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111.
Heat exchangers are used widely in residential, commercial, and industrial HVAC applications. Air-side particulate fouling in the heat exchangers of HVAC applications degrades the performance of cooling capacity, pressure drop across a heat exchanger, and indoor air quality. Indoor and outdoor air contaminants foul heat exchangers. The purpose of this study is to investigate the characteristics of the air-side particulate fouling materials in finned-tube heat exchangers of air conditioners. Air conditioners being used in the field such as inns, restaurants, and offices are collected in chronological order of use. The fouling materials attached on the evaporator heat exchangers consist of particulates and fibers. The particulates mainly originate from indoor dusts and the fibers are separated from clothes, bedclothes, papers, fur of pets, and so on. Typical fouling materials on the heat exchangers include fibers and dusts ranging from 6.6 to 20.9 μm in aerodynamic mean diameter. 相似文献
112.
Choong-Heui Chung Yoon-Ho Song Chi-Sun Hwang Seong-Deok Ahn Bong-Chul Kim Young-Rae Cho Jin Ho Lee Kyoung Ik Cho 《Thin solid films》2004,460(1-2):201-205
The effects of a wet chemical surface treatment of molybdenum-tip (Mo-tip) emitters on the electrical characteristics of an active matrix cathode composed of hydrogenated amorphous silicon thin film transistors and Mo-tip emitters are described. X-Ray photoelectron spectroscopy measurements showed that the surface treatment removed MoO3 from the surface of the e-beam evaporated Mo film. In addition, the surface roughness of the Mo film was increased as the result of the surface treatment. The surface-treated active matrix cathode showed stable emission characteristics and immunity from emitter failures during its operation. The response time of the active matrix cathode was decreased by the surface treatment of the Mo-tip emitters. A change in surface composition and surface roughness appear to be responsible for the enhancement of the active matrix cathode. 相似文献
113.
114.
The main purpose of this paper is to investigate numerically the effects of solidification on the heat transfer characteristics of the liquid metal layer, for use in accident analyses. The situation is very similar to an overlying liquid melt pool that could be fooned in the reactor lower head during the late phase of a severe nuclear accident. Based on a computational model, MPCOOL, the numerical predictions were then assessed through a comparison with the experimental data that was obtained with various boundary temperature conditions and geometrical aspect ratios, especially for the Ra-Nu relationship. For the cases with solidification, the results of the comparison show that(a) the computational model does show a good agreement with heat transter rates inferred from the experimental data, with a few exceptions at the Ra numbers which suggest a turbulent transport; and also (b) the computational model underpredicts the heat transfer rates by about 6% than that inferred from the experimental data when it is integrally evaluated with the Ra-Nu correlation. The foregoing results are mainly due to the currently limited applicability of the computational model up to the laminar-to-turbulence transition flows and its application to the turbulence flows because it is always subjected to a model uncertainty between the laminar and turbulence. Next, an additional comparison for the cases with and without solidification was made to examine the effects of the solidification on the energy partition within the liquid metal layer and its effects on the directional heat transfer rates. The results of the comparison show that the computational model for the case without solidification predicts higher heat transfer rates by about 15% than when solidification is included, but there isn't any experimental data that directly supports this trend. 相似文献
115.
Sun-Mo Yang Beumjun Ahn Kwang-Kyu Seo 《The International Journal of Advanced Manufacturing Technology》2006,28(9-10):1031-1037
Current Computer integrated manufacturing/Enterprise Resource Planning (CIM/ERP) systems require harmony and communication between humans and facilities. A user’s preferences should also be considered in CIM/ERP systems. Virtual factory (VF), also known as virtual manufacturing (VM), systems can fulfill the requirements of current CIM/ERP systems. A VF system simulates virtual production in a virtual factory environment on the computer system which allows optimization prior to going into production. In this paper, we defined a VF system as a pre-analyzing system for designing, engineering and manufacturing a product in the enterprise system of the real world. The objective of this paper is to design a VF system and to develop a prototype system that the customer can participate in and be satisfied with. We selected a telephone as a sample product for the VF system. The VF system consists of four subsystems: virtual product ordering, design, manufacturing, and CIM/ERP interface. The prototype system aims to develop a virtual product ordering and design system. 相似文献
116.
Seok-Hwan?Ahn Ki-Woo?NamEmail author 《Journal of Mechanical Science and Technology》2003,17(11):1599-1607
The characteristics of elastic waves emanated from crack initiation in 6061 aluminum alloy subjected to fatigue loading are
investigated through experiments. The objective of the study is to determine the differences in the properties of the signals
generated from fatigue test and also to examine if the sources of the waves could be identified from the temporal and spectral
characteristics of the acoustic emission (AE) waveforms. The signals are recorded using nonresonant, flat, broadband transducers
attached to the surface of the alloy specimens. The time dependence and power spectra of the signals recorded during the tests
were examined and classified according to their special features. Six distinct types of signals were observed. The waveforms
and their power spectra were found to be dependent on the crack propagation stage and the type of fracture associated with
the signals. The potential application of the approach in health monitoring of structural components using a network of surface
mounted broadband sensors is discussed. 相似文献
117.
Chinwon?LeeEmail author Kukhyun?Ahn Jang?Moo?Lee Won?Sik?Lim 《Journal of Mechanical Science and Technology》2003,17(4):521-527
Modern automatic transmissions equip torque converters with lock-up clutches to reduce the energy loss of hydraulic systems.
Instead of simply engaging the clutch disks, the new technology of clutch slip has been developed to improve the overall efficiency
of power transmission. There are two major problems with the clutch slip system. The first is how to keep the slip between
the two disks within a small range and the second is when to start or stop the slip. In this paper, the second problem is
discussed in view of the vehicle economy. With a simple vehicle dynamic model, the fuel economy is calculated to determine
the lock-up strategy. Then the lock-up strategy is developed for a slip schedule. 相似文献
118.
Kyoung-Gee Ahn Byung-Kwon Min Zbigniew J. Pasek 《The International Journal of Advanced Manufacturing Technology》2006,29(9-10):929-939
A volumetric error compensation method for a machining center that has multiple cutting tools operating simultaneously has been developed. Due to axis sharing, the geometric errors of multi-spindle, concurrent cutting processes are characterized by a significant coupling of error components in each cutting tool. As a result, it is not possible to achieve exact volumetric error compensation for all axes. To minimize the overall volumetric error in simultaneous cutting, a method to determine compensation amount using weighted least squares has been proposed. This method also allows tolerance distribution of machining accuracy for different surfaces of a workpiece. A geometric error model has been developed using an arch-type, multi-spindle machine tool, and the error compensation simulation results based on this model are presented. The simulation results demonstrated effectiveness of the proposed error compensation algorithm for use with multi-spindle simultaneous cutting applications. 相似文献
119.
Kyoungo Nam Hyunki Park Kihak Im Dongjin Kim Heejae Ahn Jaehyuk Lee Jaewhan Moon Emma Watson Robert Shaw 《Fusion Engineering and Design》2013,88(6-8):701-704
The purpose-built, ITER tokamak assembly tools, which are to be provided by Korea, should be designed to meet: the assembly plan, space reservations, safety standards, simple operations, efficient maintenance, and so on. It is very important that the ITER assembly tools are able to lift and transfer ITER components or their sub-assemblies to their assembled position safely. Furthermore, the lifting tools will lift and handle very heavy loads that can be more than 1200 tonnes sometimes. Therefore, the ITER lifting tools must be designed to endure these heavy load conditions with regard to their structural integrity. Also, these designs should be verified through an appropriate method. The preliminary design of the sector lifting tool and associated lifting attachments are introduced in this paper. The sector lifting tool was designed especially to lift and handle various ITER components by adjusting the lifting centre. The structural analysis results using ANSYS are described considering the heaviest load condition. The results of the analysis show that; all stresses applied on the lifting tool are lower than the allowable stress of the applied material. 相似文献
120.
Y Lee SA Lee JY Choi M Song H Sung S Joen SK Park KY Yoo DY Noh SH Ahn D Kang 《Nutrition journal》2012,11(1):59
ABSTRACT: BACKGROUND: The 5-year survival rate for breast cancer among Korean women has increased steadily; however, breast cancer remains the leading cause of cancer mortality among women. One-carbon metabolism, which requires an adequate supply of methyl group donors and B vitamins, may affect the prognosis of breast cancer. This aim of this study was to investigate the associations of dietary intake of vitamin B2, vitamin B6 and folate before diagnosis on the prognosis of breast cancer. METHODS: We assessed the dietary intake using a food frequency questionnaire with 980 women who were newly diagnosed and histopathologically confirmed to have primary breast cancer from hospitals in Korea, and 141 disease progression events occurred. Cox's proportional hazard regression models were used to estimate the hazard ratio (HR) and 95% confidence interval (95% CI) adjusting for age, education, recruitment sites, TNM stage, hormone status, nuclear grade and total calorie. RESULTS: There was no significant association between any one-carbon metabolism related nutrients (vitamin B2, B6 and folate) and the progression of breast cancer overall. However, one-carbon metabolism related nutrients were associated with disease progression in breast cancer patients stratified by subtypes. In ER + and/or PR + breast cancers, no association was observed; however, in ER--/PR-- breast cancers, a high intake of vitamin B2 and folate statistically elevated the HR of breast cancer progression (HR = 2.28; 95% CI, 1.20-4.35, HR = 1.84; 95% CI, 1.02-3.32, respectively) compared to a low intake. This positive association between the ER/PR status and progression of the disease was profound when the nutrient intakes were categorized in a combined score (Pinteraction = 0.018). In ER--/PR-- breast cancers, high combined scores were associated with a significantly poor DFS compared to those belonging to the low score group (HR = 3.84; 95% CI, 1.70-8.71). CONCLUSIONS: In conclusion, our results suggest that one-carbon related nutrients have a role in the prognosis of breast cancer depending on the ER/PR status. 相似文献