Chemical Weathering in a Hypersaline Effluent Irrigated Dry Ash Dump: An Insight from Physicochemical and Mineralogical Analysis of Drilled Cores

Accumulation of high ionic strength effluents (brines) that require disposal in inland industries where water recycling is necessary due to scarcity is a major challenge. A coal combustion power utility in South Africa utilizing a dry ash disposal system produces 1.765 Mt of fly ash per annum and also employs the zero liquid effluent discharge policy (ZLED) to manage its liquid effluents. Fly ash is conditioned for dust suppression before being conveyed to the ash dumps with the high saline effluent. The saline effluents results from various processes employed for maximum utilization, upgrading and re-use of various mine water and industrial effluents such as RO, EDR, softening and ion exchange in an effort to adhere to ZLED policy. In the ash dumps it is further conditioned by irrigation with the high saline effluents, therefore the ash acts as a repository for the salts. This study is an attempt to understand the chemical weathering of the effluent conditioned fly ash and species mobility in a dry disposal scenario. A combination of leaching tests was performed for fresh ash and drilled cores to estimate the highly leachable species. Results from DIN-S4 tests of the fresh and weathered ash reveal that Ca, K, Na, Mg, Ba, SO42-, Se, Mo and Cr are highly leached. Leaching tests also revealed that major soluble components in the solution at equilibrium are Ca, Na, SO42- and K. Weathering profiles of the ash dump cores were observed to follow a similar trend. The greatest weathering was observed to take place at the top layer (0.55-3 m depth) in the weathered ash cores (15 years and older), showing that infiltration of rain water over time has a profound effect on the decrease of the pore water pH.  Analysis of the extracted pore water in each of the different weathered ash cores by depth indicated the mobility of several elements through the ash. Increased cation exchange capacity at 4-5 m depth suggests a transient mineralization zone.Key words:  Weathered fly ash; Pore water; Ash dumps; Hypersaline effluents; X-ray diffraction analysis; DIN-S4 test; Cation exchange capacit

Detection of white dwarf spin period variability in the intermediate polar V2306 Cygni

Magnetic cataclysmic variables are close binaries which consist of a compact object - a white dwarf - and a red dwarf filling its Roche Lobe. Such systems are physical laboratories which enable study of the influence of magnetic fields on matter flows. They often exhibit spin-up or spin-down of the white dwarf, while some systems exhibit more complex behaviour of the spin period change. We monitor changes of the spin periods of white dwarfs in a sample of close binary systems to study interaction of the magnetic field and accretion processes as well as evolution of intermediate polars. Within the framework of our intermediate polar monitoring program, we obtained photometric CCD observations at several observatories. Two-period trigonometric polynomial fitting was used for determination of extrema timings. The (O-C) analysis was performed to study the variability of the orbital and spin periods of the systems. Using data taken during 9 years of observations of the magnetic cataclysmic variable V2306 Cygni (formerly known as 1WGA J1958.2+3232), we detected the spin period variability which shows a spin-up of the white dwarf with a characteristic time of $(53\pm5)\cdot10^4$ years. The value of the spin period was $733.33976$ seconds with the formal accuracy of $0.00015$ seconds. We derived an improved value of the orbital period of the system to be $4.371523\pm0.000009$ hours.Comment: Accepted to MNRAS 2019 July 23. 5 pages, 3 figures, supporting data onlin

An overview of Space Communication Artificial Intelligence for Link Evaluation Terminal (SCAILET) Project

A software application to assist end-users of the link evaluation terminal (LET) for satellite communications is being developed. This software application incorporates artificial intelligence (AI) techniques and will be deployed as an interface to LET. The high burst rate (HBR) LET provides 30 GHz transmitting/20 GHz receiving (220/110 Mbps) capability for wideband communications technology experiments with the Advanced Communications Technology Satellite (ACTS). The HBR LET can monitor and evaluate the integrity of the HBR communications uplink and downlink to the ACTS satellite. The uplink HBR transmission is performed by bursting the bit-pattern as a modulated signal to the satellite. The HBR LET can determine the bit error rate (BER) under various atmospheric conditions by comparing the transmitted bit pattern with the received bit pattern. An algorithm for power augmentation will be applied to enhance the system's BER performance at reduced signal strength caused by adverse conditions

Space Communication Artificial Intelligence for Link Evaluation Terminal (SCAILET)

A software application to assist end-users of the high burst rate (HBR) link evaluation terminal (LET) for satellite communications is being developed. The HBR LET system developed at NASA Lewis Research Center is an element of the Advanced Communications Technology Satellite (ACTS) Project. The HBR LET is divided into seven major subsystems, each with its own expert. Programming scripts, test procedures defined by design engineers, set up the HBR LET system. These programming scripts are cryptic, hard to maintain and require a steep learning curve. These scripts were developed by the system engineers who will not be available for the end-users of the system. To increase end-user productivity a friendly interface needs to be added to the system. One possible solution is to provide the user with adequate documentation to perform the needed tasks. With the complexity of this system the vast amount of documentation needed would be overwhelming and the information would be hard to retrieve. With limited resources, maintenance is another reason for not using this form of documentation. An advanced form of interaction is being explored using current computer techniques. This application, which incorporates a combination of multimedia and artificial intelligence (AI) techniques to provided end-users with an intelligent interface to the HBR LET system, is comprised of an intelligent assistant, intelligent tutoring, and hypermedia documentation. The intelligent assistant and tutoring systems address the critical programming needs of the end-user

Reconstruction of sub-wavelength features and nano-positioning of gratings using coherent Fourier scatterometry

Optical scatterometry is the state of art optical inspection technique for quality control in lithographic process. As such, any boost in its performance carries very relevant potential in semiconductor industry. Recently we have shown that coherent Fourier scatterometry (CFS) can lead to a notably improved sensitivity in the reconstruction of the geometry of printed gratings. In this work, we report on implementation of a CFS instrument, which confirms the predicted performances. The system, although currently operating at a relatively low numerical aperture (NA = 0.4) and long wavelength (633 nm) allows already the reconstruction of the grating parameters with nanometer accuracy, which is comparable to that of AFM and SEM measurements on the same sample, used as reference measurements. Additionally, 1 nm accuracy in lateral positioning has been demonstrated, corresponding to 0.08% of the pitch of the grating used in the actual experiment

A new technique for elucidating β\beta-decay schemes which involve daughter nuclei with very low energy excited states

A new technique of elucidating $\beta$-decay schemes of isotopes with large density of states at low excitation energies has been developed, in which a Broad Energy Germanium (BEGe) detector is used in conjunction with coaxial hyper-pure germanium detectors. The power of this technique has been demonstrated on the example of 183Hg decay. Mass-separated samples of 183Hg were produced by a deposition of the low-energy radioactive-ion beam delivered by the ISOLDE facility at CERN. The excellent energy resolution of the BEGe detector allowed $\gamma$ rays energies to be determined with a precision of a few tens of electronvolts, which was sufficient for the analysis of the Rydberg-Ritz combinations in the level scheme. The timestamped structure of the data was used for unambiguous separation of $\gamma$ rays arising from the decay of 183Hg from those due to the daughter decays