• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.49 no.2
• /
• pp.155-166
• /
• 2021

In this paper, design study of a small two-stage launch vehicle is undertaken for the dedicated launch of the Compact Advanced Satellite 500 (CAS500)-class satellite into the Low Earth Orbit (LEO) by modifying the second and third stages of the Korean Space Launch Vehicle II (KSLV-II). Since the KSLV-II has three stages, velocity increment is newly distributed for the two-stage small launch vehicle. For this end, the staging design is carried out for the design parameters such as stage mass ratios, structural coefficients and engine options for each stage followed by trajectory analysis. Investigation of the results provides the combination of design parameters for the small launch vehicle for the dedicated launch of 500 kg-class satellite into LEO.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.24 no.6
• /
• pp.1-9
• /
• 2020

Using kerosene and liquid oxygen, 1.5-tonf class liquid-liquid pintle injector with rectangular two-row orifice was designed and manufactured. The combustion test of the pintle injector was carried out to verify the combustion performance and combustion stability under a supercritical condition which is the actual operation condition of the liquid rocket engine. The combustion test result showed that the pintle tip was damaged by the high temperature combustion gas in the high-mixed ratio recirculation zone of the combustion chamber. To solve this problem, the insert nozzle was installed in the pintle injector to increase cooling performance at the pintle tip. As a result of the hot firing test, installation of the insert nozzle, AR and BF had a great effect on pintle tip cooling performance.

• Journal of Drive and Control
• /
• v.19 no.4
• /
• pp.54-61
• /
• 2022

This is a basic study analyzing emissions of an agricultural tractor during tillage operations. In this study, CO, THC, NOx, and PM considered as emission factor were analyzed during plow and rotary tillage operation by the tractor. Engine torque and rotational speed were measured through ECU. Engine power was calculated using engine torque and rotational speed. The emissions was calculated based on the number of units, rated power, load factor, and operating time. Results showed that the load factor was calculated almost twice, which was higher than 0.48. It was also observed that the emission of the tractor was variable for different agricultural operations because tractor loads were different based on operations. There was a difference in emissions due to differences in plow and rotary working hours. To estimate the emission of agricultural tractor based field operations in detail, it is necessary to consider TAF (Transient Adjustment Factor) and DFA (Deterioration factor). In the future, TAF and DFA will be considered to estimate emissions of the agricultural tractor. Finally, results of this study can contribute to the literature to estimate tractor emissions accurately.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.25 no.2
• /
• pp.110-118
• /
• 2021

In a liquid rocket engine system, the flow of oxidizer into the combustion chamber is controlled by the main oxidizer shut-off valve. When the valve is closed, the oxidizer flows via the recirculation line, not into the combustion chamber. In this situation, the measured pressure could be much higher than a design value because of the water hammer phenomenon. In this paper, the experiments on the water hammer in the recirculation line with different initial conditions were conducted in order to study the pressure wave produced in each case. According to the experimental results, characteristics of the pressure wave in the recirculation line depend on the initial condition. To be specific, the pressure surge is maximized in case that the shock is condensation-oriented in the end of the recirculation line.

• Journal of Drive and Control
• /
• v.19 no.1
• /
• pp.16-25
• /
• 2022

The purpose of this study was to calculate and analyze the engine load factor of major agricultural operations using a 78 kW class agricultural tractor for estimating the emission of air pollutants and greenhouse. Engine load data were collected using controller area network (CAN) communication. Main agricultural operations were selected as plow tillage (PT), rotary tillage (RT), baler operation (BO), loader operation (LO), driving on soil (DS), and driving on concrete (DC). The engine power was calculated using the measured engine load data. A weight factor was applied to load factor for considering usage ratio according to agricultural operations. Weight factors for different agricultural operations were calculated to be 27.4%, 32.9%, 17.5%, 7.7%, 4.5%, and 10.0% for PT, RT, BO, LO, DS, and DC, respectively. As a result of the field test, load factors were 0.74, 0.93, 0.41, 0.23, 0.27, and 0.21 for PT, RT, BO, LO, DS, and DC, respectively. The engine load factor was the highest for RT. Finally, as a result of applying the weight factor for usage ratio of agricultural operations, the integrated engine load factor was estimated to be 0.63, which was about 1.31 times higher than the conventional applied load factor of 0.48. In future studies, we plan to analyze the engine load factor by considering various horsepower and working conditions of the tractor.

• Journal of the Society of Naval Architects of Korea
• /
• v.60 no.2
• /
• pp.95-109
• /
• 2023

In the 4th industrial revolution, changes in the technological paradigm have had a direct impact on the maintenance system of ships. The 2-stroke low speed engine system integrates with the core equipment required for propulsive power. The Condition Based Management (CBM) is defined as a technology that predictive maintenance methods in existing calender-based or running time based maintenance systems by monitoring the condition of machinery and diagnosis/prognosis failures. In this study, we have established a framework for CBM technology development on our own, and are engaged in engineering-based failure analysis, data development and management, data feature analysis and pre-processing, and verified the reliability of failure mode DB using LSTM algorithms. We developed various simulated failure mode scenarios for 2-stroke low speed engine and researched to produce data on onshore basis test_beds. The analysis and pre-processing of normal and abnormal status data acquired through failure mode simulation experiment used various Exploratory Data Analysis (EDA) techniques to feature extract not only data on the performance and efficiency of 2-stroke low speed engine but also key feature data using multivariate statistical analysis. In addition, by developing an LSTM classification algorithm, we tried to verify the reliability of various failure mode data with time-series characteristics.

• Journal of Drive and Control
• /
• v.20 no.2
• /
• pp.31-39
• /
• 2023

The aim of this study was to measure and analyze engine load factor (LF) according to working conditions (operation type and gear stage) of small agricultural multi-purpose cultivator to estimate the emission of air pollutants. To calculate LF, a torque sensor capable of collecting torque and rotational speed was installed on the engine output shaft and DAQ was used to collect data. A field test was conducted with major operation of a cultivator and tillage operations (plow tillage and rotary tillage). Engine power was calculated using engine torque and rotational speed and LF was calculated using real-time power and rated power. In addition, unified LF was calculated using the weight for each operation and the average LF for each operation. As a result, average LF values at 1.87 and 3.10 km/h by plow tillage were 0.50 and 0.69, respectively. Average LF values at 1.87 and 3.10 km/h by rotary tillage were 0.70 and 0.78, respectively. Furthermore, unified LF calculated in consideration of the weight factor showed a value of 0.65, which was 135% higher than the conventional LF (0.48). Results of this study could be used as basic information for realizing LF values in the field of agricultural machinery.

• Journal of the Korea Society of Computer and Information
• /
• v.29 no.2
• /
• pp.61-66
• /
• 2024

This paper aims to design a simulation for path-finding of objects in a simulation or game environment using reinforcement learning techniques. The main feature of this study is that the objects in the simulation are trained to avoid obstacles at random locations generated on a given track and to automatically explore path to get items. To implement the simulation, ML Agents provided by Unity Game Engine were used, and a learning policy based on PPO (Proximal Policy Optimization) was established to form a reinforcement learning environment. Through the reinforcement learning-based simulation designed in this study, we were able to confirm that the object moves on the track by avoiding obstacles and exploring path to acquire items as it learns, by analyzing the simulation results and learning result graph.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.31 no.5
• /
• pp.355-363
• /
• 2013

Analysis and sharing of spatial information can be made possible through the reuse of spatial analysis processes, and the sharing of spatial models on the web. However, the deployment of spatial analysis models is possible, only when the difficult tasks of model design and the exchange of spatial data are overcome. In this study, a WPS spatial analysis model is defined, based on the OGC standards, and applied to the 'Selection of Housing Units for Water Supply' application. BPEL was used to define the sequence of processes and to enable the exchange of spatial data. To this end, WSDL was defined for WPS and WFS accesses, the sequence of spatial processes was defined in BPEL, and XSLT was defined for the exchange of XML data. The WPS model was designed and deployed using the Apache ODE which provides RESTful binding. It is expected that effective decision making will be easier using the web based spatial analysis models which are realized by WPS Orchestration with BPEL, as presented in this study.

• Korean Journal of Construction Engineering and Management
• /
• v.12 no.5
• /
• pp.137-145
• /
• 2011

BIM Data exchange using standard format can provide a user friendly and practical way of integrating the BIM tools in the life cycle of a building on the currently construction industry which is participated various stakeholder. It used IFC format to exchange the BIM data from Design software to energy analysis software. However, since we can not use the material name data in the library of an energy analysis directly, it is necessary to input the material property data for building energy analysis. In this paper, to matching the material named of name of DOE-2 default library, rhe extracted material names from BIM file are inferred by the ontology With this we can make the reliable input data of the engine by development a standard data and also increase the efficient of building energy analysis process. The methodology can enable to provide a direction of BIM-based information management system as a conceptual study of using ontology in the construction industry.