Determining Sustainable Development Density using the Urban Carrying Capacity Assessment System

Diverse urban problems in the capital region of Korea occur due to over-development and over-concentration which exceed the region’s carrying capacity. Particularly, environmental problems such as air and water pollution have become more evident and become central issues for urban planners and decision-makers. In achieving sustainable environment through resolving such problems, practical approaches to incorporate the concept of environmental sustainability into managing urban development are needed. This research aims at developing an integrated framework for assessing urban carrying capacity which can determine sustainable development density, and has yielded the following. First, seven determining factors for urban carrying capacity including energy, green areas, roads, subway systems, water supply, sewage treatment, and waste treatment were identified, and the assessment framework was developed by integrating such factors. Second, the UCCAS, a GIS-based carrying capacity assessment system was developed based upon the framework. Finally, through a case study of determining carrying capacity of an urban area, it was revealed that decision support with the UCCAS demonstrated in this research could play a pivotal role in planning and managing urban development more effectively

Effects of charge motion control during cold start of SI engines

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2005.Includes bibliographical references (p. 87-88).An experimental study was conducted to investigate the effects of various intake charge motion control approaches on the cold start-up process of a port fuel injected SI engine. Engine experiments were performed to assess the effectiveness of enhanced charge motion on mixture preparation, combustion, and hydrocarbon (HC) emissions. Different charge motions were produced by three different shapes of charge motion control valves (CMCV), which block off 75% of the engine's intake ports. Cold-fluid steady state experiments were carried out with the CMCV open and closed. Increased charge motion with the CMCV closed was found to shorten the combustion duration, which caused the 50% mass fraction burned to occur up to 5⁰ CA earlier for the same spark timing. By the use of the CMCV, significant improvements in combustion stability (up to 1.5% reduction in COV) and fuel efficiency (up to 8% reduction in ISFC) were achieved with increased levels of spark timing retard due to enhanced air-fuel mixing and relatively faster burning. Engine start-up experiments were conducted with three different geometric charge motion control valves.(cont.) The CMCV improved mixture preparation due to increased swirl and tumble intensities, which enhanced fuel distribution and evaporation. Moderate spark retard (AOp = -5⁰) was found to reduce the engine-out HC emissions during the engine start-up process. Peak engine-out HC emissions with the CMCV closed occurred in the earlier stages of engine start-up process relative to the CMCV open case. Greater fuel vaporization and faster burning rate with the CMCV closed allowed reduced fuel injection and additional spark retard, resulting in significantly reduced HC emissions. The engine-out HC emissions were reduced by 18% during the 0-3 seconds and by 7% during the 3-20 seconds.by Dongkun Lee.S.M

Effects of secondary air injection during cold start of SI engines

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2010.Cataloged from PDF version of thesis.Includes bibliographical references (p. 115-117).The paucity of exhaust oxygen during cold start of automobile SI engines limits the extent of exothermic chemical reactions in the exhaust port, manifold, and catalyst. The injection of air into the exhaust system therefore could be an effective way to utilize additional thermal and chemical energy available in the exhaust gas. This study was initiated to investigate the thermal and chemical processes associated with secondary air injection (SAI) inside the exhaust system in order to maximize the simultaneous benefit of reducing converter-in emissions and improving catalyst lightoff performance during cold start. An experimental study was performed to develop a more fundamental understanding of the effects of SAI on exhaust gas emissions and catalyst light-off characteristics during cold start of a modem SI engine. The effects of several design and operating parameters such as spark retardation, fuel enrichment, secondary air flow rate and air injection location were investigated to understand the mixing, heat loss, and thermal and catalytic oxidation processes associated with SAL. Time-resolved HC, CO and CO2 concentrations were tracked from the cylinder exit to the catalytic converter outlet and converted to mass flow rates by applying an instantaneous exhaust mass flow rate model. A phenomenological model of exhaust heat transfer combined with the gas composition analysis was also developed to define the thermal and chemical energy state of the exhaust gas with SAT. The study found that significant emissions reduction can be achieved with SAI by the thermal oxidation process prior to the catalyst, which results in enhancing the chemical process inside the catalyst by faster catalyst light-off. The engine operation, with a relative air/fuel ratio 20% rich of stoichiometric and 100% secondary air, yielded the fastest catalyst light-off (4.2 sec). The SAI system reduced HC emissions by 46% to 88% and CO emissions by 37% to 93% compared with the normal operating conditions. The analysis showed that the post-catalyst HC emissions levels were optimized with secondary air flow rates corresponding to an overall exhaust lambda of 1.3.by Dongkun Lee.Ph.D

Urban Green Space Arrangement for an Optimal Landscape Planning Strategy for Runoff Reduction

Increased impervious surfaces due to urbanization have reduced evaporation and infiltration into the soil compared with existing natural water cycle systems, which causes various problems, such as urban floods, landslides, and deterioration of water quality. To effectively solve the urban water cycle issue, green infrastructure using urban green space has emerged to reduce runoff and increase evaporation. It has the advantage of restoring the water cycle system of urban areas by complementing the failure of conventional stormwater treatment systems. However, urban areas under high-density development have limited green space for stormwater treatment. Hence, it is necessary to efficiently utilize street trees and small green spaces to improve the urban water cycle through green space. In this study, we simulated different green space distribution scenarios in the virtual domain to find the optimal strategy of green space planning. Compared to clustered scenarios, dispersed green space distribution scenarios and placing green space downstream were more effective in reducing the runoff amount. The paper provides insights into the considerations for determining green space spatial plan and zoning regulations for stormwater treatment by green infrastructure

Comparison between point cloud and mesh models using images from an unmanned aerial vehicle

Structure from motion (SfM) is a well-known algorithm used for the generating of three-dimensional (3D) spatial information using images. The objective of this study is to compare the measurements of objects ascertained from point cloud and mesh models derived from the SfM algorithm. In particular, we analyze a single tree to determine the correlation between the number of acquired images from the UAVs and the object measurement for each model. The results indicate that the number of images does not have a critical impact on surveys and the point cloud is approximately 2% more accurate than mesh models for individual tree measurement. Our results will be useful in terms of selecting the data acquisition method as well as the data itself for measuring objects based on SfM 3D data. (C) 2019 Elsevier Ltd. All rights reserved.OAIID:RECH_ACHV_DSTSH_NO:T201910909RECH_ACHV_FG:RR00200001ADJUST_YN:EMP_ID:A075721CITE_RATE:2.791DEPT_NM:조경·지역시스템공학부EMAIL:[email protected]_YN:YN

Low-Energy Intra-Task Voltage Scheduling Using Static Timing Analysis

We propose an intra-task voltage scheduling algorithm for lowenergy hard real-time applications. Based on a static timing analysis technique, the proposed algorithm controls the supply voltage within an individual task boundary. By fully exploiting all the slack times, a scheduled program by the proposed algorithm always complete its execution near the deadline, thus achieving a high energy reduction ratio. In order to validate the effectiveness of the proposed algorithm, we built a software tool that automatically converts a DVS-unaware program into an equivalent low-energy program. Experimental results show that the low-energy version of an MPEG-4 encoder/decoder (converted by the software tool) consumes less than 7#25% of the original program running on a fixed-voltage system with a power-down mode. 1

Analysis of Land Use and Land Cover Change Using Time-Series Data and Random Forest in North Korea

North Korea being one of the most degraded forests globally has recently been emphasizing in forest restoration. Monitoring the trend of forest restoration in North Korea has important reference significance for regional environmental management and ecological security. Thus, this study constructed and analyzed a time-series land use land cover (LULC) map to identify the LULC changes (LULCCs) over extensive periods across North Korea and understand the forest change trends. The analysis of LULC used Landsat multi-temporal image and Random Forest algorithm on Google Earth Engine(GEE) from 2001 to 2018 in North Korea. Through the LULCC detection technique and consideration of the cropland change relation with elevation, the forest change in North Korea for 2001–2018 was evaluated. We extended the existing sampling methodology and obtained a higher overall accuracy (98.2% ± 1.6%), with corresponding kappa coefficients (0.959 ± 0.037), and improved the classification accuracy in cropland and forest cover. Through the change detection and spatial analysis, our research shows that the forests in the southern and central regions of North Korea are undergoing restoration. The sampling method we extended in this study can effectively and reliably monitoring the change trend of North Korea forests. It also provides an important reference for the regional environmental management and ecological security in North Korea

Adaptation strategies for future coastal flooding: Performance evaluation of green and grey infrastructure in South Korea

Climate change is contributing to an increasing frequency and intensity of floods in Korea. This study predicts areas with a high probability of flooding in coastal areas of South Korea owing to future climate change, which is likely to cause extreme rainfall and sea-level rise, using a spatiotemporal downscaled future climate change scenario with random forest, artificial neural network, and k-nearest neighbor techniques. In addition, the change in coastal flooding risk probability according to the application of different adaptation strategies (green spaces and seawalls) was identified. The results showed a clear difference in the risk probability distribution in the absence and presence of either adaptation strategy. Their effectiveness in moderating future flooding risks is subject to change owing to strategy type, geographic region, and urbanization intensity and the results show that green spaces are slightly more effective than seawalls when forecasting for 2050. This demonstrates the importance of a nature-based strategy. Moreover, this study highlights the need to prepare adaptation measures according to regional characteristics to mitigate the impact of climate change. Korea is surrounded by seas on three sides that have independent geophysical and climate characteristics. The south coast has a higher risk of coastal flooding than the east and west coasts. In addition, a higher urbanization rate is associated with a higher risk probability. This implies that climate change response strategies for coastal cities are necessary as the population and socioeconomic activities of coastal urban areas are likely to increase in the future.N

Error Analysis of Non-Destructive Ultrasonic Testing of Glass Fiber-Reinforced Polymer Hull Plates

Glass fiber-reinforced polymer (GFRP) ship structures are generally fabricated by hand lay-up; thus, the environmental factors and worker proficiency influence the fabrication process and presence of error in the non-destructive evaluation results. In this study, the ultrasonic testing of GFRP hull plate prototypes was conducted to investigate the statistical significance of the influences of the design parameters, e.g., the glass fiber weight fraction (Gc) and thickness variations, on the measurement error. The GFRP hull plate prototypes were fitted with E-glass fiber chopped strand mats (40 wt % content) with different thicknesses (7.72 mm, 14.63 mm, and 18.24 mm). The errors in the thickness measurements were investigated by conducting pulse-echo ultrasonic A-scan. The thickness variation resulted in increased error. Furthermore, hull plate burn-off tests were conducted to investigate the fabrication qualities. Defects such as voids did not have a significant influence on the results. The statistical analysis of the measurement errors confirmed that the thickness variations resulted in a strong ultrasonic interference between the hull plates, although the hull plates had similar specific gravity values. Therefore, the ultrasonic interference of the layer group interface should be considered to decrease the GFRP hull NDE errors with respect to an increase in the thickness and Gc