Southeast University

About: Southeast University is a education organization based out in Nanjing, China. It is known for research contribution in the topics: MIMO & Control theory. The organization has 66363 authors who have published 79434 publications receiving 1170576 citations. The organization is also known as: SEU.

Joint Beamforming and Power Allocation for Satellite-Terrestrial Integrated Networks With Non-Orthogonal Multiple Access

Abstract: In this paper, we propose a joint optimization design for a non-orthogonal multiple access (NOMA)-based satellite-terrestrial integrated network (STIN), where a satellite multicast communication network shares the millimeter wave spectrum with a cellular network employing NOMA technology. By assuming that the satellite uses multibeam antenna array and the base station employs uniform planar array, we first formulate a constrained optimization problem to maximize the sum rate of the STIN while satisfying the constraint of per-antenna transmit power and quality-of-service requirements of both satellite and cellular users. Since the formulated optimization problem is NP-hard and mathematically intractable, we develop a novel user pairing scheme so that more than two users can be grouped in a cluster to exploit the NOMA technique. Based on the user clustering, we further propose to transform the non-convex problem into an equivalent convex one, and present an iterative penalty function-based beamforming (BF) scheme to obtain the BF weight vectors and power coefficients with fast convergence. Simulation results confirm the effectiveness and superiority of the proposed approach in comparison with the existing works.

Exceptional dielectric phase transitions in a perovskite-type cage compound.

Abstract: Progress in metal–organic framework (MOF) research has recently opened up new possibilities to realize hybrid materials with unique solid-state electric properties, such as ferroelectricity, piezoelectricity, and dielectricity. Compared with conventional pure inorganic/organic compounds, MOFs take advantage of structural tunability and multifunctionality to develop polarizable molecular materials with rich dielectric properties. Among them, switchable molecular dielectrics, which undergo transitions between high and low dielectric states, are promising materials with potential applications especially in data communication, signal processing, and sensing. However, reports of such MOFs have remained scarce owing to a lack of knowledge regarding control of the motions of the dipole moments in the crystal lattice. From the microscopic point of view, the tunable dielectric permittivity closely relates to the positional freedom of molecular dipole moments. For instance, polar molecules in the liquid state show larger dielectric permittivities than in the solid state owing to the “melting” and “freezing” of the molecular reorientations. With regard to MOFs, the dipole moments are rigidly fixed in the crystal structures in most cases, usually resulting in small and almost temperatureindependent dielectric permittivities. Fortunately, there is still much room for the integration of flexible units into the frameworks; that is, the introduction of a polarization rotation unit in the form of a solid-state molecular rotator or host–guest systems, such as porous compounds. Cage compounds, which are assembled by the inclusion of guest species into the well-matched host cages, is a very promising class of switchable molecular dielectrics. The reorientations of the polar guests in the carefully designed cage compounds may give rise to large dielectric permittivities, which are characterized by a multidimensional liquidlike state, and their freezing will lead to low-dielectric systems. Herein, we present a novel organic–inorganic hybrid cage compound (HIm)2[KFe(CN)6] (1; HIm = imidazolium) with a perovskite-type structure, in which the order– disorder behavior of the HIm polar guests give rise to striking dielectric anomalies. The (HIm)2[KFe(CN)6] crystals were grown from an aqueous solution of K3[Fe(CN)6] and (HIm)Cl salts by slow evaporation at room temperature as large red hexagonal plate perpendicular to the c axis. The existence of HIm and CN groups in 1 is verified by IR spectra. The CN group in 1 exhibits several vibrations in the range 2102–2143 cm , distinct from a single peak of 2118 cm 1 in K3[Fe(CN)6]. Thermal analysis reveals that 1 undergoes two phase transitions, at 187 K (T1) and 158 K (T2). For convenience, we label the phase above T1 as the high-temperature phase (HTP), the phase between T1 and T2 as intermediate-temperature phase (ITP), and the phase below T2 as low-temperature phase (LTP). Variable-temperature X-ray diffraction analysis reveals that 1 crystallizes in the centrosymmetric space group R3̄m at 293 K and 173 K as the HTP and ITP, respectively, and in C2/c at 83 K as the LTP. The common structural feature of the compound is the anionic cage formed by Fe CN K units in which the HIm cation resides. The metal–cyanide bond is strong and covalent in the fragment {Fe(CN)6} (Fe C = 1.9 ) and much weaker and ionic in the fragment {K(NC)6} (K N = 2.9 ; Figure 1). In the HTP, the cation reorients around the threefold c axis perpendicular to the ring plane. The cation consists of three carbon and two nitrogen atoms, which were all refined as carbon atoms. The five atoms of the

Resting brain connectivity: changes during the progress of Alzheimer disease.

Abstract: Our study results demonstrate that abnormal posterior cingulate cortex connectivity modulation of the default mode could change along with Alzheimer disease stage progression.

Engineering properties and microstructural characteristics of cement-stabilized zinc-contaminated kaolin

Abstract: This paper presents details of a study that deals with determination of engineering properties, identification of phases of major hydration products, and microstructural characteristics of a zinc-c...

Half Mode Substrate Integrated Waveguide (HMSIW) Bandpass Filter

Abstract: This letter presents the design and experiment of the half mode substrate integrated waveguide (HMSIW) bandpass filters. Three-pole and five-pole HMSIW filters are simulated by using CST software and fabricated with a single layer standard printed circuit board process. Different external-coupling approaches are adopted in the design of the two filters. The measured results are in good agreement with the simulated results. Low insertion loss and good selectivity are achieved