GO-FEAP: Global Optimal UAV Planner Using Frontier-Omission-Aware Exploration and Altitude-Stratified Planning

Autonomous exploration is a fundamental problem for various applications of unmanned aerial vehicles(UAVs). Existing methods, however, are demonstrated to static local optima and two-dimensional exploration. To address these challenges, this paper introduces GO-FEAP (Global Optimal UAV Planner Using Frontier-Omission-Aware Exploration and Altitude-Stratified Planning), aiming to achieve efficient and complete three-dimensional exploration. Frontier-Omission-Aware Exploration module presented in this work takes into account multiple pivotal factors, encompassing frontier distance, nearby frontier count, frontier duration, and frontier categorization, for a comprehensive assessment of frontier importance. Furthermore, to tackle scenarios with substantial vertical variations, we introduce the Altitude-Stratified Planning strategy, which stratifies the three-dimensional space based on altitude, conducting global-local planning for each stratum. The objective of global planning is to identify the most optimal frontier for exploration, followed by viewpoint selection and local path optimization based on frontier type, ultimately generating dynamically feasible three-dimensional spatial exploration trajectories. We present extensive benchmark and real-world tests, in which our method completes the exploration tasks with unprecedented completeness compared to state-of-the-art approaches.Comment: 7 pages,29 figure

Ion energy distributions in inductively coupled plasmas having a biased boundary electrode

In many plasma materials processing applications requiring energetic ion bombardment such as plasma etching, control of the time-averaged ion energy distributions (IEDs) to surfaces is becoming increasingly important to discriminate between surface processes having different threshold energies. Inductively coupled plasmas (ICPs) are attractive in this regard since the plasma potential is low and so the energy of ion fluxes can be more finely tuned with externally applied biases. In these situations, pulsed plasmas provide another level of control as the IEDs from different times during the pulse power period can be combined to create the desired time-averaged IED. A recent development in controlling of IEDs in ICPs is the use of a boundary electrode (BE) in which a continuous or pulsed dc bias is applied to shift the plasma potential and modify the IEDs to surfaces without significant changes in the bulk plasma properties. Combinations of pulsing the ICP power and the BE bias provide additional flexibility to craft IEDs. In this paper we discuss results from a computational investigation of IEDs to a grounded substrate in low-pressure (a few to 50 mTorr) ICPs sustained in argon. Results are compared with experimental measurements of plasma properties and IEDs. We demonstrate the ability to customize IEDs consisting of three energy peaks corresponding to the plasma potential during the plasma active glow, plasma afterglow and the plasma potential with the applied boundary voltage.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/98615/1/0963-0252_21_6_065009.pd

Advanced Control of Ion and Electron Energy Distributions and Investigation of in-situ Photo-Assisted Etching

Precise control of ion energy distribution (IED) is critical to achieve highly selective, low damage etching. A novel approach to control IED using pulsed plasma with synchronously pulsed dc bias on a boundary electrode in Ar gas is first presented. Synchronization of the dc bias applied during the afterglow of a pulsed plasma and the plasma rf power resulted in a double-peaked IED. The mean energies of the two peaks, as well as the peak separation, were controlled by adjusting the applied dc bias and the discharge pressure. Nearly mono-energetic IEDs can be extracted in the afterglow of a pulsed plasma. With precisely controlled IEDs, a new, important phenomenon is reported: photo-assisted etching of p-type Si in chlorine-containing plasmas. This mechanism was first discovered in mostly Ar plasmas with a few percent added Cl2. A substantial etching rate was observed, independent of ion energy, when the ion energy was below the ion-assisted etching threshold. Experiments were carried out with light and ions from the plasma either reaching the surface or being blocked, showing conclusively that the “sub-threshold” etching was due to photons. Sub-threshold etching rates scaled with the product of surface halogen coverage and Ar emission intensity. Etching rates measured under MgF2, quartz, and opaque windows showed that sub-threshold etching is due to photon-stimulated processes on the surface, with VUV photons being much more effective than longer wavelengths. In an effort to manipulate the electron energy distribution function (EEDF) and plasma density, a plasma reactor incorporating dual tandem plasma sources separated by a grid is presented. As feature sizes shrink to the nanometer scale, tuning the EEDF becomes increasingly important for both plasma etching and deposition. By pulsing the main plasma source, while maintaining the tandem source in continuous wave mode, a low electron temperature of ~1 eV at high plasma density (1011 cm-3) was realized. This was achieved by applying a dc bias to a boundary electrode in the tandem source. The electron temperature in the afterglow period could be controlled by changing that bias voltage.Chemical and Biomolecular Engineering, Department o

Photo-assisted etching of silicon in chlorine-and bromine-containing plasmas

Cl 2 , Br 2 , HBr, Br 2 /Cl 2 , and HBr/Cl 2 feed gases diluted in Ar (50%-50% by volume) were used to study etching of p-type Si(100) in a rf inductively coupled, Faraday-shielded plasma, with a focus on the photo-assisted etching component. Etching rates were measured as a function of ion energy. Etching at ion energies below the threshold for ion-assisted etching was observed in all cases, with Br 2 /Ar and HBr/Cl 2 /Ar plasmas having the lowest and highest sub-threshold etching rates, respectively. Sub-threshold etching rates scaled with the product of surface halogen coverage (measured by X-ray photoelectron spectroscopy) and Ar emission intensity (7504 Å ). Etching rates measured under MgF 2 , quartz, and opaque windows showed that sub-threshold etching is due to photon-stimulated processes on the surface, with vacuum ultraviolet photons being much more effective than longer wavelengths. Scanning electron and atomic force microscopy revealed that photo-etched surfaces were very rough, quite likely due to the inability of the photo-assisted process to remove contaminants from the surface. Photo-assisted etching in Cl 2 /Ar plasmas resulted in the formation of 4-sided pyramidal features with bases that formed an angle of 45 with respect to h110i cleavage planes, suggesting that photo-assisted etching can be sensitive to crystal orientation. V C 2014 AIP Publishing LLC. [http://d

Circulating cytokines and alcoholic liver disease: a two-sample bidirectional Mendelian randomization study

Increased inflammation in the liver during ethanol exposure is a major feature of alcoholic liver disease (ALD). An important contributing component to the development of ALD is the inflammatory response brought on by immunological response, however the connection between individual circulating cytokines and ALD is still unclear. To ascertain the causation, we conducted a two-sample bidirectional Mendelian randomization research. We extracted 41 cytokines and growth factors of 8293 Europeans and ALD cases of the same ethnicity (1416 cases and 217,376 controls) from the Genome-Wide Association Studies (GWAS) database for two-sample bidirectional MR analysis. Our analyses suggest that higher interleukin-7 (IL-7) levels are associated with an increased risk of ALD (p = 0.028, OR = 1.191,95% CI = 1.019–1.392), while tumor necrosis factor related apoptosis inducing ligand (TRAIL) is a protective factor for ALD (p = 0.032, OR = 0.863, 95% CI = 0.754–0.988) which can reduce the risk of disease occurrence. In addition, genetically predicted ALD does not affect the expression of circulating cytokines regulators. Our study supports that cytokines play a pivotal role in the pathogenesis of ALD. To determine the mechanisms and pathways of action of these biomarkers, further basic research is required to ensure their clinical suitability for preventing and treating ALD.</p

Variant Alleles of the ESR1, PPARG, HMGA2, and MTHFR Genes Are Associated With Polycystic Ovary Syndrome Risk in a Chinese Population: A Case-Control Study

<p>Polycystic ovary syndrome (PCOS) is the most common endocrinopathy in women of reproductive age, with a prevalence of 6–8%. Although the etiology of PCOS has been investigated extensively, the association between genetic predisposition and PCOS risk is largely unknown. In this study, we genotyped 63 SNPs in 10 genes among 361 PCOS patients and 331 healthy controls in a Chinese Han population. The following variant alleles were significantly associated with decreased PCOS risk: ESR1 rs9340799 (P = 0.000), PPARG rs709154 (P = 0.013), and rs1151996 (P = 0.013), HMGA2 rs2272046 (P = 0.000), MTHFR rs1801133 (P = 0.000). Accordingly, the following genotypes at various loci were associated with reduced PCOS risk: GA genotype at rs9340799 (P < 0.0001) in ESR1, TA genotype at rs709154(P < 0.0001) in PPARG and CA genotype at rs2272046 (P < 0.0001) in HMGA2. Moreover, GA genotype at rs1999805 (P = 0.013) in ESR1 and TT genotype at rs1801133 in MTHFR (P < 0.0001) correlated with elevated PCOS risk. Furthermore, haplotype analysis revealed significant differences in haplotype distributions of CYP11A1, ESR2 and PPARG gene between cases and controls. In addition to confirming that ESR1 rs9340799, HMGA2 rs2272046 and MTHFR rs1801133 are related to the risk of PCOS, these findings also provide the first evidence that PPARG rs709154 and ESR1 rs1999805 are significantly associated with PCOS risk in a Chinese population. Further functional studies are warranted to elucidate the underlying biological mechanisms.</p

Exosomes incorporated with black phosphorus quantum dots attenuate retinal angiogenesis via disrupting glucose metabolism

Black phosphorus quantum dots (BPQDs) have shown potential in tumor therapy, however, their anti-angiogenic functions have not been studied. Although BPQDs are easily degraded to non-toxic phosphrous, the reported toxicity, poor stability, and non-selectivity largely limit their further application in medicine. In this study, a vascular targeting, biocompatible, and cell metabolism-disrupting nanoplatform is engineered by incorporating BPQDs into exosomes modified with the Arg-Gly-Asp (RGD) peptide (BPQDs@RGD-EXO nanospheres, BREs). BREs inhibit endothelial cells (ECs) proliferation, migration, tube formation, and sprouting in vitro. The anti-angiogenic role of BREs in vivo is evaluated using mouse retinal vascular development model and oxygen-induced retinopathy model. Combined RNA-seq and metabolomic analysis reveal that BREs disrupt glucose metabolism, which is further confirmed by evaluating metabolites, ATP production and the c-MYC/Hexokinase 2 pathway. These BREs are promising anti-angiogenic platforms for the treatment of pathological retinal angiogenesis with minimal side effects