16QAM解调算法及其在HSDPA中的应用

对16QAM解调软信息输出(LLR)理论计算方法进行分析,推导出其简化解调算法.将两者在性能和计算复杂度方面进行了分析比较,并分别在高斯白噪声信道和瑞利衰落信道环境下进行仿真.结果表明,简化算法的性能只比理论计算方法的性能有少许降低,即保持相同误码率的性能下前者所需信噪比只比后者提高约0.1dB,但是计算复杂度却大大降低.同时也阐述了将其应用于第三代移动通信系统增强型技术HSDPA中星座图重排技术的实现方法.本文给出的计算方法也可推广到其它的通信系统中.     

Kinetics of the batch cationic emulsion polymerization of styrene: A comparative study with the anionic case

An in‐depth study on the kinetics of the cationic emulsion polymerization of styrene in a batch reactor is presented. This study is focused on the effect of the amount of the cationic surfactant dodecyltrimethylammonium bromide (DTAB), using two different cationic initiators: 2,2′‐azobisisobutyramidine dihydrochloride (AIBA), 2,2′‐azobis (N,N′‐dimethyleneisobutyramidine) dihydrochloride (ADIBA), on kinetics and colloidal features such as conversion, number of particles, number average of radicals per particle, mean particle diameter, and particle size distribution (PSD) of the polystyrene latices obtained by emulsion polymerization in a batch reactor. Furthermore, the results of the cationic emulsion polymerization were compared with its homologous anionic case. Using DTAB as cationic surfactant an expected increase in the total rate of polymerization was observed when the DTAB concentration increased. However, the total number of particles increased much more than in the anionic system. On the other hand, a dependence on the particle size of the rate of polymerization per particle together with the average number of radicals per particle was found. These differences between cationic and anionic emulsion polymerizations were explained taking into account the limited particle coagulation observed with cationic surfactants, and the high rate of radical formation of cationic initiators. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4461–4478, 2006     

Electromagnetically induced moiré optical lattices in a coherent atomic gas

Electromagnetically induced optical (or photonic) lattices via atomic coherence in atomic ensembles have recently received great theoretical and experimental interest. We here conceive a way to generate electromagnetically induced moiré optical lattices — a twisted periodic pattern when two identical periodic patterns (lattices) are overlapped in a twisted angle (θ) — in a three-level coherent atomic gas working under electromagnetically induced transparency. We show that, changing the twisted angle and relative strength between the two constitutive sublattices, the moiré Bloch bands that are extremely flattened can always appear, resembling the typical flat-band and moiré physics found in other contexts. Dynamics of light propagation in the induced periodic structures demonstrating the unique linear localization and delocalization properties are also revealed. Our scheme can be implemented in a Rubidium atomic medium, where the predicted moiré optical lattices and flattened bands are naturally observable.     

Lattices and Their Consistent Quantification

The order‐theoretic concept of lattices is introduced along with the concept of consistent quantification where lattice elements are mapped to real numbers in such a way that preserves some aspect of the order‐theoretic structure. Symmetries, such as associativity, constrain consistent quantification, and lead to a constraint equation known as the sum rule. Distributivity in distributive lattices also constrains consistent quantification and leads to a product rule. The sum and product rules, which are familiar from, but not unique to, probability theory, arise from the fact that logical statements form a distributive (Boolean) lattice, which exhibits the requisite symmetries.     

Magnetic-Flux-Induced Tunable Completely Flat Band and Topological Nearly Flat Band in Square Kagome Lattice

The flat bands in a square kagome lattice containing square and triangle plaquettes, are respectively investigated, and the origin of the doubly degenerated completely flat bands and the corresponding compact localized states are elucidated. It is found that the introduction of external magnetic flux enriches the modulation parameters, making the system present many interesting results. In the case that the magnetic flux penetrates through each square plaquette, the tunable completely flat band has one more tunable parameter. And when the external magnetic flux penetrates through each triangle plaquette, excepting a completely flat band, the band dispersions of the system present the topological nearly flat band, which is very useful to realize the interesting fractional quantum Hall physics. The average density of states is also calculated to corroborate the completely FB generated by the highly localized eigenstates. Furthermore, the implementation of the square kagome lattice system based on the current photonic waveguide network technology is demonstrated. The scheme opens up a way to generate the tunable completely flat band and topological nearly flat band in square kagome lattice under multi-parameter variable conditions.     

Topological Phase Transition with Larger Winding Number in the Non-Hermitian Dimerized Lattice

The topological phase transitions among normal insulator phase, two kinds of topological insulator phases, and topological semimetal phase are shown based on the non-Hermitian dimerized Su–Schrieffer–Heeger (SSH) model with the nonreciprocal intercell and long-range hopping. In contrast to the previous work, it is found that the topological insulator phase in the present SSH model can hold the larger non-Bloch winding number accompanied by exceptional winding of the generalized Brillouin zone around the gap-closing points. Compared with the usual topological insulator phase in non-Hermitian SSH model, the topological insulator with the larger winding number owns two pairs of zero energy modes with a distinct form of edge localization in the gap. The physical mechanism of the distinct edge localization for zero energy modes via a equivalent Hermitian version of the non-Hermitian SSH model is revealed. Additionally, the process of the phase transition is visualized among normal insulator phase, topological insulator phases, and topological semimetal phase in detail via the evolution of the gap-closing points on the plane of generalized Brillouin zone. This work further verifies the non-Bloch theory and enrich the investigation about the topologically nontrivial phase with the larger topological invariant in the non-Hermitian SSH model.     

Monte Carlo study of percolation on disordered triangular lattices

A simple model for amorphous solids, consisting of a mixed bond triangular lattice with a fraction of attenuated bonds randomly distributed (which simulate the presence of defects in the surface), is studied here by using computational simulation. The degree of disorder of the surface is tunable by selecting the values of (1) the fraction of regular [attenuated] bonds ρ [1−ρ] (0≤ρ≤1) and (2) the factor r, which is defined as the ratio between the value of the conductivity associated to an attenuated bond and that corresponding to a regular bond (0≤r≤1). The results obtained show how the percolation properties of the disordered system are modified with respect to the standard random bond percolation problem (r=0).     

Propagation of elastic waves through two-dimensional lattices of cylindrical empty or water-filled inclusions in an aluminum matrix

The layer-multiple-scattering method is developed to study wave propagation through two-dimensional lattices of cylindrical inclusions in an elastic medium. The lattices are a series of periodically spaced infinite one-dimensional periodic gratings (or rows) of inclusions. The layer-multiple-scattering method allows the analysis of the reflection and transmission properties of the two-dimensional lattice, provided those of each row are known. These are later determined by means of an exact multiple scattering formalism based on modal series developments. A new characteristic equation is obtained that describes the Bloch wave propagation into the infinite lattice. Lattices with empty and fluid-filled inclusions are compared. The comparison shows the existence of pass and stop bands due to the resonances of the fluid-filled inclusions. Resonant inclusions allow the opening of narrow pass bands inside phononic stop band, which is an interesting phenomenon for demultiplexing problems. It is worth noting that inclusion resonances have nothing to do with resonances due to defects, as they involve the whole lattice. In addition, it is shown that stop bands, at an oblique incidence, due to a strong coupling between longitudinal and transverse waves, are related to dispersive guided waves that propagate in the direction of the reticular planes of the lattices.     

On well-rounded sublattices of the hexagonal lattice

We produce an explicit parameterization of well-rounded sublattices of the hexagonal lattice in the plane, splitting them into similarity classes. We use this parameterization to study the number, the greatest minimal norm, and the highest signal-to-noise ratio of well-rounded sublattices of the hexagonal lattice of a fixed index. This investigation parallels earlier work by Bernstein, Sloane, and Wright where similar questions were addressed on the space of all sublattices of the hexagonal lattice. Our restriction is motivated by the importance of well-rounded lattices for discrete optimization problems. Finally, we also discuss the existence of a natural combinatorial structure on the set of similarity classes of well-rounded sublattices of the hexagonal lattice, induced by the action of a certain matrix monoid.