• Proceedings of the Korean Biophysical Society Conference
• /
• 1999.06a
• /
• pp.61-62
• /
• 1999

;The mechanisms inducing hypertension are actively investigated and are still challenging topics. Basically hypertension must be caused by the disorder of $Ca^{2+}$ metabolism in vascular smooth muscle, such as the increase of $Ca^{2+}$ influx, the decrease of ci+ efflux, or the change of sensitivity of contractile protein etc. The one of cause of the increase of ci+ influx may be the change of ci+ channel activity. Even though the relationships of ci+ channel activity and hypertension were studied using various hypertension models, still it is not clear how much change of $Ca^{2+}$ channel activity in diabetes mellitus (DM) induced hypertension is occurred. We induced DM hypertension in SD rat and compared the $Ca^{2+}$ channel activity with age-matched normotensive SD rat. For inducing DM hypertension, left kidney was removed with 200 gm rat and, after 1 month, 60 mg/kg of streptozotocin was injected into peritoneal space to induce diabetes mellitus. Usually after 4-6 weeks, hypertension was fully induced. For isolating vascular smooth muscle cells (VSMC), we used mesenteric arteriole (3rd - 4th branch of mesenteric artery) of which diameter is below 150 urn. VSMCs were isolated enzymatically. $Ca^{2+}$ current was measured using whole cell patch clamp technique. All experiments were performed at $37^{\circ}C$. The cell membrane area of VSMC of DM hypertensive rat is larger than that of control VSMC($36.6{\pm}3.64{\;}pF{\;}vs{\;}22.4{\pm}1.29{\;}pF, {\;}mean{\pm}S.E.$) When we compared the current amplitude, the $Ca^{2+}$ current amplitude in VSMC of DM hypertensive rat is much larger than that in VSMC of normotensive age-matched rat. After $Ca^{2+}$ current amplitude was normalized by cell membrane area, the current amplitude in DM hypertension is increased to $249.1{\pm}15.9{\;}%{\;}(mean{\pm}S.E.M)$, which means the ;absolute current amplitude is about 4 times larger in DM hypertension. When we compared the steady state activation and inactivation. there were no noticeable differences. From these results. one of cause of the DM hypertension is due to the increase of $Ca^{2+}$ current amplitude. But it need further study why the $Ca^{2+}$ current is so large in VSMC of DM hypertension and how much $Ca^{2+}$ influx through $Ca^{2+}$ channel contribute to the increase of intracellular $Ca^{2+}$ and eventually contribute to development of hypertension.ypertension.

• Wind and Structures
• /
• v.21 no.6
• /
• pp.693-707
• /
• 2015

The efficiency of wind turbines (WT) is primarily reflected in their ability to generate electricity at any time. Downtimes of WTs due to "conventional" inspections are cost-intensive and undesirable for investors. For this reason, there is a need for structural health monitoring (SHM) systems, to enable service and maintenance on demand and to increase the inspection intervals. In general, monitoring increases the cost effectiveness of WTs. This publication concentrates on the application of two vibration-based SHM algorithms for stability and structural change monitoring of offshore WTs. Only data driven, output-only algorithms based on stochastic subspace identification (SSI) in time domain are considered. The centerpiece of this paper deals with the rough mathematical description of the dynamic behavior of offshore WTs and with the basic presentation of stochastic subspace-based algorithms and their application to these structures. Due to the early stage of the industrial application of SHM on offshore WT on the one side and the required confidentiality to the plant manufacturer and operator on the other side, up to now it is not possible to analyze different isolated structural damages resp. changes in a systematic manner, directly by means of in-situ measurement and to make these "acknowledgements" publicly available. For this reason, the sensitivity of the methods for monitoring purposes are demonstrated through their application on long time measurements from a 1:10 large scale test rig of an offshore WT under different conditions: undamaged, different levels of loosened bolt connections between tower parts, different levels of fouling, scouring and structure inclination. The limitation and further requirements for the approaches and their applicability on real foundations are discussed along the paper.

• Proceeding of KASS Symposium
• /
• 2008.05a
• /
• pp.107-112
• /
• 2008

This paper investigates the variation of post-buckling behaviours of 2-dimensional shallow arch type truss after sizing optimization. The mathematical programming technique is used to produce the optimum member size of 2D arch truss against a central point load. Total weight of structure is considered as the objective function to be minimized and the displacement occurred at loading point and member stresses of truss are used as the constraint functions. The finite difference method is used to calculate the design sensitivity of objective function with respect to design variables. The postbuckling analysis carried out by using the geometrically nonlinear finite element analysis code ISADO-GN. It is found to be that there is a huge change of post-buckling behaviour between the initial structure and optimum structure. Numerical results can be used as useful information for future research of large spatial structures.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.34 no.6
• /
• pp.751-756
• /
• 2010

Ultrasonic nonlinearity is very sensitive to changes in material properties. This paper describes the study of the correlation between heat treatment and ultrasonic nonlinearity by taking nonlinear factors into consideration. A modified formula was proposed for ultrasonic velocity. This formula indicated that the changes occurring in nonlinearity during heat treatments cause changes in the ultrasonic velocity. The experimental results show that the relative nonlinearity parameters calculated from the modified ultrasonic velocities and the ratio of amplitudes of the second harmonic and fundamental wave are in good agreement. The experimental results prove that heat treatment can result in changes in material nonlinearity. Moreover, the relative nonlinearity parameter calculated from the modified velocity formula is has a large value. Since this parameter has high sensitivity to changes in nonlinearity, it can be used to represent the relative nonlinearity change calculated in this study by using the modified formula for ultrasonic velocity.

• Transactions of the Korean Society of Pressure Vessels and Piping
• /
• v.8 no.2
• /
• pp.14-20
• /
• 2012

Full load rejection capability of nuclear power plant depends primarily on steam dump capacity (SDCAP) and steam generator level control capability. Recently, Ulchin Units 1&2 have performed stretched power uprate (SPU) and replacement steam generator (RSG) projects, which increase the power by 4.5 percent. They change major design or operating parameters and especially reduces steam dump capacity at full power due to increase of the steam flow. The reduction of SDC after SPU results in degradation of heat removal capability in full load rejection transients. Therefore, we should perform evaluation to determine whether reactor trips occur in large load rejection transients. Uchin Units 1&2 have experienced full load rejection (FLR) three times from 2004 to 2010. Operating data from the plant occurrence of FLR at Ulchin Units 1&2 showed that steam generator (SG) level transients were limiting in point of reactor trip. However the plant had never reached reactor trip in the FLR and successfully continued in house load operation. The parameters and setpoints for the SG will be changed if the SG is replaced. Therefore, we evaluated the appropriateness of steam dump, main feedwater and steam generator water level control system preventing the plant from reactor trip in case of FLR by the parameter sensitivity study whether SG water level operated smoothly after SPU and RSG projects.

• Transactions of the Korean hydrogen and new energy society
• /
• v.30 no.6
• /
• pp.490-498
• /
• 2019

The intermittent electric power supply of renewable energy can have extremely negative effect on power grid, so long-term and large-scale storage for energy released from renewable energy source is required for ensuring a stable supply of electric power. Power to gas which can convert and store the surplus electric power as hydrogen through water electrolysis is being actively studied in response to increasing supply of renewable energy. In this paper, we proposed the novel concept of hydrogen liquefaction process combined with pre-cooling process using the liquid air. It is that hydrogen converted from surplus electric power of renewable energy was liquefied through the hydrogen liquefaction process and vaporization heat of liquid hydrogen was conversely recovered to liquid air from ambient air. Moreover, Comparisons of specific energy consumption (kWh/kg) saved for using the liquid air pre-cooling was quantitatively conducted through the performance analysis. Consequently, about 12% of specific energy consumption of hydrogen liquefaction process was reduced with introducing liquid air for pre-cooling and optimal design point of helium Brayton cycle was identified by sensitivity analysis on change of compression/expansion ratio.

• Journal of Sensor Science and Technology
• /
• v.25 no.6
• /
• pp.383-387
• /
• 2016

Well-ordered nanocolumnar indium oxide ($In_2O_3$) thin films have been successfully fabricated by glancing angle deposition (GAD) using an e-beam evaporator. Nanocolumnar structures have a porous and large surface area with a narrow neck between nanocolumns, which allows them to detect minute amounts of gases. The nanocolumnar $In_2O_3$ thin films were fabricated by the GAD process at five different positions, viz. top, bottom, center, left, and right in a four inch substrate holder. There was a divergence in the thickness and the base resistance of each sensor. However, all the sensors exhibited extremely high sensitivity that was greater than $10^3$ times the change in electrical resistance after being exposed to 50 ppm of acetone gas at $300^{\circ}C$. Furthermore, the nanocolumnar $In_2O_3$ sensors displayed an extremely low detection limit (1.2 ppb) in dry atmosphere as well as in high humidity (80%). We demonstrated that the GAD nanocolumnar $In_2O_3$ sensors have an enormous potential for many applications owing to their particularly simple and reliable fabrication process.

• Wind and Structures
• /
• v.27 no.5
• /
• pp.325-336
• /
• 2018

The physical infrastructure of the power systems, including the high-voltage transmission towers and lines as well as the poles and wires for power distribution at a lower voltage level, is critical for the resilience of the community since the failures or nonfunctioning of these structures could introduce large area power outages under the extreme weather events. In the current engineering practices, single circuit lattice steel towers linked by transmission lines are widely used to form power transmission systems. After years of service and continues interactions with natural and built environment, progressive damages accumulate at various structural details and could gradually change the structural performance. This study is to evaluate the typical existing transmission tower-line system subjected to synoptic winds (atmospheric boundary layer winds). Effects from the possible corrosion penetration on the structural members of the transmission towers and the aerodynamic damping force on the conductors are evaluated. However, corrosion in connections is not included. Meanwhile, corrosion on the structural members is assumed to be evenly distributed. Wind loads are calculated based on the codes used for synoptic winds and the wind tunnel experiments were carried out to obtain the drag coefficients for different panels of the transmission towers as well as for the transmission lines. Sensitivity analysis is carried out based upon the incremental dynamic analysis (IDA) to evaluate the structural capacity of the transmission tower-line system for different corrosion and loading conditions. Meanwhile, extreme value analysis is also performed to further estimate the short-term extreme response of the transmission tower-line system.

• Wind and Structures
• /
• v.28 no.5
• /
• pp.285-298
• /
• 2019

For super long-span bridges, the aerodynamic forces induced by the flow passing the box girder should be considered carefully. And the Reynolds number sensitively of aerodynamic characteristics is one of considerable issue. In the study, a numerical study on the Reynolds number sensitivity of aerodynamic characteristic (flow pattern, pressure distribution and aerodynamic forces) of a twin-box girder were carried out using large eddy simulation (LES) with the dynamic Smagorinsky-Lilly subgrid model. The results show that the aerodynamic characteristics have strong correlation with the Reynolds number. At the leading edge, the flow experiences attachment, departure, and reattachment stages accompanying by the laminar transition into turbulence, causing pressure plateaus to form on the surface, and the pressure plateaus gradually shrinks. Around the gap, attributing that the flow experiences stages of laminar cavity flow, the wake with alternate shedding vortices, and turbulent cavity flow in sequence with an increase in the Reynolds number, the pressures around the gap vary greatly with the Reynold number. At the trailing edge, the pressure gradually recovers as the flow transits to turbulence (the flow undergoes wake instability, shear layer transition-reattachment station), In addition, at relative high Reynolds numbers, the drag force almost does not change, however, the lift force coefficient gradually decreases with an increase in Reynolds number.

• Journal of Aerospace System Engineering
• /
• v.17 no.4
• /
• pp.1-9
• /
• 2023

Recently, as Synthetic Aperture Radar (SAR), communication, and signal surveillance missions of spacecraft have become more advanced, research has been actively conducted on the deployable large mesh antenna system with excellent storage efficiency compared to the deployment area, and light weight. Deployable Mesh antennae are characterized by an increase in the number of Openings Per Inch (OPI), which is a measure of mesh weaving density as the mission frequency band increases, and this OPI change directly affects the thermal optical properties of the mesh antenna, so research on this is required. In this paper, to verify the thermal relationship between the optical properties of the mesh and antenna reflector, thermal sensitivity analysis between the mesh and the antenna reflector is performed by in-orbit thermal analysis with various optical characteristics of the mesh based on existing overseas research cases. In addition, the temperature gradient effect of the mesh reflector is analyzed.