Initial Curve Research Articles

Fully isogeometric modeling and analysis of nonlinear 3D beams with spatially varying geometric and material parameters

We present a fully isogeometric modeling and simulation method for geometrically exact, nonlinear 3D beams with spatially varying geometric and material distributions, both along the beam axis and through its cross-section. The approach is based on the modeling of 3D beams using the Cosserat rod theory and the numerical discretization using B-Spline and NURBS parameterizations in an isogeometric collocation method. Transversally varying material constitutions are represented using non-homogeneous, functionally graded beam cross-section definitions such as laminates and continuously graded cross-sections. Furthermore, to model the axial variation of material and geometry, we introduce the parameterization of cross-section properties as spline curves along the beam centerlines. This fully isogeometric modeling and analysis concept, which is based on spline parameterizations of initial beam centerline curves, kinematic unknowns and axially varying material and geometric parameters, has various practical applications enabled by advances in manufacturing technology, including multi-material 3D printing and advanced manufacturing of composites with automated fiber placement. We verify and demonstrate the modeling and simulation approach using several numerical studies and highlight its practical applicability.

Corrosion Resistance of Additively Manufactured 625 Inconel Alloy in Seawater

Additive manufacturing (AM) of metals and metal alloys offers advantages of fast and flexible design of parts of various shapes, and low-waste operation. AM manufacturing of metals/alloys involves building materials layer-by-layer from a metal/alloy powder. The powder in each layer is melted by a high intensity laser or electron beam, and individual particles within the layer and between consecutive layers are fused together during this process. Due to peculiarities of manufacturing process, microstructure of AM manufactured alloys are significantly different from their cast or wrought counterparts [1-5]. Previous research has shown that depending on AM and post-processing parameters the difference in microstructure may be detrimental [5] or beneficial [3] for corrosion resistance of AM-manufactured alloys. For example, corrosion resistance of AlSi10Mg alloy made by selective laser melting (SLM) and subsequently heat-treated for 2 h at 300oC was found to be similar to that of the gravity cast alloy, while its corrosion fatigue endurance turned out to be superior to that of the cast alloy [3]. Here, we compare corrosion behavior of 625 Inconel alloy manufactured by SLM to its wrought counterpart in the marine environment. We find that the initial polarization curves look almost identical for 625 AM and 625 wrought specimens both in 0.6 M NaCl and ASTM seawater (Fig. 1). However, the difference in open circuit potential (OCP) and microstructure of two specimens suggest different composition of surface oxides and potentially different rates of their dissolution. In order to understand how variations in microstructure and surface composition affect alloys’ long-term corrosion resistance, we perform ex-situ surface characterization and in-situ analysis of alloy dissolution while holding electrode potential at -1, -0.5, 0.5 and 1V vs Ag/AgCl reference electrode. Electrochemical experiments were conducted in three-electrode flat electrochemical cells (PAR, Inc). Freshly polished coupons of 625 AM or 625 wrought Inconel alloys served as working electrodes (WEs), while platinum mesh and Ag/AgCl in 3 M NaCl (BioLogic, Inc) were used as a counter and reference electrodes, respectively. Initial corrosion properties of the alloy electrodes were characterized by linear polarization resistance and potentiodynamic measurements. Alloy dissolution experiments were conducted in potentiostatic conditions, and concentrations of dissolved metal species were determined by ICP-MS. X-Ray Photoelectron Spectroscopy was used to determine chemical speciation of the samples after exposure to OCP and carrying out alloy dissolution experiments.

Morphological active contour driven by local and global intensity fitting for spinal cord segmentation from MR images

BackgroundSpinal cord (SC) segmentation from magnetic resonance (MR) images can be used to study neurological disorders and facilitates group analysis. Variation of intensity inhomogeneity and small cross section of SC are difficulties that restrict automizing SC segmentation. New methodsIn this paper we present a method for accurate SC segmentation from MR images. The proposed morphological local global intensity fitting model (MLGIF) is based on region based morphological active contour model that utilizes local and global information. The local information is obtained using local morphology fitting and has been embedded into region based active contour to deal with images intensity inhomogeneity and variable contrast levels between SC and the cerebrospinal fluid. The contour evolution has been performed using successive application of a set of morphological operators. ResultsThe proposed method has been validated on 28 T1-weighted and 29 T2-weighted MR images and simulated MR images with different noise levels. Assessment of the results shows the accuracy of the proposed method for SC segmentation. Comparison to existing method(s)The proposed MLGIF method was comparable with existing SC segmentation methods. Between segmented images and corresponding ground truth images, the mean DICE similarity coefficient, mean conformity coefficient and mean Hausdorff distance were 0.90 (092), 0.8 (0.83) and 0.85 mm (0.70 mm), respectively, for T1(T2)-weighted images. ConclusionThe MLGIF model was proposed to achieve a robust method to deal with intensity inhomogeneity and lack of contrast between SC and surrounding tissues. Moreover, accuracy and less sensitivity to initial curve were seen.

Influence of Anchorage Arrangement on Uplift Resistance of Concrete Columns Reinforced by Circular Steel Tube with Ring Shear Connectors Using Taguchi Method

Using the Taguchi method, this study investigated several factors affecting the uplift resistance of the concrete columns reinforced by circular steel tube with ring shear connectors. Nine anchorage factors including steel tube cross section, concrete strength, cross section of concrete column, anchorage length of steel tube, longitudinal reinforcement ratio, transverse bar rate, center-to-center spacing of ring shear connectors, outstand width of ring shear connector, and distance of the first shear connector to the top plane of concrete column were considered for designing, each of which consisting of four levels. A total of 32 axial uplift load tests were conducted according to the $$L_{32}$$ orthogonal array proposed by the Taguchi method. The uplift load–displacement curve of the steel tubes can be simplified into three distinct regions: initial linear, curve transition, and final linear. The interpreted uplift resistances of elastic limit and failure threshold for each of the load tests were obtained. The analysis of mean and analysis of variance statistical approaches were used to evaluate the uplift load test results. The percentage contribution of each controllable factor was also determined. It revealed that the steel tube cross section showed a maximum influence on the interpreted uplift resistances of elastic limit and failure threshold with a contribution of 75.80 and 69.87%, respectively. Most interestingly, the anchorage length of steel tube and the layout of ring shear connectors had minor effects on the elastic limit and failure threshold of the uplift resistances.

Commercial Slit Lamp Anterior Segment Photography versus Digital Compact Camera Mounted on a Standard Slit Lamp with an Adapter

ABSTRACTPurpose: To compare slit lamp mounted anterior segment cameras (SLCs) versus digital compact camera (DCC) with slit-lamp adaptor when used by an inexperienced technician.Methods: In this cross sectional study, where posterior capsule opacification (PCO) was used as a comparator, patients were consented for one photograph with SLC and two with DCC (DCC1 and DCC2), with a slit lamp adaptor. An inexperienced clinic technician, who took all the photographs and masked the images, recruited one eye of each patient. Images were graded for PCO using EPCO 2000 software by two independent masked graders. Repeatability between DCC1 and DCC2, and limits-of-agreement between SLC and DCC1 mounted on slit-lamp with an adaptor were assessed. Coefficient-of-repeatability and Bland-Altmann plots were analyzed.Results: Seventy-two patients (eyes) were recruited in the study. First 9 patients (eyes) were excluded due to unsatisfactory image quality from both the systems. Mean evaluation of posterior capsule opacification (EPCO) score for SLC was 2.28 (95% CI: 2.09–2.45), for DCC1 was 2.28 (95% CI: 2.11–2.45), and for the DCC2 was 2.11 (95% CI: 2.11–2.45). There was no significant difference in EPCO scores between SLC vs. DCC1 (p = 0.98) and between DCC1 and DCC2 (p = 0.97). Coefficient of repeatability between DCC images was 0.42, and the coefficient of repeatability between DCC and SLC was 0.58.Conclusions: DCC on slit lamp with an adaptor is comparable to a SLC. There is an initial learning curve, which is similar for both for an inexperienced person. This opens up the possibility for low cost anterior segment imaging in the clinical, research, and teaching settings.

Kidney Transplantation Utilising Donors After Circulatory Death – The First Report from the African Continent

Introduction At Groote Schuur Hospital, the number of deceased donors have declined over the last two decades, necessitating more liberal donor selection. In 2007, measures to expand the deceased kidney donor pool were implemented, including a HIV positive to positive transplant program, the utilisation of Extended Criteria Donors (ECD) as well as a Donation after Circulatory Death (DCD) program (Figure 1). Despite the successful implementation of DCD programs across Europe and the United Sates, other African centres have not adopted this mode of donation. The aim of this study was to report on our institutional experience with DCD kidney transplants and to encourage this approach among other African centres to improve access to transplantation. Materials and methods Retrospective, descriptive study of consecutive DCD renal transplants at Groote Schuur Hospital over a 10 year period (1 January 2007 to 31 December 2016). Data was obtained from donor referral and recipient registries. Primary end-points were defined as 1, 2 and 5 year graft- (censored for death with functioning graft) and patient survival. Kaplan-Meier method was used for survival analysis. Secondary end-points included the incidence of delayed graft function (DGF), 30-day morbidity, length of stay and donor and recipient clinical characteristics. Results 13 DCD procurements were performed, with no kidneys discarded. Utilised donors were young (median age 22 years; IQR 21-32) with well-preserved renal function (median terminal serum creatinine 86 umol/l; IQR 73-181). 26 Renal transplants were performed with a mean cold ischaemic time of 11 hours (IQR 8-14). Cumulative incidence of DGF was 65.4%. The median length of stay was 20 days (IQR 16-28) in those who experienced DGF and 11 days (IQR 9-16) in those who did not. 30-Day morbidity (other than DGF) was 19.2% (Figure 2). Graft survival at 1, 2 and 5 years were 100%, 95.8% (95% CI 73.9% - 99.4%) and 83.6% (95% CI 56.1%-94.8%) respectively (Figure 3). Patient survival at 1, 2 and 5 years was 92.3% (95% CI 72.6-98.0), as no deaths occurred between 1 and 5 years post-transplant (Figure 4). Discussion Long term graft- and patient survival were comparable with international literature. The incidence of DGF was 65,4%. Possible explanations may include a high incidence of donor vasopressor requirements (46.2%), an initial learning curve with procurement technique and relatively long cold ischaemic times. Nevertheless, DCD may present an unique opportunity to expand deceased donation throughout Africa, particularly in areas hampered by a lack of brain death legislation and religious and/or cultural concerns regarding Donation after Brain Death. Conclusion Results from this study reaffirm the potential of DCD to expand deceased donation throughout Africa, in a religiously and culturally sensitive way.

Gamma nail in the management of intertrochanteric fractures of femur in adults

Background: Intertrochanteric fracture is an extracapsular fracture of the proximal femur. Gamma nail is a cephalomedullary nail that is emerging as the treatment of choice for intertrochanteric fractures. For intertrochanteric fractures, the use of cephalomedullary devices has increased dramatically to 67% among surgeons over the years. Aims of this study was to observe the results of operative treatment of intertrochanteric fractures with Gamma 3 trochanteric nail.Methods: This prospective study was conducted in the Post Graduate Department of Orthopaedics of Government Medical College, Srinagar. This study included 30 cases of intertrochanteric fractures who attended hospital for bone and joint surgery.Results: Excellent results were obtained in 80% patients and good results were obtained in rest 20% with an average Harris hip score of 93.8. Average time to union was 11.6 weeks. There were no non-unions, screw cut outs or peri-implant fractures. The most common complication was varus malunion occurring in 20% patients. However, significant malunion (greater than 10 degrees) was present in only one patient among them.Conclusions: This study finds Gamma 3 nail to be a versatile, easy to use and dependable implant in intertrochanteric fractures. Gamma 3 nail is an ideal implant for stable as well as unstable intertrochanteric fractures and is a distinct advance over the previous methods of treatment, though it has an initial learning curve.

Image Cosegmentation Using Shape Similarity and Object Discovery Scheme

Image cosegmentation is a newly emerging research area in image processing. It refers to the problem of segmenting the common objects simultaneously in multiple images by utilizing the similarity of foreground regions among these images. In this paper, a new active contour model is proposed by using shape-similarity and foreground discovery scheme. The foreground discovery scheme is used to obtain the rough contours of the common objects which are used as initial evolution curves. The energy function of the proposed model includes two parts: an intra-image energy and an inter-image energy. The intra-image energy explores the differences between foreground regions and background regions in each image. And the inter-image energy is used to explore the similarities of the common objects among target images, which composes of a region color feature energy term and a shape constraint energy term. The region color feature term indicates the foreground consistency and the background consistency among the images; and the shape constraint energy term allows the global changes of shapes and truncates the local variation caused by misleading features. Experimental results show that the proposed model can improve the accuracy of the image cosegmentation significantly through regularizing the changes of shapes.

Unusual magnetic properties of the polar orthorhombic BiFe0.5Sc0.5O3 perovskite

Magnetic properties of new multiferroic BiFe0.5Sc0.5O3 perovskite which exists in two different orthorhombic polymorphs, the antipolar Pnma and the polar Ima2, were studied using a SQUID-magnetometer technique in magnetic fields up to 50 kOe in the temperature range of 5–300 K. Both polymorphs show a weak ferromagnetic component below the Néel temperature, TN∼220 K. A wide cusp-like anomaly of the temperature dependent magnetic susceptibility was revealed below 200 K. The anomaly is dependent on the magnetic field applied and can be associated with the glassy magnetic behavior of the compound. The best fit of the initial magnetization curves taken at each temperature can be obtained as a sum of two contributions, namely the nonlinear in field and the linear one. The nonlinear contribution appeared to be temperature and magnetic field dependent, which is in a good agreement with the magnetization experimentally obtained as a function of temperature in different magnetic fields applied. Increase of external magnetic field leads to a decrease of the nonlinear contribution to the total magnetic moment.

Magnetic and structural properties of L10 Mn-Ga epitaxially grown islands

Magnetic and structural properties of L10 Mn53Ga47 islands epitaxially grown onto MgO(1 0 0) substrates are discussed. The samples were fabricated by sputter-deposition at a substrate temperature Ts during deposition. The samples deposited at Ts above 500 °C were found to form the island structure of Volmer-Weber type. The average size of the islands fabricated at Ts = 600 °C is around 200 nm in width and 60 nm in height. The XRD and TEM analyses indicate that those islands are of the L10 phase with the 〈0 0 1〉 axis perpendicular to the substrate surface. The lattice constants a and c are 3.91 ± 0.01 Å and 3.65 ± 0.02 Å, respectively, which are larger by 0.8%, and smaller by 1.5% respectively, as compared to the bulk values of the same composition. The order parameter of these islands is found to increase from 0.7 to 0.8 for Ts = 450–500 °C, and then remains nearly constant (≈0.8) for higher Ts. The M-H hysteresis loops exhibit a high squareness for all the samples for Ts = 450–600 °C. The saturation magnetization Ms is about 220 and 350 emu/cm3 for Ts = 450 and 600 °C, respectively. The out-of-plane coercivity Hc is 5 and 13 kOe for Ts = 450 and 600 °C, respectively. The temperature dependence of Ms for the sample made at Ts = 600 °C was measured and fitted to an empirical relation in order to estimate Tc. The estimated Tc around 600 K is in reasonable agreement with the reported value of bulk L10 Mn53Ga47. The uniaxial perpendicular magnetic anisotropy constant Ku estimated by the out-of-plane torque curves is around 1.1 × 107 and 8.3 × 106 erg/cm3 at 5 and 300 K, respectively. The initial magnetization curves of these islands exhibit a typical pinning mode for the coercivity mechanism. A phenomenological discussion of the coercivity is presented on the basis of Kronmuller’s formula. It is found that the coefficient α and effective demagnetizing factor Neff in the formula by Kronmuller are approximately 0.38 and 12. For the magnetic anisotropy mechanism, the power law relation between Ku(T) and Ms(T) is examined. It is found that the exponent n for Ku(T)∝Ms(T)n varies from 2.3 to 3.5 for T from 350 to 5 K. However, the n in a whole temperature range from 5 to 350 K is 2.6. The n = 2.6 suggests a deviation from the single-ion mechanism, and is consistent with the theoretical predictions of Ga contribution.

Idiopathic Early-onset Scoliosis: Growing Rods Versus Vertically Expandable Prosthetic Titanium Ribs at 5-year Follow-up.

Distraction-based techniques allow spinal growth until skeletal maturity while preventing curve progression. Two multicenter early-onset scoliosis databases were used to identify patients with idiopathic spine abnormalities treated with traditional growing rods (TGR) or vertically expandable titanium ribs (VEPTR). Patients underwent at least 4 lengthenings and had at least 5-year follow-up. Significance was set at P<0.05. In total, 50 patients treated with TGR and 22 treated with VEPTR were included. Mean (±SD) age at surgery was 5.5 (±2.0) years for the TGR group versus 4.3 (±1.9) years for the VEPTR group (P=0.044); other demographic parameters were similar. VEPTR patients had more procedures (mean 15±4.2) than TGR patients (mean 10±4.0) (P=0.001). Unilateral constructs were present in 18% (4 of 22) of VEPTR and 16% (8 of 50) of TGR patients. Bilateral constructs spanned a mean 2.1 additional surgical levels and exposed patients to 1.6 fewer procedures than unilateral constructs. Curve correction was similar between bilateral and unilateral constructs. TGR patients experienced greater curve correction (50%) than VEPTR patients (27%) (P<0.001) and achieved a greater percentage of thoracic height gain (24%) than VEPTR patients (12%) (P=0.024). At latest follow-up, TGR patients had better maintenance of curve correction, less kyphosis, and 15% greater absolute gain in thoracic height versus VEPTR patients. TGR patients had a lower rate of wound complications (14%) than VEPTR patients (41%) (P=0.011). In patients with idiopathic early-onset scoliosis, TGRs produced greater initial curve correction, greater thoracic height gains, less kyphosis, and lower incidence of wound complications compared with VEPTR. Level III.

Single Cell Study of Water Transport in PEMFCs with Electrosprayed Catalyst Layers

AbstractWater transport in proton exchange membrane fuel cells (PEMFCs) with electrosprayed catalyst layers is analyzed by means of water collection measurements. With this aim, single cells have been studied with different catalyst layers configuration: electrosprayed layer in cathode (EScat), in anode (ESan), and in both electrodes (ESboth). The electrosprayed catalyst layers show macroporous morphology and superhydrophobicity (water contact angle θ &gt; 150°) . Initial polarization curves, taken after a few hours from cell start‐up, show above 20% higher maximum power density of EScat and ESan cells, compared with a conventional cell (with no electrosprayed layers). The performance improvement is due to lower internal resistance of the cell according to the polarization curves. Stability of the cells under the dry‐gas operation conditions used during water collection measurements, shows to be high only for EScat, whereas ESan, ESboth, and conventional cells suffer degradation and frequent membrane failure. Water collection experiments at variable temperature and current density reflect larger water flow towards the anode for EScat cell than for the other configurations. It is concluded that the high performance and stability of EScat is due to the enhanced water back diffusion from cathode to anode driven by the superhydrophobic electrosprayed catalyst layer in cathode. Favored back diffusion improves water balance in the cell, membrane humidification, decreases the internal resistance, and precludes anode drying and cathode flooding. The optimal cell configuration is obtained with an electrosprayed catalyst layer in the cathode and a standard hydrophilic catalyst layer in the anode.

Calculation of the foundation with allowance for the shear modulus at small deformations

Continuous improvement of mathematical models of soil and software complexes implementing numerical simulation methods allows taking into account the effects characteristic of the ground environment, such as nonlinearity of deformations, creep, hardening and softening. These models require a large number of parameters to be determined during laboratory tests. The methods for determining these parameters are for the most part not represented in modern normative literature. A typical example of such parameters is the shear modulus for small deformations.The study of small deformations is of great importance in the calculation of underground structures. When designing such structures it is necessary to take into account the nonlinearity of unloading of the ground base. The currently widely used model of hardening soil [HS] does not take into account the nonlinearity of the unloading, while the improved model of hardening soil in view of small deformations [HSsmall] allows to take into account the hysteretic behavior of soils.The account of the hysteretic behavior of the soil during the cycles of unloading and repeated loading is carried out under the condition that the shear modulus at unloading is equal to the initial tangent module for the initial loading curve. In this case, the unloading and reloading curve has the same shape as the initial loading curve, but in the doubled size.Since elastoplastic soil models are not able to describe the hysteretic behavior of soils, the solution of the range of problems associated with the accumulation of deformations under vibrational and cyclic influences with the use of these models is impossible. In such cases, the forecasting of the stressed-deformed state of soil bases under the action of dynamic loads of a different nature can be performed only on the basis of the use of an elastoplastic model of a toughening ground with allowance for ultra-small deformations.In the present work, the results of laboratory determination of soil stiffness for small deformations are presented and the use of these data in numerical modelling of the problem of sediments of a foundation of finite width on a base in the PLAXIS software complex.

Efficacy of Pemafibrate on Atherogenic Dyslipidemia: Results of a Pooled Analysis of Pemafibrate Phase II/III Clinical Trials Compared with Placebo

The arthroscopic Latarjet has been proposed in the past decade to reduce the rate of bone block malpositioning, decrease soft-tissue damage associated with open approach, and possibly decrease intraoperative complications. Several recent studies have reported similar or even superior results with arthroscopic Latarjet compared with those achieved with open technique. However, arthroscopic Latarjet is known to be more technically demanding and some feel that it should be performed by expert shoulder surgeons with advanced arthroscopic skills. Surgical innovations should be adopted when they have potential advantages for patients. Despite the initial challenges and learning curve of arthroscopic Latarjet, experience and technical skills may reduce the rate of intraoperative complications for this technically demanding procedure.

Phase Interrogation of Diaphragm-Based Optical Fiber Acoustic Sensor Assisted by Wavelength-Scanned Spectral Coding

In this paper, we proposed a phase interrogation method for diaphragm-based interferometric optical fiber acoustic sensor based on the spectral coding process. The information of the sound wave is coded on the optical spectrum of the sensor head by wavelength scanning, which builds a map between time and wavelength. The acoustic signal can be reconstructed from the sound-encoded spectrum. The sound-induced phase variation of the sensor can be interrogated by comparing the sound-encoded spectrum with the initial spectrum curve, which can be acquired from the sinusoidal fitting method. In order to eliminate the phase ambiguity, a diaphragm-based Michelson interferometer is set up using a commercial 3 × 3 fiber coupler and two synchronized channels with 120° phase difference are employed for the interrogation. Experimental results indicate that the proposed method can provide stable demodulation results under random environmental fluctuations, while the commonly used edge filtering technique shows fluctuations of more than 10 dB under the same condition.

Implementation of novel hybrid approaches for power curve modeling of wind turbines

In wind energy conversion systems, a power curve links the wind speed to the power produced by a wind turbine and an accurate power curve model helps wind power providers to capture the performance of wind turbines. For this purpose, this paper presents the implementation of novel hybrid approaches to the power curve modeling process of wind turbines. As a result of employing the complementary phases called clustering, filtering and modeling in this process, the k-means-based Smoothing Spline hybrid model achieves the most accurate power curve in terms of sum of squared errors, coefficient of determination and root mean squared error. On the other hand, the k-medoids++-based Gaussian hybrid model causes the most inconsistent power curve in terms of the mentioned goodness-of-fit statistics. Furthermore, all of hybrid power curve models constructed in this paper outperform the conventional linear, quadratic, cubic, exponential and logarithmic benchmark models with the high improvement percentages. Finally, the proposed hybrid power curve models are shown not to be dependent on the initial raw power curve data.

Ratcheting testing of polytetrafluoroethylene (PTFE) under multiple-step compression

Abstract Uniaxial stress-controlled ratcheting experiments of PTFE (polytetrafluoroethylene) under cyclic compressive loads with multiple load steps were performed. The influence of stress rate, temperature, stress amplitude, loading sequence and peak holding on the compressive ratcheting behavior have been discussed systematically. Results indicate that ratcheting deformation increases significantly when enhancing temperature and stress amplitude and reducing stress rate. Only a slight, accumulated deformation occurs during the first 20 or so cycles at room temperature (RT), but it always turns to shakedown. Moreover, ratcheting strain is clearly influenced by the loading sequence. When greater compressive deformation was obtained during the prior load step due to a greater stress level (such as higher temperature or a lesser stress rate), increased compressive strain hardening and deformation resistance could be produced, which in turn restricts or even reduces ratcheting deformation in the pursuing load step. It is of great interest that no initial cyclic stress strain curve was observed under cyclic compression at peak holding time. This indicates that creep recovery due to anelastic relaxation decreases the ratcheting rate of PTFE material under compressive creep-fatigue conditions. This research provides an important testing approach and data for PTFE material subjected to repeated compressive loads influenced by temperature modulation.

Image segmentation method based on improved fuzzy Chan-Vese model

Medical image segmentation is a hot topic in the field medical image processing. The segmentation methods based on level set and the ones based on fuzzy set are currently very popular in the field of medical image segmentation. But these methods do not balance between global and local features of the image. This paper combines the advantages of these two methods, proposes a fuzzy Chan-Vese model, which introduces fuzzy clustering into Chan-Vese model. This model extends the regional energy part of Chan-Vese model to regional energy based on fuzzy clustering, meanwhile adds fuzzy cluster objects as the constraint of the model, so it can take account of global and local features of the image. In the medical image segmentation experiments, this paper uses OTSU method to execute initial segmentation for getting the initial segmentation curve, and then uses fuzzy Chan-Vese model to realize image segmentation. Experimental results show that, with the help of prior knowledge of segmentation prototypes of medical images, the proposed method has achieved very good segmentation results.

Comparison of 2-dimensional and 3-dimensional contrast-enhanced ultrasound for quantitative analysis in liver neoplasms

Objective To evaluate the correlation and consistency of dynamic three-dimensional contrast-enhanced ultrasonography (3D-CEUS) and two-dimensional contrast-enhanced ultrasonography (2D-CEUS) in the time-intensity curve (TIC) parameters of quantitative analysis in liver neoplasms. Methods Thirty patients were examined with 2D-CEUS and dynamic 3D-CEUS.The dynamic raw data were analyzed by quantitative analysis software. The regions of interest were manually selected around the entire lesion; TIC curves were generated and fitted respectively. Quality of fit (QOF) was used to evaluate the degree of fit between the fitted curve and the initial curve. The corresponding 2D-CEUS and 3D-CEUS quantitative parameters of the same lesion were compared, including peak intensity (PI), slope (S), area under curve (AUC), time to peak (TTP) and mean transit time (MTT). The correlation of the intensity-related quantitative parameters and the consistency of the time-related quantitative parameters were analyzed between the two kinds of CEUS. Results The consistency of time related quantitative parameters, including MTT and TTP, were 0.97 and 0.96, and the correlation were 0.94 and 0.93. The correlation coefficients of S, PI and AUC were 0.92, 0.72 and 0.65, respectively. Conclusions The quantitative results of 3D-CEUS are stable and reliable, and have fair concordance with 2D-CEUS. Dynamic 3D-CEUS can be used for clinical evaluation of the blood perfusion of liver neoplasms. Key words: Contrast-enhanced ultrasonography; Liver neoplasms; Quantitative analysis

Shape modeling based on specifying the initial B-spline curve and scaled BFGS optimization method

In this paper, we consider the problem of fitting the B-spline curves to a set of ordered points, by finding the control points and the location parameters. The presented method takes two main steps: specifying initial B-spline curve and optimization. The method determines the number and the position of control points such that the initial B-spline curve is very close to the target curve. The proposed method introduces a length parameter in which this allows us to adjust the number of the control points and increases the precision of the initial B-spline curve. Afterwards, the scaled BFGS algorithm is used to optimize the control points and the foot points simultaneously and generates the final curve. Furthermore, we present a new procedure to insert a new control point and repeat the optimization method, if it is necessary to modify the fitting accuracy of the generated B-spline fitting curve. Associated examples are also offered to show that the proposed approach performs accurately for complex shapes with a large number of data points and is able to generate a precise fitting curve with a high degree of approximation.