Express Oil Change on Roswell Road Possible Scam

One of the joys of having an old car is those times when you leave work, turn the key and realize that it’s going to be a long evening as your car refuses to start. Such was the case on the evening of the 9th of January when I was headed home from a long day at the lab. After two and half hours, AAA managed to get my ’95 Integra up to an Express Oil that I’ve been a loyal customer of for over a year. The next day I walked to Express Oil to have them take a look. Unfortunately, the diagnostic results showed that the car had no compression in the 3rd and 4th cylinders. This is a very bad sign, and I knew what I had to do. I talked to the guys at the shop and asked them if anyone wanted to buy it. The car was still in decent shape (besides the motor), and the parts were probably worth somewhere close to $2k. One of the guys immediately said he’d take it for $400, and I said I would take the offer. Then, I made arrangements to have my brother give me a ride to a dealership because there were some pretty good deals on leases going on.

Just before I left, the guy that was going to buy it informed me that he didn’t have my money right then, but he would on Friday (4 days away.) I told him I’d be out of town till Monday and asked what I should do with the car till then. He said that they would keep it there and look after it–no problem. I was concerned about any cost of storage that might be incurred, but he assured me there would be no cost since he was buying the car. I didn’t think much of it and left with my brother to go look at leases.

Monday rolled around, and I called the shop to speak to the guy that wanted to buy my car. He told me over the phone that a big bill came up that he had to pay or he would have been thrown in jail. At this point, I was skeptical. He said that he would still be able to buy it in two weeks after getting paid again. Then, he asked me if he could go ahead and put a new motor in it to have it ready to go when he pays me. Red flags started going off at this point, and I told him I’d have to think about it and hung up. I determined that it was probably wise to call up a salvage company, so I did. I had them meet me at the shop.

At the shop, the guy who wanted to buy the car started giving me a hard time because he felt like I was selling the car out from under him–I guess. I told him our deal was that he was going to buy it Monday, and he went against that deal. He tried to make some argument about how letting him buy the car was more cost effective since I wouldn’t be charged for storage and other fees. I said I wasn’t paying any storage fee because I never would have left the car there if he wasn’t going to buy it on the stated date. I would have just called the salvage company from day 1. That was my big mistake. Note: just call the damn salvage company.

He told me that I needed to come to the register and settle the payment. I noticed that the storage fee of $45 was still on the $130 invoice, so I demanded that he take it off. He refused. Meanwhile, the salvage company tow truck driver was getting pissed because he wanted to beat traffic. I told the autoshop guys to open the garage and let the car go, and I would work the payment details out with them. They refused multiple times, so I realized that the only way to get my car back from them was to let them charge my credit card. Since then, I’ve disputed the storage fee part of the charge with my credit card company.

Now, I’m going to offer up a theory I have as to what was going on here. I’m not stating it as fact–just a possibility. I think what they were trying to do was run up the cost of service–for example, two additional weeks of storage and a new motor. Then, they were going to low-ball me on the offer for the car and say that if I didn’t accept it that I would be charged for 17 days of storage and a new motor which could have been well over $1000. I certainly hope that wasn’t the case, but I believe I may have headed them off at the pass. That could be why they were so stand-offish. Things may have been much worse if I hadn’t acted quickly.

I’ve written this story here in hopes that other people avoid scams like this. I hope it was helpful and entertaining to read.

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Physics…What are you gonna do with that?

First, I’ll admit that in the past I’ve gone from being puzzled by this question to annoyed to down-right pissed off. It’s uncanny how often it comes up when I meet someone new. However, lately, I’ve learned to take it in stride. I’ve figured out that people are either genuinely curious what a physics student might do after they graduate, or they are pretty much clueless about life in general. It’s actually a great advantage for me to get this question from someone early on . If I figure out which of the two cases they fall into, I can quickly decide whether to continue the conversation or go do something better, like eat a burrito.

Let me explain what’s wrong with this question, but, first, let me point out that if it’s asked, by mistake, by someone who’s genuinely curious, I’m happy to let it slide. “What are you gonna do with that?” First of all, the phrasing of the question is messy, inconsiderate and displays a general ignorance about higher education. It assumes that everyone is in school to graduate and get a job–in that order only. What if I’m in school because I’m genuinely fascinated by physics? What if I don’t care to work for some middle-manager who looks at me and only sees a conveyor belt? Is there any room for those possibilities in the phrasing of that question? The question is a setup. It’s deliberately, though sometimes by mistake, cornering me and saying, “So, tell me what desk you’re gonna be jockeying when you graduate.” After all, we’ve all got to be good little string puppets because there’s no room for independent thought in our society, right?…….wrong!

Some people ask the question in a way that’s just downright snobbish. These people suck. They are actually saying, “Physics? Hahaha why would you study that? Only bankers and doctors make real money.” After all, life is all about money. When our delicate society crumbles and I get thrown in a political prison or if I make a few risky investments that go awry, my life will be over because all my precious green slips of paper will be gone. I should just end it all, right?…….wrong!

Finally, can’t we just talk about something else? Is it so hard to make conversation? Ask me about physics itself. I just might explain things in a nice way that doesn’t make your face do that thing. How about I ask you about how your Aunt Willie May makes her raccoon stew? I hear it’s mighty tasty. Let’s laugh, carry on and be friends, but if you ask me that damn question, I’ll hit you square in the face with a burrito…..haha, just kidding…..but seriously.

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Effect of Reference Pulse Width on XFROG

In preparation for the upcoming Frontiers in Optics conference, I’ve been experimenting with the cross-correlation frequency-resolved optical gating (XFROG) algorithm. We’d like to prove that it can be used to measure extremely complex laser pulses with time-bandwidth products of ~1000. Our goal is to use XFROG to measure supercontinua. Supercontinua are the result of a laser pulse that has undergone a dizzying array of both linear and nonlinear processes and, ultimately, forms a very broadband source of light. We believe that using XFROG to measure supercontinua is the first step towards measure it with double-blind XFROG for which two pulses are simultaneously measured. This would allow for the measurement of the reference pulse and supercontinua simultaneously with a fairly simple device.

Currently, I am running some tests on how the reference pulse width effects the performance of the retrieval algorithm. I’ve generated simulated pulses with time-bandwidth products of ~1000. Using these pulses along with transform-limited Gaussian references pulses of varying widths, I’ve generated FROG traces to be run through the algorithm. I’ve placed some examples of how the reference pulse width effects the polarization gating XFROG trace given by the equation below.

I(\omega,\tau) = |\int_{-\infty}^{+\infty} E_{unk}(t) |E_{ref}(t-\tau)|^2 e^{-i\omega t} dt|^2

1/10th standard deviation of  unknown I(t)

1/5th Std. Dev. I(t)

1/2 Std. Dev. I(t)

These FROG traces show intensity vs. angular frequency (vertical axis) and delay. It is clear that increasing the reference pulse width in time with respected to the unknown pulse washes out the temporal features as expected. However, the reverse will be the case for transform-limited references pulses that are broad in frequency compared to the unknown pulse. It is important to optimize the reference pulse for the best resolution is both domains.

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The Fall of American Manufacturing

What happens to a service-based economy when the countries it depends on for tangible goods decide to stop trading? It’s a troubling scenario, but it’s not far-fetched. Take a look at Sinopec: http://www.reuters.com/article/2011/03/08/china-npc-sinopec-idUSBJI00260720110308.

Source: http://www.bea.gov/industry/gdpbyind_data.htm

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How to use the FoRCE computing cluster

I’m trying to recount some of this from memory, so bare with me. The FoRCE (http://pace.gatech.edu/force-cluster) computing cluster is part of the PACE program at Georgia Tech. It is a shared resource that is available to any researcher at GT dependent on the submission and acceptance of a small proposal. Participants can add dedicated nodes to FoRCE for a fee.

  1. Submit the proposal form to force-allocations@lists.gatech.edu.
  2. Download Cygwin and Putty
    1. When installing Cygwin, it will ask  you what packages you would like to to install. Make sure that the net package, which includes ssh, and the xorg-server package are selected. The xorg-server package allows you to use GUIs (i.e. I type matlab into the command line of the head node and a matlab GUI opens up on my desktop.) If you’re still confused, read more about it at Cygwin-X.
  3. Go to Cygwin-X in your programs menu and start the XWin Server
  4. Open Putty and apply settings as shown
    1. use ssh and enter the address: <username>@force.pace.gatech.edu
    2. Enable X11 forwarding
    3. You can save this session to make things easy when you start Putty up in the future
    4. Click open and putty will ask about an RSA fingerprint. Press enter.
    5. Enter your gt password
  5. Now you are logged into the head node of the FoRCE cluster. Type “xeyes &” and you should see:
  6. If you saw the eyes, everything should be working properly. Try typing “matlab”. The matlab gui should open.

Now get to work solving the world’s problems.

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Run an ssh tunnel in the background

Usually, creating an ssh tunnel initiates a prompt on the remote ssh server, but it’s easy to run it as a background process:

ssh -f -N -L localip:localport:destinationip:destinationport username@ssh_serverip

-f forks the process
-N no command to be run on server
-L binds the port for forwarding

Now, whenever localip:localport is accessed on the machine this command was typed on, it forwards traffic to destinationip:destinationport. I had to do this to allow my mysql server on my university computer to communicate with our cluster.

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Django dynamic forms on the fly

Django is a really nice web framework for Python, and it definitely speeds up the development of web apps. In particular, Django makes it ridiculously easy to create web forms. It’s as simple as creating a new class with a few attributes:

class ContactForm(forms.Form):
    subject = forms.CharField(max_length=100)
    message = forms.CharField()
    sender = forms.EmailField()
    cc_myself = forms.BooleanField(required=False)

Any instance of ContactForm will have the methods the template engine needs to create nice looking forms automagically. In addition, it will have convenient methods for validation and cleaning data.

Django’s forms library is certainly convenient. In fact, it’s almost too convenient. There may be times when the paradigm seems a bit restrictive, and the workarounds seem to defeat the purpose of using Django’s forms library as a matter of convenience. For example, I found myself wanting a form with a variable number of fields depending on some previous input. This, in essence, is a dynamic form. Fortunately, someone had already tackled this problem as is often the case for problems I run across with Django. This elegant solution uses the type method in python to create a class that inherits forms.BaseForm and is assigned attributes via a dictionary argument. Here’s how I applied it to my madlib generator:

def make_edit_form(lib):
    fields = { 'phrase': forms.CharField(widget=forms.Textarea),}
    numBlanks = lib['numBlanks']
    for k in range(1,numBlanks+1):
        fields['blank'+str(k)] = forms.CharField(required=False)
    return type('EditLibForm',(forms.BaseForm,),{ 'base_fields': fields })

This dynamic form creates a field for each blank that exists in my madlib phrase. The output of this function is a class which thanks to the wonder of Python can be aliased and instanced:

EditLibForm = make_edit_form(current_madlib)
form = EditLibForm(request.POST)

It’s easy as pie, and I like pie. In particular, I like pecan and pumpkin pie which I will gladly accept as a donation towards this blog.

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Ubuntu 10.04 Lucid LAMP and beyond

Linode has, probably, the most complete guide to setting up a LAMP stack in Ubuntu that I have seen. They even go a step further by showing the reader how to manage and configure virtual hosts on Apache2. I’m posting it here mainly so I don’t forget about it because I find myself repeatedly referring back to it.

http://library.linode.com/lamp-guides/ubuntu-10.04-lucid/

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Check your WAN IP from the command line in Ubuntu

Create a simple script:

mkdir ~/bin
cd ~/bin
nano whatismyip.sh

Now, copy and paste these commands into the script:

#!/bin/bash

wget www.whatismyip.com/automation/n09230945.asp -O - -q
echo

exit 0

Make the script executable:

chmod u+x ~/bin/whatismyip.sh

Type ~/bin/whatismyip.sh into the terminal.

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Ridiculously Awesome and Amazing Guide to Household Light Bulbs: Incandescent, Compact Fluorescent (CFL) and LED

Choosing the right light bulbs for a home or office can lead to millions of dollars in savings! OK, maybe not millions, but choosing the right bulbs means some extra Benjamins in our pockets, improved family morale, fewer mercury-exposed children and a nicer looking home. In this article, I will consider factors like cost, spectral emission, directivity, etc. to help the reader make an educated buying decision. I will assume that all bulbs have the same brightness (measured number of lumens.) This is not a bad assumption if quality bulbs are purchased. Continue reading

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