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Contribution of Pseudolite Observations to GPS Precise Surveys
Yongqi Chen,Xiufeng He 대한토목학회 2008 KSCE JOURNAL OF CIVIL ENGINEERING Vol.12 No.1
Although GPS has been widely used for precision surveys, many survey environments, like in urban areas, deep open-pit minesand valleys, limit the number of visible GPS satellites, deteriorating the survey accuracy. In addition some engineering projectsrequire higher positioning accuracy in a particular direction. A GPS-only system hardly satisfies the requirements. Pseudolite-augmented GPS survey technique can strengthen the positioning geometry. Pseudolite (PL) measurements, however, suffer fromvarious sources of errors different from GPS observations. In order to employ them fo mustbe treated properly. This paper discusses of the major sources of errors in PL measurements and the methodologies for theirmitigation. Some experimental tests are then presented.
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GPS Satellite Orbit Prediction Based on Unscented Kalman Filter
Zuoya ZHENG,Yongqi CHEN,LU Xiushan,DU Zhixing 한국항해항만학회 2006 한국항해항만학회 학술대회논문집 Vol.1 No.-
In GPS Positioning, the error of satellite orbit will affect user’s position accuracy directly, it is important to determine the satellite orbit precise. The real-time orbit is needed in kinematic GPS positioning, the precise GPS orbit from IGS would be delayed long time, so orbit prediction is key to real-time kinematic positioning. We analyze the GPS predicted ephemeris, on the base of comparison of EKF and UKF, a new orbit prediction method is put forward based on UKF in this paper, the result shows that UKF improves the orbit predicted precision and stability. It offers a new method for others satellites orbit determination as Galileo, and so on.
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Fast Ambiguity Resolution using Galileo Multiple Frequency Carrier Phase Measurement
Shengyue Ji,Wu Chen,Chunmei Zhao,Xiaoli Ding,Yongqi Chen 한국항해항만학회 2006 한국항해항만학회 학술대회논문집 Vol.1 No.-
Rapid and high-precision positioning with a Global Navigation Satellite System (GNSS) is feasible only when very precise carrier-phase observations can be used. There are two kinds of mathematical models for ambiguity resolution. The first one is based on both pseudorange and carrier phase measurements, and the observation equations are of full rank. The second one is only based on carrier phase measurement, which is a rank-defect model. Though the former is more commonly used, the latter has its own advantage, that is, ambiguity resolution will be freed from the effects of pseudorange multipath. Galileo will be operational. One of the important differences between Galileo and current GPS is that Galileo will provide signals in four frequency bands. With more carrier-phase data available, frequency combinations with long equivalent wavelength can be formed, so Galileo will provide more opportunities for fast and reliable ambiguity resolution than current GPS. This paper tries to investigate phase only fast ambiguity resolution performance with four Galileo frequencies for short baseline. Cascading Ambiguity Resolution (CAR) method with selected optimal frequency combinations and LAMBDA method are used and compared. To validate the resolution, two tests are used and compared. The first one is a ratio test. The second one is lower bound success-rate test. The simulation test results show that, with LAMBDA method, whether with ratio test or lower bound success rate validation criteria, ambiguity can be fixed in several seconds, 8 seconds at most even when 1 sigma of carrier phase noise is 12 mm. While with CAR method, at least about half minute is required even when 1 sigma of carrier phase noise is 3 mm. It shows that LAMBDA method performs obviously better than CAR method.
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Development of a Soft Infrastructure for City-wide Land Information Management: a China Perspective
WEN, He,TANG, Conrad,CHEN, Yongqi 한국국토정보공사 2011 지적과 국토정보 Vol.41 No.1
Over the last two decades, various urban geospatial information systems were built in China. Most of them were designed to serve specific communities. Many systems just followed the wave of the so called digital city or e-government without a clear vision, leading to not being fully utilized. Nowadays the focus on geospatial information systems is increasingly shifting to the challenges associated with integrating these systems, building what has come to be called city-wide land information management system (LIMS). The existing problems China is facing are the lack of a LIMS vision and institutional framework to support the vision, resulting in the duplication of data collection, information out of date, inaccessible and limited sharing of data. Based on the current developments in the area of geospatial information systems in great China and the world good practices, we propose that the vision to build the LIMS for a city is to develop an infrastructure that allows spatial data to be available and accessible to authorized public, government department and individuals and promote proper use of integrated spatial data for effective decision-making process, and development of information economy and spatially enabled society. With this vision there are several key elements: core spatial data, availability and accessibility, infrastructure, spatially enabled society and information economy. This paper discusses the soft infrastructure for building an efficient LIMS, i.e., institutional framework and management arrangement.
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Rapid Screen of IL-5/IL-5Rα Blocking Antibodies in the HEK293-IL-5Rα-CSF2RB Transfected Cell Line
Shijie Li,Fei Han,Chang Liu,Weiyan Dai,Wenfeng Ke,Yongqi Chen,Eric Fordjour,Yankun Yang,Zhonghu Bai 한국생물공학회 2023 Biotechnology and Bioprocess Engineering Vol.28 No.4
Interleukin-5 (IL-5) binding to interleukin-5 receptor subunit alpha (IL-5Rα) increases the number of eosinophils and enhances eosinophil activity. This leads to eosinophil tissue infiltration and damage to the lungs, ultimately resulting in exacerbation of asthma. Antibodies that block IL-5 binding to IL-5Rα are thought to play an important role in advanced asthma. Currently, key methods used to screen for targeted drugs are Surface Plasmon Resonance which is costly and anti-proliferation assays which are tedious and have a low signal-to-noise ratio. Here we describe a Fluorescence Activated Cell Sorting (FACS) assay, based on human embryonic kidney (HEK)- 293 cells with stable expression of IL-5Rα and the cytokine receptor common subunit beta (CSF2RB). Cells co-expressing IL-5Rα and CSF2RB had a 16% increase in the ability to bind IL-5 compared to cells expressing only IL-5Rα. The optimal concentration of IL-5 for the FACS assay was 0.1 μg/mL. The established FACS was used to screen anti IL-5 nanobodies and hybridoma supernatants for candidate antibodies that block the IL-5/IL-5α interaction. When compared to anti-proliferation assays, this method saved up to 90% of the assay time, offering the advantage of rapidity and accuracy in vitro. The assay described here provides a novel approach for rapid screening of IL-5/IL- 5Rα blocking antibodies in vitro to accelerate the development of drugs for asthma.
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