Search

Recently, the concentration of CO2, one of the major air pollutants for greenhouse effect, is increasing due to the massive use of fossil fuels. Thus, research about gas sensors for monitoring CO2 gas has performed, and conventional methods have the challenge of requiring complex structures. Thus, research about gas sensors using nanomaterials has been conducted, and graphene-based gas sensors have been actively researched for its extraordinary conductivity. However, there are challenges that the gas absorption site is limited in chemically unstable sites. In this study, ZnO/graphene heterostructure to improve the gas absorption area with high conductivity through ZnO on graphene was presented. Each layer acted as a gas adsorption and a carrier conducting layer respectively, and the sensitivity by the thickness of ZnO and the effect of the annealing temperature were evaluated. This work exhibited a sensitivity of 78% at room temperature, and repeatability and selectivity were also studied.

In this study, yttrium oxide (Y2O3)-based resistive random-access memory (RRAM) devices were fabricated using the sol–gel method. The fabricated Y2O3 RRAM devices exhibited conventional bipolar RRAM device characteristics and did not require a forming process. The Y2O3 film thickness was controlled by varying the liquid-phase precursor concentration. As the concentration increased, thicker Y2O3 films were formed. In addition, the concentration of oxygen vacancies increased. The RRAM device properties were not observed for thin Y2O3 films, which had the lowest oxygen vacancy concentration. Moreover, RRAM devices, which consisted of the thickest Y2O3 films with the largest oxygen vacancy concentration, showed poor non-volatile properties. The optimized Y2O3-based RRAM devices with a thickness of 37 nm showed conventional bipolar RRAM device characteristics, which did not require an initial forming process. The fabricated RRAM devices showed a high resistance state to low resistance state ratio of over 104, less than +1.5 V of SET voltage, and −15.0 V of RESET voltage. The RRAM devices also showed promising non-volatile memory properties, without significant degradation after 103 s retention and 102 cycle endurance tests.

Soils are warming as air temperatures rise across the Arctic and Boreal region concurrent with the expansion of tall-statured shrubs and trees in the tundra. Changes in vegetation structure and function are expected to alter soil thermal regimes, thereby modifying climate feedbacks related to permafrost thaw and carbon cycling. However, current understanding of vegetation impacts on soil temperature is limited to local or regional scales and lacks the generality necessary to predict soil warming and permafrost stability on a pan-Arctic scale. Here we synthesize shallow soil and air temperature observations with broad spatial and temporal coverage collected across 106 sites representing nine different vegetation types in the permafrost region. We showed ecosystems with tall-statured shrubs and trees (>40 cm) have warmer shallow soils than those with short-statured tundra vegetation when normalized to a constant air temperature. In tree and tall shrub vegetation types, cooler temperatures in the warm season do not lead to cooler mean annual soil temperature indicating that ground thermal regimes in the cold-season rather than the warm-season are most critical for predicting soil warming in ecosystems underlain by permafrost. Our results suggest that the expansion of tall shrubs and trees into tundra regions can amplify shallow soil warming, and could increase the potential for increased seasonal thaw depth and increase soil carbon cycling rates and lead to increased carbon dioxide loss and further permafrost thaw.

The shape of the blade leading edge (LE) is a design variable that cannot theoretically affect the inlet flow characteristics under the definition of the velocity triangle. However, the LE is the first to encounter the working fluid in terms of streamwise direction. Depending on its shape, not only the local flow characteristics but also the performance can be affected. In this study, a numerical analysis of the hydraulic and suction performance for a mixed-flow pump was performed with different shapes of the blade LE. The blade was prepared with four sets according to the ellipse ratio (ER), including a square (ER=0), round (1), elliptic (2), and parabolic (5) shape. As the shape of the blade LE was square, the flow streamline was immediately separated from the blade surface, showing a significant drop in the hydraulic performance. As the blade LE was designed in a round, elliptic, or parabolic shape instead of a square shape, the hydraulic performance did not show a noticeable difference. On the other hand, in the prediction of suction performance, the square LE obtained the best characteristics. As the LE shape gradually became a parabolic shape, the cavity blockage was reduced, and the suction performance was also improved.

The cryogenic centrifugal submersible pump is one of the core equipment of the technology and serves to pressurize and transport the fluid with the centrifugal force generated from the impeller by rotation. Due to the structural characteristics of the working fluid and multi-stage, problems such as cavitation and axial thrust negatively affect the life, noise, vibration, and performance of the pump, so it must be considered. For this reason, this research aimed to investigate a low-pressure LNG pump for an LNG fuel supply system with a general specific speed. The main components were designed based on the previous studies and CFturbo. The numerical analysis method was established and the performance prediction was conducted using commercial CFD packages. The three-dimensional Reynolds-averaged Navier-Stokes equations were discretized to analyze the internal flow field. First, the reliability of the turbulence model was proved through Hord’s experiment in the 0.357-inch ogive. Second, the steady and unsteady simulations were conducted between the single-passage and full-passage conditions in the inducer. Third, the corresponding analysis was investigated to identify problems with existing model features and find improvement directions.

Sol–gel-processed Y2O3 films were used as an active-channel layer for resistive switching memory (RRAM) devices. The influence of post-annealing temperature on structural, chemical, and electrical properties was studied. Y2O3-RRAM devices comprising electrochemically active metal electrodes, Ag, and indium tin oxide (ITO) electrodes exhibited the conventional bipolar RRAM device operation. The fabricated Ag/Y2O3/ITO RRAM devices, which included 500 °C-annealed Y2O3 films, exhibited less oxygen vacancy and defect sites, reduced the leakage current, increased the high-/low-resistance state ratio of more than 105, and provided excellent nonvolatile memory properties without significant deterioration for 100 cycles and 104 s.

In this study, sol–gel-processed amorphous-phase ZrO2 was used as an active channel material to improve the resistive switching properties of resistive random access memories (RRAMs). ITO/ZrO2/Ag RRAM devices exhibit the properties of bipolar RRAMs. The effect of the post-annealing temperature on the electrical properties of the ZrO2 RRAM was investigated. Unlike the ZrO2 films annealed at 400 and 500 °C, those annealed at 300 °C were in amorphous phase. The RRAM based on the amorphous-phase ZrO2 exhibited an improved high-resistance state (HRS) to low-resistance state ratio (over 106) as well as promising retention and endurance characteristics without deterioration. Furthermore, its disordered nature, which causes efficient carrier scattering, resulted in low carrier mobility and the lowest leakage current, influencing the HRS values.

This paper presents surface acoustic wave (SAW)-driven self-cleaning glass aimed at removing contaminants that occur on the surfaces of automotive sensors for autonomous driving. The proposed self-cleaning glass comprises an interdigitated transducer (IDT) patterned on top of the transparent piezoelectric substrate (LiNbO3) and a hydrophobic layer (Cytop) covering the IDT. First, the sliding angle and contact angle of a droplet on a hydrophobic layer are measured in different volumes without the application of any external forces. The experiment shows that the droplets smaller than 4 μl do not slide on the inclined surface. To investigate the effect of SAW on droplet removal, the traveled distances and speeds of droplets are measured in different volumes, viscosities, and applied voltages when the droplets are removed on the surface by the SAW operation of the fabricated self-cleaning glass. Then, it is also investigated that the motion of the droplets by SAW on the inclined substrate in the direction of gravity and the opposite direction. Quantitative tests on the droplet removal performance of the SAW-driven self-cleaning glass are carried out by analyzing captured images recorded during the droplet removal by the SAW operation. As proof of concept, the proposed self-cleaning technology is demonstrated on droplets formed on a lens surface of a camera on which the SAW device is mounted. The demonstration shows that the camera image distorted by droplets that occur on the initial glass cover of the camera module is quickly restored by the SAW operation. The proposed SAW-driven drop free glass can promptly remove various contaminants on the surface of the sensors. Hence, it can be applied not only for automotive sensors but also for outdoor security cameras for daily life safety and future industries such as smart factories and smart cities.

Thin endometrium lining or severe endometrial injury which may occur during artificial abortion can cause defective endometrial receptivity and subsequent infertility. Therefore, much effort has been devoted toward regenerating thin or damaged endometrial lining by applying multiple types of stem cells. Even though there are some positive preliminary outcomes, repairing the injured endometrium with stem cells is considerably challenging, due to the lack of an adequate microenvironment for the administrated stem cells within the tissues and subsequent poor therapeutic efficiency. In this context, as an alternative, we fabricated a 3D stem cell-laden artificial endometrium by incorporating several biodegradable biomaterials (collagen and hyaluronic acid) and multiple cellular components of endometrium (endometrial stem cells, stromal cells, and vessel cells) to properly recapitulate the multicellular microenvironment and multilayered structure. Agarose was used as an inert filler substrate to enhance the mechanical integrity of the three-layered artificial endometrium. Various mechanical characteristics, such as morphology, compression properties, swelling, and viscosity, have been evaluated. Various biological features, such as steroid hormone responsiveness, specific endometrial cell-surface marker expressions, and the secretion of multiple growth factors and steroid hormones, as well as the viability of encapsulated endometrial cells are relatively well maintained within the artificial endometrium. More importantly, severe tissue injuries were significantly relieved by transplanting our 3D artificial endometrium into endometrial ablation mice. Remarkably, artificial endometrium transplantation resulted in a successful pregnancy with subsequent live birth without any morphological or chromosomal abnormalities.

We proposed a simple non-contact inspection method using a laser ultrasonic technique to measure the thickness of a surface-hardened layer. This measurement is based on the dependence of a surface-wave velocity on the thickness of the hardened layers. In this case, it is essential to measure the surface-wave velocity with a wavelength comparable to the thickness of a hardened layer. However, it is not easy to selectively generate the surface waves with a desired wavelength. Thus we proposed the method where the surface waves with a desired wavelength are extracted using bandpass electrical filters. This method is simpler than the conventional one based on dispersion because the surface-wave velocity is directly obtained from measured temporal waveforms. We applied the method to measure the thickness of hardened layers and showed that the results were in good agreement with that obtained by the conventional method and numerical results.

Monoclinic scheelite bismuth vanadate is an efficient photocatalyst for water splitting. In this paper, we perform DFT + U calculations to investigate the structural, electronic, and optical properties, water adsorption and the oxygen evolution reaction processes on BiVO4 (001) and BiVO4 (110) surfaces in acidic medium both in the gas and solution (water) phases. The structural, electronic, optical, and water adsorption properties reveal that BiVO4 (001) surface is energetically more stable than BiVO4 (110) surface in vacuum. On other hand, the water oxidation mechanisms reveal that BiVO4 (110) surface in water and in strained form in vacuum is energetically more stable than BiVO4 (001) surface in water and in strained form in vacuum both U = 0 and 2.1 V. The free energy of adsorption for all systems at U = 2.1 V reduce about 2 times than that at U = 0 V. Such analyzes provide important insights into the role of different facets on BiVO4 surface for photocatalytic reactions.

The cavitation characteristics for the head drop in a mixed-flow pump were investigated with the steady- and unsteady-state analysis. Two mixed-flow pump models exhibiting a different incidence angle were analyzed under the cavitation condition. The model with a larger incidence angle obtains relatively poor suction performance. Moreover, the steady-and unsteady-state analysis indicate different head level under the cavitation condition. The results of the unsteady-state analysis are more accurate to the experimental results. The head of a fully convergent steady-state analysis is not even distributed in the head fluctuation range of the unsteady-state analysis. However, the head drop due to the decrease of inlet pressure has almost the same distribution and gradient. In addition, the amount and shape of the bubbles were presented with the time variation, which were also compared with the averaged result of steady-state analysis. The bubbles show a larger oscillation in the model which has a larger incidence angle. The oscillation of the bubbles is related to the magnitude of the head fluctuation.

With introducing the possibility of early diagnosis through biomarker detection, this method has become important in the field of disease diagnosis. Particle sorting based on conventional digital microfluidics (DMF) mostly employs magnetic beads. In this study, the micropillar-based DMF device confirmed the ability of microbead filtering to detect specific biomarkers. The proposed device was implemented using micro-electromechanical systems, and SU-8 micropillar was realized based on the micro-patterning technology. DMF was able to control droplet movements considering the principle of electrowetting on dielectric. The moving speed of a droplet varied according to the electrode shape and applied voltage. As the droplet moved, the polystyrene bead was sorted corresponding to the interval of the fabricated SU-8 micropillar.

In x-ray CT imaging, the existence of metal in the imaging field of view deteriorates the quality of the reconstructed image. This is because rays penetrating dense metal implants are highly corrupted, causing huge inconsistency between projection data. The result appears as strong artifacts such as black and white streaks on the reconstructed image disturbing correct diagnosis. For several decades, there have been various trials to reduce metal artifacts for better image quality. As the computing power of computer processors became more powerful, more complex algorithms with improved performance have been introduced. For instance, the initially developed metal artifact reduction (MAR) algorithms based on simple sinogram interpolation were combined with computationally expensive iterative reconstruction techniques to pursue better image quality. Recently, even machine learning based techniques have been introduced, which require huge amounts of computations for training. In this paper, we introduce an image based novel MAR algorithm in which severe metal artifacts such as black shadings are detected by the proposed method in a straightforward manner based on a linear interpolation. To do that, a new concept of metal artifact classification is devised using linear interpolation in the virtual projection domain. The proposed method reduces severe artifacts very quickly and effectively and has good performance to keep the detailed body structure preserved. Results of qualitative and quantitative comparisons with other representative algorithms such as LIMAR and NMAR support the excellence of the proposed algorithm. Thanks to the nature of reducing artifacts in the image itself and its low computational cost, the proposed algorithm can function as an initial image generator for other MAR algorithms, as well as being integrated in the modalities under limited computation power such as mobile CT scanners.

Facade of building are mainly made up from red clay brick and concrete block. However, both materials are having high thermal mass and promote high indoor thermal discomfort level. Therefore, it is necessary to invent new building material that have low thermal mass and able achieve strength required. Silica aerogel possesses properties of lightweight and low thermal conductivity as compared to other construction materials. In this study, sandwich panel with silica aerogel mat was studied where the properties of sandwich panel silica aerogel mat are rarely found in previous investigations. Before checking its reliability as thermal insulation panel, the mechanical properties of this panel was investigate. The panel was made-up by concrete wythes with type N mortar and the silica aerogel mats with different thickness. Both concrete wythes were casted and then attached together with silica aerogel mat as the cover. 3 types of panel with different insulation thickness were then tested for flatwise and edgewise compression test. From the results, it was found that core thickness of silica aerogel mat has less influence in flatwise and edgewise compression strengths of the sandwich panel. All specimens achieved minimum strength of type N mortar. Therefore, it is recommended to be used in construction that has equivalent application of type N mortar.

For efficient calibration of multiple long gauge blocks (LGBs), an automatic alignment system, consisting of a multi-axis stage and an angle sensor, was developed and integrated with the Korea Research Institute of Standards and Science linear measurement system. The stage was designed to be installed in the limited space of the linear measurement system, with the ability to translate and align the linear and angular positions of LGBs. The auto-collimation angle sensor detected the tip-tilt angle of an LGB with an angular resolution of 0.11″, by image processing the intensity profile of a beam reflected from one of the measured faces of an LGB. Using this automatic alignment system, up to five LGBs were calibrated sequentially without any manual operation or thermal instability. Therefore, multiple LGBs can be calibrated in a short time with small alignment errors and under optimal thermal conditions. When four LGBs with nominal lengths of between 250 mm and 1000 mm were measured, the measurement repeatability of each LGB length was less than 22 nm, and the calibration results agreed well with those obtained by an LGB interferometer within the expanded measurement uncertainty.

Uncertain external disturbances either secular or oscillating make the satellite attitude be deviated or oscillating from the mission attitude. These disturbances should be detected in short and rejected with proper counter torques of actuators. Nonlinear second order sliding mode observer is one of the good algorithms that can be used for the detection of disturbances’ magnitude and frequencies. With a control law of the integration and dipole rejection filters based on the identified disturbance information, the actuator torques can compensate the disturbances. The spacecraft attitude is then stabilized at the mission attitude within a tolerable error. In this paper, the performances of detection and rejection algorithms are checked respectively in computer simulations. The applicability is proved on a satellite ground simulator recently developed in Korea Aerospace University. The results show that the algorithms work properly with small error, which is due to the low grade of sensors and actuators.

Sol–gel-processed Ti-doped SnO2 thin-film transistors (TFTs) were successfully fabricated for the first time, and the effects of the concentration of the Ti dopant on their structural, chemical, and optical properties were investigated. The introduced Ti dopant showed potential as a promising oxygen vacancy suppressor. Additionally, the results showed that the 0.1 wt% Ti-doped SnO2 TFT had a field-effect mobility of 10.21 cm2 V−1 s−1, a subthreshold swing of 0.87, and an I on/I off value of ∼1 × 108, as well as good negative bias stress characteristics. The success of the Ti doping could be attributed to its small ionic size, high Lewis acid strength, and strong bonding strength. Therefore, the introduced sol–gel-processed Ti-doped SnO2 TFTs stand as promising candidates with potential for application in transparent displays as well as larger area electronics applications.

Building information modelling (BIM) is one of the revolutions in construction industry. BIM is one of the long-waiting solutions for construction industry in order to solve the arisen quality and effectiveness problems. Many researchers have proved the benefits gained from BIM. In this paper, the structural package available in BIM platform is summarized and its maturity is discussed. The BIM projects in Malaysia are listed and it showed a low local BIM implementation. In the perspectives of engineers, migrating from 2D drawing to building information model is discussed with the faced problems and challenges. The technical supports such as internet supports, cloud system and etc. was lacked for small-scaled companies; and self-transformation plan is not available which is believed to minimize the lost during transformation. From structural engineers’ perspective, a better visualization with building information models is critical to address these major problems occurred throughout the migration. However, more time are expected to be consumed in producing the models as it was found that there is a low level of model sharing between engineers and architects. Although the BIM implementation in Malaysia is still in a low level, it is advised that industry players and government should work together to migrating from traditional method to BIM environment.

Malaysia is looking forward in achieving developed country status which drives several strategic plans in construction, as it plays a vital role in country’s economic growth and development. Construction Industry Transformation Programme (CITP) has been introduced to boost its performance with sustainable construction. However, most of the construction industry players are not involved in sustainable construction especially on green building concept and thus decelerating the development. Therefore, this study is conducted to identify the drivers and challenges faced by the construction industry players through questionnaire survey where the market demand from stakeholders is placed primarily in implementing green building. The findings showed that awareness and understanding of the stakeholders about green building concept are lacked due to unforeseen circumstances. Detail explanations or descriptions on the benefits and contributions from green building application are needed to be delivered to stakeholders. A framework is proposed for future implementation by improving the education and delivered information, as well as providing the mechanism of promoting the green building concept among the stakeholders.

Capacitive textile touch sensors were developed using carbon nanotube (CNT) fiber assemblies with braided insulating fibers, considering the washability, a critical factor to realize smart clothing. CNT fibers with electrical conductivity comparable to that of metal wires were fabricated by wet-spinning of purified single-walled CNTs. An insulation layer was then introduced into the CNT fiber assembly, to fabricate capacitive conductive fibers through a braiding process of insulating polymeric fibers. The effects of braiding on the insulation and washability of the conductive fibers were investigated to identify the optimal braiding configuration with respect to the insulation, electrical conductivity, and tensile strength properties of the fibers. The change in capacitance of the conductive fibers was characterized. Finally, a braided CNT fiber assembly was used to fabricate a prototype 2 × 2 textile touch sensor to demonstrate the performance of the sensor for smart textile applications.

As part of the ongoing key comparison BIPM.QM-K1, a comparison has been performed between the ozone national standard of Korea maintained by the Korea Research Institute of Standards and Science (KRISS) and the common reference standard of the key comparison, maintained by the Bureau International des Poids et Mesures (BIPM). The instruments have been compared over a nominal ozone amount-of-substance fraction range from 0 nmol/mol to 500 nmol/mol. Main text To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Searching for the ground state of a kagomé Heisenberg antiferromagnet (KHA) has been one of the central issues of condensed-matter physics, because the KHA is expected to host spin-liquid phases with exotic elementary excitations. Here, we show our longitudinal ([Formula: see text]) and transverse ([Formula: see text]) thermal conductivities measurements of the two kagomé materials, volborthite and Ca kapellasite. Although magnetic orders appear at temperatures much lower than the antiferromagnetic energy scale in both materials, the nature of spin liquids can be captured above the transition temperatures. The temperature and field dependence of [Formula: see text] is analyzed by spin and phonon contributions, and large sample variations of the spin contribution are found in volborthite. Clear changes in [Formula: see text] are observed at the multiple magnetic transitions in volborthite, showing different magnetic thermal conduction in different magnetic structures. These magnetic contributions are not clearly observed in low-[Formula: see text] crystals of volborthite, and are almost absent in Ca kapellasite, showing the high sensitivity of the magnetic excitation in [Formula: see text] to the defects in crystals. On the other hand, a clear thermal Hall signal has been observed in the lowest-[Formula: see text] crystal of volborthite and in Ca kapellasite. Remarkably, both the temperature dependence and the magnitude of [Formula: see text] of volborthite are found to be very similar to those of Ca kapellasite, despite of about an order of magnitude difference in [Formula: see text] We find that [Formula: see text] of both compounds is well reproduced, both qualitatively and quantitatively, by spin excitations described by the Schwinger-boson mean-field theory applied to KHA with the Dzyaloshinskii-Moriya interaction. This excellent agreement demonstrates not only that the thermal Hall effect in these kagomé antiferromagnets is caused by spins in the spin liquid phase, but also that the elementary excitations of this spin liquid phase are well described by the bosonic spin excitations.

The impeller and volute of a single-channel pump used for wastewater treatment were simultaneously optimized to improve the hydraulic efficiency and reduce unsteady radial force sources due to the impeller–volute interaction. Steady and unsteady Reynolds-averaged Navier–Stokes equations were solved with the shear stress transport turbulence model as the turbulence closure model using tetrahedral grids to analyze the internal flow in the single-channel pump. Five design variables related to the internal flow cross-sectional areas of the impeller and volute were selected to simultaneously optimize the hydraulic efficiency, the sweep area of the radial force during one revolution, and the distance of the mass center of the sweep area from the origin as the three objective functions. The response surface approximation model and genetic algorithm were employed to obtain three-dimensional Pareto-optimal solutions representing the trade-off between the efficiency and the radial force sources. The results of the three-objective optimization show that the representative clustered optimum designs enhanced the efficiency and reduced the radial force sources simultaneously in most cases, compared to the reference design. In addition, it was confirmed that the trade-off between the efficiency and the radial force sources clarifies with controlling the internal flow cross-sectional areas of the impeller and volute of the single-channel pump.

We present a resistive pressure sensor based on the thin film printed via melt electrospinning of polyether block amide (PEBA). This thin film is created by arranging the electrospun cylindrical fibers periodically into a narrow vertical wall. We coat this film using poly (3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) and place it between top and bottom counter electrodes for the pressure sensor. With the application of pressure, the variation of the contact area between the electrode and the cylindrical surface of the film produces a sensitive current response for detecting a wide range of pressure with tunable sensitivities. We present the optimized process conditions of the melt electrospinning for the construction of the micro structured thin film. We also develop theoretical model based on the classical contact theory to characterize and predict the sensor responses. Finally, a multi-touch interface for a mobile device is demonstrated based on the described methods. The reliable, cost effective, and scalable characteristics of the presented method offer great promise for mobile or wearable applications.

Recent years have seen researchers paying attention to the fabrication of porous structures by using additive manufacturing techniques suitable for the production of small batches. This paper focuses on the fabrication process and the compressive characteristics of a porous metal manufactured using the direct energy deposition (DED) process, which is a 3D printing technology for metals. Materials with structures containing internal pores were manufactured by spraying a mixture consisting of Ti6Al4V powder and a foaming agent (Na2CO3) onto a Ti6Al4V substrate, and subsequently fused with the substrate using a high-power laser beam. The ensuing molten pool undergoes rapid solidification, resulting in the formation of a metal layer. Before the molten metal solidifies, the carbon dioxide gas generated from Na2CO3 created pores inside the deposited layer. In this study, pored structures fabricated under various conditions were analyzed and compared from the viewpoint of compressive behavior. The results showed that the densities of the layered porous structures could be controlled by varying process parameters such as the laser power, scanning speed, powder feed rate, and mix ratio of the foaming agent. The most dominant parameters to obtain a pored structure were the amount of foaming agent and powder feed rate. The compression tests revealed that the porous materials manufactured using DED collapsed due to fracturing of the internal porous structures. After these structures fractured, the materials experienced densification, followed by crumbling. In addition, decreasing the laser power and scanning speed caused the compressive strength to decrease due to the high number of internal pores. Furthermore, before finally fracturing, the compressive strain decreased for specimens with increased porosity. The compression tests proved that the porous structure was able to effectively absorb compression loads.

The oxidation of InGaAs and the mechanisms underlying this process were investigated using a low-energy oxygen neutral beam. The thickness of the oxide layer and the components of In, O, Ga, and As were examined by cross-sectional transmission electron microscopy (TEM) and X-ray photoemission spectroscopy (XPS). Extending the oxidation duration together with the use of a high indium concentration generated a thicker InGaAs oxide layer because of the difference in chemical bond strength. The oxidation of InGaAs, which was successful even at room temperature, resulted in a high-quality interface because of the highly reactive neutral beam and its extremely low activation energy.

This paper presents a vertical magnetometer–accelerometer capable of detecting simultaneously both the acceleration and the geomagnetic field. The conceived sensor detects the magnetic field by the Lorentz force and differentiates the magnetic field and the acceleration by the modulated frequency difference. The process uses a silicon-on-glass (SOG) wafer and the gold–silicon eutectic bonding for the wafer-level hermetic packaging. When the 10 mA current flows through the conductor, the measured resistances are an average of 10 Ω, so in total, 1 mW is consumed in the current driving element. When 35 µT and 1g is applied to the sensor at the same time, the fusion sensor has a sensitivity of 73 mV/g in acceleration sensing mode, and a sensitivity of approximately 1.63 mV/µT in magnetic field sensing mode. This newly developed sensor can be used in portable navigators that need a small size, low cost and low power electronic compass.

The characteristics of amorphous-to-crystalline phase transformation in the hydrogenated Ge2Sb2Te5 and Ge8Sb2Te11 thin films were investigated by X-ray diffraction (XRD), optical transmittance (TOP), and nano-pulse reflection response. The hydrogenation was conducted under a H2 pressure (PH) of 20 atm and an annealing temperature (Ta) of 100 and 200 °C. The incorporation of hydrogens into the chalcogenide films was verified by secondary ion mass spectrometry (SIMS) depth profile. The variation of H-signals in the SIMS profile was apparently compensated by the variation of Sb and Ge signals rather than by that of Te. The results measured in hydrogenated films were compared with those in the as-deposited and post-annealed films at Ta for 4 h in pure N2 atmosphere. The hydrogenation effects led to very different dependences between the Ge2Sb2Te5 and Ge8Sb2Te11 thin films. Amorphous-to-crystalline phase-transition speed was evaluated via nano-pulse reflection response measurement. The hydrogenation inhibited the transition of Ge2Sb2Te5 but hardly affected that of Ge8Sb2Te11. In particular, the amorphous-to-crystalline transition in the hydrogenated Ge8Sb2Te11 film was very stable.

The microstructural properties of SexTe100-x (x=16,29,38) thin films are investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM) analysis. SexTe100-x thin films have a Te hexagonal structure and Te{011} interplanar spacing decreases because some Se atoms occupy Te atomic sites, forming Se helical chains within the Te helical chains. By increasing the Se contents from 16 to 29 at. %, Se5.95Te1.05 monoclinic and Se hexagonal structures coexist in a grain and at 38 at. %, a Se hexagonal structure is observed within the Te hexagonal grain. This means that SexTe100-x thin films maintain the Te hexagonal structure and that phase separation does not occur owing to the short diffusion time.

The growth direction and morphology of one-dimensional ZnO nanostructures grown by metal–organic chemical vapour deposition (MOCVD) were modulated by changing the growth temperature of previously deposited ZnO buffer layers that were used as a template. The ZnO nanorods grown on the low-temperature deposited buffer layer were regularly inclined with respect to the substrate surface and show in-plane alignment with azimuthally six-fold symmetry. In contrast, deposition of the buffer layer at higher growth temperature led to the formation of vertically well-aligned ZnO nanorods. In addition, the ZnO nanorods grown on the buffer layer deposited at low growth temperature show a growth direction of , unlike the conventional ZnO nanorods showing a growth direction of [0001]. The microstructural analysis and atomic modelling of the formation of regularly inclined nanorods using transmission electron microscopy are presented.

Various shapes of InGaN/GaN multi-quantum-well structures were grown by metal–organic chemical vapour deposition in order to investigate the compositional gradation effect on photoluminescence in the vicinity of the InGaN active quantum well region. The photoluminescence spectra at 424 and 435 nm for the symmetrically graded multi-quantum-well structure and the spectrum at 442 nm for the square-type well structure were strongly quenched, indicating the formation of nano-structures. The symmetrically graded multi-quantum-well structure exhibited a relatively short decay lifetime compared to the square-type well structure for the entire range of temperatures. The compositional gradation in the InGaN/GaN multi-quantum-well structure provides the enhanced In fluctuation with the formation of nano-clusters.

Studies aiming to significantly improve thermal properties, such as figure-of-merit, of silicon nanowires (SiNW) have focused on diameter reduction and surface or interface roughness control. However, the mechanism underlying thermal conductivity enhancement of roughness controlled NWs remains unclear. Here, we report a significant influence of stacking faults (SFs) on the lateral thermal conductivity of a single SiNW, using a combination of newly developed in situ spatially-resolved thermal resistance experiments and high-resolution transmission electron microscopy measurements. We used as-grown SiNWs tapered along the growth direction with progressively lower roughness and SFs density. The results clearly confirmed that both surface roughness and twins or SFs densities suppress the thermal conductivity of an individual SiNW. The results and measurement techniques presented here hold great potential for inspecting minute changes in thermal resistance along an individual SiNW, caused by induced SFs on the nanostructure, and for improving one-dimensional nanowire-based thermoelectric device performance.

Well-aligned ZnO nanowires were successfully synthesized on a silicon substrate at the low temperature of 550 degrees C by catalyst-free vapour phase deposition. The ZnO nanowires had diameters in the range of 70-100 nm and lengths over several tens of micrometres. The synthesized ZnO nanowires, which had a single-crystalline wurtzite structure, showed a uniform morphology and faceted planes at the tips of the nanowires. The photoluminescence of the ZnO nanowires showed a strong UV band at 3.28 eV and a broad green band at 2.29 and at 2.53 eV at room temperature. A detailed discussion regarding the growth behaviour and the growth mechanism of the ZnO nanowires on the silicon substrate is presented in this work.