Suchergebnisse

The exhaust emissions from automobiles are one of the major sources of air pollution in today's world. Thence,research and development is the key feature of the modern automotive industries to meet strict emission legislation. One of the key aspects to meet these requirements is to improve the gas exchange process within internal combustion engines. It is possible by the design optimization of the air intake manifolds for internal combustion engines. One of such advancement in air intake manifolds is variable tumble systems (VTS). In VTS system, tumble flaps are installed at the exit of the manifold runner in order to improve tumble ratio and hence air-fuel mixing. Another feature of the flow inside the intake manifolds is pressure pulsation effect. Therefore, the aim of the Ph.D. work is to simulate the pulsating air flow inside the air intake manifolds and to identify the effect of the pressure pulsations on the active components like tumble flaps. The simulation work in the present thesis has been carried out on open source CFD code OpenFOAM. In a first step, the effect of pressure pulsations is simulated inside a steel tube and a simulation methodology is developed. The results of the simulation are validated on a specific experimental device, the dynamic flow bench. Then,simulations have been carried out on the main intake manifold with tumble flaps. Firstly, the simulations are performed with five different opening positions of the tumble flap in a steady state configuration. The forces and moments acting on the flap in steady state are obtained and analyzed. Then, unsteady simulations with pressure pulsation effects are performed. The results of obtained from unsteady simulation are compared with the experimental results in terms of relative pressure fluctuations. The effect of the pressure pulsation on the aerodynamic forces and moments acting on the tumble flaps are analyzed and explained. ; Les émissions polluantes à l'échappement des véhicules automobiles sont l'une des principales sources de ...

Introduction: There has been a rapid rise in the prevalence of non communicable diseases. Still there is ignorance with regard to their prevention in the general population. Further the preventive measures are not covered in the school curriculum. Objective: The study was done to provide information about the effectiveness of community-based health education on non communicable diseases among intermediate college students. Methods: The cross sectional study was carried out at Government Intermediate College. A health education programme of the intermediate class students was conducted. The impact was evaluated by comparing the pre and post test proformas filled by 133 students. The proforma consisted of 16 questions related to different non communicable diseases. Care was being taken that the proformas were filled individually by students under the direct observation of the health educators. The proformas were then analysed using appropriate statistical techniques like percentage, paired t-test, chi-square test and p-value. Results: The 16 questions proforma was grouped 4 under categories. In pre test 35.5% correct answers were obtained which increased to 69.0% in the post test. (p = 0.0000). Significant improvement in knowledge was seen in all categories of questions which included Cardiovascular disease (p = 0.0000); hypertension (p = 0.0000); diabetes (p = 0.0000) and obesity (p = 0.0000). Conclusion: The findings of current study suggest that knowledge of students significantly improved after health education. Thus, health education programmes should regularly be conducted for improving the knowledge of students.

International audience ; Recently, the car manufacturers are moving towards innovative Spark Ignition (SI) engine architectures with unconventional combustion concepts, aiming to comply with the stringent regulation imposed by EU and other legislators. The introduction of burdensome cycles for vehicle homologation, indeed, requires an engine characterized by a high efficiency in the most of its operating conditions, for which a conventional SI engine results to be ineffective. Combustion systems which work with very lean air/fuel mixture have demonstrated to be a promising solution to this concern. Higher specific heat ratio, minor heat losses and increased knock resistance indeed allow improving fuel consumption. Additionally, the lower combustion temperatures enable to reduce NOX production.Since conventional SI engines can work with a limited amount of excess air, alternative solutions are being developed to overcome this constraint and reach the above benefit. Among all these solutions, replacing the spark-plug with a Pre-Chamber (PC) ignition system is gaining increasing interest. For this architecture, the combustion process starts in the PC and propagates in the main-chamber in the form of multiple turbulent jets of hot gas, with high-turbulence level. This ensures stable flame propagation even under extremely lean mixtures.In this research activity, an ultra-lean PC SI engine is numerically and experimentally investigated to assess the potential improvement of the thermal efficiency for ultra-lean operations. To this aim, a research single cylinder engine, fuelled with gasoline, is tested at fixed load and speed, realizing an air / fuel ratio sweep. A 1D/0D model of the examined engine is implemented in a commercial modelling framework (GT-Power™), where "in-house developed" sub-models are embedded, simulating in-cylinder phenomena, such as combustion, turbulence, heat transfer and pollutant emissions.The numerical approach, preliminarily tuned against 3D simulations and experimental outcomes, ...

International audience ; Recently, the car manufacturers are moving towards innovative Spark Ignition (SI) engine architectures with unconventional combustion concepts, aiming to comply with the stringent regulation imposed by EU and other legislators. The introduction of burdensome cycles for vehicle homologation, indeed, requires an engine characterized by a high efficiency in the most of its operating conditions, for which a conventional SI engine results to be ineffective. Combustion systems which work with very lean air/fuel mixture have demonstrated to be a promising solution to this concern. Higher specific heat ratio, minor heat losses and increased knock resistance indeed allow improving fuel consumption. Additionally, the lower combustion temperatures enable to reduce NOX production.Since conventional SI engines can work with a limited amount of excess air, alternative solutions are being developed to overcome this constraint and reach the above benefit. Among all these solutions, replacing the spark-plug with a Pre-Chamber (PC) ignition system is gaining increasing interest. For this architecture, the combustion process starts in the PC and propagates in the main-chamber in the form of multiple turbulent jets of hot gas, with high-turbulence level. This ensures stable flame propagation even under extremely lean mixtures.In this research activity, an ultra-lean PC SI engine is numerically and experimentally investigated to assess the potential improvement of the thermal efficiency for ultra-lean operations. To this aim, a research single cylinder engine, fuelled with gasoline, is tested at fixed load and speed, realizing an air / fuel ratio sweep. A 1D/0D model of the examined engine is implemented in a commercial modelling framework (GT-Power™), where "in-house developed" sub-models are embedded, simulating in-cylinder phenomena, such as combustion, turbulence, heat transfer and pollutant emissions.The numerical approach, preliminarily tuned against 3D simulations and experimental outcomes, demonstrated to accurately reproduce the engine behaviour, without requiring any case-dependent tuning of the model constants. Both numerical and experimental results proved that working in ultra-lean condition allows to significantly improve the indicated thermal efficiency, abating the NOx emissions, while penalizing the HC production.

International audience ; Recently, the car manufacturers are moving towards innovative Spark Ignition (SI) engine architectures with unconventional combustion concepts, aiming to comply with the stringent regulation imposed by EU and other legislators. The introduction of burdensome cycles for vehicle homologation, indeed, requires an engine characterized by a high efficiency in the most of its operating conditions, for which a conventional SI engine results to be ineffective. Combustion systems which work with very lean air/fuel mixture have demonstrated to be a promising solution to this concern. Higher specific heat ratio, minor heat losses and increased knock resistance indeed allow improving fuel consumption. Additionally, the lower combustion temperatures enable to reduce NOX production.Since conventional SI engines can work with a limited amount of excess air, alternative solutions are being developed to overcome this constraint and reach the above benefit. Among all these solutions, replacing the spark-plug with a Pre-Chamber (PC) ignition system is gaining increasing interest. For this architecture, the combustion process starts in the PC and propagates in the main-chamber in the form of multiple turbulent jets of hot gas, with high-turbulence level. This ensures stable flame propagation even under extremely lean mixtures.In this research activity, an ultra-lean PC SI engine is numerically and experimentally investigated to assess the potential improvement of the thermal efficiency for ultra-lean operations. To this aim, a research single cylinder engine, fuelled with gasoline, is tested at fixed load and speed, realizing an air / fuel ratio sweep. A 1D/0D model of the examined engine is implemented in a commercial modelling framework (GT-Power™), where "in-house developed" sub-models are embedded, simulating in-cylinder phenomena, such as combustion, turbulence, heat transfer and pollutant emissions.The numerical approach, preliminarily tuned against 3D simulations and experimental outcomes, demonstrated to accurately reproduce the engine behaviour, without requiring any case-dependent tuning of the model constants. Both numerical and experimental results proved that working in ultra-lean condition allows to significantly improve the indicated thermal efficiency, abating the NOx emissions, while penalizing the HC production.

Since the beginning of the COVID-19 pandemic, much research has been conducted globally, but relatively few studies have been carried out in complex emergency settings that pose numerous operational challenges. We conducted a qualitative study to explore the barriers and enablers of a COVID-19 cohort study conducted in South Sudan and Eastern Democratic Republic of the Congo, to inform future research on COVID-19 and infectious diseases in humanitarian settings. We used a case study design embedded within the original prospective cohort study. Qualitative data was collected through four health facility assessments, 28 key informant interviews, and a focus group discussion. Data were analyzed using a manual thematic analysis approach and summarized against four primary themes: testing challenges and enablers, perceptions and attitudes towards COVID-19, national health system considerations, and study management considerations. Findings suggest most of the challenges affecting the cohort study were not specific to COVID-19 research but have been a feature of previous infectious disease research carried out in complex emergencies. However, the pandemic has exacerbated certain problems. The high proportion of travellers enrolled due to testing mandates, stigmatization of infected individuals linked to the heavy global focus on COVID-19, strained resources during waves of increasing infections, and remote management requirements all negatively impacted the cohort study. Factors that facilitated the research included proactive management, data quality oversight procedures, and strong collaboration with national health stakeholders. The global impact of COVID-19, its high public profile, and specific pandemic policies pose further operational challenges for research in already complex humanitarian settings. Future studies could plan mitigation measures that include flexibility in staffing and budgets, strategies to expand testing, and early partnerships with local organizations and health authorities.

Abstract:Background:The 2019 novel coronavirus disease (COVID-19) has spread to more than 213 countries and as of 17th April 2020, 1995,983 confirmed cases and 131,037 deaths have been reported globally. Pakistan being sharing border with China and Iran, having high frequency of travel and trade has been at risk of viral transmission.Methods:We examined current state of COVID-19 epidemic and preparedness in Pakistan using publicly available data and documents on COVID-19 government dashboard.Results:Pakistan reported its first 2 confirmed cases, on 26th February 2020 linked to travel history of Iran. The number of confirmed cases nationwide rose to 7,025 on 17th April 2020 with 135 deaths and 3276 confirmed cases in Punjab,2008 cases in Sindh,993 in Khyber Pathunkhawa,303 in Baluchistan,237 in Gilgit Baltistan,154 in ICT and 46 in Azad Jammu Kashmir. To-date 7000 Pakistani pilgrims have returned from Iran and placed in quarantine in Taftan. Directing of pilgrims back to their cities without testing at the border resulted in introduction of virus in country. Pakistan's weak healthcare system with 0.6 bed for 1000 people and less than 0.75% of GDP as health spending is doubtful to bear the COVID-19 shock in case of exponential increase in cases.Conclusion:Low literacy rate and general lack of awareness leading to non-seriousness of people towards the adoption of social distancing and hand hygiene. The high population density in major cities of Pakistan can facilitate in the spread of virus. Three-pronged approach of trace, test and treat needs to be aggressively implemented to halt the community transmission leading to exponential increase in cases. Keywords:COVID-19,Preparedness,Three-pronged approach, community transmission.

BACKGROUND: In the United States, underserved communities including Blacks and Latinx are disproportionately affected by COVID-19, and widespread vaccination is critical for curbing this pandemic. This study sought to estimate the prevalence of COVID-19 vaccine hesitancy, describe attitudes related to vaccination, and identify correlates among racial minority and marginalized populations across 9 counties in North Carolina. METHODS: We conducted a cross-sectional survey with a self-administered questionnaire distributed at free COVID-19 testing events in underserved rural and urban communities from August 27 – December 15, 2020. Vaccine hesitancy was defined as the response of "no" or "don't know/not sure" to whether the participant would get the COVID-19 vaccine as soon as it became available. RESULTS: The sample comprised 948 participants including 27.7% Whites, 59.6% Blacks, 12.7% Latinx, and 63% female. Thirty-two percent earned <$20K annually, 60% owned a computer and ∼80% had internet access at home. The prevalence of vaccine hesitancy was 68.9% including 62.7%, 74%, and 59.5% among Whites, Blacks, and Latinx, respectively. Between September and December, the largest decline in vaccine hesitancy occurred among Whites (27.5 percentage points), followed by Latinx (17.6) and the smallest decline was among Black respondents (12.0). 51.2% of the respondents reported vaccine safety concerns, 23.7% wanted others to get of the respondents reported they would trust health care providers with information about the COVID-19 vaccine. Factors associated with hesitancy in multivariable logistic regression included being female (OR=1.90 95%CI[1.36, 2.64]), being Black (OR=1.68 [1.106 2.45]), calendar month (OR=0.76 [0.63, 0.92]), safety concerns (OR=4.28 [3.06, 5.97]), and government distrust (OR=3.57 [2.26, 5.63]). CONCLUSIONS: This study reached underserved minority populations in a number of different locations to investigate COVID-19 vaccine hesitancy. We built on existing relationships and further engaged the ...

The Research Centers in Minority Institutions (RCMI) program was established by the US Congress to support the development of biomedical research infrastructure at minority-serving institutions granting doctoral degrees in the health professions or in a health-related science. RCMI institutions also conduct research on diseases that disproportionately affect racial and ethnic minorities (ie, African Americans/Blacks, American Indians and Alaska Natives, Hispanics, Native Hawaiians and Other Pacific Islanders), those of low socioeconomic status, and rural persons. Quantitative metrics, including the numbers of doctoral science degrees granted to underrepresented students, NIH peer-reviewed research funding, peer-reviewed publications, and numbers of racial and ethnic minorities participating in sponsored research, demonstrate that RCMI grantee institutions have made substantial progress toward the intent of the Congressional legislation, as well as the NIH/NIMHD-linked goals of addressing workforce diversity and health disparities. Despite this progress, nationally, many challenges remain, including persistent disparities in research and career development awards to minority investigators. The continuing underrepresentation of minority investigators in NIH-sponsored research across multiple disease areas is of concern, in the face of unrelenting national health inequities. With the collaborative network support by the RCMI Translational Research Network (RTRN), the RCMI community is uniquely positioned to address these challenges through its community engagement and strategic partnerships with non-RCMI institutions. Funding agencies can play an important role by incentivizing such collaborations, and incorporating metrics for research funding that address underrepresented populations, workforce diversity and health equity.