A search algorithm for the detection of a direct path signal in the presence of dense multipath in indoor environment using UWB is Woposed. This algorithm is based on signal correlation and differential coefficient. S...A search algorithm for the detection of a direct path signal in the presence of dense multipath in indoor environment using UWB is Woposed. This algorithm is based on signal correlation and differential coefficient. Statistical analysis of the algorithm is given out and computer simulation results are presented to validate the effectiveness of the algorithm. The results based on the algorithm pml3osed are compared with those based on Maximum Likelihood Estimator（MLE） and Peak Tracking（PT） in the simulation which shows that this algorithm achieves the highest accuracy in most cases and gives out relatively stable results in different Signal Noise Ratio（SNR）.展开更多
Nickel-based catalysts display promising potential in integrated hydrogen production through methanol electrooxidation(MOR).The unavoidable selfoxidation from Ni(OH)_(2)to NiOOH severely restricts their MOR performanc...Nickel-based catalysts display promising potential in integrated hydrogen production through methanol electrooxidation(MOR).The unavoidable selfoxidation from Ni(OH)_(2)to NiOOH severely restricts their MOR performance.To inspire the progress of MOR before self-oxidation of Ni species by altering reaction pathways,a heterostructured Ni-WO_(2)catalyst is constructed to follow the direct electrooxidation pathway of methanol.Insitu/ex-situ characterization techniques combined with density functional theory calculations reveal the constructed Ni-WO_(2)hetero structure alters the electronic structure of Ni site.It's found Ni-Ni bond in Ni-WO_(2)becomes longer and the electrons transfer from Ni sites to W sites.This results in up shifted d band center of Ni site and its closing to the Fermi energy level,which optimizes the CH_(3)OH adsorption and the deprotonation of*CH_(3)O into*CH_(2)O in potential-determining step.Moreover,the formed asymmetric adsorption sites increase the polarity of the methanol and the intermediate.As expected,CH_(3)OH molecule is highly converted into HCOOH via direct electrooxidation pathway.This obtained Ni-WO_(2)exhibits superior MOR activity with high peak current density of 325.26 mA cm^(-2) and performs long term of 90 h at10 mA cm^(-2) in hydrogen production.This work provides an important guidance for designing efficient Ni-based samples for direct electrooxidation of methanol.展开更多
In this paper,we discuss the path-connectivity between two s-elementary normalized tight frame wavelets via the so-called direct paths.We show that the existence of such a direct path is equivalent to the non-existenc...In this paper,we discuss the path-connectivity between two s-elementary normalized tight frame wavelets via the so-called direct paths.We show that the existence of such a direct path is equivalent to the non-existence of an atom of aσ-algebra defined over the defining sets of the corresponding frame wavelets,using a mapping defined by the natural translation and dilation operations between the sets.In particular,this gives an equivalent condition for the existence of a direct path between two s-elementary wavelets.展开更多
A series of directional shear tests on remolded frozen soil was carried out at 10°C by using a hollow cylinder apparatus to study failure criterion under a directional shear-stress path.Directional shear tests we...A series of directional shear tests on remolded frozen soil was carried out at 10°C by using a hollow cylinder apparatus to study failure criterion under a directional shear-stress path.Directional shear tests were conducted at five shear rates(10,20,30,40,and 50 kPa/min)and five intermediate principal stress coefficients(b=0,0.25,0.5,0.75,and 1),with the mean principal stress(p=4.5 MPa)kept constant.The results show that the torsional strength and the generalized strength both increase with the increase of the shear rates.According to the failure modes of frozen soil under different shear rates,the specimens present obvious plastic failure and shear band;and the torsional shear component dominates the failure modes of hollow cylindrical specimens.A shear rate of 30 kPa/min is chosen as the loading rate in the directional shear tests of frozen soil.The shape of the failure curve in theπplane is dependent on the directional anglesαof the major prin cipal stress.It is reasonable to use the strain-hardening curves to define the deviatoric stress value atγg=15%(generalized shear strain)as the failure criterion of frozen soil under a directional shear-stress path.展开更多
To investigate the effect of solidification parameters on the solidification path and microstructure evolution of Ti-45Al-5Nb(at.%) alloy, Bridgman-type directional solidification and thermodynamics calculations were ...To investigate the effect of solidification parameters on the solidification path and microstructure evolution of Ti-45Al-5Nb(at.%) alloy, Bridgman-type directional solidification and thermodynamics calculations were performed on the alloy. The microstructures, micro-segregation and solidification path were investigated.The results show that the β phase is the primary phase of the alloy at growth rates of 5-20 μm·s^(-1) under the temperature gradients of 15-20 K·mm^(-1), and the primary phase is transformed into an α phase at relatively higher growth rates(V >20 μm·s^(-1)). The mainly S-segregation and β-segregation can be observed in Ti-45Al-5Nb alloy at a growth rate of 10 μm·s^(-1) under a temperature gradient of 15 K·mm^(-1). The increase of temperature gradient to 20 K·mm^(-1) can eliminate β-segregation, but has no obvious effect on S-segregation. The results also show that 5 at.% Nb addition can expand the β phase region, increase the melting point of the alloy and induce the solidification path to become complicated. The equilibrium solidification path of Ti-45Al-5Nb alloy can be described as L L→β L+β L+β→αα+β_R β→ααα→γα+γα→α_2+γγ_R+(α_2+γ), in which β_R and γ_R mean the residual β and展开更多
CO_(2) conversion into value-added products by electro-, photoand plasma catalysis under mild operating conditions(ambient temperature and pressure) is an emerging area to achieve carbon circularity by producing chemi...CO_(2) conversion into value-added products by electro-, photoand plasma catalysis under mild operating conditions(ambient temperature and pressure) is an emerging area to achieve carbon circularity by producing chemicals and fuels using directly renewable energy. Among all CO_(2) conversion approaches, the electrocatalytic reduction of CO_(2) is the most mature technology, capable of achieving high productivity(i.e. high current densities) at large scale, especially for producing carbon monoxide(CO), but with many examples showing selectivity to C_(2) carbon products.展开更多
基金Supported by the Education Depart ment Fund of Science and Technology Research (No.104086)
文摘A search algorithm for the detection of a direct path signal in the presence of dense multipath in indoor environment using UWB is Woposed. This algorithm is based on signal correlation and differential coefficient. Statistical analysis of the algorithm is given out and computer simulation results are presented to validate the effectiveness of the algorithm. The results based on the algorithm pml3osed are compared with those based on Maximum Likelihood Estimator（MLE） and Peak Tracking（PT） in the simulation which shows that this algorithm achieves the highest accuracy in most cases and gives out relatively stable results in different Signal Noise Ratio（SNR）.
基金financially supported by the National Natural Science Foundation of China(Nos.U24A2023 and 21571119)the Natural Science Foundation of Shanxi Province(No.202203021221136)+4 种基金"Chunhui Plan"Cooperative Scientific Research Project of Education Ministry(No.HZKY20220510)the Scientific and Technological Innovation Programs of Higher Education Institution in Shanxi(No.2019L0466)the Graduate Education Innovation Project of Shanxi Province(Nos.2023JG093,2024KY421,and 2024XSY43)the Graduate Education Innovation Project of Shanxi Normal University(No.2021XSY038)1331 Engineering of Shanxi Province
文摘Nickel-based catalysts display promising potential in integrated hydrogen production through methanol electrooxidation(MOR).The unavoidable selfoxidation from Ni(OH)_(2)to NiOOH severely restricts their MOR performance.To inspire the progress of MOR before self-oxidation of Ni species by altering reaction pathways,a heterostructured Ni-WO_(2)catalyst is constructed to follow the direct electrooxidation pathway of methanol.Insitu/ex-situ characterization techniques combined with density functional theory calculations reveal the constructed Ni-WO_(2)hetero structure alters the electronic structure of Ni site.It's found Ni-Ni bond in Ni-WO_(2)becomes longer and the electrons transfer from Ni sites to W sites.This results in up shifted d band center of Ni site and its closing to the Fermi energy level,which optimizes the CH_(3)OH adsorption and the deprotonation of*CH_(3)O into*CH_(2)O in potential-determining step.Moreover,the formed asymmetric adsorption sites increase the polarity of the methanol and the intermediate.As expected,CH_(3)OH molecule is highly converted into HCOOH via direct electrooxidation pathway.This obtained Ni-WO_(2)exhibits superior MOR activity with high peak current density of 325.26 mA cm^(-2) and performs long term of 90 h at10 mA cm^(-2) in hydrogen production.This work provides an important guidance for designing efficient Ni-based samples for direct electrooxidation of methanol.
基金supported by Natural Science Foundation of USA(Grant No.DMS-0712958)supported by SWUFE’s Key Subjects Construction Items Funds of 211 Project+1 种基金the Natural Science Foundation of Jiang Xi Province,China(Grant No.2008GZS0024)the Scientific Research Foundation for the Returned Overseas Chinese Scholars,State Education Ministry of China(Grant No.[2008]890)
文摘In this paper,we discuss the path-connectivity between two s-elementary normalized tight frame wavelets via the so-called direct paths.We show that the existence of such a direct path is equivalent to the non-existence of an atom of aσ-algebra defined over the defining sets of the corresponding frame wavelets,using a mapping defined by the natural translation and dilation operations between the sets.In particular,this gives an equivalent condition for the existence of a direct path between two s-elementary wavelets.
基金supported by the National Natural Science Foundation of China(Nos.U1703244 and 41672310)the National Natural Science Foundation of China(No.41801038)+6 种基金the State Key Laboratory for Geo Mechanics and Deep Underground Engineering,the China University of Mining and Technology(SKLGDUEK1904)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA2003020102)the Major Program of Bureau of International Cooperation,the Chinese Academy of Sciences(131B62KYSB20170012)the National Key Research and Development Program(2017YFC0405101)the Research Project of the State Key Laboratory of Frozen Soils Engineering(Grant No.SKLFSE-ZY-16)the Science and Technology Major Project of Gansu Province(143GKDA007)the Science and Technology Planning Project of Gansu Province(No.18JR3RA376)
文摘A series of directional shear tests on remolded frozen soil was carried out at 10°C by using a hollow cylinder apparatus to study failure criterion under a directional shear-stress path.Directional shear tests were conducted at five shear rates(10,20,30,40,and 50 kPa/min)and five intermediate principal stress coefficients(b=0,0.25,0.5,0.75,and 1),with the mean principal stress(p=4.5 MPa)kept constant.The results show that the torsional strength and the generalized strength both increase with the increase of the shear rates.According to the failure modes of frozen soil under different shear rates,the specimens present obvious plastic failure and shear band;and the torsional shear component dominates the failure modes of hollow cylindrical specimens.A shear rate of 30 kPa/min is chosen as the loading rate in the directional shear tests of frozen soil.The shape of the failure curve in theπplane is dependent on the directional anglesαof the major prin cipal stress.It is reasonable to use the strain-hardening curves to define the deviatoric stress value atγg=15%(generalized shear strain)as the failure criterion of frozen soil under a directional shear-stress path.
基金financially supported by the National Natural Science Foundation of China(Nos.51331005 and 51425402)
文摘To investigate the effect of solidification parameters on the solidification path and microstructure evolution of Ti-45Al-5Nb(at.%) alloy, Bridgman-type directional solidification and thermodynamics calculations were performed on the alloy. The microstructures, micro-segregation and solidification path were investigated.The results show that the β phase is the primary phase of the alloy at growth rates of 5-20 μm·s^(-1) under the temperature gradients of 15-20 K·mm^(-1), and the primary phase is transformed into an α phase at relatively higher growth rates(V >20 μm·s^(-1)). The mainly S-segregation and β-segregation can be observed in Ti-45Al-5Nb alloy at a growth rate of 10 μm·s^(-1) under a temperature gradient of 15 K·mm^(-1). The increase of temperature gradient to 20 K·mm^(-1) can eliminate β-segregation, but has no obvious effect on S-segregation. The results also show that 5 at.% Nb addition can expand the β phase region, increase the melting point of the alloy and induce the solidification path to become complicated. The equilibrium solidification path of Ti-45Al-5Nb alloy can be described as L L→β L+β L+β→αα+β_R β→ααα→γα+γα→α_2+γγ_R+(α_2+γ), in which β_R and γ_R mean the residual β and
文摘CO_(2) conversion into value-added products by electro-, photoand plasma catalysis under mild operating conditions(ambient temperature and pressure) is an emerging area to achieve carbon circularity by producing chemicals and fuels using directly renewable energy. Among all CO_(2) conversion approaches, the electrocatalytic reduction of CO_(2) is the most mature technology, capable of achieving high productivity(i.e. high current densities) at large scale, especially for producing carbon monoxide(CO), but with many examples showing selectivity to C_(2) carbon products.
