• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.26 no.10
• /
• pp.467-473
• /
• 2014

Since the operating conditions of HVAC systems are different from those for which they are designed, on-going commissioning is required to optimize the energy consumed and the environment in the building. This study presents a methodology to analyze operational data and its applications. A predicted operation model is to be produced through a statistical data analysis using multiple regressions in SPSS. In this model, the dependent variable is the pre-cooling time, and the independent variables include the power output of the supply air inverter during pre-cooling, the supply air set temperature during pre-cooling, the indoor temperature-indoor set temperature just before pre-cooling, supply heat capacity, and the lowest outdoor air temperature during non-cooling/non-heating hours. The correlation coefficient R2 of the multiple regression model between the pre-cooling hour and the internal/external factors is of 0.612, and this could be used to provide information related to energy conservation and operating guidance.

• Environmental Engineering Research
• /
• v.17 no.2
• /
• pp.89-94
• /
• 2012

Pyrolysis/gasification technology utilizes an energy conversion technique from various waste resources, such as biomass, solid waste, sewage sludge, and etc. to generating a syngas (synthesis gas). However, one of the major problems for the pyrolysis gasification is the presence of tar in the product gas. The tar produced might cause damages and operating problems on the facility. In this study, a gliding arc plasma reformer was developed to solve the previously acknowledged issues. An experiment was conducted using surrogate benzene and naphthalene, which are generated during the pyrolysis and/or gasification, as the representative tar substance. To identify the characteristics of the influential parameters of tar decomposition, tests were performed on the steam feed amount (steam/carbon ratio), input discharge power (specific energy input, SEI), total feed gas amount and the input tar concentration. In benzene, the optimal operating conditions of the gliding arc plasma 2 in steam to carbon (S/C) ratio, 0.98 $kWh/m^3$ in SEI, 14 L/min in total gas feed rate and 3.6% in benzene concentration. In naphthalene, 2.5 in S/C ratio, 1 $kWh/m^3$ in SEI, 18.4 L/min in total gas feed rate and 1% in naphthalene concentration. The benzene decomposition efficiency was 95%, and the energy efficiency was 120 g/kWh. The naphthalene decomposition efficiency was 79%, and the energy yield was 68 g/kWh.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.26 no.6
• /
• pp.381-389
• /
• 2021

Most diagnosis approaches rely on historical failure data that might not be feasible in real operating conditions because the battery voltage and internal parameters are nonlinear according to various operating conditions, such as cell-to-cell configuration and initial condition. To overcome this issue, the estimator and the predictor require integrated approaches that consider comprehensive data, with the degradation process and measured data taken into account. In this paper, vector autoregressive models (VAR) with various parameters that affect overdischarge to the cell in the battery pack were constructed, and the cell-to-cell parameters were identified using an adaptive model to analyze the influence of failure prognosis. The theoretical analysis is validated using experimental results in terms of the feasibility and advantages of fault prognosis.

• Journal of the Korean Society of Industry Convergence
• /
• v.23 no.4_2
• /
• pp.645-651
• /
• 2020

In this study, It is necessary that we should study on more effective use about reciprocating engines because there are huge increase of air pollution. Diesel Engine is operated by injecting fuel directly to combustion chamber with high pressure. Diesel Engine has greater thermal efficiency and durability than Gasoline Engine. Also, Diesel Engine emitted low harmful exhaust witch caused by Gasoline Engine. There are many ways to improve of performance and decrease of harmful exhaust by controlling injection timing, changing amount of fuel and engine speed and so on. Especially, development and application of common rail direct injection Engine cause the increase of thermal efficiency by controlling a various of operating conditions. In this study we analyze characteristics of performance by changing a various of operating conditions.

• Journal of Arbitration Studies
• /
• v.28 no.3
• /
• pp.3-20
• /
• 2018

Independence and impartiality are the operating core of an arbitration disciplinary mechanism. Due to many factors, illegalities and improper acts in arbitration cases are facts of life in our country, and have greatly damaged the credibility of arbitration. It is necessary for us to perfect the operating mechanism of arbitration discipline from the four pluralistic progressive aspects of disciplining the cause externalization, disciplining the subject duality, the quasi-judicature of disciplinary procedures and the disciplining measures so that the populace can experience fairness and justice in every case. We should perfect the supporting measures such as the strict selection conditions and procedures of arbitrators, improving the quality of the arbitrator team, exploring the management mechanisms and strengthening the evaluation dynamic. An examination is a general investigation and evaluation so as to provide encouragement for being continually engaged as arbitrators, but it does not provide an objective basis of arbitration discipline. It is urgent to perfect the arbitration guarantee system on the basis of meeting the material needs of the arbitrators so as to enhance the sense of professional rank and honour of arbitration.

• Journal of Engineering Education Research
• /
• v.25 no.3
• /
• pp.3-10
• /
• 2022

An educator may utilize various pedagogies such as hands-on practice, practicum, and project-based learning to enhance a student's competency. Among various pedagogies, project-based learning is one of the well-known pedagogies that may provide similar on-the-job experience. In general, an educator may divide the students into small groups and assign tasks to check students' cooperation skills and achievements during project-based learning. However, an educator may experience difficulties operating project-based learning due to the COVID-19 pandemic. Most of the team activities are done in non-face-to-face meetings, and as a consequence, the educator may not find an underachieving team easily and cannot intervene appropriately. This study introduces a rigorous analysis method to evaluate team activities to analyze individual students' participation and contributions. First, this study develops evaluation rubrics by conducting questionnaires to professors and students to find an appropriate weight value for the evaluation scale. Then, this research introduces an analysis environment to evaluate students automatically. The analysis environment collects dialog data from social network services and measures interactions among students in a team. After measuring interactions, the environment generates a report to visualize the team activities. We applied the proposed method and environment to the capstone design course to show the effectiveness of the method and environment. Based on the case study, the environment showed that the analysis method could easily indicate the teams' activities and check the level of participation.

• Proceedings of the KIEE Conference
• /
• 1999.07d
• /
• pp.1870-1872
• /
• 1999

Performance of 20-cell stack for direct methanol fuel cell (DMFC) was tested at constant temperature. Electrode evaluation used to the stack was tested by the performance of a single cell. A new composite electrode prepared from active carbon cloth and high porous active carbon was developed for hydrophilic layer of the cell. Characteristics of a single cell using the composite electrode showed the current density of $500mA/cm^2$ at the cell voltage of 0.4V at $120^{\circ}C$. For the operating of 20 days. the cell voltage at constant cell current densty of $100mA/cm^2$ was slightly reduced from 0.62V to 0.53V with the cell voltage decay rate of 14.5%. Power of 20-cell stack at 5.3V, $100^{\circ}C$ was about 180W.

• The Transactions of the Korean Institute of Electrical Engineers P
• /
• v.66 no.4
• /
• pp.177-181
• /
• 2017

Auxiliary power supply for railway vehicle is a equipment that focuses on the service of passengers in a vehicle. It supplies power to controllers used in heating and cooling devices, fluorescent lamps, batteries and many other electrical equipments. Most of the auxiliary power supply for railway vehicle are mainly used for the round trips and circulation routes within the metropolitan area and have a capacity of 170~200 kVA. In this study, we developed the auxiliary power supply capacity to 240kVA for 200km/h class. As such, the auxiliary power supply is an important device for securing the reliability and safety of the railway vehicle and improving the passenger convenience, so the performance verification of the performance must be ensured. In this paper, 240kVA auxiliary power supply is developed. Also, performance of the auxiliary power supply manufactured through the analysis of various characteristics related to the auxiliary power supply was confirmed while operating the actual line.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.16 no.2
• /
• pp.150-157
• /
• 2008

The main objective of this paper is to investigate the performance characteristics of a $CO_2$ air conditioning system for fuel cell electric vehicles (FCEV). The present air conditioning system for FCEV uses the electrically driven compressor and electrically controlled expansion valve for $CO_2$ as a working fluid. The experimental work has been done with various operating conditions, which are quite matching the actual vehicle's driving conditions such as different compressor speed and high pressure to identify the characteristics of the system. Experimental results show that the cooling capacity and coefficient of performance (COP) were up to 6.3kW and 2.5, respectively. This paper also deals with the development of optimum high pressure control algorithm for the transcritical $CO_2$ cycle to achieve the maximum COP.

• Proceedings of the KIEE Conference
• /
• 2007.04a
• /
• pp.451-453
• /
• 2007

This paper describes the design of an asynchronous implementation of a sensor network processor. The main purpose of this work is the reduction of power consumption in sensor network node processors and the research presented here tries to explore the suitability of asynchronous circuits for this purpose. The Handshake Solutions toolkit is used to implement an asynchronous version of a sensor processor. The design is made compact, trading area and leakage power savings with dynamic power costs, targeting the typical sparse operating characteristics of sensor node processors. It is then compared with a synchronous version of the same processor. Both versions are then compared with existing commercial processors in terms of power consumption.