• Journal of Advanced Marine Engineering and Technology
• /
• 제34권2호
• /
• pp.282-288
• /
• 2010

본 연구는 전자팽창밸브의 개도변화에 따른 가변속 수냉각기의 용량제어 특성에 관한 논문이다. 인버터에 의한 가변속 압축기를 사용한 냉각기를 최적으로 제어하기 위한 선행 연구이며 압축기 회전수별로 제어대상인 전자팽창밸브를 조절하여 증발기 출구의 과열도를 일정한 값으로 제어함으로써 최적의 냉각능력을 얻을 수 있는 과열도 값을 찾는 것을 목표로 하였다. 본 실험의 결과 압축기 회전속도가 일정할 때 팽창 밸브의 개도변화에 따라서 냉각능력이 최대가 되는 지점의 개도량을 실험을 통해서 파악할 수 있었다.

• 자원환경지질
• /
• 제32권1호
• /
• pp.83-91
• /
• 1999

Coal properties are controlled by the following two factors : One is the maceral components and the other is the degree of coalification. In other words, even if coals in question indicate the same degree of coalification, their chemical and physical properties considerably vary one another when their maceral components are different. It is well known that virtrinite reflectance is the best single criterion for the degree of coalification covering the whole range of coal rank. Some authors have recently insisted that sporinite fluorescence is more leliable coal rank parameter than vitrinite reflectance in case of low rank coals. In this paper, to examine the relince of sporinite fluorescence as coal rank parameter, fluidity analysis of coals is newly performed and the data are analyzed in comparision with those of virinite reflectance, sporinite fluorescence and maceral components. The results of this study are as follows; 1) Vitrinite reflectance becomes low when degradinite content is high within one columnar samples, and vice versa. 2) variation of vitrinite reflectance depend on degradinite content and on difference of roiginal plant. 3) In dealing with the Japanese paleogene coals, sporinite fluorescence is more reliable parameter indicating the degree of coalification than vitrinite reflectance. 4) Maximum fluidity increases exponetially in proportion to the increases of degradinite content.

• 아시안잔디학회지
• /
• 제7권1호
• /
• pp.5-12
• /
• 1993

This experiment was conducted to study on the morphological change and growth retardation of Korean Lawograss (Zoysia japonica Steud.) under various shading degrees. Dada of plant height, No. of tiller, No. of stolon, No. of rhizome and fresh weight were measured on the l47days after transplanting in 1991. The results are summarized as follows. Plant height was increased at 30% shading degree or over, Maximum plant height was observed at 60% shadeing degree which was 24.2 cm. while full sunlight(control) was most shorted as 10.1 cm. Plant height rapidly was increased as to shading degree increase. The decreasing rate was lower in tiller number and stolon number(top parts of plant) compared with the rhizome number(under ground part) was severely decreased at 30% to 60% of shading. To increase the shading degree, rhizome number was most severely decreased under shading degrees. As degree of shading increase to 30%, 60% and 90%, fresh weight decrease to 66%, 44%, 22% to full sunlight, respectively. Relative growth retadation of Korean lawngrass was decreased by the order of number of rhizome, fresh weight, number of tiller, number of stolon. And these characters were highly significant accord-ing to the different shading degrees.

• International journal of advanced smart convergence
• /
• 제10권4호
• /
• pp.233-240
• /
• 2021

The purpose of this study was to provide a 360-degree video on intensive care unit admission guidance to family members admitted to the intensive care unit, and then to identify anxiety, safety perception, and satisfaction. This study was a single-group pre-post design, and the data collection period was from October 1, 2020 to August 30, 2021. The subjects of this study were 19 people who applied 360 degree hospitalization guide video. For data analysis, SPSS WIN 24.0 program was used, and real number, percentage, mean, standard deviation, minimum value, maximum value, and Wilcoxon signed rank test were used. The subjects' anxiety before intervention was an average score of 6.21±2.30 and the anxiety after intervention was an average score of 3.95±2.46, which was statistically significant (z=4.13, p<.001). The safety consciousness of the subjects before the intervention was an average of 4.08±0.39 and the safety consciousness after the intervention was an average of 4.54±0.48, which was statistically significant (z=5.00, p=.001). The highest level of satisfaction with the 360-degree hospitalization guidance image of the subjects was 4.58±0.51 and the lowest was 4.16±0.96. In this study, when 360-degree hospitalization guide video was applied, there was a difference in anxiety and safety perception, and satisfaction was high. Based on the research results, various programs for guardian education can be developed and utilized in the future.

• Geomechanics and Engineering
• /
• 제30권3호
• /
• pp.219-231
• /
• 2022

Geotechnical materials such as silt, fine sand, or coarse granular soils may be unstable under undrained shearing or during rainfall infiltration starting an unsaturated state. Some researches are available describing the instability of coarse granular soils in drained or undrained conditions. However, there is a need to investigate the instability mechanism of unsaturated silty soil considering the effect of degree of compaction and net confining stress under partially and fully drained conditions. The specimens in the current study are compacted at 65%, 75%, & 85% degree of compaction, confined at pressures of 60, 80 & 120 kPa, and tested in partially and fully drained conditions. The tests have been performed in two steps. In Step-I, the specimens were sheared in constant water content conditions (a type of partially drained test) to the maximum shear stress. In Step-II, shearing was carried in constant suction conditions (a type of fully undrained test) by keeping shear stress constant. At the start of Step-II, PWP was increased in steps to decrease matric suction (which was then kept constant) and start water infiltration. The test results showed that soil instability is affected much by variation in the degree of compaction and confining stresses. It is also observed that loose and medium dense soils are vulnerable to pre-failure instability i.e., instability occurs before reaching the failure state, whereas, instability in dense soils instigates together with the failure i.e., failure line (FL) and instability line (IL) are found to be unique.

• Structural Engineering and Mechanics
• /
• 제46권6호
• /
• pp.755-773
• /
• 2013

One of the main requirements of the seismic design codes must be its easy application by structural engineers. The use of practically-applicable models or simplified models as single-degree-of-freedom (SDOF) systems is a good alternative to achieve this condition. In this study, deterministic and probabilistic response transformation factors are obtained to evaluate the response in terms of maximum ductility and maximum interstory drifts of multi-degree-of-freedom (MDOF) systems based on the response of equivalent SDOF systems. For this aim, five steel frames designed with the Mexican City Building Code (MCBC) as well as their corresponding equivalent SDOF systems (which represent the characteristics of the frames) are analyzed. Both structural systems are subjected to ground motions records. For the MDOF and the simplified systems, incremental dynamic analyses IDAs are developed in first place, then, structural demand hazard curves are obtained. The ratio between the IDAs curves corresponding to the MDOF systems and the curves corresponding to the simplified models are used to obtain deterministic response transformation factors. On the other hand, demand hazard curves are used to calculate probabilistic response transformation factors. It was found that both approaches give place to similar results.

• 생물환경조절학회지
• /
• 제23권3호
• /
• pp.192-198
• /
• 2014

To establish the design criteria for seasonal heating load calculation in greenhouses, standard weather data are required. However, they are being provided only at seven regions in Korea. So, instead of using standard weather data, in order to find the method to build design weather data for seasonal heating load calculation, heating degree-hour and heating degree-day were analyzed and compared by methods of fundamental equation, Mihara's equation and modified Mihara's equation using normal and thirty years from 1981 to 2010 hourly weather data provided by KMA and standard weather data provided by KSES. Average heating degree-hours calculated by fundamental equation using thirty years hourly weather data showed a good agreement with them using standard weather data. The 24 times of heating degree-day showed relatively big differences with heating degree-hour at the low setting temperature. Therefore, the heating degree-hour was considered more appropriate method to estimate the seasonal heating load. And to conclude, in regions which are not available standard weather data, we suggest that design weather data should be analyzed using thirty years hourly weather data. Average of heating degree-hours derived from every year hourly weather data during the whole period can be established as environmental design standards, and also minimum and maximum of them can be used as reference data for energy estimation.

• 한국지하수토양환경학회지:지하수토양환경
• /
• 제26권1호
• /
• pp.76-87
• /
• 2021

Groundwater is considered to be the best water resource to solve water shortage problems during drought periods. Even though excessive pumping (overdraft) during short-period may give an unprofitable effect on groundwater hydrology, it has a primary role to solve a lack of water resources and to maintain incomes of farmers. This study evaluated maximum irrigation amounts of groundwater to each local-government and province during drought periods. Maximum irrigation amounts of groundwater were evaluated using cumulative groundwater usage data of each local-government during normal and drought years. Maximum irrigation amounts of groundwater during drought periods would be roughly identified as approximately 1.3 times more than the exploitable amounts of groundwater resources for each local-government. Drawdown-limitation depth on groundwater levels at each monitoring well was determined by transforming the maximum irrigating amounts into degree of change on levels. Universal limitation depth of drawdown on groundwater levels was evaluated to be approximately three times of annual fluctuating range on groundwater levels for each monitoring well. Systematic response on groundwater demands with abiding by drawdown-limitation depth can attain an optimal irrigation of groundwater resources during short-term drought.

• Smart Structures and Systems
• /
• 제33권3호
• /
• pp.201-215
• /
• 2024

Spline chirplet transform and local maximum synchrosqueezing are introduced to present a novel structural instantaneous frequency (IF) identification method named local maximum synchrosqueezing spline chirplet transform (LMSSSCT). Namely spline chirplet transform (SCT), a transform is firstly introduced based on classic chirplet transform and spline interpolated kernel function. Applying SCT in association with local maximum synchrosqueezing, the LMSSSCT is then proposed. The index of accuracy and Rényi entropy show that LMSSSCT outperforms the other time-frequency analysis (TFA) methods in processing analytical signals, especially in the presence of noise. Numerical examples of a Duffing nonlinear system with single degree of freedom and a two-layer shear frame structure with time-varying stiffness are used to verify the effectiveness of structural IF identification. Moreover, a nonlinear supported beam structure test is conducted and the LMSSSCT is utilized for structural IF identification. Numerical simulation and experimental results demonstrate that the presented LMSSSCT can effectively identify the IFs of nonlinear structures and time-varying structures with good accuracy and stability.

• 태양에너지
• /
• 제4권2호
• /
• pp.13-28
• /
• 1984

Direct Absorption Receiver and Thermal Storage System is a complex problem. This paper describes only characteristic of fluid flow on the receiver. The fluid thicknesses of Molten Salts (Melting Point : $397^{\circ}C$) flowing on the receiver of modified protopype ($10m{\times}10m$) were calculated theorectically, changing the receiver slope from 60 degree to 85 degree (5 steps). The receiver temperatures were $430^{\circ}C$ at the top part and $950^{\circ}C$ at the low part. The flow thickness of the Molten Salts at the top part of the receiver are around 1.9mm in the case of maximum insolution ($50{\times}10^6$juoule/sec; 58.898kg/sec of flow rate) and 2.0mm at the low part. In the case of 3/10 of maximum insolation (flow rate = 17.669kg/sec) the flow thickness at the top part are around 0.9mm and 0.4mm at the low part, and in the case of 1/10 of maximum insolation (flow rate = 5.889 kg/see) the flow thickness at the top part are around 0.6mm and 0.3mm at the low part. From experimental measurements of a normal fresh water thickness flowing on the model plate ($12.7cm{\times}111.76cm$), around 0.8mm at the top part of the plate and around 0.7mm at the low part were obtained in the case of maximum insolation (flow rate = 0.12496 kg/see). In the case of 3/10 (flow rate = 0.03748 kg/see) and 1/10 (flow rate = 0.012496 kg/see) of maximum insolation, around 0.5mm and 0.4mm at the top part, and around 0.3mm and 0.2mm at the low part were obtained respectively. The reason why the thickness of the Molten Salts increase at the low part of the receiver only in case of maximum insolation is that decreasing rate of the viscosity of the Molten Salts is larger than decreasing rate of the density of the Molten Salts during temperature increase from the top to the low receiver plate and decrease of the fluid velocity in accordance with continuity principle. In all cases without the above maximum insolation, the thickness of the Molten Salts and the fresh water decreased at the low part of the plate because of gravity force effects rather than friction effects and of continuity principle. All simillar flow patterns were obtained through all cases of the insolation making an exception of only maximum insolation.