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141.
The structural, elastic, and thermodynamic properties of ZnGeP2 with chalcopyrite structure are investigated using the pseudo-potentials plane wave method based on the density functional theory with the generalized gradient approximation. The lattice parameters (a, c and u) are directly calculated and agree well with previous experimental and theoretical results. The obtained negative formation enthalpy shows that ZnGeP2 crystal has strong structural stability. We have also calculated the bulk modulus B and the elastic parameters (C11, C12, C13, C33, C44, and C66) which have not been measured yet. The accuracy and reliability of the calculated elastic constants of ZnGeP2 crystal are discussed. In addition, the pressure and temperature dependencies of the lattice parameters, bulk modulus, Debye temperature, Grüneisen parameter, entropy, volume thermal expansion coefficient, and specific heat capacity are obtained in the ranges of 0–20 GPa and 0–1200 K using the quasi-harmonic Debye model. To our knowledge this is the first quantitative theoretical prediction of the thermodynamic properties for ZnGeP2 compound and still awaits experimental confirmations. 相似文献
142.
Wireless network-on-chip (WiNoC) is a new paradigm to mitigate the long-distance transmission latency for conventional wired network-on-chip. The wireless routers in WiNoC have to handle a large number of packets which could cause data congestion, thus reducing the network performance. In this paper, we propose a novel wireless routing algorithm, called CPCA, which exploits the cross path congestion information as hints to route the packets. Under CPCA, the whole network is partitioned into sub-networks. In each subnet, the congestion information of the wireless router is propagated along the cross path. As a result, the routers in the same dimension can get the congestion degree of wireless router within the subnet. Based on the congestion information, CPCA can compute the suitable path for packets routing, which can prominently avoid the congestion aggravation in the wireless router. Experimental results show that our proposed method can effectively improve performance in terms of packets transmission latency and network throughput. 相似文献
143.
电路理论中的许多基本概念和基本规律都源于电磁场原理。本文以电路理论中的若干基本概念和基本定律,包括电流、电压、KCL、KVL和集中参数等,介绍了这些概念和定律的电磁场原理,试图尝试在教学或教材建设中适当加强学生的电磁学应用能力,强化课程之间的内在联系,从而使学生具备坚实的电路理论基础。 相似文献
144.
针对瞬时欠定盲源信号分离问题,提出一种四阶累积张量分解算法.首先构建观察信号四阶累积协方差,依据源信号具有相互独立且均值为零的性质,对累积协方差化简并扩展到张量域,得到四阶累积张量.采用分层交替最小二乘算法对四阶累积张量进行非负库克分解,求得非负库克模型的参数,同时获得非负混合矩阵并求其伪逆,最终估计出源信号.选用真实的语音信号和生物信号进行仿真实验,结果表明该方法提高了源信号和非负混合矩阵的估计性能. 相似文献
145.
Whispering gallery mode (WGM)-enhanced nonlinear optical phenomena from crown-like nanostructure zinc oxide (ZnO) samples are observed. The samples are synthesized by vapor-phase transport method. The morphology and crystal struc- ture are examined and characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM), and they are excited by femtosecond laser pulses with cen- tral wavelengths of 355 nm, 800 nm and 1150 nm, respectively. The typical stimulated emission presents a red shift com- pared with spontaneous emission, which is observed under the excitation of 355 nm with a relatively low threshold. The ultraviolet (UV) frequency up-conversion emission is obtained when the excitation pulse wavelengths are selected as 800 nm and 1150 nm, respectively. The peak position and the relationship between the emission intensity and excitation inten- sity demonstrate that the UV up-conversion photoluminescence (PL) is induced by two- and three-photon absorptions. The PL characteristics and their WGM-enhanced mechanism are investigated. 相似文献
146.
《Optical Fiber Technology》2013,19(1):40-46
It is proposed and demonstrated a design of 2-to-1 photonic data selector based on the cross-phase modulation in a highly nonlinear fiber. By using bidirectional configuration, this scheme has potentially advantages of cost effective and simple structure. The correct output logic function is obtained at 40 Gbit/s without using any additional input light beams. In addition, the output signals have a single spectrum component by reasonable selecting input signals wavelength, which is important for transmission and scalability. The dependences of performances on signal wavelength, pump power, the temporal relative position of pulses, as well as the OSNR and chirp of input signals are calculated and discussed respectively, showing impressive operation performance. This scheme could be a promising candidate for future ultrafast all-optical signal processing applications. 相似文献
147.
Sorting-based reversible data hiding (RDH) methods like pixel-value-ordering (PVO) can predict pixel values accurately and achieve an extremely low distortion on the embedded image. However, the excellent performance of these methods was not well explained in previous works, and there are unexploited common points among them. In this paper, we propose a general multi-predictor (GMP) framework to summarize PVO-based RDH methods and explain their high prediction accuracy. Moreover, by utilizing the proposed GMP framework, a more efficient sorting-based RDH method is given as an example to show the generality and applicability of our framework. Comparing with other PVO-based methods, the proposed example method can achieve significant improvement in embedding performance. It is hopeful that more efficient sorting-based RDH algorithms can be designed according to our proposed framework by designing better predictors and their combination methods. 相似文献
148.
To achieve an optimal trade-off between video quality and energy efficiency in the uplink streaming of multi-user Scalable Video Coding (SVC) videos in relay-based Orthogonal Frequency Division Multiple Access (OFDMA) cellular networks, a cross-layer design framework that jointly selects the Transmission Policy (TP) for SVC video frames, assigns OFDMA subcarriers, and allocates power for each subcarrier is proposed. We apply the dual decomposition method to the problem, and obtain a TP selection subproblem for each SVC video adaptation and a resource allocation subproblem of Joint Subcarrier, Relay and Power Allocation (JSRPA). A second level of dual decomposition is used to divide the JSRPA problem into independent subcarrier subproblems. The proposed Crosslayer Trade-off Optimization (CTO) algorithm is sub-distributed with significantly low complexity. A performance evaluation with typical SVC video traces demonstrates that the proposed algorithm is able to converge and efficiently achieve the optimal trade-off between the video quality and energy consumption at the MSs for uplink SVC streaming. 相似文献
149.
150.
《Applied Superconductivity》1996,4(1-2):41-51
The doping effect of Mn in polycrystalline YBa2Cu3O7 − δ material (YBCO) is carefully analyzed considering the transport properties of composites formed by small inclusion particles of Mn embedded whether in a YBCO matrix or in superconducting Fe-YBCO composites. In both cases, the improvement of their respective electrical resistivity was evidenced. The use of double element doping clearly shows that an a priori degradation of the YBCO electrical properties by Fe atoms can be greatly restored by appropriate Mn doping. This character can be very useful for technological applications. This improvement is mainly due to the reduction of the secondary and/or insulating phases formed at the grain boundaries, limiting the current transport. The involved mechanism is the probable existence of free charged Mn-based species which are responsible for an optimal oxygenation in the material contributing to the electrical response improvement. These species can be located in the composite, whether entering the CuO chains of the YBCO lattice or complexing and reducing the secondary phases formed during the sintering process, especially Fe2O3 and Y2BaCuO5 in the case of Fe-YBCO composites. 相似文献