Austenitic stainless steels of grade 304 were exposed to dry (Ar-75%CO2) and wet (Ar-75%CO2-12%H2O) environments at 700oC. This experimental setup involved horizontal tube furnace connected to CO2 gas and water vapour facilities. X-ray diffraction (XRD) technique, variable pressure-scanning electron microscope (VP-SEM) and optical microscope techniques were used to characterize the products of corrosion. The results of XRD showed that the phase of oxide layers consists of Cr2O3 and NiCr2O4 in dry CO2, meanwhile Fe2O3, Cr2O3, Fe0.56Ni0.34, Fe3O4 were identified in wet condition after 50 h. Adding 12%H2O in Ar-75%CO2 leads significantly in weight change occurred at 10 h exposure. However, after 20 h, the weight gain was decreased due to spallation of the oxide scale. The addition of water vapour accelerates the oxidation rate on the steel than that in dry condition. Morphologies and growth kinetics of these oxides vary with reaction condition. The oxidation behaviour at different times of exposure and the effect of water vapour were discussed in correlation with the microstructure of the oxides.
Tin selenide (SnSe) and copper indium diselenide (CuInSe2) compounds were synthesized by high temperature reaction method using combination of sealed ampoule (at relatively low pressure ~10-1 Pa without inert gas) and heating at specific temperature profile in rocking furnace. Powder X-Ray diffraction analysis showed that the products involved only single phases of SnSe and of CuInSe2 only. Using the reaction products as source materials, the SnSe and CuInSe2 thin films were vacuum-deposited on glass substrates at room temperature. Structural, elemental, surface morphological and optical properties of the as-deposited films were studied by X-Ray diffraction (XRD), energy dispersive X-Ray (EDX) analysis, field emission scanning electron microscopy (FESEM) and UV-Vis-NIR spectroscopy. Single phase of SnSe and CuInSe2 films were obtained by thermal evaporation technique from synthesized SnSe and CuInSe2 compound without further treatment.
The relaxed eddy accumulation method (REA) was applied for direct measurement of sulfate fluxes over mixed dipterocarp forest. The sampling system using a four-stage filter pack was designed to take updraft or downdraft air samples in the direction of the vertical wind velocity. The deadband of the velocity profile was set at ±0.5 σw in which an air sample with velocity within the set value is rejected. The forest site was located at a latitude of 13o 35’ 13.3’’N and longitude of 99o 30’ 3.9’’E Ratchaburi province in Thailand. The sampling period was set in 4 time intervals: 6-12, 12-18, 18-24 and 24-6 h for 3 consecutive days/month (n=144) throughout one year. All the micrometeorological parameters for flux estimation were measured in real time. The concentration and flux of sulfate were found to reach a peak value of 1.32 μg m-3 and 8.35 μg m-2 h-1, respectively, at noon time which indicated the effect of atmospheric instability caused by a high heat transfer during the day. The one-year average deposition velocity was observed to be 0.24 cm s-1.The coefficient β obtained under high ambient temperature and a humid environment in this tropical climate was 0.49. It has also been observed that βis relatively insensitive to atmospheric stability
The aim of this study was to investigate the genotoxicity effect of Cd and Zn and their binary mixtures in tilapia fish Oreochromis niloticus using the micronucleus test. Two cytogenetic end points were considered; the frequencies of micronucleated cells and nuclear abnormalities. Fishes were exposed to 4.63 mg/L Cd, 7.50 mg/L Zn and 4.63 mg/L Cd + 7.50 mg/L Zn mixture for the period of 24, 48, 72 and 96 h. The results showed that the frequencies of micronuclei and nuclear abnormalities in the erythrocyte were significantly increased in all groups of treatments when compared with the control group (0 exposures). In addition, the highest frequencies of micronucleated and nuclear abnormalities were obtained after 48 h exposure in almost all cases (except in the mixture of Cd+Zn) and decreased after 72 and 96 h exposure. Frequencies of micronuclei and erythrocytes with nuclear abnormalities exposed to a mixture of Cd+Zn in O. niloticus were always lower at all-time points (after 24, 48, 72 and 96 h) than that of a single Cd and Zn exposure. Therefore, the study demonstrated that the genotoxic potential of these metal compounds and the simultaneous treatment of Cd and Zn suggest the presence of antagonistic interactions.
MeSH terms: Animals; Cell Count; Cytogenetics; Erythrocytes; Zinc; Micronucleus Tests; Tilapia; Cichlids; Control Groups
Hidden truncation (HT) and additive component (AC) are two well known paradigms of generating skewed distributions from known symmetric distribution. In case of normal distribution it has been known that both the above paradigms lead to Azzalini's (1985) skew normal distribution. While the HT directly gives the Azzalini's ( 1985) skew normal distribution, the one generated by AC also leads to the same distribution under a re parameterization proposed by Arnold and Gomez (2009). But no such re parameterization which leads to exactly the same distribution by these two paradigms has so far been suggested for the skewed distributions generated from symmetric logistic and Laplace distributions. In this article, an attempt has been made to investigate numerically as well as statistically the closeness of skew distributions generated by HT and AC methods under the same re parameterization of Arnold and Gomez (2009) in the case of logistic and Laplace distributions.
MeSH terms: Biometry; Models, Statistical; Normal Distribution
Soft computing is an alternative to hard and classic math models especially when it comes to uncertain and incomplete data. This includes regression and relationship modeling of highly interrelated variables with applications in curve fitting, interpolation, classification, supervised learning, generalization, unsupervised learning and forecast. Fuzzy cognitive map (FCM) is a recurrent neural structure that encompasses all possible connections including relationships among inputs, inputs to outputs and feedbacks. This article examines a new methods for nonlinear multivariate regression using fuzzy cognitive map. The main contribution is the application of nested FCM structure to define edge weights in form of meaningful functions rather than crisp values. There are example cases in this article which serve as a platform to modelling even more complex engineering systems. The obtained results, analysis and comparison with similar techniques are included to show the robustness and accuracy of the developed method in multivariate regression, along with future lines of research.
This paper extends the previous works to further explore the role of the first order polarization tensor in electro-sensing by the weakly electric fish specifically for object discrimination and characterization. The first order polarization tensor for few objects used in the considered experiment are calculated and discussed to identify whether there are other evidences to suggest that a weakly electric fish able to recognize the tensor when choosing or rejecting an object. Our findings in this study suggest that all fish during most of the experiments face difficulties to discriminate two objects when their first order polarization tensors are almost similar depending on the types of training given to them.
MeSH terms: Animals; Electric Fish; Electric Organ; Face
Elektrolit dwi lapisan samarium terdop seria (sDc)lytria terstabil bismut (YsB) dikaji adalah untuk menghasilkan sel fuel oksida pepejal bersuhu sederhana (rr-soFc). Matlamat penyelidikan ialah mengkaji kesan suhu pengkalsinan terhadap penghasilan struktur elektrolit dwi lapisan SDCIYSB untuk IT-SOFC. Elektrolit dwi lapisan SDC dan YSB dihasilkan melalui kaedah sol-gel dan kaedah tindak balas keadaan pepejal. Serbuk SDC dikalsin pada suhu 800, 1000 dan 1200°C selama 5 jam dan serbuk YSB dikalsin pada suhu 550, 650 dan 750°C selama 2 jam. Analisis pembelauan sinar-X (xRD) mendapati serbuk SDC yang dihasilkan pada suhu 800-1200°C selama 5 jam mempunyai struktur Sm02Ce0.801.90, manakala YSB mempunyai struktur Y0.25Bi0.75015 pada suhu 750°C selama 2 jam. Peningkatan suhu pengkalsinan SDC pada suhu 800, 1000 dan 1200°C selama 5 jam menunjukkan peningkatan pada saiz hablur iaitu 42.4, 58.7 dan 79.9 nm. Peningkatan suhu pengkalsinan YSB sehingga suhu 750°C menyebabkan berlakunya perubahan struktur YSB daripada bentuk tetragon menjadi kiub fluorit dengan saiz hablur 28.86 nm. Hasil perbandingan ujian prestasi sel pada suhu pengoperasian sederhana (650°C), penggunaan elektrolit dwi lapisan (sDaYsR) dengan suhu pengkalsinan SDC-1200°C dan YsB-750°C menghasilkan prestasi sel paling tinggi dengan ketumpatan kuasa 81.55 mW/cm2 dan ketumpatan arus 225.36 mA/cm2.
Gentian optik polimer (P0F) mempunyai banyak kelebihan dan banyak digunakan untuk komunikasi terutamanya dalam industri automotif. Komunikasi ini memerlukan maklumat yang banyak dihantar pada satu masa dengan kos yang rendah. Untuk itu pencerai 3x3 POF yang berkonsepkan pemultipleks bahagi jarak gelombang (wDM) yang berkos rendah dan berteknologi hijau difabrikasikan. Pencerai POF ini difabrikasikan dengan menggunakan alat yang murah dan mudah didapati, iaitu tiub besi dan lilM. Teknik fabrikasi yang digunakan adalah dengan memanaskan tiga lembar POF sehingga bahagian tengahnya mencair dan melakur sehingga mengecil dan memanjang berdiameter 1 mm. Pencerai 3x3 POF yang berjaya difabrikasi dicirikan dengan mengukur kehilangan POF sebelum dan selepas hujungnya diratakan dan digilap dengan dua jenis kertas pasir yang berlainan darjah kekasaran. Ini untuk melihat kesan gilapan pada kehilangan isyarat optik. Kehilangan pencerai PoF juga diukur pada suhu yang berbeza bagi melihat kesannya pada prestasi pencerai POF. Berdasarkan keputusan yang diperoleh, dapat dilihat bahawa kebersihan dan kerataan hujung POF memberi kesan kepada kehilangan dengan penurunan antara 0.3 hingga 5.0 dB. Suhu juga memberi kesan kepada kehilangan isyarat POF, walaupun tidak begitu ketara, dengan purata peningkatan kehilangan sebanyak 0.3 dB. Walaupun secara keseluruhannya nilai kehilangan dalam pencerai POF yang difabrikasi ini masih tinggi, prestasi ini dapat diperbaiki dengan penambahbaikan pada teknik pelakuran dan penggunaan alat yang lebih berkualiti. Teknik pemfabrikasi berkos rendah ini dipercayai boleh menghasilkan pencerai POF yang murah secara komersil, tetapi dengan kajian yang lebih mendalam pada teknik pelakuran, punca kehilangan dan cara meminimumkan kehilangan boleh diperoleh dan meningkatkan isyarat optik keluaran.
A quadratic stochastic operator (Qso) is usually used to present the time evolution of differing species in biology. Some quadratic stochastic operators have been studied by Lotka and Volterra. The general problem in the nonlinear operator theory is to study the behavior of operators. This problem was not fully finished even for quadratic stochastic operators which are the simplest nonlinear operators. To study this problem, several classes of QSO were investigated. In this paper, we study the fri)-Qso defined on 2D simplex. We first classify 4-(a)-QS0 into 2 non-conjugate classes. Further, we investigate the dynamics of these classes of such operators.
In the last few years we have seen a very rapid development on solving generalized geometric programming (GGP) problems, but so far less works has been devoted to MOGP due to the inherent difficulty which may arise in solving such problems. Our aim in this paper was to consider the problem of multi-objective geometric programming (MOGP) and solve the problem via two-level relaxed linear programming problem Yuelin et al. (2005) and that is due to simplicity which occurs through linearization i.e. transforming a GP to LP. In this approach each of the objective functions in multi-objective geometric programming is individually linearized using two-level linear relaxed bound method, which provides a lower bound for the optimal values. Finally our MOGP is transformed to a multi-objective linear programming problem (moLP) which is solved by reference point approach. In the end, a numerical example is given to investigate the feasibility and effectiveness of the proposed approach.
MeSH terms: Algorithms; Problem Solving; Programming, Linear; Biophysical Phenomena
In this paper, a model called graph partitioning and transformation model (GPTM) which transforms a connected graph into a single-row network is introduced. The transformation is necessary in applications such as in the assignment of telephone channels to caller-receiver pairs roaming in cells in a cellular network on real-time basis. A connected graph is then transformed into its corresponding single-row network for assigning the channels to the caller-receiver pairs. The GPTM starts with the linear-time heuristic graph partitioning to produce two subgraphs with higher densities. The optimal labeling for nodes are then formed based on the simulated annealing technique. Experimental results support our hypothesis that GPTM efficiently transforms the connected graph into its single-row network.
A third order Nakashima type implicit Pseudo Runge-Kutta method is presented. The free parameter was determined by minimizing the error bound. The stability region of the method was presented. Some problems on delay differential equations are tested to compare the accuracy of the proposed method with third order RADAU I.
The paper reconsiders the problem of the mixed convection boundary layer flow near the lower stagnation point of a horizontal circular cylinder with a second order slip velocity model and a constant surface heat flux studied recently by RoKa et al. (2013). The ordinary (similarity) differential equations are solved numerically using the function bvp4c from Matlab for different values of the governing parameters. It is found that the similarity equations have two branches, upper and lower branch solutions, in a certain range of the mixed convection parameters. A stability analysis has been performed to show that the upper branch solutions are stable and physically realizable, while the lower branch solutions are not stable and therefore, not physically possible. This stability analysis is different by that presented by RoKa et al. (2013), who have presented a time-dependent analysis to determine the stability of the solution branches.
MeSH terms: Hot Temperature; Paper; Convection; Physical Phenomena; Hydrodynamics
Komposit epoksi berpengisi hibrid OMMT (organ-monmorilonit) dan getah asli terepoksida (ENR) telah dihasilkan dengan menggunakan kaedah penyemperitan berskru kembar pusingan searah. Ujian regangan ke atas sistem epoksi yang dihasilkan menunjukkan modulus Young bagi komposit hibrid epoksi adalah lebih tinggi daripada resin tanpa pengisi dan nilai modulus didapati meningkat dengan peningkatan komposisi OMMT dalam matriks (setinggi 40% peningkatan). Hal ini dipercayai adalah disebabkan oleh sifat tegar lapisan MMT. Sementara itu, peningkatan luas permukaan kawasan antara fasa ekoran kehadiran fasa penambah didapati telah mengurangkan tegasan alah dan terikan akhir komposit hibrid yang dihasilkan. Pemeriksaan mikrostruktur komposit hibrid epoksi melalui TEM dan xRD mendedahkan taburan OMMT dalam matriks epoksi dengan susunan interkalasi dan pengelupasan. Analisis DSC ke atas sampel yang termatang menunjukkan bahawa T g sistem komposit hibrid adalah rendah berbanding dengan sistem perduaan (ESB dan ESLE). Pengurangan ketumpatan taut silang disyaki merupakan punca penyusutan T g ini.
Hydrogels were produced from cellulose derived from kenaf core powder with weight average molecular weight of cellulose was 1.68 x 105 and was dissolved in NaOHlurea solvent at -13°C. To obtain the optimal dissolving parameters, different percentage of NaOH, urea and kenaf core cellulose was used to study the degree of dissolution and formation of hydrogel. From the results obtained, it was found that the ratio of 6% NaOHI4% urea and 2% cellulose produced a good hydrogel. uv-Vis spectroscopy and xRD analysis were performed to analyze the transparency and crystallinity index of the cellulose solution and hydrogel, respectively. It showed that the hydrogel with the highest degree of solubility gave highest transparency due to the reduction of cellulose crystallinity as a result of the dissolution process. XRD analysis results showed the crystallinity of cellulose from kenaf core decreased by 70% after dissolution and hydrogel formation. Samples with 4% urea possess highest water content of 73% and decreased with increasing urea content.
The impact of isothermal temperature and holding time on the microstructural evolution process is studied. This process is used to produce globular microstructures during partial re-melting of AISI D2 cold work tool steel. The experimental results showed that the optimum process factors should be selected according to the criteria for average grain size and shape factor and also by acknowledging the distribution of the liquid phase around the grains. With increasing isothermal temperature and holding time, the liquid phase starts to diffuse into the grain boundaries and spread more evenly. Also, the equiaxed grains were transformed into near-globular shape, which makes the grain size and shape factor more favourable for thixoforming. The work shows that the optimal process condition for the thixoforming of AISI D2 is 1340°C and 5-min holding time, having a shape factor of 1.13 and a particle size of 51 ,um.
We report the growth of few-layer graphene (FLG) on a nickel (Ni) substrate using palm oil as a single carbon source by thermal chemical vapor deposition (T-cvD). Using an ample amount of vaporized palm oil resulted in the formation of a thick, amorphous carbon film on the Ni surface. By decreasing the amount of the carbon source supply, thin films consisting of graphite grains and FLG were obtained at growth temperatures of 900 and 1000°C, confirming the potential of using palm oil as a source for graphene growth. The occasional voids were obtained on the transferred film and these voids were confirmed to be areas where FLGs are formed. These FIEs are likely removed during the transfer process. Further reducing the amount of palm oil suppressed the coverage of graphite grains and increased the void area formation on the transferred films, proving the increase of FLG coverage.
The aim of this study was to evaluate on how heat treatments by microwave oven may affect the oxidative degradation of sunflower oil (SFO) and its blend with palm olein (Po). The blend was prepared in the volume ratio of 40:60 (Po: SFO, PSF). The samples were exposed to microwave heating at medium power setting, for different periods. In this study, refractive index, free fatty acid content, peroxide value, p-anisidine value, total oxidation (Tomx), specific extinction, viscosity, polymer content, polar compounds and food oil sensor value of the oils all increased, whereas iodine value and C 18:21C16:0 ratio decreased as microwave heating progressed. Microwave heating temperature increased with increasing heating time and longer heating times resulted in a greater degree of oil deterioration. The percentage of linoleic acid tended to decrease, whereas the percentage of palmitic acid increased. The effect of adding PO to SFO on the formation of free fatty acids and conjugated dienes during microwave treatment was not significant (p< 0.05). No significant differences in food oil sensor value was observed between SFO and PSF. Based on the most oxidative stability criteria, it can be concluded that the microwave heating caused the formation of comparatively lower amounts of oxidation products in PSF compared to SFO, indicating a lower extent of oxidative degradation of PSF.
The present research has been designed to understand the histomorphological development of lymphatic tissues of Cobb 500 strains of postnatal broiler chickens, aged between day old and D14 of Kelantan, Malaysia by gross and histological study. In the present study, it was found that the gross weight, length and width of the thymus, bursa of Fabricius and spleen were increased with the advancement of ages of the broiler chickens and was found higher from D14 to D28. Fine septa of connective tissue divide the thymus into lobes and lobules. The cortex of lobule is densely populated with lymphocytes. The bursal follicles were composed of a peripheral cortex which was rich in bursal cells and centrally depopulated medulla. The mucosal folds of the bursa were lined by pseudostratified columnar epithelium. The spleen has two compartments, the red and white pulp. The red pulp consisted principally of red blood cells, while the majority of the populations of white pulp were the lymphocytes. The histological mean length and width of the thymic lobules, bursal follicles and white pulp of the spleen were grown faster with the advancement of ages at D14 and D28. In conclusion, the increment of gross and histological parameters of lymphoid organs of broilers in the present study was due to aging of broilers.
MeSH terms: Animals; Bursa of Fabricius; Chickens; Connective Tissue; Erythrocyte Count; Erythrocytes; Lymphatic System; Lymphocytes; Lymphoid Tissue; Malaysia; Spleen