A Tree Locality-Sensitive Hash for Secure Software Testing

Bugs in software that make it through testing can cost tens of millions of dollars each year, and in some cases can even result in the loss of human life. In order to eliminate bugs, developers may use symbolic execution to search through possible program states looking for anomalous states. Most of the computational effort to search through these states is spent solving path constraints in order to determine the feasibility of entering each state. State merging can make this search more efficient by combining program states, allowing multiple execution paths to be analyzed at the same time. However, a merge with dissimilar path constraints dramatically increases the time necessary to solve the path constraint. Currently, there are no distance measures for path constraints, and pairwise comparison of program states is not scalable. A hashing method is presented that clusters constraints in such a way that similar constraints are placed in the same cluster without requiring pairwise comparisons between queries. When combined with other state-of-the-art state merging techniques, the hashing method allows the symbolic executor to execute more instructions per second and find more terminal execution states than the other techniques alone, without decreasing the high path coverage achieved by merging many states together

Optimal Occulter Design for Finding Extrasolar Planets

One proposed method for finding terrestrial planets around nearby stars is to use two spacecraft--a telescope and a specially shaped occulter that is specifically designed to prevent all but a tiny fraction of the starlight from diffracting into the telescope. As the cost and observing cadence for such a mission will be driven largely by the separation between the two spacecraft, it is critically important to design an occulter that can meet the observing goals while flying as close to the telescope as possible. In this paper, we explore this tradeoff between separation and occulter diameter. More specifically, we present a method for designing the shape of the outer edge of an occulter that is as small as possible and gives a shadow that is deep enough and large enough for a 4m telescope to survey the habitable zones of many stars for Earth-like planets. In particular, we show that in order for a 4m telescope to detect in broadband visible light a planet 0.06 arcseconds from a star shining $10^{10}$ times brighter than the planet requires a specially-shaped occulter 50m in diameter positioned about $72,000$ km in front of the telescope.Comment: 14 pages, 4 figures, 15 subfigure

Modified Strength Testing Protocol For Use In Subjects With Posterior Tibial Tendon Dysfunction

Please view abstract in the attached PDF file

Investigation of Mobility Limiting Mechanisms in Undoped Si/SiGe Heterostructures

We perform detailed magnetotransport studies on two-dimensional electron gases (2DEGs) formed in undoped Si/SiGe heterostructures in order to identify the electron mobility limiting mechanisms in this increasingly important materials system. By analyzing data from 26 wafers with different heterostructure growth profiles we observe a strong correlation between the background oxygen concentration in the Si quantum well and the maximum mobility. The highest quality wafer supports a 2DEG with a mobility of 160,000 cm^2/Vs at a density 2.17 x 10^11/cm^2 and exhibits a metal-to-insulator transition at a critical density 0.46 x 10^11/cm^2. We extract a valley splitting of approximately 150 microeV at a magnetic field of 1.8 T. These results provide evidence that undoped Si/SiGe heterostructures are suitable for the fabrication of few-electron quantum dots.Comment: Related papers at http://pettagroup.princeton.ed

Fear and Resistance Far from the Border: Human Rights and Student Engagement in Immigrant and Refugee Communities in Dayton, Ohio

Similar to articles 23-27 of the UDHR, articles 25-31 of the 1990 International Convention on the Protection of the Rights of All Migrant Workers and Members of Their Families specify equal access by immigrants to educational, vocational & health/social services and equality of living and working conditions and employment contracts. Beginning in 2007, Professor Majka has involved students in his immigration classes in research on the challenges and obstacles immigrants and refugees in the Dayton area experience relevant for those areas specified by the Convention. Joined by students in Professor Linda Majka classes, students arranged and conducted interviews with representatives of Dayton-area immigrant and refugee communities and with staff of human service agencies who work with these communities. Students also helped organize and observed focus groups of specific populations. Students in Professor Hallett’s Anthropology of Human Rights class participated in the latest research beginning in 2017. In this presentation, we will describe two outcomes of student engagement. One is the impact on the students themselves. All described their participation as genuine learning experiences. Besides putting human faces on class materials, some described it as transformative. Interviewing prepared several for travel to the countries of origin of some interviewees, e.g. Mexico and El Salvador. Some found their experiences useful for post-graduate plans, e.g. volunteering, law school and MSW programs. Others made public presentations. The interviews have provided the basis of several senior research projects and honors theses. We will provides quotes from students’ reflections. The second is the impact on the larger community. The research findings have resulted in 4 conferences (2008, 2009, 2012 and 2019) that brought together Dayton-area residents, including many leaders and elected officials, with leaders of immigrant and refugee communities. The first two conferences helped provide the momentum that resulted in the 2011 Welcome Dayton initiative

Impacts of the Trump Administration’s Policies on Immigrants and Refugees in Dayton

The Trump administration’s executive orders and policy changes regarding refugee resettlement and stepped-up Immigration and Customs Enforcement (ICE) actions are likely to create serious human rights and humanitarian impacts. These include separation of children from their parents, denial of due process in immigration courts, lengthy incarceration in detention centers, denial or loss of employment, denial of visas to citizens of some predominantly Muslim countries, denial of entry to previously vetted refugees scheduled for resettlement, and return (refoulment) of persons with well-founded fears of persecution or torture. These actions will potentially impact key human rights areas and concerns, such as nondiscrimination, equality before the law, equal protection of the law, protection against arbitrary punishment, the right to asylum, and the special protections accorded to families. They involve the Universal Declaration of Human Rights, the Covenant on Civil and Political Rights, the Convention on the Elimination of All Forms of Racial Discrimination, and refugee and torture conventions protecting rights to asylum and protection from deportation when that is likely to result in persecution, torture, or death. In this presentation, we will share the results of a study examining impacts of the administration’s actions on immigrant and refugee populations in the Dayton, Ohio, area. Impacts may include increased fear and stress and changes in daily routines; detention or deportation; family separation; economic hardships; increased instances of discrimination and harassment; difficulty accessing institutional services; and restrictions on mobility or visits from family. The research involves interviews with leaders of local immigrant and refugee communities and focus groups conducted with members of these communities during spring, summer, and early fall 2017. Staff of human service agencies who work with these communities will also be interviewed to examine the role of local institutions as intermediaries. The research team includes faculty and undergraduate students from the University of Dayton