Alternative market arrangements for technology transfer

With the rapid expansion of markets for telecommunications services and equipment, both national and international, one sees an increasing frequency of alliances in which each of two firms seeks to use the other to complete its portfolio strengths. Often this combination enables firms to achieve the product differentiation that seems to be the key to competitive advantage in modern telecommunications markets. This alliance may take the form of a « joint venture », which in the paper includes as limiting cases a subsidiary wholly owned by one firm, a technology licensing arrangement, and direct exporting. The model of such a venture presented here, although simple, is rich enough to illustrate the influence of four types of factors on the negotiations that set up the venture: demand, costs, risk, and regulatory constraints. We characterize the sets of acceptable and efficient arrangements, under various assumptions about exogeneous factors. The partners must choose among these by some form of bargaining.     

Matching with don't-cares and a small number of mismatches

In matching with don't-cares and k mismatches we are given a pattern of length m and a text of length n, both of which may contain don't-cares (a symbol that matches all symbols), and the goal is to find all locations in the text that match the pattern with at most k mismatches, where k is a parameter. We present new algorithms that solve this problem using a combination of convolutions and a dynamic programming procedure. We give randomized and deterministic solutions that run in time O(nk²logm) and O(nk³logm), respectively, and are faster than the most efficient extant methods for small values of k. Our deterministic algorithm is the first to obtain an O(polylog(k)⋅nlogm) running time.     

Prerequisites for offering ultrasound services in general practice]

In the course of the past few years, sonography has become firmly established in clinical practice. The accuracy of the investigations does not only depend on the quality of the equipment used but also to a considerable degree on the standards of investigator training. To reduce the discrepancy between the number and quality of the investigations in the German Federal Republic, the "Kassen?rztliche Vereinigung" has released guidelines requiring the users of sonographic equipment to undergo theoretical and practical training. These guidelines are reviewed and commented.     

Superfast densification of nanocrystalline oxide powders by spark plasma sintering

Spark plasma sintering (SPS) is a newly discovered old technique which recently has been used for superfast densification of ceramic powders. Simultaneous application of pulsed high dc current densities and load is the necessary condition for rapid and full densification of ceramic powders by SPS. Commercial nanocrystalline magnesium oxide (nc-MgO) and yttrium aluminum garnet (nc-YAG) powders were densified to optical transparency using spark plasma sintering at distinctly different homologous temperatures (0.3 T _m for nc-MgO and 0.7 T _m for nc-YAG). The observed microstructure, density and grain size evolutions versus the SPS temperature were analyzed. The enhanced densification of the nc-MgO powder at the present SPS conditions was related to plastic deformation followed by diffusion processes. Densification of nc-YAG powder was described by the formation of viscous layer at the particle surfaces and corresponding densification by grain rotation and diffusion through the liquid phase. Densification by normal grain growth takes place at higher relative densities, regardless of the material.     

Effect of grain size on elastic modulus and hardness of nanocrystalline ZrO2-3 wt% Y2O3 ceramic

Dense nanocrystalline ZrO₂-3 wt% Y₂O₃ ceramics with grain sizes ranging between 23 to 130 nm were tested by ultrasonic pulse echo and Vickers hardness. The elastic modulus and hardness results were corrected for the residual porosity and the phase content. The corrected elastic moduli exhibited continuous decrease with decrease in the grain size. In contrast, no correlation was found between the corrected hardness and grain size. The percolative composite model was used to describe the changes in the elastic moduli in terms of percolation of the elastic wave through the intercrystalline phase at the percolation threshold. The absence of correlation with the hardness results was explained due to the other energy absorbing mechanisms such as microcracking beneath the indenter.     

Electric field effects during spark plasma sintering of ceramic nanoparticles

The effects of the applied electric field during the spark plasma sintering of ceramic nanoparticles were examined at various stages of the process. It was assumed that local intensification of the electric field arises due to the nanoscale structural features. Enhanced surface conductivity is expected in the nanoparticles during the heating, which otherwise are electrically non-conducting as a bulk. Percolation of the electric current at “optimal” electrical conductivity is obtained by fractal dimension. The defective nanoparticle surfaces experience charging–discharge cycles which lead to local breakdown and to plasma formation due to the ionized surface molecules. High local temperatures which evolved in a nonlinear fashion at the particle surfaces lead to enhanced sintering and densification kinetics, consistent with the flash sintering phenomenon. The contribution of the pondermotive force to the enhancement of the diffusion kinetics is discussed. Temperature windows for enhanced densification kinetics via plastic deformation or plasma-assisted processes are estimated for MgO, Al₂O₃, and YAG.     

Densification of nanocrystalline Y2O3 ceramic powder by spark plasma sintering

Nanocrystalline Y₂O₃ powders with 18 nm crystallite size were sintered using spark plasma sintering (SPS) at different conditions between 1100 and 1600 °C. Dense specimens were fabricated at 100 MPa and 1400 °C for 5 min duration. A maximum in density was observed at 1400 °C. The grain size continuously increased with the SPS temperature into the micrometer size range. The maximum in density arises from competition between densification and grain growth. Retarded densification above 1400 °C is associated with enhanced grain growth that resulted in residual pores within the grains. Analysis of the grain growth kinetics resulted in activation energy of 150 kJ mol^?1 and associated diffusion coefficients higher by 10³ than expected for Y³⁺ grain boundary diffusion. The enhanced diffusion may be explained by combined surface diffusion and particle coarsening during the heating up with grain boundary diffusion at the SPS temperature.     

The Effect of External Electrostatic Field Orientation on Aerosol Filtration by Granular Filters

The separation of fine aerosol particles by a packed granular-bed filter, enhanced by external electrostatic fields, was studied experimentally and theoretically. The filtration efficiencies of charged and neutralized aerosols were measured for external fields aligned with the air flow, transverse to the flow, and opposite to the flow. Theoretical models of electrostatically enhanced granular-bed filtration of micrometer and submicrometer particles were developed. Experimental results which demonstrate the relative merit of each configuration were presented and compared with the theory. The parallel-field configuration yielded the best filtration efficiency followed by the transverse configuration.     

Finding minimal herbicide concentrations in ground water? Try looking for their degradates

Extensive research has been conducted regarding the occurrence of herbicides in the hydrologic system, their fate, and their effects on human health and the environment. Few studies, however, have considered herbicide transformation products (degradates). In this study of Iowa ground water, herbicide degradates were frequently detected. In fact, herbicide degradates were eight of the 10 most frequently detected compounds. Furthermore, a majority of a herbicide's measured concentration was in the form of its degradates--ranging from 55 to over 99%. The herbicide detection frequencies and concentrations varied significantly among the major aquifer types sampled. These differences, however, were much more pronounced when herbicide degradates were included. Aquifer types presumed to have the most rapid recharge rates (alluvial and bedrock/karst region aquifers) were those most likely to contain detectable concentrations of herbicide compounds. Two indirect estimates of ground-water age (depth of well completion and dissolved-oxygen concentration) were used to separate the sampled wells into general vulnerability classes (low, intermediate, and high). The results show that the herbicide detection frequencies and concentrations varied significantly among the vulnerability classes regardless of whether or not herbicide degradates were considered. Nevertheless, when herbicide degradates were included, the frequency of herbicide compound detection within the highest vulnerability class approached 90%, and the median total herbicide residue concentration increased over an order of magnitude, relative to the parent compounds alone, to 2 microg/l. The results from this study demonstrate that obtaining data on herbicide degradates is critical for understanding the fate of herbicides in the hydrologic system. Furthermore, the prevalence of herbicide degradates documented in this study suggests that to accurately determine the overall effect on human health and the environment of a specific herbicide its degradates should also be considered.