Optimization study on neutron spectrum unfolding based on the least-squares method

The response functions and pulse height spectrum(PHS) of a 2'×2' BC501A detector were obtained through a general-purpose Monte Carlo simulation toolkit,Geant4.A relatively simple but effective method was adopted to unfold the PHS.Recommendations regarding the response matrix were proposed to optimize the unfolding results.The results indicate that the accuracy of the unfolding can be greatly improved using many incident neutrons with a wide energy range,a proper energy interval,and an appropriate channel width of the response matrix.The above-mentioned method was verified by unfolding three different types of simulated spectrum,the results of which are in good accord with the simulated distribution.     

Radiation dose detection using a high-power portable optically stimulated luminescence real-time reading system

Optically stimulated luminescence(OSL) reading systems are becoming smaller and capable of real-time detection. To improve real-time and multipurpose radiation dosimetry readings, we built a real-time continuous-wave(RCW) OSL reading system. This system is both small and lightweight, and it employs powerful laser excitation(478 mW/cm~2) at the dosimetry probe location. We investigate the possibility of using the RCW mode to read the radiation luminescence(RL) or OSL by using a singlecrystal Al_2O_3:C dosimeter in a low-dose-rate137 Cs y field.Our results indicate that the RL/OSL follows a stable and uniform distribution. The minimum detected doses associated with the RL, OSL, and RL + OSL signals are2.1 9 10~(-2), 3.17 9 10~(-1), and 5.7 9 10~(-2) l Gy, respectively. This device provides a framework for the future development of applications for practical radiation dose measurements.     

Simulation study of the dose and energy responses of FNTD personal neutron dosimetry

The objective of this work was to use the Geant4 toolkit to perform simulation studies on the personal dose response of fluorescent nuclear track detectors(FNTDs).The entire structure of the FNTD response can be designed,and the detector's energy and dose responses can be optimized in a broad energy range(0.01 eV-20 MeV). In general, the detectors used ~6LiF and CH_2 converters that have high energy and high dose response at neutron energies lower than 10 eV and greater than 1 MeV, respectively. The method of least squares was used to optimize the dose response of H*(10) and the energy response corresponding to Rtotal. The values of the optimized response of H*(10) lie between 0.8 and 1.4, corresponding to the energy ranges 0.01 eV-70 keV and 4-14 MeV, respectively. This occupies nearly eight out of the nine orders of the total energy range. Even though the optimized response of Rtotal is constrained between 0.89 and 1.1 in the energy range of 0.01 eV-20 MeV, it is suitable for obtaining the broad neutron spectrum of fluence with good accuracy.     

Ga0.51In0.49P/In0.15Ga0.85As/GaAs pseudomorphic doped-channel FET with high-current densityand high-breakdown voltage

Ga_0.51In_0.49P/In_0.15Ga_0.85 As/GaAs pseudomorphic doped-channel FETs exhibiting excellent DC and microwave characteristics were successfully fabricated. A high peak transconductance of 350 mS/mm, a high gate-drain breakdown voltage of 31 V and a high maximum current density (575 mA/mm) were achieved. These results demonstrate that high transconductance and high breakdown voltage could be attained by using In_0.15Ga_0.85As and Ga_0.51In_0.49P as the channel and insulator materials, respectively. We also measured a high-current gain cut-off frequency f_t of 23.3 GHz and a high maximum oscillation frequency f_max of 50.8 GHz for a 1-μm gate length device at 300 K. RF values where higher than those of other works of InGaAs channel pseudomorphic doped-channel FETs (DCFETs), high electron mobility transistors (HEMTs), and heterostructure FETs (HFETs) with the same gate length and were mainly attributed to higher transconductance due to higher mobility, while the DC values were comparable with the other works. The above results suggested that Ga_0.51In_0.49P/In_0.15Ga_0.85 As/GaAs doped channel FET's were were very suitable for microwave high power device application     

分光光度法测工业废水的COD的方法改进

化学需氧量（chemicaloxygendemand,简称COD）是表征水体受有机物污染程度的一项重要指标。实验采用微波消解分光光度法测定废水的COD。对影响测定废水中COD的因素进行了研究,并确定了相关的实验条件。实验结果表明,与传统重铬酸钾法相比,本方法快速,简单,结果可靠。     

基于改进D-S证据和融合权集的安全风险评估

针对信息化系统安全风险评估过程中安全风险因素指标的重要性难以赋权的问题,本文以建筑工地施工现场为应用场景,提出一种基于改进的D-S证据理论与融合权集结合的安全风险评估模型.首先,在充分研究建筑工地安全风险评估流程和要素的基础上,建立建筑工地安全评价体系;其次,采用基于权值分配和矩阵分析的D-S合成算法改进AHP法和基于数据的熵权法计算评价体系中指标层中各指标的主、客观权重;然后,运用改进的D-S证据融合算法进行多源证据的合成,获取指标权重,避免单一赋权的片面性,得到最优综合权重;最后,根据TOPSIS评价算法计算建筑工地综合评价指数.分析表明,基于改进D-S证据理论-融合权集的安全风险评估模型,能有效评估建筑工地施工现场的安全性,降低评估结果的不确定性,提高风险评估结果可信度.     

Solid-state urea biosensor based on the differential method

In this paper, the solid-state urea biosensor was successfully fabricated based on the differential method, which contains three parts: the SnO/sub 2//ITO glass electrode used as the pseudoreference electrode; the SnO/sub 2//ITO glass electrode used as the contrast electrode; and the urease/SnO/sub 2//ITO glass electrode used as the enzyme electrode. Correspondingly, this solid-state urea biosensor was fabricated based on the SnO/sub 2//ITO glass electrode, whose simple fabrication process reduces the cost of fabricating the solid-state biosensor. Additionally, as revealed in the experimental results, the solid-state urea biosensor has good sensing characteristics between 5 and 80 mg/dl. After fabricating a successful solid-state urea biosensor, an array sensing system was designed to enhance the precision of the solid-state urea biosensor, which comprises four parts: the biosensor system, the input buffer circuit, the differential circuit, and the weighted sum circuit. As indicated in the experimental results of the array sensing system, the sensing characteristic of the array sensing system is similar to the mean sensing characteristic from four solid-state biosensors. Therefore, the sensing signal of the solid-state urea biosensor can be averaged using the array sensing system. In summary, this study successfully investigated a solid-state urea biosensor and designed an array sensing system to increase the precision of solid-state urea biosensors.     

Using polypyrrole as the contrast pH detector to fabricate a whole solid-state pH sensing device

In this paper, we use the extended gate field effect transistor (EGFET) and the coated wire electrode (CWE) to design a differential pH-sensing device. The SnO/sub 2//ITO glass structure is the EGFET used as the pH sensor because of its excellent pH sensitivity of about 57.10 mV/pH. The contrast pH sensor is the polypyrrole/SnO/sub 2//ITO glass structure CWE, which has the lower pH sensitivity of about 27.81 mV/pH, and we use the third SnO/sub 2//ITO glass structure as the reference electrode to serve the base potential of the electrolyte solution. The pH sensitivity of this differential pH-sensing device is about 30.14 mV/pH and it is linear. Hence, this device is a good pH sensor. By using this technology, the differential pH-sensing device has a lot of advantages, such as simple fabrication, solid-state electrodes, easy packaging, low cost, etc.     

Temperature and optical characteristics of tin oxide membrane gateISFET

The influence of temperature and optical effects on ISFET performance are important. In this study, the temperature characteristics of the SnO₂/Si₃N₄/SiO ₂/Si ISFET are investigated by the zero temperature coefficient (T.C.) adjustment and the dual FET's configuration, respectively. The result show that a zero T.C. of the SnO₂ gate ISFET can be achieved when the appropriate operation current was set. Subsequently, the T.C. of tin oxide membrane/electrolyte interface can be evaluated by the dual FETs configuration. On the other hand, due to the SnO₂ gate ISFET is sensitive to the light exposure, thus in order to improve this drawback, a multi-structure ISFETs: SnO ₂/Al/SiO₂/Si₃N₄/Si ISFETs have been developed. In this structure, aluminum is used as a light shield, and the tin oxide is used as a pH sensitive layer. The results show the ISFETs with aluminum as a light shield have low light sensitivity compared with ISFETs without aluminum as a light shield     

Nonlinear thermal–mechanical vibration of flow-conveying double-walled carbon nanotubes subjected to random material property

The present study deals with the dynamic response variability of nonlinear thermal–mechanical vibration of the fluid-conveying double-walled carbon nanotubes (DWCNTs) by considering the effects of the temperature change, geometric nonlinearity and nonlinearity of van der Waals (vdW) force. The nonlinear governing equations of the fluid-conveying DWCNTs are derived based on the Hamilton’s principle and theory of thermal elasticity. The Young’s modulus of elasticity of the DWCNTs is assumed as stochastic with respect to position to actually describe the random material property of the DWCNTs. By utilizing the Monte Carlo simulation, the nonlinear coupled governing equations of the fluid-conveying DWCNTs become deterministic. Then we adopt the harmonic balance method in conjunction with Galerkin’s method to solve the nonlinear coupled deterministic differential equations for many different sample functions. Some statistical dynamic response of the DWCNTs such as the mean values and standard deviations (SDs) of the amplitude of the displacement are calculated, meanwhile the effects of the temperature change and flow velocity on the statistical dynamic response of the DWCNTs are investigated. It is concluded that the mean value and SD of the amplitude of the displacement increase nonlinearly with the increase of the frequencies in both low and high temperatures. Furthermore, the mean value of the amplitude of the displacement for any fixed frequency decreases due to the temperature change in low temperature; on the contrary, it increases under the temperature change in high temperature.