Parametric study of seismic performance of super-elastic shape memory alloy-reinforced bridge piers

One of the important measures of post-earthquake functionality of bridges after a major earthquake is residual displacement. In many recent major earthquakes, large residual displacements resulted in demolition of bridge piers due to the loss of functionality. Replacing the conventional longitudinal steel reinforcement in the plastic hinge regions of bridge piers with super-elastic shape memory alloy (SMA) could significantly reduce residual deformations. In this study, numerical investigations on the performance of SMA-reinforced concrete (RC) bridge bents to monotonic and seismic loadings are presented. Incremental dynamic analyses are conducted to compare the response of SMA RC bents with steel RC bents considering the peak and the residual deformations after seismic events. Numerical study on multiple prototype bridge bents with single and multiple piers reinforced with super-elastic SMA or conventional steel bars in plastic hinge regions is conducted. Effects of replacement of the steel rebar by SMA rebar on the performance of the bridge bents are studied. This paper presents results of the parametrical analyses on the effects of various design and geometric parameters, such as the number and geometry of piers and reinforcement ratio of the RC SMA bridge bents on its performance.     

Selective CO2 Capture and High Proton Conductivity of a Functional Star‐of‐David Catenane Metal–Organic Framework

Network structures based on Star‐of‐David catenanes with multiple superior functionalities have been so far elusive, although numerous topologically interesting networks are synthesized. Here, a metal–organic framework featuring fused Star‐of‐David catenanes is reported. Two triangular metallacycles with opposite handedness are triply intertwined forming a Star‐of‐David catenane. Each catenane fuses with its six neighbors to generate a porous twofold intercatenated gyroid framework. The compound possesses exceptional stability and exhibits multiple functionalities including highly selective CO₂ capture, high proton conductivity, and coexistence of slow magnetic relaxation and long‐range ordering.     

Electrical properties of conductive Ge nanocrystal thin films fabricated by low temperature in situ growth

Thin films composed of Ge nanocrystals embedded in an amorphous SiO(2) matrix (Ge-NC TFs) were prepared using a low temperature in situ growth method. Unexpected high p-type conductivity was observed in the intrinsic Ge-NC TFs. Unintentional doping from shallow dopants was excluded as a candidate mechanism of hole generation. Instead, the p-type characteristic was attributed to surface state induced hole accumulation in NCs, and the hole conduction was found to be a thermally activated process involving charge hopping from one NC to its nearest neighbor. Theoretical analysis has shown that the density of surface states in Ge-NCs is sufficient to induce adequate holes for measured conductivity. The film conductivity can be improved significantly by post-growth rapid thermal annealing and this effect is explained by a simple thermodynamic model. The impact of impurities on the conduction properties was also studied. Neither compensation nor enhancement in conduction was observed in the Sb- and Ga-doped Ge-NC TFs, respectively. This could be attributed to the fact that these impurities are no longer shallow dopants in NCs and are much less likely to be effectively activated. Finally, the photovoltaic effect of heterojunction diodes employing such Ge-NC TFs was characterized in order to demonstrate its functionality in device implementation.     

An investigation into the mechanical and tribological properties of plasma electrolytic oxidation and hard-anodized coatings on 6082 aluminum alloy

A ceramic coating on AA6082 aluminum alloy prepared by plasma electrolytic oxidation (PEO) has been studied and compared against a sulphuric acid hard-anodized coating on the same alloy. Surface morphology and microstructures of the coatings have been examined by scanning electron microscopy. X-ray diffraction is used to determine the phase composition of the coatings. The adhesion strength of the coatings has been evaluated using a scratch test method. The coating's mechanical properties such elastic modulus and hardness data have been generated using a dynamic ultra-microhardness tester. Sliding wear tests with different loading rates are performed on the coatings in order to assess their wear resistance. Test results show that the PEO treated samples exhibit significantly better mechanical properties compared to hard anodized samples. The elastic modulus and hardness of the PEO coating are 2-3 times greater than of the hard anodized coating and subsequently, an improved wear resistance of the PEO coating has been achieved. The mechanical properties of the coatings and their relations to their tribological performance are discussed.     

Management of price uncertainty in short-term generation planning

Price uncertainty is faced by gencos in the scheduling of their units in competitive power markets. the proper way to deal with the uncertainty depends on the risk preference of the genco. two important means to manage the price uncertainty are (i) suitable flexible bids and (ii) the use of hedging tools such as forward contracts. the influence of these factors in the genco's short-term generation planning and the corresponding profit performances is studied. the market price is represented by lognormal distribution, genco risk behaviour is represented by exponential utility functions, the bid functions are taken to be flexible and simple contracts for hedging are assumed available. the unit commitment problem is combined with the hedging problem to obtain the optimal solution. formulation of the problem to maximise profit in the spot market and its extension to incorporate the risk behaviour of the gencos and the forward contacts for hedging is presented. solution method based on genetic algorithms is implemented in matlab. it is observed through numerical examples that the flexible outputs and the forward contracts can be used to hedge against price risks to achieve desired profit performance according to gencos' risk behaviour.     

Structural characterizations of diglycerol monomyristate reverse micelles in aromatic solvent ethylbenzene

Using small-angle X-ray scattering (SAXS) we have investigated the shape and size of diglycerol monomyristate (designated as C14G2) nonionic surfactant reverse micelles in aromatic solvent ethylbenzene as a function of surfactant concentration, temperature, and water. When C14G2 is added into ethylbenzene globular type reverse micelles with maximum core diameter ca. 4.5 nm are formed under ambient conditions. The micellar structure (shape and size) did not change with the surfactant concentration. However, an increase in temperature decreased the micellar size due to an increase in the critical packing parameter (cpp). Surfactant becomes more lipophilic upon heating and the micellar curvature tends to become more negative at higher temperature. Addition of a small amount of water caused a significant micellar growth. For instance, incorporation of 0.3% water in the 5% C14G2/ethylbenzene system resulted in the formation of 2.1 time bigger micelles with a small water pool in the micellar core. Besides the micellar shape is modified into an ellipsoidal prolate, whose scenario can be understood in terms of hydration of the surfactant's headgroup. Hydration decreases the cpp and favors micellar growth. An increase of temperature of a water incorporated system decreased the micellar size due to dehydration, which is equivalent to rod-to-sphere type transition.     

Using global positioning system for bus priority in London: traffic signals close to bus stops

London's bus network is one of the largest and most comprehensive urban transport systems in the world. The contribution of buses is recognised by implementing a series of initiatives including bus priority at traffic signals. London has a long history of the implementation of bus priority at traffic signals. It has kept pace with the development of new technologies by updating its bus priority system. Now, London is moving towards a bus management system based on global positioning system (GPS), which will also be used to provide bus priority at traffic signals. The authors describe theoretical work carried out by TRG on behalf of Transport for London Bus Priority Team to tackle the challenge posed by locational error associated with GPS where a traffic signal is close to a bus stop     

Economic Transmission Planning Model Suitable for a Regulated Network Service Provider

Conventional transmission planning models are subject to constant debate in the context of competitive markets, due to the functional unbundling of transmission sector from generation and distribution sectors and due to the new environment regulations. A value-based transmission planning model is proposed, suitable for an unbundled transmission network service provider having no assets in the generation sector. The model minimizes the long-term transmission investment costs and the expected social costs incurred to its clients, energy producers, and consumers, in the power auctions due to transmission bottlenecks. The uncertainties involved when incorporating short-term market models into long-term planning models are modeled with probabilistic representations for the bid prices, the component availabilities, and the hourly load variations. These features make this model suitable in the new environment paradigm. Generalized Benders decomposition technique with nonsequential Monte Carlo technique is employed to solve the final stochastic mixed-integer optimization model. Case studies are given to illustrate the performance of this model by implementing it in the modified Garver’s six-bus test system and the IEEE 24-bus reliability test system for a single planning year.