Design of a lattice-based faceted classification system

We describe a software reuse architecture supporting component retrieval by facet classes. The facets are organized into a lattice of facet sets and facet n-tuples. The query mechanism supports precise retrieval and flexible browsing

Internal fibre length concentration in a pressure screen

Localised axial consistency profiles within a pressure screen of a Pinus Radiata kraft pulp are reported. Axial Samples were also analysed using a Kajaani FS-200 to obtain fibre length distribution data. Localised consistency in the feed annulus was found to vary considerably and the consistency was found to be less than the feed consistency over some portions of the screen (annular dilution). Changes in consistency along the accept side was fairly constant although subtle changes were observed. Pulp passage ratios for both the bulk and individual fibre length fractions were calculated using the consistency profiles and fibre length data. In all cases fibre passage decreased along the screen length. Fibre passage was affected by a position effect which is comprised of two factors: flocculation effects, and flow and rotor effects. Fibre fractionation efficiency was found to increase along the length of the screen. Mechanisms that account for the observed annular dilution, passage ratio and efficiency changes are proposed. These involve flow of both fluid and fibre in the forward and reverse directions across the screen plate, increased flocculation in the feed annulus and the slip velocity between incoming pulp and the rotor tip

Thermocline management of stratified tanks for heat storage

Stratified tanks are useful for maximising the thermal energy efficiency of non-continuous and semi-continuous processes. Liquid at two or more dissimilar temperatures is stored within the same tank to provide a buffer for variations in heating and cooling loads. Control of the thermocline between the hot and cold fluid regions is needed to minimise thermocline growth and maximise operation of the storage tank. An experimental programme using a scale model of an industrial stratified tank (aspect ratio 3.5) and Perspex tank (aspect ratio 8.2) is reported. The behaviour and growth of the hot-cold thermocline under various operating conditions is presented. A siphoning method to re-establish the thermocline without interrupting the use of the tank is tested. Siphoning of the thermocline region from either 20%, 50% or 80% of the tank height is an effective strategy for uninterrupted interface re-establishment. However, the rate and position of siphoning and the load balance of the exit streams are critical variables for minimising the time for effective re-establishment of the two temperature zones

Effects of new military footwear on knee loading during running

Military recruits are known to be susceptible to chronic injuries. The knee is the most common injury site and patellofemoral pain has been demonstrated as the leading mechanism for medical military discharge. Military boots have been cited as a key mechanism responsible for the high incidence of chronic injuries. The British Army has therefore introduced two new footwears – a cross-trainer and running shoe to reduce the incidence of chronic injuries. The aim of this study was to compare knee joint kinetics of the cross-trainer and running shoe in relation to conventional military boots. Twelve male participants ran at 4.0 m s−1 in each footwear condition. Knee joint kinetics was obtained and contrasted using repeated-measures ANOVAs. The results showed that patellofemoral load was significantly greater in the military boots. However, peak knee abduction moment was significantly greater in the running shoes. On the basis of the findings from this study, it is recommended that recruits who are susceptible to injuries mediated through excessive knee loads select the cross-trainer for their running activities

A Review of the Open Educational Resources (OER) Movement: Achievements, Challenges, and New Opportunities

Examines the state of the foundation's efforts to improve educational opportunities worldwide through universal access to and use of high-quality academic content

The challenge of integrating non-continuous processes-milk powder plant case study

The integration of non-continuous processes such as a milk powder plant present a challenge for existing process integration techniques. Current techniques are generally based on steady and continuous operation which for some industries is not the case. Milk production varies considerably during the year as dairy cows in New Zealand are grazed on pasture, which affects the scheduling and operation of plants on site. The frequency and duration of cleaning cycles and non-productive operating states can have a major affect on energy demand and the availability of heat sources and heat sinks. In this paper the potential for indirect heat transfer between the several plants using a heat recovery loop and stratified tank at a typical New Zealand dairy factory is investigated. The maximum amount of heat recovery is calculated for a range of recirculation loop temperatures. The maximum amount of heat recovery can be increased considerably if the temperature of the hot fluid in the recirculation loop is varied depending on which condition the site is operating under

Ensuring cost-effective heat exchanger network design for non-continuous processes

The variation in stream conditions over time inevitably adds significant complexity to the task of integrating non-continuous processes. The Time Averaging Method (TAM), where stream conditions are simply averaged across the entire time cycle, leads to unrealistic energy targets for direct heat recovery and consequently to Heat Exchanger Network (HEN) designs that are in fact suboptimal. This realisation led to the development of the Time Slice Method (TSM) that instead considers each time interval separately, and can be used to reach accurate targets and to design the appropriate HEN to maximise heat recovery. However, in practise the HENs often require excessive exchanger surface area, which renders them unfeasible when capital costs are taken in to account. An extension of the TSM that reduces the required overall exchanger surface area and systematically distributes it across the stream matches is proposed. The methodology is summarised with the help of a simple case study and further improvement opportunities are discusse

Carbon Emissions Pinch Analysis (CEPA) for emissions reduction in the New Zealand electricity sector

Carbon Emissions Pinch Analysis (CEPA) is a recent extension of traditional thermal and mass pinch analysis to the area of emissions targeting and planning on a macro-scale (i.e. economy wide). This paper presents an extension to the current methodology that accounts for increased demand and a carbon pinch analysis of the New Zealand electricity industry while illustrating some of the issues with realising meaningful emissions reductions. The current large proportion of renewable generation (67% in 2007) complicates extensive reduction of carbon emissions from electricity generation. The largest growth in renewable generation is expected to come from geothermal generation followed by wind and hydro. A four fold increase in geothermal generation capacity is needed in addition to large amounts of new wind generation to reduce emissions to around 1990 levels and also meet projected demand. The expected expansion of geothermal generation in New Zealand raises issues of GHG emissions from the geothermal fields. The emissions factors between fields can vary by almost two orders of magnitude making predictions of total emissions highly site specific

Carbon emissions reduction and net energy generation analysis in the New Zealand electricity sector through to 2050

Carbon Emissions Pinch Analysis (CEPA) and Energy Return On Energy Investment (ERoEI) analysis are combined to investigate the feasibility of New Zealand reaching and maintaining a renewables electricity target of above 80% by 2025 and 2050, while also increasing electricity generation at an annual rate of 1.5%, and with an increase of electricity generation in the distant future to accommodate a 50% switch to electric vehicle transportation. To meet New Zealand’s growing electricity demand up to 2025 the largest growth in renewable generation is expected to come from geothermal generation (four-fold increase) followed by wind and hydro. To meet expected demand up to 2050 and beyond, including electric vehicle transportation, geothermal generation will expand to 17% of total generation, wind to 16%, and other renewables, such as marine and biomass, will make up about 4%. Including hydro, the total renewable generation in 2050 is expected to reach 82%

Integrating heat recovery from milk powder spray dryer exhausts in the dairy industry

Heat recovery from milk powder spray dryer exhausts has proven challenging due to both economic and thermodynamic constraints. Integrating the dryer with the rest of the process (e.g. evaporation stages) can increase the viability of exhaust recovery. Several potential integration schemes for a milk powder plant have been investigated. Indirect heat transfer via a coupled loop between the spray dryer exhaust and various heat sinks were modeled and the practical heat recovery potential determined. Hot utility use was reduced by as much as 21% if suitable heat sinks are selected. Due to high particle loading and operating temperatures in the particle sticky regime, powder deposition in the exhaust heat exchanger is perhaps the greatest obstacle for implementing heat recovery schemes on spray dryers. Adequate cleaning systems are needed to ensure continuous dyer operation