Radiation tubular source

Many of these difficulties can be overcome by choosing an appropriate configuration of the photoreactor system. One such a system is the mechanically agitated cylindrical reactor with parabolic reflector. In this type of reactor, the reaction system is isolated from the radiation source (which could also simplify the solution of the well-known problem of wall deposits, generally more severe at the radiation entrance wall). The reactor system uses a cylindrical reactor irradiated from the bottom by a tubular source located at the focal axis of a cylindrical reflector of parabolic cross-section (Fig. 40). Since the cylindrical reactor may be a perfectly stirred tank reactor, this device is especially required. This type of reactor is applicable for both laboratory-and commercial-scale work and can be used in batch, semibatch, or continuous operations. Problems of corrosion and sealing can be easily handled in this system. 

Alfano O.M., Romero R.L. and Cassano A.E. 1985. A cylindrical photoreactor irradiated from the bottom. I. Radiation flux density generated by a tubular source and a parabolic reflector, Chem. Eng. Sci., 40, 2119-2127. 

Fig. 21-6 (a) Plots of the factor C,(0) of Eq. (21-38) as a function of the radiation angle 0q for an axisymmetric source within a step-profile fiber, (b) Normalized power P as a function of the radiation angle 0q for an axisymmetric tubular source coinciding with the interface of a step-profile fiber. The solid curve is calculated from Eq. (21-41b) and the free-space dashed curve from Eq. (21-32). 

We showed in section 21-10 that the radiation from a tubular source with the current distribution of Eq. (21-13) is directed at the angle of EQ- (21-29) relative to the fiber axis. Consequently, the total power P radiated from a tube of length 2L and radius / q < p within a step-profile fiber is given by [2]... 

Example Dipole radiation 25-13 Example Tubular-source radiation... 

We now examine how radiation from the point dipole and the tubular source is modified by the presence of a fiber. In order to relate the results to the correction factor of Section 21-12, the fiber is assumed to be weakly guiding. 

A tubular source of radius ro is located symmetrically within the core of a weakly guiding, step-profile fiber, i.e. 0 < ro < p, where p is the core radius. To account for the fiber profile, we repeat the analysis of Section 25-13 using the weakly guiding radiation modes of Table 25-4 instead of the free-space modes of Table 25-2. The modal amplitudes of Eq. (25-34a) are replaced by... 

Having set up the formalism for the calculation of free-space radiation from current sources, we now account for the effect of the fiber on the radiation fields. We could proceed by solving Eq. (34-16) for a given profile, which leads to the fields through Eqs. (34-15) and (34-13). However, rather than superpose the far fields of point sources, we prefer to determine the Green s function for the tubular source introduced in Section 21-6 and illustrated in Fig. 21-3 [7]. The advantage of the tubular source is that it has the same geometrical symmetry as the circular fiber. Furthermore, an arbitrary current source can be described either by a distribution of dipoles or by a complete set of tubular sources. Here we examine the latter approach. 

The radiation fields of the tubular source depend on the solution of Eq. (34-22) for the cartesian components of A,. Nevertheless, we can make a general deduction about these fields regardless of the fiber profile [7]. First consider the free-space solution when n = Mji everywhere. The spatial dependence of A at radius r outside of the tube is proportional to... 

Xenon lamps are available mainly as tubular and point source bulbs. The radiation produced by this type of lamps is not particularly rich at wavelengths below 400 nm, and therefore their applications are somewhat limited. However, it is possible to pulse xenon lamps, which enables them to achieve high peak irradiances. Commercially available pulsed xenon lamps are available with emissions in the UV and visible spectral range. Alternating the gas fill can produce output rich in UV. 

Extended light sources may be installed around a tubular reactor or in the axis of an annular irradiated reaction volume. In the first case, an annular (or coaxial) radiation field focalized on the axis of the tubular reactor is created (Figure 10), and, in reaction mixtures of very low absorbance, irradiance as a function of the radius of the cylindrical reactor shows highest values in the axis of the reactor (positive geometry of irradiation, Figure 11 [2,3]). 

In actual practice, any tubular light source will have a finite diameter and will not behave as a true line source. Radiation from an extended light source will emanate from points displaced from the lamp s axis, causing the lamp to appear rather like a diffuse light source. In addition, imperfections in the... 

As a brief introductory summary, vitamin D substances perform the following fundamental physiological functions (1) promote normal growth (via bone growth) (2) enhance calcium and phosphorus absorption from the intestine (3) serve to prevent rickets (4) increase tubular phosphorus reabsorpiion (5) increase citrate blood levels (6) maintain and activate alkaline phosphatase m bone (7) maintain serum calcium and phosphorus levels. A deficiency of D substances may be manifested in the form of rickets, osteomalacia, and hypoparathyroidism. Vitamin D substances are required by vertebrates, who synthesize these substances in the skin when under ultraviolet radiation, Animals requiring exogenous sources include infant vertebrates and deficient adult vertebrates, Included there are vitamin D (calciferol ergocalciferol) and vitamin D< (activated 7-dehydrocholesterol cholecalciferol). 

Radiation sources The most common radiation source used with AA is a HCL, which consists of a tubular-shaped cathode made of the metal of interest and a simple anode. A milliamp DC discharge is established between these electrodes in a low-pressure noble gas environment. The discharge results in a very line-rich spectrum of the cathode material. Electrodeless discharge lamps (EDLs) are brighter and require a microwave power supply. For elements whose HCL lines are weak, EDLs are often the lamps of choice. 

In the previous chapter we examined the excitation of modes of a fiber by illumination of the endface with beams and diffuse sources, i.e. by sources external to the fiber. Here we investigate the power of bound modes and the power radiated due to current sources distributed within the fiber, as shown in Fig. 21-1. Our interest in such problems is mainly motivated by the following chapter, where we show that fiber nonuniformities can be modelled by current sources radiating within the uniform fiber. Thus, isolated nonuniformities radiate like current dipoles and surface roughness, which occurs at the core-cladding interface, can be modelled by a tubular current source. 

The tubular current source was described in Section 21-6, where we showed that it is ineffective in exciting bound modes unless either of the resonance conditions of Eq. (21-15) is satisfied. A similar conclusion holds for the radiation fields. If the tube length 2L is large compared to the spatial period 2n/Sl, where 2 is the frequency in Eq. (21-13), it is intuitive that power will be radiated essentially at a fixed angle to the fiber axis. This is also a consequence of Floquets theorem [7]. However, unlike the current dipole, radiation now depends on the orientation of the currents on the tube. 

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