Assessment of Noise Exposure of Sawmill Workers in Southwest,Nigeria

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 (NP_m), Machine Idle Period (IP_m), and Machine Working Period (WP_m). 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 (L_np) ranged from 83.20 dB (PM) to 107.65 (BM) and 93.42 (CM and PM) – 116.00 (BM) respectively, while IP_m also gave the least noise pollution level of 95.79 dB and WP_m gave the highest level of 102.88 dB. The results revealed that all the machines’ L_np 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 L_np above 90 dB in the idle period respectively. The minimum and the maximum noise dose levels for IP_m, WP_m 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.     

Data assimilation and pollution forecasting in Burgers' equation with model error function

This article presents a correction method for a better resolution of the problem of estimating and predicting pollution, governed by Burgers' equations. The originality of the method consists in the introduction of an error function into the system's equations of state to model uncertainty in the model. The initial conditions and diffusion coefficients, present in the equations for pollution and concentration, and also those in the model error equations, are estimated by solving a data assimilation problem. The efficiency of the correction method is compared with that produced by the traditional method without introduction of an error function.Three test cases are presented in this study in order to compare the performances of the proposed methods. In the first two tests, the reference is the analytical solution and the last test is formulated as part of the “twin experiment”.The numerical results obtained confirm the important role of the model error equation for improving the prediction capability of the system, in terms of both accuracy and speed of convergence.     

富Mn鸢尾生物炭的制备及在类Fenton体系中的应用

通过在N₂气氛围下热裂解富集Mn的鸢尾可得到Mn/生物炭(BC)材料, 并按植物叶(Leaf)和根部(Root)分别将其分别命名为BC-L0, BC-L1, BC-L2, BC-R0, BC-R1和BC-R2. 采用扫描电子显微镜(SEM)、 能谱分析(EDS)仪、 X射线衍射(XRD)仪、 X射线光电子能谱(XPS)、 傅里叶变换红外光谱(FTIR)、 原子吸收光谱(AAS)和比表面积分析(BET)仪等对Mn/生物炭材料的Mn含量、 化学组成与形貌进行了表征, 发现鸢尾叶部为Mn主要富集部位, 最大富集量为13.0 mg/g, 且Mn以Mn₂O₃薄片存在于生物炭表面. 利用Mn/生物炭与H₂O₂构建了类Fenton体系, 在中性条件下BC-L2-H₂O₂体系对有机污染物罗丹明B(RhB, 3×10 ^-5 mol/L)的降解率达到50%(180 min), 表明该体系具备氧化去除RhB的能力, 并推测了该体系对RhB的催化氧化机理. 结果表明, 先将Mn超富集植物转化为Mn/生物炭材料, 再通过添加H₂O₂能构建具有氧化能力的类Fenton体系, 可用于对有机污染物的降解, 实现“以废治废”的绿色循环思路, 为Mn富集的植物后续处理提供一种新的转化及应用方式.     

工业SO2及碳黑颗粒紫外成像遥感监测技术

为了准确有效监测工业烟囱排放,基于SO2及碳黑颗粒物的光学特性,设计并研制出一套双通道紫外成像遥感监测系统.该成像系统的两个光谱通道的中心波长分别定于310 nm和330 nm,利用两个通道的光学厚度之差反演SO2浓度图像,颗粒物浓度图像由330 nm通道获取,根据浓度图像结合光流法获取烟羽运动速度,进而计算得出SO2和碳黑颗粒物的排放速率.结果表明,该工业烟囱的SO2及碳黑颗粒物排放速率分别为72.48±3.16 kg/h和6.33±1.18 kg/h.实验采用紫外相机同时对工业烟囱排放的SO2及碳黑颗粒物进行监测,实验表明双通道紫外成像遥感监测兼具高时间分辨率与高空间分辨率,测量结果准确直观,在工业废气污染、船舶尾气污染以及火山喷发污染排放遥感监测中具有非常明显的技术优势及巨大的应用前景.     

Optical diffusers based on uniform nano-sized polymer balls/nematic liquid crystals composite films

ABSTRACT

Optical diffusers are promising diffusing materials in the optical devices such as monitors, projectors, fibre optics, light-emitting diode (LED) systems and liquid crystal displays (LCDs). We report optical diffusers comprising uniformly distributed nano-sized polymer balls/nematic liquid crystals (LCs) by ultraviolet (UV) click reaction of ene monomer and thiol monomer. By optimising the mass ratio 1:1 of ene and thiol, of which the average diameter of the corresponding nano-sized polymer balls is about 900 nm, relatively high optical transmission and haze with 88.99% and 94.49% are yielded, respectively. Furthermore, by controlling the curing time, the average diameter of nano-sized polymer balls can be reduced to 810 nm, and the developed film exhibits high transmission (98.49%) without sacrificing the high haze (91.77%). This paper demonstrates that UV click reaction is an economical approach to fabricate optical diffusers in a controllable manner.     

A Water-Stable Lanthanide Coordination Polymer as Multicenter Platform for Ratiometric Luminescent Sensing Antibiotics

As a hot topic of global concern, the distinguishing and detecting of antibiotic pollution is crucial owing to its adverse effect on ecosystems and human health stemming from excessive use and poor management. Herein, a water-stable lanthanide coordination polymer sensor (Dy-TCPB) with multiple emitting centers is prepared. The versatile Dy-TCPB can conveniently differentiate various antibiotics, and displays a self-calibration luminescent response to nitrofurazone (NFZ) and furazolidone (FZD). Each antibiotic exhibits notable correlation to a unique combination of the two ligand-to-Dy ion emission intensity ratios, enabling two-dimensional fingerprint recognition. Furthermore, the novel self-calibration sensor demonstrates effective recognition of NFZ and FZD with excellent sensitivity and selectivity, and detection limits as low as 0.0476 and 0.0482 μm for NFZ and FZD, respectively. The synthetic approach for the fabrication of a singular coordination polymer exhibiting multiple emissions provides a promising strategy for the development of facile and effective ratiometric sensors.     

Recycling of polyethylene terephthalate (PET Or PETE) plastics – An alternative to obtain value added products: A review

Waste management is become one of the world's most pressing issues. Plastic is one of the most widely utilised materials in the modern world. Plastic manufacturing and usage have risen globally in recent decades due to its low weight and outstanding mechanical properties. Plastic has a wide range of applications due to such good properties include lightweight, high strength, and extended durability. Because of plastics are non- or low-biodegradable, a vast quantity of plastic waste is generated every day, making waste disposal the most pressing matter globally. Furthermore, improper waste disposal pollutes the environment. An ecologically friendly approach is necessary to locket these issues. One of the solutions is to recycle this sort of garbage. There are many plastic recycling technologies available, however practically all of them have certain restrictions. Chemical recycling of plastic, on the other hand, has been shown to be more efficient than other recycling methods. This article provides a quick overview of chemical recycling of PET post-consumer waste and the synthesis of potentially value-added products such as dye or dyestuffs, bolaform surfactant, bio-degradable polyesters, drug carrier, Metal-organic framework (MOF), bio-degradable polymeric scaffolds, polyurethane foam and coating materials etc.     

二维纳米材料的改性及其环境污染物治理方面的应用

二维纳米材料是一类具有类似二维平面形态,且厚度在纳米级甚至数个原子层的材料,其种类繁多并且具有很多与体相材料不同的物化性质,在众多领域受到了广泛关注。二维纳米材料在催化降解、吸脱附、过滤、传感检测等领域具有可观的应用潜力,还可用于环境污染的防治。通过形貌、元素、基团、缺陷的修饰、改性和材料合成等策略可以调控二维纳米材料的性质,从而研发新的材料体系或者改善二维纳米材料的性能。本文首先归纳了二维纳米材料的种类,并重点阐述了各种改性策略的作用及研究现状,以及改性的二维纳米材料在治理水体污染、大气污染和污染物检测等方面的应用,为二维纳米材料在环境治理领域的发展现状作了系统介绍和展望。     

交货批阴极铜取制样方法对铁含量影响的研究

阴极铜的取样和制样过程对检测结果中铁元素含量影响较大,按照标准中规定抽取铜板的方法能够满足取样精密度的要求。不同的清理表面、钻取方式,钻头材质、制样方法以及除铁步骤等对检测结果中铁元素含量的影响较大,利用扫描电子显微镜和X-射线能谱仪对样品中铁的污染物进行了研究,得出了影响铁元素含量变化的原因,提出了采用钨钢钻头,严格清洗研磨设备、四步法除铁和调整检测样品的称取量等方法来降低阴极铜取制样过程中铁污染的具体措施。