Minimizing Age of Information with Soft Updates

Melih Bastopcu,Sennur Ulukus 한국통신학회 2019 Journal of communications and networks Vol.21 No.3

We consider an information updating system where aninformation provider and an information receiver engage in an updateprocess over time. Different from the existing literature whereupdates are countable (hard) and take effect either immediatelyor after a delay, but instantaneously in both cases, here updatesstart taking effect right away but gradually over time. We cointhis setting soft updates. When the updating process starts, theage decreases until the soft update period ends. We constrain thenumber of times the information provider and the information receivermeet (number of update periods) and the total duration ofthe update periods. We consider two models for the decrease of ageduring an update period: In the first model, the rate of decrease ofage is proportional to the current age, and in the second model, therate of decrease of age is constant. The first model results in an exponentiallydecaying age, and the second model results in a linearlydecaying age. In both cases, we determine the optimum updatingschemes, by determining the optimum start times and optimum durationsof the updates, subject to the constraints on the number ofupdate periods and the total update duration.

Certain topological methods for computing digital topological complexity

Melih Is,Ismet Karaca 강원경기수학회 2023 한국수학논문집 Vol.31 No.1

In this paper, we examine the relations of two closely related concepts, the digital Lusternik-Schnirelmann category and the digital higher topological complexity, with each other in digital images. For some certain digital images, we introduce $\kappa-$topological groups in the digital topological manner for having stronger ideas about the digital higher topological complexity. Our aim is to improve the understanding of the digital higher topological complexity. We present examples and counterexamples for $\kappa-$topological groups.

Comparative Analysis of Vertebroplasty and Kyphoplasty for Osteoporotic Vertebral Compression Fractures

Melih Bozkurt,Gokmen Kahilogullari,Mevci Ozdemir,Onur Ozgural,Ayhan Attar,Sukru Caglar,Can Ates 대한척추외과학회 2014 Asian Spine Journal Vol.8 No.1

Study Design: A retrospective study. Purpose: The aim of this study is to compare the efficacy and outcome of vertebroplasty compared with unipedicular and bipedicular kyphoplasty for the treatment of osteoporotic vertebral compression fractures in terms of pain, functional capacity and height restoration rates. Overview of Literature: The vertebroplasty procedure was first performed in 1984 for the treatment of a hemangioma at the C2 vertebra. Kyphoplasty was first performed in 1998 and includes vertebral height restoration in addition to using inflation balloons and high-viscosity cement. Both are efficacious, safe and long-lasting procedures. However, controversy still exists about pain relief, improvement in functional capacity, quality of life and height restoration the superiority of these procedures and assessment of appropriate and specific indications of one over the other remains undefined. Methods: Between 2004 and 2011, 296 patients suffering from osteoporotic vertebral compression fracture underwent 433 vertebroplasty and kyphoplasty procedures. Visual analogue scale (VAS), the Oswestry Disability Index (ODI) and height restoration rates were used to evaluate the results. Results: Mean height restoration rate was 24.16%±1.27% in the vertebroplasty group, 24.25%±1.28% in the unipedicular kyphoplasty group and 37.05%±1.21% in the bipedicular kyphoplasty group. VAS and ODI scores improved all of the groups. Conclusions: Vertebroplasty and kyphoplasty are both effective in providing pain relief and improvement in functional capacity and quality of life after the procedure, but the bipedicular kyphoplasty procedure has a further advantage in terms of height restoration when compared to unipedicular kyphoplasty and vertebroplasty procedures.

Design and Analysis of A Modular Learning Based Cross-Coupled Control Algorithm for Multi-Axis Precision Positioning Systems

Melih Cakmakci,Nurcan Gecer Ulu,Erva Ulu 제어·로봇·시스템학회 2016 International Journal of Control, Automation, and Vol.14 No.1

Increasing demand for micro/nano-technology related equipment resulted in growing interest for precisionpositioning systems. In this paper a modular controller combining cross-coupled control and iterative learningcontrol approaches to improve contour and tracking accuracy at the same time is presented. Instead of using thestandard error estimation technique, a computationally efficient and modular contour error estimation techniqueis used. The new controller is more suitable for tracking arbitrary nonlinear contours and easier to implement tomulti-axis systems. Stability and convergence analysis for the proposed controller is presented with the necessaryconditions. Effectiveness of the control design is verified with simulations and experiments on a two-axis positioningsystem. The resulting positioning system achieves nanometer level contouring and tracking performance.

A novel harmony search based optimization of reinforced concrete biaxially loaded columns

Sinan Melih Nigdeli,Gebrail Bekdaş,김상훈,김종우 국제구조공학회 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.54 No.6

A novel optimization approach for reinforced concrete (RC) biaxially loaded columns is proposed. Since there are several design constraints and influences, a new computation methodology using iterative analyses for several stages is proposed. In the proposed methodology random iterations are combined with music inspired metaheuristic algorithm called harmony search by modifying the classical rules of the employed algorithm for the problem. Differently from previous approaches, a detailed and practical optimum reinforcement design is done in addition to optimization of dimensions. The main objective of the optimization is the total material cost and the optimization is important for RC members since steel and concrete are very different materials in cost and properties. The methodology was applied for 12 cases of flexural moment combinations. Also, the optimum results are found by using 3 different axial forces for all cases. According to the results, the proposed method is effective to find a detailed optimum result with different number of bars and various sizes which can be only found by 2000 trial of an engineer. Thus, the cost economy is provided by using optimum bars with different sizes.

Metaheuristic Optimization of Reinforced Concrete Footings

Sinan Melih Nigdeli,Gebrail Bekdaş,Xin-She Yang 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.11

The primary goal of an engineer is to find the best possible economical design and this goal can be achieved by considering multiple trials. A methodology with fast computing ability must be proposed for the optimum design. Optimum design of Reinforced Concrete (RC) structural members is the one of the complex engineering problems since two different materials which have extremely different prices and behaviors in tension are involved. Structural state limits are considered in the optimum design and differently from the superstructure members, RC footings contain geotechnical limit states. This study proposes a metaheuristic based methodology for the cost optimization of RC footings by employing several classical and newly developed algorithms which are powerful to deal with non-linear optimization problems. The methodology covers the optimization of dimensions of the footing, the orientation of the supported columns and applicable reinforcement design. The employed relatively new metaheuristic algorithms are Harmony Search (HS), Teaching-Learning Based Optimization algorithm (TLBO) and Flower Pollination Algorithm (FPA) are competitive for the optimum design of RC footings.

Optimum tuned mass damper design for preventing brittle fracture of RC buildings

Sinan Melih Nigdeli,Gebrail Bekdas 국제구조공학회 2013 Smart Structures and Systems, An International Jou Vol.12 No.2

Brittle fracture of structures excited by earthquakes can be prevented by adding a tuned mass damper (TMD). This TMD must be optimum and suitable to the physical conditions of the structure. Compressive strength of concrete is an important factor for brittle fracture. The application of a TMD to structures with low compressive strength of concrete may not be possible if the weight of the TMD is too much. A heavy TMD is dangerous for these structures because of insufficient axial force capacity of structure. For the preventing brittle fracture, the damping ratio of the TMD must be sufficient to reduce maximum shear forces below the values proposed in design regulations. Using the formulas for frequency and damping ratio related to a preselected mass, this objective can be only achieved by increasing the mass of the TMD. By using a metaheuristic method, the optimum parameters can be searched in a specific limit. In this study, Harmony Search (HS) is employed to find optimum TMD parameters for preventing brittle fracture by reducing shear force in additional to other time and frequency responses. The proposed method is feasible for the retrofit of weak structures with insufficient compressive strength of concrete.

Optimum Tuned Mass Damper Design in Frequency Domain for Structures

Sinan Melih Nigdeli,Gebrail Bekdas 대한토목학회 2017 KSCE JOURNAL OF CIVIL ENGINEERING Vol.21 No.3

The design of tuned mass dampers for reduction of seismic vibrations in multiple degree of freedom structures is also a complex problem and the optimization of design parameters of tuned mass damper are needed for the best reduction of structural responses. In the optimization process, frequency or time domain solutions can be iteratively used. In this paper, a frequency based optimization technique is presented to find design variables such as mass, period and damping ratio of tuned mass damper on the top of a structure. A music inspired metaheuristic algorithm called harmony search is employed to reach the optimum solution. The optimum results were obtained for two 10-story and one 40-story structures. According to comparisons with time domain based method, frequency domain based methods is effective to reduce maximum values and to obtain a steady stead response for critical excitations.

Optimum Design of RC Continuous Beams Considering Unfavourable Live-Load Distributions

Sinan Melih Nigdeli,Gebrail Bekdas 대한토목학회 2017 KSCE JOURNAL OF CIVIL ENGINEERING Vol.21 No.4

The cross-sections of Reinforced Concrete (RC) members are assumed in the preliminary design. With optimization, optimum dimensions of cross-sections providing required security measures can be obtained. Although, the area of the reinforcement bars is a computable value according to the cross-section, the amount and size of bars are also design variables in order to ensure the placement of bars providing adherence and other physical conditions. In this paper, the optimum design of RC continuous beams is presented by considering design constraints given in ACI-318 (Building Code Requirements for Structural Concrete). The most critical stress resultants of continuous beams are computed for all live load distribution patterns using three moment equations and were used in the analysis of continuous beam. A Random Search Technique (RST) is developed in order to minimize the material cost of the continuous beam. The RST is employed in different stages of optimization process such as cross-section and reinforcement bar optimization. The approach is effective to find the detailed optimum design of RC continuous beams with minimum cost.

Investigation of possible causes of sinkhole incident at the Zonguldak Coal Basin, Turkey

Genis, Melih,Akcin, Hakan,Aydan, Omer,Bacak, Gurkan Techno-Press 2018 Geomechanics & engineering Vol.16 No.2

The subsidence mechanism of ground surface is a complex phenomenon when multiple seam coal mining operations are carried out. Particularly, the coal mining beneath karstic formations causes a very special form of subsidence. The subsidence causes elasto-plastic deformation of the karstic layers and the collapse of cavities leads to dolinization and/or sinkhole formation. In this study, a sinkhole with a depth of 90 m and a width of 25 m formed in Gelik district within the coal-basin of Zonguldak (NW, Turkey) induced by multiple seam coal mining operations in the past has been presented as a case-history together with two-dimensional numerical simulations and InSAR monitoring. The computational results proved that the sinkhole was formed as a result of severe yielding in the close vicinity of the faults in contact with karstic formation due to multiple seam longwall mining at different levels.