Search

A new path‐independent multiaxial fatigue damage parameter σn*, which is defined as the largest normal stress range between adjacent turning points of the maximum shear stress on the critical plane, is proposed to describe multiaxial fatigue damage. By combining the maximum normal stress σn,max or the largest normal stress range σn* with the maximum shear stress range on the critical plane, two axial equivalent stress modification factors, keqσ and keqσ*, are proposed, which can account for the influence of non‐proportional additional hardening. The sensitivity of the proposed axial equivalent stress modification factors to multiaxial variable amplitude loading sequences is analyzed. Furthermore, two new multiaxial fatigue damage models based on the axial equivalent stress modification factors are proposed to estimate fatigue life. The applicability of the presented methodology was verified by the experimental data of En15R steel and 7050‐T7451 aluminum alloy, and the results showed that the predicted fatigue lifetimes agree well with the experimental data under variable amplitude multiaxial loading. [ABSTRACT FROM AUTHOR]

A new calculation approach is suggested to the fatigue life evaluation of notched specimens under multiaxial variable amplitude loading. Within this suggested approach, if the computed uniaxial fatigue damage by the pure torsional loading path is larger than that by the axial tension–compression loading path, a shear strain‐based multiaxial fatigue damage parameter is assigned to calculate multiaxial fatigue damage; otherwise, an axial strain‐based multiaxial fatigue damage parameter is assigned to calculate multiaxial fatigue damage. Furthermore, the presented method employs shear strain‐based and axial strain‐based multiaxial fatigue damage parameters in substitution of equivalent strain amplitude to consider the influence of nonproportional additional hardening. The experimental data of GH4169 superalloy and 7050‐T7451 aluminium alloy notched components are used to illustrate the presented multiaxial fatigue lifetime estimation approach for notched components, and the results reveal that estimations are accurate. [ABSTRACT FROM AUTHOR]

An innovative numerical methodology is presented for fatigue lifetime estimation of notched bodies experiencing multiaxial cyclic loadings. In the presented methodology, an evaluation approach of the local nonproportionality factor F for notched specimens, which defines F as the ratio of the pseudoshear strain range at 45° to the maximum shear plane and the maximum shear strain range, is proposed and discussed deeply. The proposed evaluation method is incorporated into the material cyclic stress‐strain equation for purpose of describing the nonproportional hardening behavior for some material. The comparison between multiaxial elastic‐plastic finite element analysis (FEA) and experimentally measured strains for S460N steel notched specimens shows that the proposed nonproportionality factor estimation method is effective. Subsequently, the notch stresses and strains calculated utilizing multiaxial elastic‐plastic FEA are used as input data to the critical plane‐based fatigue life prediction methodology. The prediction results are satisfactory for the 7050‐T7451 aluminum alloy and GH4169 superalloy notched specimens under multiaxial cyclic loading. [ABSTRACT FROM AUTHOR]

Based on the isothermal fatigue and creep damage, a life prediction approach under multiaxial thermo-mechanical loading was proposed in this investigation. In the proposed method, the multiaxial thermo-mechanical fatigue damage during one cycle period was divided into the isothermal fatigue damage and the creep damage. In order to evaluate conservatively, the isothermal fatigue damage during one cycle period was calculated by using multiaxial fatigue damage model at the maximum temperature during the whole period, and the creep damage during one cycle period was calculated by accumulating the creep damage of all portions originated from the divided time history for the axial load component and temperature history. The life prediction results by the proposed model showed a good agreement with experimental data for nickel-base alloy GH4169 and cobalt-base Haynes188 under axial-torsional thermo-mechanical loading. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The M05-2X and M06-2X are found be suitable methods for study of the weak C F⋯H interaction. • Strong C F⋯H O interactions are found in complexes between α-CF 3 ketoimine and EG. • The solvent EGs play important roles in the titled interesting catalyst-free Strecker reaction. Abstract Density functional theory (DFT) calculations have been performed to understand the role of Ethylene Glycol (EG) in a remarkable catalyst-free Strecker reaction of α-CF 3 ketoimine. The fluorine hydrogen bonds involved in titled reaction have been studied. To find the suitable calculation methods for the weak C F⋯H interaction, we chose seventeen density functionals and MP2 method for calculation of the structures of three typical C F⋯H hydrogen-bonded systems. Their structures were computed and compared with the available experimental data. The results show that the M05-2X and M06-2X functionals are better than the other methods. Based on these facts, the interactions between the α-CF 3 ketoimine and EG were investigated at the M06-2X/6-31G(d,p) level. And the results indicate the presence of strong C F⋯H O hydrogen bond in the complexes between α-CF 3 ketoimine and solvent EG. Moreover, we also studied the reaction mechanism of the titled reaction with or without the assistance of EG at the M06-2X/6-31G(d,p) level. The results show that the two possible pathways without the aid of EG have very high free energy barriers and the reaction can't proceed, which is consistent with the experiment fact. However, with the assistance of EG, the reaction activation free energy barrier can decrease greatly. For the two-EGs model with two EG molecules, the reaction free energy barrier decreases from 47.5 kcal mol−1 to 24.7 kcal mol−1. The two EGs play an important role to stabilize the transition state and decrease the activation barrier greatly. The present theoretical calculations imply the role of solvent EG in the titled interesting catalyst-free Strecker reaction of α-CF 3 ketoimine. Our theoretical calculations provide a satisfactory explanation for the experiment. [ABSTRACT FROM AUTHOR]

A theoretical study of the interactions between 2,4,6-trinitrotoluene (TNT) and ammonia (NH 3 ) has been carried out by means of MP2, DFT, and CCSD(T) methods. Eight stable structures of TNT⋯NH 3 complexes were identified at the MP2/6-311++G(d,p) level. Various interactions such as lone pair⋯π interaction (lp⋯π interaction), conventional N H⋯O, C H⋯N, N–H···π hydrogen bonds, and novel noncovalent C⋯N carbon bonding, have been observed in the titled complexes. The competition between hydrogen bonding and lp⋯π interaction in the complexes was studied and discussed. The attractive lp⋯π interactions are observed when the lone pair of NH 3 points toward TNT π ring. At the CCSD(T)/6-311++G(d,p)//MP2/6-311++G(d,p) level, the corresponding BSSE corrected interaction energy (Δ E ) is −3.7 kcal mol −1 . The calculated results also show that the lp⋯π interaction competes successfully with the N H⋯π and N H⋯O hydrogen bonds. The competition between hydrogen bonding and lp⋯π interaction in TNT⋯NH 3 complexes plays important role to affect the structures of complexes. However, the conventional C H⋯N hydrogen bond is stronger than the lp⋯π interaction. The complex I merely with C H⋯N hydrogen bond is the most stable structure among eight complexes. The theoretical studies on UV and IR spectra of the TNT⋯NH 3 complexes show that the formations of hydrogen bonding and lp⋯π interaction have small effect on the UV spectra but new IR absorption peaks in range of 100–300 cm −1 correlated to interactions between TNT and NH 3 have been predicted, which may be helpful for the detection of TNT. [ABSTRACT FROM AUTHOR]

Intraventricular hemorrhage (IVH) is a neurological urgency with a high mortality and unfavorable prognosis. Fast removal of intraventricular blood should be considered as a priority. The current treatments of IVH mainly focus on external ventricular drain and endoscopic aspiration, but neither way can remove the blood in the fourth ventricle easily and relieve the compression of brainstem. Here we report a unique procedure to solve this problem. A 41-year-old male patient who had suffered sudden attack of headache and disturbance of consciousness for 2 h was diagnosed as having high density lesion in the whole ventricular system by computed tomographic (CT) imaging. An emergent bilateral ventriculopuncture and intraventricular hematoma removal under non-line-of-sight was performed immediately; the catheter was extended to the fourth ventricle to maximally remove the hematoma. Postoperative CT scan demonstrated total removal of IVH and no sign of extra brain damage. [ABSTRACT FROM AUTHOR]

Abstract Background Fibrinogen-like protein 2 (FGL2) is an inflammatory procoagulant protein. We discerned the impact of serum FGL2 on trauma severity and 30-day mortality in patients with traumatic brain injury (TBI). Methods A total of 114 severe TBI patients were subjected to assessment of trauma severity using the Glasgow coma scale (GCS). Measurement of the serum concentrations of FGL2 was done. 114 matched control subjects for their age and sex were included for comparison of serum concentration of FGL2. Results The concentration of FGL2 was dramatically increased in the patients as compared with the control subjects. FGL2 concentration was inversely correlated with GCS score among the patients. The non-survivors within 30 days exhibited substantially higher FGL2 concentrations than the alive. FGL2 concentrations discriminated the patients at risk of 30-day death with significantly high area under receiver operating characteristic curve. Serum FGL2 emerged as an independent predictor for mortality and overall survival at 30 days after head trauma. Conclusions Serum FGL2 is a promising biomarker for assessing the severity and prognosis in severe TBI. Highlights • Serum fibrinogen-like protein 2 concentrations are elevated after craniocerebral trauma. • Serum fibrinogen-like protein 2 concentrations are associated with trauma severity. • Serum fibrinogen-like protein 2 concentrations are linked to 30-day mortality. [ABSTRACT FROM AUTHOR]

This paper discussed the response of spectral characteristics on high temperature at grain filling stage of different spring maize varieties by adopting two spectrometer (SPAD-502 Chlorophyll Meter and Sunscan Plant Canopy Analyzer), and analyzed the impact of high temperature on the photosynthetic properties of spring maize in North China Plain. The test was conductedfrom the year 2011 to 2012 in Wuqiao County, Hebei Province. This test chose three different varieties, i. e. Tianyu 198 (TY198), Xingyu 998 (XY998) and Tianrun 606 (TR606), then two sowing date (April 15th and April 25th) was set. We analyzed chlorophyll relative content (SPAD), leaf area index (LAI) and photosynthetically active radiation (PAR) at grain filling stage. The results showed that the days of daily maximum temperature above 33 °C and the mean day temperature at grain filling stage in spring maize sowing on April 15th increased 3.5 d and 0.8 °C, respectively, compared to that sowing on April 25th, moreover the sunshine hours, rainfall, diurnal temperature and length of growing period were similar. Compared with XY998 and TR606, TY198's stress tolerance indices (STI) increased by 2.9% and 11.0%, respectively. According to STI from high to low order, TY198, XY998 and TR606 respectively as heat resistant type, moderate heat resistant type and thermo-labile type variety. TY198, compared with XY998 and TR606 sowing on April 15th, yield increased by 4.1% and 13.7%, SPAD increased by 12.5% and 19.6%, LAI increased by 5.3% and 5.6%, PAR increased by 4.0% and 14.0%. Sowing on April 15th, yield increased by 1.3% and 2.8%, SPAD increased by 3.5% and 6.0%, LAI increased by 1.7% and 4.1%, PAR increased by -4.4% and 0.9%. Three varieties had significant yield differences in the environment of high temperature stress, heat resistant type have significant (p < 0.05) advantage in the aspect of yield, SPAD and LAI. The production of TY198, XY998 and TR606 sowing on April 15th compared to that sowing on April 25th decreased by 3.2%, 5.9% and 12.6%, and SPAD decreased by 8.6%, 12.4% and 15.7%, LAI decreased by 11.7%, 17.6% and 19.8%, PAR decreased by 3.4%, 11.3% and 14.5%; STI had a significant negatively correlated with SPAD fall range (r = -0.883, p < 0.05) and LAI fall range (r = -0.853, P < 0.05), and highly significantly negatively correlated with PAR fall range (r = -0.923, p < 0.01); while SPAD fall range and PAR fall range showed a significant positive correlation (r = 0.872, p < 0.05); LAI fall range and PAR fall range were significantly positive correlation (r = 0.943, p < 0.05). In conclusion, heat tolerant type varieties of spring maize under high temperature stress at gain filling stage could maintain a relatively high content of chlorophyll at the individual level, a relatively high leaf area at the group level, and then keep a higher luminous energy interception and utilization, and weakened inhibition magnitude of high temperature on photosynthetic capacity, reduced the yield fall range, then achieved high and stable yield. The heat tolerance in varieties could be one of the main indicators for identification and evaluation the response to high temperature by spectral characteristics (SPAD, LAI and PAR). Thus it provides a basis by using spectral characteristics to study heat tolerance on maize.

In order to explore a non-destructive monitoring technique, the use of digital photo pixels canopy cover (CC) diagnosis and prediction on maize growth and its nitrogen nutrition status. This study through maize canopy digital photo images on relationship between color index in the photo and the leaf area index (LAI), shoot dry matter weight (DM), leaf nitrogen content percentage (N%). The test conducted in the Chinese Academy of Agricultural Science from 2012 to 2013, based on Maize canopy Visual Image Analysis System developed by Visual Basic Version 6.0, analyzed the correlation of CC, color indices, LAI, DM, N% on maize varieties (Zhongdan909, ZD 909) under three nitrogen levels treatments, furthermore the indicators significantly correlated were fitted with modeling, The results showed that CC had a highly significant correlation with LAI (r = 0.93, p < 0.01), DM (r = 0. 94, p < 0.01), N% (r = 0.82, p < 0.01). Estimating the model of LAI, DM and N% by CC were all power function, and the equation respectively were y = 3.281 2x(0.763 9), y = 283.658 1x(0.553 6) and y = 3.064 5x(0.932 9); using independent data from modeling for model validation indicated that R2, RMSE and RE based on 1 : 1 line relationship between measured values and simulated values in the model of CC estimating LAI were 0.996, 0.035 and 1.46%; R2, RMSE and RE in the model of CC estimating DM were 0.978, 5.408 g and 2.43%; R2, RMSE and RE in the model of CC estimating N% were 0.990, 0.054 and 2.62%. In summary, the model can comparatively accurately estimate the LAI, DM and N% by CC under different nitrogen levels at maize grain filling stage, indicating that it is feasible to apply digital camera on real-time undamaged rapid monitoring and prediction for maize growth conditions and its nitrogen nutrition status. This research finding is to be verified in the field experiment, and further analyze the applicability throughout the growing period in other maize varieties and different planting density.