Jo Aug 29, 2025
Cutting tools have a decisive influence on the quality of machined parts and the efficiency of machining. Especially, the precision of cutting tools often leads to the precision of the gear class components.
There are two gear cutting methods; by forming and by generation. Because the gear cutting by forming has low machining accuracy and productivity, the gear cutting by generation is in common use. For gear generating, cutting tools such as a hob and a gear shaper cutter should be designed and manufactured precisely enough to increase the machining accuracy of gears.
The profile of a gear cutter is determined by the envelope equation of the instantaneous trajectory of the gear tooth profile. Therefore, the profile of the cutter can be determined only on the condition that the profile equation of the gear tooth to be machined is known. If the gear tooth profile is given as the measurement data or is a complex transcendental function, it is impossible to determine the profile of the cutter.
Choe Myong Chol, an institute head at the Faculty of Mechanical Science and Technology, has proposed a new method for 3D design of the toothed tool profile from the measurement data of a sample gear without any complex calculations in the way of reverse engineering.
This method can be applied to all generating cutters ranging from 2D to 3D tools.
For further details, please refer to his paper “3-D Design Method of the Gear Cutting Tool Profile Based on Reverse Engineering” in “Transactions of the Indian National Academy of Engineering” (SCI).
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Jo Aug 28, 2025
Silicoaluminophosphate (SAPO) molecular sieves have opened new perspectives in the conversion process of dimethyl ether to olefins (DTO) and recently, SAPO-18 catalysts with enhanced stability have been reported as catalysts for DTO reactions.
SAPO-18 is a microporous crystal of the AEI-type framework, in which only dimethyl ether (DME), light olefins and linear hydrocarbons can pass through the pores, while aromatic intermediates formed inside the pores cannot. This leads to coke deposition by the growth of aromatic intermediates during reactions, and the deposited coke blocks the pore entrance of the catalyst, leading to deactivation.
Therefore, it is necessary to improve the performance of catalysts that can delay their deactivation in the DTO reaction using the SAPO-18 catalyst.
Ho Yu Gyong, a researcher at the Institute of Nano Science and Technology, has steam-treated the hydrothermally synthesized SAPO-18 catalyst to investigate the catalytic performance in dimethyl ether to olefins (DTO) reactions.
After steam treatment, micropores and mesopores were created on the SAPO-18 catalyst.
To evaluate the catalytic activity of steamed SAPO-18, she carried out a DTO reaction at 673K with weight hourly space velocity (WHSV) of 3.546h-1. The result showed that the steamed SAPO-18 (S-773) steamed at 773K exhibited excellent DTO conversion performance.
You can find the details in her paper “Steam-treated SAPO-18 with well-regulated acidity and excellent DTO performance” in “Journal of the Indian Chemical Society” (SCI).
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Jo Aug 27, 2025
In a wireless rechargeable sensor network (WRSN), energy supply to the sensor nodes is performed by a wireless charging vehicle (WCV). Due to charging capability constraint such as WCV’s battery capacity, however, determining an efficient order in which sensor nodes should be charged, is a challenging problem to be solved. It means it is necessary to improve charging efficiency by making an effective use of charging capability of wireless charging vehicles (WCVs).
Proactive charging-enabled on-demand charging scheme (semi-on-demand charging scheme) has been developed to solve this problem. While replying to on-demand charging requests (CRs) preferentially, semi-on-demand charging (SoC) scheme includes proactive charging for the potential Bottleneck Nodes (pBNs), although sensor nodes do not generate CRs, so long as WCV has redundant capability.
The existing scheme, however, not only fails to exactly predict the pBNs owing to the use of a fixed deadline threshold, but also selects the proactive charging nodes randomly among the predicted pBNs, thus leaving space for further improving charging and network performance.
In order to solve this problem, Jong Nam Jun, a student at the Faculty of Communications, has proposed a new SoC scheduling algorithm using FAHP-VWA and Q-Learning, with the help of Ri Man Gun, an institute head of the same faculty.
The extensive simulations demonstrated that the proposed algorithm can improve the whole charging and network performance, in comparison to other existing schemes.
For more information, you can refer to his paper “An Efficient Scheduling Scheme for Semi-On-Demand Charging in Wireless Rechargeable Sensor Networks” in “Iranian Journal of Science and Technology, Transactions of Electrical Engineering” (SCI).
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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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