Self-Supported Defect-Rich Au-Based Nanostructures as Robust Bifunctional Catalysts for the Methanol Oxidation Reaction and Oxygen Reduction Reaction in an Alkaline Medium

Recently, alkaline direct methanol fuel cells have made great progress with the development of alkaline electrocatalysis, and a wide variety of catalysts have been explored for methanol oxidation reaction (MOR)and oxygen reduction reaction (ORR). However, the slow kinetics of the MOR and ORR remain a great challenge. In this paper, self-supported defect-rich AuCu was obtained by a convenient one-pot strategy. Self-supported AuCu presented a branched, porous nanostructure. The nanobranch consisted of several 13 nm skeletons, which connected in the kink of the structure. Different growth directions co-existed at the kink, and the twin boundaries and dislocations as defects were observed. When the Au-based nanostructure functioned as an electrocatalyst, it showed robust MOR and ORR performance. For the MOR, the forward peak current was 2.68 times greater than that of Au/C; for the ORR, the activity was close to that of Pt/C and significantly better than that of Au/C. In addition, it possessed superior electrochemical stability for MOR and ORR. Finally, an in-depth exploration of the impact of surface defects and electrochemical Cu removal on MOR and ORR activity was carried out to explain the MOR and ORR’s catalytic performance.

Experimental Research on Uniaxial Compression Constitutive Model of Hybrid Fiber-Reinforced Cementitious Composites

In order to establish accurate compressive constitutive model of Hybrid Fiber-Reinforced Concrete (HFRC), 10 groups of HFRC specimens containing polyvinyl alcohol (PVA), polypropylene (PP), and steel fibers are designed and compressive testing is conducted. On the basis of summarizing and comparing the existing research, accuracy of various stress-strain constitutive model is compared and the method of calculating fitting parameters is put forward, peak stress, peak strain, and elastic modulus of specimens with different fiber proportion are analyzed, the calculation expressions of each fitting parameter are given. The results show that, under the condition that the volume of the hybrid fiber is 2% with the proportion of the steel fiber increase, the strength of the specimen increases, the peak strain decreases slightly, and the elastic modulus increases significantly. In specimens mixed with PVA-PP hybrid fiber, with the increase of PVA fiber proportion, the peak stress and elastic modulus of the material are improved, and the peak strain are decreased. The existing stress-strain expressions agree well with the tests. Accuracy of exponential model proposed in this paper is the highest, which can be applied in engineering and nonlinear finite element analysis of components.

Experimental Analysis of Impedance-Driven Reverse Flow Dynamics

Impedance pump is a type of valveless pumping device, in which it utilizes a bio-inspired mechanism for pumping of fluid based on resonant wave interactions along a flexible media. By inducing a periodic asymmetrical compression on the flexible media will produce a unidirectional flow within the system. The impedance pump has many beneficial characteristics which make it an effective driving mechanism, especially for micro-fluidic systems. In addition, the wave-based mechanism through which pumping occurs infers many benefits in terms of simplicity of design and manufacturing. Adjustment of simple parameters such as the excitation frequency or compression location will reverse the direction of flow, providing a very versatile range of flow outputs. This paper describes the experimental analysis of such impedance-driven flow with emphasis on dynamical study of the reverse flow in open-loop environment. In this study, tapered section with converging steps is introduced at both ends of the flexible media to amplify the reverse flow. Study conducted shows that the reverse peak flow is rather significant with estimate of 23% lower than the forward peak flow. The flow dynamics on the other hand has shown to exhibit different characteristics as per the forward peak flow.

Postural disturbances resulting from unilateral and bilateral diaphragm contractions: a phrenic nerve stimulation study

Thoracoabdominal breathing movements are a complex source of postural disturbance, but there are contradictory reports in the literature with inspiration described as having either a backward or a forward disturbing effect. To elucidate the mechanisms underlying this phenomenon, the present study studied the postural disturbance caused by isolated contractions of the diaphragm. Eight male and four female healthy subjects followed an original paradigm of phrenic nerve stimulation (bilateral and unilateral) and “diaphragmatic” voluntary sniff maneuvers in the seated and standing postures. Center of gravity (CG) acceleration was calculated from force plate recordings, and respiratory kinematics were assessed with thoracic and abdominal sensor belts. CG and respiratory signals revealed that, while seated, bilateral phrenic stimulation and sniff maneuvers consistently produced expansion of the abdomen associated with a forward peak of CG acceleration. In the standing posture, the direction of the CG peak was reversed and always directed backward. Unilateral phrenic stimulation induced an additional medial-lateral acceleration of the CG, directed toward the nonactive side while seated, but in the opposite direction while standing. These results suggest that isolated diaphragmatic contractions produce a constant disturbing pattern for a given posture, but with opposite effects between standing and seated postures. This could be related to the different biomechanical configuration of the body in each posture, corresponding to distinct kinematic patterns of the osteoarticular chain. In addition, the lateral component of the CG acceleration induced by unilateral diaphragm contractions could be clinically relevant in patients with hemidiaphragm paralysis.

Effects of Different Carbon Nanotube Supported Catalysts on Methanol and Ethanol Electro-Oxidation

In this work, Pt and Pt-Ru nanoparticles were synthesized on both single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs). Effects of different nanotube supports on electrocatalytic activity of Pt and Pt-Ru nanoparticles for methanol and ethanol oxidations were investigated using cyclic voltammetry and electrochemical impedance spectroscopy. In comparison to MWCNTs, SWCNT supported Pt and Pt-Ru catalysts demonstrate better electrocatalytic activities in terms of forward peak current density, the ratio of forward peak current density to reverse peak current density, and charge transfer resistance. This study indicates that SWCNTs can serve as effective catalyst supports for both direct methanol and ethanol fuel cells.

Nucleon-Nucleon High-Energy Scattering

The high energy pn charge exchange and pp elastic scattering reactions are studied in an effective hadron model for the energy range of s ~ 50 to 400 GeV2. The main features of the observed differential cross section of the pn charge exchange reaction, the forward peak and the scaling behavior over the large energy range, are well reproduced by a combination of π-, ρ-exchange and a 4-Nucleon contact term. The latter acts as a background field which turns out to be naturally suppressed in elastic N N scattering but contributes significantly to the charge-exchange reaction.