Seven common errors in finding exact solutions of nonlinear differential equations

We analyze the common errors of the recent papers in which the solitary wave solutions of nonlinear differential equations are presented. Seven common errors are formulated and classified. These errors are illustrated by using multiple examples of the common errors from the recent publications. We show that many popular methods in finding of the exact solutions are equivalent each other. We demonstrate that some authors look for the solitary wave solutions of nonlinear ordinary differential equations and do not take into account the well - known general solutions of these equations. We illustrate several cases when authors present some functions for describing solutions but do not use arbitrary constants. As this fact takes place the redundant solutions of differential equations are found. A few examples of incorrect solutions by some authors are presented. Several other errors in finding the exact solutions of nonlinear differential equations are also discussed.Comment: 42 page

The perception of COVID-19 and avoidance behavior in Turkey: the role of income level, gender and education

Purpose This study aims to reveal both the effect of the perception of COVID-19 on avoidance behaviors and the mediating role of the perception of personal control in this relationship. COVID-19 emerged in December 2019 and since then, it has spread globally in a short period and has affected people socially, economically and culturally. Design/methodology/approach The data for the research was collected from 418 participants during COVID-19, through online questionnaires. The obtained data were analyzed through AMOS and SPSS software using structural equation modeling. Findings The research results show that some perceptions of COVID-19 affect avoidance behavior and that personal control has a mediating role. It has also been found that gender plays a moderating role in the relationship between COVID-19 and avoidance behavior. It has been found that women are especially more sensitive compared to men in perceiving COVID-19. This study also found that perception of COVID-19 changes depending on income. Practical implications After the pandemic is over, people will get in contact with each other less than before, and trade will change accordingly. People will avoid shopping in crowded places, and consumer behaviors will undergo different changes. All of these results considered, it is expected that avoidance behavior will cause some permanent behavioral changes in consumers. Originality/value The study answers the critical question about the effect of the perception of COVID-19 on avoidance behavior. Furthermore, the role of income level, gender and education in this relationship will be highlighted

Experimental investigation of charge distribution and dynamic modeling of refrigeration

Bu çalışmada R600a ile yapılan deneylerle sistem çalışma şartlarını daha iyi anlaşılmasını sağlamak amacıyla sistem elemanlarındaki şarj dağılımı ve çeşitli parametrik değişimlerin bu dağılıma etkileri incelenmiştir. Bu amaçla iki farklı deney düzeneği kurulmuştur; ilk deney düzeneği yük hücreleri ile ısı değiştiricilerin sürekli tartılması prensibine dayanmaktadır. İkinci düzenek ise soğuma sistemi elemanlarında şarjın çevrimin belli bir anında vanalar yardımıyla birbirinden ayrılarak büyük bir tanka genişletilmesi ile aşırı kızmış şartlara geçmesi ve sıcaklık, basınç değerleri yardımıyla yoğunluğunun hesap edilmesi prensibine dayanmaktadır. Bu deney düzenekleri ile sürekli çalışma ve çevrimsel çalışma durumlarındaki şarj dağılımları yanı sıra toplam şarj miktarı, değişken kapasiteli kompresör kullanımı ve çevrim süresi değişimlerinin soğutma sistemi elemanlarında biriken şarj miktarı tespit edilmiştir. Farklı toplam şarj miktarı ile yapılan deneysel çalışmalar eleman bazında incelendiğinde en önemli değişimin buharlaştırıcı şarj miktarlarında olduğu görülmektedir. Bu sonuçlardan sistemin çalışması için yeterli belli bir şarj değerinin üstünden yapılan değişikliklerin direk olarak buharlaştırıcı doluluk oranı üstünde etkili olduğu diğer elemanların belirli bir denge içinde çalışmaya devam ettikleri görülmektedir. Isı değiştirici hesaplamalarından seçilen boşluk oranı korelasyonu kararlı halde soğutma sistemi performansını hesaplandığı bir soğutma sistemi modelinde sistem elemanlarındaki şarj miktarının hesaplanması için kullanılmıştır. Deney sisteminden telli borulu ısı değiştiricili bir derin dondurucu için ölçülen değerler kararlı hal modeli sonuçları ile karşılaştırılmıştır. Karşılaştırmada vana deney düzeneği için olan ölçümlerin model sonuçları ile uyumlu olduğu, yük hücresi deney düzeneği ile buharlaştırıcıda şarj miktarını daha yüksek ölçüldüğü görülmektedir. Anahtar Kelimeler: Buhar sıkıştırmalı soğutma çevrimi, R600a, buharlaştırıcı, yoğuşturucu.Vapor compression refrigeration cycle is widely used in industrial and residential refrigeration systems. The system performance is seriously affected by refrigerant selection and amount used as well as choice of cycle components like compressor, evaporator, and condenser. One major milestone for the refrigeration industry is discovery of CFC's at 1930's. CFC's make excellent choice for vapor compression refrigeration with their high molecular weight and non-flammability properties. At 1987 the use of CFC's are limited because of their effects on Ozone layer by Montreal Protocol. In 1990 R134a is launched as a HFC class refrigerant, but the HFC's still have a high global warming potential value beside their suitable ozone depletion potential values. The following years HC's and specially R600a are became popular for small refrigeration systems, because only negative property of R600a is flammability is not a big concern in small amounts. In this study, for better understanding of vapor compression refrigeration system working conditions, the charge distribution at the system components and effects of different parameters to this distribution is investigated with R600a refrigerant. The charge distribution measurement methods expect complicated and expensive ones depend on weighting methods. The separate and weight method usually needs more time and workforce. Two experimental setups are prepared for this purpose; first one is extended version of balance system in literature with replacing balance with load cells that have a higher precision. This system gives rapid results for the measurement but needs a data reduction process for frost formation and waves formed by hanging system. Second setup is based on principle of expanding the refrigerant, closed in components by quick closing valves at a specified moment of the cycle. The refrigerant amount can be easily calculated from pressure and temperature values for the expanded gas that have superheated condition. A computer program developed in the study controls the pressure stabilization, reaching steady conditions, closing of valves at the desired data point and expanding of component charges to the tank one by one. The measurement of one data point takes nearly 8-10 hours, and measurement of an on-off cycle with lots of data points take more than a week. But the data obtained are more precise than the other system and includes results about dryer and compressor gas volume. The refrigerant distribution is measured under steady state and cyclic working conditions, and effect of parameters like total charge value, use of variable capacity compressor and different cycle times with these setups. The experiments for different total charge values show that the maximum change is in evaporator. The value of 35 g for 75 grams total charge decreases to 24 g for 57 g total charge. The other measured charge from components like dryer, compressor volume, and calculated charge dissolved in compressor oil is not affected by total charge change. The results show that for total charge values over the necessary amount of refrigerant changes the charge load for evaporator and the other components are not affected much. The refrigerant regime in heat exchangers that holds the most of the refrigerant and shows the effect of dynamic working conditions is mostly two-phase conditions. The most important parameter for two-phase charge calculations is void fraction value and assumptions for void fraction correlation. The distributed charge amount is calculated for experimental working conditions and literature void fraction correlations. It is obvious that the selection of void fraction correlation have a major effect on charge amount calculation. The Premoli void fraction correlation based on mass flux value gives best validation with the experimental results. The void fraction correlation chosen from heat exchanger calculations is used for charge predictions in a steady state model that calculates the system performance values. The model can calculate the charge amount for different heat exchanger types. The calculated charge distribution for a freezer with wire and tube heat exchangers is compared with charge measurements from two setups. The model result gives good agreement with the valve experiment setup; the evaporator charge is seemed to over measured by load cell setup. Refrigerant system charge distribution for different conditions is calculated and modeling approach for charge assumptions at design period is developed in this study. The correct assumption about refrigerant charge will obtain a shorter design time and less prototyping work. Keywords: Vapor compression refrigeration cycle, R600a, evaporator, condenser

Extractive Dearomatization of Naphthalane Oil Fraction with Ionic Liquid and -N-Methyl-2-Pyrrolidone

In the article are given an analysis of the results of researches carried out for the purpose of selective treatment of the Naphthalane oil fraction boiling at 260-3400C with ionic liquid (IL) -morfolinphormiate synthesized on the basis formic acid + morpholine and - N-methyl-2-pyrrolidon (N-MP) and  as an extractant. The aim is to remove poisonous components -  sulfur compounds and toxic carcinogenic polynuclear aromatic hydrocarbons in order to improve therapeutic properties of Naphthalane oil cut. For this purpose we have used extraction method. On the basis of the conducted researches the role of -N-methyl-2-pyrrolidone and IL-morpholinephormiatee in extraction conditions have been determined in selective treatment of Nafthalan oil, according to the results of spectral analysis residual amount of aromatic hydrocarbons decreased from 18.5% wt accordance to 2%, 1.5%. As well as the amount of sulphur decreased from 0.0354% to 0.010%,  0.011% and 0.019%.In the next stage the treated raffinates with N-methyl-2-pyrrolidone has been purified on silica. In a result amount of aromatic hydrocarbons drastically decrease to be 0.07% and 0.02%. As a result we aquire transparency and at the same time the percentage amount of aromatic hydrocarbons drastically decreased from 2% to 0,07%, 1.5%, to 0.02%. Raffinates obtained in a 2-4 stage dearomatization with N-MP and IL. Raffinate are measured on NMR, UV and IR spectral analysis

Evaluating functional capacity, and mortality effects in the presence of atrial electromechanical conduction delay in patients with systolic heart failure

Objective: Atrial functions are relatively suppressed in heart failure (HF). We aimed to investigate the associations of intra- and inter-atrial electromechanical conduction delay (EMCD) with functional class and mortality over a 12-month follow-up period. Methods: The prospective study included 65 patients with systolic HF and 65 healthy subjects with normal sinus rhythm. Left ventricular (LV) systolic functions and left atrial (LA) dimensions and volumes were evaluated by transthoracic echocardiography. Tissue Doppler imaging (TDI) signals at the lateral border of the mitral annulus (lateral PA’), septal mitral annulus (septal PA’), and tricuspid annulus (tricuspid PA’) were measured. Intra- and inter-atrial EMCD were calculated. Results: Mitral inflow velocities were studied using pulsed-wave Doppler after placing the sample volume at the leaflets’ tips. The peak early (E wave) and late (A wave) velocities were measured. The septal annular E/E’ ratio was relatively higher and lateral, septal, and right ventricular S, E’, and A’ waves were significantly lower in the HF group than in the control group (12.49±6.03 - 7.16±1.75, pE/E’ <0.0001). Intra-atrial EMCD was detected as 117.5 ms and inter-atrial EMCD as 127.5 ms in patients with prolonged atrial EMCD. A significant increase was found in prolonged intra- and inter-atrial EMCD according to functional capacity increase (p=0.012 and p=0.031, respectively). The incidence of mortality was significantly higher in patients with prolonged atrial EMCD (p=0.025), and 5 patients in the HF group died during the study over the 12-month follow-up period. Conclusions: In this study, we found a relationship between prolonged atrial conduction time and increased functional class and mortality in patients with systolic HF. © 2016 by Turkish Society of Cardiology

The new soliton solution types to the Myrzakulov-Lakshmanan-XXXII-equation

Our attention concenters on deriving diverse forms of the soliton arising from the Myrzakulov-Lakshmanan XXXII (M-XXXII) that describes the generalized Heisenberg ferromagnetic equation. This model has been solved numerically only using the N-fold Darboux Transformation method, not solved analytically before. We will derive new types of the analytical soliton solutions that will be constructed for the first time in the framework of three impressive schemas that are prepared for this target. These three techniques are the Generalized Kudryashov scheme (GKS), the (G'/G)-expansion scheme and the extended direct algebraic scheme (EDAS). Moreover, we will establish the 2D, 3D graphical simulations that clear the new dynamic properties of our achieved solutions

Simultaneous Liver-Kidney Transplantation in Liver Transplant Candidates With Renal Dysfunction: Importance of Creatinine Levels, Dialysis, and Organ Quality in Survival

IntroductionThe survival benefit from simultaneous liver-kidney transplantation (SLK) over liver transplant alone (LTA) in recipients with moderate renal dysfunction is not well understood. Moreover, the impact of deceased donor organ quality in SLK survival has not been well described in the literature.MethodsThe Scientific Registry of Transplant Recipients was studied for adult recipients receiving LTA (N = 2700) or SLK (N = 1361) with moderate renal insufficiency between 2003 and 2013. The study cohort was stratified into 4 groups based on serum creatinine (<2 mg/dl versus ≥2 mg/dl) and dialysis status at listing and transplant. The patients with end-stage renal disease and requiring acute dialysis more than 3 months before transplantation were excluded. A propensity score matching was performed in each stratified group to factor out imbalances between the SLK and LTA regarding covariate distribution and to reduce measured confounding. Donor quality was assessed with liver donor risk index. The primary outcome of interest was posttransplant mortality.ResultsIn multivariable propensity score-matched Cox proportional hazard models, SLK led to decrease in posttransplant mortality compared with LTA across all 4 groups, but only reached statistical significance (hazard ratio 0.77; 95% confidence interval, 0.62–0.96) in the recipients not exposed to dialysis and serum creatinine ≥ 2 mg/dl at transplant (mortality incidence rate per patient-year 5.7% in SLK vs. 7.6% in LTA, P = 0.005). The decrease in mortality was observed among SLK recipients with better quality donors (liver donor risk index < 1.5).DiscussionExposure to pretransplantation dialysis and donor quality affected overall survival among SLK recipients

Additive manufacturing of Ti-alloy: Thermal analysis and assessment of properties

In this study, 3D printing of Ti6Al4V alloy is realized and the characteristics of the printed layer are examined. The morphological structures and metallurgical changes in the printed layer are assessed. Temperature and stress fields are simulated in line with the experimental conditions. Since the air gaps are present in between the loose alloy powders prior to the printing, the effective properties incorporating the air fraction are determined and the effective properties are used in the simulations. Thermal conductivity of the loose alloy powders with the presence of air gaps is determined by incorporating the virtual experimental technique. It is found that the printed layer is free from micro-cracks and large scale asperities; however, some small pores sites are observed because of the release of air around the loose powders during the printing. Microhardness of the printed surface is higher in the top surface of the printed layer than that of as-received solid alloy. In addition, the friction coefficient of the printed surface remains lower than that of the conventionally produced solid surface. The columnar structures are formed in the mid-section of the printed layer and slanted grains are developed in the region of the top and the bottom surface of the printed layer.The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: The authors acknowledge the financial support of King Fahd University of Petroleum and Minerals (KFUPM) in Saudi Arabia, Gazi University and TAI (SAYP Project DDKIG1) in Turkey and King Abdullah City for Atomic and Renewable Energy (K.A.CARE) to accomplish this work