An Optimized Parallel IDCT on Graphics Processing Units

In this paper we present an implementation of the H.264/AVC Inverse Discrete Cosine Transform (IDCT) optimized for Graphics Processing Units (GPUs) using OpenCL. By exploiting that most of the input data of the IDCT for real videos are zero valued coefficients a new compacted data representation is created that allows for several optimizations. Experimental evaluations conducted on different GPUs show average speedups from 1.7× to 7.4× compared to an optimized single-threaded SIMD CPU version

Parallel H.264/AVC motion compensation for GPUs using OpenCL

Motion compensation is one of the most compute-intensive parts in H.264/AVC video decoding. It exposes massive parallelism, which can reap the benefit from graphics processing units (GPUs). Control and memory divergence, however, may lead to performance penalties on GPUs. In this paper, we propose two GPU motion-compensation kernels, implemented with OpenCL, that mitigate the divergence effect. In addition, the motion-compensation kernels have been integrated into a complete and optimized H.264/AVC decoder that supports high-profile H.264/AVC. We evaluated our kernels on GPUs with different architectures from AMD, Intel, and Nvidia. Compared with the fastest CPU used in this paper, our kernel achieves 2.0 speedup on a discrete Nvidia GPU at kernel level. However, when the overheads of memory copy and OpenCL runtime are included, no speedup is gained at application level.EC/FP7/288653/EU/Low-Power Parallel Computing on GPUs/LPGP

Optimization of a Continuous Preparation Method of Arthrospira platensis γ-linolenic acid by supercritical carbon dioxide technology using response surface methodology

γ-linolenic acid is an essential omega-6 unsaturated fatty acid made in the human body from linoleic acid. It can be metabolized to various important eicosanoids and it is also a precursor of prostaglandin E and several other active substances that are associated with anti-inflammatory properties. Arthrospira platensis is known to contain relatively large quantities of γ-linolenic acid. The aim of this study was to investigate the optimal parameters under a continuous preparation method of γ-linolenic acid from A. platensis using supercritical carbon dioxide technology. A Box-Behnken experimental design and response surface methodology were used to optimize combinations among pressure (10, 20 and 30 MPa), temperature (40, 50 and 60°C) and flow rate of A. platensis extract liquor (1, 2 and 3 mL/min) for yield of γ-linolenic acid. The results showed that the extraction of γ-linolenic acid from A. platensis was optimized at a temperature of 60°C, a pressure of 30 MPa and a flow rate of 3 mL/min. These parameters could be used as a basis for facilitating future scale-up industrial applications

Quasinormal modes of Reissner-Nordstro¨\ddot{o}m Anti-de Sitter Black Holes

Complex frequencies associated with quasinormal modes for large Reissner-Nordstr$\ddot{o}$m Anti-de Sitter black holes have been computed. These frequencies have close relation to the black hole charge and do not linearly scale with the black hole temperature as in Schwarzschild Anti-de Sitter case. In terms of AdS/CFT correspondence, we found that the bigger the black hole charge is, the quicker for the approach to thermal equilibrium in the CFT. The properties of quasinormal modes for $l>0$ have also been studied.Comment: 14 pages, 8 figures, submitted to Phys. Lett.

Nanostructures and capacitive characteristics of hydrous manganese oxide prepared by electrochemical deposition

Amorphous manganese oxide deposits with nanostructures ͑denoted as a-MnO x •nH 2 O) were electrochemically deposited onto graphite substrates from 0.16 M MnSO 4 •5H 2 O with pH 5.6 by means of the potentiostatic, galvanostatic, and potentiodynamic techniques. The maximum specific capacitance of a-MnO x •nH 2 O deposits plated in different modes, measured from cyclic voltammetry at 25 mV s Ϫ1 , is about 230 F g Ϫ1 in a potential window of 1.0 V. The high electrochemical reversibility, high-power characteristics, good stability, and improved frequency responses in 0.1 M Na 2 SO 4 for these nanostructured a-MnO x •nH 2 O deposits prepared by electrochemical methods demonstrate their promising potential in the application to electrochemical supercapacitors. The nanostructure of a-MnO x •nH 2 O, clearly observed by means of a scanning electron microscope, was found to depend strongly on the deposition mode. The similar capacitive performance of all deposits prepared in different modes was attributable to their nonstoichiometric nature with a very similar oxidation state, demonstrated by XPS spectra. Batteries and capacitors are usually the electrical energy storage devices in many applications. The energy density of the former devices is usually much higher than that of the latter while the power density of the latter devices is several orders of magnitude higher than most primary energy storage units. Since the demand for power sources delivering significant energy in the high-power or pulsepower form has increased, the development of capacitors with high energy densities ͑i.e., supercapacitors͒ for these applications has been an interesting subject of much research. 1-3 Moreover, it is now reasonable to separate the power and energy delivering devices in an integrated power system to enhance their respective performance. This point of view is supported by the fact that supercapacitors have been found to significantly improve the service life of some primary energy storage units, 5-8 The energies stored in supercapacitors mainly come from either the electrical double-layer ͑dl͒ capacitance of the materials with high specific surface areas 6-8 The former devices are also called dl capacitors, usually consisting of highly porous carbon material. 1,2,6-8,10-12 Recently, hydrous manganese oxides prepared by the sol-gel-derived, chemical coprecipitation, or cyclic voltammetric methods were found to possess capacitive-like characteristics 13-15 although the electrochemical reversibility of the redox transitions within manganese-oxide-based electrodes, suitable for rechargeable batteries, 16 is usually too low to be applicable for supercapacitors. However, the capacity of a very thin MnO 2 film ͑1-4 g cm Ϫ2 ͒ prepared by the sol-gel-derived method is unacceptable although its specific capacitance is very high ͑ca. 700 F g Ϫ1 ͒. 13 Moreover, pure a-MnO 2 •nH 2 O prepared by a chemical coprecipitation method was found to possess poor capacitive characteristics due to the high resistance of bulk a-MnO 2 •nH 2 O. 14 Based on the above points of view, anodic deposition was successfully developed to prepare an amorphous and nonstoichiometric manganese oxide ͑denoted as a-MnO x •nH 2 O) with excellent capacitive characteristics ͑i.e., high reversibility, high pulse power density, acceptable capacity, and good stability͒. 17,18 Thus, a-MnO x •nH 2 O prepared by anodic deposition is expected to be one of the most promising potential candidates in the application to supercapacitors. In our previous study, the capacitive behavior as well as the structure of a-MnO x •nH 2 O films was probably affected by the deposition variables and the deposition modes. Experimental The a-MnO x •nH 2 O deposits were electroplated directly onto 10 ϫ 10 ϫ 3 mm graphite substrates ͑Nippon Carbon EG-NPL, N.C.K., Japan͒. These substrates were first abraded with ultrafine SiC paper, degreased with acetone and water, then etched in a 0.1 M HCl solution at room temperature ͑ca. 26°C͒ for 10 min, and finally degreased with water in an ultrasonic bath. The exposed geometric area of these pretreated graphite supports is 1 cm 2 while the other surface areas were insulated with polytetrafluoroethylene ͑PTFE͒ coatings. The plating solutions, consisting of 0.16 M MnSO 4 •5H 2 O with pH of 5.6, were stirred on a hot plate during the deposition process. The deposition was performed by the potentiostatic method at 0.8 V ͑denoted as a-MnO x •nH 2 O-P), the galvanostatic mode at 3.7 mA cm Ϫ2 (a-MnO x •nH 2 O-G) with a total passed charge of 0.3 C cm Ϫ2 , or cyclic voltammetry ͑CV͒ at 10 mV s Ϫ1 between 0.4 and 1.0 V for 30 cycles (a-MnO x •nH 2 O-CV). After deposition, the PTFE films were removed from the electrodes. These electrodes were first rinsed with a flow of pure water for ca. 30 s and then dipped into a beaker containing pure water ͑at room temperature͒ that was stirred by a hot plate for 5 min. After cleaning, these electrodes were dried in a vacuum oven at room temperature overnight. The oxide loading of hydrous oxide-coated electrode is the weight difference of the electrode without PTFE coating before and after the application of oxide deposition as obtained with a microbalance with an accuracy of 10 g ͑Sartorius BP 211D, Germany͒. The average loading for the a-MnO x •nH 2 O-P, a-MnO x •nH 2 O-CV, and a-MnO x •nH 2 O-G was 0.24, 0.22, and 0.17 mg cm Ϫ2 , respectively. The X-ray diffraction ͑XRD͒ patterns obtained from XRD analysis ͑Rigaku X-ray diffractometer using a Cu target͒ at an angle speed of 4°͑2͒ min Ϫ1 show that all oxide deposits prepared with the different electrochemical modes are amorphous ͑not shown here͒. Surface morphologies of these oxide depos-* Electrochemical Society Active Member.

Nonsurjective zero product preservers between matrices over an arbitrary field

In this paper, we give concrete descriptions of additive or linear disjointness preservers between matrix algebras over an arbitrary field $\mathbb{F}$ of different sizes. In particular, we show that a linear map $\Phi: M_n(\mathbb{F}) \rightarrow M_r(\mathbb{F})$ preserving zero products carries the form $$\Phi(A)= S\begin{pmatrix} R\otimes A & 0 \cr 0 & \Phi_0(A)\end{pmatrix} S^{-1},$$ for some invertible matrices $R$ in $M_k(\mathbb{F})$, $S$ in $M_r(\mathbb{F})$ and a zero product preserving linear map $\Phi_0: M_n(\mathbb{F}) \rightarrow M_{r-nk}(\mathbb{F})$ with range consisting of nilpotent matrices. Here, either $R$ or $\Phi_0$ can be vacuous. The structure of $\Phi_0$ could be quite arbitrary. We classify $\Phi_0$ with some additional assumption. When $\Phi(I_n)$ has a zero nilpotent part, especially when $\Phi(I_n)$ is diagonalizable, we have $\Phi_0(X)\Phi_0(Y) = 0$ for all $X, Y$ in $M_n(\mathbb{F})$, and we give more information about $\Phi_0$ in this case. Similar results for double zero product preservers and orthogonality preservers are obtained.Comment: 29 page