최원 Choi Won , 김한중 Kim Hanjoong

DOI: JKWST Vol.57(No.6) 1-7, 2015

---

Most of chloride diffusion models based on finite difference method (FDM) could not express the diffusion in horizontal direction at each elevation. To overcome these weakness, two dimensional chloride ion penetration model based on finite element method (FEM) to be able to combine various multi-physics simultaneously was suggested by introducing moving mesh technique. To avoid the generation of mesh being able to be distorted depending on the relative movement of water level to static concrete, a rectangular type of mesh was intentionally adopted and the total number of meshes was empirically selected. The simulated results showed that the contents of surface chloride decreased following to the increase of elevation in the top part of low sea level, whereas there were no changes in the bottom part of low level. In the DuraCrete model, the diffusion coefficient of splashed zone is generally smaller than submerged zone, whereas the trend of Life365 model is reverse. Therefore, it could be understood that the developed model using moving mesh technique effectively reflects DuraCrete ^TM model rather than Life365 ^TM model. In the future, the model will be easily expanded to be combined with various multi-physics models considering water evaporation, heat of hydration, irradiation effect of sun and so on because it is based on FEM.

홍성구 Hong Seong Gu

DOI: JKWST Vol.57(No.6) 9-20, 2015

---

The demand of renewable energy is expected to grow in the long run in spite of current stable lower oil prices. Energy consumption for heating in horticulture greenhouse is large and affects the profits of the farms. This study analyzed the availability of biomass in rural area and proposed the strategies for utilizing the biomass for greenhouse heating. Data reveal the annual average fuel consumption in greenhouses is about 78 TOE/ha. Considering biomass resource in rural areas, agricultural residues are not sufficient to meet the biomass demand from greenhouses. Therefore it is recommended to secure further biomass including wild herbaceous biomass and woody biomass from forest. Based on the conditions of biomass gasification equipment investment and fuel prices, maximum allowable price of biomass turned out about 100,000 KRW/t to be competitive to kerosine. Biomass supply chain should be established for facilitating biomass trading between biomass consumers and biomass producers such as farmers who provide crop residues. An online trading system is an example of the system where consumers who utilize biomass make payments to suppliers and get the information about the biomass. Intermediate collection storages are required to store biomass from distributed sources. Operation of biomass heating systems in demonstration greenhouses is necessary to get information to refine and further develop commercial biomass heating systems. Relatively large greenhouses are desirable to have biomass heating systems for economic viability. The location of the greenhouse farms should be selected within the area where enough biomass resources are available for feeding the biomass facility.

이상연 Lee Sang-yeon , 이인복 Lee In-bok , 권경석 Kwon Kyeong-seok , 하태환 Ha Tae-hwan , 여욱현 Yeo Uk-hyeon , 박세준 Park Se-jun , 김락우 Kim Rack-woo , 조예슬 Jo Ye-seul , 이승노 Lee Seung-no

DOI: JKWST Vol.57(No.6) 21-33, 2015

---

Recently, the Korean government announced a new development plan for a large-scale greenhouse complex in reclaimed lands. Wind environments of reclaimed land are entirely different from those of inland. Many standard books for ventilation design didn’t include qualitative standard for natural ventilation. In this study, natural ventilation rates were analyzed to suggest standard for ventilation design of venlo type greenhouse built on reclaimed land. CFD (Computational Fluid Dynamics) simulation models were designed according to the number of spans, wind conditions and vent openings. The wind profile at a reclaimed land was designed using ESDU (Engineering Sciences Data Unit) code. Using the designed CFD simulation model, ventilation rates were computed using mass flow rate and tracer gas decay method. Additionally computed natural ventilation rates were evaluated by comparing with ventilation requirements. As a result of this study, ventilation rates were decreased with increasing of the number of spans. Ventilation rates were linearly increased with increasing of wind speed. When the wind speed was 1.0 m·s -1 , only side vent was open and wind direction was 45°, homogeneity of ventilation rate at 0∼1 m height is the worst. Finally, chart for computing natural ventilation rate was suggested. The chart was expected to be used for establishing standard of ventilation design.

조예슬 Jo Ye-seul , 권경석 Kwon Kyeong-seok , 이인복 Lee In-bok , 하태환 Ha Tae-hwan , 박세준 Park Se-jun , 김락우 Kim Rack-woo , 여욱현 Yeo Uk-hyeon , 이상연 Lee Sang-yeon , 이승노 Lee Seung-no

DOI: JKWST Vol.57(No.6) 35-46, 2015

---

Improvement in domestic poultry production has a positive effect on the export competitiveness of the poultry industry. However, overproduction and enlargement of facilities to assure a supply increase a stocking density which make a poor environment in the broiler house. In particular, an intensive rearing environment is vulnerable to dust control that causes respiratory diseases, such as asthma, bronchitis, etc., to farmers and broilers. However, monitoring data and research for environment control are not adequate, and there are no air quality regulations in broiler houses in Korea. In this study, TSP, PM10, inhalable dust and respirable dust concentration were monitored according to season, age of broiler and broiler’s activities. Air quality assessment was also performed in accordance with the threshold limit value by Donham et al. (2000). The TSP concentrations were 77.5 %, 219.7 % higher and PM10 concentrations were 121.2 %, 303.8 % higher when change of season and winter respectively than summer. There were significantly different concentrations according to season and age of broiler. Inhalable and respirable dust concentration were also clearly different according to the season and age of broiler. A high dust concentration was observed, specifically exceeding the threshold limit by 119 % in the winter. In the case of the broiler’s motion was activity according to worker’s access into the broiler house, concentration level was 769.6 % higher than broiler’s motion was stable and exceeded the threshold limit. These results suggest that the worker should put on protective equipment to protect there’s respiratory health in the broiler house.

박정수 Park Jeong-soo , 왕용 Wang Long , 강구 Kang Ku , 구본운 Gu Bon-wun , 김한중 Kim Han-joong , 홍성구 Hong Seong-gu , 홍승길 Hong Seung-gil , 박성직 Park Seong-jik

DOI: JKWST Vol.57(No.6) 47-57, 2015

---

Organic farming system has been considered environmental friendly and sustainable agricultural practice. However, the influence of organic farming on soil quality and environment is not well informed and controversial. We sampled and analyzed 0~15 cm and 15~30 cm depth soils of organic and conventional paddy fields in Yongin and Anseong. The electric conductivity and organic matter content of organic paddy soil were significantly less (p = 0.0097, 0.0067, respectively) than those of conventional paddy soil. Available phosphate and total phosphorus in 0~15 cm depth of organic paddy soil were 211.1±135.3, 872.4±286.3 mg/kg, respectively, less than those of conventional paddy soil. Available phosphate amount in conventional paddy was 358.8±246.7 mg/kg, which is higher than 300 mg/kg that can cause secondary environmental contamination by runoff. The amount of total nitrogen in organic paddy soil was less than that in conventional paddy while their difference was not significant. The concentration of the heavy metals in organic paddy soil was also lower than that in conventional paddy soil but their difference was not statistically significant. Our findings demonstrate that electric conductivity, organic matter, nutrients, and heavy metals in organic paddy soil were less than those in conventional paddy soil. However, additional monitoring of soil properties for longer period is necessary to certify such a conclusion.

최원 Choi Won , 김한중 Kim Hanjoong

DOI: JKWST Vol.57(No.6) 59-68, 2015

---

Traditional structure analysis method is based on numerical matrix analysis to use the geometries consisting of the structure. The characteristics require a lot of computer memories and computational time. To avoid these weaknesses, new approach to analyze truss structure was suggested by adopting topological load redistribution method. The axial forces to be not structurely analyzed yet against outside loads were redistributed by using nodal equation of equilibrium randomly at each node without constructing global matrix. However, this method could not calculate the axial forces if structure is statically indeterminate due to degree of many indeterminacies. Therefore, to apply the method suggested in this research, all redundancies of truss structure were replaced by unit loads. Each unit load could make the deformation of a whole structure, and a superposition method was finally adopted to solve the simultaneous equations. The axial forces and deflections agreed with the result of commercial software within the relative error of 1 %, whereas in the case that the axial forces are relatively very smaller than others, the relative errors were increased to 2 %. However, as the values were small enough not to be considered, it was practically useful as a structural analysis model. This model will be used for structural analysis of truss type of large structure such as agricultural farming facility.

박정구 Park Jung Koo , 김명환 Kim Myeong Hwan , 송창섭 Song Chang Seob

DOI: JKWST Vol.57(No.6) 69-77, 2015

---

The objective of this study was to evaluate the performance of selected sediment reduction methods to reduce sediment discharges from drain and irrigation of different types (concrete canals, soil canals). This study was carried out to analysis for the suspended sediment concentration and sediment of drain and irrigation by velocity of flow. The results of study were analysised and summerized as follow. Sedimentation characteristics and size of soil sediment from the concrete and soil canals of downstream smaller than upstream. Suspended sediment concentration and flow times from the suggestion canals bigger than open canal. Structural shape of the canal decreases the velocity of flow also affects the suspended sediment concentration and flow times.

허용구 Her Younggu , 황세운 Hwang Syewoon

DOI: JKWST Vol.57(No.6) 79-90, 2015

---

박진기 Park Jin Ki , 박종화 Park Jong Hwa

DOI: JKWST Vol.57(No.6) 91-97, 2015

---

The Unmanned Aerial Vehicles (UAVs) have several advantages over conventional RS techniques. They can acquire high-resolution images quickly and repeatedly. And with a comparatively lower flight altitude i.e. 80~400 m, they can obtain good quality images even in cloudy weather. Therefore, they are ideal for acquiring spatial data in cases of small agricultural field with mixed crop, abundant in South Korea. This paper discuss the use of low cost UAV based remote sensing for classifying crops. The study area, Gochang is produced by several crops such as red pepper, radish, Chinese cabbage, rubus coreanus, welsh onion, bean in South Korea. This study acquired images using fixed wing UAV on September 23, 2014. An object-based technique is used for classification of crops. The results showed that scale 250, shape 0.1, color 0.9, compactness 0.5 and smoothness 0.5 were the optimum parameter values in image segmentation. As a result, the kappa coefficient was 0.82 and the overall accuracy of classification was 85.0 %. The result of the present study validate our attempts for crop classification using high resolution UAV image as well as established the possibility of using such remote sensing techniques widely to resolve the difficulty of remote sensing data acquisition in agricultural sector.

윤태강 Yun Tae-kang , 손영환 Son Young-hwan , 박재성 Park Jae-sung , 노수각 Noh Soo-kack , 봉태호 Bong Tae-ho , 김동근 Kim Dong-geun

DOI: JKWST Vol.57(No.6) 99-105, 2015

---

Bottom ash and fly ash are by-product from thermoelectric power plants. Fly ash is recycled to various field. However, though an output of bottom ash have increased each year, most of them is reclaimed in ash landfill. It is necessary to find a solution that bottom ash is recycled economically and know characteristics of bottom ash to recycle. It is goal to investigate engineering properties of bottom ash, especially the particle breakage, to recycle that. Bottom ash was crushed by impact method according to compaction energy and then compared with or original sample and crushed it in terms of particle size distribution and characteristics of strength. In result, after crushed it, particle finer was increased, especially 2∼0.85 mm size, than original. It was displayed a tendency that internal friction of crushed sample was decreased but cohesion of it was not. Therefore, it is important to investigate the engineering properties of bottom ash in terms of the particle breakage to use construction materials for various field.

김동근 Kim Donggeun , 손영환 Son Younghwan , 박재성 Park Jaesung , 봉태호 Bong Taeho

DOI: JKWST Vol.57(No.6) 107-115, 2015

---

The objective of the this study is to find the breakage index and changes in permeability of Bottom ash from thermoelectric power plants in Korea. Bottom ash was crushed by compaction according to compaction energy from 0 to 1661.4 kN/m 2 . The particle size distribution was estimated by sieve analysis. The various breakage indexes were used for analyzing the change in particle size distribution and effect of compaction energy. In the result, breakage indexes were increased as compaction energy and initial upper 4.75 mm diameter ratio, but values and tendencies of breakage indexes appeared in different as calculation method of breakage indexes. The coefficient of permeability was decreased with particle breakage, but decreasing ratio of permeability was very small. Bottom ash has a higher permeability than the weathered soil and it is considered high usability as a permeable materials.

이성행 Lee Seong Haeng , 함형길 Hahm Hyung-gil , 유광식 Ryu Goang Sik

DOI: JKWST Vol.57(No.6) 117-123, 2015

---

An experimental study of model truss-type vertical gate consisting of a truss and a plate was presented in this paper to examine the structural dynamics of the gates. A 1:61 scale model was constructed for the 95 m prototype gate using an acrylic truss and an acrylonitrile butadiene styrene plate. The scaled model was tested in a 1.6 m wide concrete flume for two orientations to determine the effects of gate orientation on structural vibrations. Natural frequencies of the model gate was measured and calibrated with FEM predictions. Vertical vibrations were measured under various operational conditions, including a range of bottom opening heights and different upstream and downstream water levels. The gate model with reverse direction was preferred due to its low overall vibrational response and flow level combinations. The test results also provide a basic dataset for development of operations guidelines that minimize flow-induced vibrations of the gates.

최용훈 Yonghun Choi , 김영진 Youngjin Kim , 김승희 Seounghee Kim , 김민영 Minyoung Kim

DOI: JKWST Vol.57(No.6) 125-130, 2015

---

Field study was carried out to assess the effect of automatic inlet and filtration outlet to reduce non-point source discharge and save agricultural irrigation water from paddy. The comparison of control and treated plots showed that irrigation water was saved up to 58 mm and discharge water was reduced up to 110 mm. The filtration outlet improved the discharge water quality for SS, COD, TN and TP up to 60.1 %, 0.1 %, 4.5 %, and 26.0 %, respectively. Overall, the findings of this study indicated that non-point source pollution discharged from paddy fields where automatic inlet and filtration outlet were installed could be reduced 266.3 kg/ha/yr in SS, 10.3 kg/ha/yr in COD, 1.22 kg/ha/yr in TN, and 0.10 kg/ha/yr in TP, respectively. This clearly showed that the automatic inlet and filtration outlet are effective management method for saving of agricultural water and protecting water environment.

송호성 Song Hosung , 김유용 Kim Yu Yong , 윤남규 Yun Nam Kyu , 임성윤 Lim Seong Yoon

DOI: JKWST Vol.57(No.6) 131-140, 2015

---

This paper presents overall procedure by experimental study in order to deriving design factors of snow removal machine on roof of multi-span greenhouse. For the purpose of the testing, the scale model of the machine was made in the form to drive above the monorail. The test was performed in order to calculating friction coefficient of the machine and shear coefficient between sliced horizontal section of snow at constant temperature and humidity room in National Academic of Agricultural Science. As a result of the laboratory test, shear coefficient between sliced horizontal section of snow were calculated 1.60∼2.37. Further investigation, we will study to derive the relationship between the real and scaled model through the field test.

최원 Choi Won , 우재형 Woo Jae-hyeong , 전정배 Jeon Jeong-bae , 윤성수 Yoon Seong-soo

DOI: JKWST Vol.57(No.6) 141-152, 2015

---

Most of agricultural structures are consisted of complex components and exposed to various boundary conditions. There have been no ways to express those structures exactly for model experiment. As an alternative, 3D printer can produce any type of solid model. However, there are limited informations related to structural experiments using 3D printer. The object of this study gives the basic informations to structural engineers who try to use 3D printer for model experiment. When PLA was used as a supplier for 3D printer, the outcomes showed less heat deformation to compare with ABS. To test the material properties, two kinds of experiments (three-point flexibility test and compression test) were executed using universal testing machine. In three-point flexibility test, plastic hinge and its deformation were developed as observed in material such as steel. The behavior was in a linear elastic state, and elastic bending modulus and yield force were evaluated. In the compression test using unbraced columns with hinge-hinge boundary condition, the constant yield forces were observed regardless of different lengths in all columns with same section size, whereas the compressive elastic modulus was increased as the length of column was increased. The suggested results can be used for model experiments of various agricultural structures consisted of single material.

윤정혜 Yun Jung-hye , 황세운 Hwang Syewoon , 김동현 Kim Dong-hyeon , 김상민 Kim Sang-min

DOI: JKWST Vol.57(No.6) 153-162, 2015

---

In this study, we analyzed the trends of water quality along the main stream in Nakdong river basin using the recent data and seasonal Mann-Kendall test. Monthly averaged values of DO, BOD, SS, COD, TN, and TP from 1989 to 2014 for 14 stations (including 2 TMDLs stations) were used in the study. The trend analysis results showed that BOD and TP at most stations has decreasing temporal trend except a few stations while COD and SS showed increasing trend at most stations. Temporal trends in TN at 8 stations were found to be statistically significant and 5 of them showed increasing temporal trend. Temporally averaged BOD, COD, TN and TP were generally increasing as going downstream and the worst water quality were found at Goryeong and Hyunpung station. Overall, water quality of Nakdong river especially in COD, SS, and TN getting worse in time at most stations and as going downstream.

장민원 Jang Min-won , 박기욱 Park Ki-wook , 김성준 Kim Seong Joon , 배승종 Bae Seung-jong

DOI: JKWST Vol.57(No.6) 163-171, 2015

---

This study aimed to establish a field observation system for monitoring tempo-spatially precise changes of groundwater level and to analyze the impact of rainfall and irrigation practices on groundwater changes in paddy regions. The monitoring system comprising of all nine groundwater observation wells and four ponding depth sensors was installed in a part of paddy regions benefited from Gosam reservoir, Ansung-si. The result of grundwater level change during the irrigation period in 2002 was averagely 0.51 m higher than that during the non-irrigation period. In particular between March before puddling and June after transplanting, there was maximum 1.23 m rise in groundwater level. On the other hand, concerning the change in ponding depth, groundwater level changed similarly, and hourly rainfall was revealed to have better correlation with 24-hour delayed hourly groundwater level than with the corresponding groundwater level. Eventually, this study could be referenced for further studies to set up a more comprehensive and sustainable monitoring system of groundwater conditions.

홍민기 Hong Min-ki , 이상현 Lee Sang-hyun , 최진용 Choi Jin-yong , 이성학 Lee Sung-hack , 이승재 Lee Seung-jae

DOI: JKWST Vol.57(No.6) 173-183, 2015

---

The aim of this study was to develop a soil moisture simulation model equipped with meteorological data enhanced by WRF (Weather Research and Forecast) model, and this soil moisture model was applied for quantifying soil moisture content and irrigation requirement. The WRF model can provide grid based meteorological data at various resolutions. For applicability assessment, comparative analyses were conducted using WRF data and weather data obtained from weather station located close to test bed. Water balance of each upland grid was assessed for soils represented with four layers. The soil moisture contents simulated using the soil moisture model were compared with observed data to evaluate the capacity of the model qualitatively and quantitatively with performance statistics such as correlation coefficient (R), coefficient of determination (R2) and root mean squared error (RMSE). As a result, R is 0.76, R² is 0.58 and RMSE 5.45 mm in soil layer 1 andR 0.61, R² 0.37 and RMSE 6.73 mm in soil layer 2 and R 0.52, R² 0.27 and RMSE 8.64 mm in soil layer 3 and R 0.68, R² 0.45 and RMSE 5.29 mm in soil layer 4. The estimated soil moisture contents and irrigation requirements of each soil layer showed spatiotemporally varied distributions depending on weather and soil texture data incorporated. The estimated soil moisture contents using weather station data showed uniform distribution about all grids. However the estimated soil moisture contents from WRF data showed spatially varied distribution. Also, the estimated irrigation requirements applied WRF data showed spatial variabilities reflecting regional differences of weather conditions.