Vertical Location Research Articles

A modified viscosity approach for shear thinning lubricants

Lubrication is essential to minimize wear and friction between contacting surfaces in relative motion. Oil based lubricants are often enhanced via polymer additives to minimize self-degradation due to the shear thinning effect. Therefore, an accurate estimate of the load carrying capacity of the thin lubricating film requires careful modeling of shear thinning. Available models such as the generalized Reynolds equation (GR) and the approximate shear distribution have drawbacks such as large computational time and poor accuracy, respectively. In this work, we present a new approach, i.e., the modified viscosity (MV) model, based on calculating the strain rate only in one point along the vertical direction. We investigate, for both MV and GR, the load, the maximum pressure, and the computational time for (i) sliding (non-cavitating) contacts, (ii) cavitating, and (iii) squeezing contacts. We observe that the computational time is reduced (i) considerably for non-cavitating sliding and rolling contacts and (ii) by several orders of magnitudes for cavitating and squeezing contacts. Furthermore, the accuracy of MV is comparable with the GR model within an appreciable range of bearing numbers. Finally, for each type of boundary motion, we have determined the optimal vertical location to calculate the shear strain rate for MV; while this optimal value is close to half the height of the contact for sliding configurations, for rolling dominated and squeezing contacts it is around one quarter (or three quarter) of their height. We finally provide an analysis to a priori estimate the optimal location of the strain rate.

Evaluation of the posterior superior alveolar artery location and diameter with a newly defined stable plane

The aim of this study was to analyse the vertical location of the posterior superior alveolar artery (PSAA) using a reliable new reference plane regardless of tooth and alveolar bone, and to measure the diameter in each posterior tooth region, which is of relevance to lateral sinus floor elevation surgery. A total of 270 sinuses in 139 patients were examined in this study. The A-plane was defined by A-point and the bilateral jugal points on reconstructed three-dimensional images. The distance from the PSAA to the defined plane was measured in four regions: first premolar (P1), second premolar (P2), first molar (M1), and second molar (M2). The average distance of the PSAA above the plane in the P1, P2, M1, and M2 regions was determined to be 10.24mm, 7.35mm, 5.47mm, and 7.23mm, respectively. The PSAA was found to run above the plane in 97.4% of sinuses, below the plane in 1.1%, and on the plane in 1.5%. In conclusion, the new plane is useful for intraoperative location of the PSAA. According to the study findings, the area below the reference plane can be considered safe for lateral approach sinus surgery in terms of preserving the integrity of the PSAA.

An Investigation into a Miniature Saltless Solar Pond.

A simple, miniature saltless Solar Pond (SP) was designed and constructed in the present work. It consisted of a Plexiglas container with a square cross-section, within which cruciform baffles were suspended in the upper half of the pond, and copper coil tubing was fitted in the middle of the lower zone to function as a heat exchanger without disturbing the pond’s inertia. Different variables’ effect on the water’s temperature rise at various vertical locations within the pond were investigated. These variables included the presence of the cruciform baffles, the inclination of a mirror fixed to the top rim of the pond, a glass transparent cover (GC), and the presence or absence of a gel thickening material to increase the water viscosity inside the SP, the climatic conditions, and the presence of glass wool (GW) in the lower section of the SP. For an experiment, an estimated energy balance was performed, and the thermal storage efficiency was calculated. The best obtained thermal storage efficiency was 32.58% in the presence of the cruciform baffles, a 45° inclination of a mirror fixed to the top rim of the SP, at an ambient temperature of 30 °C on a calm, sunny day with a wind speed of 7 km/h.

Numerical simulation and protection of the dynamic change of Jinan karst spring based on coupling of seepage and conduit flow

The objective of this study was to predict the dynamic change in the spring water level more precisely, to provide timely solutions for karst spring protection. Using the Jinan spring region as a case study, this study established a numerical model of a karst groundwater system, and optimized the mining layout. The calculated maximum extraction volume following the optimized exploitation layout was 0.69 m3/s, in order to ensure the continuous flow of spring water in the median water year. A coupled karst groundwater numerical model with dual structure was developed using the MODFLOW-Conduit Flow Process (CFP), which simulates and then precisely predicts changes in the water level of the karst springs. Here, the plane extension direction of the karst conduit was determined by a tracer test and correlation analysis of the spring water levels and groundwater levels of the observation wells. Meanwhile, the vertical location of the karst conduit was determined by layered monitoring of the groundwater temperature and conductivity. Based on this, a coupling model of seepage and conduit flow was created to simulate the dynamic change in the spring water level, and the dual-media coupling model improved the simulation accuracy of the spring water level. The current study confirmed that, compared to the porous media seepage model, the dual-media coupling model can simulate the groundwater level dynamic change more accurately in a heterogeneous karst aquifer in northern China. The coupling model was used to analyze the effect of supplementation and optimize mining, to ensure that spring water continues to flow during the dry season while supplying the mining demand.

Investigating temporal changes in Jupiter’s aerosol structure with rotationally-averaged 2015–2020 HST WFC3 images

Annual imaging observations of Jupiter from 2015 onward by the Hubble Space Telescope (HST) Wide Field Camera 3 (WFC3) as part of the Outer Planet Atmospheres Legacy (OPAL) program (Simon et al., 2015) have provided a valuable data set from which Jupiter’s temporal variability can be characterized and modeled. Spectral samples at discrete filter bands from the UV to short near-IR wavelengths also provide an opportunity to connect temporal changes in reflectivity with temporal changes in cloud structure. To improve constraints on that cloud structure we used center-to-limb variations that were noise-reduced by rotational averaging during each annual OPAL observation sequence. Fitting observations at multiple and distinctly different observer zenith angles helps to make up for the lack of multiple methane-band filters in discerning the vertical distribution of aerosols. The short-wavelength limit of the OPAL observations also provides better constraints than ground-based observation on the properties of Jupiter’s chromophore, i.e., the compound that creates Jupiter’s variety of red colorations to clouds and hazes composed mainly of colorless condensates. We chose four latitudes to investigate with radiative transfer models based on a simple 3-layer aerosol structure consisting of a deep putative NH3 cloud layer, with a physically thin chromophore layer that has a fitted location at or near the top of the deep cloud, and an overlying stratospheric haze layer. Our chosen planetocentric latitudes were 5.5°S (Equatorial Zone South,EZS), 0° (Equatorial Zone, EZ), 10°N (North Equatorial Belt, NEB), and 21.75°N (North Temperate Belt, NTB). Two major color transformations occurred during the 2015–2020 period we analyzed. One is a dramatic dimming of the center of the Equatorial Zone at short wavelengths, especially after 2017, and a significant reddening of that region. The second is a significant reddening of part of the North Temperate Belt (near 22°N) between 2016 and 2017. Both reddening events can be modeled by doubling of the optical depth of the chromophore layer during the transitions. Comparison with prior 2017 model results for the NEB, EZ, and NTB have revealed agreement with Braude et al. (2020) on the vertical location of the chromophore layer but disagreements on cloud-top pressures and the vertical distribution of stratospheric haze particles. We identified what seems to be common tendency of models based on HST/WFC3 observations to either infer very little stratospheric haze opacity or to put that opacity at too high a pressure.

Artificial neural network approach for investigating the impact of convector design parameters on the heat transfer and total weight of panel radiators

The difficulty of the production stages of panel radiators used for heating purposes reveals the importance of determining the heat transfer performance and panel radiator weight values, which are determined depending on the design parameters. In the present work, an artificial neural network model is proposed for predicting the heat transfer and weight values of a panel radiator as outputs depending on the design parameters of convectors. In the multilayer network model developed with 78 numerically obtained data sets, 8 different design parameters were defined as input parameters and heat transfer and in the output layer panel weight values were obtained. The design parameters of the convectors, in other words, input parameters of network model were chosen as the height of convector, thickness of convector sheet, the trapezoidal height of convector, convector base length, opposing convector distance, tip width of convector, convector vertical location and distance between convectors. For the proposed neural network model, the mean squared errors obtained for the heat transfer and panel radiator weight are −1.25E-04 and -7.54E-05 respectively. In addition, an R-value of 0.99999 has been obtained, and the average deviation value has been calculated as 0.001%. The obtained results show that, depending on the design parameters, the proposed artificial neural network model can predict the rate of heat transfer and weight of the panel radiator with high accuracy. This investigation is supposed to fill a significant gap since it is the pioneer one in open sources on machine learning modeling of panel radiators. Thus, it can possibly make a crucial contribution to the related manufacturing industry.

On the nonlinear seismic response of liquid filled thin-walled steel elevated containers isolated by bearings to earthquake ground motions

In the present study two base isolation systems, i.e. lead-rubber and elastomeric bearings are analyzed and their seismic applicability is compared with reference to a liquid-filled conical elevated container undergoing different ground motions. The drilled shaft system is unlinked either from the base or from the top-mounted bowl by means of damping devices and the impact of such amendment on seismic performance of elevated liquid tank is examined by carrying out time-dependent finite element (FE) analyses on several pedestal-container systems. The developed FE procedure is competent in assaying the precise three-dimensional performance of the isolated elevated containers including the hysteretic performance of bi-linear isolation devices. For the input ground motions, the impacts of various parameters on the efficiency of the seismic bilinear hysteretic members are inspected. The results obtained from the FE analysis are validated against available numerical predictions in the time domain, and a good agreement is found between two methods. The sensitivity of induced forces, the internal hydrodynamic pressure, base moments and displacements in regard to some system parameters comprising lateral versus vertical isolation and locations of isolation devices, have been highlighted. Finally the numerical procedure suggests that earthquake response spectrum in various intensity levels has an influential role in the performance of elevated containers and special attention should be given to the dynamic analysis of such structures.

A 3D Wideband Channel Model for RIS-Assisted MIMO Communications

Recently, reconfigurable intelligent surface (RIS) has drawn much attention due to its capability of improving coverage and communication performance. The development of RIS-assisted communication technology relies on deep understanding of RIS channel characteristics. However, most of the existing investigations focus on the impact of RIS, ignoring the existence of local scatterers in the real propagation environment. The ideal propagation condition limits the accuracy and application of the developed channel model. In this paper, we aim to analyze the channel characteristics of RIS-assisted near-filed communication by considering different conditions of local scatterers. Specifically, we propose a three-dimensional (3D) RIS-assisted multiple-input multiple-output (MIMO) channel model based on a three-dimensional cylinder model, which considers line-of-sight, single-bounced at RIS (SBR) and double-bounced (DB) modes where radio waves reflect from RIS and scatterers near receiver. Based on the proposed channel model, we investigate some key statistical properties for SBR and DB propagation, including the time-frequency-space correlation function and Doppler power spectrum. From the simulation results, it is found that RIS element number, RIS horizontal and vertical locations, distribution of surrounding scatterers, and movement of Rx have significant impacts on channel characteristics. Finally, channel capacities of SBR and DB modes are calculated, where the large size and appropriate locations of RIS significantly improve the channel capacity of RIS-assisted communication. These numerical results and observations can be used for design of RIS-assisted near-field communication systems.

Three-dimensional visualization of thermal environments in urban canyons

Temperature distribution in urban canyons is dynamic, complex, and influenced by a range of heat resources such as radiant heat from reflected sunlight and convective heat from wind flow. While 2D data collection and presentation are the norm for UHI research, we propose using an unmanned aerial vehicle to measure temperatures at different horizontal and vertical locations in urban canyons to develop a 3D visualization of urban thermal environments. We implemented Gestalt laws and transparent and opaque color-coding to improve background recognition and visual closure as well as to better represent the spatiality of temperature data. Our design included grouped color pixels and an interactive temperature slider function. We investigated whether interface usage varied with the flexibility of closure, perceptual speed, and spatial relations of users. Responses from 102 participants indicated that users with flexibility in closure approved of the transparent colors and slider. The primary advantage of this visual model is the elimination of clutter. Visual clutter can cause users to lose their focus when searching a 2D representation of a 3D geographic space. In the proposed model, data hotspots and the boundaries produced by multiple aggregations and clustering enable users to readily and easily find the required information.

Increased Soil Fertility in Tea Gardens Leads to Declines in Fungal Diversity and Complexity in Subsoils

Soil fungi are key drivers regulating processes between ecosystem fertility and plant growth; however, the responses of soil fungi community composition and diversity in deeper soil layers to the plantation and fertilization remain limited. Using soil samples along with vertical soil profile gradients with 0–10 cm, 0–20 cm, 20–40 cm, and 40–60 cm in a tea garden, we used Illumina sequencing to investigate the fungal diversity and assemblage complexity, and correlated to the low, middle, and high-level fertilize levels. The results showed that the fungal community dissimilarities were different between adjacent forests and tea gardens, with predominate groups changed from saprotrophs to symbiotrophs and pathotrophs after the forest converted to the tea garden. Additionally, the symbiotrophs were more sensitive to soil fertility than pathotrophs and saprotrophs. Subsoil fungal communities present lower diversity and fewer network connections under high soil fertility, which contrasted with the trends of topsoil fungi. Soil pH and nutrients were correlated with fungal diversity in the topsoils, while soil K and P concentrations showed significant effects in the subsoil. Overall, the soil fungal communities in tea gardens responded to soil fertility varied with soil vertical spatial locations, which can be explained by the vertical distribution of fungal species. It was revealed that fertility treatment could affect fungal diversity, and alter network structure and potential ecosystem function in tea garden subsoils.

Interaction of two parallel free oscillating flat plates and VIV of an upstream circular cylinder in laminar flow

Flow-induced vibration of bluff bodies and especially circular cylinders have been always of great interest and flat plates are known as useful means for altering flow structure to the desired condition. This work aims to investigate the effect of two parallel downstream flat plates which are mounted in the wake of a circular cylinder. Different configurations including eight horizontal (0.5≤G ≤ 4) and two vertical gaps (H = 0.5, 1) are numerically simulated to focus on the near wake structure and FIV of objects. The results show that the response of parallel plates in the wake of a stationary cylinder depends on both their horizontal and vertical locations. Change in the vertical distance alters the vortex shedding suppression mechanism. While a smaller vertical distance leads to a larger horizontal non-oscillating range, it comes with a higher maximum vibration amplitude. In the case of simultaneous oscillation, all three objects vibrate in all horizontal distances for the smaller vertical gap. The vibration disappears for the larger gap due to weaker interaction between the plates and the shear layers for a range of horizontal distances. The higher vibration amplitude in simultaneous vibration shows the considerable potential of the current concept for developing an improved energy harvesting system.

CFD Analysis of the Location of a Rear Wing on an Aston Martin DB7 in Order to Optimize Aerodynamics for Motorsports

The purpose of this study is to identify the initial lateral and vertical location and angle of attack of a GT4-style rear wing on the rear downforce for an Aston Martin DB7 Vantage, prior to installation. The tests were completed with a two-dimensional model, using the Computational Fluid Dynamics (CFD) software, Fluent Ansys. The tests were completed using a range of velocities: 60–80 mph. Optimization of the position of the rear wing aerodynamic device was permitted under the Motorsport UK rules for multiple race series. The results show that while the drag decreases the farther back the wing is located, the desired configuration for the rear wing with regard to downforce is when it is positioned ca. 1850 mm back from the center point of the car, with an attack angle of 5°. Unusually, this is to the front of the boot/rear deck, but it is remarkably similar to where Aston Martin set the rear wing on their Le Mans car in 1995, above where the rear windscreen met the boot hinge, which was based upon wind tunnel studies using a scale model. Our results suggest that while 2D simulations of these types cannot give absolute values for downforce due to aerodynamic device location, they can provide low costs, fast simulation time, and a route for a wide range of cars, making the approach accessible to club motorsports, unlike complex 3D simulation and wind tunnel experimentation.

Theoretical aspects of root crop grinder development

The article presents results of theoretical studies on development and calculation of a root crop grinder. A mathematical description of the process of movement of cutting elements and feed particles in a cylinder-type root crop grinder with a vertical location of the cylinder is presented. Dependencies between design and operating parameters of the developed root crop grinder were obtained. The research results can be used in development of root crop grinders for preparation of root crops for cattle, pig and poultry feeding.

Vertical distribution patterns of early stages of mesopelagic fishes along 110 °E, south-east Indian Ocean

This study examines vertical distribution of the early stages of mesopelagic fishes in the south-eastern Indian Ocean and oceanographic factors that may affect it. This investigation along the 110 °E transect formed part of the second International Indian Ocean Expedition (IIOE-2). Depth-stratified samples to 500 m depth of early stages of mesopelagic fishes were obtained by means a multinet EZ-1 m2. This net captured larvae and transforming stages, but juveniles and adults were also caught, particularly at night. Diel vertical patterns of the different species and stages were analysed relative to the oceanographic conditions encountered at the 20 stations along the transect. This paper provides the ranges of vertical occurrence and weighted mean depth for larvae (135 taxa), and post-metamorphic stages (75 taxa) of fishes caught during the survey. Despite the varying vertical profiles of oceanographic parameters encountered, there were consistent patterns within species and families along the transect, with broader vertical distribution of larvae at the southern stations, where the upper mixed layer was deeper. During both day and night, larval stages of all the species were concentrated in the epipelagic zone, with some differences in terms of weighted mean depth (WMD) between taxa, but with no significant differences in vertical location between day and night. Transforming and juvenile-adult stages, however, presented a wider vertical distribution range than larval stages, and showed important differences among families and species. For example, Myctophidae and Phosichthyidae species presented the highest concentrations in the upper 50–100 m at night, and a much deeper distribution during the day, thereby indicating night vertical migration behaviour of transforming and juvenile-adult stages. By contrast, during these stages the Gonostomatidae Cyclothone spp. and the Sternoptychidae Argyropelecus spp. occurred deeper than the epipelagic layer during both day and night. Although these vertical patterns concur with results from other oceans, the WMD along 110 °E was slightly deeper than that observed in other areas, such as the eastern Atlantic, possibly related to water transparency in this oligotrophic part of the world's oceans.

Optimum vertical location and design of multiple tuned mass dampers under seismic excitations

An efficient optimum vertical location and design method of multiple tuned mass dampers (MTMDs) is proposed in order to reduce the response of building structures under seismic excitation. Governing equations are derived in frequency domain in terms of random vibration theory and probabilistic critical excitation method. In order to determine the location and optimum parameters of each tuned mass damper (TMD) which are mass, stiffness and damping coefficient, both top storey mean square absolute acceleration and displacement of shear building are chosen as the objective functions to be minimized via Differential Evolution (DE) optimization method. It is assumed that there is one TMD on each storey at the initial stage of the method. During the optimization, if the mass or stiffness parameters convergence to zero on a specific storey, then TMD is eliminated, so that optimum placement can be achieved. The sum of the critical effects corresponding to the selected bandwidths in the first, second and third frequency peak regions of the structure is taken into account, thus the high mode behaviors are also controlled. In order to understand the performance of proposed method, shear building model with multiple TMD is tested using different earthquake acceleration records and the findings are compared with some other studies available in the literature. The results show that the optimal MTMD design obtained from proposed method is very effective in reducing the dynamic response of building structure.

Pollutant dispersion by tall buildings: laboratory experiments and Large-Eddy Simulation

Pollutant dispersion by a tall-building cluster within a low-rise neighbourhood of Beijing is investigated using both full-scale Large-Eddy Simulation and water flume experiments at 1:2400 model-to-full scale with Particle Image Velocimetry and Planar Laser-Induced Fluorescence. The Large-Eddy Simulation and flume results of this realistic test case agree remarkably well despite differences in the inflow conditions and scale. Tall buildings have strong influence on the local flow and the development of the rooftop shear layer which dominates vertical momentum and scalar fluxes. Additional measurements using tall-buildings-only models at both 1:2400 and 1:4800 scales indicates the rooftop shear layer is insensitive to the scale. The relatively thicker incoming boundary layer affects the Reynolds stresses, the relative size of the pollutant source affects the concentration statistics and the relative laser-sheet thickness affects the spatially averaged results of the measured flow field. Low-rise buildings around the tall building cluster cause minor but non-negligible offsets in the peak magnitude and vertical location, and have a similar influence on the velocity and concentration statistics as the scale choice. These observations are generally applicable to pollutant dispersion of realistic tall building clusters in cities. The consistency between simulations and water tunnel experiments indicates the suitability of both methodologies.Graphical abstract

Dynamic wake tracking based on wind turbine rotor loads and Kalman filtering

In a wind farm setting, the location of the wake to which a downwind turbine is exposed is of high interest. It can be used for closed-loop active wake control, ultimately leading to fatigue load reduction and higher power generation. This work proposes a method for dynamic tracking of the meandering wake centre. The rotor takes the role of a sensor, with its blades sampling through the incoming wind field. The measurement of the flapwise blade root bending moment and its decomposition into the non-rotating yaw and tilt moments is used. The latter are linked to the lateral and vertical wake location via a parametric model, tuned with training data from aeroelastic simulations. The implementation of an Extended Kalman Filter (EKF) adds robustness to the tracking and allows to include physical knowledge of the wake meandering to the estimation. For this, the governing equations of the dynamic wake meandering model (DWM) are used to describe the meandering motion as a random walk process. The performance, possibilities and limitations of the tracking method in various inflow conditions are shown and discussed. Generally the wake tracking works satisfying, with estimation errors below 10% of the rotor diameter under moderate turbulence intensity. The Extended Kalman Filter formulation provides the confidence in the tracked wake position. The work shows how this can be effectively used for wake impingement detection.

Demands on acceleration-sensitive nonstructural components in special concentrically braced frame and special moment frame buildings

This study investigates demands on acceleration-sensitive nonstructural components (NSCs) in code-compliant Special Concentrically Braced Frame (SCBF) and Special Moment Frame (SMF) structures. Previous studies have highlighted that the assumption of ASCE 7-16 for the ratio of Peak Floor Acceleration (PFA) to Peak Ground Acceleration (PGA) is overly conservative. In most previous studies, the results were based on generic analytical models with non-deteriorating structural behavior or recorded data from instrumented buildings subjected to ground motions that were significantly weaker than the design-level earthquakes. This study evaluates the acceleration demands on NSCs in 11 archetype buildings modeled using advanced techniques. The ground motions used elicit inelastic response in the frames at the level expected by ASCE 7-16 compliant designs. The study examines the effect of the ratio of NSC period to structural period, NSC damping ratio, and NSC vertical location on these demands. Results of this investigation are compared with the provisions of ASCE 7-16 and the recommendations of the recently completed effort by the Applied Technology Council 120 project (ATC-120), which are the basis for the seismic design requirements for nonstructural components in the forthcoming ASCE 7-22 standard. Equations for the PFA/PGA ratio and NSC amplification factor, which account for the dynamic characteristics of the buildings, are developed based on regression analysis of the generated data. Results of the analyses indicate that the formula recommended by ATC-120 for estimating PFA/PGA along the height of the structure, which includes building nonlinearity effects through a constant building ductility reduction factor, overestimates floor accelerations at the top floors but underestimates them in the lower floors of the archetypes considered. At the same time, results show that the NSC seismic design force equation recommended by ATC-120 is conservative for the SCBF archetypes, while it underestimates the NSC force demands in the SMFs.

Flow Field Study of Effect of Canard Location on Aircraft Aerodynamic Performance

AbstractThe present study investigates the flow behavior due to three different vertical canard locations on the scaled‐down model aircraft by using tuft flow visualization and boundary layer measurements. The aircraft is fabricated with wing airfoil S1223 modified and canard with N22 airfoil using laser cutting technique. Three different color tufts are pasted in wing and canard at 30%, 60%, and 90%. The assembled model is placed inside the subsonic wind tunnel with flow chord Reynolds number 3.8*106, which corresponds to 35 m s−1 of the flow velocity and zero‐degree angle of attack. The boundary layers are measured at 70% of the wing chord with 00 incidence angle at three different span locations, i.e., 30%, 60%, and 90% of the wingspan with varying vertical canard positions. The results are compared with wing alone and it is found that the high wing and high canard configuration are outperformed by providing minimum velocity gradient and hence minimum skin friction drag. The tuft flow visualization also shows the identical results as the boundary layer measurements results. The aerodynamic performance of the high wing high canard configuration is found to be promising, as the skin friction drag coefficient is found to be minimum.

Resource Allocation and 3D Deployment of UAVs-Assisted MEC Network with Air-Ground Cooperation.

Equipping an unmanned aerial vehicle (UAV) with a mobile edge computing (MEC) server is an interesting technique for assisting terminal devices (TDs) to complete their delay sensitive computing tasks. In this paper, we investigate a UAV-assisted MEC network with air–ground cooperation, where both UAV and ground access point (GAP) have a direct link with TDs and undertake computing tasks cooperatively. We set out to minimize the maximum delay among TDs by optimizing the resource allocation of the system and by three-dimensional (3D) deployment of UAVs. Specifically, we propose an iterative algorithm by jointly optimizing UAV–TD association, UAV horizontal location, UAV vertical location, bandwidth allocation, and task split ratio. However, the overall optimization problem will be a mixed-integer nonlinear programming (MINLP) problem, which is hard to deal with. Thus, we adopt successive convex approximation (SCA) and block coordinate descent (BCD) methods to obtain a solution. The simulation results have shown that our proposed algorithm is efficient and has a great performance compared to other benchmark schemes.