A new insulation system with inorganic A-B-A insulators was proposed to improve the surface flashover performance in vacuum. Inorganic A-B-A insulator samples of Mo/Al2O3 cermet-Al2O3 ceramic-Mo/Al2O3 cermet were prep...A new insulation system with inorganic A-B-A insulators was proposed to improve the surface flashover performance in vacuum. Inorganic A-B-A insulator samples of Mo/Al2O3 cermet-Al2O3 ceramic-Mo/Al2O3 cermet were prepared, in which the conductivity and permittivity of the Mo/Al2O3 cermets were controlled through different amount of metallic molybdenum powder added. The effects of both conductivity and permittivity of Mo/Al2O3 cermets on the DC and impulse surface flashover voltage in vacuum were experimentally investigated. The result showed that the DC and impulse surface flashover voltage were improved by 52% and 95%, respectively. For the distribution of electric field, two triple junctions, i.e., vacuum-layer A-cathode （TJ1） and vacuum-layer A-layer B （TJ2） were prepared with the introduction of layer A into the A-B-A insulation system. Based on the electric field distribution obtained via electrostatic field simulation and Maxwell-Wagner three-layer model, the electric field of T J1 decreases while that of T J2 increases with the increase in conductivity and permittivity of layer A under applied DC and impulse voltage, respectively. Therefore, the improvement of surface flashover performance of A-B-A insulators has been reasonably explained.展开更多
A cable circuit of a substation in the United Kingdom showed high level of PD activities during a survey using hand hold PD testing equipment. The authors were invited to carry out on-site PD testing experiment to fur...A cable circuit of a substation in the United Kingdom showed high level of PD activities during a survey using hand hold PD testing equipment. The authors were invited to carry out on-site PD testing experiment to further diagnose and locate the potential problem of the cable system. This paper presents the experience of the present authors carrying out the cable test. Following a brief introduction to the experiment equipments and physical connections, the paper analyses the data collected from the testing, including PD pulse shape analysis, frequency spectrum analysis and phase resolved PD pattern analysis. Associated with PD propagation direction identification, PD source diagnosis and localisation was made. Four different types of sensors, which were adapted during the testing, are shown to have different frequency bandwidths and performed differently. Aider comparing the parameters of the sensor and the PD signals detected by individual sensor, optimal PD monitoring bandwidth for cable system is suggested.展开更多
With the rapid development of the construction industry today, external wall insulation technology has become an important part of the construction industry. Aiming at the influence of many factors such as material se...With the rapid development of the construction industry today, external wall insulation technology has become an important part of the construction industry. Aiming at the influence of many factors such as material selection, construction technology and structural design of external wall insulation technology, this paper analyzes the causes and hazards of cracks in the external wall insulation system of buildings, and sums up the parts in the structure that are prone to cracks. Through the above analysis, the corresponding crack prevention research is carried out, and measures are proposed in the aspects of construction and material selection to reduce the cracking of the external thermal insulation layer of the external wall and prolong the service life of the external thermal insulation system of the external wall, which provides a theoretical basis for the crack prevention measures in actual projects.展开更多
In order to support the physical research on the EAST tokamak,a new positive ion source with designed beam energy of 120 keV was proposed to be developed.Accelerator structure is one of the key components of the ion s...In order to support the physical research on the EAST tokamak,a new positive ion source with designed beam energy of 120 keV was proposed to be developed.Accelerator structure is one of the key components of the ion source.Through the finite element analysis method,the electrostatic analyses of insulators and grid plates were carried out,the material and structure parameters of insulators were determined.The maximum electric field around each insulator is about 4 kV/mm,and the maximum electric field between grids is about 14 kV/mm,which can meet the 120 keV withstand voltage holding.The insulation system for the positive ion source accelerator with 120 keV is designed,and the connection and basic parameters of insulators and support flanges are analyzed and determined.展开更多
Outlast Technologies GmbH has been awarded the WTiN Innovate Textile Award in the category Material Innovation for Aersulate®,its aerogel-infused insulation technology.The award honors outstanding achievements in...Outlast Technologies GmbH has been awarded the WTiN Innovate Textile Award in the category Material Innovation for Aersulate®,its aerogel-infused insulation technology.The award honors outstanding achievements in advanced material development and textile innovation.Aersulate® marks a significant advancement in thermal insulation.The technology integrates aerogel,whose highly porous structure efficiently traps air,delivering exceptional thermal performance at extremely low weight and minimal thickness.In AersulateR wadding,aerogel accounts for approximately 50%of the material volume,enabling superior insulation without bulk.展开更多
Extreme cold weather seriously harms human thermoregulatory system,necessitating high-performance insulating garments to maintain body temperature.However,as the core insulating layer,advanced fibrous materials always...Extreme cold weather seriously harms human thermoregulatory system,necessitating high-performance insulating garments to maintain body temperature.However,as the core insulating layer,advanced fibrous materials always struggle to balance mechanical properties and thermal insulation,resulting in their inability to meet the demands for both washing resistance and personal protection.Herein,inspired by the natural spring-like structures of cucumber tendrils,a superelastic and washable micro/nanofibrous sponge(MNFS)based on biomimetic helical fibers is directly prepared utilizing multiple-jet electrospinning technology for high-performance thermal insulation.By regulating the conductivity of polyvinylidene fluoride solution,multiple-jet ejection and multiple-stage whipping of jets are achieved,and further control of phase separation rates enables the rapid solidification of jets to form spring-like helical fibers,which are directly entangled to assemble MNFS.The resulting MNFS exhibits superelasticity that can withstand large tensile strain(200%),1000 cyclic tensile or compression deformations,and retain good resilience even in liquid nitrogen(-196℃).Furthermore,the MNFS shows efficient thermal insulation with low thermal conductivity(24.85 mW m^(-1)K^(-1)),close to the value of dry air,and remains structural stability even after cyclic washing.This work offers new possibilities for advanced fibrous sponges in transportation,environmental,and energy applications.展开更多
Typically used thermal insulation materials such as foam insulation and fibreglass may pose notable health risks and environmental impacts thereby resulting in respiratory irritation andwaste disposal issues,respectiv...Typically used thermal insulation materials such as foam insulation and fibreglass may pose notable health risks and environmental impacts thereby resulting in respiratory irritation andwaste disposal issues,respectively.While these materials are affordable and display good thermal insulation,their unsustainable traits pertaining to an intensive manufacturing process and poor disposability are major concerns.Alternative insulation materials with enhanced sustainable characteristics are therefore being explored,and one type of material which has gained notable attention owing to its low carbon footprint and low thermal conductivity is natural fibre.Among the few review studies conducted on Natural Fibre Reinforced Composite(NFRC)insulation boards,the multitude of factors and underlying mechanisms affecting their thermal conductivity performance have been sparsely covered.This review study aimed to address this gap by providing a holistic overview of some of the key intrinsic and extrinsic factors affecting the thermal conductivity performance of NFRCs.Key intrinsic factors pertaining to the microstructural features and to the physico-mechanical traits of NFRCs,namely the fibre lumen size,α,and the fibre-matrix thermal conductivity ratio,β,respectively,were found to largely affect the Transverse Thermal Conductivity(TTC)in NFRC boards.Extrinsic factors,which were found to indirectly affect NFRCs’thermal conductivity,such as fibre pre-processing,composite manufacturing and environmental factors,were also covered.Some of the noteworthy NFRC featureswhich were found to affect their thermal conductivity are volume fraction of fibres,bulk density and porosity.The findings of this study highlight the need for additional research investigation to address the foregoing limitations observed in NFRC thermal insulation boards by considering appropriate natural fibres,composition and fabrication techniques.The fabrication of high-grade NFRC boards,which will display an optimum balance between enhanced thermal insulation and long-term durability performance,could further replace conventionally used thermal insulation boards in the modern building and construction industry.展开更多
Atmospheric exposure tests including two experimental stages of high temperature-spraying water cycle and heating-refrigeration cycle were carried out on three currently used ETIS of expanded polystyrene（EPS） board,...Atmospheric exposure tests including two experimental stages of high temperature-spraying water cycle and heating-refrigeration cycle were carried out on three currently used ETIS of expanded polystyrene（EPS） board,polystyrene granule mortar and polyurethane foam in order to study the weatherablility of external thermal insulation system（ETIS）.The change rules of adhesive strength were hereby studied at different time period of atmospheric exposure tests.The experimental results show that the adhesive strength of three kinds of ETIS changes a little during high temperature-spraying water cycle,but the adhesive strength of ETIS with EPS board decreases significantly after heating-refrigeration cycle.The lowering rate of adhesive strength with painting finishes is obviously faster than that of tile finishes for ETIS of EPS board during heating-refrigeration cycle.The weatherability of ETIS with EPS board is worse than the other two,and ETIS of polystyrene granule mortar and polyurethane foam are more suitable than ETIS of EPS board in cold area.展开更多
The finite element model of an external thermal composite insuiation system, thin rendered expanded polystyrene （ EPS ） board, was built with ANSYS 1.0, which had two forms： one with window and one without window. ...The finite element model of an external thermal composite insuiation system, thin rendered expanded polystyrene （ EPS ） board, was built with ANSYS 1.0, which had two forms： one with window and one without window. The finite element analysis results show that the EPS board had very good insulation capacity at both high or low temperature, stress concentration was produced in the center of wall and around window, and the maximum deformation was observed at the edge of board and the minimum deformation was in the center.展开更多
Slot discharge studies are very important from the insulation diagnosis perspective.Further in practice,testing of rotating machines with power frequency requires sources which are quite bulky and costly.Instead if th...Slot discharge studies are very important from the insulation diagnosis perspective.Further in practice,testing of rotating machines with power frequency requires sources which are quite bulky and costly.Instead if the diagnosis is carried out at lower frequencies(<50 Hz),the size and cost of the test source can be reduced significantly.Therefore,it is important to know whether the study at low frequencies can be considered equivalent to study at power frequency.Hence,in this study,a slot discharge phenomenon occurring in a rotating machine insulation system was investigated experimentally at different frequencies(50,10,1 and 0.1 Hz).Slot discharges are known to have a distinct phase resolved partial discharge pattern for power frequency(50/60 Hz)excitation.These distinct patterns are useful in identifying the presence of slot discharge activity in rotating machines.Slot discharges were created on a 6.6 kV mica-epoxy stator coil and the slot discharge characteristics measured at different frequencies are compared.Slot discharge measurements were repeated by varying the air gap between the insulation surface and grounded steel plate.The changes in slot discharge characteristics due to the increase in air gap were found similar at all frequencies.The comparison suggests that the identification of slot discharge is also possible from the partial discharge(PD)measurement at low frequencies.展开更多
Measuring partial discharges in DC insulation systems is an issue due to the lack of a reference relating the voltage waveform to the physics of discharge phenomena.Also,DC is not always steady state,due to voltage an...Measuring partial discharges in DC insulation systems is an issue due to the lack of a reference relating the voltage waveform to the physics of discharge phenomena.Also,DC is not always steady state,due to voltage and load transients that generate electric field profile variations inside an insulation system,which can affect partial discharge inception likelihood and characteristics.Partial discharge measurement technology must be able to separate discharge pulses from noise and identify the type of sources generating partial discharge,which is related to condition assessment and maintenance.Eventually,measurement and analysis should be automatic and unsupervised,in order to get rid,partially or totally,of expert support.This study addresses a new approach to partial discharge measurements in DC insulation systems,presenting algorithms for separation,recognition and identification,which are effective both in DC steady state and during voltage(and load)transients.These algorithms are automatic and do not require expert support.Various cases of algorithm application on test objects consisting of multilayer polymeric specimens with an internal cavity and defective cable models are presented and discussed.Their effectiveness is proved,at least at a laboratory level,with effective noise separation and identification of discharge typology.展开更多
This article aims to present the feasibility of storing thermal energy in buildings for solar water heating while maintaining the comfort environment for residential buildings.Our contribution is the creation of insul...This article aims to present the feasibility of storing thermal energy in buildings for solar water heating while maintaining the comfort environment for residential buildings.Our contribution is the creation of insulating composite panels made of bio-based phase change materials(bio-PCM is all from coconut oil),cement and renewable materials(treated wood fiber and organic clay).The inclusion of wood fibers improved the thermal properties;a simple 2%increase of wood fiber decreased the heat conductivity by approximately 23.42%.The issues of bio-PCM leakage in the cement mortar and a roughly 56.5%reduction in thermal conductivity with bio-PCM stability in composite panels can be resolved by treating wood fibers with an adjuvant by impregnating them in bio-PCM in the presence of the treated clay generated.Clay and wood fiber were treated with adjuvants that are both biological and environmentally acceptable,as confirmed by FTIR spectroscopy.The heat transfer bench(DIDATEK)showed a decrease in thermal conductivity.By using differential scanning calorimetric(DSC)analysis,the investigation of thermal stability and enthalpy during two heating cycles of pure bio-PCM and composite bio-PCM was validated.The novel renewable material was used to create composite panels for the trial prototype,which took the shape of a component attached to the solar heating system,33.57%less heat was lost,according to the heat transfer research.The outcomes demonstrated the possibility of replacing traditional electric water heating in residential buildings with solar water heating systems.展开更多
The introduction of the electronic medical record(EHR)sharing system has made a great contribution to the management and sharing of healthcare data.Considering referral treatment for patients,the original signature ne...The introduction of the electronic medical record(EHR)sharing system has made a great contribution to the management and sharing of healthcare data.Considering referral treatment for patients,the original signature needs to be converted into a re-signature that can be verified by the new organization.Proxy re-signature(PRS)can be applied to this scenario so that authenticity and nonrepudiation can still be insured for data.Unfortunately,the existing PRS schemes cannot realize forward and backward security.Therefore,this paper proposes the first PRS scheme that can provide key-insulated property,which can guarantee both the forward and backward security of the key.Although the leakage of the private key occurs at a certain moment,the forward and backward key will not be attacked.Thus,the purpose of key insulation is implemented.What’s more,it can update different corresponding private keys in infinite time periods without changing the identity information of the user as the public key.Besides,the unforgeability of our scheme is proved based on the extended Computational Diffie-Hellman assumption in the random oracle model.Finally,the experimental simulation demonstrates that our scheme is feasible and in possession of promising properties.展开更多
Insulation systems in high-voltage electric machines play a pivotal role in the reliable operation and longevity of the equipment.Mica-based insulation materials have proven to possess and maintain excellent dielectri...Insulation systems in high-voltage electric machines play a pivotal role in the reliable operation and longevity of the equipment.Mica-based insulation materials have proven to possess and maintain excellent dielectric properties in the long run and prevent premature insulation degradation.Numerous qualifications tests,such as voltage endurance,are outlined in IEC and IEEE standards.The authors,however,take a different parametric approach,opting for reliability assessment of insulation systems using derived three-parameter Weibull models.Therefore,instead of simple pass–fail criteria,empirical data is employed to determine failure rate probabilities quantitatively and objectively.Experimental data,including breakdown,dissipation factor,and partial discharge mea-surements,are used to construct the Weibull distribution model to predict fault and failure rates and calculate hazard functions.The rigorous examinations interpreted through the analytical model help assess insulation system resilience and particularly the impact of electrical field stress and mica content.Variation of electrical stress from 66.75 to 71.20 V/mil demonstrated how the mean time to failure of the system changed from 146.4 to 85.1 at 3 Un,hence identifying opportunities for design improvement and uncovering performance boundaries.Ultimately,the developed framework enhances comprehension of insulation system failure probabilities,guiding design decisions and ensuring a secure and reliable operation of electrical machines across applications.展开更多
This study was focused on the simulation of energy performance for residential buildings incorporating different types of insulation materials. The energy consumption of residential buildings in the U.S. plays a signi...This study was focused on the simulation of energy performance for residential buildings incorporating different types of insulation materials. The energy consumption of residential buildings in the U.S. plays a significant role in the total annual energy consumption, and using insulation materials of higher performances is one of the most effective ways to reduce the building energy consumption. In this study, the building energy simulation was performed in BEopt for a typical residential house in the U.S. with several different types of insulation materials. The results show that adding insulation materials can significantly improve the building energy performance. The polyisocyanurate performed the best among the conventional insulation materials and had an annualized source energy saving of 37% in Pittsburgh. Vacuum-Insulated Panels had the best performance among all types of materials discussed in this study and showed annualized source energy of 41% in Pittsburgh. Phase Change Material was found to be the most effective way to particularly reduce the cooling energy use.展开更多
In the present work,by virtue of the synergistic and independent effects of Janus structure,an asymmetric nickel-chain/multiwall carbon nanotube/polyimide(Ni/MWCNTs/PI)composite foam with absorption-dominated electrom...In the present work,by virtue of the synergistic and independent effects of Janus structure,an asymmetric nickel-chain/multiwall carbon nanotube/polyimide(Ni/MWCNTs/PI)composite foam with absorption-dominated electromagnetic interference(EMI)shielding and thermal insulation performances was successfully fabricated through an ordered casting and directional freeze-drying strategy.Water-soluble polyamic acid(PAA)was chosen to match the oriented freeze-drying method to acquire oriented pores,and the thermal imidization process from PAA to PI exactly eliminated the interface of the multilayered structure.By controlling the electro-magnetic gradient and propagation path of the incident microwaves in the MWCNT/PI and Ni/PI layers,the PI composite foam exhibited an efficient EMI SE of 55.8 dB in the X-band with extremely low reflection characteristics(R=0.22).The asymmetric conductive net-work also greatly preserved the thermal insulation properties of PI.The thermal conductivity(TC)of the Ni/MWCNT/PI composite foam was as low as 0.032 W/(m K).In addition,owing to the elimination of MWCNT/PI and Ni/PI interfaces during the thermal imidization process,the composite foam showed satisfactory compressive strength.The fabricated PI composite foam could provide reliable electromagnetic protection in complex applications and withstand high temperatures,which has great potential in cuttingedge applications such as advanced aircraft.展开更多
Due to excellent thermal insulation performance at room temperature and ultralow density,silica aero-gels are candidates for thermal insulation.However,at high temperatures,the thermal insulation prop-erty of silica a...Due to excellent thermal insulation performance at room temperature and ultralow density,silica aero-gels are candidates for thermal insulation.However,at high temperatures,the thermal insulation prop-erty of silica aerogels decreased greatly caused by transparency to heat radiation.Opacifiers introduced into silica sol can block heat radiation yet destroy the uniformity of aerogels.Herein,we designed and prepared a silica aerogel composite with oriented and layered silica fibers(SFs),SiC nanowires(SiC_(NWs)),and silica aerogels,which were prepared by papermaking,chemical vapor infiltration(CVI),and sol-gel respectively.Firstly,oriented and layered SFs made still air a wall to block heat transfer by the solid phase.Secondly,SiC_(NWs) were grown in situ on the surface of SFs evenly to weave into the network,and the network reduced the gaseous thermal conductivity by dividing cracks in SFs/SiC_(NWs)/SA.Thirdly,SiC_(NWs) weakened the heat transfer by radiation at high temperatures.Therefore,SFs/SiC_(NWs)/SA presented remarkable thermal insulation(0.017 W(m K)^(-1) at 25℃,0.0287 W(m K)^(-1) at 500℃,and 0.094 W(m K)^(-1) at 1000℃).Besides,SFs/SiC_(NWs)/SA exhibited remarkable thermal stability(no size transform after being heat treated at 1000℃ for 1800 s)and tensile strength(0.75 MPa).These integrated properties made SFs/SiC_(NWs)/SA a promising candidate for highly efficient thermal insulators.展开更多
As the application scenarios of aerogels expand,higher requirements are put forward for the materials used to prepare aerogels.Due to the unique chemical structure,polytetrafluoroethylene(PTFE)has excellent properties...As the application scenarios of aerogels expand,higher requirements are put forward for the materials used to prepare aerogels.Due to the unique chemical structure,polytetrafluoroethylene(PTFE)has excellent properties such as high-temperature resistance,hydrophobicity,and chemical stability.However,the PTFE aerogels are difficult to be molded due to the weak interaction between resin particles.In this work,poly(ethylene oxide)(PEO)was selected as the carrier to assist the PTFE aerogels molding.The pure PTFE aerogels were prepared by homogeneously mixing PTFE aqueous dispersion and PEO,freeze-drying,and high-temperature sintering.When the mass fraction of PTFE and PEO were appropriate,the porosity of PTFE aerogels exceeded 90%and had a hierarchical honeycomb structure.Results showed that the PTFE aerogels not only had excellent hydrophobicity but also possessed superior acoustic insulation,mechanical strength,thermal insulation,and heat resistance properties.Specifically,the water contact angle is about 140°.The noise reduction coefficient is 0.34 and the average sound absorption coefficient is greater than 88%in the frequency range of 2000-6400 Hz.Meanwhile,the thermal conductivity in the air is about 0.045 W/(m·K),and the initial thermal decomposition temperature is 450℃.More importantly,the PTFE aerogels had excellent temperature and corrosion resistance.Even after extremely thermal and chemical treatment,they remained unchanged porous structure as well as acoustic and thermal insulation properties,which exhibits great potential for application in many harsh environments.展开更多
Thermally conductive papers with electrical insulation and mechanical robustness are essential for efficient thermal management in modern electronics.In this study,we introduced a metal ion-assisted interfacial crossl...Thermally conductive papers with electrical insulation and mechanical robustness are essential for efficient thermal management in modern electronics.In this study,we introduced a metal ion-assisted interfacial crosslinking strategy to strengthen sugarfunctionalized graphene fluoride(SGF)and cellulose nanofibers(CNF)by hydrogen bonding and metal ion crosslinking that leads to simultaneous enhancements in thermal conductivity and mechanical properties.The facile sugarassisted ball-milling exfoliation method was developed to achieve the exfoliation of graphite fluoride and hydroxyl group functionalization on the surface of graphene fluoride.Thanks to the good dispersibility of the SGF sheets in water,the flexible SGF/CNF composite papers with hydrogen bonding were prepared via vacuum-assisted filtration.We introduced hydrogen bonding and metal ion crosslinking into SGF/CNF papers to obtain densely packed composite papers.Ca^(2+)or Al^(3+)ion-crosslinked SGF/CNF papers exhibited superior thermal and mechanical properties owing to hydrogen bonding and metal ion crosslinking.SGF/CNF-Ca^(2+)and SGF/CNF-Al^(3+)papers at 50 wt%of SGF yield in-plane thermal conductivities of 72.93 and 75.02 W m^(-1) K^(-1),and tensile strengths of 121.5 and 135.7 MPa,respectively.A thermal percolation value was observed at 12.6 vol%of SGF filler content.In addition,the SGF/CNF papers exhibited electrical insulation properties.These remarkable characteristics of the metal ion-crosslinked SGF/CNF papers are attributed to the densely packed structures caused by the strong interfacial interactions from hydrogen bonding as well as metal ion-crosslinking that could promote phonon transport.High-performance metal ion-crosslinked SGF/CNF papers with these fascinating advantages offer great potential for the thermal management of flexible electronics.展开更多
BACKGROUND Elderly patients undergoing laparoscopic colorectal cancer surgery are at high risk for hypothermia-related complications.This study explores the efficacy of periop-erative composite insulation intervention...BACKGROUND Elderly patients undergoing laparoscopic colorectal cancer surgery are at high risk for hypothermia-related complications.This study explores the efficacy of periop-erative composite insulation interventions in maintaining normothermia and reducing postoperative risks in this vulnerable group.AIM To evaluate the efficacy of perioperative composite insulation in older patients undergoing colorectal cancer surgery.METHODS We selected 100 older patients who underwent laparoscopic surgery for colorectal cancer at Huzhou Central Hospital from September 2023 to April 2024.Using a random number table,patients were divided into a control group and inter-vention group of 50 patients each.After returning to the regular ward,the con-ventional group received traditional insulation intervention measures,while the intervention group received composite insulation nursing intervention.We ob-served and recorded postoperative blood pressure and heart rate changes,as well as postoperative anesthesia recovery time and incidence of complications.RESULTS The statistical results showed significant differences(P<0.05)in heart rate changes and systolic blood pressure between the two groups.There was a sig-nificant change in heart rate between the groups immediately after surgery and at 15 and 30 minutes after surgery(P<0.05).The heart rate and systolic blood pressure of the intervention group were significantly lower than those of the control group at 15 and 30 minutes after surgery(P<0.05).The rewarming time of the intervention group was shorter than that of the control group,and the overall incidence of postoperative complications was significantly lower than that of the control group(P<0.05).CONCLUSION For elderly patients undergoing laparoscopic colorectal cancer surgery,a composite insulation intervention during the perioperative period can maintain body temperature,reduce postoperative stress,and significantly reduce the incidence of hypothermia and related complications.展开更多
基金supported by National Science Fund for Outstanding Young Scholars of China (No. 50625721)
文摘A new insulation system with inorganic A-B-A insulators was proposed to improve the surface flashover performance in vacuum. Inorganic A-B-A insulator samples of Mo/Al2O3 cermet-Al2O3 ceramic-Mo/Al2O3 cermet were prepared, in which the conductivity and permittivity of the Mo/Al2O3 cermets were controlled through different amount of metallic molybdenum powder added. The effects of both conductivity and permittivity of Mo/Al2O3 cermets on the DC and impulse surface flashover voltage in vacuum were experimentally investigated. The result showed that the DC and impulse surface flashover voltage were improved by 52% and 95%, respectively. For the distribution of electric field, two triple junctions, i.e., vacuum-layer A-cathode （TJ1） and vacuum-layer A-layer B （TJ2） were prepared with the introduction of layer A into the A-B-A insulation system. Based on the electric field distribution obtained via electrostatic field simulation and Maxwell-Wagner three-layer model, the electric field of T J1 decreases while that of T J2 increases with the increase in conductivity and permittivity of layer A under applied DC and impulse voltage, respectively. Therefore, the improvement of surface flashover performance of A-B-A insulators has been reasonably explained.
文摘A cable circuit of a substation in the United Kingdom showed high level of PD activities during a survey using hand hold PD testing equipment. The authors were invited to carry out on-site PD testing experiment to further diagnose and locate the potential problem of the cable system. This paper presents the experience of the present authors carrying out the cable test. Following a brief introduction to the experiment equipments and physical connections, the paper analyses the data collected from the testing, including PD pulse shape analysis, frequency spectrum analysis and phase resolved PD pattern analysis. Associated with PD propagation direction identification, PD source diagnosis and localisation was made. Four different types of sensors, which were adapted during the testing, are shown to have different frequency bandwidths and performed differently. Aider comparing the parameters of the sensor and the PD signals detected by individual sensor, optimal PD monitoring bandwidth for cable system is suggested.
文摘With the rapid development of the construction industry today, external wall insulation technology has become an important part of the construction industry. Aiming at the influence of many factors such as material selection, construction technology and structural design of external wall insulation technology, this paper analyzes the causes and hazards of cracks in the external wall insulation system of buildings, and sums up the parts in the structure that are prone to cracks. Through the above analysis, the corresponding crack prevention research is carried out, and measures are proposed in the aspects of construction and material selection to reduce the cracking of the external thermal insulation layer of the external wall and prolong the service life of the external thermal insulation system of the external wall, which provides a theoretical basis for the crack prevention measures in actual projects.
基金supported by National Natural Science Foundation of China(No.11975261)。
文摘In order to support the physical research on the EAST tokamak,a new positive ion source with designed beam energy of 120 keV was proposed to be developed.Accelerator structure is one of the key components of the ion source.Through the finite element analysis method,the electrostatic analyses of insulators and grid plates were carried out,the material and structure parameters of insulators were determined.The maximum electric field around each insulator is about 4 kV/mm,and the maximum electric field between grids is about 14 kV/mm,which can meet the 120 keV withstand voltage holding.The insulation system for the positive ion source accelerator with 120 keV is designed,and the connection and basic parameters of insulators and support flanges are analyzed and determined.
文摘Outlast Technologies GmbH has been awarded the WTiN Innovate Textile Award in the category Material Innovation for Aersulate®,its aerogel-infused insulation technology.The award honors outstanding achievements in advanced material development and textile innovation.Aersulate® marks a significant advancement in thermal insulation.The technology integrates aerogel,whose highly porous structure efficiently traps air,delivering exceptional thermal performance at extremely low weight and minimal thickness.In AersulateR wadding,aerogel accounts for approximately 50%of the material volume,enabling superior insulation without bulk.
基金supported by Young Elite Scientists Sponsorship Program by China Association for Science and Technology(No.2022QNRC001)the National Natural Science Foundation of China(No.52273053)the Chenguang Program of Shanghai Education Development Foundation and Shanghai Municipal Education Commission(No.21CGA41)。
文摘Extreme cold weather seriously harms human thermoregulatory system,necessitating high-performance insulating garments to maintain body temperature.However,as the core insulating layer,advanced fibrous materials always struggle to balance mechanical properties and thermal insulation,resulting in their inability to meet the demands for both washing resistance and personal protection.Herein,inspired by the natural spring-like structures of cucumber tendrils,a superelastic and washable micro/nanofibrous sponge(MNFS)based on biomimetic helical fibers is directly prepared utilizing multiple-jet electrospinning technology for high-performance thermal insulation.By regulating the conductivity of polyvinylidene fluoride solution,multiple-jet ejection and multiple-stage whipping of jets are achieved,and further control of phase separation rates enables the rapid solidification of jets to form spring-like helical fibers,which are directly entangled to assemble MNFS.The resulting MNFS exhibits superelasticity that can withstand large tensile strain(200%),1000 cyclic tensile or compression deformations,and retain good resilience even in liquid nitrogen(-196℃).Furthermore,the MNFS shows efficient thermal insulation with low thermal conductivity(24.85 mW m^(-1)K^(-1)),close to the value of dry air,and remains structural stability even after cyclic washing.This work offers new possibilities for advanced fibrous sponges in transportation,environmental,and energy applications.
文摘Typically used thermal insulation materials such as foam insulation and fibreglass may pose notable health risks and environmental impacts thereby resulting in respiratory irritation andwaste disposal issues,respectively.While these materials are affordable and display good thermal insulation,their unsustainable traits pertaining to an intensive manufacturing process and poor disposability are major concerns.Alternative insulation materials with enhanced sustainable characteristics are therefore being explored,and one type of material which has gained notable attention owing to its low carbon footprint and low thermal conductivity is natural fibre.Among the few review studies conducted on Natural Fibre Reinforced Composite(NFRC)insulation boards,the multitude of factors and underlying mechanisms affecting their thermal conductivity performance have been sparsely covered.This review study aimed to address this gap by providing a holistic overview of some of the key intrinsic and extrinsic factors affecting the thermal conductivity performance of NFRCs.Key intrinsic factors pertaining to the microstructural features and to the physico-mechanical traits of NFRCs,namely the fibre lumen size,α,and the fibre-matrix thermal conductivity ratio,β,respectively,were found to largely affect the Transverse Thermal Conductivity(TTC)in NFRC boards.Extrinsic factors,which were found to indirectly affect NFRCs’thermal conductivity,such as fibre pre-processing,composite manufacturing and environmental factors,were also covered.Some of the noteworthy NFRC featureswhich were found to affect their thermal conductivity are volume fraction of fibres,bulk density and porosity.The findings of this study highlight the need for additional research investigation to address the foregoing limitations observed in NFRC thermal insulation boards by considering appropriate natural fibres,composition and fabrication techniques.The fabrication of high-grade NFRC boards,which will display an optimum balance between enhanced thermal insulation and long-term durability performance,could further replace conventionally used thermal insulation boards in the modern building and construction industry.
基金Funded by the Specialized Research Fund for the Doctoral Program of Higher Education of China (No. 20050487017)
文摘Atmospheric exposure tests including two experimental stages of high temperature-spraying water cycle and heating-refrigeration cycle were carried out on three currently used ETIS of expanded polystyrene（EPS） board,polystyrene granule mortar and polyurethane foam in order to study the weatherablility of external thermal insulation system（ETIS）.The change rules of adhesive strength were hereby studied at different time period of atmospheric exposure tests.The experimental results show that the adhesive strength of three kinds of ETIS changes a little during high temperature-spraying water cycle,but the adhesive strength of ETIS with EPS board decreases significantly after heating-refrigeration cycle.The lowering rate of adhesive strength with painting finishes is obviously faster than that of tile finishes for ETIS of EPS board during heating-refrigeration cycle.The weatherability of ETIS with EPS board is worse than the other two,and ETIS of polystyrene granule mortar and polyurethane foam are more suitable than ETIS of EPS board in cold area.
基金The Research Fund for the Doctoral Pro-gram of Higher Education of China(No.20050487017)
文摘The finite element model of an external thermal composite insuiation system, thin rendered expanded polystyrene （ EPS ） board, was built with ANSYS 1.0, which had two forms： one with window and one without window. The finite element analysis results show that the EPS board had very good insulation capacity at both high or low temperature, stress concentration was produced in the center of wall and around window, and the maximum deformation was observed at the edge of board and the minimum deformation was in the center.
文摘Slot discharge studies are very important from the insulation diagnosis perspective.Further in practice,testing of rotating machines with power frequency requires sources which are quite bulky and costly.Instead if the diagnosis is carried out at lower frequencies(<50 Hz),the size and cost of the test source can be reduced significantly.Therefore,it is important to know whether the study at low frequencies can be considered equivalent to study at power frequency.Hence,in this study,a slot discharge phenomenon occurring in a rotating machine insulation system was investigated experimentally at different frequencies(50,10,1 and 0.1 Hz).Slot discharges are known to have a distinct phase resolved partial discharge pattern for power frequency(50/60 Hz)excitation.These distinct patterns are useful in identifying the presence of slot discharge activity in rotating machines.Slot discharges were created on a 6.6 kV mica-epoxy stator coil and the slot discharge characteristics measured at different frequencies are compared.Slot discharge measurements were repeated by varying the air gap between the insulation surface and grounded steel plate.The changes in slot discharge characteristics due to the increase in air gap were found similar at all frequencies.The comparison suggests that the identification of slot discharge is also possible from the partial discharge(PD)measurement at low frequencies.
文摘Measuring partial discharges in DC insulation systems is an issue due to the lack of a reference relating the voltage waveform to the physics of discharge phenomena.Also,DC is not always steady state,due to voltage and load transients that generate electric field profile variations inside an insulation system,which can affect partial discharge inception likelihood and characteristics.Partial discharge measurement technology must be able to separate discharge pulses from noise and identify the type of sources generating partial discharge,which is related to condition assessment and maintenance.Eventually,measurement and analysis should be automatic and unsupervised,in order to get rid,partially or totally,of expert support.This study addresses a new approach to partial discharge measurements in DC insulation systems,presenting algorithms for separation,recognition and identification,which are effective both in DC steady state and during voltage(and load)transients.These algorithms are automatic and do not require expert support.Various cases of algorithm application on test objects consisting of multilayer polymeric specimens with an internal cavity and defective cable models are presented and discussed.Their effectiveness is proved,at least at a laboratory level,with effective noise separation and identification of discharge typology.
文摘This article aims to present the feasibility of storing thermal energy in buildings for solar water heating while maintaining the comfort environment for residential buildings.Our contribution is the creation of insulating composite panels made of bio-based phase change materials(bio-PCM is all from coconut oil),cement and renewable materials(treated wood fiber and organic clay).The inclusion of wood fibers improved the thermal properties;a simple 2%increase of wood fiber decreased the heat conductivity by approximately 23.42%.The issues of bio-PCM leakage in the cement mortar and a roughly 56.5%reduction in thermal conductivity with bio-PCM stability in composite panels can be resolved by treating wood fibers with an adjuvant by impregnating them in bio-PCM in the presence of the treated clay generated.Clay and wood fiber were treated with adjuvants that are both biological and environmentally acceptable,as confirmed by FTIR spectroscopy.The heat transfer bench(DIDATEK)showed a decrease in thermal conductivity.By using differential scanning calorimetric(DSC)analysis,the investigation of thermal stability and enthalpy during two heating cycles of pure bio-PCM and composite bio-PCM was validated.The novel renewable material was used to create composite panels for the trial prototype,which took the shape of a component attached to the solar heating system,33.57%less heat was lost,according to the heat transfer research.The outcomes demonstrated the possibility of replacing traditional electric water heating in residential buildings with solar water heating systems.
基金supported by the Network and Data Security Key Laboratory of Sichuan Province under the Grant No.NDS2021-2in part by Science and Technology Project of Educational Commission of Jiangxi Province under the Grant No.GJJ190464in part by National Natural Science Foundation of China under the Grant No.71661012.
文摘The introduction of the electronic medical record(EHR)sharing system has made a great contribution to the management and sharing of healthcare data.Considering referral treatment for patients,the original signature needs to be converted into a re-signature that can be verified by the new organization.Proxy re-signature(PRS)can be applied to this scenario so that authenticity and nonrepudiation can still be insured for data.Unfortunately,the existing PRS schemes cannot realize forward and backward security.Therefore,this paper proposes the first PRS scheme that can provide key-insulated property,which can guarantee both the forward and backward security of the key.Although the leakage of the private key occurs at a certain moment,the forward and backward key will not be attacked.Thus,the purpose of key insulation is implemented.What’s more,it can update different corresponding private keys in infinite time periods without changing the identity information of the user as the public key.Besides,the unforgeability of our scheme is proved based on the extended Computational Diffie-Hellman assumption in the random oracle model.Finally,the experimental simulation demonstrates that our scheme is feasible and in possession of promising properties.
文摘Insulation systems in high-voltage electric machines play a pivotal role in the reliable operation and longevity of the equipment.Mica-based insulation materials have proven to possess and maintain excellent dielectric properties in the long run and prevent premature insulation degradation.Numerous qualifications tests,such as voltage endurance,are outlined in IEC and IEEE standards.The authors,however,take a different parametric approach,opting for reliability assessment of insulation systems using derived three-parameter Weibull models.Therefore,instead of simple pass–fail criteria,empirical data is employed to determine failure rate probabilities quantitatively and objectively.Experimental data,including breakdown,dissipation factor,and partial discharge mea-surements,are used to construct the Weibull distribution model to predict fault and failure rates and calculate hazard functions.The rigorous examinations interpreted through the analytical model help assess insulation system resilience and particularly the impact of electrical field stress and mica content.Variation of electrical stress from 66.75 to 71.20 V/mil demonstrated how the mean time to failure of the system changed from 146.4 to 85.1 at 3 Un,hence identifying opportunities for design improvement and uncovering performance boundaries.Ultimately,the developed framework enhances comprehension of insulation system failure probabilities,guiding design decisions and ensuring a secure and reliable operation of electrical machines across applications.
文摘This study was focused on the simulation of energy performance for residential buildings incorporating different types of insulation materials. The energy consumption of residential buildings in the U.S. plays a significant role in the total annual energy consumption, and using insulation materials of higher performances is one of the most effective ways to reduce the building energy consumption. In this study, the building energy simulation was performed in BEopt for a typical residential house in the U.S. with several different types of insulation materials. The results show that adding insulation materials can significantly improve the building energy performance. The polyisocyanurate performed the best among the conventional insulation materials and had an annualized source energy saving of 37% in Pittsburgh. Vacuum-Insulated Panels had the best performance among all types of materials discussed in this study and showed annualized source energy of 41% in Pittsburgh. Phase Change Material was found to be the most effective way to particularly reduce the cooling energy use.
基金supported by the Natural Science Foundation of Shanxi Province(Nos.20210302123015 and 20210302123035)the Opening Project of State Key Laboratory of Polymer Materials Engineering(Sichuan University)(No.sklpme2022-4-06)the Open Foundation of China-Belarus Belt and Road Joint Laboratory on Electromagnetic Environment Effect(No.ZBKF2022030301).
文摘In the present work,by virtue of the synergistic and independent effects of Janus structure,an asymmetric nickel-chain/multiwall carbon nanotube/polyimide(Ni/MWCNTs/PI)composite foam with absorption-dominated electromagnetic interference(EMI)shielding and thermal insulation performances was successfully fabricated through an ordered casting and directional freeze-drying strategy.Water-soluble polyamic acid(PAA)was chosen to match the oriented freeze-drying method to acquire oriented pores,and the thermal imidization process from PAA to PI exactly eliminated the interface of the multilayered structure.By controlling the electro-magnetic gradient and propagation path of the incident microwaves in the MWCNT/PI and Ni/PI layers,the PI composite foam exhibited an efficient EMI SE of 55.8 dB in the X-band with extremely low reflection characteristics(R=0.22).The asymmetric conductive net-work also greatly preserved the thermal insulation properties of PI.The thermal conductivity(TC)of the Ni/MWCNT/PI composite foam was as low as 0.032 W/(m K).In addition,owing to the elimination of MWCNT/PI and Ni/PI interfaces during the thermal imidization process,the composite foam showed satisfactory compressive strength.The fabricated PI composite foam could provide reliable electromagnetic protection in complex applications and withstand high temperatures,which has great potential in cuttingedge applications such as advanced aircraft.
基金supported by the National Natural Science Foun-dation of China(Grant No.U2167214).
文摘Due to excellent thermal insulation performance at room temperature and ultralow density,silica aero-gels are candidates for thermal insulation.However,at high temperatures,the thermal insulation prop-erty of silica aerogels decreased greatly caused by transparency to heat radiation.Opacifiers introduced into silica sol can block heat radiation yet destroy the uniformity of aerogels.Herein,we designed and prepared a silica aerogel composite with oriented and layered silica fibers(SFs),SiC nanowires(SiC_(NWs)),and silica aerogels,which were prepared by papermaking,chemical vapor infiltration(CVI),and sol-gel respectively.Firstly,oriented and layered SFs made still air a wall to block heat transfer by the solid phase.Secondly,SiC_(NWs) were grown in situ on the surface of SFs evenly to weave into the network,and the network reduced the gaseous thermal conductivity by dividing cracks in SFs/SiC_(NWs)/SA.Thirdly,SiC_(NWs) weakened the heat transfer by radiation at high temperatures.Therefore,SFs/SiC_(NWs)/SA presented remarkable thermal insulation(0.017 W(m K)^(-1) at 25℃,0.0287 W(m K)^(-1) at 500℃,and 0.094 W(m K)^(-1) at 1000℃).Besides,SFs/SiC_(NWs)/SA exhibited remarkable thermal stability(no size transform after being heat treated at 1000℃ for 1800 s)and tensile strength(0.75 MPa).These integrated properties made SFs/SiC_(NWs)/SA a promising candidate for highly efficient thermal insulators.
基金supported by the National Natural Science Foundation of China(No.52233003)the Department of Sichuan Province(No.2022JDJQ0023)。
文摘As the application scenarios of aerogels expand,higher requirements are put forward for the materials used to prepare aerogels.Due to the unique chemical structure,polytetrafluoroethylene(PTFE)has excellent properties such as high-temperature resistance,hydrophobicity,and chemical stability.However,the PTFE aerogels are difficult to be molded due to the weak interaction between resin particles.In this work,poly(ethylene oxide)(PEO)was selected as the carrier to assist the PTFE aerogels molding.The pure PTFE aerogels were prepared by homogeneously mixing PTFE aqueous dispersion and PEO,freeze-drying,and high-temperature sintering.When the mass fraction of PTFE and PEO were appropriate,the porosity of PTFE aerogels exceeded 90%and had a hierarchical honeycomb structure.Results showed that the PTFE aerogels not only had excellent hydrophobicity but also possessed superior acoustic insulation,mechanical strength,thermal insulation,and heat resistance properties.Specifically,the water contact angle is about 140°.The noise reduction coefficient is 0.34 and the average sound absorption coefficient is greater than 88%in the frequency range of 2000-6400 Hz.Meanwhile,the thermal conductivity in the air is about 0.045 W/(m·K),and the initial thermal decomposition temperature is 450℃.More importantly,the PTFE aerogels had excellent temperature and corrosion resistance.Even after extremely thermal and chemical treatment,they remained unchanged porous structure as well as acoustic and thermal insulation properties,which exhibits great potential for application in many harsh environments.
基金supported by the Basic Science Program(No.2022R1A2C2009700)through the National Research Foundation of Korea(NRF)funded by the Ministry of Science and ICTthe Basic Science Research Capacity Enhancement Project(National Research Facilities and Equipment Center)through the Korea Ba-sic Science Institute funded by the Ministry of Education(No.2019R1A6C1010047)the Industrial Strategic Technology Development Program(No.20013248)through Korea Evaluation In-stitute of Industrial Technology funded by the Ministry of Trade,Industry&Energy(MOTIE,Korea).
文摘Thermally conductive papers with electrical insulation and mechanical robustness are essential for efficient thermal management in modern electronics.In this study,we introduced a metal ion-assisted interfacial crosslinking strategy to strengthen sugarfunctionalized graphene fluoride(SGF)and cellulose nanofibers(CNF)by hydrogen bonding and metal ion crosslinking that leads to simultaneous enhancements in thermal conductivity and mechanical properties.The facile sugarassisted ball-milling exfoliation method was developed to achieve the exfoliation of graphite fluoride and hydroxyl group functionalization on the surface of graphene fluoride.Thanks to the good dispersibility of the SGF sheets in water,the flexible SGF/CNF composite papers with hydrogen bonding were prepared via vacuum-assisted filtration.We introduced hydrogen bonding and metal ion crosslinking into SGF/CNF papers to obtain densely packed composite papers.Ca^(2+)or Al^(3+)ion-crosslinked SGF/CNF papers exhibited superior thermal and mechanical properties owing to hydrogen bonding and metal ion crosslinking.SGF/CNF-Ca^(2+)and SGF/CNF-Al^(3+)papers at 50 wt%of SGF yield in-plane thermal conductivities of 72.93 and 75.02 W m^(-1) K^(-1),and tensile strengths of 121.5 and 135.7 MPa,respectively.A thermal percolation value was observed at 12.6 vol%of SGF filler content.In addition,the SGF/CNF papers exhibited electrical insulation properties.These remarkable characteristics of the metal ion-crosslinked SGF/CNF papers are attributed to the densely packed structures caused by the strong interfacial interactions from hydrogen bonding as well as metal ion-crosslinking that could promote phonon transport.High-performance metal ion-crosslinked SGF/CNF papers with these fascinating advantages offer great potential for the thermal management of flexible electronics.
文摘BACKGROUND Elderly patients undergoing laparoscopic colorectal cancer surgery are at high risk for hypothermia-related complications.This study explores the efficacy of periop-erative composite insulation interventions in maintaining normothermia and reducing postoperative risks in this vulnerable group.AIM To evaluate the efficacy of perioperative composite insulation in older patients undergoing colorectal cancer surgery.METHODS We selected 100 older patients who underwent laparoscopic surgery for colorectal cancer at Huzhou Central Hospital from September 2023 to April 2024.Using a random number table,patients were divided into a control group and inter-vention group of 50 patients each.After returning to the regular ward,the con-ventional group received traditional insulation intervention measures,while the intervention group received composite insulation nursing intervention.We ob-served and recorded postoperative blood pressure and heart rate changes,as well as postoperative anesthesia recovery time and incidence of complications.RESULTS The statistical results showed significant differences(P<0.05)in heart rate changes and systolic blood pressure between the two groups.There was a sig-nificant change in heart rate between the groups immediately after surgery and at 15 and 30 minutes after surgery(P<0.05).The heart rate and systolic blood pressure of the intervention group were significantly lower than those of the control group at 15 and 30 minutes after surgery(P<0.05).The rewarming time of the intervention group was shorter than that of the control group,and the overall incidence of postoperative complications was significantly lower than that of the control group(P<0.05).CONCLUSION For elderly patients undergoing laparoscopic colorectal cancer surgery,a composite insulation intervention during the perioperative period can maintain body temperature,reduce postoperative stress,and significantly reduce the incidence of hypothermia and related complications.
