Background The diagnosis of diffuse hepatic lesions in early stage is a tough task at any time for clinical conventional imaging. Magnetic resonance diffusion-weighted imaging (MR DWI) can detect the changes of tissu...Background The diagnosis of diffuse hepatic lesions in early stage is a tough task at any time for clinical conventional imaging. Magnetic resonance diffusion-weighted imaging (MR DWI) can detect the changes of tissue structure at molecular level. This study was designed to determine the value of DWI in the diagnosis of diffuse liver lesions in early stage. Methods Diffuse liver lesions were induced by diethylnitrosamine in 42 rats of test group. Fourteen rats in control group were fed with pure water. Dynamic changes of MR DWI were observed every week in both groups during the early stage of diffuse liver lesions (1 to 12 weeks after drug administration in the test group). Apparent diffusion coefficient (ADC) values of liver parenchyma in different stages and pathologic changes were analyzed. Results The process of diffuse hepatic lesions in the test group was classified into three stages according to pathological changes, namely hepatitis, hepatic fibrosis and cirrhosis. No obvious morphological changes were shown by conventional imaging in both groups during this stage. But MR DWI demonstrated heterogeneous signal changes in early stage of hepatic cirrhosis in the test group. No significant change of ADC values was found in the control group between different weeks ( P >0.05). The ADC values of the test group declined from the fifth week, and after the tenth week the ADC values were significantly different between the test and control groups at gradient factor (b) value 300 sec/mm 2 ( P <0.05). At b value 600 and 1000 sec/mm 2, significant difference was seen between the two groups from the sixth week onward. The range of ADC value of the groups was (1.7-0.9)±(0.40-0.04) mm 2/sec (b=600) and (1.38-0.75)±(0.07-0.35) mm 2/sec (b=1000), respectively. Dominant pathological changes included swelled hepatocytes within 1 to 4 weeks after the administration of diethylnitrosamine in the test group, hyperplasia of fibrous tissues in 5-8 weeks and formation of cirrhotic nodules in 9-12 weeks. Conclusions 展开更多
In order to investigate the physical and mechanical properties of sandstone containing fissures after exposure to high temperatures,fissures with different angles α were prefabricated in the plate sandstone samples,a...In order to investigate the physical and mechanical properties of sandstone containing fissures after exposure to high temperatures,fissures with different angles α were prefabricated in the plate sandstone samples,and the processed samples were then heated at 5 different temperatures.Indoor uniaxial compression was conducted to analyze the change rules of physical properties of sandstone after exposure to high temperature,and the deformation,strength and failure characteristics of sandstone containing fissures.The results show that,with increasing temperature,the volume of sandstone increases gradually while the quality and density decrease gradually,and the color of sandstone remains basically unchanged while the brightness increases markedly when the temperature is higher than 585 ℃;the peak strength of sandstone containing fissures first decreases then increases when the temperature is between 25℃and 400℃.The peak strain of sandstone containing fissures increases gradually while the average modulus decreases gradually with increasing temperature,and the mechanical properties of sandstone show obvious deterioration after 400 ℃.The peak strain of sandstone containing fissures increases gradually while the average modulus decreases gradually with increasing temperature;with increasing angle αof the fissure,the evolution characteristics of the macro-mechanical parameters of sandstone are closely related to the their own mechanical properties.When the temperature is 800 ℃,the correlation between the peak strength and average modulus of sandstone and the angle α of the fissure is obviously weakened.The failure modes of sandstone containing fissures after high temperature exposure are of three different kinds including:tensile crack failure,tensile and shear cracks mixed failure,and shear crack failure.Tensile and shear crack mixed failure occur mainly at low temperatures and small angles;tensile crack failure occurs at high temperatures and large angles.展开更多
Polarization and conductance losses are the fundamental dielectric attenuation mechanisms for graphene-based absorbers, but it is not fully understood in revealing the loss mechanism of affect graphene itself. For the...Polarization and conductance losses are the fundamental dielectric attenuation mechanisms for graphene-based absorbers, but it is not fully understood in revealing the loss mechanism of affect graphene itself. For the first time, the reduced graphene oxide(RGO) based absorbers are developed with regulatory absorption properties and the absorption mechanism of RGO is mainly originated from the carrier injection behavior of trace metal Fe nanosheets on graphene. Accordingly, the minimum reflection loss(RLmin) of Fe/RGO-2composite reaches-53.38 dB(2.45 mm), and the effective absorption bandwidth achieves 7.52 GHz(2.62 mm) with lower filling loading of 2 wt%. Using off-axis electron hologram testing combined with simulation calculation and carrier transport property experiments, we demonstrate here the carrier injection behavior from Fe to graphene at the interface and the induced charge accumulation and rearrangement, resulting in the increased interfacial and dipole polarization and the conductance loss. This work has confirmed that regulating the dielectric property of graphene itself by adding trace metals can not only ensure good impedance matching, but also fully exploit the dielectric loss ability of graphene at low filler content,which opens up an efficient way for designing lightweight absorbers and may be extended to other types materials.展开更多
In this paper,a hybrid integrated broadband Doherty power amplifier(DPA)based on a multi-chip module(MCM),whose active devices are fabricated using the gallium nitride(GaN)process and whose passive circuits are fabric...In this paper,a hybrid integrated broadband Doherty power amplifier(DPA)based on a multi-chip module(MCM),whose active devices are fabricated using the gallium nitride(GaN)process and whose passive circuits are fabricated using the gallium arsenide(GaAs)integrated passive device(IPD)process,is proposed for 5G massive multiple-input multiple-output(MIMO)application.An inverted DPA structure with a low-Q output network is proposed to achieve better bandwidth performance,and a single-driver architecture is adopted for a chip with high gain and small area.The proposed DPA has a bandwidth of 4.4-5.0 GHz that can achieve a saturation of more than 45.0 dBm.The gain compression from 37 dBm to saturation power is less than 4 dB,and the average power-added efficiency(PAE)is 36.3%with an 8.5 dB peak-to-average power ratio(PAPR)in 4.5-5.0 GHz.The measured adjacent channel power ratio(ACPR)is better than50 dBc after digital predistortion(DPD),exhibiting satisfactory linearity.展开更多
In this context,we experimentally studied the anisotropic mechanical behaviors of rough-walled plaster joints using a servo-controlled direct shear apparatus under both constant normal load(CNL)and constant normal sti...In this context,we experimentally studied the anisotropic mechanical behaviors of rough-walled plaster joints using a servo-controlled direct shear apparatus under both constant normal load(CNL)and constant normal stiffness(CNS)conditions.The shear-induced variations in the normal displacement,shear stress,normal stress and sheared-off asperity mass are analyzed and correlated with the inclination angle of the critical waviness of joint surfaces.The results show that CNS condition gives rise to a smaller normal displacement due to the larger normal stress during shearing,compared with CNL condition.Under CNL conditions,there is one peak shear stress during shearing,whereas there are no peak shear stress for some cases and two peaks for other cases under CNS conditions depending on the geometry of joint surfaces.The inclination angle of the critical waviness has been verified to be capable of describing the joint surface roughness and anisotropy.The joint surface is more significantly damaged under CNS conditions than that under CNL conditions.With increment of the inclination angle of the critical waviness,both the normal displaceme nt and shea red-off asperity mass increase,following power law functions;yet the coefficient of deternination under CNL conditions is larger than that under CNS conditions.This is because the CNS condition significantly decreases the inclination angle of the critical waviness during shearing due to the larger degree of asperity degradation.展开更多
It is important to study the dilatancy property of water-saturated rock for understanding the engineering behavior of loaded rock mass. This study carried out the uniaxial and triaxial compressive experiments on the w...It is important to study the dilatancy property of water-saturated rock for understanding the engineering behavior of loaded rock mass. This study carried out the uniaxial and triaxial compressive experiments on the water-saturated red sandstone, analyzed the influences of confining pressure and pore pressure on dilatancy property of water-saturated rock, and discussed the reasonable basis of the stress of dilatancy onset as a strength design parameter of rock engineering, finally established the prediction model of the stress of dilatancy onset under the impacts of confining pressure and pore pressure. The results show that the strength parameters(the stress of dilatancy onset and peak strength) and deformation parameters(axial strain and circumferential strain) of water-saturated sandstone increase with the confining pressure, and the relations can be fitted with a positive linear function. The cohesion and internal friction angle obtained from the stress of dilatancy onset decrease by 11.57% and 7.33%, respectively, when compared with those obtained from the peak strength. The strength parameters and deformation parameters of water-saturated sandstone decrease basically with the increase of pore pressure, in which the relations between strength parameters or axial strain and pore pressure can be fitted with a negative linear function. However, the relation between the peak circumferential strain and the pore pressure should be characterized by a negative exponential function, and the circumferential strain at dilatancy onset isn't affected by the pore pressure.展开更多
In this paper,the images of tunnel surface are obtained by tunnel lining rapid inspection system,and tunnel crack forest dataset(TCFD)is established.The disaster characteristics of tunnel cracks are analyzed and summa...In this paper,the images of tunnel surface are obtained by tunnel lining rapid inspection system,and tunnel crack forest dataset(TCFD)is established.The disaster characteristics of tunnel cracks are analyzed and summarized.Solutions of tunnel crack segmentation(TCS)method are developed for the detection and recognition of cracks on tunnel lining.According to the image features of the tunnel lining and the optical principal of detection equipment,effective image pre-processing steps are carried out before crack extraction.The tunnel image of TCFD is divided into appropriate number of blocks to magnify the local features of tunnel cracks.Local threshold segmentation method is used to traverse the blocks successively,and the first target block with crack is obtained.The seed in the target block were obtained by adaptive localization method and mapped to the whole image.Region growing is performed through crack seed until complete tunnel crack is extracted.The results show that the precision,recall rate and F-measure of tunnel cracks under the TCS method can reach 92.58%,93.07%and 92.82%without strong interference.According to the binary images processed by TCS method,the projection images of different types of tunnel cracks and their respective laws are obtained.Furthermore,the TCS method is implemented and deployed as a GUI software application.展开更多
Childhood is the key stage for the development of physical and mental health in the life cycle.The nutritional and health status of childhood are not only related to adulthood health,but also have effects on the long-...Childhood is the key stage for the development of physical and mental health in the life cycle.The nutritional and health status of childhood are not only related to adulthood health,but also have effects on the long-term development of the country.Along with the rapid transitions in dietary patterns and lifestyle,the prevalence of childhood obesity in China showed an astonishing growing trend in the past few decades.Obesity is a kind of disease,moreover,it is the risk factor for a variety of chronic diseases.Obesity is a serious threat to people's health and brings huge social and economic burden.It is necessary to take effective measures to prevent and control childhood obesity.International organizations and many countries have formulated policies and launched projects to prevent and control obesity.In China,series of outline,guidance,blueprint,plans and projects has been developed and released,such as the Outline of the Programme for Food and Nutrition Development in China (2014-2020),Blueprint of Healthy China 2030,National Nutrition Plan (2017-2030),Healthy Lifestyle Campaign for All,and so on.Improving the obesogenic environment needs world cooperation:international economic agreements and policies should be formulated to prevent and control obesity;obesity prevention and control should be integrated into all policies to improve the obesogenic environment;mechanism with the lead of government,the cooperation of multisector and the engagement of public should be established;national childhood obesity surveillance system should be improved;actions to prevention and control of obesity should be initiated in early stage of life and impetrated in all life cycle;and three-tiered prevention for childhood obesity should be implemented.展开更多
<div style="text-align:justify;"> Based on the cohesive zone model, the 2D mesostructures were developed for numerical studies of multi-phase hooked-end steel fiber reinforced concrete under uniaxial c...<div style="text-align:justify;"> Based on the cohesive zone model, the 2D mesostructures were developed for numerical studies of multi-phase hooked-end steel fiber reinforced concrete under uniaxial compression. The zero-thickness cohesive interface elements were inserted within the mortar, on interfaces of mortar and aggregates and interfaces of mortar and fibers to simulate the failure process of fiber reinforced concrete. The results showed that the numerical results matched well the experimental results in both failure modes and stress-strain behavior. Hooked-end steel fiber reinforced concrete exhibited ductile failure and maintained integrity during a whole failure process. Compared with normal concrete, HES fiber reinforced concrete was greater stiffness and compressive strength;the descending branch of the stress-strain curve was significantly flatter;the residual stress was higher. </div>展开更多
In this paper,the Joule–Thomson expansion of the higher dimensional nonlinearly anti-de Sitter(Ad S)black hole with power Maxwell invariant source is investigated.The results show the Joule–Thomson coefficient has a...In this paper,the Joule–Thomson expansion of the higher dimensional nonlinearly anti-de Sitter(Ad S)black hole with power Maxwell invariant source is investigated.The results show the Joule–Thomson coefficient has a zero point and a divergent point,which coincide with the inversion temperature Tiand the zero point of the Hawking temperature,respectively.The inversion temperature increases monotonously with inversion pressure.For the high-pressure region,the inversion temperature decreases with the dimensionality D and the nonlinearity parameter s,whereas it increases with the charge Q.However,Tifor the low-pressure region increase with D and s,while it decreases with Q.The ratioηBHbetween the minimum inversion temperature and the critical temperature does not depend on Q,it recovers the higher dimensional Reissner–N?rdstrom Ad S black hole case when s=1.However,for s>1,it becomes smaller and smaller as D increases and approaches a constant when D→∞.Finally,we found that an increase of mass M and s,or reducing the charge Q and D can enhance the isenthalpic curve,and the effect of s on the isenthalpic curve is much greater than other parameters.展开更多
Along with the transitions of social and economic development,dietary patterns and physical activity and life-styles,the prevalence of childhood overweight and obesity has increased at an astonishing rate in the past ...Along with the transitions of social and economic development,dietary patterns and physical activity and life-styles,the prevalence of childhood overweight and obesity has increased at an astonishing rate in the past decades,and has become one of the most serious public health challenges.Meanwhile,the stunting rate has declined with slowly pace,while millions of young lives are still be threatened by wasting all over the word.The present situation of Double Burden of Malnutrition should be recognized clearly and addressed seriously,which refers to,the common presence of both obesity and underweight in the same populations,communities and even families.In order to provide guidance on the appropriate assessment and management of infants and children presenting to primary health-care facilities,to reduce the risk of overweight and obesity among children,the Guideline Assessing and Managing Children at Primary Healthcare Facilities to Prevent Overweight and Obesity in the Context of the Double Burden of Malnutrition was developed and released by WHO in 2017 using the procedures outlined in the WHO handbook for guideline development.The WHO Guideline(2017)is intended primarily for use in low-and medium-resource settings where both under-nutrition and obesity are prevalent.In this guideline,there are three prioritized speci c areas and questions for infants and children presenting to primary health-care facilities:anthropometric assessment,care of infants and children with acute or chronic malnutrition,and care of children who are overweight or obese.It is recommended that for infants and children aged<5 years presenting primary health-care facilities,weight and length/height should be measured and evaluate adequately,general nutrition and physical activity counselling should be provided for related caregivers and families,identi cation and appropriate management plan should be developed at primary health-care level.The discrepancies of the recommendation on the three prioritized areas in di erent guidelines are compar展开更多
Haptic(vibration)information expression is an effective human-computer interaction mode and information transfer method.It makes up shortcomings of sound under certain conditions and is an important channel of informa...Haptic(vibration)information expression is an effective human-computer interaction mode and information transfer method.It makes up shortcomings of sound under certain conditions and is an important channel of information transfer for route guidance field.As a special kind of walkers,the visually impaired pedestrians have a specific type of cognition or perception of route guidance environment(including spatial orientation,distance and walking speed etc.)and they have sharp sense of touch resources form the ordinary.This work integrated application of GPS,GIS and Haptic(vibration)technology to develop more reliable mode route guidance for the visually impaired.It provides different vibration to the user under two circumstances:key nodes of roads ahead and deviation planning path.It resists environmental noise,reflects timely and has high effectiveness.Based on Google Legend phone,we developed the prototype and realized the designed functions,and verified the effectiveness of the system.We initially determined the thresholds of deviating from the path,those at road junctions and other nodes through experiments,interviews etc.And we used the thresholds for experiments testing and guiding.Then they were inspected,corrected and improved in the field practice.Finally,more reasonable thresholds were drawn out for future applications in reality.展开更多
Sodium fulvic acid based hierarchical porous carbons(SFA-HPCs) with a specific surface area of 1919 m^2·g^(–1) and total volume of 1.7 cm^3·g^(–1) has been synthesized by a simple self-template method. The...Sodium fulvic acid based hierarchical porous carbons(SFA-HPCs) with a specific surface area of 1919 m^2·g^(–1) and total volume of 1.7 cm^3·g^(–1) has been synthesized by a simple self-template method. The carbon skeleton can be formatted by the decomposition process of sodium fulvic acid(SFA) in a N_2 atmosphere. The sodium compund in SFA is used as a self-template to create the hierarchical porous structure. The unique hierarchical structure of SFA-HPCs provides an efficient pathway for electrolyte ions to be diffused into the internal surfaces of bulk electrode particles. It results in a high charge storage capacitance of 186 F·g^(–1) at current load of 40 A·g^(–1). The capacitance of 230 F·g^(–1) at 0.05 A·g^(–1) and 186 F·g^(–1) at 40 A·g^(–1) show its good rate capability. Besides, it also achieves desirable cycling stability, 99.4% capacitance remained after 10000 cycles at 40 A·g^(–1).展开更多
Among email forwards, the Internet and misinformed friends and relatives, it＇s become harder than ever to separate health fact from fiction. Whatever their origins, misleading health ＂hearsays＂ can cause unnecessar...Among email forwards, the Internet and misinformed friends and relatives, it＇s become harder than ever to separate health fact from fiction. Whatever their origins, misleading health ＂hearsays＂ can cause unnecessary anxiety and distract you from wellness habits, which truly deserve your time and energy. Recently, some people have claimed juice fasting （also known as juice cleansing）, a fad diet in which a person consumes only fruit and vegetable juice, while otherwise abstaining from food consumption, has many miraculous health benefits. For example, the people say the diet not only helps remove toxins from your body, it also helps you slim down in a short time. In this edition, Ma explains why the ＂medical fairy tale＂ is unreliable.展开更多
文摘Background The diagnosis of diffuse hepatic lesions in early stage is a tough task at any time for clinical conventional imaging. Magnetic resonance diffusion-weighted imaging (MR DWI) can detect the changes of tissue structure at molecular level. This study was designed to determine the value of DWI in the diagnosis of diffuse liver lesions in early stage. Methods Diffuse liver lesions were induced by diethylnitrosamine in 42 rats of test group. Fourteen rats in control group were fed with pure water. Dynamic changes of MR DWI were observed every week in both groups during the early stage of diffuse liver lesions (1 to 12 weeks after drug administration in the test group). Apparent diffusion coefficient (ADC) values of liver parenchyma in different stages and pathologic changes were analyzed. Results The process of diffuse hepatic lesions in the test group was classified into three stages according to pathological changes, namely hepatitis, hepatic fibrosis and cirrhosis. No obvious morphological changes were shown by conventional imaging in both groups during this stage. But MR DWI demonstrated heterogeneous signal changes in early stage of hepatic cirrhosis in the test group. No significant change of ADC values was found in the control group between different weeks ( P >0.05). The ADC values of the test group declined from the fifth week, and after the tenth week the ADC values were significantly different between the test and control groups at gradient factor (b) value 300 sec/mm 2 ( P <0.05). At b value 600 and 1000 sec/mm 2, significant difference was seen between the two groups from the sixth week onward. The range of ADC value of the groups was (1.7-0.9)±(0.40-0.04) mm 2/sec (b=600) and (1.38-0.75)±(0.07-0.35) mm 2/sec (b=1000), respectively. Dominant pathological changes included swelled hepatocytes within 1 to 4 weeks after the administration of diethylnitrosamine in the test group, hyperplasia of fibrous tissues in 5-8 weeks and formation of cirrhotic nodules in 9-12 weeks. Conclusions
基金supported by the State Key Development Program for Basic Research of China(No.2013CB036003)the National Natural Science Foundation of China(No.51374198)the CUMT Innovation and Entrepreneurship Fund for Undergraduates(No.201509)
文摘In order to investigate the physical and mechanical properties of sandstone containing fissures after exposure to high temperatures,fissures with different angles α were prefabricated in the plate sandstone samples,and the processed samples were then heated at 5 different temperatures.Indoor uniaxial compression was conducted to analyze the change rules of physical properties of sandstone after exposure to high temperature,and the deformation,strength and failure characteristics of sandstone containing fissures.The results show that,with increasing temperature,the volume of sandstone increases gradually while the quality and density decrease gradually,and the color of sandstone remains basically unchanged while the brightness increases markedly when the temperature is higher than 585 ℃;the peak strength of sandstone containing fissures first decreases then increases when the temperature is between 25℃and 400℃.The peak strain of sandstone containing fissures increases gradually while the average modulus decreases gradually with increasing temperature,and the mechanical properties of sandstone show obvious deterioration after 400 ℃.The peak strain of sandstone containing fissures increases gradually while the average modulus decreases gradually with increasing temperature;with increasing angle αof the fissure,the evolution characteristics of the macro-mechanical parameters of sandstone are closely related to the their own mechanical properties.When the temperature is 800 ℃,the correlation between the peak strength and average modulus of sandstone and the angle α of the fissure is obviously weakened.The failure modes of sandstone containing fissures after high temperature exposure are of three different kinds including:tensile crack failure,tensile and shear cracks mixed failure,and shear crack failure.Tensile and shear crack mixed failure occur mainly at low temperatures and small angles;tensile crack failure occurs at high temperatures and large angles.
基金supported by National Natural Science Foundation of China (NSFC 52372041, 52302087, 51772060, 51672059 and 51621091)Heilongjiang Touyan Team Program+1 种基金the Fundamental Research Funds for the Central Universities (Grant No. HIT.OCEF.2021003)the Shanghai Aerospace Science and Technology Innovation Fund (SAST2022-60)。
文摘Polarization and conductance losses are the fundamental dielectric attenuation mechanisms for graphene-based absorbers, but it is not fully understood in revealing the loss mechanism of affect graphene itself. For the first time, the reduced graphene oxide(RGO) based absorbers are developed with regulatory absorption properties and the absorption mechanism of RGO is mainly originated from the carrier injection behavior of trace metal Fe nanosheets on graphene. Accordingly, the minimum reflection loss(RLmin) of Fe/RGO-2composite reaches-53.38 dB(2.45 mm), and the effective absorption bandwidth achieves 7.52 GHz(2.62 mm) with lower filling loading of 2 wt%. Using off-axis electron hologram testing combined with simulation calculation and carrier transport property experiments, we demonstrate here the carrier injection behavior from Fe to graphene at the interface and the induced charge accumulation and rearrangement, resulting in the increased interfacial and dipole polarization and the conductance loss. This work has confirmed that regulating the dielectric property of graphene itself by adding trace metals can not only ensure good impedance matching, but also fully exploit the dielectric loss ability of graphene at low filler content,which opens up an efficient way for designing lightweight absorbers and may be extended to other types materials.
基金supported in part by the National Key Research and Development Program of China(2021YFA0716601)the National Science Fund(62225111).
文摘In this paper,a hybrid integrated broadband Doherty power amplifier(DPA)based on a multi-chip module(MCM),whose active devices are fabricated using the gallium nitride(GaN)process and whose passive circuits are fabricated using the gallium arsenide(GaAs)integrated passive device(IPD)process,is proposed for 5G massive multiple-input multiple-output(MIMO)application.An inverted DPA structure with a low-Q output network is proposed to achieve better bandwidth performance,and a single-driver architecture is adopted for a chip with high gain and small area.The proposed DPA has a bandwidth of 4.4-5.0 GHz that can achieve a saturation of more than 45.0 dBm.The gain compression from 37 dBm to saturation power is less than 4 dB,and the average power-added efficiency(PAE)is 36.3%with an 8.5 dB peak-to-average power ratio(PAPR)in 4.5-5.0 GHz.The measured adjacent channel power ratio(ACPR)is better than50 dBc after digital predistortion(DPD),exhibiting satisfactory linearity.
基金partially funded by National Natural Science Foundation of China(Grant Nos.51979272 and 51709260)State Key Laboratory for Geomechanics and Deep Underground Engineering,China University of Mining and Technology,China(Grant No.SKLGDUEK1906)。
文摘In this context,we experimentally studied the anisotropic mechanical behaviors of rough-walled plaster joints using a servo-controlled direct shear apparatus under both constant normal load(CNL)and constant normal stiffness(CNS)conditions.The shear-induced variations in the normal displacement,shear stress,normal stress and sheared-off asperity mass are analyzed and correlated with the inclination angle of the critical waviness of joint surfaces.The results show that CNS condition gives rise to a smaller normal displacement due to the larger normal stress during shearing,compared with CNL condition.Under CNL conditions,there is one peak shear stress during shearing,whereas there are no peak shear stress for some cases and two peaks for other cases under CNS conditions depending on the geometry of joint surfaces.The inclination angle of the critical waviness has been verified to be capable of describing the joint surface roughness and anisotropy.The joint surface is more significantly damaged under CNS conditions than that under CNL conditions.With increment of the inclination angle of the critical waviness,both the normal displaceme nt and shea red-off asperity mass increase,following power law functions;yet the coefficient of deternination under CNL conditions is larger than that under CNS conditions.This is because the CNS condition significantly decreases the inclination angle of the critical waviness during shearing due to the larger degree of asperity degradation.
基金supported by the National Natural Science Foundation of China (Nos. 51404266 and 11502229)the National Program on Key Basic Research Project of China (No. 2013CB227900)
文摘It is important to study the dilatancy property of water-saturated rock for understanding the engineering behavior of loaded rock mass. This study carried out the uniaxial and triaxial compressive experiments on the water-saturated red sandstone, analyzed the influences of confining pressure and pore pressure on dilatancy property of water-saturated rock, and discussed the reasonable basis of the stress of dilatancy onset as a strength design parameter of rock engineering, finally established the prediction model of the stress of dilatancy onset under the impacts of confining pressure and pore pressure. The results show that the strength parameters(the stress of dilatancy onset and peak strength) and deformation parameters(axial strain and circumferential strain) of water-saturated sandstone increase with the confining pressure, and the relations can be fitted with a positive linear function. The cohesion and internal friction angle obtained from the stress of dilatancy onset decrease by 11.57% and 7.33%, respectively, when compared with those obtained from the peak strength. The strength parameters and deformation parameters of water-saturated sandstone decrease basically with the increase of pore pressure, in which the relations between strength parameters or axial strain and pore pressure can be fitted with a negative linear function. However, the relation between the peak circumferential strain and the pore pressure should be characterized by a negative exponential function, and the circumferential strain at dilatancy onset isn't affected by the pore pressure.
基金This research is supported by the Fundamental Research Funds for the Central Universities,China(300102120301)Natural Science Basic Research Plan in Shaanxi Province of China(2021JQ-216)Scientific Innovation Practice Project of Postgraduates of Chang'an University(300103714017).
文摘In this paper,the images of tunnel surface are obtained by tunnel lining rapid inspection system,and tunnel crack forest dataset(TCFD)is established.The disaster characteristics of tunnel cracks are analyzed and summarized.Solutions of tunnel crack segmentation(TCS)method are developed for the detection and recognition of cracks on tunnel lining.According to the image features of the tunnel lining and the optical principal of detection equipment,effective image pre-processing steps are carried out before crack extraction.The tunnel image of TCFD is divided into appropriate number of blocks to magnify the local features of tunnel cracks.Local threshold segmentation method is used to traverse the blocks successively,and the first target block with crack is obtained.The seed in the target block were obtained by adaptive localization method and mapped to the whole image.Region growing is performed through crack seed until complete tunnel crack is extracted.The results show that the precision,recall rate and F-measure of tunnel cracks under the TCS method can reach 92.58%,93.07%and 92.82%without strong interference.According to the binary images processed by TCS method,the projection images of different types of tunnel cracks and their respective laws are obtained.Furthermore,the TCS method is implemented and deployed as a GUI software application.
文摘Childhood is the key stage for the development of physical and mental health in the life cycle.The nutritional and health status of childhood are not only related to adulthood health,but also have effects on the long-term development of the country.Along with the rapid transitions in dietary patterns and lifestyle,the prevalence of childhood obesity in China showed an astonishing growing trend in the past few decades.Obesity is a kind of disease,moreover,it is the risk factor for a variety of chronic diseases.Obesity is a serious threat to people's health and brings huge social and economic burden.It is necessary to take effective measures to prevent and control childhood obesity.International organizations and many countries have formulated policies and launched projects to prevent and control obesity.In China,series of outline,guidance,blueprint,plans and projects has been developed and released,such as the Outline of the Programme for Food and Nutrition Development in China (2014-2020),Blueprint of Healthy China 2030,National Nutrition Plan (2017-2030),Healthy Lifestyle Campaign for All,and so on.Improving the obesogenic environment needs world cooperation:international economic agreements and policies should be formulated to prevent and control obesity;obesity prevention and control should be integrated into all policies to improve the obesogenic environment;mechanism with the lead of government,the cooperation of multisector and the engagement of public should be established;national childhood obesity surveillance system should be improved;actions to prevention and control of obesity should be initiated in early stage of life and impetrated in all life cycle;and three-tiered prevention for childhood obesity should be implemented.
文摘<div style="text-align:justify;"> Based on the cohesive zone model, the 2D mesostructures were developed for numerical studies of multi-phase hooked-end steel fiber reinforced concrete under uniaxial compression. The zero-thickness cohesive interface elements were inserted within the mortar, on interfaces of mortar and aggregates and interfaces of mortar and fibers to simulate the failure process of fiber reinforced concrete. The results showed that the numerical results matched well the experimental results in both failure modes and stress-strain behavior. Hooked-end steel fiber reinforced concrete exhibited ductile failure and maintained integrity during a whole failure process. Compared with normal concrete, HES fiber reinforced concrete was greater stiffness and compressive strength;the descending branch of the stress-strain curve was significantly flatter;the residual stress was higher. </div>
基金supported in part by the National Natural Science Foundation of China(Grant Nos.11847048,11947128 and 11947018)the Fundamental Research Funds of China West Normal University(Grant Nos.20B009,17E093 and 18Q067)。
文摘In this paper,the Joule–Thomson expansion of the higher dimensional nonlinearly anti-de Sitter(Ad S)black hole with power Maxwell invariant source is investigated.The results show the Joule–Thomson coefficient has a zero point and a divergent point,which coincide with the inversion temperature Tiand the zero point of the Hawking temperature,respectively.The inversion temperature increases monotonously with inversion pressure.For the high-pressure region,the inversion temperature decreases with the dimensionality D and the nonlinearity parameter s,whereas it increases with the charge Q.However,Tifor the low-pressure region increase with D and s,while it decreases with Q.The ratioηBHbetween the minimum inversion temperature and the critical temperature does not depend on Q,it recovers the higher dimensional Reissner–N?rdstrom Ad S black hole case when s=1.However,for s>1,it becomes smaller and smaller as D increases and approaches a constant when D→∞.Finally,we found that an increase of mass M and s,or reducing the charge Q and D can enhance the isenthalpic curve,and the effect of s on the isenthalpic curve is much greater than other parameters.
文摘Along with the transitions of social and economic development,dietary patterns and physical activity and life-styles,the prevalence of childhood overweight and obesity has increased at an astonishing rate in the past decades,and has become one of the most serious public health challenges.Meanwhile,the stunting rate has declined with slowly pace,while millions of young lives are still be threatened by wasting all over the word.The present situation of Double Burden of Malnutrition should be recognized clearly and addressed seriously,which refers to,the common presence of both obesity and underweight in the same populations,communities and even families.In order to provide guidance on the appropriate assessment and management of infants and children presenting to primary health-care facilities,to reduce the risk of overweight and obesity among children,the Guideline Assessing and Managing Children at Primary Healthcare Facilities to Prevent Overweight and Obesity in the Context of the Double Burden of Malnutrition was developed and released by WHO in 2017 using the procedures outlined in the WHO handbook for guideline development.The WHO Guideline(2017)is intended primarily for use in low-and medium-resource settings where both under-nutrition and obesity are prevalent.In this guideline,there are three prioritized speci c areas and questions for infants and children presenting to primary health-care facilities:anthropometric assessment,care of infants and children with acute or chronic malnutrition,and care of children who are overweight or obese.It is recommended that for infants and children aged<5 years presenting primary health-care facilities,weight and length/height should be measured and evaluate adequately,general nutrition and physical activity counselling should be provided for related caregivers and families,identi cation and appropriate management plan should be developed at primary health-care level.The discrepancies of the recommendation on the three prioritized areas in di erent guidelines are compar
文摘Haptic(vibration)information expression is an effective human-computer interaction mode and information transfer method.It makes up shortcomings of sound under certain conditions and is an important channel of information transfer for route guidance field.As a special kind of walkers,the visually impaired pedestrians have a specific type of cognition or perception of route guidance environment(including spatial orientation,distance and walking speed etc.)and they have sharp sense of touch resources form the ordinary.This work integrated application of GPS,GIS and Haptic(vibration)technology to develop more reliable mode route guidance for the visually impaired.It provides different vibration to the user under two circumstances:key nodes of roads ahead and deviation planning path.It resists environmental noise,reflects timely and has high effectiveness.Based on Google Legend phone,we developed the prototype and realized the designed functions,and verified the effectiveness of the system.We initially determined the thresholds of deviating from the path,those at road junctions and other nodes through experiments,interviews etc.And we used the thresholds for experiments testing and guiding.Then they were inspected,corrected and improved in the field practice.Finally,more reasonable thresholds were drawn out for future applications in reality.
基金supported by the Ningbo’s Industrial Technology Innovation and Industrialization of Scientific and Technological Achievements Program(2013B6003)
文摘Sodium fulvic acid based hierarchical porous carbons(SFA-HPCs) with a specific surface area of 1919 m^2·g^(–1) and total volume of 1.7 cm^3·g^(–1) has been synthesized by a simple self-template method. The carbon skeleton can be formatted by the decomposition process of sodium fulvic acid(SFA) in a N_2 atmosphere. The sodium compund in SFA is used as a self-template to create the hierarchical porous structure. The unique hierarchical structure of SFA-HPCs provides an efficient pathway for electrolyte ions to be diffused into the internal surfaces of bulk electrode particles. It results in a high charge storage capacitance of 186 F·g^(–1) at current load of 40 A·g^(–1). The capacitance of 230 F·g^(–1) at 0.05 A·g^(–1) and 186 F·g^(–1) at 40 A·g^(–1) show its good rate capability. Besides, it also achieves desirable cycling stability, 99.4% capacitance remained after 10000 cycles at 40 A·g^(–1).
文摘Among email forwards, the Internet and misinformed friends and relatives, it＇s become harder than ever to separate health fact from fiction. Whatever their origins, misleading health ＂hearsays＂ can cause unnecessary anxiety and distract you from wellness habits, which truly deserve your time and energy. Recently, some people have claimed juice fasting （also known as juice cleansing）, a fad diet in which a person consumes only fruit and vegetable juice, while otherwise abstaining from food consumption, has many miraculous health benefits. For example, the people say the diet not only helps remove toxins from your body, it also helps you slim down in a short time. In this edition, Ma explains why the ＂medical fairy tale＂ is unreliable.
