Underwater Fiber–Reinforced Polymers Repair of Prestressed Piles in the Allen Creek Bridge

This paper presents an overview of a demonstration project in which corroding prestressed piles located in tidal waters were wrapped underwater using carbon and glass fiber-reinforced polymer material. An innovative instrumentation scheme was developed to allow assessment of the prewrap and postwrap corrosion state using linear polarization. This system is simple to install and eliminates the need for wiring or junction boxes. The underwater wrap used a unique water-activated urethane resin system that eliminated the need for cofferdam construction. Linear polarization measurements taken before and after wrapping indicate that the corrosion rate in the wrapped specimens is consistently lower than those in its unwrapped counterpart. These preliminary findings are encouraging and suggest that underwater wrapping without cofferdam construction may provide a cost-effective solution for pile repair.     

Catalyst Design by NH4OH Treatment of USY Zeolite

Hierarchical zeolites are a class of superior catalysts which couples the intrinsic zeolitic properties to enhanced accessibility and intracrystalline mass transport to and from the active sites. The design of hierarchical USY (Ultra‐Stable Y) catalysts is achieved using a sustainable postsynthetic room temperature treatment with mildly alkaline NH₄OH (0.02 m ) solutions. Starting from a commercial dealuminated USY zeolite (Si/Al = 47), a hierarchical material is obtained by selective and tuneable creation of interconnected and accessible small mesopores (2–6 nm). In addition, the treatment immediately yields the NH₄⁺ form without the need for additional ion exchange. After NH₄OH modification, the crystal morphology is retained, whereas the microporosity and relative crystallinity are decreased. The gradual formation of dense amorphous phases throughout the crystal without significant framework atom leaching rationalizes the very high material yields (>90%). The superior catalytic performance of the developed hierarchical zeolites is demonstrated in the acid‐catalyzed isomerization of α‐pinene and the metal‐catalyzed conjugation of safflower oil. Significant improvements in activity and selectivity are attained, as well as a lowered susceptibility to deactivation. The catalytic performance is intimately related to the introduced mesopores, hence enhanced mass transport capacity, and the retained intrinsic zeolitic properties.     

The effect of dust accumulation on line-focus parabolic trough solar collector performance

Based on the major Department of Energy Solar Industrial Process Heat Program, it has been determined that the existing techniques for predicting the performance of parabolic trough solar collectors greatly overpredict the thermal output of these systems. The objective of the research reported herein is to improve the predictive capability of existing models by incorporating a factor that accounts for dust and dirt accumulation on the optical surfaces. This has been accomplished by modifying the optical efficiency with a dust factor to account for the reduced reflectivity of the mirror and reduced transmissivity of the cover glass. This technique has been developed independent of the test data used for verification. The dust factors have been developed from exposure tests conducted at six different sites, so that it is also independent of location and collector type. Wash frequency and optical degradation rate are input to the model to compute the time varying dust factors. Recommendations for these parameters are provided based on long-term observations. The complete model is then used to provide realistic predictions of real-world performance of solar IPH systems.     

Future trends of building heating and cooling loads and energy consumption in different climates

Principal component analysis of dry-bulb temperature, wet-bulb temperature and global solar radiation was considered, and a new climatic index (principal component Z) determined for two emissions scenarios – low and medium forcing. Multi-year building energy simulations were conducted for generic air-conditioned office buildings in Harbin, Beijing, Shanghai, Kunming and Hong Kong, representing the five major architectural climates in China. Regression models were developed to correlate the simulated monthly heating and cooling loads and building energy use with the corresponding Z. The coefficient of determination (R²) was largely within 0.78–0.99, indicating strong correlation. A decreasing trend of heating load and an increasing trend of cooling load due to climate change in future years were observed. For low forcing, the overall impact on the total building energy use would vary from 4.2% reduction in severe cold Harbin (heating-dominated) in the north to 4.3% increase in subtropical Hong Kong (cooling-dominated) in the south. In Beijing and Shanghai where heating and cooling are both important, the average annual building energy use in 2001–2100 would only be about 0.8% and 0.7% higher than that in 1971–2000, respectively.     

Heat and cold stresses in different climate zones across China: A comparison between the 20th and 21st centuries

Summer and winter discomfort in terms of heat and cold stresses in the nine major architectural climate zones and sub-zones across China in the 21st century were investigated using predictions from general circulation models for the low and medium emissions scenarios. For the six severe cold and cold climate zones in the north, reductions in cumulative cold stress outweighed the increase in cumulative heat stress resulting in an overall decreasing trend in the annual cumulative stress, and vice versa for the other three warmer climate zones in the south. Compared with the 20th century, significant reduction in the cumulative cold stress was observed across the six zones in severe cold and cold climates, ranging from 15.8 in cold-III to 42.3 in severe cold-II. There were modest increases in the cumulative heat stress from 0.3 in cold-II to 12.3 in cold-III. For the warmer climates in the south, reduction in cumulative cold stress ranged from 7.6 in hot summer and warm winter (HSWW) to 10.3 in hot summer and cold winter, while cumulative heat stress increased from 9.9 in the mild zone to 30.6 in HSWW. A reduction in cold stress would result in less winter heating and an increase in heat stress more cooling requirement.     

Some implementation issues associated with multidimensional interval Newton methods

This paper presents the development of an optimal interval Newton method for systems of nonlinear equations. The context of solving such systems of equations is that of optimization of nonlinear mathematical programs. The modifications of the interval Newton method presented in this paper provide computationally effective enhancements to the general interval Newton method. The paper demonstrates the need to compute an optimal step length in the interval Newton method in order to guarantee the generation of a sequence of improving solutions. This method is referred to as the optimal Newton method and is implemented in multiple dimensions. Secondly, the paper demonstrates the use of the optimal interval Newton method as a feasible direction method to deal with non-negativity constraints. Also, included in this implementation is the use of a matrix decomposition technique to reduce the computational effort required to compute the Hessian inverse in the interval Newton method. The methods are demonstrated on several problems. Included in these problems are mathematical programs with perturbations in the problem coefficients. The numerical results clearly demonstrate the effectiveness and efficiency of these approaches.