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BACKGROUND Since China has not yet constructed its own risk assessment model (RAM) for pregnancy-related venous thromboembolism (VTE), more and more hospitals use the RCOG RAM for VTE risk prediction. However, the RCOG RAM was established based on Western populations, and its applicability in China is still uncertain. Thus, we aimed to evaluate the validity of the RCOG RAM in predicting postpartum VTE in Chinese maternity. MATERIAL AND METHODS This retrospective case-control study was conducted at the International Peace Maternity and Child Health Hospital (IPMCHH) from June 2016 to June 2020. The VTE group consisted of 38 women with postpartum VTE. For each VTE patient, 4 women without VTE who gave birth on the same day were randomly selected as the control group (n=152). The receiver operating characteristic (ROC) curve, calibration curve, and decision curve analysis (DCA) were used to evaluate the discrimination, accuracy, and validity of the RCOG RAM. Univariable analysis and multivariable logistic regression analysis were used to identify other related factors for postpartum VTE. RESULTS Compared with the low-risk group, the risk of VTE was 9.75-fold greater in the intermediate-risk group, and 90.00-fold greater in the high-risk group. The area under curve (AUC) of the model was 0.828 (95% CI: 0.762-0.894), with a score of 2 as its best cut-off value, which exactly matched the criterion recommended by the RCOG guidelines for pharmacological thromboprophylaxis. The calibration curves and DCA of the model also showed good accuracy. In addition to the factors included in the RCOG RAM, glucocorticoid therapy during pregnancy (adjusted OR=6.72, 95% CI: 1.56-28.91) and previous use of IUD (adjusted OR=7.11, 95% CI: 1.45-34.93) were associated with increased risk of postpartum VTE. CONCLUSIONS The RCOG RAM was found to be effective in predicting postpartum VTE, and has certain guiding significance for postpartum thromboprophylaxis in China.

BACKGROUND: With the increasing trend of vaginal birth after caesarean delivery (VBAC), evaluation of the feasibility and safety of a second VBAC with grand multiparity is worth considering. Intrapartum uterine rupture is diagnosed in approximately one-fifth of all VBAC cases following successful vaginal delivery. To our knowledge, no report is available on the application of laparoscopy to repair postpartum uterine rupture after a successful second VBAC in China. CASE SUMMARY: A 31-year-old woman (gravida 5, para 2) at 39 wk and 5 d of gestation was admitted to the hospital in labour. After a successful VBAC and observation for approximately 13 h, the patient complained of progressive abdominal pain. Given the symptoms, signs, and auxiliary examination results, intraperitoneal bleeding was considered. Because the patient was stable and ultrasound imaging was the only method available to assess the possibility of rupture, we recommended laparoscopy to clarify the diagnosis and for prompt laparoscopic uterine repair or exploratory laparotomy if necessary. Operative findings included transverse uterine scar rupture at the lower uterine segment of approximately 5.0 cm in length and 800 mL of intraoperative pelvic haemoperitoneum. Finally, she successfully underwent laparoscopic repair of uterine rupture and recovered very well according to three-dimensional magnetic resonance imaging at 42 d postpartum. CONCLUSION: Routine postpartum intrauterine exploration is not beneficial to the mother and may even increase the risk of rupture. This case highlights a laparoscopic approach for repairing uterine rupture in the immediate postpartum period.

High strength construction materials are now attractive for composite steel-concrete construction due to their economic and architectural advantages. However, the current design codes for Steel Reinforced Concrete (SRC) columns are in general only applicable to normal strength materials. It is only allowed in Eurocode 4 (EC4) for concrete class C20/25-C50/60 and steel grades S235-S460 to be used in composite columns. On the other hand, it is permissible in Eurocode 2 (EC2) for higher strength concrete (up to C90/105) while Eurocode 3 (EC3) steel grade up to S690. While there are a lot of published works which focused on SRC columns with normal strength materials (fck ≤ 50 N/mm2 and fy ≤ 460 N/mm2), research on SRC columns with high strength materials is rather limited. This leads to insufficient test data to establish the validity of using high strength materials in SRC columns in EC4. Therefore, this study is geared to further extend the scope of EC4 to include the usage of high strength materials in SRC columns through numerical and theoretical study. A comparative study of the current confined concrete models was carried out to identify the most accurate model to be used in design and simulation. An analytical method was then proposed to predict the behaviour of SRC columns, taking into account the effect of strain-compatibility and lateral confinement. Next, a finite element (FE) model was developed to analyse the behavior of SRC columns under concentric and eccentric axial loading by ABAQUS. The FE model was validated with published test data from other researchers. Based on the reliability of the finite element simulation, a series of parametric study were conducted by varying certain variables, i.e. the structural steel strength (up to 690 N/mm2), concrete strength (up to 90 N/mm2), volumetric ratio, diameter and spacing of lateral reinforcement, column length and eccentricity ratio. The results were compared with EC4 and the proposed method. It is shown that the ultimate strengths of SRC columns increased linearly with the increase of material strength for short columns. However, increasing material strength had negligible effect on column strength for slender columns. Ultimate strength of SRC columns increased by either increasing the diameter and volumetric ratio of hoops or decreasing the spacing of hoops. The diameter, spacing and volumetric ratio of hoops had significant effects on the ultimate strength of column reinforced with high strength steel. The effect of material strength on the column strength was significant for column with smaller eccentricity. For column with higher eccentricity, the effect of material strength was only significant for concrete strength less than 70 Mpa. The comparison indicated that EC4 was conservative in predicting the bearing capacity of SRC columns with material strength (fc ≤ 90 N/mm2 and fy ≤ 550 N/mm2). However, EC4 overestimated the ultimate strength of SRC columns with steel strength higher than 550 N/mm2. Nevertheless, the proposed method was conservative in predicting the bearing capacity of columns with normal and high strength materials. The scope of EC4 can be further extended to cover a wider range of material strength including concrete strength up to 90 N/mm2 and yield strength of steel up to 550 N/mm2. The proposed method, which considering strain-compatibility and lateral confinement effects, can accurately predict the strength of SRC columns with concrete strength up to 90 N/mm2 and steel strength up to 690 N/mm2. Master of Engineering (CEE)

Combining with the outstanding performance of Ti (C, N), such as wear-resistant, withstand high temperature and alkali erosion, Ti-bearing blast furnace slag was modified, and Al-N-based materials were prepared in this paper. Based on the thermodynamic analysis, reasonable formula program was designed by the phase diagram, and then through high-temperature orthogonal experiments, a reasonable process condition was determined. The experimental results showed that the twice firing at the temperature of 1500°C was propitious to carbonitriding reaction. SiO2 was participated in carbonitriding reaction as reactant, which was conducive to the formation of Ti≡N bond. Eventually Al-N based materials that meet the design requirements were obtained.

Welded tubular joints have a weak stiffness in the chord radial direction due to the hollow section, and failure frequently occurs mostly on the chord surface along the weld toe. In the past, collar-plate has been proven to be effective in improving the stiffness and thus increasing the load carrying capacity of a tubular joint. This paper reports the results of a further study on investigating the effect of collar-plate reinforcement on the hysteretic behavior of a welded tubular joint. Overall, a total of 4 tubular T-joints with collar-plate reinforcement together with 4 corresponding un-reinforced specimens are studied experimentally. In the experimental tests, quasi-static axial cyclic loading is applied to these specimens. The hysteretic performance of the reinforced and un-reinforced T-joint specimens is then evaluated from the hysteretic curves, ductility and the energy dissipation ratio etc. Based on the experimental results, it is found that the T-joint specimens with collar-plate reinforcement can dissipate more energy before failure when they are subjected to cyclic loading compared to the un-reinforced ones, and thus they have a more ductile characteristic. Such ductility is attributed to the improved deformed capacity as well as the increased load carrying capacity of the reinforced T-joints.

Vanadium was recovered by using technology of calcified roasting→alkali leaching→ion exchange→precipitating→deaminizing, the principles of this recovery process were described in detail. Through the experiments, the parameters of roasting, leaching and ion exchange were determined, a new operational, low-polluting method to recovery vanadium was formed. This method not only can overcame the disadvantage of traditional technology, such as long process, serious pollution, but also has advantages such as high recovery and high purity of vanadium. In this study, pure V2O5 products with national standard were obtained. The total recovery was up to 65% or more, which was higher than that of the sodium roasting methods.

The MgO-Al2O3-Fe2O3 composite was prepared at 1600°C for 3h with magnesia powder and alumina powder as raw materials and with ferric oxide powder as additive. The effect of the molar ratio of MgO/Al2O3 on the sintering and thermal shock resistance of the composite materials was studied. The results showed that increasing the molar ratio of MgO/Al2O3 could improve the densification of the Al2O3-Fe2O3 composites, with the molar ratio of MgO/Al2O3 increased from 3 to 5, densification of the composites didn't increased but decreased. The optimum molar ratio of MgO/Al2O3 of the Al2O3-Fe2O3 composite is equal to 3, the sample MA-3 exhibits better sintering densification and thermal shock resistance. Its primary crystal phases are spinel and periclase, and less amount of sosoloid 20MgO·19Al2O3·Fe2O3. So, the MgO-Al2O3-Fe2O3 composite is acceptable for application in cement rotary kiln linings and high temperature gas filter support.

Using chemical vapor deposition (CVD) method and purified air as carrier and diluent gas, ZnO thin films was prepared with zinc acetate on glass substrate. Crystalline and optical properties of ZnO thin films were respectively tested by X-ray diffractometer (XRD) and UV-light spectrophotometer. The results showed that crystal face (002) of thin films was preferred orientation. In the visible region, the transmittance was over 85%. When ZnO thin films was prepared at 500 °C, the crystallization of ZnO thin films was the best, and when the temperature was 450°C, the grain size of thin films was the least, and internal stress was the least. With the substrate temperature increased, ZnO thin films both showed blue shift of the absorption edge and decrease of band gap.

The composites in the MgO-Al2O3-Fe2O3 system were prepared using high pure magnesia and alumina as raw materials and ferric oxide powder as additive. The effect of sintering temperatures on the sintering performance and thermal shock resistance of the composites was studied. The results showed that both the apparent porosity and linear change ratio of the samples decreased with the increase of sintering temperatures, and their bulk density and bending strength increased accordingly. The sample sintered at 1550°C exhibits excellent thermal shock resistance. The XRD and SEM results indicated that the crystal phase of the samples remained the same, but their microstructure became denser as the sintering temperatures increased from 1500°C to 1600°C. As a result, the composites could be sintered at about 1550°C, which has a potential application in cement rotary kiln linings.