An Implicit Form of Krasulina's k-PCA Update without the Orthonormality Constraint

We shed new insights on the two commonly used updates for the online k-PCA problem, namely, Krasulina's and Oja's updates. We show that Krasulina's update corresponds to a projected gradient descent step on the Stiefel manifold of orthonormal k-frames, while Oja's update amounts to a gradient descent step using the unprojected gradient. Following these observations, we derive a more implicit form of Krasulina's k-PCA update, i.e. a version that uses the information of the future gradient as much as possible. Most interestingly, our implicit Krasulina update avoids the costly QR-decomposition step by bypassing the orthonormality constraint. A related update, called the Sanger's rule, can be seen as an explicit approximation of our implicit update. We show that the new update in fact corresponds to an online EM step applied to a probabilistic k-PCA model. The probabilistic view of the update allows us to combine multiple models in a distributed setting. We show experimentally that the implicit Krasulina update yields superior convergence while being significantly faster. We also give strong evidence that the new update can benefit from parallelism and is more stable w.r.t. tuning of the learning rate.

Kinetics of Pyrolysis of Date Kernels

The kinetics of pyrolysis of ground date kernels was investigated using thermogravimetric analysis in order to provide the necessary information for proper biochar formation and bioreactor design. Pyrolysis was carried out at heating rates of 5, 10, 15 and 20oC.min-1 in a flow of nitrogen. One main DTG peak was obtained that corresponded to formation of bio-char. A second diffuse peak corresponds to constant rate cracking of the char formed and complete elimination of carbon leaving an ash residue. The composition of biochar was determined using EDX. Four different methods were used to follow up the kinetics of the three steps, namely, the Kissinger, the Flynn-Wall-Ozawa, the Coats-Redfern methods and multi-regression analysis. The activation energy of the main decomposition step was determined and the values obtained using different kinetic models compared. The decomposition step simply followed first order kinetics.

Development of Shoreline Extraction Method Based on Spatial Pattern Analysis of Satellite SAR Images

The extensive monitoring of shorelines is becoming important for investigating the impact of coastal erosion. Satellite synthetic aperture radar (SAR) images can cover wide areas independently of weather or time. The recent development of high-resolution satellite SAR images has made observations more detailed. Shoreline extraction using high-resolution images, however, is challenging because of the influence of speckle, crest lines, patterns in sandy beaches, etc. We develop a shoreline extraction method based on the spatial pattern analysis of satellite SAR images. The proposed method consists of image decomposition, smoothing, sea and land area segmentation, and shoreline refinement. The image decomposition step, in which the image is decomposed into its texture and outline components, is based on morphological component analysis. In the image decomposition step, a learning process involving spatial patterns is introduced. The outline images are smoothed using a non-local means filter, and then the images are segmented into sea and land areas using the graph cuts’ technique. The boundary between these two areas can be regarded as the shoreline. Finally, the snakes algorithm is applied to refine the position accuracy. The proposed method is applied to the satellite SAR images of coasts in Japan. The method can successfully extract the shorelines. Through experiments, the performance of the proposed method is confirmed.

Complex transition metal hydrides incorporating ionic hydrogen: thermal decomposition pathway of Na2Mg2FeH8 and Na2Mg2RuH8

The optimised syntheses of Na2Mg2FeH8 and Na2Mg2RuH8 are reported and their thermal decomposition pathways established. The enthalpy and entropy of each decomposition step has been determined by PCI measurements.

Facile, Alternative Synthesis of Spherical-Like Ca(H2PO4)2•H2O Nanoparticle by Aqueous-Methanol Media

Spherical-like calcium dihydrogenphosphate monohydrate (Ca (H2PO4)2H2O) nanostructure was successfully prepared by the mixing of calcium carbonate and phosphoric in aqueous-methanol media at ambient temperature for 30 min. Three thermal decomposition step and higher stability at over 800 °C of the prepared sample are different from the earlier works. Spherical-like Ca (H2PO4)2H2O nanostructure with diameter < 100 nm confirmed by SEM may be important for potential applications. This method of synthesis by aqueous-methanol media is a fast and simple method and it is expected to be applicable for the synthesis of other nanocrystalline calcium phosphates.

Thermal Decomposition Characteristics of Mg (NO3)2·6H2O and MgCl2·6H2O Composite as Phase Change Material

The thermal decomposition characteristics of Mg (NO3)2·H2O and MgCl2·6H2O composite were studied by integrated thermal analysis. Results show that there are five steps during the thermal decomposition of phase change material (PCM): the starting temperature of each step is 35.5°C, 93°C, 196°C, 260°C and 318°C, respectively. PCM was calcined at different temperatures at each decomposition step. The composition and morphology of the calcined product was characterized by XRD and SEM. Two major reactions including dehydration and hydrolysis occur in the thermal decomposition progress. Dehydration is the main process below 196 °C, while hydrolysis is predominant process when the temperature is higher than 196 °C.