• Title/Summary/Keyword: decay class

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Comparison of Mass and Nutrient Dynamics of Coarse Woody Debris between Quercus serrata and Q. variabilis Stands in Yangpyeong

  • Kim, RaeHyun;Son, Yowhan;Hwang, Jaehong
    • The Korean Journal of Ecology
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    • v.27 no.2
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    • pp.115-120
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    • 2004
  • Coarse woody debris (CWD, $\ge$ 5 cm in maximum diameter) is an important functional component, especially to nutrient cycling in forest ecosystems. To compare mass and nutrient dynamics of CWD in natural oak forests, a two-year study was conducted at Quercus serrata and Q. variabilis stands in Yangpyeong, Kyonggi Province. Total CWD (snag, stump, log and large branch) and annual decomposition mass (Mg/ha) were 1.9 and 0.4 for the Q. serrata stand and 7.5 and 0.5 for the Q. variabilis stand, respectively. Snags covered 72% of total CWD mass for the Q. variabilis stand and 42% for the Q. serrata stand. Most of CWD was classified into decay class 1 for both stands. CWD N and P concentrations for the Q. variabilis stand significantly increased along decay class and sampling time, except for P concentration in 2002. There were no differences in CWD N concentration for the Q. serrata stand along decay class and sampling time. However, CWD P concentration decreased along sampling time. CWD N and P contents (kg/ha) ranged from 3.5∼4.7 and 0.8∼1.3 for the Q. serrata stand to 22.8∼23.6 and 3.7∼4.7 for the Q. variabilis stand. Nitrogen and P inputs (kg/ha/yr) into mineral soil through the CWD decomposition were 0.7 and 0.3 for the Q. serrata stand and 1.6 and 0.3 for the Q. variabilis stand, respectively. The number of CWD and decay rate were main factors influencing the difference in CWD mass and nutrient dynamics between both stands.

EXTINCTION AND POSITIVITY OF SOLUTIONS FOR A CLASS OF SEMILINEAR PARABOLIC EQUATIONS WITH GRADIENT SOURCE TERMS

  • Yi, Su-Cheol
    • Journal of the Chungcheong Mathematical Society
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    • v.30 no.4
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    • pp.397-409
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    • 2017
  • In this paper, we investigated the extinction, positivity, and decay estimates of the solutions to the initial-boundary value problem of the semilinear parabolic equation with nonlinear gradient source and interior absorption terms by using the integral norm estimate method. We found that the decay estimates depend on the choices of initial data, coefficients and domain, and the first eigenvalue of the Laplacean operator with homogeneous Dirichlet boundary condition plays an important role in the proofs of main results.

Evaluation of Natural Decay Durability on Valuable Domestic Softwoods by European Standard Test Method (유럽규격 시험방법에 의한 국산 유용 침엽수재의 천연 내후성 평가)

  • Lee, Jong-Shin;Kim, Young-Sook;Kim, Gyu-Hyeok;Kim, Kyung-Tae;Kim, Yoon-Hee
    • Journal of the Korea Furniture Society
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    • v.26 no.3
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    • pp.222-228
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    • 2015
  • To evaluate the natural decay durability of valuable domestic softwoods which are used for preservative treatment in our country, we carried out decay test by European standard method. Of all test wood species, Japanese larch (Larix leptolepis) showed slightly high natural decay durability compared to other 4 wood species, Japanese red pine (Pinus densiflora), pitch pine (Pinus rigida), Japanese cedar (Cryptomeria japonica), and scots pine (Pinus sylvestris). However, all of evaluated domestic softwood species in this study caused high weight losses over about 30% in heartwood by test fungus, Poria placenta. We can hardly expect a good natural decay durability from these softwood species. According to the classification of the natural durability of European standard (EN 350-1), they are classified into "Not durable" or "Slightly durable". Therefore, if using these softwoods as exterior materials, we must do preservative treatment to ensure durability.

GLOBAL SOLUTION AND BLOW-UP OF LOGARITHMIC KLEIN-GORDON EQUATION

  • Ye, Yaojun
    • Bulletin of the Korean Mathematical Society
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    • v.57 no.2
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    • pp.281-294
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    • 2020
  • The initial-boundary value problem for a class of semilinear Klein-Gordon equation with logarithmic nonlinearity in bounded domain is studied. The existence of global solution for this problem is proved by using potential well method, and obtain the exponential decay of global solution through introducing an appropriate Lyapunov function. Meanwhile, the blow-up of solution in the unstable set is also obtained.

ENERGY DECAY FOR A VISCOELASTIC EQUATION WITH BALAKRISHNAN-TAYLOR DAMPING INVOLVING INFINITE MEMORY AND NONLINEAR TIME-VARYING DELAY TERMS IN DYNAMICAL BOUNDARY

  • Soufiane Benkouider;Abita Rahmoune
    • Communications of the Korean Mathematical Society
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    • v.38 no.3
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    • pp.943-966
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    • 2023
  • In this paper, we study the initial-boundary value problem for viscoelastic wave equations of Kirchhoff type with Balakrishnan-Taylor damping terms in the presence of the infinite memory and external time-varying delay. For a certain class of relaxation functions and certain initial data, we prove that the decay rate of the solution energy is similar to that of relaxation function which is not necessarily of exponential or polynomial type. Also, we show another stability with g satisfying some general growth at infinity.

Assessment of Coarse Woody Debris in Gallery Forest in the Bombo-Lumene Reserve (Democratic Republic of Congo)

  • Rusaati, Butoto Imani wa;Joo, Sung-Hyun;Yun, Gi-Yun;Park, Joowon;Cephas, Masumbuko Ndabaga;Kang, Jun-Won
    • Journal of Forest and Environmental Science
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    • v.35 no.3
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    • pp.205-211
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    • 2019
  • The objective of this research was to assess the amount of carbon stock of coarse woody debris (CWD) in Bombo-Lumene Reserve. Data on lying CWD was collected on 35 circular sampling plots using Line Intersect Sampling (LIS) method. A total of 230 samples CWD (${\geq}10cm$ diameter) were inventoried. The mean carbon stocks of CWD was $29.48Mg\;C\;ha^{-1}$, ranging from 4.32 to $73.54Mg\;C\;ha^{-1}$. The CWD carbon stocks displayed a wide range of variation in decay states. The allocation of CWD among the decay class of all the CWD samples reveals that the most important classes were class 1 and class 3 with 323.66 and $321.96Mg\;C\;ha^{-1}$, followed by class 4 with 264.56 and the last one was class 2 with $121.72Mg\;C\;ha^{-1}$. The results suggested that the dead wood component is important in carbon sequestration and should be taken into consideration for quantification of carbon stocks not only in Bombo-Lumene Reserve, but in all forest ecosystems in the Democratic Republic of Congo.

A study on charging and electrical stability characteristics with no-insulation and metal insulation in form of racetrack type coils

  • Quach, Huu Luong;Kim, Ho Min
    • Progress in Superconductivity and Cryogenics
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    • v.22 no.3
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    • pp.13-19
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    • 2020
  • This study presents the experiment and simulation results on the magnetic field response and electrical stability behaviors of no-insulation (NI) and metal insulation with stainless steel tape (MI-SS) which wound in form of racetrack type coils. First of all, the structural design of the racetrack type bobbin was shown along with its parameters. Then, the current-voltage tests were carried out to measure the critical current of both test coils. Also, the sudden discharging and charging tests were performed in the steady state to estimate the decay field time and magnetic field response, respectively. Finally, the overcurrent tests were conducted in the transient state to investigate the electrical stability of these test coils. Based on the experimental results, the contact surface resistances were calculated and applied to the field coils (FCs) of 10-MW-class second generation high temperature superconducting generator (2G HTSG) used in wind offshore environment. The charging delay time and electrical stability for NI and MI-SS HTS FCs of 10-MW-class 2G HTSG are analyzed by the equivalent circuit model and the key parameters which were obtained from the electromagnetic finite element analysis results.

Combustion Stability Evaluation of 30 ton-f Class Liquid Rocket Engine Combustor (30톤급 엑체로켓엔진 연소기의 연소안정성 평가)

  • Lim, Byoung-Jik;Lee, Kwang-Jin;Kim, Mun-Ki;Kang, Dong-Hyuk;Yang, Seung-Ho;Seo, Seong-Hyeon;Han, Yeoung-Min;Choi, Hwan-Seok
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2008.05a
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    • pp.163-167
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    • 2008
  • This paper presents pressure fluctuation characteristics of a 30 ton-f class liquid rocket engine combustor. Combustion stability of the combustor was evaluated using the results 46 firing tests performed with a varying O/F ratio and chamber pressure. The RMS value of pressure fluctuation during the steady state combustion was less than 2.6% of the static chamber pressure, demonstrating static stability of the combustion phenomenon. The decay time of pressure fluctuation caused by forced disturbance of a pulse gun was found to be less than 3.5 msec verifying dynamic stability of the combustor.

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Estimating Wildfire Fuel Load of Coarse Woody Debris using National Forest Inventory Data in South Korea

  • Choi, Suwon;Lee, Jongyeol;Han, Seung Hyun;Kim, Seongjun;Son, Yowhan
    • Journal of Climate Change Research
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    • v.6 no.3
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    • pp.185-191
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    • 2015
  • This study presents an estimate of on-site surface fuel loadings composed of coarse woody debris (CWD) using $5^{th}$ National Forest Inventory (NFI) data in South Korea. We classified CWD data into forest type, region and decay class, and used conversion factors by decay class and tonne of oil equivalent developed in the country. In 2010, the total wildfire fuel load of CWD was estimated as 8.9 million TOE; those of coniferous, deciduous and mixed forests were 3.5 million TOE, 2.8 million TOE and 2.6 million TOE, respectively. Gangwon Province had the highest wildfire fuel load of CWD (2.3 million TOE), whereas Seoul exhibited the lowest wildfire fuel load of CWD (0.02 million TOE). Wildfire fuel loads of CWD were estimated as 2.9 million TOE, 1.9 million TOE, 2.4 million TOE and 1.7 million TOE for decay classes I, II, III and IV, respectively. The total wildfire fuel load of CWD corresponded to the calorific value of 8.2 million tons crude oil, 2.46% of that of living trees. Proportionate to the growing stock, total wildfire fuel load of CWD was in a broad distinction by region, while its TOE $ha^{-1}$ was not. This implies that there is no need to establish different guidelines by region for management of CWD. The results of this work provide a baseline study for scientific policy guidelines on preventing wildfires by proposing CWD as wildfire fuel load.