Safe and Efficient Trajectory Optimization for Autonomous Vehicles using B-spline with Incremental Path Flattening

B-spline-based trajectory optimization is widely used for robot navigation due to its computational efficiency and convex-hull property (ensures dynamic feasibility), especially as quadrotors, which have circular body shapes (enable efficient movement) and freedom to move each axis (enables convex-hull property utilization). However, using the B-spline curve for trajectory optimization is challenging for autonomous vehicles (AVs) because of their vehicle kinodynamics (rectangular body shapes and constraints to move each axis). In this study, we propose a novel trajectory optimization approach for AVs to circumvent this difficulty using an incremental path flattening (IPF), a disc type swept volume (SV) estimation method, and kinodynamic feasibility constraints. IPF is a new method that can find a collision-free path for AVs by flattening path and reducing SV using iteratively increasing curvature penalty around vehicle collision points. Additionally, we develop a disc type SV estimation method to reduce SV over-approximation and enable AVs to pass through a narrow corridor efficiently. Furthermore, a clamped B-spline curvature constraint, which simplifies a B-spline curvature constraint, is added to dynamical feasibility constraints (e.g., velocity and acceleration) for obtaining the kinodynamic feasibility constraints. Our experimental results demonstrate that our method outperforms state-of-the-art baselines in various simulated environments. We also conducted a real-world experiment using an AV, and our results validate the simulated tracking performance of the proposed approach.Comment: 14 pages, 21 figures, 4 tables, 3 algorithm

Engineering vacancy and hydrophobicity of two-dimensional TaTe2 for efficient and stable electrocatalytic N2 reduction

Demand for ammonia continues to increase to sustain the growing global population. The direct electrochemical N2 reduction reaction (NRR) powered by renewable electricity offers a promising carbon-neutral and sustainable strategy for manufacturing NH3, yet achieving this remains a grand challenge. Here, we report a synergistic strategy to promote ambient NRR for ammonia production by tuning the Te vacancies (VTe) and surface hydrophobicity of two-dimensional TaTe2 nanosheets. Remarkable NH3 faradic efficiency of up to 32.2% is attained at a mild overpotential, which is largely maintained even after 100 h of consecutive electrolysis. Isotopic labeling validates that the N atoms of formed NH4+ originate from N2. In situ X-ray diffraction indicates preservation of the crystalline structure of TaTe2 during NRR. Further density functional theory calculations reveal that the potential-determining step (PDS) is ∗NH2 + (H+ + e–) → NH3 on VTe-TaTe2 compared with that of ∗ + N2 + (H+ + e–) → ∗N–NH on TaTe2. We identify that the edge plane of TaTe2 and VTe serve as the main active sites for NRR. The free energy change at PDS on VTe-TaTe2 is comparable with the values at the top of the NRR volcano plots on various transition metal surfaces

A K-Means Clustering Algorithm to Determine Representative Operational Profiles of a Ship Using AIS Data

Defining the appropriate functional requirements in the early ship design stage is important in order that costs that are caused by the over- or under-specified functional capabilities do not increase. This paper presents a K-means clustering algorithm for the determination of functional requirements. It uses automatic identification system (AIS) data from a reference ship to determine the representative operational profiles, which can support decision-makers in defining the functional requirements of ships that will be performing similar missions as those of the reference ship. In a case study, we used this method as part of a ship design project, in which the functional requirements of a battery-only electric ship are defined using AIS data from a reference ship. Results indicate that the cost can be reduced by determining the functional requirements using the proposed method

A K-Means Clustering Algorithm to Determine Representative Operational Profiles of a Ship Using AIS Data

Defining the appropriate functional requirements in the early ship design stage is important in order that costs that are caused by the over- or under-specified functional capabilities do not increase. This paper presents a K-means clustering algorithm for the determination of functional requirements. It uses automatic identification system (AIS) data from a reference ship to determine the representative operational profiles, which can support decision-makers in defining the functional requirements of ships that will be performing similar missions as those of the reference ship. In a case study, we used this method as part of a ship design project, in which the functional requirements of a battery-only electric ship are defined using AIS data from a reference ship. Results indicate that the cost can be reduced by determining the functional requirements using the proposed method

H₂ Plasma and PMA Effects on PEALD-Al₂O₃ Films with Different O₂ Plasma Exposure Times for CIS Passivation Layers

In this study, the electrical properties of Al2O3 film were analyzed and optimized to improve the properties of the passivation layer of CMOS image sensors (CISs). During Al2O3 deposition processing, the O2 plasma exposure time was adjusted, and H2 plasma treatment as well as post-metallization annealing (PMA) were performed as posttreatments. The flat-band voltage (Vfb) was significantly shifted (ΔVfb = 2.54 V) in the case of the Al2O3 film with a shorter O2 plasma exposure time; however, with a longer O2 plasma exposure time, Vfb was slightly shifted (ΔVfb = 0.61 V) owing to the reduction in the carbon impurity content. Additionally, the as-deposited Al2O3 sample with a shorter O2 plasma exposure time had a larger number of interface traps (interface trap density, Dit = 8.98 × 1013 eV−1·cm−2). However, Dit was reduced to 1.12 × 1012 eV−1·cm−2 by increasing the O2 plasma exposure time and further reduced after PMA. Consequently, we fabricated an Al2O3 film suitable for application as a CIS passivation layer with a reduced number of interface traps. However, the Al2O3 film with increased O2 plasma exposure time deteriorated owing to plasma damage after H2 plasma treatment, which is a method of reducing carbon impurity content. This deterioration was validated using the C–V hump and breakdown characteristics

Predictions of frame compliance and apex morphology in sharp nanoindentations

If all components in a nanoindentation system are well calibrated and a reference material has unique hardness, H and reduced modulus, E r independent of the indentation depths, the load, L and the penetration depth, h in the indentation loading curve of the reference material can be correlated by L=Kh 2. Here the constant K is expressed by H, E r and indenter geometry constants. By using H and E r of a fused silica and the Berkovich geometry, an analytical expression for the indentation loading curve could be derived. To compare with this analytical loading curve, experimental indentation data were measured with two commercial nanoindenters. The experimental loading curves shifted leftward or rightward from the analytical loading curve and this depth deviation was attributed to improper calibration of the nanoindenters. Quantitative calibrations of frame compliance and indenter bluntness were tried for the raw nanoindentation data and this resulted in consistent nanoindentation data regardless of the used nanoindentersclose0

Utilizing Negative Markers for Identifying Mycobacteria Species based on Mass Spectrometry with Machine Learning Methods

Matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry (MS) is a useful tool for rapid identification of microorganisms based on the protein mass profile represented in a mass spectrum of the microorganism. Typically, markers that are specific for particular microorganisms are extracted from the mass information obtained by MALDI-TOF MS, and a machine learning technique is applied to the markers. Identification of mycobacteria is of high clinical importance in that different pathogens must be treated with different antibiotics, but is still challenging because spectral patterns of different mycobacteria appear similar. In this paper, we propose a novel approach to use both positive and negative markers in order to enhance discrimination between the spectral patterns of different mycobacteria. We apply the proposed method to classify species in the Mycobacterium abscessus and Mycobacterium fortuitum groups. Experimental results demonstrate that, when combined with various classifier techniques, our method significantly improves the accuracy of mycobacteria identification.N

Self-Assembled Monolayer of a Redox-Active Calix[4]arene: Voltammetric Recognition of the Ba^(2+) Ion in Aqueous Media

The Redox-active monolayer of a novel calix[4]arene recognizing redox-inactive ionic species by voltammetry is reported. Calix[4]arene-disulfide-diquinone, which is not only redox-active but is also a highly selective ionophore for the Ba^(2+) ion, spontaneously forms a stable and dense monolayer film on gold. The redox-active calixarene monolayer selectively recognizes Ba^(2+) ion in aqueous media, and the voltammetric signals are proportional to the ionic concentration. A new voltammetric peak can be detected by square-wave voltammetry upon adding a dilute solution containing Ba^(2+) ion having a concentration as low as 1.0 x 10^(-6) M. The Langmuir plot (1/i_(p) vs 1/[Ba^(2+)]) shows a linear slope in the range from 1.0 x 10^(-6) M to 1.0 x 10^(-4) M. This modified electrode does not show any significant interference from alkali and alkaline earth metal ions except for Sr^(2+) and Ca^(2+). Only 100- and 500-fold concentrations of Sr^(2+) and Ca^(2+) ions, respectively, can lead to voltammetric responses comparable to that of Ba^(2+)

Yeast lunapark regulates the formation of trans-Sey1p complexes for homotypic ER membrane fusion

Summary: The endoplasmic reticulum (ER) consists of the nuclear envelope and a connected peripheral network of tubules and interspersed sheets. The structure of ER tubules is generated and maintained by various proteins, including reticulons, DP1/Yop1p, atlastins, and lunapark. Reticulons and DP1/Yop1p stabilize the high membrane curvature of ER tubules, and atlastins mediate homotypic membrane fusion between ER tubules; however, the exact role of lunapark remains poorly characterized. Here, using isolated yeast ER microsomes and reconstituted proteoliposomes, we directly examined the function of the yeast lunapark Lnp1p for yeast atlastin Sey1p-mediated ER fusion and found that Lnp1p inhibits Sey1p-driven membrane fusion. Furthermore, by using a newly developed assay for monitoring trans-Sey1p complex assembly, a prerequisite for ER fusion, we found that assembly of trans-Sey1p complexes was increased by the deletion of LNP1 and decreased by the overexpression of Lnp1p, indicating that Lnp1p inhibits Sey1p-mediated fusion by interfering with assembly of trans-Sey1p complexes

Human atlastins are sufficient to drive the fusion of liposomes with a physiological lipid composition

The dynamin-like GTPase atlastin is believed to be the minimal machinery required for homotypic endoplasmic reticulum (ER) membrane fusion, mainly because Drosophila atlastin is sufficient to drive liposome fusion. However, it remains unclear whether mammalian atlastins, including the three human atlastins, are sufficient to induce liposome fusion, raising doubts about their major roles in mammalian cells. Here, we show that all human atlastins are sufficient to induce fusion when reconstituted into liposomes with a lipid composition mimicking that of the ER. Although the fusogenic activity of ATL1, which is predominantly expressed in neuronal cells, was weaker than that of ATL2 or ATL3, the addition of M1-spastin, a neuron-specific factor, markedly increased ATL1-mediated liposome fusion. Although we observed efficient fusion between ER microsomes isolated from cultured, non-neuronal cells that predominantly express ATL2-1, an autoinhibited isoform of ATL2, ATL2-1 failed to support liposome fusion by itself as reported previously, indicating that cellular factors enable ATL2-1 to mediate ER fusion in vivo. Atlastins regulate the structure and function of the endoplasmic reticulum (ER). In this study, using reconstituted proteoliposomes with a lipid composition mimicking that of the ER, Jang et al. show that all human atlastins are sufficient to drive membrane fusion