Amplitude death in a ring of nonidentical nonlinear oscillators with unidirectional coupling

We study the collective behaviors in a ring of coupled nonidentical nonlinear oscillators with unidirectional coupling, of which natural frequencies are distributed in a random way. We find the amplitude death phenomena in the case of unidirectional couplings and discuss the differences between the cases of bidirectional and unidirectional couplings. There are three main differences; there exists neither partial amplitude death nor local clustering behavior but oblique line structure which represents directional signal flow on the spatio-temporal patterns in the unidirectional coupling case. The unidirectional coupling has the advantage of easily obtaining global amplitude death in a ring of coupled oscillators with randomly distributed natural frequency. Finally, we explain the results using the eigenvalue analysis of Jacobian matrix at the origin and also discuss the transition of dynamical behavior coming from connection structure as coupling strength increases.Comment: 14 pages, 11 figure

Cell integrated multi-junction thermocouple array for Solid Oxide Fuel Cell temperature sensing: N+1 architecture

Understanding the cell temperature distribution of Solid Oxide Fuel Cells (SOFC) stacks during normal operation has multifaceted advantages in performance and degradation studies. Present efforts on measuring temperature from operating SOFC stacks measure only gas channel temperature and do not reveal the cell level temperature distribution, which is more important for understanding cell’s performance and its temperature-related degradation study. Authors propose a cell integrated multi-junction thermocouple array for in-situ cell surface temperature monitoring from an operating SOFC. The proposed thermocouple array requires far fewer numbers of thermo-elements than thermocouples would require for the same number of temperature sensing points. Hence, it causes far less disturbance to the cells’ performance during sensing. The array was sputter deposited on the cathode of a commercial SOFC using alumel (Ni:Al:Mn:Si – 95:2:2:1 by wt.) and chromel( Ni:Cr – 90:10 by wt.) as thermo-element materials. The thermocouple array was tested in a furnace covering the entire operating temperature range of a typical SOFC. Each sensing point of the array could measure temperature independently, and as accurately as a thermocouple. Thus, the concept of multi-junction thermocouples is experimentally validated and its stability on a porous SOFC cathode is confirmed

In-situ temperature sensing of SOFC during anode reduction and cell operations using a multi-junction thermocouple network

Understanding in-situ temperature distribution of a SOFC stack while in operation is very important for its performance and degradation studies. The available efforts in literature are incapable of measuring the temperature of electrodes. The proposed multi-junction thermocouple network, which requires only 2N thermoelements for N2 measuring points, can measure temperature directly from electrodes. A multi-junction thermocouple network having 9 measuring points was fabricated using K-type thermocouple wires (φ 0.5mm) for an in-situ measurement of the temperature distribution on a cathode (50mmx50mm, NextCell-5). The measurements were performed during an anode reduction process and during a normal cell operation while the air/fuel ratio varies. The gas temperature was measured simultaneously using a commercial K-type thermocouple from 7 mm adjacent to the cathode. The monitored cathode temperature via the in-situ sensors was directly correlated with the cell's OCV whilst the commercial thermocouple 7mm adjacent to the electrode showed a dull change to them

Experimental observations of the co-sintering of porous triple-layer SOFCs including curvature evolution

Triple-layer co-sintering of SOFCs results in an improved production process via reduced time and effort. Understanding the sintering shrinkage behaviour of each porous layer during the co-sintering process leads to the minimisation of mismatched stresses along with avoidance of severe warping and cracking. In multilayer structure, sintering behaviour is mainly characterised by the in-plane properties rather than the thickness properties. The induced in-plane stresses contribute to curvature evolution in the structure, which can be utilised in the design of a SOFC

THERMONO: cell integrated thin-film sensor array for in-situ monitoring of SOFC temperature

In-situ temperature monitoring from a working SOFC stack indicates the overall health of the system. It also helps detecting variety of cell problems[1] while providing information to understand degradation and to develop better stack designs. Current efforts on simulating temperature distributions involve a great deal of assumptions[2]~[8], which may not present in a working stack. Existing temperature sensing technology does not qualify for in-situ temperature monitoring of a SOFC stack as it causes a significant disturbance to normal stack operation when inserted into a stack[9]. Therefore, Novel temperature sensor architecture was developed to in-situ monitor SOFC running temperature while causing only a minimum disturbance to the normal stack operation. This architecture, named as THERMONO, enables to reduce the number of external wires required: only {N+1} number of external wires for N number of independent temperature sensing points. A thin-film THERMONO having 4 independent sensing points was fabricated on the cathode of a cell (Φ52mm, Kerafol Ltd, KeraCell II). Standard K-type thermocouple materials, Alumel (Ni 95%, Mn 2%, Al 2%, Si 1%) and Chromel (Ni 90%, Cr 10%) of 99.99% purity were chosen as the THERMONO materials. THERMONO was successfully tested in a furnace up to 10500C. A commercial K-type thermocouple was placed adjacent to THERMONO as a reference. Transient response of THERMONO was in very good agreement with the thermocouple validating the sensor concept and proving its robustness on commercial cells. THERMONO is being tested in a specially designed fuel cell test rig to sense the temperature from a working SOFC. Integration of THERMONO into commercial fuel cells and short stacks is also covered in this study and the results will be useful to understand various degradation mechanisms and for advancement of SOFC stack operation conditions

SOFC temperature sensing during anode reductions and cell operations

SOFC temperature sensing during anode reductions and cell operation

Some Grüss' Type Inequalities in 2-Inner Product Spaces and Applications for Determinantal Integral Inequalities

Some new Grüss type inequalities in 2-inner product spaces are given. Using this framework, some determinantal integral inequalities for synchronous functions are also derived

The smallest quaternary ammonium salts with ether groups for high-performance electrochemical double layer capacitors

Electrochemical double layer capacitors (EDLCs) are energy storage devices that have been used for a wide range of electronic applications. In particular, the electrolyte is one of the important components, directly related to the capacitance and stability. Herein, we first report a series of the smallest quaternary ammonium salts (QASs), with ether groups on tails and tetrafluoroborate (BF4) as an anion, for use in EDLCs. To find the optimal structure, various QASs with different sized head groups and ether-containing tail groups were systematically compared. Comparing two nearly identical structures with and without ether groups, QASs with oxygen atoms showed improved capacitance, proving that ions with oxygen atoms move more easily than their counterparts at lower electric fields. Moreover, the ether containing QASs showed low activation energy values of conductivities, leading to smaller IR drops during the charge and discharge processes, resulting in an overall higher capacitance