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Surfactant-containing water droplets were produced using a 75-Vrms pondermotive force operating at 10 kHz. Heat from a 30-V direct-current source, applied to a 2 × 0.1-mm region of the fluid, was instrumental in rupturing a low-surface-energy liquid membrane and forming the droplet. The low voltage allows quick and accurate dispensing of droplets without dielectric breakdown. Nanoliter-sized (~7.6-nL) butanol-styrene droplets were formed using 133 Vrms at 900 Hz. Microliter-sized oil droplets (~0.6 to 10.5 μL) were formed using high voltage (460 to 672 Vrms at 100 Hz). Oil-water emulsions were formed and moved horizontally, overcoming frictional and surface tension forces. Large oil droplets were also moved to a wider electrode spacing, where the emulsion can take the spherical shape of a target. This was only achieved by transporting the emulsion down an inclined slope (45 deg) using gravity to augment the electric force. All the steps are in place to form targets from oil-water-oil and water-oil...

The electric-field–assembly technique proposed for making fusion targets uses the electrical force from dielectrophoresis and electrowetting-on-dielectric phenomena to form droplets of oil and wate...

Experimental results are presented from ionospheric tomography, the EISCAT Svalbard radar and the CUTLASS HF radar. Tomographic measurements on 10 October 1996, showing a narrow, field-aligned enhancement in electron density in the post-noon sector of the dayside auroral zone, are related to a temporal increase in the plasma concentration observed by the incoherent scatter radar in the region where the HF radar indicated a low velocity sunwards convection. The results demonstrate the complementary nature of these three instruments for polar-cap ionospheric studies.Key words. Ionosphere · Auroral ionosphere · Polar ionosphere · Radio science (ionospheric physics)

Ultra low frequency (ULF) wave activity in the high-latitude ionosphere has been observed by a high frequency (HF) Doppler sounder located at Tromsø, Norway (69.7°N, 19.2°E geographic coordinates). A statistical study of the occurrence of these waves has been undertaken from data collected between 1979 and 1984. The diurnal, seasonal, solar cycle and geomagnetic activity variations in occurrence have been investigated. The findings demonstrate that the ability of the sounder to detect ULF wave signatures maximises at the equinoxes and that there is a peak in occurrence in the morning sector. The occurrence rate is fairly insensitive to changes associated with the solar cycle but increases with the level of geomagnetic activity. As a result, it has been possible to characterise the way in which prevailing ionospheric and magnetospheric conditions affect such observations of ULF waves.Key words. Ionosphere (auroral ionosphere; ionosphere -magnetosphere interactions) · Magnetospheric physics (MHD waves and instabilities)

The double emulsion (DE) droplets used for fabrication of cryogenic foam targets for inertial confinement fusion experiments require precisely controlled volumes. On-chip electric field actuated mi...

The need to simultaneously reduce vehicle emissions and increase the safety of passengers is encouraging the automotive industry to incorporate new technologies and materials into today's vehicles. To remain competitive, the steel industry has developed steel grades with increased energy absorbing properties allowing down gauging of body in white components to address the competition from alternative materials such as aluminium alloys and composites. Two of the more important developments are the introduction of dual phase (DP) and transformation induced plasticity (TRIP) grades for the automotive industry. These grades offer superior strength/formability and work hardening properties compared to conventional high strength grades of similar tensile strength. Utilising thinner gauge components with increased energy absorbing properties would permit addressing the mass/safety issues by the automotive industry. This paper relates the crash performance of a range of both commercial and experimental DP...

The use of high strength steels (HSS) in automotive components is steadily increasing as automotive designers use modern steel grades to improve structural performance, reduce vehicle weight and enhance crash performance. Weight reduction can be achieved by substituting mild steel with a thinner gauge HSS, however, it must be ensured that no deterioration in performance including fatigue capability occurs. In this study, tests have been carried out to determine the effects that gauge and material strength have on the fatigue performance of a fusion welded automotive suspension arm. Current finite element (FE) modelling and fatigue prediction techniques have been evaluated to determine their reliability when used for thin strip steels. Results have shown the fatigue performance of welded components to be independent of the strength of the parent material for the steel grades studied, with material thickness and joining process the key features determining the fatigue performance. The correlation between the fatigue performance of simple welded samples under uniaxial, constant amplitude loading and complex components under biaxial in service road load data, has been shown to be unreliable. This study also indicates that with the application of modern technologies, such as tailor-welded blanks (TWB), significant weight savings can be achieved. This is demonstrated by a 19% weight reduction with no detrimental effect on the fatigue performance.

The combined need for weight reduction and increased safety in modern vehicles has led automobile manufacturers to utilise the unique properties of high strength steels in their vehicles. Standard quasi-static tensile tests allow the static mechanical properties to be evaluated for any given steel grade. However, automobile designers require more advanced data, including high strain rate tensile data to fully understand the performance of a steel grade during deformation. Knowledge of the role of strain rate on a given strip steel grades deformation characteristics is essential to fully predict the behaviour of the steel during a crash event to help ensure the safety of the vehicle passengers. In the present study, three commercial strip steel grades were subjected to room temperature deformation at variable strain rates, ranging from quasi-static to dynamic loading conditions, where their obtained mechanical properties were measured. The steel grades studied were a HSLA grade (XF450), a carbon ma...

The drive to reduce vehicle mass by substituting mild steel with thinner high strength steel means that design engineers are now working closer to the design limits with respect to the fatigue performance of spot welded structures. Consequently, the present study was initiated to evaluate the factors that influence the fatigue performance of spot welded H sections so as to optimise the performance of spot welded high strength steel structures. The results obtained indicated that steel strength had little effect on fatigue performance while, in contrast, the loading mode, weld size and sheet thickness had a significant influence on it. The results of shear loading were up to 10 times greater compared with that under peel loading conditions. Under shear loading conditions full plug failures were noted, whereas with peel loaded variants partial plug failures predominated. With respect to enhancing the fatigue properties the use of larger weld sizes was shown to be beneficial.

As a result of their unique combination of strength and ductility dual phase steels play an important role in reducing weight in automobile components and improving crashworthiness. The purpose of this paper is to quantify the crash performance of dual phase steels, as defined by the influence of low and high strain deformation rates (0·001 s-1 and 100 s-1 respectively), on the tensile and work hardening properties of a range of commercial dual phase products. The objective is to establish whether dual phase steels maintain their desirable mechanical property characteristics of low yield strength, high tensile strength and high work hardening rates during plastic deformation under the application of a high strain rate loading. The results confirmed that the yield/proof strength and tensile strength increased with increasing volume fraction of second phase constituents and increasing strain rate. In particular, a dual phase steel with a microstructure consisting of a significant volume fraction (>1...

The correlation between low and high strain rate deformation characteristics and the microstructure of novel strip steel products employed by the automotive industry has been assessed. Research has been carried out to establish whether microstructural changes during high speed deformation could explain the relative attributes of mild steel, carbon manganese steel and novel dual phase steel grades of increasing yield and tensile strength, in relation to their crash behaviour. The results obtained indicate that the dual phase steel grades having similar microstructures, although with varying strength levels, displayed the same response to high strain rate loading conditions. They both exhibited a reduction in the level of hardness at high strain rate compared with low strain rate deformation. The strain rate softening effect observed with the dual phase steel was accompanied by an increase in plastic deformation of the ferrite areas around the martensitic constituent regions.

The drive to downgauge steel components by substituting mild steel with thinner high strength steel means that design engineers are now working closer to the design limits with respect to fatigue performance of spot welded structures. This study was carried out on an interstitial free mild steel and two high strength interstitial free steels, in sheet thicknesses 0.8 and 1.2 mm, representative of sheet thicknesses and grades in typical body-in-white automotive structures. The results obtained indicate that steel strength had little effect on fatigue performance for the range of steels studied. In contrast, both the loading mode and the sheet thickness had a significant influence. The results for shear loading were up to ten times greater when compared to peel loading conditions. Under shear loading conditions full plug failures were widely observed, whereas with peel loaded variants partial plug failures predominated. With respect to enhancing the fatigue properties the use of larger weld sizes wa...

In previous attempts to detect eclipse-induced AGW, it has always been difficult to establish a direct link between individual waves and a specific source. This study reports observations of travelling ionospheric disturbances made in the UK at the time of the total solar eclipse of 11 August 1999. The speed and direction of the waves were estimated by a four-station array using the HF Doppler technique. In addition, the wave observations were supported by two other propagation paths, one in the north of England close to the main array and the other further afield, between the UK and Sweden. The AGW activity following the eclipse totality was different to the background waves detected before this time in amplitude, speed and direction. The velocity vectors are consistent with a generating mechanism for the waves based on the supersonic passage of the cooled region of the atmosphere during the eclipse.

Whilst resistance welding has been the primary joining technique for automotive body-in-white (B-I-W) assembly since the 1930s, far more welds than necessary are used to fabricate the structure to achieve the required structural performance. This can be attributed due to lack of confidence in weld quality, particularly when joining three or more sheet combinations. To achieve the necessary confidence, there is a need to understand the mechanism of heat development and weld formation, and develop appropriate welding conditions to ensure acceptable weld quality. With the high proportion of zinc coated steels in B-I-W assembly, one of the key issues is to understand the role of the zinc coating in weld nugget development. Consequently, in this study, the mechanisms of weld nugget growth for three thickness joints of both uncoated low carbon and hot dip zinc (GI) coated steels have been investigated using similar welding conditions. The welding conditions selected were based on those recommended for the uncoated low carbon steel. Since these are unlikely to be optimal in the case of the coated steel, further studies were undertaken to establish the effect of electrode force on the mechanism of weld growth. The results obtained indicated that the rate of heat development was reduced in the case of the coated steel compared to the uncoated steel variant. This can be attributed to the lower surface resistance in the presence of the zinc coating. Variations in electrode force indicated flexibility in the selection of welding conditions to produce an acceptable weld quality. Where, an increase in the level of electrode force was used, a significant change in the location of heat development and weld nugget formation was noted compared to that observed for the low force variant. This was attributed to the change in the dominant resistive heating mechanism that took place.

The use of high strength steels (HSS) in automotive components is steadily increasing as automotive designers use modern steel grades to improve structural performance, reduce vehicle weight, and enhance crash performance. Weight reduction can be achieved by substituting mild steel with a thinner gauge HSS, however it must be ensured that no deterioration in fatigue performance occurs. Fatigue studies have been carried out to determine the effects various welding processes, gauge, and material strength can have on the fatigue performance of an automotive suspensionarm.Test methodology has also been investigated and the merits of both uniaxial constant amplitude and multiaxial simulation testing have been studied. Results have shown the fatigue performance of welded components to be independent of the strength of the parent material for the steel grades studied. Also, little correlation was found between the fatigue performance of simple welded samples under uniaxial, constant amplitude loading and...

Prior to Namibia’s Independence in 1990 tourism on communal land in Namibia was dominated by white-owned businesses. Tourism brought little benefit to the people living on the communal land. They mostly had menial jobs as cleaners and gardeners or possibly as cooks. In 1996 the Namibian Government introduced legislation that gave communal area residents rights over wildlife and tourism on their land if they formed common property resource management institutions called conservancies. The conservancies have become central in the evolution of new institutional arrangements for community involvement in tourism. One of the main ways in which conservancies earn income is through “joint venture” tourism development in some form of partnership with the private sector. This chapter first considers the evolution of the conservancy institutional approach. It then compares different models of community involvement in tourism in relation to issues of community ownership, exposure to business risk and maximising income.

The authors thank the director and staff of EISCAT for the operation of the Tromso heater facility. EISCAT is an international facility funded collaboratively by the research councils of Finland (SA), France (CNRS), the Federal Republic of Germany (MPG), Japan (NIPR), Norway (NFR), Sweden (NFR), and the United Kingdom (PPARC). The SuperDARN Hankasalmi and Pykkvib•er HF radars are deployed and operated by the University of Leicester and funded by the PPARC (grant PPA/R/R/1997/00256), the Finnish Meteorological Institute, and the Swedish Institute for Space Physics. D.M.W. is supported on PPARC grant PPA/G/O/1997/000254.

The aim was to produce a radiolabelled fibre suitable for long-term carcinogenesis studies. To this end, we have successfully synthesised erionite fibres by a method adapted to incorporate (57)Co into the crystal framework. Morphologically the fibres are straight, of median length 2.5 microm, with 11% of fibres8 microm long, and median width 0.32 microm. These values are comparable to natural Oregon erionite. Autoradiography confirmed that the (57)Co was associated with the fibres themselves. The stability of the radiolabel in vivo was examined by instilling 1 mg of synthetic erionite into the lungs of F-344 rats. About half of the thoracic content of (57)Co was cleared in the first week, and over the following 5 weeks the remainder was cleared slowly with a half-time of 120 days. After 6 weeks the urinary excretion of (57)Co was only 0.054% of the initial lung content per day. This represented fibre dissolution plus any leaching of (57)Co from the fibres. It can be concluded that the (57)Co is bound into the erionite fibres with sufficient stability in vivo for studying their effects in relation to translocation to the pleura.

Single box sections and T-joints (two box sections joined together at right angles) are commonly used to represent automotive components, such as pillars and sills, in laboratory testing. In the work presented herein, the torsional properties of T-joints were determined both experimentally and numerically. A factorial-design test programme comparing adhesive-bonded and spot-welded T-joints was carried out. Numerical models, generated using a general-purpose finite element program and validated against the test results, were used to investigate further the behaviour of the connection between the two box sections in a T-joint. The joining technique and the joint eccentricity at the connection (the distance of the join from the vertical box section) were found to influence the torsional properties of T-joints. Finally, an automotive T-component was analysed to examine the applicability of the T-joint results to more complex components.

The suitability of temperature as a parameter to determine strain failure mode in press forming is examined by thermographic evaluation of the forming limit diagram (FLD). The work reported in the ...

The performance of the HF radars such as the collaborative UK twin located auroral sounding system, depends critically on the propagation characteristics of HF radio waves in the ionosphere. The transmission paths through the ionosphere have been determined by ray tracing techniques applied to suitable models of the electron density height distribution. By launching waves at a range of elevation angles, it has been possible to calculate the skip distance and ground illumination flux of each radar for the operating frequency (10 MHz). The calculated and measured positions of the ground backscatter are found to be in excellent agreement, indicating that this modelling approach can predict the performance of the radar for any conditions for which a representative electron density height profile can be established. When waves of very high power are propagated through the ionosphere, artificial irregularities are produced which can be detected by the HF radars in a similar manner to those occurring naturally. The advantage of the heater-induced irregularities is that they can be generated at will and can form a ‘window’ through which many geophysical phenomena (e.g. ULF waves) can be investigated. Examples of the applications of this technique are presented, and it is evident that it has great potential for a range of geophysical investigations.

A well-calibrated and validated finite element procedure, described in companion paper 1, was used in producing data on the stiffnesses, elastic limits and strengths of automotive box sections under torsion. The modelling procedure was first used in analysing all the experimental geometries, and these preliminary analyses helped to define the scope of further numerical work. This work, which consisted of 76 analyses, investigated the main effects identified—section thickness, cross-sectional area, model length and section design—and their interactions. Particular emphasis was given to quantifying the implications of the various effects on weight reduction by replacing spot welding with adhesive bonding as the fabrication technique. Further tests and analyses were also conducted to investigate the effects of weld pitch on torsional stiffness and to compare the properties of adhesively bonded, laser-welded and spot-welded sections.

Behaviour under torsion is an important performance-related property of automotive box sections. A previous experimental study has identified joining technique, section thickness and section area as the major influencing factors on the torsional behaviour of box hat sections. Using these test results as the basis, a finite element modelling strategy that can simulate the behaviour of adhesively bonded and spot-welded automotive box sections subjected to torsion is presented. The numerical study investigated the effects of material representation, mesh density and layout, and joining technique representation on the stiffness, elastic limit and ultimate strength of the box sections. The final model, calibrated and validated against test results obtained from previous work, was used in an extensive study, presented in the companion paper (Part 2), to further the understanding of the behaviour of torsionally loaded box sections and its implications on weight reduction of automotive structures.

A community-based natural resource management project in the arid Kunene Region of Namibia has evolved over time from a focus on halting poaching to ensuring community benefit from wildlife and ultimately to communities as proprietors of the wildlife resource. A Namibian NGO has used consistent and persistent ‘light-touch facilitation’ to assist communities to overcome problems in forming common property resource management institutions to manage the wildlife and conform with new government legislation. Pragmatic approaches to resolving conflicts over land and resources and to disputes between competing interest groups have enabled communities to make progress. Success has depended upon the intrinsic value communities place upon wildlife as much as instrumental incentives. Relations with the private sector have been governed by the degree of proprietorship enjoyed by communities. Copyright © 1999 John Wiley & Sons, Ltd.

Torsional rigidity is an important performance related property of an automotive body-in-white (BIW) structure, which consists of many box hat structures or box sections. An experimental study has been carried out to determine mainly the torsional stiffness but also the elastic limit and the strength of spot-welded and adhesively bonded (and weld-bonded) box sections. The relative contribution of a variety of factors, including joining system used, steel strength, sheet thickness, section area and section design, to the properties of box sections was analysed using factorial design experimentation techniques. It was found that a significant increase in torsional stiffness could be achieved by changing the joining technique, increasing the sheet thickness, increasing the section area and, to a lesser extent, changing the section design. The results are examined and discussed in the context of weight reduction in automotive structures.

When glass particles adsorb water from humid environments their low frequency dielectric properties change drastically. To investigate the polarization mechanism, variable frequency measurements upon individual glass particles (∼ 50 μm diameter) suspended in silicone oil were performed with a computer-controlled dielectrophoretic levitator. The electrical properties of individual particles have been measured in the frequency range between 10 Hz and 100 kHz. A relaxation in the induced dipole moment of moistened glass particles suspended in silicone oil is clearly evident in measured spectra. Surface moisture causes the characteristic relaxation times of soda-lime glass particles to change by up to 5 orders of magnitude. The relaxation spectra are satisfactorily modeled by the Debye equation and a model based on ohmic surface conduction appears to explain the phenomenon. This research has potential implications with respect to the controversy surrounding the influence of moisture on the performanc...

The response of the dayside ionospheric flow to a sharp change in the direction of the interplanetary magnetic field (IMF) measured by the WIND spacecraft from negative Bz and positive By, to positive Bz and small By, has been studied using SuperDARN radar, DMSP satellite, and ground magnetometer data. In response to the IMF change, the flow underwent a transition from a distorted twin-cell flow involving antisunward flow over the polar cap, to a multi-cell flow involving a region of sunward flow at high latitudes near noon. The radar data have been studied at the highest time resolution available (~2 min) to determine how this transition took place. It is found that the dayside flow responded promptly to the change in the IMF, with changes in radar and magnetic data starting within a few minutes of the estimated time at which the effects could first have reached the dayside ionosphere. The data also indicate that sunward flows appeared promptly at the start of the flow change (within ~2 min), localised initially in a small region near noon at the equatorward edge of the radar backscatter band. Subsequently the region occupied by these flows expanded rapidly east-west and poleward, over intervals of ~7 and ~14 min respectively, to cover a region at least 2 h wide in local time and 5° in latitude, before rapid evolution ceased in the noon sector. In the lower latitude dusk sector the evolution extended for a further ~6 min before quasi-steady conditions again prevailed within the field-of-view. Overall, these observations are shown to be in close conformity with expectations based on prior theoretical discussion, except for the very prompt appearance of sunward flows after the onset of the flow change.Key words. Ionosphere (Auroral ionosphere) · Magnetospheric physics (Magnetopause · cusp · and boundary layers; Magnetosphere · ionosphere interaction)

Four high frequency propagation paths were provided by a transmitter located within the polar cap and four receivers located variously within the polar cap and at sub-auroral latitudes. Of these paths, one was contained entirely within the polar cap at all times, two were trans-auroral at all times, and one varied from trans-auroral during the day to polar cap during the night. Fourteen frequencies within the HF band were transmitted each hour for the duration of two 24 day experimental campaigns during the summer of 1988 and the winter of 1989. The received signals were analysed to determine signal recognition and signal strength. The mean quiet-time behaviour of the propagation was determined and compared with four periods during which the ionosphere was perturbed by (relatively mild) geomagnetic storm conditions. The daily occurrence of correctly recognised signals decreased during the disturbed periods, both on polar cap and trans-auroral paths. Several geophysical causes for this decrease are identified, including a decrease in F-region electron density, decreasing the MOF, as a consequence of negative storm effects and an extended mid latitude trough. On polar cap paths, an increase in the LOF caused by mild PCA events also decreased the available HF band. Storm-time auroral-E makes propagation possible on frequencies higher than expected during the night on trans-auroral paths, mitigating to some extent the degradation in propagation. The storm-time decrease in the available HF band is quantified, falling to 0.3–0.5 of undisturbed levels even during relatively small geomagnetic storms. During the two experimental campaigns, 50% of days are identified as being storm-disturbed.

The EISCAT ionospheric modification facility (heater), together with the EISCAT UHF radar, lie within the viewing area of the newly constructed HF radar system, CUTLASS. Results are reported from the first experiments in which CUTLASS has been employed to observe artificial small scale field aligned plasma irregularities induced by the EISCAT heater. Observations include the first simultaneous CUTLASS-EISCAT UHF measurements of heating effects associated with heater induced field aligned irregularities, the first determination of the spatial distribution of these irregularities and the first examination of their motion.

During RF heating at 4.04 MHz an increase of 5 dB in the signal strength of a 4.2 MHz probe wave has been observed. This is attributed to a heater induced increase in electron density in the E region leading to the opening up of a low angle propagation path from probe transmitter to receiver. The geometry of the experiment is consistent with an electron density increase distributed in a torus in the E region centred above the heater site.

Analyses of ground backscatter measurements recently available from the CUTLASS HF radars, show that waves with large spatial scales and periods in the range of 1 2 to 3 hours, are frequently present in the high-latitude ionosphere. These periods and spatial scales are consistent with travelling ionospheric disturbances caused by thermospheric gravity waves. Waves are most clearly seen during intervals of low geomagnetic activity and tend to travel southwards. Elevation angle studies, which indicate whether scatter is from the forwards or backwards direction relative to the radar beam, enable the direction of wave travel to be interpreted correctly. Initial attempts to simulate the effects of southward travelling gravity waves indicate structures similar to those found in CUTLASS observations.

Four high frequency propagation paths were monitored from a transmitter located within the polar cap by four receivers located variously within the polar cap and at sub-auroral latitudes. Of these paths, one was contained entirely within the polar cap at all times, two were trans-auroral at all times, and one varied from trans-auroral during the day to polar cap during the night. Fourteen frequencies within the HF band were transmitted each hour for the duration of two 24 day experimental campaigns during the summer of 1988 and the winter of 1989. From an analysis of the received signals the confidence of signal recognition and signal strength were determined. During geomagnetically undisturbed periods the propagation behaviour resembled that of mid-latitude paths. During geomagnetically disturbed times, however, night-time propagation occurred on frequencies up to and sometimes over 10 MHz above the undisturbed night-time MUF, for periods of 2 to 6 h. These features appeared on the trans-auroral paths only and were attributed to E region (and occasionally F region) enhancement by auroral precipitation. APEs (auroral E propagation events) occurred on over 50% of nights. The occurrence of APEs also coincided with ionospheric storm periods when the HF band available for propagation was otherwise significantly narrowed due to a depletion of the F region electron density.

Community-based natural resource management (CBNRM) in southern Africa is a variant of what Adams and Hulme label ‘community conservation’, which they define as ‘those principles and practices that argue that conservation goals should be pursued by strategies that emphasize the role of local residents in decision-making about natural resources’ (Adams and Hulme, 2001, p13). They contrast this stance with an earlier conservation strategy (‘fortress conservation’), which sought to reserve places for nature, and to separate humans and other species. While noting that both approaches share similar roots in ideas about nature and about the need to control the human use of nature, they suggest that fortress conservation is philosophically grounded in the intrinsic values of nature and is basically biocentric, whereas community conservation is basically utilitarian and anthropocentric. We can describe this conjunction and disjunction in terms of means-end sequencing: for ‘fortress conservation’ conservation is the end and the fulfilment of human needs serves as a means to this end; for community conservation the fulfilment of human needs is the end and conservation is a means to achieving and maintaining this end.

In the coherent radar technique, bacsccatter is obtained from plasma irregularities even though the radar frequency can greatly exceed the ionospheric plasma frequency maximum. From the velocity spectrum of the received signals an estimate of the flow velocity can be obtained and hence the electric field determined. Information regarding the irregularity scattering cross section is obtained from the amplitude of the backscatter return. Current radar studies of a range of geophysical phenomena are presented. In addition, attention is drawn to the problems of interpreting the radar observations in terms of the underlying geophysical processes.