Beyond Good and Evil: Formalizing the Security Guarantees of Compartmentalizing Compilation

Compartmentalization is good security-engineering practice. By breaking a large software system into mutually distrustful components that run with minimal privileges, restricting their interactions to conform to well-defined interfaces, we can limit the damage caused by low-level attacks such as control-flow hijacking. When used to defend against such attacks, compartmentalization is often implemented cooperatively by a compiler and a low-level compartmentalization mechanism. However, the formal guarantees provided by such compartmentalizing compilation have seen surprisingly little investigation. We propose a new security property, secure compartmentalizing compilation (SCC), that formally characterizes the guarantees provided by compartmentalizing compilation and clarifies its attacker model. We reconstruct our property by starting from the well-established notion of fully abstract compilation, then identifying and lifting three important limitations that make standard full abstraction unsuitable for compartmentalization. The connection to full abstraction allows us to prove SCC by adapting established proof techniques; we illustrate this with a compiler from a simple unsafe imperative language with procedures to a compartmentalized abstract machine.Comment: Nit

Direct determination of the ambipolar diffusion length in GaAs/AlGaAs heterostructures by cathodoluminescence

A new technique for determining carrier diffusion lengths by cathodoluminescence measurements is presented. The technique is extremely accurate and can be applied to a variety of structures. Ambipolar diffusion lengths are determined for GaAs quantum well material, bulk GaAs, Al0.21Ga0.79As, and Al0.37Ga0.63As. A large increase in the diffusion length is found for Al0.37Ga0.63As and is attributed to an order of magnitude increase in lifetime

Unconventional Hall effect in oriented Ca3_3Co4_4O9_9 thin films

Transport properties of the good thermoelectric misfit oxide Ca$_3$Co$_4$O$_9$ are examined. In-plane resistivity and Hall resistance measurements were made on epitaxial thin films which were grown on {\it c}-cut sapphire substrates using the pulsed laser deposition technique. Interpretation of the in-plane transport experiments relates the substrate-induced strain in the resulting film to single crystals under very high pressure ($\sim$ 5.5 GPa) consistent with a key role of strong electronic correlation. They are confirmed by the measured high temperature maxima in both resistivity and Hall resistance. While hole-like charge carriers are inferred from the Hall effect measurements over the whole investigated temperature range, the Hall resistance reveals a non monotonic behavior at low temperatures that could be interpreted with an anomalous contribution. The resulting unconventional temperature dependence of the Hall resistance seems thus to combine high temperature strongly correlated features above 340 K and anomalous Hall effect at low temperature, below 100 K.Comment: Submitted to Physical Review B (2005

Lion metaphors in Chinese and English

This study intends to explore the cultural similarities and differences between the lion metaphors in Mandarin Chinese and British English. Most previous studies on animal metaphors focussed on the expressions with human beings as the target domain by collecting data either from questionnaires or dictionaries based on the Conceptual Metaphor Theory. This study, however, focusses on the expressions with non-humans as the target domains and is based on data collected from authoritative corpora. Three hundred and ninety-seven metaphorical expressions in Mandarin Chinese were identified from the Modern Chinese Corpus compiled by the Centre for Chinese Linguistics of Peking University (CCL Corpus) and 241 metaphorical expressions in British English were identified from the British National Corpus (BNC). After analysing the expressions from the perspective of the source domain and the target domain, the results show that first, the metaphorical expressions in Mandarin Chinese are mainly projected from the lion’s appearance to non-humans, but those in British English are mainly projected from the lion’s characteristics to non-humans. Second, the expressions are mainly mapped onto seven target domains in each language; four are the same. In addition, the dominant evaluation of the seven target domains in each language is mostly neutral. Third, ten conceptual metaphors were generalised from Mandarin Chinese and one from British English. All of these indicate the occurrence of cultural similarities as well as differences in the lion metaphors in the two languages

Supply chain strategy in post-earthquake Haiti

Thesis (M. Eng. in Logistics)--Massachusetts Institute of Technology, Engineering Systems Division, 2011.Cataloged from PDF version of thesis.Includes bibliographical references (p. [41]-[42]).Introduction: Partners In Health (PIH) is an international, non-profit healthcare organization with operations in several countries on multiple continents. PIH focuses on providing healthcare treatment to people living in some of the poorest places in the world, and has been operating in Haiti since 1985. At that time, PIH established a small community clinic in the central Haiti village of Cange. Today that facility has grown to become an entire medical complex, featuring a 104-bed, full-service hospital with two operating rooms, adult and pediatric wards, and clinics treating a variety of diseases and issues, from women's health to infectious diseases. In addition, Zamni Lasante ("Partners In Health" in Haitian Creyeol) has also expanded its operations to 11 other sites across Haiti's Central Plateau and beyond (Figure 1). Today, ZL ranks as one of the largest nongovernmental health care providers in Haiti - serving a catchment area of 1.2 million across the Central Plateau and the Lower Artibonite. ZL employs over 4,000 people, almost all of them Haitians, including doctors, nurses and community health workers (Zamni Lasante/ Haiti). From its beginnings 25 years ago, PIH/ZL has grown tremendously, and recent years have been no exception. Since 2004, patient encounters have increased almost threefold, from 0.9 million to 2.6 million, and the number of clinical sites has almost doubled. This growth has corresponded to an increase in drugs and supplies. In 2006, approximately 1000 m3 of drugs and supplies were moved through the system. Only two years later, in 2008, that number had more than doubled to 2200 m3 . This significant increase has greatly strained the underlying supply chain.by Scott C. Alexander.M.Eng.in Logistic

A novel technique for the direct determination of carrier diffusion lengths in GaAs/AlGaAs heterostructures using cathodoluminescence

A new technique for determining carrier diffusion lengths in direct gap semiconductors by cathodoluminescence measurement is presented. Ambipolar diffusion lengths are determined for GaAs quantum well material, bulk GaAs, and Al_xGa_(1-x)As with x up to 0.38. A large increase in the diffusion length is found as x approaches 0.38 and is attributed to an order of magnitude increase in lifetime

The wealth effects of REIT property acquisitions and dispositions: the creditors’ perspective

Prior studies of REIT property transaction activity focus on shareholder wealth effects. This study examines the effects of property acquisitions, dispositions, and overall trading activity on unsecured bond spreads, credit rating changes, and rating outlooks using a sample of the listed equity REITs in the U.S. We find that active property trading in general decreases creditors’ wealth, but this negative impact is significantly mitigated for REITs with positive NAV premiums and when REITs use sale proceeds to pay down debt after the transactions. We also find that property transactions followed by an increased geographic focus significantly increase bond yield spreads and decrease the probability of credit rating upgrades

Valley degeneracy in biaxially strained aluminum arsenide quantum wells

This paper details a complete formalism for calculating electron subband energy and degeneracy in strained multi-valley quantum wells grown along any orientation with explicit results for the AlAs quantum well case. A standardized rotation matrix is defined to transform from the conventional- cubic-cell basis to the quantum-well-transport basis whereby effective mass tensors, valley vectors, strain matrices, anisotropic strain ratios, and scattering vectors are all defined in their respective bases. The specific cases of (001)-, (110)-, and (111)-oriented aluminum arsenide (AlAs) quantum wells are examined, as is the unconventional (411) facet, which is of particular importance in AlAs literature. Calculations of electron confinement and strain in the (001), (110), and (411) facets determine the critical well width for crossover from double- to single-valley degeneracy in each system. The notation is generalized to include miscut angles, and can be adapted to other multi-valley systems. To help classify anisotropic inter-valley scattering events, a new primitive unit cell is defined in momentum space which allows one to distinguish purely in-plane inter-valley scattering events from those that requires an out-of-plane momentum scattering component.Comment: 17 pages, 4 figures, 2 table

A Self-learning Nonlinear Variable Gain Proportional Derivative (PD) Controller in Robot Manipulators

This paper proposes a nonlinear variable gain Proportional-Derivative (PD) controller that exhibits self-constructing and self-learning capabilities. In this method, the conventional linear PD controller is augmented with a nonlinear variable PD gain control signal using a dynamic structural network. The dynamic structural network known as Growing Multi-Experts etwork grows in time by placing hidden nodes in regions of the state space visited by the system during operation. This results in a network that is "economic" in terms of network sileo The proposed approach enhances the adaptability of conventional PD controller while preserving its' linear structure. Based on the simulation study on variable load and friction compensation, the fast adaptation is shown to be able to compensate the non-linearity and the uncertainty in the robotic system