Effect Of Different Directions Research Articles

Extended multiscale FEM-based concurrent optimization of three-dimensional graded lattice structures with multiple microstructure configurations

In this work, a novel concurrent design method for three-dimensional graded lattice structures considering multiple microstructure configurations is proposed. Firstly, the Multiple Variable Cutting (M-VCUT) level set method is employed to represent the geometry of lattice microstructures and define the optimization parameters. Then, the extended multiscale finite element method (EMsFEM) is implemented for calculating the equivalent stiffness matrices of microstructures in offline form. Compared with the traditional homogenization-based multiscale approaches, the proposed method eliminates the scale separation assumptions and takes into account the coupling effects in different directions of materials. In addition, a data-driven method and a parallel computing approach are integrated together so that computational efficiency can be greatly improved. After the iteration process, the optimized full-scale graded structures are reconstructed using interpolation technology to generate well-connected microstructures in neighboring cells. Finally, several 3D numerical examples are utilized to validate the effectiveness of the proposed method, where multiple lattice microstructure configurations are considered, including truss-lattices and plate-lattices.

Estimation of heat transfer and thermal conductivity of particle-reinforced hollow cylinder composites

With the expansion of seabed gas hydrate exploitation, particle-reinforced cement is widely used in well cementing. However, the estimation of heat transfer and thermal conductivity for hollow cylinder composites reinforced with particles remains ambiguous and requires further clarification. This paper employs the inclusion-based boundary element method (iBEM) to calculate both the local field distribution and effective thermal properties of particle-reinforced hollow cylinder composites (PRHCC). Particle interactions are simulated through the introduction of the eigen-temperature gradient, and the boundary effect is modeled using the boundary element method. Numerical simulations explore the influence of interparticle interactions, particle volume fraction, particle properties, and particle distribution on the thermal properties of PRHCC. The results show that the particle interactions have distinct effects in different directions, significantly altering the temperature spread in the central and lower regions within the particles, and then affecting the overall thermal properties of PRHCC. This method serves as a valuable reference for the engineering industry, providing insightful guidance for optimizing design, fabrication processes, and material selection, particularly in components with thermal considerations.

The influence of bias in randomized controlled trials on rehabilitation intervention effect estimates: what we have learned from meta-epidemiological studies.

This study aimed to synthesize evidence from studies that addressed the influence of bias domains in randomized controlled trials on rehabilitation intervention effect estimates and discuss how these findings can maximize the trustworthiness of an RCT in rehabilitation. We screened studies about the influence of bias on rehabilitation intervention effect estimates published until June 2023. The characteristics and results of the included studies were categorized based on methodological characteristics and summarized narratively. We included seven studies with data on 227,806 RCT participants. Our findings showed that rehabilitation intervention effect estimates are likely exaggerated in trials with inadequate/unclear sequence generation and allocation concealment when using continuous outcomes. The influence of blinding was inconsistent and different from the rest of medical science, as meta-epidemiological studies showed overestimation, underestimation, or neutral associations for different types of blinding on rehabilitation treatment effect estimates. Still, it showed a more consistent pattern when looking at patient-reported outcomes. The impact of attrition bias and intention to treat has been analyzed only in two studies with inconsistent results. The risk of reporting bias seems to be associated with overestimation of treatment effects. Bias domains can influence rehabilitation treatment effects in different directions. The evidence is mixed and inconclusive due to the poor methodological quality of RCTs and the limited number and quality of studies looking at the influence of bias and treatment effects in rehabilitation. Further studies about the influence of bias in RCTs on rehabilitation intervention effect estimates are needed.

Effects of ultrasonic vibration cutting trajectories on chip formation of tungsten alloys

Chip morphology has a close correlation with machined surface quality and tool wear in turning process. In the current research on ultrasonic vibration cutting, little is known about the effect of different directions of ultrasonic action on chip formation. In this paper, the effect of ultrasonic vibration on chip formation of tungsten alloy when acting in the direction of cutting speed and cutting depth, respectively, was analyzed by splitting the elliptical trajectory. Furthermore, the advantages of elliptical trajectory machining were also explained in terms of strain rate. The results show that ultrasonic vibration in the direction of cutting depth can effectively suppress the serrated chips and promote the formation of smooth and continuous chips. However, ultrasonic vibration in the direction of cutting speed has the opposite effect. When the tool is superimposed with two-way vibration, the chip morphology formed by the elliptical trajectory is smoother and more continuous. Moreover, it achieves the highest strain rate and the lowest cutting force. Finally, as seen from the experiments of conventional cutting and cutting with variable phase difference, the machined surface roughness decreases with the transition of chip from broken and folded shape to smooth shape. Overall, results of cutting experiment are consistent with simulation results demonstrating the effectiveness of the current work.

Arthroscopic Evaluation of Subtle Syndesmotic Instability: Are We Pulling Correctly in the Coronal Plane?

Category: Ankle; Sports; Trauma Introduction/Purpose: While the lateral hook test (LHT) has been widely used to arthroscopically evaluate syndesmotic instability in the coronal plane, it is unclear whether the angulation of the applied force has any impact on the degree of instability. The aim of this study was to determine if changing the direction of the force applied while performing the LHT impacts the amount of coronal diastasis observed in purely ligamentous syndesmotic injuries. Methods: In 10 cadaveric specimens, arthroscopic evaluation of the distal tibiofibular joint in the coronal plane was performed. Anterior and posterior third coronal plane diastasis were assessed in the intact state and repeated after sequential transection of the, 1) anterior inferior tibiofibular ligament (AITFL), 2) the interosseous ligament (IOL) and the 3) posterior inferior tibiofibular ligament (PITFL). In all scenarios, the lateral hook test (LHT) was performed under 100N of laterally directed force. Additionally, LHT was also performed under 1) anterior inclination of 15 degrees and 2) posterior inclination of 15 degrees in the intact and AITFL+IOL deficient state. One-way ANOVA with post hoc Tukey HSD was used to test for significant differences in coronal plane measurements between each stage of ligament transection, and to determine the effect of different directions of force application on coronal space measurements in the intact and AITFL+IOL transected states. Results: Compared to the intact state, the distal tibiofibular joint remained stable after transection of AITFL under laterally directed force with no angulation. However, after additional transection of the IOL, the syndesmosis became unstable in the coronal plane (p = 0.029 and 0.025 for anterior and posterior third diastasis, respectively). This instability worsened further with subsequent transection of the PITFL (p = <0.001). Moreover, there was no statistical difference in anterior and posterior-third coronal diastasis in both intact and AITFL+IOL deficient states under neutral, anterior, and posteriorly directed force(p-values ranging from 0.816-0.993 and 0.396-0.80,respectively). However, in AITFL+IOL transected state, posteriorly directed forces resulted in greater diastasis than neutral or anteriorly directed forces. Conclusion: Angulation of the applied force ranging from 15 degrees anteriorly to 15 degrees posteriorly during intraoperative LHT has no effect on coronal plane measurements in patients with subtle syndesmotic instability. On the other hand, posteriorly directed forces result in more sizable diastasis, potentially increasing their sensitivity. When arthroscopically evaluating subtle syndesmotic instability, clinicians should assess coronal diastasis with the hook angled 15 degrees posteriorly.

How diverse are sun-grown coffee plantations? Local and landscape heterogeneity drives Andean rove beetle diversity

Compared to shade coffee plantations, sun-grown coffee is not considered very biodiversity-friendly, but little is known about how the management practices for this crop and landscape characteristics affect species diversity. Some predatory staphylinids (rove beetles) are important biological control agents in many agricultural systems, but have not received much attention in tropical agroecosystems or in coffee plantations. After collecting 2074 individuals belonging to 126 species of staphylinid collected from 27 sampling sites in a region dominated by sun-grown coffee in the Colombian Andes, we evaluated how local and landscape heterogeneity affect the diversity, abundance and composition of staphylinids. We found that both local and landscape variables had effects in different directions and of different magnitudes depending on the community attribute evaluated. At the local scale, rove beetle diversity increased with the density of herbaceous plants and coffee plant cover. At the landscape scale, species richness decreased with increasing forest cover, while the number of forest patches had a positive effect. We also found a high degree of species turnover within and between coffee plantations, and this was explained by farmland habitat structural differences between the coffee plantations and also the characteristics of the surrounding landscape. Our results indicate that the Andean sun-grown coffee plantations still host diverse and taxonomically dissimilar staphylinid communities. Therefore, properly managed local vegetation structure and the preservation of forest remnants on the landscape contribute to maintaining high diversity in this coffee production system. Promoting biodiversity conservation and the provision of ecosystem services by agroecosystems—even in intense production systems—requires that environmental heterogeneity on several scales be taken into account.

Effect of traction direction and pressure load on the palatal plate on retentive force

BackgroundRecently, a denture adhesive that is easy to clean and contain moisturizing ingredients have been developed for patients with dry mouth. Although the retentive force produced by conventional denture adhesives and oral moisturizers have been compared on models, no study has reported their comparison in the oral cavity. In this study, we aimed to clarify the effects of different directions of traction and loads at the time of pressure contact on the retentive force on a palatal plate made from a dentulous jaw model.MethodsA palatal plate was fabricated with thermoplastic resin on a dentulous jaw model, and a loop-shaped traction device was attached to the centre of the palate. The test samples were a cream-type denture adhesive, a denture adhesive for dry mouth, an oral moisturizer, and a denture moisturizer. The specimens were applied to the inner surface of the plate, which was then mounted under vertical pressure. Then, the retentive force was measured, using a digital force gauge, while the plate was pulled in different directions and with different loads.ResultsNo significant difference in retentive force was observed in any of the test samples when the direction of traction was between 45° and 60°. The retentive force of the denture adhesive for dry mouth was significantly higher with a direction of traction of 90° than that of 45° or 60°. The retentive force when oral moisturizer was used was significantly higher in the 90° traction direction than in the 45° direction. There was no significant difference between a force of 4.0 kgf or 5.5 kgf when using a denture adhesive for dry mouth. Comparing the four load size conditions, the larger the load, the higher was the retentive force. Similar results were obtained for the cream-type denture adhesive and denture moisturizer. Significantly higher retentive force was observed for larger loads when oral moisturizer was used.ConclusionsThe results suggest that the direction of traction and the pressure load affect the retentive force on a palatal plate.

Thermal sensation, sick building syndrome symptoms, and physiological responses of occupants in environments with vertical air temperature differences

Vertical air temperature differences (VTDs) can have important influences on thermal comfort and the evaluation of air distributions. The air distributions might create either positive or negative VTDs. However, no research has clearly revealed the effect of different directions of VTDs on human comfort. To create environments with positive and negative VTDs in this study, the air temperature of half of the body was maintained at an air temperature of 25 °C, whereas the other half of the body (the upper or lower body part, respectively) was exposed to air temperatures of 22 °C, 25 °C, 28 °C, and 31 °C, respectively. That is two series of experiments with the same VTD value but different directions were compared, based on 16 subjects seated in a climatic box in a climate chamber. The thermal sensations, sick building syndrome (SBS) symptoms, and physiological responses of occupants were studied. The results showed that subjects were more sensitive to the VTD at the upper body part in warm environments with respect to thermal sensations, perceived air quality, and sweat intensity. The analysis indicated that there were more discomfort and heat stress for positive VTDs than negative VTDs. Thus, the criterion for acceptable negative VTDs should be different with the positive VTDs incorporated in current standards. Overall, the directions of the VTDs were suggested to be considered for evaluating the thermally stratified air distributions based on both of thermal comfort and energy efficiency in buildings.

Are There Reliable Qualitative Individual Difference in Cognition?

In this paper we propose a new set of questions that focus on the direction of effects. In almost all studies the direction is important. For example, in a Stroop task we expect responses to incongruent items to be slower than those to congruent ones, and this direction implies one theoretical explanation. Yet, if congruent words are slowed down relative to incongruent words we would have a completely different theoretical explanation. We ask a ‘does everybody’ question, such as, ‘does every individual show a Stroop effect in the same direction?’ Or, ‘does every individual respond faster to loud tones than soft tones?’ If all individuals truly have effects in the same direction that implicate a common theory, we term the differences among them as quantitative individual differences. Conversely, if all individuals truly have effects in different directions that implicate different theories, we term the differences among them as qualitative individual differences. Here, we provide a users guide to the question of whether individual differences are qualitative or quantitative. We discuss theoretical issues, methodological advances, new software for assessment, and, most importantly, how the question impacts theory development in cognitive science. Our hope is that this mode of analysis is a productive tool in researchers’ toolkits.

Entropic uncertainty relation and quantum coherence under Ising model with Dzyaloshinskii–Moriya interaction

Recently, Ming et al (Quantum Inf Process 17 267, 2018) have investigated the entropic uncertainty relation in the presence of quantum memory (EUR-QM) and quantum coherence in a thermal regime for a two-spin chain under the effect of Dzyaloshinskii–Moriya (DM) interaction. Here, we study thermal quantum coherence and EUR-QM for a three-spin chain in Ising model under the effect of different directions of DM interaction. Our results confirm the results for the two-qubit case. Increasing temperature can reduce the quantum coherence but oppositely the uncertainty will grow. We show that the coupling parameter and DM interaction have constructive effects on quantum coherence and they reduce uncertainty in measurement results of incompatible observables, and especially the y-direction of DM interaction has a better influence on decreasing the uncertainty than the x and z directions. Unfortunately, the effect of the third spin acts destructively on the uncertainty and its bound, as well as the quantum coherence between the first two spins. Notably, an explicit relationship between quantum coherence and the uncertainty lower bound is found.

AGE AND GENDER - SPECIFIC EXCESS MORTALITY DURING THE COVID-19 PANDEMIC IN HUNGARY IN 2020

The excess mortality indicator is able to capture how an epidemic affects a country’s mortality processes, taking into account direct and indirect, as well as possible effects in different directions. From the point of view of mortality processes in Hungary, the main feature of the first months of 2020 was that seasonal flu claimed fewer victims than in previous years, for this reason we examined last year’s excess mortality for the period between weeks 12 and 52 related to the coronavirus epidemic using a stochastic mathematical model. According to our calculations, excess mortality related to the coronavirus epidemic in Hungary was 13,700 people in 2020, which means a 14% excess in the period under review. Eighty-six percent of those who died were over the age of 65, 10 percent were between the ages of 50 and 64, and the proportion of those aged 49 or younger was 4 percent. In almost all age groups, the excess mortality rate was nearly twice as high for men as for women. According to our calculations, excess mortality was roughly one and a half times the number of victims claimed by the epidemic in 2020 according to official statistics, and we also found a significant difference between the time course of the two indicators.

Effects of experimental watering but not warming on herbivory vary across a gradient of precipitation.

Climate change can affect biotic interactions, and the impacts of climate on biotic interactions may vary across climate gradients. Climate affects biotic interactions through multiple drivers, although few studies have investigated multiple climate drivers in experiments. We examined the effects of experimental watering, warming, and predator access on leaf water content and herbivory rates of woolly bear caterpillars (Arctia virginalis) on a native perennial plant, pacific silverweed (Argentina anserina ssp. pacifica), at two sites across a gradient of precipitation in coastal California. Based on theory, we predicted that watering should increase herbivory at the drier end of the gradient, predation should decrease herbivory, and watering and warming should have positive interacting effects on herbivory. Consistent with our predictions, we found that watering only increased herbivory under drier conditions. However, watering increased leaf water content at both wetter and drier sites. Warming increased herbivory irrespective of local climate and did not interact with watering. Predation did not affect herbivory rates. Given predictions that the study locales will become warmer and drier with climate change, our results suggest that the effects of future warming and drying on herbivory may counteract each other in drier regions of the range of Argentina anserina. Our findings suggest a useful role for range‐limit theory and the stress‐gradient hypothesis in predicting climate change effects on herbivory across stress gradients. Specifically, if climate change decreases stress, herbivory may increase, and vice versa for increasing stress. In addition, our work supports previous suggestions that multiple climate drivers are likely to have dampening effects on biotic interactions due to effects in different directions, though this is context‐dependent.

Conditions for surface lattice resonances and enhancement of second harmonic generation based on split-ring resonators

In this paper, we theoretically study the condition for the strong coupling between magnetic resonance mode of the two-dimensional periodically arranged gold split-ring resonators and the diffraction mode of the periodic array and its influence on the second harmonic generation efficiency. By controlling the size of the period of the array structure in the <i>x</i>-axis and <i>y</i>-axis, the diffraction mode is excited near the magnetic resonance provided by the gold split-ring resonator, solely in one of the directions. In both cases, the diffraction mode and the magnetic resonance coincide in the linear resonance spectrum, but by analyzing the electric field distribution at the position of the diffraction mode, it can be found that when <inline-formula><tex-math id="M152">\begin{document}${a_x}$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="5-20201424_M152.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="5-20201424_M152.png"/></alternatives></inline-formula> is much larger than <inline-formula><tex-math id="M153">\begin{document}${a_y}$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="5-20201424_M153.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="5-20201424_M153.png"/></alternatives></inline-formula>, the electric field direction of the diffraction mode is perpendicular to the polarization direction of the incident light, and no strong coupling occurs. Therefore, the dilution effect is dominant, and the second harmonic intensity gradually decreases with the increase of the period. When <inline-formula><tex-math id="M154">\begin{document}${a_y}$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="5-20201424_M154.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="5-20201424_M154.png"/></alternatives></inline-formula> is much larger than<inline-formula><tex-math id="M155">\begin{document}${a_x}$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="5-20201424_M155.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="5-20201424_M155.png"/></alternatives></inline-formula>, the electric field direction of the diffraction mode is the same as the polarization direction of the incident light. At this time, the diffraction mode and the magnetic resonance mode are strongly coupled. As the period increases, the second harmonic intensity first increases and then decreases. The increase is due to the dominant mode coupling and the decrease is due to the dominant dilution effect. When the number density of split-ring resonators is reduced to about 1/4 of the original one, the second harmonic intensity can be increased by more than twice. From this, we find that the strong coupling between diffraction mode and magnetic resonance can occur when the electric field direction of the diffraction mode is consistent with the polarization direction of incident light, thus generating the surface lattice resonance to achieve near-field enhancement. In short, the rectangular periodic structure is used to distinguish the field enhancement effects in different directions, and the second harmonic enhancement can still be achieved when the number density of split-ring resonators is reduced, which relaxes the requirements for processing technology. This research provides a new possible way to improve the second harmonic generation efficiency based on metal metasurfaces.

Numerical investigation of the effects of fan-coil airflow direction on distribution and deposition of indoor pollutant particles

Given the high concentration of particulate pollutants in the indoor environment compared to outdoor environment and their harmful effects on human health, it is important to examine the effect of indoor ventilation systems on distribution and deposition of particulate pollutants. Floor-mounted fan-coils have various airflow directions, but the effects of different directions on particle distribution and deposition have not been investigated in previous studies. Thus, the present study aims to investigate the indoor air quality in a room with vertical, 60° inclined, 30° inclined, and horizontal discharge fan-coils. Accordingly, the concentration of particles with a uniform initial distribution was evaluated in the room while considering the occupants’ thermal comfort conditions for four different modes of airflow using computational fluid dynamics and solver packages developed in OpenFOAM® solver by the authors. The particles with 2.5, 10, and 25 μm diameters were considered to examine the effect of particles size on their distribution and deposition. The results indicated that the percentages of 2.5 μm filtered particles for vertical, 60° inclined, 30° inclined, and horizontal fan-coil discharge modes after 600 s were about 93, 84, 76 and 93%, respectively. Also, for all discharge modes, the percentage of 2.5 μm deposited particles on the floor was less than 1%. The results also indicated that after about 975, 1800, 1390 and 940 s, the concentration of 2.5 μm particles reached 1% of their initial concentration, for vertical, 60° inclined, 30° inclined and horizontal fan-coil discharge modes respectively. As the particle size increased, the percentage of filtered particles decreased, while the percentage of particles deposited on the floor increased. Specifically, the percentages of deposited 25 μm particles under the vertical, 60° inclined, 30° inclined and horizontal discharge modes were about 36, 45, 66, and 49%, respectively.

The role of different directions of attention on the extent of implicit perception in soccer penalty kicking.

The role of different directions of attention on the extent of the off-center effect (penalty takers kick to the bigger side of the goal more often, although they explicitly perceive the goalkeeper in the center of the goal) was investigated for soccer penalty kicking. Regarding the directions of attention of the striker, two conflicting assumptions (attention is paid to the goalkeeper vs. attention is only spent on target) were directly contrasted. Participants viewed a goalkeeper standing either in the middle of the goal or being displaced by different distances to the left or right. In the goal-side-related instruction condition, participants had to indicate the greater goal side and already did so at above chance-level for small displacements of 0.1%, although they were not confident in their perceptual judgments, hinting at the occurrence of the off-center effect. They became mindful of displacements of 0.8% and larger when they indicated the goal side for kicking with greater confidence. In the goalkeeper-related instruction condition, participants were asked to choose a goal side for kicking, but only when they perceived the goalkeeper in the middle of the goal. Participants chose the greater goal side at above chance-level for small displacements of 0.2%. They became mindful of the displacement for a difference of 0.8%. However, when comparing the results of both instruction conditions statistically it turned out that the effect of different directions of attention on the off-center's extent differs from those previously reported. Participants were implicitly influenced by comparably small goalkeeper displacements, but became earlier aware of goalkeeper displacements in the goal-side-related instruction condition.

Capturing anharmonic and anisotropic natures in the thermotics and mechanics of Bi2Te3 thermoelectric material through an accurate and efficient potential

Force-field-(FF)-based molecular simulation is essential but challenging in the theoretical research of complex thermoelectric (TE) materials. As they are general and crucial in TE semiconductors, the structural natures of anharmonicity and anisotropy can help us understand the inherent relation between thermal and mechanical behavior, and therefore the reliability of FF studies can be assessed. In this paper, given prior knowledge of the structural, mechanical and thermal properties as well as the limitations and necessary approximations of the FF method, a feasible and detailed FF modeling scheme and simulation has been designed for Bi2Te3, which is a typical high-performance TE material. Using the complementary approach combining quasi-harmonic lattice and molecular dynamics, the obtained potential is systematically confirmed to be accurate and efficient for the prediction of anharmonic and anisotropic behavior in thermotics and mechanics over a wide temperature range compared with the present Bi2Te3 models. This reveals that the intrinsic anisotropy and anharmonicity can measure the asymmetry of crystal lattices and the interatomic force in the current state. In addition, the significant distinction of temperature-dependent anharmonic effects in different directions of Bi2Te3 stems from its layered hierarchical structure, in which weak van der Waals bonding will probably be the key structural factor in comprehensively improving performance for mass production and wearable application. This prior-knowledge-based FF study is also suggested as a bridge between the theoretical understanding of micro-mechanisms and the experimental measurement of TE material properties, leading to a general framework of molecular simulation for other complex energy materials.

Research of Reverse Engineering on Dimensional Accuracy of Parts in Digital Casting Process

Dimensional accuracy has been recognized as the main challenges for castings that we have to overcome as manufacturing industry is proceeding at an astounding rate. The advent of rapid casting has already changed the casting patterns, which means that foundry of metal part is no longer restricted by difficulties of tooling processing especially in the case of complex design castings. It is true that this new technology which is time-saving and high-precision relatively may create new types of quality problems. The overall effort of the present article is to evaluate the dimensional accuracy of sand mold and metal part throughout the digital casting process so that a more accurate dimensional compensation could be applied to the next time. The dimensional accuracy of sand mold manufactured by 3D Printer and the final aluminum-based tire mold casted by the sand mold have been discussed quantitatively by using three-dimensional laser scanner. The effect of different directions on dimensional deviation of important surface is also discussed in this paper. It is found that the difference of sand mold mainly depends on the deviation in printing direction and a downward trend of the patterned surface would appear after the post curing. For the metal casting, appropriate dimensional compensation 1mm/m upon the pattern surface in Z direction is a good choice for further designing. This reverse engineering approach is applicable to not only the tire mold forming but also other industrially relevant parts manufacturing.

Influence of heat conduction and heat convection on hydrate dissociation by depressurization in a pilot-scale hydrate simulator

Natural gas hydrate, as an unconventional energy resource, has generated considerable research interest. It is generally accepted that depressurization method is the most practical and economically promising way to produce gas from gas hydrate sediments. Rates of hydrate dissociation by depressurization depend on heat transfer rate, and the heat transfer during hydrate dissociation mainly includes heat conduction and heat convection. In this paper the Pilot-Scale Hydrate Simulator (PHS), with an inner volume of 117.8 L, was applied to investigate the influence of heat conduction and heat convection on hydrate dissociation. Different thermal boundary conditions and different flow directions during gas recovery from hydrate reservoir by depressurization were performed in the PHS. In addition, the method of studying the effect of different directions of heat convection by changing well locations was firstly proposed in this paper. It was obtained from experimental results that the hydrate dissociation rate with an isothermal boundary is faster than that with a semi-adiabatic boundary, and heat conduction is the dominant factor in hydrate dissociation by depressurization in the constant pressure stage. The influence of heat convection on hydrate dissociation in the constant pressure stage may not be obvious, but during the depressurizing stage, the opposite direction of fluid flow and heat transfer can promote hydrate reformation, and has effect on fluid flow characteristics inside the reservoir. These findings can provide theoretical references for field tests of exploiting natural gas hydrate.

Numerical analysis of mixed convection of different nanofluids in concentric annulus

Purpose This study aims to investigate the numerical analysis of mixed convection within the horizontal annulus in the presence of water-based fluid with nanoparticles of aluminum oxide, copper, silver and titanium oxide. Numerical solution is performed using a finite-volume method based on the SIMPLE algorithm, and the discretization of the equations is generally of the second order. Inner and outer cylinders have a constant temperature, and the inner cylinder temperature is higher than the outer one. The two cylinders can be rotated in both directions at a constant angular velocity. The effect of parameters such as Rayleigh, Richardson, Reynolds and the volume fraction of nanoparticles on heat transfer and flow pattern are investigated. The results show that the heat transfer rate increases with the increase of the Rayleigh number, as well as by increasing the volume fraction of the nanoparticles, the heat transfer rate increases, and this increase is about 8.25 per cent for 5 per cent volumetric fraction. Rotation of the cylinders reduces the overall heat transfer. Different directions of rotation have a great influence on the flow pattern and isotherms, and ultimately on heat transfer. The addition of nanoparticles does not have much effect on the flow pattern and isotherms, but it is quantitatively effective. The extracted results are in good agreement with previous works. Design/methodology/approach Studying mixed convection heat transfer in the horizontal annulus in the presence of a water-based fluid with aluminum oxide, copper, silver and titanium oxide nanoparticles is carried out quantitatively using a finite-volume method based on the SIMPLE algorithm. Findings Increasing the Rayleigh number increases the Nusselt number. Increasing the Richardson number increases heat transfer. Adding nanoparticles does not have much effect on the flow pattern but is effective quantitatively on heat transfer parameters. The addition of nanoparticles sometimes increases the heat transfer rate by about 8.25 per cent. In constant Rayleigh numbers, increasing the Reynolds number reduces heat transfer. The Rayleigh and Reynolds numbers greatly affect the isotherms and streamlines. In addition to the thermal conductivity of nanoparticles, the thermo-physical properties of nanoparticles has great effect in the formation of isotherms and streamlines and ultimately heat transfer. Originality/value Studying the effect of different direction of rotation on the isotherms and streamlines, as well as the comparison of different nanoparticles on mixed convection heat transfer in annulus.

Human Perception of Inertial Mass for Joint Human-Robot Object Manipulation

In this article, we investigate human perception of inertial mass discrimination in active planar manipulations, as they are common in daily tasks, such as moving heavy and bulky objects. Psychophysical experiments were conducted to develop a human inertial mass perception model to improve usability and acceptance of novel haptically collaborating robotic systems. In contrast to existing literature, large-scale movements involving a broad selection of reference stimuli and larger sample sizes were used. Linear mixed models were fitted to model dependent errors from the longitudinal perceptual data. Differential thresholds near the perception boundary exponentially increased and resulted in constant behavior for higher stimuli. No effect of different directions (sagittal and transversal) was found; however, a large effect of different movement types (precise and imprecise) was present in the data. Recommendations to implement the findings in novel physical assist devices are given.