# Marian Stofka

's profile
Dr.

Marian Stofka is with the Slovak University of Technology, Faculty of Electrical Engineering and Information Technology in Bratislava, Slovak Republic.

## Marian Stofka

's contributions
• 05.06.2014
• Can you analyze this circuit?
• Martin, if I were a teacher in the mentioned class, I had no problem to apologize to pupils and correct the drawing as you describe. Another possibility is to replace "10 A" by "20 A"; thus "12 A" notation can remain at R1 = 2 Ohm and Ix = 8 A. A teacher, who is not apt to apologize, could claim, that parallel with a lead from positive pole of battery to upper terminal of R1 there as an another identical lead, which is invisible, transparent (SnO2 or ITO type) or hidden; yet it carries another 10 A current; so the total supply current is 20 A.
• 03.06.2014
• Ohms per square
• "even if the cross section isn't really square," - it should be stressed for young readers, that cross-section is meant here as slicing the resistor, or more precisely its resistive layer, by a plane planparallel to base of the resistor. The real SMD resistors resemble highly the above "perspective view" with the exceptions, that cyan "wires" are omitted and "Depth" within the above formula is the thickness of a resistive layer deposited atop the nonconductive body, usually alumina, of the resistor.
• 03.05.2014
• A blimp of LEDs
• Weigh of the LEDs themselves can be estimated as 235,200x1gram=235.2 kg. Even more interesting is powering of these LEDs. If all LEDs were simultaneously operating @0.1A each (some 15% of LEDs are turned on at above picture), the installed power requirement could be 3Vx23,520A= roughly 70 kW. At left bottom corner of the picture some dark line can be discerned; is it a power cable?
• 03.04.2014
• 200 lm/W efficiency barrier smashed
• I was eager to look at data of the first 200 lm/W LED commercially available. Inside the datasheet a maximum typical efficacy of 131 lm/W can be found for "Lime" LXZ1-PX01 type @ 500 mA. At 350 mA the efficacy can be expected mildly higher, as the efficacy-vs-current is a "little bit" concave curve; but scarcely it reaches 200 W/lm. A possible conclusion: April 1 is approaching fast...
• 02.20.2014
• Is Technology More Advanced than it Appears?
• "What I get from real covert sources I do not talk about on the Internet" Dennis, I am far from scaring you, but now you seem to be really threatened. The only alleviation of your situation could be, if the "sources" were associated/identified with those services, mentioned earlier.
• 02.20.2014
• Is Technology More Advanced than it Appears?
• Dennis, I start here, within this little linguistic corner. I am ready to discuss also rich amount of other topics, related to your article. But,... right after I posted my recent postings to it - my direct link to EDN become and remained inactive.... Is it a warning? BTW, aren't you afraid of attracting attention of secret services, when publishing articles as above? Now, back to little linguistic corner: German Fichte means "spruce", and not "pine". Pine needles of a spruce are shorter and of more vivid green color than those of a pine. Further, I am using this place in an attempt to put into order terminology of UFO as for term of "flying saucer", mentioned above. It should be renamed as "flying saucer-twin". You surely agree, that this kind of UFO looks like a stack of two identical saucers, where the upper one is up-side-down residing on the bottom one.
• 02.20.2014
• Is Technology More Advanced than it Appears?
• I cannot resist a lure to translate into English surname of the author of the above article (maybe he won't get angry with me): Feucht in German language means "wet-related"; Feuchtigkeit = wetness.
• 02.20.2014
• Is Technology More Advanced than it Appears?
• When you find a specific term within the above article, like "mercury antimonide oxide", people with some basic background in inorganic chemistry can make their own mental analysis of the value of offered data. As a detonator, it scarcely is more efficient than carbides of heavy metals; among them also mercury. Such detonators are used in conventional ammunition, used for guns for many decades. The idea that Hg2Sb2O7 could activate fusion within H-bomb is as crazy; as you would say, it could be activated by a classical match. BTW, a classical match contains antimony sulfide, Sb2S3.... ...hm,hm, ... what about yet using a classical match for this purpose - it would be quite economical!
• 02.05.2014
• Today single-molecule LED – Tomorrow molecular-scale computing
• "Today single-molecule LED...": perhaps a more truthful heading could be "Today single-macromolecule LED..." I dare to return to thiophene itself. For those readers, who had not a pleasure to pass through organic chemistry; or passed through, but forgot about thiophene: Thiophene is a heterocyclic organic compound with four atoms of carbon (grey balls in Fig.1 above) and one atom of sulfur (yellow ball in Fig.1) ordered with their bounds as a ring. Two of these bounds between neighboring carbon atoms are unsaturated, or double. Each of the four carbon atoms has a bound with an atom of hydrogen (white ball in Fig.1). At polymerization of thiophene, two hydrogen radicals close to sulfur atom are released and the two open bonds are coupled to two other such "depleted" molecules of thiophene; etc. Thus a string of molecules originates.