## Semester Done, School-year Done

The fall semester is in the books.  I am now about two-thirds thru the required credits for a master’s degree in computer science.  With chipping away at the degree in a part-time manner, when complete, it will have taken me around four and a half years to finish an otherwise two-year degree.

This year, the courses I took involved HCI – Human Computer Interaction.  For those who did not click on that Wikipedia link, HCI is an area of computer science that looks at (observes) how people use computers and associated technologies, as well as the creation (design) of technologies that let people computers in interesting ways.

For the spring semester, the course I took was titled, Collaborative & Social Computing.  It explored, from a fairly high-level, the many aspects of HCI.  We looked at Wikipedia, Zooniverse, Mechanical Turk, a host of dating sites, as well as Chris McKinlay’s gaming of OkCupid (there’s also a book on this, too).  The class ended with a two person project – my partner and I implemented a very crude Wikipedia-of-CompSci-course-work.  Think of this as a free and open platform to obtain questions and their answers for computer science coursework.  This was to be an instructor-centric platform where instructors could share with other instructors their courses’ questions.  We called it AssignmentHub.

This course was a bit of a gateway-drug for HCI.  Little samples – gets you hooked, gets you interested – convinces you that the next level, HCI & UI Technology, should be a great course.

The name, HCI & UI Technology, is a bit of a catch-all and does not clearly state what my fall semester’s primary course was about: research methods within the context of human-computer interaction.  What’s that I just said?  The gist of the course was look at a research paper from the HCI-world and look at the methods of research used.  Grounded theory method, surveying of individuals, was there a statistical process applied, and so on.  We read a lot.  Thirty-eight papers or chapters, likely many hundreds of pages.

Many of the papers and chapters have blended together in my mind.  Which ones were on Facebook?  Which ones used mturk?  Which ones were about designing technologies and which ones were about evaluating perceptions of technologies?

There is one paper that stands out a bit in my mind.  It is likely that it stands out because I had to co-present it to class.  The paper was Project Ernestine: Validating GOMS for predicting and explaining real-world task performance.

It’s a 74-page paper, published in 1993, that chronicles the scientific effort to compare work-times of telephone operators using two different workstations at NYNEX.  Those with a keen mind for remembering late 1960s television might realize that Ernestine was the name of one of Lily Tomlin’s characters on Rowan & Martin’s Laugh-In.  Ernestine was a sarcastic telephone operator.

The paper also draws on work from Frank and Lillian Gilbreth and their efforts to measure worker performance and study motion in a more scientific manner.

After all the readings, the term was rounded out with co-authoring a research paper.  The paper was modeled after Understanding User Beliefs About Algorithmic Curation in the Facebook Newsfeed. Instead of Facebook, we looked at Reddit and people’s perceptions of Reddit’s Best algorithm.

And, that’s it.  Lots of reading, three research projects (including the research paper).  Social and Collaborative Computing was certainly gateway-drug to the more hardcore HCI & UI Technology (HCI Research Methods in disguise).  It was interesting to learn more about the inner-workings of a sub-area of computer science, but I have definitely had my fill for a while.

Below is a table of nearly all that we read this term.  Enjoy.

Paper or Chapter NameAuthor(s)
Curiosity, Creativity, and Surprise as Analytic Tools: Grounded Theory MethodMichael Muller
An older version of the Wikipedia talk page for Edina, MNWikipedia.org
Excerpts from Old Edina, MN Wikipedia Talk PageWikipedia.org
Is it really about me?: message content in social awareness streams.Naaman, Mor, Jeffrey Boase, and Chih-Hui Lai.
Hustling online: understanding consolidated facebook use in an informal settlement in Nairobi.Susan P. Wyche, Andrea Forte, and Sarita Yardi Schoenebeck
Mediated parent-child contact in work-separated families.Yarosh, Svetlana, and Gregory D. Abowd
Experimental Research in HCIGergle and Tan
Understanding User Behavior Through Log Data and AnalysisSusan Dumais, Robin Jeffries, Daniel M. Russell, Diane Tang, Jaime Teevan
Research Ethics and HCIAmy Bruckman
Effectiveness of shared leadership in online communities.Zhu, Haiyi, Robert Kraut, and Aniket Kittur
To stay or leave?: the relationship of emotional and informational support to commitment in online health support groupsYi-Chia Wang, Robert Kraut, and John M. Levine
Practical Statistics for Human-Computer InteractionJacob O. Wobbrock
Experimental evidence of massive-scale emotional contagion through social networks.Kramer, Adam DI, Jamie E. Guillory, and Jeffrey T. Hancock
Predicting tie strength with social mediaEric Gilbert and Karrie Karahalios
Survey Research in HCIMuller et al.
Concepts, Values, and Methods for Technical Human-Computer Interaction ResearchHudson and Mankoff
Skinput: appropriating the body as an input surfaceChris Harrison, Desney Tan, and Dan Morris
The bubble cursor: enhancing target acquisition by dynamic resizing of the cursor’s activation areaTovi Grossman and Ravin Balakrishnan
Field trial of Tiramisu: crowd-sourcing bus arrival times to spur co-designJohn Zimmerman, Anthony Tomasic, Charles Garrod, Daisy Yoo, Chaya Hiruncharoenvate, Rafae Aziz, Nikhil Ravi Thiruvengadam, Yun Huang, and Aaron Steinfeld
Performance and User Experience of Touchscreen and Gesture Keyboards in a Lab Setting and in the WildShyam Reyal, Shumin Zhai, and Per Ola Kristensson
The drift table: designing for ludic engagementWilliam W. Gaver, John Bowers, Andrew Boucher, Hans Gellerson, Sarah Pennington, Albrecht Schmidt, Anthony Steed, Nicholas Villars, and Brendan Walker
Predicting human interruptibility with sensors: a Wizard of Oz feasibility studyScott Hudson, James Fogarty, Christopher Atkeson, Daniel Avrahami, Jodi Forlizzi, Sara Kiesler, Johnny Lee, and Jie Yang
Beyond the Belmont Principles: Ethical challenges, practices, and beliefs in the online data research communityVitak, J., Shilton, K., & Ashktorab
Unequal Representation and Gender Stereotypes in Image Search Results for OccupationsKay, Matthew, Cynthia Matuszek, and Sean A. Munson
y do tngrs luv 2 txt msg?Grinter, Rebecca E., and Margery A. Eldridge
Becoming Wikipedian: transformation of participation in a collaborative online encyclopedia.Bryant, Susan L., Andrea Forte, and Amy Bruckman
Wikipedians are born, not made: a study of power editors on Wikipedia.Panciera, Katherine, Aaron Halfaker, and Loren Terveen
Agent-based Modeling to Inform the Design of Multi-User SystemsRen and Kraut
Project Ernestine: Validating a GOMS analysis for predicting and explaining real-world task performance.Gray, Wayne D., Bonnie E. John, and Michael E. Atwood
Cooperative inquiry: developing new technologies for children with children.Druin, Allison
Sabbath day home automation: it’s like mixing technology and religion.Woodruff, Allison, Sally Augustin, and Brooke Foucault
SpeechSkimmer: interactively skimming recorded speech.Arons, Barry
Sensing techniques for mobile interaction.Hinckley, Ken, et al.
A touring machine: Prototyping 3D mobile augmented reality systems for exploring the urban environment.Feiner, Steven, et al.
"I regretted the minute I pressed share":
A Qualitative Study of Regrets on Facebook
Wang, Yang, et al.

## Wind and Weather

It was around mid-February of this year (2015) when the Acurite Weather station and associated things arrived.

I had waffled on whether to purchased one – it was not inexpensive, but, it is also not the cost of an entry level professional unit.  I also really only one initial use for it, too.  I wanted to answer a question that had been ruminating in the back of head for a bit over a month.  The question had come up after the solar panels went up on the chicken coop.  The solar panels only generate electricity when there is enough sun light – often poorly during the day in winter, and never during the night any time of year.  The only other obvious alternative energy generation method was wind. But, it is not as simple as buying a turbine system.  A turbine is useless without wind.  A turbine is also useless even with a small of amount of wind.

### Was there enough wind at the house to generate electricity?

We mounted the outdoor part of the weather system on a fence post near the chicken yard; the indoor receiver (with its fancy colorized screen) sits in the kitchen and the Internet bridge lives in the basement.  The Internet bridge is a device that connects via a network cable into a network switch; the indoor receiver wirelessly sends weather readings to this device, and, subsequently, forwards those readings to Acurite’s My Backyard Weather service.

Acurite’s service has limited analytical capabilities.  You can produce simple line graphs of individual readings – wind speed, temperature, barometric pressure, and so on.  But, you cannot produce fancier things like a wind rose, or pull apart temperature readings into night time lows plotted against daytime highs.

Through a bit of a virtual Rube Goldberg setup, I started collecting the readings in a database of my own.  I now have readings, on average, every 20.36 minutes, from February 21, 2015 to the present1.

Using some statistical and graphing tools2,3,4,5,6, I came up with some answers to the original question.

The short answer is it’s unlikely that from six to twelve feet above the ground, there is enough wind to generate electricity.

Let me explain a bit more.

I narrowed the focus of the question to the end of winter.  I only started the collection of data at the end of February, that left March as being the closest month to a true winter-month.

The wind turbines that I had been looking at have a wind cut-in speed of 4.2 to 6.7 MPH.  Below that speed but above 0.0 MPH, the turbine blades and head may slowly rotate, but it is not enough rotation to generate electricity.  The wind rose, above, was quite helpful in coming to an answer.  It shows that we get our dominate wind from the west — seems obvious in retrospect, as there is an enormous bluff/hill to the east.  But having direction of the wind is likely not necessary.  Plotting the March data has a histogram, you can get a very simple yet informative picture; the majority of the wind is under four miles per hour.  That’s well under what is necessary to make a turbine useful.

VariableValue
Wind > 4 MPH22.32%
Wind <= 4 MPH77.68%
Average Wind (MPH)2.49
Max Wind (MPH)10.90
Average Temperature (F)36.07
High Temperature (F)71.59
Low Temperature (F)-7.20

A wind turbine is out of the question.  There are other locations in the yard that could have more wind, but it is unlikely this would be convenient to move the generated power from that location to the battery bank at the chicken coop.  A more plausible scenario is to add both more batteries and more solar panels.  We would be able to capture more energy when it is light out, and have more storage capacity to drawn from when it is needed.

1. data sample
2. Jupyter Notebook is a web application for interactive data science and scientific computing.
3. matplotlib is a python 2D plotting library.
5. anaconda implementation of python3
6. jupyter notebook with sample graphs and calculations

## Archives and Special Collections at the University of Minnesota

Today, I had the chance of a very short tour of Archives and Special Collections that are managed, in part, by the University of Minnesota’s Libraries. Housed under the Elmer L. Andersen Library, a set of football-field-lengthclimate controlled caverns house the materials for the Charles Babbage Institute, YMCA Archives, and one of the largest Sherlock Holmes collections, among many others.  While wandering around with the small group, I took a few pictures.

## Cold Weather, The Coop and Heat Transfer

A few weeks ago, we bought a new waterer for the coop.  There was nothing wrong with the current waterer other than being an energy hog.  Throughout December, we struggled with keeping the coop’s battery charged enough power the waterer.  The waterer’s 100 watt heating element was just too much. Think of it like this: the waterer’s draw (outflow) on the battery is greater than the solar panel’s ability to recharge (inflow) the battery.

$$Outflow > Inflow$$

The new waterer, branded as Cozy Hen Waterer, is from Neora Inventors, LLC. From a cost perspective, it was expensive.  Around \$70 for the waterer, a hanging chain, and a heater.  The waterer consists of two buckets – one ¾ gallon bucket nested within a larger pail. Inside the larger pail, there is a layer of thin insulation.  The outer pail is only used as a convenient way to capsulate the inner pail in insulation.  The water, contained in the inner pail, is able to get out to the chickens byway of a chicken nipple (pictured to the right).  The other interesting bit of engineering is the encasement of the chicken nipple in an aluminum pipe.  The pipe extends into the water pail by several inches.  This is subsequently encased in a bit of insulation with an outer shell made of a PVC plumbing part.  Finally, inside the water pail, there is a 15 watt aquarium heater.  It will keep the water at around 77°F.

The aluminum pipe is clever because of what it allows: heat transfer.  Although not entirely analogous (it is a pipe and not a rod), you could get a sense of the heat transfer by using a partial differential equation (Partial Differential Equations for Scientists and Engineers is also a good place to look).  There are actually several energy-flows going on in these coop-systems if you think about it.

The heat is transferred from near the center of the water pail down to the chicken nipple byway of the aluminum pipe.  This allows for the nipple to stay mostly ice-free on those -20°F days.

If you recall from a previous post, the first-replacement waterer had a thermostatic switch that kept the water at 35°F.  In my mind, that seems like a valid temperature for water – it would minimize the energy consumption.  The new waterer with the aquarium heater and its 77°F temperature seems, on the surface, like it will use too much energy.

But, there are a few things that make the new waterer-system much easier on the consumption of electricity.  First, the larger waterer has 1.⅔ times the surface area as that of the new, insulated waterer.  More surface area results in faster transfer of energy from the warm water to the cold air.  Second, and this is likely the most important factor, the new waterer is insulated.  Top, bottom and sides – it is all insulated.  The one direct exception is the chicken nipple area, but that has the aluminum pipe to assist with heat loss (with the assumption that the heat transfer from the water + pipe is greater than the heat transfer from the end of the nipple to the air).

The more I have thought about the larger waterer and how it appears to be inefficient, the more I kept thinking of its design in comparison to the new waterer.  The larger waterer has the heating element on the bottom – the three gallons of water sit on top of the element.  This means that only one side of the element in contact with a surface that has water touching it.  That other side is hanging out in the air; sometimes, well-below-zero air.  What is the likelihood that the thermostatic switch actually switches off for any significant length of time?

A better design would be have the heating element have more contact surface with the water.  Perhaps, instead of being encased in a disc in the base of the waterer, the element would be a more rod-shaped protrusion from the base into the center of the water  reservoir.  Secondly, insulate, insulate, insulate.  The choice of insulation material is possibly debatable – the new waterer uses foil covered bubble insulation – this might be sufficient; it would certainly be better than nothing.

## Solar Coop – Update II

Since writing the first update on the solar panels on the chicken coop, we had quite the cold snap.  Along with the persistent cold, there was persistent cloud cover and strong winds.  The combination of cold weather meant the battery for the coop had diminished capacity and the cloud cover meant that there would not be enough solar irradiation to fill that reduced capacity.

Each night, I would disconnect the battery from the system and lug into the garage; connecting it to a battery charger for the night.  We also brought the chicken’s waterer into the house to prevent the need in the morning of having to thaw the water. In addition to the routine changes, I removed two things from the electrical-mix: the electric timer and the ammeter. With the battery’s stored energy being consumed so quickly and the water and battery being brought in at night, it did not seem like the timer was needed at all. The ammeter was removed because it stopped working in the sub-zero cold.  Subsequent tests, while it has been warmer outside, show that the meter still works; it just does not like the cold.

We have since made it through that cold spell, and have been in a pleasant middle ground of nice amounts of sun, above freezing day-time temperatures – several days in a row, and light amounts of wind.

With the warmer stint of weather, the battery has been under lighter duty. Even when the solar charge controller has been indicating that the battery is not strong enough to power the inverter, the next day’s sun will be more than enough to give the battery a good charge.

Being a curious, amateur scientist, I wanted to know a bit more about why a lead-acid battery appears to be quite poor at being able to provide energy when the ambient temperature is very low.  This inability to provide energy is quite noticeable and prevalent in colder regions during the winter.  For those who are familiar with starting a car while in the depths of a cold winter – think of how the car’s starter seems to struggle to turn the engine over.  It’s a battle between cold lubricants with a higher than normal viscosity and a lead acid starter battery with diminished capacity.  But, why does cold cause this diminished capacity.

With my day-job being at a university, and I am surrounded by academics and researchers, my first thought was to look into published research on batteries or modeling batteries.

The first paper I found was A mathematical model for lead-acid batteries co-authored by Dr. Ziyad Salameh – Dept. of Electrical Engineering, UMass Lowell, Margaret A. Casacca (student), and William A. Lynch (student).  The paper was published in the IEEE Transactions on Energy Conversion, Vol. 7, No.I, March 1992.

Aside from equations and a mention of a BASIC program that was developed (but this program is nowhere to be found in the paper), the main take aways from the paper are list of five factors that effect a battery’s ability to store energy; for the most part, the list of things is obvious.  (1) State of charge, (2) battery storage capacity, (3) rate of discharge, (4) environment temperature, and (5) shelf-life or age.

(This list is originally from the Complete Battery Book.)

We can say that our battery is fully charged (state of charge is 100% at the on set), has a capacity of 110 amp-hours, the waterer has a draw of at most 10 amps (this is likely not constant as the waterer will turn on when the water is below 35 degrees, and turn off when it reaches a temperature above this), the shelf-life or age is basically “brand new”.  Temperature is likely the deciding factor.

Looking at how temperature effects capacity, you can see that as the temperature drops, the capacity drops, as well.

Assuming this graph is true (there is no documentation or available analysis), at our coldest, the battery is likely to be running at a bit over 60% capacity; meaning, we’ll only get about 66ah from it.  The inverter will shut off when the voltage drops below about 12.10V; according to another battery university article, this likely means the battery has about 50% capacity remaining.  This could roughly be translated into a capacity of 33ah at our coldest, and about 55ah at optimal temperature (which we won’t have until sometime in late May).

Now that I have some numbers that better explain the observation of why didn’t the battery last more than 8 hours on the coldest day, I still want to know why does this happen.  Why does ambient cold have such an effect on lead-acid batteries?

The short answer is internal resistance.  To understand this, you first need to know a bit about how lead-acid batteries work.

A course offered at the University of Colorado Boulder‘s Electrical, Computer and Energy Engineering department has a great set of lecture slides (or here) explaining how lead-acid batteries work.

The gist of how lead-acid batteries work are electrons drifting or flowing from the negative terminal – most often made of lead ($$\ce{Pb}$$) – to the positive terminal – most often made of lead dioxide ($$\ce{PbO2}$$).  The two terminals are submerged in an electrolyte solution.  This is usually in the form of sulfuric acid ($$\ce{H2SO4}$$, where, in solution, it takes the form of aqueous ions $$\ce{{H^{+}}+{SO4^{-2}}}$$).  As you draw electricity from the battery via the positive terminal, electrons flow from the negative terminal to the positive terminal.  How easily or difficult the electrons can move from negative to positive terminals in the internal resistance.

I think of what happens with the electrolyte solution and effect of cold temperatures on it is sort of like what happens to honey when it is chilled.  It is not quite analogous but I think it gets the point across.  If little droplets of honey are running down a piece of glass and you suddenly cool the glass, the honey will begin to run much slower.

Similarly, as the electrolyte solution cools, the ability for electrons to drift efficiently to the positive terminal decreases.  The decrease in electron flow results in less power to be consumed – in our case, by the inverter and waterer.