Mark's Tech Tock

May 19

Most numbers that we encounter everyday are examples of scalar numbers. Another common type of number is a vector. Most people don’t understand what vectors are and how they are used. A vector is just a number that has a direction associated with it. Think about directions to buried treasure. Walk 15 paces to the east. Walk 20 paces north. These are vectors.

Some common measurements may be a scalar or a vector. For example, speed is a scalar but velocity is a vector. Remember the first letter of each; speed scalar and velocity vector. Distance is a scalar. The vector equivalent is called displacement. Acceleration is a vector. Mass is a scalar. Time is also a scalar. Force is a vector.

Vectors are represented by arrows. The length of the arrow represents the magnitude of the vector and the direction of the arrow represents the direction of the vector.

Everyone knows how to add scalar numbers but what about vectors? The easy way to add vectors is called the tip to tail method. Draw the arrow that represents the first vector. Start drawing the second arrow where the first ended. The sum is the vector drawn from the beginning of the first arrow to the end of the second. Perhaps a better way to visualize this is to think about walking in a city with square city blocks. Walk 3 blocks east then walk 4 blocks south. The sum is the displacement from your starting point to your ending point. Remember displacement is the vector equivalent of distance. You answer is the distance “as the crow flies.” The sum of your walk is a vector 5 blocks long in a southeastern direction. In order to get the 5 distance and the exact angle for the direction you need to understand trigonometry. That will be a lesson for another post.

May 17

Placards

Anyone traveling on a highway has probably seen diamond shaped placards on trucks. These are multicolored and generally have numbers within some of the colors. If you wondered the meaning of these numbers here is the answer.

The diamond displayed on trucks refers to the National Fire Protection Association (NFPA) hazard code. This code system is detailed in NFPA 704 rating system. The diamond shaped placard has four smaller diamonds within the larger one. The top diamond is colored red and refers to the flammability of the material being carried by the truck. The left side of the diamond is blue. The blue diamond is the health safety of the material being transported. The right diamond is yellow and speaks to the reactivity of the material being transported. The bottom diamond is white and is used for special warnings. Consider each category.

The blue health codes are numbered from 0-4

4 – Very short exposure to material can cause death or major residual injury even with prompt medical treatment.

3 – Short exposure to material can cause serious temporary or residual injury even with prompt medical treatment.

2 – Intense or continued exposure to material can cause temporary incapacitation or residual injury unless prompt medical treatment is administered.

1 – Exposure to material will cause irritation but only minor residual injury even with no treatment.

0 – Exposure to material under fire conditions will offer no hazard beyond that of ordinary combustible material.

The red flammability codes are also numbered from 0-4

4 – Material will rapidly or completely vaporize at atmospheric pressure and normal temperature, or will burn readily when dispersed in air.

3 – A liquid or solid (class I-B and C) that can be ignited under almost all ambient temperature conditions.

2 – Solid or liquid (class II and III-A) that can be ignited under almost all ambient temperature conditions.

1 – Material that must be preheated before ignition can occur.

0 – Material that will not burn.

The yellow, reactivity diamonds also contains numbers from 0-4.

4 – Material that is readily capable of detonation or explosive decomposition or reaction at normal temperatures and pressures.

3 – Material that is readily capable of detonation or explosive reaction but requires a strong initiating source or which must be heated under confinement before initiation or may react explosively with water.

2 – Material that is normally unstable and readily undergoes violent chemical change but does not detonate. Also, may react violently with water or may form potentially explosive mixtures with water.

1 – Material is normally stable but can become unstable at elevated temperatures and pressures or may react with water with some release of energy, but not violently.

0 – Material is normally stable even under fire exposure conditions and is not reactive with water.

The white diamond at the bottom contains special warnings. The letters “OX” designates oxidizing material. A letter “W” with a strike through means the material is hazardous when in contact with moisture or water. You may see other designations in the white diamond that are not part of the NFPA standard. These frequently include BIO for biological hazard, COR for corrosive, CYL or CRYO for cryogenic, SA for asphyxiant gas.

Generally a zero indicates minimal hazard and a four indicates severe hazard. The same placard system is also used at locations where these materials are stored. The system allows first responders to access how to best deal with emergency situations involving these materials. Wall charts and wallet cards are published to serve as a guide for anyone that must deal with these materials.

May 12

Lifestraw

I have previously written about the lack of clean drinking water in developing countries (see Nov 27, Water). Recently a simple solution has come to market. The Lifestraw is simply a straw that contains a water filter. The company claims that the straw removes 99.99999% of waterborne bacteria and 99.9% of water borne protozoan parasites. Turbidity is removed by an average of 99.6%. The filter uses a 1 mm prefilter followed by a hollow-fiber microfiltration membrane that filters all particles larger than 0.2 microns. Cleaning is done by simply blowing back through the straw in reverse. The backpressure flushes particles through the bottom opening.

The Lifestraw is being marketed in the US for outdoor enthusiasts. Weighing just 2 ounces it is a great tool for backup supply of water. At around $20 it is pricy for developing countries but it is likely cheaper in bulk. It would be handy after natural disasters when normal water supplies may become contaminated. The downside is that is only has a three year shelf life and it only provides mechanical filtration. Chemical or dissolved contamination will not get filtered.

http://www.vestergaard-frandsen.com/lifestraw/lifestraw

photo by petertheasianguy

May 9

CNG Vehicles

I previously discussed some of the advantages and challenges associated with adoption of compressed natural gas (CNG) as a fuel for vehicles (see PA Needs CNG Vehicles, Dec 8). Since that time natural gas prices have continued to fall. Supply is taxing storage capacity as production exceeds demand. The time is ripe to adopt CNG as a fuel source for vehicles. The only production car available to consumers at the moment is the Honda Civic. Some fleet vehicles are also available in CNG versions but not in large numbers. An alternative is a conversion. Since CNG is stored in a high pressure tank these conversions use valuable cargo space for the fuel tank and are somewhat pricey.

Another part of the equation is distribution of the fuel. I mentioned one of the early adopters is “return to base” vehicles since there is a lack of refueling infrastructure to support regular CNG vehicles. General Electric is addressing the refueling infrastructure with the introduction of CNG in a Box. This is a modular unit that compresses the gas and dispenses it in a manner similar to existing service stations.

These CNG in a box units are designed to by supplied by a gas pipeline. I don’t see any major obstacles to using a similar system feed from tanks supplied trucks much the same as most service stations. For now, GE is partnering with Chesapeak Energy to deploy 250 CNG boxes this fall. The 250 will be a total, national number. When we see 250 in a single state and more CNG production vehicles we will have a real start.

GE estimates that CNG will be about 40% cheaper than gasoline at retail. We will have to take that estimate with a grain of salt but it is clearly more abundant, likely to be less expensive than gasoline, produced in the US and has many environmental benefits. Everything points to CNG as a good short term alternative to gasoline. For the longer term, we need to improve battery technology and electric grid infrastructure to make electric vehicles more viable.

Apr 22

Experimental Error

In order to understand error you should know the difference between accuracy and precision (see Mar 25, Precision vs Accuracy). Accuracy is the measure of how close a set of results is to a known or theoretical value. Precision is how close a set of results is to each other. Characterizing error in terms of accuracy and precision helps to determine if the error is random or systematic.

Random errors are not consistent. Sometimes there is a positive error, other times the error is negative. Sometimes the error is small, other times the error is large. Random error is unpredictable. Systematic error is generally the result of some aspect of the system. A classic example is a miss calibrated instrument. Systematic errors are consistently in the same direction and approximately the same magnitude.

The difficulty is that in a real system there is most likely both types of error present. I recently asked one of my classes about error. A couple of the students observed that our experiment had multiple people timing an event. The students posited that this would increase the error. A human timing an event is fraught with random error. Some people even use the terms human error and random error interchangeably. It is true most human error is random but there could be sources of random error other than human. So what about the students’ conjecture? Remember random error is sometimes positive and sometimes negative. It is by nature evenly distributed on both sides of the correct value. This means taking an average of several trials will actually reduce random error. A larger number of trials will give better results.

This idea of reducing error by averaging many trials only works for random errors. If the nature of the error is systematic, averaging results of multiple trials will not reduce systematic error. Remember random error decreases precision. Systematic error reduces accuracy.

Apr 17

Physics and the Traffic Ticket

A professor from California received a traffic ticket for not stopping for a stop sign. He appealed the ticket in court with an academic paper explaining how the police officer may have misinterpreted the visual evidence. The judge accepted the argument and found the professor not guilty.

I obviously have no idea if the professor stopped or did not stop at the stop sign. Let’s just consider his paper. The professor argues that the police officer’s view was obstructed by another car at the moment he stopped. He argues that the officer’s vision was blocked long enough to allow the professor to stop then accelerate before being observed again by the officer. The professor assumes the other car is moving at a constant velocity. That seems to imply the other car did not stop for the stop sign. Why would not the officer stop the other car? When the professor calculated the time the officer’s vision was obstructed he only considers the length of each vehicle. He fails to consider the possibility that his car roof may have been observed over the top of the other vehicle’s hood or through the windows.

The professor’s argument also requires very high values of acceleration for both slowing and speeding up again. Even if the car were capable of this rapid stopping and starting it would surely have resulted in screeching tires. The professor only considers that the officer observed instantaneous velocity but the officer would likely also observe distance traveled which would differ between his claim and the officer’s. I did not carefully review his calculations but he seems to assume that the velocity function is continuous. If he started and stopped as he claims then there is a discontinuity at t=0 and his calculations are no longer valid. Of course you may question the whole incident given that the paper was published on April Fool’s Day.

I had a student tell me of a similar experience he had. He had received a ticket for speeding. Since the officer was a distance from the road he argued in court that the officer read the component of his velocity along the radar beam, not along his direction of travel. He explained to the judge that these values are different and the judge dismissed the case. What the judge did not know is that the velocity would be different but the velocity along the direction of travel would have to have been higher than indicated by the radar device. That’s correct, the velocities were different but his speed was actually higher than the speed indicated by the radar but the judge did not understand the Physics. This student’s experience did not occur on April Fool’s Day. Sadly, sometimes just sounding intelligent is sufficient; you don’t actually have to be intelligent.

http://www.physicscentral.com/buzz/blog/index.cfm?postid=4656335810518469535

http://arxiv.org/pdf/1204.0162v1.pdf

Apr 12

Technology News

There has been some interesting news on the technology front in the past few days. Let’s summarize some of the most interesting. The first comes from researchers in Germany. They have engineered a material reinforced with glass fibers that is intended as a type of wallpaper. When the reinforced material is applied with special mastic the result is a strong elastic reinforcement for masonry walls. The reinforced “wallpaper” absorbs energy from motion in four directions. This provides a method of binding the wall together so that it can withstand forces encountered in earthquakes. The researchers have tested the product and found it works!

This wallpaper may be useful in the US in locations near injection wells. A recently released study has found correlation and likely causation between injection wells, often tied to fracking operations, and earthquakes. It seems earthquakes occur much more frequently near sites of these injection wells when they are in operation. The earthquakes are small as measured on the Richter scale. The question that keeps occurring to me when I hear about these studies is what is the magnitude of the quakes that naturally occur? If the quakes occur more often, are they small in magnitude compared to less frequent quakes. If the quakes are smaller in magnitude, isn’t it better to have frequent mild quakes than less frequent but more severe quakes?

An entirely different product has been announced by Broadcom. Their new chip, the Broadcom 4752 offers position information using an array of sensors. In addition to GPS satellites the chip also uses Wi-Fi, inertial sensors, accelerometers, altimeters and other sensors to determine location. The combination of sensors improves accuracy and functions indoors as well as outside. Some published reports indicate that the new chip may determine location in 3 dimensions to an accuracy of a few centimeters.

A startup in San Francisco is using smartphone to facilitate electric scooter rental. The smartphone would run an app from the company, Scoot Networks. The app would serve as the key to start the scooter and then a dashboard to operate the scooter. The dashboard function would display speed and remaining range for the batteries. It will also show a map of nearby streets. When the scooter slows or stops the map automatically widens its view to show a larger area. One possible problem that may inhibit widespread use is operator licensing. Apparently California allows such operation without a special motorcycle license if it is limited to a couple of days. It is not clear if the couple of days is total or per instance. If a customer returns a scooter after 20 hours would they be able to rent a similar scooter the next day and keep for two days or is that a violation of the law? After working out the bugs in San Francisco, the company hopes to expand into additional cities.

Another news item focuses on phones, this time stolen phones. Many robberies are committed to get cell phones, especially high value smart phones. The FCC and wireless carriers have agreed to work together to create a database of stolen phones. This means that if a phone is stolen, it would not be able to be activated anywhere in the US. Similar agreements are pending to address the issue between countries. My question here is what took so long?

http://www.upi.com/Science_News/2012/04/04/High-tech-wallpaper-resists-earthquakes/UPI-11931333589780/

http://www.broadcom.com/press/release.php?id=s658603

http://www.msnbc.msn.com/id/47007056#.T4cWNtWk98E

Apr 11

Employers and Social Media

There have been many stories in the news lately about employers and prospective employers asking for Facebook credentials or access to other social media. There have already been stories of people passed up for a job or losing a job based on content on social media sites. Senators Schumer (D-NY) and Blumenthal (D-CT) have asked the US Department of Justice to determine if the practice violates any existing laws. Presumably if the practice is found to be legal under existing law, they may introduce new legislation to ban the practice. Prospective employers that have started to do this are exposing their company to liability since they would become privy to protected information. For example an employer is not allowed to ask your age on a job application. This information is however likely in you Facebook profile.

Representative Perlmutter (D-CO) tried to attach an amendment to an unrelated FCC bill that would ban the practice. The amendment failed but it appears it was due more to the original FCC bill and not the language in the Facebook amendment.

A similar measure has passed the Maryland legislature and awaits the signature of Governor O’Mailey. In Pennsylvania, Representatives White (D-46) and DePasquale (D-95) are seeking co-sponsors for legislation that would ban the practice. The proposed PA bill is called the Social Medial Privacy Protection Act. The bill would not apply to information posted as public or to public sites such as Twitter.

Apr 10

The Banana Problem

Everyone has seen and most of us have used self-checkout registers at various stores. These were seen by store owners as a way to decrease operating costs and reduce lines at the check-out. Why would some supermarket chains decide to eliminate these customer operated check-outs? It turns out that the technology is not quite up to the task of human idiosyncrasies.

Let’s consider some of the issues. Most of these systems are separate components cobbled together to create the self-checkout. The main interface is a video touch screen. Additional components include a product UPC scanner and scale, a credit card terminal, a receipt printer and usually a coin/currency counter for cash payments. The separate components are not ergonomically placed and often leave the customer to figure out where to go to complete the next step in the process. This makes even short lines frustrating for the next customers in line and/or requires employee intervention. The systems are designed for the customer to empty their cart and place all items in the bagging area before refilling their cart for the trip to their car. This helps ensure that all items are scanned. The system checks the weight of the bag to be sure it increases by the weight of the scanned item. If the bag does not increase by the weight of the scanned item the system assumes, often correctly, that the item was returned to the basket. When this happens the basket is never empty and the store has a difficult time ensuring all items are properly scanned. This system works well for grocery stores where most items are small, light and need to be bagged. This does not work so well in a home improvement store. Consider checking out a can of paint. Once scanned the customer would likely not want a bag. Without the need for a bag and with the weight of the heavy can of paint the customer would naturally return the can back to the cart, skipping the bagging operation. This stops the process since the scale hidden in the bagging area did not sense the paint can. The customer is perplexed and now requires assistance.

These issues may be solved with future systems that are better designed for ergonomics and with human behavior better accounted for in the operational design. Another problem occurs most often with items that do not have a UPC code. This is common with produce items in grocery stores. The customer must tell the computer the type of item that is being weighed. In the mind of the customer, they are buying an apple, but the store has fifteen varieties of apples each at a different price. Insert cog in the proverbial wheel. Then there is the banana problem. This is when a dishonest user tells the computer they are weighing inexpensive items when in fact they are weighing an expensive item. An expensive item such as steak is placed on the scale. It has the UPC removed, covered or oriented in such a way the scanner does not see it. When the computer asks the user to identify the item, the user chooses an inexpensive item, bananas for example.

As with the earlier issues this too may be addressed with future iterations. Manufacturers of this type of equipment are working on using video cameras in place of laser scanners. The hope is to replace the UPC codes with pattern recognition software. The computer would recognize the image of a banana from the camera without the need for a UPC. This is not much different than facial recognition technology I have previously written about (see Jun 9, Crime Fighting Video and Mar 13, Technology to Increase Sales). We will probably see few additional self-checkouts and perhaps even the removal of some between now and the introduction of the next generation of these systems. If you like self-checkouts, be patient. If you don’t like them, perhaps you will like the 2.0 version soon to come.

Apr 8

Fitness Technology

There are many devices, apps and software tools available to help and encourage you to live a healthy, active lifestyle Fitocracy is a new website that recently started to make tracking activity fun and competitive. The site has been in beta testing for a few months and just over a week ago it was updated and opened to everyone. I started using the site in January and have found it to be a good motivating tool. You earn points for various physical activities. The activities range from skipping the elevator and using the stairs to running, weight lifting and team sports like basketball. Logging each activity earns you points. Once you add a certain number of points you advance to the next level. Each time you advance it gets a little harder to advance to the next level. Since you are also getting in better physical condition the additional points accumulate easier.

The social aspect of the site is the helpful motivator. You are able to join groups of people with similar interests or abilities. There are groups for weight loss, occupation, favorite activity, geography, age group and so on. For example I am part of groups for walking, bicycling, college professors, math teachers, people from Pennsylvania, and people interested in engineering. In addition to earning points you also earn achievements and complete quests. These are motivational tools that encourage reaching goals or trying new activities. Other people can give you props which are virtual pats on your back. These are typically given if you log a good workout, earn an achievement or complete a quest. Of course you are also able to prop others. You are able to compare your progress with others in your group. If you are competitive, the group’s information may be displayed as a leader-board.

One of my favorite activities is riding a bicycle. I am comfortable riding for miles on level terrain. I especially like riding atop the levee along the river. The pave path is level except for a few road crossings that dip under a bridge and the path extends for miles. The problem is to get there from my house I must ride along the Sans Souci Parkway. The traffic is worse than the hill. I never thought much about the hill until I ran across the veloroute website. This site allows you to plot your route on a map, and then generate an elevation profile. Below is the one I created for the Sans Souci.

As I ride or walk I often use an app called sports tracker. This uses GPS to track your location and time. I then have accurate time and distance to enter into fitocracy. It is satisfying to see the distances and speed increase as I get into better shape. This weekend my son and I hiked Ricketts Glen. We started at the bottom, hiked up one side, across the top then down the other side. This is a rather challenging 7 mile hike but the view of 21 waterfalls along the way is worth it. One of the waterfalls is almost 100 feet high. After the hike I was toying with the sports tracker app and found a chart of elevation. This app provides an elevation profile along the route that you travel much like veloroute. The Ricketts Glen hike has approximately 1000 foot elevation change. No wonder I was tired at the end.

These are just a small sampling of free tools that can assist you to keep active and healthy. Of course there are many paid tools and devices. A good workout is hard but it can also be fun.

www.fitocracy.com

http://veloroutes.org/bikemaps/#

http://www.sports-tracker.com

Apr 4

Flood Prevention for Your House

First I am not referring to new technology to keep your house dry if a nearby river floods. I am referring to a flood from a busted water pipe. One of the common weak spots in most homes’ plumbing systems is the hose connections connecting the washing machine. The newer style hose that is wrapped in steel braid is better than the plain rubber ones but still a concern. One of the reasons is something called water hammer. This occurs when the washing machine shuts off the flow of water once it is filled. While filling, the water is moving rapidly through your pipes. The valve very quickly shuts off the flow when the washer is filled. The water in the pipes has significant momentum but no longer has a place to go. This place significant stress on the rubber hoses connecting the washer. The hoses also deteriorate with age and when subjected to these stresses they may fail resulting in a flood in your laundry area.

There are devices that may be installed on water pipes to absorb the energy from water hammer. I usually skip the fancy device and just install a vertical stub of pipe about 8 or 10 inches long that is capped on the end. The air in the pipe when first installed remains in the pipe after the water is turned on. Since the pipe is vertical and capped at the end there is nowhere for the air to go. Since the air is compressible, these short stubs of pipe absorb the energy from the momentum of the water. If placed near the washer connection it is a simple method to address water hammer.

Even without water hammer hoses still fail. The company Watts may be known best for the single handle valve used to shut off the water to a washer when it is not being used. The company also makes some of the fancy water hammer prevention devices. They have recently introduced a new type of washing machine hose. The hose has a special valve built into the hose. The device senses the flow of water. Under normal conditions, such as filling the washer, the valve stays open. The sensor checks for flow in excess of normal as would happen with a busted hose. If the valve senses this excessive flow the valve closes shutting off the flow of water. This action is accomplished without any electrical power or batteries.

These special devices are also available for commodes, faucet connections, ice maker connections, and dishwasher connections. This is a great idea that could save significant repair bills. I hope insurance companies recognize the reduced risk and begin to offer discounts for homes that have these installed. For more on these devices and how they work, see the promotional video from the company below. The description of how the device works is at about 4:15 in.

The company also makes a nifty toilet fill valve. The fill valve senses a leaky flapper and stops the tank from continuously refilling. It seems the Watts Company is finding ways to prevent problems you probably don’t think about until after it happens and it is too late.

Apr 2

Free Speech, But Not in Arizona

The Arizona legislator has passed and sent to the Governor HB 2541. The bill is intended to address online bulling, harassment and stalking. It is being widely criticized for its language. Many analysts see it as overly broad and stifling free speech. The issue is that it targets all Internet communication not just one to one communication or social sites such as Facebook. Websites, blogs and even mainstream media could be impacted by this bill. Read the bill at the link below to form your own opinion.

http://www.keytlaw.com/blog/2012/04/arizona-hb-2549/

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