Direction Of Path Research Articles

Hybrid Precoding Design for Wideband THz Massive MIMO-OFDM Systems With Beam Squint

The terahertz (THz) communication has been considered as a promising technique for future 6G wireless networks because of its tens of GHz bandwidth. However, the path direction for THz channel under different subcarrier frequencies is different (i.e., beam squint), which leads to the serious beam gain loss for conventional hybrid precoding design schemes. Thus, the effect of beam squint must be considered for the application of the wideband THz systems. In this paper, we consider the precoding design problem in a wideband THz massive multiple-input-multiple-output (mMIMO) orthogonal frequency division multiplexing (OFDM) systems with beam squint. We first design two new sparse radio frequency chain antenna structures, including fully connected and subarray. Based on the designed structure, we formulate an average rate maximization problem by jointly designing the hybrid analog/digital precoding at the transmitter and analog combine vector at the receiver. Since it is a challenge to optimize the precoding simultaneously, we propose an alternatively iterative algorithm to solve it under each antenna structure. Finally, the simulation results are conducted to show the effectiveness of the designed antenna structure and proposed precoding schemes.

In silico screening for the interaction of small molecules with their targets and evaluation of therapeutic efficacy by free online tools

Pharmaceutical chemistry deals with the process of isolating organic compounds from natural sources or chemically synthesizing them in order to explore potential drugs. Drugs are small molecules, used to prevent or treat various diseases. Of several lead molecules, only few of them reach clinical trial phases and emerge as effective drugs, whereas the majority will be eliminated at different stages. On the other hand, due to the lack of proper identification of their pharmacokinetic properties and biological potential, many small molecules fail to reach this stage. This could be because of the fact that it is either time consuming and costly or there is full of uncertainty due to lack of analyses that are necessary for the confirmation. In the post-genomic era, computational methods have been implemented in almost all stages of drug research and development owing to the drastic increase in the available knowledge about small molecules and the target biomacromolecule. This includes identifying the suitable and specific targets for drug candidates, lead discovery, lead optimization and ultimately preclinical phases. In this context, numerous websites have become highly valuable and influence the drug development and discovery process. Here, we have attempted to bring together some of the online computational approaches and tools that are available to facilitate research efforts in the field of drug discovery and drug design. The output information from these tools is extremely helpful in selecting and deciding about the future direction or specific path needed to be followed by the researchers. These computational methods are indeed help to focus the intended research in the right direction. As detailed in this review, the information provided about the servers and methods should be useful throughout the process of screening of synthesized or chemical database originated small molecules to find the appropriate targets along with the active sites without depending on any commercial tools or time-consuming and costly assays. It should however be remembered that the bioinformatics-based prediction cannot completely replace the wet lab data of chemical compounds or specific assays.

Characterizing the landscape of movement to identify critical wildlife habitat and corridors.

Landscape planning that ensures the ecological integrity of ecosystems is critical in the face of rapid human-driven habitat conversion and development pressure. Wildlife tracking data provide unique and valuable information on animal distribution and location-specific behaviors that can serve to increase the efficacy of such planning. Given the spatiotemporal complexity inherent to animal movements, the interaction between movement behavior and a location is often oversimplified in commonly applied analyses of tracking data. We analyzed GPS-tracking-derived metrics of intensity of use, structural properties (based on network theory), and properties of the movement path (speed and directionality) with machine learning to define homogeneous spatial movement types. We applied our approach to a long-term tracking data set of over 130 African elephants (Loxodonta africana) in an area under pressure from infrastructure development. We identified 5 unique location-specific movement categories displayed by elephants, generally defined as high, medium, and low use intensity, and 2 types of connectivity corridors associated with fast and slow movements. High-use and slow-movement corridors were associated with similar landscape characteristics associated with productive areas near water, whereas low-use and fast corridors were characterized by areas of low productivity farther from water. By combining information on intensity of use, properties of movement paths, and structural aspects of movement across the landscape, our approach provides an explicit definition of the functional role of areas for movement across the landscape that we term the movescape. This combined, high-resolution information regarding wildlife space use offers mechanistic information that can improve landscape planning.

Multi-Decadal Humpback Whale Migratory Route Fidelity Despite Oceanographic and Geomagnetic Change

Understanding how organisms respond to environmental change is one of the most pressing grand challenges of organismal biology. In the vast oceans that cover 71% of Earth’s surface, remote sensing technologies have created unprecedented opportunities to create new knowledge and deliver integrated understandings of marine organism-environment interactions via long-term monitoring. Using historic whaling records and >15 years of satellite-derived data, we show that movement parameters associated with long-distance humpback whale migrations, including utilization of a south-southeast directed migratory corridor, migration path straightness, direction, timing and velocity, have not significantly changed during a period of dynamic oceanographic and geomagnetic conditions. These findings reveal an apparent paradox: humpback whale migrations do not change in a changing ocean. Geophysical analyses of the same humpback whale movements demonstrate that these whales maintained prolonged migratory fidelity to a limited suite of spatiotemporal trajectories through gravitational coordinates, raising the possibility that migratory decisions are relatively insensitive to changing oceanographic and geomagnetic conditions. Our findings highlight the importance of filling the knowledge-gaps that currently limit our ability to understand and anticipate organismal responses to rapidly changing Earth system conditions.

Effect of stress triaxiality on fracture failure of 6061 aluminium alloy

The effect of stress triaxiality on mechanical properties of 6061 aluminium alloy extruded profiles with different specimens was studied. Macroscopic mechanical property of the various specimen was got through universal testing machine. At the same time, stress triaxiality of different specimens was obtained using the method of finite element simulation. And then the fracture strain of each specimen was outputted by DIC. Fracture modes of 6061 aluminium alloy with different stress triaxiality were studied by SEM. The results show that taking tensile samples as comparison, the cross-sectional area of some notched specimens decreases and the peak load increases. Among them, the minimum cross-sectional area of the R5 central hole specimen is 20% smaller than that of the tensile sample, and the peak load is 28% larger. The fracture strain of the alloy increased with the decrease of stress triaxiality. For the same notch specimens, along the path direction, stress triaxiality of R5 notch specimens, R5 Center-hole specimens and R20 Arc notched specimens increased 47%, 17.8%, 25% respectively. According to the analysis of fracture morphology, the main fracture of 6061 aluminium alloy was ductile fracture. When the stress triaxiality is large, the dimples are small and sparsely distributed, and when the stress triaxiality is small, the dimple is large and evenly distributed. Finally, the Johnson-Cook model material parameters of 6061 aluminum alloy are fitted based on the tensile test results of different shapes of specimens, which can accurately simulate the elastic-plastic deformation and fracture instability of 6061 aluminum alloy under different stress states.

Cross-directional feed rate optimization using tool-path surface

With the state-of-the-art technologies, NC tool paths are optimized along the feed direction of the tool path without the consideration of the consistency in the crossing (step-over) direction. As a result, the surface finishing is not fully optimal. In this paper, a method that performs the feed rate scheduling with consistency in crossing direction is proposed. The core of the method involves three steps: cross-directional information reconstruction, tool-path feature curve construction, and nominal feed rate computation. To reconstruct the cross-directional information, the neighbor projections, which are the nearest points on the adjacent pass segments of each GOTO point, are computed. For feature curve construction, feature points of the tool path are identified and then connected into curves along the crossing direction based on the neighbor projection information. The tool path is then divided according to the feature curves into feed rate intervals. The nominal feed rate of each feed rate interval is computed and blended with the nominal feed rates of the crossing neighbors, to achieve the consistency in the crossing direction. Information on the nominal feed rates and feature points is sent to the CNC to compute the final feed rate scheduling that takes advantages of the cross-consistent nominal feed rates. The proposed method is implemented in a lab-developed software program and validated experimentally using a commercial CNC. Experiments and simulations on two workpieces verify the effectiveness of the proposed cross-directional feed rate optimization method.

A displacement-based and explicit non-planar 3D crack propagation model in the generalized/extended finite element method

The displacement-based methods for the extraction of the Stress Intensity Factors (SIFs) were created decades ago and, since them, they have been used in a wide range of numerical analysis, most of them based on standard 2D Finite Element Method (FEM). Although the accuracy of the SIFs computed by the displacement-based methods generally be inferior compared with the energy release methods, the use of the former methods have been motivated by its simplicity, ease of implementation and low computational cost, even though it may yield less accurate SIFs when compared with the latter methods. A major use of the SIFs is the prediction of the crack path direction in crack propagation analysis. The modelling of crack propagation is the most frequent application of the Generalized Finite Element Method (GFEM) and Extended Finite Element Method (XFEM) and a large number of crack propagation models presented in literature uses energy release methods for SIFs evaluation. Very few works using displacement-based methods for the computation of the SIFs have been published in literature in the context of the GFEM and XFEM. This paper presents a propagation model for an explicit non-planar 3D crack in a GFEM/XFEM background. The proposed model uses the Displacement Correlation Method (DCM) for the SIFs extraction. Some crack propagation problems are investigated and the resultant crack paths are compared with reported results from literature. This work demonstrates that the model here proposed generates very reasonable crack paths even for relatively coarse meshes using linear elements.

Effect of laser scan length on the microstructure of additively manufactured 17-4PH stainless steel thin-walled parts

Components with varying dimensions are found in numerous applications. The current work examines how microstructures and phases change for additively manufactured 17-4PH thin walls as a function of laser path length, path direction, and wall thickness. Two sample sets were designed, each consisting of four walls with thicknesses of 6.4 mm to 0.8 mm. In the first set, the wall axes were parallel to the scan axes, such that the laser path length varied from layer to layer with the laser path either being parallel or perpendicular to the wall. In the second set, the walls lay at 45° to the scan axes, such that the laser path had the same length in all layers and gradually decreased with wall thickness. Substantial changes in phase stability and microstructure are observed as the wall thickness decreases, with ferritic phases and coarse grains changing to fine grains and an increasing volume fraction of austenite. These changes are attributed to changes in the local temperature-time profile as the length of the laser paths change from 19 mm to 0.8 mm. These observations demonstrate the range of microstructure and phase control options available in additive manufacturing with judicious selections of part layouts on build plates and of laser beam directions.

Eye-hand coordination in reaching and grasping vertically moving targets.

Previous investigations have uncovered a strong visual bias toward the index finger when reaching and grasping stationary or horizontally moving targets. The present research sought to explore whether the index finger or thumb would serve as a significant focus for gaze in tasks involving vertically translating targets. Participants executed right-handed reach-to-grasp movements towards upward or downward moving 2-D targets on a computer screen. When the target first appeared, participants made anticipatory fixations in the direction of the eventual movement path (i.e. well above upwardly moving targets or well below downwardly moving targets) and upon movement onset, fixations shifted toward the leading edge of the target. For upward moving targets, fixations remained toward the leading edge upon reach onset, whereas for downward moving targets, fixations shifted toward the centre of the target. The same central fixation location was observed at the time of grasp for all targets. Furthermore, for downwardly moving targets, the placement of the thumb appears to have influenced fixation location in conjunction with, not replacement of, the influence of the index finger. These findings are indicative of the increasingly relevant role of the thumb in mediating reaching and grasping downwardly moving targets.

Relationship marketing and third-party logistics: evidence from hotel industry

PurposeThis study examines the outsourcing criteria prevalent in the Hotel industry of Pakistan. In doing so, the study investigates the role of trust in the association between relationship marketing dimensions—communication, opportunistic behavior, reputation, satisfactory prior outcomes and specific investment—and third-party logistics provider’s (3PL) selection.Design/methodology/approachUsing a close-ended questionnaire, data were collected from 97 hotels of various categories operating in Pakistan and involved in 3PL outsourcing. Partial Least Square–Structural Equation Modeling was employed to estimate the modeled relationships.FindingsWith a high predictive relevance of the model, communication, satisfactory prior outcome and reputation were found to have a significant effect on the trust, whereas the results showed a significant mediating role of trust in the association between communication, reputation and 3PL provider’s selection.Research limitations/implicationsThe study uses static data from selected firms and cannot be used to analyze behavior over a period of time. Hence, a generalization of results should be made carefully.Practical implicationsFindings imply that for fully capitalizing on the benefits by virtue of their prospective relationship, the managers must streamline their processes and activities according to path directions that endorse a higher degree of trust in their service providers and establish an effective system of communications interconnecting their mutual goals and objectives.Originality/valueThe outcome of the research study illustrated the perceptions of the local businesses with regards to the 3PL service provider(s) selection via the establishment of trust.

The effect of rotating receiver hole shape on a gas turbine pre-swirl system

The life assessment and the efficiency of turbine cooling blades and vanes are seriously affected by the cooling air delivery system of a gas turbine. The pre-swirl system in a gas turbine plays an important role between the stationary and rotating parts to supply enough cooling air at the appropriate temperature at the expense of pressure drop. In the stationary part, the pre-swirl nozzle creates the flow angle in advance of the rotating orifice, called the receiver hole, to minimize energy loss. However, because of the sudden change of direction and area of the flow path, an energy loss occurs at the inlet of the receiver holes. The circumferential velocity at the receiver hole inlet decreases even though the circumferential velocity at the pre-swirl outlet is equal to the tangential velocity of the turbine rotor system. To reduce the energy loss at the pre-swirl system, various shape parameters can be applied to the receiver hole, and the area ratio between the pre-swirl nozzle throat area and the receiver hole cross-sectional area can also be varied considering the structure problem, mass flow rate, and pressure drop. In this study, the shape of the receiver holes and its effects were analyzed using a 3D CFD method that was validated by previous studies including experimental data. The edge shape, inclined angle, area ratio, and number of receiver holes were analyzed with the discharge coefficient, adiabatic effectiveness, and pressure drop. The pre-swirl system perform-ance increased as the area ratio increased, and under fixed area ratio, a large number of smalldiameter receiver holes showed better performance. The receiver hole edge fillet was the most influential shape parameter in pre-swirl performance.

Stress-localization induced toughening in CNT–silica nanocomposites

Applying a combination of atomistic and continuum scale simulations, we show that stress-localization forms the fundamental basis for toughening in “carbon nanotube reinforced amorphous silica” (CNT−aSiO2). Depending on the cohesive strength of the interface, a propagating crack renders three distinct types of failure conditions: (i) with stronger cohesive interactions both silica and nanotube undergo catastrophic failure, (ii) with moderate cohesive interactions the nanotube debonds from the matrix and undergoes severe mechanical deformation but fracture remains in the matrix, and (iii) with lower cohesive strengths the nanotube debonds from the matrix easily and allows quicker failure of the matrix, compared to the previous two failure conditions. For either of the cases, continued propagation of the crack requires renucleation at the opposite side of the nanotube. However, the renucleation criteria are mostly unaffected by the strength of interfacial interactions. Also, the effective toughness of the nanocomposite increases nonlinearly with increasing interfacial strength and the maximum possible toughness enhancement is strictly controlled by the strength of elastic interactions between the nanotube and the matrix. The overall toughening behavior of the nanocomposite is governed primarily by stress-localization at the nanotube–silica intersections along the projected crack path direction in the composite. The observations highlight the dramatic role of site-selective interatomic interactions that can affect the macroscopic mechanical behavior of the nanocomposite substantially.

A stable home-base promotes allocentric memory representations of episodic-like everyday spatial memory.

A key issue in neurobiological studies of episodic-like memory is the geometric frame of reference in which memory traces of experience are stored. Assumptions are sometimes made that specific protocols favour either allocentric (map-like) or egocentric (body-centred) representations. There are, however, grounds for suspecting substantial ambiguity about coding strategy, including the necessity to use both frames of reference occasionally, but tests of memory representation are not routinely conducted. Using rats trained to find and dig up food in sandwells at a particular place in an event arena (episodic-like 'action-where' encoding), we show that a protocol previously thought to foster allocentric encoding is ambiguous but more predisposed towards egocentric encoding. Two changes in training protocol were examined with a view to promoting preferential allocentric encoding-one in which multiple start locations were used within a session as well as between sessions; and another that deployed a stable home-base to which the animals had to carry food reward. Only the stable home-base protocol led to excellent choice performance which rigorous analyses revealed to be blocked by occluding extra-arena cues when this was done after encoding but before recall. The implications of these findings for studies of episodic-like memory are that the representational framework of memory at the start of a recall trial will likely include a path direction in the egocentric case but path destination in the allocentric protocol. This difference should be observable in single-unit recording or calcium-imaging studies of spatially-tuned cells.

Measurement of the Coordinates of Radio Emission at High Frequencies by Goniometric and Goniometric-Range Finding Methods

The coordinates of radio emission sources at high frequencies are measured using a two-position system of azimuthal-meridional direction finders by a goniometric method. Active antenna lattices of vertical vibrators and synchronized coherent radio receivers with frequency conversion are used in the direction finder stations. The amplitude and phase discrepancies are minimized by preliminary calibration of the receiver channels at the frequencies of the direction finder signals. The measurement results are used to study the mean square deviations of the radio source coordinates for emission of the type for meteorological information from airport networks in the Russian Federation and neighboring countries, radio stations with standard frequencies and times, and telecoded and continuous transmissions. The attainable accuracy of the measurements is analyzed as a function of spatial position of the direction finders, path lengths, and fluctuations in the electrical parameters and spatial distribution of the ionized layers of the atmosphere leading to changes in the beam trajectories and anomalous errors in measurements of the ray trajectories and anomalous errors in measurements of the directions of arrival of the radio waves at different times of the year and day. It is shown that in the lower part of the high frequency band the error in measuring the coordinates of the radio sources by the goniometric system is 4.7%, and that as the frequency approaches the upper boundary this indicator increases by a factor of 1.2. Range finding of signals at a single point in space and measuring the height of the layers of the atmosphere using vertical ranging stations yields coordinates of the radio sources by the goniometric-range finding method. Measurements of the coordinates of objects by the goniometric-range finding method can be carried out with a mean square deviation equal to 11–13% of the distance.

African Americans in World Language Study: The Forged Path and Future Directions

AbstractThis article examines the history of African Americans in the academic study of world languages and presents an overview of inquiry on the topic. The paper focuses on the impact of race in second language acquisition (SLA) as exemplified through the experience of black students in language education and study abroad. It discusses objectives, policies, instructional priorities and strategies, conditions, and materials related to how black students have in the past, are currently, or should be engaged in language learning. The article examines the path forged by African Americans in world language study, signals gaps in the present body of knowledge, and suggests future directions for investigations into this important topic in the field of applied linguistics and SLA forARAL's 40th anniversary.

Large herbivores in restricted ecosystems: assessment of water sources value by high-usage movement pathways at Byriuchyi Island spit

An animal population permanently living in a certain area not only adapts to environmental conditions, but changes the environment as a result of their activities. The constant movement of animals between valuable resources in a certain territory forms a system of permanent trails. They are valuable source of information for solving problems of directed formation of ecosystems, organisation of protection and rational use of the territory. The territory of our study — Byriuchyi Island — is an alluvial type of sand and shell rock spit. It is covered with a variety of wetlands, meadows, and steppe vegetation. There are no natural sources of fresh water. Since the 1950s, several species of large herbivores have lived here: red deer, fallow deer, onagers, and feral horses. To provide animals with fresh water, artificial ponds called “kopanki” were created in the 1970s. In order to determine the intensity of use of drinking water on the Biryuchy Island spit, we assessed them based on the analysis of the system of permanent trails. Materials used in the work consist of data collected in 2014–2018 during field research and satellite images of the area. During the study period, the total number of ungulates ranged between 2700 to 3400 individuals. To assess the intensity of water use, the number and direction of permanent paths were determined, the distance to other water and fodder sources, shelter, microrelief and climatic features, anthropogenic factors were estimated. Data were collected for 31 artificial water sources. It has been found that permanent trails can extend from the source in up to 25 directions. However, more often they are concentrated in the northern and north-eastern directions. This is due to the most weather-protected area of the island — providing cover with reeds and a variety of nutritious food — being located in the north. The nearest sources of fresh water are in 2.5–3 km from the coast of the estuary. In general, the average distance between water crates on the spit is 0.9 km. Analysis of the permanent trails system of the island showed that 45 % of water resources are intensively used by ungulates, and 22 % have no visible trails.

Weld orientation effects on the formability of tailor welded thin steel sheets

Abstract Tailored welded blanks (TWBs) technology can give the important possibilities to obtain components in the automobile industry. Friction stir welding (FSW) is a joining approach, which can adhere parts well with desired properties in weld zone. In this article, the main aim is investigation the effect of weld zone orientation on forming limit diagram (FLD) of the TWBs using experimental and finite element model. Three TWBs are produced FSW with three different orientations of weld zones including 0 0 , 45 0 and 90 0 against major stress direction. The microstructure of the weld zones is divided and then observed via metallography procedures. Tensile tests are carried out to determine the mechanical properties of TWB sections and duplicate the tests numerically to validate the formability results. The Nakazima stretch test is used to derive the limit strains for three different weld orientations (between rolling direction and welding path) and what can be seen is the changeable effect of these ordinations on varying strain paths. The best formability is for TWB with orientation weld 90 0 in tension mode while, results reveals that in Plane strain condition best formability is originated from TWB with weld orientation 0 0 . For biaxial tension condition e 2 = e 1 , changing the weld orientation has no effect on formability. The comparison between FEM and experimental tests reveals good agreement and high recommended FEM for this type of study.

Study on Fluid Movement Characteristics inside the Emitter Flow Path of Drip Irrigation System Using the Yellow River Water

Vigorously developing efficient water-saving agricultural technologies using the Yellow River Water is an important way to achieve sustainable use of water resources. In order to clarify the fluid movement characteristics inside the flow path of the emitter under complicated water quality conditions in a drip irrigation system using the Yellow River Water, the optimal simulation turbulence model for the flow field in the flow path of the emitter was determined by comparing the macroscopic hydraulic characteristics with the microscopic fluid motion characteristics of the fluid in the emitter. On this basis, the two-phase flow model was used to calculate and analyze the characteristics of water flow movement and particle transport in the emitter. The results show that the RNG (Re- normalization group) k-ε turbulence model was the most suitable for the simulation of the flow field in the emitter, considering the macroscopic hydraulic performance and microscopic anti-clogging ability of the emitter synthetically, and both the comprehensive calculation accuracy and the calculation efficiency. The pressure showed a step-like uniform decrease along the direction of water flow. The fluid flow showed the regional movement characteristics of the mainstream and non-mainstream regions. The energy dissipation mainly occurred at the sudden change sites of the flow path structure. The particle phase velocity was slightly lower than that of the water phase. The velocity at the near-wall surface was relatively lower than that at the center, and the velocity distribution along the depth direction of the flow path was relatively uneven. The sediment was mainly deposited in the first half of the flow path. This study can provide a theoretical basis for solving the emitter clogging in the drip irrigation systems applying water from the Yellow River.

Cross-lagged longitudinal analysis of pain intensity and sleep disturbance

BackgroundThere is substantial evidence that pain intensity and sleep are related, with findings generally suggesting more support for the influence of sleep on pain intensity than vice versa. However, the strength and direction of the relationship has been found to vary among different populations, with few studies in individuals with chronic physical disabilities. ObjectiveExamine the directionality of the sleep and pain relationship in individuals with chronic physical disabilities. MethodsCross-lagged effects models were generated using data from a longitudinal observational survey study of individuals (N = 1660) with multiple sclerosis (MS), muscular dystrophy (MD), post-polio syndrome (PPS), and spinal cord injury (SCI). Models evaluated the correlational effects of sleep disturbance and pain intensity, as well as the cross-lagged effects of sleep disturbance to pain intensity and vice versa. ResultsThe effects of pain on sleep were stronger than sleep on pain, although the magnitude of the effects were both relatively weak. Analyses within individual samples were consistent with the overall sample results for MS, MD, and PPS. In the SCI sample the magnitude and direction of the cross-lagged model paths were more variable than in the other samples. ConclusionsThe relationship between pain intensity and sleep disturbance appears bi-directional, but the effects are small in a sample of individuals with long-term disabilities. The temporal effects of pain on sleep disturbance appear stronger than the effects of sleep disturbance on pain intensity. Future research is needed to better understand this relationship in the context of pain and/or sleep disturbance treatments.

A chain model charactering the effect of interphase on electro-mechanical properties of particle reinforced polymer

In this paper, electro-mechanical properties of particle reinforced polymer composites have been investigated based on a microstructure inspired chain model. First, the chain model composed of chain, assisted chain and particle has been proposed to redefine the mechanical and electrical properties of polymers. A parameter evaluating the interphase influence has been introduced to reconstruct the structures within the model. Then, the electric response of the composites can be obtained by calculating the minimum distance along the direction of electrical path. Furthermore, the optimized responses of polymer composites have been investigated by considering several factors: interphase properties, strain and particle size. From the simulation results, it can be concluded that the model has advantage to capture the electro-mechanical behavior of composites with complex structures.