Preparation and Property Analysis of Melamine Formaldehyde Foam

Melamine formaldehyde (MF) foam is kind of fire-retardant material and has great potential in acoustic and thermal insulation area. In this article, MF resin foam was prepared by microwave radiation. We discussed the thermal stability of MF foam and the effect of different emulsifiers on its morphology, apparent density, fire-retardancy and mechanical property. The decomposition temperature of MF foam we prepared is nearly 400℃ and the constitution of residue after combustion is made up of carbon and graphite. Emulsifier influenced the apparent density of MF foam and using coemulsifiers can get flexible foam with uniform cell size, good morphology and low apparent density. When the fire-retardant MF foam’s apparent density is low of 5.53 kg/cm-3, its value of LOI can reach 32.4. The mechanical property of foam is consistent with apparent density.

Electrically Tunable Wafer-Sized Three-Dimensional Topological Insulator Thin Films Grown by Magnetron Sputtering

Three-dimensional(3 D)topological insulators(TIs)are candidate materials for various electronic and spintronic devices due to their strong spin-orbit coupling and unique surface electronic structure.Rapid,low-cost preparation of large-area TI thin films compatible with conventional semiconductor technology is the key to the practical applications of TIs.Here we show that wafer-sized Bi2Te3 family TI and magnetic TI films with decent quality and well-controlled composition and properties can be prepared on amorphous SiO2/Si substrates by magnetron cosputtering.The SiO2/Si substrates enable us to electrically tune(Bi1-xSbx)2Te3 and Cr-doped(Bi1-xSbx)2 Te3 TI films between p-type and n-type behavior and thus study the phenomena associated with topological surface states,such as the quantum anomalous Hall effect(QAHE).This work significantly facilitates the fabrication of TI-based devices for electronic and spintronic applications.

Alignment of Nanoscale Single-Walled Carbon Nanotubes Strands

Depositing single-walled carbon nanotubes(SWNTs) with controllable density, pattern and orientation on electrodes presents a challenge in today's research. Here, we report a novel solvent evaporation method to align SWNTs in patterns having nanoscale width and micronscale length. SWNTs suspension has been introduced dropwise onto photoresist resin microchannels; and the capillary force can stretch and align SWNTs into strands with nanoscale width in the microchannels. Then these narrow and long aligned SWNTs patterns were successfully transferred to a pair of gold electrodes with different gaps to fabricate carbon nanotube field-effect transistor(CNTFET). Moreover, the electrical performance of the CNTFET show that the SWNTs strands can bridge different gaps and fabricate good electrical performance CNTFET with ON/OFF ratio around 106. This result suggests a promising and simple strategy for assembling well-aligned SWNTs into CNTFET device with good electrical performance.

Sample Plot Change in the Seventh Review of Continuous National Forest Inventory in Zigui County

The following qualitative conclusions of forest resources in Zigui can be drawn by the research on 73 plots and 5 vegetation plots:forest area is increasing; forest growing stock is increasing; the adjustment of forest category structure is constantly improved; forest quality has been improving; stand structure is optimized continuously; biodiversity has initially appeared.

Standardized Cultivation Technology of Maize Jinhai 5

It is very important to adopt standardized production technology in the process of maize cultivation,which is conducive to giving full play to the high-yield,high-quality and multi-resistant characteristics of Jinhai 5.This paper standardized the cultivation technology of Jinhai 5 from the aspects of maize seed quality,fertilization before sowing,sowing,seedling management,mid-period management,later management,disease and pest control,and harvesting,so as to provide reference for the standardized production of maize Jinhai 5.

Electronic Detection of Escherichia coli O157︰H7 Using Single-Walled Carbon Nanotubes Field-Effect Transistor Biosensor

Field effect transistors (FET) based on Single-Walled Carbon Nanotubes (SWNTs) become the hot topic in fields of nano-electronic, clinical diagnostics, environmental testing etc. in recent years. In this paper, we reported a simple, scalable way to enrich semiconducting SWNTs by using HNO3/H2SO4. Then carbon nanotube field-effect transistors (CNTFET) biosensor was fabricated with the enrichment SWNTs for Escherichia coli O157︰H7 detection. The response of each CNTFET was monitored in real time before and after introduction of the Escherichia coli O157︰H7 at various concentrations. The results show that CNT-FET biosensors we fabricated are sensitive to change of concentration of solution and response time is really short.

Underwater Directional Acoustic Source Based on Pentamode Material

An underwater directional acoustic emitter is conceived with a highly anisotropic lattice material,whose acoustic characteristics manifest strong dependence on the orientation of the lattice material’s principal axis.Exploiting these features,a cylindrical structure made of such anisotropic lattice material is engineered to possess distinct impedance values in different directions,thereby facilitating wave emission along the principal axis while inducing reflection in other directions.Notably,through numerical simulations,it is demonstrated that the emission direction can be effectively manipulated by adjusting the principal axis orientation,concurrently enhancing the emitted power.In contrast to previous directional acoustic structures,the compact emitter presented in this study can get rid of the size-wavelength constraint,enabling effective control of low-frequency waves.

Lightweight design of peanut sowing machine frame based on finite element analysis

In order to reduce the weight and energy consumption of the whole machine against the heavy mechanical structure and excessive strength redundancy in current small-scale peanut seeders with one ridge and two rows,a finite element model of the frame was established and the static finite element analysis and modal analysis were conducted with ANSYS Workbench.Sensitivity analysis that focuses on the size of intermediate support beams and other components was performed so as to set up a multi-objective optimization model.Then a size optimization and multi-objective optimization collaborative scheme was adopted so that the target was optimized by the Seagull Optimization Algorithm(SOA)to obtain the optimal solution.Based on the results of the finite element analysis,the mechanical structure of the peanut seeder was optimized for lightweight design.Furthermore,response surface plots and static structural analysis were applied for validation.It turned out that the maximum stress of the optimized structure was less than the allowable stress;the weight of the frame reduced by 32.5%after optimization;and the first-order natural frequency did not coincide with the engine input speed or working speed,thus no resonance will occur.Field experiments showed that the qualified rate of row spacing was≥96%when operating at different speeds of different types of seeders;The seeding depth operation performance was stable,with an average qualified rate of seeding depth of≥92%;The performance of the seeders was also stable and reliable due to the lightweight prototype structure.The research outcomes can provide an effective technical reference and theoretical basis for the lightweight design of peanut seeders and for its continuous improvement as well in the future.

A Numerical Study on the Effect of the Backflow Hole Position on the Performances of a Self-Priming Pump

A self-priming pump is a centrifugal pump that has the ability to prime itself. Typically, its performance dependson the configuration of its reflux hole. In this study, the ANSYS FLUENT software is used to investigate the effectsof three different radial positions of the reflux hole on gas-liquid two-phase distribution, pressure pulsation, andimp during self-priming. The research results indicate that: (1) The effective channel size for the reflux liquid toenter the volute varies depending on the location of the reflux hole. The effect of the impeller rotation on thereflux liquid becomes more obvious as the setting distance of the reflux aperture decreases. (2) The position ofthe reflux hole significantly affects the gas phase mass fraction inside the impeller, resulting in a significant reductionin the time it takes for the mass fraction to exceed 80%. (3) The position of the reflux hole significantly affectsthe average pressure on each monitoring surface. (4) Placing the reflux hole at a excessively distant radial distancecan result in an excessive vertical component. (5) The self-priming performance of the pump can be improved tosome extent by placing the return hole at a small radial distance.

Assessment of potential dermal and inhalation exposure of workers to the insecticide imidacloprid using whole-body dosimetry in China

In China, although improvements to the pesticide registration process have been made in la thirty years, no occupational exposure data are required to obtain a commercial license for pesticide product. Consequently, notably little research has been conducted to establish a exposure assessment procedure in China. The present study monitored the potential derm operator exposure from knapsack electric sprayer wheat field application of imidacloprid Liaocheng City, Shandong Province and in Xinxiang City, Henan Province, China, usin whole-body dosimetry. The potential inhalation exposure was determined using a person air pump and XAD-2 sample tubes. The analytical method was developed and validate including such performance parameters as limits of detection and quantification, linear rang recovery and precision. The total potential dermal and inhalation exposures were 14.20, 16.815.39 and 20.78 mL/hr, respectively, for the four operators in Liaocheng and Xinxian corresponding to 0.02% to 0.03% of the applied volume of spray solution. In all trials, the low part（thigh, lower leg） of the body was the most contaminated, accounting for approximate76% to 88% of the total exposure. The inhalation exposure was less than 1% of the tot exposure. Such factors as the application pattern, crop type, spray equipment, operat experience and climatic conditions have been used to explain the exposure distribution ov the different parts of the body. As indicated by the calculated Margin of Exposure, the typic wheat treatment scenarios when a backpack sprayer was used are considered to be safe terms of imidacloprid exposure.

Optimized design of the 4TSQ-2 sugar beet top cutting machine

To solve the problems faced by 4TSQ-2 sugar beet top cutting machine,i.e.large structure,high power consumption and high manufacturing cost,the multi-roller mechanism for leaves removal and fixed-thickness cutting method was studied.Using five-factor and two-level tests,the structure configuration of the leaf removal device was optimized,and the scheme of two roller shafts defoliation,the roller shaft rotation speed of 800 r/min and the forward speed of 0.8 m/s were determined.Through the working process and mechanical analysis of the top cutting device,the cutting device with the slant profiling plate structure characterized by a profiling angle of 25°-45°for the profiling plate and a cutting angle of 20°-40°was studied.With the two-factor and three-level experiments,the profiling angle of profiling plate of the top cutting device was 35°,and the cutting angle was 30°.Compared with the 4TSQ-2 sugar beet top cutting machine before optimization,the structure size of the machine was reduced by 30%,the weight was reduced by 15%,the cost was reduced by 25%,the qualified rate of top cutting wad was increased by 2.6%,and the push over rate of sugar beet was reduced by 0.5%.Besides,each index met the index requirements of beet top cutting harvest.

A first comprehensive evaluation of China's GNSS-R airborne campaign: part II—river remote sensing

The Global Navigation Satellite System Reflectometry(GNSS-R) has been proven to be a powerful technique for retrieving geophysical parameters of ocean and land. Airborne GNSS-R is an important experimental platform, because it is not only needed as validation for spaceborne application, but also possesses the advantages to be capable of remote sensing of small and medium scale targets, such as rivers and lakes. This paper presents an overview of China's airborne GNSS-R campaign conducted on May 30, 2014, in Henan. The campaign has two objectives, i.e.:(1) to examine the capability of a GNSS-R payload developed by National Space Science Center,Chinese Academy of Sciences(NSSC, CAS) for airborneobservations and(2) to study the algorithms for soil moisture and river remote sensing, including altimetry and flow velocity measurement. A previous paper has presented results of soil moisture retrieval as part I, and in this paper,initial results of the Yellow River remote sensing are presented as part II. This paper presents the river altimetry results and explores a new potential application of GNSS-R technology, which is used to detect the flow velocity of the river. The river surface height results observed by code delay altimetry method were consistent with the height results of GPS dual-frequency differential positioning altimetry. The GNSS-R altimetry results showed that decimeter level heights were achieved in 1-min sliding average. Comparing with in situ measurements, the GNSSR flow velocity result was reasonable; the error was about0.027 m/s, which indicated the validity and feasibility of using GNSS-R technique to detect river flow velocity.