Customer attrition in retailing: An application of Multivariate Adaptive Regression Splines

The profit resulting from customer relationship is essential to ensure companies viability, so an improvement in customer retention is crucial for competitiveness. As such, companies have recognized the importance of customer centered strategies and consequently customer relationship management (CRM) is often at the core of their strategic plans. In this context, a priori knowledge about the risk of a given customer to mitigate or even end the relationship with the provider is valuable information that allows companies to take preventive measures to avoid defection. This paper proposes a model to predict partial defection, using two classification techniques: Logistic regression and Multivariate Adaptive Regression Splines (MARS). The main objective is to compare the performance of MARS with Logistic regression in modeling customer attrition. This paper considers the general form of Logistic regression and Logistic regression combined with a wrapper feature selection approach, such as stepwise approach. The empirical results showed that MARS performs better than Logistic regression when variable selection procedures are not used. However, MARS loses its superiority when Logistic regression is conducted with stepwise feature selection.     

Changes in the amount of kidney pigmented macrophage aggregates throughout the breeding cycle of female Ohrid trout, Salmo letnica Kar. (Teleostei, Salmonidae)

Changes in fish macrophages (Macs) are useful indicators of environmental pressures, but responses due to chemical and nonchemical stresses may be confounded by natural sources of variability. These may include sex and gonadal stage. In this study, we start addressing the following question: is the seasonally dependent ovary stage a factor to consider when using kidney Macs as biomarkers? To tackle this problem, the relative amount of pigmented Macs in kidney (head, trunk, and tail portions) was stereologically estimated in Ohrid trout, and related with the breeding status. The amount of Macs significantly increased from pre vitellogenesis to late vitellogenesis and showed a decreasing trend then after, with lower values noted after spawning in the head (1.9% versus 7.5% versus 2.0%), trunk (1.8% versus 7.5% versus 2.5%), and tail (2.5% versus 6.7% versus 2.9%) kidney. The decrease seen at spawning was significant in head and trunk kidney, and at post spawning it was significant for all kidney portions. The amounts of Macs were positively correlated with the ovary relative weights and plasma estradiol levels. We proved for the first time that fish kidney pigmented Macs can vary in amount during the breeding cycle. Our data, combined with literature, strongly support that the sex‐steroid profile and kidney status‐seasonal remodeling both influence the Macs pool; likely not only in female trout. So, while increases in Macs may warn of ecosystem problems, we show that using kidney Macs for biomonitoring should also take into account seasonally, particularly that related with ovary maturation. Microsc. Res. Tech. 2011. © 2011 Wiley Periodicals, Inc.     

Properties of Chemically Synthesized Nano-geopolymer Cement based Self-Compacting Geopolymer Concrete(SCGC)

The physical and mechanical properties of self-compacting geopolymer concrete(SCGC) using chemically synthesized nano-geopolymer cement was investigated. Nano-geopolymer cement was synthesized using nano-silica, alkali activator, and sodium aluminate in the laboratory. Subsequently, nine nanogeopolymer cement sbased SCGC mixes with varying nano-geopolymer cement content, alkali activator content, coarse aggregate(CA) content, and curing temperature were produced. The workability-related fresh properties were assessed through slump flow diameter and slump flow rate measurements. Mechanical performances were evaluated through compressive strength, splitting tensile strength, and modulus of elasticity measurements. In addition, rapid chloride penetration test, water absorption, and porosity tests were also performed. It was assessed that all mix design parameters influenced the fresh and hardened properties of SCGC mixes. Based on test results, it was deduced that nano-geopolymer cement SCGC performed fairly well. All the SCGC mixes achieved the 28-day compressive strength in the range of 60-80 MPa. Additionally, all mixes attained 60% of their 28-day strength during the first three days of elevated temperature curing. FTIR and SEM analyses were performed to evaluate the degree of polymerization and the microstructure respectively for SCGC mixes.     

Piezoelectric and electromechanical properties of relaxor ferroelectric Pb(Mg1/3Nb2/3)O3(65%)-PbTiO3(35%) thin films observed by scanning force microscopy

Relaxor ferroelectric PbMg(1/3)Nb(2/3)O(3)(65%)-PbTiO(3)(35%) (PMN-35PT) thin films were grown by a sol-gel method on Pt(111)/TiO(2)/SiO(2)/Si(100) substrates. Piezoresponse and poling behavior appear to have a relation with the relaxor behavior of the materials. Piezoelectric images were studied in a number of regions on the films with subsequent statistical analysis of the obtained data using the contact mode of scanning force microscopy. Hysteresis loops were observed with external field applied over a wide range of the vibration frequency. The piezoelectric coefficient, d(33), and the crystallographic electrostrictive constant, Q(33), were also determined as 100pm/V and 2.8x10(-3)C(-2)m(4), respectively.     

Structural properties of 0.65Pb(Mg1/3Nb2/3)O3-0.35PbTiO3 relaxor ferroelectric thin films on SrRuO3 conducting oxides

Coating of 0.65Pb(Mg(1/3)Nb(2/3))O(3)-0.35PbTiO(3) (PMN-PT) relaxor ferroelectrics by a sol-gel method is followed by growth of epitaxial SrRuO(3) (SRO) metallic oxide electrodes on SrTiO(3) (STO) single-crystal substrate by pulsed laser deposition. High-quality PMN-PT films on SRO with preferred growth orientation were successfully fabricated by controlling the operation parameters. Structural properties of relaxor ferroelectric PMN-PT thin films on SRO/STO substrates have been studied by X-ray diffraction (XRD), transmission electron microscopy (TEM) and atomic force microscopy (AFM). In-plane and out-of-plane alignments of the heterostructure are confirmed and the structural twinning of the materials are also revealed.     

A study on the forging of gear-like components

This paper describes kinematically admissible velocity fields for forging of gear-like components such as involute spur gear, trapezoidal spline, square spline, serration and trochoidal gear. Half pitch of each gear-like component was divided into several deformation zones with respect to their tooth profile. A neutral surface has been used to represent the inward flow of material during a forging operation by using a hollow billet with a flat punch. By using the suggested kinematically admissible velocity fields, the power requirements were successfully calculated and they were compared with experimental inspections. As a result, the suggested velocity fields are shown to be useful to predict the forging load. The contour of neutral surface varied with the number of teeth.     

Ultrastructure of submandibular salivary glands of mouse: TEM and HRSEM observations

The fine structure of submandibular glands of mouse were analyzed using light microscopy (LM), high resolution scanning electron microscopy (HRSEM), and transmission electron microscopy (TEM) methods. For LM, the specimens were embedded in Spurr resin, stained by toluidin blue solutions. For TEM, the tissues of submandibular salivary glands were fixed with modified Karnovsky solution and postfixed with osmium tetroxide. For HRSEM, the tissues were fixed with 2% osmium tetroxide solution in 1/15M sodium phosphate buffer (pH 7.4). The samples were immersed successively in dymethylsulphoxide and freeze cracked. The maceration was made in diluted osmium tetroxide for 24-48 h. The samples were examined by high resolution scanning electron microscopy. The intracellular components of acinar and ductal cells revealed clearly the Golgi apparatus, rough endoplasmic reticulum, secretory granules, and mitochondria. The end bulbs of Golgi lamellae and flattened cisterns of rough endoplasmic reticulum showed the luminal surface. A few mitochondria were identified intermingling between the rough endoplasmic reticulum and the mitochondriales cristae in three-dimensional HRSEM images. Secretory granules were numerous and presented different sizes. Small granules of ribosomes were attached on cistern surface, measuring 20-25 nm in diameter. Numerous arranged microvilli were found on the luminal surface of secretory canaliculus. The contact surfaces of acinar cells revealed complicated interdigitations by cytoplasmic processes. The mitochondria of duct cells were disposed vertically and surrounded by basal infoldings of plasma membranes. Basement membrane showed a spongy-like structure having an irregular surface with various strands and meshes of fine collagen fibrils.     

Response Time of a Pressure Measurement System with a Connecting Tube

Abstract

A connecting tube between the measured object and the pressure sensing element is a common component part of pressure measurement systems. Dynamic characteristics of the resulting fluid oscillator may significantly influence the magnitudes of dynamic measurement errors. This paper presents an experimental analysis of dynamic characteristics of connecting tubes of different lengths and diameters. Inlet step pressure changes were generated by a system of two loudspeakers, and pressure responses were measured by a piezoelectric measurement system. Using the measured responses, the characteristic natural frequencies and damping of the system under discussion were determined. The results were further employed to estimate the response settling time, which is required to sufficiently reduce dynamic measurement errors.