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This paper aims to solve the problem that strong noise interference seriously affects the direction of arrival (DOA) estimation in complex underwater acoustic environment. In this paper, a combined noise reduction algorithm and micro-electro-mechanical system (MEMS) vector hydrophone DOA estimation algorithm based on singular value decomposition (SVD), variational mode decomposition (VMD) and wavelet threshold denoising (WTD) is proposed.

Firstly, the parameters of VMD are determined by SVD, and the VMD method can decompose the signal into multiple intrinsic mode functions (IMFs). Secondly, the effective IMF component is determined according to the correlation coefficient criterion and the IMF less than the threshold is processed by WTD. Then, reconstruction is carried out to achieve the purpose of denoising and calibration baseline drift. Finally, DOA estimation is achieved by the combined directional algorithm of preprocessed signal.

Simulation and field experiments results show that the algorithm has good noise reduction and baseline drift correction effects for nonstationary underwater signals, and high-precision azimuth estimation is realized.

This research provides the basis for MEMS hydrophone detection and positioning and has great engineering significance in underwater detection system.

The problem of port and starboard ambiguity will exist when only utilize the vector or scalar parameters. Meanwhile, the amplitude-phase error between the vector and scalar can also cause this problem. In this paper, a compound MEMS vector hydrophone which contains cilia vector microstructure and piezoelectric ceramic tube has been presented to solve the problem. Compared with traditional MEMS vector hydrophone, the compound MEMS vector hydrophone can realize the measurement of sound pressure and vibration velocity simultaneously.

A compound MEMS vector hydrophone has been presented. The unipolar directivity of the combined signal which combine the acoustic pressure and vibration velocity is used to achieve the direction of arrival (DOA). This paper introduced the working principle and the target detection mechanism of the compound vector hydrophone. The amplitude and phase error are analyzed and corrected in the standing wave tube. After that, the authors use beam-forming algorithm to estimate the DOA.

The experimental results in the standing wave tube and the external field verified the vector hydrophone's directional accuracy up to 1 and 5 degrees, respectively.

The research of compound vector hydrophone plays an important role in marine acoustic exploration and engineering applications.

This research provides a basis for MEMS hydrophone directivity theory. The compound vector hydrophone has been applied in the underwater location, with a huge market potential in underwater detection systems.

The purpose of this paper is first, to develop constructs to measure three important concepts in the supply chain literature: contracts, trust and market environment, in the Chinese context and to further investigate the relationships amongst these three concepts based on the formulated hypothesis.

The research methodology has strictly followed the recommended scale development procedures, which include specifying each constructs, item generation, data collection, reliability and validity test, and finally test hypothesis. The primary data were collected in October 2008 in Hubei Province, China. Both exploratory factor analysis and confirmatory factor analysis are applied to assess the reliability and validity of the three constructs.

In total, 22 items were retained to measure six dimensions for the three core concepts: contract (marketing and production), trust (reliability and benevolence), and market environments (diversity and volatility). Second, the finding supported this argument that contracts and trust functions as complements. Furthermore, a positive relationship between environmental uncertainty and the use of contractual governance was found.

The measurement model for environmental volatility is less satisfied. More research should be carried out on the measurement of market environment in the future.

This paper identifies and validates key constructs underlying supply chain management research: contract, trust and market environment, in a Chinese context. These measurable concepts could be applied in similar settings to further investigate small‐scale farmer's position along the supply chain.

Chinese agri‐food chains consist of the millions of small scale farmers, who are not well structured and organized in the supply chain. Owing to market liberalization and globalization, one of the most challenging issues along agri‐food chains in China is becoming the issue of how to link these small‐scale farmers into the modern chains. Consequently, it is essential for both policy makers and private sectors to understand the governance structure in agri‐food supply chains. Therefore, the purpose of this paper is to develop a theoretical framework for supply chain governance, including its antecedents and consequences, as well as a series of hypotheses for empirical testing.

A conceptual framework of chain governance is proposed in this study, where governance structure consists of two dimensions: contractual governance and relational governance. The study intends to propose a complementary relationship between contracts and relational aspects, such as trust, in the Chinese context. Future research is needed to empirically test this model.

The proposed conceptual model is unique, since the majority of the articles addressing this topic focuses on contract farming while limited research touches upon the issues of trust and relations. However, a combination of both contracting and relationships are seldom addressed.

This paper evaluates a novel concept of two dimensional governance structure in the agri‐food supply chain, where transaction cost economics theory and relational theory are combined to study the governance relationships between small scale producers in China and their buyers.

The purpose of this paper is to investigate the effect of different heating approaches during thermal rounding of polymer powders on powder bulk properties such as particle size, shape and flowability, as well as on the yield of process.

This study focuses on the rounding of commercial high-density polyethylene polymer particles in two different downer reactor designs using heated walls (indirect heating) and preheated carrier gas (direct heating). Powder bulk properties of the product obtained from both designs are characterized and compared.

Particle rounding with direct heating leads to a considerable increase in process yield and a reduction in powder agglomeration compared to the design with indirect heating. This subsequently leads to higher powder flowability. In terms of shape, indirect heating yields not only particles with higher sphericity but also entails substantial agglomeration of the rounded particles.

Shape modification via thermal rounding is the decisive step for the success of a top-down process chain for selective laser sintering powders with excellent flowability, starting with polymer particles from comminution. This report provides new information on the influence of the heating mode (direct/indirect) on the performance of the rounding process and particle properties.

This paper investigates whether China's R&D tax deduction policy triggers firms to manipulate their R&D expenditures upward.

This paper employs the ratio of actual tax savings as a proxy for the benefits of the R&D tax deduction policy based on manually collected and systematically cross-checked data. The relationship between tax benefits and abnormal R&D spending is estimated in a sample of Chinese A-share listed companies for the period 2007–2018.

The findings suggest that tax deductions lead to positive abnormal R&D spending and that this deviation in R&D spending may be attributed to firms' upward R&D manipulation for tax avoidance. The results also indicate that this behavior is more significant for the period after the policy revision, in non-HNTEs (high and new technology enterprises), and in firms with a high ratio of R&D expenses.

It is difficult to establish a sophisticated and unified model to identify the specific strategy of upward R&D manipulation that firms use to obtain tax benefits.

Managers should take into account upward R&D manipulation when designing governance mechanisms. Policymakers in developing countries may further pursue preferential tax policies that cover every stage of innovation activities gradually; the local provincial governments need to leverage their proximity and flexibility advantages to develop a tax collection and administration system.

This study contributes to the understanding of the complex effect of R&D tax incentives and helps more fully illuminate firms' upward R&D manipulation behavior from the perspective of tax planning strategies, which are underexplored in previous research.

The purpose of this paper is to facilitate understanding of how to mitigate the privacy concerns of users who have experienced privacy invasions.

Drawing on the communication privacy management theory, the authors developed a model suggesting that privacy concerns form through a cognitive process involving threat-coping appraisals, institutional privacy assurances and privacy experiences. The model was tested using data from an empirical survey with 913 randomly selected social media users.

Privacy concerns are jointly determined by perceived privacy risks and privacy self-efficacy. The perceived effectiveness of institutional privacy assurances in terms of established privacy policies and privacy protection technology influences the perceptions of privacy risks and privacy self-efficacy. More specifically, privacy invasion experiences are negatively associated with the perceived effectiveness of institutional privacy assurances.

Privacy concerns are conceptualized as general concerns that reflect an individual’s worry about the possible loss of private information. The specific types of private information were not differentiated.

This paper is among the first to clarify the specific mechanisms through which privacy invasion experiences influence privacy concerns. Privacy concerns have long been viewed as resulting from individual actions. The study contributes to literature by linking privacy concerns with institutional privacy practice.

Currently, lubrication analysis of piston ring is generally done under engine rated operating condition. However, the engine (such as the vehicle engine) does not always operate in rated operating condition, and its operating condition changes frequently in actual use. In addition, the lubrication status of piston ring is generally assumed as the flooded lubrication or a certain form of poor lubrication in most of the lubrication analysis.

In this paper, based on the equations about the flow rate of lubricating oil and the variation of control volume, the flow model of lubricating oil in the piston ring-cylinder liner conjunction is established. The lubrication analysis of piston ring for a four-stroke engine under different engine operating conditions is done, in which the lubricating oil at the inlet of piston ring is considered as the lubricating oil attached on the relevant location of cylinder wall after the piston ring moves over at the previous stroke.

There is remarkable difference for the lubrication characteristics of the piston ring under different engine operating conditions. The worst lubrication status of piston ring may not take place under engine rated operating condition.

In this paper, based on the measured engine cylinder pressure, the lubrication analysis of piston ring for a four-stroke engine under different engine operating conditions is done in which the lubricating oil supply condition at the inlet of piston ring is considered. The results of this paper are helpful for the design and research of engine piston ring-cylinder liner conjunction.

During the authors’ practical experiments about designing hover controller for unmanned helicopter, they find pendulum motion exists, thus destroying their expected control performance, such as perfect tracking, target detection, accurate attacking etc., so they turn to study how to suppress pendulum motion through designing one additional controller to guarantee pendulum motion sufficiently small. More specifically, the detailed mechanism of hover pendulum motion is analyzed to yield one accurate nonlinear dynamical equation, corresponding to hover pendulum motion. To apply the existed linear optimal control strategy directly, the necessary linearization process is needed to derive one approximated linear state equation, including the explicit form of control input. After describing their idea about pendulum control structure from the point of practice, linear optimal control strategy is proposed to design the ideal controller without external noise. Then its improved robust controller is also given through solving their difference game problem or min-max problem. From their obtained closed forms of the pendulum controller, they are all one linear state feedback form, being convenient to implement in practical engineering. Finally, to achieve the mission of theory for application, they use their established practical platform to do some simulations, so proving the theoretical results. The purpose of this paper aims to design one optimal controller to suppress hover pendulum motion for unmanned helicopter.

First, considered the practical hover motion of unmanned helicopter, its detailed mechanism is analyzed to get one linear state equation after the authors’ complex mathematical derivation. Second, their idea of control structure and control design is applied to design one linear state feedback controller through the derived optimal control strategy. Third, one practical platform is established to prove their control idea.

From the authors’ introduction and knowledge, control exists everywhere. As unmanned helicopter has become increasingly important as one tactical weapon, so they think how to design controller for hover pendulum motion, while suppressing the hover pendulum. Specifically, they give the detailed theoretic derivation and practical platform.

To the best knowledge of the authors’ knowledge, pendulum motion control is to stop the swing as soon as possible and suppress the oscillatory motion of pendulum angle. Then, based on that linear state equation for hover pendulum motion, linear optimal control strategy is applied to achieve above two dual missions, i.e. controlling the motion or pendulum suspension point and eliminating or suppressing the pendulum phenomenon.