Nozzle Plume Impingement on Spacecraft Surfaces: Effects of Surface Roughness

Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing this collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. REPORT DATE (DD-MM-YYYY) SPONSORING / MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR'S ACRONYM(S) Air Force Research Laboratory (AFMC) AFRL/PRS SPONSOR/MONITOR'S Pollux Drive NUMBER(S) Edwards AFB CA 93524-70448 AFRL-PR-ED-JA-2005-306 DISTRIBUTION / AVAILABILITY STATEMENT Approved for public release; distribution unlimited (PA no. AFRL-ERS-PAS-2005-219). SUPPLEMENTARY NOTES Published in Journal of Spacecraft and Rockets, AIAA-2005-5065. ABSTRACT An experimental and numerical effort was undertaken to assess the effects of a cold gas (T 0 -300 K) nozzle plume impinging on simulated spacecraft surfaces. The nozzle flow impingement is investigated experimentally using a nano-Newton resolution force balance and numerically using the Direct Simulation Monte Carlo (DSMC) numerical technique. The Reynolds number range investigated in this study is from approximately 2 to 350 using nitrogen propellant. The thrust produced by the nozzle was first assessed on a force balance to provide a baseline case. Subsequently, aluminum plates were attached to the same force balance parallel to the plume flow to simulate spacecraft surfaces in proximity to the thruster. Three plates were used in this study, an electropolished plate with smooth surface, and two rough surface plates with equally spaced rectangular and triangular grooves. A 15% degradation in thrust was observed both experimentally and numerically for the plate relative to the free plume expansion case. The effect of surface roughness on thrust was found to be small due to molecules backscattered from the plate to the nozzle plenum wall. Additionally, the influence of surface roughness in the diverging part of the nozzle on thrust was examined numerically and found to be significant at Reynolds numbers less than 10. Abstract An experimental and numerical effort was undertaken to assess the effects of a cold gas (T 0 =300 K) nozzle plume impinging on a simulated spacecraft surface. The nozzle flow impingement is investigated experimentally using a nano-Newton resolution force balance and numerically using the Direct Simulation Monte Carlo (DSMC) numerical technique. The Reynolds number range investigated in this study is from approximately 2 to 600 using nitrogen propellant. The thrust produced by the nozzle was first assessed on a force balance to provide a baseline case. Subsequently, aluminum plates were attached to the same force balance parallel to the plume flow. Three plates were used in this study, an electropolished plate with smooth surface, and two rough surface plates with equally spaced rectangular and triangular grooves. A 15% degradation in thrust was observed both experimentally and numerically for the plate relative to the free plume expansion case. The effect of surface roughness on thrust was found to be small due to molecules back scattered from the plate to the plenum wall. Additionally, the influence of surface rougness in the diverging part of the nozzle on nozzle thrust was examined numerically, and found to be significant at Reynolds numbers on the order or less than 10

Training community healthcare workers on the use of information and communication technologies: a randomised controlled trial of traditional versus blended learning in Malawi, Africa

Background: Despite the increasing uptake of information and communication technologies (ICT) within healthcare services across developing countries, community healthcare workers (CHWs) have limited knowledge to fully utilise computerised clinical systems and mobile apps. The ‘Introduction to Information and Communication Technology and eHealth’ course was developed with the aim to provide CHWs in Malawi, Africa, with basic knowledge and computer skills to use digital solutions in healthcare delivery. The course was delivered using a traditional and a blended learning approach. Methods: Two questionnaires were developed and tested for face validity and reliability in a pilot course with 20 CHWs. Those were designed to measure CHWs’ knowledge of and attitudes towards the use of ICT, before and after each course, as well as their satisfaction with each learning approach. Following validation, a randomised controlled trial was conducted to assess the effectiveness of the two learning approaches. A total of 40 CHWs were recruited, stratified by position, gender and computer experience, and allocated to the traditional or blended learning group using block randomisation. Participants completed the baseline and follow-up questionnaires before and after each course to assess the impact of each learning approach on their knowledge, attitudes, and satisfaction. Per-item, pre-post and between-group, mean differences for each approach were calculated using paired and unpaired t-tests, respectively. Per-item, between-group, satisfaction scores were compared using unpaired t-tests. Results: Scores across all scales improved after attending the traditional and blended learning courses. Self-rated ICT knowledge was significantly improved in both groups with significant differences between groups in seven domains. However, actual ICT knowledge scores were similar across groups. There were no significant differences between groups in attitudinal gains. Satisfaction with the course was generally high in both groups. However, participants in the blended learning group found it more difficult to follow the content of the course. Conclusions: This study shows that there is no difference between blended and traditional learning in the acquisition of actual ICT knowledge among community healthcare workers in developing countries. Given the human resource constraints in remote resource-poor areas, the blended learning approach may present an advantageous alternative to traditional learning

Training community healthcare workers on the use of information and communication technologies: a randomised controlled trial of traditional versus blended learning in Malawi, Africa.

BACKGROUND: Despite the increasing uptake of information and communication technologies (ICT) within healthcare services across developing countries, community healthcare workers (CHWs) have limited knowledge to fully utilise computerised clinical systems and mobile apps. The 'Introduction to Information and Communication Technology and eHealth' course was developed with the aim to provide CHWs in Malawi, Africa, with basic knowledge and computer skills to use digital solutions in healthcare delivery. The course was delivered using a traditional and a blended learning approach. METHODS: Two questionnaires were developed and tested for face validity and reliability in a pilot course with 20 CHWs. Those were designed to measure CHWs' knowledge of and attitudes towards the use of ICT, before and after each course, as well as their satisfaction with each learning approach. Following validation, a randomised controlled trial was conducted to assess the effectiveness of the two learning approaches. A total of 40 CHWs were recruited, stratified by position, gender and computer experience, and allocated to the traditional or blended learning group using block randomisation. Participants completed the baseline and follow-up questionnaires before and after each course to assess the impact of each learning approach on their knowledge, attitudes, and satisfaction. Per-item, pre-post and between-group, mean differences for each approach were calculated using paired and unpaired t-tests, respectively. Per-item, between-group, satisfaction scores were compared using unpaired t-tests. RESULTS: Scores across all scales improved after attending the traditional and blended learning courses. Self-rated ICT knowledge was significantly improved in both groups with significant differences between groups in seven domains. However, actual ICT knowledge scores were similar across groups. There were no significant differences between groups in attitudinal gains. Satisfaction with the course was generally high in both groups. However, participants in the blended learning group found it more difficult to follow the content of the course. CONCLUSIONS: This study shows that there is no difference between blended and traditional learning in the acquisition of actual ICT knowledge among community healthcare workers in developing countries. Given the human resource constraints in remote resource-poor areas, the blended learning approach may present an advantageous alternative to traditional learning

Neonatal Circumcision for HIV Prevention: Cost, Culture, and Behavioral Considerations

Seth Kalichman discusses a new study that finds neonatal circumcision in Rwanda to be a cost-saving HIV prevention strategy

Rehabilitation Training for Home-Based Palliative Care Community Health Workers: A Pilot Study

Introduction: Community health workers are an essential part of the delivery of palliative care in the resource-limited country of Malawi. The purpose of this pilot study was to evaluate a training programme in rehabilitation for home-based palliative community health workers.Methods: The programme was a 3-day training in rehabilitation for palliative care for 20 community health workers at St Gabriel\u27s, a rural referral hospital in Malawi. A pre- and post- knowledge test, a skills competency check, ongoing formative assessment, observations of skills in the home visit, and reporting of skills used in the village were used to evaluate the training programme.Results: Participants (n = 20) showed significantly greater knowledge on the post-test (M = 7.35, SE = 0.406) than on the pre-test (M = 4.25, SE = 0.422, t (19) =−7.566, P = 0.000). Competency in all 22 physical therapy skills was demonstrated by 100% of the participants (n = 20). During the formative assessment and observations during the 3-day programme, participants were able to use all of the 22 physical therapy skills. At 2-week post-training, the participants surveyed (n = 14) reported using 21 of 22 physical therapy skills and teaching all 21 of the skills used to the caregiver of the patient. Discussion: This study demonstrated the knowledge and skills learned in a training programme with lecture, practice sessions and application components in a resource-limited setting. The training programme provides a basis for future training and curriculum development for palliative care community health workers

Rehabilitation Training for Home-Based Palliative Care Community Health Workers: A Pilot Study

Introduction: Community health workers are an essential part of the delivery of palliative care in the resource-limited country of Malawi. The purpose of this pilot study was to evaluate a training programme in rehabilitation for home-based palliative community health workers.Methods: The programme was a 3-day training in rehabilitation for palliative care for 20 community health workers at St Gabriel\u27s, a rural referral hospital in Malawi. A pre- and post- knowledge test, a skills competency check, ongoing formative assessment, observations of skills in the home visit, and reporting of skills used in the village were used to evaluate the training programme.Results: Participants (n = 20) showed significantly greater knowledge on the post-test (M = 7.35, SE = 0.406) than on the pre-test (M = 4.25, SE = 0.422, t (19) =−7.566, P = 0.000). Competency in all 22 physical therapy skills was demonstrated by 100% of the participants (n = 20). During the formative assessment and observations during the 3-day programme, participants were able to use all of the 22 physical therapy skills. At 2-week post-training, the participants surveyed (n = 14) reported using 21 of 22 physical therapy skills and teaching all 21 of the skills used to the caregiver of the patient. Discussion: This study demonstrated the knowledge and skills learned in a training programme with lecture, practice sessions and application components in a resource-limited setting. The training programme provides a basis for future training and curriculum development for palliative care community health workers

Area and edge effects in radiometric forces

The radiometric force on several configurations of heated plates placed in a stagnant gas is examined experimentally, with a high-resolution thrust stand, and numerically using the direct simulation Monte Carlo method and a discrete ordinate solution of a model kinetic equation. A wide range of pressure from 0.006 to 6 Pa was examined, corresponding to Knudsen numbers from 20 to 0.02, in argon and helium test gases. The radiometric force, important in a number of emerging micro- and nanoscale applications, is shown to be mostly area dependent in the transitional regime where it reaches its maximum at Kn~0.1

Training community healthcare workers on the use of information and communication technologies: a randomised controlled trial of traditional versus blended learning in Malawi, Africa.

BACKGROUND: Despite the increasing uptake of information and communication technologies (ICT) within healthcare services across developing countries, community healthcare workers (CHWs) have limited knowledge to fully utilise computerised clinical systems and mobile apps. The 'Introduction to Information and Communication Technology and eHealth' course was developed with the aim to provide CHWs in Malawi, Africa, with basic knowledge and computer skills to use digital solutions in healthcare delivery. The course was delivered using a traditional and a blended learning approach. METHODS: Two questionnaires were developed and tested for face validity and reliability in a pilot course with 20 CHWs. Those were designed to measure CHWs' knowledge of and attitudes towards the use of ICT, before and after each course, as well as their satisfaction with each learning approach. Following validation, a randomised controlled trial was conducted to assess the effectiveness of the two learning approaches. A total of 40 CHWs were recruited, stratified by position, gender and computer experience, and allocated to the traditional or blended learning group using block randomisation. Participants completed the baseline and follow-up questionnaires before and after each course to assess the impact of each learning approach on their knowledge, attitudes, and satisfaction. Per-item, pre-post and between-group, mean differences for each approach were calculated using paired and unpaired t-tests, respectively. Per-item, between-group, satisfaction scores were compared using unpaired t-tests. RESULTS: Scores across all scales improved after attending the traditional and blended learning courses. Self-rated ICT knowledge was significantly improved in both groups with significant differences between groups in seven domains. However, actual ICT knowledge scores were similar across groups. There were no significant differences between groups in attitudinal gains. Satisfaction with the course was generally high in both groups. However, participants in the blended learning group found it more difficult to follow the content of the course. CONCLUSIONS: This study shows that there is no difference between blended and traditional learning in the acquisition of actual ICT knowledge among community healthcare workers in developing countries. Given the human resource constraints in remote resource-poor areas, the blended learning approach may present an advantageous alternative to traditional learning