Analysis of undercompensation and overcompensation of friction in 1DOF mechanical systems

This paper investigates the effects of undercompensation and overcompensation of friction in PD controlled 1DOF mechanical systems. The friction force that is acting on the mechanical system and the friction compensation term in the feedback loop are described by a class of discontinuous friction models consisting of static, Coulomb and viscous friction, and including the Stribeck effect. Lyapunov's stability theorem and LaSalle's invariance principle are applied to prove that undercompensation of friction leads to steady-state errors and the properties of the ω-limit set of trajectories of a two-dimensional autonomous differential inclusion are used to show that overcompensation of friction may induce limit cycling. Furthermore, the analysis also indicates that the limit cycling effect can be eliminated by tuning the PD controller gains.     

Mode conversion in the resonance region of parallel plate magnetoplasma waveguides

Nonreciprocal propagation in parallel plate, magnetoplasma waveguide is restricted to transverse magnetic (TM) modes when the waveguide cross-section is nonsymmetrical. The analysis of this canonical structure is extended here by including collision frequency loss in the characteristic equation and by studying mode propagation in the extraordinary wave resonance region. Conversion between the dominant and first higher order mode is observed as the bias field is increased through resonance. Field plots are included to illustrate this effect.     

A numerical study on heat transfer and friction in rectangular channel with inclined perforated baffles

A three‐dimensional numerical study on the turbulent flow and heat transfer characteristics in the rectangular channel with different types of baffles is carried out. The inclined baffles have the width of 19.8 cm, the square diamond type hole having one side length of 2.55 cm, and the inclination angle of 5°. Reynolds number is varied between 23 000 and 57 000. The SST k ? ω turbulence model is used in the method to predict turbulent flow. The validity of the numerical results is confirmed by measurement. Numerical results show that the flow patterns around the different baffle type are entirely different and it significantly affects the local heat transfer characteristics. The heat transfer and friction factor characteristics are significantly affected by the perforation density of the baffle plate. The present study demonstrates that the battle type II (3 holes) can enhance the greatest heat transfer rates with advantages from the overall efficiency point of view.     

Adaptive Control of Mechanical Systems Using Neural Networks

In this paper, we consider the decentralized adaptive control design problem for uncertain mechanical systems, where uncertainty may arise due to isolated subsystem and/or interconnections among subsystems. Radial basis function neural networks are used to approximate the nonlinear functions to include both dynamic and interconnection uncertainties in each subsystem. The stability of the thus designed control system can be guaranteed by a rigid proof. Finally, a simulation example is given to illustrate the effectiveness of the proposed algorithm.     

Used lubricating oil regeneration by various solvent extraction techniques

The used lubricating oil regeneration using extraction technique has been widely known as one of the cheapest and most competent processes. The best performance of solvent was shown by R-11 as the lowest percent oil losses, followed by CFC-113, MEK, 1-butanol, and 2-propanol. This performance sequence could be also evaluated by method of solubility parameter difference (E_s) using Hildebrand and Peng–Robinson EoS approaches. The effectiveness of extraction parameters was also studied. The percent oil losses decreased with the extraction temperature. The values of optimum ratio of solvent to oil obtained by the E_s method gave reasonable results compared to the experimental method.     

Secure and imperceptible digital image steganographic algorithm based on diamond encoding in DWT domain

This paper presents a new efficient embedding algorithm in the wavelet domain of digital images based on the diamond encoding (DE) scheme. Current discrete wavelet transform (DWT) steganography adds an unacceptable distortion to the images and is considered as an ineffective in terms of security. Applying the DE scheme to the current DWT steganographic methods solves the problems of these methods, and reduces the distortion added to the images, and thus improves the embedding efficiency. The proposed algorithm first converts the secret image into a sequence of base-5 digits. After that, the cover image is transformed into the DWT domain and segmented into 2?×?1 coefficient pairs. The DE scheme is used then to change at most one coefficient of each coefficient pair to embed the base-5 digits. Experimental results depict that the proposed algorithm is more efficient in embedding compared to other methods in terms of embedding payload and image quality. Moreover, the proposed algorithm is attacked by well-known steganalysis software. Results are showing that the proposed algorithm is secure against the powerful universal steganalyzer “ensemble classifier” and the histogram attack. The results also reveal that the proposed algorithm is robust against different image processing attacks such as compression, added noise, and cropping attacks.     

PCA-based image recombination for multimodal 2D + 3D face recognition

Most of the existing approaches of multimodal 2D + 3D face recognition exploit the 2D and 3D information at the feature or score level. They do not fully benefit from the dependency between modalities. Exploiting this dependency at the early stage is more effective than the later stage. Early fusion data contains richer information about the input biometric than the compressed features or matching scores. We propose an image recombination for face recognition that explores the dependency between modalities at the image level. Facial cues from the 2D and 3D images are recombined into a more independent and discriminating data by finding transformation axes that account for the maximal amount of variances in the images. We also introduce a complete framework of multimodal 2D + 3D face recognition that utilizes the 2D and 3D facial information at the enrollment, image and score levels. Experimental results based on NTU-CSP and Bosphorus 3D face databases show that our face recognition system using image recombination outperforms other face recognition systems based on the pixel- or score-level fusion.     

Near-field detection of photon emission from silicon with 30 nm spatial resolution

We demonstrate a scanning near-field photon emission microscope (SNPEM) for monitoring photon emission sites with spatial resolution beyond the diffraction limit. Success of SNPEM analysis strongly depends on the sensitivity of photon emission detection. We show that scattering dielectric probe (SDP) is capable of providing both sub-100 nm resolution and compatible sensitivity at emission wavelengths between 1 μm and 1.4 μm. We propose a two step fabrication method which avoids any metal coating and ensures repeatability of parameters of different probes. We also predict that fabrication of SDP from a multi-mode fiber instead of a single mode fiber can significantly improve the collection efficiency of the probe.     

An agent-based model of building occupant behavior during load shedding

Load shedding enjoys increasing popularity as a way to reduce power consumption in buildings during hours of peak demand on the electricity grid. This practice has well known cost saving and reliability benefits for the grid, and the contracts utilities sign with their “interruptible” customers often pass on substantial electricity cost savings to participants. Less well-studied are the impacts of load shedding on building occupants, hence this study investigates those impacts on occupant comfort and adaptive behaviors. It documents experience in two office buildings located near Philadelphia (USA) that vary in terms of controllability and the set of adaptive actions available to occupants. An agent-based model (ABM) framework generalizes the case-study insights in a “what-if” format to support operational decision making by building managers and tenants. The framework, implemented in EnergyPlus and NetLogo, simulates occupants that have heterogeneous thermal and lighting preferences. The simulated occupants pursue local adaptive actions such as adjusting clothing or using portable fans when central building controls are not responsive, and experience organizational constraints, including a corporate dress code and miscommunication with building managers. The model predicts occupant decisions to act fairly well but has limited ability to predict which specific adaptive actions occupants will select.     

The characterization of a cascade thermoelectric cooler in a cryosurgery device

An experimental investigation using a Peltier thermoelectric cooler (TEC) to cool down a cryoprobe for cryosurgery was performed. Two prototypes of cryosurgery devices consisting of 5- and 6-stage TEC modules were analyzed using a variety of electrical voltages, circulating thermostatic bath (CTB) temperatures, and heat exchanger configurations to obtain an optimum cold side temperature and temperature differences between sides of the modules. To increase the heat exchanges at the hot side, a heat pipe system with a water block was used. Using an electric voltage of 12 V and a CTB temperature of 273.55 K, a cryogenic temperature of 177.09 K and a temperature difference of 99.87 K were achieved. These results indicate that the TEC module can be an effective cooling source for cryosurgery. The prototype has shown potential for clinical trials.