RESEARCH ON NURBS SKINNING SURFACE VIA COMPLEX CURVES

In order to design the production with complex external shapes, a newmethod is put forward using non-uniform rational B-spline(NURBS)curves to unifythe description of complex curves composed of several segments with different degrees,and then these complex curves are used to construct NURBS skinning surface. Somekinds of skills are used to dispose the knot of NURBS curves and surfaces for practicalproblems. Finally, the method is verified by several complex examples.

New Algorithm for Local Shape Preservation T-Spline Surface Skinning

Surface skinning is a widely used algorithm in CAD modeling which permits designer to pass surface through several section curves, thus providing modeling process with powerful ability to describe complex shapes and transform the 2D design intention into 3D space. This paper contributes in the combination of T-Spline technology and surface skinning modeling by introducing a new algorithm for local shape preservation T-Spline surface skinning. The examples given in the paper show that this algorithm is effective.

Optimization of Microwave Extraction of Flavonoids from Water Chestnut Skin Dregs with Response Surface Method

[Objective] In order to take full advantage of processing by-product of water chestnut, the microwave extraction method of flavonoids from water chestnut skin dregs was optimized. The extracted flavonoids had a relatively high yield. [Method] The Box-Behnken design-based response surface method was adopted to optimize the microwave extraction of flavonoids from water chestnut skin dregs, a by-product of water chestnut starch. The mathematical relationships between various influencing factors and flavonoids yield were established. [Result] The optimum extraction conditions of flavonoids from water chestnut skin dregs were as follows： ethanol concentration of 55.4%, solid/liquid ratio of 1：30 g/ml, microwave power of 320 W, microwave time of 3 min and microwave time of 2 times. Under the optimum extraction conditions, the theoretical flavonoids yield was 2.376%. However, the actual flavonoids yield under the optimum extraction conditions was 2.365%. The relative error between actual values and theoretically predicted values was 0.461%. [Conclusion] The results showed the optimized extraction method is reliable, and it can provide a reference for the comprehensive and highly efficient utilization of water chestnut processing wastes.

Skin Sensitive Difference of Human Body Sections under Clothing— Smirnov Test of Skin Surface Temperatures' Dynamic Changing

Skin sensitive difference of human body sections under clothing is the theoretic foundation of thermal insulation clothing design. By a new method of researching on clothing comfort perception, the skin temperature live changing procedure of human body sections affected by the same cold stimulation is inspected. Furthermore with the Smirnov test the skin temperatures dynamic changing patterns of main human body sections are obtained.

Ship hull plate processing surface fairing with constraints based on B-spline

The problem of ship hull plate processing surface fairing with constraints based on B-spline is solved in this paper. The algorithm for B-spline curve fairing with constraints is one of the most common methods in plane curve fairing. The algorithm can be applied to global and local curve fairing. It can constrain the perturbation range of the control points and the shape variation of the curve, and get a better fairing result in plane curves. In this paper, a new fairing algorithm with constraints for curves and surfaces in space is presented. Then this method is applied to the experiments of ship hull plate processing surface. Finally numerical results are obtained to show the efficiency of this method.

Approximate merging of B-spline curves and surfaces

Applying the distance function between two B-spline curves with respect to the L2 norm as the approximate error, we investigate the problem of approximate merging of two adjacent B-spline curves into one B-spline curve. Then this method can be easily extended to the approximate merging problem of multiple B-spline curves and of two adjacent surfaces. After minimizing the approximate error between curves or surfaces, the approximate merging problem can be transformed into equations solving. We express both the new control points and the precise error of approximation explicitly in matrix form. Based on homogeneous coordinates and quadratic programming, we also introduce a new framework for approximate merging of two adjacent NURBS curves. Finally, several numerical examples demonstrate the effectiveness and validity of the algorithm.

Treatment of Aged Skin with a pH 4 Skin Care Product Normalizes Increased Skin Surface pH and Improves Barrier Function: Results of a Pilot Study

The physiological skin surface pH is just below 5. With age the skin surface pH increases up to 6. An increased pH correlates with reduced barrier integrity/cohesion. The present pilot study assesses possible normalization of an increased skin surface pH of the elderly and improvement of barrier function via application of ≈pH 4.0 skin care products. Baseline skin surface pH was determined in elderly (80+ years old;n = 15) compared to middle aged adults (31 - 50 years old;n = 15). The effect of o/w emulsions at pH-values of 3.5, 4.0, 4.5 and 5.5 on the skin surface pH was determined in both groups. Further, the effect of a 4-week treatment with a pH 4.0 skin care product on the skin surface pH, skin hydration and barrier integrity was assessed. Thirteen elderly females were involved in this home-in-use test. Increased baseline skin surface pH of the elderly normalizes to the physiological pH of 4.5 - 5.0 over 7 hours after single application of o/w-emulsions with a given pH of 3.5 or 4.0. A 4 week treatment employing the pH 4.0 skin care product improves the epidermal barrier integrity of the elderly significantly (p = 0.005). Reduction of the increased baseline skin surface pH of the elderly is accompanied by improved epidermal barrier integrity. Skin care products for the elderly have to be adjusted in the pH range of 3.5 to 4.0.

Casting of microstructured shark skin surfaces and possible applications on aluminum casting parts

Within the project "Functional Surfaces via Micro-and Nanoscaled Structures" which is part of the Cluster of Excellence "Integrative Production Technology" established and financed by the German Research Foundation (DFG),an investment casting process to produce 3-dimensional functional surfaces down to a structural size of 1μm on near-net-shape-casting parts has been developed.The common way to realize functional microstructures on metallic surfaces is to use laser ablation,electro discharge machining or micro milling.The handicap of these processes is their limited productivity.The approach of this project to raise the efficiency is to use the investment casting process to replicate microstructured surfaces by moulding from a laser-microstructured grand master pattern.The main research objective deals with the investigation of the single process steps of the investment casting process with regard to the moulding accuracy.Actual results concerning making of the wax pattern,suitability of ceramic mould and core materials for casting of an AlSi7Mg0.3 alloy as well as the knock-out behavior of the shells are presented.By using of the example of an intake manifold of a gasoline race car engine,a technical shark skin surface has been realized to reduce the drag of the intake air.The intake manifold consists of an air-restrictor with a defined inner diameter which is microstructured with technical shark skin riblets.For this reason the inner diameter cannot be drilled after casting and demands a very high accuracy of the casting part.A technology for the fabrication and demoulding of accurate microstructured castings are shown.Shrinkage factors of different moulding steps of the macroscopic casting part as well as the microscopic riblet structure have been examined as well.

Study on manufacturing freeform surface parts in micro EDM based on skin effect theory

Micro fabrication of freeform surface parts made of hard and brittle materials is always a tough job in micro machining field. This paper tries to fabricate freeform surface feature by using smooth surface of tool electrode after tool wear in micro EDM. According to the skin effect theory, the tool end shape in the stage of uniform wear can be changed by adjusting the frequency of discharge pulse. The electrical energy distributing rule of tool electrode section in RC circuit has been investigated under the influence of skin effect, and the law of spark location change has been summarized. The experimental studies demonstrate that different shapes of tool ends can be achieved by varying the pulse frequencies of discharge power supply. Additionally, a micro part of freeform surface feature with high precision and good surface quality has been successfully obtained by micro EDM through adopting the smooth surface after tool wear.

Skin Sensitive Difference of Human Body Sections under Clothing - Multiple Analysis of Skin Surface Temperature Changes

A new researching method on clothing comfort perception is developed.By it the skin surface temperature changes and subjective psychological perception of human body sections stimulated by the same cold stimulation are studied.With the multiple comparison analysis method the changing laws of skin temperature of main human body sections is obtained.

Reconstruction of B-spline surface by interpolating boundary curves and approximating inner points

In this paper, we present an algorithm for reconstruction of B-spline surface such that it interpolates the four given bound- ary curves and simultaneously approximates some given inner points. The main idea of our method is： first, we construct an initial surface which interpolates the four given boundary curves; then, while keeping the boundary control points of the initial surface un- changed, we reposition the inner control points of the surface with energy optimization method. Examples show that our algorithm is practicable and effective.

Influence of Surface Topography on the Tactile Friction of Medical Compression Textiles against a Mechanical Skin Model

Influence of surface topography on the tactile friction of medical compression textiles was studied in this paper. The friction behavior was investigated for three kinds of medical textiles with various structures and compositions by using a textile friction analyzer under dry condition. In order to simulate the contacts of textiles/human finger, a mechanical skin model with similar texture to the skin and applied normal load oflN were selected. Meanwhile, the 3D surface topography of textiles was measured using a digital microscope. The topographical data were analyzed concerning height distribution and material ratio, and the real contact area was estimated as a function of penetration depth. Results showed that the investigated textiles revealed a significant variation on the friction coefficients, which were （ 0.41 ± 0.01 ） （ polyamide, jersey 2 × 2 ）, （0.56 ± 0. 01） （cotton, jersey 2×2） and （0. 47 ± 0. 01） （polyamide, jersey 1 × 1 ）, respectively. The textile with higher friction coefficient was found to own a relative compact and homogenous surface and larger contact area, vice versa.

Symmetric alteration of four knots of B-spline and NURBS surfaces

Modifying the knots of a B-spline curve, the shape of the curve will be changed. In this paper, we present the effect of the symmetric alteration of four knots of the B-spline and the NURBS surfaces, i.e., symmetrical alteration of the knots of surface, the extended paths of points of the surface will converge to a point which should be expressed with several control points. This theory can be used in the constrained shape modification of B-spline and NURBS surfaces.

G^0 and G^1 connection between two adjacent B-spline surfaces

In this paper, the smooth connection between two B-spline surfaces is discussed. First, a brief proof of some simple sufficient conditions of Go and G1 continuity is given. On this basis, a novel method for Go or G1 connection between two adjacent B-spline surfaces is presented. A reparameterization step is firstly taken for one of the surfaces such that they have the same parameterization in v direction, then, adjust their boundary control vertices to make them Go or Gl connected. The GI connection parameter is determined by an optimization problem. Compared with the existed methods, our method is simple and easy to be used in practice.

Monitoring the penetration and accumulation of gold nanoparticles in rat skin ex vivo using surface-enhanced Raman scattering spectroscopy

Contamination by accidental cutaneous contact with the commercial products and the air pol-hutants raised a considerable health and safety issue.This study aimed to trace the dynamics of the 20 nm gold nanopartide(GNP)penetration and accumulation in rat skin tissues using a surface-enhanced Raman scattering(SERS)techmique.After the topical application of GNPs on rat skin surface,the SERS spectra were recorded for every 15 pum to an overall depth of 75 pum from skin surface for 150 min.The processes of GNP penetration in rat skin were accompanied by aggregation of GNPs,which affected SERS spectra.The results revealed that 20 nm GNPs can penetrate through stratum corneum layer,viable epidermis layer,and then into dermis layer.This study demonstrated for the first time the potential of SERS spectroscopy to monitor the penetration and accumulation of GNPs in rat skin.

B-Spline Approximation of Ship Waves on the Free Surface

We consider the problem of a ship advancing in waves. In this method, the zone of free surface in the vicinity of body is discretized. On the discretized surface, the first-order and second-order derivatives of ship waves are represented by the B-Spline formulae. Different ship waves are approximated by cubic B-spline and the first and second order derivates of incident waves are calculated and compared with analytical value. It approves that this numerical method has sufficient accuracy and can be also applied to approximate the velocity potential on the free surface.

G^1 Continuity Conditions of B-spline Surfaces

According to the B-spline theory and Boehm algorithm, this paper presents several necessary and sufficient G1 continuity conditions between two adjacent B-spline surfaces. In order to meet the need of application, a kind of sufficient conditions of G1 continuity are developed, and a kind of sufficient conditions of G1 continuity among N(N>2) patch B-spline surfaces meeting at a common corner are given at the end.

RECONSTRUCTION OF SYMMETRIC B-SPLINE CURVES AND SURFACES

A method to reconstruct symmetric B-spline curves and surfaces is presented. The symmetry property is realized by using symmetric knot vector and symmetric control points. Firstly, data points are divided into two parts based on the symmetry axis or symmetry plane extracted from data points. Then the divided data points are parameterized and a symmetric knot vector is selected in order to get symmetric B-spline basis functions. Constraint equations regarding the control points are deduced to keep the control points of the B-spline curve or surface to be symmetric with respect to the extracted symmetry axis or symmetry plane. Lastly, the constrained least squares fitting problem is solved with the Lagrange multiplier method. Two examples from industry are given to show that the proposed method is efficient, robust and able to meet the general engineering requirements.

Fast B-spline surface extraction algorithm of seismic volume data on GPU

In the process of seismic data interpretation, the extraction of a horizon or a fault is generally needed. In this paper we present a fast extraction method. First select some feature points interactively, then reconstruct the surface according to the selected feature points by using B-spline interpolation curve or surface. In order to solve the error-drawing problem appeared in the process of interactive rendering, which is caused by the change of sampling interval as the view point changes, we combine shear-warp and splatting algorithm to render the surface. The rendering of seismic data and specific surface in our work are achieved on GPU platform using CUDA programming language, which make it able to meet the requirements of real-time rendering.

Modification of B-Spline Surfaces with Optimization

Algorithms of modifying a surface to approximate some scattered points, or pass through some characteristic points/curves are presented. Similar to variational approach, the algorithms are based on optimization. For the deviation between the modified surface and the original one is adopted as the objective functions, the change of the surface shape is as small as possible with the modified surface satisfying the specified requirements.