Coaxial Sample Research Articles

Evaluation of dipole moment of polyhedral oligomeric silsesquioxane compounds.

The aggregation state of polyhedral oligomeric silsesquioxane (POSS) within a polymer matrix plays a crucial role. Molecular interactions are key driving forces for aggregation, and one of the key physical parameters is the dipole moment (DPM). Quantum calculations such as density functional theory (DFT) calculations can be used to estimate the DPM. However, concerns exist regarding the accuracy of DPM estimates for complex structures. There have been no reports of electrochemical measurement of DPMs of POSS compounds. In this study, we developed a method to measure the DPM using a readily available inductance-capacitance-resistance (LCR) meter and a coaxial cylindrical sample cell, and we successfully measured the DPMs of POSS compounds for the first time. The DPM values obtained by our measuring method using the concentration constant method and the Halverstadt-Kumler method were in close agreement with the values reported in the literature for the known compounds limonene, methyl benzoate, and nitro benzene, indicating that the DPMs of POSS compounds can be measured accurately. It was found that heptaisobutyl-monosubstituted POSS with n-propyl (7B1Pr-POSS) had a DPM of 0 D, with allyl (7B1AL-POSS) it had a DPM of 2.82 D, with 3-aminopropyl (7B1NH2-POSS) it had a DPM of 2.83 D, and with 3-chloropropyl (7B1Cl-POSS) it had a DPM of 3.58 D. The results indicate that the DPM is affected by the organic substituents on the POSS. The DPM values in different solutions were measured. Our method can be used to measure the DPM of POSS compounds with various substituents.

One-Port Coaxial Line Sample Holder Characterisation Method of Dielectric Spectra.

A technique for solving the one-port closed coaxial transmission line sample holder scattering equation for complex permittivity inversion for lossy materials is presented. A non-linear least-squares procedure is used for the determination of parameters for the specification of the spectral functional form of the complex permittivity. The method allows for accurate retrieval of many low- and high-permittivity dielectric materials in the frequency range of 1 GHz to 3 GHz inserted into the coaxial cell. Using this method, the complex permittivity of a number of liquids and a Maltese soil known as Bajjad soil have been extracted by measurements using a short terminated coaxial transmission line sample holder. The proposed novel inversion method is mainly based on the reflection coefficient of the test material. The measured results of the complex permittivity of liquid dielectrics such as ethanol, methanol, and TX100 are validated and compared with previously published data obtained from measurements made by the National Physical Laboratory (NPL) using a two-port measurement setup made with the same commercial coaxial transmission line sample holder used in the one-port setup. Since the technique allows broadband measurements, it has been used to characterise the soil dielectric spectrum in the frequency range of 1-3 GHz, which is also compared with results from a two-port setup of the same coaxial line. The experimental results are a validation of the proposed approach for different types of materials.

Modulating Electrical Properties of Ti64/B4C Composite Materials via Laser Direct Manufacturing with Varying B4C Contents.

The modulation of electrical properties in composite materials is critical for applications requiring tailored electrical functionality, such as electromagnetic shielding and absorption. This study focuses on Ti64/B4C composites, a material combination promising enhanced electromagnetic properties. Laser direct manufacturing (LDM) was utilized to fabricate coaxial samples of Ti64 blended with TiB and TiC in various mass ratios, with sample thicknesses ranging from 0.5 mm to 3.5 mm. The electrical characterization involved assessing the dielectric and magnetic permeability, as well as impedance and reflectance, across a frequency spectrum of 2 to 18 GHz. The result reveals that TiC, when incorporated into Ti64, exhibits strong dielectric polarization and achieves a reflectivity as low as -40 dB between 7 and 14 GHz. Conversely, TiB demonstrates effective electromagnetic absorption, with reflectivity values below -10 dB in the frequency band of 8.5 to 11.5 GHz. The study also notes that a lower B4C content enhances electronic polarization and increases the dielectric coefficient, while higher contents favor ionic polarization. This shift can lead to a timing mismatch in the establishment of electron and ion polarization, resulting in a decreased dielectric coefficient. In addition, adjusting the B4C content in Ti64/B4C composites effectively modulates their electrical properties, suggesting a strategic approach to designing materials for specific electromagnetic functions.

A study on rocker arm defect inspection based on vision system

The rocker arm plays a crucial role in an internal combustion engine’s valve train system. Issues often arise when there are errors in the production of the rocker arm, such as the following: (1) misalignment of the rocker arm spindle hole and thread hole; and (2) bevel errors in the rocker arm spindle hole. This paper focuses on the development of a rocker arm chamfering and coaxial defect inspection system, which utilizes the RANSAC algorithm. The algorithm consists of five steps: (i) representing a 2D point cloud as a matrix with X and Y coordinates; (ii) detecting the number of circles present in the input point cloud; (iii) setting a tolerance threshold for the distance between the selected circle and other points, crucial for achieving high accuracy; (iv) specifying the maximum number of iterations to find the best model from the input points; (v) defining the maximum number of points that can belong to the same circle, considering point density and the anticipated circle’s surface. The real-time inspection system is designed with a camera mounted on top of the box, and two LED arrays positioned around the box at suitable distances. Test results using a collected data set demonstrate the effectiveness and accuracy of the proposed method in detecting each type of error. In the experiments, the proposed method successfully detected all coaxial defect samples and achieved a detection rate of 95.1% for chamfer defect samples.

Enhancing mechanical strength of electrospun nanofibers by coaxial electrospinning and thermal treatment

AbstractElectrospinning of nonwoven nanofibrous mats has received significant attention in recent years due to the high versatility and porosity of electrospun mats. However, electrospun mats generally suffer from low mechanical strength. This work reports a method to improve the mechanical strength of nanofiber mats by coaxial electrospinning combined with thermal treatment, without incurring significant dimensional shrinkage. Coaxial polyacrylonitrile (PAN)/polyvinylidene fluoride‐hexafluoropropylene (PVDF‐HFP) mats showed no shrinkage when tested at temperatures up to 240°C for 20 min, compared to a shrinkage of 94% for the homogenous PVDF‐HFP mats when treated at 190°C for 20 min. When treated at 178°C for up to 30 min, the coaxial fibres consistently showed changes in thickness of less than 10% and no significant change in area. The coaxial PAN/PVDF‐HFP mats showed negligible changes in average porosity after treatment at 178°C for 20 min. The mechanical strength of the coaxial samples heat treated at 178°C for 5 min was 7.72 MPa, a 22% increase from that before heating, and a 54% increase compared to the as‐spun homogenous PVDF‐HFP. Thus, the proposed technique of combining heat treatment with coaxial morphologies demonstrates significant potential for improving mechanical strength without dimensional shrinkage.

Optimization of 3×3 inch NaI(Tl) detector related to energy, distance and bias voltage

There are different types of radiation detectors (gas-filled, semiconductor, scintillator etc.) and various working principles (ionization, electron-hole pair production, excitation) used in radiation detection. It is important that any detector is selected according to its intended use and that the detector is operated under appropriate conditions. NaI(Tl) scintillation detectors are widely used in nuclear spectroscopic studies due to their known advantages. Prior to carrying out such studies, it is first necessary to know the response function of the detector against radiation under the expected operating conditions and to perform the appropriate calibrations. It is important that certain factors are optimized, such as the experimental setup (source-to-detector position, shielding, source activity etc.), gain, bias voltage, and shaping time, which can each significantly affect the response function. In addition, in computational studies based on experimentation, optimization is gain more significant since it is assumed that such experimental studies are carried out under optimum conditions. In this study, in order to determine the most suitable operating conditions for a 3 × 3 inch NaI(Tl) detector; a coaxial sample holder was manufactured to enable different source-to-detector distances (5–15 cm) to be tested, and spectra were then obtained using different bias voltages (750–850 V) and sources with different energies in the range of 81–1332 keV. Through the use of efficiency values obtained for each condition, line and 3D surface plots were drawn and the relations between efficiency and distance, energy and bias voltage examined. The results showed that the efficiency value had an exponentially decreasing characteristic that was dependent on the energy and source-detector distance, and had the highest value at a bias voltage of around 800 V.

Shielding Effectiveness Measurement Method for Planar Nanomaterial Samples Based on CNT Materials up to 18 GHz

The study and measurement of the shielding effectiveness (SE) of planar materials is required to predict the suitability of a certain material to form an enclosed electromagnetic shield. One of the most widely used standards for measuring the SE of planar materials is ASMT D4935-18. It is based on a coaxial sample holder (CSH) that operates up to 1.5 GHz. Due to this standard’s frequency limitations, new variants with higher frequency limits have been developed by decreasing the size of the CSH conductors and the samples. However, this method and its high-frequency variants require two types of samples with very specific geometries and sizes. This method is unsuitable for certain types of nanomaterials due to their complex mechanization at such undersized scales. This contribution proposes an alternative SE measurement method based on an absorber box that mitigates the problems presented by the ASTM D4935-18 standard. The SE of rigid nanomaterial samples based on several concentrations of multi-walled carbon nanotubes (MWCNT) and two different fiber reinforcements have been obtained.

EMI Shielding Effectiveness Study for Innovative Carbon Nanotube Materials in the 5G Frequency Region

It is crucial to extend the electromagnetic compatibility (EMC) studies to the new frequency regions where modern telecommunication systems operate, specifically those related to the fifth-generation (5G) technology standard for broadband cellular networks. Electric autonomous vehicles (EAVs) are systems that feature 5G technology on board and for which it is essential to ensure the proper management of EMC to prevent malfunctions. Given the considerable development of the EAV-related sector, new materials and solutions for EMI shielding with properties that reduce interference in the frequency regions of 5G technology are being investigated. Today, meatal-based solutions are the most common EMI shielding materials used to mitigate EMC problems. Nevertheless, with the appearance of EAVs, it is needed the design of novel materials that provide a significant balance in terms of shielding effectiveness (SE) and mechanical properties. Thereby, carbon nanotubes (CNTs) are an attractive alternative to conventional EMI shielding materials due to their characteristics. The lightweight condition, flexibility, cost-effectiveness, easy processing, and resistance to corrosion made this new type of material perfect to be used in the field of EAVs. This contribution focuses on describing and characterizing three nanocomposite materials manufactured by loading a polymer matrix with 5%, 7%, and 10% CNT concentrations, respectively. The SE measurement is carried out with a coaxial sample holder based on the standard ASTM D4935-18. This measurement setup makes it possible to determine the performance of the three materials under test up to 18 GHz, covering part of the operation frequencies of 5G systems.

Microstructure and Defect-Based Fatigue Mechanism Evaluation of Brazed Coaxial Ti/Al2O3 Joints for Enhanced Endoprosthesis Design.

Alumina-based ceramic hip endoprosthesis heads have excellent tribological properties, such as low wear rates. However, stress peaks can occur at the point of contact with the prosthesis stem, increasing the probability of fracture. This risk should be minimized, especially for younger and active patients. Metal elevations at the stem taper after revision surgery without removal of a well-fixed stem are also known to increase the risk of fracture. A solution that also eliminates the need for an adapter sleeve could be a fixed titanium insert in the ceramic ball head, which would be suitable as a damping element to reduce the occurrence of stress peaks. A viable method for producing such a permanent titanium–ceramic joint is brazing. Therefore, a brazing method was developed for coaxial samples, and two modifications were made to the ceramic surface to braze a joint that could withstand high cyclic loading. This cyclic loading was applied in multiple amplitude tests in a self-developed test setup, followed by fractographic studies. Computed tomography and microstructural analyses—such as energy dispersive X-ray spectroscopy—were also used to characterize the process–structure–property relationships. It was found that the cyclic loading capacity can be significantly increased by modification of the surface structure of the ceramic.

Diamond anvil cell with double coaxial chambers.

In general, pressure calibration in diamond anvil cells (DACs) has been achieved by mixing pressure calibration materials (PCMs) with the sample inside the pressure chamber. However, the chemical reactions between the sample and PCMs are sometimes unavoidable at extreme conditions, such as high pressure and high temperature. These undesired reactions will cause pollution, induce changes in physical properties or phase transformations of PCMs, and result in tremendous error of pressure calibration. In this paper, we report a new designof DAC with double coaxial pressure chambers, sample and PCM chambers, to resolve the challenge by isolating the PCM from the sample. Our test results show that the pressure of the two chambers presents interesting relations with the anvil setup. When the geometric parameters of two anvil sets are the same and the difference of chamber diameters is within a certain range (i.e., below 10 µm), the pressure correlation between the two chambers shows little correlation with the pressure transmitting medium before and after its solidification at both room temperature and high temperatures within the experimental condition range (well below 20GPa and 634K). In this case, the pressure of the sample chamber can be well calibrated by the pressure of the PCM chamber. This new DAC setup is thus proved to be effective in calibrating the sample pressure below certain conditions while avoiding undesired sample pollution and pressure induced property changes in PCMs under high pressure and high temperature conditions compared with single-chamber DACs.

Effect of second harmonic and second‐order intermodulation on third‐order passive intermodulation

Third-order intermodulation (IM3) is considered as a typical metric to evaluate passive intermodulation (PIM) in electrical connectors, which may be affected by the second-order effect in the circuit with cascaded non-linearities. In this study, the effects of second harmonics and second-order intermodulation on the IM3 powers were theoretically modelled and experimentally verified. Combined with mathematical modelling, an equivalent circuit model of a passive non-linear source was presented to investigate the effect of second-order signals on the IM3 powers. A modified non-linear transfer function was developed by considering multiple non-linear superpositions in cascaded non-linearities. Based on the designed two-tone test, a mathematical expression was provided with the determination of correlation model coefficients. Numerical simulations were performed by using the proposed model, demonstrating the effect of signals induced by the second-order non-linearity on the IM3 powers in series passive components. The IM3 powers resulting from cascaded connectors associated with different signal frequencies were predicted. Coaxial connector samples were designed as cascaded PIM sources in circuits, which were experimentally measured in a GSM 900 MHz frequency band. Good agreement was obtained between the predictions and measurements with error of 0.76 dB in average.

Conductive 3D printing: resistivity dependence upon infill pattern and application to EMI shielding

Polymers filled with conductive carbon black allow for the 3D printing of electrically conductive samples. The resistivity of these 3D printed samples depends on both the microscopic parameters of the carbon black filler and also on the macroscopic arrangement of the extrudites that build up the 3D printed sample. To investigate this dependence, we characterize the resistivity of five different printing infill patterns and find that a cross-ply pattern, which has extrudites oriented both in the direction of current flow and perpendicular to the direction of current flow has a lower resistivity of $$0.229\,\Omega {\text{m}}$$ than the resistivity of $$0.458\,\Omega {\text{m}}$$ found for a uni-ply pattern with all extrudites oriented in the direction of current flow. A Monte Carlo simulation of a large network of variable resistors illustrates the feasibility that the lower resistivity of the cross-ply pattern is caused by cross-flow which diverts current around areas of high local resistance. The same type of 3D printed conductive samples are tested as electromagnetic shields at frequencies up to 3.0 GHz using a custom-designed flanged coaxial sample holder. The shielding effectiveness of three sample infill patterns and four sample infill densities is compared. Cross-ply and angle-ply samples show the most efficient shielding effectiveness (normalized to sample density) of $$17.5\,{\text{dB}}/{\text{g}}\,{\text{cm}}^{3}$$ at an infill density of 50% and would be the infill pattern of choice in an application constrained by weight or material.

Design and Research of a Color Discrimination Method for Polycrystalline Silicon Cells Based on Laser Detection System

In this paper, a method of color discrimination based on sample sensitivity to light wavelength is proposed based on the reflection spectra of a large number of samples and the statistical calculation of the measurement data. A laser detection system is designed to realize the color discrimination. For the color discrimination of polycrystalline silicon cells, the most sensitive wavelength, 434 nm, and the least sensitive wavelength, 645 nm, of polycrystalline silicon cells is obtained according to this method. A laser detection system was built to measure the polycrystalline silicon cells. This system consists of two lasers, optical shutters, collimating beam expanding systems, an optical coaxial system, sample platform, collecting lens, and optical power meter or optical sensor. Two laser beams of different wavelengths are beamed coaxially through the optical coaxial system onto a polycrystalline silicon cell and are reflected or scattered. The reflected or scattered lights are collected through a lens with a high number aperture and received separately by the optical power meter. Then the color value of the polycrystalline silicon cell in this system is characterized by the ratio of light intensity data received. The system measured a large number of previous polycrystalline silicon cells to form the different color categories of polycrystalline silicon cells of this system in the computer database. When a new polycrystalline silicon cell is measured, the color discrimination system can automatically classify the new polycrystalline silicon cell to a certain color category in order to achieve color discrimination.

Comparative study of the hydrogen isotopes yield from Ti, Zr, Ni, Pd, Pt during thermal, electric current and radiation heating

The results of studying the hydrogen isotopes (H, D) yield of Ni, Pd, Pt, Ti, Zr metals with linear heating: a) by the accelerated electrons beam with energy up to 35 KeV, b) by joule heat of AC (50 Hz) through samples, c) by external coaxial furnace samples in metal (stainless steel) and d) quartz vacuum cells are presented. The highest temperature of the position of the maximum intensity hydrogen isotopes release at the linear heating corresponds to the samples heating in a metal vacuum cell, an external coaxial furnace. The lowest temperature position of the maximum intensity hydrogen isotopes release corresponds to the heating by accelerated electrons beam. The difference in these positions of the maximum is ΔТ ≈ 350°С. Difference in maxima position of the hydrogen and deuterium release into the low-temperature region is significant (ΔТ ≈ 50–100°С) for the Ni, Pd, Pt samples, and insignificant (ΔТ <10°С) for the Ti and Zr samples was found, when metals are heated by electric current or in a quartz vacuum cell compared to their heating in a metal vacuum cell.Possible mechanisms of non-equilibrium stimulation of the hydrogen isotopes release from metals, due to the accumulation of external energy by the hydrogen subsystem of crystals considered theoretically. The notions used wherein are in agreement with the obtained experimental results.

Improved reflection technique for the permittivity measurement of ferrites using slotted coaxial samples

This paper presents the effect of magnetic permeability on the permittivity measurement using coaxial line reflection technique. It discusses in detail about the design aspects, analysis and simulation of the slotted co-axial sample and fixture for dielectric characterization of the ferrites and garnets possessing both dielectric and magnetic properties. This technique makes use of improved coaxial fixture and APC 07 compatible slotted coaxial sample geometry to measure the complex permittivity of the ferrite material. Permittivity is calculated from the impedance of sample loaded fixture, which is independent of magnetic permeability, because of air slot cut in the coaxial hollow cylindrical sample along the length. Characterization data of dielectrics and ferrites is used in design of ferrite circulators, and pulse magnets for particle accelerator applications. This is also used in many other RF applications including design of dielectric resonator for spin wave line width measurement of ferrites. Design work is aimed at accurate measurement of complex permittivity; using reflection measurement in coaxial fixture over a wide frequency range of 20 kHz to 1 GHz. Reflection measurement technique is further explored for accurate measurement of complex permittivity.

New Measurement Method of Broadband Permittivity and Permeability of Non-Solid Materials in Small Quantity

Evaluation of permittivity (e) and permeability (μ) of magnetic/dielectric material in microwave band becomes more important with the rapid expansion of microwave technologies. Transmission/reflection line method is well known as a simultaneous measurement method of e and μ in the band. However in this method material under test (MUT) is limited to solid state. On the other hand, for measuring liquid material open ended coaxial probe method was proposed. The method is disadvantageous in terms of requiring deciliter volumes of MUT for approximating a semi-space filled by MUT. We propose a new measurement method with the aim of simultaneous measuring both of permittivity and permeability of not only solid material but also a small amount of liquid, powder, and gel state material. A plastic toroidal case was utilized to encapsulate non-solid state MUT and whole the case was evaluated by coaxial line method. In this study the cases were modeled using Acrylic 3-D printer (Stratasys, Objet 260 Connex). An example of the plastic case with a cap fabricated is shown in Fig. 1. Outer and inner diameter (7.00 and 3.00 mm) of the case was designed to fit to a coaxial sample holder (KEAD Inc., CSH2-APC7). The length of the case including a cap thickness measured by digital vernier caliper was 5.00 mm. In the same way, thickness of wall, bottom, and cap was 0.45, 0.50, and 0.50 mm, respectively. Accordingly the volume of MUT required for the case was about 70 microliters. The specimen which MUT was encapsulated was inserted to the coaxial sample holder and complex scattering (S) parameters from 1–10 GHz were taken using a vector network analyzer (Hewlett-Packard, HP 8720D). S-parameters whose reference planes were both upper and lower surface of the specimen were obtained by shifting reference planes of the measured S-parameters. After that we obtained S-parameters of MUT in numerical calculations mentioned below in order to take away unwanted plastic case portions. The specimen can be divided into three coaxial portions: Inner cylindrical wall, outer cylindrical wall, and middle core including MUT between their walls. From the viewpoint of electric circuit it corresponds to a series connection of the three two-port networks. Impedance (Z) parameters of the middle core were obtained using the relationship: Z-matrix of the specimen equals to the sum of their three Z-matrices. Z-matrix of the specimen was obtained by converting S-matrix of it by a reference impedance. Z-matrix of outer and inner wall was obtained from e and μ measured in advance using solid specimens of the plastic material and outer and inner diameters of their cylindrical walls. Z-matrix of the middle core was converted S-matrix again. The middle slender core can be divided into three coaxial portions: a part of cap, a part of bottom, and MUT. The core corresponds to a cascaded connection of the three two-port networks. Transfer (T) parameters of MUT were obtained using the relationship: T-matrix of the core equals to the product of their three T-matrices. T-matrix of the core was obtained by converting S-matrix of it. T-matrix of a part of bottom and cap was obtained from e and μ of the plastic material used and bottom and cap thickness. Finally e and μ of MUT were calculated from S-parameters of it using Nicolson-Ross-Wier algorithm [1, 2]. In this study, the air at the volume was measured as MUT in order to confirm a validity of the proposed method. The dependences of real and imaginary part of relative permittivity of air obtained by this method on frequency were shown in Fig. 2(a) and Fig. 2(b). Although the both values had a margin of error of plus or minus 10% a constant and nearly ideal relative permittivity of air was confirmed in the band measured from these figures. This result indicates that the proposed method is effective for measuring non-solid materials.

Physical model for space charge distribution measured by pressure wave propagation method in coaxial geometry

With the rapid development of the science and technology, the application of the high voltage power cable has become more and more extensive. Now, it is generally accepted that space charge has an important effect on the electrical properties of insulating material in a high voltage cable. The measurement of space charge is the research base for the behaviors and properties of space charge in the polymer dielectric. Actually, the pressure wave propagation (PWP) method and pulsed electroacoustic (PEA) method are two sophisticated methods of measuring the space charge. However, these two methods are based on a planar sample. For measuring the space charge in a real cable, it is necessary to need the correct and precise mathematical expressions for the PWP method and PEA method. According to the theoretical analysis of the space charge distributions in the plate samples, measured by the pressure wave propagation method, we propose a physical model and its mathematical method of treating space charge distribution data measured in a coaxial geometry. In terms of Poisson equation, the influences of pressure waves on coaxial samples can be divided into two parts, namely, sample deformation and particle displacement. These two parts take into consideration the variations of the sample electric field, dielectric constant and density of space charge disturbed by pressure waves. Therefore, the voltage and current equations about the space charge distribution in the coaxial structure are found. The mathematical expression for the current measured indicates that compared with the current measured in the planar structure, which is proportional to the space charge distribution, the current signal measured in the coaxial structure should be further corrected. This paper also shows the experimental results which are the induced current signals picked from the planar sample and coaxial sample respectively. The results indicate that the current measured in the planar sample is proportional to the space charge distribution. However, the current measured in the planar sample is related to the inner and outer diameter of the dielectric, which verifies the correctness of the mathematical expression. Due to the influence of the coaxial structure of the high voltage cable, the pressure wave focusing effect is obvious as the pressure wave propagates along the axis, which causes the measurement signal to increase gradually with the propagation of sound wave. As a consequence, the electric field and the space charge density will change apparently. Due to the influence of the pressure wave focusing effect, the current and voltage signal will be amplified more obviously in cable, and the current measured by the PWP method shows the distribution of space charge density in cable.

Complex Permittivity to Detect Lead in Soil with Various Salt Forms and Combinations

The response of soil-water systems to an external electric field can be described as polarization and conduction. Polarization represents the electric charges stored in a material, whereas conduction is the ability of a material to conduct free charges. The combined effects of polarization and conduction can be expressed in terms of complex permittivity. Since the complex permittivity of a soil-water system is a function of soil properties, this research was undertaken to detect soil contamination using the complex permittivity measurements. The system used in this investigation to measure the complex permittivity of a lead contaminated soil consisted of an Automatic Network Analyzer (ANA), a set of coaxial cables, a personal computer (PC) for data processing and a coaxial sample holder. Two sample holders were first used: long holder and short holder. It was found that the short holder can give reliable and close measurement to the long holder. The short holder was later adopted. Soil samples were prepared in the lab and mixed with lead nitrate solutions and with hybrid blend of lead nitrate and lead chloride solutions. The relationship between the complex permittivity and lead concentration was investigated. A chemical analysis of the pore fluids for all lead contaminated soil samples was conducted to trace the presence of lead in soil. It was found that the complex permittivity is affected by lead concentration in soil, as the real part decreased and the imaginary part increased with an increase in lead concentration. Lead was not detected in the soil pore water for the soil tested, which suggested that lead was immobilized by precipitation and the adsorption mechanism.

The controlled release of growth factor via modified coaxial electrospun fibres with emulsion or hydrogel as the core

Because of the biomimetic structure and bioactivity preservation, coaxial electrospinning was applied to prepare fibrous scaffolds for delivery growth factors. In this investigation, the coaxial electrospinning technique was modified with emulsion or chitosan hydrogel as the core, to control the release of basic fibroblast growth factor (bFGF). Compared with the conventional coaxial electrospun sample, the emulsion-core coaxial electrospun samples reduced the release amount to around 25% in the first stage, while the hydrogel-core coaxial electrospun sample increased to 63.59% in the first 7 days; and the bFGF cumulative release of all the improved coaxial electrospun samples could achieve about 90%, which was much higher than the control sample (59.89%). Though the appropriate components in the core and the degradation degree of fibres, the modified coaxial electrospun membranes could modulate the release behavior of growth factors following the desired rate and amount, which is beneficial to regeneration of several tissue types.

Polarized hard X-ray photoemission system with micro-positioning technique for probing ground-state symmetry of strongly correlated materials.

An angle-resolved linearly polarized hard X-ray photoemission spectroscopy (HAXPES) system has been developed to study the ground-state symmetry of strongly correlated materials. The linear polarization of the incoming X-ray beam is switched by a transmission-type phase retarder composed of two diamond (100) crystals. The best value of the degree of linear polarization was found to be -0.96, containing a vertical polarization component of 98%. A newly developed low-temperature two-axis manipulator enables easy polar and azimuthal rotations to select the detection direction of photoelectrons. The lowest temperature achieved was 9 K, offering the chance to access the ground state even for strongly correlated electron systems in cubic symmetry. A co-axial sample monitoring system with long-working-distance microscope enables the same region on the sample surface to be measured before and after rotation. Combining this sample monitoring system with a micro-focused X-ray beam by means of an ellipsoidal Kirkpatrick-Baez mirror (25 µm × 25 µm FWHM), polarized valence-band HAXPES has been performed on NiO for voltage application as resistive random access memory to demonstrate the micro-positioning technique and polarization switching.