac{1}{I_{zz}} [M_z + (I_{xx} - I_{yy}) \omega_x \omega_y]$$

These six equations are not sufficient to describe the motion, since the gravity acceleration vector $$\bold{g}$$ also varies with time in the non inertial reference frame A. So we need to add the next three kinematic equations to the set:

$$\frac{^{R}d}{dt}\bold{g} = \bold{0} \Rightarrow \frac{^{A}d}{dt}\bold{g} = - \bold{\omega} \times \bold{g}$$

and thus, in scalar form:

Rotation of the gravity field $$\frac{^{A}d}{dt}g_x = \omega_z g_y - \omega_y g_z$$ $$\frac{^{A}d}{dt}g_y = \omega_x g_z - \omega_z g_x$$ $$\frac{^{A}d}{dt}g_z = \omega_y g_x - \omega_x g_y$$

Finally, if we want to output the position of the aircraft, then we need to integrate it in parallel also:

Position $$\frac{^{R}d}{dt}P_x = v_x + \omega_y v_z - \omega_z v_y$$ $$\frac{^{R}d}{dt}P_y = v_y + \omega_z v_x - \omega_x v_z$$ $$\frac{^{R}d}{dt}P_z = v_z + \omega_x v_y - \omega_y v_x$$

Note that this position will be relative to the aircraft reference coordinates, so to make it mean full, all points should be remapped to the global reference frame. The program does this when loading the results using the last orientation of the model.

Numerical integration
All the equations derived above form an initial value problem with 12 variables that can be solved using an appropriate numerical integration algorithm. One would probably think of the Runge-Kutta methods as first option, however they are not a good option since they require evaluating the forces at an intermediate time step, creating a complex scheme in our case (the UVLM method is quite heavy to be called continuously). Therefore, probably the best option is to use some kind of predictor corrector method that uses a fixed time step.

The numerical algorithm programmed in OpenVOGEL follows an scheme from Preidikman. This scheme is self-starting. It starts with the Euler method, then it switches to two Adams-Bashford and Adams-Moulton steps of increasing grade, and from the fourth step on it uses the Hamming method only.

In the next frames, vector X is the array (or better said, the record) containing all independent variables of the equations, and vector DX is the array containing the associated derivatives.

Time step 1 > Predict using initial derivatives (Euler) X(1) = X(0) + Dt * DX(0) > Correct for K=0 to M (Modified Euler) Calculate new forces and derivatives... X(1) = X(0) + (0.5# * Dt) * (DX(0) + DX(1))

Time step 2 > Predict using previous derivatives (Adams-Bashford) X(2) = X(1) + (0.5# * Dt) * (3.0# * DX(1) - DX(0)) > Correct for K=0 to M (Adams-Moulton) Calculate new forces and derivatives... X(2) = X(1) + (Dt / 12.0#) * (5.0# * DX(2) + 8.0# * DX(1) - DX(0))

Time step 3 > Predict using previous derivatives (Adams-Bashford) X(3) = X(2) + (Dt / 12.0#) * (23.0# * DX(2) - 16.0# * DX(1) + 5.0# * DX(0)) > Correct for K=0 to M (Adams-Moulton) Calculate new forces and derivatives... X(3) = X(2) + Dt / 24.0# * (9.0# * DX(3) + 19.0# * DX(2) - 5.0# * DX(1) + DX(0)) TE(3) = (9.0# / 121.0#) * (X(3) - XS)

Time steps S = 4 to N (Hamming) > Predict using previous derivatives XP = X(S - 4) + (Dt * 4.0# / 3.0#) * (2.0 * DX(S - 1) - DX(S - 2) + 2.0 * DX(S - 3)) X(S) = XP + 112.0# / 9.0# * TE(S - 1) > Correct for K=0 to M Calculate new forces and derivatives... X(S) = (1.0# / 8.0#) * (9.0# * X(S - 1) - X(S - 3) + 3.0# * Dt * (DX(S) + 2.0# * DX(S - 1) - DX(S - 2))) TE(S) = (9.0# / 121.0#) * ((X(S) - XP)) X(S) = X(S) - TE(S)

Validation

Our VB.NET implementation of the algorithm has been validated for a simple 1-D harmonic oscillator. In such a system the force is a linear function of the position and the velocity:

$$F_x = - K. P_x - C. v_x $$

The analytic solution for the displacement considering only an initial velocity is :

$$P_x (t) = e^{-\xi \omega t} v_x (0) sin (\omega_d t) $$

where:

$$\omega = \sqrt {\frac{K}{M}} $$

$$C_c = 2 \sqrt {KM} $$

$$\xi = \frac {C}{C_c} $$

$$\omega_d = \omega \sqrt {1 - \xi^2} $$

The agreement of the numerical solution for this problem is excellent, as can be seen on the previous graphic. With 400 time steps and a time inteval of 0.025s, the simulation time was 10 seconds. Along the complete integration domain, the error could be maintained under 0.5%.

title: OpenVOGEL/Free flight


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User:Syaifudin857

Syaifudin857

title: User:Syaifudin857


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User:Communpedia Tribal/Guitar/Beginning Chords

This page contains the dozen or so chords that are usually first learned on guitar. These chords are taught to beginners because they are among the easiest to play, while at the same time being chords that are commonly used in many types of music. Learning these chords will:

 * Help you gain in strength and accurate placement of the fingers.
 * Enable you to strum many popular songs. With this skill you can back up your own singing or play rhythm while other players solo.
 * Enable you to play some chord-based solo music such as arpeggios and chord melodies.
 * Give you a foundation for learning more advanced chords.
 * Give you a start at learning the names of notes and at learning song structure and music theory.

The chords are shown using a common type of diagram called a chord window. This is essentially a picture of the guitar neck. The 6 strings of the guitar are shown as 6 vertical lines, and the frets are shown as horizontal lines. The thickest (6th) string is on the left. The extra-thick line at the top is the nut, or zero-th fret. The next line below it is the first fret; the next line down, the second fret; and so on.

Placement of the fingers is indicated by dots added to the diagram. For example, the following diagram shows the 2nd string being fingered at the first fret.

The note being played is, incidentally, a "c", the same as piano middle c (frequency = 262 cycles per second).

When fretting notes, it is best to position the finger just behind the fret, as close as possible to it without going over. This is the easiest way to get a clear tone -- without buzzing. The principle is that you want to apply maximum force to the fret just ahead of your finger -- the fret that is the end point of the string vibration -- while not wasting too much force in pushing the string down against the fret behind or the nut.

However, the finger should not be placed too far forward, or some of the finger meat will touch the vibrating part of the string, muting it and giving a dull sound.

Finger too far forward.


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English-Hanzi/Verbal memory disorder is related with the decline in the ability of word meaning processing

Verbal memory disorder is related with the decline in the ability of word meaning processing. Another memory disorder is episodic memory.

言语记忆障碍与词义处理能力下降有关. 另一种记忆障碍是情景记忆.


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History of wireless telegraphy and broadcasting in Australia/Topical/Biographies/Allan Galbraith Hull

Allan Galbraith Hull was a prominent radio journalist and magazine manager in Australia during the late 1920s, 1930s and 1940s. He took over editorship of the Wireless Weekly in the late 1920s from his well known brother Ross Amos Hull upon the latter's departure to the United States. He continued in that role throughout the 1930s. However, during that period, Wireless Weekly had evolved from a largely technical publication into primarily a radio programme guide. Filling the absence of technical content in Wireless Weekly, from May 1936, a competitor had arisin in Australasian Radio World. Finally in 1939, Wireless Weekly spun off a new publication Radio and Hobbies to meet the need for technical content and Hull's editorial duties were extended to include this magazine also. Hull was dissatisfied with the amount of his time subsumed in non-technical duties. When Australasian Radio World began to fail at the end of 1939, Hull entered into negotiations with Alfred Earl Read and his business partner. Purchase was successfully completed in early 1940 and Hull commenced as owner, publisher and editor of Australasian Radio World from March 1940.

A summary biography has not yet been prepared however the following resources have been assembled in preparation:

 * Transcriptions and Notes - Allan Galbraith "Braith" Hull - More than 50 transcriptions and notes

 * Photos, QSL cards and other graphics - Allan Galbraith "Braith" Hull - Nothing uploaded as yet


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User:Laysancraig

Polish-Aussie plumber who is passionate about tennis.

title: User:Laysancraig


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User:ShubhanTelang

Leave a talk page message by entering a subject topic

Hi friends, I am Shubhan Telang, now a Wikibooks editor, want to share some information about myself. I am a music lover and have a great love for Indian Classical music. I am learning the Tabla and the Harmonium from the past 10 year and have cleared many exams for the same with good marks. I made this account as a Wikipedia editor during the issue of the Global pandemic Coronavirus.

Information about Wikipedia
Talking about Wikipedia, Wikipedia is a multilingual online encyclopedia created and maintained as an open collaboration project by a community of volunteer editors, using a wiki-based editing system. It is the largest and most popular general reference work on the World Wide Web. It helps anyone at any subject. At one click of your button it gives a whole lot of information to you. Editing here is very easy. You just need to Login and you then became a Wikipedia editor. You can edit a Wikipedia page by just clicking at the edit symbol and then selecting the option of 'editing without login'. So Wikipedia wants every one to contribute to its page. This is a true example of sharing knowledge at a worldwide level. Previously when I wasn't an editor, I used to use Wikipedia alot for projects. It's not just me but everyone uses Wikipedia for information. It was a true surprise to me that some 4 years ago there was no connection of me and Wikipedia but now I too am an editor. For encouragement of number of edits done by editors, Wikipedia gives awards to editors for the same. You know, making an account as an editor in Wikipedia means that you are ready to share your knowledge with everyone (but with reliable evidences and sources).

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The meaning of my name, Shubhan is lord Ganapati. My name is a very rare one. It is a name from one of the 108 names of lord Ganapati. My name is Shubhan (शुभन), some people call me Shubham, but making it clear that my name is ..... SHUBHAN !!!

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title: User:ShubhanTelang


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History of wireless telegraphy and broadcasting in Australia/Topical/Publications/Australasian Radio World/Citations

Note that the Citation is for a specific article in the magazine, not the entire issue

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1936 08
WORKING NOTES

EXAMPLE - EDITORIAL

1946 05
Article on Future of Amateur Radio in Australasian Radio World by 2NO EXAMPLE - DON B. KNOCK

Brief autobiography by 2NO EXAMPLE - DON B. KNOCK

1950 04
No issue published

1950 05
No issue published


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History of wireless telegraphy and broadcasting in Australia/Topical/Publications/Australasian Radio World/Issue List

1950 04
No issue published

1950 05
No issue published


text: Economic Sophisms/Advertisement

title: Economic Sophisms/Advertisement


text: Economic Sophisms/Front matter

title: Economic Sophisms/Front matter


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User:Nkanyiso Muthwaa

 House Of Gerd1414

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title: User:Nkanyiso Muthwaa


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User:Lowslo

Sayam Pradhan is an Indian Author and Blogger, born on 05 April 2005. He had written many known books.

title: User:Lowslo


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User talk:SweetCanadianMullet

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title: User talk:SweetCanadianMullet


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Talk:Arimaa/risteall vs. ChrisB

What is the reason for this edit? I prefer it with the inclusion of such commentary. Risteall (discuss • contribs) 19:53, 10 July 2020 (UTC)
 * With 14g saying "The Rf1w step anticipates the silver elephant coming to c2 and thus creating a western goal threat", it seemed like 14s should first explore that possibility. However, that seemed to make the concluding thought a bit awkward. I have now placed a modified version of that thought before 14s. It wasn't just the rabbit in front of the hostage that made the difference, so I'm not sure how much we should emphasize what is in front. Belteshazzar (discuss • contribs) 04:19, 11 July 2020 (UTC)
 * Perhaps this is an improvement. More than anything, this seems like an example of pros and cons of friendly rabbit advances. Belteshazzar (discuss • contribs) 06:04, 7 September 2020 (UTC)

title: Talk:Arimaa/risteall vs. ChrisB


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History of wireless telegraphy and broadcasting in Australia/Topical/Biographies/Donald Brader Knock

Donald Brader "Don" Knock (1898-1966), generally known as "Don B. Knock", was a prominent amateur radio operator and journalist in the early 1920s in England (callsign G6XG) and from the mid 1920s through 1950s in Australia (callsign VK2NO). He was born in 1898 in Manchester, England. Wireless experimentation commenced as early as 1911 in Colchester, England. World War One military service was with the Royal Naval Air Service from 1916. A varied professional career in England included an appointment with the British Broadcasting Company. Knock (callsign G6XG) was the first English amateur to exchange messages with the U.S.A. using low power on shortwave. He emigrated to Australia in 1926, taking an appointment with Amplion Co., then technical editor with "Radio in Australia and New Zealand". In 1930 he established a network of pioneering radiocommunications facilities around the Wyndham Meatworks for the Western Australian government. During that time his station (callsign VK6NK) took the leading role in the rescue of the downed fliers Smith and Shiers in the Kimberley district. Returning to New South Wales he partnered with Marcus Oliver is establishing the commercial radio station 2MO Gunnedah. Returning to Sydney he became technical editor for "Radio Monthly". In 1933 was appointed to the "Bulletin" as editor of their "Australian Radio News" supplement and radio editor for the "Bulletin". He was a regular contributor and later technical editor in the late 1940s for the Australasian Radio World. In the late 1920s and 1930s, Knock was prominent in development of 10 metre and later 5 metre radiocommunications in the Sydney area. Following commencement of World War 2 he again volunteered for military service, concluding as Major, A.I.F. (Army Inspection). When released from the military in 1945, he took an appointment as engineer with the Philips organisation and continued with that firm until retirement. He passed in Sydney in 1966.

Early life and family
Donald was born 10 October 1898 in Manchester, only child to parents Charles Brader Knock (born 1872, Colchester; died 1936, Birkdale, Lancashire) and Winifred Annie Knock nee Hawkins (born 1866, Chacewater, Cornwall; died 1934, Southport, Lancashire). Brader was a family name, his paternal grandmother being Maria Knock nee Brader. His father was a commercial traveller in the publishing industry and the family moved around regularly but within Lancashire. The wireless novelty never failed to produce new developments in the early 20th century and was a constant subject of articles in the press of the day. Even before his teenage years, Don was experimenting with wireless technology and his autobiography refers to this commencing from age 11 years. Despite the early interest in radio and his clear aptitude for this field, his father considered the industry to be a passing fancy and pushed his son into an apprenticeship in mechanical engineering at a local steel works. Tasks there included fitting work on steam engines and motor lorries. Following the passing of his mother in 1934, his father remarried Edith Winifred Pentney the same year. When his father passed in 1936, the family estate went to his second wife.

World War One
Knock was not yet 18 and in a protected job, but receiving a white feather, mis-stated his age and enlisted as a mechanic in the Royal Naval Air Service in 1916. Training was completed at Cranwell aerodrome. Initial posting was as armourer mechanic at Eastchurch (Isle of Sheppey). Duties consisted mostly of working with high explosive bombs for aerial despatch. Additional training was undertaken at the Senior Gunnery School at Whale Island, Portsmouth. First active service posting was Mudros, Lemnos. Subsequently Knock was posted to Stavros, a small harbour on the Macedonian coast. Returning to Mudros, he supported the bombing of Constantinople. Final posting was to Petrovsk where his squadron was involved in the bombing operations against Bolshevik forces in Astrakhan and elsewhere, before withdrawing in August 1919.

Post WW1
At the insistence of his father, following the conclusion of the war, Knock took a position as an improver-apprentice with a major Liverpool shipyard. This was not to his liking and in 1921 he was successful in his application for (marine engineer) with P. & O. Co. on the SS Naldera (lately a transport ship to repatriate Australian troops). His time with P. & O. included a voyage to Sydney in 1922 and while at anchor there he was thrilled to tune in Charles Dansie Maclurcan's regular Sunday broadcasts (callsign 2CM). Back in England he took a sales representative position with a North England motor manufacturer. Finally he was offered his first position in the wireless industry, a sales engineering position with Sterling Co. (later Marconiphone). Ever a roving spirit, he then worked as a receiver service engineer for Burndept at a time when the broadcast industry was exploding in England. A final English appointment was with the British Broadcasting Company as a maintenance engineer at their Leeds-Bradford relay for Yorkshire. This position lasted for a year and was terminated by Knock's emigration to Australia.

Amateur Radio, 1924-1926
Three years of war service had left Knock with a tidy sum for his efforts and much of this was now invested in amateur radio equipment, once the wartime ban on amateur operations was lifted by the PMG. He was a foundation member of the Southport (Lancashire) Wireless Experimental Society and increased his knowledge and skills through time spent with other members. Initial receiving equipment included a war-surplus C MK III trench amplifier and loose coupler tuner with galena detector. He received a transmitting licence in 1924 and was allocated callsign G6XG. The first transmitting system was spark-based operating around 200 metres into a multi-wire cage "T" aerial. Receiver was now three coil with "swinging coil" reaction. Eventually complaints of interference by nearby broadcast listeners led to a shutdown order on G6XG by the PMG and necessarily further upgrade to a continuous wave transmission unit coupled with a Reinartz receiver. Around this time the possibility of two-way communication at medium power (about 250 watts) on shortwave (85/100 metres) between North America and Europe was proven by a contact between USA (callsign U1MO) and France (callsign F8AB). Several English amateurs then quickly duplicated the feat, but Knock's G6XG was the first to do so using low power (about 5 watts), in contacting U1BHM. He is known to have also operated from the facilities of Bloxsom (callsign G5LS) and Roper (callsign G2RK). Knock was also one of a very few to hear Ernest Thomas Fisk from his experimental station at Vaucluse, Sydney contacting Marconi on his yacht "Elettra". In respect of broadcast reception, Knock successfully tuned in the Melba broadcast from Chelmsford, the tests from the liner "Victorian" crossing the Atlantic and the BBC predecessor station 2MT Writtle by Eckersley.

Amplion Co.
On an impulse, Knock booked a passage to Australia and arrived in Sydney in mid-1926. He was soon appointed Chief Engineer to the Sydney branch of the Amplion Co. "Don" quickly became prominent within the Sydney amateur community and beyond. He joined the N.S.W. branch of the Wireless Institute of Australia. He was temporarily exempted from passing the Amateur Operator's Certificate of Proficiency examination on the basis of his prior English experience and licence. The callsign A2NO was allocated and became VK2NO following implementation of the 1927 Washington Conference recommendations. A friendship formed with Harry Turner, brother of well-known early amateur broadcaster Haswell Turner (callsign A2TM). Knock pioneered use of the Zepp antenna in Australia and was prominent in the development of radiocommunication on 20 metres. Harry Kauper (callsign A5BG) was the first to implement transmitter crystal control, but Knock followed suit soon after, being the first in N.S.W.

Wireless Weekly
From about 1927, Knock had started writing brief articles for various technical radio publications based in Sydney, mainly "Wireless Weekly" and the now commonly owned "Radio in Australia and New Zealand." The articles at first mostly described his amateur radio activities, but developed into full receiver construction articles. A detailed article describing construction of his "Go-Getter" receiver was very popular and led to a full-time appointment with "Radio in Australia and New Zealand." Subsequent publication of the "All-Empire" receiver proved equally popular and was both the first metal chassis receiver published in Australia and the first to utilise to advantage the new screen-grid valve as a T.R.F. amplifier for high frequencies. The "All-Empire" immediately proved its worth in monitoring the record breaking flight of the "Southern Cross" (callsign KHAB) by Sir Charles Kingsford Smith from Oakland, California to Australia. Knock was at the forefront developing amateur use of the 10 metre band, but long distance radiocommunications awaited increasing sunspots from 1929, when communication was progressively extended from New Zealand, Hawaii and finally the Americas.

Wyndham Meatworks
The Western Australian government had funded the establishment of a meatworks at Wyndham in 1907 with freezer and canning works as well as full port facilities. Its operation was a significant part of the WA economy and was crucial to the viability of stations and communities across a wide region. In 1930, Knock was engaged to establish a network of radiocommunications stations to service the operation. The network included the meatworks itself (callsign VIX operating on 55 metres, 100 watts), lower power fixed stations at surrounding cattle stations and drafting stations, a maritime launch station servicing the coastal regions (callsign VJQX) and a portable station (callsign VK6JU) for inland testing. Knock himself took out a wireless experimenter's licence for Wyndham (callsign VK6NK). The base station was initially plagued with problems from both natural radio noise (frequent and strong nearby lightning activity) and man-made noise (several nearby electrical motors and appliances). The former was ongoing, the latter moderated by noise-reducing antennas and feeders.

Smith and Shiers Rescue
During Knock's time at Wyndham, in April 1934, he played a leading co-ordination role in the rescue of the the fliers Dave Smith and Wally Shiers in the downed Ryan monoplane "City of Sydney." Knock had been advised that the fliers were departing Mascot aerodrome, Sydney on a flight via Wyndham to England and that the plane carried radio equipment (callsign VMZAB). Signals were received from the fliers stating that the plane had departed Newcastle Waters, Northern Territory with destination Wyndham. Two hours after departure, signals initially faded out in a manner indicative of a landed plane. An hour later SOS signals were deciphered that the plane's engine was damaged and they were forced down in the vicinity of Rosewood. Knock used his amateur equipment to relay the news via Bathurst amateur Trevor Evans (callsign VK2NS) to the authorities in Sydney. Veteran amateur Jack Pike (callsign VK2JP) handled a great volume of traffic with Knock as part of the exercise. The first search party failed to find the plane, but a second, some days later led by Sgt. King, of the W.A. police, with bushman Bill Flinders, of Wyndham located the plane and both fliers, hungry but safe and well. A few weeks later, Smith and Shiers continued their journey towards England, but crashed in Thailand with injuries confined to the plane itself.

2MO Gunnedah
Marcus Oliver had been a licensed wireless experimenter (callsign A2MO, later VK2MO) since the mid 1920s and regularly broadcast entertainment to the town of Gunnedah and surrounds. In 1931 he was granted a commercial broadcasting licence for Gunnedah, but it was the height of the depression and he lacked the funds to establish a higher power facility to give effect to the licence. Oliver joined in a partnership with Knock who relocated to Gunnedah and commissioned a suitable transmitter mostly from his own equipment. The partnership lasted about one year, but the business was not able to support both Oliver and Knock, and Don sold his share back to Oliver and returned to Sydney.

Family
Upon his return from Gunnedah, Donald Brader Knock married Laura Eileen Knock née Vince in Sydney. The couple had one child, a son, Rodney. Don's wanderlust finally abated and he lived the remainder of his life in Sydney.

The Sun
Commencing in July 1931, Knock provided a regular weekly column of radio related news for the Tuesday edition of Sydney's "The Sun" newspaper. He offered commentary on radio propagation, prospects for television, news of long distance broadcast reception, reports on local amateur radio activities. Knock also responded to correspondence from readers with insights into likely receiver problems and suggestions for construction. The column was short-lived however, with his final byline being October 1931. Knock had severed his relationship with "The Sun" in order to take on the role of technical editor of a new publication "Radio Monthly".

Radio Monthly
The first issue of the new magazine "Radio Monthly" appeared dated mid-December 1931. It was published by Federal Publications of Sydney and Knock was the editor. However in mid 1932 Knock resigned his position in order to take up a new appointment as editor of Australian Radio News published by "The Bulletin".

5 Metre Experiments
Knock was prominent in development of 5 metre radiocommunications in the Sydney area. Preliminary tests were undertaken by him at his home location of low height, but range was limited to only a few kilometres. A station was then set up on top of "The Bulletin" offices in George Street, Sydney. A Pickard antenna was utilised and range increased dramatically with limit being Sydney Colville's station at Mascot airport. Tests also included communication with planes in flight. At the 1934 Radio and Electrical Exhibition Knock arranged a popular demonstration of 5 metre duplex working between the stands of his "Australian Radio News" and Ever Ready Battery Co.'s. Directional aerials on 5 metres were also pioneered by Knock and fellow amateur operators Harry Chinner (Callsign VK2CG) and Will Dukes (Callsign VK2WD), extending range to Hazelbrook, Blue Mountains in early 1935.

The Bulletin
Back To Radio Journalism. In 1933, the writer returned to the sphere of radio journalism by an appointment as Technical Editor of "Australian Radio News," then published by "The Bulletin," and during the period until this weekly was absorbed in "The Bulletin," a considerable amount of 5-metre investigational work was done.

Australasian Radio World
Australasian Radio World was a monthly magazine catering to amateurs, radio constructors and shortwave broadcast listeners which commenced in 1936 with editor Alfred Earl "Earl" Read, an expatriate New Zealander. Kock was a regular contributor to the magazine with technical articles and a 9 instalment autobiography in 1937. The magazine was sold to Allan Galbraith "Braith" Hull in 1940 and Knock's relationship continued strong, for a period he was technical editor.

World War Two
Throughout the 1930s Knock participated in the NSW Citizen's militia in the Signals Corp with rank of lieutenant. Upon the commencement of WW2 he volunteered for service and joined the A.I.F. concluding as Major in Army Inspection. As military action wound down he was placed on the reserve of officers in April 1945.

Philips
Knock joined the Philips organisation in June, 1945, and was engaged under Chief Engineer S. O. Jones on special developmental work. In the late 1940s and early 1950s he regularly contributed articles for "Philips Technical Communication." At the end of his professional career, Knock was also engaged in a civilian capacity by the Department of Navy on radiocommunications work.

Later Life
In the mid 1950s, Knock disposed of all of his amateur radio equipment and relinquished his long-held callsign VK2NO. In the early 1960s Knock became ill and after a number of years of poor health, passed on 31 October 1966. The W.I.A. was well represented at his funeral on 3 November 1966 at St. Mary's Church of England, Waverley.

Legacy
In practical terms Donald Brader Knock is best remembered for his early 5 metre directional antenna and his contribution to range extension on the 5 metre band. But his real legacy was the education and encouragement of innumerable amateur radio operators and radio constructors through his published articles on radio construction and commentary on the radio hobby.

Links to Reference Materials - Donald Brader Knock

 * Transcriptions and Notes - Donald Brader Knock - More than 120 transcriptions and notes

 * Photos, QSL cards and other graphics - Donald Brader Knock - Nothing uploaded as yet