Non-Orthogonal Multiple Access (NOMA) has been proposed as a new radio access technique for cellular networks as an alternative to OMA (Orthogonal Multiple Access) in which the users of a group (pairs or triples of users in a group are considered in this paper) are allowed to use the wireless channel simultaneously. In this paper, for downlink single-input single-output SISO-NOMA, a heuristic power allocation algorithm within a group is first proposed which attempts to ensure that the users of a group benefit from simultaneous transmission equally in terms of achievable throughput. Moreover, a user group scheduling algorithm is proposed for downlink NOMA systems by which a user group is to be dynamically selected for transmission while satisfying long term temporal fairness among the individual contending users. The effectiveness of the proposed power allocation method along with the temporal fair scheduling algorithm for downlink NOMA is validated with simulations and the performance impact of the transmit power and the coverage radius of the base station as well as the number of users are thoroughly studied.
The influence exerted by random dopant-concentration fluctuations on the current–voltage characteristics of the current flowing through a semiconductor superlattice has been studied. It was shown that the characteristics of the current flowing through the superlattice noticeably vary with the amplitude of fluctuations of nanostructure parameters. It was possible to find for a small sample the probability-density distribution of the integrated absolute values of the difference of currents at various amplitudes of the dopantconcentration fluctuations. 相似文献
The effects of the amount of hexylbenzene additive (C12H18) on the structural, thermal, and magnetic properties of MgB2 superconductor are examined in this study. Pure and hexylbenzene-doped MgB2 bulk samples were produced with in situ solid-state reaction method. X-ray diffraction patterns of MgB2 doped with MgB2 and hexylbenzene at different ratios were determined to have MgB2 as the main phase and consisted of a small amount of MgO. Pure and different ratios of hexylbenzene-doped Mg and B starting powders were heat-treated by a differential scanning calorimeter between room temperature and 800 °C. It was determined from the differential scanning calorimetry curves obtained that the first exothermic peak pointed the MgB2 phase emerging with a solid–solid (Mg–B) reaction, and this temperature shifted towards the low temperatures as the hexylbenzene addition rates increased. It was observed that there was dependency to the applied field in all samples from the ac susceptibility measurements as a function of the temperature in pure and hexylbenzene-doped MgB2 superconductor materials, and shift towards the lower temperatures in Tc, superconducting transition temperature, with increasing content. It was observed that the changes occurred in in-phase (\(\chi ^{\prime })\) and out-off-phase (\(\chi ^{\prime \prime }\)) components of ac susceptibility both weakened the MgB2 phase structure of hexylbenzene content and, as a result of this, led to changes in the pinning mechanism. 相似文献
We evaluated the suitability, contribution to the national economy, and environmental impact of hydrocyclone and Multi-Gravity Separation (MGS) processes using fine-sized coal taken from the Soma coal sludge pond. The lignite coal tailings were treated by a two-stage concentration scheme for the recovery of fine clean coal. Pre-enrichment experiment parameters were determined by the Taguchi experimental design method, and the results were interpreted by the Statistical Packages for the Social Sciences (SPSS) 15.0 program to evaluate the optimum parameter values. The tailings initially contained 54.82% ash and had a LCV of 2,279 kcal/kg; after hydrocyclone pre-enrichment, the concentrate was 42.60% ash and had a calorific value of 2,573 kcal/kg (55.75% coal yield). After the final enrichment process, the ash of the pre-concentrated coal was decreased to 24.21% and left a clean coal with a base calorific value of 3,226 kcal/kg (36.16% coal yield). The total sulfur of the obtained clean coal was 0.52% and the combustible sulfur rate was 0.10%. To reduce the ash content of the obtained clean coal, a decantation process was performed that decreased the ash content to 21.84% and the base calorific value was increased to 4,109 kcal/kg. 相似文献
Semiconductors - The low-temperature (T = 2 K) optical spectra (transmission, reflection and luminescence) of a compositionally graded CdS1 – xSex/CdS heterostructure with a... 相似文献
Lately, it has been seen that wireless communication systems have been more developed and there has been a huge demand for multi‐spectral transactions. Using circuits for more than one function is a serious requirement in communication technology. Especially, it expected from RF output stages to show the same performance on more than one frequency. To that end, it is required to produce a solution with wideband designs. In this study, a novel power divider/combiner design with a layered conic line has been investigated for the RF energy harvesting applications. The center frequency was set at 2 GHz and concluded with three different designs. In each design, bandwidth and S parameter characteristics were compared according to the number of layers of the transmission, and it was observed that as the number of layers increases, the bandwidth also increases. According to the design result, triple layer Wilkinson power divider was selected to connect to Villard voltage doubler circuit. The Wilkinson power combiner circuit inputs were given between ?10 dBm and 5 dBm input power. As a result, when low input power was given, efficiency was observed about 70%. 相似文献
An approach that allows finding a set of robust statistic feedback controllers that ensure the given control accuracy for the controlled parameters in a multiconnected control system under bounded parametric and external perturbations of various classes is proposed. To describe the set of controllers of the given accuracy, the results of analytically solving the matrix equations based on matrix canonization and parametrization of the Lyapunov equation are used. The solvability conditions of the synthesis problem ensure the robustness and optimal suppression of the perturbations. They are homogeneously represented as linear matrix inequalities obtained based on the Lyapunov functions. A methodological example is given. 相似文献
ABSTRACTThe digital integration of built-environment practices aims to bridge a large variety of organizations to improve building delivery and operation. However, recent research on building information modelling (BIM) reported organizational challenges arising from digital integration. This suggests a need to develop a critical perspective on digital-integration-driven organizational change. Adopting a practice-based approach, this paper exposes the practice-level phenomenon responsible for the ongoing change to develop a critical understanding and enable better interventions. The concepts of ‘simplification’ and ‘systematization’ of digital integration are developed from previous literature and then used to explore and interrelate the practice-level experiences of digital integration (i.e. the experience of the change from within) and the emerging patterns of interactions (i.e. the picture of the change from outside) in a BIM-enabled design project. The concept of ‘ordering in disguise’ is proposed to capture this phenomenon. It shows that practitioners experience digital integration as various task-specific instances of unresponsive technology. However, they are unaware that their ongoing efforts to accommodate it actually further reinforce digital integration’s simplification and systematization. This makes the unresponsiveness of technology harder to challenge, and ultimately forces the organization to change and adapt to it. Implications for management of practice are outlined. 相似文献
A computational model is developed for efficient solutions of electromagnetic scattering from obstacles having random surface deformations or irregularities (such as roughness or randomly-positioned bump on the surface), by combining the Monte Carlo method with the principles of transformation electromagnetics in the context of finite element method. In conventional implementation of the Monte Carlo technique in such problems, a set of random rough surfaces is defined from a given probability distribution; a mesh is generated anew for each surface realization; and the problem is solved for each surface. Hence, this repeated mesh generation process places a heavy burden on CPU time. In the proposed approach, a single mesh is created assuming smooth surface, and a transformation medium is designed on the smooth surface of the object. Constitutive parameters of the medium are obtained by the coordinate transformation technique combined with the form-invariance property of Maxwell’s equations. At each surface realization, only the material parameters are modified according to the geometry of the deformed surface, thereby avoiding repeated mesh generation process. In this way, a simple, single and uniform mesh is employed; and CPU time is reduced to a great extent. The technique is demonstrated via various finite element simulations for the solution of two-dimensional, Helmholtz-type and transverse magnetic scattering problems. 相似文献