A formal model of emotions for an empathic rational dialog agent

Recent research has shown that virtual agents expressing empathic emotions toward users have the potential to enhance human–machine interaction. To provide empathic capabilities to a rational dialog agent, we propose a formal model of emotions based on an empirical and theoretical analysis of the users’ conditions of emotion elicitation. The emotions are represented by particular mental states of the agent, composed of beliefs, uncertainties and intentions. This semantically grounded formal representation enables a rational dialog agent to identify from a dialogical situation the empathic emotion that it should express. An implementation and an evaluation of an empathic rational dialog agent have enabled us to validate the proposed model of empathy.     

Effect of compaction method on the undrained strength of fiber-reinforced clay

The use of discrete fibers in reinforcing soils is of interest to the geotechnical engineering community. Two limitations exist in experimental studies involving fiber-reinforced clays. First, fiber-reinforced clay specimens are generally prepared in the lab using conventional “impact” compaction, whereas the compaction of clay systems in the field typically involves “kneading” action. Second, the majority of tests reported in the literature use synthetic fibers to the exclusion of other types. This paper addresses these limitations through an experimental triaxial testing program that: (1) supplements the scarce data available in the literature on the undrained load response of clays reinforced with “natural” fibers and that are compacted by “kneading”, and (2) assesses the capacity of the experimental procedures that involve “impact” compaction to produce responses that are relevant to actual field conditions. Results from 73 unconsolidated undrained triaxial tests indicate that the percent improvement in the undrained strength of the fiber-reinforced clay is highly dependent on the compaction method, with specimens that are prepared using impact compaction yielding improvements up to three times larger than identical specimens prepared by kneading. This discrepancy in the behavior can be traced back to differences in the fiber orientation distributions between specimens that were compacted by impact and kneading.     

Cooperative Communication Protocols in Wireless Networks: Performance Analysis and Optimum Power Allocation

In this paper, symbol-error-rate (SER) performance analysis and optimum power allocation are provided for uncoded cooperative communications in wireless networks with either decode-and-forward (DF) or amplify-and-forward (AF) cooperation protocol, in which source and relay send information to destination through orthogonal channels. In case of the DF cooperation systems, closed-form SER formulation is provided for uncoded cooperation systems with PSK and QAM signals. Moreover, an SER upper bound as well as an approximation are established to show the asymptotic performance of the DF cooperation systems, where the SER approximation is asymptotically tight at high signal-to-noise ratio (SNR). Based on the asymptotically tight SER approximation, an optimum power allocation is determined for the DF cooperation systems. In case of the AF cooperation systems, we obtain at first a simple closed-form moment generating function (MGF) expression for the harmonic mean to avoid the hypergeometric functions as commonly used in the literature. By taking advantage of the simple MGF expression, we obtain a closed-form SER performance analysis for the AF cooperation systems with PSK and QAM signals. Moreover, an SER approximation is also established which is asymptotically tight at high SNR. Based on the asymptotically tight SER approximation, an optimum power allocation is determined for the AF cooperation systems. In both the DF and AF cooperation systems, it turns out that an equal power strategy is good, but in general not optimum in cooperative communications. The optimum power allocation depends on the channel link quality. An interesting result is that in case that all channel links are available, the optimum power allocation does not depend on the direct link between source and destination, it depends only on the channel links related to the relay. Finally, we compare the performance of the cooperation systems with either DF or AF protocol. It is shown that the performance of a systems with the DF cooperation protocol is better than that with the AF protocol. However, the performance gain varies with different modulation types and channel conditions, and the gain is limited. For example, in case of BPSK modulation, the performance gain cannot be larger than 2.4 dB; and for QPSK modulation, it cannot be larger than 1.2 dB. Extensive simulation results are provided to validate the theoretical analysis.     

Effect of Sand Columns on the Undrained Load Response of Soft Clays

When sand columns are used as vertical drains in soil improvement schemes, the possible reinforcing role that these columns can play in regards to improving the bearing capacity is usually neglected in design. The objective of this paper is to evaluate the degree of improvement in the mechanical properties of soft clays in practical applications involving the use of sand drains or sand columns in clayey soils. For this purpose, 32 isotropically consolidated undrained triaxial tests were performed on normally consolidated kaolin specimens. The parameters that were varied were the diameter of the sand columns, the height of the columns, the type of columns (geotextile encased versus nonencased), and the effective confining pressure. Test results indicated that sand columns improved the undrained strength significantly even for area replacement ratios that were less than 18%. The increase in undrained strength was accompanied by a decrease in pore pressure generation during shear and an increase in Young’s modulus. The drained shear strength parameters were found to be relatively unaffected by the sand column reinforcement, except for fully penetrating columns with high area replacement ratios.     

Comparative study of hydrocarbon, fluorocarbon, and aromatic bonded RP-HPLC stationary phases by linear solvation energy relationships.

The retention properties of eight alkyl, aromatic, and fluorinated reversed-phase high-performance liquid chromatography bonded phases were characterized through the use of linear solvation energy relationships (LSERs). The stationary phases were investigated in a series of methanol/water mobile phases. LSER results show that solute molecular size and hydrogen bond acceptor basicity under all conditions are the two dominant retention controlling factors and that these two factors are linearly correlated when either different stationary phases at a fixed mobile-phase composition or different mobile-phase compositions at a fixed stationary phase are considered. The large variation in the dependence of retention on solute molecular volume as only the stationary phase is changed indicates that the dispersive interactions between nonpolar solutes and the stationary phase are quite significant relative to the energy of the mobile-phase cavity formation process. PCA results indicate that one PCA factor is required to explain the data when stationary phases of the same chemical nature (alkyl, aromatic, and fluoroalkyl phases) are individually considered. However, three PCA factors are not quite sufficient to explain the whole data set for the three classes of stationary phases. Despite this, the average standard deviation obtained by the use of these principal component factors are significantly smaller than the average standard deviation obtained by the LSER approach. In addition, selectivities predicted through the LSER equation are not in complete agreement with experimental results. These results show that the LSER model does not properly account for all molecular interactions involved in RP-HPLC. The failure could reside in the V2 solute parameter used to account for both dispersive and cohesive interactions since "shape selectivity" predictions for a pair of structural isomers are very bad.     

Study on the properties of multi-walled carbon nanotubes reinforced poly (vinyl alcohol) composites

Nanocomposite films based on polyvinyl alcohol(PVA) and multi-walled carbon nanotubes (MWCNTs) at different weight ratios (i.e.0.0,0.5, 1.0,1.5, 2.0 wt%), were prepared by dispersion techniques. Cationic geminisurfactant and its monomeric form (0.01 wt%) were used as dispersants to achieve homogeneous and stable dispersionof CNTs in water and subsequent PVA/CNTs nanocomposites. Surface charge of CNTs in aqueous suspension with addition of the used dispersants were investigated by measuring its zeta potential. The structural and interaction studies have been analyzed from X-ray diffraction (XRD) and Raman spectroscopy. The effect of the used surfactantson the separation and distribution of CNTs in PVA matrix was studied by visual characterization based on scanning electron microscopy (SEM). Thermal, mechanical and electrical properties of the prepared nanocomposites were evaluated and the results were discussed in relation with the CNTs content and surfactant type as dispersant. Surfactant effect improved the dispersion homogeneity of CNTs (at 1.0 wt%) within the polymer matrix. The physical interaction between. CNTs and PVA macromolecular chains resulting in nanocomposites with largely enhanced properties compared to those prepared with higher filler loading by avoiding the agglomeration phenomenon of nanotubes. On the other hand, the addition of CNTs by content up to 2 wt%, increases the electrical conductivity to be 10^?6 Scm^?1 at room temperature which highly recommends such composites to be used in electrostatic dissipation applications upon using gemini surfactant. Furthermore, useful nanosized capacitor structure based onnanocomposites containing its monomeric form, characterized by high permittivity and low dielectric loss, can be formed.