Sofia – a city of potentials, a city in a discontinuum

The article presents spatial development dilemmas of the capital city of Bulgaria, Sofia. In the urban network of mainly south-eastern Europe, Sofia is searching for new distinction, a quest comparable to other cities in united Europe. The historical fact is that Sofia developed from crisis to crisis, in difficult historical circumstances and by inherent solving of pending present problems. The need for adequate spatial development strategy, which could sustain and condition permanently stabile development intentions, is emphasised

Need a Lift? An Elevator Queueing Problem

Various aspects of the behavior and dispatching of elevators (lifts) were studied. Monte Carlo simulation was used to study the statistics of the several models for the peak demand at uppeak times. Analytical models problems were used to prove or disprove whether schemes were optimal. A mostly integer programming problem was formulated but not studied further

Thermal effects compensation and associated uncertainty for large magnet assembly precision alignment

Big science and ambitious industrial projects continually push technical requirements forward beyond the grasp of conventional engineering techniques. An example of these are the extremely tight micrometric assembly and alignment tolerances required in the field of celestial telescopes, particle accelerators, and the aerospace industry. Achieving such extreme requirements for large assemblies is limited, largely by the capability of the metrology used, namely, its uncertainty in relation to the alignment tolerance required. The current work described here was done as part of Maria Curie European research project held at CERN, Geneva. This related to future accelerators requiring the spatial alignment of several thousand, metre-plus large assemblies to a common datum within a targeted combined standard uncertainty (uctg(y)) of 12 μm. The current work has found several gaps in knowledge limiting such a capability. Among these was the lack of uncertainty statements for the thermal error compensation applied to correct for the assembly's dimensional instability, post metrology and during assembly and alignment. A novel methodology was developed by which a mixture of probabilistic modelling and high precision traceable reference measurements were used to quantify the uncertainty of the various thermal expansion models used namely: Empirical, Finite Element Method (FEM) models and FEM metamodels. Results have shown that the suggested methodology can accurately predict the uncertainty of the thermal deformation predictions made and thus compensations. The analysis of the results further showed how using this method a ‘digital twin’ of the engineering structure can be calibrated with known uncertainty of the thermal deformation behaviour predictions in the micrometric range. Namely, the Empirical, FEM and FEM metamodels combined standard uncertainties ( uc(y) ) of prediction were validated to be of maximum: 8.7 μm, 11.28 μm and 12.24 μm for the studied magnet assemblies

Österreichische Architekten in Bulgarien

The authors have taken as target of the research project to draw up a picture of the architectural influences and the heritage of the Danubian Monarchy in Bulgaria at the turn of the century. On this way one unknown site of the architecture of the Danubian Monarchy is being cleared up. The contribution of the specialists from the Danubian Monarchy and of the Bulgarian architects educated there is being presented in the first part of the research project. The study starts out from the complex and multifarious cultural context of the European turn of the century and the political changes in southeastern Europe at this time. The decisive contribution of the specialists from the Monarchy in the field of urban design is being duplicated. The architectural influences of the Monarchy are studied in the finale chapter. The phenomenon of the willing acceptance of strange cultural elements is being explained. A chapter is devoted to the specific phenomenon of the Bulgarian National Romantic because there are detected important contributions of graduates from the architectural schools of the Monarchy. In the second part of the research project the fundamental information to the different architects and artists is being summarised in a catalogue. There are biographic descriptions of 66 persons, a listing of works and their illustrations, as well as the resources of information to be found. The work is illustrated with a maximum number of authentic documents. The shorten text consists of 171 sites and is illustrated with 338 pictures. In conclusion it is established that the search for the architectural heritage of the Danubian Monarchy in Bulgaria at the same time a search for the roots of the academic architecture in Bulgaria is

An international comparison of surface texture parameters quantification on polymer artefacts using optical instruments

An international comparison of optical instruments measuring polymer surfaces with arithmetic mean height values in the sub-micrometre range has been carried out. The comparison involved sixteen optical surface texture instruments (focus variation instruments, confocal microscopes and coherent scanning interferometers) from thirteen research laboratories worldwide. Results demonstrated that: (i) Agreement among different instruments could be achieved to a limited extent; (ii) standardised guidelines for uncertainty evaluation of areal surface parameters are needed for users; (iii) it is essential that the performance characteristics (and especially the spatial frequency response) of an instrument is understood prior to a measurement

The impact of reneging in processor sharing queues

We investigate an overloaded processor sharing queue with renewal arrivals and generally distributed service times. Impatient customers may abandon the queue, or renege, before completing service. The random time representing a customer’s patience has a general distribution and may be dependent on his initial service time requirement. We propose a scaling procedure that gives rise to a fluid model, with nontrivial yet tractable steady state behavior. This fluid model captures many essential features of the underlying stochastic model, and we use it to analyze the impact of impatience in processor sharing queues. We show that this impact can be substantial compared with FCFS, and we propose a simple admission control policy to overcome these negative impacts

Packet Skipping and Network Coding for Delay-Sensitive Network Communication

We provide an analytical study of the impact of packet skipping and opportunistic network coding on the timely communication of messages through a single network element. In a first step, we consider a single-server queueing system with Poisson arrivals, exponential service times, and a single buffer position. Packets arriving at a network node have a fixed deadline before which they should reach the destination. To preserve server capacity, we introduce a thresholding policy, based on remaining time until deadline expiration, to decide whether to serve a packet or skip its service. The obtained goodput improvement of the system is derived, as well as the operating conditions under which thresholding can enhance performance. Subsequently, we focus our analysis on a system that supports network coding instead of thresholding. We characterize the impact of network coding at a router node on the delivery of packets associated with deadlines. We model the router node as a queueing system where packets arrive from two independent Poisson flows and undergo opportunistic coding operations. We obtain an exact expression for the goodput of the system and study the achievable gain. Finally, we provide an analytical model that considers both network coding and packet skipping, capturing their joint performance. A comparative analysis between the aforementioned approaches is provided

Final report on APMP regional key comparison APMP.L-K6: Calibration of ball plate and hole plate

open14sìThe comparison in this Final Report is part of the CIPM-MRA (Comité International des Poids et Mesures - Mutual Recognition Arrangement). The Report is also available in the open-access KCDB (Key Comparison Data Base) through the website of the BIPM (Bureau International des Poids et Mesures, www.bipm.org).The results of the APMP key comparisons on ball plate and hole plate (APMP.L-K6.2007) are reported. Both transfer standards were provided by NMIJ, Japan. The ball plate standard is 532 mm by 532 mm in nominal dimension and 25 spheres are embedded. Thirteen National Metrology Institutes (8 from APMP, 5 from other Regional Metrology Organizations) participated in the ball plate measurement comparison. The hole plate standard is 550 mm by 550 mm in nominal dimension and there are 44 cylindrical holes in it. Nine National Metrology Institutes (5 from APMP, 4 from other Regional Metrology Organizations) participated in the hole plate measurement comparison. The comparison started in May 2006 and finished in October 2008. The participants used different measurement techniques which were used for their routine calibration services. For determining the key comparison reference values, a two-dimensional coordinates-based analysis was performed. The measurement results on the ball plate show good agreement in ten out of thirteen participants. In contrast, those on the hole plate are in agreement for five out of nine participants.Takatsuji, Toshiyuki; Eom, Taebong; Tonmueanwai, Anusorn; Yin, Ruimin; van der Walt, Floris; Gao, Sitian; Thu, Bui Quoc; Singhal, R P; Howick, Eleanor; Doytchinov, Kostadin; Valente de Oliveira, José Carlos; Lassila, Antti; O'Donnell, Jim; Balsamo, AlessandroTakatsuji, Toshiyuki; Eom, Taebong; Tonmueanwai, Anusorn; Yin, Ruimin; van der Walt, Floris; Gao, Sitian; Thu, Bui Quoc; Singhal, R. P; Howick, Eleanor; Doytchinov, Kostadin; Valente de Oliveira, José Carlos; Lassila, Antti; O'Donnell, Jim; Balsamo, Alessandr