Space-Efficient Parallel Algorithms for Combinatorial Search Problems

We present space-efficient parallel strategies for two fundamental combinatorial search problems, namely, backtrack search and branch-and-bound, both involving the visit of an $n$-node tree of height $h$ under the assumption that a node can be accessed only through its father or its children. For both problems we propose efficient algorithms that run on a $p$-processor distributed-memory machine. For backtrack search, we give a deterministic algorithm running in $O(n/p+h\log p)$ time, and a Las Vegas algorithm requiring optimal $O(n/p+h)$ time, with high probability. Building on the backtrack search algorithm, we also derive a Las Vegas algorithm for branch-and-bound which runs in $O((n/p+h\log p \log n)h\log^2 n)$ time, with high probability. A remarkable feature of our algorithms is the use of only constant space per processor, which constitutes a significant improvement upon previous algorithms whose space requirements per processor depend on the (possibly huge) tree to be explored.Comment: Extended version of the paper in the Proc. of 38th International Symposium on Mathematical Foundations of Computer Science (MFCS

The chemisorption of hydrogen atoms on metal surfaces

Imperial Users onl

Microscopic observations of X-ray and gamma-ray induced decomposition of ammonium perchlorate crystals

The X-ray and gamma-ray induced decomposition of ammonium perchlorate was studied by optical, transmission, and scanning electron microscopy. This material is a commonly used oxidizer in solid propellents which could be employed in deep-space probes, and where they will be subjected to a variety of radiations for as long as ten years. In some respects the radiation-induced damage closely resembles the effects produced by thermal decomposition, but in other respects the results differ markedly. Similar radiation and thermal effects include the following: (1) irregular or ill-defined circular etch pits are formed in both cases; (2) approximately the same size pits are produced; (3) the pit density is similar; (4) the c face is considerably more reactive than the m face; and (5) most importantly, many of the etch pits are aligned in crystallographic directions which are the same for thermal or radiolytic decomposition. Thus, dislocations play an important role in the radiolytic decomposition process

Motivating the Generations

This paper examines the various generations that include the greatest generation, the baby-boomers, generation X, and generation Y. The research encompasses many motivational elements that each generation covets, rejects, or shares. These generations are at different stages in life and each plays a vital role within our society. The workforce has become a melting pot of generational influences that produce a unique and complex dynamic that economic entities must decipher

Perceptions of Role Conflict and Workplace Stress Among Women Working in Two Traditionally Male Professions

Role conflict and workplace stress can result in psychological and physical disorders. Research has indicated that societal forces are ingrained concerning how gendered behaviors are manifested in the workplace. However, research has not included women working in male-dominated professions, nor has research examined how stress and role conflict might differ for women in these professions. Understanding the different experiences of women in two distinct professions might illuminate the diversity of experiences in these understudied environments. This quantitative study, based on role-congruity and transactional stress theories, examined and compared women\u27s perceptions of role conflict and stress in 2 male-dominated professions. A cross-sectional survey design was used to collect data on perceived workplace role conflict and workplace stress from female aviators (n = 66) recruited from the Ninety-Nines Association of Professional Aviators and female marketing executives (n = 63) recruited from the Women\u27s Marketers of the Berkshires. ANOVA revealed that female marketers reported higher role conflict on the success, power, and competition and conflicts in family relations subscales than did female aviators. Female aviators reported higher role conflict on the restrictive emotionality and restrictive affectionate behavior subscales than did female marketers. Female aviators perceived greater workplace stress severity whereas female marketers perceived greater workplace stress frequency. Correlations revealed relationships between role conflict and stress for female marketers, but not for female aviators. This research creats greater awareness of role conflict and workplace stress in women. Organizations may use these findings to develop strategies to eliminate the negative ramifications of gender-role conflict and workplace stress on women

PENGARUH MODEL PEMBELAJARAN RECIPROCAL TEACHING TERHADAP KEMAMPUAN PENALARAN MATEMATIS DAN SELF-EFFICACY SISWA SMA

Norsibnu Herley (2017), Pengaruh Model Pembelajaran Reciprocal Teaching Terhadap Kemampuan Penalaran Matematis Dan Self-Efficacy Siswa Sma Peranan matematika sangat penting dalam pendidikan, karena matematika merupakan ratu ilmu. Dan salah satu aspek yang perlu dikembangkan yaitu kemampuan penalaran matematis. Namun kemampuan penalaran matematis siswa masih rendah. Hal ini disebabkan karena proses belajar siswa jarang melakukan penalaran terhadap pembelajaran dan materi-materi yang diberikan. Sehingga akan berpengaruh terhadapat kemampuan Self-efficacy siswa. Penggunaan model pembelajaran yang dapat mengembangkan kemampuan penalaran matematis dan Self-efficacy siswa salah satunya yaitu model pembelajaran Reciprocal Teaching. Penelitian ini bertujuan untuk mengkaji penerapan model pembelajaran Reciprocal Teaching terhadap pengaruh kemampuan penalaran matematis dan Self-efficacy siswa. Penelitian ini menggunakan metode eksperimen. Desain penelitian yang digunakan adalah desain kelompok kontrol pretest-postest. Populasi yang digunakana dalam penelitian ini adalah seluruh siswa SMAN 13 Bandung. Sampel yang dipilih dalam penelitiah ini adalah siswa kelas XI Mipa 7 sebagai kelas Eksperimen dan siswa kelas XI Mipa 6 sebagai kelas Kontrol yang dipilih secara acak. Untuk masalah yang diteliti dalam penelitian ini yaitu pengaruh model pembelajaran Reciprocal Teaching terhadap kemampuan penalaran matematis dan Self-efficacy siswa sma. instrumen yang dilakukan untuk pengumpulan data menggunakan tes kemampuan penalaran matematis dan Self-efficacy siswa. Data tes kemampuan penalaran matematis dan Self-efficacy siswa menggunakan uji normalitas. Uji homogenitas dan uji indepent sample t-test. Dan untuk data angket Self-efficacy diubah menajdi data interval kemudian dianalisis menggunakan menggunakan uji normalitas. Uji homogenitas dan uji indepent sample t-test. Hasil dari penelitian menunjukkan bahwa penalaran matematis dan Self-efficacy siswa yang memperoleh model pembelajaran menggunakan model pembelajaran Reciprocal Teaching lebih baik dari pada siswa yang memperoleh model pembelajaran Problem-Based Learning. Dengan demikian model pembelajaran Reciprocal Teaching dapat dijadikan sebagai salah satu alternatif guru dalam melaksanakan pembelajaran dikelas. Kata kunci : Model Pembelajaran Reciprocal Teaching, Kemampuan penalaran matematis, Self-efficacy, Model Pembelajaran Problem-Based Learning

Huerta urbana, labranza grande -San Blas-

Trabajo de gradoCon el ánimo de resolver el problema de la escasez de alimentos que tienen algunas familias del barrio san Blas, se propone una huerta urbana de 12.000 m2, que pretende ser distribuida mediante la asignación de parcelas a los núcleos familiares desplazados y a los menos favorecidos. Desde luego está orientada a la formación de alumnos de colegios vecinos o de otras localidades.PregradoArquitect

The Initial Public Offering Quandary: Is There a State and Time Dependency?

Initial public offerings (IPOs) continue to play a critical role in the capital markets and the overall economy. With the total number of IPOs remaining considerably below historic levels, developing a more thorough understanding of their drivers and how they vary under different conditions could benefit market participants and regulators. In this dissertation, I consider the relevant academic literature and extend the paradigm that stock market growth positively influences IPO activity, and market volatility tempers IPO volume—while also accounting for the present instability in the data through a regime-switching3 approach. I will show that the interplay of the Chicago Board Options Exchange Volatility Index (VIX Index) and the Wilshire 5000 Total Market Index (Wilshire 5000 Index) returns, along with lagged IPO values, create both state and time dependency in the IPO market. These intertemporal results are meaningful for investment bankers, academic scholars, law firms, and professional investors participating in the IPO market

Cambios microestructurales de agregados de carbonato de calcio generados a partir de secado por aspersión

El secado por aspersión es una técnica ampliamente utilizadaen las industrias química, farmacéutica y de alimentos para generar sólidos secos en polvo. Las aplicaciones de los materiales obtenidos bajo esta técnica dependeránespecialmente de la microestructura generada durante elproceso. Es posible controlar esta microestructura a partirde cambios en temperatura y flujo de aire durante el secado,presencia de biomoléculas, entre otras. En el presentetrabajo se evaluaron los cambios microestructurales deagregados de carbonato de calcio, debidos a variacionesen la temperatura del proceso de secado. El material obtenidose caracterizó por dispersión de luz estática, microscopiaelectrónica de barrido y espectroscopia infrarroja.Se encontró que la temperatura del proceso promuevecambios microestructurales del material en conjuncióncon cambios conformacionales de una proteína láctea.Las principales microestructuras encontradas fueron agregadosesféricos y toroidales