Performance enhancement of single-chamber sediment-microbial fuel cell with variation in cathode surface area

This study investigates the impact of cathode surface area on single chamber sediment-microbial fuel cell (S-MFC). A fixed graphite anode surface area of 0.000471m2 has been used on four S-MFCs coupled with four carbon fiber cloth cathode electrodes with variation of surface area. Pond sediment has been used as the anode medium that inoculated with acetate as substrate to ramp up the amount of electrochemical-active bacteria (EAB). The S-MFCs has been operated and monitored for 120 hours using Arduino based data logger. The outcomes of this observation period have indicated the S-MFC with larger cathode surface area (0.01m2) possess smaller internal resistance (123.96±2.68 Ω) and thus performed significantly better than other S-MFC with the smaller cathode surface area, resulting with average voltage and current of 0.598±0.008V and 4.827±0.124mA respectively, where a maximum power density of 2.867mW with a coulombic efficiency of 64.63% was achieved. Successful performance increase suggests enlargement of the cathode area could be the alternative to reduce the internal resistance in traditional MFCs for electricity generation

Dynamic power dissipation formulation for application in dynamic programming buffer insertion algorithm

Buffer insertion is a very effective technique to reduce propagation delay in nano-metre VLSI interconnects. There are two techniques for buffer insertion which are: (1) closed-form solution and (2) dynamic programming. Buffer insertion algorithm using dynamic programming is more useful than the closed-form solution as it allows the use of multiple buffer types and it can be used in tree structured interconnects. As design dimension shrinks, more buffers are needed to improve timing performance. However, the buffer itself consumes power and it has been shown that power dissipation of buffers is significant. Although there are many buffer insertion algorithms that were able to optimize propagation delay with power constraint, most of them used the closed-form solution. Hence, in this paper, we present a formulation to compute dynamic power dissipation of buffers for application in dynamic programming buffer insertion algorithm. The proposed formulation allows dynamic power dissipation of buffers to be computed incrementally. The technique is validated by comparing the formulation with the standard closed-form dynamic power equation. The advantage of the proposed formulation is demonstrated through a series of experiments where it is applied in van Ginneken’s algorithm. The results show that the output of the proposed formulation is consistent with the standard closed-form formulation. Furthermore, it also suggests that the proposed formulation is able to compute dynamic power dissipation for buffer insertion algorithm with multiple buffer types

Hybrid routing tree with buffer insertion under obstacle constraints

Performance optimization in very-large-scale integration (VLSI) design is the key success in today's design automation methodologies. One of the performance issues is the interconnect delay in deep sub-micron VLSI circuits. The interconnect delay becomes more dominant compared to gate delay when the size of the gates is reduced. This paper presents an algorithm to optimize the timing performance of the routing tree under obstacle constraints. It is known that simultaneous routing and buffer insertion is proven to be NP-complete while the two-step approach may produce a poor solution. Therefore, we propose a hybrid algorithm that can modify a given routing tree simultaneously with buffer insertion. This paper describes this algorithm and we present experimental results that show the proposed algorithm can improve the timing of the routing tree significantly with low execution time

Electromechanical-Traffic Model of Compression-Based Piezoelectric Energy Harvesting

Piezoelectric energy harvesting has advantages over other alternative sources due to its large power density, ease of applications, and capability to be fabricated at different scales: macro, micro, and nano. This paper presents an electromechanical-traffic model for roadway compression-based piezoelectric energy harvesting system. A two-degree-of-freedom (2-DOF) electromechanical model has been developed for the piezoelectric energy harvesting unit to define its performance in power generation under a number of external excitations on road surface. Lead Zirconate Titanate (PZT-5H) is selected as the piezoelectric material to be used in this paper due to its high Piezoelectric Charge Constant (d) and Piezoelectric Voltage Constant (g) values. The main source of vibration energy that has been considered in this paper is the moving vehicle on the road. The effect of various frequencies on possible generated power caused by different vibration characteristics of moving vehicle has been studied. A single unit of circle-shape Piezoelectric Cymbal Transducer (PCT) with diameter of 32 mm and thickness of 0.3 mm be able to generate about 0.12 mW and 13 mW of electric power under 4 Hz and 20 Hz of excitation, respectively. The estimated power to be generated for multiple arrays of PCT is approximately 150 kW/ km. Thus, the developed electromechanical-traffic model has enormous potential to be used in estimating the macro scale of roadway power generation system

An optimized buffer insertion algorithm with delay-power constraints for VLSI layouts

We propose a grid-graph algorithm for interconnect routing and buffer insertion in nanometer VLSI layout designs. The algorithm is designed to handle multiconstraint optimizations, namely timing performance and power dissipation. The proposed algorithm is called HRTB-LA, which stands for hybrid routing tree and buffer insertion with look-ahead. In recent VLSI designs, interconnect delay has become a dominant factor compared to gate delay. The well-known technique to minimize the interconnect delay is by inserting buffers along the interconnect wires. However, the buffer itself consumes power and it has been shown that power dissipation overhead due to buffer insertions is significantly high. Many methodologies to optimize timing performance with power constraint have been proposed, and no algorithm is based on dynamic programing technique using a grid graph. In addition, most of the algorithms for buffer insertion use a postrouting buffer insertion approach. In the presence of buffer obstacles, these postrouting algorithms may produce poor solutions. On the other hand, the simultaneous routing and buffer insertion algorithm offers a better solution, but it was proven to be NP complete. Hence, our main contribution is an efficient algorithm using a hybrid approach for multiconstraint optimization for multisink nets. The algorithm uses dynamic programming to compute incrementally the interconnect delay and power dissipation of the inserted buffers while an effective runtime is achieved with the aid of novel look-ahead and graph pruning schemes. Experimental results prove that HRTB-LA is able to handle multiconstraint optimizations and produces a solution up to 30% better compared to a postrouting buffer insertion algorithm in comparable runtime

Electromechanical-Traffic Model of Compression-Based Piezoelectric Energy Harvesting

Piezoelectric energy harvesting has advantages over other alternative sources due to its large power density, ease of applications, and capability to be fabricated at different scales: macro, micro, and nano. This paper presents an electromechanical-traffic model for roadway compression-based piezoelectric energy harvesting system. A two-degree-of-freedom (2-DOF) electromechanical model has been developed for the piezoelectric energy harvesting unit to define its performance in power generation under a number of external excitations on road surface. Lead Zirconate Titanate (PZT-5H) is selected as the piezoelectric material to be used in this paper due to its high Piezoelectric Charge Constant (d) and Piezoelectric Voltage Constant (g) values. The main source of vibration energy that has been considered in this paper is the moving vehicle on the road. The effect of various frequencies on possible generated power caused by different vibration characteristics of moving vehicle has been studied. A single unit of circle-shape Piezoelectric Cymbal Transducer (PCT) with diameter of 32 mm and thickness of 0.3 mm be able to generate about 0.12 mW and 13 mW of electric power under 4 Hz and 20 Hz of excitation, respectively. The estimated power to be generated for multiple arrays of PCT is approximately 150 kW/ km. Thus, the developed electromechanical-traffic model has enormous potential to be used in estimating the macro scale of roadway power generation system

Electromechanical-Traffic Model of Compression-Based Piezoelectric Energy Harvesting

Piezoelectric energy harvesting has advantages over other alternative sources due to its large power density, ease of applications, and capability to be fabricated at different scales: macro, micro, and nano. This paper presents an electromechanical-traffic model for roadway compression-based piezoelectric energy harvesting system. A two-degree-of-freedom (2-DOF) electromechanical model has been developed for the piezoelectric energy harvesting unit to define its performance in power generation under a number of external excitations on road surface. Lead Zirconate Titanate (PZT-5H) is selected as the piezoelectric material to be used in this paper due to its high Piezoelectric Charge Constant (d) and Piezoelectric Voltage Constant (g) values. The main source of vibration energy that has been considered in this paper is the moving vehicle on the road. The effect of various frequencies on possible generated power caused by different vibration characteristics of moving vehicle has been studied. A single unit of circle-shape Piezoelectric Cymbal Transducer (PCT) with diameter of 32 mm and thickness of 0.3 mm be able to generate about 0.12 mW and 13 mW of electric power under 4 Hz and 20 Hz of excitation, respectively. The estimated power to be generated for multiple arrays of PCT is approximately 150 kW/ km. Thus, the developed electromechanical-traffic model has enormous potential to be used in estimating the macro scale of roadway power generation system