User impersonation in key certification schemes

In this note we exhibit some weaknesses in two key certification schemes. We show how a legitimate user can impersonate any other user in an ElGamal-based certification scheme, even if hashing is applied first. Furthermore, we show how anybody can impersonate users of the modular square root key certification scheme, if no hashing occurs before the certification. This shows that it is essential for this certification scheme to hash a message before signing it.     

Extension of dynamic programming to nonseparable dynamic optimization problems

The use of dynamic programming is extended to a general nonseparable class where multiobjective optimization is used as a separation strategy. The original nonseparable dynamic optimization problem is first embedded into a separable, albeit multiobjective, optimization problem where multiobjective dynamic programming using the envelope approach is used as a solution scheme. Under certain conditions, the optimal solution of the original nonseparable problem is proven to be attained by a noninferior solution.     

Multivariable system reduction via modal methods and padé approximation

A combination of dominant-eigenvalues and Padé approximation methods is proposed for the reduction of a high degree multivariable system. The reduced models so derived are equivalent to those derived by the method in [7]. However, it is computationally much simpler and never fails to produce reduced models. Further it is equally applicable to systems with the number of inputs different from the number of outputs.     

RCCS: Rebar CAD/CAM System

Abstract: A CAD/CAM system that automates the design and manufacturing of rebars is described. The CAD-based design module of the system permits a semiautomated design alongside the conventional one. The uniqueness of the system resides in its ability to extract automatically the data needed for manufacturing from the graphic design database, process these data, and transfer them to the rebar-manufacturing machine. Thus all the manual data manipulation stages of traditional rebar design and production (detailing, documentation, data extraction, etc.) are avoided. In many cases the multistage manual data manipulation is a source of errors and is moreover labor-intensive. Consequently, the CAD/CAM system described here leads to cost reduction together with increased quality. This paper describes the principles underlying the development of the system and the system's structure, which is based on a design module, a data extraction module, and a data processing and transfer module.     

A non-recursive method for solving the general discrete-time riccati equations related to the H∞ control problem

In this paper we propose a nonrecursive method for solving the general discrete-time algebraic Riccati equation related to the H_∞ control problem (H_∞-DARE). We have achieved this by casting the problem of solving a given H_∞-DARE to the problem of solving an auxiliary continuous-time algebraic Riccati equation associated with the H_∞ control problem (H_∞-CARE) for which the well known nonrecursive methods of solving are available. The advantages of our approach are: it reduces the computation involved in the recursive algorithms while giving much more accurate solutions, and it readily provides the properties of the general H_∞-DARE.     

Constraint fusion for recognition and localization of articulated objects

This paper presents a method for localization and interpretation of modeled objects that is general enough to cover articulated and other types of constrained models. The flexibility between the components of the model is expressed as spatial constraints that are fused into the pose estimation during the interpretation process. The constraint fusion assists in obtaining a precise and stable pose of each of the object's components and in finding the correct interpretation. The proposed method can handle any constraint (including inequalities) between any number of different components of the model. The framework is based on Kalman filtering.     

Failure of the Routh-Hurwitz method of reduction

The Routh-Hurwitz reduction method is shown to have a serious disadvantage in that the reduced model may approximate the nondominant poles of the system and hence lead to erroneous approximations. A numerical example is given to compare the Routh-Hurwitz method to the Padé approximation method.     

Semi-global stabilization with guaranteed regional performance of linear systems subject to actuator saturation

For a linear system under a given saturated linear feedback, we propose feedback laws that achieve semi-global stabilization on the null controllable region while preserving the performance of the original feedback law in a fixed region. Here by semi-global stabilization on the null controllable region we mean the design of feedback laws that result in a domain of attraction that includes any a priori given compact subset of the null controllable region. Our design guarantees that the region on which the original performance is preserved would not shrink as the domain of attraction is enlarged by appropriately adjusting the feedback laws. Both continuous-time and discrete-time systems will be considered.     

Quinone Methide-Based Organophosphate Hydrolases Inhibitors: Trans Proximity Labelers versus Cis Labeling Activity-Based Probes

Quinone methide (QM) chemistry is widely applied including in enzyme inhibitors. Typically, enzyme-mediated bond breaking releases a phenol product that rearranges into an electrophilic QM that in turn covalently modifies protein side chains. However, the factors that govern the reactivity of QM-based inhibitors and their mode of inhibition have not been systematically explored. Foremost, enzyme inactivation might occur in cis, whereby a QM molecule inactivates the very same enzyme molecule that released it, or by trans if the released QMs diffuse away and inactivate other enzyme molecules. We examined QM-based inhibitors for enzymes exhibiting phosphoester hydrolase activity. We tested different phenolic substituents and benzylic leaving groups, thereby modulating the rates of enzymatic hydrolysis, phenolate-to-QM rearrangement, and the electrophilicity of the resulting QM. By developing assays that distinguish between cis and trans inhibition, we have identified certain combinations of leaving groups and phenyl substituents that lead to inhibition in the cis mode, while other combinations gave trans inhibition. Our results suggest that cis-acting QM-based substrates could be used as activity-based probes to identify various phospho- and phosphono-ester hydrolases, and potentially other hydrolases.     

Robust estimation of surface properties and interpolation of shadow/specularity components

The Polynomial Texture Map framework (PTM) extends the simple model of image formation from the Lambertian variant of Photometric Stereo (PST) to more general reflectances and to more complex-shaped surfaces. It forms an alternative method for apprehending object color, albedo, and surface normals. Here we consider solving such a model in a robust version, not to date attempted for PTM, with the upshot that both shadows and specularities are identified automatically without the need for any thresholds. Instead of the linear model used in few-source PST for Lambertian surfaces, PTM adopts a higher degree polynomial model. PTM has two aims: interpolation of images for new lighting directions, and recovery of surface properties. Here we show that a robust approach is a good deal more accurate in recovering surface properties. For new-lighting interpolation, we demonstrate that a simple radial basis function interpolation can accurately interpolate specularities as well as attached and cast shadows even with a medium-sized image set, with no need for reflectance sharing across pixels or extremely large numbers of interpolation coefficients.