• Industrial Engineering and Management Systems
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• v.4 no.2
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• pp.117-122
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• 2005

An assembly system (AS), a valuable tool for mass production, is generally composed of a number of workstations and a transport system. While the workstations perform some preplanned operations, the transport system moves the assemblies by special designed pallets from one station to another. One common problem associated with automatic assembly systems is that some assembly operations may have relatively long cycle times. As a consequence, the productivity, as determined by the operations with the longest cycle time, can be reduced significantly. Therefore, special forms of parallel workstations were developed to improve the performance of an assembly system. In this paper, three most commonly used parallel stations: on-line, off-line and tunnel-gated stations in a free transfer assembly system are studied via discrete event simulation. Our findings revealed that the off-line parallel system has the best performance because the two independent parallel stations can lower the buffer requirement; reduce the sensitivity to variability of processing time and balance of a line. On-line parallel systems were found to have a relatively poor performance, because the operations of two parallel stations block each other, and higher buffer capacity is required to achieve similar capacity. The tunnel-gated system was more efficient than the on-line system since the first parallel station can operate independently. More importantly, we have quantified the productivity of the three different strategies mentioned. Engineers can choose the optimal strategies for installing parallel stations under their working environment.

• Proceedings of the KIPE Conference
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• 2004.07a
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• pp.402-405
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• 2004

In this paper, the parallel operation of the IGBT and power stack for easy capacity enlargement series in the medium power capacity inverter system of the 660V voltage class is described. The parallel operation of the IGBT and power stack for 1.5MVA medium power inverter system's design is applied. The results of the parallel operation are described in this paper. The designed stack capacity for parallel operation is 800kVA class. For 1.5MVA inverter system, the 800kVA stack is applied with 2 parallel configurations. The 800kVA stack is designed with 3 parallel configurations of the IGBT Module. In this paper, the feasibility for easy capacity enlargement series in the medium power inverter by applying the parallel operation of the IGBT and power stack is verified. The experimental results show the good characteristics for the parallel operation of the IGBT and power stack.

• Journal of Institute of Control, Robotics and Systems
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• v.11 no.7
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• pp.609-614
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• 2005

Parallel manipulators have been used for a variety of applications, including the motion simulators and mechanism for precise machining. Since the ball screws used for linear motion of legs of the Stewart-Gough type parallel manipulator provide wider contact areas than revolute joints, parallel manipulators are usually more affected by frictional forces than serial manipulators. In this research, the method for detecting the frictional forces arising in the parallel manipulator using the gravitational force is proposed. First, the reference trajectories are computed from the dynamic model of the parallel manipulator assuming that it is subject to only the gravitational force without friction. When the parallel manipulator is controlled so that the platform follows the computed reference trajectory, this control force for each leg is equal to the friction force arising in each leg. It is shown that control performance can be improved when the friction compensation based on this information is added to the controller for position control of the moving plate of a parallel manipulator.

• The Korean Journal of Applied Statistics
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• v.21 no.6
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• pp.911-921
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• 2008

Visualization of the gene expression data on a low-dimensional graph is helpful in uncovering biological information contained in the data. In this study, we focus on two modified versions of the parallel coordinate plot. First one is the ePCP(enhanced parallel coordinate plot) which shows "near smooth" connecting curves between axes spaced proportionately to the proximity of re-ordered variables. Second one is APCP(Andrews' type parallel coordinate plot) which is obtained by rotating Andrews' plot that has a form of the parallel coordinate plot. Visualization procdures using ePCP and APCP are given for the lymphoma data case.

• Proceedings of the Korean Society for Emotion and Sensibility Conference
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• 2008.10a
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• pp.90-93
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• 2008

In natural language, it is common that repetitive constituents in an expression are to be left out and it is necessary to figure out the constituents omitted at analyzing the meaning of the sentence. This paper is on recognition of boundaries of parallel noun phrases by figuring out constituents omitted. Recognition of parallel noun phrases can greatly reduce complexity at the phase of sentence parsing. Moreover, in natural language information retrieval, recognition of noun with modifiers can play an important role in making indexes. We propose an unsupervised probabilistic model that identifies parallel cores as well as boundaries of parallel noun phrases conjoined by a conjunctive particle. It is based on the idea of swapping constituents, utilizing symmetry (two or more identical constituents are repeated) and reversibility (the order of constituents is changeable) in parallel structure. Semantic features of the modifiers around parallel noun phrase, are also used the probabilistic swapping model. The model is language-independent and in this paper presented on parallel noun phrases in Korean language. Experiment shows that our probabilistic model outperforms symmetry-based model and supervised machine learning based approaches.

• Proceedings of the KIEE Conference
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• 2001.07a
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• pp.233-236
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• 2001

Parallel operation scheme to several transformers is adopted because of the load increase, economic problem, or load shedding. For the transformer's parallel operation, loads proportional to each transformer's capacity must be allotted, and circulation currents must be limited as much as without causing any problem in a real operation. But, both transformers in parallel operation can be tripped when either faults at lower voltage side of a transformer or faults in a bus occurs. Therefore, parallel operation scheme to distribution transformers in Korea is not adopted in a normal state but only when loaded or load-shedded. These are due to the insufficiency of the construction in communication network and AVR scheme. Besides that, those are because bus bar protection scheme to lower voltage side of a transformer is not applied. In spite of enormous initial investment costs, advanced countries take so much account of power system reliability and stable supply that they adopt the parallel operation scheme in a normal state. One of the problems in parallel operation is the overheat of transformers due to the excessive circulation currents. This paper presents the scheme that controls voltages between both transformers using circulation currents that occurs in parallel operation.

• Journal of Internet Computing and Services
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• v.2 no.4
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• pp.69-81
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• 2001

This paper describes a parallel programming environment to help programmer to write parallel programs. Parallel program must be write according to the character of the various hardware or program. So it is difficult for the programs to write the parallel programmer. In this paper, we propose and implement a parallel programming environment using graph type intermediate representation form, and graph user interface is provided for programmer to get parallel programs easily, This parallel environment supports special functions using graph type intermediate representation form. The special functions involve program editing. data dependence analysis, loop transformation. CFG, PDG, HTG. This parallel environment helps users make parallelism and optimization easy through showing the intermediate code with graph.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.810-815
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• 2004

In this paper, we propose new parallel mechanism of a 3 dimensional biped robot whose each leg is composed of two 3-dof parallel platforms linked serially. This proposed parallel mechanism is able to move freely in the man-made environment and is applied to various fields, such as medical, welfare, and so on. And a total weight of each leg is expected to be lighter than serial linked leg. One side leg consists of a 3-dof orientation platform and 3-dof asymmetric parallel platform. The former consists of three active linear actuators and seven passive joints, and the latter of two active linear actuators, one active rotational actuator and eight passive joints. Thus, there are two kinds of parallel platforms each chain's elements and active joint's positions are different for the biped robot to move freely like a serial link without the kinematics constraints. The effectiveness and the performance of the proposed parallel mechanism and locomotion trajectory are shown in computer simulations with a 12-DOF parallel biped robot.

• Journal of Institute of Control, Robotics and Systems
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• v.15 no.5
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• pp.488-495
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• 2009

This paper presents a fast feature extraction method for autonomous mobile robots utilizing parallel processing and based on OpenMP, SSE (Streaming SIMD Extension) and CUDA programming. In the first step on CPU version, the algorithms and codes are optimized and then implemented by parallel processing. The parallel algorithms are debugged to maintain the same level of performance and the process for extracting key points and obtaining dominant orientation with respect to key points is parallelized. After extraction, a parallel descriptor via SSE instructions is constructed. And the GPU version also implemented by parallel processing using CUDA based on the SIFT. The GPU-Parallel descriptor achieves an acceleration up to five times compared with the CPU-Parallel descriptor, but it shows the lower performance than CPU version. CPU version also speed-up the four and half times compared with the original SIFT while maintaining robust performance.

• International Journal of Naval Architecture and Ocean Engineering
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• v.13 no.1
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• pp.450-465
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• 2021

In this study, an attempt has been made to investigate the water-entry characteristics of the high-speed parallel projectile numerically. The shear stress transport k-𝜔 turbulence model and the Zwart-Gerber-Belamri cavitation model based on the Reynolds-Averaged Navier-Stokes method were used. The grid independent inspection and grid convergence index is carried out and verified. The influences of the parallel water-entry on flow filed characteristics, trajectory stability and drag reduction performance for different values of initial water-entry speed (𝜈₀ = 280 m/s, 340 m/s, 400 m/s) and clearance between the parallel projectiles (L_p = 0.5D, 1.0D, 2.0D, 3.0D) are presented and analyzed in detail. Under the condition of the parallel water-entry, it can be found that due to the intense interference between the parallel projectiles, the distribution of cavity is non-uniform and part of the projectile is exposed to water, resulting in the destruction of the cavity structure and the decline of trajectory stability. In addition, the parallel projectile suffers more severe lateral force that separates the two projectiles. The drag reduction performance is impacted and the velocity attenuation is accelerated as the clearance between the parallel projectiles reduces.