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Low frequency vibration control of railway vehicles based on ahigh static low dynamic stiffness dynamic vibration absorber
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作者 SUN Yu GONG Dao +2 位作者 ZHOU JinSong SUN WenJing XIA ZhangHui 《中国科学:技术科学英文版》 SCIE EI CAS CSCD 2019年第1期60-69,共10页
In order to control the low frequency vibration of railway vehicles, a vertical two degrees of freedom(2DOF) low frequency dynamic vibration absorber(DVA) based on acceleration is proposed. Parameters of the dynamic v... In order to control the low frequency vibration of railway vehicles, a vertical two degrees of freedom(2DOF) low frequency dynamic vibration absorber(DVA) based on acceleration is proposed. Parameters of the dynamic vibration absorber are put forth to control the low frequency vibration of car body bouncing and pitching. Next, the acceleration power spectrum density(PSD)and ride quality of the car body are calculated based on the pseudo excitation method(PEM) and covariance algorithm,respectively. According to the requirement of 2DOF low frequency DVA, the isolators with high static low dynamic stiffness(HSLDS) are designed. A high-speed train dynamic model containing HSLDS isolators is established to validate the effects on the car body vibration. The results reveal that the 2D low frequency DVA can significantly reduce the vibration of the car body bouncing and pitching. Thus, the ride quality of the vehicle is increased, and passenger comfort is improved. 展开更多
关键词 railway vehicle dynamics RIDE quality LOW frequency DYNAMIC vibration ABSORBER high STATIC LOW DYNAMIC STIFFNESS
Photodynamic therapy as salvage therapy for residual microscopic cancer after ultra-low anterior resection: A case report 预览
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作者 Si-Qi Zhang Kui-Jie Liu +5 位作者 Hong-Liang Yao San-Lin Lei Zhen-Dong Lei Wen-Jun Yi Li Xiong Hua Zhao 《世界临床病例杂志》 2019年第6期798-804,共7页
BACKGROUND The rate of positive resection margins (R1) in patients with low rectal cancer is substantial. Recommended remedies such as extended resection or chemoradiotherapy have their own serious drawbacks. It has b... BACKGROUND The rate of positive resection margins (R1) in patients with low rectal cancer is substantial. Recommended remedies such as extended resection or chemoradiotherapy have their own serious drawbacks. It has been reported that photodynamic therapy (PDT) as a remedial treatment for esophageal cancer. Colorectal cancer and esophageal cancer has many similarities, however, PDT as a salvage therapy for rectal cancer is rare. CASE SUMMARY Here, we describe a 56-year-old man who was admitted to the hospital due to a 6- mo history of hemafecia, which had been aggravated for 1 mo. Colonoscopy revealed a 3 × 4 cm ulcerated mass in the rectum 4 cm from the anus. Preoperative pathological examination showed villous adenoma, moderate-tohigh- grade dysplasia, good differentiation, and invasion of the mucosal muscle. The patient had R1 after ultra-low anterior resection, but he refused extended resection and experienced severe liver function impairment after 3 cycles of chemotherapy. Ultimately, the patient underwent PDT to remove R1. After five years of follow-up, there was no liver function impairment, recurrence, metastasis, sexual dysfunction, or abnormal defecation function. CONCLUSION This is the first case worldwide in which R1 of rectal cancer were successfully treated by PDT. 展开更多
关键词 Low RECTAL CANCER Photodynamic THERAPY Positive MICROSCOPIC distal margin SALVAGE THERAPY Removal RESIDUAL MICROSCOPIC CANCER Case report
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Electrically driven uniaxial stress device for tuning in situ semiconductor quantum dot symmetry and exciton emission in cryostat 预览
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作者 Hao Chen Xiuming Dou +1 位作者 Kun Ding Baoquan Sun 《半导体学报:英文版》 EI CAS CSCD 2019年第7期75-79,共5页
Uniaxial stress is a powerful tool for tuning exciton emitting wavelength, polarization, fine-structure splitting (FSS), and the symmetry of quantum dots (QDs). Here, we present a technique for applying uniaxial stres... Uniaxial stress is a powerful tool for tuning exciton emitting wavelength, polarization, fine-structure splitting (FSS), and the symmetry of quantum dots (QDs). Here, we present a technique for applying uniaxial stress, which enables us in situ to tune exciton optical properties at low temperature down to 15 K with high tuning precision. The design and operation of the device are described in detail. This technique provides a simple and convenient approach to tune QD structural symmetry, exciton energy and biexciton binding energy. It can be utilized for generating entangled and indistinguishable photons. Moreover, this device can be employed for tuning optical properties of thin film materials at low temperature. 展开更多
关键词 UNIAXIAL stress electrically DRIVEN DEVICE low temperature quantum DOTS thin film materials
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广州市学生视力不良与户外活动时间关系
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作者 孙艺 林蓉 +4 位作者 熊莉华 陈思宇 林琳 郭重山 刘伟佳 《中国学校卫生》 CAS 北大核心 2019年第7期997-1000,共4页
目的了解广州市大、中、小学生视力不良和户外(阳光下)活动时间现状及关系,为学生视力不良防控和干预提供有针对性的科学依据。方法于2017年9—12月根据2017年《全国学生常见病及健康危险因素监测工作手册》要求,采用分层整群随机抽样... 目的了解广州市大、中、小学生视力不良和户外(阳光下)活动时间现状及关系,为学生视力不良防控和干预提供有针对性的科学依据。方法于2017年9—12月根据2017年《全国学生常见病及健康危险因素监测工作手册》要求,采用分层整群随机抽样法在广州市选取1个城区(8所学校)和1个郊区(5所学校)共2908名学生进行视力监测和问卷调查。结果广州市学生视力不良率为69.2%,女生(74.4%)>男生(64.2%),城区(76.3%)>郊区(54.1%),大学(95.0%)>职高(82.5%)>高中(81.1%)>初中(73.4%)>小学(45.6%)。除小学外,各组学生重度视力不良人数均最多。每天户外活动时间<1h、<2h报告率均为女生>男生,城区>郊区,大学和高中较高。每天户外活动时间<2h的学生视力不良率(72.3%)高于≥2h的学生(65.6%)。控制混杂因素后,每天户外活动时间<2h的学生发生视力不良的风险是≥2h学生的1.24倍(95%CI=1.04~1.48)。结论广州市学生视力不良率较高,程度以重度为主并趋于低龄化,户外活动时间不足。女生、城区学生和初中阶段应作为视力不良防控的重点。 展开更多
关键词 视力 运动活动 健康教育 学生
The predicaments and expectations in development of magnetic semiconductors 预览
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作者 Qiang Cao Shishen Yan 《半导体学报:英文版》 EI CAS CSCD 2019年第8期9-19,共11页
Over the past half a century, considerable research activities have been directing towards the development of magnetic semiconductors that can work at room temperature. These efforts were aimed at seeking room tempera... Over the past half a century, considerable research activities have been directing towards the development of magnetic semiconductors that can work at room temperature. These efforts were aimed at seeking room temperature magnetic semiconductors with strong and controllable s, p-d exchange interaction. With this s, p-d exchange interaction, one can utilize the spin degree of freedom to design applicable spintronics devices with very attractive functions that are not available in conventional semiconductors. Here, we first review the progress in understanding of this particular material and the dilemma to prepare a room temperature magnetic semiconductor. Then we discuss recent experimental progresses to pursue strong s, p-d interaction to realize room temperature magnetic semiconductors, which are achieved by introducing a very high concentration of magnetic atoms by means of low-temperature nonequilibrium growth. 展开更多
关键词 MAGNETIC SEMICONDUCTORS s p-d interaction high concentration of MAGNETIC ATOMS low temperature NONEQUILIBRIUM growth SEMICONDUCTOR SPINTRONICS
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Effects of routine rehabilitation therapy combined with low frequency electrical stimulation on monoamine neurotransmitters, NSE, ET-1 and cerebral hemodynamics in children with cerebral palsy
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作者 Sai Xun Pei-Pei Wang +5 位作者 Nuan Yang Mei Hou Jun Chen Dian-Rong Sun Jian-Hui Zhao Li-Ping Lyu 《海南医科大学学报(英文版)》 2019年第5期61-64,共4页
Objective:To investigate the effects of routine rehabilitation therapy combined with low frequency head stimulation on monoamine neurotransmitters, neuron-specific enolase (NSE), endothelin-1 (ET-1) and cerebral hemod... Objective:To investigate the effects of routine rehabilitation therapy combined with low frequency head stimulation on monoamine neurotransmitters, neuron-specific enolase (NSE), endothelin-1 (ET-1) and cerebral hemodynamics in children with cerebral palsy.Methods:From January 2017 to June 2018, 110 children with cerebral palsy were randomly divided into observation group (55 cases) and control group (55 cases). The control group received routine rehabilitation treatment, while the observation group received low-frequency head stimulation on the basis of routine rehabilitation treatment. The changes of dopamine (DA), norepinephrine (NE), serotonin (5-HT), NSE, ET-1 levels and mean blood flow velocity of anterior cerebral artery (ACA), middle cerebral artery (MCA), posterior cerebral artery (PCA) were compared in two groups.Results:Before treatment, there was no significant difference in DA, NE and 5-HT levels in two groups. After treatment, DA, NE and 5-HT levels in the observation group were (192.23±22.71) ng/mL, (98.02±11.71) ng/L, (210.07±25.03) ng/L, and in the control group. the DA, NE, 5-HT levels were (147.06±17.02) ng/mL, (83.07±11.15) ng/L, and (171.88±20.45) ng/L, respectively. The DA, NE and 5-HT levels in two groups were higher than those before treatment, and DA, NE and 5-HT levels in the observation group were higher than those in the control group. Before treatment, there was no significant difference in NSE and ET-1 levels between the two groups. After treatment, the NSE and ET-1 levels in the observation group were (7.97±2.07) μg/L and (41.01±10.07) pg/mL, and the NSE and ET-1 levels in the control group were (10.38±3.02) μg/L, (58.46±15.02) pg/mL, respectively. the NSE and ET-1 in two groups were lower than those before treatment, and the NSE and ET-1 of the observation group were lower than the control group. Before treatment, there was no significant difference in mean blood flow velocity between ACA, MCA and PCA. After treatment, the mean blood flow velocities of ACA, MCA, and PCA 展开更多
关键词 Low frequency electrical stimulation MONOAMINE NEUROTRANSMITTER NEURON specific ENOLASE ENDOTHELIN-1 Cerebral HEMODYNAMICS
An online error calibration method for spaceflight TT&C systems based on LEO-ground DDGPS
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作者 Qiao WANG Xiao-jun JIN +3 位作者 Wei ZHANG Shi-ming MO Zhao-bin XU Zhong-he JIN 《信息与电子工程前沿:英文版》 SCIE EI CSCD 2019年第6期829-841,共13页
To overcome the shortcomings of the traditional measurement error calibration methods for spaceflight telemetry, tracking and command(TT&C) systems, an online error calibration method based on low Earth orbit sate... To overcome the shortcomings of the traditional measurement error calibration methods for spaceflight telemetry, tracking and command(TT&C) systems, an online error calibration method based on low Earth orbit satellite-to-ground doubledifferential GPS(LEO-ground DDGPS) is proposed in this study. A fixed-interval smoother combined with a pair of forward and backward adaptive robust Kalman filters(ARKFs) is adopted to solve the LEO-ground baseline, and the ant colony optimization(ACO) algorithm is used to deal with the ambiguity resolution problem. The precise baseline solution of DDGPS is then used as a comparative reference to calibrate the systematic errors in the TT&C measurements, in which the parameters of the range error model are solved by a batch least squares algorithm. To validate the performance of the new online error calibration method, a hardware-in-the-loop simulation platform is constructed with independently developed spaceborne dual-frequency GPS receivers and a Spirent GPS signal generator. The simulation results show that with the fixed-interval smoother, a baseline estimation accuracy(RMS, single axis) of better than 10 cm is achieved. Using this DDGPS solution as the reference, the systematic error of the TT&C ranging system is effectively calibrated, and the residual systematic error is less than 5 cm. 展开更多
关键词 SPACEFLIGHT low Earth ORBIT (LEO) FILTER Optimization Calibration
Response of Chinese fir seedlings to low phosphorus stress and analysis of gene expression differences 预览
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作者 Jianhui Li Dingwei Luo +5 位作者 Guifang Ma Licui Jia Jinliang Xu Huahong Huang Zaikang Tong Yong-Quan Lu 《林业研究:英文版》 CAS CSCD 2019年第1期183-192,共10页
Chinese fir(Cunninghamia lanceolata)is an excellent fast-growing timber species occurring in southern China and has significant value in the forestry industry.In order to enhance the phosphorus utilization efficiency ... Chinese fir(Cunninghamia lanceolata)is an excellent fast-growing timber species occurring in southern China and has significant value in the forestry industry.In order to enhance the phosphorus utilization efficiency in Chinese fir,four clones named X6,S3,S39 and FK were used,and low phosphorus(LP)stress experiments were performed to analyze the response of different clones to phosphorus deficiency.According to the results on seedling height,maximum root length,leaf blade aspect ratio,root ratio,malondialdehyde content,acid phosphates activity,proline content,soluble protein level,and chlorophyll a and b levels of the tested clones,compared to the control groups(CK),the phosphorus high efficiency clone X6 was screen out for transcriptome sequencing experiments.De novo RNA-seq was then used to sequence the root transcriptomes of X6 under LP stress and CK,and we then compared the gene expression differences under the two conditions.A total of 3416 SDEGs were obtained by comparing the LP and CK groups,among which 1742 were up-regulated and 1682 were down-regulated.All SDEGs obtained from the LP and CK treated samples were subjected to KEGG annotation and classification.Through classification statistical analysis using WEGO software,607 SDEGs obtained KEGG pathway annotations,which were related to 206 metabolic pathways.In Chinese fir subjected to LP stress,53 SDEGs related with phosphorus metabolism,and phosphate uptake and transport were obtained from our transcriptome data.Based on the phosphorus metabolism pathway obtained by KEGG classification,combined with previously report on gene annotation related with phosphorus metabolism,the enzymes encoded by SDEG related with phosphorus metabolism and their expression pattern were mapped onto phosphorus metabolism pathway. 展开更多
关键词 Chinese FIR Low PHOSPHORUS stress Root TRANSCRIPTOMES SDEG PHOSPHORUS METABOLISM
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Cu-Promoted Cobalt Oxide Film Catalyst for Efficient Gas Emissions Abatement
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作者 EL KASMI Achraf WAQAS Muhammad +1 位作者 MOUNTAPMBEME KOUTOU Patrick TIAN Zhenyu 《热科学学报:英文版》 SCIE EI CAS CSCD 2019年第2期225-231,共7页
Thin film catalysts have been recently reported as promising catalysts owing to their good catalytic activity and reduced material amount, leading to low-cost efficient catalysts for gaseous emissions control. Here, w... Thin film catalysts have been recently reported as promising catalysts owing to their good catalytic activity and reduced material amount, leading to low-cost efficient catalysts for gaseous emissions control. Here, we report the slight loading of Cu in cobalt spinel using a one-step pulsed-spray evaporation chemical vapor deposition(PSE-CVD) synthesis technique for efficient short-chain volatile organic compounds(VOCs) emissions treatment. Crystalline structure and morphology analyses revealed nano-crystallite sizes and open-like morphology. The catalytic performance was evaluated through the complete oxidation of C3H6, as a short-chain representative model of VOCs, at a high gas hourly space velocity(GHSV). Very good activity was obtained towards the complete abatement of C3H6 at low temperature and no carbon monoxide(CO) was formed during the oxidation process. Slightly-promoted Co3O4 catalyst with Cu introduction resulted in high catalytic activity comparing to the performance of the catalysts in the literature, due to the high dispersion of Cu and high active surface oxygen amount. Moreover, to evaluate the capability of the used catalysts under near realistic reaction conditions, CO2 effect on the catalytic activity was performed and the catalyst exhibited very good results. Thus, the adopted slightly-doping strategy to tailor a high active catalyst at low temperature could establish a very promising route to strongly enhance the activity of such other catalysts towards gas emissions abatement at low temperature. 展开更多
关键词 low Cu-doping PSE-CVD technique thin film catalysts complete CATALYTIC oxidation VOCs
Association between serum estradiol level on the human chorionic gonadotrophin administration day and clinical outcome
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作者 Xin Li Cheng Zeng +3 位作者 Jing Shang Sheng Wang Xue-Lian Gao Qing Xue 《中华医学杂志:英文版》 SCIE CAS CSCD 2019年第10期1194-1201,共8页
Background: Estradiol, as an important hormone in follicular development and endometrial receptivity, is closely related to clinical outcomes of fresh in vitro fertilization embryo transfer (IVF-ET) cycles. The aim of... Background: Estradiol, as an important hormone in follicular development and endometrial receptivity, is closely related to clinical outcomes of fresh in vitro fertilization embryo transfer (IVF-ET) cycles. The aim of this retrospective study was to evaluate the association between elevated serum estradiol (E2) levels on the day of human chorionic gonadotrophin (hCG) administration and IVF-ET pregnancy and birth outcomes. Methods: A total of 1771 infertile patients with their first fresh IVF-ET cycles were analyzed retrospectively between January 2011 and January 2016 in Peking University First Hospital. Patients were categorized by serum E2 levels on the day of hCG administration into six groups: group 1 (serum E2 levels < 1000 pg/mL, n = 205), group 2 (serum E2 levels 1001-2000 pg/mL, n = 457), group 3 (serum E2 levels 2001-3000 pg/mL, n = 425), group 4 (serum E2 levels 3001-4000 pg/mL, n = 310), group 5 (serum E2 levels 4001- 5000 pg/mL, n = 237), and group 6 (serum E2 levels > 5000 pg/mL, n — 137). The retrieved oocyte and Mil oocyte numbers and implantation and clinical pregnancy rates of the groups were compared as the first objective of the study. For the 360 women with singleton births among all patients, the area under the corresponding receiver operating characteristic curve (ROC curve) was calculated to assess the predictive value of the E2 change for the probability of low birth weight (LBW) infants as the second objective. Results: The retrieved oocyte and Mil oocyte numbers and implantation and clinical pregnancy rates gradually increased from groups 1 to 5 but decreased in group 6. The parameters of group 1 were statistically worse than those of the other groups, from group 2 to group 6 (the number of retrieved oocytes, t = 13.096, t = 23.307, t = 23.086, t = 26.376, t = 19.636, P < 0.003;the number of retrieved Mil oocytes, t = 10.856, t = 20.868, t = 21.874, t = 23.374, t = 19.092, P < 0.003;the implantation rate,χ^2= 12.179,χ^2= 22.239,χ^2= 23.993,χ^2= 23.344,χ^2= 16.758, P < 0.003;the cl 展开更多
关键词 ESTRADIOL in VITRO FERTILIZATION Clinical PREGNANCY rate Low BIRTH WEIGHT
阻塞性睡眠呼吸暂停与胃食管反流病的相关性研究进展
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作者 刘丹 王玮 《国际呼吸杂志》 2019年第15期1194-1197,共4页
阻塞性睡眠呼吸暂停(OSA)是一种常见的睡眠呼吸调节紊乱性疾病。胃食管反流病(GERD)是临床上常见的消化系统疾病。多项研究表明两者关系密切,在OSA患者中胃食管反流现象远远多于健康人。现就OSA在GERD发生发展中可能存在的作用机制加以... 阻塞性睡眠呼吸暂停(OSA)是一种常见的睡眠呼吸调节紊乱性疾病。胃食管反流病(GERD)是临床上常见的消化系统疾病。多项研究表明两者关系密切,在OSA患者中胃食管反流现象远远多于健康人。现就OSA在GERD发生发展中可能存在的作用机制加以综述,为进一步实验研究及指导临床奠定基础。 展开更多
关键词 睡眠呼吸暂停 阻塞性 胃食管反流 食管括约肌 下段
LOW MACH NUMBER LIMIT OF A COMPRESSIBLE NON-ISOTHERMAL NEMATIC LIQUID CRYSTALS MODEL 预览
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作者 樊继山 栗付才 《数学物理学报:B辑英文版》 SCIE CSCD 2019年第2期449-460,共12页
In this paper, we study the low Mach number limit of a compressible nonisothermal model for nematic liquid crystals in a bounded domain. We establish the uniform estimates with respect to the Mach number, and thus pro... In this paper, we study the low Mach number limit of a compressible nonisothermal model for nematic liquid crystals in a bounded domain. We establish the uniform estimates with respect to the Mach number, and thus prove the convergence to the solution of the incompressible model for nematic liquid crystals. 展开更多
关键词 COMPRESSIBLE NON-ISOTHERMAL liquid CRYSTALS BOUNDED domain low MACH number LIMIT
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The effects of the ocean surface wave spectrum on low frequency ambient noise in deep water
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作者 XU Dong LI Fenghua +1 位作者 GUO Yonggang WANG Yuan 《声学学报:英文版》 CSCD 2019年第1期35-48,共14页
An ocean surface wave spectrum which is used for low frequency ambient noise in deep water is proposed.It explains the mechanism of low frequency ambient noise from the theoretical relation between the spectrum of sou... An ocean surface wave spectrum which is used for low frequency ambient noise in deep water is proposed.It explains the mechanism of low frequency ambient noise from the theoretical relation between the spectrum of sound pressure and wave.Combining the surface wave spectrum and local wind speed in deep water,a theoretical expression of low frequency ambient noise is obtained with wave generated noise theory.Simulation results show that the wave spectrum is crucial to the intensity and the spectral slope of radiated noise spectrum, and the theoretical noise spectrum could be used to predict the ambient noise in deep water. The predicting results are verified through the experimental data recorded by an ocean bottom seismometer that was deployed on the floor of deep water in April 2016.It is observed that the statistical noise levels from the experimental data for frequencies from 1 Hz to 100 Hz are larger than 70 dB,and the low frequency ambient noise spectrum follows the shape of inverted "N",the valley of noise spectrum is at 3-4 Hz,and the noise intensity is 70 dB.The peak of noise spectrum is at 50 Hz,and the noise intensity is 92 dB.The correlation coefficient is 0.95 between the model spectrum and measured data. 展开更多
关键词 OCEAN surface WAVE SPECTRUM low FREQUENCY AMBIENT noise DEEP water
Energy Separation and Explicit Dynamic Analysis of Low Temperature Impact Toughness of Transmission Tower Material Q420B
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作者 余兴学 张映华 +1 位作者 张晓敏 蒋渝 《上海交通大学学报:英文版》 EI 2019年第3期381-387,共7页
To determine the physical significance of the impact toughness parameters and accurately characterize the low temperature impact toughness of transmission tower material Q420 B,the finite element model of Charpy impac... To determine the physical significance of the impact toughness parameters and accurately characterize the low temperature impact toughness of transmission tower material Q420 B,the finite element model of Charpy impact test is established on the basis of experiment.The simulation and test results are verified,and the specimen fracture is analyzed by scanning electron microscope.The formation and growth mechanism of the crack are dynamically analyzed.On this basis,energy separation method is used to investigate the effect of low temperature on impact toughness.The results show that the simulation and test results are in good agreement,and the ductile-brittle transition temperature of Q420 B is about-50 ℃.The breaking process of the specimen is divided into the crack formation and propagation.When temperature drops from 20 to-60 ℃,the crack propagation energy decreases from 51.0 to 11.9 J,the crack formation energy reduces from 39.9 to 15.8 J,and the fracture time of the material drops from 1.8 to 0.6 ms. 展开更多
关键词 Q420B LOW temperature impact TOUGHNESS simulation EXPLICIT dynamic ENERGY SEPARATION
Aerodynamic Characteristics of Conventional and Innovative High Lift Swept Wings
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作者 Mojtaba Ramezani Voloojerdi Mahmoud Mani 《仿生工程学报:英文版》 SCIE EI CSCD 2019年第3期432-441,共10页
The new bird inspired wing sweep was introduced and compared with straight and conventional swept wings in gliding flight by an experimental test setup. Due to the similarity with the birds, wing, all test models have... The new bird inspired wing sweep was introduced and compared with straight and conventional swept wings in gliding flight by an experimental test setup. Due to the similarity with the birds, wing, all test models have S1223 airfoil. Swept models inspired from the bird consist of two parts: the straight part near the root and the swept part near the tip. Aerodynamic forces on each wing were measured from 0° to 24° angles of attack and Reynolds numbers of 4.3×10^4, 8.6×10^4, 1.3×10^5, and 1.7× 10^5. Wind tunnel test results show that wings with an innovative sweep at α> 0 have more lift for Reynolds numbers between 4.3× 10^4 and 8.6×10^4. Also, innovative sweep increases the stall angle, and the wing did not stall until α = 24° for Reynolds between 1.3×10^5 and 1.7×10^5. An increase in lift and having sufficient aerodynamic performance in low Reynolds numbers for birds' inspired wing sweep in gliding flight may be the answer to why the wing sweep of birds is not like conventional sweeps. 展开更多
关键词 BIO-INSPIRED WING WING SWEEP WING AERODYNAMICS BIRD WING low REYNOLDS number
Achieving high efficiency and low voltage loss simultaneously for non-fullerene organic solar cells
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作者 Liwei Yang Yanyan Jia He Yan 《中国科学:化学英文版》 SCIE EI CAS CSCD 2019年第4期405-406,共2页
Conventional organic solar cells are based on fullerene acceptors,which caused several drawbacks including poor absorption in visible and near IR regions,limited tunability of energy levels,and most importantly,large ... Conventional organic solar cells are based on fullerene acceptors,which caused several drawbacks including poor absorption in visible and near IR regions,limited tunability of energy levels,and most importantly,large voltage loss from the optical bandgap of the cell to the open circuit voltage of the solar cell[1].During the past few years,nonfullerene OSCs have emerged as a promising alternative to fullerene devices,as their optical and electronic properties can be readily tuned.Furthermore,it has been demonstrated in numerous cases that non-fullerene OSCs[2]can achieve small voltage loss of about 0.55 V,which is much improved compared to that of conventional devices.Achieving such a small voltage loss is of paramount importance to OSCs,as it indicates the maximum achievable efficiency of OSCs can be increased to nearly 20%. 展开更多
关键词 high EFFICIENCY low VOLTAGE LOSS SOLAR CELLS
Petrogenesis of Middle-Eocene granitoids and their Mafic microgranular enclaves in central Urmia-Dokhtar Magmatic Arc(Iran):Evidence for interaction between felsic and mafic magmas 预览
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作者 Kazem Kazemi Ali Kananian +1 位作者 Yilin Xiao Fatemeh Sarjoughian 《地学前缘:英文版》 CAS CSCD 2019年第2期705-723,共19页
Whole rock major and trace element geochemistry together with zircon U-Pb ages and Sr-Nd isotope compositions for the Middle Eocene intrusive rocks in the Haji Abad region are presented.The granitoid hosts,including g... Whole rock major and trace element geochemistry together with zircon U-Pb ages and Sr-Nd isotope compositions for the Middle Eocene intrusive rocks in the Haji Abad region are presented.The granitoid hosts,including granodiorite and diorite,yielded zircon U-Pb ages with a weighted mean value of 40.0±0.7 Ma for the granodiorite phase.Mafic microgranular enclaves(MMEs)are common in these plutons,and have relatively low SiO2 contents(53.04-57.08 wt.%)and high Mg#(42.6-60.1),probably reflecting a mantle-derived origin.The host rocks are metaluminous(A/CNK=0.69-1.03),arc-related calc-alkaline,and I-type in composition,possessing higher SiO2 contents(59.7-66.77 wt.%)and lower Mg#(38.6-52.2);they are considered a product of partial melting of the mafic lower crust.Chondritenormalized REE patterns of the MMEs and granitoid hosts are characterized by LREE enrichment and show slight negative Eu anomalies(Eu/Eu*=0.60-0.93).The host granodiorite samples yield(87Sr/86Sr)i ratios ranging from 0.70498 to 0.70591,positiveεNd(t)values varying from+0.21 to+2.3,and TDM2 ranging from 760 to 909 Ma,which is consistent with that of associated mafic microgranular enclaves(87Sr/86Sr)i=0.705111-0.705113,εNd(t)=+2.14 to+2.16,TDM2=697-785 Ma).Petrographic and geochemical characterization together with bulk rock Nd-Sr isotopic data suggest that host rocks and associated enclaves originated by interaction between basaltic lower crust-derived felsic and mantlederived mafic magmas in an active continental margin arc environment. 展开更多
关键词 Geochemistry U-Pb geochronology GRANITOID Haji Abad Low angle SUBDUCTION Urumieh-Dokhtar MAGMATIC Arc
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中国藏族学生视力现状及其影响因素分析
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作者 汤晓佳 董彬 +2 位作者 杨招庚 董彦会 马军 《中国学校卫生》 CAS 北大核心 2019年第2期256-258,共3页
目的了解中国7~18岁藏族学生视力现状,为学校近视防控工作开展及相关政策制定提供理论支持。方法采用横断面研究方法,收集2418名藏族学生左、右眼视力及1910名学生性别、年龄、作息时间等信息,分析藏族学生视力现状,采用Logistic回归分... 目的了解中国7~18岁藏族学生视力现状,为学校近视防控工作开展及相关政策制定提供理论支持。方法采用横断面研究方法,收集2418名藏族学生左、右眼视力及1910名学生性别、年龄、作息时间等信息,分析藏族学生视力现状,采用Logistic回归分析方法探讨视力影响因素。结果 2014年7~18岁藏族学生左眼裸眼视力平均值为(4.75±0.33),中位数为4.75(P25=4.5,P75=5.0);右眼裸眼视力平均值为(4.74±0.33),中位数为4.90(P25=4.5,P75=5.0)。检出视力不良学生1520名,检出率为62.9%。藏族女生视力不良率高于男生(P<0.01),视力不良检出率随年龄增加而增加。每周体育课课时不足与藏族学生双眼视力不良风险呈正性相关(OR=1.43,95%CI=1.05~1.94,P<0.05)。结论 7~18岁藏族学生视力不良率处于较高流行水平,且女生比男生严重,高年级学生比低年级学生严重。在控制年级、性别等因素后,学校每周开设体育课时不足为视力不良的重要影响因素。 展开更多
关键词 视力 回归分析 少数民族 学生
Synthesis and Properties of High Performance Functional Polyimides Containing Rigid Nonplanar Conjugated Fluorene Moieties
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作者 Yi-Wu Liu Li-Shuang Tang +4 位作者 Lun-Jun Qu Si-Wei Liu Zhen-Guo Chi Yi Zhang Jia-Rui Xu 《高分子科学:英文版》 SCIE CAS CSCD 2019年第4期416-427,I0008共13页
A diamine(WuFDA)containing vertical rigid non-planar conjugated fluorene moiety and low polarizability group(C—F)was designcd and synthesized through three steps of reactions(halogenated reaction,Suzuki coupling reac... A diamine(WuFDA)containing vertical rigid non-planar conjugated fluorene moiety and low polarizability group(C—F)was designcd and synthesized through three steps of reactions(halogenated reaction,Suzuki coupling reaction,and reduction reaction).Four kinds of high performance functional polyimides(WuFPI-6F,WuFPI-BP,WuFPI-BT,and WuFPI-PM)were thus prepared by the condensation polymerization of WuFDA with four commercial dianhydride 6FDA,BPDA,BTDA,and PMDA,respectively.The polyimides exhibited low dielectric constant,excellent thermal stability,outstanding solubility,good film-fonning property,and mechanical properties.The dielectric constants of the polyimides were in the range of 2.28-2.88(f=10^4 Hz).The 5%weight-loss temperatures(Td5%)in nitrogen were in the range of 555-584°C,and the glass transition temperatures(Tg)were in the range of 408-448°C.The weight loss of WuFPI-BP maintaining at 450 and 500°C for half an hour was only 0.33%and 1.26%,respectively.All the WuFPIs could be dissolved in almost all organic solvents,even chloroform.The tensile strength and tensile modulus of these films were in the ranges of 78.6-85.7 MPa and 3.1一3.2 GPa,respectively.In addition,the polyimides displayed light color with special fluorescent and resistive switching(ON-OFF)characteristics;the maximum fluorescence emission was observed at 422-424 nm in NMP solution and at 470-548 nm in film state.The memory devices with the configuration of indium tin oxideAVuFPIs/aluminum(ITO/WuFPIs/Al)exhibited distinct volatile memory characteristics of static random access memory(SRAM),with an ON/OFF current ratio of 105-106.These functional polyimides showed attractive potential applications in the field of high performance flexible polymer photoelectronic devices or polymer memory devices. 展开更多
关键词 FUNCTIONAL POLYIMIDE FLUORENE derivative MOIETIES Fluorescence polymer Low dielectric constant Thermal stability
你可以说我low 但你无法忽视我
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作者 黄峥 《中国商人》 2019年第5期36-40,共5页
按照商业逻辑做一个本分的商人小时候谈不上贫穷,但比较拮据,经常要穿妈妈同事或者是亲戚家小孩的衣服。很多消费习惯和前期的家庭环境有很大关系,比如我妈到现在都舍不得打车,她会觉得时间又不值钱,太浪费了。这对我一直有很大影响,包... 按照商业逻辑做一个本分的商人小时候谈不上贫穷,但比较拮据,经常要穿妈妈同事或者是亲戚家小孩的衣服。很多消费习惯和前期的家庭环境有很大关系,比如我妈到现在都舍不得打车,她会觉得时间又不值钱,太浪费了。这对我一直有很大影响,包括影响我的商业思考。我脑子里一直都记着我爸妈这样的普通家庭,他们是怎么思考和生活的。 展开更多
关键词 LOW 商业逻辑 性价比 用户体验 移动互联网 GOOGLE 三线城市 消费者
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