bluuebunny/crossref_metadata_2025 huggingface dataset:
Optical Time Domain Reflectometer Assessment of Attenuation in Fiber Optics Communication System
Authors: Ilouno J. , J. Audu I.
Published: October 2019

Attenuation is an undesirable factor that weakens the strength of signal as it travels down fiber optics. Attenuation level in every fiber communication link must be kept at its tolerable range in order to maintain good signal transmission. When the level of attenuation in a link is higher than the acceptable tolerance value, the transmission suffers some setbacks such as loss of signal, freezing of signal etc. An optoelectronic device, Optical Time Domain Reflectometer (OTDR) was used in the measurement of attenuations in the single-mode fiber using the uni-directional technique. It is a convenient and powerful tool for rapidly assessing attenuation behavior in optical fibers. It combines a detector and laser source to provide an inside view of the fiber link described by a trace. The injected light pulse from the laser source is received at the detector. OTDR traces were produced in accordance with the light pulses received. From these traces, the attenuation levels for the different fiber cores were obtained. An average attenuation limit of 0.188 dB/km and average section loss of 0.3dB for 1550 nm wavelength window over the span length of 1597.35 m were achieved which are within the acceptable standard range of 0.20 dB/km to 0.30 dB/km.
Impact of Partially Treated Wastewater on Downstream Water Quality of Notwane River in Botswana
Authors: K. Gaboutloeloe Gilbert , Molokwe Gugu , Kayombo Benedict
Published: October 2019

The impact of partially treated wastewater on the water quality of Notwane river stretch in the Gaborone region of Botswana was investigated. Water samples collected at effluent discharge point and three other sampling sites downstream were analyzed for pH, temperature, Biological Oxygen Demand (BOD5), Ammonia-nitrogen (Ammonia-N) and Nitrate-nitrogen (Nitrate-N). Sampling was conducted bi-weekly between February 2013 and April 2013. The ranges of measured parameters were:  pH (7.6-8.5), temperature (22-23ºC), BOD5 (11.2-27.0 mg/l), Ammonia-N (2.4-60.5 mg/l), Nitrate-N (20.6-28.6 mg/l). Analysis of variance, Games-Howel multiple comparisons and Pearson correlation were used to separate variable means. The results signal river non-point pollution due to runoff inflow of organics mainly from land use and domestic waste dumping by nearby dwellings. Temperature, BOD5, and pH range values were all within the Botswana Bureau of Standards (BOBS) limit while the maximum Ammonia-N and Nitrate-N were above BOBS limit by 50.5 mg/l and 6.6 mg/l, respectively. Regulations on indiscriminate waste dumping and discharge standards adherence should be enforced.
Development of Software for Life Cycle Cost Analysis of Solar Photovoltaic (PV) and Diesel Generator Systems in Nigeria
Authors: Chukwuma Mbah Charles , Ukachukwu Oparaku Ogbonna , Chibuikem Nnadozie Emmanuel
Published: October 2019

The human and economic development of any nation is largely tied to the availability of energy, hence the need for an adequate supply of electricity by reliable energy systems. Nigeria’s economic growth is undermined by the epileptic nature of its electricity supply system. Consequently, the populace is forced to turn to alternative sources of power. However, this presents another problem - conflict of choice between available options for power generation. There is, therefore, the need to assist electricity consumers in Nigeria make better and cost-effective choices in this regard. In this paper, a software computer program is developed to determine/compare life cycle cost (LCC) of solar photovoltaic (PV) and diesel generator systems as preferences for electricity generation in Nigeria. The software is developed through an approach involving load determination, energy resources determination, system sizing and a typical residential building. The key methodology adopted is evolutionary prototyping which focuses on vertical dimension approach. Typical load description of a household located in Amawbia Awka of Anambra state in Nigeria was used to test the efficiency of the source code. The initial cost and life cycle cost for the two systems over a period of 30 years was ascertained. The test results showed the solar PV system to be a more cost-effective solution than the diesel generator based on total life cycle costs. The study recommends among others, the need to increase awareness of the long-term benefits of solar energy systems as an alternative source of electricity in Nigeria.
Effective Implementation of Maintenance Models in Building Maintenance Process
Authors: Ogunoh, Peter E. , C. Mbanusi E. , Uchenna Peter Okoye
Published: October 2019

Buildings are essential facilities which represent a substantial percentage of most tertiary institutions assets, user needs and operating costs. The maintenance levels of these buildings are very crucial to educational effectiveness. However, in spite of the crucial role of these buildings in the education and construction sector of the economy, most educational buildings in Nigeria are in deplorable conditions as a result of lack of maintenance. The efficient and effective maintenance management of both new and old buildings constitutes a challenge to the management. Presently, studies on maintenance of buildings have not been conducted in sufficient details for educational buildings in Nigeria. This research was therefore, aimed at effective implementation of maintenance models in building maintenance process. Maintenance is reactive rather than proactive and no evidence of maintenance plan and manual were in use.
Deturbidization of Vegetable Oil Refinery Wastewater with Extracted Fish Scale Biomass via Coagulation Process; Non-linear Kinetics Studies
Authors: F. Okey-Onyesolu C. , D. Onukwuli O. , C. Okoye C.
Published: October 2019

Chito-protein was successfully synthesized from fish scale. The ability of a coagulant (chito-protein) prepared from fish scale (FSC) to carry out an effective removal of pollutants from food processing industry (vegetable oil industry wastewater, VOW) was evaluated at bench scale using a simulated jar test analysis. The coagulant was characterized via proximate analysis and instrumental analysis: Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The maximum kinetic parameters determined were recorded at K of 2x10-5L/mg.min, 1g, t1∕2= 50 min, R2= 0.9245 and pH of 2.Regression coefficient analysis (R2) was used to ascertain the accuracy of the fit to the postulated kinetic model. However, it was concluded that the second order kinetic model described the reaction most adequately. Removal efficiency of turbidity (87.21%) was obtained at optimum contact time of 30 min, pH 2, coagulant dosage of 1.5g and temperature of 323K. Kinetic study showed that Pseudo first order and pseudo second order models were the best two models in describing the coag-adsorptive kinetics of the coagulant. Similarly, the predicted kinetic data were adjured statistically significant using F- test and T-test.
Comparative Study of Fluid Package on Extractive Distillation of Ethanol-water Mixture Using Pure Glycerol and Ethylene Glycol as Extracting Solvents
Authors: Odejobi O. J. , Oladokun O. R. , Ajeigbe F. J.
Published: October 2019

The comparative study of Peng Robinson Strygek Vera (PRSV) and Non-Random Two Liquid (NRTL) fluid packages on the extractive distillation of ethanol-water mixture was done using pure glycerol and ethylene glycol as extracting agents. The process was simulated using HYSYS V. 8.4. Pure glycerol and ethylene glycol-glycerol mixture were used as separating agents. The results showed the highest molar composition of ethanol in the distillate at the solvent feed rate of 80 kmol/hr when pure glycerol was used with NRTL fluid package. With the PRSV fluid package the highest ethanol in the distillate was obtained at pure glycerol feed rate of 50 kmol/hr. The ethanol fraction in the distillate was decreasing with increasing ethylene glycol and decreasing glycerol in the ethylene glycol-glycerol mixture. The comparative study of the base case and alternative designs showed high ethanol composition in distillate in the range of 99.46 - 99.96% and 99.96 - 99.67% for NRTL and PRSV fluid package, respectively. It was concluded from the study that the PRSV fluid package could save cost of operation because of lower solvent requirement and energy consumption in the reboiler for both the base case and alternative designs.
Line Stressing Critical Processes Optimization of Scalable Package Passive Device for Successful Production Ramp-up
Authors: Sumagpang Jr Antonio R. , Gomez Frederick Ray I.
Published: October 2019

The technical paper presents a systematic and methodological approach to deal with a new product trend that will be successfully manufactured during assembly production ramp-up.  The project is intended to determine the required process flow and machine platforms for high-density and high-complexity scalable device. Critical processes are shown and top reject contributors are addressed through systematic method by using statistical tools and in-depth engineering analysis.

The Scalable Package Passive Device is one of the newest and latest developed device in the plant, which functions as a diode for mobile and computer applications.  The device is considered high density as its 6” single wafer is equivalent to 400,000 units compared to conventional device consisting of only 1,000 units.  Moreover, it is considered as a device with high complexity as state-of-the-art platforms are needed to satisfy its output process.  Furthermore, the device has a very thin die and with the smallest total package dimension.  The process of assembly manufacturing includes a step cutting method of wafers, compression molding, and in-strip testing, which are unlikely to be found on other semiconductor industries. Ultimately, complex errors and top reject contributor of identified critical processes are corrected and the target or required process capability index is effectively achieved.
Introduction of Laser Grooving Technology for Wafer Saw Defects Elimination
Authors: Sumagpang Jr Antonio R. , I. Gomez Frederick Ray
Published: October 2019

The technical paper showcased a comprehensive study on laser (light amplification by stimulated emission of radiation) grooving as breakthrough and ultimate solution in wafer sawing. The project is intended to address various defects such as chippings, metal dangling/peel off, cracks, and other wafer-related defects induced during wafer sawing process. Series of process simulations, actual processing, benchmarking, and collaborations with suppliers are carried out to attain a zero defect in wafer sawing. Critical processes and controls on this new technology are shown and how the mentioned defects are properly addressed.

The laser grooving is the newest and latest developed state-of-the-art technology over conventional mechanical sawing using blades. Sawing process is considered as one of the challenges in the plant as it deals with different wafer technologies. Different blade types also need to be properly maintained. Compared to the conventional and universal mechanical sawing using blades, complex errors and top reject contributor of identified critical processes are corrected and required process capability index is achieved.
Pick and Place Process Optimization for Thin Semiconductor Packages
Authors: Rodriguez Rennier S. , Gomez Frederick Ray I.
Published: October 2019

Nowadays, electronic manufacturers trend are to become thinner and thinner especially those electronic gadgets that is very handy and convenient on our daily necessity. Challenge with the leading manufacturers is the production and development of less size gadget yet with richness of available application and uses that we can work on with what can please its consumer for their convenience and satisfaction. As with the semiconductor company, correlation between becoming thinner versus manufacturing capability become significantly opposite, as the package become thinner the more complex its related process can be. This study covers innovative approach in die attach station on critical handling of thin die packages. Lessons and learning were documented from Ball Grid Array (BGA) packages as first to be evaluated with thin package requirements.  Also discussed herewith are documented defects and related issues during trials and die attach builds that has been a show stopper on its early production.
Differential Active Balun Design for WiMAX Applications
Authors: Gomez Frederick Ray I. , Hizon John Richard E. , Leon Maria Theresa G. De
Published: October 2019

The paper presents a design and simulation study of a differential active balun circuit implemented in a standard 90 nm complementary metal-oxide semiconductor (CMOS) process.  The active balun design is intended for Worldwide Interoperability for Microwave Access (WiMAX) applications operating at frequency 5.8 GHz and with supply voltage of 1V.  Measurements are taken for parameters such as gain difference, phase difference, and noise figure.  The differential active balun design achieved gain difference of less than 0.23 dB, phase difference of 180° ± 3.4°, and noise figure of 9.78 dB, which are comparable to past active balun designs and researches.  Lastly, the design achieved a low power consumption of 3.6 mW.
Development of a Single Wheel Test Rig for Measuring Motion Resistance
Authors: Sedara A. M.
Published: October 2019

Research on soil-wheel interaction is essential in studies of motion resistance of narrow wheels of agricultural machines. The aim of this research was to study the effects of soil moisture content and tyre inflation pressure on motion resistance of narrow wheels using a locally developed single wheel test rig. A single wheel Test Rig facility was developed at Federal University of Technology, Akure. It consists of a soil bin, carriage, single narrow wheel tester, trolley and drive system. An existing indoor soil bin facility was equipped with a soil bin which dimension was 9.76 m length x 1.98 m width x 0.92 m high. The single-wheel test facility was utilized to investigate the effect of tyre inflation pressure and vertical load on motion resistance of wheel. Two narrow wheels of 90/10-10 in width, IRC MB90 tyre were used as the test wheels on clay soil and were separately installed on a carriage that traversed the length of soil bin. Two inflation pressures of 274 kPa and 380 kPa and four levels of vertical load applied on wheel (i.e. 15, 20, 30, and 40 kg) were examined at two different soil moisture conditions (bulk density of 1.58 g/cm3 and 1.55 g/cm3, soil moisture content of 8% and 10% dry basis and soil penetration resistance of 1.02 MPa and 1.5 MPa). Exponential regression was obtained for the two wheels to check for linearity at different moisture content, R2 value for test wheel 1 with inflation pressure of 270 kPa at 8% moisture content was 0.9974 while that of inflation pressure of 380 kPa at 10% moisture content was 0.9952; also for test wheel two (2) R2 value was 0.9977 and 0.9914 at moisture content of 8% and 10% respectively, this shows for test wheel 1 with inflation pressure of 270 kPa at 8% moisture content showed more motion resistance compared to motion resistance of test wheel 1 at inflation pressure of 380 kPa and 10% moisture content, while for test wheel 2 with inflation pressure of 270 kPa showed low motion resistance at 8% motion content. The effect of different inflation pressures and vertical loads on the motion resistance of the narrow wheels has been investigated under different moisture content (8% and 10%). The contact area for all tests was in the range of 309-330 cm2, average contact pressure increased nearly linearly with increase in vertical load and increase in inflation pressure The research provides data that are relevant in the study of soil-wheel interaction.
Analysis of Near Surface Seismic Refraction for Geotechnical Parameters in Opolo, Yenagoa of Bayelsa State
Authors: Omonefe Francis , Desmond Eteh , Ebiegberi Oborie , Karo Oboshenure Kingsley
Published: October 2019

Three surface refraction seismic profiles were conducted in a site targeted for huge construction in an underdeveloped area in Opolo, Yenagoa city to portray some of the subsurface soil engineering characteristics for the purposes of construction. The Generalized Reciprocal Method (GRM) was used to interpret the acquired P and S-wave. Various shallow rock engineering parameters such as Oedometric modulus, Concentration Index, Material Index, Lame’s constant, Density Gradient, Stress Ratio, Shear modulus, Bearing capacity, and N-value were calculated in other to assess the strength of the subsurface  from a geophysical and engineering perspective. The values from the seismic velocity and strength parameters indicates that the bedrock layer (layer 3) of the area studied is characterized by more competent rock quality than layer 1 and 2. Hence, the Opolo site is suggested for construction activities with percussive measures.
Validating Visual Modflow Numerical Model to Predict Future Impact of Brine Disposal on Groundwater
Authors: El-Mageed Neveen B. Abd , Abdul-Muttalib Muhammad A. , Heiba Yasmen A.
Published: October 2019

The aim of this research was to simulate the brine disposal fate within an aquifer. The Visual MODFLOW numerical code was used to predict the salt concentration emigration over time in an aquifer. The model was calibrated using laboratory experimental data. The model results revealed that there is an acceptable agreement between the observed and simulated data.
Assessing Qualities of Different Sources of Water for Mixing Concrete
Authors: Yalley Peter P. , Appiadu-Boakye Kennedy , Adzraku Wisdom D.
Published: October 2019

This study investigates the effects of water sources on concrete properties. A mix ratio of 1:1.5:3 with 0.5w/c was used in mixing the concrete.  Water from the Stream, the hand-dug well and the borehole were used for the experiments with pipe borne water serving as the control. Cubes and beams were cast and tested for compression and flexural strengths respectively at 7-day and 28-day curing ages. Chemical and physical properties of the water samples were also tested. The results indicate that the chemical impurities of all the water types were within the limits given in GS 175-1:2009, EN 1008, ASTM C94 and AS 1379. The physical specifications were all satisfactory, except for the stream water. The water sources had no significant effect on the workability of concrete. Effects of efflorescence were not observed on hardened concrete specimens obtained from any of the water sources. Concrete Specimens mixed with water from the hand-dug well had the highest compressive strength.
Adsorption of Cyanide from Cassava Wastewater Using Calcined and Activated Oyster Shell Ash
Authors: Akpan Oto-Obong P. , Etuk B. R.
Published: October 2019

Calcined ash and activated ash adsorbents were prepared from oyster shell. The physico-chemical properties of the prepared calcined oyster shell ash (COSA) and activated oyster shell ash (AOSA) were obtained using ASTM standards and Sears method. The results show that AOSA is a better adsorbent for removal of cyanide from cassava wastewater than COSA. The adsorption of cyanide from cassava wastewater onto adsorbents (COSA and AOSA) was investigated as a function of pH, adsorbent dosage, contact time, temperature and initial cyanide concentration. The batch study reveals that the adsorption process is strongly pH dependent and maximum cyanide removal is found to occur at pH of 10. The highest percent removal of cyanide from cassava wastewater was found at contact time of 80 minutes and 30oC. The effect of temperature on the adsorption process shows a small increase in the percent cyanide removal followed by a large decrease which suggests physical adsorption as the adsorption mechanism. The percent cyanide removal efficiency decreases with increase in initial cyanide concentration and increases with increase in adsorbent dosage.
The Design, Construction and Testing of an Intelligent Device for Coating Flaws and Crack Detection in Pipelines
Authors: Lana A. R. , Idusuyi N.
Published: October 2019

The major pollutant induced by pipeline failure in Oil and Gas industry has been mitigated over the years using non-destructive techniques like liquid penetrant, magnetic particles, radiographic, ultrasound and eddy current testing. The eddy current technique’s advantage over the other testing devices remains the best suitable in the design and construction of the devices due to the nature of the pipeline materials. For this present work, a pre-test-post-test experimental design was used to test devices on a defect free pipe and a pipe with machined defects of known dimensions and different orientation (longitudinal and axial) after construction. The defect detection was done using electromagnetic technique of eddy current by exciting a coil with power supply and placed close to the tested pipe surface, as a micro-controller was used to track the irregularities on the material surface by computer systems. The device set up for the test was a coil with a power supply of a DC battery connected with micro-controller of a quantization level of 4.88mV. For visual display, result obtained indicates no variation in the amplitude of the pulse as demonstrated by a pipe with no defect while variations (deeps) occurred in the pipe with defects as the coil was traversed over the defect. The orientation had no significant effects on the sensitivity and effectiveness of the device. Results validation was done using a non-destructive technique by visual inspection. Thus, device has shown its effectiveness in detecting defects irrespective of the orientation. Similarly, the size of the defects is a determinant in the amplitude variation of the pulse displayed which implies at higher sensitivity, a high frequency is required.
Wafer Tape Selection Analysis for Adhesion Problem Mitigation
Authors: S. Bacquian Bryan Christian , I. Gomez Frederick Ray
Published: October 2019

Wafer passivation or the protective layer of the internal circuitry of the die plays a major role of providing protection and the isolation of electrical stability of the active circuit on the top area of the wafer. Passivation is normally a screen of an oxide layer on the surface of the silicon wafer or the carrier of internal circuitry of the die. Passivation is normally in the form of polyimide or a glass material. From the wafer structure, it is important to cover the active circuit to ensure no other noises will be induced to the wafer. Inclusion of the passivation layer will help maximize the functionality of the semiconductor device thus eliminating noises coming from the external sources.

As the integrated circuit (IC) package goes thinner, the requirement of having the active circuit or the die thinner is the main concern during the wafer preparation process. Wafer backgrinding or wafer thinning is the focal process involved to satisfy such requirement. Prior performing the wafer thinning process, the application of tape, normally in a form of polyolefin or polyvinyl chloride should be performed to eliminate contamination and protects the active layer of the wafer during the process. However, there should be enough adhesion between the wafer and the thinning tape itself. High adhesion strength may lead to adhesive remains or worst, passivation will be peeled off from the active layer of the wafer.

Adhesion to the passivation layer should be properly evaluated and monitored in such way that will eliminate adhesive remains during detaping process after wafer thinning. The effect of adhesion strength could be predicted by properly selecting thinning or protective tape to be used. Higher adhesion strength could be achieved but due to criticality of passivation to tape adhesion, ultra-violet (UV) process should be included to substantially decreased the adhesion. The importance of UV exposure is also discussed on this paper.
Comparative Analysis of Rescaled Range Results of Normal and Abnormal Heart Sound Recordings
Authors: Ibe Lotachukwu , Ogunniyi Salau Tajudeen Abiola
Published: October 2019

Heart acoustics can be used as an early diagnostic tool, to quickly and accurately identify medical patients who may be at risk of unfavourable cardiovascular outcomes. However, at present, there remains no universally accepted standard or technique for detecting abnormalities using Phonocardiograms. To address this, a large database containing normal and abnormal heart sound recordings of patients were studied with the rescaled range technique and the Hurst exponent, a measure of persistence for non-linear dynamic data. Using the Hurst exponent (H) as a benchmark, we compared the values of the Hurst exponent for normal heart sound recordings with that of the abnormal heart sound recordings. For this study, the recording length was limited to the first 10 seconds for all 578 distinct recordings, which were selected randomly from the database. Furthermore, two Hurst exponent values were obtained for each recording, by subjecting them to time intervals of 1 and 2 milliseconds respectively. The results from this study show that heart sound recordings are persistent (H > 0.5) for normal and abnormal heart sound recordings, with the normal recordings being slightly more persistent.
Adaptive Design and Performance Evaluation of Compact Acoustic Enclosures Built with GFRP for Portable Mini-generators
Authors: Agbo Cornelius Ogbodo Anayo
Published: October 2019

A simple, portable and effective design for enclosing portable generators to reduce the radiated noise has remained a daunting challenge to noise control advocates in many developing countries. This research aims to use an adaptive design approach to create an enclosure for minimizing portable mini-generator noise. The noise characteristics of the mini-generators was ascertained and construction of a 730 by 640 by 600 mm enclosure was accomplished by using glass fiber reinforced plastic (GFRP) to build a double walled enclosure surfacing and rock wool as the sandwiched absorbing material. The sound pressure level (SPL) around the generator before and after the application of the enclosure was measured and evaluated. The results obtained showed that the acoustic enclosure could achieve an insertion loss of up to 16 dB (A) at a distance of 1.0 m.  Also, the heat transfer characteristic of the enclosure design was put into consideration as well as the requirements of the engine air aspiration and cooling inside of the enclosure. Incorporation of fans in the acoustic enclosure design increased convectional fresh air circulation into, and discharge of the heat generated in, the enclosure, thus maintaining a safe temperature of about 40oC inside of the acoustic enclosure at the generator operating maximum load.
Effect of Liquid Phase–Assisted Sintering on the Microstructure, Mechanical Properties, and Tribological Behavior of Self‐Lubricating Ferrous Composites
Authors: de Medeiros João Pedro , Hammes Gisele , Oliveira Neves Guilherme , Martinelli Antonio Eduardo , Nelmo Klein Aloisio , Binder Cristiano
Published: October 2019

A current challenge to the development of self‐lubricating metal matrix composites by conventional powder metallurgy is the dispersion of lubricant lamellar particles between the metal powders during mixing and compaction. This event hinders neck formation during sintering, negatively affecting the mechanical properties of the material. Sintering in the presence of a liquid phase can improve both densification and the distribution of lubricant particles in the microstructure of the composite material. Herein, the effect of the addition of copper in composite powder mixtures as the liquid‐phase agent on the microstructure, mechanical properties, and tribological behavior of ferrous matrix self‐lubricating composites is evaluated. Increasing the contents of copper improves the homogenization of alloying elements, the continuity of the matrix, and the morphology of discontinuities. These phenomena result in self‐lubricating composites with superior mechanical properties and tribological behaviors.
An Evaluation of the Microstructure and Microhardness in an Al–Zn–Mg Alloy Processed by ECAP and Post‐ECAP Heat Treatments
Authors: Wang Ying Chun , Afifi Mohamed A. , Cheng Xingwang , Li Shukui , Langdon Terence G.
Published: October 2019

Herein the microstructure evolution and microhardness variations in a peak‐aged Al–Zn–Mg alloy after equal‐channel angular pressing (ECAP) for 1–8 passes followed by heat treatments at temperatures of 393–473 K for 5–20 h are examined. The results show that ECAP processing hardens the alloy, and the hardness increases with each pass due to grain refinement, the formation of large numbers of fine precipitates, and the introduction of a high dislocation density. Post‐ECAP annealing at 393 K up to 20 h after 1 and 4 passes of ECAP leads to a further increase in microhardness and this increase is substantial for an annealing time of 20 h after 1 pass due primarily to the extensive formation of a nano‐sized η′ phase. After ECAP for 8 passes, post‐ECAP annealing at 393 K for 5 h or more leads to softening due to the occurrence of recrystallization and the transformation of fine η′ to coarse η. Post‐ECAP anneals at the higher temperatures of 423 and 473 K are not capable of producing high hardness values.
Practical Chromatic Aberration Correction in Virtual Reality Displays Enabled by Cost‐Effective Ultra‐Broadband Liquid Crystal Polymer Lenses
Authors: Zhan Tao , Zou Junyu , Xiong Jianghao , Liu Xiaomin , Chen Hao , Yang Jilin , Liu Sheng , Dong Yajie , Wu Shin‐Tson
Published: October 2019

Chromatic aberration (CA) is a critical issue in immersive virtual reality displays. The current digital compensation method can reduce the CA by pre‐processing the image contents but at the cost of extra memory space, processing time, and power consumption. Moreover, it is not possible to digitally compensate the CA within each color channel. Here, a practical optical approach is presented to correct the CAs, including the sub‐channel ones, in the virtual reality system, whose functionality is verified by both ray‐tracing analysis and experimental results. In this device, a compact ultra‐broadband Pancharatnam‐Berry phase lens (PBL) with complex axial molecular structure is fabricated and then hybridized with a refractive Fresnel lens. Due to their opposite chromatic dispersion, the system's CA is significantly reduced. To eliminate ghost image from the zero‐order leakage of PBL, a broadband circular polarizer is implemented to block the stray light. As a result, clear image within the entire 100° field‐of‐view is achieved. The proposed large‐size cost‐efficient broadband wide‐view flat optics can practically benefit not only virtual reality displays but also general imaging systems for practical applications and scientific research.
Site‐Selective Alkoxylation of Benzylic C−H Bonds by Photoredox Catalysis
Authors: Lee Byung Joo , DeGlopper Kimberly S. , Yoon Tehshik P.
Published: October 2019

Methods that enable the direct C−H alkoxylation of complex organic molecules are significantly underdeveloped, particularly in comparison to analogous strategies for C−N and C−C bond formation. In particular, almost all methods for the incorporation of alcohols by C−H oxidation require the use of the alcohol component as a solvent or co‐solvent. This condition limits the practical scope of these reactions to simple, inexpensive alcohols. Reported here is a photocatalytic protocol for the functionalization of benzylic C−H bonds with a wide range of oxygen nucleophiles. This strategy merges the photoredox activation of arenes with copper(II)‐mediated oxidation of the resulting benzylic radicals, which enables the introduction of benzylic C−O bonds with high site selectivity, chemoselectivity, and functional‐group tolerance using only two equivalents of the alcohol coupling partner. This method enables the late‐stage introduction of complex alkoxy groups into bioactive molecules, providing a practical new tool with potential applications in synthesis and medicinal chemistry.
Lessons in Strain and Stability: Enantioselective Synthesis of (+)‐[5]‐Ladderanoic Acid
Authors: Hancock Erin N. , Kuker Erin L. , Tantillo Dean J. , Brown M. Kevin
Published: October 2019

The synthesis of structurally complex and highly strained natural products provides unique challenges and unexpected opportunities for the development of new reactions and strategies. Herein, the synthesis of (+)‐[5]‐ladderanoic acid is reported. En route to the target, unusual and unexpected strain release driven transformations were uncovered. This occurrence required a drastic revision of the synthetic design that ultimately led to the development of a novel stepwise cyclobutane assembly by an allylboration/Zweifel olefination sequence.
Manganese(I)‐Catalyzed β‐Methylation of Alcohols Using Methanol as C1 Source
Authors: Kaithal Akash , van Bonn Pit , Hölscher Markus , Leitner Walter
Published: October 2019

Highly selective β‐methylation of alcohols was achieved using an earth‐abundant first row transition metal in the air stable molecular manganese complex [Mn(CO)2Br[HN(C2H4PiPr2)2]] 1 ([HN(C2H4PiPr2)2]=MACHO‐iPr). The reaction requires only low loadings of 1 (0.5 mol %), methanolate as base and MeOH as methylation reagent as well as solvent. Various alcohols were β‐methylated with very good selectivity (>99 %) and excellent yield (up to 94 %). Biomass derived aliphatic alcohols and diols were also selectively methylated on the β‐position, opening a pathway to “biohybrid” molecules constructed entirely from non‐fossil carbon. Mechanistic studies indicate that the reaction proceeds through a borrowing hydrogen pathway involving metal–ligand cooperation at the Mn‐pincer complex. This transformation provides a convenient, economical, and environmentally benign pathway for the selective C−C bond formation with potential applications for the preparation of advanced biofuels, fine chemicals, and biologically active molecules
Hollow Zn−Co Based Zeolitic Imidazole Framework as a Robust Heterogeneous Catalyst for Enhanced CO2 Chemical Fixation
Authors: Tang Bo , Li Shuang , Song Wei‐Chao , Li Yan , Yang En‐Cui , Zhao Xiao‐Jun , Li Landong
Published: October 2019

The efficient chemical conversion of carbon dioxide (CO2) into value‐added fine chemicals is an intriguing but challenging route in sustainable chemistry. Herein, a hollow‐structured bimetallic zeolitic imidazole framework composed of Zn and Co as metal centers (H‐ZnCo‐ZIF) has been successfully prepared via a post‐synthetic strategy based on controllable chemical‐etching of the preformed solid ZnCo‐ZIF in tannic acid. The creation of hollow cavities inside each monocrystalline ZIFs could be achieved without destroying the intrinsic frameworks, as characterized by field‐emission scanning electron microscopy, transmission electron microscopy, and X‐ray diffraction technologies. The as‐synthesized H‐ZnCo‐ZIF exhibited remarkable catalytic activity in the cycloaddition of CO2 with epoxides to the corresponding cyclic carbonates, outperforming the solid ZnCo‐ZIF analogue due to the improved mass transfer originating from the hollow structure. More importantly, due to stabilization of metal centers in the ZIF framework by the tannic acid shell, H‐ZnCo‐ZIF exhibited good recyclability, and no activity loss could be observed in six runs. The present study provides a simple and effective strategy to enhance the catalytic performance of ZIFs by creating a hollow structure via chemical etching.
A POSS‐Phosphazene Based Porous Material for Adsorption of Metal Ions from Water
Authors: Soldatov Mikhail , Liu Hongzhi
Published: October 2019

The development of adsorptive materials continues to be an important area of research for removal of heavy metal ions from waste water. The adsorption capacity can be modulated by both physical and chemical modification of the adsorbent. Herein, we combine the unique properties of polyhedral oligomeric silsesquioxane (POSS) and organocyclophosphazene as the building units to synthesize a hybrid porous material, abbreviated as PN‐POSS. The synthetic method follows a Heck reaction between hexa(4‐bromophenoxy)cyclotriphosphazene and octavinylsilsesquioxane (OVS). The Brunauer–Emmett–Teller (BET) analysis shows that the material possesses micro‐ and mesopores of 1.5 and 3.8 nm size and a surface area on the order of 500 m2 g−1. These attributes in combination with the donor ability of the phosphazene units qualify the material for high adsorption of Pb2+, Hg2+ and Cu2+ ions with maximal adsorption capacities on the order of 1326, 1927 and 2654 mg g−1, respectively. The adsorbent exhibits a good regeneration performance and can be effectively used for water treatment.
Ultrasonic extraction, structural characterization, and bioactivities of nonstarch polysaccharides from red yeast rice
Authors: Luo Jia , Sun Qiang , Ma Zubing , Song Jiawen , Wu Chunjie , Li Xiaofang
Published: October 2019

Red yeast rice (RYRP) has been utilized for coloring food, brewing wine, and preserving meat, which is also used as a folk medicine for centuries. In this study, a water‐soluble nonstarch polysaccharide from RYRP was extracted by using ultrasonic‐assisted extraction method. By using the Box–Behnken design to optimize the parameters for extracting the RYRP, the maximum extraction yield (3.37 ± 0.78%) was obtained under the optimal extraction conditions as follows: ratio of water to raw material (40 mL/g), extraction temperature (62 °C), extraction time (75 Min), and ultrasonic power (200 W). Moreover, monosaccharide composition analysis showed that RYRP was consisted of mannose, glucosamine, glucose, and galactose with a molar ratio of 0.152:0.015:1:0.149. The molecular weight distribution analysis showed that the average molecular weight of the RYRP fraction was about 3.49 × 103 Da. Furthermore, RYRP exhibited significant antioxidant activities in vitro and the gastrointestinal‐protective effect in vivo using gastrointestinal disorders model mice. RYRP could be explored as a potential source in the pharmaceutical and functional food industries.
Learning curve of laparoscopic living donor right hepatectomy
Authors: Rhu J , Choi G-S , Kwon C H D , Kim J M , Joh J-W
Published: October 2019

Background

The feasibility and learning curve of laparoscopic living donor right hepatectomy was assessed.

Methods

Donors who underwent right hepatectomy performed by a single surgeon were reviewed. Comparisons between open and laparoscopy regarding operative outcomes, including number of bile duct openings in the graft, were performed using propensity score matching.

Results

From 2014 to 2018, 103 and 96 donors underwent laparoscopic and open living donor right hepatectomy respectively, of whom 64 donors from each group were matched. Mean(s.d.) duration of operation (252·2(41·9) versus 304·4(66·5) min; P < 0·001) and median duration of hospital stay (8 versus 10 days; P = 0·002) were shorter in the laparoscopy group. There was no difference in complication rates of donors (P = 0·298) or recipients (P = 0·394) between the two groups. Total time for laparoscopy decreased linearly (R2 = 0·407, β = –0·914, P = 0·001), with the decrease starting after approximately 50 procedures when cases were divided into four quartiles (2nd versus 3rd quartile, P = 0·001; 3rd versus 4th quartile, P = 0·023). Although grafts with bile duct openings were more abundant in the laparoscopy group (P = 0·022), no difference was found in the last two quartiles (P = 0·207).

Conclusion

Laparoscopic living donor right hepatectomy is feasible and an experience of approximately 50 cases may surpass the learning curve.
Longtime chief at Bentley emphasizes staff teamwork, community policing
Authors: Enos Gary
Published: October 2019

As the responsibilities inherent in running a campus police department have grown, longtime Bentley University Police Chief Ernest Leffler has leaned heavily on a participatory leadership style for his 41‐member department.
Mechanoenzymatic Transformations in the Absence of Bulk Water: A More Natural Way of Using Enzymes
Authors: Kaabel Sandra , Friščić Tomislav , Auclair Karine
Published: October 2019

Mechanochemical enzymatic reactions without bulk water have emerged as a low‐waste and efficient method to access useful chemicals and to depolymerize biomass components in a single step. This emergent mechanoenzymatic reaction strategy is able to take advantage of the stereospecificity, regio‐ and stereoselectivity, as well as renewability of enzymes, while avoiding bulk solvents, offering the opportunity to control the direction of the reaction, bypassing reactant solubility issues, and enabling reactions with water‐sensitive substrates or products. Enzymes are traditionally used in dilute aqueous solution, which is quite different from their crowded, water‐depleted natural environment. This review outlines recent work which demonstrates that enzymes can be equally or even more efficient under mechanochemical conditions, without bulk aqueous or organic solvent.
Effect of Substrate Characteristics and Process Fluid Percolation on Dry Anaerobic Digestion Processes
Authors: Wedwitschka Harald , Gallegos Daniela , Tietze Michael , Reinhold Jürgen , Jenson Earl , Liebetrau Jan , Nelles Michael
Published: October 2019

The dry anaerobic batch digestion process is an organic waste treatment technology most appropriate for the treatment of stackable (non‐free‐flowing) dry organic waste materials. The effect of the process fluid percolation and substrate permeability on methane production of organic household waste was investigated in anaerobic dry digestion trials at pilot scale. The container system consisted of two percolation digesters and a fixed‐bed methane digester. The experimental results indicate that material compaction occurs during the digestion process and can have a negative effect on substrate permeability. Structure material addition reduced material compaction and as a result increased the substrate permeability.
Oriented Crystallization on Organic Monolayers to Control Concomitant Polymorphism
Authors: Bora Pranita , Saikia Basanta , Sarma Bipul
Published: October 2019

Nucleation events and crystal growth can be guided by molecular recognition at interfaces through intermolecular interactions. The short‐acting antimicrobial sulfa drug sulfathiazole is known for its concomitant crystallization, which has five known polymorphs, due to conformational flexibility and hydrogen‐bond synthon variation. In its development stage of a drug the issue of concomitant crystallization needs to be addressed with respect to patent litigation, including legal actions to protect patents against infringement. A functional self‐assembled monolayer (SAM) of organic thiol on a gold surface has been employed as an efficient approach to control concomitant nucleation of such flexible drugs. The crystallization on a SAM surface is mostly kinetically driven and often leads to the nucleation of novel metastable forms. Spectroscopic, thermal analysis and X‐ray diffraction studies reveal that a previously unknown, sixth form of the drug nucleates on the designed SAM surface.
Unravelling the Promotional Effect of La2O3 in Pt/La‐TiO2 Catalysts for CO2 Hydrogenation
Authors: Wang Zhaoyu , Huang Lijuan , Su Bo , Xu Junli , Ding Zhengxin , Wang Sibo
Published: October 2019

This work reports the preparation of a La2O3‐modified Pt/TiO2 (Pt/La‐TiO2) hybrid through an excess‐solution impregnation method and its application for CO2 hydrogenation catalysis. The Pt/La‐TiO2 catalyst is characterized by XRD, H2 temperature‐programmed reduction (TPR), TEM, X‐ray photoelectron spectroscopy (XPS), Raman, EPR, and N2 sorption measurements. The Pt/La‐TiO2 composite starts to catalyze the CO2 conversion reaction at 220 °C, which is 30 °C lower than the Pt/TiO2 catalyst. The generation of CH4 and CO of Pt/La‐TiO2 is 1.6 and 1.4 times greater than that of Pt/TiO2. The CO2 temperature‐programmed desorption (TPD) analysis confirms the strengthened CO2 adsorption on Pt/La‐TiO2. Moreover, the in situ FTIR experiments demonstrate that the enhanced CO2 adsorption of Pt/La‐TiO2 facilitates the formation of the active Pt–CO intermediate and subsequently boosts the evolution of CH4 and CO. The cycling tests reveal that Pt/La‐TiO2 shows reinforced stability for the CO2 hydrogenation reaction because the La species can prevent Pt nanoparticles (NPs) from sintering. This work may provide some guidance on the development new rare‐metal‐modified hybrid catalysts for CO2 fixation.
Multimetallic Oxynitrides Nanoparticles for a New Generation of Photocatalysts
Authors: Rao Tingke , Saladino Maria Luisa , Fang Yuanxing , Wang Xinchen , Giordano Cristina
Published: October 2019

A versatile synthetic strategy for the preparation of multimetallic oxynitrides has been designed and here exemplarily discussed considering the preparation of nanoscaled zinc–gallium oxynitrides and zinc–gallium–indium oxynitrides, two important photocatalysts of new generation, which proved to be active in key energy related processes from pollutant decomposition to overall water splitting. The synthesis presented here allows the preparation of small nanoparticles (less than 20 nm in average diameter), well‐defined in size and shape, yet highly crystalline and with the highest surface area reported so far (up to 80 m2 g−1). X‐ray diffraction studies show that the final material is not a mixture of single oxides but a distinctive compound. The photocatalytic properties of the oxynitrides have been tested towards the decomposition of an organic dye (as a model reaction for the decomposition of air pollutants), showing better photocatalytic performances than the corresponding pure phases (reaction constant 0.22 h−1), whereas almost no reaction was observed in absence of catalyst or in the dark. The photocatalysts have been also tested for H2evolution (semi‐reaction of the water splitting process) with results comparable to the best literature values but leaving room for further improvement.
In‐Cage Interactions in the Clathrate Superconductor Sr8Si46
Authors: Hübner Julia‐Maria , Prots Yurii , Schnelle Walter , Bobnar Matej , König Markus , Baitinger Michael , Simon Paul , Carrillo‐Cabrera Wilder , Ormeci Alim , Svanidze Eteri , Grin Yuri , Schwarz Ulrich
Published: October 2019

The clathrate I superconductor Sr8Si46 is obtained under high‐pressure high‐temperature conditions, at 5 GPa and temperatures in the range of 1273 to 1373 K. At ambient pressure, the compound decomposes upon heating at T=796(5) K into Si and SrSi2. The crystal structure of the clathrate is isotypic to that of Na8Si46. Chemical bonding analysis reveals conventional covalent bonding within the silicon network as well as additional multi‐atomic interactions between Sr and Si within the framework cages. Physical measurements indicate a bulk BCS type II superconducting state below Tc=3.8(3) K.
Growth of GaSb Crystal and Evaluation of Its Thermoelectric Properties Along (111) Plane
Authors: Jin Min , Tang Ziqi , Zhang Rulin , Zhou Lina , Chen Yuqi , Zhao Su , Chen Yunxia , Wang Xianghu , Li Rongbin
Published: October 2019

In this study, group III–V compound semiconductor gallium antimonide (GaSb) crystal is grown by the vertical Bridgman technique. A (111) twinning is generated in the as‐grown crystal due to its polarity behavior as the GaSb crystal has a zinc‐blende structure. Hall effect measurements illustrate that the as‐grown GaSb crystal has n‐type semiconductor behavior among the whole temperature range, and the carrier concentration reaches the highest value of 3.27 × 1018 cm3 at 900 K. Thermoelectric behavior of GaSb crystals along the (111) plane is investigated. It shows the lowest electrical conductivity of 53.2 S cm−1 and the highest Seebeck coefficient of −470.0 µV K−1 at 700 K. However, the largest power factor of 13.7 µW cm K−2 takes place at 600 K. For thermal conductivity (k), the k value always decreases with increasing temperature, and the lowest k that occurred at around 900 K is about 7.44 W m−1 K−1. Finally, a maximum figure of merit of 0.082 is obtained at 700 K.