• Journal of Positioning, Navigation, and Timing
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• 제10권4호
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• pp.307-313
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• 2021

Modernized GNSS signal structures tend to use tiered codes, and all GNSSs use binary codes as secondary codes. However, recently, signals using polyphase codes such as Zadoff-Chu sequence have been proposed, and are expected to be utilized in GNSS. For example, there is Tiered Differential Polyphase Code (TDPC) using polyphase code as secondary code. In TDPC, the phase of secondary code changes every one period of the primary code and a time-variant error is added to the carrier tracking error, so carrier tracking ambiguity exists until the secondary code phase is found. Since the carrier tracking ambiguity cannot be solved using the general GNSS receiver architecture, a new receiver architecture is required. Therefore, in this paper, we describe the carrier tracking ambiguity and its cause in signal tracking, and propose a receiver structure that can solve it. In order to prove the proposed receiver structure, we provide three signal tracking results. The first is the differential decoding result (secondary code sync) using the general GNSS receiver structure and the proposed receiver structure. The second is the IQ diagram before and after multiplying the secondary code demodulation when carrier tracking ambiguity is solved using the proposed receiver structure. The third is the carrier tracking result of the legacy GPS (L1 C/A) signal and the signal using TDPC.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1996년도 한국자동제어학술회의논문집(국내학술편); 포항공과대학교, 포항; 24-26 Oct. 1996
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• pp.1388-1391
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• 1996

This paper presents the structure and functions of the differential beacon receiver for receiving DGPS error correction data. The differential beacon receiver is designed using commercially available components. Its functions are being implemented and tested in laboratory. Filed test is scheduled for the end of this year.

• Journal of Communications and Networks
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• 제12권6호
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• pp.582-591
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• 2010

Probabilistic modeling and analysis of correlation metrics have been receiving considerable interest for a long period of time because they can be used to evaluate the performance of communication receivers, including satellite broadcasting receivers. Although differential correlators have a simple structure and practical importance over channels with severe frequency offsets, closedform expressions for the output distribution of differential correlators do not exist. In this paper, we present detection error probability expressions for frame synchronization using differential correlation, and demonstrate their accuracy over channel parameters of practical interest. The derived formulas are presented in terms of the Marcum Q-function, and do not involve numerical integration, unlike the formulas derived in some previous studies. We first determine the distributions and error probabilities for single-span differential correlation metric, and then extend the result to multispan differential correlation metric with certain approximations. The results can be used for the performance analysis of various detection strategies that utilize the differential correlation structure.

• 열처리공학회지
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• 제32권6호
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• pp.270-274
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• 2019

In this study, simulation structure analysis was performed for the differential gear system for passenger cars as a prerequisite for the design of the balancing module. The differential gear system was modeled by using CATIA and simulation structure analysis was performed using ANSYS software. The material of the modeled differential gear system uses the mechanical properties of S45C (Q&T). In the structural analysis of the differential gear, the areas where the maximum stress and the maximum strain occurred can be identified. The maximum stress and maximum strain occurred in the pitch circle of the bevel gear. In evaluating the safety factor, it was found that sufficient safety factor was secured. Based on the analysis results for the differential gear, it is expected that it will be a good reference if we design the balancing module device.

• 한국지능시스템학회논문지
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• 제22권4호
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• pp.399-404
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• 2012

Evolutionary algorithms such as genetic algorithm (GA) have been proven their effectiveness when applying to the design of fuzzy models. However, it tends to suffer from computationally expensWive due to the slow convergence speed. In this study, we propose an approach to develop fuzzy models by means of an improved differential evolution (IDE) to overcome this limitation. The improved differential evolution (IDE) is realized by means of an orthogonal approach and differential evolution. With the invoking orthogonal method, the IDE can search the solution space more efficiently. In the design of fuzzy models, we concern two mechanisms, namely structure identification and parameter estimation. The structure identification is supported by the IDE and C-Means while the parameter estimation is realized via IDE and a standard least square error method. Experimental studies demonstrate that the proposed model leads to improved performance. The proposed model is also contrasted with the quality of some fuzzy models already reported in the literature.

• 전기학회논문지
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• 제60권2호
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• pp.407-415
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• 2011

In this study, we propose the design of optimized fuzzy controller for the rotary inverted pendulum system by using differential evolution algorithm. The structure of the differential evolution algorithm has a simple structure and its convergence to optimal values is superb in comparison to other optimization algorithms. Also the differential evolution algorithm is easier to use because it have simpler mathematical operators and have much less computational time when compared with other optimization algorithms. The rotary inverted pendulum system is nonlinear and has a unstable motion. The objective is to control the position of the rotating arm and to make the pendulum to maintain the unstable equilibrium point at vertical position. The output performance of the proposed fuzzy controller is considered from the viewpoint of performance criteria such as overshoot, steady-state error, and settling time through simulation and practical experiment. From the result of both simulation and practical experiment, we evaluate and analyze the performance of the proposed optimal fuzzy controller from the comparison between PGAs and differential evolution algorithms. Also we show the superiority of the output performance as well as the characteristic of differential evolution algorithm.

• Geomechanics and Engineering
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• 제35권4호
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• pp.411-424
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• 2023

Reasonable estimates of tunnel lining dislocations in the operation stage, especially under longitudinal differential settlement, are important for the design of waterproof gaskets. In this paper, a modified shell-joint model is proposed to calculate shield tunnel dislocations under longitudinal differential settlement, with the ability to consider the nonlinear shear stiffness of the joint. In the case of shell elements in the model, an elastoplastic damage constitutive model was adopted to describe the nonlinear stress-strain relationship of concrete. After verifying its applicability and correctness against a full-scale tunnel test and a joint shear test, the proposed model was used to analyze the dislocation behaviors of a shield tunnel in Shanghai Metro Line 2 under longitudinal differential settlement. Based on the results, when the tunnel structure is solely subjected to water-earth load, circumferential and longitudinal joint dislocations are all less than 0.1 mm. When the tunnel suffers longitudinal differential settlement and the curvature radius of the differential settlement is less than 300 m, although maximum longitudinal joint dislocation is still less than 0.1 mm, the maximum circumferential joint dislocation is approximately 10.3 mm, which leads to leakage and damage of the tunnel structure. However, with concavo-convex tenons applied to circumferential joints, the maximum dislocation value reduces to 4.5 mm.

• Journal of applied mathematics & informatics
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• 제41권4호
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• pp.869-882
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• 2023

In this paper, we find induced differential equations to give explicit identities of these polynomials from the generating functions of 2-variable mixed-type Hermite polynomials. Moreover, we observe the structure and symmetry of the zeros of the 2-variable mixed-type Hermite equations.

• ETRI Journal
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• 제23권4호
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• pp.158-167
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• 2001

We examine the diffusion layers of some block ciphers referred to as substitution-permutation networks. We investigate the practical and provable security of these diffusion layers against differential and linear cryptanalysis. First, in terms of practical security, we show that the minimum number of differentially active S-boxes and that of linearly active S-boxes are generally not identical and propose some special conditions in which those are identical. We also study the optimal diffusion effect for some diffusion layers according to their constraints. Second, we obtain the results that the consecutive two rounds of SPN structure provide provable security against differential and linear cryptanalysis, i.e., we prove that the probability of each differential (resp. linear hull) of the consecutive two rounds of SPN structure with a maximal diffusion layer is bounded by $p^n(resp.q^n)$ and that of each differential (resp. linear hull) of the SDS function with a semi-maximal diffusion layer is bounded by $p^{n-1}(resp. q^{n-1})$, where p and q are maximum differential and linear probabilities of the substitution layer, respectively.

• Smart Structures and Systems
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• 제17권2호
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• pp.347-361
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• 2016

A two-stage method for damage detection in truss systems is proposed. In the first stage, a modal residual vector based indicator (MRVBI) is introduced to locate the potentially damaged elements and reduce the damage variables of a truss structure. Then, in the second stage, a differential evolution (DE) based optimization method is implemented to find the actual site and extent of damage in the structure. In order to assess the efficiency of the proposed damage detection method, two numerical examples including a 2D-truss and 3D-truss are considered. Simulation results reveal the high performance of the method for accurately identifying the damage location and severity of trusses with considering the measurement noise.