Bond strength of steel bars embedded in high-performance fiber-reinforced cementitious composite before and after exposure to elevated temperatures

Interfacial bond strengths of steel reinforcing bars embedded in a high-performance fiber-reinforced cementitious composite (HPFRCC) are investigated in this paper. Out of 303 pullout specimens, 48 HPFRCC and 3 normal concrete specimens were tested without any heat treatment, and 240 HPFRCC and 12 normal concrete specimens were heated at 200, 400, 600, or 800 °C in a furnace for 2 h prior to testing. The effects of bar shape, diameter, and length embedded in HPFRCC on the bond strength of HPFRCC specimens were investigated. The bond strength decreased with the heating temperature and with the size and embedded length of steel bars. It was reduced further when the heated specimens were cooled in water instead of air. It was disaggregated into chemical adhesion and mechanical interlock from a comparative study of plain and deformed bars. The mechanical properties and microstructures of HPFRCC specimens before and after heat treatment were compared to understand the mechanisms of interfacial bonding degradation due to heat treatment.     

Dosing free nitrous acid for sulfide control in sewers: Results of field trials in Australia

Intermittent dosing of free nitrous acid (FNA), with or without the simultaneous dosing of hydrogen peroxide, is a new strategy developed recently for the control of sulfide production in sewers. Six-month field trials have been carried out in a rising main sewer in Australia (150 mm in diameter and 1080 m in length) to evaluate the performance of the strategy that was previously demonstrated in laboratory studies. In each trial, FNA was dosed at a pumping station for a period of 8 or 24 h, some with simultaneous hydrogen peroxide dosing. The sulfide control effectiveness was monitored by measuring, on-line, the dissolved sulfide concentration at a downstream location of the pipeline (828 m from the pumping station) and the gaseous H₂S concentration at the discharge manhole. Effective sulfide control was achieved in all nine consecutive trials, with sulfide production reduced by more than 80% in 10 days following each dose. Later trials achieved better control efficiency than the first few trials possibly due to the disrupting effects of FNA on sewer biofilms. This suggests that an initial strong dose (more chemical consumption) followed by maintenance dosing (less chemical consumption) could be a very cost-effective way to achieve consistent control efficiency. It was also found that heavy rainfall slowed the recovery of sulfide production after dosing, likely due to the dilution effects and reduced retention time. Overall, intermittent dose of FNA or FNA in combination with H₂O₂ was successfully demonstrated to be a cost-effective method for sulfide control in rising main sewers.     

Customer bill impacts of energy efficiency and net-metered photovoltaic system investments

Utility regulators and policymakers are concerned about potential increases in retail rates driven by energy efficiency (EE) programs and distributed solar photovoltaic (PV) systems, which may adversely affect utility customers that do not invest in these technologies (i.e., non-participants) and more so than those that do (i.e., participants). We assess customer bill impacts of illustrative EE programs and net-metered PV systems for a prototypical northeast utility. We find that the timing of customer EE or PV investments matters and that modest energy savings may fail to yield financial benefits sufficient to offset concomitant increases in retail rates.     

A study of the negotiated-settlement practice in regulation: Some evidence from Florida

Negotiated settlements have become a frequently used alternative to contested proceedings when setting prices charged by public utilities under the US rate-of-return regulatory model. The behavior of the representatives of consumer advocates and the firms during settlement negotiations determine customer prices. This paper examines this behavior by using data from the Florida Public Service Commission to estimate the payoff functions of both parties. The estimation suggests that the advocate and the firm weight the present rate change more than the consumer's future average price and the firm's future operating revenue in their settlement decisions. It also indicates that the time saved by settlements is not a primary reason for their popularity.     

The electricity balancing market: Exploring the design challenge

In the unbundled national electricity markets in Europe, the balancing market is the institutional arrangement that deals with the balancing of electricity demand and supply. This paper presents a framework for policy makers that identifies the relevant design variables and performance criteria that play a role in the design and analysis of European balancing markets. We outline the full extent of the design challenge through a discussion of trade-offs among performance criteria, uncertain effects of design variables, and the many inter-linkages between the balancing market and the electricity market at large. Policy makers can address the balancing market design challenge by adopting a structured approach in which design variables, performance criteria, market conditions, system developments, and resultant market incentives are explicitly considered.     

Efficiency of urban water supply in Sub-Saharan Africa: Do organization and regulation matter?

Using the model developed by Battese and Coelli (1995), we compare the technical efficiency of urban water utilities in Sub-Saharan Africa countries. We examine how private-sector participation, economic regulation, and their combination affects technical efficiency. We find that regulating water utility operations via performance contracts leads to higher technical efficiency compared to control by an independent regulatory agency. Private-sector participation in management has a positive effect on technical efficiency. However, there is no evidence of a statistically significant difference between the technical efficiency of publicly and privately owned utilities, respectively, when they are regulated by either an independent agency or a performance contract.