National University of Defense Technology

About: National University of Defense Technology is a education organization based out in Changsha, China. It is known for research contribution in the topics: Computer science & Radar. The organization has 39430 authors who have published 40181 publications receiving 358979 citations. The organization is also known as: Guófáng Kēxuéjìshù Dàxué & NUDT.

Economic analysis of hydrogen production from steam reforming process: A literature review

Abstract: The interest in steam reforming process as an efficient method for hydrogen production has been greatly increasing, due to its efficiency during hydrogen production and low environmental problems compared to other techniques. The main objective of this review was to present a comprehensive study of environmental, economic aspects of hydrogen production from steam reforming of raw materials such as biomass, bio-gas, ethanol, and natural gas. From literature review, it was found that among methods for hydrogen production, steam reforming of natural gas has lower installed capital due to the precence of high amounts of unconverted hydrocarbons in the produced gas (so-called tar) during other methods such as steam reforming of bio-gas.

PPEP: Online Performance, Power, and Energy Prediction Framework and DVFS Space Exploration

Abstract: Performance, power, and energy (PPE) are critical aspects of modern computing. It is challenging to accurately predict, in real time, the effect of dynamic voltage and frequency scaling (DVFS) on PPE across a wide range of voltages and frequencies. This results in the use of reactive, iterative, and inefficient algorithms for dynamically finding good DVFS states. We propose PPEP, an online PPE prediction framework that proactively and rapidly searches the DVFS space. PPEP uses hardware events to implement both a cycles-per-instruction (CPI) model as well as a per-core power model in order to predict PPE across all DVFS states. We verify on modern AMD CPUs that the PPEP power model achieves an average error of 4.6% (2.8% standard deviation) on 152 benchmark combinations at 5 distinct voltage-frequency states. Predicting average chip power across different DVFS states achieves an average error of 4.2% with a 3.6% standard deviation. Further, we demonstrate the usage of PPEP by creating and evaluating a highly responsive power capping mechanism that can meet power targets in a single step. PPEP also provides insights for future development of DVFS technologies. For example, we find that it is important to carefully consider background workloads for DVFS policies and that enabling north bridge DVFS can offer up to 20% additional energy saving or a 1.4x performance improvement.

Broadband characteristics of vibration energy harvesting using one-dimensional phononic piezoelectric cantilever beams

Abstract: Nowadays broadband vibration energy harvesting using piezoelectric effect has become a research hotspot. The innovation in this paper is the widening of the resonant bandwidth of a piezoelectric harvester based on phononic band gaps, which is called one-dimensional phononic piezoelectric cantilever beams (PPCBs). Broadband characteristics of one-dimensional PPCBs are analyzed deeply and the vibration band gap can be calculated. The effects of different parameters on the vibration band gap are presented by both numerical and finite element simulations. Finally experimental tests are conducted to validate the proposed method. It can be concluded that it is feasible to use the PPCB for broadband vibration energy harvesting and there should be a compromise among related parameters for low-frequency vibrations.