Adaptable learning assistant for item bank management

We present PKIP, an adaptable learning assistant tool for managing question items in item banks. PKIP is not only able to automatically assist educational users to categorize the question items into predefined categories by their contents but also to correctly retrieve the items by specifying the category and/or the difficulty level. PKIP adapts the “categorization learning model” to improve the system’s categorization performance using the incoming question items. PKIP tool has an advantage over the traditional document categorization methods in that it can correctly categorize the question item which lacks keywords since it adopts the feature selection technique and support vector machine approach to item bank text categorization. In our initial experimentation, PKIP was designed and implemented to manage the Thai high primary mathematics question items. PKIP was tested and evaluated in terms of both system accuracy and user satisfaction. The evaluation result shows that the system accuracy is acceptable and PKIP satisfies the need of the users.     

Paillier''s Trapdoor Function Hides up to O ( n ) Bits

At EuroCrypt '99 Paillier proposed a new encryption scheme based on higher residuosity classes. The new scheme was proven to be one-way under the assumption that computing N -residuosity classes in Z _N2 ^* is hard. Similarly the scheme can be proven to be semantically secure under a much stronger decisional assumption: given w ∈ Z _N2 ^* it is impossible to decide if w is an N -residue or not. In this paper we examine the bit security of Paillier's scheme. We prove that if computing residuosity classes is hard, then given a random w it is impossible to predict the least significant bit of its class significantly better than at random. This immediately yields a way to obtain semantic security without relying on the decisional assumption (at the cost of several invocations of Paillier's original function). In order to improve efficiency we then turn to the problem of simultaneous security of many bits. We prove that Paillier's scheme hides n-b (up to O(n) ) bits if one assumes that computing the class c of a random w remains hard even when we are told that c<2 ^b . We thoroughly examine the security of this stronger version of the intractability of the class problem. An important theoretical implication of our result is the construction of the first trapdoor function that hides super-logarithmically (up to O(n) ) many bits. We generalize our techniques to provide sufficient conditions for a trapdoor function to have this property.     

Comparison of optical and physical measurements with sensory assessment of the ripeness of tomato fruit Lycopersicon esculentum

Knowledge of the inter-relationships among objective physical and optical measurements and their relation with sensory perception of foods can be applied to improve quality control and consumer acceptance. Changes in the optical and mechanical properties of tomatoes were found to be related to the perceived ripeness of the fruit over a storage period. The sensory attributes and instrumental parameters significant in the assessment of ripening tomatoes were translucency, green, orange, lightness, hue and chroma. The chromatic co-ordinate a^* was significantly correlated with the mechanical modulus of the fruit, which in turn was inversely related to ripening associated with colour changes from green to red. It is feasible that mechanical and optical data may be combined to provide an on-line system for the evaluation of ripeness of tomato fruit.     

Reactive Liners Prepared Using Powders of Aluminum and Aluminum‐Magnesium Alloys

Cylindrical reactive liners filled with powders of aluminum, aluminum‐magnesium alloys, and aluminum‐magnesium powder blends were prepared and initiated by a centrally located explosive charge. The experiments were performed in a cubic chamber. Several transient pressure measurements were taken in addition to the quasistatic pressure caused by the explosion. Results were compared against a reference case with an inert liner filled with aluminum oxide powder. For all reactive liners, an increase in both quasistatic pressure and blast wave strength were observed compared to the case of an inert liner. In experiments with mechanically alloyed Al ⋅ Mg powders, the quasistatic pressure is effectively the same as in experiments with pure aluminum. An improvement in the achieved quasistatic pressure is observed for the liners with a cast alloyed Al ⋅ Mg powder. Most interestingly, a substantial contribution to the air blast indicative of very early reaction occurring in sub‐millisecond time scale is observed for all experiments with reactive liners. The most substantial improvement in the blast characteristics is observed in experiments with mechanically alloyed Al ⋅ Mg powders. While the mechanisms of prompt reactions of metals and alloys remain largely unexplored, the present results highlight the importance of such reactions for reactive liners and other components of energetic systems.     

Examining the ecological consequences of restoring flow intermittency to artificially perennial lowland streams: Patterns and predictions from the Broken—Boosey creek system in northern Victoria,Australia

The reinstatement of natural flow regimes is a rapidly emerging issue in river restoration worldwide. In northern Victoria, Australia, efforts are presently underway to restore a natural, intermittent flow regime to several streams which have received perennial diversions for both irrigation and stock and domestic water‐supplies for over 100 years. A pipeline to deliver water to landholders will significantly reduce transmission losses throughout the system allowing irrigation canals and diversion weirs to be decommissioned. The motivation for flow alteration in this system lies primarily in reducing inefficiencies in water delivery which, in turn, will be used to meet escalating demands on water resources. The ecological impact of the flow regime shift on these streams is likely to be substantial. This study utilized an existing artificial hydrological gradient (from perennial to intermittent) in two creek systems, to explore relationships between flow regime and a range of ecological variables. These data provide a benchmark against which to assess ecological changes once flow has been altered and form the basis for predicting changes that can assist future management decisions. Data collected from 10 sites across a strong hydrological gradient detected clear differences in geomorphology, water quality and biotic assemblages (macrophytes, macroinvertebrates and fish). By examining the relationship between flow regime and the distribution of biota we identify both the positive and negative outcomes of restoring naturally intermittent flow regimes within artificially perennial lowland streams. The reinstatement of intermittent flow regimes in artificially perennial streams will continue in many parts of the world as water delivery via these systems becomes increasingly uneconomical. While flow restoration may in principle be regarded as a positive step, these findings emphasize the need to consider fully the ecological consequences of restoring historical hydrological regimes to streams within the context of other human induced catchment disturbances. Copyright © 2009 John Wiley & Sons, Ltd.     

Nanoscale Disorder and Deintercalation Evolution in K-Doped MoS2 Analysed Via In Situ TEM

Intercalation and deintercalation processes in van der Waals crystals underpin their use in nanoelectronics, energy storage, and catalysis but there remains significant uncertainty regarding these materials’ structural and chemical heterogeneity at the nanoscale. Deintercalation in particular often controls the robustness and cyclability of the involved processes. Here, a detailed analysis of potassium ordering and compositional variations in as-synthesised K intercalated MoS₂ as well an analysis of deintercalation induced changes in the structure and K/Mo elemental composition is presented. By combining 4D scanning transmission electron microscopy (4DSTEM), in situ atomic resolution STEM imaging, selected area electron diffraction (SAED) and energy dispersive X-ray spectroscopy (EDS) the formation of previously unknown intermediate superstructures during deintercalation is revealed. The results provide evidence supporting a new deintercalation mechanism that favors formation of local regions with thermodynamically stable ordering rather than isotropic release of K. Systematic time-temperature measurements demonstrate the deintercalation behavior to follow first-order kinetics, allowing compositional and superstructural changes to be predicted. It is expected that the in situ correlative STEM-EDS/SAED methodology developed in this work has the potential to determine optimal synthesis, processing and working conditions for a variety of intercalated or pillared materials.