Experimental study of the effect of various collision angles and critical conditions on marine engine’s twin-spray collision process

To enhance the fuel-gas mixing and phase transition process, the fuel is injected by twin injectors in a large-bore low-speed two-stroke marine engine, while the cylinder condition has reached the transcritical and supercritical conditions. The twin-injector configuration has a great potential for further optimization, but the exploration on the outcome of collision and phase transition was still limited. Therefore, this work aims to study the effect of various collision angles (60°, 90°, 120°, 150°) and critical conditions (sub/trans/supercritical) on the twin-spray collision process using optical techniques. A wide range of experimental cases are conducted to provide an analysis and database for future modeling validation. The post-collisional spray structures, spatial distribution, and periphery features are analyzed to characterize the droplet’s collision. The results show that with the collision angle increasing, the higher collision velocity enhances the mass transfer while the minor vertical component results in a smaller axial dispersion. Because of the trade-off relationship between the vertical velocity component and pre-collision penetration, a higher reduction in droplet momentum results in a slighter collision behavior. At the collision angle of 150°, the subcritical condition tends to result in an off-axis collision. Under the transcritical (P) condition, the probability of head-on collision increases and presents a wider spatial distribution. But under the supercritical condition, because of the existence of the liquid collision, the thermal conversion among phases is accelerated, while the ambient resistance is reduced. Moreover, an exponential correlation of collision liquid length is formulated to predict the axial dispersion based on various critical conditions.

Spatial and temporal variation of the ambient noise environment of the Sikkim Himalaya

Ambient noise characteristics are perused to assess the station performance of 27 newly constructed broadband seismic stations across Sikkim Himalaya and adjoining Himalayan foreland basin, installed to study the seismogenesis and subsurface structure of the region. Power spectral densities obtained at each station, compared against the global noise limits, reveal that observed vertical component noise levels are within the defined global limits. However, the horizontal components marginally overshoot the limits due to the tilt effect. Ambient noise conditions significantly vary with different installation techniques, analysis revealing that seismic sensors buried directly in the ground have reduced long-period noise in comparison to pier installations. Tectonic settings and anthropogenic activities are also noted to cause a significant rise across short-period and microseism noise spectrum, varying spatially and temporally across the region. Day-time records higher cultural noise than night-time, while the microseism noise dominates during the monsoonal season. An assessment of the effect of the nationwide lockdown imposed due to COVID-19 pandemic revealed a significant decrease in the short-period noise levels at stations installed across the foreland basin marked with higher anthropogenic activity. Our study summarizes the overall ambient noise patterns, validating the stability and performance of the seismic stations across the Sikkim Himalayas.

Patellar Tendon Force Differs Depending on Jump-Landing Tasks and Estimation Methods

Patellar tendinopathy is a chronic overuse injury of the patellar tendon which is prevalent in jump-landing activities. Sports activities can require jumping not only with a vertical component but also in a forward direction. It is yet unknown how jumping in the forward direction may affect patellar tendon forces. The main purpose of this study was to compare PTF between landings preceded by a vertical jump and a forward jump in volleyball players. The second purpose was to compare two different estimation methods of the patellar tendon force. Fifteen male volleyball players performed vertical and forward jump-landing tasks at a controlled jump height, while kinetics and kinematics were recorded. Patellar tendon forces were calculated through two estimation methods based on inverse dynamic and static optimization procedures, using a musculoskeletal model. Results showed that forward jump-landing generated higher patellar tendon forces compared to vertical jump-landing for both estimation methods. Surprisingly, although the static optimization method considered muscle co-contraction, the inverse kinematic method provided statistically significant higher patellar tendon force values. These findings highlight that limiting the forward velocity component of the aerial phase appears to reduce the load on the patellar tendon during landing and may help to prevent patellar tendinopathy.

The Gulf Stream and the Californian Current as Factors Affecting the Behavior and Health of Americans

Due to the existence of the Earth's geomagnetic field, Lorentz’s forces constantly act on all sea currents. These forces distribute the charges of sea currents in both vertical and horizontal directions. In particular, this distribution manifests itself in the electric polarization of sea currents in directions perpendicular to them. So, earlier it was shown that the same Lorentz forces cause negative electrization of the Sargasso Sea. It is also shown here that the positive electrization of the western edge of the Gulf Stream and, consequently, the eastern coast of the United States is also caused by the Lorentz force arising from the interaction of this sea current with the vertical component of the geomagnetic field. It is also shown here that the positive electrization of east edge of California Current together with west coast of USA is also caused due to the similar reasons. All this allows us to conclude that an increased concentration of positive air ions is constantly retained in the air both in the east and in the west of the United States. This situation has caused the need for an analysis of how the predominantly positive electrization of the air affects both human health and their physical and mental activity. The results of this analysis are presented here. It is also shown that these results can be useful for residents of some other countries.

Mechanical Behavior of a Multisegmented Tower Anchorage Structure with an Exposed Steel Anchor Box

A tower anchorage structure with an exposed steel anchor box is commonly used for cable-stayed bridges. Many researchers have conducted studies on this structure by considering a single segment. However, in practical engineering, the stress of multisegmented tower anchorage structure is not completely similar to that of single segment, and the forces between segments affect each other. Hence, in this study, the mechanical behavior of a multisegment anchorage structure with an exposed steel anchor box was investigated via finite element analysis. Furthermore, the load transfer path and stress distribution characteristics of the structure were investigated. The results indicate that the horizontal component of the cable force is borne by the side plate of the steel anchor box, the diaphragm, and the side wall of the concrete tower column, while the vertical component is transmitted by the steel anchor box and concrete tower column. Under the action of this cable force, the horizontal component of the cable force borne by the middle segment increases, while the components at the two end segments decrease. The vertical force is greater on the lower tower segments. The stress levels on the side plate and on the diaphragm of the steel anchor box in the middle section are high. Under the cable force load, the frame formed by the end plate and side plate of the steel anchor box expands outward. The end plate is mainly under a tensile load, and the tensile stress level on the lower section exceeds that on the upper section. A high-stress area for the concrete tower is observed in the steel-concrete joint. The stud group of the anchorage structure is subjected to horizontal and vertical shear forces, and no “saddle-shaped” distribution of the stud shear is found. An optimal arrangement method for the stud group was proposed to optimize its mechanical performance.

Effect of Plano-Valgus Foot on Lower-Extremity Kinematics and Spatiotemporal Gait Parameters in Children of Age 5–9

Aim of the study was to see how a definition of the flexible flat foot (FFF) influences the results of gait evaluation in a group of 49 children with clinically established FFF. Objective gait analysis was performed using VICON system with Kistler force platforms. The gait parameters were compared between healthy feet and FFF using two classifications: in static and dynamic conditions. In static condition, the ink footprints with Clarke’s graphics were used for classification, and in dynamic condition, the Arch Index from Emed pedobarograph while walking was used for classification. When the type of the foot was based on Clarke’s graphics, no statistically significant differences were found. When the division was done according to the Arch Index, statistically significant differences between flat feet and normal feet groups were found for normalized gait speed, normalized cadence, pelvic rotation, ankle range of motion in sagittal plane, range of motion of foot progression, and two parameters of a vertical component of the ground reaction force: FZ2 (middle of stance phase) and FZ3 (push-off). Some statically flat feet function well during walking due to dynamic correction mechanisms.

Increase of dynamic stability of a basis at operation of the compressor equipment of the Abazіvka unit of complex gas preparation

The object of research is the basis of the compressor equipment of the complex gas treatment plant at the Abazivka field and the strengthening of the base soils with soil-cement elements, which are proposed to be arranged with the use of drilling technology. The research area is located on the territory of the current Abazivka Integrated Gas Preparation, near the village of Bugaivka, Poltava region, Ukraine. Abazivka Integrated Gas Preparation receives products from wells in Abazivka and Sementsivske deposits. It is proposed to carry out the reconstruction of Integrated Gas Preparation, which includes strengthening the foundation of the compressor model C1004-JGT/2-1 manufactured by «Propak» (Alberta, Canada). The amplitudes of oscillations of the compressor foundation were determined at a speed of 1400 rpm at the appropriate site with geological conditions. The magnitudes of oscillations and subsidence of the compressor foundation of the Abazivka complex of complex gas treatment were investigated experimentally. When determining the amplitudes of oscillations of the compressor foundations, only the amplitudes of oscillations in the direction parallel to the sliding of the pistons were calculated, and the influence of the vertical component of the perturbing forces was not taken into account. It is established that the amplitude of horizontal-rotational oscillations of the upper face of the compressor foundation relative to the horizontal axis exceeds the maximum allowable. It is substantiated that soil cement is a sufficiently strong and waterproof material that can be used to strengthen the base during the construction of equipment foundations. The possibility of application of the technology of application of soil-cement piles, made by brown-mixing technology for strengthening the base under the foundation of the compressor, is described and investigated. It is proposed to reinforce the base with rows of soil-cement elements, which will increase the modulus of deformation of the base, which is represented by loam, light to 14.3 MPa. In the case of strengthening the base, the amplitude of horizontal-rotational oscillations of the upper face of the compressor foundation is much less than the maximum allowable 0.1 mm. The subsidence of the foundation at reinforcement of the base, which does not exceed the maximum allowable value, is determined. Soil-cement elements are proposed to be arranged according to the drilling technology.