Using various molecular line and continuum emission criteria, we have selected a sample of six isolated, dense concentrations of molecular gas, i.e., “cores”, which are either starless (L694-2, L429, L1517B, and L1689-SMM16) or contain a protostellar Very Low Luminosity Object (VeLLO) and are currently experiencing gravitational collapse (L1014 and L1521F). Studying the molecular emission from dense gas tracers toward this sample of cores will help us gain a more detailed image of the internal physical conditions of dense cores and their evolution. We observed the cores in our sample in NH3 (1,1) and (2,2) emission using the Green Bank Telescope (GBT) and in N2H+ (1−0) emission using the Nobeyama Radio Observatory (NRO). L429 shows the most complicated structure among the cores in our sample. Also, the maxima of molecular line integrated intensities and dust continuum emission toward L429 show a significant offset. The rest of the cores in our sample are roughly round and the morphologies of line integrated intensities follow that of the corresponding continuum emission closely. Cores in our sample have gas kinetic temperatures ∼ 9 − 10 K and therefore show comparable thermal velocity dispersions. L429 and L1517B are, respectively, the most turbulent and most quiescent cores in our sample. Finally, L1521F is the most centrally concentrated core of our sample. L1689-SMM16 is the least previously studied core in our sample and had not yet been probed in molecular emission. Jeans and virial analyses made using updated measurements of core mass and size confirm that L1689-SMM16 is prestellar, i.e., gravitationally bound. It also has accumulated more mass compared to its corresponding Jeans mass in the absence of magnetic fields and therefore is a “super-Jeans” core. The high levels of X(NH3)/X(N2H+) and deuterium fractionation reinforce the idea that the core has not yet formed a protostar. Comparing the physical parameters of the core with those of a Bonnor-Ebert sphere reveals the advanced evolutionary stage of L1689-SMM16 and shows that it might be unstable to collapse. We do not detect any evidence of infall motions toward the core, however. Instead, red asymmetry in the line profiles of HCN (1−0) and HNC (1−0) indicates expansion of the outer layers of the core at a speed of ∼ 0.2 − 0.3 km s−1. For a gravitationally bound core, expansion in the outer layers might indicate that L1689-SMM16 is experiencing oscillations. Radiative transfer modelling of NH3 emission toward L694-2 and L1521F at low and high spatial resolutions show that the less evolved core, L694-2, is best described by relatively constant radial profiles of temperature and fractional NH3 abundance. On the other hand, L1521F, which contains a protostellar VeLLO, is best described by a radial abundance profile that is enhanced toward the core centre and a radial temperature profile that decreases toward the core centre. Comparison of our results with previous studies on L1544, a well-studied starless core, imply that as dense cores evolve and progress toward the moment of collapse, they become more centrally concentrated. As a result, the gas temperatures at their centres decrease, leading to increase in levels of CO depletion factor and increase in NH3 fractional abundance toward the centre. / Graduate

The world shipping freight market for the transportation of bulk cargo - liquid and dry - is characterised by the somewhat erratic and extreme fluctuations exhibited by many of the measures that can be used to describe the "state" of the market. Such 'measures' include the spot freight rates - the cost to the shipper of chartering a unit of shipping capacity 'on the spot' (that is, not reserving the vessel in advance), - the proportion of chartered tonnage at any time taken on a period (time) basis as opposed to a voyage (single) basis, and the rate at which orders for new vessels reach the shipyards. These factors are extremely variable, and have exhibited a similar form of behaviour for a large number of years. This present thesis describes an attempt to investigate the behaviour of the freight market (bulk cargo); the aim of the investigation being to identify the structure of the market system and to construct a System Dynamics model which describes the complex relationships in the market and which can be used to explore questions relating to present or future market behaviour. The construction of such a model is described, together with an exhaustive chapter on the analysis of the model, covering loop-analysis, the behaviour of the model under various test inputs, and the senstivity of the model to significant changes in parameter values. The final chapter considers the use of the model, and, in particular, describes its use in an investigation of the feasibility or desirability of introducing tonnagestabilization schemes into the market. Such schemes aim to prevent the freight rates from falling to unacceptably low values, by implementing a scheme whereby tonnage is withdrawn from operation and laid-up: the decrease in the supply of tonnage then has a positive influence on the freight rates. It is concluded that the problems involved in designing such schemes preclude the schemes from implementation. The appendices cover the various data used in the determination of market relationships, as well as the computer listing, in Fortran, of the market model. Also included in an appendix is a description of the application of System Dynamics to a hypothetical company. The tcompany model' allows for the examination of chartering policies and lay-up policies under a variety of conditions of market demand.

A long-standing question in evolutionary biology is whether adaptation will typically proceed through a few mutations with large selective effects or many mutations with small effects. Many studies have implicated few loci of major effect, but it has been predicted that small-effect mutations should exist and contribute to adaptation. However, such mutations have not been found in many studies, either because they do not exist or because the experimental design limited their detection. To determine the effects and types of mutations contributing to adaptation, I studied laboratory and wild populations of bacteria. I characterized the distribution of the effect sizes in laboratory populations of an aerobic bacterium, Methylobacterium extorquens, and studied the types of genetic changes associated with adaptation to a novel host in wild populations of Mycoplasma gallisepticum.

Today agriculture sector has a big contribution to the development of economy for many countries. Irrigation is a method which supplies amount of water required in proper time to the cropped land and contributes to the increases of agriculture productivity. Using diesel pump to deliver water to the place of use causes problems both in terms of profitability and environmental perspectives. Higher price of diesel increases operation costs of diesel water pumping system thereby reducing the incomes. In addition the use of diesel pump emits a huge amount of CO2 emissions which cause global warming. A possible solution to those problems is to use solar energy, a source of energy which is environmental friend and available for free. The main target of this thesis is to design and optimize a cost effective PVWPs considering three alternatives with tank storage, battery storage and a system without storages medium. The two areas in Eastern province of Rwanda were taken as case study to grow coffee and cassava with five hectares each. To run simulations, different tools have been used. Those includes CROPWAT to determine water requirements for two crops; MS Excel to design a PVWPs directly connected to irrigation system, make economic analysis, evaluate CO2 emissions and calculate other parameters. Furthermore in PVsyst software the design and simulation for PVWPs with storages medium has been carried out.  Results showed that using PVWPs directly connected to irrigation system is the most profitable way when compared to the rest two alternatives.  They also showed that systems designed to irrigate coffee becomes the most profitable due to huge amount of electricity surplus and higher price per kilogram of coffee. Finally fully replacement of DWPs results in annual reduction of CO2 emissions by 6.6 tonnes. Keywords: Photovoltaic system, storages medium, pumping system, economic analysis, reduction in CO2 emissions.

In this thesis I focus mainly in studying the process of star formation in both high redshift, and local star forming galaxies, by using an observational technique called integral field spectroscopy (IFS). Although these investigations are aimed at studying the star formation properties of these objects, throughout this work I will also discuss the geometric, kinematic, and chemical structures in the inter-stellar medium of these galaxies, which are intimately connected with the process of star formation itself. The studies presented here were conducted under the umbrella of two different projects. First, the HETDEX Pilot Survey for Emission Line Galaxies, where I have studied the properties of Ly-alpha emitting galaxies across the 2<z<4 range, with an emphasis in trying to understand the process by which Ly-alpha photons, produced in large quantities in the active star forming regions, are able to escape the ISM of these objects, allowing us to detect them in the Ly-alpha line. The second project from which results are presented here is the VIRUS-P Exploration of Nearby Galaxies (VENGA), an ongoing campaign to obtain spatially resolved spectroscopy over a broad wavelength range for large portions of the disks of 30 nearby spiral galaxies. In this thesis, the VENGA data is used to study the physical parameters that set the rate of star formation in the different environments present within galaxies in the local universe. / text

Wireless services have become an indispensable part of our social, economic, and everyday activities. They have facilitated and continue to facilitate rapid access to information and have created a highly-interconnected web of users who are untethered to particular locations. In fact, it is expected that in the very near future, the number of users that access the Internet through their mobile devices will surpass those access the Internet from the fixed infrastructure. Aside from mobile Internet access, wireless technologies enable many critical applications such as emergency response, healthcare and implantable medical devices, industrial automation, tactical communications, transportation networks, smart grids, smart homes, navigation, and weather services. The proliferation and wealth of wireless applications has created a soaring demand for ubiquitous broadband wireless access. This demand is further fueled by the richness of the information accessed by users. Low-bit rate voice communications and text have been replaced with graphics, high-definition video, multi-player gaming, and social networking. Meeting the growing traffic demand poses many challenges due to the spectrum scarcity, the cost of deploying additional infrastructure, and the coexistence of several competing technologies. These challenges can be addressed by developing novel wireless technologies, which can efficiently and securely manage multi-user access to the wireless medium. The multi-user access problem deals with the sharing of the wireless resource among contending users in an efficient, secure, and scalable manner. To alleviate contention and interference among the multiple users, contemporary wireless technologies divide the available spectrum to orthogonal frequency bands (channels). The availability of multiple channels has been demonstrated to substantially improve the performance and reliability of wireless networks by alleviating contention and interference. Multi-channel networks, whether cellular, sensor, mesh, cognitive radio, or heterogeneous ones, can potentially achieve higher throughput and lower delay compared to single-channel networks. However, the gains from the existence of orthogonal channels are contingent upon the efficient and secure coordination of channel access. Typically, this coordination is implemented at the medium access control (MAC) layer using a multi-channel MAC (MMAC) protocol. MMAC protocols are significantly more sophisticated than their single-channel counterparts, due to the additional operations of destination discovery, contention management across channels, and load balancing. A significant body of research has been devoted to designing MMAC protocols. The majority of solutions negotiate channel assignment every few packet transmissions on a default control channel. This design has several critical limitations. First, it incurs significant overhead due to the use of in-band or out-of-band control channels. Second, from a security standpoint, operating over a default control channel constitutes a single point of failure. A DoS attack on the control channel(s) would render all channels inoperable. Moreover, MMAC protocols are vulnerable to misbehavior from malicious users who aim at monopolizing the network resources, or degrading the overall network performance. In this dissertation, we improve the security and spectral efficiency of channel access mechanisms in multi-channel wireless networks. In particular, we are concerned with MAC-layer misbehavior in multi-channel wireless networks. We show that selfish users can manipulate MAC-layer protocol parameters to gain an unfair share of network resources, while remaining undetected. We identify possible misbehavior at the MAC-layer, evaluate their impact on network performance, and develop corresponding detection and mitigation schemes that practically eliminate the misbehavior gains. We extend our misbehavior analysis to MAC protocols specifically designed for opportunistic access in cognitive radio networks. Such protocols implement additional tasks such as cooperative spectrum sensing and spectrum management. We then discuss corresponding countermeasures for detecting and mitigating these misbehavior. We further design a low-overhead multi-channel access protocol that enables the distributed coordination of channel access over orthogonal channels for devices using a single transceiver. Compared with prior art, our protocol eliminates inband and out-of-band control signaling, increases spatial channel reuse, and thus achieves significant higher throughput and lowers delay. Furthermore, we investigate DoS attacks launched against the channel access mechanism. We focus on reactive jamming attacks and show that most MMAC protocols are vulnerable to low-effort jamming due to the utilization of a default control channel. We extend our proposed MMAC protocol to combat jamming by implementing cryptographic interleaving at the PHY-layer, random channel switching, and switching according to cryptographically protected channel priority lists. Our results demonstrate that under high load conditions, the new protocol maintains communications despite the jammer's effort. Extensive simulations and experiments are conducted to evaluate the impact of the considered misbehaviors on network performance, and verify the validity of the proposed mechanisms.

Στην παρούσα διπλωματική εργασία ϑα µελετηθεί η συµπεριφορά των γραµµών διανομής μέσης τάσης, όταν αυτές πλήττονται από κεραυνούς, είτε άµεσα είτε έµµεσα. Οι κεραυνοί είναι ένα ϕυσικό ϕαινόµενο µε επικίνδυνες συνέπειες για την ασϕάλεια των ανθρώπων, κτιρίων και ηλεκτρικών εγκαταστάσεων. Οι γραµµές του ηλεκτρικού δικτύου (είτε υψηλής, είτε μέσης, είτε χαµηλής τάσης) είναι ευάλωτες σε πλήγµατα κεραυνών. Όταν ένας κεραυνός πλήξει άµεσα µια γραµµή ή το γειτονικό της έδαφος, τότε ϑα εµφανισϑούν σϕάλµατα στο ηλεκτρικό δίκτυο υπό µορφή επικίνδυνων υπερτάσεων. Οι υπερτάσεις αυτές σε πολλές περιπτώσεις µπορεί να υπερβαίνουν την κρουστική τάση αντοχής της µόνωσης του δικτύου, µε αποτέλεσµα, αν δεν υπάρχουν διατάξεις προστασίας, να διασπαστεί το διάκενο, προκαλώντας ανεπανόρθωτη ζηµιά στον εξοπλισµό µας. Η µελέτη για τη συµπεριφορά των εναέριων γραµµών διανοµής εµπεριέχει αρκετές προσεγγίσεις. Μερικές από αυτές αφορούν κάποιες βασικές παραµέτρους, όπως η πυκνότητα των κεραυνών στο έδαφος (GFD) και το πλήθος των άµεσων πληγµάτων στη γραµµή. Προκειµένου να εξάγουµε ασϕαλή δεδοµένα, συµβουλευόµαστε τους αντίστοιχους µετεωρολογικούς πίνακες-χάρτες ( π.χ. ισοκεραυνικοί χάρτες). Στο πρώτο κεφάλαιο της εργασίας γίνεται παρουσίαση της µορφής των συστηµάτων ηλεκτρικής ενέργειας µε ιδιαίτερη έµφαση στο σύστηµα διανοµής. Παρουσιάζεται η δοµή του συστήµατος διανοµής, τα επιµέρους τμήματα και εξαρτήµατα από τα οποία αποτελείται, καθώς και τα χαρακτηριστικά τους. Στο τέλος του κεφαλαίου παρουσιάζονται δεδοµένα και στατιστικά του ελληνικού συστήµατος διανοµής. Στο δεύτερο κεφάλαιο, γίνεται µια σύντοµη παρουσίαση των σϕαλµάτων και υπερτάσεων που παρουσιάζονται στο σύστηµα διανοµής, καθώς και των µέσων προστασίας που χρησιµοποιούµε προκειµένου να εξασϕαλίσουµε την αδιάλειπτη λειτουργία και ακεραιότητα του συστήµατος µας. Στο τρίτο κεφάλαιο παρουσιάζεται το ϕυσικό ϕαινόµενο του κεραυνού, καθώς και τα βασικά χαρακτηριστικά αυτού. Εξετάζονται τα είδη των κεραυνών και η εξοµοίωσή τους σε εργαστηριακές συνθήκες µέσω κρουστικής τάσης για δοκιµές της αντοχής των µονώσεων. Στο τέταρτο κεφάλαιο περιγράφεται η οδηγία της IEEE για τη συµπεριφορά των εναέριων γραµµών διανοµής ηλεκτρικής ενέργειας έναντι κεραυνών. Σκοπός του κεφαλαίου είναι η παρουσίαση εναλλακτικών λύσεων για τη µείωση των βραχυκυκλωµάτων που προκαλούνται από κεραυνό στις εναέριες γραµµές. Συγκεκριµένα, προσδιορίζεται η συµπεριφορά των εναέριων γραµµών διανοµής σε περίπτωση πτώσης κεραυνού (πλήγµατα κεραυνών και βραχυκυκλώµατα από επαγόµενη τάση), το επίπεδο µόνωσης των γραµµών διανοµής, η προστασία των γραµµών διανοµής µε προστατευτικό αγωγό, καθώς και η προστασία των γραµµών με αλεξικέραυνα. Στο πέµπτο κεφάλαιο της εργασίας, γίνεται επεξεργασία και μελέτη των καταγρεγραμένων σφαλµάτων και βλαβών λόγω πτώσεως κεραυνών στο δίκτυο μέσης τάσης, σε µετασχηµατιστές και σε γραµµές διανοµής Μ.Τ., κατά την διάρκεια της επταετίας 2005-2011 στο νομό Αιτωλοακαρνανίας. Υπολογίζεται αναλυτικά ο ϑεωρητικός αριθµός σφαλµάτων σύµϕωνα µε την οδηγία της IEEE, και στη συνέχεια γίνεται σύγκριση µε τα πραγµατικά σφάλµατα που έχουν καταγραφεί από τις υπηρεσίες της ∆.Ε.Η. στην πόλη του Αγρινίου, µε σκοπό την εξαγωγή χρήσιμων συµπερασµάτων. Γενικά, προκύπτουν αποκλίσεις της θεωρητικής εκτίμησης από τα πραγματικά δεδομένα των καταγραφών, γεγονός που οφείλεται τόσο στον προσεγγιστικό χαρακτήρα της θεωρητικής εκτίμησης, όσο και σε πιθανά λάθη, εξ’ αιτίας της εμπλοκής του ανθρώπινου παράγοντα, στην καταγραφή των πραγματικών σφαλμάτων. Παρ’ όλα αυτά, η απόκλιση αυτή είναι θετική (τα θεωρητικά υπολογισμένα σφάλματα είναι, δηλαδή, περισσότερα από τα καταγεγραμμένα), γεγονός που δεν μειώνει την αξία της εκτίμησης που μας προσφέρει το χρησιμοποιούμενο μοντέλο. / This thesis studies the behavior of medium voltage distribution lines, after being stroked by lightning – directly or indirectly. The lightning is a natural phenomenon, with dangerous impacts on human safety, buildings or electricity premises. The electricity network lines (either of high, medium or low voltage) are prone to lightning strikes. When a lightning strikes a distribution line (or the ground nearby), then faults occur at the distribution network, in the form of dangerous overvoltage. Such overvoltage may in many cases exceed the shock impulse of network’s insulation resistance. As a result, in case no safety arrangements exist, this could lead to gap breakdown, causing irreparable damage to our equipment. The study of the behavior of air distribution lines encompasses several approaches: Some of them have to do with basic parameters, such as the ground flash density (GFD) and the number of direct lightning strikes on distribution lines. In order to export safe data, we use the corresponding meteorological tables/maps (e.g. lightning maps). The first section of this paper contains the presentation of the form of electric power systems, with special emphasis on the distribution system. It is a presentation of the distribution system structure, its individual parts and devices, as well as their features. Data and statistics of the Greek distribution system are presented at the end of the section. The second section is a brief presentation of the faults and overvoltage occurring at the distribution system, as well as of the protection measures we use, in order to ensure uninterrupted operation and integrity, regarding to our system. The third section presents the natural phenomenon of the lightning and its main features. The types of lightning are reviewed here, and its simulation under laboratory conditions through shock impulses, in order to test the insulation resistance. The fourth section is a reference to the directive of the Institute of Electrical and Electronic Engineers (IEEE), regarding to the behavior of air distribution lines in case of lightning. The purpose here is to present alternative solutions for the decrease of short-circuit occurrences caused by lightning on overhead lines. Specifically, the behavior of the overhead distribution lines in the event of lightning strikes is determined (meaning both direct lightning strikes and short-circuits arising from the induced voltage), as well as the level of insulation of distribution lines, the protection of distribution lines by employing a protective tube, and the protection of the lines using lightning rods. The fifth section of this paper is an elaboration of the faults recorded and the damages caused due to lightning strikes on the medium voltage network, as well as on transformers and on M.V. distribution lines over a 7-year period (from 2005 to 2011) about the Aitoloakarnania state. The theoretical number of faults will be calculated in detail, based on the IEEE directive and then these faults will be compared to the real faults provided by D.E.I. in the city of Agrinio (Greek Public Power Corporation), in order to reach our conclusions. In conclusion, a deviation between the theoretical number and the real number of faults is noted: this observation has to do with the approximate character of the model we used, probably as well as the involvement of the human factor in recording the real number of thoughts. However, this deviation is “positive” (meaning that the number of theoretical faults is bigger than the number of the real ones), a fact that does not reduce the value of the number suggested by using the theoretical model provided

With growing levels of organic food consumption in the retail sector and government municipality goals to increase consumption of organic foods at public schools and institutions, private, independant food service businesses in Sweden risk slipping under the radar when it comes to understanding how they are responding to the global problem of industrialised, fossil fuel intensive and highly unsustainable agriculture. In Sweden, KRAV, an incorporaed association that develops standards for organic agriculture, governs certification for a range of industry actors, including restaurants. From the perspective of corporate social responsibilty (CSR) in small to medium-sized enterprises (SMEs), independant, owner-managed food-service businesses become the subjects of a study into motives for engaging in CSR through environmental certification. Guided by an explorative case study research approach, qualitative data in the form of semi-structured interviews were conducted with management representatives of a number of food service businesses in Uppsala and Stockholm, Sweden. Supported by a thorough literature review, the motives of these persons were identified and explored with the help of a conceptual framewrk based on profitability, legitimacy and sustainability motives. Additionally, the political view of CSR, using the concept of global corporate citizenship, was considered with regard to these commincated motives. Lastly the findings were reflected upon with respect to previous research specifically related to CSR in SMEs. As it turns out, it was found that the motivating factors for certifying with the KRAV restaurant certification were difficult to demarcate from broader ethical guiding principles related to supporting the organic movement. However, it was clear that legitimacy, specifically moral legitimacy, as well as profitabilty are critical elements to consider in understanding what motives restarant owner-managers to obtain KRAV restaurant certification. Finally, it was also concluded that in reacting to globalisation, the behaviour of the restaurants can be considered as global corporate citizenship inasmuch as they are providing a channelling role with regard to citizens’ political rights to actively participate in the global space and collective will formation.

Σκοπός της εργασίας αυτής είναι να αναλύσουμε τους πιο σημαντικούς λόγους για τους οποίους ιδρύεται μια μικρομεσαία επιχείρηση με την χρήση του στατιστικού προγράμματος SPSS. Η δομή της εργασίας είναι χωρισμένη σε δυο μέρη. Το πρώτο μέρος αποτελεί το θεωρητικό "κομμάτι" των μεθόδων που χρησιμοποιούμε και το δεύτερο είναι το πρακτικό δηλαδή η εφαρμογή των μεθόδων που αναλύσαμε σε πραγματικά δεδομένα. Το θεωρητικό μέρος είναι χωρισμένο σε τέσσερα κεφάλαια. Στο πρώτο κεφάλαιο αναφέρουμε τις δυνατότητες του SPSS για την στατιστική ανάλυση μιας και δυο μεταβλητών ενός ή περισσοτέρων δειγμάτων καθώς επίσης και για το πώς μπορούμε να καθορίσουμε τη σχέση (αν υπάρχει ή όχι) μεταξύ τους. Πριν την αναφορά μας γύρω από τις μεταβλητές τονίζουμε κάποια σημεία στα οποία πρέπει να δίνουμε ιδιαίτερη βαρύτητα, και τα οποία είναι απαραίτητα στο αρχικό στάδιο επεξεργασίας των δεδομένων μας (καθορισμός μεταβλητής κτλ.). Στο δεύτερο κεφάλαιο κάνουμε μια πρώτη αναφορά γύρω από την Πολυδιάστατη Ανάλυση Δεδομένων τονίζοντας τη χρησιμότητα τους στις διάφορες επιστήμες, τον τρόπο με τον οποίο η ανάλυση αυτή "λειτουργεί" και τα κύρια χαρακτηριστικά της. Γενικά είναι ένα σύνολο μεθόδων οι οποίες ξεκινώντας από τα ίδια τα δεδομένα και χωρίς καμία υπόθεση ερευνούν τις τάσεις, τις σχέσεις και τις ομαδοποιήσεις τους. Στη συνέχεια αναλύουμε μια σημαντική μέθοδο την "ανάλυση των κύριων συνεκτικών συνιστωσών". Είναι μια τεχνική που έχει ως στόχο τη μείωση της διάστασης των δεδομένων διατηρώντας σχεδόν όλη την ολική μεταβλητότητα των αρχικών μεταβλητών. Η ανάλυση γίνεται με τη βοήθεια των μαθηματικών σχέσεων και βασίζεται στους πίνακες (δειγματικής) συσχέτισης, (δειγματικής) συνδιασποράς κτλ. Στο τρίτο κεφάλαιο κάνουμε μια προσπάθεια ερμηνείας της Παραγοντικής Ανάλυσης με δυο τρόπους. Ο ένας τρόπος είναι με τη βοήθεια της Γραμμικής Άλγεβρας, της Ανάλυσης και των πινάκων και ο άλλος με τη βοήθεια των γραφικών απεικονίσεων των σχέσεων των στοιχείων του πίνακα που αναλύουμε. Σκοπός της παραπάνω μεθόδου είναι να ομαδοποιήσει ένα μεγάλο αριθμό μεταβλητών σε ένα μικρότερο αριθμό σημαντικών μη παρατηρήσιμων τυχαίων μεταβλητών που καλούνται παράγοντες. Στο τελευταίο κεφάλαιο του θεωρητικού μέρους αναφέρουμε και αναλύουμε την Cluster Analysis η οποία είναι μια μέθοδος με την οποία επιδιώκουμε τη δημιουργία ομάδων, συνήθως ατόμων ή αντικειμένων με ομοειδή χαρακτηριστικά, ομάδες τις οποίες μπορούμε να αποκαλούμε και τάξεις. Και σ' αυτή τη μέθοδο κάνουμε δύό ειδών αναλύσεις. Το πρακτικό μέρος της παρούσας εργασίας διερευνά τους παράγοντες οι οποίοι επηρεάζουν την ίδρυση μιας μικρομεσαίας επιχείρησης (ΜΜΕ). Διεξήχθη εμπειρική έρευνα, ο δειγματικός χώρος της οποίας περιλαμβάνει 140 μικρομεσαίες επιχειρήσεις του νομού Σερρών. Τα αποτελέσματα αναδεικνύουν τη συμβολή και τη βαρύτητα μεταβλητών που σχετίζονται με: το προφίλ του επιχειρηματία (δημογραφικά χαρακτηριστικά, προηγούμενη εργασιακή και επιχειρηματική εμπειρία κ.ά.), τη διαδικασία ίδρυσης της επιχείρησης (πηγές άντλησης πληροφοριών, λήψη απόφαση, αρχική επένδυση, προβλήματα που παρουσιάσθηκαν κ.ά.), τα χαρακτηριστικά της νεοϊδρυθείσας επιχείρησης (αντικείμενο, νομικό καθεστώς, αριθμός απασχολούμενων κ.ά.) και τον 1ο χρόνο λειτουργίας (κύκλος εργασιών, πωλήσεις κ.ά.). Πιο συγκεκριμένα στο κεφάλαιο 5 αναλύουμε σχεδόν όλες τις μεταβλητές με τη βοήθεια της περιγραφικής στατιστικής και "επιμένουμε" λίγο περισσότερο σε εκείνες που αποτελούν τους παράγοντες ίδρυσης μικρομεσαίας επιχείρησης. Στο κεφάλαιο 6 περνάμε στο επόμενο στάδιο "εντοπίζοντας" σχέσεις ανάμεσα σε δυο μεταβλητές του ερωτηματολογίου. Το κριτήριο με το οποίο γίνεται ο έλεγχος είναι ο Χ έλεγχος ανεξαρτησίας και αναφέρουμε μόνο όσα παρουσιάζουν ενδιαφέρον (δηλαδή εκεί που υπάρχει κάποια σχέση ). Προχωρώντας στο κεφάλαιο 7 εισχωρούμε κατά κάποιο τρόπο στην Πολυδιάστατη Ανάλυση. Εφαρμόζουμε την Παραγοντική Ανάλυση με τη χρήση της μεθόδου των ισχυρών συνεκτικών συνιστωσών. Η εφαρμογή γίνεται πάνω στους λόγους ίδρυσης γενικά, μιας επιχείρησης. Αναφέρουμε αναλυτικά όλα τα βήματα και όλο το συλλογισμό μέχρι να καταλήξουμε στο τελικό στάδιο από το οποίο βγάζουμε συμπεράσματα. Και στο τελευταίο κεφάλαιο (8) πραγματοποιούμε την Cluster Analysis των 140 cases ώστε να μπορέσουμε να καταλήξουμε σε κάποια προφίλ επιχειρηματιών με συγκεκριμένα χαρακτηριστικά. Δηλαδή από την Παραγοντική Ανάλυση παίρνουμε κάποιες κατευθύνσεις, με τις οποίες σε συνδυασμό με την Cluster Αnalysis εντοπίζουμε συγκεκριμένους λόγους ίδρυσης μιας επιχείρησης για συγκεκριμένα προφίλ επιχειρηματιών. Τέλος , λόγω της εφαρμογής όλων των παραπάνω μεθόδων , προκύπτει ένας πολύ μεγάλος αριθμός πινάκων, ο οποίος ήτανε αδύνατο να καταχωρηθεί στην εργασία .Για το λόγο αυτό στο Παράρτημα έχουμε βάλει όλους τους πίνακες που χρησιμοποιήσαμε στο πρακτικό μέρος της εργασίας. / Aim of this work is to analyze the most important reasons for which is founded a small to medium-sized enterprise with the use of statistical program SPSS. The structure of work is separated in two parts. The first part constitutes theoretical "side" of the methods that we use and second is the practical that is to say application of methods that we analyzed in real data. The theoretical part is separated in four chapters. In the first chapter we report the possibilities of SPSS for the statistical analysis one and two variables one or more samples as well as for how we can determine the relation ([an] it exists or no) from each other. Before our report round the variables we stress certain points in which it should we give particular gravity, and which are essential in the initial stage of treatment of data our (determination variable [etc].) In the second chapter we make a first report round the Multidimensional Analysis of Data stressing their usefulness in the various sciences, the way with which this analysis "functions" and its main characteristics. In general it is a total of methods that beginning from himself given and without no affair searches tendencies, the relations and their regroupings. Afterwards we analyze an important method of the "analysis of the main cohesive components". It is a technique that aims at as the reduction of dimension of data maintaining almost the all total variability of initial variables. The analysis becomes with the help of mathematic relations and is based on the tables of a (sample) cross-correlation, (sample) codispersion etc. In the third chapter we make an effort of interpretation of Factorial Analysis in two ways. One way is with the help of Linear Algebra, Analysis and tables and the other with the help of graphic depictions of relations of elements of table that we analyze. The aim of the above method is to group a big number of variables in a smaller number of important non notable accidental variables that are called factors. In the last chapter of theoretical part we report and we analyze Cluster Analysis who is a method with which we seek the creation of teams, usually individuals or objects with similar characteristics, teams which we can call also orders. And in this method we make two types analyses. The practical part of present work investigates the factors which influence the foundation of small to medium-sized enterprise (SME). An experiental research was carried out, the sampling space of which includes 140 small to medium-sized enterprises of Serres' prefecture. The results elect the contribution and the gravity of variables that is related with: the profile of businessman (demographic characteristics, previous labour and enterprising experience Mr a.), the process of foundation of enterprise (sources of pumping of information, reception decision, initial investment, problems that were presented Mr a.), the characteristics of newly founded enterprise (object, legal regime, number of occupied Mr a.) and the 1st time of operation (turnover, sales Mr a.). More concretely in capital 5 we analyze almost the all variables with the help of descriptive statistics and we insist a little more in those that constitute the factors of foundation of small to medium-sized enterprise. In capital 6 we pass in the next stage by "detecting" relations between two variables of the questionnaire. The criterion with which it becomes the control is the H control of independence and we only report those who present interest (that is to say there that exists some relation). Advancing in capital 7 we penetrate at some way in the Multidimensional Analysis. We apply Factorial Analysis with the use of method of powerful cohesive components. The application applies on the reasons of foundation of an enterprise in general. We report the analytic all steps and the all reasoning until we lead to the final stage from which we draw conclusions. And in last capital (8) we realise Cluster Analysis the 140 cases so that we can lead to certain profiles of businessmen with concrete characteristics. That is to say from Fractional Analysis we take certain directions, with which in combination with Cluster Analysis we locate concrete reasons of foundation of enterprise for concretely profile of businessmen. Finally, because the application of all the above methods, results a very big number of tables, which it was impossible to be registered in the work. For this reason in the Annex we have put the all tables that we used in the practical part of work.

The clouds of gas and dust that constitute the Interstellar Medium (ISM) within the Milky Way and other galaxies can be studied through the spectral lines of the atoms and molecules. The ISM follows a lifecycle in which each of its phases can be traced through spectral lines in the Terahertz (THz) portion of the electromagnetic spectrum, loosely defined as 0.3 - 3 THz. Using the high spectral resolution afforded by heterodyne instruments, astronomers can potentially disentangle the large-scale structure and kinematics within these clouds. In order to study the ISM over large size scales, large format THz heterodyne arrays are needed. The research presented in this dissertation focuses on the development of two heterodyne array receiver systems for ISM studies, SuperCam and a Super-THz (>3 THz) receiver. SuperCam is a 64-pixel heterodyne imaging array designed for use on ground-based submillimeter telescopes to observe the astrophysically important CO J=3-2 emission line at 345 GHz. The SuperCam focal plane stacks eight, 1x8 mixer subarrays. Each pixel in the array has its own integrated superconductor-insulator-superconductor (SIS) mixer and Low Noise Amplifier (LNA). In spring 2012, SuperCam was installed on the University of Arizona Submillimeter Telescope (SMT) for its first engineering run with 32 active pixels. A second observing run in May 2013 had 52 active pixels. With the outliers removed, the median double sideband receiver temperature was 104 K. The Super-THz receiver is designed to observe the astrophysically important neutral atomic oxygen line at 4.7448 THz. The local oscillator is a third-order distributed feedback Quantum Cascade Laser operating in continuous wave mode at 4.741 THz. A quasi-optical hot electron bolometer is used as the mixer. We record a double sideband receiver noise temperature of 815 K, which is ~7 times the quantum noise limit and an Allan variance time of 15 seconds at an effective noise fluctuation bandwidth of 18 MHz. Heterodyne performance is confirmed by measuring a methanol line spectrum. By combining knowledge of large array formats from SuperCam and quasi-optical mixers, initial tests and designs are presented to expand the single pixel 4.7 THz receiver into a quasi-optical 16-pixel array.