• Earthquakes and Structures
• /
• v.11 no.2
• /
• pp.245-264
• /
• 2016

A suitable ground motion intensity measure (IM) plays a crucial role in the seismic performance assessment of a structure. In this paper, we introduce a scalar IM for use in evaluating the seismic response of single-layer reticulated domes. This IM is defined as the weighted geometric mean of the spectral acceleration ordinates at the periods of the dominant vibration modes of the structure considered, and the modal strain energy ratio of each dominant vibration mode is the corresponding weight. Its applicability and superiority to 11 other existing IMs are firstly investigated in terms of correlation with the nonlinear seismic response, efficiency and sufficiency using the results of incremental dynamic analyses which are performed for a typical single-layer reticulated dome. The hazard computability of this newly proposed IM is also briefly discussed and illustrated. A conclusion is drawn that this dominant vibration mode-based scalar IM has the characteristics of strong correlation, high efficiency, good sufficiency as well as hazard computability, and thereby is appropriate for use in the prediction of seismic response of single-layer reticulated domes.

• Journal of Energy Engineering
• /
• v.28 no.1
• /
• pp.30-36
• /
• 2019

The military has developed and operated a variety of military vehicles. Among them, medium tactical vehicles are developed as vehicles suitable for transporting troops, replacing existing military trucks, which have a significant impact on infantry forces' combat capability. Applying technology to increase fuel efficiency to these critical weapons systems, medium tactical vehicles, increases the distance range, which can reduce effective operational performance and oil costs. In this study, a measure was taken to improve the distance range of Medium Tactical Vehicles by applying an oil temperature control strategy to increase fuel efficiency.

• Journal of the Society of Naval Architects of Korea
• /
• v.60 no.3
• /
• pp.146-154
• /
• 2023

Efforts have been made to reduce the greenhouse gas emissions from ships by limiting the energy efficiency index, and net zero CO₂ emission was proposed recently. The most ideal measure to achieve zero emission ship is electrification, and fuel cells are considered as a practical power source of the electrified propulsion system. The electric efficiency in the electrochemical reaction of fuel cells can be achieved up to 60% practically. The remaining energy is converted to heat energy but most of them are dissipated by cooling. In the author's previous research, a hybrid propulsion system utilizing not only electricity but also heat was introduced by combining electric motor and steam turbine. In this article, long term efficiency is evaluated for the introduced hybrid propulsion system by considering a virtual 24,000 TEU class container carrier model. To reflect a more practical operating condition, the actual navigation data of a similar real ship in the real world were collected from automatic identification system data and applied. From the result, the overall efficiency of the hybrid propulsion system is expected to be higher than a conventional electric propulsion fuel cell ship by 30%.

• Solar Energy
• /
• v.18 no.4
• /
• pp.1-10
• /
• 1998

Polymer induced turbulent drag reduction in a rotating disk apparatus was investigated using four different molecular weights of poly(ethylene oxide)(PEO) in a synthetic seawater solution for the purpose of potential application to the cold water piping in the Ocean Thermal Energy Conversion(OTEC) system. To apply drag reduction to the OTEC we measured the temperature dependence on the drag reduction efficiency. From this study, it was found that the drag reduction efficiency increases with the temperature and the concentration. To measure the drag reduction efficiency during the operation period, the drag reduction behavior was detected as a function of time and the results obtained from the experiment was compared to the Brostow's model equation.

• The Journal of Industrial Distribution & Business
• /
• v.10 no.1
• /
• pp.9-17
• /
• 2019

Purpose - Urban agglomeration construction is one of national strategic plans to accelerate the development of industrialization and urbanization in China, which has threatened the eco-environmental quality at the same time. This paper selected the urban agglomeration in the middle reaches of the Yangtze River as the research area. Research design, data, and methodology - The the slack-based measurement (SBM) model considering undesirable outputs is applied to measure the eco-efficiency of this urban agglomerations during 2006-2015. Results - The empirical results show that average eco-efficiency of the urban agglomeration in the middle reaches of the Yangtze River is 0.595. Regional ecological development is unbalanced. The highest eco-efficiency is recorded at Wuhan Metropolitan Area, and the lowest one is at the Changsha-Zhuzhou-Xiangtan City Group. Energy consumption and waste dust emissions are the key factors led to ecological inefficiency. Based on this, potentials for energy saving and waste dust reducing are calculated. Conclusions - Finally, this study provides policy implications targeted to promote the coordinating development of economy and eco-environment under the construction of urban agglomeration.

• Solar Energy
• /
• v.10 no.3
• /
• pp.35-45
• /
• 1990

An analytical equation to estimate the Rankine power cycle efficiency at maximum power for the given mass flow rates of heating and cooling fluids is derived. The accuracy of the result is shown by comparing the analytical values with those calculated one using detailed thermodynamic data. The results indicate that the thermal efficiency at maximum power depends primarily on the initial temperatures of the heating and cooling fluids, and it also depends on the pinch-temperature differences between the working fluid and the heating and cooling fluids. The efficiency at maximum power provides a measure of the power available in a practical Rankine heat engine.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2016.02a
• /
• pp.308-309
• /
• 2016

Reducing surface recombination is a critical factor for high efficiency silicon solar cells. The passivation process is for reducing dangling bonds which are carrier. Tunnel oxide layer is one of main issues to achieve a good passivation between silicon wafer and emitter layer. Many research use wet-chemical oxidation or thermally grown which the highest conversion efficiencies have been reported so far. In this study, we deposit ultra-thin tunnel oxide layer by PECVD (Plasma Enhanced Chemical Vapor Deposition) using $N_2O$ plasma. Both side deposit tunnel oxide layer in different RF-power and phosphorus doped a-Si:H layer. After deposit, samples are annealed at $850^{\circ}C$ for 1 hour in $N_2$ gas atmosphere. After annealing, samples are measured lifetime and implied Voc (iVoc) by QSSPC (Quasi-Steady-State Photo Conductance). After measure, samples are annealed at $400^{\circ}C$ for 30 minute in $Ar/H_2$ gas atmosphere and then measure again lifetime and implied VOC. The lifetime is increase after all process also implied VOC. The highest results are lifetime $762{\mu}s$, implied Voc 733 mV at RF-power 200 W. The results of C-V measurement shows that Dit is increase when RF-power increase. Using this optimized tunnel oxide layer is attributed to increase iVoc. As a consequence, the cell efficiency is increased such as tunnel mechanism based solar cell application.

• Journal of Satellite, Information and Communications
• /
• v.11 no.2
• /
• pp.55-59
• /
• 2016

Conventional RF energy harvesting systems can harvest energy and decode information from same source as an Hybirid-AP (H-AP). However, harvesting efficiency is seriously dependent on distance between users and H-AP. Therefore, in this paper, we proposed a transmission model for RF harvesting consisting of information and power source separately called Decoupled RF Energy harvesting networks. Main purpose of this paper is to maximize energy efficiency under various constraints of transmit power from H-AP and power beacon (PB), minimum quality of service and quality of harvested power of each users. To measure proposed model's performance, we proposed optimal time scheduling algorithms for energy efficiency (EE) maximization using Lagrangian dual decomposition theory that locally maximizes the EE by obtaining suboptimal values of three arguments : transmit power of H-AP, transmit power of PB, frame splitting factor. Experiment results show that the proposed energy-efficient algorithms converge within a few iterations with its optimality and greatly improve the EE compared to that of baseline schemes.

• KIEAE Journal
• /
• v.13 no.5
• /
• pp.51-57
• /
• 2013

Energy saving starts by knowing how much energy is being consumed. A building factor is easier than any other things in energy saving. Since, especially, it is closely connected with user's space-use-patterns and manager's utility-operation-style. An energy metering system lets building users know about energy consumption pattern in buildings and measure energy in real time. Development and materialization of metering systems need more careful plans, so that they depend on a demand of individual facilities and available infrastructures they used to use. But, so far, there is no guidelines how to install metering systems. This paper suggested how to install meters and researched a method for how to analyze by using metered data. For that, Green Building in KIER is used as a test bed. As the results, nevertheless the smallest number of meters is basically one for the whole building energy measuring, it is too limited in analysis. So we needed to add the sort of fuel and utility types and found that it depends on all cases. For this reasons, a guideline should be created in order to install meters as soon as possible. It would be suggest a way to save more energy in building factor.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
• /
• 2002.11a
• /
• pp.191-196
• /
• 2002

In this paper we introduce novel electrode structure for high efficiency discharge. We operate discharge tube under the 0.16 torr pure Xe and apply the sinusoidal wave power to the lamp with 60kHz. We measure the electric power dissipation, plasma parameters, and 828 nm IR intensity. From these data we determine the discharge efficiency, IR intensity/watt, EEDF(Electron energy distribution function). As a result we obtain that the novel electrode structure has better performance in efficiency than that of conventional external electrode system. Also we determine the EEDF for each type of electrode structure by Boltzmann stover, EELNDIF code. The result of Boltzmann equation solving show that the noble electrode system has many high energy electrons compared with the conventional system.