153 research outputs found

    Re-Envisioning the Honors Senior Project: Experience as Research

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    One of the NCHC Basic Characteristics of a Fully Developed Honors Program is that it creates opportunities for undergraduate research, opportunities that frequently culminate in a senior thesis or capstone project (Spurrier 200–201). The senior research project typically distinguishes honors students from their non-honors counterparts in a significant way. The emphasis on undergraduate research may also distinguish an honors program or college (“or college” will be understood throughout this essay) within the university, where honors often becomes a de facto center for undergraduate research. Increasing opportunities for undergraduate research thus not only benefits honors students—by giving them a greater range of educational experiences and making them stronger candidates for jobs, fellowships, and graduate or professional school—but also helps honors programs institutionally as they seek to create alliances and obtain resources in both the university and the larger community. Promoting undergraduate research within a comprehensive university also presents a number of challenges, perhaps the most basic being how to define research. Many honors programs acknowledge this difficulty by making a distinction between a thesis and a creative activity, but research varies much more widely, as is readily apparent to any honors administrator faced with reading projects well outside her field of academic specialization. The difficulty of defining research within honors in many ways reflects challenges within universities and even individual disciplines. Some of these differences are longstanding: between qualitative and quantitative methodologies in the social sciences, for example, or between more or less overtly politically informed scholarship in the humanities. Other differences are more recent, such as the move to promote entrepreneurial research or to make universities more socially accountable by addressing “wicked problems” such as poverty, illiteracy, and climate change (Thorp and Goldstein). A second new challenge involves what might be called (to adapt a term from Alfred North Whitehead) the differing rhythms of education across a comprehensive university

    Buying Analyst and Investor Attention through IPO Proceeds

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    We examine the effect of IPO proceeds on the post-IPO information environment. We exploit variation in the amount of capital raised across IPOs that is unrelated to firm size and manager decisions using an instrumental variable approach, and find that marginal increases in IPO proceeds lead to large increases in analyst coverage and institutional ownership in the first two years a firm is public. Increases in IPO proceeds also lead to more frequent follow-on offerings and longer survival as a public firm. We find evidence that immediate shocks to ownership diversification represent one plausible channel through which changes in IPO proceeds affect long-run visibility and investor demand. Overall, our findings highlight important rewards to selling additional shares at the IPO

    An Implanted, Stimulated Muscle Powered Piezoelectric Generator

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    A totally implantable piezoelectric generator system able to harness power from electrically activated muscle could be used to augment the power systems of implanted medical devices, such as neural prostheses, by reducing the number of battery replacement surgeries or by allowing periods of untethered functionality. The features of our generator design are no moving parts and the use of a portion of the generated power for system operation and regulation. A software model of the system has been developed and simulations have been performed to predict the output power as the system parameters were varied within their constraints. Mechanical forces that mimic muscle forces have been experimentally applied to a piezoelectric generator to verify the accuracy of the simulations and to explore losses due to mechanical coupling. Depending on the selection of system parameters, software simulations predict that this generator concept can generate up to approximately 700 W of power, which is greater than the power necessary to drive the generator, conservatively estimated to be 50 W. These results suggest that this concept has the potential to be an implantable, self-replenishing power source and further investigation is underway

    Concept Developed for an Implanted Stimulated Muscle-Powered Piezoelectric Generator

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    Implanted electronic devices are typically powered by batteries or transcutaneous power transmission. Batteries must be replaced or recharged, and transcutaneous power sources burden the patient or subject with external equipment prone to failure. A completely self-sustaining implanted power source would alleviate these limitations. Skeletal muscle provides an available autologous power source containing native chemical energy that produces power in excess of the requirements for muscle activation by motor nerve stimulation. A concept has been developed to convert stimulated skeletal muscle power into electrical energy (see the preceding illustration). We propose to connect a piezoelectric generator between a muscle tendon and bone. Electrically stimulated muscle contractions would exert force on the piezoelectric generator, charging a storage circuit that would be used to power the stimulator and other devices

    Shimware: Toward Practical Security Retrofitting for Monolithic Firmware Images

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    In today’s era of the Internet of Things, we are surrounded by security- and safety-critical, network-connected devices. In parallel with the rise in attacks on such devices, we have also seen an increase in devices that are abandoned, reached the end of their support periods, or will not otherwise receive future security updates. While this issue exists for a wide array of devices, those that use monolithic firmware, where the code and data are opaquely intermixed, have traditionally been difficult to examine and protect. In this paper, we explore the challenges of retrofitting monolithic firmware images with new security measures. First, we outline the steps any analyst must take to retrofit firmware, and show that previous work is missing crucial aspects of the process, which are required for a practical solution. We then automate three of these aspects-locating attacker-controlled input, a safe retrofit injection location, and self-checks preventing modifications-through the use of novel automated program analysis techniques. We assemble these analyses into a system, Shimware, that can simplify and facilitate the process of creating a retrofitted firmware image, once the vulnerability is identified. To evaluate Shimware, we employ both a synthetic evaluation and actual retrofitting of three case study devices: a networked bench power supply, a Bluetooth-enabled cardiac implant monitor, and a high-end programmable logic controller (PLC). Not only could our system identify the correct sources of input, injection locations, and self-checks, but it injected payloads to correct serious safety and security-critical vulnerabilities in these devices.</p

    Intrinsic Point Defects (Vacancies and Antisites) in CdGeP\u3csub\u3e2\u3c/sub\u3e Crystals

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    Cadmium germanium diphosphide (CdGeP2) crystals, with versatile terahertz-generating properties, belong to the chalcopyrite family of nonlinear optical materials. Other widely investigated members of this family are ZnGeP2 and CdSiP2. The room-temperature absorption edge of CdGeP2 is near 1.72 eV (720 nm). Cadmium vacancies, phosphorous vacancies, and germanium-on-cadmium antisites are present in as-grown CdGeP2 crystals. These unintentional intrinsic point defects are best studied below room temperature with electron paramagnetic resonance (EPR) and optical absorption. Prior to exposure to light, the defects are in charge states that have no unpaired spins. Illuminating a CdGeP2 crystal with 700 or 850 nm light while being held below 120 K produces singly ionized acceptors (VCd−) and singly ionized donors (GeCd+), as electrons move from VCd2− vacancies to GeCd2+ antisites. These defects become thermally unstable and return to their doubly ionized charge states in the 150–190 K range. In contrast, neutral phosphorous vacancies (VP0) are only produced with near-band-edge light when the crystal is held near or below 18 K. The VP0 donors are unstable at these lower temperatures and return to the singly ionized VP+ charge state when the light is removed. Spin-Hamiltonian parameters for the VCd− acceptors and VP0 donors are extracted from the angular dependence of their EPR spectra. Exposure at low-temperature to near-band-edge light also introduces broad optical absorption bands peaking near 756 and 1050 nm. A consistent picture of intrinsic defects in II-IV-P2 chalcopyrites emerges when the present CdGeP2 results are combined with earlier results from ZnGeP2, ZnSiP2, and CdSiP2

    Deep Selenium Donors in ZnGeP\u3csub\u3e2\u3c/sub\u3e Crystals: An Electron Paramagnetic Resonance Study of a Nonlinear Optical Material

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    Zinc germanium diphosphide (ZnGeP2) is a ternary semiconductor best known for its nonlinear optical properties. A primary application is optical parametric oscillators operating in the mid-infrared region. Controlled donor doping provides a method to minimize the acceptor-related absorption bands that limit the output power of these devices. In the present study, a ZnGeP2 crystal is doped with selenium during growth. Selenium substitutes for phosphorus and serves as a deep donor. Significant concentrations of native defects (zinc vacancies, germanium-on-zinc antisites, and phosphorous vacancies) are also present in the crystal. Electron paramagnetic resonance (EPR) is used to establish the atomic-level model for the neutral charge state of the selenium donor. The S = 1/2 signal from the neutral donors is produced at 6 K by illuminating with 633 nm light (electrons excited from doubly ionized Zn vacancies convert Se+p donors to Se0p donors). A g matrix, with principal values of 2.088, 2.203, and 1.904, is extracted from the angular dependence of the EPR spectrum. The principal-axis direction associated with the 1.904 principal value is close to a Se–Ge bond. This indicates an asymmetric distribution of unpaired spin density around the selenium ion and thus predicts the deep donor behavior
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