Print ISSN: 1681-6900

Online ISSN: 2412-0758

Issue 11,

Issue 11


Influence of Geogrid Reinforced Loose Sand In Transfer of Dynamic Loading To Underground Structure

Mohammed Y. Fattah; Nahla M. Salim; Mohammad S. Ismaiel

Engineering and Technology Journal, 2016, Volume 34, Issue 11, Pages 1915-1927

Underground facilities are an integral part of the infrastructure of modern society and are used for a wide range of applications, including subways and railways, highways, material storage, and sewage and water transport. Underground facilities built in areas subject to dynamic activity must withstand both dynamic and static loading.
This study focuses on the effect of the geogrid reinforcement in transfer of the dynamic load to the underground structure. The underground structure was simulated as a PVC pipe 110 mm in diameter inside the sandy soil. In order to investigate the response of soil, footing and underground tunnel to dynamic loading, a physical model was manufactured. The manufactured physical model could be used to simulate the application of dynamic loading.
The total number of the tests carried out is 4 models. All the 4 model tests with relative density equal to 40% corresponding to loose sand. The applied harmonic load has an amplitude of 0.5 ton and a frequency of 2 Hz. For each amplitude and frequency of the load, the sand models were tested without geogrid and with geogrid of three series of geogrid depths from the model surface (0.5B, 1B and 1.5B) and width equal to (1B), where B is the strip footing width. The dynamic load was applied in the tests by a hydraulic jack system. The response of the tunnel to dynamic loading includes measuring the pressure above the crown of the tunnel by using a pressure cell (manufactured by Geokon company) as well as measuring the amplitude of displacement by using a vibration meter. The response of footing was elaborated by measuring the total settlement using sensors in the dynamic load apparatus.
It was found the pressure above the crown of the tunnel decreased by about (14-33) % when using geogrid reinforcement. Also, it was found the settlement decreased by about (13-20) % when using geogrid reinforcement.

Simulation Model of Al-Dura Electro-station Plant of 160 MW with Genetic Algorithm Method

Shaker H.Aljanabi; Alaa Siham Hamid

Engineering and Technology Journal, 2016, Volume 34, Issue 11, Pages 1928-1943

In the present paper, a thermodynamic analysis of Al-Dura, Baghdad station type (K– 160–13.34–0.0068), power plant has been carried out. The power plant system was simulated and a detailed parametric study undertaken. This study can be helpful to identify the plant site conditions that cause losses of useful energy taken place and also helpful to resolve some problems encountered in steam turbine, capacity unit. Developing nonlinear mathematical models based on system identification approaches during normal operation without any external excitation or disruption is always a hard effort, assuming that parametric models are available. This study included on using soft computing methods that would be helpful in order to adjust model parameters over full range of input–output operational data. In this case, the model parameters are adjusted by applying genetic algorithms as optimization methods. Comparison between the responses of the turbine – generator model with the responses of real system validates the accuracy of the proposed model in steady state and transient conditions. Simulation results shows that the efficiencies and feasibility of the developed model in term of more accurate and less deviation with the responses of read system in the steady and transient conditions, and the error of proposed function is less than 0.37%. This study presents the usage of the Cycle – tempo and Matlab/Simulink package to implement the model of the power plant. Finally, many recommendations have been suggested for improved plant performance.

A New Topology of Load Network for Class F RF Power Amplifiers

Firas Mohammed Ali Al-Raie

Engineering and Technology Journal, 2016, Volume 34, Issue 11, Pages 1944-1958

High efficiency RF power amplifiers are increasingly needed in modern mobile communication systems to reduce the battery size and power supply consumption. Class-F RF power amplifiers offer improved efficiency over the conventional class-B power amplifiers by properly controlling the harmonic components of the voltage and current signals at the output terminals of the RF device while driving it to operate as an ON/OFF switch. To do this task, a suitable load network is to be synthesized in order to present the proper harmonic impedances at the output of the RF power transistor. In this paper, a new load network for class F power amplifiers has been introduced and derived analytically. The proposed network consists of a parallel short circuited λ/8 stub, parallel open circuited λ/8 stub, and a T-section lumped-elementtransformer. The benefits of this topology include simplicity of design, controllable bandwidth, and harmonic tuning and impedance transformation at the same time.
To confirm the approach of analysis, a 10 W class-F UHF power amplifier circuit has been designed and simulated using a typical Gallium Nitride high electron mobility RF transistor (GaN HEMT) to operate at 500 MHz with the aid of the Advanced Design System (ADS)computer package. The simulated results haveindicated that the circuit gives adc-to-RF efficiency of more than 84 % and a power gain of 11 dB at 500 MHz with an operating bandwidth from 440 to 540 MHz.

Assessment of Air Pollution in AL-Nahrawan Suburban- Baghdad city by Geographic Information System(GIS)

Mays Abass; Abdulrazzak T. Ziboon; Zainab Bahaa

Engineering and Technology Journal, 2016, Volume 34, Issue 11, Pages 1959-1969

Urban air pollution is a major environmental problem in all World countries. Air pollution in urban areas may be caused by human activities such as mobility behavior, waste management, industrial development (brick industry, cement industry), production and use of energy (for processing, heating and cooking), and activities which produce dust and suspended particles. The effects of urban air pollution on public health are being felt worldwide. There are a number of factors that influence urban air quality including geographical location, climatological and meteorological factors (temperature, humidity, wind speed and direction), city planning and design, andfinally human activities in suchareas.
The aim of this study was to measure certain important pollutants (VOCs, SO2, H2S, NO2), and assessing the effect of fuel burning that use in the brick factories. Geographic Information System (GIS) was utilized to map urban air pollution dispersion in AL-Nahrawan suburban –Baghdad city -Iraq. From GIS distribution maps for SO2 , NO2 , H2S and VOCs pollutants , it was found that the value of these gasses were changed from one location to another according to the quantity and quality of fuel used and wind direction.Generally it can concluded that the concentration of measured all examined gasses in the study area wasexceeding the WHO and national standards.

BER, Throughput, Energy Efficiency Performance Analysis of Proposed Different Systems in Wireless Sensor Network

il A. H. Hadi; Safa A. A. Abass

Engineering and Technology Journal, 2016, Volume 34, Issue 11, Pages 1970-1978

One of the major weakness of Wireless Sensor Networks is the energy consumption because of limited battery resource and battery replacement or recharging difficulty. The research presented in this paper aims to reduce the energy consumption in the physical layer because most the energy consumption occurred in this layer. This reduction will be achieved via the use of ZigBee transceiver standard at the physical layer under 2.4GHz frequency band with the reduced complexity and lower power consumption than other techniques used in Wireless Sensor Network. Furthermore, such use will also enhance energy efficiency, bit error rate, and throughput of the wireless sensor network. In this paper, three different systems have been proposed according to the type of transceiver technique used in wireless sensor network. System1 uses ZigBee transceiver standard over the wireless sensor network without any additional technique whereas system2 uses ZigBee transceiver with Convolutional Coding over the WSNs model. On the other hand, system3 uses the ZigBee transceiver with both diversity techniquesVirtual Multi-Input Multi-Output and with Convolutional Coding over the wireless sensor network model. The simulation of matlab results show that system3 achieves the best energy efficiency performance compared with the other two systems at lower quality of channel. System2 achieves the best energy efficiency performance at medium quality of channel, and system1 achieves better energy efficiency at high quality of channel.

Evaluation of Noise Level: Experimental Case Study for Some External Arenas in the University of Technology at Baghdad

Asad S.M.Raouf; Eman Farouk Khallil; Ashwaq Q. Hameed

Engineering and Technology Journal, 2016, Volume 34, Issue 11, Pages 1979-1989

The problem of noise in the learning environment (schools and universities) are consider as one of the environmental problems that has an effecton the process of concentration and assimilation and on the efficiency of the performance of studentsand their educational abilities, so the goal of current research is to studythe noise in one of the educational environments by measuring and evaluate the noise level experimentally by using a Sound Pressure Level Meter Type 2 UT 351 to measure noise levels for each site 100 times for 10 minutesin some arenas in campus of the University of Technology at Baghdad,by choosinga number of selected sites (31sites) during working hours for the periodsfrom 9 to 10 AM and 11 to12 AM. After recording the data for noise level of the maximum and minimum noise levels which recorded in the measurement locations was identified for periods 9-10 AM and 11-12 AM ,then calculate the average equivalent noise level for each location in order to compared with the limits of noise allowed which defined by the World Health Organization (WHO). The results of this study showed that the equivalent noise level at all measurement locations ranged between (59.29 -79.01) dBA for a period of 9-10 AM and between (58.23- 70.1) dBA for the period of 11-12 AM, where exceeded the permissible limits, which require the level of noise less than 55 dBA for such educational institutions as recommended by the World Health Organization (WHO).

Studying of the Effect of Soil Settlement under Different Types of Footings on Multistory Buildings

Kaythar Abdulwahab Ibrahim

Engineering and Technology Journal, 2016, Volume 34, Issue 11, Pages 1990-2012

The aim of this paper isto study the effect of soil settlement under different types of footings for multistory Buildings. Soil settlement sometimes occurs under the foundations due to bad soil compaction, water pipe leakage, soil erosion and excavation on neighboring site. Also the similar effectmight occur due to columns damages happened by explosion. Settlement effect on the moment and shear in beams and footing was studied. Also the effect of columns load and maximum base pressure under footing was studied. Building with dimensions 16*16 meters with four spans in both ways was assumed for studing in this paper, the building has three stories. Software STAAD.ProV8i was used in the analysis, finite elements are used to represent the slabs and footings. The soil subgrade reaction was used to represent soil in software.
Four types of footings were taken in this study which are spread footing, spread footing with tie beam, contineous footing and raft footing. Two settlement positions in the building was studied, the first one is under the internal footing and the second one is under exterior footings. The effect of tie beam dimension increasement and settlement in part of spread footing were studied also. The study clearly show that, the continuous footing is a very good selection because it shows a very good response against settlement, keep the settlement within allowed values and has lower cost than the raft footing. The study recommends to avoid using spread footing with or without tie beam. Tie beam dimension increasement has little effect to improve spread footing. Also,the study recommends suitable values of additional saftey factors for column and beam design when settlement is expected.

Theory Effect on the Formation of General Features for Tradition Architecture (Islamic Architecture as a Model)

Suaad Khaleel Ibraheem; Ahmed Hashim Al-Aukabi; Basim Hasan Al-Majidi

Engineering and Technology Journal, 2016, Volume 34, Issue 11, Pages 2013-2030

The two subjects theory and traditions have been separately taken in general studies which refer to both general and detailed aspects of them, also explain the effect of each on community and multiple cognitive fields including architecture. However, most of these studies did not address clearly the relationship between them or their effect on each other. So this research studies all of the above in details based on the in-depth study of the intellectual aspects of both concepts, and attempts to find the bases of correlation and difference between them and to put forward the recapitulation out of them. This has been shown during the course of this research down to clarify its reflection on one of the architecture models that is the "Islamic Architecture" as an important and clear model which clarifies the correlation between theory and traditions, and its reflection on the production by displaying the urbanism privacy features for Arab-Islamic City and clarify the details of those features. Hence the research problem can be defined as "Lack of clarity of cognitive perception about the impact of theoretical foundations in contemporary architecture on the formation of general features of traditional architecture in general, and particularly on the traditional architecture which is affected by the Islamic architectural features as a model", so the aim the research is to clarify that cognitive perception. While the research hypothesis can be defined as "the effect of the general basis for the theory of contemporary architecture on specific indicators within the general features of traditional architecture, which adopted the characteristics of Islamic architecture as a model, and resulting a developed architectural feature which are in between".

Thermal Lensing Reduction in Conventional and Composite Nd:YAG Laser Rod

Mohammed Jalal AbdulRazzaq; Abdulla K. Abass; Wail Yas Nassir

Engineering and Technology Journal, 2016, Volume 34, Issue 11, Pages 2031-2035

A finite-element method (FEM) wasused to simulate numerically the effect of thermal lensing in YAG rods doped with Nd ion using LASCAD software. The temperature distribution and thermal lensing focal length of the composite laser rod (YAG/Nd:YAG) with one undoped end cap was considered and compared with conventional laser rod (Nd:YAG) by applying software. Results show that thermal lensing effects were reduced by a factor of 2 using (YAG/Nd:YAG) composite rod at pump power of 20W.

Dynamic Buckling Behavior for 304 Stainless Steel Columns Using Electrical LASER Alarm System

Hussain Jasim Al-Alkawi; Ekbal Hussain Ali; Firas Ali Jasim Al-Mahaweeli

Engineering and Technology Journal, 2016, Volume 34, Issue 11, Pages 2036-2046

The paper summarized some experimental main results of dynamic buckling under increasing compression load. The buckling behavior of 304 stainless steel was investigated using Euler and Johnson formulas, which is the most commonly used in industrial applications. It has been verified that metallic materials can exhibit non-linear buckling behavior with mechanical properties dependency. This behavior yield a non-linear model which based on Hong’s model but using the mechanical properties with cycles to failure. It was observed that the proposed model gave safe predictions while the Hong’s model yields non satisfactory predictions of critical buckling loads and also design electrical LASER alarm system to avoid the failure occurs in the specimen when access to critical buckling load.

Thermal Behavior in Dimple Square Duct with Inclined Perforated Baffles

Abeer Hashim Falih

Engineering and Technology Journal, 2016, Volume 34, Issue 11, Pages 2047-2056

This research presents a study of heat transfer enhancement and pressure drop in a dimple square duct fitted with∝ =30◦,60◦and 90◦ inclined perforated baffles(baffles open area ratio of 26.17 %). The baffle to duct height ratio (w/a) of 0.3 and the baffle pitch to duct height ratio, PR=1, 2 are introduced in the present work. The tested duct has a constant wall heat flux condition. The experiments are carried out by varying airflow rate in terms of Reynolds number ranging from 1147.8 to 15304. The experimental data of heat transfer and pressure drop of the duct fitted withthe inclined perforated baffles are compared with those of the dimple smooth duct under similar condition. The inclined baffles with PR=1 gives higher heat transfer rate than the one with PR=2 and the smooth ductrespectively ,andthe highest heat transfer and pressure drop is found by using baffle with 30◦.

Proposed Formulation Using ANSYS for Estimation Axially Strength of Steel Tubes Columns Filled with Concrete

Marwah S. Abdul Gbabar

Engineering and Technology Journal, 2016, Volume 34, Issue 11, Pages 2057-2071

In this paper, concrete filled steel tubes columns (CFT) are investigated by using finite element program ANSYS 15.0. Analysis are done for four different shapes of columns (circular, square,hexagonal andoctagonal). Results of analytical solution (for circular and square) were compared with existing experimental data provided by [Alwash et al., 2013].Comparative resultsof failure load give 4% difference between experimental and ANSYS 15.0. Also, parametric studies have been carried out to investigate the effect of concrete filled steel tubes columns shapes (for hexagonal and octagonal) on load carrying capacity.Finally, a newformulaefor predicting the ultimate strength of CFT is proposedbased on experimental data of 148 CFT columns of different cross sections with side length ranging between 200 and 4000 mm. To check the validity of the proposed equation, the loads calculated from the designmethods (American Concrete Institute (ACI 318M-14), Eurocode (EC4),New Zealand Standard of concrete structures(NZS) and American Institute of Steel Construction (AISC)) are used to compare with it. The comparison shows least convergence percentageof the proposed equation.

Energy Generation and Electrical Machine Control Parameters of DFIG in Wind Turbine

Wamidh Dhyaa Eldeen Bahaa Eldeen

Engineering and Technology Journal, 2016, Volume 34, Issue 11, Pages 2071-2085

In electrical power generation system and electrical machine, wind turbine technology has rapid developments, and wind energy become increasingly competitive. Development in turbine machine technology raises a number of challenges to be dealt with now and in the future. Study of control parameter of DFIG in Wind Turbine Energy Converter Systems (WTEC) and factors affecting its performance is important to recognize problems in new design. In this work a model has been used to study these parameters and factors.

A Proposal Technique of High Impedance Fault Detection Using Adaptive Neuro- Fuzzy Logic Control

Mohammed YahyaSuliman

Engineering and Technology Journal, 2016, Volume 34, Issue 11, Pages 2086-2095

High impedance fault HIF produced when an energized conductor falls and contact with an objects have high impedancelike: tree limb, concrete walls, or falls down to the ground. The importance of these undetectable faults isrepresent a safety hazard, also a risk of arcing that causes ignition of fires. This type of fault is cannotbe detected by overcurrent protections. The techniques of detecting HIFs are depending on harmonicanalysis of the line current.In this paper, aproposed techniqueuseddepending on themeasure of the 3rd harmonic.Takagi-Sugeno fuzzy controller is proposed and the rules are trained off-line. The practical results show the ability of the controller to detect and distinguish the HIF with high accuracy.The magnitude and angle of 3rd harmonic were 1% of fundamental and 800respectively. The experiment results obtained using the NI 6250 data acquisition board and Matlab real time toolbox.

Miniaturized Dual-Band Bandstop Filter Using Multilayered E-Shape Microstrip Structure

Raaed T. Hammed

Engineering and Technology Journal, 2016, Volume 34, Issue 11, Pages 2096-2105

This paperpresents a new design technique to realize a miniaturized dual-band rejection filter based on the E-shape microstrip structure for multifunctional wireless communication systems. The filter is designed on a double layer substrate to achieve compact size. On the bottom layer, two E-shape microstrip structures are realized and coupled through a space gap,gc, to perform the specified dual-bandstop response. The filtering response of the two bandstops is improved using a top layer substrate employing a main linestub. The main line is a half wavelength hairpin resonator. These two filter circuits are capacitivley coupled using overlapping microstrip lines.To demonstrate the proposed design technique, a multi-band bandstop filter is developed with rejection frequenciesof 2.4 and 5.3 GHz Wireless local Area Network (WLAN). The filter is designed and simulated using the momentum simulator of theAdvanced Design System (ADS) software package. The resulting filter has two second-order bandstops with four transmission poles and provides two band rejectionsof 25 dB and 35 dB at 2.4 GHz and 5.3 GHz respectively. The filter circuit size is very small, being of the order of about 26 mm2 excluding the feeding ports.

Modeling Of Micro Hydroelectric Power Plants Utilizing Artificial Falls (Weirs) On Reach of Tigris River-Iraq

Thair Sharif Kayyun; Haider Mohammed Hadi

Engineering and Technology Journal, 2016, Volume 34, Issue 11, Pages 2106-2122

Weirs are one of the world wide water resources management structures, which are beside their activity in rising water surface to become important source for electricity by using low head hydropower turbines, it improve the hydraulic and the environment of the river reach.140,000m long of Tigris River reach between Al-Fatha and Samraa cities at Salahaldeen province in Iraq was selected to evaluate the usefulness of constructing system of weirs series by calculating the range of improvements in the hydraulic properties, in the environment and estimating the hydroelectric power potential of the study reach. GIS, Global Mapper (Ver.11) and DEM (digital elevation model) combined with surveyed cross-sections of the river bed were used for the delineation and knowing the number of cross – sections and its area. 30 cross sections were used for river reach in this study. One dimensional and steady flow HEC-RAS model was used .It was calibrated to estimate water surface profiles through a group of equations and to calculate the suitable hydraulic conditions along the study reach. The optimum value of manning coefficient was 0.027. The study area was evaluated and the system of five weirs with heights of (3.7 – 6.0 m) was proposed along the river reach. Their locations depend on trial and error process, geometric of the cross – sections and the ratio of the height of the weirs to the design head. The simulated results by using HEC-RAS model were tested to know the reach behavior against three different discharge values (200, 1242, 8616 m3/s), with return period of 1, 1.15 and 42.50 years respectively, and to compare the hydraulic changes in the study reach before and after installing the weirs and to know the net heads for running the low head hydropower turbines. The results illustrate improvement in the reach hydraulic properties of the river reach. According to the criteria of hydro – power system classifications, the type of hydro – power in this case study was small and the suitable turbine was Kaplan turbine with flow rate of 30m3/sec and with ranges of net heads of (3.29 – 6.08 m). 7 and 41 turbines were chooses for the flow rates of 200 and 1242 m3/sec respectively. The Kaplan turbine is running with very high efficiency below the design flow and with suitable runner diameter. The total estimated capacity of one turbine was (5.38 –7.60 MW) and for seven units, it was (37.66 - 53.20 MW) at one weir. These capacities will cover some of the growth in demand to the electricity in Iraq. It covers about (300, 000) capita of population in the study area. It was found that the maximum cost of the electromechanical equipment for hydro project was 42.91 million US$ .

An Experimental Study on the Shear Strength of High-performance Reinforced Concrete Deep Beams without Stirrups

Sinan Abdulhkaleq Yaseen

Engineering and Technology Journal, 2016, Volume 34, Issue 11, Pages 2123-2139

High-performance fiber-reinforced concrete is a new class of concrete that has been developed in recent decades. It exhibits enhanced properties such as high compressive strength and improved tensile strength. Three types of concrete with different compressive strengths, namely, normal-strength concrete, high-strength concrete, and high-performance concrete, were used in this study. The experimental program included casting and testing sixteen reinforced concrete deep beams without stirrups to study the shear strength and behavior of these beams under two-point loading. The variables considered were the compressive strength of concrete (f′c ) (40–120 MPa), shear span-to-depth ratio (1, 1.5, 2, 2.5, and 3), and the ratio of the amount of flexural steel bar ratio (1.35%, 2.40%, 3.76%, and 6.108%). Experimental results showed that increasing concrete compressive strength and flexural steel bar ratio increased ultimate shear capacity. By contrast, increasing shear span-to-depth ratio and span-to-depth ratio reduced ultimate shear capacity. Based on the test results of this investigation (16 beams) and those of available literature (233 deep beams), an equation that considered the parameters affecting shear stress (f′c, l/d, a/d, andw) was proposed using SPSS software. The proposed equation was compared with predictions made by the American Concrete Institute (ACI) and the works of other researchers, including that of Zsutty and Aziz. The ACI predictions were conservative and the proposed equation had a lower coefficient of variation.

Assessment of Structure with Analytical Digital Close Range Photogrammetry

Abbas Zedan Khalaf; Ali Salah J. Al-Saedi

Engineering and Technology Journal, 2016, Volume 34, Issue 11, Pages 2140-2151

Photogrammetry is an approach that can determine the size and the shape of objects through analyzing images recorded by a photographic or video camera.This paper studies measuring and evaluating the structure by using analytical close range photogrammetry method since it is characterized by; high precision, low effort and cost, as well as the possibility of measuring and / or assessing inaccessible places.The objective of the present study is toassess the distortion that occur during projects execution in compare with charts and designs and detect the problem by using (DCRP) with high precision to make a decision to keep or stop working.Several methods can be applied in data processing to determine 3D coordinates of object points for two or more images. To evaluate data processing using four commercial software (LPS, PhotoModeler, Photogrammetric MATLAB and AutoCAD Civil 3D). Also to overcome the difficulty of obtaining Ground Control Points (GCPs) that covers the photogrammetric object, a Portable Control System (PCS) had been established.Using a single camera Canon EOS 500D with image size is (4752 x 3168) pixels to capturing images. Two approaches used for 3D assessment of structure (single model and all models). This study depended structure of directorate of engineering projects at the university of technology this structures represented the study area.The results of analysis processes (3D model) will help the researcher to detect the distortion and suggest the proper solution for dissolve and develop it. The precision obtained from this results show high precision. The results are very promising ranges between (0.18 – 1.77) mm.

Speech Encryption using Fixed Point Chaos based Stream Cipher (FPC-SC)

Fadhil S. Hasan

Engineering and Technology Journal, 2016, Volume 34, Issue 11, Pages 2152-2166

Fixed point chaos based stream cipher (FPC-SC) is presented in this paper to encrypt the speech signal. Fixed point chaos based pseudo random bit generator (FPC-PRBG) is used as key sequence in stream cipher system. Two chaotic Lorenz and Chen systemsare combined to generate Gold FPC-PRBG. The results show that FPC-PRBG has good statistical randomness and encryption performance measure and can be used to produce high speech security level. FPC-PRBG is implemented using Xilinx system generator (XSG) with Xilinx Virtex 4 FPGA device, the system is accessed routed in this device with throughputs 818.64,7978.88 and 780.24 Mbits/sec for Lorenz, Chen and Gold FPC-PRBG respectively, where 40 bits fixed point operation are used.

Robust PI-PD Controller Design for Systems with Parametric Uncertainties

Hazem I. Ali; Ali Hadi Saeed

Engineering and Technology Journal, 2016, Volume 34, Issue 11, Pages 2167-2173

This paper presents a robust design of the four parameters PI-PD controller for systems with parametric uncertainties. The Particle swarm Optimization (PSO) method is applied to tune the controller parameters such that the robust specifications are satisfied. For the robust stability and performance to be guaranteed, the Kharitonov's theorem of interval polynomials is combined with the time domain performance index. The effectiveness of the proposed controller is illustrated by two examples of uncertain systems.