Analysis of the Datagram Congestion Control Protocol’s connection management procedures using the sweep-line method

State space explosion is a key problem in the analysis of finite state systems. The sweep-line method is a state exploration method which uses a notion of progress to allow states to be deleted from memory when they are no longer required. This reduces the peak number of states that need to be stored, while still exploring the full state space. The technique shows promise but has never achieved reductions greater than about a factor of 10 in the number of states stored in memory for industrially relevant examples. This paper discusses sweep-line analysis of the connection management procedures of a new Internet standard, the Datagram Congestion Control Protocol (DCCP). As the intuitive approaches to sweep-line analysis are not effective, we introduce new variables to track progress. This creates further state explosion. However, when used with the sweep-line, the peak number of states is reduced by over two orders of magnitude compared with the original. Importantly, this allows DCCP to be analysed for larger parameter values. Somsak Vanit-Anunchai was partially supported by an Australian Research Council Discovery Grant (DP0559927) and Suranaree University of Technology. Guy Edward Gallasch was supported by an Australian Research Council Discovery Grant (DP0559927).     

Tedesko’s Philadelphia Skating Club: Refinement of an Idea

This paper presents new aspects of Anton Tedesko’s design for an important thin shell concrete roof. The study of this roof results from the examination of original engineering drawings and calculations which we present with the goal of promoting a greater understanding of the structural design of a major figure in the tradition of 20th century building.     

Structural Response of Nuclear Containment Shield Buildings with Construction Openings

Steam generator replacement at nuclear power plants requires large construction openings in nuclear containment structures. This study examines the effects of such openings placed in a 61?cm (2?ft) thick dome of a shield building. The dome is cast in two layers, and the limiting cases of the two layers acting as one and the lower layer carrying the entire load are considered. Without openings, the stresses due to dead load in the structure are very low when compared to the material strength. With openings, the loads are easily redistributed around the opening, and the maximum stresses for the conservative case are between three and four and one-half times larger than in the original structure with no openings. The extent of the affected area around the holes is relatively small. Smooth corners in the openings are necessary to avoid high local stress concentrations.     

Investigation of the levels of N(τ)-Methylhistidine in a range of beef cuts and offals

Protein-bound N(τ)-methylhistidine (N-MeHis) has been suggested as an index for the estimation of muscle (meat) protein in meat and meat products. This paper examines the levels of N-MeHis in a range of six prime beef cuts together with beef flank, cheek, mechanically recovered meat (MRM) and offals. The study was undertaken by two separate laboratories using a previously reported HPLC procedure involving the conversion of N-MeHis to a fluorescent derivative. It is shown that, whilst similar N-MeHis levels are present in the prime cuts, there is considerable variation in those found in the other cuts and offals. The average N-MeHis level in six prime cuts observed at both laboratories is 122 μg/g fat-free connective tissue-free (FFCF) meat; however, flank exhibits apparently high N-MeHis levels, whilst cheek and MRM contain only approximately 70% of the level found in the prime cuts. The offals contain between 0 and 65% of the N-MeHis level found in prime cuts. The greater variability and the often lower value of the N-MeHis content of these legitimate meat materials preclude the establishment of a single realistic index for FFCF beef, and present fundamental problems for the assessment of the lean meat content of manufactured beef products by N-MeHis determination.     

Exploiting equivalence reduction and the sweep-line method for detecting terminal states

State-space exploration is one of the main approaches to computer-aided verification and analysis of finite-state systems. It is used to reason about a wide range of properties during the design phase of a system, including system deadlocks. Unfortunately, state-space exploration needs to handle huge state spaces for most practical systems. Several state-space reduction methods have been developed to tackle this problem. In this paper, we develop algorithms for combining two of these methods: state equivalence class reduction and the sweep-line. The algorithms allow deadlocks to be detected by recording terminal states of the system on-the-fly during state-space exploration. We derive expressions for the complexity of the algorithms and demonstrate their usefulness with an industrial case study. Our results show that the combined method achieves at least a six-fold reduction of the state space for interesting parameter values compared with either method used in isolation while still proving the desired system property of the terminal states. The runtime performance of the combined method is almost the same as that of the equivalence class method over the chosen parameter range. Moreover, the improvement in space reduction increases with increased parameter values.     

Simplicity, Scale, and Surprise: Evaluating Structural Form

Aesthetic and ethical issues of building design are presented here to encourage meaningful discussion among today’s architectural engineering students and practitioners. The evaluative aesthetic ideas of scale, simplicity, and surprise are applied to two important structures designed by Fazlur R. Khan. Khan’s profound understanding of load flow in his buildings influenced his aesthetic ideas. Furthermore, his aesthetic ideas were intimately intertwined with his ethical ideas about structural logic and the role of structure in architecture. We explore these ideas and present new insights as well. Our goal is to encourage a public discourse within our profession on the topic of evaluating structural form.     

Setting of acute reference doses for pesticides based on existing regulatory requirements and regulatory test guidelines.

Reference doses (RfD) for the definition of tolerable food residues have traditionally been based on the lowest no observed adverse effect level (NOAEL), which usually comes from chronic toxicity studies. While this is generally agreed to be a safe approach to evaluate the overall significance of expected consumption it is clear that it is not appropriate for evaluation of the toxicological significance of residues in a single meal. Standard acute toxicity tests are not designed to generate an NOAEL, from which an RfD can be derived. They are more appropriate to evaluating risk following accidental high exposure to the product itself rather than to food residues. A typical toxicological database for a pesticide active substance contains studies which may be appropriate, on a case-by-case basis, to evaluate shorter term endpoints of interest for specific molecules, such as developmental or acute neurotoxicity studies. However, their specificity limits their scope of application. General toxicological endpoints are well covered by short-term, 28- or 90-day, guideline studies. However, neither of these studies is ideal for setting of an acute RfD (ARfD) as the treatment period is significantly longer than the duration of consumer exposure. This could be balanced by applying a reduced safety factor to the NOAEL to set the ARfD. Alternatively, a test guideline could be designed to generate a relevant acute NOAEL but the time necessary for development, validation and acceptance of such a guideline means that an interim approach is, in any case, necessary.     

Self-Anchored Suspension Bridges

This paper, summarizing the beginnings, analysis, and future of self-anchored suspension bridges, examines the development of this unique bridge form, its uses over the past century, and its advantages and disadvantages. The Konohana Bridge in Osaka, Japan, illustrates this type and provides a case study to compare conventional suspension bridge theory with the results of a finite-element model. The final portion of the paper evaluates the potential for self-anchored suspension bridge design, and provides recommendations for design engineers. The goal here is to describe the structural behavior of self-anchored bridges in general, and of the Konohana Bridge in particular.     

Bayonne Bridge: The Work of Othmar Ammann, Master Builder

The goal of this paper is to demonstrate the significance of the Bayonne Bridge and to identify it as a work of structural art, because its designer, Othmar Ammann (1879–1965), focused on efficiency, economy, and elegance. To understand Ammann’s ideas and his great arch bridge, we will: (1) briefly describe his educational background; (2) explore his design concept; (3) explain the behavior of the bridge through a careful structural analysis; (4) include a critical analysis of its design; and (5) reflect on lessons to be learned from Ammann. A full, modern technical study of the Bayonne Bridge has never been published. Since we are very fortunate to have one of the few complete sets of the plans, we will present an independent structural analysis to explain Ammann’s design concept and to demonstrate its efficiency in the complete form and its safety during construction.     

Effect of moisture protective coatings on the strength of a modern metal-reinforced glass-ionomer cement

The strength of a modern, low metal:glass ratio, metal-reinforced glass-ionomer cement was measured evaluating a number of protective barriers: one light-cured resin, two solvent-based dental varnishes and petroleum jelly. The cement was exposed to water at 10 and 60 min from start of mix. The results obtained with these protecting agents were compared with those obtained where no protection was applied. A comparison of uniaxial flexural strength and biaxial flexural strength showed the latter to be more discriminating. Proprietary dental varnishes were superior to petroleum jelly, producing similar strengths of 50 MPa. Petroleum jelly was, however, preferable to no protection. Moisture protection during the first 30 min was found to be beneficial, thereafter no further strength increase was found. A second material, a cement which has a high metal:glass ratio, was found to be more moisture resistant but weaker in strength than the modern material, with a biaxial strength of 39 MPa.