热处理工艺对车用减震板组织和性能的影响          下载免费PDF全文

徐晶晶 《唐山学院学报》2020,32(6):42-45

通过对不同热处理和时效处理工艺的Mn-Cu合金的X射线分析、微观组织分析和阻尼性能测试,分析了热处理冷却方式、时效处理时间对合金组织和阻尼性能的影响。研究表明,时效处理不会产生新相,随着时效处理时间的增加,晶粒尺寸增大,阻尼性能提高,但超过一定时间,阻尼性能反而降低,其中时效处理8 h能够获得最佳的阻尼性能。  相似文献   

安定对肉仔鸡生长性能及抗热应激能力的影响     

应如海  宁康健  钟德山 《安徽科技学院学报》1998,(4)

用120只AA肉仔鸡,分成四组（CK、Ⅰ、Ⅱ、Ⅲ组）分别喂以含安定0ppm、1ppm、2ppm、4ppm的日粮,经21天饲养,试验Ⅰ、Ⅱ、Ⅲ组比对照组摄含量分别提高4.30％、6.95％和7.88％．总增重分别提高7.42％、13.53%和17.71%,饲料转化率分别提高3.0%、6.1%和9.1%。通过试验观察,安定具有一定的抗热应激的作用,在35-37℃的环境中,Ⅰ、Ⅱ、Ⅲ组和对照组的采食量分别下降35%、31％、8%和46％,对照组下降最为明显。  相似文献   

伤寒杆菌70KD热休克蛋白的抗肿瘤作用     

王笑虹 王鸿冯仲珉  况红星 《大连大学学报》1999,20(6):80-82

纯化伤寒杆菌HSP70,观察其对小鼠S180肿瘤细胞的抑制作用,对荷瘤小鼠连续皮下注射伤寒杆菌HSP70,每只小鼠每天注射100μ／mL,的伤寒杆菌HSP70．5mL,每天一次．9天后处死小鼠,剥离肿瘤,分别称量实验组与对照组小鼠肿瘤的重量．结果表明,伤寒杆菌HSP70能明显抑制小鼠S180肿瘤细胞在小鼠体内的生长．  相似文献   

热风炉改造及相关问题分析     

苏凌均 《辽宁科技学院学报》2005,7(2):19-20

旋流顶燃式热风炉与内燃式热风炉相比在风温水平上,提高了一个档次,在整体结构上旋流顶燃式热风炉的蓄热面积更大,燃烧更充分,更均匀.在热风炉的日常维护和检修上,旋流顶燃式热风炉避免了燃烧室内部掉砖阻碍煤气畅通以及煤气泄漏等现象,减少了检修量,有利于安全生产.  相似文献   

拟南芥热激蛋白HSP70基因片段克隆实验体系的建立     

郭丽红  杨晓虹  刘开庆  袁燕 《昆明师范高等专科学校学报》2009,31(6):46-48

以拟南芥为材料,对热激蛋白HSP70基因片段进行了克隆研究,获得了最佳的分子克隆实验体系．首先提取拟南芥总DNA,接着在热激蛋白HSP70编码区设计引物,扩增出HSP70编码区的片断,再将HSP70编码区的片断加上具有EcoRⅠ酶切位点双链的人工接头,通过EcoRⅠ对其进行酶切．再与经过EcoRⅠ酶切并已经去磷酸化的PUC19载体通过T4连接酶进行连接,然后将连接产物置人到感受态大肠杆菌细胞中（即转化）,并让这种细胞在含有Amp＋／IPTG／X—Gal的LB培养基上生长．挑取培养基上蓝白斑中的白斑,进行质粒DNA提取,通过酶切质粒DNA,从而初步判断目的片段已被克隆．  相似文献   

New method of improving parts accuracy by adding heat balance support in selective laser sintering     

Bing Liu  Li-chao Zhang  Jian-hua Mo  Bo Qian 《浙江大学学报(A卷英文版)》2009,10(3):361-369

In order to improve parts accuracy, a method of adding heat balance support （HBS） was proposed, and the detailed algorithm for generating HBS was developed. A number of experiments and a comparison between similar softwares, showed that the algorithm is efficient and feasible. Moreover, different features of riBS were studied for different kinds of materials, such as PS and nylon. The research findings indicate that automatically adding HBS can significantly improve the accuracy of the parts, and that the algorithm for generating HBS is efficient and precise.  相似文献   

Prophylactic effect of hot pack on symptoms of eccentric exercise-induced muscle damage of the wrist extensors     

《European Journal of Sport Science》2013,13(5):443-453

Abstract

This study investigated whether hot pack treatment could provide prophylactic effects on muscle damage induced by eccentric exercise of the wrist extensors. Twenty-eight healthy men (age 21±1 years, weight 65±16 kg, height 171±6 cm) were randomly placed into hot pack (n = 14) and control (n = 14) groups. All participants performed an exercise consisting of 300 maximal eccentric contractions of the wrist extensors of the non-dominant arm using an isokinetic dynamometer. A hot pack was applied for 20 min to the wrist extensors of the exercised arm before the exercise for the hot pack group. The control group received no treatment before the exercise. Measured variables included pain intensity assessed by a visual analogue scale and a modified Likert's scale, cold thermal pain threshold, pressure pain threshold (PPT), range of motion in active wrist flexion (ROM-AF) and extension (ROM-AE), range of motion in passive wrist flexion (ROM-PF) and extension (ROM-PE), grip strength, and wrist extension strength. Changes in these variables before, immediately after, and 1 to 8 days following the exercise were compared between groups by a two-way repeated measures ANOVA. All outcome measures from both groups (except for the cold thermal pain threshold of the hot pack group) demonstrated a significant change within the first 2–3 days following exercise. Significant differences between groups were only found at a single point in time for PPT, ROM-PF, ROM-PE and ROM-AE, and the changes were smaller for the hot pack group in comparison to the control group. These results suggest that the prophylactic effects of hot pack treatment on eccentric exercise-induced muscle damage of the wrist extensors are limited.  相似文献   

The effects of substrate and fluid provision on thermoregulatory and metabolic responses to prolonged exercise in a hot environment     

Stuart D.R. Galloway  Ronald J. Maughan 《Journal of sports sciences》2013,31(5):339-351

A high ambient temperature reduces the capacity to perform prolonged exercise. Total carbohydrate oxidation is less, and thus glycogen depletion is not limiting. Fluid ingestion in the heat should, therefore, focus on maintenance of hydration status rather than on substrate provision. Six healthy males cycled to exhaustion at 60% of maximum oxygen consumption (VO 2max ) with no drink, ingestion of a 15% carbohydrate-electrolyte drink (1.45 - 0.29 litres) or ingestion of a 2% carbohydrate-electrolyte drink (3.12 - 0.47 litres). The ambient temperature was 30.2 - 0.6°C (mean - s ), with a relative humidity of 71 - 1% and an air speed of approximately 0.7 m.s -1 on all trials. Weighted mean skin temperature, rectal temperature and heart rate were recorded and venous samples drawn for determination of plasma volume changes, blood metabolites, serum electrolytes and osmolality. Expired gas was collected to estimate rates of fuel oxidation. Exercise capacity was significantly ( P ? 0.05) different in all trials. The median (range) time to exhaustion was 70.9 min (39.4-97.4 min) in the no-drink trial, 84.0 min (62.7-145 min) in the 15% carbohydrate trial and 118 min (82.6-168 min) in the 2% carbohydrate trial. The 15% carbohydrate drink resulted in significantly ( P ? 0.05) elevated blood glucose and total carbohydrate oxidation compared with the no-drink trial. The 2% carbohydrate drink restored plasma volume to pre-exercise values by the end of exercise. No differences were observed in other thermoregulatory or cardiorespiratory responses between trials. These results suggest that fluid replacement with a large volume of a dilute carbohydrate drink is beneficial during exercise in the heat, but the precise mechanisms for the improved exercise capacity are unclear.  相似文献   

Fluid ingestion and exercise hyperthermia: Implications for performance,thermoregulation, metabolism and the development of fatigue     

Derek Kay  Frank E. Marino 《Journal of sports sciences》2013,31(2):71-82

The development of fatigue during exercise and the subsequent onset of exhaustion occur earlier in the heat than in cooler environments. The underlying mechanisms responsible for the premature development of fatigue in the heat have yet to be clearly identified. However, the proposed mechanisms include metabolic, cardiovascular and central nervous system perturbations, together with an elevated core temperature. Fluid ingestion is one of three strategies that have been shown to be successful in enhancing the performance of endurance exercise in the heat, with the other interventions being precooling and acclimatization. However, like the development of fatigue in the heat, the mechanisms by which fluid ingestion allows for improved exercise performance remain unclear. We propose that fluid ingestion enhances exercise performance in the heat by increasing the heat storage capacity of the body. We suggest that the thermoregulatory, metabolic and cardiovascular alterations that occur as a result of this increased heat storage capacity contribute to performance enhancement when fluid is ingested during exercise heat stress.  相似文献   

Thermoregulatory responses during prolonged upper body exercise in cool and warm conditions     

M.J. Price  I.G. Campbell 《Journal of sports sciences》2013,31(7):519-544

The thermoregulatory responses of upper-body trained athletes were examined at rest, during prolonged arm crank exercise and recovery in cool (21.5 ± 0.9°C, 43.9 ± 10.1% relative humidity; mean ± s) and warm (31.5 &± 0.6°C, 48.9 - 8.4% relative humidity) conditions. Aural temperature increased from rest by 0.7 ± 0.7°C (P ? 0.05) during exercise in cool conditions and by 1.6 ± 0.7°C during exercise in warm conditions (P ? 0.05). During exercise in cool conditions, calf skin temperature decreased (1.5 ± 1.3°C), whereas an increase was observed during exercise in warm conditions (3.0 ± 1.7°C). Lower-body skin temperatures tended to increase by greater amounts than upper-body skin temperatures during exercise in warm conditions. No differences were observed in blood lactate, heart rate or respiratory exchange ratio responses between conditions. Perceived exertion at 45 min of exercise was greater than that reported at 5 min of exercise during the cool trial (P ? 0.05), whereas during exercise in the warm trial the rating of perceived exertion increased from initial values by 30 min (P ? 0.05). Heat storage, body mass losses and fluid consumption were greater during exercise in warm conditions (7.06 ± 2.25 J·g^-1 ·°C^-1, 1.3 ± 0.5 kg and 1038 ± 356 ml, respectively) than in cool conditions (1.35 ± 0.23 J·g^-1·°C^-1, 0.8 ± 0.2 kg and 530 ± 284 ml, respectively; P ? 0.05). The results of this study indicate that the increasing thermal strain with constant thermal stress in warm conditions is due to heat storage within the lower body. These results may aid in understanding thermoregulatory control mechanisms of populations with a thermoregulatory dysfunction, such as those with spinal cord injuries.  相似文献