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  • Dirk Bertels - Banjo
    of the word banjo can be found in Thomas Jefferson s notes on African American music in Notes on the State of Virginia 1781 The instrument proper to them is the banjar which they brought hither from Africa Bela Fleck who went to Africa in 2009 to research this topic and recorded with various African musicians including the great acoustic guitarist D Gary singer Oumou Sangare kora player Toumani Diabate and Bassekou Kouyate has this to say The akonting could very well be the original banjo Everyone around Banjul certainly seems to think so Huge numbers of slaves came west from this area We were told that the musicians were allowed to play these instruments on the slave ships and that many lives were saved due to it Ref Biography on Bela Flecks s website Some great articles on the subject of banjo ancestors and the Akonting can be found on the shlomo music website back to index Tuning and Strings Following are the 5 standard tunings for the banjo Each has a characteristic sound mainly due to the 5th string which is tuned to a different interval in each case The tuned strings are listed from fifth string the short one downwards Open G g D G B D Standard Bluegrass and Old Time tuning key of G fifth string is root g Sometimes the 5th string capo is set to different pitches such as a or b to facilitate playing in different keys C tuning g C G B D Bluegrass and Old Time tuning Key of C Fifth string is Fifth g Open D a D F A D Bluegrass tuning Key of D Fifth string is Third F or Fifth a Double C g C G C D Old Time tuning Key of C Fifth string is Fifth g D dorian g D G C D Old time tuning modal pentatonic The standard string gauges I use are from the 5th string down 010 023 016 012 010 As stated previously my favourite setup now is Open G tuned a Fourth down For this you need heavier gauge strings From the fifth string down John Hartford uses 012 024 020 014 012 with a wound third the 20 gauge string Ideally you use a 24 fret banjo such as the John Hartford Deering Banjo I would too if I had about 5000 dollars spare You would think that using heavier gauge strings puts more strain on the neck but that is not a given it s all relative See my writing on String Tension for more on this back to index Picking Technique In learning a new tune I often encounter unique characteristics that I know will help my technique overall I hope to convey these techniques in the following chapters as well as various approaches to difficult passages Not wanting to preach too much I would like to list some practice hints here related specifically to the banjo In determining what the best way of playing a passage is note that notes fingered on strings whose open notes are a part of the scale are less efficient D d e f g 9 7 on string 3 and 2 are better than 5 4 on strings 2 and 1 Mississippi Dew example Learn solos from other instruments eg violin mississippi dew mandolin leather britches Notice that sometimes it seems ther RH is having difficulty while it s actually the LH or the synchronization of both hands that s the problem Learn left hand with easy rh version using p s and h s then adapt right hand for best sound LH RH synchronization is the key to mastering the banjo and string instruments in general The HOs and POs should be in time I for one tend to play these to quick And some more general practice hints Speed comes from accuracy Practice the difficult passages mainly When practicing with backup always try to catch up with the tune after a mistake Don t let mistakes creep in Place notes for musicality not for convenience Difficulty of passages vary at different speeds Aim to practice close to the required tempo Suzuki method Only press on the frets as hard as needed Learn the correct fingering at the start it has to work at the proper speed Mistakes are hard to undo back to index Notation Tablature and Software People get all worked up on the topic of music notation claiming it affects the music But I suspect that s just because they re not very good at it Notation is just a means to an end a tool The trick is not to become dependent on it My advice would be to use notation to learn or notate stuff but relegate it to memory as soon as possible That way you get the best of both worlds Just as books enable the masses to read so does music notation and tablature make music available to everybody that s willing to learn it and that can t be a bad thing The music I will publish on another page will be in the TEF format These files can be opened with freely available software called TEFView With this you can display the notation both music and tablature and play the files as MIDI meaning you can transpose alter tempo and all that good stuff If you want to be able to edit create or alter the files yourself you can get TablEdit from the same page at a low cost around USD 60 The TEF file format is widely used and appears on many websites that feature tablatures While the result is generally good the software takes some getting used to For reference purposes I m adding some notes here on TablEdit because one tends to forget F4 F9 whole note to 32nd note rest TAB Advance cursor Form da capo etc Midi Reading list right column displays song list LH fingering Notes Picks strokes Fingerings

    Original URL path: http://www.dirkbertels.net/music/banjo.php (2016-04-30)
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  • Dirk Bertels - tension
    the following unit conversion Hence the fundamental equation can be written as f frequency in Hz or cycles second L string length between nut and bridge in meters T Tension Force on the string in kg F Kilogram force P Unit Weight of the string in Kg m To convert Newtons into Pound force use the unit conversion Therefore the fundamental equation can be rewritten as f frequency in Hz or cycles second L string length between nut and bridge in meters T Tension Force on the string in lb f Pound force P Unit Weight of the string in Kg m Imperial Equation for String Tension The Unit Weight P can be derived from manufacturers datasheets such as D Addario s datasheet However you ll often find it given in Pounds per linear Inch Hence we need an equation that allows for Imperial units To derive this we need to take the standard equation and multiply each factor with the amount required for the imperial unit The conversion factors are 1 Newton 1 4 448222 0 224809 lb f 1 kg 2 204622 lb 1 m 39 370079 inch Inserting these conversion factors in the standard equation gives the following proportional relationship Note that I left out the constant 2 and the f factor because they are the same in imperial the conversion factors would be 1 Solving this relation gives Hence the final equation using imperial units f frequency in Hz or cycles second L string length between nut and bridge in inches T Tension Force on the string in lb f Pound force P Unit Weight of the string in pounds linear inch Accounting for imperfection The above derived value of 386 088 is somewhat different from the value of 386 4 given on D Addario s

    Original URL path: http://www.dirkbertels.net/music/tension.php (2016-04-30)
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  • Dirk Bertels - threads
    a lot of data needs downloading the BackgroundWorker will download the files using its own process freeing up the application for the user To start the BackgroundWorker use bgw RunWorkerAsync To stop the backgroundWorker use bgw CancelAsync The following code shows the framework for the BackgroundWorker using namespace System ComponentModel for BackgroundWorker public System ComponentModel BackgroundWorker bgw InitializeBackgroundWorker bgw gcnew BackgroundWorker set required settings bgw WorkerReportsProgress true bgw WorkerSupportsCancellation true initialise the three eventhandlers bgw DoWork gcnew DoWorkEventHandler this MyClass Bgw DoWork bgw RunWorkerCompleted gcnew RunWorkerCompletedEventHandler this MyClass Bgw RunWorkerCompleted bgw ProgressChanged gcnew ProgressChangedEventHandler this MyClass Bgw ProgressChanged private void Bgw DoWork Object sender DoWorkEventArgs e get the backgroundworker that raised this event BackgroundWorker worker dynamic cast BackgroundWorker sender assign the result of the operation to the result property of the DoWorkEventArgs this now will be available to the RunWorkerCompleted EventHandler e Result MyProcedure worker e private void MyProcedure BackgroundWorker worker DoWorkEventArgs e if worker CancellationPending e Cancel true Do the work here ReportProgress int someNumber will call Bgw ProgressChanged worker ReportProgress someNumber eg update progressbar private void Bgw ProgressChanged Object sender ProgressChangedEventArgs e int value e ProgressPercentage take action such as updating your progressbar switch e ProgressPercentage case 0 break private void Bgw RunWorkerCompleted Object sender RunWorkerCompletedEventArgs e Do whatever needs doing once the process is completed Using the ThreadPool QueueUserWorkItem There are many uses for the ThreadPool class One such use is when I want to send an object service data to a server over the network By using the ThreadPool QueueUserWorkItem method you queue the service and data in its own thread and allocate a delegate to handle the task Assumimg you have created such an object ready to send you can start the process by calling ThreadPool QueueUserWorkItem The object is assumed to be derived from

    Original URL path: http://www.dirkbertels.net/computing/threads.php (2016-04-30)
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  • Dirk Bertels - fretboard
    above finding Recursive Method This method calculates each distance depending on the previously obtained result The only factor that needs to be known is the total length between the bridge and the nut referred to as the Scale It s not a big step from the above equation to the first one below d1 is the distance from the nut to the first fret s is the Scale which is the distance between the bridge and nut d2 is the distance from the nut to the second fret note that this result depends on the previously acquired value for d1 general version for the recursive equation n is the fret number e g for the 11th fret replace n with 11 Non recursive Method This equation doesn t need previously calculated results it stands on its own It too is derived from the 12 2 formula stated at the beginning d1 is the distance from the nut to the first fret s is the Scale which is the distance between the bridge and nut note that a power of 1 12 is the same as the 12 2 it s just written differently Therefore 2 to the power of 11 12 is the same as 12 2 11 the 12th root of 2 to the power of 11 d2 is the distance from the nut to the second fret note that the values decrease as the fret number increases general version derived from the 2 equations above n is the fret number There is an interesting limitation in this general equation Once we reach fret 12 the whole factor containing the power becomes 1 and the distance for fret 12 will be halfway the length remember how we described this in the intuitive explanation for the 12th root of 2

    Original URL path: http://www.dirkbertels.net/music/fretboard.php (2016-04-30)
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  • Music -> sound, scales and tuning
    the one string using whole number ratios These frequencies or pitches or tones occur naturally in all stretched strings They are therefore in harmony with nature hence the term harmonics Harmonics Note name pitch Ratio length of string Fundamental Do 1 1 1 st harmonic Dol 1 2 2 nd harmonic Sol 1 3 3 rd harmonic Do 1 4 4 th harmonic Mi 1 5 Pitches played together produce the Major chord Do Mi Sol In the above we used ratios based on the fundamental string note Do which was set to unity 1 But we can derive just by using the information we already have another set of ratios namely the ratios between each successive pair of notes This will determine the interval between these pairs To do this we need to make one of each pair unity The first pair we encounter in the above list already has the first one set to unity So we can say our first interval has the ratio of 1 2 The next pair of ratios are 1 2 and 1 3 The interval between this which is actually a ratio of ratios can be calculated as follows Make the first one unity and remember the factor needed to make it unity ie we need to multiply the 1 2 by 2 to get unity This factor 2 needs to be made common to both So to retain the interval we then need to multiply 1 3 by 2 also ie 2 3 The above argument is made for the other pairs too this way we can expand our table above Harmonics Note Ratio length of string Interval distance Interval name Note Fundamental Do 1 1 1 1 2 1 2 Octave Do 1 st harmonic Do 1 2 2 1 3 2 3 Dominant fifth Sol 2 nd harmonic Sol 1 3 3 1 4 3 4 Subdominant fourth Fa 3 rd harmonic Do 1 4 4 1 5 4 5 Mediant third Mi 4 th harmonic Mi 1 5 Temperate tuning From 1990 notebooks Note Ratio Interval Frequency c 1 Unison 128 Hz d 8 9 major second e 4 5 major third f 3 4 perfect fourth g 2 3 perfect fifth a 3 5 major sixth b 8 15 major seventh c 1 2 octave to find a n octave multiply by 2 1 perfect fifth 3 2 perfect fourth 4 3 major third 5 4 minor third 6 5 major second 9 8 minor second 16 15 major sixth 5 3 minor sixth 8 5 minor seventh major seventh 15 8 Semitone ratio x 12 2 To raise note by half a tone multiply note s frequency by x To lower note by half a tone divide note s frequency by x Finding the number of beats per second This knowledge is used by piano tuners for tempering the piano scale Octave ratio 2 1 out by 1 vibration manifests as 2 beats per second Fifth

    Original URL path: http://www.dirkbertels.net/music/scales_and_tuning.html (2016-04-30)
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  • Dirk Bertels - Digital Imaging Resolution
    one pixel For this we use the equation OF p SQRT w 2 h 2 16 000 w width of array in pixels h height of array in pixels p pixel size in micrometers Given that my camera s image size in pixels is 3072 2304 the size of one pixel for my camera is p OF 16 000 SQRT w 2 h 2 p 1 2 33 16 000 SQRT 3072 2 2304 2 p 1 788 microns This value seems quite small generally I ve seen values closer to 6 microns but it s not in the realm of impossibility back to index Spatial Resolution It is a well known fact that the resolution given by digital cameras is not true resolution it just gives you the number of pixels that the image consists of For example if the image size is 4288 x 2848 then the given resolution is 4288 x 2848 12 2 megapixel A more accurate definition of resolution is the number of pixels that covers a particular area It is generally measured in pixel per inch ppi on cameras and dots per inch dpi on printers The standard rule for high quality resolution for printers is 300 dpi at actual size A low resolution image would have 72 dpi The quality of an image depends on more than just Pixels per Inch we also need to take into account factors such as sensor quality optics interpolation used etc There is a somewhat empirical method we can use to measure what is sometimes referred to as Spatial Resolution Spatial Resolution is the hypothetical maximal number of distinguishable squares that could be fitted in an image ref Wikipedia Image Resolution The spatial resolution of current CCDs is similar to that of film while their resolution of light intensity is one or two orders of magnitude better than that achieved by film or video cameras ref Nicon Microscopy Spatial Resolution is calculated to determine the optimal resolution required for a particular camera Any more pixels above this optimal value doesn t add anything to the quality of the picture and just wastes storage space The following description describes one method to measure spatial resolution It is an elaboration on the article Wikipedia Image Resolution You need a free image editor such as Gimp and an image that has 100 100 10 000 squares We will refer to this image as the model Open the model in Gimp and zoom in until you just can see the black white alternating squares The zoom factor is not crucial just ensure that your pc displays the squares sharply Assuming adequate lighting take images with your camera of this model at ever increasing distances no need to measure your distances Rely on the auto focus to keep things in focus Open each image in Gimp and zoom into the model determine if you still can distinguish the squares From the images that were successful in the previous step select the one

    Original URL path: http://www.dirkbertels.net/imaging/resolution.php (2016-04-30)
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  • Dirk Bertels - Knots
    the trucker s hitch or Karash Rescue rope Truckers and rescuers execute this loop with one quick underhand movement of the left hand Clove Hitch Basic hitch e g to temporarily tie boat to a shore fixture Good to start lashings Bag Hitch Secure binder Used as anchor hitch for the Trucker s Hitch Variant of the Clove Hitch Constrictor Where tension is applied and maintained from 2 opposite sides Grips like a boa constrictor Very hard to undo Variant of the Clove Hitch Bowline Possibly the most standard knot to create a non slipping loop at the end of a rope The bowline has been called the king of knots A must know for general usage The proper way to tie a bowline can be seen on Youtube Bowline knot It is more practical and less prone to error than the rabbit out of a hole method However I found it still necessary to learn to tie it from the opposite point of view which seems to make more sense to me The initial loop formed in the bowline can be doubled or trippled The Cowboy Bowline where the tail ends up outside the loop is said to be more secure during ring loading The Rapid Bowline is made by passing the end of a rope around an object then tying a loose Slip knot in the main part of the rope and passing the end through it Pulling on the main part will capsize the knot into a Bowline This technique is used in the Karash Rescue Knot Figure 8 or Flemish Bend Basically a figure 8 knot that is turned in on itself Different methods of tying depending whether you need to strand it through a ring or whether the ring can be clipped into the loop Widely used by mountaineers 3 versions on Bight an open loop Follow Bend Climbers often prefer the Figure Eight Bend with some type of Stopper Knots over other bends for situations when lives are at stake Alpine Butterfly or Lineman s Loop My favourite knot Generally condidered the strongest in line loop knot Needed when creating a loop in line for tying the kayak onto the roofbar Used by climbers to hook onto the same rope Used to circumvent weak parts of a rope Also as a bend to tie two ropes together See Alpine Butterfly Bend How to There are various ways of tying this knot I prefer the method as shown in Tie an Alpine Butterfly Knot If you want to use the Alpine Butterfly loop at the end of the rope without creating the loop first such as would be needed when fastening the end of a rope around an anchor point that is fixed on both ends so that no loop can be thrown over it you need to use a follow through method as can be seen at davidmdelaney s Butterfly Bend Loop it doesn t matter which way you pass the second end of

    Original URL path: http://www.dirkbertels.net/various/knots.php (2016-04-30)
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  • Dirk Bertels - Deploying .NET projects with NSIS
    details view of the installer DetailPrint this message will show on the installation window The MessageBox Use a messagebox as per standard windows coding Messagebox MB OK MB ICONINFORMATION indicates new line SetCustom Standard pre formatted wizard page To display a page just state it Page xxx xxx is a standard wizard page Sections Each section contains zero or more instructions Sections are executed in order by the resulting installer Instructions in sections are executed at runtime Most used instructions are SetOutPath which tells installer where to extract the files to and File which simply extracts files Section xxx Functions Functions are like sections but are called differently There are 2 types user functions called by user from sections or other functions using Call keyword callback functions called by installer on certain events e g onInit NSIS Code excerpts The following script only shows the code necessary to do the following things Show Splash screen Add a serial number registration window Install proprietry drivers Check and install NET Check and install the VC 2008 Redistributable Check for previously installed versions define TEMP1 R0 Temp variable to store license key Var DotnetInstalled if OK no need to install INCLUDES include LogicLib nsh Use more familiar flow control include MUI nsh Modern GUI include x64 nsh For using RunningX64 include DotNetVer nsh for HasDotNet3 5 include nsDialogs nsh To create labels on a custom page Request application privileges for Windows Vista RequestExecutionLevel user Page custom Registration Registration Page custom InstallDrivers Drivers Page custom CheckAndInstallDotNet Dot Net Framework page custom CheckAndInstallVcRedist VC Redistributable Function onInit InitPluginsDir File oname PLUGINSDIR splash bmp DeploymentResources YourSplash BMP show x in milliseconds splash show 2000 PLUGINSDIR splash insert dialog ini file in pluginsdirectory File oname PLUGINSDIR serial ini serial ini Pop 0 Call RunUninstaller uninstall previous versions FunctionEnd Function RunUnInstaller uninstall previous versions ReadRegStr R0 HKLM Software Microsoft Windows CurrentVersion Uninstall PRODUCT NAME UninstallString StrCmp R0 done MessageBox MB OKCANCEL MB ICONEXCLAMATION PRODUCT NAME is already installed n nClick OK to remove the previous version or Cancel to cancel this upgrade IDOK uninst Abort Run the uninstaller uninst ClearErrors ExecWait R0 INSTDIR IfErrors no remove uninstaller done no remove uninstaller done FunctionEnd Function Registration insertmacro MUI HEADER TEXT Registration Push TEMP1 again InstallOptions dialog PLUGINSDIR serial ini Pop TEMP1 StrCmp TEMP1 success 0 continue read from State in Field 1 of up ini and store into 0 ReadINIStr 0 PLUGINSDIR serial ini Field 1 State ReadINIStr 1 PLUGINSDIR serial ini Field 2 State username and password can be one of 5 user1 user1 password OR user2 user2 password OR user3 user3 password StrCmp 0 user1 0 2 StrCmp 1 user1 password continue wrong StrCmp 0 user2 0 2 StrCmp 1 user2 password continue wrong StrCmp 0 user3 0 2 StrCmp 1 user3 password continue wrong StrCmp 0 user4 0 2 StrCmp 1 user4 password continue wrong StrCmp 0 user5 0 2 StrCmp 1 user5 password continue wrong wrong IntOp 2 2 1 StrCmp 2 5 kill MessageBox

    Original URL path: http://www.dirkbertels.net/computing/nsis.php (2016-04-30)
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