Microstructure evolutions of the medium-manganese wear-resistant steel Fe-8Mn-1C-1.2Cr-0.2V (in wt.%) with stacking-fault energy of 22 mJ m-2 during deformation at strain rate ranging of 10^-2-1 s^-1 were analyzed by ...Microstructure evolutions of the medium-manganese wear-resistant steel Fe-8Mn-1C-1.2Cr-0.2V (in wt.%) with stacking-fault energy of 22 mJ m-2 during deformation at strain rate ranging of 10^-2-1 s^-1 were analyzed by means of X-ray diffraction, field emission scanning electron microscopy and high-resolution transmission electron microscopy. The results indicate that the twinning-induced plasticity effect is the main strengthening mechanism of the studied steel, whilst the transformation-induced plasticity effect only occurs at high strain rate. With an increase in strain rate, volume fraction of the deformation twins, in particular that of the secondary twins, increases significantly along with decreasing average size. When applied strain rate is higher than 10^-1 s^-1, the parallel deformation twins are turned into a crossing morphology, and the original straight twin boundaries exhibit a ladder feature, which is attributed to the interactions between regular dislocations and twin dislocations at the twin boundary. The critical strain, a key indicator of the initiation of deformation twin, decreases with increasing strain rate. In addition, the ductility and strength of medium-manganese wear-resistant steel Fe-8Mn-1C-1.2Cr-0.2V are mainly determined by the shape and volume fraction of deformation twins.展开更多
Cancer cell separation is highly desirable for cancer diagnosis and therapy.Besides biochemical methods,engineered platforms are effective alternatives for sorting carcinoma cells from normal cells based on their uniq...Cancer cell separation is highly desirable for cancer diagnosis and therapy.Besides biochemical methods,engineered platforms are effective alternatives for sorting carcinoma cells from normal cells based on their unique properties in responding to the physical changes of the surrounding microenvironment.In this work,three-dimensional(3D)biomimetic scaffold platforms were developed to separate nasopharyngeal carcinoma 43(NPC43)cells from immortalized nasopharyngeal epithelial 460(NP460)cells based on precisely controlled design parameters including stiffness,number of layers,and structural layout.The migration characteristics of NPC43 and NP460 cells on the scaffold platforms revealed that NPC43 cells could squeeze into 10 lm wide,15 lm deep trenches while NP460 cells could not.The different migration behavior was mainly due to cells having different interactions with the surrounding microenvironment.NPC43 cells had filopodia-like protrusions,while NP460 cells exhibited a sheet-like morphology.Using these 3D biomimetic platforms,89%separation efficiency of NPC43 cells from NP460 cells was achieved on stiffer two-layer scaffold platforms with a 40/10 lm ridge/trench(R/T)grating on the top layer and a 20/10 lm R/T grid on the bottom layer.Moreover,the separation efficiency was further increased to 93%by adding an active conditioned medium(ACM)that caused the cells to have higher motility and deformability.These results demonstrate the capability to apply biomimetic engineered platforms with appropriate designs to separate cancer cells from normal cells for potential cancer diagnosis and treatment.展开更多
Estimating surface settlement induced by excavation construction is an indispensable task in tunneling,particularly for earth pressure balance(EPB)shield machines.In this study,predictive models for assessing surface ...Estimating surface settlement induced by excavation construction is an indispensable task in tunneling,particularly for earth pressure balance(EPB)shield machines.In this study,predictive models for assessing surface settlement caused by EPB tunneling were established based on extreme gradient boosting(XGBoost),artificial neural network,support vector machine,and multivariate adaptive regression spline.Datasets from three tunnel construction projects in Singapore were used,with main input parameters of cover depth,advance rate,earth pressure,mean standard penetration test(SPT)value above crown level,mean tunnel SPT value,mean moisture content,mean soil elastic modulus,and grout pressure.The performances of these soft computing models were evaluated by comparing predicted deformation with measured values.Results demonstrate the acceptable accuracy of the model in predicting ground settlement,while XGBoost demonstrates a slightly higher accuracy.In addition,the ensemble method of XGBoost is more computationally efficient and can be used as a reliable alternative in solving multivariate nonlinear geo-engineering problems.展开更多
In densely built-up Singapore,relatively stiffsecant-bored piles and diaphragm walls are commonly used in cut-and-cover works to minimize the impact of ground movement on the adjacent structures and utilities.For exca...In densely built-up Singapore,relatively stiffsecant-bored piles and diaphragm walls are commonly used in cut-and-cover works to minimize the impact of ground movement on the adjacent structures and utilities.For excavations in stiffresidual soil deposits,the asso-ciated wall deflections and ground settlements are generally smaller than for excavations in soft soil deposits.However,if the residual soil permeability is high and the underlying rock is highlyfissured or fractured,substantial groundwater drawdown and associated seepage-induced settlement may occur.In this study,the excavation performance of four sites in residual soil deposits with maximum excavation depths between 20 and 24 m is presented.The maximum wall deflections were found to be relatively small compared to the significantly larger maximum ground settlements,owing to the extensive lowering of the groundwater table.In this paper,details of the subsurface conditions,excavation support system,field instrumentation,and observed excavation responses are presented,with particular focus on the large groundwater drawdown and associated ground settlement.Specific issues encountered during the excavation,as well as the effectiveness of various groundwater control measures,are discussed.The case studies will provide useful references and insights for future projects involving braced excavations in residual soil.展开更多
Extensive site investigations were conducted prior to the construction of a Mass Rapid Transit project in Singapore that was predominantly in the Bukit Timah Granite(BTG)formation residual soil.This paper evaluates th...Extensive site investigations were conducted prior to the construction of a Mass Rapid Transit project in Singapore that was predominantly in the Bukit Timah Granite(BTG)formation residual soil.This paper evaluates the engineering properties of the BTG formation residual soil based on data from 208 site investigation boreholes from four different sites.Based on the results from 2481 conventional laboratory tests and 1192 in-situ tests,this paper summarizes the engineering properties of the highly variable BTG residual soil,including conventional composition analysis,index and hydraulic properties,and strength and deformation parameters required for geotechnical analysis and design.Based on these results,the BTG formation is found to be quite heterogeneous.As the degree of weathering decreases with depth from the top of the formation,the BTG residual soil becomes sandier,with reduced silt and clay fractions.The coefficient of permeability and the compression index of the BTG residual soil vary significantly.In addition,the empirical equations relating the shear strength(index)to the standard penetration test(SPT)-N,as well as the equations and charts for determining stiffness,are proposed.These findings,together with the proposed equations or charts,can be used for design guidance of similar projects related to granitic residual soils in Singapore.展开更多
Learning the Hamiltonian of a quantum system is indispensable for prediction of the system dynamics and realization of high fidelity quantum gates.However,it is a significant challenge to efficiently characterize the ...Learning the Hamiltonian of a quantum system is indispensable for prediction of the system dynamics and realization of high fidelity quantum gates.However,it is a significant challenge to efficiently characterize the Hamiltonian which has a Hilbert space dimension exponentially growing with the system size.Here,we develop and implement an adaptive method to learn the effective Hamiltonian of an 11-qubit quantum system consisting of one electron spin and ten nuclear spins associated with a single nitrogen-vacancy center in a diamond.We validate the estimated Hamiltonian by designing universal quantum gates based on the learnt Hamiltonian and implementing these gates in the experiment.Our experimental result demonstrates a well-characterized 11-qubit quantum spin register with the ability to test quantum algorithms,and shows our Hamiltonian learning method as a useful tool for characterizing the Hamiltonian of the nodes in a quantum network with solid-state spin qubits.展开更多
基金The authors gratefully appreciate the financial support by the National Natural Science Foundation of China (Grant Nos. 51471048 and U1860201)the Basic Research Program of Key Laboratory of Liaoning Province (LZ2015035).
文摘Microstructure evolutions of the medium-manganese wear-resistant steel Fe-8Mn-1C-1.2Cr-0.2V (in wt.%) with stacking-fault energy of 22 mJ m-2 during deformation at strain rate ranging of 10^-2-1 s^-1 were analyzed by means of X-ray diffraction, field emission scanning electron microscopy and high-resolution transmission electron microscopy. The results indicate that the twinning-induced plasticity effect is the main strengthening mechanism of the studied steel, whilst the transformation-induced plasticity effect only occurs at high strain rate. With an increase in strain rate, volume fraction of the deformation twins, in particular that of the secondary twins, increases significantly along with decreasing average size. When applied strain rate is higher than 10^-1 s^-1, the parallel deformation twins are turned into a crossing morphology, and the original straight twin boundaries exhibit a ladder feature, which is attributed to the interactions between regular dislocations and twin dislocations at the twin boundary. The critical strain, a key indicator of the initiation of deformation twin, decreases with increasing strain rate. In addition, the ductility and strength of medium-manganese wear-resistant steel Fe-8Mn-1C-1.2Cr-0.2V are mainly determined by the shape and volume fraction of deformation twins.
基金This work was supported by the Center for Biosystems,Neuroscience,and Nanotechnology(CBNN)of City University of Hong Kong(9360148 and 9380062)the University Grants Council of Hong Kong(GRF projects:11247716,11218017,11213018,and 11212519,CRF project:C1013-15G).
文摘Cancer cell separation is highly desirable for cancer diagnosis and therapy.Besides biochemical methods,engineered platforms are effective alternatives for sorting carcinoma cells from normal cells based on their unique properties in responding to the physical changes of the surrounding microenvironment.In this work,three-dimensional(3D)biomimetic scaffold platforms were developed to separate nasopharyngeal carcinoma 43(NPC43)cells from immortalized nasopharyngeal epithelial 460(NP460)cells based on precisely controlled design parameters including stiffness,number of layers,and structural layout.The migration characteristics of NPC43 and NP460 cells on the scaffold platforms revealed that NPC43 cells could squeeze into 10 lm wide,15 lm deep trenches while NP460 cells could not.The different migration behavior was mainly due to cells having different interactions with the surrounding microenvironment.NPC43 cells had filopodia-like protrusions,while NP460 cells exhibited a sheet-like morphology.Using these 3D biomimetic platforms,89%separation efficiency of NPC43 cells from NP460 cells was achieved on stiffer two-layer scaffold platforms with a 40/10 lm ridge/trench(R/T)grating on the top layer and a 20/10 lm R/T grid on the bottom layer.Moreover,the separation efficiency was further increased to 93%by adding an active conditioned medium(ACM)that caused the cells to have higher motility and deformability.These results demonstrate the capability to apply biomimetic engineered platforms with appropriate designs to separate cancer cells from normal cells for potential cancer diagnosis and treatment.
基金supported by the National Natural Science Foundation of China(No.51608071)Technology Plan Project(2019-0045).
文摘Estimating surface settlement induced by excavation construction is an indispensable task in tunneling,particularly for earth pressure balance(EPB)shield machines.In this study,predictive models for assessing surface settlement caused by EPB tunneling were established based on extreme gradient boosting(XGBoost),artificial neural network,support vector machine,and multivariate adaptive regression spline.Datasets from three tunnel construction projects in Singapore were used,with main input parameters of cover depth,advance rate,earth pressure,mean standard penetration test(SPT)value above crown level,mean tunnel SPT value,mean moisture content,mean soil elastic modulus,and grout pressure.The performances of these soft computing models were evaluated by comparing predicted deformation with measured values.Results demonstrate the acceptable accuracy of the model in predicting ground settlement,while XGBoost demonstrates a slightly higher accuracy.In addition,the ensemble method of XGBoost is more computationally efficient and can be used as a reliable alternative in solving multivariate nonlinear geo-engineering problems.
文摘In densely built-up Singapore,relatively stiffsecant-bored piles and diaphragm walls are commonly used in cut-and-cover works to minimize the impact of ground movement on the adjacent structures and utilities.For excavations in stiffresidual soil deposits,the asso-ciated wall deflections and ground settlements are generally smaller than for excavations in soft soil deposits.However,if the residual soil permeability is high and the underlying rock is highlyfissured or fractured,substantial groundwater drawdown and associated seepage-induced settlement may occur.In this study,the excavation performance of four sites in residual soil deposits with maximum excavation depths between 20 and 24 m is presented.The maximum wall deflections were found to be relatively small compared to the significantly larger maximum ground settlements,owing to the extensive lowering of the groundwater table.In this paper,details of the subsurface conditions,excavation support system,field instrumentation,and observed excavation responses are presented,with particular focus on the large groundwater drawdown and associated ground settlement.Specific issues encountered during the excavation,as well as the effectiveness of various groundwater control measures,are discussed.The case studies will provide useful references and insights for future projects involving braced excavations in residual soil.
基金the support from the National Natural Science Foundation of China(No.51608071)General Financial Grant of the China Postdoctoral Science Foundation(2017M620414)+2 种基金Special Funding for Post-doctoral Researchers in Chongqing(Xm2017007)the Key Laboratory of Rock Mechanics in Hydraulic Structural Engineering,Ministry of Education(RMHSE1601)the Advanced Interdisciplinary Special Cultivation program(No.106112017CDJQJ208850).
文摘Extensive site investigations were conducted prior to the construction of a Mass Rapid Transit project in Singapore that was predominantly in the Bukit Timah Granite(BTG)formation residual soil.This paper evaluates the engineering properties of the BTG formation residual soil based on data from 208 site investigation boreholes from four different sites.Based on the results from 2481 conventional laboratory tests and 1192 in-situ tests,this paper summarizes the engineering properties of the highly variable BTG residual soil,including conventional composition analysis,index and hydraulic properties,and strength and deformation parameters required for geotechnical analysis and design.Based on these results,the BTG formation is found to be quite heterogeneous.As the degree of weathering decreases with depth from the top of the formation,the BTG residual soil becomes sandier,with reduced silt and clay fractions.The coefficient of permeability and the compression index of the BTG residual soil vary significantly.In addition,the empirical equations relating the shear strength(index)to the standard penetration test(SPT)-N,as well as the equations and charts for determining stiffness,are proposed.These findings,together with the proposed equations or charts,can be used for design guidance of similar projects related to granitic residual soils in Singapore.
基金Supported by the Frontier Science Center for Quantum Information of the Ministry of Education of China,Tsinghua University Initiative Scientific Research Program,and the National Key Research and Development Program of China(2016YFA0301902)
文摘Learning the Hamiltonian of a quantum system is indispensable for prediction of the system dynamics and realization of high fidelity quantum gates.However,it is a significant challenge to efficiently characterize the Hamiltonian which has a Hilbert space dimension exponentially growing with the system size.Here,we develop and implement an adaptive method to learn the effective Hamiltonian of an 11-qubit quantum system consisting of one electron spin and ten nuclear spins associated with a single nitrogen-vacancy center in a diamond.We validate the estimated Hamiltonian by designing universal quantum gates based on the learnt Hamiltonian and implementing these gates in the experiment.Our experimental result demonstrates a well-characterized 11-qubit quantum spin register with the ability to test quantum algorithms,and shows our Hamiltonian learning method as a useful tool for characterizing the Hamiltonian of the nodes in a quantum network with solid-state spin qubits.
