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Metal-bonded ball-headed diamond wheel with small diameter has been widely used in the ultra-precision grinding of optical parts, especially in the parts with complex surface. In-position precise dressing technique of ball-headed diamond wheel is the key technology to improve grinding precision. The effect of mechanical errors on the profile accuracy of wheel dressing were theoretically analyzed firstly. Afterwards a ball-headed diamond wheel dressing equipment based on electrical discharge principle has been designed and built. Orthogonal experiments have been carried out on the dressing equipment, and the dressing quality of wheels under different dressing electrical parameters were analyzed in terms of wheel profile accuracy and wheel surface micro-topography. The influence of dressing electrical parameters on the dressing quality were investigated and the best electrical parameter combination was obtained. Experimental result showed that the wheel profile accuracy can reach upward 0.8μm after dressing, and the protrusion heights of diamond grain were uniformity and the protrusion effect was better than without dressing.

Objective: To determine if new echocardiographic imaging modalities like Tissue Doppler Imaging (TDI) can detect early abnormalities in left ventricular (LV) function in asymptomatic patients with Diabetic Retinopathy (DR). Method: Forty diabetic patients with retinopathy (mean age 45 +/- 15 ys) without typical symptoms or signs of heart failure or angina, forty diabetic patients without retinopathy and a matched healthy control group (n = 20) underwent standard transthoracic echocardiography and pulsed wave (PW — TDI) imaging of LV in addition to ophthalmological assessment of disease grading and severity. Result: LV Systolic function wasnt affected in all groups. However, LV diastolic function was significantly impaired in DR group measured by both conventional and tissue Doppler echocardiography. Conventional parameters showed significant decreased E/A ratio; p < 0.05 and highly significant increased LA diameter; p < 0.001. While Tissue Doppler parameters showed highly significant increase in E/Ea ratio; p < 0.001, significant decrease in Ea/Aa; p < 0.05 and highly significant increase in average Tei Index; p < 0.001 compared to diabetics without retinopathy and control group. Further elevated disease activity assessed with fundus examination and fluorescein angiography was inversely correlated with significantly values for LV longitudinal function measured by PW-TDI compared to diabetic patients without retinopathy and control group. Conclusion: Diabetic patients with retinopathy who are free of cardiac symptoms showed significant impairment of diastolic function compared to diabetics without retinopathy and control group. TDI provides earlier insights into cardiovascular involvement in diabetic patients and seems to be more sensitive and informative to standard echocardiography alone to detect subclinical myocardial disease.