Stack dynamics

Stacking dynamics and conformational gating also provide an explanation for the distance dependence of the yield of CT between Et and ZG, a dependence which was not manifested in the CT rates [96]. Dynamic mo-... 

A further requirement to be satisfied by the oxidant supply device is represented by dynamic performance in a wide range of air flow rates. This aspect is crucial in some hybrid power train operative modes characterized by high stack dynamics (full power or soft hybrid configurations, see Sect. 5.5). 

Chen J and Zhou B (2008), Diagnosis of PEM fuel cell stack dynamic behaviors ,... 

Semi-submersible rigs are often referred to as semis , and are a floating type of rig. Like the jack-up, a semi is self contained. The structure is supported by large pontoons which are ballasted with water to provide the required stability and height. The rig is held in position by anchors and mooring lines or dynamically positioned by thrusters. A large diameter steel pipe ( riser ) is connected to the sea-bed and serves as a conduit for the drill string. The blowout preventer (BOP) is also located at the sea-bed ( sub sea stack ). 

The key here was the theory. The pioneers familiarity with both the kinematic and the dynamic theory of diffraction and with the real structure of real crystals (the subject-matter of Lai s review cited in Section 4.2.4) enabled them to work out, by degrees, how to get good contrast for dislocations of various kinds and, later, other defects such as stacking-faults. Several other physicists who have since become well known, such as A. Kelly and J. Menter, were also involved Hirsch goes to considerable pains in his 1986 paper to attribute credit to all those who played a major part. 

T. Sinno, R. A. Brown, W. Van Ammon, E. Dornberger. Point defect dynamics and the oxidation-induced stacking-fault ring in Czochralski-grown silicon crystals. J Electrochem Soc 145 302, 1998. 

The question of relative rates of seal leakage and permeation (cf. points 1 and 3) has been considered by MERE. For the sealing of HPHT (5000 psi, ca. 345 bar, or 34.5 MPa 100°C) fluids with chevron seal-stack systems used at the bottom of oil wells in intermittently dynamic conditions, high-pressure permeation and seal-leakage tests using the equipment outlined in Section 23.3.1.2 have been conducted it has been shown that methane gas permeation rate was only ca. 1 % of the rate... 

Steady-state and Dynamic Operations of 3W DMFC stack... 

The transient response of DMFC is inherently slower and consequently the performance is worse than that of the hydrogen fuel cell, since the electrochemical oxidation kinetics of methanol are inherently slower due to intermediates formed during methanol oxidation [3]. Since the methanol solution should penetrate a diffusion layer toward the anode catalyst layer for oxidation, it is inevitable for the DMFC to experience the hi mass transport resistance. The carbon dioxide produced as the result of the oxidation reaction of methanol could also partly block the narrow flow path to be more difScult for the methanol to diflhise toward the catalyst. All these resistances and limitations can alter the cell characteristics and the power output when the cell is operated under variable load conditions. Especially when the DMFC stack is considered, the fluid dynamics inside the fuel cell stack is more complicated and so the transient stack performance could be more dependent of the variable load conditions. 

In this paper we report the effect of varying loads on a small size DMFC stack (10 cells with 9 cm active-area each). The transient responses of the stack voltage have been investigated upon variable current load conditions to obtain the information on the dynamic characteristics of the stack. Also, the transient responses of the stack current upon changing fuel flow rates have been monitored to obtain the optimal operating conditions for the staek. 

Fig. 2 shows the dynamic response of stack voltage to the step changes of various applied current densities. Like the former case of applied current pulses, the response exhibits the overshooting and relaxation which is caused by the methanol oxidation kinetics on the catalyst surface. The steady state stack voltage was found to be the same for both pulse and step loads with the same current density. 

TMs study has shown the dynamic behavior of a 5W DMFC stack when the current loads have changed by pulses and steps. In order to determine the optimum operating conditions of the stack, the dynamic behavior of the stack current has been studied under a constant voltage output of 3.8V, varying the flow rate of 2M methanol solution and air. For the stable operation of the 5W stack, the minimal fuel flow rates are found to be 3 ml/min and 2L/min for 2M methanol and air, respectively. 

In addition to the spreading dynamics, the stacking structure of the self-spreading lipid bilayer is also controllable via the NaCl concentration [54, 55]. Further experimental and theoretical investigations regarding the control of self-spreading are required before we will be able to easily control the self-spreading behavior in microfluidic devices. 

Crespo-Hernandez CE, Cohen B, Kohler B (2005) Base stacking controls excited-state dynamics in A-T DNA. Nature 436 1141-1144... 

In order to directly probe the dynamics of CT between Et and ZG, and to understand how the intervening DNA base stack regulates CT rate constants and efficiencies, we examined this reaction on the femtosecond time scale [96]. These investigations revealed not only the unique ability of the DNA n-stack to mediate CT, but also the remarkable capacity of dynamical motions to modulate CT efficiency. Ultrafast CT between tethered, intercalated Et and ZG was observed with two time constants, 5 and 75 ps, both of which were essentially independent of distance over the 10-17 A examined. Significantly, both time constants correspond to CT reactions, as these fast decay components were not detected in analogous duplexes where the ZG was re-... 

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