Establishment of a reedbed within a created surface water fed wetland nature reserve

In the early 1990's, outline designs for two wetland nature reserves were being prepared: the Teeside International Nature Reserve (TINR) and the Cardiff Bay Barrage Environmental Compensation Measures at Redwick, Gwent. The initial design for both proposals identified reedbed as a desirable habitat for establishment. The initial design works identified the importance of reedbed evapotranspiration [ET(Reed)] within the water budget, however, literature searches identified a paucity of information on this parameter. Field experiments for the measurement of ET(Reed) from Phragmites australis are described for three sites distributed across England and Wales. Reference Crop Evapotranspiration (ETo) was calculated using techniques recommended by the Food and Agriculture Organisation. A technique for the calculation of a reedbed crop coefficient [Kc(Reed)[, from ET(Reed) and ETo data is discussed. Kc(Reed) values produced in the project were found to be similar to those developed previously in continental Europe. Mean monthly and crop development stage Kc(Reed) values are presented which are applicable in the UK and possibly worldwide. A conceptual hydrological model of surface water fed reedbed systems is developed, and used to calculate the hydrological sustainability of reedbed creation areas in the UK. Finally, the water budget model is verified using data from a small clay catchment located on the TINR. In addition, a methodology is developed for the hydrological design of surface water fed reedbed systems, and recommendations required for the feasibility, design and establishment stage of reedbed creation sites. Further research needs are also identified.

A series-dynamic-resistor-based converter protection scheme for doubly-fed induction generator during various fault conditions

This paper proposes a new converter protection method, primarily based on a series dynamic resistor (SDR) that avoids the doubly-fed induction generator (DFIG) control being disabled by crowbar protection during fault conditions. A combined converter protection scheme based on the proposed SDR and conventional crowbar is analyzed and discussed. The main protection advantages are due to the series topology when compared with crowbar and dc-chopper protection. Various fault overcurrent conditions (both symmetrical and asymmetrical) are analyzed and used to design the protection in detail, including the switching strategy and coordination with crowbar, and resistance value calculations. PSCAD/EMTDC simulation results show that the proposed method is advantageous for fault overcurrent protection, especially for asymmetrical faults, in which the traditional crowbar protection may malfunction.

Low protein diet fed exclusively during mouse oocyte maturation leads to behavioural and cardiovascular abnormalities in offspring

Early embryonic development is known to be susceptible to maternal undernutrition, leading to a disease-related postnatal phenotype. To determine whether this sensitivity extended into oocyte development, we examined the effect of maternal normal protein diet (18% casein; NPD) or isocaloric low protein diet (9% casein; LPD) restricted to one ovulatory cycle (3.5 days) prior to natural mating in female MF-1 mice. After mating, all females received NPD for the remainder of gestation and all offspring were litter size adjusted and fed standard chow. No difference in gestation length, litter size, sex ratio or postnatal growth was observed between treatments. Maternal LPD did, however, induce abnormal anxiety-related behaviour in open field activities in male and female offspring (P <0.05). Maternal LPD offspring also exhibited elevated systolic blood pressure (SBP) in males at 9 and 15 weeks and in both sexes at 21 weeks (P <0.05). Male LPD offspring hypertension was accompanied by attenuated arterial responsiveness in vitro to vasodilators acetylcholine and isoprenaline (P <0.05). LPD female offspring adult kidneys were also smaller, but had increased nephron numbers (P <0.05). Moreover, the relationship between SBP and kidney or heart size or nephron number was altered by diet treatment (P <0.05). These data demonstrate the sensitivity of mouse maturing oocytes in vivo to maternal protein undernutrition and identify both behavioural and cardiovascular postnatal outcomes, indicative of adult disease. These outcomes probably derive from a direct effect of protein restriction, although indirect stress mechanisms may also be contributory. Similar and distinct postnatal outcomes were observed here compared with maternal LPD treatment during post-fertilization preimplantation development which may reflect the relative contribution of the paternal genome. © Journal compilation © 2008 The Physiological Society.

Recent research trend of economic-lot scheduling problems

Purpose - This research note aims to present a summary of research concerning economic-lot scheduling problem (ELSP). Design/methodology/approach - The paper's approach is to review over 100 selected studies published in the last 15 years (1997-2012), which are then grouped under different research themes. Findings - Five research themes are identified and insights for future studies are reported at the end of this paper. Research limitations/implications - The motivation of preparing this research note is to summarize key research studies in this field since 1997, when the ELSP problems have been verified as NP-hard. Originality/value - ELSP is an important scheduling problem that has been studied since the 1950s. Because of its complexity in delivering a feasible analytical closed form solution, many studies in the last two decades employed heuristic algorithms in order to come up with good and acceptable solutions. As a consequence, the solution approaches are quite diversified. The major contribution of this paper is to provide researchers who are interested in this area with a quick reference guide on the reviewed studies. © Emerald Group Publishing Limited.

Non-stationary stochastic inventory lot-sizing with emission and service level constraints in a carbon cap-and-trade system

Firms worldwide are taking major initiatives to reduce the carbon footprint of their supply chains in response to the growing governmental and consumer pressures. In real life, these supply chains face stochastic and non-stationary demand but most of the studies on inventory lot-sizing problem with emission concerns consider deterministic demand. In this paper, we study the inventory lot-sizing problem under non-stationary stochastic demand condition with emission and cycle service level constraints considering carbon cap-and-trade regulatory mechanism. Using a mixed integer linear programming model, this paper aims to investigate the effects of emission parameters, product- and system-related features on the supply chain performance through extensive computational experiments to cover general type business settings and not a specific scenario. Results show that cycle service level and demand coefficient of variation have significant impacts on total cost and emission irrespective of level of demand variability while the impact of product's demand pattern is significant only at lower level of demand variability. Finally, results also show that increasing value of carbon price reduces total cost, total emission and total inventory and the scope of emission reduction by increasing carbon price is greater at higher levels of cycle service level and demand coefficient of variation. The analysis of results helps supply chain managers to take right decision in different demand and service level situations.

Incorporating Water Sensitive Urban Design (WSUD) practices into the planning context:the conceptual case for lot-scale developments

In recent decades, a number of sustainable strategies and polices have been created to protect and preserve our water environments from the impacts of growing communities. The Australian approach, Water Sensitive Urban Design (WSUD), defined as the integration of urban planning and design with the urban water cycle management, has made considerable advances on design guidelines since 2000. WSUD stormwater management systems (e.g. wetlands, bioretentions, porous pavement etc), also known as Best Management Practices (BMPs) or Low Impact Development (LID), are slowly gaining popularity across Australia, the USA and Europe. There have also been significant improvements in how to model the performance of the WSUD technologies (e.g. MUSIC software). However, the implementation issues of these WSUD practices are mainly related to ongoing institutional capacity. Some of the key problems are associated with a limited awareness of urban planners and designers; in general, they have very little knowledge of these systems and their benefits to the urban environments. At the same time, hydrological engineers should have a better understanding of building codes and master plans. The land use regulations are equally as important as the physical site conditions for determining opportunities and constraints for implementing WSUD techniques. There is a need for procedures that can make a better linkage between urban planners and WSUD engineering practices. Thus, this paper aims to present the development of a general framework for incorporating WSUD technologies into the site planning process. The study was applied to lot-scale in the Melbourne region, Australia. Results show the potential space available for fitting WSUD elements, according to building requirements and different types of housing densities. © 2011 WIT Press.

A new sensorless speed control scheme for doubly-fed reluctance generators

This paper presents the development and experimental validation of a novel angular velocity observer-based field-oriented control algorithm for a promising low-cost brushless doubly fed reluctance generator (BDFRG) in wind power applications. The BDFRG has been receiving increasing attention because of the use of partially rated power electronics, the high reliability of brushless design, and competitive performance to its popular slip-ring counterpart, the doubly fed induction generator. The controller viability has been demonstrated on a BDFRG laboratory test facility for emulation of variable speed and loading conditions of wind turbines or pump drives.

Developing a new SVPWM control strategy for open-winding brushless doubly fed reluctance generators

In this paper, a new open-winding control strategy is proposed for a brushless doubly fed reluctance generator (BDFRG) used for stand-alone wind turbine or ship generators. The BDFRG is characterized with two windings on the stator: a power winding and a control winding. The control winding is fed with dual two-level three-phase converters, and a vector control scheme based on space vector pulsewidth modulation is designed. Compared with traditional three-level inverter systems, the dc-link voltage and the voltage rating of power devices in the proposed system are reduced by 50% while still greatly improving the reliability, redundancy, and fault tolerance of the proposed system by increasing the switching modes. Its performance is evaluated by simulation in MATLAB/Simulink and an experimental study on a 42-kW prototype machine.

Split converter-fed SRM drive for flexible charging in EV/HEV applications

Electric vehicles (EVs) and hybrid EVs are the way forward for green transportation and for establishing low-carbon economy. This paper presents a split converter-fed four-phase switched reluctance motor (SRM) drive to realize flexible integrated charging functions (dc and ac sources). The machine is featured with a central-tapped winding node, eight stator slots, and six rotor poles (8/6). In the driving mode, the developed topology has the same characteristics as the traditional asymmetric bridge topology but better fault tolerance. The proposed system supports battery energy balance and on-board dc and ac charging. When connecting with an ac power grid, the proposed topology has a merit of the multilevel converter; the charging current control can be achieved by the improved hysteresis control. The energy flow between the two batteries is balanced by the hysteresis control based on their state-of-charge conditions. Simulation results in MATLAB/Simulink and experiments on a 150-W prototype SRM validate the effectiveness of the proposed technologies, which may provide a solution to EV charging issues associated with significant infrastructure requirements.

Constant V/Hz control based on DSP for open winding doubly-fed wind power generator

A DSP implementation of Space Vector PWM (SVPWM) using constant V/Hz control for the open winding doubly-fed generator is proposed. This control of SVPWM modulation mode and open winding structure combination has the high voltage utilization ratio, greatly improves the control precision of the system, and reduces the stator winding output current distortion rate, though the complexity of the system is increased. This paper describes the basic principle of SVPWM and discusses the particularity of SVPWM waveform generated by hybrid vector under the condition of open winding. This method is applied to a state of doubly-fed wind power generator. The experimental verification shows that this control method can make the output voltage amplitude of the doubly-fed induction generator be 380V and the frequency be 50Hz by using of TMS32028335 chip based on constant V/Hz control of symmetric SVPWM modulation wave.

Direct power control with common mode voltage elimination for open-winding brushless doubly-fed wind power generators

In this paper, a new open-winding control strategy is proposed for a brushless doubly-fed reluctance generator (BDFRG) applicable for wind turbines. The BDFRG control winding is fed via a dual two-level three-phase converter using a single dc bus. Direct power control based on maximum power point tracking with common mode voltage elimination is designed, which not only the active and reactive power is decoupled, but the reliability and redundancy are all improved greatly by increasing the switching modes of operation, while DC-link voltage and rating of power devices decreased by 50% comparing to the traditional three-level converter systems. Consequently its effectiveness is evaluated by simulation tests based on a 42-kW prototype generator.

Performance comparison of direct power control for brushless doubly-fed wind power generator with different control winding structure

A novel open-winding brushless doubly-fed generator (BDFG) system with two two-level bidirectional converters is proposed. This topology is equivalent to a three-level bidirectional converter connected to the typical BDFG, but solves the unbalanced-voltage-division problem of DC capacitor in the three-level converter, and has lower converter capacity, more flexible control mode, and better fault-tolerant ability. The direct power control (DPC) based on the twelve sections is adopted to implement the power tracking of the open-winding BDFG system, which is compared with the typical BDFG DPC system based on the six and twelve sections to verify the advantages of the proposed scheme.