High dimension feature extraction based visualized SOM fault diagnosis method and its application in p-xylene oxidation process

Purified terephthalic acid(PTA) is an important chemical raw material. P-xylene(PX) is transformed to terephthalic acid(TA) through oxidation process and TA is refined to produce PTA. The PX oxidation reaction is a complex process involving three-phase reaction of gas, liquid and solid. To monitor the process and to improve the product quality, as well as to visualize the fault type clearly, a fault diagnosis method based on selforganizing map(SOM) and high dimensional feature extraction method, local tangent space alignment(LTSA),is proposed. In this method, LTSA can reduce the dimension and keep the topology information simultaneously,and SOM distinguishes various states on the output map. Monitoring results of PX oxidation reaction process indicate that the LTSA–SOM can well detect and visualize the fault type.

Comparison of imo and Humphrey field analyzer perimeters in glaucomatous eyes

AIM:To compare the imo perimeter,a new portable head-mounted perimeter unit that enables both eyes to be examined quickly and simultaneously,with the Humphrey field analyzer(HFA)perimeter to investigate correlations and their diagnostic ability in glaucomatous eyes.METHODS:The performance of the equipment in 128 glaucomatous eyes and 40 normal eyes were tested.We investigated the correlations of mean deviation,pattern standard deviation,visual field index,and the sensitivity.RESULTS:Measurements of mean deviation(r=0.886,P<0.001),pattern standard deviation(r=0.814,P<0.001),and visual field index(r=0.871,P<0.001)in both perimeters were strongly and positively correlated.The sensitivities in the imo perimeter were 80.5%for mean deviation,81.2%for pattern standard deviation,and 80.5%in visual field index;those in the HFA were 63.3%for mean deviation,74.5%for pattern standard deviation,and 80.5%for visual field index.Both perimeters demonstrated high diagnostic ability.CONCLUSION:The parameters by the imo and HFA in glaucomatous eyes show strong positive correlations with favorable sensitivity,specificity,and diagnostic ability.However,the difference between imo and HFA results increases with the increase in visual field disturbance.