New Preamble Sequence for WiMAX System with Improved Synchronization Accuracy

Worldwide Interoperability for Microwave Access(WiMAX)trusts Multiple Input Multiple Output-Orthogonal Frequency Division Multiplexing(MIMO-OFDM)combination for the deployment of physical layer functions and for connecting the medium access control to the wireless media.Even though Orthogonal Frequency Division Multiplexing(OFDM)facilitates reliable digital broadband transmission in the fading wireless channels,the presence of synchro-nization errors in the form of Carrier Frequency Offset(CFO)and Time Offset(TO)adversely affect the performance of OFDM based physical layers.The objective of this work is to improve the accuracy of the frequency and the time offset estimation in the WiMAX physical layer.A method to enhance the synchro-nization accuracy byfine-tuning the merit factor of the preamble sequence is sug-gested in this paper.Also,a new preamble with improved synchronization accuracy is proposed for the WiMAX system.The performance of the proposed preamble is evaluated in a Rayleigh fading channel and the results of simulations show that the Mean Square Error(MSE)in offset estimation is significantly reduced and it outperforms the standard WiMAX preamble.

Parameter uncertainty modeling of safety instrumented systems

In this study,a novel safety integrity level(SIL)determination methodology of safety instrumented systems(SISs)with parameter uncertainty is proposed by combining multistage dynamic Bayesian networks(DBNs)and Monte Carlo simulation.A multistage DBN model for SIL determination with multiple redundant cells is established.The models of function inspection test interval and function inspection test stages are alternately connected to form the multistage DBNs.The redundant cells can have different M out of N voting system architectures.An automatic modeling of conditional probability between nodes is developed.The SIL determination of SISs with parameter uncertainty is constructed by using the multistage DBNs and Monte Carlo simulation.A high-pressure SIS in the export of oil wellplatform is adopted to demonstrate the application of the proposed approach.The SIL and availability of the SIS and its subsystems are obtained.The influence of single subsystem on the SIL and availability of the SIS is studied.The influence of single redundant element on the SIL and availability of the subsystem is analyzed.A user-friendly SIL determination software with parameter uncertainty is developed on MATLAB graphical user interface.

Design of a personnel safety interlock system for proton therapy

Proton therapy is the most advanced radiotherapy approach in the world,and causes less damage to normal human tissue than traditional radiotherapy.Because the treatment process produces a high-energy proton beam,the personnel safety interlock system mainly considers measures to protect personnel from radiation hazards during beam preparation and the beam release process.Unlike other safety interlock systems,the personnel safety interlock system designed in this study focuses on the safety and stability of the system itself.The hardware and software of important interlock control loops are designed and developed according to the requirements of Safety Integrity Level 3 specified by IEC61508.A set of redundant ring networks was developed to ensure that damage to a certain network line does not affect the normal operation of the system.A set of friendly operation interfaces and data storage systems were developed to ensure that the operator can monitor the data in real time and trace the data.The personnel safety interlock system mainly includes a beam enabling function,clearance function,and emergency stop function.The system was put into actual use and successfully ensured personnel safety.

县域医疗共同体建设背景下的乡镇卫生院效率

目的了解我国乡镇卫生院的运行现状及县域医疗共同体建设前后的效率变化,为政府相关部门决策提供参考依据。方法用数据包络分析和Malmquist指数,分析我国29个省(自治区、直辖市)的乡镇卫生院的投入产出效率。结果29个省(自治区、直辖市)的乡镇卫生院的技术效率均数为0.773,最高为1.000,最低为0.384,效率的地区差异较明显。2016—2018年,除纯技术效率略有上升外,全要素生产率、技术效率、技术均有所下降。乡镇卫生院整体运行效率较低,产出不足与投入冗余是主要原因,规模效率和技术制约了乡镇卫生院生产率的增长。结论建议:因地制宜,优化卫生资源配置;发挥政府主导作用,完善医疗共同体配套政策;引导居民转变就医理念,合理就医。

Integration-centric approach to system readiness assessment based on evidential reasoning

An integration-centric approach is proposed to handle inadequate information in the system readiness level （SRL） assessment using the evidential reasoning （ER） algorithm. Current SRL assessment approaches cannot be applied to handle inadequate information as the input. The ER-based approach is proposed to synthesize inadequate input information and an integration-centric perspective is applied to reduce the computational complexity. Two case studies are performed to validate the efficiency of the proposed approach. And these studies are also performed to study how the inadequate information will affect the assessment result. And the differences caused by the system＇s structure. The importance of the system＇s structure in the SRL assessment is demonstrated and the contributions made in this study are summarized as conclusions.

An approach to operational risk modeling and estimation of safety levels for deep water work class remotely operated vehicle-A case study with reference to ROSUB 6000

This paper presents a quantitative approach to operational risk modeling and estimation of safety integrity levels,required for the deep water electric work class remotely operated vehicle with reference to ROSUB6000 developed by the National Institute of Ocean Technology,India.ROSUB6000 is used for carrying out bathymetric surveys,gas hydrate surveys,poly-metallic nodule exploration,salvage operations,and meeting emergency response situations.The system is expected to be in operation for a period of 300 h per year,and has to be extremely safe and reliable.Methods and models for the quantitative assessment of operational safety and estimation of safety integrity levels for ROV are seldom available in the deep water intervention industry.The safety instrumented functions implemented in the ROV should be able to meet the SIL requirements of specific mission.This study indicates that the required safety factors are implemented into the design of the state-of-the-art ROV ROSUB 6000,considering IEC 61508/61511 recommendations on Health,Safety and Environment and it is found that the system is able to meet the required SIL for seven identified functions.This paper gives the design and safety engineers in the ROV industry,an overview of the numerical operational risk assessment methods and safety-centered ROV engineering.

INCIDENCE MATRIX APPROACH FOR CALCULATING READINESS LEVELS

Contemporary system maturity assessment approaches have failed to provide robust quantitative system evaluations resulting in increased program costs and developmental risks.Standard assessment metrics,such as Technology Readiness Levels（TRL）,do not sufficiently evaluate increasingly complex systems.The System Readiness Level（SRL）is a newly developed system development metric that is a mathematical function of TRL and Integration Readiness Level（IRL） values for the components and connections of a particular system.SRL acceptance has been hindered because of concerns over SRL mathematical operations that may lead to inaccurate system readiness assessments.These inaccurate system readiness assessments are called readiness reversals.A new SRL calculation method using incidence matrices is proposed to alleviate these mathematical concerns.The presence of SRL readiness reversal is modeled for four SRL calculation methods across several system configurations.Logistic regression analysis demonstrates that the proposed Incidence Matrix SRL（IMSRL）method has a decreased presence of readiness reversal than other approaches suggested in the literature.Viable SRL methods will foster greater SRL adoption by systems engineering professionals and will support system development risk reduction goals.

Guest Editorial:Special Section on Integrating Ultra-High Levels of Variable Renewable Energy

Wind and solar energy have seen significant decreases in the cost of these technologies over that last decade which has lead to increasing levels integrated into the grid.They also offer unique benefits such as no fuel costs,quick installation,and no pollution.But as more variable renewable energy(VRE)such as wind and solar is integrated into electrical power systems.

Design and RAMS Analysis of a Fault-Tolerant Computer Control System

This paper presents a fault-tolerant computer system. It is designed as a double 2-out-of-2 architecture based on component redundant technique. Also, a quantitative probabilistic model is presented for evaluating the reliability, availability, maintainability and safety (RAMS) of this architecture. Hierarchical modeling method and Markov modeling method are used in RAMS analysis to evaluate the system characteristics. The double 2-out-of-2 system is compared with the other two systems, all voting triple modular redundancy (AVTMR) system and dual-duplex system. According to the result, the double 2-out-of-2 system has the highest dependability. Especially, the system can satisfy the safety integrity level (SIL) 4, which means the system’s probability of catastrophic failure less than or equal to 10-8 per hour, therefore, it can be applied to life critical systems such as high-speed railway systems.

Paleoecological Response of Corals to the End-Triassic Mass Extinction： An Integrational Analysis

The end-Triassic （also Triassic-Jurassic） mass extinction severely affected life on planet Earth 200 million years ago. Paleoclimate change triggered by the volcanic eruptions of the Central Atlantic Magmatic Province （CAMP） caused a great loss of marine biodiversity, among which 96% coral genera were get lost. However, there is precious little detail on the paleoecology and growth forms lost between the latest Triassic extinction and the Early Jurassic recovery. Here a new pilot study was conducted by analyzing corallite integration levels among corals from the latest Triassic and Early Jurassic times. Integration levels in corals from the Late Triassic and Early Jurassic were determined through both the Paleobiology Database as well as from a comprehensive museum collection of fossil corals. Results suggest that in addition to a major loss of diversity following the end-Triassic mass extinction, there also was a significant loss of highly integrated corals as clearly evidenced by the coral data from the Early Jurassic. This confirms our hypothesis of paleoecological selectivity for corals following the end-Triassic mass extinction. This study highlights the importance of assigning sim- ple to advanced paleoecological characters with integration levels, which opens a useful approach to understanding of mass extinction and the dynamics of the recovery.