72 research outputs found

    High Speed Shadowgraphy of Transparent Nozzles as an Evaluation Tool for In-Nozzle Cavitation Behavior of GDI Injectors

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    [EN] Gasoline Direct Injection (GDI) systems have become a rapidly developing technology taking up a considerable and rapidly growing share in the Gasoline Engine market due to the thermodynamic advantages of direct injection. The process of spray formation and propagation from a fuel injector is very crucial in optimizing the air-fuel mixture of DI engines. Previous studies have shown that the presence of some cavitation in high-pressure fuel nozzles can lead to better atomization of the fluid. However, under some very specific circumstances, high levels of cavitation can also delay the atomization process; spray stabilization due to hydraulic flip is the most well-known example. Therefore, a better understanding of cavitation behavior is of vital importance for further optimization of next generation fuel injectors. In contrast to the abundance of investigations conducted on the inner flow and cavitation patterns of diesel injectors, corresponding in-depth research on the inner flow of gasoline direct-injection nozzles is still relatively scarce. In this study, the results of an experiment performed on real-size GDI injector nozzles made of acrylic glass are presented. The inner flow of the nozzle is visualized using a high-power pulsed laser, a long-distance microscope and a highspeed camera. The ambiguity of dark areas on the images, which may represent cavitation regions as well as ambient air drawn into the nozzle holes, is resolved by injecting the fuel both into a fuel or gas filled environment. In addition, the influence of backpressure on the transient flow characteristics of the internal flow is investigated. In good agreement with observations made in previous studies, higher backpressure levels decrease the amount of cavitation inside the nozzles. Due to the high temporal and spatial resolution of the experiment, the transient cavitation behavior during the opening, quasi-steady and closing phases of the injector needle motion can be analyzed. For example, it is found that cavitation patterns oscillate with a characteristic frequency that depends on the backpressure. The link between cavitation and air drawn into the nozzle at the beginning of injection is also revealed.Mamaikin, D.; Knorsch, T.; Rogler, P.; Leick, P.; Wensing, M. (2017). High Speed Shadowgraphy of Transparent Nozzles as an Evaluation Tool for In-Nozzle Cavitation Behavior of GDI Injectors. En Ilass Europe. 28th european conference on Liquid Atomization and Spray Systems. Editorial Universitat Politècnica de València. 1027-1034. https://doi.org/10.4995/ILASS2017.2017.4639OCS1027103

    Quantification of mixture composition, liquid-phase fraction and temperature in transcritical sprays

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    How do fuel and air mix, if a liquid fuel is injected into an environment featuring pressure and temperature that exceed the critical pressure and the critical temperature of the fuel? It is subject of current discussion on whether and if so when, the fuel/air-mixture becomes supercritical or not. We here report experimental data comprising three mixture properties that are relevant for the current debate, all spatially and temporally resolved throughout the spray and injection event: The overall composition of the fuel/air-mixture, the liquid fraction of the fuel/air-mixture, and the temperature of the liquid phase. To this end, we applied Raman spectroscopy and gave special attention to the signature of the Raman OH-band of ethanol, which we used as fuel. Its signature is connected to the development of a hydrogen bonded network between the ethanol molecules and thus extremely sensitive to thermodynamic state and temperature. Measurements were carried out in a high-pressure, high-temperature combustion vessel in a pressure range of 3−8 MPa and a temperature range of 573−923 K. For the highest set temperature we found ethanol in liquid-like mixtures that exceeded the mixture critical temperature. This is an indication of the existence of a single-phase mixing path

    Comparison of physician referral and insurance claims data-based risk prediction as approaches to identify patients for care management in primary care: an observational study

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    BACKGROUND: Primary care-based care management (CM) could reduce hospital admissions in high-risk patients. Identification of patients most likely to benefit is needed as resources for CM are limited. This study aimed to compare hospitalization and mortality rates of patients identified for CM either by treating primary care physicians (PCPs) or predictive modelling software for hospitalization risk (PM). METHODS: In 2009, a cohort of 6,026 beneficiaries of a German statutory health insurance served as a sample for patient identification for CM by PCPs or commercial PM (CSSG 0.8, Verisk Health). The resulting samples were compared regarding hospitalization and mortality rates in 2010 and in the two year period before patient selection. No CM-intervention was delivered until the end of 2010 and PCPs were blinded for the assessment of hospitalization rates. RESULTS: In 2010, hospitalization rates of PM-identified patients were 80% higher compared to PCP-identified patients. Mortality rates were also 8% higher in PM-identified patients if compared to PCP-identified patients (10% vs. 2%). The hospitalization rate of patients independently identified by both PM and PCPs was numerically between PM- and PCP-identified patients. Time trend between 2007 and 2010 showed decreasing hospitalization rates in PM-identified patients (−15% per year) compared to increasing rates in PCP-identified patients (+34% per year). CONCLUSIONS: PM identified patients with higher hospitalization and mortality rates compared to PCP-referred patients. But the latter showed increasing hospitalization rates over time thereby suggesting that PCPs may be able to predict future deterioration in patients with relatively good current health status. These patients may most likely benefit from preventive services like CM

    Identifying factors associated with experiences of coronary heart disease patients receiving structured chronic care and counselling in European primary care

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    BACKGROUND: Primary care for chronic illness varies across European healthcare systems. In patients suffering from coronary heart disease (CHD), factors associated with patients’ experiences of receiving structured chronic care and counselling at the patient and practice level were investigated. METHODS: In an observational study comprising 140 general practices from five European countries (Austria, Germany, the Netherlands, Switzerland and the United Kingdom), 30 patients with Coronary Heart Disease (CHD) per practice were chosen at random to partake in this research. Patients were provided with a questionnaire and the Patient Assessment of Chronic Illness Care (PACIC-5A) - instrument. Practice characteristics were assessed through a practice questionnaire and face to face interviews. Data were aggregated to obtain two practice scores representing quality management and CHD care, respectively. A hierarchical multilevel analysis was performed to examine the impact of patient and practice characteristics on PACIC scores. RESULTS: The final sample included 1745 CHD-patients from 131 general practices with a mean age of 67.8 (SD 9.9) years. The overall PACIC score was 2.84 (95%CI: 2.79; 2.89) and the 5A score reflecting structured lifestyle counselling was 2.75 (95% CI: 2.69; 2.79). At the patient level, male gender, more frequent practice contact and fewer related or unrelated conditions were associated with higher PACIC scores. At the practice level, performance scores reflecting quality management (p = 0.013) and CHD care (p = 0.009) were associated with improved assessment of the structured chronic care and counselling received. CONCLUSIONS: Patients’ perceived quality of care varies. However, good practice management and organisation of care were positively reflected in patients’ assessments of receiving structured chronic illness care. This highlights the importance of integrating patient experiences into quality measurements to provide feedback to health care professionals

    A tailored programme to implement recommendations for multimorbid patients with polypharmacy in primary care practices — process evaluation of a cluster randomized trial

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    Background: We developed and evaluated a tailored programme to implement three evidence-based recommendations for multimorbid patients with polypharmacy into primary care practices: structured medication counselling including brown bag reviews, the use of medication lists and medication reviews. No effect on the primary outcome was found. This process evaluation aimed to identify factors associated with outcomes by exploring nine hypotheses specified in the logic model of the tailored programme. Methods: The tailored programme was developed with respect to identified determinants of practice and consisted of a workshop for practice teams, elaboration of implementation action plans, aids for medication reviews, a multilingual info-tool for patients on a tablet PC, posters and brown paper bags as reminders for patients. The tailored programme was evaluated in a cluster randomized trial. The process evaluation was based on various data sources: interviews with general practitioners and medical assistants of the intervention group and a survey with general practitioners of the intervention and control group, written reports on the implementation action plans, documentation forms for structured medication counselling and the log file of the info-tool. Results: We analyzed 12 interviews, 21 questionnaires, 120 documentation forms for medication counselling, 5 implementation action plans and one log file of the info-tool. The most frequently reported effect of the tailored programme was the increase of awareness for the health problem and the recommendations, while implementation of routine processes was only reported for structured medication counselling. The survey largely confirmed the usefulness of the applied strategies, yet the interviews provided a more detailed understanding of the actual use of the strategies and several suggestions for modifications of the tailored programme. Conclusions: The tailored programme seemed to have induced awareness as a first step of behaviour change. Several modifications of the tailored programme may enhance its effectiveness such as conducting outreach visits instead of a workshop, improved targeting, provision of evidence, integration of tools into the practice software and information materials in tailored formats. Trial registration: This study is linked to an outcome evaluation study with the registration ISRCTN34664024, assigned 14/08/2013

    Effectiveness and efficiency of primary care based case management for chronic diseases: rationale and design of a systematic review and meta-analysis of randomized and non-randomized trials [CRD32009100316]

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    Contains fulltext : 88751.pdf (publisher's version ) (Open Access)BACKGROUND: Case management is an important component of structured and evidence-based primary care for chronically ill patients. Its effectiveness and efficiency has been evaluated in numerous clinical trials. This protocol describes aims and methods of a systematic review of research on the effectiveness and efficiency of case management in primary care. METHODS/DESIGN: According to this protocol Medline, Embase, CINAHL, PsychInfo, the Cochrane Central Register of Controlled trials, DARE, NHS EED, Science Citation Index, The Royal College of Nursing Database, Dissertation Abstracts, registers of clinical trials and the reference lists of retrieved articles will be searched to identify reports on randomized and non-randomized controlled trials of case management interventions in a primary care setting without limitations on language or publication date. We will further ask experts in the field to avoid missing relevant evidence. Study inclusion and data extraction will be performed independently by two reviewers. After assessing risk of bias according to predefined standards, included studies will be described qualitatively. Subgroup analyses are planned for different chronic diseases and intervention strategies. If appropriate, a quantitative synthesis of data will be performed to provide conclusive evidence about the effectiveness and efficiency of primary care based case management in chronic care. REVIEW REGISTRATION: Centre for Reviews and Dissemination (University of York): CRD32009100316

    Process evaluation of five tailored programs to improve the implementation of evidence-based recommendations for chronic conditions in primary care

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    Background: Although there is evidence that tailored implementation strategies can be effective, there is little evidence on which methods of tailoring improve the effect. We designed and evaluated five tailored programs (TPs) each consisting of various strategies. The aim of this study was to examine (a) how determinants of practice prioritized in the design phase of the TPs were perceived by health care professionals who had been exposed to the TPs and whether they suggested other important determinants of practice and (b) how professionals used the offered strategies and whether they suggested other strategies that might have been more effective. Methods: We conducted a mixed-method process evaluation linked to five cluster-randomized trials carried out in five European countries to implement recommendations for five chronic conditions in primary care settings. The five TPs used a total of 28 strategies which aimed to address 38 determinants of practice. Interviews of professionals in the intervention groups and a survey of professionals in the intervention and control groups were performed. Data collection was conducted by each research team in the respective national language. The interview data were first analyzed inductively by each research team, and subsequently, a meta-synthesis was conducted. The survey was analyzed descriptively. Results: We conducted 71 interviews; 125 professionals completed the survey. The survey showed that 76% (n = 29) of targeted determinants of practice were perceived as relevant and 95% (n = 36) as being modified by the implementation interventions by 66 to 100% of professionals. On average, 47% of professionals reported using the strategies and 51% considered them helpful, albeit with substantial variance between countries and strategies. In the interviews, 89 determinants of practice were identified, of which 70% (n = 62) had been identified and 45% (n = 40) had been prioritized in the design phase. The interviewees suggested 65 additional strategies, of which 54% (n = 35) had been identified and 20% (n = 13) had been prioritized, but not selected in the final programs. Conclusions: This study largely confirmed the perceived relevance of the targeted determinants of practice. This contrasts with the fact that no impact of the trials on the implementation of the recommendations could be observed. The findings suggest that better methods for prioritization of determinants and strategies are needed. Trial registration: Each of the five trials was registered separately in recognized trial registries. Details are given in the respective trial outcome papers

    Improving continuity of patient care across sectors: study protocol of a quasi-experimental multi-centre study regarding an admission and discharge model in Germany (VESPEERA)

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    Background: Hospitalisations are a critical event in the care process. Insufficient communication and uncoordinated follow-up care often impede the recovery process of the patient resulting in a high number of rehospitalisations and increased health care costs. The overall aim of this study is the development, implementation and evaluation of a structured programme (VESPEERA) to improve the admission and discharge process. Methods: We will conduct an open quasi-experimental multi-centre study with four intervention arms. A cohort selected from insurance claims data will serve as a control group reflecting usual care. The intervention will be implemented in 25 hospital departments and 115 general practices in 9 districts in Baden-Wurttemberg. Eligibility criteria for patients are: age > 18 years, hospital admission or hospitalisation, insurance at the sickness fund “AOK Baden-Wurttemberg”, enrolment in general practice-centred care contract. Each study arm will receive different intervention components based on the point of study enrolment and the patient’s medical need. The interventions comprise a) a structured assessment in the general practice prior to admission resulting in an admission letter b) a discharge conversation by phone between hospital and general practice, c) a structured assessment and care plan post-discharge and d) telephone monitoring for patients with a high risk of rehospitalisation. The assessments are supported by a software tool (“CareCockpit”), originally developed for structured case management programmes. The primary outcome (rehospitalisation due to the same indication within 90 days) and a range of secondary outcomes (rehospitalisation due to the same indication within 30 days; hospitalisations due to ambulatory care-sensitive conditions; delayed prescription of medication and medical products/ devices and referral to other health practitioner/s after discharge; utilisation of emergency or rescue services within 3 months; average care cost per year and patient participating in the VESPEERA programme) and quality indicators will be determined based on insurance claims data and CareCockpit data. Additionally, a patient survey on satisfaction with cross-sectoral care and health related quality of life will be conducted. Discussion: Based on the results, area-wide implementation in usual care is well sought. This study will contribute to an improvement of cross-sectoral care during the admission and discharge process. Trial registration: DRKS00014294 on DRKS / Universal Trial Number (UTN): U1111–1210-9657, Date of registration 12/06/2018
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