Expanded Beads of High Melt Strength Polypropylene Moldable at Low Steam Pressure by Foam Extrusion

We explore the foam extrusion of expanded polypropylene with a long chain branched random co-polypropylene to make its production process simpler and cheaper. The results show that the presence of long chain branches infer high melt strength and, hence, a wide foamability window. We explored the entire window of foaming conditions (namely, temperature and pressure) by means of an ad-hoc extrusion pilot line design. It is shown that the density of the beads can be varied from 20 to 100 kg/m3 using CO2 and isobutane as a blowing agent. The foamed beads were molded by steam-chest molding using moderate steam pressures of 0.3 to 0.35 MPa independently of the closed cell content. A characterization of the mechanical properties was performed on the molded parts. The steam molding pressure for sintering expanded polypropylene beads with a long chain branched random co-polypropylene is lower than the one usually needed for standard polypropylene beads by extrusion. The energy saving for the sintering makes the entire manufacturing processes cost efficient and can trigger new applications.

A Model of Product Line Marketing

Firms offer a variety of products to meet different customer needs. In many horizontally differentiated markets, prices are stable, and firms make infrequent adjustments to their product lines. Although prior research focused on product line design, we investigate how firms should allocate their marketing effort when their product lines are fixed. We propose a simple model to analyze product line marketing. Our model exhibits a flagship product effect in which the firm’s optimal marketing effort is concentrated, provided that the ratio between consumer tastes dispersion and the convexity of the cost of marketing effort is below a threshold. The flagship product is selected according to a marketing effort allocation index that measures the trade-off between a product’s markup and its potential market share. This result is robust with or without competition and whether prices are exogenous or endogenous. Firms often experience shocks to their marketing cost because of technological improvement or externalities. If a monopolist’s cost of marketing effort declines, she should place more emphasis on a low-utility, high-markup product. Conversely, if the cost increases, the monopolist may find it beneficial to focus her marketing effort on a high-utility, low-markup product. When multiproduct firms compete against each other, we show that if the opponent’s cost of marketing effort decreases, there can be a spillover effect, in which the firm benefits from the opponent’s cost reduction, thereby leading to a win-win situation. This paper was accepted by Dmitri Kuksov, marketing.

ASSEMBLY LINE BALANCING IMPLEMENTATION IN MINOR AND SUB ASSEMBLY WORK SHOP AT SHIPYARDS

Recently, the competitive environment is very tough in shipbuilding industry and under these circumstances, manufacturing a ship in a shorter time becomes significantly important in order to meet the customer demands. Therefore, it is hard to do that by using traditional manufacturing techniques. The shipyards located in Turkey usually have functional locations for the machines and this situation often causes longer production times. Instead of this, assembly lines should be redesigned as workshops in the shipyard. Prefabrication work unit is a good example in which an assembly line is needed to be designed. In this study, an assembly line design for prefabrication work unit was performed. For this, assignments of work operations to work shops were carried out by using Largest Set Rule Algorithm and some alternatives were created according to compare the different values of cycle time. These alternatives were simulated by using a production simulation program and the most appropriate assembly line design was presented.

Reconstruction of Scalp Anterior Hairline with Tissue Expansion and Skin Flap

<b><i>Introduction:</i></b> Cutaneous defects involving the frontal region and anterior hairline of the scalp can result from congenital or acquired conditions. The negative esthetic impact can cause disturbances in the psychic and social sphere of the patient, causing problems in interpersonal relationships and in the body image itself. The use of skin expanders is usually effective in this region due to the bone base providing support and stability for its use. <b><i>Case Report:</i></b> We describe the case of a 64-year-old woman submitted to reconstruction of the anterior hairline of the scalp due to scar sequelae after coronal rhytidoplasty followed by pustular erosive dermatosis. We used tissue expansion (50 mL of saline per week until it reached 300 mL) and advancement flap. <b><i>Discussion/Conclusion:</i></b> Scalp reconstruction also includes vascularized soft tissue coverage, acceptable cosmetic appearance, and minimal morbidity for the donor area. The correction of scalp scars must obey 2 basic principles: tissue similarity and natural capillary pattern (direction, angle, capillary growth, and proper capillary line design). Tissue expansion and skin flap techniques can successfully correct defects in extensive scarring alopecia such as in the presented case.

Preliminary Aerodynamic Design of a S-CO2 Axial Turbine

Axial turbines are gaining prominence in supercritical carbon-di-oxide (S-CO2) Brayton cycle power blocks. S-CO2 Brayton cycle power systems designed for 10 MW and upwards will need axial turbines for efficient energy conversion and compact construction. The real gas behavior of S-CO2 and its rapid property variations with temperature presents a strong challenge for turbomachinery design. Applying gas and steam turbine philosophies directly to S-CO2 turbine could lead to erroneous designs. Very little information is available in the open literature on the design of S-CO2 axial turbines. In this paper, design of a 10 MW axial turbine for a simple recuperated Brayton cycle waste heat recovery system is presented. Three repeating stages with nominal stage loading coefficient of 2.3 and flow coefficient of 0.37 were designed. An axial turbine mean-line design method tuned to S-CO2 real gas fluid medium is discussed. 3D blade design was made suing commercial turbomachinery design software AxSTREAM. The turbine was designed for inlet temperature of 818.15 K, pressure ratio of 2.2, rotational speed of 12000 rpm and mass flow rate of 104.5 kg/s. 3D CFD simulations were carried out using the commercial RANS solver ANSYS CFX 2020 R2 with SST turbulence model for closure. S-CO2 was modelled as real gas with Refrigerant Gas Property tables generated over the appropriate pressure and temperature ranges using NIST Refprop database. CFD studies were carried out over a range of mass flow rates and speeds, covering the design and several off-design conditions. The performance maps generated using 3D CFD simulations of the turbine are presented. The geometrical parameters obtained with the mean-line design matched well with that of the 3D turbine design arrived using AxSTREAM. It was observed that the turbine produced 10 MW power at the design condition while passing the required mass flow. CFD studies also showed that the preliminary turbine design achieved a moderate total-to-total efficiency of 80 % at the design condition. The design has potential for further optimization to obtain improved efficiency and for reducing the number of stages from three to two.

Optimization of product line considering compatibility and reliability via discrete imperialist competitive algorithm

In the era of mass customization, designing optimal products is one of the most critical decision-making for a company to stay competitive. More and more customers like customized products, which will bring challenges to the product line design and the production. If a company adopts consumers' favorite levels, this may lead to lower product reliability, or incompatibility among the components that make up the product. Moreover, it is worth outsourcing certain attribute levels so as to reduce production cost, but customers may dislike these levels because of their delivery delay. If managers consider the compatibility issue, the quality issue, outsource determination, and the delivery due date in the product design and production stages, it will avoid unreasonable product configuration and many unnecessary expenses, thereby bringing benefits to the company. To solve this complicated problem, we establish a nonlinear programming model to maximize a metric about profit, termed as Per-capita-contribution Margin considering Reliability Penalty (PMRP). Since the integrated product line design and production problem is NP-hard, we propose an improved Discrete Imperialist Competitive Algorithm (DICA) that can find a most powerful imperialist (i.e., solution) by the competition among all countries in the world. The proposed DICA is compared with genetic algorithm (GA) and simulated annealing (SA) through extensive numerical experiment, and the results show that DICA has more attractive performance than GA and SA.

Experimental Evaluation of 3D Tortuosity of Long Laboratory Spark Trajectory for Sphere-Sphere and Sphere-Plane Discharges under Lightning and Switching Impulse Voltages

Evaluation of attractive areas of high- and ultra-high voltage power transmission lines to direct lightning strokes is based on modeling of propagating progress of the lightning leader approaching the transmission line. The aim of the modeling is to determine the effectiveness of lightning protection for a given line design. The statistical models are currently being developed to extend the conventional deterministic models by embracing the randomness of the discharge channel in space and hence to reproduce the statistical distribution of the striking points. These models require experimental data for understanding of the lightning leader development process and to validate the model across the measurement data. This paper reports on the measured trajectories of discharge channels of long laboratory sparks in various high voltage laboratory arrangements. The sparks were initiated by switching and lightning impulses with peak values ranging from 1200 kV to 3364 kV of positive and negative polarity for two types of high-voltage electrode systems (sphere-sphere and sphere-plane), arranged at distances of 3.3 m and 5.5 m from each other. Statistical distributions of angles describing trajectory of discharge channels in space are reported for a total number of 540 recorded discharges. The results can serve as reference measurement data to develop and evaluate the accuracy of simulation models incorporating statistical nature of the lightning leader development process.

Composite Line Designs and Accuracy Measurements for Tactile Line Tracing on Touch Surfaces

Eyes-free operation of mobile devices is critical in situations where the visual channel is either unavailable or attention is needed elsewhere. In such situations, vibrotactile tracing along paths or lines can help users to navigate and identify symbols and shapes without visual information. In this paper, we investigated the applicability of different metrics that can measure the effectiveness of vibrotactile line tracing methods on touch screens. In two user studies, we compare trace Length Error, Area Error, and Fréchet Distance as alternatives to commonly used trace Time. Our results show that a lower Fréchet distance is correlated better with the comprehension of a line trace. Furthermore, we show that distinct feedback methods perform differently with varying geometric features in lines and propose a segmented line design for tactile line tracing studies. We believe the results will inform future designs of eyes-free operation techniques and studies.

Research on Design Scheme Optimization of Transmission Line Based on Internet Technology

As an important part of the power grid, the rationality and scientificity of the design scheme of transmission line not only relates to the stability and reliability of the whole power grid system, but also plays an important function in the energy loss and efficiency amelioration of the power grid system. Based on this, this paper first analyses the function and characteristics of the transmission line, then studies the meteorological conditions of the transmission line design under the Internet tech, and finally gives the design optimization principles and strategies of the transmission line.