• Korean Journal of Agricultural Science
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• v.15 no.2
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• pp.143-152
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• 1988

This study was conducted to obtain basic data which affected engine performance of the power tiller being widely used in the rural area. Among the various factors affected engine performance, only flywheel weight was considered as the major factor in this study. Fuel consumption ratio, motoring loss, torque, vibration and mechanical efficiency of the engine tested were measured and analyzed on the four levels of flywheel weight (32.2, 29.7, 26.4, 24.2 kg). The results obtained were as follows: 1. The maximum output of 6 and 7.5 kW engine was 7.43 kW and 7.85 kW respectively. When flywheel weight was reduced from 32.2 kg to 24.2 kg, output power of the engine was increased 0.27 kW in 6 kW engine and increased 0.39 kW in 7.5 kW engine. 2. The fuel consumption ratio was decreased from 300.8 to 296.8 g/kW-hr in 6 kW engine and decreased from 313.6 to 312.8 g/kW-hr in 7.5 kW engine when the flywheel weight was reduced from 32.2 kg to 24.2 kg. 3. The mechanical efficiencies of the engine was increased from 76.1 to 76.8% in 6 kW engine and increased from 76.7 to 77.0% in 7.5 kW engine when the flywheel weight was reduced from 32.2 kg to 24.2 kg. 4. When the flywheel weight was reduced from 32.2 kg to 24.2 kg, a tendency of a little decrease of vibration at X- and Z-axis in 6 kW engine and of a little increase of vibration at Y-axis in 6 kW engine and all directions in 7.5 kW engine was observed. 5. Motoring losses was decreased from 2.33 to l.76 kW in 6 kW engine and decreased from 2.46 to 1.84 kW in 7.5 kW engine when the flywheel weight was reduced from 32.2 kg to 24.2 kg. From the above results and the flywheel weight calculated theoretically, it was recommendable that the flywheel weight should be reduced about 7 kg in 6 kW engine and about 10 kg in 7.5 kW engine, respectively.

• Korean Journal of Agricultural Science
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• v.20 no.2
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• pp.167-180
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• 1993

Most of small size diesel engines are widely used with the same size and weight flywheel in the levels of 6.0kW and 7.5kW. This study was conducted to obtain basic data which affect the engine performance of the power tiller. The flywheel weight was considered as a major factor in this research. Basically, fuel consumption ratio, motoring loss, torque, vibration and mechanical efficiency of the engine were measured and analyzed on four levels of flywheel weight, 32.2, 29.4, 26.2 and $24.2kg_f$, respectively. Results were obtained as follows: 1. The weights of flywheel were $23.7kg_f$ from design program of JSME and $24.5kg_f$ from ASME and SAE design criteria. Therefore, the flywheel weight of $32.2kg_f$ might be reduced about $8kg_f$ in 7.5kW engine. 2. The rated outputs of 6.0kW and 7.5kW engine were actually 7.43kW and 7.85kW, respectively. When flywheel weight was reduced from $32.2kg_f$ to $24.2kg_f$, outputs were increased from 7.43kW to 7.70kW in 6.0kW engine and from 7.85kW to 8.25kW in 7.5kW engine. 3. When the flywheel weight was reduced from $32.2kg_f$ to $24.2kg_f$, fuel consumption ratio was decreased from 300.8 to 296.8g/kW-hr in 6.0kW engine and also from 313.6 to 312.8g/kW-hr in 7.5 kW engine, respectively. 4. When the flywheel weight was reduced from $32.2kg_f$ to $24.2kg_f$, mechanical efficiency of engine was increased from 76.1% to 76.8% in 6.0kW engine and also from 76.7% to 77.0% in 7.5kW engine, respectively. 5. When the flywheel weight was reduced from $32.2kg_f$ to $24.2kg_f$, vibration was decreased at X-axis and Z-axis in 6.0kW engine, however, slightly increased at Y-axis in 6.0kW engine and at all axes in 7.5kW engine. 6. When the flywheel weight was reduced from $32.2kg_f$ to $24.4kg_f$ motoring loss was decreased from 2.33kW to 1.75kW in 6.0kW engine and also from 2.46kW to 1.84kW in 7.5kW engine.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.15 no.3
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• pp.198-204
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• 2022

In this paper, the 5kW and 50kW vertical axis wind turbines were studied using the ANSYS flow analysis simulation program. The 5 kW vertical shaft wind turbine has 30 units of the number of main blades and sub-blades and the electrical characteristics were analyzed by changing the tip speed ratio (TSR) from 0.2 to 06. A 50kW vertical axis wind turbine was designed based on the electrical characteristics of a 5kW vertical axis wind turbine. When the tip speed ratio was 0.5, the 5 kW wind power generation showed the maximum output of 9.5 kW and the efficiency of 0.28. The calculation of the power current(Ip) and the power voltage(Ep) show that, as the tip speed ratio increases, the power current(Ip) decreases and the power voltage(Ep) increases. And even if the tip speed ratio was changed, 5kW wind power generation was measured for output of 5 kW or higher. When the tip speed ratio was changed from 0.3 to 0.6, 50 kW wind power generation was output more than 50 kW. When the tip speed ratio of 50kW wind power generation was 0.4, the output was 58.37 [kW] and the efficiency was 0.318, and it was confirmed that the proposed 50kW wind power generation satisfies the design conditions.

• Bulletin of the Korean Mathematical Society
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• v.56 no.5
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• pp.1187-1198
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• 2019

Let R be a domain with its field Q of quotients. An R-module M is said to be weak w-projective if $Ext^1_R(M,N)=0$ for all $N{\in}{\mathcal{P}}^{\dagger}_w$, where ${\mathcal{P}}^{\dagger}_w$ denotes the class of GV-torsionfree R-modules N with the property that $Ext^k_R(M,N)=0$ for all w-projective R-modules M and for all integers $k{\geq}1$. In this paper, we define a domain R to be w-Matlis if the weak w-projective dimension of the R-module Q is ${\leq}1$. To characterize w-Matlis domains, we introduce the concept of w-Matlis cotorsion modules and study some basic properties of w-Matlis modules. Using these concepts, we show that R is a w-Matlis domain if and only if $Ext^k_R(Q,D)=0$ for any ${\mathcal{P}}^{\dagger}_w$-divisible R-module D and any integer $k{\geq}1$, if and only if every ${\mathcal{P}}^{\dagger}_w$-divisible module is w-Matlis cotorsion, if and only if w.w-pdRQ/$R{\leq}1$.

• 한국신재생에너지학회:학술대회논문집
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• 2006.06a
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• pp.308-311
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• 2006

A vibration monitoring is performed on a 1kW class stand alone wind turbine(W/T). When a W/T model is developed, general performance under various wind condition should be verified to introduce the product in the market. Especially, vibration characteristics within operating speed range are very important in the aspect of structural stability as well as generator's electrical efficiency. This paper examines the vibration performance of a home made 1kW W/T Various data of the W/T model are acquired in real time using a remote vibration monitoring system installed in Daekwanryung test site. Vibration stability of the W/T structure is diagnosed based upon the data and the result is used to estimate the applicability of the W/T model.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.12 no.5
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• pp.499-506
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• 2019

This paper is concerned with the operating stability of 7kW inverter using SIC hybrid module and verifies the validity of the simulation results by comparing the result of the loss equation and the simulation result, Simulation results using Si module and SiC hybrid module are compared to compare switch loss and diode loss. Through the loss equation calculation, the conduction loss of SiC Hybrid module is 168W, switching loss is 9.3W, diode loss is 10.5nW, When compared with the simulation results, similar values were shown. As a result of comparing the simulation results of the Si module and the SiC Hybrid module, The total device loss of the Si module was 246.2W, and the total device loss of the SiC Hybrid module was 189.9W. The loss difference was 56.3W, which was about 0.8W. thereby verifying the reverse recovery characteristics of the SiC SBD. In addition, temperature saturation test was conducted to confirm the stability of SiC Hybrid module and Si module under high temperature saturation, In the case of the Si module, the output power was stopped at 4kW, and the SiC Hybrid module was confirmed to operate at 7kW. Based on this, an efficiency graph and a temperature graph are presented, and the Si module is graphed up to 4kW and the SiC Hybrid module is graphed up to 7kW.

• Food Science and Preservation
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• v.10 no.3
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• pp.360-364
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• 2003

This study was conducted to investigate the preparation possibility of Beni-koji by Monascus pilosus using dried soybean curd residue(Biji). The additional effect of water(0-50％), glucose(0-10％, w/w), monosodium glutamate(0-0.l％, w/w) and citrus peel water extracts (0-0.5％, v/w) on the pigment and monacolin K content of the Biji Beni-koji were examined. Optimal added amounts of water was 20％ of dried Biji. The highest pigment content(OD at 500 nm) of Biji Beni-koji was 1.06 in 10％ glucose, 2.26 in 0.01％ monosodium glutamate and 2.61 in 0.4％ citrus peel water extracts. The content of monacolin K in the Biji Beni-koji added with 10％ glucose, 0.01％ monosodium glutamate and 0.4％ citrus peel water extracts showed 96.38 mg％(w/w), 118.25 mg％(w/w) and 104.50 mg％(w/w), respectively.

• Economic and Environmental Geology
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• v.40 no.6
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• pp.761-769
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• 2007

We made 712 thermal property measurements on igneous, metamorphic and sedimentary rock samples from Gyeonggi-do, Gangwon-do and Chungchung-do, Korea. The average thermal conductivities of igneous, metamorphic and sedimentary rocks are 3.58W/m-K, 4.16W/m-K and 4.53W/m-K, respectively. Thermal conductivity of granite and gneiss are 2.13-5.87W/m-K and 2.26-6.67W/m-K, with average values of 3.57W/m-K and 3.945W/m-K, respectively. The average of thermal diffusivities are $1.43mm^2/sec\;and\;1.55mm^2/sec$, respectively; the average of specific heat values are 0.914J/gK, 0.912J/gK for granite and gneiss samples, respectively. The thermal conductivity of a rock type generally have a wide range because it depends on various factors such as dominant mineral phase, micro-structure, anisotropy, and so on.

• Fire Science and Engineering
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• v.32 no.5
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• pp.6-14
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• 2018

This study was carried out with respect to the heat release rate (HRR) properties of building wood. Heat release characteristics were measured using a cone calorimeter (ISO 5660-1) with four kinds of wood. The time to ignition measured after the combustion in $25kW/m^2$ external heat flux was 35 to 55 s. Time to ignition of both lauan and red pine was marked with the most delayed value in each of 54 s, 55 s. The maximum heat release rate ($HRR_{peak}$) was $156.87{\sim}235.1kW/m^2$, and the risk of early fire was highest in spruce. Total heat release of red pine was obtained in the highest value with $114.2MJ/m^2$. The mean effective heat of combustion of Japanese cedar was 19.1 MJ/kg and the highest among the samples. Fire risk of wood by FPI was orderly increased from lauan ($0.2468s{\cdot}m^2/kW$), red pine ($0.2339s{\cdot}m^2/kW$), spruce ($0.2308s{\cdot}m^2/kW$) to Japanese cedar ($0.2231s{\cdot}m^2/kW$). Fire risk of wood by FGI get increased from lauan ($0.5088kW/m^2{\cdot}s$), red pine ($0.5111kW/m^2{\cdot}s$), Japanese cedar ($2.8522kW/m^2{\cdot}s$) to spruce ($3.0662kW/m^2{\cdot}s$). Therefore, the risk of fire on the heat release characteristics of woods were found that spruce and Japanese cedar showed the high value compared with the other specimens.

• Bulletin of the Korean Mathematical Society
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• v.57 no.3
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• pp.763-780
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• 2020

Let R be a commutative ring. An R-module M is said to be w-flat if Tor ^R₁ (M, N) is GV -torsion for any R-module N. It is known that every flat module is w-flat, but the converse is not true in general. The w-flat dimension of a module is defined in terms of w-flat resolutions. In this paper, we study the w-flat dimension of an injective w-module. To do so, we introduce and study the so-called w-copure (resp., strongly w-copure) flat modules and the w-copure flat dimensions for modules and rings. The relations between the introduced dimensions and other (classical) homological dimensions are discussed. We also study change of rings theorems for the w-copure flat dimension in various contexts. Finally some illustrative examples regarding the introduced concepts are given.