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《黄帝内经》人体骨数浅议 被引量:4
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作者 苏永强 刘斌 董福慧 《中国中医基础医学杂志》 CAS CSCD 北大核心 2013年第11期1261-1263,共3页
《黄帝内经》是中医学基础理论的奠基之作。中医骨伤科学是中医药学的重要分支,它的基础理论来源于《黄帝内经》。通过总结归纳该书人体骨的名称、数量,列举后世经典医书的有关条文,以及中西医学骨数量不一致现象等问题进行分析讨论,认... 《黄帝内经》是中医学基础理论的奠基之作。中医骨伤科学是中医药学的重要分支,它的基础理论来源于《黄帝内经》。通过总结归纳该书人体骨的名称、数量,列举后世经典医书的有关条文,以及中西医学骨数量不一致现象等问题进行分析讨论,认为《黄帝内经》人体骨数的观点,是中国古代医家在解剖学的基础上对于人体骨特有的认识,正视并正确理解这一观点,是立足中医关于人体结构的基础理论,发展中医骨伤科学术的关键所在。 展开更多
关键词 黄帝内经 骨数 解剖 中医伤科
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我国人足趾骨骨数新议(附307例足趾骨X线片观察分析)
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作者 张荣海 刘龙 《中外医用放射技术》 1993年第7期11-13,共3页
关键词 中国 人足趾 骨数 X线
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从股骨组织结构推断年龄 被引量:6
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作者 刘晓燕 《解剖学杂志》 CAS CSCD 北大核心 2003年第1期94-97,共4页
目的:从股骨组织结构的年龄变化推断年龄。方法:在23例5岁至86岁股骨中段磨片测量骨单位数(X1),非哈弗氏管数(X2)及外环板平均厚度(X3),并作回归分析。结果:求得三元及二元回归方程:Y=4.9591 X10.1485x2-0.1482X3-0.5835;Y=7.7193 X2-0.... 目的:从股骨组织结构的年龄变化推断年龄。方法:在23例5岁至86岁股骨中段磨片测量骨单位数(X1),非哈弗氏管数(X2)及外环板平均厚度(X3),并作回归分析。结果:求得三元及二元回归方程:Y=4.9591 X10.1485x2-0.1482X3-0.5835;Y=7.7193 X2-0.1524 X3-0.6389。结论:在5至50岁的标本验算二元回归方程,100%的估计年龄与真实年龄的误差在±5之内。这个结果优于三元回归方程的结果。此计算方法比朱芳武用四个一元回归方程综合推算年龄的方法更为快捷简便。 展开更多
关键词 年龄 单位 非哈弗氏管 外环板平均厚度 回归分析
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Rock skeleton models and seismic porosity inversion 被引量:3
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作者 贺锡雷 贺振华 +2 位作者 王绪本 熊晓军 蒋炼 《Applied Geophysics》 SCIE CSCD 2012年第3期349-358,363,共11页
By substituting rock skeleton modulus expressions into Gassmann approximate fluid equation, we obtain a seismic porosity inversion equation. However, conventional rock skeleton models and their expressions are quite d... By substituting rock skeleton modulus expressions into Gassmann approximate fluid equation, we obtain a seismic porosity inversion equation. However, conventional rock skeleton models and their expressions are quite different from each other, resuling in different seismic porosity inversion equations, potentially leading to difficulties in correctly applying them and evaluating their results. In response to this, a uniform relation with two adjusting parameters suitable for all rock skeleton models is established from an analysis and comparison of various conventional rock skeleton models and their expressions including the Eshelby-Walsh, Pride, Geertsma, Nur, Keys-Xu, and Krief models. By giving the two adjusting parameters specific values, different rock skeleton models with specific physical characteristics can be generated. This allows us to select the most appropriate rock skeleton model based on geological and geophysical conditions, and to develop more wise seismic porosity inversion. As an example of using this method for hydrocarbon prediction and fluid identification, we apply this improved porosity inversion, associated with rock physical data and well log data, to the ZJ basin. Research shows that the existence of an abundant hydrocarbon reservoir is dependent on a moderate porosity range, which means we can use the results of seismic porosity inversion to identify oil reservoirs and dry or water-saturated reservoirs. The seismic inversion results are closely correspond to well log porosity curves in the ZJ area, indicating that the uniform relations and inversion methods proposed in this paper are reliable and effective. 展开更多
关键词 Rock physics rock skeleton models adjusting parameters seismic porosityinversion Gassmann's equation
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Construction of a database of average cross-sections in Chinese proximal femurs
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作者 马如宇 王冬梅 +2 位作者 薛文东 戴尅戎 王成焘 《Journal of Southeast University(English Edition)》 EI CAS 2004年第2期191-194,共4页
The process of constructing a database of average cross-sections in Chinese proximal femurs is described. The main goal of creating the database is for designing hip stems for Chinese patients. Methods for constructin... The process of constructing a database of average cross-sections in Chinese proximal femurs is described. The main goal of creating the database is for designing hip stems for Chinese patients. Methods for constructing the database are introduced. According to some existing software and programs developed by the authors, a database of average cross-sections in Chinese proximal femurs was built based on CT images of eighty femur-specimens. 3-D shape of a patient's proximal femurs can be reconstructed according to the database and X-ray radiographs. Theoretical analyses and results of clinical application indicate that the database can be used to design hip stems for Chinese patients. 展开更多
关键词 Computerized tomography Database systems Hip prostheses X ray films
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A practical application of photogrammetry to performing rib characterization measurements in an underground coal mine using a DSLR camera 被引量:1
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作者 Brent A.Slaker Khaled M.Mohamed 《International Journal of Mining Science and Technology》 SCIE EI CSCD 2017年第1期83-90,共8页
Understanding coal mine rib behavior is important for inferring pillar loading conditions as well as ensuring the safety of miners who are regularly exposed to ribs. Due to the variability in the geometry of undergrou... Understanding coal mine rib behavior is important for inferring pillar loading conditions as well as ensuring the safety of miners who are regularly exposed to ribs. Due to the variability in the geometry of underground openings and ground behavior, point measurements often fail to capture the true movement of mine workings. Photogrammetry is a potentially fast, cheap, and precise supplemental measurement tool in comparison to extensometers, tape measures, or laser range meters, but its application in underground coal has been limited. The practical use of photogrammetry was tested at the Safety Research Coal Mine, National Institute for Occupational Safety and Health(NIOSH). A commercially available, digital single-lens reflex(DSLR) camera was used to perform the photogrammetric surveys for the experiment. Several experiments were performed using different lighting conditions, distances to subject,camera settings, and photograph overlaps, with results summarized as follows: the lighting method was found to be insignificant if the scene was appropriately illuminated. It was found that the distance to the subject has a minimal impact on result accuracy, and that camera settings have a significant impact on the photogrammetric quality of images. An increasing photograph resolution was preferable when measuring plane orientations; otherwise a high point cloud density would likely be excessive. Focal ratio(F-stop) changes affect the depth of field and image quality in situations where multiple angles are necessary to survey cleat orientations. Photograph overlap is very important to proper three-dimensional reconstruction, and at least 60% overlap between photograph pairs is ideal to avoid unnecessary post-processing. The suggestions and guidelines proposed are designed to increase the quality of photogrammetry inputs and outputs as well as minimize processing time, and serve as a starting point for an underground coal photogrammetry study. 展开更多
关键词 PHOTOGRAMMETRY Coal mining UNDERGROUND Rib characterization
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Flow cytometry assay of myeloid dendritic cells (mDCs)in peripheral blood during acute hepatitis C:Possible pathogenetic mechanisms 被引量:1
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作者 Alessandro Perrella Luigi Atripaldi +7 位作者 Pasquale Bellopede Tommaso Patarino Costanza Sbreglia Giovanni Tarantino Paolo Sorrentino Paolo Conca Luca Ruggiero Oreste Perrella 《World Journal of Gastroenterology》 SCIE CAS CSCD 2006年第7期1105-1109,共5页
AIM: To asses the expression of myeloid dendritic cells (CD11c+) subset during acute HCV hepatitis and its possible involvement in natural history of the infection.METHODS: We enrolled 11 patients with acute hepa... AIM: To asses the expression of myeloid dendritic cells (CD11c+) subset during acute HCV hepatitis and its possible involvement in natural history of the infection.METHODS: We enrolled 11 patients with acute hepatitis C (AHC) (Group A), 10 patients with acute hepatitis A (AHA) (as infective control-Group B) and 10 healthy donors (group C) in this study. All patients underwent selective flow cytometry gating strategies to assess the peripheral number of the myeloid dendritic cells (mDCs) to understand the possible role and differences during acute hepatitis.RESULTS: Eight of 11 patients with acute HCV hepatitis did not show any increase of mDCs compared to healthy individuals, while a significant decrease of mDCs was found in absolute cell count (z=-2.37, P〈0.05) and percentage (z=-2.30; P〈 0.05) as compared with AHA. On the contrary, The remaining three patients of the group A had a higher mDCs number and percentage as occur in group B. Interestingly, after six months, those patients did not show any increase of mDCs subset were chronically infected, while the three subjects with an increase of peripheral mDCs, as in HAV acute infection, resolved the illness.CONCLUSION: The lack of increase of mDCs during acute hepatitis C might be an important factor involved in chronicization of the infection. 展开更多
关键词 Myeloid dendritic cells HCV CD4+ CD11c+ HCV-RNA HAV
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Pathological and MR-DWI study of the acute hepatic injury model after stem cell transplantation 被引量:6
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作者 Quan-Liang Shang En-Hua Xiao +2 位作者 Qi-Chang Zhou Jian-Guang Luo Hai-Jun Wu 《World Journal of Gastroenterology》 SCIE CAS CSCD 2011年第23期2821-2828,共8页
AIM: To investigate apparent diffusion coefficient (ADC) values as an indication of reconditioning of acute hepatic injury (AHI) after allogeneic mononuclear bone marrow cell (MBMC) transplantation. METHODS: T... AIM: To investigate apparent diffusion coefficient (ADC) values as an indication of reconditioning of acute hepatic injury (AHI) after allogeneic mononuclear bone marrow cell (MBMC) transplantation. METHODS: Three groups were used in our study: a cell transplantation group (n = 21), transplantation control group (n = 21) and normal control group (n = 10). AHI model rabbits in the cell transplantation group were injected with 5 mL of MBMC suspension at multiple sites in the liver and the transplantation controls were injected with 5 mL D-Hanks solution. At the end of the 1st, 2nd and 4th wk, 7 rabbits were randomly selected from the cell transplantation group and trans- plantation control group for magnetic resonance diffu- sion-weighted imaging (MR-DWI) and measurement of the mean ADC values of injured livers. After MR-DWI examination, the rabbits were sacrificed and the livers subjected to pathological examination. Ten healthy rab- bits from the normal control group were used for MR- DWI examination and measurement of the mean ADC value of normal liver. RESULTS: At all time points, the liver pathological scores from the cell transplantation group were significantly lower than those in the transplantation control group (27.14± 1.46 vs 69.29± 6.16, 22.29 ± 2.29 vs 57.00± 1.53, 19.00 ± 2.31 vs 51.86 ± 6.04, P = 0.000). The mean ADC values of the cell transplantation group were significantly higher than the transplantation con- trol group ((1.07± 0.07) ×10^-3 mm2/s vs (0.69 ± 0.05) ×10^-3 mm2/s, (1.41± 0.04) ×10^-3 mm2/s vs (0.84± 0.03) ×10^-3 mm2/s, (1.68 ± 0.04) ×10^-3 mm2/s vs (0.86± 0.04) ×10^-3 mm2/s, P = 0.000). The pathological scores of the cell transplantation group and transplantation control group gradually decreased. However, their mean ADC values gradually increased to near that of the normal control. At the end of the 1st wk, the mean ADC values of the cell transplantation group and transplantation control group were significantly lower than those of the normal control group [(1.07 ± 0.07) ×10^-3 mm2/s vs (± 0.03) ×10^-3 mm2/s, (0.69± 0.05) ×10^-3 mm2/s vs (1.76 ± 0.03) ×10^-3 mm2/s, P = 0.000]. At any 2 time points, the pathological scores and the mean ADC values of the cell transplantation group were significantly different (P = 0.000). At the end of the 1st wk, the pathological scores and the mean ADC values of the transplantation control group were significantly different from those at the end of the 2nd and 4th wk (P = 0.000). However, there was no significant difference between the 2nd and 4th wk (P = 0.073 and 0.473, respectively). The coefficient of correlation between the pathological score and the mean ADC value in the cell transplantation group was -0.883 (P = 0.000) and -0.762 (P = 0.000) in the transplantation control group. CONCLUSION: Tracking the longitudinally dynamic change in the mean ADC value of the AHI liver may reflect hepatic injury reconditioning after allogeneic MBMC transplantation. 展开更多
关键词 Stem cells TRANSPLANTATION Hepatic injury Magnetic resonance imaging Diffusion weighted imaging
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Role of Sclerostin in the Bone Loss of Postmenopausal Chinese Women with Type 2 Diabetes 被引量:16
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作者 Yi-jun Zhou Ai Li +3 位作者 Yu-ling Song Hui Zhou Yan Li Yin-si Tang 《Chinese Medical Sciences Journal》 CAS CSCD 2013年第3期135-139,共5页
Objective To evaluate the role of sclerostin in bone loss of postmenopausal Chinese women with type 2 diabetes me|litus. Methods The postmenopausal patients suffering from type 2 diabetes mellitus and age, body mass... Objective To evaluate the role of sclerostin in bone loss of postmenopausal Chinese women with type 2 diabetes me|litus. Methods The postmenopausal patients suffering from type 2 diabetes mellitus and age, body mass index, and duration of menopause matched healthy controls were enrolled into this cross-sectional study according to criteria of inclusion and exclusion. 展开更多
关键词 SCLEROSTIN type 2 diabetes mellitus POSTMENOPAUSE bone markers bone mineral density
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Prediction of application scope of vertical fracture strike based on scattered wave fracture orientation function 被引量:1
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作者 TANG Yufei LIU Yuwei +1 位作者 LIU Xiwu YANG Guodong 《Global Geology》 2015年第1期49-53,共5页
Fracture system plays a very important role in the enrichment and accumulation of oil and gas in the reservoirs. Based on scattering wave information, Fracture Orientation Function (FOF) was built, which can be used... Fracture system plays a very important role in the enrichment and accumulation of oil and gas in the reservoirs. Based on scattering wave information, Fracture Orientation Function (FOF) was built, which can be used to predict the fracture orientations. However, this method has only been verified by physical experiments without studies on the application scope. In this study, based on the linear sliding theory, F0F of the scattering wave was applied to the numerical simulation and the application scope was further studied according to fracture flexibility tensor. According to the fractures filled with gas and liquid, numerical simulation was conducted on the models with various fracture flexibilities. Numerical simulation results were used to inverse fracture orientation with the aid of the FOF of the scattering wave. The results show that it is workable to predict the vertical fracture orientation with the F0F of the scattering wave. Application of this method is more effective when the fractures are filled with gas than liquid. Moreover, the application scope can be predicted by the fracture flexibility. 展开更多
关键词 scattering wave fracture strike fracture orientation function fracture flexibility tensor
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Experimental and Numerical Study on Heat Transfer Enhancement of a Rectangular Channel with Discontinuous Crossed Ribs and Grooves 被引量:4
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作者 唐新宜 朱冬生 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2012年第2期220-230,共11页
Experimental and numerical investigations have been conducted to study turbulent flow of water and heat transfer characteristics in a rectangular channel with discontinuous crossed ribs and grooves.The tests investiga... Experimental and numerical investigations have been conducted to study turbulent flow of water and heat transfer characteristics in a rectangular channel with discontinuous crossed ribs and grooves.The tests investigated the overall heat transfer performance and friction factor in ribbed and ribbed-grooved channels with rib angle of 30°.The experimental results show that the overall thermo-hydraulic performance for ribbed-grooved channel is increased by 10%-13.6% when compared to ribbed channel.The investigation on the effects of different rib angles and rib pitches on heat transfer characteristics and friction factor in ribbed-grooved channel was carried out using Fluent with SST(shear-stress transport) k-ω turbulence model.The numerical results indicate that the case for rib angle of 45° shows the best overall thermo-hydraulic performance,about 18%-36% higher than the case for rib angle of 0°.In addition,the flow patterns and local heat transfer characteristics for ribbed and ribbed-grooved channels based on the numerical simulation were also analyzed to reveal the mechanism of heat transfer enhancement. 展开更多
关键词 heat transfer enhancement rib GROOVE rectangular channel turbulent flow
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A force feedback master finger in exoskeleton type
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作者 Fang Honggen Liu Hong Xie Zongwu 《High Technology Letters》 EI CAS 2010年第3期299-305,共7页
In order to eliminate the drawbacks of conventional force feedback gloves, a new type of master fin- ger has been developed. By utilizing three "four-bar mechanism joint" in series and wire coupling mecha- nism, the... In order to eliminate the drawbacks of conventional force feedback gloves, a new type of master fin- ger has been developed. By utilizing three "four-bar mechanism joint" in series and wire coupling mecha- nism, the master finger transmission ratio is kept exactly 1:1.4:1 in the whole movement range and it can make active motions in both extension and flexion directions. Additionally, to assure faster data transmission and near zero delay in the master-slave operation, a digital signal processing/field programmable gate array (DSP/FPGA-FPGA) structure with 200μs cycle time is designed. The operating modes of the master finger can be contact or non-contact, which depends on the motion states of a slave finger, free motion or constrained motion. The position control employed in non-contact mode ensures unconstrained motion and the force control adopted in contact mode guarantees natural contact sensation. To evaluate the performances of the master finger, an experiment between the master finger and a DLR/HTT dexterous finger is conducted. The results demonstrate that this new type master finger can augment telepresence. 展开更多
关键词 force feedback master finger digital signal processing (DSP) field programmable gate array (FPGA) TELEPRESENCE
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A Method of Assessing Parameters of Air-Void Structure in Air-Entrained Concretes
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作者 Jerzy Wawrzeficzyk Wioletta Kozak 《Journal of Civil Engineering and Architecture》 2015年第7期798-806,共9页
The air-void size distribution and number of air voids are crucial characteristics of air-entrainment. The standard spacing factor L is based on the Powers model, in which considerable simplifications are assumed. A b... The air-void size distribution and number of air voids are crucial characteristics of air-entrainment. The standard spacing factor L is based on the Powers model, in which considerable simplifications are assumed. A better solution is provided by the Philleo factor, which determines the percentage content of protected paste located at a distance S from the edge of the nearest air void. Developing the concept put forward by Philleo, a method of determining the volume of protected paste on the basis of images generated from the numerical model of concrete grain structure including layout of aggregate-paste-air, is proposed. It is the ratio of the volume of the paste protected by air voids to the total paste volume. The PPV (protected paste volume) index accounts not only for sizes and number of air voids, but also for the role of aggregate particles in the placement of these pores, which is often disregarded in analyses. The PPV results obtained from image analysis were compared with standard spacing factor L and with the parameter developed by Philleo. The analyses conducted by the authors shows that accounting for aggregate grains in calculations substantially affects the assessment of the quality of the air-pore structure. 展开更多
关键词 Distribution of air pore sizes distribution of aggregate grain sizes protected paste area numerical model of the porosity ofthe concrete.
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Mathematical models for properties of mortars with admixtures and recycled fine aggregates from demolished concretes 被引量:1
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作者 Mi Renjie Pan Ganghua +1 位作者 Li Yang Lu Xiaojun 《Journal of Southeast University(English Edition)》 EI CAS 2018年第3期371-376,共6页
In order to expand the engineering application of recycle aggregate mortars (RAM) with aggregates from demolished concretes, the models for the properties of RAM and the replacement rate of these recycled fine aggre... In order to expand the engineering application of recycle aggregate mortars (RAM) with aggregates from demolished concretes, the models for the properties of RAM and the replacement rate of these recycled fine aggregates were proposed. First, different kinds of mathematical models for the basic properties (compressive strength, water retention rate, and consistency loss) of RAM with two kinds of admixtures, thickening powders (TP) and self-made powdery admixtures (SSCT) designed for RAM, and the replacement rates were established, while the average relative errors and relative standard errors of these models were calculated. Additionally, the models and their error analyses for the curves of drying shrinkage and curing time of RAM + SSCT at different replacement rates were put forward. The results show that polynomial functions should be used to calculate the basic properties of RAM + TP and RAM + SSCT at different replacement rates. In addition, polynonfial functions are the most optimal models for the sharp shrinkage sections in the curves of drying shrinkage-curing time of RAM + SSCT, while exponential functions should be used as the models for the slow shrinkage sections and steady shrinkage sections. 展开更多
关键词 demolished concrete recycled fine aggregates ADMIXTURES recycled aggregate mortars mathematical model
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Influences of Amazonian White and Black Waters on the Hematological and Biochemical Plasma Features of Arapaima gigas (Osteoglossiformes)
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作者 Cleverson Agner Ramos Jose Carlos Nunes Raulino +5 位作者 Glauber Cruz de Menezes Iracimar Batista do Carmo Elenice Martins Brasil Elizabeth Gusmao Affonso Oscar Tadeu Ferreira da Costa Marisa Narciso Femandes 《Journal of Life Sciences》 2014年第3期252-261,共10页
The Arapaima gigas, despite being an air breather, its gill structure is quite close to water breathers, especially in early stages of development. The effects of Amazonian waters is well notices in other Teleostei ex... The Arapaima gigas, despite being an air breather, its gill structure is quite close to water breathers, especially in early stages of development. The effects of Amazonian waters is well notices in other Teleostei expose to BW (black water), and WW (white water). However, information about hematological adjustments and its implications to ionic regulation patters are scarce. Therefore, our aim was to analyzed A. gigas hematological parameters when exposed to BW and WW providing suitable hematological data concerning about physiological responses in Amazonian waters. Fish were acclimated in three separated ponds containing BW, WW and well water as control (C). Blood samples were taken from the caudal vessel in order to perform measurement assays on levels of hemoglobin, hematocrit, mean corpuscular volume, corpuscular hemoglobin, corpuscular hemoglobin concentration, glucose, cholesterol and protein. Our findings corroborate the hypothesis stating that BW does interfere on fish adaptation specialy in smallfish (-100 g). However in largefish (-1,000 g) neither WW or BW can interfere on plasma profile of analysed fish. Despite black water systems being considered a barrier constraining the dispersion of several species, this seems not to be a problem for this specie which has kept its ion-regulatory mechanisms even in black waters. 展开更多
关键词 Amazon fish blood parameters Amazonian waters Pirarucu.
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Human skeleton proportions from monocular data
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作者 PENG En LI Ling 《Journal of Zhejiang University-Science A(Applied Physics & Engineering)》 SCIE EI CAS CSCD 2006年第7期1266-1274,共9页
This paper introduces a novel method for estimating the skeleton proportions of a human figure from monocular data. The proposed system will first automatically extract the key frames and recover the perspective camer... This paper introduces a novel method for estimating the skeleton proportions of a human figure from monocular data. The proposed system will first automatically extract the key frames and recover the perspective camera model from the 2D data. The human skeleton proportions are then estimated from the key frames using the recovered camera model without posture re- construction. The proposed method is tested to be simple, fast and produce satisfactory results for the input data. The human model with estimated proportions can be used in future research involving human body modeling or human motion reconstruction. 展开更多
关键词 MODELING Human figure MONOCULAR
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The Domino Effect
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作者 Egor Kotelnikov 《Journal of Physical Science and Application》 2012年第6期195-199,共5页
A row of dominoes which stand on edge will undergo a cascade when the first domino is tipped. First domino strokes the next and the wave of falling dominoes propagates. The purpose of this work is to investigate wave ... A row of dominoes which stand on edge will undergo a cascade when the first domino is tipped. First domino strokes the next and the wave of falling dominoes propagates. The purpose of this work is to investigate wave speed dependence on various domino parameters as the number of elements and the distance between dominoes and their dimensions. Theoretical examination of falling dominoes process is to create the mathematical model of the process and compare between the calculations and experimental results. An experiment with using of the speed camera was made. The dominoes of three different types of material were used. For theoretical investigation of the problem, the model [1] was used. The program for computer calculations was written. Time of a dominoes row falling was calculated without taking friction between neighbours. The calculation results show that the speed of falling dominoes reaches its constant value. This stable velocity depends on the geometric parameters of dominoes and the surface friction between dominoes but does not depend on the mass of dominoes. 展开更多
关键词 Dominoes domino wave domino mechanics.
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Experimental Study on 3D Geometrical and Fractal Characteristics of Fracture Surface of Rock-Like Materials Based on GIS Technique
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作者 李尤嘉 黄醒春 +1 位作者 邓建华 陈翔 《Journal of Donghua University(English Edition)》 EI CAS 2010年第4期477-485,共9页
In order to research the characteristic and mechanism of fracture of rock-like materials,the morphology of rock fracture surface under the breakages of uniaxial compression and triaxial compression was observed and me... In order to research the characteristic and mechanism of fracture of rock-like materials,the morphology of rock fracture surface under the breakages of uniaxial compression and triaxial compression was observed and measured by means of a new-type 3D laser scanning system.Based on geographic information system(GIS)technique,the fracture surfaces were 3D visualized and reestablished.According to GIS 3D statistics,the geometrical characteristics of fracture surfaces under different breakage conditions were analyzed,and then based on fractal theory,the change laws of fractal dimension of fracture surfaces were discussed under the conditions of different cell pressures and initial water contents of rock.Furthermore,the relationships between characteristics of fracture surface and mechanical properties of rock were discussed.The results indicate that cell pressure,initial water content,and mechanical parameters of rock are the important factors to influence on the geometrical characteristics of fracture surface.The research provides a new experimental method for quantitative study on the fracture characteristics of various materials under different breakage conditions. 展开更多
关键词 FRACTURE geometrical characteristic FRACTAL cell pressure water content geographic information system(GIS)
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Effect of Recycled Coarse Aggregate on Concrete Compressive Strength 被引量:7
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作者 汪振双 王立久 +1 位作者 崔正龙 周梅 《Transactions of Tianjin University》 EI CAS 2011年第3期229-234,共6页
The effect of recycled coarse aggregate on concrete compressive strength was investigated based on the concrete skeleton theory. For this purpose, 30 mix proportions of concrete with target cube compressive strength r... The effect of recycled coarse aggregate on concrete compressive strength was investigated based on the concrete skeleton theory. For this purpose, 30 mix proportions of concrete with target cube compressive strength ranging from 20 to 60 MPa were cast with normal coarse aggregate and recycled coarse aggregate from different strength parent concretes. Results of 28-d test show that the strength of different types of recycled aggregate affects the concrete strength obviously. The coarse aggregate added to mortar matrix plays a skeleton role and improves its compressive strength. The skeleton effect of coarse aggregate increases with the increasing strength of coarse aggregate, and normal coarse aggregate plays the highest, whereas the lowest concrete strength occurs when using the weak recycled coarse aggregate. There is a linear relationship between the concrete strength and the corresponding mortar matrix strength. Coarse aggregate skeleton formula is established, and values from experimental tests match the derived expressions. 展开更多
关键词 recycled coarse aggregate compressive strength concrete skeleton model skeleton formula crushing index
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Direct and Indirect Excitons in Two-Dimensional Covalent Organic Frameworks
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作者 Shan Sun Hui-zhong Ma +1 位作者 Xiao Zhang Yu-chen Ma 《Chinese Journal of Chemical Physics》 SCIE CAS CSCD 2020年第5期569-577,I0008-I0010,I0078,共13页
Highly luminescent bulk two-dimensional covalent organic frameworks(COFs)attract much attention recently.Origin of their luminescence and their large Stokes shift is an open question.After first-principles calculation... Highly luminescent bulk two-dimensional covalent organic frameworks(COFs)attract much attention recently.Origin of their luminescence and their large Stokes shift is an open question.After first-principles calculations on two kinds of COFs using the GW method and Bethe-Salpeter equation,we find that monolayer COF has a direct band gap,while bulk COF is an indirect band-gap material.The calculated optical gap and optical absorption spectrum for the direct excitons of bulk COF agree with the experiment.However,the calculated energy of the indirect exciton,in which the photoelectron and the hole locate at the conduction band minimum and the valence band maximum of bulk COF respectively,is too low compared to the fluorescence spectrum in experiment.This may exclude the possible assistance of phonons in the luminescence of bulk COF.Luminescence of bulk COF might result from exciton recombination at the defects sites.The indirect band-gap character of bulk COF originates from its AA-stacked conformation.If the conformation is changed to the AB-stacked one,the band gap of COF becomes direct which may enhance the luminescence. 展开更多
关键词 Covalent organic frameworks LUMINESCENCE EXCITONS Many-body Green’s function theory
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