Research on controlled nuclear fusion has been largely concentrated on plasma confinement using toroidal magnetic fields. Toroidal systems are complex. A simpler magnetic confinement system may provide a valuable plat...Research on controlled nuclear fusion has been largely concentrated on plasma confinement using toroidal magnetic fields. Toroidal systems are complex. A simpler magnetic confinement system may provide a valuable platform for understanding fusion plasmas. The linear mirror machine has delivered good performance with the potential of giving a direct conversion of nuclear energy into electric power. The GAMMA-10 (G-10) linear mirror confinement system at Tsukuba University demonstrated the principle of the direct conversion of plasma energy into electric power on a small scale from the exhaust plasma in the exterior divertor chamber. The tokamak fusion system has to prove that the 10 to 15 MA of plasma current can be sustained continuously with acceptable efficiency. Plasma confinement is due to the magnetic field from the plasma current in tokamaks. There is room for creative new solutions in the magnetic confinement of fusion plasmas, and consideration is given for the alternative approach of using a linear machine with high magnetic mirror fields and the direct conversion of the high temperature escaping plasma to electric power.展开更多
1 Introduction As wireless technology continues to expand,there is a growing concern about the efficient use of spectrum resources.Even though a significant portion of the spectrum is allocated to licensed primary use...1 Introduction As wireless technology continues to expand,there is a growing concern about the efficient use of spectrum resources.Even though a significant portion of the spectrum is allocated to licensed primary users(PUs),studies indicate that their actual utilization is often limited to between 5%to 10%[1].The underutilization of spectrum has given rise to cognitive radio(CR)technology,which allows secondary users(SUs)to opportunistically access these underused resources[2].However,wideband spectrum sensing,the key of CR,is limited by the need for high-speed analog-to-digital converters(ADCs),which are costly and power-hungry.Compressed spectrum sensing(CSS)addresses this challenge by employing sub-Nyquist rate sampling.The efficiency of active transmission detection heavily depends on the quality of spectrum reconstruction.展开更多
1 Introduction The fact that the spectrum resource is underutilised in certain bands has motivated the dynamic spectrum access(DSA)approach,which enables unlicensed secondary users(SUs)equipped with cognitive radio(CR...1 Introduction The fact that the spectrum resource is underutilised in certain bands has motivated the dynamic spectrum access(DSA)approach,which enables unlicensed secondary users(SUs)equipped with cognitive radio(CR)devices to access the spectrum without causing significant interference to primary users(PUs).Nowadays,the increasing bandwidth for wireless communication in millimetre-wave and Terahertz frequency bands puts higher requirements on the performance of spectrum sensing technique,the primary enabler of DSA.展开更多
文摘Research on controlled nuclear fusion has been largely concentrated on plasma confinement using toroidal magnetic fields. Toroidal systems are complex. A simpler magnetic confinement system may provide a valuable platform for understanding fusion plasmas. The linear mirror machine has delivered good performance with the potential of giving a direct conversion of nuclear energy into electric power. The GAMMA-10 (G-10) linear mirror confinement system at Tsukuba University demonstrated the principle of the direct conversion of plasma energy into electric power on a small scale from the exhaust plasma in the exterior divertor chamber. The tokamak fusion system has to prove that the 10 to 15 MA of plasma current can be sustained continuously with acceptable efficiency. Plasma confinement is due to the magnetic field from the plasma current in tokamaks. There is room for creative new solutions in the magnetic confinement of fusion plasmas, and consideration is given for the alternative approach of using a linear machine with high magnetic mirror fields and the direct conversion of the high temperature escaping plasma to electric power.
文摘1 Introduction As wireless technology continues to expand,there is a growing concern about the efficient use of spectrum resources.Even though a significant portion of the spectrum is allocated to licensed primary users(PUs),studies indicate that their actual utilization is often limited to between 5%to 10%[1].The underutilization of spectrum has given rise to cognitive radio(CR)technology,which allows secondary users(SUs)to opportunistically access these underused resources[2].However,wideband spectrum sensing,the key of CR,is limited by the need for high-speed analog-to-digital converters(ADCs),which are costly and power-hungry.Compressed spectrum sensing(CSS)addresses this challenge by employing sub-Nyquist rate sampling.The efficiency of active transmission detection heavily depends on the quality of spectrum reconstruction.
基金The challenge was sponsored by National Instruments(NI)Corpthe Engineering and Physical Sciences Research Council(EPSRC)under the Grant EP/R00711X/2,United Kingdom.
文摘1 Introduction The fact that the spectrum resource is underutilised in certain bands has motivated the dynamic spectrum access(DSA)approach,which enables unlicensed secondary users(SUs)equipped with cognitive radio(CR)devices to access the spectrum without causing significant interference to primary users(PUs).Nowadays,the increasing bandwidth for wireless communication in millimetre-wave and Terahertz frequency bands puts higher requirements on the performance of spectrum sensing technique,the primary enabler of DSA.
