Halis Bilgil

• Professor
• Professor at Kayseri University

One of the methods used for forecasting of the time series is the fractional grey modeling approach. In this paper, the OCCFGM(1,1) model is utilized to forecasting of the total energy consumption data of China. The optimal values of $\alpha$ and $r$, which are fractional parameters in the model, are calculated using the Brute Force algorithm. Data...

Alcohol dependence and alcohol abuse are the public health problems. According to World Health Organization data, approximately two billion people in the world consume alcoholic beverages and approximately 77 million people have alcohol use disorder. Epidemiologic studies show that the rate of alcohol dependence varies by region. Fractional derivat...

In this study, we established a system of differential equations with piecewise constant arguments to explain the impact of epidemiological transmission between different locations. Our main goal is to look into the need for vaccines as well as the necessity of the lockdown period. We proved that keeping social distance was necessary during the pan...

The study analyzes coal consumption using the ECFGM(1, 1) model by utilizing time series data provided by the Statistical Review of World Energy for the years 2016-2019. The optimal α value, determined using the Brute Force Algorithm, is utilized to establish the model’s parameters and formulate the solution function. Subsequently, the model’s pred...

Today, the socio-cultural lack of some countries with increased urbanization has led to the unconscious breeding of stray dogs. The failure to care for the offspring of possessive dogs or ignoring the responsibility to find a suitable family for the offspring increased the dog population on the streets and in the shelters. In this study, our main t...

Along with the developing technology, obesity and diabetes are increasing rapidly among people. The identification of diabetes diseases, modeling, predicting their behavior, conducting simulations, studying control and treatment methods using mathematical methods has become of great importance. In this paper, we have obtained numerical solutions by...

There is a pandemic situation caused by the COVID-19 epidemic almost all over the world. Despite the measures taken to prevent this epidemic and the vaccine studies developed, the course of the epidemic changes period as the virus mutates and changes its structure. The common opinion of the experts is that the most important weapon in the fight aga...

In 2020 the world faced with a pandemic spread that affected almost everything of humans' social and health life. Regulations to decrease the epidemiological spread and studies to produce the vaccine of SARS-CoV-2 were on one side a hope to return back to the regular life, but on the other side there were also notable criticism about the vaccines i...

Throughout history, infectious diseases have been the cause of outbreaks and the deaths of people. It is crucial for endemic disease management to be able to forecast the number of infections at a given moment and the frequency of new infections so that the appropriate precautions can be taken. The COVID-19 pandemic has highlighted the value of mat...

Psychological diseases and their treatment are problems related to public health. According to data from the World Health Organization, about a billion people have either mental illness or substance use disorder problems in 2017. Mental, neurological diseases and substance use disorders account for 30 percent of the global non-fatal disease burden...

We propose a new mathematical model with piecewise constant arguments of a system of ODEs to investigate the growth of colorectal cancer and its response to chemo-immunotherapy. Our main target in this paper is to analyze and represent the I.S.'s (immune system) efficiency during the chemotherapeutic process. Therefore, we proved and illustrated th...

In this study, the Stokes flow problem in an S-shaped double lid-driven cavity filled with fluid was analyzed. Side edges of the cavity were considered as immovable walls. The flow region was divided into two sub-regions, and the streamfunction in each sub-region was considered as an extension of Papkovich–Faddle eigenfunctions. Parameters in the a...

Smoking is one of the most common habits in the world. Due to the harmful substances contained in it cigarette disturb people’s health and causes their death. Every year, many people lose their health from smoking or by direct exposure to cigarettes. In this study, we conducted a new application and stability analysis related to a fractional model...

Model (EXGM (1,1)). The percentage relative error (RPE) between the actual and the predicted values. Also, the mean absolute percentage error (MAPE) were determined using the actual and the predicted data from 2011-2020. Consequently, the MAPE values were calculated as 3,32 % and 3,09 % for GM (1,1) and EXGM (1,1) models, respectively. R 2 value wh...

Disiplinler arası bir bilim alanı olan Gri sistem Teorisi az sayıda veri kullanarak bilinmeyen sistemlerin davranışını tahmin etmektedir ve birçok alana başarı ile uygulanmıştır. Bu çalışmada ise Gri Sistem Teorisi Türkiye’nin Araştırma ve Geliştirme (Ar-Ge) harcamalarını tahmin etmek için kullanılmıştır. 2011-2020 yılları arasındaki Ar-Ge harcamal...

CO 2 emissions in the world have also become one of the most important research topics. In order for policymakers to achieve the goal of reducing carbon emissions and to create environmental policies, it is important to predict how CO 2 emissions will progress. The grey modelling in the prediction of time series has been one of the interesting stud...

The new exact solutions of the conformable time-fractional Bad and Good modified Boussinesq equations are obtained using the Exp-function method, which is different from previous literature works. These equations play a significant role in mathematical physics, engineering sciences and applied mathematics. Plentiful exact solutions with arbitrary p...

The new priority in the grey modelling is to build new models that have more accurate forecasting power than the previous ones. This paper aims to develop the prediction performance of the existing continuous grey models. Therefore, a novel continuous grey model (OCCFGM (1,1)) is proposed with conformable fractional derivative. The numerical result...

Grey theory is an approach that can be used to construct a model with limited samples to provide better forecasting advantage for short-term problems. In some cases, a grey forecasting model may yield unacceptable forecasting errors. In this work, a new exponential grey prediction model, which is called as EXGM (1,1), is proposed. By using this mod...

Gri teori, zayıf bilgi veya bilgilerin eksik olduğu sistemlerle ilgilenen etkili bir teoridir. Bu teoride az sayıda veriden faydalanarak gelecek zamanlar için etkin ve oldukça yaklaşık tahminler oluşturulabilmektedir. Gri modelleme yöntemi, gri sistemler teorisinin bir alt dalı olup, modelleme işlemi ilgili fark denklemleri ve diferansiyel denkleml...

Present endeavor is devoted to estimate the air-conditioning and heating energies or loads of modern buildings in Duhok City, Iraq using new mathematical models. Many parameters have been considered in current modeling, namely, area of building, number of storeys and types of the common materials of the building walls. Regression analysis is perfor...

This paper presents the two-dimensional (2D) steady incompressible flow in a lid-driven sectorial cavity. In order to analyze the flow structures, the 2D Navier–Stokes equations are solved by using the finite element method. Different cases of the cavity aspect ratio A and three cases of the speed ratios (Formula presented.) of the upper and the lo...

Konuralp Journal of Mathematics (KJM) is a fully-refereed electronic journal. (KJM) is devoted to the high quality publication of current research developments in the all fields of Mathematics and applications in all interdisciplinary areas. The journal is published twice a year.

In this article, the fractional derivatives in the sense of modified Riemann–Liouville and the exp-function method are used to construct exact solutions for some nonlinear partial fractional differential equations via the nonlinear fractional Liouville equation and nonlinear fractional Zoomeron equation. These nonlinear fractional equations can be...

This work analyzes the Stokes flow generated in a sectorial driven cavity formed by a pair of curved stationary side walls capped by straight translating lids. The flow is governed by two physical control parameters: the cavity aspect ratio, (where and are the radii of the inner and outer curved side walls, respectively) and the ratio () of the up...

In this study, the mechanism of segregation during the filling of fresh concrete into formwork is numerically investigated. A mathematical model, which considers fresh concrete as a non-Newtonian fluid, is developed. The aggregates are considered as Lagrangian particles whose trajectories determine segregation. Aggregate segregation is partially af...

We consider the Naguma equation, Newel-Whitehead (or KPP) equation and Huxley equation. Besides, a homogeneous balance method is improved and new exact solutions of Naguma, Newel-Whitehead, Huxley equations are found.

We consider nonlinear evolution equations such as Calogero equation and Hirota-Satsuma (HS) equation. Painlevé analysis of WTC method is performed for these equations and shown that these equations have Painlevé property. Hence Calogero and HS equations are to expected to be integrable. Besides, a homogeneous balance method is improved and new exac...