The tuneable effects concept is aimed at achieving selectable blast and fragmentation output,to enable one charge to be used in different scenarios requiring different levels of blast and fragmentation lethality.It is...The tuneable effects concept is aimed at achieving selectable blast and fragmentation output,to enable one charge to be used in different scenarios requiring different levels of blast and fragmentation lethality.It is a concept Qineti Q has been developing for an energetic fill consisting of three principal components arranged in co-axial layers,two explosive layers separated by a mitigating but reactive layer.The concept was originally designed to operate in two modes,a low output mode which only detonates the central core of high explosive and a high output mode which detonated both the central core and outer layer of the explosive.Two charge case designs where manufactured and tested;one of these designs showed a reduction in blast and fragment velocities of^33%and^20%,respectively,in the low output mode.展开更多
This paper presents a simple Josephson-junction circuit with two parameters (inductance and capacitance) which can be tuned to represent different energy landscapes with different physical properties. By tuning this q...This paper presents a simple Josephson-junction circuit with two parameters (inductance and capacitance) which can be tuned to represent different energy landscapes with different physical properties. By tuning this quantum circuit through external accessible elements we can move from two to three and more energy levels depending on the parameter setting. The inductance, the capacitance as well as the external voltage (driving terms) condition the number of relevant energy levels as well as the model to be used. We show that the quantized circuit represents a multi-state system with tunneling induced by the Landau-Zener and Landau-Zener-Stückelberg transition. The special cases of single crossing and multi-crossing models are thoroughly studied and the transition probability is obtained in each case. It is proven that, the crossing time as well as the relaxation time affect drastically the transition probability;the system mimics a single passage for short relaxation and a multiple passage problem for large relaxation. The nonlinearity of energy levels modifies the transition probability and the derived adiabatic parameters help to redefine the Landau-Zener probability. The observed constructive and destructive interferences are parametrically conditioned by the initial condition set by the inductive branch. Moreover, the total population transfers as well as the complete blockage of the system are obtained in a permissible range of parameters only by changing the values of the inductance. Therefore, the system models a controllable level-crossing where the additional branches (inductive and capacitive) help in designing the number of states, the type of interferometry as well as the control of states occupation.展开更多
A theoretical analysis of a tuneable optical filter is presented by proposing an optical ring resonator (ORR) using photonic crystal fiber (PCF) as the resonance loop. The influences of the characteristic parameters o...A theoretical analysis of a tuneable optical filter is presented by proposing an optical ring resonator (ORR) using photonic crystal fiber (PCF) as the resonance loop. The influences of the characteristic parameters of the PCF on the filter response have been analyzed under steady-state condition of the ORR. It is shown that the tuneability of the filter is mainly achieved by changing the modulation frequency of the light signal applied to the resonator. The analyses have shown that the sharpness and the depth of the filter response are controlled by parameters such as amplitude modulation index of applied field, the coupling coefficient of the ORR, and hole-spacing and air-filling ratio of the PCF, respectively. When transmission coefficient of the loop approaches the coupling coefficient, the filter response enhances sharply with PCF parameters. The depth and the full-width half-maximum (FWHM) of the response strongly depends on the number of field circulations in the resonator loop. With the proposed tuneability scheme for optical filter, we achieved an FWHM of ~1.55 nm. The obtained results may be utilized in designing optical add/drop filters used in WDM communication systems.展开更多
Effective control of terahertz radiation requires fast and efficient modulators with a large modulation depth-a challenge that is often tackled by using metamaterials.Metamaterial-based active modulators can be create...Effective control of terahertz radiation requires fast and efficient modulators with a large modulation depth-a challenge that is often tackled by using metamaterials.Metamaterial-based active modulators can be created by placing graphene as a tuneable element shunting regions of high electric field confinement in metamaterials.However,in this common approach,the graphene is used as a variable resistor,and the modulation is achieved by resistive damping of the resonance.In combination with the finite conductivity of graphene due to its gapless nature,achieving 100%modulation depth using this approach remains challenging.Here,we embed nanoscale graphene capacitors within the gaps of the metamaterial resonators,and thus switch from a resistive damping to a capacitive tuning of the resonance.We further expand the optical modulation range by device excitation from its substrate side.As a result,we demonstrate terahertz modulators with over four orders of magnitude modulation depth(45.7 dB at 1.68 THz and 40.1 dB at 2.15 THz),and a reconfiguration speed of 30 MHz.These tuneable capacitance modulators are electrically controlled solid-state devices enabling unity modulation with graphene conductivities below 0.7 mS.The demonstrated approach can be applied to enhance modulation performance of any metamaterial-based modulator with a 2D electron gas.Our results open up new frontiers in the area of terahertz communications,real-time imaging,and wave-optical analogue computing.展开更多
By changing both the monomer composition and the polymer structure, we have varied the mechanical properties of resorbable polymers. The polymers were synthesized by ring-opening polymerization using L-lactide （LLA...By changing both the monomer composition and the polymer structure, we have varied the mechanical properties of resorbable polymers. The polymers were synthesized by ring-opening polymerization using L-lactide （LLA）, ε-caprolactone （εCL）, trimethylene carbonate （TMC） and 1,5-dioxepan-2-one （DXO） as monomers. Well-defined triblock copolymers, microblock copolymers and networks have been evaluated, and comparisons between them show that it is possible to tune the mechanical properties. Triblock copolymers with an amorphous middle block of poly（1,5-dioxepan-2- one） （PDXO） and semi-crystalline end-blocks of poly（ε-caprolactone） （PCL） were stronger and had a higher strain at break than triblock copolymers with poly（L-lactide） （PLLA） as end-blocks. Polymers with both DXO and TMC in the amorphous middle-block and PLLA as end-blocks showed a lower stress at break, but the material gained elasticity, a property which is very valuable in tissue engineering. Mechanical properties of networks, synthesized by a novel method, containing PDXO and PCL are also presented. Although it is difficult to compare them with the uncross-linked polymers, this is an additional way to modify and widen the properties.展开更多
The direct excitation of CO2 using fast （nanosecond） and ultrafast （femtosecond） pulsed lasers was investigated.A gas reaction cell was used to excite CO2 in a 50：50 mixture of CO2 and CH4 using nano-and femtosec...The direct excitation of CO2 using fast （nanosecond） and ultrafast （femtosecond） pulsed lasers was investigated.A gas reaction cell was used to excite CO2 in a 50：50 mixture of CO2 and CH4 using nano-and femtosecond laser systems,to induce a reaction between these two compounds.FT-IR spectra showed that CO was formed using the nanosecond and femtosecond laser systems.It was also found that hydrocarbons,containing C-C bonds were formed.For both the nanosecond and femtosecond laser,it was found that more C-C higher hydrocarbons were formed after 5 h compared to 3 h of irradiation.Irradiation at pressures of 250,350 and 500 kPa with the femtosecond laser system showed the expected increase in the amount of CO formed with an increase in pressure.Results from this study showed that carbon dioxide and methane can be activated successfully using nanosecond laser pulses at 2000 nm and femtosecond laser pulses at 795 or 2000 nm and that these activated species react to form CO and C-C containing products.展开更多
Salination of solutions of salinity gradient releases large‐scale clean and renewable energy, which can be directly and efficiently transformed into electrical energy using ion‐selective nanofluidic channel membrane...Salination of solutions of salinity gradient releases large‐scale clean and renewable energy, which can be directly and efficiently transformed into electrical energy using ion‐selective nanofluidic channel membranes. However, conventional ion‐selective membranes are typically either cation‐ or anion‐selective. A pH‐switchable system capable of dual cation and anion transport along with salt gradient energy harvesting properties has not been demonstrated in ion‐selective membranes. Here, we constructed an amphoteric heterolayer metal–organic framework (MOF) membrane with subnanochannels modified with carboxylic and amino functional groups. The amphoteric MOF‐composite membrane, AAO/aUiO‐66‐(COOH)2/UiO‐66‐NH2, exhibits pH‐tuneable ion conduction and achieves osmotic energy conversion of 7.4 and 5.7 W/m2 in acidic and alkaline conditions, respectively, using a 50‐fold salt gradient. For different anions but the same cation diffusion transport, the amphoteric membrane produces an outstanding I−/CO32− selectivity of ~4160 and an osmotic energy conversion of ~133.5 W/m2. The amphoteric membrane concept introduces a new pathway to explore the development of ion transport and separation technologies and their application in osmotic energy‐conversion devices and flow batteries.展开更多
The creation of universal strategies to affect the reaction route of the electroreduction of CO_(2) is critical.Here,we report the first work to introduce cations into diverse metals such as Cu,Bi,In,and Sn via the el...The creation of universal strategies to affect the reaction route of the electroreduction of CO_(2) is critical.Here,we report the first work to introduce cations into diverse metals such as Cu,Bi,In,and Sn via the electroreduction of related metallic oxides in quaternary ammonium surfactant solutions.Compared to their physical adsorption,cations embedded into the electrodes have a more pronounced impact on the electrical field,which effectively influences the adsorption state of intermediates.With the increase of surface field,the hydrogen evolution reaction and*COOH route are significantly reduced,favouring the*OCHO pathway instead.As a result,hydrogen,CO,and C_(2+)products almost completely vanish at−0.5 V versus RHE in 0.1 M Na_(2)SO_(4)in an H-type cell after enough cations are embedded into the Cu electrode,and the faradaic efficiency of formate rises from 18.0%to 99.5%simultaneously.展开更多
Propagation of light beams through scattering or multimode systems may lead to the randomization of the spatial coherence of the light.Although information is not lost,its recovery requires a coherent interferometric ...Propagation of light beams through scattering or multimode systems may lead to the randomization of the spatial coherence of the light.Although information is not lost,its recovery requires a coherent interferometric reconstruction of the original signals,which have been scrambled into the modes of the scattering system.Here we show that we can automatically unscramble optical beams that have been arbitrarily mixed in a multimode waveguide,undoing the scattering and mixing between the spatial modes through a mesh of silicon photonics tuneable beam splitters.Transparent light detectors integrated in a photonic chip are used to directly monitor the evolution of each mode along the mesh,allowing sequential tuning and adaptive individual feedback control of each beam splitter.The entire mesh self-configures automatically through a progressive tuning algorithm and resets itself after significantly perturbing the mixing,without turning off the beams.We demonstrate information recovery by the simultaneous unscrambling,sorting and tracking of four mixed modes,with residual cross-talk of−20 dB between the beams.Circuit partitioning assisted by transparent detectors enables scalability to meshes with a higher port count and to a higher number of modes without a proportionate increase in the control complexity.The principle of self-configuring and self-resetting in optical systems should be applicable in a wide range of optical applications.展开更多
基金financial support of the Anglo-French Materials and Components for Missiles, Innovation and Technology Partnership (MCM ITP) program jointly funded by UK MoD (Dstl) and DGA
文摘The tuneable effects concept is aimed at achieving selectable blast and fragmentation output,to enable one charge to be used in different scenarios requiring different levels of blast and fragmentation lethality.It is a concept Qineti Q has been developing for an energetic fill consisting of three principal components arranged in co-axial layers,two explosive layers separated by a mitigating but reactive layer.The concept was originally designed to operate in two modes,a low output mode which only detonates the central core of high explosive and a high output mode which detonated both the central core and outer layer of the explosive.Two charge case designs where manufactured and tested;one of these designs showed a reduction in blast and fragment velocities of^33%and^20%,respectively,in the low output mode.
文摘This paper presents a simple Josephson-junction circuit with two parameters (inductance and capacitance) which can be tuned to represent different energy landscapes with different physical properties. By tuning this quantum circuit through external accessible elements we can move from two to three and more energy levels depending on the parameter setting. The inductance, the capacitance as well as the external voltage (driving terms) condition the number of relevant energy levels as well as the model to be used. We show that the quantized circuit represents a multi-state system with tunneling induced by the Landau-Zener and Landau-Zener-Stückelberg transition. The special cases of single crossing and multi-crossing models are thoroughly studied and the transition probability is obtained in each case. It is proven that, the crossing time as well as the relaxation time affect drastically the transition probability;the system mimics a single passage for short relaxation and a multiple passage problem for large relaxation. The nonlinearity of energy levels modifies the transition probability and the derived adiabatic parameters help to redefine the Landau-Zener probability. The observed constructive and destructive interferences are parametrically conditioned by the initial condition set by the inductive branch. Moreover, the total population transfers as well as the complete blockage of the system are obtained in a permissible range of parameters only by changing the values of the inductance. Therefore, the system models a controllable level-crossing where the additional branches (inductive and capacitive) help in designing the number of states, the type of interferometry as well as the control of states occupation.
文摘A theoretical analysis of a tuneable optical filter is presented by proposing an optical ring resonator (ORR) using photonic crystal fiber (PCF) as the resonance loop. The influences of the characteristic parameters of the PCF on the filter response have been analyzed under steady-state condition of the ORR. It is shown that the tuneability of the filter is mainly achieved by changing the modulation frequency of the light signal applied to the resonator. The analyses have shown that the sharpness and the depth of the filter response are controlled by parameters such as amplitude modulation index of applied field, the coupling coefficient of the ORR, and hole-spacing and air-filling ratio of the PCF, respectively. When transmission coefficient of the loop approaches the coupling coefficient, the filter response enhances sharply with PCF parameters. The depth and the full-width half-maximum (FWHM) of the response strongly depends on the number of field circulations in the resonator loop. With the proposed tuneability scheme for optical filter, we achieved an FWHM of ~1.55 nm. The obtained results may be utilized in designing optical add/drop filters used in WDM communication systems.
基金supported by the UK Engineering and Physical Sciences Research Council(EPSRC)grant EP/S023046/1 for the EPSRC Centre for Doctoral Training in Sensor Technologies for a Healthy and Sustainable Futurefunding from the HyperTerahertz grant,no.EP/P021859/1the TeraCom grant,no.EP/W028921/1。
文摘Effective control of terahertz radiation requires fast and efficient modulators with a large modulation depth-a challenge that is often tackled by using metamaterials.Metamaterial-based active modulators can be created by placing graphene as a tuneable element shunting regions of high electric field confinement in metamaterials.However,in this common approach,the graphene is used as a variable resistor,and the modulation is achieved by resistive damping of the resonance.In combination with the finite conductivity of graphene due to its gapless nature,achieving 100%modulation depth using this approach remains challenging.Here,we embed nanoscale graphene capacitors within the gaps of the metamaterial resonators,and thus switch from a resistive damping to a capacitive tuning of the resonance.We further expand the optical modulation range by device excitation from its substrate side.As a result,we demonstrate terahertz modulators with over four orders of magnitude modulation depth(45.7 dB at 1.68 THz and 40.1 dB at 2.15 THz),and a reconfiguration speed of 30 MHz.These tuneable capacitance modulators are electrically controlled solid-state devices enabling unity modulation with graphene conductivities below 0.7 mS.The demonstrated approach can be applied to enhance modulation performance of any metamaterial-based modulator with a 2D electron gas.Our results open up new frontiers in the area of terahertz communications,real-time imaging,and wave-optical analogue computing.
基金This work was supported by the Swedish Foundation for Strategic Research(No. A302:132).
文摘By changing both the monomer composition and the polymer structure, we have varied the mechanical properties of resorbable polymers. The polymers were synthesized by ring-opening polymerization using L-lactide （LLA）, ε-caprolactone （εCL）, trimethylene carbonate （TMC） and 1,5-dioxepan-2-one （DXO） as monomers. Well-defined triblock copolymers, microblock copolymers and networks have been evaluated, and comparisons between them show that it is possible to tune the mechanical properties. Triblock copolymers with an amorphous middle block of poly（1,5-dioxepan-2- one） （PDXO） and semi-crystalline end-blocks of poly（ε-caprolactone） （PCL） were stronger and had a higher strain at break than triblock copolymers with poly（L-lactide） （PLLA） as end-blocks. Polymers with both DXO and TMC in the amorphous middle-block and PLLA as end-blocks showed a lower stress at break, but the material gained elasticity, a property which is very valuable in tissue engineering. Mechanical properties of networks, synthesized by a novel method, containing PDXO and PCL are also presented. Although it is difficult to compare them with the uncross-linked polymers, this is an additional way to modify and widen the properties.
文摘The direct excitation of CO2 using fast （nanosecond） and ultrafast （femtosecond） pulsed lasers was investigated.A gas reaction cell was used to excite CO2 in a 50：50 mixture of CO2 and CH4 using nano-and femtosecond laser systems,to induce a reaction between these two compounds.FT-IR spectra showed that CO was formed using the nanosecond and femtosecond laser systems.It was also found that hydrocarbons,containing C-C bonds were formed.For both the nanosecond and femtosecond laser,it was found that more C-C higher hydrocarbons were formed after 5 h compared to 3 h of irradiation.Irradiation at pressures of 250,350 and 500 kPa with the femtosecond laser system showed the expected increase in the amount of CO formed with an increase in pressure.Results from this study showed that carbon dioxide and methane can be activated successfully using nanosecond laser pulses at 2000 nm and femtosecond laser pulses at 795 or 2000 nm and that these activated species react to form CO and C-C containing products.
文摘Salination of solutions of salinity gradient releases large‐scale clean and renewable energy, which can be directly and efficiently transformed into electrical energy using ion‐selective nanofluidic channel membranes. However, conventional ion‐selective membranes are typically either cation‐ or anion‐selective. A pH‐switchable system capable of dual cation and anion transport along with salt gradient energy harvesting properties has not been demonstrated in ion‐selective membranes. Here, we constructed an amphoteric heterolayer metal–organic framework (MOF) membrane with subnanochannels modified with carboxylic and amino functional groups. The amphoteric MOF‐composite membrane, AAO/aUiO‐66‐(COOH)2/UiO‐66‐NH2, exhibits pH‐tuneable ion conduction and achieves osmotic energy conversion of 7.4 and 5.7 W/m2 in acidic and alkaline conditions, respectively, using a 50‐fold salt gradient. For different anions but the same cation diffusion transport, the amphoteric membrane produces an outstanding I−/CO32− selectivity of ~4160 and an osmotic energy conversion of ~133.5 W/m2. The amphoteric membrane concept introduces a new pathway to explore the development of ion transport and separation technologies and their application in osmotic energy‐conversion devices and flow batteries.
基金the National Natural Science Foundation of China(grant nos.22073104,22273108,22293015,22072156,and 22121002)the Beijing Natural Science Foundation(grant no.2222043)+1 种基金the CAS Project for Young Scientists in Basic Research(grant no.YSBR-050)the Innovation Program of the IHEP(grant no.2023000034)for their financial support of this research。
文摘The creation of universal strategies to affect the reaction route of the electroreduction of CO_(2) is critical.Here,we report the first work to introduce cations into diverse metals such as Cu,Bi,In,and Sn via the electroreduction of related metallic oxides in quaternary ammonium surfactant solutions.Compared to their physical adsorption,cations embedded into the electrodes have a more pronounced impact on the electrical field,which effectively influences the adsorption state of intermediates.With the increase of surface field,the hydrogen evolution reaction and*COOH route are significantly reduced,favouring the*OCHO pathway instead.As a result,hydrogen,CO,and C_(2+)products almost completely vanish at−0.5 V versus RHE in 0.1 M Na_(2)SO_(4)in an H-type cell after enough cations are embedded into the Cu electrode,and the faradaic efficiency of formate rises from 18.0%to 99.5%simultaneously.
基金the European Union's Seventh FP7 Programme(Grant agreement No.323734,BBOI)the European Union’s H2020 Programme(Grant No.688172,STREAMS)+1 种基金Fondazione Cariplo(Grant No.2016-0881,ACTIO)by Multidisciplinary University Research Initiative grant(Air Force Office of Scientific Research,FA9550-12-1-0024)。
文摘Propagation of light beams through scattering or multimode systems may lead to the randomization of the spatial coherence of the light.Although information is not lost,its recovery requires a coherent interferometric reconstruction of the original signals,which have been scrambled into the modes of the scattering system.Here we show that we can automatically unscramble optical beams that have been arbitrarily mixed in a multimode waveguide,undoing the scattering and mixing between the spatial modes through a mesh of silicon photonics tuneable beam splitters.Transparent light detectors integrated in a photonic chip are used to directly monitor the evolution of each mode along the mesh,allowing sequential tuning and adaptive individual feedback control of each beam splitter.The entire mesh self-configures automatically through a progressive tuning algorithm and resets itself after significantly perturbing the mixing,without turning off the beams.We demonstrate information recovery by the simultaneous unscrambling,sorting and tracking of four mixed modes,with residual cross-talk of−20 dB between the beams.Circuit partitioning assisted by transparent detectors enables scalability to meshes with a higher port count and to a higher number of modes without a proportionate increase in the control complexity.The principle of self-configuring and self-resetting in optical systems should be applicable in a wide range of optical applications.
