考虑接触效应的拉杆转子非线性动力学特性分析

本文建立了两盘拉杆式转子轴承系统动力学模型,模型受不平衡力和非线性油膜力激励,拉杆转子轮盘之间接触刚度由接触理论计算得到,采用4阶龙格库塔法进行求解,并使用分岔图和Poincare映射对比分析了不同的转速下,拉杆转子与单盘整体转子的非线性动特性的差异。通过研究得到以下结论:随着转速变化,相比于单盘整体式转子,考虑盘间接触效应的影响会使系统非线性动力学行为更加复杂,在中高转速范围内拉杆转子系统响应状态在周期运动与准周期运动或混沌运动状态之间出现多次反复,拉杆转子系统初次发生分岔的转速值变大,响应的幅值减小,在低转速范围内,盘间接触状态对系统状态影响较小,系统不受转速变化影响。

实际安装状态下的盘式拉杆转子模态测试分析

重型发电燃机的转子以盘式拉杆转子结构形式为主,因此研究拉杆转子的动力学特性对于保障燃机转子安全运行具有实际意义。拉杆转子的动力学特性既受到拉杆预紧状态影响,也受到转子两端边界状态影响。以盘式拉杆转子试验台结构为对象,对转子在连接电机和不连接电机两种状态下进行试验模态分析,测试计算了两种状态下的转子固有频率和模态振型,对比分析了两端连接电机与否对转子固有频率有影响。实验结果表明,连接电机的转子一阶和三阶固有频率高于不连接电机,因此在进行燃气轮机拉杆转子模态试验时应考虑转子的边界条件对转子固有特性的影响。试验结果为研究该类型燃气轮机拉杆转子固有特性问题提供参考意义。

富血小板血浆联合微粒皮移植治疗难愈性创面的疗效分析

目的观察应用富血小板血浆(PRP)结合微粒皮移植治疗难愈性创面的临床疗效及探讨其进一步促进创面愈合的应用价值。方法选取2017年8月—2017年9月大理大学第一附属医院收治的12例经正规治疗1个月后不愈合的创面,使用PRP结合微粒皮移植方法治疗。创面清创后,按供受比1∶4~1∶8取刃厚皮,同时制备成微粒皮。采用PRP制备用套装抽取患者静脉血50 ml,2次对血液离心得到10 ml PRP,制备成PRP凝胶备用;创面无渗血后,将微粒皮均匀涂抹于创面,再用PRP凝胶覆盖创面,最后用聚氨酯泡沫敷料包扎固定,术后第6天首次换药,隔3 d换药观察1次,连续观察2周,随访1~2个月,观察创面愈合情况。结果12例创面均在30 d内愈合,随访无复发,供皮区7 d内愈合。结论PRP结合微粒皮移植治疗难愈性创面有良好的疗效,进一步缩短创面愈合时间,提高创面愈合质量,减少供区损伤,值得继续研究并在临床中推广应用。

Effects of different statins application methods on plaques in patients with coronary atherosclerosis

BACKGROUND Discontinued application of statins may be related to adverse cardiovascular events.However,it is unclear whether different statins administration methods have effects on coronary artery plaques.AIM To evaluate the effects of different statins application methods on plaques in patients with coronary atherosclerosis.METHODS A total of 100 patients diagnosed with atherosclerotic plaque by coronary artery computed tomography were continuously selected and divided into three groups according to different statins administration methods(discontinued application group,n=32;intermittent application group,n=39;sustained application group,n=29).The effects of the different statins application methods on coronary atherosclerotic plaque were assessed.RESULTS The volume change and rate of change of the most severe plaques were significantly reduced in the sustained application group(P≤0.001).The volume change of the most severe plaques correlated positively with low-density lipoprotein(LDL-C)levels only in the sustained application group(R=0.362,P=0.013).There were no changes in plaques or LDL-C levels in the intermittent and discontinued application groups.CONCLUSION Continuous application of statins is effective for controlling plaque progression,whereas discontinued or intermittent administration of statins is not conducive to controlling plaques.Only with continuous statins administration can a reduction in LDL-C levels result in plaque volume shrinkage.

Single nucleotide polymorphisms in the CDH17 gene of colorectal carcinoma

AIM:To investigate the relationship between c.343A>G and c.2216A>C polymorphism sites in the CDH17 gene and colorectal carcinoma.METHODS:Ninety-three non-consanguineous colorectal carcinoma patients admitted to the Department of Oncology at the First Affiliated Hospital of Zhengzhou University were included in this study.Ninety-three peripheral venous blood samples,of approximately one milliliter from each patient,were collected betweenDecember 2009 and August 2010.The genomic DNA of these peripheral venous blood samples were extracted and purified using a Fermentas Genomic DNA Purification Kit(Fermentas,CA) according to the manufacturer' s protocol.The single nucleotide polymorphisms(SNPs) of the liver-intestine cadherin(CDH17) gene c.343A>G and c.2216A>C were determined by the polymerase chain reaction-single strand conformation polymorphism method(PCR-SSCP) in 93 peripheral venous blood samples from patients suffering with colorectal carcinoma.Typical samples that showed different migration bands in SSCP were confirmed by sequencing.Directed DNA sequencing was used to check the correctness of the genotype results from the PCR-SSCP method.RESULTS:There was a significant association between the c.2216 A>C SNPs of the CDH17 gene and the tumor-node-metastasis(TNM) grade,as well as with lymph node status,in 93 peripheral venous blood samples from colorectal carcinoma patients.The genotype frequencies of A/C,A/A,and C/C were 12.90%,33.33% and 53.76%,respectively.There was a significant correlation between lymph node metastasis,TNM grade,and the genotype distribution(P < 0.05).The C/C genotype raised the risk of lymph node metastasis and the TNM grade.There was a significant difference in the TNM grade and lymph node metastasis between the A/A and C/C genotypes(P = 0.003 and P = 0.013,respectively).Patients with colorectal carcinoma carrying the C allele tended to have a higher risk of lymph node metastasis and have a higher TNM grade.The difference between the TNM grades,as well as the lymph node metastasis of the two alleles,was statistically significant(P < 0.01).CONCLUSION:The SNPs of the CDH17 gene c.2216 A>C might be clinically important in the prognosis of colorectal carcinoma.

Self-made wire loop snare successfully treats gastric persimmon stone under endoscopy

BACKGROUND Large gastric persimmon stones are generally resistant to standard endoscopic treatments.We applied an alternative endoscopic method using a hand-made snare for the treatment of large gastric phytobezoars.AIM To explore the clinical efficacy of a self-made wire loop snare to treat giant gastric persimmon stones.METHODS A retrospective study evaluated the clinical data of 38 patients with gastroliths admitted to Taihe Hospital in Shiyan City,Hubei Province,China,between March 2015 and October 2020.The patients were divided into observation(n=23)and control(n=15)groups.Patients in the observation group were treated with selfmade wire loop snares for lithotripsy,and patients in the control group were treated with traditional foreign body forceps,snares,injection needles,and other tools.Successful stone removal,treatment time,and hospital stay were compared.RESULTS The average operating time was significantly shorter(P<0.001)in the observation group(53.4 min)than that in the control group(172.8 min).The average hospital stay of the observation group(5.4 d)was significantly shorter(P<0.001)than that in the control group(10.3 d).Successful one-time treatment was significantly more frequent(P<0.001)in the observation group(87%)than in the control group(7%).CONCLUSION Self-made guidewire loop snares were successfully used to treat gastrolithiasis, and were significantly more effective than foreign body forceps, snares, and other traditionalmethods.

Vulnerability of premyelinating oligodendrocytes to white-matter damage in neonatal brain injury

Premature birth is a significant economic and public health burden, and its incidence is rising. Periventricular leukomalacia （PVL） is the predominant form of brain injury in premature infants and the leading cause of cerebral palsy. PVL is characterized by selective white-matter damage with prominent oligodendroglial injury. The maturation-dependent vulnerability of developing and premyelinating oligodendrocytes to excitotoxic, oxidative, and inflammatory forms of injury is a major factor in the pathogenesis of PVL. Recent studies using mouse models of PVL reveal that synapses between axons and developing oligodendrocytes are quickly and profoundly damaged in immature white matter. Axon-glia synapses are highly vulnerable to white-matter injury in the developing brain, and the loss of synapses between axons and premyelinating oligodendrocytes occurs before any cellular loss in the immature white matter. Microglial activation and astrogliosis play important roles in triggering white-matter injury. Impairment of white-matter development and function in the neonatal period contributes critically to functional and behavioral deficits. Preservation of the integrity of the white matter is likely key in the treatment of PVL and subsequent neurological consequences and disabilities.

Polyarylene Ether Nitrile and Titanium Dioxide Hybrids as Thermal Resistant Dielectrics

With the expanding application of capacitors,thermal resistant dielectric materials are in high demand due to the increasing harsh environments where the capacitors are needed and the heat generated by the capacitors.Herein,we present polyarylene ether nitrile and titanium dioxide hybrids which can be used as thermal resistant dielectrics for these capacitors.Phthalonitrile modified titanium dioxide(TiO_(2)-CN)and phthalonitrile end-capped polyarylene ether nitrile(PEN-Ph)are firstly prepared.After being cast into TiO_(2)-CN/PEN nanocomposite films,these composites self-crosslink upon heating at 320℃for 4 h,forming the polyarylene ether nitrile and titanium dioxide hybrids(TiO_(2)-PEN).Improved dielectric constants which are stable from room temperature to 200℃of these hybrids are observed,indicating the potential application of the hybrids as thermal resistant dielectrics.

Design and Properties of Fluoroelastomer Composites via Incorporation of MWCNTs with Varied Modification

Multi-walled carbon nanotubes(MWCNTs)modified with silane coupling agent A-1120(MWCNTs-A1120)were prepared.Compared with the raw MWCNTs,acidified MWCNTs(MWCNTs-COOH),and MWCNTs grafted with EDA(MWCNTs-NH2),MWCNTs-A1120 have the best dispersion in fluoroelastomer at the same doping ratio.Therefore,fluoroelastomer/MWCNTs-A1120 composite has the best mechanical properties with tensile strength of 13.92 MPa and elongation at break of 111.78%.Then,the effects of doping amount of MWCNTs-A1120 on the electrical properties of the composites were investigated.The dielectric constant of the composite increases with the increase of MWCNTs-A1120,and the dielectric loss does not change much at the low doping amount such as 0.5 wt%.When the doping amount of MWCNTs-A1120 is 5 wt%,the dielectric constant and the dielectric loss value are greatly increased,and the volume resistivity is greatly decreased,which proves that the conductive network is formed in the composite,so the filling amount of 5 wt%is the percolation threshold.The tensile deformation of the sample also affects the electrical properties of the composites.As the tensile deformation increases,the dielectric constant and dielectric loss of the composite decrease.For the composite with 5 wt%MWCNTs-A1120,excessive tensile deformation will destroy the conductive network structure of the composite,so the composite will change from conductive material to dielectric material.Therefore,such composite is a good candidate for flexible conductive material or flexible dielectric material used in harsh environments such as high temperatures and various aggressive solvents.

PEN/BADCy Interlayer Dielectric Films with Tunable Microstructures via an Assist of Temperature for Enhanced Frequency Stability

Low dielectric in terlayer films have become an important element to ensure the development of the microelectr onics industry.A kind of flexible interlayer dielectrics,polyarylene ether nitrile/bisphenol A cyanate ester(PEN/BADCy)film,with good thermal stability and low frequency dependence,has been developed by solution casting method.Herein,materials were designed to incorporate bisphenol A cyanate ester as a part of blend,contributing to the frequency stability and structural integrity.The morphological study combined with electron microscopy revealed the uniform and flexible microstructure information with controllable morphology through self-polymerization of cyanate esters with different prepolymerization time and curing temperatures.The dielectric films could present high thermal stability with Tg>180℃.Significant improvement in the dielectric properties was achieved for the dielectric constant and loss was much stabler than neat PEN over the frequency range from 100 Hz to 5 MHz.When the prepolymerization time was 3h and final curing temperature reached 230℃,the dielectric constant and dielectric loss of the films were 3.36 and 0.013 at 100 kHz,respectively.The dimensional stability(CTE=53.67×10^-6 K^-1)was confirmed and con sidered beneficial to use as an in terlayer dielectrics.

Designing a Phthalonitrile/Benzoxazine Blend for the Advanced GFRP Composite Materials

High performance resin must be used in the high performance glass fiber-reinforced plastic（GFRP） composites, but it is sometimes difficult to balance the processabilities and the final properties in the design of advanced thermoset GFRP composites. In this study, a phthalonitrile/benzoxazine（PPN/BZ） blend with excellent processability has been designed and applied in the GFRP composite materials. PPN/BZ blend with good solubility, low melt viscosity, appropriate gel condition and low-temperature curing behavior could enable their GFRP composite preparation with the prepreg-laminate method under a relatively mild condition. The resulted PPN/BZ GFRP composites exhibit excellent mechanical properties with flexural strength over 700 MPa and flexural modulus more than 19 GPa. Fracture surface morphologies of the PPN/BZ GFRP composites show that the interfacial adhesion between resin and GF is improved. The temperatures at weight loss 5%（T_（5%）） and char residue at 800 °C of all PPN/BZ GFRP composites are over 435 °C and 65% respectively. PPN/BZ GFRP composites with high performance characteristics may find applications under some critical circumstances with requirements of high mechanical properties and high service temperatures.

Poly(arylene ether nitrile)Dielectric Film Modified by Bi_(2)S_(3)/rGO-CN Fillers for High Temperature Resistant Electronics Fields

High-quality film capacitors are widely used in many fields such as new energy vehicles,electronic communications,etc.,due to their advantages in wide frequency response and low dielectric loss.The dielectric film is a crucial part of the film capacitor,and its properties have an important impact on the performance and use conditions of the film capacitor.In this work,a novel high-temperature-resistant dielectric film was prepared.Firstly,the Bi_(2)S_(3)/rGO-CN fillers were prepared by hydrothermal method combined with cyanation treatment,and then added to the poly(arylene ether nitrile)(PEN)matrix to prepare the dielectric film materials(PEN/Bi_(2)S_(3)/rGO-CN).After high temperature treatment,the fillers Bi_(2)S_(3)/rGO-CN reacted with the PEN matrix,and the composites materials transformed into a thermosetting hybrid film(PEN-Bi_(2)S_(3)/rGO)with gel content of 97.88%.The prepared hybrid dielectric films did not decompose significantly before 400℃,and showed a glass transition temperature(Tg)of up to 252.4℃,which could increase the effective use temperature of the materials.Compared with the composite films without heat treatment,they exhibit better mechanical properties,with further improvement in tensile strength and elastic modulus,and a decrease in elongation at break.The dielectric constant of the hybrid films can be up to 6.8 while the dielectric loss is only about 0.02 at 1 kHz.Moreover,the hybrid films showed excellent dielectric stability during temperature changes,and remain relatively stable before 250℃,which is suitable as a high-temperature-resistant high-dielectric material and is more advantageous for practical applications.

Polymerizable AEE-active Dye with Optical Activity for Fluorescent Nanoparticles Based on Phenothiazine:Synthesis,Self-assembly and Biological Imaging

In consideration of various advantages such as less harm,higher sensitivity,and deeper imaging depth,etc.,AIE materials with longwave emission are attracting extensive attention in the fields of vascular visualization,organelle imaging,cells tracker,forensic detection,bioprobe and chemosensor,etc.In this work,a novel fluorescent(R)-PVHMA monomer with chirality and aggregation-induced emission enhancement(AEE)characteristics was acquired through enzymatic transesterification reaction basing on phenothiazine,and its[α]D25℃value was about-6.39°with a 3.08 eV bandgap calculated by the quantum calculations.Afterwards,a series of PEG-PVH1 and PEG-PVH2 copolymers with chirality feature were achieved through RAFT polymerization of the obtained(R)-PVHMA and PEGMA with various feed ratios.When the feed molar ratio of(R)-PVHMA increased from 21.5%to 29.6%,its actual molar fractions in the PEG-PVH1 and PEG-PVH2 copolymers accordingly increased from 18.1%to 25.7%.The molecular weight of PEG-PVH1 was about 2.2×10^(4) with a narrow PDI,and their kinetics estimation showed a first-order quasilinear procedure.In aqueous solution,the amphiphilic copolymers PEG-PVH could self-assemble into about 100 nm nanoparticles.In a 90%water solution of H_(2)O and THF mixture,the fluorescence intensity had the maximum value,and the emission wavelength presented at 580 and 630 nm.The investigation of cytotoxicity and cells uptake showed that PEG-PVH FONs performed outstanding biocompatibility and excellent cells absorption effects,which have great potential in bioimaging application.

Improving the real-time probabilistic channel flood forecasting by incorporating the uncertainty of inflow using the particle filter

An accurate and reliable real-time flood forecast is crucial for mitigating flood disasters. The errors associated with the inflow boundary forcing data are considered as an important source of uncertainties in hydraulic model. In this paper, a real-time probabilistic channel flood forecasting model is developed with a novel function to incorporate the uncertainty of the forcing inflow. This new approach couples a hydraulic model with the particle filter（PF） data assimilation algorithm, a sequential Bayesian Monte Carlo method. The stage observations at hydrological stations are assimilated at each time step to update the model states in order to improve the next time step＇s forecasting. This new approach is tested against a real flood event occurred in the upper Yangtze River. As compared with the open loop simulations, the evaluations of model performance with several deterministic and probabilistic metrics indicate that the accuracy of the ensemble mean prediction and the reliability of the uncertainty quantification are improved pronouncedly as a result of the PF assimilation. Further assessment of the prediction results at different lead times shows that the improvement of model performance deteriorates with the increase of the lead time due to the gradual diminishing of the updating effect for the initial conditions. Based on the analyses of the number of particles and the assimilation frequency, we find that the optimal number of particles can be determined by balancing the model performance and the computation cost, while a high assimilation frequency is preferred to incorporate the emerging observations to update the model states to match the real conditions.

PREPARATION OF MDPE-g-MAH COPOLYMERS AND THEIR EFFECT ON PROPERTIES OF MDPE/CaCO_3 SYSTEMS

MDPE-g-MAH copolymers were prepared with MDPE （medium density polyethylene） and MAH （maleic anhydride） under different irradiation doses of high-energy electron accelerator, and FTIR spectra confirmed their structure. The effect of the different contents of MDPE-g-MAH copolymers on properties of MDPE/CaCO3 system is studied intensively. By adding 4 Phr （parts per hundred of resin） MDPE-g-MAH in MDPE/CaCO3 system under irradiation dose of 0.7 MGy, the tensile strength increases from 16.3 MPa to 19.9 MPa, and elongation at break increases from 437% to 518%. SEM images show the domain size of CaCO3 in MDPE-g-MAH systems becomes small. Definitely, MDPE-g-MAH copolymer could improve the compatibility of MDPE/CaCO3 system effectively.