With the exponential growth of the data traffic in wireless communication systems, terahertz(THz) frequency band is envisioned as a promising candidate to support ultra-broadband for future beyond fifth generation(5G)...With the exponential growth of the data traffic in wireless communication systems, terahertz(THz) frequency band is envisioned as a promising candidate to support ultra-broadband for future beyond fifth generation(5G), bridging the gap between millimeter wave(mmWave) and optical frequency ranges. The purpose of this paper is to provide a comprehensive literature review on the development towards THz communications and presents some key technologies faced in THz wireless communication systems. Firstly, despite the substantial hardware problems that have to be developed in terms of the THz solid state superheterodyne receiver, high speed THz modulators and THz antennas, the practical THz channel model and the efficient THz beamforming are also described to compensate for the severe path attenuation. Moreover, two different kinds of lab-level THz communication systems are introduced minutely, named a solid state THz communication system and a spatial direct modulation THz communication system, respectively. The solid state THz system converts intermediate frequency(IF) modulated signal to THz frequency while the direct modulation THz system allows the high power THz sources to input for approving the relatively long distance communications. Finally, we discuss several potential application scenarios as well as some vital technical challenges that will be encountered in the future THz communications.展开更多
新疆伊犁河谷的黄土,在沉积过程中受大西洋西风环流控制,不同于受东亚季风控制的黄土高原黄土,需要专门研究。对伊犁一大型渠道工程湿陷性黄土渠基的现场大型浸水试验证明,伊犁黄土湿陷性强烈,现场实测自重湿陷量达到352 cm,最大湿陷系...新疆伊犁河谷的黄土,在沉积过程中受大西洋西风环流控制,不同于受东亚季风控制的黄土高原黄土,需要专门研究。对伊犁一大型渠道工程湿陷性黄土渠基的现场大型浸水试验证明,伊犁黄土湿陷性强烈,现场实测自重湿陷量达到352 cm,最大湿陷系数达到0.18(p=200 k Pa),且湿陷具有沉降发展早、速度快和量值大的特点。为了弄清引起伊犁黄土强烈湿陷的原因,开展了伊犁黄土沉积历史调查,及大量的黄土物理、矿物组成和显微结构试验工作,研究表明:伊犁黄土形成年代较晚,沉积过程中气候更为干冷,也基本未经受湿热气候的影响,盐分特别是碳酸钙受雨水淋滤的作用小,是典型的风积黄土样本;伊犁黄土具有天然密度、含水率和饱和度较小,易溶盐含量较高的特点,且其颗粒之间以点接触、架空结构和少胶结形式为主,结构极不稳定,这些因素是造成其强烈湿陷的历史原因和内在原因。展开更多
The hydrodynamics of turbulent flow through submerged flexible vegetation is investigated in a flume using acoustic Doppler velocimetery(ADV)measurements.The flow characteristics such as the energetics and momentum tr...The hydrodynamics of turbulent flow through submerged flexible vegetation is investigated in a flume using acoustic Doppler velocimetery(ADV)measurements.The flow characteristics such as the energetics and momentum transfer derived from convcntional spectral and quadrant analyses are considered as the flow encounters a finite vegetation patch.Consistent with numerous canopy flow experiments,a shear layer and coherent vortex structures near the canopy top emerge caused by Kelvin-Helmholtz instabilities after the flow equilibrates with the vegetated layer.These in stabilities are commonly attributed to velocity differences between non-vegetated and vegetated canopy layers in agreement with numerous experiments and simulations conducted on dense rigid canopies.The power-spectral density function for vertical velocity turbulent fluctuations at different downstream positions starting from the edge of the vegetation layer are also computed.For a preset water depth,the dominant dimensionless frequency is found to be surprisingly invariant around 0.027 despite large differences in vegetation densities.The ejection and sweep events significantly contribute to the Reynolds stresses near the top of the vegetation.The momentum flux carried by ejections is larger than its counterpart carried by the sweeps above the canopy top.However,the momentum flux carried by sweeps is larger below the top of the canopy.展开更多
A dual channel difference （DCD） method is applied to detect nighttime sea fog/stratus over the Huanghai Sea using the infrared （IR） data of shortwave （3.5-4.0 μm） and longwave （10.3-11.3 μm） channels from th...A dual channel difference （DCD） method is applied to detect nighttime sea fog/stratus over the Huanghai Sea using the infrared （IR） data of shortwave （3.5-4.0 μm） and longwave （10.3-11.3 μm） channels from the Multi-functional Transport Satellite （MTSAT）-IR, i.e., shortwave minus longwave brightness temperature difference （SLTD）. Twenty-four sea fog events over the Huanghai Sea during March to July of 2006 and 2007 are chosen to determine a suitable value of SLTD for nighttime sea fog/stratus detection, and it is found that the value of-5.5-2.5℃ can be taken as a criterion. Two case examples of sea fog events are especially demonstrated in detail utilizing the criterion, and the results show that the derived sea fog/stratus coverage is quite reasonable. This coverage information is very helpful to analyze the formation and evolution of sea fog/stratus during night and can provide sea fog researchers with observational evidences for model results verification. However, more efforts are needed to further obtain vertical extent information of sea fog/stratus and attempt to discriminate between sea fog and stratus.展开更多
The intracellular calcium ions(Ca^(2+)) act as second messenger to regulate gene transcription,cell proliferation, migration and death. Accumulating evidences have demonstrated that intracellular Ca^(2+)homeostasis is...The intracellular calcium ions(Ca^(2+)) act as second messenger to regulate gene transcription,cell proliferation, migration and death. Accumulating evidences have demonstrated that intracellular Ca^(2+)homeostasis is altered in cancer cells and the alteration is involved in tumor initiation, angiogenesis,progression and metastasis. Targeting derailed Ca^(2+)signaling for cancer therapy has become an emerging research area. This review summarizes some important Ca^(2+)channels, transporters and Ca^(2+)-ATPases,which have been reported to be altered in human cancer patients. It discusses the current research effort toward evaluation of the blockers, inhibitors or regulators for Ca^(2+)channels/transporters or Ca^(2+)-ATPase pumps as anti-cancer drugs. This review is also aimed to stimulate interest in, and support for researchinto the understanding of cellular mechanisms underlying the regulation of Ca^(2+)signaling in different cancer cells, and to search for novel therapies to cure these malignancies by targeting Ca^(2+)channels or transporters.展开更多
基金supported by the National High Technology Research and Development Program of China (863 program) of China under Grant No.2011AA010200 supported by the National Natural Science Foundation of China (NSFC) under Grant No.61771116 and No.91738102
文摘With the exponential growth of the data traffic in wireless communication systems, terahertz(THz) frequency band is envisioned as a promising candidate to support ultra-broadband for future beyond fifth generation(5G), bridging the gap between millimeter wave(mmWave) and optical frequency ranges. The purpose of this paper is to provide a comprehensive literature review on the development towards THz communications and presents some key technologies faced in THz wireless communication systems. Firstly, despite the substantial hardware problems that have to be developed in terms of the THz solid state superheterodyne receiver, high speed THz modulators and THz antennas, the practical THz channel model and the efficient THz beamforming are also described to compensate for the severe path attenuation. Moreover, two different kinds of lab-level THz communication systems are introduced minutely, named a solid state THz communication system and a spatial direct modulation THz communication system, respectively. The solid state THz system converts intermediate frequency(IF) modulated signal to THz frequency while the direct modulation THz system allows the high power THz sources to input for approving the relatively long distance communications. Finally, we discuss several potential application scenarios as well as some vital technical challenges that will be encountered in the future THz communications.
文摘新疆伊犁河谷的黄土,在沉积过程中受大西洋西风环流控制,不同于受东亚季风控制的黄土高原黄土,需要专门研究。对伊犁一大型渠道工程湿陷性黄土渠基的现场大型浸水试验证明,伊犁黄土湿陷性强烈,现场实测自重湿陷量达到352 cm,最大湿陷系数达到0.18(p=200 k Pa),且湿陷具有沉降发展早、速度快和量值大的特点。为了弄清引起伊犁黄土强烈湿陷的原因,开展了伊犁黄土沉积历史调查,及大量的黄土物理、矿物组成和显微结构试验工作,研究表明:伊犁黄土形成年代较晚,沉积过程中气候更为干冷,也基本未经受湿热气候的影响,盐分特别是碳酸钙受雨水淋滤的作用小,是典型的风积黄土样本;伊犁黄土具有天然密度、含水率和饱和度较小,易溶盐含量较高的特点,且其颗粒之间以点接触、架空结构和少胶结形式为主,结构极不稳定,这些因素是造成其强烈湿陷的历史原因和内在原因。
基金the National Natural Science Foundation of China(Grant Nos.51439007,11672213,11872285 and 51809286).
文摘The hydrodynamics of turbulent flow through submerged flexible vegetation is investigated in a flume using acoustic Doppler velocimetery(ADV)measurements.The flow characteristics such as the energetics and momentum transfer derived from convcntional spectral and quadrant analyses are considered as the flow encounters a finite vegetation patch.Consistent with numerous canopy flow experiments,a shear layer and coherent vortex structures near the canopy top emerge caused by Kelvin-Helmholtz instabilities after the flow equilibrates with the vegetated layer.These in stabilities are commonly attributed to velocity differences between non-vegetated and vegetated canopy layers in agreement with numerous experiments and simulations conducted on dense rigid canopies.The power-spectral density function for vertical velocity turbulent fluctuations at different downstream positions starting from the edge of the vegetation layer are also computed.For a preset water depth,the dominant dimensionless frequency is found to be surprisingly invariant around 0.027 despite large differences in vegetation densities.The ejection and sweep events significantly contribute to the Reynolds stresses near the top of the vegetation.The momentum flux carried by ejections is larger than its counterpart carried by the sweeps above the canopy top.However,the momentum flux carried by sweeps is larger below the top of the canopy.
基金The National Natural Science Foundation of China under contract No. 40706004the National Basic Research Program ("973" program) of China under contract No. 2005CB422301+2 种基金China Meteorological Administration’s New Technology Extension Project under contract No. CMATG2008M41the National Special Fund for public Sector Research of China under contract No. GYHY200706031Shandong Provincial Meteorological Bureau Science Fund of China under contract No. 2004SDQXJ01.
文摘A dual channel difference （DCD） method is applied to detect nighttime sea fog/stratus over the Huanghai Sea using the infrared （IR） data of shortwave （3.5-4.0 μm） and longwave （10.3-11.3 μm） channels from the Multi-functional Transport Satellite （MTSAT）-IR, i.e., shortwave minus longwave brightness temperature difference （SLTD）. Twenty-four sea fog events over the Huanghai Sea during March to July of 2006 and 2007 are chosen to determine a suitable value of SLTD for nighttime sea fog/stratus detection, and it is found that the value of-5.5-2.5℃ can be taken as a criterion. Two case examples of sea fog events are especially demonstrated in detail utilizing the criterion, and the results show that the derived sea fog/stratus coverage is quite reasonable. This coverage information is very helpful to analyze the formation and evolution of sea fog/stratus during night and can provide sea fog researchers with observational evidences for model results verification. However, more efforts are needed to further obtain vertical extent information of sea fog/stratus and attempt to discriminate between sea fog and stratus.
基金supported by NIH R01-CA185055(to Zui Pan)Chaochu Cui received postgraduate student training of internationalization level promotion program from Sun Yat-sen University(02300-52114000)
文摘The intracellular calcium ions(Ca^(2+)) act as second messenger to regulate gene transcription,cell proliferation, migration and death. Accumulating evidences have demonstrated that intracellular Ca^(2+)homeostasis is altered in cancer cells and the alteration is involved in tumor initiation, angiogenesis,progression and metastasis. Targeting derailed Ca^(2+)signaling for cancer therapy has become an emerging research area. This review summarizes some important Ca^(2+)channels, transporters and Ca^(2+)-ATPases,which have been reported to be altered in human cancer patients. It discusses the current research effort toward evaluation of the blockers, inhibitors or regulators for Ca^(2+)channels/transporters or Ca^(2+)-ATPase pumps as anti-cancer drugs. This review is also aimed to stimulate interest in, and support for researchinto the understanding of cellular mechanisms underlying the regulation of Ca^(2+)signaling in different cancer cells, and to search for novel therapies to cure these malignancies by targeting Ca^(2+)channels or transporters.
