• Journal of KIISE
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• v.44 no.10
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• pp.1034-1044
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• 2017

Although traversal strategies are important for the performance of model checking, many studies have ignored the impact of traversal strategies in model checking with a block-encoded abstract reachability graph. Studies have considered traversal strategies only for an abstract reachability graph without block-encoding. Block encoding plays a crucial role in the model checking performance. This paper therefore describes Dual-traversal strategy, a simple and novel technique to control traversal strategies in a block-encoded abstract reachability graph. This method uses two traversal strategies for a model checking, one for effective block-encoding, and the other for traversal in an encoded abstract reachability graph. Dual-traversal strategy is very simple and can be implemented without overhead compared to the existing single-traversal strategy. We implemented the Dual-traversal strategy in an open source model checking tool and compare the performances of different traversal strategies. The results show that the model checking performance varies from the traversal strategies for the encoded abstract reachability graph.

• International Journal of Railway
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• v.6 no.4
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• pp.160-168
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• 2013

A spiral lattice girder-reinforced Bi-block sleeper which has enhanced durability against increasingly growing impact force and vibration by wheel load and improved structural performance while train runs at 350km/h high speed is hereby proposed. The section of a spiral lattice girder has stable and superior structural performance thanks to its confinement effect. To compare and analyze the structural performance of spiral lattice girder-reinforced bi-block sleeper, strain and stress distribution were evaluated after applying same load condition as existing triangular lattice girder-reinforced biblock sleeper, and to compare the structural performance of triangular lattice girder and spiral lattice girder, structural analysis of lattice girder was performed separately. As a result, a spiral lattice girder proved to have had superior structural characteristics to bi-block sleeper, and furthermore as a result of evaluating the fastener interface and constructibility with shape-improved lattice girder, no interference with existing railroad structure was found and in terms of cost efficiency, a spiral lattice girder appeared to be superior to existing lattice girder.

• Transactions of the Korean Society of Automotive Engineers
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• v.7 no.6
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• pp.144-155
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• 1999

An occupant analysis code SAFE (Safety Analysis For occupant crash Environment) is utilized to simulate and improve the crash performance of an energy absorbing steering system. The safety standard FMVSS 203 is simulated and used for design evaluations . Segments and contact elliposids are utilized to model the bod blocks and the components of the steering system with SAFE. Spring-damper elements and force-deflection characteristics are utilized to model the energy absorbing components such as the plate and the polyacetal molding. The plate absorbs the impact energy through tensile deformation . Whereas, the polyacetal molding absorbs the impact energy through compression. the body block test is carried out to validate tie simulation model, and real component tests are performed to extract the force-deflection curves . After the model is validated , the parameter study is carried out to evaluate the crash performance of the energy absorbing components. A performance measure is defined for the parameter study. Using the results of the parameter study and managing the orthogonal arrays, optimum design values of energy absorbing components are determined to minize the occupant injury.

• Journal of Communications and Networks
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• v.7 no.3
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• pp.307-312
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• 2005

In this work, we study the performance of a serial concatenated scheme comprising a convolutional code (CC) and an orthogonal space-time block code (STBC) separated by an inter-leaver. Specifically, we derive performance bounds for this concatenated scheme, clearly quantify the impact of using a CC in conjunction with a STBC, and compare that to using a STBC code only. Furthermore, we examine the impact of performing antenna selection at the receiver on the diversity order and coding gain of the system. In performing antenna selection, we adopt a selection criterion that is based on maximizing the instantaneous signal-to­noise ratio (SNR) at the receiver. That is, we select a subset of the available receive antennas that maximizes the received SNR. Two channel models are considered in this study: Fast fading and quasi-static fading. For both cases, our analyses show that substantial coding gains can be achieved, which is confirmed through Monte-Carlo simulations. We demonstrate that the spatial diversity is maintained for all cases, whereas the coding gain deteriorates by no more than $10\;log_{10}$ (M / L) dB, all relative to the full complexity multiple-input multiple-output (MIMO) system.

• Geomechanics and Engineering
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• v.33 no.4
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• pp.353-367
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• 2023

The construction of a protective embankment is a suitable strategy to stop and control high-energy rock blocks' impacts during the rockfall phenomenon. In this paper, based on the discrete element numerical method, by modeling an existing embankment reinforced with geogrid, its stability status under the impact of a rock block with two types of low and high kinetic energy, namely 2402 and 4180 kJ, respectively, has been investigated. The modeling results show that the use of geogrid has caused the displacement in the front and back of the embankment to decrease by more than 30%. In this case, the reinforced embankment has stopped the rock block earlier. The displacements obtained from the DEM modeling are compared with the displacements measured from an actual practical experiment to evaluate the results' validity. Comparison between the results shows that the displacement values are close together, while the maximum percentage error in previous studies by an analytical method and the finite element method was 76.4% and 36.6%, respectively. Therefore, the obtained results indicate the discrete numerical method's high ability compared to other numerical and analytical methods to simulate and design the geogrid-reinforced soil embankment under natural disasters such as rockfall with a minor error.

• Journal of the Korean Society of Safety
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• v.29 no.6
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• pp.15-21
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• 2014

Many kinds of falling prevention systems with a safety block have been supplied in order to prevent falling accidents and acquire the long life and cost down for the maintenance. However, there are not the reliable and domestic the falling prevention system until now. Almost systems were imported from U.S.A, Japan, U.K and Germany. The structural safety of the imported safety block is satisfied sufficiently, but it has heavy weight due to the cover with the aluminum and thickness. Especially, the falling prevention system as the safety block is very expensive. It brings about flow the enormous money out of country. Furthermore it has a heavy weight when workers climbed the ladder with a falling prevention system and moved, many workers are not feeling themselves. Thus, the aim of this work is to develop a commercial self-escape SRL(Self Retracting Lifeline) with the safety block function that has a light weight and an advanced strength. The cost efficiency and convenience of the system and safety for workers also will be improved remarkably even though this system has a light weight. The results show that the maximum stress is obtained in each part by the lower more than yield strength and has sufficient safety in the developed new safety block.

• Tunnel and Underground Space
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• v.31 no.6
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• pp.415-427
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• 2021

This technical report briefly introduced the rock cutting splitting method under development. This method is a method of excavating the rock by splitting the block after the rock cutting process. After designing the cutting geometry of the rock face, the chisel is press-fitted to remove the rock block. At this time, when the cutting block is properly designed, the tensile crack propagates smoothly at the bottom of the rock block. An analytical solution was devised to estimate the indentation force required for splitting rock blocks using fracture toughness mode 1 required for tensile crack growth. The impact force of the hydraulic breaker of the excavator was analyzed, and the grade of the excavator that can be constructed according to the rock block design geometry was analyzed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.10
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• pp.640-647
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• 2018

Many harbor structures have been constructed, and some structures are now under construction in Korea, which is a peninsular state and a logistics hub in Northeast Asia. Expansions and extensions of existing harbors are also being planned to meet increasing natural disaster threats. Wave-dissipation concrete blocks are recycled or discarded based on the personal experience of engineers only, and there are no safety checks or criteria. To check the safety of used blocks, material evaluations were done by visual inspection of blocks on the ground and under water and from 20 non-destructive measurements of the rebound hardness test and 3 concrete core samples. Wave-dissipation blocks are sometimes fully or partially damaged in the process of transferring and mounting them or during construction. Therefore, a safety check is essential for recycling blocks with an evaluation of materials while considering the construction phases. To do this, a block was modeled with a 3D finite element method using ADINA, and impact analyses were done according to the transfer, mounting, and construction phases. From the results of the impact analyses and material evaluation, the safety checks and reasonable evaluation of used blocks were examined, and detailed construction methods are proposed. The methods are expected to maximize the reuse of used wave-dissipation blocks from an economical point of view.

• Journal of Korean Society on Water Environment
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• v.34 no.3
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• pp.293-300
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• 2018

Ihe purpose of this study is to evaluate the effects the storage type of permeable concrete block paving (ST-PCBP) have on runoff reduction and infiltration increasement at Andong Maskdance Festival Square. This was accomplished using the NRCS-curve number method over the last 10 years. Two different scenarios were developed in this study for low impact development (LID) design. For the $1^{st}$ scenario, the walking path and parking lot were install using the ST-PCBP and runoff from the inline skating rink ($3,808m^2$) and lawn ($11,191m^2$) were routed to the ST-PCBP, but the rooftop runoff flowed into the storm water drainage system. For the $2^{nd}$ scenario, one of the non-structural BMPs, disconnected impervious surface (DIS), was applied so additional runoff from rooftop would enter the ST-PCBP. It was determined that ST-PCBP could significantly reduce surface runoff from the study area and increase infiltration with 71% and 88% of surface runoff reduction and 151% and 215% of infiltration increasement for scenarios 1 and 2, respectively. The effect of LID in the $2^{nd}$ scenario was better than the $1^{st}$ scenario, therefore DIS in conjunction with ST-PCBP could be a more cost-effective LID application.

• International Journal of Automotive Technology
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• v.5 no.1
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• pp.23-31
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• 2004

Secondary movements of piston in the bore clearance are closely related to the side impact to the engine block as well as many tribological problems. Some of the major parameters that influence these kinds of movements are piston profile shapes (barrel and flat), piston pin offsets and the magnitudes of bore clearances. In our study, computational investigations are performed about the piston movements in the bore clearance by changing the skirt profiles and piston offsets. In this work, it is found that curved profile and larger offset magnitude to thrust side provide better performance that has low side impact during the engine cycle.