Imperfect Factors Research Articles

Condition-based maintenance policy for shared service-oriented leased equipment

Due to growing consumer demands for immediacy, personalization, and high availability, equipment manufacturers are venturing into the sharing market with expanded shared leasing services. While selling usage rights of equipment, they provide additional services to the consumer in the role of equipment operators, such as free maintenance and swap. However, uncertain usage rates and return times in the shared model pose significant maintenance challenges. This paper proposes a personalized condition-based maintenance (CBM) policy accounting for these uncertainties and heterogeneous consumer usage patterns. By considering inspection, maintenance, and penalty costs, we minimize the long-run expected maintenance cost per unit of time for operators. In the numerical example, we compare our policy against fixed inspection interval CBM policy and non-fixed inspection interval CBM under average usage rate, demonstrating that personalized CBM reduces maintenance costs. Sensitivity analysis provides some managerial insights. Firstly, operators should adjust the number of free swaps strategically to manage the intensity of equipment swaps, and strike a balance between the increased maintenance costs due to the swap intensity enhancement and the improved user satisfaction and equipment availability resulting from the increased number of free swaps. Secondly, when the acceleration effect of imperfect maintenance on the degradation rate is strengthened, operators should prioritize reducing the frequency of imperfect maintenance and increasing the frequency of perfect preventive maintenance. Moreover, operators must make strategic investments in their maintenance actions, balancing maintenance costs and penalty costs to develop cost-effective imperfect maintenance improvement factors.

Imperfect Measurement Devices Impact the Security of Tomography‐Based Source‐Independent Quantum Random Number Generator

AbstractSource‐independent quantum random number generators (SI‐QRNGs) can generate secure random numbers with untrusted and uncharacterized sources. Recently, a tomography‐based SI‐QRNG protocol has garnered significant attention for its higher randomness generation rate[Phys. Rev. A 99, 022328 (2019)], achieved through measurements utilizing three mutually unbiased bases. However, imperfect and inadequately characterized measurement devices would impact the security and performance of this protocol. In this work, considering the imperfect basis modulation, afterpulse effect and detection efficiency mismatch, it is demonstrated that the imperfect measurement devices would reduce the extractable randomness and lead to the incorrect estimation of the conditional min‐entropy. Additionally, the influences of the finite‐size effect and the performances of the protocol based on different parameter estimation methods are investigated and compared. To guarantee the security of generated random numbers, accurate conditional min‐entropy estimation methods that are compatible with imperfect factors are also developed. The work emphasizes the significance of considering the imperfections in measurement devices and establishing tighter bounds for parameter estimation, especially in high‐speed systems, thereby enhancing the robustness and performance of the protocol.

A Transformer Maintenance Interval Optimization Method Considering Imperfect Maintenance and Dynamic Maintenance Costs

As one of the most critical components of the power grid system, transformer maintenance strategy planning significantly influences the safe, economical, and sustainable operation of the power system. Periodic imperfect maintenance strategies have become a research focus in preventive maintenance strategies for large power equipment due to their ease of implementation and better alignment with engineering realities. However, power transformers are characterized by long lifespans, high reliability, and limited defect samples. Existing maintenance methods have not accounted for the dynamic changes in maintenance costs over a transformer’s operational lifetime. Therefore, we propose a maintenance interval optimization method that considers imperfect maintenance and dynamic maintenance costs. Utilizing defect and maintenance cost data from 400 220 KV oil-immersed transformers in northern China, we employed Bayesian estimation for the first time to address the distribution fitting of defect data under small sample conditions. Subsequently, we introduced imperfect maintenance improvement factors to influence the number of defects occurring in each maintenance cycle, resulting in more realistic maintenance cost estimations. Finally, we established an optimization model for transformer maintenance cycles, aiming to minimize maintenance costs throughout the transformer’s entire lifespan while maintaining reliability constraints. Taking a transformer’s strong oil circulation cooling system as an example, our method demonstrates that while meeting the reliability threshold recognized by the power grid company, the system’s maintenance cost can be reduced by 41.443% over the transformer’s entire life cycle. Through parameter analysis of the optimization model, we conclude that as the maintenance cycle increases, the factors dominating maintenance costs shift from corrective maintenance to preventive maintenance.

Clinical and genetic factors associated with tumor response to neoadjuvant (chemo)radiotherapy, survival and recurrence risk in rectal cancer.

Rectal cancer poses challenges in preoperative treatment response, with up to 30% achieving a complete response (CR). Personalized treatment relies on accurate identification of responders at diagnosis. This study aimed to unravel CR determinants, overall survival (OS), and time to recurrence (TTR) using clinical and targeted sequencing data. Analyzing 402 patients undergoing preoperative treatment, tumor stage, size, and treatment emerged as robust response predictors. CR rates were higher in smaller, early-stage, and intensively treated tumors. Targeted sequencing analyzed 216 cases, while 120 patients provided hotspot mutation data. KRAS mutation dramatically reduced CR odds by over 50% (odds ratio [OR] = 0.3 in the targeted sequencing and OR = 0.4 hotspot cohorts, respectively). In contrast, SMAD4 and SYNE1 mutations were associated with higher CR rates (OR = 6.0 and 6.8, respectively). Favorable OS was linked to younger age, CR, and low baseline carcinoembryonic antigen levels. Notably, CR and an APC mutation increased TTR, while a BRAF mutation negatively affected TTR. Beyond tumor burden, SMAD4 and SYNE1 mutations significantly influenced CR. KRAS mutations independently correlated with radiotherapy resistance, and BRAF mutations heightened recurrence risk. Intriguingly, non-responding tumors with initially small sizes carried a higher risk of recurrence. The findings, even if limited in addition to the imperfect clinical factors, offer insights into rectal cancer treatment response, guiding personalized therapeutic strategies. By uncovering factors impacting CR, OS, and TTR, this study underscores the importance of tailored approaches for rectal cancer patients. These findings, based on extensive analysis and mutation data, pave the way for personalized interventions, optimizing outcomes in the challenges of rectal cancer preoperative treatment.

Performance assessment of full-duplex two-way Internet-of-vehicles relay networks under practical imperfect conditions

Contemporary Internet-of-Things (IoT) devices in general and Internet-of-Vehicles (IoV) networks in specific are taking the benefits from using full-duplex (FD) communication with the help of relay nodes to facilitate data transmission. However, self-interference between transmit and receive antennas at the relay node may cause big trouble if self-interference cancellation (SIC) is not applied. In this paper, a rigorous analysis on the performance of FD two-way relay networks (FDTWRNs) for IoV applications under imperfect conditions is provided. Different from earlier studies on the performance of FDTWRNs where one or two imperfect factors were considered, this work simultaneously takes into account many practical issues in the implementation of the IoV networks at the physical layer, including errors in channel state information at all channel links, imperfect SIC and transceiver hardware impairment at all nodes. For relaying protocol, we consider amplify-and-forward with both fixed-gain (FG) and variable-gain (VG) protocols. The exact closed-form expressions (in terms of the system parameters) of key performance factors such as signal-to-interference-plus-noise-distortion-and-error ratio (SINER), outage probability (OP), achievable data rate (ADR), and average symbol error probabilities (ASEP) of the considered system over Rayleigh fading channels and under the combined effect of imperfect CSI, SIC, and transceiver hardware are derived mathematically using probabilistic model analysis. The correctness of the analysis is then verified by Monte Carlo simulations. Drawing upon both analytical and numerical findings, the efficacy of the FDTWRNs under consideration is meticulously and comprehensively assessed in comparison to its performance in ideal conditions characterized by one or multiple critical factors. The disparity between perfect and imperfect scenarios serves as a valuable metric for appraising the practical viability of the considered FDTWRNs when deployed in practical IoV networks.

Brain Tumor Autophagy: A New Breakthrough in Cancer Research

Autophagy is the inherent, preserved cell breakdown that removes undesirable or imperfect factors through a lysosome- correspondent definite media. It slows down necrosis in cancer cells, which in ramble slows down the inflammation that comes before necrosis, which is understood to speed up neoplasm growth but whose exact cause is intimately unclear. Hence, autophagy is nowadays noted as a pivotal element since it stops the advancement of tumor by precluding cancer cells from ageing and turning on cell death. Yet, some autophagic pathways, alike the PI3K- AKT- mTOR pathway, also amplify tumor production. This pathway has steps like inauguration, nucleation, extension and conformation of double membrane vesicles understood as autophagosomes, which fuse with lysosomes in mammals and vacuoles in yeast and plants, for the degeneration of the intravascular cargo. Because, autophagy contributes to both tumorigenesis and tumor suppression, it isn’t easy to distinguish if it results in a positive or negative stasis for cell survival. So, autophagy should be acclimated in the molecular, cellular and epigenetic environment, to deduce variety of tumor cells, in high- grade gliomas. In this review, we talk over the aim of pathways, modulators and genes of autophagy in brain neoplasms.

Self-equilibrium, stability, and accuracy degradation of imperfect prismatic tensegrities with additional cable nets

Prismatic tensegrity is an attractive structure due to the unique advantages of self-equilibrium, lightweight, small compression volume, specific super stability, ease of deployment, and functional extension. However, it is subject to geometric large deformation when suffering from imperfect factors like manufacturing errors, thermal deformation, slips of tensioning knots, and mechanical relaxation of members, which will eventually reduce the accuracy and reliability. We develop a kind of prismatic tensegrities with additional cable nets for space deployable constructions. For the specific requirements of high accuracy and high reliability, we fully consider the influence of imperfect factors, and explore their environment- and time-dependent characteristics from the view of self-equilibrium, stability, and accuracy. First, a preload optimization method is established for high-accuracy determination of the shape and uniform distribution of preload. Then, a high-fault-tolerance accuracy estimation method is proposed for accuracy degradation research, for which nonlinear force density equations and time-dependent tangential stiffness matrix are formulated to obtain deformation shapes and stability criteria beforehand. Eventually, the characteristics of the prismatic tensegrities with additional cable nets, under the influence of imperfect factors, are fully revealed and forecasted. The methods and some conclusions of this study can also be applied to other complex tensegrities or prestressed pin-jointed systems.

A Solution to the Non-Ideal Delay Line Problem in Transmitted Reference Pulse Cluster Schemes for UWB Communications

The conventional transmitted reference (TR) technique in ultra wide-band (UWB) communications has provided a springboard for a lot of studies, and a TR pulse cluster (TRPC) structure was proved to have robust performance. Most of TR and TRPC related studies hitherto are based on the assumption that the delay lines (DLs) in their schemes are ideal. However, the group delay ripple (GDR) of nonideal DLs triggered by practical imperfect factors at implementation causes an unexpected distortion in both TR and TRPC UWB systems, and there are few studies so far. In this article, we first analyze the impact of the GDR of nonideal DLs on the performance of TR and TRPC UWB systems. Then a new design solution for both TR and TRPC transceivers is proposed, where the GDR information of the nonideal DL at the receiver side is introduced into transmitter side. The performance of the new design solution is analyzed and simulation results prove the robustness and efficiency of this new design method in reducing the impaction caused by nonideal DLs. Moreover, the proposed design solution can also greatly relieve the high design requirement of DLs in both the transmitter and receiver side and therefore offer valuable insight for the practical transceiver design in both TR and TRPC related UWB systems.

Multi-antenna relay assisted NOMA network with multiple imperfect factors

In this paper, a 5G downlink multi-antenna relay assisted non-orthogonal multiple access (NOMA) communication system is investigated. The relay can work in half-duplex (HD) or full-duplex (FD) mode with maximum-ratio-combining/transmission antenna selection (MRC/TAS) scheme, and the direct links between the source and destinations are also considered. The exact expressions for the outage probability are derived when considering the effects of hardware impairment (HDI), imperfect successive interference cancellation (ipSIC), channel estimation error(CEE), antenna number and loop-interference (LI) for FD mode. Then, based on the accurate outage probability, the approximate low bound and asymptotic results are derived. From the derived formulas, we find that the maximum diversity order of the considered system is min{(1−μ)N+1,M+1} when CEE does not appear, where μ is the LI cancellation grade, N and M are the receiving and transmitting antenna number equipped at the relay. Otherwise the diversity decreases to one or zero regardless of multi-antenna when CEE appears, but multiple antennas still improve system performance by promoting the array gain. The FD mode may outperform the HD mode with less LI which is decided by μ. Monte Carlo simulations are also done to validate the correctness of theoretical analysis.

Performance analysis of ABCom NOMA systems for 6G with generalized hardware impairments

With the continuous emergence of new smart applications, the number of smart devices is increasing exponentially. Therefore, it is a great challenge to meet the rising network demands for the sixth generation (6G) communication. To solve the above problem, non-orthogonal multiple access (NOMA) and ambient backscatter communication (AmBC) technologies are introduced. However, deploying a large number of low cost components, all nodes are prone to hardware non-ideal, and the system performance is limited by the imperfect factors of in-phase and quadrature-phase imbalance (IQI) and residual hardware impairments (RHIs). Motivated by this, this paper considers an AmBC-NOMA communication system with both IQI and RHIs. In particular, we derive the analytic expressions for outage probability (OP) and ergodic rate (ER) of each node for the cases of ideal and non-ideal conditions. In order to get further insights, we analyze the asymptotic behavior of OPs and ERs at high signal-to-noise ratios (SNRs). The comparison of theoretical analysis and Monte Carlo simulation show that: (1) IQI and RHIs have negative impacts on the effectiveness and reliability of the system; (2) As the transmit SNR increases, the OP of each node converges to a non-zero constant, resulting in the diversity order approaches zero; (3) The ER of Uf is less affected by these two non-ideal factors; (4) RHIs have a greater impact on the ER of Un than Uf.

Effect of weak randomness flaws on security evaluation of practical quantum key distribution with distinguishable decoy states

Quantum key distribution provides an unconditional secure key sharing method in theory, but the imperfect factors of practical devices will bring security vulnerabilities. In this paper, we characterize the imperfections of the sender and analyze the possible attack strategies of Eve. Firstly, we present a quantized model for distinguishability of decoy states caused by intensity modulation. Besides, considering that Eve may control the preparation of states through hidden variables, we evaluate the security of preparation in practical quantum key distribution (QKD) scheme based on the weak-randomness model. Finally, we analyze the influence of the distinguishability of decoy state to secure key rate, for Eve may conduct the beam splitting attack and control the channel attenuation of different parts. Through the simulation, it can be seen that the secure key rate is sensitive to the distinguishability of decoy state and weak randomness, especially when Eve can control the channel attenuation.

Prognostic and Predictive Molecular Markers in Cholangiocarcinoma.

Simple SummaryCholangiocarcinoma (CCA) is a heterogenous and aggressive malignancy of the intra- and extrahepatic biliary tract, marked by a steeply rising incidence on a global scale. While surgery remains the only curative treatment option, most patients present with advanced or unresectable disease, and are, therefore, treated with systemic therapy, albeit with limited benefit. Biomarkers obtained from either the patients’ serum or tumor tissue might facilitate therapy guidance by selecting patients who would benefit the most from surgical and adjuvant treatment strategies, as well as by identifying those with higher risk of disease recurrence. Furthermore, several genetic aberrations in CCA have been linked with improved response upon targeted therapies, thus highlighting their role as predictive biomarkers. In this review we provide an overview of currently known prognostic and predictive biomarkers and discuss their role in CCA.Cholangiocarcinoma (CCA) is the second most common primary liver cancer and subsumes a heterogeneous group of malignant tumors arising from the intra- or extrahepatic biliary tract epithelium. A rising mortality from CCA has been reported worldwide during the last decade, despite significant improvement of surgical and palliative treatment. Over 50% of CCAs originate from proximal extrahepatic bile ducts and constitute the most common CCA entity in the Western world. Clinicopathological characteristics such as lymph node status and poor differentiation remain the best-studied, but imperfect prognostic factors. The identification of prognostic molecular markers as an adjunct to traditional staging systems may not only facilitate the selection of patients who would benefit the most from surgical, adjuvant or palliative treatment strategies, but may also be helpful in defining the aggressiveness of the disease and identifying patients at high-risk for tumor recurrence. The purpose of this review is to provide an overview of currently known molecular prognostic and predictive markers and their role in CCA.

Phase sensitivity enhancement for the SU(1,1) interferometer using photon level operations

We propose to employ photon level operations (PLOs) to enhance the phase sensitivity of the SU(1,1) interferometer (SUI). Two types of PLOs are considered, including photon subtraction scheme (PSS) and photon addition scheme (PAS). By performing either PSS or PAS on the two arms inside the SUI, we demonstrate that the phase sensitivity of the SUI can be enhanced. More interestingly, we find that both PSS and PAS are able to increase the robustness of the SUI against the internal loss of the interferometer, which is one of the main imperfect factors that limit the performance of the SUI.

Phase-matching quantum key distribution with light source monitoring

The transmission loss of photons during quantum key distribution (QKD) process leads to the linear key rate bound for practical QKD systems without quantum repeaters. Phase matching quantum key distribution (PM-QKD) protocol, an novel QKD protocol, can overcome the constraint with a measurement-device-independent structure, while it still requires the light source to be ideal. This assumption is not guaranteed in practice, leading to practical secure issues. In this paper, we propose a modified PM-QKD protocol with a light source monitoring, named PM-QKD-LSM protocol, which can guarantee the security of the system under the non-ideal source condition. The results show that our proposed protocol performs almost the same as the ideal PM-QKD protocol even considering the imperfect factors in practical systems. PM-QKD-LSM protocol has a better performance with source fluctuation, and it is robust in symmetric or asymmetric cases.

SER performance of MIMO full-duplex relay system with channel estimation errors and transceivers hardware impairments

In practice, traditional wireless communication systems are often affected by various negative factors such as channel estimation errors (CEE) and transceiver hardware impairments (THI). For in-band full-duplex (FD) communication systems, besides CEE and THI impacts, imperfect self-interference cancellation will significantly degrade the system performance because of residual self-interference (RSI). This paper aims to investigate the performance of a multiple-input multiple-output (MIMO) FD relay (FDR) system in realistic scenarios where the impacts of CEE, THI, and RSI are taken into account. We mathematically derive the exact closed-form expression of symbol error rate (SER) of the considered MIMO-FDR system and validate the derived expression by Monte-Carlo simulations. Numerical results indicate that the impacts of three imperfect factors (CEE, THI, and RSI) are remarkable. Specifically, with the considered values of CEE, THI, and RSI, the impact of CEE on the SER is most substantial. Additionally, compared with the ideal system (perfect channel estimations, transceiver hardware, and self-interference cancellation), the SER of the considered system is significantly higher and goes to the error floor fast. Therefore, it is crucial to apply all solutions for reducing the CEE, THI, and RSI in the considered MIMO-FDR system.

Chirp Spreading Spectrum in Imperfect Environment and Wireless Tree Topology Network

With the rapid development of IoT technology in recent years, higher requirements have been put forward for wireless communication technology. Low Power Wide Area Network (LPWAN) technology is emerging rapidly, the technology is characterized by low power consumption, low bandwidth, long-distance, and a large number of connections, and is specifically designed for Internet of Things applications. LoRa (Low Power Long Range Transceiver), as a typical representative of LPWAN technology, has been widely concerned and studied. This paper analyzes the performance of LoRa modulation in the tree topology network and analyzes the performance of LoRa modulation in the imperfect environment for point-to-point communication and multipoint-to-point communication. From theoretical analysis and performance simulation, it can be seen that the influence of frequency offset or multipath fading on LoRa signal is very obvious. However, when LoRa modulation is used for networking, multi-user interference will be introduced. Under the influence of many imperfect factors, the signal receiver performance of LoRa modulation will be difficult to guarantee. Because of these effects, Coordinated Multiple Points based on Timing Delay (DCoMP) is presented. Multiple nodes close to each other send the same data to the target node. Due to the inaccurate synchronization between nodes, there will be a certain relative delay when sending signals to the same target node. After the receiving node combines the signals of multiple nodes according to different relative delays, the reception performance of the signals can be improved. At the same time, the cooperative node can also actively adjust the signal sending time to improve the reception performance of the receiving node signal merging algorithm. LoRa modulation, by using DCoMP transmission, improves the reception of signals and thus the overall capacity of the system. Through the analysis of multipoint communication and single point communication, this paper is of great help to LoRa network deployment.

Responsiveness of Multi-Channel IEC-61850 Substation Communication Network Reliability Performance to Changes in Repair Factors

Power distribution centres distribute power to motor control centres in industrial facilities, as well as supply power to medium voltage drives among other loads. In reliability studies, the use of the combinatorial methods to evaluate the reliability of IEC-61850 based SCN in power distribution centres is preferred, owing to the ease of comprehension and applying the methods. The disadvantage of the methods is that repairs are assumed to be perfect and that all system faults are known; whereas it is not the case in practice. Markov model enables the impact of imperfect repairs on the system reliability performance to be investigated using the eigenvalue analysis method based on the concept of linear dynamical systems. The method presented in this paper advances the eigenvalue analysis method and focusses on the incremental responsiveness of the system to imperfect repair factors based on absorbing Markov chain and matrix calculus. The results indicate that even though the system is dependent on repair factors, the system is perfectly inelastic to the repair efficiency factors. However, the diagnostic coverage of the system is the most critical of the two factors, with higher elasticity as the factor approaches 100%. The results also indicate that both sensitivity and elasticity rapidly decrease as the diagnostic coverage of the system decrease. Thus, it is concluded that more emphasis must be put on the system diagnostic coverage because it is embedded in the system design, which can be expensive and practically not achievable once the system is commissioned and is running.

Immunoscore as a parameter predicting time to recurrence and disease-free survival in T4N0 stage II colon cancer patients.

4105 Background: Risk assessment is particularly important to decide when to propose an adjuvant treatment for Stage II Colon Cancer (CC) patients. However, the current tumor risk features are imperfect and additional risk factors are needed to guide treatment decisions. The consensus Immunoscore is an alternative and powerful approach that could be used in the T4N0 Stage II colon cancer population. Immunoscore is an in vitro diagnostic test that predicts the risk of relapse in patients with CC by measuring the host immune response at the tumor site. Methods: From the international Immunoscore consortium study (n = 2681) (Pagès et al. The Lancet 2018), a subgroup analysis was performed on T4N0 Stage II colon cancer patients (n = 208). Results: In stage II T4N0, Int+Hi Immunoscore represented 65.4% of the population and low-Immunoscore only 34.6%. T4N0 patients with Int+Hi Immunoscore presented a significantly prolonged survival for TTR compared to low Immunoscore patients (5 years recurrence rate Int+Hi: 84.6% (78.3-91.5), Lo: 46.3% (35.1-61); unadjusted HR [Int+Hi vs Lo] = 0.21; (95% CI 0.11-0.4); P< 0.0001), representing a restricted mean survival time (RMST) difference of 80.9 months (95% CI 51.1-110.6) ( P< 0.0001). The DFS was significantly different between Int+Hi and Low Immunoscore (5 years recurrence rate Int+Hi: 70.5% (95% CI 62.7-79.1), Lo: 38.5% (95% CI 28.2-52.5); unadjusted HR [Int+Hi vs Lo] = 0.31; (95% CI 0.19-0.49); P< 0.0001). Using restricted mean survival time (RMST) a significant ( P< 0.0001) difference of 60.4 months (95% CI 32.6-88.1) was observed between the 2 groups Importantly, Cox multivariate analysis in Stage II T4N0 colon cancer patients, revealed that Immunoscore was the only remaining significant parameter (HR [Int+Hi vs Lo] = 0.15; (95% CI 0.05-0.46); P= 0.0009). In contrast, all other parameters, gender, sidedness, mucinous, grade, T-stage, VELIPI, MSI were not significant in multivariate analysis. Finally, Immunoscore showed the highest relative contribution to predict relapse (76.2% chi2 relative contribution), stronger than all the other parameters, MSI (16.1%), Grade (5%), sidedness (2%), gender (2%), VELIPI (1%). Conclusions: Immunoscore is the most powerful parameter to predict the risk in T4N0 population, and could be a good tool for adjuvant treatment decision in Stage II patients.

Monitoring an untrusted light source with single-photon detectors in measurement-device-independent quantum key distribution

Measurement-device-independent quantum key distribution (MDI-QKD) is proposed to close the loopholes of the detection part in QKD systems, while it still requires the light source to be trusted. This assumption is not guaranteed in practice, leading to practical secure issues. In this paper, we propose a light source monitoring scheme with single-photon detectors for MDI-QKD, which can guarantee the security of the system under the untrusted source condition with both common decoy state method and the newly proposed five-intensity decoy state method. Moreover, our monitoring scheme performs almost the same as the ideal MDI protocol even considering the imperfect factors in practical systems. Compared to the previous scheme, our work improves the secure key rate and the transmission distance of practical MDI-QKD systems significantly.

Operation-oriented reliability and availability evaluation for onboard high-speed train control system with dynamic Bayesian network

The reliability and availability of the onboard high-speed train control system are important to guarantee operational efficiency and railway safety. Failures occurring in the onboard system may result in serious accidents. In the analysis of the effects of failure, it is significant to consider the operation of an onboard system. This article presents a systemic approach to evaluate the reliability and availability for the onboard system based on dynamic Bayesian network, with taking into account dynamic failure behaviors, imperfect coverage factors, and temporal effects in the operational phase. The case studies are presented and compared for onboard systems with different redundant strategies, that is, the triple modular redundancy, hot spare double dual, and cold spare double dual. Dynamic fault trees of the three kinds of onboard system are constructed and mapped into dynamic Bayesian networks. The forward and backward inferences are conducted not only to evaluate the reliability and availability but also to recognize the vulnerabilities of the onboard systems. A sensitivity analysis is carried out for evaluating the effects of failure rates subject to uncertainties. To improve the reliability and availability, the recovery mechanism should be paid more attention. Finally, the proposed approach is validated with the field data from one railway bureau in China and some industrial impacts are provided.