• Journal of Climate Change Research
• /
• v.5 no.4
• /
• pp.339-348
• /
• 2014

Agro-ecosystem plays an important role in the mitigation of atmospheric $CO_2$ concentration through photosynthesis and soil carbon fixation. The perennial crops have capacity of carbon accumulation because they have lived for years in the same position. Carbon dioxide fixation occurs in the fruit orchard by photosynthesis and soil carbon sequestration. The objectives of this review are to introduce the fruit orchard as a carbon dioxide sink and to summarize the methods that measure $CO_2$ flux in the orchard. There are three difference methods (chamber, biomass, and eddy covariance method) to measure $CO_2$ exchanges on sites. However, there is no standard method suitable for fruit cultivation condition in Korea. Thus the standard method have to be developed in order to exactly estimate the carbon accumulation. In foreign studies, the carbon assessments were conducted in apple, peach, olive, grape orchard and so on. On the other hand the estimation of $CO_2$ exchange was carried out for apple and mandarine orchard in Korea. According to these results, fruit orchard is a $CO_2$ sink even though amount of carbon accumulation is smaller than the forest. To introduce certainly fruit orchard as greenhouse gas sink, long-term monitoring and further study have to be conducted under each planting condition.

• Journal of Environmental Science International
• /
• v.11 no.8
• /
• pp.773-781
• /
• 2002

The natural carbon cycle has been perturbed since the mid-19th century by anthropogenic CO$_2$emissions from fossil fuel combustion and deforestation due to population growth and industrialization. The current study simulated the global carbon cycle for the past 42 years using an eight-box carbon cycle model. The results showed that since the terrestrial biospheric carbon sink was roughly offset by the deforestation source, the fossil fuel emission source was partitioned between the atmospheric and oceanic sinks. However, the partitioning ratio between the atmosphere and the ocean exhibited a change, that is, the carbon accumulation rate was faster in the atmosphere than in the ocean, due to a decrease in the so-called ocean buffering capacity. It was found that the ocean buffering capacity to take up excess CO$_2$decreased by 50% in terms of the buffer factor over the past 42 years. Accordingly, these results indicate that if the current CO$_2$emission trend continues, the future rate of increase in the atmospheric CO$_2$concentration will accelerate.

• Journal of Korea Multimedia Society
• /
• v.10 no.10
• /
• pp.1347-1355
• /
• 2007

A sensor network is composed of a large number of tiny devices, scattered and deployed in a specified regions. Each sensing device has processing and wireless communication capabilities, which enable it to gather information from the sensing area and to transfer report messages to a base station. The energy-efficient routing paths are established when the base station requests a query, since each node has several characteristics such as low-power, constrained energy, and limited capacity. The established paths are recovered while minimizing the total transmit energy and maximizing the network lifetime when the paths are broken. In this paper, we propose a routing algorithm that each sensor node reports its adjacent link information to the sink node when a sink node broadcasts a query. The sink node manages the total topology and establishes routing paths. This algorithm has a benefit to find an alternative path by reducing the negotiating messages for establishing paths when the established paths are broken. To reduce the overhead of collection information, each node has a link information before reporting to the sink. Because the node recognizes which nodes are adjacent. The proposed algorithm reduces the number of required messages, because sensor nodes receive and report routing messages for establishment at the beginning of configuring routing paths, since each node keeps topology information to establish a routing path, which is useful to report sensing tasks in monitoring environments.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.16 no.11
• /
• pp.7250-7255
• /
• 2015

The objective of this study is to experimentally investigate the heating performances of the portable air combustion heater using diesel fuel for auxiliary cabin heating of the battery electric vehicle. In order to evaluate the heating performances of the air combustion heater, the heating capacity was calculated by the temperature at inlet and outlet parts of the considered heater and the inner temperature distribution characteristics of the vehicle were measured during 1600 seconds with an interval of 1 second. The theoretical efficiency of the tested heater was calculated by temperature data of the air of supplying and exhausting to the cabin. As the air passed the heat-sink, the air temperature at the end of heat-sink reached to $101.3^{\circ}C$ and the difference of temperature on heat-sink was 67.8%. The average heating capacity of the air combustion heater showed 2.0 kW. After 1800 seconds, the inner temperature of the vehicle cabin was continuously increased. The temperatures of the top side and the bottom side of the car cabin under consideration were increased upto $42.5^{\circ}C$ and $24.3^{\circ}C$, respectively, and the theoretical efficiency of the tested heater was on average 63.7%.

• Journal of Korean Society of Industrial and Systems Engineering
• /
• v.19 no.40
• /
• pp.263-269
• /
• 1996

The most vital arc in the maximum flow problem is that arc whose removal results in the greatest reduction in the value of the maximal flow between a source node and a sink node. This paper develops an algorithm to determine such a most vital arc(MVA) in the maximum flow problem. We first define the transformed network corresponding In a given network in order to compute the minimal capacity for each candidate arc. The set of candidate arcs for a MVA consists of the arcs whose flow is at least as greate as the flow over every arc in a minimal cut As a result, we present a method in which the MVA is determined more easily by computing the minimal capacity in the transformed network. The proposed method is demonstrated by numerical example.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.16 no.1
• /
• pp.62-69
• /
• 2004

Thermoelectric module is a device that can produce cooling in a direct manner using the electrical energy. The purpose of this study is to investigate the performance of thermoelectric module and cooling system equipped with the thermoelectric module. The performance of a thermoelectric module is estimated using two methods; theoretical analysis based on one-dimensional energy equations and experimental tests using heat source, heat sink and brass conduction extenders. For the thermoelectric cooling system, the temperatures in the chamber are recorded and then compared with those of lumped system analysis. The results show that the cooling capacity and COP of the thermoelectric module increases as the temperature difference between hot and cold surface decreases, and there is particular current at which cooling capacity reaches its maximum value. The experimental results for the thermoelectric cooling system are similar to those of lumped system analysis.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.26 no.5
• /
• pp.224-230
• /
• 2014

The purpose of this paper is to investigate the performance of supplemental cooling and heating system equipped with the 1 kW thermoelectric module. The system consist of 96 thermoelectric modules, heat sink with louver fin and water cooling jacket which is attached on the hot side of the thermoelectric module. The cooling and heating performance test of the thermoelectric system is conducted with various conditions, such as intake voltage, air inlet temperature, air flow volume, water inlet temperature and water flow rate at calorimeter chamber in consideration of environmental conditions in realistic vehicle drive. The experimental results of a thermoelectric system shows that the cooling capacity and COP is 1.03 kW, and 1.0, and heating capacity and COP is 1.53 kW, and 1.5 respectively.

• Journal of the Semiconductor & Display Technology
• /
• v.15 no.2
• /
• pp.55-60
• /
• 2016

This study was developed through the secondary battery module charging/discharger possible utilization in the production process equipment circuit. The developed module is ensuring construction of efficient and productive charging and discharger through this research a limit on the yield and the price of existing single -channel charge and discharger circuit as a 5V 70A grade secondary battery Formation charge and discharger for up to 1 board 4 channels. In order to improve the sensing accuracy, through a robust differential amplifier circuit described using 16bit Analog-Digital Converter and noise was secured 16bit resolution sensing. The configuration also made demands for property Rise / Fall Time. Data Acquisition, discharge efficiency and also to fit the sink circuit temperature level for mass production.

• Journal of the Korean Operations Research and Management Science Society
• /
• v.25 no.2
• /
• pp.115-124
• /
• 2000

The most vital arc in the maximum flow problem is that arc whose removal results in the greatest reduction in the value of the maximal flow between a source node and a sink node. This paper develops an algorithm to determine such a most vital arc in the maximum flow problem. We first define the transformed network corresponding to a given network in order to compute the minimal capacity for each candidate arc. The set of candidate arcs for single most vital arc consists of the arcs whose flow is at least as great as the flow over every arc in a minimal cut. As a result we present a method in which the most vital arc is determined more easily by computing the minimal capacity in the transformed network. the proposed method is demonstrated by numerical example and computational experiment.

• Journal of Power System Engineering
• /
• v.20 no.2
• /
• pp.91-96
• /
• 2016

A fleet consists of a main vessel, light vessels and carrying vessels for purse seine fishery. Carrying vessels contains fish storages to maintain freshness of catches. Currently most carrying vessels applies the cooling system using plain ice though accompanied various shortcomings. Seawater cooling system directly chilling seawater are now in use on carrying vessels in some developed countries to make up for these shortcomings and maximize advantages. This research deals with necessity of seawater cooling systems and establishes system criteria using Aspentech HYSYS program, prior to an experiment of compact-scale seawater cooling system which now in progress of manufacture. Performance comparison on condensation capacity, mass flow rate of working fluid, compressor power input, pump power input and others of the seawater cooling system applying a flooded evaporator is conducted with respect to the temperature of surface seawater varying according to seasons. The result presents that mass flow rate circulating the system is increased about 16.7% as the temperature of surface seawater increases. At the same condition, condensation capacity and compressor input work also increase about 9.8% and 91.2%, respectively.