ГИДРООБЪЕМНО-МЕХАНИЧЕСКИЕ ТРАНСМИССИИ МОБИЛЬНЫХ МАШИН. РАСЧЕТ КИНЕМАТИЧЕСКИХ И СИЛОВЫХ ПАРАМЕТРОВ

High efficiency, stepless regulation of speed and power increasingly attracts consumers and manufacturers of technological mobile machines, especially agricultural, to use multi-flow transmissions. To date, amongs 80% of the world market of tractor equipment, produced by leading manufacturers, 18% are tractors with hydrostatic-mechanical transmissions. The aim of this work is to develop a methodology for determining the ability to work of hydrostatic-mechanical transmissions possible schemes. From the literature it is known that 12 single-circuit (with one differential) and 288 double-circuit (with two differentials) there can be only the main structural schemes of hydrostatic-mechanical transmissions. To achieve the aim, a method for estimating an ability to work of possible schemes of hydrostatic-mechanical transmissions according to the criterion of continuity of the function of angular velocities of the links from the regulation parameters of hydraulic machines is proposed. To implement the proposed method, a methodology of calculation of kinematic and power parameters by means of appraising and solving equations that describe the interaction between the elements of single-circuit and double-circuit schemes of hydrostatic-mechanical transmissions, is developed. Analytical dependences for determination of points of discontinuity of the second kind of function of angular velocities of links from the regulation parameters and the working volume of hydraulic machines, the gear ratio of planetary gear set of differential, are determined.The calculation algorithm and the software for selection of the inoperative scheme of hydrostatic-mechanical transmissions are developed. For example, by means of calculations and analysis of variants of schemes for wheeled tractor of tractive class 4, the conditions under which the transmission loses ability to work due to exceeding of angular velocities of links their allowable values, were defined. As a result, the method allows excluding from consideration 5 variants of single-circuit schemes and 257 variants from the 576 double-circuit schemes of hydrostatic-mechanical transmissions.Высокий КПД, бесступенчатое регулирование скорости и мощности все более привлекает потребителей и производителей мобильных машин технологического назначения (особенно сельскохозяйственных) к применению многопоточныхтрансмиссий. К настоящему времени из 80% мирового рынка тракторной техники 18% составляют тракторы с гидрообъемно-механическими трансмиссиями (ГОМТ).Целью данной статьи является разработка методики определения работоспособности возможных схем ГОМТ. Так как из литературных источников известно, что только основных структурных схем ГОМТ может быть 12 одноконтурных (один дифференциал) и 288 двухконтурных (два дифференциала). Для этого предложен метод оценки работоспособности возможных схем ГОМТ по критерию непрерывности функции угловых скоростей звеньев от параметров регулирования гидромашин. Для реализации метода разработана методика расчета кинематических и силовыхпараметров составлением и решением уравнений, описывающих взаимодействия компонентов одноконтурных и двухконтурных схем ГОМТ. Установлены аналитические зависимости для определения точек разрыва второго рода функции угловых скоростей звеньев от параметров регулирования, рабочего объема гидромашин, передаточного отношения планетарного ряда дифференциалов.Разработаны алгоритм и программа расчетов выбора неработоспособных схем ГОМТ. На примере расчетов и анализа вариантов схем для колесного трактора тягового класса 4 установлены условия, при которых трансмиссия теряет работоспособность вследствие превышения угловых скоростей звеньев их допустимым значениям. В результате данный метод позволяет исключить из рассмотрения 5 вариантов одноконтурных и 257 из 576 вариантов двухконтурных схем ГОМТ

Application of Respondent Driven Sampling to Collect Baseline Data on FSWs and MSM for HIV Risk Reduction Interventions in Two Urban Centres in Papua New Guinea

The need to obtain unbiased information among hard–to-reach and hidden populations for behavioural and biological surveillance, epidemiological studies, and intervention program evaluations has led researchers to search for a suitable sampling method. One method that has been tested among IDU and MSM recently is respondent-driven sampling (RDS). We used RDS to conduct a behavioural survey among FSWs and MSM in two urban centres in Papua New Guinea (PNG). In this paper we present the lessons learned implementing RDS in a developing country setting. We also present comparisons of RDSAT-adjusted versus unadjusted crude estimates of some key socio-demographic indicators as well as comparisons between the estimates from RDS and a hypothetical time–location sample (TLS). Overall, the use of RDS among the MSM and FSWs in PNG had numerous advantages in terms of collecting a required sample size in a short time period, minimizing costs and maximising security for staff and respondents. Although there were a few problems these were easily remedied and we would recommend RDS for other similar studies in PNG and other developing countries

Association of community engagement with vaccination confidence and uptake: A cross-sectional survey in Sierra Leone, 2019

Background The 2014-2016 Ebola epidemic disrupted childhood immunization in Sierra Leone, Liberia, and Guinea. After the epidemic, the Government of Sierra Leone prioritized community engagement to increase vaccination confidence and uptake. To support these efforts, we examined potential drivers of vaccination confidence and uptake in Sierra Leone. Methods We conducted a population-based household survey with primary caregivers of children in a birth cohort of 12 to 23 months in four districts with low vaccination coverage in Sierra Leone in 2019. Modified Poisson regression modeling with robust variance estimation was used to examine if perceived community engagement in planning the immunization program in the community was associated with vaccination confidence and having a fully vaccinated child. Results The sample comprised 621 age-eligible children and their caregivers (91% response rate). Half of the caregivers (52%) reported that it usually takes too long to get to the vaccination site, and 36% perceived that health workers expect money for vaccination services that are supposed to be given at no charge. When mothers were the decision-makers of the children’s vaccination, 80% of the children were fully vaccinated versus 69% when fathers were the decision-makers and 56% when other relatives were the decision-makers. Caregivers with high confidence in vaccination were more likely to have fully vaccinated children compared to caregivers with low confidence (78% versus 53%). For example, caregivers who thought vaccines are ‘very much’ safe were more likely to have fully vaccinated children than those who thought vaccines are ‘somewhat’ safe (76% versus 48%). Overall, 53% of caregivers perceived high level of community engagement, 41% perceived medium level of engagement, and 6% perceived low level of engagement. Perceiving high community engagement was associated with expressing high vaccination confidence (adjusted prevalence ratio (aPR) = 2.60; 95% confidence interval (CI) = 1.67-4.04) and having a fully vaccinated child (aPR = 1.67; 95% CI = 1.18-2.38). Conclusions In these four low coverage districts in Sierra Leone, the perceived level of community engagement was strongly associated with vaccination confidence among caregivers and vaccination uptake among children. We have provided exploratory cross-sectional evidence to inform future longitudinal assessments to further investigate the potential causal effect of community engagement on vaccination confidence and uptake

Overview of systematic reviews of therapeutic ranges : methodologies and recommendations for practice

BACKGROUND: Many medicines are dosed to achieve a particular therapeutic range, and monitored using therapeutic drug monitoring (TDM). The evidence base for a therapeutic range can be evaluated using systematic reviews, to ensure it continues to reflect current indications, doses, routes and formulations, as well as updated adverse effect data. There is no consensus on the optimal methodology for systematic reviews of therapeutic ranges. METHODS: An overview of systematic reviews of therapeutic ranges was undertaken. The following databases were used: Cochrane Database of Systematic Reviews (CDSR), Database of Abstracts and Reviews of Effects (DARE) and MEDLINE. The published methodologies used when systematically reviewing the therapeutic range of a drug were analyzed. Step by step recommendations to optimize such systematic reviews are proposed. RESULTS: Ten systematic reviews that investigated the correlation between serum concentrations and clinical outcomes encompassing a variety of medicines and indications were assessed. There were significant variations in the methodologies used (including the search terms used, data extraction methods, assessment of bias, and statistical analyses undertaken). Therapeutic ranges should be population and indication specific and based on clinically relevant outcomes. Recommendations for future systematic reviews based on these findings have been developed. CONCLUSION: Evidence based therapeutic ranges have the potential to improve TDM practice. Current systematic reviews investigating therapeutic ranges have highly variable methodologies and there is no consensus of best practice when undertaking systematic reviews in this field. These recommendations meet a need not addressed by standard protocols

Space-time clustering of childhood malaria at the household level: a dynamic cohort in a Mali village

BACKGROUND: Spatial and temporal heterogeneities in the risk of malaria have led the WHO to recommend fine-scale stratification of the epidemiological situation, making it possible to set up actions and clinical or basic researches targeting high-risk zones. Before initiating such studies it is necessary to define local patterns of malaria transmission and infection (in time and in space) in order to facilitate selection of the appropriate study population and the intervention allocation. The aim of this study was to identify, spatially and temporally, high-risk zones of malaria, at the household level (resolution of 1 to 3 m). METHODS: This study took place in a Malian village with hyperendemic seasonal transmission as part of Mali-Tulane Tropical Medicine Research Center (NIAID/NIH). The study design was a dynamic cohort (22 surveys, from June 1996 to June 2001) on about 1300 children (<12 years) distributed between 173 households localized by GPS. We used the computed parasitological data to analyzed levels of Plasmodium falciparum, P. malariae and P. ovale infection and P. falciparum gametocyte carriage by means of time series and Kulldorff's scan statistic for space-time cluster detection. RESULTS: The time series analysis determined that malaria parasitemia (primarily P. falciparum) was persistently present throughout the population with the expected seasonal variability pattern and a downward temporal trend. We identified six high-risk clusters of P. falciparum infection, some of which persisted despite an overall tendency towards a decrease in risk. The first high-risk cluster of P. falciparum infection (rate ratio = 14.161) was detected from September 1996 to October 1996, in the north of the village. CONCLUSION: This study showed that, although infection proportions tended to decrease, high-risk zones persisted in the village particularly near temporal backwaters. Analysis of this heterogeneity at the household scale by GIS methods lead to target preventive actions more accurately on the high-risk zones identified. This mapping of malaria risk makes it possible to orient control programs, treating the high-risk zones identified as a matter of priority, and to improve the planning of intervention trials or research studies on malaria

Scholarly publishing depends on peer reviewers

The peer-review crisis is posing a risk to the scholarly peer-reviewed journal system. Journals have to ask many potential peer reviewers to obtain a minimum acceptable number of peers accepting reviewing a manuscript. Several solutions have been suggested to overcome this shortage. From reimbursing for the job, to eliminating pre-publication reviews, one cannot predict which is more dangerous for the future of scholarly publishing. And, why not acknowledging their contribution to the final version of the article published? PubMed created two categories of contributors: authors [AU] and collaborators [IR]. Why not a third category for the peer-reviewer?Scopu