Jong-Ho Park

Fully Autonomous Vision-Based Net-Recovery Landing System for a Fixed-Wing UAV

This paper presents an autonomous vision-based netrecovery system for small fixed-wing unmanned aerial vehicles (UAVs). A fixed-wing UAV platform is constructed using various avionic sensors, and integrated with a flight control system and a vision system. The ground operation system consists of a vision station and ground control station that provide operation commands and monitor the UAV status. The vision algorithm to detect the recovery net and provide the bearing angle to the guidance algorithm is explained, along with the discussions on the techniques employed to improve the reliability of visual detection. The system identification process and controller are described, which enables to track given waypoints and to approach the detected net under the pursuit guidance law. Experimental results show the autonomous capabilities including take-off, waypoint following, and vision-based net recovery. The proposed technique can be an effective solution to recover fixed-wing UAVs without resorting to a complicated structure such as an instrumented landing system or expensive sensors such as a differential GPS.

A highly manufacturable low-k ALD-SiBN process for 60nm NAND flash devices and beyond

For the first time, low-k dielectric ALD-SiBN (atomic layer deposition) is successfully developed and applied on poly-Si/WSix gate as a spacer for reduction of parasitic capacitance between the cells. ALD-SiBN deposition is performed at 630/spl deg/C using dichlorosilane (SiH/sub 2/Cl/sub 2/-DCS), boron-trichloride (BCl/sub 3/) and ammonia (NH/sub 3/) as precursors. Compared with the conventional silicon nitride, ALD-SiBN exhibits similar film properties at lower dielectric constant. ALD-SiBN layer is deposited on poly-Si/WSix stack gate in 90nm NAND flash device. A significant reduction (>15%) of the floating-gate coupling voltage is achieved by employing SiBN compared with SiN spacer. In addition, excellent data retention characteristics (@HTS) is identified by applying low-k dielectric SiBN layer as a spacer on 90nm NAND flash device.

Effects of Poly(N‐isopropylacrylamide) (PNIPAAm) on the Conformational Change of Poly(N 5‐hydroxyalkyl glutamine) (PHAG) in PHAG‐PNIPAAm Block Copolymer with Temperature

Diblock copolymers consisting of poly(N 5 -hydroxyalkylglutamine) (PHAG) and poly(N-isopropylacrylamide) (PNIPAAm) were prepared by aminolysis with aminoalkanols of the side-chain ester of poly(γ-benzyl L-glutamate) (PLBG) as a part of PBLG-PNIPAAm block copolymers. The molecular weight ratio of the initial PBLG to the resulting PHAG was nearly 0.35. The effect of PNIPAAm on the conformational change of PHAG in PHAG-PNIPAAm block copolymers with temperature was investigated by circular dichroism. Poly[N 5 -(2-hydroxyethyl)-L-glutamine] (PHEG) and the PHEG-PNIPAAm copolymer (GNE) stayed in a randomly coiled conformation whereas poly(N 5 -(3-hydroxypropyl)-L-glutamine] (PHPG), poly(N 5 -(4-hydroxybutyl)-L-glutamine) (PHBG), PHPG-PNIPAAm copolymer (GNP), and PHBG-PNIIPAm copolymer (GNB) underwent conformational transitions with temperature.The conformational change of the PHPG block in GNP copolymer occurred from an α-helix to a random coil after the incorporatoin of PNIPAAm into the copolymer. The thermodynamic parameters of the thermally induced helix-coil transition for PHBG and PHBG-PNIIPAm in aqueous solution were calculated.

Study on the Mineral Admixture Replacement Ratio for Field Application of Concrete with High Volume Mineral Admixture

A variety of researches on the concrete with high volume mineral admixture have increased in recent years. In fact, it is very important to find appropriate replacement ratio of concrete with high volume mineral admixture in order to apply in the field. In this study, compressive strength according to fly ash and blast furnace slag replacement ratio as well as curing temperature was measured in the conditions of obtaining the same workability in order to examine the characteristics of concrete with high volume mineral admixture. In conclusion, it was found that the compressive strength at the age of 3 days decreased by 1.4MPa and the compressive strength at the age of 28 days decreased by 3.8MPa when the fly ash replacement ratio increased by 10%. Also, it was found that the compressive strength at the age of 3 days decreased by 1.0MPa and the compressive strength at the age of 28 days decreased by 0.9MPa when the blast furnace slag replacement ratio increased by 10%. Through the tests, we obtained the basic data for developing the future research on the concrete with high volume mineral admixture for housing structure.

Properties of Concrete for Industrial Floor using Mineral Admixtures

Recently, exposed concrete by machinery trowel is generally used in industrial floor such as warehouse. Also, concrete using only the cement has been mainly used except mineral admixture in order to secure surface abrasion resistance. However, in hot weather construction, it is causing a serious problem such as workability inhibition of trowel using only ordinary portland cement. Due to this, it was investigated the effect of application of fly-ash and ground granulated blast furnace slag on properties and abrasion resistance of concrete for industrial floor in this study. The result of this study, it was confirmed that fly-ash and ground granulated blast furnace slag can be used in concrete for industrial floor without affecting significantly the properties of concrete.

Evaluation of Impact Resistance of Steel Fiber and Organic Fiber Reinforced Concrete and Mortar

In this study, the Impact resistance of steel fiber and organic fiber reinforced concrete and mortar was evaluated and the improvement in toughness resulting from an increase in compressive strength and mixing fiber for impact resistance on performance was examined. The types of fiber were steel fiber, PP and PVA, and these were mixed in at 0.1, 0.5 and 1.0 vol.%, respectively. Impact resistance is evaluated with an apparatus for testing impact resistance performance by high-speed projectile crash by gas-pressure. For the experimental conditions, Specimen size was 100×100×20, 30mm (width×height×thickness). Projectile diameter was 7 and 10 mm and impact speed is 350m/s. After impact test, destruction grade, penetration depth, spalling thickness and crater area were evaluated. Through this evaluation, it was found that as compressive strength is increased, penetration is suppressed. In addition, as the mixing ratio of fiber is increased, the spalling thickness and crater area are suppressed. Organic fibers have lower density than the steel fiber, and population number per unit area is bigger. As a result, the improvement of impact resistance is more significant thanks to dispersion and degraded attachment performance.

Investigation of Early-Age Concrete Strength Development Using Hardening Accelerator

In this study, performance of hardening accelerator types which promote setting and hardening of cement has been reviewed in order to develop early age strength of concrete with compressive strength of 21~27 ㎫ after examination of strength development of the concrete at early age according to curing temperature and unit cement(binder) content. As results, soluble mineral salt showed better hardening acceleration effect than organic salt in the scope of this study. Also, hydration reaction accelerating effect of C₃S by Soluble mineral salt is effective on development of early age compressive strength and it was shown that the Pt’s hydration reaction accelerating effect was the best. Construction duration reduction can be expected by securing compressive strength for prevention of early aged freezing damage in 25hour-curing time under curing temperature at 15℃. Also, it was shown that compressive strength of specimen cured at 5℃ was similar with plain specimen cured at 10℃. Therefore, it is expected that fuel costs and carbon dioxide can be reduced when the same construction duration is considered.

Structural Modeling Reflected Nonlinearity for Longitudinal Dynamic Instability (POGO) Analysis of Liquid Propellant Launch Vehicles in Preliminary Design Phase

The longitudinal dynamic instability (POGO) of liquid propellant launch vehicle results from the complex interaction between the vehicle structural vibration in the longitudinal direction and liquid propellant feeding system. In the preliminary design phase of a launch vehicle, accurate prediction of the lower-mode longitudinal natural vibration characteristics enables to avoid pogo instability efficiently. In this paper, a complete vehicle including the liquid propellant tanks is analytically modeled for pogo instability analysis, focusing on the longitudinal lower natural frequencies. Moreover, liquid propellant tank modeling methods are established by use of an advanced one-dimensional mass-spring model to refine the complete vehicle model. By using these methods, parametric studies for the hydroelastic effect, evaluations of modal analysis, and pogo estimation were conducted. Consequently, the numerical results obtained by the orthotropic liquid tank modeling method were found to be in good agreement with natural vibration characteristics by the previous analyses and experiments. And, the target vehicle showed the pogo estimated areas at the first structural mode. Thus, the present simplified structural modeling and modal analysis procedure can be used to identify pogo occurrence areas and provide design criteria for pogo instability in the preliminary design phase.

OC283: Clinical use of fetal urine production rate for differentiation of the causes of polyhydramnios

included sensitivities, false-positive rates and receiver–operating characteristic (ROC) curves. Results: Of 576 pregnancies studied from 1995 to 2006, 145 (25.2%) were affected. At 12–13 weeks’ gestation, fetal cardiomegaly predicted the affected pregnancies significantly better than placentomegaly (area under ROC curve, 0.949 vs. 0.687, P < 0.05). The sensitivity for prediction of the affected pregnancies was 90.6% for fetal cardiomegaly (CTR ≥ 0.5), 69.8% for placentomegaly (PT > 18 mm) and 65.1% for combined testing. The corresponding false-positive rate was 6.8%, 50.3% and 2.8% respectively. At 14–15 weeks’ gestation, the sensitivity for prediction of affected pregnancies was 93.8% for fetal cardiomegaly, 93.8% for placentomegaly and 87.5% for combined testing. The corresponding false-positive rate was 16.7%, 76.9% and 17.7% respectively. MCAPSV was not predictive in early second trimester. However, at 18–19 weeks’ gestation, MCAPSV (at a cut-off 1.5 multiples of the median) predicted affected pregnancies significantly better than fetal cardiomegaly (area under ROC curve, 0.959 vs. 0.788, P < 0.05). The sensitivity for the prediction of affected pregnancies was 100.0% for fetal cardiomegaly and 57.1% for high MCAPSV while the corresponding false-positive rate was 46.2% and 0% respectively. Conclusions: The best ultrasonographic predictor of affected pregnancies at 12–13 weeks’ and 18–19 weeks’ gestation was fetal CTR and MCAPSV respectively.