• The Korean Journal of Ecology
• /
• v.17 no.3
• /
• pp.311-318
• /
• 1994

We examined spatial and temporal patterns of root decomposition for three and half years, from October 1986 to April 1990, in semi-arid Chihuahuan Desert. Decomposition of roots occurred in a two-phased pattern: an early period of rapid mass loss followed by a period of slower loss. The rate of root decomposition had a high negative correlation with the initial lignin concentration in roots (r=-0.84, p<0.05). Annual mass loss rate of Baileya multiradiata, a herbaceous annual, was the highest with the value of 0.60, while that of Panicum obtusum. a perennial grass which was restricted to playa, was the lowest with 0.13. The mass loss rate of roots in the playa was the lowest among the vegetation zones along the transect. After 42 months elapsed, fluffgrass roots in playa lost 40% of the initial mass, while in other sites it lost on average 55% of the initial mass. In all roots except for desert marigold, there was an initial release of nitrogen early in decomposition followed by net nitrogen immobilization. Nitrogen concentration of the desert marigold roots showed linear increase from the beginning. Lignin concentration of perennial grass roots were higher than those of herbaceous annual and woody perennial root.

• Publications of The Korean Astronomical Society
• /
• v.1 no.1
• /
• pp.1-8
• /
• 1984

Under the context of Stein's linear theory of stellar models, the luminosity-effective temperature relationship is derived for contracting pre-main sequence stars which are losing mass, according to the empirical formula, given by Reimers (1975). The effects of mass loss on their evolution are investigated by calculating evolutionary tracks of 1. $1.5M_{\odot}$, $5M_{\odot}$, and $10M_{\odot}$, stars. Our calculations reveal that the effects of mass loss show up in the radiative equilibrium stage of the evolution. It is found that an increase of mass loss rate leads to delay the onset of radiative equilibrium, thus resulting in under-luminous main sequence stars. It is also noted that the mass loss prolongs the pre-main sequence life time. Detailed results of the calculations are discussed.

• The Bulletin of The Korean Astronomical Society
• /
• v.43 no.1
• /
• pp.61.3-61.3
• /
• 2018

To understand the assembly of the galaxy population in clusters today, it is important to first understand the impact of previous environments prior to cluster infall, namely preprocessing. We use 15 cluster samples from hydrodynamic zoom-in simulation YZiCS to determine the significance of preprocessing focusing primarily on the tidal mass loss of dark matter halos. We find ~48% of the cluster member halos were once satellites of another host. The preprocessed fraction is not a clear function of cluster mass. Instead, we find it is related to each individual cluster's recent mass growth history. We find that the total mass loss is a clear function of time spent in a host. However, two factors can considerably increase the mass loss rate. First, if the satellite mass is approaching the mass of its host. Second, when the halo suffers tidal mass loss at a higher redshift. The preprocessing provides an opportunity for halos to experience tidal mass loss for a more extended period of time than would be possible if they simply fell directly into the cluster, and at earlier epochs when hosts were more destructive to their satellites.

• Journal of Electrochemical Science and Technology
• /
• v.2 no.1
• /
• pp.20-25
• /
• 2011

This work focuses on the behavior of the overpotential increase due to a utilization rise in a molten carbonate fuel cell. The behavior is generally explained by Nernst loss, which is a kind of voltage loss due to the thermodynamic potential gradients in a polarization state due to the concentration distribution of reactant species through the gas flow direction. The evaluation of Nernst loss is carried out with a traditional experimental method of constant gas utilization (CU). On the other hand, overpotential due to the gas-phase mass-transport resistance at the anode and cathode shows dependence on the utilization, which can be measured using the inert gas step addition (ISA) method. Since the Nernst loss is assumed to be due to the thermodynamic reasons, the voltage loss can be calculated by the Nernst equation, referred to as a simple calculation (SC) in this work. The three values of voltage loss due to CU, ISA, and SC are compared, showing that these values rise with increases in the utilization within acceptable deviations. When we consider that the anode and cathode reactions are significantly affected by the gas-phase mass transfer, the behavior strongly implies that the voltage loss is attributable not to thermodynamic reasons, namely Nernst loss, but to the kinetic reason of mass-transfer resistance in the gas phase.

• Fire Science and Engineering
• /
• v.24 no.1
• /
• pp.122-127
• /
• 2010

The combustion characteristics of phenol foam were analysed using variable external irradiation level (20, 25, 35, 50, and $70kW/m^2$) and in the mixture gas of oxygen/nitrogen. The oxygen index were carried out from the oxygen index tester (KS M ISO 4589-2) and ignition time, critical heat flux, and mass loss rate were carried out from the mass loss calorimeter (ISO 5660-1). As the results of this study, the critical heat flux and average mass loss rate were $28.99kW/m^2$ and $0.56{\sim}1.77g/m^2s$ respectively at the variable external irradiation level. And the limited oxygen index were 45.1% in mixture gas of oxygen/nitrogen. In conclusion, we knew that phenol foam had the best performance than other foam materials in fire safety from all data of this study.

• Journal of The Korean Astronomical Society
• /
• v.38 no.2
• /
• pp.267-270
• /
• 2005

We investigate the spectral energy distributions (SEDs) of low mass-loss rate O-rich asymptotic giant branch (AGB) stars using the infrared observational data including the Infrared Space Observatory (ISO) data. Comparing the results of detailed radiative transfer model calculations with observations, we find that the dust formation temperature is much lower than 1000 K for standard dust shell models. We find that the superwind model with a density-enhanced region can be a possible alternative dust shell model for LMOA stars.

• The Korean Journal of Ecology
• /
• v.26 no.6
• /
• pp.313-319
• /
• 2003

Dry weight loss and nutrient release from leaf litter for six tree species were studied using litter bag methods. The litter bags were incubated for f6 months on the forest floor in temperate deciduous forest in Mt. Cheonma, located at the middle part of Korean Peninsula. The changes in nutrient content and the rate of dry weight loss in leaf litter varied with litter types. The litter of Pinus densiflora showed the lowest rate of mass loss (k=0.33), nitrogen concentration (0.89%) and ash concentration (2.50%), while showed the highest C/N ratio (63.40). On the other hand, the litter of Acer pseudo-sieboldianum showed the fastest rate of mass loss (k=0.82), the highest nitrogen concentration (1.11%), and the lowest C/N ratio (49.40). During the decomposition, nitrogen, phosphorus and calcium in the leaf litters showed relatively slow decreasing pattern compared to other elements (carbon, potassium, magnesium, manganese and sodium), but potassium and sodium decreased at early stage of the decomposition for all leaf litters. Differences in annual decomposition rates of litter among species were consistent with the particular chemical characteristics of their leaf litters. The initial concentration of nitrogen was positively correlated with litter decomposition rate for six species, while litter decomposition rate of six species was negatively correlated with C:N ratio of initial leaf litters.

• Transactions of the Korean Society of Machine Tool Engineers
• /
• v.11 no.5
• /
• pp.88-92
• /
• 2002

This research is about slurry wear of SM45C and SUS304, which using standard sand and KUM river sand. The results are as follows ; 1. Mass loss rates of both standard sand and KUM river sand were linearly increased as increasement of time and velocity. 2. The average diameter of sand from relatively, less wear rate and portion of larger particles. 3. Wear resistance was linear with time and velocity of liquid jet regardless of type of sand. Also, it was able to evaluate with the formula, $HV^2$/E calibrated with n, the velocity index. 4. The wear surface in liquid jet experiment was smooth. The maximum wear depth was observed at the location 2~4mm apart from the center in the condition of $90^{\circ}$ of collision angle 6mm of nozzle diameter, and 20mm of collision distance. The sectional shape in radial appeared as 'W'shape.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2001.04a
• /
• pp.798-801
• /
• 2001

This research is about slurry wear of SM45C and SUS304, which using standard sand and KUM river sand. The results are as follows ; 1. Mass loss rates of both standard sand and KUM river sand were linearly increased as increasement of time and velocity. 2. The average diameter of sand from relatively, less wear rate and portion of larger particles. 3. Wear resistance was linear with time and velocity of liquid jet regardless of type of sand. Also it was able to evaluate with the formula, HV2/E calibrated with n, the velocity index. 4. The wear surface in liquid jet experiment was smooth. The maximum wear depth was observed at the location, 2~4mm apart from the center in the condition of 90$^{\circ}$of collision angle 6mm of nozzle diameter, and 20mm of collision distance. The sectional shape in radial appeared as 'W' shape.

• Journal of the Korean Society for Industrial and Applied Mathematics
• /
• v.12 no.1
• /
• pp.25-32
• /
• 2008

A pin fin is optimized based on the increasing rate of heat loss by using a two-dimensional analytic method. The optimum heat loss, corresponding optimum thermal resistance and fin length are presented as a function of the fin base thickness, convection characteristic numbers ratio, fin outer radius and ambient convection characteristic number. One of the results shows that both the optimum heat loss and fin length decrease linearly whereas the optimum thermal resistance increases very slightly with increase of the fin base thickness.