Federated Filter Approach for GNSS Network Processing

Xiaoming Chen,Ulrich Vollath,Herbert Landau 한국항해항만학회 2006 한국항해항만학회 학술대회논문집 Vol.1 No.-

Abstract A large number of service providers in countries all over the world have established GNSS reference station networks in the last years and are using network software today to provide a correction stream to the user as a routine service. In current GNSS network processing, all the geometric related information such as ionospheric free carrier phase ambiguities from all stations and satellites, tropospheric effects, orbit errors, receiver and satellite clock errors are estimated in one centralized Kalman filter. Although this approach provides an optimal solution to the estimation problem, however, the processing time increases cubically with the number of reference stations in the network. Until now one single Personal Computer with Pentium 3.06 GHz CPU can only process data from a network consisting of no more than 50 stations in real time. In order to process data for larger networks in real time and to lower the computational load, a federated filter approach can be considered. The main benefit of this approach is that each local filter runs with reduced number of states and the computation time for the whole system increases only linearly with the number of local sensors, thus significantly reduces the computational load compared to the centralized filter approach. This paper presents the technical aspect and performance analysis of the federated filter approach. Test results show that for a network of 100 reference stations, with the centralized approach, the network processing including ionospheric modeling and network ambiguity fixing needs approximately 60 hours to process 24 hours network data in a 3.06 GHz computer, which means it is impossible to run this network in real time. With the federated filter approach, only less than 1 hour is needed, 66 times faster than the centralized filter approach. The availability and reliability of network processing remain at the same high level.

Static Output-feedback Controller Synthesis for Positive Systems under ℓ∞ Performance

Xiaoming Chen,Mou Chen,Liqun Wang,Jun Shen,Jiapan Hu 제어·로봇·시스템학회 2019 International Journal of Control, Automation, and Vol.17 No.11

This paper investigates the ℓ∞-induced output-feedback controller synthesis problem for discrete-time positive systems. For positive linear systems, a necessary and sufficient condition for stability and ℓ∞-induced performance is first put forward using a group of linear inequalities. Then, on the basis of these inequalities, theconditions on which static output-feedback controllers exist are set up, and to solve these conditions, a method of iterative convex optimization is provided. Moreover, a complete solution to the synthesis problem of the controller is proposed based on linear programming for positive systems with single output or input. Finally, two examples are presented to illustrate and verify the effective and applicable methods derived in this paper.

Insect industrialization and prospect in commerce: A case of China

Chen Xiaoming,Chen Hang,Zhao Min,Yang Zixiang,Feng Ying 한국곤충학회 2022 Entomological Research Vol.52 No.4

Insects are the largest biological group on the earth, characterized by high biodiversity, easy rearing, and large populations. The utilization of insects in China has a long history and some insect species have contributed to the formation of characteristic industries. Insect products, such as silk and honey, are already familiar to the public; however, many beneficial insects and their products are not well known to most people, for example, lac insect and lac, gall aphid and Chinese gallnut, and insect wax. A new industry featuring the utilization and industrialization of insects has been rising in China. Chemically, insect products are used as raw materials; agriculturally, insects are utilized to pollinate crops for better yield; natural enemy insects have been reared to control pests; insect protein may be used for human food or animal feed; medicinally, chemical compounds may be extracted from insects as active ingredients for pharmaceutical usage; and ornamental butterfly has been applied in travel sightseeing. Insects’ new purpose and function will be exploited as they gain recognition for their resources. This paper reviews insect industrialization in China and discusses the prospect of insect commerce in the future.

Visual and olfactory sensory responses of the butterfly Papilio maackii during foraging and courtship

Chen Shunan,Li Mingtao,Liu Ji,Feng Ying,Yao Jun,Shi Lei,Chen Xiaoming 한국곤충학회 2021 Entomological Research Vol.51 No.10

Colors and chemicals are the most important cues for butterflies to localize mating partners and food. In this study, we used artificial flowers with different colors and plastic butterfly wing mimics to separate the impact of colors from other cues on foraging and courtship of the butterfly Papilio maackii. We found that males relied more on visual cues during foraging and courtship, but females responded more to olfactory signals. Males visited artificial flowers more frequently than females. However, when honey was applied on artificial flowers, the frequency of female’s flower visits increased and was much higher than that of male’s, suggesting that females may have stronger olfactory than visual senses. During courtship, females were passive, whereas males were very active in chasing females and driving away other males. Similar to courtship among butterflies in a natural population, males showed recognition ability to butterfly wing mimics, indicating that males could accurately identify mates using colors only without any chemical cues. We also analyzed volatiles and identified five types of male-specific chemicals while no female-specific chemicals were identified, suggesting that females might have used these male-specific volatiles to recognize and accepted males during courtship. Pollination of the plant Primula sieboldii mainly depends on P. maackii, and the plant has flowers with purple and mauve colors. Coincidently, P. maackii showed color preference to blue and purple, suggesting that the butterfly and plants might have coevolved during the long course of interactions.

An efficient error concealment algorithm for H.264/AVC using regression modeling-based prediction

Xiaoming Chen,Yuk Ying Chung,Changseok Bae,Xiangjian He,Wei-Chang Yeh IEEE 2010 IEEE transactions on consumer electronics Vol.56 No.4

<P>This paper presents a novel error concealment algorithm for H.264/AVC based on a regression model, which is constructed according to the spatial relationship between block locations and their motion activities. With the proposed algorithm, a corrupted macroblock is partitioned into subblocks and the motion vector of each sub-block is predicted through the regression model with the help of the neighbor motion vectors. The experimental results show that the proposed algorithm can achieve significant Peak Signal Noise Ratio (PSNR) improvement over existing methods with even reduced complexity. The implementation of the proposed algorithm is very simple and therefore it can be readily applied to real-time video applications running on various consumer electronic products such as mobile devices.</P>

Efficient Immobilization of Polysaccharide Derivatives as Chiral Stationary Phases via Copolymerization with Vinyl Monomers

Chen, Xiaoming,Okamoto, Yoshio,Yamamoto, Chiyo The Polymer Society of Korea 2007 Macromolecular Research Vol.15 No.2

The direct chromatographic separation of enantiomers by chiral stationary phases (CSPs) has been extensively developed over the past two decades, and has now become the most popular method for the analytical and preparative separations of enantiomers. Polysaccharide derivatives coated onto silica gel, as CSPs, playa significantly important role in the enantioseparations of a wide range of chiral compounds using high-performance liquid chromatography (HPLC). Unfortunately, the strict solvent limitation of the mobile phases is the main defect in the method developments of these types of coated CSPs. Therefore, the immobilization of polysaccharide derivatives onto silica gel, via chemical bonding, to obtain a new generation of CSPs compatible with the universal solvents used in HPLC is increasingly important. In this article, our recent studies on the immobilization of polysaccharide derivatives onto the silica gel, as CSPs, through radical copolymerization with various vinyl monomers are reported. Polysaccharide derivatives, with low vinyl content, can be efficiently fixed onto silica gel with high chiral recognition.

Evaluation Model of Simulation Based Training for Helicopter Emergency Rescue Mission

Xiaoming Chen,Hu Liu,Jinpeng Bai,Zhe Wu 보안공학연구지원센터 2015 International Journal of Multimedia and Ubiquitous Vol.10 No.9

Effect of guide vane profile on the hydraulic performance of moderate lowspecific-speed Francis turbine

Xiaoming Chen,Xide Lai,Qiuqin Gou,Dongmei Song 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.3

The matching between the guide vane (GV) and runner is essential for the stable and efficient operation of hydraulic turbines. To investigate the compatibility between GV and runner, we have conducted the numerical calculations of a moderate low-specific-speed Francis turbine at 25 operating points within the operating range of 130-190 m head and 3-19° GV outflow angle. The energy characteristics, flow field characteristics, and static pressure variation of turbines with different GV profile types have been comparatively analyzed. The results show that moderate low-specific-speed Francis turbines with symmetrical and negative curvature GV demonstrate higher efficiency under medium to high head, 55-100 % rated output operating conditions. Under small opening and medium head conditions, the static pressure in the blade leading edge is smaller, and the low-pressure area is larger for the Francis turbine with positive curvature GV. When the GV opening increases, the relationship between the comparative values of static-pressure and low-pressure areas reverses. The turbine with positive curvature GV is more favorable for increasing static-pressure and narrow low-pressure areas, which can reduce the cavitation damage. Our study provides guidelines to optimize the design of GVs and runner for hydraulic turbines.

Common edible insects and their utilization in China

Xiaoming CHEN,Ying FENG,Zhiyong CHEN 한국곤충학회 2009 Entomological Research Vol.39 No.5

This paper reviews the common edible insects and their use in China. One-hundred and seventy-eight insect species from 96 genera, 53 families and 11 orders are commonly eaten in China. Preparation of edible insects includes frying, braising, stewing, stewing after frying, boiling and roasting. The insect forms eaten range from eggs to adults; however, in restaurants most are larvae and pupae. More than 50 species have been analyzed for their nutritive elements and nutritional value and these data are reviewed here. Insect health foods sold in the Chinese market are also briefly discussed.

Load transfer and energy absorption in transversely compressed multi-walled carbon nanotubes

Chen, Xiaoming,Ke, Changhong Techno-Press 2017 Coupled systems mechanics Vol.6 No.3

We present a simple and easy-to-implement lumped stiffness model to elucidate the load transfer mechanism among all individual tube shells and intertube van der Waals (vdW) interactions in transversely compressed multi-walled carbon nanotubes (CNTs). Our model essentially enables theoretical predictions to be made of the relevant transverse mechanical behaviors of multi-walled tubes based on the transverse stiffness properties of single-walled tubes. We demonstrate the validity and accuracy of our model and theoretical predictions through a quantitative study of the transverse deformability of double- and triple-walled CNTs by utilizing our recently reported nanomechanical measurement data. Using the lumped stiffness model, we further evaluate the contribution of each individual tube shell and intertube vdW interaction to the strain energy absorption in the whole tube. Our results show that the innermost tube shell absorbs more strain energy than any other individual tube shells and intertube vdW interactions. Nanotubes of smaller number of walls and outer diameters are found to possess higher strain energy absorption capacities on both a per-volume and a per-weight basis. The proposed model and findings on the load transfer and the energy absorption in multi-walled CNTs directly contribute to a better understanding of their structural and mechanical properties and applications, and are also useful to study the transverse mechanical properties of other one-dimensional tubular nanostructures (e.g., boron nitride nanotubes).