• 한국환경농학회지
• /
• 제25권4호
• /
• pp.289-296
• /
• 2006

Various drying conditions, temperatures (40 to $80^{\circ}C$) and durations (overnight to 72 hrs), for the particulate organic matter (POM) fraction after wet-sieving size fractionation have been applied for determination of POM contents in the weight loss-on-ignition method. In this study, we investigated the optimum drying condition for POM fraction in quantification of POM and/or mineral-associated organic matter (MOM; usually indirectly estimated). The influence of the drying conditions on quantifying POM was dependent upon soil properties, especially the amount of soil organic components. In relatively high organic soils (total carbon > 40 g/kg in this study), the POM values were significantly higher (overestimated) with drying at $55^{\circ}C$ than those values at $105^{\circ}C$, which were, for example, 173.2 and 137.3 mg/kg, respectively, in a soil studied. However, drying at $55^{\circ}C$ for longer than 48 hrs of periods produced consistent POM values even though the values were much higher than those at $105^{\circ}C$. Thus, indirect estimates of MOM (MOM = SOM-POM) also tended to be significantly impacted by the dry conditions. Therefore, we suggest POM fractions should be dried at $105^{\circ}C$ for 24 hrs as determining POM and MOM contents. If the POM traction is needed to be dried at a lower temperature (e.g. $55^{\circ}C$) with a specific reason, at least 48 hrs of drying period is necessary to obtain consistent POM values, and a moisture correction factor should be determined to adjust the values back to a $105^{\circ}C$ weight basis.

• Computers and Concrete
• /
• 제25권4호
• /
• pp.311-325
• /
• 2020

In this research work, the hygrothermal and mechanical buckling responses of simply supported FG sandwich plate seated on Winkler-Pasternak elastic foundation are investigated using a novel shear deformation theory. The current model take into consideration the shear deformation effects and ensures the zero shear stresses on the free surfaces of the FG-sandwich plate without requiring the correction factors "Ks". The material properties of the faces sheets of the FG-sandwich plate are assumed varies as power law function "P-FGM" and the core is isotropic (purely ceramic). From the virtual work principle, the stability equations are deduced and resolved via Navier model. The hygrothermal effects are considered varies as a nonlinear, linear and uniform distribution across the thickness of the FG-sandwich plate. To check and confirm the accuracy of the current model, a several comparison has been made with other models found in the literature. The effects the temperature, moisture concentration, parameters of elastic foundation, side-to-thickness ratio, aspect ratio and the inhomogeneity parameter on the critical buckling of FG sandwich plates are also investigated.

• Steel and Composite Structures
• /
• 제39권5호
• /
• pp.631-643
• /
• 2021

The aim of this work is to study the hygro-thermo-mechanical bending responses of simply supported FG plate resting on a Winkler-Pasternak elastic foundation. The effect transverse shear strains is taken into account in which the zero transverse shear stress condition on the top and bottom surfaces of the plate is ensured without using any shear correction factors. The developed model contains only four unknowns variable which is reduced compared to other HSDTs models. The material properties of FG-plate are supposed to vary across the thickness of the plate according to power-law mixture. The differential governing equations are derived based on the virtual working principle. Numerical outcomes of bending analysis of FG plates under hygro-thermo-mechanical loads are performed and compared with those available in the literature. The effects of the temperature, moisture concentration, elastic foundation parameters, shear deformation, geometrical parameters, and power-law-index on the dimensionless deflections, axial and transverse shear stresses of the FG-plate are presented and discussed.

• 한국지하수토양환경학회지:지하수토양환경
• /
• 제26권1호
• /
• pp.1-7
• /
• 2021

Air-water interfacial area is of great importance for the analysis of contaminant mass transfer processes occurring in the soil systems. Capillary bundle model has been proposed to estimate the specific air-water interfacial areas in unsaturated soils. In this study, the measured air-water interfacial areas of a soil (loam) using the gaseous interfacial tracer technique were compared to those from capillary bundle model. The measured values converged to the specific solid surface area (7.6×104 ㎠/㎤) of the soil. However, the simulated air-water interfacial areas based on the capillary bundle model deviated significantly from those measured. The simulated values were substantially over-estimated at low end of the water content range, whereas the model under-estimated the air-water interfacial area for the most of the water content range. This under-estimation is considered to be caused by the nature of the capillary bundle model that replaces the soil pores with a bundle of glass capillaries and thus no surface roughness at the inner surface of the capillaries is taken into account for the estimation of the air-water interfacial area with the capillary bundle model. Subsequently, appropriate correction is necessary for the capillary bundle model to estimate the air-water interfacial area in soils. Since the soil-moisture release curve data is the basis of the capillary bundle model, the model can be of use due to its simplicity, while the gaseous tracer technique requires complicated experimental equipment followed by moment analysis of the breakthrough curves. The size distribution profile of the pores filled with gas estimated by the water retention curve was found to be similar to that of particle size at different size range. The shifted distribution of gas-filled pores toward smaller size side compared to the particle size distribution was also found.

• Steel and Composite Structures
• /
• 제43권6호
• /
• pp.821-837
• /
• 2022

This research is devoted to study the effects of humidity and temperature on the bending behavior of functionally graded (FG) ceramic-metal porous plates resting on Pasternak elastic foundation using a quasi-3D hyperbolic shear deformation theory developed recently. The present plate theory with only four unknowns, takes into account both transverse shear and normal deformations and satisfies the zero traction boundary conditions on the surfaces of the functionally graded plate without using shear correction factors. Material properties of porous FG plate are defined by rule of the mixture with an additional term of porosity in the through-thickness direction. The governing differential equations are obtained using the "principle of virtual work". Analytically, the Navier method is used to solve the equations that govern a simply supported FG porous plate. The obtained results are checked by comparing the results determined for the perfect and imperfect FG plates with those available in the scientific literature. Effects due to material index, porosity factors, moisture and thermal loads, foundation rigidities, geometric ratios on the FG porous plate are all examined. Finally, this research will help us to design advanced functionally graded materials to ensure better durability and efficiency for hygro-thermal environments.

• Computers and Concrete
• /
• 제32권1호
• /
• pp.61-74
• /
• 2023

This article investigates the wave propagation analysis of the imperfect functionally graded (FG) sandwich plates based on a novel simple four-variable integral quasi-3D higher-order shear deformation theory (HSDT). The thickness stretching effect is considered in the transverse displacement component. The presented formulation ensures a parabolic variation of the transverse shear stresses with zero-stresses at the top and the bottom surfaces without requiring any shear correction factors. The studied sandwich plates can be used in several sectors as areas of aircraft, construction, naval/marine, aerospace and wind energy systems, the sandwich structure is composed from three layers (two FG face sheets and isotropic core). The material properties in the FG faces sheet are computed according to a modified power law function with considering the porosity which may appear during the manufacturing process in the form of micro-voids in the layer body. The Hamilton principle is utilized to determine the four governing differential equations for wave propagation in FG plates which is reduced in terms of computation time and cost compared to the other conventional quasi-3D models. An eigenvalue equation is formulated for the analytical solution using a generalized displacements' solution form for wave propagation. The effects of porosity, temperature, moisture concentration, core thickness, and the material exponent on the plates' dispersion relations are examined by considering the thickness stretching influence.

• 대기
• /
• 제33권5호
• /
• pp.549-560
• /
• 2023

This study evaluates three distinct observation methods, CRDS, OA-ICOS, and OF-CEAS, in greenhouse gas monitoring equipment for atmospheric CO₂ and CH₄ concentrations. The assessment encompasses fundamental performance, high-concentration measurement accuracy, calibration methods, and the impact of atmospheric humidity on measurement accuracy. Results indicate that within a range of approximately 500 ppm, all three devices demonstrate high accuracy and linearity. However, beyond 1000 ppm, CO₂ accuracy sharply declines (84%), emphasizing the need for caution when interpreting high-concentration CO₂ data. An analysis of calibration methods reveals that both CO₂ and CH₄ measurements achieve high accuracy and linearity through 1-point calibration, suggesting that multi-point calibration is not imperative for precision. In dynamic atmospheric conditions with significant CO₂ and CH₄ concentration variations, a 1-point calibration suffices for reliable data (99% accuracy). The evaluation of humidity impact demonstrates that humidity removal devices significantly reduce air moisture levels, yet this has a negligible effect on dry CO₂ concentrations (less than 0.5% relative error). All three observation method instruments, which have integrated humidity correction to calculate dry CO₂ concentrations, exhibit minor sensitivity to humidity removal devices, implying that additional removal devices may not be essential. Consequently, this study offers valuable insights for comparing data from different measurement devices and provides crucial information to consider in the operation of monitoring sites.

• 한국토양비료학회지
• /
• 제45권6호
• /
• pp.1086-1093
• /
• 2012

본 연구는 유기성 바이오매스의 혐기소화율 평가에 주로 이용되는 VDI4630법에 대하여 소화액에 녹아 있는 탄산이온 ($CO_3{^{2-}}$)과 혐기소화 미생물 반응에 참여하는 수분 ($H_2O$)이 유기물의 혐기적 분해율에 미치는 영향을 분석하였으며, 이를 위해 탄산이온과 수분반응물에 의한 유기물의 혐기적 분해율 산출 보정식을 개발 하고자하였다. 돼지 혈액, 돼지 내장잔재물, 돼지 장내잔재물, 소 반추위잔재물의 화학조성식은 각각 $C_{3.78}H_{8.39}O_{1.46}N_1S_{0.01}$, $C_{9.69}H_{15.42}O_{2.85}N_1S_{0.03}$, $C_{25.17}H_{43.32}O_{15.04}N_1$, $C_{27.23}H_{42.38}O_{15.93}N_1S_{0.11}$으로 나타났으며, 돼지 혈액, 돼지 내장 잔재물, 돼지 장내잔재물, 소 반추위잔재물에서 이론적으로 1 mol의 유기물이 분해되는데, 0.336, 0.485, 0.227, 0.266 mol의 수분이 참여하였다. 혐기적 유기물 분해율에서 이론적 메탄생산퍼텐셜 대비 실험적 메탄생산퍼텐셜 ($B_u/B_{th}$)의 비율로 산출한 유기물 분해율은 돼지 혈액, 돼지 내장 잔재물, 돼지 장내잔재물, 소 반추위잔재물에서 각각 82.3, 81.5, 70.8, 66.1%이었으며, VDI4630에 근거한 유기물 분해율 (AB)은 각각 72.2, 87.8, 74.2, 62.0%를 보여 이론적 메탄생산퍼텐셜 대비 실험적 메탄생산퍼텐셜 ($B_u/B_{th}$)의 비율로 산출하는 유기물 분해율과는 전체 시험구에서 통계적으로 유의성 있는 차이를 보였다. VDI4630법에 소화액 중의 알칼리도를 보정한 유기물 분해율 (AB-I)은 돼지 혈액, 돼지 내장 잔재물, 돼지 장내잔재물, 소 반추위잔재물에서 각각 72.4, 88.1, 74.5, 62.1%를 보였으며, 알칼리도와 수분 반응물을 동시에 보정한 유기물 분해율 (AB-II)에서는 각각 72.5, 88.5, 74.5, 62.3%를 보여 본 연구에서 시험한 각각의 시료에서의 유기물 분해율 AB, AB-I, AB-II 간의 평균은 통계적으로 유의성 있는 차이를 보이지 않았다. 그러나 알칼리도, 수분 반응물의 보정식은 유기물의 혐기적 분해율의 측정에서 좀 더 높은 정확도를 보일 수 있을 것으로 판단된다.

• 한국근적외분광분석학회:학술대회논문집
• /
• 한국근적외분광분석학회 2001년도 NIR-2001
• /
• pp.1121-1121
• /
• 2001

A previous study (Berzaghi et al., 2001) evaluated the performance of 3 calibration methods, modified partial least squares (MPLS), local PLS (LOCAL) and artificial neural networks (ANN) on the prediction of the chemical composition of forages, using a large NIR database. The study used forage samples (n=25,977) from Australia, Europe (Belgium, Germany, Italy and Sweden) and North America (Canada and U.S.A) with reference values for moisture, crude protein and neutral detergent fibre content. The spectra of the samples were collected using 10 different Foss NIR Systems instruments, only some of which had been standardized to one master instrument. The aim of the present study was to evaluate the behaviour of these different calibration methods when predicting the same samples measured on different instruments. Twenty-two sealed samples of different kind of forages were measured in duplicate on seven instruments (one master and six slaves). Three sets of near infrared spectra (1100 to 2500nm) were created. The first set consisted of the spectra in their original form (unstandardized); the second set was created using a single sample standardization (Clone1); the third was created using a multiple sample procedure (Clone6). WinISI software (Infrasoft International Inc., Port Mathilda, PA, USA) was used to perform both types of standardization, Clone1 is just a photometric offset between a “master” instrument and the “slave” instrument. Clone6 modifies both the X-axis through a wavelength adjustment and the Y-axis through a simple regression wavelength by wavelength. The Clone1 procedure used one sample spectrally close to the centre of the population. The six samples used in Clone 6 were selected to cover the range of spectral variation in the sample set. The remaining fifteen samples were used to evaluate the performances of the different models. The predicted values for dry matter, protein and neutral detergent fibre from the master Instrument were considered as “reference Y values” when computing the statistics RMSEP, SEPC, R, Bias, Slope, mean GH (global Mahalanobis distance) and mean NH (neighbourhood Mahalanobis distance) for the 6 slave instruments. From the results we conclude that i) all the calibration techniques gave satisfactory results after standardization. Without standardization the predicted data from the slaves would have required slope and bias correction to produce acceptable statistics. ii) Standardization reduced the errors for all calibration methods and parameters tested, reducing not only systematic biases but also random errors. iii) Standardization removed slope effects that were significantly different from 1.0 in most of the cases. iv) Clone1 and Clone6 gave similar results except for NDF where Clone6 gave better RMSEP values than Clone1. v) GH and NH were reduced by half even with very large data sets including unstandardized spectra.

• 아시안잔디학회지
• /
• 제16권1호
• /
• pp.11-18
• /
• 2002

실제 골프장 토양환경에서 비료종류에 따른 계절별.토심별 토양 pH 변화를 규명하고자 안양 베네스트 골프클럽 내 들잔디 '중지'(Zoysta japonica Steud.)로 조성된 포장에서 산도 교정용으로 많이 이용하는 규산질비료(SiO$_2$) 및 석회석(CaCO$_3$) 2종류를 사용하여 규산질 비료 3수준, 석회석 비료 3수준으로 처리하여 실험한 결과 토층별로 현저한 차이가 관찰되었는데 전체 pH 평균을 보면 0~5cm의 표토가 6.54, 5~10cm가 5.80, 10~15cm의 심토에서는 5.04로 나타났다. 비료종류별 처리효과는 3개의 모든 층에서 1% 유의수준에서 고도의 유의성이 있는 것으로 나타났다. 표토인 0~5cm층에서 규산질 비료는 모두 유의한 증가를 보이지 않은 반면 석회질 비료구가 50kg/10a, 100kg/10a에서 유의적으로 증가하였으나 10~15cm 층에서는 규산질 비료 시비구가 100kg/10a, 200kg/10a에서 효과가 있었으나 석회질 비료는 유의한 증가가 인정되지 않았다. 그러나 5~10cm 층에서는 두 가지 비종 모두 유의한 증가를 나타내어 토심에 따른 차이가 있음을 알 수 있었다. 그리고 계절에 따른 경시적 토양산도 차이가 인정되고 이는 토심별로 차이가 인정되므로 토양 샘플 채취시 샘플시기를 고려해야 함을 알 수 있었다. 특히 표토(0~5cm)층의 토양산도가 지하층인(5~10cm, 10~15cm)에서보다 높은 것은 토양산도가 규소나 석회 같은 비료 함량에 의해서만 결정되는 것이 아니고 토양 모암의 상태나 유기물 함량, 강수량 등의 수분 함량, 온도, 토양의 통기성이나 호흡 등H$^{+}$ 이온농도에 영향을 미치는 제반여건이 영향을 미치는 것으로 이를 종합적으로 활용하여 토양산도를 조정해야 함을 알 수 있다.