Aquaculture has the potential for contributing significantly towards enhancing farm income and hence towards

solving the poverty problem among farm smallholders. This study attempts to evaluate the economics of mixed farming

among sampled farmers in Central Perak and to assess the contribution of aquaculture to the overall farm income.

Income from aquaculture was found to be substantial and has the potential for further increase if farm resources are

allocated optimally or integrated agriculture with freshwater fish poly culture and broiler meat production can be

implemented

Alsagoff, Syed Kadir

Ariff Hussein, Mohd

Kuperan, K.

Universiti Putra Malaysia Institutional Repository

Pertanika 15(2), 179-182 (1992)COMMUNICATION IVA Simple Wood Quality Evaluation Techniqueusing y-Ray Attenuation in Some Tropical HardwoodsABSTRAKKertas ini melaporkan suatu teknik mudah untuk menentukan kualiti fizik bagi sebahagian kayu tropika. Pekalipengecilan linearsinargama bagi limaspesis kayu telah diukur. Keputusan menunjukkan bahawa terdapat hubunganlinear di antara pekali pengecilan dan ketumpatan kayu. Kajian ini dapat menunjukkan suatu kaedah mudahpenilaian tak musnah (PTM) kualiti kayu berdasarkan pencirian fiziknya.ABSTRACTThis paperreports a simple technique to evaluate the physical quality ofsome tropical woods. The gamma ray attenuationcoefficients offive wood species were measured and the results show that there is a linearrelationship between the attenuationcoefficient and density ofwoods. This study could be used to demonstrate a simple non-destructive evaluation (NDE) ofwood quality based on physical characteristics.INTRODUCTIONIn any manufacturing, fabrication or productionprocess quality is achieved through commitment,planning and performance. Qualityassurance wouldprovide adequate confidence that products satisfYspecified requirements through quality control,surveillance and audit (Zirnhelt 1990). However, inheterogenous materials that are subjected to age,climate and soils such as wood, quality assurance isassociated more with species, grain sizes, fibreorientation and moisture content. Wood density istherefore dependent upon these parameters.Measuring wood density or, in a qualitative sense,the density gradient is very useful in the qualityevaluation of forest products. The results can beused in estimating physical and mechanicalproperties, such as hardness, porosity, bendingstrength and stiffness, nail- and screw-holdingstrength, etc.Wood density may be measured using severaltechniques such as_gravimetric method and X-raydensitometer. Their drawbacks have been discussedelsewhere,forexampleLaufenberg (1986).Anothermethod is using y-ray attenuation techniques(Laufenberg 1986; Moschler and Dougal 1988).The nondestructive quality of this measurementallows the sample to be investigated before using itas a final product without damaging the part beingtested. The principle used is to pass y radiationthrough an object and the attenuated intensity of'radiation beam is measured by a radiation detector.The attenuated intensity in a good geometryexperiment can be described by the LambertEquation 1= 10exp(-Ilx) where 1is radiation intensi tyafter attenuation (counts!s), 1 is unattenuatedradiation intensity (counts/s): Il is the linearattenuation coefficient (cm-l ) and xis the absorberthickness (cm). Since the beam intensity attenuationis due to the interaction ofphotonswith electrons ofatoms of the object the attenuation coefficient istherefore dependent upon atomic number of theatoms and energy of the photons, i.e. the linearattenuation coefficient is a function of the atomicnumber, Z, and energy, E, oq.J.(Z,E) (Elias etaL 1986,1990a) .A scintillation counting system commonlyapplied in this technique has the disadvantages ofhaving poor counting efficiency, is relativelyexpensive and requires some knowledge ofelectronic signal processing techniques. However,when the scintillation counter is not available gas-filled detectors such as G-M tubes and proportionalcounters could also be used. They are known to have-100% counting efficiency. The electronic circuitryELIAS SAlON, ZAINALABIDIN SUlAlMAN, PUVANASVARI .S, MOHD YUSOF SUlAlMAN AND MOHD HAMAMI SAHARIRESULTS AND DISCUSSIONFig. 1: Ratio of unattenuated and attenuated radiation beamcounts against wood thicknessfor kapur (Dryobalanops aromatica)at r- ray energies 59.5 keVand 122 keVFig. 1 shows the curves of the ratio of count ofthe radiation beam, log (Joll) versuswood thickness,for two y-ray energies, for Kapur. The gradient givesthe linear attenuation coefficient of the wood. Atthe lower y~ray energy the linear attenuationcoefficient is higher than that of the higher energy.Samples from other wood species produce graphs10•Wood Thicknell (CIII)59.5 keYWood Type: Kapur1.61.21.00.20.8~o 0.6! 0."The species and oven-dry volume densities of thewoods used in this experiment are shown in Table1. Also shown are the hardness classification andcolour of the samples which were taken from abooklet on common commercial timbers ofPeninsular Malaysia ofthe Forest Research Instituteof Malaysia (FRIM 1990). The results show thatthere is a consistent relationship between the densityand physical quality of classification of hardness ofthe woods. The density increases with an increase inthe hardness. For heavy hardwoods the density ishigher than that of the medium hardwoods. Notethat in the commercial timbers of PeninsularMalaysia, Cengal and Tembusu are classified asheavy hardwoods, Kapur is a medium hardwood,while Sepetir andAcaciaaJ;e lighthardwoods (FRIM1990). Also included in this study is Pine, which hasbeen classified as a softwood as indicated in thetable.radiation while closing the shutter of the sourceholder. The countingwas done several times duringand after the experiment to ensure no abnormalityin the counts of the background due to gasamplification in the counter. When there was nosample between the source and the detector thecount was taken as the unattenuated radiationintensity.MATERIALS AND METHODSof a G-M tube is often built inside a scaler, so itsusage does not require a knowledge ofelectronics,which is favourable to most wood technologists. Inpursuing our main objective to design a simplenondestructive evaluation (NDE) system for qualityevaluation offorest products (Elias et al. 1990b) ,wefirst investigated the basicprinciplesofmeasurementusing instruments commonly known to manyscientists. This paper describes a simple techniqueto evaluate quality based on "tray attenuationcoefficients ofsome tropical hardwoods using a G-M counter.Oven-dried wood samples were machined intoequal-sized blocks of rectangular shapeapproximately 4 x 2 x 2 em and weighed. Thespecimens were carefully examined for uniformappearance of the grain and straightness of fibresbefore cutting. Five samples were prepared for eachspecies and each block has at right angles, smoothand parallel surfaces. The volume ofthe samples foreach block was determined by multiplying theiraverage thickness x width x length. For each samplethe thickness, width and length were measured atseveral points. The density of the woods was thencalculated in the usual manner. The overalluncertainty ofthewood density is indicated in Table1 andwas due to volume determination ofthe woodonly.The linear attenuation coefficients for each ofthe wood species were measured separately by atransmission method. The 241Am and 57CO radioactivesources which emit low energy photons at energies59.5 keV and 122 keV respectively were used. Theactivity for 241Am and 57CO sourceswas 7.39 x 109 and6.61 x 106 becquerels respectively. Acollimated"traybeam was allowed to pass through the samplesperpendicular to the grain direction and theattenuated beam intensitywas then measured atfivedifferent thicknesses from 2 em to 10 em. For eachthickness, at leastfive series ofcounts were recordedfrom a scaler to obtain the average count. In orderto determine the operational voltage of the G-Mtube the counts atvarious applied voltageswere firstmeasured and a plateau curve was drawn. From thecurve the applied voltage was set at 600 voltsthroughout the experiment corresponding to theconstant count rate as registered by the scaler. Abackground count was established by countingradiation beam intensity of the environmental180 PERTANIKA VOL. 15 NO.2, 1992A SIMPLE WOOD QUALITY EVALUATION TECHNIQUETABLE 1Oven-dry volume density and classification of some tropical hardwoods used in this studyDensity Class RemarksLocal Name (species) (kg m-') (colour)Cengal 947±12 Heavy hardwood Yellow-brown(Neobalanocarpus heimii)Tembusu 857±16 Heavy hardwood Light yellow(Fagraea fragrans)Kapur 715±20 Medium hardwood Rose-red(Dryobalanops aromatiw)Sepetir 687±22 Light hardwood Golden-brown(Sindora velutina)Acacia 579±I6 Light hardwood Yellow-brown(Acacia mangium)Pine 530±18 Softwood Creamy-white(Pinus canbaea)ofa similar pattern butwith different gradients. Fig.2 shows the y-ray linear attenuation coefficient ofthe woods plotted against the density. The resultsshow that the attenuation coefficient increaseslinearly with an increase in wood density. Theattenuation coefficientofheavy hardwoods is higher0.18 ,..-----'---------------,'S2 0 . 17".~.;C 0.16~.~ 0.15~~ 0.14.5O. 13.5,..,0.12 +----..------,----..---,-----1500 600 700 800 900 1000Wood density (kg m-J )Fig. 2: Linear relationship beteween y-ray attenuation coejjicientand density ofsome tropical hardwoods at energies 59.5 keVand122 keV.than that of medium and light hardwoods. Ourresults are in agreement with previous results ofMoschler and Dougal (1988) who measured theattenuation coefficients for some temperate woodsof densities from about 350 to 800 kg m-3 andobtained the values ofll from about 0.05 to 0.16 cm-I using 241Am source. Nevertheless, the differencesof less than 5% compared with our results areexpected considering the fact that their equipmentand radiation beam geometry were different fromthe present work. The results indicate that woodquality can be based on the y-ray attenuationcharacteristics. Asimple non-destructive evaluationtechnique could be developed to evaluate the qualityof wood products based on the "tray attenuationcoefficients which can be made faster, are non-invasive and offer better resolution than thetraditional cutting and weighing method ofdensitydetermination.The results also show that the attenuationcoefficient at energy 59.5 keY is higher than that of .the 122 keY energy, in line with expectations. Thismeans thata better characterization ofwood qualityis achieved at lower energy than that of the higher"tray energy. Nevertheless, atvery low "trayenergiesthe variation of the attenuation coefficient withinthe same wood species was observed by someresearchers (Olson and Arganbright 1981). Sometrace elements have a large elemental attenuationcoefficient in low energy range. This could beovercome by not using radiation ofvery low energy,such as 6 keY photons from 55Fe source. Moisturepresent in wood also increases the attenuationcoefficient (Loos 1961) and thus, the moisturecontent of the wood must be determined prior toany attenuation coefficient measurements.ACKNOWLEDGEMENTSWe would like to thank the Universiti PertanianMalaysia Research Council for financial supportunder contract no. 50205-90-20. The cooperationof the Faculty of Foresty, Universiti PertanianPERTANIKA VOL. 15 NO.2, 1992 181ELIAS SAlON, ZAlNAL ABIDIN SULAIMAN, PUVANASVARI .S, MOHD YUSOF SULAIMAN AND MOHD HAMAMI SAHARIMalaysia in providing the wood samples isappreciated.ELIAS SAlON, ZAlNALABIDIN SULAlMAN,PUVANASVARI SUBRAMANIAM,MOHD YUSOF SULAlMANand MOHD HAMAMI SAHARI'Department ofPhysicsFaculty ofScience and Environmental StudiesUniversiti Pertanian Malaysia43400 UPM Serdang, Selangor DarulEhsan,Malaysia.'Department ofForest ProductsFaculty ofForestyUniversiti Pertanian Malaysia43400 UPM Serdang, Selangor DarulEhsan,Malaysia.REFERENCESELIAS, S., S. ZAI TAL ABIDIN, A. ANUAR and W.HUSI .1986. Determination of Effective AtomicNumber of Rubber. Pertanika 6(3): 95-98.ELIAS, S., S. ZAINAL ABIDIN and S. MOHO YuSOF. 1990a.Characterization of Rubber using y-RayAttenuation Technique. In Proceedings of Scienceand Nuclear Technology Conference, UKM Bangi,Malaysia 196-206. (Bahasa Melayu).ELIAS, S., S. ZAINAL ABIDIN, S. MOHO YUSOF, P.SUBRAMANIAM, S. MOHO HAMAMI and O.]AMALUOlN. 1990b. Towards Evaluation of WoodQuality using Non-destructive y-Ray AttenuationMethod. Apaperpresented at the National Seminaron Physics in Industry, UTM Skudai, Malaysia. (inMalay).FRlM. 1990. Common Commercial Timbers of PeninsularMalaysia. Forest Research Institute of Malaysia.LAUFENBERG, T.L. 1986. Using Gamma Radiation toMeasure Density Gradients in ReconstitutedProducts. ForestProdJ 36(2): 59-62.Loos, W.E. 1961. The Relationship between GammaRay Absorption and Wood Moisture ContentandDensity. Forest Prod.J 11(3): 145-149.MOSCHLER, W.W. and E. F. DOUGAL. 1988. CalibrationProcedure for a Direct Scanning Densitometerusing Gamma Radiation. Wood andFiberSci. 20(3):297-303.OLSON,]. R. and D. G. ARGANBRlGHT. 1981. Predictionof Mass Attenuation Coefficients of Wood. WoodSci. 14(2): 86-90.ZIRNHELT,]. H. 1990. QualityAssurance Through NDT,A paper presented at Seminar on Quality ThroughNDT, 27 November 1990, Subang, Malaysia.(Received 7July 1991)182 PERTANIKA VOL. 15 NO.2, 1992

A Linear Programming Analysis of

Integrated Agriculture-Aquaculture Mixed Fanning

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A Linear Programming Analysis of Integrated Agriculture-Aquaculture Mixed Fanning

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