In compliance with environmental regulations at sea and the introduction of unmanned autonomous ships, electric propulsion ships are garnering significant attention. Induction machines used as propulsion electric motor (PEM) have maintenance advantages, but speed control is very complicated and difficult. One of the most commonly used techniques for speed control is DTC (direct torque control). DTC is simple in the reference frame transformation and the stator flux calculation. Meanwhile, two-level and three-level voltage source inverters (VSI) are predominantly used. The three-level VSI has more flexibility in voltage space vector selection compared to the two-level VSI. In this paper, speed is controlled using the DTC method based on the specifications of the PEM. The speed controller employs a PI controller with anti-windup functionality. In addition, the characteristics of the two-level VSI and three-level VSI are compared under identical conditions. It was confirmed through simulation that proper control of speed and torque has been achieved. In particular, the torque ripple was small and control was possible with a low DC voltage at low speed in the three-level VSI. The study confirmed that the application of DTC, using a three-level VSI, contributes to enhancing the system's response performance.

Gas turbine engines are widely used as prime movers of generator and propulsion system in warships. This study addresses the problem of designing a DS-based PID controller for speed control of the LM-2500 gas turbine engine used for propulsion in warships. To this end, we first derive a dynamic model of the LM-2500 using actual sea trail data. Next, the PRC (process reaction curve) method is used to approximate the first-order plus time delay (FOPTD) model, and the DS-based PID controller design technique is proposed according to approximation of the time delay term. The proposed controller conducts set-point tracking simulation using MATLAB (2016b), and evaluates and compares the performance index with the existing control methods. As a result of simulation at each operating point, the proposed controller showed the smallest in , which means that the rpm does not change rapidly. In addition, IAE and IAC were also the smallest, showing the best result in error performance and controller effort.

최근, 우리나라는 겨울철 콘크리트 포장에 제설을 목적으로 한 제설제의 사용량이 점차적으로 증가하 고 있는 추세이다. 예를 들어 서울시의 경우, 현재 연간 약 4만톤 이상의 제설제가 도로포장에 살포되고 있으며, 이는 5년 전과 비교하여 약 2.5배 이상 제설제의 사용량이 증가한 것으로 보고되고 있다. 뿐만 아니라, 제설제 살포에 따른 콘크리트 포장의 표면박리(scaling) 등과 같은 내구성 저하 현상이 빈번하게 발생함에 따라 콘크리트 포장의 성능에 대한 제설제 종류 및 농도의 영향에 대한 관심도 점차 증가되고 있는 실정이다. 특히, 우리나라는 도로포장의 제설을 위하여 염화칼슘수용액 및 고체 염화나트륨을 이용 한 습염살포방식이 널리 사용되고 있다. 주지하다시피, 염화물계 제설제의 사용은 철근부식에 의한 콘크 리트의 손상을 초래할 수 있으며, 겨울철 동결융해 반복작용에 의한 콘크리트의 표면박리작용의 주요 원 인이 된다. 본 연구에서는 강도가 상이한 콘크리트(24 및 35 MPa)를 제조하여 ASTM C 672에 준하여 스케일링 실험을 실시하였으며, 동결융해 작용 50싸이클 후 콘크리트의 열화원인을 분석하기 위한 SEM 및 EDS 분석을 실시하였다. 실험결과에 의하면, 콘크리트의 스케일링 저항성은 강도등급에 따라 상이하였으며, 동결융해 반복작용에 따른 thaumasite의 생성이 스케일링의 주요 원인 중 하나라고 판단된다.

최근 국제 원유가의 폭등으로 선박의 연료비 부담이 상대적으로 가중되고 있으며, 또한 연료의 연소과정에서 발생하는 온실가스에 대한 국제적 규제 움직임도 가속되고 있다. 이와 같은 상황에서, 온실가스의 배출을 최소화하면서 연료소모량을 줄이기 위해 많은 선사들이 감속운항을 취하고 있으며, 선박용 엔진 개발 분야에서는 엔진의 연료 효율성 개선 문제와 대체에너지 사용 분야에 주력하고 있다. 따라서, 본 연구에서는 실제 해상에서의 선속대비 연료소모량을 계측하고, 건조과정에서 실시된 육상 엔진실험 자료와 2007~2009년까지의 AB-LOG를 분석하여, 특정 외력조건에서의 대상선박에 대한 연료소모량을 고려한 최적의 속력을 14~15노트, 주기관의 RPM을 140~150 RPM으로 제안하였다.

This survey was conducted to monitor the food additives, heavy metals, and microbial contamination of the dried marine products like squids, pollacks, and shrimps, including jerked beef. They were purchased from supermarkets and traditional markets in Gwangju from February to December 2009. A total of 101 samples were tested. Sorbic acid, one of the additives, was detected in 29 samples of them (32.2%) and the contents were from 21.4to 244.2 mg/kg. Among heavy metals, lead was detected, ranging from 0.000 to 0.594 mg/kg and cadmium, from 0.000 to 0.679 mg/kg and mercury, from 0.001 to 0.947 mg/kg. Sodium was detected, ranging from 0.6 to 1.7%. Aerobic bacteria were detected from 81 samples (80.2%), coliform bacteria, from 10 samples (9.9%) and Bacillus cereus,causing food poisoning, was isolated from 3 samples (3.0%).

This survey was conducted to monitor the total sugar, sodium, and artificial sweetener contents of light meals from the school zone in Gwangju, from November, 2008 to April, 2009. A total of 100 samples were tested. HPLC/ELSD was used for the determination of total sugar contents and AAS for sodium contents. Total sugar amounts were the sum of both mono-and disaccharide according to nutritional information standard defined by the Korea Food and Drug Administration. The results were as follows by the form of total sugar content(sodium content): 5.7 ± 1.9%(4.6 ± 1.6 mg/g) for Tteokbokki, 7.6 ± 5.1%(5.4 ± 2.7 mg/g) for Chicken(skewed), 15.4 ± 3.2%(3.0 ± 0.9 mg/g) for Bun(fish-shaped), 0.6 ± 0.3%(3.7 ± 1.0 mg/g) for Sundae, 0.9 ± 0.3%(7.4 ± 1.4 mg/g) for Oden(with broth), 20.5 ± 6.2%(2.9 ± 0.6 mg/g) for Waffle, 6.8 ± 2.2%(4.7 ± 1.0 mg/g) for Hotdog, 14.2 ± 2.8%(3.1 ± 1.6 mg/g) for Hotteok, 6.6 ± 2.1%(3.9 ± 0.6 mg/g) for Toast, 10.1 ± 3.7%(2.3 ± 0.7 mg/g) for Fry(sweet potato), 1.6 ± 0.7% (4.0 ± 0.7 mg/g) for Fry(etc), and 9.3 ± 2.4%(4.0 ± 0.6 mg/g) for Doughnut. In addition, sodium saccharin, one of the artificial sweeteners, was tested. Among 60 samples from February to April, 2009, 11 samples had sodium saccharin(6.7~101.0 mg/kg).

This survey was conducted to monitor the safety of children snacks circulated in a stationary store or small shop around the elementary school from March to October, 2008, in Gwangju. A total of 309 samples was tested. Of these samples, 254 were confectioneries, 41 were ready-to-eat foods like kimbap, 4 were beverages and 10 were the others like fishery products. 259 were domestic products and 50 were imported. By the origin of imported samples, 17 were from china, 6 from U.S.A., 5 from india and etc. We found out that in acid value, 2 cases of fried snacks(3.9 and 4.4) proved to exceed regulatory guidance(2.0). And among ready-to-eat foods, two kimbap had Staphylococcus aureus, and one had Escherichia coli, which microorganism could cause food poisoning.

This survey was conducted to monitor the adulteration of sesame oil circulated in Gwangju, 2007. A total of 60 samples was tested by analysis of fatty acid composition. Of these samples, 22 were from large-scale manufacturer, 25 were from small-scale manufacturer and 13 from Bangagan. First of all, in goods manufactured by large-scale company, there are no sesame oils where linolenic acid (C18:3) exceed regulatory guidance (0.5%). 5 samples from small-scale manufacturer contained linolenic acid from 0.90% to 8.38%, which means that they have other cooking oil, such as corn oil, soybean oil and rape seed oil. Among Bangagan goods, only one sample have 1.20% of linolenic acid. On the other hand erucic acid (C22:1) was not detected in 60 samples at all, which means that they were not adulterated with rape seed oil. And among 6 samples of exceeding 0.5% of linolenic acid and 12 samples from Bangagan, 13 of them had benzo(a)pyrene from 0.2 μg/kg to 0.7 μg/kg and the other 5 samples did not.

2007년 3월부터 11월까지 광주지역에 소재하는 재래시장과 할인마트에서 구입한 건과류 채소류와 건포류 등 94건, 전통 막걸리 판매점 등에서 구입한 탁류 23건, 모두 117건을 구입하여 식품첨가물인 이산화황, 타르색소와 인공감미료를 조사하였다. 건과류 채소류와 건포류 등 94건에서 이산화황을 조사한 결과 17건에서 11.5~4,452.3;mg/kg이 검출되었으며, 식품공전의 기준을 적용한 결과 건조과실류인 대추채 2건이 각각 2,476.6 mg/kg, 4,452.3 mg/kg이 검출되어 부적합하였고, 중국산 건방울 토마토에서 88.9 mg/kg, 국내산 건호박에서 1,653.7 mg/kg이 검출되어 부적합 판정되었다. 또한, 주류 23건을 구입하여 인공감미료와 타르색소를 검사한 결과, 탁주에서 사용할 수 없는 인공감미료인 삭카진나트륨이 2건에서 0.4 mg/kg, 11.1 mg/kg이 검출되었으며, 합성 착색료로 주류에서 많이 사용할 가능성이 있는 황색5호 등 타르색소는 검출되지 않았다.

Three benzimidazole pesticides commonly used in korean lettuce were subjected to a field residue trial to ensure safety of terminal residue in the harvest. The residual patterns of three benzimidazole pesticides, which were carbendazim, benomyl and thiophanate-methyl were examined after applying with the recommended dose in two types of korean lettuce (Chima and Chuckmeon) and their DT50 were calculated. In Chima lettuce, biological half-lives of carbendazim, benomyl and thiophanate-methyl were 2.56, 1.37 and 2.54 days, respectively and their required time under MRL(5.0 mg/kg as carbendazim) were 4.5, 2.2 and 1.0days. In Chuckmeon lettuce, biological half-lives of them were 3.41, 1.70 and 4.20 days, respectively and their required time under MRL were 5.4, 1.9 and 0.5days.