• Advances in materials Research
• /
• v.1 no.1
• /
• pp.83-92
• /
• 2012

The effect of under-bump-metallization (UBM) on electromigration was investigated at temperatures ranging from $135^{\circ}C$ to $165^{\circ}C$. The UBM structures were examined: 5-${\mu}m$-Cu/3-${\mu}m$-Ni and $5{\mu}m$ Cu. Experimental results show that the solder joint with the Cu/Ni UBM has a longer electromigration lifetime than the solder joint with the Cu UBM. Three important parameters were analyzed to explain the difference in failure time, including maximum current density, hot-spot temperature, and electromigration activation energy. The simulation and experimental results illustrate that the addition 3-${\mu}m$-Ni layer is able to reduce the maximum current density and hot-spot temperature in solder, resulting in a longer electromigration lifetime. In addition, the Ni layer changes the electromigration failure mode. With the $5{\mu}m$ Cu UBM, dissolution of Cu layer and formation of $Cu_6Sn_5$ intermetallic compounds are responsible for the electromigration failure in the joint. Yet, the failure mode changes to void formation in the interface of $Ni_3Sn_4$ and the solder for the joint with the Cu/Ni UBM. The measured activation energy is 0.85 eV and 1.06 eV for the joint with the Cu/Ni and the Cu UBM, respectively.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.18 no.3
• /
• pp.211-217
• /
• 2006

The three-dimensional numerical analysis has been carried out to figure out the effect of the thermoelectric element thickness on the thermal performance of the thermo-electric micro-cooler. The small-size and column-type thermoelectric cooler is considered. It is known that tellurium compounds currently have the highest cooling performance around the room temperature. Thus, in the present study, $Bi_{2}Te_{3}$ and $Sb_{2}Te_{3}$ are selected as the n- and p-type thermoelectric materials, respectively. The thermoelectric leg considered is less than $20{\mu}m$ thick. The thickness of the leg may affect the thermal and electrical transport through the interfaces between the leg and metal conductors. The effect of the thermoelectric element thickness on the thermal performance of the cooler has been investigated with parameters such as the temperature difference, the current, and the cooling power.

• Journal of the Korean Society of Safety
• /
• v.26 no.4
• /
• pp.102-110
• /
• 2011

For decreasing of the casualties and designing of the smoke control systems in the ultra high-rise building, the programs for analysis of smoke control were developed for prediction of smoke spread and distributions of pressure and temperature in building fire situation. In this study, coupling algorithm between mass and enthalpy conservations was modified for improving the applicability of the CAU_ESCAP which program can consider the energy transfer. The fire situation in ultra high-rise building was applied by using the modified CAU_ESCAP. Results of pressure difference predicted by modified CAU_ESCAP are higher than results of ASCOS as stack effect is generated due to the increasing of stairway temperature. Moreover, theoretically, the result of the neutral plane is more accurate than the result of ASCOS, in fire situation of ultra high-rise building.

• 한국해양학회지
• /
• v.27 no.3
• /
• pp.228-236
• /
• 1992

Internal temperature oscillations of tidal periods were studied using data observed by a thermistor chain in summer of 1980 off Jukbyun on the mid-east coast of korea. The vertical stratification was well established during the observation period. The spectral energy was found to be predominant in the semidiurnal tidal band and its energy increased with depth with maximum near the bottom. The coherence in the semidiurnal band between different depths is high with a small phase difference. The results suggest the existence of the internal tide of semidiurnal period. The amplitude of internal tide was of the order of 10 m and the largest just before the disappearance of the internal tide signal.

• Journal of the Korean Society of Mechanical Technology
• /
• v.13 no.3
• /
• pp.107-111
• /
• 2011

This carbon nano heating system was consisted of power supply equipment, a carbon fiber and a stainless flexible hose. carbon nano heating system was manufactured by carbon fiber of a power capacity 30kw/h and light-oil hot air heater in control plot was the heating capacity 30,000kcal/h, As the result, Temperature difference due to carbon nano heating system and hot air heater in greenhouse showed that air temperature at experimental greenhouse, comparison greenhouse were $14.8^{\circ}C$, $13.4^{\circ}C$ respectively. It was found that carbon nano heating system and light-oil hot air heater heating cost were 1,095,740won, 2,683,628won. therefore as heating cost saving 60%. Yield of tomatoes cultured in greenhouse using carbon nano heating pipe was 4% inclease. Economic analysis comparison between the carbon nano heating pipe and the hot air heater in greenhouse were 41% respectively.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2016.02a
• /
• pp.179-179
• /
• 2016

A radio-frequency (RF) Inductively Coupled Plasma (ICP) torch system was used for boron-nitride nano-tube (BNNT) synthesis. Because of electrodeless plasma generation, no electrode pollution and effective heating transfer during nano-material synthesis can be realized. For stable plasma generation, argon and nitrogen gases were injected with 60 kW grid power in the difference pressure from 200 Torr to 630 Torr. Varying hydrogen gas flow rate from 0 to 20 slpm, the electrical and optical plasma properties were investigated. Through the spectroscopic analysis of atomic argon line, hydrogen line and nitrogen molecular band, we investigated the plasma electron excitation temperature, gas temperature and electron density. Based on the plasma characterization, we performed the synthesis of BNNT by inserting 0.5~1 um hexagonal-boron nitride (h-BN) powder into the plasma. We analysis the structure characterization of BNNT by SEM (Scanning Electron Microscopy) and TEM (Transmission Electron Microscopy), also grasp the ingredient of BNNT by EELS (Electron Energy Loss Spectroscopy) and Raman spectroscopy. We treated bundles of BNNT with the atmospheric pressure plasma, so that we grow the surface morphology in the water attachment of BNNT. We reduce the advancing contact angle to purity bundles of BNNT.

• Journal of Korean Society for Atmospheric Environment
• /
• v.29 no.6
• /
• pp.734-744
• /
• 2013

In this study, the telematics device was installed on the car (OBD-II) to collect the information on the operation conditions from each sample vehicle. Based on the information the domestic driving pattern was analysed and the ratio of cold start length was estimated. As a result of analysis for driving pattern, we found a difference in the frequency of driving on the hourly or seasonal basis. Then, the driving pattern of the rush hours, weekdays, and weekends could be derived. Also, from the study, an average of 2.22 times per day occurred in a single trip and average driving distance for the trip was 15.72 km. In addition, the proportion of cold start length was analyzed to be 16.11%. The seasonal cold start length has big difference from season to season (Winter 26.63%, Summer 8.22%, Intermediate 12.65%). There was an inverse relationship between the outside temperature and ratio of cold start length. In order to improve the accuracy of the cold emission estimation, it is necessary to apply domestic ratio of cold start length that driving pattern and temperature in Korea is reflected.

• Journal of the Korean Solar Energy Society
• /
• v.22 no.3
• /
• pp.39-46
• /
• 2002

The results of experiment on the performance of natural ventilation by insulation thickness and height system of solar chimney are described. The 3-inside wall was made of concrete and 1-wall was made of glass. The two kinds of model experiment were performed. One was the varition of the 60cm, 90cm and 120cm of solar chimney, the other was the variation of the insulation thickness 10mm and 50mm and without insulation of outside wall of solar cimney. As the temperature difference between bottom and top expressed $1.7\sim2.9^{\circ}C$, air velocity measured $0.5\sim0.8m/s$ and ventilation rate was $194.4m^3/h$ in the case of the 120cm height of solar chimney, the respect of natural ventilation performance was superior to others cases in the first model experiment. Though the case of 120cm height of solar chimney was attached 50mm insulation the ventilation rate was not so much as the case of solar chimney was attached 10mm insulation. the temperature difference between bottom and top was the largest in the other cases. From this research, the natural ventilation performance of solar chimney was affected by not only height and insulation thickness of solar chimney but also wind velocity and directon.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.25 no.11
• /
• pp.1495-1504
• /
• 2021

An ultra-compact binary power generation plant converts thermal energy into electric power using temperature difference between heat source and cooling source. In the actual power generation environment, the characteristic value of the plant changes due to any negative effects such as environmental condition or corrosion of related equipment. If the characteristic value of the plant changes, it may lead to unstable output of the turbine in a conventional PID control system with fixed PID parameters. A Neuro PID control system based on Neural Network adaptively to adjust the PID parameters according to the change in the characteristic value of the plant is proposed in this paper. Discrete-time transfer function models to represent the dynamic characteristics near the operating point of the investigated plant are deduced, and a design strategy of the proposed control system is described. The proposed Neuro PID control system is compared with the conventional PID control system, and its effectiveness is demonstrated through the simulation results.

• Korean Chemical Engineering Research
• /
• v.50 no.3
• /
• pp.499-504
• /
• 2012

Characteristics of overall heat transfer were investigated in a three-phase slurry bubble column with relatively low surface tension media, which has been frequently encountered in the fields of industry. The heat transfer phenomena was examined in the system which was composed of a coaxial vertical heater and a proper of bubble column. The heat transfer coefficient was estimated from the measured mean value of temperature difference between the heater surface and the column proper at the steady state condition. Effects of gas velocity ($U_G$), solid fraction in the slurry phase ($C_S$) and surface tension (${\sigma}_L$) of continuous liquid media on the overall heat transfer coefficient (h) in the bubble column were determined. The mean value of temperature difference was estimated from the data of temperature difference fluctuations with a variation of time. The amplitude and mean value of temperature difference fluctuations with respect to the elasped time appeared to decrease with decreasing the surface tension of liquid phase. The overall heat transfer coefficient between the immersed heated and the bubble column increased with an increase in the gas velocity or solid fraction in the slurry phase, but it decreased with an increase in the surface tension of continuous liquid media. The overall heat coefficient in the slurry bubble column with relatively low surface tension media was well correlated in term of operating variables and dimensionless groups within this experimental conditions.