• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 1999년도 가을 학술발표회 논문집
• /
• pp.473-480
• /
• 1999

This paper presents the results of a parametric study on the behavior of mechanically stabilized earth retaining wall. It has been recognized that the currently available design guidelines, which is base on the limit equilibrium approach, cannot properly account the interaction effect between the components, construction sequence, and foundation settlement which may impose a significant influence on the wall behavior. A parametric study using finite element analysis was performed to investigate the behavior of MSE wall under different construction conditions and the applicability of the current design approach. In the parametric analysis, the effects of the construction sequence, the surcharge, and the foundation stiffness were studied and a detailed finite element modeling for various components of the system were employed. The results, such as wall displacement and earth pressure distributions, reinforcement forces, vertical stress distribution were then thoroughly analyzed to investigate the effect of construction details on the wall behavior.

• Journal of Advanced Marine Engineering and Technology
• /
• 제34권7호
• /
• pp.943-950
• /
• 2010

An efficient meshfree method based on a stabilized conforming nodal integration method is developed for elastoplastic contact analysis of metal forming processes. In this approach, strain smoothing stabilization is introduced to eliminate spatial instability in Galerkin meshfree methods when the weak form is integrated by a nodal integration. The gradient matrix associated with strain smoothing satisfies the integration constraint for linear exactness in the Galerkin approximation. Strain smoothing formulation and numerical procedures for path-dependent problems are introduced. Applications of metal forming analysis are presented, from which the computational efficiency has been improved significantly without loss of accuracy.

• 한국항공운항학회지
• /
• 제22권3호
• /
• pp.15-23
• /
• 2014

There have been CFIT(Controlled Flight Into Terrain) accidents that can be prevented if the crew executed go-around. This study is to analyse the common factors of three typical CFIT accidents of Korea in TEM(threat and error management) frame, and the examples of go-around gate and the countermeasures of eight airlines through the survey facilitating go-around to prevent CFIT. The common factors found in three typical CFIT accidents occurred in Korea or by Korean carriers turned out to be in mountainous terrain, in bad weather while in non-precision approach or circling approach by captain as PF(Pilot Flying) when crew make monitoring errors and communication errors. It also turned out that the crew in all three typical tragic CFIT accidents did not execute go-around in unstabilized approaches. The captains did not respond immediately when first officers advised them to go-around until it is too late. Seven out of eight Airlines answered that they use stabilized approach height as 1,000 feet to be stabilized earlier to have more safety margin by enhancing go-around gate regardless of the weather to prevent CFIT in the survey.

• 한국항공운항학회지
• /
• 제13권4호
• /
• pp.43-57
• /
• 2005

Traditionally aircraft had descended in steps to level at the MDA(Minimum Descent Altitude) during the conduct of non-precision approach. This "de-stabilized" method of flying an instrument approach procedure is considered as a major contributing factor in CFIT(Controlled Flight Into Terrain) accident and increasing pilot workload. In the effort to reduce CFIT accident and pilot workload, VNAV(Vertical Navigation) Approach has been suggested as means to manage the vertical component of non-precision approach procedure.[1] But In the actual circumstances in Korea, VNAV has not been using to reduce them because of many restriction facts and no published VNAV chart in particular airport. Therefore we are suggesting Constant Vertical Speed Approach Method, which is required few restriction facts, and the pilots who are using this method will experience a similar method like a Glideslope during proceeding non-precision approach. Consequently, We are expecting to reduce CFIT accidents and pilot workload.

• 한국항행학회논문지
• /
• 제23권2호
• /
• pp.104-113
• /
• 2019

본 연구는 정기항공사 소속 조종사들을 대상으로 그들의 비행경력과 운항능력에 대한 실증연구를 하였다. 첫째, 정기항공사 소속 조종사들의 비행경력(비행시간 및 기종)에 따른 운항능력의 차이를 분석하였다. 이를 통해 신규로 항공운송용 조종사로 진입하고자 하는 인력들에 대해 항공사가 기대하는 조종사의 운항능력의 수준을 검증할 수 있었다. 분석결과 기장의 경우 해당기종 비행시간이 500시간이든 1500시간이든 시계비행 운항심사 결과 간의 차이가 없는 것으로 나타났다. 부기장은 1,500시간 이상부터는 시계비행 운항심사 결과의 차이가 나타났다. 부기장은 기장과 달리 해당기종 비행시간을 많이 가질수록 안정적인 시계접근을 할 수 있음이 판명된 것이다. 기종특성과 관련하여 cable 또는 fly-by-wire 기종에 따라 기장 집단은 시계비행 운항능력의 차이가없었다. 즉, 시계접근의 경우는 기종에 관계없이 기장급 조종사의 기량이 평가된다고 할 수 있겠다. 부기장집단에서는 기종 특성에 따른 유의한 차이가 있는 것으로 판명되었다.

• 한국항공운항학회지
• /
• 제31권2호
• /
• pp.1-6
• /
• 2023

When landing an aircraft descent-speed, wind around the airport, and regulations are important indicators for the pilot to decide whether to land in the Final Approach. In this study, in order to maintain a decent angle accessible to the airport, the pilot predicts an appropriate decent rate suitable for wind direction, wind speed, and speed to make a stable landing. To confirm this, the decent rate according to the speed and speed of wind was calculated using the information actually measured on the B737NG aircraft and compared with the theoretical figures. The purpose of this study is to ensure that the pilot can make a stable landing at a given FPM (Feet Per Minute) when a visual approach and non-normal approach is required at an airport designed with a somewhat higher descent angle.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2011년도 춘계학술대회 논문집
• /
• pp.717-718
• /
• 2011

• Advances in Computational Design
• /
• 제2권3호
• /
• pp.225-240
• /
• 2017

This paper presents the application of multiple linear regression (MLR) and artificial neural network (ANN) techniques for developing the models to predict the unconfined compressive strength (UCS) and Brazilian tensile strength (BTS) of the fiber reinforced cement stabilized fly ash mixes. UCS and BTS is a highly nonlinear function of its constituents, thereby, making its modeling and prediction a difficult task. To establish relationship between the independent and dependent variables, a computational technique like ANN is employed which provides an efficient and easy approach to model the complex and nonlinear relationship. The data generated in the laboratory through systematic experimental programme for evaluating UCS and BTS of fiber reinforced cement fly ash mixes with respect to 7, 14 and 28 days' curing is used for development of the MLR and ANN model. The data used in the models is arranged in the format of four input parameters that cover the contents of cement and fibers along with maximum dry density (MDD) and optimum moisture contents (OMC), respectively and one dependent variable as unconfined compressive as well as Brazilian tensile strength. ANN models are trained and tested for various combinations of input and output data sets. Performance of networks is checked with the statistical error criteria of correlation coefficient (R), mean square error (MSE) and mean absolute error (MAE). It is observed that the ANN model predicts both, the unconfined compressive and Brazilian tensile, strength quite well in the form of R, RMSE and MAE. This study shows that as an alternative to classical modeling techniques, ANN approach can be used accurately for predicting the unconfined compressive strength and Brazilian tensile strength of fiber reinforced cement stabilized fly ash mixes.

• Journal of Mechanical Science and Technology
• /
• 제20권9호
• /
• pp.1459-1474
• /
• 2006

The present study is focused on the development of the RIF (Representative Interactive Flamelet) model which can overcome the shortcomings of conventional approach based on the steady flamelet library. Due to the ability for interactively describing the transient behaviors of local flame structures with CFD solver, the RIF model can effectively account for the detailed mechanisms of $NO_x$ formation including thermal NO path, prompt and nitrous $NO_x$ formation, and reburning process by hydrocarbon radical without any ad-hoc procedure. The flamelet time of RIFs within a stationary turbulent flame may be thought to be Lagrangian flight time. In context with the RIF approach, this study adopts the Eulerian Particle Flamelet Model (EPFM) with mutiple flamelets which can realistically account for the spatial inhomogeneity of scalar dissipation rate. In order to systematically evaluate the capability of Eulerian particle flamelet model to predict the precise flame structure and NO formation in the multi-dimensional elliptic flames, two methanol bluffbody flames with two different injection velocities are chosen as the validation cases. Numerical results suggest that the present EPFM model has the predicative capability to realistically capture the essential features of flame structure and $NO_x$ formation in the bluff-body stabilized flames.

• 한국분말재료학회지
• /
• 제5권2호
• /
• pp.111-121
• /
• 1998

Thick and dense deposit of higher than 97% of theoretical density was formed by induction plasma spraying. To investigate the effects of powder morphology on the density of deposit, two different kinds of Yttria-Stabilized-Zirconia powder, METCO202NS (atomized & agglomerated) and AMDRY146 (fused & crushed), were used and compared. After plasma treatment, porous METCO202NS powder was all the more densely deposited and its density was increased. In addition to the effect of powder morphology, the process parameters such as, sheath gas composition, probe position, particle size and spraying distance, and so on, were evaluated. The result of experiment with AMDRY146 powder, particle size and spraying distance affected highly on the density of the deposit. The optimum process condition for the deposition of -75 ${\mu}m$ of 20%-Yttria-Stabilized-Zirconia powder was 120/201/min of Ar/$H_2$ gas rate, 80 kW of plasma plate power, 8 cm of probe position and 150 Torr of spraying chamber pressure, at which its density showed 97.91% of theoretical density and its deposition rate was 20 mm/min. All the results were assessed by statistical approach what is called ANOVA.