Fatigue reliability quantitative analysis of cement concrete for highway pavement under high stress ratio

In order to obtain the change law of the fatigue reliability of cement concrete for highway pavement under high stress ratios, first, the probability densities of monotonic random variables including concrete fatigue life are deduced. And then, the fatigue damage probability densities of the Miner and Chaboche-Zhao models are deduced. By virtue of laboratory fatigue test results, the fatigue damage probability density functions of the two models can be obtained, considering different stress ratios. Finally, substituting load cycles into them, the change law of cement concrete fatigue reliability about load cycles can be acquired. The results show that under the same stress ratio, with the increase in the load cycle, the fatigue reliability declines from almost 100% to 0% gradually. No matter under what stress ratio, during the initial stage of the load action, there is always a relatively stable phase for fatigue reliability. With the increase in the stress ratio, the stable phase gradually shortens and the load cycle corresponding to the reliability of 0% also decreases. In the descent phase of reliability, the higher the stress ratio is, the lower the concrete reliability is for the same load cycle. Besides, compared with the Chaboche-Zhao fatigue damage model, the Miner fatigue damage model is safer.

High-Reliability Photovoltaic Converter Based on Improved PSO Algorithm

An improved particle swarm optimization(PSO)algorithm based on dynamic inertia weight and adjustment coefficient is proposed in this paper.The expressions of inertia weight and adjustment coefficient are established based on inter-particle distance and iterations.The improved algorithm is applied to a novel two-stage photovoltaic(PV)converter.The later DC/AC circuit chooses a dual-DC-input multi-level dual-buck inverter.This converter has the advantages of no shoot-through problem and high efficiency.Finally,the validity and effectiveness of the algorithm and the converter are verified with experimental results.

Technology Improvement for the High Reliability LM-2F Launch Vehicle

The Long March 2 F(LM-2F) launch vehicle, the only launch vehicle designed for manned space flight in China, successfully launched the Tiangong 2 space laboratory and the Shenzhou 11 manned spaceship into orbits in 2016 respectively. In this study, it introduces the technological improvements for enhancing the reliability of the LM-2F launch vehicle in the aspects of general technology, control system, manufacture and ground support system. The LM-2F launch vehicle will continue to provide more contributions to the Chinese Space Station Project with its high reliability and 100% success rate.

The Reliability of the Prowler in High School Male Football Players

Horizontal plane muscular power output is important in sports such as football especially for down lineman who must engage an opponent and push them for a number of yards. The Prowler resistance sled is a commonly used apparatus that aids in the development of horizontal plane muscular power output. However, there is limited documentation regarding the Prowler＇s role as a strength and conditioning training modality as well as its potential use as an assessment tool for measuring horizontal plane muscular power output. Hence, the purpose of this study was to assess the reliability of the Prowler sled push in High School male football players. High School male football players （n = 16） performed two trials of the Prowler sled push 91 kilograms （200 pounds） for a distance of 9.1 meters （10 yards）. Each trial was timed with a handheld stop watch with a 2-3 minute rest period between trials. The trial 1 and 2 scores were 5.14 ±0.95 and 5.15 ±0.88 seconds respectively. The interclass and intraclass reliability coefficients were r = 0.93 and ICC = 0.93. The standard error of the measure was SEre = 0.25 seconds with 90% confidence limits Of UL： 0.36, LL： 0.20. The mean difference between trials was 0.01 ±0.36 seconds （90% confidence limits Of UL： 0.17, LL： -0.14）. Within the parameters of this study, the Prowler sled push is a highly reliable field test for measuring horizontal plane muscular power output.

The Reliability of the 300-Yard Shuttle Run in High School Girls Basketball Players

The 300-yard shuttle run is a field test commonly used to assess anaerobic capacity. There is limited documentation regarding the reliability of the shuttle run for various populations. The purpose of this study was to assess the reliability of the 300-yard shuttle run in High School girls basketball players. Thirty nine High School girls basketball players performed two separate sessions of the 300-yard shuttle run. During each session, the participants completed two trials of the 300-yard shuttle run separated by a 5-minute rest period. The trial 1 and 2 scores were 66.2 - 4.9 and 69.1 - 6.0 seconds, respectively. The interclass and intraclass reliability coefficients were r = 0.84 and ICC = 0.83. The standard error of the measure was SEm = 2.2 seconds with 90% confidence limits Of UL： 2.6, LL： 1.9. The typical error expressed as a coefficient of variation percent was CV% = 3.2 with 90% confidence limits Of UL： 3.7, LL： 2.8. Within the parameters of this study, the 300-yard shuttle run is a sufficiently reliable field test for measuring anaerobic capacity.

Develop Highly Reliable and Low-Cost Technology for Access to Space,Embrace the New Space Economy Era

The worldwide space industry has entered a new space economy era.The question is how to develop in this new era?This paper tries to answer this question from two aspects:highly reliable and low-cost technology for access to space,and the cislunar economic zone.Firstly,the development requirement of the future space transportation system is discussed and the development path to enable high-reliability and a low cost of space transportation system is analyzed.Moreover,the concept of a routine space transportation system is proposed,upon which this paper gives some thoughts to the development of the cislunar economic zone thus embracing the new space economy era.

Evaluation on Safety and Reliability of High-Pressure Vessel in Missile System

Through theoretical analysis of reliability and simulation analysis of dispersivi of d a/ d N based on Monte Carlo method, the distribution function of n and c was set up. Meanwhile, the distribution of critical opening displacement(COD)δ c was defined by the use of coherent coefficient method, and the probabilistic model of defects assessment of military special vessel was built. Thereby the theoretical and practical fundamental research on evaluation of reliability of military high pressure vessels was carried out.

HIGH CYCLE FATIGUE RELIABILITY ANALYSIS ON ROTOR HUB BASED ON APPROXIMATION TECHNIQUE

A high cycle fatigue reliability analysis approach to helicopter rotor hub is proposed under working load spectrum. Automatic calculation for the approach is implemented through writing the calculating programs. In the system, the modification of geometric model of rotor hub is controlled by several parameters, and finite element method and S-N curve method are then employed to solve the fatigue life by automatically assigned parameters. A database between assigned parameters and fatigue life is obtained via Latin Hypercube Sampling （LHS） on toler- ance zone of rotor hub. Different data-fitting technologies are used and compared to determine a highest-precision approximation for this database. The parameters are assumed to he independent of each other and follow normal distributions. Fatigue reliability is then computed by the Monte Carlo （MC） method and the mean-value first order second moment （MFOSM） method. Results show that the approach has high efficiency and precision, and is suit- able for engineering application.

Research on Real-Time High Reliable Network File Distribution Technology

The rapid development of Internet of Things(IoT)technology has made previously unavailable data available,and applications can take advantage of device data for people to visualize,explore,and build complex analyses.As the size of the network and the number of network users continue to increase,network requests tend to aggregate on a small number of network resources,which results in uneven load on network requests.Real-time,highly reliable network file distribution technology is of great importance in the Internet of Things.This paper studies real-time and highly reliable file distribution technology for large-scale networks.In response to this topic,this paper studies the current file distribution technology,proposes a file distribution model,and proposes a corresponding load balancing method based on the file distribution model.Experiments show that the system has achieved real-time and high reliability of network transmission.

Reliability and validity of the hidden hunger assessment scale in China-revised for high school students

Objective:Hidden hunger remains a severe public health problem that affects millions of people worldwide.In China,challenges related to dietary imbalance and hidden hunger persist.Micronutrient inadequacy deserves more attention among adolescents,given its vital role in their growth and development;however,this problem appears to have been largely ignored.High school students,in particular,are often at a high risk of hidden hunger but have limited assessment tools available.Therefore,this study aims to revise the hidden hunger assessment scale for high school students(HHAS-HSS)in China and assess its reliability and validity.Methods:Based on a literature review,expert consultation,pre-experiment,and formal survey,a hidden hunger assessment scale was revised for high school students.The formal survey involved 9336 high school students in 11 of the 16 cities in Anhui Province,China,and 9038 valid questionnaires were collected and included in the analysis.The item analysis,internal consistency reliability,test-retest reliability,content validity,exploratory factor analysis,and confirmatory factor analysis of the HHAS-HSS were examined.Results:The HHAS-HSS included a total of 4 dimensions and 12 items:"vegetables and food diversity"(three items),"fruits and dairy products"(three items),"micronutrient-dense foods"(four items),and"health condition and eating habits"(two items).The results showed a Cronbach's alpha of 0.758,a split-half reliability of 0.829,and a test-retest reliability of o.793,indicating good internal consistency.Using the Bartlett's test and Kaiser-Meyer-Olkin test(KMO)to test the exploratory factor analysis presented a four-factor model of the HHAS-HSS,the KMO0 value was 0.820(P<0.001),which indicated the possibility for factor confirmatory factor analysis.Using the maximum variance rotation method,four factors were obtained,and the cumulative variance explained rate was 57.974%.Confirmatory factor analysis also supported the division of the scale into four dimensions,and the fitting indices were x^(2)=1417.656,x^(2)/df=29.534,goodness-of-fit index=0.974,adjusted goodnessof-fit index=0.958,parsimonious goodness-of-fit index=0.600,normed fit index=0.938,incremental fit index=0.940,Tucker-Lewis index=0.917,comparative fit index=0.939,and root mean square error of approximation=0.056.Except for x^(2)/df,all the indices reached the fitting standard,and the above results showed that the construct validity of the scale reached an acceptable level.Conclusions:The HHAS-HSS has good validity and reliability for Chinese high school students.It is a convenient self-report measure of hidden hunger risk.

The Reliability of the Anaerobic Power Dummy Throw Test in High School Wrestlers:A Pilot Study

AP(anaerobic power)output is an important physical characteristic that is required to succeed in sports such as wrestling.The Wingate test is considered the Gold Standard for assessing AP but is not specific to the sport of wrestling.The purpose of this study was to examine the reliability of a novel field test known as the LWAPT(Lopez wrestling anaerobic power test)for the assessment of AP.The participants were male high school wrestlers(n=10,age:17.0±0.8 yrs,mass:70.9±10.2 kgs).The participants met on one occasion in order to complete the testing protocol.The protocol initiated with the participants completing a 10-15 minute dynamic WU(warm-up)that included three practice dummy throw attempts(dummy mass=31.75 kgs).Following the dynamic WU(≈5 minutes),the participants performed two trials of the LWAPT.In order to perform the LWAPT,wrestlers stood behind the wrestling dummy in a squat position with legs bent at 45-90 degrees.Next the wrestlers wrapped their arms around the waist of the dummy and on the signal“go”the wrestlers quickly exploded up,lifting the dummy by getting triple extension with the ankles,knees and hips as one would in a power clean.After the wrestler was fully extended,he turned in midair in order to drive the dummy onto its stomach on the ground,where the wrestler was on top of the back of the dummy(a common position after an opponent has been thrown).The participant then repositioned the dummy to the original position to execute another throw.The participants completed as many dummy throws as possible during the one minute trials.The LWAPT trials were separated by 15 minutes.The trial scores were 15.6±2.5 and 17.2±1.5 throws respectively.The interclass and intraclass reliability coefficients were r=0.84 and ICC=0.80.The standard error of the measure was SEm=1.0 throws with 90%confidence limits of UL:1.7,LL:0.7.The mean difference between trials was 1.6±1.4 throws(90%confidence limits of UL:2.4,LL:0.8).Bland-Altman plots suggested agreement between trials with no evidence of heteroscedasticity.The LWAPT exhibits moderate to high reliability as an assessment of AP.The inclusion of additional dummy throw trials to the assessment protocol may enhance the degree of reliability of the dummy throw test as a measure of AP.

HYBRID REDUNDANCY APPROACH TO INCREASE THE RELIABILITY OF FPGA BASED SPEED CONTROLLER CORE FOR HIGH SPEED TRAIN

With the progress of the railway technology, the railway transportation is becoming more efficient, intelligent and faster. High speed trains, as a major part of the railway transportation, are engaged with passenger's safety, and therefore the reliability issue is very important in such vital systems. In this paper, a dependable speed controller core based on FPGA has been developed for high speed trains. To improve the reliability and mitigate single upset faults on basic speed controller, this paper proposes a new effective method which is based on hardware redundancy. In the proposed Hybrid Dual Duplex Redundancy(HDDR) method, the original controller is quadruplicated and correct values are voted through the comparator and error detection unit. We have analyzed the proposed system with Reliability, Availability, Mean time to failure and Security(RAMS) theory in order to evaluate the effectiveness of proposed scheme. Theoretical analysis shows that the Mean Time To Failure(MTTF) of the proposed system is 2.5 times better than the traditional Triple Modular Redundancy(TMR). Furthermore, the fault injection experimental results reveal that the capability of tolerating Single Event Upsets(SEUs) in the proposed method increases up to 7.5 times with respect to a regular speed controller.

High Reliability LM-2F Launch Vehicle for Space Station Mission

As China’s only manned launch vehicle,the LM-2 F Launch vehicle successfully launched the Shenzhou 12 manned spacecraft into its predetermined orbit on June 12,2021,signifying the successful completion of the first manned launch mission in the construction and key technology test stage of China Space Station(CSS).From the launch of the Shenzhou 11 manned spacecraft on October 12,2016 to the launch of Shenzhou 12 in 2021,over the past five years,the LM-2 F launch vehicle has been continuously improved in terms of product reliability through technological innovation and design improvement,and its flight reliability index has increased from 0.97 to 0.98.Based on the new launch mission requirements for the construction stage of CSS,this paper introduces the technological innovation and reliability improvement methods of the LM-2 F from the aspects of design improvement,research methods and process optimization.The LM-2 F launch vehicle will make greater contributions in supporting the construction of CSS with higher reliability and perfect launch success rate.

A Reliable Adaptive High-Definition Transmission System for Distance Learning

There is an increasing demand for supporting high-quality real-time audiovisual services for the next generation wired and wireless networks. However, due to variety of bandwidths of different networks, it is a great challenge for deployment. In this paper, a novel high-definition (HD) video transmission system was proposed which depends upon reliable compound multicast protocols and QoS control over the various kinds of networks. This system detects client's network condition and assigns it to a proper proxy. Each proxy is capable of detecting network parameters and adaptively tuning such transport parameters as bit rate, video resolution, frame rate and QoS mechanisms to this condition. It also provides FEC error recovery under consideration of characteristics of MPEG4 video codec. Our simulation demonstrates that different network clients such as ADSL, CERNET, and CERNET2 can receive more video reliability with less delay.

Evaluation of thermal resistance constitution for packaged AlGaN/GaN high electron mobility transistors by structure function method

The evaluation of thermal resistance constitution for packaged A1GaN/GaN high electron mobility transistor （HEMT） by structure function method is proposed in this paper. The evaluation is based on the transient heating measurement of the A1GaN/GaN HEMT by pulsed electrical temperature sensitive parameter method. The extracted chip-level and package-level thermal resistances of the packaged multi-finger A1GaN/GaN HEMT with 400μm SiC substrate are 22.5 K/W and 7.2 K/W respectively, which provides a non-invasive method to evaluate the chip-level thermal resistance of packaged A1GaN/GaN HEMTs. It is also experimentally proved that the extraction of the chip- level thermal resistance by this proposed method is not influenced by package form of the tested device and temperature boundary condition of measurement stage.

Reliability and sensitivity analyses of HPT blade-tip radial running clearance using multiply response surface model

To reasonably design the blade-tip radial running clearance(BTRRC) of high pressure turbine and improve the performance and reliability of gas turbine, the multi-object multi-discipline reliability sensitivity analysis of BTRRC was accomplished from a probabilistic prospective by considering nonlinear material attributes and dynamic loads. Firstly, multiply response surface model(MRSM) was proposed and the mathematical model of this method was established based on quadratic function. Secondly, the BTRRC was decomposed into three sub-components(turbine disk, blade and casing), and then the single response surface functions(SRSFs) of three structures were built in line with the basic idea of MRSM. Thirdly, the response surface function(MRSM) of BTRRC was reshaped by coordinating SRSFs. From the analysis, it is acquired to probabilistic distribution characteristics of input-output variables, failure probabilities of blade-tip clearance under different static blade-tip clearances δ and major factors impacting BTRRC. Considering the reliability and efficiency of gas turbine, δ=1.87 mm is an optimally acceptable option for rational BTRRC. Through the comparison of three analysis methods(Monte Carlo method, traditional response surface method and MRSM), the results show that MRSM has higher accuracy and higher efficiency in reliability sensitivity analysis of BTRRC. These strengths are likely to become more prominent with the increasing times of simulations. The present study offers an effective and promising approach for reliability sensitivity analysis and optimal design of complex dynamic assembly relationship.

Progress in high-speed train technology around the world

This is a review of high-speed train development in the sense of technology advances all over the world. Three generations of high-speed trains are classified according to their technical characteristics and maximum operating speed. Emphasis is given to the newly developed high-speed train in China, CRH380. The theoretical foundations and future development of CRH380 are briefly discussed.

Structural reliability analysis using a hybrid HDMR-ANN method

A new hybrid method is proposed to estimate the failure probability of a structure subject to random parameters. The high dimensional model representation(HDMR) combined with artificial neural network(ANN) is used to approximate implicit limit state functions in structural reliability analysis. HDMR facilitates the lower dimensional approximation of the original limit states function. For evaluating the failure probability, a first-order HDMR approximation is constructed by deploying sampling points along each random variable axis and hence obtaining the structural responses. To reduce the computational effort of the evaluation of limit state function, an ANN surrogate is trained based on the sampling points from HDMR. The component of the approximated function in HDMR can be regarded as the input of the ANN and the response of limit state function can be regarded as the target for training an ANN surrogate. This trained ANN surrogate is used to obtain structural outputs instead of directly calling the numerical model of a structure. After generating the ANN surrogate, Monte Carlo simulation(MCS) is performed to obtain the failure probability, based on the trained ANN surrogate. Three numerical examples are used to illustrate the accuracy and efficiency of the proposed method.

Slope reliability analysis based on Monte Carlo simulation and sparse grid method

In order to solve the problem of the reliability of slope engineering due to complex uncertainties, the Monte Carlo simulation method is adopted. Based on the characteristics of sparse grid, an interpolation algorithm, which can be applied to high dimensional problems, is introduced. A surrogate model of high dimensional implicit function is established, which makes Monte Carlo method more adaptable. Finally, a reliability analysis method is proposed to evaluate the reliability of the slope engineering, and is applied in the Sau Mau Ping slope project in Hong Kong. The reliability analysis method has great theoretical and practical significance for engineering quality evaluation and natural disaster assessment.

Reliability Assessment Method Based on Interference Variable for Stress-Strength Model

Stress-strength model is a basic and important tool for reliability analysis.There are few methods to assess the confidence limit of interference reliability when the distribution parameters of stress and strength are all unknown.A new assessment method of interference reliability is proposed and the estimates of the distribution parameters are accordingly given.The lower confidence limit of interference reliability with given confidence can be obtained with the method even though the parameters are all unknown.Simulation studies and an engineering application are conducted to validate the method,which suggest that the method provides precise estimates even for sample size of approximately.