Lower limit characterization of segregation degree for large-size low-alloy steel.

Based on the original position statistic distribution analysis technique, the characterization method of segregation for large-size metal materials gives significant guidance to the research of material properties and production. However, random errors are inevitably brought into the calculation of segregation degree for materials characterization by the Spark Mapping Analysis for Large Sample (SMALS) technique, resulting in a misguide of the segregation degree. In this paper, we present the lower limit of segregation degree (Ds(L)) method to distinguish the random error from metal material segregation for large-size samples over the SMALS method. The random error of standard material in the 95% confidence interval was utilized as Ds(L) and the method has been applied for macro-segregation quantitative analysis. The precision correlation between Spark Atomic Emission Spectrometry (Spark-AES) and SMALS was established. Furthermore, the functional relationship between the Ds(L) and element content C can be obtained in the SMALS method. The Ds(L) method as the criterion can be used to not only characterize the minimum limit of the segregation degree but also the segregation existence for large-size samples. Applying to low-alloy steel can illustrate the effective performance of the Ds(L) method. Results on both spark mapping analysis and Spark-AES verify the substantial consistency.

Analysis of Ti-inclusions in high carbon chromium bearing steel by laser-induced breakdown spectroscopy.

The presence of Ti-inclusions has a significant impact on the fatigue life of bearing steel. Laser-induced breakdown spectroscopy (LIBS) is a useful tool for analyzing Ti-inclusions, despite the fact that the effective excitation area of LIBS is actually larger than the pre-set spot diameter. The area affected by the LIBS spot ranges from 150 µm to 376.6 µm. A new parameter L has been introduced for better understanding the characterization of Ti-inclusions detected in SEM-EDS and LIBS measurements, When the L threshold falls below the value of 188.3 µm, the SEM-EDS and LIBS data are obtained from the same Ti-inclusion. The study demonstrates that there is a linear relationship between LIBS intensity and Ti-inclusions area, which was tested both theoretically and practically. The analysis of six samples of rolling GCr15 bearing steel with a Cr element content of 1.5% shows that one regression line is enough for analyzing the same type of inclusion processed under the same conditions. This method can significantly reduce the workload and analysis time during the actual analysis process.

Comparison of corneal biomechanics among primary open-angle glaucoma with normal tension or hypertension and controls.

BACKGROUND: Normal tension glaucoma (NTG) is a less pressure-dependent type of glaucoma with characteristic optic neuropathy. Recently, the biomechanical mechanism has been thought to account for glaucomatous optic neuropathy to some degree. We intended to compare dynamic corneal response parameters (DCRs) among patients with primary open-angle glaucoma with normal tension or hypertension and controls. The correlations between DCRs and known risk factors for glaucoma were also analyzed. METHODS: In this cross-sectional study, 49 NTG subjects, 45 hypertension glaucoma (HTG) subjects, and 50 control subjects were enrolled. We compared the differences in DCRs using corneal visualization Scheimpflug technology among the NTG, HTG, and control groups. We also analyzed the correlations between DCRs and known risk factors for glaucoma (eg, central corneal thickness [CCT], intraocular pressure [IOP], etc). RESULTS: The maximum inverse concave radius (NTG: 0.18 [0.17, 0.20] mm-1; control: 0.17 [0.16, 0.18] mm-1; P = 0.033), deformation amplitude ratio of 2 mm (DAR 2 mm, NTG: 4.87 [4.33, 5.39]; control: 4.37 [4.07, 4.88]; P < 0.001), and DAR 1 mm (NTG: 1.62 [1.58, 1.65]; control: 1.58 [1.54, 1.61]; P < 0.001) were significantly higher in NTG than in the controls. The integrated radius (IR, NTG: 8.40 ±â€Š1.07 mm-1; HTG: 7.64 ±â€Š1.31 mm-1; P = 0.026) and DAR 2 mm (NTG: 4.87 [4.33, 5.39]; HTG: 4.44 [4.12, 5.02]; P < 0.007) were significantly higher, whereas the stiffness parameter at the first applanation (SP-A1, NTG: 91.23 [77.45, 107.45]; HTG: 102.36 [85.77, 125.12]; P = 0.007) was lower in NTG than in HTG. There were no significant differences in the DCRs between HTG and control groups (P > 0.05). In the univariate and multivariate analyses, some of the DCRs, such as IR, were negatively correlated with CCT and IOP, whereas SP-A1 was positively correlated with CCT and IOP. CONCLUSIONS: The cornea was more deformable in NTG than in HTG or controls. There were no significant differences in corneal deformability between HTG and controls. The cornea was more deformable with the thinner cornea and lower IOP.

Individualized Visual Reality Training Improves Visual Acuity and Visual Field Defects in Patients with Glaucoma: A Preliminary Study Report.

To explore whether individualized visual training improves the visual acuity and visual field defects of patients with glaucoma. Patients with established primary glaucoma who visited the glaucoma clinic of Beijing Shijitan Hospital, Capital Medical University from January 2018 to April 2018 were recruited. The binocular visual perception examination was performed by using the visual perception examination system, and a personalized training program was developed according to the relevant threshold conditions between the eyes of the patients. The binocular visual perception training session for 20 minutes for two sessions was completed at home by using a virtual reality helmet. The visual function, intraocular pressure, and Octopus visual field were examined, before and at the first month and the third month after training. Seven patients completed the study. None of the seven patients has fine stereopsis, four of them have large stereopsis, and two patients are without large stereopsis. The visual acuity at 3 months after training was significantly improved compared with that before training. The mean defect value after 1 month of training was significantly lower than that before training, and it was further decreased after 3 months. Similarly, the mean sensitivity value was significantly increased in both follow-ups after training. There was no significant difference in loss variance after 1 and 3 months of training when compared with that before training (p > 0.05). Our small prospective observational study indicated that individualized visual perception training can improve the visual function and improve the visual field in patients with glaucoma, and a large sample size study is warranted to further assess the value of this novel treatment.

Corneal Biomechanical Parameters and Asymmetric Visual Field Damage in Patients with Untreated Normal Tension Glaucoma.

BACKGROUND: High intraocular pressure (IOP) and low central corneal thickness (CCT) are important validated risk factors for glaucoma, and some studies also have suggested that eyes with more deformable corneas may be in higher risk of the development and worsening of glaucoma. In the present study, we aimed to evaluate the association between corneal biomechanical parameters and asymmetric visual field (VF) damage using a Corvis-ST device in patients with untreated normal tension glaucoma (NTG). METHODS: In this observational, cross-sectional study, 44 newly diagnosed NTG patients were enrolled. Of these, 31 had asymmetric VF damage, which was defined as a 5-point difference between the eyes according to the Advanced Glaucoma Intervention Study scoring system. Corneal biomechanical parameters were obtained using a Corvis-ST device, such as time from start until the first and second applanation is reached (time A1 and time A2, respectively), cord length of the first and second applanation (length A1 and length A2, respectively), corneal speed during the first and second applanation (velocity A1 and velocity A2, respectively), time from start until highest concavity is reached (time HC), maximum amplitude at the apex of highest concavity (def ampl HC), distance between the two peaks at highest concavity (peak dist HC), and central concave curvature at its highest concavity (radius HC). RESULTS: Time A1 (7.19 ± 0.28 vs. 7.37 ± 0.41 ms, P = 0.010), length A1 (1.73 [1.70-1.76] vs. 1.78 [1.76-1.79] mm, P = 0.007), length A2 (1.58 [1.46-1.70] vs. 1.84 [1.76-1.92] mm, P< 0.001), peak dist HC (3.53 [3.08-4.00] vs. 4.33 [3.92-4.74] mm, P = 0.010), and radius HC (6.20 ± 0.69 vs. 6.59 ± 1.18 mm, P = 0.032) were significantly lower in the worse eyes than in the better eyes, whereas velocity A1 and def ampl HC were significantly higher (0.156 [0.149-0.163] vs. 0.145 [0.138-0.152] m/s, P = 0.002 and 1.19 ± 0.13 vs. 1.15 ± 0.13 mm, P = 0.005, respectively). There was no significant difference in time A2, velocity A2, and time HC between the two groups. In addition, no difference was observed in IOP, CCT, and axial length. In the univariate and multivariate analyses, some of the Corvis-ST parameters, including time A1 and def ampl HC, were correlated with known risk factors for glaucoma, and there was also a significant positive correlation between def ampl HC and age. CONCLUSIONS: There were differences in dynamic corneal response parameters but not IOP or CCT between the paired eyes of NTG patients with asymmetric VF damage. We suggest that the shape of the cornea is more easily altered in the worse eyes of asymmetric NTG patients.