Differential Positioning Research Articles

FPGA-based PPM Modulation System Design

As a widely used modulation technique in the field of communication, PPM modulation techniques have the advantages of high interference immunity, simple coding and high-power utilization, and are often applied in practical scenarios. PPM modulation techniques can be divided into three categories. single pulse position modulation, differential pulse position modulation and multi pulse position modulation. In different application scenarios, different kinds of pulse position modulation methods should be selected for modulation. In this paper, the frame structures of these three types of pulse position modulation are discussed using the Verilog language based on FPGA, the corresponding mapping relationships for each type of pulse position modulation are given, and the design and performance of these three types of pulse position modulation demodulation systems are compared.

Analysis of bit error rate of pulse position modulation in free-space optical communication

Pulse Position Modulation (PPM) modulation is a widely used modulation method in free-space optical (FSO) communication, which has many medium forms. This work introduces and summarises the three main PPM modulation methods, L-ary pulse position modulation (L-PPM), L-ary differential pulse position modulation (L-DPPM), and L-ary multiple pulse position modulation (L-MPPM), and summarises their respective characteristics and suitable usage scenarios. At the same time, this study analyzes several cases of combining coding methods with PPM modulation methods and finds that the right coding method can make PPM modulation methods more valuable. In addition, receiver diversity and/or aperture averaging can both improve the connection error performance.

The geopolitics of human suffering: a comparative study of media coverage of the conflicts in Yemen and Ukraine

A Saudi-led coalition of states initiated an on-going-armed conflict in Yemen on 26 March 2015. Meanwhile, Russia invaded Ukraine on 24 February 2022. Though no two armed conflicts are exactly alike, there is reason to compare US media coverage of the two because: (1) civilians have been victims of both conflicts; (2) both conflicts have undermined food security; (3) the US has provided military support to a party to each of the conflicts; and (4) the conflict in Yemen is in the Global South whereas the conflict in Ukraine is in the Global North. This article comparatively analyses US media coverage of the conflicts in Yemen and Ukraine, via New York Times headlines, by documenting the number of stories and their placement; assessing the types of media frames used; reviewing headlines for attribution of responsibility; and conducting a content analysis to identify the descriptive and normative terminology used. We find extensive biases in coverage and framing, rooted in peripheralism, culturalism and differential geopolitical US positioning. This results in reduced coverage of the war in Yemen, shielded in neutral language and lacking responsibility attribution—serving to devalue the suffering of victims and condemning the crisis to be functionally forgotten.

Image Mapping Accuracy Evaluation Using UAV with Standalone, Differential (RTK), and PPP GNSS Positioning Techniques in an Abandoned Mine Site.

Global navigation satellite systems (GNSSs) provide a common positioning method that utilizes satellite signals to determine the spatial location of a receiver. However, there are several error factors in standalone GNSS positioning due to instrumental, procedural, and environmental factors that arise during the signal transmission process, and the final positioning error can be up to several meters or greater in length. Thus, real-time kinematic (RTK) correction and post-mission precise point positioning (PPP) processing technologies are proposed to improve accuracy and accomplish precise position measurements. To evaluate the geolocation accuracy of mosaicked UAV images of an abandoned mine site, we compared each orthomosaic image and digital elevation model obtained using standalone GNSS positioning, differential (RTK) GNSS positioning, and post-mission PPP processing techniques. In the three types of error evaluation measure (i.e., relative camera location error, ground control points-based absolute image mapping error, and volumetric difference of mine tailings), we found that the RTK GNSS positioning method obtained the best performance in terms of the relative camera location error and the absolute image mapping error evaluations, and the PPP post-processing correction effectively reduced the error (69.5% of the average total relative camera location error and 59.3% of the average total absolute image mapping error) relative to the standalone GNSS positioning method. Although differential (RTK) GNSS positioning is widely used in positioning applications that require very high accuracy, post-mission PPP processing can also be used in various fields in which it is either not feasible to operate expensive equipment to receive RTK GNSS signals or network RTK services are unavailable.

Static-PPP Performance using Multi-GNSS (Single, Dual and Triple) Frequency Observations

Precise Point Positioning (PPP) is relatively modern GNSS positioning technique that proved its efficiency comparing with traditional Differential positioning technique for more than three decades. PPP requires only one receiver collecting observations at unknown station, while Differential technique requires two receivers collecting observations simultaneously one at known-position station and the other at unknown station. Extensive mitigation of different GNSS errors is essential for PPP-collected observations. Static-PPP accuracy depends on different factors such as; used GNSS system; single (GPS(G) or GLONASS(R) or BeiDou(C) or Galileo(E)) or mixed-GNSS systems (GPS/GLONASS or GPS/GLONASS/BeiDou or GPS/GLONASS/BeiDou/Galileo), observations type (single or dual or triple frequency), satellites geometry and observations duration. This research investigates static-PPP accuracy variation on three different-latitude IGS stations based on different factors; used GNSS system (single or mixed), observations type (single or dual or triple frequency) and satellites geometry. It can be concluded that GRCE combination provides 3D-accuracy of (8 cm) using single frequency observations, (1.5 mm) using dual frequency observations and (1 mm) using triple frequency observations. GRCE combination provides a convergence time of only four minutes (8 epochs) for dual frequency observations.

The use of exercise relative motion orthoses to improve proximal interphalangeal joint motion: A survey of Australian hand therapy practice

Study DesignCross-sectional online survey. IntroductionExercise relative motion (RM) orthoses are prescribed by hand therapists to improve finger motion but there is limited scientific evidence to guide practice. Purpose of the StudyTo describe Australian hand therapists’ use of exercise RM orthoses to improve PIPJ motion, including trends in orthosis design, prescription, clinical conditions, and their opinions on orthosis benefits and limitations. Methods870 Australian Hand Therapy Association members were sent an electronic survey that included multiple choice, Likert scale and open-ended questions under four subgroups: demographics, design trends, prescription, and therapist opinions. Data analysis consisted of predominantly descriptive statistics and verbatim transcription. Results108 Australian therapists completed the survey, over a third with ≥ 20 years of clinical experience. Exercise RM orthoses were prescribed weekly to monthly (82%) for between 2-6 weeks duration (81%) and used during exercise and function (87%). The most common differential MCPJ position was 11-30° extension (98%) or flexion (92%). Four-finger designs were most common for border digits (OR ≥3.4). Exercise RM orthoses were more commonly used for active and extension deficits compared to passive (OR ≥3.7) and flexion deficits (OR ≥1.4), respectively. Clinicians agreed that the orthosis allowed functional hand use (94%), increased non-intentional exercise (98%), and was challenging to use with fluctuating oedema (60%). DiscussionThis survey highlights notable clinical trends despite only reaching a small sample of Australian hand therapists. Exercise RM orthoses were frequently being used for active PIPJ extension and flexion deficits. A common MCPJ differential angle was reported, while the number of fingers incorporated into the design depended on the digit involved. Therapists’ preferences mostly agreed with the limited available evidence. Conclusion(s)This limited survey identified common exercise RM orthosis fabrication and prescription trends amongst Australian therapists. These insights may inform future biomechanical and clinical research on this underexplored topic.

Three-Dimensional Free Vibration Analysis of Hyperelastic Structures Under Bending Load Using the VDQ-Transformed Method

Using the ideas of variational differential quadrature (VDQ) technique and position transformation, an efficient numerical approach is developed herein in order to address the free vibration problem of compressible and nearly-incompressible solid bodies with arbitrary deformed shape within the framework of 3D hyperelasticity. The 3D hyperelasticity is first formulated by vector-matrix relations with the purpose of applying in coding process. An energy principle together with the Neo-Hookean strain energy function is also employed in the derivation of governing equations. The proposed numerical method is capable of addressing problems with irregular domains. Simple application, being free from the locking problem, and fast convergence rate are the key features of the approach. Hyperelastic rectangular/ sector plates and cylindrical panel subjected to bending load are selected as test problems whose free vibrations are analyzed. The developed numerical method is found to be capable of yielding accurate solutions to the considered problems. Moreover, the effects of mode transition and geometrical properties are investigated in the numerical examples.

Multivalent interactions between RNA and RNA binding proteins drive differential intra-speckle positioning of RNA transcripts.

Nuclear speckles represent a type of membraneless organelles in higher eukaryotic cells which are rich in snRNP components, certain splicing factors, including SR proteins (a family of RNA binding proteins (RBPs) named for containing regions with repetitive serine and arginine residues), polyA+ RNAs, and certain long noncoding RNAs (lncRNA). Multivalent interactions between RNAs and residing protein components drive the formation, as well as layered organization of components in nuclear speckles. Furthermore, RBPs have differential localization with respect to nuclear speckles; while SRSF1 proteins is enriched in nuclear speckles, heterogeneous nuclear ribonucleoprotein A1 (hnRNPA1) is either uniformly distributed in the nucleoplasm or slightly depleted from nuclear speckles. Using super-resolution imaging we show that the pre-mRNA transcripts containing SRSF1 motifs in the exon and hnRNPA1 motifs in the intron, are orientated in a way such that the regions containing the SRSF1 binding motifs are positioned relatively towards the interior of nuclear speckles and hnRNPA1 binding motifs are placed relatively towards the periphery of speckles. Knocking down of SRSF1 protein leads to the migration of RNA transcripts further towards the periphery of nuclear speckles, whereas knocking down of hnRNPA1 protein leads to the inward migration of RNA transcripts with respect to the speckle center. A similar effect of protein knockdown is seen on the endogenous nuclear speckle associated lncRNA, MALAT1. Our results collectively demonstrate that RNAs can adopt non-random orientation and positioning within the membraneless organelles. These observations might help explain the need for nuclear RNAs for structural integrity of nuclear speckles and the context dependent effect of SR and hnRNP proteins on splicing outcomes.

Analysis of Baseline Impact on Differential Doppler Positioning and Performance Improvement Method for LEO Opportunistic Navigation

The positioning system based on the signals of opportunity (SOPs) of low-Earth-orbit (LEO) satellites can meet the positioning requirements of the receiver in the global navigation satellite system (GNSS) denial environment. However, the received signal does not contain or cannot extract the orbit information and signal emission time of the radiation source, which has become the main error source in this positioning system. Taking the Iridium satellites as an example, a Doppler differential (DD)-LEO (DD-LEO) positioning framework is proposed in this article, and the baseline impact analysis of the differential Doppler positioning system (DDPS) and a performance improvement method are carried out. First, the workflow between a base and a rover is introduced, and the error elimination of the DDPS is analyzed. Second, the equivalent Doppler error models formed by the orbit error at the base and the rover are established, respectively, and the relationship between the baseline and the mean or variance of equivalent Doppler residual in the DDPS is derived. Then, aiming at the problem of poor positioning accuracy due to the inconsistency of space–time reference in the long-baseline DDPS, a signal emission time estimation (SETE) algorithm based on maximum likelihood estimation (MLE) is proposed to further improve the positioning accuracy. Finally, a simulation experiment of the influence of baseline length and direction on the DDPS is implemented, and several groups of field differential experiments with different baseline lengths are completed. The experimental results of long-baseline positioning show that the DDPS can reduce the 3-D positioning error by 48.0% compared with the single station without differential positioning. At the same time, the positioning accuracy of the rover station is further enhanced by 86.3% when the base station adopts the SETE algorithm, which verifies the effectiveness of the proposed algorithm.

Improving the Position Accuracy of Rover Receiver using Differential Positioning in Indian Regional Navigation Satellite System

Navigation with Indian Constellation (NavIC) is the Indian Regional Navigation Satellite System (IRNSS) developed by Indian Space Research Organization (ISRO) to provide the position and navigation services for Indian region. NavIC or IRNSS is individual satellite constellation which has seven satellites covering the Indian subcontinent. Accuracy of NavIC standalone is insufficient in certain applications such as civil aviation. To improve the position accuracy performance of NavIC system, differential positioning technique is utilized. In this paper, differential positioning is carried out, considering two IGS (IRNSS-GPS-SBAS) receivers (one as reference station and the other as rover), which are capable of receiving IRNSS signals from 7 satellites, GPS signals from 12 satellites, SBAS signals from 2 satellites. Here, NavIC constellation alone is considered for the analysis. The differential positioning is carried out using the pseudorange measurements on L5 (1176.45 MHz), S1 (2492.028 MHz) and dual (L5 and S1 both) and accuracies are compared in terms of the statistical parameters Circular Error Probability (CEP), Distance Root Mean Square (DRMS), 2DRMS (twice the DRMS). The improvement in the horizontal accuracy (2DRMS) of the rover using pseudorange measurements on L5 is observed to be 78.81%, on S1 it is 69.14 % and using dual frequency (L5 and S1 both) it is 80.73% when compared to NavIC standalone.

Long-Baseline Differential Doppler Positioning Using Space-Based SOP Based on BPVGMM

Positioning based on Low Earth Orbit (LEO) satellites Signals of OPportunity (SOPs) is an effective complement and backup positioning solution of Global Navigation Satellite System (GNSS). The major sources of error that have to be considered in the positioning technology based on LEO satellites SOP are ephemeris and satellite clock errors with space-time relevance. Although the differential positioning can effectively reduce the error, positioning error is still large due to the low orbit of the satellites in the long-baseline scenario. To address the aforementioned challenge, a differential Doppler positioning algorithm based on Baseline Projection Vector Geometric Model Modification (BPVGMM) is proposed. Simulation results show that BPVGMM algorithm has significantly better accuracy in long-baseline positioning case than the traditional algorithm, and the validity of the algorithm is verified by differential positioning experiments using signals from Iridium NEXT satellites.

Creation of a Mobile Application for Navigation for a Potential Use of People with Visual Impairment Exercising the NTRIP Protocol

The global navigation satellite systems (GNSS) have become important in conjunction with the advancement of technology, in order to improve the accuracy of positioning and navigation on mobile devices. In the current project, a mobile application for navigation using the network transport of restricted test case modeling (RTCM) via internet protocol (NTRIP) was developed, and it has been focused on the autonomous mobility of people with visual disabilities. This occurred through a web viewer that stores the base cartography in a genome database (GDB). Such information is integrated into the application interface with Java Script language within the Android Studio platform, with a personalized design. This incorporates a screen reader for selection, navigation and direction of destinations, in addition to an early warning system for obstacles. Additionally, a differential position correction was implemented using the BKG Ntrip Client (BNC) software, for the adjustment of coordinates with the precise point positioning (PPP) method through streams in the format of RTCM with casters EPEC3, IGS03 and BCEP00BKG0. The evaluation of the application was performed using the National Standard for Spatial Data Accuracy (NSSDA), establishing 30 control points. These were obtained through the fast static method, in order to compare the horizontal accuracy of the observations in static and navigation modes between high-end and mid-range mobile devices.

Design and Validation of a Variable Reluctance Differential Solenoid Transducer With an Ironless Stator

This article presents the design methodology, simulation results, and experimental results of a novel variable reluctance differential solenoid transducer (VRDST). The new ironless-stator VRDST (ISVRDST) is designed to mitigate the practical challenges inherent in the VRDST while maintaining its beneficial features compared to other linear inductive differential position sensors. The ISVRDST uses an air stator to reduce cost and increase compactness. FEA and Simulink simulations are used to predict the performance of the ISVRDST and a proof-of-concept prototype is designed to experimentally validate the simulation results. Like the VRDST, the ISVRDST is designed to utilize a complementary filter to fuse a low-speed position measurement with a high-speed velocity measurement, resulting in a single wide-bandwidth position measurement. The experimental results of the prototype ISVRDST prove that it is capable of robustly performing and fusing the two measurements utilized by the VRDST. In addition, the analytically predicted error of the fused measurement is found to be less than 1% different than the actual error relative to a high-precision laser vibrometer. When compared to the VRDST, the ISVRDST prototype is found to have a stroke-to-length ratio that is nearly four times greater and a cost that is over 100 times lower.

TMIC-17. DISCOVERING DOMINANT TUMOR CHARACTERISTICS IN CYSTIC GLIOBLASTOMA

Abstract BACKGROUND As a rare subtype of glioblastoma (GBM), the genetic features and outcomes in cystic GBM (cGBM) are largely unknown. This study aimed to evaluate the survival of cystic features, investigate genomic patterns and the immune microenvironment in patients with cGBM. METHODS Gd T1-weighted, T2-weighted, T2-Flair, DWI or ADC images were used to classify cGBM or noncystic GBM (non-cGBM). Clinical information from IvyGAP, EGA databases and Chinese cohort were used for survival analysis. Fresh cystic fluid and residual tumor tissue were collected to evaluate immunological components, pathological and genomic differences between cGBM and non-cGBM. Data from IvyGAP were included to determine difference of molecular feature among substructure. RESULTS 143 cases with cGBM and non-cGBM were screened to compare survival outcomes. Cystic features were to confer a survival benefit. It was an independent prognostic factor irrespective of IDH, MGMT and therapeutic regimen. cGBM patients have a hypomethylation state compared to non-cGBM. Active immune cells such as CD4+, CD8+ T cells were present in the cystic fluid and infiltrated into tumor. 10 cytokines/chemokines were only detected in cystic fluid, 8 cytokines/chemokines increased two-fold in cystic fluid than in peripheral blood serum (PBPs). Much differential methylated position (DMPs), differentially expressed genes (DEGs), Gene Set Enrichment Analysis (GSAE), Functional Epigenetic Modules (FEM) networks and molecular feature of substructural regions were different between cGBM and non-cGBM. CONCLUSION These results imply that cGBM could be a new subtype and has distinctive immune microenvironment which may have potential value correlating with prognosis.

With complements: C3 inhibition in the clinic.

C3 is a key complement protein, located at the nexus of all complement activation pathways. Extracellular, tissue, cell-derived, and intracellular C3 plays critical roles in the immune response that is dysregulated in many diseases, making it an attractive therapeutic target. However, challenges such as very high concentration in blood, increased acute expression, and the elevated risk of infections have historically posed significant challenges in the development of C3-targeted therapeutics. This is further complicated because C3 activation fragments and their receptors trigger a complex network of downstream effects; therefore, a clear understanding of these is needed to provide context for a better understanding of the mechanism of action (MoA) of C3 inhibitors, such as pegcetacoplan. Because of C3's differential upstream position to C5 in the complement cascade, there are mechanistic differences between pegcetacoplan and eculizumab that determine their efficacy in patients with paroxysmal nocturnal hemoglobinuria. In this review, we compare the MoA of pegcetacoplan and eculizumab in paroxysmal nocturnal hemoglobinuria and discuss the complement-mediated disease that might be amenable to C3 inhibition. We further discuss the current state and outlook for C3-targeted therapeutics and provide our perspective on which diseases might be the next success stories in the C3 therapeutics journey.

Multi-GNSS positioning for landslide monitoring: a case study at the Recica landslide

Global Navigation Satellite System (GNSS) positioning has characteristics of simple operation, high efficiency and high precision technique for landslide surface monitoring. In recent years, finalization of modern GNSS systems Galileo and BeiDou has brought a possibility of multi-GNSS positioning. The paper focuses on evaluation of possible benefits of multi-GNSS constellations in landslide monitoring. While simulating observational conditions of selected Recica landslide in the Czech Republic, one-month data from well-established permanent GNSS reference stations were processed. Besides various constellation combinations, differential and Precise Point Positioning techniques, observation data lengths and observation sampling intervals were evaluated. Based on the results, using a combination of GPS and GLONASS, or GPS, GLONASS and Galileo systems can be recommended, together with a static differential technique and observation periods for data collection exceeding eight hours. In the last step, data from GNSS repetitive campaigns realized at the Recica landslide during two years were processed with optimal setup and obtained displacement results were compared to standard geotechnical measurements.

A case-control study on the relationship between DNA methylation and occupational noise hearing loss

Objective: To explore the relationship between DNA methylation and occupational noise-induced hearing loss. Methods: A case-control study was conducted. People with hearing loss induced by occupational noise were recruited as the case group and those with normal hearing but still exposed to occupational noise were recruited as the control group. A total of 60 participants were included, of which 30 participants were in the case group and 30 in the control group. The methylation level was detected by 850k genome-wide DNA methylation chip technology. The significance of differential methylated position (DMP) was tested by R-packet 'Champ'. The differential methylated region (DMR) was analyzed by using Champ's Bumphunter algorithm. Cluster profiler was used to analyze the gene list for GO and KEGG pathway enrichment. Results: There was significant difference between two groups in binaural high-frequency average hearing threshold (P<0.05), but there was no significant difference in age, smoking, drinking, hypertension, physical exercise and cumulative noise exposure. The results of DMP and DMR analysis showed that 713875 sites were detected in the case group and the control group, and 439 methylation sites with significant difference, accounting for 0.06%; 650 regions were detected, and 72 methylation regions with significant differences, accounting for 11.08%. Compared with the control group, the results of GO enrichment analysis showed that the case group had statistically significant differences in four pathways: axogenesis of projection neurons in the central nervous system, neuronal development in the central nervous system, axogenesis of neurons in the central nervous system and neuronal differentiation in the central nervous system. KEGG enrichment analysis showed that there were significant differences in sphingolipid metabolism, aldosterone synthesis and secretion, primary bile acid biosynthesis pathway between the case group and the control group. Conclusion: The occurrence of occupational noise-induced hearing loss may be related to the regulation of gene expression related to axogenesis of projection neurons in the central nervous system, development of neurons in the central nervous system, axogenesis of neurons in the central nervous system, differentiation of neurons in the central nervous system, sphingolipid metabolism, aldosterone synthesis and secretion, primary bile acid biosynthesis and gene methylation related to metabolism.

Structural Determinants of the Specific Activities of an L-Amino Acid Oxidase from Pseudoalteromonas luteoviolacea CPMOR-1 with Broad Substrate Specificity.

The Pseudoalteromonas luteoviolacea strain CPMOR-1 expresses a flavin adenine dinucleotide (FAD)-dependent L-amino acid oxidase (LAAO) with broad substrate specificity. Steady-state kinetic analysis of its reactivity towards the 20 proteinogenic amino acids showed some activity to all except proline. The relative specific activity for amino acid substrates was not correlated only with Km or kcat values, since the two parameters often varied independently of each other. Variation in Km was attributed to the differential binding affinity. Variation in kcat was attributed to differential positioning of the bound substrate relative to FAD that decreased the reaction rate. A structural model of this LAAO was compared with structures of other FAD-dependent LAAOs that have different substrate specificities: an LAAO from snake venom that prefers aromatic amino acid substrates and a fungal LAAO that is specific for lysine. While the amino acid sequences of these LAAOs are not very similar, their overall structures are comparable. The differential activity towards specific amino acids was correlated with specific residues in the active sites of these LAAOs. Residues in the active site that interact with the amino and carboxyl groups attached to the α-carbon of the substrate amino acid are conserved in all of the LAAOs. Residues that interact with the side chains of the amino acid substrates show variation. This provides insight into the structural determinants of the LAAOs that dictate their different substrate preferences. These results are of interest for harnessing these enzymes for possible applications in biotechnology, such as deracemization.

Leader-Based Trajectory Following in Unstructured Environments—From Concept to Real-World Implementation

In this paper, the problem of vehicle guidance by means of an external leader is described. The objective is to navigate a four-wheeled vehicle through unstructured environments, characterized by the lack of availability of typical guidance infrastructure like lane markings or HD maps. The trajectory-following approach is based on an estimate of the leader’s path. For that, position measurements are stored over time with respect to an inertial frame. A new strategy is proposed to rate the significance of position measurements and ensure that a certain threshold of stored samples is not exceeded. Having an estimate of the leader path is essential to prevent the cutting-corner phenomenon and for exact path following in general. A spline-approximation technique is applied to obtain a smooth reference path for the underlying lateral and longitudinal motion controllers. For longitudinal tracking, a constant time-headway policy was implemented, to follow the leader with a constant time gap along the estimated path. The algorithm was first developed and tested in a simulation framework and then deployed in a demonstrator vehicle for validation under real operating conditions. The presented experimental results were achieved using only on-board sensors of the demonstrator vehicle, while high-accuracy differential GPS-based position measurements serve as the ground truth data for visualization.

RTK positioning based on the phase-only differential corrections

Multi-GNSS multi-frequency observations improve the accuracy, availability and reliability of the single-site RTK positioning but also simultaneously raise the communication bandwidth needed for the transmission of differential corrections. A RTK positioning algorithm is proposed that transmit the phase-only differential corrections to achieve the ambiguity-fixed RTK positioning, significantly reducing the communication bandwidth requirements. The essence of the presented method is that the code differential positioning solution implied in the conventional RTK positioning procedure can be replaced by the single point positioning solution of the rover receiver to realize RTK positioning. For typical application scenarios, the transmitted bits in a single epoch can be reduced by more than 25% when the corrections are sent with the RTCM protocol. The experiments by the GPS dual-frequency data over the 10 km and 180 km baselines shown that the performance of the presented RTK algorithm are comparable to that of the conventional RTK positioning, which verifies its feasibility and effectiveness.