Selection of Greenhouse Zucchini Varieties and High-Quality,High-Yield and High-Efficiency Cultivation Techniques

[Objectives]To select zucchini varieties suitable for cultivation in Zibo City and test its high-yield cultivation techniques.[Methods]Six zucchini varieties were introduced,and their commercial quality and yield were determined.[Results]The yield of Shengfeier,Xiuyu 170 and Xihulu 309 increased by 11.4%,6.9%and 4.6%,respectively compared with S68(control),and zucchini was straight,looked pleasing to the eye,and had strong disease resistance.[Conclusions]The zucchini varieties were selected and the high-quality,high-yield and high-efficiency cultivation techniques were integrated.

Evaluation of Application Effect of Silicon-containing Water-soluble Fertilizer on Fast Vegetables

[Objectives]The study aims to verify the application effect of silicon-containing water-soluble fertilizer on fast vegetables.[Methods]Two vegetable crops,rape and lettuce,were studied,and three treatments were set up,including treatment 1(conventional fertilization+foliar spraying of silicon-containing water-soluble fertilizer,treatment 2(conventional fertilization+foliar spraying of the same amount of clear water),and treatment 3(conventional fertilization).[Results]The yield of lettuce and rape in treatment 1 increased by 15.1%and 8.6%,respectively;compared with treatment 3,the yield of lettuce and rape rose by 18.6%and 10.9%,respectively.Variance analysis shows that the F values of lettuce and rape were 20.938 and 35.372,respectively,and the differences among various treatments were extremely significant.[Conclusions]The application of silicon-containing water-soluble fertilizer on lettuce and rape significantly increased their yield.

Synthesis and performance characterization of Hafnium-based multilayer coating applied over carbon/carbon composites with sharp leading edge

Carbon/carbon(C/C)composites have been acknowledged as potential candidates in aerospace vehicles,but their oxygen sensitivity still remains an enormous challenge.In this work,a novel multilayer coating consisted of HfC-2.5 mol.%Hf_(6)Ta_(2)O_(17),HfC-40 mol.%SiC,HfC-2.5 mol.%Hf_(6)Ta_(2)O_(17) and HfC-60 mol.%SiC sublayers from surface to inside was designed and fabricated on the surface of C/C composites with sharp leading edge by plasma spraying.Its ablation resistance was assessed using oxyacetylene torch with a maximum temperature over 2300℃ and compared with monolayered coatings.The multilayer coating revealed preferable ablation retardation capacity evidenced by its integrated profile and less flaw quantity.Such benefits were primarily stemmed from the effective structural design and rational material selection.The former was able to reduce the thermal stress within the ablated scale,the latter contributed to rising the high-temperature resistance and oxygen barrier ability of the coating.

Response mechanism study of alternate ZrC-10vol.%SiC/ZrC-70vol.%SiC coatings with various sublayer thicknesses for cyclic and long-term thermal exposure

To explore the influence of sublayer numbers on the structure evolution and thermal stress level,an alternate coating consisting of ZrC-10 vol.%SiC and ZrC-70 vol.%SiC sublayers was designed in this work.With a basically consistent general thickness,three coatings constituted by 2,4 and 6 sublayers were prepared by plasma spraying,which then were assessed using an oxyacetylene torch under cyclic and long-term exposure.The coating with 6 sublayers was supposed to be the one with the best ablation property,finite element analysis also evidenced its least thermal stress among all these samples.After being ablated for 240 s,the linear and mass ablation rates of the coating with 6 sublayers decreased by 51.27%and 14.41%as compared to that with 4 sublayers.Post-test analysis proved the existence of Si-based products,which help the outmost surface to develop a dense profile.Additionally,the yielded alternate dense/porous scale had a preferable toughness,allowing it to maintain a good integrity.

Electromagnetic wave absorbing ceramics composites made of polymer-derived SiC with BN@CNTs pyrolyzed higher than 1200℃

Polymer-derived ceramics(PDCs)pyrolyzed at high temperatures are promising electromagnetic wave(EMW)absorption materials for aerodynamically heated parts of aircraft under harsh environments.Nev-ertheless,high-temperature pyrolysis results in a significant increase of electrical and dielectric proper-ties of the ceramics,causing extensive reflection of EMW.To address this challenge,boron nitride-coated carbon nanotubes(BN@CNTs)were fabricated and introduced into polymer-derived SiC(PDC-SiC)by py-rolyzing its precursor higher than 1200℃to form SiC-BN@CNT ceramic composites.The fabricated com-posites with 3 wt.%BN@CNTs pyrolyzed at 1200℃have an effective absorption bandwidth(EAB)of 4.2 GHz(8.2-12.4 GHz)at a thickness of 3.4 mm and the minimum reflection loss(RL min)of-57.20 dB.The ultra-broad EAB of 12.62 GHz(5.38-18 GHz)is obtained by simulation through periodic structure design-ing.The RL of the metamaterials was also measured using an arch testing method at a frequency range of 2-18 GHz and an EAB of 11.52 GHz(6.48-18 GHz)is obtained.The excellent absorption is attributed to the BN layer that limits the electrical conduction of the ceramic composites while retaining the high loss of CNTs.The introduction of BN@CNTs causes the refinement of SiC grains,which provides plenty of interfaces and enhances the interface polarization loss.This work successfully solves the problem that PDCs pyrolyzed at elevated temperatures cannot be used as EMW absorption materials by applying BN coating on CNTs served as absorbers for PDC-SiC.The results of this work greatly broaden the application scope of the PDC systems for EMW absorption.