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To reflect the permeability change of loaded rock, the relationship between the permeability and stress-strain curve of rock was analyzed, and the process the deformation and failure of rock was supposed to be elastic, brittle and plastic. Based on the process the permeability evolution model for rock was presented. In this model the evolution of the permeability for the rock element include; (1) The permeability can be expressed by porosity during elastic deformation phase. (2) In the post-peak stage a shear failure rock element may be represented hydraulically as a unit of rock containing two oblique crossing conjugate fractures. (3) In the post-peak stage a tension failure rock element may be represented hydraulically as a unit of rock containing two orthogonal fractures. Then based on so-called cubic law between smooth parallel plates the permeability evolution model during dilation was presented. In the model the dilation effects of failed element on permeability was considered. Fish function method was adopted to implement the model in FLAC software. The permeability evolution process of a cubic loading rock sample under varied confined stress was simulated. The results show that the model can better reflect the permeability evolution due to elastic deformation or failure. Besides the effect of confined stress on permeability can also be better expressed. [ABSTRACT FROM AUTHOR]

The standard coal briquette specimens from Huaxing Mine, in Jilin, were made. The permeability test was performed in ZYS-1 equipment for the measurement of permeability to study the effects of confining stress, axial stress and temperature on permeability of coal briquette specimens. The results show that with the increasing confined stress, the permeability of coal briquette specimen decreases. The permeability of coal is greatly effected by differential stress. Under the condition of confined stress, with increasing differential stress (axial stress) the permeability of the specimen decreases due to the elastic contraction. When the specimen failed due to increasing differential stress their porosity volumes increase due to dilation, and the permeability also increases. Therefore the permeability of samples takes on "V" curve under low confined stress. However the permeability decreases under high confining stress. The flow of methane in coal is greatly effected by temperature. When the temperature increases, on one hand the kinematic viscosity of methane increases. On the other hand the grains of coal swell and lead to contraction of flow space and reduction of permeability. [ABSTRACT FROM AUTHOR]

In order to accurately predict the broken time and crack-growth in rock, based on non-uniform characteristics of rock material, a particular elastic-plastic-brittle constitutive model, considering the heterogeneity of rock and the features of deep engineering, was presented, and the corresponding finite element program was written and modularized. Through the simulation of two tests, including the tension test of pre-existing crack board and the compression test of rock samples, it is shown that the present model is rational and accurate, which can more accurately simulate crack growth and the development mode of localized shear band. In the strain-hardening stage of new constitutive model, stress concentration and unit yield happen before the failure of rock, especially tension failure and shear failure after the unit yield can be distinguished. [ABSTRACT FROM AUTHOR]

To reflect the effect of confining pressure on the brittleness of the post-peak rock, the degradation angle of post-peak strength of the new parameter was presented. Based on the test data for mudstone of Shanxi in triaxial compression, the linear relationship between the degradation angle and the confining stress was founded. The law between the equivalent plastic shear strain and the degradation angle was presented, and the strain softening model of rock based on the degradation angle was set up. Fish function method within FLAC was used and the numerical code was developed. In numerical case study, the strain softening processes under variable confining pressure for mudstone of Shanxi were modeled. The simulating results accord with experimental data. Those show that the degradation angle is an effective parameter to reflect the effect of confining pressure on the brittleness of the post-peak rock; the model in this paper is reasonable and can be used to model the strain softening processes of post-peak strength rock. [ABSTRACT FROM AUTHOR]

Objective: To study the effect of low-dose dopamine adjuvant therapy on inflammatory factors and prognosis in preterm infants with necrotizing enterocolitis (NEC)., Methods: A total of 100 preterm infants with NEC from June 2017 to June 2019 were enrolled and divided into a dopamine treatment group and a conventional treatment group using a random number table, with 50 infants in each group. The infants in the conventional treatment group were given symptomatic treatment, and those in the dopamine treatment group were given low-dose dopamine adjuvant therapy in addition to the conventional treatment. ELISA was used to measure the levels of C-reactive protein (CRP), tumor necrosis factor-α (TNF-α), and interleukin-8 (IL-8). The two groups were compared in terms of time to relief of clinical symptoms, fasting time, treatment outcome, prognosis, and adverse reactions., Results: Both groups had significant reductions in the levels of CRP, TNF-α, and IL-8 after treatment, and the dopamine treatment group had significantly lower levels of these markers than the conventional treatment group after treatment (P<0.05). Compared with the conventional treatment group, the dopamine treatment group had significantly shorter time to defecation improvement, time to relief of abdominal distension and diarrhea, and fasting time (P<0.05), a significantly higher response rate (P<0.05), and a significantly lower surgery rate (P<0.05). There were no significant differences in the mortality rate and incidence of adverse events between the two groups (P>0.05)., Conclusions: Low-dose dopamine adjuvant therapy can effectively improve the levels of inflammatory factors and clinical symptoms in preterm infants with NEC and has good safety, and therefore, it holds promise for clinical application.

Objective: To evaluate clinical application of transurethral plasmakinetic enucleation of the prostate (PKEP) to the treatment of benign prostatic hyperplasia (BPH)., Methods: A total of 90 BPH patients, aged 59-83 (mean 71) years and with indication of surgery, underwent transurethral resection of the prostate (the TURP group, n=50) and transurethral plasmakinetic enucleation of the prostate (the PKEP group, n=40), respectively. We recorded and analyzed the preoperative prostate volume, IPSS, QOL and Qmax, operation time, intra- and post-operative bleeding and complications, postoperative continuous bladder irrigation, and IPSS, QOL and Qmax at 2 weeks and 6 months after surgery., Results: The preoperative prostate volume and operation time were 58.9 g and 58.8 min in the TURP group versus 58.3 g and 93.0 min in the PKEP group. Mild transurethral resection syndrome (TURS) appeared in 2 TURP receivers, while no abnormality was found in electrocardiogram monitoring in those undergoing PKEP. Continuous bladder irrigation was necessitated in 3 and urgent incontinence of urine occurred in 4 cases of TURP, as compared with 1 and 4 cases in the PKEP group. None of the 90 patients needed blood transfusion. At 2 weeks before and after surgery and 6 months postoperatively, IPSS averaged 19.7, 11.6 and 5.1, QOL 4.6, 3.3 and 1.1, and Qmax 6.3, 13.0 and 18.1 ml/s in the TURP group versus 18.6, 8.4 and 4.9 (IPSS), 4.5, 2.7 and 1.1 (QOL) and 6.9, 14.2 and 19.0 ml/s (Qmax) in the PKEP group. There were significant differences in operation time, IPSS and QOL at 2 weeks postoperatively between the two groups, as well as in IPSS, QOL and Qmax at 6 months before and after surgery (P < 0.01). But no remarkable differences were found in preoperative prostate volume, IPSS, QOL and Qmax, 6-month postoperative IPSS and QOL, and Qmax at 2 weeks and 6 months after surgery between the two groups (P > 0.01)., Conclusion: Transurethral PKEP is a safe, effective and thorough surgical method to be chosen for the treatment of BPH.