increase dot grid size to be less distracting

blog/first_post.md

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+---
+author: Akbar Rahman
+pub_date: Fri, 31 Jul 2020 19:52:52 +0100
+title: first post
+tags: []
+uuid: fd338dc9-ae5f-48f4-9fc6-e02e88ab4ce5
+---
+
+# first post
+
+this is my first post

blog/g27_pedals.md

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+---
+author: Akbar Rahman
+pub_date: Tue, 04 Aug 2020 15:20:13 +0100
+title: Repurposing Racing Wheel Pedals
+tags: [ g27, sim_racing ]
+uuid: 0f09200e-fd50-451b-aae1-1117a8a704db
+---
+
+<h1>Repurposing Racing Wheel Pedals</h1>
+<p>I have a Logitech G27 I don't use much. I wondered if I could use it for anything else. I could. </p>
+
+<h2> The Pinout of the Connector </h2>
+
+<p>The first thing I had to do was figure out what each pin did on the DE-9 connector, and which
+ones I should care about.
+This was done easily after I took off the top plastic casing thing by poking the three 100k Ohm
+potentiometers and the connector in the right places at the right times:
+</p>
+
+<style> #pinout_table tr td:first-child { text-align: right } </style>
+<img src="./images/repurposing-racing-wheel-pedals-g27-pinout.svg" class="centered" style="width: 10em;">
+<table id="pinout_table">
+	<tr> <th>pin</th> <th>function</th></tr>
+	<tr> <td>1,4</td> <td>ground</td></tr>
+	<tr> <td>6</td> <td>clutch pedal</td></tr>
+	<tr> <td>7</td> <td>brake pedal</td></tr>
+	<tr> <td>8</td> <td>accelerator pedal</td></tr>
+	<tr> <td>9</td> <td>voltage in</td></tr>
+</table>
+
+<h2> Reading the Values of the Pots </h2>
+
+I'm using an Arduino to read the pots and then do something with the values.
+I very dirtily wired pin 4 on the pedals to GND on a Arduino Uno, pin 9 to 5V, and
+pins 6,7,8 to A0, A1, and A2.
+I used a basic sketch to check that everything is good:
+
+<details>
+	<summary> Show/hide test_sketch.ino </summary>
+<pre><code> void setup() {
+	Serial.begin(9600);
+}
+
+void loop() {
+	Serial.println(analogRead(A2));
+	delay(20);
+}
+</code></pre>
+</details>
+
+I noticed that the minimum and maximum values read by the Uno were quite far off 0 and 1024, like
+they should be, and voltage was being lost on the way to and from the potentiometers.
+Since the pedals have to be calibrated every time you plug them in, I assume this is normal and
+spat out this code: 
+
+<details>
+	<summary> Show/hide sketch_aug02a.ino </summary>
+<pre><code>// sensor pins
+int sa = A0;
+int sb = A1;
+int sc = A2;
+
+// minimum values detected by the sensors
+int mina = 1025;
+int minb = 1025;
+int minc = 1025;
+
+// maximum values detected by the sensors
+int maxa = 512;
+int maxb = 512;
+int maxc = 512;
+
+// raw values of the sensors
+int rva, rvb, rvc;
+
+// calculated values of the sensors (between 0 and 1, this is the value sent to computer)
+float cva, cvb, cvc;
+
+void setup() {
+	Serial.begin(9600);
+}
+
+void loop() {
+	rva = analogRead(sa);
+	rvb = analogRead(sb);
+	rvc = analogRead(sc);
+
+	if (rva &lt; mina) mina = rva;
+	if (rvb &lt; minb) minb = rvb;
+	if (rvc &lt; minc) minc = rvc;
+
+	if (rva &gt; maxa) maxa = rva;
+	if (rvb &gt; maxb) maxb = rvb;
+	if (rvc &gt; maxc) maxc = rvc;
+
+	cva = (float)(rva-mina)/(float)(maxa-mina);
+	cvb = (float)(rvb-minb)/(float)(maxb-minb);
+	cvc = (float)(rvc-minc)/(float)(maxc-minc);
+
+	Serial.print('[');
+	Serial.print(cva); Serial.print(',');
+	Serial.print(cvb); Serial.print(',');
+	Serial.print(cvc);
+	Serial.print(']');
+	Serial.println();
+	delay(20); 
+}
+</code></pre>
+</details>
+
+<h2> Actually Making the Numbers Do Something </h2>
+
+This is where you can make the pedals do fun things.
+I reworked another piece of code I wrote to do a similar thing to quickly create a script that
+reads the values sent by the Arduino, and then simulate pressing a key combination.
+The only thing I've done with this is set push-to-talk to ctrl-shift-alt-1.
+I don't know what else I could use this for, maybe temporarily muting particular things, like music.
+
+<details>
+	<summary> Show/hide pedalboard.py </summary>
+<pre><code> #!/usr/bin/env python3
+
+import sys
+import json
+import time
+from enum import Enum
+
+import keyboard
+import serial
+
+class KeyState(Enum):
+    UP = 0
+    DOWN = 1
+
+STATES = [KeyState.UP] * 3
+THRESHOLD = 0.8
+MACROS = ['ctrl+shift+alt+1', 'ctrl+shift+alt+2', 'ctrl+shift+alt+3']
+
+def get_args():
+    """ Get command line arguments """
+
+    import argparse
+    parser = argparse.ArgumentParser()
+    parser.add_argument('device')
+    return parser.parse_args()
+
+
+def main(args):
+    """ Entry point for script """
+    while True:
+        try:
+            kb = serial.Serial(port=args.device, baudrate=9600)
+            while True:
+                handle(json.loads(kb.readline()))
+        except serial.serialutil.SerialException as e:
+            print(e)
+            print("Failed to connect to device... trying again")
+            time.sleep(1)
+        except Exception as e:
+            print(e)
+    return 0
+
+def handle(data):
+    global STATES
+
+    states = [KeyState.DOWN if value &gt; THRESHOLD else KeyState.UP for value in data]
+    r = [handle_state_change(i, states[i]) if states[i] != STATES[i] else None for i in range(len(STATES))]
+    STATES = states
+    return r
+
+def handle_state_change(key, newstate):
+    print(f"{key} {newstate}")
+    return keyboard.press(MACROS[key]) if newstate == KeyState.DOWN else keyboard.release(MACROS[key])
+
+
+if __name__ == '__main__':
+    try:
+        sys.exit(main(get_args()))
+    except KeyboardInterrupt:
+        sys.exit(0)
+</code></pre>
+</details>

blog/images/repurposing-racing-wheel-pedals-g27-pinout.svg

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blog/lastfm_bookmarklets.md

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+---
+author: Akbar Rahman
+pub_date: Mon, 18 Sep 2023 16:25:48 +0100
+title: last.fm bookmarklets
+tags: [ last.fm, scripts ]
+uuid: e54ebf58-4033-4dae-81db-91db344f1311
+---
+
+# last.fm bookmarklets
+
+last.fm doesn't let you see how many scrobbled you've made in one day particularly easily.
+Here is a bookmarklet to solve that.
+
+<label for="days"> Number of days to view: </label>
+<input type="number" value="1" id="days" placeholder="Days"/><br><br>
+<label for="offset"> Offset (e.g. 0 to include today, 7 to look at last week): </label>
+<input type="number" value="0" id="offset" placeholder="Offset (Days)" /><br><br>
+<label for="username"> last.fm username </label>
+<input type="text" value="" id="username" placeholder="Username" /><br><br>
+<input type="button" id="button" value="Generate bookmarklet"><br>
+
+<p><a style="display: none" href="" id="scriptLink">Bookmark this link</a></p>
+
+When you press generate bookmarklet, the values `OFFSET`, `DAYS`, `USERNAME` will be
+subsituted and put into the link above.
+It's always best to inspect bookmarklets though.
+Inspect the page to view the script used to generate the bookmarklet.
+
+<textarea cols="109" rows="15" readonly id="scriptText">
+javascript: (() => {
+  const MILLESECONDS_PER_DAY = 1000 * 24 * 60 * 60;
+  const OFFSET;
+  const DAYS;
+  const USERNAME;
+
+  const currentDate = new Date();
+  const to = new Date(currentDate - (OFFSET * MILLESECONDS_PER_DAY));
+  const from = new Date(to - ((DAYS-1) * MILLESECONDS_PER_DAY));
+  const toDate = to.getFullYear() + "-" + (to.getMonth()+1) + "-" + to.getDate();
+  const fromDate = from.getFullYear() + "-" + (from.getMonth()+1) + "-" + from.getDate();
+
+  document.location = "https://www.last.fm/user/" + USERNAME + "/library?from=" + fromDate + "&to=" + toDate;
+})();
+</textarea>
+
+<script>
+document.getElementById("button").addEventListener("click", () => {
+	scriptText = document.getElementById("scriptText").value;
+	offset = document.getElementById("offset").value;
+	days = document.getElementById("days").value;
+	username = document.getElementById("username").value;
+
+	newscript = scriptText.replace(
+		      "OFFSET", "OFFSET = " + offset
+		      ).replace(
+			"DAYS", "DAYS = " + days
+		      ).replace(
+			"USERNAME", "USERNAME = '" + username + "'"
+		      );
+	document.getElementById("scriptLink").href = newscript;
+	document.getElementById("scriptLink").style = "";
+});
+</script>

blog/readme.md

@@ -0,0 +1,13 @@
+---
+title: alv's blog
+author: Akbar Rahman
+pub_date: Fri, 31 Jul 2020 19:50:51 +0100
+blog: true
+tags: [ alvs_blog, blog ]
+uuid: 2d03893a-eb9b-4923-8024-a223ecbe72f7
+---
+
+# alv's blog
+
+this is my blog.
+i promise i will try to keep things posted here interesting.

computery_stuff/cadence_license_manager_null_parameter.md

@@ -0,0 +1,57 @@
+---
+author: Akbar Rahman
+date: \today
+title: "Cadence License Manager Install - `java.lang.IllegalArgumentException: :locationICompSelected: Null parameter - InstallComponent ID`"
+tags: [ cadence, license_manager, flexlm, java, errors ]
+uuid: a5f46736-1ab8-4da1-8737-95de51c95d50
+---
+
+# Error
+
+```
+[root@host Downloads]# iscape/bin/iscape.sh -batch majorAction=InstallFromArchive archiveDirectory=$(realpath LCU04.30.000_lnx86.Base) installDirectory=$(realpath target)
+Initializing InstallScape using JVM at /home/alvi/Downloads/iscape.04.23-s012/runtime/LNX86/bin/java. This might take some time...
+
+WARNING: The DISPLAY environment variable has not been set.
+InstallScape might not initialize.
+
+
+InstallScape Installer (Batch Mode) - 04.23.s12
+
+:locationICompSelected: Null parameter - InstallComponent ID
+java.lang.IllegalArgumentException: :locationICompSelected: Null parameter - InstallComponent ID
+        at com.khanpur.installerng.ArchiveLocationManager.locationICompSelected(ArchiveLocationManager.java:143)
+        at com.khanpur.installerng.Installer.archiveLocationICompSelected(Installer.java:1156)
+        at com.khanpur.installer.gui.batch.BatchInstallfromarchive.execute(BatchInstallfromarchive.java:86)
+        at com.khanpur.installer.gui.batch.BatchView.initialize(BatchView.java:329)
+        at com.khanpur.installer.gui.batch.BatchView.<init>(BatchView.java:90)
+        at com.khanpur.installer.gui.InstallerUINoSplash.showBatch(InstallerUINoSplash.java:325)
+        at com.khanpur.installer.gui.BatchCommand.execute(BatchCommand.java:78)
+        at com.khanpur.util.TransactionCommand.execute(TransactionCommand.java:74)
+        at com.khanpur.util.Commandline.runCommands(Commandline.java:223)
+        at com.khanpur.installer.gui.InstallerUINoSplash.processCommandLine(InstallerUINoSplash.java:340)
+        at com.khanpur.installer.gui.InstallerUINoSplash.main(InstallerUINoSplash.java:372)
+        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
+        at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
+        at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
+        at java.lang.reflect.Method.invoke(Unknown Source)
+        at com.khanpur.installer.gui.InstallerUI.main(InstallerUI.java:123)
+Failed with InstallScape JVM.
+Now loading System JVM...
+iscape/bin/iscape.sh: line 222: java: command not found
+Error:
+/usr/bin/which: no java in (/usr/local/bin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin)
+Could not use JVM packaged with Installcape. The Java in your path did not work or could not find Java in your path.  Ensure that Java 1.6 or later is in your PATH environment variable and restart InstallScape.
+```
+
+# Cause
+
+Using the wrong filepath.
+The Cadence archives have subfolders to split the software between multiple CDs (a relic of the
+past perhaps).
+The actual folder to use is the CDs.
+
+# Solution
+
+Use the folder that contains the `.sdx` files (in my case, add `/CDROM1` onto end of
+`archiveDirectory`).

computery_stuff/cloudwatch_event_rule_lambda_ansible.md

@@ -0,0 +1,81 @@
+---
+author: Akbar Rahman
+date: \today
+title: Eventbridge Rule (Cloudwatch Rule) Does Not Invoke Lambda When Configured Through Ansible
+tags:
+  - ansible
+  - aws
+  - aws_eventbridge
+  - aws_lambda
+  - cloudwatch
+  - eventbridge
+  - lambda
+  - permissions
+uuid: df3ca083-b6ae-4e35-bb1c-8b3978117c57
+---
+
+# Eventbridge Rule (formerly Cloudwatch Rule) Does Not Invoke Lambda When Configured Through Ansible
+
+## Problem
+
+After creating an Eventbridge rule to run a Lambda function with the Ansible module
+[`amazon.aws.cloudwatchevent_rule`](https://docs.ansible.com/ansible/latest/collections/amazon/aws/cloudwatchevent_rule_module.html),
+the rule does not run Lambda function when it should:
+
+```yaml
+- name: "Create lambda function"
+  register: create_lambda
+  amazon.aws.lambda:
+    region: "{{ aws_ec2_region }}"
+    description: "My Lambda function"
+    name: "{{ lambda_name }}"
+    role: "{{ iam_role.iam_role.arn }}"
+    state: "present"
+    timeout: 120
+    vpc_security_group_ids: "{{ sec_group.group_id }}"
+    vpc_subnet_ids: "{{ subnet_ids }}"
+    image_uri: "{{ ecr.repository.repositoryUri }}:latest"
+- name: "Schedule my Lambda function"
+  register: lambda_schedule_rule
+  amazon.aws.cloudwatchevent_rule:
+    name: "a_unique_rule_name"
+    region: "{{ aws_ec2_region }}"
+    schedule_expression: "rate(1 minute)"
+    state: "present"
+    targets:
+      - arn: "{{ create_lambda.configuration.function_arn }}"
+        id: "a_unique_id"
+        input: "{{ eventbridge_rule_lambda_event_input }}"
+```
+
+Even though creating a seemingly identical setup through the AWS console works fine.
+
+## Cause
+
+The Eventbridge rule is not allowed to invoke this Lambda, as it is not in the Lambda's policy.
+
+## Solution
+
+Use the
+[`amazon.aws.lambda_policy`](https://docs.ansible.com/ansible/latest/collections/amazon/aws/lambda_policy_module.html)
+module to allow the Eventbridge rule to invoke the Lambda.
+Note that, if specifying the Lambda function name to `function_name` (as opposed to the ARN of the
+Lambda function), you must specify `version` or otherwise the Lambda function still won't be run!
+
+
+```yaml
+- name: "Allow Eventbridge (Cloudwatch) Rules to invoke lambda"
+  amazon.aws.lambda_policy:
+    action: "lambda:InvokeFunction"
+    function_name: "{{ lambda_name }}"
+    state: "present"
+    statement_id: "a_unique_statement_id"
+    region: "{{ aws_ec2_region }}"
+    principal: "events.amazonaws.com"
+    source_arn: "{{ lambda_schedule_rule.rule.arn }}"
+    version: "{{ create_lambda.configuration.version }}"
+```
+
+
+Solution found thanks to @david-kretch's answer to the same question at
+<https://stackoverflow.com/questions/45282939/cloudwatch-event-rule-creation-via-ansible-succeeds-but-not-invoked>.

computery_stuff/flask.md

@@ -0,0 +1,12 @@
+---
+author: Akbar Rahman
+date: \today
+title: Flask
+tags: [ python, flask, programming, docker ]
+uuid: e513ed96-cb19-4d4c-9894-e337c54659e5
+---
+
+# Examples
+
+- [alv.cx-glass](https://git.alv.cx/alvierahman90/alv.cx-glass) --- a pretty minimal example, probably not very production ready but has example of how to use in Docker
+- <https://flask.palletsprojects.com/> --- official documentation for Flask

computery_stuff/jetson_nano.md

@@ -0,0 +1,17 @@
+---
+author: Akbar Rahman
+date: \today
+title: Jetson Nano
+tags: [ nvidia, jetson, jetson_nano, droidcam ]
+uuid: f312451a-2cd4-468a-9eef-ca9859c7cd1e
+---
+
+
+# installing Droidcam
+
+figured out with help from <https://hizzely.hashnode.dev/instalasi-droidcam-cli-di-jetson-nano> :pray:
+
+0. build and install libjpeg-turbo version 2.1.2 from github (cmake, make, make install)
+0. build droidcam (2.1.3 confirmed working) from source (make) and install (./install-client) (may need to set `PKG_CONFIG_PATH` environment varible to whatever libjpeg turbo installed at (for me, `/opt/libjpeg-turbo/lib64/pkgconfig`))
+0. install v4l2loopback-dkms with apt
+0. run droidcam (you may need to set `LD_LIBRARY_PATH` environment variable to wherever libjpeg-turbo installed to (for me, `/opt/libjpeg-turbo/lib64`))

computery_stuff/linux.md

@@ -20,3 +20,47 @@ usermod -a -G group user
 ```bash
 usermod -g group user
 ```
+
+# help i think my device shut down after deleting the current kernel and before installing the second (no entries in systemd-boot/grub/<bootloader>)
+
+0. boot into a live usb of current disto
+1. mount the root partition to `/mnt` and the boot partition to the appropriate folder (check
+   fstab which should be in `/mnt/etc/fstab`, if it says `/efi`, mount it to `/mnt/efi`)
+2. chroot into the mounted filesystem:
+
+   on arch based systems you can simply run:
+
+   ```
+   arch-chroot /mnt
+   ```
+
+   on non arch based systems[^1]:
+
+   ```
+   mount -t proc /proc /mnt/proc/
+   mount -t sysfs /sys /mnt/ys/
+   mount --rbind /dev /mnt/dev/
+   # only if using uefi
+   mount --rbind /sys/firmware/efi/efivars /mnt/sys/firmware/efi/efivars/
+   # for internet access
+   cp /etc/resolv.conf /mnt/etc/resolv.conf
+   chroot /mnt /bin/bash
+   ```
+3. the system can now be force updated/kernel images can be generated
+
+   on arch based systems[^2]:
+
+   ```
+   # reinstall all current packages
+   pacman -Qqen > /root/pkgs.txt # list all installed packages
+   pacman -S $(< /root/pkgs.txt) # reinstall all installed packages
+   rm /root/pkgs.txt # clean up
+
+   # reinstall dependencies (if there are issues)
+   pacman -Qqdn > /root/deps.txt # list all installed dependencies
+   pacman -S $(< /root/deps.txt) # reinstall all installed dependencies
+   rm /root/deps.txt # clean up
+   ```
+
+[^1]: https://wiki.archlinux.org/title/Chroot [wayback machine](https://web.archive.org/web/20240121115548/https://wiki.archlinux.org/title/Chroot)
+[^2]: https://bbs.archlinux.org/viewtopic.php?id=193174 [wayback machine](https://web.archive.org/web/20240129153400/https://bbs.archlinux.org/viewtopic.php?id=193174)

computery_stuff/uo_nottingham.md

@@ -0,0 +1,14 @@
+---
+author: Akbar Rahman
+date: \today
+title: University of Nottingham
+tags: [ uni ]
+uuid: d1b03938-c5b4-48ad-a258-78f96880aa4b
+---
+
+### Trying to log into Microsoft 365 sends me to a different organisation's login page
+
+Try one of these links:
+
+- <https://pls.cx/uon_email> (a redirect to the link below)
+- <https://outlook.office.com/owa/nottingham.ac.uk>

gohookr.sh

@@ -6,4 +6,6 @@ cd `dirname $0`
 git pull
 cd ..
 rm -rf notes.alv.cx/*
-notes2web.py -o notes.alv.cx notes
+cd /root/gronk
+git pull
+docker compose up --build 

readme.md

@@ -0,0 +1,10 @@
+---
+title: alv's notes
+base_url: https://notes.alv.cx
+---
+
+# alv's notes
+
+These are my personal notes. Correctness is not guaranteed.
+
+Best viewed at [notes.alv.cx](https://notes.alv.cx).

styles.css

@@ -0,0 +1,12 @@
+@import url("https://styles.alv.cx/fonts/comic-mono-font.css");
+@import url("https://styles.alv.cx/modules/dotgrid.css");
+@import url("https://styles.alv.cx/modules/alwaysdark.css");
+
+:root {
+  --dotgrid-size: 15em;
+  --dotgrid-dot-size: 1px;
+}
+
+body {
+  font-family: 'Comic Mono', monospace;
+}

uni/mmme/2044_design_manufacture_and_project/MMME2044.txt

@@ -0,0 +1,102 @@
+#separator:tab
+#html:false
+what are plain bearings	- a suitable solid material fitted between shaft and support to reduce friction and wear - bearing may be dry rubbing bearing or lubricated
+what types of lubrication can be used for plain bearings	- hydrodynamic - hydrostatic - solid-film - boundary layer
+what is hydrodynamic lubrication	the shaft rotating in oil creates the oil pressure to lubricate the shaft
+what are ball and roller bearings	the rotating load is converted to rolling contact of the balls or rollers
+what are the parts of a ball bearing	
+what is the difference between a journal bearing and a thrust bearing	- a journal bearing supports the shaft radially - a thurst bearing supports the shaft axially
+when would one use a plain rubbing bearing	low load, low speed applications
+what is the pV factor and what is it the product of	a measure of the bearing's ability to cope with frictional heat generation  p- pressure V- speed at contact point
+what is the projected area of a radial sliding bearing	the area of a journal when looking down from it:
+what is the thrust area of an axial bearing	area of the bearing that isn't holey  [$]\frac\pi4 \left(D^2-d^2\right)[/$]
+what is the wear volume of an axial sliding bearing	the non holey area multiplied by the distance the bearing can wear down without issue  [$]YA_\text{thrust} = Y\frac\pi4\left(D^2-d^2\right)[/$]
+what are the main properties of plain rubbing bearings (4)	- usually made of polymers - moulded to final shape - dry lubricants added - reinforcements added
+what dry lubricants and reinforcements are added to plain rubbing bearings	- PTFE lubricant added - glass fibre reinforement added
+what limits the pressure and speed a plain bearing can be operated at	strength and temperature, respectively
+what differentiates oil lubricated porous bearings	- manufactured from sintered metal powders - porous and impregnated
+how often does lubricant need to be replenished in porous bearings	roughly 1000 hours
+list some of the lowest coefficient of friction bearing materials and their coefficient range	- babbitt metal (0.005 to 0.1) - POM (0.05-0.15) - cast iron and lead bronze with grease (0.05 to 0.15)
+list the highest pV bearing materials	- babbitt metal (2) - cast iron and lead bronze with grease (1) - porous bronze (1)
+what is the equation for wear factor, [$]K[/$]	[$]K = \frac{W}{FVt}[/$]  where $W$ is wear volume, $F$ is bearing load, $V$ is sliding velocity, and $t$ is elapsed time
+what is the main issue with hydrodynamic bearings	surfaces touch at low speeds
+draw the curve of friction against speed	
+describe the properties of boundary lubrication	continuoous and extensive contactlubricant is smeared across surfacecoefficient of friction 0.05 to 0.2wear take place & limits life
+what are the properties of mixed lubrication	higher surface speedsintermittent contact between surfacepartial hydrodynamic supportcoefficient of friction of 0.004 to 0.10very high local pressures can create elastic deformation of surfaces
+what is elastohydrodynamic lubrication	fluid film lubrication where high local pressure create elastic deformation of surfaces
+what are the properties of hydrodynamic lubrication	high speedsno contact between surfaces---no wearminimum film thickness of 8 to 20 micronsvery good surface finish and tolerances requiredcoefficient of friction between 0.002 to 0.01
+what is the Sommerfeld number	a dimensionless number describing the relationship between a bearings dimensions, speeds, and fluid properties  [$]S = \left( \frac R h\right)^2 \frac{\eta n}{P}[/$]  where R is radius, h is clearance, [$]\eta[/$] is viscosity, n is angular speed, and P is bearing pressure
+what is the equation for clearance of a bearing	[$]h = R_\text{bearing} - R_{shaft}[/$]
+what is petroff's equation and what is it used for	[$]\mu = 2\pi^2 \frac{\eta n}{P}\frac{R}{h}[/$]  used for lightly loaded bearings
+equation for hydrodynamic journal bearing capacity	[$]F = S\eta V \left(\frac{R}{h}\right)^2[/$]
+equation for thrust capacity for hydrodynamic thrust bearing	[$]F = 6\eta\left[ \frac{Ln(1+n)}{n^2} - \frac{2}{n(2+n)}\right]\frac{VL^2}{h_\text{min}^2}[/$]  where  [$]n = \frac{h_\text{max}}{h_\text{min}}-1[/$]
+what causes friction between components in relative motion	real surfaces have asperities which stick out and make contact with the other facewhen sliding, asperities catch and must be deformed or brokenthe forces required to do so is friction
+what are the different rolling element types	
+what are the types of ball bearings and what are their primary features	
+what is the equation for static load carrying capacty	[$]s_0 = \frac{C_0}{P_0}[/$]  where s is the static safety factor, P, is the equivalent static bearing load, and C is the basic static load rating
+dynamic load carrying capacity	[$]L_{10} = \left(\frac CP \right)^q[/$]  where L10 is the basic life rating in millions of revolutions, C is the basic dynamic load rating, P is equivalent dynamic bearing load, q is exponent of life: 3 for balls10/3 for rollers
+what are the equations for equivalent dynamic load (4)	constant magnitude and direction: P = F axial and radial load: [$]P = XF_r + YF_a[/$] (X and Y from manufacturers data)roller bearings: P = F_rfluctuating loads: [$]F_m = \sqrt[3]{\frac{F_1^3U_1 + \cdots}{U}}[/$]
+when would you have adjust life rating (5)	low reliabilityhigh temperaturehigh vibrationrisk of water ingressrisk of corrosion
+why should a locating bearing be used in conjunction with a floating bearing	ensures journal does not slide about axially (i think)
+what combinations of bearings can be used to support a shaft (5)	2 angular contact bearings - free sliding housing for axial adjustmentone ball + one roller - roller supports radial, ball supports axial and radial2 taper rollers - both support radial and axial, one bearing adjusted against other to required preload2 balls - radial and axial loads, one clamped axially on both races while other left free2 roller - accepts heavy radial load, some axial, each roller locates axially one in direction
+when should you slide fit the inner race with the shaft	when the load rotates with the shaft
+what is the difference between bolts, screws, and studs	bolts have an unthreaded core, and a matching nutscrews are threaded all the way and screw directly into a materialstuds do not have heads
+draw a lap joint and the forces they are designed to handle	
+draw a butt joint and the forces they are designed to handle	
+what is a rivet	a non threaded fastener that is deformed around the parts to be joined
+what are the types of rivets (3)	solidtubular - have a hole down the axisblind (pop rivets)
+what are the advantages of rivets (5)	low costrapid assemblypermanentcan join dissimilar materialswide range of shapes and materials
+what are the disadvantages of rivits (3)	slower than welding and adhesivespoor under tensile loadsjoints leak unless sealed
+draw a welded but joint and forces is designed to handle	
+draw a welded lap joint and the forces it is designed to handle	
+draw a double fillet t joint	
+draw a fillet cornet joint	
+why are bolts pre tensioned	stops faces from separatingreduces fluctuating stresses experienced by bolt -> increases fatigue life
+what is the recommend preload for non permanent joints	[$]F_i = 0.75A_s\sigma_p[/$]
+what is the rceommended preload for permanent joints	[$]F_i = 0.9A_s\sigma_p[/$]
+what is the tensile area of a bolt	[$]A_s = \frac{\pi}{16}(d_p+d_r)^2[/$]
+what is the pitch diameter of a bolt	[$]d_p = d-0.6495p[/$]
+what is the minor diameter of a bolt	[$]d_r = d-1.0825p[/$]
+what can proof strength be approximated to if unavailable	[$]\sigma_p = 0.85\sigma_y[/$]
+"what does the marking ""MX.Y"" mean on a bolt"	X - has tensile strength of X*100 MPa Y - has yield strength of Y*X*10 Mpa
+what is the bolt torque pre tension equation	[$]T= KF_id[/$]  where K is torque coefficient (around 0.2 for most cases), and d is nominal diameter
+how can the stiffness of a bolt be reduced (2)	reduce cross sectional areaincrease length
+what stress reserve factor would you want for reliable materials under controlled conditions and known stresses	1.25 to 1.5
+what stress reserve factor would you want for average materials with known loads and stresses	2 to 2.5
+what reserve factor would you want for untried materials in average conditions	3 to 3.5
+what reserve factor would you want for well known materials in uncertain conditions	3 to 3.5
+what are the steps to select a bolt (6)	consider permanent vs non permanent, define external load, number of bolts, and reserve factorestimate preload by assuming hard joint (K_c = 3K_b)choose suitable bolt size and determine preload by using table 5 of bs en iso 898-1:2009calculate stiffness of bolts and componentscalculate maximum allowable external loadcalculate reserve factor
+why is a pre tensioned bolted joint beneficial for cyclic loading	pre tension raises mean stress which increases fatigue life
+what must be considered when using helical gears	axial load generated
+what are the properties of spur gears between parallel shafts (4)	cheap to manufacturenoisyfew number number of teeth in contact at any given timesensitive to alignment
+what are the properties of helical gears	teeth cut at inclined angle to axis of rotationcontact between teeth more progressive and longercarries higher loadsquietercan be mounted at right anglesdouble helical gears (herringbone) can cancel out axial thrust for smoother power transmission at high speeds
+what is the pitch circle	circle upon which all calculations are based
+what is circular pitch	the distance between two identical points on adjacent teeth on a gear
+what is the module of a gear, m	[$]m = \frac d N [/$]  where d is pitch diameter, N is number of teeth
+what is tooth thickness and width of space	[$]t = w = 0.5p[/$]  where p is circular pitch
+what is the addendum	radial distance between pitch circle and top land  a = m
+what is the dedendum	radial distance between pitch circle and bottom land  b = 1.25 m
+what is the clearance	c = 0.25m  radial distance between bottom land of gear 1 and top land of gear 2
+what is the whole depth of a gear	ht = addendum + dedendum = 2.25m
+what is the working depth of a gear	hk = addendum + dedendum - clearance = 2m
+what are the conditions for proper meshing between gears	module is samepressure angle is same
+what are the common pressure angles	20 degrees14.5 degrees
+what is the equation for centre distance betwen two gears	[$]C = \frac m 2 (N_1 + N_2)[/$]
+what is the minimum number of teeth for standard gears of pressure angle 20 degrees	18
+what is a simple gear train	each shaft only carries one gear
+what is a compound gear train	a gear train where at least one shaft carries two or more gears
+what is a reverted train	a compond train in which the input and shaft are colinear
+what is a planetary gear train	has a sun gear, planet carrier, and one or more planet gears
+what differentiates planetary gear systems	it has two degrees of freedomhas very high gear ratios
+what are the common forms of gear failure	bending fatiguepittingmicropittingscuffing
+what is a lower pair joint	joint with surface contact (pin in a hole)
+what is a higher pair joint	a joint with point or line contact, such as a pin in a slot
+what is rectilinear translation	points in the body move in parallel straight lines
+what is curvilinear motion	points in the body move along idential curves so the link does not rotate with respect to the ground
+what is the equation for degrees of freedom of a mechanism (gruebler's)	M = 3L - 2J - 3G
+what does it mean if a structure has negative degrees of freedom	it's preloaded or overconstrained
+what is the grashof condition equation and what does it mean	S + L < P + Q: it is a grashof linkage and at least one link can make a full revolutionS + L > P + Q: non grashof and no link capable of making full revolutionS + L = P + Q: special grashof - either double-cranks or crank rockers
+what is a limit/toggle test	checks if linkage can reach all positions without encountering a limit of toggle positiontoggle positons may be determined by collinearity of two links
+what is transmission angle	angle between output link and coupler
+what is the ideal transmission angle	90 degrees
+what is the minimum transmission angle	40 degrees

uni/mmme/2044_design_manufacture_and_project/bearings.md

@@ -4,17 +4,34 @@ date: \today
 title: MMME2044 // Bearings
 tags: [ bearings ]
 uuid: 94cac3fd-c352-4fdd-833d-6129cb484b8a
-lecture_slides: [ ./lecture_slides/Lecture 7 - Bearings 1 – Plain Hydrodynamic Bearings 1.pdf ]
+lecture_slides: [ ./lecture_slides/Lecture 7 - Bearings 1 – Plain Hydrodynamic Bearings 1.pdf, ./lecture_slides/Lecture 11 - Bearings 2 - Rolling Element Bearings.pdf ]
+anki_deck_tags: [ bearings ]
 ---
 
 > I don't think I ever finished these notes.
 
+# Errata
+
+## Lecture Slides 2 (Lecture 11), slide 18
+
+Static load carrying capacity equation is
+
+$$S_0 = \frac{P_0}{C_0}$$
+
+but should be:
+
+$$S_0 = \frac{C_0}{P_0}$$
+
+If the load applied to a bearing is half of its rated capacity,
+then you have a safety factor of 2.
+Therefore the equation in the slides must be incorrect.
+
 # Types of Bearings
 
 <details>
 <summary>
 
-## Plain Journal Bearings
+### Plain Journal Bearings
 
 </summary>
 
@@ -24,7 +41,7 @@ lecture_slides: [ ./lecture_slides/Lecture 7 - Bearings 1 – Plain Hydrodynamic
 - the insert provides lower friction and less wear than if just rotating in the support
 - the bearing may be dry rubbing or lubricated
 
-### Lubrication
+#### Lubrication
 
 - hydrodynamic---a shaft continuously in oil. the load is carried by pressure generated in the oil
   as a result of the rotation
@@ -38,7 +55,7 @@ lecture_slides: [ ./lecture_slides/Lecture 7 - Bearings 1 – Plain Hydrodynamic
 <details>
 <summary>
 
-## Ball and Roller Bearings (Rolling Element Bearings)
+### Ball and Roller Bearings (Rolling Element Bearings)
 
 </summary>
 
@@ -54,7 +71,7 @@ lecture_slides: [ ./lecture_slides/Lecture 7 - Bearings 1 – Plain Hydrodynamic
 <details>
 <summary>
 
-## Plain Rubbing Bearings (Dry Sliding)
+### Plain Rubbing Bearings (Dry Sliding)
 
 </summary>
 
@@ -68,7 +85,7 @@ lecture_slides: [ ./lecture_slides/Lecture 7 - Bearings 1 – Plain Hydrodynamic
 <details>
 <summary>
 
-## Oil Lubricated Porous Bearings
+### Oil Lubricated Porous Bearings
 
 </summary>
 
@@ -82,7 +99,7 @@ lecture_slides: [ ./lecture_slides/Lecture 7 - Bearings 1 – Plain Hydrodynamic
 <details>
 <summary>
 
-# Hydrodynamic Bearings
+### Hydrodynamic Bearings
 
 </summary>
 
@@ -94,6 +111,7 @@ lecture_slides: [ ./lecture_slides/Lecture 7 - Bearings 1 – Plain Hydrodynamic
 
 ![](./images/vimscrot-2022-11-15T17:56:26,739425867+00:00.png)
 
+</details>
 
 
 # fun graphs that may be useful for bearing selection
@@ -127,7 +145,7 @@ $$p = \frac{F_\text{radial}}{bD}$$
 
 $$V = \omega\frac D2$$
 
-![](./images/vimscrot-2022-11-15T17:48:21,486895199+00:00.png)
+![](./images/vimscrot-2023-04-28T18:17:05,184873693+01:00.png)
 
 
 ## Axial Sliding Bearing
@@ -136,7 +154,23 @@ $$p = \frac{4F_\text{axial}}{\pi(D^2-d^2)}$$
 
 $$V = \omega\frac{D+d}{4}$$
 
-![](./images/vimscrot-2022-11-15T17:48:34,860294942+00:00.png)
+![](./images/vimscrot-2023-04-28T18:17:16,580658677+01:00.png)
+
+## Plain Rubbing Bearings
+
+- does not rely on liquid lubricaton
+- usually made of polymers and moulded to final shape
+- dry lubricants like ptfe are added
+- reinforcements like glass fibres can be added
+- pressure is limited by strength
+- speed is limited by temperature
+
+## Oil Lubricated Porous Bearings
+
+- manufactured from sintered metal powders
+- porous & oil impregnated
+- more porous bearings are weaker but can run at higher speeds
+- lubricant needs to be replenished at regular intervals
 
 # Wear
 

uni/mmme/2044_design_manufacture_and_project/shaft_design.md

@@ -226,10 +226,10 @@ design.
 Simply multiply the maximum stresses and loads you expect by the safety factor, $n_s$, and assume
 that as your maximum stress and load.
 
-$n_s$ | Operational conditions and use of materials
------ | -------------------------------------------
-1.25-1.50 | Reliable materials under controlled conditions, known stresses with certainty
-1.50-2.00 | Well-known materials under reasonably constant environmental condition, known stresses
-2.00-2.50 | Average materials subjected to known loads and stresses and environment (LSE)
-2.50-3.00 | Lesser well-known materials under average conditions LSE
-3.00-3.40 | Untried materials under average conditions of stresses and environment, or well known materials under uncertain LSE
+| $n_s$     | Operational conditions and use of materials                                                                         |
+|-----------|---------------------------------------------------------------------------------------------------------------------|
+| 1.25-1.50 | Reliable materials under controlled conditions, known stresses with certainty                                       |
+| 1.50-2.00 | Well-known materials under reasonably constant environmental condition, known stresses                              |
+| 2.00-2.50 | Average materials subjected to known loads and stresses and environment (LSE)                                       |
+| 2.50-3.00 | Lesser well-known materials under average conditions LSE                                                            |
+| 3.00-3.40 | Untried materials under average conditions of stresses and environment, or well known materials under uncertain LSE |

uni/mmme/2047_thermodynamics_and_fluid_dynamics/dimensional_analysis.md

@@ -175,7 +175,7 @@ When $\text{Ma} > 0.3$, the flow should be considered compressible.
 
 # Nondimensional Momentum Equation (From Navier-Stokes)
 
-$$\frac{\del \pmb{V*}}{\del t*} + \pmb{V*} \cdot (\Del* \pmb{V*} = -\Del* p* + \frac{1}{\text{Re}}\Del*^2\pmb{V*}$$
+$$\frac{\delta \pmb{V^*}}{\delta t^*} + \pmb{V^*} \cdot (\nabla^* \pmb{V^*}) = -\nabla^* p^* + \frac{1}{\text{Re}}\nabla^{*2}\pmb{V^*}$$
 
 Therefore for large values of Reynolds number, the viscous forces become negligible.
 
@@ -185,7 +185,7 @@ An airfoil model and prototype are geometrically similar, with $1:\alpha$ length
 
 - $x_m = \frac{x_p}{\alpha}$, $y_m = \frac{y_p}{\alpha}$
 - $u_m$ at $(x_m, y_m)$ must have the same direction at $u_p$ at $(x_p, y_p)$
-- $\frac{u_p}{u_m} = \Beta$ is constant at homologous points
+- $\frac{u_p}{u_m} = \beta$ is constant at homologous points
 
 ![](./images/vimscrot-2023-02-06T09:46:38,665212789+00:00.png)
 

uni/mmme/2047_thermodynamics_and_fluid_dynamics/exam_papers/2019-2020/MMME2047-2019-2020-readme.txt

@@ -1,2 +1,5 @@
 This paper is of the format used before covid and therefore is the full year in two parts.
-The length of questions in the part A is appropriate for the January exam, but the content is split between the part A and part B in this exam from 2020.  You should be able to answer Questions 1, 2, 4, 7, 10, 11; and you can usefully attempt questions 13, 16b and 17b
+The length of questions in the part A is appropriate for the January exam, but the content is split
+between the part A and part B in this exam from 2020.
+You should be able to answer Questions 1, 2, 4, 7, 10, 11;
+and you can usefully attempt questions 13, 16b and 17b

uni/mmme/2047_thermodynamics_and_fluid_dynamics/heat_transfer.md

@@ -9,12 +9,24 @@ lecture_notes: [ ./lecture_notes/ConvectHeatTrans2022-2023.pdf ]
 exercise_sheets: [ ./exercise_sheets/ExamplesConvectionHeatTransfer.pdf ]
 ---
 
+# Errata
+
+## Grashof Number (formula booklet, lecture slides p. 24, lecture recording 2, 1:19:30)
+
+The Grashof number formula should be written with $\nu$, not $\mu$,
+It is correctly written in lecture notes (p. 8), [Wikipedia](https://en.wikipedia.org/wiki/Grashof_number),
+and on this page.
+
+Somehow it is also incorrect in the formula booklet.
+
+You can check which one is correct by checking which results in a dimensionless Grashof number.
+
 # Convection
 
 - conduction and radiation heat transfer can be estimated by calculations and properties
 - convection is dependent on fluid properties, flow type, and flow characteristics
 
-The rate of convective heat transfer, $\dot Q$, is given by
+The rate of convective heat transfer, $\dot Q$, is given by Newton's law of cooling:
 
 \begin{equation}
 \dot Q = hA(T_f-T_w)
@@ -32,4 +44,93 @@ $$\dot Q = \frac{T_f-T_w}{\sum R_\text{thermal}}$$
 
 where $R_\text{thermal} = \frac{1}{hA}$.
 
-In a way this analogous to Ohm's law, specifically with resistors in series ($I = \frac{\Deta V}{\sum R_\text{electrical}}$).
+In a way this analogous to Ohm's law, specifically with resistors in series ($I = \frac{\Delta V}{\sum R_\text{electrical}}$).
+
+## Analysis of how Convection Works
+
+At a hot wall, the velocity of the fluid touching it will be zero.
+Therefore the heat transfer into the fluid must happen by conduction.
+This means that the local heat flux per unit area, $\dot Q''$ (dot for rate, double dash for per
+unit area) is given by:
+
+$$\dot Q'' = -k \frac{\delta T}{\delta y}|_{\text{wall}}$$
+
+where $k$ is the conductivity of the wall
+
+![](./images/convection.png)
+
+The heated fluid is carried away by convection, therefore at steady state we can say that:
+
+$$\dot Q'' = -k \frac{\delta T}{\delta y}|_\text{wall} = -h(T_\infty - T_\text{wall})$$
+
+Rearranging allows $h$ to be found.
+
+# Nusselt Number - Relation Between Fluid Conductivity and Convection
+
+Nusselt number is a dimensionless number:
+
+$$\text{Nu} = \frac{hL}{k_f}$$
+
+where $k_f$ is conductivity of the fluid, $L$ is the representative length (e.g. diameter, length,
+internal width, etc.), and $h$ is heat transfer coefficient.
+
+Since $h$ is unknown a lot of the time, sometimes Nusselt number must be found through approximating
+by other dimensionless numbers: Prandtl, Reynolds, and Grashof.
+
+
+Nusselt number for a laminar forced flow is around 3.66.
+For a turbulent forced flow it is estimated to be:
+
+$$\text{Nu}_x = 0.023\text{Re}_x^{0.8}\text{Pr}^{0.4}$$
+
+For a laminar forced flow over a flat plate:
+
+$$\text{Nu}_x = 0.332\text{Re}_x^{0.5}\text{Pr}^{0.33}$$
+
+For natural convection of a vertical wall:
+
+\begin{align*}
+\text{Nu}_x = 0.59(\text{Gr}_x\text{Pr})^{0.25} &\text{ for }10^3 < \text{GrPr} < 10^9 \\
+\text{Nu}_x = 0.13(\text{Gr}_x\text{Pr})^{0.25} &\text{ for }10^9 < \text{GrPr} < 10^{12}
+\end{align*}
+
+[removing annoying html syntax highlighti]: >
+
+# Prandtl Number
+
+This number relates thickness of velocity boundary layer to thickness of thermal boundary layer:
+
+$$\text{Pr} = \frac{c_p\mu}{k_f} = \frac{\nu}{\alpha}$$
+
+where $\nu$ is the kinematic viscosity and $\alpha$ is the thermal diffusivity (equations given in
+lecture notes p. 5).
+
+# Grashof Number
+
+Grashof number compares the buoyancy of the fluid (due to compressibility, $\beta = T^{-1}$,
+where $T$ is the film temperature, or average temperature between fluid and wall, in kelvin)
+and the viscous resistance to buoyant motion.
+
+$$\text{Gr} = \frac{g\beta L^3\rho^2\Delta T}{\nu^2}$$
+
+where $g$ is acceleration due to gravity, $L$ is the height or length of the tube, $\rho$ is density
+of the fluid, $\Delta T = T_\text{wall} - T_\infty$, and $\nu$ is the kinematic viscosity.
+
+# Axisymmetric Shenanigans
+
+Axisymmetric shapes are symmetric about an axis.
+
+$$\dot Q' = -kA\frac{\mathrm dT}{\mathrm dr} = -k2\pi r\frac{\mathrm dT}{\mathrm dr}$$
+
+Note that the single dash on $\dot Q'$ implies *per unit length*.
+For any length, $L$, $A = 2\pi rL$.
+
+In this case, the temperature profile is no longer linear, even if $k$ is constant:
+
+$$R_\text{th} = \frac{\ln r_o - \ln r_i}{2\pi kL}$$
+
+# Definitions
+
+- *lagging* - insulation
+
+