Random Incidence Research Articles

Worst Case and Statistics of Waveforms Involved in Wideband Intentional Electromagnetic Attacks

This work is concerned with the assessment of radiated susceptibility of a victim system subject to wideband, intentional electromagnetic interference. It is shown that the high-power electromagnetic (HPEM) pulses giving rise to worst-case interference, according to predefined susceptibility criteria, can be readily determined thanks to a reciprocity-based approach. Particularly, for a specified bandwidth and energy density, the worst-case HPEM pulse waveform maximizing the voltage peak induced across an electric port is found by solving an optimization problem. The solution requires a single full-wave simulation of the victim system, treated as an unintentional radiator, to find its input impedance and radiation pattern. A repeated-run analysis involving limited computational burden allows obtaining the statistics of the worst-case HPEM signal for random incidence and polarization. In order to exemplify the proposed theory and results, the case of a hyperband pulse impinging onto a system composed of two units interconnected by a wiring harness is addressed.

Design of a new test chamber to measure the absorption, diffusion, and scattering coefficients

This presentation will describe the design for a new 384 m3 test chamber that will allow the measurement of the random incidence absorption coefficient, according to ISO 354, the scattering coefficient, according to ISO 17497-1, the diffusion coefficient, according to ISO 17497-2 and the normal incidence low frequency absorption coefficient, according to ISO 10534-2. The rev room design incorporates optimal modal dimensional ratios in accordance with (T. Cox, P. D’Antonio & Avis, J. Audio Eng. Soc. Vol. 52, No. 6 (June 2004)), both boundary and hanging panel diffusers to allow satisfactory diffusivity, in collaboration with the research at DTU. Diffusivity will be verified using a reference absorber, consisting of 100 mm porous absorber with a 100 mm cavity. A sufficiently large reflection free volume is provided in the chamber for diffusion coefficient scale model measurements. The diffusion goniometer and 12 m2 absorber samples are rotated in accordance with test. Scattering coefficient measurements are made according the ISO 17497-2 and the correlation method, using correlated polar responses. A steel and concrete lined low frequency impedance tube measuring 600 mm x 600 mm x 5.8 m long and 7 tons will be used to measure absorption from 25 to 250 Hz.

Sound transmission loss through triple-walled cylindrical shells with porous layers.

Sound transmission loss through triple-walled sandwich cylindrical shells in the presence of an external mean flow is analytically examined. Love's theory and a simplified method based on Biot's theory are considered to describe the motions of thin isotropic shells and wave propagation in the porous material cores, respectively. The random incidence transmission loss in a diffuse field is calculated numerically by considering the limiting incidence angle due to the total internal reflection. The analytical model and numerical code are validated against both experimental and analytical results reported by previous studies. The transmission loss of triple-walled structure in the diffuse sound field is compared with its double-walled counterpart at the same weight. The results generally show a superior performance in the sound insulation for the triple-walled shell, considerably at mid-high and high frequencies, in comparison with its double-walled counterpart at the same weight. The effects of sandwich shell configuration and air gap depth are also investigated on the sound transmission loss.

How Often Do Safety Signals Occur by Chance in First-in-Human Trials?

Clinicians working on first‐in‐human clinical studies need to be able to judge whether safety signals observed on an investigational drug were more likely to have occurred by chance or to have been caused by the drug. We retrospectively reviewed 84 Novartis studies including 1,234 healthy volunteers receiving placebo to determine the expected incidence of changes in commonly measured laboratory parameters and vital signs, in the absence of any active agent. We calculated the frequency of random incidence of safety signals, focusing on the liver, cardiovascular system, kidney, and pancreas. Using the liver enzyme alanine aminotransferase (ALT) as an example, we illustrate how a predictive model can be used to determine the probability of a given subject to experience an elevation of ALT above the upper limit of the normal range under placebo, conditional on the characteristics of this subject and the study.

Iron status in relation to cancer risk and mortality: Findings from a population‐based prospective study

While experimental evidence suggests potential carcinogenic effects of increased iron load, there is a lack of data on iron status and cancer risk from epidemiological studies. Here, we evaluated prediagnostic serum concentrations of ferritin, iron and transferrin as well as transferrin saturation (TSAT) in relation to cancer risk and mortality in a prospective study by multivariable Cox regression analyses. A case-cohort sample of the population-based EPIC-Heidelberg Study including a random subcohort (n = 2738) and incident cases of breast cancer (n = 627), prostate cancer (n = 554), lung cancer (n = 195), colorectal cancer (n = 256) and cancer death (n = 759) was used. Ferritin levels were inversely associated with breast cancer risk in the multivariable Cox regression model, with a hazard ratio (HR) of 0.67 [95% confidence interval: 0.49, 0.92] for women in the highest quartile compared to those in the lowest quartile. Neither ferritin nor the other markers of iron status were significantly associated with colorectal, prostate or lung cancer risk. An inverse association was observed between ferritin and total cancer mortality (HR: 0.70 [0.53, 0.92]). There were no significant overall associations between serum iron, transferrin or TSAT and cancer mortality. The present findings do not support the notion of increased iron load constituting a cancer risk factor in the general population. By contrast, our analyses revealed inverse associations between ferritin levels and breast cancer risk as well as cancer mortality.

The effect of nature of porous material on diffuse field acoustic transmission of the sandwich aerospace composite doubly curved shell

This paper investigates a diffuse acoustic field to analyze the wave propagation on infinite doubly curved laminated composite shell sandwiching a porous material which is extensively used in aerospace structures. In fact, the main goal is to study the influence of embedded porous core on Sound Transmission Loss (STL) of the structure. Accordingly, Biot's theory is employed to model the poroelastic material which considers three types of wave propagation including two compression and one shear terms. In addition, Shear Deformation Shallow Shell Theory (SDSST) is applied to derive the wave propagation through double-walled laminated composite shell. Moreover, a numerical process is prepared to investigate a random incidence STL in a diffuse acoustic field which results in presenting the Limiting angle of incidence in which no incident wave is transmitted through structure. Then, in order to show the accuracy and the reliability of the present results, some comparisons are made between the achieved results and those of analytical as well as experimental results available in literature. Besides, the importance of using porous material as a core has been presented. Finally, some effective parameters have been studied in numerical results to inspect the insulation property of the current composite structure.

Fatigue Damage Mechanism-Based Dependent Modeling With Stochastic Degradation and Random Shocks

This paper proposes a dependent modeling method for reliability estimation of metal structures under constant amplitude loading and random shocks considering the nonlinear damage accumulation mechanism. It is well known that a large monotonic plastic zone ahead of a crack tip caused by a spike overload will retard subsequent fatigue crack growth. However, most existing degradation-and-shock dependent models cannot account for this retardation phenomenon. Moreover, the increase in damage caused by shock is usually assumed to be independent of fatigue degradation. In this investigation, both fatigue degradation and applied random shock damage are considered to have a coupled effect on the crack propagation process. The nonlinear damage superposition approach is utilized herein to model the interaction between fatigue loading and random shocks. Fatigue degradation is considered as a stochastic process influenced by the uncertainties in material properties, and the applied shocks are regarded as random incidents. Next, the piecewise deterministic Markov process is employed to describe the coupling relationship between this stochastic degradation and the random shock process. In the proposed algorithm, Paris’ equation is utilized to describe fatigue degradation, and the Willenborg model is employed to describe retardation caused by random shock loads. A simulation is performed to validate the proposed method, and the proposed method is compared with the traditional method.

Epidemiological Characteristics of Traumatic Spinal Cord Injury (TSCI) in the Middle-East and North-Africa (MENA) Region: A Systematic Review and Meta-Analysis.

To systematically search the literature and to summarize current evidence pertaining to the epidemiology of SCI in the MENA region incidence, gender, age, type of the injury and etiology of the injury. Embase, PubMed, Scopus, Web of Science and EBSCOhost were systematically searched from their dates of inception till July 2017 for English and non-English language articles. Also, regional databases were searched. Data were extracted from eligible articles and pooled under the random effect model using R. References of the included articles were also screened for potentially relevant studies. We identified 29 articles from seven countries in the MENA region (Turkey, Iran, Saudi Arabia, Egypt, Jordan, Kuwait and Qatar). The mean age of the cases at time of injury was 31.32 (95% CI: 28.74-33.91). The random pooled annual incidence of TSCI per million was 23.24 (95% CI: 5.64-49.21). Pooled proportion of male gender was 77% (95% CI 73-80%) of the cases. Complete paraplegia was the most common type of injury. Thoracic level injury predominated. Also, the most commonly affected age group was 20-29 then 30-39. Motor vehicle accidents were found to be the leading cause of injury, then falls, gunshot, violence and sports. Further meta-regression analysis showed no association between age and etiology of the injury. This review shows lack of evidence about SCI in most countries of the MENA region. More epidemiological studies are needed.

Red meat consumption and risk of cardiovascular diseases—is increased iron load a possible link?

High iron load and red meat consumption could increase the risk of cardiovascular diseases (CVDs). As red meat is the main source of heme iron, which is in turn a major determinant of increased iron load, adverse cardiometabolic effects of meat consumption could be mediated by increased iron load. The object of the study was to assess whether associations between red meat consumption and CVD risk are mediated by iron load in a population-based human study. We evaluated relations between red meat consumption, iron load (plasma ferritin), and risk of CVD in the prospective EPIC-Heidelberg Study using a case-cohort sample including a random subcohort (n = 2738) and incident cases of myocardial infarction (MI, n = 555), stroke (n = 513), and CVD mortality (n = 381). Following a 4-step mediation analysis, associations between red meat consumption and iron load, red meat consumption and CVD risk, and iron load and CVD risk were assessed by multivariable regression models before finally testing to which degree associations between red meat consumption and CVD risk were attenuated by adjustment for iron status. Red meat consumption was significantly positively associated with ferritin concentrations and MI risk [HR per 50 g daily intake: 1.18 (95% CI: 1.05, 1.33)], but no significant associations with stroke risk and CVD mortality were observed. While direct associations between ferritin concentrations and MI risk as well as CVD mortality were significant in age- and sex-adjusted Cox regression models, these associations were substantially attenuated and no longer significant after multivariable adjustment for classical CVD risk factors. Strikingly, ferritin concentrations were positively associated with a majority of classical CVD risk factors (age, male sex, alcohol intake, obesity, inflammation, and lower education). Increased ferritin concentrations may be a marker of an overall unfavorable risk factor profile rather than a mediator of greater CVD risk due to meat consumption.

Assessment of the Prevalence of Vascular Anomalies of the Circle of Willis Based on the Autopsy of Cadavers in Kurdish Race Between 2016 and 2017.

Introduction:Cerebral arterial variations are commonly associated with cerebrovascular disease and should be considered during brain surgeries. Since some cerebrovascular diseases are seen in certain breeds, it seems that different distributions of cerebral arterial variations depend on race.Aim:The aim of this study was to determine the random incidence of vascular anomalies of the circle of Willis in autopsy of the cadavers.Material and Methods:In this study, 107 autopsy cadavers were examined. The brain was removed from the skull through standard autopsy procedures and with great care, the circles of Willis were evaluated, their main branches were accurately dissected, their anatomy was examined using a glass plate and variations were recorded.Results:The mean age of the cadavers was 57.77 years, and 72.9% of them were male. The forms of circle of Willis of the cadavers were categorized according to the Lazort classification, from which 48.6% had form 1,39.3% form 4, and 12.1% form 6. Out of all patients, 51.4% had hypoplasia and 67.3% had asymmetry. There was a significant relationship between asymmetric incidence and the age of cadavers, the incidence of hypoplasia and sex of the cadavers, and the forms of the circle of Willis and the diameter of segment (p<0.05).Conclusion:Due to the high incidence of asymmetry (67.3%) and hypoplasia (51.5%), it seems necessary to perform a complete review of the details of cerebrovascular anatomy in any surgical intervention around the circle of Willis, especially in vascular lesions of this area.

Sound absorption performance of natural kenaf fibres

In recent years, kenaf fibre has been highlighted for its superiority as the filler for composite materials. However, study of the fibres as an acoustic absorber is still lacking. In this paper, the sound absorption of kenaf fibre specimens are studied both under normal and random sound incidence. The normal-incidence sound absorption coefficient measurement was conducted using the impedance tube method. The effects of thickness involving full fibre and air-fibre specimen and the effect of bulk density were discussed. For the random-incidence sound absorption coefficient, the test was conducted in a reverberation chamber. From both methods, the results in general reveal that for bulk density of 140–150kg/m3 and thickness of 25–30mm, the absorption coefficient is above 0.5 starting from 500Hz and can reach 0.85 on average above 1.5kHz. These frequency bandwidth of absorption and the level of absorption coefficient improve significantly when bulk density and thickness are increased. Additional air gap also improve the absorption toward lower frequency.

METHODOLOGICAL FEATURES FOR RESTRAINING THREATS TO ORGANIZATIONS

Methodological features of an original model for restraining threats to organizations are presented in this paper. It is worked out in three sections. Conceptual fundamentals of the model for restricting threats are clarified in the first section. Instruments of the model for restricting threats are presented in the second section. These are focus groups, an open investigation by questionnaires, and confidence intervals with four evaluations, fuzzy trapezoidal numbers, fuzzy expertons, fuzzy random incidence matrices and aggregate licensing board of threats to the organization. Stages and procedures of the model for restricting threats are explained in the third section of the paper.

Welding failure examination on a fuel tank of a 650 cm3 motorbike

Abstract The failure of a motorbike fuel tank was investigated. Leakage of fuel was detected on the stabilizing subassembly at the front side of the base. The main container was replaced. The new container ended up leaking as well after only four months of use, proving that the failure was not a random incident. The study comprises visual examination, non-destructive testing by penetrant liquids, microhardness measurements and chemical analysis. Welded samples of the leakage area were investigated from macroscopic and microscopic perspective. The microstructure was analyzed by optical and scanning electron microscopy. Welding defects were found on the failure area. Most of them could be associated to inappropriate welding parameters. Hairline cracks were detected on resistance spot welding points. The cracks originated approximately at the center of the weld nugget, propagated through the weld zone, pierced the welding interface and reached the opposite sheet surface. Findings indicated interfacial failure mode. Poor welding process is considered the main cause of the failure and the specific sequence should be improved. Detailed practice recommendations and rigorous inspection are required to assure tank integrity. The tank tightness is of pivotal importance for the safe operation of the engine, the safety of passengers and protection of the environment.

様々な吸音率測定方法 : 垂直入射吸音率,斜め入射吸音率,残響室法吸音率の違い(やさしい解説)

様々な吸音率測定方法 : 垂直入射吸音率,斜め入射吸音率,残響室法吸音率の違い(やさしい解説)

Blocking oblique wave sound transmission through a multi-element barrier using alternate resonance tuning

Alternate Resonance Tuning (ART) utilizes a structural barrier subdivided into dynamic panel subsystems with different resonant behaviors. The underlying idea involves adjacent panel subsystems tuned differently to take advantage of the outofphase vibratory behavior, causing the 180° phase shift at different frequencies. In the intermediate range between the two resonance frequencies, the panels vibrate out of phase, leading to strong cancellation of the transmitted sound field. The method has been demonstrated analytically and experimentally for waves striking a barrier at normal incidence. The current work considers the effectiveness of ART to block the transmission of incident oblique waves, and considers both discrete frequencies and angles, and more realistic broadband random incidence fields. The research goal is to show that flexibility and controlled resonant behavior in subsystems can substantially block sound transmission, even for low structural damping. The subsystems alter the vibrating surface wavenumber spectra to reduce coupling between the structure and the acoustic field. Not only is the transmission of incident oblique waves reduced, but the transmitted and reflected waves radiate at a variety of angles due to the modification of the surface wavenumber spectrum. Applications include the development of lightweight flexible sound blocking barriers for vehicles and architectural spaces.

More than just a Green Facade: The sound absorption properties of a vertical garden with and without plants

Up to 44% of EU residents are exposed to noise levels that are detrimental to health. In this context, vertical gardens could play an important role in architectural acoustics, where the main absorber material is the substrate soil. Plants have a beneficial effect for higher frequencies when planted in a large density. In this paper a vertical garden design developed at the Pontificia Universidad Católica of Ecuador (PUCE) was tested for interior acoustic design. The modules solely with substrate and planted with ferns were tested. The objective was to ascertain and explain the random incidence sound absorption coefficient of vertical garden modules. 50 modules making up a total floor area of 10.125 m2 were used for the measurements. Six different configurations were measured: connected versus dispersed and directly on the floor versus with an air cavity of 5 and 10 cm. Furthermore, each configuration was tested with modules solely filled with substrate and with substrate filled modules with densely planted ferns. The weighted random incidence sound absorption coefficient of the modules densely planted with ferns equals 1.00. This applied to all different configurations tested. The sound absorption coefficient in the lower frequencies (100–315 Hz), mid frequencies (400–1250 Hz) and high frequencies (1600–5000 Hz) was 0.59–0.80, 1.00 and 1.00 respectively. This makes this type of building technology highly suitable for applications where sound needs to be attenuated, paving the way for applying vertical garden systems as a design tool for improving the acoustics of indoor spaces or urban squares.

Intriquer traditions et émergence de nouveau

La description du moi inconscient élaboratif est analysée au regard des travaux de Freud et de Bion. La dimension heuristique est illustrée par des rêves de patients du rapporteur Michèle Van Lysebeth-Ledent. Ils succèdent à la survenue, chez l’analyste, d’incidents aléa-toires notamment à l’occasion de séparations. Cette recherche s’inscrit dans un courant psy-chanalytique contemporain qui souligne la non-linéarité des processus et les facultés auto-organisatrices de la psyché. Il en résulte une intrication, créatrice de nouveau, entre les découvertes des pionniers et les apports originaux qui s’appuient sur la notion de complexité, inconnue par Freud au moment de l’éclosion de la psychanalyse. Nouveauté et traditions se-raient alors enchevêtrées.

Determination of boundary conditions for room acoustics simulation by application of inverse calculation models

Simulation models for room acoustics simulation usually promise to deliver precise results for a certain frequency range. However, correct results can only be guaranteed if accurate input parameters are provided. Standardized methods for the determination of boundary conditions, the impedance tube and the reverberation chamber, include measurement uncertainties which might lead to different simulation results. These measurement methods also only capture valid results for special situations, e.g., normal or random wave incidence. This insufficient description of the boundary conditions makes it challenging to validate simulation models by comparing them to measured results. Even for rather simple room acoustic situations, state-of-the-art simulations fail to match measurements using in-situmeasurements or textbook values for the boundary conditions. In geometrical acoustics, these deviations can not only explained by insufficient measurement methods for the input data but also by different handling of reflection, scattering, and diffraction. To resolve the mismatch between measured and simulated results, optimization concepts have been proposed to determine input parameter sets for the simulation models. This work discusses two inverse approaches, evaluates their practicability for typical room acoustic scenarios, and presents the application in a comparison of room acoustic simulation software, the international round robin of auralization.

Cross-sectional surveys: Inferring total eventual time in current state using only elapsed time-to-date

We focus on snapshot surveying of sub-populations whose members are in a temporary state and where one of the questions asked is the elapsed time already spent in that state. From these answers we develop probabilistic and statistical procedures to estimate the distribution of total time that will eventually be spent in that state by any random individual who enters the state. The method relies on a selection bias often found in temporal sampling, sometimes called “random incidence” or “longevity bias.” We develop results for several types of sampling, including random and fixed times of surveying, random and fixed times of entering the state, and sampling only those who have already spent some minimal specified time in the targeted state. An example with post-doc data is included to demonstrate the steps.

Approaching a methodology for the development of a multilayer sound absorbing device recycling coal bottom ash

The aim of the present work has been to develop a methodology which accurately predicts the acoustic behavior of a material without having to manufacture large panels and testing them in reverberation room. Moreover, it can be predicted the sound absorbing performance at normal and random incidence of the sound wave on a material for different thicknesses and multilayer configurations, dramatically reducing the number of experimental tests. This methodology might decrease the cost of the investigation, which is particularly important when dealing with recycled materials that must compete with commercial products used in the same application.The designed methodology consists of determining the acoustic intrinsic properties (open porosity, tortuosity and static airflow resistivity) of bottom ash-based concretes with different particle sizes by an indirect method. This method uses the acoustic absorption coefficient measurements obtained in the impedance tube and the mathematical equations that describe the acoustic behavior of porous materials, implemented in the software CARAM. With the intrinsic properties, the thickness of the panel and the vibroacoustic behavior simulation software SIMAM, simulations of the sound absorption coefficient are performed and compared to the experimental results at normal incidence in the impedance tube and at diffuse incidence of a multilayer panel tested in reverberation room.From the results obtained it can be concluded that the methodology proposed in this work gives accurate results of the acoustic absorption of products at industrial scale, with the advantages of requiring small specimens of the materials to carry out the characterization tests, and decreasing the total cost of the investigation.