Practices and meanings of non-professional stock-trading in Taiwan : a case of relational work

Accepted for workshop on 21/11/2014PreprintNon peer reviewe

Stepped wedge cluster randomized controlled trials: sample size and power determinations

Stepped wedge cluster randomized controlled trials (RCTs) are increasingly used in evaluating a causal-effect relationship between an intervention and an outcome. Sample size and power calculations are critical in designing a statistical study. Thus, the purpose of our study is to evaluate the power for both the continuous and binary responses in the context of the stepped wedge cluster design including three levels (such as hospital, physician, and individual levels). The data structure of stepped wedge cluster RCTs is hierarchical and correlated, and we used the mixed models approach to account for the correlation of observations within each level. This approach, comprised of linear mixed models (LMM) and generalized linear mixed models (GLMM), is particularly appropriate for data with more than one level. For the continuous responses, we used LMM and GLMM with the identity link function; for the binary responses, we used GLMM with the logit link function. To compute the power of the hypothesis test for no intervention effect versus an assumed intervention effect, simulation studies were conducted and the empirical estimate of the power was obtained by calculating the percentage of the estimated intervention effect falling in the rejection region of the test when the hypothesis of no intervention effect is false. From the results of the simulation studies, we found that the power increased as the intervention effect increased for both the continuous and binary responses, controlling for other parameters. As the overall sample size increased, a smaller minimum detectable difference with power at least 80% can be obtained. For the continuous responses only, the power increased as the within-individual correlation increased, controlling for other parameters. This increase of power with the correlation was prominent in the low intervention effect as compared to the high intervention effect. In this study, we proposed statistical models, demonstrated power calculations, and discussed important features of sample size and power for the stepped wedge cluster design. The findings provide essential information in determining the optimal sample size and also can assure adequate power for stepped wedge cluster RCTs, which will have significant impact on research in public health in the future

Mechanical and thermal stability of hard nitride coatings

Cotutela Universitat Politècnica de Catalunya i Linköping UniversityTesi per compendi de publicacionsHard coating 's thermal stability is essential due to the high temperature environment of high-speed cutting applications, while the induced phase and microstructure evolution affects the mechanical properties. In this thesis, the mechanical stability of arc-evaporated hard nitride coatings annealed at high temperature is analyzed and connected to the phase evolution. In addition to hardness, fracture toughness is evaluated by surface and cross-sectional investigations by scanning/transmission electron microscopy of damage events by mechanical tests. The crack resistance of Ti1-xAixN with a range of Al content (x = 0.23-0.82) is studied by contact fatigue tests, where the difference in the microstructure plays a major role. Superior mechanical properties are found in annealed Ti0.63AI0.37N at 900 oC due to the spinodal decomposition. The mechanical and high-temperature properties of hard coatings can be enhanced by alloying or multi-layering. Quaternary Ti-Al-X-N (X = Cr, Nb and V) alloys are studied, and superior toughness is found in TiAI(Nb )N in both the as-deposited and annealed (1100 oC) states. The h-AIN formation in TixAI0.37Cr1-0.37-xN (x = 0.03 and 0.16) is analyzed by in-situ x-ray scattering during annealing. The kinetic energy for h-AIN formation is found to be dependent on the microstructure evolution during annealing, which varies with coating composition. High Al content h-ZrAIN/c-TiN and h-ZrAIN/c-ZrN multilayers are investigated through scratch tests followed by focused ion-beam analysis of the crack propagation. A c-Ti(Zr)N phase forms in h-ZrAIN/c-TiN multilayers at high temperatures and that contributes to enhanced hardness and fracture toughness by keeping the semi-coherency at the sub-interfaces. Finally, an in-situ analysis of coatings by x-ray scattering during a turning process is carried out. lt demonstrates the possibility of observation of stress evolution and thermal expansion of the coatings or the work piece material during machining. This experiment provides real-time information on the coating behavior during cutting.La estabilidad térmica del recubrimiento es esencial debido a que estos recubrimientos durante su aplicación son utilizados a elevada temperatura y a alta velocidad. Durante dicho proceso, la evolución microestructural afecta a las propiedades mecánicas. En dicha tesis, la estabilidad mecánica de los recubimientos duros base nitruro producidos mediante arco y recocidos a elevada temperatura son analizados y se correlacionado con su transformación de fase. La dureza, la resistencia a la fractura son evaluados mediante la observación tanto superficial como transversal mediante microscopia electrónica de barrido. La resistencia a la propagación de grieta de Ti1−xAlxN con un contenido en Al que fluctúa entre 0.23-0.82 se estudia mediante ensayos de fatiga por contacto, donde la diferencia microstructural juega un papel importante. Las mejores propiedades mecánicas se encentran en las muestras con un 0.63 de Ti donde se ha realizado un proceso de recocido a 900o C debido a la descomposición espinoidal. Las características mecánicas y de alta temperatura de recubrimientos duros pueden ser mejoradas si tenemos un recubrimiento multicapa. Aleaciones cuaternarias de Ti-Al-X-N (X = Cr, Nb y V) son estudiada, y una mejor tenacidad de fractura se encuentra para la muestra TiAl(Nb)N sin tratamiento de recocido como recocida a 1000ºC. La formación del AlN con una estructura hexagonal en la muestra TixAl0.37Cr1−0.37−xN (x = 0.03 y 0.16) son analizadas mediante ensayos in-situ de difracción de rayos X durante el proceso de recocido. Cabe mencionar que la energía cinética para la formación de la AlN con una estructura hexagonal depende del proceso de recocido, la cual hace variar la composición química del recubrimiento. Multicapas de h (hexagonal)-ZrAlN/c (cúbica)-TiN con un elevado contenido de Al son estudiadas mediante ensayos de rayado y la generación de daño es observado mediante la técnica del haz de iones focalizados. Las formas de la fase de c-Ti(Zr)N en las multicapas de (h)-ZrAlN/c-TiN formadas a elevadas temperaturas contribuyen a mejorar la dureza y la tenacidad de fractura manteniendo la semicoherencia en las intercaras entre cada capa. Finalmente, se realiza un análisis in-situ de los diferentes recubrimientos me diante dispersión de rayos X durante un proceso de torneado. En este caso, se demuestra la posibilidad de observar la evolución de las tensiones residuales y de la expansión térmica durante el proceso de conformado. Dicho experimentos proporciona información en tiempo real sobre el comportamiento del recubrimiento en condiciones de servicio.Hårda skikts högtemperaturstabilitet är viktig på grund av den höga temperaturskikten utsätts för under skärande bearbetning, och den utveckling av faser och mikrostruktur som då sker påverkar skiktets mekaniska egenskaper. I den här avhandlingen har den mekaniska stabiliteten hos arcförångade, hårda metallnitridskikt som värmebehandlats vid höga temperaturer studerats. Förutom hårdhet har även skiktens seghet utvärderats genom yt- och tvärsnittsstudier av den sprickbildning som uppstår vid mekanisk provning med hjälp av svep- och transmissionselektronmikroskopi. Segheten hos Ti1−xAlxN skikt med varierande Al-halt (x = 0.23-0.82) studerades genom utmattningsprovning och resultaten visar att förändringar i mikrostrukturen spelar en stor roll. Ti0.63Al0.37N skikten hade överlägsna mekaniska egenskaper; på grund av en fördelaktig kornstorlek i de obehandlade skikten och efter värmebehandling som ett resultat av det spinodala sönderfall som skett. De mekaniska egenskaperna och högtemperaturegenskaperna hos hårda skikt kan förbättras genom legering eller genom multilagring. I den här avhandlingen har kvarternära Ti-Al-X-N (X = Cr, Nb eller V) skikt studerats och TiAl(Nb)N skikten hade en överlägsen seghet i både obehandlat och värmebehandlat (1100oC) tillstånd. Bildandet av h-AlN i TixAl0.37Cr1−0.37−xN (x = 0.03 and 0.16) skikt studerades genom in situ röntgenspridning under värmebehandling. Den energi som krävs för att bilda h-AlN beror av mikrostrukturutvecklingen under värmebehandling vilken i sin tur beror av skiktens kemiska sammansättning. h-ZrAlN/c-TiN och h-ZrAlN/c-ZrN multilager med hög Al-halt undersöktes genom reptester följda av tvärsnittsstudier av sprickbildningen genom en analys med en fokuserad jonstråle (FIB). En c-Ti(Zr)N fas bildas vid höga temperaturer i h-ZrAlN/c-TiN multilagren och det bidrar till förhöjd hårdhet och förbättrad seghet på grund av en bibehållen koherens mellan lagren. Slutligen har in situ röntgenspridningsstudier av ytskikt utförts vid svarvning. Studien visar på möjligheten att observera spänning och värmeutvidgning av skikten eller arbetsmaterialet under bearbetning. Experimenten ger information om skiktens beteende under bearbetning i realtid.Postprint (published version

Reinforce customer satisfaction through enterprise resource planning and supply chain management integration

The purpose of this project is to try and establish a blueprint for integrating Enterprise Resource Planning (ERP) and Supply Chain Management (SCM). ERP and SCM have become popular in many industries because they help companies improve their Information Systems (IS) which helps support their operational goals. New technology is being used in resource planning and e-commerce and a stable supply chain helps corporations integrate many basic applications. This helps facilitate smooth supplier-customer interactions while minimizing transaction costs. This project is trying to provide a way in which to implement ERP systems properly into SCM. It should result in improved business performance and client satisfaction

Suppression of long-wavelength CMB spectrum from the no-boundary initial condition

The lack of correlations at the long-wavelength scales of the cosmic microwave background spectrum is a long-standing puzzle and it persists in the latest Planck data. By considering the Hartle-Hawking no-boundary wave function as the initial condition of the inflationary universe, we propose that the power suppression can be the consequence of a massive inflaton, whose initial vacuum is the Euclidean instanton in a compact manifold. We calculate the primordial power spectrum of the perturbations, and find that as long as the scalar field is moderately massive, the power spectrum is suppressed at the long-wavelength scales.Comment: 9 pages, 7 figures; journal versio

Antenatal Depressive Symptoms and Antidepressant Use in Pregnancy

Review of the current literature reveals inconsistent findings on potential associations between antidepressant use during pregnancy and adverse fetal and child health and development. This study aims to examine the effect of antenatal SSRI exposure on several neonatal (preterm birth, small- and large-for-gestational age, Apgar score, and neonatal intensive care unit admission) and child developmental outcomes (measured by Ages and Stages Questionnaire) while controlling for confounding by indication. Data were obtained from the Prenatal Health Project, a longitudinal cohort study of 2,357 women in London, Ontario. Results from univariable analysis discovered that infants exposed to in utero SSRIs were more likely to be large-for-gestational age compared to infants of women exposed to antenatal depressive symptoms but not SSRIs and to infants of women unexposed to either antenatal depression or SSRIs. The small sample size of the antidepressant-exposed population limited our study and further research is warranted to verify the significance of our findings

STABILITY OF GAA/TTC AND CTG/CAG TRINUCLEOTIDE REPEATS DURING BREAK-INDUCED REPLICATION IN YEAST

poster abstractSeveral human neurodegenerative disorders are caused by the expansion of trinucleotide repeats within or near the region of genes. To study the sta-bility of trinucleotide repeats in eukaryotic cells, we insert different number of GAA and CTG repeats in both orientations separately into the genome of Saccharomyces cerevisiae. In addition to S-phase replications, DNA can also be repaired by break-induced replication (BIR), an important process of DNA repair system that has been implicated in various chromosomal instabilities. In this study, we want to analyze the stability of trinucleotide repeats asso-ciated with BIR