Evaluation of prototype Advanced Life Support (ALS) pack for use by the Health Maintenance Facility (HMF) on Space Station Freedom (SSF)

The purpose is to evaluate the prototype Advanced Life Support (ALS) Pack which was developed for the Health Maintenance Facility (HMF). This pack will enable the Crew Medical Officer (CMO) to have ready access to advanced life support supplies and equipment for time critical responses to any situation within the Space Station Freedom. The objectives are: (1) to evaluate the design of the pack; and (2) to collect comments for revision to the design of the pack. The in-flight test procedures and other aspects of the KC-135 parabolic test flight to simulate weightlessness are presented

Comparison of modelling techniques for milk-production forecasting

peer-reviewedThe objective of this study was to assess the suitability of 3 different modeling techniques for the prediction of total daily herd milk yield from a herd of 140 lactating pasture-based dairy cows over varying forecast horizons. A nonlinear auto-regressive model with exogenous input, a static artificial neural network, and a multiple linear regression model were developed using 3 yr of historical milk-production data. The models predicted the total daily herd milk yield over a full season using a 305-d forecast horizon and 50-, 30-, and 10-d moving piecewise horizons to test the accuracy of the models over long- and short-term periods. All 3 models predicted the daily production levels for a full lactation of 305 d with a percentage root mean square error (RMSE) of ≤12.03%. However, the nonlinear auto-regressive model with exogenous input was capable of increasing its prediction accuracy as the horizon was shortened from 305 to 50, 30, and 10 d [RMSE (%) = 8.59, 8.1, 6.77, 5.84], whereas the static artificial neural network [RMSE (%) = 12.03, 12.15, 11.74, 10.7] and the multiple linear regression model [RMSE (%) = 10.62, 10.68, 10.62, 10.54] were not able to reduce their forecast error over the same horizons to the same extent. For this particular application the nonlinear auto-regressive model with exogenous input can be presented as a more accurate alternative to conventional regression modeling techniques, especially for short-term milk-yield predictions

Swarming Around New Initiatives: A Virtual Foyer for Interdisciplinary Teams

Virtual teams are commonplace today and their evolving use continues to raise a variety of interesting research questions. One specific type of virtual team is the interdisciplinary team, where team members have very different backgrounds on a variety of dimensions. A central challenge in such teams is achieving shared understanding to identify and move forward on new initiatives. We describe an initial concept and study for investigating technology and process structures to help members of an interdisciplinary virtual team identify and engage in new initiatives. We propose the concept of a “virtual foyer” as a mechanism by which team members can congregate around new ideas. The prototype implementation of the concept is described along with implications for further development and research

Synergistic Ideation through Pairing Participants in Facilitated Group Support Systems Sessions

Group Support Systems (GSS) have been used and studied in the support of facilitated ideation sessions for years. The norm for these sessions has been for participants to work individually at GSS workstations. A review of applicable literature suggests that pairing participants at GSS workstations could result in higher quality ideas and participant satisfaction. This paper reports the results of a lab experiment that tested for differences between paired and unpaired facilitated GSS sessions. These results suggest that pairing participants can yield higher quality ideas from facilitated ideation without negative consequences

Sub-2 cm/s passivation of silicon surfaces by aprotic solutions

Minimizing recombination at semiconductor surfaces is required for the accurate determination of the bulk carrier lifetime. Proton donors, such as hydrofluoric acid and superacids, are well known to provide highly effective short-term surface passivation. We demonstrate here that aprotic solutions based on bis(trifluoromethanesulfonyl)methane (TFSM) in hexane or pentane can also result in excellent passivation of (100)-orientation silicon surfaces. We show that the optimized TFSM-pentane passivation scheme can measure effective lifetimes up to 20 ms, with a surface recombination velocity of 1.7 cm s1 at an excess carrier density of 1015 cm3 . Fitting injection-dependent lifetime curves requires chemical passivation and field effect passivation from a negatively charged layer with a charge density of 1010–1011 q cm2 . The slightly higher recombination velocity of 2.3 cm s1 measured with TFSM-hexane can be explained by a lower charge density in the passivating layer, suggesting that the steric hindrance associated with the solvent size could play a role in the passivation mechanism. Finally, phosphorus nuclear magnetic resonance experiments confirm that TFSM-based solutions have Lewis acidity without being superacids, which opens up opportunities for them to be used in materials systems sensitive to superacidic environments

The Effects of Pairing Participants in Facilitated Group Support Systems Sessions

Group Support Systems (GSS) have been used to support facilitated ideation sessions for years and have been studied from a number of different perspectives. Throughout this time the norm for running electronic brainstorming sessions has been for participants to work on their own workstations. A review of applicable literature suggests that pairing participants at GSS workstations could result in higher quality inputs and participant satisfaction. This proposition is examined with a lab experiment to test for differences between paired and unpaired facilitated GSS sessions. The results of the experiment suggest that pairing participants does yield higher quality ideas from facilitated ideation without negative perceptions relating to production blocking

Hydrogenation effect on low temperature internal gettering in multicrystalline silicon

We have performed a comprehensive study into low temperature ( 500 °C) internal gettering in multicrystalline silicon (mc-Si). Two groups of as-grown mc-Si wafers from different ingot height positions were subjected to the same thermal treatments with surface passivation by either silicon nitride (SiNx:H) or a temporary iodine-ethanol (I-E) chemical solution . With either passivation scheme, lifetime in the relatively low lifetime samples from the bottom of the ingot improves substantially. There are however key passivation-dependent differences in behavior in other parts of the ingot. Lifetime in relatively good wafers from the middle of the ingot is improved significantly with silicon nitride passivation but not with iodine-ethanol, for which substantial reductions in lifetime initially occur. There are also key differences in the internal gettering behavior of bulk iron. We suggest the differences arise because silicon nitride introduces hydrogen into the bulk, whereas the iodine-ethanol does not

Combining low-temperature gettering with phosphorus diffusion gettering for improved multicrystalline silicon

We have investigated low-temperature (≤500 °C) gettering in combination with phosphorus diffusion gettering with a view to improving poor quality multicrystalline silicon. Low-temperature gettering applied after standard phosphorus diffusion gettering is found to provide a >40% improvement in minority carrier lifetime in samples from the top and bottom of an ingot. The best results are achieved at 300 °C with very long annealing times (>24 h). Improvements in the lifetime do not correlate with changes in interstitial iron concentration. Experiments are performed to assess whether the presence of a phosphorus-diffused emitter affects low-temperature gettering, and results from sister samples show the low-temperature gettering behavior is not affected by the existence of an emitter. Further experiments show that low-temperature gettering prior to phosphorus diffusion results in a 20% higher lifetime after phosphorus diffusion. Low-temperature gettering can, therefore, enhance lifetime even when used in conjunction with standard phosphorus diffusion gettering

Passivation effects on low-temperature gettering in multicrystalline silicon

Annealing at ≤ 500 °C changes minority carrier lifetime in as-grown multicrystalline silicon substantially. Part of the change arises from internal gettering of impurities, but surface passivation for lifetime measurement results in additional effects. We report experiments that aim to clarify the role of passivation. Long-term annealing (up to 60 h) is performed on silicon nitride passivated multicrystalline silicon, and lifetime and interstitial iron concentrations are monitored at each processing stage. Lifetime in all samples is improved under certain conditions, with improvements always achieved at 400 °C. Increases are pronounced in low-lifetime bottom samples, with improvement by a factor of 2.7 at 400 °C or 3.8 at 500 °C. Important differences are found compared with our previous study with iodine–ethanol passivation. First, as-received lifetime is higher with silicon nitride not due to a substantial difference in surface recombination. Second, while interstitial iron concentrations often initially increase with iodine–ethanol, they tend to reduce with silicon nitride. Third, lifetime in high-lifetime samples reduces substantially with iodine–ethanol but increases with silicon nitride. Secondary ion mass spectrometry reveals high iron concentrations in annealed silicon nitride. Results are discussed in terms of gettering of impurities to, and bulk passivation arising from, silicon nitride films

Increasing minority carrier lifetime in as-grown multicrystalline silicon by low temperature internal gettering

We report a systematic study into the effects of long low temperature (≤500 °C) annealing on the lifetime and interstitial iron distributions in as-grown multicrystalline silicon (mc-Si) from different ingot height positions. Samples are characterised in terms of dislocation density, and lifetime and interstitial iron concentration measurements are made at every stage using a temporary room temperature iodine-ethanol surface passivation scheme. Our measurement procedure allows these properties to be monitored during processing in a pseudo in situ way. Sufficient annealing at 300 °C and 400 °C increases lifetime in all cases studied, and annealing at 500 °C was only found to improve relatively poor wafers from the top and bottom of the block. We demonstrate that lifetime in poor as-grown wafers can be improved substantially by a low cost process in the absence of any bulk passivation which might result from a dielectric surface film. Substantial improvements are found in bottom wafers, for which annealing at 400 °C for 35 h increases lifetime from 5.5 μs to 38.7 μs. The lifetime of top wafers is improved from 12.1 μs to 23.8 μs under the same conditions. A correlation between interstitial iron concentration reduction and lifetime improvement is found in these cases. Surprisingly, although the interstitial iron concentration exceeds the expected solubility values, low temperature annealing seems to result in an initial increase in interstitial iron concentration, and any subsequent decay is a complex process driven not only by diffusion of interstitial iron