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41.
We demonstrate experimental all-optical code-division multiplexing (AO-CDM) systems using 64-ps optical pulses and a 2" prime code of n = 3. A distinguishing feature of this experiment is that the modulation of an ultrashort optical clock stream by electrical data is realized without using any optical intensity modulator at each transmitter. Moreover, only low-cost optical 2 x 2 couplers and fiber delay lines are employed to implement all-serial encoders and decoders for a 2n prime code. 相似文献
42.
The CD56+ lymphomas are a recently characterized high-grade malignancy of putative natural killer cell origin. They are mostly localized to the nasal areas but show a propensity to spread to or recur in the skin. We describe a unique case of CD56+ natural killer lymphoma that recurred in scrotal skin in a patient 8 years after an initial limited resection. Although this case was unusual in showing a prolonged period of apparent remission, it illustrated a characteristic clinicopathologic behavior of this rare tumor. 相似文献
43.
It has recently been noted that hemispherical structures have useful reflection characteristics. We describe a new application that makes use of these characteristics by controlling the reflectance of a surface composed of an array of hemispherical liquid droplets. In this system the reflectance state is spatially controlled through the use of electrowetting to alter the shape of an array of droplets. This may have an application in the field of electronic image displays. 相似文献
44.
The dynamic characteristics of both single-crystal and ion-implanted semiconductor layers annealed by a pulsed high-power laser beam is examined analytically for the first time by means of a parametrized perturbation method. The laser-induced lattice temperature rise is explicitly related to the laser beam parameters as well as the semiconductor properties. Specifically, the temperature in the annealed semiconductor is characterized in terms of the ambipolar diffusion length of hot, excess charge carriers, the optical attenuation coefficient of the medium, and the operating laser power, and the threshold pulse energy for surface melting is calculated for the case of silicon devices. It is shown that the pulse energy required for the onset of surface melting is sensitively dependent on the optical absorption coefficient, decreases significantly with increasing pulse intensity, and increases remarkably with increasing diffusion length of excess charge carriers. 相似文献
45.
A methodology of determining aggregated importance of engineering characteristics in QFD 总被引:3,自引:0,他引:3
Quality function deployment (QFD) is a planning and problem-solving tool that is gaining acceptance for translating customer requirements (CRs) into engineering characteristics (ECs) of a product. Deriving the importance of ECs is a crucial step of applying QFD. However, the inherent fuzziness in QFD presents a special challenge to effectively evaluate the importance of ECs and correlation among them. Furthermore, degree of impact of an engineering characteristic (EC) on the other ECs also reflects the importance of the ECs. In previous studies, those impacts were neglected or simply represented using a linear combination in determining the importance of ECs. To address this issue, in this paper, a new methodology of determining aggregated importance of ECs is presented which involves the consideration of conventional meaning of importance of ECs as well as the impacts of an EC on other ECs. In the proposed methodology, fuzzy relation measures between CRs and ECs as well as fuzzy correlation measures among ECs are determined based on fuzzy expert systems approach. These two types of measures are then used to determine the aggregated importance of ECs. An example of design of a digital camera is used to illustrate the proposed methodology. 相似文献
46.
Hybrid Model to Detect Zero Quantized DCT Coefficients in H.264 总被引:2,自引:0,他引:2
Hanli Wang Sam Kwong 《Multimedia, IEEE Transactions on》2007,9(4):728-735
In H.264 coding, there are a large number of discrete cosine transform (DCT) coefficients of the prediction residue which are quantized to zeros. Therefore, it is desired to design a method which can early detect zero quantized DCT coefficients (ZQDCT) before implementing DCT and quantization (Q) and thus reduce redundant computations for H.264 coding. To achieve this, a hybrid model is proposed in this paper in order to predict ZQDCT coefficients. First, the Gaussian distribution is applied to study the integer DCT coefficients in H.264 and hence an adaptive scheme with multiple thresholds is derived to realize different types of DCT and Q implementations. Then the adaptive scheme is further optimized by considering a more efficient condition to sufficiently detect all-zero DCT blocks. As a result, a hybrid model is developed. Compared with other methods in the literature, the proposed hybrid model is able to detect more ZQDCT coefficients and hence reduce more computations for H.264 encoding. It is shown by experimental results that the proposed hybrid model can achieve the best performance in reducing computations and obtain almost the same rate-distortion (R-D) performance as the original encoder in the H.264 reference software JM9.5 相似文献
47.
Xin Peng Wang Eu-Jin Lim A. Hong Yu Yu Ming-Fu Li Chi Ren Wei-Yip Loh Chun Xiang Zhu Chin A. Trigg A.D. Yee-Chia Yeo Biesemans S. Guo-Qiang Lo Dim-Lee Kwong 《Electron Devices, IEEE Transactions on》2007,54(11):2871-2877
A lanthanum (La)-doped HfN is investigated as an n-type metal gate electrode on SiO2 with tunable work function. The variation of La concentration in (HfinfinLa1-x)Ny modulates the gate work function from 4.6 to 3.9 eV and remains stable after high-temperature annealing (900degC to 1000degC), which makes it suitable for n-channel MOSFET application. An ultrathin high-fc dielectric layer was formed at the metal/SiO2 interface due to the (HfinfinLa1-x)Ny and SiO2 interaction during annealing. This causes a slight reduction in the effective oxide thickness and improves the tunneling current of the gate dielectric by two to three orders. We also report the tunability of TaN with Al doping, which is suitable for a p-type metal gate work function. Based on our results, several dual-gate integration processes by incorporating lanthanum or aluminum into a refractory metal nitride for CMOS technology are proposed. 相似文献
48.
Liu Ching-Ping C.-P. Yang Guu-Chang G.-C. Chiu Yu-Wen Y.-W. Kwong W.C. 《Wireless Communications, IEEE Transactions on》2007,6(6):2162-2171
In this paper, a multiple-rate, multicarrier direct- sequence code-division multiple-access (MC/DS-CDMA) system with the use of two-dimensional orthogonal variable spreading factor (2-D OVSF) codes is studied. They are the first 2-D codes that can be generated by the tree structure commonly used by one-dimensional OVSF codes in wideband-CDMA. The 2-D OVSF codes also preserve orthogonality among code matrices with different spreading factors in the code tree. The performances of the proposed system with RAKE receivers employing equal-gain and maximal-ratio combining methods are analyzed and compared. Our results show that our multiple-rate MC/DS-CDMA system with the 2-D OVSF codes is more suitable for a non-fading additive white Gaussian noise channel or a Rician weak-fading channel. However, in a Rayleigh fading channel, the system performance gets worse because the orthogonality of the 2-D OVSF codes is destroyed by the strong fading effect. 相似文献
49.
Chandrakasan A. P. Daly D. C. Finchelstein D. F. Kwong J. Ramadass Y. K. Sinangil M. E. Sze V. Verma N. 《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》2010,98(2):191-214
50.
The operation principles of a high-power high-efficiency GaAlAs superluminescent diode based on an internal absorber for lasing suppression is described. The absorber is based on an unpumped/reverse-biased section in the device, and the superluminescent diode characteristic depends heavily on the bias condition of the absorber section. The very high efficiency of the device arises from the strong waveguiding effect of the buried heterostructure. A theory which accurately describes the various device characteristics is described 相似文献