The extraction of high-quality keywords and summarising documents at a high level has become more difficult in current research due to technological advancements and the exponential expansion of textual data and digital sources. Extracting high-quality keywords and summarising the documents at a highlevel need to use features for the keyphrase extraction, becoming more popular. A new unsupervised keyphrase concentrated area (KCA) identification approach is proposed in this study as a feature of keyphrase extraction: corpus, domain and language independent; document length-free; utilized by both supervised and unsupervised techniques. In the proposed system, there are three phases: data pre-processing, data processing, and KCA identification. The system employs various text pre-processing methods before transferring the acquired datasets to the data processing step. The pre-processed data is subsequently used during the data processing step. The statistical approaches, curve plotting, and curve fitting technique are applied in the KCA identification step. The proposed system is then tested and evaluated using benchmark datasets collected from various sources. To demonstrate our proposed approach's effectiveness, merits, and significance, we compared it with other proposed techniques. The experimental results on eleven (11) datasets show that the proposed approach effectively recognizes the KCA from articles as well as significantly enhances the current keyphrase extraction methods based on various text sizes, languages, and domains.
1. INTRODUCTIONRange performance of Image Intensifier (II) tube based night vision devices depends upon the output image contrast which in turn depends on the scene integral spectral contrast, loss of contrast due to atmospheric attenuation and finally the Modulation Transfer Function (MTF) of the system.In observing normal military targets such as green painted vehicles against green vegetation, the reflectivity contrast reverses its polarity three times upto 660 nm and its net effect on the imagery is not additive but subtractive. Filtering off contrast reversal bands will improve the output image contrast at the cost of reduced signal current density. Further, filtering off lower wavelength zones will lessen the atmospheric attenuation and thereby improve the image contrast.A theoretical study has been made to predict the range capability of II tube -based night vision devices for various available photocathodes at different light levels in detecting military targets, and, to enhance the range capability by filtering off contrast reversal bands. 2. THEORY At low light levels, statistical fluctuations in the arrival rate of photons set the upper limit of achievable performance of photoelectronic imaging devices. The signal -to -noise ratio on the display (S /N)D of II tubebased night vision devices is given by Schnitzler ). Where, 0-4)0 = ( 4 E 'irtpc tYl2. Mo rr v (z ) »pc =0.6" xic 3 k J sp) Lka) R<),) da -. (z) The Demand Modulation Function (DMF) is the ratio of the threshold modulation (Mr,) to the object contrast (Oc) which, for a normal military target, is related to its range of observation (R1 and is given by ve = f Ac 0 ) 2 °` °)R f dA Where, RccA)= Spectral reflectivity contrast between green paint and green vegetation, and,«( A) = Spectral atmospheric attenuation co-efficient. The intersection of the DMF curve with the MTF curve, gives the limiting resolving power (Rp) from which the angular resolution (95) is computed by the formula # =Z here f is the focal length of the objective optics. The range of observation of any target of a given size can !hereafter be predicted from the computed value of+so obtained. 3. RESULTS AND DISCUSSIONS Fig 1 shows2) the variation of Rc (A) with ñ . Using eqns (1), (2) and (3), the DMFs have been computedfor starlight and moonlight radiatins, and for 5 -20, S -25 and GaAs photocathodes and for the following four spectral bands, assuming (S /N)D to be 3.8 for 50% detection probability, E to be 14 as suggested by Schnitzler and F to be 0.377 for 155 mm, F/1.1 catadioptric objective optics.(A) 400 -960 nm, i,e, no cut off filter (B) 520 -960 nm, i,e, low pass filter cutting off wavelengths upto 500 nm 215 PI, 30
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