Centrifugal Machine Research Articles

Fast agitated directly suspended droplet microextraction technique for the rapid analysis of eighteen organophosphorus pesticides in human blood

A new sample preparation technique named as fast agitated directly suspended droplet microextraction (FA-DSDME) was proposed as an improved version of directly suspended droplet microextraction (DSDME) for the extraction and pre-concentration of wide-range organophosphorus pesticides (OPPs) from human blood prior to liquid chromatography tandem mass spectrometric (LC–MS/MS) analysis. In this method, instead of protecting the unwanted rupturing of extraction droplet (organic solvent), it was deliberately splintered into fine droplets by providing automated high-speed agitation to the biphasic extraction system (extraction solvent and sample solution). Fine organic droplets were then recollected into one, not by using a centrifuge machine but just by giving a very slow stirring to the bottom of the extraction system. The present method has surmounted the problem of prolonged extraction time associated with old DSDME. Under optimum extraction conditions, the method showed good sensitivity with low detection limits ranging from 0.0009 to 0.122μgL−1. Mean recoveries were achieved in the range of 86–109% at three levels of spiking concentration (low, middle and high) from linearity range of individual analyte. Intra-day and inter-day precisions were ≤4.68 and ≤9.57 (%RSD) respectively. Enrichment factor (EF) for each analyte varied from 30 to 132 which prove the ability of this technique to pre-concentrate the extracted analytes up to a good extent. The sample matrices have shown an insignificant influence on method's sensitivity. The proposed method may find immense use in epidemiological, toxicological, regulatory and forensic laboratories.

An experimental investigation of flow boiling heat transfer and pressure drop of R134a in a horizontal 2.168 mm tube under hypergravity. Part II: Heat transfer coefficient

Abstract An experimental study on flow boiling of R134a under hypergravity is conducted for assessing the effect of gravity on two-phase flow boiling heat transfer coefficient. The experiments were conducted with a horizontal smooth copper tube with an inner diameter of 2.168 mm under both hypergravity (1.12–3.16 g) and normal gravity (1 g), with mass flux of 725 and 910 kg/m2 s, heat flux of 19.0 and 28.5 kW/m2, saturation pressure of 0.71 and 0.82 MPa (saturation temperature of 27.2 and 32.2 °C), and vapor quality from 0 to 0.65. The hypergravity environment was generated with a centrifugal acceleration machine. The experimental data under hypergravity are compared with those under normal gravity and with the predictions of 11 outstanding existing correlations developed for normal gravity. The results indicate that the heat transfer coefficient under hypergravity is greater than that under normal gravity and increases with increasing hypergravity. The best existing correlation developed for normal gravity has the mean absolute deviation of 14.2% against the experimental data in the hypergravity range.

Sn 및 Cu를 첨가한 치과 주조용 Co-Cr-Mo계 합금제조 및 용해과정 분석

Purpose: Dental casting #Gr I (Co-25Cr-5Mo-3Sn-1Mn-1Si), #Gr II (Co-25Cr-5Mo-5Cu-1Mn -1Si) and #Gr III (Co-25Cr-5Mo-3Sn-5Cu-1Mn-1Si) master alloys of granule type were manufactured the same as manufacturing processes for dental casting Ni-Cr and Co-Cr-Mo based alloys of ingot type. These alloys were analyzed melting processes with heating time of high frequency induction centrifugal casting machine using infrared thermal image analyzer. Methods: These alloys were manufactured such as; alloy design, the first master alloy manufatured using vacuum arc casting machine, melting metal setting in crucible, melting in VIM, pouring in the mold of bar type, cutting the gate and runner bar and polishing. These alloys were put about 30g/charge in the ceramic crucible of high frequency induction centrifugal casting machine and heat, Infrared thermal image analyzer indicated alloys in the crucible were set and operated. Results: The melting temperatures of these alloys measuring infrared thermal image analyzer were decreased in comparison with remanium GM 800+, vera PDI, Biosil f, WISIL M type V, Ticonium 2000 alloys of ingot type and vera PDS(Aabadent, USA), Regalloy alloys of shot type. Conclusion: Co-Cr-Mo based alloy in addition to Sn(#Gr I alloy) were decreased the melting temperature with heating time of high frequency induction centrifugal casting machine using infrared thermal image analyzer.

치과용 고주파 주조기를 이용한 Co-Cr-Mo계 합금 용해과정의 적외선 열화상 분석

Purpose: Dental casting Co-Cr-Mo based alloys of five kinds of ingot type and two kinds of shot type were analyzed the melting processes with heating time of high frequency induction centrifugal casting machine using infrared thermal image analyzer. Methods: When Co-Cr-Mo based alloys were put about 30g/charge in the ceramic crucible of high frequency induction centrifugal casting machine and heat, Infrared thermal image analyzer and IR thermometer indicated these alloys in the crucible were set and operated. Results: The melting temperatures of alloys measuring infrared thermal image analyzer were deviated compared to those of manufacturing company. On the other hand, the melting time of alloys were differently appeared with the shape of alloys(ingot and shot type). Conclusion: The melting temperatures of dental Co-Cr-Mo based alloys were measured the degree of and the heating time with the alloys of ingot and shot type were deviated .

Antimicrobial Effect of Clove Oil (Laung) Extract on Enterococcus faecalis

Introduction: Dental diseases are recognized as major public health problems throughout the world. Clove, a perennial aromatic herb belonging to the family Myrtaceae, is an important culinary plant with immense medicinal use. Aim: The aim was to evaluate the efficacy of alcoholic extracts of clove (Laung) on Enterococcus faecalis. Materials and Methods: Materials used includes clove (Laung), micro-organisms (E. faecalis Microbial type culture collection), agar plates, bloodagar plates, petri-dish, scale, punch, distilled water, weighing machine, centrifugal machine, sterile bottles. Ditch plate method is employed in this case after the clove oil extract and the microorganisms are obtained. Results: At 5% concentration, clove extract had no antimicrobial activity while 10% and 50% concentrations showed antimicrobial activity against E. faecalis Antimicrobial activity was observed with 5%, 10% and 50% clove extracts. Antimicrobial activity increased as the concentration increased from 5 to 50%. Conclusion: From the results obtained from the study it can be concluded that clove had antimicrobial activities against E. faecalis.

Analysis of a Nonlinear Elastic Force in a Relatively Long Annular Seal and its Impact on the Dynamics of the Rotor

The authors have developed a method of calculating the non-linear elastic force that arises in the clearance seal of a finite length. The authors have analysed the force impact on the dynamics of the rotor of a centrifugal machine.

Complex boride metal-matrix composites by SHS under high gravity

Mo2NiB2 and Mo2FeB2 metal-matrix composites (MMCs) were prepared by metallothermic SHS in a centrifugal machine. Our SEM and XRD data suggest that thus synthesized cast materials represent a ductile Ni or Co matrix doped with uniformly distributed inclusions of Mo2NiB2 or W2CoB2 particles. The metal matrix was found to contain grid-type structural elements formed by nickel aluminides. Addition of alloying agents into a green mixture was found to markedly change the microstructure and morphology of resultant MMCs. The Vickers hardness of synthesized MMCs was found to vary between 950 and 1200 HV.

Manufacturing Process for Bush Type Bearing Metal Using Centrifugal Casting

This paper regard the development for bush type bear metal using centrifugal casting by changing the rpm, amount of melting metal bush type bearing metal process was fixed also bush type bearing casting is possible by using centrifugal casting machine, bonding test results meet the specification and results of non-destructive testing meet the inspection.

Evaluation of crucible and investment materials for lost wax investment casting of Ti and NiTi alloys

The aim of this study is to assess the suitability of selected commercial ceramic crucibles for the investment casting of Ti6Al4V and NiTi alloys for jewellery purposes. A commercial vacuum tilt casting machine and a centrifugal casting machine were employed to cast the alloys in cold copper moulds or in refractory investment shells. The form filling of the shell and the crucible and investment reactions were assessed by microstructural investigation, chemical analysis and hardness profiles of the as cast items as a function of shell temperature. The reaction of the alloys strongly depended on the alloy, the crucible material, the coating of the crucibles and the temperature of the ceramic shell. Optimum results were achieved with yttria and yttria coated Al titanate crucibles for Ti6Al4V and NiTi alloys respectively. Improvement of the materials and process costs is necessary to allow the competitive casting of jewellery made from titanium alloys.

An experimental investigation of flow boiling heat transfer and pressure drop of R134a in a horizontal 2.168 mm tube under hypergravity. Part I: Frictional pressure drop

An experimental investigation on flow boiling of R134a under hypergravity is conducted to observe the effect of gravity on the two-phase frictional pressure drop. A series of experiments were conducted with a horizontal 2.168mm inner diameter tube under both hypergravity (1.12–3.16g) and normal gravity (1g) with mass flux of 725 and 910kg/m2s, heat flux of 19.0 and 28.5kW/m2, saturation pressure of 0.71 and 0.82MPa (saturation temperature of 27.2 and 32.2°C), and vapor quality from 0 to 0.65. The hypergravity environment was generated with a centrifugal acceleration machine. A comparison between the experimental frictional pressure drop under hypergravity and normal gravity is made and the results indicate that the frictional pressure drop under hypergravity is greater than that under normal gravity at high vapor quality while less than that at low vapor quality, but the difference is not significant for hypergravity within 3.16g. The experimental frictional pressure drop under different gravity levels is also compared with three best existing correlations proposed for normal gravity, and the results evince that the best correlation has a mean absolute deviation of 14.5% for normal gravity and 15.4% for hypergravity.

Multi-Objective Optimization of PID Controller for Temperature Control in Centrifugal Machines Using Genetic Algorithm

The main aim of the study focuses on the optimizing the response of the PID controllers used typically for temperature control loop in centrifugal machines in sugar industry using soft-computing. The centrifugal machines are used for the filtering sugar and molasses and the whole process is carried out at a certain fixed temperature. Any alterations from the set-point will cause instability in the system resulting in unsafe process conditions, poor product quality, unnecessary plant shutdowns, higher maintenance and operating costs, etc. This study employs the optimization of PID controllers using multi-objective genetic algorithm for better plant operations. For the initial tuning of the PID controllers, classical methods like Ziegler-Nichols, Chien-Hrones-Reswick (CHR) and robust time response have been used, but all have shown the transient response; so MATLAB’s PID Tuner has been used for the initial estimation of the parameters followed by optimization using genetic algorithm and multi-objective genetic algorithm. On comparing the results, better results have been obtained in case of multi-objective genetic algorithm optimization offering better plant operation and process safety which classical methods have failed to provide.

Analysis and measurement of the impact of diffuser width on rotating stall in centrifugal compressors

In compression systems, instability has long been an important issue. However, compared to axial machines, relatively little work has been done on the stability of centrifugal machines. Especially, many analytical models of stabilities have been developed to predict and control rotating stall, using compressor characteristic. However, stability models for centrifugal compressors are not scarce. Much research on compressor stability has focused on stalling flow coefficient and rotating stall phenomenon at the stalling flow coefficient. Given this situation, this paper presents a stability analysis of centrifugal compressors to predict rotating stall inception as well as the speed and number of cells. This analysis involves the use of compressor geometries, a steady compressor characteristic, and threedimensional flow analysis in the diffuser. The flow field perturbations at the axial inlet duct, impeller, and radial exit duct are determined via an eigenvalue analysis. The predictions are validated against experimental results from compressors with three different diffuser widths. The model accurately predicts the rotating stall inception flow coefficient. As the compressor characteristic becomes less steep with increasing diffuser width, the stalling flow coefficient increases. Also, experiment validates the model prediction that, depending on the dominant mode of flow perturbation, the number of rotating stall cells can be changed from three to two cells in the tested configurations. Furthermore, the cell speed increases as the flow coefficient decreases for a given number of stall cells. However, when the stall cell number is reduced, the cell speed decreases.

Four compartment method: a simplified and cost-effective method of noncultured epidermal cell suspension for the treatment of vitiligo

Despite continued progress towards an elucidation of pathogenetic pathways in vitiligo, a definitive cure remains elusive. Noncultured epidermal cell suspension (NCECS) is emerging as the treatment of choice for surgical management of both stable and segmental vitiligo. NCECS is very effective in repigmenting stable vitiligo, but the technique requires an expert and the support of a laboratory facility. To investigate a simplified and more cost-effective method for NCECS. We simplified the conventional NCECS method and made it more cost-effective and simple enough to be performed in the clinic without laboratory equipment. We named this the four compartment (FC) method. Six patients with vitiligo were treated with this FC method. The FC method for NCECS is highly cost-effective and simple. Six patients with vitiligo were treated and the results showed marked to complete repigmentation in four patients and > 50% repigmentation in two patients in 3 months. The FC method is a cost-effective and simple procedure to prepare epidermal cell suspensions. In this modified method we showed that there is no need for pipette, tips, centrifuge tube and most importantly a centrifuge machine or any other expensive laboratory equipment.

Some Aerodynamic Considerations in the Design of Centrifugal Compressor Impellers

A simple one dimensional approach to determine the size of the centrifugal impeller for maximum through flow has been indicated. This design procedure does not mean that the centrifugal impeller could be finally decided on the results obtained from this article. It must be borne in mind that this only deals with some aspects of the design and in itself is not a complete one by which the impeller could have its final shape and size. The major idea of introducing this paper is to highlight the importance of some of the parameters that go towards influencing the design of the centrifugal impeller. The stage pressure, temperature and work output of a centrifugal machine is basically dependant on the major dimensions like the diameter of the impeller ‘d2’ and its tip speed ′u2 ‘, the vane outlet angle ‘β2’ and the flow coefficient ‘∅2’ at exit ‘c2m/ u2’. Further, the influence of the inlet vane angle ‘β1’ and the inlet Mach number ‘M1’of the flow seriously affect the design of the high speed centrifugal impeller. Some guidelines have been indicated. The shape of the impeller channel passages are to be designed based on whether the compressor needs to have an energy build up in the impeller or a high pressure generation within the impeller of the compressor. In such cases, the radial diffuser at the exit of the impeller plays a very crucial role. Since the speed at which the impeller rotates is of interest, it is absolutely necessary for the designer to pay attention to the stress calculations of the impeller rear and front shrouds. Nomenclature: α fluid angle β vane, angle δ semi cone angle, boundary layer thickness ∅ flow coefficient cm /u2 ρ fluid density σ Slip fctor א , k ratio of specific heats cp /cv ω angular velocityType equation here. a, A constants, annulus area, area, velocity of sound b, bl, B vane height, blade c absolute velocity cp Specific heat at constant pressure cv Specific heat at constant volumeא h vane height k ratio of specific heats cp /cv m, M mas flow, Mach no. n distance normal to streamline p static pressure r, R radius t1, t ,T time, temperature V volume flow rate w,W relative velocity, Specific work X coordinate direction, linear length y, Y coordinate direction z coordinate direction, number of vanes Subscripts _ average ‘ first differentiation with reference to x Some Aerodynamic Considerations in the Design of Centrifugal Compressor Impellers www.iosrjournals.org 2 | Page “ second differentiation with reference to x bl blade h hub m meridional component 0 total r relative component t tip u tangential component 1 inlet of impeller 2 exit of impeller

In situ TiC–Fe–Al2O3–TiAl/Ti3Al composite coating processing using centrifugal assisted combustion synthesis

The composite coating of a titanium carbide aluminide–alumina-iron composite was synthesized by centrifugal-assisted self-propagating high-temperature synthesis (SHS). The in situ TiC–Al2O3–Fe with intermetallic phases of titanium aluminide (TiAl/Ti3Al) possesses excellent metallurgical properties. This composite was produced from compacted titanium (Ti) and carbon (C) powders in the form of pellets embedded in a tube, which were exposed to very high temperature generated by the thermite Fe2O3 and Al reaction. The process took place in a graphite–steel tube mounted in a centrifugal accelerator machine purposely developed for this function. Functionally graded coating was produced under the centrifugal acceleration field and the product of the thermite reaction (Al2O3 and Fe) infiltrated the TiC pellet and to create a strong, titanium aluminide intermetallic layer. The centrifugal force significantly enhanced both metallurgical alloying and mechanical interlocking between different sample layers during product formation. The purpose of the research addresses the applications of local reinforcement of the ceramic-lined tubes.

Evaluating environmental performance of concentrated latex production in Thailand

Thailand is currently the world's largest natural rubber producer. To maintain a leadership position of natural rubber producer, it has been challenging for Thai rubber entrepreneurs to seek appropriate measures towards producing environmentally friendly rubber products. The objective of this study is to assess the potential environmental impact of concentrated latex production by partial Life Cycle Assessment (LCA), and to investigate the effects of the options to reduce the impact. The methodology is based on the ISO 14040 series, taking a “Gate-to-Gate” approach (Partial LCA). The activities taken into account include production of chemicals, production of diesel and electricity, diesel combustion, and wastewater treatment. The functional unit is 1 ton of concentrated latex, and the environmental impacts considered in this study include global warming, acidification, eutrophication, human toxicity, photochemical oxidation, and the total environmental impact. The results indicate that electricity use for centrifugation has the largest share, compared with other activities, in global warming (50%), acidification (58%), and photochemical oxidation (55%). Ammonia use for latex preservation accounts for 37% of human toxicity, whereas use of DAP (Diammonium phosphate) accounts for 46% of eutrophication. Based on these results, the following reduction options are therefore identified: 1) electricity efficiency improvement (by installation of inverters to centrifugal machines); 2) improvement of ammonia preparation and storage (by chilling systems); 3) minimizing the use of DAP (by extending coagulation time); and 4) substitution of diesel by LPG. These four options were technically and practically feasible for concentrated latex production, and result in reductions of the total environmental impact by 12%, 8%, 3%, and 5%, respectively.

Characterization of Ni–Cr alloys using different casting techniques and molds

This study differentiated the mechanical properties of nickel–chromium (Ni–Cr) alloys under various casting techniques (different casting molds and casting atmospheres). These techniques were sampled by a sand mold using a centrifugal machine in ambient air (group I) and electromagnetic induction in an automatic argon castimatic casting machine (group II). The specimen casting used a graphite mold by a castimatic casting machine (group III). The characteristics of the Ni–Cr alloys, yield and ultimate tensile strength, bending modulus, microhardness, diffraction phase, grindability, ability to spring back, as well as ground microstructure and pattern under different casting conditions were evaluated. The group III specimens exhibited the highest values in terms of strength, modulus, hardness, and grindability at a grind rate of 500rpm. Moreover, group III alloys exhibited smaller grain sizes, higher ability to spring back, and greater ductility than those casted by sand investment (groups I and II). The main factor, “casting mold,” significantly influenced all mechanical properties. The graphite mold casting of the Ni–Cr dental alloys in a controlled atmosphere argon casting system provided an excellent combination of high mechanical properties and good ability to spring back, and preserved the ductile properties for application in Ni–Cr porcelain-fused system. The results can offer recommendations to assist a prosthetic technician in selecting the appropriate casting techniques to obtain the desired alloy properties.

IMPROVEMENT OF HANDLING MACHINES FOR COMMERCIAL OPERATIONS OF FRESH-CUT PINEAPPLE

Fresh-cut fruits is a growing sector of the food industry in many parts of the world. Its success depends greatly on several factors, especially the quality and consumers’ confidence. Products are prepared in ready-to-eat form whilst retaining the organoleptic characteristics of fresh fruits in terms of aroma, flavour, taste, colour and texture. Appropriate method of preparation is obligatory in order to maintain their freshness. The preparation involves cleaning, washing, trimming, coring, slicing and other related steps of which many of these processes hasten the products to perish. Uniformity, time and labour consumption have always been raised by the cut fruit operators especially for the bulk handling. Imported machines for the processing of cut fruits are available in the markets. However, high cost and suitability of the machine to the local fruits hinder the active use of the machine especially by small scale fruit operators. Intensive research had been conducted in developing a suitable mechanized system for commercial handling of fresh cut pineapple comprising of stalk and crown cutter, skin peeler, flesh slicer and centrifugal drip dryer. The newly developed machines were successfully tested during the recent commercial handling trial of fresh-cut pineapple to Perth, Australia. Uniform cutting of the stalk and crown had contributed to the stability of the fruits upon being subjected to skin peeler machine. The skin peeler machine was integrated with blade cutter which cut the flesh into two portions. Uniform semicircle cutting shape and size will be produced upon subjecting the individual portion to the flesh slicer machine. A centrifugal drip dryer machine facilitates in removing the excess water after the cut pieces were subjected to pre-treatment solutions before undertaking the packing process.

Effects of composition and heat treatment on the mechanical behavior of Ti–Cu alloys

Ti alloys are applied extensively in several fields, particularly in the aerospace, chemical, dental and medical industries, due to their outstanding properties. The mechanical behavior of Ti alloys depends on microstructural characteristics that are dictated by the amount and type of alloying elements and the processing routes employed. The aim of this work is to evaluate the effect of the cooling rate, composition and heat treatment on the microstructure and mechanical behavior of Ti–Cu hypo-, hyper- and eutectoid alloys. To this end, samples of different compositions were prepared in an arc furnace with non-consumable tungsten electrode and a water-cooled copper crucible in a high purity argon atmosphere. The samples were then cast in an arc-melting centrifugal casting machine in an argon atmosphere and copper molds. To obtain a room-temperature microstructure with stable phases, some of the cast samples were then β solution-treated at 900°C for 2h and furnace cooled. Microstructural and mechanical characterizations were performed by X-ray diffraction, Vickers hardness measurements, scanning electron microscopy, transmission electron microscopy, tensile test, differential scanning calorimetry and ultrasonic methods for the determination of Young’s modulus. The microstructure of cast samples displays a martensitic structure and heat-treated samples a microstructure composed of α/α′ and Ti2Cu intermetallic phases formed during eutectoid transformation. The mechanical characterization of the cast samples show low ductility and high mechanical strength while the heat-treated samples display slightly higher ductility and low mechanical strength.

Observations of shear adhesive force and friction of Blatta orientalis on different surfaces

The shear adhesive force of four non-climbing cockroaches (Blatta orientalis Linnaeus, 1758) was investigated by the use of a centrifugal machine, evaluating the shear safety factor (adhesion force divided by body weight) on six surfaces (steel, aluminium, copper, two sandpapers and a common paper sheet) having different roughness. The adhesive system of Blatta orientalis was characterized by means of a field emission scanning electron microscope and the surface roughness was determined by an atomic force microscope. The cockroach maximum shear safety factor, or apparent friction coefficient, is determined to be 12.1 on the less rough of the two sandpapers, while its minimum value is equal to 1.9 on the steel surface. A two-sample Student t analysis has been conducted in order to evaluate the significance of the differences among the obtained shear safety factors due to both roughness and chemistry. An interesting correlation between cockroach shear adhesion and surface roughness emerges with a threshold mechanism dictated by the competition between claw tip radius and roughness, indicating that the best adhesion is obtained for roughness larger than the claw tip radius.