ON SEMI-ARMENDARIZ MATRIX RINGS

KOZLOWSKI, KAMIL,MAZUREK, RYSZARD Korean Mathematical Society 2015 대한수학회지 Vol.52 No.4

Given a positive integer n, a ring R is said to be n-semi-Armendariz if whenever $f^n=0$ for a polynomial f in one indeterminate over R, then the product (possibly with repetitions) of any n coefficients of f is equal to zero. A ring R is said to be semi-Armendariz if R is n-semi-Armendariz for every positive integer n. Semi-Armendariz rings are a generalization of Armendariz rings. We characterize when certain important matrix rings are n-semi-Armendariz, generalizing some results of Jeon, Lee and Ryu from their paper (J. Korean Math. Soc. 47 (2010), 719-733), and we answer a problem left open in that paper.

ON SEMI-ARMENDARIZ MATRIX RINGS

Kamil Kozlowski,Ryszard Mazurek 대한수학회 2015 대한수학회지 Vol.52 No.4

Given a positive integer n, a ring R is said to be n-semi- Armendariz if whenever ∫n = 0 for a polynomial ∫ in one indeterminate over R, then the product (possibly with repetitions) of any n coefficients of ∫ is equal to zero. A ring R is said to be semi-Armendariz if R is n-semi-Armendariz for every positive integer n. Semi-Armendariz rings are a generalization of Armendariz rings. We characterize when certain important matrix rings are n-semi-Armendariz, generalizing some results of Jeon, Lee and Ryu from their paper (J. Korean Math. Soc. 47 (2010), 719–733), and we answer a problem left open in that paper.

Classical and Quantum Heat Transport

Miroslaw kozlowski,Janina Marciak Kozlowska 대한기계학회 1998 Heat transter conference Vol.5 No.1

Heat Capacity Study of Ti and Zn-doped Magnetite

A.Kozlowski 부경대학교 기초과학연구소 1998 부경대 기초과학연구논문집 Vol.1 No.-

Component method model for predicting the moment resistance, stiffness and rotation capacity of minor axis composite seat and web site plate joints

Aleksander Kozlowski 국제구조공학회 2016 Steel and Composite Structures, An International J Vol.20 No.3

Codes EN 1993 and EN 1994 require to take into account actual joint characteristics in the global analysis. In order to implement the semi-rigid connection effects in frame design, knowledge of joint rotation characteristics (<i>M</i>-<i>φ</i>relationship), or at least three basic joint properties, namely the moment resistance <i>M_R</i>, the rotational stiffness <i>S_j</i> and rotation capacity, is required. To avoid expensive experimental tests many methods for predicting joint parameters were developed. The paper presents a comprehensive analytical model that has been developed for predicting the moment resistance <i>M_R</i>, initial stiffness <i>S_j.ini</i> and rotation capacity of the minor axis, composite, semi-rigid joint. This model is based on so-called component method included in EN 1993 and EN 1994. Comparison with experimental test results shows that a quite good agreement was achieved. A computer program POWZ containing proposed procedure were created. Based on the numerical simulation made with the use of this program and applying regression analysis, simplified equations for main joint properties were also developed.

Heat Capacity Study of Ti and Zn - doped Magnetite

(A . Kozlowski),(Z . Kakol),(D . Kim),(R . Zalecki),(J . M . Honig) 부경대학교 기초과학연구소 1998 부경대 기초과학연구논문집 Vol.1 No.-

The Underutilization of Lifestyle Modifications in Primary Care Medicine

Jean-Marc Lucas(Jean-Marc Lucas ),Karl F. Kozlowski(Karl F. Kozlowski ) 사피엔시아 2019 Exercise Medicine Vol.3 No.-

Chronic disease accounts for the majority of deaths in the United States and is often attributed to obesity. A sedentary lifestyle and poor nutrition are primary contributing factors to the development of obesity and thus chronic disease. Primary care providers are optimally positioned to prescribe exercise and nutrition (lifestyle medicine) as a treatment for chronic disease. Unfortunately, this opportunity seems to be regularly lost. Primary care providers often rely too heavily on weight loss pharmaceuticals and bariatric surgeries to treat obesity. This treatment approach however also does little to prevent and treat the accumulation of chronic diseases. The purpose of this review was to evaluate the efficacy of conventional medical weight loss treatments and determine why primary care providers may not prescribe exercise and nutrition more frequently. Our findings suggest that some primary care providers may be uncomfortable prescribing lifestyle medicine as they receive little formal education in this field. In conclusion, prescription of exercise and nutrition by primary care providers may elicit greater long-term weight loss than current medical weight management practices. Medical management is most likely effective when combined with lifestyle medicine. We propose that primary care providers be better trained in lifestyle medicine through their formal and clinical education. Rates of chronic disease accumulation may potentially decrease if providers prescribe lifestyle medical treatments more frequently.

Multi-group SP₃ approximation for simulation of a three-dimensional PWR rod ejection accident

Lee, Deokjung,Kozlowski, Tomasz,Downar, Thomas J. Elsevier 2015 Annals of nuclear energy Vol.77 No.-

<P><B>Abstract</B></P> <P>Previous researchers have shown that the simplified P<SUB>3</SUB> (SP<SUB>3</SUB>) approximation is capable of providing sufficiently high accuracy for both static and transient simulations for reactor core analysis with considerably less computational expense than higher order transport methods such as the discrete ordinate or the full spherical harmonics methods. The objective of this paper is to provide a consistent comparison of two-group (2G) and multi-group (MG) diffusion and SP<SUB>3</SUB> transport for rod ejection accident (REA) in a practical light water reactor (LWR) problem. The analysis is performed on two numerical benchmarks, a 3×3 assembly mini-core and a full pressurized water reactor (PWR) core. The calculations were performed using pin homogenized and assembly homogenized cross sections for a series of benchmarks of increasing difficulty, in two-dimensional (2D) and three-dimensional (3D), 2G and MG, diffusion and transport, as well as with and without feedback. All results show consistency with the reference results obtained from higher-order methods. It is demonstrated that the analyzed problems show small group-homogenization effects, but relatively significant transport effects which are satisfactorily addressed by the SP<SUB>3</SUB> transport method. The sensitivity tests also show that, for the REA simulation, the MG is more conservative than 2G, P<SUB>1</SUB> is more conservative than SP<SUB>3</SUB> for a 1/3 MOX loaded full-core problem.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The multi-group SP<SUB>3</SUB> method developed and implemented in PARCS for the MOX analysis. </LI> <LI> The verifications were performed in 2D and 3D, 2G and MG, diffusion and transport, with and without feedback. </LI> <LI> All results show consistency with the reference results obtained from the ANL P<SUB>N</SUB> transport code VARIANT for steady-state and transport calculations. </LI> <LI> It was found that the SP<SUB>3</SUB> angular approximation captures sufficient transport effects for both steady-state and transient, and provides essentially the same results as the VARIANT P<SUB>5</SUB> method. </LI> <LI> From the transient results of the full-core problem, it was noted that MG is more conservative than 2G, and P<SUB>1</SUB> is more conservative than SP<SUB>3</SUB>. </LI> </UL> </P>

Analyzing nuclear reactor simulation data and uncertainty with the group method of data handling

Radaideh, Majdi I.,Kozlowski, Tomasz Korean Nuclear Society 2020 Nuclear Engineering and Technology Vol.52 No.2

Group method of data handling (GMDH) is considered one of the earliest deep learning methods. Deep learning gained additional interest in today's applications due to its capability to handle complex and high dimensional problems. In this study, multi-layer GMDH networks are used to perform uncertainty quantification (UQ) and sensitivity analysis (SA) of nuclear reactor simulations. GMDH is utilized as a surrogate/metamodel to replace high fidelity computer models with cheap-to-evaluate surrogate models, which facilitate UQ and SA tasks (e.g. variance decomposition, uncertainty propagation, etc.). GMDH performance is validated through two UQ applications in reactor simulations: (1) low dimensional input space (two-phase flow in a reactor channel), and (2) high dimensional space (8-group homogenized cross-sections). In both applications, GMDH networks show very good performance with small mean absolute and squared errors as well as high accuracy in capturing the target variance. GMDH is utilized afterward to perform UQ tasks such as variance decomposition through Sobol indices, and GMDH-based uncertainty propagation with large number of samples. GMDH performance is also compared to other surrogates including Gaussian processes and polynomial chaos expansions. The comparison shows that GMDH has competitive performance with the other methods for the low dimensional problem, and reliable performance for the high dimensional problem.

Loss of coolant accident analysis under restriction of reverse flow

Majdi I. Radaideh,Tomasz Kozlowski,Yousef M. Farawila 한국원자력학회 2019 Nuclear Engineering and Technology Vol.51 No.6

This paper analyzes a new method for reducing boiling water reactor fuel temperature during a Loss ofCoolant Accident (LOCA). The method uses a device called Reverse Flow Restriction Device (RFRD) at theinlet of fuel bundles in the core to prevent coolant loss from the bundle inlet due to the reverse flow aftera large break in the recirculation loop. The device allows for flow in the forward direction which occursduring normal operation, while after the break, the RFRD device changes its status to prevent reverseflow. In this paper, a detailed simulation of LOCA has been carried out using the U.S. NRC's TRACE code toinvestigate the effect of RFRD on the flow rate as well as peak clad temperature of BWR fuel bundlesduring three different LOCA scenarios: small break LOCA (25% LOCA), large break LOCA (100% LOCA), anddouble-ended guillotine break (200% LOCA). The results demonstrated that the device could substantiallyblock flow reversal in fuel bundles during LOCA, allowing for coolant to remain in the core during thecoolant blowdown phase. The device can retain additional cooling water after activating the emergencysystems, which maintains the peak clad temperature at lower levels. Moreover, the RFRD achieved thereflood phase (when the saturation temperature of the clad is restored) earlier than without the RFRD.