Abstract

Subsea pipelines are designed to transport mixtures of oil, gas, and their associated impurities from a wellhead that can be in excess of approximately 100 °C, while the external temperature may be approximately 5 °C. Heat can be lost from a subsea pipeline containing a high-temperature fluid to the surrounding environment. It is important that the pipeline be designed to ensure that the heat loss is small enough to maintain sufficient flow from the unwanted deposition of hydrate and wax, which occurs at a critical temperature of about 40 °C. Therefore, it is essential to estimate the heat loss of a subsea pipeline in various circumstances. In previous studies, overall heat transfer coefficient(OHTC) formulas were considered only for a single soil type. Thus, it is difficult to characterize the OHTC of the actual seabed with multiple soil layers. In this paper, an OHTC formula that considers multi-layered soils is proposed for more precise OHTC estimation. Document type: Article

Abstract

Wave-structure interaction is a topic of great interest in naval and offshore engineering. This interest is growing in the last years due to the boost given by the development of the marine renewable energy field. In this context the development of an efficient time-domain coupled waves-structure solver is a main request from the industry.

Up to date the numerical seakeeping simulation has been mostly carried out using the frequency domain. The reason might be that the computational cost of time domain simulations were too high and computational time was too large. Moreover assumptions like linear waves and the harmonic nature of water waves made the frequency domain to be the right choice. However nowadays computing capabilities make possible to carry out numerical simulations in the time domain in a reasonable time, with the advantage of making easier the introduction of non-linearities into the algorithm and therefore coupling with other phenomena.

This presentation shows the work of the authors in developing a time-domain unstructured Finite Element Method (FEM) algorithm for analysis of coupled wave-structure interaction. For this purpose, a new diffraction-radiation solver using the FEM was developed. The solver has been implemented in GPU, using CUDA architecture. The speed-up obtained ranges from 5 to 10 times compare to the implementation in a standard CPU with a conjugate gradient and ILU preconditioner.

The seakeeping analysis tool has been integrated within a coupled waves-structure analysis tool. The coupling algorithm is based on a partitioned iterative algorithm, using an interpolation library able to communicate pressure forces and displacements of the structure at memory level. Furthermore, an innovative wetting and drying scheme able to improve the evaluation of the water action on the structure.

The accuracy of the new seakeeping formulation for analysis of waves and floating structures interaction has been verified in different validation cases and practical applications. 

Abstract

Modern communication networks have to be capable of responding to random fluctuations of requests and errors in different ways. One of them is traffic routing i.e. resource allocation. The designing of such networks (intelligent ones) and their management represent a challenge in mathematical, engineering and economic manner. This chapter describes the scheme of dynamic routing and the derived and presented model which is useful for dimensioning of initial link capacities as well as in the analysis of network stability. Emphasis is on the telephone network for G/G communication in ATM, for which the user’s requirements have been described together with the technical requirements that are necessary to support them. For the design of AGVN the usual methods of determining the telecommunication traffic are used. It should be emphasised, however, that there is a difference in relation to public telephone networks in that the calls in ATM are shorter and the recommended GoS value is lower (0.001). The chapter presents the necessary capacities for GoS value that is used in public networks and for the recommended GoS value for AGVN. The results show substantial savings in the number of channels. Since VCSs can distinguish the type of call and allocate priorities, for the dimensioning of the transmission link capacities a higher GoS value can be used, realizing at the same time a satisfactory Quality of Services for certain calls.

Abstract

Recently, many of the foreign traffic-safety analyses point out the low level of traffic safety in multi-lane roundabouts. This problem is resolved in several ways in different countries however, the solution, whereby the number of conflict points is diminished (e.g. turbo roundabout) has proven to be the most successful. However, the turbo roundabout also has its deficiencies: it has conflict crossing points and larger reconstruction of the existing two-lane roundabout is needed when the turbo roundabout is to be implemented instead of the existing one. In the paper a new type of roundabout has been introduced the roundabout with “depressed” lanes for right turning (“the flower-roundabout”). Financially speaking, the main advantage of the new type of roundabout is that it can be implemented within the dimensions of the already existing “normal” two-lane roundabout. From the traffic-safety point of view, the main advantage of the new type of roundabout is that it has no crossing conflict points. V zadnjem času mnoge tuje prometno-varnostne analize kažejo na nizko raven prometne varnosti večpasovnih krožnih križišč. Ta problem v različnih državah rešujejo na različne načine, kot najuspešnejši pa se je pokazal način z zmanjševanjem števila konfliktnih točk (npr. turbo krožno križišče). Vendar ima tudi turbo krožno križišče svoje pomankljivosti: ima konfliktne točke križanja ter v primeru, da želimo izvesti turbo krožno križišče namesto obstoječega dvopasovnega križišča, je potrebna večja rekonstrukcija križišča. V prispevku je predstavljen novi tip krožnega križišča - krožno križišče s "pritisnjenimi" pasovi za desno zavijanje. Glavna prednost takšnega tipa krožnega križišča je, da ga je možno izvesti znotraj meja obstoječega dvopasovnega krožišča. S stališča prometne varnosti ta tip krožnega križišča nima konfliktnih točk križanja.

Abstract

The problems of low level traffic safety on multi-lane roundabouts have been resolved in various ways in different countries, usually by using alternative types of roundabouts that reduce the number of conflict points. Alternative types of roundabouts typically differ from "normal" or "standard" roundabouts in one or more design elements, as their implementation purposes could also be specific. Today, several different types of roundabouts are already in use ("mini", "double mini", "dumb-bell", those "with joint splitter islands" ("dog-bone"), those "with a spiralling circular carriageway" ("turbo"), those "with depressed lanes for right-hand turners" ("flower") etc.). This paper introduces a new type of roundabout, dual one-lane roundabouts on two levels with right-hand turning bypasses, namely the "target roundabout". This paper describes and analyses their design, traffic safety, and capacity characteristics, compared with the standard two-lane roundabouts. Problem nizke ravni prometne varnosti v obstoječih večpasovnih krožnih križiščih se v različnih državah rešuje na različne načine, običajno z uvedbo alternativnih tipov krožnih križišč, v katerih je število konfliktnih točk praviloma manjše. Za alternativne tipe krožnih križišč je tipično, da se od “normalnih” oz. “standardnih” krožnih križišč razlikujejo v enem ali več projektno–tehničnih elementov, specifični pa so lahko tudi pogoji njihove izvedbe. Danes je že znanih veliko različnih tipov krožnih križišč (“mini”, “dvojni mini”, “dumb–bell”, “s povezanima ločilnima otokoma” (“dog-bone”), “s spiralnim potekom krožnega vozišča” (“turbo”), “s pritisnjenimi pasovi za desne zavijalce” (“flower”), …) in njihov razvoj bo zagotovo potekal tudi v prihodnosti. Prispevek prikazuje novi tip krožnega križišča, dvonivojski enopasovni krožni križišči s pasovi za desne zavijalce, krajše “target roundabout”. V prispevku so predstavljene njegove projektno–tehnične, prometno–varnostne in kapacitetne lastnosti, primerjaje z običajnim dvopasovnim krožnim križiščem.

Abstract

Price fluctuation is a practice commonly used by companies to stimulate demand and a main cause of the Bullwhip effect. Assuming a staggered step demand pattern that responds elastically to retailer’s price fluctuation, and by using a supply chain management dynamic model, we will analyse the impact of these fluctuations on the variability of the orders placed along a traditional multilevel supply chain. Subsequently, the results obtained will serve to propose a forecasting model enabling to calculate the potential variability of orders placed by each echelon on the basis of the price pattern used. Finally, under the hypothesis of an environment of collaboration between the different members of the chain, we propose a predictive model that makes it possible to quantify the distortion of the orders generated by each level. En este artículo se analiza la influencia de la fluctuacion de los precios en la variabilidad de las órdenes generadas a lo largo de una cadena de suministro tradicional multinivel. Para ello, se utiliza un modelo dinámico de gestión de ca- dena de suministro en el que se introduce un patrón de de- manda tipo escalón, que responde elásticamente a la fluc- tuación de los precios ofrecidos por el minorista al cliente final. Posteriormente, utilizando los resultados obtenidos, se propone un modelo de previsión para calcular esa posible variación de las órdenes generadas en cada nivel, a partir del patrón de precios utilizado.

Abstract

In August 1999 an exceptional transportation of two steamers of 666 tonnes was performed from the Port of Koper to the Nuclear power plant in Krško. The transport covered a distance of about 200km and represented one of the largest exceptional transports in Slovenia ever. Finding the best route represented one of the major issues, because the steamers had to cross more than 50 problematic sections and bridges, most of which have not been designed for such heavy loads. It was necessary to load-test almost all bridges on the route to determine whether those bridges need any extra supports or not. Consequently, a logistic operator has an important and indispensable role and becomes a co-modeller of logistic service. A deformation analysis or a polynomial interpolation of vertical displacements could also be used. Therefore, a laboratory load test of a concrete plate was made. The concrete plate was loaded with hydraulic cylinder PZ 100 with extensiometer up to 21kN. Every increase of load by 3kN was measured with Nikon Ser 800 total station. V Sloveniji je bilo potrebno avgusta 1999 iz Koprskega pristanišča do Nuklearne elektrarne Krško prepeljati dva uparjalnika teže 666 ton na relaciji dobrih 200 km, kar še danes predstavlja enega največjih tovorov, ki je kdajkoli potoval po Slovenji. Izbira najboljše poti je predstavljala zelo pomemben del transporta, saj sta uparjalnika na poti prečkala preko 50 problematičnih odsekov in mostov, ki za tako velike ob- remenitve večinoma niso predvideni. Tako je bilo potrebno določene premostitvene objekte testno obremenjevati, da bi ugotovili ali bodo obremenitev vzdržali in ali so za to potrebne dodatne ojačitve. Izredno vlogo pri tem mora odigrati logistični operator, saj je v vlogi moderatorja logistične storitve. Pomagali bi si lahko tudi z ustrezno deformacijsko analizo oz. interpolacijo vertikalnih pomikov s pomočjo polinomov. Za to je bil v laboratoriju izveden deformacijski obremenilni preizkus betonske plošče. Betonska plošča je bila obremenjevana s hidravličnim cilindrom PZ 100 z ekstenziometrom do sile 21 kN, ki je bil računalniško krmiljen. Izmerila se je vsaka dodatna obremenitev po 3 kN. Uporabljen je bil elektronski tahimeter znamke Nikon Ser. 800.

Abstract

This paper examines the reliability of the operation of cableway systems in Slovenia, which has major impact on the quality of service in the mountain tourism, mainly in wintertime. Different types of cableway installations in Slovenia were captured in a sample and fault tree analysis (FTA) was made on the basis of the obtained data. The paper presents the results of the analysis. With these results it is possible to determine the probability of faults of different types of cableways, which types of faults have the greatest impact on the termination of operation, which components of cableways fail most, what is the impact of age of cableways on the occurrence of the faults. Finally, an attempt was made to find if occurrence of faults on individual cableway installation has also impact on traffic on this cableway due to reduced quality of service. Članek proučuje sigurnost delovanja žičniških naprav v Sloveniji, katere imajo velik vpliv na kakovost storitev v gorskem turizmu, največ v zimskem času. V vzorec so bile zajete slovenske žičniške naprave različnih vrst in na osnovi pridobljenih podatkov o odpovedi njihovega delovanja je bila narejena analiza drevesa napak (FTA). V članku so predstavljeni rezultati analize s pomočjo katere se je dalo ugotoviti, kakšna je verjetnost odpovedi posameznih vrst žičniških naprav, katere vrste napak imajo največji vpliv na odpovedi, kateri sklopi žičniških naprav največkrat odpovedo, kakšen vpliv ima starost žičniških naprav na pojav napak. Na koncu se je poskušalo ugotoviti tudi, ali ima pojav napak na posamezni žičniški napravi tudi vpliv na promet zaradi zmanjšane kakovosti storitve.

Abstract

The introduction of contemporary procedures to fleet management processes has recently changed the work planning and supervision of driver's work activities. Tendencies to control the implementation of driver's work have been present in modem professional practice for quite a long time however, the equipment available on the market limited its implementation. The intensified development of digital tachographs has, in technical terms, ensured such equipment considerably before the legislative groundwork was prepared for its practical implementation. The Commission Regulation (EC) No. 561/2006 (implementation of Social legislation relating to Road Transport) does not bring any essential novelties in terms of permitted workload. Consistent monitoring of drivers activities, made possible by digital tachographs, will have impact on the existing working methods. The topic of the present paper is in deep analysis of the impact of the mentioned regulation with special emphasis on the conditions for the regulation of the current stage of drivers work and on the expected consequences. The essential importance lies on the expected change in the mentality and approach to planning the driver's activities in the transport process on the part of the carrier: the outcome will eventually result in the efficiency of each individual carrier. Uvedba sodobnih postopkov v procese upravljanja z voznim parkom je v zadnjem času spremenila način načrtovanja dela voznega osebja ter nadzor nad njegovimi delovnimi aktivnostmi. Težnje po nadzoru izvajanja voznikovega dela so v strokovni praksi prisotne že dalj časa, njena realizacija pa je bila omejena z razpoložljivo opremo na tržišču. Pospešen razvoj digitalnih tahografov je v tehničnem smislu takšno opremo zagotovil bistveno prej, kot so bile urejene zakonodajne podlage za njegovo uvedbo v prakso. Uredba evropske komisije 561/2006 (Socialna zakonodaja v zvezi s cestnim transportom) sicer ne prinaša bistvenih novosti glede dovoljenih obremenitev. Zaradi doslednejše spremljave voznikove aktivnosti, ki jo omogočajo digitalni tahografi, pa bo vplivala na dosedanji način njihovega dela. Predmet pričujočega prispevka je detajlna analiza vpliva uredbe s posebnim poudarkom na pogojih za ureditev stanja na področju dela voznikov ter pričakovanih posledic. Ključnega pomena je pričakovana sprememba načina razmišljanja in dela prevoznikov pri načrtovanju voznikovega dela v transportnem procesu, kar bo vplivalo na uspešnost poslovanja posameznega prevoznika.