A Novel Method to Enable Trade-offs Across the Whole Product Life of an Aircraft Using Value Driven Design

The increasing need to understand complex products and systems with long life spans, presents a significant challenge to designers who increasingly require a broader understanding of the operational aspects of the system. This demands an evolution in current design practice, as designers are often constrained to provide a subsystem solution without full knowledge of the global system operation. Recently there has been a push to consider value centric approaches which should facilitate better or more rapid convergence to design solutions with predictable completion schedules. Value Driven Design is one such approach, in which value is used as the system top level objective function. This provides a broader view of the system and enables all sub-systems and components to be designed with a view to the effect on project value. It also has the capacity to include value expressions for more qualitative aspects, such as environmental impact. However, application of the method to date has been restricted to comparing value in a programme where the lifespan is fixed and known a priori. This paper takes a novel view of value driven design through the surplus value objective function, and shows how it can be used to identify key sensitivities to guide designers in design trade-off decisions. By considering a new time based approach it can be used to identify optimum programme life-span and hence allow trade-offs over the whole product life.

Development and Validation of a Forklift Truck Powertrain Simulation

Fuel economy has become an important consideration in forklift truck design, particularly in Europe. A simulation of the fuel consumption and performance of a forklift truck has been developed, validated and subsequently used to determine the energy consumed by individual powertrain components during drive cycles.
The truck used in this study has a rated lifting capacity of 2500kg, and is powered by a 2.6 litre naturally aspirated diesel engine with a fuel pump containing a mechanical variable-speed governor. The drivetrain consisted of a torque convertor, hydraulic clutch and single speed transmission.
AVL Cruise was used to simulate the vehicle powertrain, with coupled Mathworks Simulink models used to simulate the hydraulic and control systems and governor. The vehicle has been simulated on several performance and fuel consumption drive cycles with the main focus being the VDI 2198 fuel consumption drive cycle.
To validate the model, a truck was instrumented and measurements taken to compare the performance and instantaneous fuel consumption to simulated values. The fuel injector pump was modified and calibrated to enable instantaneous fuel flow to be measured.
The model has been validated to within acceptable limits and has been used to investigate the effect four different torque converters have on the fuel consumption and performance of the forklift truck. The study demonstrates how the model can be used to compare the fuel consumption and performance trade-offs when selecting drivetrain components.

A direct physiological trade-off between personal and social immunity

1. Recent work shows that organisms possess two strategies of immune response: personal immunity, which defends an individual, and social immunity, which protects other individuals, such as kin. However, it is unclear how individuals divide their limited resources between protecting themselves and protecting others.
2. Here, with experiments on female burying beetles, we challenged the personal immune system and measured subsequent investment in social immunity (antibacterial activity of the anal exudates).
3. Our results show that increased investment in one aspect of personal immunity (wound repair) causes a temporary decrease in one aspect of the social immune response.
4. Our experiments further show that by balancing investment in personal and social immunity in this way during one breeding attempt, females are able to defend their subsequent lifetime reproductive success.
5. We discuss the nature of the physiological trade-off between personal and social immunity in species that differ in the degree of eusociality and coloniality, and suggest that it may also vary within species in relation to age and partner contributions to social immunity.

Improving the Fuel Economy of a Tuned 600cc FSAE Engine

To maintain its relevance, motorsport cannot be exempt from
the trend of increasing fuel economy. This bears obvious
competitive benefits as well, either in decreasing the
frequency of pit stops or the mass of fuel carried. Given the
increased points weighting of fuel economy for the Formula
Student (FS) competition, a complete analysis was performed
on the Queen's Formula Racing 600cc motorcycle engine in
preparation for the 2011 competition.
The criteria for such high performance fuel economy differ to
a degree from most mass transportation counterparts and were
divided into three distinct regimes; full load, part load and no
load conditions.
Full load positions naturally demand maximum torque for
performance but that does not imply that fuel savings cannot
be made whilst preserving this. The point at which maximum
torque is produced with minimum air -fuel ratio, Leanest
mixture for Best Torque (LBT), was therefore sought and
mapped for full load.
At part load, torque is less of a concern, and maintaining a
sustainable engine temperature and transient response become
more important. With decreasing AFR, engine temperatures
can rise dramatically so temperatures were measured close to
the exhaust port for a wide range of air-fuel ratios.
Competition track data was analysed to highlight key part load
operating regions and these were mapped according to
measured safe temperature limits. Torque response to a step
throttle change was also measured to ensure suitable engine
transient performance was maintained.
At no load conditions, with low engine speed only idle
conditions need to be satisfied. In the situation where the
engine is still at high speed without load, the engine is being
motored and no fuel is required. An overrun fuel cut was
employed to reflect this giving significant fuel savings. The
effect on torque and engine pickup was measured.
Modifications were also made to the fuel injector location to
improve fuel mixing and evaporation at this lower air flow
condition.
These mapping regimes were implemented and tested using
fully transient lap simulations using competition track data
and a four quadrant AC engine dynamometer. The experiment
indicated a reduction in fuel consumption for 22 laps of the FS
track from 5.08litres to 3.67litres, around 27% in total. The
actual fuel used at the 2011 competition was 3.6 litres while
placing 8th in the endurance event, further validating the
benefits of these mapping regimes.

Emerging asymmetric interactions between forage and predator fisheries impose management trade-offs

A size and trait-based marine community model was used to investigate interactions, with potential implications for yields, when a fishery targeting forage fish species (whose main adult diet is zooplankton) co-occurs with a fishery targeting larger-sized predator species. Predicted effects on the size structure of the fish community, growth and recruitment of fishes, and yield from the fisheries were used to identify management trade-offs among the different fisheries. Results showed that moderate fishing on forage fishes imposed only small effects on predator fisheries, whereas predator fisheries could enhance yield from forage fisheries under some circumstances.