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Abstract
This doctoral thesis defines the relationship between the urban and rural in the 21st century, and focuses on food as a key component. The fact that food is, for the most part, produced in the countryside and then transported to the city has a significant influence on this very unbalanced relationship today. The main goal was to show that it is necessary to bring agriculture, urban gardening, the breeding of domestic farm animals, and beekeeping back to the city, which would have a positive affect on both the city and the countryside. All of this is already taking place at the local level, within the neighbourhoods of our cities and through the work of self-organised activities and initiatives, which have been taken up by city residents themselves. One example of this is the community garden, a new model of gardening which offers fertile ground for growing vegetables and to test various forms of co-existence, different ways of designing spaces, the creation of alternative values, and a positive vision for the future of city residents.
In 2010, I co-created the community urban garden Beyond a Construction Site, which is the central part of this artistic research. Throughout the entire four-year process of creating this community garden, theory and artistic practice were intertwined, and informed one another. This community garden is an example of a self-organised and self-managed community space located in a residential neighbourhood in the centre of the city of Ljubljana, and as such is a typical example of urbanism from the bottom up. I placed the creation and development of our community garden in a dialogue with the formal way of arranging urban gardening in Ljubljana, a top-down approach, which the city has been carrying out intensively since 2007. I compared the solutions being proposed by the city of Ljubljana for organising urban gardening with the way it is organised in other European cities, the UK, and the USA. I also researched the recent rapid growth of self-organised initiatives which are focused on the local production of food and seek to find more economic and ecologically friendly models to visibly influence the future of cities and the countryside. Here, community gardens play an important role, as in addition to the production of food they are also spaces for the criticism of existing urban policies, a self-organised revitalisation of neglected spaces, and places of resilience, because they differ from that which real estate agencies, large financial companies, and city authorities desire them to be.
The community garden Beyond a Construction Site has become living proof that, through a group action, the residents of a neighbourhood can influence existing city policies and the future of both their own neighbourhood and that of the entire city. The initiators of this garden are artists and architects, and we began this community garden in the context of an art festival, which also shows that art can influence the processes of everyday life and help to create much needed spaces within cities to serve various purposes. Our community garden has also shown itself to be an important platform for the exchange of knowledge on organic gardening, ecology in everyday life, and critical architecture, as well as serving to connect related initiatives. Together with these other initiatives we are stronger, and are influencing structural changes within city politics, thereby also co-creating the future of Ljubljana. This community garden is helping us to redefine our relationship with the city and re-awaken the desires and actions of residents connected with realising their fundamental right, the right to the city.
My other artworks, which I am presenting in the context of this doctoral thesis, show an optimistic vision for the future of cities. The video animations Back to the City (2011) and The Right Balance (2013), as well as the accompanying collages, visualise a city of the future where urban and rural practices live together side-by-side. This vision is being realised by city residents themselves, with their active participation in the creation of community gardens, growing their own vegetables, urban beekeeping, and by having egg-laying hens in their gardens. My desire was also to present the theoretical concept and scientific research to a non-academic public, and to people without specialised training. Using the method of storytelling I included knowledge from the research into the video animations and collages. In this way my artistic work, with an intentional playfulness, challenges today’s faith in science and theoretical concepts, as well as directing attention to working with common sense, with one’s own hands, and with the earth. This can contribute to a change in the still dominant anthropocentric view of nature, which is an urgently needed change for our future.
Keywords: rural, urban agriculture, community gardens, urban beekeeping, the bottom-up approach to urban planning, alternative spaces
In this paper, we present an empirical approach for objective and quantitative benchmarking of optimization algorithms with respect to characteristics induced by the forward calculation. Due to the professional background of the authors, this benchmarking strategy is illustrated on a selection of search methods in regard to expected characteristics of geotechnical parameter back calculation problems. Starting from brief introduction into the approach employed, a strategy for optimization algorithm benchmarking is introduced. The benchmarking utilizes statistical tests carried out on well-known test functions superposed with perturbations, both chosen to mimic objective function topologies found for geotechnical objective function topologies. Here, the moved axis parallel hyper-ellipsoid test function and the generalized Ackley test function in conjunction with an adjustable quantity of objective function topology roughness and fraction of failing forward calculations is analyzed. In total, results for 5 optimization algorithms are presented, compared and discussed.
The main objective of this thesis is to investigate the characteristics of rice husk ash RHA) and then its behaviour in self-compacting high performance concrete (SCHPC) with respects to rheological properties, hydration and microstructure development and alkali silica reaction, in comparison with silica fume (SF). The main results show that the RHA is a macro-mesoporous amorphous siliceous material with a very high silica content comparable with SF. The pore size distribution is the most important parameter of RHA besides amorphous silica content. This parameter affects pore volume, specific surface area, and thus the water demand and the pozzolanic reactivity of RHA and its behaviour in SCHPC. The incorporation of RHA decreases filling and passing abilities, but significantly increases plastic viscosity and segregation resistance of SCHPC. Therefore, RHA can be used as a viscosity modifying admixture for SCHPC. The incorporation of RHA increases the superplasticizer adsorption, the superplasticizer saturation dosage, yield stress and plastic viscosity of mortar. Fresh mortar formulated from SCHPC is a shear-thickening material. The incorporation of RHA/SF ecreases the shearthickening degree. The incorporation of RHA/SF increases the degree of cement hydration. SF appears more effective at 3 days possibly due to the better nucleation site effect, whereas RHA dominates at the later ages possibly due to the internal water curing effect. The incorporation of RHA/SF increases the degree of C3S hydration, particularly the C3S hydration rate from 3 to 14 days. The pozzolanic reaction takes place outside and inside RHA particles.
The internal pozzolanic eaction products consolidate the pores inside RHA particles rather than contribute to the pore refinement in the cement matrix. In the presence of the high alkali concentration, RHA particles act as microreactive aggregates and react with alkali hydroxide to generate the expansive alkali silica reaction products. Increasing the particle size and temperature increases the alkali silica reactivity of RHA. The mechanism for the successive pozzolanic and alkali silica reactions of RHA is theorized. Additionally, a new simple
mix design method is proposed for SCHPC containing various supplementary cementitious materials, i.e. RHA, SF, fly ash and limestone powder.
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.
Steel profiles with slender cross-sections are characterized by their high susceptibility to instability phenomena, especially local buckling, which are intensified under fire conditions. This work presents a study on numerical modelling of the behaviour of steel structural elements in case of fire with slender cross-sections. To accurately carry out these analyses it is necessary to take into account those local instability modes, which normally is only possible with shell finite elements. However, aiming at the development of more expeditious methods, particularly important for analysing complete structures in case of fire, recent studies have proposed the use of beam finite elements considering the presence of local buckling through the implementation of a new effective steel constitutive law. The objective of this work is to develop a study to validate this methodology using the program SAFIR. Comparisons are made between the results obtained applying the referred new methodology and finite element analyses using shell elements. The studies were made to laterally restrained beams, unrestrained beams, axially compressed columns and columns subjected to bending plus compression.
This thesis deals with the basic design and rigorous analysis of cryptographic schemes and primitives, especially of authenticated encryption schemes, hash functions, and password-hashing schemes.
In the last decade, security issues such as the PS3 jailbreak demonstrate that common security notions are rather restrictive, and it seems that they do not model the real world adequately. As a result, in the first part of this work, we introduce a less restrictive security model that is closer to reality. In this model it turned out that existing (on-line) authenticated encryption schemes cannot longer beconsidered secure, i.e. they can guarantee neither data privacy nor data integrity. Therefore, we present two novel authenticated encryption scheme, namely COFFE and McOE, which are not only secure in the standard model but also reasonably secure in our generalized security model, i.e. both preserve full data inegrity. In addition, McOE preserves a resonable level of data privacy.
The second part of this thesis starts with proposing the hash function Twister-Pi, a revised version of the accepted SHA-3 candidate Twister. We not only fixed all known security issues
of Twister, but also increased the overall soundness of our hash-function design.
Furthermore, we present some fundamental groundwork in the area of password-hashing schemes. This research was mainly inspired by the medial omnipresence of password-leakage incidences. We show that the password-hashing scheme scrypt is vulnerable against cache-timing attacks due to the existence of a password-dependent memory-access pattern. Finally, we introduce Catena the first password-hashing scheme that is both memory-consuming and resistant against cache-timing attacks.
Low-skilled labor makes a significant part of the construction sector, performing daily production tasks that do not require specific technical knowledge or confirmed skills. Today, construction market demands increasing skill levels. Many jobs that were once considered to be undertaken by low or un-skilled labor, now demand some kind of formal skills. The jobs that require low skilled labor are continually decreasing due to technological advancement and globalization. Jobs that previously required little or no training now require skilful people to perform the tasks appropriately. The study aims at ameliorating employability of less skilled manpower by finding ways to instruct them for performing constructions tasks. A review of exiting task instruction methodologies in construction and the underlying gaps within them warrants an appropriate way to train and instruct low skilled workers for the tasks in construction. The idea is to ensure the required quality of construction with technological and didactic aids seeming particularly purposeful to prepare potential workers for the tasks in construction without exposing them to existing communication barriers. A BIM based technology is considered promising along with the integration of visual directives/animations to elaborate the construction tasks scheduled to be carried on site.
Generell hat sich im Forschungsprojekt insbesondere durch die Gespräche mit den Hochschulvertretern bestätigt, dass für qualitativ hochwertige Lehre und Forschung qualitativ hochwertige Flächen in ausreichendem Umfang notwendig sind.
Ein Ziel der Forschungsarbeit ist die Entwicklung von Modellen zur Allokation und Steuerung von Flächenressourcen in Hochschulen. Ausgehend von Darstellungen und Erfahrungen für die Flächensteuerung aus Unternehmen, anderen Bereichen der öffentlichen Verwaltung und Forschungseinrichtungen wurden mögliche Steuerungsverfahren für Hochschulen untersucht. Es wurde ein Steuerungsmodell für Hochschulen entwickelt, das auf die hochschulinternen und die extern wirksamen Rahmenbedingungen reagiert.
Die hochschulinterne Flächenallokation wird zum einen maßgeblich von externen Rahmen-bedingungen und zum zweiten von internen Prozessen, Abläufen und Strukturen beeinflusst. Die Kenntnis dieser Bedingungen wird als Voraussetzung für die Benennung von Erfolgsfak-toren für die Implementation neuer Steuerungsmodelle angenommen. Analysiert wurden daher die liegenschaftspolitischen und die organisatorischen Rahmenbedingungen sowie die steuerungsrelevanten Eigenschaften der Flächen selber.
Aerodynamic Analysis of Slender Vertical Structure and Response Control with Tuned Mass Damper
(2015)
Analysis of vortex induced vibration has gained more interest in practical held of civil engineering. The phenomenon often occurs in long and slender vertical structure like high rise building, tower, chimney or bridge pylon, which resulting in unfavorable responses and might lead to the collapse of the structures. The phenomenon appears when frequency of vortex shedding produced in the wake area of body meet the natural frequency of the structure. Even though this phenomenon does not necessarily generate a divergent amplitude response, the structure still may fail due to fatigue damage.
To reduce the effect of vortex induced vibration, engineers widely use passive vibration response control system. In this case, the thesis studies the effect of tuned mass damper. The objective of this thesis is to simulate the effect of tuned mass damper in reducing unfavorable responses due to vortex induced vibration and initiated by numerical model validation with respect to wind tunnel test report. The reference structure that being used inside the thesis is Stonecutter Bridge, Hongkong.
A numerical solver for computational uid dynamics named VX ow which developed by Morgenthal [6] is utilized for wind and structure simulation. The comparison between numerical model and wind tunnel result shows 10% maximum tip displacement diference in the model of full erection freestanding tower. The tuned mass damper (TMD) model itself built separately in finite element software SOFiSTiK, and the efective damping obtained from this model then applied inside input modal data of VX ow simulation. A single TMD with mass ratio of TMD 0.5% to the mass of first bending frequency, the maximum tip displacement is measured to be average 67% reduced.
Considering construction limitation and robustness of TMD, the effects of multiple TMD inside a structure are also studied. An uncoupled procedure of applying aeroelastic loads obtained from VX
ow inside finite element software SOFiSTiK is also done to observe the optimum distribution and optimum mass ratio of multiple tuned mass damper. The rest of the properties of TMD are calculated with Den Hartog's formula. The results are as follows: peak displacement in the case of multiple TMD that distributed with polynomial spacing achieve 7.8% more reduction performance than
the one that distributed with equal spacing. Optimum mass of tuned mass damper achieved with ratio 1.25% mass of first bending frequency corresponds to across wind direction.
This thesis presents new interactive visualization techniques and systems intended to support users with real-world decisions such as selecting a product from a large variety of similar offerings, finding appropriate wording as a non-native speaker, and assessing an alleged case of plagiarism.
The Product Explorer is a significantly improved interactive Parallel Coordinates display for facilitating the product selection process in cases where many attributes and numerous alternatives have to be considered. A novel visual representation for categorical and ordered data with only few occurring values, the so-called extended areas, in combination with cubic curves for connecting the parallel axes, are crucial for providing an effective overview of the entire dataset and to facilitate the tracing of individual products. The visual query interface supports users in quickly narrowing down the product search to a small subset or even a single product. The scalability of the approach towards a large number of attributes and products is enhanced by the possibility of setting some constraints on final attributes and, therefore, reducing the number of considered attributes and data items. Furthermore, an attribute repository allows users to focus on the most important attributes at first and to bring in additional criteria for product selection later in the decision process. A user study confirmed that the Product Explorer is indeed an excellent tool for its intended purpose for casual users.
The Wordgraph is a layered graph visualization for the interactive exploration of search results for complex keywords-in-context queries. The system relies on the Netspeak web service and is designed to support non-native speakers in finding customary phrases. Uncertainties about the commonness of phrases are expressed with the help of wildcard-based queries. The visualization presents the alternatives for the wildcards in a multi-column layout: one column per wildcard with the other query fragments in between. The Wordgraph visualization displays the sorted results for all wildcards at once by appropriately arranging the words of each column. A user study confirmed that this is a significant advantage over simple textual result lists. Furthermore, visual interfaces to filter, navigate, and expand the graph allow interactive refinement and expansion of wildcard-containing queries.
Furthermore, this thesis presents an advanced visual analysis tool for assessing and presenting alleged cases of plagiarism and provides a three-level approach for exploring the so-called finding spots in their context. The overview shows the relationship of the entire suspicious document to the set of source documents. An intermediate glyph-based view reveals the structural and textual differences and similarities of a set of finding spots and their corresponding source text fragments. Eventually, the actual fragments of the finding spot can be shown in a side-by-side view with a novel structured wrapping of both the source, as well as the suspicious text. The three different levels of detail are tied together by versatile navigation and selection operations. Reviews with plagiarism experts confirm that this tool can effectively support their workflow and provides a significant improvement over existing static visualizations for assessing and presenting plagiarism cases.
The three main contributions of this research have a lot in common aside from being carefully designed and scientifically grounded solutions to real-world decision problems. The first two visualizations facilitate the decision for a single possibility out of many alternatives, whereas the latter ones deal with text at varying levels of detail. All visual representations are clearly structured based on horizontal and vertical layers contained in a single view and they all employ edges for depicting the most important relationships between attributes, words, or different levels of detail. A detailed analysis considering the context of the established decision-making literature reveals that important steps of common decision models are well-supported by the three visualization systems presented in this thesis.
One major research focus in the Material Science and Engineering Community in the past decade has been to obtain a more fundamental understanding on the phenomenon 'material failure'. Such an understanding is critical for engineers and scientists developing new materials with higher strength and toughness, developing robust designs against failure, or for those concerned with an accurate estimate of a component's design life. Defects like cracks and dislocations evolve at
nano scales and influence the macroscopic properties such as strength, toughness and ductility of a material. In engineering applications, the global response of the system is often governed by the behaviour at the smaller length scales. Hence, the sub-scale behaviour must be computed accurately for good predictions of the full scale behaviour.
Molecular Dynamics (MD) simulations promise to reveal the fundamental mechanics of material failure by modeling the atom to atom interactions. Since the atomistic dimensions are of the order of Angstroms ( A), approximately 85 billion atoms are required to model a 1 micro- m^3 volume of Copper. Therefore, pure atomistic models are prohibitively expensive with everyday engineering computations involving macroscopic cracks and shear bands, which are much larger than the atomistic length and time scales. To reduce the computational effort, multiscale methods are required, which are able to couple a continuum description of the structure with an atomistic description. In such paradigms, cracks and dislocations are explicitly modeled at the atomistic scale, whilst a self-consistent continuum model elsewhere.
Many multiscale methods for fracture are developed for "fictitious" materials based on "simple" potentials such as the Lennard-Jones potential. Moreover, multiscale methods for evolving cracks are rare. Efficient methods to coarse grain the fine scale defects are missing. However, the existing multiscale methods for fracture do not adaptively adjust the fine scale domain as the crack propagates. Most methods, therefore only "enlarge" the fine scale domain and therefore drastically increase computational cost. Adaptive adjustment requires the fine scale domain to be refined and coarsened. One of the major difficulties in multiscale methods for fracture is to up-scale fracture related material information from the fine scale to the coarse scale, in particular for complex crack problems. Most of the existing approaches therefore were applied to examples with comparatively few macroscopic cracks.
Key contributions
The bridging scale method is enhanced using the phantom node method so that cracks can be modeled at the coarse scale. To ensure self-consistency in the bulk, a virtual atom cluster is devised providing the response of the intact material at the coarse scale. A molecular statics model is employed in the fine scale where crack propagation is modeled by naturally breaking the bonds. The fine scale and coarse scale models are coupled by enforcing the displacement boundary conditions on the ghost atoms. An energy criterion is used to detect the crack tip location. Adaptive refinement and coarsening schemes are developed and implemented during the crack propagation. The results were observed to be in excellent agreement with the pure atomistic simulations. The developed multiscale method is one of the first adaptive multiscale method for fracture.
A robust and simple three dimensional coarse graining technique to convert a given atomistic region into an equivalent coarse region, in the context of multiscale fracture has been developed. The developed method is the first of its kind. The developed coarse graining technique can be applied to identify and upscale the defects like: cracks, dislocations and shear bands. The current method has been applied to estimate the equivalent coarse scale models of several complex fracture patterns arrived from the pure atomistic simulations. The upscaled fracture pattern agree well with the actual fracture pattern. The error in the potential energy of the pure atomistic and the coarse grained model was observed to be acceptable.
A first novel meshless adaptive multiscale method for fracture has been developed. The phantom node method is replaced by a meshless differential reproducing kernel particle method. The differential reproducing kernel particle method is comparatively more expensive but allows for a more "natural" coupling between the two scales due to the meshless interpolation functions. The higher order continuity is also beneficial. The centro symmetry parameter is used to detect the crack tip location. The developed multiscale method is employed to study the complex crack propagation. Results based on the meshless adaptive multiscale method were observed to be in excellent agreement with the pure atomistic simulations.
The developed multiscale methods are applied to study the fracture in practical materials like Graphene and Graphene on Silicon surface. The bond stretching and the bond reorientation were observed to be the net mechanisms of the crack growth in Graphene. The influence of time step on the crack propagation was studied using two different time steps. Pure atomistic simulations of fracture in Graphene on Silicon surface are presented. Details of the three dimensional multiscale method to study the fracture in Graphene on Silicon surface are discussed.
For decades in Germany, historical research on dictatorial urban design in the first half of the 20th century focused on the National Socialist period. Studies on the urban design practices of other dictatorships remained an exception. This has changed. Meanwhile, the urban production practices of the Mussolini, Stalin, Salazar, Hitler and Franco dictatorships have become the subject of comprehensive research projects. Recently, a research group that studies dictatorial urban design in 20th century Europe has emerged at the Bauhaus-Institut für Geschichte und Theorie der Architektur und der Planung. The group is already able to refer to various research results.
Part of the research group’s self-conception is the assumption that the urban design practices of the named dictatorships can only be properly understood from a European perspective. The dictatorships influenced one another substantially. Furthermore, the specificities of the practices of each dictatorship can only be discerned if one can compare them to those of the other dictatorships. This approach requires strict adherence to the research methods of planning history and urban design theory. Meanwhile, these methods must be opened
to include those of general historical studies.
With this symposium, the research group aims to further qualify this European perspective. The aim is to pursue an inventory of the various national historiographies on the topic of “urban design and dictatorship”. This inventory should offer an overview on the general national level of historical research on urban design as well as on the level of particular urban design projects, persons or topics.
The symposium took place in Weimar, November 21-22, 2013. It was organized by Harald Bodenschatz, Piero Sassi and Max Welch Guerra and funded by the DAAD (German Academic Exchange Service).
Superplasticizers are utilized both to improve the fluidity during the placement and to reduce the water content of concretes. Both effects have also an impact on the properties of the hardened concrete. As a side effect the presence of superplasticizers affects the strength development of concretes that is strongly retarded. This may lead to an ecomomical drawback of the concrete manufacturing. The present work is aimed at gaining insights on the causes of the retarding effect of superplasticizers on the hydration of Portland cement. In order to simplify the complex interactions occurring during the hydration of Portland cement the majority of the work focuses on the interaction of superplasticizer and tricalcium silicate (Ca3SiO5 or C3S, the main compound of Portland cement clinker). The tests are performed in three main parts accompanied by methods as for example isothermal conduction calorimetry, electrical conductivity, Electron Microscopy, ICP-OES, TOC, as well as Analytical Ultracentrifugation.
In the first main part and based on the interaction of cations and anionic charges of polymers, the interactions between calcium ions and superplasticizers are investigated. As a main effect calcium ions are complexed by the functional groups of the polymers (carboxy, sulfonic). Calcium ions may be both dissolved in the aqueous phase and a constitute of particle interfaces. Besides these effects it is furthermore shown that superplasticizers induce the formation of nanoscaled particles which are dispersed in the aqueous phase (cluster formation). Analogous to recent findings in the field of biomineralization, it is reasonable to assume that these nanoparticles influence the crystal growth by their assembly process.
Based on the assumption that superplasticizers hinder either or both dissolution and precipitation and by that retard the cement hydration, the impact on separate reactions is investigated. On experiments that address the solubility of C-S-H phases and portlandite, it is shown that complexation of calcium ions in the aqueous phase by functional groups of polymers increases the solubility of portlandite. Contrary, in case of C-S-H solubility the complexation of calcium ions in solution leads to decrease of the calcium ion concentration in the aqueous phase. These effects are explained by differences in adsorption of polymers on C-S-H phases and portlandite. It is proposed that adsorption is stronger on C-S-H phases compared to portlandite due to the increased specific surface area of C-S-H phases. Following that, it is claimed that before polymers are able to adsorb on C-S-H phases the functional groups must be screened by calcium ions in the aqueous phase. It is further shown that data regarding the impact of superplasticizers on the unconstrained dissolution rate of C3S does not provide a clear relation to the overall retarding effect occurring during the hydration of C3S. Both increased and decreased dissolution rate with respect to the reference sample are detected. If the complexation capability of the superplasticizers is considered then also a reduced dissolution rate of C3S is determined. Despite the fact that the global hydration process is accelerated, the addition of calcite leads to a slower dissolution rate. Thus, a hindered unconstrained dissolution of C3S as possibly cause for the retarding effect still remains open for discussion. In the last section of this part, the pure crystallization of hydrate phases (C-S-H phases, portlandite) is fathomed. Results clearly show that superplasticizers prolong the induction time and modify the rate of crystal growth during pure crystallization in particular due to the complexation of ions in solution. But this effect is insufficient to account for the overall retarding effect. Further important factors are the blocking of crystal growth faces by adsorbed polymers and the dispersion of nanoscaled particles which hinders their agglomeration in order to build up crystals.
In the last main part of the work, the previously gathered results are utilized in order to investigate hydration kinetics. During hydration, dissolution and precipitation occur in parallel. Thereby, special attention is laid on the ion composition of the aqueous phase of C3S pastes and suspensions in order to determine the rate limiting step. All in all it is concluded that the retarding effect of superplasticizers on the hydration of tricalcium silicate is based on the retardation of crystallization of hydrate phases (C-S-H phases and portlandite). Thereby, the two effects complexation of calcium ions on surfaces and stabilization of nanoscaled particles are of major importance. These mechanisms may partly be compensated by template performance and increase in solubility by complexation of ions in solution. The decreased dissolution rate of C3S by the presence of superplasticizers during the in parallel occuring hydration process can only be assessed indirectly by means of the development of the ion concentrations in the aqueous phase (reaction path). Whether this observation is the cause or the consequence within the dissolution-precipitation process and therefore accounts for the retarding effect remains a topic for further investigations.
Besides these results it is shown that superplasticizers can be associated chemically with inhibitors because they reduce the frequency factor to end the induction period. Because the activation energy is widely unaffected it is shown that the basic reaction mechanism sustain. Furthermore, a method was developed which permits for the first time the determination of ion concentrations in the aqueous phase of C3S pastes in-situ. It is shown that during the C3S hydration the ion concentration in the aqueous phase is developed correspondingly to the heat release rate (calorimetry). The method permits the differentiation of the acceleration period in three stages. It is emphasized that crystallization of the product phases of C3S hydration, namely C-S-H phases and portlandite, are responsible for the end of the induction period.
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.
Modern distributed engineering applications are based on complex systems consisting of various subsystems that are connected through the Internet. Communication and collaboration within an entire system requires reliable and efficient data exchange between the subsystems. Middleware developed within the web evolution during the past years provides reliable and efficient data exchange for web applications, which can be adopted for solving the data exchange problems in distributed engineering applications. This paper presents a generic approach for reliable and efficient data exchange between engineering devices using existing middleware known from web applications. Different existing middleware is examined with respect to the suitability in engineering applications. In this paper, a suitable middleware is shown and a prototype implementation simulating distributed wind farm control is presented and validated using several performance measurements.