• Computers and Concrete
• /
• v.14 no.1
• /
• pp.19-40
• /
• 2014

Reinforced concrete deep beams are structural beams with low shear span-to-depth ratio, and hence in which the strain distribution is significantly nonlinear and the conventional beam theory is not applicable. A strut-and-tie model is considered one of the most rational and simplest methods available for shear strength prediction and design of deep beams. The strut-and-tie model approach describes the shear failure of a deep beam using diagonal strut and truss mechanism: The diagonal strut mechanism represents compression stress fields that develop in the concrete web between diagonal cracks of the concrete while the truss mechanism accounts for the contributions of the horizontal and vertical web reinforcements. Based on a database of 406 experimental observations, this paper proposes a new strut-and-tie-model for accurate prediction of shear strength of reinforced concrete deep beams, and further improves the model by correcting the bias and quantifying the scatter using a Bayesian parameter estimation method. Seven existing deterministic models from design codes and the literature are compared with the proposed method. Finally, a limit-state design formula and the corresponding reduction factor are developed for the proposed strut-andtie model.

• 한국전산유체공학회:학술대회논문집
• /
• 2008.03b
• /
• pp.105-106
• /
• 2008

As a carrier of malaria and sneak of blood, mosquitoes are an unpleasant insect. However, there are several unknown natural secretes related with mosquitoes. Among them, we focused on the blood sucking process of a female mosquito. The main objective of this study is to understand the mosquito's blood sucking mechanism that can be used to resolve the problem encountered in the injection or transport of infinitesimal biological fluids in a micro-chip. At first, the velocity fields of blood-sucking flow in a proboscis were measured using a micro-particle image velocimetry (PIV) technique. The velocity signals of flow in the proboscis show periodic variation. This seems to be resulted from the beating of the pharyngeal pump which works as driving power. To analyze the pumping mechanism, the temporal variation of the pharyngeal pump was visualized using the synchrotron X-ray micro-imaging technique. The volume variation was estimated by the help of digital image processing techniques. Once the main mechanism of blood sucking process was found, a effective micro-pumping system with high efficiency would be developed in near future.

• Journal of Nutrition and Health
• /
• v.30 no.8
• /
• pp.930-935
• /
• 1997

Fatty acid binging proteins(FABP) are distinct but related gene productes which are found in many mamalian cell types. FABP bind long chain fatty acids in vitro. However, their functions and mechanisms of action, in vivo, remain unknown . Also not known is whether all FABP function similaryly in their respective cell types. or whether different FABP have unique functions. The puropose of the present study was to assess whether different members of the FABP family exhibit different structural and function properties. A comparison was made between heart(H-FABP) and liver (L-FABP). The results show that the binding sites of both FABP are hydrophobic in nature, although the L-FABP site is more nonpolar than the H-FABP site. Additionally, the bound ligand experiences less motional constraint within the H-FABP binding site than within the L-FABP binding site. In accordance with these differences in structural properties, it was found that anthroyloxy-fatty acid transfer from H-FABP to membranes is markedly faster than from L-FABP. moreover, the mechanism of fatty acid transfer to phospholipid membranes appears to occur via transient collisional interactions between H-FABP and membranes. In contrast , transfer of fatty acid from L-FABP occurs via an aqueous diffusion mechanism.

• Journal of Communications and Networks
• /
• v.4 no.2
• /
• pp.108-117
• /
• 2002

TCP, which was developed on the basis of wired links, supposes that packet losses are caused by network congestion. In a wireless network, however, packet losses due to data corruption occur frequently. Since TCP does not distinguish loss types, it applies its congestion control mechanism to non-congestion losses as well as congestion losses. As a result, the throughput of TCP is degraded. To solve this problem of TCP over wireless links, previous researches, such as split-connection and end-to-end schemes, tried to distinguish the loss types and applied the congestion control to only congestion losses; yet they do nothing for non-congestion losses. We propose a novel transport protocol for wireless networks. The protocol called VS-TCP (Variable Segment size Transmission Control Protocol) has a reaction mechanism for a non-congestion loss. VS-TCP varies a segment size according to a non-congestion loss rate, and therefore enhances the performance. If packet losses due to data corruption occur frequently, VS-TCP decreases a segment size in order to reduce both the retransmission overhead and packet corruption probability. If packets are rarely lost, it increases the size so as to lower the header overhead. Via simulations, we compared VS-TCP and other schemes. Our results show that the segment-size variation mechanism of VS-TCP achieves a substantial performance enhancement.

• Journal of the Korean Society of Combustion
• /
• v.9 no.2
• /
• pp.10-17
• /
• 2004

A two-dimensional direct numerical simulation is performed to investigate the flame structure of $CH_4/N_2-Air$ counterflow nonpremixed flame interacting with a single vortex. The detailed transport properties and a modified 16-step augmented reduced mechanism based on Miller and Bowman#s detailed reaction mechanism are adopted in this calculation. To quantify the strain on flame induced by a vortex, a scalar dissipation rate (SDR) is introduced. The results show that fuel-side and air-side vortex cause an unsteady extinction. In this case, the flame interacting with a vortex is extinguished at much larger SDR than steady flame. It is also found that air-side vortex extinguishes a flame more rapidly than fuel-side vortex. The unsteady effect induced by flame-vortex interaction does not lead to a transient OH overshoot of the maximum steady concentration observed in experiment, while $HO_2$ radical increases more than the maximum steady concentration with increasing SDR. In addition, it is seen that NO and $NO_2$ are not sensitive to the unsteady variation of SDR.

• The Journal of Korean Academy of Prosthodontics
• /
• v.27 no.1
• /
• pp.123-141
• /
• 1989

The purpose of this study was to investigate the tendency of color change of ceramic, and its mechanism un der the influence of Pd-Ag alloy. The specimens were made by firing porcelain on tile metal plates cast with Au-Pt alloy, Pd-Cu alloy and Pd-Ag alloy. In the case of Pd-Ag alloy, specimens were fired under three different conditions as follows, 1) without protection, 2) protection with ceramic metal conditioner, 3) protection with carbon block. For the specimens of element analysis, a barrier was constructed with platinum foil between metal plate and ceramic. Color change was measured with colorimeter and elemental changes in ceramic were calculated with DC argon plasma emission spectrophotometer. The results were as follows : 1. Color change of ceramic by Pd-Ag alloy was negligible in hue, but decreased in value and increased in chroma (yellow discoloration). 2. Color change of ceramic by Pd-Ag alloy was appeared through vapor transport mechanism. 3. As the protection method for the color change of ceramic by Pd-Ag alloy, application of ceramic metal conditioner was superior to utilization of carbon block.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
• /
• v.1
• /
• pp.317-323
• /
• 2006

The objective of this study is to test and modify the gantry travel mechanism of an ALV(automated lifting vehicle) as a main technology of development of ALV. For the purpose of the improvement of container terminal productivity, this study performed to develop the ALV as a part of R&D. In order to verify the design data and detect the errors of detailed drawings, we performed the various limited weight test under load and unload conditions. Through the reflect of final drawing based on the this test, we could use to produce the more complete vehicle.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.6 no.1
• /
• pp.305-321
• /
• 2012

Since Internet Protocol (IP) is the most important protocol in Next Generation Networks (NGNs), 3rd Generation Partnership Project (3GPP) utilizes Session Initial Protocol (SIP) based on IP as the base protocol for negotiating sessions in IP Multimedia Subsystem (IMS). Different from traditional circuit-switched network, in IMS, the media traffic and signaling are delivered through IP transport. The media traffic may affect the signaling efficiency in core network, due to traffic collisions and best effort packets delivery. This paper proposes a novel path-migration mechanism for enhancing the traffic efficiency in integrated NGN-IMS. The simulation results show that the interference and traffic collision can be reduce by applying proposed path-migration mechanism and the signaling efficiency in core network can be improved with higher system capability and voice quality.

• Environmental Engineering Research
• /
• v.23 no.4
• /
• pp.442-448
• /
• 2018

This paper presents the numerical simulation of advection-diffusion mechanism of BOD concentration which was used as an indicator of waste only in one flow-direction of waste stabilization ponds (1-dimension (1-D)). This model was represented in partial differential equation order 2. The purpose of this paper was to determine the simulation of the model 1-D of wastewater transport phenomena based advection-diffusion mechanism and did validate the model. Numerical methods which was used for the solution of this model is finite difference method with Forward Time Central Space scheme. The simulation results which was obtained would be compared with field observation data as a validation model. Collection of field data was carried out in the Wastewater Treatment Plant Sewon, Bantul, D.I. Yogyakarta. The results of numerical simulations were indicate that the advection-diffusion mechanism takes place continuously over time. Then validation of the model was state that there was a difference between the calculation results with the field data, with a correlation value of 0.998.

• The Korean Journal of Pharmacology
• /
• v.7 no.1
• /
• pp.67-76
• /
• 1971

The excretion of uric acid in man has been of great interest because of its importance as an end product in purine metabolism as well as of its role in causing gout. There are many differences in the modes of renal handling of urate among various species of animals. Uric acid actively secreted by the renal tubules of most vertebrate including amphibians, reptiles, and birds. On the other hand, in most mammals net tubular reabsorption of urate appears to be occurred with some exception, such, as Dalmatian dog. In the rabbits, however, the mechanism of renal excretion of uric acid has long been a subject of controversial results. Within a given group it was possible to find individuals with either net secretion or net reabsorption of urate depend on the experimental conditions. Excretion of urate can be depressed or enhanced by a variety of drugs belonging mainly to the aromatic acid group. Diodrast, probenecid, cinchophen and salicylates have been reported as uricosuric agents, on the other hand, lactate, benzoate, pyrazinoic acid, acetazolamide and chlorothiazide are known to be contraindicated to use for the patient with gout since these agents depress the excretion of uric acid from the kidney. However, complex and sometimes the paradoxical effects on the urate excretion by those above mentioned drugs are not uncommon. The experiments were designed to investigate the mechanisms of renal handling of urate as well as the effects of variety of drugs on the tubular transport of uric acid in the rabbits. Male or female white rabbits, from 1.5 to 2.5 kg in weight, were used. The experimental methods used in these studies were clearance, stop-flow, and retrograde injection techniques. The effects of saline, salicylate, chlorothiazide and probenecid were investigated in each experimental conditions. Results of the experiments were summarized as follows; 1. In the rabbits, the rate of urate clearance was always lower than the rate of inulin clearance. The filtration fraction of the urate was one third on an average, therefore, it is estimated that approximately two thirds of filtered urate was reabsorbed. 2. In the kidneys of rabbits, the urate clearance was increased significantly by administration of chlorothiazide and decreased by probenecid. The administration of salicylate had no effect on the rate of urate clearance. The filtration fraction of urate was increased by chlorothiazide and decreased by probenecid. 3. In the stop-flow studies, the U/P ratio of urate was higher than the U/P ratio of inulin in the proximal region, indicating the secretion of uric acid in the proximal tubules. The proximal peak was increased by chlorothiazide and inhibited by probenecid.4. In the retrograde injection studies, the reabsorption of urate in the proximal region was observed, and these reabsorptive transport of urate was depressed by either probenecid or by chlorothiazide. 5. No distal tubular activity was observed under any of these experimental conditions concerning urate transport. The results of these experiments show that probenecid inhibits both secretory and reabsorptive transport of uric acid in the kidney of the rabbits. The enhancement of secretory transport of urate by chlorothiazide in the clearance study was due to the secondary action of chlorothiazide which inhibits the reabsorptive transport of urate in the proximal tubules. It is evident that the urate transport in the kidneys of rabbits is bidirectional nondiffusive flux both secretory and reabsorptive directions in the proximal tubules.