This paper contributes to explain the global warming instead of"giving up"and thinking about passively adapting to climate change or global warming.It makes more sense to tackle what creates the greenhouse e...This paper contributes to explain the global warming instead of"giving up"and thinking about passively adapting to climate change or global warming.It makes more sense to tackle what creates the greenhouse effect and contributes to global warming.The greenhouse effect is not only due to GHGs emissions,but also to the excess IR radiation emitted during the day,by artificial surfaces,following the absorption of solar radiation.The phenomenon should be compared to that of radiative forcing well known by climatologists and which makes the link between atmospheric pollution and the density of heat fluxes stopped by the atmosphere inducing global warming.It becomes clear that type an equation here.The surplus CO2 and IR radiation emissions influence global warming,not to mention the direct part of the heat released by the combustion of fossil fuels and even renewable(wood fires,biogas,friction of wind turbine propellers with the air).展开更多
Based on electromagnetic radiation characteristics, the present research studied the damage evolution of rock under uniaxial compression. Besides, this research built the coal-rock damage evolution model considered re...Based on electromagnetic radiation characteristics, the present research studied the damage evolution of rock under uniaxial compression. Besides, this research built the coal-rock damage evolution model considered residual strength. The applicability and accuracy of the model were verified through experiments. The results show that coal-rock damage evolution consists of four periods. The first period is from the beginning of compression to nearly 20% of the stress peak value, during which the damage variable changes stably about 0.1, and accordingly a few of electromagnetic radiation signals emerge. The second period is from about 20% to 70% of the stress peak value. The damage has stable development, and the parameter of electromagnetic radiation characteristics turns larger continuously with the increase of stress. The third period is when the damage has accelerated development, the coal-rock was broken which result from sharp increasing of the damage variable, meanwhile a great quantity of electromagnetic radiation signals emerge. The fourth period is after the coal-rock fracture, during which the damage variable corresponding to the parameter of electromagnetic radiation characteristics has a stable development. This research has great academic and realistic significance for further studies the electromagnetic radiation characteristics of coal-rock under loading and damage and the forecasting of coal-rock dynamic disasters.展开更多
A unified analysis is presented to calculate the incoherent spontaneous power of cooperative radiations based on self-amplified spontaneous emission. Using quantum mechanical tools, we derive analytical expressions fo...A unified analysis is presented to calculate the incoherent spontaneous power of cooperative radiations based on self-amplified spontaneous emission. Using quantum mechanical tools, we derive analytical expressions for the incoherent spontaneous power of undulator and Cherenkov free-electron lasers (FELs). The undulator and Cherenkov FELs are considered as two different examples for the radiation that accumulate cooperatively. In the case of the undulator FEL, we show an excellent agreement between an expression for the incoherent radiation power derived in the present work and that obtained using a completely different approach [Phys. Ftev. E 65 (2002) 026501]. For the Cherenkov radiation, we demonstrate a satisfactory agreement between the incoherent power predicted in our analysis and previous experimental results.展开更多
Nowadays,it is a great challenge to reduce energy consumption and exhaust emission for human activities,in particular,high temperature industries.Among many efforts made to realize energy savings for high temperature ...Nowadays,it is a great challenge to reduce energy consumption and exhaust emission for human activities,in particular,high temperature industries.Among many efforts made to realize energy savings for high temperature furnaces and kilns,the use of high emissivity materials is considered to be an effective route to increase their thermal efficiency by enhancing heat transfer.Most materials with high refractoriness and superior chemical stability have weak infrared absorption and radiation properties;however,their emissivity in infrared regions(1 —25 μm) could be effectively increased by ion doping.This is attributed to three main mechanisms:1) distortion of the crystal lattice;2) increase of free carrier absorption; 3) formation of impurity energy level.In this paper,the development and advancement of various material systems with high emissivity including non-oxides and oxide based ceramics were reviewed.It is also suggested that the establishment of evaluation models or instruments for energy savings would be beneficial to design and application of high emissivity materials in various high-temperature environment.Furthermore,more efforts should be made on durability of high emissivity materials at high service temperatures and on the standardization of testing methods for emissivity.展开更多
The problem of excessive radiated emission for a certain type of laser scanner is discussed in this paper.Firstly,the frequency characteristics of the laser scanner can be obtained by traditional test methods.Accordin...The problem of excessive radiated emission for a certain type of laser scanner is discussed in this paper.Firstly,the frequency characteristics of the laser scanner can be obtained by traditional test methods.According to the frequency and electronic equipment characteristics,the interference source can be estimated and established.Then based upon analysis,modified methods are proposed.By applying the above methods,the interference source can be identified and the amount of radiated emission from the scanner can be reduced effectively.Finally,the scanner can op erate in a compatible manner with other electronic systems at the same time.The above methods can provide a reference for electronic equipment design ensuring electromagnetic compatibility and passing the radiated emission test.展开更多
As per the entail in wireless communication, the ever increasing switching speeds of digital devices pose significant challenges. Signal quality is more important for high speed products and the signal integrity ...As per the entail in wireless communication, the ever increasing switching speeds of digital devices pose significant challenges. Signal quality is more important for high speed products and the signal integrity must ensure reliable transmission where signal integrity is a measure of the quality of an electrical signal. A high speed differential signal will result in signal integrity issues such as crosstalk and radiated emission. One of the solutions to suppress radiated emission is defected ground pattern. This paper introduces a novel trident incurvature shaped defected ground structure to suppress radiated emission that arises in high speed differential signal. The proposed defected ground structure is implemented using Ansoft HFSS simulation tool and its performance is quantified in terms of scattering parameters. The proposed trident incurvature shaped defected ground pattern reduces near end coupling and far end coupling by more than 6 dB and 2 dB respectively. It also provides better return loss and insertion loss in the frequency range 1 - 6 GHz.展开更多
This paper presents a study on the effects of radiation from electronic equipment in hospitals. This study was performed in Argentinean, Colombian and Spanish hospitals. The work consists of two parts: a survey to det...This paper presents a study on the effects of radiation from electronic equipment in hospitals. This study was performed in Argentinean, Colombian and Spanish hospitals. The work consists of two parts: a survey to determine the hospital personnel’s knowledge of the problem and a technical part consisting of a measurements campaign to determine the levels of radiated electrical and magnetic fields in several hospitals due to the presence of electromagnetic interferences, such as the use of mobile phones. The study of this problem has been of special interest in countries such as the USA and Canada, and this paper attempts to convey the necessity of creating regulations that can be applied to the hospitals of the countries analyzed. More than fifty hospitals were studied in these three countries, considering the following aspects: the hospital personnel’s awareness of the problem, whether the hospitals have performed previous studies of this type, the appearance of problems in medical equipment due to this interference, the origin of the interference, and the failures that have appeared in computers due to electromagnetic interference. The results show that, most hospitals have a lack of knowledge regarding this issue and that field levels above those allowed by international regulations are present. Therefore, a regulation must be established to avoid the problem.展开更多
This paper investigated radiation heat transfer and temperature distributions of solar thermochemical reactor for syngas production using the finite volume discrete ordinate method (fvDOM) and P1 approximation for r...This paper investigated radiation heat transfer and temperature distributions of solar thermochemical reactor for syngas production using the finite volume discrete ordinate method (fvDOM) and P1 approximation for radiation heat transfer. Different parameters including absorptivity, emissivity, reflection based radiation scatter- ing, and carrier gas flow inlet velocity that would greatly affect the reactor thermal performance were sufficiently investigated. The fvDOM approximation was used to obtain the radiation intensity distribution along the reactor. The drop in the temperature resulted from the radiation scattering was further investigated using the P1 approx- imation. The results indicated that the reactor temperature difference between the P1 approximation and the fvDOM radiation model was very close under different operating conditions. However, a big temperature difference which increased with an increase in the radiation emissivity due to the thermal non-equilibrium was observed in the radiation inlet region. It was found that the incident radiation flux distribution had a strong impact on the temperature distribution throughout the reactor. This paper revealed that the temperature drop caused by the boundary radiation heat loss should not be neglected for the thermal performance analysis of solar thermochemical reactor.展开更多
Realizing all-day and all-weather energy-saving heating is crucial for mitigating the global energy and ecology crisis.Electric/solar heating are two promising heating approaches,yet materials with high elec-trical co...Realizing all-day and all-weather energy-saving heating is crucial for mitigating the global energy and ecology crisis.Electric/solar heating are two promising heating approaches,yet materials with high elec-trical conductivity,high solar absorptivity,and low infrared emissivity at the same time are rare in na-ture,which are highly anticipated and of great significance for highly efficient electric/solar heating.In this work,we demonstrate that Ti_(3)C_(2)T_(x) MXene with low IR emissivity(14.5%)fills the gap in the absence of the above materials,exhibiting a remarkable electric/solar heating performance.The saturated heating temperature of Ti_(3)C_(2)T_(x) film reaches a record-high value of 201°C at a low driving voltage of 1.5 V,and reaches 84.3°C under practical solar irradiation(750 W/m^(2))with a high solar to the thermal conversion efficiency of 75.3%,which is far superior to other reported materials.Meanwhile,the low IR emissivity endows Ti_(3)C_(2)T_(x) with a remarkable passive radiative heating capability of 7.0°C,ensuring zero-energy heating without electric/solar energy supply.The intrinsic characteristic of high electrical conductivity,high solar absorptivity,and low IR emissivity makes Ti_(3)C_(2)T_(x) unique existence in nature,which is highly promising for all-day and all-weather energy-saving heating.展开更多
The radiation emission (RE) of multilayer primed circuit board (PCB) will cause electromagnetic compatibility problem. An efficient numerical method for evaluating the effectiveness of decoupling capacitors in red...The radiation emission (RE) of multilayer primed circuit board (PCB) will cause electromagnetic compatibility problem. An efficient numerical method for evaluating the effectiveness of decoupling capacitors in reducing RE from power ground (P/G) planes in PCB was presented. A two-dimensional boundary-element method (BEM) was used to establish the radiation model. Then, the RE was calculated by equivalent magnetic current of edge field around P/G planes. Furthermore, the radiation and input impedance of P/G planes mounted decoupling capacitors were calculated for frequency up to 5 GHz The results were compared to those of the case without decoupling capacitors. It shows that the decoupling capacitors can effectively decrease RE except for anti-resonant frequency. At higher frequencies, the decoupling effectiveness mainly depends on the parasitic inductance of capacitor pin rather than the value.展开更多
文摘This paper contributes to explain the global warming instead of"giving up"and thinking about passively adapting to climate change or global warming.It makes more sense to tackle what creates the greenhouse effect and contributes to global warming.The greenhouse effect is not only due to GHGs emissions,but also to the excess IR radiation emitted during the day,by artificial surfaces,following the absorption of solar radiation.The phenomenon should be compared to that of radiative forcing well known by climatologists and which makes the link between atmospheric pollution and the density of heat fluxes stopped by the atmosphere inducing global warming.It becomes clear that type an equation here.The surplus CO2 and IR radiation emissions influence global warming,not to mention the direct part of the heat released by the combustion of fossil fuels and even renewable(wood fires,biogas,friction of wind turbine propellers with the air).
基金provided by the National Key Technology R&D Program of China (No. 2012BAK09B01)the National Natural Science Foundation of China (Nos. 50904067 and 51104156)+1 种基金the Program for the New Century Excellent Talents in University of China (No. NCET-10-0768)the Jiangsu Planned Projects for Postdoctoral Research Funds of China (No. 1102085C)
文摘Based on electromagnetic radiation characteristics, the present research studied the damage evolution of rock under uniaxial compression. Besides, this research built the coal-rock damage evolution model considered residual strength. The applicability and accuracy of the model were verified through experiments. The results show that coal-rock damage evolution consists of four periods. The first period is from the beginning of compression to nearly 20% of the stress peak value, during which the damage variable changes stably about 0.1, and accordingly a few of electromagnetic radiation signals emerge. The second period is from about 20% to 70% of the stress peak value. The damage has stable development, and the parameter of electromagnetic radiation characteristics turns larger continuously with the increase of stress. The third period is when the damage has accelerated development, the coal-rock was broken which result from sharp increasing of the damage variable, meanwhile a great quantity of electromagnetic radiation signals emerge. The fourth period is after the coal-rock fracture, during which the damage variable corresponding to the parameter of electromagnetic radiation characteristics has a stable development. This research has great academic and realistic significance for further studies the electromagnetic radiation characteristics of coal-rock under loading and damage and the forecasting of coal-rock dynamic disasters.
基金Supported by the ASRT-INFN Joint Project between the Academy of Scientific Research and Technology in Egypt and INFN in Italy
文摘A unified analysis is presented to calculate the incoherent spontaneous power of cooperative radiations based on self-amplified spontaneous emission. Using quantum mechanical tools, we derive analytical expressions for the incoherent spontaneous power of undulator and Cherenkov free-electron lasers (FELs). The undulator and Cherenkov FELs are considered as two different examples for the radiation that accumulate cooperatively. In the case of the undulator FEL, we show an excellent agreement between an expression for the incoherent radiation power derived in the present work and that obtained using a completely different approach [Phys. Ftev. E 65 (2002) 026501]. For the Cherenkov radiation, we demonstrate a satisfactory agreement between the incoherent power predicted in our analysis and previous experimental results.
基金Natural Science Foundation of China ( NSFC,Grant no. 51372255 )Beijing Natural Science Foundation ( BNSF,Grant no. 2131006 )+2 种基金International Science and Technology Cooperation Program of China ( Grant no. 2014DFR51010)External Cooperation Program of Chinese Academy of Sciences ( Grant no. GJHZ201310 )Open Foundation of State Key Laboratory of Advanced Refractories ( Grant no. 201401,Sinosteel Luoyang Institute of Refractories Research Co. ,Ltd. ) for the financial support
文摘Nowadays,it is a great challenge to reduce energy consumption and exhaust emission for human activities,in particular,high temperature industries.Among many efforts made to realize energy savings for high temperature furnaces and kilns,the use of high emissivity materials is considered to be an effective route to increase their thermal efficiency by enhancing heat transfer.Most materials with high refractoriness and superior chemical stability have weak infrared absorption and radiation properties;however,their emissivity in infrared regions(1 —25 μm) could be effectively increased by ion doping.This is attributed to three main mechanisms:1) distortion of the crystal lattice;2) increase of free carrier absorption; 3) formation of impurity energy level.In this paper,the development and advancement of various material systems with high emissivity including non-oxides and oxide based ceramics were reviewed.It is also suggested that the establishment of evaluation models or instruments for energy savings would be beneficial to design and application of high emissivity materials in various high-temperature environment.Furthermore,more efforts should be made on durability of high emissivity materials at high service temperatures and on the standardization of testing methods for emissivity.
文摘The problem of excessive radiated emission for a certain type of laser scanner is discussed in this paper.Firstly,the frequency characteristics of the laser scanner can be obtained by traditional test methods.According to the frequency and electronic equipment characteristics,the interference source can be estimated and established.Then based upon analysis,modified methods are proposed.By applying the above methods,the interference source can be identified and the amount of radiated emission from the scanner can be reduced effectively.Finally,the scanner can op erate in a compatible manner with other electronic systems at the same time.The above methods can provide a reference for electronic equipment design ensuring electromagnetic compatibility and passing the radiated emission test.
文摘As per the entail in wireless communication, the ever increasing switching speeds of digital devices pose significant challenges. Signal quality is more important for high speed products and the signal integrity must ensure reliable transmission where signal integrity is a measure of the quality of an electrical signal. A high speed differential signal will result in signal integrity issues such as crosstalk and radiated emission. One of the solutions to suppress radiated emission is defected ground pattern. This paper introduces a novel trident incurvature shaped defected ground structure to suppress radiated emission that arises in high speed differential signal. The proposed defected ground structure is implemented using Ansoft HFSS simulation tool and its performance is quantified in terms of scattering parameters. The proposed trident incurvature shaped defected ground pattern reduces near end coupling and far end coupling by more than 6 dB and 2 dB respectively. It also provides better return loss and insertion loss in the frequency range 1 - 6 GHz.
基金supported by E.S.E METROSALUD and Instituto Tecnologico Metropolitano—ITM.
文摘This paper presents a study on the effects of radiation from electronic equipment in hospitals. This study was performed in Argentinean, Colombian and Spanish hospitals. The work consists of two parts: a survey to determine the hospital personnel’s knowledge of the problem and a technical part consisting of a measurements campaign to determine the levels of radiated electrical and magnetic fields in several hospitals due to the presence of electromagnetic interferences, such as the use of mobile phones. The study of this problem has been of special interest in countries such as the USA and Canada, and this paper attempts to convey the necessity of creating regulations that can be applied to the hospitals of the countries analyzed. More than fifty hospitals were studied in these three countries, considering the following aspects: the hospital personnel’s awareness of the problem, whether the hospitals have performed previous studies of this type, the appearance of problems in medical equipment due to this interference, the origin of the interference, and the failures that have appeared in computers due to electromagnetic interference. The results show that, most hospitals have a lack of knowledge regarding this issue and that field levels above those allowed by international regulations are present. Therefore, a regulation must be established to avoid the problem.
基金This work was supported by the National Natural Science Foundation of China (Grant Nos. 51522601 and 51421063) and the program for New Century Excellent Talents in University (Grant No. NCET- 13-0173).
文摘This paper investigated radiation heat transfer and temperature distributions of solar thermochemical reactor for syngas production using the finite volume discrete ordinate method (fvDOM) and P1 approximation for radiation heat transfer. Different parameters including absorptivity, emissivity, reflection based radiation scatter- ing, and carrier gas flow inlet velocity that would greatly affect the reactor thermal performance were sufficiently investigated. The fvDOM approximation was used to obtain the radiation intensity distribution along the reactor. The drop in the temperature resulted from the radiation scattering was further investigated using the P1 approx- imation. The results indicated that the reactor temperature difference between the P1 approximation and the fvDOM radiation model was very close under different operating conditions. However, a big temperature difference which increased with an increase in the radiation emissivity due to the thermal non-equilibrium was observed in the radiation inlet region. It was found that the incident radiation flux distribution had a strong impact on the temperature distribution throughout the reactor. This paper revealed that the temperature drop caused by the boundary radiation heat loss should not be neglected for the thermal performance analysis of solar thermochemical reactor.
基金support of the National Natural Science Foundation of China(Nos.52003248 and 82004001)the China Postdoctoral Science Foundation(Nos.2018M642780 and 2021T140613)+1 种基金the Open-ing Project of State Key Laboratory of Polymer Materials Engineer-ing(Sichuan University)(No.sklpme2019-4-31)the Key Research and Development and Promotion projects of Henan Province(No.202102210032)are gratefully acknowledged.
文摘Realizing all-day and all-weather energy-saving heating is crucial for mitigating the global energy and ecology crisis.Electric/solar heating are two promising heating approaches,yet materials with high elec-trical conductivity,high solar absorptivity,and low infrared emissivity at the same time are rare in na-ture,which are highly anticipated and of great significance for highly efficient electric/solar heating.In this work,we demonstrate that Ti_(3)C_(2)T_(x) MXene with low IR emissivity(14.5%)fills the gap in the absence of the above materials,exhibiting a remarkable electric/solar heating performance.The saturated heating temperature of Ti_(3)C_(2)T_(x) film reaches a record-high value of 201°C at a low driving voltage of 1.5 V,and reaches 84.3°C under practical solar irradiation(750 W/m^(2))with a high solar to the thermal conversion efficiency of 75.3%,which is far superior to other reported materials.Meanwhile,the low IR emissivity endows Ti_(3)C_(2)T_(x) with a remarkable passive radiative heating capability of 7.0°C,ensuring zero-energy heating without electric/solar energy supply.The intrinsic characteristic of high electrical conductivity,high solar absorptivity,and low IR emissivity makes Ti_(3)C_(2)T_(x) unique existence in nature,which is highly promising for all-day and all-weather energy-saving heating.
基金supported by the National Natural Science Foundation of China (61171051)
文摘The radiation emission (RE) of multilayer primed circuit board (PCB) will cause electromagnetic compatibility problem. An efficient numerical method for evaluating the effectiveness of decoupling capacitors in reducing RE from power ground (P/G) planes in PCB was presented. A two-dimensional boundary-element method (BEM) was used to establish the radiation model. Then, the RE was calculated by equivalent magnetic current of edge field around P/G planes. Furthermore, the radiation and input impedance of P/G planes mounted decoupling capacitors were calculated for frequency up to 5 GHz The results were compared to those of the case without decoupling capacitors. It shows that the decoupling capacitors can effectively decrease RE except for anti-resonant frequency. At higher frequencies, the decoupling effectiveness mainly depends on the parasitic inductance of capacitor pin rather than the value.