Vibration Analysis of a Split Path Gearbox

Split path gearboxes can be attractive alternatives to the common planetary designs for rotorcraft, but because they have seen little use, they are relatively high risk designs. To help reduce the risk of fielding a rotorcraft with a split path gearbox, the vibration and dynamic characteristics of such a gearbox were studied. A mathematical model was developed by using the Lagrangian method, and it was applied to study the effect of three design variables on the natural frequencies and vibration energy of the gearbox. The first design variable, shaft angle, had little influence on the natural frequencies. The second variable, mesh phasing, had a strong effect on the levels of vibration energy, with phase angles of 0 deg and 180 deg producing low vibration levels. The third design variable, the stiffness of the shafts connecting the spur gears to the helical pinions, strongly influenced the natural frequencies of some of the vibration modes, including two of the dominant modes. We found that, to achieve the lowest level of vibration energy, the natural frequencies of these two dominant modes should be less than those of the main excitation sources

The determinants of handwashing behaviour among internally displaced women in two camps in the Kurdistan Region of Iraq.

BACKGROUND: Diarrhoea is one of the most common causes of mortality and morbidity among populations displaced due to conflict. Handwashing with soap has the potential to halve the burden of diarrhoeal diseases in crisis contexts. This study aimed to identify which determinants drive handwashing behaviour in post-conflict, displacement camps. METHODS: This study was conducted in two camps for internally displaced people in the Kurdistan Region of Iraq. A Barrier Analysis questionnaire was used for assessing the determinants of hand washing behaviour. Participants were screened and classified as either 'doers' (those who wash their hands with soap at critical times) or 'non-doers' (those who do not wash their hands with soap at critical times). Forty-five doers and non-doers were randomly selected from each camp and asked about behavioural determinants. The Barrier Analysis standard tabulation sheet was used for the analysis. RESULTS: No differences were observed between doers and non-doers in relation to self-efficacy, action efficacy, the difficulties and benefits of handwashing, and levels of access to soap and water. In the first of the two camps, non-doers found it harder to remember to wash their hands (P = 0.045), had lower perceived vulnerability to diarrhoea (P = 0.037), lower perceived severity of diarrhoea (P = 0.020) and were aware of 'policies' which supported handwashing with soap (P = 0.037). In the second camp non-doers had lower perceived vulnerability to diarrhoea (P = 0.017). CONCLUSIONS: In these camp settings handwashing behaviour, and the factors that determine it, was relatively homogenous because of the homogeneity of the settings and the socio-demographics of population. Handwashing programmes should seek to improve the convenience and quality of handwashing facilities, create cues to trigger handwashing behaviour and increase perceived risk. We identify several ways to improve the validity of the Barrier Analysis method such as using it in combination with other more holistic qualitative tools and revising the statistical analysis

Geotechnical Solutions for Soil Improvement, Rapid Embankment Construction, and Stabilization of the Pavement Working Platform, Performance Assessment of Lime and Fly Ash Chemically Treated Subgrade

Chemical treatment and stabilization of subgrades is a long-standing method to construct working platforms and improve the support conditions for pavement systems. Lime, cement, and fly ash are common chemical stabilization agents and are often incorporated with subgrade materials to improve volumetric stability, freeze-thaw performance, and/or subgrade stiffness. Although laboratory test methods and design procedures are relatively well established, the long-term (5+ years) field performance characteristics of treated or stabilized subgrades is poorly documented and was the focus of this study. The main objectives of this project were as follows: Document engineering properties (in situ strength/stiffness) and mineralogical/micro-structural characteristics of chemical stabilized subgrades, in comparison with natural subgrades at the same sites Understand factors that contribute to long-term engineering behavior of stabilized subgrade Nine test sections were selected to assess engineering properties of old stabilized subgrades in Texas, Oklahoma, and Kansas. The selection of the test sites was based on the type of subgrade, availability of old construction records, and age. Subgrades at six of these sites were stabilized with lime and the other three with fly ash. Eight of these test sites were more than 10 years old, and one test site was about 5 years old. Eight sites consisted of flexible pavement supported on base and stabilized subgrade or just stabilized subgrade, and one site consisted of concrete pavement supported on cement treated base and stabilized subgrade Results from this study provide new information that should be of great interest to pavement designers dealing with selection of design parameters for chemically stabilized subgrade layers

Laparoscopic heller esophagomyotomy is safe and effective in rural East Africa

Background: The incidence of achalasia in sub- Saharan Africa is not known. Experience in our region suggests the disorder affects mainly younger patients. Esophagomyotomy is the gold standard treatment for achalasia. Benefits of laparoscopic treatment are well documented in western populations. African data isinsufficient.Methods: A retrospective review of patients over 16 years who underwent esophagomyotomy at Tenwek Hospital (2008–2017). The primary outcome was improvement in symptoms before and after surgery as measured using the Eckardt score— lower scores for dysphagia, regurgitation, pain, weight loss indicate less severe symptoms. The secondary outcomes were duration of surgery, length of myotomy, length of hospital stay, and complication rate. Data analysis used ANOVA.Results: 54 patients were included: 28 with laparoscopic Heller myotomy (LHM), 26 with open Heller myotomy (OHM). LHM patients were younger than OHM patients (p<0.05). Patients who had LHM had lower postoperative Eckardt scores (p<0.05). Duration of surgery for LHM was longer (p<0.001) than for OHM, conversion rate was 10.71%, and length of the myotomy was unaltered. No difference was seen in hospital stay or complication rate between the two groups.Conclusion: LHM is effective and safe in a rural East African setting, with excellent functional outcomes compared with open techniques. Thus, laparoscopy can be feasible worldwide.Keywords: Laparoscopic, Heller Esophagomyotomy, Tenwek Hospital, Achalasi