Jo Aug 26, 2025
Hydrogen sulfide (H2S) is a toxic gas abundant in industrial gases such as ammonia synthesis tail gas, methanol synthesis tail gas, coke oven gas and refinery gas. Carbon dioxide always exists along with hydrogen sulfide in industrial gases. Hence, there is a growing interest in the selective removal of H2S from gas streams with high concentration of CO2, compared to H2S.
However, a considerable amount of CO2 can also be absorbed during the conventional desulfurization process by the wet oxidation method because both H2S and CO2 are acidic and similar in their physical and chemical properties. Consequently, it can increase the consumption of absorption liquid and aggravate the energy load of solution regeneration units. Therefore, absorbents for industrial gas sweetening processes should be able to selectively absorb hydrogen sulfide against carbon dioxide, which will then greatly intensify the process efficiency and bring social and economic benefits.
Ri Jin Hyok, a researcher at the Faculty of Chemical Engineering, has investigated the selective removal of H2S from high-concentration CO2 by using Na2CO3+NaHCO3 solution doped with “888” catalyst in a microporous tube-in-tube microchannel reactor (MTMCR).
As a result, he has found that the removal efficiency and selectivity of H2S are significantly affected by catalyst concentration, alkalinity of adsorbent, NaHCO3 content and gas–liquid ratio. In other words, with increasing alkalinity and liquid flow rate, the removal efficiency of H2S increases but its selectivity decreases, and the selectivity increases with increasing NaHCO3 contents.
For more information, please refer to his paper “Selective removal of H2S from high concentration CO2 by catalytic wet oxidation in microporous tube-in-tube microchannel reactor” in “Brazilian Journal of Chemical Engineering” (SCI).
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Jo Aug 25, 2025
In WSNs, sensor nodes can usually be characterized by mutually conflicting multiple criteria.
How to combine these multiple criteria and design the optimum cluster-based routing protocol is still a challenge to be solved.
Ri Man Gun, an institute head at the Faculty of Communications, has proposed a novel joint optimization uneven cluster-based routing protocol, using an integrated FCNP-VWA-ELECTRE in the whole processing of the cluster route establishment phase.
This protocol operates in a cluster-route establishment phase and a data gathering phase. In the cluster-route establishment phase, FCNP-VWA allocates relative weights to 6 criteria, and based on these weights, ELECTRE selects a Cluster Head (CH) node, enlists the Cluster Member (CM) nodes in the proper CH node, and selects a next hop CH node for inter-cluster communication.
The simulation results show that the proposed protocol is superior to the existing schemes in terms of network lifetime.
You can find the details in his paper “An Uneven Cluster-based Routing Protocol for WSNs using an Integrated FCNP-VWA-ELECTRE” in “9th International Conference on Computer and Communication Systems (ICCCS)” (EI).
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Jo Aug 24, 2025
The suction valve and the discharge valve placed at the inlet port and outlet port of the cylinder in a reciprocating compressor or a piston-type compressor are important elements. They make gas flow in one-way into and out of the cylinder, so they have the greatest influence on the operating performance of machines, i.e., on the mechanical efficiency and reliability. In particular, the failure of a single valve in a multi-valve cylinder does not result in a significant difference in the temperature of the cylinder, but leads to the reduction in the discharge flow rate and the efficiency.
The valve is a component with the greatest impact on the efficiency, discharge rate and reliability of a reciprocating compressor and, according to the statistics, about 60% of the failure of reciprocating compressors is caused by valve failure. Therefore, the study on fault diagnosis of pneumatic valves is of great practical significance.
Among the valves of a reciprocating compressor, the suction valve is a very important working component. Generally, in order to analyze diagnosis of the leakage failure of a suction valve and investigate the valve leakage failure characteristics of compressors, simulations on the leakage failure of suction valves are conducted, and field observations on the compressors at different situations of fault operation and normal operation are performed using thermal energy parameters, indicator diagram and vibration method.
Ri Tong Ju, a researcher at the Faculty of Mechanical Science and Technology, has analyzed the effect of valve cracking pressure on the discharge flow rate of a reciprocating multistage large compressor. He used AMESim for the analysis of its operating characteristics.
He has confirmed that the stiffness of the first stage valve alone has a significant effect on the discharge flow rate of the reciprocating large compressor.
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Jo Aug 22, 2025
Induction heating generators are series resonant inverters (SRI) or parallel resonant inverters (PRI) in which the resonant tank consists of an induction coil and a capacitor. They are used to heat metals to be welded, melted, brazed or hardened.
In order to regulate the output power, SRI uses a diode bridge rectifier as a DC voltage source, and employs frequency (FC), phase-shift (PS) variation or pulse density modulation (PDM). These power control schemes, however, may result in an increase of switching losses and electromagnetic noise because it is impossible for switching devices to be always turned on and off under zero-current condition.
Therefore, only MOSFET inverters can be used in high-frequency induction heating applications. Nevertheless, isolated-gate bipolar transistors (IGBTs) are preferred in high-power industrial applications.
Ri Nam Jin, a researcher at the Faculty of Automation Engineering, has proposed an induction heating system of 15kW and 30kHz for industrial applications, which uses a novel control scheme based on a PS IGBT full-bridge SRI that allows us to significantly improve its reliability by increasing the lifetime of IGBTs.
In this power control mode, load adaptive variable frequency regulation and automated dead-time management are performed simultaneously in order to ensure that the inverter ensures zero voltage switching at all power levels and load conditions.
The comparative study between the proposed method and standard PS power control has demonstrated the effectiveness of the proposed one.
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Jo Aug 21, 2025
354 aluminum cast alloy is widely used for the manufacture of complex parts in various fields such as automotive industry due to its light weight and high strength. However, the tensile properties of this alloy, like other Al-Si alloys, decline rapidly at the temperatures above 300℃.
Up to date, many researchers have carried out numerous studies to improve the microstructure and high-temperature tensile properties of Al-Si-Cu-Mg alloys, by micro additions of alloying elements such as Zr, Ni and Ce and heat treatments. However, no studies have focused on determining the optimum addition amounts of Zr, Ni and Ce and heat treatment process parameters to maximize the tensile properties of 354 alloy at 300℃.
Ri Wi Song, a researcher at the Faculty of Materials Science and Technology, has conducted a study to determine the optimum addition amounts of Zr, Ni and Ce and heat treatment process parameters for the maximum tensile properties at 300℃ of 354 alloy, using TOPSIS method and Taguchi method.
As a result, he has found that the optimum addition amounts and heat treatment process parameters are as follows: Zr 0.3%, Ni 0.2%, Ce 0.1%, SHT (solution heat treatment) temperature 510℃, SHT time 10h, aging temperature 180℃ and aging time 6h.
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Jo Aug 20, 2025
Efficient block assembly scheduling is very important for building ships in the shortest possible time with efficient use of the facilities and resources of shipyards. Process planning is usually focused on determining the precedence constraints and weight factors of appropriate assembly units and tasks, but previous studies have mainly dealt with manufacturing processes such as welding.
The hull is a complex structure, so the deformation and stress generated during welding are also complex. The confinement of deformation during welding will increase residual stress, whereas the freedom of deformation will increase residual strain, making it difficult to assemble hull blocks. Therefore, the longitudinal strength of a hull must be taken into account when assembling it.
Ro Un Hyok, a researcher at the Faculty of Shipbuilding and Ocean Engineering, has proposed a process planning method based on the determination of precedence constraints and weighting factors for hull block assembly scheduling, taking into account the longitudinal strength of hulls.
According to the practical situation where precedence constraints and machine constraints exist, he proposed a mathematical model for hull block assembly scheduling, and a solution algorithm based on Lagrangian relaxation.
By addressing the precedence constraints based on assembly sequence and weight factor determination according to welding method in the hull block assembly process, he has laid a theoretical basis for process planning for block assembly scheduling, and he developed mathematical modeling and solution methods for these problems.
The results of the practical examples show that the proposed method provides rapid and effective solutions and it can be applied to the industry.
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