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The NVH noise performance of electric vehicles greatly affects driving comfort, and the NVH performance has become a key indicator for verifying the quality of their products; strengthening the research can greatly promote the high-quality development of reducers. Aiming at the problem that the noise data acquisition environment of the noise test stand is highly disturbed and difficult to be eliminated, a noise signal decomposition based on variational modal decomposition (VMD) and fast independent component analysis (FastICA) and a background noise component identification and noise reduction method based on signal correlation analysis were proposed. The method firstly adopted the VMD to decompose the speed reducer mixed signal into multiple modal components, and then further separated and demixed the obtained modal components through the FastICA to obtain the multidimensional independent components. Finally, the multidimensional independent components were identified and filtered out by using the signal correlation analysis to reduce the noise and complete the separation of the background noise in the test. The results show that the proposed VMD-FastICA can correctly separate the background noise signal in the mixed signal, and effectively separate the noise. Through the reducer noise test stand 9 000 r/min speed conditions of operation test comparison, the decomposition filters out the background noise and reduces the sound pressure level by an average of 3.09 dB(A), with an average error of 0.32 dB(A), to further optimize new energy vehicle gearbox noise performance test methods, and to enhance the accuracy of the gearbox noise test to provide a technical guarantee.

The purpose of the study was to characterize the response, as well as the regularitity of soil microorganisms in Podocarpus macrophyllus to different levels of nitrogen (N), phosphorus (P), and potassium (K). Using two-year old P. macrophyllus seedlings as the test species, the researchers controlled the gradients of N, P and K nutrient levels using the L9 orthogonal test in the potted soil. The dilution plate coating method and Biolog-ECO microplate method were used to explore the effects of different soil nutrient levels on the amount and community diversity of P. macrophyllus soil microorganisms and their utilization characteristics of six carbon sources. The results were as follows: (1) The number of soil bacteria (P

Residues of fipronil and its metabolites in paddy fish soil were detected using high performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS). Samples were extracted with oscillation and acetonitrile in constant temperature, and subsequently purified by solid phase extraction using ENVI 18 column and 10 mg GCB. The target compounds were separated on an Agilent ZORBAX Extend C18 column (2.1 mm× 100 mm×1.8 μm), and determined using electrospray ionization (ESI) source at negative mode with multiple reation monitoring (MRM). The analytes were quantified with external standard using the matrix matched standard calibration curve method. The results indicated that the average spiked recoveries of fipronil, fipronil desulfinyl, fipronilsulfone and fipronilsulfide in paddyfish soil were 83.5%~110.3% with the relative standard deviations (RSDs) of 1.9%~11.5%. Good linearities were obtained in the range of 0.5~100 μg/L, and the correlation coefficients were greater than 0.998, the limits of detection (LODs) were 1.0 μg/kg, and the limits of quantification (LOQs) were 3.0 μg/kg. This method is simple, accurate and reliable, which can meet the detection requirements of fipronil and its metabolites in paddy fish soil.

The study was to thoroughly investigate the weather resistance of polyethylene for rotational molding under different conditions, and to comprehensively understand the changing rules of their structure and performance. The structure and properties of polyethylene rotational molding special materials were investigated under different xenon lamp aging levels by using scanning electron microscopy (SEM), infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and other characterization methods. The results show that with the increase of xenon aging time, the surface morphology of the rotational plastic undergoes significant deformation and cracking, while the intensity of the internal carbonyl characteristic peaks also shows an increasing trend. The xenon lamp aging causes a significant shortening of the oxidation induction period of the rotational plastics. However, the rotational plastics show relatively stable characteristics in terms of melting and crystallization temperatures and processing properties. In addition, the yield stress of the rotational plastics increases, while the strain at fracture, stress at break and tensile strength show a decreasing trend. The experimental data in this study provide detailed information on the weather resistance of polyethylene for rotational molding, offering references for further optimizing product performance and applications. [ABSTRACT FROM AUTHOR]

Structure of polyethylene is the key factor affecting the properties of polyethylene. For high-density and linear low-density polyethylene, the choice of different comonomers and their content is crucial in determining the degree of branching in the polymer chains. In the formation of long-chain branching (LCB), an increase in comonomer content often leads to a decrease in the degree of LCB. This study conducted a comprehensive analysis of high-density polyethylene samples, namely D6095H, L6095-1, and L6095-2, produced by three domestic manufacturers. Various fundamental properties such as comonomer content, molecular weight distribution, thermal performance, mechanical properties, and microstructure were tested with respect to different comonomer contents. The results show that D6095H, with a slightly higher comonomer content, exhibits higher melt flow rate and branching degree compared to L6095-1 and L6095-2, but lower crystallinity. D6095H also has a broader molecular weight distribution, higher tensile stress than L6095-1 and L6095-2, while L6095-1 and L6095-2 exhibit higher impact strength. [ABSTRACT FROM AUTHOR]

The outbreak and continuous spread of African swine fever (ASF) since 2019 has caused serious losses to the Asian pig industry, the effective prevention and control of ASF is directly related to the stability of the pig industry. This paper evaluated the effects of ASF prevention and control measures, industrial support policies, and market regulations and proposes the recommendations for the optimizing the policies and measure of ASF control and pig industry stabilization in China by analyzing the situation of ASF in Southeast Asia, the causes of the outbreak, and the impact on the pig industry and market in Vietnam and the Philippines, the 2 biggest pig producers in the region. The results showed that the key factors contributing to the outbreak and ongoing spread of ASF in Vietnam and the Philippines were the challenge on the industry management for low scale, low biosecurity awareness, and transportation of large amounts of live pigs. Following the outbreak of ASF, the significant decreased in pork output, the sharp falled and rised of live pig prices, and the significant increased in pork imports as well as the significant transformation of pig industry chain were observed in both countries. By the reference of the prevention and control experiences of the two countries, China should increase the support on the small and medium-sized pig farms for the prevention and control of ASF to encourage their upgrading towards for modernization, accelerate the development of production scale level and organization level, improve the effect of epidemic prevention and control, strengthen the rural veterinary service system for the ability to prevent and control the major animal diseases, optimize the starting mechanism of governmental frozen pork storage to improve the effect of market intervention. [ABSTRACT FROM AUTHOR]

Combined with the practical engineering case, we analyzed the damage reason of floating oil seals and put forward the measures of improvement. There is great significance for improving the service life of the equipment and environment protection. [ABSTRACT FROM AUTHOR]

we predicted the onboard dredge pump's hydraulic performance based on numerical simulation and model experiment, and fluid simulation software, used the standard k -ε turbulence model to simulate three-dimensional flow field of large submerged dredge pump. The hydraulic efficiency of pump was up to 86 % was achieved by increasing blade's wrap angle, reducing outlet angle and adjusting the lines in this simulation. Based on similar laws, we manufactured a model pump with the ratio of 1:4, carried the model pump external characteristics test. The results show the efficiency of optimized large dredge pump matches the simulation's prediction and it has verified the design method of the high-efficiency dredge pump [ABSTRACT FROM AUTHOR]

PURPOSE: To evaluate bone regeneration in defects at titanium implants with nHA/BG coating in conjunction with Bio--Oss. METHODS: Four mandibular premolars were extracted in 6 Beagle dogs. After 3 months, buccal dehiscence--type defects (2.25 mmx3 mmx4 mm) were surgically created following implant site. The three treatment modalities were randomly allocated: nHA/BG implant/Bio-Oss, nHA/BG implant/blood clot, and mHA implant/Bio-Oss. After 8 and 16 weeks, the dogs were sacrificed respectively. A histomorphometric analysis was performed. The data was analyzed with SPSS 13.0 software package for Student's t test and ANOVA. RESULTS: At 8- and 16-week, nHA/BG implant group revealed comparable mean BIC (30% to 18% versus 61% to 53%). However, mHA implant/Bio-Oss group revealed significantly lower mean BIC (21% versus 46%) values than nHA/BG implant/Bio-Oss group. A significant difference was observed for the mean BIC and RA values at 8-week between nHA/BG implant/Bio-Oss group and mHA implant/Bio-Oss group. CONCLUSIONS: It is concluded that the application of Bio-Oss graft did not seem to interfere with the nHA/BG coating activity, but ensured a stabilization of the newly formed bone for defects. [ABSTRACT FROM AUTHOR]

PURPOSE: To investigate the effect of induced- mineralization on the expression of SOST gene in human periodontal ligament cells, and explore the effect of SOST on periodontal tissues. METHODS: Human periodontal ligament cells were cultured by tissue explant in vitro, the cells were continuously induced by mineralization solution for 7,14 and 21 days. The mineralized ability, SOST and related osteogenie genes(ALP, OCN)expression were detected. The data was analyzed with SPSS 17.0 software package. RESULTS: Under the condition of mineralization solution in culture medium, human periodontal ligament cells had stronger ALP activity and Alizarin red staining, SOST and related osteogenic genes (ALP,OCN) expression were significantly upregulated in a time-dependent manner(P<0.05). CONCLUSIONS: After continuous induced- mineralization culture, human periodontal ligament cells can express SOST mRNA and related osteogenic genes in a time-dependent manner, which suggests that SOST may play a role in the regeneration of periodontal tissues. [ABSTRACT FROM AUTHOR]

PURPOSE: To quantitatively evaluate the cortical bone thickness at upper molar miniscrew sites. METHODS: Sixty Angle's Class II division I patients were involved in this study (30 males and 30 females), measurements of cortical bone thickness were done with cone beam computer tomography (CBCT) scanning. The contact point of upper second premolar and upper first molar was chosen for center of coordinate. Totally 20 layers of cortical bone were measured every 1 mm. Paired t test was performed with SPSS 15.0 for Windows to evaluate the differences between both sides, and one-way ANOVA was performed to compare the changes in different layers. RESULTS: The cortical bone thickness had no significant difference between left and right side. Below the 7th layer, cortical bone could not be seen or very thin (less than 0.5mm). Above the 10th to 12th layers, thickness of cortical bone was more than 1.5mm. The average cortical bone thickness was 2.12±0.72mm in male, and 1.86±0.83mm in female (above 7th layer). In the cortical area above the 6th layer, 13 layers of cortical bone thickness were significantly different (P<0.05) and only 2 layers had no significant difference (P>0.05). CONCLUSIONS: In this area, the cortical bone thickness is gradually increased from occlusal to gingival directions; and the cotical bone is thicker in male than in female at the same level. [ABSTRACT FROM AUTHOR]