Thermal Optimization of Injection Molds Produced by Layered Manufacturing Techniques

Producing injection tooling with cooling channels of almost any form seems to be one of the most promising advantages of Layered Manufacturing Techniques (like Selective Laser Sintering). It could be efficiently exploited to achieve higher productivity or better quality parts in injection molding. Unfortunately, at the present time, the lack of data-processing tools to design optimal cooling systems still prevents us from fully benefiting from this new potential. The first objective of this paper is to present a methodology for the optimal design of cooling systems in three-dimensional injection molds. Our optimization process is based on a finite element model of the mold and on the standard gradient method. In the second part of this paper, we compare a conventional mold and a mold equipped with a cooling system optimized by means of the proposed methodology. The comparison is carried out thanks to an appropriate protocol. The conclusion is that the optimization of the cooling system doubled the productivity of the mold.Mechanical Engineerin

High voltage pulser for ion shutters in ion mobility spectrometry based on an optocoupler

A novel high voltage pulser for an ion shutter used in drift-tube ion-mobility spectrometers is described. The simple design suitable for the in-house construction of these spectrometers relies on a special optocoupler to isolate the triggering circuitry from the high voltage at the ion shutter. The device was tested with an electrospray-ionization ion-mobility device with a 10 cm drift tube operated at 4 kV into which a standard test mixture of four tetraalkylamines was injected with a negative going gating pulse of about 50 V on top of 4 kV. A fall time of 15.7 µs and a rise time of 2.0 µs were determined for the pulse, which was adequate for the required injection pulse width of 450 µs. Resolving powers between 61 and 81 were determined for the four quaternary amines, which were found to be comparable to the performance obtained with a previously reported pulser circuitry of a different design used as a reference

Artes marciales, el arte secreto de la salud y la buena forma física

[ES] Tras una atenta lectura del texto, puedo afirmar que la redacción es correcta, rica y clara, tanto por terminología empleada como por sistematización de los argumentos. En cuanto a los temas tratados, su discusión, explicación técnica y filosófica, y en general, las consideraciones de los autores son correctas y bien entramada

Artes marciales, el arte secreto de la salud y la buena forma física

Claudio A. Iedwab y Roxanne L. Standefer. Madrid: Miraguano, 2000. 256 páginas. 24x17 cm. I.S.B.N.: 84-7813-213-9

Artes marciales, el arte secreto de la salud y la buena forma física

Claudio A. Iedwab y Roxanne L. Standefer. Madrid: Miraguano, 2000. 256 páginas. 24x17 cm. I.S.B.N.: 84-7813-213-9

Microtechnology in Space Bioreactors

Space biology is a young and rapidly developing discipline comprising basic research and biotechnology. In the next decades it will play a prominent role in the International Space Station (ISS). Therefore, there is an increasing demand for sophisticated instrumentation to satisfy the requirements of the future projects in space biology. Bioreactors will be needed to supply fresh living material (cells and tissues) either to study still obscure basic biological mechanisms or to develop profitable bioprocesses which will take advantage of the peculiar microgravity conditions. Since more than twenty years, the Space Biology Group of the ETHZ is carrying out research projects in space (Space Shuttle/Spacelab, MIR Station, satellites, and sounding rockets) that involve also the development of space-qualified instrumentation. In the last ten years we have developed, in collaboration with Mecanex SA, Nyon, and the Institute of Microtechnology of the University of Neuchatel, a space bioreactor for the continuous culture of yeast cells under controlled conditions. Sensors, pH control, nutrients pump and fluid flowmeter are based on state-of-the-art silicon technology. After two successful space flights, a further improved version is presently prepared for a flight in the year 2000

Fish behavior during hydropeaking in a channel equipped with a lateral shelter

In the framework of a research project focusing on mitigation measures for hydropeaking, a lateral embayment at the channel bank is studied as a fish refuge. Systematic experiments with different refuge configurations were carried out. The basic configuration is rectangular with a length of 2 m and a width of 1.2 m installed at the right bank of a 12 m long and 1.2 m wide flume supplied with freshwater from a natural river. In order to trigger water exchange between the flume and the rectangular refuge a wall acting like a groyne was installed inside the refuge protruding slightly in the main channel. Position, inclination and protrusion rate of this groyne were varied systematically in order to obtain an optimal water exchange and the best attractiveness of the shelter for fishes during hydropeaking. Each configuration was tested three times with juvenile wild brown trout (Salmo trutta fario) (0+ and 1+), with 2 different groups of 10 and the combined group of 20 brown trout. They where exposed during 3 hours each time to a hydropeaking flow of 220 l/s in the main channel. During every test, the movements of the fish were recorded continuously by video camera and their positions were observed every 20 minutes. 6 series of 20 fishes were used for 36 sequences corresponding to the 12 configurations tested. For each configuration the analysis of the fish positions gave a global frequentation rate as well as the favorite staying places in the shelter. Some in- and outgoing fish trajectories were obtained by the treatment of video pictures. A particular focus was given to the interface section between the refuge and the main channel in order to relate the spatial distribution and the frequency of fish passage from up- and downstream into the shelter. In order to link the swimming trajectories of the trout with the flow conditions, systematic measurement of the velocity field was performed using UVP technique. The flow velocities were analysed in several horizontal and vertical transects across the refuge and flume. Comparing the velocity patterns with the fish trajectories, the attractiveness of different configurations of fish refuges could be analyzed. The tests reveal that a very basic refuge configuration, with low water exchange between shelter and channel, is not interesting for fish. When forcing a water exchange by introducing a deviation groyne into the shelter, its frequentation can be increased significantly. The fish can easily detect the refuge by the exchange flux when searching its way upstream. The refuge attractiveness can be optimized by testing different groyne orientations, creating an expanded velocity field close to the exit and the entrance. Important is a high velocity field leaving the refuge at its lower end but also a backwater zone near the groyne. The high velocity field attracts the fish and the close backwater zone allows the fish to enter the shelter. For the best configuration, more than 80% of the fish found the refuge by swimming mainly from downstream, 20 minutes after the beginning of hydropeaking

Flow exchange between a channel and a rectangular embayment equipped with a diverting structure

In the framework of a research project focusing on mitigation measures for hydropeaking, a lateral embayment in riverbank is studied as a fish shelter. With the goal to find attractive configurations of shelter, systematic experiments with wild juvenile brown trout (Salmo trutta fario) were carried out in a flume supplied with freshwater from a natural river. The experimental is equipped with a rectangular lateral embayment. In order to follow the fish trajectories, their movements were recorded continuously by video camera during every test, and their positions were periodically observed. In order to link the swimming trajectories of the trout with the flow conditions, 2D simulations were computed to obtain the diverted discharge in the shelter, and systematic UVP measurement of the velocity field was performed. The flow velocities were analysed in the vertical interface between the shelter and the flume. Comparing the velocity patterns with the fish trajectories, the attractiveness of different configurations of fish shelters could be analyzed. The first tests reveal that a very basic shelter configuration, with low water exchange between shelter and channel, is not interesting for fish. When forcing a water exchange By introducing a deviation groyne into the shelter with the aim to force the water exchange, the frequentation rate can be increased significantly. The fish can easily detect the refuge by the exchange flux when searching its way upstream. The shelter attractiveness was optimized by testing different groyne orientations, in order to create an expanded velocity field close to the exit and entrance sections. Important is a high velocity field leaving the refuge at its lower end but also a backwater zone near the groyne. The high velocity field attracts the fish and the close backwater zone allows the fish to enter the shelter. For the best configuration, more than 80% of the fish found the shelter by swimming mainly from downstream, during the next 20 minutes after the beginning of hydropeaking

Attractiveness of a lateral shelter in a channel as a refuge for juvenile brown trout during hydropeaking

Peak power production in hydroelectric storage power plants results in frequent and intense flow variations in the rivers downstream of the plants. Fish populations can be negatively impacted when subjected to these so-called hydropeaking phenomena. In researching mitigation solutions, shelters in the riverbanks of channelized rivers have been identified as a means of protecting fish from excessive flow velocities. These shelters were studied systematically using juvenile brown trout (Salmo trutta fario) in an experimental configuration in which a straight channel was equipped with a lateral embayment. The purpose of the experiments was to generate hydrodynamic hydropeaking conditions in the channel that are undesirable for juvenile trout, thereby causing them to enter the shelter. The flow velocity distribution in the intersection plane between the main channel and the lateral shelter was found to be a significant parameter for attracting fish to the shelter. The utilization rate of trout in the shelter was used as a performance indicator. Using a basic rectangular shelter configuration without forced water exchange between the shelter and the channel, the utilization rate was only 35 %. This rate was more than doubled by introducing a deviation groyne to force water exchange between the channel and the shelter. The position and orientation angle of this groyne were systematically varied to maximize the utilization rate. Maximum utilization rates approaching 90 % were obtained for an optimum configuration in which an island-type groyne was placed in the shelter. The results of the systematic channel tests showed the potential of the shelter to attract fish. Such a shelter could be used in channelized rivers both for morphological revitalization and to improve fish habitats. As a next step in this research, prototype shelters will be built on a natural river and monitored for 2–3 years under a hydropeaking flow regime

Development of a Space Bioreactor using Microtechnology

A miniature bio-reactor for the cultivation of cells aboard Spacelab is presented. Yeast cells are grown in a 3 milliliter reactor chamber. A supply of fresh nutrient medium is provided by a piezo-electric silicon micro-pump. In the reactor, pH, temperature, and redox potential are monitored and the pH is regulated at a constant value. The complete instrument is fitted in a standard experiment container of 63 x 63 x 85 mm. The bioreactor was used on the IML-2 mission in July 1994 and is being refurbished for a reflight in the spring of 1996