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This paper proposes an adaptive atomistic- continuum numerical method for quasi-static crack growth. The phantom node method is used to model the crack in the continuum region and a molecular statics model is used near the crack tip. To ensure self-consistency in the bulk, a virtual atom cluster is used to model the material of the coarse scale. The coupling between the coarse scale and fine scale is realized through ghost atoms. The ghost atom positions are interpolated from the coarse scale solution and enforced as boundary conditions on the fine scale. The fine scale region is adaptively enlarged as the crack propagates and the region behind the crack tip is adaptively coarsened. An energy criterion is used to detect the crack tip location. The triangular lattice in the fine scale region corresponds to the lattice structure of the (111) plane of an FCC crystal. The Lennard-Jones potential is used to model the atom–atom interactions. The method is implemented in two dimensions. The results are compared to pure atomistic simulations; they show excellent agreement.
This paper extends further the strain smoothing technique in finite elements to 8-noded hexahedral elements (CS-FEM-H8). The idea behind the present method is similar to the cell-based smoothed 4-noded quadrilateral finite elements (CS-FEM-Q4). In CSFEM, the smoothing domains are created based on elements, and each element can be further subdivided into 1 or several smoothing cells. It is observed that: 1) The CS-FEM using a single smoothing cell can produce higher stress accuracy, but insufficient rank and poor displacement accuracy; 2) The CS-FEM using several smoothing cells has proper rank, good displacement accuracy, but lower stress accuracy, especially for nearly incompressible and bending dominant problems. We therefore propose 1) an extension of strain smoothing to 8-noded hexahedral elements and 2) an alternative CS-FEM form, which associates the single smoothing cell issue with multi-smoothing cell one via a stabilization technique. Several numerical examples are provided to show the reliability and accuracy of the present formulation.
This paper presents several aspects of characterization of welding heat source parameters in Goldak’s double ellipsoidal model using Sysweld simulation of welding of two overlapping beads on a substrate steel plate. The overlap percentages ranged from 40% to 80% in increments of 10%. The new material properties of the fused metal were characterized using Weldware and their continuous cooling transformation curves. The convective and radiative heat transfer coefficients as well as the cooling time t8/5 were estimated using numerical formulations from relevant standards. The effects of the simulation geometry and mesh discretization were evaluated in terms of the factor F provided in Sysweld. Eventually, the parameters of Goldak’s double ellipsoidal heat source model were determined for the welding simulation of overlapping beads on the plate and the simulated bead geometry, extent of the molten pool and the HAZ were compared with the macrographs of cross-sections of the experimental weldments. The results showed excellent matching, thus verifying this methodology for determination of welding heat source parameters.
Explicit solutions for the cohesive energy between carbon nanotubes, graphene and substrates are obtained through continuum modeling of the van der Waals interaction between them. The dependence of the cohesive energy on their size, spacing and crossing angles is analyzed. Checking against full atom molecular dynamics calculations and available experimental results shows that the continuum solution has high accuracy. The equilibrium distances between the nanotubes, graphene and substrates with minimum cohesive energy are also provided explicitly. The obtained analytical solution should be of great help for understanding the interaction between the nanostructures and substrates, and designing composites and nanoelectromechanical systems.
The distinguishing structural feature of single-layered black phosphorus is its puckered structure, which leads to many novel physical properties. In this work, we first present a new parameterization of the Stillinger–Weber potential for single-layered black phosphorus. In doing so, we reveal the importance of a cross-pucker interaction term in capturing its unique mechanical properties, such as a negative Poisson's ratio. In particular, we show that the cross-pucker interaction enables the pucker to act as a re-entrant hinge, which expands in the lateral direction when it is stretched in the longitudinal direction. As a consequence, single-layered black phosphorus has a negative Poisson's ratio in the direction perpendicular to the atomic plane. As an additional demonstration of the impact of the cross-pucker interaction, we show that it is also the key factor that enables capturing the edge stress-induced bending of single-layered black phosphorus that has been reported in ab initio calculations.
Durch Reifungs- und Strukturbildungsprozesse kann es bei silikatischen und alumosilikatischen Bindern zu Rissbildung bei behinderter Verformung, Festigkeitsverlust und somit Verlust der Dauerhaftigkeit kommen. Die Bewertung dieser Prozesse erfolgt an silikatischen Materialien mit einem Ausblick auf die alumosilikatischen Binder.
Durch Reifungs- und Strukturbildungsprozesse kann es bei silikatischen und alumosilikatischen Bindern zu Rissbildung bei behinderter Verformung, Festigkeitsverlust und somit Verlust der Dauerhaftigkeit kommen. Die Bewertung dieser Prozesse erfolgt an silikatischen Materialien mit einem Ausblick auf die alumosilikatischen Binder
Patients and staff in hospitals are exposed to a complex sound environment with rather high noise levels. In intensive care units, the main noise sources are hospital staff on duty and medical equipment, which generates both operating noise and acoustic alarms. Although noise in most cases is produced during activities for the purpose of saving life, noise can induce significant changes in the depth and quality of sleep and negatively affect health in general. Results of a survey of hospital staff are presented as well as measurements in two German hospital wards: a standard two-bed room and a special Intermediate Care Unit (IMC-Unit), each in a different Intensive Care Unit (ICU). Sound pressure data were collected over a 48 hour period and converted into different levels (LAFeq, LAFmax, LAFmin, LAF 5%), as well as a rating level LAr, which is used to take tonality and impulsiveness into account. An analysis of the survey and the measured data, together with a comparison of thresholds of national and international regulations and standards describe the acoustic situation and its likely noise effects on staff and patients.
Im Aufsatz "Zwei Pater noster-Vertonungen von Melchior Vulpius und die Missa V. vocum super Pater noster qui es in Coelis Melchioris Vulpii von Georg Vintz" werden Pater noster-Vertonungen aus dem OPUSCULUM NOVUM SELECTISSIMARVUM CANTIONVM SACRARVM (Erfurt 1610) und aus der PARS PRIMA CANTIONVM SACRARVM (Jena 1602) des Weimarer Kantors und Komponisten Melchior Vulpius (1570 - 1615) besprochen und miteinander verglichen. Ebenso wird untersucht, in welcher Weise der Naumburger Organist Georg Vintz (ca. 1580 - ca. 1635) eine dieser Motetten als Grundlage für die Parodiemesse "MISSA V. VOCUM,Super Pater noster [...] Melchioris Vulpii" genutzt und bearbeitet hat.
Der Aufsatz beruht auf einem Vortrag bei einer Tagung über Vulpius, die 2015 in Meiningen stattfand. Der Tagungsband, den Maren Goltz herausgeben wird, erscheint vermutlich 2018. Da im Band nicht genügend Platz für ausführliche Notenbeispiele ist, werden die besprochenen Kompositionen vollständig als Noten- und Klangdateien durch diesen Permalink zur Verfügung gestellt.
La prima edizione di questo testo è apparsa, in tedesco, nel volume II.2.: Anthologie zum Städtebau. Das Phänomen Großstadt und die Entstehung der Stadt der Moderne, a cura di Vittorio Magnago Lampugnani, Katia Frey, Eliana Perotti, con il sostegno di Departement Architektur der Eidgenössischen Technischen Hochschule, Zürich (Gebr. Mann Verlag, Berlin 2014, pp. 1307-1390). Previ specifici accordi con l’editore, viene qui presentata la versione originaria, in italiano, dell’intero capitolo: Modernität und Emphase. Städtebau im italienischen Faschismus, e comprendente: i) una capiente saggio introduttivo – in una versione più ampia ed articolata (comprensiva della “Bibliografia sistematica”, di riferimento) del testo in tedesco; ii) la versione in italiano del repertorio antologico di riferimento – e comprensiva di una “Scheda introduttiva”, sull’Autore-Opera, e di una selezione del testo in esame.
Spazio sacro e fondazione della comunità. Il tragico òikos dei villaggi di fondazione del fascismo
(2007)
La prima edizione di questo testo è apparsa − in una versione più ridotta −, nel volume: Pasquale Culotta, Giuliano Gresleri, Glauco Gresleri (a cura di), Città di fondazione e “Plantatio Ecclesiae”, Compositori, Bologna 2007, pp. 214-236. Un nutrito pool nazionale, specializzato sulle “Città di fondazione”, in Italia e nelle sue ex-colonie, si è misurato sul tema con una complessa storiografia interdisciplinare, che poneva al centro della sua diagnosi una connotazione teologico-ecumenica – la Plantatio Ecclesiae, appunto – della fenomenologia urbana della fundatio.
Die Bauinformatik ist eine Säule der modernen Bau- und Umweltingenieurwissenschaften und befasst sich mit der Erforschung grundlegender informatorischer Methoden sowie mit der Anwendung und Weiterentwicklung der Informationswissenschaften im Bau- und Umweltbereich. Der Arbeitskreis Bauinformatik konstituiert sich aus Wissenschaftlern, die an Universitäten im deutschsprachigen Raum auf dem Fachgebiet Bauinformatik lehren und forschen. Ausgehend vom erreichten Entwicklungsstand der Bauinformatik skizziert dieses Positionspapier die Aufgaben des Arbeitskreises und formuliert eine Grundlage für eine abgestimmte Weiterentwicklung an den deutschsprachigen Universitäten.
Water substantially affects nearly all physical, chemical and biological processes on the Earth. Recent Mars observations as well as laboratory investigations suggest that water is a key factor of current physical and chemical processes on the Martian surface, e.g. rheological phenomena. Therefore it is of particular interest to get information about the liquid-like state of water on Martian analogue soils for temperatures below 0 °C. To this end, a parallel plate capacitor has been developed to obtain isothermal dielectric spectra of fine-grained soils in the frequency range from 10 Hz to 1.1 MHz at Martian-like temperatures down to −70 °C. Two Martian analogue soils have been investigated: a Ca-bentonite (specific surface of 237 m2 g−1, up to 9.4% w / w gravimetric water content) and JSC Mars 1, a volcanic ash (specific surface of 146 m2 g−1, up to 7.4% w / w). Three soil-specific relaxation processes are observed in the investigated frequency–temperature range: two weak high-frequency processes (bound or hydrated water as well as ice) and a strong low-frequency process due to counter-ion relaxation and the Maxwell–Wagner effect. To characterize the dielectric relaxation behaviour, a generalized fractional dielectric relaxation model was applied assuming three active relaxation processes with relaxation time of the ith process modelled with an Eyring equation. The real part of effective complex soil permittivity at 350 kHz was used to determine ice and liquid-like water content by means of the Birchak or CRIM equation. There are evidence that bentonite down to −70 °C has a liquid-like water content of 1.17 monolayers and JSC Mars 1 a liquid-like water content of 1.96 monolayers.
By allocating real estate investments into the logistics sector, investors highly participate in the economic development of the respective country or city. However, the submarket is very cyclical and special economic influences – such as growing online trade and new logistic networks – affect the performance of the properties. Important parameters on the potential returns are found not only within the real estate market, but also within the global economy and the development of specific industries. This paper aims at examining factors affecting the performance of logistics properties.
Expected dependencies between macroeconomic factors and real estate economic indicators are examined for six major European logistics locations using econometric models, especially correlation and regression. Data series over a period of 25 years were used. The construction of an econometric model was an iterative process integrating both the statistical result and the economic causality.
This text proposes a genealogy of biopolitics based on Michel Foucault’s thought, and on an understanding of it as a philosophico-political notion. In order to elaborate this genealogy, the text takes as its starting point not only politics but also life, as the second component of the term. The hypothesis is the following: To understand what biopolitics means, we have to take seriously Foucault’s assertion of an indetermination of life, as the correlate of power and knowledge. This notion emerges in the epistemic break that takes place around 1800 and that entails the opening up of the notion of biopolitics under the name of governmentality, implying that life is not only the object of biopolitics but also serves as its model.
A coupled thermo-hydro-mechanical model of jointed hard rock for compressed air energy storage
(2014)
Renewable energy resources such as wind and solar are intermittent, which causes instability when being connected to utility grid of electricity. Compressed air energy storage (CAES) provides an economic and technical viable solution to this problem by utilizing subsurface rock cavern to store the electricity generated by renewable energy in the form of compressed air. Though CAES has been used for over three decades, it is only restricted to salt rock or aquifers for air tightness reason. In this paper, the technical feasibility of utilizing hard rock for CAES is investigated by using a coupled thermo-hydro-mechanical (THM) modelling of nonisothermal gas flow. Governing equations are derived from the rules of energy balance, mass balance, and static equilibrium. Cyclic volumetric mass source and heat source models are applied to simulate the gas injection and production. Evaluation is carried out for intact rock and rock with discrete crack, respectively. In both cases, the heat and pressure losses using air mass control and supplementary air injection are compared.
Tensile strain and compress strain can greatly affect the thermal conductivity of graphene nanoribbons (GNRs). However, the effect of GNRs under shear strain, which is also one of the main strain effect, has not been studied systematically yet. In this work, we employ reverse nonequilibrium molecular dynamics (RNEMD) to the systematical study of the thermal conductivity of GNRs (with model size of 4 nm × 15 nm) under the shear strain. Our studies show that the thermal conductivity of GNRs is not sensitive to the shear strain, and the thermal conductivity decreases only 12–16% before the pristine structure is broken. Furthermore, the phonon frequency and the change of the micro-structure of GNRs, such as band angel and bond length, are analyzed to explore the tendency of thermal conductivity. The results show that the main influence of shear strain is on the in-plane phonon density of states (PDOS), whose G band (higher frequency peaks) moved to the low frequency, thus the thermal conductivity is decreased. The unique thermal properties of GNRs under shear strains suggest their great potentials for graphene nanodevices and great potentials in the thermal managements and thermoelectric applications.
The Carbon journal is pleased to introduce a themed collection of recent articles in the area of computational carbon nanoscience. This virtual special issue was assembled from previously published Carbon articles by Guest Editors Quan Wang and Behrouz Arash, and can be accessed as a set in the special issue section of the journal website homepage: www.journals.elsevier.com/carbon. The article below by our guest editors serves as an introduction to this virtual special issue, and also a commentary on the growing role of computation as a tool to understand the synthesis and properties of carbon nanoforms and their behavior in composite materials.
Water content is a key parameter to monitor in nuclear waste repositories such as the planed underground repository in Bure, France, in the Callovo-Oxfordian (COx) clay formation. High-frequency electromagnetic (HF-EM) measurement techniques, i.e., time or frequency domain reflectometry, offer useful tools for quantitative estimation of water content in porous media. However, despite the efficiency of HF-EM methods, the relationship between water content and dielectric material properties needs to be characterized. Moreover, the high amount of swelling clay in the COx clay leads to dielectric relaxation effects which induce strong dispersion coupled with high absorption of EM waves. Against this background, the dielectric relaxation behavior of the clay rock was studied at frequencies from 1 MHz to 10 GHz with network analyzer technique in combination with coaxial transmission line cells. For this purpose, undisturbed and disturbed clay rock samples were conditioned to achieve a water saturation range from 0.16 to nearly saturation. The relaxation behavior was quantified based on a generalized fractional relaxation model under consideration of an apparent direct current conductivity assuming three relaxation processes: a high-frequency water process and two interface processes which are related to interactions between the aqueous pore solution and mineral particles (adsorbed/hydrated water relaxation, counter ion relaxation and Maxwell-Wagner effects). The frequency-dependent HF-EM properties were further modeled based on a novel hydraulic-mechanical-electromagnetic coupling approach developed for soils. The results show the potential of HF-EM techniques for quantitative monitoring of the hydraulic state in underground repositories in clay formations.
This paper presents a novel numerical procedure based on the combination of an edge-based smoothed finite element (ES-FEM) with a phantom-node method for 2D linear elastic fracture mechanics. In the standard phantom-node method, the cracks are formulated by adding phantom nodes, and the cracked element is replaced by two new superimposed elements. This approach is quite simple to implement into existing explicit finite element programs. The shape functions associated with discontinuous elements are similar to those of the standard finite elements, which leads to certain simplification with implementing in the existing codes. The phantom-node method allows modeling discontinuities at an arbitrary location in the mesh. The ES-FEM model owns a close-to-exact stiffness that is much softer than lower-order finite element methods (FEM). Taking advantage of both the ES-FEM and the phantom-node method, we introduce an edge-based strain smoothing technique for the phantom-node method. Numerical results show that the proposed method achieves high accuracy compared with the extended finite element method (XFEM) and other reference solutions.
We apply keyquery-based taxonomy composition to compute a classification system for the CORE dataset, a shared crawl of about 850,000 scientific papers. Keyquery-based taxonomy composition can be understood as a two-phase hierarchical document clustering technique that utilizes search queries as cluster labels: In a first phase, the document collection is indexed by a reference search engine, and the documents are tagged with the search queries they are relevant—for their so-called keyqueries. In a second phase, a hierarchical clustering is formed from the keyqueries within an iterative process. We use the explicit topic model ESA as document retrieval model in order to index the CORE dataset in the reference search engine. Under the ESA retrieval model, documents are represented as vectors of similarities to Wikipedia articles; a methodology proven to be advantageous for text categorization tasks. Our paper presents the generated taxonomy and reports on quantitative properties such as document coverage and processing requirements.
Many researchers are working on developing robots into adequate partners, be it at the working place, be it at home or in leisure activities, or enabling elder persons to lead a self-determined, independent life. While quite some progress has been made in e.g. speech or emotion understanding, processing and expressing, the relations between humans and robots are usually only short-term. In order to build long-term, i.e. social relations, qualities like empathy, trust building, dependability, non-patronizing, and others will be required. But these are just terms and as such no adequate starting points to “program” these capacities even more how to avoid the problems and pitfalls in interactions between humans and robots. However, a rich source for doing this is available, unused until now for this purpose: artistic productions, namely literature, theater plays, not to forget operas, and films with their multitude of examples. Poets, writers, dramatists, screen-writers, etc. have studied for centuries the facets of interactions between persons, their dynamics, and the related snags. And since we wish for human-robot relations as master-servant relations - the human obviously being the master - the study of these relations will be prominent. A procedure is proposed, with four consecutive steps, namely Selection, Analysis, Categorization, and Integration. Only if we succeed in developing robots which are seen as servants we will be successful in supporting and helping humans through robots.
Identity management provides PET (privacy enhancing technology) tools for users to control privacy of their personal data. With the support of mobile location determination techniques based on GPS, WLAN, Bluetooth, etc., context-aware and location-aware mobile applications (e.g. restaurant finder, friend finder, indoor and outdoor navigation, etc.) have gained quite big interest in the business and IT world. Considering sensitive static personal information (e.g. name, address, phone number, etc.) and also dynamic personal information (e.g. current location, velocity in car, current status, etc.), mobile identity management is required to help mobile users to safeguard their personal data. In this paper, we evaluate certain required aspects and features (e.g. context-to-context dependence and relation, blurring in levels, trust management with p3p integration, extended privacy preferences, etc.) of mobile identity management
A simple multiscale analysis framework for heterogeneous solids based on a computational homogenization technique is presented. The macroscopic strain is linked kinematically to the boundary displacement of a circular or spherical representative volume which contains the microscopic information of the material. The macroscopic stress is obtained from the energy principle between the macroscopic scale and the microscopic scale. This new method is applied to several standard examples to show its accuracy and consistency of the method proposed.
VHB-JOURQUAL represents the official journal ranking of the German Academic Association for Business Research. Since its introduction in 2003, the ranking has become the most influential journal evaluation approach in German-speaking countries, impacting several key managerial decisions of German, Austrian, and Swiss business schools. This article reports the methodological approach of the ranking’s second edition. It also presents the main results and additional analyses on the validity of the rating and the underlying decision processes of the respondents. Selected implications for researchers and higher-education institutions are discussed.
Spatial time domain reflectometry (spatial TDR) is a new measurement method for determining water content profiles along elongated probes (transmission lines). The method is based on the inverse modeling of TDR reflectograms using an optimization algorithm. By means of using flat ribbon cables it is possible to take two independent TDRmeasurements from both ends of the probe, which are used to improve the spatial information content of the optimization results and to consider effects caused by electrical conductivity. The method has been used for monitoring water content distributions on a full-scale levee model made of well-graded clean sand. Flood simulation tests, irrigation tests, and long-term observations were carried out on the model. The results show that spatial TDR is able to determine water content distributions with an accuracy of the spatial resolution of about ±3 cm compared to pore pressure measurements and an average deviation of ±2 vol % compared to measurements made using another independent TDR measurement system.
Physicochemical forces are responsible for the swelling pressure development in saturated bentonites. In this paper, the swelling pressures of several compacted bentonite specimens for a range of dry density of 1.10–1.73 Mg/m3 were measured experimentally. The clay used was a divalent-rich Ca-Mg-bentonite with 12% exchangeable Na+ ions. The theoretical swelling pressure–dry density relationship for the bentonite was determined from the Gouy-Chapman diffuse double-layer theory. A comparison of experimental and theoretical results showed that the experimental swelling pressures are either smaller or greater than their theoretical counterparts within different dry density ranges. It is shown that for dry density of the clay less than about 1.55 Mg/m3, a possible dissociation of ions from the surface of the clay platelets contributed to the diffuse double-layer repulsion. At higher dry densities, the adsorptive forces due to surface and ion hydration dominated the swelling pressures of the clay. A comparison of the modified diffuse double-layer theory equations proposed in the literature to determine the swelling pressures of compacted bentonites and the experimental results for the clay in this study showed that the agreement between the calculated and experimental swelling pressure results is very good for dry densities less than 1.55 Mg/m3, whereas at higher dry densities the use of the equations was found to be limited.
The work has studied the structure and properties of gypsum compositions modified with the manmade modifier based on metallurgical dust and multi-walled carbon nanotubes. The results show that changing the structure of solid gypsum leads to the increase in bending and compressive strength by 70,5% and 138% correspondingly, the water resistance increasing and the softening factor reaching 0,85. Modifying gypsum composition with complex additive leads to the formation of amorphous structures based on calcium hydrosilicates on the surface of primary gypsum crystallohydrates that bond gypsum crystals and reduce the access of water.
Media anthropology is a new and interdisciplinary field of research with very different subjects and methods that seems to be already heavily informed by a comparatively narrow understanding of media as mass media (e.g. TV, Internet, social web, etc.). Therefore, most theories in this field, at least implicitly, employ a hierarchical and often dichotomic preconception of the two poles of media-human relations, by analysing the operationalities and ontologies of the human and the media independently from one another. This article deviates from this line of thought by advocating an expanded, symmetrical and relational understanding of the terms media and human, taking them as always already intermingled facets of a broader dynamic configuration. Starting from a consideration of the historically powerful, yet overlooked media of the so-called habitat diorama, the heuristic concept of “anthropomediality” is to be developed. Eventually, this relational approach may open up a new, interesting field for interrogation of (media-)anthropological analysis in general.
The article presents preliminary results and qualitative analysis obtained from the doctoral research provisory entitled “How do Brazilian ‘battlers’ reside?”, which is in progress at the Institute for European Urban Studies, Bauhaus Univer-sity Weimar. It critically discusses the contradictions of the production of residences in Brazil made by an emerging so-cial group, lately called the Brazilian new middle class. For the last ten years, a number of government policies have provoked a general improvement of the purchasing power of the poor. Between those who completely depend on the government to survive and the upper middle class, there is a wide (about 100 million people) and economically stable lower middle group, which has found its own ways of dealing with its demand for housing. The conventional models of planning, building and buying are not suitable for their technical, financial and personal needs. Therefore, they are con-currently planners, constructors and residents, building and renovating their own properties themselves, but still with very limited education and technical knowledge and restricted access to good building materials and constructive ele-ments, formal technicians, architects or engineers. On the one hand, the result is an informal and more or less autono-mous self-production, with all sorts of technical problems and very interesting and creative spatial solutions to every-day domestic situations. On the other hand, the repercussions for urban space are questionable: although basic infrastructure conditions have improved, building densities are high and green areas are few. Lower middle class neigh-bourhoods present a restricted collective everyday life. They look like storage spaces for manpower; people who live to work in order to be able to consume—and build—what they could not before. One question is, to what extent the lat-est economic rise of Brazil has really resulted in social development for lower middle income families in the private sphere regarding their residences, and in the collective sphere, regarding the neighbourhoods they inhabit and the ur-ban space in general.
A known phenomenon during laser welding of thin sheets is the deformation caused by thermally induced stresses. This deformation can result in a change of the gap width between the welded parts, which leads to an unstable welding process. Inducing displacements by using a second heat source will compensate for the change in gap width, hence optimizing the welding process. The base material is 1 mm thick austenitic stainless steel 1.4301, which is welded by a CO2 laser. The second heat source is a diode laser. The gap between the welded parts was set between 0.05 mm and 0.1 mm. The influence of the second heat source on the welding process and the welding result is described. The usage of a second heat source allows a higher gap width to be set prior to the welding process. The results of the numerical simulation were found to be corresponding to those of the experiments.
Strain measurement is important in mechanical testing. A wide variety of techniques exists for measuring strain in the tensile test; namely the strain gauge, extensometer, stress and strain determined by machine crosshead motion, Geometric Moire technique, optical strain measurement techniques and others. Each technique has its own advantages and disadvantages. The purpose of this study is to quantitatively compare the strain measurement techniques. To carry out the tensile test experiments for S 235, sixty samples were cut from the web of the I-profile in longitudinal and transverse directions in four different dimensions. The geometry of samples are analysed by 3D scanner and vernier caliper. In addition, the strain values were determined by using strain gauge, extensometer and machine crosshead motion. Three techniques of strain measurement are compared in quantitative manner based on the calculation of mechanical properties (modulus of elasticity, yield strength, tensile strength, percentage elongation at maximum force) of structural steel. A statistical information was used for evaluating the results. It is seen that the extensometer and strain gauge provided reliable data, however the extensometer offers several advantages over the strain gauge and crosshead motion for testing structural steel in tension. Furthermore, estimation of measurement uncertainty is presented for the basic material parameters extracted through strain measurement.
We conducted extensive molecular dynamics simulations to investigate the thermal conductivity of polycrystalline hexagonal boron-nitride (h-BN) films. To this aim, we constructed large atomistic models of polycrystalline h-BN sheets with random and uniform grain configuration. By performing equilibrium molecular dynamics (EMD) simulations, we investigated the influence of the average grain size on the thermal conductivity of polycrystalline h-BN films at various temperatures. Using the EMD results, we constructed finite element models of polycrystalline h-BN sheets to probe the thermal conductivity of samples with larger grain sizes. Our multiscale investigations not only provide a general viewpoint regarding the heat conduction in h-BN films but also propose that polycrystalline h-BN sheets present high thermal conductivity comparable to monocrystalline sheets.
Stonecutters and Sutong Bridge have pushed the world record for main span length of cable-stayed bridges to over 1000m. The design of these bridges, both located in typhoon prone regions, is strongly influenced by wind effects during their erection. Rigorous wind tunnel test programmes have been devised and executed to determine the aerodynamic behaviour of the structures in the most critical erection conditions. Testing was augmented by analytical and numerical analyses to verify the safety of the structures throughout construction and to ensure that no serviceability problems would affect the erection process. This paper outlines the wind properties assumed for the bridge sites, the experimental test programme with some of its results, the dynamic properties of the bridges during free cantilevering erection and the assessment of their aerodynamic performance. Along the way, it discusses the similarities and some revealing differences between the two bridges in terms of their dynamic response to wind action.
In Zeiten volatiler Immobilienmärkte und einer hohen Wettbewerbsintensität sind leistungsfähige Systeme der Analyse und Entscheidungsunterstützung unverzichtbar. Entscheidungen zu Investitionsstrategien und Einzelinvestitionen basieren zumeist auf mehreren entscheidungsrelevanten Kriterien. Unterschiedliche immobilienwirtschaftliche Entscheidungsalternativen können dabei durchaus Kriterienausprägungen aufweisen, die eine bestimmte Alternative nicht als stets besser bzw. stets schlechter ausweisen. Klassische finanzwirtschaftliche Modelle oder verbreitete qualitative Verfahren wie das Scoring können die gegebene Komplexität meist nicht angemessen berücksichtigen. Eine Weiterentwicklung immobilienwirtschaftlicher Entscheidungsmodelle ist durch die Übertragung und Spezifizierung multikriterieller Verfahren der Entscheidungsunterstützung möglich. Speziell die Untergruppe des Outranking beschäftigt sich mit der schrittweisen Strukturierung, Ordnung und Priorisierung von komplexen Auswahlalternativen. Als spezifische immobilienwirtschaftliche Fragestellung dient hier die Auswahl und Priorisierung von Zielmärkten im taktischen Portfoliomanagement eines institutionellen Immobilienportfoliosmit internationaler Ausrichtung. Die Formalisierung des Entscheidungsproblems „Priorisierung von Zielmärkten“ erfolgt mit dem ELECTRE-Verfahren.
Lack of Information technology applications on construction projects lead to complex flow of data during project life cycle. Building Information Modeling (BIM) has gained attention in the Architectural, Engineering and Construction (AEC) industry, envisage the use of virtual n-dimensional (n-D) models to identify potential conflicts in design, construction or operational of any facility. A questionnaire has been designed to investigate perceptions regarding BIM advantages. Around 102 valid responses received from diversified stakeholders. Results showed very low BIM adoption with low level of ‘Buzz’. BIM is a faster and more effective method for designing and construction management, it improves quality of the design and construction and reduces rework during construction; which came out as the top thee advantages according to the perception of AEC professionals of Pakistan.BIM has least impact on reduction of cost, time and human resources. This research is a bench mark study to understand adoption and advantageous of BIM in Pakistan Construction Industry.
Water substantially affects nearly all physical, chemical and biological processes on the Earth. Recent Mars observations as well as laboratory investigations suggest that water is a key factor of current physical and chemical processes on the Martian surface, e.g. rheological phenomena. Therefore it is of particular interest to get information about the liquid-like state of water on Martian analogue soils for temperatures below 0 °C. To this end, a parallel plate capacitor has been developed to obtain isothermal dielectric spectra of fine-grained soils in the frequency range from 10 Hz to 1.1 MHz at Martian-like temperatures down to −70 °C. Two Martian analogue soils have been investigated: a Ca-bentonite (specific surface of 237 m2 g−1, up to 9.4% w / w gravimetric water content) and JSC Mars 1, a volcanic ash (specific surface of 146 m2 g−1, up to 7.4% w / w). Three soil-specific relaxation processes are observed in the investigated frequency–temperature range: two weak high-frequency processes (bound or hydrated water as well as ice) and a strong low-frequency process due to counter-ion relaxation and the Maxwell–Wagner effect. To characterize the dielectric relaxation behaviour, a generalized fractional dielectric relaxation model was applied assuming three active relaxation processes with relaxation time of the ith process modelled with an Eyring equation. The real part of effective complex soil permittivity at 350 kHz was used to determine ice and liquid-like water content by means of the Birchak or CRIM equation. There are evidence that bentonite down to −70 °C has a liquid-like water content of 1.17 monolayers and JSC Mars 1 a liquid-like water content of 1.96 monolayers.
The mechanism and the kinetics of hydration reactions are important for the application of a salt hydrate as a thermochemical heat storage material. MgSO4·H2O and Na2SO4 were chosen in this study because they are both promising candidates for such an application. Considering that the hydration of these salts yields MgSO4·7H2O and Na2SO4·10H2O as the reaction products, the maximum overall heat effect can be calculated from the heat of condensation of water vapor (44 kJ mol–1) and the heats of hydration of 75 kJ·mol-1 (for MgSO4·H2O) and 81 kJ mol-1 (for Na2SO4). Based on the densities of the two hydrated phases, this results in the very high theoretical energy densities of 2.3 GJ·m-3 and 2.4 GJ·m-3, respectively, for MgSO4·7H2O and Na2SO4·10H2O. Not only the energy density is important for the dimensioning of a storage system, but also the kinetics of hydration reactions play a major role for the application as storage material. In the present study, hydration reactions under varying climatic conditions were investigated by using water vapor sorption measurements and in-situ Raman microscopy. Using the phase diagrams, it can be clearly shown that the mechanism and the kinetics depend on the climatic conditions. Below the deliquescence humidity of the lower hydrated phase the hydration proceeds as solid state reaction, whilst above the deliquescence humidity a through solution mechanism takes place.