33 research outputs found
Ground Monitors to Support Navigation Operations of ARAIM and GBAS
No full textReceiver Autonomous Integrity Monitoring (RAIM) currently provides safehorizontal navigation guidance to en route civil aircraft using the GPS L1 frequency.
As an evolution of RAIM, Advanced RAIM (ARAIM) is being developed to provide
vertical guidance in addition to horizontal using multiple constellations and dual frequency
thus facilitating precision approach without ground support for civil aircraft.
However, navigation guidance during zero-visibility (Category III) precision landing
requires an additional support in real time from a Ground Based Augmentation
System (GBAS). To improve the aircraft navigation solution, GBAS broadcasts a
differential correction and monitors any failure on transmitted satellite signals. This
dissertation contributes to ARAIM and GBAS to improve existing navigation operations
in order to enable precision approach and landing.The achievable performance of ARAIM is highly dependent on the assumptionson a constellation’s nominal Signal-In-Space (SIS) error models and a priori
fault probability. In the framework of ARAIM, an Integrity Support Message (ISM)
is envisioned to carry the required SIS error-model parameters and fault statistics
for users. The ISM is generated and validated through offline monitoring, and disseminated
along the navigation message. The first dissertation contribution is to
provide necessary satellite positions and clock biases as a truth product to evaluate
nominal SIS range errors (SISREs). An estimator is developed to generate accurate
ephemeris parameters to provide these truth products. The estimator’s performance
is demonstrated for the Global Positioning System (GPS) constellation by utilizing
the International GNSS Service (IGS) ground network to collect dual-frequency raw
GPS code and carrier phase measurements. The resulting SISREs from the estimator
are predicted to have a standard deviation of 0.5 m. When estimated ephemeris
parameters and clock biases are compared with precise IGS orbit and clock products, the resulting SISREs are within ±2! at all times. In the second contribution,
a new approach is proposed to generate the ISM by modeling the ephemeris parameter
errors directly. In preliminary analysis, an ephemeris parameter error model is
developed for the broadcast GPS legacy navigation message (LNAV) under nominal
conditions. Then, the proposed approach is demonstrated to provide the nominal
bias and standard deviation on GPS SISREs.As a part of fault monitoring in the GBAS, a ground monitor is developedto detect ephemeris failures, incorrect broadcast satellite positions, and hazardous
ionosphere storms using either single- or dual frequency. The monitor also addresses
the challenge of fault-free differential correction when satellites are rising, newly acquired,
and re-acquired. The monitor utilizes differential code and carrier phase
measurements across multiple reference receiver antennas as the basis for detection.
Finally, the analytical performance of the monitor is demonstrated to meet Category
III precision approach and landing requirements
Ground Monitors to Support Navigation Operations of ARAIM and GBAS
No full textReceiver Autonomous Integrity Monitoring (RAIM) currently provides safehorizontal navigation guidance to en route civil aircraft using the GPS L1 frequency.
As an evolution of RAIM, Advanced RAIM (ARAIM) is being developed to provide
vertical guidance in addition to horizontal using multiple constellations and dual frequency
thus facilitating precision approach without ground support for civil aircraft.
However, navigation guidance during zero-visibility (Category III) precision landing
requires an additional support in real time from a Ground Based Augmentation
System (GBAS). To improve the aircraft navigation solution, GBAS broadcasts a
differential correction and monitors any failure on transmitted satellite signals. This
dissertation contributes to ARAIM and GBAS to improve existing navigation operations
in order to enable precision approach and landing.The achievable performance of ARAIM is highly dependent on the assumptionson a constellation’s nominal Signal-In-Space (SIS) error models and a priori
fault probability. In the framework of ARAIM, an Integrity Support Message (ISM)
is envisioned to carry the required SIS error-model parameters and fault statistics
for users. The ISM is generated and validated through offline monitoring, and disseminated
along the navigation message. The first dissertation contribution is to
provide necessary satellite positions and clock biases as a truth product to evaluate
nominal SIS range errors (SISREs). An estimator is developed to generate accurate
ephemeris parameters to provide these truth products. The estimator’s performance
is demonstrated for the Global Positioning System (GPS) constellation by utilizing
the International GNSS Service (IGS) ground network to collect dual-frequency raw
GPS code and carrier phase measurements. The resulting SISREs from the estimator
are predicted to have a standard deviation of 0.5 m. When estimated ephemeris
parameters and clock biases are compared with precise IGS orbit and clock products, the resulting SISREs are within ±2! at all times. In the second contribution,
a new approach is proposed to generate the ISM by modeling the ephemeris parameter
errors directly. In preliminary analysis, an ephemeris parameter error model is
developed for the broadcast GPS legacy navigation message (LNAV) under nominal
conditions. Then, the proposed approach is demonstrated to provide the nominal
bias and standard deviation on GPS SISREs.As a part of fault monitoring in the GBAS, a ground monitor is developedto detect ephemeris failures, incorrect broadcast satellite positions, and hazardous
ionosphere storms using either single- or dual frequency. The monitor also addresses
the challenge of fault-free differential correction when satellites are rising, newly acquired,
and re-acquired. The monitor utilizes differential code and carrier phase
measurements across multiple reference receiver antennas as the basis for detection.
Finally, the analytical performance of the monitor is demonstrated to meet Category
III precision approach and landing requirements
Prone Position Lateral Interbody Fusion-A Narrative Review
No full textBACKGROUND AND OBJECTIVE: Lateral access lumbar interbody fusion is an increasingly popular procedure that allows for anterior column support through discectomy, endplate preparation, and interbody insertion. This procedure was initially described and performed with the patient in the lateral decubitus position. This would typically be followed by repositioning the patient to the prone position for pedicle screw fixation. Increasingly common is the lateral access lumbar interbody fusion in the prone position. This narrative review seeks to summarize the available literature on advantages, disadvantages, and unique features of the prone position lateral access lumbar interbody fusion. METHODS: We performed a narrative review of articles published up to 01 November 2022 through a PubMed search. The search terms prone lateral spine surgery and lateral approach spine surgery AND prone position were used. Articles not available in English were excluded. The search result abstracts were independently reviewed by 2 authors and 28 full text articles were reviewed. Both reviewing authors were orthopedic surgery chief residents. KEY CONTENT AND FINDINGS: There are several unique advantages as well as disadvantages to the prone position lateral interbody fusion. Some advantages include ease of placing pedicle screws, simultaneous posterior and lateral access, greater ease in achieving segmental lumbar lordosis, and a relatively safer positioning of the psoas muscle, lumbar plexus, and abdominal structures. Disadvantages include more difficulties with exposure and retraction, as well as visualization, positioning and ergonomics of surgery. CONCLUSIONS: Prone position lateral interbody fusion is an increasingly prevalent and useful surgical technique with several advantages and disadvantages when compared to lateral interbody fusion in the lateral decubitus position. There are several surgical indications and goals for which prone lateral interbody fusion may provide significant benefit when compared to other interbody fusion techniques
Streamlining Postoperative Care After Pediatric Supracondylar Humerus Fractures: Is Follow-up After Pin Removal Routinely Needed?
No full textA survey on IoT based road traffic surveillance and accident detection system (A smart way to handle traffic and concerned problems)
No full text
Clustering Using a Combination of Particle Swarm Optimization and K-means
No full textAbstractClustering is an unsupervised kind of grouping of data points based on the similarity that exists between them. This paper applied a combination of particle swarm optimization and K-means for data clustering. The proposed approach tries to improve the performance of traditional partition clustering techniques such as K-means by avoiding the initial requirement of number of clusters or centroids for clustering. The proposed approach is evaluated using various primary and real-world datasets. Moreover, this paper also presents a comparison of results produced by the proposed approach and by the K-means based on clustering validity measures such as inter- and intra-cluster distances, quantization error, silhouette index, and Dunn index. The comparison of results shows that as the size of the dataset increases, the proposed approach produces significant improvement over the K-means partition clustering technique.</jats:p
