bluuebunny/crossref_metadata_2025 huggingface dataset:
The prevalence and risk factors of venous thromboembolism in hospitalized patients with acute exacerbation of chronic obstructive pulmonary disease
Authors: Pang Hongyan , Wang Lei , Liu Jie , Wang Shengfeng , Yang Yuanhua , Yang Ting , Wang Chen
Published: September 2018

Introduction

Venous thromboembolism (VTE) in patients with acute exacerbation of chronic obstructive pulmonary disease (AECOPD) is not rare, which would affect the patient’s prognosis.

Objectives

To examine the prevalence, risk factors and clinical characteristics of AECOPD patients with VTE.

Methods

We performed this multi‐center, prospective, observational study that involved 16 hospitals in China. Patients admitted to hospital due to AECOPD were consecutively enrolled. Baseline characteristics, VTE risk factors, symptoms, signs and auxiliary examination results were collected. Lower limb venous ultrasound and computed tomography pulmonary angiography were examined.

Results

Between June 2009 and October 2010, a total of 1144 AECOPD patients (the average age 72.0 ± 9.1 years, 761 males) were enrolled in this study. Seventy‐eight (6.8%) were diagnosed with VTE, including 24 PE, 64 DVT, 10 combined PE and DVT. VTE patients were older than non‐VTE patients. History of venous thromboembolism and lower extremity varicose vein, and presence of longer immobility (≥3 days), lower limbs problems of swelling, pain and walking difficulties, diuretics use, fever, syncope, higher d‐dimer and lower hemoglobin were more common in VTE patients than in non‐VTE patients. After adjusting the covariates, venous thrombosis history, prolonged immobility (≥3 days), lower limb pain before hospitalization, higher d‐dimer independently associated with VTE development. Regular glucocorticoid use was not associated with increased risk of VTE in this set of patients.

Conclusion

VTE is relatively common among hospitalized AECOPD patients. Conventional prophylactic anticoagulant therapy may be considered for those hospitalized AECOPD patients with risk factors.
Comparative risk of genital infections associated with sodium‐glucose co‐transporter‐2 inhibitors
Authors: Dave Chintan V. , Schneeweiss Sebastian , Patorno Elisabetta
Published: September 2018

The extent to which sodium‐glucose co‐transporter‐2 (SGLT2) inhibitors increase the risk of genital infections in routine clinical care, compared with other antidiabetic medications, is not clear, or whether the increased risk is consistent across gender or age subgroups, within individual SGLT2 agents, or if it is more pronounced at a particular time after treatment initiation. We conducted a retrospective cohort study using two US commercial claims databases (2013‐2017). In the primary analysis, 1:1 propensity score‐matched cohorts of female and male subjects with type 2 diabetes mellitus initiating SGLT2 versus dipeptidyl peptidase‐4 inhibitors were created. The outcome was a composite of genital candidal infections, vaginitis or vulvovaginitis in women, and genital candidal infections, balanitis, balanoposthitis, phimosis or paraphimosis in men. Among propensity score‐matched cohorts of 129 994 women and 156 074 men, the adjusted hazard ratio (HR) and excess risk per 1000 person‐years for SGLT2 versus DPP‐4 inhibitors was 2.81 (95% confidence interval [CI], 2.64, 2.99) and 87.4 (95% CI, 79.1, 96.2) respectively for women, and was 2.68 (95% CI, 2.31, 3.11) and 11.9 (95% CI, 9.3‐15.0) for men. Findings were similar in the SGLT2 inhibitor versus GLP‐1 agonist comparison, more pronounced in the subgroup of patients aged ≥60 (HR, 4.45 [95% CI, 3.83‐5.17] in women and 3.30 [95% CI, 2.56‐4.25] in men), and no meaningful difference across individual SGLT2 inhibitors was identified. This increase in risk was evident in the first month of treatment initiation and remained elevated throughout the course of therapy. SGLT2 inhibitors were associated with an approximately 3‐fold increase in risk of genital infections.
Silage and haylage for horses
Authors: Müller Cecilia Elisabeth
Published: September 2018

This review covers current understanding on the use of wrapped forages such as silage and haylage as forage sources in equine nutrition. Silage (dry‐matter content <500 g per kg) generally have higher concentration of lactic acid and other fermentation products and has a lowerpHcompared to haylage (dry‐matter content >500–840 g per kg), as the lack of water in haylage restricts fermentation. The differences in biochemical and microbial composition in forage conserved as silage, haylage and hay have not been reported to influence digestion or hindgut function in horses differently. Studies on equine intake and preference of forages conserved as silage, haylage or hay are scarce and contradictory; both low voluntary intake and preference for silage have been reported. Studies on aerobic storage stability of opened bales are few, but are needed, as daily forage consumption is often low on horse farms, which may increase the risk of aerobic deterioration of forage in opened bales before they have been fed. A high hygienic quality of wrapped forages for horses is crucial: (a) as mould spores may cause chronic respiratory disorders; (b) as mycotoxins may cause intoxications, skin problems, gastrointestinal disorders and reproduction failures; (c) as presence ofClostridium botulinumand its toxin botulin may cause fatal disease; and (d) as other microbes (e.g.,Listeria monocytogenes) may cause illness in the horse. Further research is needed especially for systems of assessment of hygienic quality of haylage, and how to prolong aerobic storage stability in opened bales.
Global warming and the Anthropocene
Authors: Summerhayes Colin P. , Zalasiewicz Jan
Published: September 2018

By burning fossil fuels, humans have changed the carbon cycle, loading the atmosphere with extra carbon dioxide (CO2). Before the current Ice Age, high atmospheric CO2 levels generated warm climates. The Ice Age developed as the volcanic supply of CO2 lessened, and rock weathering increased. The CO2 lost from the atmosphere by chemical weathering was transferred to the ocean and trapped in carbonate sediments. Humans now replicate what volcanic activity did in the distant past, our CO2 emissions driving global warming. Earth's present climate should be cool, based on the present configuration of the Earth's orbit and the tilt of its axis, and on the decline in sunspot activity since 1990. Warming will grow further with rising emissions, further raising sea level. If business continues as usual we will end with an Eocene‐like ‘greenhouse climate’ and drowned coastal cities.
American Headache Society Survey About Urgent and Emergency Management of Headache Patients
Authors: Minen Mia T. , Ortega Emma , Lipton Richard B. , Cowan Robert
Published: September 2018

Background

Emergency department (ED) visits for migraine are burdensome to patients and to the larger healthcare system and society. Thus, it is important to determine strategies used to prevent ED visits and the common communication patterns between headache specialists and the ED team.

Objective

We sought to understand: (1) Whether headache specialists use headache management protocols. (2) The strategies they use to try and reduce the number of ED visits for headache. (3) Whether protocols are used in the EDs with which they are affiliated. (4) The level of satisfaction with the coordination of care between headache physicians and the ED.

Methods

We surveyed via SurveyMonkey members of the American Headache Society Emergency Department/Refractory/Inpatient (EDRI) Section to understand their practice regarding patients who call their office to be seen urgently, and to understand their communication with their local EDs.

Results

There were 96 eligible AHS members, 50 of whom responded to questionnaires either by email or in person (52%). Of these, 59% of respondents reported giving rescue treatment to their patients to manage acute attacks. Fifty‐four percent reported using standard protocols for outpatients not responding to usual acute treatments. In the event of a request for urgent care, 12% of specialists reported bringing patients into the office most or all of the time, and 20% reported sending patients to the ED some or most of the time for headache management. Thirty‐six percent reported prescribing a new medicine and 30% reported providing telephone counseling some/most/all of the time. Sixty percent reported that their ED has a protocol for migraine management. Overall, 38% were usually or very satisfied with the headache care in the ED.

Conclusions

A substantial number of headache specialists are dissatisfied with the care their patients receive in the ED. More standardized protocols for ED visits by patients with known headache disorders, and clear guidelines for communication between ED providers and treating physicians, along with better methods for follow‐up following discharge from the ED, might appear to improve this issue.
Exercise and glucose control in children with insulin resistance: prevalence of non‐responders
Authors: Álvarez C. , Ramírez‐Campillo R. , Cano‐Montoya J. , Ramírez‐Vélez R. , Harridge S. D. R. , Alonso‐Martínez A. M. , Izquierdo M.
Published: September 2018

Background

Exercise training improves cardiometabolic outcomes in ‘mean terms’, but little information is available in children about the impact of the frequency/week and the wide inter‐individual variability to exercise training reported in adults.

Objectives

We compared the effects of resistance training (RT) and high‐intensity interval training (HIT), and ‘high’ and ‘low’ frequency of training/week, for their effectiveness in decreasing insulin resistance (IR) levels in schoolchildren. A second aim was to decscribe and compare the prevalence of non‐responders (NRs) between the different frequencies of training protocol.

Methods

Fifty‐three schoolchildren with IR were randomly assigned into four groups: RT at high frequency (three times/week), HIT at high frequency, RT at a low frequency (two times/week) and HIT at low frequency. The intervention lasted 6 weeks. Blood samples and body composition, blood pressure and performance measurements were taken before and after the intervention.

Results

The prevalence of NRs was similar between the RTHF and HITHF (25.0% vs. 25.0%, P > 0.05) and RTLF and HITLF groups (20.0% vs. 46.6%, P = 0.174) for decreasing homeostasis model assessment of IR. However, significant differences in the prevalence of NRs were detected between RTHF and HITHF groups in fasting glucose (FGL) (18.7% vs. 58.3%, P < 0.031).

Conclusions

Both RT and HIT improves the glucose control parameters in schoolchildren over 6 weeks, but only HIT is independent of a high or low frequency of training/week. The prevalence of NRs is similar for decreasing homeostasis model assessment of IR comparing each exercise mode in high vs. low frequency/week. However, both high‐ and low‐frequency RT and HIT results in differences in the prevalence of NRs for FGL and other cardiometabolic and performance outcomes.
Do Countries Matter More in Determining the Relationship Between Employee Welfare and Financial Performance?
Authors: Gupta Kartick , Krishnamurti Chandrasekhar
Published: September 2018

Extant literature suggests that employee‐friendly practices influence corporate decision‐making. Using a bargaining framework, we examine the role of country‐level determinants in influencing employee‐friendly practices and their impact on value creation. Utilizing a comprehensive sample of 25,483 firm‐year observations from 56 countries, we find that firms domiciled in countries with weak employment protection and regulations can potentially benefit by voluntarily undertaking employee‐friendly practices. Also, in countries with flexible labor market conditions, firm value is enhanced by undertaking employee‐friendly practices. Furthermore, the importance of employee‐friendly practices in value creation is observed strongly in countries that provide better infrastructure, productivity, and incentives.
Association between the T6459C point mutation of the mitochondrial MT‐CO1 gene and susceptibility to sepsis among Chinese Han people
Authors: Shen Xiaodong , Han Guoxin , Li Shuoshuo , Song Yang , Shen Hong , Zhai Yongzhi , Wang Yingchan , Zhang Fei , Dong Ning , Li Tanshi , Yao Yongming , Zhu Haiyan
Published: September 2018

To search for an association between sepsis and mitochondrial genetic basis, we began our study. In this study, a proband harbouring mitochondrial T6459C mutation with sepsis and his Chinese Han pedigree including 7 members of 3 generations were enrolled. General information, blood parameters and mitochondrial full sequence scanning of all members were performed, and cellular functions, including cellular reactive oxygen species (ROS) levels, mitochondrial membrane potential (MMP), degrees of cell apoptosis and adenosine triphosphate (ATP) concentrations, were measured in members with and without the T6459C mutation. Through mitochondrial full sequence scanning and analysis of all members we found, the maternal members (I‐1, II‐1, II‐2 and II‐4) in this Chinese Han pedigree all had the mitochondrial T6459C mutation and were used as the mutation group. The non‐maternal members (II‐3, III‐1 and III‐2) did not have this mutation and were used as the non‐mutation group. The differences in all indicators, including the blood routine, blood biochemistry and coagulation function tests, between members in these two groups were not significant. Under the non‐stimulation condition, the mutation group had higher ROS levels (4210.42 ± 1043.35 vs 3387.78 ± 489.66, P = .028) and apoptosis ratios (P = .004) and lower ATP concentrations (P = .049) and MMP levels (P = .047) than the non‐mutation group. After 6 hours of simulated LPS stimulation, the mutation group had significantly increased ROS levels (5759.25 ± 2297.90 vs 3862.00 ± 1519.77, P = .045) compared with the non‐mutation group, whereas the mutation group continued to demonstrate higher ROS levels (P = .045) and apoptosis ratios (P = .003) and lower MMP levels (P = .005) and ATP concentrations (P = .010). We speculated that the mtDNA T6459C mutation might be the basis for the genetic susceptibility to sepsis.
Fear, Segregation, and Civic Engagement in Urban Trinidad
Authors: Forde Maarit
Published: September 2018

Este ensayo investiga una economía espacial de segregación y confinamiento que da forma al compromiso cívico de los pobres urbanos que también perpetúa las jerarquías raciales y de clase. Basado en un estudio etnográfico de un barrio empobrecido de Puerto España, el ensayo explora la morale colonial y neoliberal que perpetúa la segregación de clases en la Trinidad y Tobago contemporánea. La economía espacial resultante de confinamiento restringe la movilidad geográfica y social de los pobres urbanos. También regula su acceso al espacio público y reduce sus oportunidades de participar en debates públicos y hacer declaraciones políticas. En un espacio nacional fragmentado, los pobres urbanos quedan excluidos de las negociaciones de vida y futuro en común. [antropología social, Caribe, clase social, colonialismo, postcolonialismo, urbano]
Indigenous Intermediaries in Prior Consultation Processes: Bridge Builders or Silenced Voices?
Authors: Eichler Jessika
Published: September 2018

El derecho a la consulta previa ejemplifica uno de los avances jurídicos más fundamentales en Latino América y específicamente el estado plurinacional de Bolivia. El sector hidrocarburífero en el Gran Chaco boliviano demuestra qué desafíos afrontamos hoy en día. Esta contribución busca iluminar un desafío en la aplicación de dicho derecho en particular, el rol de intermediarios indígenas, lo que es esencial para determinar el resultado del proceso. La función de dos actores se examinará en más detalle. Primeramente, líderes indígenas al nivel local, regional y nacional juegan un papel importante en influir los procesos de consulta previa y, por consiguiente, se encuentran en una situación más vulnerable frente a prácticas estatales o empresariales. Segundo, nuevos actores tales como asesores indígenas—incluyendo traductores, abogados e ingenieros—pueden tender puentes entre las comunidades y el estado. Se brindará una evaluación de estos dos grupos para demostrar cómo afectan los procesos de consulta y qué rol asumen hacia las comunidades y el estado.
Evaluation of consumers’ perception regarding frankfurter sausages with different healthiness attributes
Authors: Polizer Rocha Yana Jorge , Lapa‐Guimarães Judite , de Noronha Regina Lucia F. , Trindade Marco Antonio
Published: September 2018

The objective of this study was to evaluate consumers’ perception regarding frankfurter sausages with different healthiness attributes. Descriptions of different frankfurter sausages were used (traditional, with natural antioxidants, with sodium reduction, with fat reduction, source of dietary fiber, and with omega 3) as stimuli. All consumers evaluated the six stimuli and performed a test of word association before evaluating the acceptance of each concept, along with the familiarity level, consumers’ emotional responses, and their perceptions of food with healthiness attributes. The category “healthiness” presented the highest frequency mentions for the stimuli with healthier attributes. The negative associations related to the traditional frankfurter sausages were unhealthy, fat/cal, and high blood pressure. Regarding the emotional evaluations, significant differences were found between different types of sausage. It is possible to conclude that different types of frankfurter sausage promoted distinctive associations and emotions when recurring categories were considered, suggesting that the development and promotion of these kinds of products must consider all the particularities obtained through these results.

Practical applications

There is a potential market for the development of healthier meat products, due to the exposure of traditional meat products in the media regarding possible adverse health effects. The information and peculiarities obtained in this study on the perception of consumers in relation to sausage with different attributes of healthiness can direct the industry in the development and promotion of these products. Besides that, these results indicate the importance of carrying out research with product concepts to evaluate consumer perception in order to develop and launch those products in the consumer market.
Intergenerational influences on childhood anaemia
Authors: Onyeneho Nkechi G. , Corsi Daniel J. , Kurpad Anura , Subramanian SV
Published: September 2018

Prior research on assessing intergenerational influences on child anaemia has largely approached it from purely maternal perspective. Although there is much merit to focus on that, it is an extremely limited/reductionist view of understanding intergenerational influences. We expanded the intergenerational influences to include the fathers and overall of intergenerational household transfers. We analysed a sample of 19,619 mother–father‐offspring trios from the 2015–2016 Indian National Fertility and Health Survey with available data on haemoglobin (Hb). Multinomial logistic regression models were used to establish associations between parent anaemia, household characteristics, and categories of offspring anaemia. Maternal and paternal Hb was measured as in children using a finger prick blood sample. The primary outcome was child's Hb level (in g/dl) and grades of anaemia defined as mild (10–10.9 g/dl), moderate (7–9.9 g/dl), and severe (<7 g/dl). Mean Hb was 10.1 g/dl for children, 14.2 g/dl among fathers, and 11.4 g/dl among mothers. Hb correlation was 0.1 between fathers and offspring and 0.2 between mothers and offspring (P < 0.001 for all correlations). Maternal–paternal Hb correlations were consistent across quintiles of wealth index. Maternal anaemia was associated with odds ratio of 1.3 (95% CI [1.1, 1.4]) and 1.6 (95% CI [1.4, 1.7]) for childhood mild and moderate/severe anaemia, respectively. Paternal mild anaemia was associated with an odds ratio of 1.1 (95% CI [0.9, 1.4]) and 1.4 (95% CI [1.2, 1.7]) for child moderate/severe anaemia. The clustering of poor circumstances suggests that public health strategies target social deprivation at the household level. A comprehensive perspective will provide holistic interventions to control childhood anaemia.
Rapid palatal expansion (RPE): Meta‐analysis of long‐term effects
Authors: Cannavale Rosangela , Chiodini Paolo , Perillo Letizia , Piancino Maria Grazia
Published: September 2018

Objects

Rapid palatal expansion (RPE) is a widespread orthopaedic procedure used in several clinical situations. The aim of the study was to provide a systematic review and meta‐analysis of transverse intercanine and intermolar width changes after RPE and long‐term effects.

Setting and Sample Population

A systematic literature search was conducted until January 2018 on original studies with RPE treatment.

Material and Methods

Intercanine and intermolar distance were measured at the start of RPE (T1, median age 9.2 years) and at the end of treatment (T2). The long‐term evaluation was conducted on a subset of articles with 5‐year follow‐up (T3).

Results

Eighteen studies T1‐T2 and 5 studies T3 were selected. Regarding the intercanine distance, the RPE resulted in a gain of space T1‐T2 of 3.73 mm with a significant heterogeneity (P < 0.0001; I2 = 94.21%) and a relapse T2‐T3 of −0.81 mm with a significant heterogeneity (P < 0.0001; I2 = 95.8%); the overall gain of space was 2.91 mm. Regarding the intermolar distance, the RPE resulted in a gain of space T1‐T2 of 4.85 mm with a significant heterogeneity (P < 0.0001; I2 = 92.41%) and a relapse T2‐T3 of −0.47 mm with a significant heterogeneity (P < 0.0001; I2 = 87.5%); the overall gain of space was 4.38 mm. Meta‐regression analysis showed that at younger age, the amount of anterior expansion is similar to posterior. With increasing age, the anterior opening diminishes significantly more than the posterior, being half of the posterior at 15 years.

Conclusion

Because long‐term results were obtained with simultaneously fixed appliances and long upper retention, RPE should be carefully considered before using.
Ultrasound assessment of the prevalence of increased gastric contents and volume in elective pediatric patients: A prospective cohort study
Authors: Bouvet Lionel , Bellier Nicolas , Gagey‐Riegel Anne‐Charlotte , Desgranges François‐Pierrick , Chassard Dominique , De Queiroz Siqueira Mathilde
Published: September 2018

Background

Though pulmonary aspiration of gastric contents occurs mainly in the setting of emergency surgery, it may also occur in children scheduled for elective surgery without any obvious clinical risk factor. Increased gastric content volume is one the predisposing factors for pulmonary aspiration that could affect such children and may be identified using ultrasound examination of the gastric antrum.

Aims

We aimed to assess the prevalence of “at‐risk stomach” defined by ultrasound visualization of any solid content in the antrum and/or by calculated gastric fluid volume > 1.25 mL/kg, in children scheduled for elective surgery.

Methods

Children scheduled for elective surgery were consecutively included into this prospective cohort study. Preoperative ultrasound examination of the antrum was performed in both the supine and the right lateral decubitus positions. Gastric fluid content was assessed using a 0‐2 qualitative grading scale. The antral cross‐sectional area was also measured in both the supine and the right lateral decubitus positions, allowing the calculation of the gastric fluid volume according to a formula previously described.

Results

We analyzed 200 elective children. Median duration of fasting was 4 hours for liquids and >13 hours for solids. None of the children included in this study had evidence of solid content. Six (3%) children had a Grade 2 antrum (fluid content seen in both the supine and the right lateral decubitus positions). Two children had a gastric fluid volume >1.25 mL/kg. The prevalence of “at‐risk stomach” was 1% (95% confidence interval: 0.2%‐3.9%).

Conclusion

According to our results, only 1% of elective children had potentially increased risk for pulmonary aspiration. Further studies should be performed in order to define the target population of elective children for which ultrasound assessment of gastric content should be performed prior to general anesthesia.
Oral manifestations of Langerhans cell histiocytosis: A case series
Authors: Neves‐Silva Rodrigo , Fernandes Diego Tetzner , Fonseca Felipe Paiva , Rebelo Pontes Helder Antonio , Brasileiro Bernardo Ferreira , Santos‐Silva Alan Roger , Vargas Pablo Agustin , Lopes Marcio Ajudarte
Published: September 2018

Aim

Langerhans cell histiocytosis (LCH) is an unusual proliferative disorder of bone marrow‐derived histiocytes (Langerhans cells) that can produce focal or systemic manifestations. Oral manifestations of LCH can present as single or multiple lesions and can be a challenge in clinical practice. The aim of this paper is to present the clinicopathological features of a series of nine patients with oral involvement.

Methods and results

The patient's age ranged from 2 to 63 years being five males and four females. The most common oral site involvement was the hard‐palate mucosa. Ulceration was the main clinical feature. Only two patients showed clearly jawbone involvement. In eight out of nine patients, the diagnosis of LCH was established because of the oral manifestations.

Conclusion

The recognition of the clinical features of LCH oral manifestation is important to avoid misdiagnosis and to the establishment of the correct treatment. Thus, dentists can play a vital role in the diagnosis of LCH since oral lesions may be the earliest manifestation and sometimes the only sign of the disease. Furthermore, oral lesions may be the early signs of disease reactivation or a multisystem disease indication.
Aid for trade and export diversification in recipient‐countries
Authors: Gnangnon Sèna Kimm
Published: September 2018

The Aid‐for‐Trade (AfT) Initiative was launched by the Members of the World Trade Organization (WTO) with a view to helping developing countries and the least‐developed countries (LDCs) expand their trade. The current paper contributes to the literature on AfT effectiveness by examining how AfT affects recipient‐countries' export product diversification. The analysis has been carried out on a sample of 104 AfT recipient‐countries over the period 2002–2015 and uses the two‐step system generalised methods of moments (GMM) approach. Results show that AfT flows are conducive to export product diversification in recipient‐countries. In addition, the analysis has shown a positive impact of the cumulative AfT flows on the export product diversification path of these countries. These results apply as well to the subsamples of LDCs and other developing countries. One policy implication of these results is that a scale‐up of AfT would help recipient‐countries to diversify their export products baskets and hence facilitate their greater integration into the global trading system.
Identifying the Relationships Between Response Behaviors for Reading Comprehension Items and Student Characteristics
Authors: Özyeter Neslihan T. , Kutlu Ömer
Published: September 2018

The study aimed to identify the students’ characteristics (perception of self-efficacy, resistance, persistence, taking responsibility and competence for their cognitive processes) that might affect the response behaviors of fifth grade students for open ended questions written in different cognitive levels. This study was designed as relational survey model research. Sample consisted of 392 5th grade students selected by purposeful sampling from Yenimahalle, Mamak and Cankaya districts in Ankara city. Data was collected with reading comprehension achievement test, response behaviors form and student information survey. Analysis was conducted with 366 students’ data after missing values were removed. MPlus package program was utilized to analyze data and structural equation modelling was used. The findings of the research revealed that response behaviors for open ended questions written in different cognitive levels in Turkish learning area were found to be predicted low and at a significant level by students’ perception of self-efficacy, persistence, resistance, taking responsibility and cognitive skills. It might be concluded that improving children’s perception for cognitive and metacognitive skills can enhance their thinking process, lead them to perform complex response behaviors and affect positively their higher order thinking process. In other words, students with high cognitive and metacognitive skills show higher level response behaviors such as putting themselves into author’s shoes, relating their own life to the event in the text or using imagination. Therefore, they can comprehend what they read easily and express it back.
Computational Fluid Dynamics Simulations of Nonlinear Sloshing in a Rotating Rectangular Tank Using the Level Set Method
Authors: Grotle Erlend Liavåg , Bihs Hans , Æsøy Vilmar , Pedersen Eilif
Published: September 2018

In this paper, numerical simulations of nonlinear sloshing in rectangular tanks are presented. Model implementations in the open source software reef3d are tested, and the results are compared with experimental data from three different conditions. The interface location is compared for both linear and nonlinear sloshing. The nonlinear sloshing is simulated in both two-dimensional (2D) and three-dimensional (3D). Video images from the SPHERIC project are compared with simulations for the interface. A condition with lateral wave impacts in sloshing, with a frequency close to the natural frequency of the first mode, can be found in this case. The numerical model is solving the Reynolds-averaged Navier–Stokes (RANS) equations with the k–ω turbulence model. The level set method is used to capture the interface. Higher order discretization schemes are implemented to handle time-evolution and convective fluxes. A ghost cell method is used to account for solid boundaries and parallel computations. It is found that the limiting factor for the eddy-viscosity has significant influence in the nonlinear sloshing cases. As the sloshing becomes more violent, the increased strain at the gas–liquid interface overproduces turbulence energy with unrealistically high damping of the motion. Three-dimensional simulations show slightly better comparison than 2D. Due to nonlinearities and small damping, the time to reach steady-state may take several cycles. The last case shows promising results for the global motion. As expected, the breakup of the liquid surface makes it difficult to resolve each phase. But overall, the numerical model predicts the sloshing motion reasonably well.
Numerical and Experimental Fluid–Structure Interaction-Study to Determine Mechanical Stresses Induced by Rotating Stall in Unshrouded Centrifugal Compressor Impellers
Authors: Mischo B. , Jenny P. , Mauri S. , Bidaut Y. , Kramer M. , Spengler S.
Published: September 2018

Unshrouded industrial centrifugal compressor impellers operate at high rotational speeds and volume flow rates. Under such conditions, the main impeller blade excitation is dominated by high frequency interaction with stationary parts, i.e., vaned diffusers or inlet guide vanes (IGVs). However, at severe part load operating conditions, sub-synchronous rotating flow phenomena (rotating stall) can occur and cause resonant blade vibration with significant dynamic (von-Mises) stress in the impeller blades. To ensure high aerodynamic performance and mechanical integrity, part load conditions must be taken into account in the aeromechanical design process via computational fluid dynamics (CFD) and finite element method (FEM) analyzes anchored by experimental verification. The experimental description and quantification of unsteady interaction between rotating stall cells and an unshrouded centrifugal compression stage in two different full scale compression units by Jenny and Bidaut (“Experimental Determination of Mechanical Stress Induced by Rotating Stall in Unshrouded Impellers of Centrifugal Compressors”, ASME J. Turbomach. 2016; 139(3):031011-031011-10) were reproduced in a scaled model test facility to enhance the understanding of the fluid–structure interaction (FSI) mechanisms and to improve design guide lines. Measurements with strain gauges and time-resolved pressure transducers on the stationary and rotating parts at different positions identified similar rotating stall patterns and induced stress levels. Rotating stall cell induced resonant blade vibration was discovered for severe off-design operating conditions and the measured induced dynamic von-Mises stress peaked at 15% of the mechanical endurance limit of the impeller material. Unsteady full annulus CFD simulations predicted the same rotating stall pressure fluctuations as the measurements. The unsteady Reynold's Averaged Navier-Stokes simulations were then used in FEM FSI analyses to predict the stress induced by rotating stall and assess the aerodynamic damping of the corresponding impeller vibration mode shape. Excellent agreement with the measurements was obtained for the stall cell pressure amplitudes at various locations. The relative difference between measured and mean predicted stress from fluid–structure interaction was 17% when resonant blade vibration occurred. The computed aerodynamic damping was 27% higher compared to the measurement.
Iterative Learning Method for Drilling Depth Optimization in Peck Deep-Hole Drilling
Authors: Han Ce , Luo Ming , Zhang Dinghua , Wu Baohai
Published: September 2018

Due to the enclosed chip evacuation space in deep hole drilling process, chips are accumulated in drill flutes as drilling depth increases, resulting in the increase of drilling torque and lead to drill breakage. Peck drilling is a widely used method to periodically alleviate the drilling torque caused by chip evacuation; the drilling depth in each step directly determines both drill life and machining efficiency. The existing drilling depth optimization methods face problems including low accuracy of the prediction model, the hysteresis of signal diagnosis, and onerous experiments. To overcome these problems, a novel drilling depth optimization method for peck drilling based on the iterative learning optimization is proposed. First, the chip evacuation torque coefficients (CETCs) are introduced into the chip evacuation torque model to simplify the model for learning. Then, the effect of chip removal process in peck drilling on drilling depth is analyzed. The extended depth coefficient by chip removal (EDCbCR) is introduced to develop the relationship between the extended depth in each drilling step and drilling depth. On the foundation of the modeling above, an iterative learning method for drilling depth optimization in peck drilling is developed, in which a modified Newton's method is proposed to maximize machining efficiency and avoid drill breakage. In experiments with different cutting parameters, the effectiveness of the proposed method is validated by comparing the optimized and measured results. The results show that the presented learning method is able to obtain the maximum drilling depth accurately with the error less than 10%.
An Integrated Dual Ultrasonic Selective Powder Dispensing Platform for Three-Dimensional Printing of Multiple Material Metal/Glass Objects in Selective Laser Melting
Authors: Zhang Xiaoji , Wei Chao , Chueh Yuan-Hui , Li Lin
Published: September 2018

In this paper, we present a new approach of combining point-by-point selective powder delivery with powder bed fusion for multiple material (metal/glass) components printing. Dual ultrasonic vibration was used to achieve stable flowrates of both 316 L steel and soda-lime glass powders which were dispensed selectively and separately. The effects of the stand-off distance and the scanning speeds on the quality of the formed layers were investigated. The results showed that the ratio between the stand-off distance and the powder size (h/d) should be lower than 3 for accurate selective material deposition. However, in practical processing, for preventing the nozzle from being damaged by the parts, the stand-off distance was larger than three times of the powder size. Different laser processing parameters were developed for processing the metal and glass due to material property differences. The interfaces between 316 L and soda-lime glass were examined. A number of 3D objects consisting of metal and glass were printed using this method.
Corrosion Interaction of 9%Cr Ferritic/Martensitic Steels at 450 and 550 °C With Flowing Pb–Bi Eutectic Containing 10−7 Mass % Dissolved Oxygen
Authors: Tsisar Valentyn , Schroer Carsten , Wedemeyer Olaf , Skrypnik Aleksandr , Konys Jürgen
Published: September 2018

Corrosion behavior of 9%Cr F/M P92, E911, and EUROFER steels was investigated in flowing (2 m/s) Pb–Bi with 10−7 mass % O at 450 and 550 °C for up to 8766 and 2011 h, respectively. The steels show mixed corrosion modes simultaneously revealing protective scale formation, accelerated oxidation, and solution-based attack. At 450 °C, the accelerated oxidation resulted in a metal recession averaging 6 μm (± 2 μm) after ∼ 8766 h, while local solution-based corrosion attack ranged from ∼40 to 350 μm. At 550 °C, the accelerated oxidation resulted in a metal recession of about 10 μm (± 2 μm) after ∼ 2011 h. Solution-based corrosion attack appears more regularly at 550 °C, with a maximum depth ranged from ∼90 to 1000 μm. The incubation time for the solution based attack at 450 °C is 500–2000 h and < 300 h at 550 °C.
Stress Intensity Factor Interaction for Subsurface to Surface Flaw Transformations Under Stress Concentration Fields
Authors: Dulieu Pierre , Lacroix Valéry , Hasegawa Kunio
Published: September 2018

If a single subsurface flaw is detected that is close to a component's free surface, a flaw-to-surface proximity rule is used to determine whether the flaw should be treated as a subsurface flaw, or transformed to a surface flaw. The transformation from subsurface to surface flaw is adopted as flaw-to-surface proximity rules in all fitness-for-service (FFS) codes. These proximity rules are applicable when the component's free surface is without a stress concentration. On the other hand, subsurface flaws have been found under notches, such as roots of bolts, toes in welded joints, or geometrical discontinuities of components. The stress intensity factors of the subsurface flaws are affected by the stress concentrations caused by the notches. The stress intensity factor of the subsurface flaw increases with increasing stress concentration factor of the notch and decreasing ligament distance between tip of the subsurface flaws and the notch, for a given notch width. Such subsurface flaws are transformed to surface flaws at a distance from the notch tip for conservative evaluations. This paper shows the interactions of stress intensity factors of subsurface flaws under stress concentration fields. Based on the interaction, a flaw-to-surface proximity criterion is proposed for a circular flaw under the stress concentration field induced by a notch.
A Micromachined Pb(Mg1/3Nb2/3)O3-PbTiO3 Single Crystal Composite Circular Array for Intravascular Ultrasound Imaging
Authors: Li Sibo , Tian Jian , Jiang Xiaoning
Published: September 2018

This paper describes the design, fabrication, and characterization of a micromachined high-frequency Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) single crystal/epoxy 1–3 composite ultrasound circular array. The 1–3 composites were fabricated by deep reactive ion etching (DRIE) of PMN-PT single crystal. The feature size of single crystal pillars was 18 μm in diameter. The kerf between pillars was less than 4 μm. A 50-element circular array transducer (radially outward) with the pitch of 100 μm was wrapped around a needle resulting in an outer diameter of 1.7 mm. The array test showed that the center frequency reached 39±2 MHz and −6-dB fractional bandwidth was 82±6%. The insertion loss was −41 dB, and crosstalk between adjacent elements was −24 dB. A radial outward imaging testing with phantom wires (D = 50 μm) was conducted. The image was in a dynamic range of 30 dB to show a penetration depth of 6 mm by using the synthetic aperture method. The −6-dB beam width was estimated to be 60 μm in the axial direction at 3.1 mm distance away from the probe. The results suggest that the 40 MHz micromachined 1–3 composite circular array is promising for intravascular ultrasound (IVUS) imaging applications.
Semiglobal Nonmemoryless Attitude Controls on the Special Orthogonal Group
Authors: Lee Taeyoung , Chang Dong Eui , Eun Yongsoon
Published: September 2018

This paper presents tracking strategies for the attitude dynamics of a rigid body that are global on the configuration space SO(3) and semiglobal over the phase space SO(3)×ℝ3. It is well known that global attractivity is prohibited for continuous attitude control systems on the special orthogonal group. Such topological restriction has been dealt with either by constructing smooth attitude control systems that exclude a set of zero measure in the region of attraction or by introducing discontinuities in the control input. This paper proposes nonmemoryless attitude control systems that are continuous in time, where the region of attraction guaranteeing exponential convergence completely covers the special orthogonal group. This provides a new framework to address the topological restriction in attitude controls. The efficacy of the proposed methods is illustrated by numerical simulations and an experiment.
Numerical Study of Deterministic Fluxes in Compressor Passages
Authors: Wang Feng , Carnevale Mauro , di Mare Luca
Published: September 2018

Computational fluid dynamics (CFD) has been widely adopted in the compressor design process, but it remains a challenge to predict the flow details, performance, and stage matching for multistage, high-speed machines accurately. The Reynolds Averaged Navier-Stokes (RANS) simulation with mixing plane for bladerow coupling is still the workhorse in the industry and the unsteady bladerow interaction is discarded. This paper examines these discarded unsteady effects via deterministic fluxes using semi-analytical and unsteady RANS (URANS) calculations. The study starts from a planar duct under periodic perturbations. The study shows that under large perturbations, the mixing plane produces dubious values of flow quantities (e.g., whirl angle). The performance of the mixing plane can be considerably improved by including deterministic fluxes into the mixing plane formulation. This demonstrates the effect of deterministic fluxes at the bladerow interface. Furthermore, the front stages of a 19-blade row compressor are investigated and URANS solutions are compared with RANS mixing plane solutions. The magnitudes of divergence of Reynolds stresses (RS) and deterministic stresses (DS) are compared. The effect of deterministic fluxes is demonstrated on whirl angle and radial profiles of total pressure and so on. The enhanced spanwise mixing due to deterministic fluxes is also observed. The effect of deterministic fluxes is confirmed via the nonlinear harmonic (NLH) method which includes the deterministic fluxes in the mean flow, and the study of multistage compressor shows that unsteady effects, which are quantified by deterministic fluxes, are indispensable to have credible predictions of the flow details and performance of compressor even at its design stage.
A Comprehensive Hydrodynamics-Salinity-pH Model for Analyzing the Effects of Freshwater Withdrawals in Calcasieu Lake and Surrounding Water Systems
Authors: Zhang Ning , Han Xiao , Wang Weihao
Published: September 2018

The study is a continuation of the authors' previous works on hydrodynamics and sediment transport modeling for Calcasieu Lake area (located in southwest Louisiana) (Zhang, N., Zheng, Z. C., and Yadagiri, S., 2011, “A Hydrodynamic Simulation for the Circulation and Transport in Coastal Watersheds,” Comput. Fluids, 47(1), pp. 178–88; Zhang, N., Kee, D., and Li, P., 2013, “Investigation of the Impacts of Gulf Sediments on Calcasieu Ship Channel and Surrounding Water Systems,” Comput. Fluids, 77, pp. 125–133; Yadav, P. K., Thapa, S., Han, X., Richmond, C., and Zhang, N., 2015, “Investigation of the Effects of Wetland Vegetation on Coastal Flood Reduction Using Hydrodynamic Simulation,” ASME Paper No. AJKFluids2015-3044). The major purposes of the study are: (1) to demonstrate the new model features and validate the model results, (2) to disclose the effects of Gulf Intracoastal Waterway (GIWW) and determine the boundary conditions for GIWW in the model, and (3) to use the model to analyze the effects of excessive freshwater withdrawals on the changes of hydrodynamics and salinity in the Calcasieu Lake system. Several new model features were added to the existing model framework, including the extension of modeling domain, vegetation model, salinity transport model, and pH calculation. Measurement data from NOAA and USGS are used as boundary conditions for the model. Simulation results were compared with measurement data from NOAA, USGS and other sources for validation. Due to lack of measured data for GIWW in the target area, the effect of GIWW flow conditions on the modeling results was investigated and appropriate GIWW boundary condition was determined based on numerical tests. Numerous petrochemical plants in the area use tremendous amount of fresh surface water. Recent industry expansions may further increase the demands of freshwater withdrawals. One of the purposes of the study is to use developed model to test and analyze the effects of increased freshwater withdrawal from Calcasieu River at the north boundary of the study area on the hydrodynamics and salinity in the downstream Calcasieu Lake system.
Experimental Validation of the Adaptive Gaussian Process Regression Model Used for Prediction of Stress Intensity Factor as an Alternative to Finite Element Method
Authors: Keprate Arvind , Chandima Ratnayake R. M. , Sankararaman Shankar
Published: September 2018

Currently, in the oil and gas industry, finite element method (FEM)-based commercial software (such as ANSYS and abaqus) is commonly employed for determining the stress intensity factor (SIF). In their earlier work, the authors proposed an adaptive Gaussian process regression model (AGPRM) for the SIF prediction of a crack propagating in topside piping, as an inexpensive alternative to FEM. This paper is the continuation of the earlier work, as it focuses on the experimental validation of the proposed AGPRM. For validation purposes, the values of SIF obtained from experiments available in the literature are used. The experimental validation of AGPRM also consists of the comparison of the prediction accuracy of AGPRM and FEM relative to the experimentally derived SIF values. Five metrics, namely, root-mean-square error (RMSE), average absolute error (AAE), mean absolute percentage error (MAPE), maximum absolute error (MAE), and coefficient of determination (R2), are used to compare the accuracy. A case study illustrating the development and experimental validation of the AGPRM is presented. Results indicate that the prediction accuracy of AGPRM is comparable with and even higher than FEM, provided the training points of AGPRM are chosen aptly. Good prediction accuracy coupled with less time consumption favors AGPRM as an alternative to FEM for SIF prediction.