Theoretical and experimental characterisation of energy in an electrostatic discharge

Electrostatic discharges have been identified as the most likely cause in a number of incidents of fire and explosion with unexplained ignitions. The lack of data and suitable models for this ignition mechanism creates a void in the analysis to quantify the importance of static electricity as a credible ignition mechanism. Quantifiable hazard analysis of the risk of ignition by static discharge cannot, therefore, be entirely carried out with our current understanding of this phenomenon. The study of electrostatics has been ongoing for a long time. However, it was not until the wide spread use of electronics that research was developed for the protection of electronics from electrostatic discharges. Current experimental models for electrostatic discharge developed for intrinsic safety with electronics are inadequate for ignition analysis and typically are not supported by theoretical analysis. A preliminary simulation and experiment with low voltage was designed to investigate the characteristics of energy dissipation and provided a basis for a high voltage investigation. It was seen that for a low voltage the discharge energy represents about 10% of the initial capacitive energy available and that the energy dissipation was within 10 ns of the initial discharge. The potential difference is greatest at the initial break down when the largest amount of the energy is dissipated. The discharge pathway is then established and minimal energy is dissipated as energy dissipation becomes greatly influenced by other components and stray resistance in the discharge circuit. From the initial low voltage simulation work, the importance of the energy dissipation and the characteristic of the discharge were determined. After the preliminary low voltage work was completed, a high voltage discharge experiment was designed and fabricated. Voltage and current measurement were recorded on the discharge circuit allowing the discharge characteristic to be recorded and energy dissipation in the discharge circuit calculated. Discharge energy calculations show consistency with the low voltage work relating to discharge energy with about 30-40% of the total initial capacitive energy being discharged in the resulting high voltage arc. After the system was characterised and operation validated, high voltage ignition energy measurements were conducted on a solution of n-Pentane evaporating in a 250 cm3 chamber. A series of ignition experiments were conducted to determine the minimum ignition energy of n-Pentane. The data from the ignition work was analysed with standard statistical regression methods for tests that return binary (yes/no) data and found to be in agreement with recent publications. The research demonstrates that energy dissipation is heavily dependent on the circuit configuration and most especially by the discharge circuit's capacitance and resistance. The analysis established a discharge profile for the discharges studied and validates the application of this methodology for further research into different materials and atmospheres; by systematically looking at discharge profiles of test materials with various parameters (e.g., capacitance, inductance, and resistance). Systematic experiments looking at the discharge characteristics of the spark will also help understand the way energy is dissipated in an electrostatic discharge enabling a better understanding of the ignition characteristics of materials in terms of energy and the dissipation of that energy in an electrostatic discharge.

Nonlinear mechanical property of tracheal cartilage: A theoretical and experimental study

Background: Despite being the stiffest airway of the bronchial tree, the trachea undergoes significant deformation due to intrathoracic pressure during breathing. The mechanical properties of the trachea affect the flow in the airway and may contribute to the biological function of the lung. Method: A Fung-type strain energy density function was used to investigate the nonlinear mechanical behavior of tracheal cartilage. A bending test on pig tracheal cartilage was performed and a mathematical model for analyzing the deformation of tracheal cartilage was developed. The constants included in the strain energy density function were determined by fitting the experimental data. Result: The experimental data show that tracheal cartilage is a nonlinear material displaying higher strength in compression than in tension. When the compression forces varied from -0.02 to -0.03 N and from -0.03 to -0.04 N, the deformation ratios were 11.03±2.18% and 7.27±1.59%, respectively. Both were much smaller than the deformation ratios (20.01±4.49%) under tension forces of 0.02 to 0.01 N. The Fung-type strain energy density function can capture this nonlinear behavior very well, whilst the linear stress-strain relation cannot. It underestimates the stability of trachea by exaggerating the displacement in compression. This study may improve our understanding of the nonlinear behavior of tracheal cartilage and it may be useful for the future study on tracheal collapse behavior under physiological and pathological conditions.

Which One Is Preferred: Myers-Saito Cyclization of Ene-Yne-Allene or Garratt-Braverman Cyclization of Conjugated Bisallenic Sulfone? A Theoretical and Experimental Study

A competitive scenario between Myers-Saito (MS) and Garraff-Braverman (GB) cyclization has been created in a molecule. High-level computations indicate a preference for GB over MS cyclization. The activation energies for the rate-determining steps of the GB and MS cyclizations were found to be the same (24.4 kcal/mol) at the B3LYP/6-31G* level of theory; thus, from the kinetic point of view, both reactions are feasible. However, the main biradical intermediate GB2 of the GB reaction is 6.2 kcal/mol lower in energy than the biradical MS2, which is the main intermediate of MS reaction, so GB cyclization is thermodynamically favored over MS cyclization. To verify the prediction by computational techniques, bisenediynyl sulfones 1-4 and bisenediynyl sulfoxide 17 were synthesized. Under basic conditions, these molecules isomerized to a system possessing both the ene-yne-allene and the bisallenic sulfone. The isolation of only one product, identified as the corresponding naphthalene- or benzene-fused sulfone 8-11, indicated the occurrence of GB cyclization as the sole reaction pathway. No product corresponding to the MS cyclization pathway could be isolated. Though the theoretical prediction showed a preference for the GB pathway over the MS pathway, the exclusive preference for GB over MS cyclization is very striking. Further analysis showed that the intramolecular self-quenching nature of the GB pathway may play an important role in the complete preference for this reaction. Apart from the mechanistic studies, these sulfones showed DNA cleavage activity that had an inverse relation with the reactivity order. Our findings are important for the design of artificial DNA-cleaving agents.

Theoretical and Experimental Studies on an Ammonia-Based Loop Heat Pipe With a Flat Evaporator

An ammonia loop heat pipe (LHP) with a flat plate evaporator is developed and tested. The device uses a nickel wick encased in an aluminum-stainless steel casing. The loop is tested for various heat loads and different sink temperatures, and it demonstrated reliable startup characteristics. Results with the analysis of the experimental observation indicate that the conductance between the compensation chamber and the heater plate can significantly influence the operating temperatures of the LHP. A mathematical model is also presented which is validated against the experimental observations.

Stereochemically constrained peptides. Theoretical and experimental studies on the conformations of peptides containing 1-aminocyclohexane carboxylic acid

Conformational energy calculations on the model system N-acetyl- 1 -aminocyclohexanecarboxylic acid N'methylamide (Ac-Acc6-NHMe), using an average geometry derived from 13 crystallographic observations, establish that the Acc6 residue is constrained to adopt conformations in the helical regions of In contrast, the a,a-dialkylated residue with linear hydrocarbon side chains, a,a-di-n-propylglycine favors fully extended backbone structures (6 1= $ = 180'). The crystal structures of two model peptides, Boc-(Acc6),-OMe (type 111 @-turn at -Acc6(1)-Acc6(2)-) and Boc-Pro-Acc6-Ala-OMe (type I1 P-turn at -Pro-Acc6-), establish that Acc6 residues can occupy either position of type 111 P-turns and the i + 2 position of type I1 @-turns. The stereochemical rigidity of these peptides is demonstrated in solution by NMR studies, which establish the presence of one intramolecular hydrogen bond in each peptide in CDCI, and (CDJ2S0. Nuclear Overhauser effects permit characterization of the @-turn conformations in solution and establish their similarity to the solid-state structures. The implications for the use of Acc6 residues in conformational design are considered.

Theoretical and experimental investigation of framed structure-layered soil interaction problems

The plane stress solution for the interaction analysis of a framed structure, with a foundation beam, resting on a layered soil has been studied using both theoretical and photoelastic methods. The theoretical analysis has been done by using a combined analytical and finite element method. In this, the analytical solution has been used for the semi-infinite layered medium and finite element method for the framed structure. The experimental investigation has been carried out using two-dimensional photoelasticity in which modelling of the layered semi-infinite plane and a method to obtain contact pressure distribution have been discussed. The theoretical and experimental results in respect of contact pressure distribution between the foundation beam and layered soil medium, the fibre stresses in the foundation beam and framed structure have been compared. These results have also been compared with theoretical results obtained by idealizing the layered semi-infinite plane as (a) a Winkler model and (b) an equivalent homogeneous semi-infinite medium

Theoretical and Experimental Evaluation of Pulsating Torque Produced by Induction Motor Drives Controlled With Advanced Bus-Clamping Pulsewidth Modulation

This paper investigates possible reduction of pulsating torque in open-loop and vector-controlled induction motor drives through deployment of certain advanced bus-clamping pulsewidth modulation (ABCPWM) method. Toward this goal, a simple and machine-independent method is proposed to analyze the torque harmonic spectrum of a voltage source inverter fed induction motor, operated with any real-time pulsewidth modulation (PWM) method. The analytically evaluated torque harmonic spectra, pertaining to conventional space vector PWM (CSVPWM), bus-clamping PWM (BCPWM), and ABCPWM, are validated through simulation and experimental results. Theoretical and experimental studies bring out the superiority of the ABCPWM in terms of torque harmonics over CSVPWM and BCPWM. The magnitude of the dominant torque harmonic with the ABCPWM scheme is shown to be significantly lower than that with CSVPWM, over a wide range of speed. The rms torque ripple (i.e., total rms value of all harmonic torques) is lower with ABCPWM than with BCPWM over the entire range of speed.

Theoretical and experimental studies of the bell-jar-top inductively coupled plasma

The present paper describes a systematic study of argon plasmas in a bell-jar inductively coupled plasma (ICP) source over the range of pressure 5-20 mtorr and power input 0.2-0.5 kW, Experimental measurements as well as results of numerical simulations are presented. The models used in the study include the well-known global balance model (or the global model) as well as a detailed two-dimensional (2-D) fluid model of the system, The global model is able to provide reasonably accurate values for the global electron temperature and plasma density, The 2-D model provides spatial distributions of various plasma parameters that make it possible to compare with data measured in the experiments, The experimental measurements were obtained using a tuned Langmuir double-probe technique to reduce the RF interference and obtain the light versus current (I-V) characteristics of the probe. Time-averaged electron temperature and plasma density were measured for various combinations of pressure and applied RF power, The predictions of the 2-D model were found to be in good qualitative agreement with measured data, It was found that the electron temperature distribution T-e was more or less uniform in the chamber, It was also seen that the electron temperature depends primarily on pressure, but is almost independent of the power input, except in the very low-pressure regime. The plasma density goes up almost linearly with the power input.

Theoretical and experimental researches of post-micro-buckling for fiber-reinforced composites

Post-microbuckling is a fundamental feature of compressive failure process for the unidirectional-fiber-reinforced composites and laminated composites. The post-microbuckling behavior of composites under compression in the light of the Kevlar49-reinforced 648/BF3.400 (brittle epoxy) and EP (flexible epoxy) is studied, theoretically and experimentally. Analytical results of compressive strength are in good agreement with experimental results, qualitatively and quantitatively. By the experimental research, the post-microbuckling feature of the advancing kink band model is clearly displayed.

Personal identity. A theoretical and experimental analysis

Published as article in: Journal of Economic Methodology, 2010, vol. 17, issue 3, pages 261-275.

Theoretical and experimental study on femtosecond laser induced damage in CaF2 crystals

We report on the damage threshold in CaF2 crystals induced by femtosecond laser at wavelengths of 800 nm and 400 nm, respectively. The dependences of ablation depths and ablation volumes on laser fluences are also presented. We investigate theoretically the coupling constants between phonon and conduction band electrons (CBE), and calculate the rates of CBE absorbing laser energy. A theoretical model including CBE production, laser energy deposition, and CBE diffusion is applied to study the damage mechanisms. Our results indicate that energy diffusion greatly influences damage threshold and ablation depth.