bluuebunny/crossref_metadata_2025 huggingface dataset:
Property of Sn-37Pb solder bumps with different diameter during thermal shock
Authors: Gan Guisheng , Yang Donghua , Wu Yi-ping , Liu Xin , Sun Pengfei , Xia Daquan , Cao Huadong , Jiang Liujie , Tian Mizhe
Published: January 2021

Purpose

The impact strength of solder joint under high strain rate was evaluated by board level test method. However, the impact shear test of single solder bump was more convenient and economical than the board level test method. With the miniaturization of solder joints, solder joints were more prone to failure under thermal shock and more attention has been paid to the impact reliability of solder joint. But Pb-free solder joints may be paid too much attention and Sn-Pb solder joints may be ignored.

Design/methodology/approach

In this study, thermal shock test between −55°C and 125°C was conducted on Sn-37Pb solder bumps in the BGA package to investigate microstructural evolution and growth mechanism of interfacial intermetallic compounds (IMCs) layer. The effects of thermal shock and ball diameter on the mechanical property and fracture behavior of Sn-37Pb solder bumps were discussed.

Findings

With the increase of ball size, the same change tendency of shear strength with thermal shock cycles. The shear strength of the solder bumps was the highest after reflow; with the increase of the number of thermal shocks, the shear strength of the solder bumps was decreased. But at the time of 2,000 cycles, the shear strength was increased to the initial strength. Minimum shear strength almost took place at 1,500 cycles in all solder bumps. The differences between maximum shear strength and minimum shear strength were 9.11 MPa and 16.83 MPa, 17.07 MPa and 15.59 MPa in φ0.3 mm and φ0.4 mm, φ0.5 mm and φ0.6 mm, respectively, differences were increased with increasing of ball size. With similar reflow profile, the thickness of IMC decreased as the diameter of the ball increased. The thickness of IMC was 2.42 µm and 2.17 µm, 1.63 µm and 1.77 µm with increasing of the ball size, respectively.

Originality/value

Pb-free solder was gradually used to replace traditional Sn-Pb solder and has been widely used in industry. Nevertheless, some products inevitably used a mixture of Sn-Pb and Pb-free solder to make the transition from Sn-Pb to Pb-free solder. Therefore, it was very important to understand the reliability of Sn-Pb solder joint and more further research works were also needed.
Using floristic gradient mapping to assess seasonal thaw depth in interior Alaska
Authors: Döpper Veronika , Panda Santosh , Waigl Christine , Braun Matthias , Feilhauer Hannes
Published: January 2021

Questions

Is it possible to map floristic gradients in heterogeneous boreal vegetation by using remote‐sensing data? Does a continuous vegetation map enable the creation of a spatially continuous map of seasonal permafrost soil thaw depth?

Location

Bonanza Creek LTER, Fairbanks, Alaska, USA.

Methods

Vegetation records are subjected to an ordination to extract the predominant floristic gradient. The ordination scores are then extrapolated using Sentinel 2 imagery and a digital elevation model (DEM). As the relation between vegetation pattern and seasonal thaw depth was confirmed in this study, the spatial distribution of ordination scores is then used to predict seasonal thaw depth over the same area.

Results

The first dimension of the ordination space separates species corresponding to moist and cold soil conditions from species associated with well‐drained soils. This floristic gradient was successfully mapped within the sampled plant communities. The extrapolated thaw depths follow the typical distribution along a topographical and geomorphological gradient for this region. Besides vegetation information also DEM derivatives show high contributions to the thaw depth modeling.

Conclusion

We demonstrate that floristic gradient mapping in boreal vegetation is possible. The accuracy of the thaw depth prediction model is comparable to that in previous analyses but uses a more parsimonious set of predictors, underlining the efficacy of this approach.
Market competition, relocation and lobbying*
Authors: Mukherjee Vivekananda , Bhattacharyya Amrita Kamalini
Published: January 2021

This paper attempts to answer whether market competition makes relocation of a firm to an inefficient location easier through lobbying. It models a case where a larger market is more efficient location choice of the firm. It shows that if the agglomeration effect is not too high, the presence of market competition at its original location makes relocation easier. However, “race to the bottom” competition between the locations fails to take advantage of the market competition; no relocation takes place. The paper shows that instead of lobbying only with the firm, if the legislatures of the smaller market also lobby with legislatures of the larger market, “race to the bottom” is avoided, and the scope for relocation opens. At such an equilibrium, market competition makes relocation to a much smaller market possible.
Detection of cutaneous prion protein deposits could help diagnose GPI‐anchorless prion disease with neuropathy
Authors: Honda Hiroyuki , Matsuzono Kosuke , Satoh Kota , Fujisawa Masayoshi , Suzuki Satoshi O. , Furuyama Chiaki , Kitamoto Tetsuyuki , Fujimoto Shigeru , Abe Koji , Iwaki Toru
Published: January 2021

Background and purpose

To investigate prion protein (PrP) deposits in cutaneous tissues of patients of glycosylphosphatidylinositol (GPI)‐anchorless prion diseases with neuropathy.

Methods

Cutaneous tissue samples from three patients with GPI‐anchorless prion diseases were obtained, two cutaneous biopsy samples from the lower leg of Case 1 (Y162X) and Case 3 (D178fs25), and a cutaneous sample taken from the abdomen during an autopsy of Case 2 (D178fs25). We performed immunohistochemistry for PrP to look for abnormal PrP deposits.

Results

PrP deposits were observed in the dermal papilla, the sweat glands, the hair follicles, the arrector pili muscles, and peripheral nerves of all examined cases of GPI‐anchorless prion disease with neuropathy. The abnormal PrP accumulation was frequently localized at the basement membrane, and colocalized with laminin.

Conclusion

Immunohistochemical detection of PrP in cutaneous samples could be used to definitively diagnose GPI‐anchorless PrP disease with neuropathy.
Pain, depression, and quality of life in adults with MOG‐antibody–associated disease
Authors: Asseyer Susanna , Henke Eugenia , Trebst Corinna , Hümmert Martin W. , Wildemann Brigitte , Jarius Sven , Ringelstein Marius , Aktas Orhan , Pawlitzki Marc , Korsen Melanie , Klotz Luisa , Siebert Nadja , Ruprecht Klemens , Bellmann‐Strobl Judith , Wernecke Klaus‐Dieter , Häußler Vivien , Havla Joachim , Gahlen Anna , Gold Ralf , Paul Friedemann , Kleiter Ingo , Ayzenberg Ilya ,   Neuromyelitis Optica Study Group
Published: January 2021

Background and purpose

Myelin oligodendrocyte glycoprotein‐antibody–associated disease (MOGAD) is an inflammatory autoimmune condition of the central nervous system. However, data on pain and depression have remained scarce. The aim of this study was to assess features of chronic pain and depression as well as their impact on health‐related quality of life (hr‐QoL) in MOGAD.

Methods

Patients with MOGAD were identified in the Neuromyelitis Optica Study Group registry. Data were acquired by a questionnaire, including clinical, demographic, pain (PainDetect, Brief Pain Inventory–Short Form, McGill Pain Questionnaire–Short Form), depression (Beck Depression Inventory‐II), and hr‐QoL (Short Form‐36 Health Survey) items.

Results

Twenty‐two of 43 patients suffered from MOGAD‐related pain (11 nociceptive, eight definite neuropathic, three possible neuropathic) and 18 from depression. Patients with neuropathic pain had the highest pain intensity and most profound activities of daily living (ADL) impairment. Fifteen patients reported spasticity‐associated pain, including four with short‐lasting painful tonic spasms. Later disease onset, profound physical impairment, and depression were associated with chronic pain. Physical QoL was more affected in pain sufferers (p < 0.001) than in pain‐free patients, being most severely reduced by neuropathic pain (p = 0.016). Pain severity, visual impairment, and gait impairment independently predicted lower physical QoL. Depression was the only factor reducing mental QoL. Twelve patients still suffering from moderate pain (pain severity 4.6 ± 2.3) received pain medication. Only four out of 10 patients with moderate to severe depression took antidepressants.

Conclusions

Being highly prevalent, pain and depression strongly affect QoL and ADL in MOGAD. Both conditions remain insufficiently controlled in real‐life clinical practice.
Novel seM‐types of Streptococcus equi subsp. equi identified in isolates circulating in Argentina
Authors: Bustos Carla P. , Muñoz Alejandra J. , Guida Nora , Waller Andrew , Mesplet María
Published: January 2021

Background

Strangles is a worldwide infectious disease caused by Streptococcus equi subsp. equi that affects the upper respiratory tract of horses. Streptococcus equi subsp. equi characterisation by seM‐typing is internationally used for epidemiological studies and comparison of isolates.

Objectives

To identify and to compare the seM‐types of Argentinian isolates of Streptococcus equi subsp. equi.

Study design

Investigation of bacterial isolates using molecular and phylogenetic approaches.

Methods

A total of 59 Argentinian isolates of Streptococcus equi subsp. equi obtained between 2007 and 2019 were studied by seM‐typing. The sequence similarity of Argentinian seM‐types and the other alleles available on the seM database was determined using BLAST and phylogenetic analysis was performed using the Neighbour‐Joining algorithm. The amino acid sequences were predicted and compared with the predicted amino acid sequence of the reference strain 4047 using the MEGA 7 software and PROVEAN tool.

Results

Eight seM‐types were found among the isolates. Only one of them (seM‐61) has been previously reported and the other seven alleles (seM‐129, seM‐130, seM‐131, seM‐132, seM‐133, seM‐134 and seM‐135) were novel seM sequences. High genetic similarity was observed among the Argentinian seM‐types, with the exception of seM‐130. No functional effects of amino acid differences were predicted.

Main limitations

The number of related and unrelated isolates per year.

Conclusions

Seven novel seM‐types and seM‐61 that were previously reported in Brazil were circulating in Argentina which were identified as circulating in Argentinian horses between 2007 and 2019. The high genetic similarity among the Argentinian and Brazilian seM‐types suggests that there is a geographical distribution of strain types. The geographical restriction of strains is likely to reflect the movement of horses between different equine disciplines and neighbouring countries.
Distinctive characteristics of collagen and gelatin extracted from Dosidicus gigas skin
Authors: Sun Bolun , Li Chao , Mao Yuhong , Qiao Zhaohui , Jia Ru , Huang Tao , Xu Dalun , Yang Wenge
Published: January 2021

Squid skin, often discarded as processing by‐product, is a good resource of collagen/gelatin. In this study, acid soluble collagen (ASC), pepsin soluble collagen (PSC) and water soluble gelatin (WSG) were extracted from squid (Dosidicus gigas) skin and physicochemically examined. The lowest yield of 33.5% was obtained for ASC extracted at 4 °C, and the addition of pepsin increased the collagen yield by around 35.0% (PSC). The highest yield of 81.9% (WSG) was achieved by thermal extraction at 60 °C. A low temperature can largely retain the native helix structures of ASC and PSC, contrariwise, thermal treatment converted collagen into gelatin with unordered and renatured structures. The proline and hydroxyproline contents of ASC, PSC and WSG were 183/1000 residues, 194/1000 residues and 175/1000 residues, respectively. In addition, WSG showed a denaturation temperature at 80.7 °C which was much higher than that of ASC (24.2 °C) and PSC (26.2 °C), while a significant lower resistance towards enzymatic digestion.
Effect of grinding on the structure of pea protein isolate and the rheological properties of its acid‐induced gels
Authors: Liu Qiaozhen , Li Zhuowa , Pan Xiaoxue , Dai Yangyong , Hou Hanxue , Wang Wentao , Ding Xiuzhen , Zhang Hui , Li Xiangyang , Dong Haizhou
Published: January 2021

The purpose of this study was to expand the application range of pea protein isolates by improving the rheological properties of their acid‐induced gels. A pea protein isolate was ground for different durations, and changes in the structure and properties of its gels were studied. Furthermore, the influence mechanism of grinding on gelation was revealed. The results showed that grinding slightly changed the secondary structure of the pea protein isolate and had a great impact on its tertiary structure. Compared with the unground pea protein isolate, the solubility of the ground pea protein isolate increased from 45.89% to 69.84%, and the water‐holding capacity of the gels increased from 52.04% to 94.67% at 7.5 min of grinding. After grinding for 15 min, the particle size of the pea protein isolate decreased from 1292.4 to 945.7 nm, and the polydispersity index decreased from 0.387 to 0.321. Rheological measurements showed that the storage modulus (G′), viscosity and recovery of protein gel samples improved after grinding. Thus, grinding enhanced the potential of protein gels for new applications.
Nurses’ barriers to caring for patients with COVID‐19: a qualitative systematic review
Authors: Joo Jee Young , Liu Megan F.
Published: January 2021

Aim

The aim of this qualitative systematic review is to identify and synthesize qualitative studies of frontline nurses’ experiences and challenges when caring for patients with COVID‐19 in hospitals.

Background

This review is the first qualitative systematic review of nurses’ experiences since the beginning of the COVID‐19 pandemic in 2020. Understanding nurses’ experiences with COVID‐19 is important because nurses are among the most vital of healthcare workers.

Methods

This study used a qualitative systematic review methodology with thematic synthesis to analyse the included studies. Five databases (CINAHL, PubMed, Ovid, Web of Science, and PsycINFO) were searched from January to mid‐August 2020, and 25 abstracts were screened. Based on inclusion criteria, this qualitative systematic review included nine studies.

Results

Five themes were identified as barriers to COVID‐19 care by 133 hospital‐based nurses: limited information about COVID‐19, unpredictable tasks and challenging practices, insufficient support, concerns about family, and emotional and psychological stress.

Conclusions

The five barriers identified in this review should be overcome to improve nurses’ experiences and, in turn, the quality of care patients with COVID‐19 receive.

Implications for nursing and health policy

The findings from this review can be used to reform current healthcare and hospital‐support systems for populations with COVID‐19. They can also be used to point towards areas of research interested in improving frontline nursing. Finally, nursing leaders, healthcare policymakers and governments should use these findings to better support the nursing workforce in the current or a future pandemic.
Office blood pressure measurement: A comprehensive review
Authors: Siddique Saulat , Hameed Khan Aamir , Shahab Hunaina , Zhang Yu‐Qing , Chin Tay Jam , Buranakitjaroen Peera , Turana Yuda , Verma Narsingh , Chen Chen‐Huan , Cheng Hao‐Min , Wang Tzung‐Dau , Van Minh Huynh , Chia Yook‐Chin , Kario Kazuomi
Published: January 2021

The conventional auscultatory methods for measuring blood pressure have been used to screen, diagnose, and manage hypertension since long. However, these have been found to be prone to errors especially the white coat phenomena which cause falsely high blood pressure readings. The Mercury sphygmomanometer and the Aneroid variety are no longer recommended by WHO for varying reasons. The Oscillometric devices are now recommended with preference for the Automated Office Blood Pressure measurement device which was found to have readings nearest to the Awake Ambulatory Blood Pressure readings. The downside for this device is the cost barrier. The alternative is to use the simple oscillometric device, which is much cheaper, with the rest and isolation criteria of the SPRINT study. This too may be difficult due to space constraints and the post‐clinic blood measurement is a new concept worth further exploration.
Spatial and temporal shifts in photoperiod with climate change
Authors: Ettinger A. K. , Buonaiuto D. M. , Chamberlain C. J. , Morales‐Castilla I. , Wolkovich E. M.
Published: January 2021

Climate change causes both temporal (e.g. advancing spring phenology) and geographic (e.g. range expansion poleward) species shifts, which affect the photoperiod experienced at critical developmental stages (‘experienced photoperiod’). As photoperiod is a common trigger of seasonal biological responses – affecting woody plant spring phenology in 87% of reviewed studies that manipulated photoperiod – shifts in experienced photoperiod may have important implications for future plant distributions and fitness. However, photoperiod has not been a focus of climate change forecasting to date, especially for early‐season (‘spring’) events, often assumed to be driven by temperature. Synthesizing published studies, we find that impacts on experienced photoperiod from temporal shifts could be orders of magnitude larger than from spatial shifts (1.6 h of change for expected temporal vs 1 min for latitudinal shifts). Incorporating these effects into forecasts is possible by leveraging existing experimental data; we show that results from growth chamber experiments on woody plants often have data relevant for climate change impacts, and suggest that shifts in experienced photoperiod may increasingly constrain responses to additional warming. Further, combining modeling approaches and empirical work on when, where and how much photoperiod affects phenology could rapidly advance our understanding and predictions of future spatio‐temporal shifts from climate change.
Your EHD Rig May Not Be As Elastohydrodynamic As You Think
Authors: Bair Scott , Habchi Wassim
Published: January 2021

The concentrated contact formed between a steel ball and a glass disc—the optical elastohydrodynamic lubrication (EHD) rig—has been the primary instrument for experimental investigations of elastohydrodynamic film thickness. It has been a source for values of pressure-viscosity coefficient, a difficult-to-define property of liquids. However, comparisons with the pressure dependence of the viscosity obtained in viscometers show little agreement. There are multiple reasons for this failure including shear-thinning and compressibility of the oil. Another reason for the poor agreement is the subject of this short note. The optical EHD rig using glass as one surface will only be in the piezoviscous-elastic (EHD) regime when the pressure-viscosity coefficient is large. For low values, it would be operating in the isoviscous-elastic regime (soft EHD).
Numerical and Experimental Investigation of the Reynolds Number and Reduced Frequency Effects on Low-Pressure Turbine Airfoils
Authors: Bolinches-Gisbert M. , Robles David Cadrecha , Corral Roque , Gisbert Fernando
Published: January 2021

This article compares experimental and numerical data for a low-speed high-lift low pressure turbine (LPT) cascade under unsteady flow conditions. Three Reynolds numbers representative of LPTs have been tested, namely, 5 × 104, 105, and 2 × 105; at two reduced frequencies, fr = 0.5 and 1, also representative of LPTs. The experimental data were obtained at the low-speed linear cascade wind tunnel at the Polytechnic University of Madrid using hot wire, Laser Doppler Velocimetry (LDV), and pressure tappings. The numerical solver employs a sixth-order compact scheme based on the flux reconstruction method for spatial discretization and a fourth-order Runge–Kutta method to march in time. The longest case ran 550 h on 40 GPUs to reach a statistically periodic state. Pressure coefficients around the profile, boundary layer profiles and exit cross section distributions of velocity, pressure loss defect, shear Reynolds stress, and angle are compared against high-quality experimental data. Cascade loss and exit angle have also been compared against the experimental data. Very good agreement between experimental and numerical data is seen. The results demonstrate the suitability of the present methodology to predict the aerodynamic properties of unsteady flows around LPT linear cascades accurately.
Scalable Heat Transfer Characterization on Film Cooled Geometries Based on Discrete Green’s Functions
Authors: Saavedra Jorge , Athmanathan Venkat , Paniagua Guillermo , Meyer Terrence , Straub Doug , Black James , Ramesh Sridharan
Published: January 2021

The aerothermal characterization of film-cooled geometries is traditionally performed at reduced temperature conditions, which then requires a debatable procedure to scale the convective heat transfer performance to engine conditions. This paper describes an alternative engine-scalable approach, based on Discrete Green’s Functions (DGF) to evaluate the convective heat flux along film-cooled geometries. The DGF method relies on the determination of a sensitivity matrix that accounts for the convective heat transfer propagation across the different elements in the domain. To characterize a given test article, the surface is discretized in multiple elements that are independently exposed to perturbations in heat flux to retrieve the sensitivity of adjacent elements, exploiting the linearized superposition. The local heat transfer augmentation on each segment of the domain is normalized by the exposed thermal conditions and the given heat input. The resulting DGF matrix becomes independent from the thermal boundary conditions, and the heat flux measurements can be scaled to any conditions given that Reynolds number, Mach number, and temperature ratios are maintained. The procedure is applied to two different geometries, a cantilever flat plate and a film-cooled flat plate with a 30 degree 0.125 in. cylindrical injection orifice with length-to-diameter ratio of 6. First, a numerical procedure is applied based on conjugate 3D unsteady Reynolds-averaged Navier–Stokes (URANS) simulations to assess the applicability and accuracy of this approach. Finally, experiments performed on a flat plate geometry are described to validate the method and its applicability. Wall-mounted thermocouples are used to monitor the surface temperature evolution, while a 10 kHz burst-mode laser is used to generate heat flux addition on each of the discretized elements of the DGF sensitivity matrix.
Effects of Attack Angle and Relative Thickness of Novel Wing-Shaped Turbulators on Turbulent Hydrothermal Performance in a Two-Pass Square Channel
Authors: Liou Tong-Miin , Chen Chieh-Chu , Wang Chun-Sheng
Published: January 2021

This work aims to combine the effects of the near-wall and core flow disturbance by proposing novel wing-shaped turbulators. The new turbulators are fabricated with the fused deposition modeling (3D printing) technology. To explore their effects on detailed flow fields, local temperature distributions, and pressure drops in a two-pass square channel, particle image velocimetry (PIV), infrared thermography (IR camera), and pressure transducer measurements are performed. The turbulator pitch, clearance, and truncation gap ratio based on the channel hydraulic diameter of 45.5 mm are, respectively, fixed at 0.7, 0.25, and 0.06. Varied parameters include turbulator attack angle (α = 10 deg, 15 deg, 20 deg, and 30 deg), maximum thickness to chord line ratio (t/C = 0.08, 0.13, 0.16, 0.20, and 0.23), and bulk Reynolds number (Re = 5000–20,000). From the experimental results and flow parameters analyzed, the dimensionless spanwise-averaged mean transverse velocity and cross-sectionally averaged vorticity magnitude are identified to be the most relevant ones to spanwise-averaged local Nusselt number ratio in the first and second pass. Among all examined cases and previous data with Fanning friction factor ratio (f¯/fo) less than 50, the case with α = 20 deg and t/C = 0.20 attains the highest thermal performance factor (TPF) and overall Nusselt number ratio Nu¯/Nuo up to 1.68 and 5.36, respectively. Furthermore, empirical correlations of Nu¯/Nuoandf¯/fo versus α, t/C, and Re are proposed.
A Perturbation Analysis Approach for Studying the Effect of Swelling Kinetics on Instabilities in Hydrogel Plates
Authors: Ilseng Arne , Skallerud Bjørn H. , Stokke Bjørn T. , Prot Victorien
Published: January 2021

The onset of surface instability during diffusion-driven swelling of hydrogels depends on the kinetics of the swelling process. Here, we outline a perturbation analysis framework using a finite difference approach for calculating the stability limit of swelling hydrogel plates with graded material properties accounting for kinetic effects. The framework is implemented as a Python routine which is made freely available. Results obtained for bilayered hydrogel plates illustrate that the onset of instability occurs earlier in time and at a lower global swelling ratio when kinetics is accounted for compared to the homogeneous swelling case. This work presents an accessible calculation tool for stability analysis of swelling gels, providing input for the design of novel hydrogel systems.
Shortcut Method for “L” and “Z” Pipe Bend Sizing
Authors: Jaćimović Nikola , Ivošević Miloš
Published: January 2021

In the engineering practice, it may often prove necessary to provide quick and relatively accurate estimates of piping routing and material requirements in very early stages of a project. In these cases, there is typically no time to perform detailed pipe stress analysis in order to obtain accurate routing, which allows for sufficient piping system flexibility, and the designer is constrained to the use of rule of thumb approach and good engineering judgment. This approach, although often used, may prove challenging in many situations, one of which is establishing sufficient pipe loop dimensions. Method proposed by the authors in Jacimovic and Ivosevic (2020, “Shortcut Method for Pipe Expansion Loop Sizing,” ASME J. Pressure Vessel Technol. 142(4), p. 041505) provides a procedure for quick estimation of U loops, while the present procedure aims to provide additional procedures for estimation of L and Z bends, thus completing the circle of shortcut methods for quick estimation of expansion requirements of piping systems.
Experimental Investigations on the Pressure Fluctuations in the Sealing Gap of Dry Gas Seals With Embedded Pressure Sensors
Authors: Luo Jingjing , Brillert Dieter
Published: January 2021

Dry gas–lubricated noncontacting mechanical seals (DGSs), most commonly found in centrifugal compressors, prevent the process of gas flow into the atmosphere. Especially when high speed is combined with high pressure, DGS is the preferred choice over other sealing alternatives. Even though the noncontacting seal is proved reliable, the ultrathin gas film can still lead to a host of potential problems due to possible contact. In order to investigate the flow field in the sealing gap and to facilitate the numerical prediction of the seal performance, a dedicated test facility is developed to carry out the measurement of key parameters in the gas film. Gas in the sealing film varies according to the seal inlet pressure, and the thickness of gas film depends on this fluctuated pressure. In this paper, the test facility, measurement methods, and the first results of static pressure measurements in the sealing gap of the DGS obtained in the described test facility are presented. An industry DGS with three-dimensional grooves on the surface of the rotating ring, where experimental investigations take place, is used. The static pressure in the gas film is measured, up to 20 bar and 8100 rpm, by several high-frequency ultraminiature pressure transducers embedded into the stationary ring. The experimental results are discussed and compared with the numerical model programed in matlab (Luo, J., Dohmen, H. J., and Benra, F. K., 2018, “Coupled Thermal-Structural-Fluid Numerical Analysis of Gas Lubricated Mechanical Seals,” ASME Paper No. GT2018-75458), the characteristic and magnitude of which have a good agreement with the numerical simulations. It suggests the feasibility of measuring pressure profiles of the standard industry DGS under pressurized dynamic operating conditions without altering the key components of the seal, and thereby affecting the seal performance.
On the Efficiency of a Conical Underplatform Damper for Turbines
Authors: Denimal E. , Wong C. , Salles L. , Pesaresi L.
Published: January 2021

Underplatform dampers (UPDs) are commonly used in aircraft engines to limit the risk of high-cycle fatigue of turbine blades. The latter is located in a groove between two consecutive blades. The dry friction contact interface between the damper and the blades dissipates energy and so reduces the vibration amplitudes. Two common geometries of dampers are used nowadays, namely wedge and cylindrical dampers, but their efficiency is limited when the blades have an in-phase motion (or a motion close to it), since the damper tends to have a pure rolling motion. The objective of this study is to analyze a new damper geometry, based on a conical shape, which prevents from this pure rolling motion of the damper and ensures a high kinematic slip. The objective of this study is to demonstrate the damping efficiency of this geometry. Hence, in a first part, the kinematic slip is approximated with analytical considerations. Then, a nonlinear dynamic analysis is performed, and the damping efficiency of this new geometry is compared to the wedge and the cylindrical geometries. The results demonstrate that the conical damper has a high damping capacity and is more efficient and more robust than the two others.
Optimal Estimation of the Roughness Coefficient and Friction Factor of a Pipeline
Authors: Santos-Ruiz Ildeberto , López-Estrada Francisco-Ronay , Puig Vicenç , Torres Lizeth , Valencia-Palomo Guillermo , Gómez-Peñate Samuel
Published: January 2021

This work addresses the estimation of two interrelated parameters of the fluid flow in pipes. First, a numerical and experimental evaluation of some proposed methods to compute the friction factor in turbulent regime is presented. Special attention is given to an explicit solution obtained through the Lambert W-function. Subsequently, a method to estimate the roughness coefficient using nonlinear optimization techniques is proposed, which then allows determining the friction factor from it. Numerical tests were performed for a wide range of operating points of a pipeline. In order to validate the proposed approach, experimental analysis was carried out on a pipeline pilot-plant. The results show the applicability and effectiveness of the proposed method.
Computational Simulation of Spontaneous Liquid Penetration and Depression Between Vertical Parallel Plates
Authors: Naghashnejad Mohammad , Shabgard Hamidreza , Bergman Theodore L.
Published: January 2021

A computational fluid dynamics model is developed to study the dynamics of meniscus formation and capillary flow between vertical parallel plates. An arbitrary Lagrangian–Eulerian approach is employed to predict and reconstruct the shape of the meniscus with no need to employ implicit interface tracking schemes. The developed model is validated by comparing the equilibrium capillary height and meniscus shape with those predicted by available theoretical models. The model was used to predict the capillary flow of water in hydrophilic (silver) and hydrophobic (Teflon) vertical channels with wall spacings ranging from 0.5 mm to 3 mm. It is shown that the computational model accurately predicts the capillary flow regardless of the channel width, whereas the theoretical models fail at relatively large wall spacings. The model captures several important hydrodynamic phenomena that cannot be accounted for in the theoretical models including the presence of developing flow in the entrance region, time-dependent formation of the meniscus, and the inertial effects of the liquid in the reservoir. The sharp interface tracking technique enables direct access to the flow variables and transport fluxes at the meniscus with no need to use averaging techniques.
High Pressure Vertical Axis Wind Pump
Authors: Keisar D. , Eilan B. , Greenblatt D.
Published: January 2021

A novel positive displacement, high pressure, vertical axis wind pump (HP-VAWP) was evaluated for the application of stand-alone high-pressure reverse-osmosis desalination and drip irrigation systems. The direct interface between a vertical axis wind turbine (VAWT) and a positive displacement pump that delivers a constant liquid volume per revolution has never been studied before. Understanding the interaction between turbine and pump efficiencies, where delivery pressure is determined by back-pressure alone, is critical for efficient design. Wind tunnel experiments were conducted on a small-scale two-bladed turbine (0.4 m2 cross-sectional area) that operated on a dynamic stall principle. At these small laboratory scales, the turbine and pump peak efficiencies were relatively low (15% and 28%, respectively); nevertheless, the system produced nearly constant pressures in excess of 1.5 bar for a broad operational range. Moreover, the system exhibited a basic self-priming capability, and the turbine could easily be braked by overloading the pump. A conservative field-scale analysis of an HP-VAWP system indicated that a medium-size turbine (12.5 m2 cross-sectional area) could attain a peak efficiency of 12.9%. Realistic efficiencies greater than 20% are attainable, significantly exceeding the 4%–8% typical peak efficiency of the widely used American multibladed wind pumps. Indeed, our research indicates that an HP-VAWP system is viable and requires further development. The benefits of zero carbon emissions during operation, high relative efficiency, and easy manufacturing and maintenance render the HP-VAWP ideal for stand-alone or off-grid environments.
Synergistic Technology Combinations for Future Commercial Aircraft Using Liquid Hydrogen
Authors: Rompokos Pavlos , Rolt Andrew , Nalianda Devaiah , Isikveren Askin T. , Senné Capucine , Gronstedt Tomas , Abedi Hamidreza
Published: January 2021

Liquid hydrogen (LH2) has long been seen as a technically feasible fuel for a fully sustainable greener aviation future. The low density of the cryogenic fuel would dictate the redesign of commercial aircraft to accommodate the large tanks, which are unlikely to be integrated within the whole internal volume of the wing. In the ENABLEH2 project, the morphological aspects of a LH2 aircraft design are discussed and a methodology for rapid concept comparative assessment is proposed. An exercise is then carried on to down-select short-to-medium range (SMR) and long-range (LR) concepts, able to carry 200 passengers for 3000 nmi and 414 passengers for 7500 nmi, respectively. The down-selection process was split into two phases with the first considering 31 potential airframe architectures and 21 propulsion-system arrangements. The second phase made the final down-selections from a short-list of nine integrated design concepts that were ranked according to 34 criteria, relating to operating cost, revenue, noise, and safety. Upon completion of the process, a tube and wing design with the tanks integrated into extended wing roots, and a blended-wing-body design were selected as the best candidates for the SMR and LR applications, respectively. Both concepts feature distributed propulsion to maximize synergies from integrating the airframe and propulsion systems.
Dynamic Instability Analysis of a Spring-Loaded Pressure Safety Valve Connected to a Pipe by Using Computational Fluid Dynamics Methods
Authors: Zheng Fengjie , Zong Chaoyong , Zhang Chao , Song Xueguan , Qu Fuzheng , Dempster William
Published: January 2021

As the ultimate protection of a pressure system, pressure safety valves (PSV) can respond in an unstable manner in the form of flutter and chatter, which will affect service life, reliability, and performance. In order to study the dynamic instability caused by multisource forces including the flow force, the spring compression force, and the pressure wave forces, a high-fidelity computational fluid dynamics (CFD) model of the system is proposed. A complete CFD model, incorporating the PSV, connected pipes, and the pressure vessel, is developed, in which advanced techniques in Fluent using User Defined Function (UDF) and Dynamic Layering method are combined to allow the PSV to be coupled to the system dynamics. Based on this model, the valve's opening and reclosing process is monitored to examine the influence of design parameters on the dynamic instability of the PSV. Specifically, the propagation of pressure waves along the connecting pipes is successfully captured, helping to assess the instability mechanism and provide the ability to optimize the design and setup of pressure relief systems.
Effect of Different Fuels on Combustion Instabilities in an Annular Combustor
Authors: Rajendram Soundararajan Preethi , Vignat Guillaume , Durox Daniel , Renaud Antoine , Candel Sébastien
Published: January 2021

Combustion instability in annular combustors of jet engines is a recurring issue. In this study, the characteristics of instabilities for different fuels are investigated by combining the instability maps obtained in a laboratory-scale annular combustor equipped with multiple swirling spray injectors (MICCA-spray) and flame describing functions (FDFs) from a single sector configuration (SICCA-spray). Two types of liquid fuels are injected as hollow cone sprays: heptane, which is fairly volatile, and dodecane, which is less volatile. Experiments are also conducted with gaseous propane, perfectly premixed with air, which serves as a reference. An instability map is systematically drawn by varying the global equivalence ratio and thermal power. The data indicate that the amplitude and frequency of instabilities depend, for the same operating point, on the fuel injection conditions (premixed or spray) and fuel type. Overall trends show that premixed propane is unstable in a broad operating domain. Injection of liquid fuels induces changes in flame time lag that modifies the unstable regions. For heptane, the instability map is closer to the propane reference map, whereas dodecane exhibits wider stable regions. An attempt is made to understand these features by examining the FDF, which gives the ratio of relative fluctuations in heat release rate to the relative fluctuations in velocity. The FDFs measured in a single sector configuration give access to gain and phase information that can be used to determine unstable bands and calculate an instability index guiding the interpretation of the differences in instabilities of the three fuels.
Simulation of Premixed and Partially Premixed Jet-in-Crossflow Flames at High Pressure
Authors: Stiehl Bernhard , Otero Michelle , Genova Tommy , Worbington Tyler , Reyes Jonathan , Martin Scott , Velez Carlos , Ahmed Kareem
Published: January 2021

In this paper, we explore the operational map of a lean axial-staged combustor of premixed and partially premixed reacting jet-in-crossflow flames at high -pressure (5 atm). This study attempts to expand the data to relatively high pressure and could significantly aid scaling to real gas turbine engine conditions at 20–30 atm. High-speed camera, particle image velocimetry (PIV), CH* chemiluminescence, temperature, and pressure measurements were taken and processed to allow accurate reconstruction of six operating points relative to computational fluid dynamics (CFD) simulations under minimal adjustments. Variation of lean main stage (φ = 0.575 and 0.73) and rich jet (φ = 1.1, 4, and 8) equivalence ratio has been investigated for a four mm axial jet. The fully premixed flames were found to be controlled by the crossflow temperature before ignition and the crossflow oxygen content during combustion. Analysis of flame shape and position for the partially premixed operating points describes a lee stabilized as well as a more unsteady windward flame branch. Adjustment of added jet fuel and crossflow temperature along with its corresponding oxygen level is required to attain a compact flame body. The risk of delaying combustion progress is significantly increased at a richer jet φ = 8 and an overshooting, spatially divided flame was attained with a main stage φ = 0.73. Control toward a compact flame body is critical to allow combustion at reasonable reaction rate.
Investigations on the Tribological Characteristics of TiO2-Doped Nanofluid Fuel (Biodiesel/Diesel Blend) at Different Contact Parameters
Authors: Saxena Vishal , Kumar Niraj , Saxena Vinod Kumar
Published: January 2021

The fuels (diesel/biodiesel blends) for diesel engines must possess a minimum of lubricating characteristics to prolong the life of some of the engine vital parts lubricated by the fuel itself. Hence, the tribological characteristic of the modified nanofluid fuel blends needs to be investigated for its suitability and sustainability. In the present study, an experimental analysis on the tribological aspect of fuel blends comprising 40% Acacia concinna biodiesel and 60% diesel (by volume) mixed with titanium dioxide (TiO2) nanoparticles in a concentration of 50–200 mg/l was conducted. The prepared fuel blends in varying volume concentrations were tested on a four-ball tribotester. The effects of varying operating parameters such as load and temperature as well as oxidation of biodiesel fuel blend on friction and wear behavior were evaluated with the help of three-dimensional (3D) surface plots (response surface methodology approach). Further, wear patch diameter, wear debris, wear volume, and flash temperature parameter were analyzed using optical micrographs and ferrographs. The obtained results revealed that despite having an influence of all parameters, the effect of TiO2 nanoparticles is more significant in improving the antiwear/friction characteristics of modified nanofluid fuel blends. It was observed that a TiO2 concentration of 150 mg/l in fuel blend was found to be the most suitable to reduce the friction, wear, and wear volume compared with those of diesel and biodiesel blend.
Multiscale Tomographic Wave–Matter Interaction Modeling to Enable Artifact-Free Material Defect Reconstruction
Authors: Steuben John C. , Michopoulos John G. , Iliopoulos Athanasios P. , Graber Benjamin D. , Birnbaum Andrew J.
Published: January 2021

Technologies for material defect detection/metrology are often based on measuring the interactions between defects and waves. These interactions frequently create artifacts that skew the quantitative character of the relevant measurements. Since defects can have a significant impact on the functional behavior of the materials and structures they are embedded in, accurate knowledge of their geometric shape and size is necessary. Responding to this need, the present work introduces preliminary efforts toward a multiscale modeling and simulation framework for capturing the interactions of waves with materials bearing defect ensembles. It is first shown that conventional approaches such as ray tracing result in excessive geometric errors. Instead, a more robust method employing solutions to the wave equation (calculated using the Finite Element Method) is developed. Although the use of solutions to the general wave equation permits application of the method to many wave-based defect detection technologies, this work focuses exclusively on the application to X-ray computed tomography (XCT). A general parameterization of defect geometries based on superquadratic functions is also introduced, and the interactions of defects modeled in this fashion with X-rays are investigated. A synthetic two-dimensional demonstration problem is presented. It is shown that the combination of parameterization and modeling techniques allows the recovery of an accurate, artifact-free defect geometry utilizing classical inverse methods. The path forward to a more complete realization of this technology, including extensions to other wave-based technologies, three-dimensional problem domains, and data derived from physical experiments is outlined.
Methodology of Experiment to Investigate Connection Between Hydraulic Fractures and Vugs in Fracture–Vug Carbonate Formations
Authors: Zhou Z. , Wang W. , Xu T.
Published: January 2021

Fracture–vug carbonate formations are significant oil and gas reservoirs in China, Middle East, and North America. During development, it is required to connect between hydraulic fracture and as many vugs as possible which are the main geological component to store oil and gas. This paper introduces an advanced experimental methodology to directly observe the connection of hydraulic fractures with vugs. It studies the factors that could affect that connection. The work was based on geological information of the Tarim basin, which is the largest fracture–vug carbonate formation in China. According to the experiment, under higher horizontal stress difference more vugs could be connected. In addition, higher fracture density could improve the connection. This methodology could be used in the future study for the fracture–vug carbonate formation. In addition, the experimental result could be used to design and evaluate hydraulic fracturing works.
Late return focusing algorithm for circular synthetic aperture sonar data
Authors: Park J. Daniel , Blanford Thomas E. , Brown Daniel C.
Published: January 2021

Synthetic aperture sonar processing is used to generate imagery for remote sensing applications such as environmental characterization and object detection. Images primarily represent the initial geometric response of acoustic scattering, but there are additional information embedded in the raw data that are not well-represented in images. For example, responses such as internal multiple scattering or elastic scattering are delayed in time, and they appear defocused in imagery. A complementary processing algorithm is presented that improves the focus of late acoustic scattering responses, which can potentially provide additional information about the object and aid data interpretability.
Numerical investigation of wave steepening and shock coalescence near a cold Mach 3 jet
Authors: Pineau Pierre , Bogey Christophe
Published: January 2021

Wave steepening and shock coalescence due to nonlinear propagation effects are investigated for a cold Mach 3 jet. The jet flow and near pressure fields are computed using large-eddy simulation. The near acoustic field is propagated to the far field by solving the linearized or the weakly nonlinear Euler equations. Near the angle of peak levels, the skewness factors of the pressure fluctuations for linear and nonlinear propagations display positive values that are almost identical. Thus, the positive asymmetry of the fluctuations originates during the wave generation process and is not due to nonlinear propagation effects. Compressions in the signals are much steeper for a nonlinear than for a linear propagation, highlighting the crucial role of nonlinear distortions in the formation of steepened waves. The power transfers due to nonlinear propagation are examined for specific frequencies by considering the spatial distribution of the Morfey–Howell indicator in the near and far acoustic fields. They are in good agreement with the direct measurements performed by comparing the spectra for nonlinear and linear propagations. This shows the suitability of the Morfey–Howell indicator to characterize nonlinear distortions for supersonic jets.