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  1. We introduce the scheduler subversion problem, where lock usage patterns determine which thread runs, thereby subverting CPU scheduling goals. To mitigate this problem, we introduce Scheduler-Cooperative Locks (SCLs), a new family of locking primitives that controls lock usage and thus aligns with system-wide scheduling goals; our initial work focuses on proportional share schedulers. Unlike existing locks, SCLs provide an equal (or proportional) time window called lock opportunity within which each thread can acquire the lock. We design and implement three different scheduler-cooperative locks that work well with proportional-share schedulers: a user-level mutex lock (u-SCL), a reader-writer lock (RWSCL), and a simplified kernel implementation (k-SCL). We demonstrate the effectiveness of SCLs in two user-space applications (UpScaleDB and KyotoCabinet) and the Linux kernel. In all three cases, regardless of lock usage patterns, SCLs ensure that each thread receives proportional lock allocations that match those of the CPU scheduler. Using microbenchmarks, we show that SCLs are efficient and achieve high performance with minimal overhead under extreme workloads.
  2. Despite increased calls for the need for more diverse engineers and significant efforts to “move the needle,” the composition of students, especially women, earning bachelor’s degrees in engineering has not significantly changed over the past three decades. Prior research by Klotz and colleagues (2014) showed that sustainability as a topic in engineering education is a potentially positive way to increase women’s interest in STEM at the transition from high school to college. Additionally, sustainability has increasingly become a more prevalent topic in engineering as the need for global solutions that address the environmental, social, and economic aspects of sustainability have become more pressing. However, few studies have examined students’ sustainability related career for upper-level engineering students. This time point is a critical one as students are transitioning from college to industry or other careers where they may be positioned to solve some of these pressing problems. In this work, we answer the question, “What differences exist between men and women’s attitudes about sustainability in upper-level engineering courses?” in order to better understand how sustainability topics may promote women’s interest in and desire to address these needs in their future careers. We used pilot data from the CLIMATE survey given tomore »228 junior and senior civil, environmental, and mechanical engineering students at a large East Coast research institution. This survey included questions about students’ career goals, college experiences, beliefs about engineering, and demographic information. The students surveyed included 62 third-year students, 96 fourth-year students, 29 fifth-year students, and one sixth-year student. In order to compare our results of upper-level students’ attitudes about sustainability, we asked the same questions as the previous study focused on first-year engineering students, “Which of these topics, if any, do you hope to directly address in your career?” The list of topics included energy (supply or demand), climate change, environmental degradation, water supply, terrorism and war, opportunities for future generations, food availability, disease, poverty and distribution of resources, and opportunities for women and/or minorities. As the answer to this question was binary, either “Yes,” or “No,” Pearson’s Chi-squared test with Yates’ continuity correction was performed on each topic for this question, comparing men and women’s answers. We found that women are significantly more likely to want to address water supply, food availability, and opportunities for woman and/or minorities in their careers than their male peers. Conversely, men were significantly more likely to want to address energy and terrorism and war in their careers than their female peers. Our results begin to help us understand the particular differences that men and women, even far along in their undergraduate engineering careers, may have in their desire to address certain sustainability outcomes in their careers. This work begins to let us understand certain topics and pathways that may support women in engineering as well as provides comparisons to prior work on early career undergraduate students. Our future work will include looking at particular student experiences in and out of the classroom to understand how these sustainability outcome expectations develop.« less
  3. Abstract The EXO-200 experiment searched for neutrinoless double-beta decay of 136 Xe with a single-phase liquid xenon detector. It used an active mass of 110 kg of 80.6%-enriched liquid xenon in an ultra-low background time projection chamber with ionization and scintillation detection and readout. This paper describes the design and performance of the various support systems necessary for detector operation, including cryogenics, xenon handling, and controls. Novel features of the system were driven by the need to protect the thin-walled detector chamber containing the liquid xenon, to achieve high chemical purity of the Xe, and to maintain thermal uniformity across the detector.
    Free, publicly-accessible full text available February 1, 2023