Jinsong Zhang, Xinlong Wang, Chen Yang, Mingkang Sun and Zhenwei Huang
This study aims to investigate the noise-inducing characteristics during the start-up process of a mixed-flow pump and the impact of different start-up schemes on pump noise.
Abstract
Purpose
This study aims to investigate the noise-inducing characteristics during the start-up process of a mixed-flow pump and the impact of different start-up schemes on pump noise.
Design/methodology/approach
This study conducted numerical simulations on the mixed-flow pump under different start-up schemes and investigated the flow characteristics and noise distribution under these schemes.
Findings
The results reveal that the dipole noise is mainly caused by pressure fluctuations, while the quadrupole noise is mainly generated by the generation, development and breakdown of vortices. Additionally, the noise evolution characteristics during the start-up process of the mixed-flow pump can be divided into the initial stage, stable growth stage, impulse stage and stable operation stage.
Originality/value
The findings of this study can provide a theoretical basis for the selection of start-up schemes for mixed-flow pumps, reducing flow noise and improving the operational stability of mixed-flow pumps.
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The purpose of this paper is to overcome the limitations of existing celestial horizon references, and improve the navigation accuracy of the strap‐down inertial navigation…
Abstract
Purpose
The purpose of this paper is to overcome the limitations of existing celestial horizon references, and improve the navigation accuracy of the strap‐down inertial navigation system/celestial navigation system (SINS/CNS) integrated system with an innovative scheme of deep integration.
Design/methodology/approach
First, a novel conception of mathematical horizon reference (MHR) provided by the strap‐down matrix of SINS is proposed. Then, the realization mechanism of the MHR‐based vertical vector is introduced from the viewpoint of vector rotation. Moreover, the MHR implementation scheme of high precision and reliability is presented, and on this basis, the method which utilizes vertical vector to achieve celestial navigation is introduced. In addition, with considering the characteristics of SINS and the MHR‐based CNS, the SINS/CNS deep integrated navigation system and its specific realization are proposed. Finally, simulation tests are implemented to validate this SINS/CNS deep integrated navigation method.
Findings
The innovative SINS/CNS deep integrated system could make full use of SINS and CNS navigation information to achieve higher navigation accuracy for the long‐duration and high‐altitude vehicles.
Originality/value
This paper provides a novel realization method of high precision MHR and the MHR‐based SINS/CNS deep integration.
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Yu Jie, Wang Xinlong and Ji Jiaxing
The purpose of this paper is to improve the tracking performance of the carrier phase lock loop (PLL) in the strapdown inertial navigation system/global positioning system…
Abstract
Purpose
The purpose of this paper is to improve the tracking performance of the carrier phase lock loop (PLL) in the strapdown inertial navigation system/global positioning system (SINS/GPS) integrated system with an innovative scheme of ultra‐tight integration.
Design/methodology/approach
First, providing the Doppler frequency for PLL using SINS velocity could enlarge the loop equivalent bandwidth and reduce the dynamic effect on the carrier loop. Meanwhile, lowering the filter bandwidth could increase the immunity to noise. Second, the relationships between the PLL and SINS errors have been analyzed, and then the PLL error model is established to eliminate the correlation between the pseudo‐range‐rate error and SINS velocity error. Third, the carrier frequency is regulated to improve the tracking accuracy, according to the error estimations of Kalman filter.
Findings
The innovative ultra‐tightly integrated system could not only enhance the anti‐jamming capability and the dynamic tracking performance of the tracking loops, but also improve the pseudo‐range‐rate measurements accuracy for the integrated filter.
Originality/value
This paper provides further study on the method of enhancing the carrier‐tracking performance and improving the integration mode in the ultra‐tightly integrated system based on the software‐defined GPS receiver.
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– The purpose of this paper is to improve the tracking performance of the tracking loops under high dynamic and severe jamming conditions.
Abstract
Purpose
The purpose of this paper is to improve the tracking performance of the tracking loops under high dynamic and severe jamming conditions.
Design/methodology/approach
First, as the two dominant measurement error sources of the tracking loops, the thermal noise jitter and the dynamic stress error are thoroughly analyzed. Second, a scheme of adaptive tracking loops, which could adaptively adjust the order and the bandwidth of tracking loops, is proposed. Third, real-time detections of the vehicle dynamics and the carrier-to-noise density ratio, and the adaptive bandwidth of the carrier loop are presented, respectively. Finally, simulations are operated to validate the excellent tracking performance of the adaptive tracking loops.
Findings
Based on the principle of minimizing the measurement errors, the loop order and bandwidth are adaptively adjusted in the proposed scheme. Thus, the anti-jamming capability and dynamic tracking performance of the tracking loops could be effectively enhanced.
Practical implications
This paper provides further study on the method of improving the tracking capability under complexly applied conditions of high dynamics and severe jamming.
Originality/value
The detections of carrier-to-noise density ratio and vehicle dynamics are used to adaptively adjusting the loop order and bandwidth, which could not only improve the measurement accuracy but also ensure the stable operation of tracking loops.
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The purpose of this paper is to discuss the applicability of Global Positioning System (GPS) ionospheric delay correction models. Ionospheric delay is the most influential error…
Abstract
Purpose
The purpose of this paper is to discuss the applicability of Global Positioning System (GPS) ionospheric delay correction models. Ionospheric delay is the most influential error source in GPS positioning, and ionospheric refraction is difficult to be corrected by dual frequency measurement for the common single frequency GPS receivers. Generally, ionospheric models are employed to correct errors. In order to analyze the ionospheric influence to GPS signals and the accuracy and adaptability of GPS ionospheric error correction models a quantificational analysis for ionospheric error correction models is absolutely necessary.
Design/methodology/approach
On the base of the mechanism of ionospheric error, the Klobuchar model that is widely used and actual measured correction model (including local and global ionospheric error correction models) are analyzed in detail. With the data about ionosphere obtained from GPS authority Crustal Dynamics Data Information System, the precision and adaptability of two kinds of ionospheric error correction model are validated, and a predigested method of investigating precision of local ionospheric error correction model is presented.
Findings
Klobuchar model has higher precision in middle or low latitude than in high latitude, and ionospheric delay fluctuates acutely in a day with a day‐cycle. Ionospheric delay varies as the latitude changes: ionospheric delay is largest around equator and smallest in the areas of two poles, which shows symmetry. The relationship between ionospheric delay and longitude is similar to the relationship between ionospheric delay and latitude. The fitting model has better effect than Klobuchar model.
Originality/value
This paper thoroughly researches GPS ionospheric error correction models. The conclusions are presented for the selection of GPS correction models, that it is useful for practical engineering application and will be the theoretic foundation for the improvement of the GPS accurate positioning.
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Wang Xinlong, Ji Jiaxing and Li Yafeng
Troposphere delay is one of the important error sources in global positioning system (GPS) positioning. The purpose of this paper is to analyze the accuracy and adaptability of…
Abstract
Purpose
Troposphere delay is one of the important error sources in global positioning system (GPS) positioning. The purpose of this paper is to analyze the accuracy and adaptability of GPS troposphere error correction models, and to provide theoretic foundation for model selection in GPS accurate positioning.
Design/methodology/approach
The principle of troposphere delay error effecting on GPS signals is theoretically analyzed. The model peculiarity and modeling method of the four common troposphere delay correction models: Hopfield, Saastamoinen, Black, and Egnos models are discussed detailedly. With the measurement data from Crustal Dynamics Data Information System of the technical support institution for GPS, the accuracy and applicability of the four models are quantificationally studied.
Findings
For a low elevation, Hopfield, Saastamoinen, and Black models show great agreement with each other, and have quite high precision. In the zenith direction, the maximal troposphere delay error of three models are all less than 1 dm, but Black and Hopfield models have higher precision than Saastamoinen model. Black model can be regarded as the improved form of Hopfield model: for a high elevation, precision of two models are close, while for a low elevation, Black model shows to be more effective than Hopfield model. The precision of Egnos model is quite lower than that of Black, Hopfield, and Saastamoinen models. However, Egnos model can be a better choice when it is difficult to obtain real‐time meteorological data in certain application environment.
Originality/value
This paper makes thorough research on GPS troposphere delay error correction models. The conclusions are presented for selecting troposphere delay models, which are useful for practical engineering application.
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Wang Xinlong and Shen Liangliang
In order to accomplish real‐time alignment of Shipborne strapdown inertial navigation system (SINS) on moving bases, a novel solution method of utilizing neural networks for rapid…
Abstract
Purpose
In order to accomplish real‐time alignment of Shipborne strapdown inertial navigation system (SINS) on moving bases, a novel solution method of utilizing neural networks for rapid transfer alignment of Shipborne SINS was investigated.
Design/methodology/approach
The system error state equations and measurement equations of the Shipborne transfer alignment were established. Based on the nonlinear and time‐variant SINS model on moving bases, a neural network learning algorithm based on Kalman filtering was presented, and the methods of constructing and training of neural networks input‐output sample pairs suitable for Shipborne SINS were proposed.
Findings
Velocity and attitude errors between the master and slave inertial navigation system (INS) are chosen as network's inputs, and the information of sample pairs is affluent, which can advance the stability and generalization of the neural networks. The neural networks algorithms based on Kalman filtering not only have the self‐learning ability, but also remain recursive optimal estimation capability of Kalman filtering. Through the introducing of the local level trajectory frame, the trained neural networks can be independent on a ship heading, and only dependent on the relative position errors between master with slave INS and the inertial sensor errors.
Originality/value
This article presents an innovative solution method of utilizing neural networks for rapid transfer alignment of Shipborne SINS.
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Weilong Wang, Jilian Wu and Xinlong Feng
The purpose of this paper is to propose a new method to solve the incompressible natural convection problem with variable density. The main novel ideas of this work are to…
Abstract
Purpose
The purpose of this paper is to propose a new method to solve the incompressible natural convection problem with variable density. The main novel ideas of this work are to overcome the stability issue due to the nonlinear inertial term and the hyperbolic term for conventional finite element methods and to deal with high Rayleigh number for the natural convection problem.
Design/methodology/approach
The paper introduces a novel characteristic variational multiscale (C-VMS) finite element method which combines advantages of both the characteristic and variational multiscale methods within a variational framework for solving the incompressible natural convection problem with variable density. The authors chose the conforming finite element pair (P2, P2, P1, P2) to approximate the density, velocity, pressure and temperature field.
Findings
The paper gives the stability analysis of the C-VMS method. Extensive two-dimensional/three-dimensional numerical tests demonstrated that the C-VMS method not only can deal with the incompressible natural convection problem with variable density but also with high Rayleigh number very well.
Originality/value
Extensive 2D/3D numerical tests demonstrated that the C-VMS method not only can deal with the incompressible natural convection problem with variable density but also with high Rayleigh number very well.
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Ye Bai, Xinlong Li and Hongye Sun
In online purchase for dietary supplements, due to the lack of professional advice from pharmacists, electronic word-of-mouth (eWOM) has become an important source of information…
Abstract
Purpose
In online purchase for dietary supplements, due to the lack of professional advice from pharmacists, electronic word-of-mouth (eWOM) has become an important source of information for consumers to make purchase decisions. How can firms use eWOM resources to increase sales? The purpose of this paper is to provide practical methods for firms by exploring the effects of eWOM on sales and developing a sales prediction model based on eWOM.
Design/methodology/approach
The data came from 120 dietary supplements on Tmall.com. The authors extracted the product sales as dependent variable and 11 eWOM factors as independent variables. The multicollinearity was tested by using variance inflation factor and least absolute shrinkage and selection operator. The multiple linear regression was used to investigate the effects of eWOM on sales. Drawing on white- and black-box approaches, six models were developed. Comparing the root mean square error, the authors selected the optimal one as their target sales prediction model.
Findings
Product ratings, total reviews and favorites are positively and strongly associated with sales. Questions and additional reviews have negative effects on sales. The random forest model has the best prediction performance.
Originality/value
The research focuses on eWOM of dietary supplement. First, the authors show that easily accessible eWOM from online platforms can be used to evaluate effects and predict sales. Second, the authors introduce white- and black-box models through machine learning to assess eWOM. Firms could use the described models to foster their marketing initiatives.
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Xiuliang Hou, Li Wei, Xinlong Zhang, Huihui Wu, Qicheng Zhou and Shan-yuan Wang
Catechu liquor, which is deep brown-red in color, was purified with a micro-filtration membrane and the stability of catechu dye to different levels of temperatures and pH were…
Abstract
Catechu liquor, which is deep brown-red in color, was purified with a micro-filtration membrane and the stability of catechu dye to different levels of temperatures and pH were investigated in this paper. The effects of the dyeing conditions on color characteristic values and color fastnesses of the dyed wool fabrics were also investigated. The results show that the liquor of catechu dye is stable at pH values of 3-7 and its color changes to a deeper brown-red when its pH value is above 8. The preferable dyeing conditions for wool fabric with refined powder catechu dye are as follows: dyeing temperature of 100±C, pH value of 6.5 for the dye bath and catechu dye of 1-4% (o.w.f).
The dyed wool fabric has good color fastnesses to washing, alkali perspiration and dry rubbing. However, its color fastness rating to wet rubbing is poor, ranging from 2-3. Further research will be needed on this aspect.