Inapproximability of Truthful Mechanisms via Generalizations of the VC Dimension

Algorithmic mechanism design (AMD) studies the delicate interplay between computational efficiency, truthfulness, and optimality. We focus on AMD's paradigmatic problem: combinatorial auctions. We present a new generalization of the VC dimension to multivalued collections of functions, which encompasses the classical VC dimension, Natarajan dimension, and Steele dimension. We present a corresponding generalization of the Sauer-Shelah Lemma and harness this VC machinery to establish inapproximability results for deterministic truthful mechanisms. Our results essentially unify all inapproximability results for deterministic truthful mechanisms for combinatorial auctions to date and establish new separation gaps between truthful and non-truthful algorithms

Program and Abstracts of the Annual Meeting of the Georgia Academy of Science, 2013

The annual meeting of the Georgia Academy of Science took place March 29-30, 2013, at Valdosta State University, Valdosta, Georgia. Presentations were provided by members of the Academy who represented the following sections: I. Biological Sciences II Chemistry III. Earth & Atmospheric Sciences IV. Physics, Mathematics, Computer Science, Engineering & Technology V. Biomedical Sciences VI. Philosophy & History of Science VII. Science Education VIII. Anthropology

Advanced Mechanism Design for Electric Vehicle Charging Scheduling in the Smart Infrastructure

Electric vehicle (EV) continues to grow rapidly due to low emission and high intelligence. This thesis considers a smart infrastructure (SI) as an EV-centered ecosystem, which is an integrated and connected multi-modal network involving interacting intelligent agents, such as EVs, charging facilities, electric power grids, distributed energy resources, etc. The system modeling paradigm is derived from distributed artificial intelligence and modelled as multi-agent systems (MAS), where the agents are self-interested and reacting strategically to maximize their own benefits. The integration, interaction, and coordination of EVs with SI components will raise various features and challenges on the transportation efficiency, power system stability, and user satisfaction, as well as opportunities provided by optimization, economics, and control theories, and other advanced technologies to engage more proactively and efficiently in allocating the limited charging resources and collaborative decision-making in a market environment. A core challenge in such an EV ecosystem is to trade-off the two objectives of the smart infrastructure, of system-wide efficiency and at the same time the social welfare and individual well-being against agents’ selfishness and collective behaviors. In light of this, scheduling EVs' charging activities is of great importance to ensure an efficient operation of the smart infrastructure and provide economical and satisfactory charging experiences to EV users under the support of two-way flow of information and energy of charging facilities. In this thesis, we develop an advanced mechanism design framework to optimize the charging resource allocation and automate the interaction process across the overall system. The key innovation is to design specific market-based mechanisms and interaction rules, integrated with concepts and principles of mechanism design, scheduling theory, optimization theory, and reinforcement learning, for charging scheduling and dynamic pricing problem in various market structures. Specifically, this research incorporates three synergistic areas: (1) Mathematical modelling for EV charging scheduling. We have developed various mixed-integer linear programs for single-charge with single station, single-charge with multiple stations, and multi-charge with multiple stations in urban or highway environments. (2) Market-based mechanism design. Based on the proposed mathematical models, we have developed particular market-based mechanisms from the resource provider’s prospective, including iterative bidding auction, incentive-compatible auction, and simultaneous multi-round auction. These proposed auctions contain bids, winner determination models, and bidding procedure, with which the designer can compute high quality schedules and preserve users’ privacy by progressively eliciting their preference information as necessary. (3) Reinforcement learning-based mechanism design. We also proposed a reinforcement mechanism design framework for dynamic pricing-based demand response, which determines the optimal charging prices over a sequence of time considering EV users’ private utility functions. The learning-based mechanism design has effectively improved the long-term revenue despite highly-uncertain requests and partially-known individual preferences of users. This Ph.D. dissertation presents a market prospective and unlocks economic opportunities for MAS optimization with applications to EV charging related problems; furthermore, applies AI techniques to facilitate the evolution from manual mechanism design to automated and data-driven mechanism design when gathering, distributing, storing, and mining data and state information in SI. The proposed advanced mechanism design framework will provide various collaboration opportunities with the research expertise of reinforcement learning with innovative collective intelligence and interaction rules in game theory and optimization tools, as well as offers research thrust to more complex interfaces in intelligent transportation system, smart grid, and smart city environments

Large area CMOS photosensors for time-resolved measurements

Viele Industrieanwendungen benötigen lineare Photosensoren, die eine hohe Empfindlichkeit besitzen und geringes Rauschen verursachen. Die Atom-Emissionsspektroskopie ist eine dieser Anwendungen. Dieses spektroskopische Verfahren ergibt Informationen über die qualitative und quantitative Zusammensetzung eines Analyten. Seit 1960 sind Photoelektronenverfielfacher (photomultiplier tubes, PMT) als Standarddetektoren im Bereich der Spektrometrie im Einsatz, da sie eine kurze Reaktionszeit und niedrigen Dunkelstrom aufweisen. In der jüngeren Zeit sind Feststoffliniensensoren als vielversprechende Alternative zu den Photoelektronenverfielfachern ins Augenmerk gerückt. Neuerdings auch in hybriden Emissionspektrometern im Einsatz, sind CCD-Liniensensoren in der Lage, im Ultraviolett gelegene (für Wellenlängen über ca. 250 nm), sichtbare und nah-infrarote Spektralbereiche zu registrieren, die von einem Lichtgitter mit geringer Bandbreite an diese gesendet werden. Jedoch gibt es mit der CCD-Technologie keine Möglichkeit, zufällige Pixel zu adressieren, nichtlöschend auszulesen und Daten nach der Zeit aufgelöst erfassen, was zur Notwendigkeit führt, den gesamten Sensor mehrere Male auszulesen, um die erforderliche Ladungssammelzeit einzustellen, welche dafür benötigt wird, um zwischen benachbarten Zeilen im Spektrographen zu unterscheiden. Das braucht sehr viel Messzeit, fügt überdies Reset-Rauschen hinzu und vermindert das Signal-Rausch-Verhältnis. Der Einsatz von CMOS kann eine gute Alternative zu CCD darstellen. Ein in dieser Arbeit entwickelter und optimierter, auf einem Lateral Drift-Field Photodetector (LDPD) basierender CMOS-Zeilensensor eröffnet die Möglichkeit eines sogenannten Time-Gating und die Besonderheit eines nichtlöschenden Auslesens und einer Ladungssammlung über mehrere Zyklen, ohne, dass dabei eine Reset-Phase vonnöten ist. Große fotoaktive Bereiche von bis zu 1 mm sind, gleich wie schneller Ladungstransfer und niedriger Dunkelstrom, entscheidende Anforderungen an Sensoren, die in der optischen Emissionspektroskopie eingesetzt werden. Dies sind damit auch die Hauptziele, die mit den in dieser Arbeit eingebrachten Strukturen zu erreichen sein müssten. Der Transfer der Pixelladung vom fotoaktiven Bereich in den Sensorknoten wird in dieser Arbeit im Detail analysiert. Es werden verschiedene Mechanismen des Ladungstransports studiert. Der Dunkelstrom im LDPD-Pixel wird durch die Verwendung verschiedener Pixelstrukturen analysiert. Außerdem wird ein neuartiges Pixeldesign präsentiert, durch welches der Tranfer von Pixelladungen effizienter erfolgt. Es werden verschiedene Pixeltypen vorgeschlagen und eingehend charakterisiert. Schließlich wird die am besten geeignete Pixelstruktur herangezogen, um den Prototypen eines Zeilensensors herzustellen, dessen Arbeitscharakteristika ebenso im Detail untersucht werden.Many industrial applications require linear photosensors, which exhibit high sensitivity and low noise. The atomic emission spectroscopy is one of such applications. This spectroscopic method delivers the information about the qualitative and quantitative composition of an analyte. Since 1960 photomultiplier tubes (PMT) were used as standard detectors in the field of spectrometry due to their high speed of response and low dark current. Recently, solid-state line sensors have established themselves as a promising alternative to the photomultiplier tubes. Newly used in hybrid emission spectrometers, CCD line sensors are able to detect the part of the spectra in the ultra-violet (for wavelengths longer than some 250 nm), visible, and near infra-red ranges sent to them by a narrow bandwidth optical grid. However, CCD technology does not have the ability of random pixel addressing, non-destructive readout and time-resolved measurements, which causes the necessity of reading out the complete sensor several times to adjust the necessary charge collection period required to be able to distinguish between neighbouring lines in the spectrograph. This consumes a lot of measuring time and also adds additional reset noise and diminishes the signal-to-noise ratio after each readout. A CMOS approach can be a good alternative to CCD. Developed and optimized in this thesis, a lateral drift-field photodetector (LDPD) based CMOS line sensor offers the possibility for the so called time-gating together with the feature of non-destructive readout and charge accumulation over several cycles without the need for the reset phase. Large photoactive areas of up to 1 mm as well as fast charge transfer and low dark currents are all dominant requirements for the sensors used in optical emission spectroscopy. These are the main goals that should be achievable with the structures proposed in this thesis. Pixel charge transfer from the photoactive area into the sense node is examined in detail in this work. Different mechanisms of the charge transport are studied. Dark current in the LDPD pixel is analysed on using varied pixel structures. A novel pixel design to enhance the charge transfer efficiency is presented. Different pixel types are proposed and thoroughly characterized. Finally, the best pixel structure is used to fabricate a prototype line sensor, the operating characteristics of which are also examined in detail

Program and Abstracts of the Annual Meeting of the Georgia Academy of Science, 2014

The annual meeting of the Georgia Academy of Science took place March 28-29, 2014, at Georgia Regents University, Augusta, Georgia. Presentations were provided by members of the Academy who represented the following sections: I. Biological Sciences II Chemistry III. Earth & Atmospheric Sciences IV. Physics, Mathematics, Computer Science, Engineering & Technology V. Biomedical Sciences VI. Philosophy & History of Science VII. Science Education VIII. Anthropology

Index to NASA Tech Briefs, 1972

Abstracts of 1972 NASA Tech Briefs are presented. Four indexes are included: subject, personal author, originating center, and Tech Brief number