Comparative Analysis of Internal and External-Hex Crown Connection Systems – A Finite Element Study

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The abutment connection with the crown is fundamental to the structural stability of the implant system and to the prevention of mechanical exertion that can compromise the success of the implant treatment. The aim of this study is to clarify the difference in the stress distribution patterns between implants with internal and external-hex connections with the crown using the Finite Element Method (FEM). Material and Methods: The internal and external-hex connections of the Neoss and 3i implant systems respectively, are considered. The geometrical properties of the implant systems are modeled using three-dimensional (3D) brick elements. Loading conditions include a masticatory force of 200, 500 and 1000N applied to the occlusal surface of the crown along with an abutment screw torque of 110, 320 and 550Nmm. The von Mises stress distributions in the crown are examined for all loading conditions. Assumptions made in the modeling include: 1. half of the implant system is modeled and symmetrical boundary conditions applied; 2. temperature sensitive elements are used to replicate the torque within the abutment screw. Results: The connection type strongly influences the resulting stress characteristics within the crown. The magnitude of stress produced by the internal-hex implant system is generally lower than that of the external-hex system. The internal-hex system held an advantage by including the use of an abutment between the abutment screw and the crown. Conclusions: The geometrical design of the external-hex system tends to induce stress concentrations in the crown at a distance of 2.89mm from the apex. At this location the torque applied to the abutment screw also affects the stresses, so that the compressive stresses on the right hand side of the crown are increased. The internal-hex system has reduced stress concentrations in the crown. However, because the torque is transferred through the abutment screw to the abutment contact, changing the torque has greater effect on this hex system than the masticatory force. Overall the masticatory force is more influential on the stress within the crown for the external-hex system and the torque is more influential on the internal-hex system.

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STADEN, R. , GUAN, H. , LOO, Y. and W. JOHNSON, N. (2008) Comparative Analysis of Internal and External-Hex Crown Connection Systems – A Finite Element Study. Journal of Biomedical Science and Engineering, 1, 10-14. doi: 10.4236/jbise.2008.11002.

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Virtual Water on the Southern High Plains of Texas: The Case of a Nonrenewable Blue Water Resource

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ABSTRACT

This paper utilizes the virtual water concept to evaluate water usage of agricultural production in West Texas. This work evaluates the measure of virtual water, as it relates to informing water policy in a semi-arid, agriculture-intensive region, which relies upon a minimally renewable groundwater resource. The results suggest that production in the region reflects a collective effort to capture the highest value from the water resource, consistent with the virtual water philosophy, even in the absence of specific water policy toward that goal. Additionally, this work takes advantage of high resolution data to reinforce the need to calibrate virtual water calculations to account for regional differences.

Cite this paper

Williams, R. and Al-Hmoud, R. (2015) Virtual Water on the Southern High Plains of Texas: The Case of a Nonrenewable Blue Water Resource. Natural Resources, 6, 27-36. doi: 10.4236/nr.2015.61004.

References

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Spanish-Language Home Visitation to Disadvantaged Latino Preschoolers: A Means of Promoting Language Development and English School Readiness

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Author(s)

ABSTRACT

This study reports five years of a school readiness intervention called “HABLA” (Home Based Activities Building Language Acquisition), designed to increase and enrich speech and literacy activities in the homes of economically and educationally disadvantaged Latino families with children between the age of 2 and 4. A team of trained home visitors provided two years of a 23-week program of visitation in which they met with parent(s) and child twice weekly. Both years presented a Spanish language adaptation of the parent-child home program model; home visitors provide intensive modeling and coaching of non-directive Spanish language use, conversation, and literacy activities. Administration of the PLS-3 in Spanish at the onset and culmination of each year of the program indicates significant increases in receptive and expressive language for each year of visitation (7.8 standard points for the first year, 4.4 for the second) with effect-size r ranging from .24 to 42. Participants had significantly improved their levels of oral Spanish skill and scored much higher than a comparison group of non-treated. A subset of graduates of the two-year program was tested as kindergarteners; they showed a continued advantage over a comparison group of 18 peers who had not received the intervention. For the graduates, both their Spanish PLS-3 scores and English PLS-4 scores were significantly higher, and their parents reported a continued effort to provide literacy experiences at home. The HABLA participants also showed a clear advantage for an English language test of phonological awareness, one of the strongest predictors of school success.

Cite this paper

Mann, V. (2014) Spanish-Language Home Visitation to Disadvantaged Latino Preschoolers: A Means of Promoting Language Development and English School Readiness. Creative Education, 5, 411-426. doi: 10.4236/ce.2014.56051.

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Numerical Investigation of Wind Flow around a Cylindrical Trough Solar Collector

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http://www.scirp.org/journal/PaperInformation.aspx?PaperID=53017#.VLR7J8nQrzE

ABSTRACT

The goal of this study is to model the effects of wind on Cylindrical Trough Collectors (CTCs). Two major areas are discussed in this paper: 1) heat losses due to wind flow over receiver pipe and 2) average forces applied on the collector’s body. To accomplish these goals a 2D modeling of CTC was carried out using commercial codes with various wind velocities and collector orientations. Ambient temperature was assumed to be constant at 300 K and for specific geometries different meshing methods and boundary conditions were used in various runs. Validation was done by comparing the simulation results for a horizontal collector with empirical data. It was observed that maximum force of 509.1 Newton per Meter occurs at +60 degrees. Nusselt number is almost the constant for positive angles while at negative angles it varies considerably with the collector’s orientation.

Cite this paper

Shojaee, S. , Moradian, M. and Mashhoodi, M. (2015) Numerical Investigation of Wind Flow around a Cylindrical Trough Solar Collector. Journal of Power and Energy Engineering, 3, 1-10. doi: 10.4236/jpee.2015.31001.

References

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Implementation and Evaluation of Transport Layer Protocol Executing Error Correction (ECP)

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http://www.scirp.org/journal/PaperInformation.aspx?PaperID=48728#.VKNvE8nQrzE

ABSTRACT

Technologies for retransmission control and error correction are available for communications over the Internet to improve reliability of data. For communications that require the data reliability be ensured, TCP, which performs retransmission control, is often employed. However, for environments and services where response confirmation and retransmission are difficult, error correction technologies are employed. Error correction is generally implemented on UDP, but the existing framework implemented on UDP frequently does not consider the maximum frame size of the data link layer and relegates data division to the IP module. The IP module divides data according to the maximum size for the data link, and the receiving IP module reconstructs the divided data. For a data link layer typified by the current Ethernet with an error detection function, the frame is often destroyed upon error detection. At the IP module, the specification allows destruction of the entire dataset whenever divided data necessary for reconstruction is incomplete. Consequently, an error in a single bit results in a total loss of data handed to the IP module, and thus error correction performance declines with the increase in data size handed to the IP module. The present study considers the MTU of the data link layer and proposes error correction protocol (ECP) over IP, which decreases the transfer data volume flowing to the data link layer by dividing data into blocks of appropriate size based on designated error correction code and its parameters (thus improving error correction performance) and assesses the performance of ECP. Experimental results demonstrate that performance is comparable or better than existing error correction frameworks. Results also show that when a specification not ensuring the reliability of the data link layer was employed, error correction was superior to existing frameworks on UDP.

Cite this paper

Matsuzawa, T. and Shimazu, K. (2014) Implementation and Evaluation of Transport Layer Protocol Executing Error Correction (ECP). Communications and Network, 6, 175-185. doi: 10.4236/cn.2014.63019.

References

[1] Watson, M., Began, A. and Roca, V. (2011) Forward Error Correction (FEC) Framework. Request for Comments, 6363 (Internet Engineering Task Force).
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[11] McCann, J., Deering, S. and Mogul, J. (1996) Path MTU Discovery for IP Version 6. Request for Comments, 1981 (Internet Engineering Task Force).                                                                                       eww141231lx
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Experimental Evaluation of Fixing Equipment for Improving the Efficiency of Modular Unit Systems

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http://www.scirp.org/journal/PaperInformation.aspx?PaperID=52800#.VKNricnQrzE

ABSTRACT

Modular unit systems provide an eco-friendly advanced construction method that improves productivity and reduces carbon emissions and construction waste. In these systems, the prefabrication ratio of the modules should be high in order to support these eco-friendly features. The purpose of this study was to verify the functionality and driving safety of fixing a modular unit with a high prefabrication ratio to a vehicle for transportation to the site using two novel adapter blocks specially developed for this purpose. When asked to evaluate their performance for this study, the truck drivers selected adaptor block type B as providing the highest convenience and functionality. In real-world driving experiments, maximum loads of 15 kN and 25 kN were measured on adapter block types A and B, respectively. Future improvements in the adapter blocks that take the safety ratio and the improved convenience of use into account are confidently expected to contribute to the eco-friendliness and the improved productivity of modular unit systems.

Cite this paper

Kim, K. and Park, N. (2014) Experimental Evaluation of Fixing Equipment for Improving the Efficiency of Modular Unit Systems. Journal of Building Construction and Planning Research, 2, 244-254. doi: 10.4236/jbcpr.2014.24022.

References

[1] Kim, K.T., Chae, M.J., Park, N.C. and Park, S.Y. (2013) Development of Construction Technologies for One Day Housing. Strategy Project Report of KICT, Ilsan (Korea), December 2013, 1-104.
[2] Lim, S.H., Park, K.S., Chae, C.U. and Kwon, B.M. (2007) A Study on Factory Production of Modular Unit Housing Systems in Korea, United States, Japan, Europe. Journal of the Korean Housing Association, 8, 27-35.
[3] Song, Y.H., Lim, S.H., Lee, G.K. and Lee, W.H. (2011) A Study of the Current State Status of Prefab Architecture and Manufacturers. Proceedings of the Architectural Institute of Korea, Gyeongsan (Korea), October 2011, 65-66.
[4] Kim, K.T., Kim, S., Park, N.C. and Lee, Y.R. (2014) Development of Fixing Equipment for Transporting Modular Units. Proceedings of the Korean Institute for Structural Maintenance and Inspection, Jeju (Korea) October 2014, 709-710.
[5] Park, S.Y., Kim, K.T., Park, N.C. and Chung, I.S. (2012) Study of Improved Transportation Methods for Modular Units. Proceedings of the Korean Institute of Building Construction (Industry), Ansan (Korea), November 2012, 243- 244.
[6] Park, S.Y., Kim, K.T. and Park, N.C. (2013) Development and Evaluation of Fixation Equipment for Transporting Modular Units. Journal of the Korean Institute of Building Construction, 13, 609-618.
[7] Lee, K.B., Lim, K.R., Shin, D.W. and Cha, H.S. (2011) A Proposal for Optimizing the Modular Unit System Process to Improve Efficiency in Off-Site Manufacture, Transportation and On-Site Installation. Korean Journal of Construction Engineering and Management, 12, 14-21.
[8] Kim, K.T., Jung, I.S., Park, N.C. and Park, S.Y. (2012) Development of Construction Technologies for One Day Housing. Strategy Project Report of KICT, Ilsan (Korea), December 2012, 1-104.
[9] Park, N.C., Kim, K.T. and Kim, S. (2014) Correlation Analysis of a Working Load for Transporting Modular Units. Proceedings of the Korean Institute for Structural Maintenance and Inspection, Jeju (Korea), October 2014, 628-630.
[10] Kim, K.T., Park, N.C. and Lee, Y.R. (2014) A Test of Fixation Equipment for Transporting Modular Units. Proceedings of the Architectural Institute of Korea, Busan (Korea), October 2014, 695-696.        eww141231lx

Barriers to Intrauterine Device Use at an University-Based Women’s Clinic

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http://www.scirp.org/journal/PaperInformation.aspx?PaperID=52161#.VIZQXGfHRK0

ABSTRACT

Objective: The purpose of this study was to determine the barriers to intrauterine device (IUD) use at a University-Based Women’s Clinic. Methods: This study is a cross-sectional survey of a convenience sample of subjects receiving obstetrical care at a University-Based Women’s Clinic. Eligible women who consented to participate self-administered a 16-question survey during a routine prenatal visit. Descriptive statistics were used to report participants’ demographics and history of contraception use. Additionally, subjects were asked if they would consider IUD use in the future. Results: A total of 160 women participated in this study. The average age of this sample was 24.9 (SD = 6.3). The majority were in low income and low education categories. Only 5% of women reported previous IUD use. 27% of women surveyed desired more information regarding IUD contraception. 19% of participants would consider using an IUD in the future and 25% would consider IUD in the future if they knew more about them. Insurance and financial constraints were cited as barriers to IUD use. 4% of the sample reported that they had used an IUD previously and were unhappy with it due to pain and discomfort. 18% would not consider an IUD because they had heard about side effects. 68% of the surveyed sample reported unintended pregnancies. Conclusion: The two most common barriers to IUD use in this patient population was lack of knowledge and concern about side effects. Increasing patients’ knowledge of IUDs has the potential to increase IUD utilization in this clinic population which reported a 68% rate of unintended pregnancy.

Cite this paper

Ragland, D. , Paykachat, N. and Dajani, N. (2014) Barriers to Intrauterine Device Use at an University-Based Women’s Clinic. Open Journal of Obstetrics and Gynecology, 4, 1058-1064. doi: 10.4236/ojog.2014.416145.

References

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