Reliability Sensitivity-based Correlation Coefficient Calculation in Structural Reliability Analysis

The correlation coefficients of random variables of mechanical structures are generally chosen with experience or even ignored,which cannot actually reflect the effects of parameter uncertainties on reliability.To discuss the selection problem of the correlation coefficients from the reliability-based sensitivity point of view,the theory principle of the problem is established based on the results of the reliability sensitivity,and the criterion of correlation among random variables is shown.The values of the correlation coefficients are obtained according to the proposed principle and the reliability sensitivity problem is discussed.Numerical studies have shown the following results：（1） If the sensitivity value of correlation coefficient ρ is less than（at what magnitude 0.000 01）,then the correlation could be ignored,which could simplify the procedure without introducing additional error.（2） However,as the difference between ρs,that is the most sensitive to the reliability,and ρR,that is with the smallest reliability,is less than 0.001,ρs is suggested to model the dependency of random variables.This could ensure the robust quality of system without the loss of safety requirement.（3） In the case of ｜Eabs｜ρ0.001 and also ｜Erel｜ρ0.001,ρR should be employed to quantify the correlation among random variables in order to ensure the accuracy of reliability analysis.Application of the proposed approach could provide a practical routine for mechanical design and manufactory to study the reliability and reliability-based sensitivity of basic design variables in mechanical reliability analysis and design.

A nonlinear interface structural damage model between ice crystal and frozen clay soil

The shear properties of ice-frozen soil interface are important when studying the constitutive model of frozen soil and slope stability in cold regions. In this research, a series of cryogenic direct shear tests for ice-frozen clay soil interface were conducted. Based on experimental results, a nonlinear interface structural damage model is proposed to describe the shear properties of ice-frozen clay soil interface. Firstly, the cementation and friction structural properties of frozen soil materials were analyzed, and a structural parameter of the ice-frozen clay soil interface is proposed based on the cryogenic direct shear test results. Secondly, a structural coefficient ratio is proposed to describe the structural development degree of ice-frozen clay soil interface under load, which is able to normalize the shear stress of ice-frozen clay soil interface,and the normalized data can be described by the Duncan-Chang model. Finally, the tangent stiffness of ice-frozen clay soil interface is calculated, which can be applied to the mechanics analysis of frozen soil. Also, the shear stress of ice-frozen clay soil interface calculated by the proposed model is compared with test results.

Variability of phytoplankton absorption in the northern South China Sea:influence of the size structure and pigment composition of algal populations

Data from three cruises conducted in the Zhujiang River （ZR）, coastal waters of Guangdong （CWGD） and the northern South China Sea （NSCS） during 2003 and 2004 were examined for assessing the relative importance of pigment composition and packaging effect in modifying the specific absorption coefficients of phytoplankton. The three survey regions differ widely in their phytoplankton community with large cells dominating the ZR and CWGD waters and small cells dominating the NSCS region. Variations in the size structure and the accessory pigments have much effect on the chlorophyll a-specific absorption coefficient of phytoplankton. The size index accounted for about 42% and 33% of the variation of the specific absorption coefficient at 440 and 675 nm, respectively. Using the multiple regression analysis approach, pigment concentrations for each sample were calculated. The accessory pigments other than chlorophyll a contribute to absorption mainly in the blue - to - green region of the spectrum and their absorptions account for about 44%, 43% and 53% on the average of the total phytoplankton absorption at 440 nm for the ZR, CWGD and NSCS regions. Among the accessory pigments, the photosynthetic carotenoids （noted PSC） play a dominant role in the ZR and CWGD waters, while in the NSCS the nonphotosynthetic carotenoids （noted PPG） as well as PSC have important contributions. Because the variations of both the size structure and accessory pigments in algal populations contributed to the variability of the specific absorption coefficient in the study regions, these factors may be considered explicitly in future bio - optical algorithms to derive chlorophyll a concentration more accurately.

Application of Air-cooled Blast Furnace Slag Aggregates as Replacement of Natural Aggregates in Cement-based Materials：A Study on Water Absorption Property

The influence of air-cooled blast furnace slag aggregates as replacement of natural aggregates on the water absorption of concrete and mortar was studied, and the mechanism was analyzed. The interface between aggregate and matrix in concrete was analyzed by using a micro-hardness tester, a laser confocal microscope and a scanning electron microscope with backscattered electron image mode. The pore structure of mortar matrixes under different curing conditions was investigated by mercury intrusion porosimetry. The results showed that when natural aggregates were replaced with air-cooled blast furnace slag aggregates in mortar or concrete, the content of the capillary pore in the mortar matrix was reduced and the interfacial structure between aggregate and matrix was improved, resulting in the lower water absorption of mortar or concrete. Compared to the concrete made with crushed limestone and natural river sand, the initial absorption coefficient, the secondary absorption coefficient and the water absorption capacity through the surface for 7 d of the concrete made from crushed air-cooled blast furnace slag and air-cooled blast furnace slag sand were reduced by 48.9%, 52.8%, and 46.5%, respectively.

Evaluating agricultural water-use efficiency based on water footprint of crop values: a case study in Xinjiang of China

Efficient agricultural water use is crucial for food safety and water conservation on a global scale. To quantitatively investigate the agricultural water-use efficiency in regions exhibiting the complex agricultural structure, this study developed an indicator named water footprint of crop values(WFV) that is based on the water footprint of crop production. Defined as the water volume used to produce a unit price of crop(m^3/CNY), the new indicator makes it feasible to directly compare the water footprint of different crops from an economic perspective, so as to comprehensively evaluate the water-use efficiency under the complex planting structure. On the basis of WFV, the study further proposed an indicator of structural water-use coefficient(SWUC), which is represented by the ratio of water-use efficiency for a given planting structure to the water efficiency for a reference crop and can quantitatively describe the impact of planting structure on agricultural water efficiency. Then, a case study was implemented in Xinjiang Uygur Autonomous Region of China. The temporal and spatial variations of WFV were assessed for the planting industries in 14 prefectures and cities of Xinjiang between 1991 and 2015. In addition, contribution rate analysis of WFV for different prefectures and cities was conducted to evaluate the variations of WFV caused by different influencing factors: agricultural input, climatic factors, and planting structure. Results from these analyses indicated first that the average WFV of planting industries in Xinjiang significantly decreased from 0.293 m^3/CNY in 1991 to 0.153 m^3/CNY in 2015, corresponding to an average annual change rate of –3.532%. WFV in 13 prefectures and cities(with the exception of Karamay) has declined significantly during the period of 1991–2015, indicating that agricultural water-use efficient has effectively improved. Second, the average SWUC in Xinjiang decreased from 1.17 to 1.08 m^3/CNY in the 1990 s, and then declined to 1.00 m^3/CNY in 2011–2015. The value of SWUC was highly consistent with the relative value of WFV in most prefectures and cities, showing that planting structure is one of the primary factors affecting regional agricultural water-use efficiency. Third, the contribution rate of WFV variations from human factors including agricultural input and planting structure was much more significant than that from climatic factors. However, the distribution of agricultural input and the adjustment of planting structure significantly differed among prefectures and cities, suggesting regional imbalances of agricultural development. This study indicated the feasibility and effectiveness of controlling agricultural water use through increasing technical input and rational selection of crops in the face of impending climate change. Specifically, we concluded that, the rational application of chemical fertilizers, the development of the fruit industry, and the strict restriction of the cotton industry should be implemented to improve the agricultural water-use efficiency in Xinjiang.

Adaptive evolvement of information age C^4ISR structure

Command, control, communication, computing, intel- ligence, surveillance and reconnaissance （C^4ISR） in information age is a complex system whose structure always changes ac- tively or passively during the warfare. Therefore, it is important to optimize the structure, especially in ambiguous and quick-tempo modern warfare. This paper proposes an adaptive evolvement mechanism for the C^4ISR structure to survive the changeable warfare. Firstly, the information age C^4ISR structure is defined and modeled based on the complex network theory. Secondly, taking the observe, orient, decide and act （OODA） model into consideration, four kinds of loops in the C^4ISR structure are pro- posed and their coefficient of networked effects （CNE） is further defined. Then, the adaptive evolvement mechanisms of the four kinds of loops are presented respectively. Finally, taking the joint air-defense C^4ISR as an example, simulation experiments are im- plemented, which validate the evolvement mechanism and show that the information age C41SR structure has some characteristics of small-world network and scale-free network.

Study on Ecological Carrying Capacity of Land in Henan Province

In order to explore the technical methods to improve the ecological carrying capacity of regional land under the premise of limited land use area,an open ecological footprint model is established based on the traditional ecological footprint model.Using the two models,this paper evaluates the ecological carrying capacity of Henan Province in 2017.The results indicate that the ecological productive footprint of cultivated land in Henan Province is much larger than the ecological carrying capacity,but the ecological consumption footprint is lower than the ecological carrying capacity.The open ecological footprint model can clearly distinguish the internal and the external ecological consumption footprint after corrected by the consumption adjustment coefficient and the land-use structure adjustment coefficient.Based on the open ecological footprint model,the ecological carrying capacity evaluation results of Henan Province are more realistic.The comprehensive ecological carrying capacity in Henan Province has a surplus,but there are significant differences among different land use types.The cultivated land has the largest ecological carrying capacity surplus,while the fossil energy land has a larger ecological carrying capacity deficit.In the process of achieving sustainable development,Henan Province should focus on reducing energy consumption and improving the ecological carrying capacity of fossil energy land.The paper concludes that the open ecological footprint model can simulate the ecological carrying capacity under different land use structures and different consumption structures.According to the simulation results,the technical methods to improve the ecological carrying capacity under the premise of limited land use scale can be proposed.The research can provide reference for land use structure adjustment,land use planning and land protection in Henan Province.It can also provide scientific basis for ecological protection and high-quality development of the Yellow River basin.

Music/voice separation based on the multi-repeating structure of Mel cepstrum coefficient

For the poor adaptability of the original repeating pattern, an improved music separation method of multi-repeating structure of Mel cepstrum coefficient （MFCC） is proposed. Firstly, the MFCC coefficient matrix （39-dimensional data） of the music signal was extracted. Then the cosine characteristic was applied to the count of similarity matrix of MFCC, and the fragments with consistent similarity are putted together. Next different repeating patterns are built for different groups. Thereby the spectrums of the background music and vocal were separated combined with ideal binary masking （IBM）, and the corresponding time domain signals were obtained by inverse Fourier transform. Fnally, the improved method was tested on the music database of different types and length, and the separation results were compared with repeating method of Rafii and the non-negative matrix factorization based on flexible framework method of Ozerov. The experimental results showed that the separation performance of improved method was improved about 3 dB, and the performance of music with melody changed larger was significantly improved. Experiments verified that the improved method was an effective music separation algorithm and more stability.

Ferroelectric-to-relaxor transition and ultrahigh electrostrictive effect in Sm^(3+)-doped Pb(Mg_(1/3)Nb_(2/3))O_(3)-PbTiO_(3)ferroelectrics ceramics

Rare-earth Sm^(3+)-doped Pb(Mg_(1/3)Nb_(2/3))O_(3)-0.25PbTiO_(3)(PMN-0.25PT)ferroelectric ceramics with doping amounts between 0%-3%were developed via a conventional solid-state method.The doping effect of Sm^(3+)ions on the PMN-0.25PT matrix was systematically investigated on the basis of the phase structure,temperature-dependent dielectric,ferroelectric,and electrotechnical properties.Due to the disruption of long-range ferroelectric order,the addition of Sm^(3+)ions effectively lowers the Tm(temperature corresponding to maximum permittivity)of the samples,leading to enhanced relaxor ferroelectric(RFE)characteristic and superior electric field-induced strain(electrostrain)properties at room temperature.Intriguingly,a considerable large-signal equivalent piezoelectric coefficient d∗_(33)of 2376 pm/V and a very small hysteresis were attained in the PMN-0.25PT component doped with 2.5 mol.%Sm^(3+).The findings of piezoelectric force microscopy indicate that the addition of Sm^(3+)increases the local structural heterogeneity of the PMN-0.25PT matrix and that the enhanced electromechanical performance is due to the dynamic behavior of polar nanoregions.Importantly,strong temperature-dependent electrostrain and electrostrictive coefficient Q33 are observed in the critical region around Tm in all Sm^(3+)-modified PMN-0.25PT ceramic samples studied.This work elucidates the phase transition behavior of Sm^(3+)-doped PMN-0.25PT and reveals a critical region where electrostrictive properties can be greatly improved due to a strong temperature-dependent characteristic.

Anti-clogging ability of the labyrinth emitter and its evaluation method

Emitter clogging is one of the most serious factors that restrict the drip irrigation system operation and water use efficiency.To scientifically characterize and evaluate emitter clogging risk,a literature review,short-period emitter anti-clogging tests,and CFD(Computational Fluid Dynamics)hydraulic performance tests were conducted.Results showed that the emitter anti-clogging ability is related to its structure,material,and processing technology,not external factors.This was evidenced in the irrigation tests,as with the different water qualities,the same emitters were repeatedly prone to clog or to avoid clogging.A predictive model of structural resistance coefficient(Cs),a quantitative indicator of the emitter anti-clogging ability,whose value ranges between 0 and 1,was utilized.Larger Cs values indicate a lower anti-clogging ability and thus a higher risk of clogging.A good linear relationship between Cs and the relative flow rate was detected,and the Cs relationship with the fluidity index(x)was determined to be a power function.The Cs should be controlled within the range of 0.146-0.461 when designing new emitters to ensure that they have good anti-clogging properties.This research will provide theoretical guidance for the anti-clogging management of drip irrigation systems and for the design of optimal emitter structures.