Search

In this paper, the phase detection method is demonstrated to determine the film thicknesses of bimetallic layers by surface plasmon resonance (SPR) prism coupler. It was proposed and developed by matching the experimental results to the theoretical curves of the phase difference with different angles of incidence. The results of both of the two metallic film thicknesses obtained by our method coincide well with the measurement results of atomic force microscope (AFM) and spectroscopic ellipsometer (SE) measurement. Both theoretical analysis and experimental results indicate that the method proposed is stable and reliable, and feasible to be used to determine the film thickness of bimetallic layers directly with nanometer order resolution.

In the wireless microsensor networks with heterogeneous characteristics between users, the paper carries research on how to appropriately assign available secondary users (SUs) to sense some channels in order to achieve a good balance among energy consumption, sensing performance and spectrum opportunity. To begin with, considering the characteristics of microsensors, and using network topology information, the optimization problem with the objective of maximizing energy efficiency under performance constrains is formulated. Then, the closed-form solution is derived based on Karush-Kuhn-Tucker (KKT) condition, which can determine the priority of SUs, and the location-aware energy-efficient assignment (LEA) algorithm is proposed to approximate the optimal solution. Finally, by simulating different location distribution scenarios of users, the results show that the proposed algorithm can not only assign the optimal users group more quickly, but also obtain a higher energy efficiency than other algorithms. And the performance of the proposed algorithm is nearly the same as that of the optimal algorithm with exhaustive search, but with the greatly decreased complexity.

In order to solve the problem the existing vertical handoff algorithms of vehicle heterogeneous wireless network do not consider the diversification of network’s status, an optimized vertical handoff algorithm based on markov process is proposed and discussed in this paper. This algorithm takes into account that the status transformation of available network will affect the quality of service (QoS) of vehicle terminal’s communication service. Firstly, Markov process is used to predict the transformation of wireless network’s status after the decision via transition probability. Then the weights of evaluating parameters will be determined by fuzzy logic method. Finally, by comparing the total incomes of each wireless network, including handoff decision incomes, handoff execution incomes and communication service incomes after handoff, the optimal network to handoff will be selected. Simulation results show that: the algorithm proposed, compared to the existing algorithm, is able to receive a higher level of load balancing and effectively improves the average blocking rate, packet loss rate and ping-pang effect.

The evanescent wave, occurred when the incident light generates total internal reflection on the interface between glass and metallic film, can raise the surface plasmon (SP) on the metallic film. SP and evanescent wave can resonate under certain angle of incidence when they have the same frequency and wave number. In this case, the power of reflection beam decreases dramatically, and the resonance peak appears in the reflection spectroscopic. The positions of resonance peaks are different when the refraction indexes of medium on the metallic film or the thicknesses of the metallic film are different. And it is found that the phase position of p-component of reflected light changes with the metal film thickness, while the phase position of s-component almost doesn’t change in the Surface Plasmon Resonance effect. S-polarized light is taken as reference and interferometry is adopted to turn the change of the phase position into the change of interference fringes position in the paper, and the film thickness can be derived from it. The simulation results indicated that, through making use of piecewise quadratic fitting on the phase data, the inaccuracy with the range of film thickness is between 30 and 80 nanometers is not more than 0.33 nm.

The mobile intelligent terminal equipment represented by smart-phones, applied to the terminal at the beginning of the software in the design and you need to follow applicable, open, short, quantitative goals and principles of humanized. Based on this, in turn, to formulate the overall design of software framework, and through the software development technology to achieve.

In the three-dimensional angle measurement, yaw and pitch angle can be detected easily by several convention optical devices. While the roll angle is difficult to measure since its rotation axis is parallel to the incident plane. This work is based on the application of the Talbot effect with a Ronchi grating. The period of Moire fringes which generated by two gratings will be changed with small rotation. The roll angle can be calculated by the width change of fringes.

This paper presents a wind turbine concept based on a dual-stator-single-rotor (or sandwich-typed) PMSG and a novel converter. First, the structure of the sandwich-typed PMSG is explained. Then, according to the principle of the PMSG, a novel converter topology is proposed. Finally, a detailed direct drive wind turbine model based on the converter and the PMSG is built in the Matlab/Simulink. Thorough simulation results under different wind conditions verify the effectiveness of the generator+converter combination and the typical functionalities of the wind turbine.

Most anticancer drugs entering clinical trials fail to achieve approval from the US FDA. Drug development is hampered by the lack of preclinical models with therapeutic predictive value. Herein, we report the development and validation of a tumorgraft model of renal cell carcinoma (RCC) and its application to the evaluation of an experimental drug. Tumor samples from 94 patients were implanted in the kidney of mice without additives or disaggregation. Tumors from 35 patients formed tumorgrafts, and 16 stable lines were established. Samples from metastatic sites engrafted at high frequency, and stable engraftment of primary tumors in mice correlated with decreased patient survival suggesting that tumor growth in mice may reveal the acquisition by the tumor of an ability to thrive at distant sites and metastasize. Tumorgrafts retained the histology, gene expression, DNA copy number alterations, and over 90% of the protein-coding gene mutations of the corresponding tumors. As determined by the induction of hypercalcemia in tumorgraft-bearing mice, tumorgrafts were able to act on the host causing paraneoplastic syndromes. In studies simulating drug exposures in patients, RCC tumorgraft growth was inhibited by sunitinib and sirolimus (into which temsirolimus is converted in humans), but not by erlotinib, which was used as a control. Dovitinib, a drug in clinical development, showed greater activity than sunitinib and sirolimus. The routine incorporation of models recapitulating the molecular genetics and drug sensitivities of human tumors into preclinical programs has the potential to improve oncology drug development.

In this paper, based on a novel two-user cognitive radio channel model, under the assumption that secondary user can obtain partial primary user's information and transmit power of secondary user is controlled properly according to the scenario whether primary user exists or not, then the relationship between channel capacity and sensing duration is respectively analyzed in the two cases that whether ignoring the false judgements of secondary user or not. Subsequently, an expression of the optimal sensing duration is obtained to maximize the channel capacity. Finally, numerical simulation results show that there exists an optimal sensing duration to maximize the channel capacity; in the cooperative sensing environment, the longer sensing duration, the fewer cooperative cognitive users when channel capacity reaches maximum.

Interference alignment (IA) improves the system performance because it makes maximally overlap the interference in multi-user MIMO system. However, the current study was based on a given power; it does not take full advantage of the system's total power. How to allocate power among the users based on interference alignment is the key to this paper. Firstly, a framework of MIMO interference channel was developed and subspace interference alignment was analyzed. Secondly, a novel interference alignment scheme based on dynamic power allocation that can fully use of system power was proposed. Finally, a performance simulation in LTE system was present. The result shows that the average BER and interference power have a significant improvement at the expense of only a tiny system capacity.

Motivated by the demand for alternative ways to enhance wireless security, this paper proposes a technique to enhance wireless security at physical layer. It takes advantage of rich multipath environment to focus radio energy on some desired spatial spot, while achieving nulling at other spots. This can be viewed as a physical-layer security enhancement. What makes spatial focusing and nulling possible is transmit waveform optimization based on propagation environments. The concept and principle are studied in an ultra-wideband (UWB) relay network scenario. Using a matched filter receiver at test points, the optimization problem is actually the Quadratically Constrained Quadratic Program (QCQP) which is known as an NP-hard problem, thus the Semidefinite Program (SDP) as a relaxation technique is used to obtain suboptimal results. The feasibility is numerically validated using the UWB outdoor channel model. It is found that, by choosing a proper transmit waveform, the worst-case information leakage at unintended locations can be significantly minimized, with acceptable attenuation at the intended location.

The sensing performance of local detection in cognitive radio systems will be degraded when the channel experience fading and shadowing, and hidden terminal problem is inevitable for the primary transmitter-sensing. To overcome this problem, cooperative spectrum sensing has been proposed. We propose a twice-cooperative sensing algorithm to improve the sensing performance. By comparing to the single-cooperative, the simulations show that the proposed algorithm can enhance the sensing performance and the proposed algorithm can also save the band width of the control channel.

MIMO schemes can improve the capacity observably. The co-channel interference (CCI) and noise are two major impairments to a multi-user MIMO downlink. The precoding based on signal-to-leakage-and-noise ratio (SLNR) makes a balance between eliminating the CCI and the noise, so it improves the system performance. But the channel state of every user is different, the channel quality effects the performance of the system. This paper designs a dynamic power allocation can get a better performance. Simulation results prove the theory at last. We also illustrate that the system performance will degrade when the transmitter knows the imperfect channel state information.

In the trust model for P2P network, to get the accurate value of global trust is becoming difficult because of the complex of net environment and the dishonest peers. This article proposed the computation method for the value of globe trust based on the MAX-MIN ant system. Through this advanced ant colony algorithm, search several recommendation paths to compute the best global trust valuation from source peer to the destination peer. It uses the MMAS, dynamic adjust the degree of pheromones and the new policy of searching. These measures have strengthened the effectiveness of positive feedback, shortened the time of searching, and speeded up convergence rate. It can improve the accuracy of the global trust valuation using the method that this article mentioned, and reduce the potential safety hazard which the unite cheat behavior brought. Theoretical analysis and simulation show that this method is more efficient than the traditional method, and is better to adapt to the complex network environment.

For the downlink of MIMO TDD/CDMA mobile radio systems joint transmission (JT) which has low receiver complexity is recently proposed. First investigations concerned linear transmitter algorithms and nonlinear transmitter algorithms based on the principle of THP. The nonlinear transmitter algorithms studied by M. Meurer have preferable energy efficient but restricted by coding complexity. In this paper we present a power distribution algorithm in multi-user downlink of linear JT in MIMO system (JT MIMO). First, a model of JT MIMO downlink and interference is introduced, then, we present a joint power distribution algorithm for JT MIMO downlink. By distributing the transmission power of users rationally, under achieving the SINR, minimizes the total transmitted power.

Publisher Summary Methane is the major component of natural gas and its catalytic conversion to desired chemical products or liquid fuel is not only a promising approach for the utilization of natural gas resource but also a great subject to catalysis science that deals with the activation of small molecules. Obviously, direct methane conversion to higher hydrocarbons seems to be one reasonable way to overcome this economic problem. In recent years, the catalytic conversion of methane has been actively studied using dioxygen or other oxidants. The most extensive study has been the oxidative coupling of methane (OCM) since 1982. But the difficulty in meeting the conditions required by the industrial application of the oxidative coupling of methane is still left. Meanwhile, the conversion of methane to benzene over high silica zeolite based catalysts in a pulse-reactor was reported, but limited information was provided. In this chapter the optimizing procedure of methane aromatization over Mo/HZSM-5 is presented and the mechanism for methane activation and aromatization is proposed.