190 research outputs found
Collision-Aware Fast Simulation for Soft Robots by Optimization-Based Geometric Computing
Soft robots can safely interact with environments because of their mechanical
compliance. Self-collision is also employed in the modern design of soft robots
to enhance their performance during different tasks. However, developing an
efficient and reliable simulator that can handle the collision response well,
is still a challenging task in the research of soft robotics. This paper
presents a collision-aware simulator based on geometric optimization, in which
we develop a highly efficient and realistic collision checking / response model
incorporating a hyperelastic material property. Both actuated deformation and
collision response for soft robots are formulated as geometry-based objectives.
The collision-free body of a soft robot can be obtained by minimizing the
geometry-based objective function. Unlike the FEA-based physical simulation,
the proposed pipeline performs a much lower computational cost. Moreover,
adaptive remeshing is applied to achieve the improvement of the convergence
when dealing with soft robots that have large volume variations. Experimental
tests are conducted on different soft robots to verify the performance of our
approach
Efficient Jacobian-Based Inverse Kinematics With Sim-to-Real Transfer of Soft Robots by Learning
This paper presents an efficient learning-based method to solve the inverse
kinematic (IK) problem on soft robots with highly non-linear deformation. The
major challenge of efficiently computing IK for such robots is due to the lack
of analytical formulation for either forward or inverse kinematics. To address
this challenge, we employ neural networks to learn both the mapping function of
forward kinematics and also the Jacobian of this function. As a result,
Jacobian-based iteration can be applied to solve the IK problem. A sim-to-real
training transfer strategy is conducted to make this approach more practical.
We first generate a large number of samples in a simulation environment for
learning both the kinematic and the Jacobian networks of a soft robot design.
Thereafter, a sim-to-real layer of differentiable neurons is employed to map
the results of simulation to the physical hardware, where this sim-to-real
layer can be learned from a very limited number of training samples generated
on the hardware. The effectiveness of our approach has been verified on
pneumatic-driven soft robots for path following and interactive positioning
OpenPneu: Compact platform for pneumatic actuation with multi-channels
This paper presents a compact system, OpenPneu, to support the pneumatic
actuation for multi-chambers on soft robots. Micro-pumps are employed in the
system to generate airflow and therefore no extra input as compressed air is
needed. Our system conducts modular design to provide good scalability, which
has been demonstrated on a prototype with ten air channels. Each air channel of
OpenPneu is equipped with both the inflation and the deflation functions to
provide a full range pressure supply from positive to negative with a maximal
flow rate at 1.7 L/min. High precision closed-loop control of pressures has
been built into our system to achieve stable and efficient dynamic performance
in actuation. An open-source control interface and API in Python are provided.
We also demonstrate the functionality of OpenPneu on three soft robotic systems
with up to 10 chambers
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Surface Emissions Modulate Indoor SVOC Concentrations through Volatility-Dependent Partitioning.
Measurements by semivolatile thermal desorption aerosol gas chromatography (SV-TAG) were used to investigate how semivolatile organic compounds (SVOCs) partition among indoor reservoirs in (1) a manufactured test house under controlled conditions (HOMEChem campaign) and (2) a single-family residence when vacant (H2 campaign). Data for phthalate diesters and siloxanes suggest that volatility-dependent partitioning processes modulate airborne SVOC concentrations through interactions with surface-laden condensed-phase reservoirs. Airborne concentrations of SVOCs with vapor pressures in the range of C13 to C23 alkanes were observed to be correlated with indoor air temperature. Observed temperature dependencies were quantitatively similar to theoretical predictions that assumed a surface-air boundary layer with equilibrium partitioning maintained at the air-surface interface. Airborne concentrations of SVOCs with vapor pressures corresponding to C25 to C31 alkanes correlated with airborne particle mass concentration. For SVOCs with higher vapor pressures, which are expected to be predominantly gaseous, correlations with particle mass concentration were weak or nonexistent. During primary particle emission events, enhanced gas-phase emissions from condensed-phase reservoirs partitioned to airborne particles, contributing substantially to organic particulate matter. An emission event related to oven-usage was inferred to deposit siloxanes in condensed-phase reservoirs throughout the house, leading to the possibility of reemission during subsequent periods with high particle loading
Assessing environmental fate of β-HCH in Asian soil and association with environmental factors
Chinese Gridded Pesticide Emission and Residue Model was applied to simulate long-term environmental fate of beta-HCH in Asia spanning 1948-2009. The model captured well the spatiotemporal variation of beta-HCH soil concentrations across the model domain. beta-HCH use in different areas within the model domain was simulated respectively to assess the influence of the different sources of beta-HCH on its environment fate. A mass center of soil residue (MCSR) was introduced and used to explore environmental factors contributing to the spatiotemporal variation of beta-HCH soil residue. Results demonstrate that the primary emission dominates beta-HCH soil residues during the use of this pesticide. After phase-out of the pesticide in 1999, the change in beta-HCH soil residues has been associated with the Asian summer monsoon, featured by northward displacement of the MCSR. The displacement from several major sources in China and northeastern Asia shows a downward trend at a 95% confidence level, largely caused by environmental degradation and northward delivery of beta-HCH under cold condition in northern area. The MCSRs away from the India and southern and southeastern Asia sources show a rapid northward displacement at a 99% confidence level, featuring the cold trapping effect of the Tibetan Plateau.Chinese Gridded Pesticide Emission and Residue Model was applied to simulate long-term environmental fate of beta-HCH in Asia spanning 1948-2009. The model captured well the spatiotemporal variation of beta-HCH soil concentrations across the model domain. beta-HCH use in different areas within the model domain was simulated respectively to assess the influence of the different sources of beta-HCH on its environment fate. A mass center of soil residue (MCSR) was introduced and used to explore environmental factors contributing to the spatiotemporal variation of beta-HCH soil residue. Results demonstrate that the primary emission dominates beta-HCH soil residues during the use of this pesticide. After phase-out of the pesticide in 1999, the change in beta-HCH soil residues has been associated with the Asian summer monsoon, featured by northward displacement of the MCSR. The displacement from several major sources in China and northeastern Asia shows a downward trend at a 95% confidence level, largely caused by environmental degradation and northward delivery of beta-HCH under cold condition in northern area. The MCSRs away from the India and southern and southeastern Asia sources show a rapid northward displacement at a 99% confidence level, featuring the cold trapping effect of the Tibetan Plateau
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Characterizing sources and emissions of volatile organic compounds in a northern California residence using space‐ and time‐resolved measurements
We investigate source characteristics and emission dynamics of volatile organic compounds (VOCs) in a single‐family house in California utilizing time‐ and space‐resolved measurements. About 200 VOC signals, corresponding to more than 200 species, were measured during 8 weeks in summer and five in winter. Spatially resolved measurements, along with tracer data, reveal that VOCs in the living space were mainly emitted directly into that space, with minor contributions from the crawlspace, attic, or outdoors. Time‐resolved measurements in the living space exhibited baseline levels far above outdoor levels for most VOCs; many compounds also displayed patterns of intermittent short‐term enhancements (spikes) well above the indoor baseline. Compounds were categorized as “high‐baseline” or “spike‐dominated” based on indoor‐to‐outdoor concentration ratio and indoor mean‐to‐median ratio. Short‐term spikes were associated with occupants and their activities, especially cooking. High‐baseline compounds indicate continuous indoor emissions from building materials and furnishings. Indoor emission rates for high‐baseline species, quantified with 2‐hour resolution, exhibited strong temperature dependence and were affected by air‐change rates. Decomposition of wooden building materials is suggested as a major source for acetic acid, formic acid, and methanol, which together accounted for ~75% of the total continuous indoor emissions of high‐baseline species
WiSer: A Highly Available HTAP DBMS for IoT Applications
In a classic transactional distributed database management system (DBMS),
write transactions invariably synchronize with a coordinator before final
commitment. While enforcing serializability, this model has long been
criticized for not satisfying the applications' availability requirements. When
entering the era of Internet of Things (IoT), this problem has become more
severe, as an increasing number of applications call for the capability of
hybrid transactional and analytical processing (HTAP), where aggregation
constraints need to be enforced as part of transactions. Current systems work
around this by creating escrows, allowing occasional overshoots of constraints,
which are handled via compensating application logic.
The WiSer DBMS targets consistency with availability, by splitting the
database commit into two steps. First, a PROMISE step that corresponds to what
humans are used to as commitment, and runs without talking to a coordinator.
Second, a SERIALIZE step, that fixes transactions' positions in the
serializable order, via a consensus procedure. We achieve this split via a
novel data representation that embeds read-sets into transaction deltas, and
serialization sequence numbers into table rows. WiSer does no sharding (all
nodes can run transactions that modify the entire database), and yet enforces
aggregation constraints. Both readwrite conflicts and aggregation constraint
violations are resolved lazily in the serialized data. WiSer also covers node
joins and departures as database tables, thus simplifying correctness and
failure handling. We present the design of WiSer as well as experiments
suggesting this approach has promise
Sources and preservation of organic matter in soils of the wetlands in the Liaohe (Liao River) Delta, North China
Total organic carbon, total nitrogen, delta C-13(org), delta N-15, and aliphatic and polyaromatic hydrocarbons of fifty-five soil samples collected from the coastal wetlands of the Liaohe Delta were measured, in order to determine the sources and possible preservation of organic matter (OM). The delta(15)(N) and delta C-13(org) values in the samples ranged from 3.0 parts per thousand to 9.4 parts per thousand and from -30.4 parts per thousand to -20.3 parts per thousand, respectively, implying that the OM in the soils is predominantly derived from C-3 plant. The long-chain n-alkanes had a strong odd-over-even carbon number predominance, suggesting a significant contribution from waxes of higher plants. The ubiquitous presence of unresolved complex mixture, alkylated polycylic aromatic hydrocarbons and typical biomarkers of petroleum hydrocarbons (pristane, phytane, hopanes and steranes) indicates that there is a contribution of petroleum hydrocarbons to the organic carbon pool in the wetland soils. P. australis-vegetated wetlands have strong potentials for the preservation of organic carbon in the wetlands. (C) 2013 Elsevier Ltd. All rights reserved.Total organic carbon, total nitrogen, delta C-13(org), delta N-15, and aliphatic and polyaromatic hydrocarbons of fifty-five soil samples collected from the coastal wetlands of the Liaohe Delta were measured, in order to determine the sources and possible preservation of organic matter (OM). The delta(15)(N) and delta C-13(org) values in the samples ranged from 3.0 parts per thousand to 9.4 parts per thousand and from -30.4 parts per thousand to -20.3 parts per thousand, respectively, implying that the OM in the soils is predominantly derived from C-3 plant. The long-chain n-alkanes had a strong odd-over-even carbon number predominance, suggesting a significant contribution from waxes of higher plants. The ubiquitous presence of unresolved complex mixture, alkylated polycylic aromatic hydrocarbons and typical biomarkers of petroleum hydrocarbons (pristane, phytane, hopanes and steranes) indicates that there is a contribution of petroleum hydrocarbons to the organic carbon pool in the wetland soils. P. australis-vegetated wetlands have strong potentials for the preservation of organic carbon in the wetlands. (C) 2013 Elsevier Ltd. All rights reserved
Loop-mediated isothermal amplification (LAMP)/Cas12a assay for detection of Ralstonia solanacearum in tomato
Introduction: Bacterial wilt (BW) caused by the aerobic, Gram-negative pathogenic species Ralstonia solanacearum (RS) is a major disease impacting commercial agriculture worldwide. Asian phylotype I of RS is the cause of tomato bacterial wilt, which has caused severe economic losses in southern China for many years. An urgent priority in control of bacterial wilt is development of rapid, sensitive, effective methods for detection of RS.Methods: We describe here a novel RS detection assay based on combination of loop-mediated isothermal amplification (LAMP) and CRISPR/Cas12a. crRNA1, with high trans-cleavage activity targeting hrpB gene, was selected out of four candidate crRNAs. Two visual detection techniques, involving naked-eye observation of fluorescence and lateral flow strips, were tested and displayed high sensitivity and strong specificity.Results and Discussion: The LAMP/Cas12a assay accurately detected RS phylotype Ⅰ in 14 test strains, and showed low detection limit (2.0 × 100 copies). RS in tomato stem tissue and soil samples from two field sites with suspected BW infection was identified accurately, suggesting potential application of LAMP/Cas12a assay as point-of-care test (POCT). The overall detection process took less than 2 h and did not require professional lab equipment. Our findings, taken together, indicate that LAMP/Cas12a assay can be developed as an effective, inexpensive technique for field detection and monitoring of RS
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