• Applied Science and Convergence Technology
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• 제25권6호
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• pp.158-161
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• 2016

Debye temperature is an important thermodynamical factor in quantum dots (QDs); it can be used to determine the degree of homogeneity of a QD structure as well as to study the interdiffusion mechanism during growth. Direct estimation of the Debye temperature can be obtained using the Varshni relation. The Varshni relation is an empirical formula that can interpret the change of emission energy with temperature as a result of phonon interaction. On the other hand, phonons energy can be calculated using the Fan Expression. The Fan expression and Varshni relation are considered equivalent at a temperature higher than Debye temperature for InAs quantum dot. We investigated InAs quantum dot optically, the photoluminescence spectra and peak position dependency on temperature has been discussed. We applied a mathematical treatment using Fan expression, and the Varshni relation to obtain the Debye temperature and the phonon energy for InAs quantum dots sample. Debye temperature increase about double compared to bulk crystal. We concluded that the In/Ga interdiffusion during growth played a major role in altering the quantum dot thermodynamical parameters.

• Journal of Pharmaceutical Investigation
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• 제30권3호
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• pp.207-211
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• 2000

The objective of this work is to investigate the effect of molecular weight of poly(ethylene oxide) (PEO) and release medium on the release of nifedipine (NP) from PEO tablets containing NP and to get some mechanistic insights into the release of NP. The tablets containing NP were prepared by direct compression, using a flat-faced punch and die. The molecular weights of PEOs used were 200K, 900K, 2000K and 7,000K. The release kinetics were studied for 24 hours in aqueous ethanol solution, using a dissolution tester at $36.5^{\circ}C$ and 100 rpm. Drug release rate increased, as the concentration of ethanol in the dissolution medium increased, due to the increased solubility of NP. As the molecular weight of PEO increased, release rate decreased, due to the slower swelling and dissolution of PEO. The power values obtained by fitting data to the power law expression $(M_t/M_{\infty}=kt^n)$ indicated that, at low ethanol concentration, the release of NP is governed by anomalous diffusion. However, as the ethanol concentration increases, diffusional release becomes to prevail over anomalous or zero-order release. Overall, these results provided some insights into the release of NP from PEO tablet.

• 한국연소학회지
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• 제11권1호
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• pp.19-26
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• 2006

Structure of edge flame established in a mixing layer, formed between two uniformly flowing pure $CH_4$ and pure $O_2$ streams, is numerically investigated by employing a detailed methane-oxidation mechanism. The numerical results exhibited the most outstanding distinction of using pure oxygen in the fuel-rich premixed-flame front, through which the carbon-containing compound is found to leak mainly in the form of CO instead of HC compounds, contrary to the rich $CH_4-air$ premixed flames in which $CH_4$ as well as $C_2H_m$ leakage can occur. Moreover, while passing through the rich premixed flame, a major route for CO production, in addition to the direct $CH_4$ decomposition, is found to be $C_2H_m$ compound formation followed by their decomposition into CO. Beyond the rich premixed flame front, CO is further oxidized into $CO_2$ in a broad diffusion-flame-like reaction zone located around moderately fuel-rich side of the stoichiometric mixture by the OH radical from the fuel-lean premixed-flame front. Since the secondary CO production through $C_2H_m$ decomposition has a relatively strong reaction intensity, an additional heat-release branch appears and the resulting heat-release profile can no longer be seen as a tribrachial structure.

• 한국IT서비스학회:학술대회논문집
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• 한국IT서비스학회 2008년도 추계학술대회
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• pp.153-156
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• 2008

In recent years, IPTV attracts great attention along with the digital convergence of communication and media technologies. IPTV combines the advantages of TV and Internet and changes our lifestyle dramatically. In addition, the IPTV service is capable of becoming a new business model which has huge growth potentials in technology-converging marketplaces. This study examines critical factors on the consumer's adoption of the IPTV service. Based on the Innovation Diffusion Theory (IDT), IPTV specific attributes and personal characteristics, we derive eight key factors in the research model. compatibility, ease of use, image, diversity of contents, interactivity, monetary value, social influence, and user satisfaction. Using the partial least square (PLS) method on the data collected through a web-based survey, we test our research model with several hypotheses. From this study, we find that diversity of contents, compatibility and interactivity have a significant indirect effect on the use of IPTV service via user satisfaction, and user satisfaction and social influence also have a significant direct impact on the IPTV use. These findings not only provide practical insights on the consumer acceptance of new technology-converging services, but also help managers to plan their marketing strategies better.

• Journal of Mechanical Science and Technology
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• 제18권7호
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• pp.1169-1176
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• 2004

Soot has a great effect on the formation of PM (Particulate Matter) in D.I. (Direct Injection) Diesel engines. Soot in diesel flame is formed by incomplete combustion when the fuel atomization and mixture formation were poor. Therefore, the understanding of soot formation in a D.I. diesel engine is mandatory to reduce PM in exhaust gas. To investigate soot formation in diesel combustion, various measurements have been performed with laser diagnostics. In this study, the relative soot diameter and the relative number density in a DJ. engine was measured by using LIS (Laser Induced Scattering) and LII (Laser Induced Incandescence) methods simultaneously which are planar imaging techniques. And a visualization D.I. diesel engine was used to introduce a laser beam into the combustion chamber and investigate the diffusion flame characteristics. To find the optimal condition that reduces soot formation in diesel combustion, various injection timing and the swirl flow in the cylinder using the SCV (Swirl Control Valve) were applied. From this experiment, the effects of injection timing and swirl on soot formation were established. Effective reduction of soot formation is possible through the control of these two factors.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2004년도 제22회 춘계학술대회논문집
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• pp.180-185
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• 2004

Our previous study showed that although the hybrid rocket engine with swirling gaseous oxygen had high performance, a direct injection of LOX with swirl into the combustion chamber of the hybrid rocket engine lowered the performance of the engine, compared to that with gaseous oxygen. In order to clarify this reason, combustion tests of a small PMMA combustor with an inner port diameter of 2 mm were conducted in liquid oxygen flow by comparison with gaseous oxygen flow. Although the oxygen mass fluxes of LOX were about two orders of magnitude larger than those of gaseous oxygen, the fuel regression rate of LOX were remarkably smaller than those of gaseous oxygen. For both liquid and gaseous oxygen, diffusion flames in the port of the grain controlled the combustion process of PMMA in oxygen flow. These results may be explained by the fact that only small amount of LOX vaporized and consumed in the combustion with PMMA while flowing through the port due to relatively larger latent heat of injected liquid oxygen compared to the heat of release by combustion which depended on the burning surface area of PMMA.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제49권5호
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• pp.327-337
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• 2000

In this paper, the design sensitivity formula for the control of the transient temperature distribution is developed using the direct differentiation method, and used for the optimal design of induction heating coil position. The temperature distribution is calculated using the heat source of the induced eddy current and heat diffusion equation. The physical property variations of the workpiece depending on the temperature are considered. The eddy current distribution and the temperature distribution are calculated with the 2D finite element procedure. The adjoint variable technique is employed in expressing the design sensitivity. The goal of the design is to have the desired distribution of the temperature on a specific region of the sensitivity. The goal of the design is to have the desired distribution of the temperature on a specific region sensitivity. The goal of the design is to have the desired distribution of the temperature on a specific region of the workpiece. The numerical example shows that the proposed design sensitivity analysis for the control of the transient temperature distribution is very useful and practical in the optimal design of induction heating coils.

• 한국자동차공학회논문집
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• 제14권5호
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• pp.172-180
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• 2006

This study was to analyze the effect of mixed fuel composition and mass fraction on the characteristics of evaporating diesel spray and combustion under the various ambient conditions. The characteristics of vaporization distribution and combustion were visualized by laser induced fluorescent method and direct photography. The experiments were conducted in the constant volume vessel and rapid compression expansion machine with optical access. Multi-component fuels mixed i-octane, n-dodecane and n-hexadecane were injected the vessel and rapid compression expansion machine with electronically controlled common rail injector. Experimental results show that fuel vapor formed stratified distribution. And vaporization and diffusion are become actively increasing in mass fraction of low boiling point component. Consequently multi-component fuels were expected to control the evaporating behavior according to their suitable mass fraction.

• 한국기후변화학회지
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• 제7권3호
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• pp.357-371
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• 2016

Buildings in the city acts as a cause of distorted wind direction, wind speed, causing the stagnation of the air flow. In the recent trend of climate change can not but consider the temperature rise of the urbanization. This study was aimed to analyze the thermal comfort of planetary boundary layer in different artificial constructions areas which has a direct impact on urban climate, and estimating the warming phenomena. Envi-met model was used to consider the urban structure associated with urban growth in order to precisely determine the impact of the building on the city weather condition. The analyzed values of thermal comfort index were temperature, wind speed, horizontal and vertical turbulent diffusivity. In particular, analysis of the PPD(Predicted Percentage of Dissatisfied) represents the human thermal comfort. In this study, by adjusting the arrangement and proportion of the top floor building in the urban it was found that the inflow of the fresh air and cooling can be derived low PPD. Vertical heat flux amount of the city caused by climate change was a factor to form a high potential temperature in the city and the accumulation of cold air does not appear near the surface. Based on this, to make the city effectively respond to climate change may require a long-term restructuring of urban spatial structure and density management.

• Biomolecules & Therapeutics
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• 제30권3호
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• pp.221-231
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• 2022

Adiponectin (Ad), a 30 kDa molecule, is an anti-diabetic adipokine; although derived from adipose tissue, it performs numerous activities in various other tissues. It binds to its own receptors, namely adiponectin receptor 1(AdipoR1), adiponectin receptor 2 (AdipoR2), and T-cadherin (CDH13). Ad plays several roles, especially as a regulator. It modulates lipid and glucose metabolism and promotes insulin sensitivity. This demonstrates that Ad has a robust correlation with fat metabolism. Furthermore, although Ad is not in direct contact with other tissues, including the skin, it can be delivered to them by diffusion or secretion via the endocrine system. Recently it has been reported that Ad can impact skin cell biology, underscoring its potential as a therapeutic biomarker of skin diseases. In the present review, we have discussed the association between skin cell biology and Ad. To elaborate further, we described the involvement of Ad in the biology of various types of cells in the skin, such as keratinocytes, fibroblasts, melanocytes, and immune cells. Additionally, we postulated that Ad could be employed as a therapeutic target to maintain skin homeostasis.