Towards formal open standards: formalizing a standard’s requirements

Open standardization seems to be very popular among software developers as it simplifies the standard’s adoption by the software engineering. Formal specification methods, while very promising, are being adopted slowly as the industry seems to have little motivation to move into this territory. In this paper the authors present (1) the idea of applying formal specification techniques to open standards’ specifications, and (2) an example of a formal specification of the Rich Site Summary (RSS) v2.0 open standard. The authors provide evidence for the advantages of the open standards formal specification over natural language documentations: formal specifications are more concise, less ambiguous, more complete with respect to the original documentation and, when using certain kinds of specification languages, executable and reusable as they support module inheritance. The merging of formal specification methods and open standards allows (1) a more concrete standard design; (2) an improved understanding of the environment under design; (3) an enforced certain level of precision into the specification, and also (4) provides software engineers with extended property checking/verification capabilities, especially if they opt to use any algebraic specification language. The authors showcase how the RSS standard can be formally specified using an algebraic specification language and demonstrate how can that be beneficial.     

Blocking reduction for distributed transaction processing within MANETs

Atomic commit protocols for distributed transactions in mobile ad-hoc networks have to consider message delays and network failures. We consider ad-hoc network scenarios, in which participants hold embedded databases and offer services to other participants. Services that are composed of several other services can access and manipulate data of physically different databases. In such a scenario, distributed transaction processing can be used to guarantee atomicity and serializability throughout all databases. However, with problems like message loss, node failure, and network partitioning, mobile environments make it hard to get estimations on the duration of a simple message exchange. In this article, we focus on the problem of setting up reasonable time-outs when guaranteeing atomicity for transaction processing within mobile ad-hoc networks, and we show the effect of setting up “wrong” time-outs on the transaction throughput and blocking time. Our solution, which does not depend on time-outs, shows a better performance in unreliable networks and remarkably reduces the amount of blocking.     

The virtual stuntman: dynamic characters with a repertoire of autonomous motor skills

An ambitious goal in the area of physics-based computer animation is the creation of virtual actors that autonomously synthesize realistic human motions and possess a broad repertoire of lifelike motor skills. To this end, the control of dynamic, anthropomorphic figures subject to gravity and contact forces remains a difficult open problem. In this paper, we report on our ongoing development of a virtual stuntman, a dynamic graphical character that possesses a nontrivial repertoire of lifelike motor skills. The repertoire includes basic actions such as balance, protective stepping when balance is disturbed, protective arm reactions when falling, multiple ways of rising upright after a fall, and several more vigorously dynamic motor skills. Our virtual stuntman is the product of a recently proposed framework for integrating motor controllers, which includes among other ingredients an explicit model of pre-conditions; i.e., those regions of a dynamic figure's state space within which a given motor controller is applicable and expected to work properly.     

The influence of build strategies in selective inhibition sintering (SIS)

Selective Inhibition Sintering of metal alloys (SIS-metal) has been proven effective in the additive manufacture (AM) of low resolution bronze parts. Recent advancements in the use of a high-precision inkjet print head represented an order of magnitude improvement in SIS-metal resolution. However, the fabrication of complex three-dimensional metallic parts required new SIS-metal compatible, cross-sectional image generation based on the part boundary profile. In the proposed study, five candidate layer-processing approaches were identified and validated for basic geometries. These approaches were chosen from previous research as well as preliminary investigations and were applied to a modified SIS-metal process for validation. The validation criteria were based upon the amount of powder waste produced, the ability to handle complex geometries, printing speed, extraction (post-processing) speed, and part integrity. Results are discussed for implementation of the five candidate layer processing approaches in the fabrication of basic shapes. A preliminary evaluation is presented for their use on more complex geometries. Two approaches were then chosen for the construction of more complex geometries, the results of which are presented.     

Towards energy efficiency in virtual topology design of elastic optical networks

Elastic optical networks offer a reliable platform for achieving energy efficiency by supporting extensive optical grooming of variable‐rate data traffic along with the traditional electrical data aggregation methods. The procedure of routing and spectrum allocation in a topology of nodes has explicit effect to the amount of consumed power. A new energy‐efficient method for designing the virtual topology in IP‐over‐elastic networks is introduced and evaluated. It is concluded that it consumes less power under different elastic transponder types, it designs the virtual topology using fewer transponders, and finally, there is a slight increase in the number of end‐to‐end lightpath hops. The proposed method is characterized by high performance and low lightpath establishment complexity. Therefore, it is suitable for a broad range of network configurations and transponder types.     

Optimal and control of hybrid multirate systems

The problem of using a synchronous multirate digital controller for a continuous-time plant is considered. The performance objectives considered are the H^∞ and the H² norms of the periodically time-varying continuous-time input-output behavior of the closed loop system. A continuous-time lifting technique is used to solve these hybrid sampled-data problems. This approach yields equivalent purely discrete-time problems while preserving the multirate causality of the systems. The later problems can then be solved using known techniques.     

Development and Evaluation of a High Loading PM2.5 Speciation Sampler

A high loading sampler for the chemical characterization of fine particles (PM _2.5 ) was developed and validated through laboratory and field experiments. This speciation sampler consists of two identical serially connected impaction stages to remove particles larger than 2.5 μm, following by a chamber to allow use of one or two all-glass honeycomb diffusion denuders, and a holder for a 47 mm filter. Two configurations of the sampler allow sampling at flows of 10 lpm and 16.7 lpm. System performance was evaluated in laboratory experiments using artificially generated polydisperse aerosols. This novel sampler provides a much larger mass loading capacity than previous impactors that use flat, rigid substrate surfaces. The polyurethane foam (PUF) substrate maintains adequate performance characteristics (retention of size cut-off, sharpness of cut-off curve, and minimal particle bounce and re-entrainments) at loadings of at least 35 mg. This is equivalent to 728 μg/m³ for a 48 h sampling period (or 500 h of sampling at 70 μg/m³). System performance was also evaluated in a series of field intercomparison experiments for both flow configurations (10 and 16.7 lpm). Measurements of PM _2.5 mass and sulfate concentrations showed excellent agreement between the US EPA Federal Reference Method (FRM) Sampler and the speciation sampler.     

Sampling Conditions for the Measurement of Nucleation Mode Particles in the Exhaust of a Diesel Vehicle

A novel porous tube diluter was characterized to define sampling parameters for repeatable measurements of nucleation-mode particles (NMPs) in the exhaust of a modern diesel passenger car at moderate engine load. This porous tube diluter permits the variation of sampling parameters independently and in a wide range. We investigated the sampling parameters: primary dilution temperature (PDT; 15–55°C), primary dilution ratio (PDR; 8–45), residence time (RT; 0.5–4.0 s), and relative humidity of primary dilution (PRH; 5–90%). Decreased PDT and increased PRH led to a growth of particle number and size in the nucleation mode. While a maximum number of NMPs was found at moderate PDRs between 20 and 30, a maximum volume of NMPs was achieved at PDRs below 20. Coagulation explains the number reduction of NMPs under sampling conditions of prolonged RT and decreased PDR. However, the size growth of the nucleation mode can only partly be attributed to coagulation, and thus growth due to organic compounds from the exhaust probably plays an important role. Sensitivity analysis was conducted as a function of PDR-PDT and revealed two optimal sampling conditions for repeatable NMPs in number or repeatable maximum NMPs in volume. In addition to the sampling parameters, exhaust line conditioning was found to affect NMPs strongly and thus needs to be controlled to minimize effects on the history of measurements.     

Inertial Separation of Ultrafine Particles Using a Condensational Growth/Virtual Impaction System

ABSTRACT

A system for the separation of ultrafine particles (i.e., particles smaller than 0.1 μm) has been developed and evaluated. Ultrafine particles are first grown by means of supersaturation to a size that can be easily separated in a virtual impactor. Thus, inertial separation of ultrafine particles occurs without subjecting them to a high vacuum. The condensational growth/virtual impaction system has been evaluated using monodisperse 0.05 and 0.1 μm fluorescent PSL particles, as well as polydisperse ultrafine ammonium sulfate and potassium nitrate aerosols. The generated aerosols were first drawn over a pool of warm water (50°C) where they became saturated. Subsequently, the saturated aerosol was drawn through a cooling tube (8°C) where particles grew due to supersaturation to sizes in the range 1.0–4.0 μm. By placing a virtual impactor with a theoretical 50% cutpoint of 1.4 μm downstream of the condenser, ultrafine particles were separated from the majority (i.e., 90%) of the surrounding gas. The sampling flow rate of the virtual impactor was 8 L/min and its minor-to-total flow ratio was 0.1. For these operating conditions, the particle collection efficiency of the virtual impactor averaged to about 0.9 for particle concentrations in the range 7 × 10⁴-5 × 10⁵ particles/cm³. Particle losses through the system were found less than 5%. Increasing the particle concentration to levels in the range 106–107 particles/cm³ resulted in a decrease in the collection efficiency of the virtual impactor to about 50–70%, presumably due to the smaller final droplet size to which the ultrafine particles grew for the available supersaturation.