共查询到20条相似文献,搜索用时 15 毫秒
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隐藏狄利克雷分配(Latent Dirichlet Allocation ,LDA )模型被广泛应用于文本分析、图像识别等领域。但由于LDA及其扩展模型多为无监督学习模型,无法将其应用于分类任务中。本文通过研究文档标记与LDA模型中主题的映射关系,提出一种新的Labeled LDA模型(Shared Background Topics Labeled LDA ,SBTL-LDA )。在SBTL-LDA模型中每个标记除了存在若干个独享的局部主题外,还存在若干个共享的背景(Background )主题,这样可以有效分析不同标记所含主题之间的依赖关系,而文档标记被映射为局部主题和共享主题的组合,因此SBTL-LDA模型可以有效提升文档标记判别的准确性。同时SBTL-LDA模型还可以看成是一种半监督聚类模型,在对文档进行聚类分析的过程中模型可以有效的利用文档的标记信息提升文档聚类效果。实验证明SBTL-LDA模型能够有效解决PLDA模型中主题之间的相似性和依赖关系,具有良好的多标记判别能力,并且具有优于LDA、PLDA模型的文档聚类效果。 相似文献
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基于P2P的文件共享模型及相关问题的分析 总被引:2,自引:0,他引:2
对等网(P2P)技术的提出对当前的客户/服务器(C/S)技术是一种巨大挑战,它相对 于现有网络模型有很多优势.文中对几种典型的P2P技术模型和成果进行分析,包括Napster、Gnutel la、Freenet、JXTA等,对当前存在的问题提出了看法,并对P2P的未来发展进行了展望. 相似文献
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A case study designed to examine the degree of congruence in management attitudes and sccioeconomic background factors between executive superiors and executive subordinates, tested the hypothesis that the greater the correlation the greater the probability of promotion. Those subordinates being promoted did not necessarily share common background and attitudes with superiors but, perceptually, were significantly more aware of their superiors' views than were those not considered for promotion. 相似文献
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分析了模拟硬件描述语言Verilog-A的特点,介绍了一种基于Verilog-A HDL行为模型的模拟电路自顶向下设计方法。这种方法适用于片上系统(soc)模拟部分的设计。根据压控振荡器(VCO)和二阶无源低通滤波器(LPF)的数学模型,建立了它们基于Verilog-A的行为模型,并用该方法实现了包含中心频率为120MHz的VCO和截止频率为300.0kHz的LPF在内的电荷泵锁相环系统设计。最后利用Cadence Spectre仿真器对模型进行了验证及PLL系统级仿真。 相似文献
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A new and simple method for modeling an antenna under test (AUT) from spherical near-field (NF) measurements is presented. This method utilizes NF data to determine an equivalent behavioral model composed of magnetic and electric dipoles placed over a fictitious sphere surrounding the AUT. A spherical wave expansion (SWE) of the measured NF is developed to derive a linear relation between the transmission coefficients of the AUT and the transmission coefficients of each dipole. Dipole transmission coefficients are determined using the translational and rotational addition theorems. Finally, a least square method is employed to compute the excitation of each current source. Once the equivalent model is obtained, it can be used to study the behavior of the original AUT in different environments. Computations with electromagnetic simulation data illustrate the accuracy of the proposed method and the reliability of the derived model. 相似文献
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为检验翻转课堂教学效果,对其与传统课堂进行了实证对比研究.采用数字电路作为研究目标,研究内容包括:课程内容涵盖率、学生成绩、学生对翻转课堂的认识看法.研究发现,比起传统的授课方式,翻转课堂可以涵盖更多的知识面;能提高学生的成绩,尤其是在一些设计性问题上;学生对翻转课堂模式接受很快,发现它是一种令人满意与有效的方式. 相似文献
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《Vehicular Technology, IEEE Transactions on》2009,58(1):14-20
Ricean fading is common in dense urban cellular networks and, as a mobile moves through that environment, the K-factor of the Ricean fading will change. This paper presents a statistical model for dense urban vehicular nonstationary Ricean fading, where the K-factor gradually changes due to movement through changing surroundings. This model is empirical and is based on K-factor fluctuations that are observed in dense urban cellular radio channel measurements. The K -factor is modeled using a random process with a distribution that is fit to the measured K-factor values. An autoregressive (AR) model is also used to ensure that the autocorrelation of the simulated K-factor process matches the empirical data. The nonstationary Ricean fading envelope that is generated using this model is verified by comparing it with the fading envelope that is observed in the measurements. 相似文献
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针对传统假设中个体寿命独立同分布的不足,在个体寿命的基准危险率为分段常数危险率的条件下,引入刻画随机效应所产生影响的脆弱性因子,构建出基于比例危险率扩展模型的半参数共享脆弱性模型.运用基于Gibbs抽样的马尔可夫链蒙特卡罗(MCMC)方法,动态模拟出参数后验分布的马尔可夫链;在脆弱性因子的先验分布为Gamma分布时,引入基准危险率的鞅过程,并给出随机截尾条件下参数的贝叶斯估计,提高计算的精度.利用数值算例验证了该模型在可靠性应用中的直观性与有效性. 相似文献
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SenseWeb: An Infrastructure for Shared Sensing 总被引:5,自引:0,他引:5
《Multimedia, IEEE》2007,14(4):8-13
Peer-produced systems can achieve what might be infeasible for stand-alone systems developed by a single entity. The SenseWeb's goal is to enable these kinds of capabilities. Using SenseWeb, applications can initiate and access sensor data streams from shared sensors across the entire Internet. The SenseWeb infrastructure helps ensure optimal sensor selection for each application and efficient sharing of sensor streams among multiple applications. 相似文献
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《固体电子学研究与进展》2017,(2)
功率器件在开关过程中的电压尖峰、电流尖峰及开通时间、关断时间等问题是评估一款器件乃至电力系统装置可靠性的重要因素。文中从动态特性出发,研究了一种基于Pspice的绝缘栅双极型晶体管(IGBT)模型。以Trench-FS(Field-stop)型IGBT晶体管KWBW25N120S1E2为例,根据该器件的结构和工艺参数,得到了Pspice模型参数。双脉冲测试仿真结果表明,得到的该器件开通延时、上升和关断时间以及关断延时等动态参数与实测数据基本一致。最后,给出了该模型应用到实际焊机仿真结果与实测的比较,进一步验证了模型的合理性与可靠性。 相似文献
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In this paper, we investigate possible timecorrelation of answered call arrivals in sets of real GSM telephone traffic data. Instead of attempting to model the empirical distribution of the call interarrival time, as done in several previous works in literature, we emphasize results obtained by the Modified Allan Variance (MAVAR), a widely used time-domain quantity with excellent capability of discriminating power-law noise types. The call arrival rate exhibits a diurnal trend, with peak hours in the morning and late afternoon. Besides this diurnal rate change, the number of call arrivals in a second is found perfectly uncorrelated to the number of arrivals in other seconds and Poisson distributed, with good consistency by X/sup 2/- test evaluation. Uniform and accurate whiteness of call arrivals per second is verified in all hours, regardless the time of the day. In all series analyzed, the empirical statistics of both originated and terminated call arrivals proves excellent consistency with the ideal Poisson model with diurnal variable rate λ(t). This study may be valuable to researchers concerned about realistic traffic modelling in planning and performance evaluation of cellular networks. 相似文献
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高山被孢霉的扫描电镜观察 总被引:1,自引:0,他引:1
本文对三株高山被孢霉(Mortierella alpina)菌株200012201、88335和87649进行了研究。PDA(potato dextrose agar,马铃薯葡萄糖琼脂培养基)平板观察,200012201菌株的菌落呈波浪状或高山状,菌丝为白色;扫描电镜观察,菌丝发达,分支繁密,很少发现孢囊孢子,但观察到少量的高山被孢霉接合孢子。而88335和87649菌株的PDA平板的菌落平铺于表面,菌丝白色,呈绒毛状;扫描电镜观察,与200012201菌的菌丝相比,菌丝较细,同样分支繁密,容易观察到大量由菌丝梗分化产生的成串的分生孢子。 相似文献