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81.
82.
Eul?Cheong?Hong Jee?Young?Shin Min?Soo?KimEmail author Kyungdoug?Min Sung?Tack?Ro 《Journal of Mechanical Science and Technology》2003,17(6):935-944
Forced convective boiling heat transfer coefficients were predicted for an annular flow inside a horizontal tube for pure
refrigerants and nonazeotropic binary refrigerant mixtures. The heat transfer coefficients were calculated based on the turbulent
temperature profile in liquid film and vapor core considering the composition difference in vapor and liquid phases, and the
nonlinearity in mixing rules for the calculation of mixture properties. The heat transfer coefficients of pure refrigerants
were estimated within a standard deviation of 14% compared with available experimental data. For nonazeotropic binary refrigerant
mixtures, prediction of the heat transfer coefficients was made with a standard deviation of 18%. The heat transfer coefficients
of refrigerant mixtures were lower than linearly interpolated values calculated from the heat transfer coefficients of pure
refrigerants. This degradation was represented by several factors such as the difference between the liquid and the overall
compositions, the conductivity ratio and the viscosity ratio of both components in refrigerant mixtures. The temperature change
due to the concentration gradient was a major factor for the heat transfer degradation and the mass flux itself at the interface
had a minor effect. 相似文献
83.
GN Taylor RD Lloyd CW Mays SC Miller WS Jee S Mori L Shabestari XJ Li 《Canadian Metallurgical Quarterly》1997,73(4):679-683
A comparison of the risk coefficients for 239Pu- or 226Ra-induced bone cancer in two canine breeds, one with a relatively low (beagle) and the other with a very high (St. Bernard) natural incidence, indicated only slightly higher risk in the giant breed. The differences in risk for skeletal malignancy in 239Pu and 226Ra dogs were nonsignificant (p > 0.05). Likewise, the values of the 239Pu:226Ra "toxicity ratios" for these respective breeds, using bone cancer as the endpoint, were not significantly different at the 0.05 level. The anatomical distribution of the radiation-induced bone tumors tended to be a function of both the bone mass and the skeletal distribution of the radionuclide, not the site of predilection for naturally occurring bone neoplasia. Although the etiology of the higher natural incidence of bone cancer in the St. Bernard was not determined, several possible factors, including a higher osteoblastic activity level in the St. Bernards, are presented. These data suggest that making extrapolations of radiation-induced bone cancer risk from animals to humans is valid. 相似文献
84.
Sung Chul Jee Ho Jae Lee Do Wan Kim 《International Journal of Control, Automation and Systems》2016,14(2):452-460
A direct discrete-time design methodology for sampled-data sensor fault detection for nonlinear systems in Takagi–Sugenos form is proposed. Contrary to the conventional schemes in this way that rely on an approximate discrete-time model of the nonlinear system, our result is established based on an exact one. Condition to design the observer and the residual gain under an H-/H ∞ performance criterion is presented in matrix inequality format. An example is given to illustrate the effectiveness of the proposed methodology. 相似文献
85.
Next‐Generation Activated Carbon Supercapacitors: A Simple Step in Electrode Processing Leads to Remarkable Gains in Energy Density 下载免费PDF全文
Jee Y. Hwang Mengping Li Maher F. El‐Kady Richard B. Kaner 《Advanced functional materials》2017,27(15)
The global supercapacitor market has been growing rapidly during the past decade. Today, virtually all commercial devices use activated carbon. In this work, it is shown that laser treatment of activated carbon electrodes results in the formation of microchannels that can connect the internal pores of activated carbon with the surrounding electrolyte. These microchannels serve as electrolyte reservoirs that in turn shorten the ion diffusion distance and enable better interaction between the electrode surfaces and electrolyte ions. The capacitance can be further increased through fast and reversible redox reactions on the electrode surface using a redox‐active electrolyte, enabling the operation of a symmetric device at 2.0 V, much higher than the thermodynamic decompostion voltage of water. This simple approach can alleviate the low energy density of supercapacitors which has limited the widespread use of this technology. This work represents a clear advancement in the processing of activated carbon electrodes toward the next‐generation of low‐cost supercapacitors. 相似文献
86.
In order to find promising materials for bio-carriers, five kinds of spherical beads of 1 cm diameter were manufactured using
natural soil including organic clay and inorganic clay such as diatomite, zeolite, bentonite, and germanium, which are cheap
and favorable for pot-planting. Their performance was comparatively investigated according to material properties, microbial
attachment and growth, and the biofiltration effect of H2S and VOC vapor when applied to biofilters. A composite-ceramic carrier made of 1:1 mixture of diatomite and bentonite clay
showed the best performance among these carriers, according to the maximum removal capacity of these gases. Particularly,
bentonite clay appears to be a good material for bio-carriers. The organic-clay carrier can be used as an alternative to peat
and compost, being readily dried with a high flow rate particularly in the absence of a water supply. 相似文献
87.
The Pore Mouth Tailoring of Coal and Coconut Char Through Acid Treatment Followed by Coke Deposition
Kim Tae-Hwan S. Vijayalakshmi Son Seok-Jin Kim Jee Dong 《Journal of Porous Materials》2002,9(4):279-286
Carbon Molecular Sieves (CMS) obtained by coke deposition through deep cracking of hydrocarbons on the wide pore mouths of coal and coconut char are important adsorbents for separation of, difficult to separate, gaseous as well as liquid mixtures. The adsorption studies on these CMS show a high selectivity towards the adsorption of one or the other component from its mixture. In this work, CMS is prepared from pre treated raw materials like bituminous coal and coconut shell. The product samples are characterized in terms of kinetic adsorption and equilibrium adsorption of various gas adsorbents. It is observed that, all these samples are very good for CO2 removal from mixtures containing CH4 or H2 in it. The CMS prepared from coconut shell showed an uptake ratio 4, for adsorption of O2 and N2, indicating that separation of nitrogen from air is viable by choosing suitable conditions in Pressure Swing Adsorption (PSA) Technique. 相似文献
88.
Jin?Yeon?ChoEmail author Young?Burm?Jee 《Journal of Mechanical Science and Technology》2003,17(7):986-998
In this paper, an adaptive numerical integration scheme, which does not need non-overlapping and contiguous integration meshes,
is proposed for the MLPG (Meshless Local Petrov-Galerkin) method. In the proposed algorithm, the integration points are located
between the neighboring nodes to properly consider the irregular nodal distribution, and the nodal points are also included
as integration points. For numerical integration without well-defined meshes, the Shepard shape function is adopted to approximate
the integrand in the local symmetric weak form, by the values of the integrand at the integration points. This procedure makes
it possible to integrate the local symmetric weak form without any integration meshes (non-overlapping and contiguous integration
domains). The convergence tests are performed, to investigate the present scheme and several numerical examples are analyzed
by using the proposed scheme. 相似文献
89.
Yun Joo Chyung Jee Yon Lee Sun Young Jung Pyoung Won Kim 《Multimedia Tools and Applications》2017,76(23):24847-24858
In this paper, we propose an efficient deinterlacing method for HDTV that preserves image structures, edges, and details. In the human visual system, the eyes are more sensitive to high-frequency information such as edge details than low-frequency information such as image background. Therefore, averaging low-pass filter results is not effective for image enhancement. The proposed method is a weighted filtering approach that generates a half-pixel 9-by-9 edge-based line average window. We also propose pixel-resemblance- and pixel-expansion-based fuzzy weights, which are assigned using a triangular membership function. Compared to conventional format conversion methods, the proposed method outperforms all benchmarks in terms of both objective and subjective qualities. 相似文献
90.
The working principle of the laser-aided direct metal tooling(DMT) process is the use of a laser to selectively clad metallic powder on the substrate material part. A high-powered laser beam is focused on a metal substrate to create a molten weld pool; as the laser passes by the deposit is quickly cooled, leaving behind a thin line of metal clad. The major advantage of the DMT process is its capability of depositing a multitude of materials. Since the material deposition relies only on the feeding of a powder, it is relatively simple to use multiple kinds of materials. In fact, recent research has shown that DMT is capable of manufacturing binary functionally graded materials as well. The study is to develop a software support tool, visual simulation technique, as one of the e-manufacturing capability established for a unique DMT process. 相似文献