LED调制带宽制约着可见光通信(VLC)系统的数据传输速率。为此,提出一种基于双重调制技术COB(chip on board)封装的LED灯具,通过实现16级脉冲振幅调制(PAM),将系统数据传输速率提升4倍;结合脉冲宽度调制(PWM)技术进行调光,同时兼顾室内...LED调制带宽制约着可见光通信(VLC)系统的数据传输速率。为此,提出一种基于双重调制技术COB(chip on board)封装的LED灯具,通过实现16级脉冲振幅调制(PAM),将系统数据传输速率提升4倍;结合脉冲宽度调制(PWM)技术进行调光,同时兼顾室内的照明及通信。采用Matlab软件模拟仿真视频传输试验。结果表明,在相同信噪比(SNR)的情况下,基于双重调制技术的VLC系统的误码率(BER)比传统使用开关键控(OOK)调控技术系统的BER更低。本文系统在不增加器件带宽前提下,成倍提高了无线通信的质量与数据传输速率;从照明与通信的角度优化了VLC系统的信源,具有广阔的应用前景。展开更多
Global warming has been the subject of concern in today’s world with elevating temperature causing the melting of polar ice and increasing sea level.The aim of this study was to investigate the physiological and phot...Global warming has been the subject of concern in today’s world with elevating temperature causing the melting of polar ice and increasing sea level.The aim of this study was to investigate the physiological and photosynthetic performance of two polar Chlorella,namely Chlorella UMACC 250 and Chlorella UMACC 234 to elevating temperatures as might be experienced under future warming scenarios.The cultures were exposed to three different temperatures of 4℃,8℃and 12℃.The growth and photosynthetic activity were determined every 2 d for a period of 10 d.At the end of the experiment,the cultures were harvested and analysed for biochemical composition.Both Chlorella strains were able to tolerate higher temperatures than their ambient temperature.The final pigments content showed an increasing trend with increased temperatures for both strains.The photosynthetic activities were measured using pulse-amplitude modulation(PAM)fluorometer.The photosynthetic parameters including maximum quantum efficiency(Fv/Fm),maximum relative electron transport rate(r ETRmax),light harvesting efficiency(a)and photoadaptive index(Ek)were derived from the rapid light curves(RLCs).Both Chlorella strains showed a slight decline in growth and photosynthetic activities at the initial part of the experiment.However,they showed the ability to recuperate with Chlorella UMACC 250 recovers better compared to Chlorella UMACC 234.Both Chlorella strains showed similar trend in their carbohydrate content at 12℃,while the protein content of Chlorella UMACC 234 decreased when exposed to increasing temperatures.The results indicated that polar Chlorella are able to survive at increased temperatures throughout the experiment.展开更多
文摘LED调制带宽制约着可见光通信(VLC)系统的数据传输速率。为此,提出一种基于双重调制技术COB(chip on board)封装的LED灯具,通过实现16级脉冲振幅调制(PAM),将系统数据传输速率提升4倍;结合脉冲宽度调制(PWM)技术进行调光,同时兼顾室内的照明及通信。采用Matlab软件模拟仿真视频传输试验。结果表明,在相同信噪比(SNR)的情况下,基于双重调制技术的VLC系统的误码率(BER)比传统使用开关键控(OOK)调控技术系统的BER更低。本文系统在不增加器件带宽前提下,成倍提高了无线通信的质量与数据传输速率;从照明与通信的角度优化了VLC系统的信源,具有广阔的应用前景。
基金funded by a research grant from the Ministry of Higher Education Malaysia under the Fundamental Research Grant Scheme(Grant no.FRGS/1/2017/STG05/TAYLOR/02/2)。
文摘Global warming has been the subject of concern in today’s world with elevating temperature causing the melting of polar ice and increasing sea level.The aim of this study was to investigate the physiological and photosynthetic performance of two polar Chlorella,namely Chlorella UMACC 250 and Chlorella UMACC 234 to elevating temperatures as might be experienced under future warming scenarios.The cultures were exposed to three different temperatures of 4℃,8℃and 12℃.The growth and photosynthetic activity were determined every 2 d for a period of 10 d.At the end of the experiment,the cultures were harvested and analysed for biochemical composition.Both Chlorella strains were able to tolerate higher temperatures than their ambient temperature.The final pigments content showed an increasing trend with increased temperatures for both strains.The photosynthetic activities were measured using pulse-amplitude modulation(PAM)fluorometer.The photosynthetic parameters including maximum quantum efficiency(Fv/Fm),maximum relative electron transport rate(r ETRmax),light harvesting efficiency(a)and photoadaptive index(Ek)were derived from the rapid light curves(RLCs).Both Chlorella strains showed a slight decline in growth and photosynthetic activities at the initial part of the experiment.However,they showed the ability to recuperate with Chlorella UMACC 250 recovers better compared to Chlorella UMACC 234.Both Chlorella strains showed similar trend in their carbohydrate content at 12℃,while the protein content of Chlorella UMACC 234 decreased when exposed to increasing temperatures.The results indicated that polar Chlorella are able to survive at increased temperatures throughout the experiment.
