Energy resources and use: The present (2008) situation and possible sustainable paths to the future

Recent estimates and forecasts of the oil, gas, and coal resources and their reserve/production ratio, nuclear and renewable energy potential, and energy uses are surveyed. A brief discussion of the status and prospects of fossil, nuclear and renewable energy use, and of power generation (including hydrogen, fuel cells, micropower systems, and the futuristic concept of generating power in space for terrestrial use) is given. Ways to resolve the problem of the availability, cost, and sustainability of energy resources alongside the rapidly rising demand are discussed. The author's view of the promising energy R&D areas, their potential, foreseen improvements and their time scale, and last year's trends in government funding, are presented.     

Erosion of POSS-polyimide films under hypervelocity impact and atomic oxygen: The role of mechanical properties at elevated temperatures

Low Earth orbital debris impacts on the external surfaces of satellites have increased dramatically in recent years. Polyimides are used as the outer layer of thermal control insulation blankets, covering most of the external spacecraft surfaces that are exposed to the space environment. A recently developed material, named polyhedral oligomeric silsesquioxane (POSS)-polyimide, shows significant enhancement in withstanding the space environment. In this work, the combined effect of ground-simulated hypervelocity space debris impacts and atomic oxygen (AO) on the erosion of POSS-containing polyimide films was investigated. During such hypervelocity impacts, elevated temperatures, on the order of hundreds degrees, are formed. A laser-driven flyer system was used to accelerate aluminum flyers to impact velocities of up to 3 km s^?1. The impacted films were exposed to an oxygen RF plasma environment, simulating the effect of AO in the low Earth orbit. Impacted polyimide films exposed to AO revealed synergistic erosion effect, while impacted POSS-containing samples showed improved erosion resistance. The increased erosion rate of the impacted polyimide film is explained by formation of residual stresses that affect the oxidation mainly by increasing the diffusivity of oxygen into the subsurface layers. Mechanical properties of the POSS-containing samples performed at 450 °C and fractographic examination supports the above hypothesis.     

Concentrating solar thermal power as a viable alternative in China's electricity supply

Study of low-carbon and pollution renewable alternatives for China revealed that concentrating solar thermal (CST) electric power generation was underemphasized in China's renewable energy plan. The analysis shows the competitive viability of CST: (1) China has the key prerequisites to make CST power generation economical including high-quality insolation and appropriate land, (2) CST's proven history, scale, and dispatchability makes it a good utility-scale power option, especially in the economically underdeveloped Western regions, (3) while CST power is currently more expensive than coal-fired electricity on a nominal basis, when costs of externalities are accounted for, CST, at 11.4 US cents/kWh, can become 57% cheaper than scrubbed coal and 29% cheaper than nuclear power, (4) CST power continues dropping in cost due to economies of scale and technological improvements and can potentially realize a levelized electricity cost of around 4 cents/kWh within ten years, (5) it would significantly rise in competitiveness if and when China completes the extensive smart grid for connecting its solar-abundant western regions with the high-demand eastern regions, (6) CST has the potential to positively impact Western China's economy, but proper policy and deal structure must be in place to ensure that the local community shares the benefit.     

The energy situation and its sustainable development strategy in China

The paper briefly summarizes China’s energy situation and sustainable development strategy as they were by 2009. The energy consumption in 2009 is reported to be 3.1 billion tons standard coal equivalent, 1/7 of the world total, 6.3% higher than in the year 2008, and its share of world CO₂ emissions increased rapidly to 20.3% in 2006. These trends are most likely to continue with China’s plan to accomplish its social and economy development goals. To address these problems and also respond to increasing world pressure for reduction of greenhouse gas emissions, the Chinese government plans and has legislated promotion of energy conservation, efficiency, renewable energy technologies and use, and reduction of energy-related environmental impacts to reduce energy intensity by 20% during the 2006-2010 period, and to reduce the CO₂ emission/GDP ratio by 40-45% by 2020 relative to 2005. China is facing severe energy-related challenges that conflict resources shortages with the planned rapid economic development, energy use with the related environmental pollution, and new technology with the old production/consumption patterns. It is recognized that energy development must, however, follow a sustainable path to coordinate economy growth, social development, and environmental protection.     

Sparse weighted voting classifier selection and its linear programming relaxations

We consider the problem of minimizing the number of misclassifications of a weighted voting classifier, plus a penalty proportional to the number of nonzero weights. We first prove that its optimum is at least as hard to approximate as the minimum disagreement halfspace problem for a wide range of penalty parameter values. After formulating the problem as a mixed integer program (MIP), we show that common “soft margin” linear programming (LP) formulations for constructing weighted voting classsifiers are equivalent to an LP relaxation of our formulation. We show that this relaxation is very weak, with a potentially exponential integrality gap. However, we also show that augmenting the relaxation with certain valid inequalities tightens it considerably, yielding a linear upper bound on the gap for all values of the penalty parameter that exceed a reasonable threshold. Unlike earlier techniques proposed for similar problems (Bradley and Mangasarian (1998) [4], Weston et al. (2003) [14]), our approach provides bounds on the optimal solution value.     

Partial Matching of Nonrigid Shapes by Learning Piecewise Smooth Functions

Learning functions defined on non-flat domains, such as outer surfaces of non-rigid shapes, is a central task in computer vision and geometry processing. Recent studies have explored the use of neural fields to represent functions like light reflections in volumetric domains and textures on curved surfaces by operating in the embedding space. Here, we choose a different line of thought and introduce a novel formulation of partial shape matching by learning a piecewise smooth function on a surface. Our method begins with pairing sparse landmarks defined on a full shape and its part, using feature similarity. Next, a neural representation is optimized to fit these landmarks, efficiently interpolating between the matched features that act as anchors. This process results in a function that accurately captures the partiality. Unlike previous methods, the proposed neural model of functions is intrinsically defined on the given curved surface, rather than the classical embedding Euclidean space. This representation is shown to be particularly well-suited for representing piecewise smooth functions. We further extend the proposed framework to the more challenging part-to-part setting, where both shapes exhibit missing parts. Comprehensive experiments highlight that the proposed method effectively addresses partiality in shape matching and significantly outperforms leading state-of-the-art methods in challenging benchmarks. Code is available at https://github.com/davidgip74/Learning-Partiality-with-Implicit-Intrinsic-Functions     

Energy,exergy, and Second Law performance criteria

Performance criteria, such as efficiencies and coefficients of performance, for energy systems, are commonly used but often without sufficient understanding and consistence. The situation becomes particularly incoherent when simultaneous energy interactions of different types, such as work, heating and cooling, take place with a system. Also, the distinction between exergy and Second Law efficiencies is not clearly recognized by many. It is attempted here to clarify the definitions and use of energy and exergy based performance criteria, and of the Second Law efficiency, with an aim at the advancement of international standardization of these important concepts.     

Optimal insulation of solar heating system pipes and tanks

A compact and time-effective insulation design procedure for solar heating system piping and water-filled thermal storage tanks was developed. Recognizing the particular sensitivity of solar systems to cost, the economic aspect of the problem was treated by a comprehensive present-value life-cycle cost analysis. In the development of the method, a numerical sensitivity analysis was performed to determine the relative effects of all relevant independent variables (within their pertinent ranges) on piping and tank heat transfer coefficient values. For the acceptable error limits of ± 14% for pipes and ± 19% for tanks, it was found that one may assume that only the nominal pipe diameter (or tank diameter), the thermal conductivity of the insulation, and the insulation's thickness have an effect on the overall heat transfer coefficient. Based on this result, design graphs and tables are presented which can be used to determine the optimal insulation thickness and type, total annual heat losses, present-value annual costs of insulation and lost heat, and overall insulation R-values. The use of the method is illustrated by calculating all the above quantities for all piping and storage tanks for the University of Pennsylvania SolaRow House. The present method provided insulation thicknesses slightly greater than those obtained by the ETI technique.A major conclusion of the study is that the cost of insulation in solar systems is not insignificant (e.g., ~15% in SolaRow), and that heat losses through insulation could amount to an important percentage of the useful solar energy collected (e.g., 24% in SolaRow). This re-emphasizes the need for a careful design of insulation in solar systems.