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1

Statistical Estimation and Mathematical Modelling of Tropospheric Radio Refractivity Based on Meteorological Data

Alimgeer K. S., Awais M., Ijaz B., Khan S. A., Subhan F., Ahmad N.

Metrology and Measurement Systems

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2018

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Vol. 25, nr 1

115--128

EN

To obtain optimal performance, estimation of radio refractivity is essential in planning and design of radio links/systems. The dependence of radio refractivity on different climatic parameters such as temperature, pressure, humidity and scale height is studied. The method proposed by International Telecommunication Union (ITU) is used in calculation of tropospheric radio refractivity. The main objective of this work is to formulate a mathematical equation/expression which can be used to predict/estimate the value of radio refractivity for an arbitrary day of any year, with a low error of estimation, in a local environment. Sensitivity of radio refractivity to temperature, pressure and humidity has been evaluated for a period of 5 years from 2008 to 2012, in a particular area under consideration. The results presented for tropospheric radio refractivity take into consideration both the location height and scale height parameters. The results are analysed in terms of statistical measures such as the moving averages, probability density function, monthly mean values, and their corresponding standard deviations. Finally, a mathematical model is formulated to calculate the radio refractivity for any day of a whole year. Reliability of error analysis in respect to accuracy is also shown. It was implemented in the industrial enterprise.

2

The Site Preference Analysis and Ordering Characteristics of Ternary Cu0.5(Zn1–xMx)0.5 (M = Transition Metals) Alloys

Ahmad N., Ziya A. B., Atiq S., Saifullah K., Hashim M., Saleem M.

Archives of Metallurgy and Materials

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2018

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Vol. 63, iss. 3

1531--1535

EN

The site preference of some transition metals during B2-type ordering has been investigated in the ternary Cu0.5 (Zn1-x Mx )0.5 alloys with M = Ti, V, Ag, Au, Cr, Mn, Fe, Co, Ni, Nb, Mo, Hf, Ta, W, Re or Pt (x ≤ 0.01). The statistic-o-thermodynamical theory combined with the electronic theory of alloys has been used to calculate the partial ordering energies, partial short range order parameters and the order-disorder transformation temperatures. The values of partial short range order parameters have been used to determine the site preference of the metal M. The analysis shows that the metals M can be divided into two groups with regard to lattice site occupancy. One group comprising of Cr, Mn, Fe, Co, Ni, Nb, Mo, Hf, Ta, W, Re or Pt was found to prefer Zn sublattice sites, while the second group of Ti, V, Ag or Au atoms prefer Cu sublattice sites. It is found that order-disorder transformation temperature and the site preference of metal M both depend strongly on the partial ordering energies and ternary alloying addition of metal M.

3

Ecological assessment of water quality in the Kabul River, Pakistan, using statistical methods

Khuram I., Barinova S., Ahmad N., Ullah A., Ud Din S., Jan S., Hamayun M.

Oceanological and Hydrobiological Studies

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2017

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Vol. 46, No. 2

140--153

EN

We identified 209 species of algae and cyanobacteria at 4 sites in the Kabul River. Green algae, diatoms, and charophytes dominated in the river, which reflects regional features of agricultural activity. Species richness and algal abundance increased down the river. The Water Quality Index characterizes the quality of water down the river as medium to bad. The index of saprobity S reflects Class III water quality. The Water Ecosystem Sustainability Index (WESI) shows contamination with nutrients. According to the River Pollution Index (RPI), waters in the river have low alkalinity and low salinity, and are contaminated with nutrients. Pearson coefficients showed that water temperature plays a major role in the total species richness distribution (0.93*) and in the green algae distribution (0.89*), while cyanobacteria were stimulated also by water salinity (0.91*). Stepwise regression analysis indicated water temperature as the major regional factor that determines riverine algal diversity. Surface plots and Canonical Correspondence Analysis (CCA) showed that salinity, nitrates, temperature, and Biochemical Oxygen Demand (BOD) can be defined as major factors affecting algal diversity. Dendrites mark the upper site of the Warsak Dam as the source of the community species diversity. Bioindication methods can give relevant and stable results of water quality and self-purification assessment that can be employed to monitor the regional water quality.

4

Effect of Weave Structure on Thermo-Physiological Properties of Cotton Fabrics

Ahmad S., Ahmad F., Afzal A., Rasheed R., Mohsin M., Ahmad N.

Autex Research Journal

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2015

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Vol. 15, no. 1

30--34

EN

This paper aims to investigate the relationship between fabric weave structure and its comfort properties. The two basic weave structures and four derivatives for each selected weave structure were studied. Comfort properties, porosity, air permeability and thermal resistance of all the fabric samples were determined. In our research the 1/1 plain weave structure showed the highest thermal resistance making it suitable for cold climatic conditions. The 2/2 matt weave depicted the lowest thermal resistance which makes it appropriate for hot climatic conditions.

5

Freshwater green algal biofouling of boats in the Kabul River, Pakistan

Khuram I., Ahmad N., Jan S., Barinova S.

Oceanological and Hydrobiological Studies

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2014

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Vol. 43, No. 4

329--336

EN

Freshwater green algal biofouling of boats refers to the accrual of freshwater green algae on boats immersed in water. The current research focused on the morphological characteristics of the isolates, species ecology, and the physicochemical properties of the water at the sampling sites. Two localities, Haji Zai and Sardaryab, were sampled at the Kabul River in the district of Charsadda, Pakistan. Freshwater green algae causing biofouling were isolated from the boats. A total of three genera: Cladophora, Rhizoclonium, and Spirogyra with fifteen species belonging to the families Cladophoraceae and Zygnemataceae were observed. Statistical analysis reveals significant stimulation of green algal species in the boats’ fouled communities by increases in water temperature, conductivity, and Total Suspended Solids (TSS). The algal growth at the Haji Zai site is suppressed by TDS in autumn (Pearson −0.56) and is stimulated by water temperature in spring (Pearson 0.44). At the Sardaryab site, algae were stimulated in spring by pH of water (Pearson 0.61), and suppressed by Total Dissolved Solids (TDS) in autumn (Pearson −0.43). Statistical analysis indicates that pH, conductivity, and temperature are the main factors determining the algal biofouling in the Kabul River.

6

Determination of aquifer geometry through geophysical methods: A case study From Quetta Valley, Pakistan

Alam K., Ahmad N.

Acta Geophysica

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2014

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Vol. 62, no. 1

142--163

EN

Due to increase in population and agricultural activities, the aquifer of Quetta Valley is under tremendous stress and the water table is declining at an increasing rate. This situation necessitates evaluation of the aquifer system, for which information about geometry of the aquifer is a prerequisite. However, there are no drilling-to-bedrock data available; therefore, electrical resistivity, seismic reflection and gravity methods were employed to determine geometry of the aquifer. Interpretation of vertical electrical soundings provided information about the depth-tobedrock at some specific points, whereas seismic reflection delineated bedrock topography along two lines. The depths to bedrock inferred from electrical resistivity and seismic reflection data were used as constraints in the modeling of gravity data. 2.75D gravity models were constructed along lines with a regular spacing. Map of depth-to-bedrock was prepared by contouring the depth given by the gravity models. Combination of these geophysical methods depicted the geometry of the aquifer. This example shows that in a similar geological setting proper integration of geophysical exploration methods can determine the aquifer geometry with an acceptable reliability and at an appropriate cost.