Motor adaptation reshapes behaviors to habituate novel predictable demands caused by dramatic changes in our body (or environment). In the absence of error signals, behaviors rapidly return to the ...manner before adaptation. It is still in debate whether this behavioral unlearning is due to memory decay. Recent studies suggested that unlearning may be related to the detection of a context change between adaptation phase and error-absent phase. This context-dependent idea is extended in the present study, which examined the motor adaptation in a ball-tossing task. To facilitate the manipulation of the task and the measurement of the behavior, this tossing task was conducted in a virtual environment. Experiment 1 found that unlearning was more likely to occur when the context in the adaptation phase was less similar to that in the error-absent phase. Experiment 2 further demonstrated that the memory of motor adaptation can bias behavior even after behavioral unlearning. Experiment 3 confirmed that the results in Experiment 1 and 2 were not artifacts. These findings indicate that memories of adaptation are independent of behavioral unlearning, and the contextual similarity between adaptation and error-absent phase determines the unlearning rate.
Space perception is systematically biased. Few theories of spatial bias address the possible functional advantages of mechanisms that produce spatial biases. The scale expansion hypothesis proposes ...that many spatial biases are due to the perceptual expansion of visual angles, which acts somewhat like a natural magnifying glass in vision. The present study examined the idea that visual expansion may improve motor precision (i.e., reduce motor variability) in movements when using closed-loop control but not when using open-loop control. Experiment 1 tested this idea in an online tracking task (closed-loop control), whereas Experiment 2 tested it in a fast-hitting task (open-loop control). The results were consistent with the hypothesis. To rule out the effect of the task difference (i.e., tracking vs fast hitting), Experiment 3 examined the effect of visual expansion on the variability of motor performance in a line-reproduction task. The control type (closed-loop or open-loop) was manipulated by the form of visual feedback (online or offline). The results were again consistent with the present assumption. Taken together, the present data suggest that perceptual expansion in vision improves motor-control precision when using closed-loop control (but not when using open-loop control), which supports the scale expansion hypothesis. In addition, the present findings also improve our understanding of how visual error amplification affects motor control.
Geopolymer concrete is an effective solution for widely limiting the negative environmental impacts of the cement manufacturing world. In this research, the polypropylene fibers (PP fiber) with ...various volume fractions, lengths, reinforcing index as well as water-binder ratios (WBR) were mixed into geopolymers to evaluate the effect on their FrT (fracture toughness). A total of 28 experimental groups of different polypropylene fiber geopolymers were considered. In the three-point bending fracture examination, the deformation and displacement fields of polypropylene fiber reinforced geopolymer (PPFRG) notched beams during the fracture process were observed through digital image correlation (DIC). The results show that, the fiber reinforcing index can be used to consider the influence of fiber length and fiber content. In increasing the reinforcing index, the FrT first increased, but after reaching the peak, it decreased. In terms of fracture properties, the PPFRG with a low WBR (0.35) is generally more significant than that of a high WBR (0.38). Comparing the PP fiber with the other fibers in literature, the more substantial toughness enhancement effect and better economy of PP fiber have been proved. Furthermore, this paper established a fracture toughness calculation model through regression analysis.
Silicone rubber (SiR) is used as an insulating material for cables installed in a nuclear power plant. Gamma rays irradiated SiR sheets for various periods at temperatures of 145 and 185 °C, and the ...resultant changes were analyzed by examining complex permittivity spectra and surface potential decay characteristics. Three different processes, namely, instantaneous polarization, electrode polarization due to the accumulation of ions to form double charge layers at dielectric/electrode interfaces, and DC conduction caused by directional hopping of ions, contribute to the complex permittivity. By fitting the spectra to theoretical equations, we can obtain the dielectric constant at high frequencies, concentration and diffusion coefficient of ions and DC conductivity for the pristine and degraded samples. The instantaneous polarization becomes active with an increase of dose and ageing temperature. The thermal expansion coefficient estimated from the temperature dependence of dielectric constant at high frequencies becomes smaller with an increase in dose, which is in good agreement with the experimental results of the swelling ratio. Additionally, trap distributions are calculated from surface potential decay measurements and analyzed to explain the variation in conductivity. Trap energy increases firstly, and then decreases with an increase in dose, leading to a similar change in DC conductivity. It is concluded that generations of both oxidative products and mobile ions, as well as the occurrence of chain scission and crosslinking are simultaneously induced by gamma rays.
Polyimide has excellent electrical, thermal, and mechanical properties and is widely used as a dielectric material in electrical equipment and electronic devices. However, the influencing mechanism ...of sample thickness on electrical breakdown of polyimide has not been very clear until now. The direct current (DC) electrical breakdown properties of polyimide as a function of thickness were investigated by experiments and simulations of space charge modulated electrical breakdown (SCEB) model and charge transport and molecular displacement modulated (CTMD) model. The experimental results show that the electrical breakdown field decreases with an increase in the sample thickness in the form of an inverse power function, and the inverse power index is 0.324. Trap properties and carrier mobility were also measured for the simulations. Both the simulation results obtained by the SCEB model and the CTMD model have the inverse power forms of breakdown field as a function of thickness with the power indexes of 0.030 and 0.339. The outputs of the CTMD model were closer to the experiments. This indicates that the displacement of a molecular chain with occupied deep traps enlarging the free volume might be a main factor causing the DC electrical breakdown field of polyimide varying with sample thickness.
The present study explored the role of emotion regulation and emotion lability/negativity as a moderator in the relation between child social avoidance and social adjustment (i.e., interpersonal ...skills, asocial behavior, peer exclusion) in Chinese culture. Participants were
= 194 children (102 boys, 92 girls,
= 70.82 months, SD = 5.40) recruited from nine classrooms in two public kindergartens in Shanghai, People's Republic of China. Multi-source assessments were employed with mothers rating children's social avoidance and teachers rating children's emotion regulation, emotion lability/negativity and social adjustment outcomes. The results indicated that the relations between social avoidance and social adjustment difficulties were more negative among children lower in emotion regulation, but not significant for children with higher emotion regulation. In contrast, the relations between social avoidance and social adjustment difficulties were more positive among children higher in emotion lability/negativity, but not significant for children with lower emotion lability/negativity. This study informs us about how emotion regulation and emotion lability/negativity are jointly associated with socially avoidant children's development. As well, the findings highlight the importance of considering the meaning and implication of social avoidance in Chinese culture.
This study investigates the utilization of polyethylene fiber (PEF) and microsilica for the production of high-strength and high-toughness geopolymer concrete (HSHTGC). The influence of the PEF ...factor or microsilica content on fracture parameters and strength is evaluated, while acoustic emission (AE) response and crack morphologies are employed to validate the fracture performance results. By combing PEF with microsilica, this study successfully prepared HSHTGC with compressive strength exceeding 90 MPa, significant multi-cracking characteristics, as well as high toughness and ductility. The optimal microsilica content and fiber volume fraction are determined to be 32 wt% and 1.5 vol%, respectively. It is observed that when the fiber factor exceeds 800, there is a decline in compressive strength, initiation, and unstable fracture toughness, however, the fracture energy and ductility index consistently increase monotonically. These findings indicate that fiber toughening has a more pronounced effect than fiber strengthening. Moreover, microsilica plays a crucial role in filling voids and improving bonding between fibers and matrix under both tensile and compressive loads throughout the entire process. HSHTGCs with high fiber factors and increased microsilica contents exhibit a multi-cracking mode along with elevated RA values but reduced AF values during failure process, which correspondingly reflect their enhanced toughness.
•Impacts of PEF and microsilica on compressive and fracture properties of HSHTGC was studied.•AE and crack were used to verify the synergistic effect of PEF and microsilica.•Correlation between fracture parameters and PEF factor or microsilica content were evaluated.
This study presents an investigation focusing on the advancement of a robot designed for subretinal injections in the context of macular degeneration treatment. The technique of subretinal injection ...surgery stands as the most efficacious approach for the successful transplantation of stem cells into the retinal pigment epithelium layer. This particular procedure holds immense significance in advancing research and implementing therapeutic strategies involving retinal stem cell transplantation. The execution of artificial subretinal surgery poses considerable challenges which can be effectively addressed through the utilization of subretinal injection surgery robots. The development process involved a comprehensive modeling phase, integrating computer-aided design (CAD) and finite element analysis (FEA) techniques. These simulations facilitated iterative enhancements of the mechanical aspects pertaining to the robotic arm. Furthermore, MATLAB was employed to simulate and visualize the robot’s workspace, and independent verification was conducted to ascertain the range of motion for each degree of freedom.
Speeding up Distributed Request-Response Workflows JALAPARTI, Virajith; MENACHE, Ishai; BODIK, Peter ...
Computer communication review,
10/2013, Letnik:
43, Številka:
4
Conference Proceeding, Magazine Article
We found that interactive services at Bing have highly variable datacenter-side processing latencies because their processing consists of many sequential stages, parallelization across 10s-1000s of ...servers and aggregation of responses across the network. To improve the tail latency of such services, we use a few building blocks: reissuing laggards elsewhere in the cluster, new policies to return incomplete results and speeding up laggards by giving them more resources. Combining these building blocks to reduce the overall latency is non-trivial because for the same amount of resource (e.g., number of reissues), different stages improve their latency by different amounts. We present Kwiken, a framework that takes an end-to-end view of latency improvements and costs. It decomposes the problem of minimizing latency over a general processing DAG into a manageable optimization over individual stages. Through simulations with production traces, we show sizable gains; the 99th percentile of latency improves by over 50% when just 0.1% of the responses are allowed to have partial results and by over 40% for 25% of the services when just 5% extra resources are used for reissues.
Objective
Intraocular foreign body (IOFB), a frequent cause of ocular trauma, causes serious damage to the eyes. This study was designed to elaborate and compare the characteristics of different ...magnetic resonance imaging (MRI) sequences in detecting wooden IOFBs in rabbits.
Methods
The right vitreous of 24 healthy rabbits was randomly implanted with diverse wooden foreign bodies (diameter φ = 0.2 mm). The T1-weighted imaging (T1WI), T2-weighted imaging (T2WI), proton density-weighted imaging (PDWI), and susceptibility-weighted imaging (SWI) sequences were applied individually 2 weeks after the implantation.
Results
IOFBs were detected as linear low signals on T1WI, T2WI, PDWI, and SWI (SWI image). The detectable rates of poplar wood with a length of 0.5 mm were 0%, 50%, 0%, and 67% for T1WI, T2WI, PDWI, and SWI, respectively. SWI and T2WI sequences exhibited higher sensitivity than T1WI and PDWI. The detectable rates of the first three SWI sequences (magnitude, phase, and SWI) were all 67%, which was higher than that of the minimum intensity projection sequence (33%).
Conclusion
MRI is practicable in the diagnosis of wooden IOFBs. SWI and T2WI are optimal for the integrated diagnosis of wooden IOFBs and could be used for diagnosis and immediate treatment.
PDF
