NixNote2 has been forked.

One of the apps which I like to use under Android, is the Evernote Web-clipper. But because I am not using Windows anymore, I no longer have the official Windows client application for this service. Yet, I have a paid-for Premium subscription to Evernote. Therefore, I am interested in synchronizing my clippings with my desktop computer, even though I’m using Linux.

One solution which exists for people like me, is the NixNote2 (Linux) application, which is essentially a clone of the Evernote client application. But before Linux users go ahead to install and use this program, there is a recent fact which they need to be aware of. Under Debian / Stretch, aka Debian 9, the version which we may install from the package manager, is currently only version 2.0~beta11-1. This version is badly broken, and trying to use it could lead to some confusion, about why it malfunctions.

The behaviour might already be familiar to some other, unfortunate Linux users: When we first authorize it to sync with our account, it stores its token but only syncs once. After that, attempts to sync fail, and, the (Qt5) System Tray Icon misbehaves badly.

From what I heard this version is broken because the package maintainer for it has failed to maintain the code properly. Maybe he has moved on to different projects? But if he has, the defective version should not really be in the repositories anymore. And so a different developer has come forward, who will allow people to download his up-to-date version, that seems to work fine. This up-to-date version is available as an Appimage.

Screenshot_20190611_183556

I suppose that a type of question may arise, as to why software like this needs to be maintained, or, why it stops working. And in this case, the best answer I can decipher is that Evernote allows third-party client programs to connect, but tightens the protocol with which any client – mainly their own – needs to communicate with their server, either to improve security, to add features, or both.

Situations like this can even lead to some feelings of persecution, which may be stronger in the manufacturers of third-party devices or the programmers of third-party client apps, than they need to be for users. But what might just be happening is the provider trying to improve their infrastructure, and perhaps also, being a bit sluggish in communicating changes they make to the protocol to independent developers and users.

What users need to know, is to start with a healthy client app, before searching for other answers as to why, perhaps, the sync is malfunctioning. ;-)

Screenshot_20190611_183651

 

Dirk

 

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OpenCV Reinstalled on Computer Phosphene

One of the things I needed to do a few months ago, was a complete reinstall of software on a computer which was named ‘Phoenix’, but which had suffered from a hard-drive controller failure, so that it needed to be resurrected as the computer ‘Phosphene’. Both times that hardware had Debian / Stretch installed, even though the first time it was not an official Kanotix install. The second time it was.

When I need to reinstall the O/S, I also need to install much software again. And one piece of software which I’ve been focusing on somewhat in recent days, is “OpenCV“.

‘OpenCV’ is a library and a series of header files, and a set of Python modules, and a Java Interface, that specialize in Computer Vision, which could therefore be classified as a rudimentary AI, although it should be said that This form of AI is still of such a variety, that the computer is only performing remarkably complicated calculations, to be able to do things, which were not feasible only a few decades ago. It provides Image Recognition. Because of the way I am, I value having many computing resources installed, even if I rarely use them. OpenCV would be one such resource.

What tends to happen on Debian-based platforms, is that the version of OpenCV available from the package manager is a somewhat old version – in the case of Debian / Stretch, v2.4.9 – which is only important to install the library packages for, not the ‘-dev’ packages, and the former because the library packages are also dependencies of many other packages, which use OpenCV in the background, but not in any way that the user would want to write his own applications with.

What I additionally did, was to install v4.1 from the OpenCV Web-site, from source-code, and this seems like a good move because v4.1 is rumoured to be easier to write programs with, than v3.2 was, especially if the power-user does not want to end up shoulder-high in low-level code, to do many of the uninteresting parts of what his application needs to do, to be user-friendly.

But then, before writing our own applications with OpenCV, what we might also want is a demo program, that just shows users what the capabilities of this library and of this SDK are. And so the main program to do this with is called “OpenCV Demonstrator“. This could be a way to intrigue ourselves, as well to show off what our computers can do, maybe to friends?

 

Screenshot_20190610_082145

 

But here I ran into a bit of a snag. ‘OpenCV Demonstrator’ has only been compiled, by its author, as an application that uses OpenCV 3.2, and according to examination of my blog entries from before the reinstall, was compatible with v3.4. It’s not compatible with v4.1, even though v4.1 is more powerful. Whenever there is a major version update, let’s say from 3 to 4, applications built against one version will no longer run, when compiled against the next version. But I wanted that Demonstration Program. And so the following is what I did:

Continue reading OpenCV Reinstalled on Computer Phosphene

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Two Examples of Improper Integrals

In a recent posting I proposed to answer a question using an indefinite integral, which would more-correctly have been solved using the corresponding, definite integral. The issue there was that if this integral was rewritten as some arbitrary definite integral, this could in some cases have resulted in what’s called an ‘improper integral’. And what my reader may not realize, is that improper integrals exist, with well-behaved solutions, just as some infinite series converge.

And so, I have written a work-sheet below, which reminds people who may not remember their Calculus 2 exactly, of what forms improper integrals can take:

Link to a Letter-Sized PDF File

Link to an EPUB File for Phones

 

(Edit 6/05/2019, 18h25 : )

I have just revised the work-sheets above, to include some plots, and to provide a clearer understanding to anybody who might be interested in them, but who did not study Calculus 2. But some readers of the EPUB version may notice wonky formatting.

When I export Math notation to regular HTML, or to anything which is based on regular HTML, such as to an EPUB File which is not using MathML, I am faced with a problem every time correct Mathematical notation requires that 3 glyphs be stacked, as is the case with the (definite) integral operator, and with the Sigma operator, the latter of which denotes a summation. The only way I see around this issue is, to give the operator in question both a subscript and a super-script.

While the result can be read and understood, doing so requires additional concentration by the reader. I’ve written earlier postings, in which I described this problem, but the advantages here are, a notation which regular EPUB readers can display, as well as my ability to include the Computer Algebra and thus the plots, of “SageMath”, using the “LyX” graphical front-end to LaTeX, which makes the typesetting easier for me.


 

This limitation does not exist when only exporting the results to a PDF-File. But, in order to take advantage of the more-correct formatting of the resulting PDF File, I’d need to create two separate versions of my own document, one for export to (exact) PDF, and one for export to (messy) EPUB. While I did this amount of work for simpler work-sheets, I’m unwilling to do this for the more-complex work-sheet I just linked to.

 

(Edit 6/05/2019, 18h55 : )

There’s an added challenge to me, in the form of something my particular software is unable to perform. When I’m using LyX to typeset my work-sheets, the following two possibilities emerge:

  • Those work-sheets may consist entirely of Math written in my own hand, in which case I am able to export them to an XHTML File that contains MathML, and this will enable me to set up a master document, in which 2 but not 3 elements can be stacked. Then, the ‘Limus’ notation will be correct, and the integrals will be so-so. But the resulting master document can then be exported in two ways that eventually end up as a PDF and as an EPUB3 File, the latter requiring MathML from the EPUB reader app.
  • Those work-sheets may contain Computer Algebra and/or Plots that are essential, in which case only .TEX Files of the SageTex variety can be exported, which in turn can only be converted into plain HTML. This will result in an EPUB File that is inferior, but that all mobile EPUB reader apps can view. But simultaneously, through a separate master document and additional work on my part, a pristine PDF File can result, which still requires a full-sized monitor or other output device to read.

So, unless I find ways to export SageTex Files specifically, to XHTML with MathML, I’ll be facing issues in how to create typeset documents in the near future.

Dirk

 

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A Change In Fashion, In The Design Of Home Appliances Today.

I’m over the age of 50. One of the features which some ‘plug-in appliances’ had in my youth, was a rechargeable battery, which allowed them to keep an internal clock running, and therefore to keep track of time, beyond a power failure.

A feature which some ‘smart appliances’, i.e., Internet-connected appliances have today, which seems to be intentional, is the absence of a rechargeable battery. After a power failure, these appliances actually need to set their internal clock, either via a newly established Internet-connection, or via user action. And the main rationale behind this design decision seems to be, ‘The presence of a battery which recharges itself via the A/C may represent some improvement in battery lifespan, but would only represent a slight improvement in lifespan.’ In other words, if such appliances did in fact have such a battery, then instructions would also need to be distributed somewhere, on how to replace them, when they eventually fail. And many appliances’ manufacturers prefer not to broadcast such embarrassing instructions, but rather, to change the design as not to require a battery.

Two appliances which I own that seem to follow this model, are:

  1. My Dyson Air Purifier / Fan,
  2. My Security Cams.

In the second case, the trouble has plagued me in the past, that after a very long period of not monitoring the cams, their motion sensor would seem to trip while I’m monitoring them, but would seem to fail to leave any recorded footage, in the app panel where such footage should be found. I’d notice that some amount of storage on the SD Card has been consumed, which corresponded to video recordings, but the list of recordings to be played back would ‘look empty’. Additionally, to reformat the SD Card would succeed.

I finally found out what’s up with that.

Continue reading A Change In Fashion, In The Design Of Home Appliances Today.

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