Application of high porosity metal foams as air-cooled heat exchangers to high heat load removal systems

A numerical study has been conducted to investigate the fluid flow and heat transfer of an air-cooled metal foam heat exchanger under the high speed laminar jet confined by two parallel walls for which the range of the Reynolds number is 600–1000. Two independent numerical solvers were used and cross-validated being a FORTRAN code and the commercially available software CFD-ACE. The effects of local thermal non-equilibrium, thermal dispersion, porosity, and pore density on the heat transfer augmentation are examined for different Reynolds numbers. Application of energy flux vectors, for convection visualization, is also illustrated for a more comprehensive analysis of the problem. Finally, the performance of the metal foam heat exchanger is compared to that of conventional finned design. It is observed that the heat removal rate can be greatly improved at almost no excess cost.     

A new criterion to design reactive coal stockpiles

This paper proposes a new criterion to design the self-heating coal stockpiles. The generated heat can be removed if air is blown to the self-heating stockpile. At the same time, introducing more air to the system boosts the aforementioned chemical reactions. Hence, there is a tradeoff between the two opposing effects. Monitoring such a tradeoff, which pinpoints both qualitatively and quantitatively the safe characteristics (geometry, porosity, and permeability) of a stockpile, can be referred to as a design criterion to be implemented in industry. In order to validate the application of the newly-proposed criterion, two independent numerical solvers are used being a FORTRAN code and the commercially available software CFD-ACE. Different key parameters including approaching wind speed, porosity, and permeability are examined. Finally, application of energy flux vectors for convection visualization is also illustrated for a more comprehensive analysis of the problem.     

Significant Capacity and Cycle‐Life Improvement of Lithium‐Ion Batteries through Ultrathin Conductive Film Stabilized Cathode Particles

Atomic layer deposition (ALD), as a thin film deposition technique, has been explored as a viable path to improve the performance of lithium‐ion batteries. However, a trade‐off between the species transport (capacity) and protection (lifetime), resulting from the insulating properties of ALD films, is the key challenge in ALD technology. Here we report a breakthrough to overcome this trade‐off by coating an ultrathin conformal cerium dioxide (CeO₂) film on the surfaces of LiMn₂O₄ particles. The optimized CeO₂ film (≈3 nm) coated particles exhibit a significant improvement in capacity and cycling performance compared to uncoated (UC), Al₂O₃ coated, and ZrO₂ coated samples at room temperature and 55 °C for long cycling numbers. The initial capacity of the 3 nm CeO₂‐coated sample shows 24% increment compared to the capacity of the uncoated one, and 96% and 95% of the initial capacity is retained after 1000 cycles with 1C rate at room temperature and 55 °C, respectively. The detailed electrochemical data reveal that the suppression of the impedance rise and the facile transport of the species are the main contributors to the success.     

Compositional verification of a distributed real-time arbitration protocol

A distributed real-time arbitration protocol is specified and verified using an assertional method. The formalism is based on classical Hoare triples which have been extended to deal with real-time properties. To verify design steps, a compositional proof system has been formulated for these extended triples. The intention of the protocol is to resolve contention between a number of concurrent modules that compete to acquire control of a common bus. Therefore our proof method has been adapted to deal with concurrent processes that communicate by means of a common bus. Compositionality makes it possible to verify the required properties of the protocol using only the specifications of the modules. Next we give a top-down derivation of a program implementing a module according to its real-time specification.     

A novel high dynamic range differential LNA using quartet topology

In some applications such as short-range radars, a large target can desensitize the receiver. A high dynamic range low-noise amplifier (LNA), as a key component of a transmitter/receiver module, can improve the entire system performance. This study presents a high dynamic range differential LNA that uses a differential quartet topology for the first time. The LNA shows more linearity than the conventional differential common source LNAs. For a typical 0.18 µm CMOS technology, it achieves a power gain of about 5.5 dB at 24 GHz, a low noise figure (NF) of 3.5 dB, very good linearity performance, an input-referred third-order intercept point (IIP3) of +?6.3 dBm, and an input-referred 1 dB compression point (P1dB) of ??4.5 dBm.     

An optimized system of GMDH-ANFIS predictive model by ICA for estimating pile bearing capacity

The pile bearing capacity is considered as the most essential factor in designing deep foundations. Direct determination of this parameter in site is costly and difficult. Hence, this study presents a new technique of intelligence system based on the adaptive neuro-fuzzy inference system (ANFIS)-group method of data handling (GMDH) optimized by the imperialism competitive algorithm (ICA), ANFIS-GMDH-ICA for forecasting pile bearing capacity. In this advanced structure, the ICA role is to optimize the membership functions obtained by ANFIS-GMDH technique for receiving a higher accuracy level and lower error. To develop this model, the results of 257 high strain dynamic load tests (performed by authors) were considered and used in the analysis. For comparison purposes, ANFIS and GMDH models were selected and built for pile bearing capacity estimation. In terms of model accuracy, the obtained results showed that the newly developed model (i.e., ANFIS-GMDH-ICA) receives more accurate predicted values of pile bearing capacity compared to those obtained by ANFIS and GMDH predictive models. The proposed ANFIS-GMDH-ICA can be utilized as an advanced, applicable and powerful technique in issues related to foundation engineering and its design.

     

An analog circuit model for drive mode of MEMS vibratory gyroscope

Microsystem Technologies - In this paper, an analog circuit model for the drive mode of a two-degree-of-freedom MEMS vibratory gyroscope is presented. This model is implemented on a printed circuit...     

Optimal opportunistic routing and network coding for bidirectional wireless flows

There is growing interest in recent years in routing methods for wireless networks that leverage the broadcast nature of the wireless medium and the ability of nodes to overhear their neighbors’ transmissions. Such methods include opportunistic routing (OR), which generally choose the next hop on a routing path only after the outcome of the previous transmission is known; and wireless network coding (NC), which linearly combines packets from different flows coexisting in the network. In this paper, we study the potential benefits of forwarding schemes that combine elements from both the OR and NC approaches, when traffic on a bidirectional unicast connection between two nodes is relayed by multiple common neighbors. We present a theoretically optimal scheme that provides a lower bound on the expected number of transmissions required to communicate a packet in both directions as a function of link error probabilities, and demonstrate that this bound can be up to 20% lower than with either OR or NC employed alone even in a small network. Using simulation, we further explore the control overhead in a direct implementation of the scheme with a simple coordination mechanism and show that the optimal bound can be closely approached for a wide range of link error rates.     

Integration of CATHENA Thermal-Hydraulic Model with CANDU 6 Analytical Simulator Controller

This paper introduces a powerful design and analysis tool named SIMCAT, that is developed to support applications to license a CANDU nuclear reactor, refurbish projects, and support the existing CANDU stations. It consists of the CATHENA （Canadian Algorithm for Thermo-Hydraulic Network Analysis）, the control logics from C6SIM （CANDU 6 Analytical Simulator）, and a communication protocol, PVM （parallel virtual machine）. This is the first time that CATHENA has been successfully coupled directly with a program written in another language. The independence of CATHENA and the C6SIM controllers allows the development of both CATHENA and C6SIM controller to proceed independently.