Best Sensor Configuration and Accommodation Rule Based on Navigation Performance for INS with Seven Inertial Sensors

This paper considers the best sensor configuration and fault accommodation problem for inertial navigation systems which use seven inertial sensors such as gyroscopes and accelerometers. We prove that when six inertial sensors are used, the isolation of a double fault cannot be achieved for some combinations of fault magnitudes, whereas when seven inertial sensors are used, the isolation of any double fault can be achieved. There are many configurations which provide the minimum position errors. This paper proposes four configurations which show the best navigation performance and compares their FDI performances. Considering the FDI performance and the complexity of the accommodation rule, we choose one sensor configuration and provide accommodation rules for double faults. A Monte Carlo simulation is performed to show that the accommodation rules work well

Analysis of the Effect of Time Delay on the Integrated GNSS/INS Navigation Systems

The performance of tightly coupled GNSS/INS integration is known to be better than that of loosely coupled GNSS/INS integration. However, if the time synchronization error occurs between the GNSS receiver and INS(Inertial Navigation System), the situation reverses. The performance of loosely coupled GNSS/INS integration and tightly coupled GNSS/INS integration is analyzed and compared due to time synchronization error by computer simulation

Optimal Configuration of Redundant Inertial Sensors for Navigation and FDI Performance

This paper considers the optimal sensor configuration for inertial navigation systems which have redundant inertial sensors such as gyroscopes and accelerometers. We suggest a method to determine the optimal sensor configuration which considers both the navigation and FDI performance. Monte Carlo simulations are performed to show the performance of the suggested optimal sensor configuration method

Bronchoesophageal fistula in a patient with Crohn’s disease receiving anti-tumor necrosis factor therapy

Tuberculosis is an adverse event in patients with Crohn’s disease receiving anti-tumor necrosis factor (TNF) therapy. However, tuberculosis presenting as a bronchoesophageal fistula (BEF) is rare. We report a case of tuberculosis and BEF in a patient with Crohn’s disease who received anti-TNF therapy. A 33-year-old Korean woman developed fever and cough 2 months after initiation of anti-TNF therapy. And the symptoms persisted for 1 months, so she visited the emergency room. Chest computed tomography was performed upon visiting the emergency room, which showed BEF with aspiration pneumonia. Esophagogastroduodenoscopy with biopsy and endobronchial ultrasound with transbronchial needle aspiration confirmed that the cause of BEF was tuberculosis. Anti-tuberculosis medications were administered, and esophageal stent insertion through endoscopy was performed to manage the BEF. However, the patient’s condition did not improve; therefore, fistulectomy with primary closure was performed. After fistulectomy, the anastomosis site healing was delayed due to severe inflammation, a second esophageal stent and gastrostomy tube were inserted. Nine months after the diagnosis, the fistula disappeared without recurrence, and the esophageal stent and gastrostomy tube were removed

Synthesis of Heterogeneous Li4Ti5O12 Nanostructured Anodes with Long-Term Cycle Stability

The 0D-1D Lithium titanate (Li4Ti5O12) heterogeneous nanostructures were synthesized through the solvothermal reaction using lithium hydroxide monohydrate (Li(OH)·H2O) and protonated trititanate (H2Ti3O7) nanowires as the templates in an ethanol/water mixed solvent with subsequent heat treatment. A scanning electron microscope (SEM) and a high resolution transmission electron microscope (HRTEM) were used to reveal that the Li4Ti5O12 powders had 0D-1D heterogeneous nanostructures with nanoparticles (0D) on the surface of wires (1D). The composition of the mixed solvents and the volume ratio of ethanol modulated the primary particle size of the Li4Ti5O12 nanoparticles. The Li4Ti5O12 heterogeneous nanostructures exhibited good capacity retention of 125 mAh/g after 500 cycles at 1C and a superior high-rate performance of 114 mAh/g at 20C

Trends in Epidemiology of Neonatal Sepsis in a Tertiary Center in Korea: A 26-Year Longitudinal Analysis, 1980-2005

There were many reports of longitudinal changes in the causative organisms of neonatal sepsis in Western countries but few in Asia. We aimed to study longitudinal trends in the epidemiology of neonatal sepsis at Seoul National University Children's Hospital (SNUCH), a tertiary center in Korea, and compared the results to previous studies of Western countries. The medical records of all of the neonates who were hospitalized at SNUCH from 1996 to 2005 with positive blood cultures were reviewed. We also compared the findings to previous 16-yr (1980-1995). One hundred and forty-nine organisms were identified in 147 episodes from 134 infants. In comparison with the previous 16-yr studies, there was a decrease in the number of Escherichia coli infections (16.2% vs 8.7%: odds ratio [OR] 0.495; 95% confidence interval [CI], 0.255-0.962; P = 0.035), but an increase in Staphylococcus aureus (16.6% vs 25.5%: OR 1.720; 95% CI, 1.043-2.839; P = 0.033) and fungal infections (3.3% vs 18.7%: OR 6.740; 95% CI, 2.981-15.239; P < 0.001), predominantly caused by Candida species. In conclusion, the incidence of sepsis caused by E. coli decreases, but S. aureus and fungal sepsis increases significantly. Compared with Western studies, the incidence of sepsis caused by S. aureus and fungus has remarkably increased

An Unambiguous Delay-And-Multiply Acquisition Scheme for GPS L1C Signals

The GPS provides positioning information almost anytime and anywhere on Earth, regardless of the weather conditions, and has become an essential technology for positioning and navigation. As a modernization program, the fourth civil GPS signal, denoted as L1C, will be transmitted from Block III satellites. One distinction of the L1C signal from the former signals is the use of binary offset carrier (BOC) modulation, which is necessary for compatibility and the reduction of interference between the legacy L1 signal and L1C signal, despite their use of the same carrier frequency. One drawback of using BOC modulation is the ambiguity problem, which comes from the multiple peaks in the correlation function and causes difficulties finding the code phase in the acquisition process. In this paper we suggest two delay-and-multiply (DM) methods for the L1C signal to solve the ambiguity problem. For the DM acquisition schemes we suggest the optimal delay time for the delay signal, and prove that the correlation function of the received DM signal and the generated DM signal has a triangular shape, as seen in the legacy GPS L1 signal. The noise characteristics of the decision variable are obtained and the performance of the DM acquisition scheme is given in terms of the probability of detection, and compared with that of the conventional method. We provide the procedure to find the Doppler frequency after obtaining the code phase through the proposed DM method

A Carathkodory-Fejkr Approach to Simultaneous Fault Detection and Isolation

In this paper we address the problem of detecting and isolating faults from noisy input/output measurements of a MIMO uncertain-system. The main result of the paper shows that this problem can be solved by using CarathCodory-Fejtr&apos;s theorem to reduce it to an LMI feasibility problem. These results are illustrated with a simple example.

Performance Analysis of Direct GPS Spoofing Detection Method with AHRS/Accelerometer

The global positioning system (GPS) is an essential technology that provides positioning capabilities and is used in various applications such as navigation, surveying, mapping, robot simultaneous localization and mapping (SLAM), location-based service (LBS), etc. However, the GPS is known to be vulnerable to intentional attacks such as spoofing because of its simple signal structure. In this study, a direct method is proposed for GPS spoofing detection, using Attitude and Heading Reference System (AHRS) accelerometer and analyzing the detection performance with corresponding probability density functions (PDFs). The difference in the acceleration between the GPS receiver and the accelerometer is used to detect spoofing. The magnitude of the acceleration error may be used as a decision variable. Additionally, using the magnitude of the north (or east) component of the acceleration error as another decision variable is proposed, which shows better performance in some conditions. The performance of the two decision variables is compared by calculating the probability of spoofing detection and the detectable minimum spoofing acceleration (DMSA), given a pre-defined false alarm probability and a pre-defined detection probability. It turns out that both decision variables need to be used together to obtain the best spoofing detection performance