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Dartmouth College

2010

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Articles 31 - 60 of 66

Full-Text Articles in Physical Sciences and Mathematics

Block Sensitivity Versus Sensitivity, Karn Seth Jun 2010

Block Sensitivity Versus Sensitivity, Karn Seth

Dartmouth College Undergraduate Theses

Sensitivity and block sensitivity are useful and well-studied measures of computational complexity, but in spite of their similarities, the largest possible gap between them is still unknown. Rubinstein showed that this gap must be at least quadratic, and Kenyon and Kutin showed that it is at worst exponential, but many strongly suspect that the gap is indeed quadratic, or at worst polynomial. Our work shows that for a large class of functions, which includes Rubinstein's function, the quadratic gap between sensitivity and block sensitivity is the best we can possibly do.

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Predictive Yasir: High Security With Lower Latency In Legacy Scada, Rouslan V. Solomakhin Jun 2010

Predictive Yasir: High Security With Lower Latency In Legacy Scada, Rouslan V. Solomakhin

Dartmouth College Master’s Theses

Message authentication with low latency is necessary to ensure secure operations in legacy industrial control networks, such as power grid networks. Previous authentication solutions by our lab and others looked at single messages and incurred noticeable latency. To reduce this latency, we develop Predictive YASIR, a bump-in-the-wire device that looks at broader patterns of messages. The device (1) predicts the incoming plaintext based on previous observations; (2) compresses, encrypts, and authenticates data online; and (3) pre-sends a part of ciphertext before receiving the whole plaintext. I demonstrate the performance properties of this approach by implementing it in the Scalable Simulation …

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Optimization Algorithms For Site-Directed Protein Recombination Experiment Planning, Wei Zheng Jun 2010

Optimization Algorithms For Site-Directed Protein Recombination Experiment Planning, Wei Zheng

Dartmouth College Ph.D Dissertations

Site-directed protein recombination produces improved and novel protein variants by recombining sequence fragments from parent proteins. The resulting hybrids accumulate multiple mutations that have been evolutionarily accepted together. Subsequent screening or selection identifies hybrids with desirable characteristics. In order to increase the "hit rate" of good variants, this thesis develops experiment planning algorithms to optimize protein recombination experiments. First, to improve the frequency of generating novel hybrids, a metric is developed to assess the diversity among hybrids and parent proteins. Dynamic programming algorithms are then created to optimize the selection of breakpoint locations according to this metric. Second, the trade-off …

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Graph Algorithms For Nmr Resonance Assignment And Cross-Link Experiment Planning, Fei Xiong Jun 2010

Graph Algorithms For Nmr Resonance Assignment And Cross-Link Experiment Planning, Fei Xiong

Dartmouth College Ph.D Dissertations

The study of three-dimensional protein structures produces insights into protein function at the molecular level. Graphs provide a natural representation of protein structures and associated experimental data, and enable the development of graph algorithms to analyze the structures and data. This thesis develops such graph representations and algorithms for two novel applications: structure-based NMR resonance assignment and disulfide cross-link experiment planning for protein fold determination. The first application seeks to identify correspondences between spectral peaks in NMR data and backbone atoms in a structure (from x-ray crystallography or homology modeling), by computing correspondences between a contact graph representing the structure …

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Intermode Dephasing In A Superconducting Stripline Resonator, Oren Suchoi, Baleegh Abdo, Eran Segev, Oleg Shtempluck, M. P. Blencowe, Eyal Buks May 2010

Intermode Dephasing In A Superconducting Stripline Resonator, Oren Suchoi, Baleegh Abdo, Eran Segev, Oleg Shtempluck, M. P. Blencowe, Eyal Buks

Dartmouth Scholarship

We study a superconducting stripline resonator (SSR) made of niobium, which is integrated with a superconducting interference device (SQUID). The large nonlinear inductance of the SQUID gives rise to a strong Kerr nonlinearity in the response of the SSR, which in turn results in strong coupling between different modes of the SSR. We experimentally demonstrate that such intermode coupling gives rise to dephasing of microwave photons. The dephasing rate depends periodically on the external magnetic flux applied to the SQUID, where the largest rate is obtained at half integer values (in units of the flux quantum). To account for our …

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The Curious Timekeeper: Creative Thesis In Interactive Sculpture, Kate I. Schnippering May 2010

The Curious Timekeeper: Creative Thesis In Interactive Sculpture, Kate I. Schnippering

Dartmouth College Undergraduate Theses

When we interact with computers, we have set expectations about our interactive experience, operating a mouse and keyboard to elicit predictable responses on a screen. Intersecting the world of Computing with Fine Art gains us potential to innovate outside these bounds by restricting the expected performance of a computer-- setting it to a particular purpose rather than allowing it to run anyone's software. To challenge standard human-computer interaction, this work set out to create an interesting and unusual interactive experience, fully integrated into a sculpture. The approach was to design a system to form a small environment, having many components …

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An Exponentially Convergent Nonpolynomial Finite Element Method For Time-Harmonic Scattering From Polygons, A. H. Barnett, T. Betcke May 2010

An Exponentially Convergent Nonpolynomial Finite Element Method For Time-Harmonic Scattering From Polygons, A. H. Barnett, T. Betcke

Dartmouth Scholarship

In recent years nonpolynomial finite element methods have received increasing attention for the efficient solution of wave problems. As with their close cousin the method of particular solutions, high efficiency comes from using solutions to the Helmholtz equation as basis functions. We present and analyze such a method for the scattering of two-dimensional scalar waves from a polygonal domain that achieves exponential convergence purely by increasing the number of basis functions in each element. Key ingredients are the use of basis functions that capture the singularities at corners and the representation of the scattered field towards infinity by a combination …

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Results From Electrostatic Calibrations For Measuring The Casimir Force In The Cylinder-Plane Geometry, Q. Wei, D. A. R. Dalvit, F. C. Lombardo, F. D. Mazzitelli, R. Onofrio May 2010

Results From Electrostatic Calibrations For Measuring The Casimir Force In The Cylinder-Plane Geometry, Q. Wei, D. A. R. Dalvit, F. C. Lombardo, F. D. Mazzitelli, R. Onofrio

Dartmouth Scholarship

We report on measurements performed on an apparatus aimed to study the Casimir force in the cylinder-plane configuration. The electrostatic calibrations evidence anomalous behaviors in the dependence of the electrostatic force and the minimizing potential upon distance. We discuss analogies and differences of these anomalies with respect to those already observed in the sphere-plane configuration. At the smallest explored distances we observe frequency shifts of non-Coulombian nature preventing the measurement of the Casimir force in the same range. We also report on measurements performed in the parallel-plane configuration, showing that the dependence on distance of the minimizing potential, if present …

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Noncommutative Topology And The World’S Simplest Index Theorem, Erik Van Erp May 2010

Noncommutative Topology And The World’S Simplest Index Theorem, Erik Van Erp

Dartmouth Scholarship

In this article we outline an approach to index theory on the basis of methods of noncommutative topology. We start with an explicit index theorem for second-order differential operators on 3-manifolds that are Fredholm but not elliptic. This low-brow index formula is expressed in terms of winding numbers. We then proceed to show how it is derived as a special case of an index theorem for hypoelliptic operators on contact manifolds. Finally, we discuss the noncommutative topology that is employed in the proof of this theorem. The article is intended to illustrate that noncommutative topology can be a powerful tool …

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The Nature Of The Strong 24 Μmspitzersource J222557+601148: Not A Young Galactic Supernova Remnant, Robert A. Fesen, Dan Milisavljevic May 2010

The Nature Of The Strong 24 Μmspitzersource J222557+601148: Not A Young Galactic Supernova Remnant, Robert A. Fesen, Dan Milisavljevic

Dartmouth Scholarship

The nebula J222557+601148, tentatively identified by Morris et al. as a young Galactic supernova remnant (SNR) from Spitzer Galactic First Look Survey images and a follow-up mid-infrared spectrum, is unlikely to be an SNR remnant based on Hα, [O III], [S II] images, and low-dispersion optical spectra. The object is seen in Hα and [O III] λ5007 images as a faint, roughly circular ring nebula with dimensions matching that seen in 24 μm Spitzer images. Low-dispersion optical spectra show it to have narrow Hα and [N II] λλ6548,6583 line emissions with no evidence of broad or high-velocity (v ≥ …

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Neurophone: Brain-Mobile Phone Interface Using A Wireless Eeg Headset, Matthew K. Mukerjee May 2010

Neurophone: Brain-Mobile Phone Interface Using A Wireless Eeg Headset, Matthew K. Mukerjee

Dartmouth College Undergraduate Theses

Neural signals are everywhere just like mobile phones. We propose to use neural signals to control mobile phones for hands-free, silent and effortless human-mobile interaction. Until recently, devices for detecting neural signals have been costly, bulky and fragile. We present the design, implementation and evaluation of the NeuroPhone system, which allows neural signals to drive mobile phone applications on the iPhone using cheap off-the-shelf wireless electroencephalography (EEG) headsets. We demonstrate a mind-controlled address book dialing app, which works on similar principles to P300-speller brain-computer interfaces: the phone flashes a sequence of photos of contacts from the address book and a …

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A 3-D Photo Forensic Analysis Of The Lee Harvey Oswald Backyard Photo, Hany Farid May 2010

A 3-D Photo Forensic Analysis Of The Lee Harvey Oswald Backyard Photo, Hany Farid

Computer Science Technical Reports

More than forty-five years after the assassination of U.S. President Kennedy theories continue to circulate suggesting that the accused assassin, Lee Harvey Oswald, acted as part of a larger conspiracy. It has been argued, for example, that incriminating photographs of Oswald were manipulated, and hence evidence of a broader plot. We describe a detailed 3-D analysis of the Oswald photos to determine if such claims of tampering are warranted.

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A Note On Randomized Streaming Space Bounds For The Longest Increasing Subsequence Problem, Amit Chakrabarti May 2010

A Note On Randomized Streaming Space Bounds For The Longest Increasing Subsequence Problem, Amit Chakrabarti

Computer Science Technical Reports

The deterministic space complexity of approximating the length of the longest increasing subsequence of a stream of N integers is known to be Theta~(sqrt N). However, the randomized complexity is wide open. We show that the technique used in earlier work to establish the Omega(sqrt N) deterministic lower bound fails strongly under randomization: specifically, we show that the communication problems on which the lower bound is based have very efficient randomized protocols. The purpose of this note is to guide and alert future researchers working on this very interesting problem.

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Saluki: A High-Performance Wi-Fi Sniffing Program, Keren Tan, David Kotz May 2010

Saluki: A High-Performance Wi-Fi Sniffing Program, Keren Tan, David Kotz

Dartmouth Scholarship

Building a campus-wide wireless LAN measurement system faces many efficiency, scalability and security challenges. To address these challenges, we developed a distributed Wi-Fi sniffing program called Saluki. Compared to our previous implementation and to other available sniffing programs, Saluki has the following advantages: (1) its small footprint makes it suitable for a resource-constrained Linux platform, such as those in commercial Wi-Fi access points; (2) the frame-capture rate increased more than three-fold over tcpdump with minimal frame loss; (3) all traffic between this sniffer and the back-end server was secured using 128-bit encryption; and (4) the traffic load on the backbone …

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Information Cost Tradeoffs For Augmented Index And Streaming Language Recognition, Amit Chakrabarti, Graham Cormode, Ranganath Kondapally, Andrew Mcgregor Apr 2010

Information Cost Tradeoffs For Augmented Index And Streaming Language Recognition, Amit Chakrabarti, Graham Cormode, Ranganath Kondapally, Andrew Mcgregor

Dartmouth Scholarship

This paper makes three main contributions to the theory of communication complexity and stream computation. First, we present new bounds on the information complexity of AUGMENTED-INDEX. In contrast to analogous results for INDEX by Jain, Radhakrishnan and Sen [J. ACM, 2009], we have to overcome the significant technical challenge that protocols for AUGMENTED-INDEX may violate the “rectangle property” due to the inherent input sharing. Second, we use these bounds to resolve an open problem of Magniez, Mathieu and Nayak [STOC, 2010] that asked about the multi-pass complexity of recognizing Dyck languages. This results in a natural separation between the standard …

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Equilibrium States Of A Test Particle Coupled To Finite-Size Heat Baths, Qun Wei, S. Taylor Smith, Roberto Onofrio Mar 2010

Equilibrium States Of A Test Particle Coupled To Finite-Size Heat Baths, Qun Wei, S. Taylor Smith, Roberto Onofrio

Dartmouth Scholarship

We report on numerical simulations of the dynamics of a test particle coupled to competing Boltzmann heat baths of finite size. After discussing some features of the single bath case, we show that the presence of two heat baths further constrains the conditions necessary for the test particle to thermalize with the heat baths. We find that thermalization is a spectral property in which the oscillators of the bath with frequencies in the range of the test particle characteristic frequency determine its degree of thermalization. We also find an unexpected frequency shift of the test particle response with respect to …

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Low-Frequency Turbulence In A Linear Magnetized Plasma, B. N. Rogers, Paolo Ricci Mar 2010

Low-Frequency Turbulence In A Linear Magnetized Plasma, B. N. Rogers, Paolo Ricci

Dartmouth Scholarship

Plasma turbulence in a linear device is explored for the first time with three-dimensional global two-fluid simulations, focusing on the plasma parameters of the Large Plasma Device. Three instabilities are present in the simulations: the Kelvin-Helmholtz instability, a sheath-driven instability, and a resistive drift wave instability. The Kelvin-Helmholtz mode is shown to dominate the transport of plasma across the magnetic field. Simple scaling laws are obtained for the plasma profiles.

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Quantum Information Encoding, Protection, And Correction From Trace-Norm Isometries, Francesco Ticozzi, Lorenza Viola Mar 2010

Quantum Information Encoding, Protection, And Correction From Trace-Norm Isometries, Francesco Ticozzi, Lorenza Viola

Dartmouth Scholarship

We introduce the notion of trace-norm isometric encoding and explore its implications for passive and active methods for protecting quantum information against errors. Beside providing an operational foundation to the “subsystems principle” [E. Knill, Phys. Rev. A 74, 042301 (2006)] for faithfully realizing quantum information in physical systems, our approach allows additional explicit connections between noiseless, protectable, and correctable quantum codes to be identified. Robustness properties of isometric encodings against imperfect initialization and/or deviations from the intended error models are also analyzed.

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Arbitrarily Accurate Dynamical Control In Open Quantum Systems, Kaveh Khodjasteh, Daniel A. Lidar, Lorenza Viola Mar 2010

Arbitrarily Accurate Dynamical Control In Open Quantum Systems, Kaveh Khodjasteh, Daniel A. Lidar, Lorenza Viola

Dartmouth Scholarship

We show that open-loop dynamical control techniques may be used to synthesize unitary transformations in open quantum systems in such a way that decoherence is perturbatively compensated for to a desired (in principle arbitrarily high) level of accuracy, which depends only on the strength of the relevant errors and the achievable rate of control modulation. Our constructive and fully analytical solution employs concatenated dynamically corrected gates, and is applicable independently of detailed knowledge of the system-environment interactions and environment dynamics. Explicit implications for boosting quantum gate fidelities in realistic scenarios are addressed.

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Studying The Small Scale Ism Structure With Supernovae, F. Patat, N. L. J. Cox, J. Parrent, D. Branch Mar 2010

Studying The Small Scale Ism Structure With Supernovae, F. Patat, N. L. J. Cox, J. Parrent, D. Branch

Dartmouth Scholarship

In this work we explore the possibility of using the fast expansion of a Type Ia supernova photosphere to detect extra-galactic ISM column density variations on spatial scales of ∼100 AU on time scales of a few months. We constructed a simple model which describes the expansion of the photodisk and the effects of a patchy interstellar cloud on the observed equivalent width of Nai D lines. Using this model we derived the behavior of the equivalent width as a function of time, spatial scale and amplitude of the column density fluctuation

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Conserving Migratory Land Birds In The New World: Do We Know Enough?, John Faaborg, Richard T. Holmes, Angela D. Anders, Keith L. Bildstein Mar 2010

Conserving Migratory Land Birds In The New World: Do We Know Enough?, John Faaborg, Richard T. Holmes, Angela D. Anders, Keith L. Bildstein

Dartmouth Scholarship

Migratory bird needs must be met during four phases of the year: breeding season, fall migration, wintering, and spring migration; thus, management may be needed during all four phases. The bulk of research and management has focused on the breeding season, although several issues remain unsettled, including the spatial extent of habitat influences on fitness and the importance of habitat on the breeding grounds used after breeding. Although detailed investigations have shed light on the ecology and population dynamics of a few avian species, knowledge is sketchy for most species. Replication of comprehensive studies is needed for multiple species across …

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On The Reliability Of Wireless Fingerprinting Using Clock Skews, Chrisil Arackaparambil, Sergey Bratus, Anna Shubina, David Kotz Mar 2010

On The Reliability Of Wireless Fingerprinting Using Clock Skews, Chrisil Arackaparambil, Sergey Bratus, Anna Shubina, David Kotz

Dartmouth Scholarship

No abstract provided.

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Constant Rmr Solutions To Reader Writer Synchronization, Vibhor Bhatt, Prasad Jayanti Feb 2010

Constant Rmr Solutions To Reader Writer Synchronization, Vibhor Bhatt, Prasad Jayanti

Computer Science Technical Reports

We study Reader-Writer Exclusion, a well-known variant of the Mutual Exclusion problem where processes are divided into two classes--readers and writers--and multiple readers can be in the Critical Section (CS) at the same time, although no process may be in the CS at the same time as a writer. Since readers don't conflict with each other, they should not obstruct each other. Specifically, the concurrent entering property must be satisfied: if all writers are in the remainder section, each reader should be able to enter the CS in a bounded number of its own steps. Three versions of the Reader-Writer …

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Core Gas Sloshing In Abell 1644, Ryan E. Johnson, Maxim Markevitch, Gary A. Wegner, Christine Jones, William R. Forman Feb 2010

Core Gas Sloshing In Abell 1644, Ryan E. Johnson, Maxim Markevitch, Gary A. Wegner, Christine Jones, William R. Forman

Dartmouth Scholarship

We present an analysis of a 72 ks Chandra observation of the double cluster Abell 1644 (z = 0.047). The X-ray temperatures indicate that the masses are M 500 = (2.6 ± 0.4) × 1014 h –1 M ☉ for the northern sub-cluster and M 500 = (3.1 ± 0.4) × 1014 h –1 M ☉ for the southern, main cluster. We identify a sharp edge in the radial X-ray surface brightness of the main cluster, which we find to be a cold front, with a jump in temperature of a factor of ~3. This edge possesses …

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Effects Of Socioeconomic Status On Brain Development, And How Cognitive Neuroscience May Contribute To Levelling The Playing Field, Rajeev Raizada, Mark M. Kishiyama Feb 2010

Effects Of Socioeconomic Status On Brain Development, And How Cognitive Neuroscience May Contribute To Levelling The Playing Field, Rajeev Raizada, Mark M. Kishiyama

Dartmouth Scholarship

The study of socioeconomic status (SES) and the brain finds itself in a circumstance unusual for Cognitive Neuroscience: large numbers of questions with both practical and scientific importance exist, but they are currently under-researched and ripe for investigation. This review aims to highlight these questions, to outline their potential significance, and to suggest routes by which they might be approached. Although remarkably few neural studies have been carried out so far, there exists a large literature of previous behavioural work. This behavioural research provides an invaluable guide for future neuroimaging work, but also poses an important challenge for it: how …

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Flexible Object Manipulation, Matthew P. Bell Feb 2010

Flexible Object Manipulation, Matthew P. Bell

Dartmouth College Ph.D Dissertations

Flexible objects are a challenge to manipulate. Their motions are hard to predict, and the high number of degrees of freedom makes sensing, control, and planning difficult. Additionally, they have more complex friction and contact issues than rigid bodies, and they may stretch and compress. In this thesis, I explore two major types of flexible materials: cloth and string. For rigid bodies, one of the most basic problems in manipulation is the development of immobilizing grasps. The same problem exists for flexible objects. I have shown that a simple polygonal piece of cloth can be fully immobilized by grasping all …

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The Bernstein Problem For Embedded Surfaces In The Heisenberg Group H, Donatella Danielli, Nicola Garofalo, Duy-Minh Nhieu, Scott D. Pauls Jan 2010

The Bernstein Problem For Embedded Surfaces In The Heisenberg Group H, Donatella Danielli, Nicola Garofalo, Duy-Minh Nhieu, Scott D. Pauls

Dartmouth Scholarship

In the paper [13] we proved that the only stable C 2 minimal surfaces in the first Heisenberg group H 1 which are graphs over some plane and have empty characteristic locus must be vertical planes. This result represents a sub-Riemannian version of the celebrated theorem of Bernstein. In this paper we extend the result in [13] to C 2 complete em-bedded minimal surfaces in H 1 with empty characteristic locus. We prove that every such a surface without boundary must be a vertical plane. This result represents a sub-Riemannian coun-terpart of the classical theorems of Fischer-Colbrie and Schoen, [16], …

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Quantification Of Artistic Style Through Sparse Coding Analysis In The Drawings Of Pieter Bruegel The Elder, James M. Hughes, Daniel J. Graham, Daniel N. Rockmore Jan 2010

Quantification Of Artistic Style Through Sparse Coding Analysis In The Drawings Of Pieter Bruegel The Elder, James M. Hughes, Daniel J. Graham, Daniel N. Rockmore

Dartmouth Scholarship

Recently, statistical techniques have been used to assist art historians in the analysis of works of art. We present a novel technique for the quantification of artistic style that utilizes a sparse coding model. Originally developed in vision research, sparse coding models can be trained to represent any image space by maximizing the kurtosis of a representation of an arbitrarily selected image from that space. We apply such an analysis to successfully distinguish a set of authentic drawings by Pieter Bruegel the Elder from another set of well-known Bruegel imitations. We show that our approach, which involves a direct comparison …

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The Determination Of Reddening From Intrinsic Vr Colors Of Rr Lyrae Stars, Andrea Kunder, Brian Chaboyer, Andrew Layden Jan 2010

The Determination Of Reddening From Intrinsic Vr Colors Of Rr Lyrae Stars, Andrea Kunder, Brian Chaboyer, Andrew Layden

Dartmouth Scholarship

New R-band observations of 21 local field RR Lyrae variable stars are used to explore the reliability of minimum light (V – R) colors as a tool for measuring interstellar reddening. For each star, R-band intensity mean magnitudes and light amplitudes are presented. Corresponding V-band light curves from the literature are supplemented with the new photometry, and (V – R) colors at minimum light are determined for a subset of these stars as well as for other stars in the literature. Two different definitions of minimum light color are examined, one which uses …

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The Acs Survey Of Galactic Globular Clusters. Viii. Effects Of Environment On Globular Cluster Global Mass Functions, Nathaniel E. Q. Paust, I. Neill Reid, Giampaolo Piotto, Antonio Aparicio, Jay Anderson, Ata Sarajedini, Luigi R. Bedin, Brian Chaboyer Jan 2010

The Acs Survey Of Galactic Globular Clusters. Viii. Effects Of Environment On Globular Cluster Global Mass Functions, Nathaniel E. Q. Paust, I. Neill Reid, Giampaolo Piotto, Antonio Aparicio, Jay Anderson, Ata Sarajedini, Luigi R. Bedin, Brian Chaboyer

Dartmouth Scholarship

We have used observations obtained as part of the Hubble Space Telescope/ACS Survey of Galactic Globular Clusters to construct global present-day mass functions for 17 globular clusters utilizing multi-mass King models to extrapolate from our observations to the global cluster behavior. The global present-day mass functions for these clusters are well matched by power laws from the turnoff, ≈0.8 M ☉, to 0.2-0.3 M ☉ on the lower main sequence. The slopes of those power-law fits, α, have been correlated with an extensive set of intrinsic and extrinsic cluster properties to investigate which parameters may influence the form …

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