Rate Equations for 1.3-$mu$ m Dots-Under-a-Well and Dots-in-a-Well Self-Assembled InAs–GaAs Quantum-Dot Lasers

A rate-equation model, in which three discrete quantum-dot (QD) energy levels are assumed and all possible relaxation paths and carrier transport in the GaAs barrier are considered, is presented to analyze the steady-state performance of 1.3 mum undoped and doped dots-under-a-well (DUW) and dots-in-a-well (DWELL) InAs-GaAs QD lasers. DWELL QD lasers have higher saturation value of QD level occupation probabilities and characteristic temperature (T₀) than that of DUW QD lasers due to the improvement of hole confinement. The p-doped QD laser shows lower threshold current density than n-doped QD laser at the same threshold condition, and the T₀ of n-doped DWELL laser is higher than that of p-doped DWELL laser at room temperature. Optimized QD layer number of DUW and DWELL QD lasers with different QD density is discussed     

Direct conversion radio for digital mobile phones-design issues, status, and trends

Applications of direct frequency-conversion techniques have been rapidly getting attention of radio designers worldwide. This paper focuses on bringing out key implementation challenges of direct conversion receivers and transmitters targeted for different second- and third-generation mobile phone standards like global system for mobile communication, code division multiple access (cdmaOne and CDMA 2000), and wide-band code division multiple access. Techniques and tradeoffs to arrive at optimal implementation are highlighted. Some of the commercially available application-specific integrated circuits that are based on direct conversion architecture and their salient features are summarized.     

Comparing classical and quantum PageRanks

Following recent developments in quantum PageRanking, we present a comparative analysis of discrete-time and continuous-time quantum-walk-based PageRank algorithms. Relative to classical PageRank and to different extents, the quantum measures better highlight secondary hubs and resolve ranking degeneracy among peripheral nodes for all networks we studied in this paper. For the discrete-time case, we investigated the periodic nature of the walker’s probability distribution for a wide range of networks and found that the dominant period does not grow with the size of these networks. Based on this observation, we introduce a new quantum measure using the maximum probabilities of the associated walker during the first couple of periods. This is particularly important, since it leads to a quantum PageRanking scheme that is scalable with respect to network size.     

Histochemistry of mucin secreting components in mucoepidermoid and adenosquamous carcinoma of the oesophagus

AIMS: To determine the direction of differentiation of the mucin secreting components in a rare group of oesophageal tumours--oesophageal squamous cell carcinomas with prominent mucin secreting components (mucoepidermoid carcinomas and adenosquamous carcinomas). METHODS: In a review of 617 cases of primary carcinoma of the oesophagus, 16 cases of squamous cell carcinoma with prominent mucin secreting components were studied using a battery of histochemical techniques. RESULTS: The mucin produced by these tumours was mixed and included a variable content of enzyme labile sialomucin (positive for mucicarmine, periodic acid Schiff, and alcian blue, and sensitive to sialidase digestion and negative for high iron diamine-alcian blue). Retrospective analysis of endoscopic biopsy specimens taken from these tumours showed that mucin was present in five (42%) cases. CONCLUSIONS: The glandular component of this group of tumours histochemically differentiated in the direction of oesophageal glands: examination of the mucin secreting component in squamous cell carcinoma in resected specimens is therefore required for recording the true incidence of this type of tumour.     

On the pattern recognition of noisy subsequence trees

We consider the problem of recognizing ordered labeled trees by processing their noisy subsequence-trees which are “patched-up” noisy portions of their fragments. We assume that H, a finite dictionary of ordered labeled trees, is given. X* is an unknown element of H, and U is any arbitrary subsequence-tree of X*. We consider the problem of estimating X* by processing Y, which is a noisy version of U. The solution which we present is, to our knowledge, the first reported solution to the problem. We solve the problem by sequentially comparing Y with every element X of H, the basis of comparison being a new dissimilarity measure between two trees, which implicitly captures the properties of the corrupting mechanism that noisily garbles U into Y. The algorithm which incorporates this constraint has been used to test our pattern recognition system, and the experimental results obtained demonstrate good accuracy     

Electrical leakage at low-K polyimide/TEOS interface

The effect of low-K polymer passivation on electrical leakage was investigated to evaluate the reliability of polymer integration on device wafers. Polyimide passivation over Al(0.5% Cu) interconnects inlaid in TEOS increases the intralevel leakage current mainly along the polyimide/TEOS interface. Moisture absorbed in the polyimide further increases the inter facial as well as bulk leakages. These findings emphasize the importance of separating interconnects from direct contact with polyimide/TEOS interfaces to alleviate electrical isolation problems in multilevel interconnect architecture that employs low-K polymer dielectrics     

An efficient quantum circuit analyser on qubits and qudits

This paper presents a highly efficient decomposition scheme and its associated Mathematica notebook for the analysis of complicated quantum circuits comprised of single/multiple qubit and qudit quantum gates. In particular, this scheme reduces the evaluation of multiple unitary gate operations with many conditionals to just two matrix additions, regardless of the number of conditionals or gate dimensions. This improves significantly the capability of a quantum circuit analyser implemented in a classical computer. This is also the first efficient quantum circuit analyser to include qudit quantum logic gates.

Program summary

Program title:CUGates.mCatalogue identifier: AEJM_v1_0Program summary: URL: http://cpc.cs.qub.ac.uk/summaries/AEJM_v1_0.htmlProgram obtainable from: CPC Program Library, Queen?s University, Belfast, N. IrelandLicensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.htmlNo. of lines in distributed program, including test data, etc.: 8168No. of bytes in distributed program, including test data, etc.: 173 899Distribution format: tar.gzProgramming language: MathematicaComputer: Any computer installed with Mathematica 6.0 or higher.Operating system: Any system with a copy of Mathematica 6.0 or higher installed.Classification: 4.15Nature of problem: The CUGates notebook simulates arbitrarily complex quantum circuits comprised of single/multiple qubit and qudit quantum gates.Solution method: It utilizes an irreducible form of matrix decomposition for a general controlled gate with multiple conditionals and is highly efficient in simulating complex quantum circuits.Running time: Details of CPU time usage for various example runs are given in Section 4.