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排序方式: 共有107条查询结果,搜索用时 0 毫秒
1.
R. Polini S. Kumashiro M. J. Jackson M. Amar W. Ahmed H. Sein 《Journal of Materials Engineering and Performance》2006,15(2):218-222
Deposition of diamond films onto various substrates can result in significant technological advantages in terms of functionality
and improved life and performance of components. Diamond is hard, wear resistant, chemically inert, and biocompatible. It
is considered to be the ideal material for surfaces of cutting tools and biomedical components. However, it is well known
that diamond deposition onto technologically important substrates, such as co-cemented carbides and steels, is problematic
due to carbon interaction with the substrate, low nucleation densities, and poor adhesion. Several papers previously published
in the relevant literature have reported the application of interlayer materials such as metal nitrides and carbides to provide
bonding between diamond and hostile substrates. In this study, the chemical vapor deposition (CVD) of polycrystalline diamond
on TiN/SiN
x
nc (nc) interlayers deposited at relatively low temperatures has been investigated for the first time. The nc layers were
deposited at 70 or 400 °C on Si substrates using a dual ion beam deposition system. The results showed that a preliminary
seeding pretreatment with diamond suspension was necessary to achieve large diamond nucleation densities and that diamond
nucleation was larger on nc films than on bare sc-Si subjected to the same pretreatment and CVD process parameters. TiN/SiN
x
layers synthesized at 70 or 400 °C underwent different nanostructure modifications during diamond CVD. The data also showed
that TiN/SiN
x
films obtained at 400 °C are preferable in so far as their use as interlayers between hostile substrates and CVD diamond
is concerned.
This paper was presented at the fourth International Surface Engineering Congress and Exposition held August 1–3, 2005 in
St. Paul, MN. 相似文献
2.
Optimal training signals for MIMO OFDM channel estimation 总被引:6,自引:0,他引:6
This paper presents general classes of optimal training signals for the estimation of frequency-selective channels in MIMO OFDM systems. Basic properties of the discrete Fourier transform are used to derive the optimal training signals which minimize the channel estimation mean square error. Both single and multiple OFDM training symbols are considered. Several optimal pilot tone allocations across the transmit antennas are presented and classified as frequency-division multiplexing, time-division multiplexing, code-division multiplexing in the frequency-domain, code-division multiplexing in the time-domain, and combinations thereof. All existing optimal training signals in the literature are special cases of the presented optimal training signals and our designs can be applied to pilot-only schemes as well as pilot-data-multiplexed schemes. 相似文献
3.
Ji Hye Kim Sein Hwang Ji-Hye Lee Se Seul Im Jaekyoung Son 《International journal of molecular sciences》2022,23(20)
Cumulative studies have indicated that high-dose vitamin C has antitumor effects against a variety of cancers. However, the molecular mechanisms underlying these inhibitory effects against tumorigenesis and metastasis, particularly in relation to pancreatic cancer, are unclear. Here, we report that vitamin C at high concentrations impairs the growth and survival of pancreatic ductal adenocarcinoma (PDAC) cells by inhibiting glucose metabolism. Vitamin C was also found to trigger apoptosis in a caspase-independent manner. We further demonstrate that it suppresses the invasion and metastasis of PDAC cells by inhibiting the Wnt/β-catenin-mediated epithelial-mesenchymal transition (EMT). Taken together, our results suggest that vitamin C has therapeutic effects against pancreatic cancer. 相似文献
4.
Abstract Three different ways of using fly ash, namely, partial replacement of cement, or sand, or both cement and sand in the cement mortar, were studied in this investigation. The replacement varied from 10 percent to 60 percent by weight. The effects of design parameters such as water‐cement ratio and curing temperature on the replacements were studied. In this paper, strategies of using fly ash in concrete construction were also proposed in order to conserve resources. 相似文献
5.
Shu Feng Hlaing Minn Liang Yan Lu Jinhui 《Wireless Communications, IEEE Transactions on》2010,9(1):86-91
OFDM data detection in doubly-selective fading channels requires high complexity due to intercarrier interferences (ICI). We present a low-complexity receiver consisting of a semidefinite relaxation (SDR) based detector and parallel interference cancellation (PIC). The entire band is divided into clusters of adjacent subcarriers. SDR is applied on each cluster while PIC tackles ICI from other clusters. An upper bound of ICI power is derived and used to omit far-away clusters in performing PIC. Finally, an adaptive detector based on PIC, PIC-based SDR and the snap-shot SNR in channel is proposed to achieve a better tradeoff between complexity and performance. 相似文献
6.
Arno C. Alting Fred van de Velde Marja W. Kanning Maurits Burgering Leo Mulleners Arjen Sein Piet Buwalda 《Food Hydrocolloids》2009
Amylomaltase-treated starch (ATS) is an excellent creaminess enhancer in yoghurt. Small amounts of ATS raised the creaminess perception of low-fat yoghurt (1.5%) to that of full-fat yoghurt (5%). In this way, a reduction in fat-related energy value could be achieved from 45 to 21.5 kcal/100 g product. The functionality of ATS in set yoghurt resulted from discrete domains of ATS that resemble the microstructural behaviour of fat particles. The microstructure of the yoghurt is dominated by the protein and the ATS domains are enclosed in or bound to this protein network. The perceived creaminess resulted from in-mouth melting of these ATS domains due to a combined effect of their physical melting and hydrolysis by amylase present in the saliva. 相似文献
7.
目标变量的马尔科夫毯(MB)是用于预测其状态的最优特征子集。提出一种新的约束学习类MB推导算法FSMB,它遵循后向选择的搜索策略,并依赖条件独立(CI)测试删除任意结点对之间的伪连接。与传统约束学习类算法不同,FSMB能从已执行的CI测试推导出不同结点扮演d 分割(d separation)结点的优先等级;而后基于该信息在未来优先执行条件集中包含高优先级结点的CI测试,从而更快速地判断并删除伪连接边。该策略可帮助快速缩小搜索空间,从而大大提升学习效率。基于仿真网络的实验研究显示,FSMB在计算效率上较经典的PCMB和IPC MB有显著的提升,而学习效果相当;在面对较大网络结构时(比如100和200个结点),甚至比公认最快速的IAMB还节省近40%的计算量,但学习效果要远优于IAMB。基于16个UCI数据集和4个经典的分类模型的实验显示,基于FSMB输出的特征集合所训练模型的分类准确率普遍接近或高于基于原有特征全集训练所得模型。因此,FSMB是快速且有效的MB推导算法。 相似文献
8.
9.
A robust timing and frequency synchronization for OFDM systems 总被引:5,自引:0,他引:5
Hlaing Minn Bhargava V.K. Letaief K.B. 《Wireless Communications, IEEE Transactions on》2003,2(4):822-839
A robust symbol-timing and carrier-frequency synchronization scheme applicable to orthogonal frequency-division-multiplexing systems is presented. The proposed method is based on a training symbol specifically designed to have a steep rolloff timing metric. The proposed timing metric also provides a robust sync detection capability. Both time domain training and frequency domain (FD) training are investigated. For FD training, maintaining a low peak-to-average power ratio of the training symbol was taken into consideration. The channel estimation scheme based on the designed training symbol was also incorporated in the system in order to give both fine-timing and frequency-offset estimates. For fine frequency estimation, two approaches are presented. The first one is based on the suppression of the interference introduced in the frequency estimation process by the training symbol pattern in the context of multipath dispersive channels. The second one is based on the maximum likelihood principle and does not suffer from any interference. A new performance measure is introduced for timing estimation, which is based on the plot of signal to timing-error-induced average interference power ratio against the timing estimate shift. A simple approach for finding the optimal setting of the timing estimator is presented. Finally, the sync detection, timing estimation, frequency estimation, and bit-error-rate performance of the proposed method are presented in a multipath Rayleigh fading channel. 相似文献
10.
H Minn M Lapela PJ Klemi R Grénman S Leskinen P Lindholm J Bergman E Eronen M Haaparanta H Joensuu 《Canadian Metallurgical Quarterly》1997,38(12):1907-1911
The aim of this prospective study was to investigate if high uptake of 18F-fluoro-2-deoxy-D-glucose (FDG) is associated with aggressiveness in head and neck cancer and low probability of survival. METHODS: Thirty-seven patients with squamous-cell carcinoma of the head and neck underwent FDG-PET in the fasting state before cancer treatment. FDG uptake in primary tumor was quantitated as the standardized uptake value of FDG normalized to the predicted lean body mass (SUVlean, n = 37) and as the graphically determined metabolic rate for FDG (rMR[FDG], n = 34). Paraffin-embedded tumor samples were used for histologic evaluation, and expression of cytokeratin and Ki-67 antigen were assessed by immunohistochemistry. RESULTS: Interobserver agreement for the determination of quantitative uptake of FDG in tumors was excellent (r2 = 0.996, p < 0.00001), and all 37 primary tumors were visualized. A high uptake of FDG as assessed by SUVlean was associated with a higher than the median mitotic count (p = 0.01), absence of keratinization (p = 0.03), low or moderate histological grade of differentiation (p = 0.046) and advanced stage (p = 0.03), but not with Ki-67 expression (p = 0.11). The overall survival of patients with a SUVlean lower than or equal to the median value (9.0) was clearly better in univariate analysis than that of patients with a SUVlean higher than the median (3-yr survival 73% versus 22%, relative risk of death (RR) 4.2, 1.6-11.0). However, in a multivariate analysis the only independent predictors of survival were the mitotic count (RR 4.0, 1.4-11.7) and stage (3.8, 1.2-12.2). CONCLUSION: High uptake of FDG in untreated head and neck cancer is associated with advanced disease, and may portend poor survival. Aggressive treatment approaches should be considered for patients presenting with a tumor with high uptake of FDG. 相似文献