Nous avons développé un microscope versatile combinant microscopie de force (AFM) et microscopie à effet tunnel (STM) à très basse température. Ce microscope permet d'étudier la densité locale d'états électroniques (LDOS) sur des nanocircuits supraconducteurs polarisables en courant.<br />La sonde du microscope est basée sur un diapason en quartz qui permet une détection entièrement électrique des interactions pointe-surface en mode AFM et qui hors résonance propose la rigidité nécessaire à la stabilité de la jonction tunnel en mode STM. Le diapason est bien adapté à un environnement cryogénique, dissipant une énergie inférieure à 1 nW. Notre microscope atteint en mode AFM la résolution atomique selon l'axe vertical et autorise en mode STM des jonctions tunnels de consigne Rtunnel < 10 MOhms<br />Nous avons développé un procédé de nanofabrication pour mettre au point des fils supraconducteurs de niobium (Nb) ayant pour section 10 x 300 nm2. Ce procédé permet d'obtenir une surface de Nb avec une rugosité subnanométrique.<br />Nous décrivons également la fabrication des pointes que nous collons sur les diapasons pour en faire des sondes.<br />Les LDOS mesurées à T=100 mK sur les fils de Nb sont comparées à la théorie BCS prenant en compte une énergie relative au processus inélastique, appelée paramètre de Dynes. Nos mesures sont en très bon accord avec ce modèle, en prenant en compte une température électronique effective supérieure à la température du cryostat. Enfin nous mesurons la LDOS sur un fil de Nb polarisé en courant qui démontrent la faisabilité des mesures de supraconductivité hors-équilibre par STM.

In thesis thesis, studies associated with the rehabilitation of the Malatya-Narli No: 7 Railroad Tunnel are presented. The rehabilitation work includes cleaning of two collapses and stopping of deformations occurring in the tunnel as well as characterizing the rock-mass by evaluating the cores obtained from 67 drill holes. Due to two collapses ocurred in the tunnel a large sinkhole (15x10x20 meters) was developed at the surface and the tunnel closed to train traffic for 10 months (September, 2002-July, 2003) covering the initiation of Iraq War. Originally, the tunnel had been opened into the paleo-landslide material in 1930. The rock-mass surrounding the tunnel consists of limestones, metavolcanics, and schists. Although the main problem in the tunnel is the reduced tunnel span caused by displacements triggerred by underground water, poor rock mass and time dependent deformations, from engineering point of view the other problems can be sited as collapses occurred in the tunnel, sinkhole devoloped at the surface and unstable sections existing in the tunnel. During the field studies, 15 deformation monitoring stations were installed aimed at determining the deviation from tunnel alignment. In order to provide stability of the tunnel Self Drilling Anchors (Mai bolts) were installed systematically around the tunnel. The details of the rock reinforcement design was presented in this thesis.

Οι COUP-TFs είναι πυρηνικοί μεταγραφικοί παράγοντες, οι οποίοι υπάγονται στην υπεροικογένεια των πυρηνικών υποδοχέων. Τα μέλη της οικογένειας COUP-TF γενικά θεωρούνται καταστολείς της μεταγραφής και πολυάριθμοι μηχανισμοί έχουν προταθεί να υποστηρίζουν αυτή τους τη δράση. Με σκοπό να αποσαφηνιστεί ο μηχανισμός καταστολής των μελών της οικογένειας των COUP-TFs, χρησιμοποιήθηκε η μέθοδος yeast two-hybrid για να αναγνωριστούν πρωτεΐνες που εκφράζονται επίσης στον εγκέφαλο και ταυτόχρονα αλληλεπιδρούν άμεσα με μέλη της συγκεκριμένης οικογένειας. Η πρωτεΐνη CTIP1, ένα μέλος της καινούργιας οικογένειας των C2H2 πρωτεϊνών δακτύλου ψευδαργύρου, που απομονώθηκε σαν μία πρωτεΐνη που αλληλεπιδρά άμεσα με τον ARP1 και πιθανόν να εμπλέκεται στη μεταγραφική καταστολή που διαμεσολαβείται από τον ARP1, η οποία είναι ανεξάρτητη από την ευαίσθητη στην τριχοστατίνη Α αποακετυλίωση των ιστονών. Τόσο η CTIP1 όσο και η CTIP2 εκφράζονται σε μεγάλο βαθμό στον εγκέφαλο μια περιοχή για την οποία είναι γνωστό ότι εκφράζονται τα μέλη της οικογένειας των COUP-TFs, υπονοώντας ότι αυτή η καινούρια οικογένεια των πρωτεϊνών C2H2 δακτύλου ψευδαργύρου πιθανόν να εμπλέκεται στο σηματοδοτικό μονοπάτι των COUP-TFs. Στο πρώτο μέρος της παρούσας μεταπτυχιακής διατριβής, ο στόχος μας ήταν να διερευνήσουμε το πρότυπο έκφρασης της πρωτεΐνης COUP-TF Interactive Protein (CTIP) στα πρώιμα αναπτυξιακά στάδια του αχινού Paracentrotus lividus με τη μέθοδο του ανοσοφθoρισμού και να συγκρίνουμε το πρότυπο αυτό με το πρότυπο έκφρασης του COUP-TF και ταυτόχρονα να ελέγξουμε αν οι δύο αυτοί μεταγραφικοί παράγοντες αλληλεπιδρούν μέσω πειραμάτων ανοσοκατακρήμνισης. Ταυτόχρονα σημαντική ήταν και η προσπάθεια να μελετηθεί και η κατανομή των δύο ισομορφών του COUP-TF στα Μετάζωα. Το γονίδιο του COUP-TF αποτελείται, σε όλους τους μέχρι σήμερα μελετημένους οργανισμούς, από τρία εξώνια και δύο εσώνια που διακόπτουν την κωδική περιοχή του γονιδίου σε συντηρημένες θέσεις. Ωστόσο, έχει βρεθεί ότι ο αχινός Paracentrotus lividus διαφοροποιείται από αυτό το μοντέλο καθώς το γονίδιο αποτελείται από τέσσερα εξώνια (αδημοσίευτα αποτελέσματα του εργαστηρίου μας). Συγκεκριμένα, έχει βρεθεί ότι το επιπλέον εξώνιο βρίσκεται μεταξύ του πρώτου και του δεύτερου εξωνίου και έχει μέγεθος 63nt. Στο πρωτογενές μετάγραφο του COUP-TF συμβαίνει εναλλακτικό μάτισμα που έχει ως αποτέλεσμα την παραγωγή δύο m RNAs που κωδικοποιούν δύο πρωτεΐνες, οι οποίες διαφέρουν ως προς το μέγεθος λόγω της εισαγωγής 21 επιπρόσθετων αμινοξέων στην καρβόξυτελική περιοχή (CTE) της περιοχής πρόσδεσης στο DNA (DBD). Αν και πολλά δεν είναι γνωστά σχετικά με την ενδοκυτταρική τοποθέτηση κυρίως της μεγάλης ισομορφής, πειράματα EMSA ωστόσο εδειξαν οι δύο αυτές πρωτεΐνες διαφέρουν ως προς την ικανότητα πρόσδεσής τους στο DNA, με τη μεγάλη υπομονάδα του COUP να στερείται της ικανότητας να προσδένεται σε COUP στοιχείο απόκρισης. Σε μια προσπάθεια να μελετηθεί διεξοδικότερα το φαινόμενο του εναλλακτικού ματίσματος και συγκεκριμένα να διαπιστωθεί αν πρόκειται για ένα φαινόμενο συντηρημένο στα εχινοειδή, αποκλειστικό ή όχι αυτών, το συμπέρασμα που προέκυψε είναι ότι το εναλλακτικό μάτισμα είναι συντηρημένο και εμφανίζεται σταθερά στα είδη των αχινών που μελετήθηκαν (Paracentrotus lividus, Spaerechinus granularis, Strongylocentrotus purpuratus). Το εναλλακτικό μάτισμα λαμβάνει χώρα σε όλα τα στάδια από τα αγονιμοποίητα ωάρια εως τον πλουτέα και σε όλους τους ιστούς που o COUP-TF εκφράζεται (κοιλωματικά κύτταρα, μύες, έντερο). Για να μελετήσουμε την εξάπλωση του εναλλακτικού ματίσματος στα Μετάζωα, επιλέχθηκαν αντιπρόσωποι απ΄ όλες τις ομοταξίες του φύλου των Εχινόδερμων (Strongylocentrotus purpuratus, Amphiura filiformis, Patiria miniata, Marthasteria glacialis, Holothuria polii, Oxycomanthus japonicas), του φύλου των Ημιχορδωτών (Sakoglossus kowalevski), του φύλου των Χαιτόγναθων (Sagita minima), του υπόφυλου των Ουροχορδωτών (Ciona intestinalis) και του φύλου Xenoturbella (Xenoturbella bocki) για την απομόνωση ολικού RNA από καθέναν από αυτούς τους οργανισμούς. Αυτό το υλικό αποτέλεσε το υπόστρωμα για την πραγματοποίηση μιας σειράς πειραμάτων RT-PCR και Nested PCR με τη χρήση ειδικά σχεδιασμένων εκκινητών (degenerate primers). Η κλωνοποίηση των προιόντων σε κατάλληλο φορέα συνέβαλλε στην αλληλούχηση των κατάλληλων κλώνων. Παράλληλα, με το πρόγραμμα BLAST ψάξαμε για ομολογία της μικρής ισομορφής της πρωτεΐνης του COUP-TF του Paracentrotus lividus με άλλες πρωτεΐνες άλλων οργανισμών. Τα αποτελέσματα που προέκυψαν τόσο μέσα από τη νουκλεοτιδική αλληλούχηση όσο και μέσω της ηλεκτρονικής διερεύνησης συνηγορούσαν υπέρ της παρουσίας του εναλλακτικού ματίσματος ως ενός φαινομένου καθολικού που αφορά ευρύτερες (αν όχι όλες) ομάδες των Μεταζώων. / --

Semantic text matching is a fundamental task for many applications in NaturalLanguage Processing (NLP). Traditional methods using term frequencyinversedocument frequency (TF-IDF) to match exact words in documentshave one strong drawback which is TF-IDF is unable to capture semanticrelations between closely-related words which will lead to a disappointingmatching result. Neural networks have recently been used for various applicationsin NLP, and achieved state-of-the-art performances on many tasks.Recurrent Neural Networks (RNN) have been tested on text classificationand text matching, but it did not gain any remarkable results, which is dueto RNNs working more effectively on texts with a short length, but longdocuments. In this paper, Convolutional Neural Networks (CNN) will beapplied to match texts in a semantic aspect. It uses word embedding representationsof two texts as inputs to the CNN construction to extract thesemantic features between the two texts and give a score as the output ofhow certain the CNN model is that they match. The results show that aftersome tuning of the parameters the CNN model could produce accuracy,prediction, recall and F1-scores all over 80%. This is a great improvementover the previous TF-IDF results and further improvements could be madeby using dynamic word vectors, better pre-processing of the data, generatelarger and more feature rich data sets and further tuning of the parameters.

Railway foundations play an integral role in controlling the stability of the overlying track structure and the maintenance of the overall track geometry. Premature failures of railway track foundation are likely to result in frequent maintenance, which may entail significant costs since railway track foundations are less easily accessible than the other layers of railway track. Premature failures of track foundations may arise if the service loads exceed the design specifications, but may also develop as a result of the shortcomings of the design codes to simulate in situ stress paths, which involve cyclic stress changes in the horizontal as well as vertical direction, which result in principal stress rotation (PSR). Laboratory investigations have suggested that cyclic changes in the horizontal as well as vertical direction may result in a higher rate of plastic strain accumulation than cycling the vertical stress only. The effect of PSR on the soil stiffness is less certain however. Furthermore little consideration has been given to how the gradation of different soils may affect in situ drainage conditions and therefore influence the rate of railway track deterioration during PSR. A knowledge gap exists as to how cyclic changes in the directions of principal stresses may affect the pore pressure and stiffness of soils under different drainage conditions. In order to improve our understanding of the effects of PSR on the long term performance of railway track foundations, a series of laboratory tests were conducted which investigated the effects of cyclic changes in the direction of principal stresses on the pore pressure, stiffness and susceptibility to failure of saturated railway track foundation soils under different drainage conditions. The investigated sand-clay mixes were selected so as to replicate the gradation of an in situ railway track foundation. It was found that even small additions of clay to the volume of a sand significantly affected the response of the mixes during cyclic changes in principal stress direction. Moderate additions of clay in the pore space of a sand reduced the susceptibility to principal stress rotation by reducing the tendency for excess pore pressure generation and by increasing the cyclic shear stress the mixes were able to sustain before rapid plastic strain accumulation occurred. Increases in principal stress rotation below the cyclic shear threshold increased the resilient stiffness of the sand-clay mixes, however once this threshold was exceeded rapid stiffness degradation occurred. Below the cyclic shear threshold, the response of the mixes was stable over a high number of loading cycles and no abrupt fatigue failures were observed. The sand-clay mixes were sensitive to even small changes in the magnitude of PSR near the cyclic shear threshold. Small increases in PSR could trigger the sudden collapse of a previously stable sand-clay mix. Under conditions where the rate of pore pressure dissipation was regulated by the permeability and the volumetric compressibility of the soil, the sand clay mixes with moderate additions of fines were stable over a range of cyclic increases in PSR which correspond to the maximum expected changes in magnitude within the depth of a ballasted railway track foundation.

No description available.

In recent decades the Public Private Partnership (PPP) has been widely regarded as an innovative way to construct transport infrastructures and to improve the quality of service. As the number of PPP cases has increased, many countries have tried to standardise PPP models to minimise the costs of trial and error. South Korea, where 426 PPP projects have been undertaken since 1994, usually preferred the BTO (Build-Transfer-Operate) model for transport. In the BTO model, the private sector recoups its investment by charging end users directly and hence should bear the traffic demand risk. However, the Korean Government shared the demand risk through a minimum revenue guarantee to induce private sector involvement, and this led to many criticisms of the BTO model. Tariffs in the BTO case were much higher than those of public operators, but the Government still had to pay large amounts of guaranteed revenue. Thus, BTL (Build-Transfer-Lease), where the demand risk is on the public sector, has become an alternative model. The BTL is the “service sold to the public sector” model which is similar to the DBFO (Design-Build-Finance-Operate) in the UK. This thesis examines which of the BTO and the BTL PPP models is optimal to save governmental expenditure for transport infrastructures such as road and rail. Appropriate traffic demand risk sharing, which a particularly controversial issue in South Korea, is explored. These research objectives are examined through five case studies: the Incheon Airport Expressway and the Oksan-Ochang Expressway cases for road PPP; the Incheon Airport Railway, the Daegok-Sosa Railway and the Seoul Metro 9 cases for rail PPP. Through a detailed literature review and five case studies, the thesis shows that the optimal PPP model, which is measured by the VFM (Value for Money) assessment, needs to satisfy the interests of public sector, private sector, and end users. Based on these assessments and including these three viewpoints, it is concluded that the optimal PPP model for road can be the BTL where the public sector can save expenditure or reduce the level of tariff. Traffic demand risk for roads is relatively low, so the public sector does not have to transfer it to the private sector with high profit rate. In the case of rail, the limited revenue and high cost make a project difficult to be financially free standing by the BTO model. However, the BTO can be a better option in urban rail if traffic demand risk is shared appropriately.

The relationship between computer technology and supervision is examined with reference to new empirical evidence drawn from a study of the computerisation of freight operations in British Rail. Attention is focused on the extent to which computerisation allows for a more integrated system of management control, and the possibility of devolving additional elements of control from middle management to the local supervisory level. Contemporary research often claims that the first-line supervisor is becoming more peripheral to the direct control of operations, as computerised equipment takes over the execution of many supervisory tasks, and as operatives who are skilled in the use of new technology overtake the apparent skill superiority of first-line supervisors. This thesis contends that it is misleading to focus on the 'pure' role of the first-line supervisor when studying the effects of computer technology on supervision. The main body of empirical data is drawn from an in-depth study of the effects of change in five traditional marshalling yards in three British Rail regions. The case study examines how the application of a comprehensive computer system to process and transmit information over diverse and spatially distant freight yards can transform the distribution of responsibilities for operational control within management. It is argued that the redistribution of management control functions over a network of organisational levels has resulted in a far more complex redefinition of supervision than is implied by the apparent erosion of the role of the first-line supervisor. A broader conception of supervision is presented in order to explain changes in the distribution of supervisory tasks across various supervisory levels, within the context of changes in work organisation and the system of management control. Finally, it is argued that whilst computerisation may erode the traditional basis of supervision, it may also result in the emergence of a new type of computer-oriented supervisor, whose role is to use the 'realtime' information provided by the computer to co-ordinate and control previously diverse areas of production or service operations.

While technical failures remain the most common triggers for overruns in metro projects, the causes have not typically been deficiencies in the underlying engineering principles but in project management. This work involves the complementary use of requirements and risk management processes and real options theory. The Crossrail project provides a case study with a scheme design for an underground station at Farringdon being considered in detail. The requirements process documented in this research is capable of providing an interactive format for managing project requirements and importantly, any changes that are made to them. This is achieved using commercial software (Telelogic DOORS®) and it is shown that this process is effective when working on multidisciplinary metro projects. This process is then expanded to consider the interaction between risks on a project. This is identified as being crucial given the impacts that technical, project and external risks can have on each other. The developed risk process therefore allows the interactions between all risks to be recorded and provides a holistic view of all risks for management purposes. The requirements and risk processes are complemented by a fuzzy logic methodology to evaluate global and elemental risks (such as political or client risks). Over 50 external risk factors which are known to have caused overruns on previous projects are identified and the performance of Crossrail is evaluated against each risk factor by way of a questionnaire circulated to industry professionals. An approach to avoiding cost overruns is demonstrated by the application of real options theory where the chosen design for Farringdon station is developed alongside an alternative design. Real options theory is used to value the cost of implementing the design alternative should it be needed during the project construction cycle due to cost increases and the potential occurrence of major risks. This implementation cost is presented as a fixed cost agreed prior to construction rather than being an added cost to the agreed budget once construction has started. It is proposed that using real options in this context can avoid significant cost overruns by predetermining the value of payments to be made for changing from one design to another. This thesis will show how additions and adjustments to existing processes and the inclusion of real options valuation in the procurement of metro projects can help practitioners avoid cost overruns in a metro rail project.

The research described in this dissertation centres on the application of a discipline of formal methods in railway signalling system design. A generic abstract model of railway track networks and signals has been developed in Higher-Order Logic(HOL). It consists of several theories arranged in a hierarchy. Railway track networks are modelled by a class of constraint labelled directed graphs. HOL theories of graphs and paths have been developed for representing track networks. HOL theories modelling individual track components and signals have also been developed. These theories are then combined to create a theory of track network. Three applications of this model are described. The first is a network verifier which verifies a formal specification of track layout against its abstract model by proving theorems automatically. The second application is to extract information from the specifications and to create control tables automatically. Lastly, a method of modelling the interlocking processor using finite state machines is described. Although this research has centred on railway signalling, it can be viewed as a case study of how to apply formal methods in the analysis and design of safety- critical systems. The approach and methods used can be generalized in order to be useful in other industries.