bluuebunny/crossref_metadata_2025 huggingface dataset:
Derivation of suspended sediment data for Al-Adhiam watershed-Iraq using artificial neural network model
Authors: Al-Khafaji Mahmoud Saleh , Al-Mukhtar Mustafa , Mohena Ahmed Saud
Published: May 2018

The mean part of river sediments is suspended sediment load, its prediction and simulation has important significance to manage the water resources and environments. In Iraq, most researchers avoid to fighting in sediment researches when related with hydrological models spatially with that need enough observed sediment data for calibration and validation because the sediment data very limitation or scars. The aim of this study is employing the Artificial Neural Network (ANN) model to estimate the suspended sediment load of Al-Adhaim watershed in Iraq from available measured sediment data, identify the suitable pattern of input and target data sampling and obtaining the best nonlinear equation between the river discharge and suspended sediment load. To this end, the ANN model was training and tested with the available sediment data, which was for water year (1983-1984). Two modes were applied for input and target data sampling each mode has two cases, where in the first mode the time series data sampling was used with flow as an input for case one while flow and average precipitation in case two with used suspended sediment as a target variable. For second mode the supervise data sampling was used with the same input and target division in first mode. The performance of the model was evaluated by using Coefficient of determination (R2) and the Nash- Sutcliffe efficiency (NS) and standardization of root mean square error (RSR), the statistical analysis model testing for Al-Adhiam watershed showed satisfactory agreement between observed and estimated daily values for Mode2- Case2. R2, NS and RSR of the testing period were 0.99 and 0.8and 0.2 respectively. The result shows that the conducted ANN model can be used with the best net as a predictor for sediment yield in this watershed. The model was used to predict daily sediment load data for period from 1Oct. 1984 to 31Spt 1985. The predicted daily sediment data was plotted against daily measured flow. The correlation between predicted sediment and measured flow was in good agreement with R2 =0.89 and the best relation was polynomial equation from second degree.
Utilization of urban sustainability approaches to deal with ancient cities: a case study of Hit Castle, Iraq
Authors: Mahmood Thaer
Published: May 2018

This research aims to highlight the current situation of some Iraqi ancient cities by taking the Hit Castle as a case study. It is one of the oldest cities in Iraq. Due to the previous circumstances that Iraq has one through, this city was ignored and not looked after. Furthermore, due to the expensive land in this city, many old houses were demolished and rebuilt in a modern style. In order to conserve this ancient city, the urban sustainable approaches are suggested to be used. For this purpose, a study was made and a site observation was carried out. Based on that, it was found that this city could be redeveloped/ rehabilitated by employing the urban sustainability approaches and concepts. Important recommendations have been identified and the governmental bodies will be invited to conserve the ancient cities using these recommendations as guidelines.
Assessment of land surface temperature variation over Rusafa side of Baghdad city, Iraq
Authors: Beg Ayad
Published: May 2018

The current study is concerned with Rusafa side of Baghdad city, which extends on 362 square kilometres and is inhabited by 3738371 people. It suffers from population growth, which led to decline in municipal services and rising of land surface temperature (LST) during the summer season. The current study aims to assess the spatial and temporal variation of LST using different dated satellite images of Landsat 4, 7 and 8 at path 168 and raw 037 during July 16, 1989, April 25, 2000, April 26, 2006, and May 31, 2016. Eight analysis models which were built using ERDAS 2014 software are used to calculate the LST parameters; while the land use/land cover (LULC) types are classified using ENVI v.5.3 software. The maximum surface temperature recorded at barren lands are between 26 and 41°C, while at vegetation cover ranging from 25 to 34°C and an inverse correlation are recorded between LST and NDVI ranging from -0.5 to -0.81. The built-up area was increased by 23%, whereas open spaces and vegetation cover are decreased by 16% and 6% respectively all that consequently will make the environment of the study area prone to be warmer.
Serviceability limit state of two-way reinforced concrete slab strengthened with different techniques
Authors: Sayhood Eyad , Ali Ammar , Sharhan Zahraa
Published: May 2018

The experimental results for service load of sixteen simply supported two way reinforced concrete slabs under the action of concentrated patch load were determined based on the amount of permissible deflections and the crack widths.All the slabs had the same overall dimensions and flexural steel reinforcement. Five types of strengthening were adopted. The first and second methods include applying either near surface mounted (NSM) or near reinforcement mounted (NRM) ferrocement layers. While the third method includes applying a concrete layer reinforced with welded wire fabric mesh of various diameters. The fourth and fifth methods include fixing CFRP rods and laminates, respectively, on the bottom surface of slabs. Strengthening techniques were applied on the bottom surface of fifteen slab specimens. In addition, a control slab specimen without any strengthening was used for the purpose of comparison. The calculated results for ultimate loads based on serviceability requirements (deflection and crack width according to both ACI and BS formulae) were lower than the experimental results.
Influence of flange on the shear capacity of reinforced concrete beams
Authors: Sarsam Kaiss , Khalel Raid , Mohammed Nisreen
Published: May 2018

In structural engineering (RC, steel, etc.) it is usual to base the shear strength of members on the web only- e.g. in RC the stirrups used are usually called “web reinforcement”. Presently all codes, and several researches, base the strength of members on the capacity of the web alone. 93 tests of T-beams failing in shear available from the literature are studied in this work to estimate the influence of flanges on the shear capacity of RC beams. These include 32 ones without web reinforcement and 61 with stirrups. Comparison between test results and theoretical shear capacity show that all available equations conservatively estimate the occurrence of shear failure. In this work an equation for predicting the contribution of the flange to shear capacity in T-beams is presented.

The best available design method obtained from the literature leads to a coefficient of variation (COV) of 17.58% compared to 13.46% for the proposed design method in this work.
Experimental comparative study of reactive powder concrete: mechanical properties and the effective factors
Authors: Kadhem Eyad , Ali Ammar , Tobeia Sameh
Published: May 2018

Reactive Powder Concrete (RPC) is a type of ultra-high performance concrete, this dense composite material generally characterized by high cement content, high durability, low porosity, low water/cement ratio and in most cases contains steel fibers as new types of concrete appears, further investigation for their mechanical properties are needed. This work aims to give a better understanding of RPC behavior by deriving formulas to calculate the modulus of elasticity and the splitting tensile strength in relation with compressive strength and steel fibers content. This study is based on data obtained from the experimental investigation done in this work and from others pervious works. The parametric study is based mainly on the silica fume content which is used in four different ratios (12 %, 15 %, 20 % and 25 %), the use of micro steel fibers 15 mm in length, 0.2 mm in diameter and aspect ratio of 75 added in ratios of (0 %, 1 %, 1.5 % and 2 %), and water/cement in ratios of (16 %, 18 %, 20 % and 22 %), respectively. The proposed equations show a better behavior in comparison to some available equations that were used in the estimation of modulus of elasticity and splitting tensile strength of reactive powder concrete, the coefficient of variation for the proposed equations (COV) decrease to 10.677% and 10.455% respectively.
The effectiveness of CFRP strengthening of steel plate girders with web opening subjected to shear
Authors: Hamood Mohammed , AbdulSahib Wael , Abdullah Ali
Published: May 2018

The present study is experimental by nature; it involves applying shear buckling test on seven steel-plated girders that are subjected to shear loading. Four of these girders represent the strengthened girders whereas the other three are reference girders. One of the latter type of girders has a square web opening; the second has a diamond web opening while the last one has no opening at all. The webs of the strengthened girders were adhesively attached to CFRP sheets of different patterns. This step was carried out to evaluate the most effective strengthening scheme by CFRP composite. The study aims at examining the effect of several parameters on the behavior of web girders. It further examines the percentage of increase in the ultimate shear capacity of the perforated girders that have a fixed location and size where the latter is equal to 40 percent of the web depth. Results have shown that, first, the ultimate shear load of the CFRP-strengthened girders with square web opening is higher than that of the reference girder with a square web opening; ranging from 8.7% to 15.7%. The obtained ranges depend on the orientation of the CFRP strips. Second, the ultimate shear load of the CFRP-strengthened girders with a diamond web opening is higher than the reference girder with a range of 9.8% to 21.5%. Again, the obtained ranges depend on the orientation of the CFRP strips. Analytically speaking, Von Mises stresses have been used to predict the ultimate shear load of girders with square and diamond web openings and without web opening.
Behavior of self-compact reinforced concrete deep beams with small shear span to depth ratio
Authors: Hassan Hassan , Medhlom Mu’taz , Hatem Mohammed
Published: May 2018

This research is devoted to investigate the experimental and theoretical behavior of deep beams under monotonic two points loading. An experimental program examining six RC deep beams is carried out. The investigated parameters include shear span to depth ratio varying from 1.0 to 0.276. A comparative study is conducted in this paper by using finite element software ANSYS. The experimental and numerical results show that concrete strength and shear span to depth ratio are the two most important parameters in controlling the behavior of RC deep beams. Comparison of experimental results was made with corresponding predicted values using the Strut and Tie procedure presented ACI 318M-11Code and with other procedures mentioned in the literature. It was found that the Strut and Tie procedure presented in ACI 318M-11Code give conservative results as compared with the experimental tested results. The results showed reliability of analysis in predicting deep beams behavior in terms of failure load, failure mode as well as crack propagation.
Investigation on the performance of bridge approach slab
Authors: Abdelrahman Amr , Tawfik Mohamed , El-Saify A.
Published: May 2018

In Egypt, where highway bridges are to be constructed on soft cohesive soils, the bridge abutments are usually founded on rigid piles, whereas the earth embankments for the bridge approaches are directly founded on the natural soft ground. Consequently, excessive differential settlement frequently occurs between the bridge deck and the bridge approaches resulting in a “bump” at both ends of the bridge deck. Such a bump not only creates a rough and uncomfortable ride but also represents a hazardous condition to traffic. One effective technique to cope with the bump problem is to use a reinforced concrete approach slab to provide a smooth grade transition between the bridge deck and the approach pavement. Investigating the geotechnical and structural performance of approach slabs and revealing the fundamental affecting factors have become mandatory. In this paper, a 2-D finite element model is employed to investigate the performance of approach slabs. Moreover, an extensive parametric study is carried out to appraise the relatively optimum geometries of approach slab, i.e. slab length, thickness, embedded depth and slope, that can yield permissible bumps. Different geo-mechanical conditions of the cohesive foundation soil and the fill material of the bridge embankment are examined.
Reinforcement bars tying types in reinforced concrete
Authors: Hamid Marawan , Joudah Ali , Mohammed Alyaa
Published: May 2018

In huge reinforced concrete structures, it is often difficult to distribute the reinforcing bars, especially at the connection regions, to keep the spacing between bars within the minimum acceptable limits as recommended in the global specifications standard, by using the common methods such as, overlapping or welding, therefore, a new method for bonding was introduced, using mechanical joints and electro fusion bonding method, and comparing these methods with the maximum strength of reinforcing bars without joints and the failure location within maximum strength limits outside the joints.
Experimental and numerical study for the post buckling behaviour of plate girders subjected to bending and shear
Authors: Shawky Wael , Nabil Ghaidaa
Published: May 2018

This research offers experimental and numerical study for the ultimate strength analysis and post buckling behaviour of plate girders subjected to shear and bending stresses. Two Plate girders of length 2.5m are designed consisting from three separate structural steel plates welded together to form I - section. The dimensions of the first girder section is 512 mm × 120 mm while the second girder section is 412mm × 120 mm. Mechanical properties for plate girders components were found by testing three samples of each plate. The ultimate shear strength was found by examining two plate girders in the laboratory under concentrated load applied at the middle span. A numerical study of the tested plate girders was carried out by using the software program (ANSYS) to study the behaviour of girders steel under the influence of loads application. The results showed that the ratio of the experimental ultimate load strength to the numerical ultimate load strength is 97% 94% for plate girders 1 and 2 , respectively. For the part of using theoretical study. The results obtained from the equations , it was observed that the ratio of the experimental ultimate load strength to the theoretical ultimate load strength is 83% for plate girders1 and 90% for the plate girder 2.Through comparison between experimental, numerical and theoretical results it was observed good andacceptable agreement. Thus confirming the accuracy of the modelling between this methods and obtain convergent results in all cases. Also it was found when an increase in the depth of the web has effect in increasing the ultimate shear strength for plate girder by about 19%.
Evaluation water quality of Diyala River in Iraq using Bhargava method
Authors: Al-Musawi Nawar
Published: May 2018

Diyala River is a tributary of Tigris River, it is one of the important rivers in Iraq. It covers a total distance of 445 km (275 miles). 32600 km2is the area that drains by Diyala River between Iraqi-Iranian borders. This research aims to evaluate the water quality index WQI of Diyala River, where three stations were chosen along the river. These stations are D12 at Jalawlaa City at the beginning of Diyala River, the second station is D15 at Baaquba City at the mid distance of the river, and the third station is D17 which is the last station before the confluence of Diyala River with Tigris River at Baghdad city. Bhargava method was used in order to evaluate the water quality index for both irrigation and drinking uses. The results indicated that Diyala river water quality at its beginning was excellent for irrigation and good for drinking, while at the mid distance of the river, it was good for irrigation but heavily polluted and unsafe for drinking. Water quality of the river at the third site was acceptable for irrigation but again severely polluted and unsafe for drinking.
Hydrochemical properties of ground water of Rahaliya-Ekhedhur region, west Razzaza lake, iraq
Authors: Al-Dabbas Moutaz , Al-Kubaisi Qusai , Hussein Tariq , Al-Qaraghuli Shahad
Published: May 2018

Rahaliya - Ekhedur region is located to the west of Razzaza Lake (M.IRAQ). It is within the Salman - Rutba tectonic zones characterized by the existence of Abu Jir and Imam Ahmad bin Hashim Fault Systems. The major geological formations in the studied area consists of Tertiary and Quaternary deposits described from the oldest to the youngest as : Dammam, Euphrates, Nfayil and Injana, formations, and the slope of beds is less than one degree in the direction of east and northeast towards Al-Razzaza lake. To evaluate the hydrochemical properties and the quality groundwater samples were collected from 16 wells at different depths 80-120 m, during April and October 2013. These samples have been chemically analyzed and the results indicated that the ground water is of mixed origin, very hard (TH ranging from 227.5 to 1032.8 ppm), having high pH values, while the Total Dissolved Solids (TDS) ranging from 1700 to 2750 mg/l so that the water is of brackish type. On the basis of the major cation and anion concentration the groundwater during April 2013 was of mixed Mg and Na -SO4 group having two families which are Na2SO4 family with Na+>Ca2+>Mg2+-SO42- >Cl->HCO3- and MgSO4 water family with Mg2+>Ca2+>Na+-SO42- >Cl->HCO3-. While, the groundwater during October 2013 is of two groups (Na -SO4) having two families which are (Na2SO4) family with Na+>Ca2+>Mg2+-SO42- >Cl->HCO3-and (MgSO4) water family with Mg2+> Ca2+>Na+-SO42- >Cl->HCO3-. The second group was Na - Cl with Na+> Mg2+>Ca2+ - Cl->SO42- > HCO3- and Na+>Ca2+>Mg2+ - Cl->SO42- > HCO3- . Therefore, the ground water in the region is not good for drinking due to high salinity and it is of Doubtful to unsuitable-Unsuitable for irrigation but it can be used to irrigate sensitive crops in areas.
Removal of iron and manganese from groundwater: a study of using potassium permanganate and sedimentation
Authors: Elsheikh Mohamed , Guirguis H. , Fathy A.
Published: May 2018

Experiments are done for different combinations of Fe+2 and Mn+2 concentrations. The obtained results show that Potassium Permanganate (PP) gives good results in iron and manganese removal. By using PP dose near to half of the theoretically required one, it can remove up to 100 % and 90 % of iron and manganese, respectively over different tested concentrations at pH=7.0. Increasing rate of filtration influences the Mn+2 removal process obviously. Sedimentation is required when combined concentrations of iron and manganese are greater than 5.0 ppm to reduce filter rapid clogging. Using conventional treatment with adding alum, flocculation, sedimentation and filtration can remove up to 97% and 18% of iron and manganese, respectively. Using PP in addition to alum enhances manganese removal but decreases iron removal. However, using alum with increasing pH to 10 leads to 100 % and 95 % of Fe+2 and Mn+2 removal and increases filter working period.
Energy saving in air conditioning of buildings
Authors: Mohamed Mousa , Almarshadi Mohammed
Published: May 2018

The external heat load of residential buildings in summer is the dominant parameter of the required cooling load and refrigeration capacity of air conditioning systems. The consumed energy of air conditioning system is proportional to the outside conditions and intensity of solar radiation. The maximum heat load of building may occur at 3 O’clock PM, although the peak of solar radiation occurs at noon. The construction materials of building is playing an important rolls of heat transmission through buildings outside walls and glazing windows. The walls thermal insulation can be effective in energy conservation by reducing the cooling load and required electrical energy. The building is constructed from common materials with 0~12 cm thermal insulation in outside walls, ceilings, and double layers glazing windows. The building heat loads are calculated for two models of walls. The optimum thickness of thermal insulation is also determined and is found between 6~8 cm for insulation of thermal conductivity of 0.039 W/m.K the energy saving is 50.45% at 6 cm insulation thickness.
Colored asphalt and street print are decorating paving in public spaces
Authors: Kawther Khawla
Published: May 2018

Asphalt is the main material used to finish the internal and external streets of cities. Newly emerged in some countries, the use of colors which is added to the asphalt, it would be possible to use in the paving of this material widely in walking pavements, bicycle paths, parks and open spaces. By analyzing the international experiences as well as practical study, by a survey that was done by Iraqi professors in the specialized field of civil and road engineering, as well as architects, urban designer, and landscapers. Non-proliferation of Colored Asphalt and Street Print applications locally, this application has not been used in Iraq till now. There is a lack of knowledge on this subject, hence, the studies and research need to be carried out on this aspect, and find out their suitability for the local environment. The reasons that it is not used in Iraq are: cost of devices, staff, lack of experience, unavailability of materials, laws - culture- traffic engineering and lack of desire for development. It was found that, it is necessary to legislate engineering laws related to traffic engineering and educate vehicle owners about this new culture.
Catalyst-Free One-Pot Synthesis of Chromeno-Imidazo-Pyridinones by an Aza-Michael Addition/Rearrangement/Heterocyclization Tandem Reaction
Authors: Talhi Oualid , Bennamane Norah , Silva Artur , Lakhdari Houria , Hassaine Ridha , Taibi Nadia , Mendes Ricardo , Almeida Paz Filipe , Nedjar-Kolli Bellara , Bachari Khaldoun
Published: May 2018

A one-pot synthesis of a novel series of chromeno-imidazo-pyridinone derivatives from 3-[(2-hydroxyphenyl)-3-oxoprop-1-en-1-yl]chromones and ethane-1,2-diamine at room temperature under catalyst-free conditions has been successfully developed. This approach involves a tandem aza-Michael addition reaction, a chromone-to-chromanone rearrangement, and a heterocyclization sequence, leading to chromeno-imidazo-pyridinone polyheterocycles. The structure and absolute configurations of the new compounds were elucidated by a combination of 1D- and 2D-NMR analyses and single-crystal X-ray diffraction.
Prediction of Ischemic Events after Percutaneous Coronary Intervention: Thrombelastography Profiles and Factor XIIIa Activity
Authors: Kreutz Rolf , Schmeisser Glen , Schaffter Andrea , Kanuri Sri , Owens Janelle , Maatman Benjamin , Sinha Anjan , von der Lohe Elisabeth , Breall Jeffrey
Published: May 2018

Background High plasma fibrin clot strength (MA) measured by thrombelastography (TEG) is associated with increased risk of cardiac events after percutaneous coronary interventions (PCIs). Factor XIIIa (FXIIIa) cross-links soluble fibrin, shortens clot formation time (TEG-K), and increases final clot strength (MA).

Methods We analyzed platelet-poor plasma from patients with previous PCI. Kaolin-activated TEG (R, K, MA) in citrate platelet-poor plasma and FXIIIa were measured (n = 257). Combined primary endpoint was defined as recurrent myocardial infarction (MI) or cardiovascular death (CVD). Relationship of FXIIIa and TEG measurements on cardiac risk was explored.

Results FXIIIa correlated with TEG-MA (p = 0.002) and inversely with TEG-K (p < 0.001). High MA (≥35.35 mm; p = 0.001), low K (<1.15 min; p = 0.038), and elevated FXIIIa (≥83.51%; p = 0.011) were associated with increased risk of CVD or MI. Inclusion of FXIIIa activity and low TEG-K in risk scores did not improve risk prediction as compared with high TEG-MA alone.

Conclusion FXIIIa is associated with higher plasma TEG-MA and low TEG-K. High FXIIIa activity is associated with a modest increase in cardiovascular risk after PCI, but is less sensitive and specific than TEG-MA. Addition of FXIIIa does not provide additional risk stratification beyond risk associated with high fibrin clot strength phenotype measured by TEG.
Fabrication and magnetic properties of structure-tunable Co2FeGa-SiO2 Heusler nanocompounds
Authors: Xu Yunli , Yang Dongchao , Luo Zhaochu , Wu Fengyu , Chen Cheng , Liu Min , Yi Lizhi , Piao Hong-Guang , Yu Guanghua
Published: May 2018

Co2FeGa-SiO2 nanocompounds were chemically synthesized by using SBA-15 as template, which has the L21 Heusler phase. The reactants comprised CoCl2 · 6H2O, Fe(NO3)3 · 9H2O and Ga(NO3) · xH2O with the addition of SBA-15 with different contents. The structure and morphology of the product were controlled by modulating the ratio of reactants to templates. After high-temperature annealing under H2 atmosphere and the removal of the template, the Co2FeGa nanowires, which are of about 125∼200 nm length, 4∼7 nm width and the length-to-width ratio of about 30 were observed by transmission electron microscope. The structure and component of the nanowires were confirmed by selected area electron diffraction, X-ray diffraction and energy-dispersive X-ray spectroscopy, respectively. The magnetic test showed that the saturation magnetization (Ms) was 87.5 emu/g for the Co2FeGa nanowires, and the Curie temperature was higher than 380K. The effective anisotropy constant Keff=4.196 × 105 J/m3 was calculated using magnetization curve, which is below the value of bulk Co2FeGa 6.54 × 105 J/m3. The dynamic magnetic properties study performed by ferromagnetic resonance indicated that the Gilbert damping coefficient α were about 0.1944-0.0288 for different samples. The high damping coefficient makes the nanocomposites promising to be used as a microwave absorber in the GHz band.
Plasma parameters of the cathode spot explosive electron emission cell obtained from the model of liquid-metal jet tearing and electrical explosion
Authors: Tsventoukh M. M.
Published: May 2018

A model has been developed for the explosive electron emission cell pulse of a vacuum discharge cathode spot that describes the ignition and extinction of the explosive pulse. The pulse is initiated due to hydrodynamic tearing of a liquid-metal jet which propagates from the preceding cell crater boundary and draws the ion current from the plasma produced by the preceding explosion. Once the jet neck has been resistively heated to a critical temperature (∼1 eV), the plasma starts expanding and decreasing in density, which corresponds to the extinction phase. Numerical and analytical solutions have been obtained that describe both the time behavior of the pulse plasma parameters and their average values. For the cell plasma, the momentum per transferred charge has been estimated to be some tens of g cm/(s C), which is consistent with the known measurements of ion velocity, ion erosion rate, and specific recoil force. This supports the model of the pressure-gradient-driven plasma acceleration mechanism for the explosive cathode spot cells. The ohmic electric field within the explosive current-carrying plasma has been estimated to be some tens of kV/cm, which is consistent with the known experimental data on cathode potential fall and explosive cell plasma size. This supports the model that assumes the ohmic nature of the cathode potential fall in a vacuum discharge.
Impacts of opinion leaders on social contagions
Authors: Liu Quan-Hui , Lü Feng-Mao , Zhang Qian , Tang Ming , Zhou Tao
Published: May 2018

Opinion leaders are ubiquitous in both online and offline social networks, but the impacts of opinion leaders on social behavior contagions are still not fully understood, especially by using a mathematical model. Here, we generalize the classical Watts threshold model and address the influences of the opinion leaders, where an individual adopts a new behavior if one of his/her opinion leaders adopts the behavior. First, we choose the opinion leaders randomly from all individuals in the network and find that the impacts of opinion leaders make other individuals adopt the behavior more easily. Specifically, the existence of opinion leaders reduces the lowest mean degree of the network required for the global behavior adoption and increases the highest mean degree of the network that the global behavior adoption can occur. Besides, the introduction of opinion leaders accelerates the behavior adoption but does not change the adoption order of individuals. The developed theoretical predictions agree with the simulation results. Second, we randomly choose the opinion leaders from the top h% of the highest degree individuals and find an optimal h% for the network with the lowest mean degree that the global behavior adoption can occur. Meanwhile, the influences of opinion leaders on accelerating the adoption of behaviors become less significant and can even be ignored when reducing the value of h%.
Low noise 874 GHz receivers for the International Submillimetre Airborne Radiometer (ISMAR)
Authors: Hammar A. , Sobis P. , Drakinskiy V. , Emrich A. , Wadefalk N. , Schleeh J. , Stake J.
Published: May 2018

We report on the development of two 874 GHz receiver channels with orthogonal polarizations for the International Submillimetre Airborne Radiometer. A spline horn antenna and dielectric lens, a Schottky diode mixer circuit, and an intermediate frequency (IF) low noise amplifier circuit were integrated in the same metallic split block housing. This resulted in a receiver mean double sideband (DSB) noise temperature of 3300 K (minimum 2770 K, maximum 3400 K), achieved at an operation temperature of 40 °C and across a 10 GHz wide IF band. A minimum DSB noise temperature of 2260 K at 20 °C was measured without the lens. Three different dielectric lens materials were tested and compared with respect to the radiation pattern and noise temperature. All three lenses were compliant in terms of radiation pattern, but one of the materials led to a reduction in noise temperature of approximately 200 K compared to the others. The loss in this lens was estimated to be 0.42 dB. The local oscillator chains have a power consumption of 24 W and consist of custom-designed Schottky diode quadruplers (5% power efficiency in operation, 8%–9% peak), commercial heterostructure barrier varactor (HBV) triplers, and power amplifiers that are pumped by using a common dielectric resonator oscillator at 36.43 GHz. Measurements of the radiation pattern showed a symmetric main beam lobe with full width half maximum <5° and side lobe levels below −20 dB. Return loss of a prototype of the spline horn and lens was measured using a network analyzer and frequency extenders to 750–1100 GHz. Time-domain analysis of the reflection coefficients shows that the reflections are below −25 dB and are dominated by the external waveguide interface.
Thermodynamics of dilute 3He–4He solid solutions with hcp structure
Authors: Chishko K. A.
Published: May 2018

To interpret the anomalies in heat capacity CV(T) and temperature-dependent pressure P(T) of solid hexagonal close-packed (hcp) 4He we exploit the model of hcp crystalline polytype with specific lattice degrees of freedom and describe the thermodynamics of impurity-free 4He solid as superposition of phononic and polytypic contributions. The hcp-based polytype is a stack of 2D basal atomic monolayers on triangular lattice packed with arbitrary long (up to infinity) spatial period along the hexagonal c axis perpendicular to the basal planes. It is a crystal with perfect ordering along the layers, but without microscopic translational symmetry in perpendicular direction (which remains, nevertheless, the rotational crystallographic axis of third order, so that the polytype can be considered as semidisordered system). Each atom of the hcp polytype has twelve crystallographic neighbors in both first and second coordination spheres at any arbitrary packing order. It is shown that the crystal of such structure behaves as anisotropic elastic medium with specific dispersion law of phonon excitations along c axis. The free energy and the heat capacity consist of two terms: one of them is a normal contribution [with CV(T) ∼ T3] from phonon excitations in an anisotropic lattice of hexagonal symmetry, and another term (an “excessive” heat) is a contribution resulted by packing entropy from quasi-one-dimensional system of 2D basal planes on triangular lattice stacked randomly along c axis without braking the closest pack between neighboring atomic layers. The excessive part of the free energy has been treated within 1D quasi-Ising (lattice gas) model using the transfer matrix approach. This model makes us possible to interpret successfully the thermodynamic anomaly (heat capacity peak in hcp 4He) observed experimentally.
Sorption of hydrogen by silica aerogel at low-temperatures
Authors: Dolbin A. V. , Khlistyuck M. V. , Esel'son V. B. , Gavrilko V. G. , Vinnikov N. A. , Basnukaeva R. M. , Martsenuk V. E. , Veselova N. V. , Kaliuzhnyi I. A. , Storozhko A. V.
Published: May 2018

The programmed thermal desorption method is used at temperatures of 7–95 K to study the sorption and subsequent desorption of hydrogen by a sample of silica aerogel. Physical sorption of hydrogen owing to the weak van-der-Waals interaction of hydrogen molecules with the silicon dioxide walls of the pores of the sample was observed over the entire temperature range. The total capacity of the aerogel sample for hydrogen was ∼1.5 mass %. It was found that when the sample temperature was lowered from 95 to 60 K, the characteristic sorption times for hydrogen by the silica aerogel increase; this is typical of thermally activated diffusion (Ea ≈ 408 K). For temperatures of 15–45 K the characteristic H2 sorption times depended weakly on temperature, presumably because of the predominance of a tunnel mechanism for diffusion over thermally activated diffusion. Below 15 K the characteristic sorption times increase somewhat as the temperature is lowered; this may be explained by the formation of a monolayer of H2 molecules on the surface of the aerogel grains.
Particle-in-cell simulations of magnetically driven reconnection using laser-powered capacitor coils
Authors: Huang Kai , Lu Quanming , Gao Lan , Ji Hantao , Wang Xueyi , Fan Feibin
Published: May 2018

In this paper, we propose an experimental scheme to fulfill magnetically driven reconnections. Here, two laser beams are focused on a capacitor-coil target and then strong currents are wired in two parallel circular coils. Magnetic reconnection occurs between the two magnetic bubbles created by the currents in the two parallel circular coils. A two-dimensional particle-in-cell simulation model in the cylindrical coordinate is used to investigate such a process, and the simulations are performed in the (r,z) plane. The results show that with the increase of the currents in the two coils, the associated magnetic bubbles expand and a current sheet is formed between the two bubbles. Magnetic reconnection occurs when the current sheet is sufficiently thin. A quadrupole structure of the magnetic field in the θ direction (Bθ) is generated in the diffusion region and a strong electron current along the r direction (Jer) is also formed due to the existence of the high-speed electron flow away from the X line in the center of the outflow region. Because the X line is a circle along the θ direction, the convergence of the plasma flow around r=0 will lead to the asymmetry of Jer and Bθ between the two outflow regions of magnetic reconnection.
Fine-tuning of noise in gene expression with nucleosome remodeling
Authors: Megaridis Melina R. , Lu Yiyang , Tevonian Erin N. , Junger Kendall M. , Moy Jennifer M. , Bohn-Wippert Kathrin , Dar Roy D.
Published: May 2018

Engineering stochastic fluctuations of gene expression (or “noise”) is integral to precisely bias cellular-fate decisions and statistical phenotypes in both single-cell and multi-cellular systems. Epigenetic regulation has been shown to constitute a large source of noise, and thus, engineering stochasticity is deeply intertwined with epigenetics. Here, utilizing chromatin remodeling, we report that Caffeic acid phenethyl ester (CA) and Pyrimethamine (PYR), two inhibitors of BAF250a, a subunit of the Brahma-associated factor (BAF) nucleosome remodeling complex, enable differential and tunable control of noise in transcription and translation from the human immunodeficiency virus long terminal repeat promoter in a dose and time-dependent manner. CA conserves noise levels while increasing mean abundance, resulting in direct tuning of the transcriptional burst size, while PYR strictly increases transcriptional initiation frequency while conserving a constant transcriptional burst size. Time-dependent treatment with CA reveals non-continuous tuning with noise oscillating at a constant mean abundance at early time points and the burst size increasing for treatments after 5 h. Treatments combining CA and Protein Kinase C agonists result in an even larger increase of abundance while conserving noise levels with a highly non-linear increase in variance of up to 63× untreated controls. Finally, drug combinations provide non-antagonistic combinatorial tuning of gene expression noise and map a noise phase space for future applications with viral and synthetic gene vectors. Active remodeling of nucleosomes and BAF-mediated control of gene expression noise expand a toolbox for the future design and engineering of stochasticity in living systems.
Anharmonic phonon-polariton dynamics in ferroelectric LiNbO3 studied with single-shot pump-probe imaging spectroscopy
Authors: Kuribayashi T. , Motoyama T. , Arashida Y. , Katayama I. , Takeda J.
Published: May 2018

We demonstrate that single-shot pump-probe imaging spectroscopy with an echelon mirror enables us to disclose the ferroelectric phonon-polariton dynamics across a wide temperature range from 10 K to 375 K while avoiding the photorefractive effects that appear prominently at low temperatures. The E-mode phonon-polaritons corresponding to the two transverse optical modes, TO1 and TO3, up to ∼7 THz were induced in LiNbO3 through an impulsive stimulated Raman scattering process. Subsequently, using single-shot pump-probe imaging spectroscopy over a minimal cumulative time, we successfully visualized the phonon-polariton dynamics in time-wavelength space even at low temperatures. We found that the phase-matching condition significantly affected the observed temperature-dependent phonon-polariton frequency shift. The anharmonicity of the TO1 and TO3 modes was then evaluated based on an anharmonic model involving higher-order interactions with acoustic phonons while eliminating the influence of the frequency shift due to the phase-matching condition. The observed wavenumber-dependent damping rate was analyzed by considering the bilinear coupling of the TO1 or TO3 modes with the thermally activated relaxation mode. We found that the phonon-polariton with a higher frequency and wavenumber had a higher damping rate at high temperatures because of its frequent interaction with the thermally activated relaxation mode and acoustic phonons. The TO3 mode displayed greater bilinear coupling than the TO1 mode, which may also have contributed to the observed high damping rate. Thus, using our unique single-shot spectroscopy technique, we could reveal the overall anharmonic characteristics of the E-mode phonon-polaritons arising from both the acoustic phonons and the relaxation mode.
High-efficiency generation of Bessel beams with transmissive metasurfaces
Authors: Wang Zhuo , Dong Shaohua , Luo Weijie , Jia Min , Liang Zhongzhu , He Qiong , Sun Shulin , Zhou Lei
Published: May 2018

Circularly polarized Bessel beams (BBs) are important in biomolecule-sensing-related applications, but the available generators are too bulky in size and/or exhibit low efficiencies. Here, we design and fabricate ultra-thin (∼λ/6) transmissive Pancharatnam-Berry metasurfaces and perform near-field scanning measurements to show that they can generate circularly polarized BBs within a frequency window of 10.7–12.3 GHz. We experimentally demonstrate that the generated BBs exhibit a self-healing effect, illustrating their non-diffraction characteristics. Finally, we employ far-field measurements to demonstrate that the working efficiency of our devices can reach 91%, while the simulated efficiency reaches 92%. All experimental results are in perfect agreement with full-wave simulations.
PAL-XFEL soft X-ray scientific instruments and X-ray optics: First commissioning results
Authors: Park Sang Han , Kim Minseok , Min Changi-Ki , Eom Intae , Nam Inhyuk , Lee Heung-Soo , Kang Heung-Sik , Kim Hyeong-Do , Jang Ho Young , Kim Seonghan , Hwang Sun-min , Park Gi-Soo , Park Jaehun , Koo Tae-Yeong , Kwon Soonnam
Published: May 2018

We report an overview of soft X-ray scientific instruments and X-ray optics at the free electron laser (FEL) of the Pohang Accelerator Laboratory, with selected first-commissioning results. The FEL exhibited a pulse energy of 200 μJ/pulse, a pulse width of <50 fs full width at half maximum, and an energy bandwidth of 0.44% at a photon energy of 850 eV. Monochromator resolving power of 10 500 was achieved. The estimated total time resolution between optical laser and X-ray pulses was <270 fs. A resonant inelastic X-ray scattering spectrometer was set up; its commissioning results are also reported.
Super-resolution imaging based on the temperature-dependent electron-phonon collision frequency effect of metal thin films
Authors: Ding Chenliang , Wei Jingsong , Xiao Mufei
Published: May 2018

We herein propose a far-field super-resolution imaging with metal thin films based on the temperature-dependent electron–phonon collision frequency effect. In the proposed method, neither fluorescence labeling nor any special properties are required for the samples. The 100 nm lands and 200 nm grooves on the Blu-ray disk substrates were clearly resolved and imaged through a laser scanning microscope of wavelength 405 nm. The spot size was approximately 0.80 μm, and the imaging resolution of 1/8 of the laser spot size was experimentally obtained. This work can be applied to the far-field super-resolution imaging of samples with neither fluorescence labeling nor any special properties.
Probing dynamics of micro-magnets with multi-mode superconducting resonator
Authors: Golovchanskiy I. A. , Abramov N. N. , Stolyarov V. S. , Shchetinin I. V. , Dzhumaev P. S. , Averkin A. S. , Kozlov S. N. , Golubov A. A. , Ryazanov V. V. , Ustinov A. V.
Published: May 2018

In this work, we propose and explore a sensitive technique for investigation of ferromagnetic resonance and corresponding magnetic properties of individual micro-scaled and/or weak ferromagnetic samples. The technique is based on coupling the investigated sample to a high-Q transmission line superconducting resonator, where the response of the sample is studied at eigen frequencies of the resonator. The high quality factor of the resonator enables sensitive detection of weak absorption losses at multiple frequencies of the ferromagnetic resonance. Studying the microwave response of individual micro-scaled permalloy rectangles, we have confirmed the superiority of fluxometric demagnetizing factor over the commonly accepted magnetometric one and have depicted the demagnetization of the sample, as well as magnetostatic standing wave resonance.
Predict-first experimental analysis using automated and integrated magnetohydrodynamic modeling
Authors: Lyons B. C. , Paz-Soldan C. , Meneghini O. , Lao L. L. , Weisberg D. B. , Belli E. A. , Evans T. E. , Ferraro N. M. , Snyder P. B.
Published: May 2018

An integrated-modeling workflow has been developed for the purpose of performing predict-first analysis of transient-stability experiments. Starting from an existing equilibrium reconstruction from a past experiment, the workflow couples together the EFIT Grad-Shafranov solver [L. Lao et al., Fusion Sci. Technol. 48, 968 (2005)], the EPED model for the pedestal structure [P. B. Snyder et al., Phys. Plasmas 16, 056118 (2009)], and the NEO drift-kinetic-equation solver [E. A. Belli and J. Candy, Plasma Phys. Controlled Fusion 54, 015015 (2012)] (for bootstrap current calculations) in order to generate equilibria with self-consistent pedestal structures as the plasma shape and various scalar parameters (e.g., normalized β, pedestal density, and edge safety factor [q95]) are changed. These equilibria are then analyzed using automated M3D-C1 extended-magnetohydrodynamic modeling [S. C. Jardin et al., Comput. Sci. Discovery 5, 014002 (2012)] to compute the plasma response to three-dimensional magnetic perturbations. This workflow was created in conjunction with a DIII-D experiment examining the effect of triangularity on the 3D plasma response. Several versions of the workflow were developed, and the initial ones were used to help guide experimental planning (e.g., determining the plasma current necessary to maintain the constant edge safety factor in various shapes). Subsequent validation with the experimental results was then used to revise the workflow, ultimately resulting in the complete model presented here. We show that quantitative agreement was achieved between the M3D-C1 plasma response calculated for equilibria generated by the final workflow and equilibria reconstructed from experimental data. A comparison of results from earlier workflows is used to show the importance of properly matching certain experimental parameters in the generated equilibria, including the normalized β, pedestal density, and q95. On the other hand, the details of the pedestal current did not significantly impact the plasma response in these equilibria. A comparison to the experimentally measured plasma response shows mixed agreement, indicating that while the equilibria are predicted well, additional analysis tools may be needed. Finally, we note the implications that these results have for the success of future predict-first studies, particularly the need for scans of uncertain parameters and for close collaboration between experimentalists and theorists.
Performance of waste-paper/PETG wood–plastic composites
Authors: Huang Lijie , An Shuxiang , Li Chunying , Huang Chongxing , Wang Shuangfei , Zhang Xiaoxiao , Xu Mingzi , Chen Jie , Zhou Lei
Published: May 2018

Wood–plastic composites were prepared from polyethylene terephthalate- 1,4-cyclohexanedimethanol ester (PETG) and waste-paper fiber that was unmodified, modified with alkyl-ketene-dimer (AKD), and modified with a silane-coupling agent. The mechanical properties, water absorption properties, surface structure, and thermal properties of the three prepared materials were compared. The results showed that the optimum amount of waste-paper powder is 10 wt%, while that of the waste-paper particles is 60–80 mesh. The use of AKD and coupling agent KH550 can reduce the water absorption of the composite; however, the reductive effect of the coupling agent is better, in that it is reduced by 0.3%. Modification using a 1-wt% KH550 coupling agent can effectively increase the tensile strength of a composite from 31.36 to 41.67 MPa (increase of 32.8%), while the bending strength increased from 86.47 to 98.31 MPa (increase of 13.7%). This also enhances the thermal stability of the composites. With the addition of the coupling agent, the composite material maintains good mechanical properties even after being immersed in water; this can enable the safe use of these composite materials in outdoor environments.