Common Enhancement Techniques Research Articles

Latent Heat Storage Systems for Thermal Management of Electric Vehicle Batteries: Thermal Performance Enhancement and Modulation of the Phase Transition Process Dynamics: A Literature Review

Electric vehicles battery systems (EVBS) are subject to complex charging/discharging processes that produce various amount of stress and cause significant temperature fluctuations. Due to the variable heat generation regimes, latent heat storage systems that can absorb significant amounts of thermal energy with little temperature variation are an interesting thermal management solution. A major drawback of organic phase change materials is their low thermal conductivity, which limits the material charging/discharging capacity. This review paper covers recent studies on thermal performance enhancement of PCM thermal management for electric vehicles batteries. A special focus is placed on the constraints related to electric vehicles battery systems, such as mass/volume minimization, integration with other battery thermal management systems, operational temperature range, adaptability to extreme regimes and modulation of the melting/solidification behavior. The main research outcomes are as follows: quantitative/comparative assessment of common enhancement technique in terms of performance; approaches to deal with special constraints related to EVBS from the thermal control point of view.

A Hybrid Domain Color Image Watermarking Based on DWT–SVD

In recent years, digital image watermarking has been emerged as a promising solution for copyright protection and authentication problem of digital images. Among several existing watermarking schemes, very few have been designed for the authenticity and copyright protection problem of color images. To protect the copyright and validate the authenticity of color images, in this paper a hybrid robust image watermarking scheme based on discrete wavelet transform (DWT) and singular value decomposition is proposed and simulated. Initially, RGB color image is switched to YCbCr color space from which only Y achromatic component is considered for watermark data insertion. In the next step, Y component of the YCbCr color model is decomposed into non-overlapping blocks and subsequently DWT are applied to each block. In this work, non-overlapping decomposed gray watermark image blocks are embedded into singular values of DWT-transformed cover image blocks. Proposed technique’s simulation result established the robustness by extracting adequate watermark data from the restructured cover image after applying common geometric transformation attacks (like rotation, flip operation, cropping, scaling, shearing and deletion of lines or column operation), common enhancement technique attacks (like lowpass filtering, histogram equalization, sharpening, gamma correction, noise addition), JPEG compression attacks and combinational attacks (like combination of geometric transformation attacks and common enhancement technique attacks, combination of geometric transformation attacks and JPEG compression attacks, combination of common enhancement technique attacks and JPEG compression attacks, and combination of geometric transformation attacks and geometric transformation attacks).

An SVD Based Location Specific Robust Color Image Watermarking Scheme Using RDWT and Arnold Scrambling

In recent times, effectiveness of the robust image watermarking scheme almost successfully solves the authenticity and copyright protection problem of images. Among several existing robust watermarking schemes, very few have been designed for color images. In this paper, the authors have proposed a redundant discrete wavelet transform (RDWT) and singular value decomposition based hybrid robust color image watermarking method where scrambled watermark is used for embedding purpose to provide extra security to authentic logo. At first, RGB color image is converted to YCbCr color image and then the Y component of YCbCr color space is used to insert Arnold scrambled grayscale watermark. In the next step, Y component of the YCbCr color model is decomposed into non overlapping blocks and subsequently RDWT are applied to each block. For better imperceptibility and effectiveness, in this proposed algorithm some singular values of RDWT transformed Y component blocks are modified by non overlapping decomposed and scrambled watermark blocks. Robustness of the proposed method is experimented against common geometric transformation attacks (like rotation, flip operation, cropping, scaling, shearing and deletion of lines or column operation etc.), common enhancement technique attacks (like lowpass filtering, histogram equalization, sharpening, gamma correction, noise addition etc.), jpeg compression attacks, some combinational attacks and satisfactory results are achieved. For better evaluation, proposed scheme is verified against standard benchmark software “Checkmark”.

An indirect watermark hiding in discrete cosine transform-singular value decomposition domain for copyright protection.

Digital image watermarking has emerged as a promising solution for copyright protection. In this paper, a discrete cosine transform (DCT) and singular value decomposition (SVD) based hybrid robust image watermarking method using Arnold scrambling is proposed and simulated to protect the copyright of natural images. In this proposed scheme, before embedding, watermark is scrambled with Arnold scrambling. Then, the greyscale cover image and encrypted watermark logo are decomposed into non-overlapping blocks and subsequently some selected image blocks are transformed into the DCT domain for inserting the watermark blocks permanently. For better imperceptibility and effectiveness, in this proposed algorithm, watermark image blocks are embedded into singular values of selected blocks by multiplying with a feasible scaling factor. Simulation result demonstrates that robustness is achieved by recovering satisfactory watermark data from the reconstructed cover image after applying common geometric transformation attacks (such as rotation, flip operation, cropping, scaling, shearing and deletion of lines or columns operation), common enhancement technique attacks (such as low-pass filtering, histogram equalization, sharpening, gamma correction, noise addition) and jpeg compression attacks.

Biomechanical Weakening of Different Re-treatment Options After Small Incision Lenticule Extraction (SMILE).

To determine the corneal weakening induced by different re-treatment options after small incision lenticule extraction (SMILE) and investigate the potential of corneal cross-linking (CXL) to reestablish the original corneal stress resistance. A total of 96 freshly enucleated porcine corneas were used. The initial refractive correction was defined to be -11.00 diopters (D) and the required enhancement to be -3.00 D. Three different re-treatment options were analyzed: -3D Re-SMILE, -3D photorefractive keratectomy (PRK) on top of the SMILE cap, and cap-to-flap conversion and -3D excimer ablation on the stromal bed (LASIK). The control condition did not receive any treatment. Subsequently, accelerated CXL (9 mW/cm2, 10 min) was performed in two groups with currently common enhancement techniques: following cap-to-flap conversion (-3D LASIK enhancement) and in controls. Biomechanical properties were measured with stress-strain extensometry ranging from 1.27 to 12.5 N. The Re-SMILE and PRK enhancement did not significantly reduce the overall elastic modulus of the cornea compared to controls (24.7 ± 2.23 and 22.7 ± 2.61 versus 23.8 ± 3.35 MPa, P ≥ .176), whereas LASIK enhancement did (22.2 ± 3.37 MPa, P = .048). CXL treatment significantly increased the elastic modulus compared to all non-cross-linked conditions (P ≤.001). Refractive surgery decreased the overall elastic modulus by 7%, whereas CXL increased it by 20%. In enhancement, the corneal biomechanical integrity is less affected with both Re-SMILE and PRK enhancement. Corneal weakening through laser refractive surgery is small compared to the stiffening effect after CXL. [J Refract Surg. 2017;33(3):193-198.].

A blind DCT based color watermarking algorithm for embedding multiple watermarks

Multiple watermarking based techniques are receiving more attention in recent times for its wide variety of applications in different fields. To protect the copyright ownership and validate the authenticity of multiple owners, in this paper a color multiple watermarking method based on DCT (Discrete Cosine Transform) and repetition code is proposed and simulated. Initially, green and blue components of color host image are selected for inserting multiple watermarks. Then, each green and blue component of the image is decomposed into non overlapping blocks and subsequently DCT is employed on each block. In this technique, a binary bit of watermark is embedded into green/blue component’s transformed block by modifying some middle significant AC coefficients using repetition code. During multiple watermarks embedding in green and blue components of the proposed method, DC and some higher AC coefficients are kept intact after zigzag scanning of each DCT block to ensure the imperceptibility of the watermarked host image. The proposed scheme is experimented to establish the validity by extracting adequate multiple watermark data from the restructured cover image after applying common geometric transformation attacks (like rotation, cropping, scaling and deletion of lines/columns etc.), common enhancement technique attacks (like lowpass filtering, histogram equalization, sharpening, gamma correction, noise addition etc.) and JPEG compression attacks.

A robust blind hybrid image watermarking scheme in RDWT-DCT domain using Arnold scrambling

To compromise between imperceptibility and robustness property of robust image watermarking technique, a RDWT-DCT based blind image watermarking scheme using Arnold scrambling is presented in this paper. Firstly, RDWT (Redundant Discrete Wavelet Transform) is applied to each gray scale cover image block after the image is decomposed into fixed size non overlapping blocks. Secondly, the binary watermark logo is encrypted by Arnold chaotic map and reshaped to a sequence to improve the security of the logo. In the subsequent step, DCT (Discrete Cosine Transform) is employed on each LH subband of the non-overlapping host image block. Finally, after zigzag scanning of each DCT block a binary bit of watermark is embedded into each block by adjusting some middle significant AC coefficients using repetition code. Experimental results show that robustness is achieved by recovering satisfactory watermark data from the reconstructed cover image after applying common geometric transformation attacks (like rotation, cropping, scaling, shearing and deletion of lines or column operation etc.), common enhancement technique attacks (like lowpass filtering, histogram equalization, sharpening, gamma correction, noise addition etc.) and JPEG compression attacks. The proposed scheme is also tested to verify the robustness performance against standard benchmark software "Checkmark" and satisfactory results are achieved against the Checkmark attacks such as Hard and Soft Thresholding, Template Removal, Warping, Dithering, Remodulation and Downsampling/Upsampling etc.

Chemical enhancement of soil based footwear impressions on fabric

This study investigates the enhancement of footwear impressions prepared with soils from different locations on a variety of fabric surfaces with different morphology. Preliminary experiments using seventeen techniques were carried out and the best responding reagents were evaluated further. Results indicated that the soils investigated (a cross-section of soils from Scotland) are more likely to respond to reagents that target iron ions rather than calcium, aluminium or phosphorus ions. Furthermore, the concentration of iron and soil pH did not appear to have an effect on the performance of the enhancement techniques. For the techniques tested, colour enhancement was observed on all light coloured substrates while enhancement on dark coloured fabrics, denim and leatherette was limited due to poor contrast with the background. Of the chemical enhancement reagents tested, 2,2'-dipyridil was a suitable replacement for the more common enhancement technique using potassium thiocyanate. The main advantages are the use of less toxic and flammable solvents and improved clarity and sharpness of the enhanced impression. The surface morphology of the fabrics did not have a significant effect on the enhancement ability of the reagents apart from a slight tendency for diffusion to occur on less porous fabrics such as polyester and nylon/lycra blends.

Comparative Evaluation of Ultrasound Kidney Image Enhancement Techniques

Evaluation have been done to different enhancement techniques applied to ultrasound kidney images to see which enhancement techniques is the most suitable techniques that can be applied to the kidney images before segmenting the edge of the kidney. Five common enhancement techniques have been used including the spatial domain filtering, frequency domain filtering, histogram processing, morphological filtering and wavelet filtering. The techniques applied were assessed by few methods which are the observer sensitivity, measuring the image quality by calculating the MSE and PSNR of the image and applying one of the segmentation techniques to the output images. In conclusion, for ultrasound kidney image, if the whole image were taken into consideration (by measuring MSE and PSNR), morphological filtering seems to be the best option in enhancing the image. If the evaluator is concerning more on the kidney edges, enhancement techniques that should be taken into consideration are median filtering and histogram equalization.

The Effect of the Corrugation Rib Angle of Attack on the Fluid Flow and Heat Transfer Characteristics Inside Corrugated Ribbed Passage

Heat transfer enhancement using corrugated ribbed passages is one of the common enhancement techniques inside heat exchangers. The present study investigated numerically the effect of the corrugation rib angle of attack on the fluid flow and heat transfer characteristics inside the corrugated ribbed passage. The commercial computational fluid dynamics code PHOENICS 2006 was used to perform the numerical analysis by solving the Navier–Stokes and energy equations. The experimental part of this study was used only to validate the numerical model, and a good agreement between the experimental results and the model was obtained. The flow field characteristics and heat transfer enhancement were numerically investigated for different corrugated rib angles of attack as follows: 90 deg, 105 deg, 120 deg, 135 deg, and 150 deg. The corrugation rib angle of attack has a great effect on the reversed flow zone, the flow reattachments, and the enhancement of the heat transfer coefficient through the duct. The recommended rib angle of attack, which gives the optimum thermohydraulic performance, is found to be between 135 deg and 150 deg. The value of the maximum thermohydraulic performance is about 3.6 for the 150 deg rib angle of attack at a Reynolds number equal to 10,000.

Augmentation of Laminar Forced Convective Heat Transfer of an Oil Flow in an Enhanced Tube by EHD Effect

Heat transfer enhancement using an applied electric field has fascinating application perspective since it can realize a good enhancement effect at the expense of only a little cost of energy. Many fundamental studies have been carried out in this field and the emphasis of the study has been gradually turning to application study. The electrohydrodynamic ~EHD! enhancement of the forced convective heat transfer refers to the coupling of an electric field with the fluid field in a dielectric fluid medium: The net effect is production of electrically induced secondary motions that destabilize the thermal boundary layer near the heat transfer surface. The effect of electrohydrodynamics on the phase-change heat transfer has been under investigation for the past two decades. On the other hand, the studies of the convective heat transfer enhancement by the EHD effect are relatively little. The experimental results reported by Franke and Hogue @1# and Hasegawa et al. @2# denoted that the strong electric field could disrupt the laminar thermal boundary layer of air or refrigerants in-tube and shift the flow conformation from the laminar flow to the turbulent flow. Compared with air and refrigerants, oil is a so viscous fluid that it keeps still the laminar flow when the external electric field is applied although the secondary flow may be aroused. It is quite meaningful to reinforce the forced convective heat transfer of oil in-tube, since it has a low heat transfer coefficient, but a widely practical perspective. In general, it is difficult to enhance the laminar forced convective heat transfer of oil in-tube. Common enhancement techniques use mainly various surface-worked tubes such as the two-dimensional or three-dimensional extended surfaces tubes ~see, for example, @3#! and the helical groove tubes ~see, for example, @4#!, the smooth tube inserted swirl-flow de-