Journal of Engineering and Sustainable Development (JEASD)

Negative resistance radio frequency (RF) and microwave oscillators are widely used in modern wireless communication systems. In these circuits, the active device is imposed to work in the unstable region in order to present a negative resistance at its input or output port. This paper discusses the effect of the load impedance on the large signal behavior of the oscillator circuit throughout a design process of a practical 900 MHz RF oscillator circuit. New closed-form expressions for the optimum load resistance and reactance that maximize the output power have been derived analytically in terms of the transistor Z-parameters, and a design criterion for the RF oscillator is proposed based on the evaluated optimum load impedance. It has been shown through computer simulation that the optimum load resistance and reactance for maximum output power are dependent on each other. Furthermore, it has been verified that the optimum load impedance for maximum negative resistance differs slightly from its value required for maximum output power and this deviation increases with the increase in the RF power level. The designed oscillator circuit has been implemented and tested successfully.

The main object of this study is to figure out the effects of the volume of fibers (Vf) on the punching shear behavior of hybrid system of flat slab that made of Lightweight Concrete (LWC) and Reactive Powder Concrete (RPC). Five flat slabs, two of them made fully of Normal Strength Concrete (NSC) (named as S1) and LWC (named as S2), and the rest three made of LWC and RPC (named as S3, S4 and S5). The variable in S3, S4 and S5 is the values of Vf which are (0.5%, 1% and 2%) respectively. The hybrid flat slabs are designed that RPC to fill the critical zone of the punching shear area, and LWC to fill the remaining area. At 28 day age of concrete, the slabs are simply supported along the all edges and single point load applied at the center of slab until the failure is happened. The experimental work indicates that S1, S2 and S3 are failed with punching shear failure. While S4 and S5 are suddenly failed in the region occupied by LWC. The results show that S2 exhibits the weaker behavior, followed by S1. S3 has the best behavior of failure among all. The load deflection curves for all tested slabs behaves first as linear relation followed by nonlinear relation up to failure. The values of of (fcu), (Pc) and (Pu) for S1 are higher than those for S2 by about (69%, 29% and 42%) respectively.

The aim of this work is to design and implement a simple MIPS CPU by using Cyclone II FPGA without complex control unit. MIPS- Processor has been studied and realized to design, simulate and implement its components by using VHDL and FPGA Board under Quartus version “8.1 software packages. This design in a modern FPGA environment has done and used to finally realize the hardware components (RF, PC, ALU, RAM, ROM and Multiplexer). Also, the design has used a module principle to implement the components of the Microprocessor which provides high flexibility in expanding the hardware and software units of its components when there is a need to change the structure of the design without a complex central control unit. This method of design provides high flexibility especially for embedded systems which are planted in a variety of applications. The success of the design has been tested through the work of the processor as an integrated in all components under its instructions with simple control unit.

Impingement cooling jet is widely used in different industrial applications due to high rate of heat removal on the surface being subjected to impinging. Ribs are used to enhance convective heat transfer by the promotion of higher turbulence levels. The aim of present work is to perform an experimental verification of the using modified surface with ribs on heat transfer enhancement. Experiments were performed to characterize heat transfer to a normally impinging air jet on uniformly heated surfaces modified with ribs from a single orifice of different diameters D of (5, 12, 20 mm). A centrifugal blower is used for air impinging with jet velocity in the range (18.4-36 m/s). Local heat transfer distribution on the impingement surface is investigated for orifice-to-plate spacing ratio (Z/D) of (4, 6, 8, 10) using thermal infrared imaging technique. Different configurations of modified surfaces in form of ribs surface are studied in the present work which are: rectangular ribs, and circular ribs with different sizes spaced at different pitch on the target ribbed surface. Heat transfer enhancement for five rib geometries is evaluated by comparison with results for a smooth flat surface. The enhancement ratio of heat transfer, as compared to the smooth flat surface is demonstrated by a factor ranging from 1.2 to 3. It is observed that the different shape of the ribs causes different effects on heat transfer coefficient between the impinging air jet and the target plate.

This research investigates experimentally torsional behavior of reinforced self-compacting concrete beams with variables including plain and reinforced concrete beams, spacing of transverse reinforcement, concrete compressive strength, hollow and solid sections.The experimental work includes investigation of eleven beams tested under pure torsion and divided into three groups. Group (A) denotes the normal strength SCC beams with compressive strength of 32.84MPa. Group (B) covers the high strength SCC beams with compressive strength of 64.65MPa, and finally group (C) is normal strength SCC hollow beams. Test results are discussed based on torque-twist and beam longitudinal elongation behavior.

Centrifugal fans are used widely in most of the manufacturing processes for ventilating and/or air conditioning the working areas. Because of relatively limited documentation on the design of this type of fans, experimental and theoretical works are investigated in this paper for forward backward centrifugal fan to calculate the average dynamic pressure and axial thrust forces at different speed conditions. The flow in centrifugal fan is highly complex with taking place on the impeller. The centrifugal fan simulated using computational fluid dynamic (CFD) approach. Flow in centrifugal fan with duct is simulated by Navier – Stokes equation and performance curved are obtained. Most of companies creates in 3D model in Solid works version 2013 and the conduct analyses by the CFD programs. At first step, an experimental step was developed and prototypes of impeller was made to carry out at the south Baghdad power plant for the sake of flow measurements and next, computational fluid dynamics model was developed for the above step and the result are validated with experimental measurement. Fine mesh is generated for centrifugal fan with duct in GAMBIT programs to carry out analyses for whole computational domain in fluent programs. Further parametric studies were carried out to calculate the average dynamic pressure when rotating the impeller backward and forward rotation modes. The parameter considered in this study are changing in dimension of outlet duct at different speeds...

Naphthalene biodegradation using acclimatized mixed culture from sewage waste sludge was studied. Different initial Naphthalene concentrations (30to1000 mg/L) were used to evaluate the biodegradation rate of naphthalene. When the initial concentration of naphthalene increased from 30 to 1000mg/L the time required to utilize naphthalene increases from 2 to 21 days. The specific growth rate increases from 0.0092 to 0.0346 h-1 when the initial naphthalene concentration increases from 100 to 700 mg/L. Then the specific growth decreases to 0.0201 h-1 for 1000mg/L naphthalene concentration, indicating that there is an inhibitory effect on the microbial growth at high concentration. Different kinetic models for microbial growth, Monod’s, Haldane, Webb and Aiba were used. The experimental results confirm well with Haldane model as compared with the other models. Logistic models were used to describe the microorganism’s growth and the naphthalene degradation. A good fitting was obtained between the logistic models and the experimental data.

In this search, study and investigate is done on the fracture toughness in linear elastic and elastic-plastic fracture mechanics LEFM and EPFM for each cadaveric bovine cortical bone and human cortical bone. Fresh and frozen human cadaveric cut as a compact tension CT specimen from the tibia for five males are prepared from the forensic medicine department ages (25, 31, 39, 45 and 51) years and (18) months for bovine cortical bone are examined, where no known skeletal pathologies. The crack length is measured without removed the specimen from the grips by using ZBL F101 technique. The experimental results are compared with numerical analysis by ABAQUS program. Roughness of fracture surface for each bovine and human specimen is examined by scanning electron microscope SEM. The appropriate method for cutting the bone has been studied. The results showed that the fracture toughness of bovine is greater than by 111% of human cortical bone and vice in the strain energy release rate for human is greater than by 124% of bovine cortical bone. So, the fracture toughness in elastic-plastic fracture mechanics showed that the for bovine is 108% greater than human cortical bone,but gets the opposite in crack tip opening displacement toughness where is larger in human approximately 106% as compared with bovine cortical bone. The numerical results are showed agree with experimental results. From this work, the elastic- plastic fracture toughness (and for human cortical bone is larger than the bovine cortical bone that due to prevent the catastrophic failure …

The large numbers of terrorist attacks and the difficulty of the situations in Iraq led to the rise of the amputees’ numbers. However, typically 80% of the amputations are trans-tibial (below knee (BK) lower limb amputations). This research included the fabrication of a new type of socket by a new method (modular socket system)(MSS) that used direct lamination on residual limb of patients. Socket materials were subjected to tensile and creep (500 C) in order to determine their mechanical properties. Creep test data were analyzed in order to obtain time dependent creep compliance using the standard linear solid (the zener) model, the socket failure characteristics at room temperature and at high temperature (500oC) were determined by fatigue testing. Interface pressure between the socket and the residual limb was calculated using F-Socket software; In addition, a numerical method was used by applying the program ANSYS 15. The present work aim to study the experimental, theoretical and numerical results of tests and compared with the results of other reference. The experimental results show the specimens that manufactured by (MSS) have higher yield stress, medium young modulus, higher resistance to creep and low temperature effect on the S-N curve, where the reducing rate of S-N curve in the presence of temperature of group A (4.5%) compared with group C in which reducing rate (50%). Theoretical results of groups A, B show the creep compliance increased at first at rate (200%, 11%), respectively but after (50min.) The creep compliance becomes constant...

Lemon peel, a discarded agro-waste, was used as a biosorbent for removal of phosphate from simulated wastewater by sorption process. The characteristics of this adsorbent were tested by using FTIR in order to study the chemical compounds and oxidizing compounds, also to know the functional groups of organic compounds such as amino groups, carboxyl, hydroxyl and carbonyl. The influence of various practical factors such as pH; adsorbent dosage, contact time, initial concentrations of phosphate and temperature have been investigated through a set of batch experiments on the removal process efficiency. Equilibrium isotherm and kinetic study models of phosphate sorption onto adsorbents were also studied, Langmuir isotherm was found to be the appropriate equation and a second-order kinetic model was used to calculate the kinetic constants of inclusive adsorption rate. The results indicated that adsorption is an endothermic process for phosphate removal.

Concrete Filled Double-Skinned Steel Tubular Columns CFDSST are composite columns consisting of two concentric circular steel tubes with concrete filler in between. This research studies the behavior of the CFDSST columns under axial compression load. An experimental program included the fabrication of scaled columns of (5) CFDSST specimens of an outer tube diameter of (114 mm), and length of (600 mm). Three of them have three different thicknesses of outer steel tube and two with different hollowness ratios subjected to axial compression load. Making use of its ability to flow under its self weight, Self Compacting Concrete (SCC) used as the filled concrete. The experimental test results were presented in terms of load displacement curves and the axial and hoop strains at mid height of the outer tubes. Effect of the outer steel tube thickness on the axial capacity was studied as well the effect of Hollowness ratio was taken into account in this study. It was found that the axial load carrying capacity increased as the thickness of the outer steel tube increased since the confinement pressure increased.

The aim of this paper is to enhance the desired signal reception while suppressing the reception of inference signals to get maximum signal to interference plus noise ratio (SINR) at the output. Airborne interference sources need to be canceling in two planes azimuth and elevation to ensure an active cancellation for these sources. It is found that a circular array adaptive antenna system has a good capability to track any source in two planes simultaneously so that it has been chosen .The function of proposed model is to put the main lobe in the direction of desired signal while creating nulls in the direction of interference sources .In this paper we proposed a circular adaptive antenna array system configuration in conjunction with minimum mean square error (MMSE) algorithm to suppress or cancel the effect of deliberated interference sources in the elevation and azimuth planes .The effect of interference signal parameters on the designed system performance is analyzed and investigated such as the output signal plus interference to noise ratio (SINR) and interference to noise ratio (INR).The results show that the proposed system exhibit a good cancellation performance in the azimuth and elevation plane in the direction of interferences sources while keeping track a maximum reception in the direction of desired signal.

The main objective of this research was studied the flexure behavior of hybrid reinforced concrete beams combining reactive powder concrete (RPC) and lightweight concrete (LWC). The experimental work consists of casting and testing in flexure 12 simply supported reinforced concrete beams. The dimensions of (12) beams were geometrically similar, having rectangular cross-section, of dimensions (125×200×1600) mm. Lightweight concrete was used in tension layer and reactive powder concrete was used in compression layer for all hybrid concrete beams. The main variables were type of concrete (LWC and RPC), thicknesses of RPC layer (hR =0, 50 and 100) mm, volumetric steel ratios (Vf =1%) in LWC and type of LWC (porecilenite aggregate, polystyrene and sawdust). The results showed that the characteristic strength (first and ultimate loads) was increased when the thickness of RPC layer was increased; this increased percentage were (7-100) % and (32-133) % respectively for first cracking loads and ultimate loads. In addition to that, these parameters were decreased the values of deflection from (1-17) %. However that it can be seen from the experimental results, the concrete with steel fiber and porecilenite had more effective than the concrete with other types of aggregate (sawdust and polystyrene). Also the concrete with porecilenite type reflected more number of cracks than sawdust and polystyrene, respectively. All beams failed by flexure mode without any shear cracks which achieved by yielding of tensile steel in the tension zone. Also, for all hybrid beams, the slip was absent between the concrete layers.

The first step in performing a subsurface investigation is a thorough review of the project requirements. The necessary information that should be provided by the designer to the geotechnical engineer includes the project location, roadway alignment and profile, structure locations, substructure locations and estimated scour depths (if applicable). The geotechnical engineer should have access to typical sections, plan and profile sheets, and cross sections. This information allows the geotechnical engineer to properly plan and execute the subsurface exploration program [5]. Considerable information on the geological conditions of Wasit governorate can often be obtained from this studying. This studying often shows the relative position of the different geologic strata and provides information on the general characteristics for the sub-soil layers. This information is extremely useful in establishing preliminary boring locations and depths and in predicting problem areas.

This study discusses the development of a multi-axial fatigue testing machine, and studies the fatigue behavior of cantilever glass fiber composites beam under in phase bending-torsion dynamic loadings. The effect of bending–twisting deflections and the number of layers on the peak strength, fatigue life, and failure mechanisms are analyzed. Two types specimen (two dimension woven fiberglass (2D) and three dimension stitching fiberglass (3D)) are investigated. The results of both 2D and 3D show that the strength is increased significantly with increase bending-torsion stresses, while the damage becomes faster. The strength is reduced rapidly in about the first 30% of its fatigue life due to matrix cracking, which is then followed by a much slower rate of strength reduction until the failure. And the samples strength is increased as the number of layers increased by 20±3 % when tested under the same loading conditions. Furthermore the strength in 2D specimen is higher than the strength in the 3D specimen by about 20% when subjected to the same bending deflection-twisting angle. The fatigue life in 3D sample is greater than fatigue life in 2D samples by about 17% when tested under the same loading conditions.

In this investigation CK35 steel was treated by using laser surface treatment and make comparison with conventionally heat treatment. Laser hardening was done by using pulse ND: YAG laser with energy of 1000mj, whilst the conventionally heat treatment was carried out by quenching at 840 with cooling in oil and then tempered at 200for 2hr. Mechanical tests were made for all the specimens which were used in this research before and after heat treatments such as: Tensile test and Microhardness test. Also grain size measurement and microstructural evaluation were done by using computerized optical microscopy. The results of this work showed that obviously improvement in mechanical properties for the specimen treated by laser more than the specimen treated conventionally as the following: From tensile test it showed that increasing in yield strength, ultimate tensile strength, elongation percentage and plasticity constant (k). Also decreasing in young modulus (E) and the coefficient of strain hardening (n). Whilst the microhardness results showed that the highest value was obtained by laser hardening at the surface of the specimen and deceased far from the surface with depth of hardening equal to 0.5 mm. Also metallographic examination of the specimens after heat treatments showed that refining in grain size of the specimen treated by laser treatment more than the specimen treated by conventional heat treatment.