Earticle

최근, 디지털전환의 확대로 사이버공격의 위협에 더욱 더 노출되고 있으며, 각 기관 및 기업은 공격이 유입되는 것 을 막기 위해 시그니처 기반의 침입차단시스템을 네트워크 가장 앞단에 운영중에 있다. 그러나, 관련된 ICT시스템에 적절한 서비스를 제공하기 위해 엄격한 차단규칙을 적용할 수 없어 많은 오이벤트가 발생되고, 운영효율이 저하되고 있다. 따라서, 공격탐지 정확도 향상을 위하여 인공지능을 이용한 많은 연구과제가 수행되고 있다. 대부분의 논문은 정 해진 연구용 데이터셋을 이용하여 수행하였지만, 실제 네트워크에서는 연구용 학습데이터셋과는 다른 로그를 이용해야 만 하기 때문에 실제 시스템에서는 사용사례는 많지 않다. 본 논문에서는 실제 시스템에서 수집한 보안이벤트 로그에 대하여 주요 공격키워드를 분류하고, 주요 키워드별로 가중치를 부과, TF-IDF를 이용하여 유사도 검사를 수행후 실제 공격여부를 판단하는 기법에 대하여 제안하고자 한다.

As the expansion of digital transformation, we are more exposed to the threat of cyber attacks, and many institution or company is operating a signature-based intrusion prevention system at the forefront of the network to prevent the inflow of attacks. However, in order to provide appropriate services to the related ICT system, strict blocking rules cannot be applied, causing many false events and lowering operational efficiency. Therefore, many research projects using artificial intelligence are being performed to improve attack detection accuracy. Most researches were performed using a specific research data set which cannot be seen in real network, so it was impossible to use in the actual system. In this paper, we propose a technique for classifying major attack keywords in the security event log collected from the actual system, assigning a weight to each key keyword, and then performing a similarity check using TF-IDF to determine whether an actual attack has occurred.

A multilevel inverter employing a cascade transformer is proposed for a silent-discharge-tube ozone generating system. The proposed inverter consists of four full-bridge inverters and fourteen transformers which have a series-connected secondary. It can accurately control the amplitude of the output voltage; hereby, it improves a linear characteristic of the rate of ozone yielding. The power regulation characteristics and operational principle of the proposed system are explained from a practical point of view. High precision ozone generating performance of the proposed multilevel inverter is verified by computer-aided simulations and experiment results.

The feasibility of precision fertilizing for small size fields was studied by determining fertilizing amount of nitrogenous and calcareous to a cite specific region. A detailed soil survey at three experimental fields of $672m^2$, $300m^2$ and $140m^2$ revealed a considerable spatial variation of the pH and organic matter(OM) levels. Soil organic matter was measured using Walkley-Black method and soil pH was measured with a pH sensor. Soil sample was obtained by Grid Node Sampling Method. The soil sampling depth was 10∼20 cm from the soil surface. To display soil nutrient variation, a soil map was made using Geographic Information System (GIS) software. In soil mapping, soil data between nodes was interpolated using Inverse Distance Weighting (IDW) method. The variation was about 1∼1.8 in pH value and 1.4∼7% in OM content. Fertilizing Amount of nitrogenous and calcareous was determined by th fertilizing equation which was proposed by National Institute of Agricultural Science and Technology(NIAST). The variation of fertilizing amount was about 3∼11 kg/10a in nitrogenous and 70∼140 kg/10a in calcareous. The results showed a feasibility of precision fertilizing for small size fields.

We prepared carbon nanotube (CNT) paper by a vacuum filtration method for the use of a chip-typed resistor as a precision passive device with a constant resistance. Hybrid resistor composed of the CNT resistor with a negative temperature coefficient of resistance (T.C.R) and a metal alloy resistor with a positive T.C.R could lead to a constant resistance, because the resistance increase owing to the temperature increase at the metal alloy and decrease at the CNT could counterbalance each other. The constant resistance for the precision passive devices should be maintained even when a heat was generated by a current flow resulting in resistance change. Performance reliabilities of the CNT resistor for the precision passive device applications such as electrical load limit, environmental load limit, and life limit specified in IEC 60115-1 must be ensured. In this study, therefore, the rated power determination and T.C.R tests of the CNT paper were conducted. -900~-700 ppm/℃ of TCR, 0.1~0.2 A of the carrying current capacity, and 0.0625~0.125 W of the rated power limit were obtained from the CNT paper. Consequently, we confirmed that the application of CNT materials for the precision hybrid passive devices with a metal alloy could result in a better performance reliability with a zero tolerance.

정밀 농업 시행에 있어서 포장 변이성에 대한 이해가 필수적이므로, 직파 재배 논에서 포장 변이성 조사와 토양 검정 결과에 다른 질소 변량 시비에 대한 현장 시험이 전북 김제의 직파 재배 논 시험 포장과 농가 시범 포장에서 이루어졌다. $35m{\times}112m$ 단위 포장에서 10 m 간격의 방격형으로 표토의 토양 시료를 채취하여 분석하였다. 토양 유기물, 유효 인산 및 규산, 그리고 치환성 칼륨 등에 대한 분석이 이루어졌다. 시험 포장에 대한 토양 검정 결과에 의해 다수확과 저투입 농업을 위한 질소 시비 추천량을 계산하여 그 분포도를 작성하였다. 2001년과 2002년의 시험 포장에서의 질소 변량 시험을 토대로, 2003년에는 농가 포장 3개를 선정하여 저투입 질소 시비량을 기준으로 질소 변량 시비에 대한 농가 실증 시험을 하였고, 경제성을 분석하였다. 변량 시비에 의해 수량 중가 및 수량 변이 감소 효과를 알 수 있었다. 변량 시비에 의한 수량 증가와 시비량 절감에도 불구하고, 토양 검정에 소요되는 비용이 절감 비용을 초과하였다.

Since understanding on spatial variability of a field is essential to pursue precision agricultural technology, a field study for field variability and variable rate fertilization of nitrogen in a direct seeding paddy was attempted. Variable rate application of nitrogen was designed with soil test, and field application was tested in a direct seeding paddy in the Kimje, Jeonbuk, Korea. The grid samples of soil was collected from the field of which unit size was 35 m by 112 m on February before irrigating of the field. Soil organic matter, available phosphate and silicate, and extractable potassium were analyzed. Variable rate fertilizer recommendation maps of nitrogen for high yielding, HY, and low input sustainable agriculture, LISA, were derived based on the soil analysis. Direct seeding of rice was performed for variable rate treatment, VRT, for the experimental plot in 2001 and 2002, and so did for three volunteer farmers' field in 2003. Yield mapping was performed by harvesting. Economic feasibility of direct seeding of rice by variable rate fertilization was evaluated. Though increased yield of variable rate application and benefit of reducing fertilizer use and environmental impact, the cost for soil test exceeded the total reduced fertilizer cost.

Anesthetic machines may be equipped with either a precision or nonprecision vaporizer. A precision vaporizer is designed to deliver an exact concentration of anesthetic agent. Goldman vaporizer is a low-flow, closed-circle circuit with a low resistance vaporizer, in circuit. Vaporizers used within circle system(VIC) are not usually temperature compensated and this is generally thought to be a disadvantage. As the volatile agent is vaporized, heat is extracted from the liquid and temperature decreases. This cooling of the liquid leads to a decrease in concentration of the anaesthetic agent delivered by the vaporizer. The purpose of this study is to examine the mechanical consistency of the delivery of isoflurane from Goldman vaporizer and precision vaporizer at various gas flow rates and temperatures. And we first studied isoflurane concentration according to room temperature changes delivered by a Goldman vaporizer and precision vaporizer using different gas flow. The room temperature of $15^{\circ}C,$ $20^{\circ}C,$ $28^{\circ}C$ and fresh gas flow rates of 0.5, 1.0, 1.5, 2.0, 3.0 l/min were used. The inspired agent concentration was measured using a Datex-Ohmeda multigas analyzer. As rose in room temperature, the isoflurane concentration of precision vaporizer approximated the dial setting. On the other hand, at a dial setting concentration of 5.0 percent the delivered isoflurane concentration of precision vaporizer was more than the dial setting in high temperature. The isoflurane concentration of precision vaporizer remained constant despite the increase in temperature. The isoflurane concentration of Goldman vaporizer was increased with rise in room temperature and decreased with rise in gas flow.