The Square Root Velocity Framework for Curves in a Homogeneous Space

In this paper we study the shape space of curves with values in a homogeneous space $M = G/K$, where $G$ is a Lie group and $K$ is a compact Lie subgroup. We generalize the square root velocity framework to obtain a reparametrization invariant metric on the space of curves in $M$. By identifying curves in $M$ with their horizontal lifts in $G$, geodesics then can be computed. We can also mod out by reparametrizations and by rigid motions of $M$. In each of these quotient spaces, we can compute Karcher means, geodesics, and perform principal component analysis. We present numerical examples including the analysis of a set of hurricane paths.Comment: To appear in 3rd International Workshop on Diff-CVML Workshop, CVPR 201

An Underactuated Flexible Instrument for Single Incision Laparoscopic Surgery

More and more patients and surgeons have switched from open surgery to minimally invasive surgery over these years. This exciting advancement has brought massive benefits to patients. Researchers and institutions have proposed robot assisted surgery which combines the advantage of developed robot system and human experience. This thesis reviews state of the art in this area and analyze some advanced surgical instrument for single incision laparoscopic instrument, then propose a design of robotic instrument for single incision laparoscopic surgery which can be integrated with collaborative robot manipulator to construct a surgical robot system.Single-incision laparoscopic surgery (SILS) has its own features and advantages compare to other minimally invasive surgery techniques which also lead to special design requirements for SILS instruments, among which increased flexibility compare to multi-incision surgery instruments is an important part. So we want to design a robotic surgical instrument that has increased flexibility compare to traditional instruments for other MIS techniques. As a laparoscopic robotic instrument compactness and light weight are also our considerations.Single incision laparoscopic surgery (SILS) inserts multiple instruments and laparoscopes through a single trocar which reduces trauma. But this improvement for patients caused difficulty in operation because of instruments triangulation, laparoscope field-of-view, etc. That brings up our challenges in designing a robotic instruments. Designing a highly flexible robotic instrument that provides sufficient workspace and good triangulation in order to relieve the difficulties introduced by narrow instrument trocars.We want to implement a highly recognized surgical instrument with a designed robotic instrument actuation pack. These two parts compose a robotic surgical instrument for single incision laparoscopic surgery. And we want to analyze the performance and viability of our design approach for SILS application

Improved Thermoelectric Performance of P-type Polycrystalline Bi2Te3 via Hydrothermal Treatment with Alkali Metal Salts

The field of thermoelectric research has attracted a lot of interest in hope of helping address the energy crisis. In recent years, low-dimensional thermoelectric materials have been found promising and thus become a popular school of thought. However, the high complexity and cost for fabricating low-dimensional materials give rise to the attempt to further improve conventional bulk polycrystalline materials. Polycrystals are featured by numerous grain boundaries that can scatter heat-carrying phonons to significantly reduce the thermal conductivity κ whereas at the same time can unfortunately deteriorate the electrical resistivity ρ. Aiming at the dualism of the grain boundaries in determining the transport properties of polycrystalline materials, a novel concept of \u27grain boundary engineering\u27 has been proposed in order to have a thermoelectrically favorable grain boundary. In this dissertation, a polycrystalline p-type Bi2Te3 system has been intensively investigated in light of such a concept that was realized through a hydrothermal nano-coating treatment technique. P-type Bi0.4Sb1.6Te3 powder was hydrothermally treated with alkali metal salt XBH4 (X = Na, K or Rb) solution. After the treatment, there formed an alkali-metal-containing surface layer of nanometers thick on the p-Bi2Te3 grains. The Na-treatment, leaving the Seebeck coefficient α almost untouched, lowered κ the most while the Rb-treatment at the same time increased α slightly and decreased ρ the most. Compared to the untreated sample, Na- and Rb-treatments improved the dimensionless figure of merit ZT by ~ 30% due to the reduced κ and ~ 38% owing to the improved the power factor PF, respectively. The grain boundary phase provides a new avenue by which one can potentially decouple the otherwise inter-related α, ρ and κ within one thermoelectric material. The morphologic investigation showed this surface layer lacked crystallinity, if any, and was possibly an amorphous phase. Once Na- and Rb-treatments with various molar ratios were applied to the same sample, a similar grain boundary layer formed with a compositional gradient along the depth direction. The Hall effect measurements showed that the grain boundary phase introduced new carriers into the system and thereby compensated the loss in mobility. With α almost untouched, the &rho to κ ratio has been optimized by varying the Na:Rb ratio in the starting solution. As a result, the Na:Rb = 1:2 ratio yielded the best ZTvalue of ~ 0.92 at 350K, comparable with that of the state-of-the-art p-Bi2Te3 commercial ingot. Besides ZT, the hydrothermal treatment lessened the temperature dependence of compatibility factor S of as-treated polycrystalline samples, helping a thermoelectric device have overall better performance even if it did not work under its optimal condition

Characterization of a Variable Diameter Bioreactor (VDB)

Bioreactors for cell culture or fermentation are widely used for the production of proteins and other value-added products. Operation of bioreactors at large scale involves progressively increasing the culture volume in 4 to 10 folds increments to inoculate the culture and scale it up stepwise. To initiate the cell growth in a typical bioreactor of 20,000L, it often requires a train from benchtop scale at 1L to 10L, 100L, 1000L, 4000L and finally the 20,000L bioreactor. The transfer of cells from one bioreactor to the next one inevitably involves “lag phase” at the beginning of each culture, during which cells do not grow but adapt to the new environment. The existing of multiple lag phases increases the time cost of the production process. In addition, the use of multiple bioreactors leads to more operational problems such as higher contamination risk, higher cleaning costs, and more cleanroom space and equipment footprint, all of which further increase the overall production costs. To solve this problem, Lonza’s facility in Portsmouth designed a novel variable diameter bioreactor (VDB) which has variable diameter sections utilizing a novel continuous impeller. It is capable of operating from 1000L to 20,000L, which will eliminate the need of the 1000L and 4000L bioreactors in the train. Using CFD modeling, Lonza optimized the design of the VDB and the continuous impeller, which is comparable to conventional stir tank bioreactors based on simulation results. However, experimental characterization is needed to compare VDB with traditional bioreactors and further optimize the operational parameters before implementing it at large scale. In this study, the mixing time and mass transfer coefficient (kLa) of VDB, the conventional reactor with conventional impeller and the conventional reactor with continuous impeller in different volumes, agitation speed and airflow rate were experimentally characterized. From the experiment, the mixing time of VDB and conventional reactor with continuous impeller was found to be higher than that of the conventional reactor with conventional, which is constant with the CFD prediction. The mass transfer coefficients of VDB and conventional reactor with continuous impeller was found to be higher than conventional reactor with conventional impeller when the reactors were full filled. When the reactor was filled 20L, the mass transfer coefficients of VDB and conventional reactor with continuous impeller have similar mass transfer coefficients. When the reactor was filled 40L, the mass transfer coefficients of VDB and conventional reactor with conventional impeller have similar mass transfer coefficients. Besides, it is found that at higher airflow rates, increase the agitation cannot reduce the mixing time significantly. It is also found that higher airflow rates, higher agitation speeds, and smaller volumes led to higher mass transfer coefficients (kLa), and the influence of airflow rate on mass transfer coefficients is more significant. The combined effect of these factors on the mixing time and mass transfer coefficients were evaluated. The results will provide insights on determining the operational parameters of VDB at different volumes in the scaled-up operations

Learning Sensor Feedback Models from Demonstrations via Phase-Modulated Neural Networks

In order to robustly execute a task under environmental uncertainty, a robot needs to be able to reactively adapt to changes arising in its environment. The environment changes are usually reflected in deviation from expected sensory traces. These deviations in sensory traces can be used to drive the motion adaptation, and for this purpose, a feedback model is required. The feedback model maps the deviations in sensory traces to the motion plan adaptation. In this paper, we develop a general data-driven framework for learning a feedback model from demonstrations. We utilize a variant of a radial basis function network structure --with movement phases as kernel centers-- which can generally be applied to represent any feedback models for movement primitives. To demonstrate the effectiveness of our framework, we test it on the task of scraping on a tilt board. In this task, we are learning a reactive policy in the form of orientation adaptation, based on deviations of tactile sensor traces. As a proof of concept of our method, we provide evaluations on an anthropomorphic robot. A video demonstrating our approach and its results can be seen in https://youtu.be/7Dx5imy1KcwComment: 8 pages, accepted to be published at the International Conference on Robotics and Automation (ICRA) 201

Effects of (-)-epigallocatechin gallate and quercetin on the activity and structure of α-amylase

Purpose: To investigate the effects of (-)-epigallocatechin gallate (EGCG) and quercetin on the activity and structure of α-amylase. Methods: The inhibitory effects of 7 functional factors were compared by measuring half maximal inhibitory concentration (IC50) values. Lineweaver-Burk plots were used to determine the type of inhibition exerted by EGCG and quercetin against α-amylase. The effect of EGCG and quercetin on the conformation of α-amylase was investigated using fluorescence spectroscopy. Results: Quercetin and EGCG inhibited α-amylase with IC50 values of 1.36 and 0.31 mg/mL, respectively, which were much lower than the IC50 values of the other compounds (puerarin, paeonol, konjac glucomannan and polygonatum odoratum polysaccharide). The Lineweaver−Burk plots indicated that EGCG and quercetin inhibited α-amylase competitively, with ki values of 0.23 and 1.28 mg/mL, respectively. Fluorescence spectroscopy revealed that treatment with EGCG and quercetin led to formation of a loosely-structured hydrophobic hydration layer. Conclusion: This study has unraveled the mechanism underlying the inhibition of α-amylase activity by EGCG and quercetin in vitro. This should make for better understanding of the mechanisms that underlie the antidiabetic effects of EGCG and quercetin in vivo

The Metric Completion of the Space of Vector-Valued One-Forms

The space of full-ranked one-forms on a smooth, orientable, compact manifold (possibly with boundary) is metrically incomplete with respect to the induced geodesic distance of the generalized Ebin metric. We show a distance equality between the induced geodesic distances of the generalized Ebin metric on the space of full-ranked one-forms and the corresponding Riemannian metric defined on each fiber. Using this result we immediately have a concrete description of the metric completion of the space of full-ranked one-forms. Additionally, we study the relationship between the space of full-ranked one-forms and the space of all Riemannian metrics, leading to quotient structures for the space of Riemannian metrics and its completion