A Generalization of Short-Cut Fusion and its Correctness Proof

Short-cut fusion is a program transformation technique that uses a single, local transformation—called the foldr-build rule—to remove certain intermediate lists from modularly constructed functional programs. Arguments that short-cut fusion is correct typically appeal either to intuition or to free theorems—even though the latter have not been known to hold for the languages supporting higher-order polymorphic functions and fixed point recursion in which short-cut fusion is usually applied. In this paper we use Pitts' recent demonstration that contextual equivalence in such languages is relationally parametric to prove that programs in them which have undergone short-cut fusion are contextually equivalent to their unfused counterparts. For each algebraic data type we then define a generalization of build which constructs substitution instances of its associated data structures, and use Pitts' techniques to prove the correctness of a contextual equivalence-preserving fusion rule which generalizes short-cut fusion. These rules optimize compositions of functions that uniformly consume algebraic data structures with functions that uniformly produce substitution instances of those data sructures.     

优化负荷及发电管理

热电系统或水-热电系统的运营商对运营进行长远规划,从而确定自身发电及采用其他可利用能源的供应量,如以合同形式采购能源.该计划的目的是最小化电力系统的运行成本,或最大化利润.     

Privacy4DRM: Nutzer-und datenschutz-freundliches Digital Rights Management

Zusammenfassung  Die DRM-Diskussion ist festgefahren: Weil die Verwertungsindustrie ihre digitalen Rechte mit Hilfe von Technik und staatlichem Zwang zu verteidigen versucht, verweigern sich die Nutzer. Diese Blockade ist nur aufzul?sen, wenn die digitalen Rechte der Urheber auch an den Interessen der Nutzer und damit dem Datenschutz ausgerichtet werden.     

Spectroscopic ellipsometry of anisotropic materials: application to the optical constants of HgI2

A variable angle-of-incidence spectroscopic fixed-polarizer, rotating-polarizer, fixed-analyzer ellipsometer (PRPSE) across a spectral range from 300 to 800 nm is used to determine the optical properties of anisotropic uniaxial tetragonal red mercuric iodide (HgI(2)). For the first time, to our knowledge, the bulk crystal HgI(2) surface measured by ellipsometry was not subjected to potassium iodide cutting or etching. Measurements were made at an air-HgI(2) interface with the optic axis parallel to the sample surface. To determine the optical constants, we varied both the angle of incidence and the azimuth of the optic axis with the plane of incidence. The detailed formulas needed for reliable procedures for analyzing the data are presented. The ordinary and extraordinary complex indices of refraction, (n(o) - ik(o)) and (n(e) - ik(e)), respectively, are determined. Good agreement between PRPSE and the prism technique for the refractive index is observed. The surface aging effects of the ellipsometric parameters of HgI(2), during 30 h of exposure to air, were detected by PRPSE.     

Methods for the Reduction of Odometry Errors in Over-Constrained Mobile Robots

This paper presents an analysis of odometry errors in over-constrained mobile robots, that is, vehicles that have more independent motors than degrees of freedom. Examples of over-constrained vehicles are the various 6-wheeled Mars Rovers like Rocky-7, Rocky-8, or Fido.Based on our analysis we developed two novel measures aimed at reducing odometry errors. We also developed a novel method that serves as a framework for the implementation of the two new measures, as well as for other, conventional error reducing measures.One of the two new measures, called Fewest Pulses Measure, makes use of the observation that most terrain irregularities, as well as wheel slip, result in an erroneous overcount of encoder pulses. The second new measure, called Cross-coupled Control Measure, optimizes the motor control algorithm of the robot to reduce synchronization errors that would otherwise result in wheel slip with conventional controllers.The novel method that serves as a framework for other measures is based on so-called Expert Rules. In this paper we formulate three expert rules aimed at reducing dead-reckoning errors. Two of these expert rules are related to the foregoing discussion on error reducing measures. The third expert rule adds a gyroscope to the system and we re-examine the effectiveness of the odometry error-reducing measures in the context of this addition.In the work described in this paper we modified a Pioneer AT skid-steer platform by providing it with four independent drive motors and encoders. We implemented our error-reducing measures and the expert rule method on this over-constrained platform and present experimental results.     

Membranes prepared from keratin–polyacrylonitrile graft copolymers

Graft copolymerization of acrylonitrile onto a soluble wool keratin derivative was studied with the reduced and carboxymethylated low-sulfur protein fraction from wool. Copolymerization was carried out under a variety of conditions with a redox system of (NH₄)₂S₂O₈–Na₂SO₃ in 60% (w/w) aqueous ZnCl₂ solution at 10°C. Monomer conversions higher than 90% were obtained by the stepwise addition of initiator. The graft products were successfully separated into grafted copolymer and homopolyacrylonitrile (PAN) by fractional precipitation or solvent extraction with DMF. Grafted PAN were isolated by acid hydrolysis of the keratin backbone. Characterization of grafted and homo-PAN was carried out by IR spectroscopy, amino acid endgroup analysis, and viscometry. On the basis of the results, effects of polymerization conditions on grafting parameters were discussed. Membranes were prepared from 60% aqueous ZnCl₂ solution by using ice-cold water as the regenerating medium. All the membranes formed from the graft products were transparent. Observation by scanning electron microscopy showed that the surface consisted of rather spherical keratin domains regularly distributed in the PAN matrix. Selective hydrolysis of the keratin domains allowed a new type of porous PAN membrane to be obtained, with the inner walls of the pores being charged with amino acid residues attached to PAN chains as the endgroup.