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1.
冲积河流阻力是泥沙运动力学中的一个重要问题.利用1844组实测资料,基于水流功率的概念建立了总水流功率与有效水流功率的经验关系.在泥沙起动前后总水流功率与有效水流功率基本一致;在低能态区,由于有沙垄、沙纹出现,总水流功率明显大于有效水流功率;在高能态区,从动平整床面到沙浪的出现,总水流功率又逐渐背离有效水流功率.用近10000组水槽和天然河道资料验证表明,该经验关系式精度较高.  相似文献   

2.
针对ATM/CDMA无线通信网综合业务传输的需要,提出了“不等功率控制”,即反向信道中功率控制的目标是使接收端所接收的不同业务用户的信号功率一般彼此不等,而同种业务用户的信号功率相等.以语音/数据综合业务为例,对不等功率控制条件下的最佳功率因子、反向信道的通过量和容量进行了分析,并与等功率控制作了比较.结果表明:与等功率控制相比,不等功率控制可以扩大系统的允许负载区域,并大大提高系统容量.  相似文献   

3.
利用谐波分析等方法分别探讨单相全波整流电路的功率问题.分析结果表明:不考虑传输损耗的理想情况下,在全波整流电路中,输出功率与输入功率之比为1:1.实现了谐波分析法在整流电路功率问题研究中的应用,有助于对整流电路的功率问题以及谐波分析法有进一步的理解和认识.  相似文献   

4.
利用谐波分析等方法分别探讨单相全波整流电路的功率问题.分析结果表明:不考虑传输损耗的理想情况下,在全波整流电路中,输出功率与输入功率之比为1:1.实现了谐波分析法在整流电路功率问题研究中的应用,有助于对整流电路的功率问题以及谐波分析法有进一步的理解和认识.  相似文献   

5.
在方棒拔制变形区沿拔制速度变化最大方向设定速度场、应力场与功率场,速度场的设定满足体积不变原则,以近似塑性条件与入口功率边界条件求出功率分布微分方程及其解.令外功率等于出口功率求拔制应力.  相似文献   

6.
挖掘机单神经元比例-积分-微分节能控制系统   总被引:3,自引:0,他引:3  
从节能角度考虑,通过对液压挖掘机功率匹配的分析。提出了将液压泵的功率曲线设定在发动机的功率曲线之上的功率匹配方法.随着负载压力的变化,主控制器对液压泵的排量进行控制,使液压泵能够完全吸收发动机的功率,保证了发动机始终在设定的转速下运行。实现了发动机功率充分利用和节能的目的.研究了单神经元比例-积分-微分(PID)控制器在节能控制系统上的应用,试验结果表明,文中提出的功率匹配方法可行,单神经元PID控制器能够根据不同的环境和作业工况进行参数自调整,具有自适应的能力.研究结果为进一步研究开发智能化挖掘机提供了依据.  相似文献   

7.
从小波包多载波调制(WPT-MCM)系统的结构出发,给出了小波包多载波调制峰均功率比(PAPR)的定义.借助仿真工具,分析了子载波路数对小波包多载波调制峰均功率比的影响,比较了小波包多载波调制和正交频分复用(OFDM)两种系统的峰均功率比特性.提出了基于SLM技术降低小波包多载波调制峰均功率比的方法。给出了仿真结果.结果表明,子载波路数的增多使小波包多载波调制的峰均功率比增大,基于SLM技术降低小波包多载波调制峰均功率比是非常有效的.  相似文献   

8.
提出了数字调制信号功率谱的一种求法,这一方法利用维纳-辛钦定理和时间平均的自相关概念,它适合于求解一般线性数字调制的功率谱,首先讨论线性数字调制信号功率谱的一般求解方法,给出了详细的推导过程和公式.最后,计算了2个典型信号16QAM和9QPR的功率谱密度.  相似文献   

9.
提出了一种基于最优量化的变步长CDMA闭环功率控制方法.利用信道的统计特性,针对不同出现概率的信号幅度区间采用不同的量化间隔,从而得到不同的控制步长,较好地解决了功率控制精度与控制时间之间的矛盾.仿真结果表明,所提出方法的性能优于已有的闭环功率控制方法.  相似文献   

10.
底吹条件对电弧炉熔池表面突起高度的影响   总被引:3,自引:0,他引:3  
用30t底吹电弧炉1:7水模型探讨了底吹喷嘴孔数,孔径,气体搅拌功率及熔池深度对液面突起高度及上升速度的影响;得到了液面突起高度液体上升速度与气体搅拌功率的关系分别为:Δh=0.361,W^0.664,vL=84.144.W^0.332,液面突起高度与气体搅拌功率及熔池深度的关系为:Δh=0.815.W^0.664.h^-0.659。  相似文献   

11.
Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.  相似文献   

12.
The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.  相似文献   

13.
王慧 《科技信息》2008,(10):240-240
Wuthering Heights, Emily Bronte's only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.  相似文献   

14.
何延凌 《科技信息》2008,(4):258-258
Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women's language from these perspectives: pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women's language, more attention should be paid to language use in social context. What's more, the linguistic phenomena in a speaking community can be understood more thoroughly.  相似文献   

15.
The discovery of the prolific Ordovician Red River reservoirs in 1995 in southeastern Saskatchewan was the catalyst for extensive exploration activity which resulted in the discovery of more than 15 new Red River pools. The best yields of Red River production to date have been from dolomite reservoirs. Understanding the processes of dolomitization is, therefore, crucial for the prediction of the connectivity, spatial distribution and heterogeneity of dolomite reservoirs.The Red River reservoirs in the Midale area consist of 3~4 thin dolomitized zones, with a total thickness of about 20 m, which occur at the top of the Yeoman Formation. Two types of replacement dolomite were recognized in the Red River reservoir: dolomitized burrow infills and dolomitized host matrix. The spatial distribution of dolomite suggests that burrowing organisms played an important role in facilitating the fluid flow in the backfilled sediments. This resulted in penecontemporaneous dolomitization of burrow infills by normal seawater. The dolomite in the host matrix is interpreted as having occurred at shallow burial by evaporitic seawater during precipitation of Lake Almar anhydrite that immediately overlies the Yeoman Formation. However, the low δ18O values of dolomited burrow infills (-5.9‰~ -7.8‰, PDB) and matrix dolomites (-6.6‰~ -8.1‰, avg. -7.4‰ PDB) compared to the estimated values for the late Ordovician marine dolomite could be attributed to modification and alteration of dolomite at higher temperatures during deeper burial, which could also be responsible for its 87Sr/86Sr ratios (0.7084~0.7088) that are higher than suggested for the late Ordovician seawaters (0.7078~0.7080). The trace amounts of saddle dolomite cement in the Red River carbonates are probably related to "cannibalization" of earlier replacement dolomite during the chemical compaction.  相似文献   

16.
Location based services is promising due to its novel working style and contents.A software platform is proposed to provide application programs of typical location based services and support new applications developing efficiently. The analysis shows that this scheme is easy implemented, low cost and adapt to all kinds of mobile nework system.  相似文献   

17.
以AC-13级配为基础,将橡胶颗粒代替部分集料掺入混合料中,以低温弯曲试验为评价方法对不同橡胶颗粒掺量下沥青混合料的低温抗裂性进行研究,并引入应变能密度值对混合料的低温抗裂性进行综合评价.试验结果表明:橡胶颗粒沥青混合料试件的破坏微应变均超过2 300,满足冬寒区的技术指标;无论是否掺加橡胶颗粒,随着温度的下降,沥青混合料破坏时的最大弯拉强度增大,弯拉应变降低,劲度模量增大;弯曲应变能密度在胶粒掺量为1%左右时具有较大的弯曲应变能密度值,此时橡胶颗粒沥青混合料具有较好的低温抗裂性.  相似文献   

18.
理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。  相似文献   

19.
Quality traits in wheat (Triticum aestirum L.) were studied by quantitative trait locus (QTL) analysis in a recombinant inbred line (RIL) population, a set of 131 lines derived from Chuan 35050 × Shannong 483 cross (ChSh). Grains from RILs were assayed for 21 quality traits related to protein and starch. A total of 35 putative QTLs for 19 traits with a single QTL explaining 7.99-40.52% of phenotypic variations were detected on 10 chromosomes, 1D, 2A, 2D, 3B, 3D, 5A, 6A, 6B, 6D, and 7B. The additive effects of 30 QTLs were positive, contributed by Chuan 35050, the remaining 5 QTLs were negative with the additive effect contributed by Shannong 483. For protein traits, 15 QTLs were obtained and most of them were located on chromosomes 1 D, 3B and 6D, while 20 QTLs for starch traits were detected and most of them were located on chromosomes 3D, 6B and 7B. Only 7 QTLs for protein and starch traits were co-located in three regions on chromosomes 1D, 2A and 2D. These protein and starch trait QTLs showed a distinct distribution pattern in certain regions and chromosomes. Twenty-two QTLs were clustered in 6 regions of 5 chromosomes. Two QTL clusters for protein traits were located on chromosomes 1D and 3B, respectively, three clusters for starch traits on chromosomes 3D, 6B and 7B, and one cluster including protein and starch traits on chromosome 1D.  相似文献   

20.
As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.  相似文献   

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