Adjacent Satellite Research Articles

Research on Design and Staged Deployment of LEO Navigation Constellation for MEO Navigation Satellite Failure

Low Earth orbit (LEO) satellites have unique advantages in navigation because of their high signal intensity and rapid geometric changes in a short period. In order to solve the problem of constellation performance degradation after a potential failure pertaining one or more medium Earth orbit (MEO) navigation satellites, this paper designs the LEO navigation constellation and considers the task requirements of different stages of constellation deployment. Firstly, the LEO navigation constellation is designed by a non-dominated sorting genetic algorithm II (NSGA-II). The average position dilution of precision (PDOP) is 1.676, which is an improvement compared to the average PDOP offered by the four traditional GNSS. Secondly, the staged deployment of constellation takes into account the degradation of constellation performance caused by the failure of MEO navigation satellites, and the Monte Carlo method is used to analyze the case of three simultaneous satellite failures. The results show that a single satellite failure within each orbital plane and adjacent satellites with close phase separation has a great impact on the performance of the MEO navigation constellation. On this basis, a staged deployment strategy was adopted in order to balance cost, risk, and performance. The three phases deploy 66, 156, and 288 satellites, respectively; as a make-up constellation under contingencies, a navigation enhancement constellation, and an independent navigation constellation, the deployment of the staged sub-constellations meets the mission requirements. The constellation design and staged deployment method proposed in this paper can provide reference for the future study of LEO navigation constellations.

Autonomous semi-major axis adjustment for mega constellation continuous coverage

Mega constellations have larger number of satellites and higher distribution density compared with traditional constellations, that lead to huge tracking, telemetry and command (TT&C) requirement, heavy computation load for configuration design, and frequent configuration control due to low-Earth perturbations, collision avoidance emergencies, etc. This paper proposes a novel constellation control scheme for mega constellations with the same semi-major axis, that is based on the inter-satellite boundary constraints. Satellites do not follow the designed configuration, but keep bounded and stable flight with respect to adjacent satellites. The continuous coverage requirement is considered for priority. The inter-satellite continuous coverage constraint is formulated as right ascension of ascending node constraint and relative distance boundary constraint between every two adjacent coplanar satellites. To reduce control consumption, the boundary constraint is kept by adjusting the semi-major axes of coplanar satellites. To that end, the relationship between relative distance boundary and semi-major axis difference is studied. The semi-major axis adjustment strategy for a single satellite is proposed, and the control rules for coplanar satellites are determined. The proposed control method is verified in GW-2 sub-constellation, and is compared with relative station-keeping control method. Results indicate its effectiveness and good performance in control frequency and consumption.

Strong configuration-interaction contributions to the angle-resolved 4p photoelectron spectra of atomic xenon

High-resolution photoelectron spectra of xenon (Xe) were measured in the $4p$ photoionization region. The anisotropy parameters \ensuremath{\beta} were obtained for several photoelectron peaks with angle-resolved photoelectron measurements. The various complicated spectral features were observed due to the perturbed $4{p}^{\ensuremath{-}1}$ spin-orbit doublet and adjacent satellite structures. An analysis based on a relativistic multiconfiguration calculation has been carried out. The key role of the strong interactions between the $4{p}^{\ensuremath{-}1}$ core hole and the $4{d}^{\ensuremath{-}2}nl$ configurations has been investigated in detail. Experimental peak energies and intensities are in good agreement with theory. We find that the many of the complicated features are $4{d}^{\ensuremath{-}2}nl$ satellite lines, and their intensities are determined mostly by the amount of $4{p}^{\ensuremath{-}1}$ configurations that are mixed in. The experimental \ensuremath{\beta} values agree quite well with theory, indicating that the photoelectron angular distributions are also strongly influenced by the $4p$ direct-ionization contributions.

Automatic Dynamic Estimation of On-Orbit Satellites Through Spaceborne ISAR Imaging

With the continuous development of satellite constellations worldwide, dynamic estimation of on-orbit spacecraft plays a more and more important role in space situation awareness applications. Based on high-resolution inverse synthetic aperture radar (ISAR) imaging from the ground, some exploratory methods have been proposed to estimate target dynamic parameters, such as its attitude pointing and spin period. Due to the limited observation view from the ground, most of them rely on the long-term measurement, and the robust association of image features needs to be ensured. In this article, a novel approach based on spaceborne ISAR images is proposed to achieve the dynamic estimation of spin satellites. In order to build a synchronous similar-resolution ISAR imaging system, two adjacent satellites are picked up from low earth orbit constellations according to the radar tracking parameters. With obtained a pair of ISAR images, the explicit expression between target dynamic parameters and projection feature is deduced. Inspired by the existing works on shape extraction of the human body, a feature extraction network is built on the framework of ResNet for achieving the automatic processing in spaceborne equipments. In this way, target dynamic parameters can be solved in instantaneous attitude optimization and spin motion optimization in steps. Simulation experiments of a typical spin spacecraft, Tiangong-I, illustrate the feasibility of the proposed method. Besides, a comparison experiment with an existing ground-based work is also made to analyze its advantage in practical applications.

Exploring Convolutional Neural Networks for Predicting Sentinel-C Backscatter Between Image Acquisitions

Sentinel-1 C-band radar backscatter satellite images provide a repeating sequence of fine-resolution (10-m) observations that can be used for a number of applications, but the 12-day interval between satellite observations is too infrequent for many applications, such as measuring moisture dynamics. For a variety of applications, moisture information is demanded at high temporal frequency and fine spatial resolution over large areas. Machine learning approaches have been used to predict higher spatial resolutions than the original satellite images, but little effort has been made to increase the temporal resolution of acquired backscatter images. This study extends machine learning approaches to infer fine-resolution backscatter between observations relying on auxiliary data observations, including elevation and daily gridded weather. Several variations of Multi-modal Fully Convolutional Neural Network architectures, problem setup, and training methods are explored for a predominantly rural area in southwest Oklahoma near the transition between humid subtropical and semiarid climates. The training area lies in the overlap zone for adjacent Sentinel-1 satellite tracks, allowing for training with several different temporal offsets. We find that the UNET architecture produced the most accurate and robust estimated backscatter patterns, with superior prediction compared to a prior observation baseline in nearly all cases investigated when geography was included in the training data. This superior performance also generalized to nearby areas when training data for a given geography was not available, where 86% of predictions performed superior compared to a prior observation baseline.

Self-Organizing Control of Mega Constellations for Continuous Earth Observation

This work presents a novel self-organizing control method for mega constellations to meet the continuous Earth observation requirements. In order to decrease the TT&C pressure caused by numerous satellites, constellation satellites are not controlled according to the designed configurations but are controlled with respect to intersatellite constraints. By analyzing the street-of-coverage (SOC) of coplanar constellation satellites, the continuous coverage constraint of the mega constellation is transformed into constraints of the right ascension of ascending node (RAAN) and relative motion bound between every two adjacent coplanar satellites. The proposed continuous coverage constraint can be satisfied by most ongoing or planned mega constellations. Artificial potential functions (APFs) are used to realize self-organizing control. The scale-independent relative orbital elements (SIROEs) are innovatively presented as the self-organizing control variables. Using the Gaussian equations and Lyapunov’s theory, the stability of the APF control in quadratic form is proven, from which it can be concluded that the APF control variables of the controlled satellite should have the same time derivative as the target satellite states under two-body Keplerian motion condition, and SIROEs are ideal choices. The proposed controllers and self-organizing rules are verified in the sub-constellation of the GW-2 mega constellation by simulation. The results demonstrate the goodness in control effect and ground coverage performance.

FP.14 Dystrophin and satellite cell quantification in Duchenne and Becker muscular dystrophies

The dystrophinopathies are a group of muscular dystrophies stemming from mutations in the <i>DMD</i> gene. We have developed a series of sensitive and reproducible dystrophin and satellite cell quantification methods in order to better define associations between dystrophin expression and disease severity, as well as the molecular mechanisms of mutations in the N-terminal region of dystrophin. In a pilot study of 18 dystrophinopathy patient muscle biopsies, we employed western blot, capillary western immunoassay, and automated quantitative immunofluorescence analysis to quantify dystrophin expression and Pax7-positive satellite cells. Among 9 patients with a Duchenne muscular dystrophy phenotype, the mean dystrophin protein level by capillary western was 1.8% of normal. These biopsies displayed a mean of 6.8% immunofluorescence staining intensity of individual fibers and 26% dystrophin positive fibers (PDPF). This high PDPF reflects the use of a sensitive cutoff to improve the discriminating power of the assay at low expression levels. By contrast, patients with intermediate or Becker muscular dystrophy had 11% dystrophin expression by capillary western and 70% PDPF. Several truncating mutations in the first 4 exons of DMD were associated with milder phenotypes and significantly higher dystrophin expression (16% by capillary western and 79% PDPF), in keeping with activation of an internal ribosome entry site in exon 5. There was poor overall correlation between Pax7-positive satellite cell count and dystrophin expression. Analysis of individual muscle fibers however demonstrated that fibers with one or more adjacent Pax7-positive satellite cells had a lower mean dystrophin expression, indicating concentration of satellite cells around dystrophin-deficient fibers. This study lays the groundwork for a comprehensive characterization of genotype, phenotype, and molecular features in a broader cohort of dystrophinopathy patients.

Thermal environment analysis for TianQin: II. Solar irradiance disparity across constellation

Space-borne gravitational wave (GW) detectors aim to detect GWs in low and middle frequency ranges, as a complement to the terrestrial detectors like LIGO and VIRGO. As the detectors are extremely sensitive to temperature fluctuation, great efforts have been taken to perform thermal analyses on the satellite platforms. Our previous work analysed the external thermal environment of an individual satellite for the TianQin mission. This paper raises the issue of thermal disparity across the triangular constellation. Based on optimized orbits of the TianQin, the LISA, the eLISA/NGO, and the ASTROD-GW, we evaluate the solar irradiance differences between adjacent satellites and make comparisons of the results among the missions. We subsequently introduce a universal relation to describe how orbit type and arm lengths may affect the maximum disparity. For the geocentric orbits of TianQin, we further extend the discussion on the science observation windows.

A Disruption Tolerant Distributed Routing Algorithm in LEO Satellite Networks

The low earth orbit (LEO) constellation network has become a promising approach to provide global communication services, due to its advantages in wide global coverage, low transmission delay, and convenient networking. However, the instability of the intersatellite laser terminal and the high relative speed between adjacent satellites cause frequent network topology changing problems for data routing. In this paper, a disruption tolerant distributed routing algorithm (DTDR) is proposed, where the satellites calculate the alternate path for transmission when the network topology changes, which improves the performance of packet loss. Specifically, each satellite maintains the intersatellite link (ISL) information within a specified number of hops. When an ISL state changes within the specified number of hops, the corresponding satellite calculates and switches to the detour path. Furthermore, the traffic is balanced through the detour process. Various simulations were constructed and show that the proposed algorithm outperforms the existing algorithm in terms of packet loss ratio and transmission delay.

A Low-Sidelobe-Level Variable Inclination Continuous Transverse Stub Antenna with a Nonlinear Slow-Wave Structure

The sidelobe level (SLL) is an essential performance factor for satellite communication antennas. A low-SLL design can effectively suppress adjacent satellite interference. A low-SLL design method for a variable inclination continuous transverse stub (VICTS) antenna is proposed in this paper. The VICTS antenna is composed of three rotatable parts: a feeding plate, a radiation plate, and a polarization plate. The radiation plate comprises two groups of stubs with different radiation ratios. Combined with the nonlinear slow-wave structure attached to the feeding plate, the radiation ratio of the unit can be adjusted. The aperture field of the VICTS antenna using this method can be tapered in order to suppress the SLL. To verify the effectiveness of this method, the antenna prototype is fabricated and measured in a microwave anechoic chamber. The simulation and the measurement are in good agreement. The reflection coefficient of the antenna is kept below −15 dB and between 13.75 GHz and 14.5 GHz. When the radiation plate and the feeding plate rotate relative to each other, the pattern beam can be scanned from 5° to 70 ° . In the scanning range, the typical SLL can reach −18 dB.

Plasmonic Core-Shell-Satellites with Abundant Electromagnetic Hotspots for Highly Sensitive and Reproducible SERS Detection.

In this work, we develop a Ag@Al2O3@Ag plasmonic core–shell–satellite (PCSS) to achieve highly sensitive and reproducible surface-enhanced Raman spectroscopy (SERS) detection of probe molecules. To fabricate PCSS nanostructures, we employ a simple hierarchical dewetting process of Ag films coupled with an atomic layer deposition (ALD) method for the Al2O3 shell. Compared to bare Ag nanoparticles, several advantages of fabricating PCSS nanostructures are discovered, including high surface roughness, high density of nanogaps between Ag core and Ag satellites, and nanogaps between adjacent Ag satellites. Finite-difference time-domain (FDTD) simulations of the PCSS nanostructure confirm an enhancement in the electromagnetic field intensity (hotspots) in the nanogap between the Ag core and the satellite generated by the Al2O3 shell, due to the strong core–satellite plasmonic coupling. The as-prepared PCSS-based SERS substrate demonstrates an enhancement factor (EF) of 1.7 × 107 and relative standard deviation (RSD) of ~7%, endowing our SERS platform with highly sensitive and reproducible detection of R6G molecules. We think that this method provides a simple approach for the fabrication of PCSS by a solid-state technique and a basis for developing a highly SERS-active substrate for practical applications.

Imaging of odontogenic keratocysts: a pictorial review.

The aim of the present article was to review and depict the main radiological features of odontogenic keratocysts (OKCs), thus helping the differential diagnoses from other odontogenic cysts and neoplasms. A review of articles published between January 2000 and October 2020 using Medline and the MeSH Term "odontogenic keratocyst" in combination with the following terms "imaging," "radiology," "panoramic radiograph," and "computed tomography," was performed. Radiographically, OKCs are well-defined unilocular or multilocular radiolucencies bounded by corticated margins. Most lesions are unilocular; instead, multilocular OKCs represent about the 30% of cases, mainly involving the posterior mandible. When, particularly in large lesions, OKCs display a multilocular presentation with adjacent satellite cysts (daughter cysts) a "soap-bubble appearance" can be recognized. Panoramic radiograph and CT still play an important role in the diagnosis and treatment planning of OKCs. Unfortunately, it may not be easy to differentiate OKCs from other odontogenic lesions, especially when they are small and unilocular. Histopathological findings are still necessary to obtain a definitive diagnosis.

Transceiver design for high altitude pseudo satellite aided dual satellite systems

This work focuses on a dual satellite system (DSS) where two multiple spot beam geosynchronous satellites transmit simultaneously on the same frequency across all spot beams. The intra-satellite co-channel interference is managed through precoding, while the inter-satellite co-channel interference is managed with successive interference cancellation (SIC) at the user terminals. The SIC eliminates the strongest co-channel interference from an adjacent satellite while treating the remaining interfering signals as noise. The power required at the transmitter to achieve the desired data rate is formulated as a semidefinite programming problem and relaxed rank constraints. The SIC-based receivers are shown to achieve a better data rate than traditional detectors that treat co-channel interference as noise while saving transmit power at the satellites. Though SIC-based DSS achieves better throughput than a single satellite system, the receiver complexity is high. A high-altitude pseudo satellite (HAPS) aided DSS is proposed to address this issue. In the case of HAPS-aided DSS, users within each spot beam are served by a HAPS, and the HAPSs use SIC to detect signals from satellites. The user terminals in HAPS-aided DSS can use simple detectors as HAPS eliminates co-channel interference through precoding. The full-duplex HAPS-aided DSS is shown to outperform SIC-based DSS.

Transmit diversity and performance analysis for aeronautical broadband satellite communication systems

This paper analyzes the downlink transmission performance of an aeronautical broadband satellite communication system operating at millimeter wave (mmWave) band. Specifically, by considering that two adjacent satellites cooperatively communicate with an airplane employing an antenna array, we first propose a simple transmit scheme combining Alamouti space time block coding (STBC) with receive beamforming (BF) to improve the system performance. Then, by considering the phase shift errors in phased array antenna deployed at the airplane, we analyze the equivalent output signal-to-noise ratio (SNR) of the considered communication system. Further, with the help of the moment generating function (MGF) approach, we derive the average symbol error rate (ASER) of the system with the proposed transmit scheme, where the satellite links undergo correlated shadow-Rician (SR) fading. Finally, computer simulations are conducted to confirm the validity of the theoretical analysis and reveal the effect of phase errors on the performance of the aeronautical broadband communication system.

Building the Galilean moons system via pebble accretion and migration: a primordial resonant chain

ABSTRACT The origins of the Galilean satellites – namely Io, Europa, Ganymede, and Callisto – is not fully understood yet. Here we use N-body numerical simulations to study the formation of Galilean satellites in a gaseous circumplanetary disc around Jupiter. Our model includes the effects of pebble accretion, gas-driven migration, and gas tidal damping and drag. Satellitesimals in our simulations first grow via pebble accretion and start to migrate inwards. When they reach the trap at the disc inner edge, scattering events and collisions take place promoting additional growth. Growing satellites eventually reach a multiresonant configuration anchored at the disc inner edge. Our results show that an integrated pebble flux of ≥2 × 10−3 MJ results in the formation of satellites with masses typically larger than those of the Galilean satellites. Our best match to the masses of the Galilean satellites is produced in simulations where the integrated pebble flux is ∼10−3 MJ. These simulations typically produce between three and five satellites. In our best analogues, adjacent satellite pairs are all locked in 2:1 mean motion resonances. However, they have also moderately eccentric orbits (∼0.1), unlike the current real satellites. We propose that the Galilean satellites system is a primordial resonant chain, similar to exoplanet systems as TRAPPIST-1, Kepler-223, and TOI-178. Callisto was probably in resonance with Ganymede in the past but left this configuration – without breaking the Laplacian resonance – via divergent migration due to tidal planet–satellite interactions. These same effects further damped the orbital eccentricities of these satellites down to their current values (∼0.001). Our results support the hypothesis that Io and Europa were born with water-ice rich compositions and lost all/most of their water afterwards. Firmer constraints on the primordial compositions of the Galilean satellites are crucial to distinguish formation models.

Configuration reconstruction elastic mechanics method for repairing a faulted Walker constellation performance

Walker constellation is the most effective constellation for global coverage and is often used for earth observation, navigation and internet communication. A scenario that several faulted satellites in a Walker constellation lead to its performance degradation can be quickly repaired to a certain extent by reconstructing the on-orbit satellite configuration. Different from the classical strategies such as adjusting the phase of the adjacent satellites, uniform the on-satellites' phase and adjusting the plane of the adjacent satellites, this paper proposes a bionic reconstruction method which uses the elastic mechanics method of thin film plate to generate the satellite maneuver strategy in the constellation reconstruction process, minimizes the performance degradation between the repaired configuration and the previous configuration. Thus, the maneuver strategy of each satellite can be calculated in reversely. The simulation example shows that the maneuver strategy by the bionic reconstruction method is more harmonious and natural than the classical strategies.

Enhancing Spectrum Efficiency for Multiple Users in Hybrid Satellite-Terrestrial Networks

In the paper, we present a study on the performance analysis of a non-orthogonal multiple access (NOMA) underlay cognitive hybrid satellite-terrestrial relaying network (CSTRN) and highlight the performance gaps between multiple users. The satellite source communicates with users by enabling cognitive radio scheme to forward signals to secondary destinations on the ground which belong to dedicated groups following the principle of NOMA. In this scenario, the secondary source acts a relay and employs Amplify and Forward (AF) mode to serve distant NOMA users under a given interference constraint. To characterize the transmission environment, the shadowed-Rician fading and Nakagami- $m$ fading models are widely adopted to the relevant hybrid channels. To provide detailed examination of the system performance metrics, we aim to derive closed-form formulas for the outage probability of the secondary destinations in the presence of the primary interference power constraint imposed by the adjacent primary satellite network. Finally, our simulation results showed that a greater number of antennas, better quality of wireless channels and power allocation factors exhibit the main effects on system performance.

S3568 Metastatic Jejunal Carcinoid Masquerading as a Pelvic Mass

INTRODUCTION: Neuroendocrine tumors (NETs), also known as carcinoid tumors, are epithelial neoplasms that arise from enterochromaffin cells and are classified according to their histologic features and confirmed by immunohistochemical staining. NETs most commonly occur in the gastrointestinal tract, pancreas, appendix, rectum and the lungs but they can develop anywhere in the body. Due to their common embryonic origin, neuroendocrine tumors of the jejunum, ileum and appendix are collectively called midgut carcinoid tumors. NETs are now the most common small bowel tumor. Small bowel NETs are difficult to diagnose as they follow an insidious course; early on in the disease, symptoms are vague and nonspecific. Late diagnosis when regional or distant metastasis have already occurred is common. Forty percent of symptomatic patients without carcinoid syndrome present with vague abdominal pain. CASE DESCRIPTION/METHODS: We present a case of a 58 yo female with complaints of abdominal pain. The patient had six months of alternating fevers, chills and fatigue. She was placed on antibiotics but her fevers returned upon completion. Three months thereafter, the patient developed left lower quadrant abdominal pain that was sharp in nature and radiated to her groin. A CT scan of the abdomen and pelvis demonstrated an enhancing soft tissue mass with internal cystic and necrotic changes located in the midline upper pelvis, measuring 2.8 by 2 cm and two adjacent satellite nodules located superior to the mass. The location of this mass made it un-amenable to a percutaneous biopsy. The patient underwent an Endoscopic Ultrasound Guided Fine Needle Aspiration (EUS-FNA) with cytology demonstrating low grade neuroendocrine carcinoma with the malignant cells being positive for chromogranin A and synaptophysin. Endoscopic evaluation was negative. A capsule endoscopy revealed two small areas in the jejunum that were concerning for small bowel tumors. A subsequent octreoscan was positive, showing an abnormal activity in the mid-abdomen. The patient subsequently underwent surgical excision. The surgical pathology confirmed the mesenteric mass finding as metastatic low grade neuroendocrine tumor and identified two distinct small bowel low grade carcinoid tumors. DISCUSSION: Carcinoid tumors can vary in their presentation and delay the time of diagnosis. Early consideration for NETs in the differential for patients with vague undiagnosed abdominal symptoms could lead to more prompt diagnosis and treatment prior to metastatic spread.Figure 1.: Tumor Positive for Chromogranin A.Figure 2.: Tumor Positive for Synaptophysin.

S2894 Jaundice, Elevated Beta-Human Chorionic Gonadotropin, and Female Gender: Duodenal Choriocarcinoma, Not Pregnancy

INTRODUCTION: Beta-hCG-secreting choriocarcinomas are rare, rapidly-growing, highly-invasive malignant tumors that present most often in the uterus after pregnancy or abortion, as it is a remnant from trophoblastic or totipotent germ cells. Primary extragonadal choriocarcinomas of the GI tract are very rare, with the majority within or along with adenocarcinomas of the organ in question. CASE DESCRIPTION/METHODS: A 29-year-old woman presented with 2.5 weeks of jaundice of the skin. The patient had severe microcytic anemia (Hb 6.8 g/dL), elevated liver enzymes (AST 77 U/L, ALT 95 U/L, Alk Phos 362 U/L), total bilirubin (9.5 mg/dL; 4.4 mg/dL direct), lipase (325 U/L), and CA19-9 (68 U/mL). Pregnancy tests revealed elevated serum and urine beta-hCG. Subsequent ultrasound showed no intrauterine pregnancy. CT of the abdomen with IV contrast revealed a large (7.5 × 5.0 × 7.0 cm), non-obstructing, lobulated mass in the second and third part of the duodenum, displacing the head of the pancreas (Figure 1). An adjacent lesion to the left of the dominant mass measured 3.5 × 2.5 cm, with two regional lymph nodes in the adjacent bowel mesentery. Both pancreatic duct dilation (6 mm) and CBD dilation (15 mm), with accompanying intrahepatic duct dilation, are shown (Figure 1). Endoscopy with biopsies revealed an invasive, well-differentiated adenocarcinoma, with cytoplasmic-stained cells with antibody to beta-hCG antigen, suggesting a choriocarcinoma (Figures 2–3). Treatment included biliary drainage with a percutaneous transhepatic catheter and FOLFOX chemotherapy. A CT scan five months later revealed an increase in duodenal tumor size with invasion into the pancreas and right hepatic lobe. Palliative radiotherapy was initiated, but the patient died several months later. DISCUSSION: We present the case of a never-pregnant female with jaundice found to have a lobular duodenal adenocarcimoa with histology positive for a rare beta-hCG-secreting duodenal choriocarcinoma. One choriocarcinoma theory suggests that remnant totipotent stem cells recently differentiated into neoplastic beta-hCG-secreting cells. Another choriocarcinoma theory, called the dedifferentiation theory, states that malignant adenocarcinoma cells dedifferentiated to ectodermal cells then re-differentiated to beta-hCG-secreting trophoblastic cells. Patients may present with anemia or bleeding from the ulcerated mass, mimicking peptic ulcer disease. Our patient’s advanced duodenal tumor caused biliary obstruction-induced jaundice as initial presentation.Figure 1.: The large 7.5 × 5.0 × 7.0 cm lobulated, non-obstructing, duodenal mass is seen displacing the head of the pancreas superiorly and anteriorly. An adjacent satellite lesion to the left of the dominant mass measures 3.5 × 2.5 cm, with two regional lymph nodes in the adjacent bowel mesentery. The dominant mass abuts the inferior vena cava and aorta. Both pancreatic duct dilation (6 mm at site of pancreatic head) and common bile duct dilation (15 mm), with accompanying intrahepatic duct dilation, are shown.Figure 2.: Cytoplasmic-stained cells with antibody to beta-hCG antigen, suggesting a choriocarcinoma. Tumor sequencing found 14 genomic mutations, including KRAS and TP53.Figure 3.: Cytoplasmic-stained cells with antibody to beta-hCG antigen, suggesting a choriocarcinoma. Tumor sequencing found 14 genomic mutations, including KRAS and TP53.

QoE-Driven Intelligent Handover for User-Centric Mobile Satellite Networks

Recently, many satellites are being launched for providing global internet broadband service to individual consumers. Since satellites and users could move separately, providing seamless connectivity has become one of the most important tasks for mobile satellite networks. Current handover methods are based on either signal strength or service time, however, due to the randomness of user terminal (UT) arrivals and the unbalanced traffic distribution for high-mobility satellite networks, the success rate can hardly be guaranteed. To this end, we propose a QoE-driven intelligent handover mechanism for user-centric mobile satellite networks, through which the access satellites can be selected by predicted service time and communication channel resources. Accordingly, to ensure the service duration, a spatial relationship coupling model is proposed to predict relative motion pattern between UT and satellites; To improve the effectiveness of handover, an available channel estimation model is then developed based on the mobility pattern of adjacent satellites. Finally, reinforcement learning is adopted to maximize the UT <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^\prime$</tex-math></inline-formula> s Quality of Experience (QoE) through predicted handover factors. Simulation results show that the proposed handover mechanism offers good performance in terms of handover times, handover success rate and end-to-end delay.