Hexapod Design For All-Sky Sidereal Tracking

In this paper we describe a hexapod-based telescope mount system intended to provide sidereal tracking for the Fly's Eye Camera project -- an upcoming moderate, 21"/pixel resolution all-sky survey. By exploiting such a kind of meter-sized telescope mount, we get a device which is both capable of compensating for the apparent rotation of the celestial sphere and the same design can be used independently from the actual geographical location. Our construction is the sole currently operating hexapod telescope mount performing dedicated optical imaging survey with a sub-arcsecond tracking precision.Comment: Accepted for publication in PASP, 10 page

From MALDI-TOF Mass Spectrometry to Soft-Landing for Electronics

Within this PhD thesis matrix assisted laser desorption/ionization mass spectrometry (MALDI-MS) has been used as a reliable tool for the quantitative characterization of giant molecules, such as alkyl substituted and unsubstituted large polycyclic aromatic hydrocarbons (PAH), which cannot be characterized by conventional analytic techniques due to their lack of solubility. The use of the MALDI solvent-free technique for the sample preparation and the application of the standard addition method have allowed the quantitative characterization of synthetic PAH mixtures. The knowledge, acquired by studying these representative systems, has been then transferred to the quantitative analyses of complex and slightly soluble natural PAH mixtures, such as mesophase pitch. Moreover, the possibility to ionize intractable and insoluble molecules via mass spectrometry has been recognized to be not only a powerful analytical method, but also to represent a unique change to handle giant aromatic systems and to deposit them on a surface for further investigations, in a process, which is defined as “soft-landing”. Within this novel deposition technique, ions of the desired analytes or analyte mixtures are generated by means of an MS ionization source, discriminated by their different mass to charge ratios via a mass analyzer and landed with retention of their structure on a desired surface. This soft-deposition is guaranteed by the use of decelerating potentials, which have in this work been recognized to influence the final packing of the analyte molecules reaching the landing surface. For a more detailed study of the electrical field action on disc-like and rod-like molecules, soft-landing-independent experiments have been additionally carried out. As a result unidirectionally ordered films of the analyte molecules have been obtained due to the application of an external electrical strength. This versatile alignment technique has then been used for obtaining ordered layers of semiconducting materials for the fabrication of organic field effect transistors (OFET) with improved performances.“From MALDI TOF Mass Spectrometry to Soft Landing for Electronics” Anna Maria Cristadoro Zusammenfassung Im Rahmen dieser Doktorarbeit wurden Methoden entwickelt, um unlösliche Stoffe mittels MALDI-TOF-Massenspektrometrie zu quantifizieren, als Modellsysteme dienten dabei Mischungen aus verschiedenen polyzyklischen aromatischen Kohlenwasserstoffe (PAH). Die Kombination aus einer lösungsmittelfreien Probenvorbereitung und der Verwendung einer Standardadditionsreihe zeigte sich dabei als überaus geeignet, um neben diesen Modellsystemen auch natürlich vorkommende Schlacken quantitativ zu charakterisieren. Der zweite Teil der Arbeit beschäftigt sich mit den Ionisierungseigenschaften von unlöslichen Polymeren und niedermolekularen Verbindungen, welche Anwendungen in der organischen Elektronik finden. Hierbei zeigte sich, dass die Ionisierbarkeit dieser Materialien ausgenutzt werden kann, um einzelne Molekülisotope dieser Stoffe gezielt auf Oberflächen anzureichern. Die als „Soft-Landing“ bekannte Methode basiert dabei auf der Trennung der ionisierten Moleküle in einem Sektorfeld und anschließender Deposition auf einem geeigneten Substrat. Durch das Anlegen eines elektrischen Feldes nahe der Oberfläche konnte dabei sichergestellt werden, dass die anzureichernden Moleküle während der Depostion nicht fragmentieren. Zudem wurde gefunden, dass die Überstruktur, welche die Moleküle auf der Oberfläche ausbilden, durch die Charakteristik des angelegten Feldes beeinflusst werden kann. Als Ergebnis konnten dadurch unidirektional ausgerichtete und halbleitende Polymerfilme erzeugt werden, welche ihre Anwendungsmöglichkeiten im Aufbau von organischen Feldeffekttransitoren finden

An Improved Method for the Geometrical Calibration of Parallelogram-based Parallel Robots

International audienceThis paper presents an improved method for the geometrical calibration of parallel robots for which the structure is based upon some parallelogram mechanisms. Its originality is to identify the complete geometry of the mechanism's parallelograms, and to compensate the positioning error of the TCP (Tool Centre Point), due to the infinitesimal rotation of the traveling plate, induced by the parallelogram geometrical errors. The main difficulties are: (i) to derive the calibration model relative to all geometrical parameters, and (ii) to reuse the identified errors in a control model in order to compensate the positioning errors. In fact, the position relationship taking into account the full geometry of the parallelograms is difficult, not to say impossible, to derive in a close form; therefore a linear approximation of the model is proposed. The formulas necessary to run the method on a Delta robot are given. Then a simple mechanism is used to illustrate the benefits of this method compared to classical ones

Organic pi-stacking Semiconducting Material: Design, Synthesis and the Analysis of Structure and Properties

Organic semiconducting materials have been under intensive investigation in the recent decades for potential applications in various electronic or optoelectronic devices such as light emitting diodes, photovoltaic cells and field effect transistors. Compared to inorganic counterparts, organic charge transport materials are attractive for their abilities of forming thin-films, large area manufacturing, compatibility with flexible substrate, light weight and potential low fabrication cost. The charge transport property of the organic active layer is one of the key factors to the electronic or optoelectronic performance of devices. Research projects presented in this thesis focused on improving charge carrier mobility of organic charge transport materials as it is a property determined by the hierarchical structure of the material. Strong effort has been made to the design of advanced molecular structures and controlling self-assembly behaviors. Chapter 1 introduces the general background of charge transport materials, including: the nature of charge transport in organic semiconducting materials, three widely used methods for charge carrier mobility measurements and the current development of organic charge transport materials. Advantages and drawbacks in applications were analyzed with ordered and disordered organic systems. A more thorough review was given to the engineering and the application of the discotic columnar liquid crystalline (DCLC) phase. Chapter 2 describes a DCLC phase with a novel hierarchical structure in which each supra-molecular column features a bundled-stack structure. The molecular design rationale was explained and the thermal behavior and phase structure were characterized. Charge carrier mobility of compound 1 was measured to be 0.05 cm2V-1s-1 with pulse radiolysis time-resolved microwave conductivity. The incorporation of the bundled stack structure may potentially be a fundamental solution towards enhancing the organic semiconductor\u27s electronic performance. Chapter 3 introduces three chain functionalized perylene tetracarboxylic monoimide diester derivatives (PEIs) with monotropic DCLC phases. The intra-column rotation angle was determined to be 60 o between neighboring PEI molecules, which is a substantial improvement of the transfer integral compared to the perylene tetracarboxylic diimides with a 90 o rotation angle. The rotation angle was further tuned by incorporating branched aliphatic substitution to the PEI core as described in chapter 4. By reducing the length of the alkyl swallow tail, the rotation angle changes from 60 o to 72 o which is even more favorable to the electronic coupling between neighboring PEI units. Through those studies, we have shown that the engineering of DCLC phase may lead to substantial improvements on charge transport properties of organic semiconducting materials.

Calibration of Parallel Kinematic Machines: theory and applications

Introduction As already stated in the chapter addressing the calibration of serial manipulators, kinematic calibration is a procedure for the identification and the consequent compensation of the geometrical pose errors of a robot. This chapter extends the discussion to Parallel Manipulators (also called PKM Parallel Kinematic Machines). As described in the following (Section 2) this extension is not obvious but requires special care. Although for serial manipulators some procedures for the calibration based on automatic generation of a MCPC (Minimum Complete Parametrically Continuos) model exist, for PKMs only methodologies for individual manipulators have been proposed but a general strategy has not been presented since now. A few examples of the numerous approaches for the calibration of individual PKMs are proposed in (Parenti-Castelli & Di Gregorio, 1995), (Jokiel et al., 2000) for direct calibration and (Neugebauer et al., 1999), (Smollett, 1996) for indirect or self calibration techniques. This paper makes one significant step integrating available results with new ones and reordering them in simple rules that can be automatically applied to any PKM with general kinematic chains. In all the cases a MCPC kinematic model for geometrical calibration is automatically obtained. In Section 2 the main features of PKMs calibration is pointed out and the total number of the necessary parameters is determined; this is an original contribution. In Sections 3 and 4 two novel approaches for the generation of a MCPC model are described. Sections 5 and 6 are dedicated to the analysis of the singular cases and to the procedure for the elimination of the redundant parameters respectively; actual cases are discussed. Section 7 presents several examples of application of the two proposed procedures to many existing PKMs. Section 8 eventually draws the conclusions