Collaborative filtering with information-rich and information-sparse entities

In this paper, we consider a popular model for collaborative filtering in recommender systems. In particular, we consider both the clustering model, where only users (or items) are clustered, and the co-clustering model, where both users and items are clustered, and further, we assume that some users rate many items (information-rich users) and some users rate only a few items (information-sparse users). When users (or items) are clustered, our algorithm can recover the rating matrix with \(\omega (MK \log M)\) noisy entries while \(MK\) entries are necessary, where \(K\) is the number of clusters and \(M\) is the number of items. In the case of co-clustering, we prove that \(K^2\) entries are necessary for recovering the rating matrix, and our algorithm achieves this lower bound within a logarithmic factor when \(K\) is sufficiently large. Extensive simulations on Netflix and MovieLens data show that our algorithm outperforms the alternating minimization and the popularity-among-friends algorithm. The performance difference increases even more when noise is added to the datasets.     

Symbolic algorithms for qualitative analysis of Markov decision processes with Büchi objectives

We consider Markov decision processes (MDPs) with Büchi (liveness) objectives. We consider the problem of computing the set of almost-sure winning states from where the objective can be ensured with probability 1. Our contributions are as follows: First, we present the first subquadratic symbolic algorithm to compute the almost-sure winning set for MDPs with Büchi objectives; our algorithm takes $O(n \cdot\sqrt{m})$ symbolic steps as compared to the previous known algorithm that takes O(n ²) symbolic steps, where n is the number of states and m is the number of edges of the MDP. In practice MDPs have constant out-degree, and then our symbolic algorithm takes $O(n \cdot\sqrt{n})$ symbolic steps, as compared to the previous known O(n ²) symbolic steps algorithm. Second, we present a new algorithm, namely win-lose algorithm, with the following two properties: (a) the algorithm iteratively computes subsets of the almost-sure winning set and its complement, as compared to all previous algorithms that discover the almost-sure winning set upon termination; and (b) requires $O(n \cdot\sqrt{K})$ symbolic steps, where K is the maximal number of edges of strongly connected components (scc’s) of the MDP. The win-lose algorithm requires symbolic computation of scc’s. Third, we improve the algorithm for symbolic scc computation; the previous known algorithm takes linear symbolic steps, and our new algorithm improves the constants associated with the linear number of steps. In the worst case the previous known algorithm takes 5?n symbolic steps, whereas our new algorithm takes 4?n symbolic steps.     

Studies on Fourier transform infrared spectroscopy,scanning electron microscope,and direct current conductivity of polyaniline doped zinc ferrite

In situ polymerization of aniline was carried out in the presence of zinc ferrite to synthesize polyaniline/ZnFe₂O₄ composites (PANI/ZnFe₂O₄) by chemical oxidation method. The composites have been synthesized with various compositions (10, 20, 30, 40, and 50 wt %) of zinc ferrite in PANI. From the Fourier transform infrared spectroscopy (FTIR) studies on polyaniline/ZnFe₂O₄ composites, the peak at 1140 cm⁻¹ is considered to be measure of the degree of electron delocalization. The surface morphology of these composites was studied with scanning electron micrograph (SEM). The dc conductivity has been studied in the temperature range from 40–160°C and supports the one‐dimensional variable range hopping (1DVRH) model proposed by Mott. The results obtained for these composites are of scientific and technological interest. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

IT Innovations: Evaluate, Strategize, and Invest

Technology innovations have shaped the IT Industry since its inception. Adoption of a particular innovation is often a key survival factor: "fast followers" learn from others, monetize an innovation, and almost always make abnormal profits. Thus, the important question for IT professionals is, "How can I evaluate an emerging trend for its investment worthiness?" To answer this question, the author describes a diffusion of IT innovations framework that can evaluate emerging trends in the IT space. He also analyzed some current trends using this framework and suggests strategies for investing in them.     

Fair Resource Allocation in Wireless Networks Using Queue-Length-Based Scheduling and Congestion Control

We consider the problem of allocating resources (time slots, frequency, power, etc.) at a base station to many competing flows, where each flow is intended for a different receiver. The channel conditions may be time-varying and different for different receivers. It is well-known that appropriately chosen queue-length based policies are throughput-optimal while other policies based on the estimation of channel statistics can be used to allocate resources fairly (such as proportional fairness) among competing users. In this paper, we show that a combination of queue-length-based scheduling at the base station and congestion control implemented either at the base station or at the end users can lead to fair resource allocation and queue-length stability.     

Impurity modulated excitation profile of doped quantum dot subject to oscillatory magnetic field

We explore the excitation profile of a repulsive impurity doped quantum dot under periodically fluctuating magnetic field. We have considered Gaussian impurity centers. The investigation reveals the roles subtly played by the dopant coordinate and the region of influence of the dopant to modulate the excitation pattern. The rate of transition to the excited states has been invoked to analyze the interplay between the above two impurity parameters in influencing the excitation process. The ratio of cyclotron frequency and harmonic confinement potential has important impact on excitation rate.     

Comparative evaluation of in vitro efficacy of colesevelam hydrochloride tablets

Context: Colesevelam hydrochloride is used as an adjunct to diet and exercise to reduce elevated low-density lipoprotein (LDL) cholesterol in patients with primary hyperlipidemia as well as to improve glycemic control in patients with type 2 diabetes. This is likely to result in submission of abbreviated new drug applications (ANDA).

Objective: This study was conducted to compare the efficacy of two tablet products of colesevelam hydrochloride based on the in vitro binding of bile acid sodium salts of glycocholic acid (GC), glycochenodeoxycholic acid (GCDA) and taurodeoxycholic acid (TDCA).

Methods: Kinetic binding study was carried out with constant initial bile salt concentrations as a function of time. Equilibrium binding studies were conducted under conditions of constant incubation time and varying initial concentrations of bile acid sodium salts. The unbound concentration of bile salts was determined in the samples of these studies. Langmuir equation was utilized to calculate the binding constants k₁ and k₂.

Results: The amount of the three bile salts bound to both the products reached equilibrium at 3?h. The similarity factor (f₂) was 99.5 based on the binding profile of total bile salts to the test and reference colesevelam tablets as a function of time. The 90% confidence interval for the test to reference ratio of k₂ values were 96.06–112.07 which is within the acceptance criteria of 80–120%.

Conclusion: It is concluded from the results that the test and reference tablets of colesevelam hydrochloride showed a similar in vitro binding profile and capacity to bile salts.     

Differential superhydrophobicity and hydrophilicity on a thin cellulose layer

Here we have developed cellulosic materials (cotton fabric or paper) with differential superhydrophobicity and hydrophilicity on each side of the surfaces by coating with polyvinylidene fluoride and fluorinated silane molecules using electro-spraying. Such materials are advantageous in various textile and medical applications.Analysis of surface morphology indicated that, not only surface chemical property and roughness, but also particle diameter affects surface superhydrophobicity. Smaller particle diameter enhances superhydrophobicity, if the surface roughness and surface chemical property remain constant. By controlling these three factors, superhydrophobicity with a water contact angle of more than 160° can be achieved at one side of a thin cellulosic material while maintaining the hydrophilicity (contact angle is 0°) at the opposite side.     

An Equivalent Circuit for Quantum Cascade Lasers

A new simpler equivalent circuit model of a quantum cascade laser based on two level rate equations is presented. The model is valid for small and large signals. A realistic current voltage model based on experimental results is included in the circuit model. Incorporation of the current voltage characteristic makes the circuit model fully compatible with parasitics and drive electronics. The model is validated by comparison of simulated results with analytica results and large signal numerical results reported earlier.