检索结果-南通市图书馆

Numerical Study on Local Flow and Heat Transfer Characteristics of Supercritical CO_(2) in PCHE with Sinusoidal Channels

在线全文

学校读者我要写书评

暂无评论

Journal of Thermal Science 2024年第1期33卷 41-55页

作者： WENZhexi lv Yigao LI qing WU Jinglin School of Energy Science and Engineering Central South UniversityChangsha 410083China

Local heat transfer and flow characteristics,which is crucial to the overall performance of supercritical CO_(2) recuperators,is rarely examined in details in reported *** this paper,the local heat transfer and flow characteristics of supercritical CO_(2) in sinusoidal channel printed circuit heat exchangers are numerically investigated under the working conditions of *** on the simplified physical model constituted by10 pitches,the variations of Re,heat flux,Nu,secondary flow and other relevant parameters along the flow direction are analyzed *** is further made between the high and low temperature recuperators(HTR and LTR).It's observed that the local heat transfer and flow characteristics vary greatly from the inlet to the outlet,especially in the *** of 127.5% and 61.7% can be observed on the cold side of the LTR for Re and heat transfer coefficient h, *** indicate that the temperature difference and heat transfer coefficient h should not be regarded as constant and the distribution of h should be carefully considered in the design of the *** complicated interactions among the varying thermophysical properties,buoyancy and the periodically changed centrifugal force are believed to be the key that shapes the flow ***,the changes of the wavy angle θ are found to have greater influence than the changes of mass flow rate in reshaping the flow field when θ>25°.Though gravity direction strongly affects the local heat transfer and flow characteristics,it's also found that the effects on the overall thermal-hydraulic performance are relatively *** the installation direction that yields a_y=g should better be avoided for the sinusoidal channel printed circuit heat exchanger.

关键词： printed circuit heat exchanger supercritical CO_(2) sinusoidal channel heat transfer recuperator

在线全文

学校读者我要写书评

暂无评论

成人牙面色素沉积与口腔产黑菌关系的研究

牙体牙髓牙周病学杂志 2012年第11期22卷 650-652页

作者：张明珠税艳青吕罕鲜任晓斌黄松靖王小洁昆明医学院附属口腔医院口腔内科云南昆明650031 云南省第一人民医院口腔预防科云南昆明650032

目的:对口腔常见4类产黑菌进行检测,研究口腔产黑菌与口腔色素沉积的关系。方法:分别采集18～40岁牙面有色素沉积(非食用含色素食物和吸烟)和无色素沉积各30名受试者的牙菌斑样本,通过DNA抽提和二步PCR扩增方法,对口腔常见4类产黑菌:牙... 详细信息

目的:对口腔常见4类产黑菌进行检测,研究口腔产黑菌与口腔色素沉积的关系。方法:分别采集18～40岁牙面有色素沉积(非食用含色素食物和吸烟)和无色素沉积各30名受试者的牙菌斑样本,通过DNA抽提和二步PCR扩增方法,对口腔常见4类产黑菌:牙龈卟啉单胞菌(porphyromonas gingivalis,Pg)、牙髓卟啉单胞菌(porphyromonas endodontalis,Pe)、中间普氏菌(porphyromonas intermedius,Pi)、变黑普氏菌(Pre-votella nigrescens,Pn)进行检测。结果:所有样本均检测到目标细菌,30例无色素沉积者的标本中Pg、Pe、Pi、Pn的检出率分别为27%、40%、30%、87%;30例有色素沉积标本中的检出率分别为60%、80%、73.3%、80%。有色素沉积者的Pg、Pe、Pi的检出率明显高于无色素沉积者,差异有统计学意义(P<0.05);Pn二组无统计学差异(P﹥0.05)。结论:牙面有色素沉积者口腔产黑色素杆菌检出率高。

关键词：色素沉积产黑菌相关性

N,P-co-Doped Graphdiyne as Efficient Metal-free Catalysts for Oxygen Reduction Reaction

在线全文

学校读者我要写书评

暂无评论

Chemical Research in Chinese Universities 2021年第6期37卷 1283-1288页

作者： LI Meiping WANG Kaihang lv qing Science Center for Material Creation and Energy Conversion School of Chemistry and Chemical EngineeringInstitute of Frontier and Interdisciplinary ScienceShandong UniversityJinan250100P.R.China

The carbon-based metal-free catalyst is one of the ideal alternatives to Pt as electrocatalysts for oxygen reduction reaction,which can reduce the cost of fuel cells and zinc-air ***,graphdiyne(GDY),a carbon material with uneven charge distribution,was used as *** doping nitrogen and phosphorus,a N-P-GDY catalyst was prepared,which further regulated the electron structure of *** sheet-like morphology of GDY was preserved in *** N and P were distributed uniformly in the catalyst,whereas defects and active sites were created by doping N and P,as demonstrated by the element mapping images and Raman spectra.X-Ray photoelectron spectroscopy results indicated N and P existed in many forms in *** N-P-GDY exhibited higher activity for ORR than only N or P doped GDY,due to the synergistic effect of N and P in ***,the activity of N-P-GDY changed little after a long time cyclic voltammetry test or injecting methanol in the ***,the four electrons transfer reaction to produce water was the main process for ORR on N-P-GDY catalysts.

关键词： Graphdiyne Oxygen reduction reaction Metal-free catalyst

Comparative study on flow and heat transfer characteristics of sinusoidal and zigzag channel printed circuit heat exchangers

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Science China(Technological Sciences) 2020年第4期63卷 655-667页

作者： WEN Zhe-Xi lv Yi-Gao LI qing School of Energy Science and EngineeringCentral South UniversityChangsha 410083China

Printed circuit heat exchangers(PCHEs)are promising candidates for recuperators in supercritical CO2 Brayton cycles.A comparative study is given in this paper on the flow and heat transfer characteristics of PCHEs with sinusoidal and zigzag *** mass flow rates of 0.6–1.8 kg/h and the bend angles of 15°–30°,the thermal-hydraulic performance of the PCHEs is *** show that the sinusoidal channel is superior to the zigzag channel in its comprehensive *** bend angles result in greater reductions in pressure drop if sinusoidal channels are used instead of zigzag channels and a maximum of 48.4%reduction can be obtained in the considered working ***,the inlet sections should be carefully optimized since these sections account for up to 31%and 17%of the total pressure drop in the sinusoidal and zigzag channels,*** corner shape of the zigzag channel can be specially designed to further reduce the pressure *** nonuniform density and heat flux distributions in both channels are found to be related to the periodic changes of flow directions and the centrifugal forces should not be ignored when optimizing the sinusoidal and zigzag channels.

关键词： printed circuit heat exchanger supercritical CO2 thermal-hydraulic performance sinusoidal channel numerical simulation

Existence of Positive Periodic Solutions for Nonautonomous Predator-prey Systems with Discrete and Continuously Distributed Delays

在线全文

学校读者我要写书评

暂无评论

Acta Mathematicae Applicatae Sinica 2007年第1期23卷 39-48页

作者： yan lv Wei lv Jian-hua Sun Department of Mathematics Nanjing University Nanjing 210008 China Department of Mathematics Xi'an Jiao Tong University Xi'an 710049 China

By using the continuation theorem of coincidence degree theory, the sufficient conditions to guarantee the existence of positive periodic solutions are established for nonautonomous predator-prey systems with discrete... 详细信息

关键词： Predator-prey system time delay positive periodic solution Fredholm operator coincidence degree

Structure, charge transfer, and superconductivity of M-doped phenanthrene(M = Al, Ga, and In): A comparative study of K-doped cases

在线全文

学校读者我要写书评

暂无评论

Science China(Physics,Mechanics & Astronomy) 2019年第5期62卷 107-113页

作者： Hai-yan lv Guo-Hua Zhong Ming Chen Chun-Lei yang Xiao-Jia Chen Hai-qing Lin Shenzhen Institutes of Advanced Technology Chinese Academy of Sciences Nano Science and Technology Institute University of Science and Technology of China Beijing Computational Science Research Center Center for High Pressure Science and Technology Advanced Research

Aromatic hydrocarbons doped with K have been shown to be potential high-temperature superconductors. To investigate the doping effects of trivalent metals(Al, Ga, and In) that have a smaller radii than K, we studied the crystal structure, stability,charge transfer, band structure, and superconductivity of trivalent metal-doped phenanthrene via first-principles *** with Al/Ga/In considerably differs from doping with K and cannot be simply regarded as a linear developmental change in the structural and electronic characteristics caused by a change in the valence electron numbers. Al/Ga/In atoms are difficult to dope into the intralayer region, and the charge transfer is close to zero, which is far less than the effect of K doping. We found that the metallization of the Al/Ga/In-doped system originates from the formation of gap states instead of charge transfer. The weak superconductivity obtained in the Al/Ga/In-doped system is also different from the K-doped system. These results are helpful in terms of understanding the structure and superconductivity of metal-doped aromatic superconductors.

关键词： phenanthrene aromatic hydrocarbons trivalent metals charge transfer superconductivity

Beads-on-string hierarchical structured electrocatalysts for efficient oxygen reduction reaction

在线全文

学校读者我要写书评

暂无评论

Carbon Energy 2023年第2期5卷 225-235页

作者： yang Yuan qing Zhang Yinling Li Luyao lv yan Hou Ge Li Jing Fu Lin yang Zhengyu Bai Collaborative Innovation Center of Henan Province for GreenManufacturing of Fine Chemicals Key Laboratory of Green Chemical Media and ReactionsMinistry of EducationSchool of Chemistry and Chemical EngineeringHenan Normal UniversityXinxiangHenanPeople's Republic of China Department of Mechanical Engineering University of AlbertaEdmontonAlbertaCanada Key Laboratory of Advanced Civil Engineering Materials of Ministry of Education School of Materials Science and EngineeringTongji UniversityShanghaiPeople's Republic of China

Rational design of hierarchically structured electrocatalysts is particularly important for electrocatalytic oxygen reduction reaction(ORR).Here,ZIF-67 crystals are stringed on core-shell Ag@C nanocables using a coordinationmodulated *** pyrolysis,Ag@C strings of Co nanoparticles embedded with three-dimensional porous carbon with beads-on-string hierarchical structures are *** to the advantages of the rich electrochemical active sites of Co-based“beads”and the efficient electron transfer pathways via Ag@C“strings,”the resultant NH_(3)-Ag@C@Co-N-C-700 catalyst shows an improved electrocatalytic activity toward ***_(3)-Ag@C@Co-N-C-700 shows a high onset potential of 0.99 V versus RHE,a high half-wave potential of 0.88 V versus RHE,and a large limiting current of 5.8 mA cm^(-2),which are better than those of commercial Pt/C ***,the NH_(3)-Ag@C@Co-N-C-700 catalyst shows high stability and preeminent methanol tolerance,which makes NH_(3)-Ag@C@Co-N-C-700 a promising catalyst for oxygen electrocatalysis in fuel cell applications.

关键词： beads-on-string structure electrocatalyst metal-organic framework oxygen reduction reaction

Predicting lymph node metastasis in colorectal cancer:An analysis of influencing factors to develop a risk model

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

World Journal of Gastrointestinal Surgery 2023年第10期15卷 2234-2246页

作者： Yun-Peng Lei qing-Zhi Song Shuang Liu Ji-yan Xie Guo-qing lv Department of Gastrointestinal Surgery Peking University Shenzhen HospitalShenzhen 518036Guangdong ProvinceChina Department of Gastrointestinal Surgery Shenzhen Peking University-The Hong Kong University of Science and Technology Medical CenterPeking University Shenzhen HospitalShenzhen 518036Guangdong ProvinceChina

BACKGROUND Colorectal cancer(CRC)is a significant global health issue,and lymph node metastasis(LNM)is a crucial prognostic *** prediction of LNM is essential for developing individualized treatment strategies for patients with ***,the prediction of LNM is challenging and depends on various factors such as tumor histology,clinicopathological features,and molecular *** most reliable method to detect LNM is the histopathological examination of surgically resected specimens;however,this method is invasive,time-consuming,and subject to sampling errors and interobserver *** To analyze influencing factors and develop and validate a risk prediction model for LNM in CRC based on a large patient *** This study retrospectively analyzed 300 patients who underwent CRC surgery at two Peking University Shenzhen hospitals between January and December 2021.A deep learning approach was used to extract features potentially associated with LNM from primary tumor histological images while a logistic regression model was employed to predict LNM in CRC using machine-learning-derived features and clinicopathological variables as *** The prediction model constructed for LNM in CRC was based on a logistic regression framework that incorporated machine learning-extracted features and clinicopathological *** model achieved high accuracy(0.86),sensitivity(0.81),specificity(0.87),positive predictive value(0.66),negative predictive value(0.94),area under the curve for the receiver operating characteristic(0.91),and a low Brier score(0.10).The model showed good agreement between the observed and predicted probabilities of LNM across a range of risk thresholds,indicating good calibration and clinical *** The present study successfully developed and validated a potent and effective risk-prediction model for LNM in patients with *** model utilizes machine-learning-derived features extracted from pr

关键词： Colorectal cancer Lymph node metastasis Machine learning Risk prediction model Clinicopathological factors Individualized treatment strategies

Control of chiral-optical activities by magnetic field based on the transformation of achiral binary crystals into chiral ternary crystals

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Science China Chemistry 2024年第7期67卷 2300-2305页

作者： Zhiyan Chen yan lv Wei Qin College of Physics Qingdao UniversityQingdao 266071China School of Physics State Key Laboratory of Crystal MaterialsShandong UniversityJinan 250100China Shandong Linuo Photovoltaic Hi-Tech Co. Ltd.Jinan 250100China

Multicomponent self-assembled chiral systems have attracted great attention due to their promising application in the area of spin-photonics and *** this work,through introducing an achiral third component into an achiral binary crystal,a chiral organic ternary crystal is fabricated,where both pronounced chiral-optical coupling and magnetic field dependence of chiral-optical activities are *** transformation of achiral structure into chiral structure generates a significant effect on the polarized state of light and the electron spin resonance ***,the coupling between circularly polarized photon and spin is observed in chiral ternary crystal with pronounced chiral orbit,where obvious magnetic field-transmissivity loop is ***,temperature could increase the magnitude of lattice parameters to lead to a larger helix radius to increase the chiral orbit ***,this work indicates that the further exploration of photon-chiral orbit-spin interactions in organic chiral ternary crystals is promising.

关键词： organic chiral ternary crystals chiral orbit chiral-optical activities magnetic field