Stuttgart University of Applied Sciences
Stuttgart, Germany
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Bortfeldt A.,University of Hagen | Homberger J.,Stuttgart University of Applied Sciences
Computers and Operations Research | Year: 2013

The Vehicle Routing and Loading Problem (VRLP) results by combining vehicle routing, possibly with time windows, and three-dimensional loading. Some packing constraints of high practical relevance, among them an unloading sequence constraint and a support constraint, are also part of the VRLP. Different formulations of the VRLP are considered and the issue is discussed under which circumstances routing and packing should be tackled as a combined task. A two-stage heuristic is presented following a packing first, routing second approach, i.e. the packing of goods and the routing of vehicles is done in two strictly separated stages. High quality results are achieved in short computation times for the 46 VRLP instances recently introduced by Moura and Oliveira. Moreover 120 new large benchmark instances including up to 1000 customers and 50,000 boxes are introduced and results for these instances are also reported. © 2012 Elsevier Ltd.

Bryde D.,University of Liverpool | Broquetas M.,Polytechnic University of Catalonia | Volm J.M.,Stuttgart University of Applied Sciences
International Journal of Project Management | Year: 2013

Theoretical developments in Building Information Modelling (BIM) suggest that not only is it useful for geometric modelling of a building's performance but also that it can assist in the management of construction projects. The purpose of this paper is to explore the extent to which the use of BIM has resulted in reported benefits on a cross-section of construction projects. This exploration is done by collecting secondary data from 35 construction projects that utilised BIM. A set of project success criteria were generated and content analysis was used to establish the extent to which each individual project met a criterion. The most frequently reported benefit related to the cost reduction and control through the project life cycle. Significant time savings were also reported. Negative benefits were mainly focused on the use of BIM software. Cost/benefit analysis, awareness raising and education and training are important activities to address the challenges of BIM usage. © 2013 Elsevier Ltd and APM IPMA.

Xu Z.,Polytechnic University of Turin | Coors V.,Stuttgart University of Applied Sciences
Building and Environment | Year: 2012

Constructing and improving urban residential areas is an eternal critical subject in the process of the whole urban development which is connected with a series of challenges and problems. During the past decades, urban residential development has speed up extremely with massive population mobility in cities. The purpose of this study is to propose an integrated approach for sustainability assessment of urban residential development, considering sustainability indicators, housing equilibrium and building visualization. Firstly based on merging DPSIR (Driving Forces, Pressure, State, Impact and Response) framework and Analytic Hierarchy Process (AHP), the indicators were systematized for the sustainability modeling. Due to the urban activities cause impacts not only on local level but also a broader scale, a simulation model, using System Dynamics (SD) methodology, was structured to quantitatively investigate the developmental tendency of the indicators. And then the estimated results were displayed in 2D density maps in ArcGIS and 3D visualization in CityEngine. A real case study was presented for the Stuttgart Region of the state of Baden-Württemberg in Southern Germany and its Plieningen district to experience the usefulness and feasibility of the developed approach. The integration of GIS, SD model and 3D visualization, called GISSD system here, can better explain the interaction and the variation of the sustainability indicators for residential development. Hence it is able to support the Decision Maker to view the sustainable level of urban residential areas more comprehensively. © 2011 Elsevier Ltd.

Ben Hassine I.,Stuttgart University of Applied Sciences | Eicker U.,Stuttgart University of Applied Sciences
Applied Thermal Engineering | Year: 2013

A model for district heating and cooling networks was developed. It was designed for the hydraulic and thermal simulation of networks with multiple loop topologies. The network description is based on a graph-theoretical method and the Newton algorithm was used for solving the system of nonlinear equations. To validate the model and to demonstrate structural improvement potentials, a case study for a biomass powered district heating network in Scharnhauser Park, Germany was carried out. Taking into account the existing network topology, the consumer stations were redistributed in the model in order to obtain four different load repartitions. By means of three quality indicators (the primary energy factor PEF, the relative importance of losses RiL and the CO2 emissions) it could be shown that the different geographical distributions of consumers within the network have a slight impact on the primary energy use and on the CO2 emissions of the system. The network model was also used to analyse different solar thermal energy supply strategies. It is concluded that the existing collector area can maximally contribute to 0.3% of the total heating energy demand. © 2012 Published by Elsevier Ltd.

Eicker U.,Stuttgart University of Applied Sciences | Dalibard A.,Stuttgart University of Applied Sciences
Solar Energy | Year: 2011

A new photovoltaic-thermal (PVT) system has been developed to produce electricity and cooling energy. Experimental studies of uncovered PVT collectors were carried out in Stuttgart to validate a simulation model, which calculates the night radiative heat exchange with the sky. Larger PVT frameless modules with 2.8m2 surface area were then implemented in a residential zero energy building and tested under climatic conditions of Madrid. Measured cooling power levels were between 60 and 65Wm-2, when the PVT collector was used to cool a warm storage tank and 40-45Wm-2, when the energy was directly used to cool a ceiling. The ratio of cooling energy to electrical energy required for pumping water through the PVT collector at night was excellent with values between 17 and 30. The simulated summer cooling energy production per square meter of PVT collector in the Madrid/Spain climatic conditions is 51kWhm-2a-1. In addition to the thermal cooling gain, 205kWhm-2a-1 of AC electricity is produced under Spanish conditions. A comparative analysis for the hot humid climate of Shanghai gave comparable results with 55kWhm-2a-1 total cooling energy production, mainly usable for heat rejection of a compression chiller and a lower electricity production of 142kWhm-2a-1. © 2011 Elsevier Ltd.

Eicker U.,Stuttgart University of Applied Sciences
Applied Energy | Year: 2010

One of the first rehabilitated passive energy standard office buildings in Europe was extensively monitored over two years to analyse the cooling performance of a ground heat exchanger and mechanical night ventilation together with the summer comfort in the building. To increase the storage mass in the light weight top floor, phase change materials (PCM) were used in the ceiling and wall construction. The earth heat exchanger installed at a low depth of 1.2 m has an excellent electrical cooling coefficient of performance of 18, but with an average cooling power of about 1.5 kW does not contribute significantly to cooling load removal. Mechanical night ventilation with 2 air changes also delivered cold at a good coefficient of performance of 6 with 14 kW maximum power. However, the night air exchange was too low to completely discharge the ceilings, so that the PCM material was not effective in a warm period of several days. In the ground floor offices the heat removal through the floor to ground of 2-3 W m-2 K-1 was in the same order of magnitude than the charging heat flux of the ceilings. The number of hours above 26 °C was about 10% of all office hours. The energy performance of the building is excellent with a total primary energy consumption for heating and electricity of 107-115 kW h m-2 a-1, without computing equipment only 40-45 kW h m-2 a-1. © 2009 Elsevier Ltd. All rights reserved.

Homberger J.,Stuttgart University of Applied Sciences
4OR | Year: 2010

An automated negotiation mechanism for decentralized production coordination is presented and evaluated. The coordination problem contains a set of self-interested software agents, representing the production facilities of a supply chain, searching for a mutually agreeable production plan, while taking private information into account. The negotiation mechanism is applied and evaluated using a multi-facility production coordination problem, which is a reformulation of the well-known multi-level uncapacitated lot-sizing problem (MLULSP). The basic element of the mechanism is a decentralized simulated annealing method, consisting of a transition rule carried out by a neutral mediator agent and a cooperative acceptance rule carried out by negotiating agents. We use 176 benchmark problems from relevant literature for the evaluation. Experimental results show that the proposed negotiation mechanism comes close to those results which are obtained by centralized planning. Furthermore, the developed simulated annealing method applied in a single, centralized planning task is competitive with the best known solution methods for the MLULSP. It was possible to compute new best solutions for 24 of the benchmark problems. © 2009 Springer-Verlag.

Schulze T.,Stuttgart University of Applied Sciences | Eicker U.,Stuttgart University of Applied Sciences
Energy and Buildings | Year: 2013

Natural ventilation of buildings has the potential to significantly save cooling and fan electrical energy. However, it is still not widely applied, because only limited information is available on the thermal comfort and indoor air quality of office buildings without air conditioning. Steady state ventilation air flow rates were therefore systematically simulated using both analytical and airflow network methods for different boundary conditions such as temperature and pressure differences across openings for different opening types. Coupled airflow network and dynamic building simulations were carried out to determine the annual thermal comfort and energy savings. The results for the three moderate climate locations Germany, Italy and Turkey show that while indoor air quality can be easily maintained for all opening typologies, the summer cooling potential and thermal comfort strongly depends on the natural ventilation strategy. Control over the openings is crucial for all cases, as otherwise the office rooms tend to cool down too much even in summer conditions. © 2012 Elsevier B.V. All rights reserved.

Mohammadi M.,Stuttgart University of Applied Sciences
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences - ISPRS Archives | Year: 2012

Hyperspectral data has remarkable capabilities for automatic identification and mapping of urban surface materials because of its high spectral resolution. It includes a wealth of information which facilitates an understanding of the ground material properties. For identification of road surface materials, information about their relation to hyperspectral sensor measurements is needed. In this study an approach for classification of road surface materials using hyperspectral data is developed. The condition of the road surface materials, in particular asphalt is also investigated. Hyperspectral data with 4m spatial resolution of the city of Ludwigsburg, Germany consisting of 125 bands (wavelength range of 0.4542μm to 2.4846 μm) is used. Different supervised classification methods such as spectral angle mapper are applied based on a spectral library established from field measurements and in-situ inspection. It is observed that using the spectral angle mapper approach with regions of interest is helpful for road surface material identification. Additionally, spectral features are tested using their spectral functions in order to achieve better classification results. Spectral functions such as mean and standard deviation are suitable for discriminating asphalt, concrete and gravel. Different asphalt conditions (good, intermediate and bad) are distinguished using the spectral functions such as mean and image ratio. The mean function gives reliable results. Automatisierte Liegenschaftskarte (ALK) vector data for roads is integrated in order to confine the analysis to roads. Reliable reference spectra are useful in evaluation of classification results for spectrally similar road surface materials. The classification results are assessed using orthophotos and field visits information.

Gulch E.,Stuttgart University of Applied Sciences
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences - ISPRS Archives | Year: 2012

Several flights have been undertaken with PAMS (Photogrammetric Aerial Mapping System) by Germap, Germany, which is briefly introduced. This system is based on the SmartPlane fixed-wing UAV and a CANON IXUS camera system. The plane is equipped with GPS and has an infrared sensor system to estimate attitude values. A software has been developed to link the PAMS output to a standard photogrammetric processing chain built on Trimble INPHO. The linking of the image files and image IDs and the handling of different cases with partly corrupted output have to be solved to generate an INPHO project file. Based on this project file the software packages MATCH-AT, MATCH-T DSM, OrthoMaster and OrthoVista for digital aerial triangulation, DTM/DSM generation and finally digital orthomosaik generation are applied. The focus has been on investigations on how to adapt the "usual" parameters for the digital aerial triangulation and other software to the UAV flight conditions, which are showing high overlaps, large kappa angles and a certain image blur in case of turbulences. It was found, that the selected parameter setup shows a quite stable behaviour and can be applied to other flights. A comparison is made to results from other open source multi-ray matching software to handle the issue of the described flight conditions. Flights over the same area at different times have been compared to each other. The major objective was here to see, on how far differences occur relative to each other, without having access to ground control data, which would have a potential for applications with low requirements on the absolute accuracy. The results show, that there are influences of weather and illumination visible. The "unusual" flight pattern, which shows big time differences for neighbouring strips has an influence on the AT and DTM/DSM generation. The results obtained so far do indicate problems in the stability of the camera calibration. This clearly requests a usage of GCPs for all projects, independent on the application. The effort is estimated to be even higher as expected, as also self-calibration will be an issue to handle a possibly instable camera calibration. To overcome some of the encountered problems with the very specific features of UAV flights a software UAVision was developed based on Open Source libraries to produce input data for bundle adjustment of UAV images by PAMS. The empirical test results show a considerable improvement in the matching of tie points. The results do, however, show that the Open Source bundle adjustment was not applicable to this type of imagery. This still leaves the possibility to use the improved tie point correspondences in the commercial AT package.

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