Technique of Earthworms Restoring Soil in Greenhouse Cultivation

The production environment of greenhouse cultivation is relatively closed,the multiple cropping index is high,the management of fertilizationwatering and pesticideapplication isblindtosomeextent,andthe phenomenonofcontinuous cropping isalsocommonSoilquali-ty affects the sustainable development of greenhouse cultivation.Earthworm is a ubiquitous invertebrate organism in soil,an important part of soil system,a link between terrestrial organisms and soil organisms,an important link in the small cycle of soil material organisms,and plays an important role in maintaining the structure and function of soil ecosystem.Different ecotypes of earthworms are closely related to their habi-tats(soil layers)and food resource preferences,and then affect their ecological functions.The principle of earthworm regulating soil function is essentially the close connection and interaction between earthworm and soil microorganism.Using different ecotypes of earthworms and bio-logical agents to carry out combined remediation of greenhouse cultivation soil is a technical model to realize sustainable development of green-house cultivation.

环氧化天然橡胶在制备天然橡胶/炭黑/碳纳米管复合材料中的应用

以环氧化天然橡胶(ENR)作为界面改性剂,用于制备天然橡胶/炭黑/碳纳米管(NR-ENR/CB/CNTs)复合材料,研究了ENR用量对NR-ENR/CB/CNTs复合材料的力学性能、动态力学性能,以及填料在复合材料中的分散性等的影响。实验结果表明,加入ENR明显改善了填料CNTs和CB在天然橡胶基体中分散性,提升了界面相容性,促进了填料与天然橡胶分子的结合,有效地提高了NR-ENR/CB/CNTs复合材料的物理力学性能、抗老化性能和耐屈挠龟裂性能,同时提高了硫化加工安全性能和硫化速率。当ENR用量达到6 phr后,NR-ENR/CB/CNTs复合材料的拉伸强度、撕裂强度和拉断伸长率有明显提高。随着ENR用量的增加,NR-ENR/CB/CNTs复合材料的Payne效应降低,加工性能提升,动态力学性能提高。

腰果酚对二氧化硅/天然橡胶湿炼胶结构和性能的影响

以腰果酚作为增塑剂,采用湿法混炼的方法制备了腰果酚/二氧化硅(SiO_(2))/天然橡胶(NR)易加工复合材料。借助门尼黏度仪、橡胶加工分析仪、无转子流变仪、动态力学热分析、扫描电镜等方法研究了腰果酚/SiO_(2)/NR复合材料的结构与性能。结果表明,腰果酚作为增塑剂采用湿法混炼的方式添加到SiO_(2)/NR复合材料能明显降低了复合材料的门尼黏度,并显著提高了复合材料的加工性能;在硫化特性方面,相较于未添加腰果酚的SiO_(2)/NR复合材料,添加腰果酚的SiO_(2)/NR复合材料最小转矩值和转矩差均有下降、硫化时间缩短,复合材料的流动性和硫化效率提升;在物理力学性能方面,添加腰果酚的复合材料与未添加腰果酚的复合材料具有相似的物理力学性能;在动态黏弹性方面,复合材料的Payne效应明显降低,填料的分散性改善;在动态力学方面,复合材料的抗湿滑性提高。

Precipitation behaviors and mechanical properties of a solution-treated Mg-Gd-Nd-Zn-Zr alloy during equal-channel angular pressing process

A magnesium alloy processed by equal-channel angular pressing (ECAP) exhibited excellent microstructure refinement and improved strength and hardness.The comprehensive mechanical properties of magnesium alloys have supported the expansion of their applications in the automotive,aerospace,and biomedical industries.Herein,pre-treatment of a solution-treated Mg-2.9Gd-1.5Nd-0.3Zn-0.3Zr alloy was conducted to investigate the precipitate behavior and microstructure evolution during the ECAP process.β;phase grains quickly precipitated from the solution-treated alloy,which accelerated grain refinement and enhanced the ductility after the ECAP process,as compared to the as-cast alloy reported in our previous study.Moreover,spherical precipitates (~200 nm) and fine phases (~100 nm) precipitated along the stripe-like Zn;Zr;phase,which formed a kabap-like structure dispersing homogeneously in the solution-treated alloy during the ECAP process.Owing to grain refinement,dislocations,sphericalβ;precipitates,and texture evolution,the solution-treated alloy after eight passes of ECAP exhibited good comprehensive mechanical properties,with the ultimate tensile strength,yield strength,and elongation values reaching210.9 MPa,263.9 MPa,and 27.9%,respectively.

Large Spacing Array with Offset Phase Center Elements for Highly Integrated Applications

A scanning and uniform array architecture with large spacing,low complexity and high scalability is presented for high integration massive array applications.It is constructed by offset phase center elements arranged in a uniform and regular way,but its spacing can be larger than that of traditional arrays.An ideal model of the offset phase center element is established and its far-field distribution is derived.To suppress grating lobes,the phase center of any element is designed to be movable without changing its physical position.Using genetic algorithm(GA),a new constraint condition limiting the number of phase center changes is proposed to solve the objective function of the minimum values of grating lobes(GLs)and side lobes(SLs).It is shown that the optimal results can be achieved by two changes of phase centers.A multimode circular patch is developed and designed,and characteristics of the offset phase center are analyzed and verified.A prototype array of 12×12 offset phase center elements is implemented based on multi-mode circular patches.Full wave simulation results of radiation patterns show that the level of grating lobes is suppressed at least 7dB with 1.12λ spacing,while the scanning angle is 20°.

Cyanobacterial blooms in China:ecology,toxicity,and treatment

Cyanobacterial blooms are one of the major threats to the health of aquatic ecosystems,and are increasing globally due to the synergistic eff ects of human activities and global climate change.The 7^(th) National Cyanobacteria Bloom Forum was successfully held in May 28-30,2021 in Guiyang,Guizhou Province,China.The forum established a platform for exchanging views on the concerns of cyanobacterial blooms from Chinese researchers,lake managers,and treatment engineers.This special issue,“Cyanobacterial blooms in China:ecology,toxicity,and treatment”in Journal of Oceanography and Limnology,presents a collection of 14 papers on the physiological features and the infl uence on their concurrent aquatic biology of diff erent cyanobacterial groups.

A dynamic speed guidance method at on-ramp merging areas of urban expressway considering driving styles

Dynamic speed guidance for vehicles in on-ramp merging zones is instrumental in alleviating traffic congestion on urban expressways.To enhance compliance with recommended speeds,the development of a dynamic speed-guidance mechanism that accounts for heterogeneity in human driving styles is pivotal.Utilizing intelligent connected technologies that provide real-time vehicular data in these merging locales,this study proposes such a guidance system.Initially,we integrate a multi-agent consensus algorithm into a multi-vehicle framework operating on both the mainline and the ramp,thereby facilitating harmonized speed and spacing strategies.Subsequently,we conduct an analysis of the behavioral traits inherent to drivers of varied styles to refine speed planning in a more efficient and reliable manner.Lastly,we investigate a closed-loop feedback approach for speed guidance that incorporates the driver’s execution rate,thereby enabling dynamic recalibration of advised speeds and ensuring fluid vehicular integration into the mainline.Empirical results substantiate that a dynamic speed guidance system incorporating driving styles offers effective support for human drivers in seamless mainline merging.

新建川藏铁路(雅安–昌都段)沿线外来入侵植物种类及分布特征

横断山区为全球生物多样性热点地区之一,也是全国生态屏障的重要组成部分。新建川藏铁路雅安至昌都段横跨横断山核心地区,铁路建设形成的交通网络将沿线生物多样性热点区域与外界相连,导致生物入侵风险陡增。为获得区域内外来入侵植物的种类及分布特征信息,为即将开始的铁路工程建设、生态保护及生态修复等工作提供参考,我们在雅安–昌都段内选择43个位点各进行长度1 km、宽度20 m的样线调查。研究结果显示:雅安–昌都段共发现外来入侵植物58种,隶属于18科42属,其中出现频度最高的种类依次是牛膝菊(Galinsoga parviflora)、秋英(Cosmos bipinnatus)和鬼针草(Bidens pilosa)。从危害等级来看,其中10种为恶性入侵种,16种为严重入侵种,8种为局部入侵种,15种为一般入侵种,9种为有待观察种,超过半数种类具有明显入侵性。原产地分析结果显示美洲是该区域外来入侵植物的主要原产地。基于海拔及主要河流区段的比较研究发现:入侵植物的种类数量呈现出明显的由东向西、由低海拔向高海拔逐渐递减的趋势,该分布格局是环境因子和人类活动共同作用的结果。结合铁路沿线入侵现状和生境特征,本文分析了铁路建设可能造成的外来植物入侵风险,并针对入侵的防范提出了相应的建议。

Nitrated and parent PAHs in the surface water of Lake Taihu,China:Occurrence,distribution,source,and human health risk assessment

Nitrated polycyclic aromatic hydrocarbons(NPAHs)have toxic potentials that are higher than those of their corresponding parent polycyclic aromatic hydrocarbons(PAHs)and thus have received increasing attention in recent years.In this study,the occurrence,distribution,source,and human health risk assessment of 15 NPAHs and 16 PAHs were investigated in the surface water from 20 sampling sites of Lake Taihu during the dry,normal,and flood seasons of 2018.The PAH concentrations ranged from 255 to 7298 ng/L and the NPAH concentrations ranged from not-detected(ND)to 212 ng/L.Among the target analytes,2-nitrofluorene(2-n Flu)was the predominant NPAH,with a detection frequency ranging from 85%to 90%and a maximum concentration of 56.2 ng/L.The three-ringed and four-ringed NPAHs and PAHs comprised the majority of the detected compounds.In terms of seasonal variation,the highest levels of the NPAHs and PAHs were in the dry season and flood season,respectively.Diagnostic ratio analysis indicated that the prime source of NPAHs was direct combustion,whereas in the case of PAHs the contribution was predominantly from a mixed pattern including pollution from unburned petroleum and petroleum combustion.The human health risk of NPAHs and PAHs was evaluated using a lifetime carcinogenic risk assessment model.The carcinogenic risk level of the targets ranged from 2.09×10^(-7)to 5.75×10^(-5)and some surface water samples posed a potential health risk.

Estimation of chlorophyll content in maize canopy using wavelet denoising and SVR method

In order to estimate the chlorophyll content of maize plant non-destructively and rapidly,the research was conducted on maize at the heading stage using spectroscopy technology.The spectral reflectance of maize canopy was measured and processed following wavelet denoising and multivariate scatter correction(MSC)to reduce the noise influence.Firstly,the signal to noise ratio(SNR)and curve smoothness(CS)were used to evaluate the denoising effect of different wavelet functions and decomposition levels.As a result,the Sym6 wavelet basis function and the 5th level decomposition were determined to denoise the original signal.The MSC method was used to eliminate the scattering effect after denoising.Then three spectral ranges were extracted by interval partial least squares(IPLS)including the 525-549 nm,675-749 nm and 850-874 nm.Finally,the chlorophyll content estimation model was developed by using support vector regression(SVR)method.The calibration Rc2 of the SVR model was 0.831,the RMSEC was 1.3852 mg/L;the validation Rv2 was 0.809,the RMSEP was 0.8664 mg/L.The results show that the SNR and CS indicators can be used to select the parameters for wavelet denoising and model can be used to estimate the chlorophyll content of maize canopy in the field.

A novel wavelength selection strategy for chlorophyll prediction by MWPLS and GA

The research proposed a novel wavelength selection strategy by the combination of moving window partial least squares(MWPLS)and genetic algorithm(GA)for the chlorophyll content detection of winter wheat canopy using spectroscopy technology.Firstly,the original spectral dataset was pre-processed by wavelet denosing,multiple scatter correction.Then,abnormal data samples were removed by Pauta Criterion and the dataset was divided into modeling set and validation set by SPXY.Finally,the sensitive wavebands were selected using MWPLS method and MWPLS+GA respectively and partial least squares(PLS)models were established for chlorophyll content prediction.For the model established by using all the wavebands in the region of 400-900 nm,its R_(c)^(2) and R_(v)^(2) were 0.4468 and 0.3821 respectively;its modeling root mean square error(RMSEM)and verification root mean square error(RMSEV)were 2.9057 and 1.7589 respectively.For the model established by using 151 wavebands selected by MWPLS,its R_(c)^(2) and R_(v)^(2) were 0.6210 and 0.5901 respectively;its RMSEM and RMSEV were 2.4007 and 1.6408 respectively.For the model established by using 36 wavebands selected by MWPLS+GA,its R_(c)^(2) and R_(v)^(2) were 0.7805 and 0.7497 respectively;its RMSEM and RMSEV were 1.8504 and 1.1315 respectively.The results show that wavelength selection can remove redundant information and improve model performance.The strategy of combining MWPLS with GA has also been proved to work well in selecting sensitive wavebands for chlorophyll content prediction.

What They Learned Won't Go Away:The Impacts ofan International Exchange Program on Chinese Teacher Candidates' Understanding of and Practice in Science Education

Purpose:The Canadian university where this study took place has established an international exchange program in teacher education with a large Chinese university.This study was designed to examine how the international exchange program influenced Chinese science teacher candidates'understanding of science education and how such learning impacted their teaching in China.Design/Approach/Methods:The study adopted a qualitative research design with interview and reflective journal as the main approaches for data collection.Findings:Participants greatly appreciated the opportunity of exchange.They reported an improved understanding of Canadian school education and its science curriculum and pedagogy,which changed many aspects of their original values about the relationship between the teacher and students,classroom environment,and so on.Although they faced many constraints to implement what they learned from the exchange in Chinese science classrooms,what they learned had never been forgotten.Participants tried to apply them here and there at the level they could control.Originality/Value:There are many reported studies in the literature about Chinese international students on Western campuses.However,research on Chinese students who participate in international exchange programs is very rare.The findings of this study can inform policymakers and education practitioners about student international exchange programs and benefit future exchange participants.

Gastrochilus wolongensis(Orchidaceae):a new species from Sichuan,China,based on molecular and morphological data

Gastrochilus wolongensis(Orchidaceae),a new orchid species from Sichuan Province,Southwest China,is described and illustrated.It morphologically resembles G.sinensis,but differs markedly from the latter in having black-purple stripes(vs.purplish-red spots)on the adaxial side of the petals and sepals,a reniform epichile densely covered with long papillate hairs(vs.sparsely pubescent)with purplish-red spots(vs.unspotted),and outside the sac of the hypochile with purplish-red stripes(vs.purplish-red spotted).The molecular phylogenetic analysis based on nuclear ribosome internal transcribed spacer(nrITS)and four chloroplast DNA fragments(matK,psbA-trnH,psbM-trnD,and trnL-F)of 36 Gastrochilus species showed that G.wolongensis was closely related to G.ciliaris and G.formosanus.

Bactericidal efficacy of slightly acidic electrolyzed water(SAEW)against Listeria monocytogenes planktonic cells and biofilm on food-contact surfaces

In the present study,the bactericidal efficacy of slightly acidic electrolyzed water(SAEW)against Listeria monocytogenes(L.monocytogenes)planktonic cells and biofilm on food-contact surfaces including stainless steel and glass was systematically evaluated.The results showed that SAEW(pH 5.09 and available chlorine concentration(ACC)of 60.33 mg/L)could kill L.monocytogenes on food-contact surfaces completely in 30 s,a disinfection efficacy equal to that of NaCIO solutions(pH 9.23 and ACC of 253.53 mg/L).The results showed that long exposure time and high ACC contributed to the enhancement of the disinfection efficacy of SAEW on L.monocytogenes on food-contact surfaces.Moreover,the log reduction of SAEW treatment presented an increasing tendency within the prolonging of treatment time when SAEW was used to remove the L.monocytogenes bioflm formed on stainless steel and glass surfaces,which suggested that SAEW could remove L.monocytogenes bio-film effectively and its disinfection efficacy is equal to(in the case of stainless steel)or higher than(in the case of glass)that of high-ACC NaCIO solutions.In addition,the results of the crystal violet staining and scanning electron microscopy also demonstrated that SAEW treatment could remove the L.monocytogenes biofilm on food-contact surfaces.