bluuebunny/crossref_metadata_2025 huggingface dataset:
Sponged Structured Silica Containing Cobalt Oxide as Catalyst for Hydrolysis of Water Solution of Sodium Borohydride
Authors: Efendi Jon , Lai Sin Yuan , Nur Hadi
Published: October 2017

Micro structured silica containing cobalt oxide materials was prepared by the calcination of silica containing cobalt salicylaldimine complexes. The SEM image showed that the prepared materials from higher content of cobalt salicylaldimine complexes had sponge-like structured. The IR and DR UV-Vis, spectra confirmed the presence of different species of cobalt oxide in materials originated from higher contain of the complex, which is attributed as Co3O4. The Co3O4 was believed as active species in catalytic hydrolysis of sodium borohydride. The catalytic testing also showed that the material originated from higher content of complex generated much higher hydrogen gas compare to the lower ones.
Geometrical Representation of Automata over Some Abelian Groups
Authors: Gan Y.S. , Fong W.H. , Sarmin N.H. , Turaev S.
Published: October 2017

One of the classic models of automata is finite automata, which determine whether a string belongs to a particular language or not. The string accepted by automata is said to be recognized by that automata. Another type of automata, so-called Watson-Crick automata, with two reading heads that work on double-stranded tapes using the complimentary relation. Finite automata over groups extend the possibilities of finite automata and allow studying the properties of groups using finite automata. In this paper, we consider finite automata over some Abelian groups ℤn and ℤn × ℤn. The relation of Cayley table to finite automata diagram is introduced in the paper. Some properties of groups ℤn and ℤn × ℤn in terms of automata are also presented in this paper.
Some Numerical Methods for Solving Stochastic Impulse Control in Natural Gas Storage Facilities
Authors: Ranjbari Leyla , Bahar Arifah , Abdul Aziz Zainal
Published: October 2017

The valuation of gas storage facilities is characterized as a stochastic impulse control problem with finite horizon resulting in Hamilton-Jacobi-Bellman (HJB) equations for the value function. In this context the two catagories of solving schemes for optimal switching are discussed in a stochastic control framework. We reviewed some numerical methods which include approaches related to partial differential equations (PDEs), Markov chain approximation, nonparametric regression, quantization method and some practitioners’ methods. This paper considers optimal switching problem arising in valuation of gas storage contracts for leasing the storage facilities, and investigates the recent developments as well as their advantages and disadvantages of each scheme based on dynamic programming principle (DPP).
Comparison QA methods of brachytherapy using well ionization chamber and in-air method
Authors: Nor Azmi Nor Faranaz Shamin , Zakaria Ahmad , Abdullah Reduan , Abdul Hadi Norha
Published: October 2017

The aim of this project is to do comparative study in calibrating Ir-192 source using well ionization chamber and air measurement using Farmer ionization chamber. To calibrate the Ir-192 using well ionization chamber, the HDR unit was programmed so that the source was at the most sensitive position inside the well-chamber. The charges were measured at 45 second time interval two times using the electrometer operated at +300V and -300V. Sources air kerma strength was determined based on the AAPM task group 43 brachytherapy dosimetry protocol. In the in-air method using the Farmer ionization chamber and calibration jig, the HDR unit was programmed so that the source was at the position that gave the maximum response in the catheter. The source air kerma strength was calculated using a formula proposed by Goestch et al, (1991). The Ir-192 source air kerma strength by the well chamber was 2.7780cGym2/h while in the in-air measurement was 2.609cGym2/h. Both results are less than 3% from the source strength written in the calibration certificate. The well chamber method is quite direct and less time consuming compare to the in-air measurement and this is the method utilised in HUSM.
Overview of the Sensitivity of Ge- and Al-doped Silicon Dioxide Optical Fibres to Ionizing Radiation
Authors: Tou Ying Lim , Wagiran Husin , Hashim Suhairul , Hussin Rosli
Published: October 2017

This paper reviews the thermoluminescence sensitivity of Ge- and Al- doped SiO2 optical fibre subjected to various ionizing radiations. It is found that the Ge- doped SiO2 optical fiber has the thermoluminescence response superior to Al-doped SiO2 optical fibre at certain energy and dose range in alpha, beta, photon and electron irradiation. High thermoluminescence intensity per unit dose goes to photon and electron irradiation than alpha and beta irradiation of lower energy. This probably due to the linear energy transfer that influence the dose deposition in the material as incident ionizing radiation striking the surface of Ge- and Al- doped SiO2 optical fibre. However, both doped SiO2 optical fibres show good linearity at studied dose range. It has been proven by researchers providing great potential as a dose absorbed measuring devices especially in radiotherapy energy and dose range.
Combining multiple survival endpoints within a single statistical analysis
Authors: Zain Zakiyah , Whitehead John
Published: October 2017

Multiple endpoints are common in survival data and this scenario complicates the analysis. For example, sets of responses concerned with survival times in a single clinical trial include: time to first cardiac event and time to death from any cause; time to loss of vision in the left eye and time to loss of vision in the right eye; and times from entry to a trial until the first, the second and the third asthma exacerbations. In a clinical trial evaluating the treatment effect of a new drug, often a single statistic is required to measure its overall performance. The cumulative treatment advantage is often measured by the score statistic for each endpoint. The aim of this paper is to develop methodology for combining multiple endpoints within a single statistical analysis that compares the responses of patients treated with a novel treatment with those of control patients treated conventionally. The focus is on interval-censored bivariate survival data, and a real dataset from previous study concerning multiple responses are used for illustration. In this paper we take a direct approach to combining the univariate score statistics for comparing treatments with respect to each survival endpoint. Recurrent events are considered in this investigation and the accuracy of the estimator is evaluated. The combined methodology is accurate, consistent and comparable to the established method of Wei, Lin and Weissfeld.
EFFECT OF OXYGEN ON SIZE-CONTROLLED SYNTHESIS OF CdSe QDs
Authors: Ubani Charles Ahamefula , Sulaiman Mohamad Yusof , Zahari Ibarahim , Sopian Kamarruzaman , Ibrahim Noor bayaa , Hj. Othman Mohd Yusof
Published: October 2017

Unique properties of quantum dots (QDs) are controlled by their customizable particle sizes which can be engineered to suit local need. One-pot organometallic injection synthesis of cadmium selenide (CdSe) QDs is reported. The operation started with the injection of a week old selenium (Se) precursor into a boiling non-coordinating octadecene (ODE) at 195oC resulting in the formation of monodispersed size tunable CdSe QDs with discrete homogeneous nucleation. Differences in the injection and withdrawal time of the sample resulted to the dissimilarity in the shape, size and the opto-electronic properties of the QDs. The effect of oxygen on the synthesized CdSe QDs was studied by exposing freshly prepared sample to atmospheric oxygen for 206 days. The samples were characterized using optical absorption spectroscopy (UV-vis), optical photoluminescence (PL), X-ray diffraction (XRD), atomic force microscopy (AFM) and transmission electron microscopy (TEM), electron dispersive X-ray (EDX) X-ray diffraction spectroscopy (XRD), and X-ray photoelectron spectroscopy (XPS). Noticeable deformation on the size, shape and the crystalline orientation of the CdSe QDs were observed on the oxygen-interacted sample.Although the synthesis method is safe and produced good quality CdSe QDs, the interaction of the sample with oxygen degrades their opto-electronic quality.
Assessing material densities by vibration analysis and independent component analysis
Authors: Razaghi Hajar , Saatchi Reza , Offiah Amaka , Burke Derek , Bishop Nick , Gautam Santosh
Published: October 2017

The aim of this study was to investigate vibration analysis and independent component analysis (ICA) to assess the density of multiple materials making up a single structure. Density is important as it reveals information about physical properties of materials. The density of a single material can be determined from the relationship between its mass and volume. However, when a structure consists of multiple materials, identification of their individual densities from the structure is complicated. Vibration analysis is a technique that reveals information about an object’s physical properties such as its density. The investigation was carried out using a plastic test tube filled separately with three liquids of known densities; water, Chloroform and Methanol. Vibration was inducted into the tube, through an electronic system that produced a single impact at a predefined location on the tube. The resulting vibration signals were recorded using two vibration sensors placed on the tube. A signal source separation technique called ICA was used to obtain the vibration effects of the liquid and the tube. The power spectral densities (PSD) of ICA extracted vibration signals were examined. The frequency of the largest peak in the PSD was related to the liquid’s density under test. The study indicated that vibration analysis may be effective in assessing materials’ densities in a structure that contains multiple materials, however a larger study is needed to explore the findings.
Noncontact respiration rate monitoring based on sensing exhaled air
Authors: Alkali A.H. , Saatchi R. , Elphick H. , Burke D. , Evans R.
Published: October 2017

Respiration rate is the average number of times air is inhaled and exhaled per minute. Respiration rate is an important indicator of a person’s health and therefore, it needs to be measured accurately. Existing respiration monitoring systems are generally contact based that means the sensing element needs to be attached to the subject's body. The attached sensor can cause distress in some children, affecting their respiration rate. The device can also become dislodged interrupting the monitoring. This work presents an air flow sensing approach to noncontact respiration rate monitoring. The exhaled air is guided through a small funnel to a chamber that contains a heating element. The heated air leaves the chamber and is then detected by a thermistor that converts the air flow temperature variations to an electrical signal. The signal is amplified, filtered and digitised. Signal processing techniques are used to extract respiration rate from the signal in real time. The device provides respiration rate at distances from 15 to 30 cm from the subject’s face.
A new proof on sequence of fuzzy topographic topological mapping
Authors: Mohd Yunus Azrul Azim , Ahmad Tahir
Published: October 2017

Fuzzy Topological Topographic Mapping (FTTM) is a model for solving neuromagnetic inverse problem. FTTM consists of four components and connected by three algorithms. FTTM version 1 and FTTM version 2 were designed to present 3D view of an unbounded single current and bounded multicurrent source, respectively. In 2008, Suhana proved the conjecture posed by Liau in 2005 such that, if there exists n number of FTTM, then n4-n new elements of FTTM will be generated from it. Suhana also developed some new definitions on geometrical features of FTTM, and discovered some interesting algebraic properties. In this paper, new proof on sequence of FTTM will be presented. In the proof, the sequence of FTTM is transformed into a system of differential equation.
SEALiP: A simple and efficient algorithm for listing permutation via starter set method
Authors: Ibrahim Haslinda , Zake Lugean , Omar Zurni , Karim Sharmila
Published: October 2017

Algorithm for listing permutations for n elements is an arduous task. This paper attempts to introduce a novel method for generating permutations. The fundamental concept for this method is to seek a starter set to begin with as an initial set to generate all distinct permutations. In order to demonstrate the algorithm, we are keen to list the permutations with the special references for cases of three and four objects. Based on this algorithm, a new method for listing permutations is developed and analyzed. This new permutation method will be compared with the existing lexicographic method. The results revealed that this new method is more efficient in terms of computation time.
Spatial interaction of electroencephalography signal during epileptic seizure on flat electroencephalography
Authors: Chien Yong Goh , Ahmad Tahir , Maan Normah
Published: October 2017

Electroencephalography (EEG) is one of the fields in clinical neurophysiology, which is a recording of the electrical activity of the brain from the scalp. One of the major roles of EEG is as an aid to diagnose epilepsy. Abnormal patterns such as spikes, sharp waves and, spikes and wave complexes can be seen. It is important to extract spatial information about the dynamics from a few observations of this recorded signal regardless where EEG sensors are located. A developed method by Theoretical & Computational Modelling for Complex System (TCM), UTM, namely Flat EEG for mapping high dimensional signal into a low dimensional space will be used as platforms to analyse EEG signal spatially during epileptic seizure. The spatial interactions among clusters are identified through spatial interaction model, namely gravity model. This paper also reveals that gravity model used is a measure.
Structural and composition of natural hydroxyapatite (HA) at different sintering temperatures
Authors: Baco Saturi , Bambang Lisnawaty , Joseph Norlaila , MD.Yassin Fouziah , Basri Nur Fadzilah
Published: October 2017

Hydroxyapatite (HA) is one of the most attractive biomaterials and widely used as a bone substitute due to its compositions are similar to the minerals in teeth and bones. Understanding of natural HA properties are useful in order to produces high quality of HA. In this paper, we report an easy and low cost method to extract the natural HA from femur cow bone and subsequently sintered at different temperature from 900 oC to 1300 oC. Structural, composition and surface morphology of natural Hydroxyapatite (HA) at different sintering temperatures (900 ̊ C, 1000 ̊ C, 1100 ̊ C, 1200°C and 1300 ̊ C) were discussed. The HA structural, composition and surface morphology were studied by using X-Ray Diffractometer (XRD), Fourier Transform Infrared (FTIR) and Scanning Electron Microscope (SEM), respectively. The results show the main HA phases were detected in the range of 31.72o - 31.82o (2Ө) for all sintered HA corresponding to 211 plane. The crystallite size of HA increases with sintering temperature from 900 ̊C to 1100 ̊C. Spectrums of FTIR revealed the existences of functional groups of carbonate (CO3 2-), phosphate (PO4 3-) and hydroxyl (OH-) peaks. SEM micrographs presented small and homogenous grains from 900°C to 1100°C. The grains look interconnected as sintering temperature increased at 1200°C and 1300°C. From this study, sintering process was found to be an easy and low cost method to produce natural HA from femur cow bones.
Comparison of EEG source localization using meromorphic approximation to fuzzy C-mean
Authors: Saeidias Leila , Ahmad Tahir , Alias Norma , Ghanbari Mehdi
Published: October 2017

Electroencephalography (EEG) is a neuroimaging technique for localizing active sources within the brain, from knowledge of electromagneticmeasurements outside the head. Recognition of point sources from boundary measurements is an ill-posed inverse problem. InEEG, measurements areonly accessible at electrode positions, the number of sources is not known a prior. This paper proposes a comparison between two approaches for EEGsource localization. First method based on Meromorphic approximation techniques in the complex plane and second one belongs to EEG’s methodwhich is processed using Fuzzy C-Means (FCM). Comparison results on simulated data are used to verify the superior of the Meromorphicapproximation with regarding to Fuzzy c-means, due to it provides the way for solving inverse problem of EEG source localization in 3D from boundarymeasurement based on Harmon function in the innermost layer .
Promotive effect of hydrogen in n-hexane isomerization over Ni/PtHY catalyst
Authors: Aziz M.A.A. , Jalil A.A. , Triwahyono N.S.
Published: October 2017

Bifunctional catalyst containing 0.1 wt% Ni and 0.1 wt% Pt supported on HY were prepared by incipient wetness impregnation method. The properties of the catalyst were determined by XRD analysis and pyridine adsorbed FTIR spectroscopy. The catalytic activities were tested on n-hexane isomerization by pulse method in a microcatalytic reactor under atmospheric pressure in the presence of hydrogen or nitrogen carrier gas. XRD result showed the decrease of the crystallinity of PtHY after introduction of 0.1 wt% of Ni. While, the ratio of Lewis to Brønsted acid sites increased after the introduction of Ni on PtHY as evidenced by pyridine adsorbed FTIR spectroscopy. In the presence of hydrogen gas, 0.1 wt% Ni increased the yield of isohexane by about 24 % and decreased the activation energy from 124.1 to 111.2 kJ/mol at the temperature range of 403-423 K. In addition, the activation energy decreased to 48.3 kJ/mol for Ni/PtHY at high temperature range of 478-498 K. The presence of hydrogen as a carrier gas gave a promotive effect on the reaction which led to increase the formation of isohexane and suppress the cracking process. While, the presence of nitrogen as a carrier gas promoted dimerization of nhexane which formed the cracking products.
The Role of Online Privacy Concern as a Mediator between Internet Self-Efficacy and Online Technical Protection Privacy Behavior
Authors: Lee Wan Ying , Tan Chee-Seng , Siah Poh Chua
Published: October 2017

Online risks may result in unnecessary harm but these risks can be minimized by being online privacy concerned and by taking privacy protective actions. Few studies examined the impact of privacy concern and internet self-efficacy on the online technical protection privacy behavior. Therefore, this research aims to investigate the effect of privacy concern and internet self-efficacy on technical protection. Quantitative and purposive sampling methods were used in this study. Data were gathered via questionnaire surveys from 235 undergraduates from six universities in Malaysia. The questionnaire includes participants’ demographic data, internet addiction test, web user self-efficacy scale, privacy concern, and technical protection scale. Hierarchical multiple regression analyses were conducted to examine the effect of internet self-efficacy and privacy concern on technical protection, while controlling for gender, course type, and internet addiction. Results showed that both privacy concern and internet self-efficacy were significant predictors of technical protection. Moreover, mediation analysis showed that there was an indirect effect of internet self-efficacy on technical protection through privacy concern. The results contribute to literature by revealing how internet self-efficacy and privacy concern increase technical protection. The government and policy makers can design intervention and prevention programs that aim to boost privacy concern and internet self-efficacy, so that internet users are more capable of safeguarding their online privacy.
Comparison of Adaptive Behaviour among Children with Learning Difficulties
Authors: Peter Cassandra Rani , Chan Samuel
Published: October 2017

The objective of this study is to explore the nature of adaptive behaviour in terms of fine and gross motor skills in children with learning difficulties.  This research aims to find whether there are any differences between the fine and gross motor skills among the children from the age of four to fourteen with learning difficulties.  This study used Vineland Adaptive Behaviour Scales Classroom Edition survey questionnaire to explore the differences in the adaptive behaviour of children with learning difficulties in the motor skills domain. A quantitative within-participants experimental design was employed to assess the adaptive behaviour among children with learning difficulties in motor skill domain. The independent variable was the motor skills consisting of two levels which are the fine motor skills and gross motor skills.  The dependent variable was the difference in adaptive behaviour of the children with learning difficulties.  Paired-samples t-test was used to study the differences between the variables. It was evident that the paired sample t-test conducted implied that there was no significant difference between the variables which are the fine and gross motor skills.  Future researchers could also compare other demographic factors such as age, gender or cultural background that influences the adaptive behaviour of children with learning difficulties in various domains besides motor skills such as socialisation and communication domains.
Pengkonsepsian dan Pembinaan Instrumen Kualiti Kehidupan Kerja Guru
Authors: Abd Razak Nordin , Thien Lei Mee
Published: October 2017

This study aims to conceptualise and develop an instrument measures teacher quality of work life based on four main theories, namely (1) socio-technical systems theory, (2) two factor Herzberg theory, (3) organisation management theory, including structure and human relationship theories, and (4) psychological interactive theory. Based on these theories, the construct of teacher quality of work life has been conceptualised to have four main dimensions, namely (1) psychological need, (2) social need, (3) political need, and (4) economical need. A total of 1,080 school teachers were selected from 30 primary schools in Penang and Kedah and measured with more 44 items. Exploratory factor analysis and confirmatory factor analysis were performed to examine the reliability and validity of the instrument measures teacher quality of work life using IBM SPSS 20.0 and AMOS 20.0 computer software. Findings revealed that 12 out of 32 items need to be excluded because of its poor psychometric properties.  The remaining 20 items that measure these four main dimensions of teacher quality of work life have shown satisfactory construct validity with the values of goodness-of-fit indices lie within the proposed acceptable range. Political need contributed the highest variance to explain teachers’ quality of work life compared to other dimensions. Implications and suggestions for future studies were presented.
Surface and Thermal Characteristics of Single-Use Electrosurgical Pencils After Clinical Reuse and In-Hospital Reprocessing
Authors: Tessarolo Francesco , Torres Sebastian , Ballesteros Luis Miguel , Rigoni Marta , Piccoli Federico , Caola Iole , Caciagli Patrizio , Montoya Yesid , Nollo Giandomenico
Published: October 2017

Safety and efficacy issues are associated with reprocessing of single-use electrosurgical pencils (EPs), requiring methods for assessing the reprocessing protocol before clinical reuse. This study aimed at monitoring the surface characteristics of single-use EPs subjected to multiple clinical use and in-hospital reprocessing. A total of 24 single-use-labeled EPs were divided in five test groups and one control group. The test groups were subjected to a different number of clinical uses, ranging from one to five. A multitechnique approach based on optical stereomicroscopy (OM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDXS), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA) was applied. The silicon coating of the tip was significantly reduced, and foreign bodies were occasionally found on reprocessed EPs. The amount of biological debris and chemical residuals increased with the number of reprocessing cycles in critical areas. The degradation temperature of the EP handle polymer showed a progressive significant reduction. Cable cord showed no modification after reprocessing. EP tip could undergo major surface modifications that can affect functionality. The efficacy of the reprocessing protocol in removing debris from the EP handle should be carefully assessed. Surface and thermal characteristics have to be considered for validating a reprocessing protocol of single-use labeled EP.
Experimental Fitting of Rotor Models by Using a Special Three-Node Beam Element
Authors: Antali Mate , Takacs Denes , Stepan Gabor
Published: October 2017

In this paper, a special type of beam element is developed with three nodes and with only translational degrees-of-freedom (DOFs) at each node. This element can be used effectively to build low degree-of-freedom models of rotors. The initial model from the Bernoulli theory is fitted to experimental results by nonlinear optimization. This way, we can avoid the complex modeling of contact problems between the parts of squirrel cage rotors. The procedure is demonstrated on the modeling of a machine tool spindle.
Resistant Statistical Methodologies for Anomaly Detection in Gas Turbine Dynamic Time Series: Development and Field Validation
Authors: Fabio Ceschini Giuseppe , Gatta Nicolò , Venturini Mauro , Hubauer Thomas , Murarasu Alin
Published: October 2017

The reliability of gas turbine (GT) health state monitoring and forecasting depends on the quality of sensor measurements directly taken from the unit. Outlier detection techniques have acquired a major importance, as they are capable of removing anomalous measurements and improve data quality. To this purpose, statistical parametric methodologies are widely employed thanks to the limited knowledge of the specific unit required to perform the analysis. The backward and forward moving window (BFMW) k–σ methodology proved its effectiveness in a previous study performed by the authors, to also manage dynamic time series, i.e., during a transient. However, the estimators used by the k–σ methodology are usually characterized by low statistical robustness and resistance. This paper aims at evaluating the benefits of implementing robust statistical estimators for the BFMW framework. Three different approaches are considered in this paper. The first methodology, k-MAD, replaces mean and standard deviation (SD) of the k–σ methodology with median and mean absolute deviation (MAD), respectively. The second methodology, σ-MAD, is a novel hybrid scheme combining the k–σ and the k-MAD methodologies for the backward and the forward windows, respectively. Finally, the biweight methodology implements biweight mean and biweight SD as location and dispersion estimators. First, the parameters of these methodologies are tuned and the respective performance is compared by means of simulated data. Different scenarios are considered to evaluate statistical efficiency, robustness, and resistance. Subsequently, the performance of these methodologies is further investigated by injecting outliers in field datasets taken on selected Siemens GTs. Results prove that all the investigated methodologies are suitable for outlier identification. Advantages and drawbacks of each methodology allow the identification of different scenarios in which their application can be most effective.
Estimation of Forcing Functions on a Mistuned Bladed Rotor From Harmonic Response
Authors: Sinha Alok
Published: October 2017

This paper deals with the estimation of forcing functions on a mistuned bladed rotor from measurements of harmonic response via Kalman filter (KF) in time domain. An unique feature of this approach is that the number of estimated variables can be far greater than the number of measurements. The robustness of this method to measurement errors is shown. It is also shown that direct prediction of amplitude and phase of sinusoidal force vector from input/output frequency response function has a large amount of errors in the presence of unavoidable measurement noise. Numerical examples contain both frequency mistuning and geometric mistuning.
Low-Temperature Distillation Process for CO2/CH4 Separation: A Study for Avoiding CO2 Freeze-Out
Authors: Yousef Ahmed M. , El-Maghlany Wael M. , Eldrainy Yehia A. , Attia Abdelhamid
Published: October 2017

In published literature, only very limited studies were carried out for low-temperature biogas upgrading for CO2/CH4 mixture separation due to the freeze-out of CO2 under low temperature, which causes several operational problems. Therefore, the present study aims to provide in-depth analysis for a low-temperature distillation process of a typical model of biogas mixture (CH4 + CO2) to tackle the problem of freezing. The process has been optimized by means of varying distillation column feed pressure, temperature and CO2 concentration, reflux ratio, feed stage number, and produced methane purity to lower the risk of CO2 freezing in the column. The modeling results reveal a substantial feature of the low-temperature process that it can capture CO2 in liquid phase with a purity of 99.5 mol % as a valuable byproduct for transport. Additionally, it is found that increasing the column reflux ratio mitigates the risk of CO2 freeze-out allowing the column to reach higher CH4 purities (up to 97 mol %) without CO2 solidification. Moreover, the occurrence of CO2 freeze-out in the column is not affected within a relatively wide range of feed CO2 concentrations. The low-temperature technique can serve as a new promising approach for biogas upgrading overcoming the risk of CO2 frosting.
A Nonlinear Viscoelastic Model for Adipose Tissue Representing Tissue Response at a Wide Range of Strain Rates and High Strain Levels
Authors: Naseri Hosein , Johansson Håkan , Brolin Karin
Published: October 2017

Finite element human body models (FEHBMs) are nowadays commonly used to simulate pre- and in-crash occupant response in order to develop advanced safety systems. In this study, a biofidelic model for adipose tissue is developed for this application. It is a nonlinear viscoelastic model based on the Reese et al.'s formulation. The model is formulated in a large strain framework and applied for finite element (FE) simulation of two types of experiments: rheological experiments and ramped-displacement experiments. The adipose tissue behavior in both experiments is represented well by this model. It indicates the capability of the model to be used in large deformation and wide range of strain rates for application in human body models.
Analytical Solutions of Period-1 to Period-2 Motions in a Periodically Diffused Brusselator
Authors: Luo Albert C. J. , Guo Siyu
Published: October 2017

In this paper, the analytical solutions of periodic evolutions of the periodically diffused Brusselator are obtained through the generalized harmonic balanced method. Stable and unstable solutions of period-1 and period-2 evolutions in the Brusselator are presented. Stability and bifurcations of the periodic evolution are determined by the eigenvalue analysis, and the corresponding Hopf bifurcations are presented on the analytical bifurcation tree of the periodic motions. Numerical simulations of stable period-1 and period-2 motions of Brusselator are completed. The harmonic amplitude spectra show harmonic effects on periodic motions, and the corresponding accuracy of approximate analytical solutions can be prescribed specifically.
Critical Heat Flux of Flowing Water in Tube for Pressure Up to Near Critical Point—Experiment and Prediction
Authors: Chen Yuzhou , Zhao Minfu , Bi Keming , Yang Bin , Zhang Dongxu , Du Kaiwen
Published: October 2017

Critical heat flux (CHF) experiment with uniform heating was performed in a tube of 8.2 mm in inner diameter and 2.4 m in heated length. The water flowed upward through the test section. The pressure covered the range from 8.6 to 20.8 MPa, mass flux 1157 to 3776 kg/m2s, inlet quality −2.79 to −0.08 (subcooling 19–337 °C), and local quality −0.97 to 0.53. For the pressure close to the near-critical point, the CHF decreased substantially with the pressure increasing. For the subcooling larger than a certain value, the CHF was related to the local condition. But for low subcooling and saturated condition, the CHF was related to the total power. The present results were in agreement with the previous experiment for the same local subcooled condition. Based on the present experimental results with subcooled and saturated conditions an empirical relation of the CHF was presented.
Assessment of 11 Available Materials With Custom Three-Dimensional-Printing Patterns for the Simulation of Muscle, Fat, and Lung Hounsfield Units in Patient-Specific Phantoms
Authors: Okkalidis Nikiforos , Chatzigeorgiou Chrysoula , Okkalides Demetrios
Published: October 2017

A couple of fused deposition modeling (FDM) three-dimensional (3D) printers using variable infill density patterns were employed to simulate human muscle, fat, and lung tissue as it is represented by Hounsfield units (HUs) in computer tomography (CT) scans. Eleven different commercial plastic filaments were assessed by measuring their mean HU on CT images of small cubes printed with different patterns. The HU values were proportional to the mean effective density of the cubes. Polylactic acid (PLA) filaments were chosen. They had good printing characteristics and acceptable HU. Such filaments obtained from two different vendors were then tested by printing two sets of cubes comprising 10 and 6 cubes with 100% to 20% and 100% to 50% infill densities, respectively. They were printed with different printing patterns named “Regular” and “Bricks,” respectively. It was found that the HU values measured on the CT images of the 3D-printed cubes were proportional to the infill density with slight differences between vendors and printers. The Regular pattern with infill densities of about 30%, 90%, and 100% were found to produce HUs equivalent to lung, fat, and muscle. This was confirmed with histograms of the respective region of interest (ROI). The assessment of popular 3D-printing materials resulted in the choice of PLA, which together with the proposed technique was found suitable for the adequate simulation of the muscle, fat, and lung HU in printed patient-specific phantoms.
ASETS-II Oscillating Heat Pipe Space Flight Experiment: Ground Truth Results
Authors: Taft Brent S. , Smith Sally M.
Published: October 2017

The ASETS-II experiment consists of three oscillating heat pipes (OHPs), an electronics box, and mounting structures that control boundary conditions. Each OHP consists of 34 channels in a typical single-layer closed loop design. Butane was selected as the working fluid for OHP #1 and #2 for its performance stability. R-134a was selected for OHP #3 in order to explore the Bond number limit’s influence on OHP operation in microgravity.

The ASETS-II Flight and Flight Spare hardware were subjected to a comprehensive set of ground testing to baseline performance prior to flight testing. For most test conditions, the Flight and Flight Spare test results for OHP #1 and OHP #2 are within the margin of uncertainty in the measurements. OHP #3 on the Flight hardware performs similarly to OHP #3 on the Flight Spare hardware; however, the difference in performance is outside the margin of uncertainty in the measurements. This variation in performance may be attributable to the fact that OHP #3 is being pushed to operate near its Bond number limit.
Local-Scale Simulations of Nucleate Boiling on Micrometer-Featured Surfaces
Authors: Sitaraman Hariswaran , Moreno Gilberto , Dede Ercan M. , Joshi Shailesh N. , Zhou Feng , Narumanchi Sreekant
Published: October 2017

A high-fidelity computational fluid dynamics (CFD)-based model for bubble nucleation of the refrigerant HFE7100 on micrometer-featured surfaces is presented in this work. The single-fluid, incompressible Navier-Stokes equations, along with energy transport and natural convection effects, are solved on a featured surface resolved grid. An a priori cavity detection method is employed to convert raw profilometer data of a surface into well-defined cavities. The cavity information and surface morphology are represented in the CFD model by geometric mesh deformations. Surface morphology is observed to initiate buoyancy-driven convection in the liquid phase, which in turn results in faster nucleation of cavities. Simulations pertaining to a generic rough surface show a trend where smaller size cavities nucleate with higher wall superheat. This local-scale model will serve as a self-consistent connection to larger device scale continuum models where local feature representation is not possible.
Effects of Particle Shape on Nanofluids Laminar Forced Convection in Helically Coiled Tubes
Authors: Liu Fang , Cai Yang
Published: October 2017

In this study, effects of particle morphology (shape and size) on nanofluids laminar forced convection in helically coiled tubes are investigated numerically using Eulerian-Lagrangian two-phase approach. The laminar forced convective heat transfer and pressure drop of Al2O3-water nanofluids containing nanoparticles with various particle shapes (sphere, platelet, blade, cylinder and brick) and sizes at different volume fractions in the developing and fully developed regions are investigated using the validated two-phase model. It is found that the nanofluids containing platelet particle shape has the highest heat transfer enhancement, which is followed by nanofluids containing cylinder, blade, sphere and brick nanoparticle shapes, respectively. Non-spherical nanoparticles with larger aspect ratio, small particle size and a suitable particle volume concentration are beneficial for heat transfer enhancement of forced convection. Heat transfer efficiency reaches minima at Re of 1250 for laminar forced convection with 1% volume fraction. The correlations of Nusselt number and pressure drop with nanoparticle shape and size were developed to predict convective heat transfer of nanofluids containing spherical nanoparticles and non-spherical nanoparticles.
Liquid-Liquid Flow Patterns in Microchannels
Authors: Cao Zhen , Wu Zan , Sattari Najafabadi Mehdi , Sunden Bengt
Published: October 2017

In the present work, liquid-liquid flow patterns positioned 40 mm downstream the inlet of microchannels were experimentally investigated, including the effect of hydraulic diameter (Dh), liquid properties, aspect ratio of cross section (a) and inlet configuration. Deionized water, butanol, toluene and hexane were selected as probe fluids with water as the continuous phase. Cross-inlet microchannels of 200 μm * 200 μm (Dh = 200 μm), 400 μm * 400 μm (Dh = 400 μm), 600 μm * 600 μm (Dh = 600 μm) and 600 μm * 300 μm (Dh = 400 μm) as well as a T-inlet microchannel of 600 μm * 300 μm (Dh = 400 μm) were tested. For the tests in the microchannels of Dh = 600 μm and 400 μm, the superficial velocities of the dispersed phase and continuous phase varied between 0.3 mm/s and 12 mm/s and between 0.2 mm/s and 50 mm/s, while in the microchannel of Dh = 200 μm the superficial velocities of the dispersed phase and continuous phase ranged from 0.3 mm/s to 21 mm/s and from 0.2 mm/s to 150 mm/s. Annular flow, deformed interface flow, slug flow, intermittent flow, droplet and slug train flow and droplet flow were detected in the experiment. It shows that flow patterns depend on the hydraulic diameter, liquid properties, inlet configuration and aspect ratio significantly. Dimensionless analysis was employed to develop universal flow pattern maps regardless of the hydraulic diameter and liquid properties. It is indicated that an acceptable universal flow pattern map was derived based on the redefined dimensionless number Rei0.2 *Wei0.4, especially for the boundaries of the slug-droplet transitions, which are independent on the hydraulic diameter to some extent. The other dimensionless number Wei*Ohi worked rather effectively to develop a universal flow pattern map independent on liquid properties. The boundaries of the flow pattern transitions in different liquid-liquid flow almost overlap with each other.
Heat Transfer Analysis of Graphite Foam Embedded Vapor Chamber for Cooling of Power Electronics in Electric Vehicles
Authors: Patel Anand K. , Zhao Weihuan
Published: October 2017

The power density of power electronics in electric vehicles (EVs) is expected to be significantly enhanced, which would result in higher heat flux generation. Therefore, it is critical to find an efficient heat spreading and removal technology to reduce the junction temperature for high power density power electronics application. Vapor chamber using evaporation and condensation of the inside working fluid (i.e., water) as a heat spreader can remarkably improve the uniform heat spreading and heat removal for the power electronics compared to the traditional copper heat spreader. Furthermore, high thermal conductivity graphite foam (GF) would be embedded in the vapor core of the vapor chamber to further enhance the heat transfer performance. Numerical heat transfer simulations were performed for copper heat spreader, vapor chambers (with and without the presence of graphite foam) by using ANSYS. Various parametric effects on vapor chamber thermal performance were investigated, including the effects of heat flux from power electronics, heat transfer coefficient at heat sink, vapor chamber thickness, and graphite foam. Through the simulation studies, it was found that thinner vapor chamber (1.35 mm thickness) had better heat transfer performance than thicker vapor chamber (5 mm thickness) because of the extreme high effective thermal conductivities of ultra-thin vapor chamber. Furthermore, the effect of graphite foam on thermal performance improvement was very minor for ultra-thin vapor chamber, but significant for thick vapor chamber. The GF could help reduce the junction temperature by 15–30% in the 5-mm thick vapor chamber. Use of GF embedded vapor chamber could achieve 250–400 W/cm2 local heat removal for power electronics.
Two-Phase Flow Patterns in Microfluidic Cross-Shaped Junctions and Slug Hydrodynamics in the Dripping Regime
Authors: Wu Zan , Cao Zhen , Sunden Bengt
Published: October 2017

Flow patterns for water-butanol, water-toluene and water-hexane two-phase flows were visualized in the cross-shaped junctions of three square glass microchannels with hydraulic diameters of 200 μm, 400 μm and 600 μm. Typical flow pattern maps for water-butanol two-phase flow were developed based on Capillary number of the continuous phase and Weber number of the dispersed phase, and compared with a previous flow pattern map in the literature. Three main flow pattern groups were observed, including the tubing/threading regime group, the dripping regime and the jetting regime. The geometry confinement and fluid properties affected the viscous shear and interfacial tension forces and therefore their influence on flow pattern transitions was clarified. Besides, in the dripping regime, the dimensionless slug length can be scaled as a function of the flow rate ratio and the Capillary number of the continuous phase.
A Novel Modeling Approach to Estimate Segmental and Intersegmental Ventilation and Heat Transport From a Walking Clothed Human Using Electric Circuit Analogy
Authors: Ismail Nagham , Ghaddar Nesreen , Ghali Kamel
Published: October 2017

When the clothed human body experiences relative wind due to walking and external wind, heat and vapor transfers from the body to the environment are enhanced by ventilation through clothing. The clothing ventilation is related to the clothing permeability, open and close apertures, relative wind, clothed limbs swinging motion as well as the inter-segmental ventilation that occurs at the interconnection between the clothed human trunk and arms.

In this study, a computationally effective model is developed to estimate clothing ventilation based on the analogy between the air flow in the microclimate air layer and an electric circuit composed of resistance and inductance elements. The model takes into account the inter-connection between the segments for the clothed human upper part driven by difference of pressure in the microclimate air of the trunk and the upper arms. The estimation of the segmental ventilation, taking into account the inter-connection, allows the correction of the clothing dry resistances in a bio-heat model that will be used to predict the sensible heat losses of the clothed human.
Experimental Study on Effective Placement of PCM Packets in Cooling Vest to Improve Performance in Warm Environment
Authors: Itani Mariam , Ghaddar Nesreen , Ghali Kamel , Khater Beatrice , Ouahrani Djamel , Chakroun Walid
Published: October 2017

Global warming has increased the risk of heat stress of outdoor workers and one measure against heat stress is wearing passive personal cooling clothing. Passive body cooling systems, including phase change material (PCM) cooling vests, are considered as an effective solution to improve the working endurance of outdoor active workers.

The objective of this study is to assess the effective placement of PCM packets in the cooling vest by examining the local and overall sensation and comfort when: (i) only the frontal segment of the human torso is covered (ii) only the back segment of the human torso is covered and (iii) both segments are covered. The PCM cooling vest is worn by human subjects performing cycling at about 3 Mets and for 30 minutes in a climatic chamber maintained at 28 °C and 60 % relative humidity. The used PCM melting temperature is 28 °C with a coverage area of 642 cm2 and total weight of the vest of 1.19 kg including 8 PCM packets (87.5 grams each). The physiological/thermal responses such as body core and mean skin temperatures, heart rate, and skin wittedness are monitored during the experiments while exercising and wearing the vest. In particular, the frontal and back torso skin temperatures are examined after being subjected to local cooling compared to the case when no PCM packets cover the torso segment. Moreover, subjective votes of thermal comfort, whole body and torso thermal sensations, skin and clothing wetness sensation and perceived exertion are recorded throughout the experiment. The experiment was repeated on five male subjects to ensure robustness of the obtained results. It was found that the core temperature changed slightly when wearing the vest, however the local skin temperature of the back and front torso segments decreased by about 5 °C and 3 °C at the end of the exercise, respectively. Gradual improvement in comfort that reaches a stable level when the PCM starts melting till the end of the exercise was also noticed.
Analysis of Film Cooling With High-Aspect-Ratio Holes: Heat Transfer Mechanisms
Authors: Li Hao-Ming , Ghaly Wahid , Hassan Ibrahim
Published: October 2017

A new advanced film cooling scheme, named high-aspect-ratio holes has been proposed. Four configurations were designed, and numerically simulated under density ratio of 2 and different blowing ratios. All configurations demonstrate extremely high film cooling effectiveness values, some are as high as the so-called perfect performance, while their mechanical strength are similar to the conventional schemes. The new scheme exhibits two traits distinctive from the conventional geometries: Its film cooling effectiveness is much higher than the coverage ratio (t/P), and the high film cooling effectiveness is obtained under strong counter-rotating vortex pair (CRVP). It has been found that, in the new scheme, along with the aspect ratio value increase, the CRVP move away from the coolant-mainstream interface, and the coolant laterally expands in the vicinity of the exit. Consequently, a continuous coolant film would occur near the trailing edge position if aspect ratio is high enough. The approach of high-aspect-ratio holes could be used to design the highest film cooling performance geometries.