Comparative effects of oxygenates-gasoline blended fuels on the exhaust emissions in gasoline-powered vehicles.

This study aimed to investigate the comparative effects of oxygenates such as ethanol (EA), methyl tertiary-butyl ether (MTBE), and ethyl tertiary butyl ether (ETBE) by fixing the oxygen contents as 0.82 wt% 1.65 wt%, and 2.74 wt% of the fuels on the regulated (CO, NMHC and NOx) and unregulated (formaldehyde, acetaldehyde and BTEX) exhaust emissions in gasoline-powered vehicles. The most widely used type of vehicles (light-duty, medium-duty, heavy-duty) in Korea were tested on a chassis dynamometer under the CVS-75 Cycle. When EA, MTBE and ETBE percentage increased, the CO and NMHC concentration decreased. The NOx emission decreased at 1.65 wt% and 2.74 wt% oxygen content of MTBE and ETBE. The emissions of CO decreased by 0.363 g/km, 0.266 g/km and 0.356 g/km for light-duty vehicle when EA, MTBE and ETBE oxygenates blending ratio increased. Increased EA, MTBE and ETBE oxygenates blending ratio demonstrated no specific reducing effect on CO emissions from low-mileage vehicle, but NMHC emissions decreased by 0.011 g/km (medium-duty), 0.015 g/km (light-duty) and 0.018 g/km (heavy-duty). More CO was emitted from MTBE among three oxygenates at same oxygen content. The emitted concentrations of NMHC from three oxygenates at same oxygen content were almost similar, but reduced NOx emissions from EA (10%) to MTBE (20.4%) and ETBE (23.6%) were observed at 2.74 wt% oxygen content. Reducing effect on CO emissions was order of EA > ETBE > MTBE. Formaldehyde emissions increased up to 54.3% as MTBE ratio increased. When oxygen content of ETBE, EA, and MTBE increased from 0.82 wt% to 2.74 wt%, the acetaldehyde emissions increased up to 177.4%, 39.5% and 31.0%, respectively. There was significant formaldehyde concentration difference between high emission vehicle type (light-duty and medium-duty) and low emission vehicle type (heavy-duty and low-mileage) for three oxygenates. Reduction effect of MTBE and ETBE on BTEX was the order of toluene > benzene > ethylbenzene > xylene, and MTBE showed more reduction effect than ETBE at same oxygen content.

Validation of the MCNP6 code for SFR shielding design analysis.

In this paper, the uncertainty of the Monte Carlo code MCNP6 for the sodium-cooled fast reactor (SFR) shielding design is studied. Shielding analysis, which ensures the radiation safety of the core design, is challenging for the Monte Carlo modeling because it is associated with large uncertainties. In order to evaluate the performance of the MCNP6 relative to the shielding design of the SFR, four SFR shielding benchmarks from the Shielding Integral Benchmark Archive Database benchmark suite, i.e. JANUS Phase VIII, SDT12, EURAC_Na and HARMO_Na were selected and analysed. In this research, the weight window variance-reduction technique and the neutron data library ENDF/B-VII.1 were used in the modeling of the benchmark problems. The results and the validation of the MCNP6 models with the available measurement data are presented in this paper. These results contribute to the assessment of radiological protection and shielding design of the Korean Prototype Gen-IV Sodium-cooled Fast Reactor.

Energy-Based Unified Models for Predicting the Fatigue Life Behaviors of Austenitic Steels and Welded Joints in Ultra-Supercritical Power Plants.

The development of a cost-effective and accurate model for predicting the fatigue life of materials is essential for designing thermal power plants and assessing their structural reliability under operational conditions. This paper reports a novel energy-based approach for developing unified models that predict the fatigue life of boiler tube materials in ultra-supercritical (USC) power plants. The proposed method combines the Masing behavior with a cyclic stress-strain relationship and existing stress-based or strain-based fatigue life prediction models. Notably, the developed models conform to the structure of the modified Morrow model, which incorporates material toughness (a temperature compensation parameter) into the Morrow model to account for the effects of temperature. A significant advantage of this approach is that it eliminates the need for tensile tests, which are otherwise essential for assessing material toughness in the modified Morrow model. Instead, all material constants in our models are derived solely from fatigue test results. We validate our models using fatigue data from three promising USC boiler tube materials-Super304H, TP310HCbN, and TP347H-and their welded joints at operating temperatures of 500, 600, and 700 °C. The results demonstrate that approximately 91% of the fatigue data for all six materials fall within a 2.5× scatter band of the model's predictions, indicating a high level of accuracy and broad applicability across various USC boiler tube materials and their welded joints, which is equivalent to the performance of the modified Morrow model.

Critical Hazard Factors in the Risk Assessments of Industrial Robots: Causal Analysis and Case Studies.

BACKGROUND: With the increasing demand for industrial robots and the "noncontact" trend, it is an appropriate point in time to examine whether risk assessments conducted for robot operations are performed effectively to identify and eliminate the risks of injury or harm to operators. This study discusses why robot accidents resulting in harm to operators occur repetitively despite implementing control measures and proposes corrective actions for risk assessments. METHODS: This study collected 369 operator-injured robot accidents in Korea over the last decade and reconstructed them into the mechanism of injury, work being undertaken, and bodily location of the injury. Then, through the techniques of Systematic Cause Analysis Technique (SCAT) and Root Cause Analysis (RCA), this study analyzed the root and direct causes of robot accidents that had occurred. Causes identified included physical hazards and complex combinations of hazards, such as psychological, organizational, and systematic errors. The requirements of risk assessments regarding robot operations were examined, and three case studies of robot-involved tasks were investigated. The three assessments presented were: camera module processing, electrical discharge machining, and a panel-flipping robot installation. RESULTS: After conducting RCA and comparing the three assessments, it was found that two-thirds of injury-occurring from robot accidents, causative factors included psychological and personal traits of robot operators. However, there were no evaluations of the identifications of personal aspects in the three assessment cases. CONCLUSION: Therefore, it was concluded that personal factors of operators, which had been overlooked in risk assessments so far, need to be included in future risk assessments on robot operations.

An Energy-Based Unified Approach to Predict the Low-Cycle Fatigue Life of Type 316L Stainless Steel under Various Temperatures and Strain-Rates.

An energy-based low-cycle fatigue model was proposed for applications at a range of temperatures. An existing model was extended to the integrated approach, incorporating the simultaneous effects of strain rate and temperature. A favored material at high temperature, type 316L stainless steel, was selected in this study and its material characteristics were investigated. Tensile tests and low-cycle fatigue tests were performed using several strain rates at a temperature ranging from room temperature to 650 °C. Material properties were obtained in terms of temperature using the displacement-controlled tensile tests and further material response were investigated using strain-controlled tensile tests. Consequently, no pronounced reduction in strengths occurred at temperatures between 300 and 550 °C, and a negative strain rate response was observed in the temperature range. Based on the low-cycle fatigue tests by varying strain rates and temperature, it was found that a normalized plastic strain energy density and a strain-rate modified cycle were successfully correlated. The accuracy of the model was discussed by comparing between predicted and experimental lives.

Effects of silicon cross section and neutron spectrum on the radial uniformity in neutron transmutation doping.

The effects of silicon cross section and neutron spectrum on the radial uniformity of a Si-ingot are examined experimentally with various neutron spectrum conditions. For the cross section effect, the numerical results using silicon single crystal cross section reveal good agreements with experiments within relative difference of 6%, whereas the discrepancy is approximately 20% in free-gas cross section. For the neutron spectrum effect, the radial uniformity in hard neutron spectrum is found to be more flattening than that in soft spectrum.

Evaluation of a thor dummy rigid-body model in frontal crash environment using objective rating techniques - biomed 2009.

The THOR dummy has been developed and continuously improved by NHTSA to provide manufactures an advanced tool that can be used to assess injury risk in crash tests. The main goal of this study is to evaluate a commercial rigid-body Thor Dummy Model in frontal crash environment using test data and objective rating methods. The kinematics of the Thor-NT dummy, restrained by a standard belt system and positioned in a rigid seat, was recorded by means of a 3D VICON motion capture system in a 40 km/h frontal sled test. In the numerical study, the test setup was modeled in Madymo environment, and the TNO Thor Dummy model was positioned using the same procedure employed in testing. Small spheres were attached to the dummy model at the locations of Vicon markers and their 3D displacements were calculated from the crash simulation with the sled test deceleration pulse. The time histories of the 3D photo-target displacements and the interaction forces of dummy with the sled and the belt obtained in simulation were in reasonable agreement with the corresponding test data. The dummy model obtained an overall score was in the "fair-to-acceptable" range, based on three objective criteria used to compare the simulation results with the test data. While the validations of the model under additional test conditions are suggested (e.g., deceleration pulses with different shapes, and directions), the reasonable performance of the dummy model in 40 km/h sled tests would recommend it for use in impact simulations intended to improve the design of new vehicles and their restraint systems.