bluuebunny/crossref_metadata_2025 huggingface dataset:
The Use of Gaussian Mixture Model for Counting Human Object on Video
Authors: Soeleman Moch Arief , Haq Irfanul , Muslih  , Karis W , R. Anggi P
Published: April 2021

Video monitoring has been widely used in various places, for example, tourist attractions, stations, terminals, offices, supermarkets, minimarkets, and other places. The use of video monitoring has the aim to improve security aspects in a place that is considered quite helpful. The rapid development of technology, video monitoring has been implemented for purposes other than for security, such as people counting systems. People counting to find out the number of visitors in a place or building is a difficult job to do, requires a lot of time and often the data obtained is not appropriate. Gaussian Mixture Model (GMM) is a background reduction method, which is used to identify the background and foreground. Background reduction is an approach that is widely used to detect moving objects on video from static cameras. While blob detection is detecting a group of pixels connected in an image that has a different colour (white or black). Blob is used for object classification, whether the object is a person or not. From the results of system testing shows that counting people can be done well, with an average percentage of 95.83% recall, 94.5% precision and 90.88% accuracy of the entire video test data. The use of GMM in counting people in this study can also count people who carry objects properly as long as they are not drawn as in the morning test video. In addition, this system can store the calculated data.
Enhancing Learning Performance of Students in Higher Education with Adaptive Navigation Support
Authors: Hamzah Almed , Haryono Kholid , Jayadi Puguh , Ningrum Sari Kurnia
Published: April 2021

The study work on the development of a system prototype to aid the students in managing their assignments. The prototype employs Adaptive Navigation Support as an approach in providing personalized recommendation for the quiz that students must work on. With this prototype, the students can manage their quizzes better and complete more quizzes. In addition, the students are able to monitor their progress as well as their performance in particular course. Prototyping methodology was used to develop the prototype in mobile environment.
Mechanical and dynamic properties of composite rubber (RSS and SBR) with waste rubber crumb and copper fiber
Authors: Tirtoputro Shendyanto , Priyosulistyo Henricus , Faizah Restu
Published: April 2021

Waste rubber tire is difficult to decompose by nature, but it can be reused as a part of composite rubber materials. In this research, waste rubber crumb was mixed into Ribbed Smoked Sheets (RSS) and Styrene-Butadiene Rubber (SBR) compound to form a composite rubber. The aim of this research is to investigate the mechanical and dynamic properties of RSS and SBR compounds with waste rubber crumb and copper fibber. For this purpose, another composite material in the form of copper fiber is also added which is expected to increase the damping properties of the rubber even though the mechanical properties of the rubber will decrease. RSS and SBR rubber compounds consist of 25-phr and 50-phr waste rubber crumb. Waste rubber crumb is taken from used vehicle tires with the granular size passes through the mesh sieve number # 100. 5-phr, 10-phr, 20-phr, and 30-phr of copper fibers were added into 25-phr and 50-phr respectively. The copper fiber used is 0.3 ± 0.05 mm in diameter and length to diameter ratio is 40. The results of this study indicate that the addition of waste rubber 25-phr and 50-phr decreases the tensile strength, elastic modulus, and shear modulus but increases the damping properties. The addition of copper fiber 5-phr until 30-phr decreses the tensile strength and elastic modulus but increases the shear modulus and the damping properties.
Development of work breakdown structure standard for safety planning on stadium construction work based on risk
Authors: Anggraini Amelia , Latief Yusuf
Published: April 2021

Purpose: The purpose of this study is to reduce the level of work accidents in stadium construction by developing risk-based work breakdown structures. Methodology: The research methodology includes several stages, namely the literature study, analysis of data archives and previously related project and research, as well as through the validation of experts. Result: The results of this study are WBS standards, implementation methods, activities, resources, potential hazard risks and safety planning using risk-based WBS standards on stadium construction work, as a method in preventing, reducing, eliminating or even nulliying the chance of accident throughout the development of a construction work. Applications/Originality/Value: This research will hopefully provide benefits to the construction world by presenting work accidents prevention methods by incorporating risk elements into each level of project work in the Work Breakdown Structure which will be used as input in the making of a safety plan.
Improvement Palmprint Recognition System by Adjusting Image Data Reference Points
Authors: Kusban Muhammad
Published: April 2021

Nowadays, the palmprint recognition method is an attractive tool for people recognition besides face recognition and fingerprint. To get a good palmprint recognition system requires a series of algorithms that are united and worked together to create a preferred method. The biometric system in palmprint recognition is said to be preferred when the choice of the algorithm applied has the advantage of each phase. Generally, The palmprint recognition system starts from the selection of image filters, image positioning, dimension reduction, and finally, end with the distance method. Image normalization position is a problem for researchers because the palmprint is always moving and shows a curved shape making it difficult for the system in the identification and verification process. For this reason, the research focuses on the selection of orientation scale operator value from the Gabor technique to get the best parameter value for palmprint biometrics. The desired system is when the overall performance of the algorithm used will produce an output with a low EER value and a high level of verification. From the research that has been carried out, the range of 8 × 5 becomes a good alternative for the choice of Gabor value pairs.
A conceptual design of modified Human Factor Analysis and Classification System mobile application
Authors: Salma Sheila Amalia , Pratama Gradiyan Budi , Widyanti Ari
Published: April 2021

This article aims to provide a conceptual design of the medication error identification based on a mobile application using the modified HFACS approach. The conceptual design in this study discusses the user and functional requirements based on the organizational structure and business process of medication prescription. This study used DFD that aims to describe the relationship among the user. Interface and prototype of the application is developed based on a focused group discussion of ergonomics expert. The user involved in the prescription process are the doctors, hospital workers from the pharmaceutical department, and hospital workers from the Hospital Patient Health department. The role of HFACS investigation is played by the patient-health department. The developed interface of HFACS focuses on the evaluation and documentation of medication error cases. This present study is the first study focus on the development of HFACS mobile application in evaluating and documenting medication error.
Optimization of bucket tooth excavator design using topology optimization and finite element method
Authors: Suryo Sumar Hadi , Sastra Rachmat Suryadi , Muchammad  , Harto
Published: April 2021

Purpose: This research discusses the optimization design of bucket tooth on the market to produce a lighter design but still maintains its strength, the type of bucket tooth is Verona PC200. Methodology: The optimization process in a bucket tooth applies the concept of topology optimization. A static linear analysis is performed using the finite element method to see the maximum stress that occurs in the bucket tooth. Then the method is determining the design variable of bucket tooth with applied a manufacturing constraint. Optimization gives the new design. Result: The maximum VonMises value is 403.81 MPa. After that topology optimization is done by selecting several variations of the design area which results in a reduction in mass in first variation of 0.72 kg and the second variation 1.49 kg. The mass reduction causes a change in stress that occurs in the bucket tooth to 451.8 MPa in first variation and 458.6 MPa in variation 2, but the stress is still in a safe condition. Value: Optimization of bucket tooth design in this paper can reduce the cost of production for bucket tooth with considering to keep the strength of bucket tooth.
The Development of Android for Indonesian Sign Language Using Tensorflow Lite and CNN: An Initial Study
Authors: Fadlilah Umi , Mahamad Abd Kadir , Handaga Bana
Published: April 2021

Deaf people in the world have different sign language according to their living place. They tend to use simple sign language to communicate with others. Whereas every country has their own sign language. Usually a country has one national sign language, but there are 2 kinds of sign languages (SIBI and BISINDO) in Indonesia. However, BISINDO (Indonesian Sign Language) had not recognized yet as a formal sign language like as SIBI (Indonesian Sign Language System), it is only a daily sign language among them and with normal people. Thus, researcher propose to promote BISINDO by developing BisAndro (BISINDO using Android) application. At the start, researcher prepare to compare BISINDO systems in cyberspace, develope basic BISINDO website by PHP and MySQL, train some gestures in TensorFlow lite, and make CNN (Convolutional Neural Network) plan before developing BisAndro application. BisAndro application will be built by Python programming, Tensorflow as an image recognition technology, and Android mobile phone as the launcher device. The application is expected can be used by deaf people to communicate with others easily because it facilitates two ways communication through mobile phone. So, the preparation is needed to know about initial requirement of the next BISINDO learning application using Android smartphone in order to be more useful for deaf and normal people directly.
Optimization on The Hydrolysis Process of Cellulose from Corn Husk to Glucose with Activated Carbon Catalyst Sulfonated
Authors: Anggoro Didi Dwi , Buchori Luqman , Djaeni Mohamad , Ratnawati  , Retnowati Diah Susetyo , Hadiyanto  , shidqi Ashar
Published: April 2021

The design of this research consisted of four stages, that is manufacture of catalysts, cellulose hydrolysis process, glucose yield test and optimization process.The research data is plotted in a mathematical model that is optimized using software of Statistica 10 with Response Surface Methodology (RSM) and ANOVA methods. From the RSM method was obtained mathematical equation model for the relationship of the combination of temperature, time and amount of catalyst to glucose levels, that is: Y = -20, 0457 + 5,341x1 -3, 245

x
2
1

+ 6, 471x2 -2,798

x
2
2

+4,697x3 -2,965x2
3 +1,241x1x2 -0,996x1x3 +0,675

x
2
3

. ANOVA method produces a value of determination coefficient (R2) as big 0.91545. In this research, the optimum temperature is at 70°C, the optimum time is at 2 hours, and the optimum amount of catalyst is at 11 grams. The results of glucose yield obtained from the optimal operating conditions is 31%.
Development of system information of building code checking in planning and permitting phase to improve building code compliance based on work breakdown structure (WBS) using building information modeling (BIM)
Authors: Yogana Endiq , Latief Yusuf
Published: April 2021

Purpose: Audit of the requirements for construction project regulations in DKI Jakarta is still conducted conventionally (paper and CAD based) which requires a long time, resource intensive, different interpretations of the regulations, the process of revised repetitive, the process of tracking difficult requirements, inaccurate and not transparent, and has significant time and cost implications. Examination of conventional requirements causes that there are still many buildings in DKI Jakarta that have not yet met the technical requirements requested for building completion and public dissatisfaction. Automatic requirements checking is possible when the computer representation of the product data model (Product Data Model (PDM)) is integrated with the Legal Knowledge Model (LKM) as input for data processing systems or machines with algorithmic procedures as Compliant Design Processes (CDP) to produce an accurate automatic regulatory check report. Methodology: The Building Model developed in Building Information Making (BIM) is made as a building representation. The scope of building technical requirements based on BIM is managed dynamically using Work Breakdown Structure (WBS) in one database that is validated by the Government and can be applied by planners in any planning. This research uses the BIM model and develops a WBS-based Information System with a BIM application. Results: The scope of requirements can be managed by decomposition of work known as Work Breakdown Structure to produce a BIM component that will be subject to regulatory requirements checking. The ability of the BIM can produce building models that can be subject to audit of regulatory requirements. Examination of regulatory requirements can be carried out at each stage of developing the BIM model according to the level of detail of the BIM object. Examination of regulatory requirements can be carried out independently by planners at each stage by using a Web-based Information System developed in the BIM format that has been validated by the Government. Applications/Originality/Value: By grouping requirements based on the stages of development of the BIM model, it will maximize the fulfillment of the requirements at each stage so as to reduce the risk of redesign while at the same time increasing the fulfillment of the technical requirements of the building.
Optimization of batch extraction of functional ingredients from stevia leaves with response surface methodology
Authors: Hartini  , Tara Mega Renovasi , Harismah Kun , Fuadi Ahmad Muhamad
Published: April 2021

The aim of the study was to reveal an effective extraction procedure for maximization of the yield of stevioside, flavonoid, and total phenolic compounds as well as antioxidant activity in stevia extract. Extraction was carried out at temperature variations of 75 ÂΩC, 80 ÂΩC, 90 ÂΩC and variations of water solvents 280 mL/g, 290 mL/g, 300 mL/g. Stevioside and flavonoid analysis used spectrophotometer method, while phenol analysis used the Folin-Cioccalteau reagent method. The result is a change in temperature and solvent ratio affect the changes in stevioside, flavonoid, and phenol levels. Optimal conditions of stevioside, flavonoid, and phenol using response surface methodology (RSM) occur at a temperature range of 75 ÂΩC with a solvent ratio of 280-290 mL/g.
Discrete cosine transform and multi class support vector machines for classification cardiac atrial arrhythmia and cardiac normal
Authors: Ratnadewi  , Hangkawidjaja Aan Darmawan , Prijono Agus , Suherman Jo
Published: April 2021

The electrocardiogram signal is the most important analysis to detect cardiac arrhythmia. Machine learning classification is used as a first step to detect someone’s arrhythmia or normal heart. This paper discusses one method for detecting arrhythmia by using digital images of cardiac signals and R-R intervals. The process electrocardiogram digital image is divided into two, first the process of calculating the R-R intervals and second the process of extraction feature using Discrete Cosine Transform, followed by calculating the Euclidean Distance or Cityblock Distance with normal electrocardiogram signal reference. Euclidean Distance results or Cityblock Distance and R-R distance of electrocardiogram signals are then classified using Multiclass Support Vector Machine. The results of accuracy the classification four classes that are cardiac normal, atrial premature beat arrhythmia, atrial flutter arrhythmia, and atrial fibrillation arrhythmia, are 81.9%. The originality is used image to detect cardiac normal or cardiac arrhythmia by combined Discrete Cosine Transform, Euclidean distance or City block distance and Multiclass Support Vector Machine.
Modular Production System Control Using Supervisory Control Theory Method
Authors: Sartika Erwani Merry , Sarjono T.Rudi , Christian Kevin
Published: April 2021

Modular Production System (MPS) is a mini industrial automation process that simulates product processing. MPS uses a Programmable Logic Controller (PLC) to observe and control system processes. The MPS used is the Festo Processing Station which is composed of several components that are numerous and varied so that the control is quite difficult, especially when using a basic PLC program. Therefore, this paper proposes that MPS is classified as a Discrete Event System (DES). The method used to control DES is the Supervisory Control Theory (SCT). MPS is used to process two types of materials (metal and non-metal). The drilling process is carried out only for metal. PLC-based MPS is successfully controlled using the SCT method. MPS with the SCT method can process the material with 100% success. The PLC program using the SCT method can save data memory by 2.3% compared to without SCT.
The rise big data for maintenance roadside greenery (Study the damage tree database in Surakarta, Central Java)
Authors: Indrawati I. , Nurhasan N. , Sari Siti Kartika
Published: April 2021

This research question is ‘how to build the database of trees roadside in Surakarta?’ The reasearch objectives are: (1) Identification of the trees characteristics (type and size); (2) Identification level of the healthy trees, and (3) Trees location. This research used categorized methods by healthy of tree, that is: healthy, little damage, moderate damage and heavy damage. The research location at Jalan Slamet Riyadi, Jalan Jenderal Sudirman and Jalan Urip Sumohardjo at Surakarta City. There are several resuts can be drawn: (1) This research has build a Tree Inventory Application, named SIPPOHON. Through SIPPOHON trees can be inventoryed by the name, type and characteristics. Tree location is integrated in a global positioning system (GPS); (2) The Polyalthia longifolia, Mangifera kemanga, Diospyros blancoi have a strong endurance tree; (3) Pterocarpus indicus, Erythrina, Manilkara kauki, langerstroemia and Casuarina tend to be damaged or unhealthy; (4) Some forms of tree damage are caused by: hollow and hollow trunks; mechanical damage (scratches and cuts that hurt the tree to the cortex); pest attacks that cause the stems to become brittle; swelling of the stem; the partial canopy is dead; trees tilted into the electricity grid; and roots come to the surface. The result of the research are applicaton to manage the green roadside, expecialy: (1) Treatment of pest are needed to prevent the spread of disease; (2) Routine maintenance and monitor the tree condition.
Active layer thickness as a function of soil water content
Authors: Clayton Leah K , Schaefer Kevin , Battaglia Michael J , Bourgeau-Chavez Laura , Chen Jingyi , Chen Richard H , Chen Albert , Bakian-Dogaheh Kazem , Grelik Sarah , Jafarov Elchin , Liu Lin , Michaelides Roger John , Moghaddam Mahta , Parsekian Andrew D , Rocha Adrian V , Schaefer Sean R , Sullivan Taylor , Tabatabaeenejad Alireza , Wang Kang , Wilson Cathy J , Zebker Howard A , Zhang Tingjun , Zhao Yuhuan
Published: April 2021

Active layer thickness (ALT) is a critical metric for monitoring permafrost. How soil moisture influences ALT depends on two competing hypotheses: (a) increased soil moisture increases the latent heat of fusion for thaw, resulting in shallower active layers, and (b) increased soil moisture increases soil thermal conductivity, resulting in deeper active layers. To investigate their relative influence on thaw depth, we analyzed the Field Measurements of Soil Moisture and Active Layer Thickness (SMALT) in Alaska and Canada dataset, consisting of thousands of measurements of thaw depth and soil moisture collected at dozens of sites across Alaska and Canada as part of NASA’s Arctic Boreal Vulnerability Experiment (ABoVE). As bulk volumetric water content (VWC) integrated over the entire active layer increases, ALT decreases, supporting the latent heat hypothesis. However, as VWC in the top 12 cm of soil increases, ALT increases, supporting the thermal conductivity hypothesis. Regional temperature variations determine the baseline thaw depth while precipitation may influence the sensitivity of ALT to changes in VWC. Soil latent heat dominates over thermal conductivity in determining ALT, and the effect of bulk VWC on ALT appears consistent across sites.
Skillful prediction of tropical Pacific fisheries provided by Atlantic Niños
Authors: Gómara Iñigo , Rodríguez-Fonseca Belén , Mohino Elsa , Losada Teresa , Polo Irene , Coll Marta
Published: April 2021

Tropical Pacific upwelling-dependent ecosystems are the most productive and variable worldwide, mainly due to the influence of El Niño Southern Oscillation (ENSO). ENSO can be forecasted seasons ahead thanks to assorted climate precursors (local-Pacific processes, pantropical interactions). However, due to observational data scarcity, little is known about the importance of these precursors for marine ecosystem prediction. Previous studies based on Earth System Model simulations forced by observed climate have shown that multiyear predictability of tropical Pacific marine primary productivity is possible. With recently released global marine ecosystem simulations forced by historical climate, full examination of tropical Pacific ecosystem predictability is now feasible. By complementing historical fishing records with marine ecosystem model data, we show herein that equatorial Atlantic sea surface temperatures (SSTs) constitute a valuable predictability source for tropical Pacific fisheries, which can be forecasted over large-scale areas up to three years in advance. A detailed physical-biological mechanism is proposed whereby equatorial Atlantic SSTs influence upwelling of nutrient-rich waters in the tropical Pacific, leading to a bottom-up propagation of the climate-related signal across the marine food web. Our results represent historical and near-future climate conditions and provide a useful springboard for implementing a marine ecosystem prediction system in the tropical Pacific.
An intervention study of the rural elderly for improving exposure, risk perception and behavioral responses under high temperature
Authors: Lou Jianing , Ban Jie , Zhang Ting , Wang Peng , Wu Yangyang , Huang Lei , Li Tiantian , Bi Jun
Published: April 2021

The frequency and intensity of high-temperature events continue to increase, resulting in a surge of pathogenicity and mortality. People with low levels of risk perception and adaptability, such as the elderly, suffer more from high temperatures. Effective intervention measures may lead to reduced levels of high temperature-related risk. The purpose of this study was to compare changes in temperature exposure, risk perception and coping behaviors under different intervention methods. Herein we conducted three different interventions including education, subsidies for electricity and uses of spray-cooling appliances as well as collected data about temperature exposure, risk perception, and coping behaviors. Before and after the experiment, we evaluated the intervention effectiveness with a number of variables related to alerting human responses under high temperatures. We conducted nonparametric tests for paired samples and generalized linear mixed effect models. Compared with subsidy support and outdoor spray-cooling methods, education is more effective as it leads to lower levels of temperature exposure, higher levels of risk perception, and more behavioral responses. The subsidy support intervention is useful in increasing risk perception and promoting home cooling practices as well. In comparison, spray cooling barely contributes to the reduction of personal temperature exposure. The encouragement of risk-related education and continued government subsidy may prevent elderly individuals from experiencing high-temperature exposure.
Uncertainty in the extreme flood magnitude estimates of large-scale flood hazard models
Authors: Devitt Laura , Neal Jeffrey , Wagener Thorsten , Coxon Gemma
Published: April 2021

The growing worldwide impact of flood events has motivated the development and application of global flood hazard models (GFHMs). These models have become useful tools for flood risk assessment and management, especially in regions where little local hazard information is available. One of the key uncertainties associated with GFHMs is the estimation of extreme flood magnitudes to generate flood hazard maps. In this study, the 1-in-100 year flood (Q100) magnitude was estimated using flow outputs from four global hydrological models (GHMs) and two global flood frequency analysis datasets for 1350 gauges across the conterminous US. The annual maximum flows of the observed and modelled timeseries of streamflow were bootstrapped to evaluate the sensitivity of the underlying data to extrapolation. Results show that there are clear spatial patterns of bias associated with each method. GHMs show a general tendency to overpredict Western US gauges and underpredict Eastern US gauges. The GloFAS and HYPE models underpredict Q100 by more than 25% in 68% and 52% of gauges, respectively. The PCR-GLOBWB and CaMa-Flood models overestimate Q100 by more than 25% at 60% and 65% of gauges in West and Central US, respectively. The global frequency analysis datasets have spatial variabilities that differ from the GHMs. We found that river basin area and topographic elevation explain some of the spatial variability in predictive performance found in this study. However, there is no single model or method that performs best everywhere, and therefore we recommend a weighted ensemble of predictions of extreme flood magnitudes should be used for large-scale flood hazard assessment.
An Analysis of the Application of Energy Storage Technology in Power Systems
Authors: Li Guosheng
Published: April 2021

With the rapid development of China’s economy, the coverage area of China’s power grid is expanding, and users have higher requirements for the quality and reliability of electrical energy. And the development of energy storage technology has improved the stability of power system operation, voltage and frequency regulation, load compensation, and also injected new development ideas into the planning and design of power systems, manufacturing control, etc. Energy storage technology occupies a very important position in the power system, the needs of its power system so as to enhance the availability of renewable energy and ensure that the power system can operate safely and stably. This paper provides further analysis and discussion on the application of energy storage technology in power systems.
Structural Parameter Analysis of Self-Tightening Metal U-Shaped Seal Ring
Authors: Cheng Tianfu , Li Shuangxi
Published: April 2021

The effects of different structural parameters on the sealing performance of self-tightening metal U-shaped seal rings were studied. A two-dimensional axisymmetric model of a self-tightening U-shaped seal ring was established using finite element software. The influence of structural parameters such as side wall thickness, bottom wall thickness and boss radius on the sealing performance of the seal ring was analyzed by the control variable method. The results show that as the thickness of the side wall increases, the stress shows a downward parabolic trend, which is the smallest at 0.55 to 0.65 mm; as the bottom wall thickness increases, the stress first increases steadily, and then decreases slowly after 0.8 to 0.9 mm; When the inclination angle is from 0 to 9 °, the sealing ring can obtain better sealing performance. The results have guiding significance for the design, optimization and application of subsequent seal ring structures.
Numerical analysis of magnetic grease seal pole teeth optimization based on pressure bearing capacity
Authors: Shuwen-Li  , Rao-Zheng  , Qiuxiang-Zhang  , Shuangxi-Li
Published: April 2021

The static magnetic field model of the magnetic grease seal was established by the nonlinear magnetic field finite element method. The influence of three typical pole teeth with different seal gaps, namely rectangular teeth, single-side trapezoid, and symmetrical teeth, on pressure bearing capacity was analyzed. The results show that the maximum pressure bearing capacity of the optimized structure is from large to small: symmetric trapezoid teeth, single-sided trapezoid teeth, rectangular teeth. The seal gap increased by 0.1 mm and pressure bearing capacity decreased by 12 %. If the teeth width was doubled, the pressure bearing capacity can be increased by 17.8%, with an optimum range of 1.8 mm to 2.2 mm. The interval length of the teeth doubled, the pressure bearing capacity increased by 30.65 %, and the optimum range for the interval length of the teeth was 1.8 mm to 2.0 mm. There was no significant correlation between teeth height and pressure bearing capacity. The study on the optimization of the teeth structure based on pressure bearing capacity could provide a reference for technical personnel to improve the efficiency and rationality of the design of the teeth for the sealing of the magnetic grease.
Study on the Influence of High Temperature and High Speed Working Conditions on the Leakage Characteristics of Flexible Bristle Brush Seal
Authors: Ma Y H , Li S X , Zhang S Y , Liao H R , Sha L X
Published: April 2021

Compared with the metal bristles, the flexible bristles can reduce the heat and wear caused by the friction between the bristles bundle and the rotor, and improve the working stability and working life of the brush seal. In this paper, the L-shaped numerical mode is established to analyze leakage characteristics of flexible bristle brush seal. The flow field of brush seal is analyzed, and the effects of differential pressure, rotating speed and temperature on the leakage rate were studied as well. The leakage rate of the flexible bristles brush seal under different pressure and rotating speed was measured and compared with the numerical results. The results show that: Pressure drop mainly occurred in bristles pack; Small pressure difference, high temperature and high speed can improve the sealing performance, which, shows that the flexible bristles brush seal can well adapt to high temperature and high speed conditions; The leakage rate after running-in is slightly lower than that before running-in, and has better sealing performance, and the brush bristles arrangement is complete and tight after test, indicating that the flexible bristle brush seal has the ability of lasting and stable seal; The error between experimental results and numerical simulation results is less than 10%, and the variation trend is consistent, confirming the accuracy of the leakage rate obtained by numerical simulation.
Design method and research of high temperature gas floating ring seal with slightly variable gap
Authors: Shi Ren-jie , Li Shuang-xi , Zhen Rao , Ma Li-jun , Zhang Jing-bo
Published: April 2021

The problem of seal failure caused by rubbing between floating ring and shaft directly affects the actual production efficiency. In this paper, the mathematical model of floating ring seal was established, the expression of seal clearance under the working condition of floating ring was calculated, and the design method of “slightly variable gap” gas floating ring was proposed. The finite element model was established by using Workbench, and the correctness of the mathematical model was verified. The results show that the ideal insert ring material calculated by the “slightly variable gap” design method can keep the working clearance of floating ring seal stable. In practical application, the insert ring with the same material as the axle runway can also be selected to achieve a more stable working clearance. The design method can avoid the rubbing between the runway and the inside of the floating ring under harsh conditions.
Performance Analysis and Optimization of Internal Spiral Groove Dry Gas Seal Based on Fluid-solid-thermal Coupling Method
Authors: Li S X , Liao H R , Zheng R , Li S C , Ma Y H , Chen K Y
Published: April 2021

Internal spiral groove dry gas seal (ISGDGS) are used to seal special positions of rotating machinery. There is an urgent need to address the problems caused by contacting of rotating and static rings during high-speed rotation of ISGDGS. The main aim of this study is to investigate the influence of spiral groove structural parameters on ISGDGS sealing performance. Fluid-solid-thermal coupling method was used to analysis the relationship of sealing performance (opening force, leakage, friction power, and gas film stiffness) and spiral-groove structural parameters. The test analysis method is used to study the sealing performance under four different structural parameters, and the obtained trends are the same as the analysis results. According to the analysis results, the value range of structural parameters for optimal sealing performance is proposed This thesis has provided a deeper insight into the influence of the structural parameters of end face on the sealing performance, and provides a basis for its optimal design.
Bifurcation Characteristics of Airfoil-NESs coupled System
Authors: Zhang Wenfan , Zhou Genbiao , Zhou Yafeng , Wang Lei , Zhang Jiazhong
Published: April 2021

Aeroelastic instability has become a hot research topic. It has increasingly high-lighted its importance in the aircraft and fluid machinery industry and brings challenges to the safe flight of various aircraft and the safe operation of fluid machinery. Numerical simulations were performed to study the flow-induced oscillation of a two-dimensional airfoil with two non-linear energy sinks (NES). The main system has two degrees of freedom-pitch and heave. These two NESs are considered as subsystems, with the first NES at the leading edge and the second NES at the trailing edge. The bifurcation behaviour and the mechanism of the system leading to chaos of the coupled system under different parameters and initial conditions is studied by nonlinear analysis, and the relationship between large amplitude limit cycle oscillation and the chaotic occurrence point of the main system is revealed, this corresponding relationship has important theoretical significance for mastering and adjusting system parameters to make NES work within its ideal oscillation suppression parameters.
Study on Acid Corrosion Characteristics in Low-Pressure Stage Initial Condensation Zone of Supercritical H2O/CO2 Turbine
Authors: Ma Zi-yue , Wang Xiao-fang , Jiang Tao , Wang Wei , Xu Yang
Published: April 2021

Compared with the traditional steam turbine, the supercritical H2O/CO2 turbine has a relatively high CO2 content in the working fluid. In the initial condensation zone, CO2 dissolves in the condensed water to form carbonic acid, which intensifies the corrosion of blade. In order to study the acid corrosion characteristics in the initial condensation zone of supercritical H2O/CO2 turbine, the acid corrosion rate of the blades in the initial condensation zone of supercritical H2O/CO2 turbine was calculated and analyzed based on the numerical model of non-equilibrium condensation flow and a numerical model of CO2 corrosion reaction. The results show that the temperature, pressure, proportion of CO2 in the gas phase and thickness of the solution on blade surface are the main factors affecting the acid corrosion rate in the initial condensation zone of the turbine. The influence of temperature and pressure is more significant. Overall, the acid corrosion rate decreases stage by stage.
Study on Stiffness of Angular Contact Ball Bearing and Its Evolution Rule under Excessive Preload
Authors: Yun Xianghe , Li Ning , Wen Baogang , Han Qingkai
Published: April 2021

There are many factors influencing the bearing stiffness variation, among which, preload has more significant effect. In addition, bearing stiffness is developing accompanying with its performance deterioration, which leads to vibration variation of bearing-rotor system. In this paper, system support stiffness model and system dynamics model of micro-turbine bearing-rotor system test rig are built to obtain the bearing stiffness identification method by model simplification based on modal theory. The identification method is validated adopting modal test. The stiffness evolution rule and rotor vibration of different stages are achieved via employing the identification method to extract bearing stiffness over the process of bearing run-to-failure. The results indicate that bearing stiffness is the main source of system support stiffness. Bearing stiffness will change during the whole life, which affects the vibration responses in time and frequency domain. Rotor stability is influenced by cage movement.
Analysis of cage slip in angular contact ball bearing considering non-Newtonian behavior of elastohydrodynamic lubrication
Authors: Wen Baogang , Wang Meiling , Yun Xianghe , Zhang Xu , Han Qingkai
Published: April 2021

A dynamic model of angular contact ball bearing considering non-Newtonian behavior and interaction between balls and cage is deduced to predict cage slip. And then the cage slip are investigated and compared with measured results under different rotational speeds and axial loads to verify the proposed dynamic model of bearing. It is concluded that the results based on the non-Newtonian behavior of elastohydrodynamic lubrication is more agreement in trend with the tests than that based on the Newtonian assumption, and so the non-Newtonian behavior of elastohydrodynamic lubrication are needed in the cage slip analysis.
Effect of ball bearing misalignment on dynamic characteristics of rotor system
Authors: Wen Baogang , Wang Meiling , Han Qingkai , Yu Changxin
Published: April 2021

A theoretical model with 5 degrees of freedom (DOF) is derived for a rigid rotor system supported by two ball bearings considering the changes of the bearing stiffness due to misalignment. And then radial and axial vibrations of the rotor system and its bearing reactions under different misaligned offsets are investigated with theoretical and numerical analysis. Then, the effects of misalignment on the vibrations of rotor and the bearing, the variation of stiffness and reaction characteristics of the misaligned ball bearing are predicted theoretically. It is concluded that angular misalignment may cause axial vibration and parallel misalignment can bring out extra moment loads for misaligned bearing.
Design and Research of New Type High-speed Hydrostatic Spindle Test Rig
Authors: Xiao Yunfeng , Song Di , Meng Bo , Wang Lingyu , Zhang Hao , Mingyue Wang
Published: April 2021

Aiming at the air dynamic pressure foil bearing performance test rig, design and research a new high-speed static pressure spindle test rig. Carry out aerodynamic design of the driving turbine and compressor, obtain the three-dimensional impeller shape and carry out the strength calculation, design a new high-speed static pressure spindle test rig; use the finite element method to model the test bed rotor system, and use the transfer matrix method to analyse the shaft system structure critical speed and mode, so that the test rig can effectively avoid the critical speed and run stably. Analyse the unbalanced response and stability of the rotor system, and reasonably arrange the test rig device to achieve the purpose of measuring the performance of the dynamic pressure foil bearing, and ensure that the turbine static pressure spindle test rig can provide for the measurement of the air dynamic pressure foil bearing performance stable high speed.
Investigation of Time-series Prediction for Turbine Machinery Condition Monitoring
Authors: Liu Chang-Jun , Liu Hai-Tao , Bian Chao , Chen Xu-Dong , Yang Shu-Hua , Wang Xiao-Fang
Published: April 2021

A running compressor generates a huge amount of data every day. Some of the data contains useful information that allows the user to determine in advance whether the machine will fail or not. Forecasting in advance cannot only avoid the huge loss caused by unnecessary downtime but also ensure the safety of staff. The main tasks of compressor condition monitoring include data acquisition, data preprocessing, data analysis, alarm module, response strategy analysis, etc. Prediction is one of the tasks of condition monitoring. This paper mainly studies the performance of different time prediction models on the running data produced by a centrifugal compressor. In the data preprocessing part, this paper uses Bayesian wavelet denoising and probabilistic principal component analysis methods proposed by the research group to remove the useless parts in the data. In the part of time series model, the prediction performance of LSTM, GRU and ARIMA on the same dataset is compared. The comparative results indicate that since the dataset is non-stationary, the LSTM and GRU outperform the statistical ARIMA model.
Impact of exploration-exploitation trade-off on UCB-based Bayesian Optimization
Authors: Bian Chao , Wang Xiaofang , Liu Changjun , Xie Xinyu , Haitao Liu
Published: April 2021

As an efficient global optimization method to deal with expensive black-box functions, Bayesian optimization (BO) has great potential in the field of turbomachinery component design. It can relieve the complexity, long cycle, and excessive dependence on experience of the design process. A core of Bayesian optimization is acquisition functions which aim to guide the search to efficiently find the optimum. An excellent acquisition function can greatly improve the performance of the algorithm. The well-known acquisition function, upper confidence bound (UCB), in Bayesian optimization achieves the balance between local exploitation and global exploration through an explicit trade-off coefficient. The trade-off coefficient is a key to the quality of UCB-based Bayesian optimization. Currently, this coefficient is either manually specified according to some criterion or sampled from a specific distribution. Due to the lack of a comparative study on existing trade-off strategies, this paper attempts to comprehensively analyse and highlight the impact of various trade-off strategies on the performance of UCB-based BO algorithm through eleven numerical examples and two turbomachinery design cases. The comparative results indicate that the proper trade-off is key for the optimization quality, and the strategy of looping through a trade-off set shows superiority in our numerical experiments.
Numerical study on film cooling characteristics of BESA hole with water mist/air two-phase flow
Authors: Kang Huang , Pei-jie Shi , An-lin Jiang , Hu-sheng Ma
Published: April 2021

In view of a new type of film cooling hole, the backward-expanding shoulder arm(BESA) hole proposed by the author, a numerical model of two-phase flow film cooling with water mist is established. The numerical simulation of water mist / air two-phase flow film cooling characteristics shows that the comprehensive performance of water mist / air two-phase flow film cooling is significantly improved compared with pure air film cooling. For the round hole plate model, when the blowing ratio is 0.5, the film cooling efficiency of two-phase flow film cooling with 2% water spray is 37.5% higher than that of pure air film cooling (20D from the film hole outlet), When the blowing ratio is 1.0, the film cooling efficiency of the flat two-phase flow with 2% water spray is 49.0% higher than that of the pure air film cooling (20D away from the film hole outlet). When the spray amount of water is the same, the film cooling efficiency of the BESA hole is higher than that of the round hole, the expanding hole and the shoulder arm hole. For the flat film cooling model of the BESA hole, When other factors remain unchanged, the cooling efficiency of the two-phase flow film increases monotonously from 2% to 5%. The cooling characteristics of the two-phase flow film on the pressure surface of the turbine blade of the BESA hole are similar to those of the flat model, and the film coverage effect is better than that of the round hole, the expanding hole and the shoulder arm hole.
Experimental and numerical investigation on the influence of the diffuser blade setting angle on the performance of centrifugal compressor
Authors: Fang Junyi , Ji Chunjun , Li Chunyang , Zhang Ruiwu , Denis Shalyaev
Published: April 2021

Setting angle of the front blade row of tandem cascade diffuser was investigated experimentally to understand its influence on the performance of centrifugal compressor. Three diffusers with different setting angles were tested. The change of front blade setting angle mainly alters. The angle of attack (AOA) on the leading edge of front blades, which affects the surge point of the compressor. The throat area of the blade row is also modified, which affect the chock point of the compressor. With the increase of setting angle, performance curves of centrifugal compressor move to large flow rate side, the operation range is increased at the same time. In addition, numerical simulation was used to investigate the flow details on the passage of diffuser blades. Overall, the setting angle of front blade row has a significant influence of the performance of centrifugal compressor.
Effect of Hub Gap on Expanding Stability of Centrifugal Compressor
Authors: Li Chunyang , Ji Chunjun , Fang Junyi
Published: April 2021

In this paper, the possibility of using hub gap (“ HG ”for short) to suppress gas stall and expand the range of stable working condition of compressor is verified by numerical method. The research shows that when designing flow rate, HG increases, the efficiency and pressure ratio of model level decrease. When there is a large flow, the efficiency and pressure ratio of HG model are higher than those without HG. The larger HG is, the higher the efficiency and pressure ratio is. From the analysis of the expanding stability capacity, the model-level flow margin of small HG and large HG is 5% and 15% higher than that of models without HG, and the comprehensive stall margin is 6.87% and 23.59% higher on average. When operating at unstable working conditions, the action of HG causes the airflow in the high pressure zone to flow into the gap and out of the low pressure zone, which improves the flow distribution in the blade passage and makes the flow field stable. However, when operating near the design condition, the leakage flow and its mixing with the momentum of the mainstream are the main sources of aerodynamic loss. The larger HG is, the greater the pressure loss caused by the leakage flow is. Generally speaking, HG can play the role of compressor expansion stability, but at the cost of efficiency; The bigger HG is, the stronger the role of expanding stability is and the greater the efficiency loss is.
Numerical Study on Hydrodynamic Characteristics in a Centrifugal Pump at off Design Conditions Based on a Cycling-System Model
Authors: Yin Wen-Hui , Wang Xi , Yu Tao , Jian Jie , Zhang Xiang-Yuan , Shuai Zhi-Jun , Li Wan-You , Jiang Chen-Xing
Published: April 2021

In this paper, the unsteady hydrodynamic characteristics of a centrifugal pump handled at low-flow-rate conditions are numerically investigated. A cycling-system model is established to capture the influence of off-design operation on the internal flow field and the pressure pulsation. The preliminary results show that the cycling-system model can predict the flow field of the pump more conforming to the practical situation than that of the pump alone; besides, the generation of stall clusters in the impeller will induce low-frequency pressure pulsation.