Molecular beam millimeter sidebands Fourier transform spectrometer (MB-MMSBFT)

The high resolution Fourier transform technique has been extensively applied in the centimeter range. In the past few years great progress have been made in observing molecular complexes. Most instruments operate between 2 and 26 GHz. So, very light interesting molecular species cannot be observed. The extension of the method towards the millimeter range suffers important technological shortcomings. A sidebands generation technic allowing the generation of very short pulses, all over the millimeter wave range, is described. For the first time, the experiment is performed in a resonant cavity and on a supersonic nozzle beam.     

Improving the relaxivity by dimerizing Gd-AAZTA: Insights for enhancing the sensitivity of MRI contrast agents

The synthesis of a dimeric derivative of Gd-AAZTA is reported. It retains the basic properties of the parent complex (q = 2, high stability) and displays a relaxivity of 14.0 mM^?1 s^?1 at 20 MHz and 298 K. The outstanding relaxivity is the result of the increased molecular reorientational time and of the contribution arising from 4 to 5 water molecules in the second coordination sphere of the Gd(III) ions.     

A rotor speed estimation algorithm in variable speed permanent magnet synchronous generator wind energy conversion system

A rotor speed estimation algorithm in a direct vector controlled permanent magnet synchronous generator wind energy conversion system is proposed. The proposed method is based on a simple equation obtained from the flux model of the machine and contains only stator flux and current. Constant gain recursive least squares estimator is used for implementing the speed estimation algorithm. Rotor position information used for coordinate transformation is computed using the estimated speed. Stator flux information required by the speed estimator is obtained using the stator voltage equation by implementing a programmable low pass filter. The estimated speed is used as the feedback signal for the speed control loop of the vector controlled machine side converter control system whose command speed is obtained from a wind speed sensorless maximum power point tracking controller, thus, we obtain a complete rotor speed and wind speed sensorless permanent magnet synchronous generator wind energy conversion system. Simulation is carried out to validate the performance of the proposed method. Copyright © 2012 John Wiley & Sons, Ltd.     

A vapor chamber using extended condenser concept for ultra-high heat flux and large heater area

We proposed an extended vapor chamber (EVC), consisting of an evaporator part and an extended condenser part. A layer of compressed copper foam was sintered on the inner evaporator surface. The extended condenser includes a circular-straight groove network and a fin region. The groove network distributes generated vapor everywhere in the internal volume of EVC. A set of capillary holes are machined within fins. A sliced copper foam bar is inserted in each of capillary hole. The peaks of copper foam bar are tightly contacted with the evaporator copper foam piece. Water is used as the working fluid with a heater area of 0.785 cm². A minimum thermal resistance of 0.03 K/W is reached for the bottom heating. The heat flux is up to 450 W/cm² without reaching dryout. The transition point of thermal resistances versus heat fluxes is significantly delayed with the heat flux exceeding 300 W/cm², beyond which thermal resistances are only slightly increased. EVC not only improves temperature uniformity on the evaporator and fin base surfaces, but also evens the temperature distribution along the fin height direction to increase the fin efficiency. Inclination angles and charge ratios are combined to affect the thermal performance of EVC. An optimal charge ratio of 0.3 was recommended. EVC can be used for ultra-high heat flux and larger heater area conditions.     

Bewertung des Nutzens von Cold‐Flow‐Versuchen bei der Charakterisierung von Kolonneneinbauten

Cold flow experiments with air and water as model fluids can make an important contribution to the characterization of column internals. They can be performed with comparatively low effort, however, on the other hand serve as an essential base for fluid dynamic model approaches, which in turn provide a bridge to technically relevant systems and operating conditions. In combination with other valuation methods, such as test mixture analyses or mathematical models, they can make a very important contribution to the safe and pinpoint design of column internals. Possibilities, but also limits of cold flow experiments are shown and related to tests with organic systems.     

Monodimensional modeling and experimental study of the dynamic behavior of proton exchange membrane fuel cell stack operating in dead-end mode

The dynamic behavior of a five cells proton exchange membrane fuel cell (PEMFC) stack operating in dead-end mode has been studied at room temperature, both experimentally and by simulation. Its performances in “fresh” and “aged” state have been compared. The cells exhibited two different response times: the first one at about 40 ms, corresponding to the time needed to charge the double-layer capacitance, and the second one at about 15–20 s. The first time response was not affected by the ageing process, despite the decrease of the performances, while the second one was. Our simulations indicated that a high amount of liquid water was present in the stack, even in “fresh” state. This liquid water is at the origin of the performances decrease with ageing, due to its effect on decreasing the actual GDL porosity that in turn cause the starving of the active layer with oxygen. As a consequence, it appears that water management issue in a fuel cell operating in dead-end mode at room temperature mainly consists in avoiding pore flooding instead of providing enough water to maintain membrane conductivity.     

Peptide derivatized lamellar aggregates as target-specific MRI contrast agents

The relaxivity behaviour and the structural characterization of new supramolecular aggregates (bilayer structures and micelles) obtained by combining two different amphiphilic monomers are reported. One monomer, (C18)(2)DTPAGlu-Gd, contains a very stable gadolinium complex, and the other, DSPE-PEG(2000)-CCK8, contains the bioactive CCK8 peptide. Samples that contained only DSPE-PEG(2000)-CCK8, or up to 50 % (C18)(2)DTPAGlu-Gd, aggregated as double-layer structures (lamellar aggregates) with a thickness of approximately 80-100 A, as evaluated by SANS measurement and Cryo-TEM imaging. A transition to micelle formation was observed when the amount of (C18)(2)DTPAGlu-Gd in the aggregate was increased. These were rod-like micelles approximately 40 A in radius and >200 A in length. The proton relaxivities for both lamellar aggregates and rod-like micelles were the same (17.2 mM(-1) s(-1)), although the values were the results of different combinations of local and global contributions. The in vitro target selectivity of aggregates that contained the CCK-8 peptide was demonstrated by using nuclear medicine techniques.     

厌氧—混凝—高级氧化工艺处理转运站污水的中试研究

开发了转运站污水厌氧生化调节池和基于混凝沉淀及高级氧化技术的快速处理设备,在转运站现场建立中试系统,优化系统运行的工艺参数,研究中试规模下组合工艺对转运站污水的处理效果,并进行了技术经济分析。该组合工艺可将CODCr从进水的15 000 mg/L降至1 230 mg/L,油脂从进水的10 000 mg/L以上降至50 mg/L,色度去除率在90%以上,出水澄清透明且无恶臭。     

Topology optimization of connections in mechanical systems

One of the issues for the automotive industry is weight reduction. For this purpose, topology optimization is used for mechanical parts and usually involve