Barrier Attenuation Research Articles

Geometric optimization for localized attenuation of subsonic slit-based open acoustic barriers

In recent years, many solutions have been developed to reduce noise from different sources. One of these solutions is acoustic barriers. An acoustic barrier is a structure designed to reduce noise transmission between areas by blocking the direct path of sound. Open acoustic barriers are a valuable solution for technical and industrial plants. They allow airflow and visibility. Given the need for localized attenuation in these environments, it is possible to use numerical models to improve effectiveness and thus increase insertion loss in a region of interest. This study has used numerical simulation tools to provide degrees of freedom in placing the different elements of a subsonic slit-based open barrier. It has been shown that by rotating some of the elements and determining an area of interest, it is possible to improve the effectiveness of the barrier. These results allow using all the elements with the same topology to individually attack noise pollution problems in their location and frequency range.

Model calculations and measurements of shooting sound in practical situations

Shooting sound in practical situations with propagation distances up to 300 m is investigated by means of model calculations and measurements. The results illustrate uncertainties in the model calculations for practical situations. The measurements were performed with various small-caliber weapons. Microphones were placed at positions screened by a noise barrier, and also at unscreened positions. The measured signals contain muzzle sound and bullet sound. The model calculations for muzzle sound and bullet sound take into account emission spectra and various propagation attenuation terms, including ground attenuation and barrier attenuation. The bullet sound model is based on a nonlinear theory of N waves generated by supersonic projectiles. For the unscreened situation, model and measurement results show that the sound levels are considerably reduced by ground attenuation. Ground-level variations and ground roughness in the measurement area play an important role. At a 300 m distance, the A-weighted bullet sound level is higher than the A-weighted muzzle sound level, which underlines the importance of bullet sound. For the screened situation, model and measurement results are used to analyze diffraction of bullet sound by the horizontal and vertical edges of the barrier. The diffraction is explained by considering Fresnel zones on the bullet trajectory.

Broadband wave attenuation and topological transport in novel periodic pile barriers

Topological insulator (TI) has received enormous attention in recent years due to its intriguing dynamic characterizes of topologically protected wave transport and defect immunity. Besides, the elastic waves can propagate along the pre-designed interface but body, which may dramatically promote practical applications of novel devices. This work introduces the concept of TI into the design of periodic pile barriers, which is expected to realize vibration mitigation and waveguiding simultaneously. By tuning the difference of pile radius, the inversion symmetry is broken and the attenuation zone (AZ) emerges. Then, the topological phase transitions happen when pile positions are interchanged in a unit cell and the opposite valley Chern numbers (Cv) are obtained meanwhile. Based on the complex dispersion (k(ω) method) analysis of supercell, the existence of topological edge states between two types of unit cells with distinct topological phases is confirmed at first. Second, some key parameters affecting the design of periodic pile barriers is discussed comprehensively, especially the influence of soil damping on attenuation zones and edge states. Compared to the traditional real dispersion (ω(k) method), the complex dispersion can describe the propagation property and attenuation property synchronously, providing useful guidances for this novel multifunctional periodic pile barriers. Subsequently, broadband wave attenuation and topological wave transport of novel periodic pile barriers are further validated by the analysis in both frequency domain and time domain, showing high vibration reduction and transmission efficiency. This new kind of wave barriers may have great potential for both vibration mitigation and elastic wave energy harvesting.

Centering inclusivity in the design of online conferences-An OHBM-Open Science perspective.

As the global health crisis unfolded, many academic conferences moved online in 2020. This move has been hailed as a positive step towards inclusivity in its attenuation of economic, physical, and legal barriers and effectively enabled many individuals from groups that have traditionally been underrepresented to join and participate. A number of studies have outlined how moving online made it possible to gather a more global community and has increased opportunities for individuals with various constraints, e.g., caregiving responsibilities. Yet, the mere existence of online conferences is no guarantee that everyone can attend and participate meaningfully. In fact, many elements of an online conference are still significant barriers to truly diverse participation: the tools used can be inaccessible for some individuals; the scheduling choices can favour some geographical locations; the set-up of the conference can provide more visibility to well-established researchers and reduce opportunities for early-career researchers. While acknowledging the benefits of an online setting, especially for individuals who have traditionally been underrepresented or excluded, we recognize that fostering social justice requires inclusivity to actively be centered in every aspect of online conference design. Here, we draw from the literature and from our own experiences to identify practices that purposefully encourage a diverse community to attend, participate in, and lead online conferences. Reflecting on how to design more inclusive online events is especially important as multiple scientific organizations have announced that they will continue offering an online version of their event when in-person conferences can resume.

440-P: Dual Long-Term Effects of Free Fatty Acid on Human Endothelial Barrier In Vitro Are Mediated by NO, Mitochondrial ROS, and Dicarbonyl Stress

In diabetes-associated hyperlipidemia, free fatty acids (FFAs) are thought to induce insulin resistance and endothelial dysfunction leading to vascular injury and cardiovascular T2DM complications. However, evidence is scarce regarding the effects of FFA on vascular endothelial barrier. We used human umbilical vein endothelial cells (HUVEC) to model, in vitro, the endothelial barrier and reveal its responses to experimental hyperlipidemia induced by long-term treatment with palmitic acid in complex with albumin. Palmitate was continuously present in the growth medium at 0.8 mM to reproduce FFA levels typical for T2DM. We developed conditions to maintain the HUVEC monolayers in the presence of the high palmitate concentration for up to 2 weeks by adding exogenous carnitine to facilitate mitochondrial β-oxidation of FFA. In this model system, palmitate readily augmented the transendothelial electric resistance (TER) of HUVEC via increased NO production by endothelial NO-synthase (eNOS). Western blots showed that palmitate neither disturbed insulin signaling cascade towards eNOS nor upregulated eNOS expression. After the initial 3-4-day rise in TER, further treatment with palmitate led to barrier stabilization and attenuation as compared to FFA-free conditions. This later phase was associated with increased ROS and malondialdehyde (MDA) accumulation, both prevented by the mitochondria-targeted antioxidant SkQ1. Treatment of HUVEC with exogenous MDA impaired the TER and barrier suggesting that accumulation of MDA-modified proteins may contribute to the barrier dysfunction upon long-term experimental hyperlipidemia. Altogether, obtained evidence suggests that prolonged exposure of vascular endothelium to high levels of palmitate compromises endothelium barrier capacity and insulin-mediated eNOS regulation turning the enzyme permanently active. Disclosure M. Samsonov: None. V. P. Shirinsky: None. N. Podkuychenko: None. A. Y. Khapchaev: None. T. Vlasik: None. V. Lankin: None. M. Skulachev: Other Relationship; Self; Mitotech LLC. I. Stafeev: None. A. V. Vorotnikov: None. M. V. Shestakova: None. Funding Russian Science Foundation (19-15-00361)

Comparative Analysis of Different Types of Sources on the Performance of Rigid Noise Barriers on Rigid Ground Using Analytical Formulae, a 2.5-D BEM Method and Scale Modelling Tests

With the aim of a perfect source model to simulate railway traffic noise within a shorter computational time, this paper compares coherent line, incoherent point and incoherent line sources on the performance of barriers by using an analytical solution, a 2.5-D BEM method and scale modelling tests. The comparison between the analytical solutions and the 2.5-D BEM prediction results shows that the BEM calculations for a coherent line source can be used to approximately show the barrier attenuation spectrum for a one-point source and the single-number rating for an incoherent line source when the barrier is straight on the ground. Then, validations with scale modelling tests were performed outdoors under controlled conditions. The results obtained by using several loudspeakers radiating incoherent sounds simultaneously show good agreement with the 2.5-D BEM prediction results for the one-point source and incoherent point sources, not only for a simple barrier on the ground but also for a double-straight barrier on a viaduct. Based on these agreements, the frequency and longitudinal distance dependences on the barrier attenuation for incoherent point sources are discussed to understand the barrier attenuation spectrum for the incoherent line source.

Buprenorphine in the United States: Motives for abuse, misuse, and diversion

Opioid use disorder (OUD) and its consequences are a major public health concern. The partial agonist buprenorphine is a safe and effective treatment for OUD, but concerns about abuse, misuse, and diversion of buprenorphine have been raised. This narrative review examined the rates and motives for use of illicit buprenorphine in the United States. Findings from the 17 included studies suggest the majority of study participants using illicit buprenorphine do so for reasons related to misuse (to manage opioid withdrawal symptoms or achieve or maintain abstinence from other opioids). A smaller percentage of study respondents reported using buprenorphine for reasons related to abuse (to get high). There appears to be a gap between need for buprenorphine and access to adequate treatment. Attenuation of policy-related barriers and adoption of appropriate buprenorphine use by the treatment community are critical tools in the continued effort to reduce the burdens associated with OUD.

Pressure induced semiconductor-metallic transition of selenium nanoribbons generated by laser ablation in liquids

Single crystalline Selenium (Se) nanoribbons with large length-diameter ratio was catalytically synthesized by laser ablation in liquids. In this study, the unique growth, pressure-dependent phase evolution and superconducting transition of Se nanoribbons are systematically investigated. Importantly, we first found that the semiconductor-metal transition pressure of such Se nanoribbons located at 11.1 GPa at room temperature, which was extremely close to the theoretically predicated value of 11.16 GPa of hexagonal Se. The structure evolution of Se nanoribbons revealed via in situ Raman spectrum indicated three subsequent phase transition stages. The temperature dependence of resistance measurements revealed the occurrence of superconducting state of monoclinic Se at 11.8 GPa, which is markedly lower than reported pressures to date. The phase transition barrier attenuation originating from the volumetric contraction of Se lattice is assumed to offset the influences of temperature and surface energy in low-dimensional Se nanoribbons with large length-diameter ratios, resulting in a transition pressure approaching the predicted value.

Three-dimensional analysis of a noise barrier using a quasi-periodic boundary element method

Two-dimensional (2D) numerical models are often used to estimate the environmental noise attenuation of a roadside barrier. The prediction of noise barrier attenuation using a 2D boundary element model assumes an infinitely long barrier with constant cross section. However, for barrier geometries that do not have constant cross section in the third dimension, three-dimensional (3D) models should be used for greater accuracy of noise reduction due to the barrier. The size of a numerical model and hence its computational cost can be significantly reduced using a 3D quasi-periodic structure, whereby the structure is truncated using a finite number of periodic sections. In this study, a quasi-periodic model developed using the boundary element method is used to predict the acoustic performance of 3D noise barriers. The convergence behavior of the quasi-periodic model is discussed. Results from the quasi-periodic model are compared with results from both a 3D analytical model and a 2D finite element model, showing good agreement. Quasi-periodic models of different noise barrier designs are developed and their acoustic performances in terms of frequency and receiver positions are discussed. The quasi-periodic boundary element method provides a computationally efficient tool to examine the acoustic performance of 3D noise barrier designs.

Analysis of Sound Insulation of Substation Barrier

Substation noise pollution as one of the most important environmental problems has been paid more and more attention. A model of substation sound barrier is built in this paper. On the basis of the model, the effects of sound isolation of the barrier with different positions, different heights are analyzed. The setting of the sound barrier that can bring best sound insulation effect will be obtained from the simulation results. Moreover, as the substation control buildings can be seen as barriers, the analysis of the sound barrier attenuation can provide a certain basis for the layout of substation buildings, and the setting of noise reduction barriers for noise controlling.

Identification and Attenuation of Barriers to Entrepreneurship

Results are reported from a Latino immigrant entrepreneur needs assessment survey. The research project was conducted to identify barriers to business formation and continuation within the target population. A total of 171 surveys representing more than 200 businesses from 39 communities in 21 counties in western Arkansas were collected. Nearly 42% of respondents cited start-up capital as their biggest barrier with another 15% naming it as the second biggest barrier. Understanding government regulations and tax information rated as the second biggest barrier that Latinos encountered. This barrier is more pronounced in rural areas than in urban areas. Other top concerns include advertising, location, and obtaining licenses and permits. A closer examination of barriers finds nuanced differences between rural and urban entrepreneurs. Outreach programs and materials developed in response to research findings are presented.

Optimized height of noise barrier for non-urban highway using artificial neural network

This study applies artificial neural network (ANN) for the determination of optimized height of a highway noise barrier. Field measurements were carried out to collect traffic volume, vehicle speed, noise level, and site geometry data. Barrier height was varied from 2 to 5 m in increments of 0.1 m for each measured data set to generate theoretical data for network design. Barrier attenuation was calculated for each height increment using Federal Highway Administration model. For neural network design purpose, classified traffic volume, corresponding traffic speed, and barrier attenuation data have been taken as input parameters, while barrier height was considered as output. ANNs with different architectures were trained, cross validated, and tested using this theoretical data. Results indicate that ANN can be useful to determine the height of noise barrier accurately, which can effectively achieve the desired noise level reduction, for a given set of traffic volume, vehicular speed, highway geometry, and site conditions.

Barrier height distribution and dipolar relaxation in metal-insulator-semiconductor junctions with molecular insulator: Ageing effects

Electrical transport through molecular monolayers being very sensitive to disorder effects, admittance and current density characteristics of Hg//C12H25 – n Si junctions incorporating covalently bonded n-alkyl molecular layers, were investigated at low temperature (150–300 K), in the as-grafted state and after ageing at the ambient. This comparison reveals local oxidation effects both at the submicron scale in the effective barrier height distribution and at the molecular scale in the dipolar relaxation. In the bias range dominated by thermionic emission and modified by the tunnel barrier (TB) attenuation, exp(−β0dT), where dT is the thickness of the molecular tunnel barrier and β0 is the inverse attenuation length at zero applied bias, some excess current is attributed to a distribution of low barrier height patches. Complementary methods are used to analyze the current density J(V, T) characteristics of metal-insulator-semiconductor tunnel diodes. Assuming a Gaussian distribution of barrier heights centered at qΦB provides an analytical expression of the effective barrier height, qΦEFF(T)=qΦB+(kT)β0dT−(qδΦ)2/2kT; this allows fitting of the distribution standard deviation δΦ and tunnel parameter (β0dT) over a wide temperature range. In a more realistic modeling including the voltage dependence of barrier height and circular patch area, the so-called “pinch-off” effect is described by a distribution of parameter γ=3(ΔPRP2/4)1/3, which combines interface potential modulation and patch area variations. An arbitrary distribution of γ values, fitted to low-temperature J(V) data, is equally well described by Gaussian or exponential functions. Ageing in air also increases the interface oxidation of Si substrate and affects the density of localized states near mid gap, which typically rises to the high 1011 eV−1 cm−2 range, as compared with DS < 1011 eV−1 cm−2 in the as-grafted state. The bias-independent relaxation observed near 1 kHz at low temperature may be attributed either to dipoles in the alkyl chain induced by the strong permanent dipoles of interface silicon oxide or to a local relaxation of water molecules trapped at the OML/silicon interface. The respective roles of SiO2 formation and water physisorption on the decrease of patch barrier height are also discussed.

Temperature dependence of current density and admittance in metal-insulator-semiconductor junctions with molecular insulator

Electrical transport in ultrathin Metal-insulator-semiconductor (MIS) tunnel junctions is analyzed using the temperature dependence of current density and admittance characteristics, as illustrated by Hg//C12H25 – n Si junctions incorporating n-alkyl molecular layers (1.45 nm thick) covalently bonded to Si(111). The voltage partition is obtained from J(V, T) characteristics, over eight decades in current. In the low forward bias regime (0.2–0.4 V) governed by thermionic emission, the observed linear T-dependence of the effective barrier height, qΦEFF(T)=qΦB+(kT)β0dT, provides the tunnel barrier attenuation, exp(-β0dT), with β0= 0.93 Å−1 and the thermionic emission barrier height, ΦB=0.53 eV. In the high-forward-bias regime (0.5–2.0 V), the bias dependence of the tunnel barrier transparency, approximated by a modified Simmons model for a rectangular tunnel barrier, provides the tunnel barrier height, ΦT=0.5 eV; the fitted prefactor value, G0 = 10−10 Ω−1, is four decades smaller than the theoretical Simmons prefactor for MIM structures. The density distribution of defects localized at the C12H25 – n Si interface is deduced from admittance data (low-high frequency method) and from a simulation of the response time τR(V) using Gomila’s model for a non equilibrium tunnel junction. The low density of electrically active defects near mid-gap (DS < 2 × 1011 eV−1.cm−2) indicates a good passivation of dangling bonds at the dodecyl – n Si (111) interface.

Effects of the soil on the noise attenuation of environmental berm barriers

Berm mounds are a commonly used technique to reduce the environmental noise levels produced by highways. A berm is a natural noise barrier constructed of soil, stone, rock, or rubble, often landscaped, running along a highway to protect adjacent communities from noise pollution. An earth mound may be constructed using surplus materials at project site, provided there is sufficient land area available for its construction. Therefore, berms are natural environmental barriers, having relative low costs and they are subjectively well perceived by residents. However, exact noise attenuation provided by berms has not been enough explored in the technical literature, as opposed to common barriers made of vertical rigid walls. Although, some highway noise prediction models assign a noise reduction bonus of 3 dB(A) to sound barriers made of earth mounds, experimental assessments have yielded mixed results. Few theoretical reports have studied this particular problem. In this work, numerical analysis using the classical theory of diffraction is performed on a berm made of different types of soil. The model assumes a line source and includes flow resistant data as boundary conditions. By integrating the results, noise attenuation is given in third-octave bands. It is concluded that soil's properties significantly influence the measured results and that this may be one of the causes of varied in-site empirical evidence.

Explosives Detection by Terahertz Spectroscopy—A Bridge Too Far?

Terahertz spectroscopy has been investigated as a technique for concealed explosives detection since spectroscopic signatures in common explosives were first identified almost 10 years ago. This paper explores the progress towards practical development of the technology and the physical basis of the challenges involved in creating a deployable person-borne IED detection system. We conclude that, despite the theoretical potential of terahertz to provide a safe, through-barrier spectroscopic detection technique, this is unlikely to be possible in practice. The relatively weak and broad explosives features tend to be masked by the combined effects of atmospheric water vapor absorption, barrier attenuation and scattering from both clothing and the target explosives. Imaging at the lower end of the terahertz frequency range, although not offering the same specificity, is a more promising technique for security applications.

Poster — Thur Eve — 41: Determination of Realistic Workload and Use Factors Using the Varian ARIA Database

Shielding design calculations used in megavoltage radiation therapy essentially reduce to determination of barrier thicknesses. A shielding barrier serves to attenuate the radiation dose from a high level produced inside a therapy room to a lower “design goal” level at a point‐of‐interest outside. The calculation must account for both radiation physics (barrier attenuation) and for the various clinic‐specific parameters that serve to modulate the design goal and the dose that impinges on the barrier. While the physical data relating to attenuation of megavoltage beams in concrete and other barrier materials is readily available (eg in NCRP Report 151 or via the NIST website), clinic‐specific parameters must be determined by the clinical physicist. Such parameters include the workload W of the treatment machine, the use factor U of the barrier in question and the occupancy T at the point‐of‐interest. In this submission we show how data archived in a clinic's record‐and‐verify system can be used to compile realistic workload and use factors.

NIPPV: Prevalence, Approach and Barriers to Use at Canadian ALS Centres

The purpose of this study was to evaluate Canadian amyotrophic lateral sclerosis (ALS) centres with respect to: 1) the prevalence of Non-invasive positive pressure ventilation (NIPPV) and invasive mechanical ventilation via tracheostomy (TV) utilization, 2) the approach to NIPPV use, focusing upon the currently employed initiation criteria and 3) the barriers influencing NIPPV administration. A descriptive survey research design aimed to obtain quantitative data and open-ended responses from an active physician at each of the 15 multidisciplinary Canadian ALS centres. The principal findings of this study were: 1) NIPPV and TV are used in 18.3% and 1.5% of patients at Canadian ALS centres, respectively, 2) symptoms of respiratory insufficiency, namely orthopnea (clinical significance rated at 9.00/10 +/- 1.48), dyspnea (8.27 +/- 1.95) and morning headache (7.55 +/- 1.21) are the most significant indicators for NIPPV initiation, 3) the primary barriers to NIPPV utilization are patient intolerance (70% of centres) and inaccessibility of respirologists and ventilation technologists (50% of centres). Variability in NIPPV use has an impact upon the management of Canadian ALS patients. The establishment of more definitive NIPPV initiation criteria, emphasizing respiratory symptoms, and the attenuation of barriers to NIPPV use should be targeted so as to ensure optimal care for all ALS patients.

Predicted and experimental attenuation of obstructed projectile shock waves.

Acoustic sniper localization algorithms are well established for open field detection; however, these algorithms are less accurate in urban environments due to reverberation and diffraction. Research is being performed to understand the effects of obstructions on shock wave propagation. Barrier attenuation calculations that use Fresnel number to characterize obscurity will be compared to measured attenuation of shock wave frequency components. An artificial building was set up and shock waves from bullets were recorded by microphones with varying degrees of obscurity. The experimental setup allowed for a range of Fresnel numbers between 5 and 11 resulting in attenuation up to 30 dB. Attenuation increased as obscurity and Fresnel number increased up to a threshold. Beyond this point the magnitude of attenuation decreases in both theory and experiment. These data support the relationship between attenuation and microphone obscurity and may provide a means to estimate the amplitude and N‐wave slope of the shock wave prior to obstruction.

SU‐FF‐T‐326: Monte Carlo Based Simulation and Analysis of SRS X‐Ray 6 MV Beam Tenth‐Value‐Layer Data for Common Shielding Materials

Treatment room shielding design depends on barrier attenuation data. It is common practice to use tenth‐value‐layers (TVLs) or related quantities measured for a given beam quality and shielding material. This investigation has applied Monte Carlo simulation to accurately determine the first, second and third TVLs for the three most common building materials: ordinary concrete, lead, and steel (iron). The radiation beam is 6 MV x‐rays coming from a robotically mounted stereotactic radiosurgery (SRS) accelerator which has a maximum field diameter of 6 cm at 80 cm from the target. The first three TVLs are presented for a range of field sizes up to the broad beam equivalent of a 40 cm by 40 cm field at 1 m. The x‐ray spectrum used to perform these simulations was generated for the CyberKnife™ accelerator with the BEAMnrc Monte Carlo code. This spectrum was used as input to the MCNP5 Monte Carlo code, to predicted tissue‐maximum‐ratio (TMR) values for a 6 cm diameter field (at 80 cm from the target) and benchmarked against measured TMR data. The MCNP5 code was used to simulate all barrier transmission factors, keeping the standard error of each data point below 1% of the mean. The results show that SRS TVLs change rapidly with the diameter of the radiation field incident on the barrier (with a slower rate of increase above about 15 cm diameter). Also analyzed were the characteristics of TVLs (specifically, the ordering TVL1, TVL2, and TVL3) as a function of field diameter at the barrier for all materials, with special attention given to the TVL properties in iron. The TVL results compare very well with previously measured concrete TVLs for the SRS machine and, also, with published broad‐beam 6 MV TVL data for all three barrier materials.