Optical Studies of 10 Hard X-Ray-selected Cataclysmic Binaries

We conducted time-resolved optical spectroscopy and/or photometry of 10 cataclysmic binaries that were discovered in hard X-ray surveys, with the goal of measuring their orbital periods and searching for evidence that they are magnetic. Four of the objects in this study are new optical identifications: IGR J18017−3542, PBC J1841.1+0138, IGR J18434−0508, and Swift J1909.3+0124. A 311.8 s, coherent optical pulsation is detected from PBC J1841.1+0138, as well as eclipses with a period of 0.221909 days. A 152.49 s coherent period is detected from IGR J18434−0508. A probable period of 389 s is seen in IGR J18151−1052, in agreement with a known X-ray spin period. We also detect a period of 803.5 s in an archival X-ray observation of Swift J0717.8−2156. The last four objects are thus confirmed magnetic cataclysmic variables of the intermediate polar class. An optical period of 1554 s in AX J1832.3−0840 also confirms the known X-ray spin period, but a stronger signal at 2303 s is present whose interpretation is not obvious. We also studied the candidate intermediate polar Swift J0820.6−2805, which has low and high states differing by ≈4 mag and optical periods or quasi-periodic oscillations not in agreement with proposed X-ray periods. Of note is an unusually long 2.06-day orbital period for Swift J1909.3+0124, manifest in the radial velocity variation of photospheric absorption lines of an early K-type companion star. The star must be somewhat evolved if it is to fill its Roche lobe.

Detection of Building Response Changes Using Deconvolution Interferometry: A Case Study in Bogota, Colombia

Seismic structural health monitoring allows for the continuous evaluation of engineering structures by monitoring changes in the structural response that can potentially localize associated damage that has occurred. For the first time in Colombia, a permanent and continuous monitoring network has been deployed in a 14-story ecofriendly steel-frame building combined with a reinforced concrete structure in downtown Bogota. The six three-component ETNA-2 accelerometers recorded continuously for 225 days between July 2019 and February 2020. We use deconvolution-based seismic interferometry to calculate the impulse response function (IRF) using earthquake and ambient-vibration data and a stretching technique to estimate velocity variations before and after the Ml 6.0 Mesetas earthquake and its aftershock sequence. A consistent and probably permanent velocity variation (2% reduction) is detected for the building using ambient-vibration data. In contrast, a 10% velocity reduction is observed just after the mainshock using earthquake-based IRFs showing a quick recovery to about 2%. A combination of both earthquake-based and ambient-vibration-based deconvolution interferometry provides a more complete picture of the state of health of engineering structures.

The Influence of Headform/Helmet Friction on Head Impact Biomechanics in Oblique Impacts at Different Tangential Velocities

Oblique impacts of the helmet against the ground are the most frequent scenarios in real-world motorcycle crashes. The combination of two factors that largely affect the results of oblique impact tests are discussed in this work. This study aims to quantify the effect of the friction at the interface between the headform and the interior of a motorcycle helmet at different magnitudes of tangential velocity. The helmeted headform, with low friction and high friction surface of the headform, was dropped against three oblique anvils at different impact velocities resulting in three different magnitudes of the tangential velocity (3.27 m/s, 5.66 m/s, 8.08 m/s) with the same normal component of the impact velocity (5.66 m/s). Three impact directions (front, left-side and right-side) and three repetitions per impact condition were tested resulting in 54 impacts. Tangential velocity variation showed little effect on the linear acceleration results. On the contrary, the rotational results showed that the effect of the headform’s surface depends on the magnitude of the tangential velocity and on the impact direction. These results indicate that a combination of low friction with low tangential velocities may result into underprediction of the rotational headform variables that would not be representative of real-world conditions.

An Atomization Model of Air Spraying Using the Volume-of-Fluid Method and Large Eddy Simulation

When painting complex surfaces, such as large-curvature surfaces, poor coating quality is often obtained, which may be caused by lack of an appropriate atomization model, insufficient understanding of atomization mechanisms and laws, and improper painting parameters. This paper presents a numerical model of paint atomization of air spraying using the volume-of-fluid method and large eddy simulation. The interface capture and the turbulent flow were mainly considered in the model: the former was tracked by the volume-of-fluid method and the latter was predicted by the large eddy simulation. After the computational domain being meshed by the staggered-grid method, the governing equations were discretized by the finite volume method and were solved by the SIMPLE (Semi-Implicit Method for Pressure-Linked Equations) Consistent algorithm. The results of numerical simulations show that the characteristics of atomization flow field, such as velocity variation, pressure distribution, and paint volume fraction are in agreement with the regularities of atomization. Moreover, the primary and secondary atomization phenomena can be clearly observed: as soon as the paint issues from the nozzle, the paint flow begins to distort and the paint fragments continuously eject from the main paint flow and then these paint fragments distort and disintegrate into smaller elements. A comparison with the experimental data from the literature proves that the model of the whole atomization process of air spray is effective. The model is suitable for simulating the whole atomization process and easy to obtain initial conditions, which can be applied to set the appropriate painting parameters and study paint atomization mechanisms and laws in depth.

The effect of time and velocity variation in sequencing batches reactor on TSS and nitrogen removal in tofu waste

The tofu industry is one of the home industries which in the processing process, produces liquid waste. Tofu liquid waste is known to contain very high organic matter such as Nitrogen and TSS so that if it is directly discharged into water bodies, if discharged directly into the environment will cause water. The purpose of this study was to determine and analyse the effect of variations in times and velocity of sequence batch reactor on the optimization of Nitrogen and TSS removal in tofu industrial wastewater by anaerobic bacteria originating from natural sediments. This study uses a Sequencing Batch Reactor, and the waste used is artificial by the characteristics in the preliminary test. In this study, time and speed variations were used in the mixing process. The artificial waste has a TSS value of 2,910 mg/l and Nitrogen of 18.82 mg/l. The results show that using a sequence batch reactor can reduce the TSS value to 66 mg/l and reduce the nitrogen value to 1.214 mg/l.

The effect of time and velocity variation in sequencing batches reactor on cod and bod, removal efficiency in tofu waste

The tofu industry produces liquid waste that can cause pollution if it is not processed first. Tofu liquid waste has the characteristics of containing high organic matter such as BOD and COD so that if it has directly discharged into the environment, it will reduce the carrying capacity of the environment. The purpose of this study was to determine and analyse the effect of variations in times and velocity of sequence batch reactor on the optimization of COD and BOD removal in tofu industrial wastewater by anaerobic bacteria originating from natural sediments. The method used is an experimental method where the method is to find the effect on other things controlled by using artificial waste. The removal of COD and BOD in tofu industrial wastewater can be done by biological treatment process with attached growth using Sequencing Batch Reactor. The reactor inoculated by the septic tank sediment was fed with artificial waste containing a concentration of COD of 7,000 mg/l and BOD of 2,000 mg/l. For 35 days, this reactor will be operated in batches. Results showed a decrease in BOD and COD parameters using a sequencing batch reactor with BOD concentration 176 mg/l and COD concentration 570 mg/l.

Comparative Numerical Study of Thermal Features Analysis between Oldroyd-B Copper and Molybdenum Disulfide Nanoparticles in Engine-Oil-Based Nanofluids Flow

Apart from the Buongiorno model, no effort was ably accomplished in the literature to investigate the effect of nanomaterials on the Oldroyd-B fluid model caused by an extendable sheet. This article introduces an innovative idea regarding the enforcement of the Tiwari and Das fluid model on the Oldroyd-B fluid (OBF) model by considering engine oil as a conventional base fluid. Tiwari and Das’s model takes into account the volume fraction of nanoparticles for heat transport enhancement compared to the Buongiorno model that depends significantly on thermophoresis and Brownian diffusion impacts for heat transport analysis. In this paper, the thermal characteristics of an Oldroyd-B nanofluid are reported. Firstly, the transformation technique is applied on partial differential equations from boundary-layer formulas to produce nonlinear ordinary differential equations. Subsequently, the Keller-box numerical system is utilized to obtain final numerical solutions. Copper engine oil (Cu–EO) and molybdenum disulfide engine oil (MoS2–EO) nanofluids are considered. From the whole numerical findings and under the same condition, the thermodynamic performance of MoS2–EO nanofluid is higher than that of Cu–EO nanofluid. The thermal efficiency of Cu–EO over MoS2–EO is observed between 1.9% and 43%. In addition, the role of the porous media parameter is to reduce the heat transport rate and to enhance the velocity variation. Finally, the impact of the numbers of Reynolds and Brinkman is to increase the entropy.

Experimental Study on the Influence Factors of Flow Velocity Structure and Turbulent Characteristics in Open Channel with Biomimetic Grass

The problem of suspension treatment of subsea oil-gas pipelines has been highly concerned by engineering construction units and researchers. The current research indicates that the bionic sea grass can effectively reduce the flow rate, promote sediment deposition, and control the development of the pipeline suspension area. The velocity distribution of open channel flow with bionic grass is very complex. The height and laying space of bionic grass will affect the flow velocity distribution. At present, the flow velocity in open channels with bionic grass is mainly studied by measuring the velocity variation at the front, middle, and back of bionic grass. Few effective measurements are made for the full velocity field. The velocity field distribution of bionic aquatic grass along the vertical plane is measured by using standard particle image velocimetry (PIV). The effects of height and laying space of bionic grass on probability density distribution, spatial correlation of pulsating velocity, turbulence intensity, Reynolds stress and turbulent kinetic energy in the open channel after the protection section of bionic grass are further analyzed.