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Room-temperature exciton-polariton is observed in GaN/InGaN core-shell microrods grown by metal-organic vapor phase epitaxy. We demonstrate a large Rabi splitting in the core-shell microrod structure over 265 meV. Room-temperature lasing in core-shell microrods is confirmed by power-dependent photoluminescence spectra. The lasing in the shell layer results to a modulated lasing wavelength and takes one step further to more stable polariton lasing in MQW core-shell microrods.

High-redshift quasars ionize HeII into HeIII around them, heating the IGM in the process and creating large regions with elevated temperature. In this work, we demonstrate a method based on a convolutional neural network (CNN) to recover the spatial profile for $T_0$, the temperature at the mean cosmic density, in quasar proximity zones. We train the neural network with synthetic spectra drawn from a Cosmic Reionization on Computers simulation. We discover that the simple CNN is able to recover the temperature profile with an accuracy of $\approx 1400$ K in an idealized case of negligible observational uncertainties. We test the robustness of the CNN and discover that it is robust against the uncertainties in quasar host halo mass, quasar continuum and ionizing flux. We also find that the CNN has good generality with regard to the hardness of quasar spectra. Saturated pixels pose a bigger problem for accuracy and may downgrade the accuracy to $1700$ K in the outer parts of the proximity zones. Using our method, one could distinguish whether gas is inside or outside the HeIII region created by the quasar. Because the size of the HeIII region is closely related to the total quasar lifetime, this method has great potential in constraining the quasar lifetime on $\sim $Myr timescales., 10 pages, 11 figures, comments welcome

Electron leakage currents seriously limit the power conversion efficiencies (PCEs) of gallium nitride (GaN)-based laser diodes (LDs). To minimize the leakage currents, electron blocking layers are generally applied in the p-type region. However, few works have discussed the electron blocking effect of a p-cladding layer, which is found to be critical in suppressing the leakage currents of an LD. In this work, we compare the blocking performance of uniform AlGaN p-cladding layers and AlGaN/GaN superlattice (SL) p-cladding layers with the same average Al component respectively. Both light-emitting diodes (LEDs) and LDs with the same epitaxy structures are characterized by light–current (L–I) and current–voltage (I–V) measurements. The latest analytical model of leakage currents is applied to fit the L–I curves of LEDs, where smaller leakage coefficients are observed in the SL structures compared with the uniform-layer structures. Eighty LDs with varying ridge widths are studied by comparing the threshold current densities, slope efficiencies, and PCEs. The SL-based p-cladding layer shows statistically significant advantages over a uniform AlGaN layer. The blocking effects of both scattering- and bound-state electrons in SLs are investigated theoretically. Repetitive reflection and thermal relaxation are responsible for the blocking effect of scattering-state electrons. Simulation results indicate that the tunneling effect of bound-state electrons through a miniband mechanism is insignificant at a large injection level due to a negative differential conductivity by the Esaki–Tsu effect. We demonstrate a better electron blocking performance of p-cladding layers based on SLs than uniform AlGaN layers in GaN-based LDs.

Maintaining crystal quality during the growth of very thick multiple-quantum-wells is challenging due to the progressive deterioration in thick low-temperature barriers. The insertion of several high-temperature crystallinity restoring (CR) layers can significantly improve the surface morphology. Nevertheless, owing to their relatively high growth temperatures, their position still affects the luminescence of the nearby quantum well (QW). We observe that the photoluminescence (PL) intensity of the QW does not drop significantly when a high-temperature CR layer is grown directly on top of the QW; rather the intensity drops badly when an underlying CR layer is placed too close to the QW. Nitrogen vacancies (VN) generated in a CR layer can move upward into the QW and harm its optical properties. We believe a burying effect enables GaN spacers to block VN introduced by the CR layers, thus reduces the impact of CR layers on the QWs. We find the optimal position for the CR layers is right after each QW. 1 μm-thick MQWs with a smooth surface and good luminescence intensity are demonstrated with the implementation of CR layers.

Two-dimensional (2D) single-crystalline perovskites are a suitable material for investigating the strong exciton–photon interaction due to the large exciton binding energy. Here, we grow high-quality 2D single-crystalline PEA2PbBr4 thin film in situ in between a pair of distributed Bragg reflectors and construct an anisotropic exciton–polariton microcavity. Clear evidence for strong exciton–photon coupling is observed and represented by a large coupling strength of 211.8 meV. The observed transverse electric–transverse magnetic splitting at the point where the in-plane wave vector is zero indicates crystal birefringence. The effective refractive indices for these two orthogonal polarization directions are derived to have a large difference, corresponding to a material index difference of 0.28, and then an in-plane refractive index ellipse is built for the material. This work shows that the 2D anisotropic perovskite microcavity can not only behave as a platform for characterizing the anisotropic properties of a material but also as a promising room-temperature polaritonic device.

The electrical-to-optical power conversion efficiencies of the light-emitting devices based on gallium nitride (GaN) are seriously limited by electron leakage currents due to the relatively low mobility and activation ratio of holes. However, there have been few theoretical models on the behavior of the leakage current with an increasing total current. We develop an Ohmic-law-like method to describe the transport behaviors of the systems with electron and hole currents simultaneously. Based on reasonable assumptions, the ratio of the leakage current to the total current is related to the differential resistances of the devices. Through the method, we develop analytical models of the leakage currents in GaN-based laser diodes (LDs) and light-emitting diodes (LEDs). The ratios of the leakage currents with total currents in LDs and LEDs are shown to increase, which explains the sublinear behaviors of the luminescence-current (LI) curves of the devices. The theory agrees well with the numerical simulation and experimental results in larger current ranges in comparison to the traditional ABC model. The above analytical model can be used to fast evaluate the leakage currents in GaN-based LDs and LEDs.

We present a new investigation of the intergalactic medium (IGM) near reionization using dark gaps in the Lyman-$\beta$ (Ly$\beta$) forest. With its lower optical depth, Ly$\beta$ offers a potentially more sensitive probe to any remaining neutral gas compared to commonly used Ly$\alpha$ line. We identify dark gaps in the Ly$\beta$ forest using spectra of 42 QSOs at $z_{\rm em}>5.5$, including new data from the XQR-30 VLT Large Programme. Approximately $40\%$ of these QSO spectra exhibit dark gaps longer than $10h^{-1}{\rm Mpc}$ at $z\simeq5.8$. By comparing the results to predictions from simulations, we find that the data are broadly consistent both with models where fluctuations in the Ly$\alpha$ forest are caused solely by ionizing ultraviolet background (UVB) fluctuations and with models that include large neutral hydrogen patches at $z, Comment: 17 pages, 13 figures, accepted for publication in ApJ. The Figure set and machine readable table are available at https://ydzhuastro.github.io/lyb.html

Electron leakage currents seriously hinder GaN-based blue laser diodes (LDs) from high wall-plug efficiencies. Inserting an ultra-thin AlGaN electron blocking layer (EBL) in the epitaxy structure is a major technique to suppress the leakage currents for which a high Al composition in the EBL is necessary. Despite many studies on the optimization of the compositions of EBLs, it is questionable whether they reach the designed value in real growths by metal-organic vapor phase epitaxy. We investigate the influence of the growth conditions of upper cladding layers (CLs) on the underlying EBLs. A strong composition degradation of the EBL is observed when the growth rate of the CL is low, which drastically reduces the output performance of both LEDs and LDs. A 30-nm fast-growing protecting layer can efficiently prevent the EBL from such degradation. The phenomenon cannot be explained by a composition pulling effect nor an etch effect by hydrogen, but by a mutual solid solution between the EBL and the adjacent CL. The solution process is found thermally favored by calculating the Gibbs energy where strain and entropies are considered. It is inferred that the chemically active Ga adatoms at the surface play an important role in accelerating the solution process. Based on these considerations, we introduce a random walk model to clarify the kinetic influence of CL growth rates on EBL degradation semi-quantitatively. The results help to understand the subtle process in the growth of heterostructures and the transport process of GaN-based LDs.

Using a suite of self-similar cosmological simulations, we measure the probability distribution functions (PDFs) of real-space density, redshift-space density, and their geometric mean. We find that the real-space density PDF is well-described by a function of two parameters: $n_s$, the spectral slope, and $\sigma_L$, the linear rms density fluctuation. For redshift-space density and the geometric mean of real- and redshift-space densities, we introduce a third parameter, $s_L={\sqrt{\langle(dv^L_{\rm pec}/dr)^2\rangle}}/{H}$. We find that density PDFs for the LCDM cosmology is also well-parameterized by these three parameters. As a result, we are able to use a suite of self-similar cosmological simulations to approximate density PDFs for a range of cosmologies. We make the density PDFs publicly available and provide an analytical fitting formula for them., Comment: 9 pages, 10 figures, submitted to ApJ, comments welcome

Taking the Yulou oil-bearing sets in some experimental area of the West Depression in Liaohe Basin as an example, based on logs from 400 wells, cores from seven wells, three-dimensional seismic data, and analysis and test data, fine stratigraphic correlation and sedimentary facies analysis have been carried out. The researches are conducted to find out the developmental characteristics of barrier layers and interlayers in the target horizon and their influence on the heavy oil thermal recovery. From the perspective of oil genesis, the barrier layers and interlayers are divided into three types. Thickness of barrier layers sandwiched between different layers is mostly more than 2 m. It is shown that the existence of barrier layers and interlayers greatly enhances the spatial heterogeneity of reservoir. The production practice shows that the interlayers have strong impact on the reservoir development.

Taking some steam flooding experimental area in the western depression of the Liaohe Basin in China as an example, it quantitatively evaluates the flow units of the sedimentary facies in fan delta front and analyzes the influences of the flow units on the development of the oilfields. Comprehensive analysis of multifarious data such as geology, core analysis and well logs indicates that porosity, permeability and FZI are key parameters for classification and evaluation of the reservoir flow units. Then using SPSS cluster analysis software platform, cluster analysis are conducted on reservoir physical properties of cored wells, and based on which discriminant analysis are performed to obtain the discriminant formula. The discriminant analysis of reservoir physical properties of the wells without core data is based on fine interpretation of well logging data. Combined with the results of cored wells, the classification and evaluation of the flow units has been completed in the target layer of ​​the whole study area. Finally the flow units are divided into four classes, namely, Class A, Class B, Class C and Class D. Classes A and B flow units represent high-quality reservoirs. The flow units are mainly controlled by sedimentation. Classes A and B are mainly sedimentary microfacies of underwater distributary channel and distributary mouth sand bar. The paper proposes five principles of judging the rationality of flow units, describes the development characteristics of different classes of flow units on section and plane, analyzes the influence of flow units on oilfield development and suggests countermeasures. Specially, in the process of steam flooding, target injection layers should be optimized and steam injection pressure should be effectively controlled to prevent steam channeling; when planning infill wells, injection and production wells should be deployed in the same class of flow unit to ensure good connectivity; the development of remaining oil should focus on Classes A and B flow units, and meanwhile pay more attention to the fine interpretation results of well logging data.

Room-temperature polariton lasing is achieved in GaN microrods grown by metal-organic vapor phase epitaxy. We demonstrate a large Rabi splitting (Ω = 2g0) up to 162 meV, exceeding the results from both the state-of-the-art nitride-based planar microcavities and previously reported GaN microrods. An ultra-low threshold of 1.8 kW/cm2 is observed by power-dependent photoluminescence spectra, with the linewidth down to 1.31 meV and the blue shift up to 17.8 meV. This large Rabi splitting distinguishes our coherent light emission from a conventional photon lasing, which strongly supports the preparation of coherent light sources in integrated optical circuits and the study of exciting phenomena in macroscopic quantum states.

Taking a steam flooding experimental area in the West depression in Liaohe Basin in China as an example, the development characteristics of reservoir oil-gas-water system is studied using methods of geological statistics and comparative analysis based on the comprehensive of core, well logging, analytical test, and development performance data. The aimed stratum has good oil-bearing properties, and the oil content level of cores is mainly oil sand and oil-bearing sandstone. The lower limit of effective reservoir has a porosity of 28% and a permeability of 30 mD. In the aimed stratum, the oil viscosity increases gradually with the increase of oil density, and the correlation between the wax content and density of oil is not obvious. With the increase of oil viscosity, the resin and asphaltene contents increase. And with the increase of oil density, the resin and asphaltene contents gradually increase as well. The oil density is relatively big, and most of the 14 samples have a density greater than 0.97 g/cm3. The oil viscosity is mostly greater than 5000 mpa s. The wax content is relatively low (mostly less than 2.5%) with the maximum of 4%. The contents of resin and asphaltene are both greater than 38%, which are relatively high. The formation water is NaHCO3 type which is slightly alkaline. The oil-water contacts of different reservoirs in Yulou oil-bearing sets I are between depth of 1020 m and 1060 m. The distribution of oil layers is jointly controlled by the sediments and structures factors. For the thickness of single oil layer, the maximum is more than 5 m, while the minimum is only one to 2 m. The edge and bottom water plays a very important role in the development of oilfields. In designing and executing various EOR methods in the process of thermal recovery, the influence of reservoir oil-gas-water system should be fully taken into account.

Measuring the density of the intergalactic medium using quasar sightlines in the epoch of reionization is challenging due to the saturation of Lyman-$\alpha$ absorption. Near a luminous quasar, however, the enhanced radiation creates a proximity zone observable in the quasar spectra where the Lyman-$\alpha$ absorption is not saturated. In this study, we use $10$ high-resolution ($R\gtrsim 10,000$) $z\sim 6$ quasar spectra from the extended XQR-30 sample to measure the density field in the quasar proximity zones. We find a variety of environments within $3$ pMpc distance from the quasars. We compare the observed density cumulative distribution function (CDF) with models from the $\textit{Cosmic Reionization on Computers}$ simulation, and find a good agreement between $1.5$ to $3$pMpc from the quasar. This region is far away from the quasar hosts and hence approaching the mean density of the universe, which allows us to use the CDF to set constraints on the cosmological parameter $\sigma_8=0.6\pm0.3$. The uncertainty is mainly due to the limited number of high-quality quasar sightlines currently available. Utilizing the more than $>200$ known quasars at $z\gtrsim 6$, this method will allow us in the future to tighten the constraint on $\sigma_8$ to the percent level. In the region closer to the quasar within $1.5$ pMpc, we find the density is higher than predicted in the simulation by $1.23 \pm 0.17$, suggesting the typical host dark matter halo mass of a bright quasar ($M_{\rm 1450}, Comment: 16 pages, 11 figures, submitted to ApJ, comments are welcome

The matter density field at $z\sim 6$ is very challenging to probe. One of the traditional probes of the low density IGM that works successfully at lower redshifts is the Lyman-alpha forest in quasar spectra. However, at the end of reionization, the residual neutral hydrogen usually creates saturated absorption, thus much of the information about the gas density is lost. Luckily, in a quasar proximity zone, the ionizing radiation is exceptionally intense, thus creating a large region with non-zero transmitted flux. In this study we use the synthetic spectra from simulations to investigate how to recover the density fluctuations inside the quasar proximity zones. We show that, under ideal conditions, the density can be recovered accurately with a small scatter. We also discuss how systematics such as the quasar continuum fitting and reionization models affect the results. This study shows that by analyzing the absorption features inside quasar proximity zones we can potentially constrain quasar properties and the environments they reside in., Comment: 12 pages, 12 figures, comments welcome

Quasi two-dimensional (2D) perovskites are a new class of laser gain medium; however, the thickness of the solution-processed perovskite layer is usually too thin to support an optical mode due to the low solubilities of precursors. Here, we report a flexible large-area film transfer method to lengthen the cavity according to the resonant condition. Then a single-mode vertical-cavity quasi 2D (PEA)2Csn-1PbnX3n+1 (X:Br, Cl) perovskite pure green laser is demonstrated, which has a low threshold of 39.3 μJ/cm−2, a high-quality factor of 1159, and a highly linear polarization degree of 92.5% under nanosecond pulsed optical pumping. This is a significant step toward low-cost practical perovskite lasers.

Strong spontaneous polarization and piezoelectric effects in hexagonal gallium nitride (h-GaN) seriously limit the efficiency of h-GaN-based devices. To overcome this issue, a pyramidal-shaped four V-grooved silicon (4PVG-Si) patterned substrate is introduced for transforming h-GaN into cubic GaN (c-GaN) at the nanoscale. The purpose of using 4PVG-Si instead of simple V-grooved Si (VG-Si) is to improve the crystal quality with the maximum cubic volume of GaN. The growth of c-GaN was verified by high-resolution x-ray diffraction and cathodoluminescence, whereas high-resolution transmission electron microscopy (HRTEM) was further used to analyze the excessive and smooth c-GaN growth. The HRTEM images revealed that optimizing the growth of an aluminum nitride layer with 10–15 nm thicknesses promotes the maximum c-GaN volume. However, exceeding this thickness tended to the reduction in c-GaN volume, resulting in the development of big voids with abnormal tip-shaped growth. In the presence of big voids and abnormal tip-shaped growth, the hexagonal growth closed very late, and the cubic volume of c-GaN is reduced. To further promote the cubic phase of GaN, the growth conditions of GaN were also optimized. Our results proved that the design of 4PVG-Si and optimized growth conditions promote the maximum cubic volume of GaN.

Gallium nitride (GaN) is a promising semiconductor for the fabrication of a wide range of electronic and optoelectronic devices. For GaN grown on widely used sapphire substrate, bundles of threading dislocations (TDs) are induced by thermal and lattice mismatch. These TDs intersect the surface of GaN and degrade the internal quantum efficiency (IQE) of GaN-based devices. To address this issue, two innovative techniques are proposed for effective filtration of TDs. First, a novel design of serpentine channel pattern sapphire substrate (SCPSS) is applied for effective filtration of TDs at the interface. Transmission electron microscopy (TEM) indicated that SCPSS plays an effective role in the filtration of TDs; however, cathodoluminescence (CL) revealed that many TDs still intersect the surface of GaN. To further optimize the growth of GaN, the temperature was ramped down to the intermediate level and an interlayer (IL) of InGaN was introduced near the window of SCPSS. CL analysis indicated that additional use of InGaN-IL further reduced the TDs. Raman microscopy showed that incorporation of IL lead to drastic reduction in compressive stress. Atomic force microscopy (AFM) confirmed the achievement of excellent surface topography with InGaN-IL. Moreover, it is observed that growth of GaN by SCPSS is better than conventional growth because of improved surface morphology and low TDs. The reduction of TDs by SCPSS and InGaN-IL is an effective approach for the growth of high-quality GaN towards efficient devices.

In this paper, we study the sizes of quasar proximity zones with synthetic quasar absorption spectra obtained by post-processing a Cosmic Reionization On Computers (CROC) simulation. CROC simulations have both relatively large box sizes and high spacial resolution, allowing us to resolve Lyman limit systems, which are crucial for modeling the quasar absorption spectra. We find that before reionization most quasar proximity zone sizes grow steadily for $\sim 10$ Myr, while after reionization they grow rapidly but only for $\sim 0.1$ Myr. We also find a slow growth of $R_{\rm obs}$ with decreasing turn-on redshift. In addition, we find that $\sim 1-2\%$ of old quasars ($30$ Myr old) display extremely small proximity zone sizes ($, Comment: 18 pages, 15 figures, comments welcome!

Fracture, as an important factor affecting the quality of reservoirs, has always been one of the most crucial research contents in the process of oil and gas field development. The basis of research on fault systems in oil and gas field development was introduced from two aspects, namely, data foundation and research methods. The volcanic reservoir of the Yingcheng Formation in the Xudong Area of the Songliao Basin, the glutenite reservoir of the Lower Karamay Formation in a block in the northwestern margin of the Junggar Basin, and the heavy oil reservoir developed by thermal recovery in the Yulou Oil Bearing Sets in an experimental area in the western slope of the western depression of the Liaohe Basin, were taken as examples to elaborate the application of fault research in oil and gas field development from three aspects: design of volcanic gas reservoir development program, architecture analysis of glutenite reservoir, and fault systems in heavy oil reservoirs developed by thermal recovery. Based on these different Chinese examples, the difficulties and hot issues in the research of fault systems in oil and gas field development were discussed. The results show that the fine characterization of location, scale, and distribution law of faults and fractures, analysis of fault architecture of reservoirs, fine interpretation and modeling of faults, and evaluation of fault sealing property are closely related to the effective development of oil and gas fields; therefore, they should be given adequate attention in the process of oil and gas field development.

The development of heavy oil by thermal recovery technology has a significant impact on reservoir properties. The study on the changes of reservoir properties during the development process is important for improving reservoir development and enhancing oil recovery. Taking some experimental areas in the Western Depression of the Liaohe Basin as an example, this paper analyzes the changing laws and causes of reservoirs in the process of heavy oil thermal recovery, and investigates the influences on oilfield development and finally proposes corresponding countermeasures based on core observation, thin slice analysis under scanning microscope, SEM and lab testing, and analytical data. Reservoir property characteristics in the study area are high porosity and high permeability, with an average porosity of 31.25% and an average permeability of 1829.3 mD. Sedimentary characteristics are the material basis for the changes of reservoirs in the development process, and the heat provided in the thermal recovery process has some effects on diagenesis. In the development process, many changes may take place on reservoirs, such as sensitivity to water, steam injection rate, and salt. Accordingly, reservoir properties may change too. Reservoirs may be sensitive to water, more to injection rate, and the most to acid. As thermal recovery progresses, the properties of clay minerals in reservoirs become more stable under the influence of diagenesis. Generally, steam flooding leads to lower porosity and permeability and poorer physical properties of reservoirs. When shifting steam stimulation to steam flooding, the changing law of reservoirs should be fully understood, more studies should be given to diagenesis, and steam should be injected at the appropriate pressure and rate, into finely separated layers, so as to increase oil recovery.

We use a statistical sample of galaxy clusters from a large cosmological $N$-body$+$hydrodynamics simulation to examine the relation between morphology, or shape, of the X-ray emitting intracluster medium (ICM) and the mass accretion history of the galaxy clusters. We find that the mass accretion rate (MAR) of a cluster is correlated with the ellipticity of the ICM. The correlation is largely driven by material accreted in the last $\sim 4.5$~Gyr, indicating a characteristic time-scale for relaxation of cluster gas. Furthermore, we find that the ellipticity of the outer regions ($R\sim R_{\rm 500c}$) of the ICM is correlated with the overall MAR of clusters, while ellipticity of the inner regions ($\lesssim 0.5 R_{\rm 500c}$) is sensitive to recent major mergers with mass ratios of $\geq 1:3$. Finally, we examine the impact of variations in cluster mass accretion history on the X-ray observable-mass scaling relations. We show that there is a {\it continuous\/} anti-correlation between the residuals in the $T_x-M$ relation and cluster MARs, within which merging and relaxed clusters occupy extremes of the distribution rather than form two peaks in a bi-modal distribution, as was often assumed previously. Our results indicate the systematic uncertainties in the X-ray observable-mass relations can be mitigated by using the information encoded in the apparent ICM ellipticity., 10 pages, 7 figures, comments welcome

Full author list: R. Morgan, M. Soares-Santos, J. Annis, K. Herner, A. Garcia, A. Palmese, A. Drlica-Wagner, R. Kessler, J. García-Bellido, T. G. Bachmann, N. Sherman, S. Allam, K. Bechtol, C. R. Bom, D. Brout, R. E. Butler, M. Butner, R. Cartier, H. Chen, C. Conselice, E. Cook, T. M. Davis, Z. Doctor, B. Farr, A. L. Figueiredo, D. A. Finley, R. J. Foley, J. Y. Galarza, M. S. S. Gill, R. A. Gruendl, D. E. Holz, N. Kuropatkin, C. Lidman, H. Lin, U. Malik, A. W. Mann, J. Marriner, J. L. Marshall, C. E. Martínez-Vázquez N. Meza, E. Neilsen, C. Nicolaou, F. Olivares E., F. Paz-Chinchón, S. Points, J. Quirola-Vásquez, O. Rodriguez, M. Sako, D. Scolnic, M. Smith, F. Sobreira, D. L. Tucker, A. K. Vivas, M. Wiesner, M. L. Wood, B. Yanny, A. Zenteno, T. M. C. Abbott, M. Aguena, S. Avila, E. Bertin, S. Bhargava, D. Brooks, D. L. Burke, A. Carnero Rosell, M. Carrasco Kind, J. Carretero, L. N. da Costa, M. Costanzi, J. De Vicente, S. Desai, H. T. Diehl, P. Doel, T. F. Eifler, S. Everett, B. Flaugher, J. Frieman, E. Gaztanaga, D. W. Gerdes, D. Gruen, J. Gschwend, G. Gutierrez, W. G. Hartley, S. R. Hinton, D. L. Hollowood, K. Honscheid, D. J. James, K. Kuehn, O. Lahav, M. Lima, M. A. G. Maia, M. March, R. Miquel, R. L. C. Ogando, A. A. Plazas, A. Roodman, E. Sanchez, V. Scarpine, M. Schubnell, S. Serrano, I. Sevilla-Noarbe, E. Suchyta, and G. Tarle, On 2019 August 14, the LIGO and Virgo Collaborations detected gravitational waves from a black hole and a 2.6 solar mass compact object, possibly the first neutron star-black hole merger. In search of an optical counterpart, the Dark Energy Survey (DES) obtained deep imaging of the entire 90% confidence level localization area with Blanco/DECam 0, 1, 2, 3, 6, and 16 nights after the merger. Objects with varying brightness were detected by the DES Pipeline, and we systematically reduced the candidate counterparts through catalog matching, light-curve properties, host-galaxy photometric redshifts, Southern Astrophysical Research spectroscopic follow-up observations, and machine-learning-based photometric classification. All candidates were rejected as counterparts to the merger. To quantify the sensitivity of our search, we applied our selection criteria to full light-curve simulations of supernovae and kilonovae as they would appear in the DECam observations. Because the source class of the merger was uncertain, we utilized an agnostic, three-component kilonova model based on tidally disrupted neutron star (NS) ejecta properties to quantify our detection efficiency of a counterpart if the merger included an NS. We find that, if a kilonova occurred during this merger, configurations where the ejected matter is greater than 0.07 solar masses, has lanthanide abundance less than 10-8.56, and has a velocity between 0.18c and 0.21c are disfavored at the 2σ level. Furthermore, we estimate that our background reduction methods are capable of associating gravitational wave signals with a detected electromagnetic counterpart at the 4σ level in 95% of future follow-up observations., R. Morgan thanks the LSSTC Data Science Fellowship Program, which is funded by LSSTC, NSF Cybertraining Grant #1829740, the Brinson Foundation, and the Moore Foundation; his participation in the program has benefited this work. F. O.E. acknowledges support from the FONDECYT grant No. 1201223. This material is based upon work supported by the National Science Foundation Graduate Research Fellowship Program under grant No. 1744555. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation. Funding for the DES Projects has been provided by the U.S. Department of Energy, the U.S. National Science Foundation, the Ministry of Science and Education of Spain, the Science and Technology Facilities Council of the United Kingdom, the Higher Education Funding Council for England, the National Center for Supercomputing Applications at the University of Illinois at Urbana-Champaign, the Kavli Institute of Cosmological Physics at the University of Chicago, the Center for Cosmology and AstroParticle Physics at The Ohio State University, the Mitchell Institute for Fundamental Physics and Astronomy at Texas A&M University, Financiadora de Estudos e Projetos, Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro, Conselho Nacional de Desenvolvimento Científico e Tecnológico and the Ministério da Ciência, Tecnologia e Inovação, the Deutsche Forschungsgemeinschaft, and the Collaborating Institutions in the Dark Energy Survey. The Collaborating Institutions are Argonne National Laboratory, the University of California at Santa Cruz, the University of Cambridge, Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas-Madrid, the University of Chicago, University College London, the DES-Brazil Consortium, the University of Edinburgh, the Eidgenössische Technische Hochschule (ETH) Zürich, Fermi National Accelerator Laboratory, the University of Illinois at UrbanaChampaign, the Institut de Ciències de l’Espai (IEEC/CSIC), the Institut de Física d’Altes Energies, Lawrence Berkeley National Laboratory, the Ludwig-Maximilians Universität München and the associated Excellence Cluster Universe, the University of Michigan, NFS’s NOIRLab, the University of Nottingham, The Ohio State University, the University of Pennsylvania, the University of Portsmouth, SLAC National Accelerator Laboratory, Stanford University, the University of Sussex, Texas A&M University, and the OzDES Membership Consortium. The UCSC team is supported in part by NASA grant NNG17PX03C, NSF grant AST-1815935, the Gordon & Betty Moore Foundation, the Heising-Simons Foundation, and by fellowships from the David and Lucile Packard Foundation to R.J.F. Based in part on observations at Cerro Tololo InterAmerican Observatory at NSFʼs NOIRLab (NOIRLab Prop. ID 2012B-0001; PI: J. Frieman), which is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation. Based on observations obtained at the Southern Astrophysical Research (SOAR) telescope, which is a joint project of the Ministério da Ciência, Tecnologia, Inovação e Comunicações (MCTIC) da República Federativa do Brasil, the U.S. NSF’s NOIRLab, the University of North Carolina at Chapel Hill (UNC), and Michigan State University (MSU). The DES data management system is supported by the National Science Foundation under grant Nos. AST-1138766 and AST-1536171. The DES participants from Spanish institutions are partially supported by MICINN under grants ESP2017-89838, PGC2018-094773, PGC2018-102021, SEV2016-0588, SEV-2016-0597, and MDM-2015-0509, some of which include ERDF funds from the European Union. IFAE is partially funded by the CERCA program of the Generalitat de Catalunya. Research leading to these results has received funding from the European Research Council under the European Union’s Seventh Framework Program (FP7/2007- 2013), including ERC grant agreements 240672, 291329, and 306478. We acknowledge support from the Brazilian Instituto Nacional de Ciência e Tecnologia (INCT) e-Universe (CNPq grant 465376/2014-2). This paper has gone through internal review by the DES collaboration. This manuscript has been authored by the Fermi Research Alliance, LLC under Contract No. DE-AC02- 07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics.

We analyzed the lithology and sedimentary structures of the lower Karamay formation alluvial fan of Karamay oilfield in Junggar basin and subdivided its lithofacies into six types. The depositional regimes of the lower Karamay formation regressive alluvial fans contain (1) cohesive debris flows, (2) sandy debris flows, (3) grain flows, (4) turbidity currents, and (5) traction currents in the light of sedimentary fabrics and lithofacies association. In terms of lithofacies association, depositional succession, boundary surface hierarchy and wireline logs, fourth-order reservoir architectures for this alluvial fan are composed of nine types: (1) trench channel conglomerates, (2) trench sandy conglomerates, (3) trench proximal sandbody, (4) trench sheetflood lithosome, (5) trench distal sandbody, (6) braided channel, (7) channel gravel bar, (8) overflow sandbody, and (9) runoff channel. On the basis of the reservoir architecture identification of all wells, we established a three-dimensional (3D) architectural element model of the lower Karamay formation with a method of sequential indicator simulation to reveal the reservoir architecture spatial distribution. Integrated three-dimensional reservoir architecture models with contemporary depositional characteristics of alluvial fans, we concluded the depositional patterns of reservoir architectures for different alluvial fan subfacies, which shows the geometric features and aspects of the reservoir architectures. This information provided a technical foundation for the remaining oil prediction, development strategy optimization, and oil recovery enhancement of the conglomeratic oil reservoirs at the high water-cut stage.