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Benford’s law, also known as the Newcomb–Benford law, the law of anomalous numbers, or the first-digit law, is an observation that in many real-life sets of numerical data, the leading digit is likely to be small. In sets that obey the law, the number 1… Read more

This is a work-in-progress… Run compiled Matlab applications or components without installing Matlab. Download and install the Windows version of the MATLAB Runtime for R2024a from the following link on the MathWorks website: https://www.mathworks.com/products/compiler/mcr/index.html (right mouse click, open link in new tab) Next, download vibrationdata_sa_3_6_26.zip… Read more

Matlab’s App Designer’s listbox lacks some of functionality of GUIDE’s listbox. App Designer’s listbox currently offers no direct method to obtain the index number of a selected item. Here is a roundabout method for a sample listbox named listbox_type: Items = char(app.listbox_type.Items); im=app.listbox_type.Value; [n]=find_index(Items,im) %… Read more

The top image is the air conditioner mounted near a back corner of my home. It is Carrier model 24AHA424A003. It has a scroll compressor, model ZP20K6E-PFV-130. I measured its output sound using my Android Smartphone. The condenser motor nominal speed is 800 RPM (13.3… Read more

I made a video using my Android Smartphone of this aircraft taking off from SeaTac airport, headed northward. The image above was extracted from the video. The date was July 20, 11:50 AM. This was Delta flight 1172 headed to Fairbanks, Alaska, if my interpretation… Read more

MV Chetzemoka Ferry Air Vent Pipes I recently rode on the MV Chetzemoka Ferry which was running between Tacoma’s Port Defiance and Vashon Island’s Tahlequah terminal. The ship is powered by a pair of EMD 12-710 diesel engines rated at 3000 hp each at 900… Read more

Matlab’s built-in function for Butterworth filtering has stability issues. The following code snippet yields an unstable filter. The cutoff frequency is 4 Hz. The sample rate is 20000 Hz. The filter is a high pass, sixth order. fh=4;sr=20000;order=6;Wn=fh/(sr/2);[bb,aa] = butter(order,Wn,’high’);flag = isstable(bb,aa);if(flag==1)fprintf(‘\n filter is stable… Read more

The aircraft is a De Havilland Canada DHC-3 Otter, Single Engine, Seaplane. It is powered by a Pratt & Whitney R-1340 Wasp, 600 hp, air cooled, radial engine with a propeller hub speed of 2250 rpm (37.5 Hz). This aircraft is used for tours and… Read more

Teeter-Totter, Playground along Riverview Blvd, Kent, Washington State I gave the teeter-totter an initial displacement, without human riders, and recorded the damped sine oscillation with my Android smartphone accelerometer app. The natural frequency was 2.1 Hz with 0.6% damping. The frequency would decrease with riders.… Read more

This rustic bridge is popular with fishermen during the Salmon season from Summer through Fall. The Duwamish supports chinook, coho, chum and steelhead, as well as the more rare sockeye, sea-run cutthroat trout and bull trout. Pink salmon run in the millions every odd-numbered years… Read more