• Journal of the Korean Wood Science and Technology
• /
• 제27권4호
• /
• pp.30-37
• /
• 1999

The effects of heat treatment on the dimensional stability and bending properties of radiata pine sapwood were investigated. The dimensional stability was almost achieved by heat treatment though the loss of strength was accompanied as a negative effect. The improvement in dimensional stability of wood and the resultant reduction in bending properties were closely related to treatment temperature and duration. The optimum treatment conditions, which could be used to achieve a desired improvement in dimensional stability with resultant losses in modulus of rupture were proposed based on the results obtained in this study.

• Structural Engineering and Mechanics
• /
• 제32권3호
• /
• pp.429-445
• /
• 2009

Thermal stability of quasi-isotropic composite and polymeric structures is considered one of the most important criteria in predicting life span of building structures. The outdoor applications of these structures have raised some legitimate concerns about their durability including moisture resistance and thermal stability. Exposure of such quasi-isotropic composite/polymeric structures to various and severe climatic conditions such as heat flux and frigid climate would change the material behavior and thermal viability and may lead to the degradation of material properties and building durability. This paper presents an analytical model for the generalized problem. This model accommodates the non-linearity and the non-homogeneity of the internal heat generated within the structure and the changes, modification to the material constants, and the structural size. The paper also investigates the effect of the incorporation of the temperature and/or material constant sensitive internal heat generation with four encountered climatic conditions on thermal stability of infinite cylindrical quasi-isotropic composite/polymeric structures. This can eventually result in the failure of such structures. Detailed critical analyses for four case studies which consider the population of the internal heat generation, cylindrical size, material constants, and four different climatic conditions are carried out. For each case of the proposed boundary conditions, the critical thermal stability parameter is determined. The results of this paper indicate that the thermal stability parameter is critically dependent on the cylinder size, material constants/selection, the convective heat transfer coefficient, subjected heat flux and other constants accrued from the structure environment.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2003년도 춘계학술대회
• /
• pp.1372-1377
• /
• 2003

The stabilization of propane/air lean premixed flames by a heated cylindrical rod is investigated experimentally. The flame stability limits, heat flux, surface temperatures, equivalence ratios, and mixture velocities are measured in order to understand the role of heat flux or surface temperature on the flame stabilization of lean premixed flames. The flame stability limits are lowered by a heated cylindrical rod and extended even below the flammability limit of propane/air mixture when sufficient heat flux is provided. The flame stability limit decreases with the increase of heat flux or surface temperature and decreases with the higher mixture velocity. The diameter of cylindrical rod, however, dose not significantly affect the flame stability limit. The laminar flame speed has been measured for ultra lean propane/air premixed flames. The flame stabilization by a heated cylindrical rod provides the useful tool for the measurement of flame speed under very fuel-lean conditions.

• Preventive Nutrition and Food Science
• /
• 제3권2호
• /
• pp.133-142
• /
• 1998

Effects of protein heat treatment and surfactant additionoo the orthokindetic stability of $\beta$-lactoglobulin-stabilized emulsions have been investigated under turbulent flow conditions. In studies on protein-stabilized emulsions, samples which had been subjected to heat treatment(i.e. the protein solution orthe emulsion) have been found to be more prone to orthokinetic coalescene than the untreated ones. The emulsions stabilized with protein heated above the denaturation temperature(i.e. 7$0^{\circ}C$) showed the bigger initial average droplet size, which resulted in an increased orthokinetic coalescenece rate. The storage of the protein-stabilized emulsion at high temperature prior to the shearing experiment also made the emulsion less stable in the shear field. Interestingly. the addition of DATEM has been found to produce a substantial increase in orthokinetic stability of the heat-denatured protein-stabilized emulsion system, although Tween 20 is the opposite case.

• Journal of the Korean Wood Science and Technology
• /
• 제47권5호
• /
• pp.567-578
• /
• 2019

A common problem with fast-growing hardwoods is dimensional instability that limits use of their wood. In this study, we investigated the effects of pre-drying methods, temperatures, and heating duration on the specific gravity, water absorption, and dimensional stability of three tropical fast-growing hardwoods, jabon (Neolamarckia cadamba Roxb.), sengon (Falcataria moluccana Miq.), and mangium (Acacia mangium Willd.). Wood samples were pre-dried by two methods (fan and oven at $40^{\circ}C$), and heat treatments were performed at three temperatures (120, 150, and $180^{\circ}C$) for two different time periods (2 and 6 hours). The specific gravity, water absorption, dimensional stability, and structural changes of the samples were evaluated. The results revealed that heat treatments slightly reduced the specific gravity of all three wood species. In addition, the heat treatments reduced water absorption and significantly improved dimensional stability of the samples. Oven pre-drying followed by heat treatment at $180^{\circ}C$ for 6 hours resulted in good physical improvement of jabon and sengon wood. Fan pre-drying followed by heat treatment at $180^{\circ}C$ for 2 hours improved the physical properties of mangium wood. The heat treatment shows a promising technique for improving the physical characteristic of fast growing hardwoods.

• Tribology and Lubricants
• /
• 제11권5호
• /
• pp.47-54
• /
• 1995

An advanced liquid lubricants for heat engines has been developed and tested successfully in a prototype engine. The lubricant possesses superior oxidation stability and high temperature stability and is capable of surviving for a minimum of three minutes at 425$^{\circ}$C (800$^{\circ}$C) at the ring zone and maintains stability at an oil sump temperature of 171$^{\circ}$C. The lubricant has been evaluated by the Cummins Engine Co. Out of a field of several dozens of lubricant, six lubricant was selected for a prototype 200 hours endurance testing. The NIST lubricant was one of the two lubricants that successfully finished the endurance testing. This paper describes the key lubricant considerations including oxidation and thermal stability, volatility, deposit control. The engine test conditions and the results will be presented.

• BMB Reports
• /
• 제41권2호
• /
• pp.108-111
• /
• 2008

Some proteins of E. coli are stable at temperatures significantly higher than $49^{\circ}C$, the maximum temperature at which the organism can grow. The heat stability of such proteins would be a property which is inherent to their structures, or it might be acquired by evolution for their specialized functions. In this study, we describe the identification of 17 heat-stable proteins from E. coli. Approximately one-third of these proteins were recognized as having functions in the protection of other proteins against denaturation. These included chaperonin (GroEL and GroES), molecular chaperones (DnaK and FkpA) and peptidyl prolyl isomerases (trigger factor and FkpA). Another common feature was that five of these proteins (GroEL, GroES, Ahpc, RibH and ferritin) have been shown to form a macromolecular structure. These results indicated that the heat stability of certain proteins may have evolved for their specialized functions, allowing them to cope with harsh environments, including high temperatures.

• 열처리공학회지
• /
• 제23권2호
• /
• pp.83-89
• /
• 2010

Diamond-like carbon (DLC) coating was studied to be a good tribological problem-solver due to its low friction characteristics and high hardness. However, generally hydrogenated DLC film has shown a weak thermal stability above $300^{\circ}C$. However, the silicon doping DLC process by DC pulse plasma enhanced chemical vapor deposition (PECVD) for the new DLC coating which has a good characterization with thermal stability at high temperature itself has been observed. And we were discussed a process for optimizing silicon content to promote a good thermal stability using various tetramethylsilane (TMS) and methane gas at high-temperature. The chemical compositions of silicon-containing DLC film was analyzed using X-ray photoelectron spectroscopy (XPS) before and after heat treatment. Raman spectrum analysis showed the changed structure on the surface after the high-temperature exposure testing. In particular, the hardness of silicon-containing DLC film showed different values before and after the annealing treatment.

• 한국연소학회:학술대회논문집
• /
• 한국연소학회 2015년도 제51회 KOSCO SYMPOSIUM 초록집
• /
• pp.247-250
• /
• 2015

The characteristics of opposed nonpremixed tubular flames with radiation heat loss are investigated using linear stability analysis and 2-D numerical simulations. Two extinction limits, as the $Damk{\ddot{o}}hler$ number is small or large, are confirmed using finite difference method with a simple continuation method. It is verified that the results of linear stability analysis predict the number of flame cells and the critical Da starting cellular instability or amplification of temperature near both extinction limits with good resolution.

• Food Science and Biotechnology
• /
• 제17권3호
• /
• pp.637-641
• /
• 2008

This study investigated the heat stability of L-ascorbic acid (AA) in acetic acid solution. To analyze the degradation of AA using high performance liquid chromatography (HPLC), AA was measured at a wavelength of 244 nm in acetic acid and 265 nm in distilled water. During the storage of AA in acetic acid or distilled water at $37^{\circ}C$, degradation of AA was slower in acetic acid than in distilled water. On examining various ratios of AA to acetic acid, the stability of AA at $100^{\circ}C$ for 30 min was the highest when the concentration of acetic acid was 10 times higher than the concentration of AA. After acetic acid was added into AA degraded by heating, the AA is stabilized by reheating. Ultimately, these results indicate that degraded AA is reduced by hydrogen ions dissociated from acetic acid, and the rate of reduction of degraded AA in acetic acid solution is improved with heat processing.