• Journal of the Korean Society for Precision Engineering
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• v.20 no.2
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• pp.104-111
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• 2003

Micro force measurement is required more frequently for a precision manufacturing and investment in fields of precision industries such as semiconductor, chemistry and biology, and so forth. Null balance method has been introduced as an alternative of a loadcell. Loadcells have advantages in aspects of low cost and easy manufacturing, but have also the limitation in resolution and sensitivity to environment variations. In this paper, null balance method is explained and the dominant parameters related to system performances are mentioned. Null position sensor, electromagnetic system and controller are investigated. Also, the characteristic experiment is carried out in order to estimate the resolution and the measurement range. In order to overcome the limitation by the drift of position sensor and the performance of controller, double electromagnetic force compensation method is proposed and experimented. After controlling and filtering, the resolution under $\pm$ 1mg and measurement range over 300g could be obtained.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.161-166
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• 2001

The static characteristics of four-nozzle flapper valves are investigated with both constant flow and constant supply pressure. The ranges, in which linearization of these characteristics would be valid, are discussed. Linearized dynamic model is also derived. Numerical simulations of nonlinear dynamic model are carried out by HyPneu to make an assessment of the effect of input step size in both cases of no-load and blocked-load operation.

• Language and Information
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• v.9 no.2
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• pp.69-83
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• 2005

This paper discusses the distribution of a null complementizer C, as opposed to an overt counterpart 'that', presenting empirical support both for and against the PF-merge analysis of C proposed by Boscovic and Lasnik (2003, henceafter B&L) who in turn attribute to the proposal in Pesetsky (1992) and Halle & Marantz (1993). In Section I, as a background, I discuss B&L's proposal that a null complementizer C is a PF-affix which undergoes a PF-merger operation at the PF component. In Section 2, after a brief sketch of the distribution of a null C mostly in bare-relatives, I explore the possibility of extending B&L's analysis to accomodate the null C's in the bare-relative constructions. In Section 3, I argue that despite some empirical difficulties, B&L's analysis of a null C as a PF-affix can still be maintained, if Adverb Fronting is an operation to Spec-C position. Furthermore, I propose a rule - PF Spell-Out Constraint - to account for the C-trace (i.e. that-trace) effect in relative constructions. With the PF Spell-Out Constraint and B&L's PF-merge account, the distribution of a null C can better be analyzed.

• Journal of Advanced Navigation Technology
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• v.20 no.3
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• pp.218-225
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• 2016

Null steering and beam steering are known well as anti-jamming methods in GPS anti-jamming system. Null steering gets a noise attenuation effect for the direction of jamming and beam steering earns additional gain synthesis for the direction of satellite signals. According to the research in the article for signal processing, it expresses that the N array antenna is effective for N-1 number of jamming signal by math public interest, however, the two algorithms analysis is not unknown for the operating condition of the realistic vehicle. In this paper, we modeled anti-jamming system using 4 and 7 array antenna and showed the two algorithms performance (PM, LCMV) when considering the number of antenna array, jammers and vehicle position (horizontal, vertical). In result, we showed that the case of vertical position of the vehicle which has large tilt angle for the relative position of satellites and jammers, has about 10 dB gain more in comparison with one of vertical position in spite of same JSR condition.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.2 s.95
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• pp.50-59
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• 1999

The effect of a variant drain orifice damping on the characteristics of a servovalve flapper-nozzle stage is analyzed. Steady-state characteristics of flapper-nozzle stage and the linearized dynamics of flapper-nozzle assembly with a spool valve show that the variant drain orifice damping could improve such null performance characteristics as null pressure sensitivity and linearity of gain function. Generalized design criterion and a sufficient condition for servovalve stability are also established.

• The Journal of Engineering Geology
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• v.5 no.1
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• pp.105-113
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• 1995

If broadband interference signals are incident at an array of sensor/antenna elements, it is desirable to form a set of bnoadband nulls around the directions of the interference signals to improve the array performance. An efficient way of generating a broadband null is to synthesize a derivative null. The performance of a derivative null in a constrained linear array which is subjected to random variations with respect to array weight and element Position is discussed. Computer simulation results are presented.

• Journal of the Korean Data Analysis Society
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• v.20 no.6
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• pp.2711-2719
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• 2018

When an observable is described by a single value, the statistic significance may be estimated by construction of null distribution using permutation and counting the portion of it that exceeds the observed value by chance. Genome-wide association study usually focuses on the association measure between a single or interacting genotypes with a single phenotype. However investigation of common genotypes associated simultaneously on multiple phenotypes may involve the observables that should be described with multiple numbers. Statistical significance for such an observable would involve null distribution in multiple dimensions. In this study, extension of the p-value estimation process using null distribution in one dimension has been sought that may be applicable to two dimensional case. Comparison of the position of points within the set of points they form has been proposed to use a positioning parameter inspired by the extension of the Kolmogorov-Smirnov statistic to two dimensions.

• The Journal of the Korea institute of electronic communication sciences
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• v.16 no.3
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• pp.407-416
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• 2021

An active phased array antennas can not only electrically steer the beam by controlling the weighting of the excitation signal, but can also form a pattern null in the direction of the interference source. The weight of the excitation signal to steer the main beam can be easily calculated based on the position of the radiating element. In addition, the weight of the excited signal for pattern null formation can also be calculated by setting the required radiation pattern and using WLSM(Weighted Least Squares Method). However, in a general wireless communication network environment, the location of the interference source is unknown. Therefore, an adaptive pattern null synthesis is needed. In this paper, it was confirmed that pattern null synthesis according to the required radiation characteristic was possible. And based on this, adaptive pattern null synthesis into the direction of an interference source was studied using a binary search algorithm based on observation area. As a result of conducting a simulation based on the presented technique, it was confirmed that adaptive pattern null forming into the direction of an interference is possible in efficient way.

• Journal of the Korean Society for Precision Engineering
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• v.6 no.4
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• pp.119-125
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• 1989

This paper presents a method of analog signal processing for a coordinate transformation. Through the proposed method, two-dimensional position information obtanided from any type of null-detector can be transformed into the information with repect to world coordinate system. In order to implement the method, a null- detection device which consists of four optical proximity sensor is developed. Through the experiments for performance evaluation, the effectiveness of the proposed method has been demonstrated.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.539-542
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• 1996

The forces exerted on an object by the end-effectors of multi-manipulators are decomposed into the motion-inducing force and the internal force. Motion-inducing force effects the motion of an object and internal force can't effect it. The motion of an object can't track exactly the desired motion because of internal force component, therefore internal force component must be considered. In this paper using the resolved acceleration control method and the fact that internal force lies in the null space of jacobian matrix, we construct independently the position, motion-inducing force and internal force controller. Secondly we construct the robust controller to preserve the robustness with respect to the uncertainty of manipulator parameters.