Design of the PMXL-1 Platform

This paper presents the design of the Mexilha˜o-1 Platform (PMXL-1), located at Brazilian Santos Basin, focusing in the concept development and design of the light weight optimized jacket. PXML-1 is a gas and condensate production hub platform with 525 MMscf/d processing capacity and 18350 metric tons (mton) topside design load. Installed in 172m water depth, is the deepest fixed production unit in Brazil. Jacket concept was developed aiming to structural and functional optimization, based on previous company work on Campos Basin. Due to height, top and base dimensions and expected weight, lift option was discarded and a 4-leg launched and self upended jacket was selected. To increase structural efficiency, bracing was provided by fewer but larger diameter and heavier walled members. Launch trusses, with conventional bay spans, form a central core that is used also to support risers, I-tubes and other appurtenances. Face bays are double spanned, X-braced, with central cross nodes stabilized by members connected to the central core. Horizontal levels have no peripheral members and are double X-braced. Top horizontal frame level is located above operational wave crest, reducing environmental loads, and bottom level is elevated about 6m from mudline. Topside modules are directly supported by jacket main legs and two additional dummy legs, eliminating a module support frame. Foundation is provided by eight large diameter vertical skirt piles. Comparison with PNA-2, a conventional 8-leg platform, installed about 20 years ago in Campos Basin, in similar environmental conditions, with analogous functional requirements, shows considerable advantages and savings. In comparison to PNA-2, PMXL-1 jacket weight is reduced by 32% and pile weight is reduced by 65%. Number of structural elements and tubular connections to be fabricated and erected is also drastically reduced.

Functional morphology of the Chelipeds, mouthparts and gastric mill of Ozius truncatus (Milne Edwards) (Xanthidae) and Leptograpsus variegatus (Fabricius) (Grapsidae) (Brachyura)

Field and laboratory observations show that O. truncatus is a predator on gastropod molluscs, using dimorphic crusher-cutter chelipeds to remove the shell. The soft gastropod body is then presented to the maxillipeds. The third maxillipeds and mandibles tear the food, but the fragments reaching the foregut are still relatively large. The gastric mill ossicles of O. truncatus are robust, with few setae. L. variegatus is an opportunistic omnivore using equal cutting-scraping chelipeds in an alternating action, mainly in plucking and scraping algae. The food fragments reaching the maxillipeds are finely shredded by the chelipeds. The small food fragments are ingested directly, being pushed into the mouth by the mandibular palps. The maxillipeds and mouthparts do not triturate the food. The gastric mill ossicles of L. variegatus are finely toothed and setose. Analogous functional relationships between ingestion mechanisms and gastric mill occur in Anomura. The need for further studies on Brachyura is stressed.

Functional limit theorems for stochastic processes based on embedded processes

The techniques used by Doeblin and Chung to obtain ordinary limit laws (central limit laws, weak and strong laws of large numbers, and laws of the iterated logarithm) for Markov chains, are extended to obtain analogous functional limit laws for stochastic processes which have embedded processes satisfying these laws. More generally, it is shown how functional limit laws of a stochastic process are related to those of a process embedded in it. The results herein unify and extend many existing limit laws for Markov, semi-Markov, queueing, regenerative, semi-stationary, and subordinated processes.

Functional limit theorems for stochastic processes based on embedded processes

The techniques used by Doeblin and Chung to obtain ordinary limit laws (central limit laws, weak and strong laws of large numbers, and laws of the iterated logarithm) for Markov chains, are extended to obtain analogous functional limit laws for stochastic processes which have embedded processes satisfying these laws. More generally, it is shown how functional limit laws of a stochastic process are related to those of a process embedded in it. The results herein unify and extend many existing limit laws for Markov, semi-Markov, queueing, regenerative, semi-stationary, and subordinated processes.

Derivatives of 2-Mercaptobenzothiazole and Dimethyldithiocarbamic Acid as Vulcanization Accelerators

1. We have synthesized and investigated as vulcanization accelerators the derivatives of 2-mercaptobenzothiazole (MBT) in which the thiol hydrogen is replaced by the nonpolar methyl radical, as well as compounds in which methyl hydrogen of the methyl derivative is replaced by various functional groups. 2. It has been shown that methyl-2-thiolbenzothiazole is not an accelerator. The replacement in this compound of one of the methyl hydrogens by a polar hydroxyl group substantially enhances the activity (see, however, editors note in the text). The substitution of hydrogen by a carboxyl group does not increase vulcanizing activity. 3. We have determined that replacement of a methyl hydrogen by an amino radical increases sharply the accelerating activity. The structure obtained as a result of this reaction, benzothiazolyl-2-thiolmethyldiethylamine (BTMA), is of great practical interest as an accelerator. 4. The accelerator BTMA in stocks of natural and SKS rubber gives vulcanizates which are substantially superior in their properties to rubbers cured with MBT, and are practically equal to vulcanizates obtained with sulfenamide accelerators—sulfenamide BT and sulfenamide Z (Santocure). 5. The accelerator BTMA is much cheaper than sulfenamide BT since its production requires much less diethylamine. 6. It has been determined that, just as in the case of 2-mercaptobenzothiazole derivatives, for the derivatives of dimethyldithiocarbamic acid containing analogous functional groups the same results are obtained for the change in activity depending upon the chemical structure of the accelerator.