Performance Measurement Paper free essay sample

In the world of business there are many cliche’s about how performance measurements are implemented and what they actually do such as â€Å"if your company doesn’t measure results then you can’t tell success from failure. † http://www. balancedscorecard. org/Home/tabid/36/Default. aspx The key focus on strategic objectives should always articulate precisely what the organization wants to accomplish which is the key to finding accurate, true, strategic measurements. The strategic performance measures will allow the organization to monitor the implementation and effectiveness of the operational efficiency. The best performance measures will provide a way to monitor and see if that strategy is actually working. Focusing on the importance of the employee’s contribution to the success of the organization is another important measure that can be added along with providing a common language for the communication of everyone. Performance measurement is so vital in the structure of an organization because it is an ongoing and constant reporting and monitoring of accomplishments. We will write a custom essay sample on Performance Measurement Paper or any similar topic specifically for you Do Not WasteYour Time HIRE WRITER Only 13.90 / page Typically the program is implemented by agency management. The different program activities are measured by this system as well. A program may be considered any project, activity, or function that has a set of objectives. The three types in which will be compared and contrasted begins with the output type of performance measures which indicates a specific workload that is processed throughout a period of time. The next type of performance type of selection is the efficiency type, which indicates the different ratio’s of the resources to work the product. The resources of this particular type are primarily considered budget dollars. The final performance measurement type that will be under contrast is the outcome type which tells the results over a period of time from work which was performed by the organization in order to benefit the people receiving the service. (EOM) or enterprise output management is a practice used in information technology dealing with the organization of data that is created for banking systems, insurance database systems, customer relationship management, as well as many others. Output distributed management is defined as middle ware that threatens to drive out the process originally supported in order to implement an auto mated one. EOM output managment could potentially reduce the cost of traditional printing because it uses digital output channel such as fax and email. The potential of this is depends on how the concept is adopted by the targeted customer group. Management information systems allow organizations to get right people the correct information at a timely and efficient manner. The efficiency type of performance management works by pulling together information. Therefore improving the products and expanding the customer base at the same time. A manger with a good management information system can eliminate redundant miscues that waste time and may instead focus on what actually works for the betterment of the organization. If an MIS is added into the equation then the amount of time saving that will benefit the organization will be tremendous because there is more time being focused on the specific task at hand. The computer program can collect data from employees much faster than the alternative time consuming method of not taking advantage of the technology. The over-all term performance management is defined as the output of employees and groups individually. The employees may be divided into groups and departments within the organization as a whole. Therefore the performances can be evaluated much more effectively by knowing what everyone’s production levels are and by gathering this information will definitely help to improve the quality of production in the organization which will lead to good things for everyone. In order for the performance management procedures to be put in place and do the job that they are needed to do there should be a performance definition done as soon as humanly possible because this knowledge will help drive the rest of the tasking in sequence for what needs to be done for the organization.

Smile and Smiling Specific Purpose Essay Example

Smile and Smiling Specific Purpose Essay Example Smile and Smiling Specific Purpose Essay Smile and Smiling Specific Purpose Essay Preparation Outline: Informative Speech on Smiling Specific Purpose: to inform my speech class about the many things Your Smile can do. Thesis: After listening to my speech, my audience should be informed about how â€Å"Your Smile† can do many things; have an effect on you and others around you, and how it has an effect on your brain. Introduction I. Smiling is something most people enjoy. I’m a happy and very positive person, so I smile a lot. It turns out that when I smile, the world smiles back. In my research about smiling I referred to sources such as cbsnews. com, science. owstuffworks. com, bizzikid. co. uk II. Smiling can affect the way you feel. It feels good to smile and be smiled at. People like to be surrounded by others who are positive and make them feel good. III. A smile is a great way to start any conversation, and makes others more receptive to you. It adds to what you have to offer. Transition: Let’s start with how a smile can affect you and o thers around you. Body I. A smile can affect you and others around you. A. It lifts our mood as well as the moods of those around us. B. It can make us appear more attractive to others. C. It can be contagious. D. Make you look younger E. Help you build rapport F. Helps reassure the other person of your sincerity. Transition: Now that we have talked about how your smile can affect you and others around you, let’s move on to how your smile affects your brain. II. How Your Smile Affects Your Brain A. Each time you smile at a person, their brain coaxes them to return the favor. B. Facial changes involved in smiling have direct effects on certain brain activities associated with happiness. Smiling triggers your feel good chemicals in your brain. C. Just the simple act of smiling releases endorphins from the brain into the blood. In conclusion, today we have discussed how your smile can affect you and others around you. We also talked about how a smile affects your brain. Conclusion I. Smiling is a way to promote happiness within yourself and others. Smiling is a very important part of connecting and getting to know someone. II. Choosing to smile can make a difference in everything you do that day. A smile can brighten your mood, improve your outlook, and lead you to make positive choices. So when you smile not only will you make yourself feel better, you will also attract positive energy into your life. References Makes you look younger. Freeman, D. W. (2011, November 10). Smiling makes people look younger, study shows. . Retrieved from cbsnews. com/8301-504763_162-57322365-10391704/smiling-makes-people-look-younger-study-shows/ How your smile affects your brain. science. howstuffworks. com Layton, J. (n. d. ). Retrieved from http://science. howstuffworks. com/life/smilinghappy1. htm Feel good chemicals. Bizzikid . (n. d. ). Retrieved from bizzikid. co. uk/healthwellbeingsmiling. html

Make a research on a geography Essay Example | Topics and Well Written Essays - 500 words

Make a research on a geography - Essay Example McDonald’s dates its origin to the opening of a franchised restaurant by Ray Kroc, in Des Plaines, Illinois in the year 1955, the ninth McDonalds restaurant overall. Ray Kroc in the later years purchased the McDonald brothers equity in the company and launched its worldwide expansion. In fact the company became so popular that with the successful expansion into the international markets it was called as the symbol of globalization. However, in the recent years it was also debated that the company was responsible for spreading unhealthy eating habits and has increased the incidence of obesity and other health problems. Besides, its prominence has also made it a common subject of public debates about corporate ethics and consumer responsibility. McDonalds restaurants are found in about 100-120 countries and territories around the world. In general, it is estimated that it serve nearly 54 million customers each day. McDonalds has become symbolic of globalization and since it is directly identified with United States culture and lifestyle, its expansion into the international market has been pointed out by critics as a part of Americanization and American cultural imperialism. Anti-globalization is a common term used to describe the political stance of people and groups who oppose the aspects of globalization and McDonalds remains a target of anti-globalization protesters worldwide (Wikipedia, 2007). Additionally, film’s such as â€Å"Super Size Me† that explores the horror of school lunch programs, declining health and physical education classes, food addictions were also blaming fast food restaurants like McDonald’s. Even will all these resistance and reparations in the world around, the company has improved and grown with more than 31,800 flagship restaurants serving burgers and fries in different countries and today McDonalds is more than a household name. It is estimated that about 30% of its locations are company-owned

Organizational culture is fundamentally about symbolic meaning and as Essay - 5

Organizational culture is fundamentally about symbolic meaning and as such cannot be managed. Discuss - Essay Example Symbolism in the organisation refers to the wide variety of meaning and expression functions in the organisation. Organisational culture is a network of shared experiences and accepted reality through which tangible expressions are depicted in the symbols of the organisation. Symbolic organisational culture is displayed in the language, mode of dressing, rituals and routines that define the interactions among the stakeholders of the organisation (Brown 1998). Artifacts like pictures on the walls of the building, the smell and emotional overall feel of the organisation are used by the outsiders to gauge whether the company is bureaucratic or informal. For instance, a bouquet of flowers on the reception may be a symbol of stakeholders’ appreciation. The bouquet of flowers may have other associated elements such as the arrangement and texture that will indicate the historic experience of the stakeholders. According to prospective symbolization, artifacts in the organisation are n ot imitations but objects that portray the reality of organisational culture. According to Schein, the first level of organisational culture includes the artifacts that symbolize how employees interact in the organisation and guide the behaviour of employees (Schein 2009). ... The last level of the organisational culture is the assumptions that reflect the shared traditions and beliefs within the organisational culture (Schein 2009). Stories and myths also define the symbolic nature of organisational culture. Stories are used to highlight the past struggles and successes of the organisation. Stories and myths may either be written or oral and are used to orient the new employees to the organisation. Ordinary tells such as weekly sales levels or historic legends like the founders of the organisation help employees understand the strategic mission of the organisation. Effective stories will affirm the strategic and core values of organisation to employees. For instance, stories can be geared at enhancing creativity, professionalism, integrity and hard work thus facilitating the commitment to organisational objectives. The organisation can manage this symbolic element through having written core values that are displayed in walls and company websites. In addi tion, the beliefs are aimed at enhancing the job motivation and increased productivity, thus beliefs can be managed through expression of humor in the workplace (Daft 2010). Organisational routine actions and rituals such as ceremonies like the end of year parties, team retreats and company meetings add a symbolic value to the organisation. The leaders in the organisation should ensure regular performance reports, open performance discussions and board meetings in order to facilitate the evaluation of the past performance of the organisation (Nel 2009). Material objects such as corporate logos, company product designs and status symbols inspire or demoralize the employees. Symbols in the organisation justify

Human Resource Interview Essay Example | Topics and Well Written Essays - 1000 words - 1

Human Resource Interview - Essay Example We are supported by the state government and our staff strength comprise of 440 full time and about 200 part time faculty/employees. While leading a non-profit organization my role is to supervise the smooth running of the institution and objective try to achieve the goals set by the vision and mission statement. I am responsible for managing the Human Resources and to arrange and organize funding, training and administration of this division. I report to the Principal. The mission statement: We identify and meet the educational needs, primarily of adults, in our principal geographic service area of northeast Dallas, Richardson, and Harland. We offer courses, programs, and services to enable students to achieve their educational goals, and become lifelong leaders, community builders, and global citizens. We enable employees to model excellence in their service to students, colleagues, and community. A2: We own several properties that have been converted into campuses. Richmond is located in Dallas and is the largest amongst them. It comprises of ten buildings surrounded by lakes and parks. Being environment friendly is one great challenge. The other is dealing with a great number of nationalities that constitute our students. Managing cultural diversities harmoniously is another great challenge. All this requires that the faculty and staff be very considerate and this is a great HRM challenge to ensure an amicable atmosphere all around. But this human capital needs monetary capital for training and compensation and that too poses a great challenge for me. A3: Of course there are other challenges that one faces in such a diverse and large organization. All problems relate to people in the end. However I see to it that I restrict my activities to my department only without bringing personal feelings or value judgments into actions or decisions. A4: My job requires for me to be

Mechanisms for Optical Limiting

Mechanisms for Optical Limiting Chapter 2 2.1. Reverse Saturable Absorption In the mid 1960s shortly after the invention of the laser, many researchers were investigating dyes for potential application to Q-switching of the laser cavity. For this application, dyes were sought that would bleach to transparency under intense illumination (saturable absorbers). Guiliano and Hess [2a] in 1967 were investigating vat dyes and their modified cousins and noted some examples that not only did not bleach to transparency but instead darkened at high intensities. This was the first recognition of the property of reverse saturable absorption (RSA). Reverse saturable absorption generally arises in a molecular system when the excited state absorption cross section is larger than the ground state cross section. The process can be understood by considering a system that is modeled using three vibronically broadened electronic energy levels, as shown in figure 2.1. The cross section for absorption from the ground state 1 is à ¯Ã‚ Ã‚ ³1. à ¯Ã‚ Ã‚ ³2 is the cross section for absorption from the first excited state 2 to the second excited state 3. The lifetime of the first excited state is à ¯Ã‚ Ã‚ ´2 (seconds). Figure 2.1: Three level and Four level models for RSA As light is absorbed by the material, the first excited state begins to become populated and contributes to the total absorption cross section. If à ¯Ã‚ Ã‚ ³2 is smaller than à ¯Ã‚ Ã‚ ³1, then the material becomes more transparent or ‘bleaches’ i.e. it is a saturable absorber. If à ¯Ã‚ Ã‚ ³2 is larger than à ¯Ã‚ Ã‚ ³1, then the total absorption increases, and the material is known as a reverse saturable absorber. This behavior is shown in figure 2.2 Figure 2.2: Plot of the incident intensity versus the transmitted intensity of a typical three level RSA material. The change in intensity of a beam as it propagates through the material is: , (2.1) Where z is the direction traversed, NT is the total number of active molecules per area in the slice dz, N2 is the population of level 2 and the population of level 3 has been neglected. Initially, the material obeys Beer’s law when 2 is unpopulated, and the transmission is constant as the incident fluence is increased. The slope is given by. At a sufficiently high fluence, however, the first excited state 2 becomes substantially populated and in the limit of complete ground state depletion the slope again becomes constant at the new value of. The optical limiting action is not truly limiting, as the fluence, which is transmitted, is still increasing with increasing incident fluence, but it does so more slowly. If the ratio à ¯Ã‚ Ã‚ ³2/à ¯Ã‚ Ã‚ ³1, is sufficiently large, however, the new transmission will be small and in a properly designed system the dynamic range of the sensor will be greatly extended. The three level diagrams describe the simplest case for RSA materials but can generally only be applied for subnanosecond pulses and under circumstances such that transitions from the second excited state are negligible. The energy states involved in three level materials usually consists of singlet states and the transitions are all allowed. The transition cross sections are therefore large, but a disadvantage is that de-excitation is rapid (à ¯Ã‚ Ã‚ ´2 is small). This necessitates larger intensities for long pulses to activate the nonlinearity through populating the excited electronic state. Fortunately, on longer timescales in some systems, significant intersystem crossing to other states can occur from the first excited state. In this case the five level diagrams shown in figure 2.1 is applicable. The excited state 4 is usually a triplet or other long-lived state, and for long pulses it can act as a metastable state that accumulates population during the pulse. The lifetime of 4 gives an indication of the maximum pulse width for which the material is efficient to act as an optical limiter. Pulses with duration longer than the metastable state allow some of the metastable molecules generated by the leading edge of the pulse to decay to the ground state before the trailing edge have passed, thereby reducing the RSA. In most systems, à ¯Ã‚ Ã‚ ´3 and à ¯Ã‚ Ã‚ ´5 are very small and significant populations of 3 and 5 do not accumulate. Therefore, N3 and N5 can be set to zero, considerably simplifying the dynamical equations describing. The equations representing the full five level models are given below by: (2.2) (2.3) (2.4) (2.5) (2.6) (2.7) and (2.8) Where hà ¯Ã‚ Ã‚ ® is the energy per photon, I is the intensity of the pulse and stimulated emission has been neglected. The latter assumes that optical coupling to the excited states is well above the bottom of the vibronic manifolds and that relaxation from the optically-coupled states to the bottom of the manifolds occurs on a time scale that is much shorter than the pulse duration. To completely understand the response of an RSA device, these equations must be solved as the pulse propagates through the material. The material parameters necessary to solve the equations are à ¯Ã‚ Ã‚ ³1, à ¯Ã‚ Ã‚ ³2, à ¯Ã‚ Ã‚ ³4, à ¯Ã‚ Ã‚ ´2, à ¯Ã‚ Ã‚ ´4 and à ¯Ã‚ Ã‚ ´24. For optimum optical limiting performance, certain parameters need to be maximized. The ratio of the excited state absorption to the ground state, à ¯Ã‚ Ã‚ ³2/à ¯Ã‚ Ã‚ ³1, à ¯Ã‚ Ã‚ ³4/à ¯Ã‚ Ã‚ ³1 should be large to minimize the transmission of the limiter at high incident intensity. For maximum efficiency, the lifetime of the triplet state (à ¯Ã‚ Ã‚ ´2) and the intersystem crossing rate l/à ¯Ã‚ Ã‚ ´24 should be large to populate the triplet state and maintain the population throughout the pulse. By the mechanism of RSA we get better performance on optical limiting. 2.2. Two-Photon Absorption (TPA): Two-photon absorption (TPA) can also be used in a manner similar to RSA to construct optical limiters. In contrast with reverse saturable absorption, TPA is an instantaneous nonlinearity that involves the absorption of photon from the field to promote an electron from its initial state to a virtual intermediate state, followed by the absorption of a second photon that takes the electron to its final state. Since the intermediate state for such transitions is virtual, energy need not be conserved in the intermediate state but only in the final state. The mechanism of TPA can be thought of in terms of the three level RSA model for the case where the lifetime of the intermediate state approaches zero and the ground state absorption is extremely low (highly transparent). The intensity of the beam as it traverses the material is: (2.9) Where z is the linear absorption coefficient and à ¯Ã‚ Ã‚ ¢ is the TPA coefficient which is related to the imaginary part of à ¯Ã‚ Ã‚ £(3) by the equation (SI units): (2.10) Here, à ¯Ã‚ Ã‚ · is the circular frequency of the optical field, n0 is the linear index of refraction, and c is the speed of light in vacuum. The solution to the propagation equation for à ¯Ã‚ Ã‚ ¡= 0 (transparent material at low intensities) is given by (2.11) Where L is the sample length. This clearly demonstrates that the output intensity decreases as the input intensity increases, exactly the behavior that is desired for an optical limiter. The strength of this reduction is explicitly dependent on the TPA coefficient, the incident intensity and the sample thickness. For TPA, the material response is of the order of an optical cycle and is, therefore, independent of the optical pulse length for a fixed intensity. The device will respond virtually instantaneously to the pulse. On the other hand, because of the limited magnitude of à ¯Ã‚ Ã‚ ¢ in existing materials, high intensities are required to realize significant TPA. Since the intensity is essentially the energy density divided by the pulse duration, short pulses are required to achieve limiting with TPA for energy densities that may be high enough to damage an optical sensor. 2.3. Free-Carrier Absorption: This type of limiting occurs in semiconductor materials. Once carriers are optically generated in a semiconductor, whether by single photon or two-photon absorption, these electrons (holes) can be promoted to states higher (lower) in the conduction (valence) band by absorbing additional photons. This process is often phonon assisted, although depending on the details of the band structure and the frequency of the optical excitation, it may also be direct. The phonon assisted phenomenon is referred to as free-carrier absorption, and it is analogous to excited-state absorption in a molecular system. It is clearly an accumulative nonlinearity, since it depends on the buildup of carrier population in the bands as the incident optical pulse energy is absorbed. Free-carrier absorption always plays some role in the operation of a semiconductor limiter, if the excitation process results in the generation of significant free carrier populations in the bands. While it certainly contributes to the limiter performance and its inclusion is important in the precise modeling of the response of such devices, just as in the case of TPA, its importance typically pales in comparison with nonlinear refractive effects, whether the carriers are generated by single photon or two photon transitions. 2.4. Nonlinear Refraction Optical limiters based on self focusing and defocusing form another class of promising devices. The mechanism for these devices may arise from nonlinear refraction associated with carrier generation by either linear or two photon absorption in a semiconductor. Both self focusing and defocusing devices operate by refracting light away from the sensor as opposed to simply absorbing the incident radiation. Compared to strictly absorbing devices, these limiters can, therefore, potentially yield a larger dynamic range before damage to the limiter itself. Figure 2.3 (a) shows the typical device configuration for a self defocusing limiter, while figure 2.3 (b) shows a similar device based on self focusing. A converging lens is used to focus the incident radiation so it passes through the nonlinear medium. This lens provides optical gain to the system, allowing the device to activate at low incident intensities. The output passes through an aperture before impinging on the detector. At low input levels, the nonlinear medium has little effect on the incident beam, and the aperture blocks an insignificant portion of the beam, thus allowing for a low insertion loss for the device. When nonlinear refraction occurs, however, the nonuniform beam profile within the medium results in the generation of a spatially nonuniform refractive index. This acts as either a negative or positive lens, depending on the sign of the refractive nonlinearity, causing the incident beam to either defocus or focus. Figure 2.3: (a) Typical self defocusing optical limiter configuration (b) Typical self focusing optical limiter configuration. In a properly designed system, this self lensing results in significant energy blocked by the system aperture, thereby protecting the sensor. The location of the nonlinear medium is critical to the operation of the refractive limiting device. A self-focusing limiter works best if the nonlinear medium is placed approximately a Rayleigh range before the intermediate focus of the device. When the focusing lens is induced the effective focal length of the device is reduced, and hence a larger beam appears at the exit aperture. For a self-defocusing material, the optimum geometry is approximately one Rayleigh range after the focus. This geometry dependence can be exploited to determine not only the sign of the nonlinear refraction in a given medium, but the magnitude as well. This is the principle behind the so-called Z-scan technique, which has been pioneered by Van Stryland and coworkers [2b,2c]. The technique consists of moving the nonlinear medium through the focal region of a tightly focused beam while measuring the transmittance through an aperture placed in the far field of the focal plane. When the medium is far before the focal plane, no self-lensing occurs. As the medium approaches the focal plane, the high intensity begins to induce a lens in the medium. For a negative nonlinearity, this lens tends to collimate the beam, thereby increasing the transmittance through the aperture. Near the focal plane, even though the intensity is highest, the influence of the induced lens is minimized, resulting in a transmittance comparable to the linear transmittance. This is similar to placing a thin lens at the focus of a beam; this results in minimal effect on the far field beam pattern. As the sample is moved beyond the focal plane, the negative lens tends to increase the beam divergence, resulting in a decrease in the aperture transmittance. As the medium is moved still farther from focus, the intensity again becomes weak enough that the induced lensing is negligible. This sequence results in a change in transmittance with a characteristic peak, followed by a null, followed by a valley as the sample is moved from the input lens, through focus, toward the output lens. For a positive nonlinearity, the pattern consists of a valley, a null, and then a peak. Thus, the sign of the nonlinearity is readily determined. While nonlinear absorption has been neglected in this discussion, if present, it must also be accounted for. This is readily done by removing the aperture in the limiter and collecting all the light transmitted by the nonlinear material. This measurement is then insensitive to nonlinear refraction. The response in this case is a valley symmetrically located about the focal plane. It should be noted that nonlinear absorption and induced scattering cannot be distinguished by this technique. The general shape of the Z-scan for a positive index change, negative index change, and a nonlinear absorber or scatterer is shown in figure 2.4 . Figure 2.4: Schematic representation of z-scan results for a negative refractive nonlinearity (dashed curve) and a positive refractive nonlinearity (dotted curve). Both curves have been corrected for absorption. The solid curve shows the result of removing the aperture from the measurement apparatus and collecting all the transmitted light, thus isolating the nonlinear absorption [1e]. 2.5. Induced Scattering Scattering roots from interaction of light with small centers which may be physical particles or simple interfaces sandwiched between non-excited and excited molecular groups. The size of the scattering centers determines whether the scattering will be quite directional or reasonably uniform. Transmission of a medium, for a given solid angle, decreases when scattering centers are induced in the medium by an optical signal. Therefore, this phenomenon of scattering induced by optical signal may be applied to manufacture of optical limiters for sensor protection. Optical limiters based on induced scattering are usually focused on liquid media, as the phenomenon is usually reversible in these media. That is to say, the liquid in the excited state can return to equilibrium with ease in the absence of chemical or structural decomposition. However, in solids, usually irreversible decomposition processes generate the scattering centers which can lead to degradation in the device’s lin ear operation. When light is incident on a particle, the electric charges within the particle oscillate due to its interaction with the electric field. Radiations are then caused by the oscillation. In 1899, Lord Rayleigh originally presented the analytic expression and theory of the elastic scattering of light from particles with dimensions smaller than the wavelength of light. Rayleigh scattering is the name given to the phenomenon. This applies only to particles whose dimensions are quite smaller than the wavelength of light or which are non-absorbing. However, in 1908, Mie developed a theory for particles with dimensions comparable to the wavelength of light or greater [2d]. The transmitted intensity equations of the Mie scattering are notably more intricate than of Rayleigh scattering. In Mie scattering, a bigger percentage of the scattered radiation is in forward direction as the size of the scattering particles increases, implying that limiting based on Mie scattering will not be as effectiv e as Rayleigh scattering. 2.6. Photorefraction Two devices, namely coherent-beam excisor and the beam fanning limiter based on the photorefractive effect are used to limit coherent optical radiation. Materials showing photorefraction should have a nonzero χ(2). The traditional photorefractive mechanism is based on the photorefractive crystal which possesses deep levels that can be excited optically to generate free charge in the conduction or valence band. In a material showing photorefraction, when two coherent beams interfere, additional mobile charge are generated at the peaks of the intensity pattern than at the valleys through photoexcitation of the deep levels of the crsytal. These charges which are photoexcited at the peaks diffuse into the valleys ensuing a variation of charge spatially, in correspondence to the material’s interference pattern. These charges results in an electrostatic space-charge field which gives rise to a change in refractive index through the electro-optic effect in a properly oriented cry stal. Energy coupling and energy exchange can then be achieved between the two beams through the grating generated, which is 90 degrees phase shifted from the intensity of the photon field. A high intensity coherent beam when incident singly on a photorefractive crystal, the energy can be coupled into a large amount of low intensity scattered beams. Fields with new wave vectors are generated inside the crystal by the scattering of the incident beam at the crystal imperfections. The photorefractive gratings are then produced by the interference of the incident field with these scattered fields. Optical signal can later be coupled from the incident beam to the scattered beams through diffraction from these gratings. The light gets preferentially scattered to one side of the crystal as there is a preferred direction of energy transfer for photorefractive gratings which is determined by the direction of the c-axis of the crystal and the charge carriers’ sign. This photorefractive beam fanning phenomenon can be quite efficient in reducing the intensity of the transmitted beam. Construction of an optical limiter using this beam fanning process has been demonstrated by Cronin-Golomb and Yariv [2e]. The photorefractive excisor is another device which provides a weak seed beam to interfere with the incident beam. It is assembled to protect the sensor in such a way that the photorefractive grating produced by the interference of the primary beam with the seed beam at high intensities couples energy from the strong incident beam to the weak seed beam. The speed and efficiency of the device is thus improved. 2.7. Summary All of the nonlinear phenomena discussed above can be used for optical limiting, and figure 2.5 schematically illustrates the application of some of these processes. Figure 2.5 (a) depicts the use of induced absorption, such as reverse saturable absorption, two-photon absorption, and free-carrier absorption. Figures 2.5(b) and 2.5(d) represent, respectively, a self-defocusing limiter, self-focusing limiter, and an induced scattering limiter. Finally, figures 2.5(e) and 2.5(f) illustrate a photorefractive beam fanning limiter and a photorefractive excisor device. While it is often the case that any given material will exhibit multiple nonlinear properties, for simplicity the effects of each individual process have been separately depicted in figure 2.5. Figure 2.5: Some optical limiters based on different mechanisms (a) an induced absorption limiter (b) Self defocusing limiter (c) Self focusing limiter (d) Induced scattering limiter (e) Beam fanning limiter (f) Photorefractive excisor device [1e].

Grandma :: essays research papers

Grandma   Ã‚  Ã‚  Ã‚  Ã‚  As I drifted down the hallway, it seemed endless. With my stomach in my throat I walked. I could not feel my feet hitting the ground, nor notice anyone around me. I just walked. The smell of the place was intoxicating. It reminded me of insulin or disinfectant spray. I entered her room; it was dark. The sound of beeping machines echoed in my ears. I walked to her bed. She was sleeping soundly. Her body was frail and looked as if she was bone covered with skin. She was weak and tired.   Ã‚  Ã‚  Ã‚  Ã‚  The cancer had been eating away at her, slowly devouring her body, life and spirit. She had been sick for a couple of months now. I hated visiting, seeing her so sick it made my stomach churn. I stayed with her at the hospital for a short time visiting. I hated seeing her, my grandma, that way. She was sick from the cancer that came back and this time it was worse.   Ã‚  Ã‚  Ã‚  Ã‚  The cancer began in the fall months of 1992. My grandma had felt a hard, pea-sized lump on her breast. She preceded to see a specialist, Dr. Whall. What she heard wasn’t exactly what she had expected. She had breast cancer. I didn’t expect it either. I was scared for her, scared for me. She was my closest friend, and my confidant and I loved her very much. I spent a lot of time with her. What would I do if I lost her? Fortunately the cancer didn’t take her away. She lost her hair and her left breast, but she made full recovery.   Ã‚  Ã‚  Ã‚  Ã‚  My grandma was as good as new. She and I spent even more time together. I cherished every minute of it, trying not to take it for granted. We went to garage sales in the summer and cooked pies in the winter. Our favorite thing to do was to watch butterflies in her garden. She was the wisest woman I knew always giving me the best advice. Wether her advice was about boys, friends, or other aspects of life she was almost always right. Everything between us was perfect again.   Ã‚  Ã‚  Ã‚  Ã‚  My grandma had been in remission for nine years. She always went for a yearly check up with Dr. Whall. Every year the tests came back topnotch. She was in perfect health. But the good health was short lived, when she went for a check up in 2001.