• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.14 no.2
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• pp.79-87
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• 1978

This is an experimental study on friction welding and heat treatment of engine exhaust valve materials whose welding combination is SCr4 as stem to 21-4N as head and SUH3 to 21-4N. In this study, not only the experiments of friction welding under the selected optimum welding condition and the examination of the mechanical properties were carried out, but also the heat treatment of friction welded specimens under the two selected conditions was taken to obtain the better welding character, eliminating the latent stress and the hardness peak which appeared at the welded zones of heat resisting steel(21-4N, SUH3) and low alloyed steel ($SCr_4$) friction weldments. The results obtained by the experiments and consideration in this study are as follows: I) It was experimentally proved quite reasonable that 'speed=3,OOO rpm, heating pressure Pl=8 kg/ mm2, upsetting pressure p, = 20 kg/mm', heating time $t_1$ = 3 see, upsetting time TEX>$t_2$ = 2.5 sec' was selected as the optimum welding condition for friction-welding the engine exhaust valve materials $SCr_4$ to 21-4 Nand SUH 3 to 21-4 N. 2) The results of the previous study and this one on friction welding of such dissimilar materials as SUH 3-SUH 31, SCr 4-SUH 31, SCr 4-SUH 3, SUH 3-CRK 22, SCr4-21-4 Nand SUH3-21-4 N agreed with each other substantially in the friction welding characteristics at welded interface zones. 3) It was also certified quite satisfactory that '600\ulcornerCX30 min. Xroom air cooling' as an optimum heat treatment condition of the friction welded materials SCr 4-21-4 Nand SUH 3-21-4 N was experimentally determined to eliminate the latent stress and the hardness peak at welded zones. 4) About 20% of the tensile strength before heat treatment of friction welded specimens was decreased after heat treatment 600\ulcornerCX30 min. Xair cooling, but the location of fracture was moved from heat affected zone to parent $SCr_4$ & SUH3. 5) Microscopic examination of the weld joints friction-welded and heat-treated under the above mentioned conditions revealed that the weld zone is very narrow and has a fine grained intermixed structure without any welding defects. 6) The above mentioned conditions can be also utilized as friction welding parameters of the other dissimiar materials for engine valve production.

• Proceedings of the KIPE Conference
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• 2010.07a
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• pp.71-72
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• 2010

This paper deals with the SCR thyristor switching characteristics of a 3-phase voltage disturbance generator. The series transformers of the generator require bypass SCR thyristors to provide the source voltage to the output terminal in normal operating mode. The SCR thyristor switching characteristics is quite different according to the connection point to the series transformer. The switching characteristics is analysed and verified through simulation results.

• Proceedings of the KIPE Conference
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• 2010.07a
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• pp.532-533
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• 2010

This paper deals with the SCR thyristor switching characteristics of a 3-phase voltage disturbance generator. The series transformers of the generator require bypass SCR thyristors to provide the source voltage to the output terminal in normal operating mode. The SCR thyristor switching characteristics is quite different according to the connection point to the series transformer. The switching characteristics is analysed and verified through simulation results.

• Ocean Systems Engineering
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• v.4 no.3
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• pp.215-241
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• 2014

Steel catenary riser (SCR) is a popular/economical solution for the oil/gas production in deep and ultra-deep water. The behavioral characteristics of SCR have a high correlation with the motion of floating production facility at its survival and operational environments. When large motions of surface floaters occur, such as FPSO in 100-yr storm case, they can cause unacceptable negative tension on SCR near TDZ (touch down zone) and the corresponding elastic deflection can be large due to local dynamic buckling. The generation, propagation, and decay of the elastic wave are also affected by SCR and seabed soil interaction effects. The temporary local dynamic buckling vanishes with the recovery of tension on SCR with the upheaval motion of surface floater. Unlike larger-scale, an-order-of-magnitude longer period global buckling driven by heat and pressure variations in subsea pipelines, the sub-critical local dynamic buckling of SCR is motion-driven and short cycled, which, however, can lead to permanent structural damage when the resulting stress is greatly amplified beyond the elastic limit. The phenomenon is extensively investigated in this paper by using the vessel-mooring-riser coupled dynamic analysis program. It is found that the moment of large downward heave motion at the farthest-horizontal-offset position is the most dangerous for the local dynamic buckling.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.1
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• pp.123-128
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• 2001

The function of SCR system in refuse incineration plant is to reduce the harmful combustion gases especially NOx which make serious environmental pollution. The SCR system normally have a NOx measurement system such as inlet NOx analyzer and outlet T.M.S.(Tele Monitoring System) to control the outlet NOx in stack. The NOx measurement system is very important, however there are frequently happened sensing problems and it need maintenance periodically. In this paper, we propose an estimation method of inlet NOx of SCR system by using general structured observer. The inlet NOx is considered as an input disturbance and it is modelled by applying FFT method in frequency domains. Through the design of general structured observer, the outlet NOx can be estimated by using observation error between real outlet NOx and estimated outlet NOx. The effectiveness of the proposed method is shown by comparing to a measured inlet NOx data.

• Journal of Power System Engineering
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• v.13 no.4
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• pp.5-10
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• 2009

Urea-SCR system, the selective catalytic reduction using urea as reducing agent, is a powerful technique to reduce nitrogen oxides(NOx) emitted from diesel engines. However, a tank of urea(32.5 wt%)-water solution can be frozen in low ambient temperature levels of below $-11^{\circ}C$. The purpose of this study is to understand freezing and melting phenomena of the urea-water solution, and its can be applied to get the urea-water solution from frozen it within 5 minutes after cold start. Factors considered were the type of heater and the urea tank shape. From the results, it was found that melting volume of cartridge heater B during 5 minutes of heating period was 83ml when supplying electric power of 150W. Horizontal heater B, which was put in the narrow bottom space of the tank T1, had fast melting characteristics.

• Korean Journal of Clinical Laboratory Science
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• v.36 no.2
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• pp.222-232
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• 2004

The sample collection room(SCR) will have much more influence than all the other departments for the improvement of hospital image, if anyone coming to the SCR in the hospital goes back with the perfect complacency and because most clients who have much stresses and fatigues pay a final visit to the SCR via receipt-diagnosis- acceptance process. SCR has improved its image for the purpose of gratifying clients, in order for clients to visit the hospital again, the quality improvement(QI) team in the Diagnosis Inspection Medical Department has come to a conclusion as follows. The degree of client gratification before improvement marks 65.9 point, but the degree after improvement was 74.2 point. Therefore, satisfaction has increased by 8.3 points. The degree of client gratification in groups before improvement marks (1) service parts-89.2 points (2) facilities and environments-49.1 point (3) toilet facilities-46.3 point. But its gratification after improvement marks (1) 92.5 point (2) 60.1 point (3) 61.0 point. Therefore the degree of satisfaction has increased by (1) 3.3 point, (2) 11.0 point, (3) 14.7 point. The progress of facility improvement plans and the exclusion of improvement on the facility contents in the hospital have made facilities and environments of SCR and toilet facilities to be poorly improved. Although service parts have a good mark, and the facilities and environments are not scoring well, the whole degree clients' gratification of SCR couldn't be helped by the low grade. Therefore the bottom line for the clients' gratification of SCR in the future is to ameliorate the facilities and environments. SCR will take the clients' gratification survey every year and if any items get low marks, that is, below 90 point throughout the survey, SCR will immediately starts the improvement work for the clients' gratification with operating the programs of controlling quality continually, and SCR should induce the operation of services, participating in the kind campaign drive for clients. So SCR will adopt the incentive system for the best staff members who perform these kinds of services.

• Journal of Energy Engineering
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• v.24 no.4
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• pp.140-145
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• 2015

This study was aimed at analyzing NOx conversion characteristics in the HC-SCR with biodiesel content changes of the secondary fuel injection (BD0, BD10, BD25). Test conditions for temperature were set to $290^{\circ}C$, $320^{\circ}C$ and $350^{\circ}C$ considering the upstream temperature of a HC-SCR, distillation of the secondary injected fuels and etc. The amount of fuel injection was adjusted with a fixed space velocity of 55,000(1/h). According to the test results of distillation, the T90 was the same level about $350^{\circ}C$ on all test fuels and the amount of evaporation was reduced at lower than $350^{\circ}C$ temperature condition with increasing biodiesel content. As biodiesel content which is mixed with the secondary injected fuel is increased, NOx reduction efficiency was determined to decrease. The difference of the Nox reduction ratio in a high temperature condition($320^{\circ}C$ and $350^{\circ}C$) than the low temperature($290^{\circ}C$) was more significant. These results are thought to be poor evaporation properties (distillation) and high molecular weight of the biodiesel.

• Journal of IKEEE
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• v.23 no.1
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• pp.338-341
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• 2019

In this paper, we propose a novel ESD device with improved characteristics of LVTSCR, which is a representative ESD protection device, and verify the N-stack technology for design optimized for each required voltage of a specific application. The characteristics of the holding voltage and the trigger voltage, which are the main parameters, are examined and the temperature characteristic, which is an indicator of the tolerance characteristic, is also verified. well region and a parasitic NPN to form a series-connected structure. We used synopsys' T-cad simulation tool for characterization.

• Proceedings of the KIPE Conference
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• 2017.07a
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• pp.278-279
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• 2017

The SCR AC voltage controller controls the magnitude of the output voltage by controlling the delay angle based on the zero-crossing points of the input AC voltage. This paper presents a method to generate digitally SCR gate signal by using AVR in order to minimize the effects of ripples or noises including AC input voltage. The validity of the proposed SCR gate signal generation technique is verified through experiment result.