并行计算六十年

并行计算是实现高性能计算的主要技术手段。本文回顾了并行计算技术六十多年来的发展历史,重温了并行可扩展性度量公式在并行计算发展进程中的重要地位。分析了并行计算向未来E级计算发展时面临的挑战,并建立了新的并行计算可扩展性度量模型,建模了访存、通信、可靠性、能耗等影响E级计算的因素。通过定量分析,发现和研究了并行计算向更高性能发展面临的可扩展性"墙"。最后,针对我国国情,提出了作者关于我国高性能计算未来发展的体会与思考。     

Estimating northern peatland CO2 exchange from MODIS time series data

Studies using satellite sensor-derived data as input to models for CO₂ exchange show promising results for closed forest stands. There is a need for extending this approach to other land cover types, in order to carry out large-scale monitoring of CO₂ exchange. In this study, three years of eddy covariance data from two peatlands in Sweden were averaged for 16-day composite periods and related to data from the Moderate Resolution Imaging Spectroradiometer (MODIS) and modeled photosynthetic photon flux density (PPFD). Noise in the time series of MODIS 250 m vegetation indices was reduced by using double logistic curve fits. Smoothed normalized difference vegetation index (NDVI) showed saturation during summertime, and the enhanced vegetation index (EVI) generally gave better results in explaining gross primary productivity (GPP). The strong linear relationships found between GPP and the product of EVI and modeled PPFD (R² = 0.85 and 0.76) were only slightly stronger than for the product of EVI and MODIS daytime 1 km land surface temperature (LST) (R² = 0.84 and 0.71). One probable reason for these results is that several controls on GPP were related to both modeled PPFD and daytime LST. Since ecosystem respiration (ER) was largely explained by diurnal LST in exponential relationships (R² = 0.89 and 0.83), net ecosystem exchange (NEE) was directly related to diurnal LST in combination with the product of EVI and modeled PPFD in multiple exponential regressions (R² = 0.81 and 0.73). Even though the R² values were somewhat weaker for NEE, compared to GPP and ER, the RMSE values were much lower than if NEE would have been estimated as the sum of GPP and ER. The overall conclusion of this study is that regression models driven by satellite sensor-derived data and modeled PPFD can be used to estimate CO₂ fluxes in peatlands.     

Are ICT investments paying off in Africa? An analysis of total factor productivity in six West African countries from 1995 to 2002

In the past two decades, we have seen increasing debate about information and communication technology (ICT) as an engine of growth that could lift developing nations out of poverty. Many African nations have implemented market liberalization and invested huge sums of money into their ICT sectors. But few studies have been conducted to assess the effectiveness of these investments. Demonstrating ICT sector performance is especially important because of challenges of the development of ICT policy and the United Nations agencies inability to state firmly if there are benefits to these investments. In this article, we investigated the total factor productivity (TFP) of the ICT sectors in six West African countries from 1995 to 2002. While the findings demonstrate positive growth in TFP, there is cause for concern. TFP growth in the ICT sector has been declining, and these countries are not yet able to take advantage of scale efficiencies. Careful attention must be given to future ICT investment strategies and performance management of existing ICT infrastructure if continued growth is to be achieved. © 2008 Wiley Periodicals, Inc.     

Analysis of Productivity of a Technological Cell Taking into Account Its Reliability

A semi-Markovian model with a discrete-continuous phase space of states is constructed for a technological cell. The productivity of the technological cell operating with failures of different types is determined.     

浅析建筑业内部的劳动分工

从建筑业内部的劳动专业化分工程度的角度剖析了目前建筑业内部的劳动分工和作用 ,提出了一些调动劳动者积极性、发挥劳动者潜能的有效措施 ,有助于提高企业劳动生产率     

Do high-quality local institutions shape labour productivity in Western European manufacturing firms?

We investigate the extent to which regional institutional quality shapes firm labour productivity in Western Europe, using a sample of manufacturing firms from Austria, Belgium, France, Germany, Italy, Portugal and Spain, observed over the period 2009–2014. The results indicate that regional institutional quality positively affects firms' labour productivity and that government effectiveness is the most important institutional determinant of productivity levels. However, how institutions shape labour productivity depends on the type of firm considered. Smaller, less capital endowed and high-tech sectors are three of the types of firms whose productivity is most favourably affected by good and effective institutions at the regional level.     

Organic amendment effects on crop productivity and nutrient uptake on reclaimed natural gas wellsites

Restoration of productivity on agricultural soils disturbed by industrial activity is important for agronomic and environmental reasons. Because of the role of organic matter in soil health and quality, organic amendments have been widely used in the reclamation of disturbed soils such as those on abandoned oil and natural gas wellsites. This study examined the effects of one-time applications of alfalfa (Medicago sativa L.) hay or beef cattle (Bos taurus) feedlot manure compost on wheat (Triticum aestivum L.) yield and nutrient uptake on two abandoned natural gas wellsites that had recently been reclaimed in southern Alberta, Canada. The base amendment rate (1×) [dry wt.] was 5.3 Mg ha⁻¹ for compost and 3.1 Mg ha⁻¹ for alfalfa. The five treatment amendment rates of 0, 1×, 2×, 4×, and 8× were soil-incorporated at the wellsites. Yields and plant nutrient uptake were generally higher at Hussar than at Turin, reflecting the higher inherent fertility of the soil at Hussar. Grain yields were similar for alfalfa and compost amendments, indicating that either amendment can be used depending on availability and/or transportation costs. Our results show that spring wheat yields on these reclaimed soils can be optimized at alfalfa and compost rates of no more than 6 and 10 Mg ha⁻¹, respectively. Continued monitoring of crop productivity and soil properties may provide insight into the long-term benefits of alfalfa and compost amendments in wellsite reclamation schemes. Lethbridge Research Centre contribution no. 387-07030.     

提高连铸生产能力的措施与效果

铁水增多所导致的转炉生产节奏加快以及连铸机改造后差异性的扩大,使宝钢分公司第一连铸分厂的产能压力和生产组织难度增大。为此,优化了连铸生产组织,并从连铸机生产计划的分工、工序和生产线交叉、特殊钢种的生产组织、中间包利用最大化、浇铸速度和异钢种连浇的优化等方面,提出了提高连铸产能的措施,且实施后取得了明显效果,连铸日浇钢增加了2.4炉。     

Requirements Engineering and Downstream Software Development: Findings from a Case Study

Requirements management is being recognized as one of the most important albeit difficult phases in software engineering. The literature repeatedly cites the role of well-defined requirements and requirements management process in problem analysis and project management as benefiting software development throughout the life cycle: during design, coding, testing, maintenance and documentation of software. This paper reports on the findings of an investigation into industrial practice of requirements management process improvement and its positive effects on downstream software development. The evidence reveals a strong relationship between a well-defined requirements process and increased developer productivity, improved project planning through better estimations and enhanced ability for stakeholders to negotiate project scope. These results are important since there is little empirical evidence of the actual benefits of sound requirements practice, in spite of the plethora of claims in the literature. An account of these effects not only adds to our understanding of good requirements practice but also provides strong motivation for software organizations to develop programs for improvement of their requirements processes.