• Geomechanics and Engineering
• /
• v.18 no.6
• /
• pp.615-626
• /
• 2019

Lightweight concrete (LWC) provides an attractive alternative to conventional piles by improving the durability of deep foundations. In this paper, the drivability of cylindrical and tapered piles made of lightweight and common concrete (CC) under hammer impacts was investigated by performing field tests and numerical analysis. The different concrete mixtures were considered to compare the mechanical properties of light aggregate which replaced instead of the natural aggregate. Driving tests were also conducted on different piles to determine how the pile material and geometric configurations affect driving performance. The results indicated that the tapering shape has an appropriate effect on the drivability of piles and although lower driving stresses are induced in the LWC tapered pile, their final penetration rate was more than that of CC cylindrical pile under hammer impact. Also by analyzing wave propagation in the different rods, it was concluded that the LWC piles with greater velocity than others had better performance in pile driving phenomena. Furthermore, LWC piles can be driven more easily into the ground than cylindrical concrete piles sometimes up to 50% lower hammer impacts and results in important energy saving.

• Clean Technology
• /
• v.29 no.2
• /
• pp.145-150
• /
• 2023

Tele-metering systems have been useful tools for managing domestic wastewater treatment plants (WWTP) over the last decade. They mostly generate water quality data for discharged water to ensure that it complies with mandatory regulations and they may be able to produce every operation parameter and additional measurements in the near future. A sub-big data group, comprised of about 150,000 data points from four domestic WWTPs, was ready to be classified and also analyzed to optimize the WWTP process. We used the Statistical Product and Service Solutions (SPSS) 25 package in order to statistically treat the data with linear regression and correlation analysis. The major independent variables for analysis were water temperature, sludge recycle rate, electricity used, and water quality of the influent while the dependent variables representing the water quality of the effluent included the total nitrogen, which is the most emphasized index for discharged flow in plants. The water temperature and consumed electricity showed a strong correlation with the total nitrogen but the other indices' mutual correlations with other variables were found to be fuzzy due to the large errors involved. In addition, a multilayer perceptron analysis method was applied to TMS data along with root mean square error (RMSE) analysis. This study showed that the RMSE in the SS, T-N, and TOC predictions were in the range of 10% to 20%.

• Journal of Advanced Marine Engineering and Technology
• /
• v.8 no.1
• /
• pp.17-36
• /
• 1984

Since 1973, the competition on the development of fuel saving type internal combustion engines has become severe by the two times oil shock, and new type engines are reported every several months. Whenever these new type engines are developed, new designs are required and they will be offered in the market after performing the endurance test for a long time. But the engine market is faced with a heavy burden of finance, as the developing of a new engine requires tremendous expenses. For this reason, the computer simulation method has been lately developed to cope with it. The computer simulation method can be available to perform the reasonable research works by the theoretical analysis before carrying out practical experiments. With these processes, the developing expenses are cut down and the period of development is curtailed. The object of this study is the development of simulation computer program for the small naturally aspirated four-stroke diesel engine which is intended to product by the original design of our country. The process of simulation is firstly investigated for the ideal engine cycle, and secondly for the real engine cycle. In the ideal engine cycle, each step of the cycle is simulated by the energy balance according to the first law of thermodynamics, and then the engine performance is calculated. In the real cycle imulation program, the injection rate, the preparation rate and the combustion rate of fuel and the heat transfer through the wall of combustion chamber are considered. In this case, the injection rate is supposed as constant through the crank angle interval of injection and the combustion rate is calculated by the Whitehouse-Way equation and the heat transfer is calculated by the Annand's equation. The simulated values are compared with measured values of the YANMAR NS90(C) engine and Mitsubishi 4D30 engine, and the following conclusions are drawn. 1. The heat loss by the exhaust gas is well agree with each other in the lower load, but the measured value is greater than the calculated value in the higher load. The maximum error rate is about 15% in the full load. 2. The calculated quantity of heat transfer to the cooling water is greater than the measured value. The maximum error rate is about 11.8%. 3. The mean effective pressure, the fuel consumption, the power and the torque are well agree with each other. The maximum error is occurred in the fuel consumption, and its error rate is about 7%. From the above remarks, it may be concluded that the prediction of the engine performance is possibly by using the developed program, although the program needs to reform by adding the simulation of intake and exhaust process and assumping more reliable mechanical efficiency, volumetric efficiency, preparation rate and combustion rate.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2018.10a
• /
• pp.329-331
• /
• 2018

In this paper, we propose a monitoring system that starts with the supply of raw materials for threading, is processed into a lathe machine, and checks for defects of the product are automatically performed by the robot with Smart Factory technology through assembly and disassembly. Completion check according to the production instruction quantity and production instruction is made by checking the production status according to whether or not the raw material is worn by the displacement sensor, and checking the pitch and the contour of the processed female and male to determine OK and NG. The robotic system acts as a relay for loading and unloading of raw materials, pallet transfer, and overall process, and it acts as an intermediary for organically driving. The location information of the threaded products is collected by using the non-contact wireless tag and the energy saving system Production efficiency and utilization rate were checked. The environmental sensor collects the air-conditioning environment data (temperature, humidity), measures the temperature and humidity accurately, and checks the quality of product processing. It monitors and monitors the driving hazard level environment (overheating, humidity) of the product. Controls for CNC and robot module PLC as a heterogeneous system.

• Korean Journal of Construction Engineering and Management
• /
• v.14 no.4
• /
• pp.55-64
• /
• 2013

As GHG target management is introduced in Korea, designated establishment takes responsibilities to reduce more than 30% of expected GHG emission until 2020. Although decreasing GHG has been requested to universities which consume great amount of energy, there are difficulties to apply high cost countermeasures. Therefore, this research suggest a low cost, easily-applicable energy saving method, and derive potential GHG reduction amount in the case of SNU, Kwan-ak campus. First of all, 11 rooms of different use were chosen as the samples, and energy consumption in each room was measured. Standard models for each room were built through researching on the electric devices in each room. Moreover, energy consumption was computed for each devices through analyzing the pattern of electricity consumption. 32 GHG reduction technology and action program were chosen, and they were applied to the standard models for individual rooms. Through multiplying energy reduction rate of each program to energy consumption of each electric device, maximum energy reduction of each electric device is derived. Through that, Maximum GHG reduction for individual rooms and each month and the total GHG reduction capacity of Kwan-ak campus were computed. It was found out that approximately $5,311tCO_2$-eq can be reduced, when reduction technology and action program suggested by this research are applied. It appeared 24.48% of requested reduction amount to SNU can be reduced, till 2016.

• 한국신재생에너지학회:학술대회논문집
• /
• 2010.11a
• /
• pp.73.1-73.1
• /
• 2010

For the successful cold starting of a fuel cell engine, either internal of external heat supply must be made to overcome the formation of ice from water below the freezing point of water. In the present study, switchable vanadium oxide compounds as variable temperature-electrical resistance materials onto the surface of flat metallic bipolar plates have been prepared by a dip-coating technique via an aqueous sol-gel method. Subsequently, the chemical composition and micro-structure of the polycrystalline solid thin films were analyzed by X-ray diffraction, X-ray fluorescence spectroscopy, and field emission scanning electron microscopy. In addition, it was carefully measured electrical resistance hysteresis loop over a temperature range from $-20^{\circ}C$ to $80^{\circ}C$ using the four-point probe method. The experimental results revealed that the thin films was mainly composed of Karelianite $V_2O_3$ which acts as negative temperature coefficient materials. Also, it was found that thermal dissipation rate of the vanadium oxide thin films partially satisfy about 50% saving of the substantial amount of energy required for ice melting at $-20^{\circ}C$. Moreover, electrical resistances of the vanadium-based materials converge on an extremely small value similar to that of pure flat metallic bipolar plates at higher temperature, i.e. $T{\geq}40^{\circ}C$. As a consequence, experimental studies proved that it is possible to apply the variable temperature-electrical resistance material based on vanadium oxides for the cold starting enhancement of a fuel cell vehicle and minimize parasitic power loss and eliminate any necessity for external equipment for heat supply in freezing conditions.

• Journal of Bio-Environment Control
• /
• v.9 no.4
• /
• pp.212-222
• /
• 2000

This study was performed to investigate the performance of heat recovery device attached to exhaust gas flue connected to combustion chamber of greenhouse heating system. The experimental heat recovery system is mainly consisted of LPG combustion chamber and two heat recovery units; unit-A is attached directly to the exhaust gas flue, and unit-B is connected with unit-A. Heat recovery performance was evaluated by estimating total energy amounts by using enthalpy difference between two measurement points together with mass flow rate of gas and/or air passing through each heat recovery unit depending on 5 different flow rates controlled by voltage meter. The results of this experimental study, such as heat exchange behavior of supply air tubes and exhaust air passages crossing the tubes, pressure drop between inlet and outlet, heat recovery performance of exchange unit, etc., will be used as fundamental data for designing optimum heat recovery device to be used for fuel saving purpose by reducing heat loss amounts mostly wasted outside of greenhouse through flue.

• Journal of Advanced Marine Engineering and Technology
• /
• v.39 no.9
• /
• pp.967-972
• /
• 2015

Because of recent interests in energy conservation and prevention of environmental pollution, research related to these topics is increasing. The U.S. Navy has started to study the HED (hybrid electric drive) system in order to improve the COGAG propulsion system's fuel efficiency in AEGIS destroyers. (This ship's fuel consumption is 40% of the total fuel consumption of the U.S. Navy.) In addition, the Korean Navy is considering applications of the HED system in AEGIS destroyers. The purpose of this study is to analyze the U.S.A.'s HED system and to simulate its generating mode energy saving rate using LabVIEW. The results confirmed that the fuel savings are about 700 kg/h.

• Proceedings of the SAREK Conference
• /
• 2007.11a
• /
• pp.459-465
• /
• 2007

This study was conducted to calculate the LCC of a apartment complex with a type of heating system, district heating and cogeneration system. For the purpose of analyzing LCC according to size of apartment complex, 500, 1,500 and 4,000 houses of model apartment selected. This research performs design of heating system and the life cycle cost analysis including an initial cost, energy cost, maintenance and operation cost, replacement cost and renovation cost during the project period(15years). According to the calculated results, 1) Initial cost of cogeneration system with 500, 1500 and 4000 houses is higher than district heating system each of 20%, 13%, 12%. 2) In case of cogeneration system, the payback period by electric generation is 5.21, 4.92 and 4.47 years and saving cost was calculated 29 billion won, 94 billion won and 262 billion won after payback period. 3) Cogeneration system LCC was 1.12, 1.07 and 1.06 times larger than district system with the size of apartment complex. According to the case of this study district heating system is more efficient than cogeneration system in terms of the reduction of LCC. 4) Gas Engine Co-generation System is more efficient than other systems because it can collect progressive part from electric charge progressive stage system. However, the efficiency is decreasing because of raising of fuel bills(LNG) and lowering of power rate for house use. Especially the engine is foreign-made so the cost of maintenance and repair is high and the technical expert is short. 5) District heating is also affected by fuel bills so we should improve energy efficiency through recovering of waste heat(incineration heat, etc.). Also, we should supply district cooling on the pattern of heat using of let the temperature high in winter and low in summer.

• Journal of Korea Technical Association of The Pulp and Paper Industry
• /
• v.35 no.4
• /
• pp.8-16
• /
• 2003

The objective of this study was to investigate the potential application of the separated refining system in the papermaking process using cotton pulps. The cotton staple and linter fibers were expected to show a great difference in their refining responses due to their morphological and physical differences. Experiments were conducted to examine the differences in flocculation tendency, CED viscosity, fiber length, handsheet properties and the SEM surface images between staple and linter fibers at a given refining degree. These fibers were also subjected to separated refining in a laboratory-scale beater and in a mill-scale refiner as well. The effect of the separated refining on the refining rates and papermaking properties were evaluated. Results obtained are summarized as follows: 1. Fiber flocculation tendency of cotton staple was estimated to be significantly greater than that of linter fibers; 2. The staple fibers showed higher cellulose DP, longer fiber length and higher sheet strength at a given refining degree compared to linter fibers, but remarkably slower refining rate was observed; 3. The separated refining system exhibited a significant increase in sheet strengths, especiauy in folding endurance, with an increase in the fibrillation on the surface of staple fibers, but slightly lower or comparable fiber length after refining to the mixed refining system; 4. Similar results were also obtained from the machine trial in which about 7-8％ energy saving effects were achived in the separated refining system. On the basis of the results observed in this study, it was concluded that a significant increase in paper strength and a substantial reduction in refining energy consumption could be achieved using the separated refining system for the cotton staple and linter fiber stock refining.