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  • Web: proxy and reverse proxy, part0

    One hears about proxy and reverse proxy in the context of web servers. What are they, and why are they used?

    The following is by my understanding.

    A forward proxy server, or just proxy server, is a middleman: a request comes to it from a client, then the proxy sends along said request to the site that can fulfill it. The fulfillment site then sends its response back to the proxy, which forwards the response to the client.

    In the case of the proxy server, the fulfillment site thinks it’s interacting with the proxy; it doesn’t know about the client on the other side. Hence, the proxy can offer anonymity to the client, although the proxy itself knows all.

    A reverse proxy server is similar to a proxy server, but the client in this case is the fulfillment site. A web surfer sends a request to, they think, the fulfillment site. However, the request arrives to the fulfillment site’s proxy. Said proxy decides whether to pass the request along, and if so, to which specific port of the fulfillment site’s architecture.

    The requester, aka the web surfer, doesn’t know their request was processed by the reverse proxy.

    To its sponsor, the reverse proxy offers filtration of the incoming web requests. It sends each request to its appropriate destination, perhaps eliminating the bogus or dangerous requests.

    Source:

    Cloudflare. (2026). “What is a reverse proxy? Proxy servers explained.” https://www.cloudflare.com/learning/cdn/glossary/reverse-proxy/

    -js

  • Accessories: charging cords, usb c to usb c

    Charging a device, a cord is often needed. What are some considerations about charging at a usb c port?

    The following is by my understanding.

    This post is connected to my post from August 11 about laptop power banks, etc.

    Herein, “cord” and “cable” are used interchangeably.

    The charging brick and laptop power bank arrived. Neither came with a cord. I plugged the charging brick to the wall. Then, I connected the charging brick to the laptop power bank via the usb c cord I use to charge my phone.

    The laptop power bank’s display lit up. It indicated charging happening at around 56W. Yet, the charging brick could deliver 140W, and the laptop power bank could also receive 140W.

    I’d read that a particular specification of charging cord is needed beyond 60W; here was proof. It seems that basic, standard usb c to usb c cable allows up to 3A. Caveat: some usb c to usb c cord may not be made to that standard, so won’t even accommodate 3.0A.

    So, the laptop power bank was charging fine at just under 60W, but the charging brick could deliver 140W, and the laptop power bank could accept 140W as well. The limitation seemed to be the cord: it just couldn’t handle past 60W.

    I went out yesterday, seeking usb c to c charging cords. Serious ones have ratings on the packaging, by Watts and/or Amps. I bought one rated at 100W and one rated at 240W, around ten dollars each. Then I bought a “normal” usb c to usb c cable, rated for 3A, 60W.

    I haven’t had a chance to try out the 100W or 140W cables because right now everything is charged. However, I plan to follow up when the opportunity arises:)

    Source:

    Cherchian, R. (Aug 2, 2025). “USB-C Cable Types Explained: Speed, Power, and Video Differences.” YouTube: https://www.youtube.com/watch?v=guegsQSZYD4&t=64s

    -js

  • Accessories: laptop power banks

    Some people need their computer battery to last longer between charges. A laptop power bank can be a solution.

    The following is by my understanding and research.

    As I’ve come to see it, a laptop power bank is a particular kind of charging bank. (See my post from Jun 6 about charging banks.) Being intended to charge a laptop instead of, or besides, a phone, the laptop power bank might typically have capacity between one and two times a laptop’s battery. Yet, laptop charging banks are typically are constrained to less than 100Wh because of airline restrictions.

    A working scenario might be like this: a laptop has battery capacity of 50Wh. The laptop power bank to replenish it might be 25000mAh, which translates to a 92.5Wh (see my post from Aug 3). From it, the user might get almost two additional use cycles on the laptop without having to plug into the wall.

    Then, at some other time, the laptop power bank itself will need to be replenished. To do so reasonably quickly, another accessory is needed, called a charging brick, which connects to a wall socket on one end and then to the laptop power bank on the other. Charging bricks are often not mentioned in the context of laptop power banks, but are inherent in the scenario. A fast charging brick may be able to fully recharge a laptop power bank in about an hour. The recharging is done by USB-C PD.

    Charging and recharging speeds of laptop power banks and charging bricks I intend to discuss in a future post.

    Laptop charging banks often have numerous ports, so that a laptop and a phone can be recharged simultaneously.

    Source:

    My Laptop Spares. (Mar 27, 2026). “How To Choose The Right Laptop Battery Capacity.” https://mylaptopspares.com/blogs/news/how-to-choose-the-right-laptop-battery-capacity?srsltid=AfmBOor5KdU74YcRPtfXPFNtuX9I5b_cqXkBydRwLHJ-GTx1USU0xs64

    ca.ecoflow.com

    -js

  • Infrastructure: steam heating?

    Sometimes, infrastructure might have interesting history. Radiators might be a case.

    The following is by my understanding.

    When I was a kid, we had radiators in houses and buildings. It was eastern Canada, so the weather was cold in the winter.

    The places I recall radiators from most clearly were in classrooms. The radiators were often about three to four feet tall, and resided under the windows. They were painted white or off-white. One soon took them for granted, yet one might be intrigued to see one today.

    I didn’t realize at the time that it’s possible those radiators held steam. Moreover, one did hear of a boiler room at the school.

    Somewhat interestingly, around eighty percent of large buildings in New York City use steam heating as of 2022.

    What pointed me in this direction was a this intriguing video on YouTube, from SdS construction (Mar 19, 2023), showing a homeowner’s steam heating setup using restored radiators.

    Source:

    Zhadanovsky, I. (Jun 21, 2022). “Steam Heating Conundrum of High-Rise Buildings.” https://www.intechopen.com/chapters/84666

    -js

  • Materials: polystyrene foam, part0

    Some materials that seem disposable might be worth holding on to.

    The following is by my understanding.

    The other day I was handling some polystyrene foam that arrived in a package. Like one would expect, it had been fitted around the package’s contents to protect them from damage. Said product had been unpacked, and the polystyrene remained.

    I noticed, as I handled it, how strong it was relative to its mass. I decided to look it up.

    It turns out that one-pound polystyrene foam has a shear strength of around 20PSI. It’s a pound per cubic foot.

    By way of comparison, Douglas fir has sheer strength of around 900PSI. However, it’s around 29 pounds per cubic foot.

    So, Douglas fir has greater shear strength by weight, perhaps by a factor of around 1.5. However, for temporary set-ups, such as forms to hold wood parts in place for fastening, polystyrene could be used effectively.

    Source:

    Foam Factory. (Oct 12, 2014). Polystyrene Foam (EPS) Physical Data Sheet. https://canada.foambymail.com/polystyrene-foam-sheet.html

    Hiziroglu, S. (Jul 2016). “Strength Properties of Wood for Practical Applications.” https://extension.okstate.edu/fact-sheets/strength-properties-of-wood-for-practical-applications

    -js

  • Energy: how 27000mAh might “become” 100Wh

    Researching specs of charging banks, one might at first be confused by capacity comparisons.

    The following is by my understanding.

    I was reading about charging banks that might be used to charge a laptop. There seems a common limit of the capacity of those: airlines don’t allow more than 100Wh of energy storage without special permission.

    Some places were saying 100Wh, while others, 27000mAh. In one place, it even said those are the same. Yet, from the point of view of physics, they can’t be, because a W (W) is not the same unit as a milliAmp (mA). Specifically, W measures power, while mA measures current. I knew more research was required.

    It turns out it’s because many power banks use lithium-ion cells, which produce energy, internally, at around 3.7V.

    So, since 1000mA=1A, and W=V*A, 27000mAh*3.7V=99.9Wh≈100Wh in the context of many power banks.

    Source:

    service.anker.com

    benzo energy (Aug 20, 2019). “What type of cells is used for power bank?” https://www.benzoenergy.com/blog/post/type-of-cells-used-for-power-bank.html

    “Guidelines for Batteries.” (Jun 10, 20206) Canadian Air Transport Security Authority. https://www.catsa-acsta.gc.ca/en/what-can-bring/guidelines-batteries

    -js

  • Hardware: charging Milwaukee RedLithium cell: flashing red/green

    Apparently I’m not the only one who’s tried to charge a Milwaukee RedLithium cell and had the charger flash red/green. Here’s what happened.

    The following is by my understanding.

    My wife got me a drill/impact wrench set from Milwaukee tools maybe a year ago. It revolutionized my handyman chores.

    I recall having to charge the cells before using the drill and the impact drill. When I slid one cell into the charger, the indicator went solid red, which means it’s charging. You want that.

    Then, when charging is finished, the indicator light on the charger turns solid green: you want that, too.

    Such happened with the first cell. However, with the second, the indicator light flashed red/green when I slid it in. You don’t want that; the manual seems to suggest that it means either the contact isn’t good, or there’s a hardware problem either with the cell, the charger, or both.

    Since the set was brand new, I didn’t want to think it was already defective. I played around a bit, slightly changing its geometry in the charger. After a couple of minutes of this, the indicator turned solid red: charging. I wanted that.

    Holding the cell in place in the charger, and my breath, I continued to watch the indicator light, wondering if it would start to flash. It did once, but by readjusting the position of the cell I was able to bring it back to solid red. Eventually, I could let go, and the indicator remained solid red. A few minutes later, I checked back: solid green. I wanted that:)

    Charging time doesn’t seem very long, anyway. I didn’t time it, but it seems maybe it took half an hour(?) from near-dead to full charge. That’s a very loose guess.

    Best of luck:)

    -js

  • JavaScript: defer

    Getting JavaScript to load when a webpage loads can be a consideration.

    The following is by my understanding.

    Lately I’ve been doing a lot of hands-on, physical tasks, as my posts have reflected. However, yesterday I had to incorporate some JavaScript into a web page. I’d done so many times in the past, but wondered if I’d done so the best way, if there’s a better way now, etc. I decided to look it up.

    I discovered that a way to load JavaScript after the web page loads seems to be to put defer in the script tag where the JavaScript source is given: something like this:

    <script src=”script.js” defer></script>

    It seemed to work great.

    Source:

    developer.mozilla.org

    -js

  • Autos: how much torque to turn healthy engine?

    The idea of how much torque is required for tasks in mechanics can be fascinating.

    The following is by my understanding.

    In my previous post I mention the idea of drive size, torque, etc. Ideas of aligning drive size with socket size, as well as torque requirements of certain tasks, naturally arise thence.

    The idea of turning over a car engine, by hand, is one I’ve been hearing about lately. One wonders what torque that might require.

    It turns out, apparently, that it might only take around 20 ft*lbs of torque to crank over a healthy engine by hand. Such can be done, at least in some cases, using a 1/2″ drive torque wrench.

    Source:

    YouTube: MotorCarNut: “How To Tell If Your Engine Is Seized”

    -js

  • Autos, hardware: drive size for sockets

    Most people might be familiar with a basic socket set. Yet, drive size might be less obvious.

    The following is by my understanding.

    I recall buying a socket one time to remove the anode of a hot water heater. It was, I think, one-and-one-sixteenth. I bought it from a discount bin, and it came on a straight bar. I was in a hurry, so didn’t think much of it.

    Later, I had to buy a 15/16″ socket to undo an oil filter casing. The clerk asked me what drive I was using. I didn’t know. The socket was 1/2″ drive. He assumed, correctly, that I would need an adapter from 3/8″ drive to 1/2″.

    Back then, I just had a standard socket set from Mastercraft. It had both 1/4″ and 3/8″ drives, and its largest socket was 3/4″. It hadn’t occurred to me that bigger drives – for instance, 1/2″, were called for sometimes. However, when I got home from buying the 15/16″ socket, I inspected the one-and-one-sixteenth socket, on its bar, that I’d bought years ago to remove the water heater anode. Indeed, that socket, too, was 1/2″ drive.

    When I thought about it, the reasoning was obvious why 1/2″ drive might be called for: a bigger fastener might well mean it’s under more strain, so needs to be tighter. In turn, a larger-diameter drive would be stronger, so less likely to break when removing such a fastener.

    It turns out that, for 3/8″ drive, the torque range tops out around 75 ft*lbs, then for 1/2″, around 250 ft*lbs.

    It’s hard to imagine me, personally, applying more than 250 ft*lbs of torque, but apparently that’s when 3/4″ drive becomes relevant.

    Source:

    eTork. (Sept 4, 2024). “Torque Wrench Sizes Explained.” https://etork.com/torque-wrench-sizes/

    -js