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The Satellite Altimetry-Derived Free-air Gravity Anomalies (SAFAGAs) are correlated with undulations of crustal density variations under the seafloor. In this study, shipborne bathymetry from the Korea Rural Community Corporation (KRC) and the SAFAGAs from Scripps Institution of Oceanography were combined to predict the bathymetry in shallow waters near shore around Saemangeum Seawall located on the southwest coast of the Korean Peninsula. The density contrast of 5.0 g/cm3 estimated by the checkpoints of the Gravity-Geologic Method (GGM) between the seawater and the seafloor topographic mass was applied to predict the bathymetry in shallow waters. The root mean square error of the bathymetry differences between GGM and KRC on the KRC shipborne tracks in shallow waters around Saemangeum Seawall is 0.6 m. The advantages of GGM in the short-wavelength components from the results of the power spectral density and coherency analysis in shallow waters proved that the satellite-derived bathymetry by GGM is highly correlated with shipborne bathymetry. The topographic effects in the off-tracks extracted from the SAFAGAs in GGM can be effectively utilized to improve the bathymetry by combining them with the shipborne depth data in shallow waters, where the shipborne depth data are limited.

This study aims to analyze the accuracy for feasibility study of Network-RTK(VRS) surveying inside and outside of Korean CORS network. The southwest coast of Korea where some part of mainland and islands are outside of CORS network is chosen as the test area. To evaluate the accuracy of VRS surveying at surveying points, several Unified Control Points (UCPs) inside and outside of Korean CORS network were selected as the points in the test area. The feasibility of VRS surveying was analyzed by investigating the errors related to the location of points inside and outside of CORS network and the difference of 3-dimensional coordinates observed on different date. As the results of this study, the orthometric height errors of points outside of CORS network based on KNGeoid14 were improved about 5.0 cm in RMSE in comparison with KNGeoid13. The height errors of VRS surveying were considered to be less relevant to the results from PDOP and number of satellites (GPS and GLONASS). However, the orthometric errors caused by the geoidal height of KNGeoid and the ellipsoidal height of VRS surveying at points located outside of CORS network need to be addressed carefully for control surveying. When a point surveyed twice on different date, the difference of the ellipsoidal height of the point outside of CORS network was larger than that of the point inside of CORS network.

Precise geoid heights are not as important for understanding Earth&rsquo, s gravity field, but they are important to geodesy itself, since the vertical datum is defined as geoid in a cm-level accuracy. Several high-degree geopotential models have been derived lately by using satellite tracking data such as those from Gravity Recovery and Climate Experiment (GRACE) and Gravity Field and Steady-State Ocean Circulation Explorer (GOCE), satellite altimeter data, and terrestrial and airborne gravity data. The Korean national geoid (KNGeoid) models of the National Geographic Information Institute (NGII) were developed using the latest global geopotential models (GGMs), which are combinations of gravity data from satellites and land gravity data. In this study, geoid heights calculated from the latest high-degree GGMs were used to evaluate the accuracy of the three GGMs (European Improved Gravity model of Earth by New techniques (EIGEN)-6C4, Earth Gravitational Model 2008 (EGM2008), and GOCE-EGM2008 combined model (GECO)) by comparing them with the geoid heights derived from the Global Navigation Satellite System (GNSS)/leveling of the 1182 unified control points (UCPs) that have been installed by NGII in South Korea since 2008. In addition, the geoid heights derived from the KNGeoid models were compared with the geoid heights derived from the GNSS/leveling of the 1182 UCPs to assess the accuracy of the KNGeoid models in terms of relative geoid heights for further gravimetric geoid determination studies in South Korea. As a result, the EGM2008 model could be selected as the suitable GGM from among the three GGMs for determining a gravimetric geoid model for South Korea.

Bathymetric mapping was traditionally implemented by shipborne single-beam, multi-beam, and side-scan sonar sensors. There are big tidal effects and the foreshore on western coastal zones of Korea. These days airborne bathymetric LiDAR technique has been attempted to get seamless geospatial data from land to submarine topography. This study focuses on generating bathymetric data near coastlines from multi-beam bathymetry and satellite altimetry gravity anomalies. The estimated bathymetry is compared with multi-beam and airborne bathymetric LiDAR data for the accuracy assessment.

In this study, the Zn-Mg alloy coatings with various Mg contents were deposited using an unbalanced magnetron sputtering process. Their surface microstructure, chemical composition, phase, and corrosion property were investigated. The microstructure of the Zn-Mg coatings changed from porous microstructure to dense one with increasing Mg contents in the coatings. As Mg contents in coatings increased, intermetallic phases such as Mg2Zn11 and MgZn2 were detected from X-ray diffraction (XRD) results. The corrosion resistance of the Zn-Mg alloy coatings was investigated quantitatively using electrochemical impedance spectroscopy (EIS) measurement with 3.5% NaCl solution. The results of EIS measurement showed that the charge transfer resistance and the phase angle of the Zn-Mg alloy coatings were increased from 162.1 Ω·cm 2 to 558.8 Ω·cm2 and from about 40o to 60o with increasing Mg contents from 5.1 wt.% to 15.5 wt.% in the coatings. These results demonstrate that the Zn-Mg coatings with increasing Mg contents showed an enhanced corrosion resistance.

Kim, K.B.; Yun, H.S., and Kim, T. W., 2019. Height recomputation of the Korean vertical origin point using new mean sea level of Incheon Bay. In: Lee, J.L.; Yoon, J.-S.; Cho, W.C.; Muin, M., and Lee, J. (eds.), The 3rd International Water Safety Symposium. Journal of Coastal Research, Special Issue No. 91, pp. 396-400. Coconut Creek (Florida), ISSN 0749-0208.The mean sea level (MSL) of Incheon Bay using the long-term tidal observations more than 18.6 years (January 1, 1999 ∼ August 31, 2017) was determined by harmonic analysis. In comparison with the current MSL of Incheon Bay provided by Korea Hydrographic and Oceanographic Agency, the difference of the MSL is 0.035 m. The height of the current Korean vertical original point (KVOP) was reexamined by the newly computed MSL of Incheon Bay and height difference was computed between Tidal Gauge Bench Mark (TGBM) installed near Incheon Harbor and the KVOP. There is a difference of 2.27 cm in between the recalculated height and the current height of the KVOP. In order to check height error in the geodetic leveling network generated from single vertical origin point system based on the KVOP of Incheon, it would be necessary to consider the application of height deviation in multiple vertical origin point systems based on the local (Mokpo, Busan, and Mukho) MSLs.

Kim, T.W.; Yun, H.S.; Kim, K.B., and Hong, S.B., 2019. Development of real-time HABs detection technique using Unmanned Aerial Vehicle (UAV). In: Lee, J.L.; Yoon, J.-S.; Cho, W.C.; Muin, M., and Lee, J. (eds.), The 3rd International Water Safety Symposium. Journal of Coastal Research, Special Issue No. 91, pp. 391-395. Coconut Creek (Florida), ISSN 0749-0208.If HABs flow into the seawater desalination plant by surprise, it can inflict some serious damages on the plant such as plant contamination. A monitoring system capable of detecting and tracking HABs based on UAV has been developed in order to solve this problem. The monitoring system is based on the HSV Color Detection Image Processing Algorithm, which demonstrates an excellent price/performance ratio for monitoring the HABs behavior, as well as excellent monitoring range and maneuverability. The HSV color detection algorithm, which has a superior detection range under sunlight, was able to continuously track the HABs, extracting the velocity and direction data. Finally, these results were compared with those obtained by conventional technologies to verify its effectiveness.

The gravity-geologic method (GGM) was used to enhance the bathymetry of the East Sea (Sea of Japan) with satellite altimetry-derived free-air gravity anomalies and shipborne depth measurements. By comparison with the bathymetry model of Smith and Sandwell’s (SAS) approach (1994), GGM was found to have an advantage with short wavelength (≤12 km) components, while SAS better predicts longer wavelength (≥25 km) components, despite its dependency on density contrast. To mitigate this limitation, a tuning density contrast of 10.25 g/cm3 between seawater and the seafloor was primarily estimated by the downward continuation method and then validated by the check points method with GGM. Similarly, SAS is limited by the “A” value in low-pass part of the Wiener filter, which defines the effective range of the wavelength components on bathymetry. As a final result, we present an enhanced GGM bathymetry model by integrating all available data.

Applying brittle intermetallic compound coating on metals can enlarge the range of their use. In this instance, the properties of the coating layer are influenced by the constituent phases of intermetallic compound coating layer. In this study, the mixtures of Ni and Al powder have been reacted at different heating rates in an induction furnace in order to obtain the intermetallic compound coating layer with a single phase structure on a ductile cast iron. The microstructures and mechanical properties of the coating layer are investigated and the effects of heating rate in the induction furnace on the properties of intermetallic compound coating layers are evaluated. It was found that the ignition temperature and the maximum temperature increase significantly with increasing heating rate. It was also found that the coating layer is composed of single phase NiAl corresponding to the initial composition of mixed powder and adhesion qualities with substrate are improved with increasing heating rate.

Sn-3.0Ag-0.5Cu lead fee solder was generally utilized in electronics assemblies. But it is insufficient to research about activation energy(Q) that is applying to evaluate the solder joint reliability of environmental friendly electronics assemblies. Therefore this study investigated Q values which are needed to IMC formation and growth of Sn-3.0Ag-0.5Cu/Cu and Sn-40pb/Cu solder joints during aging treatment. We bonded Sn-3.0Ag-0.5Cu and Sn-40Pb solders on FR-4 PCB with Cu pad$(t

In this paper, the determination of gravity anomalies in the Great Lakes using satellite altimeter data of GEOSAT Geodetic Mission (GM) and TOPEX/Poseidon is discussed. The seasonal change of lake level was observed from TOPEX/Poseidon satellite altimeter data. This analysis of lake level change was made to determine the mean lake surface profiles along the TOPEX/Poseidon repeat tracks. The least squares collocation was used to predict gravity anomalies. The gravity anomalies are determined by using mean lake surface profiles derived from TOPEX altimeter data and along-track slopes and azimuth derived from lake surface heights measured by the GEOSAT altimeter. To remove influences of the cycle-to-cycle time variation of lake level, along-track slopes of altimeter height are used. These results are compared to the exisiting surface gravit data measured in the Great Lakes. The gravity anomaly in the Lake Huron derived from the altimeter data using the least squares collocation shows slightly better comparison with the surface gravity anomaly than that implied by the EGM-96 gravity model.

This paper addresses a real-time grasp synthesis of multi-fingered robot hands to find grasp configurations which satisfy the force closure condition of arbitrary shaped objects. We propose a fast and efficient grasp synthesis algorithm for planar polygonal objects, which yields the contact locations on a given polygonal object to obtain a force closure grasp by a multi-fingered robot hand. For an optimum grasp and real-time computation, we develop the preference and the hibernation process and assign the physical constraints of a humanoid hand to the motion of each finger. The preferences consist of each sublayer reflecting the primitive preference similar to the conditional behaviors of humans for given objectives and their arrangements are adjusted by the heuristics of human grasping. The proposed method reduces the computational time significantly at the sacrifice of global optimality, and enables grasp posture to be changeable within 2-finger and 3-finger grasp. The performance of the presented algorithm is evaluated via simulation studies to obtain the force-closure grasps of polygonal objects with fingertip grasps. The architecture suggested is verified through experimental implementation to our developed robot hand system by solving 2- or 3-finger grasp synthesis.

The role of the electroplated nickel layer on hydrogen permeation through AISI 4340 steel was investigated by a electrochemical hydrogen permeation test. The permeation test, composed of three steps, was conducted to measure the hydrogen diffusivity and surface hydrogen concentration. A constant current of 20 mAcm-2 and a constant potential of -100 mV vs. Ag/AgCl electrode were applied to the hydrogen entry and exit cells, respectively. The thickness of the electroplated nickel layer on AISI 4340 steel increased in a linear fashion with an increase in electroplating time. The nickel coated layer contributed to a decrease in the hydrogen permeability of nickel coated AISI 4340 steel specimens. This is due to the fact that the surface hydrogen concentration and hydrogen diffusivity in nickel coated layer were lower than those of AISI 4340 steel substrate. Especially, low hydrogen diffusivity decreased significantly with hydrogen permeability. The critical effective hydrogen diffusivity for barrier of nickel electroplated AISI 4340 steel specimens was higher than the hydrogen diffusivity of AISI 4340 steel specimen. It is proposed then that the thin nickel layer on AISI 4340 steel acts as a barrier for hydrogen permeation through AISI 4340 steel.

Two adaptive nonlinear control schemes are presented for an induction motor: tuning function and modular design approaches. The objective here is to control the speed and flux in an independent manner despite rotor resistance uncertainty. In most existing adaptive schemes with this objective, load torque is regarded as a constant but unknown parameter to be estimated rather than a disturbance. On the other hand, this paper uses an integrator to deal with the low-frequency load torque instead of trying to estimate it. Simulations show that the proposed adaptive schemes lead to uniform closed-loop performance despite the uncertainty of the rotor resistance.

For precise tracking control of a class of nonlinear systems over a finite time interval, an iterative learning control method using the relative degree of a system is proposed. The class of nonlinear systems, where the iterative learning control is applied, can be extended by using the proposed method. A sufficient condition is derived for guaranteeing a uniform convergence of the output to the desired output. The results obtained for a class of nonlinear systems are shown to be a generalization of the existing results for linear time-invariant systems.

A process control language using function block diagram approach is designed for real-time control of continuous manufacturing process automation system, in which five groups of primitIVe functIon blocks and macro-type function blocks are defined to make an operator easy to implement target programs. To effectively utilize the proposed function block diagram language, a graphic editor, compiler and executer are also designed. The validity of the concept in its design and implementation is assured by on-line simulation in the multi-function controller designed for continuous process automation.

A novel model reference adaptive control (MRAC) scheme for electrical servo drives is proposed, in which the control input is synthesized without any parameter identification mechanism and a PI controller is inserted ahead of the plant to reduce the steady state chattering. The proposed scheme is shown to be asymptotically stable in case that load torque disturbance sati sfies a certain condition. An application to a permanent magnet synchronous motor drive shows that the output error between the plant and the reference model tends to zero and the chattering is greatly reduced.

When electronic ballasts are used for fluorescent lamps, lifetime of the lamp is greatly affected by starting scenario and crest factor. A new method to reduce the crest factor of the lamp is proposed, and the proposed electronic ballast is controlled in the mode of pulse frequency modulation (PFM). Electronic ballasts with 50% valley-fill PFC are dealt with in this paper. The characteristics of electronic ballast with the proposed PFM control scheme are comprehensively investigated through several simulations and experiments.

For precise tracking control of a class of discrete-time nonlinear control systems, an interative learning control law is proposed and the robustness of the learning control system is investigated. The authors derive a sufficient condition under which the output of a system converges to a desired output and show that the asymptotic errors for the control input and the corresponding output are bounded even in the presence of initial condition errors and disturbances. >

This paper presents a comprehensive study on the stability of several control schemes for the induction motor driven by current source inverters. A stator voltage-controlled current source inverter driven system without a speed sensor is investigated in order to find appropriate control schemes, which are primarily based on a direct or, alternatively, an indirect frequency control scheme. The overall control systems with either a voltage control loop or current and voltage control loops, provided in addition to each frequency control scheme, are analyzed by utilizing the root locus method and simulated by computer to show the validity of this analysis. >

The evaluation and interpretation of eigenvalue sensitivity for a speed-sensorless LCCSI-fed induction motor drive system are presented. It is well known that the sensitivity of the dynamic stability with respect to any parameter variations of the system matrix, A, can be characterized by the sensitivity of the eigenvalues with respect to the parameter variations. Based on a control system devised for stable operation of the LCCSI-induction motor system without a speed sensor, the eigenvalue sensitivity analysis corresponding to the three related control plants from open loop to closed loop is described. The eigenvalue sensitivity analysis clearly shows the possible sources of the system instability as well as comprehensive results against the system parameter variations over the nominal operating frequency range. >

Online efficiency control optimization of induction motor drives is important from the viewpoints of energy saving and controlling a system whose characteristics are not fully unknown. The paper presents a neural network-based online efficiency control optimization for an induction motor drive which adopts slip angular frequency control. In the proposed scheme, a neurocontroller adjusts the slip angular frequency adaptively for minimum loss operation based on the measured input power. Simulation results show that considerable energy savings are achieved in comparison with the conventional method of operating under the condition of constant voltage to frequency ratio.

In this paper, we consider a dynamics of actuator driving system as well as actuator itself to design a robust adaptive controller for robot manipulators. We propose an adaptation law to guarantee the boundedness of parameter estimates irrespective of the boundedness of other closed-loop signals without data normalization. We also propose a control law to ensure the uniform stability of the closed-loop system without a priori knowledge of the unmodeled dynamics. We show that the tracking error belongs to the normalized error bound, and also show the robustness of the proposed adaptive controller by using an experiment referred to a two-link direct drive manipulator. >

The authors present a systematic study of an induction motor drive system employing a load commutated current source inverter (LCCSI). The steady-state characteristics of a LCCSI-fed induction motor are shown to be the intermediate characteristics between the voltage source inverter (VSI) and the auto sequentially commutated current source inverter (ASCI). The dynamic characteristics of the LCCSI-fed induction motor are investigated using a linearised model. A study through the pole/zero locations of the linearized system shows that a V/Hz ratio control loop plays an essential role in the stabilization of the system. >

A new control scheme using a torsional torque estimator based on a neural network is proposed and investigated for improving control characteristics of the high-performance motion control system. This control method presents better performance in the corresponding speed vibration response, compared with the disturbance observer-based control method. This result comes from the fact that the proposed neural network estimator keeps the self-learning capability, whereas the disturbance observer based torque estimator with the low pass filter should adjust the time constant of the adopted filter according to the natural resonance frequency determined by considering the system parameters varied. The simulation results show the validity of the proposed control scheme.

A synthesis method of the reduced-order extended Luenberger observer (ROELO) and its design procedure for a nonlinear dynamic system are presented. This paper proposes a method to reduce the order of the observer and to select the observer gain matrix. The main features of the proposed observer are discussed and compared with the characteristics of the other observers. The proposed algorithm is applied for high-performance induction motor drives without a speed sensor. The simulation results show that the proposed ROELO provides both the rotor flux and rotor speed estimation with good transient and steady state performance.

The downward continuation (DWC) method was used to determine the density contrast between the seawater and the ocean bottom topographic mass to estimate accurate bathymetry using the gravity-geologic method (GGM) in two study areas, which are located south of Greenland (Test Area #1: 40-50°W and 50-60°N) and south of Alaska (Test Area #2: 140-150°W and 45-55°N). The data used in this study include altimetry-derived gravity anomalies, shipborne depths and gravity anomalies. Density contrasts of 1.47 and 1.30 g cm^(-3) were estimated by DWC for the two test areas. The considerations of predicted density contrasts can enhance the accuracy of 3~4 m for GGM. The GGM model provided results closer to the NGDC (National Geophysical Data Center) model than the ETOPO1 (Earth topographical database 1) model. The differences along the shipborne tracks between the GGM and NGDC models for Test Areas #1 and #2 were 35.8 and 50.4 m in standard deviation, respectively. Furthermore, these differences were more strongly correlated with gravity anomalies than bathymetry in the test areas. It is shown that an accuracy of under 40 m can be obtained with comparisons to shipborne depths only in Test Area #1.

A method for designing a fault-tolerant control system with an additive redundant controller is presented. In the case when the main controller is a pole assignment controller and the redundant controller is an MRAC whose reference model is the closed-loop combination of the plant and the main controller, it is shown that the overall control system ensures the performance of set-point tracking even under failure in one of the two controllers. >