Nondestructive Observation Research Articles

The effect of loading duration on damage initiation in high-strength concrete

The rate sensitivity of the failure strength of concrete and other brittle materials is well documented. However, the underlying mechanism(s) that gives rise to this phenomenon remains a topic of debate. Experimental results suggest that the time-dependent failure process plays a significant role in the observed strength increase. This study investigates the failure process in high-strength concrete (HSC) specimens under uniaxial compression loading. This is accomplished through the use of a modified Kolsky compression bar to apply controlled and repeatable mechanical loading in combination with the non-destructive observation capability of high-resolution X-ray computed-microtomography (micro-CT). The evolution of specimen damage morphology is observed as a result of intermittent short-duration uniaxial stress loadings. Experimental results show that HSC specimens are capable of supporting the applied stress above their quasi-static failure strength for short durations. This duration is found to be a function of the overload stress level. Additionally, micro-CT results reveal that specimens undergo a brief period of void compaction followed by the coalescence and propagation of cracks before completely losing load bearing capability.

X-Ray CT Measurement of All Solid State Lithium-Ion Battery Under High Pressure Condition

All Solid-state lithium ion Battery (ASB) with sulfide Solid Electrolyte (SE) would achieve high energy density and high-speed charging with high ion conductivity and wide potential window of solid electrolyte, therefore, ASB can be a solution to improve the cruising distance of electrical vehicle. The charging speed, energy density, and battery life of the ASB is depend on internal structure in the electrode due to the lithium ion is transported in the contact surface of the SE and Active Material (AM). Several studies with surface measurement of ASB have been conducted with SEM (Scanning Electron Microscope) and Laser-microscope to reveal the internal structure of ASB. In these studies, the observed area is only the surface and cross section of ASB, and is not the inside. Moreover, the ASB is mainly used under high pressure condition to suppress the ion transportation resistance in SE-SE interface and SE-AM interface and it is difficult to observe the structure under pressured condition with the SEM and Laser-microscope. X-ray CT imaging is an only method to observe the internal structure of ASB under high pressure condition. 3D image is generated with the reconstruction of X-ray tomography images, therefore, non-destructive observation can be achieved. Several X-ray CT measurement of ASB are conducted and internal structure of ASB have been visualized. However, in these experiments, the applied pressure (9MPa) is low and X-ray CT measurement under high pressure condition should be conducted. The pressurizing condition is also important and is not discussed in the previous studies. The ASB can be pressured by uni-axial compression and multi-axial compression. If the battery cell is enough big, the edge region of the cell is compressed uni-axially and the balk region is compressed multi-axially. The mechanical and electrochemical characteristics can be changed with these compression condition. From the background mentioned above, we conducted X-ray CT measurement of all solid-state lithium ion battery under high pressure condition (up to 400MPa). To achieve high S/N ratio X-ray CT image under this high-pressure condition, we successfully developed a high-pressure X-ray CT cell in which the dew point is lower than -70℃ to prevent the corrosion of SE by water vapor. The multi-axial pressuring is achieved with Boron Nitride pressure medium. The experimental results are as follows. Figure 1 illustrates the cross-section view of ASB w/o pressure medium. Micro-scale clacks are generated at 35MPa. These clacks are generated by the crash of ASB with uni-axial compression. With the increase of pressure, the micro-scale clacks are disappeared. The gap between the side-wall and ASB is filled and side-pressure is induced, and the pressurizing is changed from uni-axial compression to multi-axial compression. The multi-axial compression flows the SE and AM in cross-sectional plane and the micro-scale clacks are disappeared. Figure 2 illustrate the cross-sectional view of ASB with the pressure medium. In this case, the micro-scale clacks are not generated in any pressure. This finding suggests that the internal structure strongly depend on the pressurizing condition (uni-axial or multi-axial) and the uni-axial compression generates the micro-crack. Figure 3 and 4 shows the thickness of Anode, Separator, and Cathode measured by the CT scan as a function of the applied pressure. In the case w/o pressure medium (Fig.3), the total thickness decreases by 20% from 0MPa to 35MPa due to the uni-axial compression with generating the micro-scale clacks. From 35MPa to 100MPa, the thickness decreases slightly by the refilling the clacks with the flow of the SE and AM. After the refilling, the thickness is not changed over 100MPa. In the case with pressure medium (Fig.4), contrast to the w/o pressure medium case, the compression amount is very small and is only -5%. From these experimental results, following conclusions can be drawn. The uni-axial compression clashes the battery structure and micro-scale clacks are generated. This micro-scale clack is refilled by solid electrolyte and active material with the increase of the applied pressure to 100MPa. The clack is not generated at 0MPa-400MPa when the compression is multi-axial compression and the decrease of the thickness is smaller than that with uni-axial compression. Figure 1

Cross-sectional imaging of quenched region in a steel rod using energy-resolved neutron tomography

Abstract We demonstrate the collection and analysis of energy-resolved neutron tomography for the nondestructive inspection of a martensite phase in a quenched iron rod. The energy-resolved (4D) tomography technique can extract the internal information of crystalline phase and microstructural features, such as the distribution of martensite. However, care must be taken when performing energy-resolved neutron tomography on a strongly textured sample in which the crystal grains are preferentially oriented and the neutron attenuation spectrum depends on the direction. As the standard tomography algorithm is based on the assumption that the attenuation is isotropic, anisotropy in the neutron attenuation distorts the reconstructed information. In other words, energy-resolved neutron tomography can be a powerful tool for nondestructive martensite observation in iron materials, which are usually not strongly textured.

Prediction of strength based on defect analysis in Al<sub>2</sub>O<sub>3</sub> ceramics via non-destructive and three-dimensional observation using optical coherence tomography

Prediction of strength based on defect analysis in Al<sub>2</sub>O<sub>3</sub> ceramics via non-destructive and three-dimensional observation using optical coherence tomography

Feasibility Study on Application of Synchrotron Radiation μCT Imaging to Alloy Steel for Non-Destructive Inspection of Inclusions

In order to examine the feasibility of applying synchrotron radiation μCT imaging to alloy steels for non-destructive inspection of inclusions for potential origins of internal fatigue damage in the very high cycle region, synchrotron radiation μCT imaging was utilized for repeated non-destructive observation of Cr-Mo steel. An ultrasonic fatigue testing machine was used in aid of the repeated observation. As a result, it was found that the synchrotron radiation μCT imaging with 70 keV was useful for non-destructive observation of inclusions of more than 10 μm, one of which may be an internal fatigue origin. No identifiable damage was observed around every inclusion, and in the base metal, at least up to 70% of fatigue life was observed in the imaging volume.

Label-Free Fried Starchy Matrix: Investigation by Harmonic Generation Microscopy.

An innovative methodology based on non-destructive observation by using harmonic generation microscopy is proposed for detection and location of starch granules and oil in a fried starchy matrix and topography analysis of food products. Specific fluorescent probes were used to label the main biochemical components of the starchy fried matrix, namely starch and oil. Fluorescence of starch and oil respectively stained with Safranin O and Nile red was observed from non-linear microscopy. By using sequential scanning and specific emission filters, it was possible to merge fluorescence and harmonic generation signals. Second harmonic generation (SHG) generated by starch granules was superposed with safranin fluorescence, whereas third harmonic generation (THG), not restricted to the superposition with Nile red fluorescent signal, was used to investigate the topography of the fried product. By these experiments, starch granule mapping and topography of the starchy fried product were obtained without any destructive preparation of the sample. This label-free approach using harmonic generation microscopy is a very promising methodology for microstructure investigation of a large panel of starchy food products.

Adaptive minirhizotron for pepper roots observation and its installation based on root system architecture traits

BackgroundRoot is the principal part of plants to absorb water and nutrient, anchor the plant and affect yield and quality. Non-destructive detection of root traits is difficult to perform due to the hidden nature of the root. Therefore, improved methods to measure roots are necessary to support plant breeding, and optimization of cultivation and management. In this study, we present an adaptive minirhizotron along with installation patterns to focus on micro and local changes in multipoint of pepper roots.ResultsThe method is to improve minirhizotron by reducing its size to a microrhizotron (1.1 × 1.1 × 1.2 cm) and improving installation validity and rationality according to spatial distribution characteristics of Capsicum annuum root system. This adaptive minirhizotron could acquire root image in multipoint, and through image processing, root traits such as root length (including very fine roots or root hairs) and root width could be calculated. In order to install the microrhizotron reasonably and effectively, root system architecture (Capsicum annuum) was reconstructed using a three-dimensional caliper, and were quantified in circumferential distribution, vertical direction and root extension. The results showed that most lateral roots were constrained to 45° in horizontal direction to root initial position; Vertical angles were large, almost perpendicular to the root center line at initial position, and it became smaller when roots began to deepen. Root length density decreased with the increase of distance to plant center. According to Capsicum annuum root system traits, totally 8 installation methods were tested and verified to determine high probability of root interception. Horizontal angle 45° showed much higher interception probability than that of 90°. Vertical angle 45° has slightly higher root interception probability than that of 30°. Installation pattern horizontal angle 45° + radius 30 mm + vertical angle 45° showed the best performance in root interception with probability of 96.7%, followed by pattern horizontal angle 45° + radius 30 mm + vertical angle 30°. Comparison experiment showed that when root hair and very fine root were excluded, relative error was 12.1% between microrhizotron and soil sampling in root length, and 15.4% in root diameter. Microrhizotron was able to observe fine roots about 0.1 mm in diameter.ConclusionA new adaptive minirhizotron has been established for nondestructive observation on local and micro changes of roots in multipoint, and its application and installation patterns has been suggested according to root architecture traits. The microrhizotron can be used to study a wide range of research questions focused on quantitative trait locus analysis, root width changes, and root hair growth.

Comparing Non-Destructive Methods to Estimate Volume of Three Tree Taxa in Beijing, China

Establishing the tree volume table is an important aspect of forest inventory for managing the forest ecosystem. The traditional volume models used to build tree volume tables are time consuming and expensive, demanding huge labor and material resources. Aiming at the improvement of the current destructive, costly and time-consuming volume model, we propose a new non-destructive, low-cost and efficient method for calculating the tree volume model with high precision by using the electronic theodolite. For testing and comparing the accuracy of our model with the traditional model, we collected data of three main tree taxa including Platycladus orientalis (L.) Franco, Larix principis-rupprechtii Mayr and Populus spp. L. from different districts and counties of Beijing, China. We collected a total of 1750 tree samples (250 Platycladus orientalis, 300 Larix principis-rupprechtii, and 1200 Populus spp.) to establish our models; 721 pieces of accurate data (94 Platycladus orientalis, 149 Larix principis-rupprechtii, and 478 Populus spp.) were used as test samples, to evaluate the accuracy of the newly established volume models of three tree species (group). After that, the established volume models (unary/binary models) were compared and analyzed with the corresponding ministerial models for applicability and accuracy. The results showed that the difference between the data observed by the new method and the measurement data of parsing trees was not significant. The total relative error (TRE) and the mean system error (MSE) of the newly established unary/binary volume models were all within ±3%, satisfying the accuracy standard specified by the technical indicators. Compared with the ministerial models applied to the same data, our models’ performance and accuracy were higher (close to the field measurements). Our results also showed that the accuracy of ministerial models was lower than the required standards. It is a promising methodology to use the electronic theodolite non-destructive observation method to establish tree volume tables in the future, especially in areas where cutting is prohibited or restricted and there is a lack of tree volume tables. In addition, this method has also shown a great potential of applicability in forest ecology and environmental protection.

High-resolution non-destructive observation of microstructure in high strength metallic materials using synchrotron radiation micro/nano CT

High-resolution non-destructive observation of microstructure in high strength metallic materials using synchrotron radiation micro/nano CT

Cavity-induced emergent topological spin textures in a Bose–Einstein condensate

The coupled nonlinear dynamics of ultracold quantum matter and electromagnetic field modes in an optical resonator exhibits a wealth of intriguing collective phenomena. Here we study a Λ-type, three-component Bose–Einstein condensate coupled to four dynamical running-wave modes of a ring cavity, where only two of the modes are externally pumped. However, the unpumped modes play a crucial role in the dynamics of the system due to coherent backscattering of photons. On a mean- field level we identify three fundamentally different steady-state phases with distinct characteristics in the density and spatial spin textures: a combined density and spin-wave, a continuous spin spiral with a homogeneous density, and a spin spiral with a modulated density. The spin-spiral states, which are topological, are intimately related to cavity-induced spin–orbit coupling emerging beyond a critical pump power. The topologically trivial density-wave–spin-wave state has the characteristics of a supersolid with two broken continuous symmetries. The transitions between different phases are either simultaneously topological and first-order, or second-order. The proposed setup allows the simulation of intriguing many-body quantum phenomena by solely tuning the pump amplitudes and frequencies, with the cavity output fields serving as a built-in nondestructive observation tool.

Nondestructive Observations using Scanning Electron-induced Thermal and Acoustic Wave Microscope

Nondestructive Observations using Scanning Electron-induced Thermal and Acoustic Wave Microscope

Nondestructive investigation on the nanocomposite ordering upon holography using Mueller matrix ellipsometry

Ordered materials, which hold organized structures of heterogeneous matter and thus always present superior performance than their non-ordered counterparts, have been constantly pursued. Nevertheless, the direct, precise and nondestructive observation of the ordering process, which is especially critical for evaluating the quality of consecutive manufacturing, remains a formidable challenge. Herein, we introduce Mueller matrix ellipsometry (MME) as a nondestructive method to quantitatively investigate the nanocomposite ordering process upon holography. This nondestructive investigation directly offers the exact width of, refractive index and nanoparticle fraction in each bright (constructive) and dark (destructive) interference area, which is impossible to be implemented using other existing techniques. Interestingly, the width of dark regions in the formed holographic gratings is observed to decrease while the width of bright regions increases with an augmentation of holographic recording time, distinct from previous width-equal assumption. Meanwhile, an apparent diffusion coefficient of 2 × 10−15 m2 s−1 for nanoparticles is determined on the basis of time dependent grating parameter variation, which is 3 orders of magnitude lower than the initial value theoretically predicted by the Stokes-Einstein diffusion equation. The distinct diffusion coefficient is attributed to the rapid increase of viscosity driven by polymerization during holography. No depolarization is observed in these holographic polymer nanocomposites, indicating uniform dispersion of nanoparticles in the polymer matrices. The proposed protocol herein is envisioned to pave the way for precisely and nondestructively understanding the formation of ordered structure in electronics, photonics, photovoltaics, biomaterials and other disciplines.

Effect of temperature on growth of roots of juvenile asparagus (Asparagus officinalis L.) plants

It is difficult to observe the growth of root system and to measure its morpho-physiological parameters when asparagus is grown in the open field. Therefore, different from that cultivation method, juvenile asparagus plants were cultivated in aeroponics in greenhouse in this study. Under such conditions, investigation on the growth of roots became easier since it allowed nondestructive observation and examination of root system of asparagus. Seven asparagus cultivars from countries differing in climatic conditions were used in the study. When stems of juvenile plants were fully developed, their storage roots were taken for root respiration rate (R(r)) measurement at three temperatures: 10, 20 and 30°C. Regressions between R(r) and temperatures were analyzed for each cultivar. From these results, soil temperature was estimated based on the standard root respiration rate (R(rs)) observed from the experiment. Significant difference was found on R(r) of juvenile plants among cultivars at three temperatures. Reaction of roots to temperature changes also varied at different degrees among cultivars. Some cultivars were shown to be more suitable for growing at higher soil temperatures, indicating that the others should be cultivated in much lower soil temperature if R(r) needed to be equal to R(rs).

Laboratory Foamed-Cement-Curing Evolution Using CT Scanning: Insights From Elevated-Pressure Generation

Summary Computed-tomography (CT) scanning has become a mainstay among scientists (Wildenschild and Sheppard 2013) because it enables nondestructive observation of material processes and formation in real time. Foamed cement is a high-strength, low-density material containing nitrogen gas, and is used to stabilize wellbore casings both onshore and offshore. In-situ foamed cement is subject to pressure changes because the slurry is pumped downhole and cures at depth. To correlate the influence of pressure to the gas-void size and the curing evolution of a foamed cement, two laboratory foamed cements were generated and CT scanned as they cured. One cement was generated following the American Petroleum Institute (API) industry standard API RP 10B-4 (2015) at atmospheric conditions using a blender, and the other cement was created using a foamed-cement generator (FCG) (resembling that of de Rozières and Ferrière 1991) to produce a sample at an elevated pressure. FCG-generated cement qualities (in the range of 20, 25, 30, 35, and 40%) were scanned at their cured state for comparison. From the CT-image time series and the single FCG scans, the volumetric void properties were characterized and compared. The time-series blender voids were an order of magnitude larger than the FCG voids, and void growth was stagnant after a curing period of 100 minutes, whereas the FCG voids gradually increased in volume after 100 minutes. The Hsü-Nadai plots (Brandon 1995) reveal that the FCG and blender voids are weakly prolate, and all FCG voids, regardless of generation quality, relax to a greater final-magnitude strain than the blender voids. These findings confirm that both the void size and the curing process are influenced by the pressure at which a foamed cement is generated.

Three-dimensional X-ray thermography using phase-contrast imaging

Thermal management is a key technology to desterilize unused energy sources for building sustainable societies. However, conventional temperature measurement methods such as infrared thermography can detect only the surface temperature of objects because they use infrared light. We thus present a novel three-dimensional X-ray thermography using a phase-contrast X-ray imaging technique, which enables non-destructive observations of the inner thermal distribution of samples. The sensitivity of phase-contrast X-ray imaging is about 1000 times higher than that of conventional X-ray imaging. Therefore, temperature changes can be detected by using density changes caused by thermal expansion. We applied X-ray interferometric imaging (XI) that detects phase-shift by using a crystal X-ray interferometer. The highest sensitivity of XI was utilized to successfully obtain the first three-dimensional image that visualizes the thermal distribution in heated water nondestructively. Additionally, projection images visualizing the dynamic thermal flow in heated water were also obtained, and their distribution and diffusion velocity agreed well with those of the calculated images obtained by computational fluid dynamics analysis. These results show that the novel thermography enables nondestructive observations of inner temperature and thermal flow and can provide solutions for optimum thermal design of electrical devices, motors, and engines.

Asssesment of Initial Colony Founding by Swarming Reproductives of the Western Drywood Termite, Incisitermes minor

Colony founding activities in drywood termite is difficult to assess, since the colony forage and nest inside the wood. Non-destructive observation using X-ray computed tomography was used to evaluate nest-gallery establishment and colony breeding of the incipient colonies. The infested timbers were marked by year of infestation and were left on its original position to allow termite colonies develop in natural environment. Selected timbers were subjected for X-ray scanning analysis in Kyushu National Museum, Japan, in which colony founding from 5 royal pairs in the first year development was monitored. The CT data of the first six months colony founding indicated two different outcome in colony founding; two colonies distributed the energy to breed and slowed down in foraging simultaneously and other three concentrated in foraging. The CT scan after one year showed that only one royal pair showed no breeding activity, while the other four had been observed to have 2 – 5 new colony members. Colony extraction also confirmed that colony size in the first and second year varied from 0 – 5 new colony members. The new colony members were mostly in larval instars, sometimes with the presence of one small soldier. Colony founding through nuptial flight is a risky process, as 59% of the observed chambers were failed colony founding, resulted from the dead of a royal pair or being abandoned (empty chamber).

In situ experimental investigation on the out-plane damage evolution of 3D woven carbon-fiber reinforced composites

The damage evolution study on 3D woven carbon-fiber reinforced composites has always been a challenge to the research community. In this paper, a new in situ experimental method is proposed to realize the non-destructive observation of the failure process of 3D woven carbon-fiber reinforced composites. Synchrotron radiation computer tomography (SRCT), an in situ load frame and new-style specimens are integrated. With the method, the 3D crack initiation and propagation can be continuously recorded by the SRCT scanner. Through analyzing the experimental results, the out-plane failure mechanism under tension and shear loads is found. Particularly, it is shown that the interface property is the leading factor affecting out-plane strengths. Moreover, the effect of braiding angle on the out-plane strengths in different directions is discussed. According to the failure modes, it can be concluded that with the increasing of the braiding angle, the out-plane tension strength will increase but the out-plane shear strength will decrease. The proposed in situ experimental method and the above findings are significant to calibration of failure prediction model and the novel design of woven composites.

(Invited) Direct Observations of Liquid Water Formation at Nano- and Micro-Scale in Platinum Group Metal-Free Electrodes By Operando X-Ray Computed Tomography

Platinum group metal (PGM)-free catalyst materials are promising alternatives to Pt-based catalysts for use in polymer electrolyte fuel cells (PEFCs) providing for reduced cost and potentially broadening technology footprint because of sources availability. Optimizing the morphology of these PGM-free catalyst layers for enhanced transport properties is critical for reaching high power-density targets. Unfortunately, the current understandings of both morphology and transport processes are very limited due to the novelty of the materials and the challenges in designing operando characterization techniques. In order to bridge these gaps in understanding, we used operando synchrotron X-ray computed tomography to visualize water transport in operating PEFCs. In this study, we present a non-destructive observation of operando morphology and water transport processes for PGM-free PEFCs. Our previous studies highlighted some of the morphological features of PGM-free electrodes on nano and micro-scale (1, 2). Ex-situ nano-CT data complements operando micro-CT observation by providing water distribution in smaller macropores (< 1 µm). Figure 1 shows grey-scale cross-section four stitched FOVs along one of the channels for OCV and 50 % RH (Figure 1a) and 40 mAcm-2 at 100 % RH (Figure 1b) operando conditions. The anode, cathode layers, as well, as membrane are clearly seen from this cross-section view. No liquid water was observed at 50 % RH condition, whereas for 100 % RH and under applied current density large water droplets are seen in the cathode channel and within the cathode PGM-free layer. Figure 1b and c show zoom-in locations within the MEA. Tree-like agglomerates were observed within the cathode PGM-free GDE that were compressed against 50 µm membrane. Under applied current density of 40 mAcm-2 liquid water was clearly observed within both large and small voids of the GDE and membrane swelling to 72 µm was also measured. From Figure 1d and b membrane expands into the GDE voids upon humidification resulting in several locations in loss of contact with the anode GDE. In this presentation we demonstrate that (1) gas-diffusion electrodes (GDEs) form highly non-uniform interfaces with the membrane and under constant current operation, liquid water formed in electrochemical reactions fills the larger macropores within the PGM-free electrode and at the electrode-membrane interface; (2) from nano-CT data ionomer swelling in macropores is 16 % going from 50 % RH to 100 % RH but no notable structural changes occur within CL at nano-scale; (3) water is removed into the cathode channel and is also observed under location of the land-area (which is cooler but also has larger voids); and (4) water preferentially fills larger voids, that are lower capillary pressure locations, due to hydrophobic nature of the catalyst. Figure 1. Along-the-channel cross-section tomographs for temperature 60oC a) 50 % RH OCV and b) 100 % RH 40 mAcm-2, where c and d) are corresponding zoom-in locations from a and b. Locations for liquid water are marked, as well as membrane thicknesses. References A. Serov, A. D. Shum, X. Xiao, V. De Andrade, K. Artyushkova, I. V. Zenyuk and P. Atanassov, Applied Catalysis B: Environmental (2017).S. Kabir, K. Lemire, K. Artyushkova, A. Roy, M. Odgaard, D. Schlueter, A. Oshchepkov, A. Bonnefont, E. Savinova, D. C. Sabarirajan, P. Mandal, E. J. Crumlin, I. Zenyuk, P. Atanassov and A. Serov, Journal of Materials Chemistry A (2017). Figure 1

Morphology of Surface Integrity as Effect of Cold Forging of Aluminum Alloy

ABSTRACT Aluminum and its alloys represent a common raw material for components released through a cold machining routine (i.e., forging, cold heading, and rolling processes). They offer easy manufacturing and high plastic strength, together with light weight, long life span, and easy recycling and are heavily used in the transport industry (P. M. G. P. Moreira, et al. (1), Theoretical and Applied Fracture Mechanics, 50, pp 81–91, 2008; H. Yoshimura and K. Tanaka (2), Journal of Materials Processing Technology, 98, pp 196–204, 2000). However, during processing, the sample–tool interfaces can generate sticking mechanisms that result in an increase in friction values and high wear rates, leading to irreversible damage to the workpiece surface. The surface morphology provides characteristics that allow detection of the damage amplitude. The hard contact between asperities causes nucleation and the formation of adhesive wear. The normal load and lubrication conditions may further affect the quantity of wear elements (A. Hase and H. Mishina (3), Tribology International, 42, pp 1684–1690, 2009). Optical nondestructive observations permit the detection of the quantity of wear elements as per material transfer from one side (specimen surface) to the other side (contactor surface). This article presents the mechanisms of the adhesive layer and material transfer that are directly proportional to the new roughness stature. A robust finite element method analysis was embedded to establish a relationship between time, plastic deformation, friction coefficients, and surface defects.

The development development of non-destructive observation method usable in the paddy field for observation of rice root growth

The development development of non-destructive observation method usable in the paddy field for observation of rice root growth