Theoretical and Experimental Study on the Performance of Hermetic Diaphragm Squeeze Film Dampers for Gas-Lubricated Bearings

Low damping characteristics have always been a key sticking points in the development of gas bearings.The application of squeeze film dampers can significantly improve the damping performance of gas lubricated bearings.This paper proposed a novel hermetic diaphragm squeeze film damper(HDSFD)for oil-free turbomachinery supported by gas lubricated bearings.Several types of HDSFDs with symmetrical structure were proposed for good damping performance.By considering the compressibility of the damper fluid,based on hydraulic fluid mechanics theory,a dynamic model of HDSFDs under medium is proposed,which successfully reflects the frequency dependence of force coefficients.Based on the dynamic model,the effects of damper fluid viscosity,bulk modulus of damper fluid,thickness of damper fluid film and plunger thickness on the dynamic stiffness and damping of HDSFDs were analyzed.An experimental test rig was assembled and series of experimental studies on HDSFDs were conducted.The damper fluid transverse flow is added to the existing HDSFD concept,which aims to make the dynamic force coefficients independent of frequency.Although the force coefficient is still frequency dependent,the damping coefficient at high frequency excitation with damper fluid supply twice as that without damper fluid supply.The results serve as a benchmark for the calibration of analytical tools under development.

Synergistically biomimetic platform that enables droplets to be self-propelled

Droplet transport still faces numerous challenges,such as a limited transport distance,large volume loss,and liquid contamination.Inspired by the principle of‘synergistic biomimetics’,we propose a design for a platform that enables droplets to be self-propelled.The orchid leaf-like three-dimensional driving structure provides driving forces for the liquid droplets,whereas the lotus leaf-like superhydrophobic surface prevents liquid adhesion,and the bamboo-like nodes enable long-distance transport.During droplet transport,no external energy input is required,no fluid adhesion or residue is induced,and no contamination or mass loss of the fluid is caused.We explore the influence of various types and parameters of wedge structures on droplet transportation,the deceleration of droplet speed at nodal points,and the distribution of internal pressure.The results indicate that the transport platform exhibits insensitivity to pH value and temperature.It allows droplets to be transported with varying curvatures in a spatial environment,making it applicable in tasks like target collection,as well as load,fused,anti-gravity,and long-distance transport.The maximum droplet transport speed reached(58±5)mm·s^(−1),whereas the transport distance extended to(136±4)mm.The developed platform holds significant application prospects in the fields of biomedicine and chemistry,such as high-throughput screening of drugs,genomic bioanalysis,microfluidic chip technology for drug delivery,and analysis of biological samples.

Built defects of homogeneous junction to enhance the lithium storage capacity of niobium pentoxide materials

Niobium pentoxide(Nb_(2)O_(5))is deemed one of the promising anode materials for lithium-ion batteries(LIBs)for its outstanding intrinsic fast Li-(de)intercalation kinetics.The specific capacity,however,is still limited,because the(de)intercalation of excessive Li-ions brings the undesired stress to damage Nb_(2)O_(5) crystals.To increase the capacity of Nb_(2)O_(5) and alleviate the lattice distortion caused by stress,numerous homogeneous H-and M-phases junction interfaces were proposed to produce coercive stress within theNb_(2)O_(5)crystals.Such interfaces bring about rich oxygen vacancies with structural shrinkage tendency,which pre-generate coercive stress to resist the expansion stress caused by excessive Li-ions intercalation.Therefore,the synthesized Nb_(2)O_(5) achieves the highest lithium storage capacity of 315 mA h g−1 to date,and exhibits high-rate performance(118 mA h g^(-1) at 20 C)as well as excellent cycling stability(138 mA h g^(-1) at 10 C after 600 cycles).

乙炔氢氯化反应用无汞铜基催化剂的研究现状

阐述了铜基催化剂的研究现状,包括催化反应机理、失活和再生、单组分铜基催化剂、铜基多金属催化剂及催化剂载体,并对铜基催化剂的工业化应用进行了展望。

A road hypnosis identification method for drivers based on fusion of biological characteristics

Risky driving behaviors,such as driving fatigue and distraction have recently received more attention.There is also much research about driving styles,driving emotions,older drivers,drugged driving,DUI(driving under the influence),and DWI(driving while intoxicated).Road hypnosis is a special behavior significantly impacting traffic safety.However,there is little research on this phenomenon.Road hypnosis,as an unconscious state,is can frequently occur while driving,particularly in highly predictable,monotonous,and familiar environments.In this paper,vehicle and virtual driving experiments are designed to collect the biological characteristics including eye movement and bioelectric parameters.Typical scenes in tunnels and highways are used as experimental scenes.LSTM(Long Short-Term Memory)and KNN(K-Nearest Neighbor)are employed as the base learners,while SVM(Support Vector Machine)serves as the meta-learner.A road hypnosis identification model is proposed based on ensemble learning,which integrates bioelectric and eye movement characteristics.The proposed model has good identification performance,as seen from the experimental results.In this study,alternative methods and technical support are provided for real-time and accurate identification of road hypnosis.

PVC塑料改性用氯化聚乙烯生产工艺及结构性能

本文通过对PVC塑改性氯化聚乙烯生产工艺及结构性能研究现状进行分析,为PVC塑改性氯化聚乙烯未来发展方向及关键参数控制提供了参考。

Visible light triggered exfoliation of COF micro/nanomotors for efficient photocatalysis

We report a new facile light-induced strategy to disperse micron-sized aggregated bulk covalent organic frameworks(COFs)into isolated COFs nanoparticles.This was achieved by a series of metal-coordinated COFs,namely COF-909-Cu,-Co or-Fe,where for the first time the diffusio-phoretic propulsion was utilized to design COF-based micro/nanomotors.The mechanism studies revealed that the metal ions decorated in the COF-909 backbone could promote the separation of electron and holes and trigger the production of sufficient ionic and reactive oxygen species under visible light irradiation.In this way,strong light-induced self-diffusiophoretic effect is achieved,resulting in good dispersion of COFs.Among them,COF-909-Fe showed the highest dispersion performance,along with a drastic decrease in particle size from 5μm to500 nm,within only 30 min light irradiation,which is inaccessible by using traditional magnetic stirring or ultrasonication methods.More importantly,benefiting from the outstanding dispersion efficiency,COF-909-Fe micro/nanomotors were demonstrated to be efficient in photocatalytic degradation of tetracycline,about 8 times faster than using traditional magnetic stirring method.This work opens up a new avenue to prepare isolated nanosized COFs in a high-fast,simple,and green manner.

Simulation of gas–liquid two-phase flow in a flow-focusing microchannel with the lattice Boltzmann method

A lattice Boltzmann method for gas–liquid two-phase flow involving non-Newtonian fluids is developed. Bubble formation in a flow-focusing microchannel is simulated by the method. The influences of flow rate ratio, surface tension,wetting properties, and rheological characteristics of the fluid on the two-phase flow are analyzed. The results indicate that the flow pattern transfers from slug flow to dry-plug flow with a sufficiently small capillary number. Due to the presence of three-phase contact lines, the contact angle has a more significant effect on the dry-plug flow pattern than on the slug flow pattern. The deformation of the front and rear meniscus of a bubble in the shear-thinning fluid can be explained by the variation of the capillary number. The reduced viscosity and increased contact angle are beneficial for the drag reduction in a microchannel. It also demonstrates the effectiveness of the current method to simulate the gas–liquid two-phase flow in a microchannel.

Establishment of a non-lethal model of antibody-dependent enhancement of infection in A129 mice based on a non-mouse-adapted dengue virus strain

DEAR EDITOR,Dengue fever(DF),caused by dengue virus(DENV)infection,is a highly prevalent mosquito-borne infectious disease.The development of antiviral drugs and vaccines relies on the clinical utility of dengue infection models,particularly those involving antibody-dependent enhancement(ADE).

Extreme gradient boosting algorithm based urban daily traffic index prediction model:a case study of Beijing,China

The exhaust emissions and frequent traffic incidents caused by traffic congestion have affected the operation and development of urban transport systems.Monitoring and accurately forecasting urban traffic operation is a critical task to formulate pertinent strategies to alleviate traffic congestion.Compared with traditional short-time traffic prediction,this study proposes a machine learning algorithm-based traffic forecasting model for daily-level peak hour traffic operation status prediction by using abundant historical data of urban traffic performance index(TPI).The study also constructed a multi-dimensional influencing factor set to further investigate the relationship between different factors on the quality of road network operation,including day of week,time period,public holiday,car usage restriction policy,special events,etc.Based on long-term historical TPI data,this research proposed a daily dimensional road network TPI prediction model by using an extreme gradient boosting algorithm(XGBoost).The model validation results show that the model prediction accuracy can reach higher than 90%.Compared with other prediction models,including Bayesian Ridge,Linear Regression,ElatsicNet,SVR,the XGBoost model has a better performance,and proves its superiority in large high-dimensional data sets.The daily dimensional prediction model proposed in this paper has an important application value for predicting traffic status and improving the operation quality of urban road networks.

OBE教育理念下应用化学专业综合实验课程的创新实践

针对应用化学综合实验课程内容陈旧、教学模式不利于学生创新能力的培养,及其自主学习能力发挥、教学评价方式单一等问题,基于OBE (Outcome-based education)教育理念对该课程进行了系统的教学设计:采取将科研成果与教学内容相融合的方式设计创新型实验项目,提高实验内容的前沿性、创新性及科学性;课堂教学增加设计性、探索性及挑战性环节,激发学生的学习兴趣及自主学习意识,培养学生的创新能力及科学精神;建立以成果为导向的教学评价模式,强化过程考核,完成课程目标达成度评价。根据课程目标达成度评价结果及持续改进的原则优化教学方案,推动实验教学向能力导向培养模式发展。

Value of radiofrequency ablation in the treatment of hepatocellular carcinoma

Hepatocellular carcinoma(HCC)is a malignant disease that substantially affects public health worldwide.It is especially prevalent in east Asia and sub-Saharan Africa,where the main etiology is the endemic status of chronic hepatitis B.Effective treatments with curative intent for early HCC include liver transplantation,liver resection(LR),and radiofrequency ablation(RFA).RFA has become the most widely used local thermal ablation method in recent years because of its technical ease,safety,satisfactory local tumor control,and minimally invasive nature.This technique has also emerged as an important treatment strategy for HCC in recent years.RFA,liver transplantation,and hepatectomy can be complementary to one another in the treatment of HCC,and the outcome benefits have been demonstrated by numerous clinical studies.As a pretransplantation bridge therapy,RFA extends the average waiting time without increasing the risk of dropout or death.In contrast to LR,RFA causes almost no intraabdominal adhesion,thus producing favorable conditions for subsequent liver transplantation.Many studieshave demonstrated mutual interactions between RFA and hepatectomy,effectively expanding the operative indications for patients with HCC and enhancing the efficacy of these approaches.However,treated tumor tissue remains within the body after RFA,and residual tumors or satellite nodules can limit the effectiveness of this treatment.Therefore,future research should focus on this issue.

Experimental infection of tree shrews(Tupaia belangeri) with Coxsackie virus A16

Coxsackie virus A16(CA16) is commonly recognized as one of the main human pathogens of hand-foot-mouth disease(HFMD). The clinical manifestations of HFMD include vesicles of hand, foot and mouth in young children and severe inflammatory CNS lesions. In this study, experimentally CA16 infected tree shrews(Tupaia belangeri) were used to investigate CA16 pathogenesis. The results showed that both the body temperature and the percentages of blood neutrophilic granulocytes / monocytes of CA16 infected tree shrews increased at 4-7 days post infection. Dynamic distributions of CA16 in different tissues and stools were found at different infection stages. Moreover, the pathological changes in CNS and other organs were also observed. These findings indicate that tree shrews can be used as a viable animal model to study CA16 infection.

Atropine 0.01% eye drops slow myopia progression: a systematic review and Meta-analysis

AIM: To evaluate the effects of atropine 0.01% on slowing myopia progression. METHODS: We searched for relevant studies in the Cochrane Library, PubMed, Embase, Ovid, CBM, CNKI, VIP and Wan Fang Data in Chinese. A supplementary search was conducted in OpenGrey(System for Information on Grey Literature in Europe), the ISRCTN registry, Clinical Trials.gov, and the WHO International Clinical Trials Registry Platform(ICTRP) from the dates of inception to June 30, 2018. RESULTS: Seven randomized controlled trials(RCTs) with a total of 1079 subjects were included(505 in the atropine 0.01% group and 574 in the control group). The results showed that the atropine 0.01% group exhibited significantly greater control of axial growth than the control group (MD=-0.12, 95%CI(-0.19,-0.06))There was also a statistically significant difference between the atropine 0.01% and control groups in the changes in axial length [MD=-0.14, 95%CI(-0.25,-0.03)], but the quality of evidence was low. There were no significant differences between the atropine 0.01% and control groups in the overall effect with respect to diopter value, change in diopter, distance vision and intraocular pressure (MD=0.08, 95%CI(-0.27, 0.42);MD=0.09, 95%CI(-0.17, 0.36);MD=-0.01, 95%CI(-0.02, 0.00);MD=0.08, 95%CI(-0.56,0.40))The sensitivity analysis showed that the conclusion of the Meta-analysis is relatively stable. With respect to adverse events, there were significant differences between the atropine 0.01% and control groups (OR=0.26, 95%CI(0.11, 0.61))CONCLUSION: Based on the available evidence, atropine 0.01% eye drops offer benefits in controlling axial growth and safety without causing significant differences in diopter values, distance vision and intraocular pressure.

The genome sequence of celery(Apium graveolens L.),an important leaf vegetable crop rich in apigenin in the Apiaceae family

Celery(Apium graveolens L.)is a vegetable crop in the Apiaceae family that is widely cultivated and consumed because it contains necessary nutrients and multiple biologically active ingredients,such as apigenin and terpenoids.Here,we report the genome sequence of celery based on the use of HiSeq 2000 sequencing technology to obtain 600.8 Gb of data,achieving~189-fold genome coverage,from 68 sequencing libraries with different insert sizes ranging from 180 bp to 10 kb in length.The assembled genome has a total sequence length of 2.21 Gb and consists of 34,277 predicted genes.Repetitive DNA sequences represent 68.88%of the genome sequences,and LTR retrotransposons are the main components of the repetitive sequences.Evolutionary analysis showed that a recent whole-genome duplication event may have occurred in celery,which could have contributed to its large genome size.The genome sequence of celery allowed us to identify agronomically important genes involved in disease resistance,flavonoid biosynthesis,terpenoid metabolism,and other important cellular processes.The comparative analysis of apigenin biosynthesis genes among species might explain the high apigenin content of celery.The whole-genome sequences of celery have been deposited at CeleryDB(http://apiaceae.njau.edu.cn/celerydb).The availability of the celery genome data advances our knowledge of the genetic evolution of celery and will contribute to further biological research and breeding in celery as well as other Apiaceae plants.

In-situ/operando techniques to identify active sites for thermochemical conversion of CO_(2) over heterogeneous catalysts

The catalytic conversion of CO_(2) to fuels or chemicals is considered to be an effective pathway to mitigate the greenhouse effect. To develop new types of efficient and durable catalysts, it is critical to identify the catalytic active sites, surface intermediates, and reaction mechanisms to reveal the relationship between the active sites and catalytic performance. However, the structure of a heterogeneous catalyst usually dynamically changes during reaction, bringing a great challenge for the identification of catalytic active sites and reaction pathways. Therefore, in-situ/operando techniques have been employed to real-time monitor the dynamic evolution of the structure of active sites under actual reaction conditions to precisely build the structure–function relationship. Here, we review the recent progress in the application of various in-situ/operando techniques in identifying active sites for catalytic conversion of CO_(2) over heterogeneous catalysts. We systematically summarize the applications of various optical and X-ray spectroscopy techniques, including Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and X-ray absorption spectroscopy (XAS), in identifying active sites and determining reaction mechanisms of the CO_(2) thermochemical conversion with hydrogen and light alkanes over heterogeneous catalysts. Finally, we discuss challenges and opportunities for the development of in-situ characterization in the future to further enlarge the capability of these powerful techniques.

Endpoint temperature prediction of molten steel in RH using improved case-based reasoning

An improved case-based reasoning （CBR） method was proposed to predict the endpoint temperature of molten steel in Ruhrstahl Heraeus （RH） process. Firstly, production data were analyzed by multiple linear regressions and a pairwise comparison matrix in analytic hierarchy process （AHP） was determined by this linear regression＇s coefficient. The weights of various influencing factors were obtained by AHP. Secondly, the dividable principles of case base including ＂0-1＂ and ＂breakpoint＂ were proposed, and the case base was divided into several homogeneous parts. Finally, the improved CBR was compared with ordinary CBR, which is based on the even weight and the single base. The results show that the improved CBR has a higher hit rate for predicting the endpoint temperature of molten steel in RH.

TRAF6 polymorphisms not associated with the susceptibility to and severity of sepsis ina Chinese population

BACKGROUND： The tumor necrosis factor recepter associated factor （TRAF） 6 is an important intracellular adapter protein that plays a pivotal role in activating multiple inflammatory and immune related processes induced by cytokines. TRAF6 represents a strong candidate susceptibility factor for sepsis. We investigated whether polymorphisms at the TRAF6 gene are associated with the susceptibility to and severity of sepsis.METHODS： A hospital-based case-control study was conducted with 255 patients with sepsis and 260 controls who were recruited from Zhengzhou, China. Haplotype tagging single nucleotide polymorphisms （htSNPs） were selected from the HapMap database and genotyped using the SNPstream genotyping platform. The associations with the susceptibility and disease severity of sepsis were estimated by logistic regression, and adjusted for age, sex, smoking, drinking, chronic diseases status, APACHEII score and critical illness status.RESULTS： A total of 13 TRAF6 SNPs were tagged by 7 htSNPs. Five htSNPs （rs5030490, rs5030411, rs5030416, rs5030445 and rs3740961） were genotyped in the case control study. Genotype frequencies of the htSNPs were conformed to the Hardy-Weinberg equilibrium in both patients and controls. No significant association was found between the 5 htSNPs and the susceptibility to and severity of sepsis. Compared with the main haplotype -11120A/-10688T/-9423A/805G/12967G, no certain haplotype was associated with the signi？ cantly susceptibility to or severity of sepsis.CONCLUSION： TRAF6 gene polymorphisms might not play a major role in mediating the susceptibility to and severity of sepsis in the Chinese population. A larger population-based case-control study is warranted.

Integrative genome,transcriptome,microRNA,and degradome analysis of water dropwort(Oenanthe javanica)in response to water stress

Water dropwort(Liyang Baiqin,Oenanthe javanica(BI.)DC.)is an aquatic perennial plant from the Apiaceae family with abundant protein,dietary fiber,vitamins,and minerals.It usually grows in wet soils and can even grow in water.Here,whole-genome sequencing of O.javanica via HiSeq 2000 sequencing technology was reported for the first time.The genome size was 1.28 Gb,including 42,270 genes,of which 93.92%could be functionally annotated.An online database of the whole-genome sequences of water dropwort,Water dropwortDB,was established to share the results and facilitate further research on O.javanica(database homepage:http://apiaceae.njau.edu.cn/waterdropwortdb).Water dropwortDB offers whole-genome and transcriptome sequences and a Basic Local Alignment Search Tool.Comparative analysis with other species showed that the evolutionary relationship between O.javanica and Daucus carota was the closest.Twenty-five gene families of O.javanica were found to be expanded,and some genetic factors(such as genes and miRNAs)related to phenotypic and anatomic differentiation in O.javanica under different water conditions were further investigated.Two miRNA and target gene pairs(miR408 and Oja15472,miR171 and Oja47040)were remarkably regulated by water stress.The obtained reference genome of O.javanica provides important information for future work,thus making in-depth genetic breeding and gene editing possible.The present study also provides a foundation for the understanding of the O.javanica response to water stress,including morphological,anatomical,and genetic differentiation.

高效液相色谱法测定马来酸、丁二酸和富马酸的含量

建立了高效液相色谱法测定马来酸、丁二酸和富马酸的方法。采用Agilent XDB-C18色谱柱(4.6mm×150mm,5μm),流动相为0.1%磷酸水溶液和甲醇混合液(V∶V=88∶12),流速0.5mL·min^(-1),进样量10μL,柱温30℃,检测波长210nm,采用外标法定量。结果表明,3种有机酸的分离度好,线性范围内,各酸的浓度与色谱峰面积的线性关系良好,相关系数为0.9991~0.9999,平均加标回收率为80%~10%,RSD(n=3)在1%以下。该方法简便快速,分离效果好,精密度高,是同时分离测定3种有机酸的有效方法。