• 제어로봇시스템학회논문지
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• 제18권9호
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• pp.806-811
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• 2012

In this paper Hartley functions are used to approximate the solutions of continuous time linear dynamical system. The Hartley function and its integral operational matrix are first presented, an efficient algorithm to solve the Stein equation is proposed. The algorithm is based on the compound matrix and the inverse of sum of matrices. Using the structure of the Hartley's integral operational matrix, the full order Stein equation should be solved in terms of the solutions of pure algebraic matrix equations, which reduces the computation time remarkably. Finally a numerical example is illustrated to demonstrate the validity of the proposed algorithm.

• Geomechanics and Engineering
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• 제7권2호
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• pp.149-164
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• 2014

One of the most advanced classes of techniques for ground response analysis is based on the use of Transfer Functions. They represent the ratio of Fourier spectrum of amplitude motion at the free surface to the corresponding spectrum of the bedrock motion and they are applied in frequency domain usually by FFT method. However, Fourier spectrum only shows the dominant frequency in each time step and is unable to represent all frequency contents in every time step and this drawback leads to inaccurate results. In this research, this process is optimized by decomposing the input motion into different frequency sub-bands using Wavelet Multi-level Decomposition. Each component is then processed with transfer Function relating to the corresponding component frequency. Taking inverse FFT from all components, the ground motion can be recovered by summing up the results. The nonlinear behavior is approximated using an iterative procedure with nonlinear soil properties. The results of this procedure show better accuracy with respect to field observations than does the Conventional method. The proposed method can also be applied to other engineering disciplines with similar procedure.

• International Journal of Computer Science & Network Security
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• 제23권6호
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• pp.84-90
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• 2023

In this article the problem of computing floating-point reciprocal cube root functions is considered. Our new algorithms for this task decrease the number of arithmetic operations used for computing $1/{\sqrt[3]{x}}$. A new approach for selection of magic constants is presented in order to minimize the computation time for reciprocal cube roots of arguments with movable decimal point. The underlying theory enables partitioning of the base argument range x∈[1,8) into 3 segments, what in turn increases accuracy of initial function approximation and decreases the number of iterations to one. Three best algorithms were implemented and carefully tested on 32-bit microcontroller with ARM core. Their custom C implementations were favourable compared with the algorithm based on cbrtf(x) function taken from C ＜math.h＞ library on three different hardware platforms. As a result, the new fast approximation algorithm for the function $1/{\sqrt[3]{x}}$ was determined that outperforms all other algorithms in terms of computation time and cycle count.

• 한국화재소방학회논문지
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• 제28권2호
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• pp.69-75
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• 2014

본 연구에서는 방화발생에 영향을 미치는 요인을 도출하기 위하여 발생건수를 종속변수로 하고 경제 인구 사회적 요인을 독립변수로 하는 다중회귀분석을 실시하였다. 다중회귀분석은 선형함수, 준로그함수, 역준로그함수, 이중로그함수 4가지 함수형태에 대해 적용하였으며, 각 단계별로 변수의 선택과 제외를 고려하는 단계적선택 방식을 적용하였다. 다중공선성 문제와 자기상관 문제를 해결하기 위하여 분산확대지수(VIF)와 Durbin-Watson 계수 이용하였으며, 4가지 함수모형에 대하여 수정된 R 제곱(설명력) 값이 0.935 (93.5%)로 가장 값이 높고 통계적으로 유의한 선형함수모형을 최적의 모형으로 결정하고 모형에 대한 해석을 진행하였다. 선형함수모형 결과 방화발생에 영향을 미치는 요인은 범죄발생건수(0.829), 일반이혼율(0.151), 재정자주도(0.149), 소비자물가상승률(0.099) 순으로 도출되었다.

• 생물정신의학
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• 제25권4호
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• pp.110-117
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• 2018

Objectives This study aimed to investigate the relationship between depressive and anxiety symptoms and tardive dyskinesia (TD) and reveal the association of cognitive function and TD in patients with schizophrenia. Methods We recruited 30 schizophrenia patients with TD and 31 without TD from a national mental hospital in South Korea. To assess depressive and anxiety symptoms, the Beck Depression Inventory-II (BDI-II) and the Beck Anxiety Inventory (BAI) were conducted. Using the five-factor structure of the BDI-II and BAI, somatic anxiety, cognitive depression, somatic depression, subjective anxiety, and autonomic anxiety were assessed. Computerized neurocognitive function test (CNT) was performed to assess levels of cognitive functions. We compared the clinical characteristics, levels of cognitive functions, and depressive and anxiety symptoms between schizophrenia patients with TD and without TD. Chi-square test, Fisher's exact test, independent t-test and Mann Whitney U test were conducted to compare two groups. Pearson correlation analysis was conducted to evaluate relationships among the abnormal involuntary movement scale (AIMS), BDI-II, BAI, somatic anxiety, cognitive depression, somatic depression, subjective anxiety, and autonomic anxiety. Results The subjects with TD had significantly lower score on the cognitive depression than those without TD (t = -2.087, p = 0.041). There were significant correlations between the AIMS score and the BDI-II score (r = -0.386, p = 0.035) and between the AIMS score and cognitive depression score (r = - 0.385, p = 0.035). Conclusions Our findings suggest the inverse relationship between severities in TD and depression and support the assumption that there is an inverse relationship between the pathophysiology of TD and depression.

• Journal of Mechanical Science and Technology
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• 제20권3호
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• pp.426-434
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• 2006

The impact of leakage was incorporated into the transfer functions of the complex head and discharge. The impedance transfer functions for the various leaking pipeline systems were also derived. Hydraulic transients could be efficiently analyzed by the developed method. The simulation of normalized pressure variation using the method of characteristics and the impulse response method shows good agreement to the condition of turbulent flow. The leak calibration could be performed by incorporation of the impulse response method with Genetic Algorithm (GA) and Harmony Search (HS). The objective functions for the leakage detection can be made using the pressure-head response at the valve, or the pressure-head or the flow response at a certain point of the pipeline located upstream from the valve. The proposed method is not constrained by the Courant number to control the numerical dissipation of the method of characteristics. The limitations associated with the discreteness of the pipeline system in the inverse transient analysis can be neglected in the proposed method.

• 정보처리학회논문지B
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• 제11B권3호
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• pp.303-308
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• 2004

Gabor 코사인과 사인 변환은 영상주파수 성분을 국부적으로 표현하므로 영상과 비디오 압축 알고리즘에 사용될 수 있다. 압축과 복원에 사용되는 순방향과 역방향 행렬 변환식의 계산 복잡도는 O($N^3$)이다. 이 논문에서는 기저함수들의 길이를 절단하여, 희소기저행렬을 생성하고, 영상압축과 복원에 적용하여 실시간 처리에 용이하게 변환 계산량을 감소시키고자 한다. 기저함수 길이가 감소함에 따라서, 기저함수 에너지에 미치는 절단의 영향을 조사하고 다른 여러 측정량의 변화를 살펴본다. 실험 결과로부터 약 1% 이하의 성능저하로 11배의 곱하기/더하기 수를 감소시킬 수 있음을 보았다.

• Journal of Communications and Networks
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• 제1권3호
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• pp.166-181
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• 1999

The object of this paper is to investigate the influence of antenna pattern on indoor radio channel characteristics. Different from previous works where this analysis was carried out at a fixed frequency using different antennas, in the present paper (where measurements were taken in a wide frequency range) the variation of the radiation pattern was caused by two factors: the change of the radiation pattern when the same antenna was used at different frequenicies and the use of different type of antennas. To carry out this analysis, frequency domain measurements of the indoor radio channel at 1 GHz, 5.5 GHz, 10 GHz and 18 GHz were collected. Measurements were taken using a network analyzer. Serveral re-alizations of the channel transfer function were obtained varying, for each measurement, the positon of the transmitter and keep-ing the receiver fixed. Estimate of the channel impulse response was obtained from the Inverse Fourier Transform (IFT) of the fre-quency response. The measurements were performed in an office enviroment with mostly metallic walls and inner separations. The obtained data were elaborated to obtain the power versus distance relationship, the Cummulative Distribution Functions(CDFs) of rms Delay Spread(DS) and of the 3 dB frequency correlation band-width. Finally, the 3 dB width of the frequency correlation func-tion has been empirically related to the inverse of the rms DS of the impulse response.

• 한국소음진동공학회논문집
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• 제24권4호
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• pp.299-309
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• 2014

When biped robots make turns, the ability to walk stably and precisely along any circular path is crucial. In this context, inverse kinematics solutions are found for accurate gait realization, and new zero moment point(ZMP) equations are derived with respect to the cyclindrical coordinate system to facilitate generation of stable walking patterns. Then, appropriate steady and transitional walking patterns are both proposed in form of time functons. Subsequently, walking patterns for a path but of different speeds are generated using the functions and associated formulas, and preliminarily checked for stability based on the ZMP equations. Upon comparison of those cases, one can see how and when robots may fall down during circular walking. Finally, those patterns are put to test on the sample robot by ADAMS(R) along with the inverse kinematics solutions and a new balance control scheme compensating for insufficient stability particulary during the initial transition period. Test results show that the robot can walk along the circular path as predicted at a resonably high speed despite the distributed mass and ground contact effects, validating effectiveness of the suggested approach.

• 한국분말재료학회지
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• 제5권4호
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• pp.334-339
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• 1998

In purpose of introducing the inverse magnetostrictive properties into the structural ceramics, $Al_2O_3$ based nanocomposites dispersed with nano-sized Ni-Co particles were studied. The composites were fabricated by the hydrogen reduction and hot-pressing of $Al_2O_3$ and NiO-CoO mixed powders. The mixtures were prepared by using Ni- and Co-nitrate $(Ni(NO_3)_2\;{\cdot}\;6H_2O\;and\;Co(NO_3)_2\;{\cdot}\6H_2O)$ as source materials for the Ni-Co particles. Microstructural observations revealed that nano-sized Ni-Co particles were dispersed homogeneously at $Al_2O_3$ grain boundaries. High strength above 1 GPa was obtained for the $Al_2O_3/10$ wt% Ni-Co nanocomposite fabricated by a controlled powder preparation process. The inverse magnetostrictive response to applied stress was obtained due to the presence of dispersed Ni-Co particles, which indicates a possibility to incorporate new functions into the structural ceramics without loosing the mechanical properties.