Vladimír Pata

Comparison of metrological techniques for evaluation of the impact of a cosmetic product containing hyaluronic acid on the properties of skin surface

The aim of this research was to evaluate mutual interchangeability of four principally different biometric instrumental techniques designed for objective measurement of changes in the physical, mechanical, and topographical properties of the skin surface treated with commercial antiaging cosmetic products with hyaluronic acid. The following instrumental devices were used: Visioscope PC 35, Corneometer Multiprobe Adapter MPA 6, Reviscometer RVM 600, and 3D scanner Talysurf CLI 500. The comparison of the individual methods was performed using cluster analysis. The study involved 25 female volunteers aged 40-65. Measurements were taken before and after 30 daily in vivo applications of an antiaging preparation to the skin surface in the periorbital area. A slight reduction in skin surface roughness was recorded in 55% of the volunteers. On the contrary, a worsening from their initial states was detected in 25% of the subjects, while for 20%, no significant change was reported. Cluster analysis confirmed that the mentioned methodologies can be divided into two basic clusters, namely, a cluster of methods recording the changes in skin relief by means of optical techniques, and a cluster of methods investigating changes in hydration and anisotropy. In practice, the techniques in different clusters are not interchangeable and should be assessed separately.

Objective measurements of skin surface roughness after microdermabrasion treatment

The aim of this article is to present a new methodology for assessment of skin topology using a three‐dimensional image (3D).

Structural Changes in Metals during Laser Cutting

The presented paper deals with the problems associated with laser machining of metal materials. Specifically, it solves the question of structural changes that occur as a result of the transfer of heat to the material. Experimental machining of selected technical materials was carried out, and on the basis of the hardness measurement near the cutting point, the heat-affected zone was evaluated after passing the laser beam. To confirm the detection of the affected zone width the models of transient temperature field were arranged, to represent the distribution of temperature in the vicinity of the cutting edge.

The Influence of Laser Beam Technological Parameters on the Polymethyl Methacrylate Surface Quality

The paper is focused on the determination of the course and change of the surface quality parameters obtained by the laser engraving of the material known under commercial name polymethyl methacrylate. The paper aims to find mathematical relations based on regression analysis for amplitudes parameters Ra and Rz. For this purpose, a sample of variable technology parameters will be machined followed by the surface measuring and evaluation using the Talysurf CLI 500 3D Surface Scanner. Thus the data obtained will be subjected to the detailed statistical analysis to check homoscedasticity, the presence of outliers, and multidimensional normality testing.

The “Laser Machinability” of Polymeric Materials

This article deals with the area of non-conventional technologies, in particular results of CO2 laser micro-machining are the subject of this experimental study. Laser beam and its impact on different types of polymeric materials were studied in details. The aim was to find an optimal combination of laser cutting parameters (power and feed) for ABS, POM, PS, PMMA, PA 6, PA 66, PC, POM, PP, PTFE and PVC. The laser machinability was evaluated with different technological parameters. Next, the Theory of hypothesis testing for evaluation of the laser machinability was applied.

Resolving Problems of Finding Surface Boundaries during Laser Machining

During of aluminum alloy materials, it is possible to find three surface types which can be distinguish as primary, secondary and tertiary sections. In practice this is a big problem in case of finding the basic parameters of roughness and waviness as described by ISO 4288. According to our research, it is possible to use optical microscopy in the first step and subsequently to scan the surface in 3D in order to distinguish the type of. Another problem is how to determine the boundaries between the individual structures. The article describes methods to distinguish the boundaries in a more precise way by the cumulative functions, leading to more accurate determination of the surface quality parameters.

Simulation of the Transient Temperature Field when Laser Machining Polymeric Materials

The paper deals with possibilities of using the laser in technologies. The parametric temperature field analysis was realized by the finite element method. The analysis was run in COSMOS/M software solver. A thermal module HSTAR makes it possible to realize cases of the temperature dependences on the material properties. Material data can be entered as a function of a temperature. The thermal and physical characteristics of the polymeric materials change significantly. The output of the analysis was described by spectrograms with temperature field distribution of various materials.

Influence of Technological Parameters on Surface Quality of Injection-Molded Parts

In the most cases manufacturing of injection mold and its cavities comprise more than half of the total production time. Very fine finishing operations can increase production time and cost of injection mold. Appropriate choice of finishing operations and injection technological parameters can reduce price of injection mold production, shorten production time and thus lower price of small and thin injection molded parts. Tool material X38CrMoV5-1, used for cavity in injection mold, was finished by fine turning, grinding, lapping and polishing with different technological conditions to achieve various surface roughness. The main aim of this research is to find an influence of surface quality of cavity and injection technological parameters on the surface quality of injection molded parts.

Use of Theory of Hypothesis at Evaluation of Creep Curves

This article focuses on the evaluation of tests with a small repeatability which are characterized by their financial or time demands. The beginning of the article assess the current state of the problem and different approaches to it, focusing on the evaluation of creep tests characterized especially by their very typical little repeatability. Then the article describes the method for testing the creep properties of the irradiated material at raised temperatures. Next, the results are graphically confronted with the subjective evaluation of the observer and using the Mann-Whitney test. This test is used to determine whether the measured data comes from the same basic set or originate with the chosen confidence level. The results show the significance of the use of this test which is calculated with a certain probability.

Application of Theory of Hypothesis Testing in Process of Laser Micromachining

The article focuses on the field of PMMA laser micromachining at change of the technological parameters. The aim was to evaluate machined surface roughness at different setting of DPI definition (number of dots – paths on square inch). The aim is application of the Theory of Hypothesis testing for evaluation changing of final surface during imputing variable technological parameters.