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1.
A vertebral cage is a hollow medical device which is used in spine surgery. By implanting the cage into the spine column,
it is possible to restore disc and relieve pressure on the nerve roots. Most cages have been made of titanium alloys but they
detract the biocompatibility. Currently PEEK (polyether ether ketone) is applied to various implants because it has good properties
like heat resistance, chemical resistance, strength, and especially biocompatibility. A new shape of vertebral cage is designed
and injection molding of PEEK is considered for production. Before injection molding of the cage, it is needed to evaluate
process conditions and properties of the final product. Variables affecting the shrinkage of the cage are considered, e.g.,
injection time, packing pressure, mold temperature, and melt temperature. By using the numerical simulation program, MOLDFLOW,
several cases are studied. Data files obtained by MOLDFLOW analysis are used for stress analysis with ABAQUS, and shrinkage
and residual stress fields are predicted. With these results, optimum process conditions are determined. 相似文献
2.
Soo Jin Baek Seong Yun Kim Seung Hwan Lee Jae Ryoun Youn Sung Hee Lee 《Fibers and Polymers》2008,9(6):747-754
In order to investigate effects of injection molding conditions on viscoelastic behavior and thermal deformation of film insert
molded (FIM) parts, injection molding was performed with various conditions such as injection speed, melt temperature, and
packing time. It was shown that variation of the warpage was decreased monotonically with increasing injection speed and exhibited
a bell-shaped curve as a function of melt temperature. Warpage variation was not affected by the packing time significantly
and the proportional relationship between warpage of the film insert molded part and shrinkage of the injection molded part
without film was observed. The FIM specimens produced with unannealed films showed the warpage reversal phenomenon (WRP) during
annealing and the magnitude of reversed warpage was affected significantly by the injection parameters and the extent of thermal
shrinkage of the unannealed film. Warpage of the FIM specimen was predicted by three dimensional numerical flow and stress
analyses and the predicted values showed a good agreement with the experimental results. 相似文献
3.
Choon Gil Lee 《Fibers and Polymers》2006,7(1):51-56
Power net fabric is one of the highly extensible two-way fabrics. Power net structure shows special characteristics in the
wearing of final functional clothes. This research evaluated effects of treatment temperature on proportional extensibility
and shrinkage ratio of spandex at a given wale length. As treatment temperature increased, extensibility increased proportionally
to the standard length of the sample and the shrinkage ratio in the direction of course and wale increased. The pulling-out
length increased proportionally to the standard length of the sample. However it was affected by the effect of treatment time
and temperature due to the thermal properties of spandex filament yarn. 相似文献
4.
Jinho Park Sung Chan Lim Jong Sung Won Seung Goo Lee Wan Gyu Hahm Jong Kyoo Park Young Gyu Jeong 《Fibers and Polymers》2016,17(6):827-835
We report the isothermal and non-isothermal crystallization kinetics and associated transcrystalline morphological features of polyarylate(PAR)/nylon6 islands-in-a-sea fibers, where 74 PAR islands serve as reinforcing fibers and nylon6 sea component acts as a semicrystalline matrix in final thermoplastic composites. The temperature-dependent polarized optical microscopic images obtained during a cooling process exhibit that the melt-crystallization is dominated by the interfacial crystallization of nylon6 on the surface of PAR fibers, leading to developing a transcrystalline structure. From the isothermal and non-isothermal melt-crystallization analyses of the islands-in-a sea fiber by using differential scanning calorimetry and the Avrami equation, the overall crystallization rates of the nylon6 sea component in the islands-in-a-sea fiber are found to be highly accelerated by the heterogeneous nucleating effect of the PAR island fibers. In addition, it is revealed that the isothermal and non-isothermal melt-crystallization kinetics of the nylon6 in the islands-in-a-sea fibers consists of two different mechanisms of the primary crystallization owing to the interfacial crystallization and the secondary crystallization due to the bulk crystallization. 相似文献
5.
为了解冻害对不同基因型稻茬小麦苗期幼茎细胞结构的影响,选用皖麦50(半冬性品种)、皖麦48(弱春性品种)和郑麦9023(春性品种)为材料,在低温条件下连续用显微镜观测幼茎分蘖节薄壁细胞质壁分离变化情况。结果表明,在低温天气发生的初期,三个品种只发生了轻微的质壁分离,回暖后可恢复。当0℃以下低温持续10d以上时,质壁分离现象加重,皖麦48和郑麦9023分蘖节薄壁细胞原生质体出现不规则收缩,导管和筛管破裂,细胞失水收缩率最高达到30%左右,明显高于皖麦50。不同品种细胞失水收缩最大值均出现在连续低温之后,与最低温度出现时间不一致。 相似文献
6.
This paper is aiming to develop high shrinkable differential shrinkage and mixed fibre nylon composite yarns by applying the
high shrinkable polyester manufacturing technology. The wet and dry thermal shrinkages and mechanical properties of developed
nylon composite yarns are measured and discussed with processing factors in the spinning and texturing processes. And the
effects of the processing factors on the physical properties of high shrinkable nylon composite yarns are investigated. For
this purpose, twenty seven nylon 30d/12f SDY were prepared with variation of spinning temperature, 2nd godet roller temperature
and draw ratio on the spinning machine. The optimum spinning condition which showed maximum wet thermal shrinkage and stress
was determined and high shrinkable nylon 30d/12f SDY spun under this optimum condition used as a core and three kinds of regular
nylon filaments used as sheath were processed on the texturing machine with variation of 1st and 2nd heater temperatures.
The optimum texturing process condition was decided through analysis of dry thermal shrinkage of these core and sheath nylon
filaments. Finally, high shrinkable differential shrinkage and mixed fibre nylon composite yarns were made under the optimum
texturing condition on the texturing machine, its wet thermal shrinkage was 13.8 %, which was much more higher than that of
regular nylon composite yarns. The differential shrinkage effect of the developed nylon composite yarns was found in the yarn
surface and cross section profiles by microscope and SEM. 相似文献
7.
Residual stresses were predicted by a flow analysis in the mold cavity and residual stress distribution in the injection molded
product was measured. Flow field was analyzed by the hybrid FEM/FDM method, using the Hele Shaw approximation. The Modified
Cross model was used to determine the dependence of the viscosity on the temperature and the shear rate. The specific volume
of the polymer melt which varies with the pressure and temperature fields was calculated by the Tait’s state equation. Flow
analysis results such as pressure, temperature, and the location of the liquid-solid interface were used as the input of the
stress analysis. In order to calculate more accurate gap-wise temperature field, a coordinate transformation technique was
used. The residual stress distribution in the gap-wise direction was predicted in two cases, the free quenching and the constrained
quenching, under the assumption that the shrinkage of the injection molded product occurs within the mold cavity and that
the solid polymer is elastic. Effects of the initial flow rate, packing pressure, and mold temperature on the residual stress
distribution was discussed. Experimental results were also obtained by the layer removal method for molded polypropylene. 相似文献
8.
《Journal of Cereal Science》1999,29(3):217-226
An experimental method is reported for extensional measurements on wheat flour doughs in contraction flow geometry. In this method the transient stress under constant extension rate was measured, followed by stress relaxation measurement after cessation of flow. Four different wheat cultivars (with large differences in bread volume) were used to evaluate the usefulness of the method and to find how different parameters relevant to baking quality could be extracted from the data. The plot of transient viscosity against time showed the effect known as strain hardening, appearing at a Hencky strain roughly independent of the strain rate but differing between the wheat varieties. The relaxation rate curves for the four wheat varieties were similar except at the highest strain rate, 7·40 s−1. It was decided in the following case study to use the highest strain rate, 7·40 s−1and to extract three parameters from the stress growth plot and three parameters from the stress relaxation rate plot. In the case study, flours of 17 wheat varieties were mixed in the Mixograph to maximum resistance before being subjected to the contraction flow measurement. The six parameters extracted from each wheat flour dough measurement, together with the corresponding protein content, Zeleny value, and bread volume, were evaluated by multivariate analysis. A model for predicting the bread volume from the contraction flow parameters explained 94·6% of the variation in bread volume, while a model with Zeleny values and protein contents included explained 97·2%. 相似文献
9.
温度胁迫下宝莲灯的生理及光合特性 总被引：2，自引：0，他引：2
以两年生宝莲灯苗为试验材料,利用植物培养箱对宝莲灯植株进行温度处理,研究不同温度对宝莲灯叶片生理及光合特性的影响。结果表明：与对照相比,高温胁迫下宝莲灯叶片的相对电导率、过氧化氢酶（CAT）活性及可溶性蛋白、游离脯氨酸（Pro）、丙二醛（MDA）含量随着温度的升高呈不同程度的增加,而叶绿素含量显著减少,过氧化物酶（POD）、超氧化物歧化酶（SOD）活性呈下降趋势;低温胁迫下相对电导率、Pro、MDA含量随着温度的下降呈上升趋势,可溶性蛋白、叶绿素含量、过氧化氢酶（CAT）活性下降趋势不明显,POD、SOD活性显著降低;随着温度的升高或降低,宝莲灯叶片的光合速率（Pn）、气孔导度（Gs）、水分利用率（WUE）均呈下降趋势,而胞间CO2浓度（Ci）呈先降低后升高;蒸腾速率（Tr）却随着温度的下降而降低。高温胁迫引起的相对电导率、MDA含量的变化幅度明显小于低温胁迫,而POD、SOD活性高于低温胁迫。说明高、低温胁迫均抑制了宝莲灯的光合作用,宝莲灯对低温胁迫相对较敏感。研究结果对宝莲灯的栽培管理具有指导意义。 相似文献
10.
Polyacrylonitrile (PAN) precursor fibers were modified for different periods of time using hydrogen peroxide aqueous solution. A variety of tests were employed to characterize the fibers. The modification could induce cyclization and oxidation in the precursor fibers, as reflected by the changes in length and diameter of the fibers, and the results of Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Compared with the unmodified fiber, the modified fibers released less heat during a heating process similar to stabilization of PAN precursor fiber. Also, the modified fibers showed lower characteristic temperatures on differential scanning calorimetry (DSC) thermograms, and lower onset temperature of weight loss on thermal gravimetry (TG) curves. The modified fibers had more surface defects and hence exhibited lower tenacity and tensile modulus. Compared with the unmodified fibers, however, the modified fibers had smoother surface and fewer defects after stabilization. The strain decreased with increasing temperature under a constant tension for all the fibers. At the temperatures above 200 °C, the shrinkage of the fibers decreased with the increase of modification time, because a certain degree of cyclization and oxidation occurred in modified fibers, making them shrink less in the temperature range equivalent to stabilization. 相似文献
11.
The effect of hydration (in the range of aw 0.981–0.090) on changes of macroscopic and mechanical features of triticale snacks produced in different conditions (feed moisture - 16 and 20%; extrusion temperature - 135 and 175 °C) was analysed. Changes of snacks depended both on the hydration level and the extrusion process conditions.As a result of storage at the highest hydration level (aw = 0.981) contraction of snacks was observed. The shrinkage was more pronounced in case of extrudates obtained from raw material containing 16% of water regardless of the extrusion temperature. The hardness of extrudates depended both on the feed moisture and hydration. Samples obtained from the raw material containing 20% moisture were harder than those prepared at the feed moisture of 16%. Based on the results of molecular dynamics study by low field NMR technique, a model of hydration was developed and critical hydration value of extruded snacks was calculated. Higher values of the critical hydration were obtained for snacks extruded at temperature 135 °C than for those obtained at 175 °C. The feed moisture level affected critical hydration values to a lesser extent. Obtained results suggest that the state of water in extrudates depends on extrusion process conditions. 相似文献
12.
PET yarns textured at different texturing conditions were treated with superheated steam or dry heat at different temperatures
for different times. The effects of the treatment conditions on the thermomechanical and structural changes of the yarn were
examined by shrinkage, X-ray diffraction and birefringence measurements. With increase in superheated steam temperature, the
crystalline orientation factor and birefringence decreased, whereas crystal size increased. Dry heat treatment had a smaller
effect on shrinkage and structural properties in comparison with superheated steam treatment. The additional shrinkage after
texturing process was investigated. The effect of heat-setting in both media was more significant at 200 °C. The time dependence
of the properties was not linear. 相似文献
13.
Onweluzo JC Obanu ZA Okwandu MC 《Plant foods for human nutrition (Dordrecht, Netherlands)》2004,59(4):137-141
Raw beef burgers containing graded levels (0.25, 0.5, 0.75, and 1.0%) of polysaccharide gums extracted from Detarium microcarpum (DM) and Mucuna flagellipes (MF) were produced. Unstabilized beef burgers and beef burgers containing gum tragacanth (TR) were also produced simultaneously to serve as control. The raw beef burgers were evaluated for selected physicochemical and sensory properties so as to assess the stabilization potentials of DM and MF polysaccharide gums relative to the conventional TR. Beef burgers containing the polysaccharide gums had significantly (P<0.05) lower shrinkage, higher water holding capacity (WHC), and better stability under ambient conditions (27±1°C and RH 90.6%) then the unstabilized burgers. Among the stabilized burgers, DM gum burgers had lower (P0.05) shrinkage and higher WHC than MF and TR gums burgers. All the gum-stabilized beef burgers required 9–26% higher compression force indicating a less friable product than the unstabilized burgers. At 0.25 and 0.5% levels of gum incorporation DM gum burgers had comparable compression force with TR gum burgers and this was lower (P0.05) than the compression force of MF gum burgers. Sensory panel results indicated a lower score for finger feel in gum-stablized burgers than the unstabilized burgers. DM and TR gum burgers had comparable scores with TR gum burgers in all the sensory attributes tested. Overall acceptability score showed that all the gum-stabilized beef burgers were acceptable. It was evident from the study that polysaccharide gums from DM and MF seeds can serve as effective stabilizers in beef burgers without adverse effect on the quality of the product. 相似文献
14.
Using statistical experimental design, the effects of multi-stage hot drawing process on thermal shrinkage and crystallographic
order of linear aliphatic-aromatic co-polyester fibres were statistically analyzed. Thermal shrinkage and fullwidth half-maximum
(FWHM) of an X-ray scattering profile of the fibres have been quantitatively assessed, and the direction of increasing or
decreasing the significant process parameters has been characterized. It has been found that the number of drawing stages,
drawing temperature and relaxing stage ratio affect the shrinkage and crystallographic order together. Plate temperature and
the interaction between drawing stages and drawing temperature or drawing ratio have an effect on thermal shrinkage; Spin
finish application and relaxing temperature have an effect on crystallographic order. The data analysis has been characterized
with regard to the relationship between the studied factors statistically analyzed and the scientific reasons suggested. Factorial
statistical analysis simulates the combination of drawing process parameters and the selected as-spun environmentally friendly
biodegradable fibre. 相似文献
15.
Gelatinized waxy and normal corn starches at various concentrations (20–50%) in water were stored under temperature cycles of 4°C and 30°C (each for 1 day) up to 7 cycles or at a constant temperature of 4°C for 14 days to investigate the effects of temperature cycling on the retrogradation of both starches. Compared to starches stored only at 4°C, both starches stored under the 4/30°C temperature cycles exhibited smaller melting enthalpy for retrogradation (ΔHr), higher onset temperature (To), and lower melting temperature range (Tr) regardless of the starch concentration tested. Fewer crystallites might be formed under the temperature cycles compared to the isothermal storage, but the crystallites formed under temperature cycling appeared more homogeneous than those under the isothermal storage. The effect of starch content on the retrogradation was greater when the starch gels were stored under cycled temperatures. The reduction in ΔHr and the increase in conclusion temperature (Tc) by retrogradation under 4/30°C temperature cycles became more apparent when the starch concentration was lower (20 or 30%). Degree of retrogradation based on melting enthalpy was greater in normal corn starch than in waxy corn starch when starch content was low. 相似文献
16.
This article reports the outcome of a study conducted for examining the effect of heat setting parameters on some properties of PLA knitted fabric. Three heat setting parameters, namely, treatment time, treatment temperature, and tension, were considered for optimizing the heat setting process with fabric shrinkage after dyeing and color yield as the evaluation factors. Experimental results revealed that lower shrinkage and higher color yield can be achieved when: (i) heat setting time = 60 s; heat setting temperature=130 oC; and tension=0%. After that, the PLA knitted fabric was treated under the optimum heat setting condition and was dyed with 1% depth disperse dye, which produced a better dyeing result. However, the handle of the heat set PLA knitted fabric, as measured by Kawabata Evaluation System for Fabric (KES-F), became stiffer and more resistant to shearing movement and had worse drape and bending recovery ability, while the appearance became fluffier and rougher. 相似文献
17.
以650 ℃下制备甘蔗渣生物质炭（BC650）为研究对象,在模拟自然条件下,在BC650上负载环境中常见的溶解性有机质（DOMs）即小分子没食子酸（GA）和大分子黄腐酸（HA）,并对其性质进行表征;再以典型抗生素土霉素为目标污染物,探究外源DOMs耦合生物质炭对抗生素的吸附性能的影响。结果表明,DOMs的负载提高了生物质炭的比表面积,生物质炭的表面化学性质发生改变;预载DOMs后,生物质炭对土霉素的吸附能力明显降低,且GA负载的抑制作用较HA更为显著,就平衡吸附量而言,HA处理后其下降了10%,而GA的处理使其降低了30%,DOMs的预载对生物质炭吸附抗生素的影响可能是由DOMs处理改变了生物质炭的表面化学性质而致;DOMs负载前后生物质炭对土霉素表现出非线性吸附,氢键作用为主要吸附机制。所得结果可为生物质炭在抗生素污染控制中的实际应用提供重要的理论依据。 相似文献
18.
在人工气候室采用盆栽模拟水稻生殖生长阶段的高温胁迫热害,研究不同时期及不同持续时间的高温胁迫对水稻产量及产量特征的影响。结果表明,超级杂交水稻Y两优1号与常规优质稻桂育9号,以抽穗扬花期计为0 d,分别在-9 d、-6 d、-3 d、0 d、3 d、6 d、9 d、12 d不同生育时间遭遇高温胁迫时的颖花结实率变化趋势相当,抽穗扬花期当天遭遇高温胁迫处理的颖花结实率最低,且随胁迫处理时间的延长,损害加重;在持续处理5 d的条件下,-3 d期的高温处理对颖花结实率的降低也很严重,甚至低于抽穗扬花当天高温胁迫处理3 d时的结实率。不同时期的高温胁迫处理的损害在品种间存在显著差异,选择耐热性较强的品种有利于应对局部生态点易发生的热害天气。 相似文献
19.
Germination responses of the halophyte Chloris virgata to temperature and reduced water potential caused by salinity,alkalinity and drought stress 
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下载免费PDF全文 Chloris virgata is considered a useful grass species for grassland restoration in northern China. However, little information exists concerning the germination responses of this species to temperature and water potential caused by stress conditions. Experiments were conducted in growth chambers to assess the effect of temperature, salinity, alkalinity, drought and the interactions of temperature and stress on seed germination. Seeds were germinated at three diurnal temperature regimes, with four water potentials in NaCl, NaHCO3 and PEG solutions. Results showed that optimal germination under stress occurred at 15–25 °C, and germination percentages and rates were inhibited by either an increase or decrease in temperature from the optimal temperature. The inhibitory effects of the low water potential caused by salinity and drought on germination were greater at 25–35 °C, but seeds were subjected to more stress despite the relatively higher water potential because of the alkalinity at this temperature. The recovery percentage under salinity was highest at ?1·2 MPa at 15–25 °C, and more than 80% of seeds also germinated at this water potential after they were transferred from drought stress. However, seeds lost their viability in higher alkalinities under all temperatures, and at 25–35 °C, there was lower recovery percentage under stress. Results suggest that salinity, alkalinity and drought stress have different impacts on seed germination, and the tolerance to stress of C. virgata seeds is affected by the interactions of temperature and water potential caused by salinity, alkalinity and drought. Chloris virgata shows potential utility as a promising grass species in salinity–alkalinity and drought‐stressed environments. 相似文献
20.
A finite element method is employed for a flow analysis of the melt spinning process of a non-circular fiber, a PET(polyethylene
terephthalate) filament. The flow field is divided into two regions of die channel and spin-line. A two dimensional analysis
is used for the flow within the die channel and a three dimensional analysis for the flow along the spin-line. The Newtonian
fluid is assumed for the PET melt and material properties are considered to be constant except for the viscosity. Effects
of gravitation, air drag force, and surface tension are neglected. Although the spin-line length is 4.5 m, only five millimeters
from the spinneret are evaluated as the domain of the analysis. Isothermal and non-isothermal cases are studied for the flow
within the die channel. The relationship between the mass flow rate and the pressure gradient is presented for the two cases.
Three dimensional flow along the spin-line is obtained by assuming isothermal conditions. It is shown that changes in velocity
and cross-sectional shape occur mostly in the region of 1mm from the die exit. 相似文献