bluuebunny/crossref_metadata_2025 huggingface dataset:
Ultra‐low fired fluoride composite microwave dielectric ceramics and their application for BaCuSi2O6‐based LTCC
Authors: Song Xiao‐Qiang , Lei Wen , Zhou Yan‐Yan , Chen Tao , Ta Shi‐Wo , Fu Zhen‐Xiao , Lu Wen‐Zhong
Published: September 2019

A total of 14 fluoride composite ceramics were prepared through solid‐state method and their microwave dielectric properties were investigated. Among the fluoride composite ceramics, 0.36LiF–0.39MgF2–0.25SrF2 (LMS) had the lowest sintering temperature (600°C) and presented a dielectric constant (εr) of 6.24 ± 0.05, a quality factor (Q × f) of 33 274 ± 900 GHz, and a temperature coefficient resonant frequency (τf) of −86.74 ± 8 ppm/°C. As the LMS ceramic had a low melting point (646°C), it can be used as sintering aid for LTCC applications. The sintering temperature of BaCuSi2O6 decreased from 1050°C to 875°C with 2 wt% LMS doped and excellent microwave dielectric properties of εr = 8.16 ± 0.04, Q × f = 24 351 ± 300 GHz, and τf = −9.74 ± 1 ppm/°C were obtained. Moreover, BaCuSi2O6‐2 wt% LMS can be co‐fired with Ag powders, which makes it a potential new candidate for LTCC applications.
Evaluation and predictive modeling of the effect of chitosan and gamma irradiation on quality of stored chilled chicken meat
Authors: Bhoir Shraddha A. , Jhaveri Mitali , Chawla Surinder P.
Published: September 2019

The development and validation of mathematical model for predicting shelf life of minced chicken meat processed with chitosan (0.1%), gamma irradiation (0.5 kGy), or their combinations during chilled storage are presented. The samples were evaluated for their microbial and chemical qualities at regular intervals. The total viable count (TVC) reduced from 5.92 log (CFU/g) in untreated samples to 5.39, 5.28, and 4.76 log (CFU/g) in the samples treated with irradiation, chitosan, or both, respectively. Samples treated with both radiation and chitosan remained microbiologically safe till Day 14. Statistically significant difference in thiobarbituric acid reactive substances (TBARS) and trichloroacetic acid (TCA) soluble protein content among different treatment groups was observed after 11 days. The results obtained were fitted in Gompertz (TVC) and second‐order polynomial (TBARS and TCA soluble protein) function. This model enables variable labeling of “best before date,” thus ensuring acceptable chemical parameters along with the microbial safety of chicken meat, both of which depend largely on the initial conditions of meat.

Practical Application

The present study reports the mathematical models obtained to estimate the microbial and chemical qualities of minced chicken treated with 0.5 kGy of gamma irradiation, 0.1% chitosan, and their combination. The shelf life is partly determined by the initial quality of the chicken; hence, its consideration while estimating the shelf life is valuable. The models reported will enable variable labeling of “best before date” on the basic of initial quality. This will reduce the economic loss caused due to rejection of products of acceptable quality.
CXCR5+CD4+ T cell subsets and their relationship to immune dysfunction in chronic hepatitis B‐associated liver cirrhosis
Authors: Zhao Shuang , Xu Wen , Xie Yang‐xin , Chen Wei‐wei , Zhao Min
Published: September 2019

Background and Aim

Hepatitis B‐associated liver cirrhosis (HBC) leads to profound alterations of immune systems, especially disruptions of B cell immune responses. CXCR5+CD4+ T cells (including T follicular helper [Tfh] cells and T follicular regulatory [Tfr] cells) are responsible for the regulation of B cell functions. The aim of this study was to dissect the roles of CXCR5+CD4+ T cell subset in B cell disruption caused by HBC.

Methods

Forty‐one patients with HBC and 15 healthy controls were enrolled in this study. ELISA, flow cytometric analysis, and cell coculture were performed to analyze the properties of Tfh and Tfr.

Results

We observed significantly decreased memory B cells and increased plasma B cells in HBC patients, as well as significant upregulation of lipopolysaccharide binding protein and soluble CD14 in plasma of decompensated HBCs patients. The downregulation of Tfh17 was observed in HBC patients with spontaneous bacterial peritonitis compared with those without. The decrease of Tfh17 was paralleled with Child–Pugh grade and negatively correlated with plasma B cells and soluble CD14 in HBC patients. Interleukin (IL)‐21+Tfh of HBC patients was also downregulated compared with healthy controls, and it was positively correlated with memory B cells and the upregulation of IL‐10+Tfr. It was then revealed that Tfr could inhibit the secretion of IL‐21 by Tfh, and the blocking of IL‐10 could diminish this effect.

Conclusions

The changes of the frequency and function of Tfh and Tfr may play an important role in disease progression and immune dysfunction of HBC.
The health needs of Aboriginal and Torres Strait Islander children in out‐of‐home care
Authors: Shmerling Eli , Creati Mick , Belfrage Mary , Hedges Susan
Published: September 2019

Aim

Children in statutory out‐of‐home care (OOHC) are known to have poorer physical, developmental and mental health outcomes compared with their peers. The number of children in OOHC is increasing in Australia, with Aboriginal and Torres Strait Islander children disproportionately represented. To document the health needs of Aboriginal and Torres Strait Islander children and adolescents in OOHC attending the paediatric service at the Victorian Aboriginal Health Service (VAHS) between February 2014 and February 2016.

Methods

The electronic medical records of all patients in OOHC seen by a paediatrician at VAHS between February 2014 and February 2016 were audited. Demographic data, including age and type of OOHC placement, were recorded, as were their health needs.

Results

Of the 200 children seen by a paediatrician over this 2‐year period, 103 were identified as being in OOHC for all or some of this same period: 43 in foster care, 8 in residential care and 52 in kinship care. Of the 103 children, 35 were <6 years of age, 51 between 6 and 13 years and 17 between 13 and 18 years; 66% were identified as having mental health problems, 37% hearing problems, 34% vision problems, 40% dental caries and 46% developmental delay including 36% with speech delay.

Conclusions

Aboriginal and Torres Strait Islander children in OOHC seen by the paediatric service at VAHS have high rates of physical, developmental and psychological health needs. These data have significant potential to inform government policy and investment in effective models of care to better meet the needs of Aboriginal and Torres Strait Islander children in OOHC.
Dental caries vaccine: are we there yet?
Authors: Patel M.
Published: September 2019

Dental caries, caused by Streptococcus  mutans, is a common infection. Caries vaccine has been under investigation for the last 40 years. Many in vitro and in vivo studies and some human clinical trials have determined many pertinent aspects regarding vaccine development. The virulence determinants of Strep. mutans, such as Ag I/II, responsible for adherence to surfaces, glucosyltransferase, responsible for the production of glucan, and the glucan-binding protein, responsible for the attachment of glucan to surfaces, have been known to elicit an antigen-specific immune response. It is also known that more than one antigen or a functional part of the genome responsible for these virulence determinants provide a better host response compared with the monogenic vaccine or complete genome of a specific antigen. To enhance the host response, the use of adjuvants has been studied and the routes of antigen administration have been investigated. In recent years, some promising vaccines such as pGJA-P/VAX, LT derivative/Pi39-512, KFD2-rPAc and SBR/GBR-CMV-nirB have been developed and tested in animals. New virulence targets need to be explored. Multicentre collaborative studies and human clinical trials are required and some interest from funders and public health experts should be generated to overcome this hurdle.

Significance and Impact of the Study

Dental caries is an irreversible, multifactorial opportunistic infection. The treatment is costly, making it a public health problem. Despite many years of promising laboratory research, animal studies and clinical trials, there is no commercially available vaccine today. The research objectives have become more refined from lessons learnt over the years. Multigenic DNA/recombinant vaccines, using the best proved adjuvants with a delivery system for the nasal or sublingual route, should be developed and researched with multicentre collaborative efforts. In addition, new vaccine targets can be identified. To overcome the economic hurdle, funders and public health interest should be stimulated.
High prevalence of occult hepatitis B infection (OBI) among healthy children and their parents in Alborz province, Iran; Vertical OBI, myth or truth?
Authors: Ghaziasadi Azam , Fakhari Zahra , Aghcheli Bahman , Poortahmasebi Vahdat , Farahmand Mohammad , Norouzi Mehdi , Ghalichi Leila , Soleimani Alireza , Hedayat Yaghoobi Mojtaba , Ravanshad Mehrdad , Jazayeri Seyed Mohammad
Published: September 2019

Background

Occult hepatitis B infection (OBI) has been described in various clinical settings including after hepatitis B virus (HBV) immunization. The purpose of study was to characterize the prevalence of OBI among immunized children from a subset of general population and the parents of OBI‐positive cases.

Methods

Sera of 1200 children from general population who have been previously immunized by HBV vaccine were assayed for anti‐HBs. 660 were randomly selected for HBV DNA testing by different polymerase chain reaction (PCR) methods and were analysed by direct sequencing on surface genes.

Results

None of participants were positive for HBsAg and anti‐HBc. 549 (45.7%) and 651 (54.3%) cases had anti‐HBs > 10 mIU/mL (responders) and < 10 mIU/mL (nonresponders) respectively. Of 660 selected specimens, 91 (16%) of children were positive for OBI. 23 (25.2%) and 68 (74.8%) of HBV DNA positive cases were belonged to responders and nonresponders, respectively, showing significant difference (P < .001). The mean levels of anti‐HBs in OBI‐positive and OBI‐negative groups, showed no considerable variations. The mean viral load for OBI‐positive cases showed substantial differences between responders and nonresponders (P = .007). Of 49 parents (98 individuals) of OBI‐positive children 11 (22%) and 18 (36%) were positive for anti‐HBc and anti‐HBs respectively. Molecular testing was positive in 32 subjects (16 couples, 32.6%). In total, 6 mothers and 11 fathers were positive for OBI.

Conclusion

A proportion of OBI‐positive vaccinated children could be existed in different populations. This finding could be arisen from vertical HBV transmission or vertical OBI possibly from their parents.
Disparities between Aboriginal and non‐Aboriginal perinatal mortality rates in Western Australia from 1980 to 2015
Authors: Adane Akilew A. , Bailey Helen D. , Marriott Rhonda , Farrant Brad M. , White Scott W. , Stanley Fiona J. , Shepherd Carrington C. J.
Published: September 2019

Background

Perinatal mortality rates are typically higher in Aboriginal than non‐Aboriginal populations of Australia.

Objectives

This study aimed to examine the pattern of stillbirth and neonatal mortality rate disparities over time in Western Australia, including an evaluation of these disparities across gestational age groupings.

Methods

All singleton births (≥20 weeks gestation) in Western Australia between 1980 and 2015 were included. Linked data were obtained from core population health datasets of Western Australia. Stillbirth and neonatal mortality rates and percentage changes in the rates over time were calculated by Aboriginal status and gestational age categories.

Results

From 1980 to 2015, data were available for 930 926 births (925 715 livebirths, 5211 stillbirths and 2476 neonatal deaths). Over the study period, there was a substantial reduction in both the Aboriginal (19.6%) and non‐Aboriginal (32.3%) stillbirth rates. These reductions were evident in most gestational age categories among non‐Aboriginal births and in Aboriginal term births. Concomitantly, neonatal mortality rates decreased in all gestational age windows for both populations, ranging from 32.1% to 77.5%. The overall stillbirth and neonatal mortality rate differences between Aboriginal and non‐Aboriginal birth decreased by 0.6 per 1000 births and 3.9 per 1000 livebirths, respectively, although the rate ratios (RR 2.51, 95% CI 2.14, 2.94) and (RR 2.94, 95% CI 2.24, 3.85), respectively reflect a persistent excess of Aboriginal perinatal mortality across the study period.

Conclusions

Despite steady improvements in perinatal mortality rates in Western Australia over 3½ decades, the gap between Aboriginal and non‐Aboriginal rates remains unchanged in relative terms. There is a continuing, pressing need to address modifiable risk factors for preventable early mortality in Aboriginal populations.
Genotypic diversity and acidogenicity of Streptococcus mutans in Down syndrome children
Authors: Moreira Maurício José Santos , Klaus Natália Mincato , Dall'Onder Ana Paula , Grando Débora , Parolo Clarissa Cavalcanti Fatturi , Faccini Lavinia Schuler , Hashizume Lina Naomi
Published: September 2019

Aims

To evaluate the genotypic diversity and acidogenicity of Streptococcus mutans (S. mutans) and the potential association of these factors with dental caries experience in children with DS compared to non‐DS children (controls).

Methods and results

Seventeen children (age 6‐12 years) with high salivary S. mutans counts (> 2.5 × 105 CFU/mL) were selected and divided into two groups: DS and non‐DS. Five children in each group were caries‐free, while the remainder had elevated caries experience. S. mutans isolates were obtained from each participant. The genotypic profile of the isolates was analyzed with the AP‐PCR methodology. The acidogenicity of a representative strain from each genotype of S. mutans was also evaluated. DS children had 16 different S. mutans genotypes, while the control group had 21. Twelve genotypes were present in both groups and one of them was associated with caries‐free status (P < .05). Although the acidogenicity of the genotypes found in DS children was significantly lower (P < .05) compared to controls, this fact was not associated with caries experience in both groups.

Conclusions

DS children have a lower S. mutans genotypic diversity and genotypes with lower acidogenicity than those of non‐DS children. However these findings were not associated with their caries experience.
Out with the old, in with the new: Virtual versus physical crossmatching in the modern era
Authors: Morris Anna B. , Sullivan H. C. , Krummey Scott M. , Gebel Howard M. , Bray Robert A.
Published: September 2019

The virtual crossmatch (VXM) is gaining acceptance as an alternative approach to assess donor:recipient compatibility prior to transplantation. In contrast to a physical crossmatch, the virtual crossmatch does not require viable donor cells but rather relies on complete HLA typing of the donor and current antibody assessment of the recipient. Thus, the VXM can be performed in minutes which allows for faster transplant decisions thereby increasing the likelihood that organs can be shipped across significant distances yet safely transplanted. Here, we present a brief review of the past 50 years of histocompatibility testing; from the original complement‐dependent cytotoxicity crossmatch in 1969 to the new era of molecular HLA typing, solid‐phase antibody testing and virtual crossmatching. These advancements have shaped a paradigm shift in our approach to transplantation. That is, foregoing a prospective physical crossmatch in favor of a VXM. In this review, we undertake an in‐depth analysis of the pros‐ and cons‐ of physical and virtual crossmatching.Finally, we provide objective data on the selected use of the VXM which demonstrate the value of a VXM in lieu of the traditional physical crossmatch for safe and efficient organ transplantation.
Decommissioned places: Ruins, endurance and care at the end of the first nuclear age
Authors: Dawney Leila
Published: September 2019

This paper argues for a geography of deindustrialising places as spaces of inhabitation and endurance, rather than one based on narratives of progres, decline and ruination. Ruins have long been a concern for geographers, yet the material remains of modernity's grand schemes feed easily into ways of seeing and knowing deindustrialised spaces that can efface the practices through which lives and worlds are made in the present. Drawing on fieldwork in the former Soviet atomgrad of Visaginas, Lithuania, the paper both acknowledges and pulls back from the draw of the ruin. Moving away from the ruin‐temporalities of progress and decline, it offers an account of ongoing practices and modes of habitation in spaces defined by ruination. A reflexive acknowledgement of our contaminated role in making sense of such spaces allows us to be both enchanted by grand narratives of hubris and decline and to see other stories – stories of living on, of endurance, and of making lives in places circumscribed as futureless by political and economic regimes. As such, the paper offers an alternative geography of places that are decommissioned from above, paying attention to the care, commitment, makeshift practices and aesthetic projects through which their inhabitants live on. Engaging this approach through a series of small stories based on ethnographic and collaborative fieldwork alongside two photographers in Visaginas, I posit that the material and subjective remains of the dreams of the first nuclear age give rise to emergent forms of life that stand in excess to narratives of progress and decline. The ruins of Soviet nuclear modernity here operate as containers for practices of endurance and living on through changing relations of power and capital, rather than objects of melancholic loss, and as raw materials through which to forge ways of living in spaces characterised as surplus to requirement.
Public, private, and the appeal to common good: Practices of justification in a peer‐to‐peer economy
Authors: Koch Regan
Published: September 2019

Relations between public and private are implicit within much of everyday life, yet public/private distinctions are often invoked when there is a need to justify or critique a set of social arrangements. This paper attends to such moments, demonstrating how practices of justification provide insights into the values and reasoning through which different forms of collective life are negotiated and managed. It does so through a theoretically pragmatist approach that responds to recent calls for researchers to engage more closely with ordinary forms of normativity and builds on an emerging geographical interest in everyday talk. The case study in focus is a popular yet illegal food trend in New York City where established and aspiring chefs welcome strangers into their homes for a meal in exchange for payment. Underground restaurants and secret supper clubs, as these events are known, fit within a much broader trend of peer‐to‐peer “sharing economy” business models that open up resources and relations normally considered private to a provisionally public audience. Often celebrated for facilitating cooperation, efficiency, and empowerment, they can also be deeply unsettling to existing social and economic orders. Participation in, and governance of, peer‐to‐peer activities demands navigating tensions between freedom and collective obligation, managing risk, establishing trust, and delegating responsibility when problems arise. Our capacity as geographers to analyse and weigh in on these issues can be enhanced by attending to the justifications through which public, private, and other concepts for organising collective life are being upheld, transgressed, or actively transformed.
Spatial housing market polarisation: National and urban dynamics of diverging house values
Authors: Hochstenbach Cody , Arundel Rowan
Published: September 2019

Housing is central in the reproduction of social inequalities. Beyond divides across populations, trends point to increasingly unequal housing‐market dynamics across space. Nonetheless, little systematic evidence exists on the spatial inequality of housing values. In this paper we address this through a detailed investigation of house‐value developments in the Netherlands over time and space. We draw on national registers including longitudinal and geocoded data for the entire housing stock over the 2006–2018 period. Spatial polarisation is examined across different scales at the national, provincial, and urban level. We further investigate how housing‐market inequality trends vary over time, particularly between periods of economic boom and house‐price increases or, conversely, periods of downturn. Our analyses expose a substantial and widespread trend of spatial polarisation. Rising spatial inequality between neighbourhoods is clearly apparent at the national level, within all but one province, as well as for 44 of the 50 largest municipalities. The polarising trend appears structural and pervasive. While boom periods saw the strongest increases, inequality levels, remarkably, remained stable or even saw continued increases over the period of declining house prices. These patterns of spatial polarisation in house values have fundamental societal implications towards uneven wealth accumulation and in amplifying socio‐economic cleavages across populations and space.
The effects of bilateral attitudes on imports
Authors: Bao Xiaohua , Liu Qing , Qiu Larry D. , Zhu Daming
Published: September 2019

Research based on the gravity model has shown that non‐economic factors affect international trade, and recent studies have shown that people's perception affects economic exchange. In this study, we explore the effects of attitudes on bilateral trade. Using survey data from the Pew Research Center's Global Attitudes Projects for 68 countries from 2002 to 2015, we find that a more favourable attitude of a country towards another country will increase the former country's imports from the latter. The result is robust to an endogeneity check, to different measures of attitudes and to different estimation methods. However, heterogeneity is observed across different types of goods and countries. The result holds for trade in intermediate and consumer goods, but the effects are not statistically significant for capital goods. The effects are statistically significant for bilateral trade between different country groups, except for high‐income countries' imports from non‐high‐income countries.
A Boiti-Leon Pimpinelli equations with time-conformable derivative
Authors: Touchent Kamal Ait , Hammouch Zakia , Mekkaoui Toufik , Unlu Canan
Published: September 2019

In this paper, we derive some new soliton solutions to $(2+1)$-Boiti-Leon Pempinelli equations with conformable derivative by using an expansion technique based on the Sinh-Gordon equation. The obtained solutions have different expression such as trigonometric, complex and hyperbolic functions. This powerful and simple technique can be used to investigate solutions of other  nonlinear partial differential equations.
An Innovative Ex Vivo Vascular Bioreactor as Comprehensive Tool to Study the Behavior of Native Blood Vessels Under Physiologically Relevant Conditions
Authors: Vanerio Noemi , Stijnen Marco , de Mol Bas A. J. M. , Kock Linda M.
Published: September 2019

Ex vivo systems represent important models to study vascular biology and to test medical devices, combining the advantages of in vitro and in vivo models such as controllability of parameters and the presence of biological response, respectively. The aim of this study was to develop a comprehensive ex vivo vascular bioreactor to long-term culture and study the behavior of native blood vessels under physiologically relevant conditions. The system was designed to allow for physiological mechanical loading in terms of pulsatile hemodynamics, shear stress, and longitudinal prestretch and ultrasound imaging for vessel diameter and morphology evaluation. In this first experience, porcine carotid arteries (n = 4) from slaughterhouse animals were cultured in the platform for 10 days at physiological temperature, CO2 and humidity using medium with blood-mimicking viscosity, components, and stability of composition. As expected, a significant increase in vessel diameter was observed during culture. Flow rate was adjusted according to diameter values to reproduce and maintain physiological shear stress, while pressure was kept physiological. Ultrasound imaging showed that the morphology and structure of cultured arteries were comparable to in vivo. Histological analyses showed preserved endothelium and extracellular matrix and neointimal tissue growth over 10 days of culture. In conclusion, we have developed a comprehensive pulsatile system in which a native blood vessel can be cultured under physiological conditions. The present model represents a significant step toward ex vivo testing of vascular therapies, devices, drug interaction, and as basis for further model developments.
Effect of Noise and Nonlinearities on Thermoacoustics of Can-Annular Combustors
Authors: Ghirardo G. , Moeck J. P. , Bothien M. R.
Published: September 2019

Can-annular combustors consist of N distinct cans setup symmetrically around the axis of the gas turbine. Each can is connected to the turbine inlet by means of a transition duct. At the turbine inlet, a small gap between the neighboring transition ducts allows acoustic communication between the cans. Thermoacoustic pulsations in the cans are driven by the respective flames, but also the communication between neighboring cans through the gap plays a significant role. In this study, we focus on the effect of the background noise intensity and of the nonlinear flame saturation. We predict how usually clusters of thermoacoustic modes are unstable in the linear regime and compete with each other in the nonlinear regime, each cluster consisting of axial, azimuthal and push-pull modes. Since linear theory cannot predict the nonlinear solution, stochastic simulations are run to study the nonlinear solution in a probabilistic sense. One outcome of these simulations is the various pulsation patterns, which are in principle different from one can to the next. We recover how not only a stronger flame response in one can gives rise to the phenomenon of mode localization, but also how the nonlinearity of the flame saturation and the competition between modes have an effect on the nonlinear mode shape. We finally predict the coherence and phase between cans on the linearized system subject to noise, and compare the predictions with engine measurements, in terms of spectra of amplitude in each can and coherence and phase, observing a good match.
Design and Performance Study of a Novel Minimally Invasive Active Surgical Needle
Authors: Varnamkhasti Zahra Khashei , Konh Bardia
Published: September 2019

Many medical treatments such as brachytherapy, thermal ablation, and biopsy are performed using percutaneous needle-based procedures. The success of these procedures highly depends on accurate placement of the needle tip at target positions. A novel active needle was designed and developed in this work that can steer inside the tissue via a shape memory alloy (SMA) actuator attached to its body. With actuation and control offered by the actuator, the active needle can reach the target positions with more accuracy, and thereby potential improvement in clinical outcomes. An integrated system was also developed to robotically operate the active needle insertion. The performance of the active needle was evaluated with finite element methods and experimental tests on a fabricated prototype in air. Active needle insertion tests in a tissue phantom were also performed to evaluate the performance of the active needle. The deflection in air and tissue phantom demonstrated the capability of the active needle to reach target positions.
Steady and Transient Behavior of Cross-Flow Three-Fluid Heat Exchanger With Temperature Nonuniformity in All the Fluids—A Detailed Investigation
Authors: Aasi Harpreet Kaur , Mishra Manish
Published: September 2019

Cross-flow three-fluid plate-fin heat exchanger is analyzed under both steady-state and transient conditions with a nonuniform inlet temperature of all the three fluids. The influence of the longitudinal heat conduction and axial dispersion in the separating sheets and three fluids, respectively, is also considered. Five different combinations (modes) of temperature nonuniformity in the three fluids have been considered and compared for the performance. An important phenomenon of temperature cross between/among the fluids has been observed and presented for certain modes of temperature nonuniformity and operating conditions. The effect in the performance has been presented on the basis of mean exit temperature and deterioration factor. Implicit finite difference technique has been used for the numerical solution. The heat exchanger's performance is found to be dependent on the mode of temperature nonuniformity, number of transfer units, and the operating parameters.
When the Joukowsky Equation Does Not Predict Maximum Water Hammer Pressures
Authors: Walters Trey W. , Leishear Robert A.
Published: September 2019

The Joukowsky equation has been used as a first approximation for more than a century to estimate water hammer pressure surges. However, this practice may provide incorrect, nonconservative, pressure calculations under several conditions. These conditions are typically described throughout fluid transient text books, but a consolidation of these issues in a brief paper seems warranted to prevent calculation errors in practice and to also provide a brief understanding of the limits and complexities of water hammer equations. To this end, various issues are discussed here that result in the calculation of pressures greater than those predicted by the Joukowsky equation. These conditions include reflected waves at tees, changes in piping diameter, and changes in pipe wall material, as well as frictional effects referred to as line pack, and the effects due to the collapse of vapor pockets. In short, the fundamental goal here is to alert practicing engineers of the cautions that should be applied when using the Joukowsky equation as a first approximation of fluid transient pressures.
Condition Monitoring of Wind Turbine Planetary Gearboxes Under Different Operating Conditions
Authors: Mauricio Alexandre , Sheng Shuangwen , Gryllias Konstantinos
Published: September 2019

Digitally enhanced services for wind power could reduce operations and maintenance costs as well as the levelized cost of energy. Therefore, there is a continuous need for advanced monitoring techniques, which can exploit the opportunities of internet of things and big data analytics, revolutionizing the future of the energy sector. The heart of wind turbines is a rather complex epicyclic gearbox. Among others, extremely critical gearbox components, which are often responsible for machinery stops, are the rolling element bearings. The vibration signatures of bearings are rather weak compared to other components, such as gears, and as a result, an extended number of signal processing techniques and tools have been proposed during the last decades, focusing toward accurate, early, and on time bearing fault detection with limited false alarms and missed detections. Envelope analysis is one of the most important methodologies, where an envelope of the vibration signal is estimated usually after filtering around a frequency band excited by impacts due to the bearing faults. Different tools, such as Kurtogram, have been proposed in order to accurately select the optimum filter parameters (center frequency and bandwidth). Cyclic spectral correlation (CSC) and cyclic spectral coherence (CSCoh), based on cyclostationary analysis, have been proved as very powerful tools for condition monitoring. The monitoring techniques seem to have reached a mature level in case a machinery operates under steady speed and load. On the other hand, in case the operating conditions change, it is still unclear whether the change of the monitoring indicators is due to the change of the health of the machinery or due to the change of the operating parameters. Recently, the authors have proposed a new tool called improved envelope spectrum via feature optimization-gram (IESFOgram), which is based on CSCoh and can automatically select the filtering band. Furthermore, the CSCoh is integrated along the selected frequency band leading to an improved envelope spectrum (IES). In this paper, the performance of the tool is evaluated and further extended on cases operating under different speeds and different loads. The effectiveness of the methodology is tested and validated on the National Renewable Energy Laboratory (NREL) wind turbine gearbox vibration condition monitoring benchmarking dataset, which includes various faults with different levels of diagnostic complexity as well as various speed and load operating conditions.
Fan Flow Field in an Installed Variable Pitch Fan Operating in Reverse Thrust for a Range of Aircraft Landing Speeds
Authors: Rajendran David John , Pachidis Vassilios
Published: September 2019

The installed flow field for a variable pitch fan (VPF) operating in reverse thrust for the complete aircraft landing run is described in this paper. To do this, a VPF design to generate reverse thrust by reversing airflow direction is developed for a representative 40,000 lbf modern high bypass ratio engine. Thereafter, to represent the actual flow conditions that the VPF would face, an engine model that includes the nacelle, core inlet splitter, outlet guide vanes, bypass nozzle, core exhaust duct, aft-body plug, and core nozzle is designed. The engine model with the VPF is attached to a representative airframe in landing configuration to include the effects of installation. A rolling ground plane that mimics the runway during the landing run is also included to complete the model definition. Three-dimensional (3D) Reynolds-averaged Navier–Stokes (RANS) solutions are carried out for two different VPF stagger angle settings and rotational speeds to obtain the fan flow field. The dynamic installed VPF flow field is characterized by the interaction of the freestream and the reverse stream flows. The two streams meet in a shear layer in the fan passages and get deflected radially outward before turning back onto themselves. The flow field changes with stagger setting, fan rotational speed, and the aircraft landing speed because of the consequent changes in the momentum of the two streams. The description of the installed VPF flow field as generated in this study is necessary to (a) qualify VPF designs that are typically designed by considering only the uninstalled static flow field and (b) choose the VPF operating setting for different stages of the aircraft landing run.
Exploration of Coriolis Force on the Linear Stability of Couple Stress Fluid Flow Induced by Double Diffusive Convection
Authors: Naveen Kumar S. B. , Shivakumara I. S. , Shankar B. M.
Published: September 2019

In this paper, the effect of Coriolis force is explored on convective instability of a doubly diffusive incompressible couple stress fluid layer with gravity acting downward. A linear stability analysis is used to obtain the conditions for the onset of stationary and oscillatory convection in the closed form. Being a multiparameter instability problem, results for some isolated cases have been presented to illustrate interesting corners of parameter space. It is found that the neutral curve for oscillatory onset forms a closed-loop which is separate from the neutral curve for stationary onset indicating the requirement of three critical thermal Rayleigh numbers to specify the linear instability criteria instead of the usual single value. Besides, the simultaneous presence of rotation and the addition of heavy solute to the bottom of the layer exhibit an intriguing possibility of destabilizing the system under certain conditions, in contrast to their stabilizing effect when they are present in isolation. The implication of couple stresses on each of the aforementioned anomalies is clearly brought out. The spatial wavelength of convective cells at the onset is also discussed.
A Novel Activated Carbon Enabled Steam Generation System Under Simulated Solar Light
Authors: Mishra Ashreet , Nnanna Agwu A. G.
Published: September 2019

Studies on carbon nanotubes (CNT), Au, and Ag solar enabled steam generation with potential application in water purification, distillation, and sterilization of medical equipment are ongoing. The key challenge with these nanoparticles is the cost of production hence limiting its full application for clean water production. This work for the first time reports on activated carbon enabled steam generation hence addressing the cost limitations of metallic nanoparticles. Activated carbon has high solar absorptivity at various wavelengths of visible light under low concentration. Experiments were carried out using activated carbon and CNT nanofluids and polyurethane (PU) membrane with immobilized activated carbon and CNT. A simulated solar light of 1 kW ∼1 sun was used. The rate of evaporation, temporal and spatial evolution of bulk temperature in the water were monitored automatically and recorded for further data reductions. Parametric studies of the effect of nanoparticle concentration, water quality, and salinity were performed. Experimental evidence showed that activated carbon has potential in water purification. We reported for the first time that optimal activated carbon concentration for maximum steam generation is 60 vol %. We also obtained a 160% increase in steam production rate at 60% concentration of activated carbon when compared with de-ionized water.
Numerical Investigation on the Effect of Tube Geometry and Feeder Height on the Heat Transfer Performance of Horizontal Tube Falling Film Evaporation
Authors: Balaji D. , Velraj R. , Ramana Murthy M. V.
Published: September 2019

This paper discusses about the effect of tube geometry and liquid feeder height on the heat transfer performance of falling film evaporation over the horizontal heated plain tubes. To investigate this, a two-dimensional computational fluid dynamics (CFD) model was developed, compared, and validated with published data available in the literature. A numerical simulation was carried out for varying liquid load, tube diameter, liquid feeder height, and corresponding changes in the heat transfer co-efficient (HTC), and mass transfer rate was recorded and analyzed. An attempt was also made to measure the thickness of the film around the tubes from the simulation model. Mechanisms that control the factors such as HTC, film thickness, and mass transfer were numerically investigated and discussed in this work. Numerical results indicated that low value of liquid film thickness appears approximately at the angular position of the range between 90 deg and 125 deg. Also the numerical investigation revealed that liquid film thickness decreases and HTC and mass transfer rate increases with the increase of feeder height. No remarkable change in film thickness was observed with increase in the tube diameter. This numerical study also proved that the prediction of thermally developed boundary region on the circumference of the tube could be possible in terms of mass transfer rate. It was also observed from the numerical study that the highest mass transfer rate takes place between the angle 135–165 deg near to the bottom of the tube.
On the Interaction of Swirling Flames in a Lean Premixed Combustor
Authors: Ramachandran Gopakumar , Dutta Ankit Kumar , Durairaj Harish , Chaudhuri Swetaprovo
Published: September 2019

Premixed or partially premixed swirling flames are widely used in gas turbine applications because of their compactness, high ignition efficiency, low NOx emissions and flame stability. A typical annular combustor consists of about twenty swirling flames, which interact (directly or indirectly) with their immediate neighbors even during stable operation. These interactions significantly alter the flow and flame topologies thereby bringing in some discrepancies between the single nozzle (SN) and multinozzle (MN), ignition, emission, pattern factor and flame transfer function (FTF) characteristics. For example, in MN configurations, application of a model based on SN FTF data could lead to erroneous conclusions. Due to the complexities involved in this problem in terms of size, thermal power, cost, optical accessibility etc., a limited amount of experimental studies has been reported, that too on scaled down models with reduced number of nozzles. Here, we present a detailed experimental study on the behavior of three interacting swirl premixed flames, arranged in-line in an optically accessible hollow cuboid test section, which closely resembles a three-cup sector of an annular gas turbine combustor with very large radius. Multiple configurations with various combinations of swirl levels between the adjacent nozzles and the associated flame and flow topologies have been studied. Spatio-temporal information of the heat release rate obtained from OH* chemiluminescence imaging is used along with the acoustic pressure signatures to compute the Rayleigh index (RI) so as to identify the regions within the flame that pumps energy into the self-excited thermoacoustic instability modes. It is found that the structure of the flame–flame interaction regions plays a dominant role in the resulting thermoacoustic instability. To resolve the flow and reactive species distributions in the interacting flames, two-dimensional (2D), three component stereoscopic particle image velocimetry (SPIV) and planar laser-induced fluorescence (PLIF) of hydroxyl radical is applied to all the test conditions. Significant differences in the flow structures among the different configurations were observed. Simultaneous OH-PLIF and SPIV techniques were also utilized to track the flame front, from which the curvature and stretch rates were computed. Flame surface density (FSD) which is defined as the mean surface area of the reaction zone per unit volume, is also computed for all the test cases. These measurements and analyses elucidate the structure of the interaction regions, their unique characteristics, and possible role in thermoacoustic instability.
Application of Stiffness Confinement Method in Transient Transport Calculation
Authors: Tang Chuntao
Published: September 2019

Stiffness confinement method (SCM) can effectively alleviate the stiffness in the neutron kinetics equation and can use larger time steps to obtain the same calculation accuracy and improve the computational efficiency. However, the existing SCM is mainly used to solve two group transient diffusion equations. In this paper, the SCM is employed to solve the multigroup transient transport calculation. On the basis of the original method of characteristics (MOC) code PEACH, the transient function is added, and the PEACH-K program is developed. Based on the numerical results of the latest published OECD/NEA C5G7-TD benchmark, it shows that the PEACH-K program developed in this paper has both high computing precision and good numerical stability.
A Study of the Reproducibility and Diversity of the Supply Chain in Manufacturing Hot Isostatically Pressed Type 316L Stainless Steel Components for the Civil Nuclear Sector
Authors: Kyffin William , Gandy David , Burdett Barry
Published: September 2019

Hot isostatic pressing (HIP) of type 316 L stainless steel powder has been an established manufacturing practice for more than 25 years in the oil and gas sector and more recently in the naval defense sector. To demonstrate the capability of the powder metallurgy HIP (PM/HIP) for nuclear power applications, a systematic study of 316 L commercial powder production, encapsulation/consolidation providers, and selected HIP parameters was undertaken by the Nuclear AMRC in collaboration with the Electric Power Research Institute (EPRI). In this study, the 316 L powder specification limited the oxygen content of the powder to under 130 parts per million (ppm), which reflects the improvements that commercial powder suppliers have been making over the past decade to ensure greater powder cleanliness. The test program assessed powder supply, HIP service provider, and HIP sustain time. Excellent test results were achieved across the full range of variables studied with all billets meeting the specification requirements of ASTM A988 and additional requirements imposed based on nuclear manufacturing standards. Significantly, the study demonstrated the robustness of the PM/HIP supply chain, as material produced via differing HIP service providers resulted in very consistent material properties across the destructive test program. Furthermore, no significant difference in material properties was noted for material HIP between 2 and 8 h hold time, suggesting that the HIP process window is large. Both these results are significant from an end-user standpoint as they highlight the uniformity of the process through the full manufacturing cycle from powder procurement to destructive testing. Despite all material passing specification requirements, some property variation was noted for differing powder suppliers. Considering the systematic approach, this was attributed to powder composition, with both low oxygen and high nitrogen contents contributing to improvements in Charpy impact strength and tensile strength, respectively.
Hydrodynamic Cause Analysis for Roof Damage on Water Storage Tank
Authors: Ryu Ki-Wahn
Published: September 2019

The causes of roof damage found on a large-scale water storage tank were investigated using hydrodynamic analysis. All operation and weather data, such as temperature inside and outside of the storage tank, atmospheric pressure, water level according to time, condensed water check inside pipelines, snowfall, and wind speed, were precisely reviewed. Four potential scenarios were postulated to estimate the vacuum pressure, presumed to be a direct cause of the roof damage to the storage tank. In the scenarios, an energy equation with a friction loss for pipelines and fittings was adopted to compute the pressure differences between the inlet and outlet of the ventilation and overflow pipes. A timewise pressure drop for the condition of fully clogged connected lines during a discharge operation was also carried out. A sequence solution for the unsteady Bernoulli equation to represent the dynamic motion of a water column inside a loop seal was successfully derived. This can predict the vacuum pressure limit inside the storage tank required to drain out the water from the loop seal. The predicted vacuum pressure was compared with the vacuum pressure required to cause the buckling phenomena at the roof support structures. In-depth analysis of each scenario showed that the roof damage of the storage tank developed when the vacuum pressure reached over the estimated vacuum pressure limit. To prevent further roof damage, including the storage tank of the same design at other plant, change of the layout of the air ventilation line was recommended.