Optimal Error-Detecting Codes for General Asymmetric Channels via Sperner Theory

Several communication models that are of relevance in practice are asymmetric in the way they act on the transmitted "objects". Examples include channels in which the amplitudes of the transmitted pulses can only be decreased, channels in which the symbols can only be deleted, channels in which non-zero symbols can only be shifted to the right (e.g., timing channels), subspace channels in which the dimension of the transmitted vector space can only be reduced, unordered storage channels in which the cardinality of the stored (multi)set can only be reduced, etc. We introduce a formal definition of an asymmetric channel as a channel whose action induces a partial order on the set of all possible inputs, and show that this definition captures all the above examples. Such a general approach allows one to treat all these different models in a unified way, and to obtain a characterization of optimal error-detecting codes for many interesting asymmetric channels by using Sperner theory.Comment: To be presented at the IEEE Information Theory Workshop (ITW), Mumbai, India, Nov. 202

Osvrt na "Jednu metodu izravnanja slobodne triangulacione mreže"

Kroz analizu i primjedbe u članku se osporavaju tvrdnje prof. dr. S. Pašalića objavljene u radu: "Jedna metoda izravnanja slobodne triangulacione mreže" (GL 1983, 4–6)

Monetarni transmisioni mehanizam

Jedno od ključnih pitanja za procjenu monetarnog sistema i monetarne politike u nekoj zemlji predstavlja analiza monetarnog transmisionog mehanizma – veza i kanala putem kojih odluke o monetarnoj politici utiču na likvidnost i prinose na finansijskim trištima, što u konačnom utiče na odluke o potrošnji i investicijama domaćinstava i preduzeća. Transmisioni kanali preko kojih funkcioniše monetarna politika su najčešće kompleksni i međusobno isprepleteni, pri čemu se efekti mjera monetarne politike na ključne makroekonomske varijable, kao što su inflacija i autput, javljaju uz duge i varijabilne vremenske pomake. Njihova identifikacija je značajna zbog toga što oni determinišu najefikasniji set instrumenata monetarne politike, tajming promjena politike, a samim time i osnovna ograničenja sa kojima se centralna banka suočava pri donošenju odluka o monetarnoj politici. U literaturi je identifikovano nekoliko kanala: kanal kamatnih stopa, kanal (ostalih) cijena aktiva, kanal deviznog kursa, kreditni kanal, kanal očekivanja i kanal preuzimanja rizika, pri čemu se nerijetko izdvaja i kanal troškova kao zaseban kanal monetarne transmisije. Jačina pojedinačnih kanala mijenja se tokom vremena, tako da se proces monetarne transmisije mora kontinuirano izučavati i iznova procjenjivati. Značaj svakog od tih kanala zavisi od niza faktora, prije svega od ekonomske, zakonske i finansijske strukture posmatrane zemlje. Monetarni transmisioni mehanizam u zemljama u razvoju i tranziciji može biti u značajnoj mjeri različit od onoga koji se obično opisuje u ekonomijama sa sofisticiranijim finansijskim sistemima. Specifično makroekonomsko i finansijsko okruženje tih zemalja ima značajne implikacije na različite konvencionalne kanale monetarne transmisije. Niz faktora, kao što su slabi institucionalni okviri, umanjena uloga tržišta hartija od vrijednosti, nesavršena konkurencija u bankarskom sektoru, rezultirajući visoki troškovi bankarskih kredita privatnim preduzećima i druge slabosti predstavljaju smetnju funkcionisanju pojedinih tradicionalnih kanala. Dodatno, postoji uvjerenje da monetarna transmisija može biti slaba i nepouzdana u kontekstu tih zemalja, pri čemu su postojeći empirijski dokazi konzistentni sa ovim stanovištem.One of the key issues in assessing monetary system and monetary policy in an economy is the analysis of the monetary transmission mechanism – links and channels through which monetary policy decisions influence liquidity and returns in financial markets, and ultimately spending and investment decisions of households and enterprises. The transmission channels through which monetary policy operates are often complex and intertwined, while the effects of monetary policy measures on key macroeconomic variables, such as inflation and output, appear with long and variable time lags. Their identification is significant because they determine the most efficient set of monetary policy instruments, the timing of monetary policy changes, and thus the main limitations a central bank is facing in making monetary policy decisions. Several channels have been identified in the literature: interest rate channel, (other) assets prices channel, exchange rate channel, credit channel, expectations channel and risk taking channel, while the cost channel is often singled out as a separate channel of the monetary transmission. The strength of individual channels changes through time so the process of the monetary transmission has to be continuously analyzed and repeatedly assessed. The significance of those channels depends on several factors, primarily on economic, legal and financial structure of the observed economy. Monetary transmission mechanism in developing and transitional economies may to a significant degree be different from that often depicted in economies with more sophisticated financial systems. The specific macroeconomic and financial environment of those economies has significant implications on different conventional channels of monetary transmission. Various factors, such as weak institutional frameworks, diminished role of securities market, imperfect competition in the banking sector, resulting high costs of bank credits to private enterprises and other weaknesses impede the functioning of individual traditional channels. Additionally, there is belief that the monetary transmission can be weak and unreliable in the context of those countries, while the existing empirical evidence is consistent with this view. Improving capabilities to quantify specific links in the monetary transmission mechanism that xiv operates in individual developing and transitional countries requires opening of the „black box“ of monetary transmission in those countries

Obeležavanje osovine tunela u krivini analitičko-grafičkom metodom

Obeležavanje osovine tunela u krivini analitičko-grafičkom metodom

THE IMPACT OF FINITE DIMENSIONS ON THE SENSING PERFORMANCE OF TERAHERTZ METAMATERIAL ABSORBER

This paper investigates the impact of finite number of unit cells on the sensing performance of chosen THz metamaterial absorber. Sensor models with different number of unit cells varying from 16 to infinite have been created using WIPL-D software. The results of comparison show that as the sensor’s size increases, its absorption response becomes more similar to the one of an infinite sensor structure. Metamaterial absorber with 50 unit cells expresses the similar behavior in terms of the corresponding frequency and amplitude shifts as the infinite absorber when the H9N2 virus sample of variable thickness is uniformly deposited on the top of the sensors’ surface. The uneven distribution of sample affects the sensor’s absorption response which has been proven on the example of sensor with 50 unit cells