Computer Science & Engineering Stuff

My computers

A few year ago I made a list about all my computers. I thought, it would be nice to make a new one:

Lenovo Thinkpad X1 Carbon – Main computer (work and personal)

CPU: Intel Core i7-3667U, 2 GHz
Graphic Card: Intel HD graphics 4000
Memory (RAM): 8 GB
Ports: 1x USB 3.0, 1x powered USB 2.0, mini-display port, microphone/earphone port, 4-in-1- card reader
Onboard storage: 180 GB SSD
Wireless: Bluetooth, W-LAN, GSM/UMTS/HSDPA/HSUPA
Display: 14″
Weight: 1.36 kg
OS: Win 7
Mainly used for: backup of Iphone & Itunes library (Itunes), work emails (MS Exchange), personal/work calender (MS Exchange), writing (MS Office, TeXworks), receiving SVN files, simulations (Matlab), online research (Firefox), other personal & work stuff

Lenovo Thinkpad X220 – Work laptop (for simulations)

CPU: Intel Core i7-2620M
Graphic Card: Intel HD graphics
Memory (RAM): 8 GB
Ports: 3 x USB 2.0 (one powered), 4-in-1- card reader, VGA, display port
Onboard storage: 320 GB HDD
Wireless/Communication: Ethernet LAN, W-LAN, Bluetooth, UMTS
Display: 12.5″
Weight: 1.67 kg
OS: Ubuntu
Mainly used for: receiving SVN files, online research (Firefox) and simulations for work

Streaming (online and DVB-T) / Data / E-Mail PC

CPU: Intel Pentium D, 3,2 GHz x 2 (I really need to upgrade the CPU and main board: The CPU fan is just too noisy)
Graphic Card: Nvidia GeForce GT630
Memory (RAM): 2 GB
Onboard storage: 240 GB
OS: Ubuntu
Mainly used for: DVB-T (Kaffeine), online streaming (Firefox), E-Mails (Thunderbird), data storage / backup

Banking PC

CPU: AMD Athlon 64 3500+, 2,21 GHz
Graphic Card: Radeon X1900XTX
Memory (RAM): 1 GB
Onboard storage: 240 GB (SATA)
OS: Ubuntu
Mainly used for: Online banking (Firefox)

Raspberry Pi – Model B – Media Center

CPU: ARM1176JZF-S (700 MHz)
Graphic Card: Broadcom VideoCore IV GPU
Memory (SDRAM): 512 MB
Ports: 2 USB 2.0
Video Output: FBAS, HDMI
Audio Output: 3.5mm jack, HDMI
Onboard storage: SD / MMC / SDIO card slot
Communication: Ethernet LAN
OS: Openelec
Mainly used for: watching DVD films

And of course various HDDs for backup.

I bought a new DVB-T stick (my old one was so old, that it is not even supported by Windows anymore… I think even under XP it was not possible to use). I bought a really cheap one: I don’t watch TV that often and normally the online streams are enough. But sometimes there are no online streams at all or they are not live or the connection gets lost. So a cheap one is really fine. I am really happy that the one I chose (CSL DVB-T Stick with a Realtek-Chip) is functioning also under Ubuntu (and, of course, also under Win 7), since my streaming PC (connected to the TV) runs with Ubuntu. 🙂 Installation was (surprisingly) simple: With my last stick, it even took some effort to make it run under Win, but under Linux? Not possible at all!

I just installed Kaffeine (compared to the Win Software on the Stick-DVD (TotalMedia), it is so much nicer to use) and followed the steps under https://help.ubuntu.com/community/DVB-T_%28USB%29. On the page you can also find an instruction, if you card is not (generally) supported. My Stick was not on the list, so I recommend you to first try the following steps:

Get the required packages:

$ sudo apt-get install git linux-headers-$(uname -r) build-essential patchutils libproc-processtable-perl

Fetch source code:

$ git clone git://linuxtv.org/media_build.git

Change to the directory created before:

$ cd media_build

Compile the code (takes some time):

$ ./build

Install the compiled code:

sudo make install

Restart your system. Start Kaffeine, select an appropriate Source and search for the channels.

Computers – „Repair“ and Update Session

I wanted to structure the computers I have and use a bit better:

I have a Thinkpad X220 from work with Ubuntu for working stuff.
(Of course there is also my desktop pc at work…)

Then I have a Thinkpad X1 Carbon: This is the computer I usually use. I use it for personal stuff, work related stuff, it has Itunes, Exchange (from work) with my work-mails and (most important) my calender (work/personal) and some other programs I use.

I have a Desktop PC with Ubuntu for data storage and email storage (I have one mail account I access directly on my iphone, I can access the others ones from this PC).

I have a Raspberry Pi (Modell B) with Openelec as a media computer: It has a backup of my DVD collection. Openelec is quite nice: It offers a nice menu where you see the movies, some short description and so on and you can control it with the xbmc iphone app directly from the phone. The only thing missing is „standard“ webbrowser:
I have satellit tv in my flat, but don’t want to have a receiver. I also do not watch much the normal tv program (the few things I watch are also available online directly from the television transmitters). At the moment I just watch the stuff on my Thinkpad, but I got the idea that I could simply take my data storage desktop PC, connect it to the TV and use it also for streaming from the television transmitter websites. On the Raspberr Pi streaming is difficult: You get problems with the usually necessary (for streaming) Flash Player and I also read that it is too slow for really using it for streaming. Also my Wii U did not have the necessary version of the Flash Player, so it was also not possible to use it for this kind of application.

Last but not least: My old media-computer: It was used for watching DVDs and other media before I got my Raspberry Pi. I havent’t really used it afterwards. But now I will install Ubuntu on this one an will use it purely for online banking. I havent’t used online banking up to now because of the security risks there… But I mean: The bank will nevertheless store your informations and transfers somewhere, so this point against online banking is out… The next thing: Trojaners could access your online banking account or someone could hack into it: If I use one pc purely for online banking, only type in the adress manually, don’t click any links, the risks are minimized. Of course: Use a strong password and change it often. 🙂

But for using desktop and old-media pc, I had to „repair“ them (okay, if you call fixing the CMOS checksum error a repair 😉 ) and change some components: I exchanged the graphic cards (the desktop/streaming PC needs to be connected to the TV now and I wanted to use the HDMI port of the old media PC’s graphic card), bought a new PCI Wlan Card (put this in the desktop/streaming PC and the old one from there in the old media PC).

Really a fun evening. 🙂 Everything is functioning as it should and I did not get any problem (at least so far, the desktop/streaming PC is finished, but I have to install Ubuntu on the media PC which shouldn’t cause any problems).

/Update: Everything is finished and working as it should. Although… I should really update the mainboard and RAM of the desktop/streaming PC: Streaming is functioning, but a bit slow (or was it just because I tested it with ARD where a WM game is shown and too many people are watching?! I will test tomorrow again…)

Style sheets in TeXworks / MikTeX

For incorporating new .sty style sheet files using TeXworks / MikTeX on windows do the following:

Create a folder (e.g. C:/Local Tex Files/tex/latex/misc) and put the new style sheet file (e.g. „myfile.sty) in there
Go to MikTeX settings and in the tab „Roots“. Click „Add“ and select the folder you created before
To use the new style sheet in your document: Add „\usepackage{myfile}“ to the document preamble

The Manga guide to Electricity

I found a very nice book for a first contact with the topic Electricity. It should be really used in schools, since it teaches basics about electriticy, circuit components, creation of electricity, … by using manga form and a sweet story. I think the authors really succeed in writing the book in an understandable way and they find nice analogons (e.g. explaining voltage/current with water flow). There are also some pages in text-form to tell more details. I really enjoy reading the book, even if nothing really new or suprising is in it for me. There are also more books in the „The manga guide to“ series, e. g. Calculus, Physics, Statistics, Databases, Relativity, Molecular Biology, Biochemistry and Universe. I should really buy the rest of those books too.

Stuff you shouldn’t write in an exam

It is really terrifying how ill-prepared some students are in exams. Okay, I really understand that you do not like every subject you must take during your course of studies, but I think that you should at least try to revise the important stuff. Most of the times this is all it takes to at least pass the exams, even if your grade is not good. But how can you go to an exam when you not even know the basic facts!? A very good example what you shouldn’t write is the following. And yes, this is something a student really wrote in an exam!! (Okay, the student did not paint a flower, but I wanted to anonymous this case. So yes, the picture you see with this entry is not the real painting this student painted.) The student wrote that he does not know how to solve the problem and that he will paint something instead. And so this student painted a flower…

Japanese Multiplication Method

Do you have problems with the multiplication of large numbers? Or do you have kids and want to show them an easy way to multiply two numbers? Then you should probably watch the following video.

I think this method is really useful. With it the only difficult thing left when doing multiplications is the drawing of straight lines. 😉

[via gizmodo.com]

Semiconductors in electronical devices – Thermal Metrics

During the work regarding my PhD I found a nice paper that explains some thermal metrics like the junction temperature $T_J$ the case temperature $T_C$ , the ambient temperature $T_A$ and the corresponding thermal resistances. This is done with an example of a coffee-cup. It’s that nice and memorable that I want to post this explanation here. I took it from an Texas Instrument’s Application Report with the title „Thermal Derating Curves for Logic-Products Packages from May 2009. You can find the whole paper here. You can find also a nice picture of the coffee-cup and the metrics in the paper.

„Consider a closed cup of heated coffee at a certain temperature (see Figure 1). The temperature of the coffee is analogous to the junction temperature ( $T_J$ ) of a semicondutor device. The outer surface of the coffee cup is at some temperature analogous to the temperature of the outside of the semiconductor package, or case temperature, ( $T_C$ ). Finally, the room is at ambient, or free-air, temperature ( $T_A$ ). Clearly, $T_J > T_C > T_A$ .

Heat transfers from the coffee through the cup by conduction. Thus, there is a temperature differential between the coffee and the outer surface. The rate of heat transfer through the cup is determined by the thermal resistance of the walls of the cup. The thermal resistance is a function of the material used to make the cup (e.g., paper, Styrofoam (trademark of Dow Chemical Company), or porcelain), the thickness of the walls of the cup, and the overall geometry of the cup. The higher the thermal resistance, the slower the heat travels through the cup. The thermal resistance between the junction (the coffee) and the case (cup) can be designated $\Theta_{JC}$ .

Moving away from the junction, heat then transfers from the surface of the cup by radiation and convection. There is a thermal resistance associated with this transfer that is expected to be a function of the geometry, smoothness, and color of the surface. This thermal-resistance value is termed $\Theta_{CA}$ .

The overall rate of heat transfer is then a combination of $\Theta_{JC}$ and $\Theta_{CA}$ . There is a temperature drop (much like a voltage drop) from the inner side to the outer side of the cup and another drop from the surface of the cup to the ambient environment. Of course, the objective is to keep coffee warm. But, with semiconductors, the objective is to move heat away from the IC chip as quickly as possible.“

USB-Stick Kette

(Originaleintrag von 29.04.2008, Edit vom 02.02.2009)

Als ich letztens zufällig einen meiner USB-Sticks mit einem dieser „Bändchen“, die häufig bei den Sticks dabei sind, um den Hals hatte kam mir eine gute Idee: Eine USB-Stick Kette. So hat man den USB-Stick immer dabei und er macht sich auch noch gut.

Was benötigt man also für solch eine Kette? Zum einen, natürlich, einen USB-Stick. Hierbei sollte man besonders darauf achten, dass der USB-Stick recht klein und leicht ist. Zudem muss natürlich eine Öse vorhanden sein um den Stick an der Kette festzumachen. Ich habe auf meiner Suche nach einem für mich passenden Stick relativ viele Sticks gefunden, die in Frage kommen würden. Hier verlinke ich nur die 4GB Versionen. Die meisten der Sticks sind aber auch mit weniger oder mehr GB erhältlich. Des weiteren sind viele der Sticks auch in anderen Farben erhältlich.

Kingston Data Traveler Mini Fun: Dieser Stick wäre es fast geworden, da die Form einfach außergewöhnlich ist und sich bestimmt gut am Hals gemacht hätte. Jedoch war die grelle Farbe doch nicht so mein Fall.
Pretec I-Disk Wave: Dieser Stick steht stellvertretend für viele weitere kleine Sticks mit „Dreh-Kappe“. Für diese Variante habe ich mich nicht entschieden, aus Angst, dass sich die Dreh-Kappe während des Tragen dreht.
Transcend TS4GJFV90C JetFlash: Ein sehr stylischer und kleiner Stick, der auf der Vorderseite mit einem Muster bedruckt ist. Leider befindet sich hier aber die Öse, an dem man den Stick fest machen kann, an einer der Ecken, was also zu einer Schieflage beim Tragen führen würde.
takeMS Dribe VStyle: Diese USB-Stick ist definitiv ein richtiger Hingucker: In Dosen-Form und in auffallendem Rot. Diesen Stick gibt es übrigens auch in silber. Lediglich das Anschließen an einen PC könnte durch die Form vielleicht Probleme geben. Dies ist aber nur eine Vermutung von mir.
LG Mini Retractable USB Flash Drive: Der Stick, für den ich mich schließlich entschieden habe. Der dezente Aufdruck ist beim Tragen kaum sichtbar. Zudem sieht das Hochglanz-Schwarz sehr schön aus. Einzig den Slim USB connector finde ich nicht allzu toll. Ich hoffe aber, dass er ebenso stabil ist, wie ein normaler connector.

Wenn man sich nun für einen der zahlreichen USB-Sticks entschieden hat, folgt die Auswahl einer geeigneten Kette. Natürlich kann man hier einfach eine (vorhandene) Silber- oder Goldkette verwenden. Ebenso auch einfach ein schlichtes Lederband. Neben dem Kauf einer bereits fertigen Kette, lohnt sich auch der Gang in ein Bastlerbedarfs Geschäft, welches Bauteile für Schmuck führt. Hier kann man aus den verschiedenen Bauteilen eine Kette selbst zusammenbasteln oder auch einfach ein fertiges Set kaufen, an welches nur noch die Verschlüsse angebracht werden müssen. So bekommt man eine sehr individuelle Kette für wenige Euro.

/edit: Heute habe ich dann auch noch eine ganze Reihe von bereits fertigen USB-Stick Ketten gefunden. Unter anderem ein roter Stick mit Kappe in Herz-Form. In dem Shop gibt es auch noch weitere USB-Stick Ketten bzw. -Anhänger. Über den Shop „DealExtreme“ kann ich zwar leider keine Bewertung geben, da ich dort noch nicht bestellt habe. Positiv ist jedenfalls der weltweit kostenlose Versand.

Curse of Silence (25C3)

Der diesjährige 25C3 neigt sich dem Ende. Ich war diesmal leider nicht dabei. Aber die Videos gibt’s ja immerhin auch online und diese werde ich die Tage mal durchforsten. Einen netten „Hack“ (wenn man’s denn überhaupt als solchen bezeichnen kann) habe ich aber bereits jetzt schon im dysternis-Blog gefunden:

Wer seine Freunde mit Nokia-Handy (nur bestimmter Modelle, alle vom S60 Typ) mal von der „lästigen“ Angelegenheit des SMS-Empfangs entbinden möchte, hat dazu mit einem kleinen Trick Gelegenheit: Diese Nokia-Modelle können SMS vom „e-Mail“-Typ empfangen. Jedoch ist der Buffer für die e-Mail Adresse nur 32-Zeichen lang. Wenn man nun eine mindestens 33 Zeichen lange Mail-Adresse eingibt, folgt als Resultat, dass das Handy keine SMS mehr anzeigt. Egal, wie viele SMS man nach der „Curse of Silence“-SMS noch erhält, oder ob man einen Reboot durchführt. Lediglich ein Factory-Reset hilft…

Die Operanden könnten sowas zwar verhindern, bisher kann dies aber nur T-Mobile (und das auch nur für das Absenden…).

Weitere Informationen gibt’s im Advisory oder dem Demo-Video.

Kategorie: Computer Science & Engineering Stuff