eChapters

Hydraulic turbines is a device which transforms the hydraulic energy or potential energy existing with the working medium to mechanical energy. The working medium is normally water which run the hydraulic turbine. The hydraulic energy is available with water by virtue of its height or altitude. The water which flow through the mountains is stored by constructing a dam or reservoir.

Hydraulic pumps are the devices utilized to transfer pressure energy to liquids at the expense of electrical energy. The electrical energy is transferred to a motor which converts it into mechanical work and a pump is coupled to the shaft. The pump converts the mechanical energy to hydraulic or potential energy. 

Machine: It is a device capable to doing work on application of some effort. Work done by machine is to raise load or to lower load or to do some other types of work like rotation of shaft.

Mechanical power is usually transmitted from one shaft to another by using belts, ropes, chains, gears and clutches.

1. Belts and ropes are utilized if distance between the shafts is large. Belts and ropes are flexible and bend easily. But slip occurs between the belt and the pulley.

Whenever a thin hanging wire is loaded, it elongates and the load moves downwards. Increase in length of wire is governed by the magnitude of the load and nature of wire material. Experimentally it is found that the cohesive force between the molecules of hanging wire offers resistance against the deformation.

Thermal stress arises whenever there is some increase or decrease in temperature of a body which causes either expansion or contraction in the dimension of body. If body is free to expand or contract, with the rise or fall of temperature, there exist no stress in the body. But if deformation of the body is partially or completely resisted then stresses are set up in the body which is known as Thermal Stress. However amount of stress induced in partially prevented deformation will be small than in case deformation is totally prevented.

When any beam is loaded, stresses are induced and so to calculate those stresses, shear force and bending moment acting at load or support location must be required to calculate.

So far we studied direct stress (Tensile or compressive) and tangential stress (shear stress) acting on plane individually. But in many engineering problems these both stresses are acts on a plane at a same time. In such cases resultant stress on that plane will be neither pure normal nor purely shear but there will be combined effect of normal and shear stress.

Over the period of time, the dairy sector has added distinct significance to growing Indian economy. India contributes nearly 19.54% to the global annual milk production with an impressive upliftment of 3.6% in yearly production rate as per the latest available data from FAO International.

Loose smut of wheat occurs worldwide but is more abundant and serious in humid and sub – humid regions. In India, this disease is found in all wheat growing areas but the incidence is generally more in comparatively cooler and moist parts of north India than south India. The yield loss may go up to 30% due to this disease.

The disease was fi rst reported in Java in 1893 and is prevalent in all sugarcane growing countries. In India the disease occurs in an epiphytotic form in Uttar Pradesh and Bihar during 1939-1940 and 1946-1947 and cause severe damage that threatened the existence of sugar industries.

The plants wilt at the time of grain fi lling stage. A light brown water soaked area is seen at the stem base. Sclerotia can be seen on the outer region of stalk when the plants get older. White mycelial growth with large sclerotial bodies is seen over the stem pith. The stem often breaks down at the point of infection.

The initial symptom of Alternaria brassiciola appears as small, dark colored spots which enlarge rapidly to form circular lesions. Under humid conditions a bluish velvety fungal growth is seen in the centre of these spots. Spots caused by Alternaria brassicae are almost similar to those produce by Alternaria brassicicola but are comparatively smaller and lighter in colour. When many spots are formed on the leaves, the leaves turn yellow and dry prematurely. Formation of pods and seeds are adversely affected.

All the above ground parts of the plant are affected. There is development of round and elongated spots surrounded by brownish red margin on the leafl ets. At later stage spots coalesce and entire leaf turns brown. On green pods, the lesions are usually circular with dark margin and pin head like dark dots representing the pycnidia in concentric circles.

Wilt appears in the fi eld as patches is both seedling stage and developed plants. Symptoms include drooping and wilting of uppermost leaves. Plants become completely yellow and die. Plants are affected during the pod fi lling stages, seeds are often shrivelled. There will be rotting at the basal portion of the plant. Discoloration of vascular bundle are noticed when the stem is spitted
open.

The disease i s seen at all crop growing stages. The fi rst symptoms appear at the time of emergence of seedlings, when the cotyledons are attacked. They become yellow and turn brown followed by wilting and drying of the affected seedlings. In the fi eld, the wilting symptoms appear in patches. First of all, the older leaves become yellow, loose their turgidity, wilt, turn brown and droop.

The disease is seen at 3-4 leaves stage. Scattered, irregular, yellowish patches appear on the upper surface of the leaves and stipules. On the corresponding under surface of these patches, a greyish violet fi ne cottony mildew growth is seen. Infected tissue soon dies and turns brown. The disease fi rst appears on lower leaves and later spreads to upper leaves.

Disease appears later part of the crop season mostly during blossoming period. The first sign of the disease is the appearance of small brown patches on the leaves mostly on basal leaves which starts from tip or margin of leaves and spread downwards or inward directions.

It is a very common disease found in all the onion and garlic growing areas. It mostly attacks the bulb as well as the seed crop. The infection or severity of the disease is more in Kharif crop causing 60% yield loss.

It is a very important and commonly found disease of chili which observed in field as well as in storage. It is also known as anthracnose disease which is mostly seen in tropical and sub tropical regions.

It is a very common disease of mango. It is otherwise known as blossom blight, leaf spot, twig blight or wither tip.

Citrus crop includes lime, lemon, sweet orange, mandarin orange, Kamala orange, grapefruit, malta and pomelo etc. The disease which attacks one species of citrus mostly attacks other species also.

The disease attacks all the growth stages of plant affecting all above-ground parts. Plant covered with powdery patches leads to distortion, malformation and discolouration of leaves especially young leaves. Powdery patches gradually turn to grey and fi nally dark colour. Affected fl ower fails to develop fruit. Young berries turn black, irregular in shape and develop cracks. Sometimes berries ripe partially and rot. Vines get wilted.

It is a serious disease of apple which not only reduces the quality and size of fruit but also cause premature fruit drop and defoliation. Fruit loses its marketability due to poor quality. It also reduces storage time and cause loss up to 70%.

The fi rst symptom of disease appears in early spring soon after leaves come out of buds. Affected leaves become distorted and fold over as tips directed backwards. The whole lamina puckered except tip and blistered. In some leaves, part of leaf show distortion. Blistered portions are thicker, softer than the normal leaf blade. The affected areas remain green for a while and gradually become yellow and fi nally turn reddish-purple in colour. 

It is known by different names such as Ramularia leaf spot, rust, bird’s eye spot, grey spots, and white spot. It mostly attacks leaves but can also attack fruit stalks and also fruits.

The symptom appears as numerous, circular, light yellow to dark yellow spots on both the surfaces of leaves but is more prominent on the upper surface. The spot may coalesce to form large, irregular patches and soon entire leaf turns yellow and dries. Affected leaves appear as reddish-brown in colour. Excessive spotting destroys green tissues and becomes weak and yield reduced drastically

The disease appears as tumour like swelling or galls on leaf veins, leaf stalks, peduncles, stems and on fruits. The galls on the vein give a swollen and hanging appearance to the leaves. These are elongated, looks glossy in beginning but later rupture to become rough and corky. When stems remain succulent, numerous tumours may form on them. In severe case, the plant may kill prematurely.

All varieties of rose are susceptible to this disease. It is an important disease of rose which causes a sharp reduction in number and size of fl owers.

Agricultural crops are being affected by a wide range of organisms such as insects, mites, fungi, bacteria etc. Another important and unseen enemy is known as plant parasitic nematodes. The study on nematodes is known as Nematology.

In light of the high population of nematodes, N.A. Cobb (1915) who is considered to be the father of American Nematology, provided a dramatic description of the abundance of nematodes. He stated, “if all the matter in the universe except the nematodes were swept away, our world still would be dimly recognisable.

Eventhough nematodes occupy nearly every habitat on earth, they are remarkably similar in morphology and life stages. Despite their structural complexity, certain basic principles are common to all nematodes. Nematodes are triploblastic, bilaterally symmetrical, unsegmented, pseudocoelomate, vermiform and colourless animals.

Life cycle of nematode has six stages. The egg stage, first stage juvenile (J1), second stage juvenile (J2), third stage juvenile (J3), fourth stage juvenile (J4) and the adult stage.

Plant parasitic nematodes cause serious problems in sustained crop production. For a successful management of nematodes, their morphology, biology and host - parasitic relationship should be thoroughly studied. A thorough study is achieved only when its taxonomical position is known. Thus, in a simple way taxonomy can be defined as the theroretical study of classification of an
organism.

Sampling for nematode communities has been the basis for the development of appropriate control strategy. The major purposes of sampling for nematodes include population estimation for general detection, advisory or predictive programme, disease diagnosis and also for research purposes.

The nematode feeding on plant can be divided into above ground feeders and below ground feeders.

Most of the plant parasitic nematodes affect the root portion of plants except Anguina spp., Aphelenchus spp., Aphelenchoides spp., Ditylenchus spp., Bursaphelenchus cocophilus and B. xylophilus. Nematodes suck the sap of the plants with the help of stylet and causes leaf discolouration, stunted growth, reduced leaf size and fruits, lesions on roots, galls, reduced root system and finally wilting.

Plant parasitic nematodes favour the establishment of secondary pathogens viz., fungi, bacteria, virus etc. The nematodes alter the host in such a way that the host tissue becomes suitable for colonization by the secondary pathogens. Even though the nematodes themselves are capable of causing considerable damage to the crops, their association with other organisms aggravate the disease.

Plant parasitic nematodes cause serious damage to rice crop. Thirty two species belonging to 13 genera were observed in association with the crop. Among them few are considered to be important. They are the rice white - tip nematode (Aphelenchoides besseyi), rice stem nematode (Ditylenchus angustus), rice root nematode (Hirschmanniella oryzae), root-knot nematode
(Meloidogyne graminicola) and the cyst nematode (Heterodera oryzicola).

Citrus is an important fruit crop and ranks third in area which is followed by mango and banana. They are grown in 105,396 hectares in India. Among the oranges, mandarin oranges, limes and sweet oranges are very popular while lemons, grape fruits, pummelos, sour and bitter oranges are of minor importance. The Citrus spp. are grown in larger extent in the states
of Maharashtra, Karnataka, Kerala, Tamil Nadu, Andhra Pradesh, Punjab, Haryana, Rajasthan, Assam, Orissa and Bihar.

Potato is one of the most important vegetable crop grown in India. It thrives best in cool climate. Therefore it is a summer crop in the hills and a winter crop in plains.

Crossandra (Crossandra undulaefolia) is one of the important commercially grown flower crop in Tamil Nadu. In recent years there is a marked decline in the cultivation of this crop in Madurai, Dindigul, Coimbatore, Salem, Thiruvannamalai and Tiruchirappalli districts. The common problem with the crop is death of plants in patches during the second and third year. This is due to the nematode-fungal complex disease in the crop.

Black pepper (Piper nigrum) is indigenous to the tropical forests of Western Ghats of South India. The crop is grown in Kerala, Karnataka, Tamil Nadu, Andra Pradesh and Assam.

Plant parasitic nematodes can be controlled by several methods. The nematode control aims to improve growth, quality and yield by keeping the nematode population below the economical threshold level. The control measures to be adopted should be profitable and cost effective. It is essential to calculate the cost benefit ratio before adopting control measures.

Nematode associated with insects are referred as entomophilic, entomogenous and entomophagous nematodes. Generally they belong to the superfamilies Tylenchoidea, Rhadbitoidea, Oxyuroidea and Mermithoidea of the phylum Nematoda.

Model organisms are widely used in biological researches to describe basic biological processes. When selecting living organisms as models to work with, a wide range of characteristics are used which include: 1) rapid development with short life cycles, 2) small adult size, 3) ready availability and 4) tractability. 

Acids are chemical substances that are sour in taste and highly corrosive. The term ‘Acid’ was derived from a Latin word ‘acidus’, meaning ‘sour’. They emit sharp odour and transform litmus colour from blue to red. They lose their properties when alkalis are added to them. However, in this process, alkalis also lose their alkaline properties.

Volumetric analysis, also known as titrimetric analysis, is an analytical method of estimating the concentration of a known solute (analyte) in a solution by measuring the volume of a second known solution of known concentration (standard solution), that reacts completely with the known solute of unknown concentration. The prerequisite of titration is that the two different analytes, present in solution form, must involve in a fast chemical reaction. The standard solution is more commonly known as ‘titrant’ and the solution whose concentration needs to be determined is frequently called ‘titrand’.

Indicators are the natural or synthetic chemical compounds that are used to detect the equivalence point in a volumetric analysis where unknown compound in a solution form is quantitatively estimated with the help of a known standard solution. The equivalence point, also known as the stoichiometric end point, is the point or stage of a titration reaction where the equivalent amount of the reacting substances are mixed together, and this point is identified by monitoring the rate of change in pH, conductivity, flow of current, adsorption, fluorescence, changing of solution colour, occurrence or disappearance of turbidity, flocculation or deflocculation, etc.

Centrifugation is a technique that promotes accelerated settling of particles in a solid-liquid mixture by the application of centrifugal force. The device that accelerates the separation with the help of centrifugal force is known as ‘Centrifuge’. The centrifuge consists of a fixed base or frame and a rotating part in which the mixture is placed and is then spun at high speed.