WAVY SYCAMORE MAPLE: RELATIONSHIPS BETWEEN
ANATOMICAL, PHYSICAL, MECHANICAL, AND
VIBRATIONAL PROPERTIES
AHMAD ALKADRI
GRADUATE SCHOOL
BOGOR AGRICULTURAL UNIVERSITY BOGOR
iii
COPYRIGHTS STATEMENT
I declare that this thesis, entitled Wavy Sycamore Maple: Relationships be-tween Anatomical, Physical, Mechanical, and Vibrational Properties is my own work with the direction of the supervising committee and has not been submitted in any form for any college except in AgroParisTech centre de Nancy and Univer-sité de Lorraine, France (required by the Double Degree Master Program—the joint Master program held between the Program Study of Forest Products Science and Technology of Bogor Agricultural University and Bois Forêt et Développe-ment Durable of AgroParisTech centre de Nancy and Université de Lorraine). Information and quotes from journals and books have been acknowledged and mentioned in the parts of the thesis where they appear. All complete references are given at the end of the paper.
I understand that my thesis will become part of the collection of Bogor Ag-ricultural University. My signature below gives the copyright of my thesis to Bo-gor Agricultural University.
iv
SUMMARY
AHMAD ALKADRI. Wavy Sycamore Maple: Relationships between Anatomi-cal, PhysiAnatomi-cal, MechaniAnatomi-cal, and Vibrational Properties. Supervised by IMAM WAHYUDI and IRIS BRÉMAUD.
Sycamore maple (Acer pseudoplatanus L.) is a wood species particularly known for its wavy grain figures and its high-value utilization among luthiers and craftsmen for musical instruments or furniture making. Although past separate studies had determined its properties, little had been done in order to quantify the waviness characteristics of its unique patterns and the correlations between its properties which include the anatomical, physical, mechanical, and vibrational or acoustical characteristics. Backed by its high degree of valuation and utilization, this research was conducted in order to study the characteristics of sycamore ma-ple and how they correlate with each other.
The specimens taken for the measurements were procured from different trees with various surface figures. Vibrational and mechanical measurements were conducted using Vybris, a semi-automated device developed by Gifu and Kyoto University, Japan and manufactured in LMGC (Laboratoire de Mécanique et Gé-nie Civil) in Montpellier, France by taking into account the radial and longitudinal directions and its local variations. Waviness’ characteristics were quantified by measuring the wood blocks which were splitted parallel to the grain, while ana-tomical properties such as microfibril angle and rays’ dimensions were measured using light microscopy.
Results from this study provide a dataset regarding the properties of wavy sycamore maple. Through statistical analysis, it can be concluded that there are significant correlations between the measured parameters, particularly between waviness, microfibril angle, the specific modulus elasticity, and damping coeffi-cient by internal friction of the wood in longitudinal direction. The anisotropy properties were found to be very low but was not satisfactorily explained by the anatomical features studied. Future studies using similar methods should be con-ducted with larger number of speciments and refined statistical analysis models. Analysis regarding the mechanical model of wavy-grain wood, which may include variables such as MFA, grain angle, and waviness, should be conducted.
v
RINGKASAN
AHMAD ALKADRI. Maple Sycamore Bergelombang: Hubungan antara Sifat Anatomi, Fisis, Mekanis, dan Akustik. Dibimbing oleh IMAM WAHYUDI dan IRIS BRÉMAUD.
Maple sycamore (Acer pseudoplatanus L.) adalah spesies kayu yang dikenal karena pola seratnya yang bergelombang dan pemakaiannya sebagai bahan baku furnitur serta alat musik. Walaupun banyak penelitian terdahulu telah berhasil menentukan berbagai macam karakteristiknya, sedikit di antaranya yang telah melakukan kuantifikasi pola gelombang seratnya dan hubungan antar sifat-sifatnya yang mencakup dari anatomis, fisis, mekanis, hingga akustik. Mengingat penggunaannya yang intensif dan nilai ekonominya yang tinggi, penelitian ini pun dilakukan untuk menentukan sifat-sifat kayu maple sycamore dan korelasinya an-tara satu sama lain.
Spesimen yang digunakan dalam pengukuran diperoleh dari berbagai pohon yang memiliki pola permukaan bergelombang yang berbeda-beda. Penentuan sifat mekanis dan akustik dilakukan dengan menggunakan Vybris, alat semi-otomatis yang dikembangkan oleh Universitas Gifu dan Kyoto di Jepang serta dirakit di LMGC (Laboratoire de Mécanique et Génie Civil) di kota Montpellier, Perancis pada arah orientasi radial dan longitudinal. Variasi lokal untuk kedua arah orienta-si tersebut juga ditentukan. Kuantifikaorienta-si karakteristik pola serat gelombang dil-aksanakan dengan mengukur spesimen balok yang dibelah pada arah sejajar dengan serat, sedangkan sifat-sifat anatomi seperti sudut mikrofibril dan dimensi jari-jari diukur menggunakan mikroskop cahaya.
Penelitian ini menghasilkan set data hasil pengukuran sifat-sifat kayu maple sycamore bergelombang. Melalui analisis statistik, korelasi signifikan antar pa-rameter berhasil ditentukan, terutama antara derajat kegelombangan dengan sudut mikrofibril, dan antara sifat-sifat anatomi dengan modulus elastisitas spesifik serta peredaman oleh friksi internal kayu pada arah longitudinal. Pada penelitian ini, nilai sifat-sifat anisotropi kayu yang diamati sangat rendah dan tidak bisa dijelas-kan dengan cukup memuasdijelas-kan menggunadijelas-kan sifat-sifat anatomi yang telah diten-tukan. Penelitian berikutnya yang menggunakan metode serupa harus dilakukan dengan jumlah spesimen lebih besar dan model analisis statistik yang lebih men-dalam. Analisis model mekanis kayu bergelombang, yang dapat mencakup varia-bel-variabel seperti MFA, sudut serat, dan derajat kegelombangan serat, pun sebaiknya dilakukan.
vi
© Copyright 2017, Bogor Agricultural University (IPB)
All Rights Reserved by Law
It is prohibited to quote part or all of this paper without mentioning or citing the sources. Quotation is allowed only for educational purposes, research, writing papers, preparing reports, writing criticism, or review of an issue, and the cita-tions will not harm the interests of IPB
Thesis
In partial fulfillment of the requirements for the degree of Master of Science
at
Forest Products Science and Technology Study Program
WAVY SYCAMORE MAPLE: RELATIONSHIPS BETWEEN
ANATOMICAL, PHYSICAL, MECHANICAL, AND
VIBRATIONAL PROPERTIES
GRADUATE SCHOOL
BOGOR AGRICULTURAL UNIVERSITY BOGOR
2017
x
FOREWORD
The author would like to thank the administration of Master of Science pro-gram of Forest Products Science and Technology of Bogor Agricultural Univer-sity and Master Program of Bois Forêts et Développement Durable (BFD) of Ag-roParisTech centre de Nancy and Université de Lorraine for their academic co-operation in the form of Double Degree Master Program, supported with the scholarships of Beasiswa Unggulan from Ministry of Education and Culture of Indonesia and Bourse de couverture social de gouvernement Française from French’s Ministry of Foreign Affairs. Without said cooperation, such chance to conduct this research will not come into fruitition.
The author is grateful to LMGC (Laboratoire de Mécanique et Génie Civil) and Cirad (Centre international de cooperation et recherche en agronomie) in the city of Montpellier, France, who offered the information and opportunity for this research. Without all their supports, both in materials, equipment, and financial, this research would not be able to be conducted. The authors would also like to thank La Région Languedoc-Roussillon for the financial support, as part of the project “Chercheur(se)s d’Avenir” awarded to Dr. Iris Brémaud.
Special thanks to Professor Joseph Gril, the head of Wood Research Group at LMGC; to Dr. Iris Brémaud and Dr. Patrick Langbour who supervised this re-search in Montpellier. Special thanks also directed to Professor Imam Wahyudi, the author’s supervisor in the Department of Forest Products, Faculty of Forestry, Bogor Agricultural University, Indonesia; to Professor I Wayan Darmawan, the coordinator of the double degree Master program of Bogor Agricultural Universi-ty, Indonesia; and to Professor Mériem Fournier, the director and coordinator of double degree Master program of AgroParisTech centre de Nancy. Special thanks are also directed to Capucine Carlier, the PhD student in LMGC’s Wood Research Group, who worked on the violin-making tonewood, for sharing and exchanging the scientific information about the subject.
Finally, the author would like to express his gratitude to his friends and col-leagues: Capucine (again), Agnès, and Vivien for their companionships, high spir-it attspir-itude, great work ethos, posspir-itive outlooks, and the bicycle; to Anna for the guitar; to Alban, Daniel, and Marie-France Thèvenon for their help and hospitality during the course of this research at the laboratory of wood anatomy at Cirad; and to all other professors, researchers, staff, technicians, Post-Docs, PhD students, in-terns and any other individuals at LMGC, Cirad, AgroParisTech, and Bogor Agri-cultural University who have helped the author, both directly and indirectly, in conducting this research.
The author recognizes that this research is still far from perfect. Thus, sug-gestions and constructive criticisms are expected in order to improve this work.
Bogor, December 2016
xi
TABLE OF CONTENTS
SUMMARY iv
RINGKASAN v
SHEET OF APPROVAL ix
FOREWORD x
TABLE OF CONTENTS xi
LIST OF TABLES xii
LIST OF FIGURES xii
1 INTRODUCTION 1
Background 1
Formulation 2
Objective 2
Benefits 2
2 MATERIALS AND METHODS 3
Location and Period of Research 3
Materials Preparations 3
Measurements 4
Data Analysis 8
3 RESULTS 10
Vibrational Properties 10
Microfibril Angle 11
Waviness 12
Ray Dimensions 14
Correlation Between Parameters 14
4 DISCUSSIONS 21
5 CONCLUSIONS AND SUGGESTIONS 24
Conclusions 24
Suggestions 24
REFERENCES 24
xii
LIST OF TABLES
1 Measurement results of the sycamore maple wood’s physical and
vibrational properties 16
2 Measurement results of the sycamore maple wood’s anatomy features 17 3 Measurement results of the sycamore maple wood’s wavy grain
properties 18
4 r and p-value of pearson-product moment correlation between paired
parameters 19
5 Coefficients of regression of tanδL with MFA and waviness 20 6 Coefficients of regression of E’L/ρ with MFA and waviness 20
LIST OF FIGURES
1 Specimen preparation from the back plates toward the small blocks
needed for MFA and ray dimensions measurements 3
2 Preparation of specimens used in vibrational measurement 4 3 Depiction of split block specimen, from which two parameters can be
measured: the wavelength (λ) and amplitude (A=2A/2) 7
4 Illustration of grain angle measurement. 8
5 Vibrational properties results for both R and L directions. 10 6 Local variations (of specimens from each plate) of E’/ρ and tanδ of L
and R specimens. 11
7 MFA measurement methods 12
8 Microfibril angle (MFA) results for the twelve plates/specimens 13 9 Waviness (w) results for the twelve original plates/specimens 13 10 Example of waviness figures of the sycamore maple wood 14 11 Rays of the waviest wood and the least wavy one (specimen H, images
on the right) 15
1
1
INTRODUCTION
Background
Sycamore maple (Acer pseudoplatanus L.) is a hardwood tree species well-adapted for cold temperatures and mountainous climate and broadly distributed throughout European land (Krabel and Wolf 2013). Because of its rapid growth and high versatility (it can grow almost everywhere as long as the soil is not too dry or poor), it is considered as an invasive species in several regions (Peterken 2001; Chytrý et al. 2008; Morecroft et al. 2008). Although its low biological dura-bility makes it unsuitable for outdoor construction purposes, its creamy timber and excellent wood surface make it aesthetically pleasing, and it is mainly used in fur-niture, flooring, and musical instruments (Bucur 2006; Krabel and Wolf 2013).
Sycamore maple is particularly favored by luthiers and craftsmen in manu-facturing the violin, guitar, mandolin, and other musical instruments (Bucur 2006; Wegst 2006). Several factors contribute in the favorability of sycamore maple as a material in musical instrument making. Although some studies such as Wegst (2006) suggest that its acoustical properties are what make it highly suitable for the back-board of several types of musical instruments such as violin or guitar, others have suggested that craftsmen tend to determine the selectability of wood based on more multi-factorial criteria including also visual or cultural preferences (Brémaud 2012; Buksnowitz et al. 2012).
Psychosensory study on this subject is currently still limited; however, it has been suggested that there is a correlation between the wood’s physical appear-ance—or, in the case of sycamore maple, its wavy-grain—with its mechanical-acoustical properties (Kudela and Kunštár 2011). It needs to be noted that, in their study, Kudela and Kunštár (2011) compared the physical-mechanical-acoustical characteristics of wavy maple wood with those of the control (non-wavy wood). Thus, even though they have determined that there are significant differences in characteristics between wavy and non-wavy or normal wood, the degree of corre-lation, or the depth of the relationships between the wood’s wavy-figure charac-teristics and physical-mechanical-acoustical properties, such as the factors causing and being affected, has still not been determined.
Although little is known on the relations between the wavy grain character-istics and physical-mechanical-acoustical properties, several studies have tried to determine the factors causing the formation of this particular trait in order to re-produce it. Various studies have shown the possibility of giving external stresses, for the wavy grain is also known as another form of reaction wood, to stimulate the specific genetical agents within the tree to produce phytohormones like auxin and ethylene for prompting the formation of wavy grain (Nelson and Hillis 1978; Rohr and Hanus 1987; Ewald and Naujoks 2015). These studies have also shown that the formation of wavy grain are affected by genes and phytohormones, which is also the case with the formation of wood on microstructural level (Pilate et al. 2004). However, study on the anatomical characteristics of sycamore maple with wavy wood characteristics is still very limited.
2
Evans 2003; Beery et al. 2007). Several anatomical factors affecting wood me-chanical properties have been determined. Along the grain (longitudinal direction of wood), microfibril angle (MFA), is known as the main determinant of modulus of elasticity (MOE, or E’, or Young’s Modulus) and specific modulus (E’/ρ), as well as of internal friction (or damping, tanδ) (Obataya et al. 2000). Fiber angle has a similar effect on mechanical-vibrational properties (Brémaud et al. 2011). The rays may affect the mechanical and physical properties on radial section (Burgert and Eckstein 2001; Reiterer et al. 2002) and possibly also, to a lower extent, on longitudinal direction (Tippner et al. 2013). In short, the relationships between anatomical and physical-mechanical-acoustical properties of the wood have been well-documented. However, in sycamore maple with wavy grain wood, the correlations between those characteristics have not yet been well-studied.
Formulation
Interested by the high value and utilization of wavy sycamore maple, many researchers had conducted studies in order to better understand its properties. However, the correlations between its physical, mechanical, acoustical, and ana-tomical properties (including the wavy grain) have not been clearly determined. Therefore, the questions that needed to be asked: how do said properties of syca-more maple correlate with each other? Which characteristics are related with oth-ers, and how much of those relationships are significant?
Objective
This research aims to better characterise sycamore maple wood presenting a gradient of wavy figure and to determine the potential correlations among anatom-ical (wavy grain, MFA, rays’ characteristics), physanatom-ical, mechananatom-ical, and acoustanatom-ical properties (including specific modulus of elasticity, damping coefficient, and their anisotropy). The sample selection included a wide variability of wood surface with varying level of grain waviness, making it possible to determine the relation-ships between those parameters by using statistical analysis.
Benefits
3
2
MATERIALS AND METHODS
Location and Period of Research
This research was conducted at the Laboratory of Mechanics and Civil En-gineering (Laboratoire de Mécanique et Génie Civil) and French Agricultural Re-search Centre for International Development (Centre international de cooperation et recherche en agronomie) in Montpellier, France from February to July 2016.
Materials Preparations
Specimens Preparations for Anatomical Measurements
Twelve quarter-cut wedge shaped boards for violin back plates, labelled A to L, were used in this study, with the approximate dimensions of ± 40 cm × 13 cm ×
2.5 cm (connecting side) or 1 cm (edge). They were obtained from several violin makers and specialized wood suppliers from Romania, Bosnia, and France. Spec-imens from each plate were prepared according to Figure 1. The first cut produced a trapesium-shaped block 2.5—3 cm high, named block i. From block i, second cuttings were conducted to produce block ii and block iii, with dimensions 2 × 2.5
× 3 cm3. Each block ii from each specimens were used for waviness measurement. Block iii were then cut to produce block iv and block v used for MFA and ray di-mensions measurements, respectively.
4
Specimens Preparations for Vibrational Measurements
For vibrational properties measurement, using the existing sampling plan that was also used in other assessments of within-plate variability using vibratio-nal tests (Brémaud et al. 2010, 2012), the back plates were cut into small strip specimens with the dimension of 150×12×2 mm3 (L×R×T) for longitudinal spec-imens, and 120×12×2 mm3 (R×L×T) for radial specimens (Figure 2). The sam-pling plan allows to study the distribution of properties within plates.The variation of specimen thickness must be reduced as much as possible for it provides a pri-mary source of errors in the measurement of the specific modulus (E’/ρ) (Bré-maud et al. 2012). Thus, after being procured, all specimens for vibrational testing were conditioned for at least 2 weeks in standard air-dry conditions (20±1°C and 65±5% relative humidity-RH) in order for them to reach dimensional stabilization.
Figure 2 Preparation of specimens used in vibrational measurement
Measurements
MFA Measurements
Specimens for MFA measurement were prepared based on the light micros-copy MFA methods described by Senft and Bendtsen (1985). The blocks used for MFA measurements were those of block iv. Each of them were submerged in wa-ter, taken out, oven dried, and then re-submerged again. This cycle was conducted at least two times in order to create cracks within the wood cells which will en-hance the appearance of MFA.
5 immersed in a solution of 2% iodine-potassium iodide (IKI) for 2 to 10 seconds. Then, sections were placed on a slide and excess solution were blotted using a paper towel. Two drops of 60% nitric acid (HNO3) were added to the section before applying a coverslip. The iodine filled the cracks between the microfibrils, thus making the MFA visible as dark streaks along the cell wall. Pictures of the MFA were taken using a light microscope with 600× enlargement and the angles were measured using ImageJ.
During the course of the measurements, because of the different surface cut condition of each sample, the angles measurements were not always conducted according to the same strict rule. The MFA themselves are very hard to be ob-served directly using light microscopy because the fibrils in the cell walls, espe-cially in S2 layer, are tightly formed (Long et al. 2000). The pretreatment given before the slicings relieved the tightness a little, but not by a wide margin, and thus the resulting surfaces made it necessary to measure the MFA using one of the following techniques:
a. the MFA was measured according to the angle of the cracks between microfibrils and complemented by the angle of the pits (Donaldson 2007),
b. the MFA was measured according to the MFA directly. This rarely occured, for in order to be able to observe and measure the MFA using light microscopy, the “crackings” or defibrilation between the microfibrils must happened exactly between each one of them within one fiber cells. These rare occurences could be chalked up to the low tightness between the microfibrils and the low amount of lignin or however small they are, within the same or neighbouring cells. If the angles between them are consistent and not vary by a high amount, then the angle of the pits can be said to be similar, or the same, with the MFA. Also observed were the “tails” of the pits, or the elonged lines from both end of the pits, which normally correspond more with the MFA than the “body” of the pits.
Examples of each of the mentioned MFA measurement methods can be seen in Figure 7.
Rays Dimensions Measurement
6
sections were dehydrated in several levels of alcohol solution, starting from 25%, 50%, 75%, towards absolute (>99%). Fully dehydrated, the sections were placed on a slide and given a coverslip. Pictures were taken using a light microscope with 40× enlargement and the rays’ dimensions were measured using ImageJ. Meas-ured parameters were the height and width of, respectively, large rays and small rays, and the percentage of the surface of the section they represent.
Wavy Figure and Grain Angle Measurement
Block ii were splitted parallel to the grain direction (Figure 3). The resulting splits show clear wave-like figures which were then scanned and measured using ImageJ. To measure the wavy grain, it was assumed that: a) the wave-like figures were consistent throughout the part of the wood which possesses it, b) the wave-like figures followed the standard equation form of a sinusoidal wave (formula 1) with two parameters taken into account: the amplitude (A) and wavelength (l).
y=A⋅sin 2πx calculated as dy/dx (Figure 4). Slope = tanθ with θ in radians (rad) unit. Thus:
θ = 180 Therefore, the θ (rad) can be calculated as:
θ =dy
7
This led us to be able to express the degree of waviness, or ‘how wavy’ the wood is, through the calculation of average grain angle (θaverage, formula 4) and max grain angle (θmax, formula 5). The grain angle (θ) is calculated because it has been known to strongly influence the mechanical and physical characteristics in wood, and thus the results will be valuable for further experiment and reference for other studies in this field.
Moreover, the third way to express the degree of waviness is by simply calculating the ratio between the A and λ, as shown in formula 6. This value is also written as waviness (w) and, as can be clearly seen, derived from the θaverage (formula 4) It is, however, much simpler to calculate and the value can be used to visualize the wood’s waviness better.
w= A
λ (formula 6)
8
Figure 4 Illustration of grain angle measurement.
Explanation: Maximum grain angle can be measured in the transition point between peak and valley of the wave, which means x = 0.5λ
Vibrational Measurement
The measurement of vibrational properties of the specimens was conducted upon the principle of non-contact forced vibrations of free-free slender beams (Obataya et al. 2000; Ono and Norimoto 1983), using a semi-automated device « Vybris » developed and manufactured in LMGC (Laboratoire de Mécanique et Génie Civil) in Montpellier, France (Brémaud 2006). The device uses a laser-triangulation sensor in order to measure the displacement with 10 µm resolution, while simplifying the positioning of the specimens with a distance of detection 40±4 mm. Testing was conducted through a program specifically developed with Labview® by (Brémaud et al. 2012). Measured values are internal friction or damping coefficient (tanδ), determined both in the frequency (tanδ ≈ Q-1) and time (tanδ ≈ λ/π) domains (both of those methods produce identical results on average), and the specific dynamic modulus of elasticity (E’/ρ in GPa) (Brémaud et al. 2012).
Two scans were performed in the measurement of each single specimen. In the first one, a wide frequency range (150—750 Hz for longitudinal (L) specimens and 80—500 Hz for radial (R) ones) was emitted and the resulting vibration is measured to identify the first resonant frequency fR. Afterward, a second scan was conducted using narrower frequency range (0.98×fR—1.02×fR) in order to measure the damping by bandwidth or quality factor (Q = 1/tanδ or tanδ = Q-1). At least three repetitions were conducted for each specimen, with ex-perimental error being ≤2.5%, andpresented values are the average ones.
Data Analysis
determina-9 tion (R2 or r2) which indicates the proportion of the variance in the dependent variable that is predictable from the independent variable. After the r has been determined, its significance was tested using p-value, which was then compared to the specified value for the considered degree of freedom ( = number of samples – 2 ). In this study, the degree of confidence used is 5%, which means if the p-value is lower than 0.05, the r between the two datasets will be regarded as indicating a significant correlation.
The analysis return parameters as follow:
a. Pearson product-moment coefficient of correlation (r), a measure of linear correlation between two sets of data ({x1,....,xn} and {y1,....,yn} containing n values) which is then calculated through the following formula:
r= i=1(xi−x CORREL(array1, array2) with the array1 is the cell range of first data sets ({x1,....,xn}) and array2 is the cell range of the second data sets ({y1,....,yn}).
c. Coefficient of determination (R2 or r2), which indicates the proportion of the variance in the dependent variable that is predictable from the independent variable. In this study, the intercept is included thus the r2 is simply the square of the coefficient of correlation (r).
10
3
RESULTS
Vibrational Properties
Results from the vibrational measurements on all specimens (Figure 5) show that, overall, the relationship between damping coefficient tanδ and specific modulus E’/ρ of sycamore maple followed a trend similar to the “standard” rela-tionship established on numerous species (Ono and Norimoto 1983; Brémaud et al. 2012). However, in L direction, tanδL of the most wavy specimens tend to be higher than the standard trend. While in R directions, both E’R/ρ and tanδR of all tested maple tend to be smaller (Figure 5).
Figure 5 Vibrational properties results for both R and L directions.
Explanation: in this figure, comparison also made between the relationship found between internal friction tanδ and E’/ρ as obtained on all specimens measured in this study with the “standard” relationship established on numerous species (Ono and Norimoto 1983; Bré-maud et al. 2012).
11
Figure 6 Local variations (of specimens from each plate) of E’/ρ and tanδ of L and R specimens.
Explanation: Distance between locations is 2 cm. For L specimens, location N°1 is closer to the pith and N°7 is closer to the bark in the tree. For R specimens, the location indicates the vertical (axial) position; Nº 1 closer to the top and Nº 4 closer to the bottom. Continu-ous red line indicates the average trend over all plates.
When considering the average values of vibrational properties per plate (Ta-ble 1), longitudinal properties ranged from 9.7 to 19.7 GPa for E’L/ρ and from 0.0085 to 0.0156 for tanδL. By comparison, the average values over 105 species of temperate hardwoods were of 17 GPa for E’L/ρ and of 0.0103 for tanδL (Brémaud 2012). Radial properties ranged from 1.9 to 3.0 GPa for E’R/ρ and from 0.022 to 0.026 for tanδR. Furthermore, ratios of anisotropy ranged from 4.0 to 7.3 for spe-cific modulus E'/ρ (L/R) and from 1.7 to 2.8 for damping tanδ (R/L). Wavy syca-more maple is less anisotropic than other hardwood species, for which the average anisotropic ratios were 7.8 (L/R) for specific modulus E'/ρ and of 2.7 (R/L) for damping tanδ (Brémaud et al. 2011).
Microfibril Angle
12
The average MFA per plate ranged from 8.7° to 20.4° (Table 2). The statistical summary of the whole MFA data shows that there were several outliers from plate B, C, E, G, and L (Figure 8).
Figure 7 MFA measurement methods
Explanation: from left to right, a) using the angle of the cracks and pits, b) the MFA di-rectly, visible after stained with iodine, c) angle of the pit windows, which are small but still observable; scale line = 10 µm.
Waviness
13
Figure 8 Microfibril angle (MFA) results for the twelve plates/specimens Explanation: x = samples’ plate label and y = MFA (º). Boxes represent the inter-quartile range (IQR) (25th to 75th percentile), whiskers indicate the R’s default distance from the median, which is 1.5×IQR. The horizontal bold line in each box represents the median of each sample.
14
Figure 10 Example of waviness figures of the sycamore maple wood Explanation: (from left to right) severely wavy (specimen C), wavy (specimen J), and low wavy grain (specimen G) wood
Ray Dimensions
It was observed that the sycamore maple possesses uniseriate and multiseri-ate rays: in addition to multiserimultiseri-ate rays, large rays consisting of up to 6—8 ray cells were also present and visible to the naked eyes (Figure 10). This confirms the previous study on the anatomical aspect of wavy sycamore maple in France (Keller 1992).
The rays were divided into two categories: large and small rays. This cate-gorization was based on the width of the rays. On average, the diameter of one ray cell of the sycamore maple was approximately 15.5 µm, similar to a past study (Schoch et al. 2004), thus the rays which exceeded 31 µm in width, or the rays which possessed more than 2 seriates, were categorized as large rays.
From the measurement results (Table 3), it can be seen that there are no clear differences between the plates, except that in the waviest one (specimen C), the rays appeared to be more tightly packed and frequent than those in the least wavy wood.
Correlation Between Parameters
15 MFA, E’L/ρ with w, and Young's modulus of L specimens (E’L) with w. The est correlation is observed between MFA and w: the larger the waviness, the high-er the MFA. Following the correlation test, linear multiple regression analysis were also conducted for tanδL with MFA and w, and for E’L/ρ with MFA and w (Table 5 and 6).
Figure 11 Rays of the waviest wood and the least wavy one (specimen H, images on the right)
16
Table 1 Measurement results of the sycamore maple wood’s physical and vibrational properties
Parameters Plates
A B C D E F G H I J K L
ρ (g/cm3)
[n] [13] [15] [12] [12] [13] [14] [14] [14] [13] [12] [12] [11]
m 0.655 0.688 0.588 0.664 0.637 0.618 0.631 0.588 0.643 0.693 0.552 0.626
(σ) (0.025) (0.012) (0.008) (0.015) (0.009) (0.012) (0.015) (0.014) (0.012) (0.012) (0.007) (0.013)
E'R/ρ (GPa)
[n] [5] [5] [4] [4] [5] [5] [5] [5] [4] [4] [4] [4]
m 2.98 2.69 2.83 2.75 1.92 2.82 2.82 2.89 2.87 2.09 3.02 2.36
(σ) (0.11) (0.19) (0.03) (0.08) (0.10) (0.08) (0.08) (0.15) (0.06) (0.06) (0.05) (0.07)
tanδR (×1000)
[n] [5] [5] [4] [4] [5] [5] [5] [5] [4] [4] [4] [4]
m 22.1 22.4 24.0 23.1 24.1 23.0 23.0 20.8 20.9 25.5 21.7 21.5
(σ) (0.4) (0.6) (0.6) (0.4) (0.8) (0.5) (0.5) (0.3) (0.7) (2.7) (1.5) (1.0)
E'L/ρ (GPa)
[n] [8] [10] [8] [8] [8] [9] [9] [9] [9] [8] [8] [7]
m 17.4 15.5 11.4 15.2 13.8 17.2 20.7 15.9 17.0 14.2 17.2 14.1
(σ) (3.4) (1.4) (2.1) (1.1) (1.1) (1.4) (1.7) (1.3) (1.1) (0.4) (0.5) (0.9)
tanδL (×1000)
[n] [8] [10] [8] [8] [8] [9] [9] [9] [9] [8] [8] [7]
m 10.1 11.0 13.8 10.5 11.0 9.6 8.3 9.1 9.5 11.7 9.2 11.2
(σ) (1.8) (0.7) (2.2) (1.1) (0.8) (0.9) (0.5) (0.6) (0.6) (0.4) (0.7) (0.7)
E'/ρ(L/R) m 5.83 5.77 4.03 5.52 7.2 6.09 7.33 5.51 5.92 6.78 5.71 5.99
tanδ(R/L) m 2.19 2.03 1.74 2.20 2.19 2.40 2.77 2.28 2.20 2.18 2.36 1.91
Explanation:
n : number of specimens
m : mean or average value of parameter σ : standard deviation value of parameter
17
Table 2 Measurement results of the sycamore maple wood’s anatomy features
Parameters Plates
m: mean or average value of parameter
σ : standard deviation value of parameters
18
Table 3 Measurement results of the sycamore maple wood’s wavy grain properties
Parameters Plates
A B C D E F G H I J K L
A (mm)
[n] [6] [9] [6] [6] [6] [3] [10] [7] [7] [6] [6] [6]
m 0.31 0.17 0.28 0.26 0.30 0.19 0.15 0.14 0.10 0.32 0.17 0.17
(σ) (0.07) (0.06) (0.08) (0.07) (0.10) (0.10) (0.04) (0.08) (0.06) (0.10) (0.03) (0.04)
λ (mm)
[n] [3] [4] [3] [3] [3] [3] [5] [4] [4] [3] [3] [3]
m 8.9 6.1 5.0 12.7 6.1 23.5 8.4 18.1 10.0 7.5 8.9 4.3
(σ) (0.7) (3.0) (1.3) (4.2) (1.1) (13.8) (0.8) (11.9) (5.8) (2.1) (0.2) (0.9)
θmax (º)
[n] [3] [3] [3] [3] [3] [3] [3] [3] [3] [3] [3] [3]
m 12.57 9.83 19.43 7.52 16.81 2.99 6.92 2.94 4.30 15.36 6.81 14.13
(σ) (1.10) (1.22) (1.16) (1.47) (2.10) (0.60) (0.84) (1.54) (0.99) (6.14) (1.10) (1.53)
θaverage (º)
[n] [3] [3] [3] [3] [3] [3] [3] [3] [3] [3] [3] [3]
m 8.14 6.32 12.87 4.81 11.02 1.91 4.43 1.87 2.74 10.02 4.36 9.19
(σ) (0.70) (0.78) (0.74) (0.94) (1.34) (0.38) (0.54) (0.98) (0.63) (3.92) (0.70) (0.97)
w
[n] [3] [4] [3] [3] [3] [3] [5] [4] [4] [3] [3] [3]
m 0.035 0.027 0.056 0.021 0.048 0.008 0.018 0.008 0.011 0.044 0.019 0.040
(σ) (0.003) (0.003) (0.003) (0.004) (0.006) (0.002) (0.003) (0.004) (0.003) (0.017) (0.003) (0.004)
Explanation:
N : number of measurements
M : mean or average value of parameter σ : standard deviation value of parameters
19
Table 4 r and p-value of pearson-product moment correlation between paired parameters
p-value correlation between the two parameters, albeit a low one
a
: Big rays’ height e : Ratio between big rays’ surface to to-tal area in tangential section
b
: Big rays’ width ** : p-value less than 0.01, which shows a strong significant
20
Table 5 Coefficients of regression of tanδL with MFA and waviness
Independent
variable Estimate Standard Error t-value Pr (>|t|)
Intercept 0.007122 0.002337 3.048 0.0138*
MFA 0.000145 0.000261 0.556 0.5919
Waviness 0.063876 0.054615 1.170 0.2722 Signif. codes: 0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1
Multiple R2 = 0.6757 ; adjusted R2 = 0.6037 ; p-value = 0.006295
Table 6 Coefficients of regression of E’L/ρ with MFA and waviness
Independent
variable Estimate Standard Error t-value Pr (>|t|)
Intercept 19.9896 3.5103 5.695 0.000296***
MFA -0.2328 0.3920 -0.594 0.567182
Waviness -64.3900 82.0482 -0.785 0.452742 Signif. codes: 0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ‘ 1
Multiple R2 = 0.5699 ; adjusted R2 = 0.4743 ; p-value = 0.02245
From the multivariate regression analysis of tanδL with MFA and w (Table 5), the output shows that p = 0.006295, indicating that the null hypothesis that the variables MFA and w collectively have no effect on tanδL should be rejected (confidence level = 95%). Results also show that variable MFA is not significantly controlling for the variable w (p = 0.5919), and that the variable w is not significant controlling for the MFA (p = 0.2722). However, overall it can be seen that collectively, MFA and w indeed affect the tanδL with the R2 = 0.6757 and R2adjusted = 0.6037. Thus, the equation can be written as follow:
tanδL = 0.007122 + 0.000145MFA + 0.063876w (formula 5)
From the multivariate regression analysis of E’L/ρ with MFA and w (Table 6), the output shows the p-value = 0.02245, indicatng the the null hypothesis that the variables MFA and w collectively have no effect on E’L/ρshould be rejected (confidence level also = 95%). The results also show that the MFA is not significantly controlling for the w (p = 0.567182) and that w is not significantly controlling the MFA (p = 0.452742). Similar with the results of table 5, collectively, MFA and w affect the E’L/ρ with the R2 = 0.5699 and R2adjusted = 0.4743. Thus, the equation can be written as follow:
21
4
DISCUSSIONS
From the results, it can be seen that there is a high intra-species variability of w (waviness, formula 6) and θaverage (mean angle, formula 4). Among wavy
ma-ple trees, some possess low to no wavy grain, while others possess a grain so wavy that it forms stripes-like figures on the radial plane of the wood, called ‘wave front’ (Harris 1989). Although the methods of waviness measurements used in the present study differ from some previous research, the average values of wave amplitude (≈0.21 mm) and of wavelength (10 mm) are comparable with other recent results on a different and wide sampling (Krajnc et al. 2015).
In the present results, the degree of waviness is not correlated with the wood density. This is in contrast with other findings, on reduced samplings, which sug-gested that wavy wood would have higher density than non-figured one (Bucur 2006; Kudela and Kunstar 2011). Anatomical features related to rays also show nearly no correlation with waviness.
Positively correlated with the θaverage (or waviness), according to the statis-tical analysis that has been conducted, is MFA (Table 4, Figure 12). This original finding is important because both the MFA and the grain angle (here caused by wavy grain) are known to strongly affect mechanical properties in the longitudinal direction of wood, both lowering E’/ρ and increasing tanδ (Obataya et al. 2000, Brémaud et al. 2011). One can wonder about the origin of this strong correlation between MFA and waviness, for past studies have shown that the MFA has to be ruled out from the list of possible factors causing the existence of spiral grain (Harris 1989). This suggestion was brought forward given that the grain angles are almost certainly determined by cambial orientation in the early formation of the fiber cells, while the MFA within the second layer is formed by the microtu-bules and made into its final structure in the late formation of the fiber cells (Har-ris 1989; Barnett and Bonham 2004).
Nevertheless, there is a possibility that the genes which express the for-mation of wavy grain are those who also affect the forfor-mation of reaction wood on microstructural scale, thus linking the MFA and grain waviness directly (Plomion et al. 2001; Pilates et al. 2004). Another biomechanical theory has also involved the MFA as an influencing factor of spiral grain in link with maturation growth stresses (Schulgasser and Witztum 2007). Besides theoretical considerations, however, there are still few experimental evidences of potential correlations be-tween MFA and grain angle: some have been found in a case of interlocked grain (Brémaud et al. 2010), but not reproduced in interlocked grain of other species (Cabrolier 2007).
22
is higher than the individual effect of MFA or of grain angleon these properties. However, results from multivariate regression analysis also show that both MFA and w are not significantly controlling each other in their collective relationships with both E’L/ρand tanδL. It needs to be taken into account, though, that such sta-tistical analysis is not sufficient as it is based on linear relations, while it is known that the dependence of mechanical properties on MFA or on grain angle is not of a linear form (Obataya et al. 2000; Brémaud et al. 2011, 2013).
Figure 12 MFA ( ) plotted against waviness (w), E’L/ρ ( ) and tanδL ( ) against MFA, and E’L/ρ and tanδL against mean grain angle or θaverage.
char-23
acteristics of rays. Results (Table 4) also show that there are low significant corre-lations between ray dimensions with mechanical and vibrational properties. This is the opposite of other findings which have determined that there are correlations between rays and acoustic-physical properties in other wood species (Fujiwara 1992; Baar et al. 2013). There are only significant correlations between the ratio of the amount of small rays per surface area with E’R/ρ, strangely not observed for
large rays.
The results discussed above concern the average results for the different sample plates. However, some maple trees may form wavy grain within wood produced when they were at least 10 years old, before stopping and reproducing it in wood developed years later (Ewald and Naujoks 2015), suggesting that the production of the grain is not completely constant and consistent during tree growth. In the results presented in Figure 6, trends in L mechanical properties are indeed observed along the trunk’s radius (E’L/ρ increases and tanδL decreases
from innerwood to outerwood). However, due to time constraints, in this study the variations along radius were only studied for vibrational mechanical properties, not for anatomical features. It will be beneficial if, in the future, the measurements of waviness and MFA are also conducted on the wood from other parts of the tree, such as the top, middle, and lower part of the tree, closer to the pith or to the bark, for it may enable us to determine the intra-tree variability and to better understand the structure-properties relationships.
In summary, the findings show significant correlation between the waviness and vibrational properties in the L direction, most likely due to the additive effect of grain angle and microfibril angle which are the most relevant factors for the L direction of wood, while few of the studied anatomical features had significant correlations to vibrational properties in R direction. Nevertheless, sycamore maple plates under study tend to have low to very low ratios of anisotropy (Table 3), especially for the most wavy ones, when compared to other hardwood species (Brémaud et al. 2011). It is also determined that the tanδL in a more wavy wood is
higher than the standard relationship (Ono and Norimoto 1983) which is followed by the less wavy specimens. It is suggested to conduct more study comparing the vibrational properties between wavy-figured wood with various kinds of anatomi-cal features (either by extending the sampling on sycamore maple, or by including other species to allow more variations in the different types of cells), and maybe also to observe in parallel possible chemical variations as affecting factors (Lon-gui et al. 2012; Brémaud et al. 2013).
24
5
CONCLUSIONS AND SUGGESTIONS
Conclusions
From this study, the wavy grain characteristics of sycamore maple wood were quantitatively determined. There are intra-species variabilities of grain wav-iness which contribute to the large variation of surface and structure of the wood. This research proves that the wavy grain affects the wood quality from the acous-tical characteristics point of view for it can be seen that, indeed, the wavy grain possesses significant correlations with the wood’s mechanical and vibrational
properties such as E’/ρ and tanδ on the longitudinal direction. Moreover, the wavy
grain also correlates with microfibril angle, one of the most important anatomical properties of wood. Therefore, it is possible to use these waviness characteristics in complement with other properties in order to determine a wood’s suitability for crafting musical instruments.
Suggestions
Further studies with similar methods using larger number of specimens and other wood species should be conducted to refine the statistical analysis models and results. Moreover, analysis about the mechanical model of wavy wood, which may include variables such as MFA, grain angle and waviness, should be con-ducted in the future to deepen the knowledge about this pari ticular type of wood. Experiments on methods to reproduce the wavy grain by manipulating external factors and genetical aspects of the sycamore maple wood should also be ex-plored, complemented by research focused on finding experimental evidence of correlation between anatomical properties and wavy grain.
REFERENCES
Baar J, Tippner J, Gryc V. 2013. The relation of fibre length and ray dimensions to sound propagation velocity in wood of selected tropical hardwoods. IAWA J. 34(1):49–60. doi: 10.1163/22941932-00000005.
Barnett JR, Bonham VA. 2004. Cellulose microfibril angle in the cell wall of
wood fibres. Biol Rev 79:461–472. doi: 10.1017/S1464793103006377.
Beery WH, Ifju G, McLain TE. 2007. Quantitative wood anatomy—relating
anatomy to transverse tensile strength. Wood Fiber Sci. 15(4):395–407.
Brémaud I. 2006. Diversité des bois utilisés ou utilisables en facture d’instruments de musique. Étude expérimentale des propriétés vibratoires en direction axiale de types de bois contrastés en majorité tropicaux: Relations à des déterminants de microstructure et de composition chimique secondaire [disertasi]. Montpellier (FR): Université de Montpellier II - Sciences et Techniques du Languedoc.
Brémaud I. 2012. Acoustical properties of wood in string instruments
25
Acoust Soc Am. 131(1):807–818.
Brémaud I, Kaïm YE, Guibal D, Minato K, Thibaut B, Gril J. 2011. Characterisation and categorisation of the diversity in viscoelastic vibrational properties between 98 wood types. Ann For Sci. 69:373–386. doi: 10.1007/s13595-011-0166-z.
Bucur V. 2006. Wood Species for Musical Instruments. In: Czeschlik, editor.
Acoustics of Wood. Berlin/Heidelberg (DE): Springer-Verlag. hlm 173–216.
http://link.springer.com/10.1007/3-540-30594-7_7 (Accessed August 6, 2016).
Buksnowitz C, Evans R, Müller U, Teischinger A. 2012. Indented rings (hazel growth) of Norway spruce reduce anisotropy of mechanical properties.
Wood Sci Technol. 46:1239–1246. doi:10.1007/s00226-012-0480-0.
Burgert I, Eckstein D. 2001. The tensile strength of isolated wood rays of beech
(Fagus sylvatica L.) and its significance for the biomechanics of living
trees. Trees. 15:168–170. doi:10.1007/s004680000086.
Cabrolier P. 2007. Description et comportement mécanique des bois contrefileés [tesis]. Montpellier (FR): Université de Montpellier II - Sciences et Tech-niques du Languedoc.
Carlier C, Brémaud I, Gril J. 2014. Violin making 'tonewood' : comparing makers' empirical expertise with wood structural/visual and acoustical properties. In: Proceedings of the International Symposium on Musical Acoustics ISMA
2014 [internet]. 2014 July 7-12; Le Mans, France. Le Mans (FR): French
Acoustical Society. hlm 325–330; [downloaded 2016 Jun 21]. Available at: https://hal.archives-ouvertes.fr/hal-01233098.
Chytrý M, Maskell LC, Pino J, Pyšek P, Vilà M, Font X, Smart SM. 2008. Habitat invasions by alien plants: a quantitative comparison among Mediterranean, subcontinental and oceanic regions of Europe. J Appl Ecol. 45:448–458. doi: 10.1111/j.1365-2664.2007.01398.x.
Donaldson LA. 2007. The use of pit apertures as windows to measure microfibril angle in chemical pulp fibers. Wood Fiber Sci. 23(2):290–295.
Ewald D, Naujoks G. 2015. Vegetative propagation of wavy grain Acer
pseudoplatanus and confirmation of wavy grain in wood of vegetatively
propagated trees: a first evaluation. Dendrobiology. 74:135–142. doi: 10.12657/denbio.074.013.
Fujiwara S. 1992. Anatomy and properties of Japanese hardwoods II. Variation of dimensions of ray cells and their relation to basic density. IAWA J. 13(4):397–402. doi:10.1163/22941932-90001295.
Harris JM. 1989. Anatomy of Changing Grain Angles. In: Spiral Grain and Wave
Phenomena in Wood Formation. Berlin (DE): Springer Berlin Heidelberg.
hlm 98–130.
Keller R. 1992. Le bois des grands érables: état des connaissances, facteurs de variabilités, aptitudes technologiques. Rev For Fr. 133. doi:10.4267/2042/ 26370.
Krabel D, Wolf H. 2013. Sycamore Maple (Acer pseudoplatanus L.). In: Pâques LE, editor. Forest Tree Breeding in Europe. Amsterdam (NL): Springer Netherlands. hlm 373–402.
26
66(3):213–220. doi: 10.5552/drind.2015.1447.
Kudela J, Kunštár M. 2011. Physical-acoustical characteristics of maple wood with wavy structure. Ann Wars Univ Life Sci For Wood Techn. 75:12–18. Long JM, Conn AB, Batchelor WB, Evans R. 2000. Comparison of methods to
measure wood fibres. Appita J. 53(3):206–209.
Morecroft MD, Stokes VJ, Taylor ME, Morison JIL. 2008. Effects of climate and management history on the distribution and growth of sycamore (Acer pseudoplatanus L.) in a southern British woodland in comparison to native competitors. Forestry. 81(1):59–74. doi: 10.1093/forestry/cpm045.
Nelson ND, Hillis WE. 1978. Ethylene and tension wood formation in Eucalyptus gomphocephala. Wood Sci Technol. 12:309–315.
Obataya E, Ono T, Norimoto M. 2000. Vibrational properties of wood along the grain. J Mater Sci. 35:2993–3001. doi: 10.1023/A:1004782827844.
Ono T, Norimoto M. 1983. Study on Young’s modulus and internal friction of wood in relation to the evaluation of wood for musical instruments. Jpn J Appl Phys. 22(4):611–614. doi: 10.1143/JJAP.22.611.
Peterken GF. 2001. Ecological effects of introduced tree species in Britain. For Ecol Manag. 141:31–42.
Pilate G, Déjardin A, Laurans F, Leplé JC. 2004. Tension wood as a model for functional genomics of wood formation. New Phytol. 164: 63–72. doi: 10.1111/j.1469-8137.2004.01176.x.
Plomion C, Leprovost G, Stokes A. 2001. Wood formation in trees. Plant Physiol. 127: 1513—1523. doi: 10.1104/pp.010816.
Reiterer A, Burgert I, Sinn G, Tschegg S. 2002. The radial reinforcement of the wood structure and its implication on mechanical and fracture mechanical properties—a comparison between two tree species. J Mater Sci. 37:935– 940.
Rohr R, Hanus D. 1987. Vegetative propagation of wavy grain sycamore maple. Can J For Res. 17:418–420. doi: 10.1139/x87-072.
Schoch W, Heller I, Schweingruber FH, Kienast F. 2004. Acer pseudoplatanus L. Wood Anat Cent Eur Species. http://www.woodanatomy.ch/species.php? code=ACPS (Accessed 2016 July 4).
Senft JF, Bendtsen BA. 1985. Measuring microfibrillar angles using light microscopy. Wood Fiber Sci. 17(4):564–567.
Wegst UGK. 2006. Wood for sound. Am J Bot. 93(10):1439–1448. doi: 10.3732/ajb.93.10.1439.
Wegst UGK, Oberhoff S, Weller M, Ashby MF. 2007. Materials for violin bows. Int J Mater Res. 98:1230–1237. doi: 10.3139/146.101580.
27
CURRICULUM VITAE
Ahmad Alkadri was born on Thursday, 19 December 1991, in Jakarta, In-donesia. He is the first son of Mr. and Mrs. Salahudin. He grew up in Cilacap, Central Java, where he was enrolled in SD YKPP 01 Cilacap (primary school) and SMP Negeri 1 Cilacap (junior high school). He went to Magelang where he was enrolled in high school, SMA Taruna Nusantara. Afterwards, he took part in SNMPTN, a national examination for high school graduates, in order to enroll at the Department of Forest Products, Faculty of Forestry, Bogor Agricultural Uni-versity. During his bachelor years, he participated in numerous field studies and became specialized in Forest Economics, particularly in the utilization of forest resources in rural villagers. In 2014, he was awarded a scholarship from Indone-sian Ministry of Education, Beasiswa Unggulan, to enroll at a double degree Mas-ter program held between Department of Forest Products, Bogor Agricultural University, and Formation du Bois Forêt et Développement Durable (Wood, For-est and Sustainable Development) at AgroParisTech in France.
During his first year of Master (2015), he participated in a team research held at the Laboratory of Biophysics, Bogor Agricultural University. The results of this research have been published on Integrated Ferroelectrics: An Interna-tional Journal under the title “Characterization of Optical and Structural of Lan-thanum Doped LiTaO3 Thin Films” with the authorsips consist of Dr. Irzaman (a
researcher and teacher at Department of Biophysics, Bogor Agricultural Universi-ty), four Master students of Department of Biophysics (Yunus Pebriyanto, Epa Rosidah Apipah, Iman Noor), and Ahmad himself. In his second year of Master (2016), he participated at WoodMusICK International Conference in Barcelona, presenting parts of study he conducted with the partnership of Capucine Carlier, a PhD student working at Laboratoire de Mécanique et Génie Civil (LMGC), under the tutelage of Iris Brémaud (a researcher at LMGC), Patrick Langbour (a re-searcher at Cirad Montpellier), and Joseph Gril (the research director of LMGC’s Wood Research Group).
