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Pest identification-based deep convolutional object detection is an important application of smart agriculture,which performs pest monitoring and ensures stable agricultural production.To solve the problems of high missed detection rate of small pests and low precision of small samples,a pest identification method based on the TPH-YOLOv5 algorithm and small sample learning is proposed.First,data augmentation for small objects and small samples is designed.Through copy and pasting,cropping,and oversampling,the number of training samples increases and the pest locations are diversified,which improves the contribution to training loss.Second,a two-stage small sample learning strategy based on fine-tuning is constructed.By learning the characteristics of basic and new categories of pests in different stages,the recognition precision of basic categories will not decrease while identifying new pests,which is suitable for the actual agricultural application of continuously collecting pest data.Finally,TPH-YOLOv5 is introduced as the pest identification algorithm.Rigorous tests are conducted on the 28 categories of pest images.The results show that the proposed method achieves high learning efficiency and recognition accuracy,with precision,recall,and mean average precision(mAP) of 87.6%,84.9% and 85.7%,respectively.

According to the description of 50 Gbit/s-Ethernet Passive Optical Network (EPON) in IEEE 802.3ca new standard, multi-wavelength dynamic bandwidth allocation is needed in network uplink. In this paper, long short-term memory neural network is used to predict the network traffic in order to improve the efficiency of bandwidth allocation. At the same time, considering the different requirements of network delay and bandwidth for different types of services in the network, different allocation schemes are adopted for different priority services. The simulation results show that the neural network prediction method can effectively reduce the delay of the network. When different allocation schemes are adopted for different services, the latency of high-priority services decreases, and the latency varies with the increase of network load. The algorithm proposed in this paper meets the requirements of high-priority service. Although the latency of low-priority service is increased compared with the previous method, it has little impact on the overall service quality of the network considering that low-priority service does not have high latency requirements.

BACKGROUND In the past twenty years, methods for metal isotopes analysis (iron, copper, zinc, magnesium, calcium, lithium, molybdenum, selenium, mercury, chromium, cadmium, alum, barium, titanium, etc.) have been established. The sample pretreatment during metal isotope analysis includes two processes: the digestion of the sample; and the separation and purification of the analyzed elements. In order to ensure the accuracy and precision of metal isotopes data, two general principles of sample treatment must be followed. Elements that may interfere with the isotope analysis of the analyzed elements should not be introduced into the analysis. The analyzed elements should not be lost during the experiment. OBJECTIVES In order to understand the pretreatment methods for metal isotope analysis. METHODS Common sample digestion methods and chemical separation (ion exchange separation) were introduced in detail and were discussed in this paper. RESULTS The common sample digestion method for metal isotope analysis is the acid dissolution method (Teflon bombs and microwave digestion). The separation and purification of the element to be measured mainly uses the ion exchange separation method. The same resin can be used for the chemical separation of different elements, and the same element can also be chemically separated by using different resins. The matrices of different types of samples are quite different, and different processes are required to separate the analyzed elements. The separation requirements of different samples can be met by changing the separation process of the predecessors, including changing the resin or the amount, changing the eluent or the amount, and increasing the separation steps. CONCLUSIONS Based on the authors' experience, details should be paid attention to during treatments for metal isotope analysis: (1) HClO4 must be thoroughly removed at high temperature during sample digestion, because its strong oxidization can destroy the effectiveness of resins; (2) when the same volume of resin is put into the column, the thinner the column is, the slower the flow rate of the eluent, and the later elution of the elements to be measured; (3) the smaller the volume of the eluent added each time, the better the separation effect during ion exchange purification.

BACKGROUND The Sr and Nd isotopic compositions of a sample depend on its initial isotopic ratios, the ratios between the parent nuclide and daughter product, and the decay time. Due to their significance for the tracing of reservoirs, they were widely applied in the geological studies. Traditional cation resin was applied to purify Sr and Nd for isotope analysis, which involved the organic reagent and pH adjustment. The complex chemical procedure was time-consuming. In recent years, the appearance of special resins has made it easy to separate these elements. However, due to the influence of sulfates and other factors, the use of special resins is limited. OBJECTIVES To shorten the chemical purification time of Sr and Nd, and to avoid the damage of sulfate ions on the Sr and REE specific resins, we proposed a new chemical purification method, where multiple columns were utilized. METHODS The method combines cationic resin and special resin to realize the rapid separation of Sr and Nd and can extend the using time of special resin. The experiment uses cationic resin, Sr special resin and LN rare earth special resin to analyze the basalt standard BCR-2. RESULTS The recoveries of Sr and Nd with this method were larger than 90%. The 87Sr/86Sr and 143Nd/144Nd isotope ratios were 0.705016±0.000016 (n=36, 1SD) and 0.512624±0.000012 (n=39, 1SD), respectively, which were in coincidence with the values previously reported by TIMS method within the analytical error. The complied 87Sr/86Sr and 143Nd/144Nd isotope ratios obtained TIMS were 0.705000-0.705023 and 0.512630-0.512650, respectively. The 85Rb/86Sr and 147Sm/144Nd rations of the purified Sr and Nd solution were less than 0.01 and 0.001, respectively. CONCLUSIONS The proposed chemical purification procedure can efficiently separate Rb, Sr, Sm and Nd, and realize the accurate analysis of Sr and Nd isotopes.

BACKGROUND Critical problems such as ion diffusion and uncontrollable flow rate exist when applying the traditional natural flow chromatography column method to isotope analysis. The proposed automated chemical purification system improves the efficiency of isotope analysis, and reduces the time required for element purification. OBJECTIVES To develop an automated chemical separation and purification system. METHODS The automated chemical separation and purification system was composed of multi-way valves, plunger pump, autosampler, etc. All of the components were connected using a computer and each of them can be controlled independently. By combining two chromatographic columns multiple functions can be achieved, including reversed elution, which cannot be achieved by the traditional natural flow chromatography column method. In order to investigate the performance of the automated chemical separation and purification system, fresh seawater was purified with the proposed system and the traditional method simultaneously. RESULTS The elution peak of boron had a width of 2.5mL to 3.0mL for the traditional method, but only ca. 1.0mL for the proposed system, if the loading volume of seawater was 1.0mL. The flow rate of the elution depended on the acidity using the traditional natural flow chromatography column method. However, the flow rate could be strictly controlled with the automated chemical separation and purification system. CONCLUSIONS The precisely controlled flow rate of the system makes an easier prediction of the elution time and elution peak. The reversed column technology of the system can be applied to the separation and purification of elements for isotope analysis.

[Objectives] The manual lifting mode is often used for the shafting installation at present,for which a lot of manpower and man hours are required to complete the installation and it is not easy to repair and adjust. In order to improve the automation level of the shafting installation, a special six-degree-of-freedom parallel motion platform is designed to realize the intelligent installation of the shafting.[Methods] A sensor-based observation model was established to use the trilateral centroid localization algorithm to locate the shaft segment. The positional conditions of the contact point between the motion platform and the shaft segment were calculated,and the limit position conditions of various working conditions of the motion platform were analyzed to obtain the working space of the shaft segment.[Results] In view of the above,the safety of the working space for installation of the shaft segment can be estimated,and unnecessary damage during assembly work can be effectively avoided,[Conclusions] the study can provide theoretical guidance and technical support for engineering applications.

[Objectives]In order to study the laws of the propulsion shafting deformation and variation of the bearing load of a underwater vehicle under various conditions,[Methods]a mixed finite element model of the shaft system and the underwater vehicle was established,with a underwater vehicle as the research object,to which the realistic load and boundary conditions were applied under three conditions including on the slipway,at the pier and underwater to calculate the hull deformation respectively and the deformation of the bearing and the bearing load were extracted. Taking the connecting line of the bearing 1 and bearing 3 as the reference line,the relative deformation of the bearing under three conditions was obtained.[Results]The analysis results show that,for this underwater vehicle,the relative deformation of the centerline of the shaft system,its size and the changing trend of the bearing load are different under the conditions from the slipway to the pier and then to the underwater;the initial deformation of bearing 2 of the shaft system on the slipway is preset to be 0.090 9 mm upward,so that the shaft system is in ideal state on the underwater.[Conclusions]The study in this paper can provide reference for the subsequent shafting alignment.

[Objectives] To achieve lightweight design of double-arm propeller shaft brackets.[Methods] By comparing and analyzing the requirements of the current domestic rules and the main classification societies in the world for the dimension of propeller shaft brackets,this paper interprets the differences between the rules,and searches for ways to reduce the weight of the double-arm shaft brackets from such differences. According to the differences between the rules,DNV-GL rules with significant differences from the CCS rules in the relevant aspects are selected. Based on the same propeller parameters, double-arm propeller shaft brackets are designed according to the minimum sizes requirements specified in the two rules. Subsequently,the strength and vibration performance of the double-arm propeller shaft brackets are verified by the relevant regulations of the national military standard.[Results] The results show that the strength and vibration performance of the propeller shaft brackets designed according to the two rules meet the requirements. The total weight of the propeller shaft brackets designed according to the minimum sizes requirements of DNV-GL rules is reduced by about 16.8%.[Conclusions] If the double-arm propeller shaft brackets are designed with the DNV-GL rules,the weight thereof can be reduced to some extent. This paper provides an idea for the lightweight design of the double-arm propeller shaft brackets in practical engineering.

Tools are the key parts in the process of NC milling machine. They are in high-speed processing for a long time and are prone to failure. Aiming at the problems of less tool wear state data,low diagnostic efficiency,high maintenance cost and lack of effective diagnostic methods during CNC machine tool processing,A method of extracting features by wavelet packet analysis and kernel principal component analysis,and using BP Ada Boost algorithm to diagnose tool wear state is proposed.The tool vibration signal and the cutting force signal are collected by installing an acceleration sensor on the machined workpiece of the numerical control machine tool and a force gauge on the workbench; Then the wavelet packet decomposition is performed on the signal to pass the signal through the low-pass filter and the high-pass filter of different dimensions,so that the conditional selection can be performed to form the energy value corresponding to the different frequency bands. The data after the dimension reduction of the kernel principal component analysis is taken as the characteristic parameter of the tool wear state; Finally,the eigenvectors are used to train and validate the BP AdaBoost classification model. The experimental result shows that the BP Ada Boost algorithm can effectively diagnose the wear state of the tool in CNC machine tools compared with the SVM algorithm.

The catalytic flame retardant system has the characteristics of the low addition amount, high char formation efficiency, stable carbon structure at high temperature and so on. The research on flame retardant method and mechanism of the catalytic flame retardant system has become more and more important. In this paper, the status of research and development on catalytic flame-retardant polymer systems at home and abroad was reviewed. The applications research progress on metal oxides, carbon materials, metal salts, montmorillonite, molecular sieves and boron phosphors in catalytic flame-retardant polymer systems was introduced. The catalytic mechanism in the char-forming process of condensed phase was discussed. At last, it was pointed out that the development trend of catalytic flame retardant polymer materials is to develop new carbon materials represented by graphene and to achieve superfine and organic of catalytic flame retardant.

[Objectives] This paper aims to analyze the thermal equilibrium performance of a piston hydraulic damper in a stable working state so as to solve the problem in which the oil circuit of the hydraulic damping system of a longitudinal vibration-reduction thrust bearing is closed and the external disturbance input is unknown. [Methods] To this end,a micro-mechanism for the heat production calculation of piston friction loss and hydraulic fluid loss is applied to the thermal analysis of the hydraulic damping system in order to deduce the formula of the power loss calculation of the piston vibration and the reciprocating flow of the hydraulic oil. Meanwhile,the piston friction loss and head loss of the model are calculated,and the heat production variation of the hydraulic damping system with dynamic frequency and piston stroke is analyzed. In addition,the input power of the external disturbance is ascertained and the thermal finite element model of the bearing part established,allowing the steady temperature rise and heat flow distribution of the structure to be calculated.[Results] The calculation results show that the input power of the external disturbance is roughly equal to the sum of the thermal power of each part,the steady temperature rise of the system is fairly low and the heat flow division is reasonable.[Conclusions] The results show that the heat production calculation method described in this paper is quite feasible. Furthermore, the calculated temperature rise of the system is within the permissible range, and corresponding effective measures can be taken to reduce local temperature rise at intensive heat flow parts according to the heat flow division diagram of the system.

[Objectives] One-way periodic stiffened plates are widely used in ship structures, and their vibro-acoustic characteristics provide a theoretical reference for the analysis and optimization of the sound and vibration characteristics of stiffened plates.[Methods] Considering the force and torque of the stiffeners to the plate, along with the coupling effect between the fluid acoustic medium and the plate, a structural dynamic model of infinite one-dimensional and two-dimensional periodically stiffened plates is established. The spatial domain is transformed into a space wave number domain using the Fourier transforms method. The vibration equation of the stiffened structure is deduced using the constructor, Poisson's formula and periodic function. The analytical solution of the motion equations of typical periodic stiffened plates is obtained and calculated under a time-harmonic point force or harmonic excitation. Combined with the stationary phase method, the far field radiated sound pressure can be obtained. The influence of the torque of the stiffener, excitation types, excitation locations, plate thickness, periodicity spacing and parameters of stiffeners on the sound radiation characteristics of three different models of periodic stiffened plates are numerically quantified.[Results] The torque of the stiffener has a lesser effect on structural vibration characteristics. The influence of the stiffener parameters on the phonon crystal band gap can be used to attenuate the vibration at certain peak frequencies. The excitation load on the strong structural components can effectively weaken the vibration. The periodicity spacing and parameters of the stiffeners have obvious effects on structural vibration characteristics.[Conclusion] The underwater acoustic vibration characteristics of reinforced plate structures can be effectively optimized by the reasonable setting of the excitation types and parameters of the stiffeners.

[Objectives] A large number of structures with openings are used in engineering projects, which is of great significance for studying the vibration characteristics of plates with openings.[Methods] By introducing an improved Fourier series, the permissible displacement function of rectangular plates with openings is simulated. By using displacement springs and angle springs, arbitrary boundary conditions are simulated. While obtaining the overall energy functional, the kinetic energy and strain energy of the opening part are subtracted. Based on the Rayleigh-Ritz method, the Lagrange energy functional of the structure is constructed and the variational extremum of unknown coefficients in the Fourier series obtained, transforming the original vibration problem into a problem of eigenvalue equations. The paper studies the influence on the free vibration of rectangular plates with different shaped and sized openings.[Results] A comparison with the results of finite element software ANSYS shows that the current method is accurate and reliable,[Conclusions] providing a reference for practical engineering.

Plate structures with openings are common in many engineering structures. The study of the vibration characteristics of such structures is directly related to the vibration reduction, noise reduction and stability analysis of an overall structure. This paper conducts research into the free vibration characteristics of a thin elastic plate with a rectangular opening parallel to the plate in an arbitrary position. We use the improved Fourier series to represent the displacement tolerance function of the rectangular plate with an opening. We can divide the plate into an eight zone plate to simplify the calculation. We then use linear springs, which are uniformly distributed along the boundary, to simulate the classical boundary conditions and the boundary conditions of the boundaries between the regions. According to the energy functional and variational method, we can obtain the overall energy functional. We can also obtain the generalized eigenvalue matrix equation by studying the extremum of the unknown improved Fourier series expansion coefficients. We can then obtain the natural frequencies and corresponding vibration modes of the rectangular plate with an opening by solving the equation. We then compare the calculated results with the finite element method to verify the accuracy and effectiveness of the method proposed in this paper. Finally, we research the influence of the boundary condition, opening size and opening position on the vibration characteristics of a plate with an opening. This provides a theoretical reference for practical engineering application.

Aiming at the current lack of analytical research concerning the cylindrical shell-flow field coupling vibration and sound radiation system under the influence of a free surface, this paper proposes an analytical method which solves the vibration response and far-field acoustic radiation of a finite cylindrical shell immersed at a finite depth. Based on the image method and Graf addition theorem, the analytical expression of the fluid velocity potential can be obtained, then combined with the energy functional of the variation method to deduce the shell-liquid coupling vibration equation, which can in turn solve the forced vibration response. The research shows that, compared with an infinite fluid, a free surface can increase at the same order of resonance frequency; but as the depth of immersion gradually increases, the mean square vibration velocity tends to become the same as that in an infinite fluid. Compared with numerical results from Nastran software, this shows that the present method is accurate and reliable, and has such advantages as a simple method and a small amount of calculation. The far-field radiated pressure can be obtained by the vibration response using the Fourier transformation and stationary phase method. The results indicate that the directivity and volatility of the far-field acoustic pressure of a cylindrical shell is similar to that of an acoustical dipole due to the free surface. However, the far-field acoustic pressure is very different from the vibration characteristics, and will not tend to an infinite fluid as the submerging depth increases. Compared with the numerical method, the method in this paper is simpler and has a higher computational efficiency. It enables the far-field acoustic radiation of an underwater cylindrical shell to be predicted quickly under the influence of external incentives and the free surface, providing guiding significance for acoustic research into the half space structure vibration problem.

Abstract Background The clonal spread of multiple drug-resistant Acinetobacter baumannii is an emerging problem in China. We analysed the molecular epidemiology of Acinetobacter baumanni isolates at three teaching hospitals and investigated the risk factors, clinical features, and outcomes of hospital-acquired pneumonia caused by extensive drug-resistant Acinetobacter baumannii (XDRAB) infection in Guangzhou, China. Methods Fifty-two A. baumannii isolates were collected. Multilocus sequence typing (MLST) was used to assess the genetic relationships among the isolates. The bla OXA-51-like gene was amplified using polymerase chain reaction (PCR) and sequencing. The resistance phenotypes were determined using the disc diffusion method. A retrospective case-control study was performed to determine factors associated with XDRAB pneumonia. Results Most of the 52 A. baumannii isolates (N = 37, 71.2%) were collected from intensive care units (ICUs). The respiratory system was the most common bodily site from which A. baumannii was recovered (N = 45, 86.5%). Disc diffusion classified the isolates into 17 multidrug-resistant (MDR) and 35 extensively drug-resistant (XDR) strains. MLST grouped the A. baumannii isolates into 5 existing sequence types (STs) and 7 new STs. ST195 and ST208 accounted for 69.2% (36/52) of the isolates. The clonal relationship analysis showed that ST195 and ST208 belonged to clonal complex (CC) 92. According to the sequence-based typing (SBT) of the bla OXA-51-like gene, 51 A. baumannii isolates carried OXA-66 and the rest carried OXA-199. There were no significant differences with respect to the resistance phenotype between the CC92 and non-CC92 strains (P = 0.767). The multivariate analysis showed that the APACHE II score, chronic obstructive pulmonary disease (COPD) and cardiac disease were independent risk factors for XDRAB pneumonia (P

Nitriding reaction of Mn pellets prepared under different conditions was investigated with a self-made air-proofed nitriding system. The effects of Mn particle size, pelletizing pressure and binder content on the nitriding reaction were studied, and the real-time variation curves of temperature and Mn pellet mass were measured. The results show that with the decrease of particle size from 16-40 mesh to 60-80 mesh, the time for the pellet center temperature reaching peak (tp) shifts from 164s to 101 s, the maximum temperature increment at the pellet center (ΔTmax) increases from 147 ℃ to 233 ℃, and the conversion ratio at 1 h rises from 90, 81% to 93.64%. With increasing pelletizing pressure from 266 MPa to 443 MPa, tp decreases by 89 s, ΔTmax increases by 22 ℃, and the conversion ratio at 1 h rises from 91.59% to 94.92%. With the increase of binder addition from 1 g to 3 g, the conversion ratio at 1 h drops from 92.90% to 89.80%. The data points of the conversion rate and the nitriding time can be approximately fitted with the probability density function of the log-normal distribution.

In recent decades, Fe, Cu and Zn isotopes have been the hot topic with the development of analytical methods of these isotopes. However, the standard materials for isotope analysis are very sparse. There is only one Fe isotope standard material and one Zn isotope standard in The European Institute for Reference Materials and Measurements (IRMM). The former is sold out and therefor unobtainable, whereas the latter is expensive. There is one Cu isotope standard material in National Institute of Standards and Technology (NIST). In order to adapt to the development of Fe, Cu and Zn isotope analyses in China, three new standard solutions to be used as references for Fe, Cu and Zn isotopic composition have been prepared in the Institute of Geology, Chinese Academy of Geological Sciences, Beijing. Fe, Cu and Zn isotopic standard solutions are named CAGS-Fe, CAGS-Cu and CAGS-Zn, respectively. Fe, Cu and Zn isotopic compositions of these standard solutions were measured by high precision Nu Plasma High-resolution Multi-collector Inductively Coupled Plasma-Mass Spectrometry (MC-ICP-MS). Three standard solutions show high homogeneity and stability by F investigation. The Fe, Cu and Zn isotopic compositions have shown no obvious variations over 38 months, indicating good homogeneity. The reference values for standard solutions and their associated uncertainties at 95% confidence level are 0.80±0.05 (δ56FeIRMM014, ‰), 1.20±0.10 (δ57FeIRMM014, ‰), 0.57±0.06 (δ65CuNBS976, ‰), -0.77±0.10 (δ66ZnIRMM3702, ‰) and -1.55±0.13 (δ68ZnIRMM3702, ‰). Standard solutions can be used for instrumental calibration and analytical monitoring, which is meaningful for inter-laboratory data comparison.

Automotive transmission system load spectrum is the indispensable data foundation of automotive transmission system designing,testing and evaluating.Aiming at the off-road vehicle transmission system of an enterprise,considering the design,test,analysis other purposes,choosing the measured parameters of torque,speed,gear position,brake pedal station,clutch pedal position,lubricating oil temperature,strain,acceleration signals and etc signals,the complete synchronous test scheme for transmission system load spectrum is constructed.Rounded and accurate measurement of the transmission system load spectrum based on the Pascar test specification provide basic data and important guidance for the design,test,analysis of automotive transmission system.Wireless torque measurement problem and the synchronization problem of different channels are solved and a complete solution scheme of data collection for automotive transmission system is provided.

Background: Anti-apoptotic mechanism for cell protection on reperfusion may provide a new method to reduce reperfusion injury. Aims: The aim of the present study is to explore the effect of mitochondrial ATP sensitive potassium channel (Mito-KATP) opener diazoxide (DZ) preconditioning on hypoxia/ reoxygen (H/R) injury of rat myocardium microvascular endothelial cells (MMECs) against apoptosis and relation of PI3K/Akt pathway. Study Design: Animal experimentation. Methods: The rat MMECs were cultivated, and H/R model was made to imitate ischemia-reperfusion injury. The cells were seeds in 96-wellplates (100μL/hole) or in 6cm diameter dishes (2 mL/dish) with the density of 1×106/mL and randomly divided into 4 groups (n=6 each): control group (Group N), hypoxia-regoxygen group (Group H/R), Diazoxide preconditioning+H/R group (Group DZ) and Diazoxide preconditioning +mitochondrial KATP blocker 5-hydroxydecanoate (5-HD) + H/R group (Group DZ+5-HD). The cells were exposed to 2h hypoxia followed by 2h reoxygenation. Diazoxide 100μmol/L and diazoxide 100μmol/L+ 5-HD100μmol/L were added to the culture medium 2h before hypoxia in DZ and DZ+5-HD groups respectively. Each group was observed the proliferation in MTT, apoptotic rate in Annexin V-FITC/PI double standard, cell structure of Hoechst staining, and the levels of PI3K, Akt and p53 mRNA by RT-qPCR. Results: Compared with Group N, apoptotic rate of Group H/R increased (p

With the development of Fe isotope technique, the carbonate minerals in normal carbonate whole rocks have been selectively extracted by lower concentration HCl and HAc solution, respectively, for Fe isotope determination. However, the applicability of the two methods for those samples with complex mineral compositions such as Bayan Obo ore samples requires further examination. The experiment carried out in this study can be separated into two steps. In the first one, lower concentration 0.5-1 mol/L HCl was used to dissolve different minerals, including dolomite, magnetite, hematite, pyrite, riebeckite, and biotite, at room temperature for about 3 hours. The results indicated that the lower concentration HCl can effectively dissolve the carbonate minerals, while the solubility of Fe released from Fe oxides, sulfides and silicate minerals were all less than 1%. Secondly, the lower concentrations of HCl and HAc were both used to dissolve the typical ore-hosting dolomite marble in Bayan Obo and then the Fe isotopes were measured. The results showed that the δ56Fe values of Fe-bearing carbonates extracted by HCl and HAc were in good agreement with those of separated dolomite mineral within uncertainties. They were -0.69‰, -0.62‰ and -0.69‰, respectively, for sample E-16, and -0.19‰, -0.18‰ and -0.12‰, respectively, for sample E-26. Additionally, Fe isotope fractionation was not observed during the partial dissolution of carbonate minerals using HAc, which indicated that both lower concentration HCl and HAc were reliable to partially dissolve Fe-bearing carbonate minerals from the Bayan Obo dolomite samples for the Fe isotopic determination. This study provided a good example for the application of a selective extraction technique for carbonate minerals from geological samples.