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For a steel factory production of 55SiCr spring steel，the reduction of area of the oil quenched and tempered treatment wire rod after processing is less than 40%， which affects the subsequent spring coiling process and the service life of the spring. The casting billet and wire rod were evaluated by methods of low-magnification pickling test， tensile test， oil quenched and tempered treatment， drill cuttings test， etc， it was found that the center segregation of the casting billet was the main cause of poor drawing performance. Through the optimization test study of continuous casting process， the results showed that high superheat had a significant effect on the segregation of billet and the drawing performance of wire rod.When the superheat was 35 ℃ compared with 18 ℃， the reduction of area and elongation increased by 2% and 0. 8% respectively. The electromagnetic stirring current of the mold was increased from 150 A to 320 A， and the center equiaxed grain rate was increased from 8%-8. 5% to 10. 5%， but the average center carbon segregation index also increased. When using the same mould electromagnetic stirring technology， reducing the electromagnetic stirring intensity at the solidified end was beneficial to improve the center segregation. When the average center carbon segregation index of the slab decreased from 1. 10 to 1. 02， the reduction of area of the oil quenched and tempered treatment wire rod increased from 39% to 47%.

The number density, size and composition of inclusions in U75V heavy rail steel during ladle furnace (LF)–RH refining process were studied by an Aztec-Feature inclusion automatic software which equipped with a field emission microscope. The results showed that the MnO–SiO2–Al2O3-type inclusions were the main inclusions at LF start. The MnO–SiO2–Al2O3-type inclusions were transformed into the CaO–SiO2–Al2O3-type inclusions during the LF refining process because of the Ca and Al elements which were brought by ferroalloy. At the RH start stage, the main inclusions were CaO–SiO2–Al2O3-type inclusions with low melting temperature and CaO–MgO–Al2O3-type inclusions with high melting temperature in the sample. And, the CaO–MgO–Al2O3-type inclusions were obviously removed during RH vacuum treatment. The average compositions of CaO–SiO2–Al2O3-type inclusions had no obvious change from RH vacuum holding for 15 min, RH vacuum break to RH soft blowing.

The shape of shaft furnace is a crucial feature of direct reduction processes, as it affects both particle and gas flow during production. However, current knowledge on the impact of furnace shape on particle flow is limited. Herein, the discrete element method is employed for numerical simulations, in which two different methods of varying the wall angle (i.e., changing the radius or the height) are utilized to investigate the effect of wall angle on the flow behavior of particles in a shaft furnace. The effect of wall angle under different combinations of radius and height on the transformation of the particle flow pattern is innovatively examined, compared to previous studies on charging particles and internal furnace conditions. It is demonstrated in the results that the wall angle of the shaft furnace has a significant influence on the transformation of particle flow mode, with a reduction in the wall angle facilitating the transformation of particle flow mode to mass flow. Furthermore, it is shown in the study that different methods of changing the wall angle have varying effects on the transformation of particle flow mode. [ABSTRACT FROM AUTHOR]

This paper describes the application of co-occurrence and latent Dirichlet allocation (LDA)-based topic analyses in stem cell-related literature research. On account of the deficiency of parameter estimation in LDA, this study integrated co-occurrence theory and clustering judgement indicators and constructed an ATNLDA (Auto Topic Number LDA) model for topic segmentation. Next, ATNLDA was used to determine the optimal topic number of stem cell research literatures from 2006 to 2011 in PubMed, which was then used for topic segmentation of research content in stem cell data set. After stem cell research topics were obtained, they were analysed in terms of topic label, topic research content and interrelation between topics. The results verified that application of ATNLDA in topic segmentation in stem cell literature research is effective and feasible. Current deficiencies of ATNLDA and future study plan were also discussed. [ABSTRACT FROM PUBLISHER]

Objective: To evaluate the effectiveness of unstable pelvic fractures treated with minimally invasive percutaneous bridge internal fixator or traditional external fixator., Methods: The clinical data of 45 patients with unstable pelvic fractures who met the selection criteria between January 2013 and February 2018 were retrospectively analyzed. According to the different surgical methods, they were divided into two groups. In the observation group (25 cases), minimally invasive percutaneous bridge internal fixators were used, and three-dimensional printing pelvic models were used to simulate the reduction and fixation before operation to develop individual reduction strategies. In the control group (20 cases), external fixators were used. There was no significant difference between the two groups in gender, age, cause of injury, fracture type (according to Tile classification), and time from injury to operation ( P >0.05). The operation time, intraoperative blood loss, fracture healing time, and complications were recorded and compared between the two groups. The reduction quality was evaluated according to the Matta standard, and functional recovery was evaluated according to the Majeed scoring standard., Results: All patients were followed up 12-20 months (mean, 15 months). The operation time of the observation group was significantly longer than that of the control group ( t =2.719, P =0.009); no significant difference in intraoperative blood loss was found between the two groups ( t =0.784, P =0.437). There was no significant difference between the two groups in fracture healing time ( t =0.967, P =0.341). According to the Matta standard, the excellent and good rate of the observation group was 92%, and that of the control group was 70%, showing no significant difference between the two groups ( χ 2 =3.748, P =0.053). At last follow-up, according to the Majeed scoring standard, the excellent and good rate of the observation group was 88%, and that of the control group was 60%, showing significant difference between the two groups ( χ 2 =4.717, P =0.030). The incidences of incision and nailway infection, secondary displacement of fracture, and malunion in the observation group were significantly lower than those in the control group ( P <0.05); the differences in incidences of iatrogenic injury of lateral femoral cutaneous nerve, deep vein thrombosis, and loosening of fixation between the two groups were not significant ( P >0.05)., Conclusion: Minimally invasive percutaneous bridge internal fixator is a safe and effective method for the treatment of unstable pelvic fractures. It has the advantages of minimal trauma, stable fixation, less interference to patients' daily life, early functional exercise, and quickly recovery after operation.

Objective: To investigate the hemostasis effect of compression dressing therapy after total hip arthroplasty (THA)., Methods: Thirty-four patients undergding unilateral THA between December 2014 and March 2015 were randomly divided into observation group (compression dressing group, n = 17) and control group (ordinary dressing group, n = 17). There was no significant difference in gender, age, height, weight, lesion hips, pathogeny, disease duration, and preoperative hemoglobin between 2 groups (P > 0.05). The total blood loss theoretical value, the postoperative drainage volume, the visible blood loss, the hidden blood loss, the total blood transfusion volume, the number of patients receiving blood transfusion, and the related complications were compared between 2 groups., Results: No significant difference was found in operation time and hospitalization time between 2 groups (t = 0.337, P = 0.738; t = 0.140, P = 0.889). The incisions healed by first intention in all patients. Six cases had incision subcutaneous hematoma in the control group, no incision subcutaneous hematoma occurred in the observation group (χ² = 7.286, P = 0.018). No postoperative complications of wound superficial infection and venous thrombosis occurred in 2 groups. After operation, blood transfusion was given in 1 case of observation group and 7 cases of control group, showing significant difference (χ² = 5.885, P = 0.039), and the total blood transfusion volume was 600 mL and 3 200 mL, respectively. There was no significant difference in preoperative blood volume and intraoperative blood loss between 2 groups (P>0.05), but the total blood loss theoretical value, the postoperative drainage volume, the visible blood loss, and the hidden blood loss in observation group were significantly less than those in control group (P < 0.05)., Conclusion: The compression dressing should be performed after THA because it can effectively reduce postoperative blood loss and the incidence of wound hematoma.

Objective: To investigate the effectivness of the clinging lesser trochanter osteotomy with the Wagner cone in total hip arthroplasty (THA) for Crowe type IV developmental dysplasia of the hip (DDH) in adult., Methods: Between November 2009 and September 2012, 7 female patients (9 hips) with Crowe type IV DDH were treated by THA procedures of clinging lesser trochanter osteotomy with Wagner cone, aged 24-62 years (mean, 42 years). All patients experienced severe pain and claudication. The left hip was involved in 2 cases, the right hip in 3 cases, and bilateral hips in 2 cases. The Harris score of involved hip was 50.00?7.04. The both limps were discrepancy with an average length difference of 3.4 cm (range, 3-4 cm). The results of Trendelenburg sign were positive. X-ray films showed high complete dislocation of the involved hips., Results: The incisions healed by first intention. There was no complication such as infection, dislocation, prosthesis loosening, neurovascular injury. The average follow-up was 36.4 months (range, 25-48 months). Pain and claudication were improved and all patients could restore to work. The Harris score was improved to 83.42 +/- 6.47, showing significant difference when compared with preoperative score (t=8.90, P=0.00). The results of Trendelenburg sign were negative. X-ray films showed that all patients got a bony union at osteotomy site of greater trochanter at 3-6 months after operation. And the interface between prosthesis and bone was stable. There was no prosthesis loosening or sinking during the follow-up., Conclusion: Clinging lesser trochanter osteotomy with Wagner cone could be an option to shorten the femur in THA for patients with Crowe type IV DDH. It is effective in decreasing the risk of neurovascular injury.