Introduction

Non-imaging types of IR guided missiles make use of infrared emission corresponding to the thermal signatures of the exhaust and the mainframe of the target aircraft to home on to it. Emission in 3−5 and 8−12 micron bands is characteristic of electromagnetic emission from jet exhausts and mainframe of the aircraft. Spectral content of infrared emission as received by an IR seeker head is the superposition of the spectral emission from the aircraft on the transmission characteristics of the atmosphere and is shown in Fig. 16.1[5]. This spectral signature is judiciously used in guidance of air-to-air and surface-to-air IR guided missiles. Both air-to-air and surface-to-air IR guided missiles receive the target's infrared signatures in the presence of background radiation from the sky and also infrared signatures of flares, if any, deployed by target aircraft platform. The seeker head should be able to discriminate between infrared signatures of the background and flares from those of the target.

Infrared signatures of target and flare

Signature prediction and analysis component in the design of test systems that simulate true battlefield like scenario. This topic has been extensively researched and reported in literature.

Major sources of background infrared noise include the earth, the sky, thermal emissions from clouds and solar reflections[6]. The background sources are generally modelled as a black body whose radiance is dependent upon its temperature and emissivity. The total radiance incident on the missile seeker is estimated after taking into consideration contributions from all these sources and also the transmission characteristics of the atmosphere. Though background signatures are dynamic in nature and vary with weather condition, path length and altitude; for the purpose of IR guided missile guidance, static background noise spread over 3−12 micron band is a reasonably good approximation.

Different sources of infrared radiation in an aircraft can be classified as internal and external sources[7]. Internal sources include hot engine parts, airframe skin heated by the engine and aerodynamic heating, combustion of the hot gases in the plume and the skin of the airframe. External sources include reflected ambient radiation from the sun, the sky and the ground. The hotter surfaces like the hot engine parts, the tail pipe region and the plume mainly contribute in the lower wavelength band whereas the fuselage region, the airframe and the reflected radiation are the dominant factors in the longer wavelength region.

This chapter makes a comprehensive analysis of groundwater governance, one of the most important issues facing the water sector in India at present. It analyses the institutional measures taken to deal with the challenge, explains the reasons why these were not effective and suggests an alternative framework.

Phenomenal expansion of groundwater and the challenge of governance

As pointed out in Chapter 5, groundwater has emerged as the most important source for irrigation as well as for other uses of water, including domestic and industrial. It has been a major factor in raising agricultural production and productivity and sustaining subsistence farming for millions of small and marginal farmers. It has played an important role in helping food security and poverty alleviation.

The stage of groundwater development increased from 37.2 per cent in 1998 to 61 per cent in 2009. This has resulted in over-exploitation of this resource in several areas. It is a matter of special concern that over-exploitation has become an acute problem in a number of agriculturally important states, e.g. Punjab, Haryana, Gujarat, Maharashtra, Rajasthan, Uttar Pradesh and Tamil Nadu, with adverse implications for agricultural production and food security. Besides, there are adverse impacts on water quality, health, livelihood and environment. Groundwater flow to rivers also tends to decrease, resulting in reduced supply for canal irrigation and drinking water. Other adverse effects include increase in cost of pumping, decrease in yield, expenditure on replacement or upgradation of pumps, non-functioning of hand pumps, etc. The situation of over-exploitation is not only unsustainable but also iniquitous. It favours better‑off farmers who are already enjoying greater benefits from groundwater as against small and marginal farmers who derive less benefits due to increase in costs of extraction and consequent reduction in accessibility to the resource.

How to check the fast depleting groundwater reserves has, therefore, become a major challenge in India at present. Supply-side measures such as recharge through rain water harvesting may reduce the problem to some extent but cannot solve it altogether because of the limited potential. Hence, the paramount need is to moderate demand in water-stressed areas so as to bring about equilibrium between demand and supply.

Introduction

Non-linear optical phase conjugation by degenerate four-wave mixing (DFWM) is an important technique with applications in many fields of science and technology including image transmission, optical image processing, optical filtering, and laser resonators[14, 29, 8]. When two counter-propagating and intense light beams interact with a non-linear medium, together with a less intense third one, a fourth beam is generated from the medium, which will be the phase conjugation of the third beam. This technique is called four-wave mixing. The unique feature of a pair of phase conjugate beams is that the aberration influence imposed on the forward (signal) beam passed through an inhomogeneous or disturbing medium can be automatically removed from the backward (phase conjugated) beam passed through the same disturbing medium[11]. The main applications of degenerate DFWM techniques are non-linear spectroscopy, real time holography, and phase conjugation. Phase conjugation by DFWM has been demonstrated in many organic and inorganic materials using pulsed or continuous-wave (CW) lasers[27, 12].

The phase conjugate light has a variety of characteristics and properties not associated with normal light and they can be enumerated as follows:

• (1) Phase compenzation effect: Waves that pass through an aberrating medium are injected into a phase conjugate mirror. If the outgoing wave is re-propagated through the medium, the waves phase distortion is compensated.

• (2) Space domain multiplicative interaction: Since phase conjugate waves are produced by interaction in a non-linear medium, the spatial multiplicative effect among the light waves appears in the phase conjugate waves.

• (3) Intensity dependant phase shift: Due to the optical Kerr effect in a non-linear medium, the phase shift of the electric field depends on the wave intensity.

• (4) Detuning dependence: The reflectance of a phase conjugate mirror strongly depends on the detuning between the pump and probe wave frequencies.

• (5) Time inversion: A phase conjugate wave can be regarded as a time inverted wave since its direction of propagation is exactly opposite that of the probe wave and the wave front is identical to that of the probe wave.

• (6) Time domain multiplicative interaction: When pulsed waves are used in the production of phase conjugate light, the resulting polarization, that is, the generalized phase conjugate wave intensity depends on the product of the interacting waves in the waves’ temporal domains.

The chapter provides a critical review of participatory irrigation management (PIM) in canal irrigation, which is regarded as an internationally acclaimed institutional set up for a more efficient irrigation system. It also examines the case for PIM, provides background information of its introduction in India along with the support measures offered by the government, explains the salient features of the laws enacted for this purpose, draws attention to its slow progress along with reasons for the same, throws light on some key aspects of PIM experience in India, including socio-economic impact, highlights conditions for its success and indicates some macro-implications.

Case of PIM

The vast canal network in India has traditionally been administered by the State Irrigation Departments, which directly deal with individual farmers. This puts tremendous pressure on the Departments in preparing the water distribution schedule for individual farmers. Faced with unpredictable water flows, supplies tend to be made arbitrarily or in a haphazard manner. Because of this, objectives of optimum utilization of the created irrigation potential, equitable distribution of water at the farm level and maximum increase in farm productivity are not achieved on a sustainable basis. There is neither any practical effort on the part of farmers to maintain field channels constructed by the government, nor the sense of economic use of water generated among them. Moreover, larger benefits are often derived by those having privileged position in the community or having their land located in an outlet command or in head reaches of a canal system at the cost of socially or economically weaker sections and tail-enders.

Hence, policy makers and thinkers started realizing that the complex tasks involved in water management could not be performed efficiently by a centralized bureaucracy and that it would be better to transfer much of the power and responsibilities to the actual users of water. It was hoped that farmers’ involvement would reduce water distribution cost and ensure proper maintenance of irrigation system at the micro-level. The understanding that they own the system would motivate farmers towards better use of water. They would pay irrigation charges at the main outlet level on volumetric basis which would be less than crop-wise irrigation charges on acreage basis.

Introduction

Chemical oxygen−iodine laser (COIL) was first demonstrated by McDermott et al. in 1978 and is the only chemical laser based on electronic transition. It operates on 2P1/2 → 2P3/2 transition of iodine atom at 1.315 μm and is pumped by the following reaction scheme,

This laser due to its short wavelength, high efficiency and scalability has found application in various military and civilian scenarios in the last decade. The possibility of carrying high power beams via optical fibers makes it extremely useful for decommissioning and dismantling dangerous structures such as obsolete nuclear reactors through remotely operated mechanisms by Tei et al.

The pumping source, O2(1) is an excited form of oxygen molecule with energy level very close to that of atomic iodine enabling near resonant energy transfer as shown in Fig. 8.1. Although, different techniques such as chemical, RF discharge, photo-sensitizer, have been reported for the production of O2(1), the chemical method is the only one till date that has been successful for scaling up power. Therefore, amongst the variousmechanisms studied for the production of O2(1), the chemical method still remains at the forefront for the development of large-scale COIL systems. The chemical method is based on chemical reactions between chlorine gas and basic hydrogen per-oxide (BHP) solution resulting in production of singlet oxygen, which in turn dissociates iodine molecules into iodine atoms and also subsequently excites these atoms.

For an efficient production of singlet oxygen, jet type singlet oxygen generator (JSOG) by Rajesh et al. has proved its potential over the other techniques such as rotating disc or bubbler type. Other forthcoming generators such as twisted aerosol and centrifugal bubble/ flow type are yet to be proven for large-scale power levels.

Figure 8.2 shows the functional block diagram of chemical oxygen iodine laser[3, 9] which exhibits coupling of all subsystems. BHP solution is prepared in a separate preparation tank and supplied to the SOG reaction chamber in the form of jets. Chlorine is supplied to the SOG reaction chamber from the bottom in a counter-flow direction to the jets so that it reacts at the surface of the liquid jets to produce singlet oxygen molecules.

Before taking into consideration the quantum mechanical operators, it is perhaps the best to clear the meaning of the term operator in the mathematical sense. The term operator may be defined in the following manner:

It means, operator. function = new function

Here symbol d/dx is an operator that alters the function sin x into first derivative with respect to x, i.e., cos x.

Similarly, the symbol () is an operator, the instruction being to take the square root of the quantity, which follows it. For example, if a number, say 25, is kept under operator (), it alters 25 into its square root, i.e., 25 = 5. Addition, subtraction, multiplication, division, log, differentiation, integration, etc., are also operators. It is to be noted that the operators always operate on the function written to the right of them and the operator has no physical significance if written alone.

An operator is normally written with a cap sign (ˆ) overhead, e.g., Â. Thus,  represents an operator. To make it clearer, if we write  f (x) = g(x), it means  is an operator operating on the function f (x). g(x) is an another function, which is a new one obtained after the operation of operator  on the function f (x).

If  = d/dx and f (x) = ax2, then  f (x) = d/dx(ax2) = 2ax = g(x). Similarly, we can cite other examples similar to the above.

Water sector in the coming decades in India must unfold a much brighter picture if the prosperity of our people is to be ensured over a long period. This requires knowledge and understanding of the challenges facing the water sector in India at present and the overall approach that should be adopted in future to deal effectively with the challenges. This chapter provides an overview of the same along with major highlights of the required policy framework, the components of which have already been explained in detail in the respective chapters.

The challenges

The water resource scenario in India is markedly worse than what it used to be decades earlier and may get further worse in future. The increasing scarcity of water has started threatening the stability and prosperity of our people, with adverse effects on growth and social justice. It results in over-exploitation of aquatic ecosystems, which affects the sustainability of the resource. As a result, the ecosystems and organisms, including humans dependent on them for survival and well-being, suffer in the end. How to cope with this scenario so as to ensure water security to all in the coming decades has emerged as a major challenge at present in India and may become daunting in future, unless the authorities take appropriate measures in time. Further, there is the challenge of removal of poverty along with provision of food security in which too water has a pivotal role. There is a special problem of women and other vulnerable sections, which suffer more due to scarcity of water. The problem gets aggravated due to the intense controversy related to choice between large and small projects. How to resolve this controversy has emerged as an additional challenge.

The above challenges become greater because of the dwindling scope for the usually adopted supply-driven options. But, how to adopt other options, such as increasing water use efficiency, reversing the trend of degradation of rivers and aquifers and enforcing a system of demand management, is a real challenge, as these depend on governance. Poor people often lack access to safe water and basic sanitation because the management system is not up to the mark.