선박의 설계과정에 있어, 선박의 중량은 유체역학적 성능에 큰 영향을 미치는 가장 중요한 요소 중 하나이다. 선박은 일반적으 로 최적의 흘수와 배수량을 갖는 하나의 조건으로 설계되지만, 실제로는 연료의 소비, 선박 평형수의 충전과 적재 조건과 같은 운항 활동 으로 인해 선박의 중량 및 흘수가 일정 범위 내에서 바뀐다. 본 연구에서는 소형선박을 대상으로 3가지 하중조건에 따른 선박의 저항성능 변화를 모형실험과 수치해석을 통해 연구하였다. 마지막으로 2050년까지 CO2 배출 가스를 50% 감축한다는 국제해사기구(IMO) 목표를 따 라 선박의 저항 성능을 개선하여 동력 요구 사항을 줄이기 위해 선박의 중량 변화에 따른 저항성능의 민감도를 연구하였다. 연구 결과, 선박의 중량변화에 따른 효과는 낮은 프루드 수에서 크게 나타나는 것으로 확인되며, 저항성능에 대한 연구 결과, 설계 흘수의 적재조건 을 기준으로 배수량이 11.1% 증가하고, 흘수가 5% 증가한 Over load의 적재조건에서 운항 시 선체의 총 저항이 모형시험과 CFD 시뮬레이 션에서 각각 15.97%, 14.31%까지 증가하는 것을 볼 수 있다.

This study focuses on the application of a new measurement method that quantifies the residual color of filtered water using a spectrocolorimeter after filtering the discolored substances. It was confirmed through the color and turbidity cross-test that the discolored substances cannot be measured effectively with the current legal color and turbidity test method. Therefore, the National Institute of Environmental Research's filter testing method, which involves filtering the sample through 0.45 μm filter and visually inspecting the color, was improved. A membrane filter colorimetry (MFC) method was established by measuring the color difference (ΔE*ab(65)) of the filtered filter using a spectrophotometer and expressing it as filter color unit (FCU). Using the MFC method, the FCU for reference materials such as iron and manganese, as well as field samples, was measured. The results showed a high correlation with turbidity, and the color difference patterns varied depending on the type of reference materials and field samples. This indicates that the MFC method is an effective new measurement method of discolored tap water.

In this study, a comparative test operation was conducted through the alternate haul method to examine the selectivity of the four mesh sizes (60 mm, 90 mm, 110 mm, and 130 mm) of the trawl codend. The selectivity was analyzed using the SELECT model considering the fishing efficiency (split parameter) of each fishing gear in the comparative test fishing operation in the trawl and the maximum likelihood method for parameter estimation. A selectivity master curve was estimated for several mesh sizes using the extended-SELECT model. As a result of analyzing the selectivity for silver croaker based on the results of three times hauls for each experimental gear, it was found that the size of the fish caught increased as the size of the mesh size increased. When the selectivity for each mesh size analyzed by the SELECT model considering the split ratio was evaluated based on the size of the AIC value, the estimated split model was superior to the equal split model. Based on the master curve, the 50% selection length value was 2.893, which was estimated to be 136 mm based on the mesh size of 60 mm. In some selectivity models, there was a large deviance between observed and theoretical values due to the non-uniformity of the distribution of fished length classes. As a result, it is considered that appropriate sea trials and selectivity evaluation methods with high reliability should be applied to present trawl fishery resource management methods.

PURPOSES : In this study, the alkali aggregate reactivity and expansion characteristics of mortar mixed with waste glass (a recycled aggregate) were confirmed to verify the alkali-silica reaction (ASR) stability and review the appropriateness of the alkali aggregate reactivity test method following the replacement of recycled aggregate. METHODS : The alkali-aggregate reactivity of waste glass aggregates was measured using the chemical and physical methods described in KS F 2545 and ASTM C 1260, respectively. The reactivity was classified by comparing the results. Cement with a high-alkali content was used to simulate an environment that can induce ASR. Non-reactive fine aggregates, waste glass fine aggregates, reactive general aggregates, and Ferronickel slag aggregates were used as control groups. RESULTS : Waste glass fine aggregates were classified as reactive when applying the chemical method. In the physical method, they were classified as reactive at 100% and latent reactive at 1%, based on the mixing ratio. Additionally, we discovered that the reliability of the chemical method was low since the ASR of the aggregates was classified differently based on the evaluation method, while the results of the chemical and physical test methods were inconsistent. CONCLUSIONS : To determine the alkali reactivity of recycled aggregates, the complex use of chemical and physical methods and analysis based on the mixing ratio of the reactive aggregates are required. Small amounts of waste glass aggregate replacements affected the ASR. Because ASR reaction products can affect the long-term thermal expansion of the structure, further research is needed to use ASR aggregates in structures.

Controller modeling is essential for the design. It allows various control techniques to be simulated in advance, and various interpretations can be performed. If this is not the case, we need to reverse engineering in the real system developed by others. In this paper, controller modeling was reversely designed using the frequency test results of the target system. First, the characteristic equation of the target equipment was based on and a block diagram was assumed. Thereafter, controller variables were estimated using the frequency test results for each of the four control loops. In addition, time response simulations were performed using the estimated controller modeling. This method is thought to be of great help to reverse engineering in situations where there is completed equipment but no controller modeling.

PURPOSES : In this study, an existing speed-controlled Marshall stability tester was systemized as an Internet of Things(IoT) system. The Marshall stability test data were transmitted to the cloud in real-time, and an IoT optional-controlled board capable of additional load and displacement control was proposed. METHODS : The IoT systemization was built based on an improvement of an IoT height measuring system, the re-verification of standard samples for comparative analysis, and the development of a wireless IG-IoT board. The developed wireless Induk-GeoTS(IG)-IoT board was compared with existing commercial data logger using displacement- and load- calibration equipment. After the conformity of the developed wireless IoT board was established, a urethane standard sample was reproduced and verified using the recipe presented in a previous study to conduct a round-robin test. In addition, the adequacy of the speed, load, and displacement control tests for the optional-controlled characteristics was verified. the round-robin test for the Marshall stability and deformation strength and the comparative test of indirect tensile strength with the existing Marshall tester were performed using the re-verified standard sample. RESULTS : The improved two-point IoT height measurement system reduced the average relative error by 2.11% relative to the one-point measurement. From the re-verification results of the regenerated urethane standard sample, it was suitable with relative error of 3.65% in the loading elastic modulus and 4.07% in the unloading elastic modulus, compared to the existing standard sample. From the comparative analysis of the developed wireless IG-IoT board and existing commercial data logger, it was confirmed that the wireless IoT board could be reliably used, based on the average relative error of the wireless IoT board, 0.64% and that of the data logger, 3.79% in terms of the displacement(flow value) and an average relative error of 0.78% for the wireless IoT board and 0.79% for the data logger in terms of the load(stability). By analyzing the optional-controlled characteristics, it was found that the Marshall stability speed control conditions were satisfied based on the error results, with an average relative value of 2.96% under deformation strength test condition of 30mm/min, 3.23% under the indirect tensile strength test condition of 50mm/min, and 2.6% under the Marshall stability test condition of 50.8mm/min. It was also found that proper control characteristics were obtained, with an average relative error of 0.72% within the experimental load range in the load control conditions, and an average relative error of 2.4% in the experimental displacement range in the displacement control conditions. The results from the round-robin Marshall stability and deformation strength testing to verify the applicability of the IoT optional-controlled board show that the data were reliable based on the 3σ quality control method. In addition, by comparing the results of the indirect tensile strength tests, the usability of the wireless IG-IoT board was verified, with an average relative error of 0.96%. CONCLUSIONS : The IoT height measuring system was improved, and a wireless IG-IoT board that can transmit test data to a cloud platform was developed. The usability of the developed wireless IoT board was verified by round-robin testing using a re-verified urethane specimen. The IG-IoT optional-controlled board extends the verified wireless IG-IoT board, it was developed and validated for not only the existing speed control, but also for load, and displacement control.

PURPOSES : The aim of this study is to review freeze-and-thaw testing apparatuses, develop a freeze-and-thaw testing setup with a test protocol, test the freeze-and-thaw properties of soils collected from different parts of South Korea, and suggest an index for frost susceptibility criteria for soils found in South Korea. METHODS : Based on a literature review, a new freeze-thaw testing setup was developed. In addition, a test protocol was developed for freeze-thaw testing. Soils collected from different parts of South Korea and bedding sand used for block pavements were tested to determine whether the measurements from the newly developed test setup could capture important freeze-thaw characteristics of the soils. Finally, to develop local frost susceptibility criteria, a parameter including both the vertical deformation and thermal conductivity characteristics of the soils was suggested. RESULTS : The results from the laboratory experiments indicate that the newly developed freeze-and-thaw setup captures the required parameters to quantify the responses of soils subjected to cyclic freeze-and-thaw testing. In addition, a vertical deformation of up to 2.437 mm is measured. Moreover, seven soils out of the nine tested soils are classified as having a medium frost susceptibility, whereas the remaining two show low frost susceptibility. The bedding sand experiment also shows that there is a possibility of having a frost susceptible condition based on the moisture content. When submerged, the bedding sand is classified as having a medium frost susceptibility. CONCLUSIONS : The "HEART" freeze-thaw testing setup was able to capture the parameters required for evaluating the frost susceptibility of soils. This setup and testing procedure could be further used to test and prepare criteria for classifying the frost susceptibility of soils found in South Korea.

The ship security accidents that occur in ships, at sea, and in ports have become increasingly more serious in recent years, and in particular, maritime terrorism and the abduction by pirates are emerging as an international problem. Accordingly, the International Maritime Organization implemented a measures to enhance ship security by adopting SOLAS Chapter 11-2, ISPS-code in 2004. In this study, it was investigated whether JDS-S4, a directional sound receiver developed for responding to ship security accident, has durability and safety suitable for ships. For the purpose, the conducted emission test (CE102) of the US military standard test (MIL-STD-461F) was performed, and it was confirmed that JDS-S4 satisfies the test conditions sufficiently.