Cooperative transaction hierarchies: Transaction support for design applications

Traditional atomic and nested transactions are not always well-suited to cooperative applications, such as design applications. Cooperative applications place requirements on the database that may conflict with the serializability requirement. They require transactions to be long, possibly nested, and able to interact with each other in a structured way. We define a transaction framework, called acooperative transaction hierarchy, that allows us to relax the requirement for atomic, serializable transactions to better support cooperative applications. In cooperative transaction hierarchies, we allow the correctness specification for groups of designers to be tailored to the needs of the application. We usepatterns andconflicts to specify the constraints imposed on a group's history for it to be correct. We also provide some primitives to smooth the operation of the members. We characterize deadlocks in a cooperative transaction hierarchy, and provide mechanisms for deadlock detection and resolution. We examine issues associated with failure and recovery.     

Efficient parallel algorithms for path problems in directed graphs

In this paper we describe a technique for finding efficient parallel algorithms for problems on directed graphs that involve checking the existence of certain kinds of paths in the graph. This technique provides efficient algorithms for finding dominators in flow graphs, performing interval and loop analysis on reducible flow graphs, and finding the feedback vertices of a digraph. Each of these algorithms takesO(log² n) time using the same number of processors needed for fast matrix multiplication. All of these bounds are for an EREW PRAM.     

Case Study: Sediment Control at Water Intake for Large Thermal-Power Station on a Small River

A large thermal-power station drawing water from a small alluvial river had a chronic problem with alluvial-bed sediment buildup at the station’s river-water intake structure. The problem required expensive corrective dredging and adversely affected the station’s fuel-consumption efficiency. This case-study paper describes how the sediment problem was successfully controlled by means of modifications to the area in front of the intake and the upstream riverbank. The modifications comprised erosion-promoting vanes and a skimming wall, together with realignment of the riverbank upstream of the intake. A hydraulic model was used to aid the design of the modifications. Installation of the modifications required construction techniques that enabled the intake and power station to continue operating while the modifications were being installed.     

Polarization dynamics and non-equilibrium switching processes in ferroelectrics

Time- and temperature-dependent effects are critical for the operation of non-volatile memories based on ferroelectrics. In this paper, we assume a domain nucleation process of the polarization reversal and we discuss the polarization dynamics in the framework of a non-equilibrium statistical model. This approach yields analytical expressions which can be used to explain a wide range of time- and temperature-dependent effects in ferroelectrics. Domain wall velocity derived in this work is consistent with a domain wall creep behavior in ferroelectrics. In the limiting case of para-electric equilibrium, the model yields the well-known Curie law. We also present experimental P-E loops data obtained for soft ferroelectrics at various temperatures. The experimental coercive fields at various temperatures are well predicted by the coercive field formula derived in our theory.     

Sub-micrometer particulate air pollution and cardiovascular mortality in Beijing, China

Background

While the link between particulate matter and cardiovascular mortality is well established, it is not fully investigated and understood which properties of the aerosol might be responsible for the health effects, especially in polluted mega-city areas.

Objectives

Our goal was to explore the association between daily cardiovascular mortality and different particle metrics in the sub-micrometer range in Beijing, China.

Methods

We obtained daily counts of cause-specific cardiovascular deaths in the Beijing urban area for the period March 2004 to August 2005. Concurrently, continuous measurements of particle number size distributions were performed. Particle number concentrations (NC) between 0.003 μm and 0.8 μm were converted to particle mass and surface area concentrations assuming spherical particles. Semi-parametric Poisson regression models adjusting for trend, seasonality, day of the week, and meteorology were used to estimate immediate, delayed and cumulative particle effects. Additionally, effect modification by air mass origin was investigated.

Results

We observed associations between daily cardiovascular mortality and particle NC for a 2-days delay. Moreover, nearly all particle metrics showed 2-days delayed associations with ischemic heart disease mortality. The strongest association was found for particle NC in the size range 0.03-0.1 μm (7.1% increase in daily mortality with a 95%-confidence interval of 2.9%-11.5%, per an increase of 6250 particles/cm³). Results for surface and mass concentrations with a lag of two days indicated effect modification by air mass origin, whereas effects of particle NC were not modified.

Conclusions

Results show an elevated risk of cardiovascular mortality in Beijing from short-term exposure to particulate air pollution in the sub-micrometer range. Results also indicate that locally produced smaller particles and regionally transported particles may exhibit different effects in Beijing.     

Innovations in Large-Scale Supported Distance Teaching: Transformation for the Internet,Not Just Translation

This paper reports on large-scale trials of Internet-based university-level distance teaching. The use of technology, and more specifically the Internet, has been an important advance for distance education. However, simply translating material from familiar media into electronic form is rarely productive—and is certainly inadequate for supported distance education, which aims to engage the student in a “community of learning.” The value Internet technology brings to distance education lies not in direct translation from other media but in transformation of support mechanisms to exploit its potential range. The paper addresses how instruction and support functions can be served and potentially enhanced by an Internet-based structure. It considers which changes in culture help to preserve or improve teaching quality while adapting to screen-based and often asynchronous interactions. It discusses our trials of mechanisms for interactions among students and tutors; assignment marking using an electronic marking tool; electronic assignment handling; synchronous and asynchronous Internet-based problem sessions; and automatic student registration. The paper summarizes qualitative and quantitative findings of an extensive evaluation involving several hundred students over three courses and considering learning, student experience, assignment marking, problem sessions, scalability, and integration into existing administrative structures. It highlights both costs and gains of using the Internet to transform the distance learning environment for those associated with it: students, tutors, administrators, and institutions.     

Less is more: Meta-analyses of sensitivity and attachment interventions in early childhood.

Is early preventive intervention effective in enhancing parental sensitivity and infant attachment security, and if so, what type of intervention is most successful? Seventy studies were traced, producing 88 intervention effects on sensitivity (n=7,636) and/or attachment (n=1,503). Randomized interventions appeared rather effective in changing insensitive parenting (d=0.33) and infant attachment insecurity (d=0.20). The most effective interventions used a moderate number of sessions and a clear-cut behavioral focus in families with, as well as without, multiple problems. Interventions that were more effective in enhancing parental sensitivity were also more effective in enhancing attachment security, which supports the notion of a causal role of sensitivity in shaping attachment. (PsycINFO Database Record (c) 2010 APA, all rights reserved)