The Norwegian Public Roads Administration(NPRA) is planning for an upgrade of the E39 highway route at the westcoast of Norway. Fixed links shall replace ferries at seven fjord crossings. Wide spans and large depths a...The Norwegian Public Roads Administration(NPRA) is planning for an upgrade of the E39 highway route at the westcoast of Norway. Fixed links shall replace ferries at seven fjord crossings. Wide spans and large depths at the crossings combined with challenging subsea topography and environmental loads call for an extension of existing practice. A variety of bridge concepts are evaluated in the feasibility study. The structures will experience significant loads from deadweight, traffic and environment. Anchoring of these forces is thus one of the challenges met in the project. Large-size subsea rock anchors are considered a viable alternative. These can be used for anchoring of floating structures but also with the purpose of increasing capacity of fixed structures. This paper presents first a thorough study of factors affecting rock anchor bond capacity. Laboratory testing of rock anchors subjected to cyclic loading is thereafter presented. Finally, the paper presents a model predicting the capacity of a rock anchor segment, in terms of a ribbed bar, subjected to a cyclic load history. The research assumes a failure mode occurring in the interface between the rock anchor and the surrounding grout. The constitutive behavior of the bonding interface is investigated for anchors subjected to cyclic one-way tensile loads. The model utilizes the static bond capacity curve as a basis, defining the ultimate bond sbuand the slip s1 at τ. A limited number of input parameters are required to apply the model. The model defines the bond-slip behavior with the belonging rock anchor capacity depending on the cyclic load level(τcy/τ), the cyclic load ratio(R= τcy/τcy), and the number of load cycles(N). The constitutive model is intended to model short anchor lengths representing an incremental length of a complete rock anchor.展开更多
Acute respiratory tract infection</span><span style="font-family:""><span style="font-family:Verdana;"> (ARTI) in children is the most common infectious disease in childhood,...Acute respiratory tract infection</span><span style="font-family:""><span style="font-family:Verdana;"> (ARTI) in children is the most common infectious disease in childhood, and its pathogens include viruses, bacteria and fungi, mycoplasma, chlamydia and rickettsia. In recent years, with the continuous development of pathogen detection methods, the diagnosis and treatment of acute respiratory infections has received more and more clinical attention. The clinical diagnosis and treatment characteristics of acute respira</span><span style="font-family:Verdana;">tory infections in children and the research of clinical laboratory detection </span><span style="font-family:Verdana;">methods have also been continuously developed. The author collected refer</span><span style="font-family:Verdana;">ences to review the clinical features and new developments in laboratory</span><span style="font-family:Verdana;"> testing of acute respiratory tract infection in children.展开更多
Recently a research team at Ohio University,USA,conducted a unique full-scale feld load test to simulate the aeration pipe installations at a copper extraction mine operated in Chile.The overliner material taken from ...Recently a research team at Ohio University,USA,conducted a unique full-scale feld load test to simulate the aeration pipe installations at a copper extraction mine operated in Chile.The overliner material taken from the mine was used in recreating the in situ conditions.Electric heaters were utilized to raise the temperature inside each pipe to simulate the essential element of the copper extraction process.The maximum vertical deflection reached by the test pipes was close to 20%,when the simulated heap pile height was 80 m.The plastic pipes and the overliner material were also tested in the laboratory.Based on the results,the maximum heap pile fll depth was recommended for the aeration system.The results indicated that the vertical deflection was the primary performance index for the aeration pipes installed in heap piles at mines.Lastly,the pipe made of polypropylene resin was super.展开更多
Acute respiratory infection in children (ARTI) is the most common childhood infectious disease, and its pathogens include bacteria, fungi, viruses, chlamydia, mycoplasma and rickettsia. In recent years, with the conti...Acute respiratory infection in children (ARTI) is the most common childhood infectious disease, and its pathogens include bacteria, fungi, viruses, chlamydia, mycoplasma and rickettsia. In recent years, with the continuous development of pathogen detection methods, the diagnosis and treatment of acute respiratory infections has received more and more attention from clinicians. The clinical diagnosis and treatment of acute respiratory infections in children and the research of laboratory detection methods have also been continuously developed. The manuscript presents a review of progress in the clinical diagnosis, treatment and laboratory testing of acute respiratory infections in children by collecting references.展开更多
The compelling case report by Xie et al,published in a renowned medical journal,is an excellent example of meticulous clinical evaluation,comprehensive labo-ratory testing,advanced imaging,and genetic analysis.The aut...The compelling case report by Xie et al,published in a renowned medical journal,is an excellent example of meticulous clinical evaluation,comprehensive labo-ratory testing,advanced imaging,and genetic analysis.The authors identified novel compound heterozygous mutations in the hemojuvelin gene of a patient diagnosed with juvenile hemochromatosis.They suggested that long-term,strategic phlebotomy might offer a novel therapeutic strategy for severe juvenile hemochromatosis,challenging the traditional treatment paradigms.展开更多
Background:Existing hepatocellular carcinoma(HCC)prediction models lack transferability and generalizability when applied to female populations,resulting in diminished performance and inadequate tools for accurate HCC...Background:Existing hepatocellular carcinoma(HCC)prediction models lack transferability and generalizability when applied to female populations,resulting in diminished performance and inadequate tools for accurate HCC risk stratification among females.This study aims to develop and validate a score-based prediction model for early detection of HCC in female hepatitis B surface antigen(HBsAg)carriers.Methods:Participants were recruited from a multicenter prospective cohort engaged in liver cancer screening across China including seven high-risk rural areas and one additional high-risk rural area.The study involved 7080 females as the derivation cohort and 2069 as the validation cohort,with all participants aged 35-70 years and HBsAg positive.Laboratory tests and epidemiological surveys were conducted.Key predictor variables were identified through LASSO regression analysis,and score-based prediction models were developed based on Cox proportional hazards model.Model performance including discrimination and calibration was evaluated,and compared to existing prediction models and screening strategies.Results:After a median follow-up of 3.69 and 5.42 years,147 and 45 HCC cases were identified in the derivation and validation cohorts,respectively.The female HCC(HCCF)model incorporating five independent variables:age,α-fetoprotein(AFP),albumin,alanine aminotransferase,and platelet,showed excellent performance with an area under the receiver operating characteristic curve(AUC)of 0.82(95%CI:0.78-0.86).The HCCF-Enhanced model which included cirrhosis,achieved an AUC of 0.85(95%CI:0.81-0.89).Both models demonstrated superior predictive performance than existing models,with strong predictive accuracy in the validation cohort:AUCs of 0.83(95%CI:0.77-0.89)and 0.88(95%CI:0.83-0.92),respectively.The HCCF model,at a score threshold of 7,achieved the largest Youden’s index and identified 32.80%of high-risk individuals.When combined with ultrasonography(US),the model detected 37 additional cases,significantly improved screening sensitivity and accuracy compared to the traditional AFP plus US strategy.Conclusions:The developed HCCF models with good performance for HCC prediction in HBsAg-positive females significantly improve screening efficiency and provide an effective tool for surveillance,ultimately helping to optimize prevention and management strategies for HCC.展开更多
Attributed to its superior water-to-solid ratio and quick setting time,the highwater material is widely adopted in underground spaces as a cost-effective and environmentally friendly backfill material.To elucidate the...Attributed to its superior water-to-solid ratio and quick setting time,the highwater material is widely adopted in underground spaces as a cost-effective and environmentally friendly backfill material.To elucidate the bleeding mechanism of high-water material under the high confining pressure,a total of 57 tubular specimens were prepared and tested,critical parameters of which included the water-to-solid ratio,curing time,and lateral confinement pressure.Test results showed that no obvious cracks were observed from the surface of confined highwater material,which is different from that of unconfined high-water material,which featured shear cracks.Moreover,the volume of these confined high-water materials under compaction exhibited a continuous shrinkage associated with the water bleeding.The threshold values of the water bleeding are significantly affected by the water-to-solid ratio,followed by the confining pressure and curing time.When other parameters are constant,the higher confinement is requested for these specimens with a small water-to-solid ratio.Meanwhile,the mass of bleeding water increased with the lateral confinement,showing a quick increase at the initial stage.During the bleeding process,the free water stored in the pores was compacted,the evidence of which is the transformation of the hydration products(calcium aluminate hydrate)from its natural fibrous structure into the rod-shaped or dense agglomerate structures.These research outcomes provide an in-depth insight into the fundamental mechanics of the high-water material under the high lateral confinement when it is used for underground spaces.展开更多
The destabilization of overhanging rock is a dangerous geological problem.In this study,a generalized model of typical overhanging cliffs from the Three Gorges Reservoir area in China with different fracture angles,fr...The destabilization of overhanging rock is a dangerous geological problem.In this study,a generalized model of typical overhanging cliffs from the Three Gorges Reservoir area in China with different fracture angles,fracture lengths,and free surface depths is constructed to investigate the cracking and deformation behavior of overhanging rocks.Laboratory tests and deformation field monitoring using the digital image correlation(DIC)method are performed on these specimens to reproduce the destabilization and failure process of overhanging rock under external loading.The influence of peak load is found to be the most sensitive to the fracture length,followed by the free surface depth,and to be the least sensitive to the fracture angle.The DIC-based strain fields reveal that the fracture angle and free surface depth significantly alter the crack propagation paths,whereas the influence of the fracture length is weaker.These parameters also affect the crack initiation time.The relative displacement evolution characteristics indicate that fracture angle,fracture length,and free surface depth affect the shape and size of the rotating block,the rotation center,and the rotation pivot point and degree,respectively.The grayscale characteristic evolution trends are similar for all examined overhanging rock specimens.The evolution of the grayscale indices based on DIC can be divided into high-frequency oscillation,smooth decline(or smooth downward concavity),and stable development stages.Furthermore,the multistage properties of the indices can be used to identify the fracture state of overhanging rocks,providing a theoretical basis for graded early warning of rockfall disasters.展开更多
This paper presents a method for obtaining the displacement of sand particles in a sand–bentonite mixture(SBM)when saturated with water,based on particle tracking velocimetry(PTV).The raw photographs were first conve...This paper presents a method for obtaining the displacement of sand particles in a sand–bentonite mixture(SBM)when saturated with water,based on particle tracking velocimetry(PTV).The raw photographs were first converted into binary images.The sand particles were then detected,and the displacement of the sand particles was obtained by comparing their positions in adjacent images.The swelling strain induced by saturation was also obtained using the proposed PTV method.This method was validated by comparing the result with those obtained using a displacement transducer.Subsequently,a comparative analysis of sand particle displacements was conducted for specimens with varying bentonite content(BC),initial thickness,and water infiltration directions.The experimental results obtained were as follows:(1)For specimens with different BCs,local swelling displacement of sand particles at the top part of the specimen increased with higher BCs;(2)For specimens with various heights(hsp),larger local swelling displacement was generated at lower hsp at the initial state;(3)Local swelling characteristics differed in different water infiltration directions.Top-side infiltration showed a significant downward movement of particles during the first several hours of swelling.An estimation method for the dry density distribution of the specimen was proposed based on PTV data and then verified by slicing dry density and water content measurement results.展开更多
Dissolution of soluble soil,biodegradation of municipal solid waste(MSW),and internal erosion of gap-graded soil are typical mass loss processes of geomaterials,which result in various engineering problems.These three...Dissolution of soluble soil,biodegradation of municipal solid waste(MSW),and internal erosion of gap-graded soil are typical mass loss processes of geomaterials,which result in various engineering problems.These three processes are conceptually analogous and examined by a unified assessment of their behaviors considering the initial properties of geomaterials and testing conditions.This study collected additional data from twelve soil dissolution tests and five long-term MSW biodegradation tests.We then established a comprehensive mass loss behavior dataset based on the available studies and the supplementary data obtained from this study.In addition to the flow-reactive fraction,two initial volumetric properties are also critical,which are void ratio before mass loss(esolid,0)and inert-to-reactive size ratio.A characteristic parameter(Λ),describing the ratio between the change in voids volume and the change in flow-reactive solids volume,is correlated with the strain and change in esolid.The volumetric and structural changes of all the flow-reactive geomaterials are categorized into Λ=−1 for pseudo-stable,−1≤Λ<0 for collapsible,0≤Λ<esolid,0 for hyper-collapsible,and Λ≥esolid,0 for readily densified.A three-dimensional plot constructed by the three critical initial properties is divided into eight zones based on the differentΛvalues,which correspond to distinct mass loss behaviors.The a priori Λ estimation and corresponding zonation for a wide variety of flow-reactive geomaterials is shown to be beneficial for research and practice.展开更多
Underground mine pillars provide natural stability to the mine area,allowing safe operations for workers and machinery.Extensive prior research has been conducted to understand pillar failure mechanics and design safe...Underground mine pillars provide natural stability to the mine area,allowing safe operations for workers and machinery.Extensive prior research has been conducted to understand pillar failure mechanics and design safe pillar layouts.However,limited studies(mostly based on empirical field observation and small-scale laboratory tests)have considered pillar-support interactions under monotonic loading conditions for the design of pillar-support systems.This study used a series of large-scale laboratory compression tests on porous limestone blocks to analyze rock and support behavior at a sufficiently large scale(specimens with edge length of 0.5 m)for incorporation of actual support elements,with consideration of different w/h ratios.Both unsupported and supported(grouted rebar rockbolt and wire mesh)tests were conducted,and the surface deformations of the specimens were monitored using three-dimensional(3D)digital image correlation(DIC).Rockbolts instrumented with distributed fiber optic strain sensors were used to study rockbolt strain distribution,load mobilization,and localized deformation at different w/h ratios.Both axial and bending strains were observed in the rockbolts,which became more prominent in the post-peak region of the stress-strain curve.展开更多
Thermal damage mechanisms are crucial in reservoir stimulation for enhanced geothermal system(EGS).This study investigates the thermal damage mechanisms in granite samples from the Gonghe Basin,Qinghai,China.The grani...Thermal damage mechanisms are crucial in reservoir stimulation for enhanced geothermal system(EGS).This study investigates the thermal damage mechanisms in granite samples from the Gonghe Basin,Qinghai,China.The granite samples were heated to 400℃ and then cooled in air,water,or liquid nitrogen.The physical and mechanical properties of the thermally treated granite were evaluated,andmicrostructural changes were analyzed using a scanning electron microscope(SEM)and computed tomography(CT).The results indicate that cooling with water and liquid nitrogen significantly enhancespermeability and brittleness while reducing P-wave velocity,strength,and Young's modulus.Specifically,liquid nitrogen cooling increased granite permeability by a factor of 5.24 compared to the untreatedsamples,while reducing compressive strength by 13.6%.After thermal treatment,the failure mode of thegranite shifted from axial splitting to a combination of shear and tension.Microstructural analysisrevealed that liquid nitrogen-cooled samples exhibited greater fracture complexity than those cooledwith water or air.Additionally,acoustic emission(AE)monitoring during damage evolution showed thatliquid nitrogen cooling led to higher cumulative AE energy and a lower maximum AE energy rate,withnumerous AE signals detected during both stable and unstable crack growth.The results suggest thatliquid nitrogen induces a stronger thermal shock,leading to more significant thermal damage andpromoting the development of a complex fracture network during EGS reservoir stimulation.This enhancesboth the heat exchange area and the permeability of the deep hot dry rock(HDR)in EGS reservoirs.The insights from this study contribute to a deeper understanding of thermal damagecharacteristics induced by different cooling media and provide valuable guidance for optimizing deepgeothermal energy extraction.展开更多
To assess the effectiveness of vacuum preloading combined electroosmotic strengthening of ultra-soft soil and study the mechanism of the process, a comprehensive experimental investigation was performed. A laboratory ...To assess the effectiveness of vacuum preloading combined electroosmotic strengthening of ultra-soft soil and study the mechanism of the process, a comprehensive experimental investigation was performed. A laboratory test cell was designed and applied to evaluate the vacuum preloading combined electroosmosis. Several factors were taken into consideration, including the directions of the electroosmotic current and water induced by vacuum preloading and the replenishment of groundwater from the surrounding area. The results indicate that electroosmosis together with vacuum preloading improve the soil strength greatly, with an increase of approximately 60%, and reduce the water content of the soil on the basis of consolidation of vacuum preloading, howeve~ further settlement is not obvious with only 1.7 mm. The reinforcement effect of vacuum preloading combined electroosmosis is better than that of electroosmosis after vacuum preloading. Elemental analysis using X-ray fluorescence proves that the soil strengthening during electroosmotic period in this work is mainly caused by electroosmosis-induced electrochemical reactions, the concentrations of Al2O3 in the VPCEO region increase by 2.2%, 1.5%, and 0.9% at the anode, the midpoint between the electrodes, and the cathode, respectively.展开更多
Pre-stressed bolt anchorage is the key technology for jointed rock masses in rock tunnelling,slope treatment and mining engineering.To investigate the mechanical properties and reinforcement effect of jointed rock mas...Pre-stressed bolt anchorage is the key technology for jointed rock masses in rock tunnelling,slope treatment and mining engineering.To investigate the mechanical properties and reinforcement effect of jointed rock masses with pre-stressed bolts,in this study,uniaxial compression tests were conducted on specimens with different anchoring types and flaw inclination angles.ABAQUS software was used to verify and supplement the laboratory tests.The laws of the uniaxial compressive strength(UCS)obtained from the numerical simulations and laboratory tests were consistent.The results showed that under the same flaw angle,both the UCS and elastic modulus of the bolted specimens were improved compared with those of the specimens without bolts and the improvements increased with an increase in the bolt pre-stress.Under the same anchoring type,the UCS and elastic modulus of the jointed specimens increased with an increase in the flaw angle.The pre-stressed bolt could not only restrain the slip of the specimens along the flaw surface but also change the propagation mode of the secondary cracks and limit the initiation of cracks.In addition,the plot contours of the maximum principal strain and the Tresca stress of the numerical models were influenced by the anchoring type,flaw angle,anchoring angle and bolt position.展开更多
This paper presents the results of laboratory test on the feasibility of soil conditioning for earth pressurebalance （EPB） excavation in a tar sand, which is a natural material never studied in this respect. Thelabo...This paper presents the results of laboratory test on the feasibility of soil conditioning for earth pressurebalance （EPB） excavation in a tar sand, which is a natural material never studied in this respect. Thelaboratory test performed is based on a procedure and methods used in previous studies with differenttypes of soils, but for this special complex material, additional tests are also conducted to verify particularproperties of the tar sands, such as the tilt test and vane shear test usually used in cohesive materials, anda direct shear test. The laboratory test proves that the test procedure is applicable also to this type of soiland the conditioned material can be considered suitable for EPB excavations, although it is necessary touse a certain percentage of fine elements （filler） to create a material suitable to be mixed with foam. Thetest results show that the conditioned material fulfils the required standard for an EPB application.展开更多
Objective: Hepatocellular carcinoma(HCC) development among hepatitis B surface antigen(HBs Ag) carriers shows gender disparity, influenced by underlying liver diseases that display variations in laboratory tests. We a...Objective: Hepatocellular carcinoma(HCC) development among hepatitis B surface antigen(HBs Ag) carriers shows gender disparity, influenced by underlying liver diseases that display variations in laboratory tests. We aimed to construct a risk-stratified HCC prediction model for HBs Ag-positive male adults.Methods: HBs Ag-positive males of 35-69 years old(N=6,153) were included from a multi-center populationbased liver cancer screening study. Randomly, three centers were set as training, the other three centers as validation. Within 2 years since initiation, we administrated at least two rounds of HCC screening using Bultrasonography and α-fetoprotein(AFP). We used logistic regression models to determine potential risk factors,built and examined the operating characteristics of a point-based algorithm for HCC risk prediction.Results: With 2 years of follow-up, 302 HCC cases were diagnosed. A male-ABCD algorithm was constructed including participant's age, blood levels of GGT(γ-glutamyl-transpeptidase), counts of platelets, white cells,concentration of DCP(des-γ-carboxy-prothrombin) and AFP, with scores ranging from 0 to 18.3. The area under receiver operating characteristic was 0.91(0.90-0.93), larger than existing models. At 1.5 points of risk score,26.10% of the participants in training cohort and 14.94% in validation cohort were recognized at low risk, with sensitivity of identifying HCC remained 100%. At 2.5 points, 46.51% of the participants in training cohort and 33.68% in validation cohort were recognized at low risk with 99.06% and 97.78% of sensitivity, respectively. At 4.5 points, only 20.86% of participants in training cohort and 23.73% in validation cohort were recognized at high risk,with positive prediction value of 22.85% and 12.35%, respectively.Conclusions: Male-ABCD algorithm identified individual's risk for HCC occurrence within short term for their HCC precision surveillance.展开更多
The current researches of wheel vibration and sound radiation mainly focus on the low noise damped wheel. Compared with the traditional research, the relationship between the sound and wheel/rail contact is difficulty...The current researches of wheel vibration and sound radiation mainly focus on the low noise damped wheel. Compared with the traditional research, the relationship between the sound and wheel/rail contact is difficulty and worth studying. However, there are few studies on the effect of wheel load on wheel vibration and sound radiation. In this paper, laboratory test carried out in a semi-anechoic room investigates the effect of wheel load on wheel natural frequencies, damping ratios, wheel vibration and its sound radiation, The laboratory test results show that the vibration of the wheel and total sound radiation decrease significantly with the increase of the wheel load from 0 t to 1 t. The sound energy level of the wheel decreases by 3.7 dB. When the wheel load exceeds 1 t. the attenuation trend of the vibration and sound radiation of the wheel becomes slow. And the increase of the wheel load causes the growth of the wheel natural frequencies and the mode damping ratios. Based on the finite element method （FEM） and boundary element method （BEM）, a rolling noise prediction model is developed to calculate the influence of wheel load on the wheel vibration and sound radiation. In the calculation, the used wheel/rail excitation is the measured wheel/rail roughness. The calculated results show that the sound power level of the wheel decreases by about 0.4 dB when the wheel load increases by 0.5 t. The sound radiation of the wheel decreases slowly with wheel load increase, and this conclusion is verified by the field test. This research systematically studies the cffcct of wheel load on wheel vibration and sound radiation, gives the relationship between the sound and wheel/rail contact and analyzes the reasons, therefore, it provides a reference for further research.展开更多
Low frequency vibrations induced by underground railways have attracted increasing attention in recent years. To obtain the characteristics of low frequency vibrations and the low frequency performance of a floating s...Low frequency vibrations induced by underground railways have attracted increasing attention in recent years. To obtain the characteristics of low frequency vibrations and the low frequency performance of a floating slab track (FST), low frequency vibration tests on an FST in an underground laboratory at Beijing Jiaotong University were carried out. The FST and an unbalanced shaker SBZ30 for dynamic simulation were designed for use in low frequency vibration experiments. Vibration measurements were performed on the bogie of the unbalanced shaker, the rail, the slab, the tunnel invert, the tunnel wall, the tunnel apex, and on the ground surface at distances varying from 0 to 80 m from the track. Measurements were also made on several floors of an adjacent building. Detailed results of low frequency vibration tests were reported. The attenuation of low frequency vibrations with the distance from the track was presented, as well as the responses of different floors of the building. The experimental results could be regarded as a reference for developing methods to control low frequency vibrations and for adopting countermeasures.展开更多
This study aims to examine the influence of pre-existing discontinuities on the strengths of four natural rocks of different origins.A series of unconfined compression tests was performed on specimens of two types of ...This study aims to examine the influence of pre-existing discontinuities on the strengths of four natural rocks of different origins.A series of unconfined compression tests was performed on specimens of two types of sandstones,argillite and basalt that contain open and filled cracks.It was found that the presence of cracks tends to decrease the overall strength for all studied rocks;however,the magnitude of strength reduction is related to the property of rock.The larger strength decrease was observed for the relatively harder argillite and basalt,compared to the softer sandstone.It was also found that the infill material could increase the strength of rock specimens,while the obtained strength depended on the characteristics of the fill material.展开更多
基金sponsored by the Norwegian Public Roads Administration(NPRA)
文摘The Norwegian Public Roads Administration(NPRA) is planning for an upgrade of the E39 highway route at the westcoast of Norway. Fixed links shall replace ferries at seven fjord crossings. Wide spans and large depths at the crossings combined with challenging subsea topography and environmental loads call for an extension of existing practice. A variety of bridge concepts are evaluated in the feasibility study. The structures will experience significant loads from deadweight, traffic and environment. Anchoring of these forces is thus one of the challenges met in the project. Large-size subsea rock anchors are considered a viable alternative. These can be used for anchoring of floating structures but also with the purpose of increasing capacity of fixed structures. This paper presents first a thorough study of factors affecting rock anchor bond capacity. Laboratory testing of rock anchors subjected to cyclic loading is thereafter presented. Finally, the paper presents a model predicting the capacity of a rock anchor segment, in terms of a ribbed bar, subjected to a cyclic load history. The research assumes a failure mode occurring in the interface between the rock anchor and the surrounding grout. The constitutive behavior of the bonding interface is investigated for anchors subjected to cyclic one-way tensile loads. The model utilizes the static bond capacity curve as a basis, defining the ultimate bond sbuand the slip s1 at τ. A limited number of input parameters are required to apply the model. The model defines the bond-slip behavior with the belonging rock anchor capacity depending on the cyclic load level(τcy/τ), the cyclic load ratio(R= τcy/τcy), and the number of load cycles(N). The constitutive model is intended to model short anchor lengths representing an incremental length of a complete rock anchor.
文摘Acute respiratory tract infection</span><span style="font-family:""><span style="font-family:Verdana;"> (ARTI) in children is the most common infectious disease in childhood, and its pathogens include viruses, bacteria and fungi, mycoplasma, chlamydia and rickettsia. In recent years, with the continuous development of pathogen detection methods, the diagnosis and treatment of acute respiratory infections has received more and more clinical attention. The clinical diagnosis and treatment characteristics of acute respira</span><span style="font-family:Verdana;">tory infections in children and the research of clinical laboratory detection </span><span style="font-family:Verdana;">methods have also been continuously developed. The author collected refer</span><span style="font-family:Verdana;">ences to review the clinical features and new developments in laboratory</span><span style="font-family:Verdana;"> testing of acute respiratory tract infection in children.
文摘Recently a research team at Ohio University,USA,conducted a unique full-scale feld load test to simulate the aeration pipe installations at a copper extraction mine operated in Chile.The overliner material taken from the mine was used in recreating the in situ conditions.Electric heaters were utilized to raise the temperature inside each pipe to simulate the essential element of the copper extraction process.The maximum vertical deflection reached by the test pipes was close to 20%,when the simulated heap pile height was 80 m.The plastic pipes and the overliner material were also tested in the laboratory.Based on the results,the maximum heap pile fll depth was recommended for the aeration system.The results indicated that the vertical deflection was the primary performance index for the aeration pipes installed in heap piles at mines.Lastly,the pipe made of polypropylene resin was super.
文摘Acute respiratory infection in children (ARTI) is the most common childhood infectious disease, and its pathogens include bacteria, fungi, viruses, chlamydia, mycoplasma and rickettsia. In recent years, with the continuous development of pathogen detection methods, the diagnosis and treatment of acute respiratory infections has received more and more attention from clinicians. The clinical diagnosis and treatment of acute respiratory infections in children and the research of laboratory detection methods have also been continuously developed. The manuscript presents a review of progress in the clinical diagnosis, treatment and laboratory testing of acute respiratory infections in children by collecting references.
文摘The compelling case report by Xie et al,published in a renowned medical journal,is an excellent example of meticulous clinical evaluation,comprehensive labo-ratory testing,advanced imaging,and genetic analysis.The authors identified novel compound heterozygous mutations in the hemojuvelin gene of a patient diagnosed with juvenile hemochromatosis.They suggested that long-term,strategic phlebotomy might offer a novel therapeutic strategy for severe juvenile hemochromatosis,challenging the traditional treatment paradigms.
基金supported by the Capital’s Funds for Health Improve-ment and Research(grant number:2024-1G-4023)。
文摘Background:Existing hepatocellular carcinoma(HCC)prediction models lack transferability and generalizability when applied to female populations,resulting in diminished performance and inadequate tools for accurate HCC risk stratification among females.This study aims to develop and validate a score-based prediction model for early detection of HCC in female hepatitis B surface antigen(HBsAg)carriers.Methods:Participants were recruited from a multicenter prospective cohort engaged in liver cancer screening across China including seven high-risk rural areas and one additional high-risk rural area.The study involved 7080 females as the derivation cohort and 2069 as the validation cohort,with all participants aged 35-70 years and HBsAg positive.Laboratory tests and epidemiological surveys were conducted.Key predictor variables were identified through LASSO regression analysis,and score-based prediction models were developed based on Cox proportional hazards model.Model performance including discrimination and calibration was evaluated,and compared to existing prediction models and screening strategies.Results:After a median follow-up of 3.69 and 5.42 years,147 and 45 HCC cases were identified in the derivation and validation cohorts,respectively.The female HCC(HCCF)model incorporating five independent variables:age,α-fetoprotein(AFP),albumin,alanine aminotransferase,and platelet,showed excellent performance with an area under the receiver operating characteristic curve(AUC)of 0.82(95%CI:0.78-0.86).The HCCF-Enhanced model which included cirrhosis,achieved an AUC of 0.85(95%CI:0.81-0.89).Both models demonstrated superior predictive performance than existing models,with strong predictive accuracy in the validation cohort:AUCs of 0.83(95%CI:0.77-0.89)and 0.88(95%CI:0.83-0.92),respectively.The HCCF model,at a score threshold of 7,achieved the largest Youden’s index and identified 32.80%of high-risk individuals.When combined with ultrasonography(US),the model detected 37 additional cases,significantly improved screening sensitivity and accuracy compared to the traditional AFP plus US strategy.Conclusions:The developed HCCF models with good performance for HCC prediction in HBsAg-positive females significantly improve screening efficiency and provide an effective tool for surveillance,ultimately helping to optimize prevention and management strategies for HCC.
基金Regional Fund of National Natural Science Foundation of China,Grant/Award Numbers:52164011,52464008National Natural Science Foundation of China-Xinjiang Joint Fund,Grant/Award Number:2022D01E31+2 种基金Graduate student scientific research innovation projects in Xinjiang Uygur Autonomous Region,Grant/Award Number:XJ2024G097Xinjiang Uygur Autonomous Region Special Program for Key R&D Tasks,Grant/Award Numbers:2022B01034,2022B01051,2023B01010Xinjiang Uygur Autonomous Region“Tianshan Talent Training”Program,Grant/Award Numbers:2022TSYCCX0037,2023TSYCJC0009,2023TSYCJC0095。
文摘Attributed to its superior water-to-solid ratio and quick setting time,the highwater material is widely adopted in underground spaces as a cost-effective and environmentally friendly backfill material.To elucidate the bleeding mechanism of high-water material under the high confining pressure,a total of 57 tubular specimens were prepared and tested,critical parameters of which included the water-to-solid ratio,curing time,and lateral confinement pressure.Test results showed that no obvious cracks were observed from the surface of confined highwater material,which is different from that of unconfined high-water material,which featured shear cracks.Moreover,the volume of these confined high-water materials under compaction exhibited a continuous shrinkage associated with the water bleeding.The threshold values of the water bleeding are significantly affected by the water-to-solid ratio,followed by the confining pressure and curing time.When other parameters are constant,the higher confinement is requested for these specimens with a small water-to-solid ratio.Meanwhile,the mass of bleeding water increased with the lateral confinement,showing a quick increase at the initial stage.During the bleeding process,the free water stored in the pores was compacted,the evidence of which is the transformation of the hydration products(calcium aluminate hydrate)from its natural fibrous structure into the rod-shaped or dense agglomerate structures.These research outcomes provide an in-depth insight into the fundamental mechanics of the high-water material under the high lateral confinement when it is used for underground spaces.
基金supported by the China National Natural Science Foundation(Grant No.42362034)the Applied Basic Research Foundation of Yunnan Province,China(Grant No.202401AS070068).
文摘The destabilization of overhanging rock is a dangerous geological problem.In this study,a generalized model of typical overhanging cliffs from the Three Gorges Reservoir area in China with different fracture angles,fracture lengths,and free surface depths is constructed to investigate the cracking and deformation behavior of overhanging rocks.Laboratory tests and deformation field monitoring using the digital image correlation(DIC)method are performed on these specimens to reproduce the destabilization and failure process of overhanging rock under external loading.The influence of peak load is found to be the most sensitive to the fracture length,followed by the free surface depth,and to be the least sensitive to the fracture angle.The DIC-based strain fields reveal that the fracture angle and free surface depth significantly alter the crack propagation paths,whereas the influence of the fracture length is weaker.These parameters also affect the crack initiation time.The relative displacement evolution characteristics indicate that fracture angle,fracture length,and free surface depth affect the shape and size of the rotating block,the rotation center,and the rotation pivot point and degree,respectively.The grayscale characteristic evolution trends are similar for all examined overhanging rock specimens.The evolution of the grayscale indices based on DIC can be divided into high-frequency oscillation,smooth decline(or smooth downward concavity),and stable development stages.Furthermore,the multistage properties of the indices can be used to identify the fracture state of overhanging rocks,providing a theoretical basis for graded early warning of rockfall disasters.
基金support from a Grant-in-Aid for Scientific Research(KAKENHI B),Japan(Project/Area code:23H01505)the Institute for Sustainable Future Society,Waseda Research Institute for Science and Engineering,Research Initiatives in Japansupport from the Chinese Scholar Council for PhD scholarships(Grant No.202206220061)was acknowledged。
文摘This paper presents a method for obtaining the displacement of sand particles in a sand–bentonite mixture(SBM)when saturated with water,based on particle tracking velocimetry(PTV).The raw photographs were first converted into binary images.The sand particles were then detected,and the displacement of the sand particles was obtained by comparing their positions in adjacent images.The swelling strain induced by saturation was also obtained using the proposed PTV method.This method was validated by comparing the result with those obtained using a displacement transducer.Subsequently,a comparative analysis of sand particle displacements was conducted for specimens with varying bentonite content(BC),initial thickness,and water infiltration directions.The experimental results obtained were as follows:(1)For specimens with different BCs,local swelling displacement of sand particles at the top part of the specimen increased with higher BCs;(2)For specimens with various heights(hsp),larger local swelling displacement was generated at lower hsp at the initial state;(3)Local swelling characteristics differed in different water infiltration directions.Top-side infiltration showed a significant downward movement of particles during the first several hours of swelling.An estimation method for the dry density distribution of the specimen was proposed based on PTV data and then verified by slicing dry density and water content measurement results.
基金Nanyang Technological University(NTU,Singapore)and Nanyang Environment and Water Research Institute for the financial support and scholarships of this research.
文摘Dissolution of soluble soil,biodegradation of municipal solid waste(MSW),and internal erosion of gap-graded soil are typical mass loss processes of geomaterials,which result in various engineering problems.These three processes are conceptually analogous and examined by a unified assessment of their behaviors considering the initial properties of geomaterials and testing conditions.This study collected additional data from twelve soil dissolution tests and five long-term MSW biodegradation tests.We then established a comprehensive mass loss behavior dataset based on the available studies and the supplementary data obtained from this study.In addition to the flow-reactive fraction,two initial volumetric properties are also critical,which are void ratio before mass loss(esolid,0)and inert-to-reactive size ratio.A characteristic parameter(Λ),describing the ratio between the change in voids volume and the change in flow-reactive solids volume,is correlated with the strain and change in esolid.The volumetric and structural changes of all the flow-reactive geomaterials are categorized into Λ=−1 for pseudo-stable,−1≤Λ<0 for collapsible,0≤Λ<esolid,0 for hyper-collapsible,and Λ≥esolid,0 for readily densified.A three-dimensional plot constructed by the three critical initial properties is divided into eight zones based on the differentΛvalues,which correspond to distinct mass loss behaviors.The a priori Λ estimation and corresponding zonation for a wide variety of flow-reactive geomaterials is shown to be beneficial for research and practice.
基金the funding support from Alpha Foundation for the Improvement of Mine Safety and Health Inc.(ALPHAFOUNDATION,Grant No.AFC820-52)。
文摘Underground mine pillars provide natural stability to the mine area,allowing safe operations for workers and machinery.Extensive prior research has been conducted to understand pillar failure mechanics and design safe pillar layouts.However,limited studies(mostly based on empirical field observation and small-scale laboratory tests)have considered pillar-support interactions under monotonic loading conditions for the design of pillar-support systems.This study used a series of large-scale laboratory compression tests on porous limestone blocks to analyze rock and support behavior at a sufficiently large scale(specimens with edge length of 0.5 m)for incorporation of actual support elements,with consideration of different w/h ratios.Both unsupported and supported(grouted rebar rockbolt and wire mesh)tests were conducted,and the surface deformations of the specimens were monitored using three-dimensional(3D)digital image correlation(DIC).Rockbolts instrumented with distributed fiber optic strain sensors were used to study rockbolt strain distribution,load mobilization,and localized deformation at different w/h ratios.Both axial and bending strains were observed in the rockbolts,which became more prominent in the post-peak region of the stress-strain curve.
基金support from the National Natural Science Foundation of China(Grant Nos.52192622 and 52304003)the National Key Research and Development Program of China(Grant No.2023YFF0614102).
文摘Thermal damage mechanisms are crucial in reservoir stimulation for enhanced geothermal system(EGS).This study investigates the thermal damage mechanisms in granite samples from the Gonghe Basin,Qinghai,China.The granite samples were heated to 400℃ and then cooled in air,water,or liquid nitrogen.The physical and mechanical properties of the thermally treated granite were evaluated,andmicrostructural changes were analyzed using a scanning electron microscope(SEM)and computed tomography(CT).The results indicate that cooling with water and liquid nitrogen significantly enhancespermeability and brittleness while reducing P-wave velocity,strength,and Young's modulus.Specifically,liquid nitrogen cooling increased granite permeability by a factor of 5.24 compared to the untreatedsamples,while reducing compressive strength by 13.6%.After thermal treatment,the failure mode of thegranite shifted from axial splitting to a combination of shear and tension.Microstructural analysisrevealed that liquid nitrogen-cooled samples exhibited greater fracture complexity than those cooledwith water or air.Additionally,acoustic emission(AE)monitoring during damage evolution showed thatliquid nitrogen cooling led to higher cumulative AE energy and a lower maximum AE energy rate,withnumerous AE signals detected during both stable and unstable crack growth.The results suggest thatliquid nitrogen induces a stronger thermal shock,leading to more significant thermal damage andpromoting the development of a complex fracture network during EGS reservoir stimulation.This enhancesboth the heat exchange area and the permeability of the deep hot dry rock(HDR)in EGS reservoirs.The insights from this study contribute to a deeper understanding of thermal damagecharacteristics induced by different cooling media and provide valuable guidance for optimizing deepgeothermal energy extraction.
基金Project(2009B13014) supported by the Fundamental Research Funds for the Central Universities of ChinaProject(IRT1125) supported by the Program for Changjiang Scholars and Innovative Research Team in University,China
文摘To assess the effectiveness of vacuum preloading combined electroosmotic strengthening of ultra-soft soil and study the mechanism of the process, a comprehensive experimental investigation was performed. A laboratory test cell was designed and applied to evaluate the vacuum preloading combined electroosmosis. Several factors were taken into consideration, including the directions of the electroosmotic current and water induced by vacuum preloading and the replenishment of groundwater from the surrounding area. The results indicate that electroosmosis together with vacuum preloading improve the soil strength greatly, with an increase of approximately 60%, and reduce the water content of the soil on the basis of consolidation of vacuum preloading, howeve~ further settlement is not obvious with only 1.7 mm. The reinforcement effect of vacuum preloading combined electroosmosis is better than that of electroosmosis after vacuum preloading. Elemental analysis using X-ray fluorescence proves that the soil strengthening during electroosmotic period in this work is mainly caused by electroosmosis-induced electrochemical reactions, the concentrations of Al2O3 in the VPCEO region increase by 2.2%, 1.5%, and 0.9% at the anode, the midpoint between the electrodes, and the cathode, respectively.
基金Project(51979281)supported by the National Natural Science Foundation of ChinaProject(ZR2018MEE050)supported by the Natural Science Foundation of Shandong Province,ChinaProject(18CX02079A)supported by the Fundamental Research Funds for the Central Universities,China。
文摘Pre-stressed bolt anchorage is the key technology for jointed rock masses in rock tunnelling,slope treatment and mining engineering.To investigate the mechanical properties and reinforcement effect of jointed rock masses with pre-stressed bolts,in this study,uniaxial compression tests were conducted on specimens with different anchoring types and flaw inclination angles.ABAQUS software was used to verify and supplement the laboratory tests.The laws of the uniaxial compressive strength(UCS)obtained from the numerical simulations and laboratory tests were consistent.The results showed that under the same flaw angle,both the UCS and elastic modulus of the bolted specimens were improved compared with those of the specimens without bolts and the improvements increased with an increase in the bolt pre-stress.Under the same anchoring type,the UCS and elastic modulus of the jointed specimens increased with an increase in the flaw angle.The pre-stressed bolt could not only restrain the slip of the specimens along the flaw surface but also change the propagation mode of the secondary cracks and limit the initiation of cracks.In addition,the plot contours of the maximum principal strain and the Tresca stress of the numerical models were influenced by the anchoring type,flaw angle,anchoring angle and bolt position.
文摘This paper presents the results of laboratory test on the feasibility of soil conditioning for earth pressurebalance （EPB） excavation in a tar sand, which is a natural material never studied in this respect. Thelaboratory test performed is based on a procedure and methods used in previous studies with differenttypes of soils, but for this special complex material, additional tests are also conducted to verify particularproperties of the tar sands, such as the tilt test and vane shear test usually used in cohesive materials, anda direct shear test. The laboratory test proves that the test procedure is applicable also to this type of soiland the conditioned material can be considered suitable for EPB excavations, although it is necessary touse a certain percentage of fine elements （filler） to create a material suitable to be mixed with foam. Thetest results show that the conditioned material fulfils the required standard for an EPB application.
基金supported by State Key Projects Specialized on Infectious Diseases (No. 2017ZX10201201-006)Key research projects for precision medicine (No. 2017YFC0908103)+1 种基金Innovation Fund for Medical Sciences of Chinese Academy of Medical Sciences (CIFMS, No. 2019-I2M-2-004, 2016-I2M-1-007, 2019-I2M-1-003)National Natural Science Foundation Fund (No. 81972628, No. 81974492)。
文摘Objective: Hepatocellular carcinoma(HCC) development among hepatitis B surface antigen(HBs Ag) carriers shows gender disparity, influenced by underlying liver diseases that display variations in laboratory tests. We aimed to construct a risk-stratified HCC prediction model for HBs Ag-positive male adults.Methods: HBs Ag-positive males of 35-69 years old(N=6,153) were included from a multi-center populationbased liver cancer screening study. Randomly, three centers were set as training, the other three centers as validation. Within 2 years since initiation, we administrated at least two rounds of HCC screening using Bultrasonography and α-fetoprotein(AFP). We used logistic regression models to determine potential risk factors,built and examined the operating characteristics of a point-based algorithm for HCC risk prediction.Results: With 2 years of follow-up, 302 HCC cases were diagnosed. A male-ABCD algorithm was constructed including participant's age, blood levels of GGT(γ-glutamyl-transpeptidase), counts of platelets, white cells,concentration of DCP(des-γ-carboxy-prothrombin) and AFP, with scores ranging from 0 to 18.3. The area under receiver operating characteristic was 0.91(0.90-0.93), larger than existing models. At 1.5 points of risk score,26.10% of the participants in training cohort and 14.94% in validation cohort were recognized at low risk, with sensitivity of identifying HCC remained 100%. At 2.5 points, 46.51% of the participants in training cohort and 33.68% in validation cohort were recognized at low risk with 99.06% and 97.78% of sensitivity, respectively. At 4.5 points, only 20.86% of participants in training cohort and 23.73% in validation cohort were recognized at high risk,with positive prediction value of 22.85% and 12.35%, respectively.Conclusions: Male-ABCD algorithm identified individual's risk for HCC occurrence within short term for their HCC precision surveillance.
基金Supported by National Science and Technology Support Program of China(Grant No.2009BAG12A01-B06)National Hi-tech Research and Development Program of China(863 Program,Grant No.2011AA11A103-2-2)+3 种基金Funds for Innovation Research Team of Ministry of Education of China(Grant Nos.IRT1178,SWJTU12ZT01)Fundamental Research Funds for the Central Universities and the Science of China(Grant No.SWJTU12ZT01)2015 Doctoral Innovation Funds of Southwest Jiaotong University of ChinaProject of State Key Laboratory of Traction Power of China(Grant No.2011TPL_T05)
文摘The current researches of wheel vibration and sound radiation mainly focus on the low noise damped wheel. Compared with the traditional research, the relationship between the sound and wheel/rail contact is difficulty and worth studying. However, there are few studies on the effect of wheel load on wheel vibration and sound radiation. In this paper, laboratory test carried out in a semi-anechoic room investigates the effect of wheel load on wheel natural frequencies, damping ratios, wheel vibration and its sound radiation, The laboratory test results show that the vibration of the wheel and total sound radiation decrease significantly with the increase of the wheel load from 0 t to 1 t. The sound energy level of the wheel decreases by 3.7 dB. When the wheel load exceeds 1 t. the attenuation trend of the vibration and sound radiation of the wheel becomes slow. And the increase of the wheel load causes the growth of the wheel natural frequencies and the mode damping ratios. Based on the finite element method （FEM） and boundary element method （BEM）, a rolling noise prediction model is developed to calculate the influence of wheel load on the wheel vibration and sound radiation. In the calculation, the used wheel/rail excitation is the measured wheel/rail roughness. The calculated results show that the sound power level of the wheel decreases by about 0.4 dB when the wheel load increases by 0.5 t. The sound radiation of the wheel decreases slowly with wheel load increase, and this conclusion is verified by the field test. This research systematically studies the cffcct of wheel load on wheel vibration and sound radiation, gives the relationship between the sound and wheel/rail contact and analyzes the reasons, therefore, it provides a reference for further research.
基金Project supported by the National Natural Science Foundation of China (No. 51008017)the Fundamental Research Funds for the Central Universities of China (Nos. 2009JBM074 and 2009JBM075)
文摘Low frequency vibrations induced by underground railways have attracted increasing attention in recent years. To obtain the characteristics of low frequency vibrations and the low frequency performance of a floating slab track (FST), low frequency vibration tests on an FST in an underground laboratory at Beijing Jiaotong University were carried out. The FST and an unbalanced shaker SBZ30 for dynamic simulation were designed for use in low frequency vibration experiments. Vibration measurements were performed on the bogie of the unbalanced shaker, the rail, the slab, the tunnel invert, the tunnel wall, the tunnel apex, and on the ground surface at distances varying from 0 to 80 m from the track. Measurements were also made on several floors of an adjacent building. Detailed results of low frequency vibration tests were reported. The attenuation of low frequency vibrations with the distance from the track was presented, as well as the responses of different floors of the building. The experimental results could be regarded as a reference for developing methods to control low frequency vibrations and for adopting countermeasures.
基金The authors would like to acknowledge Mr.Beau McDonald for his invaluable help with laboratory testing.
文摘This study aims to examine the influence of pre-existing discontinuities on the strengths of four natural rocks of different origins.A series of unconfined compression tests was performed on specimens of two types of sandstones,argillite and basalt that contain open and filled cracks.It was found that the presence of cracks tends to decrease the overall strength for all studied rocks;however,the magnitude of strength reduction is related to the property of rock.The larger strength decrease was observed for the relatively harder argillite and basalt,compared to the softer sandstone.It was also found that the infill material could increase the strength of rock specimens,while the obtained strength depended on the characteristics of the fill material.
