A bilayer membrane acoustic metamaterial was proposed to overcome the influence of the mass law on traditional acoustic materials and obtain a lightweight thin-layer structure that can effectively isolate low frequenc...A bilayer membrane acoustic metamaterial was proposed to overcome the influence of the mass law on traditional acoustic materials and obtain a lightweight thin-layer structure that can effectively isolate low frequency noise. The finite element analysis（FEA） results agree well with the experimental results.It is proved that the sound transmission losses（STLs） of the proposed structures are higher than those of same surface density acoustic materials. The introduction of the magnetic mass block is different from the traditional design method, in which only a passive mass block is fixed on the membrane. The magnetic force will cause tension in the membrane, increase membrane prestress, and improve overall structural stiffness. The effects of the geometry size on the STLs are discussed in detail. The kind of method presented in this paper can provide a new means for engineering noise control.展开更多
In this paper, a new carbon fiber based cathode — a low-outgassing-rate carbon fiber array cathode — is investigated experimentally, and the experimental results are compared with those of a polymer velvet cathode. ...In this paper, a new carbon fiber based cathode — a low-outgassing-rate carbon fiber array cathode — is investigated experimentally, and the experimental results are compared with those of a polymer velvet cathode. The carbon fiber array cathode is constructed by inserting bunches of carbon fibers into the cylindrical surface of the cathode. In experiment, the diode base pressure is maintained at 1×10^（-2） Pa–2×10^（-2） Pa, and the diode is driven by a compact pulsed power system which can provide a diode voltage of about 100 kV and pulse duration of about 30 ns at a repetition rate of tens of Hz.Real-time pressure data are measured by a magnetron gauge. Under the similar conditions, the experimental results show that the outgassing rate of the carbon fiber array cathode is an order smaller than that of the velvet cathode and that this carbon fiber array cathode has better shot-to-shot stability than the velvet cathode. Hence, this carbon fiber array cathode is demonstrated to be a promising cathode for the radial diode, which can be used in magnetically insulated transmission line oscillator（MILO） and relativistic magnetron（RM）.展开更多
A waterproof nanocrystalline soft magnetic alloy core with a size of O.D.850 mm×I.D.316 mm×H.25 mm for radio frequency acceleration was successfully developed by winding 18μm 1k107b MA ribbons.Theμ'_(p...A waterproof nanocrystalline soft magnetic alloy core with a size of O.D.850 mm×I.D.316 mm×H.25 mm for radio frequency acceleration was successfully developed by winding 18μm 1k107b MA ribbons.Theμ'_(p)Qf products reached 7.5,10,and 12 GHz at 1,3,and 5 MHz,respectively.Theμ'_(p)Qf products of the MA core(O.D.250 mm×I.D.100 mm×H.25 mm)manufactured using a 13μm MA ribbon further increased by 30%.Detailed improvements on the MA core manufacture process are discussed herein.Continuous high-power tests on the new MA cores demonstrated its good performance of waterproofness,particularly its stability of highμ'_(p)Qf products.The MA core with highμ'pQf product and large size can operate under a high average RF power,high electric field,and in deionized water,which will be used in the China Spallation Neutron Source PhaseⅡ(CSNS-Ⅱ).展开更多
Picture this.On a freezing December day,a few days before Christmas,2008 an electrical fire started in the basement utility room.The burn damage was so severe at the origin site that the exact cause could not be deter...Picture this.On a freezing December day,a few days before Christmas,2008 an electrical fire started in the basement utility room.The burn damage was so severe at the origin site that the exact cause could not be determined,but the theory is that a transfer switch connected to an emergency power generator started the fire when an auto test series was initiated.The fire quickly spread to the ceiling of the basement utility room,which was not fire rated,and burned the floor out of the kitchen above,at the center of the two-story home.In a very short time,the kitchen collapsed into the basement.The fire began shortly after the five family members left for work and school and was discovered by a worker who arrived to complete a bathroom remodel.Thick black smoke poured through every vent to the outside.By the time firefighters gained control of the blaze,the 3,000-sq-ft house and everything in it was ruined.If this image conjures a big black carbon cloud for you,imagine what the family was going through.Everything they owned was burned or covered with black soot and ice.It was a devastating blow to a smart young family going about their daily lives.It was the epitome of a dark cloud,and a silver lining seemed only like a myth.About the same time,a group of local tradesmen called the Hamptons Green Alliance(HGA),who organized a few months earlier,were busy soliciting local architects.Through the AIA Peconic,the HGA sent an e-mail blast to all members in order to find a project they could initiate in order to exercise their old and new sustainable building skills.Their goals were to apply their cumulative knowledge and expertise in sustainable practices and integrate them into a sum greater than the parts.Each individual company had experience,but never before had they consciously collaborated on a design that integrated all their systems at once.All would share the benefit and help the HGA raise the bar on sustainable building so they could offer experience,expertise,and specific energy usage and production data,including life cycle analysis,to future clients.They offered their services at their cost,to any architect’s client interested in a new house or remodel that would be rebuilt with the highest and best sustainable practices possible.At the peak of the financial panic,AIA members found no takers.Richard(Ric)Stott,AIA LEED AP,architect,was a friend of the fire-struck family and of course offered help.After the first meeting with another family friend and architect Craig Lee,AIA,it struck Ric that this would be the perfect project for the Hamptons Green Alliance.The owner agreed,a meeting was scheduled,and a project involving all major trades,the architects,owners,and even the insurance adjusters was born.It was not hard for Ric to convince the team that the LEED for Homes program would be appropriate for this project and soon the team began meeting once a week to focus on goals,discuss strategy,and learn about the requirements of the LEED for Homes system.By default,it was an“Integrated Project Delivery”(IPD).All the team members were in play from the beginning,the budget was fixed at what the insurance claim paid,plus the owners’out-of-pocket expense to add a family room and bedroom.The commitment was made by the HGA members to work for no profit,which allowed the family to make the additions and improvements.At weekly meetings,the team decided to pursue LEED Platinum status,to incorporate all renewable technologies that were economically feasible,but first and foremost we would incorporate high performance building science as our basic energy conservation methodology.Besides aiming for LEED Platinum status,the team also established the goal to rebuild this project as carbon neutral.A major decision had to be made with respect to the existing structure.To demolish the house or salvage the frame was a dilemma.Building from scratch would be easier,faster,and probably cheaper,but was it the most sustainable?Does saving the remains of a charred wood frame add or subtract from the overall carbon footprint?Certainly,bringing the framing and sheathing to the landfill is not a carbon friendly concept.The family was concerned that if we saved the structure,it would retain the smoky smell and wanted a guarantee that no odors would be perceived,even on the hottest summer days.We contacted a number of fire renovation companies and they all agreed that full encapsulation would have to be performed on the structure after we cleared the burned and structurally compromised framing away.The majority of the frame was structurally sound and it would be difficult to recycle it,so the decision was made to re-use the frame and most of the exterior sheathing including a good portion of the existing cedar shingles.展开更多
基金supported by the National Natural Science Foundation of China (11474230)the Fundamental Research Funds for the Central Universities (3102016QD056) for financial support
文摘A bilayer membrane acoustic metamaterial was proposed to overcome the influence of the mass law on traditional acoustic materials and obtain a lightweight thin-layer structure that can effectively isolate low frequency noise. The finite element analysis（FEA） results agree well with the experimental results.It is proved that the sound transmission losses（STLs） of the proposed structures are higher than those of same surface density acoustic materials. The introduction of the magnetic mass block is different from the traditional design method, in which only a passive mass block is fixed on the membrane. The magnetic force will cause tension in the membrane, increase membrane prestress, and improve overall structural stiffness. The effects of the geometry size on the STLs are discussed in detail. The kind of method presented in this paper can provide a new means for engineering noise control.
基金Project supported by the National Natural Science Foundation of China(Grant No.61671457)
文摘In this paper, a new carbon fiber based cathode — a low-outgassing-rate carbon fiber array cathode — is investigated experimentally, and the experimental results are compared with those of a polymer velvet cathode. The carbon fiber array cathode is constructed by inserting bunches of carbon fibers into the cylindrical surface of the cathode. In experiment, the diode base pressure is maintained at 1×10^（-2） Pa–2×10^（-2） Pa, and the diode is driven by a compact pulsed power system which can provide a diode voltage of about 100 kV and pulse duration of about 30 ns at a repetition rate of tens of Hz.Real-time pressure data are measured by a magnetron gauge. Under the similar conditions, the experimental results show that the outgassing rate of the carbon fiber array cathode is an order smaller than that of the velvet cathode and that this carbon fiber array cathode has better shot-to-shot stability than the velvet cathode. Hence, this carbon fiber array cathode is demonstrated to be a promising cathode for the radial diode, which can be used in magnetically insulated transmission line oscillator（MILO） and relativistic magnetron（RM）.
基金supported by the funds of the National Natural Science Foundation of China (Nos. 11175194, 11875270, and U1832210)Youth Innovation Promotion Association CAS (No. 2018015)Guangdong Basic and Applied Basic Research Foundation (No.2019B1515120046)
文摘A waterproof nanocrystalline soft magnetic alloy core with a size of O.D.850 mm×I.D.316 mm×H.25 mm for radio frequency acceleration was successfully developed by winding 18μm 1k107b MA ribbons.Theμ'_(p)Qf products reached 7.5,10,and 12 GHz at 1,3,and 5 MHz,respectively.Theμ'_(p)Qf products of the MA core(O.D.250 mm×I.D.100 mm×H.25 mm)manufactured using a 13μm MA ribbon further increased by 30%.Detailed improvements on the MA core manufacture process are discussed herein.Continuous high-power tests on the new MA cores demonstrated its good performance of waterproofness,particularly its stability of highμ'_(p)Qf products.The MA core with highμ'pQf product and large size can operate under a high average RF power,high electric field,and in deionized water,which will be used in the China Spallation Neutron Source PhaseⅡ(CSNS-Ⅱ).
文摘Picture this.On a freezing December day,a few days before Christmas,2008 an electrical fire started in the basement utility room.The burn damage was so severe at the origin site that the exact cause could not be determined,but the theory is that a transfer switch connected to an emergency power generator started the fire when an auto test series was initiated.The fire quickly spread to the ceiling of the basement utility room,which was not fire rated,and burned the floor out of the kitchen above,at the center of the two-story home.In a very short time,the kitchen collapsed into the basement.The fire began shortly after the five family members left for work and school and was discovered by a worker who arrived to complete a bathroom remodel.Thick black smoke poured through every vent to the outside.By the time firefighters gained control of the blaze,the 3,000-sq-ft house and everything in it was ruined.If this image conjures a big black carbon cloud for you,imagine what the family was going through.Everything they owned was burned or covered with black soot and ice.It was a devastating blow to a smart young family going about their daily lives.It was the epitome of a dark cloud,and a silver lining seemed only like a myth.About the same time,a group of local tradesmen called the Hamptons Green Alliance(HGA),who organized a few months earlier,were busy soliciting local architects.Through the AIA Peconic,the HGA sent an e-mail blast to all members in order to find a project they could initiate in order to exercise their old and new sustainable building skills.Their goals were to apply their cumulative knowledge and expertise in sustainable practices and integrate them into a sum greater than the parts.Each individual company had experience,but never before had they consciously collaborated on a design that integrated all their systems at once.All would share the benefit and help the HGA raise the bar on sustainable building so they could offer experience,expertise,and specific energy usage and production data,including life cycle analysis,to future clients.They offered their services at their cost,to any architect’s client interested in a new house or remodel that would be rebuilt with the highest and best sustainable practices possible.At the peak of the financial panic,AIA members found no takers.Richard(Ric)Stott,AIA LEED AP,architect,was a friend of the fire-struck family and of course offered help.After the first meeting with another family friend and architect Craig Lee,AIA,it struck Ric that this would be the perfect project for the Hamptons Green Alliance.The owner agreed,a meeting was scheduled,and a project involving all major trades,the architects,owners,and even the insurance adjusters was born.It was not hard for Ric to convince the team that the LEED for Homes program would be appropriate for this project and soon the team began meeting once a week to focus on goals,discuss strategy,and learn about the requirements of the LEED for Homes system.By default,it was an“Integrated Project Delivery”(IPD).All the team members were in play from the beginning,the budget was fixed at what the insurance claim paid,plus the owners’out-of-pocket expense to add a family room and bedroom.The commitment was made by the HGA members to work for no profit,which allowed the family to make the additions and improvements.At weekly meetings,the team decided to pursue LEED Platinum status,to incorporate all renewable technologies that were economically feasible,but first and foremost we would incorporate high performance building science as our basic energy conservation methodology.Besides aiming for LEED Platinum status,the team also established the goal to rebuild this project as carbon neutral.A major decision had to be made with respect to the existing structure.To demolish the house or salvage the frame was a dilemma.Building from scratch would be easier,faster,and probably cheaper,but was it the most sustainable?Does saving the remains of a charred wood frame add or subtract from the overall carbon footprint?Certainly,bringing the framing and sheathing to the landfill is not a carbon friendly concept.The family was concerned that if we saved the structure,it would retain the smoky smell and wanted a guarantee that no odors would be perceived,even on the hottest summer days.We contacted a number of fire renovation companies and they all agreed that full encapsulation would have to be performed on the structure after we cleared the burned and structurally compromised framing away.The majority of the frame was structurally sound and it would be difficult to recycle it,so the decision was made to re-use the frame and most of the exterior sheathing including a good portion of the existing cedar shingles.
