Author Archives: mathscinotes

Relative Cost of WW2 US Fighters

Posted on 19-October-2020 by mathscinotes

A reader of this blog mentioned in a comment that cost might be a big reason for the US Army Air Corps (USAAC) switchover to the P-51 from P-38s and P-47s. I thought I would put together a quick report on the relative cost of the three main USAAC fighters. The cost of these fighters by year was available in the Army Air Forces Statistical Digest (Hyperwar Site). The approach to Extracting, Transforming, and Loading (ETL) the data are the same as I used to determine the on-hand numbers of aircraft (link). For those who are interested in the details, my workbook is available here. Continue reading →

 
Posted in Excel, History Through Spreadsheets | 2 Comments

Lake Water Temperature Report Using Power Query and FILTERXML

Posted on 18-October-2020 by mathscinotes

I have a cabin in northern Minnesota on a small lake where I have been staying isolated from the rest of the US while COVID rages around me.  I track various lake metrics like height relative to sea level, clarity, and temperature.  I gather this information into a report that I send to the other folks who live on the lake. In this post, I show how I put together a chart of lake water temperature vs time using Excel and Power Query. I also demonstrate how to use the FILTERXML function to parse some rather messy data. I find myself using FILTERXML for data parsing more and more. Continue reading →

 
Posted in Cabin, Excel | 1 Comment

US Army Air Corp Fighters on Hand During WW2

Posted on 17-October-2020 by mathscinotes

Many years ago, at the start of my career, I worked with an excellent safety engineer who had served in WW2 as a fighter pilot in Europe with the US Army Air Corps (USAAC). You could tell that flying was the love of his life. Though we were working on naval weapons systems, our lunchtime talks often focused on his experiences flying aircraft during the war. His war service began in a P-47 (Figure 1) and his unit later transitioned to the P‑51 (Figure 2). Continue reading →

 
Posted in Excel, History Through Spreadsheets, Military History | 2 Comments

APR of Payday Loan

Posted on 5-October-2020 by mathscinotes

I watched a video (Figure 2) that shows Rep. Katie Porter (Figure 1) grilling the Director of the Consumer Financial Protection Bureau (CFPB) Kathy Kraninger in regards to the calculation of a payday loan's Annual Percentage Rate (APR). This blog post will show how to compute the APR for the payday loan example Rep. Porter attempts to get Ms. Kraninger to compute. I am not sure Ms. Kraninger knows exactly what APR is. The questioning is a bit uncomfortable because Ms. Kraninger is in no mood for a math exercise and Rep. Porter is not going to give up. Ms. Kraninger clearly is uncomfortable, but her discomfort is nothing compared to the discomfort experienced by a payday loan customer. Continue reading →

 
Posted in Financial | 1 Comment

US Government Management of Western Forest Lands

Posted on 19-September-2020 by mathscinotes

I am always looking for data analysis exercises for the young folks that I tutor online. While watching the coverage of the massive forest fires on the west coast of the US, I noticed that all the media were reporting that much of the forest land in these states are managed by the US government, which makes them responsible for managing these forests. I thought it would be a good exercise to show the students how to calculate the percentage of forest land that is managed by the US government. Continue reading →

 
Posted in Civics Through Spreadsheets, Excel | 3 Comments

Computing Bacteria Reproduction Rate and Doubling Time

Posted on 22-July-2020 by mathscinotes

Until the arrival of the coronavirus, I looked forward every week to volunteering at a local library as a tutor for university students. Now that COVID is raging around me, I have moved the tutoring online. Most of the students are training for some form of a medical career. This week a student presented me with bacterial growth data and was wondering how to estimate the growth rate and doubling time for the bacteria using Excel. This exercise nicely illustrates the entire data analysis process (Figure 1) in a single example and I decided to post my solution here. Continue reading →

 
Posted in Excel, General Mathematics, Health, optics, Statistics | 2 Comments

Estimated Range Between Radios Based on RSSI

Posted on 18-July-2020 by mathscinotes

I recently have been working on Bluetooth Low Energy (BLE) systems and estimating the distance between two devices based on the Received Signal Strength Indicator (RSSI) value is one of my tasks. There are all sorts of uses for this distance information in wireless systems. Continue reading →

 
Posted in Electronics, Physics | 4 Comments

Gravity on Von Braun Station

Posted on 25-April-2020 by mathscinotes

I have been reading about Wernher von Braun's work with Disney on popularizing the idea of spaceflight with the public. He was a genius at marketing and a tireless champion for space flight. In addition to his television work, he also gave numerous speeches to any group that would listen. I smile as I think about my high‑school physics teacher beaming with pride when he spoke of von Braun arriving in a helicopter to speak to local physics teachers about space and flying to the moon. My physics teacher could not remember the details of what von Braun spoke about, but his entrance and exit in a helicopter made a huge impression on a town of 1800 people! Continue reading →

 
Posted in Space | 6 Comments

The Amazing de Havilland Mosquito

Posted on 18-April-2020 by mathscinotes

During the routine demolition of an old de Havilland Aircraft building in 2017, a treasure trove of 20K aperture cards (a microfilmed archive) was uncovered that contained plans for the Mosquito fighter-bomber (Figure 1). These plans have been lost since Mosquito production ended in  1950. Continue reading →

 
Posted in History Through Spreadsheets, Military History | 2 Comments

USNS Comfort Bed Count Relative To Other US Hospitals

Posted on 4-April-2020 by mathscinotes

Because of COVID-19, I am currently sheltering-in-place at my cabin in northern Minnesota. I was reading news reports of the USNS Comfort docking in New York City to provide the city with another 1000 bed hospital. I had no idea as to the average size of a hospital and decided to take a quick look at the number of beds in hospitals around the United States using a histogram. Continue reading →

 
Posted in Civics Through Spreadsheets, Excel | 3 Comments