孩子们喜欢故事,老师也喜欢故事,因此,通过故事的方式引导小学生学习英语已经成为当前一种有效的英语教学方式。《义务教育英语课程标准》(2011年版)在"语言技能"二级要求中就英语故事教学做出如下描述:"能听懂简单的配...孩子们喜欢故事,老师也喜欢故事,因此,通过故事的方式引导小学生学习英语已经成为当前一种有效的英语教学方式。《义务教育英语课程标准》(2011年版)在"语言技能"二级要求中就英语故事教学做出如下描述:"能听懂简单的配图小故事,能在教师的帮助下和图片的提示下描述或讲述简单的小故事,能正确朗读所学故事或短文,能在教师的帮助下表演小故事或小短剧。"为此,当前很多小学英语教材都在权重板块设置了"Story Time",旨在通过故事的方式引导学生开展富有趣味的英语学习活动。确实,故事教学给小学英语课堂带来了新的活力、新的气象,然而,当一些英语小故事被抹上过于浓重的"教学味"的时候,它们在学生眼中便失去了原有的魅力,所谓的"Story Time"也就或多或少地缺失了故事该有的滋味。因此,如何使故事教学更具有故事的味儿,也是我们当今面对的一个重要课题。多年来,钱希洁老师对此进行了深入的实践与探索,本文主要以她执教的译林出版社出版的《义务教育教科书·英语》(五年级上册)Unit 1 Story time板块中的故事"Goldilocks and the three bears"教学中的几个片段为例,阐述了她对小学英语故事教学的思考,旨在与广大同行朋友们探讨:如何使小学英语故事教学散发出更为浓郁的故事味。我们相信,这样的探讨对于其它学科的教学,也有一定的借鉴意义。展开更多
In the second quarter of 2018, the Chinese economy grew at 6.7 percent which is in line with expectations and marginally slower than the 6.8-percent growth recorded in the previous three quarters. Growth during the fi...In the second quarter of 2018, the Chinese economy grew at 6.7 percent which is in line with expectations and marginally slower than the 6.8-percent growth recorded in the previous three quarters. Growth during the first half this year also stands at 6.7 percent. Amidst the ongoing trade war with the United States, as of July 27, the renminbi （RMB） has fallen 8.2 percent against the dollar since April 2. Having fallen below 3,000 in June for the first time in two years.展开更多
The Johannesburg Summit of the Forum on China-Africa Cooperation held in South Africa in December 2015has raised the level of agricultural cooperation between China and African countries,as evidenced by the achievemen...The Johannesburg Summit of the Forum on China-Africa Cooperation held in South Africa in December 2015has raised the level of agricultural cooperation between China and African countries,as evidenced by the achievements made by Chinese agricultural missions working on the continent.展开更多
The need for the mitigation of brown bears has become so severe that many nomads have given up repairing their houses in Maryo Township’s Mendang Village(also named the First Administrative Village),a remote place lo...The need for the mitigation of brown bears has become so severe that many nomads have given up repairing their houses in Maryo Township’s Mendang Village(also named the First Administrative Village),a remote place located in the southwestern section of the Changtang National Nature Reserve(CNNR).Only part of the village belongs to Serling Tso Nature Reserve.展开更多
An expeditious method for ascertaining species between black bear (Selenarctos thibetanus G. cuiver) and brown bear (Ursus arctos Linnaeus) was developed using tooth measurements from previously identified specimens. ...An expeditious method for ascertaining species between black bear (Selenarctos thibetanus G. cuiver) and brown bear (Ursus arctos Linnaeus) was developed using tooth measurements from previously identified specimens. The measurement and analysis on 18 tooth measurement indexes (i.e. T1. Length of Pm1-Pm4, T2. L. of M1-M3, T3. M1L., T4. M1 width, T5. M2L., T6. M2W., T7.M3L., T8. M3W., T9. L. of C1 alveolus, T10. W. of C1 alveolus, T11. L. of C1-M2, T12. L. of Pm4 M2,T13.M1L., T14. M1W., T15. M2L., T16. M2W., T17.L. of C1 alveolus, T18. W. of C1 alveolus) of 59 skulls (black bears 25, brown bears 34) indicates that there are significant or the most significant difference between two species in every indexes, however T1, T9, T10, T17 and T18 are not suitable for species discriminator because of their high percent of overlap. The efficient species discriminators and standards (mm) are as follows T2(63.0), T3(22.0), T4(10.2), T5(23.8), T6(13.6), T7(18.0), T8(13.5), T11(110.0),T12(66.0), T13(20. 1), T14(15.8), T15(33.0) and T16(17.3). Those who are less than or equal to standard are classified to black bear, the others are brown bear. The method is very convenient and useful with high reliability. Their lowest accuracy percent are 95.0%, most of them over 97%. Different indexes will be chosen refer to the degree of specimen destroyed.展开更多
From 1991 to 1992, we observed behavior of 7 brown bears (5 females, 2 males) in mating season. Re-Sults showed tkat the oertrus of brown bears was mainly from May to July. The oeStrus ofmost individuals occwred at th...From 1991 to 1992, we observed behavior of 7 brown bears (5 females, 2 males) in mating season. Re-Sults showed tkat the oertrus of brown bears was mainly from May to July. The oeStrus ofmost individuals occwred at theend of May and the beginning of June. There were some differences in the oestrus among individuals. Average duration ofthe oestrus 30.8 days (16-50 days). The mating behavior was mainly observed during 8.00-9.00 a.m., and 15.00-16.00p.m.. Rest and sleep were the next behavior after mating for most bears, especially for male bears. All bears had poor appe-the. The Pattern and process of a successful mating was that a male bear approached a female, smelled the pudendum of thefemale, climbed on female hip, mated, parted and rested. Oestrus females approached males sometimes.展开更多
According to the principle of enzyme reaction rate, healthy pent black bears’ myocardial enzyme activity is assayed by visual colorimetry and compared with that of healthy human beings. The determination at 37 °...According to the principle of enzyme reaction rate, healthy pent black bears’ myocardial enzyme activity is assayed by visual colorimetry and compared with that of healthy human beings. The determination at 37 °C and the statistic analysis of the experimental data work out the following findings. For male black bears, the average CK activity is 163.20 U/L, the confidence interval of its expected value (127.70 to 198.70) U/L, and the coefficient of variation 39.2%; the average CK-MB activity 21.62 U/L, the confidential interval (17.72 to 25.51) U/L, and the coefficient of variation 34.26%; the average LDH activity 604.20 U/L, the confidence interval (524.56 to 683.83) U/L, and the coefficient of variation 23.80%; the average HBDH activity 516.70 U/L, the confidence interval (453.06 to 580.34) U/L, and the coefficient of variation 22.24%; the average GOT activity 69.70 U/L, the confidence interval (60.21 to 79.19) U/L, and the coefficient of variation 24.59%. For female black bears, the average CK activity is 145.50 U/L, the confidence interval (114.59 to 176.21) U/L, and the coefficient of variation 38.27%; the average CK-MB activity 18.84 U/L, the confidence interval (14.64 to 23.04) U/L, and the coefficient of variation 40.34%; the average LDH activity 563.70 U/L, the confidence interval (473.80 to 652.60) U/L, and the coefficient of variation 28.80%; the average of HBDH activity 475.50 U/L, the confidence interval (412.10 to 538.40) U/L, and the coefficient of variation 24.07%; the average of GOT activity is 62.37 U/L, the confidential interval (52.54 to 72.20) U/L, and the coefficient of variation 28.46%. The male black bear’s average myocardium enzyme activities are slightly higher than those of the female. But the statistical results indicate that the difference is not significant.展开更多
Populations of the European brown bear (Ursus arctos L.) differ substantially in size, degree of geographic isolation and level of genetic diversity. Present patterns result from phylogeographic processes and profound...Populations of the European brown bear (Ursus arctos L.) differ substantially in size, degree of geographic isolation and level of genetic diversity. Present patterns result from phylogeographic processes and profound human intervention. We assessed the genetic variability of a subpopulation of brown bears near the periphery of their range in the Western Carpathian Mountains and compared their genetic properties with those of bears in the core of the same population and elsewhere. Samples were collected non-invasively in 2007-2008 and2010 in Strázovské Vrchy Protected Landscape Area (PLA) in Slovakia (included in the NATURA 2000 networking programme). Seven polymorphic microsatellite loci (UaMU26, UaMU64, G10B, G1D, G10L, UaMU50 and UaMU51) were amplified using a nested PCR in order to assess the following parameters: variability, allelic combinations, heterozygosity, number of alleles and inbreeding coefficient. Sufficient brown bear DNA for analysis was obtained from 57 out of 140 samples (41%), among which 45 different genotypes were identified. Loci had a mean of 2.71 ± 0.76 alleles. Average observed heterozygosity was 0.59. The inbreeding coefficient was negative for all but one of the analysed loci (2007-2008). In the year 2010 was negative three of seven loci. These results imply that gene flow with other parts of the population has been maintained in the reduced level and the isolation level of bears in the study area was not so low. Nevertheless, the genetic variability of bears in Strázovské Vrchy PLA was lower than that reported from other localities in the Carpathian Mountains. The results are discussed in the context of behavioural ecology and conservation genetics.展开更多
To date,various micro/nanofabrication techniques have been developed during the global nanotechnology race,such as electron-beam lithography[1],photolithography[2],nanoimprint lithography[3],and 3D nanoprinting[4,5].B...To date,various micro/nanofabrication techniques have been developed during the global nanotechnology race,such as electron-beam lithography[1],photolithography[2],nanoimprint lithography[3],and 3D nanoprinting[4,5].Benefiting from these functional techniques,micro/nanoscale patterns can be easily generated onto a broad range of materials,including metals,semiconductors,ceramics,and polymers.However,a bold and even visionary question can be raised,is it possible to make patterns on living organisms rather than inanimate objects?Despite the emergence of numerous electronic devices for biological applications,directly processing biological samples remains a challenge due to the poor biocompatibility of many micro/nanofabrication methods[6].Researchers have attempted to prepare and transfer micro/nanopatterns onto cell surfaces[7],the structural integrity of these modifications can be compromised by the growth and development of cells during culture.Moreover,intact animal skin presents greater challenges for integration with metal patterns compared to cell surfaces.展开更多
The high-temperature dissolution behavior of primary carbides in samples taken from GCr15 continuous-casting bloom was observed in-situ by confocal laser scanning microscopy.Equations were fitted to the dissolution ki...The high-temperature dissolution behavior of primary carbides in samples taken from GCr15 continuous-casting bloom was observed in-situ by confocal laser scanning microscopy.Equations were fitted to the dissolution kinetics of primary carbides during either heating or soaking.Dissolution of carbides proceeded in three stages(fast→slow→faster)as either temperature or holding time was increased.During the heating process and during the first and third stages of the soaking process,the original size of the carbides determined the steepness of the slope,but during the middle(“slow”)stage of the soaking process,the slope remained zero.The initial size of the carbides varied greatly,but their final dissolution temperature fell within the narrow range of 1210-1235℃,and the holding time remained within 50 min.Fractal analysis was used to study the morphological characteristics of small and medium-sized carbides during the dissolution process.According to changes in the fractal dimension before and after soaking,the carbides tended to evolve towards a more regular morphology.展开更多
Bearing is an indispensable key component in mechanical equipment,and its working state is directly related to the stability and safety of the whole equipment.In recent years,with the rapid development of artificial i...Bearing is an indispensable key component in mechanical equipment,and its working state is directly related to the stability and safety of the whole equipment.In recent years,with the rapid development of artificial intelligence technology,especially the breakthrough of deep learning technology,it provides a new idea for bearing fault diagnosis.Deep learning can automatically learn features from a large amount of data,has a strong nonlinear modeling ability,and can effectively solve the problems existing in traditional methods.Aiming at the key problems in bearing fault diagnosis,this paper studies the fault diagnosis method based on deep learning,which not only provides a new solution for bearing fault diagnosis but also provides a reference for the application of deep learning in other mechanical fault diagnosis fields.展开更多
Rolling contact fatigue performance is among the most important issues for applications of bearing steels.In this work,a recently developed surface modification technique,surface mechanical rolling treatment,was appli...Rolling contact fatigue performance is among the most important issues for applications of bearing steels.In this work,a recently developed surface modification technique,surface mechanical rolling treatment,was applied on a rare-earth addition bearing steel.And rolling contact fatigue behavior of treated samples was compared with that of as-received counterparts at different contacting stresses.The results demonstrated that a 700μm-thick gradient nanostructured surface layer is produced on samples by surface mechanical rolling treatment.The grain size decreases while the microhardness increases gradually with decreasing depth,reaching~23 nm and~10.2 GPa,respectively,at the top surface.Consequently,the rolling contact fatigue property is significantly enhanced.The characteristic life of treated samples is~3.2 times that of untreated counterparts according to Weibull curves at 5.6 GPa.Analyses of fatigue mechanisms demonstrated that the gradient nanostructured surface layer might not only retard material degradation and microcrack formation,but also prolong the steady-state elastic response stage under rolling contact fatigue.展开更多
In this work,fow behavior and dynamic recrystallization(DRX)mechanism of a low carbon martensitic stainless bearing steel,CSS-42L,were investigated using a thermomechanical simulator under the temperature and strain r...In this work,fow behavior and dynamic recrystallization(DRX)mechanism of a low carbon martensitic stainless bearing steel,CSS-42L,were investigated using a thermomechanical simulator under the temperature and strain rate ranges of 900 to 1100℃ and 0.1 to 20 s^(−1),respectively.The Arrhenius-type constitutive equation was established based on the fow stress curves.Moreover,the peak stress decreased with the increase in deformation temperature and the decrease in strain rate.There were two DRX mechanisms during hot deformation of the current studied steel,the main one being discontinuous dynamic recrystallization mechanism,acting through grain boundary bulging and migration,and the auxiliary one being continuous dynamic recrystallization mechanism,working through the rotation of sub-grains.On the basis of microstructural characterizations,power dissipation maps and fow instability maps,the optimized hot deformation parameters for CSS-42L bearing steel were determined as 1050℃/0.1 s^(−1) and 1100℃/1 s^(−1).展开更多
A bearing fault diagnosis method based on the Markov transitionfield(MTF)and SEnet(SE)-IShufflenetV2 model is proposed in this paper due to the problems of complex working conditions,low fault diagnosis accuracy,and poo...A bearing fault diagnosis method based on the Markov transitionfield(MTF)and SEnet(SE)-IShufflenetV2 model is proposed in this paper due to the problems of complex working conditions,low fault diagnosis accuracy,and poor generalization of rolling bearing.Firstly,MTF is used to encode one-dimensional time series vibration sig-nals and convert them into time-dependent and unique two-dimensional feature images.Then,the generated two-dimensional dataset is fed into the SE-IShufflenetV2 model for training to achieve fault feature extraction and classification.This paper selects the bearing fault datasets from Case Western Reserve University and Paderborn University to experimentally verify the effectiveness and superiority of the proposed method.The generalization performance of the proposed method is tested under the variable load condition and different signal-to-noise ratios(SNRs).The experimental results show that the average accuracy of the proposed method under different working conditions is 99.2%without adding noise.The accuracy under different working conditions from 0 to 1 HP is 100%.When the SNR is 0 dB,the average accuracy of the proposed method can still reach 98.7%under varying working conditions.Therefore,the bearing fault diagnosis method proposed in this paper is characterized by high accuracy,strong anti-noise ability,and generalization.Moreover,the proposed method can also overcome the influence of variable working conditions on diagnosis accuracy,providing method support for the accurate diagnosis of bearing faults under strong noise and variable working conditions.展开更多
To investigate the evolution of load-bearing characteristics of pre-stressed beams throughout their service life and to provide a basis for accurately assessing the actual working state of damaged pre-stressed concret...To investigate the evolution of load-bearing characteristics of pre-stressed beams throughout their service life and to provide a basis for accurately assessing the actual working state of damaged pre-stressed concrete T-beams,destructive tests were conducted on full-scale pre-stressed concrete beams.Based on the measurement and ana-lysis of beam deflection,strain,and crack development under various loading levels during the research tests,combined with the verification coefficient indicators specified in the codes,the verification coefficients of bridges at different stages of damage can be examined.The results indicate that the T-beams experience complete,incom-plete linear,and non-linear stages during the destructive test process.In the complete linear elastic stage,both the deflection and bottom strain verification coefficients comply with the specifications,indicating a good structural load-bearing capacity no longer adheres to the code’s requirements.In the non-linear stage,both coefficients exhi-bit a sharp increase,resulting in a further decrease in the structure’s load-bearing capacity.According to the pro-visions of the current code,the beam can be in the incomplete linear stage when both values fall within the code’s specified range.The strain verification coefficient sourced from the compression zone at the bottom of theflange is not recommended for assessing the bridge’s load-bearing capacity.展开更多
To meet the demand for miniaturized,compact,high-reliability,and long-life cryocoolers in small satellite platforms,the development of a linear Stirling cryocooler has been undertaken.Computational Fluid Dynamics(CFD)...To meet the demand for miniaturized,compact,high-reliability,and long-life cryocoolers in small satellite platforms,the development of a linear Stirling cryocooler has been undertaken.Computational Fluid Dynamics(CFD)numerical simulation software was used to conduct simulation analyses,verifying the impact of porous media channel layout,eccentricity,viscous resistance coefficient of the porous media,and piston position on the designed aerostatic bearing piston employing self-supplied gas bearing technology.The calculation results indicate that both the aerostatic force and leakage increase synchronously with eccentricity,while the two designed gas lift channel layouts are capable of providing sufficient load-bearing capacity while ensuring minimal leakage.Through calculations,it was determined that the viscous resistance coefficient of the porous media material,used as a throttling mechanism,is most suitable within the range of 81011 to 810131/m2.When studying the piston position,it was found that××due to the influence of the gas film length,the aerostatic force gradually increases as the piston moves from the maximum compression stroke state to the maximum low-pressure stroke state.To validate combining simulation with experimental platform testing,a support fixture platform for testing the load-bearing capacity of the gas bearings was independently constructed.The development of the aerostatic bearing piston prototype was completed,and performance tests were conducted,confirming that the trend of aerostatic force variation with gas film length is consistent with calculations.Additionally,it was verified that under the two aerostatic channel layouts,the aerostatic force closely matches the calculated values.展开更多
Rotating machinery in the aviation industry is increasingly embracing high speeds and miniaturization,and foil dynamic pressure gas bearing has great application value due to its self-lubrication and self-adaptive def...Rotating machinery in the aviation industry is increasingly embracing high speeds and miniaturization,and foil dynamic pressure gas bearing has great application value due to its self-lubrication and self-adaptive deformation characteristics.This study explores the interaction mechanism between micro-scale variable-sectional shearing flow with hyper-rotation speeds and a three-layer elastic foil assembly through bidirectional aero-elastic coupling in a Multi-layer Thrust Gas Foil Bearing(MTGFB).The bearing capacity of the MTGFB varies non-linearly with the decrease of gas film clearance,while the collaborative deformation of the three-layer elastic foil assembly can deal with different load conditions.As the load capacity increases,the enhanced dynamic pressure effect causes the top foil to evolve from a single arch to multiple arches.The hydrodynamic effects in the gas film evolve to form multiple segmented wedges with different pitch ratios,while the peak pressure of the gas film always occurs near the vaults of the top foil.As the rotational speed frequency approaches the natural frequency,the resonance of the gas film and elastic foil assembly system occurs,and a phase delay occurs between the pressure pulsation and the vibration of foils.The load capacity of the MTGFB also depends on the elastic moduli of the elastic foil assembly.Increasing the elastic modulus decreases the deformation amplitude of the top foil,whereas it increases those of the backboard and middle foil,increasing the load capacity.展开更多
When a coin is tossed to a gravity well,it will spiral instead of falling directly to the center.Inspired by this phenomenon,a gravity well-inspired double friction pendulum system(GW-DFPS)is developed to extend the l...When a coin is tossed to a gravity well,it will spiral instead of falling directly to the center.Inspired by this phenomenon,a gravity well-inspired double friction pendulum system(GW-DFPS)is developed to extend the length of sliding trajectories of bridge superstructures during pulse-like near-fault earthquakes.As a result,a greater amount of energy will be dissipated due to the frictional sliding of the isolators.The GW-DFPS consists of a spherical surface and an outer surface described by a 1/x or logarithmic function to build gravity well.Full-scale isolators were fabricated and their response was characterized considering various parameters such as the friction material of slider,surface roughness of sliding surfaces,and applied vertical loads.Additionally,a finite element model of the isolator was created using the experimental test data.Numerical simulations were performed on a case-study bridge structure isolated using both a conventional DFPS system and the proposed GW-DFPS systems.The experimental results reveal that the proposed isolators exhibit stable response under vertical loads varying from 200 kN to 1000 kN with a negative stiffness response when the isolator slides at the outer sliding surface.The numerical simulations of the selected bridge structure demonstrate that the GW-DFPS significantly extends the sliding trajectory lengths of the superstructure during half of the earthquake pulses,resulting in increased energy dissipation during this interval.The kinetic energies of the bridge isolated by GW-DFPS are consistently lower than those of the bridge isolated by the other two kinds of isolators,resulting lower shear forces on the bridge.展开更多
文摘孩子们喜欢故事,老师也喜欢故事,因此,通过故事的方式引导小学生学习英语已经成为当前一种有效的英语教学方式。《义务教育英语课程标准》(2011年版)在"语言技能"二级要求中就英语故事教学做出如下描述:"能听懂简单的配图小故事,能在教师的帮助下和图片的提示下描述或讲述简单的小故事,能正确朗读所学故事或短文,能在教师的帮助下表演小故事或小短剧。"为此,当前很多小学英语教材都在权重板块设置了"Story Time",旨在通过故事的方式引导学生开展富有趣味的英语学习活动。确实,故事教学给小学英语课堂带来了新的活力、新的气象,然而,当一些英语小故事被抹上过于浓重的"教学味"的时候,它们在学生眼中便失去了原有的魅力,所谓的"Story Time"也就或多或少地缺失了故事该有的滋味。因此,如何使故事教学更具有故事的味儿,也是我们当今面对的一个重要课题。多年来,钱希洁老师对此进行了深入的实践与探索,本文主要以她执教的译林出版社出版的《义务教育教科书·英语》(五年级上册)Unit 1 Story time板块中的故事"Goldilocks and the three bears"教学中的几个片段为例,阐述了她对小学英语故事教学的思考,旨在与广大同行朋友们探讨:如何使小学英语故事教学散发出更为浓郁的故事味。我们相信,这样的探讨对于其它学科的教学,也有一定的借鉴意义。
文摘In the second quarter of 2018, the Chinese economy grew at 6.7 percent which is in line with expectations and marginally slower than the 6.8-percent growth recorded in the previous three quarters. Growth during the first half this year also stands at 6.7 percent. Amidst the ongoing trade war with the United States, as of July 27, the renminbi （RMB） has fallen 8.2 percent against the dollar since April 2. Having fallen below 3,000 in June for the first time in two years.
文摘The Johannesburg Summit of the Forum on China-Africa Cooperation held in South Africa in December 2015has raised the level of agricultural cooperation between China and African countries,as evidenced by the achievements made by Chinese agricultural missions working on the continent.
文摘The need for the mitigation of brown bears has become so severe that many nomads have given up repairing their houses in Maryo Township’s Mendang Village(also named the First Administrative Village),a remote place located in the southwestern section of the Changtang National Nature Reserve(CNNR).Only part of the village belongs to Serling Tso Nature Reserve.
文摘An expeditious method for ascertaining species between black bear (Selenarctos thibetanus G. cuiver) and brown bear (Ursus arctos Linnaeus) was developed using tooth measurements from previously identified specimens. The measurement and analysis on 18 tooth measurement indexes (i.e. T1. Length of Pm1-Pm4, T2. L. of M1-M3, T3. M1L., T4. M1 width, T5. M2L., T6. M2W., T7.M3L., T8. M3W., T9. L. of C1 alveolus, T10. W. of C1 alveolus, T11. L. of C1-M2, T12. L. of Pm4 M2,T13.M1L., T14. M1W., T15. M2L., T16. M2W., T17.L. of C1 alveolus, T18. W. of C1 alveolus) of 59 skulls (black bears 25, brown bears 34) indicates that there are significant or the most significant difference between two species in every indexes, however T1, T9, T10, T17 and T18 are not suitable for species discriminator because of their high percent of overlap. The efficient species discriminators and standards (mm) are as follows T2(63.0), T3(22.0), T4(10.2), T5(23.8), T6(13.6), T7(18.0), T8(13.5), T11(110.0),T12(66.0), T13(20. 1), T14(15.8), T15(33.0) and T16(17.3). Those who are less than or equal to standard are classified to black bear, the others are brown bear. The method is very convenient and useful with high reliability. Their lowest accuracy percent are 95.0%, most of them over 97%. Different indexes will be chosen refer to the degree of specimen destroyed.
文摘From 1991 to 1992, we observed behavior of 7 brown bears (5 females, 2 males) in mating season. Re-Sults showed tkat the oertrus of brown bears was mainly from May to July. The oeStrus ofmost individuals occwred at theend of May and the beginning of June. There were some differences in the oestrus among individuals. Average duration ofthe oestrus 30.8 days (16-50 days). The mating behavior was mainly observed during 8.00-9.00 a.m., and 15.00-16.00p.m.. Rest and sleep were the next behavior after mating for most bears, especially for male bears. All bears had poor appe-the. The Pattern and process of a successful mating was that a male bear approached a female, smelled the pudendum of thefemale, climbed on female hip, mated, parted and rested. Oestrus females approached males sometimes.
基金Key Scientific Research Foundation of Educational Committee of Sichuan Province (No. 2004 A101) and Key Discipline Construction Project in Sichuan Province (No. SZD0420)
文摘According to the principle of enzyme reaction rate, healthy pent black bears’ myocardial enzyme activity is assayed by visual colorimetry and compared with that of healthy human beings. The determination at 37 °C and the statistic analysis of the experimental data work out the following findings. For male black bears, the average CK activity is 163.20 U/L, the confidence interval of its expected value (127.70 to 198.70) U/L, and the coefficient of variation 39.2%; the average CK-MB activity 21.62 U/L, the confidential interval (17.72 to 25.51) U/L, and the coefficient of variation 34.26%; the average LDH activity 604.20 U/L, the confidence interval (524.56 to 683.83) U/L, and the coefficient of variation 23.80%; the average HBDH activity 516.70 U/L, the confidence interval (453.06 to 580.34) U/L, and the coefficient of variation 22.24%; the average GOT activity 69.70 U/L, the confidence interval (60.21 to 79.19) U/L, and the coefficient of variation 24.59%. For female black bears, the average CK activity is 145.50 U/L, the confidence interval (114.59 to 176.21) U/L, and the coefficient of variation 38.27%; the average CK-MB activity 18.84 U/L, the confidence interval (14.64 to 23.04) U/L, and the coefficient of variation 40.34%; the average LDH activity 563.70 U/L, the confidence interval (473.80 to 652.60) U/L, and the coefficient of variation 28.80%; the average of HBDH activity 475.50 U/L, the confidence interval (412.10 to 538.40) U/L, and the coefficient of variation 24.07%; the average of GOT activity is 62.37 U/L, the confidential interval (52.54 to 72.20) U/L, and the coefficient of variation 28.46%. The male black bear’s average myocardium enzyme activities are slightly higher than those of the female. But the statistical results indicate that the difference is not significant.
基金supported by Structural Funds of EU Project of the Agency of the Ministry of Education,Science,Research and Sport of the Slovak Republic,Bratislava,ITMS No.26110230078
文摘Populations of the European brown bear (Ursus arctos L.) differ substantially in size, degree of geographic isolation and level of genetic diversity. Present patterns result from phylogeographic processes and profound human intervention. We assessed the genetic variability of a subpopulation of brown bears near the periphery of their range in the Western Carpathian Mountains and compared their genetic properties with those of bears in the core of the same population and elsewhere. Samples were collected non-invasively in 2007-2008 and2010 in Strázovské Vrchy Protected Landscape Area (PLA) in Slovakia (included in the NATURA 2000 networking programme). Seven polymorphic microsatellite loci (UaMU26, UaMU64, G10B, G1D, G10L, UaMU50 and UaMU51) were amplified using a nested PCR in order to assess the following parameters: variability, allelic combinations, heterozygosity, number of alleles and inbreeding coefficient. Sufficient brown bear DNA for analysis was obtained from 57 out of 140 samples (41%), among which 45 different genotypes were identified. Loci had a mean of 2.71 ± 0.76 alleles. Average observed heterozygosity was 0.59. The inbreeding coefficient was negative for all but one of the analysed loci (2007-2008). In the year 2010 was negative three of seven loci. These results imply that gene flow with other parts of the population has been maintained in the reduced level and the isolation level of bears in the study area was not so low. Nevertheless, the genetic variability of bears in Strázovské Vrchy PLA was lower than that reported from other localities in the Carpathian Mountains. The results are discussed in the context of behavioural ecology and conservation genetics.
基金supported by the National Natural Science Foundation of China(52203305,U21A20494,and 61927820)。
文摘To date,various micro/nanofabrication techniques have been developed during the global nanotechnology race,such as electron-beam lithography[1],photolithography[2],nanoimprint lithography[3],and 3D nanoprinting[4,5].Benefiting from these functional techniques,micro/nanoscale patterns can be easily generated onto a broad range of materials,including metals,semiconductors,ceramics,and polymers.However,a bold and even visionary question can be raised,is it possible to make patterns on living organisms rather than inanimate objects?Despite the emergence of numerous electronic devices for biological applications,directly processing biological samples remains a challenge due to the poor biocompatibility of many micro/nanofabrication methods[6].Researchers have attempted to prepare and transfer micro/nanopatterns onto cell surfaces[7],the structural integrity of these modifications can be compromised by the growth and development of cells during culture.Moreover,intact animal skin presents greater challenges for integration with metal patterns compared to cell surfaces.
基金supported by Independent Research Project of State Key Laboratory of Advanced Special Steel,Shanghai Key Laboratory of Advanced Ferrometallurgy,Shanghai University(SKLASS-2023-Z13)the Science and Technology Commission of Shanghai Municipality(No.19DZ2270200)+1 种基金A portion of the work was performed at US National High Magnetic Field Laboratory,which is supported by the National Science Foundation(Cooperative Agreement No.DMR-1157490 and DMR-1644779)the State of Florida.Thanks also to Mary Tyler for editing.
文摘The high-temperature dissolution behavior of primary carbides in samples taken from GCr15 continuous-casting bloom was observed in-situ by confocal laser scanning microscopy.Equations were fitted to the dissolution kinetics of primary carbides during either heating or soaking.Dissolution of carbides proceeded in three stages(fast→slow→faster)as either temperature or holding time was increased.During the heating process and during the first and third stages of the soaking process,the original size of the carbides determined the steepness of the slope,but during the middle(“slow”)stage of the soaking process,the slope remained zero.The initial size of the carbides varied greatly,but their final dissolution temperature fell within the narrow range of 1210-1235℃,and the holding time remained within 50 min.Fractal analysis was used to study the morphological characteristics of small and medium-sized carbides during the dissolution process.According to changes in the fractal dimension before and after soaking,the carbides tended to evolve towards a more regular morphology.
文摘Bearing is an indispensable key component in mechanical equipment,and its working state is directly related to the stability and safety of the whole equipment.In recent years,with the rapid development of artificial intelligence technology,especially the breakthrough of deep learning technology,it provides a new idea for bearing fault diagnosis.Deep learning can automatically learn features from a large amount of data,has a strong nonlinear modeling ability,and can effectively solve the problems existing in traditional methods.Aiming at the key problems in bearing fault diagnosis,this paper studies the fault diagnosis method based on deep learning,which not only provides a new solution for bearing fault diagnosis but also provides a reference for the application of deep learning in other mechanical fault diagnosis fields.
基金The financial supports by the Chinese Academy of Sciences(Nos.XDC04030300 and XDB0510303)CAS-HK Joint Laboratory of Nanomaterials and MechanicsShenyang National Laboratory for Materials Science are acknowledged.
文摘Rolling contact fatigue performance is among the most important issues for applications of bearing steels.In this work,a recently developed surface modification technique,surface mechanical rolling treatment,was applied on a rare-earth addition bearing steel.And rolling contact fatigue behavior of treated samples was compared with that of as-received counterparts at different contacting stresses.The results demonstrated that a 700μm-thick gradient nanostructured surface layer is produced on samples by surface mechanical rolling treatment.The grain size decreases while the microhardness increases gradually with decreasing depth,reaching~23 nm and~10.2 GPa,respectively,at the top surface.Consequently,the rolling contact fatigue property is significantly enhanced.The characteristic life of treated samples is~3.2 times that of untreated counterparts according to Weibull curves at 5.6 GPa.Analyses of fatigue mechanisms demonstrated that the gradient nanostructured surface layer might not only retard material degradation and microcrack formation,but also prolong the steady-state elastic response stage under rolling contact fatigue.
基金fnancially supported by the Scientifc Research Project of the Department of Education in Hunan Prov ince,China(Grant No.23B0533).
文摘In this work,fow behavior and dynamic recrystallization(DRX)mechanism of a low carbon martensitic stainless bearing steel,CSS-42L,were investigated using a thermomechanical simulator under the temperature and strain rate ranges of 900 to 1100℃ and 0.1 to 20 s^(−1),respectively.The Arrhenius-type constitutive equation was established based on the fow stress curves.Moreover,the peak stress decreased with the increase in deformation temperature and the decrease in strain rate.There were two DRX mechanisms during hot deformation of the current studied steel,the main one being discontinuous dynamic recrystallization mechanism,acting through grain boundary bulging and migration,and the auxiliary one being continuous dynamic recrystallization mechanism,working through the rotation of sub-grains.On the basis of microstructural characterizations,power dissipation maps and fow instability maps,the optimized hot deformation parameters for CSS-42L bearing steel were determined as 1050℃/0.1 s^(−1) and 1100℃/1 s^(−1).
基金supported by Hebei Natural Science Foundation under Grant No.E2024402079Key Laboratory of Intelligent Industrial Equipment Technology of Hebei Province(Hebei University of Engineering)under Grant No.202206.
文摘A bearing fault diagnosis method based on the Markov transitionfield(MTF)and SEnet(SE)-IShufflenetV2 model is proposed in this paper due to the problems of complex working conditions,low fault diagnosis accuracy,and poor generalization of rolling bearing.Firstly,MTF is used to encode one-dimensional time series vibration sig-nals and convert them into time-dependent and unique two-dimensional feature images.Then,the generated two-dimensional dataset is fed into the SE-IShufflenetV2 model for training to achieve fault feature extraction and classification.This paper selects the bearing fault datasets from Case Western Reserve University and Paderborn University to experimentally verify the effectiveness and superiority of the proposed method.The generalization performance of the proposed method is tested under the variable load condition and different signal-to-noise ratios(SNRs).The experimental results show that the average accuracy of the proposed method under different working conditions is 99.2%without adding noise.The accuracy under different working conditions from 0 to 1 HP is 100%.When the SNR is 0 dB,the average accuracy of the proposed method can still reach 98.7%under varying working conditions.Therefore,the bearing fault diagnosis method proposed in this paper is characterized by high accuracy,strong anti-noise ability,and generalization.Moreover,the proposed method can also overcome the influence of variable working conditions on diagnosis accuracy,providing method support for the accurate diagnosis of bearing faults under strong noise and variable working conditions.
文摘To investigate the evolution of load-bearing characteristics of pre-stressed beams throughout their service life and to provide a basis for accurately assessing the actual working state of damaged pre-stressed concrete T-beams,destructive tests were conducted on full-scale pre-stressed concrete beams.Based on the measurement and ana-lysis of beam deflection,strain,and crack development under various loading levels during the research tests,combined with the verification coefficient indicators specified in the codes,the verification coefficients of bridges at different stages of damage can be examined.The results indicate that the T-beams experience complete,incom-plete linear,and non-linear stages during the destructive test process.In the complete linear elastic stage,both the deflection and bottom strain verification coefficients comply with the specifications,indicating a good structural load-bearing capacity no longer adheres to the code’s requirements.In the non-linear stage,both coefficients exhi-bit a sharp increase,resulting in a further decrease in the structure’s load-bearing capacity.According to the pro-visions of the current code,the beam can be in the incomplete linear stage when both values fall within the code’s specified range.The strain verification coefficient sourced from the compression zone at the bottom of theflange is not recommended for assessing the bridge’s load-bearing capacity.
文摘To meet the demand for miniaturized,compact,high-reliability,and long-life cryocoolers in small satellite platforms,the development of a linear Stirling cryocooler has been undertaken.Computational Fluid Dynamics(CFD)numerical simulation software was used to conduct simulation analyses,verifying the impact of porous media channel layout,eccentricity,viscous resistance coefficient of the porous media,and piston position on the designed aerostatic bearing piston employing self-supplied gas bearing technology.The calculation results indicate that both the aerostatic force and leakage increase synchronously with eccentricity,while the two designed gas lift channel layouts are capable of providing sufficient load-bearing capacity while ensuring minimal leakage.Through calculations,it was determined that the viscous resistance coefficient of the porous media material,used as a throttling mechanism,is most suitable within the range of 81011 to 810131/m2.When studying the piston position,it was found that××due to the influence of the gas film length,the aerostatic force gradually increases as the piston moves from the maximum compression stroke state to the maximum low-pressure stroke state.To validate combining simulation with experimental platform testing,a support fixture platform for testing the load-bearing capacity of the gas bearings was independently constructed.The development of the aerostatic bearing piston prototype was completed,and performance tests were conducted,confirming that the trend of aerostatic force variation with gas film length is consistent with calculations.Additionally,it was verified that under the two aerostatic channel layouts,the aerostatic force closely matches the calculated values.
基金the financial support from the National Natural Science Foundation of China(No.52206091)the Aeronautical Science Foundation of China(No.201928052008)the Natural Science Foundation of Jiangsu Province,China(No.BK20210303)。
文摘Rotating machinery in the aviation industry is increasingly embracing high speeds and miniaturization,and foil dynamic pressure gas bearing has great application value due to its self-lubrication and self-adaptive deformation characteristics.This study explores the interaction mechanism between micro-scale variable-sectional shearing flow with hyper-rotation speeds and a three-layer elastic foil assembly through bidirectional aero-elastic coupling in a Multi-layer Thrust Gas Foil Bearing(MTGFB).The bearing capacity of the MTGFB varies non-linearly with the decrease of gas film clearance,while the collaborative deformation of the three-layer elastic foil assembly can deal with different load conditions.As the load capacity increases,the enhanced dynamic pressure effect causes the top foil to evolve from a single arch to multiple arches.The hydrodynamic effects in the gas film evolve to form multiple segmented wedges with different pitch ratios,while the peak pressure of the gas film always occurs near the vaults of the top foil.As the rotational speed frequency approaches the natural frequency,the resonance of the gas film and elastic foil assembly system occurs,and a phase delay occurs between the pressure pulsation and the vibration of foils.The load capacity of the MTGFB also depends on the elastic moduli of the elastic foil assembly.Increasing the elastic modulus decreases the deformation amplitude of the top foil,whereas it increases those of the backboard and middle foil,increasing the load capacity.
基金financially supported by the National Natural Science Foundation of China(Grants 52178124,52478151).
文摘When a coin is tossed to a gravity well,it will spiral instead of falling directly to the center.Inspired by this phenomenon,a gravity well-inspired double friction pendulum system(GW-DFPS)is developed to extend the length of sliding trajectories of bridge superstructures during pulse-like near-fault earthquakes.As a result,a greater amount of energy will be dissipated due to the frictional sliding of the isolators.The GW-DFPS consists of a spherical surface and an outer surface described by a 1/x or logarithmic function to build gravity well.Full-scale isolators were fabricated and their response was characterized considering various parameters such as the friction material of slider,surface roughness of sliding surfaces,and applied vertical loads.Additionally,a finite element model of the isolator was created using the experimental test data.Numerical simulations were performed on a case-study bridge structure isolated using both a conventional DFPS system and the proposed GW-DFPS systems.The experimental results reveal that the proposed isolators exhibit stable response under vertical loads varying from 200 kN to 1000 kN with a negative stiffness response when the isolator slides at the outer sliding surface.The numerical simulations of the selected bridge structure demonstrate that the GW-DFPS significantly extends the sliding trajectory lengths of the superstructure during half of the earthquake pulses,resulting in increased energy dissipation during this interval.The kinetic energies of the bridge isolated by GW-DFPS are consistently lower than those of the bridge isolated by the other two kinds of isolators,resulting lower shear forces on the bridge.
