• The KIPS Transactions:PartA
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• v.18A no.3
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• pp.109-114
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• 2011

We describe a technique for automatically proving compiler optimizations sound, meaning that their transformations are always semantics-preserving. As is well known, IR (Intermediate Representation) optimization is an important step in a compiler backend. But unfortunately, it is difficult to detect and debug the IR optimization errors for compiler developers. So, we introduce a C level error check system for detecting the correctness of these IR transformation techniques. In our system, we first create an IR-to-C converter to translate IR to C code before and after each compiler optimization phase, respectively, since our technique is based on the Memory Comparison-based Clone(MeCC) detector which is a tool of detecting semantic equivalency in C level. MeCC accepts only C codes as its input and it uses a path-sensitive semantic-based static analyzer to estimate the memory states at exit point of each procedure, and compares memory states to determine whether the procedures are equal or not. But MeCC cannot guarantee two semantic-equivalency codes always have 100% similarity or two codes with different semantics does not get the result of 100% similarity. To increase the reliability of the results, we describe a technique which comprises how to generate C codes in IR-to-C transformation phase and how to send the optimization information to MeCC to avoid the occurrence of these unexpected problems. Our methodology is illustrated by three familiar optimizations, dead code elimination, instruction scheduling and common sub-expression elimination and our experimental results show that the C level error check system is highly reliable.

• The Transactions of the Korean Institute of Power Electronics
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• v.20 no.6
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• pp.526-533
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• 2015

A new algorithm is proposed for the estimation of equivalent grid impedance at the point of common coupling of a grid-tie inverter output. The estimated impedance parameter can be used for the improvement of the performance and the stability of the distributed generation system. The estimation error is inevitable in the conventional estimation method because of the axis rotation due to PLL. In the conventional estimation error, the d-q voltage and current are used for the calculation of the impedance with active and reactive current injections. Conversely, in the proposed algorithm, the negative sequence current is injected, and then the negative sequence voltage is measured for the impedance estimation. As the positive and negative sequence current controller is independent and the PLL is based on the positive sequence component only, the estimation of the equivalent impedance can be achieved with high accuracy. Simulation and experimental results are compared to validate the proposed algorithm.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.5
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• pp.1028-1033
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• 2014

We investigate the OFDM-based wireless LAN systems operating in the 60 GHz frequency band as part of the fourth-generation (4G) systems. The 60 GHz band is of much interest since this is the band in which a massive amount of spectral space has been allocated worldwide for dense wireless local communications. This paper gives an overview of 60 GHz band channel characteristics and an effect on phase noise. The performance of OFDM system is severely degraded by the local oscillator phase noise, which causes both common phase error and inter-carrier interference. In this paper, we apply phase noise suppression (PNS) algorithm that is easy for implementation to OFDM based 60 GHz wireless LAN system and analyze the SER performance. In case of using the PNS algorithm, SER performance is improved about 6 dB, 7.5 dB, respectively in 16, 64-QAM.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.12C
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• pp.1248-1255
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• 2005

We investigate the OFDM-based wireless LAN systems operating in the 60 GHz frequency band as part of the fourth-generation (4G) systems. The 60 GHz band is of much interest since this is the band in which a massive amount of spectral space has been allocated worldwide for dense wireless local communications. This paper gives an overview of 60 GHz bandchannel characteristics and an effect on phase noise. The performance of OFDM system is severely degraded by the local oscillator phase noise, which causes both common phase error and inter-carrier interference. In this paper, we apply phase noise suppression (PNS) algorithm that is easy for implementation to OFDM based 60 GHz wireless LAM system and analyze the SER performance. In case of using the PNS algorithm, SER performance is improved about 6dB, 7.5dB, respectively in 16, 64-QAM.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.17 no.9
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• pp.939-950
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• 1992

The performance of common spreading code scheme employing multiple-capture receiver is compared to that of transmitter-oriented (T/O) code division multiple access (CDMA) scheme in view of the possibility of collision-free transmissions and the effect of secondary multiple-access interference. For performance comparisons, secondary multiple-access interference is characterized for the common code scheme and the T/O CDMA scheme that assures perfectly collision-free transmissions. Throughput performance is then evaluated for these two schemes with direct-sequence spread-spectrum/differential-phase-shift-keying (DS-SS/DPSK) data modulation and forward-error-control coding (BCH codes) in the presence of an additive white Gaussian noise (AWGN). It is shown that when the number of radios is relatively large, the maximum normalized throughput is greater for the common code scheme than for the T/O CDMA scheme at a moderate signal-to-noise ration(SNR).

• Journal of Electrical Engineering and Technology
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• v.11 no.6
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• pp.1729-1734
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• 2016

The surface inspection of a steel billet is a common practice in the steel manufacturing process prior to hot rolling to produce steel wire for tire cord. This billet surface inspection is an important process because flaws on the surface may cause major failures during the product manufacturing phase. This paper presents a computer simulation based on a finite element method for a magnetic flaw detector with a function of the current intensity, the number of coil turns, and the billet proceeding speed during the production phase based on the typical condition of conventional apparatus. Based on the simulation result, the magnitude of the electromagnetic field on the surface diminished with distance from the electromagnet. In addition, the increased current intensity and the increased number of coil turns actually induced a stronger electromagnetic field on the billet surface. On the other hand, the proceeding speed of a billet in its production line had no significant effects. The result in this study may assist to reduce trial and error and to minimize the opportunity costs during the optimization process by applying the findings of this study into the operation condition in the steel billet production line.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.58 no.3
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• pp.316-322
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• 2009

This paper presents an analytical design method of a passive harmonic filter for a three-phase diode rectifier and uses a new transfer function approach in the analysis and design. The transfer function approach derives an analytical formulation of an utility system including passive filters with a basis of Laplace transform and provides a graphical formulation so that a visualized insight into an interaction between individual filter and system response can be attainted. Harmonic impedance, voltage division and current division transfer function are used as a design tool, which makes a calculated filter parameters to satisfy IEEE-519 distortion limits. A simple five-step design procedure is introduced in the filter design, which consists of system analysis, selection of PCC(Point of Common Coupling), filter specification calculation, appropriate filter design for system and filter implementation. Philosophy governing the design procedure is based on a numerical/graphical iterative solution, trial and error with visualization feed-back based on "algebra on the graph". Finally, performance of the designed passive harmonic filter is verified by experiment and shows that 5th, 7th, 9th, 11th and 13th harmonics are decreased within IEEE-519 distortion limits, respectively.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.44 no.6 s.360
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• pp.60-68
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• 2007

A technique is presented to extract differential second harmonic output from common source nodes of a cross-coupled P-& N-FET oscillator. Provided the impedances at the common source nodes are optimized and the fundamental swing at the VCO core stays in a proper mode, it is found that the amplitude and phase errors can be kept within $0{\sim}1.6dB$ and $+2.2^{\circ}{\sim}-5.6^{\circ}$, respectively, over all process/temperature/voltage corners. Moreover, an impedance-tuning circuit is proposed to compensate any unexpectedly high errors on the differential signal output. A Prototype 5-GHz VCO with a 2.5-Hz LC resonator is implemented in $0.18-{\mu}m$ CMOS. The error signal between the differential outputs has been measured to be as low as -70 dBm with the aid of the tuning circuit. It implies the push-push outputs are satisfactorily differential with the amplitude and phase errors well less than 0.34 dB and $1^{\circ}$, respectively.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.11a
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• pp.232-233
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• 2021

As construction projects become larger and more complex in the construction environment, and as the Building Information Model(BIM) is technically introduced, the demand for construction costs in units of space is increasing. Cost estimating of spacial element can reduce the error in cost prediction method based on cost of work type and to utilize the construction cost data for each space in the design phase. The purpose of this study is to extract spatial statements by utilizing spacial information of quantitative statements based on items that are common elements of the Quantity Take-Off and Bill of Quantity.

• The Journal of the Acoustical Society of Korea
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• v.20 no.4
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• pp.35-41
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• 2001

This paper describes Linear Discriminant Analysis and common vector extraction for speech recognition. Voice signal contains psychological and physiological properties of the speaker as well as dialect differences, acoustical environment effects, and phase differences. For these reasons, the same word spelled out by different speakers can be very different heard. This property of speech signal make it very difficult to extract common properties in the same speech class (word or phoneme). Linear algebra method like BT (Karhunen-Loeve Transformation) is generally used for common properties extraction In the speech signals, but common vector extraction which is suggested by M. Bilginer et at. is used in this paper. The method of M. Bilginer et al. extracts the optimized common vector from the speech signals used for training. And it has 100％ recognition accuracy in the trained data which is used for common vector extraction. In spite of these characteristics, the method has some drawback-we cannot use numbers of speech signal for training and the discriminant information among common vectors is not defined. This paper suggests advanced method which can reduce error rate by maximizing the discriminant information among common vectors. And novel method to normalize the size of common vector also added. The result shows improved performance of algorithm and better recognition accuracy of 2％ than conventional method.