Bingbing Qi and Dunge Liu
The existing dimensionality reduction algorithms suffer serious performance degradation under low signal-to-noise ratio (SNR) owing to the presence of noise. To address these…
Abstract
Purpose
The existing dimensionality reduction algorithms suffer serious performance degradation under low signal-to-noise ratio (SNR) owing to the presence of noise. To address these problems, an enhanced spatial smoothing scheme is proposed that exploits the subarray time-space correlation matrices to reconstruct the data matrix to overcome this weakness. This method uses the strong correlation of signal and the weak correlation of noise in time and space domains, which improves the noise suppression ability.
Design/methodology/approach
In this paper, an enhanced spatial smoothing method is proposed. By using the strong correlation of signal and the weak correlation of noise, the time-space smoothed array covariance matrix based on the subarray time-space correlation matrices is constructed to improve the noise suppression ability. Compared with the existing Toeplitz matrix reconstruction and spatial smoothing methods, the proposed method improves the DOA estimation performance at low SNR.
Findings
Theoretical analysis and simulation results show that compared with the existing dimensionality reduction processing algorithms, the proposed method improves the DOA estimation performance in cases with a low SNR. Furthermore, in cases where the DOAs between the coherent sources are closely spaced and the snapshot number is low, our proposed method significantly improves the performance of the DOA estimation performance.
Originality/value
The proposed method improves the DOA estimation performance at low SNR. In particular, for the cases with a low SNR, the proposed method provides a better RMSE. The convergence of the proposed method is also faster than other methods for the low number of snapshots. Our analysis also confirms that in cases where the DOAs between the coherent sources are closely spaced, the proposed method achieves a much higher angular resolution than that of the other methods.
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Bingbing Qi, Lijun Xu and Xiaogang Liu
The purpose of this paper is to exploit the multiple-Toeplitz matrices reconstruction method combined with quadratic spatial smoothing processing to improve the…
Abstract
Purpose
The purpose of this paper is to exploit the multiple-Toeplitz matrices reconstruction method combined with quadratic spatial smoothing processing to improve the direction-of-arrival (DOA) estimation performance of coherent signals at low signal-to-noise ratio (SNRs).
Design/methodology/approach
An improved multiple-Toeplitz matrices reconstruction method is proposed via quadratic spatial smoothing processing. Our proposed method takes advantage of the available information contained in the auto-covariance matrices of individual Toeplitz matrices and the cross-covariance matrices of different Toeplitz matrices, which results in a higher noise suppression ability.
Findings
Theoretical analysis and simulation results show that, compared with the existing Toeplitz matrix processing methods, the proposed method improves the DOA estimation performance in cases with a low SNR. Especially for the cases with a low SNR and small snapshot number as well as with closely spaced sources, the proposed method can achieve much better performance on estimation accuracy and resolution probability.
Research limitations/implications
The study investigates the possibility of reusing pre-existing designs for the DOA estimation of the coherent signals. The proposed technique enables achieve good estimation performance at low SNRs.
Practical implications
The paper includes implications for the DOA problem at low SNRs in communication systems.
Originality/value
The proposed method proved to be useful for the DOA estimation at low SNR.
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The purpose of this paper is to study the governance effect of total environmental target constraint policy (TETC) on border polluted areas. China’s administrative border areas…
Abstract
Purpose
The purpose of this paper is to study the governance effect of total environmental target constraint policy (TETC) on border polluted areas. China’s administrative border areas are “pollution havens.” The paper analyzes how TETC affects the pollution situation in border areas. The TETC policy sets overall emission reduction targets for each province, and the achievement of these targets is closely related to the promotion of local officials. So, can TETC provide pollution control incentives for enterprises and governments? This deserves further research. By evaluating China’s overall environmental target policies, we can obtain directions for optimizing policy design.
Design/methodology/approach
The paper uses the difference-in-differences model to evaluate the impact of TETC on air pollution in boundary areas. Industrial enterprises located at the provincial border are in the treatment group, while industrial enterprises located within the province are in the control group. We also use group regression to analyze the policy impact effects caused by differences in urban resource endowment, types of corporate pollution and marketization levels. Finally, we constructed a spatial difference-in-differences model to analyze the distance heterogeneity of policy impacts.
Findings
TETC significantly reduces the SO2 emissions of enterprises in province borders areas compared with intra-provincial enterprises. TETC has reduced the proportion of highly polluting enterprises at province borders. Incentives for promoting officials have prompted local governments to increase environmental law enforcement and environmental protection investment, and the pollution emissions of border enterprises have been effectively alleviated. The heterogeneity analysis shows that TETC significantly restrains the pollution emissions with high pollution types, non-resource-based cities and enterprises with low market levels.
Research limitations/implications
As a developing country, China has generated a large amount of pollution during the process of industrialization. The government has taken a series of measures to reduce pollution emissions. The TETC is a typical policy with high policy constraints. Although this article tries to control the impact of some important air pollution policies as much as possible, it cannot control the impact of all other policies. So, the impact effects we empirically obtained may include some other policy factors, but these effects are relatively small and do not affect the overall regression results.
Originality/value
This paper has theoretical reference significance for optimizing the design of environmental policies, reducing the “principal-agent” problem of environmental governance and improving pollution control at province borders.
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Chengchen Liu, Ya Zhang and Jing Zhang
There is growing interest among marketers in advertising and promoting their brands by adopting an online celebrity endorsement strategy. However, how online celebrities build…
Abstract
Purpose
There is growing interest among marketers in advertising and promoting their brands by adopting an online celebrity endorsement strategy. However, how online celebrities build their own brand equity and how online celebrity brand equity impacts fans’ purchase behavior have not been extensively researched in the extant literature. This paper aims to explore the factors that contribute to online celebrity branding and improving fans’ purchase intentions.
Design/methodology/approach
A survey and an experiment were conducted among consumers from the mainland of China. A total of 12 hypotheses were proposed to exam how self-congruity and virtual interactivity impact online celebrity branding and to explore the moderating role of perceived quality and product type.
Findings
This paper reveals that customers’ perceived self-congruity with online celebrities’ image and virtual interactivity positively impact the brand equity of online celebrities. Additionally, compared with virtual interactivity, the effect of customer perceived self-congruity on a brand is more significant. The brand equity of online celebrities thereby drives followers’ purchase intentions and the perceived quality of products positively moderates this relationship.
Originality/value
The research conclusions provide managerial implications for marketing practitioners for how to use human brands on social media platforms in the web 2.0 era and ultimately enhance consumer purchase intentions.
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Yabao Hu, Hanning Chen, Xiaodan Liang and Jianbo Lei
Studies on titanium implants have shown that the mechanical properties of the parts are affected by the microstructure characteristic derived from the manufacturing process. The…
Abstract
Purpose
Studies on titanium implants have shown that the mechanical properties of the parts are affected by the microstructure characteristic derived from the manufacturing process. The properties of different orientations of specimens under the same process parameters will be different, which should be considered in the application of bone implants. This paper aims to understand the influence of microstructure on micro-hardness, wear and corrosion resistance in different orientations.
Design/methodology/approach
The authors manufactured titanium parts and carried out micro-hardness, wear tests and electrochemical corrosion of different orientations under the same process conditions. Then, finally studied the evolution mechanism of the microstructure in different orientations and its influence mechanism on wear and corrosion mechanism.
Findings
The melting method makes the grains on the surface in XY orientation finer. The wear mechanism of XY orientation is abrasive wear, that of XZ and YZ orientations are adhesive wear. During corrosion, XY orientation forms a stable passivation film earlier. Compared with XZ and YZ orientations, XY orientation has higher micro-hardness, better wear and corrosion resistance.
Originality/value
In this paper, the microstructure, wear and corrosion resistance of selective laser melted parts were discussed and the differences in different orientations under the same experimental conditions were discussed. The evolution mechanism of the microstructure in different orientations and its influence mechanism on wear mechanism and corrosion mechanism was studied. The mechanical anisotropy of selective laser melted components was discussed.
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The purpose of this paper is to investigate the association between ownership structure and the properties of analysts’ forecasts in China’s unique corporate setting.
Abstract
Purpose
The purpose of this paper is to investigate the association between ownership structure and the properties of analysts’ forecasts in China’s unique corporate setting.
Design/methodology/approach
Multiple regression models were used to examine the influence of ownership structure mechanisms on analysts’ forecast properties for listed Chinese firms during the period 2008-2012.
Findings
The paper finds that analysts’ forecast accuracy is higher for listed firms with high levels of foreign ownership and managerial ownership. However, the complex pyramidal ownership structure could make corporate information less transparent and then increase the complexity of forecasting; hence, it results in less precise analysts’ forecasts. Interestingly, the relationship between state ownership and analysts’ forecast properties appears to be non-linear (an inverted U-shape), and the inflection point at which the relationship becomes negative occurs at state ownership over 45 per cent.
Originality/value
To the best of the author’s knowledge, this paper is the first to investigate the influence of ownership structure mechanisms on the properties of analysts’ forecasts in an emerging market, and the findings provide some insight on how the properties of analysts’ forecast might be shaped by certain ownership and control features in the context of concentrated state ownership and complex pyramidal ownership structure.
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Jiehao Li, Shoukun Wang, Junzheng Wang, Jing Li, Jiangbo Zhao and Liling Ma
When it comes to the high accuracy autonomous motion of the mobile robot, it is challenging to effectively control the robot to follow the desired trajectory and transport the…
Abstract
Purpose
When it comes to the high accuracy autonomous motion of the mobile robot, it is challenging to effectively control the robot to follow the desired trajectory and transport the payload simultaneously, especially for the cloud robot system. In this paper, a flexible trajectory tracking control scheme is developed via iterative learning control to manage a distributed cloud robot (BIT-6NAZA) under the payload delivery scenarios.
Design/methodology/approach
Considering the relationship of six-wheeled independent steering in the BIT-6NAZA robot, an iterative learning controller is implemented for reliable trajectory tracking with the payload transportation. Meanwhile, the stability analysis of the system ensures the effective convergence of the algorithm.
Findings
Finally, to evaluate the developed method, some demonstrations, including the different motion models and tracking control, are presented both in simulation and experiment. It can achieve flexible tracking performance of the designed composite algorithm.
Originality/value
This paper provides a feasible method for the trajectory tracking control in the cloud robot system and simultaneously promotes the robot application in practical engineering.