首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 296 毫秒
1.
拟订了带传动多目标优化设计的数学模型。采用正态模糊分布,将理想解和非劣解转化为目标函数值空间上的模糊子集,藉助于贴近度方法,从非劣解中找出了最贴近理想的最优解。  相似文献   

2.
建立了以增力倍数M、行程比C、空循环次数Z为目标函数的多目标优化计算的数学模型。采用惩罚函数法调用鲍威尔法进行优化运算,并藉助于模糊相似优先此法,从非劣解中找出最接近理想解的最优解。  相似文献   

3.
针对基本遗传算法容易陷入局部最优解的缺点,提出了一种求解全局最优解的变区域搜索遗传算法。该算法以上一代最优解为导向,在它所在的随机局部区域内搜索,以提高当代最优解附近的搜索密度,加快遗传算法的收敛速度。基于标准函数的仿真测试研究表明,本算法能有效地减小进化代数和提高最优解的精度,尤其适合维数较多的函数寻优。  相似文献   

4.
首先将文题转化为一个具有H∞性能和系统闭环极点位置约束的系统H2性能优化问题。进而通过引入一个辅助性能函数,将其转化成有一处矩阵方程约束的辅助性能函数的最小优化问题,并给出这个问题静态输出反馈控制器的解。  相似文献   

5.
本文提出的解法,是由两部份组成。先利用物理模型(力学系统)来求各个单目标的最优解,次最优解……,从而构成一个矩阵(解序表)T,然后从这个T中按本文列举的几种主观评价判据之一,求出在这一判据下的最满意解或满意解。它也适用于解决其它类似的多级系统之评价和决策。  相似文献   

6.
为了提高多目标粒子群算法(MOPSO)的收敛性和多样性,以及增加多目标粒子群算法的适用范围,提出了一种ε约束处理混合三点随机Gbest选择多目标粒子群(ε-TMOPSO)算法。采用一种全新的三点随机Gbest选择机制,用粒子与档案集中非支配解的欧氏距离最近、最远以及处于中间位置的3个粒子构建一个备选池,然后随机选择一个粒子作为Gbest,提高算法的收敛性和多样性;采用改进的带松弛阶段ε约束处理机制处理约束条件,在前期允许加入部分优秀的不可行解,提高算法跳出局部最优的能力;融入Sigmoid函数离散变量编码处理机制,使算法能够处理混合整数问题,增加算法的适用范围。通过测试函数仿真,与EM-MOPSO、NSGA2以及SNSGA算法进行对比,结果表明本文算法在收敛性和分布性上有一定的优势。将该算法应用于乙烯装置蒸汽动力系统优化中取得了较好的效果,进一步证明了该算法的有效性。  相似文献   

7.
利用期望值原理计算保费,以最大化消费者的投保效用为目标函数建立数学模型,对均衡状态下解的变化进行分析.结果表明:巨灾保险的有效需求随免赔额的增加而减少,随附加费率的减少而增加;最优的免赔额随消费者的财富增长而增长.  相似文献   

8.
提出了振动主动控制系统中最大主动阻尼耗能准则,以先准则为目标函数求解检测器和作动器的最优配置问题,为了获得全局最优解,引入了模拟退火(SA)算法,并对其进行了改进,对一离散的三自由度系统和连续梁系统中检测器和作动器的最优配置进行了数值计算和实验验证,计算结果与实验结果一致性很好,证明了所建立的准则和算法的可行性和实用性。  相似文献   

9.
本研究提出一种可将临床偏好量化为优先级列表,并在此基础上建立自动调整约束并生成该条件下优化解的IMRT多目 标优化方法。本优化方法由计划剂量学约束自动调整机制和约束下的基于体素权重因子的自动FMO模型嵌套组成。剂量约 束的自动调整需首先根据临床对各感兴趣区域剂量约束的重视程度提炼为约束优先级列表,后以列表为依据,分步对剂量约束 进行调整,使各约束随迭代进行时逐步达到最佳设置状态。剂量约束每调整1次,紧随调用基于体素权重因子的FMO模型,解 得满足当前约束的全局最优计划。为验证本优化方法的可行性与有效性,临床收集6例已治宫颈癌IMRT计划,使用本文方法 对其重新自动生成优化的计划,并比较原始(临床)计划和优化计划的质量,含计划DVH曲线和临床关注的剂量约束指征项的 具体数值,查看其计划质量提高成效。6例临床IMRT计划表明,使用本文方法生成的优化计划较原始计划可得到相当PTV覆 盖率、均匀性的同时,有效减少OAR受量,提高计划质量。其中,优化计划直肠的平均V45 从原始计划的(41.99±13.31)%降到 (32.55±22.27)%;膀胱的平均V45 从(44.37±4.08)%降到(28.99±15.25)%。计划优化过程可实现基本自动化。  相似文献   

10.
实际作业车间调度中多目标的动态优化更符合生产的需求。利用多目标优化问题的Pareto解集思想构建最大完工时间最小以及总拖期时间最小的数学模型,以事件驱动作为动态调度策略实现作业车间的动态调度。采用多目标蚁群算法优化启发式算法,并对算法的转移概率及全局信息素更新进行改进,加快算法的搜索收敛速度同时避免陷入局部最优。仿真实验证明,改进后的算法能实现Pareto前沿较好的均匀性与分布性,对双目标调度以及单个目标独自调度时的甘特图对比,表明双目标优化算法能更好地平衡各个目标的解。最后对急件插入以及机器故障两种动态事件进行仿真,验证了改进蚁群算法在实际动态调度中有较好的实现。  相似文献   

11.
Objective: To evaluatel the value of D-dimers in patients with acute aortic dissection (AAD). Methods: This study consisted of 16 patients with AAD and 27 non-AAD patients. Serum D-dimets were measured by Sta-Liatest D-DI immunoturbidimetric assay. Results: D-dimer level was higher (P < 0.001) in patients with AAD(7.91 ± 5.52 μg/ml) than that in non- AAD group(1.57±1.24 μg/ml). D-dimer was positive (>0.4 μg/ml) in all patients with AAD and in 10 control group patients (37%). Among patients with acute AAD, D-dimers tended to be higher in Stanford A than in Stanford B (8.67 ± 4.31 μg/ml vs. 3.24±1.27 μg/ml, P <0.01). D-dimer values tended to be higher in more extended disease(3.84 ± 1.65 μg/ml, 8.57 ± 3.58 μg/ml and 11.87 ± 5.69 μg/ml in thoracic aorta, thoracic and abdominal aorta, thoracic and abdominal aorta and iliacal arteries, respectively, P < 0.05 for both 8.57 ± 3.58 and 11.87 ± 5.69 vs. 3.84 ± 1.65 ). Including the control group into the analysis, we found a sensitivity of 100%, a negative predictive value of 100%, and a specificity of 66% and a positive predictive value of 64% for D-dimer in diagnosis of AAD in our patients with suspected AAD. Conclusion: D-dimer was elevated in patients with AAD. A negative D-dimer test result could be useful in excluding AAD.  相似文献   

12.
Objective: To set up a simple and reliable rat model of combined liver-kidney transplantation. Methods: SD rats served as both donors and recipients. 4℃ sodium lactate Ringer's was infused from portal veins to donated livers,and from abdominal aorta to donated kidneys, respectively. Anastomosis of the portal vein and the inferior vena cava (IVC) inferior to the right kidney between the graft and the recipient was performed by a double cuff method, then the superior hepatic vena cava with suture. A patch of donated renal artery was anastomosed to the recipient abdominal aorta. The urethra and bile duct were reconstructed with a simple inside bracket. Results: Among 65 cases of combined liver-kidney transplantation, the success rate in the late 40 cases was 77.5%. The function of the grafted liver and kidney remained normal. Conclusion: This rat model of combined liver-kidney transplantation can be established in common laboratory conditions with high success rate and meet the needs of renal transplantation experiment.  相似文献   

13.
Objective To observe blood pressure change with age in salt-sensitive teenagers whose salt sensitivity were determined by repeated testing.Methods Salt sensitivity was determined through intravenous infusion of normal saline combined with volume-depletion by oral diuretic furosemide in 55 teenagers. After five years, salt sensitivity was re-examined and subject blood pressure was followed up. Blood pressure changes in salt-sensitive teenagers were compared to that of non-salt sensitive teenagers over five years.Results After 5 years, the repetition rate of salt sensitivity determined by intravenous saline loading is 92.7%. In teenagers with salt sensitivity on the baseline, both the systolic blood pressure increments and increment rates were much higher than non-salt sensitive teenagers (12.7±12.1 mmHg vs. 2.8±5.2 mmHg, P< 0.01; 12.2%± 12.0% vs. 2.5% ±4.4%, P< 0.001,respectively). There was a similar trend for diastolic blood pressure (8.4 ± 6.4 mmHg vs. 3.7 ± 6.4 mmHg, P = 0.052; 13.2% ±10.6 % vs. 6.8%± 10.1%, P = 0.053, respectively).Conclusions Salt sensitivity determined by intravenous saline loading showed good reproducibility. Blood pressure increments with age were much higher in salt-sensitive teenagers than non-salt sensitive teenagers, especially in terms of systolic blood pressure.  相似文献   

14.
目的:评价使用安心颗粒对急诊经皮冠状动脉介入术(PPCI)术后生活质量的影响.方法:将160例接受PPCI的急性ST段抬高型心肌梗死患者随机分为安心颗粒组(术前顿服安心颗粒8.8g,术后安心颗粒4.4 g/次,每日2次)和对照组(仅接受基础药物治疗).所有患者均服用阿司匹林、氯吡格雷和阿托伐他汀.分别在入院时、出院前1d、出院后180 d时,应用心肌梗死多维度量表(MIDAS)、中文版SF-36评价量表对患者生活质量评分.并观察术后30 d以内的出血并发症、血小板减少症发生情况.结果:入院时和出院前1d,两组患者的心肌梗死MIDAS、SF-36量表评分比较无差异(P>0.05);出院后180 d时,与对照组比较,安心颗粒组MIDAS、SF-36评分明显减低(P<0.05);组内与入院时比较,两组出院前1d、出院后180 d时,MIDAS、SF-36评分均降低(P<0.05).两组患者在随访期间均无大量出血、少量出血、重度和极重度血小板减少症发生,安心颗粒组有4例、对照组有7例发生不明显出血(P>0.05).两组发生轻度血小板减少症的患者数比较无差异(P>0.05).结论:PPCI使用安心颗粒,能改善急性ST段抬高型心肌梗死患者的生活质量,且不增加出血风险.  相似文献   

15.
Objective:To investigate the influences of urapidil and nicardipine on rabbit sinus function,atrio-ventricular node function and hemodynamics.Methods:Thirty-two Angora's rabbits were selected and randomly divided into four groups.U1 group:urapidil 0.25 mg/kg;U2 group:urapidil 0.5 mg/kg;N1 group:nicardipine 10 μg/kg;N2 group:nicardipine 20 μg/kg.All these medicine were administrated within 30 seconds.Measurements were taken before and after the administration of urapidil or nicardipine for the following data:mean blood pressure(MAP),heart rate(HR),sino-atrial conduction time(SACT),maximal sinoatrial recovery time(SNRTmax)corrected sinus node recovery time(CSNRT),index of sinus node recovery time(SNRTI),Wenckebach A-V conduction frequency (WB),and P-R interval.Results:Significant MAP and HR changes were identified in all of the four groups before and after administration of both urapidil and nicardipine.No significant changes could be found in the rest of the parameters.Intergroup analysis showed that SACT and CSNRT of N1 and N2 groups were shorter than those of the U2 group(P<0.01);the MAP decreased(P<0.01)and the HR increased drastically(P<0.01).Conclusions:Neither urapidil(0.25 mg/kg,0.5 mg/kg)nor nicardipine(10μg/kg,20μg/kg)has any significant influence on rabbit sinus function or rabbit atrio-ventricular node function.Nicardipine could be a better choice than urapidil for parafunctional sinus node patients.  相似文献   

16.
Objective:To investigate the gene expression of osteoprotegerin(OPG) and osteoclast differentiation factor(ODF) in the bone tissue of patients with hip fracture due to osteoporosis. Methods:OPGmRNA and ODFmRNA in the bone tissue in 50 cases of osteoporosis sufferers(over 50 years old) with hip fracture(Observer Group) and 30 cases of hip facture sufferers with no osteoporosis(Control group) were analyzed with the Semi-Quantitative RT-PCR method. Results:The mRNA expressed of ODF, OPG were both high in the patients with hip fracture. In the control group, the expression of OPG mRNA was observed, while the expression of ODF mRNA was very slight. Conclusion:Aged patients contained all signals including OPG, ODF that are essential for inducing osteoclastogenesis and promoting bone resorption.  相似文献   

17.
Objective:To investigate the clinical features, pathological characteristics and immunophenotype of solid-pseudopapillary tumor of the pancreas(SPTP). Methods:Nine surgically treated cases of SPTP were retrospectively reviewed. Hematoxylin and Eosin(HE) staining and immunohistochemical staining were used to analyze all cases, and the general clinical data was collected. Results:Six patients were asymptomatic except for a palpable mass. Two patients complained of vague-epigastric pain. One patient appeared jaundice. The tumor was encapsulated and solid tissues alternately with cystic tissues. Histologically, the histological structure of solid portion was pseudopapillary with a fibrovascular core. Tumor cells were uniform and medium-sized which were arranged in sheets ets or nests or pseudopapillary patterns. Immunohistochemical studies demonstrated that SPTP proved positive in vimentin(9/9 cases), AAT(9/9 cases), NSE(9/9 cases), ACT(7/9 cases), CK20(2/9 cases), CgA(1/9 cases), S-100(3/gcases), PR(4/gcases), Syn(3/9 cases) and CD56(5/9cases), negative in CEA and ER. Conclusion:SPTP is a tumor predominantly occurring in young women frequently without special symptoms. This tumor has various characteristical histological patterns with different immunophenotype.  相似文献   

18.
Objective:To probe into the influence of changes of ovarian hormones on the pathogenesis of the specific sub-type premenstrual syndrome(PMS)and reveal partial microcosmic mechanisms of adverse flow of liver-qi.Methods:Estradiol(E2)and progesterone(P)levels in serum were determined at different phases of menstrual cycle by radioimmunoassay.Results:In the group of PMS with adverse flow of liver-qi.the secretive peak value Of E2 and P at the follicular phase significantly decreased,and the secretive peak value at the luteal phase did not come into being.Conclusions:Low E2 and P secretive peak at the follicular phase and absence of secretive peak at the luteal phase is one of the microcosmic mechanisms of PMS with adverse flow of liver-qi.One of the pathophysiologic mechanisms of specific sub-type PMS is probably the continuous low level of E2and P.  相似文献   

19.
Real-time three-dimensional echocardiography (RT3DE)is a new ultrasound technique that enables dynamic threedimensional visualization and quantification of the heart in real time. Investigation of feasibility and methodology of RT3DE in determining left ventricular (LV) and right ventricular (RV) volumes, RT3DE was performed in 35 normal adults using Philips SONOS 7500 system with a 2-4 MHz matrix array transducer. The 60°×60° "pyramid" volume database was obtained and analyzed on a TomTec echo workstation. Both LV and RV volumes were calculated with four 3DE methods (i.e. apical 2, 4, 8, and 16-plane) through manually tracing ventricular endocardial borders in end diastole and end systole. Stroke volumes were then calculated. LV volume was also measured by 2DE Simpson's rule using GE VIVID 7 ultrasound machine.  相似文献   

20.
Increasing maternal age is the only etiological factor unequivocally linked to Down's syndrome in humans. The occurrence rate of newborns with Down's syndrome is about 1/220 in women over 35 years old. However, the occurrence rate in embryos fertilized in vitro, of the elder woman is unclear. Using FISH we screened the number of chromosome 21 in preimplanted embryos of 5 elderly women (average age, 38.4 years) to study the feasibility and necessity of screening trisomy 21 in embryos in patients over 35 years old at the in vitro fertilization (IVF) center.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号