The numerical simulation of noncharring thermal degradation and its application to the prediction of compartment fire development

In this paper we present some work concerned with the development and testing of a simple solid fuel combustion model incorporated within a Computational Fluid Dynamics (CFD) framework. The model is intended for use in engineering applications of fire field modeling and represents an extension of this technique to situations involving the combustion of solid fuels. The CFD model is coupled with a simple thermal pyrolysis model for combustible solid noncharring fuels, a six-flux radiation model and an eddy-dissipation model for gaseous combustion. The model is then used to simulate a series of small-scale room fire experiments in which the target solid fuel is polymethylmethacrylate. The numerical predictions produced by this coupled model are found to be in very good agreement with experimental data. Furthermore, numerical predictions of the relationship between the air entrained into the fire compartment and the ventilation factor produce a characteristic linear correlation with constant of proportionality 0.38 kg/sm5/12. The simulation results also suggest that the model is capable of predicting the onset of "flashover" type behavior within the fire compartment.

Kappa calculus and evidential strength: A note on Åqvist's logical theory of legal evidence

Lennart Åqvist (1992) proposed a logical theory of legal evidence, based on the Bolding-Ekelöf of degrees of evidential strength. This paper reformulates Åqvist's model in terms of the probabilistic version of the kappa calculus. Proving its acceptability in the legal context is beyond the present scope, but the epistemological debate about Bayesian Law isclearly relevant. While the present model is a possible link to that lineof inquiry, we offer some considerations about the broader picture of thepotential of AI & Law in the evidentiary context. Whereas probabilisticreasoning is well-researched in AI, calculations about the threshold ofpersuasion in litigation, whatever their value, are just the tip of theiceberg. The bulk of the modeling desiderata is arguably elsewhere, if one isto ideally make the most of AI's distinctive contribution as envisaged forlegal evidence research.

Computational modelling of particle degradation in dilute phase pneumatic conveyors

The aim of this paper is to develop a mathematical model with the ability to predict particle degradation during dilute phase pneumatic conveying. A numerical procedure, based on a matrix representation of degradation processes, is presented to determine the particle impact degradation propensity from a small number of particle single impact tests carried out in a new designed laboratory scale degradation tester. A complete model of particle degradation during dilute phase pneumatic conveying is then described, where the calculation of degradation propensity is coupled with a flow model of the solids and gas phases in the pipeline. Numerical results are presented for degradation of granulated sugar in an industrial scale pneumatic conveyor.

Numerical predictions of particle degradation in industrial-scale pneumatic conveyors

This paper presents an Eulerian-based numerical model of particle degradation in dilute-phase pneumatic conveying systems including bends of different angles. The model shows reasonable agreement with detailed measurements from a pilot-sized pneumatic conveying system and a much larger scale pneumatic conveyor. The potential of the model to predict degradation in a large-scale conveying system from an industrial plant is demonstrated. The importance of the effect of the bend angle on the damage imparted to the particles is discussed.

Computational model for prediction of particle degradation during dilute phase pneumatic conveying: the use of a laboratory scale degradation tester for the determination of degradation propensity

The overall objective of this work is to develop a computational model of particle degradation during dilute-phasepneumatic conveying. A key feature of such a model is the prediction of particle breakage due to particle–wall collisions in pipeline bends. This paper presents a method for calculating particle impact degradation propensity under a range of particle velocities and particle sizes. It is based on interpolation on impact data obtained in a new laboratory-scale degradation tester. The method is tested and validated against experimental results for degradation at 90± impact angle of a full-size distribution sample of granulated sugar. In a subsequent work, the calculation of degradation propensity is coupled with a ow model of the solids and gas phases in the pipeline.

Computational model for prediction of particle degradation during dilute-phase pneumatic conveying: modeling of dilute-phase pneumatic conveying

A complete model of particle impact degradation during dilute-phase pneumatic conveying is developed, which combines a degradation model, based on the experimental determination of breakage matrices, and a physical model of solids and gas flow in the pipeline. The solids flow in a straight pipe element is represented by a model consisting of two zones: a strand-type flow zone immediately downstream of a bend, followed by a fully suspended flow region after dispersion of the strand. The breakage matrices constructed from data on 90° angle single-impact tests are shown to give a good representation of the degradation occurring in a pipe bend of 90° angle. Numerical results are presented for degradation of granulated sugar in a large scale pneumatic conveyor.

Wire bond reliability for power electronic modules - effect of bonding temperature

In this paper, thermal cycling reliability along with ANSYS analysis of the residual stress generated in heavy-gauge Al bond wires at different bonding temperatures is reported. 99.999% pure Al wires of 375 mum in diameter, were ultrasonically bonded to silicon dies coated with a 5mum thick Al metallisation at 25degC (room temperature), 100degC and 200degC, respectively (with the same bonding parameters). The wire bonded samples were then subjected to thermal cycling in air from -60degC to +150degC. The degradation rate of the wire bonds was assessed by means of bond shear test and via microstructural characterisation. Prior to thermal cycling, the shear strength of all of the wire bonds was approximately equal to the shear strength of pure aluminum and independent of bonding temperature. During thermal cycling, however, the shear strength of room temperature bonded samples was observed to decrease more rapidly (as compared to bonds formed at 100degC and 200degC) as a result of a high crack propagation rate across the bonding area. In addition, modification of the grain structure at the bonding interface was also observed with bonding temperature, leading to changes in the mechanical properties of the wire. The heat and pressure induced by the high temperature bonding is believed to promote grain recovery and recrystallisation, softening the wires through removal of the dislocations and plastic strain energy. Coarse grains formed at the bonding interface after bonding at elevated temperatures may also contribute to greater resistance for crack propagation, thus lowering the wire bond degradation rate

Shear strength analysis of ball grid array (BGA) solder interfaces

Ball shear test is the most common test method used to assess the reliability of bond strength for ball grid array (BGA) packages. In this work, a combined experimental and numerical study was carried out to realize of BGA solder interface strength. Solder mask defined bond pads on the BGA substrate were used for BGA ball bonding. Different bond pad metallizations and solder alloys were used. Solid state aging at 150degC up to 1000 h has been carried out to change the interfacial microstructure. Cross-sectional studies of the solder-to-bond pad interfaces was conducted by scanning electron microscopy (SEM) equipped with an energy dispersive X-ray (EDX) analyzer to investigate the interfacial reaction phenomena. Ball shear tests have been carried out to obtain the mechanical strength of the solder joints and to correlate shear behaviour with the interfacial reaction products. An attempt has been taken to realize experimental findings by Finite Element Analysis (FEA). It was found that intermetallic compound (IMC) formation at the solder interface plays an important role in the BGA solder bond strength. By changing the morphology and the microchemistry of IMCs, the fracture propagation path could be changed and hence, reliability could be improved

HPLC-ESI-MS method development for the elucidation of nicardipine degradation products

Purpose: Nicardipine is a member of a family of calcium channel blockers named dihydropiridines that are known to be photolabile and may cause phototoxicity. It is therefore vital to develop analytical method which can study the photodegradation of nicardipine. Method: Forced acid degradation of nicardipine was conducted by heating 12 ml of 1 mg/ml nicardipine with 3 ml of 2.5 M HCl for two hours. A gradient HPLC medthod was developed using Agilent Technologies 1200 series quaternary system. Separation was achieved with a Hichrome (250 x 4.6 mm) 5 μm C18 reversed phase column and mobile phase composition of 70% A(100%v/v water) and 30% B(99%v/v acetonitrile + 1%v/v formic acid) at time zero, composition of A and B was then charged to 60%v/v A;40%v/v B at 10minutes, 50%v/v A; 50%v/v B at 30minutes and 70%v/v A; 30%v/v B at 35minutes. 20μl of 0.8mg/ml of nicardipine degradation was injected at room temperature (25oC). The gradient method was transferred onto a HPLC-ESI-MS system (HP 1050 series - AQUAMAX mass detector) and analysis conducted with an acid degradation concentration of 0.25mg/ml and 20μl injection volume. ESI spectra were acquired in positive ionisation mode with MRM 0-600 m/z. Results: Eleven nicardipine degradation products were detected in the HPLC analysis and the resolution (RS) between the respective degradants where 1.0, 1.2, 6.0, 0.4, 1.7, 3.7, 1.8, 1.0, and 1.7 respectively. Nine degradation products were identified in the ESI spectra with the respective m/z ratio; 171.0, 166.1, 441.2, 423.2, 455.2, 455.2, 331.1, 273.1, and 290.1. The possible molecular formulae for each degradants were ambiguously determined. Conclusion: A sensitive and specific method was developed for the analysis of nicardipine degradants. Method enables detection and quantification of nicardipine degradation products that can be used for the study of the kinetics of nicardipine degradation processes.

Assessment of the degradation of Aspirin by Differential Scanning Calorimetry (DSC)

Purpose. To study thermal stability of Aspirin and define thermal events that are associated with the thermal degradation of aspirin. Methods. Experiments were performed using a DSC 823e (Mettler Toledo, Swiss). Aspirin is prone to thermal degradation upon exposure to high temperatures. The melting point of aspirin is 140.1±0.4ºC (DSC). Aspirin has been examined by heating samples to 120ºC, 155ºC and 185ºC with subsequent cooling to -55ºC and a final heating to 155ºC. Although different heating and cooling ranges have been used, only results obtained at a rate of 10ºC/min will be presented. All runs where conducted in hermetically sealed pans. Results. Upon heating the sample to 120ºC no significant thermal event can be detected. After cooling the sample and reheating a glass transition can be observed at ~-8ºC, followed by the melting of aspirin at ~139ºC. By heating the sample to 155ºC melting of aspirin has been detected at ~139ºC. On cooling and subsequent heating a glass transition occurs at ~-32ºC, together with a broad crystallisation (onset at ~38ºC and peak maximum at ~57ºC) followed by a broad melting with an onset at 94ºC and peak maximum at ~112ºC. Finally, by heating the sample to 185ºC melting at ~ 139ºC was observed, and upon cooling and reheating a glass transition was detected at ~-26ºC and no further events could be recorded. Conclusions. This research demonstrates that the degradation steps of Aspirin depend on the thermal treatment. The main degradation products of different thermal treatments are currently unknown it is clear that acetic acid, which is one of the degradation products, acts as an antiplasticiser by lowering the glass transition temperature. In addition, due to the presence of the degradation products in liquid form (observed by hot stage microscopy), Aspirin is still present in the sample and recrystallises during the second heating step and melts at much lower temperatures.

Caking strength of granulated clay under frozen conditions

Transport of particulate clay occurs during some extremely cold weather conditions typically in the winter in the far North area. During the transport and temporary storage time, the clay may cake inside a rail or road wagon or in a silo, and consequently be difficult to be discharged from the containers. This paper studied caking strength of a granulated clay powder with a certain water moisture content of 18% for influences of temperature, packing stress and freezing time. The temperature tested was -5 oC, -10 oC and -20 oC. Because the clay powder may be packed at different bed depth, the study was undertaken across the packing stress range at 8.3 kPa (1 m bed depth), 25.0 kPa (3 m) and 75.0 kPa (9 m). Freezing time varied between 4 hours (transport) and 18 hours (overnight). During the tests, failure of caked materials was measured using a QTS texture analyzer and the caking strength of frozen samples was calculated. Influences on freeze caking of granular clay in storage or transport are discussed briefly. Some conclusions are made at the end of the paper,including recommendations for practical methods for mitigating these problems.

Evaluation of particle degradation due to high-speed impacts in a pneumatic handling system

Particle degradation can be a significant issue in particulate solids handling and processing, particularly in pneumatic conveying systems, in which high-speed impact is usually the main contributory factor leading to changes in particle size distribution (comparing the material to its virgin state). However, other factors may strongly influence particles breakage as well, such as particle concentrations, bend geometry,and hardness of pipe material. Because of such complex influences, it is often very difficult to predict particle degradation accurately and rapidly for industrial processes. In this article, a general method for evaluating particle degradation due to high-speed impacts is described, in which the breakage properties of particles are quantified using what are known as "breakage matrices". Rather than a pilot-size test facility, a bench-scale degradation tester has been used. Some advantages of using the bench-scale tester are briefly explored. Experimental determination of adipic acid has been carried out for a range of impact velocities in four particle size categories. Subsequently, particle breakage matrices of adipic acid have been established for these impact velocities. The experimental results show that the "breakage matrices" of particles is an effective and easy method for evaluation of particle degradation due to high-speed impacts. The possibility of the "breakage matrices" approach being applied to a pneumatic conveying system is also explored by a simulation example.

Prediction of reinforcement corrosion in concrete and its effects on concrete cracking and strength reduction

Based on extensive research on reinforcing steel corrosion in concrete in the past decades, it is now possible to estimate the effect of the progression of reinforcement corrosion in concrete infrastructure on its structural performance. There are still areas of considerable uncertainty in the models and in the data available, however This paper uses a recently developed model for reinforcement corrosion in concrete to improve the estimation process and to indicate the practical implications. In particular stochastic models are used to estimate the time likely to elapse for each phase of the whole corrosion process: initiation, corrosion-induced concrete cracking, and structural strength reduction. It was found that, for practical flexural structures subject to chloride attacks, corrosion initiation may start quite early in their service life. It was also found that, once the structure is considered to be unserviceable due to corrosion-induced cracking, there is considerable remaining service life before the structure can be considered to have become unsafe. The procedure proposed in the paper has the potential to serve as a rational tool for practitioners, operators, and asset managers to make decisions about the optimal timing of repairs, strengthening, and/or rehabilitation of corrosion-affected concrete infrastructure. Timely intervention has the potential to prolong the service life of infrastructure.