Use of Modified Concrete Layers Primers in Composite Concrete Constructions

The issue of contact joints in composite reinforced concrete structures is considered. It is shown that there are many factors affecting the shear resistance of the contact joint. It is noted that the use of modified concrete, layers and primers increases resistance to shear of the contact joint

Influence of the waste composition on the properties of paper sheets

The paper studies the influence of the properties of the waste paper on the properties of a paper sheet. The obtained data demonstrate the ability of different types of waste to the dissolution and grinding. It has been shown that paper properties such as breaking length, absorbency at unilateral wetting, elongation, wet strength, breaking force of various types of fibrous materials recycled fibrous materials must be taken into consideration in paper and cardboard mills in the manufacture of paper and cardboard with a different field of application. It is concluded that the selected samples of waste paper can be recycled in paper mills of the Republic of Belarus as fibrous raw material to produce various kinds of paper

Radio Emission from Cosmic Ray Air Showers: Coherent Geosynchrotron Radiation

Cosmic ray air showers have been known for over 30 years to emit pulsed radio emission in the frequency range from a few to a few hundred MHz, an effect that offers great opportunities for the study of extensive air showers with upcoming fully digital "software radio telescopes" such as LOFAR and the enhancement of particle detector arrays such as KASCADE Grande or the Pierre Auger Observatory. However, there are still a lot of open questions regarding the strength of the emission as well as the underlying emission mechanism. Accompanying the development of a LOFAR prototype station dedicated to the observation of radio emission from extensive air showers, LOPES, we therefore take a new approach to modeling the emission process, interpreting it as "coherent geosynchrotron emission" from electron-positron pairs gyrating in the earth's magnetic field. We develop our model in a step-by-step procedure incorporating increasingly realistic shower geometries in order to disentangle the coherence effects arising from the different scales present in the air shower structure and assess their influence on the spectrum and radial dependence of the emitted radiation. We infer that the air shower "pancake" thickness directly limits the frequency range of the emitted radiation, while the radial dependence of the emission is mainly governed by the intrinsic beaming cone of the synchrotron radiation and the superposition of the emission over the air shower evolution as a whole. Our model succeeds in reproducing the qualitative trends in the emission spectrum and radial dependence that were observed in the past, and is consistent with the absolute level of the emission within the relatively large systematic errors in the experimental data.Comment: 17 pages, 18 figures, accepted for publication by Astronomy & Astrophysic

Study of the time-differentiated particle flux density at various distances from EAS axis

The EAS time structure is studied using the enlarged EAS array of the Moscow State University. The time measurements are made using 22 scintillators which form 13 rectanges of 180x190 sq m size covering the entire array area. The array is triggered by a signal of 4-fold coincidences of the pulses from the detectors forming each of the rectangles. The data were obtained during 2200 hours of the array operation in 1984. A total of 816 showers, to which at least 14 of 22 scintillator detectors responded, were selected among all those detected. The coordinates of the EAS axis in the observation plane and the EAS sizes were determined by the maximum likelihood method using a computer on the assumption that the electron LDF is the NKG form. A total of 492 showers in the interval of EAS size Ne = 5x10 to the 6th power - 2x10 to the 8th power (N bar e = 1.7x 10 to the 7th power) with zenith angles theta or = 45 deg and axes within the array are analyzed

Coherent synchrotron emission from cosmic ray air showers

Coherent synchrotron emission by particles moving along semi-infinite tracks is discussed, with a specific application to radio emission from air showers induced by high-energy cosmic rays. It is shown that in general, radiation from a particle moving along a semi-infinite orbit consists of usual synchrotron emission and modified impulsive bremsstrahlung. The latter component is due to the instantaneous onset of the curved trajectory of the emitting particle at its creation. Inclusion of the bremsstrahlung leads to broadening of the radiation pattern and a slower decay of the spectrum at the cut-off frequency than the conventional synchrotron emission. Possible implications of these features for air shower radio emission are discussed.Comment: 8 pages, 10 figures, accepted for publication in MNRA

May water matrix components limit real application of electrochemical reduction of nitrate?

International audienceNitrate (NO3-) pollution is one of the top ten water quality violations reported worldwide. High levels of this contaminant are associated to respiratory and reproductive system illness, thyroid problems, and cancer. Recently, the electrochemical reduction process has demonstrated satisfactory results to the conversion of nitrate to the innocuous nitrogen gas. However, most studies have been focused on ideal synthetic solutions, not considering the coexistence of different species in real water matrices that may compete for the electrons, decreasing the conversion constant kinetics (k1) of the target pollutant. There is a necessity to reframe research questions to translate the electrochemical reduction of nitrate (ERN) process to higher technology readiness levels and commercialization.The research undertaken in this work aimed to identify in what extent the components of natural water matrices may affect the electrochemical reduction of nitrate (ERN). A concentration of 30 mg NO3--N L-1 was selected as a representative common maximum value found in groundwaters. A lab-made solution with ultrapure water containing the pollutant and Na2SO4 was prepared and used as a blank experiment. After 360 min, electrochemically reducing this solution with a dimensional stable anode and a Sn-cathode at 40 mA cm-2, 75% of NO3--N was converted with a k1 of 6.4×10-5 s-1. The calculated selectivity towards Ngas (SNgas) was 72 %. Under similar operating conditions, a mixture of different inorganic ions (Ca2+, Mg2+, F-, HCO3-, PO43-, SiO2, typically present in groundwater) was tested, leading to a decrease of 4.1 times the initial k1, which represents a conversion of NO3—N of 30% with a SNgas=35%. These results clearly highlight that the ERN is significantly affected by the media where the treatment process occurs. To gain a better understanding at this phenomenon, the ERN was conducted by testing the inorganic ions individually revealing that the species that most influenced the system were Ca2+, Mg2+ and HCO3-. This means that the technology will be limited for treatment of soft waters.This work brings up to light the relevance of studying the characteristics of water matrix components before applying an electrochemical process. In fact, these results emphasize the opportunity to apply the ERN to specific waters (as the soft waters). Additionally, depending on the composition of the water matrix the ERN, can be applied as a direct treatment or as a post-treatment, opening the doors to specific niche markets

Overcoming barriers for nitrate electrochemical reduction: By-passing water hardness

International audienceWater matrix composition impacts water treatment performance. However, matrix composition impacts have rarely been studied for electrochemical water treatment processes, and the correlation between the composition and the treatment efficiency is lacking. This work evaluated the electrochemical reduction of nitrate (ERN) using different complex water matrices: groundwater, brackish water, and reverse osmosis (RO) concentrate/brine. The ERN was conducted using a tin (Sn) cathode because of the high selectivity towards nitrogen evolution reported for Sn electrocatalysts. The coexistence of calcium (Ca 2+), magnesium (Mg 2+), and carbonate (CO 3 2-) ions in water caused a 4-fold decrease in the nitrate conversion into innocuous nitrogen gas due to inorganic scaling formation on the cathode surface. XRF and XRD analysis of fouled catalyst surfaces detected brucite (Mg(OH) 2), calcite (CaCO 3), and dolomite (CaMg(CO 3) 2) mineral scales formed on the cathode surface. Surface scaling created a physical barrier on the electrode that decreased the ERN efficiency. Identifying these main sources of ERN inhibition was a key to devising potential fouling mitigation strategies. For this reason, the chemical softening pre-treatment of a real brackish water was conducted and this significantly increased nitrate conversion and faradaic efficiency during subsequent ERN treatment, leading to a lower electric energy consumption per order. Understanding the ionic foulant composition responsible for influencing electrochemically-driven technologies are the first steps that must be taken to move towards niche applications such as decentralized ERN. Thus, we propose either direct ERN implementation in regions facing high nitrate levels in soft waters, or a hybrid softening/nitrate removal system for those regions where high nitrate and high-water hardness appear simultaneously

Influence of the waste composition on the properties of paper sheets

The paper studies the influence of the properties of the waste paper on the properties of a paper sheet. The obtained data demonstrate the ability of different types of waste to the dissolution and grinding. It has been shown that paper properties such as breaking length, absorbency at unilateral wetting, elongation, wet strength, breaking force of various types of fibrous materials recycled fibrous materials must be taken into consideration in paper and cardboard mills in the manufacture of paper and cardboard with a different field of application. It is concluded that the selected samples of waste paper can be recycled in paper mills of the Republic of Belarus as fibrous raw material to produce various kinds of paper