• Journal of the Korean Society of Industry Convergence
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• v.25 no.5
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• pp.783-789
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• 2022

In this study, STS316L rolled at five rolling degrees were treated with two types of subzero temperatures for 10, 30, and 60 minutes, respectively, and the dominant frequencies of elastic waves was investigated. The dominant frequency was higher as the subzero temperature was lower and the subzero treatment time was longer at each rolling degree. On the other hand, the dominant frequency was higher as the elongation decreased. In the time-frequency analysis for subzero temperature and time of the specimen with a rolling degree of 33%, the dominant frequency was higher at a subzero temperature of -196℃ than -50℃ regardless of subzero treatment time.

• Journal of the Korean Society of Industry Convergence
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• v.24 no.3
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• pp.295-300
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• 2021

This study investigated the dominant frequency of the elastic waves from the tensile test. The specimen was rolled with five different rolling degrees (10, 22, 33, 42 and 50%), which was treated subzero. The specimen was rolled at room temperature, which was transformed from austenite to martensite (only α'-martensite). The dominant frequency increased with an increase in the rolling degree regardless of the subzero temperature, and decreased after 33% of the rolling degree. On the other hand, higher frequency band was obtained at lower temperature and long time. The dominant frequency increased when the amount of α'-martensite increased and decreased with the α'-martensite amount between 50-65%. The lower subzero treatment temperature increased the amount of α'-martensite, which resulted in the higher dominant frequency. The longer treatment time at the same subzero temperature led to an increase in the amount of α'-martensite, leading to high dominant frequency.

• Korean Journal of Metals and Materials
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• v.47 no.3
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• pp.169-174
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• 2009

The effect of sub zero treatment on the damping capacity in austempered ductile cast iron investigated. Austenite transformed in to martensite by subzero treatment, and with the decrease of subzero treatment temperature, volume fraction of martensite increased. Damping capacity of austempered ductile cast iron was highly increased by subzero treatment, with the decrease of subzero treatment temperature, damping capacity was slowly increased. With the decrease of subzero treatment time, damping capacity was rapidly increased to 30 min. and then slowly increased. With the increase of volume fraction of martensite, damping capacity rapidly increasing to 5% and then slowly increased.

• Korean Journal of Veterinary Research
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• v.59 no.1
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• pp.43-45
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• 2019

To establish appropriate conditions for a disinfectant efficacy test at subzero temperatures, this study examined mixtures of frozen foot-and-mouth disease virus or avian influenza virus solutions and disinfectant diluents at $-5^{\circ}C$ and monitored temperature and freezing status of an anti-freezing diluent (AFD, 15% ethanol + 30% propylene glycol + 55% distilled water) over time at various subzero temperatures. Viral solutions and disinfectant diluents froze before the mixtures reached $-5^{\circ}C$, whereas the AFD was not frozen at $-30^{\circ}C$. The times taken for the AFD to reach -10, -20, -30, and $-40^{\circ}C$ from room temperature were 36, 39, 45, and 48 min, respectively.

• Journal of the Korean Society for Heat Treatment
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• v.25 no.5
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• pp.233-238
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• 2012

The effect of subzero treatment on the mechanical properties of cold rolled high manganese austenitic stainless steel was investagated. ${\alpha}$'-martensite was formed by cold rolling, and it was formed with surface relief and specific direction or crossing each other. The volume fraction of martensite increased by subzero treatment, and it was increased with longer time of subzero treatment and higher temperature of subzero treatment. The hardness and strength increased by subzero treatment, while the elongation decreased. With the increase of volume fraction of martensite, the hardness and strength was increased steeply with proportional relationship, elongation was decreased slowly. The results show that the hardness and strength was strongly controlled by the volume fraction of martensite, and the elongation was affected by transformation behavior of deformation induced martensite in the initial stage of deformation.

• Food Science and Biotechnology
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• v.16 no.4
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• pp.610-614
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• 2007

Dynamic rheological properties of honeys with invert sugar at different mixing ratios of honey and invert sugar (10/0, 812, and 6/4 ratios) were evaluated at various low temperatures (-15, -10, -5, and $0^{\circ}C$) using a controlled stress rheometer for small-deformation oscillatory measurements. Honey-invert sugar mixtures displayed a liquid-like behavior, with loss modulus (G") predominating over storage modulus (G') (G">>G'), showing the high dependence on frequency (${\omega}$). The magnitudes of G' and G" increased with a decrease in temperature while their predominant increases were noticed at -10 and $-15^{\circ}C$. The greater tan ${\delta}$ values were found at higher temperature and ratio of honey to invert sugar, indicating that the honey samples at subzero temperatures become more viscous with increased ratio of honey to invert sugar and temperature. The time-temperature superposition (TTS) principle was used to bring G" values at various temperatures together into a single master curve. The TTS principle was suitable for the honey samples in the liquid-like state. The progress of viscous property (G") was also described well by the Arrhenius equation with high determination coefficients ($R^2=0.99$). Dynamic rheological properties of honey samples seem to be greatly influenced by the addition of invert sugar.

• Journal of the Korean Society for Heat Treatment
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• v.2 no.2
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• pp.33-37
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• 1989

In order to improve hardness uniformity of standard-hardness blocks. experimental procedure was designed using Taguchi Method. For this purpose the following factors were studied: austenitizing temperature, tempering condition, grinding condition, subzero treatment, lapping time, $15{\mu}m$ polishing time, final polishing time. These factors were processed and then ten hardness values were measured on each specimen. SN (signal to noise) ratio for each condition was calculated with standard variations of these values. Finally, from the calculated value of ANOVA on SN ratios, the lapping time was found to be the main factor Better uniformity with longer lapping time implies that residual stress that was formed after quenching is a dominent parameter that affects on the uniformity of hardness. Therefore, step-quenching method was adapted to minimize the residual stress. By this modification of quenching procedure, the hardness uniformity was improved remarkably and the yield ratio was increased from 55% to 88%.

• Korean Journal of Environmental Agriculture
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• v.41 no.3
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• pp.199-205
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• 2022

BACKGROUND: The freezing injury by pruning can be reduced by suspending pruning work when severe cold weather (-23 to -49℃) is forecast. Minimum air temperature of the study area, Gunwi region at February 3, 2012 was -21.9℃, and the subzero temperature continued until April 8, 2012. This study was conducted in two years to investigate the effect of delaying winter pruning until full bloom on shoot growth and fruit quality of 'Fuji'/M.9 apple trees. METHODS AND RESULTS: The time of pruning were March 26 for dormant, April 3 for bud break, and May 2 for full bloom. The winter pruning at full bloom significantly reduced fruit weight for two years compared with the control (winter pruning at dormant), and shoot growth was reduced only in the following year. There was no significant effect of delaying winter pruning at bud break on soluble solid content, fruit red color, return bloom, and pruning weight for two years compared with the control. CONCLUSION(S): These results indicated the delaying winter pruning at bud break of 'Fuji'/M.9 apple tree did not offer any disadvantage over comparable dormant pruning, since the fruit quality was not affected. The delayed pruning at full bloom resulted in decreased fruit weight, though shoot growth, fruit quality, and return bloom were not affected by the delayed pruning. So, the delayed pruning should be considered carefully only for the fruit tree orchards in diseases.

• Journal of the Korean association of regional geographers
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• v.4 no.2
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• pp.49-64
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• 1998

Bing-gye valley(Kyongbuk Province, South Korea) is well known as a tourist attraction because of its meteorologic characteristics that show subzero temperature during midsummer. Also, there are some interesting geomorphic features in the valley area. Therefore, the valley is worth researching in geomorphology field. The aim of this paper is to achieve two purposes. These are to clarify geomorphic features on talus within Bing-gye valley area, and to infer the origin of Bing-gye valley. The main results are summarized as follows. 1) The formation of Bing-gye valley It would be possible to infer the following two ideas regarding the formation of Bing-gye valley. One is that the valley was formed by differential erosion of stream along fault line, and the other is that the rate of upheaval comparatively exceeded the rate of stream erosion. Especially, the latter may be associated with the fact that the width of the valley is much narrow. Judging that the fact the width of the valley is much narrow, compared with one of its upper or lower valley, it is inferred that Bing-gye valley is transverse valley. 2) The geomorphic features of talus (1) Pattern It seems to be true that the removal of matrix(finer materials) by the running water beneath the surface can result in partly collapse hollows. Taluses are tongue-shaped or cone-shaped in appearance. They are $120{\sim}200m$ in length, $30{\sim}40m$ in maximum width. and $32{\sim}33^{\circ}$ in mean slope gradient. The component blocks are mostly homogeneous in size and shape(angular), which reflect highly jointed free face produced by frost action under periglacial environment. (2) Origin On the basis of previous studies, the type of the talus is classified into rock fall talus. When considered in conjunction with the degrees of both weathering of blocks and hardness of blocks, it can be explained that the talus was formed under periglacial environment in pleistocene time. (3) The inner structure of block accumulation I recognize a three-layered structure in the talus as follows: (a) superficial layer; debris with openwork texture at the surface, 1.3m thick. (b) intermediate layer: small debris(about 5cm in diameter) with fine matrix(including humic soil), 70cm thick. (c) basal layer: over 2m beneath surface, almost pure soil horizon without debris (4) The stage of landform development Most of the blocks are now covered with lichen, and/or a mantle of weathering. It is believed that downslope movement by talus creep well explains the formation of concave slope of the talus. There is no evidence of present motion in the deposit. Judging from above-mentioned facts, the talus of this study area appears to be inactive and fossil landform.