针对非高分子专业学生进行高分子化学课程综合教学模式的探索与实践

由于受到新型冠状病毒肺炎疫情的影响,教师无法顺利开展2020春季学期线下教学活动。为了更好地落实教育部提出的"停课不停教、停课不停学"的要求,确保教学质量,特别是针对化学专业(非高分子专业)的100多名本科生的教学,吉林大学化学学院高分子教学团队利用吉林大学在线学堂作为线上教学平台,后期配合线下教学课堂,同时辅助采用以课堂教学为切入点的课程思政体系建设,成功地开展了高分子化学课程在线教学的探索和实践。本课程根据化学专业本科生的教学基础和特点,以培养学生对于高分子学科的研究兴趣,而非直接灌输学生大量的概念、公式让学生死记硬背为理念,实现思想政治教育与知识体系教育的有机统一。通过在线和线下教学形式的组合有效地重组了教学资源,优化了教学过程,特别是思政元素与线上及线下课堂教学各环节的融合,有力地保证了新冠疫情防控期间教学进度的顺利完成与教学质量的提升。

Measurement of lumber moisture content based on PCA and GSSVM

Lumber moisture content(LMC) is the important parameter to judge the dryness of lumber and the quality of wooden products.Nevertheless the data acquired are mostly redundant and incomplete because of the complexity of the course of drying,by interference factors that exist in the dryness environment and by the physical characteristics of the lumber itself.To improve the measuring accuracy and reliability of LMC,the optimal support vector machine(SVM) algorithm was put forward for regression analysis LMC.Environmental factors such as air temperature and relative humidity were considered,the data of which were extracted with the principle component analysis method.The regression and prediction of SVM was optimized based on the grid search(GS) technique.Groups of data were sampled and analyzed,and simulation comparison of forecasting performance shows that the main component data were extracted to speed up the convergence rate of the optimum algorithm.The GS-SVM shows a better performance in solving the LMC measuring and forecasting problem.

Reversibly photochromic wood constructed by depositing microencapsulated/polydimethylsiloxane composite coating

Photochromic wood was fabricated by coating microencapsulated photochromic material(MP)/polydimethylsiloxane composites onto wood using a simple drop-coating method.Urea-melamine–formaldehyde resin was used to microencapsulate the photochromic material(PM)via in situ polymerization.The concentration of the MP affected the photochromic property of the wood surface.The total color change(ΔE*)reached 82.2 when the concentration of the composite coating is 8%.Adhesion tests confirmed that the composite coating adhered firmly to the wood.This method is potentially useful for the production of functional wooden products,such as anti-counterfeiting materials and aesthetic wood.

Robust optimization for volume variation in timber processing

Volume variation is an uncertainty element which affects timber processing. We studied the volume variation of logs caused by quality defects in traditional timber processing and set up an optimization approach,using a robust optimization method. We used total number of acceptable boards produced to study the relationship between board thickness and raw material logs, using a heuristic search algorithm to control the variation of board volume to improve the output of boards, reduce the quantity of by-products, and lower production costs. The robust optimization method can effectively control the impact of volume variations in timber processing, reduce cutting waste as far as possible using incremental processing and increase profits, maximize the utilization ratio of timber, prevent waste in processing, cultivate the productive type of tree species and save forest resources.

大别山黏菌的物种多样性调查

为揭示大别山黏菌的物种组成和分布特征,在2020年8月至2022年9月期间,作者先后对大别山21个自然保护区和国家森林公园进行了黏菌物种调查。通过野外采集和基物湿室培养,获得黏菌标本984份。按照形态分类学鉴定为6目13科32属93种,其中,11种为丰富种(相对多度RA>3%),8种为常见种(RA=1.5%–3%),30种为偶见种(RA=0.5%–1.5%),44种为稀有种(RA<0.5%)。苔生高杯菌(Crateriummuscorum)和易碎双皮菌(Didermafragile)在我国现仅知分布于大别山,掌状夹被菌(Ophiothecapedata)、草生发网菌(Stemonitisherbatica)、环壁团毛菌(Trichiavaria)等48种首次在大别山报道。丰富度分析表明,大别山不同调查地点、林型和基物类型的黏菌物种数量和种属比存在差异,大别山区域的河南董寨自然保护区黏菌物种数量高于其他地点,发现黏菌41种,种属比为1.95,特有种为3种;针阔混交林中的黏菌物种数量高于针叶林和阔叶林两种单一林型,生长黏菌81种,种属比为2.89,独有种有28种;生长于腐木上的黏菌77种,物种数量高于凋落物、活草和树皮等基物,种属比为2.75,腐木上特有种有42种。研究结果表明,黏菌在大别山21个自然保护区和国家森林公园具有不同的物种组成和丰富度,从而形成了不同的分布格局,且物种多样性在腐木上和针阔混交林中高于其他生长基物和单一林型,为全面认识大别山的黏菌生物多样性奠定了良好基础。

Effect of different operation conditions on PCDD/F inhibition by ammonium dihydrogen phosphate:concentrations,distributions and mechanisms

Phosphorus-containing compounds are considered as the potential alternatives of traditional inhibitors for suppressing the formation of polychlorinated dibenzo-p-dioxins and dibenzofurans(PCDD/Fs),but the suppression characteristics are scarcely studied.In this study,ammonium dihydrogen phosphate(ADP)was selected as the inhibitor to inhibit the PCDD/F formation via de novo synthesis at 350℃.The influence of oxygen content and addition method on PCDD/F inhibition was systematically investigated by means of statistical analysis and morphological characterization.The results showed that oxygen enhanced the formation of PCDD/Fs from 1470 ng g^(−1)(9.78 ng I-TEQ g^(−1))to 2110 ng g^(−1)(14.8 ng I-TEQ g^(−1)).ADP significantly inhibited the PCDD/F formation,with inhibition efficiencies ranging from 82.0%to 97.7%.Herein,a higher oxygen content and the premixed way intensified the suppression effect.Dibenzo-p-dioxin(DD)/dibenzofuran(DF)chlorination was proven to be effectively suppressed while chlorophenol(CP)route was not obviously influenced.With the addition of ADP,Cl source was significantly reduced and the formation of organic Cl was effectively inhibited.Also,it decreased the proportion of C–O/C=N and C=O,revealing the efficient inhibition of carbon oxidation.Meanwhile,the formation of copper phosphate and copper pyrophosphate was observed in XPS(X-ray photoelectron spectroscopy)spectra,indicating that the catalytic metal Cu was chelated and passivated by ADP.The premixed way had a better effect on reducing Cl resources,inhibiting oxidation and chelating metals,due to the direct contact with inhibitor.However,the separation method could only depend on the decomposed gases,resulting in a lower inhibition efficiency.

Carbon dots-enhanced pH-responsive lubricating hydrogel based on reversible dynamic covalent bondings

Due to the various pH liquid environment in nature,the pH-responsive lubricating hydrogel is widely investigated and developed for tissue interface substitute.However,the applied liquid environment will lead to poor mechanical property and weaken the pH-responsive capability.In this work,a carbon dotsenhanced pH-responsive lubricating hydrogel is developed by combining a pH-responsive section of dynamic PVA-borax network into a PAAm covalent polymer network.The formed hydrogel presents a partial gel-sol transition under controlled pH environments.At low pH environments(<6.0),the formed lubricating layer originated from dynamic disassembly of PVA-borax hydrogel,and brings the lubricating properties on the hydrogel surface.Moreover,the mechanical strength and lubrication properties are well promoted by introducing the carbon dots into the hydrogel,the blue sol layer can be observed more visually under the fluorescence microscope.The pH-response also exhibits well reversibility.The prepared hydrogel broadens the idea for designing pH-responsive soft materials for soft lubricating actuator or robot.

Supramolecular Semi-convertible Hydrogel Enabled Self-Healing Responsive Lubrication Under Dynamic Shearing

Cartilage-inspired hydrogel has attracted great interest due to its tunable mechanics and low friction.However,it is incapable of self-healing under a complex dynamic shearing environment.In this work,a self-healing semi-convertible hydrogel(SHSCH)is developed,which can recover its unique active lubricating function under shearing.Based on the cooperating strategy of noncovalent and covalent bonding,the SHSCH is composed of three interpenetrated networks including:(1)shearresponsive N-fluorenylmethoxycarbonyl-L-tryptophan(FT)supramolecular network,(2)self-healing polyhydroxyethyl acrylamide(PHEAA)network,and(3)rigid polyvinyl alcohol(PVA)covalent network.The shearresponsive lubricating function and mechanical property can be self-healed under a shearing environment through the noncovalent hydrogen-bonding assembly of PHEAA associated by theπ–πassembly of FT.The asdeveloped SCH provides a self-healing model comparable with traditional self-healing lubricating materials through encapsulating lubricant microcapsules or infusing lubricants onto surfaces.We demonstrated a proofof-concept of the self-healing lubrication of a simplified artificial worn cartilage model under a dynamic shearing condition.This study will offer a potential strategy on designing the self-healing soft devices under dynamic stimuli far beyond the lubricating materials.

Brasenia-inspired hydrogel with sustained and sequential release of BMP and WNT activators for improved bone regeneration

Although bone morphogenetic protein(BMP) and WNT signaling play pivotal roles in bone development,homeostasis, and regeneration, the applications of proteins to stimulate corresponding signaling pathways showed limited outcomes in the repair and regeneration of bone defects that might be attributed to the reciprocal interventions of these pathways. In order to satisfy the combinational and sequential activation of BMP and WNT pathways, inspired by the heterogeneous hydrogel-liked structures of Brasenia, heterogeneous alginate/chitosan hydrogels were fabricated and spatially loaded with FK506 and BIO to achieve sustained and sequential release of the activators. Alkaline phosphatase staining, alizarin red staining and q RT-PCR results suggested that FK506 and BIO enhanced osteoblastic differentiation in vitro when used separately. Besides, by mixing and matching the activators and the hydrogel layers, a superior releasing mode that a combination of early FK506 release and following BIO release was identified via both in vitro and in vivo explorations for most efficient bone regeneration. These results suggested that drug-loaded heterogeneous hydrogels possess great potentials in treating bone loss defects for future clinical practice.

Tunable multi-stage wettability and adhesion force on polymer brushes triggered by temperature and pH

Smart wettable surface is the base of constructing microfluidic devices and protein chips for highly functional integration under different extra-stimuli[1–5].The responsive wettability could endow the microchannels with the ability of controlling liquid behaviors[6–8],and meanwhile the stable wettable region on the surface would ensure a stable liquid flow in the microchannels.In recent years,responsive wettable surfaces under different stimuli including temperature[9–11],pH[12–14],light[15–17],electric[18–20]and magnetic field[21–23]are realized by atom transfer radical polymerization(ATRP)[24],electrochemical deposition[25],chemical/physical vapor deposition[26,27],self-assembly[28],template method[29]and so on.For these single-stimuli responsive wettable surfaces,there are two stable wettable regions before and after being triggered by the stimuli.In recent years,multistimuli wettable materials have attracted more attention due to their applications in controlled drug release[30],protein adsorption[31],and catalysis[32].These multistimuli wettable surfaces are aiming to integrate more functions on the smart devices,such as dual-responsive(temperature and pH[33,34],temperature and light[35],pH and light[31],voltage and pH[36])and threeresponsive(temperature,glucose and pH)wettable surfaces[30].Single-stage wettability change,namely two stable wettable regions(hydrophilic and hydrophobic),can be observed before and after stimulated in these studies.

Krein-space approach to robust fltering for uncertain systems with time-varying bias

In this paper, a novel Krein space approach to robust estimation for uncertain systems with accumulated bias is proposed. The bias is impacted by system uncertainties and exists in both state transition and observer matrices. Initial conditions and cross-correlated uncertainty inputs are described by the sum quadratic constraint （SQC）. Without modifying the SQC, the minimal state of the SQC is obtained through Krein space method. The inertia condition for a minimum of a deterministic quadratic form is derived when the coefficient of observer uncertainty input is non-unit matrix. Recursions of Krein space state filtering and bias filtering are developed respectively. Since the cross correlation between uncertainties is considered, a cross correlation gain is introduced into the posteriori estimator. Finally, a numerical example illustrates the performance of the proposed filter.