Effect of fuel injection strategies on performance and emissions in HCCI engines: a review

Homogeneous charge compression ignition (HCCI) technology in internal combustion engines has improved several performance characteristics of engines. For instance, it has improved thermal efficiency and it has lowered the level of engine emissions, too. The application of this technology requires the usage of various blends of fuels, which are popularly injected into the engine using direct injection method at different timings i.e. early direct, late direct, and Single/Split (multiple) injections. This paper reviews the research that has shown that these three types of injection strategies have different impacts on the performance and on the emissions of engines with a particular interest in power output and thermal efficiency, cylinder pressure, heat release, pressure rise, combustion rate, energy consumption, combustion efficiency and brake mean effective pressure. Different researchers have applied varying methods in studying the impacts of these injection strategies, e.g. a method that involved a variation of the injection angles in investigating the rates of emissions at different injection timings. Furthermore, early direct injection timing strategy has proved to be more advantageous if compared to the other two injection timing strategies as it increases ignition delay (ID) thus resulting in the formation of a well-mixed fuel-oxidizer homogeneous mixture. Consequently, the early direct approach is recommended for usage in engines that adopt the HCCI technology

The use of different types of piston in an HCCI engine: a review

Homogenous charge compression ignition (HCCI) combines the advantages of spark ignition (SI) and compression ignition (CI) engines to improve fuel consumption and emission levels. HCCI engines have the advantage of relatively higher engine efficiency than SI engines while maintaining lower emissions levels than CI engines. Combustion in HCCI engines occurs spontaneously at any location once the fuel-air mixture reaches its chemical activation energy. Pistons have a major effect on controlling the combustion inside the combustion chamber of an HCCI engine. Many researchers have studied various designs for pistons to improve HCCI engines. The aim of this study is to explore these different types of pistons and their designs in terms of improving the performance of HCCI engines fuelled with gasoline. The most common pistons used in HCCI are two-stroke pistons, bowl types, specialised pistons, and dome-shaped pistons; each offers distinct advantages and disadvantages. Software simulation is the latest way of determining the best piston to be used for HCCI engines, as it is more cost effective and less time consuming than experiments. Overall, bowl type pistons offer reduced fuel consumption and a higher load capacity when used in an HCCI engine

Experimental investigation into the effects of voids on the response of buried flexible pipes subjected to incrementally increasing cyclic loading

YesIn this study, large-scale fully instrumented laboratory tests were conducted to investigate the behaviour of buried flexible high-density polyethylene (HDPE) pipes, in sand beds with and without voids subjected to incrementally increasing cyclic loading. Voids with a predetermined size were created at one side of the springlines of the pipes, which were buried at variable depths, H, of 1.5, 2.0 and 2.5 times the diameter of the pipe, D. Results showed that increasing the pipe burial depth, H/D, contributed to decreasing the settlement of the footing, deformation of the pipe crown and invert, lateral displacement of the spring-line, and the stress and strain generated along the pipe crown and invert. Void presence led to a significant increase in the footing settlement, which ranged from 3 % up to 18 %, according to H/D. Furthermore, void presence led to a sharp increase in the crown, invert, and spring-line settlements, which ranged from 34 % to 52 %, 10 %–12.5 %, and 13 %–38 %, respectively. Increasing pipe burial depth was found to be highly effective in protecting buried pipes, minimising inevitable consequences of the presence of voids. However, this was combined with an increase in the pressure at the pipe spring-line that led to a positive horizontal support at the pipe’s spring-lines resulting in reducing pipe deformation

Cardiometabolic Morbidity (Obesity and Hypertension) in PTSD: A Preliminary Investigation of the Validity of Two Structures of the Impact of Event Scale-Revised

This article belongs to the Special Issue Review Special Issue Series: Recent Advances in Epidemiology & Public Health).Acknowledgments: The researchers would like to thank the Deanship of Graduate Studies and Scientific Research at Qassim University for the financial support (QU-APC-2024-9/1).Background: Posttraumatic stress disorder (PTSD) and/or specific PTSD symptoms may evoke maladaptive behaviors (e.g., compulsive buying, disordered eating, and an unhealthy lifestyle), resulting in adverse cardiometabolic events (e.g., hypertension and obesity), which may implicate the treatment of this complex condition. The diagnostic criteria for PTSD have lately expanded beyond the three common symptoms (intrusion, avoidance, and hyperarousal). Including additional symptoms such as emotional numbing, sleep disturbance, and irritability strengthens the representation of the Impact of Event Scale-Revised (IES-R), suggesting that models with four, five, or six dimensions better capture its structure compared to the original three-dimensional model. Methods: Using a convenience sample of 58 Russian dental healthcare workers (HCWs: mean age = 44.1 ± 12.2 years, 82.8% females), this instrumental study examined the convergent, concurrent, and criterion validity of two IES-R structures: IES-R3 and IES-R6. Results: Exploratory factor analysis uncovered five factors, which explained 76.0% of the variance in the IES-R. Subscales of the IES-R3 and the IES-R6 expressed good internal consistency (coefficient alpha range = 0.69–0.88), high convergent validity (item total correlations r range = 0.39–0.81, and correlations with the IES-R’s total score r range = 0.62–0.92), excellent concurrent validity through strong correlations with the PTSD Symptom Scale-Self Report (PSS-SR: r range = 0.42–0.69), while their criterion validity was indicated by moderate-to-low correlations with high body mass index (BMI: r range = 0.12–0.39) and the diagnosis of hypertension (r range = 0.12–0.30). In the receiver-operating characteristic (ROC) curve analysis, all IES-R models were perfectly associated with the PSS-SR (all areas under the curve (AUCs) > 0.9, p values < 0.001). The IES-R, both hyperarousal subscales, and the IES-R3 intrusion subscale were significantly associated with high BMI. Both avoidance subscales and the IES-R3 intrusion subscale, not the IES-R, were significantly associated with hypertension. In the two-step cluster analysis, five sets of all trauma variables (IES-R3/IES-R6, PSS-SR) classified the participants into two clusters according to their BMI (normal weight/low BMI vs. overweight/obese). Meanwhile, only the IES-R, PSS-SR, and IES-R3 dimensions successfully classified participants as having either normal blood pressure or hypertension. Participants in the overweight/obese and hypertensive clusters displayed considerably higher levels of most trauma symptoms. Input variables with the highest predictor importance in the cluster analysis were those variables expressing significant associations in correlations and ROC analyses. However, neither IES-R3 nor IES-R6 contributed to BMI or hypertension either directly or indirectly in the path analysis. Meanwhile, age significantly predicted both health conditions and current smoking. Irritability and numbing were the only IES-R dimensions that significantly contributed to current smoking. Conclusions: The findings emphasize the need for assessing the way through which various PTSD symptoms may implicate cardiometabolic dysfunctions and their risk factors (e.g., smoking and the intake of unhealthy foods) as well as the application of targeted dietary and exercise interventions to lower physical morbidity in PTSD patients. However, the internal and external validity of our tests may be questionable due to the low power of our sample size. Replicating the study in larger samples, which comprise different physical and mental conditions from heterogenous cultural contexts, is pivotal to validate the results (e.g., in specific groups, such as those with confirmed traumatic exposure and comorbid mood dysfunction).info:eu-repo/semantics/publishedVersio

Space Shift Keying Modulation in Non-Orthogonal Multiple Access Hybrid Visible Light Communication Systems (Invited Paper)

Visible light communication (VLC) is considered a breakthrough wireless communication technology that has been proven capable of achieving very high data rates. This is a key advantage in indoor communication scenarios, since the vast majority of wireless traffic is witnessed in indoor communications. In every wireless system, the trade-off between achievable throughput, transmit signal power and corresponding error rate performance is largely dependent upon the considered modulation format. This is also the case in VLC systems, which are typically characterized by stringent performance requirements. Motivated by this, in the present contribution we introduce the space shift keying (SSK) modulation scheme in the context of non-orthogonal-multiple-access (NOMA) communications, which have been shown to be a performance enhancer of indoor based VLC systems. Based on this, all network users in the considered set up receive the same superimposed signal of all NOMA users, which is transmitted from the activated transmitters corresponding to the multiplexed SSK users information. Based on this and assuming a unique maximum likelihood detection, we quantity the system performance in terms of the corresponding bit error rate (BER) performance at each receiver. This analysis leads to the development of useful insights of theoretical and practical interest, which are expected to be useful in the effective design, implementation and deployment of SSK in NOMA based VLC systems.acceptedVersionPeer reviewe

Effects of Hormonal Replacement Therapy and Mindfulness-Based Stress Reduction on Climacteric Symptoms Following Risk-Reducing Salpingo-Oophorectomy

This article belongs to the Special Issue Mental Health Promotion and Illness Prevention in Vulnerable Populations—2nd Edition.Supplementary Materials The following supporting information can be downloaded at https://www.mdpi.com/article/10.3390/healthcare12161612/s1: Supplementary Table S1: Fit indices of multi-group analysis models examining the differences in the effects of mindfulness-based stress reduction (MBSR) and hormone replacement therapy (HRT) among women with RRSO, File S2: Possible mechanism of menopausal symptom flaring following HRT treatment in RRSO patients with BRCA1 mutation and a history of cancer.Funding: This work was supported by FCT—Fundação para a Ciência e a Tecnologia, I.P. (UIDB/05704/2020 and UIDP/05704/2020) and by the Scientific Employment Stimulus—Institutional Call [https://doi.org/10.54499/CEECINST/00051/2018/CP1566/CT0012, accessed on 30 July 2024].Breast Cancer Associated Susceptibility Proteins Type 1/2 (BRCA1/2) promote cellular functioning by modulating NRF2-mediated antioxidant signaling. Redox failure in women with BRCA1/2 insufficiency increases the risk for breast/ovarian/uterine cancers. Risk-reducing salpingo-oophorectomy (RRSO) is a prophylactic surgery of the reproductive organs, which is frequently conducted by the age of 40 to lower the occurrence of cancer in women with BRCA1/2 mutations. However, abrupt estrogen decline following RRSO causes ovarian failure, which implicates various cellular physiological processes, resulting in the increased release of free radicals and subsequent severe onset of menopausal symptoms. Comfort measures (e.g., hormonal replacement therapy (HRT) and mindfulness-based stress reduction (MBSR)) may improve chronological menopause-related quality of life, but their specific effects are not clear in women with gene mutations. Aiming to fill the gap, this study used path analysis to examine the effects of HRT and MBSR on menopausal symptoms among RRSO patients (N = 199, mean age = 50.5 ± 6.7 years). HRT directly alleviated the levels of urogenital symptoms (β = −0.195, p = 0.005), which mediated its indirect significant effects on the somatic–vegetative and psychological symptoms of menopause (β = −0.046, −0.067; both p values = 0.004, respectively), especially in BRCA2 carriers and in women who were currently physically active, premenopausal at the time of RRSO, had a high BMI, and had no history of breast cancer. It increased the severity of urogenital symptoms in women with a history of cancer. MBSR, on the other hand, was associated with indirect increases in the intensity of the somatic–vegetative and psychological symptoms of menopause (β = 0.108, 0.029; p = 0.003, 0.033, respectively). It exerted positive direct effects on different menopausal symptoms in multigroup analysis. The results suggest that young women undergoing recent RRSO may benefit from HRT at an individual level, while their need for extensive measures to optimize their psychological wellbeing is ongoing. The adverse effects of MBSR, which are captured in the present study, imply that MBSR may interfere with redox sensitivity associated with estradiol fluctuations in BRCA1/2 carriers. Investigations are needed to test this hypothesis and elaborate on the underlying mechanisms in these women.info:eu-repo/semantics/publishedVersio

Repurposing existing medications for coronavirus disease 2019: protocol for a rapid and living systematic review

BACKGROUND Coronavirus disease 2019 (COVID-19) has no confirmed specific treatments. However, there might be in vitro and early clinical data as well as evidence from severe acute respiratory syndrome and Middle Eastern respiratory syndrome that could inform clinicians and researchers. This systematic review aims to create priorities for future research of drugs repurposed for COVID-19. METHODS This systematic review will include in vitro, animal, and clinical studies evaluating the efficacy of a list of 34 specific compounds and 4 groups of drugs identified in a previous scoping review. Studies will be identified both from traditional literature databases and pre-print servers. Outcomes assessed will include time to clinical improvement, time to viral clearance, mortality, length of hospital stay, and proportions transferred to the intensive care unit and intubated, respectively. We will use the GRADE methodology to assess the quality of the evidence. DISCUSSION The challenge posed by COVID-19 requires not just a rapid review of drugs that can be repurposed but also a sustained effort to integrate new evidence into a living systematic review. TRIAL REGISTRATION PROSPERO 2020 CRD42020175648

Analysis of the functional repertoire of a mutant form of survivin, K129E, which has been linked to lung cancer

Background Survivin is a protein that is normally present only in G2 and M-phases in somatic cells, however, in cancer cells, it is expressed throughout the cell cycle. A prosurvival factor, survivin is both an inhibitor of apoptosis and an essential mitotic protein, thus it has attracted much attention as a target for new oncotherapies. Despite its prevalence in cancer, reports of survivin mutations have mostly been restricted to loci within its promoter, which increase the abundance of the protein. To date the only published mutation within the coding sequence is an adenine > guanine substitution in exon 4. This polymorphism, which was found in a cohort of Korean lung cancer patients, causes a lysine > glutamic acid mutation (K129E) in the protein. However, whether it plays a causative role in cancer has not been addressed. Methods Using site directed mutagenesis we recapitulate K129E expression in cultured human cells and assess its anti-apoptotic and mitotic activities. Results K129E retains its anti-apoptotic activity, but causes errors in mitosis and cytokinesis, which may be linked to its reduced affinity for borealin. Conclusion K129E expression can induce genomic instability by introducing mitotic aberrations, thus it may play a causative role in cancer

A cross-sectional study on the impact of the COVID-19 pandemic on psychological outcomes: Multiple indicators and multiple causes modeling

Although the psychological impact of coronavirus disease 2019 (COVID-19) has been evaluated in the literature, further research is needed, particularly on post-traumatic stress disorder (PTSD) and psychological outcomes, is needed. This study aims to investigate the effect of the COVID-19 pandemic on psychological outcomes (depression, anxiety, and insomnia). A cross-sectional study using an online survey was conducted using the following instruments: Impact of Event Scale-Revised (IES-R), Patient Health Questionnaire-9 (PHQ-9), Generalized Anxiety Disorder (GAD-7), and Insomnia Severity Index (ISI). Confirmatory factor analysis (CFA), structural equation model (SEM), multiple indicators and multiple causes (MIMIC) modeling, and differential item functioning (DIF) were performed to analyze the collected data. According to the results, participants with PTSD (n = 360) showed a higher level of depression, anxiety, and insomnia than those without PTSD (n = 639). Among the participants, 36.5% experienced moderate to severe symptoms of depression, and 32.6% had mild depressive symptoms. Moreover, 23.7% of participants experienced moderate to severe anxiety symptoms, and 33.1% had mild anxiety symptoms. In addition, 51.5% of participants experienced symptoms of insomnia. In conclusion, the PTSD caused by COVID-19 is significantly associated with depression, anxiety, and insomnia at the level of latent constructs and observed variables.Scopu