This study examines the connectedness between the US yield curve components(i.e.,level,slope,and curvature),exchange rates,and the historical volatility of the exchange rates of the main safe-haven fiat currencies(Can...This study examines the connectedness between the US yield curve components(i.e.,level,slope,and curvature),exchange rates,and the historical volatility of the exchange rates of the main safe-haven fiat currencies(Canada,Switzerland,EURO,Japan,and the UK)and the leading cryptocurrency,the Bitcoin.Results of the static analysis show that the level and slope of the yield curve are net transmitters of shocks to both the exchange rate and its volatility.The exchange rate of the Euro and the volatility of the Euro and the Canadian dollar exchange rate are net transmitters of shocks.Meanwhile,the curvature of the yield curve and the Japanese Yen,Swiss Franc,and British Pound act mainly as net receivers.Our static connectedness analysis shows that Bitcoin is mainly independent of shocks from the yield curve’s level,slope,and curvature,and from any main currency investigated.These findings hint that Bitcoin might provide hedging benefits.However,similar to the static analysis,our dynamic analysis shows that during different periods and particularly in stressful times,Bitcoin is far from being isolated from other currencies or the yield curve components.The dynamic analysis allows us to observe Bitcoin’s connectedness in times of stress.Evidence supporting this contention is the substantially increased connectedness due to policy shocks,political uncertainty,and systemic crisis,implying no empirical support for Bitcoin’s safe-haven property during stress times.The increased connectedness in the dynamic analysis compared with the static approach implies that in normal times and especially in stressful times,Bitcoin has the property of a diversifier.The results may have important implications for investors and policymakers regarding their risk monitoring and their assets allocation and investment strategies.展开更多
For general volatility structures for forward rates, the evolution of interest rates may not be Markovian and the entire path may be necessary to capture the dynamics of the term structure. This article identifies con...For general volatility structures for forward rates, the evolution of interest rates may not be Markovian and the entire path may be necessary to capture the dynamics of the term structure. This article identifies conditions on the volatility structure of forward rates that permit the dynamics of the term structure to be represented by a finite-dimensional state variable Markov process. In the deterministic volatility case, we interpret then-factor model as a sum ofn unidimensional models.展开更多
In light of the nonlinear approaching capability of artificial neural networks ( ANN), the term structure of interest rates is predicted using The generalized regression neural network (GRNN) and back propagation ...In light of the nonlinear approaching capability of artificial neural networks ( ANN), the term structure of interest rates is predicted using The generalized regression neural network (GRNN) and back propagation (BP) neural networks models. The prediction performance is measured with US interest rate data. Then, RBF and BP models are compared with Vasicek's model and Cox-Ingersoll-Ross (CIR) model. The comparison reveals that neural network models outperform Vasicek's model and CIR model, which are more precise and closer to the real market situation.展开更多
Short Retraction NoticeThe paper does not meet the standards of "Journal of Applied Mathematics and Physics". This article has been retracted to straighten the academic record. In making this decision the Ed...Short Retraction NoticeThe paper does not meet the standards of "Journal of Applied Mathematics and Physics". This article has been retracted to straighten the academic record. In making this decision the Editorial Board follows COPE's Retraction Guidelines. The aim is to promote the circulation of scientific research by offering an ideal research publication platform with due consideration of internationally accepted standards on publication ethics. The Editorial Board would like to extend its sincere apologies for any inconvenience this retraction may have caused.Editor guiding this retraction: Prof. Wen-Xiu Ma (EiC of JAMP)The full retraction notice in PDF is preceding the original paper, which is marked "RETRACTED".展开更多
A term structure model bearing features of stochastic volatility and stochastic mean drift with jump (SVJ-SD model for short) is built in the paper to describe the stochastic behavior of interest rates.Based on samp...A term structure model bearing features of stochastic volatility and stochastic mean drift with jump (SVJ-SD model for short) is built in the paper to describe the stochastic behavior of interest rates.Based on sample data of an interest rate of national bond repurchase,maximum likelihood (ML),linear Kalman filter and efficient method of moments (EMM) are used to estimate the model.While ML works well for simple models,it may lead to considerable deviation in parameter estimation when dynamic risks of interest rates are considered in them.Linear Kalman filter is a tractable and reasonably accurate technique for estimation cases where ML was not feasible.Moreover,when compared with the first two approaches,using EMM can obtain better parameter estimates for complex models with non-affine structures.展开更多
Application of fertilizer has been found to significantly affect soil N cycling. However, a comprehensive understanding of the effects of long-term fertilization on soil gross N transformation rates is still lacking. ...Application of fertilizer has been found to significantly affect soil N cycling. However, a comprehensive understanding of the effects of long-term fertilization on soil gross N transformation rates is still lacking. We compiled data of observations from 10 long-term fertilization experiments and conducted a meta-analysis of the effects of long-term fertilization on soil gross N transformation rates. The results showed that if chemical fertilizers of N, P and K were applied in balance, soil p H decreased very slightly. There was a significantly positive effect of long-term fertilization, either chemical or organic fertilizers or their combinations, on gross N mineralization rate compared to the control treatment(the mean effect size ranged from 1.21 to 1.25 at 95% confidence intervals(CI) with a mean of 1.23), mainly due to the increasing soil total N content. The long-term application of organic fertilizer alone and combining organic and chemical fertilizer could increase the mineralization-immobilization turnover, thus enhance available N for plant while reduce N losses potential compared to the control treatment. However, long-term chemical fertilizer application did not significantly affect the gross NH4+ immobilization rate, but accelerated gross nitrification rate(1.19; 95% CI: 1.08 to 1.31). Thus, long-term chemical fertilizer alone would probably induce higher N losses potential through NO3– leaching and runoff than organic fertilizer application compared to the control treatment. Therefore, in the view of the effects of long-term fertilization on gross N transformation rates, it also supports that organic fertilizer alone or combination of organic and chemical fertilizer could not only improve crop yield, but also increase soil fertility and reduce the N losses potential.展开更多
A structured perturbation analysis of the least squares problem is considered in this paper.The new error bound proves to be sharper than that for general perturbations. We apply the new error bound to study sensitivi...A structured perturbation analysis of the least squares problem is considered in this paper.The new error bound proves to be sharper than that for general perturbations. We apply the new error bound to study sensitivity of changing the knots for curve fitting of interest rate term structure by cubic spline.Numerical experiments are given to illustrate the sharpness of this bound.展开更多
Nelson-Siegel model ( NS model) and 2 extended NS models were compared by using daily interbank government bond data Based on the grouping of bonds according to the residual term to maturity, the empirical research ...Nelson-Siegel model ( NS model) and 2 extended NS models were compared by using daily interbank government bond data Based on the grouping of bonds according to the residual term to maturity, the empirical research proceeded with in-sample and outof-sample tests. The results show that the 3 models are almost equivalent in estimating interbank term structure of interest rates. Within the term to maturities between 0 and 7 years, the gap of the absolute errors of the 3 models between in-sample and out-of-sample is smRller than 0.2 Yuan, and the absolute values of the in-sample and out-of-sample errors are smaller than 0. 1 Yuan, so the estimation is credible. Within the term to maturities between 7 and 20 years, the gap of the absolute errors of the 3 models between in-sample and out-of-sample is larger than 0.4 Yuan, and the absolute values of the in-sample and out-of-sample errors are larger than 1.0 Yuan, so the estimation is incredible.展开更多
The analysis of the microstructural characterization and phase composition of electron beam welded joint zones of Ti- 43Al-9V-O. 3Y alloy has been done in this study. The welded seam is mainly composed of B2 phase, th...The analysis of the microstructural characterization and phase composition of electron beam welded joint zones of Ti- 43Al-9V-O. 3Y alloy has been done in this study. The welded seam is mainly composed of B2 phase, the partial γ + α2 twophase lamellar structure and granular γm phase. And the lanthanon Y existed as YAl2 phase and served as grain refined. The impact of different cooling rates on joint microstructure, fracture characteristic and tensile strength were investigated. The high cooling rate restrained the structural transformation and resulted in the ordering structure. The fracture of the joint was brittle cleavage fracture because the ordering structure went against restraining the crack propagation. With the decrease of cooling rate, the transformation amounts of lamellar structure increased, and the fracture presented the layered and crosslayered characteristic.展开更多
The transformation behavior and microstructure development in the heat affected zone(HAZ) of 800MPa grade ultra fine structured steel was investigated. It was found thatthe HAZ has intermediate temperature transformat...The transformation behavior and microstructure development in the heat affected zone(HAZ) of 800MPa grade ultra fine structured steel was investigated. It was found thatthe HAZ has intermediate temperature transformation characteristics in a wide rangeof cooling rates, with the bainite sheaves consisting of bainite ferrite plates withoutcarbide precipitation and retained austenite in the fast cooling regime. At relativelyhigh cooling rates, which corresponded to low heat inputs, the hardness of the simulatedHAZ was above that of the base metal. When the cooling rate was below 9℃/s, thewelding HAZ would have an obvious softening. The analysis of transformation ratesin continuous cooling processes was completed by numerical differential method. Theresult indicated that the microstructure transformation rate of the HAZ in 800MPagrade ultra fine structured steel changed sharply to slow speeds when the cooling timet_(8/5) is longer than 7s.展开更多
To reduce the cost of backfilling coal mining and utilize the underground space of coal mines,a new backfilling mining method with low backfilling rate called constructional backfilling coal mining(CBCM)is proposed.Th...To reduce the cost of backfilling coal mining and utilize the underground space of coal mines,a new backfilling mining method with low backfilling rate called constructional backfilling coal mining(CBCM)is proposed.The "backfilling body-immediate roof" cooperative bearing structure of CBCM is analyzed by establishing the model of the medium thick plate on an elastic foundation.The influence of the backfilling rate on the stability of overlying strata is analyzed by the numerical simulation experiment.The control effect of CBCM is verified by a physic similar simulation test.The economic benefit of CBCM is analyzed.The conclusions are:the deformation characteristics of the immediate roof and critical backfilling spacing in CBCM can be analyzed based on the Hu Haichang’s theory.Exerting the bearing capacity of the immediate roof is beneficial to the stability of the overlying strata.The CBCM has a good control effect on the overburden in Xinyang Mine when the backfilling rate is lower than 25%.The backfilling cost of per ton coal is 37.39 yuan/t when the backfilling rate is 13.7%,with a decrease rate of 56.63%than the full-filling.The research results can provide theoretical support for the application of CBCM in coal mining.展开更多
The response statistics of a compliant offshore structure excited by slowly varying wave drift forces is calculated by use of a numerical path integral solution method. The path integral solution is based on the Ganss...The response statistics of a compliant offshore structure excited by slowly varying wave drift forces is calculated by use of a numerical path integral solution method. The path integral solution is based on the Ganss-Legendre interpolation scheme, and the values of the response probability density are obtained at the Gauss quadrature points in sub-intervals. It is demonstrated that a distinct advantage of the path integral solution is that the joint probability density of the response displacement and velocity is one of the by products of the calculations. This makes it possible to calculate the mean level up-crossing rates, which provides estimates of the exceedance probabilities of specified response levels for given time periods.展开更多
Transport infrastructure development and perception vary across and within countries, influencing mode choice among road users. This study explores how road users perceive the development of infrastructure modes, serv...Transport infrastructure development and perception vary across and within countries, influencing mode choice among road users. This study explores how road users perceive the development of infrastructure modes, service attributes, embedded safety levels, and commuting modes. Additionally, the research examines whether participants’ environmental backgrounds impact their mode choice patterns. The study gathered responses from 1169 participants residing in two regions of Amman, Jordan, each with distinct infrastructure development and population densities. Participants completed a standardized questionnaire, and several statistical techniques were employed for analysis. The findings revealed that facilities’ infrastructure attributes, development, and safety were assessed using three indices. Both participant groups perceived these indices differently on average. Residents of low population density areas with relatively developed infrastructure showed more consistent assessments, irrespective of their most frequently used mode of transportation, tending towards lower scores. Interestingly, subjective ratings of infrastructure development were higher (4.96) than attribute-based ratings (4.32). Despite their generally low-quality perception, public transportation services received the highest appraisal (4.9). Conversely, pedestrian infrastructure complementing public transport received the lowest assessment (4.57), only slightly higher than street environments (4.59). The study found weak associations between subjective service characteristics ratings. Traveler and trip characteristics influenced mode choice and trips more than infrastructure perception. In conclusion, the study suggests that policies should be developed to encourage green transportation, ensure social equality and safety. In addition, the study contributes to understanding perceptions about transport infrastructure, modes of transportation, and the factors that influence sustainable and equitable transportation systems.展开更多
The effect of vibration(50 Hz)on the formation of aluminum castings of 99.5%purity at various cooling rates was studied.It was found that the presence of vibration leads to an increase in the cooling rate of the casti...The effect of vibration(50 Hz)on the formation of aluminum castings of 99.5%purity at various cooling rates was studied.It was found that the presence of vibration leads to an increase in the cooling rate of the castings.It was found that the higher the speed without vibration,the stronger the effect of increasing the speed when vibration was applied.Apparently,this effect is associated with additional mixing of the melt by free-floating crystals.展开更多
Fiber is highly escapable in conventional slickwater,making it difficult to form fiber-proppant agglomerate with proppant and exhibit limited effectiveness.To solve these problems,a novel structure stabilizer(SS)is de...Fiber is highly escapable in conventional slickwater,making it difficult to form fiber-proppant agglomerate with proppant and exhibit limited effectiveness.To solve these problems,a novel structure stabilizer(SS)is developed.Through microscopic structural observations and performance evaluations in indoor experiments,the mechanism of proppant placement under the action of the SS and the effects of the SS on proppant placement dimensions and fracture conductivity were elucidated.The SS facilitates the formation of robust fiber-proppant agglomerates by polymer,fiber,and quartz sand.Compared to bare proppants,these agglomerates exhibit reduced density,increased volume,and enlarged contact area with the fluid during settlement,leading to heightened buoyancy and drag forces,ultimately resulting in slower settling velocities and enhanced transportability into deeper regions of the fracture.Co-injecting the fiber and the SS alongside the proppant into the reservoir effectively reduces the fiber escape rate,increases the proppant volume in the slickwater,and boosts the proppant placement height,conveyance distance and fracture conductivity,while also decreasing the proppant backflow.Experimental results indicate an optimal SS mass fraction of 0.3%.The application of this SS in over 80 wells targeting tight gas,shale oil,and shale gas reservoirs has substantiated its strong adaptability and general suitability for meeting the production enhancement,cost reduction,and sand control requirements of such wells.展开更多
To investigate the effects of long-term fertilization systems on soil microbial community structure,labile organic carbon and nitrogen and enzyme activity in yellow sand paddy field and upland,a field experiment was c...To investigate the effects of long-term fertilization systems on soil microbial community structure,labile organic carbon and nitrogen and enzyme activity in yellow sand paddy field and upland,a field experiment was conducted at the experimental station of Dongyang Institute of Maize Research in Zhejiang Province,China in 2009.The experiment consisted of six treatments with three replicates,and they were arranged in a completely randomized design,including no fertilization in paddy field (PCK),conventional fertilization in paddy field (PCF),formulated fertilization by soil testing in paddy field (PSTF),formulated fertilization by soil testing with organic manure in paddy field (PSTF+OF),conventional fertilization on upland (DCF),and formulated fertilization by soil testing with organic manure on upland (DSTF+OF).Soil nutrients,enzyme activity,microbial biomass and community structure were determined in 2015.The results showed that compared with no fertilization in paddy field (PCK),fertilization increased soil phosphorus and potassium content,and decreased pH value.No fertilization in paddy field (PCK) had no significant effect on soil culturable microorganisms in paddy field and upland,but formulated fertilization by soil testing with organic manure on upland (DSTF+OF) significantly increased the number of fungi.Formula fertilization by soil testing with organic manure (PSTF+OF) also significantly increased soil microbial biomass carbon and nitrogen in paddy field and upland.Moreover,fertilization had no significant effect on soil cellulase activity,but formula fertilization by soil testing with organic manure (PSTF+OF) significantly increased soil dehydrogenase and catalase activity.Therefore,long-term application of chemical fertilizer with organic fertilizer can effectively improve soil fertility.展开更多
Presents the coordinated controls of nonlinear variable structure with an equivalent control term designed for turbo generators following the theory of nonlinear variable structure control, which integrates the valve ...Presents the coordinated controls of nonlinear variable structure with an equivalent control term designed for turbo generators following the theory of nonlinear variable structure control, which integrates the valve control with the excitation control and reduce the problem of high frequency shiver with conventional variable structure control in addition to a simplified design, and concludes from simulation results that the use of this control can improve the transient of the system.展开更多
After introducing the status quo of farmers' net income and gross output value of agriculture of Sichuan Province,and the changes of agricultural output structure,the regression analysis was conducted on the impac...After introducing the status quo of farmers' net income and gross output value of agriculture of Sichuan Province,and the changes of agricultural output structure,the regression analysis was conducted on the impact of the changes in agricultural structure on the farmers' net income per capita on the strengthen of the data from Sichuan statistical yearbook and by the way of econometrics.The multiple linear regression analysis was conducted on the impact the changes in crop farming on farmers' net income by using logarithmic demand model.The results show that the agricultural structure has transformed from the dominant crop farming to the all-around developmental trend covering the dominant industry,animal husbandry and forestry,fishery and the other industries;the animal husbandry has greatest impact on famers' income per capita and the impact of crop farming is slightly weaker than animal husbandry;the crop farming and animal husbandry develop fairly rapid simultaneously and the two all have great impact in farmers' income;among animal husbandry,the meat and eggs have relatively great impact on farmers' income,while in crop farming,grain plays the dominant role in affecting farmers' income,followed by cash crop.Hence,the relevant countermeasures applied to increase farmers' income are put forward in terms of optimizing the internal structure of agriculture,adjusting the internal structure of crop farming,adjusting the internal structure of animal husbandry and strengthening the support of farmers.展开更多
This study was undertaken to apply Geographic Information System “GIS” (ArcGIS 9.3) for calculating shoreline change rates and back-shore surface area due to these changes, particularly after constructing marine str...This study was undertaken to apply Geographic Information System “GIS” (ArcGIS 9.3) for calculating shoreline change rates and back-shore surface area due to these changes, particularly after constructing marine structures: including seawall, detached breakwaters and groins. Modelbuilder in ArcGIS software was used to design and develop an automated technique, module, for estimating such changes (rate and area). These changes are deduced from analysis of beach-nearshore profile surveys between 1970 and 2010 and shoreline position versus prevailing coastal processes. The results show that the major erosion occurred along the Delta promontories;the shoreline of Rosetta retreated (1.6 km) at an average rate of 60 m/yr with loss of back-shore area 6.4 km2;the coastline of Burullus bulge recessed at mean rate of 6 m/yr and decreasing in beach area of 1.31 km2;and at Damietta (Ras El-Bar) the shoreline moved backward (6 m/yr) with disappeared in beach area of 1.13 km2. The shape and orientation of these promontories contributed to create alternation between wave convergence zone that eventually causes erosion, and divergence zones that experienced shoreline accretion. Finally, the engineering structures didn’t solve or stop the erosion problem but shifted it from one place to another.展开更多
文摘This study examines the connectedness between the US yield curve components(i.e.,level,slope,and curvature),exchange rates,and the historical volatility of the exchange rates of the main safe-haven fiat currencies(Canada,Switzerland,EURO,Japan,and the UK)and the leading cryptocurrency,the Bitcoin.Results of the static analysis show that the level and slope of the yield curve are net transmitters of shocks to both the exchange rate and its volatility.The exchange rate of the Euro and the volatility of the Euro and the Canadian dollar exchange rate are net transmitters of shocks.Meanwhile,the curvature of the yield curve and the Japanese Yen,Swiss Franc,and British Pound act mainly as net receivers.Our static connectedness analysis shows that Bitcoin is mainly independent of shocks from the yield curve’s level,slope,and curvature,and from any main currency investigated.These findings hint that Bitcoin might provide hedging benefits.However,similar to the static analysis,our dynamic analysis shows that during different periods and particularly in stressful times,Bitcoin is far from being isolated from other currencies or the yield curve components.The dynamic analysis allows us to observe Bitcoin’s connectedness in times of stress.Evidence supporting this contention is the substantially increased connectedness due to policy shocks,political uncertainty,and systemic crisis,implying no empirical support for Bitcoin’s safe-haven property during stress times.The increased connectedness in the dynamic analysis compared with the static approach implies that in normal times and especially in stressful times,Bitcoin has the property of a diversifier.The results may have important implications for investors and policymakers regarding their risk monitoring and their assets allocation and investment strategies.
文摘For general volatility structures for forward rates, the evolution of interest rates may not be Markovian and the entire path may be necessary to capture the dynamics of the term structure. This article identifies conditions on the volatility structure of forward rates that permit the dynamics of the term structure to be represented by a finite-dimensional state variable Markov process. In the deterministic volatility case, we interpret then-factor model as a sum ofn unidimensional models.
基金National Natural Science Foundation of China (No.70471051 & No.70671074)
文摘In light of the nonlinear approaching capability of artificial neural networks ( ANN), the term structure of interest rates is predicted using The generalized regression neural network (GRNN) and back propagation (BP) neural networks models. The prediction performance is measured with US interest rate data. Then, RBF and BP models are compared with Vasicek's model and Cox-Ingersoll-Ross (CIR) model. The comparison reveals that neural network models outperform Vasicek's model and CIR model, which are more precise and closer to the real market situation.
文摘Short Retraction NoticeThe paper does not meet the standards of "Journal of Applied Mathematics and Physics". This article has been retracted to straighten the academic record. In making this decision the Editorial Board follows COPE's Retraction Guidelines. The aim is to promote the circulation of scientific research by offering an ideal research publication platform with due consideration of internationally accepted standards on publication ethics. The Editorial Board would like to extend its sincere apologies for any inconvenience this retraction may have caused.Editor guiding this retraction: Prof. Wen-Xiu Ma (EiC of JAMP)The full retraction notice in PDF is preceding the original paper, which is marked "RETRACTED".
基金Sponsored by the National Natural Science Foundation of China(60979010)
文摘A term structure model bearing features of stochastic volatility and stochastic mean drift with jump (SVJ-SD model for short) is built in the paper to describe the stochastic behavior of interest rates.Based on sample data of an interest rate of national bond repurchase,maximum likelihood (ML),linear Kalman filter and efficient method of moments (EMM) are used to estimate the model.While ML works well for simple models,it may lead to considerable deviation in parameter estimation when dynamic risks of interest rates are considered in them.Linear Kalman filter is a tractable and reasonably accurate technique for estimation cases where ML was not feasible.Moreover,when compared with the first two approaches,using EMM can obtain better parameter estimates for complex models with non-affine structures.
基金supported by the National Natural Science Foundation of China (41330744)the “973” Program of China (2014CB953803)the Priority Academic Program Development of Jiangsu Higher Education Institutions, China (164320H116)
文摘Application of fertilizer has been found to significantly affect soil N cycling. However, a comprehensive understanding of the effects of long-term fertilization on soil gross N transformation rates is still lacking. We compiled data of observations from 10 long-term fertilization experiments and conducted a meta-analysis of the effects of long-term fertilization on soil gross N transformation rates. The results showed that if chemical fertilizers of N, P and K were applied in balance, soil p H decreased very slightly. There was a significantly positive effect of long-term fertilization, either chemical or organic fertilizers or their combinations, on gross N mineralization rate compared to the control treatment(the mean effect size ranged from 1.21 to 1.25 at 95% confidence intervals(CI) with a mean of 1.23), mainly due to the increasing soil total N content. The long-term application of organic fertilizer alone and combining organic and chemical fertilizer could increase the mineralization-immobilization turnover, thus enhance available N for plant while reduce N losses potential compared to the control treatment. However, long-term chemical fertilizer application did not significantly affect the gross NH4+ immobilization rate, but accelerated gross nitrification rate(1.19; 95% CI: 1.08 to 1.31). Thus, long-term chemical fertilizer alone would probably induce higher N losses potential through NO3– leaching and runoff than organic fertilizer application compared to the control treatment. Therefore, in the view of the effects of long-term fertilization on gross N transformation rates, it also supports that organic fertilizer alone or combination of organic and chemical fertilizer could not only improve crop yield, but also increase soil fertility and reduce the N losses potential.
基金Funds for Major State The work of the second author is partly supported by the Special Basic Research Projects (2005CB321700)the National Science Foundation of China under grant No. 10571031The work of the third author is partly supported by the National Science Foundation of China under grant No. 10571031.
文摘A structured perturbation analysis of the least squares problem is considered in this paper.The new error bound proves to be sharper than that for general perturbations. We apply the new error bound to study sensitivity of changing the knots for curve fitting of interest rate term structure by cubic spline.Numerical experiments are given to illustrate the sharpness of this bound.
文摘Nelson-Siegel model ( NS model) and 2 extended NS models were compared by using daily interbank government bond data Based on the grouping of bonds according to the residual term to maturity, the empirical research proceeded with in-sample and outof-sample tests. The results show that the 3 models are almost equivalent in estimating interbank term structure of interest rates. Within the term to maturities between 0 and 7 years, the gap of the absolute errors of the 3 models between in-sample and out-of-sample is smRller than 0.2 Yuan, and the absolute values of the in-sample and out-of-sample errors are smaller than 0. 1 Yuan, so the estimation is credible. Within the term to maturities between 7 and 20 years, the gap of the absolute errors of the 3 models between in-sample and out-of-sample is larger than 0.4 Yuan, and the absolute values of the in-sample and out-of-sample errors are larger than 1.0 Yuan, so the estimation is incredible.
文摘The analysis of the microstructural characterization and phase composition of electron beam welded joint zones of Ti- 43Al-9V-O. 3Y alloy has been done in this study. The welded seam is mainly composed of B2 phase, the partial γ + α2 twophase lamellar structure and granular γm phase. And the lanthanon Y existed as YAl2 phase and served as grain refined. The impact of different cooling rates on joint microstructure, fracture characteristic and tensile strength were investigated. The high cooling rate restrained the structural transformation and resulted in the ordering structure. The fracture of the joint was brittle cleavage fracture because the ordering structure went against restraining the crack propagation. With the decrease of cooling rate, the transformation amounts of lamellar structure increased, and the fracture presented the layered and crosslayered characteristic.
文摘The transformation behavior and microstructure development in the heat affected zone(HAZ) of 800MPa grade ultra fine structured steel was investigated. It was found thatthe HAZ has intermediate temperature transformation characteristics in a wide rangeof cooling rates, with the bainite sheaves consisting of bainite ferrite plates withoutcarbide precipitation and retained austenite in the fast cooling regime. At relativelyhigh cooling rates, which corresponded to low heat inputs, the hardness of the simulatedHAZ was above that of the base metal. When the cooling rate was below 9℃/s, thewelding HAZ would have an obvious softening. The analysis of transformation ratesin continuous cooling processes was completed by numerical differential method. Theresult indicated that the microstructure transformation rate of the HAZ in 800MPagrade ultra fine structured steel changed sharply to slow speeds when the cooling timet_(8/5) is longer than 7s.
基金supported by the Youth Funds of National Natural Science Foundation of China(No.52004173)the Distinguished Youth Funds of National Natural Science Foundation of China(No.51925402)+2 种基金the Science and Technology Innovation Project of Colleges and Universities in Shanxi Province(No.2020L0066)the China Postdoctoral Science Foundation(No.2022M712922)the Shanxi-Zheda Institute of Advanced Materials and Chemical Engineering(Nos.2021SX-TD001 and 2022SXTD008).
文摘To reduce the cost of backfilling coal mining and utilize the underground space of coal mines,a new backfilling mining method with low backfilling rate called constructional backfilling coal mining(CBCM)is proposed.The "backfilling body-immediate roof" cooperative bearing structure of CBCM is analyzed by establishing the model of the medium thick plate on an elastic foundation.The influence of the backfilling rate on the stability of overlying strata is analyzed by the numerical simulation experiment.The control effect of CBCM is verified by a physic similar simulation test.The economic benefit of CBCM is analyzed.The conclusions are:the deformation characteristics of the immediate roof and critical backfilling spacing in CBCM can be analyzed based on the Hu Haichang’s theory.Exerting the bearing capacity of the immediate roof is beneficial to the stability of the overlying strata.The CBCM has a good control effect on the overburden in Xinyang Mine when the backfilling rate is lower than 25%.The backfilling cost of per ton coal is 37.39 yuan/t when the backfilling rate is 13.7%,with a decrease rate of 56.63%than the full-filling.The research results can provide theoretical support for the application of CBCM in coal mining.
文摘The response statistics of a compliant offshore structure excited by slowly varying wave drift forces is calculated by use of a numerical path integral solution method. The path integral solution is based on the Ganss-Legendre interpolation scheme, and the values of the response probability density are obtained at the Gauss quadrature points in sub-intervals. It is demonstrated that a distinct advantage of the path integral solution is that the joint probability density of the response displacement and velocity is one of the by products of the calculations. This makes it possible to calculate the mean level up-crossing rates, which provides estimates of the exceedance probabilities of specified response levels for given time periods.
文摘Transport infrastructure development and perception vary across and within countries, influencing mode choice among road users. This study explores how road users perceive the development of infrastructure modes, service attributes, embedded safety levels, and commuting modes. Additionally, the research examines whether participants’ environmental backgrounds impact their mode choice patterns. The study gathered responses from 1169 participants residing in two regions of Amman, Jordan, each with distinct infrastructure development and population densities. Participants completed a standardized questionnaire, and several statistical techniques were employed for analysis. The findings revealed that facilities’ infrastructure attributes, development, and safety were assessed using three indices. Both participant groups perceived these indices differently on average. Residents of low population density areas with relatively developed infrastructure showed more consistent assessments, irrespective of their most frequently used mode of transportation, tending towards lower scores. Interestingly, subjective ratings of infrastructure development were higher (4.96) than attribute-based ratings (4.32). Despite their generally low-quality perception, public transportation services received the highest appraisal (4.9). Conversely, pedestrian infrastructure complementing public transport received the lowest assessment (4.57), only slightly higher than street environments (4.59). The study found weak associations between subjective service characteristics ratings. Traveler and trip characteristics influenced mode choice and trips more than infrastructure perception. In conclusion, the study suggests that policies should be developed to encourage green transportation, ensure social equality and safety. In addition, the study contributes to understanding perceptions about transport infrastructure, modes of transportation, and the factors that influence sustainable and equitable transportation systems.
基金This work was supported by the National Academy of Sciences of Ukraine under Grants#III-21-18-685 and#III-36-21-708.
文摘The effect of vibration(50 Hz)on the formation of aluminum castings of 99.5%purity at various cooling rates was studied.It was found that the presence of vibration leads to an increase in the cooling rate of the castings.It was found that the higher the speed without vibration,the stronger the effect of increasing the speed when vibration was applied.Apparently,this effect is associated with additional mixing of the melt by free-floating crystals.
文摘Fiber is highly escapable in conventional slickwater,making it difficult to form fiber-proppant agglomerate with proppant and exhibit limited effectiveness.To solve these problems,a novel structure stabilizer(SS)is developed.Through microscopic structural observations and performance evaluations in indoor experiments,the mechanism of proppant placement under the action of the SS and the effects of the SS on proppant placement dimensions and fracture conductivity were elucidated.The SS facilitates the formation of robust fiber-proppant agglomerates by polymer,fiber,and quartz sand.Compared to bare proppants,these agglomerates exhibit reduced density,increased volume,and enlarged contact area with the fluid during settlement,leading to heightened buoyancy and drag forces,ultimately resulting in slower settling velocities and enhanced transportability into deeper regions of the fracture.Co-injecting the fiber and the SS alongside the proppant into the reservoir effectively reduces the fiber escape rate,increases the proppant volume in the slickwater,and boosts the proppant placement height,conveyance distance and fracture conductivity,while also decreasing the proppant backflow.Experimental results indicate an optimal SS mass fraction of 0.3%.The application of this SS in over 80 wells targeting tight gas,shale oil,and shale gas reservoirs has substantiated its strong adaptability and general suitability for meeting the production enhancement,cost reduction,and sand control requirements of such wells.
基金Supported by National Modern Agricultural Industrial Technology System(CARS-02-69)Major Agriculture Science Foundation of Upland Grain Crops Breeding of Zhejiang Province(2016C02050-9-1)Project for Training of Youth Talents of Zhejiang Academy of Agricultural Sciences(2015)
文摘To investigate the effects of long-term fertilization systems on soil microbial community structure,labile organic carbon and nitrogen and enzyme activity in yellow sand paddy field and upland,a field experiment was conducted at the experimental station of Dongyang Institute of Maize Research in Zhejiang Province,China in 2009.The experiment consisted of six treatments with three replicates,and they were arranged in a completely randomized design,including no fertilization in paddy field (PCK),conventional fertilization in paddy field (PCF),formulated fertilization by soil testing in paddy field (PSTF),formulated fertilization by soil testing with organic manure in paddy field (PSTF+OF),conventional fertilization on upland (DCF),and formulated fertilization by soil testing with organic manure on upland (DSTF+OF).Soil nutrients,enzyme activity,microbial biomass and community structure were determined in 2015.The results showed that compared with no fertilization in paddy field (PCK),fertilization increased soil phosphorus and potassium content,and decreased pH value.No fertilization in paddy field (PCK) had no significant effect on soil culturable microorganisms in paddy field and upland,but formulated fertilization by soil testing with organic manure on upland (DSTF+OF) significantly increased the number of fungi.Formula fertilization by soil testing with organic manure (PSTF+OF) also significantly increased soil microbial biomass carbon and nitrogen in paddy field and upland.Moreover,fertilization had no significant effect on soil cellulase activity,but formula fertilization by soil testing with organic manure (PSTF+OF) significantly increased soil dehydrogenase and catalase activity.Therefore,long-term application of chemical fertilizer with organic fertilizer can effectively improve soil fertility.
文摘Presents the coordinated controls of nonlinear variable structure with an equivalent control term designed for turbo generators following the theory of nonlinear variable structure control, which integrates the valve control with the excitation control and reduce the problem of high frequency shiver with conventional variable structure control in addition to a simplified design, and concludes from simulation results that the use of this control can improve the transient of the system.
基金Founded by the "211" Construction Item of Sichuan Agricultural University
文摘After introducing the status quo of farmers' net income and gross output value of agriculture of Sichuan Province,and the changes of agricultural output structure,the regression analysis was conducted on the impact of the changes in agricultural structure on the farmers' net income per capita on the strengthen of the data from Sichuan statistical yearbook and by the way of econometrics.The multiple linear regression analysis was conducted on the impact the changes in crop farming on farmers' net income by using logarithmic demand model.The results show that the agricultural structure has transformed from the dominant crop farming to the all-around developmental trend covering the dominant industry,animal husbandry and forestry,fishery and the other industries;the animal husbandry has greatest impact on famers' income per capita and the impact of crop farming is slightly weaker than animal husbandry;the crop farming and animal husbandry develop fairly rapid simultaneously and the two all have great impact in farmers' income;among animal husbandry,the meat and eggs have relatively great impact on farmers' income,while in crop farming,grain plays the dominant role in affecting farmers' income,followed by cash crop.Hence,the relevant countermeasures applied to increase farmers' income are put forward in terms of optimizing the internal structure of agriculture,adjusting the internal structure of crop farming,adjusting the internal structure of animal husbandry and strengthening the support of farmers.
文摘This study was undertaken to apply Geographic Information System “GIS” (ArcGIS 9.3) for calculating shoreline change rates and back-shore surface area due to these changes, particularly after constructing marine structures: including seawall, detached breakwaters and groins. Modelbuilder in ArcGIS software was used to design and develop an automated technique, module, for estimating such changes (rate and area). These changes are deduced from analysis of beach-nearshore profile surveys between 1970 and 2010 and shoreline position versus prevailing coastal processes. The results show that the major erosion occurred along the Delta promontories;the shoreline of Rosetta retreated (1.6 km) at an average rate of 60 m/yr with loss of back-shore area 6.4 km2;the coastline of Burullus bulge recessed at mean rate of 6 m/yr and decreasing in beach area of 1.31 km2;and at Damietta (Ras El-Bar) the shoreline moved backward (6 m/yr) with disappeared in beach area of 1.13 km2. The shape and orientation of these promontories contributed to create alternation between wave convergence zone that eventually causes erosion, and divergence zones that experienced shoreline accretion. Finally, the engineering structures didn’t solve or stop the erosion problem but shifted it from one place to another.