An automatic focusing and stigmating system for the SEM

A digital minicomputer has been interfaced with a scanning electron microscope, and programmed to control the excitations of the objective lens and the stigmator of the microscope. The electron beam is scanned by a digital scan generator and the digitised video signal is used for computations. To focus the microscope, a parameter related to the 'sharpness' of the image is maximised, and to set the stigmator, the directional information in the above- and below-focus images is used. | A digital minicomputer has been interfaced with a scanning electron microscope, and programmed to control the excitations of the objective lens and the stigmator of the microscope. The electron beam is scanned by a digital scan generator and the digitized video signal is used for computations. To focus the microscope, a parameter related to the 'sharpness' of the image is maximized, and to set the stigmator, the directional information in the above and below-focus images is used.

Topographical analysis in the SEM using an automatic focusing technique

A novel technique for automated topographical analysis in the SEM has been investigated. It utilizes a 16-bit minicomputer arranged to act as an automatic focusing unit. The computer is coupled to the objective lens of the microscope, by means of a digital to analogue converter, and may regulate the excitation of the lens under program control. Further digital-to-analogue converters allow the computer to act as a programmable scan generator by applying ramp waveforms to the scan amplifiers, permitting the beam to be swept over a small sub-region of the field of interest. The video signal is sampled and applied to an analogue-to-digital converter; the resultant binary numbers are stored in computer memory as an array of values representing relative image intensities within a subregion. A differencing algorithm applied to the collected data allows the level of objective lens excitation to be found at which the sharpness of the image is optimized, and the excitation may be related to the working distance for that subregion through a previous calibration experiment. The sensitivity of the method for detecting small height changes is theoretically of the order of 1 μm.

Length-weight relationship of a hill-stream fish, Glyptothorax telchitta (Ham.) from Saptakoshi River of Nepal

The length-weight relationship of a hill-stream fish, Glyptothorax telchitta from Saptakoshi River of Nepal was analysed using the formula W=aLᵇ. The exponential values computed for total length and standard length in relation to body weight were 2.991 and 2.888 respectively.

Length-weight relationship of intertidal molluscs from Mumbai, India

A study on the length-weight relationship of common intertidal molluscs from Mumbai showed a high degree of correlation between their length and weight. Most of the molluscs exhibited isometric growth pattern but in some species, allometric growth was found, which is attributed to maturity, nonlinear growth of shell and the ecological conditions. The variations in the growth rate of Gafriarium divaricatum sampled from two geographically separate sites, Bandstand and NCPA, is a result of variation in ecological conditions.

Length-weight relationship in the Asian seabass, Lates calcarifer (Bloch) under culture condition

Asian seabass, Lates calcarifer (Bloch) - a catadromous centropomid perch, is a good candidate species for brackishwater aquaculture in India. The length-weight relationship and the relative condition of L. calcarifer were assessed under culture condition. The length of the fish samples ranged from 25 to 240 mm and the relative condition (w sub(r)) of the fish for different length groups ranged from 99.54 to 104.39, indicating the good condition of the fish. The regression analysis of log-transformed length-weight data was carried out and the 'b' coefficient indicates the good condition of fish showing an isometric growth in the juvenile phase under culture condition.

Length-weight studies of Epinephelus chlorostigma and E. areolatus from Arabian Gulf

Regression coefficient value (b) of the length-weight relation of Epinephelus chlorostigma was registered as 2.6383, which is significantly (p<0.01) less than the hypothetical value (3). This coefficient of E. areolatus was registered as 2.9500, a value close to 3. The correlation coefficients (r) were registered as 0.9725 and 0.9837 for E. chlorostigma and E. areolatus, respectively, which show a good relationship between the two parameters.

Studies on length-weight relationship of Gerres filamentosus Cuvier from the estuaries of the southern Karnataka coast

Random samples of Gerres filamentosus Cuvier from the Netravathi-Gurpur, Mulky, Kallayanapura, Mabukala and Kundapura estuaries of the southern Karnataka Coast were collected in the years 2000, 2001 and 2002, and length-weight relationships for each estuary were derived using multiple linear regression technique with one dummy variable. Hence, combined or sex-wise length-weight relationships were obtained after testing for homogeneity and isometric growth condition of fishes for each estuary by t-test. The extent of closeness of length-weight relationships between sexes and among estuaries for different years is explained by a trend line graph. The whole process of multiple linear regression analysis with one dummy variable is a better substitute for the analysis of covariance technique.

Distribution and length-weight relationship of tunas and tuna-like fishes around Ceylon

Tunas and tuna-like fishes have contributed considerably towards the increase in fish production from Ceylon's coastal waters, during the last five years and in this blood fish group lies a potential resource for a further increase in production. Consequently considerable attention is being paid to the study of these species. Length frequency sampling of these species are being carried out and quite often it becomes necessary to convert catch in terms of weight to catch in terms of number, when estimating apparent abundance of the stock. The length-weight relationship in addition to its usefulness in converting length frequency data to weight frequency data for such purpose is of general value to biologists and even to fishermen. The six species studied are yellowfin tuna (Thunnus alacares, Bonneterre), skipjack tuna (Katsuwonus pelamis, Linnaeus), mackerel tuna (Buthynnus affinis, Cantor), frigate mackerel (narrow corseleted Auxis thazard, Lacepede and broad corseleted A. rochie, Risso) and bonito (Saida orientalis, T&S).

MPC: A paradigm shift for automatic control

Model Predictive Control (MPC) represents a major paradigm shift in the field of automatic control. This radically affects synthesis techniques (illustrated by control of an unstable system) and underlying concepts (illustrated by control of a multivariable system), as well as lifting the control engineer's focus from prescriptions to specifications ('what' not 'how', illustrated by emulation of a conventional autopilot). Part of the objective of this paper is to emphasize the significance of this paradigm shift. Another part is to consider the fact that this shift was missed for many years by the academic community, and what this tells us about teaching and research in the field.

The modified Kanerva model for automatic speech recognition

A parallel processing network derived from Kanerva's associative memory theory Kanerva 1984 is shown to be able to train rapidly on connected speech data and recognize further speech data with a label error rate of 0·68%. This modified Kanerva model can be trained substantially faster than other networks with comparable pattern discrimination properties. Kanerva presented his theory of a self-propagating search in 1984, and showed theoretically that large-scale versions of his model would have powerful pattern matching properties. This paper describes how the design for the modified Kanerva model is derived from Kanerva's original theory. Several designs are tested to discover which form may be implemented fastest while still maintaining versatile recognition performance. A method is developed to deal with the time varying nature of the speech signal by recognizing static patterns together with a fixed quantity of contextual information. In order to recognize speech features in different contexts it is necessary for a network to be able to model disjoint pattern classes. This type of modelling cannot be performed by a single layer of links. Network research was once held back by the inability of single-layer networks to solve this sort of problem, and the lack of a training algorithm for multi-layer networks. Rumelhart, Hinton & Williams 1985 provided one solution by demonstrating the "back propagation" training algorithm for multi-layer networks. A second alternative is used in the modified Kanerva model. A non-linear fixed transformation maps the pattern space into a space of higher dimensionality in which the speech features are linearly separable. A single-layer network may then be used to perform the recognition. The advantage of this solution over the other using multi-layer networks lies in the greater power and speed of the single-layer network training algorithm. © 1989.

Use of length-weight relationship in grading processed beche-de-mer

Holothurians, belonging to the species Holothuria scabra, have been collected by diver-fishermen and processed for export. There is an active fishery for these animals in Palk Bay and Gulf of Mannar, off the north-western coast of Sri Lanka. The absence of standardized method of grading has led to unwarranted variation in sale prices and sometimes in loss of foreign exchange in Sri Lanka. In this paper an attempt is made to present a method to grade processed beche-de-mer by using the lenght-weight relationship.

Morphometry and length-weight relationship of Coilia dussumieri, Valenciennes, 1848 from Mumbai waters

Coilia dussumieri Valenciennes, 1848 a component of 'dol' net fishery forms an important pelagic resource along northwest coast of India. The present communication deals with morphometry and length-weight relationship of this species along Mumbai coast. Morphometric study showed a positive correlation among the compared characters. The length-weight relationship for the species from Mumbai coast was found to be W=0.017L super(2.4223).

Studies on fecundity of Puntius sarana (Ham.) in relation to total length, total weight and ovary weight

A total of 43 mature female of Puntius sarana (Ham.) ranging from 204 mm to 320 mm in length and 102 to 482 g in weight were used for present studies. The relationship between fecundity with respect to total length (TL), total weight (TW) and ovary weight (OW) was found to be linear. The coefficient of co-relation 'r' of the above relationships was found to be 0.5947, 0.5761 and 0.9837 respectively. All these values are highly significant (P=0.01) indicating a close relationship between these parameters. However, as indicated by value of 'r' (0.9837), the fecundity is more closely related to ovary weight and hence the ovary weight may be a better index of fecundity than the total length or weight.

Morphometry, length-weight relationship and biology of Sepia aculeata (d'Orbigny, 1848) from Mumbai coast, India

Seventeen morphometric characters of Sepia aculeata of Mumbai coast have been studied and the relationships of morphometric characters with dorsal mantle length (DML) were established. The characters compared showed a fair to high degree of correlation ('r' 0.63-0.99). Number of arm suckers and shell rings were related with DML. The shell rings also showed high degree of correlation with DML ('r' 0.79-0.95). However, the relationship between arm suckers and DML was not so good ('r' 0.1-0.4). The length-weight relationship is described as W=0.1821336 L sub(2.801102). Food and feeding analysis confirm the carnivorous feeding behaviour of the species. Mature females found in all months indicate that it has prolonged spawning season with two peaks, september and march-april. Absolute fecundity ranged from 214 to 4143 eggs.

Studies on fecundity of Rita pavimentata (Gunther) in relation to total length, total weight and ovary weight

A total of thirty eight ripe ovaries from the specimens of Rita pavimentata, measuring 230 to 355 mm in total length (TL) and 250 to 750 g in total weight (TW), were selected to study the fecundity. The relationship between fecundity 'and total length (TL), total weight (TW) and ovary weight (OW) was found to be linear. The coefficient of co-relation 'r' of the above relationship was found to be 0.92, 0.94 and 0.96 respectively. All these values are highly significant (P=0.01) indicating a close relationship between compared parameters. However, as indicated by value of 'r' (0.96), the fecundity is more closely related to ovary weight and hence the ovary weight may be a better index of fecundity than the total body length or weight.