Bim: Promises and reality

The building information modeling - BIM is a technology developed toward creation of computer based information model that encompasses whole building lifecycle. Toward that goal a number of information technology standards have been developed that enable different professions in AEC to cooperatively develop electronic building model. The paper gives overview of essential technologies, discusses their intended purpose, and gives outline of the currently achieved functionality

Piezoelectric anisotropy and free energy instability in classic perovskites

Several members of the perovskite family are investigated: the temperature dependence of dielectric, elastic, piezoelectric and coupling coefficients of KNbO3 in its orthorhombic ferroelectric phase is determined experimentally; the values of dielectric stiffness coefficients at constant stress, α, are estimated for the 6th order Landau-Ginzburg-Devonshire phenomenological description of KNbO3; the origins of the enhanced piezoelectric responses along non polar directions in perovskites are investigated by studying phenomenologically the temperature evolution of the piezoelectric anisotropy in a material with a sequence of ferroelectric-ferroelectric phase transitions (BaTiO3) and in a material with only one ferroelectric phase (PbTiO3); the influence of external bias fields on piezoelectric response and its anisotropy in ferroelectric perovskites is discussed phenomenologically by studying tetragonal BaTiO3, PbTiO3 and Pb(Zr,Ti)O3 under electric bias field applied anti-parallel to the spontaneous polarization and uniaxial compressive bias stress along the polarization direction; a discussion about a common underlying thermodynamic process able to generally describe the enhancement of the piezoelectric response and its anisotropy is given by investigating the Gibbs free energy flattening in tetragonal BaTiO3, PbTiO3 and Pb(Zr,Ti)O3 upon changes of temperature, bias fields and composition. The main conclusions resulting from this work are: a comparison of the results of electromechanical properties measurements on KNbO3 obtained in this work, the ones found in the literature, and estimates using LGD phenomenology from this work gives discrepancies that suggest that published measurements should be redone; in the absence of bias fields, the intrinsic origin of the enhanced piezoelectric responses in perovskites is the anticipation of a phase transition, no matter what is the cause of that transition (temperature, composition); in the presence of sufficiently high bias fields, an enhanced piezoelectric response along non-polar direction can be predicted in some materials (PbTiO3 under high uniaxial compressive stress along the polar direction); the influence of the external bias fields on electromechanical properties of perovskites may generally be of significant importance: if the electric fields applied anti-parallel to the spontaneous polarization or the uniaxial compressive bias stresses applied along the polarization axis are high enough, the perovskite system can be strongly dielectrically softened (metastable state), increasing the values of dielectric permittivities and piezoelectric coefficients; in the vicinity of a coercive field or a phase transition these electromechanical coefficients can increase by several orders of magnitude; the flattening of the Gibbs free energy profile of each of examined perovskite systems, regardless of whether this flattening is caused by temperature or composition variation, or by applying compressive pressure or antiparellel electric field bias, leads to enhancements of dielectric susceptibilities and of the piezoelectric response; the anisotropy of the free energy flattening is the origin of the anisotropic enhancement of the piezoelectric response, which can occur either by polarization rotation or by polarization contraction

An Overview of Indicators and Indices Used for Urban Mobility Assessment

The urban mobility is affected by global trends resulting in a growing passenger and freight transport demand. In order to improve the understanding of urban mobility in general, to evaluate mobility services and to quantify the overall transport system performance, it is necessary to assess urban mobility. Urban mobility assessment requires the application of methodology integrating different metrics and explicitly applying a multi-dimensional approach. Since scientific community does not define urban mobility in an unambiguous way, part of this paper is devoted to the analysis of the definition of urban mobility. This step enables better understanding of urban mobility in general, as well as understanding of the urban mobility assessment process. Usually, a three-layered approach that includes urban mobility data, indicators and indices is used for the assessment. Therefore, the aim of this paper was to perform extensive research in order to synthesize, define and organize the elements of those layers. The existing urban mobility indicators and indices have been developed for specific urban areas, taking into account local specifications, and they are not applicable in other cities. Also, the choice of urban mobility indicators is mainly related to the existence of data sources, which limits the objective and comparable assessment of the mobility of cities where such data do not exist.</p

Bim: Promises and reality

The building information modeling - BIM is a technology developed toward creation of computer based information model that encompasses whole building lifecycle. Toward that goal a number of information technology standards have been developed that enable different professions in AEC to cooperatively develop electronic building model. The paper gives overview of essential technologies, discusses their intended purpose, and gives outline of the currently achieved functionality

Expectations, reality and perspectives in using bim for the green building design

In the late 1970s when the first programs for building energy consumption simulation appeared, architectural practice was based on paper documentation and 2D drafting programs were considered as state of the art technologies. The requirement for 3D building models for computer-based energy simulation minimized the use of this technology in everyday practice. With the appearance of BIM applications that enable creation of information rich 3D building models, everyone expected that this technology can easily provide all data necessary for energy consumption simulation. Today, the market is full of different BIM related applications that are advertised as solutions for the green building design. The paper gives an overview of energy consumption simulation tools and their connection to two BIM applications - ArchiCAD and Revit and demonstrates that recent development of both technologies does not fully meet expectations. The paper indicates means to avoid overoptimistic expectations from software tools that can help designers to achieve better comprehension of the real merits that BIM can bring to green building design. The paper addresses usability of using BIM for sustainable refurbishment. The paper concludes with the analysis of the Semantic Web technologies which can contribute to a better understanding of simulation results, and can provide more information about energy efficiency of the components used in BIM applications' libraries

Data Envelopment Analysis for Determining the Efficiency of Variant Solutions for Traffic Flow Organisation

There is a small number of empirical modelling study cases available that are related to the calculation of variant solutions efficiency from the aspect of sustainable mobility in the urban areas. In practice, it is often necessary - especially when it comes to the urban transport network - to evaluate the solutions for traffic flow organisation and routing, in order to implement the one(s) with the maximum potential to reduce the possibility of congestion during peak travelling periods i.e. during transport network peak load. The paper presents an approach to the aforementioned problem by the application of the transport system efficiency analysis. The aspect of traffic flow organisation and routing efficiency in variant solutions is clarified through the analysis model development, built on the premises of Data Envelopment Analysis (DEA) method and the principles of unnecessary traffic flow intersections (TFI) theory. The proposed model defines the efficiency limit for data attributed to variant solutions, based on the calculation of the optimal TFI model and the possibilities of DEA method that include comparison and definition of relative routing efficiency for every optional traffic flow against the efficiency limit (optimal model) in order to calculate relative efficiency in relation to other solutions.</p

Techno-economic analysis of heat exchangers with parallel helical tube coils

The paper deals with the investment and exploitation costs for shell and tube heat exchangers with parallel helical tube coils. The most common correlations for estimating prices of shell and tube heat exchangers found in open literature were tested using the market data for a comparison and they have shown significant deviations. A new correlation for calculating prices of heat exchangers with helical tubes (when the shell is made of carbon steel and the helical tube of copper) was determined. In addition, the costs of electricity needed to drive pumps, as well as the costs of chemical cleaning of the apparatuses with inhibited mineral acids were estimated

Rotator and extender ferroelectrics: Importance of the shear coefficient to the piezoelectric properties of domain-engineered crystals and ceramics

The importance of a high shear coefficient d15 (or d24) to the piezoelectric properties of domain-engineered and polycrystalline ferroelectrics is discussed. The extent of polarization rotation, as a mechanism of piezoelectric response, is directly correlated to the shear coefficient. The terms "rotator" and "extender" are introduced to distinguish the contrasting behaviors of crystals such as 4mm BaTiO3 and PbTiO3. In "rotator" ferroelectrics, where d15 is high relative to the longitudinal coefficient d33, polarization rotation is the dominant mechanism of piezoelectric response; the maximum longitudinal piezoelectric response is found away from the polar axis. In "extender" ferroelectrics, d15 is low and the collinear effect dominates; the maximum piezoelectric response is found along the polar axis. A variety of 3m, mm2 and 4mm ferroelectrics, with various crystal structures based on oxygen octahedra, are classified in this way. It is shown that the largest piezoelectric anisotropies d15/d33 are always found in 3m crystals; this is a result of the intrinsic electrostrictive anisotropy of the constituent oxygen octahedra. Finally, for a given symmetry, the piezoelectric anisotropy increases close to ferroelectric-ferroelectric phase transitions; this includes morphotropic phase boundaries and temperature induced polymorphic transitions.Comment: accepted in J. Appl. Phy

High-Temperature Ultrasound NDE Systems for Continuous Monitoring of Critical Points in Nuclear Power Plants Structures

High temperature pipe cracks are the root of a steam power failure in the EU typically every 4 years, resulting in loss of human life, serious accidents and massive financial losses. According to IAEA’s Reference Technology Database, such an event on a nuclear power plant has an average cost of €120 million, including outage costs, emergency repair costs, insurance and legal costs. Since only one growing crack is needed to cause a major failure, they have to be inspected and monitored thoroughly. Breakdowns at extreme conditions (e.g. 580°C, 400 bar) are a result of two major weld failure modes: a) creep cracks near pipe welds; b) fatigue cracks on pipe welds. Current maintenance practice is to proceed with repairs on a detected crack according to its severity. For cost reasons, cracks that are not judged as severe enough will not be repaired. Crack severity judgement is based on its probability to cause a failure and this probability is derived taking into account the crack size and operational lifetime. More variables such as operating temperature and vibrations may rarely be found in other studies. Recent data from fracture mechanics statistical studies shows this connection between the size of a crack on a nuclear power plant pipe and its probability to lead to a failure. To deal with the above problems two Structural Health Monitoring (SHM) systems have been developed and they are presented in this work. These systems are able to achieve continuous operation for an extended time period at operating temperatures of nuclear power plants. The developed systems employ novel phased array (PA) ultrasonic and ultrasound guided wave (UGW) probes able to withstand and continuously operate even up to 580 °C. The systems are designed to be permanently mounted on superheated steam pipes, at locations of known defects and to continuously monitor their size. However, this supposes that defects will have already been detected by a traditional method during an outage. The PA transducers are placed according to the Time-of- Flight Diffraction (TOFD) technique’s topology, thus creating a novel configuration, while the UGW transducers are placed on a stainless steel ring in a circular array configuration. These configurations can enable continuous tracking of cracks growth with high accuracy, enabling maintenance crews to estimate the severity directly and not through statistics