• Structural Engineering and Mechanics
• /
• v.74 no.4
• /
• pp.533-545
• /
• 2020

An optimal design method for a spoke double-layer cable-net structure (SDLC) is proposed in this study. Simplified calculation models of the SDLC are put forward to reveal the static responses under vertical loads and wind loads. Next, based on an energy principle, the relationship among the initial prestress level, cross-sectional areas of the components, rise height, sag height, overall displacement, and relative deformation is proposed. Moreover, a calculation model of the Foshan Center SDLC is built and optimized. Given the limited loading cases, material properties of the components, and variation ranges of the rise height and sag height, the self-weight and initial prestress level of the entire structure can be obtained. Because the self-weight of the cables decreases with increasing of the rise height and sag height, while the self-weight of the inner strut increases, the total weight of the entire structure successively exhibits a sharp reduction, a gradual decrease, a slow increase, and a sharp increase during the optimization process. For the simplified model, the optimal design corresponds to the combination of rise height and sag height that results in an appropriate prestress level of the entire structure with the minimum total weight.

• Journal of Ship and Ocean Technology
• /
• v.8 no.2
• /
• pp.41-60
• /
• 2004

Ship design process requires lots of complicated analyses for determining a large number of design variables. Due to its complexity, the process is divided into several tractable designs or analysis problems. The interdependent relationship requires repetitive works. This paper employs collaborative optimization (CO), one of the multidisciplinary design optimization (MDO) techniques, for treating such complex relationship. CO guarantees disciplinary autonomy while maintaining interdisciplinary compatibility due to its bi-level optimization structure. However, the considerably increased computational time and the slow convergence have been reported as its drawbacks. This paper proposes the use of an approximation model in place of the disciplinary optimization in the system-level optimization. Neural network classification is employed as a classifier to determine whether a design point is feasible or not. Kriging is also combined with the classification to make up for the weakness that the classification cannot estimate the degree of infeasibility. For the purpose of enhancing the accuracy of a predicted optimum and reducing the required number of disciplinary optimizations, an approximation management framework is also employed in the system-level optimization.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.19 no.7
• /
• pp.1604-1618
• /
• 1995

In the process of mechanical assembly design, assembly modeling systems have been used mainly for the design verification before manufacturing by enabling to check the interference and/ or the dynamic and kinematic performance. However, the conventional assembly modeling systems have a shortcoming that they can not be used in the initial design stage but can be used only after the design is fully completed. In other words conventional assembly modeling systems provide bottom-up modeling which means that the detailed modeling of components must precede the definition of relationships between them. To resolve this problem, an assembly modeling system is proposed to provide a top-down modeling environment in which components and assembly can be modeled simultaneously. To this end, an assembly data structure suitable for top-down assembly modeling has been established. Feature positioning Module(FPM) using geometric constraints has been also developed. The Sekective Solving Method proposed for FPM is based on the priority between the constraint equations and enables the designer's intent expressed by geometric constraints to be maintained throughout the whole modeling process. Finally, the feature based modeling technique using two-level features has been developed. Two-level features include an abstract model and a detailed model in a merged form in non-manifold data frame.

• The Korean Journal of Applied Statistics
• /
• v.15 no.1
• /
• pp.45-55
• /
• 2002

The 2-level rotation design based on 3 rotation groups is discussed in view of Monthly Retail Trade Survey conducted by the Bureau of Census in U.S., and composite estimators for population characteristics are concerned. The generalized composite estimators and the recursive composite estimators are presented at 2-level rotation design with design gap and variance formulas for the composite estimators are provided. Also under the response variability related with covariance structure and correlation structure from repeated response, relative efficiencies of the composite estimators are compared.

• Journal of the Ergonomics Society of Korea
• /
• v.32 no.6
• /
• pp.529-534
• /
• 2013

Objective: This study determines which of two types of 2D menu is better on iPhone. Background: Menu systems have been important components in modern graphical user interfaces. Review of menu design studies for human-computer interaction suggests that menu design guidelines for smartphones need to be reappraised. Method: A nested factorial design was used. Twenty-four participants were divided into two groups. The subjects were nested within the menu type. Two types of menus are an overview menu and a text menu. Two different breadth levels are 16 and 64. The participants performed five tasks in each breadth level. A task is defined as locating a product or product class on the deepest level of the hierarchy. An Apple iPhone 2G was used. Results: The results for ANOVA indicated a lack of a significant difference for time to respond between the two types of 2D menus. The overview menu showed the better satisfaction score between the two menu types. Conclusion: Even though the differences were not significant, an overview menu tended to show better performance and preference scores than a text menu that required scrolling. Application: This study can provide menu design guidelines when 2D menus are considered for small displays in a high breadth level.

• Korean Journal of Computational Design and Engineering
• /
• v.11 no.4
• /
• pp.315-325
• /
• 2006

It is very often necessary to search for similar parts during designing a new product because its parts are often easily designed by modifying existing similar parts. In this way, the design time and cost can be reduced. Thus it would be nice to have an efficient similarity comparison algorithm that can be used anytime in the design process. There have been many approaches to compare shape similarity between two solids. In this paper, two parts represented in B-Rep is compared in two steps: one for overall appearances and the other for detail features. In the first step, geometric information is used in low level of detail for easy and fast pre-classification by the overall appearance. In the second step, feature information is used to compare the detail shape in high level of detail to find more similar design. To realize the idea above, a multi resolution algorithm is proposed so that a given solid is described by an overall appearance in a low resolution and by detail features in high resolution. Using this multi-resolution representation, parts can be compared based on the overall appearance first so that the number of parts to be compared in high resolution is reduced, and then detail features are investigated to retrieve the most similar part. In this way, computational time can be reduced by the fast classification in the first step while reliability can be preserved by detail comparison in the second step.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.26 no.3
• /
• pp.227-236
• /
• 2021

This research proposes a modeling and controller design of a three-level boost (TLB) converter for the implementation of maximum power point tracking (MPPT) in the photovoltaic power conditioning system (PCS). Contrary to the output voltage control of the conventional controller, the Photovoltaic PCS requires an input voltage controller for MPPT operation. A TLB converter has the advantage of decreasing the inductor size and increasing efficiency compared with the existing booster converter. However, an optimal controller is difficult to design due to the complexity of the TLB operations, which have two operational modes on the duty ratio boundary of 0.5. Therefore, the unified linear model equations of the TLB converters, which can be applicable to both operational modes, are derived using linearized solar cell expressions. Furthermore, the transfer functions are obtained for the controller design. The MPPT voltage controller is designed using MATLAB SISOTOOL. In addition, a controller for capacitor voltage unbalancing is described and designed. The simulations and experimental verifications are conducted to verify the effectiveness of the small-signal analysis and control system design.

• Structural Engineering and Mechanics
• /
• v.80 no.6
• /
• pp.677-688
• /
• 2021

The building design codes and standards in many countries usually are either fully or partially adopted from the international codes. However, regional conditions like the quality of construction industry and different statistical parameters of load and resistance have essential roles in the code calibration of building design codes. This paper presents a probabilistic approach to assess the reliability level of adopted national building codes by simulating design situations and considering all load combinations. The impact of the uncertainty of wind and earthquake loads, which are entirely regional condition dependent and have a high degree of uncertainty, are quantified. In this study, the design situation is modeled by generating thousands of numbers for load effect ratios, and the reliability level of steel elements for all load combinations and different load ratios is established and compared to the target reliability. This approach is applied to the Iranian structural steel code as a case study. The results indicate that the Iranian structural steel code lacks safety in some load combinations, such as gravity and earthquake load combinations, and is conservative for other load combinations. The present procedure can be applied to the assessment of the reliability level of other national codes.

• Structural Monitoring and Maintenance
• /
• v.10 no.3
• /
• pp.243-260
• /
• 2023

Indonesia has had seismic codes for earthquake-resistant structures designs since 1970 and has been updated five times to the latest in 2019. In updating the Indonesian seismic codes, seismic hazard maps for design also update, and there are changes to the Peak Ground Acceleration (PGA). Indonesian seismic design uses the concept of building performance levels consisting of Immediate occupancy (IO), Life Safety (LS), and Collapse Prevention (CP). Related to this performance level, cases still found that buildings were damaged more than their performance targets after the earthquake. Based on the above issues, this study aims to analyze the performance of base isolation design on existing target buildings and analyze the seismic fragility for a case study in Indonesia. The target building is a prototype design 8-story medium-rise residential building using the reinforced concrete moment frame structure. Seismic fragility analysis uses Incremental Dynamic Analysis (IDA) with Nonlinear Time History Analysis (NLTHA) and eleven selected ground motions based on soil classification, magnitude, fault distance, and earthquake source mechanism. The comparison result of IDA shows a trend of significant performance improvement, with the same performance level target and risk category, the base isolation structure can be used at 1.46-3.20 times higher PGA than the fixed base structure. Then the fragility analysis results show that the fixed base structure has a safety margin of 30% and a base isolation structure of 62.5% from the PGA design. This result is useful for assessing existing buildings or considering a new building's performance.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.45 no.4
• /
• pp.78-85
• /
• 2008

This paper presents a high-level design methodology applied on an SoC using SystemC. The topic will emphasize on high-level design approach for intensive architecture exploration and verifying cycle accurate SystemC models comparative to real Verilog RTL models. Unlike many high-level designs, we started the poject with working Verilog RTL models in hands, which we later compared our SystemC models to real Verilog RTL models. Moreover, we were able to use the on-chip test board performance simulation data to verify our SystemC-based platform. This paper illustrates that in high-level design, we could have the same accuracy as RTL models but achieve over one hundred times faster simulation speed than that of RTL's. The main topic of the paper will be on architecture exploration in search of performance degradation in source.