Xournal++

Joel3 Comments

Has anyone tried xournal++ ?

I tried out Xournal a few years back, but I had problems with it on Windows 10. I’m having a look at Xournal++ today, and it looks like they’ve fixed all the issues that I didn’t like.

There used to be an issue where when you wanted a new page it always duplicated the background of the page you were on. That was good when the background was lined/squared paper, but it didn’t work well for my PDF skeletons for annotated slides in lectures. But now you can insert a choice of style of pages.

You can’t just “open” a PDF file (at least not my PDF files!), but “Annotate PDF” in the file menu works well.

You can save as a .xopp file and open that, and you can export to PDF when you want to. But I need to check whether the skeleton PDF files still look as good as they did when you started. (This used to be a bit of a problem with Windows Journal.)

I always liked the vertical space tool in Journal/Xournal. But I am used to the feature that if you push the annotation off the foot of the page that you should be offered a new page. That doesn’t happen for me with Xournal++ (on first view, by default). Perhaps there is a setting?

Now I should check out pressure sensitivity etc. …

Notes added:

Xournal++ is really good in many ways. The features are amazing! But, while annotating, I find the view on DrawBoard PDF is nicer. Ink strokes on Xournal++ look pixelated on my Surface. (Maybe there is a setting to fix that?) Ink strokes on DrawBoard look really smooth by comparison. And pinch and pan gestures seem to work much better in DrawBoard. They are painfully slow (at the moment) on Xournal++. But I may do some Googling to see if there are some options that I am missing.

Taster Sessions Update October 10 2021

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For other messages in this series, see https://explainingmaths.wordpress.com/?s=Taster+Sessions

(This post combines the most recent two messages sent to the Taster Sessions Mailing List, numbered 10a and 10b.)

Our next two online Taster Sessions will be

  • Wed Oct 13th 2021 5PM Lisa Mott, Taster Lecture on Statistics
  • Wed Oct 20th 2021 5PM Professor Silke Weinfurtner, The Black Hole Laboratory at the University of Nottingham

Here are some more details.

  • To join these events, you don’t need to register. Just visit our Taster Sessions page at https://tinyurl.com/uonmathstaster on the day and click on the relevant ‘Join event’ button.
  • Wed Oct 13th 2021 5PM Lisa Mott, Taster Lecture on Statistics
    This session will give you a taste of what a university lecture on Statistics is like. We will consider a range of problems in statistics and common misconceptions when solving these.
    In particular we look at extrapolation and its limitations and some uses of the normal distribution. You will have the opportunity to have a go at solving some statistics problems yourself and to vote on answers.
    This talk is suitable for students taking A-level mathematics and some familiarity with the sample mean and sample variance is assumed.
  • Wed Oct 20th 2021 5PM Professor Silke Weinfurtner, The Black Hole Laboratory at the University of Nottingham
    Professor Silke Weinfurtner will explain how her research group uses quantum technology to study black hole processes in the laboratory.
    This talk will be suitable for anyone interested in quantum sciences and black holes.

Simpson’s paradox: when intuition lets you down when working with fractions

JoelLeave a comment

I was talking to my daughter today about how intuition can let you down when it comes to maths. In fact my recent Taster Lecture on Pure Maths has a bit at the end about Simpson’s Paradox that I think will still make sense to non-mathematicians.

Which vet is better if one vet does better with male patients than the other and also does better with female patients than the other, but the second vet does better overall with its patients? And how is that even possible?

My brief discussion of this paradox is at https://www.youtube.com/watch?v=GzWvpCIwexs&t=1801s
In fact, after looking at the definition of paradox more carefully again recently, it seems that “paradox” can already refer to something that is only apparently impossible, rather than something that really is impossible. So I have changed my mind about “it’s not really a paradox, it’s only an apparent paradox”.

For more of our recent Taster Sessions, see https://tinyurl.com/uonmathsytv

University of Nottingham Open Days – back on campus!

JoelLeave a comment

I will finally be back on campus in the Mathematical Sciences Building at the end of this week for the University of Nottingham Undergraduate Open Days!

See https://www.nottingham.ac.uk/open-days/ from where I quote:

On campus at last!

Campus visits are your opportunity to soak up the atmosphere and explore some of the UK’s most green and beautiful campuses. Learn more about your course, meet academics and chat to our current students so that you can decide whether life as a Nottingham student is right for you.

Campus visit dates will be:

Friday 10 September 2021

Saturday 11 September 2021

Saturday 9 October 2021

But you don’t have to wait until then to find out more about the University of Nottingham, watch pre-recorded lectures and general talks to learn more about subjects, student life and to see some of our academics in action.

Quantifier packaging, convergence of sequences, and absorption

JoelLeave a comment

One of my first ever blog posts (from 2008) was on “quantifier packaging” when teaching convergence of sequences. In fact I first posted about this on Blogger, before moving over to WordPress. I have now produced an updated version of that post at https://explaining-maths.blogspot.com/2021/09/quantifier-packaging-when-teaching.html

(The WordPress version is at https://explainingmaths.wordpress.com/2008/12/12/quantifier-packaging-when-teaching-convergence-of-sequences/, but the new Blogger version has a few tweaks, and uses MathJax for the maths.)

Here is a screenshot from the Blogger post (where I use MathJax for the maths) of the standard definition of what it means to say that x_n \to x as n \to \infty (working in the real numbers).

Definition of what it means for a sequence of real numbers (x_n) to converge to a real number x

That probably looks a bit scary to first-year students (and possibly beyond first year!). My idea with ‘quantifier packaging’ is to look at some easier concepts first, before building up to the full definition.

Anyway, if you are interested in this idea, see the new Blogger post at https://explaining-maths.blogspot.com/2021/09/quantifier-packaging-when-teaching.html

Cartesian squares and ordered pairs

JoelLeave a comment

Here is another question and answer from my FPM Piazza forum last autumn.

Question: Suppose that S is a set with two elements, say S=\{a,b\}. When looking at elements of the Cartesian square S \times S, are (a,b) and (b,a) the same element, or are they different elements? Does S \times S have four different elements, or only three?

My answer:

Hi,
The key term in the definition of Cartesian squares, and generally Cartesian products, is “ordered pair”. When you use standard round brackets in this way, the order does matter. You have specified a first coordinate and a second coordinate.
For example, if you work in \mathbb{R} \times \mathbb{R} = \mathbb{R}^2, the point (1,0) (which lies on the x-axis) is different from the point (0,1) (on the y-axis).

Many of the sets S we have looked at are subsets of \mathbb{R}, and this results in S \times S being a subset of \mathbb{R}^2. When this happens, you can often think of points in our Cartesian square as being points in 2-dimensional space.

For example, if S=\{1,3\}, then S \times S has four different points, which you can think of as being points in \mathbb{R}^2 that are at the corners of a square:
         S \times S = \{(1,1), (1,3), (3,1), (3,3)\}\,.
On the other hand, if S is the closed interval [0,1]=\{x \in \mathbb{R}: 0 \leq x \leq 1\}, then S \times S really is the “unit square” \{(x,y) \in \mathbb{R}^2: 0 \leq x \leq 1, 0 \leq y \leq 1\,\}.

Best wishes,
Dr Feinstein

Taster Sessions Update September 1 2021

JoelLeave a comment

For other messages in this series, see https://explainingmaths.wordpress.com/?s=Taster+Sessions

Hi everyone,

As mentioned in my previous message, we have recently added to our YouTube channel (https://tinyurl.com/uonmathsyt) a video of a masterclass by Jorma Louko. Here is some information about this masterclass.

From satellite navigation to quantum black holes
Speaker: Dr Jorma Louko

Continue reading →

What is the best way to discuss FPM quiz challenge problems?

JoelLeave a comment

I am wondering how best to proceed with the FPM quiz challenge problems (and maybe some other problems I post). Of course, I could simply post full solutions here on WordPress and/or on my Blogger blog (where the maths can be presented using MathJax). Or I could issue some hints first. Or readers could suggest solutions, or give hints. Or I could post some hints on social media (Twitter etc.).

Continue reading →

Challenge questions from FPM quizzes: First quiz on sets and subsets

JoelLeave a comment

My fourth FPM quiz last autumn was on sets and subsets. Again the “challenge” question isn’t too hard, as long as you understand the basic concepts and definitions, though it is easy to make mistakes.

Here is a screenshot of the question. As usual, the buttons don’t do anything, but you can enlarge the image by clicking on it.

Click on the screenshot to enlarge the image

Here \mathbb{R}, \mathbb{Q} and \mathbb{Z} have their usual meanings, and \emptyset is the empty set.

You also need to know about the operations of intersection (denoted by \cap) and set difference (denoted by a backslash, \setminus) and the “subset” relation (denoted by \subseteq). Here I use the “subset or equals” notation \subseteq to make it clear that sets which are equal do count as subsets of each other.

In particular, note that the notation Y \nsubseteq X means that Y is not a subset of X, which is equivalent to saying that there is at least one element of Y that is not an element of X.