• The KIPS Transactions:PartC
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• v.14C no.3 s.113
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• pp.229-238
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• 2007

Sensor networks consist of many tiny sensor nodes that collaborate among themselves to collect, process, analyze, and disseminate data. In sensor networks, sensor nodes are typically powered by batteries, and have limited computing resources. Moreover, the redeployment of nodes by energy exhaustion or their movement makes network topology change dynamically. These features incur problems that do not appear in traditional, wired networks. Security in sensor networks is challenging problem due to the nature of wireless communication and the lack of resources. Several efforts are underway to provide security services in sensor networks, but most of them are preventive approaches based on cryptography. However, sensor nodes are extremely vulnerable to capture or key compromise. To ensure the security of the network, it is critical to develop suity mechanisms that can survive malicious attacks from "insiders" who have access to the keying materials or the full control of some nodes. In order to protect against insider attacks, it is necessary to understand how an insider can attack a sensor network. Several attacks have been discussed in the literature. However, insider attacks in general have not been thoroughly studied and verified. In this paper, we study the insider attacks against routing protocols in sensor networks using the Ad-hoc On-Demand Distance Vector (AODV) protocol. We identify the goals of attack, and then study how to achieve these goals by modifying of the routing messages. Finally, with the simulation we study how an attacker affects the sensor networks. After we understand the features of inside attacker, we propose a detect mechanism using hop count information.

• Journal of Korean Society of Transportation
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• v.22 no.3 s.74
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• pp.7-16
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• 2004

The purpose of this study was to find the characteristics of travel behavior and accessibility in terms of spatial structure. We analyzed travel behaviors and accessibility using a mode choice model and the Complementary Accessibility Index(CAI). The urban spatial structures that were compared were a compact city (CC) versus a sprawled city (SC), and high residential density districts (HD) versus low residential density districts (LD). First, CC and HDs residents had a shorter commuting distance than the CC and LDs residents. Second, behavior models showed that the use of Private cars for commuting in SCs was found to be greater than private car use in CCs, and that public transportation modes would be encouraged in CCs. Third, changes associated with the time and cost of commuting by private car generally affect the demand for public transportation modes in the CC. Also, analysis of cross elasticity suggests that changes of subway travel time affect the demand for buses very elastically. Fourth, the CAI of SC and LD were superior to the CC and HD even though the SC inefficient urban forms in terms of spatial structure. So, the spatial distribution of population density was also found to be an important factor affecting accessibility and energy savings.

• Journal of the Korean Operations Research and Management Science Society
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• v.17 no.1
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• pp.117-117
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• 1992

Pubilc utility industries including the electric utility industry are facing a new stream of privatization com-petition with the private sector and deregulation. The necewssity to solve now and in the future power supply and demand problems has been increasing through the sophisticated generation expansion plan(GEP) approach con-sidering not only KEPCo's supply-side resources but also outside resources such as non-utility generation(NUG) demand-side management (DSM). Under the environmental situation in the current electric utility industry a new approach is needed to acquire multiple resources competitively. This study presents the development of a modified electric generation expansion analysis system(EGEAS) model with avoided cost based on the existing EGEAS model which is a dynamic program to develope an optimal generation expansion plan for the electric utility. We are trying to find optimal GEP in Korea's case using our modified model and observe the difference for the level of reliabilities such as the reserve margin(RM) loss of load probability(LOLP) and expected unserved energy percent(EUEP) between the existing EGEAS model and our model. In addition we are trying to calculate avoided cost for NUG resources which is a criterion to evaluate herem and test possibility of connection calculation of avoided cost with GEP implementation using our modified model. The results of our case study are as follows. First we were able to find that the generation expansion plan and reliability measures were largely influenced by capacity size and loading status of NUG resources, Second we were able to find that avoided cost which are criteria to evaluate NUG resources could be calculated by using our modified EGEAS model with avoided cost. We also note that avoided costs were calculated by our model in connection with generation expansion plans.

• Korean Journal of Environment and Ecology
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• v.33 no.5
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• pp.596-604
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• 2019

This study conducted a sediment culture experiment to investigate the effects of sediment oxygen demand (SOD) and environmental factors on sediment and water quality. We installed a leaching tank in the laboratory, cultured it for 20 days, and analyzed the relationship between P and Fe in the sediment. As a result, the dissolved oxygen of the water layer decreased with time, while the oxidation-reduction potential of the sediment progressed in the negative direction to form an anaerobic reducing environment. The SOD was measured to be 0.05 mg/g at the initial stage of cultivation and increased to 0.09 mg/g on the 20th day, indicating the tendency of increasing consumption of oxygen by the sediment. The change is likely to have caused by oxygen consumption from biological-SOD, which is the decomposition of organic matter accumulated on the sediment surface due to the increase of chl-a, and chemical-SOD consumed when the metal-reducing product produced by the reduction reaction is reoxidized. The correlation between SOD and causality for sediment-extracted sediments was positive for Ex-P and Org-P and negative for Fe-P. The analysis of the microbial community in the sediment on the 20th day showed that anaerobic iron-reducing bacteria (FeRB) were the dominant species. Therefore, when the phosphate bonded to the iron oxide is separated by the reduction reaction, the phosphate is eluted into the water to increase the primary productivity. The reduced substance is reoxidized and contributes to the oxygen consumption of the sediment. The results of this study would be useful as the reference information to improve oxygen resin.

• Journal of the Korean GEO-environmental Society
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• v.22 no.2
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• pp.15-23
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• 2021

A method of improving the post-management end system of a landfill that reflected total pollutant load was applied to the SUDOKWON 1st Landfill Site. Modeling results showed that the ratio of remaining methane, when compared to the total maximum potential of 2,521 × 106 Nm3, was estimated to be 8.8% in 2020, 7.0% in 2030, and 6.5% in 2040. If the average oxidation rate of 89.1% in 2005-2019 was applied, the ratio decreased by 1.01% in 2020, 0.76% in 2030, and 0.70% in 2040. This suggests that if the amount of methane generated is all emitted from the surface of the landfill after 2025, the real amount emitted to the atmosphere is less than that in 2019; therefore, the post-management end is possible. According to the results of trend analysis of the quality of leachate water, effluent criteria for Biochemical Oxygen Demand (BOD) can be satisfied in 2024, while those for Chemical Oxygen Demand (COD) and Total Nitrogen (T-N) can be satisfied in 2047 and 2117, respectively. If the post-management end system changed based on total pollutant load, the post-management can be terminated BOD today and COD within a few years; however, the fact that T-N could be terminated only after 2041 shows the need to fundamentally change management methods.

• Journal of the Korean Ceramic Society
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• v.53 no.2
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• pp.194-199
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• 2016

Presently, for the cement industry, studies that seek to reduce $CO_2$, because of the development of the plastic industry and demand for reduction of energy use, have been actively conducted among them, studies attempting to use Gamma-$C_2S({\gamma}-C_2S)$ to fix $CO_2$ have been actively conducted. The ${\gamma}-C_2S$ compound has an important function in reacting to $CO_2$ and stiffening through carbonatization in the air. The ${\gamma}-C_2S$ compound, reacting to $CO_2$ in the air, generates $CaCO_2$ within the pore structure of cement materials and densifies the pore structure this leads to an improvement of the durability and to the characteristic of resistance against neutralization. Therefore, in this experiment, in order to synthesize ${\gamma}-C_2S$, limestone sludge and waste foundry sands are used these materials are plasticized for 30 or 60 minutes at $1450^{\circ}C$, and are prevented from being cooled in the temperature range of $30{\sim}1000^{\circ}C$ when they are about to be cooled. XRD analysis and XRF analysis are used to determine the effects of this process on ${\gamma}-C_2S$ synthesization, the temperature at which a thing is plasticized, and the conditions for cooling that obtain in the plasticized clinker also, in order to confirm the $CO_2$ capture function, analysis of the major hydration products is conducted through an analysis of carbonatization depth and compressive strength, and through MIP analysis and XRD Rietveld analysis. As a result of these analyses, it is found that when ${\gamma}-C_2S$ was synthesized, the clinker that was plasticized at $1450^{\circ}C$ for one hour demonstrated the highest yield rate the sample with which the ${\gamma}-C_2S$ was mixed generated $CaCO_3$ when it reacted with $CO_2$ therefore, carbonatization depth and porosity were reduced, and the compressive strength was increased.

• Analytical Science and Technology
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• v.35 no.5
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• pp.205-211
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• 2022

Deuterium (D) is an isotope with one more neutron number than hydrogen (H). Heavy elements rarely change their chemical properties with little effect even if the number of neutrons increases, but low-mass elements change their vibration energy, diffusion rate, and reaction rate because the effect cannot be ignored, which is called an isotope effect. Recently, in the semiconductor and display industries, there is a trend to replace hydrogen gas (H₂) with deuterium gas (D₂) in order to improve process stability and product quality by using the isotope effect. In addition, as the demand for D₂ in industries increases, domestic gas producers are making efforts to produce and supply D₂ on their own. In the case of high purity D₂, most of them are produced by electrolysis of heavy water (D₂O), and among D₂, hydrogen deuteride (HD) molecules are present as isotope impurities. Therefore, in order to maximize the isotope effect of hydrogen in the electronic industry, HD, which is an isotope impurity of D₂ used in the process, should be small amount. To this end, purity analysis of D₂ for industrial processing is essential. In this study, HD quantitative analysis of D₂ for high purity D₂ purity analysis was established and hydrogen isotope RM (Reference material) was developed. Since hydrogen isotopes are difficult to analyze with general gas analysis instrument, they were analyzed using a high-precision mass spectrometer (Gas/MS, Finnigan MAT271). High purity HD gas was injected into Gas/MS, sensitivity was determined by a signal according to pressure, and HD concentrations in two bottles of D₂ were quantified using the corresponding sensitivity. The amount fraction of HD in each D₂ was (4518 ± 275) μmol/mol, (2282 ± 144) μmol/mol. D₂, which quantifies HD amount using the developed quantitative analysis method, will be manufactured with hydrogen isotope RM and distributed for quality management and maintenance of electronic industries and gas producers in the future.

• Magazine of the Korean Society of Agricultural Engineers
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• v.17 no.4
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• pp.3943-3955
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• 1975

The purposes of this study are to evaluate the utilization characteristics of electrical power consumption, to grasp the present trends in the use of electrical equipments, to estimate the demand factor and load factor being held, and to evaluate the efficiency of electical uses for the recently electrified farms cultivating paddy rice. For the purposes, 109 sample farms located in eleven villiages electrified in six different years from 1968 to 1973, were chosen at random and investigated on 35 items concerning to electrical uses and wiring systems. The survey was carried out in 1975, in the vinicity of Suweon city. The results are summarized as follows: i) The average annual power consumption on sample farms is considered to be low, being 242.9 Kwh. in 1974, and varied according to the different electrified year and size of cultivated land, respectively. It has significant positive correlation to the area of farm, too. ii) Between the number of year of electrical uses and the power consumption, there is very significant positive correlation, which could be expressed as Y=43.041+16.108 X, where X represents the number of years of electrical uses. The annual increment of power consumption is much greater at the beginning of the electrification than that at the later years, its average being approximately 20 percent. However, it is recommended that any estimation of long-term increments should be carefully investigated. iii) The monthly power consumption varies considerably throughout a year, in which the heaviest farm load occurs in November. Observing the seasonal variation of consumption, the winter-time is the heaviest season while the summer is the lowest. The result implies house lighting is chief contribution to the present electrical consumption on the farms. Comparing the variation of monthly consumption ratios between the sample farms and industries, the electrical uses on the farms are independant of the industrial uses, and further, the agricultural uses are of inverse pattern to the farms from the results that there is negative correlationship between them, iv) The number of electrical equipments used on the farms are occupied chiefly by lighting sources. Next to the lighting sources, household appliances of small quantity and some motors are used. The mean electrical quantity is about 1, 127.4 watt, which corresponds to about 37.6 per cent to the contracted quantity. The composition of quantity is chiefly occupied by the electrical motor of about 1.5 hp., single-phased. The number of the annual utilization hours of each equipment is tabulated in Table IV-5. In contradiction to the high utilization of lighting sources and small household appliances, the motor is poorly used for approximately 22 hours in a year. v) More than 55 per cent of farms want to purchase new electrical equipments such as small household appliances and electrical motors in their number. The impulse of purchasing such items is stimulated by the contacts to the mass media and their knowledge on such equipments. Consequently, the increase of electrical uses could be prompted by such trials as education and demonstration. vi) The demand and load factors on the farms vary considerably according to the greater variation of the power consumption, daily or monthly. The daily demand factor is 22.4 per cent and load factor 18.6 per cent, while the annual demand factor is 1.3 per cent and load factor 70 per cent approximately. Therefore, the low efficiency of construction cost requires re-evaluation of the present contracted quantity of 3 Kw. or increase of electrical uses. vii) The electrical energy on the farms devoted chiefly to lighten the farm residences does not contribute to the farm incomes. Consequently, the cost of electrical consumption presses considerably upon the farm economy. Therefore, there is great need to build up the electrical uses on the farms through the development of new works and techinques to utilize any electrical equipments on the production of farm products. Further more, such the development should be related to increase the actual income of the farm consumers.

• Environmental and Resource Economics Review
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• v.32 no.1
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• pp.47-75
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• 2023

Compared to the EU, which legislates the Carbon Border Adjustment System (CBAM), the United States' carbon border adjustment policy movement is still relatively slow. Recently, however, a related bill has been proposed in the United States, and research institutes have been presenting research results on how to introduce an upstream carbon tax rather than an emission trading system and carry out carbon border adjustment based on it. Therefore, in this study, we looked at the economic and environmental effects of introducing this type of upstream carbon tax and carbon border adjustment in Korea. If an upstream carbon tax of KRW 30,000 per ton of CO₂ is applied to the net supply of domestic fossil energy, the expected carbon tax revenue is approximately KRW 22.9961 trillion, equivalent to about 5.7% of the total revenue of the Korean government of KRW 402 trillion in 2019. In addition, the carbon dioxide content of the steel sector, calculated based on the energy supply and demand status of the steel sector, which emits the most greenhouse gas emissions in Korea and has a considerable amount of overseas exports, was 106.22 million tons of CO₂. On the other hand, assuming that the upstream carbon tax of 30,000 won per ton of CO₂ embodied is directly passed on to the production cost of the steel sector, the carbon tax burden in the steel sector is estimated to reach approximately KRW 3.1865 trillion. Even after deducting KRW 1.1599 trillion in export refunds estimated by using the share of exports of steel products, the net carbon tax burden on steel products for domestic demand amounts to KRW 2.0266 trillion, which is analyzed to act as a factor in increasing the price of steel products.

• Journal of the Korean Society of Marine Environment & Safety
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• v.29 no.6
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• pp.697-703
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• 2023

As a part of the global industrial efforts to reduce environmental pollution owing to air pollution, regulations have been established by the International Maritime Organization (IMO). The IMO has implemented various regulations such as EEXI, EEDI, and CII to reduce air pollution emissions from ships. They are also promoting measures to decrease the power consumption in ships, aiming to conserve energy. Most of the power used in ships is consumed by electric motors. Among the motors installed on ships, the engine room blower that takes up a significant load, operates at a constant irrespective of demand. Therefore, energy savings can be expected through frequency control. In this study, we demonstrated the efficacy of energy savings by controlling the frequency of the electric motor of the generator blower that supplies combustion air to the generator's turbocharger. The system was modeled based on the output data of the turboharger outlet temperature in response to the blower frequency inpu. A PI control system was established to control the frequency with the target being the turbocharger outlet temperature. By maintaining the turbocharger design standard outlet temperature and controlling the blower frequency, we achieved an annual energy saving of 15,552kW in power consumption. The effectiveness of energy savings through frequency control of blower fans was verified during the summer (April to September) and winter (March to October) periods. Based on this, we achieved annual fuel cost savings of 6,091 thousand won and reduction of 8.5 tons of carbon dioxide, 2.4 kg of SOx, and 7.8 kg of NOx air pollutants on the training ship.