Elements of design and a field application of a TDR-based soil moisture and electrical conductivity monitoring system are described with detailed presentation of the time delay units with a resolution of 10 ps. Other issues discussed include the temperature correction of the applied time delay units, battery supply characteristics and the measurement results from one of the installed ground measurement stations in the Polesie National Park in Poland.

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A b s t r a c t. The paper presents scientific foundation and some examples of agrophysical applications of dielectric spectroscopy techniques. The aim of agrophysics is to apply physical methods and techniques for studies of materials and processes which occur in agriculture. Dielectric spectroscopy, which describes the dielectric properties of a sample as a function of frequency, may be successfully used for examinations of properties of various materials. Possible test materials may include agrophysical objects such as soil, fruit, vegetables, intermediate and final products of the food industry, grain, oils, etc. Dielectric spectroscopy techniques enable non-destructive and non-invasive measurements of the agricultural materials, therefore providing tools for rapid evaluation of their water content and quality. There is a limited number of research in the field of dielectric spectroscopy of agricultural objects, which is caused by the relatively high cost of the respective measurement equipment. With the fast development of modern technology, especially in high frequency applications, dielectric spectroscopy has great potential of expansion in agrophysics, both in cognitive and utilitarian aspects.K e y w o r d s: agrophysics, dielectric spectroscopy, food quality INTRODUCTIONAgrophysics is a specialized scientific field derived from the branch of the agricultural sciences (Micha³ek, 2006). Its aim is to apply physical methods for studies of properties of materials and processes occurring in production and processing of crops and food of agricultural origin. Dielectric properties of all materials existing in Nature are dependent on their molecular structure. Specifically, they depend on the distribution of electric charges, which are either constantly embedded within the molecules or become temporarily induced on their surfaces. It is also known that the molecular structure of objects determine their physical and chemical properties. Therefore, one may suppose that the dielectric properties of mixtures of various molecules constituting a given material will uniquely identify it. It means that dielectric properties can successfully diversify physical and chemical properties of a tested material. This idea is presented in Fig. 1. The crucial point of the application of the dielectric spectroscopy measurement techniques in agrophysics is the utilization of their advantages for rapid and non-destructive assessment of the quality of the agricultural objects. It may be done by searching for dependencies between the dielectric properties and other physical and chemical properties of tested materials of agricultural origin.Behaviour of any material in the electric field is unique, because of the unique molecular structure of each material. On the other hand, physical and chemical properties of materials determine their quality, which in the case of food products is closely related to their commercial and nutritional value. Therefore, it is reasonable to assume that the dielectric properties, uniquely describing each...

This paper presents the application of a frequency-domain reflectometry (FDR) sensor designed for soil salinity assessment of sandy mineral soils in a wide range of soil moisture and bulk electrical conductivity, through the determination of soil complex dielectric permittivity spectra in the frequency range 10–500 MHz. The real part of dielectric permittivity was assessed from the 380–440 MHz, while the bulk electrical conductivity was calculated from the 165–325 MHz range. The FDR technique allows determination of bulk electrical conductivity from the imaginary part of the complex dielectric permittivity, without disregarding the dielectric losses. The soil salinity status was determined using the salinity index, defined as a partial derivative of the soil bulk electrical conductivity with respect to the real part of the soil complex dielectric permittivity. The salinity index method enables determining the soil water electrical conductivity value. For the five sandy mineral soils that have been tested, the relationship between bulk electrical conductivity and the real part of dielectric permittivity is essentially linear. As a result, the salinity index method applied for FDR measurements may be adapted to field use after examination of loam and clayey soils.

We study the effect of extra dimensions on the process of massive Dirac fermion emission in the spacetime of (4 + n)-dimensional black hole, by examining the Dirac operator in arbitrary spacetime dimension. We comment on both bulk and brane emission and find absorption cross section and luminosity of Hawking radiation in the low-energy approximation.PACS numbers: 04.50.+h, 04.70.Dy I. INTRODUCTIONScientists have devoted many years to the ongoing quest to unify the forces in Nature. Higher-dimensional theories provide a promising framework for the unification of gravitation with other fundamental forces. In this context braneworld models [1,2] with large extra dimensions point us the way out of the long standing hierarchy problem by lowering the fundamental scale of gravity down to order of TeV. It has been also argued that mini black holes might be created through high-energy particle collisions at TeV-energy scales. These objects are expected to evaporate through Hawking radiation both in the bulk as well as on the brane. Mini black holes created in high-energy collisions will undergo a number of phases, i.e. balding phase when black hole will emit mainly gravitational radiation, spindown phase during which black hole will loose its angular momentum through emission of Hawking radiation and Schwarzschild phase in which black hole will lose its actual mass by Hawking radiation. Finally in Planck phase quantum gravity theory is needed to study its behaviour. The TeV scale gravity opens up the possibility of producing black holes and observing their decay product. The aforementioned range of energy will be soon achieved by CERN Large Hadron Collider. One hopes that it proves or merely restricts the parameter range (e.g., number or size of extra dimensions) of higher dimensional theories.Studies of particle emission from multidimensional black hole have their own long history. Namely, in Ref.[3] massless scalar emission were studied in the spacetime of (4 + n)-dimensional Schwarzschild black hole while the case of massless spinor and gauge particles was treated in [4]. Then, radiation emitted from higher-dimensional black holes were considered both analytically and numerically (see, e.g., Refs.[5]-[8] for a non-exhaustive sampling of this widely treated subject). On the other hand, graviton emission in the bulk from a higher dimensional Schwarzschild black hole was elaborated in Refs. [9], where it was established that the low-energy emission rate decreases with the number of extra-dimensions as was previously found for the case of bulk massless scalar field.The complexity of the aforementioned problem in the background of a rotating (4 + n)-dimensional black hole was revealed in Refs. [10]. The argument of the effect of mass on the emission spectrum in four-dimensions was quoted in [11] (see also [12] where the particle and light motion in the vicinity of five-dimensional rotating black hole was investigated). In Ref.[13] the scalar massless Hawking emission into the bulk by a higher dimensional rotating black hole...

We investigate the intermediate and late-time behaviour of the massive Dirac spinor field in the background of static spherically symmetric brane-world black hole solutions. The intermediate asymptotic behaviour of the massive spinor field exhibits a dependence on the field's parameter mass as well as the multiple number of the wave mode. On the other hand, the late-time behaviour power law decay has a rate which is independent of those factors.

This paper presents a novel seven-rod sensor used for time-domain reflectometry (TDR) and frequency-domain reflectometry (FDR) measurements of soil water content in a well-defined sample volume. The probe directly measures the complex dielectric permittivity spectrum and for this purpose requires three calibration media: air, water, and ethanol. Firstly, electromagnetic simulations were used to study the influence of the diameter of a container on the sensitivity zone of the probe with respect to the measured calibration media and isopropanol as a verification liquid. Next, the probe was tested in three soils—sandy loam and two silt loams—with six water contents from air-dry to saturation. The conversion from S 11 parameters to complex dielectric permittivity from vector network analyzer (VNA) measurements was obtained using an open-ended liquid procedure. The simulation and measurement results for the real part of the isopropanol dielectric permittivity obtained from four containers with different diameters were in good agreement with literature data up to 200 MHz. The real part of the dielectric permittivity was extracted and related to the moisture of the tested soil samples. Relations between the volumetric water content and the real part of the dielectric permittivity (by FDR) and apparent dielectric permittivity (by TDR) were compared with Topp’s equation. It was concluded that the best fit to Topp’s equation was observed in the case of a sandy loam. Data calculated according to the equation proposed by Malicki, Plagge, and Roth gave results closer to Topp’s calibration. The obtained results indicated that the seven-rod probe can be used to accurately measure of the dielectric permittivity spectrum in a well-defined sample volume of about 8 cm3 in the frequency range from 20 MHz to 200 MHz.

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