5 research outputs found
Metric-aligned Sample Selection and Critical Feature Sampling for Oriented Object Detection
Arbitrary-oriented object detection is a relatively emerging but challenging
task. Although remarkable progress has been made, there still remain many
unsolved issues due to the large diversity of patterns in orientation, scale,
aspect ratio, and visual appearance of objects in aerial images. Most of the
existing methods adopt a coarse-grained fixed label assignment strategy and
suffer from the inconsistency between the classification score and localization
accuracy. First, to align the metric inconsistency between sample selection and
regression loss calculation caused by fixed IoU strategy, we introduce affine
transformation to evaluate the quality of samples and propose a distance-based
label assignment strategy. The proposed metric-aligned selection (MAS) strategy
can dynamically select samples according to the shape and rotation
characteristic of objects. Second, to further address the inconsistency between
classification and localization, we propose a critical feature sampling (CFS)
module, which performs localization refinement on the sampling location for
classification task to extract critical features accurately. Third, we present
a scale-controlled smooth loss (SC-Loss) to adaptively select high
quality samples by changing the form of regression loss function based on the
statistics of proposals during training. Extensive experiments are conducted on
four challenging rotated object detection datasets DOTA, FAIR1M-1.0, HRSC2016,
and UCAS-AOD. The results show the state-of-the-art accuracy of the proposed
detector
Nano α-FeOOH Modified Carbon Paste Electrode for Arsenic Determination in Natural Waters
A novel method for determination of inorganic arsenic in natural water, based on nano ferric hydroxides (FeOOH) preconcentration and electrochemistry detection has been developed. As the nano α-FeOOH could successfully act as the adsorbent and electrode matrix modifier, the method presents great potential in practical routine analysis of inorganic arsenic. With optimization of the experimental conditions, nano α-FeOOH modified carbon paste electrode (α-FeOOH@CPE) was obtained by mixing 0.03 g of nano α-FeOOH and 0.02 g graphite powder in n-eicosane as an adhesive and then embedding them in a Teflon tube. Cyclic voltammetry, chronoamperometry and high resolution transmission electron microscopy were used to check and confirm the presence of nano α-FeOOH on the carbon paste electrodes. According to the results, α-FeOOH@CPE showed a considerably higher response to As(III) in comparison with the bare CPE, indicating the α-FeOOH has well selective enrichment for As(III). The developed modified electrode showed a linear range of 1.0 × 10-8 ~ 2.0 × 10-5 mol·L-1 and detection limit of 5.0 nmol·L-1 (S/N = 3). The newly prepared carbon paste electrode was successfully applied for As(III) determination in Yangzonghai Lake water with RSD of less than 3.6 % (n = 3) and recovery in the range of 100.7 ~ 115.0 %. DOI: http://dx.doi.org/10.5755/j01.ms.24.4.18499</p
A Study on Dynamic Stiffening of a Rotating Beam with a Tip Mass
Flexible structure, Dynamic stiffening, Assumed mode method, Flexible beam
This paper presents a dynamic model of a rotating beam with a tip mass undergoing large angle, high speed maneuvering. This type of model may also be useful in modeling, analysis and development of various inertial sensors and transducers with similar operating principles. With the consideration of the second-order term of the coupling deformation field, the complete first-order approximated model (CFOAM) of a flexible spacecraft system is developed by using assumed mode method (AMM) and Lagrangian principle. A first-order approximated model (FOAM) is obtained by neglecting the high order terms of the generalized coordinates in CFOAM. A lower order simplified first-order approximated model (SFOAM) is derived by deleting the terms related to the axial deformation. Numerical simulations and theoretical analysis show that: (i) the second-order term has a significant effect on the dynamic characteristics of the system and the dynamic stiffening is accounted for, while the traditional linear approximated model (TLAM) presents invalid simulation results; (ii) the end mass has a ‘stiffening’ effect on the flexible system in FOAM, but a ‘softening’ effect in TLAM; and (iii) the SFOAM describes the dynamic behavior well and can be used for controller design