Energy Efficient Error Resilient Multiplier Using Low-power Compressors

The approximate hardware design can save huge energy at the cost of errors incurred in the design. This article proposes the approximate algorithm for low-power compressors, utilized to build approximate multiplier with low energy and acceptable error profiles. This article presents two design approaches (DA1 and DA2) for higher bit size approximate multipliers. The proposed multiplier of DA1 have no propagation of carry signal from LSB to MSB, resulted in a very high-speed design. The increment in delay, power, and energy are not exponential with increment of multiplier size ( n ) for DA1 multiplier. It can be observed that the maximum combinations lie in the threshold Error Distance of 5% of the maximum value possible for any particular multiplier of size n . The proposed 4-bit DA1 multiplier consumes only 1.3 fJ of energy, which is 87.9%, 78%, 94%, 67.5%, and 58.9% less when compared to M1, M2, LxA, MxA, accurate designs respectively. The DA2 approach is recursive method, i.e., n -bit multiplier built with n/2-bit sub-multipliers. The proposed 8-bit multiplication has 92% energy savings with Mean Relative Error Distance (MRED) of 0.3 for the DA1 approach and at least 11% to 40% of energy savings with MRED of 0.08 for the DA2 approach. The proposed multipliers are employed in the image processing algorithm of DCT, and the quality is evaluated. The standard PSNR metric is 55 dB for less approximation and 35 dB for maximum approximation.

CORIDOR: Using CO herence and Tempo R al Local I ty to Mitigate Read D isurbance Err OR in STT-RAM Caches

In the deep sub-micron region, “spin-transfer torque RAM” (STT-RAM ) suffers from “read-disturbance error” (RDE) , whereby a read operation disturbs the stored data. Mitigation of RDE requires restore operations, which imposes latency and energy penalties. Hence, RDE presents a crucial threat to the scaling of STT-RAM. In this paper, we offer three techniques to reduce the restore overhead. First, we avoid the restore operations for those reads, where the block will get updated at a higher level cache in the near future. Second, we identify read-intensive blocks using a lightweight mechanism and then migrate these blocks to a small SRAM buffer. On a future read to these blocks, the restore operation is avoided. Third, for data blocks having zero value, a write operation is avoided, and only a flag is set. Based on this flag, both read and restore operations to this block are avoided. We combine these three techniques to design our final policy, named CORIDOR. Compared to a baseline policy, which performs restore operation after each read, CORIDOR achieves a 31.6% reduction in total energy and brings the relative CPI (cycle-per-instruction) to 0.64×. By contrast, an ideal RDE-free STT-RAM saves 42.7% energy and brings the relative CPI to 0.62×. Thus, our CORIDOR policy achieves nearly the same performance as an ideal RDE-free STT-RAM cache. Also, it reaches three-fourths of the energy-saving achieved by the ideal RDE-free cache. We also compare CORIDOR with four previous techniques and show that CORIDOR provides higher restore energy savings than these techniques.

A Design Methodology for Energy-Aware Processing in Unmanned Aerial Vehicles

Unmanned Aerial Vehicles (UAVs) have rapidly become popular for monitoring, delivery, and actuation in many application domains such as environmental management, disaster mitigation, homeland security, energy, transportation, and manufacturing. However, the UAV perception and navigation intelligence (PNI) designs are still in their infancy and demand fundamental performance and energy optimizations to be eligible for mass adoption. In this article, we present a generalizable three-stage optimization framework for PNI systems that (i) abstracts the high-level programs representing the perception, mining, processing, and decision making of UAVs into complex weighted networks tracking the interdependencies between universal low-level intermediate representations; (ii) exploits a differential geometry approach to schedule and map the discovered PNI tasks onto an underlying manycore architecture. To mine the complexity of optimal parallelization of perception and decision modules in UAVs, this proposed design methodology relies on an Ollivier-Ricci curvature-based load-balancing strategy that detects the parallel communities of the PNI applications for maximum parallel execution, while minimizing the inter-core communication; and (iii) relies on an energy-aware mapping scheme to minimize the energy dissipation when assigning the communities onto tile-based networks-on-chip. We validate this approach based on various drone PNI designs including flight controller, path planning, and visual navigation. The experimental results confirm that the proposed framework achieves 23% flight time reduction and up to 34% energy savings for the flight controller application. In addition, the optimization on a 16-core platform improves the on-time visit rate of the path planning algorithm by 14% while reducing 81% of run time for ConvNet visual navigation.

Evaluating energy consumption, indoor air quality, and student productivity

Smart energy conservation research is gaining traction in a variety of industries throughout the world. The current research is projected to cut energy consumption in the construction sector, which has already reached 49% globally and is expected to rise by 2% annually, costing millions of dollars per month. Balancing energy savings with thermal satisfaction is a current difficulty, as most researchers have concentrated on attaining energy savings without reaching the thermal contentment of the occupant, which could pose a health risk to both young and old occupants. To address the problem, we conducted empirical studies with 193 participants in the Northern part of Nigeria, where they were exposed to an indoor temperature of 22°C to determine their thermal environment, choice and comfort votes, viewed and favored control, and overall thermal satisfaction, which will help calculate and define the unused thermal satisfaction thermostat and later.

3D printing towards implementing Industry 4.0: sustainability aspects, barriers and challenges

Purpose Environmental degradation has emerged as one of the major limitations of industrial revolution and has led to an increased focus towards developing sustainable strategies and techniques. This paper aims to highlight the sustainability aspects of three-dimensional (3D) printing technology that helps towards a better implementation of Industry 4.0. It also aims to provide a brief picture of relationships between 3D printing, Industry 4.0 and sustainability. The major goal is to facilitate the researchers, scholars, engineers and recommend further research, development and innovations in the field. Design/methodology/approach The various enabling factors for implementation of Industry 4.0 are discussed in detail. Some barriers to incorporation of 3D Printing, its applications areas and global market scenario are also discussed. A through literature review has been done to study the detailed relationships between 3D printing, Industry 4.0 and sustainability. Findings The technological benefits of 3D printing are many such as weight savings, waste minimization and energy savings. Further, the production of new 3D printable materials with improved features helps in reducing the wastage of material during the process. 3D printing if used at a large scale would help industries to implement the concept of Industry 4.0. Originality/value This paper focuses on discussing technological revolution under Industry 4.0 and incorporates 3D printing-type technologies that largely change the product manufacturing scenario. The interrelationships between 3D printing, Industry 4.0 and sustainability have been discussed.

The Development and Issues of Energy-ICT: A Review of Literature with Economic and Managerial Viewpoints

This paper reviews the economic and managerial literature on the relationship between energy-ICT and the development of the green energy economy. It is summarized that there are four lines of existing literature on energy-ICT: cost and benefit analysis, fair competition issues, cybersecurity issues, and promotion policy issues. Even though ICT is energy-consuming, most of the existing empirical studies support the idea that energy-ICT has net positive effects on energy savings, energy efficiency improvement, emission reduction, and economic growth at both enterprise and economy-wide levels. Energy-ICT equips the platform operator with higher bargaining power, such that a governance mechanism to assure the fair access right of each entitled participant is required. A smarter energy-ICT network also becomes riskier, and hence the cybersecurity protection is more important than before. Future research and development opportunities remain on these issues of the fair competition, cybersecurity, and promotion policy of energy-ICT.

Exploring the Energy Saving Potential in Private, Public and Non-Motorized Transport for Ten Swedish Cities

Transport energy conservation research in urban transport systems dates back principally to the Organization of the Petroleum Exporting Countries’ (OPEC) “Arab Oil Embargo” (1973–1974) and the Iranian revolution (1979), when global oil supplies became threatened and costs rose steeply. Two subsequent Gulf Wars (1991 and 2003) highlighted the dangerous geo-political dimensions of Middle-Eastern oil. In latter times, the urgency to reduce global CO2 output to avoid catastrophic climate change has achieved great prominence. How to reduce passenger transport energy use therefore remains an important goal, which this paper pursues in ten Swedish cities, based on five scenarios: (1) increasing the relatively low public transport (PT) seat occupancy in each Swedish city to average European levels (buses 35%, light rail 48%, metro 60% and suburban rail 35%); (2) doubling existing PT seat occupancy in each Swedish city; (3) increasing existing car occupancy in each Swedish city by 10%; (4) decreasing existing energy use per car vehicle kilometer by 15%; (5) increasing existing modal split for daily trips by non-motorized modes to 50% in each city. A sixth “best-case scenario” is also explored by simultaneously combining scenarios 2 to 5. The data used in the paper come from systematic empirical research on each of the ten Swedish cities. When applied individually, scenario 2 is the most successful for reducing passenger transport energy use, scenarios 1 and 4 are next in magnitude and produce approximately equal energy savings, followed by scenario 5, with scenario 3 being the least successful. The best-case, combined scenario could save 1183 million liters of gasoline equivalent in the ten cities, representing almost a 60% saving over their existing 2015 total private passenger transport energy use and equivalent to the combined 2015 total annual private transport energy use of Stockholm, Malmö and Jönköping. Such findings also have important positive implications for the de-carbonization of cities. The policy implications of these findings and the strategies for increasing public transport, walking and cycling, boosting car occupancy and decreasing vehicular fuel consumption in Swedish cities are discussed.

Analyzing the Time-Varying Thermal Perception of Students in Classrooms and Its Influencing Factors from a Case Study in Xi’an, China

Owing to movement in the spatial environment and changes in activity levels, students’ thermal perception is time varying in classrooms throughout different periods of the day. However, previous studies have rarely considered the time-varying thermal perception in different periods of the day, which may cause discomfort for students and lead to energy wastage. Therefore, a study was conducted to investigate the time-varying thermal perception of students and its influencing factors in different classes of the day. In addition, the differences in students’ adaptive behaviors in different periods were also explored. A total of 578 university students were surveyed using questionnaire surveys during the heating season in Xi’an, China. The following results can be obtained: (1) The thermal sensation vote and thermal preference vote values in the afternoon were significantly higher than those in the morning. At the start of the first class in the morning/afternoon, the thermal sensation of the students had the highest sensitivity to outdoor temperature changes. (2) The students’ thermal perception was greatly affected by the preclass activity state at the start of the first class in the morning/afternoon. However, in other periods, the above phenomenon was not obvious. (3) In the afternoon, the frequency of clothing adjustment was greater than that in the morning, and this behavior would significantly affect the students’ thermal sensation. (4) Compared with the current classroom heating strategy, the heating strategy of dynamically adjusting the indoor set temperature according to the time-varying characteristics of the students can theoretically achieve energy savings of 25.6%.

Increase the Efficiency of an Induction Motor Feed from Inverter for Low Frequencies by Combining Design and Control Improvements

Speed-controlled induction motors have the most significant potential for energy savings. The greatest problems with obtaining high efficiency occur in motors with a wide range of rotational speed regulation, as in the motors for driving industrial washing machines under consideration. While for the highest speeds, the dominant phenomenon is at field weakening. The problem is obtaining the optimal size of the magnetic flux for low rotation speed to prevent excessive saturation increasing current, and reduction of efficiency. This problem is usually solved by selecting the appropriate control for an already built machine. The authors propose a combination of activities when designing the motor structure with the selection of proper control, which allows for high efficiency. Since the drive does not require precise speed control or obtaining the required dynamics, it was possible to use an inexpensive control in an open loop, avoiding the cost of transmitters. Furthermore, the number of design parameters that are subject to change is significantly limited by technological factors and the available space in the washing machine. Proper parameter selection was made using a peripheral method assisted by field-circuit simulations. The proposed approach can be used in designing structures and selecting motors controls for other applications.

A practical water–energy–climate solution for sustainable and resilient coastal cities: smart use of seawater in municipal services

Municipal services for buildings in developed (sub)tropical coastal cities contributed 18% of greenhouse gases (GHGs) in 2020. One mitigatory solution is the direct use of seawater for district cooling and toilet flushing, which has been applied in Hong Kong on various scales and achieved 30% water and energy savings. However, no systematic evaluation and strategy for this solution are available. Herein, we develop a high-resolution quantitative scheme to elaborate the co-benefits and optimal strategies for expanding this use of seawater. We find that in Hong Kong, Jeddah, and Miami, using local seawater at the city-scale would achieve life-cycle GHG mitigation (42%–56%), energy savings (45%–49%), and freshwater savings (11%–43%). High-resolution analysis reveals that population density and district marginal performance are essential to optimize the efficiency of seawater use. Our scheme confirms the utility of seawater for municipal services and is an effective tool for innovative municipal-service enhancement.