Signal Control Strategy for Supersaturated Traffic at Urban Road Intersections with a Large Technical Grade Gap

To reduce the risk of queuing overflow on the urban minor road at the intersection under supersaturation where the capacity of the arterial and minor roads shows extreme disparity, reduce the adverse effects caused by long queues of vehicles on the minor road, and comprehensively balance the multiobjective requirements such as priority of the main road, queuing restrictions, and delay on the minor road, the minor road queue model at the end of red, a road remaining capacity model, and multiparameter coordinated signal control model were established, and a multiobjective genetic algorithm was used to optimize this solution. As an example, the multiparameter coordinated control strategy decreased the delay per vehicle by approximately 17% and the queue length by approximately 30%–50% on the minor road and slightly increased the delay per vehicle at the intersection and the length on the main road queue. This control strategy can make full use of the capacity of the main road to control the queue length on the minor road, effectively reduce the risk of minor road queue overflow blocking local road network traffic operation involved, and comprehensively balance the traffic demand between arterial and minor roads. It provides a reference control method for coping with the transfer of the main traffic contradiction under the oversaturated state of the road intersection with large disparity.

Synergistic Combination of TiO2 and S-PAN for Li-S Batteries with Long-Term Cyclability at High C-Rates

A ternary compound was synthesized from titanium dioxide, elemental sulfur and polyacrylonitrile throughout a simple ball-milling and heating process in inert atmosphere, and was fully characterized. The novel compound belongs to the family of sulfurized polyacrylonitrile compounds (SPAN) and was incorporated as active material in the cathode of Li-S batteries. The cells achieve high and stable capacity values at 0.5 C reaching 1885 mAh/gS for the 10th cycle and ~1600 mAh/gS after 200 cycles (498 and 422 mAh/g composite, respectively). To the best of our knowledge, we are the first to report the combination of SPAN and TiO2, and to show the synergistic behaviour of these compounds. The high capacity values observed, higher than the theoretical capacity of elemental sulfur (1675 mAh/g), are explained by the extra capacity provided by the lithiation/delithiation process of TiO2. The metallic oxide also improves the overall kinetics of the redox processes in SPAN, which helped to achieve good cycling performance at 3.3 C, with a remaining capacity of 672 mAh/gS after 1400 cycles, and even at 5 C where a remaining capacity of 660 mAh/gS after 500 cycles was recorded.

Improvements on High Temperature Lithium Oxyhalide Primary Battery for Downhole Tools Power Applications

Commercial lithium oxyhalide batteries have a very flat voltage curve. It is challenging to determine a battery's remaining capacity during and after powering downhole drilling tools. It is wasteful and environmentally hazardous to dispose of lightly used battery packs. Through innovations in battery cell design and electrolyte formulation, laboratory cells showed multiple voltage plateaus allowing easy estimation of remaining capacity at room temperature. Prototyped DD-size batteries validated the unique feature at high temperatures. If the batteries are used in downhole drilling and measurement tools, non-productive time may be shortened, and costs reduced over time. Small coin cells were assembled in an inert argon gas filled glovebox. The assembled coin cell, lithium metal foil disk, carbon electrode, and other cell components were weighted to determine electrolyte weight accurately. Carbon black electrodes were prepared by coating carbon black paste on nickel foam substrate. After overnight air drying, coated nickel foam was hot pressed to 1 mm thickness at 230 °C. DD-size cells were prototyped at a battery vendor with selected cell configurations. Performance of coin cells and prototyped DD-size cells were measured during constant current discharge tests. Discharge voltage curves of baseline coin cells mimicking commercial battery products were flat at 3.4 until sudden voltage crash at the end of discharge. Coin cells OP-33 and OP-36, with the improved design and electrolyte formula, showed two main voltage plateaus. The higher voltage plateau was around 3.85-3.60 V, and the lower voltage plateau was around 3.50-3.40 V. The sharp voltage transition from 3.60 V to 3.50 V was easy for a user or a battery management system to detect. Capacity percentage in the higher voltage plateau and the lower voltage plateau depends on the energy active chemical compositions of electrolyte. A cell design and electrolyte formulation were selected to prototype scaled-up DD-size cells. Three repeating DD-size cells were discharged at 150 °C. The overall sloping voltage curves and the obvious voltage transition between two discharge stages around 3.5 V can greatly facilitate battery capacity estimation. As of today, there is no commercial high temperature lithium oxyhalide primary battery with such a unique feature of staged and sloping battery voltage shape for capacity estimation. Compared to capacity estimation by charge counting method utilized in some battery monitoring chips, capacity estimation based on voltage change is much simpler, more accurate, and consumes less battery energy without needs of frequent current measurement and charge calculation. Any previously lightly discharged battery pack can be easily determined whether further usage is possible for the next downhole tools power application, which saves cost and reduces battery waste.

Capacity of concrete structures with corroded reinforcement and prestressing tendons

The main degradation mechanism for concrete structures is corrosion of the reinforcement and prestressing tendons. Management of structures with such degradation requires detailed understanding of their remaining strength and safety and if necessary, make a decision regarding repairs or replacement of the structure or components. Some simplified methods for estimating the residual capacity of concrete structures do exist, primarily based on a reduction of the flexural capacity equal to the percentage of the corroded area. In this paper, a more physical understanding and description of the influence of corrosion on the strength is investigated, based on a reduction of the area of the reinforcement and prestressing tendons both due to uniform corrosion and pitting corrosion. The results of these models are successfully compared to experimental results of concrete beams with corrosion. Particularly corrosion of post-tensioned tendons is a concern for concrete structures. Some disturbing examples of collapse of concrete bridges have been seen as a result of such corrosion. The paper highlights the importance of the significant strength loss of the reinforcement as a result of corrosion itself, but also the loss of ductility due to possible hydrogen embrittlement and hydrogen induced stress corrosion cracking. The paper also suggests sulphate reducing bacteria as a possible explanation to corrosion issues related to corrosion of post-tensioned tendon structures where no chloride is found. The aim of the paper is to propose a method to calculate a lower bound estimate of the remaining capacity of concrete beams with corrosion damage to reinforcement and to the prestressing tendons.

Management of a Solar-PV System with Energy Storage

A solar-PV system is generally connected to distributed generation (DG) by the utility grid. The solar inverter retains some capacity after active power generation. Reactive power compensation can be achieved by utilizing the remaining capacity of the solar-PV inverter. This paper introduces an energy management system (EMS) for real and reactive power management. The proposed EMS includes two modes: PV-STATCOM and islanding. In PV-STATCOM mode, the PI control is used whereas for the islanding mode, voltage frequency control is employed. This paper proposes the energy management of reactive power by utilizing the solar photovoltaic (PV) inverter as a static synchronous compensator (PV-STATCOM). Therefore, no other additional flexible AC transmission system controllers or series/shunt capacitors are required. During the islanding mode, the storage provides continuous supply to the load. The system is simulated using single-phase and three-phase modes with the hardware results also revealed. The proposed scheme provides a significant improvement in power factor while reducing the total harmonic distortion.

Corrosion-induced degradation assessment of steel beam using vibration-based scheme

PurposeCatastrophe of steel-structured bridges due to progressive localized corrosion may lead to a major loss in terms of life and cost if not monitored continuously or periodically. The purpose of this paper is to present a vibration-based strategy to assess the severity and monitor the deterioration caused by corrosion-induced localized damage in a simply-supported steel beam.Design/methodology/approachThe threshold damage level is defined up to the yield limit of a simply supported steel beam of size ISMB 150 × 8 × 5 under three-point bending test and the progressive damage is induced through a continuous accelerated corrosion test. Change in the fundamental natural frequency due to localized damage in the experimental beam and the modulus of elasticity (E) in the corroded zone of an updated finite element (FE) model is evaluated.FindingsThe updated FE model of the damaged beam shows a clear trend with the progressive damage of the beam and, hence, can be used to monitor the severity of damage and remaining capacity assessment of the monitored beam.Originality/valueSteel-structured bridges are prone to localized corrosion attack, and there are no standardized process or predictive model available by international steel design codes on how to consider corrosion damage in the condition assessment analysis. The vibration-based methods have gained popularity for condition assessment, and are mostly confined to damage assessment of corroded reinforced concrete (RC) beams. In this work, a vibration-based approach is presented for degradation assessment of steel beam due to progressive localized corrosion using modal hammer test.