A comparison of headway and time to collision as safety indicators

The two safety indicators "headway" and "time to collision (TTC)" are discussed and compared with respect to their usefulness in determining the safety of different traffic situations, like different locations in a junction. Over a 6-day-period traffic flow measures were taken in a four-way junction with stop signs on the minor road. It was found that for vehicles in a car following situation headway and TTC are independent of each other. The percentage of small headways is relatively constant across different locations in the junction, while the percentage of small TTC values varies between different locations. It is recommended to use headway for enforcement purposes, because small headways generate potentially dangerous situations. TTC, on the other hand, should be used when a certain traffic environment is to be evaluated in terms of safety, because it indicates the actual occurrences of dangerous situations.     

A multi-criteria assessment tool for screening preliminary product platform concepts

Platform concept evaluation is a more challenging task than evaluating a single product concept since a platform must effectively support multiple product variants over a prolonged period of time. Existing platform methods develop specific criteria in depth, yet an evaluation of alternative platforms should be based on a broad set of criteria. Based on expert interviews, personal experience, and a literature search we propose a platform assessment tool consisting of 19 criteria for platform evaluation. The criteria are group into six categories: customer satisfaction, variety, after-sale, organization, flexibility, and complexity. The tool is focused on the early platform architecture phase, before proof-of-concept prototyping. However, it can also be used subsequently for platform refinement when more data becomes available. We demonstrate our platform assessment tool through an example with a cordless drill platform.     

A Method for Patching Interleaving-Replay Attacks in Faulty Security Protocols

The verification of security protocols has attracted a lot of interest in the formal methods community, yielding two main verification approaches: i) state exploration, e.g. FDR [Gavin Lowe. Breaking and fixing the needham-schroeder public-key protocol using FDR. In TACAs'96: Proceedings of the Second International Workshop on Tools and Algorithms for Construction and Analysis of Systems, pages 147–166, London, UK, 1996. Springer-Verlag] and OFMC [A.D. Basin, S. Mödersheim, and L. Viganò. An on-the-fly model-checker for security protocol analysis. In D. Gollmann and E. Snekkenes, editors, ESORICS'03: 8th European Symposium on Research in Computer Security, number 2808 in Lecture Notes in Computer Science, pages 253–270, Gjøvik, Norway, 2003. Springer-Verlag]; and ii) theorem proving, e.g. the Isabelle inductive method [Lawrence C. Paulson. The inductive approach to verifying cryptographic protocols. Journal in Computer Security, 6(1-2):85–128, 1998] and Coral [G. Steel, A. Bundy, and M. Maidl. Attacking the asokan-ginzboorg protocol for key distribution in an ad-hoc bluetooth network using coral. In H. König, M. Heiner, and A. Wolisz, editors, IFIP TC6 /WG 6.1: Proceedings of 23rd IFIP International Conference on Formal Techniques for Networked and Distributed Systems, volume 2767, pages 1–10, Berlin, Germany, 2003. FORTE 2003 (work in progress papers)]. Complementing formal methods, Abadi and Needham's principles aim to guide the design of security protocols in order to make them simple and, hopefully, correct [M. Abadi and R. Needham. Prudent engineering practice for cryptographic protocols. IEEE Transactions on Software Engineering, 22(1):6–15, 1996]. We are interested in a problem related to verification but far less explored: the correction of faulty security protocols. Experience has shown that the analysis of counterexamples or failed proof attempts often holds the key to the completion of proofs and for the correction of a faulty model. In this paper, we introduce a method for patching faulty security protocols that are susceptible to an interleaving-replay attack. Our method makes use of Abadi and Needham's principles for the prudent engineering practice for cryptographic protocols in order to guide the location of the fault in a protocol as well as the proposition of candidate patches. We have run a test on our method with encouraging results. The test set includes 21 faulty security protocols borrowed from the Clark-Jacob library [J. Clark and J. Jacob. A survey of authentication protocol literature: Version 1.0. Technical report, Department of Computer Science, University of York, November 1997. A complete specification of the Clark-Jacob library in CAPSL is available at http://www.cs.sri.com/millen/capsl/].     

From human to humanoid locomotion—an inverse optimal control approach

The purpose of this paper is to present inverse optimal control as a promising approach to transfer biological motions to robots. Inverse optimal control helps (a) to understand and identify the underlying optimality criteria of biological motions based on measurements, and (b) to establish optimal control models that can be used to control robot motion. The aim of inverse optimal control problems is to determine—for a given dynamic process and an observed solution—the optimization criterion that has produced the solution. Inverse optimal control problems are difficult from a mathematical point of view, since they require to solve a parameter identification problem inside an optimal control problem. We propose a pragmatic new bilevel approach to solve inverse optimal control problems which rests on two pillars: an efficient direct multiple shooting technique to handle optimal control problems, and a state-of-the art derivative free trust region optimization technique to guarantee a match between optimal control problem solution and measurements. In this paper, we apply inverse optimal control to establish a model of human overall locomotion path generation to given target positions and orientations, based on newly collected motion capture data. It is shown how the optimal control model can be implemented on the humanoid robot HRP-2 and thus enable it to autonomously generate natural locomotion paths.     

Low friction CrN/TiN multilayer coatings prepared by a hybrid high power impulse magnetron sputtering/DC magnetron sputtering deposition technique

High power impulse magnetron sputtering (HIPIMS) has gained increasing scientific and industrial attention as it allows high plasma densities without the drawback of droplet formation. Recently, we showed that by a combination of HIPIMS with dc magnetron sputtering the properties of the coatings are comparable to those prepared solely with HIPIMS, but with the advantage of increased deposition rate.Here, we show that for CrN_HIPIMS/TiN_DCMS multilayered coatings the friction coefficient µ decreases from 0.7 to 0.35 (with an almost constant hardness H around 25 GPa, and modulus of indentation around 375 GPa) when decreasing the bilayer period λ from 7.8 to 6.4 nm, while keeping the CrN_HIPIMS layer thickness constant at 3.2 nm. A further reduction of the friction coefficient at room temperature dry-sliding testing to ∼ 0.25 or 0.05 is obtained when an additional HIPIMS cathode equipped with a Cr or Ti target material, respectively, is added to the process. Contact angle measurements of distilled water drops on as deposited film surfaces were carried out to investigate their wettability. The measurements show, that with increasing contact angle from 70° to 90°, for the individual coatings prepared, also their friction coefficient increases from ∼ 0.05 to ∼ 0.8. The depositions of all coatings were achieved with two- and threefold substrate rotation, which meet the industrial requirements of uniform deposition on complex shaped specimens.     

Annotated reasoning

The application of deduction in various domains resulted in a variety of different techniques to guide the proof search. Many of these techniques incorporate additional knowledge to restrict or select possible proof steps. As a consequence, usually the underlying calculus has to be modified to keep track of this information during the proof search. In this paper we present a general framework for maintaining additional strategic knowledge within a proof. We introduce a formal notion of annotations attached to the constituents of formulas and illustrate how a generic method of inheriting these annotations can be instantiated for various purposes. This revised version was published online in June 2006 with corrections to the Cover Date.     

西九文化区

正OMA发展西九文化区,必须面对一项挑战:将一个盛载政府极大抱负,以及持分者多元利益的超大型多用途项目,转化成一个既有趣又严肃、既有规划又允许即兴、既中国化又国际化的文化区。这个文化区规模庞大,但不失亲密融洽的感觉;富地标性,但十分谦和;容易理解,却能带来惊喜。为避免造成过分冲击,OMA采纳了一种每个香港市民都熟悉的建筑类型作为方案的发展     

Synthesis and rheological properties of an associative star polymer in aqueous solutions

Rheological properties of aqueous solutions and hydrogels formed by an amphiphilic star block copolymer, poly(acrylic acid)-block-polystyrene (PAA₅₄-b-PS₆)₄, were investigated as a function of the polymer concentration (C_p), temperature, and added salt concentration. The water-soluble polymer synthesised by atom transfer radical polymerization (ATRP) was found to form hydrogels at room temperature at polymer concentrations, C_p, over 22 g/L due to the interpolymer hydrophobic association of the PS blocks. Increasing C_p leads to stronger elastic networks at room temperature that show a gel-to-solution transition with increasing temperature. Increase of ionic strength decreases the moduli compared with the pure hydrogel but did not affect the gel-sol transition temperature significantly. Small-angle X-ray experiments showed two distinct scattering correlation peaks for samples above the gelling C_p, which indicates the aggregates formed due to hydrophobic association. Upon heating the intensity of the scattering correlation peaks was found to decrease indicating the loss of the network structure due to thermal motion.     

Prebiotic potential of barley derived β-glucan at low intake levels: A randomised,double-blinded,placebo-controlled clinical study

This randomised, double-blinded, placebo-controlled clinical study aimed to evaluate the in vivo prebiotic potential of barley β-glucan. Fifty-two healthy volunteers aged 39–70 years were randomly assigned to consume daily a cake containing 0.75 g of barley β-glucan or a placebo for 30 d. Stool samples were collected before, during and 2 weeks after the intervention for bacterial enumeration. Gastrointestinal side effects were recorded during the treatment period. In older subjects (?50 years old), barley β-glucan induced a strong bifidogenic effect and an increase of bifidobacteria into traceable range in cases of no detectable baseline levels. A concurrent significant increase in bacteroides was also observed in this age group. Ingestion of the experimental food resulted in no undesirable gastrointestinal side effects in older subjects. We concluded that the daily intake of a cake containing barley β-glucan is well-tolerated and demonstrated significant bifidogenic properties in older healthy volunteers consuming their usual diets.