Open Access Commentary

Discussion of Foster & Brown's Time and Tide: Analysis of Sea Level Time Series

A. Parker, C. D. Ollier

Physical Science International Journal, Page 119-130
DOI: 10.9734/PSIJ/2015/15652

The recognition of the non-accelerating, periodic pattern of sea levels as described by the tide gauges measurements does not require any special mathematical tool. Providing enough data of sufficient quality have been recorded, If the classical linear fitting is used to compute the rate of rise at any time, then the acceleration is simply the time rate of change of this velocity. By using this technique, the lack of any acceleration over the last few decades is evident in the naturally oscillating, slow rising, tide gauges of appropriate quality and length. Contrary to what is claimed in the commented paper, the accuracy in the computation of the periodicities of the natural oscillations does not impact at all on this result. As the measured sea level oscillations are not perfectly sinusoidal, clearly different assumptions about the shape of the periodic functions, their number and the definition of the algorithm used to compute the parameters of the selected periodic functions all affect the determination of the periodicities. This has however very little influence on the present sea level debate questioning the presence or the absence of acceleration at the tide gauges.  

 

Open Access Original Research Article

Geophysical Evaluation of Erosion Sites in some Parts of Abia State, Southeastern Nigeria

U. J. John, M. U. Igboekwe, C. Amos-Uhegbu

Physical Science International Journal, Page 66-81
DOI: 10.9734/PSIJ/2015/13821

This work evaluates the external and internal structures of erosion sites in parts of Abia state, Nigeria and determines the gully erosion sensitivity of the sediments. Attributes such as lithology, land use, geomorphology, and climate were factored-in as gully erosion predisposing factors. The geophysical method used was the electrical method which employed the Schlumberger electrode configuration with maximum half current electrode spacing of AB/2 = 150 m, and 8 vertical electrical sounding (VES) data were acquired. The computer-aided resist software method was used for further processing and interpretation of the VES data. Thereafter some geo-electrical sections were drawn and hence the geologic units of the area obtained. Results show that the resistivity of the erosive materials range between 812.0 Ωm-3,738 Ωm, while the depth ranges from 16.6 m (VES 3) to 90.7 m (VES 6).  A correction factor was used in determining the true thickness of sediments where surface resistivity sounding data were acquired. The method depicts a valuable tool for assessing depth, thickness and nature of erosive material.

 

Open Access Original Research Article

Geoelectrical Investigation of Soils as Foundation Materials in Umudike Area, Southeastern Nigeria

E. U. Nwokoma, G. U. Chukwu, C. Amos-Uhegbu

Physical Science International Journal, Page 82-95
DOI: 10.9734/PSIJ/2015/14667

Geoelectrical investigation of soils in Umudike area of Abia State was undertaken in order to determine the competence of the soils as foundation materials. A total of 18 Vertical Electrical Sounding (VES), using Schlumberger configuration was carried out.  The results revealed three to six distinct geoelectric sequences with resistivities ranging from about 8 Ωm to about 38,000 Ωm and a variation in topsoil thicknesses with the least as 0.2 m at vicinity of VES Station 2 Ahiaeke and the highest as 5.0 m at VES Station 14 MOUAU. The topsoils are composed of sands, silts, sandy clays, clays and laterites. The study also revealed the cause of frequent cracking and collapse of a portion of the Umuahia-Ikot-Ekpene road. Based on the results of the survey, the most competent soils within which large civil engineering structures will be founded within the study area are encountered at VES 8,9 (inside ABSUPAC), 6 (opposite GCU), 14 and 15 ( inside MOUAU).

 

Open Access Original Research Article

Evaluation of Solar Cell Using Terahertz Time-Domain Spectroscopy

K. A. Salek, I. Kawayama, H. Murakami, M. Tonouchi

Physical Science International Journal, Page 96-102
DOI: 10.9734/PSIJ/2015/15338

Terahertz time-domain spectroscopy (THz-TDS) has been used to investigate the optical properties of mono silicon solar cell. The sample was optically excited using continuous-wave (CW) light of wavelengths of 800 nm and 365 nm and the carrier density and mobility were extracted from the THz-TDS data by fitting with the simple Drude model. The conductivity shows nonlinear increase with the optical excitation power. The mobility of the photo-excited carriers also increases nonlinearly with the CW light power. However, the mobility shows tendency to saturate with the increase of illumination power, which can be explained by carrier trapping effect to the impurity states existing in the band-gap region of the base material of solar cell. In addition, it is observed that the carrier density and mobility are smaller for 365 nm light illumination due to surface recombination.

 

Open Access Original Research Article

Structural, Optical and Electrical Properties of Chemical Vapour Deposited Nitrogen Doped Diamond Like Carbon Films

S. Kundoo, S. Kar

Physical Science International Journal, Page 103-111
DOI: 10.9734/PSIJ/2015/15698

Aim: Deposition of undoped and nitrogen doped amorphous diamond like carbon films and investigation of improved electrical, optical, field emission as well as structural properties of the films due to nitrogen doping.

Materials and Methods: Nitrogen doped diamond like carbon (N-DLC) films were deposited on silicon and glass substrates by using direct current plasma enhanced chemical vapour deposition (PECVD) process. Precursor gases used were acetylene and nitrogen. The films were characterized by different techniques such as XRD, FTIR, UV-Vis-NIR spectroscopy. Also electrical conductivities and field emission parameters of the films were measured.

Results and Discussion: XRD spectra showed the amorphous nature of the deposited films. Fourier-transform infrared spectroscopy (FTIR) measurements showed different vibrational modes of tetrahedrally bonded carbon present in the DLC films. With the incorporation of nitrogen into the DLC matrix different CN absorption bands appeared in the FTIR spectra. From FTIR spectra variation of sp3/sp2 ratios in the films with nitrogen concentration in the plasma were measured. The results showed that sp3 fraction decreased with increase in nitrogen concentration. N-DLC films showed higher room temperature conductivity and better field emission properties. Tauc gap of the films was decreased with the increase in nitrogen percentage in the plasma, as with the increase of nitrogen content in the DLC films sp2 carbon content was increased, which is consistent with the FTIR results. Nitrogen doped films showed higher emission currents at lower turn-on fields.

Conclusions: FTIR measurements showed various C–H bonding vibrations and different CN absorption bands present in the spectra of N-DLC films, thus confirmed incorporation of nitrogen into DLC matrix. Highest sp3/(sp2+sp3) ~ 85.65% was achieved in the undoped DLC film. N-DLC films showed two orders of magnitude more room temperature conductivity than undoped ones.  The lowest turn-on field achieved was 6.56 volt/mm for current density of 0.5 mA/cm2.

 

Open Access Original Research Article

Aproximations in Divisible Groups: Part I

Jeffery Ezearn, William Obeng-Denteh

Physical Science International Journal, Page 112-118
DOI: 10.9734/PSIJ/2015/10666

This is the first in a series of papers on Dirichlet-type approximation in the setting of Cauchy sequences in normed divisible groups. In particular, we demonstrate that the concept of approximation exponents are extendable to elements belonging to the completion of a normed uniquely divisible group and other such groups that enjoy a form of divisibility. To give a measure of how “best” the approximation can be, we introduce group theoretic functions (dubbed proximity functions), which generalise the notion of the order of elements in a group. A proximity function ϱ on a group with identity e is defined by three axioms: (i) Ï±(g≠e)=ϱ(g^(-1) )>0, (ii) Ï±(gh^(-1) )≤Cϱ(g)ϱ(h) and (iii) Ï±(gh^(-1) )≤Cϱ(g) if Ï±(g)=ϱ(h), where C>0 is an absolute constant. The main result in this paper is to show that given a proximity function that is in a certain sense discontinuous at the identity, then Cauchy sequences in a uniquely divisible group G do not converge inside G; in the sequels, we consider the case of convergence inside the completion of G but not inside G.