3D 콘크리트 프린팅 기술은 거푸집 없이 콘크리트를 출력하고 제작하여 콘크리트 표면의 대부분이 외기에 노출되고, 이로 인해 콘크리트 내부 수분이 빠르게 증발하고 수축이 크게 발생한다. 또한, 결합 재 대비 낮은 골재 함량과 낮은 물/결합재 비(W/B)를 가지는 사용 배합의 특성상 수축으로 인한 균 열이 발생하기 쉽다. 이러한 3D 콘크리트 프린팅의 수축에 대한 문제는 섬유 혼입을 통해 해결할 수 있고, 부가적으로 적층성 향상의 이점을 얻을 수 있다. 본 연구에서는 이러한 섬유 보강 3D 프린팅 모르타르의 역학적 특성을 살펴보고자 섬유 혼입률을 변수로 실험하였다. 보강 섬유로는 PP섬유를 사 용하였고, 섬유 혼입률 0, 0.2, 0.5, 0.8%를 변수로 실험하였다. 갠트리 방식의 3D 프린터에 30 × 30 mm 사각형 개구부를 가진 노즐을 설치해 1300× 800mm 크기의 직사각형 형태로 모르타르를 출력 하였다. 호퍼 회전속도 6 rpm, 노즐 이동 속도 1500 mm/min을 적용하여 출력하였고, 1층 높이를 30mm로 출력하여 5층 적층하였다. 적층 완료 후 압축강도, 휨인장강도, 층간 부착강도를 측정하기 위 한 시험체를 각각 추출하였고, 28일 수중 양생 후 각 강도실험을 통해 역학적특성을 평가하였다.

The heat transfer characteristics of double-pipe spiral heat exchanger were investigated by various curvature sizes, experimentally. The three different sizes of heat exchanger were made and tested with water as a working fluid to analyze the heat transfer characteristics. The heat transfer rates, overall heat transfer coefficient and pressure drop were analyzed with various heat exchanger sizes (i.e., curvature ratios). As result, the heat transfer rate increased with increasing the size of the heat exchanger as the flow rate increased due to increasing the area size of heat transfer. However, the overall heat transfer coefficient and pressure drop increased with decreasing the heat exchanger size (i.e., increased curvature ratio) due to the enhanced centrifugal force and inertia.

Asphalt concrete, which is used as a road base material, accounts for >90% of a road pavement. A huge amount of waste concrete and waste asphalt concrete aggregates are generated. Recently, carbon neutrality is promoted across all industries for sustainability. Therefore, to achieve carbon neutrality in the asphalt concrete industry, waste asphalt concrete aggregates should be recycled. Additionally, road base materials are prepared using additives to ensure structural stability, durability, and economic efficiency. In this study, recycled asphalt concrete aggregates were used to evaluate the physical properties of road base materials according to the type of polymer additive and mixing method, and the applicability of road base each material was evaluated. Results showed that when the acrylate-based polymer additive was mixed, the uniaxial compressive strength was 30% higher. Furthermore, the compressive strength of the split mix was improved by ~29% compared to the total mix.

This study quantitatively evaluated size selectivity for three netting shapes (T0; regular, T45, T90) and hanging ratio (35%, 70%) of T0 netting used for trawl codend. The size selectivity experiment was performed in a tank using a cube experimental model with a length of 50 cm on one side and 389 experimental individuals, jack mackerel (Trachurus japonicus). In the selectivity analysis, a selectivity curve was created based on the selection ratio using a logistic function, and the 25%, 50%, and 70% selection length and selection range  were obtained. The T0 netting was 19.54 cm when the 50% selective length, which is a selectivity evaluation index, had a hanging ratio of 35%, a selection range of 0.51 cm, and 22.70 cm and 3.08 cm for the hanging ratio of 70%. The T45 netting was 24.34 cm and 2.13 cm, and the T90 netting was 23.51 cm and 2.84 cm. The results of the T45 netting and the T90 netting are similar, and the 50% selection length and selection range were relatively larger than the T0 netting. There was a significant difference in the correlation between the circumference of the inner circle of the mesh by the shape of the netting and the body girth of the experimental individual (Pearson test,      ). There was no significant difference in the correlation between the selection ratio by the T0 netting, T45 netting, and T90 netting with a 70% hanging ratio (one-way ANOVA,   ). The results of this study showed that selectivity such as T45 netting and T90 netting appeared when the hanging ratio, which maximizes the area of T0 netting, was maintained at 70%.

지진은 예상하지 못한 위치와 규모로 지반을 흔들어서 막대한 물적 및 인적 피해를 발생시킨다. 따라서 지진으로 인 한 진동을 최소화하고 피해를 방지하기 위하여 다양한 내진 기술 개발 연구가 수행되고 있다. 최근에는 우수한 성능을 나타내 는 다양한 신소재가 개발되고 있으며 이를 접목된 내진 기술 개발 연구가 하나의 트렌드가 되고 있다. 본 연구에서는 반영구적 이고 자동복원이 가능한 신소재를 적용한 새로운 개념의 영구마찰 자동복원 댐퍼를 제안하고 핵심 부재에 대한 물리적 특성 검 증 연구를 수행한다. 영구마찰 자동복원 댐퍼의 핵심은 복원 특성을 나타내는 초탄성 형상기억합금과 폴리우레탄을 부재로 장 착시키고 추가적인 마찰 특성을 나타내는 네오디뮴 영구자석을 사용하였다. 이러한 핵심 부재는 재료실험을 통해 특성을 검증 하였고 도출된 거동 응답 결과를 통해 영구마찰 자동복원 댐퍼의 구조실험 예측 거동을 도출하였다. 우수한 복원 성능을 나타 내는 영구마찰 자동복원 댐퍼는 최대 하중 성능과 에너지 소산 능력이 우수하여 구조물에 적용 시 강한 지진에도 버티면서 발 생된 손상도 회복 시킬 수 있을 것으로 기대된다.

Most of the steam turbine control valves used for the fossil and nuclear power plants operation in South Korea were developed by GE (General Electric) and manufactured by DHIC (Doosan Heavy Industry Company). For may years, DHIC have tried to develop their own technologies related to the power generation. DHIC has launched many R&D projects and ‘Development of a Control Valve Flow Code for Steam Turbine Operation Control of Fossil Power Plant’ was one of the R&D projects. Through our project, we accomplished the experimental method to obtain a steam turbine control valve characteristic curve using the atmospheric air and the reduced model instead using the steam and the real model. Also, we developed the correction method to calculate the real steam mass flow rate from the characteristic curve obtain by the experiment. In this paper, the effectiveness of the correction method was reviewed and it was concluded that the corrected mass flow rate complies well with the real steam mass flow rate.

In the present study, the experimental study was conducted using a multi-calorie meter, to investigate the cooling performance and cycle operation changes of the multi-heat pump (3 indoor units) for the low outside temperature in summer. The test temperature condition was the low cooling temperature, and the normal performance and dynamic behavior of 3 rooms, 2 rooms, and 1 room were measured to understand the operating characteristics of seven 7 indoor unit combinations. As a result of the experiment, the cooling capacity and COP of the multi-heat pump at low cooling temperature were about 10% and 6% higher than those of the cooling standard temperature. In addition, the dynamic behavior of the indoor units of 3 and 2 rooms was observed differently due to the load difference according to the indoor unit combinations and the non-uniformity of the refrigerant amount. And, when starting the heat pump, the compressor had a maximum peak value and stabilized by repeating the decrease and increase for each indoor unit combination.

Test of the operating characteristics and energy saving performance of a container cooling system that reduces the operating energy of a refrigeration system using a loop thermosyphon heat exchanger that removes heat by temperature difference between outdoor and indoor was performed. As a result of the experiments, when the loop thermosyphon and the refrigeration system were operated simultaneously, the refrigeration system operated intermittently by reducing the heat load. As the temperature difference between indoor and outdoor increased, the operating time of the refrigeration system decreased and the energy efficiency rate increased. Energy efficiency rate showed a tendency to increase with increasing temperature difference, and the predicted correlation of energy efficiency rate using the performance of the loop thermosyphon heat exchanger and the refrigeration system was relatively consistent with the experimental value.

In the present study, to investigate the cooling characteristics of the multi-heat pump with 3 indoor units, 7 indoor unit combinations and 3 setting temperatures are selected to study the cooling characteristics during steady-state operation. The cooling capacity, power consumption, COP, compressor high and low pressure of the heat pump are tested under the cooling standard temperature conditions using an air enthalpy multi-calorimeter. The experimental results show that, except for an operation with an indoor unit capacity of 30% or less, the cooling capacity, power consumption, and compressor operation frequency increase as the capacity of the indoor unit increases and the setting temperature of the indoor unit decreases. COP increases or decreases according to the compressor frequency, and is the best at 50-80% capacity of the indoor unit. As the compressor frequency increases, the compressor outlet pressure increases by about 30%.

In order to experimentally investigate the operation characteristics of the multi-heat pump with 3 indoor units, the dynamic characteristics of the cooling cycle is studied using the psychrometric multi-calorimeter. The compressor of the heat pump is the scroll inverter type, and since 3 indoor units operate cooling at the same time, it is operated at 100% full load. In particular, 3 types of indoor unit temperatures (20, 24, 26°C) are selected to understand the operation process of the multi-heat pump by the setting temperature. From this experiment, the compressor controls the EEV opening for each indoor unit while varying the frequency according to the initial start, transient, and steady operation. In addition, as the setting temperature increases in the steady range, the frequency of the compressor and the average opening degree of the EEV decrease.

In the present study, it is conducted to understand the heating performance and compressor operation characteristics according to 7 indoor unit combinations and 3 setting temperatures of the inverter multi-heat pump under heating standard temperature conditions. Heating capacity, COP and compressor frequency are investigated using the multi-calorimeter. The indoor unit combinations are simultaneous operation(A+B+C), partial operation(A+C, A+B, B+C) and independent operation(A, B, C), and the setting temperature is 20, 21, and 30°C. Since the increase in the setting temperature increases the compress frequency, the heating capacity increases, but COP decreases due to the increase in power consumption. The frequency increases as the indoor unit combination capacity increases, and decreases as the setting temperature decreases in the steady state.

Flow prediction was carried out through observational survey and three dimensional multi-layered numerical diagnostic model experiment to clarify the time and spatial structure of tidal current and residual flow dominant in the sea exchange and material circulation of the waters around Geumo Islands in the southern waters of Korea. The horizontal variation of tidal current is so large that it causes asymmetric tidal mixing due to horizontal eddies and the topographical effect creating convergence and dispersion of flow direction and velocity. Due to strong tidal currents flowing northwest-southeast, counterclockwise and clockwise eddies are formed on the left and right sides of the south of Sori Island. These topographical eddies are created by horizontal turbulence and bottom friction causing nonlinear effects. Baroclinic density flows are less than 5 cm/s at coastal area in summer and the entire sea area in winter. The wind driven currents assuming summer and winter seasonal winds are also less than 5 cm/s and the current flow rate is high in winter. Density current in summer and wind driven current in winter have a relatively greater effect on the net residual flows (tidal residual current + density current + density driven current) around Geumo Islands Sea area.

The performance characteristics and usefulness of the duct-type gas removal system to which the catalytic combustion method was applied were investigated by experiment. Benzene, toluene, ethylbenzene, and xylene were selected for performance tests on gas detection and removal of the catalytic combustion system. Accelerated experiments were performed to evaluate the gas sensing performance, the adsorption performance of activated carbon, and the basic performance and durability of the catalytic combustion system. The amount of gas adsorption in the adsorption stage was changed according to the type of activated carbon, adsorption temperature and time. The adsorption amount increased with increasing temperature and particle size. BTEX gas removal rate was about 96%, and the performance of the module was maintained for more than 4,000 hours.

The styling of automobile wheels and their effect on vehicle appearance has increased in importance in recent years. The wheel designer has been given the task of insuring that a wheel design meets its engineering objectives without affecting the styling theme. The wheel and tire system is considered as a vehicle component whose dynamic modal information of the tire/wheel system are employed in the modal synthesis model of the vehicle. The Modal characteristics of a Automobile wheel play an important role to judge a ride comfortability and quality for a Automobile. In this paper, the modal characteristics of a Al-alloy and steel wheel for Automobile are studied. Natural frequency, damping and mode shape are determined experimentally by frequency response function method. Results show that wheel material property, size and design are parameter for shift of natural frequency and damping.

Experimental analysis has been carried out on double glazed glass of a commercial vehicle to analyze thermal characteristics for various air flow conditions. This double glazed glass has an important effect on the blocking performance of heat transfer with the vehicle's moving speed and ambient thermodynamic conditions. Calculated thermal resistances and heat transmission coefficient through the glass were compared with measured air indoor and outdoor temperatures including the glass surfaces using an experimental apparatus. The thermal resistance through the glass was increased with the indoor air temperature while overall heat transmission coefficient was decreased due to the convective heat transfer effect. As indoor air became warmer, the effect of air flow velocity on the heat transmission coefficient was reduced significantly. It is expected that these results can be used as applicable design data for the development of the double glazed glass system for many commercial vehicles.

In order to study the drying performance of the dryer, the performance characteristics of the heat pump dryer applied a PF heat exchanger is applied were experimentally investigated. The capacity, COP, drain and SMER of the dryer were measured by the refrigerant charge and EEV opening. Heat pump dryers are refrigerant-air systems. For the dryer performance test, an air enthalpy calorimeter was used. From the experimental results, the heat exchanger performances according to the change in the refrigerant charge and EEV opening were the maximum at 0.5kg refrigerant and 30% EEV opening, respectively. In addition, SMER suggested a satisfactory level of drying performance. This shows that the refrigeration cycle of the dryer must be operated at an appropriate refrigerant amount and EEV opening degree to secure optimal drying performance. On the other hand, the time to reach the target setting temperature of the dryer was increased by about 2.5 times depending on with/without the sample.