Cambered and Non-flat Polyethylene Webs Induced by Thickness Variation

One of the most common web defects is web bagginess. Although it appears in most web materials, it is very difficult to categorize since its appearance changes from one case to the other; hence it has been given different definitions by different people. The most general way to define a baggy web is a web that does not lie flat/straight and has an intrinsic length difference across the width of the web. In this study, polyethylene webs were used as the main material to develop an understanding on some of the web bagginess cases through experimentation. Viscoelastic material properties behavior of polyethylene web was also characterized using time-temperature superposition. Digital image acquisition was used to detect web bagginess. With these results, it is now possible to correctly model this defect using a numerical simulation under development by the Web Handling Research Center.Mechanical & Aerospace Engineerin

Pseudo 3D viscoelastic winding model

A pseudo 3D winding model that has considered orthotropic viscoelastic effects during winding and storage has been developed and implemented in a code revised from the 2D viscoelastic winding code developed by Qualls and Good [1]. The model discretizes the web into smaller segments of equal width, each having a constant web thickness within a segment. Tension is assigned to each segment using Hakiel's approach [2]; the tension is updated after the winding of each lap based on the deformed radius of the segment relative to the relaxed radius profile of that lap. In each segment, a 2D winding model is applied. The pseudo 3D model is capable of dealing with (1) a varying thickness profile in both CMD (cross machine direction) and MD (machine direction); (2) winding tension variation with the winding laps; and (3) varying core stiffness in the CMD. Moreover, with the consideration of viscoelastic behavior in the web the effects of winding conditions, such as winding speed and tension, on the wound roll stress can be determined. The model is especially suitable for viscoelastic materials with relatively short characteristic relaxation times, such as plastic webs with glass transition temperature close to room temperature. Numerical methods were used to determine the stress distributions in the wound roll. The pseudo 3D viscoelastic winding model was validated by comparing results on the dimensional changes of a web in three situations. They include (1) the formation of cambered web (in-plane imperfection) due to linearly varying thickness; and (2) the formation of localized baggy lanes due to an edge burr following slitting; and (3) the formation of baggy web (out-of-plane imperfection) due to increased web thickness in the middle of the web. Simulation results compare favorably with experimental data.Mechanical and Aerospace Engineerin

The Breadth, but Not the Magnitude, of Circulating Memory B Cell Responses to P. falciparum Increases with Age/Exposure in an Area of Low Transmission

BACKGROUND: Malaria caused by Plasmodium falciparum remains a major cause of death in sub-Saharan Africa. Immunity against symptoms of malaria requires repeated exposure, suggesting either that the parasite is poorly immunogenic or that the development of effective immune responses to malaria may be impaired. METHODS: We carried out two age-stratified cross-sectional surveys of anti-malarial humoral immune responses in a Gambian village where P. falciparum malaria transmission is low and sporadic. Circulating antibodies and memory B cells (MBC) to four malarial antigens were measured using ELISA and cultured B cell ELISpot. FINDINGS AND CONCLUSIONS: The proportion of individuals with malaria-specific MBC and antibodies, and the average number of antigens recognised by each individual, increased with age but the magnitude of these responses did not. Malaria-specific antibody levels did not correlate with either the prevalence or median number of MBC, indicating that these two assays are measuring different aspects of the humoral immune response. Among those with immunological evidence of malaria exposure (defined as a positive response to at least one malarial antigen either by ELISA or ELISPOT), the median number of malaria-specific MBC was similar to median numbers of diphtheria-specific MBC, suggesting that the circulating memory cell pool for malaria antigens is of similar size to that for other antigens

Identifying needs for the mobile data services : a cross-border strategic perspective

This study focuses on Singapore, Hong Kong SAR and China, as viewed from Shenzhen. It focuse s on strategic issues including entry to multiple markets, market segmentation, venture formation and strategic alliances, etc.Master of Business Administration (Marketing

WEBS INDUCED BY THICKNESS VARIATION

you will always be in my thoughts…. iii ACKNOWLEDGEMENTS In our lifetime, rarely we will encounter significant people who are willing to go the distance with us; to assist, to nurture life’s hard-earned lessons and most importantly to guide us through uncharted waters till we reached safe harbor. The important roles these people play, to whom we are always grateful. First and foremost, I will like to extend my deepest gratitude to my mentor, advisor and thesis chair, Dr. Hongbing Lu, for his insightful guidance, encouraging confidence and immeasurable kindness. To whom which without generous financial assistance, this thesis will never materialize. As well, my heartfelt appreciation goes to my other committee members Dr. J. Keith Good and Dr. Eric Price; for the encouragement, experimental equipments and invaluable trust. I will also like to take the opportunity to thank two most esteem authority in the field of web handling: Prof. Bruce Feiertag; for taking me into his wing as an apprentice and teaching me everything there is to know about web handling, and Prof. John Shelton; for helpful suggestions and valuable discussion, especially when I was stuck