• Journal of Positioning, Navigation, and Timing
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• 제10권3호
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• pp.179-187
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• 2021

To estimate the location of the train, we consider an integrated navigation system that combines Inertial Navigation System (INS) and Global Navigation Satellite System (GNSS). This system provides accurate navigation results in open sky by combining only the advantages of both systems. However, since measurement update cannot be performed in GNSS signal blocked areas such as tunnels, mountain, and urban areas, pure INS is used. The error of navigation information increases in this area. In order to reduce this problem, the train's Non-Holonomic Constraints (NHC) information can be used. Therefore, we deal with the INS/GNSS/NHC integrated navigation system in this paper. However, in the process of installing the navigation system on the train, a Mounting Misalignment Error of the IMU (MMEI) inevitably occurs. In this case, if the NHC is used without correcting the error, the navigation error becomes even larger. To solve this problem, a method of easily estimating the MMEI without an external device is introduced. The navigation filter is designed using the Extended Kalman Filter (EKF) by considering the MMEI. It is assumed that there is no vertical misalignment error, so only the horizontal misalignment error is considered. The performance of the integrated navigation system according to the presence or absence of the MMEI and the estimation performance of the MMEI according to the method of using NHC information are analyzed based on simulation. As a result, it is confirmed that the MMEI is accurately estimated by using the NHC information together with the GNSS information, and the performance and reliability of the integrated navigation system are improved.

• 한국정밀공학회지
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• 제19권5호
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• pp.126-132
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• 2002

Misaligned shafts of the rotating machinery have caused noise, vibration. bearing failures, and stress concentration of coupling parts which decrease the efficiency and life of shaft systems. Therefore the proper shaft alignment of those system should be monitored continuously in dynamic condition. To solve these problems under dynamic condition a telemetry system is used. In this study, the condition of the least bending moment which is known by analyzing the structure and stress induced by misalignment is found. After the shaft is aligned by dial gage, a telemetry system with strain gages is installed on shaft. The relationship between bearing displacement and moment of coupling part influenced by misalignment is investigated. The moment derived from two shaft strain at the nearby coupling is measured. The bending strain is measured 5 times for average in static state as well as in dynamic state with 100∼700 rpm.

• 대한기계학회논문집
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• 제14권6호
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• pp.1509-1514
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• 1990

본 연구에서는 비압축성 유체가 온도의 영향을 받아 변화하는 경우에 대한 시 일링 간극내에서의 압력분포를 유한차분법을 이용하여 해석하였다. 여러기서 얻어진 결과를 이용하여 시일의 축력과 모멘트를 해석함으로써 시일의 동적 불안정성에 대하 여 논하였다. 이 때 기계평면시일의 형상은 코닝이 있고, 시일의 중심축이 경사진 경우를 고려하였다.

• Journal of Mechanical Science and Technology
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• 제14권4호
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• pp.408-417
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• 2000

The design and simulation of meshing of a single enveloping worm-gear drive with modified surfaces is presented. Generally worm-gear is generated by the hob which is identical to the worm. This process guarantees the conjugation between the worm and the gear but results in a line contact at every instant which is very sensitive to misalignment. The localization of bearing contact is necessary to reduce the sensitivity of the worm-gear drive to misalignment. Practically this localization is achieved by application of an oversized worm type hob to cut the worm-gear. The oversized hob approach is very practical and effective to localize bearing contact but can not provide the conjugation between the worm and the modified worm-gear. This work proposes an analytical procedure to make the worm surface conjugate to the worm-gear which is cut by the oversized hob. The developed computer program allows the investigation of the influence of misalignment on the shift of the bearing contact and the determination of the transmission errors, the contact ratio and the principle curvatures. The developed approach has been applied for ZK type of single-enveloping worm-gear drives and the developed theory is illustrated with a numerical example.

• 전기학회논문지
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• 제65권6호
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• pp.1038-1044
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• 2016

In this paper, a SDINS(Strapdown Inertial Navigation System) rapid initial alignment technique robust to the pyro-shock in multi-launch rocket system is proposed. The proposed method consists of three steps. Firth, transfer alignment is performed to estimate misalignment between MINS(Master INS) and SINS(Slave INS), and the estimated misalignment is written in the memory when transfer alignment is completed. Next, the pre-filtering process is performed to get rid of the acceleration error induced by launcher vibration. Finally, the horizontal alignment is performed to compensate misalignment variation caused by pyro-shock. We verified the performance of the proposed alignment method comparing with the conventional transfer alignment method. The simulation shows that the proposed initial alignment technique improves alignment performance.

• 대한조선학회 특별논문집
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• 대한조선학회 2008년도 특별논문집
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• pp.1-9
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• 2008

This report contains the results of structural analysis for the verification of the optimum offset range on the top of T-Bar with stiffener and BKT using at DSME Offset range as $6.0{\sim}10.0mm$ based on the 3-D FE analysis and experimental results of angie type stiffener as described in Annex 1 has been used as yard standard over ten (10) years under all Classification approval. Recently, Owner and Class have requested the confirmation for the misalignment based on the Yard's Standard so that a couple of locations for LNGC and LPGC has been investigated the structural strength by FE method using the offset ranges from 0.0 to 18.0 mm.

• The Journal of Asian Finance, Economics and Business
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• 제7권8호
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• pp.131-141
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• 2020

This study is designed to investigate the impact of China exchange rate policy on its trading partners by using a country multi-dataset GVAR model. Our model includes samples of 30 countries, six from high-income, six from middle-income and eighteen from low-income countries. This study used annual time series data over the period 1992 to 2017. We constructed currency misalignment index and it provided some interesting features about the currency undervaluation and overvaluation. The results of the currency misalignment shows that China's Renminbi is structurally more undervalued over the sample period as compared to other countries, and fluctuation in major currencies effects the global trade around the world. The overall empirical results of the GVAR model indicate that RMB undervaluation affects the trade pattern and macroeconomic performance of China's trading partners. Overall, China's exchange rate undervaluation has mixed effects on trading partner's GDP, exports and imports. The devaluation of China's RMB efficiently stimulated China's exports and reduced imports. While, in some countries, this effect is reverse, the RMB undervaluation increases the GDP of partner countries and also increases their exports to China. The results confirm the strong and leading role of the Chinese Renminbi in the global trade.

• ETRI Journal
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• 제40권1호
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• pp.26-38
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• 2018

To overcome considerable path loss in millimeter-wave propagation, high-gain directional beamforming is considered to be a key enabling technology for outdoor 5G mobile networks. Associated with beamforming, this paper investigates propagation power loss characteristics in two aspects. The first is beamwidth effects. Owing to the multipath receiving nature of mobile environments, it is expected that a narrower beamwidth antenna will capture fewer multipath signals, while increasing directivity gain. If we normalize the directivity gain, this narrow-beamwidth reception incurs an additional power loss compared to omnidirectional-antenna power reception. With measurement data collected in an urban area at 28 GHz and 38 GHz, we illustrate the amount of these additional propagation losses as a function of the half-power beamwidth. Secondly, we investigate power losses due to steering beam misalignment, as well as the measurement data. The results show that a small angle misalignment can cause a large power loss. Considering that most standard documents provide omnidirectional antenna path loss characteristics, these results are expected to contribute to mmWave mobile system designs.

• 마이크로전자및패키징학회지
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• 제19권2호
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• pp.29-33
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• 2012

The demand for 3D wafer level integration has been increasing significantly. Although many technical challenges of wafer stacking are still remaining, wafer stacking is a key technology for 3D integration due to a high volume manufacturing, smaller package size, low cost, and no need for known good die. Among several new process techniques Cu-to-Cu wafer bonding is the key process to be optimized for the high density and high performance IC manufacturing. In this study two main challenges for Cu-to-Cu wafer bonding were evaluated: misalignment and bond quality of bonded wafers. It is demonstrated that the misalignment in a bonded wafer was mainly due to a physical movement of spacer removal step and the bond quality was significantly dependent on Cu bump dishing and oxide erosion by Cu CMP.

• 한국군사과학기술학회지
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• 제15권4호
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• pp.374-380
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• 2012

In guided missile systems, reducing terminal-position error is the primary objective of the inertial navigation system. As a seeker is used to sense and track a target, the critical function of the inertial navigation system is to provide the seeker with accurate missile attitude information and help the seeker to keep tracking a target continuously. As inertial sensor body and missile body alignment errors are taken into account, it is desirable to minimize the alignment errors between the missile seeker and the attitude of inertial navigation system. Among the alignment errors, this paper addresses the methods of measuring and compensating misalignment between inertial sensor body and housing frame and shows test results of several experiments.