Analytical Survey of Construction Change Systems: Gaps & Opportunities

AbstractThis paper surveys the studies on construction change systems and reveals some of the potential future works. It is tried to pick up the critical works to derive a true timeline of the systems. The findings show that leaping from best practice guides in late 1990s and generic process models in early 2000s to very advanced modelling environments in mid 2000s and early 2010s have made gaps along with opportunities for change researchers in order to develop some more easy and applicable models. Another finding is that there is a compelling similarity between the change and risk prediction models. So, integrating these two concepts, specifically from proactive management point of view, may lead to a synergy and help project teams avoid rework. Also, the findings show that exploitation of cause- effect relationship models, in order to facilitate the dispute resolutions, seems to be an interesting field for future works

Using System Dynamics to Study the Effect of Change Orders on Labor Productivity

Change orders in construction projects lead to numerous negative impacts, including loss of labor productivity, delays, and cost overruns. Owners and contractors are usually in disagreement when it comes to allocating the extent of responsibilities with respect to the resulting overruns. Each party tries to hold the other party fully responsible for such overruns through a series of claims and disputes. Several delay analysis techniques have been developed to aid in settling such disputes, however, they do not fully grasp the rippled impacts of change orders and do not assist parties in reaching consensus when it comes to finding the isolated rippled impacts of each change order. This research aims to develop a framework that supports delay analysis based on dynamic modeling with a focus on the impacts of change orders. System dynamics is utilized as the base modeling methodology due to its capability of capturing rippled impacts and complex interrelations. A novel calibration methodology is also developed to enable using this framework in any construction project. After development and verification, the framework was tested on a sample construction project that faced delays due to change orders. The developed model was able to quantitatively link the productivity losses and delays to each change order, which helped in clearly allocating the responsible parties for the delays. In addition, several what-if-scenarios were conducted to enhance the understanding of how such impacts could have been avoided. This research is envisaged to support owners and contractors in quickly reaching consensus regarding the impacts of change orders; thus, minimizing the corresponding disputes and fostering a healthier contracting environment

Understanding and managing iterative error and change cycles in large-scale concurrent design and construction projects

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2006.Vita.Includes bibliographical references (v. 1, leaves 174-180).Construction projects are uncertain and complex in nature. One of the major driving forces that may account for these characteristics is iterative cycles caused by errors and changes. Errors and changes worsen project performance and consequently, cause schedule and cost overruns to be prevalent. In particular, these iterative cycles are more detrimental when large-scale concurrent design and construction is applied. In an effort to address these issues, this research proposes Dynamic Planning and control Methodology (DPM) as a robust design and construction planning methodology for large-scale concurrent design and construction. The proposed DPM is composed of: 1) an error and change management framework that enables understanding of the construction processes associated with errors and changes and how they affect construction performance; 2) a proactive buffering strategy for reducing sensitivity to iterative error and changes cycles; 3) a System Dynamics-based construction project model which provides policy guidelines for the planning and control of projects; and(cont.) 4) a web-based error and change management system, which supports coordination of errors and changes among contractors and design professionals without hardware and software compatibility issues. Applying all research components into a couple of real world case projects, this research concludes that a concurrently developed project can benefit by: 1) adding realism to planning taking into account iterative error and change cycles; 2) implementing a proactive mechanism to look and act ahead against uncertainties; 3) making appropriate policies with the help of the system dynamics-based simulation model; and 4) facilitating coordination from the IT-supported management system; even if the time frame of a project is shortened. Also, future research opportunities are discussed extending the findings from this research.by SangHyun Lee.Ph.D

Computational modelling of latent heat storage systems with integrated phase change materials in building applications

89 σ.Εθνικό Μετσόβιο Πολυτεχνείο--Μεταπτυχιακή Εργασία. Διεπιστημονικό-Διατμηματικό Πρόγραμμα Μεταπτυχιακών Σπουδών (Δ.Π.Μ.Σ.) “Υπολογιστική Μηχανική”Ο σκοπός αυτής της διπλωματικής εργασίας είναι να εκτιμήσει την επίδραση θερμικών συστημάτων, τα οποία ενσωματώνουν υλικά αλλαγής φάσης, με την ανάπτυξη υπολογιστικών εργαλείων. Στην εισαγωγή, μια σύντομη θεώρηση καταλήγει στο ότι, ο σύγχρονος τρόπος ζωής απαιτεί μεγάλες ποσότητες ενέργειας στον κτιριακό τομέα, ούτως ώστε να καλυφθούν οι ανάγκες φωτι- σμού και θερμικής άνεσης. Τα συστήματα αερισμού, θέρμανσης και κλιματισμού καταναλώνουν, ίσως, την περισσότερη ενέργεια, και για τον λόγο αυτό η απόδοσή τους παίζει σημαντικό ρόλο στην εξοικονόμηση ενέργειας. Μία, σχετικά, νέα γενιά εφαρμογών μπορεί να καταστήσει τα συστήματα αυτά πιο αποδοτικά. Οι εφαρμογές αυτές υιοθετούν την χρήση υλικών αλλαγής φάσης. Τα υλικά αυτά μπορούν και συσσωρεύουν ενέργεια υπό την μορφή λανθάνουσας θερμότητας. Με τον τρόπο αυτό επιτυγχάνεται η θερμοκρασιακή ομοιομορφία. Επίσης, η αποθηκευμένη θερμότητα μπορεί να χρησιμοποιηθεί σε μελοντικό χρόνο. Τα υλικά αυτά, ο τρόπος λειτουργίας τους, καθώς και τα ιδιαίτερα χαρακτηριστικά τους μελετώνται στο δεύτερο κεφάλαιο. Στις περιπτώσεις που μελετώνται, οι κτιριακές εγκαταστάσεις θερμαίνονται λόγω της ηλιακής ακτινοβολίας. Επίσης, λόγω θερμοκρασιακών διαφορών, παρατηρούνται φαινόμενα φυσικής συναγωγής. Για τους λόγους αυτούς, ο ρόλος του τρίτου κεφαλαίου είναι να λειτουργήσει ως μια εισαγωγή σε φαινόμενα μεταφοράς και ρευστοδυναμικής. Επιπροσθέτως, θα αποδειχθεί, ότι η αναλυτική επίλυση του θερμοκρασιακού και του ροϊκού πεδίου είναι αδύνατη, συνεπώς η αριθμητική προσέγγιση κρίνεται απαραίτητη. Στοιχεία της υπολογιστικής μεθόδου των πεπερασμένων όγκων θα κλείσουν το κεφάλαιο αυτό. Στο τέταρτο κεφάλαιο, λαμβάνει χώρα η υπολογιστική μελέτη δύο περιπτώσεων. Αρχικά, περιγράφεται η πειραματική μελέτη συστήματος περσίδων, στο οποίο έχει εγκατασταθεί υλικό αλλαγής φάσης. Εν συνεχεία, αναλύονται τα χαρακτηριστικά του υπολογιστικού μοντέλου. Τελικά, παρουσιάζονται τα αποτελέσματα της προσομοίωσης, τα οποία παρέχουν ικανοποιητική συμφωνία με τις τιμές του πειράματος, παρέχοντας πιστοποίηση στο υπολογιστικό εργαλείο. Στο δεύτερο σκέλος, μελετήθηκε ένα νέο σύστημα, το οποίο αποτελείται από περιστρεφόμενες περσίδες. Οι περσίδες ενσωματώνουν ένα στρώμα μονωτικού καθώς και υλικό αλλαγής φάσης. Εκτιμήθηκε η επίδραση του συστήματος στην θερμική συμπεριφορά εξωτερικού τοιχώματος, υπό δύο διαφορετικές κλιματικές συνθήκες. Τα αποτελέσματα δείχνουν ευνοϊκή επίδραση έναντι σε περιπτώσεις χωρίς την εγκατάσταση του συστήματος. Ωστόσο, προτείνονται συμπληρωματικές προσομοιώσεις και βελτιώσεις στο υπολογιστικό μοντέλο, για την εξαγωγή περαιτέρω χρήσιμων συμπερασμάτων. Τέλος, γενικά συμπεράσματα και προτάσεις για μελλοντική δουλειά κλείνουν αυτή την διπλωματική. Τα υλικά αλλαγής φάσης παρουσιάζουν θετικό αντίκτυπο σε κτιριακές εφαρμογές, ενώ το υπολογιστικό εργαλείο, που αναπτύχθηκε, δείχνει να έχει δυνατότητες εξέλιξης.The purpose of this thesis is to assess the effect of thermal systems that incorporate phase change materials, with the development of a computational tool. In the introduction, a brief consideration concludes, that the modern way of life requires large amounts of energy in the building sector, in order to meet the needs of lighting and thermal comfort. The ventilation, heating and air conditioning systems consume more energy, and therefore their performance plays a significant role in saving energy. A, relatively, new generation of applications can make these systems more efficient. These applications adopt the use of phase change materials. These materials can store energy in the form of latent heat. Thereby, it is necessary to study their behaviour, their advantages and, also, their limitations. In addition, previous works were investigated. This contributed in gaining insight and, also, a valuable fashion to treat the heat capacity: the effective heat capacity method. These topics are discussed in the second part. The investigated cases in this work, present complicated features: the buildings are heated with thermal radiation, natural convection is observed and multi-layer objects are employed. Hence, the role of the third chapter is to serve as an introduction to heat transfer phenomena and fluid dynamics. It is discussed, that an analytical approach on the temperature and flow fields is impossible. Hence, the computational method of finite volume will close this chapter The fourth chapter presents the computational study of two cases. Initially, the experimental study of a blind, which integrated a phase change material, is described. Then, the characteristics of the numerical model are presented. Eventually, the results of the simulation show a very good agreement to the experiment, verifying the method. Furthermore, a new developed system is investigated under two different environment conditions. This system consists of slats, in which an insulation layer and a phase change material are embedded. It will be installed on walls of existing building to improve their thermal characteristics. The results show the beneficial role of the specific applications in the summer period. More tests should be performed to obtain more useful information for winter days as well. In addition, an overview reveals the positive and negative features of this method, and countermeasures are suggested. Finally, general remarks of this work with comments and overall observations conclude this work. Thermal energy storage systems have, in general, a positive impact and we can gain the most out of them with careful design. The presented numerical method is considered suitable to simulate heat transfer phenomena and future simulation work is outlined.Ιωάννου Νικόλαο

Design, modelling and control of a brachiating power line inspection robot

The inspection of power lines and associated hardware is vital to ensuring the reliability of the transmission and distribution network. The repetitive nature of the inspection tasks present a unique opportunity for the introduction of robotic platforms, which offer the ability to perform more systematic and detailed inspection than traditional methods. This lends itself to improved asset management automation, cost-effectiveness and safety for the operating crew. This dissertation presents the development of a prototype industrial brachiating robot. The robot is mechanically simple and capable of dynamically negotiating obstacles by brachiating. This is an improvement over current robotic platforms, which employ slow, high power static schemes for obstacle negotiation. Mathematical models of the robot were derived to understand the underlying dynamics of the system. These models were then used in the generation of optimal trajectories, using nonlinear optimisation techniques, for brachiating past line hardware. A physical robot was designed and manufactured to validate the brachiation manoeuvre. The robot was designed following classic mechanical design principles, with emphasis on functional design and robustness. System identification was used to capture the plant uncertainty and a feedback controller was designed to track the reference trajectory allowing for energy optimal brachiation swings. Finally, the robot was tested, starting with sub-system testing and ending with testing of a brachiation manoeuvre proving the prospective viability of the robot in an industrial environment

EIU Graduate Catalog 1990-1991

https://thekeep.eiu.edu/gradcatalogs/1011/thumbnail.jp

Civil society leadership in the struggle for AIDS treatment in South Africa and Uganda

Includes abstract.Includes bibliographical references.This thesis is an attempt to theorise and operationalise empirically the notion of ‘civil society leadership’ in Sub-Saharan Africa. ‘AIDS leadership,’ which is associated with the intergovernmental institutions charged with coordinating the global response to HIV/AIDS, is both under-theorised and highly context-specific. In this study I therefore opt for an inclusive framework that draws on a range of approaches, including the literature on ‘leadership’, institutions, social movements and the ‘network’ perspective on civil society mobilisation. This framework is employed in rich and detailed empirical descriptions (‘thick description’) of civil society mobilisation around AIDS, including contentious AIDS activism, in the key case studies of South Africa and Uganda. South Africa and Uganda are widely considered key examples of poor and good leadership (from national political leaders) respectively, while the Treatment Action Campaign (TAC) and The AIDS Support Organisation (TASO) are both seen as highly effective civil society movements. These descriptions emphasise ‘transnational networks of influence’ in which civil society leaders participated (and at times actively constructed) in order to mobilise both symbolic and material resources aimed at exerting influence at the transnational, national and local levels

Space station systems: A bibliography with indexes (supplement 9)

This bibliography lists 1,313 reports, articles, and other documents introduced into the NASA scientific and technical information system between January 1, 1989 and June 30, 1989. Its purpose is to provide helpful information to researchers, designers and managers engaged in Space Station technology development and mission design. Coverage includes documents that define major systems and subsystems related to structures and dynamic control, electronics and power supplies, propulsion, and payload integration. In addition, orbital construction methods, servicing and support requirements, procedures and operations, and missions for the current and future Space Station are included

Development of a Nonlinear Estimator-Based Model of Pilot Performance During Brownout Conditions

During conditions of visual occlusion, pilots are forced to rapidly adapt their scan to accommodate the new observable states via instruments rather than the visual environment. During this transition, the provision of aircraft state information via other than visual modalities improves pilot performance presumably through the increase in situational awareness provided immediately following the visual occlusion event. The Tactile Situational Awareness System (TSAS) was developed to provide continuous position information to the pilot via tactile rather than visual means. However, as a low-resolution display, significant preprocessing of information is required to maximize utility of this new technology. Development of a nonlinear time varying estimator based multivariable model enables more accurate reproduction of pilot performance than previous models and provides explanations of many observed phenomena. The use of LQR feedback and an optimal estimator is heuristically consistent with reported strategies and was able to match pilot incorporation of multi-modal displays. Development of a nonlinear stochastic map of pilot move-and-hold control performance was able to accurately match increased pilot control noise at higher frequencies, a phenomenon formerly attributed to closed loop neuromuscular effects. The continued improvement of this model could eventually result in the early stage mathematical prediction of the effectiveness of emerging cockpit technology and preprocessing algorithms, prior to costly hardware development and flight evaluation