Hyock Ju Kwon

Adhesion of Polymers in Paper Products from the Macroscopic to Molecular Level — An Overview

Polymers are widely used in the manufacture, converting, and end-use of paper products where the quality of polymer adhesion is important at both paper and fiber levels. This article reviews a number of relevant theories of polymer adhesion, and such adhesion phenomena as revealed in recent investigations of the adhesion between polymer thin films and paper surfaces, the adhesion of polymer molecules to cellulose fibers, and surface forces measurements between model cellulosic surfaces. It is concluded that molecular adhesion and viscoelasticity of cellulose–polymer–cellulose joints play primary roles in the paper strength, which can be tailored by a rational design of polymer additives either as strength enhancers for strong paper products or debonding agents for soft paper tissues.

Compressive stress-strain response of covalently crosslinked oxidized-alginate/N-succinyl-chitosan hydrogels.

Novel injectable hydrogels have been formed at 37°C under physiological pH using a polymer-polymer crosslinking reaction. Three different formulations were tested. After 1-day cure time at body temperature, the elastic modulus of unswollen samples ranged between 3 and 5 kPa but after 11 additional days at 4°C exceeded the target modulus of 10 kPa. Modulus data showed good agreement with theoretical crosslink density, enabling the prediction of stiffer/faster curing gel formulations. Rubber elasticity theory provided a good fit to the experimental data up to 73% compressive true strain. Based on an analysis of modulus results, it was inferred that despite the presence of two aldehyde functional groups, only one mechanically significant crosslink can form per oxidized repeat unit on the alginate chain.

Application of Eshelby’s Solution to Elastography for Diagnosis of Breast Cancer

Eshelby’s solution is the analytical method that can derive the elastic field within and around an ellipsoidal inclusion embedded in a matrix. Since breast tumor can be regarded as an elastic inclusion with different elastic properties from those of surrounding matrix when the deformation is small, we applied Eshelby’s solution to predict the stress and strain fields in the breast containing a suspicious lesion. The results were used to investigate the effectiveness of strain ratio (SR) from elastography in representing modulus ratio (MR) that may be the meaningful indicator of the malignancy of the lesion. This study showed that SR significantly underestimates MR and is varied with the shape and the modulus of the lesion. Based on the results from Eshelby’s solution and finite element analysis (FEA), we proposed a surface regression model as a polynomial function that can predict the MR of the lesion to the matrix. The model has been applied to gelatin-based phantoms and clinical ultrasound images of human breasts containing different types of lesions. The results suggest the potential of the proposed method to improve the diagnostic performance of breast cancer using elastography.

Braking Availability Tester for Realistic Assessment of Aircraft Landing Distance on Winter Runways

AbstractThis paper is concerned with the development of a new measurement device for the realistic assessment of braking capability of landing airplanes for winter runways. The conventional and current practice of runway condition monitoring has been focused on identifying the maximum tire-pavement frictional drag (μ value) and often neglected the characteristics of actual aircraft braking systems as well as the comprehensive effects coming from various factors such as deformable contaminants on the winter runway. The braking availability tester (BAT) proposed in this paper is designed to take a different approach for the realistic assessment of braking availability of landing airplanes. The main idea of the BAT is to mimic the braking operation of actual aircrafts as closely as possible by incorporating the same brake mechanism and antiskid braking system (ABS) used in existing aircrafts. In doing so, the BAT also incorporates a suite of sensors for monitoring the status of braking operation in real time...

The rheological injectability of N-succinyl-chitosan solutions.

The viscosity of a set of N-succinyl-chitosan (NSC) solutions was characterized near the 0.2Pas rheological injectability limit. This is believed to be the first such report in the open literature. Viscosity was characterized at physiological pH and ionic strength as a function of NSC degree of substitution, NSC concentration, temperature, and shear rate. NSC was synthesized via Yamagucis method and characterized using H-NMR, membrane osmometry, TGA and isothermal vacuum drying. NSC synthesis results were shown to fit a reproducible log-linear correlation and both optimum drying temperature and thermal decomposition temperature were found to be a function of NSC degree of substitution. Viscosity results were explained using Katchalskys full model for polyampholyte ionization combined with a charge induced excluded volume model proposed by Higgs. The model predicted a polyelectrolyte/polyampholyte transition which agreed well with experimental data. For minimally injectable formulations a maximum in primary amine concentration is expected at 32sub% amine NSC.

Low-cost quasi-real-time elastography using B-mode ultrasound images.

A low cost, quasi real-time elastography system, displacement-gradient elastography (DGE), was developed by applying digital image correlation (DIC) method and smoothing algorithm to B-mode ultrasound images. In order to achieve quasi real-time elastogram display, a new fast pattern matching algorithm, decoupled cross-correlation (DCC), was proposed and validated. By applying the DGE to various phantoms, elastograms were generated to identify the lesion with wide variations of stiffness ratio and applied strain. The performance of DGE was qualitatively compared with those from a high-end ultrasound scanner using the elastograms of a commercial elastography breast phantom. DGE was also applied to the ultrasound images of human breast lesions in various BI-RADS categories. This study suggests that DGE may have comparable performance to conventional elastography in detecting breast cancer, while it can be easily implemented onto conventional ultrasound scanners.

An Experimental and Numerical Study on Tactile Neuroimaging: A Novel Minimally Invasive Technique for Intraoperative Brain Imaging

The success of tumour neurosurgery is highly dependent on the ability to accurately localize the operative target, which may shift during the operation. Performing intraoperative brain imaging is crucial in minimally invasive neurosurgery to detect the effect of brain shift on the tumours location, and to maximize the efficiency of tumour resection.

Compressed Sensing for Elastography in Portable Ultrasound

Portable ultrasound is recently emerging as a new medical imaging modality featuring high portability, easy connectivity, and real-time on-site diagnostic ability. However, it does not yet provide ultrasound elastography function that enables the diagnosis of malignant lesions using elastic properties. This is mainly due to the limitations of hardware performance and wireless data transfer speed for processing the large amount of data for elastography. Therefore, data transfer reduction is one of the feasible solutions to overcome these limitations. Recently, compressive sensing (CS) theory has been rigorously studied as a means to break the conventional Nyquist sampling rate and thus can significantly decrease the amount of measurement signals without sacrificing signal quality. In this research, we implemented various CS reconstruction frameworks and comparatively evaluated their reconstruction performance for realizing ultrasound elastography function on portable ultrasound. Combinations of three most common model bases (Fourier transform [FT], discrete cosine transform [DCT], and wave atom [WA]) and two reconstruction algorithms (L1 minimization and block sparse Bayesian learning [BSBL]) were considered for CS frameworks. Echoic and elastography phantoms, were developed to evaluate the performance of CS on B-mode images and elastograms. To assess the reconstruction quality, mean absolute error (MAE), signal-to-noise ratio (SNRe), and contrast-to-noise ratio (CNRe) were measured on the B-mode images and elastograms from CS reconstructions. Results suggest that CS reconstruction adopting BSBL algorithm with DCT model basis can yield the best results for all the measures tested, and the maximum data reduction rate for producing readily discernable elastograms is around 60%.

Diagnosis of Breast Tumor Using 2D and 3D Ultrasound Images

DIC and DVC algorithms combined with smoothing algorithm were applied to ultrasound B mode images to generate 2D and 3D elastograms. The DIC based elastograms have better accuracy than conventional time-gradient based elastograms, and can estimate the size and the relative elastic modulus of the inclusion with a reasonable accurately. The study shows the potential to apply DIC and DVC based elastograms to the in-vivo diagnosis of pathological tissue within the body, and to provide new information that is related to tissue structure and/or pathology.Copyright