• 한국주거학회논문집
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• 제17권2호
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• pp.11-18
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• 2006

For the more comfortable thermal environment in residential buildings, it was necessary for variable components like as automatic flow limiting valves and/or balancing valves in hydronic system. And, these components had an effect on flow-rate and pressure inside pipe. In this case, the incompatibility between the design for the heating system and the selection of equipment was the causes of several problems in heating pipe network. In this study, we peformed measurements and analyses of flow rate and pressure inside pipe for radiant floor heating in residential buildings through field surveys and experiments in order to find out the actual conditions and problems. On the basis of this, we suggested the approach for the optimal flow-rate and pressure maintaining inside pipe in individual heating system.

• 상하수도학회지
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• 제26권1호
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• pp.1-12
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• 2012

The purpose of water distribution system is supplying water to users by maintaining appropriate pressure and water quality. For efficient monitoring of the water distribution system, determination of optimal locations for pressure monitoring is essential. In this study, entropy theory was applied to determine the optimal locations for pressure monitoring. The entropy which is defined as the amount of information was calculated from the pressure change due to the variation of demand reflected the abnormal conditions at nodes, and the emitter function (fire hydrant) was used to reproduce actual pressure change pattern in EPANET. The optimal combination of monitoring points for pressure detection was determined by selecting the nodes receiving maximum information from other nodes using genetic algorithm. The Ozger's and a real network were evaluated using the proposed model. From the results, it was found that the entropy theory can provide general guideline to select the locations of pressure sensors installation for optimal design and monitoring of the water distribution systems. During decision-making phase, optimal combination of monitoring points can be selected by comparing total amount of information at each point especially when there are some constraints of installation such as limitation of available budget.

• FOCUS: LIFE SCIENCE
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• 제1호
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• pp.7.1-7.4
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• 2024

The document "Understanding the Relationship Between Particle Size, Performance, and Pressure" explores the impact of particle size on chromatographic performance and system pressure. The study highlights how smaller particles can improve separation efficiency by providing higher resolution and faster analysis times. However, this comes at the cost of increased backpressure, which can challenge the system's hardware and require higher operating pressures. The document discusses the balance needed between particle size, column dimensions, and system pressure to optimize performance without exceeding the pressure limits of chromatographic systems. It outlines the advantages of using superficially porous particles (SPPs) over fully porous particles (FPPs) in achieving high efficiency with lower backpressure. The study also emphasizes the importance of selecting appropriate column dimensions and flow rates to manage system pressure while maintaining optimal performance. In conclusion, understanding the interplay between particle size, performance, and pressure is crucial for optimizing chromatographic separations, ensuring system longevity, and achieving high-quality analytical results.

• 한국조리학회지
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• 제14권3호
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• pp.196-209
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• 2008

This study was conducted to mass-produce brown stock optimized by using a high-pressure heating extractor and to use brown stock as a material for developing various products. For these purposes, we attempted to produce standardized brown stock by extracting brown stock using a high-pressure heating extractor and compared it with brown stock extracted by the traditional method in terms of general elements and mechanical and sensory characteristics. With regard to how to prepare optimal brown stock, the best brown stock was that extracted seven times repeatedly by the traditional method, but the method had a large economic loss in terms of material consumption and took a long time in extraction. Thus, considering time and labor, it was concluded that extraction at 120$^{\circ}C$ for 15 hours using a high-pressure heating extractor is the optimal extraction condition in terms of economic efficiency and quality. The results of this study are expected to be useful as a practical material for making brown stock production process more convenient, applying cooks' traditional cooking techniques to mass production, maintaining standardized superior quality and taste, and improving shelf life.

• Neonatal Medicine
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• 제25권1호
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• pp.1-6
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• 2018

Extremely low birth weight infants remain at increased risk of intraventricular hemorrhage from the fragile vascular bed of the germinal matrix; the roles of hypotension (ischemia) and reperfusion (hyperemia) in the development of intraventricular hemorrhage are still debated. Cerebrovascular pressure autoregulation protects the brain by maintaining constant cerebral blood flow despite changes in blood pressure. The ontogeny of cerebrovascular pressure autoregulation has not been well established and uncertainty remains about the optimal arterial blood pressure required to support brain perfusion. Another important aspect of premature cerebral hemodynamics is the critical closing pressure--the arterial blood pressure at which cerebral blood flow ceases. Interestingly, in premature infants, the critical closing pressure approximates the mean arterial blood pressure. Often in this unique population, cerebral blood flow occurs only during systole when the diastolic arterial blood pressure is equal to the critical closing pressure. Moreover, the diastolic closing margin, a metric of cerebral perfusion that normalizes diastolic arterial blood pressure to the critical closing pressure, may be a better measure than arterial blood pressure for defining cerebral perfusion in premature infants. Elevated diastolic closing margin has been associated with intraventricular hemorrhage. This review summarizes the current state of understanding of cerebral hemodynamics in premature infants.

• The Journal of the Acoustical Society of Korea
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• 제25권1E호
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• pp.25-31
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• 2006

Two twin microphones may produce particular patterns of binaural directivity by time delays between the twin microphones. The boundary element method (BEM) was used for the simulation of the sound pressure field around the KEMAR head model in order to quantify the acoustic head effect. The sound pressure onto the microphone was calculated by the BEM to an incident sound pressure. Then a planar directivity pattern was formed by four sound pressure signals from four microphones. The optimal binaural directivity pattern may be achieved by adjusting time delays at each frequency while maintaining the forward beam pattern is relatively bigger than the backward beam pattern. The simulation results were verified by the experimental measurement.

• The Journal of the Acoustical Society of Korea
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• 제24권3E호
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• pp.115-122
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• 2005

Two twin microphones may produce particular patterns of binaural directivity by time delays between twin microphones. The boundary element method (BEM) was used for the simulation of the sound pressure field around the head model in order to quantify the acoustic head effect. The sound pressure onto the microphone was calculated by the BEM to an incident sound pressure. Then a planar directivity pattern was formed by four sound pressure signals from four microphones. The optimal binaural directivity pattern may be achieved by adjusting time delays at each frequency while maintaining the forward beam pattern is relatively bigger than the backward beam pattern.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2005년도 하계학술발표대회
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• pp.4-4
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• 2005

• 대한기계학회논문집B
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• 제29권1호
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• pp.9-15
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• 2005

From the geometric parameter study, an optimal ejector design procedure of pressure recovery system for chemical lasers was acquired. For given primary flow reservoir conditions, an up-scaled ejector was designed and manufactured. In the performance test, secondary mass flow rate of 100g/s air was entrained satisfying the design secondary pressure, $40{\sim}50torr$. Performance validation of a supersonic ejector system along with an investigation of effects of supersonic diffuser was conducted. Placement of the diffuser at the secondary inlet further reduced diffuser upstream pressure to 7torr. Lastly, the duplicate of apparatus (air 500g/s secondary mass flow rate each) was built and connected in parallel to assess proportionality behavior on a system to handle larger mass flow rate. Test and comparison of the parallel unit demonstrated the secondary mass flow rate was proportional to the number of individual units that were brought together maintaining the lasing pressure.

• International Journal of Advanced Culture Technology
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• 제8권2호
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• pp.246-251
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• 2020

Dimethyl Ether(DME) engine use a highly efficient alternative fuel having a great quantity of oxygen and has a advantage no polluting PM gas. The existing DME fuel cam material is a highly expensive carbide alloy, and it is difficult to take a price advantage. Therefore the study of replacing body area with inexpensive steel material excluding piston shoe and contact area which demands high characteristics is needed. The development of WC-Ni base carbide alloy optimal bonding composition technique was accomplished in this study. To check out the influence of bonding temperature and time, bonding characteristics of sintering temperature was experimented. The hardness of specimen and bonding rate were measured using ultrasound equipment. The bonding state of each condition was excellent, and the thickness of mid-layer, temperature and maintaining time were measured. The mid-layer thickness according to bonding temperature and maintaining time were observed with optical microscope. We analyzed the micro-structural analysis, formation of bonding specimen, wafer fabrication and fuel cam abrasion test. Throughout this study, we confirmed that the fuel cam for DME engine which demands high durability against velocity and pressure is excellent.