To protect the material at the backside of a workpiece during laser drilling or cutting, an absorbing material is used. Here a nanoparticle-suspension provides a particularly efficient protection wLaser drilling without backing material damages the workpiece. A nanoparticle-suspension helps to prevent the damage. (Source: Patent application DE102013212665B4)ith further advantages like cooling. During laser drilling, material situated behind the bore can be easily damaged by laser radiation. A common problem, for example, during the manufacturing of injection nozzles. To prevent the damage, a material which absorbs the majority of the laser radiation is placed at the working side. The material can be a solid which typically absorbs almost all of the radiation but has the disadvantage that it cannot be used if the geometry of the workpiece makes it impossible to place a solid material behind the bore. Figure (Laser drilling without backing material damages the workpiece. A nanoparticle-suspension helps to prevent the damage. (Source: Patent application DE102013212665B4))



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Parameters which have been obtained from ultrasonic spectrometry, dynamic light scattering and shear viscosity are presented in Table (5.9). It is a fascinating aspect of the dynamic scaling theory of ultrasonic attenuation that, due to scaling of frequency data of different critical mixtures fall on one scaling function.  However, the most curious specific system parameter is the characteristic relaxation rate amplitude Γ_0, which according to Bhattacharjee-Ferrell theory, corresponds with the mutual diffusion coefficient D and the fluctuation correlation length ξ.  In Table (5.9) parameters Γ_0  and ξ_0  are listed for various binary mixtures with critical demixing point. The isobutoxyethanol-water system exhibits by far the smallest amplitude Γ_0 in the relaxation rate of order parameter fluctuations. In comparison, with the system n-pentanol-nitromethane, Γ_0 is 35 times larger.  Assuming, that the life time of fluctuations τξ  = Γ_0^−1, as inverse characteristic relaxation rate reflects intermolecular properties as well the geometry of considered components the strong variation of Γ_0  of various liquids can be understood. In addition, due to the Coulombic interactions, relaxation from a local nonequilibrium distribution of electrical charges into thermal equilibrium will involve extensive redistribution of ions in ionic solutions and may, therefore, proceed with a smaller relaxation rate than a molecular liquid mixture at the same reduced temperature.  A quantity, which may be taken to summarize the above mentioned molecular properties, is the surface tension σ. If considering critical fluctuations, reflected by the fluctuation relaxation rate Γ_0  , to depend on the  surface  tension,  a correlation  between  both  quantities  should  exist.           

The following project deals with the dynamic scaling aspects within the framework of Bhattacharjee-Ferrell theory. Furthermore, relationships between the critical sound attenuation and the dynamic scaling function are presented. Moreover, crossover effects for binary and ternary fluids are presented.

Bhattacharjee-Ferrell scaling hypothesis - binary systems:

Critical phenomena, as all continuous phase transitions, Show universal characteristics of their thermodynamic properties, if they belong to the same universality class and if their dimension is identical. The concepts and consequences of critical slowing down have been presented in 2005-(II)-Critical Phenomena and Universality.  In particular, the light scattering is well represented and described by dynamic scaling theories, resulting from the mode-coupling considerations. However, the treatment of critical ultrasonic attenuation necessitates the development of new theories in order to get an access to critical fluctuations in a sound field. Bhattacharjee and Ferrell have presented a general theory of the critical ultrasonic attenuation, based on an extension of the concept of the frequency-dependent specific heat. This conception was firstly introduced by Herzfeld and Rice in 1928.

The use of flat displays is already standard in many homes, offices and in the industry today. No matter in which area you find your application, they are the most important interfaces between man and machine. The most widely used representatives of their kind today are the Active Matrix Liquid Crystal Displays (AMLCD) and organic light emitting diodes (OLEDs), whose market has been growing steadily since 2007.

 

 

One of the global players is certainly the company SAMSUNG and LG. For the manufacturers of flat screens, it is particularly important to use inexpensive glass substrates coated with poly-crystalline silicon (p-Si) (from which TFTs are made). The use of pulsed excimer lasers, which melt the silicon for a short time while the thermal limits of the glass substrate are not hurt,is especially good for that. The most commonly used laser in the literature is the XeCl Excimer laser with one wavelength of λ = 308 nm. The radiation penetrates at this wavelength only a few nanometers into the silicon surface. In the display industry it is crucial to work with formation of the largest possible and defect-free crystallites with little variation in the statistical size distribution over the entire substrate. Since the processing, by the glass substrate, is thermally limited to about 500-650 °C, Today, the so-called low-temperature crystallization process (Low Temperature Poly Silicon Technology = LTPS) are applied. This method can be great realized  with an Excimerlaser. As the demands of the display manufacturers grow, it is endeavored to expose larger and larger substrates. Since one depends on a constant energy density in the annealing process, it clear that with the enlargement of the substrates the Energy of the laser must rise. Since it is technically very complicated to increase the energy provided by an Excimer-Discharge unit, it is close to use two or three couple of several discharge units. This strategy is also pursued by Coherent and represented in their product range: LineBeam 750 (VYPER), LineBeam 1000 (TwinVYPER) and LineBeam 1500 (TriVYPER). The flagship of the company is the TriVYPER; an energy output of 6000 mJ and consists of 6 laser subunits or 3 VYPER subunits. The biggest challenge is to synchronize all laser discharge units. The company has also succeeded. The synchronization of the laser subunits is in the single-digit range of nanoseconds. Since the properties of an Excimerlaser by itself are not exactly
characterized by homogeneity in the energy distribution, it is essential to use for the six laser beams (in the case of TriVYPER, for example) an optical system. This function is realized by the so-called Beam Delivery System or LineBeam. Here are the rays mixed and homogenized through different optics and geometries, so that finally in the exposure chamber we use a homogeneous UV 308 nm radiation.

 

Watch "Smart phones, tablets and TVs from AMLCD to OLED". Take a look at Coherent's vision for the future with excimer laser annealing at the heart of it.

Coherent ELA (Excimer Laser Annealing)

 

 

The idea of the project, under the direction of Dr. Günther Hahn,  was (with the help of "Electrical impedance tomography") to study the behavior of the lungs in micro gravitation (0~g,) (1-g), and (2-g). The experiment provided important results for research in micro gravitational environment, as well as data for human medicine on earth. The experiments were conducted aboard the Zero-G, during several parabolic flight maneuvers.

Source: University of Göttingen

"Electrical impedance tomography (EIT) is a noninvasive type of medical imaging in which the electrical conductivity, permittivity, and impedance of a part of the body is inferred from surface electrode measurements and used to form a tomographic image of that part. Electrical conductivity varies considerably among various biological tissues (absolute EIT) or the movement of fluids and gases within tissues (difference EIT). The majority of EIT systems apply small alternating currents at a single frequency, however, some EIT systems use multiple frequencies to better differentiate between normal and suspected abnormal tissue within the same organ (multifrequency-EIT or electrical impedance spectroscopy)." wiki


Project Impressions:

 

Nature comprises a multitude of critical phenomena. Spontaneous symmetry breaking at the origin of the universe and gravitation collapse are spectacular examples. Critical phenomena occur at phase transitions. Theories of phase transitions use methods of catastrophe theory and also of theory of percolation which currently attract considerable attention. In order to understand critical phenomena,  investigations of liquid-liquid phase transitions in binary and ternary mixtures are very instructive. Especially the understanding of the phase behavior and the critical phenomena in ternary mixtures, biophysics and membrane physics have attracted attention during the last years . The essential and most amazing feature of critical phenomena was the discovery of critical point universality indicating that the microscopic structure of fluids becomes unimportant in the vicinity of the critical point. The understanding of such phenomena is also of great importance for chemistry and chemical engineering in procedures like liquid and solid extraction, drying, absorption, distillation and many other chemical reaction processes, as well as for biology in operations like fermentation, biological filtration and syntheses. Moreover, theories of critical phenomena are substantial for many innovative applications such as supercritical extraction, enhanced oil recovery and supercritical pollution oxidation. The importance of the understanding and application of critical phenomena is demonstrated by the recently (08.28.07) provided studies performed in the International Space Station (ISS).

The fascination about critical phenomena is based on the universality of the behaviour of systems, which can be quite different in many of their properties. Theoretical models of critical behavior are based on the terms renormalization and scaling. Such a new model shall be verified by comprehensive measurement of coupled parameters of critically segregating binary fluids. In addition, binary mixtures are to be investigated whose spectra reflect both universal and individual behaviour. Of particular interest is the coupling of critical dynamics to elementary chemical processes.

The similarity of different systems can be described by universal power laws which determine the thermodynamic and transport properties close to a critical point.  In order to study the critical behavior in different systems it is convenient to use the so-called reduced temperature:

When the temperature T of a system is close to its critical temperature T , some relevant parameters F follow a power law:

with x  > 0.   At ε → 0, that is T  → T , all terms except the 1 in the brackets disappear. Therefore, F satisfies the power law: 

with ϕ, denoting the critical exponent for the particular variable F.