A new distance correction method for sulfur analysis in coal using online XRF measurement system

When X-ray fluorescence （XRF） technology is used to measure the sulfur concentration in coal online, the measurement accu- racy is affected by the coal＇s uneven surface and the particle size. In order to improve the accuracy of sulfur concentration measurement, an online measurement system, consisting of a portable X-ray fluorescence instrument and an auxiliary distance correction module, was developed in this paper. By measuring the standard coal samples of known sulfur concentration, we obtained a calibration curve that can be used to analyze the sulfur concentration. We studied the relationship between the X-ray fluorescence intensity （I） and the distance （D） from surfaces to instrument. The results showed that there was a good linear re- lationship between 1 and D when the sulfur content was certain. Based on these knowledge, the distance correction formula of X-ray fluorescence intensity was proposed. By applying the distance correction formula to experimental sulfur concentration measurement, we demonstrated that the measurement accuracy can be significantly increased.

Phacoemulsification versus small incision cataract surgery in patients with uveitis

AIMTo compare the safety and efficacy of phacoemulsification and small incision cataract surgery (SICS) in patients with uveitic cataract.METHODSIn a prospective, randomized multi-centric study, consecutive patients with uveitic cataract were randomized to receive phacoemulsification or manual SICS by either of two surgeons well versed with both the techniques. A minimum inflammation free period of 3mo (defined as less than 5 cells per high power field in anterior chamber) was a pre-requisite for eligibility for surgery. Superior scleral tunnel incisions were used for both techniques. Improvement in visual acuity post-operatively was the primary outcome measure and the rate of post-operative complications and surgical time were secondary outcome measures, respectively. Means of groups were compared using t-tests. One way analysis of variance (ANOVA) was used when there were more than two groups. Chi-square tests were used for proportions. Kaplan Meyer survival analysis was done and means for survival time was estimated at 95% confidence interval (CI). A P value of <0.05 was considered statistically significant.RESULTSOne hundred and twenty-six of 139 patients (90.6%) completed the 6-month follow-up. Seven patients were lost in follow up and another six excluded due to either follow-up less than six months (n=1) or inability implant an intraocular lens (IOL) because of insufficient capsular support following posterior capsule rupture (n=5). There was significant improvement in vision after both the procedures (paired t-test; P<0.001). On first postoperative day, uncorrected distance visual acuity (UDVA) was 20/63 or better in 31 (47%) patients in Phaco group and 26 (43.3%) patients in SICS group (P=0.384). The mean surgically induced astigmatism (SIA) was 0.86±0.34 dioptres (D) in the phacoemulsification group and 1.16±0.28 D in SICS group. The difference between the groups was significant (t-test, P=0.002). At 6mo, corrected distance visual acuity (CDVA) was 20/60 or better in 60 (90.9%) patients in Phaco group and 53 (88.3%) in the manual SICS group (P=0.478). The mean surgical time was significantly shorter in the manual SICS group (10.8±2.9 versus 13.2±2.6min) (P<0.001). Oral prednisolone, 1 mg/kg body weight was given 7d prior to surgery, continued post-operatively and tapered according to the inflammatory response over 4-6wk in patients with previously documented macular edema, recurrent uveitis, chronic anterior uveitis and intermediate uveitis. Rate of complications like macular edema (Chi-square, P=0.459), persistent uveitis (Chi-square, P=0.289) and posterior capsule opacification (Chi-square, P=0.474) were comparable between both the groups.CONCLUSIONManual SICS and phacoemulsification do not differ significantly in complication rates and final CDVA outcomes. However, manual SICS is significantly faster. It may be the preferred technique in settings where surgical volume is high and access to phacoemulsification is limited, such as in eye camps. It may also be the appropriate technique for uveitic cataract under such circumstances.

A New Method for Detecting Internal Defects in Composite Materials Based on Time of Flight

Carbon-fiber reinforced polymer composites have been widely used to achieve the light-weighted design and high performance due to superior performance. Internal defects in the composite materials are the main factors that determine their performance,which makes reliable and effective detection methods of internal defects essential. Nondestructive testing(NDT)methods are the most widely-used way due to their tremendous advantages. Though the theoretical background is found,experimental results could be quite complicated and confusing,especially for composite materials with complex defects characteristics. In this paper,experimental study on internal defects in composite materials based on the time of flight(ToF)are investigated. The Gaussian echo model and the parameter estimation methods are established to build a theoretical model for measurements. Then,the distance amplitude correction(DAC)method is proposed to effectively improve the signal-to-noise ratio(SNR)and to reduce distortion of the signal during measurements. Finally,the ToF is adopted to determine depth of internal defects. Experiment study is conducted to investigate the porosity defects and the anti-impact performance of composite materials,as well as defects in objects with various thicknesses. Experimental results show that the proposed method is quite helpful for obtaining the intuition and deep understanding of internal defects,thus contributing to the determination of product performance and its improvement.

Presbyopic correction on the cornea

Purpose:The aim of this systematic review was to synthesize and appraise the evidence of the benefits of presbyopic correction on the cornea for visual function.Summary:Comprehensive search was conducted in MEDLINE using keywords like“presbylasik”,“presbyopic refractive surgery”,“corneal pseudoaccommodation”and“corneal multifocality”.We reviewed corrected and uncorrected visual acuities for distance and near(uncorrected distance visual acuity(UDVA),uncorrected near visual acuity(UNVA),corrected distance visual acuity(CDVA),distance corrected near visual acuity(DCNVA),corrected near visual acuity(CNVA)),along with the refractive outcomes in spherical equivalent(SE)and astigmatism comparing the differences observed between preoperative myopic and hyperopic patients,as well as among techniques.Thirty-one studies met the inclusion and quality criteria.Monovision provides excellent distance and near uncorrected acuities,but with a 17%retreatment and a 5%reversal rate.Initial multifocal ablations result in 12%loss of 2 or more lines of CDVA,and a 21%retreatment rate.Laser Blended Vision provides excellent UDVA,but with a 19%retreatment rate.Initial experiences with Supracor show moderate predictability and a 22%retreatment rate.Intracor results in 9%loss of 2 or more lines of CDVA.KAMRA provides excellent UDVA,with only a 1%retreatment rate,but a 6%reversal rate.Initial experiences with PresbyMAX provided excellent UNVA and DCNVA,showing excellent predictability and a 1%reversal rate.Conclusions:The findings have implications for clinicians and policymakers in the health-care industry and emphasize the need for additional trials examining this important and widely performed clinical procedure.