• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.32 no.10B
• /
• pp.630-637
• /
• 2007

In this paper, we propose an effective handoff mechanism using events at the layer 2 and a tunnel-based mechanism that is performed by sharing information of a mobile node and anticipated-based handoff. Also, we propose a novel anticipated-reservation mechanism using the events triggered at layer 2 to make easy a resource reservation procedure. Comparing with the existing mobile IPv6 handoff mechanism, our proposed handoff mechanism can reduce an amount of handoff latency and traffic volume between access routers where handoff is performed. In the anticipated-reservation mechanism, the amount of signaling traffics between an mobile node and the correspondent nodes can be reduced and then the allocation of resource can be accomplished. We present the performance of our proposed handoff mechanism in the wireless network environment by ns-2 simulation. Although the anticipated-reservation mechanism including a proxy agent is explained without performance evaluation, we can validate the operation of our proposed model only by the procedure of message flow.

• Journal of Advanced Navigation Technology
• /
• v.26 no.4
• /
• pp.226-234
• /
• 2022

With advances in autonomous vehicles and networked control, there is a growing interest in the consensus control of a multi-agents system to control multi-agents with distributed control beyond the control of a single agent. Since consensus control is a distributed control, it is bound to have delay in a practical system. In addition, it is often difficult to have a very accurate mathematical model for a system. Even though a reinforcement learning (RL) method was developed to deal with these issues, it often experiences slow convergence in the presence of large uncertainties. Thus, we propose a slide RL which combines the sliding mode control with RL to be robust to the uncertainties. The structure of a sliding mode control is introduced to the action in RL while an auxiliary sliding variable is included in the state information. Numerical simulation results show that the slide RL provides comparable performance to the model-based consensus control in the presence of unknown time-varying delay and disturbance while outperforming existing state-of-the-art RL-based consensus algorithms.

• Nuclear Engineering and Technology
• /
• v.53 no.6
• /
• pp.1970-1978
• /
• 2021

The aim of this study was to optimize the target, moderator, and collimator (TMC) in a neutron beam generator for the accelerator-based BNCT (A-BNCT) system. The optimization employed the Monte Carlo Neutron and Photon (MCNP) simulation. The optimal geometry for the target was decided as the one with the highest neutron flux among nominates, which were called as angled, rib, and tube in this study. The moderator was optimized in terms of consisting material to produce appropriate neutron energy distribution for the treatment. The optimization of the collimator, which wrapped around the target, was carried out by deciding the material to effectively prevent the leakage radiations. As results, characteristic of the neutron beam from the optimized TMC was compared to the recommendation by the International Atomic Energy Agent (IAEA). The tube type target showed the highest neutron flux among nominates. The optimal material for the moderator and collimator were combination of Fluental (Al₂0₃+AlF₃) with ⁶⁰Ni filter and lead, respectively. The optimized TMC satisfied the IAEA recommendations such as the minimum production rate of epithermal neutrons from thermal neutrons: that was 2.5 times higher. The results can be used as source terms for shielding designs of treatment rooms.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.24 no.3
• /
• pp.15-20
• /
• 2024

Path planning for unmanned aerial vehicles (UAV) is crucial in avoiding collisions with obstacles in complex environments that include both static and dynamic obstacles. Path planning algorithms like RRT and A^* are effectively handle static obstacle avoidance but have limitations with increasing computational complexity in high-dimensional environments. Reinforcement learning-based algorithms can accommodate complex environments, but like traditional path planning algorithms, they struggle with training complexity and convergence in higher-dimensional environment. In this paper, we proposed a reinforcement learning model utilizing a cell decomposition algorithm. The proposed model reduces the complexity of the environment by decomposing the learning environment in detail, and improves the obstacle avoidance performance by establishing the valid action of the agent. This solves the exploration problem of reinforcement learning and improves the convergence of learning. Simulation results show that the proposed model improves learning speed and efficient path planning compared to reinforcement learning models in general environments.

• Journal of KIISE:Computing Practices and Letters
• /
• v.9 no.3
• /
• pp.322-331
• /
• 2003

As the complexity of a 3D game is increased by various factors of the game scenario, it has a problem for controlling the interrelation of the game objects. Therefore, a game system has a necessity of the coordination of the responses of the game objects. Also, it is necessary to control the behaviors of animations of the game objects in terms of the game scenario. To produce realistic game simulations, a system has to include a structure for designing the interactions among the game objects. This paper presents a method that designs the dynamic control mechanism for the interaction of the game objects in the game scenario. For the method, we suggest a game agent system as a framework that is based on intelligent agents who can make decisions using specific rules. Game agent systems are used in order to manage environment data, to simulate the game objects, to control interactions among game objects, and to support visual authoring interface that ran define a various interrelations of the game objects. These techniques can process the autonomy level of the game objects and the associated collision avoidance method, etc. Also, it is possible to make the coherent decision-making ability of the game objects about a change of the scene. In this paper, the rule-based behavior control was designed to guide the simulation of the game objects. The rules are pre-defined by the user using visual interface for designing their interaction. The Agent State Decision Network, which is composed of the visual elements, is able to pass the information and infers the current state of the game objects. All of such methods can monitor and check a variation of motion state between game objects in real time. Finally, we present a validation of the control method together with a simple case-study example. In this paper, we design and implement the supervised classification systems for high resolution satellite images. The systems support various interfaces and statistical data of training samples so that we can select the most effective training data. In addition, the efficient extension of new classification algorithms and satellite image formats are applied easily through the modularized systems. The classifiers are considered the characteristics of spectral bands from the selected training data. They provide various supervised classification algorithms which include Parallelepiped, Minimum distance, Mahalanobis distance, Maximum likelihood and Fuzzy theory. We used IKONOS images for the input and verified the systems for the classification of high resolution satellite images.

• Asian Pacific Journal of Cancer Prevention
• /
• v.17 no.2
• /
• pp.799-805
• /
• 2016

Background: There is no standard treatment for patients with platinum-resistant or refractory epithelial ovarian cancer. Single agent chemotherapies have evidence of more efficacy and less toxicity than combination therapy. Most are very expensive, with appreciable toxicity and minimal survival. Since it is difficult to make comparison between outcomes, economic analysis of single-agent chemotherapy regimens and best supportive care may help to make decisions about an appropriate management for the affected patients. Objective: To evaluate the cost effectiveness of second-line chemotherapy compared with best supportive care for patients with platinum-resistant or refractory epithelial ovarian cancer. Materials and Methods: A Markov model was used to estimate the effectiveness and total costs associated with treatments. The hypothetical patient population comprised women aged 55 with platinum-resistant or refractory epithelial ovarian cancer. Four types of alternative treatment options were evaluated: 1) gemcitabine followed by BSC; 2) pegylated liposomal doxorubicin (PLD) followed by BSC; 3) gemcitabine followed by topotecan; and 4) PLD followed by topotecan. Baseline comparator of alternative treatments was BSC. Time horizon of the analysis was 2 years. Health care provider perspective and 3% discount rate were used to determine the costs of medical treatment in this study. Quality-adjusted life-years (QALY) were used to measure the treatment effectiveness. Treatment effectiveness data were derived from the literature. Costs were calculated from unit cost treatment of epithelial ovarian cancer patients at various stages of disease in King Chulalongkorn Memorial Hospital (KCMH) in the year 2011. Parameter uncertainty was tested in probabilistic sensitivity analysis by using Monte Carlo simulation. One-way sensitivity analysis was used to explore each variable's impact on the uncertainty of the results. Results: Approximated life expectancy of best supportive care was 0.182 years and its total cost was 26,862 Baht. All four alternative treatments increased life expectancy. Life expectancy of gemcitabine followed by BSC, PLD followed by BSC, gemcitabine followed by topotecan and PLD followed by topotecan was 0.510, 0.513, 0.566, and 0.570 years, respectively. The total cost of gemcitabine followed by BSC, PLD followed by BSC, gemcitabine followed by topotecan and PLD followed by topotecan was 113,000, 124,302, 139,788 and 151,135 Baht, respectively. PLD followed by topotecan had the highest expected quality-adjusted life-years but was the most expensive of all the above strategies. The incremental cost-effectiveness ratios (ICER) of gemcitabine followed by BSC, PLD followed by BSC, gemcitabine followed by topotecan and PLD followed by topotecan was 344,643, 385,322, 385,856, and 420,299 Baht, respectively. Conclusions: All of the second-line chemotherapy strategies showed certain benefits due to an increased life-year gained compared with best supportive care. Moreover, gemcitabine as second-line chemotherapy followed by best supportive care in progressive disease case was likely to be more effective strategy with less cost from health care provider perspective. Gemcitabine was the most cost-effective treatment among all four alternative treatments. ICER is only an economic factor. Treatment decisions should be based on the patient benefit.

• Journal of radiological science and technology
• /
• v.32 no.1
• /
• pp.61-67
• /
• 2009

Purpose : The purpose of this study was to investigate the applicability of poly-L-guluronic alginate (PGA) gel in vascular embolization with angiography simulation. Materials and Methods : To prepare a gel-forming PGA from no guluronate-rich Laminaria japonica, a new acid hydrolysis method was employed with a lower HCL concentration (0.03 M) and a shorter treatment time (5 min). The obtained PGAs were selected based on gel stability and viscosity. Glass aneurysm model was used to simulate gel embolization in vitro. Then, finally, the PGA was used to embolize the renal vascular system by using a rabbit model and angiography. Results : Glass aneurysm model was made to simulate gel embolization procedure. PGA solution was injected from pump through 2-way catheter. Subsequent injection of $CaCl_2$ successfully formed gels inside aneurysm model that conforming to its inner contour. In rabbit model, first, renal artery and aorta leading to the right kidney were ligated to block blood flow, then conventional contrast agent was injected through aorta to check the arterial patency to the left kidney. In sequential artery injection method, PGA and $CaCl_2$ were injected through renal artery sequentially via a single catheter. Re-injection of contrast agent after removing ligated aorta showed blood flow to the right kidney but no flow in the left kidney. This result demonstrated a complete blocking of blood flow due to gel formation in vascular bed of the left kidney. Conclusion : Instillation of calcium alginate into aneurysm model and arterial system in vivo produced an embolization that better fills and conforms to the contour of aneurysms or blocking vascular bed completely. Therefore, PGA was effective endovascular occlusion materials and provide an efficiency of vascular angiography.

• Asian Pacific Journal of Cancer Prevention
• /
• v.16 no.15
• /
• pp.6267-6272
• /
• 2015

Background: Extra nodal lymphoma (ENL) constitutes about 33 % of all non-Hodgkin's lymphoma. 18-28% develops in the head and neck region. A multimodality treatment with multi-agent chemotherapy (CT) and radiotherapy (RT) is considered optimum. Materials and Methods: We retrieved the treatment charts of patients of HNENL treated in our institute from 2001-2012. The charts were reviewed and the demographic, treatment details and outcome of HNENL patients were retrieved using predesigned pro-forma. Results: We retrieved data of 75consecutive patients HNENL. Median age was 47years (Range: 8-76 years). Of the 75 patients 51 were male and 24 were female. 55patients were evaluable. The patient and tumor characteristics are summarized in Table 1. All patients were staged comprehensively with contrast enhanced computed tomography of head, neck, thorax, abdomen, pelvis and bone marrow aspiration and biopsy 66 patients received a combination multi-agent CT with CHOP being the commonest regimen. 42 patients received 4 or lesser number of cycles of chemotherapy whereas 24received more than 4 cycles chemotherapy. Post radiotherapy, 41 out of 42 patients had a complete response at 3 months. Only 21patients had a complete response after chemotherapy. All patients received radiation (mostly involved field radiation) as a part of the treatment. The median radiation dose was 45 Gray (Range: 36 Gray-50 Gray). The radiation was planned by 2D fluoro simulation based technique in 37cases and by 3 Dimensional conformal radiation therapy (3DCRT) in 36 cases. Two patients were planned by the intensity modulated radiation therapy (IMRT) technique. IMRT was planned for one thyroid and one nasal cavity primary. 5 patients experienced relapse after a median follow up of 19 months. The median survival was not reached. The estimated two and three year survival were 92.9% (95%CI- 68.6- 95.35) and 88% (95%CI- 60.82 - 92.66) respectively. Univariate analysis revealed higher stage and poorer baseline performance status to be significantly associated with worse progression free survival. 5 patients progressed (relapse or primary disease progression) after treatment. Of the 5 patients, two patients were primary orbital NHL, two patients had NHL nasal cavity and one was NHL thyroid. Conclusions: Combined modality treatment in HNENL confers excellent disease control with acceptable side effects.

• Journal of the Korean Society of Radiology
• /
• v.11 no.2
• /
• pp.87-94
• /
• 2017

Monte Carlo simulations were used to assess dose enhancement effects for 60-, 90-, 120-, and 150-kV X-rays, and for 6- and 15-MV X-rays. The MCNPX code was used for a computer simulation of the ICRU slab phantom, and gold, gadolinium, and iron oxide (Fe2O3) were employed as dose enhancement agents. In consideration of the buildup region of the incident energy, agent concentrations of 5, 10, 15, and 20 mg/g were inserted on the surface of the phantom at a depth of 5 cm. Based on baseline values obtained in the absence of dose enhancement agents, a quantitative analysis was performed by evaluating depth-dependent changes in the absorbed energy and the dose enhancement factor (DEF). A higher concentration of dose enhancement agents led to a greater dose enhancement effect with iron oxide, gadolinium, and gold in descending order. For kilovoltage (kV) X-rays, as the incident energy was decreased and as the energy became closer to the ionization potential of the atoms in the enhancement agent, the dose enhancement effect increased. In the megavoltage (MV) X-ray range, dose enhancement was higher at 6 MV compared with 15 MV. However, the overall dose enhancements were significantly lower compared to the results obtained with kV X-rays.

• Environmental and Resource Economics Review
• /
• v.21 no.1
• /
• pp.27-67
• /
• 2012

This paper analyzed the effect of transaction costs on the prices and trading volumes at the initial stage of emission markets and also examined how the size of the effect differs depending on the characteristics of the transactions. We built trading protocols modeling a recursive process to search the trading partner and make transactions with several behavioral assumptions considering the situations of early markets. The simulations results show that adding transaction costs resulted in reduction of trading volumes. Furthermore, the speed of reduction in trading volume to the increase of transaction costs is higher when there is scale economy. With a certain level of scale economy, the trading volumes abruptly fall down to almost zero as the transaction cost gets over a certain level. This suggests the possibility of a failed market. Since the scale economy is thought to be significant in the early stage of emission trading market, it is desirable to design a trading system that maximizes trading volumes and minimizes unit transaction costs at the outset. One of the alternatives to meet these conditions is to establish a centralized exchange and take measures to increase trading volumes.