• Journal of the Korean Society for Precision Engineering
• /
• v.11 no.1
• /
• pp.71-79
• /
• 1994

The aim of this study is to analyze the behavier of SUS 304 during the cutting process and the resulting cutting temperaturce. Since SUS 304 is a difficult-to-machine material, tool damage is largely affected by the suitability of cutting conditions. Therefore, in varying such cutting conditions, the experiment investigates the relations between cutting temperature and tool wear during the cutting process. All the cutting temperature data were manipulated successfully, and the tool temperature distributions were analyzed by a finite element method based on the acquisition data. In the results, the characteristics of cutting temperature are related to the difficulty of machining characteristics.

• Journal of the Korean housing association
• /
• v.1 no.1
• /
• pp.91-102
• /
• 1990

The aim of this study is to discover thermal characteristics of Ondol heating systems. The housing subjected was categorized into detached single family houses and apartments, reinforced concrete and brick structures, intermittent and continous heating system, and the space subjected was bedroom. In order to understand the thermal characteristics of each floor heating systems, the vertical distribution of indoor temperature and the distribution of surface temperature on the floor were measured. The vertical distribution of indoor temperature except the measurement point 1 largely showed average temperature distribution, and the temperature of the measurement point 1 in the housing surveyed showed the highest temperature in the house "sample A" because of the radiation heating from the floor of the Ondol room. As the result of the measurement, the thermal characteristics of each heating system were more stable distribution in apartments of R.C structure.structure.

• Journal of the Korean Society of Combustion
• /
• v.11 no.1
• /
• pp.11-18
• /
• 2006

In this work, $TiO_2$ nanoparticles were synthesized using $N_2-diluted$ and Oxygen-enriched coflow hydrogen diffusion flames. The effect of flame temperature on the characteristics of the formed $TiO_2$ nanoparticles was investigated. The measured maximum centerline temperature of the flame ranged from 2,103 K for oxygen-enriched flame to 1,339 K for $N_2-diluted$ flame. The visible flame length and the height of the main reaction zone were characterized by direct photographs. The characteristics of synthesized $TiO_2$ nanoparticles were analyzed by SEM and TEM images. From these images, it was evident that the formed nanoparticles were divided into two sorts. In the higher temperature region, over the 1,700 K, $TiO_2$ nanoparticles having spherical shapes with diameters about 60 nm were synthesized. In the lower temperature region, below the 1,600 K, the diameters of formed nanoparticles having unclear boundaries were ranged from 35 - 50 nm.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.21 no.7
• /
• pp.373-379
• /
• 2009

In this study, frosting experiment was conducted to investigate the characteristics of frost formed on heat exchanger fins of non-uniform temperature distribution. Temperature distribution and frost characteristics of a 2-D fin surface were investigated in the airflow direction and the direction perpendicular to airflow. Temperature gradient was very small in the airflow direction, while it was large in the direction perpendicular to airflow due to fin heat conduction. The variations of the frost thickness gradient and the frost density gradient in the direction perpendicular to airflow were significant. On the other hand, the temperature gradient on frost surface in the direction perpendicular to airflow was significant at the early stage of frosting, while it decreased gradually as time elapsed.

• Journal of the Semiconductor & Display Technology
• /
• v.16 no.3
• /
• pp.116-120
• /
• 2017

Temperature uniformity of a wafer in a semiconductor process is a very important factor that determines the overall yield. Therefore, it is very important to confirm the temperature characteristics of the chuck surface on which the wafer is lifted. The temperature characteristics of the chuck depend on the external heat source, the shape of the cooling channel inside the chuck, the material on the chuck surface, and so on. In this study, CFD confirms the change of temperature characteristics according to the stacking order of ceramic materials on the chuck surface, and suggests the best lamination method.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.24 no.7
• /
• pp.525-531
• /
• 2011

In this paper, experimental analyses have been performed to compare the electrical characteristics of n channel LT(low temperature) and HT(high temperature) poly-Si TFTs(polycrystalline silicon thin film transistors) on quartz substrate according to activated step annealing. The size of the particles step annealed at low temperature are bigger than high temperature poly-Si TFTs and measurements show that the electric characteristics those are transconductance, threshold voltage, electric effective mobility, on and off current of step annealed at LT poly-Si TFTs are high more than HT poly-Si TFT's. Especially we can estimated the defect in the activated grade poly crystalline silicon and the grain boundary of LT poly-Si TFT have more high than HT poly-Si TFT's due to high off electric current. Even though the size of particles of step annealed at low temperature, the electrical characteristics of LT poly-Si TFTs were investigated deterioration phenomena that is decrease on/off current ratio depend on high off current due to defects in active silicon layer.

• Journal of the Korean Ceramic Society
• /
• v.46 no.3
• /
• pp.330-335
• /
• 2009

We investigated the effects of the re-oxidation temperature and time on the positive temperature coefficient (PTC) of resistivity characteristics of Sm-doped $BaTiO_3$ sintered at $1200{\sim}1260^{\circ}C$ for 2 h in a reducing atmosphere (3% $H_2/N_2$), followed by re-oxidization processes in air, in which re-oxidization temperature and time were $600{\sim}1000^{\circ}C$ and $1{\sim}10$h, respectively. The result reveals that Smdoped (Ba,Ca)$TiO_3$ ceramics fired in a reducing atmosphere exhibit low PTC characteristics, whereas the sample re-oxidized at $800^{\circ}C$ for 1 h in air exhibit pronounced PTC characteristics. The room-temperature resistivity and jumping characteristics of resistivity (${\rho}_{max}/{\rho}25^{\circ}C$) decrease with Sm contents. The PTC characteristics with reoxidization time at $800^{\circ}C$ have improved about $2{\sim}3$ orders of magnitude whereas differed according to the sintering temperature. The 0.7 at% Sm-doped (Ba,Ca)$TiO_3$ samples reveal the best PTC characteristics in the present range of formula and processes.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.26 no.12
• /
• pp.1-8
• /
• 2012

The performance and lighting characteristics of the LED depend on cooling condition because the power LED generates lots of heat. In this paper, the effect of the generated heat from power LED module on lighting characteristics and performance is measured and evaluated. For experiments, the transient temperature of a power LED module with cooling condition is measured. In addition, the temperature and lighting characteristics of the LED module are measured during the steady state. As a result, the cooling condition is less effective on the lighting characteristics of the LED module at rated current but the cooling condition extremely affects those of the LED module over the rated current. Because high temperature of the power LED module causes the low phosphor conversion, luminance efficiency becomes low and color temperature becomes high. When power LED module are driven over the rated condition, higher temperature is directly related to lighting characteristics and performance of the LED module rather than higher current.

• Journal of Sensor Science and Technology
• /
• v.29 no.4
• /
• pp.275-278
• /
• 2020

In this study, we evaluated the temperature-dependent characteristics of homojunction InGaAs vertical Fin-shaped Tunnel Field-Effect Transistors (Fin TFETs), which were fabricated using a novel nano-fin patterning technique in which the Au electroplating and the high-temperature InGaAs dry-etching processes were combined. The fabricated homojunction InGaAs vertical Fin TFETs, with a fin width and gate length of 60 nm and 100 nm, respectively, exhibited excellent device characteristics, such as a minimum subthreshold swing of 80 mV/decade for drain voltage (V_DS) = 0.3 V at 300 K. We also analyzed the temperature-dependent characteristics of the fabricated TFETs and confirmed that the on-state characteristics were insensitive to temperature variations. From 77 K to 300 K, the subthreshold swing at gate voltage (V_GS) = threshold voltage (V_T), and it was constant at 115 mV/decade, thereby indicating that the conduction mechanism through band-to-band tunneling influenced the on-state characteristics of the devices.

• Tribology and Lubricants
• /
• v.27 no.2
• /
• pp.109-114
• /
• 2011

The low temperature characteristics of automotive diesel have been legally regulated due to the fact that solid particle in diesel at low temperature can cause severe problems in the vehicle. The biodiesel is well known for eco-friendly fuel, which is one of the most popular alternative petrodiesel, but it is easy to solidified at low temperature than petrodiesel at low temperature. For that reason, in this study, we investigated the low temperature fuel characteristics of diesel-biodiesel blends which were prepared to mix 6 different kinds of biodiesel to winter diesel fuel, respectively. Also, we confirmed to improve low temperature fuel characteristics by pour point depressant.