bluuebunny/crossref_metadata_2025 huggingface dataset:
Spatial and Temporal Variation of Precipitation in Greece and Surrounding Regions Based on Global Precipitation Climatology Project Data
Authors: Hatzianastassiou N. , Katsoulis B. , Pnevmatikos J. , Antakis V.
Published: March 2008

In this study, the spatial and temporal distribution of precipitation in the broader Greek area is investigated for the 26-yr period 1979–2004 by using monthly mean satellite-based data, with complete spatial coverage, taken from the Global Precipitation Climatology Project (GPCP). The results show that there exists a clear contrast between the more rainy western Greek area (rainside) and the drier eastern one (rainshadow), whereas there is little precipitation over the islands, particularly in the southern parts. The computed long-term areal mean annual precipitation amount averaged for the study area is equal to P = 639.8 ± 44.8 mm yr−1, showing a decreasing trend of −2.32 mm yr−1 or −60.3 mm over the 26-yr study period, which corresponds to −9.4%. This decrease of precipitation, arising primarily in winter and secondarily in spring, is the result of a decreasing trend from 1979 through the 1980s, against an increase during the 1990s through the early 2000s, followed again by a decrease up to the year 2004. The performed analysis reveals an increasing trend of precipitation in the central and northern parts of the study region, contrary to an identified decreasing trend in the southern parts, which is indicative of threatening desertification processes in those areas in the context of climatic changes in the climatically sensitive Mediterranean basin. In addition, the analysis shows that the precipitation decrease is due to a corresponding decrease of maximum precipitation against rather unchanged minimum precipitation amounts. The analysis indicates that the changing precipitation patterns in the region during winter are significantly anticorrelated with the North Atlantic Oscillation (NAO) index values, against a positive correlation during summer, highlighting thus the role of large-scale circulation patterns for regional climates. The GPCP precipitation data are satisfactorily correlated with instrumental measurements from 36 stations uniformly distributed over the study area (correlation coefficient R = 0.74 for all stations; R = 0.63–0.91 for individual stations).
What Has Changed the Proportion of Intense Hurricanes in the Last 30 Years?
Authors: Wu Liguang , Wang Bin
Published: March 2008

The recently reported increase in the proportion of intense hurricanes is considerably larger than those projected by the maximum potential intensity (MPI) theory and the results of numerical simulation. To reconcile this discrepancy, the authors examined the best-track datasets for the North Atlantic (NA), western North Pacific (WNP), and eastern North Pacific (ENP) basins. It was found that the changes in the tropical cyclone formation locations and prevailing tracks may have contributed to the changes in the proportion of the intense hurricanes over the past 30 yr. The authors suggest that the changes in the formation locations and prevailing tracks have a profound impact on the basinwide tropical cyclone intensity. Thus, how the atmospheric circulation in the tropical cyclone basins responds to the global warming may be a critical factor in understanding the impacts of global warming on tropical cyclone intensity.
On the Changes in the Number and Intensity of North Atlantic Tropical Cyclones
Authors: Briggs William M.
Published: March 2008

Bayesian statistical models were developed for the number of tropical cyclones, the rate at which these cyclones became hurricanes, and the rate at which hurricanes became category 4+ storms in the North Atlantic using data from 1966 to 2006 and from 1975 to 2006. It is found that, controlling for the cold tongue index (CTI), North Atlantic Oscillation index (NAOI), and the Atlantic Multidecadal Oscillation (AMO), it is improbable that the number of tropical cyclones has linearly increased since 1966, but that the number has increased since 1975. The differences between these two results have to do with the numbers of storms at the start of these two periods: it was easier to say a linear increase was present starting from circa 1975 since the storms in that period were at a low point. The rate at which storms become hurricanes appears to have decreased, and the rate at which category 4+ storms evolved from hurricanes appears to have increased. Both of these results are also dependent on the starting year. Storm intensity was also investigated by measuring the distribution of individual storm lifetimes in days, storm track length, and Emanuel’s power dissipation index. Little evidence was found that mean individual storm intensity has changed through time, but it is noted that the variability of intensity has certainly increased. Any increase in cumulative yearly storm intensity and potential destructiveness is therefore due to the increasing number of storms and not due to any increase in the intensity of individual storms. CTI was not always significant, but lower CTIs were associated with more storms, higher rates of conversion, and higher intensities. NAOI was only weakly associated: the effect was negative for the number of storms, the rate of hurricanes evolving from storms, and intensity, but it was positive for the rate of category 4+ storms evolving from hurricanes. AMO was rarely significant except in explaining the number of storms using the 1966–2006 data. Its direction was always positive as expected; however, higher values of the AMO were associated with more storms, higher rates of conversion, and higher intensities.
Hemispherical Asymmetry of Tropical Precipitation in ECHAM5/MPI-OM during El Niño and under Global Warming
Authors: Chou Chia , Tu Jien-Yi
Published: March 2008

Similarities and differences between El Niño and global warming are examined in hemispherical and zonal tropical precipitation changes of the ECHAM5/Max Planck Institute Ocean Model (MPI-OM) simulations. Similarities include hemispherical asymmetry of tropical precipitation changes. This precipitation asymmetry varies with season. In the boreal summer and autumn (winter and spring), positive precipitation anomalies are found over the Northern (Southern) Hemisphere and negative precipitation anomalies are found over the Southern (Northern) Hemisphere. This precipitation asymmetry in both the El Niño and global warming cases is associated with the seasonal migration of the Hadley circulation; however, their causes are different. In El Niño, a meridional moisture gradient between convective and subsidence regions is the fundamental basis for inducing the asymmetry. Over the ascending branch of the Hadley circulation, convection is enhanced by less effective static stability. Over the margins of the ascending branch, convection is suppressed by the import of dry air from the descending branch. In global warming, low-level moisture is enhanced significantly due to warmer tropospheric temperatures. This enhances vertical moisture transport over the ascending branch of the Hadley circulation, so convection is strengthened. Over the descending branch, the mean Hadley circulation tends to transport relatively drier air downward, so convection is reduced.
Influence of the Meridional Overturning Circulation on Tropical Atlantic Climate and Variability
Authors: Haarsma Reindert J. , Campos Edmo , Hazeleger Wilco , Severijns Camiel
Published: March 2008

The influence of the meridional overturning circulation on tropical Atlantic climate and variability has been investigated using the atmosphere–ocean coupled model Speedy-MICOM (Miami Isopycnic Coordinate Ocean Model). In the ocean model MICOM the strength of the meridional overturning cell can be regulated by specifying the lateral boundary conditions. In case of a collapse of the basinwide meridional overturning cell the SST response in the Atlantic is characterized by a dipole with a cooling in the North Atlantic and a warming in the tropical and South Atlantic. The cooling in the North Atlantic is due to the decrease in the strength of the western boundary currents, which reduces the northward advection of heat. The warming in the tropical Atlantic is caused by a reduced ventilation of water originating from the South Atlantic. This effect is most prominent in the eastern tropical Atlantic during boreal summer when the mixed layer attains its minimum depth. As a consequence the seasonal cycle as well as the interannual variability in SST is reduced. The characteristics of the cold tongue mode are changed: the variability in the eastern equatorial region is strongly reduced and the largest variability is now in the Benguela, Angola region. Because of the deepening of the equatorial thermocline, variations in the thermocline depth in the eastern tropical Atlantic no longer significantly affect the mixed layer temperature. The gradient mode remains unaltered. The warming of the tropical Atlantic enhances and shifts the Hadley circulation. Together with the cooling in the North Atlantic, this increases the strength of the subtropical jet and the baroclinicity over the North Atlantic.
Clinical Review : Purulent Meningitis in Newborn Babies
Authors: McDonald Robert
Published: March 2008

An account is given of 82 cases of purulent meningitis in the first month of life. The mortality rate of 50 per cent is similar to most published figures. The best form of therapy is still undecided. For the present, high dosage gentamycin by intramuscular and intraventricular injection is suggested, together with tri methoprimsulphamethoxazole by mouth. Until it is shown that the infecting agent is not a pneumococcus, intravenous penicillin is recommended as an addi tional drug. Adverse prognostic signs are hypothermia, convulsions, loss of con sciousness, a subnormal temperature, and onset of the disease in the first week of life. If results are to be improved, treatment must be early, effective and pro longed, preferably at childrens' hospitals well equipped to deal with the problem.
Regional Lymphadenitis Following BCG Vaccination (BCGitis)
Authors: Chaves-Carballo Enrique , Sanchez Gil A.
Published: March 2008

Among 1,295 children vaccinated with BCG during a 16-month period, 25 developed regional lymphadenopathy (BCGitis) for an incidence of 1.9 per cent. In half of the cases, the enlarged nodes progressed to suppuration, most often in infants. Different lots of BCG varied in their capability to induce BCGitis. Technic in administration did not ap pear to be related to this complication. Subsequent change from fluid to freeze-dried vaccine markedly reduced the incidence of BCGitis.
The Problem Student in a Rural School Setting
Authors: McNamara John J. , Thorsted Dale
Published: March 2008

A model has been developed and implemented for community involvement in a multidiscipli nary educational/medical approach to problem pupils. The complexity of the pupils' problems re quires evaluation of this nature. Some of the con straints imposed by the rural setting can be overcome by education and community involve ment. Other constraints are more resistant to solutions. Preliminary evaluations suggest that the program here described is beneficial.
Homogenous Modeling of VARTM Processes with Hybrid Layered Media
Authors: Yoon Myung-Keun , Dolan Daniel F.
Published: March 2008

Numerical methods have been widely used to simulate vacuum assisted resin transfer molding (VARTM) processes to obtain optimum process parameters. Many VARTM parts have very large in-plane dimensions compared to the thickness. However, the incorporation of a highly permeable distribution media on the surface of a fibrous preform results in significant through thickness flow particularly at the flow front where large gradients can exist. In general, flow simulations that can model the distribution media as a discrete layer are needed, which, however, significantly increases the number of elements and thus computational costs in the numerical analyses. The present study introduces a homogenous preform system using equivalent porosity and permeability over the out-of-plane direction that retains the through-thickness flow characteristics in order to reduce complexity in modeling the distribution media in VARTM processes. First, a mass-average approach was developed to reduce the number of dimensions that needs to be modeled (e.g., 3-D is reduced to 2-D in-plane and 2-D cross section is reduced to a 1-D flow problem). Parametric studies were carried out over a reasonable range of the input parameters such as preform thickness, length, porosity, and permeability and showed limitations in using the mass average approach with homogenous models. Second, a reconstruction method was developed to predict accurately the flow pattern in the out-of-plane direction from the homogenous models. The flow pattern was successfully reconstructed using the flow data obtained from the homogenous model with an analytic solution of the flow front shape in the out-of-plane direction. Average flow front locations and the flow front patterns were investigated by numerical analyses for a few flow scenarios, which validated the present methods and quantified error levels in the resin flow pattern and resin fill time. The mass-average and reconstruction approaches successfully estimated the resin flow locations and patterns with respect to time and significantly reduced complexity in modeling complex geometries as well as computational costs.
Constrained Globalized Nelder—Mead Method for Simultaneous Structural and Manufacturing Optimization of a Composite Bracket
Authors: Ghiasi Hossein , Pasini Damiano , Lessard Larry
Published: March 2008

The optimized design of composite structures is a difficult task. It requires optimizing simultaneously both structural and manufacturing objectives. The objectives do not have closed form solutions and have multiple local optima that calls for a global search. This paper improves the global search method called GBNM [1], which is based on several restarts of the Nelder—Mead method. Two issues are addressed here. First, the restart procedure is improved by using a one-dimensional probability function and a weighted selection procedure. Second, nonlinear constraints are included by projecting the infeasible points onto the nonlinear constraints. The improved procedure is applied to four mathematical test functions. Numerical results show the proposed approach is more efficient in terms of computational time and probability of finding the global minimum. The improved GBNM is then applied to the simultaneous structural and manufacturing design of a Z-shaped composite bracket. The results are compared to those obtained with the genetic algorithm.
Long-term Fatigue Strength Prediction of CFRP Structure Based on Micromechanics of Failure
Authors: Hongneng Cai  , Miyano Yasushi , Nakada Masayuki , Sung Kyu Ha
Published: March 2008

A prediction method for the fatigue strength of polymer composites under arbitrary frequency, load ratio and temperature was developed with the combined method of the micromechanics of failure (MMF) developed by Ha and the accelerated testing methodology (ATM) developed by Miyano and Nakada. The time— temperature dependent master curves of MMF/ATM critical parameters were constructed by tensile and compressive static and fatigue tests for the longitudinal and transverse directions of unidirectional CFRP under various temperatures based on the three-dimensional micromechanics of fibers and matrix resin and the time— temperature superposition principle which holds for the viscoelastic behavior of matrix resin. These master curves can be used to predict the fatigue strength of composite structures with multi-directional laminations at any time, temperature, and number of cycles to failure. The applicability of MMF/ATM combined method to predict the long term strength of CFRP structures was experimentally confirmed by prediction of the open hole compression fatigue strength of the quasi-isotropic CFRP laminates.
Families of Hygrothermally Stable Asymmetric Laminated Composites
Authors: Cross Richard J. , Haynes Robert A. , Armanios Erian A.
Published: March 2008

Necessary and sufficient material-independent conditions are derived for hygrothermal stability of a laminated composite plate with plies made of the same specially orthotropic material based on classical lamination theory. The minimum number of plies required to obtain an asymmetric hygrothermally stable stacking sequence is proven to be five, and families of stable laminates are identified for six, seven, and eight plies. A sensitivity analysis demonstrates the robustness of hygrothermally stable solutions to small errors in ply orientation. A finite element analysis of geometric and ply orientation imperfections was performed to verify the robustness of the classical lamination theory results. Hygrothermally stable asymmetric laminate specimens were fabricated to confirm the analytical predictions.
Thermal Expansion of Sheet Molding Compound Materials
Authors: Kia Hamid G.
Published: March 2008

The coefficient of linear thermal expansion (CLTE) of composites is an important property that has to be well understood. In this study, using a mathematical expression, graphic relationships were established for predicting the general trend of CLTE variations with temperature as affected by the materials properties. Subsequently, the CLTE of different types of sheet molding compound (SMC) materials was measured at various temperatures in the direction parallel to the cosmetic surface. It was observed that the CLTE variations with temperature go through a maximum. The experimental results were then interpreted with the help of the developed theoretical relationships. More specifically, the effect of low profile additive on the CLTE of SMC was studied, and it was observed that increasing the concentration of the low profile additive, a high CLTE ingredient, reduces the overall CLTE, and at the same time, shifts the position of the maximum to lower temperatures. As to the effect of glass content, it was observed that changing the glass content from 27% to 37% does not affect the position of the maximum in the CLTE-temperature curves noticeably, although this variation reduces the overall CLTE significantly. These observations were all consistent with the theoretical predictions. The information generated in this work enables one to control the CLTE of composites as required by specific applications. An example is the use of SMC in the production of inner panels for deck lids and hoods, in which a controlled CLTE is essential in order to avoid bond line readout.
Static and Fatigue Strengths of a G40-800/5260 Carbon Fiber/Bismaleimide Composite Material at Room Temperature and 150°C
Authors: Shimokawa Toshiyuki , Kakuta Yoshiaki , Hamaguchi Yasumasa , Aiyama Takenori
Published: March 2008

The objective of this study was to investigate the static and fatigue strengths of a G40-800/5260 carbon fiber/bismaleimide composite material, a type of high temperature CFRP, at room temperature (RT) and 150°C and to evaluate the practicality of this material. The stacking sequence of the material is quasi-isotropic, 32 plies [+45/0/-45/90]4s. Static tensile and compressive tests were performed at RT and high temperatures for non-hole (NH) and open-hole (OH) specimens. In addition, the effectiveness of notched strength criteria was discussed on the basis of test results. Fatigue tests yielded the S-N relationships of OH specimens for three kinds of stress ratio R (=minimum stress/maximum stress), R=0.1 (tension), 10 (compression), and -1 (tension-compression) at RT and 150°C. This study laid emphasis on investigating the static and fatigue strengths at 150°C and the role of compression load repetition in tension-compression fatigue. Major findings are as follows. (1) Static NH and OH compressive strengths, OH compression fatigue strength, and OH tension-compression fatigue strength were temperature-dependent and classified as matrix-dominant properties. These fatigue strengths decreased with increasing load cycles. (2) An open hole greatly reduced static tensile and compressive strengths at both RT and 150°C. (3) The ratio of compression strength to tension strength under static or fatigue loading was fairly low for both NH and OH specimens at RT and 150°C, except for the case of NH static strength at RT. (4) The compression stress range mostly controlled fatigue lives in tension-compression fatigue tests at RT and 150°C. (5) The material tested showed no large static and fatigue strength reduction at 150°C except for NH compressive strength; however, it should be used with care when structures have open holes and encounter compression loading, especially at high temperatures.
Effects of Laundering on the Surface Properties and Dimensional Stability of Plain Knitted Fabrics
Authors: Quaynor Leticia , Takahashi Masaoki , Nakajima Masaru
Published: March 2008

The effects of laundering and laundering temperatures on surface properties and dimensional stability are investigated for plain flat knit silk, cotton, and polyester fabrics with varying cover factors. The fabrics are subjected to relaxation processes and an extended series of wash and tumble-dry cycles in laundering baths of various tempera tures. Dimensions, surface friction, and roughness of the fabrics are measured in every process. Changes in dimensional stability and surface properties with relaxation processes and laundering temperatures are clarified. Relations between frictional motion and struc tural parameters are also discussed. The results reveal that the dimensional stability of silk is sensitive to a particular temperature. The highest shrinkage is recorded with slackly knitted cotton at the highest temperature. There is a considerable effect of wet relaxation on dimensional stability as well as surface properties. Silk's coefficient of friction is the highest, and the lowest surface friction for cotton occurs at the highest temperature. Slackly knitted fabrics also show higher friction than tightly knitted fabrics. The coeffi cient of friction has a tendency to decrease with increasing tightness, while the surface roughness shows an opposite tendency. There is a good correlation between stick-slip motion and ribs on the fabrics.
Fatigue Behavior of Aramid Nonwoven Fabrics Under Hot-Press Conditions
Authors: Watanabe Akira , Miwa Minoru , Yokoi Teruyuki
Published: March 2008

Nonwovens used as components of laminated cushion materials for multi-daylight press molding are subjected to repeated hot-press fatiguing. Preferred heat-resistant nonwovens show little change in mechanical properties such as tensile and compression after repeated fatiguing. In Part III, needle-punched nonwovens had superior recovery from hot-press fatiguing compared with paper-like nonwovens and four-ply wovens, because the 3-D fiber arrangement (fibers arranged in the thickness direction) provided by the needle caused these fibers to behave like springs in the nonwovens. In Part VI, the 3-D fiber arrangement was maintained by the stable base fabrics after repeated fatiguing, and was one of the important factors determining the mechanical properties of these nonwovens.

The 3-D fiber arrangement can be mainly constructed by the barb and throat of the needle. In this study, we discuss the influences of the barb and throat shapes on fiber arrangement and fiber-to-fiber entanglement. In particular, we discuss the relationship between the cross-sectional area of the throat and compression-recovery properties. Three kinds of nonwovens prepared with different needle types are subjected to repeated hot-press fatiguing treatments, and their compression-recovery behaviors are analyzed. The nonwoven made by the needle with the large cross-sectional throat area is thinner, very elastic, and provides good recovery from compression. This is because the fibers arranged in the thickness direction by the needles get more tightly entangled and may behave somewhat like springs during compression and recovery.
Surface Morphologies of Polypropylene Fibers Studied by Atomic Force Microscopy
Authors: Hautojärvi Joni , Niemi Heidi
Published: March 2008

Surface morphologies of compact-spun polypropylene fibers spun with varying spin and tow draw ratios are characterized with atomic force microscopy (AFM). The surface structures are correlated to x-ray diffraction, birefringence, and fiber tenacity: The surface morphology of as-spun fibers is spherulitic at spin draw ratios lower than 500. With increasing spin draw ratio, the morphologies develop into epitaxially crystallized struc tures, and a shish-kebab morphology is evident with spin draw ratios higher than 1000. When tow drawing is applied to spherulitic as-spun fibers, the surface morphology transforms into a fibrillar structure between draw ratios of 2.0 and 3.0. With the highest applicable draw ratio of 4.4, the microfibrils consist of alternating crystal blocks and amorphous regions with a periodicity of 12.3 nm. The difference between the long period values determined by AFM and SAXS is 2% on average, indicating that the lamellae spacing between the surface and the bulk of the fibers is almost equal. Discontinuities in the long period as a function of spin and tow draw ratios are assigned to the morphological transformations revealed by AFM.
Deterioration of Silk Fabrics and Their Crystallinity
Authors: Yanagi Yoshikuni , Kondo Yoshiyuki , Hirabayashi Kiyoshi
Published: March 2008

We report an investigation of the deterioration mechanism of aged silk fabrics treated in various ways. When we examine the deteriorated silk with thermal and amino acid analyses, we find that the decomposition temperature (above 300°C) of aged silk is higher than that of newer silk fabrics, and the amino acids in the amorphous region of aged silk are much reduced compared to those in the crystalline region. This suggests that the degree of silk's crystallinity increases relative to the aging period. Moreover, the decom position temperature of y-ray irradiated silk is reduced according to the increased amount of irradiation, and all amino acids in the crystalline and amorphous regions are reduced without exception. Amino acid analysis of coagulated silk in the silk gland with heat treatment shows that the amino acids are remarkably reduced in air above 250°C, and the reduction of tyrosine and phenyl alanine in the amorphous region is less in nitrogen gas.
Factors Influencing Air Flow Through Unbacked Tufted Carpets
Authors: Lee Hsi-Lung Stephen , Carr Wallace W. , Beckham Haskell W. , Wepfer William J.
Published: March 2008

Through-air dryers are widely used for drying unbacked tufted carpets after dyeing- steaming-washing processes. Since the drying rate depends greatly on air velocity, carpet air permeability is a very important parameter affecting drying time. We study the effects of several carpet construction and process parameters on the air permeability of unbacked cut-pile nylon carpets with woven polypropylene primary backing using a modified Frazier air permeability tester and a laboratory through-air dryer. We then present a model predicting pressure drop over the carpets versus apparent velocity.
Scanning Force Microscopy Studies of the Surface Structure of Activated Carbon Fabric
Authors: Huang Ju-Ming , Wang Ing-Jing , Wang Chi-Hsian
Published: March 2008

The surface structures of activated carbon fabrics and their precursors are examined by scanning force microscopy and scanning tunneling microscopy. Results indicate clear dissim ilarities in the characteristic surface structures of both activated carbon fabrics prepared from different precursors of regenerated cellulosic fibers. The surface structure of these fabrics is resolved over a larger area (2 X 2 μm), showing that the distance between peaks and valleys is larger for one activated carbon fabric (V900) prepared from regular viscose rayon fiber precursors than for another (P900816) made from polynosic fiber precursors. In other words, the BET specific surface area and total pore volume are larger for the former than for the latter. Resolution over (8X8 nm) areas confirms that the surface of the activated carbon fabric develops a microporous structure. The BET specific surface area tester confirms data for the high specific surface area and total pore volume of activated carbon fabrics.
Thermochemical Degradation of Melezitose and Trehalulose as Related to Cotton Stickiness
Authors: Gamble Gary R.
Published: March 2008

The melezitose and trehalulose contents of a cotton sample heavily contaminated by whitefly honeydew are analyzed by high performance anion exchange chromatography (HPAEC) as a function of heating time at 200°C. Results indicate that the concentrations of melezitose and trehalulose on the surface of the cotton decrease exponentially as a result of thermochemical reactions. The mechanism and rate of each reaction is elucidated by similar heat treatment of pure melezitose and trehalulose with subsequent analysis of reaction products. The rate of thermochemical degradation in the case of trehalulose is of sufficient magnitude that its concentration on the cotton surface may be substantially decreased under controlled conditions of heat and time. The degradation rate of melezitose is nearly an order of magnitude smaller, and its concentration on the cotton surface is not substantially affected under similar conditions.
Modeling and Computer Simulation of the Compressional Behavior of Fiber Assemblies
Authors: Beil Norman B. , Roberts William W.
Published: March 2008

In this study, the model presented in Part I is used to investigate phenomena related to the compression of fiber assemblies that are not accounted for by van Wyk's theory of the uniaxial compression of an initially random fiber assembly. In order to do this, the potential energy, the work done on the assembly, and a discrete orientation density function for the assembly are calculated. Realistic looking hysteresis plots are produced. and the model can predict the amount of frictional energy dissipated as a function of time. Irrecoverable compression does not increase for as many cycles as has been experimen tally reported, which may be a result of the neglect of viscoelastic effects. Crimp has a large effect on the compressional properties, in that more highly crimped fibers absorb more energy as they are compressed. They also absorb a higher proportion of their energy in the twisting mode, which previous investigators have neglected. A lower induced orientation effect than that resulting from Stearn's theory [12] is predicted, but this discrepancy cannot currently be resolved. Future work may incorporate viscoelasticity into the model and predict the most probable initial volume fraction for an assembly with given fiber properties.
Morphology Gradients in Thermally Point-Bonded Poly(ethylene Terephthalate) Nonwovens
Authors: Xueqin Wang  , Michielsen Stephen
Published: March 2008

In a previous article, a sharp change in the birefringence and density of polypropylene fibers was reported at the edge of thermal point bonds in nonwovens. In this article, similar results are shown for polyester nonwovens. First, in both isotactic polypropylene (ipp) and poly(ethylene terephthalate) (PET), the morphology of the fibers between the bond points is identical to that of the original feed fibers. Second, the morphology of the bond points is substantially different from that of the fibers. Third, there is a rapid change in the morphology going from the fiber into the bond at the bond edge. Fourth, the birefringence of the fibers decreases by approximately 50% going from the fibers into the bonds. The change in birefringence is a function of processing conditions. In PET, the density in the bond point is lower than in the bridging fibers, while in ipp, the density in the bond point is higher than in the bridging fiberts. This difference is readily understood based on the different crystallization rates of ipp and PET.
Dyeing Chitin/Cellulose Composite Fibers with an Acid Dye
Authors: Shimizu Yoshiaki , Nakajima Tetsuo , Yoshikawa Masatoshi , Takagishi Toru
Published: March 2008

The dyeing properties of a chitin/cellulose composite fiber, Crabyon® (CR), for CI Acid Orange 7 dye are examined at equilibrium compared with those for protein fibers of silk and wool and a regenerated cellulosic fiber, viscose rayon. The adsorption isotherms of the dye by CR are the sigmoid type, different from silk and wool, which are the Langmuir type. The most remarkable feature of CR is its adsorption of the dye, which greatly depends on the dyebath pH. Hence, it seems that the adsorption is due to the electrostatic interaction of the dye anion with the protonated amino group of the partially deacetylated chitin in CR. Under the same conditions, the greater the content of the basic groups in amorphous regions in the substrate, the greater the dye uptake at equilibrium: CR(20) > wool > CR(10) > silk ≧ CR(3).
Air Permeability of Multilayered Nonwoven Fabrics: Comparison of Experimental and Theoretical Results
Authors: Mohammadi M. , Banks-Lee P.
Published: March 2008

The experimental and theoretical air permeabilities of twelve multilayered. needle punched nonwoven samples are compared in this paper. Samples are made from ceramic and glass with varying layer structures. The density and diameter of all fibers used to make individual webs are approximately the same, and so the fabric samples made from these webs are assumed to be homogeneous, multilayered structures. The porosity of all fabric structures is greater than 0.96. Thus, the theoretical air permeability is based on a modified Kozeny equation. Experimental measurements involve the Frazier air permeability tester.
Damage to Natural and Synthetic Fibers Treated in Supercritical Carbon Dioxide at 300 bar and Temperatures up to 160°C
Authors: Schmidt Andreas , Bach Elke , Schollmeyer Eckhard
Published: March 2008

This paper examines and discusses fiber damage in cotton, viscose, polyester, poly amide 6.6, silk, and wool in supercritical carbon dioxide at 100. 120. 140, and 160°C for I and 4 hours at a pressure of 300 bar. For comparison, experiments are conducted for 4 hours at 160°C in nitrogen and air under atmospheric conditions. Damage is determined by fiber-specific reactions, staining tests, shrinkage, stress-strain measurements. viscosi metric molecular weight, and amino acid analyses. Shrinkage occurs only in polyamide 6.6 and polyester, and is comparable to water dyeing. During all treatments above 120°C in carbon dioxide, the degree of polymerization of polyamide 6.6 decreases, which is also detectable by stress-strain measurements. Polyester is not damaged by any treatment. Damaging effects on cotton, viscose, silk, and wool are only revealed by stress-strain measurements after 4 hours at 160°C in carbon dioxide, but not in nitrogen and air. The degree of polymerization of cellulose fibers starts to decrease slightly after 4 hours at 120°C, while amino acid analyses of silk and wool indicate damage only after 4 hours at 160°C. Generally, the combination of heat, treatment time, and carbon dioxide seems to be responsible for the damaging effects. The results show that except for polyamide 6.6, where treatment conditions are limited to 120°C at 300 bar for 1 hour, supercritical carbon dioxide is a suitable solvent for dyeing or other treatments, even for the most sensitive textiles up to 140°C. The treatment time at 160°C should not be longer than 1 hour.
Changes in the Static and Dynamic Drape Coefficients of Polyester Fabrics Through the Finishing Stages
Authors: Matsudaira Mitsuo , Minzhang Yang  , Kinari Toshiyasu , Shintaku Sukenori
Published: March 2008

Static and dynamic drape behaviors of polyester woven fabrics are s died through representative finishing stages using two sets of fabrics with different conditions of relaxation and weight reduction. The node number n, the revolving drape increase coefficient Dr, and the dynamic drape coefficient Dd increase through the finishing stages, especially with relaxation. The static drape coefficient D, and revolving drape coefficient at 200 rpm D200 decrease through the finishing stages, especially with relaxation. These parameters do not change much after dyeing and raising. The effect of elaxation in a washer is stronger than in a jet-dyeing machine for these parameters. The e fect of weight reduction on D, and D200 appears clearly: the former increases and the latter decreases with a higher ratio of weight reduction.
Properties of Wool/PET Composite Yarns
Authors: Xiongying Wu  , Fumei Wang  , Shanyuan Wang
Published: March 2008

This paper reports an investigation of the differences in structures and mechanical properties of two kinds of composite yarns and of conventional two-ply staple yarns. The cross section of one composite yarns (Sirofil) shows a circular shape, which is similar to the structure of single spun yarns and to the helical geometry line of two-ply yarns. The other composite yarn structure (twisted ring spun singles yarns with filaments) is similar to that of two-ply yams. The tensile properties of composite yarns mainly depend on the tensile properties of the filaments, and their tenacity is higher than that of two-ply wool/PET staple fiber yams. The bending rigidity of these two kinds of composite yams is lower than that of two-ply staple fiber yams. Wool/PET composite yarns show higher residual torque than conventional two-ply staple yarns, and the reason is their structure and lower torque-relaxation.
Reducing Yarn Hairiness with a Modified Yam Path in Worsted Ring Spinning
Authors: Xungai Wang  , Lingli Chang
Published: March 2008

The spinning geometry of a ring frame plays an important role, and the twist triangle is the critical region in ring spinning. Changes in the spinning geometry may affect yarn properties. This paper examines the idea of ring spinning with a "diagonal" yarn path, and the effect of such a path on yam properties, particularly hairiness. Both "left diagonal" and "right diagonal" yam arrangements are tried on a 24-spindle Cognetex FLC worsted ring frame. The hairiness results obtained from the Zweigle hairiness meter show that the right diagonal yam path produces yams of lower hairiness than the conventional ring spun yarn in almost all the hair length groups. Yam evenness and tenacity are not as sensitive to the change in yarn path. The mean spindle speed at break is also tested, and there is some deterioration in spinning efficiency with the right diagonal yarn path, particularly at higher spinning speeds. Results from this study may help explain variations in yarns spun on poorly aligned ring frames.
Assessing Structural Changes in Knits During Processing
Authors: Abou-Ana M. , Youssef S. , Pastore C. , Gowayed Y.
Published: March 2008

An automatic fabric evaluation system is developed to analyze knit structures and objectively evaluate fabric properties. Fabric images are captured with a CCD camera, and digital images are processed by histogram equalization, binary morphological operators, and pattern recognition. Six knitted fabrics are evaluated at different phases of manufac turing. Fabric construction parameters such as courses and wales per unit length, fabric cover, and areal density are measured and evaluated using the new approach and manual methods. Structural changes that occur in the fabrics at different levels of relaxation are also documented. Our image capturing and analysis system is capable of on-line control of knit structures' spatial characteristics before and after wet treatments.
Quantitative Fiber Mixture Analysis by Scanning Electron Microscopyl
Authors: Wortmann F.-J. , Phan K.-H. , Augustin P.
Published: March 2008

Test Method 58 was established by the International Wool Textile Organization in 2000 to analyze textile products made from specialty fibers, sheep's wool, and their blends. The method specifies the use of scanning electron microscopy to discriminate wool from all specialty fibers, such as cashmere, mohair, etc., mainly according to the cuticle scale height criterion. In this work, after the first step of the analysis, where 150 fibers are identified for their type, three cases are distinguished for which either a purity check, a two-component analysis by number, or a quantitative analysis of a two-component blend is conducted. The consequences of the thresholds separating the three cases are considered in detail for the first two cases. For various hypothetical samples of practical relevance, the minimum and maximum potential weight fractions of small admixtures are assessed. Extended analysis protocols are investigated, which enable the operator to sensibly adjust the course of a given analysis to its specific, technical, legal, and economic requirements.
Quantitative Fiber Mixture Analysis by Scanning Electron Microscopy
Authors: Wortmann F.-J. , Phan K.-H. , Augustin P.
Published: March 2008

Test Method 58 was established by the International Wool Textile Organization in 2000 to analyze textile products made from specialty fibers, sheep's wool. and their blends using the scanning electron microscope. This part of the series critically examines the design of the analytical approach for quantitative analysis of binary blends specified in IWTO-58. The 95% confidence range is established as a suitable measure for the precision and accuracy of the method. The most critical, legal, and technical issue of quantitative analyses of binary wool/specialty fiber blends is the requirement of 3 weight-% accuracy. This accuracy is not consistently reached with the current analytical protocol. that is. for 50:50 blends, though the course of the analysis already operates at its feasible technical and economical limits. Extended analysis protocols are investigated showing the require ments for meeting this pre-set accuracy. The results show that a substantially higher number of diameter measurements for the fiber components and a substantial increase in the number of identified fibers are required for routine analysis, which is beyond the reach of the current operator-based and thus rather tedious methodology.
Optimal Pick-up Locations for Transport and Handling of Limp Materials
Authors: Lankalapalli Shrinivas , Eischen Jeffrey W.
Published: March 2008

Pick-up locations are obtained on strips of limp material that minimize a measure of deformation (strain energy). The strips are modeled as continuous beams subjected to a uniformly distributed load using small and large deflection beam theories. Pick-up locations correspond to n support locations of the continuous beam. Strain energy is computed from a finite element solution, and optimal locations are obtained by solving unconstrained and bound constrained optimization problems. Results are in terms of a nondimensional number that characterizes the flexibility of the beam and are applicable to a wide range of limp materials. Some results for fabric strips are also presented.
Crosslinking of Cotton Cellulose in the Presence of Alpha-Amino Acids
Authors: Wang Tzy-Jian , Chen Jui-Chin , Chen Cheng-Chi
Published: March 2008

We have used alpha-amino acids (aspartic acid and glutamic acid) to join with dimethyloldihydroxyethyleneurea (DMDHEU) as crosslinking agents, and have found that at a given resin concentration, the wet crease recovery angle (WCRA) and tensile strength retention (TSR) values of the treated fabrics are in the order of DMDHEU- glutamic acid > DMDHEU-aspartic acid > DMDHEU; however, the dry crease recovery angle (DCRA) values are in the inverse rank. Nitrogen content and wicking height (wH) values for the various finished fabrics rank as DMDHEU-aspartic acid > DMDHEU- glutamic acid > DMDHEU. We have also found that the WCRA and DCRA of DMDHEU- alone treated fabrics are lower than those of the DMDHEU-alpha-amino-acid treated fabrics, and are ranked as DMDHEU-glutamic acid > DMDHEU-aspartic acid > DMDHEL' alone at a given TSR. The reaction between the —OH of DMDHEU and the amino and acid groups of alpha-amino acids in a pad-dry-cure process are confirmed by IR spectra. Surface distribution of the crosslinking agent on the finished fabrics is similar for DMDHEU alone and DMDHEU-alpha-amino acid.
Effect of Fiber Arrangement on the Mechanical Properties of Thermally Bonded Nonwoven Fabrics
Authors: Lin Jia-Horng , Xu Zhan-Hong , Lei Chen-Hwan , Lou Ching-Wen
Published: March 2008

Anisotropy is important to the structure and application of nonwoven fabrics. The arrange ment of the fibers and their orientation distribution are related to the mechanical structure of the web. In this study, we used a doffer of the roller card accompanied by a random roller to produce nonwoven fabrics. Partial random fiber arrangement is obtained by transferring the fibers on the rollers. As a result, the ratios of tensile and tearing strengths of the random web are below 3.0 and above 0.5, respectively. We can use this novel random arrangement of fibers in webs to improve the anisotropy of nonwoven fabrics.
Fiber Migration and Twist Radial Distribution in Rotor Spun Yarns
Authors: Hongwei Zhang  , Dongsheng Chen  , Yabo Wan
Published: March 2008

In this study, using a tracer fiber technique, the three dimensional trajectory of a tracer fiber in a rotor spun yarn is tested with the Questar Hi-scope video microscope system. Measuring the half pitch and maximum height of a bow-shaped segment along the spatial helix tracer fiber, the twists of any radial position are calculated. The results show that the twists distribute unevenly along the radial direction of the rotor spun yarn. A quadratic parabola model for twist radial distribution in rotor spun yams is revealed by polynomial regression analysis. The migration coefficient of a random tracer fiber is also obtained. The results may provide a foundation for further study of the structure and mechanical properties of rotor spun yarns.
Continuous Spun-Like Textured Yarn Processed with Various Plied Filaments and Different Stages of Emery Wheels
Authors: Lei Chen-Hwan
Published: March 2008

A new rotor twister is used to fabricate spun-like filament yarns. The raw material, draw-textured yarn (DTY), becomes as the core yarn and the wrapping yarn. During twisting, the core yarn passes through a pair of emery wheels to make the surface hairy. In this experiment, the rotor speed, twist multiplier, number of emery wheels, and denier of the DTY are varied. The effects of these parameters on tenacity, elongation, and hairiness numbers are examined and discussed. Reducing the number of emery wheels increases hairiness but reduces tenacity and elongation. The twist multiplier influences both tenacity and elongation. Increasing the twist multiplier reduces the hairiness numbers but increases yarn strength. In addition, increasing the speed of the emery wheels under fixed processing conditions increases hairiness but also reduces the tenacity and elongation of the spun-like filament yarns.
Physical Properties of Surface Oxidized Wool
Authors: Ma B. , Zheng C. , Sun R.
Published: March 2008

A wool surface is oxidized with potassium permanganate in saturated salt solutions. The surface patterns, breaking strength, friction coefficient, and electrical resistance of oxi dized and un-oxidized wool are then examined, and the static electricity in two resulting fabrics is investigated. Changes in the wool surface have a significant effect on its physical properties.
A New Approach to UV-Blocking Treatment for Cotton Fabrics
Authors: Xin J.H. , Daoud W.A. , Kong Y.Y.
Published: March 2008

In this study, a new approach to a uv-blocking treatment for cotton fabrics is developed using the sol-gel method. The treatment forms a thin layer of titania on the surface of cotton fibers, and the treated fabrics show much improved protection against UV radiation. with a UPF factor of 50+ or excellent protection according to the Australian/New Zealand standards. The treated fabrics are also tested for washfastness. The results show that the excellent uv protection rating of the treated fabrics can be maintained even after 55 home launderings, indicating a high level of adhesion between the titania layer and the cotton. A bursting strength test of the treated fabrics shows no adverse effect from the treatment.