Positive pressure induced channeled suction cups

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2013.Cataloged from PDF version of thesis.Includes bibliographical references (pages 39-40).Leaking in water pipe is a critical issue in Middle Eastern countries such as Kuwait where water is scarce. In-pipe robots can be dispatched to discover the network and inspect the inner surface of the pipe. This thesis describes the design and characterization of suction pads for in-pipe robots. The suction cups are made of hyperelastic materials that contain air channels inside. Instead of using conventional suction technique that is prone to leaking and loosing adhesion force, the suction cup is actuated by compressed air or liquid, which deforms the geometry of the cup to achieve suction. In order to verify the geometry changes during actuation, a uniaxial tension test was done on the elastic material used to acquire the material properties and the suction cup designs were then simulated using FEA in ABAQUS. Next, prototypes were designed in SolidWorks and fabricated using soft lithography techniques. To measure the suction force, pressure measurements were taken both inside the prototype channels and underneath the suction cup. Results show that a Positive Pressure Actuated Suction-cup (PPAS) of diameter forty millimeters can achieve suction force up to 68 N. As more air is inserted into PPAS, the suction force also increases. The concept has proved to be a feasible solution for pipe inspection robot.by Shannon X. Yang.S.B

XX and ZcsZ_{cs} in B+→J/ψϕK+B^+\to J/\psi\phi K^+ as ss-wave threshold cusps and alternative spin-parity assignments to X(4274)X(4274) and X(4500)X(4500)

Recent LHCb's amplitude analysis on $B^+\to J/\psi \phi K^+$ suggests the existence of exotic $X$ and $Z_{cs}$ hadrons, based on an assumption that Breit-Wigner resonances describe all the peak structures. However, all the peaks and also dips in the spectra are located at relevant meson-meson thresholds where threshold kinematical cusps might cause such structures. This points to the importance of an independent amplitude analysis with due consideration of the kinematical effects, and this is what we do in this work. Our model fits well $J/\psi \phi$, $J/\psi K^+$, and $K^+\phi$ invariant mass distributions simultaneously, demonstrating that all the $X$, $Z_{cs}$, and dip structures can be well described with the ordinary $s$-wave threshold cusps. Spin-parity of the $X(4274)$ and $X(4500)$ structures are respectively $0^-$ and $1^-$ from our model, as opposed to $1^+$ and $0^+$ from the LHCb's. With all relevant threshold cusps considered, the number of fitting parameters seems to be significantly reduced. The LHCb data requires $D_s^{(*)}\bar{D}^{*}$ scattering lengths in our model to be consistent with zero, disfavoring $D_s^{(*)}\bar{D}^{*}$ molecule interpretations of $Z_{cs}(4000)$ and $Z_{cs}(4220)$ and, via the SU(3) relation, being consistent with previous lattice QCD results.Comment: 10 pages, 6 figures, 1 table, accepted to be published as a letter in pr

Comparisons of stomatal parameters between normal and abnormal leaf of Bougainvillea spectabilis Willd

In this study, stomatal density (SD), stomatal index (SI), epidermal cell density (ED), guard cell length (GCL) and guard cell width (GCW) of normal and abnormal leaf of Bougainvillea spectabilis Willd were studied. This can be useful for further research of physical mechanism of abnormal leaf. Epidermal cells were polygonal with straight anticlinal walls in the adaxial epidermis of normal leaf; while in the abaxial epidermis of normal leaf, the epidermal cells were irregular with repand anticlinal walls. The stomata were anomocytic on normal leaf. No stomata were found in the adaxial epidermis of abnormal leaf. In abaxial epidermis of abnormal leaf, the epidermal cells were repand or sinuous. The stomata were anomocytic on abnormal leaf. The guard cells were kidney-shaped on normal and abnormal leaf. SD and SI of normal leaf were significantly higher than that of abnormal leaf. ED and GCL of abnormal leaf were higher than that of normal leaf in relative leaves length 37.5 and 50%. At other four stages, ED and GCL of abnormal leaf were smaller than that of normal leaf. SD, SI and ED had a negative correlation with relative leaf length; a significant positive correlation was observed between GCL and relative leaf length.Key words: Bougainvillea spectabilis Willd, normal leaf, abnormal leaf, stomatal density, epidermal cell density, stomatal index

In situ photogalvanic acceleration of optofluidic kinetics: a new paradigm for advanced photocatalytic technologies

A multiscale-designed optofluidic reactor is demonstrated in this work, featuring an overall reaction rate constant of 1.32 s¯¹ for photocatalytic decolourization of methylene blue, which is an order of magnitude higher as compared to literature records. A novel performance-enhancement mechanism of microscale in situ photogalvanic acceleration was found to be the main reason for the superior optofluidic performance in the photocatalytic degradation of dyes as a model reaction

A switchable pH-differential reactor with high reactivity and efficiency for CO<font size=-1>₂</font> utilization

published_or_final_versio

Numerical modelling of a dual electrolyte membraneless electrolytic cell for CO<font size=-1>₂</font> to fuel conversion

published_or_final_versio

Early differentiation of the bulk silicate Earth as recorded by the oldest mantle reservoir

An emerging challenge for understanding the Earth system is to determine the relative roles of early planetary processes versus progressive differentiation in shaping the Earth’s chemical architecture. An enduring tenet of modern chemical geodynamics is that the Earth started as a well-mixed and homogeneous body which evolved progressively over the geologic time to several chemically distinct domains. As a consequence, the observable chemical heterogeneity in mantle-derived rocks has generally been attributed to the Earth’s dynamic evolution over the past 4.5 Ga. However, the identification of chemical heterogeneity formed during the period 4.53–4.45 Ga in the ca. 60 Ma Baffin Bay high-magnesium lavas provides strong evidence that chemical effects of early differentiation can persist in mantle reservoirs to the present day. Here, we demonstrate that such an ancient mantle reservoir is likely composed of enriched and depleted dense melts, and propose a model for early global differentiation of the bulk silicate Earth that would produce two types of dense melts with distinctive chemical compositions in the deep Earth.These dense melts ultimately became parts of the thermo-chemical piles near the core-mantle boundary that have been protected from complete entrainment by subsequent mantle convection currents. We argue that although such dense melts likely exhibit some ‘primordial’ geochemical signatures, they are not representative of the bulk silicate Earth. Our work provides a strong case for the mantle chemical heterogeneity being formed by a major differentiation event shortly after planet accretion rather than through the subsequent geodynamic evolution

Isogeometric analysis for functionally graded microplates based on modified couple stress theory

Analysis of static bending, free vibration and buckling behaviours of functionally graded microplates is investigated in this study. The main idea is to use the isogeometric analysis in associated with novel four-variable refined plate theory and quasi-3D theory. More importantly, the modified couple stress theory with only one material length scale parameter is employed to effectively capture the size-dependent effects within the microplates. Meanwhile, the quasi-3D theory which is constructed from a novel seventh-order shear deformation refined plate theory with four unknowns is able to consider both shear deformations and thickness stretching effect without requiring shear correction factors. The NURBS-based isogeometric analysis is integrated to exactly describe the geometry and approximately calculate the unknown fields with higher-order derivative and continuity requirements. The convergence and verification show the validity and efficiency of this proposed computational approach in comparison with those existing in the literature. It is further applied to study the static bending, free vibration and buckling responses of rectangular and circular functionally graded microplates with various types of boundary conditions. A number of investigations are also conducted to illustrate the effects of the material length scale, material index, and length-to-thickness ratios on the responses of the microplates.Comment: 57 pages, 14 figures, 18 table

Explicitly and implicitly exploiting the hierarchical structure for mining website interests on news events

© 2017 Elsevier Inc. After a news event, many different websites publish coverage of that event, each expressing their own unique commentary, perspectives, and viewpoints. Websites form around a specific set of interests to cater to different audiences, and discovering these interests can help audiences C especially people and organizations that are interested in news C select the most appropriate websites to use as their sources of information. This paper presents three methods for formally defining and mining a websites interests, each of which is explicitly or implicitly based on a hierarchial structure: website-webpage-keyword. The first, and most straightforward, method explicitly uses keyword-layer network communities and the mapping relations between websites and keywords. The second method expands upon the first method with an iterative algorithm that combines both the mapping relations and the network relations from the website-webpage-keyword structure to further refine the keyword-layer network communities. In the third method, a website topic model implicitly captures the mapping relations among the websites, webpages, and keywords. The performance of three proposed methods in website interest mining is compared using a bespoke evaluation metric. The experimental results show that the iterative procedure designed in the second method is able to improve website interest mining performance, and the website topic model in the third method achieves the best performance among the three methods