Learning-based NLOS Detection and Uncertainty Prediction of GNSS Observations with Transformer-Enhanced LSTM Network

The global navigation satellite systems (GNSS) play a vital role in transport systems for accurate and consistent vehicle localization. However, GNSS observations can be distorted due to multipath effects and non-line-of-sight (NLOS) receptions in challenging environments such as urban canyons. In such cases, traditional methods to classify and exclude faulty GNSS observations may fail, leading to unreliable state estimation and unsafe system operations. This work proposes a Deep-Learning-based method to detect NLOS receptions and predict GNSS pseudorange errors by analyzing GNSS observations as a spatio-temporal modeling problem. Compared to previous works, we construct a transformer-like attention mechanism to enhance the long short-term memory (LSTM) networks, improving model performance and generalization. For the training and evaluation of the proposed network, we used labeled datasets from the cities of Hong Kong and Aachen. We also introduce a dataset generation process to label the GNSS observations using lidar maps. In experimental studies, we compare the proposed network with a deep-learning-based model and classical machine-learning models. Furthermore, we conduct ablation studies of our network components and integrate the NLOS detection with data out-of-distribution in a state estimator. As a result, our network presents improved precision and recall ratios compared to other models. Additionally, we show that the proposed method avoids trajectory divergence in real-world vehicle localization by classifying and excluding NLOS observations.Comment: Accepted for the IEEE ITSC202

The finite element analysis of the in plane and out of plane harmonic responses of piezoresponse force microscopy cantilever

The harmonic response under the in plane and out of plane driving force separately and model analysis of the widely used SCM-PIT probe were carried out in the consideration of the typical piezoresponse force microscopy working condition by finite element method. It is shown that there are symmetric modes of the resonance at 68, 408, 1139, 2244 kHz, and antisymmetric modes at 646, 1020, and 3077 kHz in the first seven eigenmodes. The symmetric modes of the harmonic response are verified by the frequency sweep method from the piezoresponse phase signals experimentally. It is also revealed that different driving frequencies should be used in the resonance-enhanced PFM imaging in the consideration of the domain structures. The driving frequency of 68, 408, 1139, 2244 kHz should be preferred in the resonance-enhanced PFM imaging of the out of plane domains, while the driving frequency of 646, 1020 and 3077 kHz should be used for the imaging of in plane domains in order of achieved the best resonance-enhanced effect

Hydrogels based on seafood chitin: from extraction to the development

Chitin is extensively applied in vast applications due to its excellent biological properties, such as biodegradable and non-toxic. About 50 % of waste generated during seafood processing is chitin. Conventionally, chitin is extracted via chemical method. However, it has many shortcomings. Many novel extraction methods have emerged, including enzymatic hydrolysis, microbial fermentation, ultrasonic or microwave-assisted, ionic liquids, and deep eutectic solvents. Chitin and its derivatives-based hydrogels have attracted much attention due to their excellent properties. Nevertheless, they all have many limitations. Therefore, the preparation and application of chitin and its derivatives-based hydrogels are still facing great challenges. This review focuses on the challenges and prospects for sustainable chitin extraction from seafood waste and the preparation and application of chitin and its derivatives-based hydrogels. First section summarizes the mechanism and application of several methods of extracting chitin. The different extraction methods were evaluated from the aspects of yield, degree of acetylation, and protein and mineral residuals. The shortcomings of the extraction methods are also discussed. Next section summarizes the preparation and application of chitin and its derivatives-based hydrogels. Overall, we hope this mini-review can provide a practical reference for selecting chitin extraction methods from seafood and applying chitin and its derivatives-based hydrogels

The finite element analysis of the in plane and out of plane harmonic responses of piezoresponse force microscopy cantilever

The harmonic response under the in plane and out of plane driving force separately and model analysis of the widely used SCM-PIT probe were carried out in the consideration of the typical piezoresponse force microscopy working condition by finite element method. It is shown that there are symmetric modes of the resonance at 68, 408, 1139, 2244 kHz, and antisymmetric modes at 646, 1020, and 3077 kHz in the first seven eigenmodes. The symmetric modes of the harmonic response are verified by the frequency sweep method from the piezoresponse phase signals experimentally. It is also revealed that different driving frequencies should be used in the resonance-enhanced PFM imaging in the consideration of the domain structures. The driving frequency of 68, 408, 1139, 2244 kHz should be preferred in the resonance-enhanced PFM imaging of the out of plane domains, while the driving frequency of 646, 1020 and 3077 kHz should be used for the imaging of in plane domains in order of achieved the best resonance-enhanced effect

Watt-level femtosecond Tm-doped “mixed” sesquioxide ceramic laser in-band pumped by a Raman fiber laser at 1627 nm

We report on a semiconductor saturable absorber mirror mode-locked Tm:(Lu,Sc)2O3 ceramic laser in-band pumped by a Raman fiber laser at 1627 nm. The nonlinear refractive index (n2) of the Tm:(Lu,Sc)2O3 ceramic has been measured to be 4.66 × 10-20 m2/W at 2000 nm. An average output power up to 1.02 W at 2060 nm is achieved for transform-limited 280-fs pulses at a repetition rate of 86.5 MHz, giving an optical efficiency with respect to the absorbed pump power of 36.4%. Pulses as short as 66 fs at 2076 nm are produced at the expense of output power (0.3 W), corresponding to a spectral bandwidth of 69 nm. The present work reveals the potential of Tm3+-doped sesquioxide transparent ceramics for power scaling of femtosecond mode-locked bulk lasers emitting in the 2-μm spectral range

The TLR9 ligand, CpG-ODN, Induces Protection Against Cerebral Ischemia/Reperfusion Injury via Activation of pi3k/Akt Signaling.

Toll-like receptors (TLRs) have been shown to be involved in cerebral ischemia/reperfusion (I/R) injury. TLR9 is located in intracellular compartments and recognizes CpG-DNA. This study examined the effect of CpG-ODN on cerebral I/R injury. C57BL/6 mice were treated with CpG-ODN by i.p. injection 1 hour before the mice were subjected to cerebral ischemia (60 minutes) followed by reperfusion (24 hours). Scrambled-ODN served as control-ODN. Untreated mice, subjected to cerebral I/R, served as I/R control. The effect of inhibitory CpG-ODN (iCpG-ODN) on cerebral I/R injury was also examined. In addition, we examined the therapeutic effect of CpG-ODN on cerebral I/R injury by administration of CpG-ODN 15 minutes after cerebral ischemia. CpG-ODN administration significantly decreased cerebral I/R-induced infarct volume by 69.7% (6.4±1.80% vs 21.0±2.85%, P\u3c0.05), improved neurological scores, and increased survival rate, when compared with the untreated I/R group. Therapeutic administration of CpG-ODN also significantly reduced infarct volume by 44.7% (12.6±2.03% vs 22.8±2.54%, P\u3c0.05) compared with untreated I/R mice. Neither control-ODN, nor iCpG-ODN altered I/R-induced cerebral injury or neurological deficits. Nissl staining showed that CpG-ODN treatment preserved neuronal morphology in the ischemic hippocampus. Immunoblot showed that CpG-ODN administration increased Bcl-2 levels by 41% and attenuated I/R-increased levels of Bax and caspase-3 activity in ischemic brain tissues. Importantly, CpG-ODN treatment induced Akt and GSK-3β phosphorylation in brain tissue and cultured microglial cells. PI3K inhibition with LY294002 abolished CpG-ODN-induced protection. CpG-ODN significantly reduces cerebral I/R injury via a PI3K/Akt-dependent mechanism. Our data also indicate that CpG-ODN may be useful in the therapy of cerebral I/R injury

SESAM mode-locked Tm:Y2O3 ceramic laser

We demonstrate a widely tunable and passively mode-locked Tm:Y2O3 ceramic laser in-band pumped by a 1627-nm Raman fiber laser. A tuning range of 318 nm, from 1833 to 2151 nm, is obtained in the continuous-wave regime. The SESAM mode-locked laser produces Fourier-transform-limited pulses as short as 75 fs at ∼ 2.06 µm with an average output power of 0.26 W at 86.3 MHz. For longer pulse durations of 178 fs, an average power of 0.59 W is achieved with a laser efficiency of 29%. This is, to the best of our knowledge, the first mode-locked Tm:Y2O3 laser in the femtosecond regime. The spectroscopic properties and laser performance confirm that Tm:Y2O3 transparent ceramics are a promising gain material for ultrafast lasers at 2 µm

The Winners in China’s Urban Housing Reform

Housing reform in China has proceeded on two tracks: privatization of public housing and development of a new private housing sector. During this period of transition, rents have remained relatively low in the remaining public housing, and purchase prices offered to occupants of public housing have been well below market prices. Although these rents and prices are partly based on known formulas, there is considerable variability in how much people pay for similar apartments. This study uses 2000 Census data to estimate the housing subsidy received by the remaining renters in the public sector and purchasers of public housing, based on private sector prices for housing of comparable quality and size. The paper also analyzes variation in the estimated discount from market prices that these people receive. The findings show that the biggest winners in China’s transition from socialist housing allocation are those who were favored in the previous system, based on such factors as residence status, education and occupation

Social stratification in migrant-concentrated communities in China : findings from a five-city study of migration and urban poverty

Based on recent large-scale survey data, this paper examines the patterns of integration/segregation and social stratification of migrants in the host communities in China.12 page(s