一种新的γ能谱型放射性检测仪

介绍了自行研制成功的既可用于建筑材料和环境空气放射性检测 ,又可以进行现场石材勘探、评价 ,还可用于核设施周围环境以及事故发生情况下γ剂量进行监测的放射性检测仪。该仪器以AT89C5 2单片机作为控制核心 ,选用φ5 0 mm× 5 0 mm Na I(Tl)闪烁计数器配 GDB4 4光电倍增管作为γ射线探测器 ,可连续进行 2 5 6点的全谱测量工作。

扫描电镜X线能谱检测在诊断电击伤(死)中的应用

电流斑是法医学诊断电击伤(死)的经典改变,而在法医日常工作中,因尸体发生腐败等原因,常会遇到形态学上无法确认电流斑的情况,这种情况下除结合现场勘验、法医学尸体解剖和病理组织学检查外,还可以采用特殊的手段辅助诊断。本文报道1例用扫描电镜X线能谱方法辅助诊断电击后溺死的案例,以供法医工作者参考。

实验性鼠肺组织中Si沉积量的X—射线能谱分析

利用x—射线能谱仪和扫描电镜连机,测量大白鼠正常肺组织和矽肺组织中Si的相对含量,是一种快速、准确、很方便的方法。本文在国内首次采用这种技术,用测定肺组织中Si(I)/S(I)比的方法,研究了振动对鼠肺组织中Si沉积量的影响。通过计算:Si(I)/S(I)比值正常组(C组)为0.13±O.04,矽肺组(Q组)为1.00±0.53,矽肺振动组(QV组)为0.57±0.36,经t检验,QV组低于Q组,且差异显著(P<0.01)。这一结果表明振动可以减少石英在肺脏的滞留,促进石英从肺脏排出。

秦山核电站周围及上海地区放射性水平航空检测

本文介绍应用航空γ能谱方法对秦山核电厂周围及上海地区环境γ放射性水平和地面１３７Ｃｓ、６０Ｃｏ面密度进行检测的方法和主要结果。结果表明，秦山核电站及周围地区环境γ空气吸收剂量率平均值为５２．７ｎＧｙ／ｈ，属正常偏低，没有发现可检测到的来自核电站的污染。意外发现了奉贤县青村镇化肥厂和海盐县耐火材料厂两个人为活动所致的异常点。

Development status and prospect of cold chain logistics of fruits,vegetables,and agricultural products based on intelligent technology

The cold chain in the production area of fruits and vegetables is the primary link to reduce product loss and improve product quality,but it is also a weak link.With the application of big data technology in cold chain logistics,intelligent devices,and technologies have become important carriers for improving the efficiency of cold chain logistics in fruit and vegetable production areas,extending the shelf life of fruits and vegetables,and reducing fruit and vegetable losses.They have many advantages in fruit and vegetable pre-cooling,sorting and packaging,testing,warehousing,transportation,and other aspects.This article summarizes the rapidly developing and widely used intelligent technologies at home and abroad in recent years,including automated guided vehicle intelligent handling based on electromagnetic or optical technology,intelligent sorting based on sensors,electronic optics,and other technologies,intelligent detection based on computer vision technology,intelligent transportation based on perspective imaging technology,etc.It analyses and studies the innovative research and achievements of various scholars in applying intelligent technology in fruit and vegetable cold chain storage,sorting,detection,transportation,and other links,and improves the efficiency of fruit and vegetable cold chain logistics.However,applying intelligent technology in fruit and vegetable cold chain logistics also faces many problems.The challenges of high cost,difficulty in technological integration,and talent shortages have limited the development of intelligent technology in the field of fruit and vegetable cold chains.To solve the current problems,it is proposed that costs be controlled through independent research and development,technological innovation,and other means to lower the entry threshold for small enterprises.Strengthen integrating intelligent technology and cold chain logistics systems to improve data security and system compatibility.At the same time,the government should introduce relevant policies,provide necessary financial support,and establish talent training mechanisms.Accelerate the development and improvement of intelligent technology standards in the field of cold chain logistics.Through technological innovation,cost control,talent cultivation,and policy guidance,we aim to promote the upgrading of the agricultural industry and provide ideas for improving the quality and efficiency of fruit and vegetable cold chain logistics.

以粒状铵油炸药为基体的示踪安检影响因素

为研究爆炸物示踪安检技术,以各类工业炸药为基体,均匀混合微量示踪剂,采用能谱检测方法,通过探测示踪元素的特征X射线,对示踪剂质量分数、炸药质量、介质材料和探测距离等影响因素进行了系列试验研究。以粒状铵油炸药为基体的试验结果表明,示踪剂质量分数由0.01%增至0.1%,50g粒状铵油炸药在空气中的探测距离由40mm增至180mm;示踪剂质量分数0.05%,粒状铵油炸药质量由10g增至100g,在空气中的最大探测距离由40mm增至180mm,50g粒状铵油炸药分别在空气、布料、纸张、木板和泡沫等介质材料中的最大探测距离为120、80、35、70、90mm,分别用厚度0.4、0.6和6mm的铜、铁、铝作介质材料,最大探测距离分别为40、1和10mm;探测距离为0时,示踪剂质量分数0.05%、质量大于4g的粒状铵油炸药可被准确探测到。可见,通过探测示踪元素特征X射线对爆炸物进行安检,不仅技术上可行,而且达到了较高的精度。数据表明,最大探测距离分别与示踪剂质量分数和炸药质量呈线性增长关系,与介质材料的密度呈负相关性。

Energy-aware cooperative spectrum sensingfor underground cognitive sensor networks

With the development of wireless technologies,multifarious standards are currently used in the underground coal mine communication systems.In this paper,the coexistence of 802.15.4 based wireless senser networks （WSNs） with other wireless networks using cognitive radio technique are discussed.Multiple sensor nodes are involved in the spectrum sensing to avoid the interference from other wireless users.The more the sensor nodes cooperate in the sensing,the better the detection performance can be obtained; however,more energy is consumed.How to get the tradeoff between energy efficiency and detection performance is a key problem.According to the requirements for detection,we first give the least required detection time of a single sensor node.Then,the voting fusion rule is adopted for the final decision making.Finally,the relationship between final detection performance and energy consumption is analyzed.

Blind multiple watermarking algorithm for audio

To make digital watermarking accomplish several goals, a new method for simultaneously embedding multiple watermarks into the same audio signal is proposed. First, the original audio signal is segmented into frames of appointed lengths and all the element watermarks are encoded to achieve a mixed watermark. Then, the binary bits in the mixed watermark are embedded into the audio frames with the echo hiding technique. The watermark extraction can be performed without an original audio signal. Furthermore, in order to enhance the extraction accuracy and the robustness of the proposed algorithm against common signal manipulations, the autocorrelafion of the power cepstrum is utilized to estimate the echo delays in the watermarked audio frames to extract the mixed watermark and the corresponding decoding method is applied to achieve the element watermarks. Computer simulation results indicate that the proposed scheme has great robustness against common signal manipulations of Mp3 compressing, re-sampling, re-quantizing, low-pass filtering and white noise addition.

Optimal decision threshold for soft decision cooperative spectrum sensing

In order to achieve higher spectrum efficiency in cognitive radio （CR） systems, a closed-form expression of the optimal decision threshold for soft decision cooperative spectrum sensing based on the minimum total error probability criterion is derived. With the analytical expression of the optimal decision threshold, the impact of different sensing parameters on the threshold value is studied. Theoretical analyses show that the optimal threshold achieves an efficient trade-off between the missed detection probability and the false alarm probability. Simulation results illustrate that the average signal-to-noise ratio （SNR） and the soft combination schemes have a great influence on the optimal threshold value, whereas the number of samples has a weak impact on the optimal threshold value. Furthermore, for the maximal ratio combing （MRC） and the modified deflection coefficient （MDC） schemes, the optimal decision threshold value increases and approaches a corresponding individual limit value while the number of CR users increases. But the number of CR users has a weak influence on the optimal decision threshold for the equal gain combining （EGC） scheme.

Mitigation of primary user emulation attack using a new energy detection method in cognitive radio networks

A most promising solution to the expansion of spectrum efficiency is cognitive radio(CR)and this expansion is achieved by permitting the licensed frequency bands to be accessed by unlicensed secondary users(SUs)with a lack of interference with licensed primary users(PUs).This utilization of CR networks in the spectrum sensing causes vulnerable attacks like primary user emulation(PUE)attack and here PUs play the role of malicious user and do not permit other users to utilize PUs channel even in their unavailability.On the basis of the traditional single-threshold energy detection algorithm,a novel modified double-threshold energy detector is formulated in the CR network and the detection probability,miss detection probability,probability of false alarm,and their inter-relationship are analyzed.This paper develops a modified double threshold energy detection cooperative spectrum sensing technique to alleviate the PUE attack.Finally,performance-based evaluation is carried out between the proposed and the existing energy detection spectrum sensing method that had no consideration on PUE attack.The resultant of the simulation in MATLAB has revealed that the proposed model has significantly mitigated PUE attack by means of providing outstanding performance.

Determination of Threshold for Energy Detection in Cognitive Radio Sensor Networks

The Internet of Things （loT） is called the world＇ s third wave of the information industry. As the core technology of IoT, Cognitive Radio Sensor Networks （CRSN） technology can improve spectrum utilization efficiency and lay a sofid foundation for large-scale application of IoT. Reliable spectrum sensing is a crucial task of the CR. For energy de- tection, threshold will determine the probability of detection （Pd） and the probability of false alarm Pf at the same time. While the threshold increases, Pd and Pf will both decrease. In this paper we focus on the maximum of the difference of Pd and Pf, and try to find out how to determine the threshold with this precondition. Simulation results show that the proposed method can effectively approach the ideal optimal result.

Detection Performance Analysis of Spectrum Sensing in Cognitive Radio Networks with Mobile Secondary Users

The majority of existing papers about spectrum sensing have the assumption that secondary users(SUs) are stationary. However,mobility is an essential feature of mobile communications networks. In this paper,the detection performance of spectrum sensing by mobile SUs was analyzed. Three performance metrics,i.e.,detection probability,miss detection probability and false alarm probability,were thoroughly investigated. In our analysis,a critical variable was the real-time received primary user signal power by a mobile SU. Its probability distribution and mathematical expectation were analytically derived. Moreover,the three performance metrics in single-node spectrum sensing and multi-node collaborative spectrum sensing systems were also derived. Extensive simulations were performed. The results are consistent with the theoretical analysis. And it is concluded that SU mobility has a significant impact on the detection probability and the miss detection probability,but not on the false alarm probability.

Cooperative detection algorithm of spectrum holes in cognitive radio

To improve the detection performance of sensing users for primary users in the cognitive radio, an optimal cooperative detection algorithm for many sensing users is proposed. In this paper, optimal decision thresholds of each sensing user are discussed. Theoretical analysis and simulation results indicate that the detection probability of optimal decision threshold rules is better than that of determined threshold rules when the false alarm of the fusion center is constant. The proposed optimal cooperative detection algorithm improves the detection performance of primary users as the attendees grow. The 2 dB gain of detection probability can be obtained when a new sensing user joins in, and there is a 17 dB improvement when the accumulation number increases from 1 to 50.