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排序方式: 共有336条查询结果,搜索用时 15 毫秒
1.
Abiola O. Ajayeoba Adewoye A. Olanipekun Wasiu A. Raheem Oluwaseun O. Ojo Ayowumi R. Soji–Adekunle 《声与振动》2021,55(1):69-85
Economic wood processing employs the use of industrial machines for cutting, shaping, milling, and sawing timber, thereby leading to the generation of high levels of noise. Published data from empirical studies have categorized noise as an environmental hazard of global significance. Furthermore, noise exposure limits for different industries and all the industrial machines available has not been formally established as it presently exists in developed nations around the world. Therefore, this study assessed the daily exposure of sawmills workers to noise in Southwestern Nigeria. Reconnaissance surveys were first carried out in Osun, Oyo, Ondo, Ekiti, Lagos, and Ogun States to select sawmills that were fully operational and fit for the study. Two fully functional sawmills in two cities of each State were eventually selected for data collection, making a total of 24 sawmills, while the Circular Machines (CM), Planer Machines (PM), and Band-saw Machines (BM) were the machines in each sawmill considered. Two machines each of CM, PM, and BM were considered in each sawmill, making a total of forty-eight (48) machines each of CM, PM, and BM. Sound data were collected between 7 am and 7 pm each day for six days (between Monday and Saturday) using Extech 407732 sound level meter and all stabilized measurements were taken three times at different intervals. The data collected were in three different periods: Machine No-work Period (NPm), Machine Idle Period (IPm), and Machine Working Period (WPm). A two–way Analysis of Variance (ANOVA) was carried out at P < 0.05 to determine whether there is a significant difference in the sound level average before and after the break, for both the idle and working periods of the three machines considered. This was also done to determine whether there is a significant difference between the sound level average of the results collected during idle and working periods of the three machines. Noise Pollution Levels (Lnp) ranged from 83.20 dB (PM) to 107.65 (BM) and 93.42 (CM and PM) – 116.00 (BM) respectively, while IPm also gave the least noise pollution level of 95.79 dB and WPm gave the highest level of 102.88 dB. The results revealed that all the machines’ Lnp values in the working period are more than the 90 dB acceptable limit the recommendation value of 90 dB while 89.6% of CMs, 75% of PMs, and 89.6% of BM had their Lnp above 90 dB in the idle period respectively. The minimum and the maximum noise dose levels for IPm, WPm and overall are 0.09 (BM) and 2.37 (CM), 0.50 (CM), and 4.77 (PM) and 0.69 (BM) and 6.64 (PM) respectively. The study found out that the fundamental contributing factors to the high noise levels in sawmills are poor machine maintenance, use of old and obsolete machines, poor housekeeping strategy, limited space, workers’ negligence, lack of PPE, and lack of occupational safety training. The study recommends that proper workplace practices such as use of personal protective equipment, new and modern machines, training, and occupational safety programmes be implemented in the considered sawmills. 相似文献
2.
Jiri Kudr Sylvie Skalickova Lukas Nejdl Amitava Moulick Branislav Ruttkay–Nedecky Vojtech Adam Rene Kizek 《Electrophoresis》2015,36(19):2367-2379
Nanofluidics is becoming an extensively developing technique in the field of bioanalytical chemistry. Nanoscale hole embed in an insulating membrane is employed in a vast variety of sensing platforms and applications. Although, biological nanopores have several attractive characteristics, in this paper, we focused on the solid‐state nanopores due to their advantages as high stability, possibility of diameter control, and ease of surface functionalizing. A detection method, based on the translocation of analyzed molecules through nanochannels under applied voltage bias and resistive pulse sensing, is well established. Nevertheless, it seems that the new detection methods like measuring of transverse electron tunneling using nanogap electrodes or optical detection can offer significant additional advantages. The aim of this review is not to cite all related articles, but highlight the steps, which in our opinion, meant important progresses in solid‐state nanopore analysis. 相似文献
3.
Structure Modification Function of g‐C3N4 for Al2O3 in the In Situ Hydrothermal Process for Enhanced Photocatalytic Activity 下载免费PDF全文
Prof. Fa‐tang Li Shao‐jia Liu Ya‐bin Xue Dr. Xiao‐jing Wang Dr. Ying‐juan Hao Dr. Jun Zhao Rui‐hong Liu Prof. Dishun Zhao 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(28):10149-10159
Heterojunctions of g‐C3N4/Al2O3 (g‐C3N4=graphitic carbon nitride) are constructed by an in situ one‐pot hydrothermal route based on the development of photoactive γ‐Al2O3 semiconductor with a mesoporous structure and a high surface area (188 m2g?1) acting as electron acceptor. A structure modification function of g‐C3N4 for Al2O3 in the hydrothermal process is found, which can be attributed to the coordination between unoccupied orbitals of the Al ions and lone‐pair electrons of the N atoms. The as‐synthesized heterojunctions exhibit much higher photocatalytic activity than pure g‐C3N4. The hydrogen generation rate and the reaction rate constant for the degradation of methyl orange over 50 % g‐C3N4/Al2O3 under visible‐light irradiation (λ>420 nm) are 2.5 and 7.3 times, respectively, higher than those over pristine g‐C3N4. The enhanced activity of the heterojunctions is attributed to their large specific surface areas, their close contact, and the high interfacial areas between the components as well as their excellent adsorption performance, and efficient charge transfer ability. 相似文献
4.
5.
B.?Fathi–VajargahEmail author M.?Navidi 《Journal of Contemporary Mathematical Analysis (Armenian Academy of Sciences)》2018,53(4):232-236
In this paper, theorems about asymptotic behavior of the local probabilities of crossing the linear boundaries by a perturbed random walk are proved. 相似文献
6.
该文基于牛血清白蛋白模板金纳米簇(BSA@AuNCs)与羟基氧化钴(CoOOH)纳米片构建了一种激活型荧光纳米探针用于生物硫醇的检测。带负电的BSA@AuNCs能通过静电吸附作用组装到带正电的CoOOH纳米片表面,与此同时,BSA@AuNCs的荧光由于内滤效应(IFE)有效地被CoOOH纳米片猝灭,形成BSA@AuNCs-CoOOH纳米探针。当向纳米探针溶液加入生物硫醇(0.05~150 μmol/L)时,生物硫醇与纳米探针中的CoOOH纳米片发生氧化还原反应,CoOOH纳米片被降解生成Co2+,同时释放出BSA@AuNCs,BSA@AuNCs荧光信号恢复。结果表明,该纳米探针可以检测低浓度的生物硫醇,对生物硫醇(半胱氨酸、谷胱甘肽和高半胱氨酸)的检出限为30 nmol/L。相对于其他的氨基酸、金属离子及糖类化合物,该纳米探针对生物硫醇具有较高的选择性并成功应用于人血清样品中生物硫醇的检测。 相似文献
7.
8.
A spectral element method using the modal basis and its application in solving second‐order nonlinear partial differential equations 下载免费PDF全文
We present a high‐order spectral element method (SEM) using modal (or hierarchical) basis for modeling of some nonlinear second‐order partial differential equations in two‐dimensional spatial space. The discretization is based on the conforming spectral element technique in space and the semi‐implicit or the explicit finite difference formula in time. Unlike the nodal SEM, which is based on the Lagrange polynomials associated with the Gauss–Lobatto–Legendre or Chebyshev quadrature nodes, the Lobatto polynomials are used in this paper as modal basis. Using modal bases due to their orthogonal properties enables us to exactly obtain the elemental matrices provided that the element‐wise mapping has the constant Jacobian. The difficulty of implementation of modal approximations for nonlinear problems is treated in this paper by expanding the nonlinear terms in the weak form of differential equations in terms of the Lobatto polynomials on each element using the fast Fourier transform (FFT). Utilization of the Fourier interpolation on equidistant points in the FFT algorithm and the enough polynomial order of approximation of the nonlinear terms can lead to minimize the aliasing error. Also, this approach leads to finding numerical solution of a nonlinear differential equation through solving a system of linear algebraic equations. Numerical results for some famous nonlinear equations illustrate efficiency, stability and convergence properties of the approximation scheme, which is exponential in space and up to third‐order in time. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
9.
Bożena Tyliszczak Sonia Kudłacik–Kramarczyk 《International Journal of Polymer Analysis and Characterization》2018,23(3):226-235
Capability of materials to self-repair is an innovative and unique property from a point of view both chemistry and physics. Moreover, such property could arouse special interests if such an ability could be caused by the selection of the environmental parameters. Such materials—polymers based on acryloyl-6-aminocaproic acid (A6ACA)—were synthesized in the present paper. In addition, mentioned polymers have been modified with different amount of magnetic nanoparticles solution. Subsequently, sorption capacity and behavior of synthesized polymers in simulated body fluids have been determined. What is also important, studies on cytotoxicity of prepared materials in relation to fibroblasts and cells of cancer origin have been conducted. Materials have also been analyzed by Fourier transform infrared spectroscopy and scanning electron microscopy method. Based on the research aiming at physicochemical characteristics of abovementioned materials it was proved that prepared hydrogels showed self-repair property in a low pH environment. Apart from this essential issue, these were characterized by high sorption capacity, high porosity which decreases with the introduced amount of nanoparticles and, what is important, cytotoxicity to cancer cells. Such combination is a very interesting from a point of view of many realms and due to its unique features may be widely applicable in the nearest future. 相似文献
10.
高效液相色谱-串联质谱法测定黄瓜与土壤中烯酰吗啉和氰霜唑及其代谢物的残留量 总被引:1,自引:0,他引:1
为评价烯酰吗啉和氰霜唑在黄瓜和土壤中的安全性,建立了同时检测烯酰吗啉和氰霜唑及其代谢物4-氯-5-(4-甲苯基)-1H-咪唑-2-腈(CCIM)的高效液相色谱-串联质谱法。样品经乙腈提取,乙二胺-N-丙基硅烷键合相(PSA)和十八烷基硅烷键合相(C18)净化后,质谱多反应监测模式扫描,基质匹配标准曲线外标法定量。烯酰吗啉、氰霜唑和CCIM在0. 01~0. 5 mg/L范围内均具有良好的线性关系,相关系数(r)均大于0. 994 0,在0. 05、0. 1、0. 5 mg/kg加标浓度下,3种待测物在黄瓜和土壤中的平均回收率为78%~105%,相对标准偏差(RSD)为1. 3%~14. 8%,定量下限为0. 05 mg/kg。对35%氰霜唑·烯酰吗啉悬浮剂在黄瓜和土壤中的残留动态及最终残留量进行分析,发现烯酰吗啉、氰霜唑及CCIM之和在黄瓜和土壤中消解较快,烯酰吗啉在黄瓜和土壤中的半衰期分别为1. 2~2. 1、3. 0~9. 6 d;氰霜唑及CCIM之和在黄瓜和土壤中的半衰期为0. 9~2. 3、1. 8~6. 2 d。该方法简单、快速、灵敏度及准确度高,能够满足黄瓜和土壤中烯酰吗啉、氰霜唑及CCIM残留量的检测要求。 相似文献