• Environmental Engineering Research
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• v.21 no.4
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• pp.355-364
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• 2016

Beijing, as a cradle of modern industry and the third largest metropolitan area in China, faces more responsibilities to adjust industrial structure and mitigate carbon emissions. The purpose of this study is aimed at predicting and comparing industrial carbon emissions of Beijing in ten scenarios under different policy focus, and then providing emission-cutting recommendations. In views of various scenarios issues, system dynamics has been applied to predict and simulate. To begin with, the model has been established following the step of causal loop diagram and stock flow diagram. This paper decomposes scenarios factors into energy structure, high energy consumption enterprises and growth rate of industrial output. The prediction and scenario simulation results shows that energy structure, carbon intensity and heavy energy consumption enterprises are key factors, and multiple factors has more significant impact on industrial carbon emissions. Hence, some recommendations about low-carbon mode of Beijing industrial carbon emission have been proposed according to simulation results.

• Journal of Mechanical Science and Technology
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• v.19 no.12
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• pp.2321-2329
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• 2005

One means of fulfilling $CO_2$ emission legislation is to downsize engines by boosting their power using turbochargers or mechanical superchargers. This reduces fuel consumption by decreasing the engine displacement. When a turbocharger, which is preferable to a mechanical supercharger in terms of fuel efficiency, is used, there is insufficient availability of exhaust gas energy at low engine speeds, resulting in an unfavorable engine response. Therefore, mechanically driven superchargers have increased in popularity due to their quick response to changing speeds in the transient phase. However, since a mechanical supercharger obtains its driving power from the engine, it is difficult to decrease its fuel consumption. This remains a large negative factor for superchargers, despite their excellent dynamic performance. This study aims to develop a power control concept to improve the fuel economy of a mechanical screw supercharger, which could then be used for engine downsizing.

• Proceedings of the KIEE Conference
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• 2004.04a
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• pp.24-26
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• 2004

For past decade, medium voltage circuit breakers have used the spring-driven mechanical system for interrupting of electric power. However, these mechanisms have many disadvantages of high power consumption, mechanical control components and electrical switching ones for the coil current. Recently, the vacuum interrupter operated by permanent magnet actuator gives outlook on improved characteristic, higher reliability and cost price reduction as well as the feature of simple structure and few components. This paper deals with the dynamic characteristics of permanent magnet actuator used in the medium voltage distribution systems. Coupled finite element method is used to analysis the dynamic characteristics of permanent magnetic actuator and we compared with those of conventional ones.

• Journal of Power System Engineering
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• v.9 no.1
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• pp.82-88
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• 2005

This paper presents numerical study on dynamic characteristics of evaporator to control evaporator superheat and compressor capacity with optimum condition in refrigeration system. It is very important to reduce energy consumption and to keep room temperature within a very restricted range with minimum oscillation in some special applications of the refrigeration system. Heat exchange is mainly happened in the evaporator. So, making mathematical model of evaporator and analyzing evaporator characteristics are necessary in order to control the superheat and the capacity of the system. A mathematical model based on the one dimensional partial differential equations representing mass and energy conservation and a tube-wall energy is described. A set of ordinary differential equation is formulated by integrating separately over the two regions(two-phase and vapor) generally presented in a heat exchanger.

• Proceedings of the KIEE Conference
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• summer
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• pp.1040-1042
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• 2004

For past decade, medium voltage circuit breakers have used the spring-driven mechanical system for interrupting of electric power. However, these mechanisms have many disadvantages of high power consumption, mechanical control components and electrical switching ones for the coil current. Recently, the vacuum interrupter operated by permanent magnet actuator gives outlook on improved characteristic, higher reliability and cost price reduction as well as the feature of simple structure and few components. This paper deals with the dynamic characteristics of permanent magnet actuator used in the medium voltage distribution systems. Coupled finite element method is used to analysis the dynamic characteristics of permanent magnetic actuator and we compared with those of conventional ones

• ETRI Journal
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• v.41 no.3
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• pp.383-395
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• 2019

Clock Controlled Dual keeper Domino logic structures (CCDD_1 and CCDD_2) for achieving a high-speed performance with low power consumption and a good noise margin are proposed in this paper. The keeper control circuit comprises an additional PMOS keeper transistor controlled by the clock and foot node voltage. This control mechanism offers abrupt conditional control of the keeper circuit and reduces the contention current, leading to high-speed performance. The keeper transistor arrangement also reduces the loop gain associated with the feedback circuitry. Hence, the circuits offer less delay variability. The design and simulation of various wide fan-in designs using 180 nm CMOS technology validates the proposed CCDD_1 and CCDD_2 designs, offering an increased speed performance of 7.2% and 8.5%, respectively, over a conventional domino logic structure. The noise gain margin analysis proves good robustness of the CCDD structures when compared with a conventional domino logic circuit configuration. A Monte Carlo simulation for 2,000 runs under statistical process variations demonstrates that the proposed CCDD circuits offer a significantly reduced delay variability factor.

• Journal of Information Display
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• v.6 no.1
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• pp.17-21
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• 2005

We explored a new way of designing dynamic logic gates with low temperature polysilicon thin film transistors to increase the speed. The proposed architecture of logic gates utilizes the structural advantage of smaller junction capacitance of thin film transistors. This method effectively blocks leakage of current through the thin film transistors. Furthermore, the number of transistors used in logic gates is reduced thereby reducing power consumption and chip area. Through HSPICE .simulation, it is confirmed that the circuit speed is also improved in all logic gates designed.

• Journal of Korea Multimedia Society
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• v.11 no.5
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• pp.641-650
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• 2008

As portable devices are used widely, power management algorithm is essential to extend battery use time on small-sized battery power. Although many methods have been proposed, they assumed the voltage transition overhead was negligible or was considered partially. However, the voltage transition overhead might not guarantee to schedule real-time tasks in portable multimedia systems. This paper proposes the adaptive power-aware algorithm to minimize the power consumption by considering the voltage transition overhead. It selects only a few discrete frequencies from the whole frequencies of a system and adjusts the interval between two consecutive frequencies based on the system utilization to reduce the number of frequency change. This algorithm saves the power consumption about 10 to 25 percent compared to a CC RT-DVS method and a frequency-smoothing method.

• Journal of Communications and Networks
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• v.12 no.2
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• pp.158-167
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• 2010

The energy efficiency of wireless infrastructure and terminals has been drawing renewed attention of late, due to their significant environmental cost. Emerging green communication paradigms such as cognitive radios, are also imposing the additional requirement of flexibility. This dual requirement of energy efficiency and flexibility poses new design challenges for implementing radio functional blocks. This paper focuses on the area vs. power trade-offs for the type of channel filters that are required in the digital frontend of a flexible, energy-efficient radio. In traditional CMOS circuits, increased area was traded for reduced dynamic power consumption. With leakage power emerging as the dominant mode of power consumption in nanoscale CMOS, these trade-offs must be revisited due to the strong correlation between area and leakage power. The current work discusses how the increased timing slacks obtained by increasing the parallelism can be exploited for overall power reduction even in nanoscale circuits. In this context the paper introduces the notion of 'area efficiency' and a metric for evaluating it. The proposed metric has also been used to compare the area efficiencies of different classes of time-shared filters.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.10
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• pp.5168-5181
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• 2017

The popularity of augmented reality (AR) applications and games are in high demand. Currently, the best common platform to implement AR services is on a smartphone, as online games, navigators, personal assistants, travel guides are among the most popular applications of smartphones. However, the power consumption of an AR application is extremely high, and therefore, highly adaptable and dynamic low power control schemes must be used. Dynamic voltage and frequency scaling (DVFS) schemes are widely used in smartphones to minimize the energy consumption by controlling the device's operational frequency and voltage. DVFS schemes can sometimes lead to longer response times, which can result in a significant problem for AR applications. In this paper, an AR response time monitor is used to observe the time interval between the AR image input and device's reaction time, in order to enable improved operational frequency and AR application process priority control. Based on the proposed response time monitor and the characteristics of the Linux kernel's completely fair scheduler (CFS) (which is the default scheduler of Android based smartphones), a response time step control (RSC) scheme is proposed which adaptively adjusts the CPU frequency and interactive application's priority. The experimental results show that RSC can reduce the energy consumption up to 10.41% compared to the ondemand governor while reliably satisfying the response time performance limit of interactive applications on a smartphone.