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Simultaneous localization and mapping (SLAM) is a well-known and fundamental topic for autonomous robot navigation. Existing solutions include the FastSLAM family-based approaches which are based on Rao–Blackwellized particle filter. The FastSLAM methods slow down greatly when the number of landmarks becomes large. Furthermore, the FastSLAM methods use a fixed number of particles, which may result in either not enough algorithms to find a solution in complex domains or too many particles and hence wasted computation for simple domains. These issues result in reduced performance of the FastSLAM algorithms, especially on embedded devices with limited computational capabilities, such as commonly used on mobile robots. To ease the computational burden, this paper proposes a modified version of FastSLAM called Adaptive Computation SLAM (ACSLAM), where particles are predicted only by odometry readings, and are updated only when an expected measurement has a maximum likelihood. As for the states of landmarks, they are also updated by the maximum likelihood. Furthermore, ACSLAM uses the effective sample size (ESS) to adapt the number of particles for the next generation. Experimental results demonstrated that the proposed ACSLAM performed 40% faster than FastSLAM 2.0 and also has higher accuracy.
Coastal lake sediments are valuable paleoclimate archives provided that they can be accurately dated. Here, we report radiocarbon ages of bulk sediment organic matter (OM), plants, shells, particulate OM, and dissolved OM from coastal lakes in Florida. Bulk sediment OM yielded ages that are consistently older than contemporaneous plants and shells, indicating significant radiocarbon deficiencies in sedimentary OM in these lakes. The data show that the OM radiocarbon deficiency varies over time and with location, making it impossible to determine a proper correction factor for radiocarbon ages of bulk sediments from these lakes. As a result, we consider ages obtained from bulk sediment OM from these lakes unreliable. The age reversals in bulk sediment OM observed in the sediment cores are likely caused by rapid increases in erosion and sedimentation resulting from large storm events. The data also show that sedimentation rate can vary considerably within a given lake, implying that an age-depth model established for one core cannot be directly applied to other cores despite their close proximity. Analyses of shells from one of the lakes suggest that fresh/brackish-water shells may serve as a good substrate for radiocarbon dating owing to a small reservoir effect on inorganic carbon.
Precious metals represent some of the least abundant elements in the earth’s crust. There is an urgent need to maximize the utilization efficiency of these metals and thereby attain affordable and sustainable products. One approach for achieving this goal is based on the development of hollow nanocrystals with a well-controlled surface structure, together with a wall thickness kept below 2 nm, or roughly 10 layers of atoms. The hollow structure eliminates the waste of interior atoms and creates an inner surface, while the controllable surface structures contribute to the optimization of catalytic activity and selectivity. In this article, we begin with a brief introduction to two methods that have been developed for the synthesis of hollow nanocrystals: the first relying on the galvanic replacement with a sacrificial template, and the second involving layer-by-layer deposition of metal atoms followed by etching. We then showcase some remarkable properties and applications of this novel class of nanostructures, including their use as effective catalysts for energy conversion, photoresponsive carriers for controlled release and drug delivery, and theranostic agents. A discussion of the existing barriers to their commercialization is also presented.
The TiCxN1−x(001)/TiC(001) interface was studied by the first-principles method to provide the theoretical basis for developing TiCxN1−x/TiC coatings. The partial density of state (PDOS), charge density, charge density difference, and Mulliken population analysis were utilized to investigate the bonding nature and the electronic characteristic of the TiC0.25N0.75/TiC interface. The corresponding results indicate that the bonding nature at the interface is ionic and covalent characteristics, which also exist in bulk materials. The extreme similarity of PDOS among interfacial C, N, and Ti atoms and their bulk counterparts reveals that the electronic structure transition at the interface is smooth. The results of Mulliken population analysis and plots of charge density and charge density difference demonstrate that the charge increased for C in the TiC side is less than that for N in the TiC0.25N0.75 side, which reveals that the ionic bond in TiC0.25N0.75 is stronger than that in TiC. Therefore, TiC0.25N0.75 coating can be an alternative choice to combine with TiC coating in the actual production process of multilayer coatings.
On August 12, 2015, a hazardous chemical explosion occurred in the Tianjin Port of China. The explosions resulted in 165 deaths, 8 missing people, injuries to thousands of people. We present the responses of emergency medical services and hospitals to the explosions and summarize the lessons that can be learned.
This study was a retrospective analysis of the responses of emergency medical services and hospitals to the Tianjin explosions. Data on injuries, outcomes, and patient flow were obtained from the government and the hospitals.
A total of 46 ambulances and 143 prehospital care professionals were dispatched to the scene, and 198 wounded were transferred to hospitals by ambulance. More than 4000 wounded casualties surged into hospitals, and 798 wounded were admitted. Both emergency medical services and hospitals were quick and successful in the early stage of the explosions. The strategy of 4 centralizations (4Cs) for medical services management in a mass casualty event was successfully applied.
The risk of accidental events has increased in recent years. We should take advantage of the lessons learned from the explosions and apply these in future disasters. (Disaster Med Public Health Preparedness. 2018; 12: 411–414)
Nitrogen is an essential element for biological activity, and nitrogen isotopic compositions of geological samples record information about both marine biological processes and environmental evolution. However, only a few studies of N isotopes in the early Cambrian have been published. In this study, we analysed nitrogen isotopic compositions, as well as trace elements and sulphur isotopic compositions of cherts, black shales, carbonaceous shales and argillaceous carbonates from the Daotuo drill core in Songtao County, NE Guizhou Province, China, to reconstruct the marine redox environment of both deep and surface seawater in the study area of the Yangtze shelf margin in the early Cambrian. The Mo–U covariation pattern of the studied samples indicates that the Yangtze shelf margin area was weakly restricted and connected to the open ocean through shallow water flows. Mo and U concentrations, δ15Nbulk and δ34Spy values of the studied samples from the Yangtze shelf margin area suggest ferruginous but not sulphidic seawater and low marine sulphate concentration (relatively deep chemocline) in the Cambrian Fortunian and early Stage 2; sulphidic conditions (shallow chemocline and anoxic photic zone) in the upper Cambrian Stage 2 and lower Stage 3; and the depression of sulphidic seawater in the middle and upper Cambrian Stage 3. Furthermore, the decreasing δ15N values indicate shrinking of the marine nitrate reservoir during the middle and upper Stage 3, which reflects a falling oxygenation level in this period. The environmental evolution was probably controlled by the changing biological activity through its feedback on the local marine environment.
In this paper, we propose a new SSOR-like method with four parameters to solve the augmented system. And we analyze the convergence of the method and get the optimal convergence factor under suitable conditions. It is proved that the optimal convergence factor is the same as the GMPSD method [M.A. Louka and N.M. Missirlis, A comparison of the extrapolated successive overrelaxation and the preconditioned simultaneous displacement methods for augmented systems, Numer. Math. 131(2015) 517-540] with five parameters under the same assumption.
This study examines the usage of the Meaning in Life Questionnaire in Chinese students aged from 10 to 25 within four age groups (N = 5,510): early adolescence (10–13 years old, n = 1,258), middle adolescence (14–17 years old, n = 1,987), late adolescence (18–21 years old, n = 1,950) and early adulthood (22–25 years old, n = 315); and analyses the structure and levels of meaning in life, as well as the relationship between meaning in life and mental health. Results showed that: (1) the Meaning in Life Questionnaire in the four age groups of Chinese students had good construct validity and internal consistency reliability; (2) the average levels of the presence of meaning and search for meaning of Chinese students were moderate or above, and had obvious differences according to gender and family location (i.e., urban vs. rural); (3) the level of presence of meaning showed a trend of rising rapidly in middle adolescence and the level of search for meaning continued to rise in early adolescence and fell rapidly towards the end of adolescence; (4) presence of meaning was positively related to life satisfaction and positive affect and negatively related to depression and negative affect, and the same correlations were found with search for meaning.
In this paper, the recent studies of laboratory astrophysics with strong magnetic fields in China have been reviewed. On the Shenguang-II laser facility of the National Laboratory on High-Power Lasers and Physics, a laser-driven strong magnetic field up to 200 T has been achieved. The experiment was performed to model the interaction of solar wind with dayside magnetosphere. Also the low beta plasma magnetic reconnection (MR) has been studied. Theoretically, the model has been developed to deal with the atomic structures and processes in strong magnetic field. Also the study of shock wave generation in the magnetized counter-streaming plasmas is introduced.
Infectious bovine keratoconjunctivitis (IBK) is a common and important disease of calves. Without effective vaccines, antibiotic therapy is often implemented to minimize the impact of IBK. This review updates a previously published systematic review regarding comparative efficacy for antibiotic treatments of IBK. Available years of Centre for Biosciences and Agriculture International and MEDLINE databases were searched, including non-English results. Also searched were the American Association of Bovine Practitioners and World Buiatrics Congress conference proceedings from 1996 to 2016, reviews since 2013, reference lists from relevant trials, and U.S. Food and Drug Administration New Animal Drug Application summaries. Eligible studies assessed antibiotic treatment of naturally-occurring IBK in calves randomly allocated to group at the individual level. Outcomes of interest were clinical score, healing time, unhealed ulcer risk, and ulcer surface area. A mixed-effects model comparing active drug with placebo was employed for all outcomes. Heterogeneity was assessed visually and using Cochran's Q-test. Thirteen trials assessing nine treatments were included. Compared with placebo, most antibiotic treatments were effective. There was evidence that the treatment effect differed by day of outcome measurement. Visually, the largest differences were observed 7–14 days post-treatment. These results indicate improved IBK healing with many antibiotics and suggest the need for randomized trials comparing different antibiotic treatments.
The reporting period has shown that Space has become a firmly established domain in observational Astrophysics, also in the low energy astrophysics area. The launching of new spacecraft is always an important addition to the capabilities of the Astronomers, but the availability of space observatories is strongly affected by the fact that they disappear as their subsystems become damaged or, for other reasons, become inoperable. The relatively short life of astronomical space facilities has generated new dynamic in the life cycle of observational tools for the astronomer, rather different from that for ground facilities. Launch failures or the final in-orbit functionality verification can also very strongly affect the availability of observational capabilities in space astrophysics. The only spacecraft designed without this built-in life time restriction, is the Hubble Space Telescope, which can be serviced by the Space Shuttle.
Areas with low, adequate and excessive I content in water co-exist in China. Limited data are currently available on I nutrition and thyroid disease in lactating women and their breast-fed infants with different I intakes. This study aimed to evaluate I nutrition in both lactating women and their infants and the prevalence of thyroid disease in areas with different levels of I in water. From January to June 2014, a total of 343 healthy lactating women (excluding those taking anti-thyroid drugs or I supplements within a year of the study, consuming seafood at the time of the study or those diagnosed with congenital thyroid disease) from Beihai in Guangxi province and Jiajiazhuang, Yangcheng, Jicun and Pingyao townships in Shanxi province were selected. Compared with the I-sufficient group, median urinary I concentrations in both lactating women and infants as well as breast milk I levels were significantly lower in the I-deficient group (P<0·001). The prevalence of thyroid disease in lactating women, particularly subclinical hypothyroidism, was higher in the I-excess group than in the I-sufficient group (P<0·05). In areas with excessive water I content, high thyroid peroxidase antibody and high thyroglobulin levels were risk factors for abnormal thyroid-stimulating hormone levels. Our data collectively suggest that excessive I intake potentially causes subclinical hypothyroidism in lactating women. Moreover, enhanced monitoring of I status is important to avoid adverse effects of I deficiency or excess, particularly in susceptible populations such as pregnant or lactating women and infants.
The objective of this paper is to investigate an online method to generate an optimal ascent trajectory for air-breathing hypersonic vehicles. A direct method called the Pseudo-spectral method shows promise for real-time optimal guidance. A significant barrier to this optimisation-based control strategy is computational delay, especially when the solution time of the non-linear programming problem exceeds the sampling time. Therefore, an online guidance algorithm for an air-breathing hypersonic vehicles with process constraints and terminal states constraints is proposed based on the Pseudo-spectral method and sensitivity analysis in this paper, which can reduce online computational costs and improve performance significantly. The proposed ascent optimal guidance method can successively generate online open-loop suboptimal controls without the design procedure of an inner-loop feedback controller. Considering model parameters' uncertainties and external disturbance, a sampling theorem is proposed that indicates the effect of the Lipschitz constant of the dynamics on sampling frequency. The simulation results indicate that the proposed method offers improved performance and has promising ability to generate an optimal ascent trajectory for air-breathing hypersonic vehicles.
In this work, we report on development of one-dimensional reaction-diffusion simulator needed to understand the kinetics of Cu-related metastabilities observed in CdTe PV devices. Evolution of intrinsic and Cu-related defects in CdTe solar cells has been studied in time-space domain self-consistently with free carrier transport. Resulting device performance was simulated as a function of stress time, thus showing pronounced effect that the evolution of associated acceptor and donor states can cause on device characteristics. Although 1D simulation has intrinsic limitations when applied to poly-crystalline films, the results presented confirm the validity and the potential of the approach presented in better understanding of the performance and metastabilities of CdTe photovoltaic devices.
Temperature seasonality, the difference between summer and winter temperature, has significant influences on global terrestrial and marine ecosystems. However, most of proxy-based climate records are of limited temporal resolution and thus insufficient to quantify the past temperature seasonality. In this study, high-resolution Sr/Ca ratios of modern (live-caught) and fossil (dead-collected) Tridacna gigas shells from the South China Sea (SCS) were used to reconstruct the seawater temperature seasonality during the late Holocene. The averaged seawater temperature seasonality around 2165 ± 75 BC (4.46 ± 1.41°C, derived from the data of 18 yr) were similar to the seasonality of recent decade (4.41 ± 0.82°C during AD 1994–2005), but the temperature seasonality around AD 50 ± 40 (3.69 ± 1.37°C, derived from the data of 48 yr) and AD 990 ± 40 (3.64 ± 0.87°C, derived from the data of 11 yr) was significantly lower than that during AD 1994–2005. The reduced seasonality around AD 990 ± 40 was attributable to the unusually warm winter during the medieval times, probably caused by the weakening of East Asian Winter Monsoon. Our study highlighted the potential of T. gigas shells in providing high-resolution seasonality climate information during the late Holocene.
Undoped and Zinc-doped GaN films have been grown using TMGa, DEZn and Ammonia by MOVPE. The GaN blue-green LEDs of m-i-n structure have been fabricated. They can be operated at forward bias less than 5 volts. The EL peak wavelength was from 455 nm to 504 nm.
Large-area Cu2ZnSnS4 (CZTS) thin films were deposited by low-cost spray pyrolysis technique on Mo-coated soda-lime glass (SLG) substrates at varied substrate temperatures of 563-703°K. Deposition conditions were optimized to obtain best quality films and effect of post deposition thermal processing of the as-deposited films under H2S ambient were investigated. Structural, morphological, and compositional characterization of as-deposited and H2S treated CZTS absorber layers were carried out by x-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM) and energy dispersive x-ray analysis (EDX). Optical and electrical properties were measured by UV-Vis spectroscopy, van der Pauw, and Hall-effect measurements. Films grown at ∼360°C substrate temperature showed superior optoelectronic properties, improved stoichiometry and smoother morphology compared to films grown at much higher or lower temperatures. Film properties were significantly improved after the H2S processing. Our results show that large area high quality CZTS films can be fabricated by low-cost spray pyrolysis technique for high throughput commercial production of CZTS based heterojunction solar cells.