Small Gap Research Articles

Rigid Ligand Confined Synthesis of Carbon Supported Dimeric Fe Sites with High‐Performance Oxygen Reduction Reaction Activity for Quasi‐Solid‐State Rechargeable Zn‐Air Batteries

AbstractDimeric metal sites (DiMSs) in carbon‐based single atom catalysts (SACs) offer distinct advantages in optimizing the adsorption energies of the catalytic intermediates and reaction pathways over single atom sites, which inspires the investigations on the rational design of DiMSs‐based SACs and the accurate discernment of catalytic mechanisms. Here, dimeric Fe sites on carbon blacks (DiFe‐N/CBs) are prepared using the precursor of metal‐organic complex with a controlled structure, and the rigid ligand confinement secures the preservation of dimeric Fe sites during the thermal treatment. DiFe‐N/CBs shows excellent electrocatalytic performance for oxygen reduction reaction (ORR) with a high half‐wave potential of 0.917 V, and excellent durability with negligible activity decay. Theoretical studies reveal that the dimeric Fe sites have an optimal adsorption of OOH* with the Yeager‐type binding, illustrating the advantages of DiMSs over SAs in catalyzing ORR. The rechargeable aqueous and quasi‐solid‐state Zn‐air batteries assembled using DiFe‐N/CBs‐based air cathodes achieve small voltage gaps after long term charge/discharge test, showing great promises for practical applications. This synthetic strategy serves a novel platform to produce a scope of catalysts incorporating multimeric metal sites, and studies on the catalytic mechanism lay the foundation for establishing cooperative effect for multidentate adsorption reactions.

The impact of leak gap size and position on surgical mask performance of source control: A numerical study

Surgical masks are widely used for infectious source control by preventing infected individuals from transmitting pathogens. However, poor fit can create gaps between the mask and face, reducing their effectiveness. In this study, a numerical model was developed based on realistic surgical mask geometry with peripheral gaps of varying sizes and positions, fitted onto a breathing manikin. Exhalation leakage airflow dynamics and aerosol pathogen dispersion were investigated using a validated computational fluid dynamics (CFD) model with porous media. Results indicate that despite the presence of leaks, surgical masks are effective in controlling the spread of pathogens, with maximum airflow leakage at 9.11% and pathogen leakage at 16.83%. The average velocity of leaked airflow ranged from 0.12 m/s to 1.43 m/s, depending on the gap size and position. The position of the gap had little impact on the airflow and pathogen leakage fractions. Correlations between the average velocity of net leakage flow, leakage fractions of airflow and pathogens, and gap size were developed. Pathogens spread most widely from bottom leaks, followed by side and top leaks, with bottom leaks releasing up to 9.7 times more contaminated air than top leaks and 6.5 times more than side leaks. The findings also suggest that smaller gaps are associated with higher initial velocities of leakage, which in turn lead to wider dispersion of pathogens.

Strong Antiferromagnetic Interactions in the Binuclear Cobalt(II) Complex with a Bridged Nitroxide Diradical

A binuclear cobalt–radical complex formed by the reaction of Co(hfac)2·2H2O (hfac = hexafluoroacetylacetonate) with the 2,2-bis(1-oxyl-3-oxide-4,4,5,5-tetramethylimidazolinyl) biradical (BR) has been synthesized. The complex {(hfac)CoII(BN)CoII(hfac)} crystallizes in the triclinic space group P1¯ : C34H28Co2F24N4O12, a = 11.1513(5) Å, b = 12.8362(7) Å, c = 18.2903(8) Å, α = 103.061(1)°, β = 100.898(2)°, γ = 102.250(1)°, Z = 2. The compound consists of two non-equivalent pseudo-octahedral CoII ions, each bearing two hfac ancillary ligands bridged by the tetradentate bis-nitroxide (BN). The temperature dependence of the magnetic susceptibility indicates a strong antiferromagnetic exchange between each of the Co2+ ions and the nitroxyl biradical, as well as between the spins within the bridging ligand, forming a spin-frustrated system. Micro-squid investigations, performed on a single crystal of {(hfac)CoII(BN)CoII(hfac)}, reveal a peculiarity of the M(H) graph at temperatures below 0.4 K displaying a step that is a result of ground and first excited levels mixing by the applied magnetic field due to a small energy gap between them, as inferred from ab initio calculation. The latter was also carried out for two models of mononuclear Co2+ complexes in order to obtain a set of initial parameters for fitting the experimental magnetic curves using the Phi program. Moreover, direct CAS(12,10)/def2-TZVP calculations of the magnetic dependences χT(T) and M(H) were performed, which satisfactorily reproduced the experimental ones.

Small gaps between primes that satisfy the Goldbach equation

Small gaps between primes that satisfy the Goldbach equation

Three-dimensional vegetation structure drives patterns of seed dispersal by African hornbills.

Three-dimensional (3D) vegetation structure influences animal movements and, consequently, ecosystem functions. Animals disperse the seeds of 60%-90% of trees in tropical rainforests, which are among the most structurally complex ecosystems on Earth. Here, we investigated how 3D rainforest structure influences the movements of large, frugivorous birds and resulting spatial patterns of seed dispersal. We GPS-tracked white-thighed (Bycanistes albotibialis) and black-casqued hornbills (Ceratogymna atrata) in a study area surveyed by light detection and ranging (LiDAR) in southern Cameroon. We found that both species preferred areas of greater canopy height and white-thighed hornbill preferred areas of greater vertical complexity. In addition, 33% of the hornbills preferred areas close to canopy gaps, while 16.7% and 27.8% avoided large and small gaps, respectively. White-thighed hornbills avoided swamp habitats, while black-casqued increased their preference for swamps during the hottest temperatures. We mapped spatial probabilities of seed dispersal by hornbills, showing that 3D structural attributes shape this ecological process by influencing hornbill behaviour. These results provide evidence of a possible feedback loop between rainforest vegetation structure and seed dispersal by animals. Interactions between seed dispersers and vegetation structure described here are essential for understanding ecosystem functions in tropical rainforests and critical for predicting how rainforests respond to anthropogenic impacts.

Dye-Containing Polymers with π-Extened Diketopyrropyrrole Derivatives for Semi-Transparent Organic Photovoltaics.

Dye-containing polymers P1 (PEDPP-OT-BDT) and P2 (PEDPP-OT-BDTT) including a π-extended diketopyropyrrole (DPP) derivative and electron-rich thiophene fused ring units (4,8-bis((2-ethylhexyl)oxy)benzo[1,2-b:4,5-b']dithiophene for P1 and 4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b']dithiophene for P2) were synthesized as narrow band gap dyes. A π-extended DPP (EDPP-OT-BrPh), fragment of the polymers P1 and P2, was obtained by extending the π-conjugation of DPP using Ru(III)-catalyzed C-H and N-H activation reported by Gońka et al. in 2019, exhibiting a high quantum yield (ϕem=0.84) and small HOMO-LUMO gap (Eg=1.69 eV) due to the spatial overlap of the HOMO and LUMO orbitals. The solubility of the π-extended DPP was improved by introducing four 2-octylthophene side chains around the periphery of the planer dye moiety, while maintaining the high planarity of the dye molecule, which is essential to the function of optoelectronic devices. As a result, P1 and P2, polymerized with the π-extended DPP and BDT derivatives, exhibit carrier mobility of approximately 10-5 cm2/Vs in organic field-effect transistors (OFETs). In bulk heterojunction (BHJ) solar cells with [6,6]-phenyl-C61-butyric acid methyl ester (PCBM), they demonstrate a power conversion efficiency (PCE) of 1.0 % with an average transmittance (AVTs) of around 60 %.

Sr4Os3O12 – A Layered Osmate(V,VI) that is Magnetic Close to Room Temperature

AbstractBlack crystals of the mixed‐valence osmate(V,VI) Sr4Os3O12 were grown via a gas phase reaction in an evacuated silica tube. The material is attracted to a permanent magnet at room temperature (295±5 K) but loses this property when heated or cooled. In this temperature interval, soft magnetic behavior with vanishing coercivity is observed, but the saturation magnetization is only 0.05 μB per formula unit. Resistivity measurements show that Sr4Os3O12 is a semiconductor with a small band gap of about 0.26 eV at room temperature. X‐ray diffraction on a single‐crystal revealed a rhombohedral structure with the space group R m and lattice parameters ar=554.64(2) pm and cr=2700.1(1) pm at 300(1) K. The compound crystallizes in the La4Ti3O12 structure type and is isostructural to Sr4CoRe2O12. The structure is a rhombohedral stack of layered blocks, each of which can be considered as a section of three layers of the cubic perovskite structure cut perpendicular to one of its threefold axes. The Os–O−Os bond angle of about 175° favors superexchange that leads to antiferromagnetic coupling between the osmium atoms with 5d3 and 5d2 configurations. Sr4Os3O12 exhibits strong lattice dynamics. One aspect is the antiferro‐rotative lattice modes of the corner‐sharing [OsO6] octahedra, which freeze upon cooling. At 100 K, an ordered, yet twinned triclinic superstructure is formed. Strong spin‐orbit coupling and other effects cause deformations of the [OsO6] octahedra that differ significantly at 300 K and 100 K, suggesting a change in the electronic configuration. Competing ground states could also explain the temperature‐dependent band gap and the magnetic fluctuations manifested in the magnetization peak at room temperature.

Electronic and Optical Properties of 2D Heterostructure Bilayers of Graphene, Borophene and 2D Boron Carbides from First Principles.

In the present work the atomic, electronic and optical properties of two-dimensional graphene, borophene, and boron carbide heterojunction bilayer systems (Graphene-BC3, Graphene-Borophene and Graphene-B4C3) as well as their constituent monolayers are investigated on the basis of first-principles calculations using the HSE06 hybrid functional. Our calculations show that while borophene is metallic, both monolayer BC3 and B4C3 are indirect semiconductors, with band-gaps of 1.822 eV and 2.381 eV as obtained using HSE06. The Graphene-BC3 and Graphene-B4C3 bilayer heterojunction systems maintain the Dirac point-like character of graphene at the K-point with the opening of a very small gap (20-50 meV) and are essentially semi-metals, while Graphene-Borophene is metallic. All bilayer heterostructure systems possess absorbance in the visible region where the resonance frequency and resonance absorption peak intensity vary between structures. Remarkably, all heterojunctions support plasmons within the range 16.5-18.5 eV, while Graphene-B4C3 and Graphene-Borophene exhibit a π-type plasmon within the region 4-6 eV, with the latter possessing an additional plasmon at the lower energy of 1.5-3 eV. The dielectric tensor for Graphene-B4C3 exhibits complex off-diagonal elements due to the lower P3 space group symmetry indicating it has anisotropic dielectric properties and could exhibit optically active (chiral) effects. Our study shows that the two-dimensional heterostructures have desirable optical properties broadening the potential applications of the constituent monolayers.

Non-Kekulé meta-Quinodimethane Singlet Diradicals Based on Classical N-Heterocyclic Carbenes.

Diradicals based on a meta-quinodimethane (m-QDM) scaffold generally have a triplet ground state and are rather scarce. Herein, m-QDM-based non-Kekulé diradicals [3,3'-(NHC)2BP] (3-NHC) (NHC = SIPr = C{N(Dipp)CH2}2; IPr = C{N(Dipp)CH}2, Me-IPr = C{N(Dipp)CMe}2; Dipp = 2,6-iPr2C6H3; BP = 1,1'-C6H4C6H4) featuring N-heterocyclic carbene (NHC) pendants are reported as crystalline solids. The EPR spectra of 3-NHC show both allowed (Δms = 1) and forbidden (Δms = 2; 'half-field') transitions characteristic for triplet diradicals. Variable temperature EPR studies however reveal a singlet ground state for 3-SIPr. Consistent with the EPR spectra, calculations predict a remarkably small singlet-triplet energy gap (ΔEST ≤ 0.26 kcal/mol) for the 3-NHC compounds. The calculated singlet diradical character for the ground states of the 3-NHC compounds amounts to ~99 %.

From layered 2D carbon to 3D tetrahedral allotropes C12 and C18 with physical properties related to diamond: Crystal chemistry and DFT investigations

Mechanisms of changes from 2D to 3D (D = dimensionality) involving 2D C(sp2) trigonal paving to C(sp3) tetrahedral stacking are proposed through puckering of the 2D layers on one hand and interlayer insertion of extra C on the other hand. Such transformations, led to 3D hexagonal C12 and C18 allotropes respectively characterized by lon and bac topologies. Using density functional theory DFT calculations, the two allotropes were found cohesive and stable both mechanically (elastic properties) and dynamically (phonons). Comparisons of the physical properties with known uni C6 were established letting identify ranges of large Vickers hardness: HV (uni C6) = 89 GPa, HV (lon C12) = 97 GPa, and HV (bac C18) = 70 GPa. Whilst C6 was identified with acoustic phonons instability, C12 and C18 were found stable dynamically throughout the acoustic and optic frequency ranges. Furthering on the thermal properties the allotropes were characterized with a temperature dependence curve of the specific heat CV close to experimental data of diamond with best fit for novel C18. The electronic band structures reveal a small band gap of 1 eV for uni C6 and larger direct band gap of 3 eV for the two other 3D allotropes. Such modulations of the electronic and physical properties should open scopes of carbon research.

Precise Regulation of the Reverse Intersystem Crossing Pathway by Hybridized Long-Short Axis Strategy for High-Performance Multi-Resonance TADF Emitters.

Multi-resonance thermally activated delayed fluorescence (MR-TADF) molecules have experienced great success in organic light-emitting diodes (OLEDs) owing to their outstanding quantum efficiencies and narrow full width at half-maximums (FWHMs). However, the reverse intersystem crossing (RISC) rates of MR-TADF emitters are usually small, which will lead to relatively long triplet exciton lifetime and severe efficiency roll-off. Here, we report an effective molecular design strategy to introduce multichannel RISC pathways and thus increase RISC rates without compromising the color fidelity and emission efficiency by the "hybridized long-short axis (HLSA)" strategy. The TPA-CN-BN shows a near-unity photoluminescence quantum yield, rapid RISC rate of 1.4 × 105 s-1, narrow FWHM of 23 nm, and small singlet-triplet energy gap (ΔEST) of 0.06 eV in solution. The non-sensitized OLED based on TPA-CN-BN exhibits a narrowband emission with the FWHM of 31 nm, in company with external quantum efficiency (EQE) of 37.9%. Notably, the device exhibits the low efficiency roll-off as the EQEs maintain 34.8% and 21.8% at 100 and 1000 cd m-2, respectively, representing the best performance for single-host OLEDs based on the BCzBN skeleton. This study provides a fresh and promising approach to realize high-performance OLEDs with high color purity and remarkable device efficiency.

New Parameter for Benchmarking Plasmonic Gas Sensors Demonstrated with Densely Packed Au Nanoparticle Layers.

Localized surface plasmon resonance (LSPR) gas sensitivity is introduced as a new parameter to evaluate the performance of plasmonic gas sensors. A model is proposed to consider the plasmonic sensors' surface sensitivity and plasmon decay length and correlate the LSPR response, measured upon gas exchange, with an equivalent refractive index change consistent with adsorbed gas layers. To demonstrate the applicability of this new parameter, ellipsoidal gold nanoparticles (NPs) arranged in densely packed hexagonal lattices were fabricated. The main advantages of these sensors are the small and tunable interparticle gaps (18-29 nm) between nanoparticles (diameters: 72-88 nm), with their robust and scalable fabrication technology that allows the well-ordered arrangement to be maintained on a large (cm2 range) area. The LSPR response of the sensors was tested using an LSPR sensing system by switching the gas atmosphere between inorganic gases, namely He/Ar and Ar/CO2, at constant pressure and room temperature. It was shown that this newly proposed parameter can be generally used for benchmarking plasmonic gas sensors and is independent of the type and pressure of the tested gases for a sensor structure. Furthermore, it resolves the apparent disagreement when comparing the response of plasmonic sensors tested in liquids and gases.

Optimizing cooling strategies in the Czochralski process for large-diameter silicon ingots

As the semiconductor industry shifts towards larger wafer sizes, such as 300 mm and 450 mm, controlling defects is crucial to ensure device performance and yield. Conversely, a high cooling rate is essential for achieving higher production rates. Therefore, finding the optimal cooling strategy is critical to maintaining high production rates while ensuring high-quality wafer production. This paper employs a simulation model to investigate the impact of various cooling strategies on point defect formation during the CZ process for 450 mm diameter silicon ingots. Using the 3D energy equation coupled with the Navier-Stokes equation and moving mesh theory, the transient CZ process is simulated, incorporating defect evaluation equations. Beside original CZ puller configuration, two cooling strategies are examined: one with a small gap and long cooling jacket (Case II) and another with a large gap and short cooling jacket (Case III), compared against a baseline setup (Case I). The simulations reveal that Case II, while enhancing the crystallization rate, increases non-uniformity. Conversely, Case III produces a flatter solid-liquid interface and lower defect concentrations, achieving a maximum Cv-Ci of 0.4 × 1014 cm−3, compared to 1.1 × 1014 cm−3 and -2.5 × 1014 cm−3 in Case I and II. These findings suggest that adjusting cooling strategies can significantly impact the quality and uniformity of large- diameter silicon ingots.

A Multichamber Pulsating-Flow Device With Optimized Spatial Shear Stress and Pressure for Endothelial Cell Testing.

Design and analysis are presented for a new device to test the response of endothelial cells to the simultaneous action of cyclic shear stresses and pressure fluctuations. The design consists of four pulsatile-flow chambers connected in series, where shear stress is identical in all four chambers and pressure amplitude decreases in successive chambers. Each flow chamber is bounded above and below by two parallel plates separated by a small gap. The design of the chamber planform must ensure that cells within the testing region experience spatially uniform time-periodic shear stress. For conditions typically encountered in applications, the viscous unsteady flow exhibits order-unity values of the associated Womersley number. The corresponding solution to the unsteady lubrication problem, with general nonsinusoidal flowrate, is formulated in terms of a stream function satisfying Laplace's equation, which can be integrated numerically to determine the spatial distribution of shear stresses for chambers of general planform. The results are used to optimize the design of a device with a hexagonal planform. Accompanying experiments using particle tracking velocimetry (PTV) in a fabricated chamber were conducted to validate theoretical predictions. Pressure readings indicate that intrachamber pressure variations associated with viscous pressure losses and acoustic fluctuations are relatively small, so that all cells in a given testing region experience nearly equal pressure forces.

Lowering of the singlet-triplet energy gap via intramolecular exciton-exciton coupling

Organic dyes typically have electronically excited states of both singlet and triplet multiplicity. Controlling the energy difference between these states is a key factor for making efficient organic light emitting diodes and triplet sensitizers, which fulfill essential functions in chemistry, physics, and medicine. Here, we propose a strategy to shift the singlet excited state of a known sensitizer to lower energies without shifting the energy of the triplet state, thus without compromising the ability of the sensitizer to do work. We covalently connect two to four sensitizers in such a way that their transition dipole moments are aligned in a head-to-tail fashion, but, through steric encumbrance, the delocalization is minimized between each moiety. Exciton coupling between the singlet excited states considerably lowers the first excited singlet state energy. However, the energy of the lowest triplet excited state is unperturbed because the exciton coupling strength depends on the magnitude of the transition dipole moments, which for triplets are very small. We expect that the presented strategy of designed intramolecular exciton coupling will be a useful concept in the design of both photosensitizers and emitters for organic light emitting diodes as both benefits from a small singlet-triplet energy gap.

Prediction by DFT and Docking Calculations of a Series of Hypothetical 3d Transition Element Isostructural Complexes [M(hfac)2(TTF)2]: A Comparative Study

AbstractThe study aims to predict and compare the structural, electronic, conductivity, and biological properties of a series of 3d transition element complexes with those of the previously studied isostructural copper complex [Cu(hfac)2(TTF)2][PF6]2 (TTF: tetrathiafulvalene, hfac: hexafluoroacetylacetonate). Because transition metals hold open electronic shells, all possible spin states for all divalent compounds have to be considered in order to determine the most stable configurations. These configurations are those corresponding to the highest spin state (5 for Mn, 4 for Fe, 3 for Co, 2 for Ni, 1 for Cu, and 0 for Zn). However, the configurations with the smallest gap are Mn(3) and Co(1), suggesting that these are the most conductive complexes. A significant metal–ligand charge transfer is observed for both Mn and Co complexes. Antifungal (CYP121 (PDB: 2IJ7) and CYP51 (PDB: 1EA1)) and antibacterial (Escherichia coli (PDB: 1KZN)) properties of the compounds studied were evaluated by molecular docking; the results obtained reveal that the following complexes show significant activity: Zn(hfac)2(TTF)2] [PF6]2 (−8.9 kcal/mol), Ni(hfac)2(TTF)2] [PF6]2 (−7.8 kcal/mol), and Cu(hfac)2(TTF)2] [PF6]2 (−8.2 kcal/mol).

High beta diversity of gaps contributes to plot-level tree diversity in a tropical forest.

Canopy gaps are widely recognized as being crucial for maintaining the diversity of forest tree communities. But empirical studies have found mixed results because the differences in diversity between individual gaps and non-gaps are often small and statistically undetectable. One overlooked factor, however, is how small individual gap versus non-gap differences may accumulate across sites and potentially have a large effect on forest diversity at the plot scale. Our study investigated sapling richness, density, and composition in 124 treefall gaps, and 200 non-gap sites in the 50-ha tropical forest plot at Barro Colorado Island (BCI), Panama. Additionally, we analyzed species accumulation curves to understand how species richness increases with increasing stem numbers. We observed that sapling richness and density were only slightly higher in gaps 7 years after formation and statistically indistinguishable from non-gaps after 12 years. However, species accumulation curves across multiple gaps were substantially higher than those across non-gaps. Species composition showed small differences between individual gaps and non-gaps but differed significantly between collections of gaps and non-gaps. Specifically, 55 species specialized in 7-year-old gaps compared with 24 in non-gaps; of these, 23 gap-specialized species and zero non-gap species were pioneers. Our results indicate that tree species richness is higher in gaps because of both higher stem density and the presence of gap-specialized species. Our study has finally provided compelling evidence to support the idea that gaps enhance the overall diversity of tropical forest tree communities.

Experiment and Numerical Prediction on Shock Sensitivity of HMX–Based Booster Explosive with Small Scale Gap Test at Low and Elevated Temperatures

In order to analyze the effect of temperature changes on the shock initiation performance of HMX–based booster explosive, which consists of 95% HMX and 5% FPM2602 by weight, a temperature calibration test of acceptor was designed. The temperature changes in the booster at low and elevated temperatures under the constraint of steel sleeve were obtained. Based on the temperature calibration results, polymethyl methacrylate (PMMA) was selected as gap material to conduct a small scale gap test (SSGT) of HMX–based booster under different temperature conditions. The corresponding critical gap thickness was tested. Based on SSGT results at different temperatures, the shock initiation processes were simulated by adjusting parameters of ignition and growth reactive rate model. The critical gap thickness and critical initiation pressure of HMX–based booster at different temperatures were numerically predicted. By combining SSGT experimental data and simulation results, the attenuation law and fitting prediction formula of the critical initiation pressure of HMX–based booster were proposed. The mechanism of temperature effect on the shock sensitivity of HMX–based booster explosive was analyzed. The research results indicate that the critical gap thickness of HMX–based booster gradually increases with the rise in temperature, and the critical initiation pressure gradually decreases during the shock initiation process under the heating temperature conditions. In addition, the simulation results show that the heated HMX–based booster under steel constraints becomes more sensitive at high temperatures (>120 °C), while the cooled booster is more insensitive, but its critical initial pressure does not change significantly between 88 °C and 120 °C. The experimental and numerical prediction results are important for the shock initiation safety and design of an insensitive booster explosive.

Analysis of the Variation in Salaries of Employees of Government Ministries in Iraq by Using of The Lorenz Curve and The Gini Coefficient*H.

The disparity in the distribution of income is one of the main reasons for the failure to achieve social justice among members of society, which creates an unhealthy environment for workers in government sectors and institutions and also works to reduce the quality of work and lower the level of productivity. Conversely, reducing disparity leads to increased productivity and creates a suitable environment. It contributes to increasing productivity rates and improving the quality of institutional performance. The research discussed an important topic related to the extent of the discrepancy between the salaries of employees in Iraqi government institutions using the Lorenz curve and the Gini coefficient through a presentation of the research problem, which is the extent of the discrepancy in the salaries of state employees according to the approved salary scale, and what impact this has on social justice in the distribution of income, assuming that the adoption of A salary scale set by the authorities is based on reducing financial disparities between state employees with equal qualifications, such as educational attainment and work tasks, and reduces disparities of discrimination between workers in various government sectors and achieves social justice in income distribution. The research concluded that the actual distribution curve was very close to the symmetry line curve, in addition to the presence of a very small gap between the two lines, which indicates fairness in the distribution of monthly salaries among workers in government ministries who are in the fourth degree/first stage of the approved salary scale. The value of the Gini coefficient complementary to the work of the Lorenz curve was about (0.4), which means that the value of the Gini coefficient is close to zero. This indicates that the distribution of salaries of employees of government ministries is close to equitable distribution.

Examination of the effect of air gaps on impact sound insulation performance of dry-type double floor system

The dry-type double floor system is a floor finishing structure widely installed for apartments and offices in Japan. However, after installing the double floor system, it is found that the impact sound insulation performance using a heavy-weight impact source is usually reduced due to the resonance of the air layer between the floor panels and the concrete slab. To reduce this adverse effect, small air gaps are set between the floor panels and the surrounding walls. In this paper, an experimental study is conducted firstly. A small specimen including particle board, support legs and air gaps is made to examine the effect of air gaps experimentally. Then, the air gaps are built as a Maxwell model considering that the air gaps act as the orifice of air spring. The theoretical analysis is conducted to explain the mechanism of impact sound insulation of the double floor system with or without air gaps. Finally, a parametric study is conducted to investigate the effect of air gaps with different dimensions on the impact sound insulation performance of the double floor system.