Influence Of Power Distribution Research Articles

Investigations on opportunities and challenges of brilliant high-power laser beam welding with 24 kW and adjustable power distribution for different materials

Solid-state laser beam sources offer the possibility of generating high-brilliance laser beams with low expansion and high usable intensity at the focal point. New approaches include beam shaping with the use of core and ring fiber and, therefore, variable power distribution in the laser beam focal point and material interaction area. Particularly, high-power laser beam welding benefits from beam shaping because of the stabilizing effect on the weld pool. Furthermore, the technical progress achieved with regard to beam quality also allows one to achieve high Rayleigh lengths and, therefore, a more uniform beam diameter over the whole material thickness. In this study, investigations on high-power laser beam welding with a 24 kW disk laser beam source are conducted for three different materials (mild steel, aluminum alloy, and copper), which are of high interest for welding in different sectors. The influence of power distribution between the core and the ring as well as welding speed on weld geometry (depth and width), weld pool stability, and the resulting weld seam quality is investigated. It is shown that the welding process cannot just be scaled up in comparison with welding with lower laser beam power but has its own challenges. It is possible that high welding depths (12 mm for copper, more than 12 mm is possible for aluminum, and 25 mm for mild steel) could be achieved in one pass. To achieve this, aluminum needs the lowest energy per unit length per mm of sheet thickness and copper the highest.

Analysis of Power Transmission Characteristics of a Novel Secondary Side LCD Series Forward Converter

A novel secondary-side LCD series forward converter is proposed, and the power transmission characteristics of the excitation inductance of the proposed converter under different modes are analyzed. By analyzing the relationship between the transmission power of forward branch and additional branch and excitation inductance, it is concluded that when the excitation inductance Lm works in CCM (continuous conduction mode), the transmission power of forward branch and additional branch has nothing to do with the value of excitation inductance. When the excitation inductance Lm works in DCM (discontinuous conduction mode), the transmission power of forward branch increases with the increase of excitation inductance, while the transmission power of additional branch decreases with the increase of excitation inductance. At the same time, the influence of power distribution on the efficiency of transformation topology is explored, and the relationship between the transmission power of the forward branch and the current stress of the switching tube was derived, and the parameter design method of magnetic element is put forward. Finally, the circuit model of the novel secondary side LCD series Forward converter is established, and the experimental results verify the correctness of the theoretical analysis and the feasibility of the parameter design method.

Innovation linkages in societies with a high power distance

Innovation linkages are one of the important conditions for innovative development of the country. A confirmation of this is the calculation methodology of the Global Innovation Index, which takes them into account. The article explores the problem of innovation linkages formation in societies with a high power distance, which are characterised in tolerance for so cial inequality. The methodological basis of the study embraces the concept of stakeholders and the theory of inter-organizational networks in combination with the approach of cross-cultural research of power relations. To describe the structure and influence of power distribution on in novator’s behaviour the researcher uses the method of classification of innovation linkages’ par ticipants into actors and actants. To identify societies with a high power distance and which are relatively successful in innovative development the author draws on the comparative analysis of countries. Using the cases of some of them (China, Malaysia and the United Arab Emirates) the author shows the mechanisms of formation and development of innovation linkages: 1) exclu sive (or external) development through the use of foreign innovation infrastructure; 2) informal linkages based on the values of humanism and paternalism; and 3) co-optation of institutional centers of responsibility for change. The study may be of interest both to enterprises for develop ing strategies to promote their innovative solutions, and to government agencies that solve the problem of weak innovation linkages.

Influence of power distribution on weld seam quality and geometry in laser beam welding of aluminum alloys

In laser beam welding of aluminum alloy there is a high susceptibility of pore formation at low feed rates. Porosity can be improved by application of several laser spots to form the shape of the vapor capillary. In this regard, flexible, concentrically arranged laser spots with variable power distribution have recently been developed. Nevertheless, the influence of power distribution on weld quality and geometry has not been investigated. Therefore, this paper presents investigations regarding the influence of power distribution on the weld seam properties like penetration depth, seam width and porosity. Welding trials are carried out with three different aluminum alloys EN AW-1050, EN AW-6082 and EN AW-5083. Compared to a mono-spot the porosity can be reduced from 12 % to 8 % with power distribution of 75/25 of inner core and outer ring.

Accident safety analysis of flow blockage in an assembly in the JRR-3M research reactor using system code RELAP5 and CFD code FLUENT

The main purpose of the paper is to execute the thermal-hydraulic analysis of flow blockage in a single fuel assembly in the JRR-3M research reactor (Upgraded Japan Research Reactor No. 3). Using the one-dimensional system analysis code RELAP5/MOD3.4, flow region in a standard fuel assembly (SFA) is lumped into a coolant channel. 5 similar coolant channels representing 5 independent assemblies are modeled to consider the interaction between blocked channel and adjacent channels. The rest of the core is lumped into 1 average channel and 1 bypass channel. The coolant system is also modeled in detail. Meanwhile, a three-dimensional model of heated part in the assembly is built using the computational fluid dynamics (CFD) code FLUENT. Results calculated by RELAP5/MOD3.4 are used as the boundary conditions of the 3D model. The user-defined function (UDF) is adopted to describe phase change and the power distribution in axial and radial direction in the assembly. Results indicate that it is necessary for assembly blockage to consider the influence of power distribution on accident consequence. When the blockage ratio is 64%, coolant in the hottest subchannel is still supercooled while coolant temperature at outlet is close to saturation temperature. It is the critical blockage ratio to ensure the reactor safety. When the blockage ratio is 70%, departure from nucleate boiling (DNB) will occur. According to the FLUENT code, the process of bubble generation and growth is discussed. It can be found that if the bubbles largely generate, there will be obvious impacts on heat transfer of fuel plate and coolant flow. Fuel plates may damage locally.

Power concentration or parity? The conditional influence of power distribution in regional economic integration

Power concentration or parity? The conditional influence of power distribution in regional economic integration

Forced convection burnout for water in rod bundles at high pressures

Burnout data from several new 12-rod test sections are presented. The influence of power distribution, minimum wall-to-rod separation, and mass flux is investigated. The gross behavior of these test sections has been re-analysed by two computer programs which allow the determination of local coolant conditions in an internally connected, boiling bundle as was used in this study. The rods were 0.440 in in diameter and wrapped with 0.22 in O.D. hypodermic needle tubing on a 6 in pitch. Burnout data were obtained at 1200 psia and at mass fluxes from 1–5 × 10 6 lb/ h ft 2. Differences between the heat generation rates in the two interior rods and the remaining ten peripheral rods were 1:1, 1.55:1, and 2.64:1. The minimum wall-to-rod separation was 0.022 in in four test sections and approximately 0.032 in in a fifth test section. The gross and local behavior of the test sections are compared to tubular data. Such a comparison indicates that a cold wall effect exists in the peripheral channels whereas the local behavior in the interior channels agrees closely with the tubular data.