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排序方式: 共有5628条查询结果,搜索用时 15 毫秒
1.
研究基于用户需求的设计方法在电热炉产品设计中的运用。以满足单身用户需求的电热炉产品设计为例,运用定性人物角色构建法构建出目标用户角色模型,使用户的需求具体化、形象化,在此基础上设计了具有多种加热模式且方便用户携带与收纳的电热炉结构与造型,通过计算机辅助设计与样品制作,验证了设计方案的可行性,为电热炉的开发设计提供参考。 相似文献
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通过物理模型试验,研究了有植被的河道水流紊动特性.试验结果表明,在复式断面河道滩地种植柔性植被后,滩地糙率增大,水流紊动更为剧烈,河道水流紊动强度峰值由原先的滩槽交界区转移到滩地区.滩地的水流紊动强度沿程递减;滩槽交界区的水流紊动强度沿程不断增大;主槽的水流紊动强度主要与床面糙率有关,滩地植被影响了滩地水流的归槽时间,使主槽水流流速沿程增大. 相似文献
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O Ukkola MJ Savolainen PI Salmela K von Dickhoff T Kiema YA Kes?niemi 《Canadian Metallurgical Quarterly》1995,73(6):307-311
In the search for new risk factors for diabetic macroangiopathy the insertion/deletion (I/D) polymorphism in the angiotensin-converting enzyme gene was studied in 237 consecutive patients (125 men and 112 women) with non-insulin-dependent diabetes. The female population showed an excess of ischemic electrocardiographic changes or definite myocardial infarctions in the patients homozygous for the deletion [D/D; odds ratio (OR) 2.8; 95% confidence interval (CI) 1.4-5.3] and in the insertion/deletion heterozygotes (I/D; OR 1.8; CI 1.1-3.1) compared with the patients homozygous for the insertion (I/I). In the total series coronary heart disease, cerebrovascular disease, and claudication were more often observed in the patients with I/D (OR 1.5; CI 1.0-2.2) or the D/D genotype patients (OR 1.7; CI 1.1-2.6) than in those with the genotype I/I. The systolic blood pressure was lower in patients with genotype I/I (138 +/- 19 mmHg) than in those with the genotype I/D (149 +/- 22 mmHg) or D/D (150 +/- 21 mmHg; P < 0.02). The prevalence of hypertension and the median urinary albumin excretion rate also tended to be lowest in the I/I genotype patients. Multiple logistic analysis revealed that in women the angiotensin-converting enzyme D/D genotype is independently associated with coronary heart disease. Our findings suggest that variation at the angiotensin-converting enzyme gene locus is one of the factors involved in the predisposition of diabetic patients to the development of arterial disease and hypertension. 相似文献
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PI Mitchell L León Vintró H Dahlgaard C Gascó JA Sánchez-Cabeza 《Canadian Metallurgical Quarterly》1997,202(1-3):147-153
Diabetes complicates 2-3% of all pregnancies and is associated with an increase in both perinatal morbidity and mortality, though reasons for these adverse outcomes are unknown. Estrogen biosynthesis is a critical factor during pregnancy and is carried out in the placenta via aromatase (cytochrome P450 19A1), which catalyzes the conversion of C-19 androgens to C-18 estrogens. Previous studies have shown that hormones such as insulin-like growth factors and insulin regulate aromatase activity when studied in vitro. Interestingly, levels of these hormones are altered in patients with diabetes. Thus, we hypothesized that the presence of maternal diabetes may alter placental aromatase activity and thus estrogen biosynthesis, possibly serving as one factor in the adverse outcomes of babies born to mothers with diabetes. To this end, we measured the production of 19-hydroxyandrostenedione, 19-oxoadrostenedione and estrone in 30 placental tissues from diabetic patients, using [7-3H]androst-4-ene-3,17-dione as a model substrate for aromatase (P450 19A1). A statistical difference was detected in the percentage of 19-oxoandrostenedione formed between the overt and control groups (P < 0.05). Additionally, NADPH P450-reductase levels were measured in these same tissues to determine whether alterations in this enzyme necessary for aromatase activity could be affected by diabetes. No differences in reductase levels were detected among the patient groups. However, a statistical correlation was found between NADPH P450-reductase activity and the formation velocities of all three estrogen products (P < 0.05). Thus, it appears that the presence of diabetes does not affect placental aromatase activity. 相似文献
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地震数据采集系统中频谱均衡滤波器的理论设计 总被引:2,自引:0,他引:2
地层的高频吸收衰减效应是导致地震勘探分辨率不高的主要原因,在高分辨率野外地震数据系统中,频谱均衡滤波器所设置的重要部件。文章以频谱均衡滤波器的原理和地层吸收衰减特性为基础,用计算机模拟的方法研究地层吸收衰减使分辨率降低的程度和频谱均衡滤波器对分辨率的补偿效果,给出了较好的频谱均衡滤波器的设计方案。 相似文献
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PI Lobo C Spencer MT Douglas WC Stevenson TL Pruett 《Canadian Metallurgical Quarterly》1993,55(5):1063-1066
Recent reports indicate a higher incidence of both acute and chronic liver allograft rejection when, at the time of transplantation, the recipients serum contains donor-specific anti-HLA antibodies. From 9/89 to 5/91, 133 liver allografts were performed at our institution. Thirteen liver recipients had donor-specific IgG anti-HLA antibodies (complement-fixing) at the time of transplantation. In eleven patients, antibodies reacted to donor class I antigens while in 1 patient the donor-specific antibody had class II reactivity. Twelve patients have been followed for a minimum of 12 months (median 18 months, range 28-12 months). No hyperacute rejection was seen in any of the cases and four patients had acute rejections. Thus far only one of the twelve patients has biopsy evidence suggestive of chronic liver injury. The remaining have normal liver enzymes and bilirubin. Three of these twelve patients died (one from a myocardial infarction and the others from sepsis) accounting for a one-year graft survival of 75%. There was no significant statistical difference in the one-year graft survival in those recipients without donor-specific antibodies (i.e., 80.5%). In eight of the twelve patients, pretransplant preformed antibody level (PRA) was > 50%. In six of the thirteen patients donor-specific antibody was present at dilutions greater than 1:64. As previously reported, the donor-specific antibody disappeared from the serum posttransplant within hours and did not reappear. In vitro studies demonstrated no factor in portal or hepatic artery blood that could inhibit rabbit complement mediated lysis of anti-HLA antibodies. We conclude that it is not a contraindication to do liver transplants in the presence of donor-specific anti-HLA antibodies. 相似文献
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DX型数据采集与无线传输系统能对油井压力、温度、载荷和流量等参数进行自动采集 ,并通过无线传输向总站提供实时参数 ,为及时决策提供信息。数据采集系统采用STD总线 ,测量精度高、故障低 ;无线传输系统采用短波电台和具有自动纠错功能的数传机 ,抗噪能力强、可靠性高。文章介绍了DX型数据采集与无线传输系统的组成、工作原理、功能和主要技术指标 相似文献