The error coefficients of the pendulous integrating gyroscopic accelerometer (PIGA) mainly include the bias, scale factor, and nonlinear error. Previous works have fully studied and suppressed the ...bias and scale factor of PIGAs. At present, the nonlinear error is the most critical factor restricting the measurement accuracy of PIGAs. To address this barrier, a study on the analysis and suppression of the nonlinear error of PIGAs at the instrument level was carried out. Firstly, the error model of a PIGA is established by kinematics and dynamics analyses. Then, nonlinear error is analyzed based on the established model. Finally, a suppression method for the nonlinear error is proposed based on the analysis results. The nonlinear error analysis found that (1) the nonlinear error includes a quadratic term error caused by unequal inertia and the inertia product, cross-coupling error is caused by lateral accelerations, and error is caused by unequal stiffness; (2) unequal inertia and the inertia product were the most critical factors resulting in nonlinear error. Based on the results in the nonlinear error analysis, the suppression method for error focuses on unequal inertia and the inertia product. The proposed method of analysis and suppression was validated experimentally as the quadratic term coefficient was reduced by an order of magnitude from 1.9 × 10
/
to 1.91 × 10
/
.
Nonlinear error has become the most critical factor restricting the measurement accuracy of pendulous integrating gyroscopic accelerometers (PIGA) during their improvement. The key to nonlinear error ...suppression for PIGA is the precise measurement and compensation of the micro product of inertia (MPOI) of the float assembly. However, the existing equipment and procedure for product of inertia (POI) measurement and compensation do not meet the accuracy requirements for MPOI. To solve this problem, novel equipment and procedures are proposed for the measurement and compensation of MPOI. The principle of the proposed measurement method is to simulate the error produced by MPOI in PIGA by using a single-axis turntable to rotate the float assembly along the eccentric axis to generate a centrifugal moment due to MPOI. The principle of the proposed compensation method is to remove the asymmetric mass to reduce the MPOI to zero. Through experimental validation, it is concluded that: (1) the measurement and compensation accuracy of the proposed method are better than 1 × 10
kg·m
and 3 × 10
kg·m
, respectively; (2) the proposed method is validated as the MPOI is reduced from 7.3 × 10
kg·m
to 3 × 10
kg·m
for a real float assembly in PIGA, and the quadratic error of PIGA is reduced from 10
/g
to 3 × 10
/g
.
Texture orientation explicitly influences the mechanical properties and deformation mechanism of AZ31 wrought magnesium alloy. Continuous variable channel direct extrusion can use its unique cavity ...structure to promote the formation of different texture distributions of magnesium alloy, which affects the material’s mechanical properties and deformation mechanism. Therefore, this paper selects the CVCDE AZ31 magnesium alloy rod and sheet as the research object and studies the mechanical properties of CVCDE AZ31 magnesium alloy under different process conditions with the help of crystal plastic finite element (CPFEM). The results show that the stress-strain curve shows a downward trend with the increase in loading angle. For CVCDE sheets, due to the influence of texture weakening and grain refinement, there is an anti- Hall-Petch relationship between yield strength and grain size. The relationship between yield strength and grain size of the CVCDE rod shows a strong linear correlation. Hall-Petch constant k first decreases and then increases in the tensile process of different loading directions (0°, 45°, and 90°). This clarifies the internal relationship between texture orientation and mechanical properties of CVCDE AZ31 magnesium alloy to a certain extent and reveals the strengthening law of CVCDE under different process conditions.
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•The CVCDE magnesium alloy was studied by using the crystal plastic finite element technique.•The effect of texture orientation on the mechanical properties of CVCDE magnesium alloy was studied.•It is found that the CVCDE sheet does not conform to the hall Petch relationship.•The effect of texture orientation on H-P constant k of CVCDE bar was analyzed.
Globally, climate change impacts on marine ecosystems are evident in physical, chemical, and biological processes, and are generally more extensive in faster warming regions. China makes the largest ...contribution of any country to global fisheries production and has experienced severe declines in marine health and biodiversity, and so the current and potential impacts of marine climate change are a large concern for both fisheries and biodiversity. China also has marine regions warming in the top 10% globally, necessitating a thorough understanding of how marine systems are changing so that appropriate corresponding countermeasures can be identified and prioritized. Here, we review and collate what is currently understood about documented and projected responses of marine systems to climate change in Chinese coasts and oceans, from physical, biological, and ecological perspectives, through to impacts on key ecosystems. Our results show extensive change attributed to climate change throughout Chinese marine systems, including red tide bloom events that have been recorded an order of magnitude more frequently in recent decades. Ocean acidification has led to the increased mortality of marine calcifying organisms through effects on the biomineralization process and physiological functions. Moreover, many species have been documented undergoing extensive changes in geographic distribution, with potential implications for species interactions and trophic food webs, as well as important habitats like coral reefs, seagrass, and mangroves. Some constructive laws and actions have been introduced in response to these climate-driven changes, such as actions to reduce pollution and increase artificial propagation and replanting of habitat species, however, addressing the impacts of marine climate change remains a considerable and escalating challenge.
The construction sector plays a significant role in national economic development and accounts for a dominant portion of national economic growth. The international construction industry’s ...development has been explored from the perspective of the economy. Internationalization improves awareness about participation in international trade activities. This paper aims to quantify the internationalization of the construction industry in the global value chain. The sectoral participation index and interaction index are conducted to evaluate the internationalized degree of the construction industries. In the results, the distribution of the backward participation indices shows nearly all countries’ internationalization processes were still at the stage of benefiting from primary resources. The forward support index is easily influenced by the scale effect. The backward independence index accounts for a small percentage of national imports measured by value added. The main source of value-added supply was the local construction sector. This study proposes a comprehensive indicator to quantify the internationalization of the construction industries in the sight of national and global points. The references have a positive value for policymakers in the management of value-added flows in the international market and adjustment of the foreign trade environment.
More frequent global warming events, biological disasters, and anthropogenic activities have caused extensive damage to coral reefs around the world. Coral reefs in the Xisha Islands (also known as ...the Paracel Islands) have been damaged following rounds of heatwaves and crown-of-thorns starfish (CoTS) outbreaks over recent decades. Based on a comprehensive community survey in 2020, we determined a diagnosis for the present state of six coral regions in the Xisha Islands. The findings suggested that these regions had a total of 213 species of scleractinian corals belonging to 43 genera and 16 families. Living coral coverage across sites was widely divergent and ranged from 0.40% (IQR: 7.74-0.27%) in Panshi Yu to 38.20% (IQR: 43.00-35.90%) in Bei Jiao. Coral bleaching prevalence was 23.90% (IQR: 41.60-13.30%) overall and topped out at 49.30% (IQR: 50.60-48.10%) in Bei Jiao. Five of the coral regions (all but Yongxing Dao) were under threat of CoTS outbreaks. High mortality combined with excellent recruitment rates suggested potential rehabilitation after recent deterioration. We employed a quantifiable Deterioration Index (DI) to evaluate the intensity of deterioration of coral reefs in the Xisha Islands. The results showed that Yongxing Dao and Langhua Jiao had low recent deterioration (DIrecent = 0.05, IQR: 0.07-0.02 and 0.04, IQR: 0.11-0.01, respectively), while Bei Jiao, Yongle Atoll, Yuzhuo Jiao, and Panshi Yu had high recent deterioration (DIrecent > 0.16). Different monitoring sites within the same coral region were heterogeneous with regards to all above indexes. Moreover, we reviewed and discussed potential disturbances that threaten the health of the Xisha Islands' corals. It is crucial to identify severely afflicted areas and find successful methods to better manage coral reef health in this region.
The hemispherical dynamic pressure motor (HDPM) has the advantages of high speed, wear resistance and stability, which is widely used in inertial instruments to produce the gyroscopic effect. The ...ultra-thin gas film between the stator and rotor of the motor provides dynamic pressure lubrication and bearing capacity, whose dynamic characteristics determine the motor performance. However, the influence mechanism of some key factors such as ball center distance on the film characteristics is not clear, which has become the bottleneck restricting the performance improvement of HDPMs. Therefore, in this paper, a series of gas film similarity models were solved under different geometric and working parameters, and the influence law of the ball center distance, rotor displacement and stopping process on the aerodynamic characteristics was obtained, the results show that these primary parameters have significant effects on the pressure distribution, resistance moment and frictional heat of the ultra-thin gas film. This work can not only provide a theoretical basis for the aerodynamic performance optimization of HDPMs, but also serve as a reference for the design of other aerodynamic instruments.
H62 copper alloy is a commonly used material in engineering, and stress cracking of copper alloys has always been concerned. In this paper, a two-dimensional model of H62 copper alloy was established ...by COMSOL electrochemical module, and the stress corrosion of H62 copper alloy was analyzed by using measured engineering stress-strain curve. The results show that the tensile stress has a serious effect on the stress corrosion, and the excessive tensile stress will lead to the fracture failure of the contact.
The genus Plesiastrea used to be a member of the traditional family Faviidae, falling into the challenging ‘Bigmessidae’ clade, and was re-established until recent molecular phylogenies published. ...The entire mitogenome of the symbiotic coral Plesiastrea versipora (Lamarck, 1816), the type species of the family Plesiastreidae, was sequenced. The length of the mitochondrial genome is 15,320 bp and it includes thirteen protein-coding genes (PCGs), two rRNAs and two tRNAs. The nucleotide composition of GC is 32%. We perform phylogenetic reconstruction based on maximum likelihood (ML) and Bayesian analysis(BI) using all PCGs. Our result indicates that P. versipora clusters closely with species which belong to Mussidae, Merulinidae and Lobophylliidae. Our phylogenetic analyses provide solid evidence for phylogenetic placement of P. versipora and the evolutionary relationships among different families within the traditional robust clade of Scleractinia. In addition, the mitogenome data provide useful information for further molecular systematic investigations on Plesiastreidae as well as conservation biology research of P. versipora.
In this study, the whole mitochondrial genomes of
Physogyra lichtensteini
and
Plerogyra sinuosa
have been sequenced for the first time. The length of their assembled mitogenome sequences were 17,286 ...bp and 17,586 bp, respectively, both including 13 protein-coding genes, two tRNAs, and two rRNAs. Their mitogenomes offered no distinct structure and their gene order were the same as other typical scleractinians. Based on 13 protein-coding genes, a maximum likelihood phylogenetic analysis showed that
Physogyra lichtensteini and Plerogyra sinuosa
are clustered in the family Plerogyridae, which belongs to the “Robust” clade. The 13 tandem mitogenome PCG sequences used in this research can provide important molecular information to clarify the evolutionary relationships amongst stony corals, especially at the family level. On the other hand, more advanced markers and more species need to be used in the future to confirm the evolutionary relationships of all the scleractinians.
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