Fatigue Cracking of Pavement

Fatigue Cracking of Pavement Introduction to fatigue cracking of pavement Fatigue or alligator cracking is the most common type of pavement distress, it is infact the major one. This is the type of distress in which series of interconnected cracks appears due to the fatigue failure of the HMA surface when the pavement experience repeated traffic loading. These type of cracks later allow moisture infiltration into the pavement, the road surface gradually gets more rough, the infiltrated moisture then again accelerate the existing cracking which in worst case may end up being a small to large sized pothole. In other words, as the traffic loads get repeated on the pavement, fatigue cracking starts to initiate at the bottom of the flexible layer, which accounts for the tensile strains at the bottom of the HMA layer (Huang 1993).   Researchers suggested that, for the M-E structural design process of pavement, this tensile strength must be kept in limit in order to check against fatigue cracking (Shook,1982). Figure 1: Schematic diagram of Fatigue Craking Mechanism in Pavement Cross Section (Priest et al., 2006) Apart from the repeated stresses incurred upon the pavement surface, fatigue cracking may take place due to aging, temperature changes or inadequate drainage. The effects of these factors are really complicated which my lead to undesirable changes to asphalt, associated with the poor durability properties of the HMA layer. (Finn 1967). Though due to previous research, it was believed that, most of the cracks initiates at the bottom and then make its way to the top of the asphalt layer, which is also termed as bottom up fatigue cracking, recent studies shows that, in most cases, cracks initiates at the pavement surface on the wheel path and then make its way down to the bottom (Myers and Roque, 2001). Federal Highway Administrations Distress Identification Manual for the Long-Term Pavement Performance Program mentioned about three levels of severity for fatigue cracking, which are high severity fatigue cracking, moderate severity fatigue cracking and low severity fatigue cracking. High severity fatigue cracking is the ultimate stage of fatigue cracking. When the pavement has been stressed to the limit of its fatigue life, it is no longer attractive and is barely functional. This stage is called high severity of fatigue cracking. In this case, the cracks are formed in large areas and there are several pieces of loose surface asphalt. Pavement in this condition needs repair immediately. Moderate severity fatigue cracking is the stage when distinguished the arrival of connecting cracks are well recognized. The cracks tends to increase gradually and lower layers of road materials become evident. Heavy traffic load usually break the surface asphalt layer in pieces. Low severity fatigue cracking usually indicates an area of asphalt having only small cracks with very few or none of them connecting to display the zig zag alligator type shape. Also the cracks are not evidently removing lower layers of the road materials. (Miller, 2003) Figure 2: Fatigue Cracking in Pavement (Priest et al., 2006) Over the years, the researchers are trying to come up with a simple and standard fatigue testing procedure as till this date, there is no such standard test for fatigue cracking, as different states are evaluating performance against fatigue cracking differently. Tangella et el (1990), came up with an equation to measure the fatigue life, which also accounts for the varying temperature and loading frequency. Nf= k1 (1/ÃŽÂ µt)^k2 (1/E)k3 Where, Nf= Number of load cycles until fatigue failure ÃŽÂ µt= Applied horizontal tensile strain E= HMA mixture stiffness K1,k2,k3= Regression constant In their study, they emphasized on the flexural fatigue test, diametral fatigue, and tests employing fracture mechanics principals, as the most promising test procedures to characterize fatigue cracking. Later till this period, there are different test procedures such as, Overlay (OL) test, Indirect Tension (IDT) test, Direct Tension (DT) test, Semicircular Bending (SCB) test, are most commonly used to categorize fatigue cracking in the lab. In addition, comparison with the observed result with the field cores is also important. Hajj et al. (2005) emphasized on the mechanistic analysis to understand the interaction between structure, stiffness, and laboratory testing so that a balance can be made for the given field and traffic conditions on a per-project basis. They concluded that, as the field pavement has stiffer structure which will generate lower strains under traffic therefore a longer fatigue life will be observed in the field. Therefore, an overall study is required to charac terize fatigue cracking of the pavement. References: Huang, Yang H. Pavement Analysis and Design New Jersey: Prentice Hall,1993 Shook, J.F., F.N. Finn, M.W. Witczak, and C.L. Monismith. Thickness Design of  Asphalt Pavements The Asphalt Institute Method, Proceedings, 5th International  Conference on the Structural Design of Asphalt Pavements, Vol.1, The Netherlands,  1982, pp. 17-44. Miller J.S., Bellinger W.Y. Distress Identification Manual for the Long-Term Pavement Performance Program (Fourth Revised Edition), Technical Research Report FHWA-RD-03-031. Federal Highway Administration 6300 Georgetown Pike McLean, VA 22101-2296, 2003. Priest A.L. Timm D.H. Methodology And Calibration Of Fatigue Transfer Functions For Mechanistic-Empirical Flexible Pavement Design, NCAT Report 06-03. National Center for Asphalt Technology, Auburn University, Alabama, 2006. Tangella, R., J. Craus, J. A. Deacon, and C. L. Monismith. Summary Report on Fatigue Response of Asphalt Mixtures. TM-UCB-A-003A-89-3, SHRP Project A-003-A. University of California, Berkeley: Institute of Transportation Studies, 1990 Hajj, E. Y., P. E. Sebaalay, and D. Weitzel. Fatigue Characteristics of Superpave and  Hveem Mixtures. Journal of Transportation Engineering, ASCE , 2005, pp. 302-10.

Regulatory Agency Essay

The role and responsibility of the U. S. Food and Drug Administration (FDA), most importantly, is to uphold the laws dictated by the government concerning products that include drugs, medical products, food, and non-health related products and to protect and promote public health across the country. This essay focuses on several aspects of the FDA, from the role of the agency and its effect on health care in the United States, to the authority this agency carries in relation to health care. There will also be an explanation of how the FDA carries out these responsibilities on a day-to-day basis. The FDA has held a strong presence in the realm of public health since 1848 when it began as a consumer protection agency (FDA, 2013). The FDA, formed after the 1906 Pure Food and Drug Act was put in place and inspired by the scientific work of Harvey Washington Wiley, who was the Chief Chemist at the U. S. Department of Agriculture. Wiley worked to eliminate the dangerous practices of marketing unregulated drugs and food products to consumers (FDA, 2013). Since that time, the FDA has become a powerful force, monitoring and working to protect public health in the United States. FDA Role The FDA is an agency that works within the Department of Health and Human Services. The Office of the Commissioner takes the lead role with four other branches that manage other functions (FDA, 2013). The Office of the Commissioner takes â€Å"leadership of the agency’s scientific activities, communication, legislative liaison, policy and planning, women’s and minority health initiatives, agency operations, and toxicological research† (FDA, 2013). The four groups that work under the Office of the Commissioner are the Office of Foods, the Office of Global Regulatory Operations and Policy, the Office of Medical Products and Tobacco, and the Office of Operations. The function of these five entities of the FDA is to protect and promote public health in the U. S. and to uphold the laws dictated by the government regarding public health. This is accomplished through close monitoring and testing of regulated products used by U. S. consumers. These products consist of drugs, food, cosmetics, radiation-emitting products, vaccines and other biologics, veterinary drugs and products, and tobacco products (FDA, 2013). The FDA is also constantly looking for ways to advance public health by assisting other organizations to make medications safe and more effective (FDA, 2013). Not only does the FDA monitor the food supply coming into the U. S. to ensure its safety but also plays a role in counterterrorism efforts by developing products and medications to respond to a public health threat (FDA, 2013). Issuing and enforcing warning labels for drugs and other products is another function in the role of the FDA. The labels serve to educate the public and medical professionals on the use and hazards of using a specific medication or product. However, these labels do not always have the desired effect. Impact on Health Care The efforts of the FDA throughout its history, has created a much safer consumer environment as it relates to food products, cosmetics, and other non-medical items. Foods are carefully scrutinized before they are allowed on the market to ensure these products are safe for the public to consume. Strict guidelines are in place for all types of products that are available to consumers. However, there is some controversy concerning warning labels on prescription drugs. There have been recent reports that communications by the FDA regarding drug risks are not immediately effective (Hitt, 2012). It is the duty of the FDA to monitor and enforce warnings for prescription drugs involving the safety risks to public health. According to Emma Hitt, some of the warnings that recommended increased monitoring of a patient while taking a prescription drug or increase laboratory monitoring generally caused a decrease in the use of the drug and very low increases in monitoring (Hitt, 2012). These types of oversights in clinical practice likely cause adverse effects to patients by not heeding the proper warnings set forth by the FDA. This is just a minute area in which the FDA impacts health care. Just as the FDA is responsible for monitoring drugs, products, and foods, their communications to health care providers and consumers must also be taken seriously. As Hitt states, â€Å"as the goals of risk communication are to minimize potential harms, understanding the impact of an FDA communication’s intended (and unintended) consequences on patient health outcomes should be a priority† (Hitt, 2012). Duties of the FDA The FDA carries an enormous responsibility daily to monitor, investigate, and enforce the safety of the public in general. As discussed earlier, this includes products and medications used by consumers daily. There are times when the regulations and guidelines set forth by the FDA on specific products are not followed and thus the FDA must follow up with inspections, enforce compliance, and conduct criminal investigations (FDA, 2013). The Office of Regulatory Affairs (ORA) is the lead office in this function of the FDA. It is the duty of the ORA to carry out investigations if a breach in regulation is suspected. Once a questionable observation is made by an investigator of the ORA, a form entitled â€Å"Form 483† is filled out by the investigator (FDA, 2013). On this form, the investigator cites what the law or regulation is and proceeds to list the questionable conditions and what law or regulation is violated. These 483 forms are maintained and revisited periodically. Some of the areas investigated are biologics, drugs, human tissue for transplantation, foods, and radiological health, to name a few. This is a major function of the FDA to ensure compliance to laws and regulations. Regulatory Authority The FDA has regulatory authority provided in the â€Å"Federal Food, Drug, and Cosmetic Act† (FD&C) passed by Congress in 1983. The creation of this legislation was driven by an incident where more than 100 patients died due to improperly prepared sulfanilamide medications. It replaced the earlier Pure Food and Drug Act of 1906 (FDA, 2013). The agency has authority to mandate preventative actions for food facilities to ensure food safety. They also have the power to conduct compliance inspections on facilities the scope of which include access to records and testing by accredited laboratories. The FDA also has several responses it can take to enforce compliance and ensure safety of consumers. It can enforce a mandatory recall of a product, and it can suspend the registration of a facility if it is determined to pose a threat of serious health consequences or the threat of death to humans or animals (FDA, 2013). Accreditation, Certification, and Authorization The FDA’s Center for Drug Evaluation and Research is the division of the agency charged with the evaluation and approval of any drug prior to its release on the market. There are three phases in this certification and approval process. The research phase is conducted during the manufacture of a drug, along with the testing, then sent to a review board for recommendation (Writing, 2013). Once the recommendation is given, the drug can move to the second phase, the pre-clinical trials. Here the drug is tested on small groups of humans while measuring interactions and its effectiveness. Once this phase is complete with no adverse issues, the third phase can take place. This is a Phase 2 clinical trial that allows researchers to see if the drug works on a specific illness on patients and allows scientists to determine any side effects that may occur (Writing, 2013). The clinical phases are monitored closely, while working directly with patients to ensure that the testing remain within the standards of medical ethics. Once all of the trials are complete and all recommendations have been given, all of the results are analyzed and only then can be submitted to the FDA for approval to be sold on the market (Writing, 2013). The accreditation and approval process for all products that must be in compliance with FDA guidelines is a rigorous process but necessary for the common good. Conclusion The FDA carries so many responsibilities to provide high quality medications, foods, cosmetics, and many other products. The laws and regulations are complex and detailed. So much, in fact, most people are not aware when a regulation or guideline is being violated. The resources available to research the FDA and their functions and laws are many and well worth the time to gain education on how this enormous entity works to protect and promote public health and safety.

Clinical Reflective Journal

Clinical Reflective Journal The first day I visited psychiatric ward, I felt nervous and excited because of the psychiatric ward which is totally different from general ward. I sensed that all patients who are walking in the corridor and some of them keep murmuring, and those behaviors I seen are seldom appearing in the general ward. However, after I found that they can communicate with others normally and have no aggressive behavior after approaching the patients.I learnt we should establish therapeutic relationship in the communication with patients via using non-judgmental, empathetic, active listening and supportive attitude. But I found difficulties in approaching patients who are introverted due to their unconcerned response. However, I think that we should obtain their confidence through persistent contact with them.Besides, I realized that being a psychiatric nurse, the observational skills is very importance, as the emotional or mental condition of psychiatric patient can be fluctuated between day and night. Therefore, nurses can implement corresponding precautions beforehand. In the private hospital, there are seldom opportunities to perform those skills, but there provide many chances for me to practice the professional skills and of injection and physical restraint.For instance, choosing which type of restrained device should be applied on the patient and related assessment we should made. Moreover, through the guidance of the nurse, I could realize the rationales behind the intervention, weakness in my performance and how to improve it. After caring of psychiatric patient in these two weeks, it helps clear up my misunderstanding of them and I hope that the nursing care of psychiatric patient can be helpful for them to return the society.

Barnes Surname Meaning and Origin

The common Barnes  surname is often of topographical origin, deriving from the  Middle English barn, for  barn or granary, and  meaning of the barn (barley house). The use of the name was generally associated with a significant barn in the local region.  Barnes may also be an occupational surname for someone who worked in a barn. An alternative origin for the Barnes last name may be suggested by the parish of Barnes in Aberdeenshire, Scotland which derives its name from the Gaelic word bearn, meaning gap. Barnes was the 101st most common last name in the United States at the time of the 2000 U.S. census. Surname Origin: English, Scottish Alternate Surname Spellings:  BARNS, BERNES Famous People with the Surname BARNES: Jim Barnes - English golfer and first winner of the PGA championshipBrenda Barnes -  Former president of  PepsiCo North America Genealogy Resources for the Surname BARNES: 100 Most Common U.S. Surnames Their MeaningsSmith, Johnson, Williams, Jones, Brown... Are you one of the millions of Americans sporting one of these top 100 common last names from the 2000 census? The Barnes Family YearbookAn annual publication issued under the authority of the Barnes Family Association. Several volumes are available for free viewing from this digital archive of genealogical information. Barnes DNA Surname ProjectLarry Bowling heads up this DNA project through FamilyTreeDNA with a goal of sorting out various lines of Barnes ancestors from around the world. Barnes Family Genealogy ForumSearch this popular genealogy forum for the Barnes surname to find others who might be researching your ancestors, or ask your own question about your Barnes ancestors. FamilySearch - BARNES GenealogyFind records, queries, and lineage-linked family trees posted for the Barnes surname and its variations. BARNES Surname Family Mailing ListsRootsWeb hosts several free mailing lists for researchers of the Barnes surname. DistantCousin.com - BARNES Genealogy Family HistoryFree databases and genealogy links for the last name Barnes. -- Looking for the meaning of a given name? Check out First Name Meanings -- Cant find your last name listed? Suggest a surname to be added to the Glossary of Surname Meanings Origins. ----------------------- References: Surname Meanings Origins Cottle, Basil. Penguin Dictionary of Surnames. Baltimore, MD: Penguin Books, 1967. Menk, Lars. A Dictionary of German Jewish Surnames. Avotaynu, 2005. Beider, Alexander. A Dictionary of Jewish Surnames from Galicia. Avotaynu, 2004. Hanks, Patrick and Flavia Hodges. A Dictionary of Surnames. Oxford University Press, 1989. Hanks, Patrick. Dictionary of American Family Names. Oxford University Press, 2003. Smith, Elsdon C. American Surnames. Genealogical Publishing Company, 1997. Back to Glossary of Surname Meanings Origins