This paper addresses the problem of road safety regarding barrier placement as relative to the curb. A short summary of existing regulations is presented. Numerical simulations using the explicit finite element system Ls-Dyna are shown. In the analysis, variable distance between the barrier and the curb is assumed. The obtained result reveals that the distance has little impact on the working width of the barrier.
The main issue of this article are eco-bridges, pedestrian-friendly imaginary sites (enclave) of greenery in urban tissues. Discussed cases include the implementations of projects such as: the High Line in New York and the Garden Bridge in London. The main theme of the article is to compare the green bridges in the urban tissue embedded with “living root bridges”. The author of the article highlights the potential limits for “living root bridges” in the urban tissue, resulting from the climate, time of their creation and limits of urban space. She also notes the strong tendency to create green areas in the “concrete” urban structure, but also the use of artificial materials in tissue of “living root bridges”.
There is a considerable increase in the use of noise barriers in recent years. Noise barriers as a control noise solution can increase the insertion loss to protect receivers. This paper presents the results of an investigation about the acoustic efficiency of primitive root sequence diffuser (PRD) on an environmental single T-shape barrier design. A 2D boundary element method (BEM) is used to predict the insertion loss of the tested barriers. The results of rigid and with a different sequence diffuser coverage are also predicted for comparison. Employing PRD on the top surface of T-shape barrier has been found to improve the performance of barriers in comparison with the use of rigid and QRD coverage at the examined receiver locations. It has been found that decreasing the design frequency of PRD shifts the frequency effects towards lower frequencies, and therefore the overall A-weighted insertion loss is improved. It was also found that using wire mesh with reasonably efficient resistivity on the top surface of PRD improves the efficiency of the reactive barriers; however utilizing wire meshes with flow resistivity higher than the specific acoustic impedance of air on the PRD top of a diffuser barrier significantly reduces the performance of the barrier within the frequency bandwidth of the diffuser. The performance of a PRD covered T-shape barrier at 200 Hz was found to be higher than that of its equivalent QRD barriers in both the far field and in areas close to the ground. The amount of improvement compared made by PRD barrier compared with its equivalent rigid barrier at far field is about 2 to 3 dB, while this improvement relative to the barrier model "QR4" can reach up to 4-6 dB.
One of the most effective designs to control the road traffic noise is the T-shaped barrier. The aim of this study was to examine the performance of T-shape noise barriers covered with oblique diffusers using boundary element method. A 2D simulation technique based on the boundary element method (BEM) was used to compute the insertion loss at the center frequency of each one-third octave band. In designed barriers, the top surface of the T-shaped noise barriers was covered with oblique diffusers. The width and height of the barrier stem and the width of its cap were 0.3, 2.7, and 1 m, respectively. Angles of he oblique diffusers were 15, 30, and 45 degrees. The oblique diffusers were placed on the top surface with two designs including same oblique diffusers (SOD) and quadratic residue oblique diffusers (QROD). Barriers considered were made of concrete, an acoustically rigid material. The barrier with characteristics of QROD, forward direction, and sequence of angles (15, 30, and 45 degrees) had the greatest value of the overall A-weighted insertion loss equal to 18.3 to 21.8 dBA at a distance of 20 m with various heights of 0 to 6 m.
High-temperature solid oxide fuel cells (SOFCs) are considered as suitable components of future large-scale clean and efficient power generation systems. However, at its current stage of development some technical barriers exists which limit SOFC’s potential for rapid large-scale deployment. The present article aims at providing solutions to key technical barriers in SOFC technology. The focus is on the solutions addressing thermal resistance, fuel reforming, energy conversion efficiency, materials, design, and fuel utilisation issues.
An efficient system of micropropagation via somatic embryogenesis from root-derived callus was established in Arabica coffee (Coffea arabica L.). Twenty-six callus lines were induced on MS (Murashige and Skoog, 1962) medium supplemented with combinations of NAA (0, 0.1, 0.5, 1 and 2 mg/L) plus BA (0, 1 and 2 mg/L), or 2,4-D (0, 0.1, 0.5, 1 and 2 mg/L) plus TDZ (0, 1 and 2 mg/L). Subsequently, two types of somatic embryos were obtained from callus cultures and named S-type and I-type embryos. The S-type embryos were obtained from an 18-monthold callus line which was induced and maintained at 2 mg/L TDZ and 0.1 mg/L 2,4-D near the end of each period of the subculture. These embryos have a developmental barrier, which did not pass through the torpedo stage and could be overcome by a supplement of 2 or 5 mg/L BA. The I-type embryos were induced from 3-month-old callus when transferred onto induction media, i.e., MS supplemented with TDZ (2 and 5 mg/L) plus 2,4-D (0 and 0.1 mg/L). The significantly highest response, i.e., 13.3 embryos per callus clump was obtained at 2 mg/L TDZ. In this study, the results reveal that TDZ has a crucial effect on embryogenic callus induction, proliferation and subsequent somatic embryogenesis.
In this work studies of barrier height local values are presented. Distribution of the gate-oxide EBG(x, y) and semiconductor-oxide EBS(x, y) barrier height local values have been determined using the photoelectric measurement methods. Two methods were used to obtain the local values of the barrier heights: modified Powell-Berglund method and modified Fowler method. Both methods were modified in such a way as to allow determination of the EBG(x, y) and EBS(x, y) distribution over the gate area using a focused UV light beam of a small diameter d = 0.3 mm. Measurements have been made on a series of Al-SiO2-Si(n+) MOS structures with semitransparent (tAl = 35 nm) square aluminum gate (1 x 1 mm2). It has been found that the EBG(x, y) distribution has a characteristic dome-like shape, with highest values at the center of the gate, lower at the gate edges and still lower at gate corners. On the contrary, the EBS(x, y) distribution is of a random character. Also, in this paper, both barrier height measurements have been compared with the photoelectric effective contact potential difference fMS(x, y) measurements. These results show good agreement between distribution of the barrier heights EBG(x, y) and EBS(x, y) measurements and independently determined shape of the effective contact potential difference fMS(x, y) distribution.
The object of investigation was the one-strand tundish with flow control device such as gas permeable barrier (GPB). The aim of this flow control device was to activate the motion of liquid steel in the tundish longitudinal axis region. Computer simulation of the liquid steel flow and argon behaviour in isothermal turbulent motion conditions was done using the Ansys-Fluent computer program. For the validation of the hydrodynamic patterns obtained from computer simulations, a isothermal tundish glass model was used. Tundish glass model enables the recording of the visualization of fluid medium motion through the particle image velocimetry (PIV) method. Based on computer simulations, the liquid steel flow path lines in the tundish with GPB was obtained. For explain the hydrodynamic phenomena occurring in the tundish working space, the Buoyancy number has been calculated.
In the last two decades several new concepts of photodetectors to improve their performance have been proposed. New strategies are especially addressed to the group of so called high-operating-temperature detectors where - apart from increasing of operating temperature - both the size and power consumption reduction is expected. In this paper a new strategy in the photo-detector design is presented - the barrier detectors: CnBn; CnBnN+, CpBn and unipolar barrier photodiodes. In spite of considering barrier detectors based on AIIIBV bulk compounds and type-II superlattices as having theoretically a better performance than those based on HgCdTe, the latter compound is also used to fabricate barrier detectors. Among many new applications of barrier detectors the detection of explosives can be extremely important due to an increased threat of terrorist attacks. This paper presents the status of the barrier detectors and compares the performance of mid-wave HgCdTe barrier detectors and unipolar barrier photodiodes.
The subject of the research is one of the largest World’s mine tailings disposal sites, i.e. Żelazny Most in the Legnica-Głogów Copper Mining District (south-western Poland), where flotation tailings are poured out after copper ore treatment. The protective hydraulic barrier made of 46 vertical drainage wells was characterized and evaluated in view of reduction of major contaminants (Cl, Na, SO4, Ca) migrating from the facility to its foreground. The efficiency of groundwater protection was determined on the basis of a new approach. In applied method the loads of characteristic and commonly recognizable compounds, i.e. salt (NaCl) and gypsum (CaSO4) were calculated, instead their chemical components. The temporal and spatial variability of captured main contaminants loads as well as its causes are discussed. The paper ends with the results of efficiency analyses of the barrier and with respect to the predicted increase in contaminant concentrations in the pulp poured out to the tailings site.
The presented work gives an overview on simulation and experimental results of the power supply parameters’ influence on DBD discharge uniformity. The proposed study is about the use of quasi-pulsed, power electronic power supply and a saturable inductor in series with the discharge cell . The simulation results are presented with a parallel DBD reactor model with linear critical voltage distribution. A more uniform current waveform is observed, however, due to small reactor capacitances no streamer formation could be verified in calculations. An experimental test stand was prepared with a double dielectric barrier discharge arrangement. The experimental results are presented with regard to the electrical oscilloscope waveforms and ICCD camera imaging. A more homogenous plasma was observed in the case of saturable inductor with saturation current set at the point of discharge formation. Two possible mechanisms are connected with this phenomenon – inductive element current support during discharge and/or current rise-time limitation .
In this work we present the design and the manufacturing processes, as well as the acoustics standardization tests, of an acoustic barrier formed by a set of multi-phenomena cylindrical scatterers. Periodic arrangements of acoustic scatterers embedded in a fluid medium with different physical properties are usually called Sonic Crystals. The multiple scattering of waves inside these structures leads to attenuation bands related to the periodicity of the structure by means of Bragg scattering. In order to design the acoustic barrier, two strategies have been used: First, the arrangement of scatterers is based on fractal geometries to maximize the Bragg scattering; second, multi-phenomena scatterers with several noise control mechanisms, as resonances or absorption, are designed and used to construct the periodic array. The acoustic barrier reported in this work provides a high technological solution in the field of noise control.