TAILORED SYNTHESIS OF PRECIPITATED MAGNESIUM CARBONATES AS CARBON-NEUTRAL FILLER MATERIALS DURING CARBON MINERAL SEQUESTRATION

Predictions of global energy usage and demand trends suggest that fossil fuels will remain as the main energy source for the foreseeable future. Unfortunately, the increased amount of anthropogenic carbon emitted during the energy production leads to environmental issues, including climate change. Thus, reducing carbon dioxide emissions in order to stabilize atmospheric CO2 levels is crucial, and this would not be achieved without significant changes in the energy conversion processes and the implementation of carbon capture and storage (CCS) technologies. Currently, the geological storage of carbon dioxide is considered to be the most economical method of carbon sequestration, while mineral carbonation is a relatively new and less explored method of sequestering CO2. The advantage of carbon mineral sequestration is that it is the most permanent and safe method of carbon storage, since the gaseous carbon dioxide is fixed into a solid matrix of Mg-bearing minerals (e.g., serpentine) forming a thermodynamically stable solid product. The current drawback of carbon mineral sequestration is its relatively high cost. Therefore, this study focuses on tailored synthesis of high purity precipitated magnesium carbonate (PMC) to mimic commercially available CaCO3-based filler materials, while sequestering CO2. The effects of pH, reaction time and reaction temperature on the mean particle size, particle size distribution, and particle morphological structures, have been investigated for the synthesis of magnesium carbonates as carbon-neutral filler materials

MODIFIKASI BOLA VOLI UNTUK MENINGKATKAN HASIL BELAJAR SERVIS BAWAH BOLA VOLI MINI PADA SD NEGERI 02 PETANG JAKARTA UTARA

This study attempts to reform and improve students ability in learning serve under volley ball mini through variations media the ball. This study was conducted in public primary schools 02 evening north jakarta grade 5 , carried out on semester II academic year 2017 / 2018. The research phase for two weeks , started on sunday to 2, 12 july - 18 july 2016 , carried out as many as 4 (four) meeting , methods used is the method research the act of a class (classroom action research) such quantitative data. In its implementation , this research involving 2 a person skilled in education sector physical especially the branch sports volley ball as collaborators. This research using two stage cycle , namely cycle I and cycle II and started by activities preliminary observations. This research being implemented together to learning physical education at school. Activities first cycle that was realized through the action of I results from as follows: 1 students still did not know about the concept of serve under volley ball. 2) students not can do the preparatory attitude foot with perfect that is because both legs not in a position stepped weight not divided balanced, the position of hands not below the ball. 3) students not can do motion perkenaan with the ball because a ball thrown too high and too back , the ball is not struck with palms clenched. 4) Students not able to conduct movement an end by perfect because they after striking the ball not followed position ready for to enter into the field. 5) Students have showed a positive attitude especially motivation and courage that rises. Activities cycle II that was realized through the action of II give you the result as the following: 1 students understand will the concept of serve under volley ball. 2) students can do stage serve take. Standard finished learn set by school of public elementary school 02 evening north jakarta the subjects physical education is 70 (seventy). Change and increased capacity students in learning serve under volley ball mini variation media the ball can be seen in the assessment results of the processes and the final test serve under volley ball mini. To finished study results students on a pre-test expressed be completed a number of 12 students (34. 3 %) and on a test the end of a number of 35 students (100 %), there is an increase of 65,7 %. The research can be concluded that variations media the ball can improve learning outcomes serve under volley ball mini in public primary elementary schools 02 evening north jakarta

Second harmonic generation in suspensions of spherical particles

We study the second harmonic generation (SHG) in a suspension of small spherical particles confined within a slab, assuming undepleted pump and applying (i) single scattering approximation and (ii) diffusion approximation. In the case (i), the angular diagram, the differential and total crossections of the SHG process, as well as the average cosine of SH scattering angle are calculated. In the case (ii), the average SH intensity is found to show no explicit dependence on the linear scattering properties of the suspension. The average intensity of SH wave scales as I_0 L / \Lambda_2 in both cases (i) and (ii), where I_0 is the intensity of the incident wave, L is the slab thickness, and \Lambda_2 is an intensity-dependent "SH scattering" length.Comment: PDF, 20 pages, 4 figure

DC-electric-field-induced and low-frequency electromodulation second-harmonic generation spectroscopy of Si(001)-SiO2_2 interfaces

The mechanism of DC-Electric-Field-Induced Second-Harmonic (EFISH) generation at weakly nonlinear buried Si(001)-SiO$_2$ interfaces is studied experimentally in planar Si(001)-SiO$_2$-Cr MOS structures by optical second-harmonic generation (SHG) spectroscopy with a tunable Ti:sapphire femtosecond laser. The spectral dependence of the EFISH contribution near the direct two-photon $E_1$ transition of silicon is extracted. A systematic phenomenological model of the EFISH phenomenon, including a detailed description of the space charge region (SCR) at the semiconductor-dielectric interface in accumulation, depletion, and inversion regimes, has been developed. The influence of surface quantization effects, interface states, charge traps in the oxide layer, doping concentration and oxide thickness on nonlocal screening of the DC-electric field and on breaking of inversion symmetry in the SCR is considered. The model describes EFISH generation in the SCR using a Green function formalism which takes into account all retardation and absorption effects of the fundamental and second harmonic (SH) waves, optical interference between field-dependent and field-independent contributions to the SH field and multiple reflection interference in the SiO$_2$ layer. Good agreement between the phenomenological model and our recent and new EFISH spectroscopic results is demonstrated. Finally, low-frequency electromodulated EFISH is demonstrated as a useful differential spectroscopic technique for studies of the Si-SiO$_2$ interface in silicon-based MOS structures.Comment: 31 pages, 14 figures, 1 table, figures are also available at http://kali.ilc.msu.su/articles/50/efish.ht

Broadband stimulated four-wave parametric conversion on a tantalum pentoxide photonic chip

We exploit the large third order nonlinear susceptibility (?(3) or “Chi 3”) of tantalum pentoxide (Ta2O5) planar waveguides and realize broadband optical parametric conversion on-chip. We use a co-linear pump-probe configuration and observe stimulated four wave parametric conversion when seeding either in the visible or the infrared. Pumping at 800 nm we observe parametric conversion over a broad spectral range with the parametric idler output spanning from 1200 nm to 1600 nm in infrared wavelengths and from 555 nm to 600 nm in visible wavelengths. Our demonstration of on-chip stimulated four wave parametric conversion introduces Ta2O5 as a novel material for broadband integrated nonlinear photonic circuit applications

Shear-strain-induced two-dimensional slip avalanches in rhombohedral MoS2

Slip avalanches are ubiquitous phenomena occurring in 3D materials under shear strain and their study contributes immensely to our understanding of plastic deformation, fragmentation, and earthquakes. So far, little is known about the role of shear strain in 2D materials. Here we show some evidence of two-dimensional slip avalanches in exfoliated rhombohedral MoS2, triggered by shear strain near the threshold level. Utilizing interfacial polarization in 3R-MoS2, we directly probe the stacking order in multilayer flakes and discover a wide variety of polarization domains with sizes following a power-law distribution. These findings suggest slip avalanches can occur during the exfoliation of 2D materials, and the stacking orders can be changed via shear strain. Our observation has far-reaching implications for developing new materials and technologies, where precise control over the atomic structure of these materials is essential for optimizing their properties as well as for our understanding of fundamental physical phenomena.Comment: To be published in Nano Letter

Promoting Connectivity of Network-Like Structures by Enforcing Region Separation

We propose a novel, connectivity-oriented loss function for training deep convolutional networks to reconstruct network-like structures, like roads and irrigation canals, from aerial images. The main idea behind our loss is to express the connectivity of roads, or canals, in terms of disconnections that they create between background regions of the image. In simple terms, a gap in the predicted road causes two background regions, that lie on the opposite sides of a ground truth road, to touch in prediction. Our loss function is designed to prevent such unwanted connections between background regions, and therefore close the gaps in predicted roads. It also prevents predicting false positive roads and canals by penalizing unwarranted disconnections of background regions. In order to capture even short, dead-ending road segments, we evaluate the loss in small image crops. We show, in experiments on two standard road benchmarks and a new data set of irrigation canals, that convnets trained with our loss function recover road connectivity so well, that it suffices to skeletonize their output to produce state of the art maps. A distinct advantage of our approach is that the loss can be plugged in to any existing training setup without further modifications

Non-trivial scaling of self-phase modulation and three-photon absorption in III-V photonic crystal waveguides

We investigate the nonlinear response of photonic crystal waveguides with suppressed two-photon absorption. A moderate decrease of the group velocity (~ c/6 to c/15, a factor of 2.5) results in a dramatic (30x) enhancement of three-photon absorption well beyond the expected scaling, proportional to 1/(vg)^3. This non-trivial scaling of the effective nonlinear coefficients results from pulse compression, which further enhances the optical field beyond that of purely slow-group velocity interactions. These observations are enabled in mm-long slow-light photonic crystal waveguides owing to the strong anomalous group-velocity dispersion and positive chirp. Our numerical physical model matches measurements remarkably.Comment: 10 pages, 4 figure

Observation of oscillatory relaxation in the Sn-terminated surface of epitaxial rock-salt SnSe {111}\{111\} topological crystalline insulator

Topological crystalline insulators have been recently predicted and observed in rock-salt structure SnSe $\{111\}$ thin films. Previous studies have suggested that the Se-terminated surface of this thin film with hydrogen passivation, has a reduced surface energy and is thus a preferred configuration. In this paper, synchrotron-based angle-resolved photoemission spectroscopy, along with density functional theory calculations, are used to demonstrate conclusively that a rock-salt SnSe $\{111\}$ thin film epitaxially-grown on \ce{Bi2Se3} has a stable Sn-terminated surface. These observations are supported by low energy electron diffraction (LEED) intensity-voltage measurements and dynamical LEED calculations, which further show that the Sn-terminated SnSe $\{111\}$ thin film has undergone a surface structural relaxation of the interlayer spacing between the Sn and Se atomic planes. In sharp contrast to the Se-terminated counterpart, the observed Dirac surface state in the Sn-terminated SnSe $\{111\}$ thin film is shown to yield a high Fermi velocity, $0.50\times10^6$m/s, which suggests a potential mechanism of engineering the Dirac surface state of topological materials by tuning the surface configuration.Comment: 12 pages, 13 figures, supplementary materials include

Mid-Infrared Silicon Photonics

A mid-infrared silicon nanophotonic integrated circuit platform can have broad impact upon environmental monitoring, personalized healthcare, and public safety applications. Development of various mid-IR components, including optical parametric amplifiers, sources, modulators, and detectors, is reviewed