Search

Taylor series expansions are widely used in engineering approximations, for instance, to develop finite differences schemes or numerical integration methods. This technical note presents a novel technique to generate, display and manipulate Taylor series expansion by using matrices. The resulting approach allows algebraic manipulation as well as differentiation in a very intuitive manner in order to experiment with different numerical schemes, their truncation errors and their structures, while avoiding manual calculation errors. A detailed explanation of the mathematical procedure to generate a matrix form of the Taylor series expansion for a function of two variables is presented along with the algorithm of an implementation in MATLAB®. Example cases of different orders are tabulated to illustrate the generation and manipulation capabilities of this technique. Additionally, an extended application is developed to determine the modified equations of finite difference schemes for partial differential equations, with one-dimensional examples of the wave equation and the heat equation using explicit and implicit schemes.

Sensing coverage and network connectivity are two of the most fundamental problems in wireless sensor networks. Finding an optimal node deployment strategy that would minimize cost, reduce computation and communication overhead, be resilient to node failures, and provide a high degree of coverage with network connectivity is extremely challenging. Coverage and connectivity together can be treated as a measure of quality of service in a sensor network; it tells us how well each point in the region is covered and how accurate is the information gathered by the nodes. Therefore, maximizing coverage as well as maintaining network connectivity using the resource constrained nodes is a non-trivial problem. In this survey article, we present and compare several state-of-the-art algorithms and techniques that aim to address this coverage-connectivity issue.

Membrane damage is one of the main reasons for reduced motility and fertility of sperm cells during cryopreservation. Using a model system of sperm cryopreservation developed in our laboratory, we have investigated the detailed changes due to cryopreservation in the plasma membrane lipid composition of the goat epididymal sperm cells. Total lipid and its components, i.e., neutral lipids, glycolipids and phospholipids decreased significantly after cryopreservation. Among neutral lipids sterols, steryl esters and 1-O-alkyl-2,3-diacyl glycerols decreased appreciably, while among phospholipids, major loss was observed for phosphatidyl choline and phosphatidyl ethanolamine. Unsaturated fatty acids bound to the phospholipids diminished while the percentage of saturated acids increased. The cholesterol:phospholipid ratio enhanced and the amount of hydrocarbon, which was unusually high, increased further on cryopreservation. The data indicates that profound increase of the hydrophobicity of the cell membrane is one of the major mechanisms by which spermatozoa acquire potential to resist or combat stress factors like cryodamage. The results are compatible with the view that for survival against cryodamage, sperm cells modulate the structure of their outer membrane by shedding off preferentially some hydrophilic lipid constituents of the cell membrane.

This paper describes a new method for generating optimal path and gait simultaneously of a six-legged robot using a combined GA-fuzzy approach. The problem of combined path and gait generations involves three steps, namely determination of vehicle’s trajectory, foothold selection and design of a sequence of leg movements. It is a complicated task and no single traditional approach is found to be successful in handling this problem. Moreover, the traditional approaches do not consider optimization issues, yet they are computationally expensive. Thus, the generated path and gaits may not be optimal in any sense. To solve such problems optimally, there is still a need for the development of an efficient and computationally faster algorithm. In the proposed genetic-fuzzy approach, optimal path and gaits are generated by using fuzzy logic controllers (FLCs) and genetic algorithms (GAs) are used to find optimized FLCs. The optimization is done off-line on a number of training scenarios and optimal FLCs are found. The hexapod can then use these GA-tuned FLCs to navigate in test-case scenarios.

This investigation was carried out to develop a simple sperm cryopreservation model using a chemically defined synthetic medium (modified Ringer's solution) and mature goat cauda epididymal sperm as the model system. Rates of cooling, freezing, and maximum freezing temperature were manipulated with the help of a computer-controlled programmable biofreezer. Highly motile goat cauda sperm dispersed in a modified Ringer's solution was subjected to the freezing protocol: cooling 0.25 degrees C min(-1) to 5 degrees C, 5 degrees C min (-1) to -20 degrees C, 20 degrees C min(-1) to -100 degrees C, prior to plunging into liquid nitrogen. In the absence of any cryoprotective agent, all of the spermatozoa lost their motility. Addition of glycerol (0.22 to 0.87 M) caused a dose-dependent increase of sperm motility recovery. The highest recovery of forward and total motility was (32 and 35%, respectively) at 0.87 M. Further increase of the glycerol concentration caused a marked decrease in motility. Changes in the cooling rate particularly before and during freezing had a notable effect on the sperm motility recovery. There was no or low recovery (0-18%) of sperm motility when the cells were transferred directly to liquid nitrogen from the initial two cooling stages. The data demonstrate the importance of all of the cooling stages in the cryopreservation of the cells. Like glycerol, dimethyl sulfoxide (Me(2)SO) and ethylene glycol also showed a dose-dependent increase in motility recovery as well as a biphasic curve of cryoprotection. At optimal concentrations, dimethyl sulfoxide (1.00 M) and ethylene glycol (1.29 M) were effective in recovering sperm motility to the extent of 20 and 13%, respectively. Thus these reagents have markedly lower cryoprotection potential than glycerol.

In Electro Discharge Machining (EDM), melting is the main process for metal removal. However, for short pulses (discharge duration 100 μs), this electrostatic force becomes very small and does not play a significant role in the removal of metal. In the model proposed, the electrostatic force acting on the metal surface and the stress distribution inside the metal due to this electrostatic force have been estimated. The variation of the yield strength with depth inside the metal has also been found out and finally the 'crater depth' due to this electrostatic force has been calculated.

Optimum use of the cutting tool is a growing need in modern industries. The objective of the present work is to evaluate the optimal cutting conditions with the minimum number of experiments. To determine the optimal conditions the tool-life equation should be well defined. A model has been developed for evaluating the Taylorian Exponent n and constant C using the minimum number of experiments. This model has been used for developing an adaptive control system for on-line monitoring of tool wear. Experiments were carried out to determine the tool-life by correlating the increase in the cutting force with tool wear. The model would be useful to industries where the tool and work material change frequently and the performance is sensitively dependent upon the optimal cutting conditions.

Electrochemical discharge machining is a very recent technique in the field of non-conventional machining to machine electrically non-conducting materials using the electrochemical discharge (ECD) phenomenon. If a beyond-critical voltage is applied to an electrochemical cell, discharge initiates between one tool of the electrodes and the surrounding electrolyte, which is termed here ‘electrochemical discharge’. In the present work a simplified model is developed to predict the characteristics of the material removal rate for varying input parameters with the objective of finding the possibility of enhancing the capability of the process. The ECD phenomenon has been analysed as a switching process between the tool (one of the electrodes) and the electrolyte and it has been found that an extra control parameter can be obtained by introducing an additional inductance in the circuit. The theoretical and experimental results indicate that a substantial increase in the material removal rate can be achieved due to the additional inductance introduced.

The air breathing fish Boleophthalmus boddaerti has been studied for its lipids and fatty acids of body flesh. The nonpolar lipids identified were wax esters, steryl esters, l-O-alkyl-2,3-diacylglycerol, triacylglycerols and sterols. Phospholipid was predominant (51%), the major component being phosphatidylcholine (67%). Polyenoic fatty acids of the ω3 series, i.e. EPA and DHA, were at considerably high concentrations in the phosphatidylcholine and phosphatidylethanolamine fractions. Cholesterol was the major component (35%) of the different sterols found. In neutral glyceryl ethers, fatty acids up to 28 carbons were recorded with unsaturated, anteiso, iso and normal chains. In wax esters, up to 32 carbon chains were recorded. © 1997 Elsevier Science Ltd

Use of electrochemical discharge (ECD) phenomenon for generating intense localized heat in a controlled manner is not unknown in the field of unconventional machining, especially when the work material is electrically non-conducting. In this paper the authors investigate the feasibility and the characteristics of microwelding using BCD. One of the major applications of microwelding is the fabrication of thermocouples using very thin wires, and this investigation is dedicated to microwelding thermocouple wires to produce satisfactory joints. It has been shown that such welds can be very conveniently achieved using ECD in a self-controlled manner. The major process parameters have been identified and their influence on the weld characteristics has been investigated. An attempt has been made to develop a theoretical model. The results are in good qualitative agreement with the experimental observations.

The paper presents a computer simulation of the cut-and-try procedure for designing tool shapes in the electrochemical machining of prescribed work geometry. The procedure is capable of tackling complex work geometries where other existing methods fail. The variation of electrolyte conductivity has also been taken into account. It has been shown that an optimum value of the feed-back factor for iterative modification of the tool shape exists, which results in the minimum number of iterations to achieve the final result. The optimum value of the parameter has been shown to depend on some particular geometrical features. A parameter has been identified which determined the unique tool shape for a prescribed complex work geometry.

The use of the electrochemical discharge phenomenon to machine materials is a very recent technique in the field of non-conventional machining. When the machined material is electrically conducting, the process is usually termed ‘electrochemical arc machining’ (ECAM), whereas for non-conducting work materials it is termed ‘electrochemical discharge machining’ (ECDM). Although in both cases electrical discharge takes place through the electrolyte and plays a critical role, the mechanism of spark generation has not been investigated adequately. In the present work a theoretical model of this discharge phenomenon is developed. With the help of the model, the critical voltage and current required to initiate discharge between the electrode and the electrolyte are estimated. The theoretically-predicted values compare quite well with experimental observations.

The phospholipids and their fatty acids of the inner and outer plasma membrane leaflets of the maturing goat caput-, corpus- and cauda-epididymal spermatozoa were analyzed by treating the intact spermatozoa with phospholipase C and trinitrobenzene sulphonate. The inner and outer membrane showed marked differences in the phospholipid composition at all stages of epididymal sperm maturation. The outer membrane was rich in phosphatidylcholine (PC) and sphingomyelin (SPH) whereas the inner leaflet was dominated by phosphatidylethanolamine (PE). Although the ratio of PE/PC in the inner membrane was similar in both the mature cauda sperm and the immature caput sperm, it decreased significantly in sperm undergoing maturation in the corpus-epididymis. The distribution of the saturated and unsaturated fatty acids in the phospholipid fractions of both the membrane leaflets underwent profound alterations during the epididymal maturation. The data demonstrate asymmetry of phospholipids and their fatty acids in the sperm inner and outer plasma membranes and this lipid asymmetry is greatly altered during epididymal maturity of the male gametes.

Porteresia coarctata collected, at Prentice and Chuksar Islands of the Sunderban mangrove ecosystem, was studied for its lipid composition. Hydrocarbon, wax ester, sterol esters, triacylglycerols, sterols and terpenoids, were all found in higher proportions in the Prentice Island sample. Palmitic acid was the major fatty acid in all fractions except for the steryl esters of P. coarctata collected from Prentice Island, where oleic and linoleic acids were the major components. Sterols found were, sitosterol, stigmasterol, campesterol and cholesterol, of which, sitosterol and stigmasterol were the major components. Terpenoids present were, β-amyrin, α-amyrin, lupeol, betulin, oleanolic acid and ursolic acid, of which, lupeol and oleanolic acid were the major components. Quantitative variations of the lipid constituents were found between the two samples studied.

Mangrove plant leaves of Avicennia officinalis , Acanthus illicifolius and Bruguiera gymnorhiza , grown under tidal water stress, were found to biosynthesize higher proportions of hydrocarbons, wax esters, sterol esters, triglycerides, sterols and low- M , terpenes, compared to the plants grown normally. Hydrocarbons and n -alcohols of wax esters, with longer chain lengths were found in higher proportions in the plants grown normally. Higher proportions of unsaturated n -alcohols of wax esters were present in the leaves of periodically submerged plants. Proportions of unsaturated fatty acids of wax esters, sterol esters and triglycerides were also higher in the submerged plants. Sitosterol, stigmasterol and campesterol of the sterol esters, were higher in submerged plants, whereas 28-isofucosterol was higher in normal plants. Of the free sterols, sitosterol was higher in submerged plants, whereas stigmast-7-en-3β-ol and campesterol were higher in normal plants and 28-isofucosterol was found only in submerged plants. Pentacyclic triterpenoids were found only in normal plants, whereas, the submerged plants contained low- M , terpenes in higher proportions.

The hydrolysis of steryl esters on thin-layer chromatographic plates by porcine pancreatic lipase is described. The sterols and fatty acids produced were separated on the same plate, recovered, and analysed by gas-liquid chromatography for their compositions. Synthetic cholesteryl esters containing various saturated and unsaturated fatty acids and synthetic steryl oleates with various sterols were lipolysed along with steryl esters of Acanthus ilicifolius , Bruguiera gymnorhiza and Rhizophora mucronata mangrove leaves. The major sterol was sitosterol which was accompanied by cholesterol, campesterol, stigmasterol and 28-isofucosterol. In addition, stigmast-7-en-3β-ol was present in R. mucronata leaves. The component fatty acids found in all three species were 16:0, 18:0, 18:1, 18:2 and 18:3. The relative proportions of the sterols and fatty acids were significantly different from the chemotaxonomic standpoint. The results obtained by carrying out plate lipolysis for 45 min at 40° compared well with those produced by conventional chemical hydrolysis.

The gastropod mollusc Cerithidea obtusa was examined for its lipids and fatty acids. The non-polar lipids identified were hydrocarbons, steryl esters, triglycerides, free fatty acids and sterols. The major phospholipid was phosphatidyl choline. The predominant fatty acids were myristic, palmitic, stearic, oleic, linolenic, arachidonic and eicosapentaenoic acids. Combinations of chromatographic techniques have been employed for the qualitative and quantitative determination of the lipids and fatty acids of C. obtusa .

A comparison of some physicochemical and structural properties of the lectins from the seeds of different species of the genus Erythrina is presented. The amino acid compositions of E. indica , E. arborescens , E. lithosperma and E. suberosa lectins are closely similar and resemble those of E. cristagalli [ Eur. J. Biochem. (1982) 123 , 247–2521 and E. corallodendron [ Can. J. Biochem. (1981) 59 , 315–320]. They are rich in acidic and hydroxy amino acids and poor in sulphur containing amino acids. All contain valine as the only N -terminal amino acid. They are glycoproteins containing high mannose type complex oligosaccharide chains. In addition to mannose they contain arabinose, xylose, fucose, glucose and galactose. Glucosamine is the amino sugar present. E. indica , E. arborescens and E. lithosperma lectins bind to Concanavalin A-Sepharose but not to lentil and pea lectin-Sepharose indicating the presence of terminal non-reducing α- d -mannose and/or internal 2- O -α-linked mannose residues in these lectins, and the absence of α(1 → 6) linked l -fucose residues in the core regions of the oligosaccharide moieties. These lectins are metalloproteins containing about 2 g atoms of Mn 2+ and 3 g atoms of Ca 2+ . The M r s of E. arborescens , E. lithosperma and E. suberosa lectins are 58 000, 57 000 and 59 000, respectively. Each lectin consists of two noncovalently bound subunits which are of identical or very similar M r s. The UV spectra of E. indica , E. arborescens and E. lithosperma lectins have similar features and in the presence of inhibitory sugars the absorbance at 278–281 nm and 290 nm increases in all cases indicating involvement of tryptophan residue(s) in sugar binding. The properties of Erythrina lectins show striking similarities and indicate close phylogenic relationships among these lectins.

Ribbons of Metglas® 2826 MB were tested for their wear, creep and stress relaxation properties in magnetic and non-magnetic environments. The internal stress was lower, by a very small amount, in a magnetic field while the creep rate in a magnetic environment increased over that in a nonmagnetic environment. The wear of Metglas when rubbed against ferromagnetic material was enhanced marginally in a magnetic environment. With mild steel, enhancement was slightly more than with brass.

Seven species of fresh mangrove leaves were found to contain saturated normal and branched chain hydrocarbons, mostly between C 16 and C 36 with both odd and even carbon numbers. Significant quantitative variations were found between species. Wax esters were found to contain fatty acids with chain lengths between C 12 and C 22 . Palmitic (16:0) and stearic (18:0) acids were the major component saturated fatty acids, whereas, oleic (18:1) and linolenic (18:3) acids were the major unsaturate α-acids. Chain lengths of the alcohols of wax esters were between C 14 and C 36 . Significant quantitative and minor qualitative differences were noted in the alcohol composition of wax esters. Hydrocarbon and wax ester compositions were characterised by the presence of low M , components in high proportions.

The isolation of pentacyclic triterpenoids from seven species of fresh mangrove leaves using a simple and rapid method is described. The leaves were homogenized using chloroform—methanol and the extract was diluted with water to precipitate out triterpenoids which were separated into neutral and acidic fractions. These were analysed by gas-liquid chromatography as acetyl and trimethylsilyl ether derivatives on a 3% OV-17 column. Sterols were isolated from the chloroform layer by preparative thin layer chromatography and were analysed by gas-liquid chromatography as their trimethylsilyl ether derivatives on a 3% OV-17 column. The triterpenoids found were α-amyrin, β-amyrin, lupeol, oleanolic acid and ursolic acid in most of the samples. Sterols found in all the samples were cholesterol, campesterol, stigmasterol, sitosterol and stigmast-7-en-3β-ol. Retention indices of the triterpenoids and sterols have been determined.

A new diterpene glucoside, phloganthoside, has been isolated from Phlogacanthus thyrsiflorus and its structure has been established as phlogantholide-A-19- O -β- d -glucopyranoside.