800 publications from this institution
The excess tin chloride addition produces black mercury precipitation and is about to seriously affect the determination of iron by using potassium chromate volumetric analysis method. Air oxidation we use without any other reagent is able to resolve the effect of mercury in the range of 8 to 12 minutes. This treatment saves more time and effort than the traditional doing throw it away and try again. It is proved satisfactory in the assay of iron ore sample.
Abstract Within a certain range of total transmission ratios, a preferred design of a heavy-duty planetary gear three-stage transmission system, with the volume of the gearing system as the optimization objective, was proposed to address problems such as the difficulty in coordinating the transmission ratios of the heavy-duty planetary gear multi-stage gearing system, the challenging balance between lightweight design and load-carrying capacity, and the low space utilization rate. Firstly, based on the sequential quadratic programming algorithm, eight kinds of transmission ratio preferential assignments were made for the heavy-duty planetary gear three-stage transmission system. By analyzing the results of the volume optimization, the preliminary transmission scheme for the heavy-duty planetary gear three-stage transmission system, in which the ratios of the first two stages were both reduced and the ratio of the tertiary stage was increased, was preferred. Secondly, on this basis, and in combination with the response surface method, the second-order response model for the relationship between the transmission ratios of all stages of the heavy-duty planetary gear three-stage transmission system and the total volume of the system was established. The reasonableness of the initial selection scheme was verified by solving the response surface objective function, and the optimal allocation result was obtained. This result was allocated as follows: The primary transmission ratio was 1.5635, the secondary transmission ratio was 5.7158, and the tertiary transmission ratio was 4.8800. The volume under this allocation was 5.32573 × 108 mm³, which decreased by 7.75% compared to the maximum volume of 5.77307 × 108 mm³ among all lightweighting schemes. The lightweight design of the heavy-duty planetary gear three-stage transmission system was realized. The results could provide helpful references for the lightweight design and optimization of planetary gear transmission systems, the coordinated distribution of transmission ratios, and the improvement of space utilization in transmission systems.
Clamped fiber Bragg grating (FBG) sensors have been widely applied in engineering strain measurements due to their advantages of high flexibility and efficiency. However, due to the existence of the interlayer, the strain measured by the encapsulated FBG sensor is not equal to the strain of the host material, which causes strain measurement errors. In this paper, the strain transfer analysis of a clamped FBG sensor based on the shear-lag theory is conducted to improve the accuracy of strain measurements. A novel theoretical model for the axial strain distribution of a clamped FBG sensor is proposed. It is also discussed how the gauge ratio and interlayer thickness affect the strain transfer rate. The accuracy of the proposed theoretical model is verified by experimental tensile tests. The theoretical value of the strain transfer rate matches well with the tested value.
This paper introduces a package of a high-speed and high-density switching ASIC with over 1000 pins and hundreds of high-speed transmission lines crowded in two layers of the substrate, and also demonstrates Signal Integrity (SI) and Power Integrity (PI) implementation. In order to route the transmission lines with minimum distortion, crosstalk and attenuation, routing is co-designed with die and BGA maps. To guarantee that over a hundred transmission lines will be matched identically, each transmission line is designed to have a corresponding continuous return path routed among integrated copper shapes. Various routing schemes designed to take advantage of the physical and electrical performance of materials and structures are also implemented to optimize the performance of the transmission line. Various simulations are carried out on test segments to evaluate performance and signal integrity in the frequency and time domains.
The cutting blade selection has been important issue for manufacturing systems due to the fact that it might affect productivity, precision and manufacturing cost. It is a multiple-criteria decision making problem for evaluating blade alternatives. In this paper, the hybrid approach is discussed,which combined the fuzzy AHP and benefit cost analysis. An improved AHP method based on triangular fuzzy number is used to analyze the cutting performance of blade alternatives. It can make up for the deficiency in the conventional AHP. Furthermore, the benefit cost analysis is carried out to evaluate the economic performance of alternatives. The benefit cost ratio is calculated by using the fuzzy AHP score and tool consumption cost. Tool consumption cost is obtained in consideration of tool service life and procurement cost. The optimal blade alternative with highest benefit/cost ratio can be found out. In addition, the proposed approach is also illustrated on a sample case study.
<title>Abstract</title> A questionnaire survey was conducted among 1043 adolescents by cluster stratified sampling method to explore the influence mechanism of exercise goal content on adolescents' subjective well-being. The results show that: (1) Health management, social affiliation and skill development have significant positive effects on adolescents' subjective well-being; Social recognition has a significant negative impact on adolescents' subjective well-being, while image has no significant impact on adolescents' subjective well-being. (2) Psychological need satisfaction and autonomous motivation for exercise mediate the relationship between intrinsic exercise goals and adolescents' subjective well-being. (3) The mediating effect of psychological need satisfaction and controlled motivation for exercise between extrinsic exercise goals and adolescents' subjective well-being is not established. Different types of exercise goals may have different mechanisms on subjective well-being. In addition, it is necessary to pay more attention to the influence of exercise goals on adolescents' negative emotions in follow-up research.
Because slope detection is often subject to various electromagnetic disturbances and weather limitations, there is an urgent need to develop a monitoring system that has the advantages of strong anti-electromagnetic interference capability, long service life, and small external environmental impact.Based on this demand, a real-time slope monitoring system based on fiber Bragg grating angle, crack, and osmotic pressure sensors is designed.The design idea is to use the sensitivity of FBG to the external stress, and the angle and crack penetrating pressure information are obtained from the offset of wavelength in different sensors to determine the stability of the slope.The design and implementation of the FBG slope monitoring system can better solve the existing problems in the slope monitoring, improve the ability to predict dangers, and strengthen the safety monitoring capability.The utility value of the system is high.
An optical fiber sensor based on Mach-Zehnder interferometer (MZI) cascaded with a fiber Bragg grating (FBG) for simultaneous measurement of temperature and gas pressure is proposed and demonstrated. The MZI is fabricated by inserting a piece of tapered SMF in between two sections of MMF, which performs as the gas pressure sensing element. A FBG is cascaded with the MZI to eliminate the temperature induced wavelength shift of the MZI due to the thermal optic and thermal expansion effect of silica. Experimental results show that the MZI with gas pressure and temperature responses of -8.82 nm/MPa and 33.1 pm/℃ respectively. The FBG exhibits a temperature response of 12.3 pm/℃ and shows insensitive to gas pressure. By tracing the transmission dips of the MZI and FBG simultaneously, gas pressure and temperature variation can be monitored at the same time.
Accounting information distortion and accounting information error are two different concepts. In the discussion of countermeasures to tackle accounting information distortion, it is necessary to distinguish between the two concepts. The author probes in this essay into their different meanings, causes, harm, and countermeasures.
The AC charging pile is the main energy supply facility for household electric vehicles, which uses a vehicle mounted charger to charge the power battery. The current standard of the State Grid Corporation of China clearly stipulates the function of the AC charging pile and does not take into account the impact of the harmonics of the vehicle mounted charger on the power grid. Therefore, in view of the deficiency that AC charging piles cannot suppress the current harmonics of the vehicle mounted charger, application of the active power filtering technology to the design of AC charging piles is proposed to form a new type of AC charging pile with better functions. In the experimental prototype that was built, for vehicle mounted chargers with two load characteristics, the composite control method of traditional PI control and repetitive control is adopted, where the new AC charging pile effectively suppresses the harmonics of the vehicle-mounted charger. Experiments show that the AC charging pile using active power filtering technology cannot only improve the power quality of the grid side but also reduce the impact of harmonics on the power metering and billing system, ensuring the stability of the charging communication system.
Bridge influence line (BIL) is a promising tool for the real applications in the fields of bridge weight-in-motion (BWIM), model updating, damage identification, and load carrying capacity evaluation. The key of such applications is how to obtain the accurate results of BIL. To accurately identify BIL based on bridge dynamic responses induced by a moving vehicle, two critical problems, including how to construct a general representation function of BIL and how to deal with the ill-posed inverse problem, should be properly resolved. This paper proposes a novel approach based on the adaptive B-spline basis dictionary and sparse regularization technique for BIL identification. A representation of basis function is first established to construct BIL, and then integrated with a redundant B-spline basis dictionary to ensure the sparsity of solution. A curvature-based adaptive node optimization method is proposed to automatically adjust the spatial arrangement of nodes according to the shape of BILs. Numerical and experimental validations are conducted to verify the accuracy and robustness of the proposed approach. The identified BIL results are accurate, indicating that the proposed node-adaptive optimization and sparse regularization techniques are effective to improve the quality of BIL identification. It is also shown that the proposed approach is not sensitive to the noise interference and configuration of testing vehicle. Through the robustness testing, it is proved that the proposed approach has the merits of high accuracy and strong robustness.
