bluuebunny/crossref_metadata_2025_split huggingface dataset:
Investigation of sediment erosion in low head Francis turbines and its effect on the structural integrity
Authors: Bhattarai Aasma , Kunwar Prashant , Chitrakar Sailesh , Gautam Saroj 
Published: June 2022

Abstract
The geographical condition of Nepal has always challenged the hydropower plants in Nepal. The huge potential run-off rivers flowing through this terrain carry an immense amount of sediment. This sediment constitutes quartz particles with enough hardness, which corrodes the material of the hydraulic turbines and other components of the hydropower plant. The sediment erosion hindered the growth of hydropower plants as it significantly increased the maintenance cost and decreased the efficiency and life span of the plant itself. This paper takes this problem into account to investigate the structural integrity of one of the reference cases of eroded low head Francis turbine of Nepal by performing one-way FSI. CFD analysis was conducted on the single passage of the runner and structural analysis of the runner was conducted as well. For the structural integrity, the thickness of the blade at the trailing edge was decreased to 80 percent of its span. From the results of the structural integrity, the stresses imposed on the reference runner due to the erosion were observed to be within the allowable stress even in the extreme case condition.
Mass transfer rate effects on the cavitating vortex shedding flow around a circular cylinder at a low Reynolds number
Authors: Chen J , Escaler X 
Published: June 2022

Abstract
Cavitating vortex shedding is a flow phenomenon commonly encountered behind bluff bodies in hydraulic machinery and systems. The generated vapor bubbles significantly change the dynamic behaviors of the vortices. In addition, the collapses of the cavities become major sources of unwanted effects such as vibration, noise and material erosion. In this study, the numerical results of the cavitating vortex shedding behind a circular cylinder at a low Reynolds number have been compared and analyzed using different mass transfer rate values between the vapor and the liquid water phases. For that, the transport equation for the vapor volume fraction coupled with the source term based on the simplification of the Rayleigh-Plesset equation has been solved. Commonly, this source term that accounts for the mass transfer rate is a function of the pressure difference, the vapor volume fraction, and the empirical factors. To understand the effects of this rate, its has been gradually increased from its default value up to the infinite when the equilibrium assumption is satisfied. The current results show that as the rate increases, higher gradients of the vapor volume fraction and of the pressure near the interface between the vapor and the liquid phases are predicted. As a consequence, the frequency of the vortex shedding is also affected by the variation of the mass transfer rate.
Evolution and influence of high-head pump-turbine cavitation during runaway transients
Authors: Wu W D , Liu K , Li L , Hou X X , Zhang P C , Du C , Liu X Y , Cheng Y G 
Published: June 2022

AbstractPumped-storage hydropower stations (PSHSs) play irreplaceable roles in promoting the stability and flexibility of power grids. Runaway process is one of the most dangerous transients for PSHSs, and the cavitation in the pump-turbine seriously affects the stability and safety of the unit. However, the evolution and influence of pump-turbine cavitation during runaway transients are still unclear. In this study, the runaway transients of a high-head pump-turbine considering the cavitation effects were simulated by using the three-dimensional (3D) computational fluid dynamics (CFD) method. The results show that the cavitation cavities in the runner appear and disappear periodically, influenced by the backflows around the leading and trailing edges of the runner blades. The wedge-shaped cavities near the leading edges occur around the peak rotational speed moment when the pressure pulsations in the vaneless space show the peak magnitude. And the tongue-shaped shaped cavities near trailing edges appear around zero discharge moment when the hydraulic radial forces reach the peak. The two types of cavitation occur at dangerous moments, to which attention should be paid in the preliminary design stage of PSHSs.
Erosion wear in a double-suction centrifugal pump using an improved erosion model
Authors: Qian Zhongdong , Su Jiahui , Guo Zhiwei , Dong Jing 
Published: June 2022

AbstractPrediction of erosion wear in double-suction centrifugal pumps is studied numerically using an improved erosion model (EM). Experiments are also performed to verify the improved EM’s prediction ability. In the experiments, painted layers of five colors are applied to the blade surfaces using spray guns to show the erosion wear distribution, where the colors and the order are selected based on the simulated results. In simulations based on the Oka model, the small-angle scratching effect is specifically added to the improved erosion model (called the Qian EM here). For the chosen double-suction centrifugal pump, the Oka EM and the Qian EM are used to predict erosion wear, including the wear area and intensity. Both EMs effectively predict the erosion areas of the leading edge, the suction side inlet part and the pressure side outlet part of the blade, but the Qian EM shows better ability to predict the erosion area of the outlet part on the suction side. Additionally, the erosion intensity seems more reasonable with the Qian EM. Inclusion of all different particle sizes in the numerical simulations is found to be necessary to predict erosion wear accurately because each single particle size may provide important information.
Experimental study of Crossflow turbine under different operating conditions
Authors: Shrestha O , Kapali A , Thapa B , Neopane H P , Lee Y H 
Published: June 2022

Abstract
In the present study, experiments were conducted to investigate the performance of Cross-flow turbines (CFT). A CFT runner with 16 degrees of angle of attack and a ratio of 0.67 inner to the outer diameter is selected for the experiment. The efficiency of the turbine was studied using a 3D printed runner with 30 blades at a constant head of 10m and varying rpm from 350 to 750 with an increment of 100 rpm and guide vane opening ranging from 10% to 100% with an increment of 10%. The results of the study indicate that CFT can be used effectively as it contains a flat curve that works well over wide flow conditions. CFT efficiency increases with increasing rpm to a certain point, after which it begins to decrease with increasing rpm.
Pressure pulsation analysis of runner and draft tube of pump turbine under different working conditions
Authors: Wang Dong , Li Zhenggui , Zhao Qing , Li Deyou , Deng Wanquan , Ji Lei , Shengyang Peng 
Published: June 2022

Abstract
As the core component of pumped storage power station, the pump turbine usually needs to adjust the operating condition point according to the electricity demand during operation. Pressure pulsation is an inevitable phenomenon in the operation of pump turbine, which affects the safe and stable operation of the unit. In this paper, the method of combining numerical simulation and experiment is adopted to carry out three-dimensional full flow channel numerical simulation of the pump turbine by using CFD. The flow pattern and pressure pulsation of the runner and draft tube of the pump turbine were analyzed at the three working conditions of PL (50% maximum load), BEP (70% maximum load) and HL (90% maximum load). It is found that under the three conditions, the pressure pulsation from the leafless area to the downstream of the draft tube shows a weakening trend. Because the flow pattern in the bladed area of the unit is poor, the pressure pulsation in the bladed area is the most obvious. From low load to high load, the pressure pulsation tends to weaken at first and then increase. Combined with flow pattern analysis and vortex analysis, it can be concluded that the number and scale of vortex flow are positively correlated with the pressure pulsation, and the vortex flow inside the unit is an important factor that causes the flow disorder inside the unit, and then becomes an important factor that affects the pressure pulsation inside the pump turbine unit.
Static Characteristics Analysis of Shaft Rotor of Vertical Long-Shaft Fire Pump Under the Connection of Different Shaft Lengths
Authors: Zhang J F , Yu X H , Jin S B , Yang Z J , Song H Q , Fu L H , Zhang W J 
Published: June 2022

Abstract
In this paper, a vertical long-shaft fire pump XBC18-178-240LC3 was taken as the research object to study the static characteristics of the pump rotor-shaft system under different shaft length connection. To analyse the influence of the length and number of the intermediate shaft section of the pump shaft on the deformation and equivalent stress of the shafting rotor, three shafting rotor models Z4(modified model), Z5(original model) and Z6(modified model) were designed, and then the static characteristics of them were analysed and compared under four operating conditions of 0.65Q
d(0.65 times design flow),1.0Q
d, 1.2Q
d and 1.4Q
d by numerical simulation. The results suggested that the changed rules of the three models' deformation and equivalent stress were basically the same. After the rated operating condition, the maximum deformation of the impeller of Z5 model was smaller than that of the Z4 and Z6 models. Under the four operating conditions, the maximum equivalent stress of the impeller of Z5 model was the smallest. This showed that the length and number of the intermediate shaft section affected the deformation and equivalent stress of the shaft rotor. Therefore, Z5 model was selected as the best rotor structure design scheme.
Determination of Generator Efficiency on Performance Test of Prototype Turbine
Authors: Cao Dengfeng , Zhang Peng , Zhou Ye , Zhang Xaocheng 
Published: June 2022

Abstract
As an essential parameter to be determined on performance test of prototype turbine, the output power of turbine is generally determined by measured active power and efficiency of generator. Determination method of generator efficiency on turbine performance test is discussed in this paper. A determination method is presented as generator efficiency could be determined by actual generator losses. Analysis results show that it is a better solution rather than reading from the generator efficiency curve. Furthermore, due to the location of active power measurement, excitation loss must be excluded from the generator losses in determining generator efficiency. And the copper losses of rotor and stator must be converted to the actual measured temperature on turbine performance test. Then correct generator efficiency and output power of turbine are determined.
Analysis of deformation characteristics of flood gates of runoff hydropower stations under different operating conditions in case of frequent floods
Authors: Shao S , Li Z G , Kong X Y , Kang J 
Published: June 2022

Abstract
The safety and reliability of flood gates of runoff hydropower stations in the basin are very important. There is no clear rule on the mechanical causes of flood gate deformation in runoff hydropower stations under frequent floods. Therefore, this paper takes a hydropower station as the research object, adopts the unidirectional fluid-solid coupling method, and investigates the stress displacement of flood gate under typical frequent flood conditions by using ANSYS and Fluent software. The results show that the maximum stress of the flood gate is located at the intersection of the bottom two sides of the gate panel and the gate pier, and the stress meets the stiffness requirement. When the gate is opened, the stress distribution range of the panel is shifted from the top to the bottom, and the stress decreases with the increase of the gate opening degrees. The maximum total displacement is concentrated at the bottom of the central axis in the direction of the panel span, and gradually decreases from the middle of the gate panel to the left and right sides, showing a fan-shaped distribution, and basically symmetrical along the central axis of the panel. The flood gate is mainly deformed along the downstream direction, with obvious depression characteristics.
Performance Analysis of Micro Francis Turbine Manufactured Locally in Nepal
Authors: Dahal D R , Kayastha A , Chitrakar S , Thapa B S , Neopane H P , Thapa B 
Published: June 2022

Abstract
The manufacturing of micro-hydro turbines, especially Cross-Flow, Pelton, Propeller turbine, has been carried for more than 50 years in Nepal. A prominent opportunity in the manufacturing of Francis turbines has been perceived in recent years as the requirements of turbines for future installations falls on the Francis turbine range and are above 60%. However, none of the manufacturers step forward to accept the challenges of manufacturing Francis turbines which may be due to the lack of know-how in design and the manufacturing technology of Francis Turbine as a whole. Nevertheless, many attempts have been put forward with the initiation of the Turbine Testing Laboratory, Kathmandu University, for the development of both the design and manufacturing methodology. In this paper, the performance analysis of two different Francis runners, manufactured using local technology of investment casting and pressing-welding method, was conducted. For making the manufacturing, installation and, operations of the turbine as simple as possible, the trapezoidal spiral casing with fixed guide vanes was implemented. In addition the leading and trailing edge modification had not been carried out so as to observe the efficiency rise after these modifications. A comparison of the efficiency for both the turbines indicates Francis turbines with fairly good efficiencies can be manufactured using locally available tools and technology.
Tunnel support practice in small hydropower tunnels in the Himalayas through observational approach
Authors: Karki Sujan , Chhushyabaga Bimal , Khadka Shyam Sundar 
Published: June 2022

Abstract
With the high mountains, steep terrain and fast flowing river, the Himalayan region has a great opportunity and potential for hydropower development. In Nepal, many hydropower projects have been constructed and many are under construction among which majority of the project are small to medium scale project. For such project, medium size tunnel provides an economic and safe route for water convergence. Squeezing and collapse have been observed in most of the hydropower tunnels, which have resulted in support failure, as the tunnel passes through weak rock mass under high in-situ stress during construction. Due to insufficient tunnel closure measurements, field-based observation has been conducted to study the installed support at different tunnels in the Himalayas. The observational approach is used for analysis and recommendations have been made for designing a stable and safe support system for tunnels. Through an analysis of a case study from Nepal, comparison has been made on the design and practiced support systems, and description of supports used in various case histories from Nepal have been provided.
Experimental research of the damping characteristics of the fatigue stand caused by changes in material properties
Authors: Pawliczek R , Lagoda T , Kurek M , Robak G 
Published: June 2022

Abstract
The paper presents the results of research on changes in the damping characteristics of the MZGS100 fatigue test stand. The work of the stand is influenced by the type of material of the tested samples, where different properties affect the dynamic characteristics of the stand. It is important to assess the impact of changes in properties during the test on the work of the test stand. Fatigue tests were carried out for three materials: S355J0 steel 2017A-T4 aluminium alloy and CuZn40Pb2 brass. The tests were carried out under fatigue bending loads for the number of failure cycles in the low-cycle range. During the investigation, the test was interrupted and the impulse response of the stand at various stages was recorded and the change in system response was assessed. It was observed that in the case of brass, the damping curve of the system changed continuously, and the damping factor of the system increased by 23%. In the case of steel, practically no changes were noticed, while the aluminium alloy showed changes of 9%. In the final stage of the test for steel and aluminium alloy, a change in the frequency of natural vibrations was observed, which indicates a decrease in the system stiffness caused by the weakening of the specimen's cross-section. This effect was not noticed for brass samples, which together with the change of the damping coefficient indicates a cyclical change of the material properties.
CFD simulation of heat transfer and airflows in an open refrigerated display cabinet
Authors: Vengalis Tadas , Mokšin Vadim 
Published: June 2022

Abstract
This paper uses CFD (Computational Fluid Dynamics) method to study the efficiency of the airflow curtain in an empty and full open refrigerated display cabinet. Numerical simulation results show that changing of the angle of the honeycomb can reduce the infiltration of warm ambient air into the refrigerator. It was established that the average intake air temperature in modified design decreased by 0.6 °C compared to the original design. The CFD model presented in the paper can be used to study airflows inside and to design and develop open-type refrigerated cabinets.
Gold nanoparticle-based biofuel cell catalytic efficiency reliance on medium pH
Authors: Zinovicius Antanas , Rozene Juste , Sataite Vakare Guoba , Merkelis Timas , Juska Joris , Morkvenaite-Vilkonciene Inga 
Published: June 2022

Abstract
Over the past several decades, biology, chemistry, and medicine took advantage of gold nanoparticles (AuNPs) for their fascinating characteristics. Today these nanomaterials can be synthesized in various methods from biosynthesis, when particles are made by microbial culture, to physical. Using the fast scan cyclic voltammetry, AuNPs can be electrodeposited from chloroauric acid (HAuCl4) directly onto the surface of a graphite electrode. This method provides high reproducibility and allows to control the size of the nanoparticles (from 4 to 75 nm) and electrode coverage by changing HAuCl4 concentration, scan speed, and a number of applied cycles. Gold nanoparticles are known to express comparable catalytic activity to natural enzymes such as glucose oxidase or horseradish peroxidase. Despite the advantages over natural enzymes, inorganic enzyme mimicking catalysts exhibit limited catalytical efficiency and selectivity. To increase efficiency, we used low size AuNPs which increase reactivity; the lack of selectivity in a biofuel cell is advantageous since AuNPs can reduce/oxidize several substrates in the medium. Biofuel cell based on AuNP’s has a superior life span, as the main active part of the system is inorganic, and thus it is not affected by oxygen stress, where typical microbial biofuel cells are struggling. The observed catalytic activity had a minimal dependency on temperature change. pH was changed from 4 to 10 with the smallest synthesized AuNPs. However, pH has an impact on the reaction speed. Results showed that biofuel cell is suitable for raw wastewater as it usually deviates from pH 7, and usable current can be generated.
In vitro circulation model driven by tissue-engineered dome-shaped cardiac tissue
Authors: Kikuchi Tetsutaro , Matsuura Katsuhisa , Shimizu Tatsuya 
Published: June 2022

Abstract
The heart is an essential organ for animals and humans. With the increased availability of pluripotent stem cells, the use of three-dimensional cardiac tissues consisting of cultured cardiomyocytes in in vitro drug evaluation has been widely studied. Several models have been proposed for the realization of the pump function, which is the original function of the heart. However, there are no models that simulate the human circulatory system using cultured cardiac tissue. This study shows that a dome-shaped cardiac tissue fabricated using the cell sheet stacking technique can achieve a heart-like pump function and circulate culture medium, there by mimicking the human circulatory system. Firstly, human induced pluripotent stem cells were differentiated into autonomously beating cardiomyocytes, and cardiomyocyte cell sheets were created using temperature-responsive culture dishes. A cardiomyocyte sheet and a human dermal fibroblast sheet were stacked using a cell sheet manipulator. This two-layered cell sheet was then inflated to create a dome-shaped cardiac tissue with a base diameter of 8 mm. The volume of the dome-shaped cardiac tissue changed according to the autonomous beating. The stroke volume increased with the culture period and reached 21 ± 8.9 μl (n = 6) on day 21. It also responded to β-stimulant and extracellular calcium concentrations. Internal pressure fluctuations were also recorded under isovolumetric conditions by dedicated culture devices. The peak heights of pulsatile pressure were 0.33 ± 0.048 mmHg (n = 3) under a basal pressure of 0.5 mmHg on day 19. When the tissue was connected to a flow path that had check valves applied, it drove a directional flow with an average flow rate of approximately 1 μl s−1. Furthermore, pressure–volume (P–V) diagrams were created from the simultaneous measurement of changes in pressure and volume under three conditions of fluidic resistance. In conclusion, this cardiac model can potentially be used for biological pumps that drive multi-organ chips and for more accurate in vitro drug evaluation using P–V diagrams.
fast.adonis: a computationally efficient non-parametric multivariate analysis of microbiome data for large-scale studies
Authors: Li Shilan , Vogtmann Emily , Graubard Barry I , Gail Mitchell H , Abnet Christian C , Shi Jianxin 
Published: June 2022

Abstract

Motivation
Nonparametric multivariate analysis has been widely used to identify variables associated with a dissimilarity matrix and to quantify their contribution. For very large studies (n≥5000) and many explanatory variables, existing software packages (e.g. adonis and adonis2 in vegan) are computationally intensive when conducting sequential multivariate analysis with permutations or bootstrapping. Moreover, for subjects from a complex sampling design, we need to adjust for sampling weights to derive an unbiased estimate.

Results
We implemented an R function fast.adonis to overcome these computational challenges in large-scale studies. fast.adonis generates results consistent with adonis/adonis2 but much faster. For complex sampling studies, fast.adonis integrates sampling weights algebraically to mimic the source population; thus, analysis can be completed very fast without requiring a large amount of memory.

Availability and implementation
fast.adonis is implemented using R and is publicly available at https://github.com/jennylsl/fast.adonis.

Supplementary information
Supplementary data are available at Bioinformatics Advances online.
Political Selection and Economic Policy
Authors: Meriläinen Jaakko 
Published: June 2022

Abstract
Does political selection matter for policy in representative governments? I use administrative data on local politicians in Finland and exploit exogenous variation generated by close elections to show that electing more high-income, incumbent and competent politicians (who earn more than observably similar politicians) improves fiscal sustainability outcomes, but does not decrease the size of the public sector. I also provide suggestive evidence that electing more university-educated local councillors leads to more public spending without adverse effects on fiscal sustainability. I reconcile these findings with survey data on candidate ideology and demonstrate that different qualities are differentially associated with economic ideology.