• Journal of Navigation and Port Research
• /
• v.46 no.3
• /
• pp.168-178
• /
• 2022

In this study, the resistance test, the vertical static angle of the attack test and VPMM test will be conducted to estimate the maneuverability of underwater vehicles with ahead propeller. The vertical static test will be conducted within the range of -40deg to 40deg, to investigate the cross-flow drag at high incidence angles. The tests will be conducted by dividing the propeller rotation into a case in which the propeller rotates at a specific rpm, and a case in which the propeller rotates naturally, according to the towing speed. Hydrodynamic coefficients of vertical direction will be estimated by the captive model tests. Additionally, the vertical dynamic stability index based on estimated hydrodynamic coefficients will be calculated and the impact of the propeller revolution state on the index will be investigated. The results are expected to be used as reference test data for underwater vehicles with ahead propeller.

• Transactions of the Korean hydrogen and new energy society
• /
• v.25 no.5
• /
• pp.509-515
• /
• 2014

At the fuel processing system (FPS) of fuel cell vehicle, hydrogen recirculation blower (HRB) is used for the recirculation of remained hydrogen after reaction. In this paper, noise and vibration improvement of HRB is studied by changing design and control. It is checked the campbell diagram and critical speed for stability of rotor, and housing stiffness is improved using simulation of frequency response function (FRF). A method is suggested that can decrease the unbalance amount of the rotor and impeller which main source of noise and vibration. In order to reduce the noise during deceleration of blower, electrical braking is applied and tested the risk impact of durability. Founded the optimum switching frequency of the motor control, and reduced the idle rpm by increasing of aerodynamic performance. The superiority of paper is proved by measurement of the improved product's noise and vibration.

• International Journal of Highway Engineering
• /
• v.10 no.1
• /
• pp.1-9
• /
• 2008

Five bases for of highways are sight distance, vehicle stability, driver comfort, drainage and aesthetics. Among these bases, the sight distance is the most critical one in the highway alignment design. It is certain that highways and drivers' observation actions are 3-dimensional in nature. But, the highway alignment design and the sight distance analysis have been performed on 2-dimensional planes because of various constraints and complexity of calculating 3-dimensional sight distance. The purpose of this study is to derive a model for determining exact available sight distance in 3-D combined horizontal and vertical alignments. Application of the model is illustrated using numerical examples. The proposed model should be useful in quantifying the criteria for 3-D highway alignments.

• Journal of Pharmaceutical Investigation
• /
• v.38 no.4
• /
• pp.241-247
• /
• 2008

Paclitaxel is a taxane diterpene amide, which was first extracted from the stem bark of the western yew, Taxus brevifolia. This natural product has proven to be useful in the treatment of a variety of human neoplastic disorders, including ovarian cancer, breast and lung cancer. Paclitaxel is a highly hydrophobic drug that is poorly soluble in water. It is mainly given by intravenous administration. Therefore, The pharmaceutical formulation of paclitaxel ($Taxol^{(R)}$; Bristol-Myers Squibb) contains 50% $Cremophor^{(R)}$ EL and 50% dehydrated ethanol. However the ethanol/Cremophor EL vehicle required to solubilize paclitaxel in $Taxol^{(R)}$ has a pharmacological and pharmaceutical problems. To overcome these problems, new formulations for paclitaxel that do not require solubilization by $Cremophor^{(R)}$ EL are currently being developed. Therefore this study utilized a supercritical fluid antisolvent (SAS) process for cremophor-free formulation. To select hydrophilic polymers that require solubilization for paclitaxel, we evaluated polymers and the ratio of paclitaxel/polymers. HP-${\beta}$-CD was used as a hydrophilic polymer in the preparation of the paclitaxel solid dispersion. Although solubility of paclitaxel by polymers was increased, physical stability of solution after paclitaxel/polymer powder soluble in saline was unstable. To overcome this problem, we investigated the use of surfactants. At 1/20/40 of paclitaxel/hydrophilic polymer/ surfactant weight ratio, about 10 mg/mL of paclitaxel can be solubilized in this system. Compared with the solubility of paclitaxel in water ($1\;{\mu}g/mL$), the paclitaxel solid dispersion prepared by SAS process increased the solubility of paclitaxel by near 10,000 folds. The physicochemical properties was also evaluated. The particle size distribution, melting point and amophorization and shape of the powder particles were fully characterized by particle size distribution analyzer, DSC, SEM and XRD. In summary, through the SAS process, uniform nano-scale paclitaxel solid dispersion powders were obtained with excellent results compared with $Taxol^{(R)}$ for the physicochemical properties, solubility and pharmacokinetic behavior.

• Journal of computational fluids engineering
• /
• v.15 no.2
• /
• pp.7-13
• /
• 2010

Flight vehicles such as wheel wells and bomb bays have many cavities. The flow around a cavity is characterized as an unsteady flow because of the formation and dissipation of vortices brought by the interaction between the free stream shear layer and the internal flow of the cavity. The resonance phenomena can damage the structures around the cavity and negatively affect the aerodynamic performance and stability of the vehicle. In this study, a numerical analysis was performed for the cavity flows using the unsteady compressible three-dimensional Reynolds-Averaged Navier-Stokes (RANS) equation with Wilcox's turbulence model. The Message Passing Interface (MPI) parallelized code was used for the calculations by PC-cluster. The cavity has aspect ratios (L/D) of 5.5 ~ 7.5 with width ratios (W/D) of 2 ~ 4. The Mach and Reynolds numbers are 0.4 ~ 0.6 and $1.6{\times}10^6$, respectively. The occurrence of oscillation is observed in the "shear layer and transient mode" with a feedback mechanism. Based on the Sound Pressure Level (SPL) analysis of the pressure variation at the cavity trailing edge, the dominant frequencies are analyzed and compared with the results of Rossiter's formula. The dominant frequencies are very similar to the result of Rossiter's formula and other experimental datum in the low aspect ratio cavity (L/D = ~4.5). In the high aspect ratio cavity, however, there are other low dominant frequencies of the leading edge shear layer with the dominant frequencies of the feedback mechanism.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.40 no.1
• /
• pp.1-8
• /
• 2016

In this study, we propose a control algorithm for Inertially Stabilized Platforms (ISP), which combines Disturbance Observer (DOB) with conventional proportional integral derivative (PID) control algorithm. A single axis ISP system was constructed using a direct drive motor. The joint friction was modeled as a nonlinear function of joint speed while the accuracy of the model was verified through experiments and simulation. In addition, various Q-filters, which have different orders and relative degrees of freedom (DOF), were implemented. The stability and performance of the ISP were compared through experimental study. The performance of the proposed PID-plus-DOB algorithm was compared with the experimental results of the conventional double loop PID control under artificial vehicle motion provided motion simulator with six DOF.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.15 no.1
• /
• pp.9-14
• /
• 2020

In this paper, we studied on-board antenna(primary link/secondary link/satellite link) used in UAV Data-link system. As a result, it is ideal to configure the Data-link as a triple link to secure the flight stability of the UAV, but the communication link should be configured according to the operating platform. As a result of overseas R&D trend analysis, the on-board Data-link antenna is installed and operated in a location where it is easy to secure LOS. The primary link consists of a directional antenna for basic operation and an omni-directional antenna for emergency operation. The secondary link uses a monopole/dipole antenna in the UHF/C band. Satellite link has been developed to apply phased array antenna to improve UAV operability.

• The Journal of The Korea Institute of Intelligent Transport Systems
• /
• v.9 no.2
• /
• pp.87-95
• /
• 2010

A Vehicular Ad-Hoc Network (VANET) is form of the Mobile Ad-hoc Network (MANET) to provide temporary communication among vehicles via wireless links. In VANET, the vehicle is one of the nodes in networks and communicates with each other. However, the wireless links disconnect very frequently, because vehicles have mobility and move freely. The reason why data accessibility degrades is that disconnection occurs frequently. To improve data accessibility, data replica allocation methods that made group to allocate data replica have proposed in MANET. However, those are not suitable because it is difficult to maintain stable links among the nodes moving fast by centralized group. In this paper, we proposed TBG (Tree Based Grouping) to allocate data replica with the distributed grouping method. Each node has own TBG and allocates data replica based on stability of links to improve data accessibility. The experiment demonstrates that the proposed method outperforms traditional methods in term of data accessibility.

• Geomechanics and Engineering
• /
• v.13 no.1
• /
• pp.43-61
• /
• 2017

The inverted T-type abutments are generally used in highway bridges constructed in Korea. This type of abutment is used because it has greater stability, with more pile foundations embedded in the bedrock, while simultaneously providing support for lateral earth pressure and vertical loads of superstructures. However, the cross section of inverted T-type abutments is large compared with the piers, which makes them more expensive. In addition, a differential settlement between the abutment and embankment, as well as the expansion joints, causes driving discomfort. This study evaluated the driving comfort of several types of abutments to improve driving comfort on the abutment. To achieve this objective, a traditional T-type abutment and three types of candidate abutments, namely, mechanically stabilized earth wall (MSEW) abutment supported by a shallow foundation (called "true MSEW abutment"), MSEW abutment supported by piles (called "mixed MSEW abutment"), and pile bent and integral abutment with MSEW (called "MIP abutment"), were selected to consider their design and economic feasibility. Finite element analysis was performed using the design section of the candidate abutments. Subsequently, the settlements of each candidate abutment, approach slabs, and paved surfaces of the bridges were reviewed. Finally, the driving comfort on each candidate abutment was evaluated using a vehicle dynamic simulation. The true MSEW abutment demonstrated the most excellent driving comfort. However, this abutment can cause problems with respect to serviceability and maintenance due to excessive settlements. After our overall review, we determined that the mixed MSEW and the MIP abutments are the most appropriate abutment types to improve driving comfort by taking the highway conditions in Korea into consideration.

• International Journal of Industrial Entomology and Biomaterials
• /
• v.33 no.2
• /
• pp.85-91
• /
• 2016

Exosomes are homogenous vesicles of 40-100 nm diameter produced endogenously. Exosomes are generated by inward budding into multi-vesicular bodies (MVB) and then released to extracellular space. Exosomes contain various nucleic acid and protein cargoes from their cells of origin and this endosomal cellular molecules are used for intracellular communication and for both promotion and suppression of immune responses. Recently, they are also considered as delivery vehicle for therapeutic proteins due to their characteristics of stability in body fluids and ability for target uptake. Also, they show less immune reactivity because the isolated exosome harboring therapeutic proteins can be from the same host. White-spotted flower chafer, Protaetia brevitarsis is one of the major insect commercially reared in Korea. There are bacterial and fungal pathogens causing diseases in the beetle, and these diseases incur economic loss to the larva-rearing farms. Due to their endosomal cargoes, exosomes are good candidates in use of disease diagnosis. In this study, we isolated insect exosome from the hemolymph of P. brevitarsis, and verified it by analysis of the exosome-specific surface proteins and RNA.