Reliability improvement of electronic circuits based on physical failure mechanisms in components

Traditionally the position of reliability analysis in the design and production process of electronic circuits is a position of reliability verification. A completed design is checked on reliability aspects and either rejected or accepted for production. This paper describes a method to model physical failure mechanisms within components in such a way that they can be used for reliability optimization, not after, but during the early phase of the design process. Furthermore a prototype of a CAD software tool is described, which can highlight components likely to fail and automatically adjust circuit parameters to improve product reliability

Fluid-structure interaction on the combustion instability

The multi-domain problem, the limit cycle behaviour of unstable oscillations in the LIMOUSINE model combustor has been investigated by numerical and experimental studies. A strong interaction between the aerodynamics-combustion-acoustic oscillations has been observed during the operation. In this regime, the unsteady heat release by the flame is the acoustic source inducing pressure waves and subsequently the acoustic field acts as a pressure load on the structure. The vibration of the liner walls generates a displacement of the flue gas near the wall inside the combustor which generates an acoustic field proportional to the liner wall acceleration. The two-way interaction between the oscillating pressure load in the fluid and the motion of the structure under the limit cycle oscillation can bring up elevated vibration levels, which accelerates the degradation of liner material at high temperatures. Therefore, fatigue and/or creep lead the failure mechanism. In this paper the time dependent pressures on the liner and corresponding structural velocity amplitudes are calculated by using ANSYS workbench V13.1 software, in which pressure and displacement values have been exchanged between CFD and structural domains transiently creating two-way fluid-structure coupling. The flow of information is sustained between the fluid dynamics and structural dynamics. A validation check has been performed between the numerical pressure and liner velocity results and experimental results. The excitation frequency of the structure in the combustor has been assessed by numerical, analytical and experimental modal analysis in order to distinct the acoustic and structural contribution

Sensitivity of combustion driven structural dynamics and damage to thermo-acoustic instability: Combustion-acoustics-vibration

The dynamic combustion process generates high amplitude pressure oscillations due to the thermo-acoustic instabilities, which are excited within the gas turbine. The combustion instabilities have a significant destructive impact on the life of the liner material due to the high cyclic vibration amplitudes at elevated temperatures. This paper presents a methodology developed for mechanical integrity analysis relevant to gas turbine combustors and the results of an investigation of combustion-acoustics-vibration interaction by means of structural dynamics. In this investigation, the combustion dynamics was found to be very sensitive to the thermal power of the system and the air-fuel ratio of the mixture that feed into the combustor. The unstable combustion caused a dominant pressure peak at a characteristic frequency, which is the first acoustic eigenfrequency of the system. Besides, the higher-harmonics of this peak were generated over a wide frequency-band. The frequencies of the higher-harmonics were observed to be close to the structural eigenfrequencies of the system. The structural integrity of both the intact and damaged test specimens mounted to the combustor were monitored by vibration-based and thermal-based techniques during the combustion operation. The flexibility method was found to be accurate to detect, localize and identify the damage. Furthermore, a temperature increase was observed around the damage due to the hot gas leakage from the combustor that can induce detrimental thermal stresses to consume the lifetime

Bitloading with reduced computational complexity order for a multicarrier multimode PON

Nowadays, multicarrier transmission technique, e.g., optical OFDM, receives quite intense attention in the optical communications and networking field due to its potential to provide dispersion compensation. Adaptive modulation level is commonly and naturally employed in relation to multicarrier transmission, provided (sub)channel state information is available. The modulation level adaptation is usually done by a bitloading mechanism. In our work, given some modulation formats that are to be used, we attempt to reduce the computational complexity order of the bitloading algorithm from the one that has been presented in the literature. The bitloading algorithm is applied to a multicarrier multimode PON

Number of Patients Studied Prior to Approval of New Medicines: A Database Analysis

Background: At the time of approval of a new medicine, there are few long-term data on the medicine's benefit-risk balance. Clinical trials are designed to demonstrate efficacy, but have major limitations with regard to safety in terms of patient exposure and length of follow-up. This study of the number of patients who had been administered medicines at the time of medicine approval by the European Medicines Agency aimed to determine the total number of patients studied, as well as the number of patients studied long term for chronic medication use, compared with the International Conference on Harmonisation's E1 guideline recommendations. Methods and Findings: All medicines containing new molecular entities approved between 2000 and 2010 were included in the study, including orphan medicines as a separate category. The total number of patients studied before approval was extracted (main outcome). In addition, the number of patients with long-term use (6 or 12 mo) was determined for chronic medication. 200 unique new medicines were identified: 161 standard and 39 orphan medicines. The median total number of patients studied before approval was 1,708 (interquartile range [IQR] 968-3,195) for standard medicines and 438 (IQR 132-915) for orphan medicines. On average, chronic medication was studied in a larger number of patients (median 2,338, IQR 1,462-4,135) than medication for intermediate (878, IQR 513-1,559) or short-term use (1,315, IQR 609-2,420). Safety and efficacy of chronic use was studied in fewer than 1,000 patients for at least 6 and 12 mo in 46.4% and 58.3% of new medicines, respectively. Among t

Curci-Ferrari mass and the Neuberger problem

We study the massive Curci-Ferrari model as a starting point for defining BRST quantisation for Yang-Mills theory on the lattice. In particular, we elucidate this proposal in light of topological approaches to gauge-fixing and study the case of a simple one-link Abelian model.Comment: 10 pages, uses elsart.cls style file. Eq.(18) corrected for final publicatio