bluuebunny/crossref_metadata_2025 huggingface dataset:
NAFLD is related to Post‐prandial Triglyceride‐enrichment of HDL Particles in Association with Endothelial and HDL Dysfunction
Authors: Verwer Bart J. , Scheffer Peter G. , Vermue Rick P. , Pouwels Petra J. , Diamant Michaela , Tushuizen Maarten E.
Published: July 2020

NAFLD is closely related with the metabolic syndrome (MetS) and increased risk of cardiovascular disease. Liver fat associates with post‐prandial hypertriglyceridemia, potentially contributing to triglyceride‐enrichment of high‐density lipoproteins (HDL‐TG), and subsequent HDL dysfunction. We assessed liver fat by MR spectroscopy, and its association with HDL physiochemical properties, and endothelial function, measured as flow‐mediated dilation (FMD), before and following three consecutive meals, in 36 men with type 2 diabetes mellitus (T2DM), with the MetS, and controls. Plasma triglycerides increased significantly following the meals (P < .001). Fasting HDL‐TG was highest in T2DM, relative to MetS and controls (P = .002), and increased post‐prandially in all groups (P < .001). HDL function was negatively associated with HDL‐TG following three meals (r = −.32, P<.05). Liver fat associated with HDL‐TG after three meals (r = .65, P < .001). HDL‐TG was independently associated with FMD following three consecutive meals (r = −.477, P = .003). We conclude liver fat is associated with post‐prandial HDL‐TG enrichment which was closely related with endothelial and HDL dysfunction.
Serum progranulin levels in paediatric patients with Gaucher disease; relation to disease severity and liver stiffness by transient elastography
Authors: Tantawy Azza A. , Adly Amira A. , Ismail Eman A. , Salah Nouran Y. , Abdel Alem Shereen , Elsantiel Hesham I.
Published: July 2020

Background

Non‐invasive screening for liver fibrosis using transient elastography (TE) could be of value in the management of Gaucher disease (GD). Progranulin (PGRN) is a novel disease modifier in GD and an independent marker of liver fibrosis.

Objectives

We determined PGRN levels in paediatric patients with GD and assessed its role as a potential marker for disease severity and relation to liver stiffness by TE.

Methods

Fifty‐one GD patients (20 had type 1 and 31 had type 3) with a median age of 9.5 years were compared to 40 age‐ and sex‐matched healthy controls and were studied focusing on visceral manifestations, neurological disease, haematological profile and PGRN levels as well as abdominal ultrasound and TE. Patients were on enzyme replacement therapy (ERT) for various durations and those with viral hepatitis infection were excluded.

Results

By TE, 14 GD patients (27.5%) had elevated liver stiffness ≥7.0 kPa. Liver stiffness was significantly higher in type 1 GD patients than type 3 (P = .002), in splenectomized patients (P = .012) and those with dysphagia (P < .001). Liver stiffness was positively correlated with age of onset of ERT (P < .001). PGRN levels were significantly lower in GD patients compared with controls (P < .001). PGRN was significantly lower in GD patients with squint (P = .025), dysphagia (P = .036) and elevated liver stiffness (P = .015). PGRN was positively correlated with white blood cell count (r = .455, P = .002) and haemoglobin (r = .546, P < .001), while negatively correlated with severity score index (r = −.529, P < .001), liver volume (r = −.298, P = .034) and liver stiffness (r = −.652, P < .001).

Conclusions

Serum PGRN levels were associated with clinical disease severity and elevated liver stiffness in paediatric GD patients.
Robust geographical determinants of infection prevalence and a contrasting latitudinal diversity gradient for haemosporidian parasites in Western Palearctic birds
Authors: Clark Nicholas J. , Drovetski Sergei V. , Voelker Gary
Published: July 2020

Identifying robust environmental predictors of infection probability is central to forecasting and mitigating the ongoing impacts of climate change on vector‐borne disease threats. We applied phylogenetic hierarchical models to a data set of 2,171 Western Palearctic individual birds from 47 species to determine how climate and landscape variation influence infection probability for three genera of haemosporidian blood parasites (Haemoproteus, Leucocytozoon, and Plasmodium). Our comparative models found compelling evidence that birds in areas with higher vegetation density (captured by the normalized difference vegetation index [NDVI]) had higher likelihoods of carrying parasite infection. Magnitudes of this relationship were remarkably similar across parasite genera considering that these parasites use different arthropod vectors and are widely presumed to be epidemiologically distinct. However, we also uncovered key differences among genera that highlighted complexities in their climate responses. In particular, prevalences of Haemoproteus and Plasmodium showed strong but contrasting relationships with winter temperatures, supporting mounting evidence that winter warming is a key environmental filter impacting the dynamics of host‐parasite interactions. Parasite phylogenetic community diversities demonstrated a clear but contrasting latitudinal gradient, with Haemoproteus diversity increasing towards the equator and Leucocytozoon diversity increasing towards the poles. Haemoproteus diversity also increased in regions with higher vegetation density, supporting our evidence that summer vegetation density is important for structuring the distributions of these parasites. Ongoing variation in winter temperatures and vegetation characteristics will probably have far‐reaching consequences for the transmission and spread of vector‐borne diseases.
Potential adaptive divergence between subspecies and populations of snapdragon plants inferred from QST–FST comparisons
Authors: Marin Sara , Gibert Anaïs , Archambeau Juliette , Bonhomme Vincent , Lascoste Mylène , Pujol Benoit
Published: July 2020

Phenotypic divergence among natural populations can be explained by natural selection or by neutral processes such as drift. Many examples in the literature compare putatively neutral (FST) and quantitative genetic (QST) differentiation in multiple populations to assess their evolutionary signature and identify candidate traits involved with local adaptation. Investigating these signatures in closely related or recently diversified species has the potential to shed light on the divergence processes acting at the interspecific level. Here, we conducted this comparison in two subspecies of snapdragon plants (eight populations of Antirrhinum majus pseudomajus and five populations of A. m. striatum) in a common garden experiment. We also tested whether altitude was involved with population phenotypic divergence. Our results identified candidate phenological and morphological traits involved with local adaptation. Most of these traits were identified in one subspecies but not the other. Phenotypic divergence increased with altitude for a few biomass‐related traits, but only in A. m. striatum. These traits therefore potentially reflect A. m. striatum adaptation to altitude. Our findings imply that adaptive processes potentially differ at the scale of A. majus subspecies.
From one side to two sides: the effects of stomatal distribution on photosynthesis
Authors: Xiong Dongliang , Flexas Jaume
Published: July 2020

The functions of stomata have been studied for a long time; however, a clear understanding of the influences of stomatal distribution on photosynthesis, especially the CO2 diffusion, is still unclear.

Here, we investigated the stomatal morphology, distribution on leaf surfaces, vein traits and gas exchange parameters of 61 species, of which 29 were amphistomatous, spanning 32 families.

Photosynthesis (A) was tightly coupled with operational stomatal conductance (gs) and mesophyll conductance (gm) regardless of whether phylogenetic relationships were accounted for. Although the enhancement of gs from ferns and gymnosperms to angiosperms could largely be explained by the increase in leaf vein density (VLA) and stomatal density (SD), the gs was decoupled from VLA and SD across angiosperm species. Instead, A in angiosperms was further influenced by the allocation of stomatal pores on leaf surfaces, which dramatically increased gs and gm. Moreover, the ratio of gs to anatomically based maximum gs was, on average, 0.12 across species.

Our results show that the shift of stomatal pores from one leaf side to both sides played an important role in regulating CO2 diffusion via both stomata and mesophyll tissues. Modifications of stomata distribution have potential as a functional trait for photosynthesis improvement.
A debt repaid? A case of an unusual foreign body found in the nasal cavity
Authors: Gamieldien M.Y. , Musson C.G. , Uys A. , Buchanan G.D.
Published: July 2020

The appearance of nasal foreign bodies is well reported in children but hardly ever seen in adults. These objects are often easily identified and removed. This report documents an unusual case of a bank note lodged in the nasal cavity of an adult male. The foreign body in question presented a significant diagnostic challenge both from a clinical and radiological perspective. Careful review of the case history, as well as clinical and radiographic features, led to appropriate management and avoidance of unnecessary interventions. Clinicians involved in head and neck surgery and radiology should suspect, and be aware of the radiographic appearance, of a wide variety of foreign bodies.
Sinonasal papilloma: diagnosis following dental pain
Authors: Gallacher N. , Gormley M. , Pring M. , Revington P.
Published: July 2020

Sinonasal papillomas (SPs) are benign neoplasms that arise within the nasal cavity. Diagnosis may be challenging, given the often non‐specific symptoms including nasal obstruction, headaches and rhinorrhoea. SPs can be locally destructive, have a high tendency to reoccur and may be associated with transformation to squamous cell carcinoma. Management, therefore often, involves surgical excision and careful follow‐up.
Post‐Dural Puncture Headache Evolving to a Subdural Hematoma: A Case Report
Authors: Dehaene Seppe , Biesemans Jeroen , Van Boxem Koen , Vidts Wesley , Sterken Joeri , Van Zundert Jan
Published: July 2020

Introduction

Cervical epidural corticosteroid injections are frequently used for the treatment of subacute cervicobrachial pain. This therapy is considered safe, with the vast majority of the complications being minor and transient.

Case Report

We present a case of a woman in her fifties who suffered from cervicobrachialgia and received 2 cervical epidural corticosteroid infiltrations. On day 3 after the second infiltration, a new headache appeared and on day 16 a bilateral subdural hematoma was visualized on CT scan. Complete resorption of the hematoma was seen on day 25 without surgical intervention.

Discussion

Up until now, only 1 case report of an intracranial subdural hematoma after a cervical epidural steroid injection has been published. But several cases of an intracranial subdural hematoma after spinal, epidural, or combined spinal and epidural anesthesia have been reported. Physicians should be aware of this potentially dramatic complication since post‐dural puncture headache after any type of procedure can evolve into a subdural hematoma. Clinical differentiation between the two can be difficult; post‐dural puncture headache is characterized by relief of symptoms in the supine position and photophobia/phonophobia. A subdural hematoma should be considered if the headache changes in character, does not respond to treatment, or there are neurological signs such as nausea/vomiting and blurred vision. Immediate medical imaging should then be performed.
Significance of tumor microenvironment in acquiring resistance to vascular endothelial growth factor‐tyrosine kinase inhibitor and recent advance of systemic treatment of clear cell renal cell carcinoma
Authors: Mikami Shuji , Mizuno Ryuichi , Kosaka Takeo , Tanaka Nobuyuki , Kuroda Naoto , Nagashima Yoji , Okada Yasunori , Oya Mototsugu
Published: July 2020

The development of systemic therapies, including vascular endothelial growth factor‐tyrosine kinase inhibitors (VEGF‐TKI) and mammalian target of rapamycin (mTOR) inhibitors, represents a major breakthrough in the treatment of patients with renal cell carcinoma (RCC). However, inherent resistance is observed in some patients and acquired resistance commonly develops in many patients within several months of the initiation of systemic therapies. Since these treatments rarely cure patients, their aim is to suppress tumor progression and prolong survival. Therefore, the establishment of dependable criteria that predict responses and resistance to systemic therapies is clinically important, and the underlying molecular mechanisms also need to be elucidated for the future development of more effective therapies. We herein review recent advances in research on the molecular mechanisms underlying resistance, with a focus on morphological characteristics, tumor angiogenesis, and the tumor immune microenvironment in RCC and their relationships with VEGF‐TKI treatments. Recent therapies using immune checkpoint inhibitors (ICI) and newly developed VEGF‐TKI also appear to be effective for advanced RCC, with stable and durable responses to ICI being observed in some RCC patients. These new drugs and their outcomes have been briefly described.
HKT sodium and potassium transporters in Arabidopsis thaliana and related halophyte species
Authors: Ali Akhtar , Raddatz Natalia , Pardo Jose M. , Yun Dae‐Jin
Published: July 2020

High salinity induces osmotic stress and often leads to sodium ion‐specific toxicity, with inhibitory effects on physiological, biochemical and developmental pathways. To cope with increased Na+ in soil water, plants restrict influx, compartmentalize ions into vacuoles, export excess Na+ from the cell, and distribute ions between the aerial and root organs. In this review, we discuss our current understanding of how high‐affinity K+ transporters (HKT) contribute to salinity tolerance, focusing on HKT1‐like family members primarily involved in long‐distance transport, and in the recent research in the model plant Arabidopsis and its halophytic counterparts of the Eutrema genus. Functional characterization of the salt overly sensitive (SOS) pathway and HKT1‐type transporters in these species indicate that they utilize similar approaches to deal with salinity, regardless of their tolerance.
Current account and international networks
Authors: Grechyna Daryna
Published: July 2020

This paper explores the impact of international trade and financial networks on the current account balances. The network centrality measures are computed based on the structure and volume of trade and financial flows among the countries. A more central position in the international trade network improves the current account balance in developed countries but has no impact on the current account in developing countries. A more central position in the international financial network improves the current account balance in developed and developing countries. Besides, the impact of the international financial network on the current account has become stronger over time.
What will studies of Fulani individuals naturally exposed to malaria teach us about protective immunity to malaria?
Authors: Troye‐Blomberg Marita , Arama Charles , Quin Jaclyn , Bujila Ioana , Östlund Farrants Ann‐Kristin
Published: July 2020

There are an estimated over 200 million yearly cases of malaria worldwide. Despite concerted international effort to combat the disease, it still causes approximately half a million deaths every year, the majority of which are young children with Plasmodium falciparum infection in sub‐Saharan Africa. Successes are largely attributed to malaria prevention strategies, such as insecticide‐treated mosquito nets and indoor spraying, as well as improved access to existing treatments. One important hurdle to new approaches for the treatment and prevention of malaria is our limited understanding of the biology of Plasmodium infection and its complex interaction with the immune system of its human host. Therefore, the elimination of malaria in Africa not only relies on existing tools to reduce malaria burden, but also requires fundamental research to develop innovative approaches. Here, we summarize our discoveries from investigations of ethnic groups of West Africa who have different susceptibility to malaria.
Effects of crop residue mulch and seedbed preparation methods on soil properties and rainfed groundnut production in Alfisols of semi‐arid India
Authors: Pandian Kannan , Subramaniayan Ponmani , Gnasekaran Prabukumar , Chitraputhirapillai Swaminathan
Published: July 2020

Decreased frequency but greater intensity of rainfall in semi‐arid India severely affects growth and the yield of rainfed annual food crops, where there is no other source of water, leading to moisture stress during protracted dry spells. As Indian farmers growing rainfed crops are small landholders, their better option is in situ rainwater harvesting. This ensures moisture storage and increases soil moisture available to rainfed crops with less‐costly investment. Accordingly, a field investigation was established over 2011, 2012 and 2013 at the Dryland Agricultural Research Station, Chettinad, India. We studied the effects of seedbed preparation method (SBPM) and mulching with crop residues (CRM) on soil physicochemical properties, growth, yield and yield attributes of groundnut. Greater soil moisture content was measured under compartmental bunding (CB) and raised bed (RB) with CRM than under flatbed (FB). Soil bulk density was considerably smaller under CB and RB with CRM (1.36 and 1.37 Mg m−3) compared with FB (1.39 Mg m−3). Soil microbial biomass carbon (SMBC) was larger under CB and RB with CRM (563 and 542 mg kg−1soil, respectively) than FB with and without CRM. RB with CRM application contained more soil organic carbon (SOC) stock (3.1 Mg ha−1) than FB. CB with CRM resulted in larger groundnut yield (1,604 kg ha−1) and rainwater use efficiency (5.8 kg ha−1 mm−1) than the FB with and without CRM; RB and RF with CRM were intermediate. The ideal seedbed preparation for groundnut crop in Alfisol under semi‐arid conditions was compartmental bunding (CB) and raised bed (RB) along with CRM.
Disseminated cryptococcosis with cutaneous manifestation
Authors: Johnson Matthew M. , Gajurel Kiran
Published: July 2020

Cutaneous cryptococcosis is uncommon. It is usually a result of disseminated infection and can present with a wide variety of skin lesions. We report a case of disseminated cryptococcosis in a kidney transplant recipient who presented with nodular lesions in the forehead following a bout of acute cellular rejection.
Bugs, breathing and blood pressure: microbiota–gut–brain axis signalling in cardiorespiratory control in health and disease
Authors: O'Connor Karen M. , Lucking Eric F. , Cryan John F. , O'Halloran Ken D.
Published: July 2020

There is clear evidence of physiological effects of the gut microbiota on whole‐body function in health and disease. Microbiota–gut–brain axis signalling is recognised as a key player in behavioural disorders such as depression and anxiety. Recent evidence suggests that the gut microbiota affects neurocontrol networks responsible for homeostatic functions that are essential for life. We consider the evidence suggesting the potential for the gut microbiota to shape cardiorespiratory homeostasis. In various animal models of disease, there is an association between cardiorespiratory morbidity and perturbed gut microbiota, with strong evidence in support of a role of the gut microbiota in the control of blood pressure. Interventions that target the gut microbiota or manipulate the gut–brain axis, such as short‐chain fatty acid supplementation, prevent hypertension in models of obstructive sleep apnoea. Emerging evidence points to a role for the microbiota–gut–brain axis in the control of breathing and ventilatory responsiveness, relevant to cardiorespiratory disease. There is also evidence for an association between the gut microbiota and disease severity in people with asthma and cystic fibrosis. There are many gaps in the knowledge base and an urgent need to better understand the mechanisms by which gut health and dysbiosis contribute to cardiorespiratory control. Nevertheless, there is a growing consensus that manipulation of the gut microbiota could prove an efficacious adjunctive strategy in the treatment of common cardiorespiratory diseases, which are the leading causes of morbidity and mortality.

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Micro-Tubular Solid Oxide Fuel Cell Polarization and Impedance Variation With Thin Porous Samarium-Doped Ceria and Gadolinium-Doped Ceria Buffer Layer Thickness
Authors: Milcarek Ryan J. , Ahn Jeongmin
Published: July 2020

Porous buffer layers for anode-supported solid oxide fuel cells (SOFCs) have been investigated for many years with different thicknesses of the buffer layer in each study. In this work, micro-tubular SOFCs having samarium-doped ceria (SDC) and gadolinium-doped ceria (GDC) buffer layers are compared using the current–voltage technique, electrochemical impedance spectroscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The thickness of the porous SDC and GDC buffer layer is investigated systematically with the thickness varying between 0.3 and 2.0 μm. The power density varies between 212 and 1004 mW/cm2 for samples having different SDC buffer layer thickness. Comparable changes occur for the SOFCs with a GDC buffer layer, but less variation in polarization losses resulted. Variation in electrochemical performance varies due to changes in ohmic resistance, cathode activation polarization, and interfacial reactions between the cathode and electrolyte materials.
Integrated Prediction of Mechanical Behavior for the Non-Aligned Fiber Composites With Experimental Validation
Authors: Jiang Bingyun , Tian Chen
Published: July 2020

This paper aims to present an integrated multi-scale method for predicting the anisotropic and nonlinear elasto-plastic behavior of short glass fiber-reinforced polymer (GFRP) materials typically produced by injection molding. The proposed method combines injection molding and microstructure together, with considering the nonaligned fibers and their corresponding anisotropy, to semi-analytically estimate the local effective mechanical properties at every point of GFRP. Micro-computed tomography measurement and injection molding simulation are used to obtain the fiber orientation tensor. The two-step mean-field homogenization method is applied to calculate the mechanical behaviors of the PA66GF30 GFRP with distributed-orientation fibers based on the fiber orientation tensor. Reverse engineering is used to obtain the optimized parameters of J2-plasticity and Tsai-Hill three-dimensional transversely isotropic stain-based failure criterion. Moreover, the integral mapping method can complete the transformation of the fiber orientation tensor from injection simulation to structure simulation model. The proposed integrated approach with the optimized parameters is verified by predicting the ring samples’ behavior from injection plates. The results from this investigation are expected to provide some design guidelines for GFRP composites.
Dynamic Crack Propagation and Its Interaction With Micro-Cracks in an Impact Problem
Authors: Candaş Adem , Oterkus Erkan , İmrak Cevat Erdem
Published: July 2020

The dynamic fracture behavior of brittle materials that contain micro-level cracks should be examined when material subjected to impact loading. We investigated the effect of micro-cracks on the propagation of macro-cracks that initiate from notch tips in the Kalthoff–Winkler experiment, a classical impact problem. To define predefined micro-cracks in three-dimensional space, we proposed a two-dimensional micro-crack plane definition in the bond-based peridynamics (PD) that is a non-local form of classical continuum theory. Randomly distributed micro-cracks with different number densities in a constant area and number in expending area models were examined to monitor the toughening of the material. The velocities of macro-crack propagation and the time required for completing fractures were considered in several predefined micro-cracks cases. It has been observed that toughening mechanism is only initiated by exceeding a certain number of micro-cracks; therefore, there is a positive correlation between the density of predefined micro-cracks and macro-crack propagation rate and, also, toughening mechanism.
Fracture Behavior of Ultrafine-Grained Titanium Under Tension at Elevated Temperatures
Authors: Sajadifar S. V. , Maier H. J. , Niendorf T. , Yapici G. G.
Published: July 2020

This investigation focused on the deformation response and microstructural changes of severely deformed titanium during post-severe plastic deformation tension, at temperatures of 300–600 °C and at strain rates of 0.001–0.1 s−1. The obtained results suggest that SPD enhances the strength of grade 4 titanium up to 500 °C. At above 600 °C, the severely deformed microstructure showed comprehensive recovery. Severely deformed titanium was seen to be highly sensitive to the deformation rate, where strain rate sensitivity increased with the increase of test temperature. Analysis of fracture surfaces reveals that at elevated temperatures, growth of dimples and void coalescence occurs due to the enhanced diffusion rate and occurrence of recrystallized grains.
Computational Fluid Dynamics Based Mixing Prediction for Tilt Pad Journal Bearing TEHD Modeling—Part I: TEHD-CFD Model Validation and Improvements
Authors: Yang Jongin , Palazzolo Alan
Published: July 2020

The core contributions of Part I (1) present a computational fluid dynamics (CFD)-based approach for tilting pad journal bearing (TPJB) modeling including thermo-elasto hydrodynamic (TEHD) effects with multi-mode pad flexibility, (2) validate the model by comparison with experimental work, and (3) investigate the limitations of the conventional approach by contrasting it with the new approach. The modeling technique is advanced from the author’s previous work by including pad flexibility. The results demonstrate that the conventional approach of disregarding the three-dimensional flow physics between pads (BP) can generate significantly different pressure, temperature, heat flux, dynamic viscosity, and film thickness distributions, relative to the high-fidelity CFD model. The uncertainty of the assumed mixing coefficient (MC) may be a serious weakness when using a conventional, TPJB Reynolds model, leading to prediction errors in static and dynamic performance. The advanced mixing prediction method for “BP” thermal flow developed in Part I will be implemented with machine learning techniques in Part II to provide a means to enhance the accuracy of conventional Reynolds based TPJB models.
Computational Fluid Dynamics Based Mixing Prediction for Tilt Pad Journal Bearing TEHD Modeling—Part II: Implementation With Machine Learning
Authors: Yang Jongin , Palazzolo Alan
Published: July 2020

Reynolds based thermo-elasto-hydrodynamic (TEHD) simulations of tilting pad journal bearings (TPJBs) generally provide accurate results; however, the uncertainty of the pad’s leading edge thermal boundary conditions causes uncertainty of the results. The highly complex thermal-flow mixing action between pads (BPs) results from the oil supply nozzle jets and geometric features. The conventional Reynolds approach employs mixing coefficients (MCs), estimated from experience, to approximate a uniform inlet temperature for each pad. Part I utilized complex computational fluid dynamics (CFD) flow modeling to illustrate that temperature distributions at the pad inlets may deviate strongly from being uniform. The present work retains the uniform MC model but obtains the MC from detailed three-dimensional CFD modeling and machine learning, which could be extended to the radially and axially varying MC case. The steps for implementing an artificial neural network (ANN) approach for MC regression are provided as follows: (1) utilize a design of experiment step for obtaining an adaptable training set, (2) conduct CFD simulations on the BP to obtain the outputs of the training set, (3) apply an ANN learning process by Levenverg–Mardquart backpropagation with the Bayesian regularization, and (4) couple the ANN MC results with conventional TEHD Reynolds models. An approximate log fitting method provides a simplified approach for MC regression. The effectiveness of the Reynolds TEHD TPJB model with ANN regression-based MC distributions is confirmed by comparison with CFD based TEHD TPJB model results. The method obtains an accuracy nearly the same as the complete CFD model, but with the computational economy of a Reynolds approach.
Evaluation of Tribological Performance of Jatropha Oil Modified With Molybdenum Disulphide Micro-Particles for Steel–Steel Contacts
Authors: Mushtaq Zahid , Hanief M.
Published: July 2020

Crude oil reserves are sapping with time, therefore researchers have considerably shifted their focus to bio-lubricants which can be surrogated for petroleum-based lubricants. The objective of the present research is to cater an idea to the researchers about the lubricating potentials of Jatropha oil (JO). The study was performed using reciprocating friction monitor (RFM) machine having ball-on-flat arrangement with 52100 chromium steel ball and EN-31 steel as a tribo-pair. The experiments were conducted at three different loads at a temperature of 40 °C. JO was mixed with glycerol (G) and different percentages of molybdenum disulphide (0.5%, 1%, 2%, and 3%) micro-particles to prepare a lubricant. The friction and wear of the tribo-pair was assessed in the presence of these mixtures. The results revealed that MoS2 micro-particles were effective in reducing both friction and wear, with minimum friction recorded at 2% MoS2 concentration. The coefficient of friction (COF) was reduced by 18–52% with the addition of MoS2 as compared to the base JO. The results showed that JO has better lubrication ability as compared to the commercial lubricant SAE 10W/30. The experimental results were substantiated by examinations of tribo-pairs on scanning electron microscope, optical microscope, and optical three-dimensional profilometer. The results were found to be in close agreement with each other. It was concluded that the blend (80% JO + 20% G + 2% MoS2) is a strong candidate that can be used in the place of mineral oils as a lubricant.
Advanced Exergy, Exergoeconomic, Exergoenvironmental Evaluation of a Solar Hybrid Trigeneration System Based on Solar Gas Turbine for an Office Building
Authors: Miar Naeimi Masoud , Eftekhari Yazdi Mohammad , Salehi Gholam Reza
Published: July 2020

In this article, optimal design and advanced exergetic, exergoeconomic, and exergoenvironmental analyses of a trigeneration system for an office building based on integration flat plate solar collector and gas turbine have been performed. The proposed system includes a heat recovery steam generator, a steam turbine, a solar plate collector, and an absorption chiller. The transient simulation for solar calculation has been done using transys software. In addition, a computer code was built to compute conventional and advanced exergy, exergoeconomic, and exergoenvironmental evaluation dynamically. Furthermore, multiobjective optimization by NSGA-II and cuckoo Search algorithm with maximum exergetic efficiency, minimum total exergetic cost, and minimum exergetic environmental impacts has been carried out simultaneously. The results demonstrate that the three objective parameters have been enhanced. Also, the endogenous, exogenous, available, and unavailable parts of exergy destruction have been determined.
Transient Thermodynamic Modeling of Air Cooler in Supercritical CO2 Brayton Cycle for Solar Molten Salt Application
Authors: Deshmukh Ankur , Kapat Jayanta , Khadse Akshay
Published: July 2020

Supercritical carbon dioxide Brayton power cycle is getting commercially attractive for power generation due to numerous advantages like zero water usage, compactness, low environmental emission, and potential to reach high thermal efficiency at lower costs. A typical recuperated closed cycle consists of three heat exchangers (main heat exchanger, cooler, and recuperator) and two turbomachinery (turbine and compressor). Rapid changes in ambient temperature, operating loads, start-ups, and shutdowns affect the performance and operation of the turbomachinery and heat exchangers. The purpose of this research article is to study the thermodynamic parameters of the air cooler during transient operations by running dynamic simulations. Magnitude of change in carbon dioxide temperature due to change in air temperature is calculated. The simulation is a setup by having a steady-state design of 100 MWe cycle with operating temperature of 700 °C and pressure of 250 bar. Dynamic simulations are done using lms amesim. Transients studied in this article include: (i) step variation, (ii) standard variation, and (iii) linear variation of air temperature. This study thus serves as a framework to develop a design and control basis governed by transient scenarios.
Fuel-Adaptability Analysis of Intermediate-Temperature-SOFC/Gas Turbine Hybrid System With Biomass Gas
Authors: Ding Xiaoyi , Lv Xiaojing , Weng Yiwu
Published: July 2020

The tolerance and adaptability to various kinds of fuels make intermediate-temperature solid oxide fuel cell (IT-SOFC) and gas turbine (GT) hybrid system one of the most attractive technologies in the future energy market. In this paper, based on a detailed model established on matlab/simulink, a thermodynamic analysis of IT-SOFC/GT hybrid system fueled with different types of biomass gases is presented. During the process of this research, the composition fluctuations of CH4, H2, CO, CO2, N2, and H2O are considered to simulate the practical situation. Operating states of IT-SOFC/GT hybrid system fueled with wood chip gasified gas and farm biogas are compared under the same power scale of 180 kW. Performance and safety evaluations of hybrid system in response to composition fluctuations of wood chip gas and farm biogas are carried out. Results show that the hybrid system can reach an efficiency of 60.78% with wood chip gas and 59.09% with farm biogas. Meanwhile, with each composition of wood chip gas varying from 80% to 120%, the IT-SOFC/GT hybrid system could maintain the electrical efficiency higher than 59%. However, in the case of farm biogas, the efficiency of system drops to as low as 55%. It is also found that composition fluctuations of H2 in wood chip gas and CH4 in farm biogas leave the most significant effects on system performance. For safety consideration, fluctuation range of CH4 in farm biogas should be controlled between 86% and 116%; otherwise, failure of gas turbine would occur due to unsafe operating temperatures. Compared with wood chip gas, operation of IT-SOFC/GT hybrid system with farm biogas requires more water vapor available to prevent failure of the reformer due to carbon deposition.
Random Forest Machine Learning Model for Predicting Combustion Feedback Information of a Natural Gas Spark Ignition Engine
Authors: Liu Jinlong , Ulishney Christopher , Dumitrescu Cosmin Emil
Published: July 2020

Engine calibration requires detailed feedback information that can reflect the combustion process as the optimized objective. Indicated mean effective pressure (IMEP) is such an indicator describing an engine’s capacity to do work under different combinations of control variables. In this context, it is of interest to find cost-effective solutions that will reduce the number of experimental tests. This paper proposes a random forest machine learning model as a cost-effective tool for optimizing engine performance. Specifically, the model estimated IMEP for a natural gas spark ignited engine obtained from a converted diesel engine. The goal was to develop an economical and robust tool that can help reduce the large number of experiments usually required throughout the design and development of internal combustion engines. The data used for building such correlative model came from engine experiments that varied the spark advance, fuel-air ratio, and engine speed. The inlet conditions and the coolant/oil temperature were maintained constant. As a result, the model inputs were the key engine operation variables that affect engine performance. The trained model was shown to be able to predict the combustion-related feedback information with good accuracy (R2 ≈ 0.9 and MSE ≈ 0). In addition, the model accurately reproduced the effect of control variables on IMEP, which would help narrow the choice of operating conditions for future designs of experiment. Overall, the machine learning approach presented here can provide new chances for cost-efficient engine analysis and diagnostics work.
Anhydrite (Calcium Sulfate) Mineral as a Novel Weighting Material in Drilling Fluids
Authors: Murtaza Mobeen , Tariq Zeeshan , Mahmoud Mohamed , Kamal Muhammad Shahzad , Al-Shehri Dhafer
Published: July 2020

Different additives such as barite, calcium carbonate, hematite, and ilmenite having high-density and fine solid materials are used to increase the density of drilling fluids. However, some of the weighting additives can cause some serious drilling problems such as barite (particle settling, formation damage, erosion, and insoluble filter cake). In this study and for the first time, anhydrite (calcium sulfate) is used as a weighting additive in the drilling fluids. Several laboratory experiments such as density, rheology, fluid loss, resistivity, and pH were carried out to assess the performance of calcium sulfate as a weighting additive in the drilling fluids. The performance of calcium sulfate as a weighting additive was compared with the commonly used weight enhancing additive calcium carbonate. The results showed that calcium sulfate has higher solubility than calcium carbonate. The fluid loss test showed that both additives lost the same volume of fluid and created the same thickness of filter cake; however, the solubility of calcium sulfate-based filter cake with organic and inorganic acids was higher compared with other weighting materials. Calcium sulfate-based filter cake was completely dissolved using a new formulation that consists of glutamic-diacetic acid (GLDA) chelating agent and potassium carbonate as a convertor. The removal efficiency after 10 h reached 100% in 20 wt% GLDA and 10 wt% potassium carbonate solution at 100 °C.
Experimental Investigation on Mixed Combustion Characteristics of Coal, Tobacco Straw, and Cinder in an Energy-Saving Bake Process
Authors: Yan Yunfei , Zhao Ting , Guo Hongliang , Xu Fulei , Zhang Li , Yang Zhongqing , Ran Jingyu
Published: July 2020

In view of high-energy consumption, high baking cost, and serious pollution emission during the baking process of tobacco leaves, thermogravimetric analysis is employed to investigate the combustion characteristics of coal, tobacco straw, and cinder. Analyzing thermogravimetric-derivative of thermogravimetric (TG-DTG) characteristics of samples with different blending ratios and based on the ignition temperature and burnout temperature, the combustion characteristics of the samples are obtained. Compared with the individual combustion of coal, the blending ratio of the optimal positive effect is obtained. It is illustrated that different blending ratios of coal, tobacco straw, and cinder result in different effects between promotion and inhibition. Tobacco straw is beneficial to burn on fire but adverse to keep combustion of fixed carbon. Compared with the TG and DTG characteristics in different blending ratios of coal, tobacco straw, and corresponding combustion characteristic parameter, it is illustrated that the best blending ratio of tobacco straw is 40%. According to the TG and DTG characteristics of different blending ratios of coal, cinder, and corresponding combustion characteristic parameter, it is shown that the more blending ratio of cinder, the more adverse effect to fixed carbon burning. The composite fuels with 40% tobacco straw, 10% coal cinder, and 50% coal have two obvious advantages. On the one hand, it can maintain quick burning and the volatile combustion of the tobacco straw at low-temperature stage. On the other hand, it can keep continuous combustion of the fixed carbon in coal at high-temperature stage.
Control Optimization of Pump Cycles in Onshore Oilfields With Network and Electric Power Constraints
Authors: Camponogara Eduardo , Seman Laio Oriel
Published: July 2020

In onshore oilfields, sucker rod pumps are deployed to lift fluids from wells to the surface, which are then transferred by a pipeline network to a central facility. Each pump operates according to a cyclic control policy that alternates between a period of production and a period of recess, allowing the reservoir to replenish the fluids. To minimize the peak in the electric power drawn by the sucker rods, previous works have considered the scheduling of the control policies over time. However, when the production system sprawls over a large area, the energy required to force the flow through the pipelines and the pressure drops are significant. To this end, this article develops mixed-integer nonlinear formulations and mixed-integer linear approximations for baseline control-policy scheduling and reconfiguration.
Modal Velocity-Based Multiaxial Fatigue Damage Evaluation Using Simplified Finite Element Models
Authors: Kersch Kurthan , Woschke Elmar
Published: July 2020

This work proposes a new method for the fatigue damage evaluation of vibrational loads, based on preceding investigations on the relationship between stresses and modal velocities. As a first step, the influence of the geometry on the particular relationship is studied. Therefore, an analytic expression for Euler Bernoulli beams with a non-constant cross section is derived. Afterward, a general method for obtaining geometric factors from finite element (FE) models is proposed. In order to ensure a fast fatigue damage evaluation, strongly simplified FE-models are used for the determination of both factors and measurement locations. The entire method is demonstrated on three mechanical structures and indicates a better compromise between effort and accuracy than existing methods. For all examples, the usage of velocities and geometric factors obtained from simplified FE models enables a sufficient fatigue damage calculation.
Properties of Porous PDMS and Stretchability of Flexible Electronics in Moist Environment
Authors: Pan Peng , Bian Zuguang , Song Xin , Zhou Xiaoliang
Published: July 2020

Polydimethylsiloxane (PDMS) is a good choice for the substrate and encapsulation of clinical flexible electronics, since it possesses some distinguished characteristics such as high elasticity, excellent optical characteristic, good biocompatibility, and stability. In the present study, the emulsion polymerization technique was used once more to fabricate porous PDMS, which is expected to assure the sweat penetration through the flexible electronics, and therefore to reduce the irritation to the skin due to the flexible electronics. To assess the mechanical performance of flexible electronics with moisture, the saturated moisture concentration, coefficient of moisture expansion, and elastic modulus of porous PDMS for different relative wetness fraction were measured in experiment. Meanwhile, an asymptotic homogenization method (AHM) was adopted to predict these parameters theoretically. Results indicate that the saturated moisture concentration is linear to the porosity, while the coefficient of moisture expansion is independent of the porosity, both of which are well verified by the experimental data. The fitted formula on the elastic modulus for different porosities suggested in our previous study was developed to take account of the relative wetness fraction based on the experimental data. These three parameters were finally applied in calculating the stretchability of a flexible electronic with serpentine interconnects in moist environment. Numerical stimulation reveals that the stretchability increases with the porosity and relative wetness fraction of the substrate and encapsulation. The present work is hoped to pave the way for flexible electronics in clinical applications.
A Review of Physically Based and Thermodynamically Based Constitutive Models for Soft Materials
Authors: Xiang Yuhai , Zhong Danming , Rudykh Stephan , Zhou Haofei , Qu Shaoxing , Yang Wei
Published: July 2020

In this paper, we review constitutive models for soft materials. We specifically focus on physically based models accounting for hyperelasticity, visco-hyperelasticity, and damage phenomena. For completeness, we include the thermodynamically based viscohyperelastic and damage models as well as the so-called mixed models. The models are put in the frame of statistical mechanics and thermodynamics. Based on the available experimental data, we provide a quantitative comparison of the hyperelastic models. This information can be used as guidance in the selection of suitable constitutive models. Next, we consider visco-hyperelasticity in the frame of the thermodynamic theory and molecular chain dynamics. We provide a concise summary of the viscohyperelastic models including specific strain energy density function, the evolution laws of internal variables, and applicable conditions. Finally, we review the models accounting for damage phenomenon in soft materials. Various proposed damage criteria are summarized and discussed in connection with the physical interpretations that can be drawn from physically based damage models. The discussed mechanisms include the breakage of polymer chains, debonding between polymer chains and fillers, disentanglement, and so on.
Probabilistic Finite Element Analysis of Cooled High-Pressure Turbine Blades—Part B: Probabilistic Analysis
Authors: Högner Lars , Voigt Matthias , Mailach Ronald , Meyer Marcus , Gerstberger Ulf
Published: July 2020

Modern high-pressure turbine (HPT) blade design stands out due to high complexity comprising three-dimensional blade features, multipassage cooling system (MPCS), and film cooling to allow for progressive thermodynamic process parameters. During the last decade, probabilistic design approaches have become increasingly important in turbomachinery to incorporate uncertainties such as geometric variations caused by manufacturing scatter. In Part B of this two-part article, real geometry effects are considered within a probabilistic finite element (FE) analysis that aims at sensitivity evaluation. The knowledge about the geometric variability is derived based on a blade population of more than 400 individuals by means of parametric models that are introduced in Part A. The HPT blade population is statistically assessed, which allows for reliable sensitivity analysis and robustness evaluation taking the variability of the airfoil, profiled endwalls (PEWs) at hub and shroud, wedge surfaces (WSFs), and the MPCS into account. The probabilistic method—Monte Carlo simulation (MCS) using an extended Latin hypercube sampling (eLHS) technique—is presented subsequently. Afterward, the FE model that involves thermal, linear-elastic stress, and creep analysis is described briefly. Based on this, the fully automated process chain involving computer-aided design (CAD) model creation, FE mesh morphing, FE analysis, and postprocessing is executed. Here, the mesh morphing process is presented involving a discussion of the mesh quality. The process robustness is assessed and quantified referring to the impact on input parameter correlation. Finally, the result quantities of the probabilistic FE simulation are evaluated in terms of sensitivities. For this purpose, regions of interest are determined, wherein the statistical analysis is conducted to achieve the sensitivity ranking. A significant influence of the considered geometric uncertainties onto mechanical output quantities is observed, which motivates to incorporate these in modern design strategies or robust optimization.