• 한국환경농학회지
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• 제38권1호
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• pp.1-9
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• 2019

BACKGROUND: Accurate and simple analytical method determining Fluxametamid residue was necessary in various food matrices. Additionally, fulfilment of the international guideline of Codex (Codex Alimentarius Commission CAC/GL 40) was required for the analytical method. In this study, we developed Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS) method to determine the Fluxametamid residue in foods. METHODS AND RESULTS: Fluxametamid was extracted with acetonitrile, partitioned and concentrated with dichloromethane. To remove the interferences, silica SPE cartridge was used before LC-MS/MS (Liquid Chromatography-Tandem Mass Spectrometry) analysis with $C_{18}$ column. Five agricultural commodities (mandarin, potato, soybean, hulled rice, and red pepper) were used as a group representative to verify the method. The liner matrix-matched calibration curves were confirmed with coefficient of determination ($r^2$) greater than 0.99 at calibration range of 0.001-0.25 mg/kg. The limits of detection and quantification were 0.001 and 0.005 mg/kg, respectively. Mean average accuracies were shown to be 82.24-115.27%. The precision was also shown to be less than 10% for all five samples. CONCLUSION: The method investigated in this study was suitable to the Codex guideline for the residue analysis. Thus, this method can be useful for determining the residue in various food matrices as routine analysis.

• Journal of Communications and Networks
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• 제18권6호
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• pp.892-901
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• 2016

In the multi-user multiple-input multiple-output (MIMO) system, orthogonal random beamforming (ORBF) scheme is proposed to serve multiple users simultaneously in order to achieve the multi-user diversity gain. The opportunistic space-division multiple access system (OSDMA-S) scheme performs multiple weighting matrices during the training phase and chooses the best weighting matrix to be used to broadcast data during the transmitting phase. The OSDMA-S scheme works better than the original ORBF by decreasing the inter-user interference during the transmitting phase. To save more time in the training phase, a partly random multiple weighting matrices selection scheme is proposed in this paper. In our proposed scheme, the Base Station does not need to use several unitary matrices to broadcast pilot symbol. Actually, only one broadcasting operation is needed. Each subscriber generates several virtual equivalent channels with a set of pre-saved unitary matrices and the channel status information gained from the broadcasting operation. The signal-to-interference and noise ratio (SINR) of each beam in each virtual equivalent channel is calculated and fed back to the base station for the weighting matrix selection and multi-user scheduling. According to the theoretical analysis, the proposed scheme relatively expands the transmitting phase and reduces the interactive complexity between the Base Station and subscribers. The asymptotic analysis and the simulation results show that the proposed scheme improves the throughput performance of the multi-user MIMO system.

• 한국해양공학회지
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• 제26권4호
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• pp.86-91
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• 2012

A new identification method for a nonproportional damping matrix using the finite element (FE) model updating technique is proposed. Mass and stiffness matrices of the undamped system are identified by FE model updating method. Sensitivity analysis is used to update the FE model, and zero frequencies are considered as design parameters to supplement the information of vibration characteristics. The nonproportional damping matrix is identified through the proposed method. A numerical example is considered to verify the performance of the proposed method. As a result, the damping matrix of the nonproportional system is estimated accurately.

• 농약과학회지
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• 제8권2호
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• pp.107-111
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• 2004

농약의 특성 및 과일별 농약의 잔류특성을 구명하기 위하여 복숭아, 포도 및 배 등 과수를 시험작물로 하여 침투성 살균제인 hexaconazole 2% SC와 비침투성 살균제인 chlorothalonil 53% SC를 혼용 희석하여 시험과수의 지상부에 1회 살포한 후 2시간, 3, 7, 14, 21일 째에 과일을 시료로 채취하였고, 시험기간 중 과일의 증체량을 조사하였다. 또한 경시적으로 농약 잔류량과 과육 및 과피 중 잔류농약의 분포비율을 조사하였다. 과일의 증체량은 털이 있는 복숭아는 약제 살포 21일 후에 약 57%, 털이 없는 천도복숭아는 약 40% 증가되었고, 포도와 배는 변화가 거의 없었다. 농약살포 직후와 대비한 21일 후의 잔류량을 비교한 결과 hexaconazole의 경우 복숭아에서는 13%, 포도에서는 24%, 배에서는 36% 농약이 잔류하였고, chlorothalonil의 경우에는 각각 11%, 27% 및 44%의 농약이 잔류하였다. 과일의 과피와 과육 등 부위별 잔류량을 조사한 결과 과육에서는 모든 시험구에서 검출한계 미만으로 검출되지 않았다.

• Bulletin of the Korean Chemical Society
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• 제34권6호
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• pp.1708-1714
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• 2013

Polyhexamethylene guanidine (PHMG) polymers used as an active ingredient in an antibacterial humidifier disinfectant were reported to cause harm to the human health when inhaled, although physical contact with this material was known to present low toxicity to humans. It is therefore necessary to develop an optimal analysis method which enables detection and analysis of PHMG polymers. MALDI-TOF investigations of PHMG are performed with a variety of matrices, and it is found that CHCA and 2,5-DHB are excellent matrices which well reflects the polymer population even at high mass. For the provided PHMG sample, the number-average ($M_n$) and weight-average ($M_w$) molecular masses were determined to be 744.8 and 810.7, respectively, when the CHCA was used as a matrix. The rank of the matrices in terms of averaged molecular weight was CHCA ~2,5-DHB > 5-NSA > DHAP, THAP > ATT > IAA ~ super-DHB ~ HABA. In addition, PSD of the PHMG oligomer ions exhibited a few unique fragmenation characteristics. The formation of a- and c-type fragments was the major fragmentation pathway, and the 25-Da loss peaks generally accompanied a- and c-type fragments.

• 대한전자공학회논문지SD
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• 제38권12호
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• pp.56-65
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• 2001

본 논문은 이상적인 균일한 무손실 유전체를 갖는 일반적인 3차원 연결선 구조에서의 커패시턴스 추출 시, 널리 사용되는 일차 대조법(First-order collocation) 외에 고차 구적법을 결합하여 사용함으로써 정확성을 제고하고, 반복적 행렬-벡터의 곱을 효율적으로 수행하기 위한 알고리즘을 제안한다. 제안된 기법은 연결선에서 전기적 성질이 집중되어 있는 코너나 비아를 포함한 경우에 일차 대조법 대신에 구적법을 이용하여 고차로 근사함으로써 정확성을 보장한다. 또한, 이 기법은 경계 요소 기법에서 행렬의 대부분이 수치적으로 저차 계수(low rank)를 이룬다는 회로상의 전자기적 성질을 이용하여 모형차수를 축소함으로써 효율성을 증진한다. 이 기법은 SVD(Singular Value Decomposition)에 기반한 저차 계수 행렬 축소 기법과 신속한 행렬의 곱셈 연산을 위한 Krylov-subspace 차수 축소 기법인 Gram-Schmidt 알고리즘을 도입함으로써 효율적인 연산을 수행할 수 있다. 제안된 방법은 허용 오차 범위 내에서 효율적으로 행렬-벡터의 곱셈을 수행하며, 이를 기존의 연구에서 제시된 기법과의 성능 평가를 통하여 보인다.

• 대한수학회지
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• 제51권4호
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• pp.655-663
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• 2014

Let R be a ring with identity, X(R) the set of all nonzero, non-units of R and G(R) the group of all units of R. We show that for a matrix ring $M_n(D)$, $n{\geq}2$, if a, b are singular matrices of the same rank, then ${\mid}o_{\ell}(a){\mid}={\mid}o_{\ell}(b){\mid}$, where $o_{\ell}(a)$ and $o_{\ell}(b)$ are the orbits of a and b, respectively, under the left regular action. We also show that for a semisimple Artinian ring R such that $X(R){\neq}{\emptyset}$, $$R{{\sim_=}}{\oplus}^m_{i=1}M_n_i(D_i)$$, with $D_i$ infinite division rings of the same cardinalities or R is isomorphic to the ring of $2{\times}2$ matrices over a finite field if and only if ${\mid}o_{\ell}(x){\mid}={\mid}o_{\ell}(y){\mid}$ for all $x,y{\in}X(R)$.

• ETRI Journal
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• 제42권3호
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• pp.333-340
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• 2020

We consider a hybrid combiner design for downlink massive multiple-input multiple-output systems when there is residual inter-user interference and each user is equipped with a limited number of radio frequency (RF) chains (less than the number of receive antennas). We propose a hybrid combiner that minimizes the mean-squared error (MSE) between the information symbols and the ones estimated with a constant amplitude constraint on the RF combiner. In the proposed scheme, an iterative alternating optimization method is utilized. At each iteration, one of the analog RF and digital baseband combining matrices is updated to minimize the MSE by fixing the other matrix without considering the constant amplitude constraint. Then, the other matrix is updated by changing the roles of the two matrices. Each element in the RF combining matrix is obtained from the phase component of the solution matrix of the optimization problem for the RF combining matrix. Simulation results show that the proposed scheme performs better than conventional matrix-decomposition schemes.

• Structural Engineering and Mechanics
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• 제41권5호
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• pp.591-604
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• 2012

This paper provides an iteration approach for the solution of multiple notch problem, which is based on the complex variable boundary integral equation (CVBIE). The contours of notches are applied by some loadings. The source points are assumed on the boundary of individual notch and the displacements along the boundaries become unknowns to be investigated. After discretization of the BIE, many influence matrices are obtained. One does not need to assemble many influence matrices into a larger matrix. This will considerably reduce the work in the program. The displacements along the many boundaries can be obtained from an iteration. There is no limitation for the configuration of notches. Several numerical examples are provided to prove the efficiency of the suggested approach.

• 대한수학회보
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• 제56권5호
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• pp.1273-1283
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• 2019

In matrix analysis, the Wielandt-Mirsky conjecture states that $$dist({\sigma}(A),{\sigma}(B)){\leq}{\parallel}A-B{\parallel}$$ for any normal matrices $A,B{\in}{\mathbb{C}}^{n{\times}n}$ and any operator norm ${\parallel}{\cdot}{\parallel}$ on $C^{n{\times}n}$. Here dist(${\sigma}(A),{\sigma}(B)$) denotes the optimal matching distance between the spectra of the matrices A and B. It was proved by A. J. Holbrook (1992) that this conjecture is false in general. However it is true for the Frobenius distance and the Frobenius norm (the Hoffman-Wielandt inequality). The main aim of this paper is to study the Hoffman-Wielandt inequality and some weaker versions of the Wielandt-Mirsky conjecture for matrix polynomials.