Aggregate Demand and Supply Models Essay Example for Free

Aggregate Demand and Supply Models Essay When examining unemployment and supply and demand it is imperative to examine the affects one has on the other and vice versa. If no new jobs are created or layoffs occur, there are no jobs to supply the needs. As the availability of money lessens a smaller amount is available for the purchase of goods, therefore fewer goods are sold. As the demand lessens sales forecasts also become smaller, these forecasts project fewer orders placed to the manufacturers. Merchants do not want to hold onto a disproportionate amount of inventory, which can be extremely expensive, both from the standpoint of cash/credit expenditure and for the storage fees. The smaller the orders are for manufactured products will result in a smaller customer supply level (United States Unemployment Rate, 2013). It is essential to amplify government funding to generate new jobs in order for the unemployment rate to be reduced. From a Keynesian viewpoint increasing government, spending is a multifaceted benefit for everyone, and this will control the aggregate level. From a Classical perspective, it is best to let the economy naturally adjust, to incorporate the unemployment ratio. Consequently, for that reason, increased spending would not be fitting in this economic model. Expectations In the first three months of 2013, the GDP in the United States has grown at a 2. 5% annual rate. Although the GDP has risen from the last quarter of 2012, 2. 5 is still almost a full point under the expectations of economists for the year. Although the economy is in a more stable point than in the 2008 collapse it has become apparent the United States economy has been stuck for quite some time now. According to Neil Irwin (2013 Washington Post) â€Å"the biggest culprit in the weak report was the government sector, which fell at a 4. 1 percent rate, after a 7 percent pace of decline in the fourth quarter. Unfortunately, this year the private sector of business has proved of no expansion and no signs point to change. As for the expectations for the rest of the 2013 year, its economist’s jobs to identify trends in the market and make assumptions of change in the economy based on those findings. Unfortunately, there seems to be little to any trends that look promising enough to quicken the recovery of the 2008 collapse. As it stands currently, the United States economy will slowly continue to grow, but not quickly. * Consumer Income According to Sivy (2013), â€Å"Personal income fell 3. 6 percent in January, the biggest decline in 20 years† (p. ). If one takes into account taxes and inflation, the accurate disposable income is closer to 4%. Many economists believe that even though there is a slow recovery from the recession the standard of living for many American’s has declined. It has become difficult for the middle-class income to keep up with rising taxes and unemployment. There does not seem to be any movement toward restoring income for middle-class households, which affects the GDP in a negative manner. The relationship to the aggregate supply and demand curve is that the consumers will only consume the number of goods and services their budget allows. When a consumer has a lower level of income, he or she is less likely to purchase high quantities of products and services, causing a negative effect on the aggregate supply and demand. Less wealth leads to less consumption, bring down the demand for goods, and causing a shift in output (to the left). Interest Rates The Federal Reserve Board (also known as the Fed†) controls interest rates. â€Å"When the Fed raises or lowers short term interest rates, banks can raise or lower the interest rates they charge borrowers, including the prime rate† (Northrop Grumman, 2013). In today’s current economy, there is a rise in interest rates. One may ask, what does this mean for the consumers in our economy as well as businesses. A number of things can happen. If the interest rates rise, consumers may not be inclined to purchase home and auto loans. Ehling (2013), â€Å"Since April, mortgage rates have jumped almost 1 percent, causing concern for those in the market to buy a home† (Para 2). This rise in interest rates can hurt businesses because fewer consumers are spending money. However, businesses can also use this to their advantage because they can put pressure on consumers to buy sooner rather than later before the rates increase even higher. When rates increase, the economy is usually strong and in good health. The Fed is usually trying to slow down economic growth. While interest rates rise, the aggregate demand curve shifts up and to the right. When interest rates are lowered, the aggregate demand curve shifts down and to the left. The short-term aggregate supply curve is also affected. When interest rates are low, this will cause the curve to shift to the right, and when the interest rates are higher the curve shifts to the left. It would be wise to lower the interest rates a little because the economy is still recovering. Raising the interest rates in a span of weeks could result in hurting the economy’s health. In today’s economy, if we lowered interest rates a small amount this would increase consumer spending and will create more jobs. Recommendations After reviewing the above mentioned, we have determined the following recommendations to help the economy grow. The above are in some way or another intertwined and affects each other as well. Our recommendation is to spend less, owe less, and grow the economy (Joint Economic Committee, 2011). To reduce government budget the use of more fiscal consolidations are essential. These programs ultimately reduce government spending, which in turn can accelerate short and long-term economic growth. Increasing tax rates are not good for the economy because it affects the long-term economic growth. In addition, decreasing the number of government workers would be a way for the government to reduce its spending, along with compensations (Joint Economic Committee, 2011). Eliminating agencies and programs is also another way to reduce spending costs. Last, reforming and reducing transfer payments to households will boost GDP growth because it will enhance the credibility of fiscal consolidation programs (Joint Economic Committee, 2011). This will also encourage younger workers to work more, save, and retire older. Part Two Evaluation of Recommendations Keynesian economists believe in applying financial and fiscal policies to lessen the effects of economic recessions. Keynes argued that in times of recession, spending is a public good that benefits everyone (Colander, 2013). The government should be spending and providing jobs to stimulate the economy. Unfortunately, during a recession most do the opposite. Businesses and government seems to cut back on military spending and cause major layoffs. Businesses are reluctant to invest because they already have more capacity than they can use. However, the government can jump-start the economy through increased spending and investment. These investments would go a long way to strengthen the economy. Currently the leadership in the White House has implemented policies that stem from the Keynesian theory. This is in large due to the previous recession that the country faced after the attacks of 9/11. The Keynesian theories allow the government to intervene and help stimulate the economy. During a stagnate or failing economy the government generates revenue and jobs sometimes by adding money into the economy and thus keeping interest rates low. This has shown to be an effective approach because the economy is starting to recover and grow again Classical economists believe on creating long-term solutions for economic problems. They argue that any imperfections in the economy will be corrected automatically, and no government intervention is needed. â€Å"While the Keynesian economists believe in implementing monetary and fiscal policies, the classical economists believe that the best monetary policy during a crisis is no monetary policy† (Patil, 2012). Although both theories are important, one may say the best solution is to have a mixture of both theories. There are many economic situations where one theory might work better than the other is; however, a wise economist is not only preparing for short-term solutions, but long-term solutions as well. Conclusion In conclusion, it is important in business to be open to looking at situations (i. e. the economy) from angles. Looking at the economy from both points of views could be critical to the success and forecasting of our economy in the future. However, after reviewing both Keynesian and Classical we still feel that the Keynesian approach will have a more significant impact on the economy. The recommendations we have suggested for the President reaffirm this.

Micro Strip Patch Antenna

Micro Strip Patch Antenna Chapter 1 Introduction The project which we have chosen to do as our final year project for the under graduate program involves the characterization of micro strip patch antenna. In this project we have carried out simulations of different types of antennas, which include dipole, monopole and patch. The purpose of designing all of these is to gain knowledge and experience in the designing of antennas for different purposes by using commercially available CEM. The frequency band, which we have chosen as our relevant band, is the GSM-900 band, which is of wide use in the cellular network. The purpose of choosing this band is to gain valuable knowledge of this frequency band. Antennas are a fundamental part of every system in which wireless or free space is the medium of communication. Basically, an antenna is a transducer and is designed to transmit or receive electromagnetic waves. It is a transducer as it converts radio frequency electrical currents into electromagnetic waves. Common applications of antennas include radio, television broadcasting, point-to-point radio communication, wireless networks and radar. A detailed study of antennas is discussed in chapter two and chapter three of this report. The CEM softwares that we have used for the designing include XFDTD ® provided by Remcom Inc. and CST Microwave Studio ®, which is a full wave, 3-Dimensional, Electromagnetic simulation software and CST Microwave Studio ®. XFDTD ® utilizes a numerical electromagnetic code for antenna design, that is, the finite difference time domain technique (FDTD). Finite-difference time-domain (FDTD) is a popular computational electrodynamics modeling technique. The first antenna structure modeled is the dipole. A dipole antenna consists of two conductors on the same axis with a source at the center. It is also modeled in XFDTD ® by following the procedure provided by the software and mentioned in the Appendix. The results are verified by comparing with analytical papers of (lambda/2) dipole. After completing this, the next goal is to model the micro strip (patch) antenna which is one of the main focuses of this project. It comprises of a metallic patch bonded to a dielectric substrate with a metal layer bonded to the opposite side of the substrate forming a ground plane. This metal layer is very thin. Hence, it can be fabricated very easily using printed circuit techniques. Therefore, they are inexpensive to manufacture and are easily integrate able with microwave integrated circuits. The software modeling is carried out in XFDTD ® and on CST Microwave Studio ®. The verification of the results with the experimental results obtained leads to the final phase and the conclusion of the project. 1.1 Purpose The purpose of this project is to gain knowledge and experience about computational electromagnetic, as it applies to antenna design. It was also our sole purpose to gain experience in fabrication and experimental characterization of micro strip patch antennas. To achieve these objectives we used two commercially available CEM softwares, XFDTD ® and CST Microwave Studio ®, to design a micro strip patch antenna for 900 MHz. We also gained experimental experience by characterizing the return loss of this patch antenna using the vector network analyzer. 1.2 Project Scope 1.2.1 Description We will study some basic types of antennas; extending basic knowledge of antenna to complex antenna designs such as micro strip patch antennas and also modeled them on antenna design and simulation software. This report has been divided into a number of chapters each discussing a different stage of the project. They are briefly described below: Chapter 2 describes the fundamentals of antennas and thoroughly discusses the theory of fundamental parameters and quantities of antenna. In this chapter the basic concept of an antenna is discussed and its working is explained. Some critical performance parameters of antennas are also discussed. Finally, some common types of antennas are also discussed for understanding purposes. Chapter 3 discusses the important characteristics of antennas as radiators of electromagnetic energy. These characteristics are normally considered in the far field as the antenna pattern or radiation pattern of an antenna is the three-dimensional plot of its radiation at far field. It also discusses the types of antenna patterns in detail. Some important mathematical equations are also solved in this chapter for the better understanding of how an antenna works. Chapter 4 discusses in detail the modeling of the half wave dipole and micro strip patch antenna using XFDTD ®. It describes the modeling of the antenna, the feeding, and the resultant plots obtained. Furthermore it concludes with comparison of the results obtained with the simulations already available in the software. Chapter 5 discusses the theory, calculations involved and the fabrication of the micro strip (patch) antenna in detail. The calculations for the dimensions of the rectangular patch in detail are in this chapter. Also, this chapter describes the results obtained through simulation of the model on the software CST Microwave Studio ®. Chapter 6 discusses conclusions drawn from the whole project. Chapter 2 Antenna Fundamentals In this chapter, the basic concept of an antenna is discussed and its working is explained. Next, some critical performance parameters of antennas are discussed. Finally, some common types of antennas are introduced. The treatment for these is taken from the reference [4], [6] and [9]. 2.1 Introduction Antenna is a metallic structure designed for radiating and receiving electromagnetic  energy. An antenna acts as a transitional structure between the guiding devices (e.g. waveguide,  transmission line) and the free space. The official IEEE definition of an antenna as given by  Stutzman and Thiele [9] is as follows:   â€Å"That part of a transmitting or receiving system that is designed to radiate or receive electromagnetic waves†. 2.2 How an Antenna radiates? In order to understand how an antenna radiates, we have to first know how radiation occurs. A  conducting wire radiates because of time-varying current or an acceleration or deceleration of charge. If there is no motion of charges in a wire, no radiation will occur, since no flow of current occurs. Radiation will not occur even if charges are moving with uniform or constant velocity along a straight wire. Also, charges moving with uniform velocity along a curved or bent wire will produce radiation. If charge is oscillating with time, then radiation will occur even along a straight wire as explained by Balanis [4]. The radiation pattern from an antenna can be further understood by considering a voltage source connected to a two-conductor transmission line. When a sinusoidal voltage source is applied across the transmission line, an electric field is generated which is sinusoidal in nature. The bunching of the electric lines of force can indicate the magnitude of this electric field. The free electrons on the conductors are forcefully displaced by the electric lines of force and the motion of these charges causes the flow of current, which leads to the creation of a magnetic field. Due to time varying electric and magnetic fields, electromagnetic waves are created which travel between the conductors. When these waves approach open space, connecting the open ends of the electric lines forms free space waves. As the sinusoidal source continuously creates electric disturbance, electromagnetic waves are generated continuously and these travel through the transmission line, the antenna and are radiated into the free space. 2.3 Near and Far Field Regions The field patterns of an antenna, change with distance and are associated with two types of energy radiating and reactive energy. Hence, the space surrounding an antenna can be divided into three regions. Figure 2.1: Field regions around an antenna The three regions that are depicted in above figure are described as: 2.3.1 Reactive Near-Field Region: In this region the reactive field dominates. The reactive energy oscillates towards and away from the antenna, thus appearing as reactance. In this region, energy is stored and no energy is dissipated. The outermost boundary for this region is at a distance ÃŽ » (2.1) where R1is the distance from antenna surface, D is the largest dimension of the antenna and ÃŽ » is the wavelength. 2.3.2 Radiating Near-Field Region: This region also called Fresnel region lies between the reactive near-field region and the far field region. In this region, the angular field distribution is a function of the distance from the antenna. reactive fields are smaller in this field as compared to the reactive near-field region and the radiation fields dominate. The outermost boundary for this region is at a distance (2.2) where R2is the distance from the antenna surface. 2.3.3 Far-Field Region: The region beyond is the far field region also called Fraunhofer region. The angular field distribution is not dependent on the distance from the antenna in this region. In this region, the reactive fields are absent and only the radiation fields exist and the power density varies as the inverse square of the radial distance in this region. 2.4 The Hertzian Dipole A hertzian dipole or infinitesimal dipole, which is a piece of straight wire whose length L and diameter are both very small, compared to one wavelength. A uniform current I is assumed to flow along its length. Although such a current element does not exist in real life, it serves as a building block from which the field of a practical antenna can be calculated (Sadiku [6]). Consider the hertzian dipole shown in figure. We assume that it is located at the origin of a coordinate system and that it carries a uniform current. i.e. I=IË ³ cosωt. The retarded magnetic vector potential at the field point, due to dipole is given by (2.3) Where [I] is the retarded current given by (2.4) Where ÃŽ ²=ω/u=2Ï€/ÃŽ », and u=1/ the current is said to be retarded at point under consideration because there is a propagation time delay r/u or phase delay. By substitution we may also write A in phasor form as t(2.5) Transforming this vector in Cartesian to spherical coordinates yields Where But (2.6) We find the E field using (2.7) (2.8) Where, A close observation of the field equations reveals that we have terms varying as The 1/ term is called the electrostatic field since it corresponds to the field of an electric dipole. This term dominates over other terms in a region very close to the hertzian dipole. The is called the inductive field, and it is predictable from the from the Biot Savart law. The term is important only at near field, that is, at distances close to the current element. The 1/r term is called the far field or radiation field because it is the only term that remains at the far zone, that is, at a point very far from the current element. Here, we are mainly concerned with the far field or radiation zone (ÃŽ ²r˃˃1), where the terms in can be neglected in favor of the 1/r term. Thus at far field, (2.9) The radiation terms of and are in time phase and orthogonal just as the fields of a uniform plane wave. The near and far zone fields are determined respectively to be the in equalities We define the boundary between the near and far zones by the value of r given by . where d is the largest dimension of the antenna. The time average power density is obtained as ) (2.10) Substitution yields time average radiated power as But And hence above equation becomes If free space is the medium of propagation, ÃŽ ·=120 and (2.11) This power is equivalent to the power dissipated in a fictitious resistance by current That is, (2.12) Where is the root mean square value of I. From above equations we obtain Or (2.13) The resistance is a characteristic property of the hertzian dipole antenna and is called its radiation resistance. We observe that it requires antennas with large radiation resistances to deliver large amounts of power to space. The above equation for is for a hertzian dipole in free space. 2.5 Half Wave Dipole Antenna The Half Wave dipole is named after the fact that its length is half of the wavelength i.e. . It is excited through a thin wire fed at the midpoint by a voltage source connected to the antenna via a transmission line. The radiated electromagnetic field due to a dipole can be obtained if we consider it as a chain of hertzian dipoles (Sadiku [6]). ÃŽ »/2 I z x y I Figure 2.3: Half Wave Dipole The magnetic Vector potential P due to length dl of the dipole carrying a phasor current is (2.14) We have assumed a sinusoidal current distribution because the current must vanish at the ends of the dipole. Also note that the actual current distribution on an antenna is not precisely known. It can be determined by using Maxwells equations subject to the boundary conditions on the antenna by a mathematically complex procedure. The sinusoidal current assumption approximates the distribution obtained by solving the boundary value problem and is commonly used. O Y X Z Figure 2.4. Magnetic field at point o If r >> à ¢Ã¢â‚¬Å¾Ã¢â‚¬Å", then Hence we can substitute in the denominator of the first equation where the magnitude of the distance is needed. In the numerator for the phase term, the difference between ÃŽ ² and ÃŽ ² is significant, so we will replace by . We maintain the cosine term in the exponent while neglecting it in the denominator because the exponent involves the phase constant while the denominator does not. So, (2.15) Using the following integrating equation, Applying this equation gives on (2.15) Since and the above equation becomes, Using identity = 2cos x, we obtain (2.16) We use in conjunction with the fact that to obtain electric and magnetic fields at far zone as (2.17) The radiation term of and are in time phase and orthogonal. We can obtain the time-average power density as (2.18) The time average radiated power can be determined as In the previous equations has been substituted assuming free space as the medium of propagation. The last equation can be written as Changing the variables, and using partial fractions reduces the above equation to Replacing with in the first integrand with in the second results in (2.19) Solving the previous equation of yields value of . The radiation resistance for the half wave dipole antenna is readily obtained from the following equation and comes out to be. (2.20) Chapter 3 Antenna Characteristics In the previous chapter we have discussed the basics of antennas and the elementary types of antennas. Now we will discuss the important characteristics of antennas as radiators of electromagnetic energy. These characteristics are normally considered in the far field and are as follows. And have been treated from the references [4], [6] and [9]. 3.1 Antenna Patterns The Antenna Pattern or Radiation Pattern of an antenna is the three-dimensional plot of its radiation at far field. There are two types of Radiation Patterns of antennas. The Field and the Power Pattern. 3.1.1 Field Pattern When the amplitude of the E-field is plotted, it is called the Field Pattern or the Voltage Pattern. A three dimensional plot of an antenna pattern is avoided by plotting separately the normalized versus for a constant which is called an E-Plane pattern or vertical pattern and the normalized versus for called the H-plane pattern or horizontal pattern. The normalization of is with respect to the maximum value of the so that the maximum value of the normalized is unity as explained by Sadiku [6]. For Example, for the hertzian Dipole, the normalized comes out to be, (3.1) Which is independent of From this equation we can obtain the E-plane pattern as the polar pattern of by varying from 0 to 180 degrees. This plot will be symmetric about the z-axis. For the H-plane pattern we set so that , which is a circle of radius 1. 3.1.2 Power Pattern When the square of the amplitude of E is plotted, it is called the power pattern. A plot of the time-average power, for a fixed distance r is the power pattern of the antenna. It is obtained by plotting separately versus for constant and versus for constant. The normalized power pattern for the hertzian dipole is obtained from the equation. (3.2) 3.2 Radiation Intensity The Radiation intensity of an antenna is defined as (3.3) Using the above equation, the total average power radiated can be expressed as (3.4) (3.5) Where dÃŽ ©= is the differential solid angle in steradian (sr). The radiation intensity is measured in watts per steradian (W/sr). The average value of is the total radiated power divided by ; that is, (3.6) 3.3 Directive Gain The directive gain of an antenna is a measure of the concentration of the radiated power in a particular direction It can also be regarded as the ability of the antenna to direct radiated power in a given direction. It is usually obtained as the ratio of radiation intensity in a given direction to the average radiation intensity, that is (3.7) may also be expressed in terms of directive gain as (3.8) The directive gain depends on antenna pattern. For the hertzian dipole as well as for the half wave dipole is maximum at and minimum at . Hence they radiate power in a direction broadside to their length. For an isotropic antenna, . However, such an antenna is not in reality but an ideality. The directivity D of an antenna is the ratio of the maximum radiation intensity to the average radiation intensity. D is also the maximum directive gain So, (3.9) Or, (3.10) For an isotropic antenna, D=1, which is the smallest value that D can have. For the hertzian dipole, as derived in equation (3.7) For half wave dipole, Where, ÃŽ ·=120 and (3.11) 3.4 Bandwidth (Impedance Bandwidth) By definition Bandwidth of an antenna is the difference between the highest and the lowest operational frequency of the antenna. Mathematically, (3.12) If this ratio is 10 to 1, then the antenna I classified as a broadband antenna. Another definition for Bandwidth is: Where, . 3.5 Gain We define that G is the actual gain in power over an ideal isotropic radiator when both are fed with same power. The reference for gain is the input power, not the radiated power. This efficiency is defined as the ratio of the radiated power () to the input power (). The input power is transformed into radiated power and surface wave power while a small portion is dissipated due to conductor and dielectric losses of the materials used. The power gain of the antenna as (3.13) The ratio of the power gain in any specified direction to the directive gain in that direction is referred to as the radiation efficiency of the antenna i.e. (3.14) Antenna gain can also be specified using the total efficiency instead of the radiation efficiency only. This total efficiency is a combination of the radiation efficiency and efficiency linked to the impedance matching of the antenna. Hence, from equation 3.14 (3.14(a)) 3.6 Polarization The definition for polarization can be quoted from Balanis [4] as: â€Å"Polarization of a radiated wave can be expressed as â€Å"that property of an electromagnetic wave describing the time-varying direction and relative magnitude of the electric field vector; specifically, the figure traced as a function of time by the extremity of the vector at a fixed location in space, and in the sense in which it is traced, as observed along the direction of propagation.† Polarization then is the curve traced by the end point of the arrow representing the instantaneous electric field. The field must be observed along the direction of propagation.† 3.7 Return Loss The Return Loss (RL) is the parameter which indicates the amount of power that is lost to or consumed by the load and is not reflected back as waves are reflected which leads to the formation of standing waves. This occurs when the transmitter and antenna impedance do not match. Hence, the RL is a parameter to indicate how well the matching between the transmitter and antenna has taken place. The RL is given as: (3.15) For perfect matching between the antenna and transmitter, RL = ∞ and Γ = 0 which means no power is being reflected back, whereas a Γ = 1 has a RL = 0 dB, which implies that all incident power is reflected. For practical applications a RL of -9.54 dB is acceptable. Chapter 4 Modeling of Half-Wave Dipole Micro Strip Patch Antenna Using XFDTD ® 4.1 Introduction For the purpose of modeling and simulation of antennas we have used modeling softwares, which are widely used in industries. These softwares are specially used for the purpose of electromagnetic (EM) modeling, which refers to the process of modeling the interaction of electromagnetic fields with physical objects and the environment. The first such software brought into use is XFDTD ®. It is a three-dimensional full wave electromagnetic solver based on the finite difference time domain method. It is fully three-dimensional.   Complex CAD ® objects can be imported into XFDTD ® and combining and editing can be done within XFDTD ® using the internal graphical editor. It is a powerful software which offers a lot of options to its users. This software has been initially used for modeling of basic antennas to get familiarity with interface and working of the software. Dipole is one of such basic antennas with a simple structure; as the name suggests dipole antenna consists of two wires on the same axis with a source applied at the center point. In this chapter, we begin with the analysis of a half-wave dipole antenna by derivation of field equations and the MATLAB ® plot. After the analysis the modeling is done using XFDTD ®. Finally, all the results are matched by plotting the data in MATLAB ®. 4.2 Derivation of Vector Magnetic Potential We begin with the derivation done in chapter 2 for of the radiated fields for a half-wave dipole antenna in equation 3.11 which gives us the following expression for (4.11) 4.2.1 MATLAB ® Plots of Half Wave Dipole Antenna The expression can be plotted in MATLAB ® using the following code clear all; theta = [0:360]*pi/180; F = cos((pi/2)*cos(theta))./(0.0000001 + sin(theta)); Pn = F./max(F); Pn=abs(Pn); title (POLAR PLOT OF HALF WAVE DIPOLE ) polar(0,1); hold on; polar (theta,Pn,r); The MATLAB ® generated plot of normalized electric field for half-wave dipole for above code is as follows Figure 4.1: MATLAB ® plot for Normalized Electric Field 4.3 Modeling of Half Wave Dipole Using XFDTD ® 4.3.1 Introduction XFDTD ® is a full wave, 3D, Electromagnetic Analysis Software. XFDTD ® used solid, dimension based modeling to create geometries. To create geometry, library objects and editing functions may be used. Modeling of half-wave dipole antenna was carried out in XFDTD ® to test the softwares capability of generating far field radiation pattern. And also to get in depth knowledge of XFDTD ® before using it for the modeling of patch antennas, which is the foremost objective of this project. 4.3.2 Validity of Model As in the previous section the electromagnetic theory of half-wave dipole was studied and its mathematical equations for normalized radiated field was derived and plotted. This plot will be our reference plot while doing the modeling of half-wave dipole. 4.3.3 Modeling of Half Wave Dipole As we know the length of a half-wave dipole antenna should be half the wavelength of the operating carrier wave frequency. Thus the dipole modeled in XFDTD ® has the following specifications: Length of 30cm Frequency used 1 GHz Thin wire was used to create the dipole Source was attached in the middle Figure below shows the geometry of dipole being modeled in XFDTD ®. Figure 4.2: XFDTD ® geometry of Half-Wave Dipole 4.3.4 Results The far fields of dipole antenna were calculated by XFDTD ® and plots were obtained for far field versus both Phi and Theta, as shown in Figure 4.3 Figure 4.4. The results matched with the theoretically established results. Figure 4.3: Far Field vs. Theta Figure 4.4: Far Field vs. Phi 4.3.5 Plotting XFDTD ® Results in MATLAB ® The data for far fields from XFDTD ® was exported and matched with the theoretical results in MATLAB ® for the purpose of confirming the results. Help was taken from the XFDTD ® reference manual to learn how to export far field data. The XFDTD ® file was copied and the extension was changed to ‘.dat and name was changed to ‘XFTDT.dat Next this file was read by MATLAB ® using the MATLAB ® code provided [angle1, a1, c1, d1, e1] = textread(XFDTD.dat,%f %f %f %f %f, 361); angle1=angle1*pi/180; q=find(c1 c1(q)=-9; c1=c1+9; m=max(c1); c1=c1./m; polar(angle1,c1,g) The MATLAB ® result is shown n figure below. Figure 4.8: XFDTD ® radiation pattern in MATLAB ® The experimentally produced curve qualitatively matches with our theoretical calculations. The shape of the curve is similar to the theoretical description, whereas the scale is different. For the purpose of confirming this result, the data of this curve is also exported into MATLAB ® to be compared with previously simulated results. 4.4 Modeling of Micro Strip Patch Antenna Using XFDTD ® 4.4.1 Introduction After gaining confidence on the design of dipole antenna by comparing its results with the simulations and the results obtained from MATLAB ®, we use the same computational software for the modeling of micro strip patch antenna. 4.4.2 Validity of Model For the modeling of micro strip patch antenna, a paper of IEEE â€Å"Application of Three-Dimensional Finite-Difference Time Domain Method of the Analysis of Planar Micro strip Circuits† is reproduced. This paper is used as a reference so that the results could be compared in order to check the validity. The result of our exercise confirms the results of the IEEE paper; this takes us to design a micro strip antenna of our desired parameters. This training will help us gain the expertise over the computational software, which can be used for the modeling of multiple different antennas. 4.4.3 Modeling of Micro Strip Patch Antenna The antenna is designed for the frequency range from 0 GHz (dc) to 20 GHz. The dimensions used for the antenna centers it at 7.8 GHz. Although its results at the higher frequencies are also examined for the accuracy, the parameters for the antenna are given below: Duroid substrate is used with =2.2 Thickness is 1/32 inch=0.794mm Length = 12.45mm Width = 16mm Transmission line feed is used and is placed at 2.09mm away from the left corner. With these specifications the center frequency comes out to be 7.8 GHz and this can be verified from the link www.emtalk.com/mpaclac.php Figure 4.5 shows the geometry of micro strip patch modeled in XFDTD ®. Figure 4.5 Geometry of the micro strip patch antenna 4.4.4 Results The S11 plot of micro strip patch antenna was calculated by XFDTD ®, as shown in Figure 4.6 Figure 4.7 is the plot of the IEEE paper. This gives us the comparison between the two. Figure 4.6 obtained from the XFDTD ® Figure 4.7: Results of S11 parameters from published IEEE Papers Chapter 5 Micro Strip Antennas 5.1 Introduction These days there are many commercial applications, such as mobile radio and wireless communication, where size, weight, cost, performance, ease of installation, and aerodynamic profiles are constraints and low profile antennas may be required. To meet these requirements micro strip antennas can be used. These are low profile antennas and are conformable to planar and non-planar surfaces. These are simple and inexpensive to manufacture using modern printed circuit technology. They are also mechanically robust and can be mounted on rigid surfaces. In addition, micro strip antennas are very versatile in terms of resonant frequency, polarization, pattern and impedance as explained by Balanis [4]. 5.1.1 Basic Characteristics Micro strip antennas consist of a very thin metallic strip or patch placed a small fraction of a wavelength above a ground plane. The micro strip patch is designed so its pattern maximum is normal to the patch hence making it a broadside radiator. This is accomplished by properly choosing the mode or field configuration of excitation beneath the patch. End-fire radiation can also be accomplished by judicious mode selection. For a rectangular patch, the length L of the element is usually . The conducting micro strip or patch and the ground plane are separated by the substrate (Balanis [4]). There are numerous substrates that can be used for the design of micro strip antennas and their dielectric constants are usually in the range of . The substrate that we are using in our designs has a value of 4.6. Often micro strip antennas are also referred to as patch antennas. The radiating elements and the feed lines are usually photo etched on the dielectric substrate. The radiating patch may be square, rectangular, thin strip, circular, elliptical, triangular or any other configuration. Arrays of micro strip elements with single or multiple feeds are used to achieve greater directivities. 5.1.2 Feeding Methods There are numerous methods that can be used to feed micro strip antennas. The four most common and popular are the micro strip line, coaxial probe, aperture coupling and proximity coupling. In our designs we have selected coaxial probe as our method of feeding the Micro strip antenna. Following is a brief explanation of coaxial feeding as explained by Balanis [4]. Coaxial-line feeds, where the inner conductor of the coax is attached to the radiation patch while the outer conductor is connected to the ground plane are widely used. The coaxial probe feed is also easy to fabricate and match, and it has low spurious radiation. However is has narrow bandwidth and it is more difficult to model. 5.2 Rectangular Patch The rectangular patch is one of the most widely used configurations of Micro strip antennas. It is very easy to analyze using either the transmission line model or the cavity model, which have higher accuracy for thin substrates as explained by Balanis [4]. In our desig

My First Driving Experience

My First Driving Experience My First Driving Test Some people think that their lives are hard and full of disappointment; well I am one of those people. I am a hard worker, but no matter what I do, I still face problems. It is as if my life is an ocean of endless problems and disappointments; however one of the disappointments I have faced happens to be the most interesting part of my life. I had been learning how to drive for a whole month. I was spending part of my everyday life in a car listening to instructions from a boring old man, but I kept up with that to get my license and enjoy the freedom of being able to go wherever I wanted, whenever I wanted. The day I had my driving test was the day I would find out if all the effort and time I had put into driving was worth it or not. The day before my driving test was one of the worst and darkest days of my life because I was extremely nervous and worried about the judgment day, which was the next day. My brothers and sisters teased me for studying so hard to get my driving permit. Although I studied hard, I got my permit after doing my second test, which most of my family and friends thought was ridiculous. I spent four hours with my driving instructor making sure I knew everything that I had to know. We went through all the instructions and all other details that there was to know. I usually sleep late, but on the day before my driving test I slept unusually early. During my sleep, I dreamt of being in a car with the police officer sitting on the passenger seat screaming â€Å"You are a failure in driving† and that made me wake up in the middle of the night sweating. I kept imagining failing the test the next day, and I couldnt stop thinking about it. However, I tried to stop thinking about tomorrow and tried to get a good nights sleep, which would be an advantage for me when taking the test. Finally, I slept like a baby without any nightmares this time. On the big day, I woke up to my alarm and got ready to be picked up by my instructor to go to the police station, where I would have my driving test. I was very nervous, and my instructor, while we were on the way to the police station, said that I was not driving as well as I always do. I had been turning without informing other drivers that I was going to, by using the indicator. Once I got to the police station, I was waiting in the car for the police officer to arrive and start my test. I couldnt help it but imagine that he would be an old man with eyes crossed and that he would be laughing evilly, when failing me. When the officer got in the car, thats when I got even more nervous and my legs were vibrating as if I was a phone that was being called. My dad told me, the day before, not to let the officer see me tense, or else he wouldnt pass me in the test. Unfortunately, any person who laid his eyes on me would notice how tense I was. However, I tried to calm myself down, so I t hought about the long period I had been learning how to drive and convinced myself that it would be a piece of cake. Moreover, my older brothers and sisters got their licenses without learning as much as I did. Before leaving the police station, I took one last look at the place where I would be coming back to get my license. Then I started the car and the officer was directing me on where to go; however, I kept imagining all the things that could have went wrong or even worst if I failed the test. I was told to make a right turn, when my mind went blank and I didnt know where my left was, or my right. I tried remembering that my right would be towards the arm I use to write. Once I got to my first stop sign I asked myself â€Å"Is this going to be the sign that would fail me?† It failed two of my friends in the past. Luckily, I stopped at the sign smoothly thanks to all the training I had. After that, the officer took me to the parking lot of a gas station where I was tested for parallel parking. The space in which I had to park looked so extremely small that it would be impossible to park in. I did my best and tried recalling every step my instructor taught me and finally did it in success. When I was leaving the parking spot, something unexpected happened. A teenage girl was walking in front of the car, but I failed to notice her because I was looking at the cars coming from the back. Instinctively, I had to hit the brakes hard and caused both of us, the police officer and me, to bend towards the front of the car. At that moment, I thought I had ruined my perfect driving and gave the officer the excuse he was looking for to fail me. In order to reduce the tension, I asked the officer calmly, â€Å"Are you alright?† and he replied, â€Å"I am fine, but dont do that again, concentrate.† Then, I found out that I might still have a chance to pass this test, since the officer didnt ask me to go back to the station. I pulled myself together and continued driving, while listening to the instruction from the officer. Just when I felt relieved and everything was going well, I heard a siren. It was a fast ambulance approaching from behind, which got me all nervous again because the road was so slim that I couldnt move to the right to provide enough space for the ambulance to pass. Suddenly, I started accelerating to keep a distance from the ambulance and hoped eventually it would turn at some other street. Luckily, the ambulance did disappear from my rearview mirror; I guess it did turn somewhere. Ive always tried to figure out why I chose to speed up, instead of waiting for the officers instructions, but I never found an answer. After losing the ambulance, I was shocked for a while, and I was in a separate world wondering about what just happened. I couldnt hear the officer instructing me to turn right. He kept telling me to turn till he eventually slapped my shoulders to get my attention. That is when I snapped out of my daydream and heard the officer instructing me to turn back to the station. Unfortunately, I failed the test because of lack of concentration and speeding. Every time I recall my first driving test, I really feel disappointed in myself because of my bad decision-making. However, I did pass the test eventually and got my license. I am a good driver now, and my friends dont have to worry about my driving when sitting in my car anymore. At last, I am also able to experience the freedom of being able to go wherever I desire. Although I was really disappointed about the test result, it was something that reminds me to stand up every time I fall. People shouldnt give up once they fail in any part of life because hard work isnt the only factor that plays roles in the results of different events in life. Other factors may influence the results too, such as luck, place and time. I was unlucky because I was on the same road as the ambulance, while I was taking my driving test, and that made me fail the test. I have just came to America to start studying higher education, and I was told that I have to do the driving test, in order to get a temporary Texas driving license and be able to drive here. Therefore, I would have to go through the bad experience of a driving test again. I just hope that it will be easier this time and I wont be out of luck.

The effectiveness of urine on Cancer :: essays research papers

The Greek audience would have been familiar with the story told in Antigone and with the background of the characters. An understanding of Antigone's family and her father's fate helps to put the events of the play in context. Antigone is of the Labdacids, a great but star-crossed family. Her father was Oedipus. Oedipus was born of Laius and Jocasta, the rulers of Thebes, but his parents were warned in prophecy that the boy would grow up to murder his father and marry his mother. A herdsman was charged with killing the child, but out of pity he gave the boy to another herdsman from a neighboring kingdom. This second herdsman gave the child to his own king and queen, who raised the child as their own. The child Oedipus never knew that his adoptive parents were not his biological parents. When a young man, Oedipus was warned by an oracle that he would kill his father and marry his mother. He fled home, thinking he would be able to avoid this fate, embarking on a series of adventures th at resulted in the exact fulfillment of the prophecy. Along the way, he solved the riddle of the Sphinx, saving Thebes and becoming her king as well as Jocasta's new husband†¹but not before he killed, in a fit of uncontrolled anger, a stranger at a crossroads. The stranger, of course, was his true father, Laius. After Oedipus had been in power in Thebes for some time, a plague began to kill Theban citizens. An oracle informed the king that Thebes was being punished because Laius' murderer was dwelling among them. Oedipus, the great riddle-solver, set out to learn the culprit's identity. Finally, he learned that Laius was the man at the crossroads, and worse, that Jocasta and Laius were his true parents. Jocasta was able to put the pieces of the puzzle together some time before her husband-son, and in despair she hanged herself. Oedipus, on discovering her body, blinded himself with her broaches and left the city. He entrusted his daughters, Antigone and Ismene, to Creon's care. In the days preceding the start of the action of Antigone, Thebes has been torn by war. Many years have passed since Oedipus's reign, and war eventually broke out between Oedipus's two sons. During the conflict, the two brothers, Polyneices and Eteocles, fought against each other as leaders of the two different sides.

Islam :: essays research papers

The five pillars The Five Pillars of Islam are the structure of Muslim religion. They are the testimony of faith, prayer, giving, fasting during the month of Ramadan, and if you are lucky the pilgrimage to Makkah once in a lifetime. The first pillar, entitled the testament of faith, exploits the Belief in one God, Allah, whom constitutes the very foundation of Islam. Prayer is the next pillar of Islam. Prayers do not take more than five minutes and are required five times daily. In prayer, a person feels inner happiness, peace, and a direct connection between the worshipper and Allah. Giving Zakat, other known as supporting the needy, is the third pillar of Islam. Initially, Zakat was the issue that altered Muhammad’s views of the world and turned him into a political figure. Fasting for the month of Ramadan is the fourth pillar of Islam. Even the Quran states, "O you who believe fasting is prescribed to you as it was prescribed to those before you so that you can learn Taqwa" (Quran 2:183). Ramadan consists of fasting from dawn until sundown while concurrently abstaining from food, drink, and sexual contact. Finally, the pilgrimage to Mecca is the last pillar. Although these conditions seem intense, there are actually many benefits to these submitters. The temptations of the world seem to erase our understanding for religion and g-d. Fasting will remind you of what has been handed down to us. Ramadan can draw one closer to g-d by seclusion from the surrounding world. Ramadan will help achieve a willingness to give to the needy. Now you have been in their shoes and understand how it feels. Understanding discipline is important, since g-d has given us a free will, and the torture of Ramadan is a great reminder of how to view life. In the Quran one can find references to ritual prayer or salat. Holy Qur'an 2:149 "From whencesoever thou startest forth turn thy face in the direction of the Sacred Mosque; that is indeed the truth from thy Lord.

Approaches for Green Computing

Approaches for Green Computing The advancements of technologies and machines by humans have led to one significant change all over the world and that is the climate change and other environment related changes and problems. People in all countries are thus trying to reduce their consumption of power and depleting natural resources for protecting the future of their future generations. This is one of the major agendas on which the people are working to make sure that the world doesn’t go worse than what it is.Hence, green computing has been adopted by all computer enthusiasts and computer scientists. We would discuss the major approaches that can help achieving green computing. Development of hardware that requires lesser power is one of the most commonly used approaches for green computing. Engineers from everywhere are developing new hardware systems that would consume less power. Special screens, special processing units and even devices run on solar power are being develope d on a regular basis.Human minds work in mysterious ways and one of the weird yet smart ways in which people have decided to reduce on the use of power by computers is virtualization, wherein the computer software is modified and designed in a way such that it can stimulate the hardware. Several companies making use of large servers and numerous systems have started adopting this method of virtualization for better output.Computer scientists have also initiated the use of cloud computing, a special measure that includes saving of all the information and even artificial intelligence over the internet. The power utilization of the servers making use of cloud computing becomes extremely less and hence this is one of the biggest advantages of the same. Where computer scientists are trying to adopt lower power consuming hardware, cloud computing is something that would assist in the process.Green computing is not only about lesser power consumption but includes several other measures and approaches. Computer scientists need to even take care of the recycling and disposal of the waste from manufacture and that of the computer systems themselves. Computer manufacturers need to make sure that they use the smartest technology available for production and even dispose of the production waste in a way such that it does not harm the environment.Thus we see that green computing is definitely the need of the future. Where computers have helped us in several ways and made our tasks easier, at the same time they have also caused some environmental harm. And it is crucial for us to identify these harm and then come up with technologies or ways of green computing to help save the future while making complete use of the technology for our own benefit. Reference link: http://classof1. com/homework-help/computer-science-homework-help

Psychology and Research Essay

1. There are various methods in psychological research, both qualitative and quantitative. Among them are field experiment, which is more qualitative and the statistical survey which, as the name suggests, a highly quantitative approach. Field experiment is a scientific method in research approach where the researchers (psychology-related researchers in this case) examine the participants or the data in the real world rather than doing the research in the laboratory, but all the same, the â€Å"field researchers have followed the structured approach†1 in research. Statistical survey, on the other hand is used to gather quantitative information on a given subject or participant in a population. It involves statistical processes in arranging data for them to be useful information to readers. It is worth noting however that a research rarely relies on a single method alone. Oftentimes, it is a combination of two or more methods to make it/the theory or contention stronger and more reliable. 2. With the psychosis studies and experiences of R.D. Lang, a psychoanalyst and a radical psychiatrist, he was able to observe his patients for real or â€Å"on field† when he developed his research regarding the subject (psychosis). It is a condition when an individual lost contact with the real world. Psychosis is best described by broad diagnostic concepts such as schizophrenia or bipolar disorder, and that these concepts describe brain diseases that are probably inherited. The task of psychology and its related researches on the subject matter aims to identify neuropsychological abnormalities in patients, in the hope that these might provide clues about the aetiology of the presumed brain pathology. Within this method, there is little scope for psychological intervention, as it is assumed that brain diseases are unresponsive to this kind of treatment. Another psychological research is the intelligence test of Binet or the currently evolved Stanford-Binet Scale which is one of the psychologically related tests or research where statistical approach may be applied. This method was developed containing the idea of graded tests series, the concept of intelligence and the conception of the fundamental qualities of an intelligence test. It was originally composed of thirty items in increasing difficulty, with grouped testees either according to age or gender or any other classification that may be applied. 3 This is where the current IQ Tests evolved. 3. When conducting research with human participants, consent and confidentiality4 are the two very important aspects of the study. Consent of the subjects should be obtained first to let them be aware of the entire study and will let them adjust and not to feel deceived. This will also help the researchers and the participants work together in harmony and will facilitate the entire research process. Aside from these, respect is another reason why consent of the participants must be obtained first. Confidentiality, on the other hand, will secure the safety and honor of the subjects/participants and at the same time will protect the reliability and soundness of the research itself. All the ethical concerns mentioned are generally for the respect of human life, as an individual and in order for the psychology profession be respectable as well. No one can respect the profession if in return, it does not know how to value the dignity of humans in the case that the latter be a participant or a subject in a psychology-related research.