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The ability to transition between surfaces (e.g., from the ground to vertical barriers, such as walls, tree trunks, or rock surfaces) is important for the Peking gecko's (Gekko swinhonis Günther 1864) survival. However, quantitative research on gecko's kinematic performance and the effect of obstacle height during transitional locomotion remains scarce. In this study, the transitional locomotion of geckos facing different obstacle heights was assessed. Remarkably, geckos demonstrated a bimodal locomotion ability, as they could climb and jump. Climbing was more common on smaller obstacles and took longer than jumping. The jumping type depended on the obstacle height: when geckos could jump onto the obstacle, the vertical velocity increased with obstacle height; however, geckos jumped from a closer position when the obstacle height exceeded this range and would get attached to the vertical surface. A stability analysis of vertical surface landing using a collision model revealed that geckos can reduce their restraint impulse by increasing the landing angle through limb extension close to the body, consequently dissipating collision energy and reducing their horizontal and vertical velocities. The findings of this study reveal the adaptations evolved by geckos to move in their environments and may have applicability in the robotics field.

Polycyclic aromatic hydrocarbons (PAHs) and phthalate esters (PAEs) are internationally recognized as priority pollutants; hence, it is important to monitor their concentrations in the environment. However, the low concentrations of PAHs and PAEs in surface water make the direct and sensitive determination of these compounds by instrumental methods difficult. Therefore, the development of an accurate and rapid sample pretreating method for the determination of PAHs and PAEs in water has always been the goal of environmental scientists. Dispersive liquid-liquid microextraction based on solidification of floating organic droplet (DLLME-SFO) is a simple, rapid, low-cost, sensitive, and environmentally friendly method. Methods based on DLLME-SFO for the simultaneous determination of PAHs and PAEs in surface water have rarely been reported. In this study, a novel DLLME-SFO method was developed for the simultaneous determination of 16 PAHs and 6 PAEs in surface water samples. To optimize the extraction efficiency for the target compounds, various parameters, including the types and volumes of extractants and dispersants, ionic strength, and extraction time, were investigated. First, 1-undecanol (melting point:19℃) and 1-dodecanol (melting point:24℃) were selected as extractive solvents, and their extraction efficiency was investigated. The results showed that 1-dodecanol had better extraction efficiency. The melting point of 1-undecanol was relatively low, and the droplets that solidified during the experiment were easy to melt and break, which led to the low recovery rate of extraction. Then, the effect of the volume (10, 20, 30, 40, 50 μL) of 1-dodecanol was investigated, and the extraction efficiency of the target compounds was found to decrease with increasing volume of 1-dodecanol. Second, the effect of four dispersive solvents (methanol, ethanol, acetonitrile, and acetone) on the extraction efficiencies was studied. The extraction efficiencies of the target compounds were the highest when methanol was used as the dispersant; hence, the effect of different volumes of methanol on the extraction efficiency was further examined. When the volume of methanol was less than 500 μL, the contact area between the extraction solvent and the water phase increased with increasing methanol volume, and the extraction efficiency increased. However, when the volume of methanol was more than 500 μL, the excessive dispersant increased the solubility of the target compound in the water phase, which led to a decrease in the extraction efficiency. Finally, the effects of salt addition and vortex oscillation time on the extraction efficiency were probed. The experimental results indicated that the extraction efficiency increased with an increase in the quantity of NaCl. When the NaCl quantity was greater than 0.2 g, there was no notable change in the extraction efficiency. Vortex oscillation could accelerate the establishment of the extraction equilibrium, and the extraction efficiency reached a stable state when the vortex oscillation time was more than 2 min. According to the abovementioned results, the optimized DLLME-SFO conditions were established as follows:for 5.0 mL water samples, 10 μL of 1-dodecanol was chosen as the extraction solvent, 500 μL of methanol was used as the dispersive solvent, the vortex oscillation extraction time was 2 min, and the NaCl quantity was 0.2 g. The target compounds were analyzed by high-performance liquid chromatography. Separation of the PAHs and PAEs was achieved on a SUPELCOSIL

Geckos show versatility by rapidly maneuvering on diverse complex terrain because they benefit from their distributed, setae-covered toes and thus have the ability to generate reliable and adaptive attachment. Significant attention has been paid to their adhesive microstructures (setae), but the effectiveness of the gecko’s adaptive attachment at the level of toes and feet remains unclear. In order to better understand the geckos’ attachment, we first focused on the deployment of toes while challenging geckos to locomote on varying inclines. When the slope angle was less than 30°, their feet mainly interacted with the substrate using the bases of the toes and generated anisotropic frictional forces. As the slope angle increased to 90°, the participation of the toe bases was reduced. Instead, the setae contribution increased for the middle three toes of the front feet and for the first three toes of the hind feet. As the incline changed from vertical to inverted, the adhesive contribution of the toes of the front feet became more equal, whereas the effective adhesion contact of the hind feet gradually shifted to the toes oriented rearwards. Second, a mathematical model was established and then suggested the potential advantages of distributed control among the toes to regulate foot force. Finally, a physical foot model containing five compliant, adjustable toes was constructed and validated the discoveries with regard to the animals. Using the gecko toes’ control strategies, the artificial foot demonstrated diverse behavior regulating attachment forces. The success of the foot prototype not only tested our understanding of the mechanism of biological attachment, but also provided a demonstration for the design and control of gecko-inspired attachment devices, grippers and other manipulators.

Ti-13Nb-13Zr alloy was fabricated by selective laser melting (SLM), and the densification, microstructure evolution, nanohardness, tensile strength and fatigue behavior of the alloy were systematically investigated. A narrow, feasible process window (laser power 325 W, scanning speed 1000 mm/s, scanning distance 0.13 mm, and layer thickness 0.03 mm) was accordingly determined. With the increase of scanning speed, the coarse acicular-shaped α′ grains changed to refined acicular-shaped α′ grains and then defect formed in the microstructure. The optimally prepared Ti-13Nb-13Zr sample had a very high hardness of 519.448 HV and tensile strength of 1106.07 MPa, which are superior higher than that prepared by traditional thermomechanical technique (280 ± 15 HV and 732 MPa). Owing to the change of BCC to HCP structure ([111] β→ [1-21-3] α′), the accumulation of dislocations and the finer grains, the SLM-processed samples exhibited higher fatigue strength than that the alloy processed by cast and was commensurate with the cast Ti-6Al-4 V. Moreover, the influences of phase transition on fatigue behavior have been discussed carefully.

The effect of electric current on the atomic diffusion of W-Ti system using spark plasma sintering (SPS) was investigated. The interdiffusion coefficient of W-Ti system during SPS was observed to be higher compared to that in the traditional sintering. The electromigration effect was observed in W-Ti system and an improved kinetics model was applied to reveal the role of electric current in atomic diffusion kinetics. It was found that the interdiffusion coefficient increased with increasing current density, while the activation energies were constant. This phenomenon is mainly because the atomic moving velocity is accelerated by the electron wind force in the direction of electron flow, but the diffusion mechanism remains unchanged, resulting in the invariability of activation energy of binary substitution-diffusion. Additionally, the interdiffusion coefficient is independent of the pulse pattern but strongly relies on the effective current density, implying the main acceleration mechanism of pulse current remains to be electromigration.

As the typical refractory metal, the W-Ni-Cu alloy faces severe challenge in machining of complex shapes. To deal with the problem, we use selective laser melting (SLM) additive manufacturing to consolidate W-10%Ni-10%Cu composite powder. The effects of laser parameters on densification, microstructural evolution and nano-crystalline formation were studied. With the increase of laser energy density, the absolute density increases apparently and the surface unevenness is slightly alleviated. Except the typical W and Ni-Cu solid solution phases, interestingly, the amorphous W-Ni solid solution was detected in the SLM processed sample. The typical microstructure contains un-melted W region, W dendrite region with the melting of W and Ni-Cu region. The W solidification microstructure adjacent to the un-melt W presents cellular grain and then transforms into columnar dendrite, until it finally becomes equiaxed dendrite. A large number of W-based nanocrystals formed during the solidification process, which was caused by Marangoni migration that the Ni-Cu phase tends to break the liquid W into small ones, yielding the formation nano-crystalline. Better understanding of the corresponding metallurgical mechanisms will help pave the way towards newly refractory metal design for additive manufacturing application.

Geckos are excellent climbers using compliant, hierarchically arranged adhesive toes to negotiate diverse terrains varying in roughness at multiple size scales. Here, we complement advancements at smaller size scales with measurements at the macro scale. We studied the attachment of a single toe and whole foot of geckos on macroscale rough substrates by pulling them along, across and off smooth rods and spheres mimicking different geometric protrusions of substrates. When we pulled a single toe along rods, the force increased with the rod diameter, whereas the attachment force of dragging toes across rods increased from about 60% on small diameter rods relative to a flat surface to ∼100% on larger diameter rods, but showed no further increase as rod diameter doubled. Toe force also increased as the pulling changed from along-rod loading to across-rod loading. When toes were pulled off spheres, the force increased with increasing sphere diameter as observed for along-rod pulling. For feet with separated toes, attachment on spheres was stronger than that on rods with the same diameter. Attachment force of a foot decreased as rod and sphere size increased but remained sufficient to support the body weight of geckos. These results provide a bridge to the macroscale roughness seen in nature by revealing the importance of the dimension, shape and orientation of macroscale substrate features for compliant toe and foot function of geckos. Our data not only enhance our understanding of geckos’ environmental adaptive adhesion but can also provide inspiration for novel robot feet in development.

An equimolar hexahydroxy AlCoCrCuFeNi high-entropy alloy (HEA) was produced by selective laser melting (SLM) gas-atomized powders, with emphasis on investigating its microstructure and properties. SLM printed AlCoCrCuFeNi HEA shows high crack sensitivity with faced centered cubic (FCC) and body-centered cubic (BCC) phases. High-angle grain boundary, segregation of Cu element and the misfit between BCC and FCC phase account for the crack formation during SLM process. The content of FCC phase gradually increases from 30.55% to 40.20% as VED increases from 52.08 J/mm3 to 83.3 J/mm3. The formation of BCC is restrained owing to rapid solidification. Moreover, unique fine columnar grains growing along the building direction are perpendicular to the boundary of molten pools and present (001), (111) and (101) grain orientation. Also, the fine grains and the high-density dislocation network induced by rapid cooling of the SLMed AlCoCrCuFeNi HEA are observed. The SLMed AlCoCrCuFeNi HEA possesses outstanding properties with a Vickers hardness of 710.4 Hv compared to its counterpart prepared by traditional methods of 500 Hv.

Si and Zr modified Al–Zn–Mg–Cu alloy powders were consolidated by selective laser melting (SLM) and spark plasma sintering (SPS) routes and their microstructures as well as mechanical properties were comparatively studied. The scanning electron microscopy equipped with electron-dispersive spectroscopy was applied to characterize microstructures. Grains were characterized with X-ray diffraction and electron backscatter diffraction. Mechanical properties were characterized by tensile tests and Vickers hardness measurements. The results show that average grain sizes of the SPS and SLM processed samples are basically the same while SLM sample possesses a bimodal grain size distribution, which is different from the SPS sample with uniform grain size. Si element is randomly distributed in SPS sample in the cluster form while the Si element are uniformly distributed in SLM sample. The strength and hardness of the SLM printed sample are much higher than the SPS processed sample.

A novel copper-catalyzed synthesis of substituted 2,3-dihydropyrroles via one-pot N-alkenylation and N-alkylation of amides with 1,4-diiodobut-1-ene derivatives has been developed. The reactions proceed in good to high yields using CuI as the catalyst, K2CO3 as the base, and rac-trans-N,N′-dimethylcyclohexane-1,2-diamine as the ligand.

In this paper a smart home remote control system is designed, which uses the popular SNS open platform as the external network communication media. Software for remote controlling on Android mobile terminals and gateway application based on Java software platform are designed. And the network within home is built using ZigBee technology. This system allows the user to use the mobile phone software to control remote device and get environment information, such as temperature and humidity, via mobile Internet. This system avoids the use of dedicated server in the home side and has good performance in maintainability, safety and usability.

A novel copper-catalyzed synthesis of substituted 2,3-dihydropyrroles via one-pot N-alkenylation and N-alkylation of amides with 1,4-diiodobut-1-ene derivatives has been developed. The reactions proceed in good to high yields using CuI as the catalyst, K2CO3 as the base, and rac-trans-N,N′-dimethylcyclohexane-1,2-diamine as the ligand.

Although the coding mode of non-RDO in H.264 greatly increases the execution speed of intra prediction, shorter execution time is required. A new intra prediction mode decision algorithm is proposed. First, the intra prediction mode of two chroma macroblocks of same location is only decided by one chroma block. Second, the idea of low resolution and SAD criterion are exploited to select the best 16 times 16 intra prediction mode of luma macroblock quickly, and the number of candidates for the intra prediction modes of 4 times 4 subblock of luma macroblock is reduced by the best 16 times 16 intra prediction mode and block location. Then the coding type and the prediction mode of the luma macroblock are decided by flexible cost comparison. Simulation results show that the proposed algorithm greatly reduce computational load of the intra prediction mode decision with negligible loss of PSNR and little increase of bite-rate.

An efficient copper-catalyzed double alkenylation of amides with (1Z,3Z)-1,4-diiodo-1,3-dienes is reported for the first time. The reactions proceed to afford di- or trisubstituted N-acylpyrroles in good to excellent yields using CuI as the catalyst, Cs2CO3 as the base, and rac-trans-N,N‘-dimethylcyclohexane-1,2-diamine as the ligand.

This paper describes a novel segmentation method for image sequence of traffic scenes recorded by a stationary camera. The process of segmentation includes two stages. In the first stage, the frame difference of the current frame is binarized, and the binary image of the frame difference is processed by morphological operation, then the current frame updates the background according to the binary image processed by morphology, and the background is extracted after dozens of iterative operations of the subsequent frames. In the second stage, the process of every frame is as follows: the noise parameters of the camera are derived from the histogram of the difference image between the current frame and background, and the double thresholds which segment the difference image are acquired from the histogram, and the difference image is binarized by the thresholds, then moving objects are found and the background is updated according to the segmentation result. The experiment results show that the method can realize segmentation effectively and quickly.