Egyptian Cultural Term Paper Example | Topics and Well Written Essays - 750 words

Egyptian Cultural - Term Paper Example Ancient Egyptians relied on cosmology to prophesize what the future holds. They exhibit a â€Å"set of values and a cluster of ideas that made them Egyptian rather than Ethiopian or Greek.† 1 In this modern era, an Egyptian is identified no longer by a particular genotype or language; â€Å"rather is comprised of many different people who participate in one general Arab culture.† 2 As it happens, being an Egyptian is like being American; the term is associated to citizenship. Egyptians were legendary for revering their pharaohs not merely as rulers, but gods. Today, Islam is the most prevalent religion in the country, with Christianity and Judaism that both adhered to the teachings of Jesus Christ, as the minor group. Islam was introduced by the Arabs during the 600 A.D. It points to Allah as the one God, and indoctrinates the philosophies of the prophet Mohammad. Muslims, as the followers refer to themselves, read from their holy book Qur’an and pray to Allah fi ve times daily (Moscovitch 2008). â€Å"Long years of coercion and exploitation by foreign ruling powers and native autocratic states have left its mark on the Egyptian personality.†3 Based on their current political situation, the fact evidently shaped the character of the Egyptians and their attitudes towards the government. It is an Islamic ideology to concentrate power in one person, the Caliph, and hail him the "ruler of the world", and this remains the main characteristic of all the Muslim rulers in Egypt (Fahmy 2002). Muhammad Ali who led Egypt from 1805 to 1848, Gamal Abd al-Nasser from 1952 to 1970, Mu?ammad Anwar el-Sadat from 1970 to 1981, and Muhammad Hosni Sayyid Mubarak from 1981 to 2011 all epitomized a government of absolute despotism; the â€Å"executive, civilian, military, and judicial functions†4 are vested solely upon the head of the state. In despotic states the nature of government requires the most passive obedience and when once the prince's wi ll is made known, it ought infallibly to produce its effect. Here they have no limitations or restrictions, no mediums, terms, equivalents or remonstrance, no change to propose, man is a creature that blindly submits to the absolute will of the sovereign.5 II. POLITICAL REVOLUTION IN EGYPT: CAUSE AND IMPACT Countless protests are heard throughout Egypt; nevertheless, it is believed that the tensions rooted from these three issues: 1) Muslim terrorism that lead to some 200 deaths in the following 18 months during the 1990s, 2) the ratification of the Martial Law that imprisoned around 2000 militants mostly associated with the Muslim Brotherhood—a mainstream movement in Egypt with followers at all levels of society, and 3) the allegation of the Coptic Christians concerning mistreatments by the government and its failure to put the sought-after democracy into practice (History World 2010). In his 30 years of presidency, Mubarak retained the emergency laws initiated by his predec essor. These laws gave him a greater presidential power â€Å"including the right to appoint the Cabinet, without any provision for parliamentary majority, and the role of supreme commander of the armed forces, and chief policy-maker in matters of security, diplomacy, and the economy.†6 The president was ousted in a national uprising on February 11, 2011, making way for constitutional

Writing Process Check Point Essay Example for Free

Writing Process Check Point Essay The writing process I read about in this class differs from the processes that I have used in the past, in that I have never used on purpose in-text citations. I do not like the look of papers that have citations in text they break my concentration when I am reading. I am trying to use them more in papers because the instructors want them, and they do make the paper look better. I always use mind-mapping, listing, and free writing. The listing and mind-mapping steps are the easiest for me to complete, and they get my mind completely focused on the task at hand. I list by making a very informal ugly outline, and that is my first step. A teacher would not credit my outlines, but they help me get my thoughts in order so that my paper flows better. Mind-mapping I do by hand with pencil and paper, I put my main idea in the middle of the page, and then draw anything related to the topic on the page in little bubbles. The step that is the most difficult for me is designing a thesis statement that grabs the attention of the audience, includes everything my paper is about. The thesis statement is something that I have never tried to do, so it is a little scary. I will be able to overcome this obstacle over thesis statements in this class when we learn about them. I know after that week I will be able to make a proper thesis statement for my final project. Reference Page: Steps in the Writing Process, Axia College Material

Fracture Resistance of Esthetic Post and Core Systems

Fracture Resistance of Esthetic Post and Core Systems Comparison of fracture resistance of three recent esthetic post and core systems with cast metal post and core to compressive loading An in vitro Study ABSTRACT: Aim: To determine and compare the fracture resistance of three recently introduced esthetic post and core systems with a cast metal post and core to compressive loading using a clinically related test method. Materials and Methods: Forty maxillary central incisors were selected, sectioned and their roots endodontically treated and assigned to 4 experimental groups (n=10).The cast metal post and core (CMPC) served as control group.The other groups are zirconium dioxide post and ceramic core group (ZCER), zirconium dioxide posts and composite core group (ZCOM) and glass fiber post and composite core group (GFCOM).The post spaces were prepared, posts were seated and cores were formed. A compressive load was applied to the inclined surface on each specimen until failure occurred and measured in newtons. Results: CMPC and ZCER groups exhibited the highest resistance fracture and the values are : 680.6 N and 630.03 N respectively . ZCOM group exhibited fracture resistance greater than GFCOM but less than ZCER and CMPC. Conclusion: CMPC group and ZCER group were found to be more fracture resistant than the ZCOM group and GFCOM group. Aside from its desirable esthetic properties,the ZCER group demonstrated high resistance to fracture. Keywords: compressive loading, endodontic treatment, fracture resistance, post and core INTRODUCTION Endodontic therapy has provided dentistry the ability to retain teeth that just a few decades ago would have been extracted without hesitation.When there is substantial loss of coronal tooth structure due to caries, trauma or both, a post and core is often required to retain a definitive restoration. A post is usually placed in an attempt to strengthen the tooth.1,2,3 However, in vitro and in vivo studies have demonstrated that a post cannot reinforce endodontically treated teeth.4,5,6 Posts are required for supporting a core foundation when there is insufficient clinical crown remaining.4,5,6,7 Although cast post and core foundations are the gold standard for endodontically treated teeth, due to their superior physical properties and proven clinical effectiveness8 yet its mechanical properties may increase the risk of root fracture9. The esthetic properties of these materials are limited since the gray colored post is apparent when used to support translucent all ceramic restorations. Coupled with a high lip line, cast metal post and core foundation may create esthetic problems. In the recent times, there has been a tremendous increase in the use of all ceramic crowns, particularly for anterior teeth because of their superior natural appearance compared to metal ceramic restorations.10 Both the declining acceptance of cast post and core restorations as well as patients interest in dental esthetics has resulted in the development of esthetic posts, especially Glass Fiber and Zirconia Ceramics.These increase the transmission of light within the root and overlying gingival tissues, enhancing the esthetics. They also eliminate the potential hazards of corrosion and allergic hypersensitivity as they are metal free materials.11 Glass fibers such as silica or quartz reinforced epoxy resin posts have low modulus of elasticity similar to that of dentin.12 This property has been reported to reduce the risk of root fracture. 13,14 Glass fiber reinforced posts also have the advantage of easy removal if endodontic re-treatment is required. 15,16 A prefabricated zirconia ceramic post system has been introduced to satisfy esthetic needs presented by endodontically treated anterior teeth. The translucency of all ceramic crowns can be successfully maintained with the use of ceramic post and core materials. Moreover improvements in adhesive porcelain bonding systems have accelerated the trend toward the use of ceramic core materials. Many dentists prefer to use prefabricated post systems because they are more practical, less expensive and in some situations less invasive than customized post and core systems. They also save time and can provide satisfactory results. 17,18,19 The purpose of this in vitro study is to determine and compare fracture resistance of three esthetic post and core systems, Zirconia post and Ceramic core, Zirconia post and Composite core and Glass Fiber post and Composite core with cast posts under compressive loading. METHODOLOGY Forty extracted human permanent central incisors were selected based on similar dimensions,caries free,no restorations and cracks.The teeth were soaked in 3% sodium hypochlorite (Vishal Dentocare PVT LTD), for 6 hours. These forty teeth were divided into 4 groups: Group 1: Cast Metal post and core (CMPC) Group 2: Zirconia posts and Ceramic core (ZCER) Group 3: Zirconia posts and Composite core (ZCOM) Group 4: Glass Fiber posts and Composite core (GFCOM) The coronal aspect of each tooth was resected perpendicular to the long axis and 1mm incisal to the cementoenamel junction, with a diamond coated disc (Horico) mounted in a straight handpiece (NSK, Japan). Labiolingual and mesiodistal measurements of the sectioned tooth surfaces were made with a digital vernier calipers (Aero space, China).The roots were endodontically instrumented to the apex using protaper rotary instruments (Dentsply,Maillefer) till F3 and obturated with protaper GP points (Dentsply,Maillefer) using ZOE sealer. Procedure for fabricating standardized cores: To obtain standardized cores, a wax pattern was fabricated from casting wax (Sk Dental waxes, Bombay) which had 6.5mm diameter base, 7.3 mm diameter cervico incisally and 6.2mm buccolingually. Impression of the wax pattern was taken with rubber base impression material (Exaflex). Then dies were made from the impression material. Polyvinyl material was vacuum pressed on these dies.In this way a hollow matrix was fabricated which had the same dimensions as that of the wax pattern. The base of the matrix was fitted flush to the sectioned tooth surfaces. Then 1 mm of the matrix was cut at the open end so that it acted as an inlet for the placement of composite resin. Procedure for preparation of forty samples: For all the groups the post spaces were enlarged with peeso reamers no 2 and 3 (MANI CE 0197 Prime Dental Products PVT LTD) initially to a depth of 9mm. The final enlargements were accomplished with the 1.4 mm diameter drills that were specifically given with 1.4mm zirconia posts (Cosmoposts,Ivoclar Vivadent) and 1.4mm GF posts (Bioloren,Ammdent). All the posts have 1.4mm diameter and were sectioned to a standard length of 13mm using carbide fissure bur and high speed airotor handpiece The length of the posts was 4 mm from the finish line into the core.In groups 2, 3 and 4 all the post spaces were etched using 37% orthorphosphoric acid (3M ESPE), for 30 sec and bonding was done using a bonding agent (3M ESPE) polymerized for 20 sec. Cementation was done using dual curing resin luting agent ( Kerr,Orange,CA). Group 1: A direct technique was used. The post pattern was fabricated using inlay wax. For the core part ,the polyvinyl matrix was placed on the tooth, resin wax (Leva) was injected in to the matrix and polymerized. After polymerization, the matrix was removed from the molded core. Then the entire pattern was retrieved from the root, invested and cast. The cast post and core systems were then cemented into the roots using GIC. Group 2: Posts were seated into the prepared post space.Polyvinyl matrix was placed on the tooth surface, resin wax was then injected in to the matrix and polymerized for 20 sec to form the core. Matrix was then removed and retrieved post and core foundations from the roots were invested with a phosphate bonded investment (Deguvest). Wax was eliminated from the invested units in a pre heated furnace (Unident) (800ËÅ ¡C for 45 minutes). Cores around zirconia posts were prepared using ceramic ingots (e-max, Ivoclar vivadent) heat-pressing process (975ËÅ ¡C for 45 min.) in a heat pressing furnace (Ivoclar vivadent). The formed ZCER foundations were then cemented into the post spaces. Group 3: After etching and bonding,posts were cemented in to the prepared post spaces. The matrix was seated on the sectioned tooth surface and composite core material (Z350, 3M ESPE) was placed in 2mm increments and polymerized for 20 sec. After polymerization, the matrix was removed from the molded cores. Group 4: Following etching and bonding posts were cemented into the prepared post spaces. The matrix was placed on the sectioned tooth surface and composite was placed in 2mm increments and was then polymerized for 20 sec. After polymerization, the matrix was removed from the molded cores. LOADING PROCEDURE: Following thermal cycling (5000 cycles between 5ËÅ ¡C and 55ËÅ ¡ C with a dwell time of 30 second) a universal testing machine (Shimadzu, Japan) was used to apply a constant compressive load at a crosshead speed of 1mm/min, at a 130Â º angle to the long axes of the test specimens, until failure ocurred. The tip of the loading bar was positioned to contact the centre of the palatoincisal surface at an angle of 90Â ºC. The force at failure was measured in newtons. RESULTS One-way Analysis of Variance (ANOVA) with Post HocTukey test was used to compare the score between the groups. A 95% confidence level was used for the ANOVA test. Results showed that there was significant difference in the fracture resistance values obtained with different groups (p

Lacanian Psychoanalytic Criticism in Harry Potter Essay -- Lacan Child

Lacanian Psychoanalytic Criticism in Harry Potter The inhabitants of a faraway country known for its ivory towers and for its export of literary monographs were forever quarreling over who might best represent them. One day two tiny factions decided to join forces: the adherents of the Princess Childlit and the followers of Prince Psychian, the great-great-grandson of Empress Psyche. Both groups had for a long time felt themselves unduly spurned†¦ by the powerful Board of Canonizers who had ruled Arkedemia for over a century. Might not a wedding between the two claimants strengthen their status?... just as the engagement was about to be announced, the whole affair was abruptly called off. What had happened?†¦Their cohorts had begun to quarrel most bitterly with each other†¦ The wedding did not take place†¦Soon the board of Canonizers issued an edict pronouncing both groups to be out of the system. Hereafter, their passports would be stamped with the word â€Å"marginal† in red gothic print. (Knoepfl macher, 131-132) [1] U.C. Knoepflmacher’s wonderful parody of the current situation of children’s literary criticism and the psychoanalytic approach to literature perfectly sums up what will be the major obstacle of this critical paper. It would seem that modern literary criticism has an unfortunate tendency to overlook children’s literature extensively; to relegate it to a position of only secondary importance in the critic’s glossary of â€Å"good literature.† On top of that, psychoanalytic criticism, as it is applied to children’s literature, seems to have taken on a startlingly simplistic, static approach to the analysis of the text, that does very little justice to the diversity and complexity that the field possesses. (132-133) ... ...nnual of the Modern Language Association Division on Children’s Literature and the Children’s Literature Association.18 (1990): 131-134. Lesnik-Oberstein, Karin. Children’s Literature: Criticism and the Fictional Child. Oxford: Oxford University Press, 1994. McGillis, Roderick. â€Å"Another Kick at La/can: ‘I Am a Picture.’† Children’s Literature Association Quarterly.20.1 (1995): 42-46. Murfin, Ross, Ed. â€Å"What is Psychoanalytic Criticism?† The Rime of the Ancient Mariner, Samuel Taylor Coleridge. Boston: Bedford/ St. Martin’s, 1999. Rowling, J.K. Harry Potter and the Sorcerer’s Stone. New York: Scholastic, Inc., 1998. Trites, Roberta Seelinger. â€Å"Psychoanalytic Approaches to Children’s Literature: Landmarks, Signposts, Maps.† Children’s Literature Association Quarterly. 25.2 (2000): 66-67.

A Preprocessing Framework for Underwater Image Denoising Essay

Abstract A major obstacle to underwater operations using cameras comes from the light absorption and scattering by the marine environment, which limits the visibility distance up to a few meters in coastal waters. The preprocessing methods concentrate on contrast equalization to deal with nonuniform lighting caused by the back scattering. Some adaptive smoothing methods like anisotropic filtering as a lengthy computation time and the fact that diffusion constants must be manually tuned, wavelet filtering is faster and automatic. An adaptive smoothing method helps to address the remaining sources of noise and can significantly improve edge detection. In the proposed approach, wavelet filtering method is used in which the diffusion constant is tuned automatically. Keywords: underwater image, preprocessing, edge detection, wavelet filtering, denoising. I. INTRODUCTION The underwater images usually suffers from non-uniform lighting, low contrast, blur and diminished colors. A few problems pertaining to underwater images are light absorption and the inherent structure of the sea, and also the effects of colour in underwater images. Reflection of the light varies greatly depending on the structure of the sea. Another main concern is related to the water that bends the light either to make crinkle patterns or to diffuse it. Most importantly, the quality of the water controls and influences the filtering properties of the water such as sprinkle of the dust in water. The reflected amount of light  is partly polarised horizontally and partly enters the water vertically. Light attenuation limits the visibility distance at about twenty meters in clear water and five meters or less in turbid water. Forward scattering generally leads to blur of the image features, backscattering generally limits the contrast of the images. The amount of light is reduced wh en we go deeper, colors drop off depending on their wavelengths. The blue color travels across the longest in the water due to its shortest  wavelength. Current preprocessing methods typically only concentrate on local contrast equalization in order to deal with the nonuniform lighting caused by the back scattering. II. UNDERWATER DEGRADATION A major difficulty to process underwater images comes from light attenuation. Light attenuation limits the visibility distance, at about twenty meters in clear water and five meters or less in turbid water. The light attenuation process is caused by the absorption (which removes light energy) and scattering (which changes the direction of light path). Absorption and scattering effects are due to the water itself and to other components such as dissolved organic matter or small observable floating particles. Dealing with this difficulty, underwater imaging faces to many problems: first the rapid attenuation of light requires attaching a light source to the vehicle providing the necessary lighting. Unfortunately, artificial lights tend to illuminate the scene in a non uniform fashion producing a bright spot in the center of the image and poorly illuminated area surrounding. Then the distance between the camera and the scene usually induced prominent blue or green color (the wavelength corresponding to the red color disappears in only few meters). Then, the floating particles highly variable in kind and concentration, increase absorption and scattering effects: they blur image features (forward scattering), modify colors and produce bright artifacts known as â€Å"marine snow†. At last the non stability of the  underwater vehicle affects once again image  contrast. To test the accuracy of the preprocessing algorithms, three steps are followed. 1) First an original image is converted into grayscale image. 2)  Second salt and pepper noise added to the grayscale image. 3) Third wavelet filtering is applied to denoise the image. Grayscale images are distinct from one-bit bi-tonal black-and-white images, which in the context of computer imaging are images with only the two colors, black, and white. Grayscale images have many shades of gray in between. Grayscale images are also called monochromatic, denoting the presence of only one (mono) color (chrome). Grayscale images are often the result of measuring the intensity of light at each pixel in a single band of the electromagnetic spectrum and in such cases they are monochromatic proper when only a given frequency is captured. Salt and pepper noise is a form of noise typically seen on images. It represents itself as randomly occurring white and black  pixels. An image containing salt-and-pepper noise will have dark pixels in bright regions and bright pixels in dark regions. This type of noise can be caused by analog-to-digital converter errors, bit errors in transmission. Wavelet filtering gives very good results compared to other denoising methods because, unlike other methods, it does not assume that the coefficients are independent. III. A PREPROCESSING ALGORITHM The algorithm proposed corrects each underwater perturbations sequentially.  addressed in the algorithm. However, contrast equalization also corrects the effect of the exponential light attenuation with distance. B. Bilateral Filtering Bilateral filtering smooth the images while preserving edges by means of a nonlinear combination of nearby image values. The idea underlying bilateral filtering is to do in the range of an image what traditional filters do in its domain. Two pixels can close to one another, occupy nearby spatial location (i.e) have nearby values. Closeness refers to vicinity in the domain, similarity to vicinity in the range. Traditional filtering is a domain filtering, and enforces closeness by weighing pixel values with coefficients that fall off with distance. The range filtering, this averages image values with weights that decay with dissimilarity. Range filters are nonlinear because their weights depend on image intensity or color. Computationally, they are no more complex than standard nonseparable  filters. So the combination of both domain and range filtering is known as bilateral filtering. A. Contrast equalization Contrast stretching often called normalization is a simple image enhancement technique that attempts to improve the contrast in an image by ‘stretching’ the range of intensity values. Many well-known techniques are known to help correcting the lighting disparities in underwater images. As the contrast is non uniform, a global color histogram equalization of the image will not suffice and local methods must be considered. Among all the methods they reviewed, Garcia, Nicosevici and Cufi [2] constated the empirical best results of the illuminationreflectance model on underwater images. The low-pass version of the image is typically computed with a Gaussian filter having a large standard deviation. This method is theoretically relevant backscattering, which is responsible for most of the contrast disparities, is indeed a slowly varying spatial function. Backscattering is the predominant noise, hence it is sensible for it to be the first noise Anisotropic filtering Anisotropic filter is used to smoothing the image. Anisotropic filtering allows us to simplify image features to improve image segmentation. This filter smooths the image in homogeneous area but preserves edges and enhance them. It is used to smooth textures and reduce artifacts by deleting small edges amplified by homomorphic filtering. This filter removes or attenuates unwanted artifacts and  remaining noise. The anisotropic diffusion algorithm is used to reduce noise and prepare the segmentation step. It allows to smooth image in homogeneous areas but it preserves and even enhances the edges in the image. Here the algorithm follow which is proposed by Perona and Malik [5]. This algorithm is automatic so it uses constant parameters selected manually. The previous step of wavelet filtering is very important to obtain good results with anisotropic filtering. It is the association of wavelet filtering and anisotropic filtering which gives such results. Anisotropic algorithm is  usually used as long as result is not satisfactory. In our case few times only loop set to constant value, to preserve a short computation time. For this denoising filter choose a nearly symmetric orthogonal wavelet bases with a bivariate shrinkage exploiting interscale dependency. Wavelet filtering gives very good results compared to other denoising methods because, unlike other methods, it does not assume that the coefficients are independent. Indeed wavelet coefficients in natural image have significant dependencies. Moreover the computation time is very short. IV. EXPERIMENTAL SETUP AND EVALUATION To estimate the quality of reconstructed image, Mean Squared Error and Peak Signal to Noise Ratio are calculated for the original and the reconstructed images. Performance of different filters are tested by calculating the PSNR and MSE values. The size of the images taken is 256Ãâ€"256 pixels. The Mean Square Error (MSE) and the Peak Signal to Noise Ratio (PSNR) are the two error metrics used to compare image compression quality. The MSE represents the cumulative squared error between the compressed and the original image, whereas PSNR represents a measure of the peak error. The lower the value of MSE, the lower the error. In Table 1, the original and reconstructed images are shown. In table 2, PSNR and MSE values are calculated for all underwater images. PSNR value obtained for denoised images is higher, when compare with salt and pepper noise added images. MSE value obtained for the denoised images has lower the error when compared with salt and pepper noise added images. e D. Wavelet filtering Thresholding is a simple non-linear technique, which operates on one wavelet coefficient at a time. In its most basic form, each coefficient is thresholded by comparing against threshold, if the coefficient is smaller than threshold, set to zero; otherwise it is kept or modified. Replacing the small noisy coefficients by zero and inverse wavelet transform on the result may lead to reconstruction with the essential signal characteristics and with the less noise. A simple denoising algorithm that uses the wavelet transform consist of the following three steps, (1) calculate the wavelet  transform of the noisy image (2) Modify the noisy detail wavelet coefficients according to some rule (3) compute the inverse transform using the modified coefficients. Multiresolution decompositions have shown significant advantages in image denoising. best denoised image. In clearly, the comparisons of PSNR and MSE values are shown in Fig -1a and Fig -1b. V. CONCLUSION In this paper a novel underwater preprocessing algorithm is present. This algorithm is automatic, requires no  parameter adjustment and no a priori knowledge of the acquisition conditions. This is because functions evaluate their parameters or use pre-adjusted defaults values. This algorithm is fast. Many adjustments can still be done to improve the whole pre-processing algorithms. Inverse filtering gives good results but generally requires a priori knowledge on the environment. Filtering used in this paper needs no parameters adjustment so it can be used systematically on underwater images before every pre-processing algorithms. REFERENCES [1] Arnold-Bos, J. P. Malkasse and Gilles Kervern,(2005) â€Å"Towards a model-free denoising of underwater optical image,† IEEE OCEANS 05 EUROPE,Vol.1, pp.234256. [2] Caefer, Charlene E.; Silverman, Jerry. &Mooney,JonathanM,(2000) â€Å"Optimisation of point target tracking filters†. IEEE Trans. Aerosp. Electron. Syst., pages 15-25. [3] R. Garcia, T. Nicosevici, and X. Cufi. (2002) â€Å"On the way to solve lighting problems in underwater imaging†. In Proceedings of the IEEE Oceans 2002, pages 1018–1024. [4] James C. Church, Yixin Chen, and Stephen V., (2008) â€Å"A Spatial Median Filter for Noise Removal in Digital Images†, page(s):618 – 623. [45 Jenny Rajan and M.R Kaimal., (2006) â€Å"Image Denoising Using Wavelet Embedded anisotropic Diffusion†, Appeared in the Proceedings of IEEE International Conference on Visual Information Engineering, page(s): 589 – 593. [6] Z. Liu, Y. Yu, K. Zhang, and H. Huang.,(2001) â€Å"Underwater image transmission and blurred image restoration†. SPIE Journal of Optical Engineering, 40(6):1125–1131. [7] P. Perona and J.Malik, (1990) â€Å"Scale space and edge detection using anisotropic diffusion,† IEEE Trans on Pattern Analysis and Machine Intelligence, pp.629-639. [8] Schechner, Y and Karpel, N., (2004) â€Å"Clear Underwater Vision†. Proceedings of the IEEE CVPR, Vol. 1, pp. 536-543. [9] Stephane Bazeille, Isabelle, Luc jaulin and Jean-Phillipe Malkasse, (2006) â€Å"Automatic Underwater image PreProcessing†, cmm’06 – characterisation du milieu marine page(s): 16-19. [10] Yongjian Yu and Scott T. Acton, (2002) â€Å"Speckle Reducing Anisotropic Diffusion†, IEEE Transactions on Image Processing, page(s): 1260-1270, No. 11, Vol.11.

Angkor Wat, Cambodia

Angkor Wat, Cambodia The temple complex at Angkor Wat, just outside of Siem Reap, Cambodia, is world famous for its intricate lotus blossom towers, its enigmatic smiling Buddha images and lovely dancing girls (apsaras), and its geometrically perfect moats and reservoirs. An architectural jewel, Angkor Wat itself is the largest religious structure in the world. It is the crowning achievement of the classical Khmer Empire, which once ruled most of Southeast Asia. The Khmer culture and the empire alike were built around a single critical resource: water. Lotus Temple on a Pond: The connection with water is immediately apparent at Angkor today. Angkor Wat (meaning Capital Temple) and the larger Angkor Thom (Capital City) are both surrounded by perfectly square moats. Two five-mile-long rectangular reservoirs glitter nearby, the West Baray and the East Baray. Within the immediate neighborhood, there are also three other major barays and numerous small ones. Some twenty miles to the south of Siem Reap, a seemingly inexhaustible supply of freshwater stretches across 16,000 square kilometers of Cambodia. This is the Tonle Sap, Southeast Asias largest freshwater lake. It may seem odd that a civilization built on the edge of Southeast Asias great lake should need to rely on a complicated irrigation system, but the lake is extremely seasonal. During the monsoon season, the vast amount of water pouring through the watershed causes the Mekong River to actually back up behind its delta, and begin to flow backward. The water flows out over the 16,000 square kilometer lake-bed, remaining for about 4 months. However, once the dry season returns, the lake shrinks down to 2,700 square kilometers, leaving the Angkor Wat area high and dry. The other problem with Tonle Sap, from an Angkorian point of view, is that it is at a lower elevation than the ancient city. Kings and engineers knew better than to site their wonderful buildings too close to the erratic lake/river, but they did not have the technology to make water run uphill. Engineering Marvel: In order to provide a year-round supply of water for irrigating rice crops, the engineers of the Khmer Empire connected a region the size of modern-day New York City with an elaborate system of reservoirs, canals, and dams. Rather than using the water of Tonle Sap, the reservoirs collect monsoon rainwater and store it for the dry months. NASA photographs reveal the traces of these ancient waterworks, hidden at ground level by the thick tropical rainforest. A steady water supply allowed for three or even four plantings of the notoriously thirsty rice crop per year and also left enough water for ritual use. According to Hindu mythology, which the Khmer people absorbed from Indian traders, the gods live on the five-peaked Mount Meru, surrounded by an ocean. To replicate this geography, the Khmer king Suryavarman II designed a five-towered temple surrounded by an enormous moat. Construction on his lovely design began in 1140; the temple later came to be known as Angkor Wat. In keeping with the aquatic nature of the site, each of Angkor Wats five towers is shaped like an unopened lotus blossom. The temple at Tah Prohm alone was served by more than 12,000 courtiers, priests, dancing girls and engineers at its height - to say nothing of the empires great armies, or the legions of farmers who fed all the others. Throughout its history, the Khmer Empire was constantly at battle with the Chams (from southern Vietnam) as well as different Thai peoples. Greater Angkor probably encompassed between 600,000 and 1 million inhabitants - at a time when London had perhaps 30,000 people. All of these soldiers, bureaucrats, and citizens relied upon rice and fish - thus, they relied upon the waterworks. Collapse: The very system that allowed the Khmer to support such a large population may have been their undoing, however. Recent archaeological work shows that as early as the 13th century, the water system was coming under severe strain. A flood evidently destroyed part of the earthworks at West Baray in the mid-1200s; rather than repairing the breach, the Angkorian engineers apparently removed the stone rubble and used it in other projects, idling that section of the irrigation system. A century later, during the early phase of what is known as the Little Ice Age in Europe, Asias monsoons became very unpredictable. According to the rings of long-lived po mu cypress trees, Angkor suffered from two decades-long drought cycles, from 1362 to 1392, and 1415 to 1440. Angkor had already lost control of much of its empire by this time. The extreme drought crippled what remained of the once-glorious Khmer Empire, leaving it vulnerable to repeated attacks and sackings by the Thais. By 1431, the Khmer people had abandoned the urban center at Angkor. Power shifted south, to the area around the present-day capital at Phnom Pehn. Some scholars suggest that the capital was moved to better take advantage of coastal trading opportunities. Perhaps the upkeep on Angkors waterworks was simply too burdensome. In any case, monks continued to worship at the temple of Angkor Wat itself, but the rest of the 100 temples and other buildings of the Angkor complex were abandoned. Gradually, the sites were reclaimed by the forest. Although the Khmer people knew that these marvelous ruins stood there, amidst the jungle trees, the outside world did not know about the temples of Angkor until French explorers began to write about the place in the mid-nineteenth century. Over the past 150 years, scholars and scientists from Cambodia and around the world have worked to restore the Khmer buildings and unravel the mysteries of the Khmer Empire. Their work has revealed that Angkor Wat truly is like a lotus blossom - floating atop a watery realm. Photo Collections from Angkor: Various visitors have recorded Angkor Wat and surrounding sites over the past century. Here are some historic photos of the region. Margaret Hays photos from 1955. National Geographic/Robert Clarks photos from 2009. Â   Sources Angkor and the Khmer Empire, John Audric. (London: Robert Hale, 1972). Angkor and the Khmer Civilization, Michael D. Coe. (New York: Thames and Hudson, 2003). The Civilization of Angkor, Charles Higham. (Berkeley: University of California Press, 2004). Angkor: Why an Ancient Civilization Collapsed, Richard Stone. National Geographic, July 2009, pp. 26-55.