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We propose a context-aware trust management model called CATrust for service-oriented ad hoc networks such as peer-to-peer and Internet of Things networks wherein a node can be a service requester or a service provider. The novelty of our design lies in the use of logistic regression to dynamically estimate trustworthiness of a service provider based on its service behavior patterns in response to context environment changes. We develop a recommendation filtering mechanism to effectively screen out dishonest recommendations even in extremely hostile environments in which the majority recommenders are dishonest. We demonstrate desirable convergence, accuracy, and resiliency properties of CATrust. We also demonstrate that CATrust outperforms contemporary peer-to-peer and Internet of Things trust models in terms of service trust prediction accuracy against collusion recommendation attacks.

With the ever increasing volume of geo-referenced datasets, there is a real need for better statistical estimation and prediction techniques for spatial analysis. Most existing approaches focus on predicting multivariate Gaussian spatial processes, but as the data may consist of non-Gaussian (or mixed type) variables, this creates two challenges: (1) how to accurately capture the dependencies among different data types, both Gaussian and non-Gaussian; and (2) how to efficiently predict multivariate non-Gaussian spatial processes. In this article, we propose a generic approach for predicting multiple response variables of mixed types. The proposed approach accurately captures cross-spatial dependencies among response variables and reduces the computational burden by projecting the spatial process to a lower dimensional space with knot-based techniques. Efficient approximations are provided to estimate posterior marginals of latent variables for the predictive process, and extensive experimental evaluations based on both simulation and real-life datasets are provided to demonstrate the effectiveness and efficiency of this new approach.

Anomaly detection in mixed-type data is an important problem that has not been well addressed in the machine learning field. Existing approaches focus on computational efficiency and their correlation modeling between mixed-type attributes is heuristically driven, lacking a statistical foundation. In this paper, we propose MIxed-Type Robust dEtection (MITRE), a robust error buffering approach for anomaly detection in mixed-type datasets. Because of its non-Gaussian design, the problem is analytically intractable. Two novel Bayesian inference approaches are utilized to solve the intractable inferences: Integrated-nested Laplace Approximation (INLA), and Expectation Propagation (EP) with Variational Expectation-Maximization (EM). A set of algorithmic optimizations is implemented to improve the computational efficiency. A comprehensive suite of experiments was conducted on both synthetic and real world data to test the effectiveness and efficiency of MITRE.

This paper presents an unsupervised method for systematically identifying anomalies in music datasets. The model integrates categorical regression and robust estimation techniques to infer anomalous scores in music clips. When applied to a music genre recognition dataset, the new method is able to detect corrupted, distorted, or mislabeled audio samples based on commonly used features in music information retrieval. The evaluation results show that the algorithm outperforms other anomaly detection methods and is capable of finding problematic samples identified by human experts. The proposed method introduces a preliminary framework for anomaly detection in music data that can serve as a useful tool to improve data integrity in the future.

Phosphor-free monolithic InGaN-based white-light LED has the advantages of simpler device process and potentially higher efficiency. Several techniques have been developed for implementing such white-light LEDs. Among them, the key issue is the growth of a high-quality high-indium InGaN/GaN quantum well (QW). An underlying InGaN layer growth technique is introduced for enhancing the crystal quality of a high-indium QW. To demonstrate the superior properties of a QW grown with this technique, a green LED is fabricated based on the underlying growth technique to compare with another LED of the same emission wavelength based on the conventional growth method. Then, the underlying growth technique is used to grow three yellow-emitting QWs of high efficiency. The yellow photons mix with blue light from an overgrown blue-emitting QW to produce white light. The improved properties of the phosphor-free monolithic white-light LED are discussed in detail.

In this paper, we proposed a new design of the test mask to measure the amount of the out-of-band (OOB) light from an extreme-ultraviolet (EUV) light source by detuning the period of the multilayer (ML), rather than changing the material of the absorber, to suppress reflection of EUV light. The new OOB test mask also reflects essentially the same OOB light as that of the production mask at each wavelength in the whole OOB spectral range. With the help of the new OOB test mask, the contributions to the background intensity from in-band flare and OOB light can be correctly separated and an accurate optical-proximity-correction (OPC) model can be established.

Due to the use of reflective optics in extreme-ultraviolet lithography (EUVL), the chief ray angle of incidence at the object (mask) side (CRAO) cannot be zero. If the conventional resolution enhancement technique (RET) of off-axis illumination (OAI) is used, such mask-side non-telecentricity degrades aerial image contrast partly because of asymmetry (w.r.t. the mask) of the two beams in an incident beam pair and partly because of asymmetry (w.r.t. the mask) of the two diffraction orders of either incident beam. The former leads to intensity imbalance of the two incident beams (after leaving the mask) and the latter leads to amplitude and phase imbalance of the two diffraction orders of either incident beam. Solutions proposed previously only alleviate the former and have little help for the latter. In this paper, we introduce n=1 absorber to eliminate the phase imbalance so that the transverse shift between the two aerial images formed by the two incident beams can be minimized and the contrast of the final aerial image (by superposition of the two) can be restored.

We compared the nano-structures of three samples of ZnO thin film on sapphire under different growth temperature conditions. Although disconnected domain structures (on the scale of 100 nm in size) were observed in the samples of high-temperature (450 °C) growth, their crystal quality is generally better than the one grown at a low temperature (200 °C), either near or away from the sapphire interface. Lattice misfits and threading dislocations were observed within a domain with the separation of around 8 nm. The sample grown at the low temperature showed a continuous structure through the ZnO layer although void-like structures might exist inside. However, its crystal quality is relatively poorer. Of the two samples with high-temperature growth, the one with initial low-temperature growth had a larger domain structure (around 150 nm in size) and relatively lower crystal quality. In particular, strong strains existed near the interface of this sample. The samples of high-temperature growth generally have higher photon emission efficiencies. Temperature-dependent integrated photoluminescence intensities of the high-temperature-growth samples show that the exciton trapping by either intrinsic donors or acceptors leads to a higher thermal quenching rate in comparison with free excitons.

Nanoposts of 10?40?nm top diameter on an InGaN/GaN quantum well structure were fabricated using electron-beam lithography and inductively coupled plasma reactive ion etching. Significant blue shifts up to 130?meV in the photoluminescence (PL) spectrum were observed. The blue-shift range increases with decreasing post diameter. For nanoposts with significant strain relaxation, the PL spectral peak position becomes less sensitive to carrier screening. On the basis of the temperature-dependent PL and time-resolved PL measurements and a numerical calculation of the effect of quantum confinement, we conclude that the optical behaviours of the nanoposts are mainly controlled by the combined effect of 3D quantum confinement and strain relaxation.

We study the depth-dependent variation of optical property beyond the critical thickness in an InGaN thin film. In the sample, both free-carrier and localized-state recombination activities are observed. The emission peak corresponding to the localized states in photoluminescence (PL) measurement becomes more prominent with increasing sample depth, implying stronger clustering in the deeper layers. Although the PL spectral peak variation is weak, that of cathodoluminescence (CL), corresponding to the activities of the localized states, shows a clear red shift trend with depth. The red shift trend is attributed to the stronger clustering behavior and possibly stronger quantum-confined Stark effect in the nano-clusters, which is due to the residual strain beyond the critical thickness, in a deeper layer.

We compared the nano-structures of three samples of ZnO thin films grown on GaN with different growth temperature conditions. Although disconnected spiral domain structures (of the order of 100?nm in width) were observed in the samples of high-temperature growth, their crystal qualities are generally better than the one grown at low temperature, either near the GaN interface or far away from the interface. In the sample of high-temperature growth through the whole process, the domain structures extend from the interface with a smaller scale and almost vertical sharp boundaries. The sample grown at the low temperature showed a generally continuous structure from the interface. However, its crystal quality is quite poor. In the sample with initial low-temperature growth and then high-temperature growth, the ZnO layer started with a continuous structure, like the sample of low-temperature growth. However, it evolved into domain structures similar to the sample of high-temperature growth beyond about 200?nm in thickness. The samples of high-temperature growth generally have higher photon emission efficiencies. The sample grown at the high temperature through the whole growth process has the highest emission quantum efficiency.

We study thermal annealing effects on the size and composition variations of indium-aggregated clusters in two InGaN thin films with photoluminescence (PL) in the yellow and red ranges. The methods of investigation include optical measurement, nanoscale material analysis, and theoretical calculation. Such a study is important for determining the relation between the band gap and the average indium content of InGaN. In one of the samples, the major part of the PL spectrum is shifted from the yellow band into the blue range upon thermal annealing. In the other sample, after thermal annealing, a broad spectrum covering the whole visible range is observed. Cathodo-luminescence (CL) spectra show that the spectral changes occur essentially in the photons emitted from the shallow layers of the InGaN films. Photon emission spectra from the deeper layers are essentially unaffected by thermal annealing. The spectral changes upon thermal annealing are mainly attributed to the general trend of cluster size reduction....

This paper presents TREADS, a novel travel route recommendation system that suggests safe travel itineraries in real time by incorporating social media data resources and points of interest review summarization techniques. The system consists of an efficient route recommendation service that considers safety and user interest factors, a transportation related tweets retriever with high accuracy, and a novel text summarization module that provides summaries of location based Twitter data and Yelp reviews to enhance our route recommendation service. We demonstrate the system by utilizing crime and points of interest data in the Washington DC area. TREADS is targeted to provide safe, effective, and convenient travel strategies for commuters and tourists. Our proposed system, integrated with multiple social media resources, can greatly improve the travel experience for tourists in unfamiliar cities.

It has been an important issue to improve customers' satisfaction in theme parks for which become a major role of recreation in our daily life. Waiting for rides has been identified as a factor decreasing satisfaction. A previous study indicated that a virtual queuing system can reduce the total waiting time so the customer's satisfaction is improved. The results from a simulation tool Arena show that an index Satisfaction Value (SV) increases when the queuing system is introduced. In this study, a more complex scenario of theme park queuing system (TPQS) is first designed, followed by comparison of a number of combinations of the rides with various waiting time and distribution factors. Analysis is also carried out.

Blue-red polychromatic light-emitting devices are fabricated by attaching red-emitting CdSe-ZnS nano-crystals on a blue-emitting InGaN-GaN multiple-quantum-well (MQW) structure. To improve the red/blue intensity contrast, holes of different diameters are fabricated for increasing the direct contact area between the MQW active regions and CdSe-ZnS nano-crystals. By comparing the devices of 10-, 50-, 60-, and 70-mum hole diameters, and a reference device of no hole, it is found that the hole diameter of 60 mum represents an optimized condition from the viewpoint of maintaining high quantum efficiency. However, the device of 10-mum holes has the highest red/blue intensity ratio, which corresponds to a 36% increase. This result is attributed to its largest side-wall area in the holes among various samples

In extreme ultraviolet lithography (EUVL), the application of off-axis illumination (OAI) leads to degradation in aerial image contrast, resulting in an unacceptably high mask error enhancement factor as the pattern pitch becomes smaller, even if an attenuated phase-shifting mask (AttPSM) of optimized attenuation is employed. We show that this is an intrinsic problem of OAI and cannot be remedied by adopting a thinner absorber, a smaller chief ray angle of incidence at the object side, or a projection optics box with a higher numerical aperture. Based on simulation results using the best conditions for OAI, we may conclude that single-patterning EUVL will probably end at a technology node with the minimum pitch of 22 nm, unless we can come up with other innovative ways for performing EUVL imaging or designing and formulating resists with blurs less than 5 nm at reasonable exposure dose.

In this paper, the impact of resist on the lithographic process window is investigated. To estimate the resolution limit of EUVL due to the limitation from resist performance, a simplified resist model, called diffused aerial image model (DAIM), is employed. In the DAIM, the resist is characterized by the acid diffusion length, or more generally, resist blur. Lithographic process windows with resists of various blurs are then calculated for different technology nodes. It is concluded that the resist blur needs to be smaller than 8 nm to achieve a reasonable window for the technology node with the minimum pitch of 32 nm. The performance of current resists can barely fulfill this requirement. Investigation of a more refined resist model is also initiated.

The experimental demonstrations of light-emitting diode (LED) fabrication with surface plasmon (SP) coupling with the radiating dipoles in its quantum wells are first reviewed. The SP coupling with a radiating dipole can create an alternative emission channel through SP radiation for enhancing the effective internal quantum efficiency when the intrinsic non-radiative recombination rate is high, reducing the external quantum efficiency droop effect at high current injection levels, and producing partially polarized LED output by inducing polarization-sensitive SP for coupling. Then, we report the theoretical and numerical study results of SP-dipole coupling based on a simple coupling model between a radiating dipole and the SP induced on a nearby Ag nanoparticle (NP). To include the dipole strength variation effect caused by the field distribution built in the coupling system (the feedback effect), the radiating dipole is represented by a saturable two-level system. The spectral and dipole-NP distance dependencies of dipole strength variation and total radiated power enhancement of the coupling system are demonstrated and interpreted. The results show that the dipole-SP coupling can enhance the total radiated power. The enhancement is particularly effective when the feedback effect is included and hence the dipole strength is increased.

Summary form only given. The characterization of microplasmas driven by DC and AC (50~1000 Hz) power supplies with a voltage up to 1000 V at atmospheric pressure is performed. Parallel planar aluminum electrodes with an inter-electrode gap 20~200 mm are patterned on a glass substrate by semiconductor fabrication processes. Pure argon and helium are used as the feedstock. Filamentary-like discharges are mostly observed in argon discharges and highly-nonuniform discharges result in locally high current densities, which lead to a severe damage of the electrode. In helium discharges, a corona-like discharge is observed when the plasma is ignited with the applied voltage slightly higher than the breakdown voltage. Under certain conditions, such discharges occupy the entire inter-electrode space. With the increase in the applied voltage, the transition to filamentary-like discharges is occurred. It is shown that the breakdown voltage increases with the gap, and the voltage is 100-200 V higher than that shown in the right branch of the Paschen curve. Oscillations of current and voltage waveforms at different frequencies are observed after the plasma is ignited. Preliminary studies show that the MHz-high frequency oscillation is associated with the external circuits due to the sudden voltage drop after the breakdown. The low frequency oscillation, few tens of kHz, is a result of the repetitive ignition and extinguishment of the discharge. No stable discharge is obtained. Such a behavior is seen in both DC-and AC-driven discharges. P-spice circuit simulation is performed to study the effects of the external circuitry on the discharge behavior. The I-V characteristics are simulated, and results qualitatively agree with the experimental measurements. The optical emission emanating from the plasma is monitored and the broadening of hydrogen emission lines is used to estimate the plasma characteristics, namely the electron density and neutral gas temperature. Finally, the potential using such a discharge in materials processing will be demonstrated.

A programmed-defect mask consisting of both bump- and pit-type defects on the LTEM mask substrate has been successfully fabricated. It is seen that pit-type defects are less printable because they are more smoothed out by the employed MLM deposition process. Specifically, all bump-type defects print even at the smallest height split of 1.7 nm whereas pit-type defects print only at the largest depth split of 5.7 nm. At this depth, the largest nonprintable 1D and 2D defect widths are about 23 nm and 64 nm, respectively.

In this paper, definition of line/space patterns at 44-, 32-, and 22-nm pitches using extreme-ultraviolet lithography (EUVL) is investigated by aerial image simulation. The results indicate that extending EUVL to the 22-nm pitch requires reducing the mask shadowing effect, which implies reducing the mask absorber thickness as well as maintaining the 6-degree angle of incidence on the mask, if the reduction ratio of the imaging system is to be kept at 4. Reduction of the mask absorber thickness can be realized by implementing attenuated phase-shifting masks. Otherwise, all critical patterns must be laid out in single orientation.

Based on Davis' Technology Acceptance Model, the research proposed a new model includes variables such as social-economic class, gender role, gender equality, and self-image. The results indicate that there were significant differences (p = 004) exist in gender role based on different college year of female students. The younger female students tend to have less traditional gender role stereotype than elder female students. However, no significant differences exist in gender role, gender equality, and self-image based on female student parents' social-economic status.

With a dielectric layer between metal and semiconductor for generating surface plasmon, the dissipation rate of metal is reduced and the evanescent-field range is increased such that surface plasmon coupling leads to stronger emission enhancement.

The simulation results of the coupling of a radiation dipole with a surface plasmon (SP), which is induced on a metal/dielectric interface of a single groove (SG) plus a grating structure, are demonstrated. With the SG structure, the dipole can effectively couple energy into an SP feature, which has a mixed nature of localized surface plasmon (LSP) and surface plasmon polariton (SPP). The SPP energy is confined by a grating structure with a well designed grating period and position. With such a cavity configuration, the SPP energy can be well preserved. Both the dipole-SP coupling behaviors in the frequency and time domains are numerically illustrated. The results are useful for designing a metal/dielectric interface nanostructure for implementing a SPASER (surface plasmon amplification by stimulated emission of radiation) system.

Surface plasmon polariton and localized surface plasmon couplings with InGaN/GaN quantum wells in bluegreen light-emitting diodes are used for enhancing their emission efficiencies by 25-200 % depending on the used quantum well crystal quality.

We observe the enhancement of photoluminescence excitation through the coupling of an InGaN/GaN quantum well (QW) with surface plasmons which are generated on an Ag nanostructure deposited on the SiN-coated QW epitaxial sample.

The observation of the enhanced absorption of an InGaN/GaN quantum well through the coupling with localized surface plasmons (LSPs) and the dependence of LSP resonance energy on the geometry of a metal layer are reported.

Studies of contrast sensitivity of the human eyes show that logarithmic curves obey the Weber-Fechner law of just noticeable difference response in human perception. In this paper, we propose a local contrast enhancement algorithm with logarithm-based curves for both high dynamic and low dynamic images and this algorithm can adaptively change the curvature with local information. We also define two parameters to decide the level of contrast enhancement in the tone mapping procedure. For halo artifact which is suffered from local operator, a two-stage procedure is designed to solve the problem. We present experimental results to show performance of our algorithm compared with other existing methods.

We analyze the contribution of the screening of the quantum-confined Stark effect (QCSE) to the light emission enhancement behavior in the surface plasmon (SP) coupling process with an InGaN/GaN quantum well (QW). From the measurements of excitation power-dependent photoluminescence and time-resolved photoluminescence (TRPL), and the fitting to the TRPL data based on a rate-equation model, it is found that when the excitation level is high, the QCSE screening effect not only contributes significantly to the emission enhancement, but also enforces the SP coupling process because of the blue shift of emission spectrum caused by the screening effect. Therefore, the emission strength from SP radiation, relative to that from QW radiative recombination, increases with the excited carrier density.

We demonstrate the loss of surface plasmon (SP) energy through oscillating electron leakage via the ohmic contact of either p-type or n-type GaN layer in the coupling process between SP and an InGaN/GaN quantum well (QW). The observation implies that in using the SP-QW coupling for enhancing emission in a light-emitting diode, the metals for ohmic contact and SP generation must be separated. A thin dielectric interlayer is required in the region for SP-QW coupling to avoid the leakage of SP energy.

We demonstrate the temperature dependent behavior of the surface plasmon (SP) coupling with an InGaN/GaN quantum well (QW). The SP coupling efficiency relies on the availability of carriers with sufficient momentum for transferring the energy and momentum into the SP modes. At low temperatures, the carriers are trapped by the potential minima in the QW and the SP coupling is weak. As temperature increases, more and more carriers escape from the potential minima leading to the stronger and stronger SP coupling. When the temperature is close to the room condition, the SP coupling strength saturates because most carriers have escaped from the potential minima. The three temperature ranges of different SP coupling behaviors can be clearly identified from the data of photoluminescence (PL) enhancement ratio and PL intensity decay rate.

Nitride nanostructures and nano-photonics, including an MOCVD prestrained InGaN/GaN quantum well growth technique for orange and white LED fabrication and surface plasmon coupling with an InGaN/GaN quantum well for light emission enhancement, are reported.

After several fundamental phenomena of surface plasmon coupling with an InGaN/GaN quantum well for light emission enhancement are studied, we evaluate the application of such a coupling process to a light-emitting diode with experimental supports.

We use a non-degenerate pump-probe scheme of an extremely broad probe spectrum to monitor the ultrafast carrier relaxation process from the excitation levels down to the free-carrier and the localized states in an InGaN thin-film.