Multi-Scale, Multi-Phase Modelling of a Slurry-Phase Catalytic Ziegler-Natta HDPE Continuous Process

Continuous slurry-phase polymerization, in the presence of a heterogeneous Ziegler–Natta (Z–N) catalyst, is one of the most commonly employed processes in the production of polyolefins, including high-density polyethylene (HDPE), isotactic polypropylene (IPP) as well as their copolymers with higher olefins. Polymerization in a series of reactors is often employed to control comonomer distribution, which is important for resin grades such as pipe applications that require excellent environmental stress crack resistance. The slurry HDPE process technology employs two or more stirred-tank reactors in series and utilizes a Z-N catalyst system composed of a titanium chloride compound and an alkyl aluminum cocatalyst. The process uses hydrogen as a chain-termination agent to control the molecular weight of the product and a comonomer to control the density of the polyethylene grade. The process operates in a continuous mode in a cascade of two or three autoclave-type vessels. Each reactor can operate under a different hydrogen partial pressure, thereby allowing the control of the molecular weight distribution. Typical reaction operating conditions are temperature 70 - 90 °C and a pressure less than 10 bar with a residence time 45 min per reactor. Please click Additional Files below to see the full abstrac

Žanas Batistas Kolberas (J. B. Colbert) – teoretikas ir praktikas

The main purpose of this article is to analyse the theoretical and practical work of Jean Baptiste Colbert – the grandee of French economics and the representative of mercantilism. This article deals with almost all areas of his work: state economy, trade policy, national defence, culture and art. This article mainly focuses on economics. First of all, the article widely analyses the works of J. B. Colbert in the area of tax reform. Colbert focused on the shift in the tax load from the poor onto the pros­perous, not forgetting the simplification of tax ad­ministration. The ideas of Colbert, which remained purely theoretic, are introduced alongside. In addition, Colbert focused on the industrial development of the country. The State promoted the establishment of manufactories, high-skilled labour imports, estimated the quality standards of produc­tion, aimed at the effective administration of supplies. Moreover, an effort was made to restrict imports and expand exports, as well as to establish transatlantic trade companies. At the end of the article, other activities of Col­bert and changes in the situation after he passed away are briefly analysed. This article is topical for today’s realities. Re­cent turmoil both in the global and in the national economy stimulates the search for analogies and methods of how similar situations were handled in the past

Modeling of Free Radical Styrene/Divinylbenzene Copolymerization with the Numerical Fractionation Technique

The modeling approach called “numerical fractionation” has been incorporated into a PREDICI model to simulate crosslinking copolymerization. To take into account inhomogeneities of the considered copolymerization, the kinetic parameters of the model are proposed to be different for each generation of the numerical fractionation. Using this approach the chain-length dependence of termination has been incorporated into the model so that even the method of moments could be applied to study crosslinking copolymerization. The styrene/m-divinylbenzene crosslinking copolymerization at low content of crosslinker has been simulated. The chain-length dependence of termination has been found to accelerate the gel point in monovinyl/divinyl copolymerization and must be taken into account for correct description of the gel points

From Labyrinth to Dungeons: The meanings of Labyrinthine and Underground from Analog to Digital Fantasy Games

Περίληψη: Στόχος της παρούσας ερευνητικής εργασίας είναι η κατανόηση της προέλευσης, της φύσης και της λειτουργίας των χωρικών συστημάτων των παιχνιδιών φαντασίας και η ανάδειξή τους ως ολοκληρωμένες αρχιτεκτονικές κατασκευές. Έχοντας ως αφετηρία την Υπόγεια φύση και την Δαιδαλώδη δομή του αρχετυπικού χωρικού-μοντέλου περιπέτειας 'Dungeon', αναλύονται τα χαρακτηριστικά του 'δαιδαλώδους' και κατ' επέκταση του λαβυρίνθου ως αρχιτεκτονικό σύστημα, τα χαρακτηριστικά του 'υπογείου' και η φαντασιακή τους δυναμική, καθώς και ο τρόπος με τον οποίο οι δύο έννοιες σχετίζονται με την σύνθεση του χωρικού περιβάλλοντος των παιχνιδιών φαντασίας. Τέλος, παρουσιάζονται ορισμένα καίρια παραδείγματα αρχετυπικών ψηφιακών παιχνιδιών φαντασίας, αναγνωρίζοντας την 'Δαιδαλώδη-Υπόγεια' λογική στον πυρήνα της σύνθεσης και της λειτουργίας τους.Presented on

Currency crisis, 2007 – myth or reality?

A currency crisis is best described as a forced currency devaluation. Historically, speculative attacks, psychological effects - like contagion - played a great role in the process. However, it is the macroeconomic and financial instability that usually underlies these forces and causes the countries to devalue or float their national currencies. [...] This article presents an overview of the major financial indicators in the Baltic region, mainly Lithuania. The major goal was to assess, given the history of the currency crisis and reasons thereof, the likelihood of such a scenario in Lithuania and its neighbouring countries - Latvia and Estonia - in 2007. The results show a significant macroeconomic pressure on all the currencies, primarily the Latvian lat. As a matter of fact, the country ran the biggest and growing current account deficit and skyrocketing inflation, which means great reliance on foreign financing and the loss of competitiveness. In view of the fact that Latvia has both economic and non-economic links with Lithuania, its currency devaluation might come as a significant pressure for the Lithuanian litas as well. On the other hand, some factors - like institutional background, political commitments and possible devaluation costs - make such a scenario unlikely, unless a more significant slowdown or "hard landing" strikes the region

Valstiečių paskolų-taupymo draugijos Lietuvoje iki pirmojo pasaulinio karo

The first savings bank in the territory of present-day Lithuania was founded approximately in 1830 in Klaipėda. The first credit union was already functioning in Šilutė in 1865. These towns belonged 10 Germany at that time. Some years later credit unions also appeared in another part of Lithuania, the region that belonged to Russia. For example, the first peasant savings and loan societies were established in the Kaunas district only in 1873. Before the First World War these societies accumulated approximately 4 million roubles of credit resources. These credit resources could only amount to 20–25 percent of all Lithuanian peasants’ savings

Dynamic Monte Carlo Simulation of the l,l -Lactide Ring-Opening Polymerization

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