We consider the problem of energy efficiency aware dynamic adaptation of data transmission rate and transmission power of the users in carrier sensing based Wireless Local Area Networks(WLANs)in the presence of path l...We consider the problem of energy efficiency aware dynamic adaptation of data transmission rate and transmission power of the users in carrier sensing based Wireless Local Area Networks(WLANs)in the presence of path loss,Rayleigh fading and log-normal shadowing.For a data packet transmission,we formulate an optimization problem,solve the problem,and propose a rate and transmission power adaptation scheme with a restriction methodology of data packet transmission for achieving the optimal energy efficiency.In the restriction methodology of data packet transmission,a user does not transmit a data packet if the instantaneous channel gain of the user is lower than a threshold.To evaluate the performance of the proposed scheme,we develop analytical models for computing the throughput and energy efficiency of WLANs under the proposed scheme considering a saturation traffic condition.We then validate the analytical models via simulation.We find that the proposed scheme provides better throughput and energy efficiency with acceptable throughput fairness if the restriction methodology of data packet transmission is included.By means of the analytical models and simulations,we demonstrate that the proposed scheme provides significantly higher throughput,energy efficiency and fairness index than a traditional non-adaptive scheme and an existing most relevant adaptive scheme.Throughput and energy efficiency gains obtained by the proposed scheme with respect to the existing adapting scheme are about 75%and 103%,respectively,for a fairness index of 0.8.We also study the effect of various system parameters on throughput and energy efficiency and provide various engineering insights.展开更多
The relationship between infrared light （IR） and vacuum ultraviolet （VUV） emission in shadow mask plasma display panels （SMPDP） at high xenon content and high voltage is investigated. The respective ratios of VI...The relationship between infrared light （IR） and vacuum ultraviolet （VUV） emission in shadow mask plasma display panels （SMPDP） at high xenon content and high voltage is investigated. The respective ratios of VIS/IR-823 am, VIS/IR-828 nm and of efficacy/VIS/IR-823 nm, efficacy/VIS/IR-823 nm are calculated to determine the behavior of the xenon excitation efficiency and the electron excitation efficiency as a function of the driving voltage and xenon content. It is found that the xenon excitation efficiency is almost independent of the driving voltage, and increases approximately linearly with the xenon content. The values for efficacy/VIS/IR-828 nm increase rapidly with the xenon content, but saturate at a xenon ratio of about 30% while, on the other hand, the efficacy/VIS/IR-823 nm values decrease continuously with the xenon content.展开更多
To reduce solar gains,regions of the sky dome are masked,where the solar path will pass in the moments in which the shade will be desirable.But these regions masked by the shadow devices could also provide diffuse lig...To reduce solar gains,regions of the sky dome are masked,where the solar path will pass in the moments in which the shade will be desirable.But these regions masked by the shadow devices could also provide diffuse lighting,reducing the need for daytime artificial lighting.When a shadow device is perfectly designed it does not mask more sky than necessary avoiding unwanted solar incursion.During the early stages of architectural design many decisions that will affect the project’s energy efficiency have not yet been made and information is lacking to carry out realistic energy or daylighting simulations.The objective was to define an index to qualify,from minimum input data,the effectiveness of a shaded opening by maximizing the visibility to the sky while minimizing undesirable unshaded solar paths.Using basic 3D models and AutoLISP algorithms,it was possible to calculate the aforementioned index.The results demonstrate that similar shadow devices present variable Solar Coupling Indices,explaining why the pre-design of an efficient shadow device is an unintuitive task.The method allows quantifying the gap between the best solar performance achievable and the performance achieved by a specific solar control device,helping to increase the energy efficiency of the architectural enclosures from the early design stages.展开更多
The energy efficiency(EE) of distributed antenna system with quality of service(Qo S) requirement is investigated over composite Rayleigh fading channel,where the shadow fading,path loss and Rayleigh fading are all co...The energy efficiency(EE) of distributed antenna system with quality of service(Qo S) requirement is investigated over composite Rayleigh fading channel,where the shadow fading,path loss and Rayleigh fading are all considered. Our aim is to maximize the EE which is defined as the ratio of the transmission rate to the total consumed power subject to the maximum transmit power of each remote antenna constraint and Qo S(target BER) requirement. According to the definition of EE and using the upper bound of average EE,the optimized objective function is provided. Based on this,utilizing Karush-KuhnTucker conditions and numerical calculation,a suboptimal energy efficient power allocation(PA) scheme is developed,and the closedform expression of PA coefficients is derived. The scheme may obtain the EE performance close to the existing optimal scheme. Moreover,it has relatively lower complexity than the existing scheme because only the statistic channel information and less iteration are required. Simulation results show the presented scheme is valid and can meet the target BER requirement,and the EE can be increased as target BER requirement decreases.展开更多
We characterized strip-like shadows in cast multicrystalline silicon(mc-Si) ingots. Blocks and wafers were analyzed using scanning infrared microscopy, photoluminescence spectroscopy, laser scanning confocal microscop...We characterized strip-like shadows in cast multicrystalline silicon(mc-Si) ingots. Blocks and wafers were analyzed using scanning infrared microscopy, photoluminescence spectroscopy, laser scanning confocal microscopy, field-emission scanning electron microscopy, X-ray energy-dispersive spectrometry, and microwave photoconductivity decay technique. The effect on solar cell performance is discussed. The results show that the non-microcrystalline shadow region in Si ingots consists of precipitates of Fe, O, and C. The size of these Fe–O–C precipitates found at the shadow region is25 μm. Fe–O–C impurities can slightly reduce the minority carrier lifetime of the wafers while severely decrease in shunt resistance, leading to the increase in reverse current of the solar cells and degradation in cell efficiency.展开更多
文摘We consider the problem of energy efficiency aware dynamic adaptation of data transmission rate and transmission power of the users in carrier sensing based Wireless Local Area Networks(WLANs)in the presence of path loss,Rayleigh fading and log-normal shadowing.For a data packet transmission,we formulate an optimization problem,solve the problem,and propose a rate and transmission power adaptation scheme with a restriction methodology of data packet transmission for achieving the optimal energy efficiency.In the restriction methodology of data packet transmission,a user does not transmit a data packet if the instantaneous channel gain of the user is lower than a threshold.To evaluate the performance of the proposed scheme,we develop analytical models for computing the throughput and energy efficiency of WLANs under the proposed scheme considering a saturation traffic condition.We then validate the analytical models via simulation.We find that the proposed scheme provides better throughput and energy efficiency with acceptable throughput fairness if the restriction methodology of data packet transmission is included.By means of the analytical models and simulations,we demonstrate that the proposed scheme provides significantly higher throughput,energy efficiency and fairness index than a traditional non-adaptive scheme and an existing most relevant adaptive scheme.Throughput and energy efficiency gains obtained by the proposed scheme with respect to the existing adapting scheme are about 75%and 103%,respectively,for a fairness index of 0.8.We also study the effect of various system parameters on throughput and energy efficiency and provide various engineering insights.
基金supported by National Natural Science Foundation of China (No. 60571033)the National Hi'Tech projects of China (No. 2008AA03A308)Programme of Introducing Talents of Discipline to Universities of China (B07027)
文摘The relationship between infrared light （IR） and vacuum ultraviolet （VUV） emission in shadow mask plasma display panels （SMPDP） at high xenon content and high voltage is investigated. The respective ratios of VIS/IR-823 am, VIS/IR-828 nm and of efficacy/VIS/IR-823 nm, efficacy/VIS/IR-823 nm are calculated to determine the behavior of the xenon excitation efficiency and the electron excitation efficiency as a function of the driving voltage and xenon content. It is found that the xenon excitation efficiency is almost independent of the driving voltage, and increases approximately linearly with the xenon content. The values for efficacy/VIS/IR-828 nm increase rapidly with the xenon content, but saturate at a xenon ratio of about 30% while, on the other hand, the efficacy/VIS/IR-823 nm values decrease continuously with the xenon content.
文摘To reduce solar gains,regions of the sky dome are masked,where the solar path will pass in the moments in which the shade will be desirable.But these regions masked by the shadow devices could also provide diffuse lighting,reducing the need for daytime artificial lighting.When a shadow device is perfectly designed it does not mask more sky than necessary avoiding unwanted solar incursion.During the early stages of architectural design many decisions that will affect the project’s energy efficiency have not yet been made and information is lacking to carry out realistic energy or daylighting simulations.The objective was to define an index to qualify,from minimum input data,the effectiveness of a shaded opening by maximizing the visibility to the sky while minimizing undesirable unshaded solar paths.Using basic 3D models and AutoLISP algorithms,it was possible to calculate the aforementioned index.The results demonstrate that similar shadow devices present variable Solar Coupling Indices,explaining why the pre-design of an efficient shadow device is an unintuitive task.The method allows quantifying the gap between the best solar performance achievable and the performance achieved by a specific solar control device,helping to increase the energy efficiency of the architectural enclosures from the early design stages.
基金partially supported by National Natural Science Foundation of China (61571225)Research Founding of Graduate Innovation Center in NUAA (kfjj20150410)+4 种基金the Fundamental Research Funds for the Central Universities (NS2015046,NS2016044)Shenzhen Strategic Emerging Industry Development Funds (JSGG20150331160845693)Qing Lan Project of JiangsuSix Talent Peaks Project in Jiangsu (DZXX-007)Open Research Fund of National Mobile Communications Research Laboratory of Southeast University (2012D17)
文摘The energy efficiency(EE) of distributed antenna system with quality of service(Qo S) requirement is investigated over composite Rayleigh fading channel,where the shadow fading,path loss and Rayleigh fading are all considered. Our aim is to maximize the EE which is defined as the ratio of the transmission rate to the total consumed power subject to the maximum transmit power of each remote antenna constraint and Qo S(target BER) requirement. According to the definition of EE and using the upper bound of average EE,the optimized objective function is provided. Based on this,utilizing Karush-KuhnTucker conditions and numerical calculation,a suboptimal energy efficient power allocation(PA) scheme is developed,and the closedform expression of PA coefficients is derived. The scheme may obtain the EE performance close to the existing optimal scheme. Moreover,it has relatively lower complexity than the existing scheme because only the statistic channel information and less iteration are required. Simulation results show the presented scheme is valid and can meet the target BER requirement,and the EE can be increased as target BER requirement decreases.
基金supported by the National Natural Science Foundation of China(No.51532007)the Fundamental Research Funds for the Central Universities
文摘We characterized strip-like shadows in cast multicrystalline silicon(mc-Si) ingots. Blocks and wafers were analyzed using scanning infrared microscopy, photoluminescence spectroscopy, laser scanning confocal microscopy, field-emission scanning electron microscopy, X-ray energy-dispersive spectrometry, and microwave photoconductivity decay technique. The effect on solar cell performance is discussed. The results show that the non-microcrystalline shadow region in Si ingots consists of precipitates of Fe, O, and C. The size of these Fe–O–C precipitates found at the shadow region is25 μm. Fe–O–C impurities can slightly reduce the minority carrier lifetime of the wafers while severely decrease in shunt resistance, leading to the increase in reverse current of the solar cells and degradation in cell efficiency.
