Jo Feb 16, 2023
Choe Chol Min, a researcher at the Faculty of Electronics, has developed a portable photocolorimetric ozone meter for regular calibration of a real-time ozone meter at disinfection stations, based on indigo carmine spectrophotometry.
Ozone disinfection process needs both correct real-time measurement of ozone concentration at disinfection stations and regular calibration of ozone meters.
All over the world, indigo carmine spectrophotometry is the choice of the standard method for measurement of ozone concentration and it is being widely used for the air and ozone generators.
The photocolorimetric ozone meter is based on Lambert-Beer’s law, which explains that absorbance is proportional to the concentration of chemical sorts absorbing the light when a solution absorbs the light of given wavelength and the thickness of the solution layer is fixed.
The photocolorimetric ozone meter consists of a driving circuit for light source, a light detection circuit, a filtering and amplifing circuit, a source supply stabilizing circuit and a microprocessor.
The driving circuit for light source contains a constant-current source circuit to stabilize the maximum of light source brightness. The light source driving current can be changed from 0mA to 22mA. For exact driving current, an operational amplifier AD8602 with 80㎶ of input bias voltage, 0.2pA of bias current, and 80dB of PSRR is used in the constant-current source circuit.
In the light detection circuit, higher accuracy of measurement is provided by the difference in the light intensity from the light source (I0) and that passed through the sample (I). Here, a low noise operational amplifier OPA111 is used.
The technical characteristics of the device are as follows.
Measuring range: 0~200ppm
Relative error: Less than 0.4%FS
Relative standard deviation: Less than 1% (n=11)
At persent, the meter is in wide use at several disinfection stations.
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Jo Feb 12, 2023
Flexible metallic film temperature sensors play an important role in some modern engineering applications such as temperature measurements of curved surfaces or interlayer structures with narrow gaps of industrial equipment (e.g. iron cores of generators, motors and transformers).
Platinum is generally used for metallic film temperature sensors thanks to its high accuracy and stability, but it is expensive. Recently, copper film temperature sensors are widely utilized for temperature measurement instead of platinum sensors as the design based on PCB technology allows cost-efficient fabrication, easy handling, and simple retrofitting and replacement. However, defects existing on the PCB leads result in the decline of the performance and stability of the sensor.
A research team led by Pak Yong Thaek, head of Semiconductor Institute, has developed a temperature measurement system for generator protection in consideration of the operation characteristics of generators. For this, they designed a new structure of temperature sensors and proposed a method to design the most suitable thermometer and communication hub for the conditions of power plants.
The system consists of sensors, one-channel and multi-channel thermometers and communication hubs.
The one-channel and multi-channel thermometers measure in real-time the temperature of local points, display the temperature values and output alarm sounds and protection relay signals. The thermometers also transmit measured data to the communication hub.
In order to avoid the lethal defects of PCB leads like disconnection and fall, detour leads are added to the new design. Thus, the copper film resistive lead of the sensor consists of four parts: main resistive lead, detour lead, correction lead and pads. In addition, 3-line mode is used to prevent low accuracy due to the connection wire from the sensor to the amplifing circuit.
The measurement range is -50~170℃ and the error is 0.5℃.
Tested for a long time of over 3 000 hours at 150℃, the sensor proved its reliability. The deviation rate of resistance of the sensor is less than 0.1%. TCR is 4.1×10-3℃-1 and the maximum current is 10mA.
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Jo Feb 11, 2023
“Samgukyusa” (History of the Three Kingdoms), together with “Samguksagi” (Chronicles of the Three Kingdoms), is known as the oldest historical book of all existing national classical legacies.
It was written by a Buddhist monk Il Yon (1206―1289) at the end of the thirteenth century. The histories of Koryo and other ancient states in our country with the main focus on the history of the period of the Three Kingdoms (Koguryo, Paekje and Silla), and the episodes of well-known monks are recorded in the style of unofficial history.
It is in five volumes and nine parts.
At the beginning of Volume 1 is “Wangryok”, a chronological table of dynasties of the Three Kingdoms and Karakguk. The rest of Volume 1, and Volume 2 have 36 articles from every king’s ruling period of Silla and other states after Ancient Korea and 23 articles from Later Silla, Later Paekje and Karakguk.
Volume 3 to Volume 5 mainly deal with Buddhist monks who contributed to the spread of Buddhism, other celebrated monks, towers, Buddhist statues and bells erected on famous mountains and at temples.
The book also contains poems and songs including 14 pieces of old Korean folksongs (native songs pronounced in Chinese characters), tales, history of old names of places, buildings and ways of life and other valuable data in every field including literature, fine art, sculpture, language, geography, folk customs, etc.
Therefore, it reveals some historical limitations. However, for its rich and precious content that cannot be found in other historical books, it is indispensable for research into the history and culture of our country.
Kim Chol Ryong, researcher at the Academy of Social Sciences
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Jo Feb 9, 2023
It is of great importance to make a proper classification of underwater sediments for protecting the ecological environment and dredging materials such as sand or gravel, mud, etc. in rivers or oceans.
Ri Un Song, a section head at the Faculty of Shipbuilding and Ocean Engineering, has newly defined some characteristic parameters and established Artificial Neural Network (ANN) with these parameters as input layers. By doing so, he has managed to find a way to raise the accuracy of acoustic sediment classification on rough riverbeds.
The neurons of input layers used include the newly-defined roughness and monotonic decreasingness of the tail potion of the first echo signal as well as the roughness index and hardness index usually employed in Rox Ann and QTCView.
The proposed method has raised the accuracy of acoustic classification of sediments in the water areas with rough floors to 95%.
It is now in effective use for search for gravels and sand by dredging vessels on riverbeds, and for classification of sediments accumulated on the dams of floodgates, tidelands, etc.
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Jo Feb 8, 2023
Ullim Falls is situated six kilometres east of Tonghung-ri, Chonnae County, Kangwon Province, and about ten kilometres north-east of Ryongpho Revolutionary Site in Poptong County.
75 metres in height, it is one of the most famous waterfalls in our country.
The name Ullim (literally echo) Falls means that the sound of the magnificent waterfall resounds far away across the whole valley.
Around the falls rise high mountain peaks one after another, whose feet are sword-shaped cliffs.
There are several facilities such as a sightseeing road, a bridge, an outdoor eating place, a car park, etc.
The magnificent view of Ullim Falls adds ardent love for the beautiful landscape of our motherland.
Sin Kwang Il, researcher at the Academy of Social Sciences
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Jo Feb 7, 2023
A research team led by Sin Jung Sok, a researcher at the Faculty of Earth Science and Technology, has developed an ultrasonic mixer to improve the combustibility of heavy oil burners by ultrasonic waves generated by the steam in a tubular furnace.
This technology can help to make ultrasonic waves by high pressure steam to change the carbon chain structure of heavy oil whose relative viscosity is over 200 and to decrease the viscosity. It leads to the improvement of spraying characteristics of burners and to the sharp reduction of consumption of heavy oil necessary for oil processing.
The ultrasonic mixer has 1st ultrasonic wave generator, mixing unit of heavy oil ― steam, 2nd ultrasonic wave generator, spraying unit, etc.
In the 1st ultrasonic wave generator, high pressure steam that passes through the jet orifice, resonator and reflector can make ultrasonic waves of 14~17kHz, which enter the heavy oil ― steam distributor.
In the heavy oil ― steam mixing unit, the heavy oil coming in four tangential directions through the heavy oil ― steam distributor is mixed with steam. Then, the mixed liquid is sprayed. At this time, the chain structure of the heavy oil is destroyed primarily by the ultrasonic waves.
When the sprayed liquid causes the 2nd resonance while passing the resonator of the 2nd ultrasonic wave generator, most of the heavy oil particles are pulverized to be smaller than 20㎛. The purpose of the 2nd ultrasonic wave generation is to break up the liquid particles mixed through the heavy oil ― steam distributor into smaller ones.
In the spraying unit, heavy oil and steam are mixed evenly and sprayed through 8 holes. The size of about 90% of heavy oil particles is within the range of 10~20㎛.
The intensity of ultrasonic wave is 200dB at the 1st ultrasonic wave generator and 220dB at the 2nd one.
If the size of heavy oil particles is below 30㎛, the combustion efficiency of heavy oil in tubular furnaces reaches higher than 95%, which equals the case of combustion of heavy oil whose relative viscosity is 100.
The introduction of this device to tubular furnaces for oil processing can lower the flue temperature by 15~20℃ and reduce the consumption rate of oil. It can also improve the spraying quality of liquid and raise the combustion efficiency in the burners of tubular furnaces.
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