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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

Base pressure behaviour in a suddenly expanded duct at supersonic Mach number regimes using Taguchi design of experiments

Quadros J. D., Khan S. A., Antony A. J.

Mechanics and Mechanical Engineering

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2018

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Vol. 22, nr 4

1077--1097

EN

Experimental investigations are carried out to study the control of base pressure without and with the use of micro-jets through suddenly expanded axi-symmetric passage in the supersonic regime. Four micro jets having an orifice diameter of 1mm were located at 90˚ intervals. In the base area, active controls jets have been placed on a pitch of a circle diameter that is 1.3 times the exit diameter of the nozzle. The jets were dispensed abruptly into the axi-symmetric tube maintained at a cross-sectional area of 4.84 times the exit nozzle area. The variation of base pressure as a function of flow control parameters namely Mach number, nozzle pressure ratio (NPR) and length to diameter) ratio (L=D) are evaluated experimentally. This study also assesses the impact of flow control variables on base pressure for two cases viz. with control and without control respectively. An L9 orthogonal array of Taguchi and the analysis of variance were employed to investigate the percentage of contribution of these parameters and their interactions affecting the base pressure. The correlations between the various factors affecting the base pressure were obtained by using multiple linear regression equations. Confirmation tests were conducted in order to test the developed linear regression equations for their practical significance. Both the regression models were found to be significant and reliable with a percentage deviation lying in the range of -6:12% to 10.26% for base pressure without control and -13:92% to 6.58% for base pressure with control. Analysis of variance was also performed in order to determine the statistical significance of each parameter on the total variability of base pressure. The study concluded that Mach number is the most in fluential parameter affecting base pressure followed by NPR and L=D.

3

Study of base pressure behavior in a suddenly expanded duct at supersonic Mach number regimes using statistical analysis

Quadros J. D., Khan S. A., Antony A. J.

Journal of Applied Mathematics and Computational Mechanics

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2018

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Vol. 17, nr 4

59--72

EN

The present experimental evaluation deals with the behavior of base pressure (BP) in a suddenly expanded duct at supersonic Mach number regimes. The experiments have been conducted for two cases viz. Without and with the use of microjets or active control. The plan of experiments was planned as per Taguchi design of experiments for acquiring data in a controlled manner. An L27 orthogonal array and analysis of variance (ANOVA) has been employed to investigate the contribution (in terms of percentage) of distinct process parameters like Mach number (M), Nozzle Pressure Ratio (N), Area Ratio (A) and their interactions affecting base pressure. The correlation between these parameters affecting base pressure has been obtained using multiple linear regression analysis. It has been concluded that the Mach number and area ratio were the factors that had high statistical significance on the behavior of base pressure for both cases. The performances of the developed linear regression models have been validated for accuracy prediction by use of 15 test cases. The performance of both the base pressure models was found to be better with percentage prediction in deviation lying in the range of –12.92% to +15.88% for base pressure without control and –10.27% to +19.23% for base pressure with control.

4

Redesigning supply chain network of a lubricant company : an innovative approach

Khan S. A., Sawicka H.

LogForum

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2016

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Vol. 12, no. 2

165--180

EN

Background: The purpose of this paper is to redesign the supply chain network of a lubricant company by implementing an innovative solution concentrated on the delivery of products and minimizing total loading, unloading and transportation costs. Methods: In this paper the authors' approach to redesigning the supply chain network (SCN) is presented. It comprises 3 phases: analysis of the current state of the SCN, identification of disadvantages in the SCN and SCN improvement. This step-wise procedure is verified on a real-world supply chain network, which is analyzed, evaluated and redesigned. Based on this analysis, the most important strengths and weaknesses are identified. The main criteria for evaluation are loading, unloading and transportation costs. A redesign of the company is proposed, the stakeholders' opinions are gathered and the innovative solution is implemented. Results: After successful implementation of the innovative solution, the result shows savings in loading, unloading and transportation costs and an improvement in the level of service. Research Limitations: The proposed methodology can be implemented in other supply chain networks. However, the way of limiting the loading, unloading and transportation costs presented in this paper cannot be regarded as a general rule applicable to all companies. Conclusions: This study presents innovative thinking in the logistics network of a company and the results obtained prove that companies which are innovative in terms of products can also become innovative in their services.

PL

Wstęp: Celem niniejszego artykułu jest reorganizacja łańcucha dostaw firmy funkcjonującej w branży olejowej, poprzez wdrożenie innowacyjnego rozwiązania skoncentrowanego na dostawach produktów i poprzez minimalizację całkowitego załadunku, wyładunku towarów i kosztów transportu. Metody: W niniejszym artykule jest przedstawione podejście do reorganizacji łańcucha dostaw (ŁD). Składa się ono z 3 faz, tj. analizy stanu aktualnego ŁD, identyfikacji słabych stron ŁD oraz poprawy funkcjonowania ŁD. Przedstawiona wielofazowa procedura jest zweryfikowana na przykładzie rzeczywistego łańcucha dostaw, który jest poddany analizie, ocenie i reorganizacji. Na podstawie przeprowadzonej analizy, są definiowane jego najważniejsze mocne i słabe strony. Głównymi kryteriami oceny są koszty załadunku, wyładunku i transportu. Rekomendowana jest reorganizacja przedsiębiorstwa, zbierane są opinie osób zainteresowanych funkcjonowaniem łańcucha i zaimplementowane jest innowacyjne rozwiązanie. Wyniki: Po udanym wdrożeniu innowacyjnego rozwiązania, uzyskany rezultat pokazuje oszczędności w kosztach załadunku, wyładunku i transportu oraz poprawę poziomu świadczonych usług. Ograniczenia badawcze: Proponowana metodyka może być zastosowana w innych łańcuchach dostaw. Jednak przedstawiony sposób ograniczenia kosztów załadunku, wyładunku i transportu nie może być uznany, jako ogólna zasada dla wszystkich przedsiębiorstw. Ponadto badania nie uwzględniają sytuacji ewentualnych niedoborów magazynowych. Wnioski: Przedstawione wyniki badań koncentrują się na innowacyjnym podejściu do sieci logistycznej w wybranej firmie, a uzyskane wyniki dowodzą, że przedsiębiorstwo świadczące innowacyjne produkty, może stać się innowacyjne w sferze usług.

5

Metals uptake by wastewater irrigated vegetables and their daily dietary intake in Peshawar, Pakistan

Khan S. A., Liu X., Shah B. R., Fan W., Li H., Khan S. B., Ahmad Z.

Ecological Chemistry and Engineering. S

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2015

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Vol. 22, nr 1

125--139

EN

Vegetables are important source of nutrients for human body. Wastewater irrigation may lead to contamination of these vegetables and cause possible health risk. In the present study impact of waste water irrigation on metals uptake (Fe, Mn, Ni, Co, Zn, Cd, Cr and Pb) by five commonly consumed vegetables (radish, cabbage, lettuce, cauliflower and spinach) grown in the suburbs of Peshawar were investigated using AAS (Atomic Absorption spectrophotometer). The uptake and accumulation of metals for vegetables irrigated with wastewater were significantly (p < 0.05) higher than tube well irrigated vegetables and permissible limits of WHO/FAO. Among the edible parts of vegetables maximum accumulation of Mn, Pb and Cd occurred in radish followed by Ni and Fe in spinach while Cr and Zn were high in cauliflower and cabbage. The estimated daily intake of metals (DIM) revealed that at present the consumption of studied vegetables were under the tolerable limits of (US-EPA, IRIS), however intake of metals in waste water irrigated vegetables were significantly high and can cause health hazards in the long run.

PL

Warzywa są ważnym źródłem składników odżywczych dla organizmu człowieka. Nawadnianie ściekami może prowadzić do zanieczyszczenia tych warzyw i powodować zagrożenie dla zdrowia. Zbadano wpływ nawadniania roślin ściekami na pobieranie metali (Fe, Mn, Ni, Co, Zn, Cd, Cr i Pb) przez pięć powszechnie spożywanych warzyw (rzodkiewka, kapusta, sałata, kalafior i szpinak), uprawianych na przedmieściach Peszawaru. Stężenia metali oznaczono za pomocą AAS (atomowej spektrometrii absorpcyjnej). Pobieranie i akumulacja metali w warzywach nawadnianych ściekami były istotnie (p < 0,05) wyższe niż dopuszczalne granice podawane przez WHO/FAO. Wśród części jadalnych warzyw maksymalna akumulacja Mn, Pb i Cd wystąpiła w rzodkiewce, Ni i Fe w szpinaku, natomiast Cr i Zn w kalafiorze i kapuście. Oszacowane dzienne stężenie metali w diecie ludności wykazało, że obecna ich ilość w badanych warzywach mieściła się w dopuszczalnych granicach (US-EPA, IRIS), jednak stężenia metali w warzywach nawadnianych ściekami były wysokie, co może powodować zagrożenie dla zdrowia w dłuższym okresie.

6

Planar Monopole Stair Case Antenna for Ultra-wide Band

Alimgeer K. S., Khan S. A., Qamar Z., Abbas S. M.

Przegląd Elektrotechniczny

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2013

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R. 89, nr 1a

227--229

EN

Planar monopole antennas are extensively used in many wireless communication applications due to their compact size, low weight and ease of integration with active devices. Many antennas with different band characteristics have been designed such as dual, multi, wide and ultra wide band. In this paper simple monopole antenna is proposed for Ultra wide band applications. The antenna is analysed for bandwidth increment with addition of linear multiple steps, mathematical model is also proposed. Simulation results show that the proposed design can be used for UWB applications with reasonable accuracy. Prototype of proposed design with measured results are also presented. Reasonable agreement is found between the simulated and measured results. Details of the proposed antenna design, simulated and measured results are presented and discussed.

PL

W artykule opisano prostą antenę mono-polarną w zastosowaniu do ultra-szerokich pasm przepustowych. Przedstawiono model matematyczny i analizę wzrostu przepustowości pod wpływem liniowych stopni mnożących. Wyniki badań symulacyjnych zostały zweryfikowane poprzez porównanie z pomiarami rzeczywistymi.

7

Planar monopole UWB antenna with 5GHz dual notched band characteristics

Alimgeer K. S., Khan S. A., Qamar Z., Abbas S. M.

Przegląd Elektrotechniczny

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2012

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R. 88, nr 6

295-299

EN

These days most of the research work in the area of antenna design is focused on monopole antennas for UWB communications due to their high data rate, precision and low complexity. However, interference effect increases within the Ultra wide Band due to the increasing growth of 802.11a wireless LAN in the frequency band of 5 GHz in many countries. To minimize this closely found in-band interference effect, antennas with closely found notch band characteristics are becoming essential. The idea of band notch is extended in this paper by the placement of parasitic strips at different positions on the bottom of the substrate to achieve dual notches in 5 GHz band. Experimental results show that this technique can be employed to generate sharp controllable notch and/or dual notch bands with reasonable accuracy.

PL

Przedstawiono projekt anteny do szerokopasmowej komunikacji w paśmie 5 GHz w sieciach bezprzewodowych standardu 802.11a. Właściwości anteny kształtowano przez dodanie dodatkowych pasków w różnych pozycjach.

8

Minimizing Unnecessary Handovers in a Heterogeneous Network Environment

Hussain R., Malik S.A., Riaz S.A., Abrar S., Khan S.A.

Przegląd Elektrotechniczny

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2012

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R. 88, nr 6

300-303

EN

In this paper, we have provided a model to minimize the unnecessary handovers from a cellular network to a WLAN. Exploiting traveling distance prediction method, the proposed handover necessity estimation mechanism uses distance threshold parameters to avoid unnecessary handovers. Our analysis and simulation results suggest that the proposed mechanism can keep the probabilities of handover failure and unnecessary handover close to the predetermined designed values.

PL

Przedstawiono model umożliwiający minimalizowanie niepotrzebnych przełączeń typu handover między siecią komórkowa a siecią bezprzewodową WLAN.

9

Microstrip Antenna Array for Beamforming Systems

Abbas S. M., Ali L R., Nawaz H., Saleem I., Khan S. A.

Przegląd Elektrotechniczny

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2012

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R. 88, nr 11a

170-173

PL

W artykule przedstawiono dwu- i czteroelementowy układ anten o wąskim strumieniu promieniowania, o częstotliwości rezonansowej 2,4 GHz oraz możliwości wykorzystania w przesyle sygnału.

EN

A dual and quad element antenna array resonating at 2.4 GHz with narrow beam is proposed in this paper. An intention to put forward this work is to make use of microstrip patch antennas in beamforming to form directional beams in analog and digital domains; reducing co-channel / multipath interferences and improving Quality of Service (QoS) for senor arrays and 3G wireless networks. The size of dual and quad element antenna array is 60 x 130 mm2 and 60 x 240 mm2 respectively. Simulations in HFSS (High Frequency Structure Simulator) showed least mutual coupling among adjacent elements and prototypes have been fabricated using FR4 to verify the efficiency of the presented work for IEEE 802.11b/g WLAN standards.

10

A Host Based Autonomous Scheme for Seamless Vertical Handover

Hussain R., Malik S.A., Riaz R. A., Ahmed S., Shafiq G., Iqbal A., Abrar S., Khan S. A.

Przegląd Elektrotechniczny

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2012

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R. 88, nr 9b

314-318

EN

In this paper we suggest a host based, end-to-end selfreliant scheme for handover in heterogeneous network environment. It directly involves the correspondent node in the handover process. The proposed scheme imitates the Network Address Translation. It maps a logical address to another logical address. It modifies the address information in the header of the packet while it is in transition. In principle the process is identical to the NAT box operation, but the goal is different. While NAT is primarily used in conjunction with masquerading to hide the private IP address space, HaMAT works in conjunction with MIH and serves to hide the IP address change of the mobile node encountered due to the vertical handover. HaMAT is a functional entity just like Media Independent Handover Function, and it resides inside the Mobile Node and Correspondent Node. By eliminating the need for rerouting, tunneling and route optimization as required in Mobile IP, HaMAT achieves high performance results in terms of handover delay, end to end packet latency, jitter and the overhead involved. The service disruption time for HaMAT is as low as 10 msec compared to reported handover delays of 260 msec and 1 sec for MIPv4 and MIPv6 respectively.

PL

W artykule zaproponowano bazujący na hoście schemat przełączania typu handover w niejednorodnym środowisku sieciowym. Schemat imituje Network Address Translation i mapuje logiczny adres orasz modyfikuje nagłówek w pakiecie.

11

Overcoming Localization Errors due to Node Power Drooping in a Wireless Sensor Network

Khan S. A., Daachi B., Djouani K.

International Journal of Electronics and Telecommunications

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2011

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Vol. 57, No. 3

341-346

EN

Received Signal Strength Indication (RSSI) plays a vital role in the range-free localization of sensor nodes in a wireless sensor network and a good amount of research has been made in this regard. One important factor is the battery voltage of the nodes (i.e., the MICAz sensors) which is not taken into account in the existing literature. As battery voltage level performs an indispensable role for the position estimation of sensor nodes through anchor nodes therefore, in this paper, we take into a account this crucial factor and propose an algorithm that overcomes the problem of decaying battery. We show the results, in terms of more precise localization of sensor nodes through simulation. This work is an extension to [1] and now we also use neural network to overcome the localization errors generated due to gradual battery voltage drooping.