bluuebunny/crossref_metadata_2025 huggingface dataset:
A Modifying Effect of Trait Empathy on Frustration-Related Attentional Processing of Aggression-Related Words
Authors: He Wen , Jiang Wenjun , Zhu Jiali , Xu Yuepei , Zhao Huanhuan
Published: May 2022

Abstract. This study describes two experiments conducted to investigate the modifying effect of trait empathy on attentional processing of emotionally laden (i.e., aggression-related) words in frustrating situations. A dot-probe task was used in the first experiment. The results showed that low-empathy individuals exhibited attentional bias toward aggressive words under both frustrating and nonfrustrating conditions. High-empathy individuals demonstrated attentional bias only under frustrating conditions. In the second experiment, the effect of frustration on high-empathy individuals’ aggression was reflected by N200, P300, and late positive potential amplitudes. It was discussed that these amplitudes might indicate that frustrating situations caused high-empathy individuals to show attentional bias toward aggressive words. Our findings suggested that high-empathy individuals were sensitive to emotionally laden (i.e., aggression-related) stimuli under frustrating conditions.
Dual Influence of Climate Change and Anthropogenic Activities on the Spatiotemporal Vegetation Dynamics Over the Qinghai‐Tibetan Plateau From 1981 to 2015
Authors: Wei Yanqiang , Lu Haiyan , Wang Jinniu , Wang Xufeng , Sun Jian
Published: May 2022

Climate change and human activities have already caused degradation in a large fraction of vegetation on the Qinghai‐Tibetan Plateau (QTP). Many studies report that climate variability instead of overgrazing has been the primary cause for large‐scale vegetation cover changes on the QTP, for example, Lehnert et al., 2016, https://doi.org/10.1038/srep24367. However, it remains unclear how human activities (mainly livestock grazing) regulate vegetation dynamics under climate change. This paper takes the AVHRR/GIMMS Normalized Difference Vegetation Index (NDVI) as an indicator to analyze the growth status of vegetation zones in the QTP, which has highly sensitive to climate change. The spatiotemporal dynamics of vegetation growth between 1981 and 2015 were analyzed. The dual effects of climate change and human activities were examined by correlation analyses of data from 87 meteorological stations and economic statistical data of the QTP. Results show that: (a) The vegetation in central and southwestern QTP with high altitudes was improving due to the warm‐humid climate trend. An increase in temperature and a reduction in the harsh frigid climate at high altitudes due to global warming has resulted in expansions of the vegetated areas, with the NDVI showing a concordant increase. (b) The degraded areas were mainly confined to the northern and eastern QTP, which have high human and livestock population densities. In comparison to gently changing climate regimes, anthropogenic activities such as chronic concentration of population and livestock in the valleys with a less harsh climate exerts a much stronger pressure on vegetation. The study indicates that the anthropogenic pressures are much more intensive than the impact of climate change and are critical for the conservation and sustainable management of the QTP vegetation.
Phytoplankton Bloom in the Gulf of Elat/Aqaba: Physical Versus Ecological Forcing
Authors: Berman Hadar , Gildor Hezi
Published: May 2022

Phytoplankton bloom in the Gulf of Elat/Aqaba (the Gulf) was studied before, mainly using one‐dimensional models and observations from the northern Gulf. Thus, the spatial variability within the Gulf and the contribution of physical processes such as horizontal advection to the bloom have not yet been studied. Moreover, various factors such as the effect of light limitation on phytoplankton growth in the Gulf are still debated. Here, we used a three‐dimensional coupled physical‐ecological model for the Gulf to study the mechanisms for phytoplankton bloom throughout the Gulf. We found the southern surface bloom to be higher than the northern surface bloom. In contrast, southern integrated bloom is lower than the northern integrated bloom. These differences result from spatial variations in the mixed layer depth, which is much deeper in the northern Gulf compared with the south. Moreover, horizontal advection controls phytoplankton integrated biomass during the northern bloom, a process often neglected when dealing with phytoplankton blooms. Finally, we found that light limits growth in the northern integrated bloom. The results from the northern Gulf are compared to the North Atlantic bloom, while those from the southern Gulf are compared to the bloom in subtropical oceans due to similarities in mixing depth and consequently in nutrient versus light limitation on phytoplankton growth.
Shallow Calcium Carbonate Cycling in the North Pacific Ocean
Authors: Subhas Adam V. , Dong Sijia , Naviaux John D. , Rollins Nick E. , Ziveri Patrizia , Gray William , Rae James W. B. , Liu Xuewu , Byrne Robert H. , Chen Sang , Moore Christopher , Martell‐Bonet Loraine , Steiner Zvi , Antler Gilad , Hu Huanting , Lunstrum Abby , Hou Yi , Kemnitz Nathaniel , Stutsman Johnny , Pallacks Sven , Dugenne Mathilde , Quay Paul D. , Berelson William M. , Adkins Jess F.
Published: May 2022

The cycling of biologically produced calcium carbonate (CaCO3) in the ocean is a fundamental component of the global carbon cycle. Here, we present experimental determinations of in situ coccolith and foraminiferal calcite dissolution rates. We combine these rates with solid phase fluxes, dissolved tracers, and historical data to constrain the alkalinity cycle in the shallow North Pacific Ocean. The in situ dissolution rates of coccolithophores demonstrate a nonlinear dependence on saturation state. Dissolution rates of all three major calcifying groups (coccoliths, foraminifera, and aragonitic pteropods) are too slow to explain the patterns of both CaCO3 sinking flux and alkalinity regeneration in the North Pacific. Using a combination of dissolved and solid‐phase tracers, we document a significant dissolution signal in seawater supersaturated for calcite. Driving CaCO3 dissolution with a combination of ambient saturation state and oxygen consumption simultaneously explains solid‐phase CaCO3 flux profiles and patterns of alkalinity regeneration across the entire N. Pacific basin. We do not need to invoke the presence of carbonate phases with higher solubilities. Instead, biomineralization and metabolic processes intimately associate the acid (CO2) and the base (CaCO3) in the same particles, driving the coupled shallow remineralization of organic carbon and CaCO3. The linkage of these processes likely occurs through a combination of dissolution due to zooplankton grazing and microbial aerobic respiration within degrading particle aggregates. The coupling of these cycles acts as a major filter on the export of both organic and inorganic carbon to the deep ocean.
Circumpolar Variations in the Chaotic Nature of Southern Ocean Eddy Dynamics
Authors: Hogg Andrew McC. , Penduff Thierry , Close Sally E. , Dewar William K. , Constantinou Navid C. , Martínez‐Moreno Josué
Published: May 2022

Circulation in the Southern Ocean is unique. The strong wind stress forcing and buoyancy fluxes, in concert with the lack of continental boundaries, conspire to drive the Antarctic Circumpolar Current replete with an intense eddy field. The effect of Southern Ocean eddies on the ocean circulation is significant—they modulate the momentum balance of the zonal flow, and the meridional transport of tracers and mass. The strength of the eddy field is controlled by a combination of forcing (primarily thought to be wind stress) and intrinsic, chaotic, variability associated with the turbulent flow field itself. Here, we present results from an eddy‐permitting ensemble of ocean model simulations to investigate the relative contribution of forced and intrinsic processes in governing the variability of Southern Ocean eddy kinetic energy. We find that variations of the eddy field are mostly random, even on longer (interannual) timescales. Where correlations between the wind stress forcing and the eddy field exist, these interactions are dominated by two distinct timescales—a fast baroclinic instability response; and a multi‐year process owing to feedback between bathymetry and the mean flow. These results suggest that understanding Southern Ocean eddy dynamics and its larger‐scale impacts requires an ensemble approach to eliminate intrinsic variability, and therefore may not yield robust conclusions from observations alone.
7000-year-old evidence of fruit tree cultivation in the Jordan Valley, Israel
Authors: Langgut Dafna , Garfinkel Yosef
Published: May 2022

This study provides one of the earliest examples of fruit tree cultivation worldwide, demonstrating that olive (Olea europaea) and fig (Ficus carica) horticulture was practiced as early as 7000 years ago in the Central Jordan Valley, Israel. It is based on the anatomical identification of a charcoal assemblage recovered from the Chalcolithic (7200–6700 cal. BP) site of Tel Tsaf. Given the site’s location outside the wild olive’s natural habitat, the substantial presence of charred olive wood remains at the site constitutes a strong case for horticulture. Furthermore, the occurrence of young charred fig branches (most probably from pruning) may indicate that figs were cultivated too. One such branch was14C dated, yielding an age of ca. 7000 cal. BP. We hypothesize that established horticulture contributed to more elaborate social contracts and institutions since olive oil, table olives, and dry figs were highly suitable for long-distance trade and taxation.
In situ green synthesis of lysozyme/silver nanoparticles sol and their antimicrobial properties
Authors: Huang Shan , Liu Mengru , Li Hailong
Published: May 2022

Lysozyme/silver nanoparticles sol (LZM/AgNPs) were synthesized in situ with the assistance of ultraviolet irradiation with enhanced antibacterial activity.
Nonlinear programming problem for stronglyE-invex sets and stronglyE-preinvex functions
Authors: Iqbal Akhlad , Hussain Askar
Published: May 2022

The concepts of stronglyE-invex sets, stronglyE-invex, stronglyE-preinvex, and strongly pseudoE-preinvex functions are introduced in this paper. We have included several non-trivial examples to support our definitions. The family of stronglyE-invex sets has been shown to form a vector space overR, and other interesting properties have been addressed. The epigraph of stronglyE-preinvex function has been derived, as well as the relationship between the stronglyE-preinvex function and the strongly pseudoE-preinvex function has been established. To show an important relationship between stronglyE-invex and stronglyE-preinvex functions, a new Condition A has been introduced. A nonlinear programming problem for stronglyE-preinvex functions is explored as an application. Under a few conditions, it has been proved that the local minimum point is the global minimum for a nonlinear programming problem.
Patterns of Use and Self-reported Effectiveness of Cannabis for Hyperemesis Gravidarum
Authors: First Olivia K. , MacGibbon Kimber W. , Cahill Catherine M. , Cooper Ziva D. , Gelberg Lillian , Cortessis Victoria K. , Mullin Patrick M. , Fejzo Marlena S.
Published: May 2022

Introduction There is limited research on effective treatment of Hyperemesis Gravidarum (HG), the most extreme version of nausea and vomiting during pregnancy (NVP). This paper
examines current patterns of use and self-reported effectiveness of cannabis/cannabis-based products (CBP) to treat HG.

Materials/Methods The study employed a 21-question survey to gather information on demographics, antiemetic prescription use, and experience with cannabis/CBPs among individuals who
experienced extreme nausea and vomiting or HG during their pregnancy. Age-adjusted unconditional logistic regression was used to compare odds of symptom relief and weight gain between
respondents who used prescription antiemetics and those who used cannabis.

Results Of the 550 survey respondents, 84% experienced weight loss during pregnancy; 96% reported using prescription antiemetics and 14% reported cannabis use for HG. Most
respondents reported using cannabis/CBPs (71%) because their prescribed antiemetics were self-reported to be ineffective. More than half of cannabis/CBP users reported using products daily
or multiple times per day (53%), primarily via smoke inhalation (59%), and mainly either delta-9-tetrahydrocannabinol (THC) only or THC dominant preparations (57%). Eighty-two percent of
cannabis/CBP users reported symptom relief, compared to 60% of prescription antiemetic users. Among patients who reported weight loss during pregnancy, 56% of cannabis users reported gaining
weight within two weeks of treatment, compared to 25% of prescription antiemetic users.

Conclusions Respondents reported using cannabis primarily because prescribed medications were self-reported to be ineffective. Although the survey approach has inherent limitations
so results should be interpreted with caution, in this sample, cannabis was self-reported to be more effective than prescription medications in alleviating HG symptoms and enabling pregnancy
weight gain. Therefore, depending on the safety profiles, randomized, double-blinded, placebo-controlled trials of cannabis compared to other antiemetics are warranted to determine whether
cannabinoids may provide an effective alternative treatment for HG.
Antibody Response and Maternofetal Antibody Transfer in SARS-CoV-2-Positive Pregnant Women: A Multicenter Observational Study
Authors: Enengl Sabine , Pecks Ulrich , Oppelt Peter , Stelzl Patrick , Trautner Philip Sebastian , Shebl Omar , Lamprecht Bernd , Longardt Ann Carolin , Eckmann-Scholz Christel , Keil Corinna , Mand Nadine , von Kaisenberg Constantin Sylvius , Jegen Magdalena , Doppler Stefan , Lastinger Julia
Published: May 2022

Introduction Awareness of SARS-CoV-2 infection in pregnant women and the potential risk for infection of their neonates is increasing. The aim of this study was to examine the immune
status of affected women and evaluate the dynamics of placental antibody transfer.

Materials and Methods The study included 176 women with SARS-CoV-2 infection during pregnancy who delivered between April 2020 and December 2021 at eight obstetric maternity sites.
Demographic data, maternal and neonatal characteristics were summarized. Antibody testing for IgA and IgG in maternal blood sera and umbilical cord samples was evaluated and IgG transfer
ratios were calculated. Values were related to the time of infection during pregnancy and birth.

Results The percentage of IgG positive women increased from 29.0% (95% CI 23.8 – 37.8) at presentation with a positive PCR test result to 75.7% (95% CI 71.6 – 79.8), the percentage
of IgG positive umbilical cord blood samples increased from 17.1% (95% CI 13.0 – 21.3) to 76.4% (95% CI 72.2 – 80.7) at more than six weeks after infection. Regression lines differed
significantly between maternal and fetal IgG responses (p < 0.0001). Newborns react with a latency of about one week; umbilical cord blood antibody concentrations are highly correlated
with maternal concentration levels (ρ = 0.8042; p < 0.0001). IgG transplacental transfer ratios were dependent on infection-to-birth interval. Two of the umbilical cord blood samples
tested positive for IgA.

Conclusions These findings confirm vertical SARS-CoV-2 transmission is rare; however, antibodies are transferred to the fetus soon after infection during pregnancy. Since
transplacental antibody transfer might have a protective value for neonatal immunization this information may be helpful when counseling affected women.
Übermäßiges Körpergewicht und Krebsrisiko
Authors: Scherübl Hans
Published: May 2022

Übermäßiges Körpergewicht (ÜKG) stellt derzeit die zweitwichtigste vermeidbare Krebsursache in Deutschland dar. Für viele Karzinome ist eine Dosis-Wirkungs-Beziehung belegt, d. h. je ausgeprägter das ÜKG, desto größer ist das Krebsrisiko. Bedenklich: Etwa 60 % der erwachsenen Bundesbürger weisen ein ÜKG auf und mehr als 23 % sind adipös. Mittlerweile sind von ÜKG-assoziierten Tumoren immer öfter 20–40-Jährige betroffen.
Psychometric Evaluation of a Patient Experience Questionnaire (PEQ) for Outpatient Appointments: Analysis Using Data from a U.K. National Health Service Audiology Department
Authors: Aazh Hashir , Ballinger Judith , Hayes Chloe , Pepler Anna , Lammaing Karen , Moore Brian C. J. , Danesh Ali A. , Vitoratou Silia
Published: May 2022

Abstract Background The Audiology Department at the Royal Surrey NHS Foundation Trust (RSFT), United Kingdom, developed a patient experience questionnaire (PEQ) to assess and compare patients' experiences of attending a wide range of appointments (e.g., hearing
assessment, hearing aid fitting, hearing aid review, tinnitus therapy, balance assessment, and balance rehabilitation). Purpose The aim of this study was to assess the psychometric properties of the PEQ. The PEQ is a unidimensional instrument with four items that assess a patient's
experience of an outpatient appointment. Research Design Retrospective cross-sectional study. Study Sample Patients attending appointments for audiology services at RSFT between January and March 2020. Data Collection and Analysis All patients
(n = 656) attending appointments for audiology services at RSFT during randomly selected days between January and March 2020 were given the questionnaire to complete themselves (PEQ-self) or to complete on their child's behalf (PEQ-parent). The factor structures for the
PEQ-self and PEQ-parent were assessed separately, using confirmatory factor analysis. A multiple-causes, multiple-indicators (MIMIC) model was fitted to explore potential bias due to gender and age. Internal consistency was assessed using Cronbach's α. The bivariate correlations between
PEQ scores and other variables were evaluated using the nonparametric Spearman correlation coefficient. Floor and ceiling effects were assessed using the distribution of total scores. Results Confirmatory factor analysis revealed that a one-factor model gave a close fit to
the data for both the self and parent versions. Cronbach's α for the total score was 0.77 for the PEQ-self and 0.86 for the PEQ-parent. The MIMIC model showed no significant direct effects of age or gender for either version. Conclusions Both the PEQ-self and PEQ-parent
questionnaire can be reliably used to measure patients' experiences of outpatient audiology appointments. Future studies should aim to assess the psychometric properties of the PEQ-self and PEQ-parent for a range of outpatient appointments other than audiology.
X-ray nanodiffraction imaging reveals distinct nanoscopic dynamics of an ultrafast phase transition
Authors: Ahn Youngjun , Cherukara Mathew J. , Cai Zhonghou , Bartlein Michael , Zhou Tao , DiChiara Anthony , Walko Donald A. , Holt Martin , Fullerton Eric E. , Evans Paul G. , Wen Haidan
Published: May 2022

Significance

Phase transitions, the changes between states of matter with distinct electronic, magnetic, or structural properties, are at the center of condensed matter physics and underlie valuable technologies. First-order phase transitions are intrinsically heterogeneous. When driven by ultrashort excitation, nanoscale phase regions evolve rapidly, which has posed a significant experimental challenge to characterize. The newly developed laser-pumped X-ray nanodiffraction imaging technique reported here has simultaneous 100-ps temporal and 25-nm spatial resolutions. This approach reveals pathways of the nanoscale structural rearrangement upon ultrafast optical excitation, different from those transitions under slowly varying parameters. The spatiotemporally resolved structural characterization provides crucial nanoscopic insights into ultrafast phase transitions and opens opportunities for controlling nanoscale phases on ultrafast time scales.
Structural insights into Ras regulation by SIN1
Authors: Zheng Yuyuan , Ding Lei , Meng Xianhui , Potter Meg , Kearney Alison L. , Zhang Jie , Sun Jie , James David E. , Yang Guang , Zhou Chun
Published: May 2022

Significance

Both the mTORC2 and Ras-ERK pathways respond to growth factor stimulation and play critical roles in cell growth and proliferation, disarray of these pathways leads to many diseases, especially cancer. These two signaling pathways crosstalk at many levels; recently it's become clear that the SIN1 component of mTORC2 could interact with Ras family small GTPases, but how these two proteins interact at the molecular level and the functional outcomes of this interaction remain to be addressed. In this work we determined the high-resolution structure of Ras-SIN1 complexes and revealed the detailed interaction mechanism. We also showed that Ras-SIN1 association inhibits insulin-induced ERK activation. Insights from this work could improve our understanding of the disease-causing mechanism of errant mTORC2 or Ras proteins.
ARX-based EEG data balancing for error potential BCI
Authors: Farabbi Andrea , Aloia Vanessa , Mainardi Luca
Published: May 2022

Objective. Deep learning algorithms employed in brain computer interfaces (BCIs) need large electroencephalographic (EEG) datasets to be trained. These datasets are usually unbalanced, particularly when error potential (ErrP) experiment are considered, being ErrP’s epochs much rarer than non-ErrP ones. To face the issue of unbalance of rare epochs, this paper presents a novel, data balancing methods based on ARX–modelling. Approach. AutoRegressive with eXogenous input (ARX)-models are identified on the EEG data of the ‘Monitoring error-related potentials’ dataset of the BNCI Horizon 2020 and then employed to generate new synthetic data of the minority class of ErrP epochs. The balanced dataset is used to train a classifier of non-ErrP vs. ErrP epochs based on EEGNet. Main results. Compared to classical techniques (e.g. class weights, CW) for data balancing, the new method outperforms the others in terms of resulting accuracy (i.e. ARX

91.5
%

vs CW

88.3
%

), F1-score (i.e. ARX

78.3
%

vs CW

73.7
%

) and balanced accuracy (i.e. ARX

87.0
%

vs CW

81.1
%

) and also reduces the number of false positive detection (i.e. ARX 51 vs CW 104). Moreover, the ARX-based method shows a better generalization capability of the whole model to classify and predict new data. Significance. The results obtained suggest that the proposed method can be used in BCI application for tackling the issue of data unbalance and obtain more reliable and robust performances.
Approximation of hub leakage flow in a high speed axial flow compressor rotor with adjoint method
Authors: Ito Sasuga , Furukawa Masato , Yamada Kazutoyo
Published: May 2022

This paper focuses the effect of hub leakage flow on the performance of a high speed transonic rotor. The rotor considered here is NASA rotor 37. General computational fluid dynamics of this rotor have been unable to predict a total pressure deficit from the hub wall to the mid span height observed in the experiments. In this study, computations have been performed on the rotor with the boundary condition assumed the leakage flow from the tip gap at the upstream of the rotor. In the computations, the velocity distribution is determined on the computational domain corresponding to the location of the tip gap. The swirl velocity at the boundary is calculated with the rotational speed and the radial length of the hub wall. The radial velocity is estimated based on the leakage mass flow. However, the mass flow is an uncertain quantity, and it has effect to the prediction of the total pressure deficit. Therefore, an adjoint method has been applied for the approximation to the uncertain quantity. The simulation results using the leakage flow boundary and the result without the boundary condition have been compared with the experiment. The comparisons have shown that the boundary condition and the approximation with the adjoint method have enabled to predict the total pressure deficit.
Lattice Boltzmann simulation of flow and sound fields around an axial flow fan
Authors: Okuyama K , Yamada K
Published: May 2022

In this study, not only the flow field but the aerodynamic sound field around the axial flow fan were directly simulated using the lattice Boltzmann method (LBM). To validate the LBM results obtained in this study, they were compared with the experimental results in terms of the pressure rise performance characteristics. In order to investigate the change in the flow and sound fields due to different operating points, calculations were conducted at two operating points; one is the low flow rate point where the fan is stalled and the other is the high flow rate point where the flow field in the fan is sound. In the comparison of the performance characteristics, the calculation results showed good agreement with the experimental results, and the flow fields were well reproduced with high accuracy. The analysis in terms of the vortical flow structures and the relative velocity distributions showed that the tip vortex was generated by the pressure difference between both sides of the fan blade at the high flow rate point while at the low flow rate point the flow field near the fan tip was covered with the low velocity region and the leading edge separation occurred on the tip side of the fan blade. Therefore, it was confirmed from the flow field as well as the performance that the fan blade was stalled with the blade loading lost at the low flow rate point. Large pressure fluctuations on the fan blade surface were caused by the interaction with the tip vortex from the adjacent blade at the high flow rate point and the occurrence of leading edge separation at the low flow rate point. With regard to the comparison of the far field sound spectrum, the calculation results for both two flow rate points were in good agreement with the experimental results in a low frequency range, and the aerodynamic sounds generated from the fan were predicted well with the LBM simulation.
Numerical simulation of cavitating flow around a twist hydrofoil focusing on the erosion behaviour
Authors: Wang Zhengdong , Li Linmin , Li Xiaojun , Zhu Zuchao
Published: May 2022

The erosion risk in cavitating flow is a challenging issue due to the instantaneity and complexity. In this paper, the energy balance approach (EBA)-based cavitation erosion model is employed to investigate the erosion behavior around a Delft Twist-11 hydrofoil utilizing large eddy simulation (LES) approach. The results show that the predicted erosion region is qualitative agreement with the experimental paint tests. The adaptive mesh refinement (AMR) method is conducted on a coarse mesh to verify its preponderance in save computing resources and ensuring accuracy. It is found that the case using AMR obtains more accurate cavitation features within less computational cells than that of the fine mesh, including the predicted shedding frequency and U-type structure of shedding cloud.
Prediction of incipient cavitation in micro tubular propeller turbine
Authors: Jang Seungsoo , Song Ji-Hun , Kim Youn-Jea
Published: May 2022

Cavitation is a phenomenon that cavities or bubbles form in a liquid when static pressure falls below the vapor pressure. It can damage the machine, hence it is recommended to be avoided in the design and operation of the machine. In this study, the cavitation characteristics were numerically investigated with a change in the flow rate of a micro tubular propeller turbine. Here, the rotational speed was set to the value corresponding to the best efficiency point for each flow rate. A multiphase flow analysis incorporating water and water vapor was conducted, using the Zwart-Gerber-Belamri (ZGB) model as the cavitation model. Results show that the tip clearance is the first region where the cavitation starts to occur as the flow rate increases. At this time, the Thoma number was found to be 1.178. The second region where the cavitation occurs with further increases in the flow rate is in the vicinity of the leading edge. It turned out that the leading edge cavitation occurs when the Thoma number is below 1.111. As the tip clearance increases, the range of the flow rate that cavitation does not occur increases, but it reduces turbine performance. Therefore, the selection of appropriate tip clearance given the operating flow rate range and performance needs to be considered.
A Venturi tube design for studying travelling bubble cavitation
Authors: Li Zehao , Zuo Zhigang , Qian Zhongdong
Published: May 2022

Travelling bubble cavitation always appears in forms of nearly spherical travelling bubbles. These bubbles grow from the freestream/surface nuclei in the low-pressure region in the flow channel. As the inception of travelling bubble cavitation is very sensitive to the boundary layer flow, attached cavitation would be likely to appear simultaneously if the flow is not well-controlled. In this study, based on the interaction between cavitation inception and boundary layer, a Venturi tube for studying travelling bubble cavitation is designed with the aid of a computational fluid dynamics (CFD) approach. The flow channel of this Venturi tube is composed of an inlet straight pipe (10 mm × 10 mm square), a contraction section, a throat section (5 mm × 5 mm square) and two diffuser sections (diffuser 1 and diffuser 2). For visualization convenience, each cross section of the Venturi tube is square. From CFD results, no flow separation occurs near the throat section and the adverse pressure gradient is relatively small, which indicates attached cavitation may not occur. The manufactured Venturi tube is installed in a blow-down type tunnel and tested with Reynolds number at roughly 3 - 3.75 × 104 and the pressure recovery number at 2.95 - 4.41. The velocity of the Venturi inlet varies from about 6 m/s to 7.5 m/s. Experiment results shows travelling bubble cavitation can be generated successfully and pure travelling bubble cavitation inception is achieved in this Venturi tube. The formation of travelling bubbles is recorded by a Phantom VEO 710L high-speed camera with framing rate of 24000 fps.
Internal flow characteristics in the draft tube of a Francis turbine model by air injection under low flow rate condition
Authors: Kim Seung-Jun , Cho Yong , Kim Jin-Hyuk
Published: May 2022

Undesirable internal flow features under low flow rates in the draft tube of a Francis turbine are caused by the vortex ropes with precession. These vortex ropes cause performance degradation and increase the instability of turbine systems. The effects of anti-swirl fins on the wall of the draft tube were observed in the previous study to suppress the generation of the vortex rope. However, vortex ropes still remained near the cone of the draft tube. Thus, extra methods to suppress the vortex rope are needed. In this study, the influences of air injection were investigated from the cone of the runner to suppress the vortex rope characteristics in the draft tube of a Francis turbine model. For investigating the unsteady flow and pressure phenomena by injecting the air in the draft tube, unsteady-state Reynolds-averaged Navier–Stokes calculations were carried out with a turbulence model of a scale-adaptive simulation shear stress transport. By injecting the air into the draft tube, the hydraulic efficiency was reduced, however, the visible vortex ropes in the draft tube were suppressed. Additionally, the unsteady pressure phenomena also were reduced by injecting the air.
The development of a high-speed miniature pump with dynamic bearing
Authors: Song Xueyi , Li Hao Yuan , Li Ying , Luo Xianwu
Published: May 2022

A high-speed miniature pump is proposed for the application in aerospace area, where high efficiency and reliability are expected for the pump under the microgravity operation condition. In this paper, a miniature centrifugal pump with dynamic bearing is selected as the objective for the performance development. The prototype of the miniature pump is manufactured and tested by experiments at the rotational speed of 10,000r/min. The comparison of hydraulic performance near the design operation shows good agreement between the numerical results and experimental data. In order to improve hydraulic performance of the pump, the effects of splitter blades, number of blades, and wrap angle of blades are analyzed numerically. For each operating condition, in order to compare the influence of splitter blades on the performance and the internal flow, the impellers with and without splitter blades are designed respectively. In addition, for the splitter blades, the influence of the splitter blade position and the splitter blade thickness are also investigated. The numerical result shows that the highest efficiency among all the impellers is achieved with the blade number of 5, wrap angle of 160° and with no splitter blades. Moreover, for the impellers with the splitter blades, hydraulic performance of the pump is mainly decided by the main blades, while the splitter blades hardly help to improve the efficiency of the pump. The study is helpful for the further application of the high-speed miniature pump in various societies.
Optimization design of the groove flow control technique to suppress flow instability in axial-flow pump
Authors: Rui Zhang
Published: May 2022

As an effective fluid control technology, the groove flow control technique is used to improve axial-flow pump energy performance. Determining the values of groove parameters reasonably is essential to maximize the energy performance of axial-flow pumps. In order to solve the limitation of traditional groove design in groove flow control technology, this paper presents a multi-objective groove optimization method developed by integrating OD (orthogonal design), RSM (response surface methodology), and PSO (particle swarm optimization). A case study of an axial-flow pump is conducted. By using the OD method, the sample space has been designed. The performance prediction model of axial flow pump is established by RSM. In addition, the linear weighted method is employed to construct a comprehensive evaluation function as the fitness value of PSO. Finally, an optimal combination of the groove flow control technique parameters is determined using the PSO algorithm. The result shows that this method proposed in this paper is helpful for solving multi-objective optimization of the groove flow control technique and could effectively improve the hydraulic performance of the axial-flow pump under three typical stall conditions. The optimization effectively suppresses the formation of a saddle zone. In addition, the optimization increases the pump head by 0.30, 4.41 and 9.70 m under the critical stall condition, moderate stall condition and deep stall condition, respectively. Moreover, the optimization leads to better inflow conditions for the impeller and enhances its performance under the stall conditions. This study provides a basis for the early-stage design of the groove flow control technique for axial-flow pump and provides a valuable reference for the optimal design of groove for other fluid machineries.
Influence of runner leading edge radius on the pump-turbine performance
Authors: Ono Kodai , Tsuru Wakana , Yokota Kazuhiko
Published: May 2022

In pump-turbines, serious fluid oscillations were reported. It is known that the performance curves of the pump-turbines have an S-shape. In order to reduce the flow oscillation, we investigated the relation between the leading edge radius and the S-shaped characteristics. The effects of the radius on the pump-turbine performance is investigated by the experiments, the numerical calculations and theoretical analyses. The numerical and experimental results agree well. The theoretical loss coefficients were calculated based on the numerical results. The leading edge vorticity causes the inner blade loss. Vortices expand with an increase of the radius.
Characteristics and suppression of vibration in cross-flow turbine with a cavity
Authors: Otsuka K , Ogawa N , Iio S , Kitahora T , Choi Y D , Inagaki M
Published: May 2022

Cross-flow turbine is widely used for small hydropower in run-of-river type stations because of its excellent partial load characteristics, easy manufacturing, and low cost. The Banki-Michell turbine is the origin, and various studies have focused on improving the turbine performance. The authors have developed a new cross-flow turbine with a cavity and a guide wall from the outer nozzle wall tip to suppress flow separation on the guide wall and make the casing smaller. However, little researches are focusing on vibration, and it is also essential to get knowledge for suppressing vibration and noise from the turbine aiming to install at higher head sites. Our previous studies showed that high-pressure fluctuation occurs near the outer nozzle tip, and the cavity suppresses the pressure fluctuations, but the suppression mechanism is not fully understood. Therefore, this study experimentally investigates the pressure fluctuation generation mechanism and the cavity’s effect on suppressing the vibration. Furthermore, it aims to suppress the vibration by modifying the nozzle tip shape. The vibration level was measured on a lab-scale turbine and CFD analysis to reveal the generation of pressure fluctuation. As a result, the predominant frequency of the vibration corresponds to the blade passing frequency and the pressure fluctuation at the nozzle tip. The cavity and nozzle tip shape show a significant influence on pressure and vibration characteristics and turbine performance.
Effects of air chamber and curtain wall geometries on energy conversion performance in a fixed oscillating water column-type wave energy converter
Authors: Murakami T , Imai Y , Nagata S , Takao M
Published: May 2022

An oscillating water column-type wave energy extractor is composed of an air chamber, an air turbine and a generator. The energy conversion process is compounded of the primary conversion in an air chamber and the secondary conversion of an air turbine. The oscillating water column-type wave energy extractor is considered to be safe even under dirty weather conditions. For societal implementation, there is a need to make a design method which can consider the water surface motion, the pressure fluctuation in an air chamber, the rotations of an air turbine and a generator. At here, the authors carried out the 2-dimensional wave tank tests using the model oscillating water column equipped with the impulse turbine and a generator to obtain the experimental data needed to make this design method. In the experiments, the effects of the air chamber and curtain wall geometries on energy conversion performance in regular wave conditions were investigated. As the results, it is noticed that the geometry of the curtain wall and the vortex shedding from the corners of curtain wall affect the primary conversion efficiency.
Numerical investigation on flow collector with guide vane for tidal energy conversion
Authors: Sakaguchi M , Hirayama K , Kinoue Y , Murakami T , Shiomi N , Imai Y , Nagata S , Takao M
Published: May 2022

In ocean-based renewable energies, such as wave motion, ocean current, tidal current and ocean thermal energy, many studies have been conducted on the wave energy conversion system and they have been tested in many countries. In this study, a tidal current energy is focused. Collecting a tidal flow is very important because it is generally known that a power available from a stream of water is proportional to the cube of the free stream velocity of the current. In this research, a bi-directional turbine system is investigated for a tidal flow that changes the direction periodically. Numerical investigations are conducted on a bi-directional flow collector with guide vane to collect the flow, in which the effects of vane skew angle and blade number are investigated. Calculated results showed that the collector with eight guide vanes was the highest angular moment at turbine inlet. The axial velocity at turbine inlet was larger for smaller value of the vane skew angle, whereas the tangential velocity at the turbine inlet was larger for larger value of the vane skew angle. As the results of both the profiles of axial and tangential velocity, the angular moment took the local maximum value at around the angle of 180 deg. in this study.
Influence of the blade leaning angle on the performance of a radial impulse turbine for OWC converters
Authors: Valladares Aitor Vega , Díaz Manuel Garcia , Pereiras Bruno , Pérez José Gonzalez
Published: May 2022

Oscillating Water Column systems (OWC) have been in the spotlight in the last 20 years since these devices are considered one of the most promising devices among wave energy technology. These systems produce electricity by means a generator driven by a turbine, which takes advantage of the bidirectional flow created by the OWC itself. Among these turbines suitable for bidirectional flows, it is possible to find radial impulse turbines, which are the focus of this work. Traditionally, the radial impulse turbines have shown lower efficiencies than their competitors. However, the radial turbines present interesting mechanical features and, recently, some research show that the difference has been reduced. Following this thread, this work deals with another modification in the radial impulse turbine looking for a further improvement. By using a validated CFD model, it has been analysed the influence of the lean angle of the blade. Until now, all the turbines present in the literature are leaned zero degrees, leading to a strong interaction between the guide vanes and the blades. This work shows results of the same turbine, equipped with blades leaning from -5deg to 25deg, in order to determine the influence such a modification on the maximum total-to-static efficiency. Results have revealed a slight improvement in the maximum efficiency for positive leaning angles, whereas negative angles drive the turbine to worse performance.
Analytical study on a turbine housing with inner insulation structure for rapid catalyst light-off
Authors: Kitamura T , Hoshi T , Ebisu M
Published: May 2022

The analytical study on a turbine housing with inner insulation structure has been conducted for rapid light-off of a catalyst unit, which is located at the downstream side of turbochargers. CHT (Conjugate Heat Transfer) calculations, working for simulating heat transfer with mutual dependence between solid structures and fluid, are applied to the turbocharger including the turbine section, the bearing housing and the catalyst unit to evaluate the time reduction for activation of the catalyst unit. Feasible inner-insulation structures to be installed in the turbine housing have been also designed. Eventually, the inner-insulated turbine housing has been proven highly effective for rapid catalyst light-off.
Effect of pulsating flow on mild / deep surge phenomena of turbocharger compressor
Authors: Kawana Genshu , Asanaka Yuji , Miyagawa Kazuyoshi
Published: May 2022

It is known that a compressor causes a flow instability phenomenon called surge when the flow rate becomes reduced. Previous studies performed a compressor performance test using an apparatus that simulated a turbocharger for cars. As a result, they have confirmed that surge frequencies differ depending on the capacity of the tank. In this study, performance tests of a compressor for a turbocharger were conducted to understand a mechanism of surge phenomena and to understand differences between them under the steady flow and the pulsating flow. The apparatus which was used at this time consists of a compressor, a pulsating flow generator, a tank, and a valve. Except for the compressor, they install on the downstream side of it in this apparatus. The pulsating flow generator and the tank are equivalent to an automobile engine. First, to understand the difference between the mild surge and the deep surge under steady flow, the flow rate and the pressure of the tank were measured by controlling the valve under five different rotational speeds. And the two types of surge phenomena (i.e. the mild surge and the deep surge) were determined. Compared to the mild surge and the deep surge, it was judged that the former has smaller fluctuations of the flow rate and weaker surge phenomena. And, Fast Fourier Transform (FFT) analysis was performed on the measured pressure. It was found that the higher the rotation speed became, the lower the surge frequencies of the deep surge were, and the lower the rotation speed became, the weaker the strength of the surge phenomenon became. Next, it was investigated the difference in surge frequencies between the mild surge and the deep surge under pulsating flow with the rotation speed fixed. It was found that in the mild surge, the effect of pulsating flow on the surge phenomenon was significant, and it was confirmed that the surge frequencies were drawn into the pulsating frequencies. On the other hand, in the deep surge, the pressure fluctuation of the surge phenomenon became stronger than that of the mild surge, and a pattern of drawing was changed. In addition, unlike the mild surge, in the deep surge, the frequency range of draw in the same magnification between the given pulsating frequency and the obtained surge frequency narrowed. And, it was confirmed that the surge frequency was drawn into the pulsating frequency at half times rate and two times rate.
Design and Simulation of Photo-excited Tunable Perfect Absorber Based on Semiconductor-incorporated Metamaterial Structure
Authors: Ge Tingting , Li Zhijin , Song Wei , Sheng Xinqing
Published: May 2022

The perfect metamaterial absorber with sandwich structure is capable to realize nearly 100% microwave absorption. We designed and simulated a photo-excited tunable perfect absorber based on semiconductor-incorporated metamaterials using HFSS (Ansoft). This absorber composes of semiconductor Ge in designed pattern in the unit cell. Under different pump power of the incident laser light, the conductivity of Ge on the metamaterial varies. In this way, the absorption frequency of the absorber can be tuned. Simulation results showed that, under the two pump light conditions, the absorber is with maximum absorbances of over 97% in both cases. We also analyzed the loss in the absorber through numerical experiments.
Research on An Improved Phase Generation Carrier Demodulation Algorithm
Authors: Wei Shuangjiao , Li Bin’ai , Xue Min , Zhao Wenbin , Bian Zhenglan , Chu Fenghong
Published: May 2022

Traditional phase generation carrier (PGC) demodulation algorithm is often affected by modulation depth C and carrier phase delay θ. An improved PGC demodulation method was put forward in this article. The results show that when in different modulation depth, the demodulation result was stable and almost identical to the original signal to be test. With different phase delay values, such as θ=30°and 60°, the signal amplitude demodulated by the improved algorithm was consistent with the original signal. The new demodulation method can make the accuracy of the phase generation carrier technology better and improve the system performance.
Modeling and Simulation of Wide-range Current Transformer and Optimization of Core Size
Authors: Lei Jingting , Song Xiaolin , Liang Pan , Xu Zhongda , Tang Xiaojun
Published: May 2022

When the current transformer for traditional measurement is too large or too small, the measurement error will fluctuate greatly, resulting in a sharp deterioration of the measurement accuracy. In response to this paper establishes a simulation model of the corresponding current transformer based on SIMULINK and analyzed the error source factors of the current transformer; then, according to theoretical derivation, the simulation established the core size, ratio difference, and angle difference of the current transformer. Finally, a genetic algorithm based on nonlinear programming is used to iteratively optimize the core size of the current transformer, and finally the error of the current transformer after the core is optimized and when the core is not optimized is compared through simulation. The results show that current transformer’s ratio difference and angle difference of the current transformer are significantly reduced. Among them, the ratio difference is reduced to about 50% of the original, and the angle difference of the transformer is reduced to about 60% of the original, which greatly broadens the range of the current transformer.