Search results

Higher energy conversion efficiency of internal combustion engine can be achieved with optimal control of unsteady in-cylinder flow fields inside a direct-injection (DI) engine. However, it remains a daunting task to predict the nonlinear and transient in-cylinder flow motion because they are highly complex which change both in space and time. Recently, machine learning methods have demonstrated great promises to infer relatively simple temporal flow field development. This paper aims to feature a physics-guided machine learning approach to realize high accuracy and generalization prediction for complex swirl-induced flow field motions.

To achieve high-fidelity time-series prediction of unsteady engine flow fields, this work features an automated machine learning framework with the following objectives: (1) The spatiotemporal physical constraint of the flow field structure is transferred to machine learning structure. (2) The ML inputs and targets are efficiently designed that ensure high model convergence with limited sets of experiments. (3) The prediction results are optimized by ensemble learning mechanism within the automated machine learning framework.

The proposed data-driven framework is proven effective in different time periods and different extent of unsteadiness of the flow dynamics, and the predicted flow fields are highly similar to the target field under various complex flow patterns. Among the described framework designs, the utilization of spatial flow field structure is the featured improvement to the time-series flow field prediction process.

The proposed flow field prediction framework could be generalized to different crank angle periods, cycles and swirl ratio conditions, which could greatly promote real-time flow control and reduce experiments on in-cylinder flow field measurement and diagnostics.

Combustion of fuel with oxidizer inside a combustion chamber of an internal combustion engine forms inevitable oxides of nitrogen (NOx) due to high temperature at different locations of the combustion chamber. This study aims to quantify NOx formed inside the combustion chamber using two fuels, a conventional diesel (n-heptane) and a biodiesel (methyl oleate).

This research uses a computational fluid dynamics simulation of chemically reacting fluid flow to quantify and compare oxides of nitrogen (NOx) in a compression ignition (CI) engine. The study expends species transport model of ANSYS FLUENT. The simulation model has provided the temperature profile inside the combustion chamber, which is subsequently used to calculate NOx using the NOx model. The simulation uses a single component hydrocarbon and oxygenated hydrocarbon to represent fuels; for instance, it uses n-heptane (C₇H₁₆) for diesel and methyl-oleate (C₁₉H₃₆O₂) for biodiesel. A stoichiometric air–fuel mixture is used for both fuels. The simulation runs a single cylinder CI engine of 650 cm³ swept volume with inlet and exhaust valves closed.

The pattern for variation of velocity, an important flow parameter, which affects combustion and subsequently oxides of nitrogen (NOx) formation at different piston locations, is similar for the two fuels. The variations of in-cylinder temperature and NOx formation with crank angles have similar patterns for the fuels, diesel and biodiesel. However, the numerical values of in-cylinder temperature and mass fraction of NOx are different. The volume averaged static peak temperatures are 1,013 K in case of diesel and 1,121 K in case of biodiesel, while the mass averaged mass fractions of NOx are 15 ppm for diesel and 141 ppm for biodiesel. The temperature rise after combustion is more in case of biodiesel, which augments the oxides of nitrogen formation. A new parameter, relative mass fraction of NOx, yields 28% lower value for biodiesel than for diesel.

This work uses a new concept of simulating simple chemical reacting system model to quantify oxides of NOx using single component fuels. Simplification has captured required fluid flow data to analyse NOx emission from CI engine while reducing computational time and expensive experimental tests.

The purpose of this paper is to study the electronic transport performance of Ag-ZnO film under dark and UV light conditions.

Ag-doped ZnO thin films were prepared on fluorine thin oxide (FTO) substrates by sol-gel method. The crystal structure of ZnO and Ag-ZnO powders was tested by X-ray diffraction with Cu Kα radiation. The absorption spectra of ZnO and Ag-ZnO films were recorded by a UV–visible spectrophotometer. The micro electrical transport performance of Ag-ZnO thin films in dark and light state was investigated by photoassisted conductive atomic force microscope (PC-AFM).

The results show that the dark reverse current of Ag-ZnO films does not increase, but the reverse current increases significantly under illumination, indicating that the response of Ag-ZnO films to light is greatly improved, owing to the formation of Ohmic contact.

To the best of the author’s knowledge, the micro electrical transport performance of Ag-ZnO thin films in dark and light state was firstly investigated by PC-AFM.

This paper aims to understand the maternal health vulnerabilities of migrant women in slums and explore their challenges during and after childbirth.

The study used a qualitative approach, including in-depth interviews through purposive and snowball sampling techniques. Thematic analysis was used for analysing data. The consolidated criteria for reporting qualitative studies (COREQ)-32 items were followed for reporting this study.

The study found that migrant women were highly susceptible to adverse birthing outcomes due to risks involved in birthing, lack of care and hygiene, lack of skilled care in dealing with complicated pregnancies and exposure to domestic and obstetric violence.

The study intends to highlight the narratives of female migrants’ birthing and maternal health challenges. The entire process of childbirth in slums with consequences can result in maternal and infant morbidities and mortalities.

This case is mainly about the development journey of Tujia, a unicorn in China's accommodations-sharing sector, as well as the development status of the sector. On December 1, 2011, Tujia.com—China's first medium- and high-end vacation apartment booking platform—was formally launched, and it announced the first round of capital injection in less than half a year after its launch. It completed D and D+ round of financing on August 3, 2015, securing $300 million with an estimated value exceeding $1 billion. The completion of this financing round meant that Tujia formally entered the $1 billion club composed of “unicorn” Internet companies. In June 2016, it announced the strategic M&A of Mayi; in October 2016, it announced its strategic agreement with Ctrip.com and Qunar.com for the M&A of their apartment and homestay businesses. The completion of these transactions manifested the matrix with the four major platforms Tujia, Mayi, Ctrip, and Qunar. Since then, Tujia has become the absolute pacesetter in China's online accommodations-sharing sector.

This study aims to investigate the corrosion inhibitor effect of migrating corrosion inhibitor (MCI) on Q235 steel in high alkaline environment under cathodic polarization.

This study investigated the electrochemical characteristics of Q235 steel with and without MCI by polarization curve and electrochemical impedance spectroscopy. Besides, the surface composition of Q235 steel under different environments was analyzed by X-ray photoelectron spectroscopy. In addition, the migration characteristic of MCI and the adsorption behavior of MCI under cathodic polarization were studied using Raman spectroscopy.

Diethanolamine (DEA) and N, N-dimethylethanolamine (DMEA) can inhibit the increase of Fe(II) in the oxide film of Q235 steel under cathodic polarization. The adsorption stability of DMEA film was higher under cathodic polarization potential, showing a higher corrosion inhibition ability. The corrosion inhibition mechanism of DEA and DMEA under cathodic polarization potential was proposed.

The MCI has a broad application prospect in the repair of damaged reinforced concrete due to its unique migratory characteristics. The interaction between MCIs, rebar and concrete with different compositions has been studied, but the passivation behavior of the steel interface in the presence of both the migrating electric field and corrosion inhibitors has been neglected. And it was investigated in this paper.

Globally, hepatitis C treatment uptake is lower among people who are homeless or unstably housed compared to those who are housed. Understanding and addressing this is essential to ensure no one is left behind in hepatitis C elimination efforts. This study aims to explore peoples’ experiences of unstable housing and health care, and how these experiences influenced engagement in hepatitis C treatment.

Purposive sampling was used to recruit people with lived experience of injection drug use, hepatitis C and unstable housing in Melbourne, Australia. In-depth semistructured interviews were conducted and a case study approach with interpretative phenomenological analysis was used to identify personal experiential themes and group experiential themes.

Four people were interviewed. The precarious nature of housing for women who inject drugs was a group experiential theme, however, this did not appear to be a direct barrier to hepatitis C treatment. Rather, competing priorities, including caregiving, were personal experiential themes and these created barriers to treatment. Another group experiential theme was “right place, right time, right people” with these three elements required to facilitate hepatitis C treatment.

There is limited research providing in-depth insight into how personal experiences with unstable housing and health care shape engagement with hepatitis C treatment. The analyses indicate there is a need to move beyond a “one size fits-all” approach to hepatitis C care. Instead, care should be tailored to the needs of individuals and their personal circumstances and regularly facilitated. This includes giving greater attention to gender in intervention design and evaluation, and research more broadly.

The purpose of this study is to investigate the impact of the construction and operation of underground gas storage (UGS) facilities, under the prism of the recent rise in energy prices. The focus is on developing energy markets interconnected with gas producers through pipelines and has access to liquefied natural gas (LNG) facilities in parallel.

Through a focal market in Europe, the authors estimate the economic value for both stakeholders and consumers by introducing a methodology, appropriately adjusted to the specificities of the domestic energy market. The Transmission System Operator, the Energy Market Regulator, the Energy Exchange and Eurostat are the main data sources for our calculations and conclusions.

The authors investigate the perspectives of UGS facilities, identifying financial challenges considering specific energy market conditions which are barriers to new storage facilities. Nevertheless, the energy price rocketing coupled with the security of gas supply issues, which arose in autumn 2021 and were continuing in 2022 due to the Russia–Ukraine crisis, highlight that gas storage remains, at least for the midterm, at the core of European priorities.

The paper emphasizes on developing markets toward green transition, proposing tangible policy recommendations regarding gas storage. A new methodological approach is proposed, appropriate to quantify the economic value of UGSs in such markets. Last, a mix of energy policy options is suggested which include regulatory reforms, support schemes and new energy infrastructures that could make the gas storage investments economically viable.

The aim of this study is to optimize the electrospinning parameters used in the production process of polyvinyl chloride (PVC) nanofibers.

The response surface methodology (RSM) was used to determine the experimental design. The 30 nanofiber prototypes candidates were electrospun using a needle-based electrospinning machine. PVC polymer, N-dimethyl formamide and tetrahydrofuran solvents were used to prepare the electrospinning solution.

The electrospun nanofibers had a mean diameter of 386 ± 136.57 nm, in the range of 200−412 nm. The mean porosity was 31.60 ± 6.37% in the range of 15.33−41.53%. The webs made from electrospun nanofibers had a mean pressure loss of 194.23 ± 47.7 pa in the range of 124−300 pa. The highest statistically significant correlation was observed between solution concentration and nanofiber diameter (r = 0.756, p < 0.05).

The optimal electrospinning parameters were determined to be: a solution concentration of 11 weight percent, a voltage of 16.5 kV, a needle-collector distance of 13.5 cm and an electrospinning duration of 4 h.

The paper provides a theoretical framework for interdisciplinary accounting scholars interested in performances of accountability in front of live audiences.

This is a processual case study of “Falkirk in crisis” that covers the period from September 2021 to September 2022. The focus of this paper is two-fan-Q&A sessions held in October 2021 and June 2022. Both are naturally occurring discussions between two groups such as are found in previous research on routine events and accountability. This is a theoretically consequential case study.

A key insight of the paper is to identify the practical and symbolic dimensions of accountability. The paper demonstrates the need to align these two dimensions when responding to questions: a practical question demands a practical answer and a symbolic question requires a symbolic answer. Second, the paper argues that most fields contain conflicting logics and highlights that a complete performance of accountability needs to cover the different conflicting logics within the field. In this case, this means paying full attention to both the communitarian and results logics. A third finding is that a performance of accountability cannot succeed if the audience rejects attempts to impose an unpalatable definition of the situation. If these three conditions are not met, the performance is bound to fail.

An important theoretical coontribution of the study is the application of Jeffery Alexander’s work on political performance to public performances of accountability.

The phenomenon explored in the paper (what the authors term “grassroots accountability”) has broad applicability to any situation in organizational or civic life where the power apex of an organization is required to engage with a group of informed and committed stakeholders – the “community”. For those who find themselves in the position of the fans in this study, the observations set out in the empirical narrative can serve as a useful practical guide. Attempts to answer a practical complaint with a symbolic answer (or vice versa) should be challenged as evasive.

This paper studies an engagement of elite actors with ordinary (or grassroots) actors. The study shows important rules of engagement, including the importance of respecting the power of practical questions and the need to engage with these questions appropriately.

This paper offers a new vista for interdisciplinary accounting by synthesizing the accountability literature with the political performance literature. Specifically, the paper employs Jeffery Alexander’s work on practical and symbolic performance to study the microprocesses underpinning successful and unsuccessful performances of accountability.