MC-DTC系统的无速度传感器控制算法研究

对于无速度传感器的研究主要针对电动机的矢量控制系统,而应用于直接转矩控制(DTC)系统很少.本文研究基于矩阵变换器(MC)直接转矩控制系统(MC-DTC)应用无速度传感器技术以及将三者融合的技术.讨论了无速度传感器的直接计算方法和模型自适应方法,重点讨论了速度自适应辨识方法与满足系统融合要求的控制策略.仿真实验表明,速度自适应辨识速度高于直接计算精度,动态响应好.同时能发挥MC和DTC的优势,成为一种高性能的交流调速系统.     

美国脱水马铃薯产品在胚料上的应用

二次膨化技术,也称间接膨化技术,是指将混合,搅拌好的物料输送到挤出机,经过高压,低温挤出,经干燥后,在热风和沸油中膨化。我们研究了美国马铃薯粉在二次膨化中的应用,并探索了美国马铃薯在胚料生产中的作用以及其他辅料在胚料中的作用。     

The role of parathyroid hormone in the pathogenesis, prevention and treatment of postmenopausal osteoporosis

BACKGROUND: Nuclear deoxyribonucleic acid (DNA) content is a prognostic factor in several tumors, and decisions regarding treatment have been made using this parameter. Nevertheless, there is no agreement in head and neck cancer. The purpose of the present study was to ascertain whether tumor DNA content correlated with prognosis in cases of primary squamous cell carcinoma (SCC) of the oral cavity and tongue base. METHODS: A retrospective study of formalin-fixed, paraffin-embedded tissue from patients with histologically confirmed SCC of the oral cavity and tongue base was performed using flow cytometry. Tumor DNA content was studied in 109 sets of specimens from previously untreated patients. All of them underwent surgical resection at the University "Hospital de La Princesa" between 1982 and 1992. Clinical parameters (age, sex, site of primary tumor, clinical stage, adjuvant therapy received, and disease-free and overall survival) and histologic parameters (histopathologic stage, tumor differentiation, type of inflammatory infiltration, presence of perineural invasion) were recorded in all cases. An exhaustive statistical analysis was applied. RESULTS: Only the histograms of 93 patients were adequate for consideration. In flow cytometric analysis, DNA aneuploidy was observed in 51 tumors (55%). The proportion of aneuploid tumors was significantly higher in advanced-stage carcinomas (p < .05), tumors with perineural invasion (p < .05) and in men (p < .05). In the 24 patients with lymph node metastasis, the incidence of aneuploidy was 82% (19 of 24) (p < .05). The rate of metastasis and aneuploidy increased as the degree of differentiation decreased (p < .05 for both). Patients with aneuploid carcinomas in both early and advanced stages had shorter relapse-free and overall survival periods than did the patients with diploid tumors (p < .001 for both). A Cox regression analysis demonstrated that ploidy was the single most important prognostic factor in determining relapse and death (p < .001 for both). CONCLUSIONS: The results indicate that tumor DNA analysis by flow cytometry appears to be useful as a supplement to clinical and histologic evaluation in predicting the tendency of SCC of the oral cavity and tongue base to metastasize to regional lymph nodes and to predict the outcome of the disease.     

The nuclear cap-binding complex is a novel target of growth factor receptor-coupled signal transduction

In an attempt to further understand how nuclear events (such as gene expression, nuclear import/export, and cell cycle checkpoint control) might be subject to regulation by extracellular stimuli, we sought to identify nuclear activities under growth factor control. Using a sensitive photoaffinity labeling assay that measured [alpha-32P]GTP incorporation into nuclear proteins, we identified the 20-kDa subunit of the nuclear cap-binding complex (CBC) as a protein whose binding activity is greatly enhanced by the extracellular stimulation of serum-arrested cells. The CBC represents a 20- and 80-kDa heterodimer (the subunits independently referred to as CBP20 and CBP80, respectively) that binds the 7-methylguanosine cap on RNAs transcribed by RNA polymerase II. This binding facilitates precursor messenger RNA splicing and export. We have demonstrated that the [alpha-32P]GTP incorporation into CBP20 was correlated with an increased ability of the CBC to bind capped RNA and have used the [alpha-32P]GTP photoaffinity assay to characterize the activation of the CBC in response to growth factors. We show that the CBC is activated by heregulin in HeLa cells and by nerve growth factor in PC12 cells as well as during the G1/S phase of the cell cycle and when cells are stressed with UV irradiation. Additionally, we show that cap-dependent splicing of precursor mRNA, a functional outcome of CBC activation, can be catalyzed by growth factor addition to serum-arrested cells. Taken together, these data identify the CBC as a nuclear target for growth factor-coupled signal transduction and suggest novel mechanisms by which growth factors can influence gene expression and cell growth.     

The diffusional transport of water and small solutes in isolated endothelial cells and erythrocytes

The diffusional permeability coefficients, PD, for tritiated water (3HHO) 14C-antipyrine (AP) and 14C-iodoantipyrine (IAP) in isolated calf pulmonary artery endothelial cells and dog erythrocytes are measured with the linear diffusion technique at 11.5, 15, 20 and 37 degrees C. The PD values for both cell populations follow the sequence 3HHO > IAP > AP at each of the temperatures. PD for water is higher in the erythrocyte compared to the endothelial cells. The differences in PD for AP and IAP in the erythrocytes and endothelial cells are not dramatic and are similar to the differences seen in comparing permeation of the same solute through bilayers of different composition. A comparison of the values of PD calculated for the endothelial cells with those for isolated capillaries and the structured endothelium in whole lungs validates the use of the isolated cells as models for the endothelial cells in situ. Incubation of the endothelial cells with cis-vaccenic acid or cholesterol produces a reduction in PD for water and antipyrine. These data are analyzed in terms of Stokesian and non-Stokesian diffusion. The interpretation which best accommodates the data is that the phospholipid area of the membrane, rather than the hydrocarbon core, provides the greatest resistance to permeation for these solutes.     

1994 America on display… American LCDs playing catch-up

With each sensational new development, the real life race for American dominance over Japan in next-generation flat panel displays is looking progressively more like a rough draft of a techno-thriller (with the likelihood of getting even rougher). The real life drama that is unfolding is not only exciting, it often seems less believable than fiction. In this episode of “America On Display,” we'll try to sort through what some of the leading characters have been up to lately, who they're working with (or against), and what the U.S. government and various “cooperative” catalysts are contributing to the chain of chaotic events.     

女性掌握某些科技产品使用权

在某些科技产品的使用过程中,美国女性的主导权超过男人,比如观看电视节目、DVR使用、浏览社会类媒体网站,甚至是打游戏。这个调查结果是由Solution Research Group发布的一个新的、关于“女性和数字生活方式”报告发布的。     

Methods and rates of application of Mn and its critical levels for wheat following rice on coarse textured soils

Two field experiments were conducted on Mn-deficient soils to evaluate the efficiency of rates, methods and time of MnSO₄.H₂ O application for wheat. Manganese sulphate was broadcast and mixed in soils at the rate of 5 to 50kg Mn ha^–1 before seeding and 10 to 40 kg Mn ha^–1 as top dress at 28 days — just before first irrigation. Three sprays of 1% MnSO₄·H₂O unneutralised solutions were applied, the first at 26 days — 2 days before first irrigation and the others afterward at weekly intervals. Both the methods caused a significant and marked increase in grain yield. Three foliar sprays were as effective as soil applications of 20 to 40 Kg Mn ha^–1 before seeding. The difference in grain yield resulting from soil applications of Mn before seeding and applications at the first irrigation was not significant. The DTPA-Mn status of 20 fields, selected on the basis of varying degree of Mn deficiency, was related to grain yield (r = 0.77^**). Also grain yield of all the experiments had a significant correlation with Mn content of grain (r = 0.55^** to 0.82^**) and straw (r = 0.77^** to 0.82^**). The critical limits calculated by statistical method were 1.25, 2.18 and 3.5 mg Mn kg^–1 soil for severe deficiency, deficiency and latent deficiency respectively for wheat.     

Evaluation of levels and methods of zinc application to rice in sodic soils

Field experiments were conducted in zinc-deficient sodic soil to study the effect of levels and methods of zinc fertilization on yield, concentration and uptake of zinc by rice. Zinc was incorporated in the soil at the rate of 0, 5.6, 11.2 and 22.4 kg Zn per ha as zinc sulfate; sprayed on the plants at 1% and 2% zinc sulfate solution; and roots of rice seedlings were dipped in 2% and 4% ZnO suspensions in water. Grain yield, zinc content and its uptake increased in all the experiments up to 22.4 kg Zn per ha. Soil applied zinc was significantly correlated with yield of rice (r = 0.80^**) and zinc uptake (r = 0.89^**). Zinc content in 45-day old plants gave a significantly higher correlation with grain yield (r = 0.84^**) than the zinc content of rice straw and grain at maturity. Roots of rice seedlings dipped in 2% or 4% zinc oxide suspension in water were not only comparable with soil application of Zn at 5.6 and 11.2 kg Zn per ha, but also proved to be more economical for sodic soils showing moderate zinc deficiency.