• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.1B
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• pp.15-20
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• 2012

In this paper, an algorithm that enhances the conventional directional CSMA/CA protocol in IEEE 802.15.3c is proposed under saturation environments. For the algorithm, a Markov chain model is presented and analyzed in no-ACK mode. The effects of directional antennas and the features of IEEE 802.15.3c MAC are considered in the model. The optimal sizes of contention window are derived from the numerical results. The numerical results show that the proposed directional CSMA/CA algorithm outperforms conventional one. The overall analysis is verified by simulation. The obtained results provide the criterion for selecting the optimal parameters and developing a MAC protocol that enhances the performance of mmWave WPANs.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.9
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• pp.1843-1853
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• 1997

The channel throughput and packet delay of wireless media control (MAC) protocols with Rayleigh fading, log-normal shoadowing and near-far effects are analyzed. We consider CSMA/CA protocols as the wireless MAC protocols, since CSMA/CA protocols are based on the standard for wireless Local Area Networks (LANs) IEEE 802. 11. We have found that the performance of CSMA/CA in radion channel model is reduced above 50% than those of error free channel model in low traffic load. We also found that 4-Way Handshake CSMA/CA protocol is supterior to the other CSMA/CA protocols in high traffic load.

• Asian Pacific Journal of Cancer Prevention
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• v.13 no.8
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• pp.4199-4202
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• 2012

Objective: The aim of our study is to compare an ovarian malignancy prediction model based on age and four sonographic findings (OMPS1) with a new model called OMPS2 which differs just by adding serum CA125 measurement to (OMPS1). Methods: In a cross sectional comparative study OMPS1 was validated in 830 operated ovarian masses within a 3 years period (2006-2009). Logistic regression analysis was used to construct OMPS2 based on OMPS1 adding serum CA125 findings. The area under the curve for two models was compared in 411 patients. Results: OMPS2 was calculated as follows: OMPS1 + 1.444 (if serum CA125= 36-200) or 3.842 (if serum CA125 is more than 200). AUC of OMPS2 was increased to 84.3% (CI 95% 78.1- 89.8) in comparison to OMPS1 with AUC of 78.1% (CI 95% 71.8-84.5). Conclusion: Our second model is more accurate in prediction of ovarian malignancy, compared with our first model.

• Journal of the Korea Society of Computer and Information
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• v.17 no.12
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• pp.121-129
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• 2012

In this paper, we proposed WBAN system model to management an application that requires low rate data transfer in IEEE 802.15.4. We have to use different wireless sensor network technology to transfer different date rate and emergency message in medical application service. A suitable system model for WBAN and a WBAN MAC protocol in order to solve these existing system problems are proposed. Firstly, the priority queuing was applied to contention access period, and the system model which could guarantee transmission of a MAC command frame was proposed. Secondly, the MAC frame was newly defined to use the system model which was proposed above. Thirdly, WBAN CSMA/CA back-off algorithm based on data transmission rate was proposed to enhance data throughput and transmission probability of the data frame which does not have priority in the proposed WBAN system. The proposed algorithm is designed to be variable CSMA/CA algorithm parameter, depending on data rate. For the evaluation of WBAN CSMA/CA algorithm, we used Castalia. As a result of the simulation, it is found that the proposed system model can not only relieve loads of data processing, but also probability of collision was decreased.

• Journal of Institute of Control, Robotics and Systems
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• v.6 no.7
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• pp.537-543
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• 2000

mathematical models for a hydraulic brake actuator and a brake control law for vehicle collision warning/collision avoidance (CW/CA) systems will be presented in this paper. The control law have been designed for optimzied safety and comfort. A solenoid-valve-controlled hydraulic brake actuator system for the CW/CA systems has been investigated, A nonlinear computer model and a linear model of the hydraulic brake actuator system have been developed. Both models were found to represent the actual system with good accuracy. Uncertainties in the brake actuator model have been considered in the design of the control law for the roubustness of the controller. The effects of brake control on CW/CA vehicle response has been investigated via simulations. The simulations were performed using the hydraulic brake system model and a complete nonlinear vehicle model. The results indicate that the proposed brake control law can provide the CW/CA vehicles with an opimized compromise between safety and comfort.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2012.05a
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• pp.253-254
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• 2012

In this study, it carried out measurement experiment Ca(OH)₂ and chemically bound water to verify Ca(OH)₂ and chemically bound water prediction model out of hydration model of cement incorporating blast furnace slag. It compared and analyzed prediction results using prediction model with measurement results of Ca(OH)₂ quantity using thermogravimetric differential temperature analysis and chemically bound water quantity using electronic furnace. It agrees well experiments results with prediction results.

• Nutritional Sciences
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• v.7 no.3
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• pp.144-150
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• 2004

We have investigated the effect of calcium spirulan(Ca-SP) isolated from a blue-green alga Spirulina platensis, which is a sulfated polysaccharide chelating calcium and mainly composed of rhamnose and fructose, on invasion of both B16- BL6 melanoma cells, Colon 26 carcinoma and HT-1080 fibrosarcoma cells through reconstituted basement membrane (Matrigel). Ca-SP significantly inhibited the invasion of these tumor cells through Matrigel/fibronectin-coated filters in a concentration-dependent manner. Ca-SP also inhibited the haptotactic migration of tumor cells to laminin, but it had no inhibitory effect on tumor cell migration to fibronectin-coated filters. Ca-SP prevented the adhesion of B16-BL6 cells to Matrigel- and laminin-substrates but did not affect the adhesion to fibronectin. The pretreatment of tumor cells with Ca-SP inhibited the adhesion to laminin in a concentration-dependent fashion, while the pretreatment of laminin-substrates did not. Ca-SP had no effect on the production and activation of type IV collagenase in gelatin zymography. In contraset, Ca-SP significantly inhibited degradation of heparan sulfate by purified heparanase. The experimental lung metastasis was significantly reduced by co-injection of B16-BL6 cells with Ca-SP in a dose-dependent manner. Seven intermittent ⅰ.ⅴ. injection of 100$\mu\textrm{g}$ of Ca-SP caused a marked decrease of lung tumor colonization of B16-BL6 cells in a spontaneous lung metastasis model. These results suggest that Ca-SP, a novel sulfated polysaccharide, could reduce the lung colonization of B16-BL6 melanoma cells in experimental metastasis model, by inhibiting the tumor invasion of basement membrane Matrigel, probably through the prevention of the adhesion and migration of tumor cells to laminin-substrate and of the heparanase activity.

• Journal of Korean Society of Transportation
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• v.21 no.1
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• pp.91-102
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• 2003

There are two goals in this paper. The one is development of existing CA(Cellular Automata) model to explain more realistic deceleration process to stop. The other is the application of the updated CA model to forecasting simulation to predict short term link travel time that takes a key rule in finding the shortest path of route guidance system of ITS. Car following theory of CA models don't makes not response to leading vehicle's velocity but gap or distance between leading vehicles and following vehicles. So a following vehicle running at free flow speed must meet steeply sudden deceleration to avoid back collision within unrealistic braking distance. To tackle above unrealistic deceleration rule, “Slow-to-stop” rule is integrated into NaSch model. For application to interrupted traffic flow, this paper applies “Slow-to-stop” rule to both normal traffic light and random traffic light. And vehicle packet method is used to simulate a large-scale network on the desktop. Generally, time series data analysis methods such as neural network, ARIMA, and Kalman filtering are used for short term link travel time prediction that is crucial to find an optimal dynamic shortest path. But those methods have time-lag problems and are hard to capture traffic flow mechanism such as spill over and spill back etc. To address above problems. the CA model built in this study is used for forecasting simulation to predict short term link travel time in Kangnam district network And it's turned out that short term prediction simulation method generates novel results, taking a crack of time lag problems and considering interrupted traffic flow mechanism.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.15 no.4
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• pp.1293-1316
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• 2021

Using directional antennas in wireless Ad hoc networks has many superiorities, including reducing interference, extending transmission range, and increasing space division multiplexing. However, directional transmission introduces two problems: deafness and directional hidden terminals problems. We observe that these problems result in saturation throughput disparity among the competing flows in directional CSMA/CA based Ad hoc networks and bring challenges for modeling the saturation throughput of the flows. In this article, we concentrate on how to model and analyze the saturation throughput disparity of different flows in directional CSMA/CA based Ad hoc networks. We first divide the collisions occurring in the transmission process into directional instantaneous collisions and directional persistent collisions. Then we propose a four-dimensional Markov chain to analyze the transmission state for a specific node. Our model has three different kinds of processes, namely back-off process, transmission process and freezing process. Each process contains a certain amount of continuous time slots which is defined as the basic time unit of the directional CSMA/CA protocols and the time length of each slot is fixed. We characterize the collision probabilities of the node by the one-step transition probability matrix in our Markov chain model. Accordingly, we can finally deduce the saturation throughput for each directional data stream and evaluate saturation throughput disparity for a given network topology. Finally, we verify the accuracy of our model by comparing the deviation of analytical results and simulation results.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.19 no.1
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• pp.1-7
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• 2021

The pH dependence of sorption distribution coefficient (Kd) of Np(IV) on MX-80 in Ca-Na-Cl type solution with the ionic strength of 0.3 M, which was similar to one of the reference groundwaters in crystalline rock, was experimentally investigated under the reducing conditions. The overall trend of Kd on MX-80 was independent of pH at 5 ≤ pH ≤ 10 but increased as pH increased at pH ≤ 5. The 2-site protolysis non-electrostatic surface complexation and cation exchange model was applied to the experimentally measured pH dependence of Kd and the optimized surface complexation constants of Np(IV) sorption on MX-80 were estimated. The values of surface complexation constants in this work agreed relatively well with those in the Na-Ca-Cl solution previously evaluated, suggesting that compared to Na+, the competition of Ca2+ with Np(IV) for surface complexation on MX-80 was not much strong in Ca-Na-Cl solution. The sorption model well predicted the pH dependence of Kd values but slightly overestimated the sorption at the low pH region.