We will describe how Linux is embedded into DESY's unix computing,our support concept and policies,tools used and developed,and the challenges which we are facing now that the number of supported PCs is rapidly ap...We will describe how Linux is embedded into DESY's unix computing,our support concept and policies,tools used and developed,and the challenges which we are facing now that the number of supported PCs is rapidly approaching one thousand.展开更多
Polymer dielectrics capable of operating efficiently at high electric fields and elevated temperatures are urgently demanded by next-generation electronics and electrical power systems.While inorganic fillers have bee...Polymer dielectrics capable of operating efficiently at high electric fields and elevated temperatures are urgently demanded by next-generation electronics and electrical power systems.While inorganic fillers have been extensively utilized to improved high-temperature capacitive performance of dielectric polymers,the presence of thermodynamically incompatible organic and inorganic components may lead to concern about the long-term stability and also complicate film processing.Herein,zero-dimensional polymer dots with high electron affinity are introduced into photoactive allyl-containing poly(aryl ether sulfone)to form the all-organic polymer composites for hightemperature capacitive energy storage.Upon ultraviolet irradiation,the crosslinked polymer composites with polymer dots are efficient in suppressing electrical conduction at high electric fields and elevated temperatures,which significantly reduces the high-field energy loss of the composites at 200℃.Accordingly,the ultraviolet-irradiated composite film exhibits a discharged energy density of 4.2 J cm^(−3)at 200℃.Along with outstanding cyclic stability of capacitive performance at 200℃,this work provides a promising class of dielectric materials for robust high-performance all-organic dielectric nanocomposites.展开更多
Photocatalytic H_(2) evolution from seawater splitting presents a promising approach to tackle the fossil energy crisis and mitigate carbon emission due to the abundant source of seawater and sunlight on the earth.How...Photocatalytic H_(2) evolution from seawater splitting presents a promising approach to tackle the fossil energy crisis and mitigate carbon emission due to the abundant source of seawater and sunlight on the earth.However,the development of efficient photocatalysts for seawater splitting remains a formidable challenge.Herein,a 2D/2D ZnIn_(2)S_(4)/WO_(3)(ZIS/WO_(3))heterojunction nanostructure is fabricated to efficiently separate the photoinduced carriers by steering electron transfer from the conduction band minimum of WO_(3) to the valence band maximum of ZIS via constructing internal electric field.Subsequently,plasmonic Au nanoparticles(NPs)as a novel photosensitizer and a reduction cocatalyst are anchored on ZIS/WO_(3) surface to further enhance the optical absorption of ZIS/WO_(3) heterojunction and accelerate the catalytic conversion.The obtained Au/ZIS/WO_(3) photocatalyst exhibits an outstanding H_(2) evolution rate of 2610.6 or 3566.3μmol g^(-1)h~(-1)from seawater splitting under visible or full-spectrum light irradiation,respectively.These rates represent an impressive increase of approximately 7.3-and 6,6-fold compared to those of ZIS under the illumination of the same light source.The unique 2D/2D structure,internal electric field,and plasmonic metal modification together boost the photocatalytic H_(2) evolution rate of Au/ZIS/WO_(3),making it even comparable to H_(2) evolution from pure water splitting.The present work sheds light on the development of efficient photocatalysts for seawater splitting.展开更多
We report on an experiment performed at the FLASH2 free-electron laser(FEL)aimed at producing warm dense matter via soft x-ray isochoric heating.In the experiment,we focus on study of the ions emitted during the soft ...We report on an experiment performed at the FLASH2 free-electron laser(FEL)aimed at producing warm dense matter via soft x-ray isochoric heating.In the experiment,we focus on study of the ions emitted during the soft x-ray ablation process using time-of-flight electron multipliers and a shifted Maxwell–Boltzmann velocity distribution model.We find that most emitted ions are thermal,but that some impurities chemisorbed on the target surface,such as protons,are accelerated by the electrostatic field created in the plasma by escaped electrons.The morphology of the complex crater structure indicates the presence of several ion groups with varying temperatures.We find that the ion sound velocity is controlled by the ion temperature and show how the ion yield depends on the FEL radiation attenuation length in different materials.展开更多
Employing colliding-pulse injection has been shown to enable the generation of high-quality electron beams from laser-plasma accelerators.Here,by using test particle simulations,Hamiltonian analysis,and multidimension...Employing colliding-pulse injection has been shown to enable the generation of high-quality electron beams from laser-plasma accelerators.Here,by using test particle simulations,Hamiltonian analysis,and multidimensional particle-in-cell simulations,we lay the theoretical framework for spin-polarized electron beam generation in the colliding-pulse injection scheme.Furthermore,we show that this scheme enables the production of quasi-monoenergetic electron beams in excess of 80%polarization and tens of pC charge with commercial 10-TW-class laser systems.展开更多
Herein,a simple synthetic approach is employed for the atomic dispersion of Rh atoms(Rh SAs)over the surface of interconnected Mo_(2)C nanosheets intimately embedded in a three-dimensional Ni_(x)MoO_(y)nanorod arrays(...Herein,a simple synthetic approach is employed for the atomic dispersion of Rh atoms(Rh SAs)over the surface of interconnected Mo_(2)C nanosheets intimately embedded in a three-dimensional Ni_(x)MoO_(y)nanorod arrays(Ni_(x)MoO_(y)NRs)framework;we found that the introduction of both isolated Rh SAs and Ni_(x)MoO_(y)NRs adjusts the electrocatalytic function of the host Mo_(2)C toward the direction of being an advanced and highly stable electrocatalyst for efficient hydrogen evolution at pH-universal conditions.As a result,the proposed catalyst outperforms most recently reported transition metal-based catalysts,and its performance even rivals that of commercial Pt/C,as demonstrated by its ultralow overpotentials of 31.7,109.7,and 95.4 mV at a current density of 10 mA cm^(-2),along with its small Tafel slopes of 42.4,51.2,and 46.8 mV dec^(-1)in acidic,neutral,and alkaline conditions,respectively.In addition,the catalyst shows remarkable long-term stability over all pH values with good maintenance of its catalytic activity and structural characteristics after continuous operation.展开更多
Several years ago DESY faced the need to change the Electronic Mail service to support it on a central cluster of servers.The centralized architecture was necessary for deployment of unified internal E-Mail standards,...Several years ago DESY faced the need to change the Electronic Mail service to support it on a central cluster of servers.The centralized architecture was necessary for deployment of unified internal E-Mail standards,better quality of service and security,To implemnet a new policy for Electronic Mail Service and avoid huge modifications to a few hundreds network nodes,an additional DNS feature has been added to ISC's (Internet Software Consortium)software bind-4.9.7.The DNS servers running at DESY are capable of distingushing between DNS queries coming from inside and outside of the campus netwokr and reply with different list of MX(Mail Exchanger)records.The external hosts always get a list of MX records pointing to the central mail servers while the internal hosts may use different paths for mail exchange within the campus network.A modified version of DNS software has been used at DESY since 1997,It is fully compliant with the original goal of the projcet and shows good operational performance and reliability.展开更多
The infiuence of small calcium additions on the high-temperature mechanical behaviour in an extruded Mg-6Zn-l Y(wt.%)alloy reinforced by the I-phase has been investigated.Calcium promotes the formation of the intermet...The infiuence of small calcium additions on the high-temperature mechanical behaviour in an extruded Mg-6Zn-l Y(wt.%)alloy reinforced by the I-phase has been investigated.Calcium promotes the formation of the intermetallic Mg6Zn3Ca2 phase instead of 1-phase,which results in a noticeable improvement of the yield strength and ultimate tensile strength of the alloy above 100℃.The strength of the alloys was analysed taking into account the contribution due to the grain size,the crystallographic texture and the volume fraction and nature of second phase particles.In situ synchrotron radiation diffraction experiments have been used to evaluate the load partitioning between the magnesium matrix and the second phase particles(1-and MgeZgCa?phases)in both alloys.The load transfer from the magnesium matrix towards the MgeZihCa?phase is markedly more effective than that for the I-phase over the entire temperature range,especially at 200°C,temperature at which the reinforcement effect of the I-phase is null.展开更多
The structural changes around a crack tip in a high density polyethylene were investigated by means of scanning synchrotron microfocus small-angle X-ray scattering technique. The scattering data confirm the process of...The structural changes around a crack tip in a high density polyethylene were investigated by means of scanning synchrotron microfocus small-angle X-ray scattering technique. The scattering data confirm the process of craze structure development near a crack tip based on the evolution of voids. In addition, it was found that the main stress in the plastic zone near a crack tip exhibited a gradient distribution with respect to its strength and direction. The whole damaged area showed a strain distribution indicating a flow behavior toward the crack tip.展开更多
The electrical conductivity of water under extreme temperatures and densities plays a central role in modeling planetary magnetic fields.Experimental data are vital to test theories of high-energy-densitywater and ass...The electrical conductivity of water under extreme temperatures and densities plays a central role in modeling planetary magnetic fields.Experimental data are vital to test theories of high-energy-densitywater and assess the possible development and presence of extraterrestrial life.These states are also important in biology and chemistry studies when specimens in water are confined and excited using ultrafast optical or free-electron lasers(FELs).Here we utilize femtosecond optical lasers to measure the transient reflection and transmission of ultrathin water sheet samples uniformly heated by a 13.6 nm FEL approaching a highly conducting state at electron temperatures exceeding 20000 K.The experiment probes the trajectory ofwater through the high-energy-density phase space and provides insights into changes in the index of refraction,charge carrier densities,andACelectrical conductivity at optical frequencies.At excitation energy densities exceeding 10MJ/kg,the index of refraction falls to n0.7,and the thermally excited free-carrier density reaches ne531027 m−3,which is over an order of magnitude higher than that of the electron carriers produced by direct photoionization.Significant specular reflection is observed owing to critical electron density shielding of electromagnetic waves.Themeasured optical conductivity reaches 23104 S/m,a value that is one to two orders of magnitude lower than those of simplemetals in a liquid state.At electron temperatures below 15000 K,the experimental results agreewell with the theoretical calculations using density-functional theory/molecular-dynamics simulations.With increasing temperature,the electron density increases and the system approaches a Fermi distribution.In this regime,the conductivities agree better with predictions from the Ziman theory of liquid metals.展开更多
A method for noninvasive determination of fat and water content in the human body is examined. A spatially resolved spectroscopy method is used which can record low intensity near infrared spectra. This novel approach...A method for noninvasive determination of fat and water content in the human body is examined. A spatially resolved spectroscopy method is used which can record low intensity near infrared spectra. This novel approach is compared to other methods for the determination of fat and water content. Monte Carlo simulations of light propagation in tissue are shown and the production and characterization of optical phantoms of adipose tissue are investigated.展开更多
The hydrogen-induced defeats in FZ silicon grown in hydrogen atmosphere hare been investigated by both the conventional and the in situ white beam synchrotron radiation topography.The formation process of the defects ...The hydrogen-induced defeats in FZ silicon grown in hydrogen atmosphere hare been investigated by both the conventional and the in situ white beam synchrotron radiation topography.The formation process of the defects is discussed.展开更多
文摘We will describe how Linux is embedded into DESY's unix computing,our support concept and policies,tools used and developed,and the challenges which we are facing now that the number of supported PCs is rapidly approaching one thousand.
基金the National Natural Science Foundation of China(No.51973080,92066104).
文摘Polymer dielectrics capable of operating efficiently at high electric fields and elevated temperatures are urgently demanded by next-generation electronics and electrical power systems.While inorganic fillers have been extensively utilized to improved high-temperature capacitive performance of dielectric polymers,the presence of thermodynamically incompatible organic and inorganic components may lead to concern about the long-term stability and also complicate film processing.Herein,zero-dimensional polymer dots with high electron affinity are introduced into photoactive allyl-containing poly(aryl ether sulfone)to form the all-organic polymer composites for hightemperature capacitive energy storage.Upon ultraviolet irradiation,the crosslinked polymer composites with polymer dots are efficient in suppressing electrical conduction at high electric fields and elevated temperatures,which significantly reduces the high-field energy loss of the composites at 200℃.Accordingly,the ultraviolet-irradiated composite film exhibits a discharged energy density of 4.2 J cm^(−3)at 200℃.Along with outstanding cyclic stability of capacitive performance at 200℃,this work provides a promising class of dielectric materials for robust high-performance all-organic dielectric nanocomposites.
基金supported by the National Natural Science Foundation of China(21872104,21501131,21978216 and 22272082)the Natural Science Foundation of Tianjin for Distinguished Young Scholar(20JCJQJC00150)the Analytical&Testing Center of Tiangong University for PL work。
文摘Photocatalytic H_(2) evolution from seawater splitting presents a promising approach to tackle the fossil energy crisis and mitigate carbon emission due to the abundant source of seawater and sunlight on the earth.However,the development of efficient photocatalysts for seawater splitting remains a formidable challenge.Herein,a 2D/2D ZnIn_(2)S_(4)/WO_(3)(ZIS/WO_(3))heterojunction nanostructure is fabricated to efficiently separate the photoinduced carriers by steering electron transfer from the conduction band minimum of WO_(3) to the valence band maximum of ZIS via constructing internal electric field.Subsequently,plasmonic Au nanoparticles(NPs)as a novel photosensitizer and a reduction cocatalyst are anchored on ZIS/WO_(3) surface to further enhance the optical absorption of ZIS/WO_(3) heterojunction and accelerate the catalytic conversion.The obtained Au/ZIS/WO_(3) photocatalyst exhibits an outstanding H_(2) evolution rate of 2610.6 or 3566.3μmol g^(-1)h~(-1)from seawater splitting under visible or full-spectrum light irradiation,respectively.These rates represent an impressive increase of approximately 7.3-and 6,6-fold compared to those of ZIS under the illumination of the same light source.The unique 2D/2D structure,internal electric field,and plasmonic metal modification together boost the photocatalytic H_(2) evolution rate of Au/ZIS/WO_(3),making it even comparable to H_(2) evolution from pure water splitting.The present work sheds light on the development of efficient photocatalysts for seawater splitting.
文摘We report on an experiment performed at the FLASH2 free-electron laser(FEL)aimed at producing warm dense matter via soft x-ray isochoric heating.In the experiment,we focus on study of the ions emitted during the soft x-ray ablation process using time-of-flight electron multipliers and a shifted Maxwell–Boltzmann velocity distribution model.We find that most emitted ions are thermal,but that some impurities chemisorbed on the target surface,such as protons,are accelerated by the electrostatic field created in the plasma by escaped electrons.The morphology of the complex crater structure indicates the presence of several ion groups with varying temperatures.We find that the ion sound velocity is controlled by the ion temperature and show how the ion yield depends on the FEL radiation attenuation length in different materials.
基金The original version of the PIC code EPOCH adapted here is funded by UK EPSRC Grant Nos.EP/G054950/1,EP/G056803/1,EP/G055165/1m,and EP/M022463/1.Z.G.would like to thank Rong-Hao Hu for useful discussions.The authors gratefully acknowledge the Gauss Centre for Supercomputing e.V.(https://www.gauss-centre.eu/)for providing computing time used for the FBPIC simulations through the John von Neumann Institute for Computing(NIC)on the GCS Supercomputer JUWELS at the Jülich Supercomputing Centre(JSC).
文摘Employing colliding-pulse injection has been shown to enable the generation of high-quality electron beams from laser-plasma accelerators.Here,by using test particle simulations,Hamiltonian analysis,and multidimensional particle-in-cell simulations,we lay the theoretical framework for spin-polarized electron beam generation in the colliding-pulse injection scheme.Furthermore,we show that this scheme enables the production of quasi-monoenergetic electron beams in excess of 80%polarization and tens of pC charge with commercial 10-TW-class laser systems.
基金Supported from the Regional Leading Research Center Program(2019R1A5A8080326)through the National Research Foundation funded by the Ministry of Science and ICT of Republic of Korea.
文摘Herein,a simple synthetic approach is employed for the atomic dispersion of Rh atoms(Rh SAs)over the surface of interconnected Mo_(2)C nanosheets intimately embedded in a three-dimensional Ni_(x)MoO_(y)nanorod arrays(Ni_(x)MoO_(y)NRs)framework;we found that the introduction of both isolated Rh SAs and Ni_(x)MoO_(y)NRs adjusts the electrocatalytic function of the host Mo_(2)C toward the direction of being an advanced and highly stable electrocatalyst for efficient hydrogen evolution at pH-universal conditions.As a result,the proposed catalyst outperforms most recently reported transition metal-based catalysts,and its performance even rivals that of commercial Pt/C,as demonstrated by its ultralow overpotentials of 31.7,109.7,and 95.4 mV at a current density of 10 mA cm^(-2),along with its small Tafel slopes of 42.4,51.2,and 46.8 mV dec^(-1)in acidic,neutral,and alkaline conditions,respectively.In addition,the catalyst shows remarkable long-term stability over all pH values with good maintenance of its catalytic activity and structural characteristics after continuous operation.
文摘Several years ago DESY faced the need to change the Electronic Mail service to support it on a central cluster of servers.The centralized architecture was necessary for deployment of unified internal E-Mail standards,better quality of service and security,To implemnet a new policy for Electronic Mail Service and avoid huge modifications to a few hundreds network nodes,an additional DNS feature has been added to ISC's (Internet Software Consortium)software bind-4.9.7.The DNS servers running at DESY are capable of distingushing between DNS queries coming from inside and outside of the campus netwokr and reply with different list of MX(Mail Exchanger)records.The external hosts always get a list of MX records pointing to the central mail servers while the internal hosts may use different paths for mail exchange within the campus network.A modified version of DNS software has been used at DESY since 1997,It is fully compliant with the original goal of the projcet and shows good operational performance and reliability.
基金The authors would like to acknowledge financial support of the Spanish Ministry of Science and Innovation under project number MAT2016-78850-RWe would like to acknowledge the expert support of A.Garcia,A.Tomas and M.Maier for assistance with SEM.The Deutches Elektronen-Synchrotron DESY is acknowledged for the provision of beamtime at the P07 beamline of the PETRA III synchrotron facility in the framework of proposal I-20170054EC.
文摘The infiuence of small calcium additions on the high-temperature mechanical behaviour in an extruded Mg-6Zn-l Y(wt.%)alloy reinforced by the I-phase has been investigated.Calcium promotes the formation of the intermetallic Mg6Zn3Ca2 phase instead of 1-phase,which results in a noticeable improvement of the yield strength and ultimate tensile strength of the alloy above 100℃.The strength of the alloys was analysed taking into account the contribution due to the grain size,the crystallographic texture and the volume fraction and nature of second phase particles.In situ synchrotron radiation diffraction experiments have been used to evaluate the load partitioning between the magnesium matrix and the second phase particles(1-and MgeZgCa?phases)in both alloys.The load transfer from the magnesium matrix towards the MgeZihCa?phase is markedly more effective than that for the I-phase over the entire temperature range,especially at 200°C,temperature at which the reinforcement effect of the I-phase is null.
基金supported by the"Hundred Talents Project"of the Chinese Academy of Sciences,the National Basic Research Program of China(No.2005CB623800)National Natural Science Foundation of China(Nos.50603024, 50621302) and HASYLAB projectⅡ-20052011
文摘The structural changes around a crack tip in a high density polyethylene were investigated by means of scanning synchrotron microfocus small-angle X-ray scattering technique. The scattering data confirm the process of craze structure development near a crack tip based on the evolution of voids. In addition, it was found that the main stress in the plastic zone near a crack tip exhibited a gradient distribution with respect to its strength and direction. The whole damaged area showed a strain distribution indicating a flow behavior toward the crack tip.
基金supported by the U.S.Department of Energy,Office of Science,Fusion Energy Science under Grant No.FWP 100182support from the Natural Sciences and Engineering Research Council of Canada(NSERC)+4 种基金supported by the U.S.Department of Energy,Office of Science,Office of Basic Energy Sciences under Contract No.DE-AC02-76SF00515support from the U.S.Department of Energy,Laboratory Directed Research and Development(LDRD)Program at SLAC National Accelerator Laboratory,under Contract No.DE-AC02-76SF00515support within the Research Unit Grant No.FOR 2440supported in part by the U.S.Department of Energy,Office of Science,Office of Workforce Development for Teachers and Scientists(WDTS)under the Science Undergraduate Laboratory Internships(SULI)Programsupport from the LOEWE Excellence Initiative of the State of Hessen.
文摘The electrical conductivity of water under extreme temperatures and densities plays a central role in modeling planetary magnetic fields.Experimental data are vital to test theories of high-energy-densitywater and assess the possible development and presence of extraterrestrial life.These states are also important in biology and chemistry studies when specimens in water are confined and excited using ultrafast optical or free-electron lasers(FELs).Here we utilize femtosecond optical lasers to measure the transient reflection and transmission of ultrathin water sheet samples uniformly heated by a 13.6 nm FEL approaching a highly conducting state at electron temperatures exceeding 20000 K.The experiment probes the trajectory ofwater through the high-energy-density phase space and provides insights into changes in the index of refraction,charge carrier densities,andACelectrical conductivity at optical frequencies.At excitation energy densities exceeding 10MJ/kg,the index of refraction falls to n0.7,and the thermally excited free-carrier density reaches ne531027 m−3,which is over an order of magnitude higher than that of the electron carriers produced by direct photoionization.Significant specular reflection is observed owing to critical electron density shielding of electromagnetic waves.Themeasured optical conductivity reaches 23104 S/m,a value that is one to two orders of magnitude lower than those of simplemetals in a liquid state.At electron temperatures below 15000 K,the experimental results agreewell with the theoretical calculations using density-functional theory/molecular-dynamics simulations.With increasing temperature,the electron density increases and the system approaches a Fermi distribution.In this regime,the conductivities agree better with predictions from the Ziman theory of liquid metals.
文摘A method for noninvasive determination of fat and water content in the human body is examined. A spatially resolved spectroscopy method is used which can record low intensity near infrared spectra. This novel approach is compared to other methods for the determination of fat and water content. Monte Carlo simulations of light propagation in tissue are shown and the production and characterization of optical phantoms of adipose tissue are investigated.
文摘The hydrogen-induced defeats in FZ silicon grown in hydrogen atmosphere hare been investigated by both the conventional and the in situ white beam synchrotron radiation topography.The formation process of the defects is discussed.
