he algorithm is equivalent to Infomax by Bell and Sejnowski 1995 [1] using a maximum likelihood formulation. No noise is assumed and the number of observations must equal the number of sources. The BFGS method [2] is used for optimization.
The number of independent components are calculated using Bayes Information Criterion [3] (BIC), with PCA for dimension reduction.
Browser-based (HTTP) file uploading is a great way to transfer arbitrary files from a client machine to the Web server which adds another dimension to Web-based applications.
We introduce a sub-cell WENO reconstruction method to evaluate spatial derivatives in the high-order ADER scheme. The basic idea in our reconstruction is to use only r stencils to reconstruct the point-wise values of solutions and spatial derivatives for the 2r-1 th order
ADER scheme in one dimension, while in two dimensions, the dimension-by-dimension sub-cell reconstruction approach for spatial derivatives is employed. Compared with the original ADER scheme of Toro and Titarev (2002) [2] that uses the direct derivatives of reconstructed polynomials for solutions to evaluate spatial derivatives, our method not only reduces greatly the computational costs of the ADER scheme on a given mesh,
but also avoids possible numerical oscillations near discontinuities, as demonstrated by a number of one- and two-dimensional numerical tests. All these tests show that the 5th-order ADER scheme based on our sub-cell reconstruction method achieves the desired accuracy, and is essentially non-oscillatory and computationally cheaper for problems with discontinuities.
Thisbookfocusesontheemergingresearchtopic‘green(energy-efficient)wirelessnetworks’
that has drawn huge attention recently from both academia and industry. This topic is highly
motivated due to important environmental, financial and quality-of-experience (QoE) consid-
erations.Duetosuchconcerns,varioussolutionshavebeenproposedtoenableefficientenergy
usage in wireless networks, and these approaches are referred to as green wireless communi-
cations and networking. The term ‘green’ emphasizes the environmental dimension of the
proposed solutions. Hence, it is not sufficient to present a cost-effective solution unless it is
eco-friendly.
By inventing the wireless transmitter or radio in 1897, the Italian physicist Tomaso
Guglielmo Marconi added a new dimension to the world of communications. This
enabled the transmission of the human voice through space without wires. For this
epoch-making invention, this illustrious scientist was honored with the Nobel Prize
for Physics in 1909. Even today, students of wireless or radio technology remember
this distinguished physicist with reverence. A new era began in Radio
Communications.
The explosion in demand for wireless services experienced over the past 20 years
has put significant pressure on system designers to increase the capacity of the
systems being deployed. While the spectral resource is very scarce and practically
exhausted, the biggest possibilities are predicted to be in the areas of spectral reuse
by unlicensed users or in exploiting the spatial dimension of the wireless channels.
The former approach is now under intense development and is known as the cogni-
tive radio approach (Haykin 2005).
目前cPU+ Memory等系統(tǒng)集成的多芯片系統(tǒng)級(jí)封裝已經(jīng)成為3DSiP（3 dimension System in Package，三維系統(tǒng)級(jí)封裝）的主流，非常具有代表性和市場(chǎng)前景，SiP作為將不同種類的元件，通過不同技術(shù)，混載于同一封裝內(nèi)的一種系統(tǒng)集成封裝形式，不僅可搭載不同類型的芯片，還可以實(shí)現(xiàn)系統(tǒng)的功能。然而，其封裝具有更高密度和更大的發(fā)熱密度和熱阻，對(duì)封裝技術(shù)具有更大的挑戰(zhàn)。因此，對(duì)SiP封裝的工藝流程和SiP封裝中的濕熱分布及它們對(duì)可靠性影響的研究有著十分重要的意義本課題是在數(shù)字電視（DTV）接收端子系統(tǒng)模塊設(shè)計(jì)的基礎(chǔ)上對(duì)CPU和DDR芯片進(jìn)行芯片堆疊的SiP封裝。封裝形式選擇了適用于小型化的BGA封裝，結(jié)構(gòu)上采用CPU和DDR兩芯片堆疊的3D結(jié)構(gòu)，以引線鍵合的方式為互連，實(shí)現(xiàn)小型化系統(tǒng)級(jí)封裝。本文研究該SP封裝中芯片粘貼工藝及其可靠性，利用不導(dǎo)電膠將CPU和DDR芯片進(jìn)行了堆疊貼片，分析總結(jié)了SiP封裝堆疊貼片工藝最為關(guān)鍵的是涂布材料不導(dǎo)電膠的體積和施加在芯片上作用力大小，對(duì)制成的樣品進(jìn)行了高溫高濕試驗(yàn)，分析濕氣對(duì)SiP封裝的可靠性的影響。論文利用有限元軟件 Abaqus對(duì)SiP封裝進(jìn)行了建模，模型包括熱應(yīng)力和濕氣擴(kuò)散模型。模擬分析了封裝體在溫度循環(huán)條件下，受到的應(yīng)力、應(yīng)變、以及可能出現(xiàn)的失效形式：比較了相同的熱載荷條件下，改變塑封料、粘結(jié)層的材料屬性，如楊氏模量、熱膨脹系數(shù)以及芯片、粘結(jié)層的厚度等對(duì)封裝體應(yīng)力應(yīng)變的影響。并對(duì)封裝進(jìn)行了濕氣吸附分析，研究了SiP封裝在85℃RH85%環(huán)境下吸濕5h、17h、55和168h后的相對(duì)濕度分布情況，還對(duì)SiP封裝在濕熱環(huán)境下可能產(chǎn)生的可靠性問題進(jìn)行了實(shí)驗(yàn)研究。在經(jīng)過168小時(shí)濕氣預(yù)處理后，封裝外部的基板和模塑料基本上達(dá)到飽和。模擬結(jié)果表明濕應(yīng)力同樣對(duì)封裝的可靠性會(huì)產(chǎn)生重要影響。實(shí)驗(yàn)結(jié)果也證實(shí)了，SiP封裝在濕氣環(huán)境下引入的濕應(yīng)力對(duì)可靠性有著重要影響。論文還利用有限元分析方法對(duì)超薄多芯片SiP封裝進(jìn)行了建模，對(duì)其在溫度循環(huán)條件下的應(yīng)力、應(yīng)變以及可能的失效形式進(jìn)行了分析。采用二水平正交試驗(yàn)設(shè)計(jì)的方法研究四層芯片、四層粘結(jié)薄膜、塑封料等9個(gè)封裝組件的厚度變化對(duì)芯片上最大應(yīng)力的影響，從而找到最主要的影響因子進(jìn)行優(yōu)化設(shè)計(jì)，最終得到更優(yōu)化的四層芯片疊層SiP封裝結(jié)構(gòu)。
