Shower-head Type Research Articles

Assessing the impact of anti-microbial showerheads on the prevalence and abundance of opportunistic pathogens in shower water and shower water-associated aerosols

Respiratory infections from drinking water-associated pathogens that can cause infections in the immunocompromised (DWPIs) are increasing, yet knowledge of DWPI aerosolization and if dynamics are DWPI-specific is lacking. Although there are several DWPI mitigation strategies, the use of antimicrobial showerheads is one of the easiest and most economical. There are many manufacturers and designs of antimicrobial showerheads that claim to remove microorganisms from shower water, yet all fail to assess efficacy in realistic conditions. In this study, a custom-built shower laboratory housing triplicates of three different showerheads (antimicrobial filter-based, antimicrobial silver-embedded and conventional acrylonitrile butadiene styrene plastic) were used to assess the physiochemical and microbial dynamics in shower water and respirable shower water-associated aerosols (1µm – 5 µm) over the course of 84 days. Collectively, findings from the study suggest that showerheads marketed as antimicrobial produce similar chemical and DWPI water quality to non-antimicrobial showerheads (p= >0.05) when operated under real-world conditions, however marked differences in the rare microbial community were present. In addition, although there were no differences in absolute DWPI abundance between showerhead type, each DWPI peaked in concentration at a different biofilm ages, suggesting that potential DWPI inhalation risk is DWPI- specific and influenced by the number of days of operation of the showerhead.

In-situ radon-in-water detection for high resolution submarine groundwater discharge assessment

Submarine groundwater discharge (SGD), including both land-based fresh groundwater that enters the ocean from coastal aquifers as well as recirculated seawater that is continuously recharged and discharged on the seabed, has been considered as an important component of the global water and biogenic element (e.g., nitrogen, phosphorus, silicon and carbon) sources and a significant pathway for material exchange at the land-sea interface of coastal ecosystems. Some researchers reported that SGD associated nutrient additions to coastal waters have caused unwanted ecological issues, including red tides, coastal acidification and hypoxia. Natural radon isotope (222Rn, t1/2 = 3.8 d) is an excellent tracer for studying SGD and other oceanographic processes including air-sea gas exchange, sediment-water diffusion, and earthquake prediction. However, the conventional radon measurement methods suffer many technical disadvantages. We consequently developed a convenient submersible radon determination approach (“OUC-Rn”) using a commercial pulsed ionization chamber (PIC) radon sensor and gas extraction membrane module to produce high precision and high resolution observations. We demonstrate the radon degassing efficiency of the membrane contactor is comparable to the shower-head type air-water exchanger but is independent of operating position. The radon measurement efficiency of the PIC is 2-fold higher than the RAD7 detector and is far less influenced by moisture. We successfully deployed the system in 2.5 meters water depth over a 100 hours period in an anthropogenic influenced bay. Based on our high temporal resolution observations, the SGD flux was estimated to be 0-43.0 cm/d (mean: 25.4 ± 14.5 cm/d). The SGD fluxes pattern plotted together with the tidal variations revealed that tidal pumping may be the main force driving seawater recirculation into aquifers and thus affecting nutrient, carbon and other dissolved matters dynamics in coastal regions.

Comparative Study of Tungsten Films Grown By Atomic Layer Deposition with Newly Synthesized Metalorganic and Halide Precursor

For continuous scaling down of semiconductor devices, metal deposition has been developed as a plug filling process for interlayer connecting. Tungsten (W) has a wide range of industrial applications since it has a relatively good electrical conductivity and a high electromigration durability due to its high melting point of 3380 °C. [1] Among various techniques, atomic layer deposition (ALD) has been investigated to find the most feasible way to grow uniform, dense, conformal, and conductive W thin film to thicknesses of a few nanometers in more complicated structures, since its growth mechanism is entirely based on self-limited surface reaction. [2] To date, several W precursors have been employed. Among them, the halide precursors have been widely used as precursors for metal deposition since it can fabricate a high-purity film compared to metal organic precursors. Tungsten hexafluoride (WF6) is the most widely reported halide-based precursor to date due to its simple structure and high reactivity. [3] However, the toxic by-product (HF) can provoke the interfacial Si consumptions and corrosion of devices. In this respect, in halide-based precursors, fluorine (F)-free tungsten precursors have recently received attention, but study on development of F-free tungsten precursor is still in its infancy. In contrast, the organic precursor is free from the formation of corrosive by-product. However, the carbon species derived from the organic ligand of the precursor can deteriorate film properties and device performance. [4] For this reason, studies for pure tungsten metal deposition with organic precursors have not been reported. Eventually, since the halide and organic precursors have their own strengths and weaknesses, there has been considerable controversy over the choice of precursors between the two groups.In this work, we fundamentally investigated the growth characteristics, chemical composition, crystallinity of W films on SiO2 substrate using two newly synthesized precursors (tungsten pentachloride (WCl5) and ethylcyclopentadienyltungsten(Ⅴ) tricarbonyl hydride (HEtCpW(CO)3)). Ar/H2 plasma as the reactant was generated between the showerhead and the substrate during the reactant exposure by capacitively coupled plasma (CCP) with a radiofrequency (RF) of 13.56 MHz at 200 W. We used Commercial showerhead type ALD chamber which has 8-inch wafer capacity, and the precursors were contained in individual stainless-steel bubblers and evaporated at 135 and 55 °C, respectively, to obtain a sufficient vapor pressure. The delivery lines were heated to a temperature approximately 10–15 °C higher than that of the bubbler to prevent the condensation of the precursor. The microstructure of W film were analyzed using Grazing-incidence X-ray diffraction (GIXRD), the film density of W film was analyzed via X-ray reflectivity (XRR), and the resistivity was electrically measured via Four point probe (FPP) with semiconductor analyzer. Growth characteristics and film properties were significantly affected by ligands of precursors. In addition, the electrical properties, including resistivity depending on the ALD cycles, and conformality at trench were evaluated for potential application. These results provide fundamental and useful information, with respect to the selection of the suitable precursor, for practical implementation of device fabrication.

Experimental validation of liquid hydrocarbon based fuel rich gas generator for high speed propulsion systems

For long duration hypersonic flight vehicles, research on high speed air-breathing propulsion systems has been progressing across the world for the past few decades. Ramjets/Scramjets fueled with hydrogen/liquid hydrocarbon fuels are the propulsion systems considered for different regimes of flight envelope. Dual Combustion Ramjet (DCR) engine is a prospective candidate for one of such kind of applications, where the engine is expected to work for a wider range of flight Mach number regime. It has a fuel rich subsonic dump combustor and a supersonic combustor, which work in tandem. In the present work, extensive experimental and analytical work has been carried out to develop a fuel rich gas generator often called as dump combustor suitable for operation from 20 to 28 km altitude and in the range of 4–6 flight Mach number. Connect pipe mode testing has been carried out by varying the throat area of dump combustor for Mach 4 conditions. Tests have been carried out with Jet-A fuel at different equivalence ratio and with fuel injection in different combination and stages. Fuel injection scheme used here is of shower head type in intake arm and a single simplex swirler with film cooling holes in the dump combustor. Study has been also carried out by varying the location of swirler along the combustor length. Combustor air entry conditions are simulated using H2–O2 based air heater and a test bed nozzle. An exhaustive amount of tests have been carried out to establish condition suitable for consistent ignition & sustained combustion in this highly fuel rich condition. A One dimensional (1D) mathematical model with NASA CEA interface has been developed to predict & compare the test performance. Sustained ignition is achieved for fuel flow rate of 0.8 kg/s and at an equivalence ratio of 0.8–0.9.

Estimates of methane emissions from the Southern Ocean from quasi-continuous underway measurements of the partial pressure of methane in surface seawater during the 2012/13 austral summer

We used a new underway measurement system to investigate the partial pressure of methane (CH4) in surface seawater and overlying air in the Southern Ocean from late November 2012 to mid-February 2013. The underway system consisted of a cavity ring-down spectroscopy analyser and a shower-head type equilibrator. The monthly mean atmospheric CH4 mixing ratios obtained agreed well (within 5 ppb) with those recorded at onshore baseline stations. CH4 saturation ratios (SR, %), defined as CH4 concentration in seawater divided by CH4 concentration equilibrated with atmospheric CH4, varied between 85 and 185%; most of the ratios we calculated indicated supersaturation, except for those from south of the Southern limit of Upper Circumpolar Deep Water. SR was higher at the lower latitudes, including coastal areas north of the Sub-Antarctic Front, but decreased gradually and monotonously between the Sub-Antarctic Front and the Upper Circumpolar Deep Water. At high latitudes south of the Polar Front, SR decreased to below 100% due to the effects of upwelling and vertical mixing. We found a strong linear correlation between SR and apparent oxygen utilisation (AOU) south of the Polar Front. Observed SR decreased with increasing AOU and reached 85% at high AOU (41 µmol kg−1) and low temperature (–1.8 °C). On the basis of the linear relationship between SR and AOU, we evaluated the climatological sea–air flux of CH4 from December to February for the entire Southern Ocean south of 50°S: Sea–air CH4 emission was estimated to be 0.027 Tg yr−1 in December, 0.04 Tg yr−1 in January, and 0.019 Tg yr−1 in February.

Uniform coating of Ta2O5 on vertically aligned substrate: A prelude to forced flow atomic layer deposition

Uniform tantalum oxide thin films, with a growth rate of 0.6 Å/cycle, were fabricated on vertically aligned, 10 cm-long, silicon substrates using an innovative atomic layer deposition (ALD) design. The ALD system, with a reaction chamber depth of 13.3 cm and 18 vertical enclosed channels (inner diameter 1.3 cm), was coupled with a shower-head type precursor conduit plate bearing 6 radial channels. This design enabled deposition on 6 silicon substrates at a time. The degrees of non-uniformity of deposits along the length of the silicon wafer and across different positions in the ALD chamber were found to be 1.77%-6.21% and 3.27%-5.45%, respectively. A further advantage of the design is that the conduit plate may be modified and the number of channels increased to process 18 substrates simultaneously, thus moving toward efficient and expedited ALD systems.

Enhanced Electrochemical Properties of LiNi0.5Co0.2Mn0.3O2 Cathode Materials with RuO2 Coating Layer By Atomic Layer Deposition

Ni-based cathode materials have been as an alternative to LiCoO2[1,2]. Therefore, many studies have been performed to solve the inherent problems of Ni-base cathode materials [3]. However, reasonable solution for rate performance and thermal stability of Ni-based cathode materials has not been reported. Coating method on the cathode material may become the solution technique for electrochemical properties. In this study, LiNi0.5Co0.2Mn0.3O2 cathode materials were prepared by co-precipitation method. RuO2 coating layer was deposited on LiNi0.5Co0.2Mn0.3O2powder using a shower head type PEALD reactor (Lucida-M100, NCD Technology), with IMBCH Ru [IMBCH = (η6-1-isopropyl-4-methylbenzene)(η4-cyclohexa-1,3-diene)] as a precursor. We propose a new coating method for cathode materials using atomic layer deposition. The physical and electrochemical properties of RuO2 coated LiNi0.5Co0.2Mn0.3O2 cathode materials have been thoroughly investigated. Compared to various metal oxides, we will show that the optimization of RuO2 coating layer can be significantly improved the electrochemical performance of LiNi0.5Co0.2Mn0.3O2cathode materials.

Influence of process pressure on β-SiC growth by CVD

3C-SiC films grown on Si (100) substrates by CVD method using silane-propane- hydrogen system were analyzed for crystallinity at various process pressures. The deposition experiments were carried out in a shower-head type cold-wall CVD reactor. The influence of growth conditions on a structural modification of experimental samples was studied by X-ray diffraction (XRD) measurements, Fourier transform infrared spectroscopy (FTIR) and spectroscopic ellipsometry (SE).

Photoluminescence features and carrier dynamics in InGaN heterostructures with wide staircase interlayers and differently shaped quantum wells

We present a comprehensive study of photoexcited carrier dynamics in differently grown InGaN/InGaN multiple quantum well (MQW) structures, modified by insertion of a wide interlayer structure and subsequent growth of differently shaped quantum wells (rectangular, triangular, trapezoidal). This approach of strain management allowed the reduction of dislocation density due to gradually increasing In content in the interlayer and shaping the smooth quantum well/barrier interfaces. A set of c-oriented MQW structures emitting at 470 nm were grown at Vilnius University, Institute of Applied Research, using a closed coupled showerhead type MOCVD reactor. Photoluminescence (PL) spectra of MQW structures were analysed combining continuous wave and pulsed PL measurements. Reactive ion etching of the structures enabled discrimination of PL signals originated in the InGaN interlayer structure, underlying quantum wells, and quantum barriers, thus providing growth-related conditions for enhanced carrier localization in the wells. Time-resolved PL and differential transmission kinetics provided carrier lifetimes and their spectral distribution, being the longest in triangular-shape QWs which exhibited the highest PL intensity. The light-induced transient grating (LITG) technique was used to determine the spatially averaged carrier lifetime in the entire heterostructure, in this way unravelling the electronic quality of the LED internal structure at conditions similar to device performance. LITG decay rates at low and high excitation energy densities revealed increasing with photoexcitation nonradiative recombination rate in the triangular and trapezoidal wells.

Study of Y2O3 Thin Film Prepared by Plasma Enhanced Atomic Layer Deposition

Y2O3 thin films are fabricated on Si (100) wafer by using showerhead type direct PEALD system. The commercial tris (methylcyclopenta dienyl) yttrium ((MeCp3)3Y) precursor and oxygen plasma are used as a precursor and as a reactant. The growth rate per cycle is increased slightly from 0.1nm/cycle to 0.13nm/cycle, as the substrate temperature is increased from 175¢ªC to 325¢ªC. The crystallinity and density of Y2O3 thin films are also increased as the substrate temperature is increased. Carbon contaminations and film stoichiometry are improved due to high reactivity of plasma species. Dielectric constants of Y2O3 thin films are in range of 15~17 calculated by capacitance – voltage characteristics.

HAN/메탄올 추진제를 사용하는 1 N급 추력기 성능 평가

이온성 액체 추진제인 HAN은 무독성의 높은 저장성을 갖는 단일 추진제로서 메탄올을 혼합하여 비추력을 향상시켜 하이드라진을 대체할 수 있을 있다. HAN은 하이드록실아민과 질산의 산-염기 반응을 통해 합성하며, 메탄올과 8.2:1의 비율로 혼합한다. HAN의 분해를 위해서 이리듐 촉매를 사용하며, 하나의 오리피스를 갖는 1 N급 추력기를 사용하여 HAN/메탄올 추진제의 성능 평가를 수행하였다. 메탄올 연소로 인해 반응 생성물의 온도가 높기 때문에 디스트리뷰터의 열적 안정성을 향상시키기 위해 세라믹 재료를 적용하였다. 완전한 분해를 위해서는 최소 <TEX>$400^{\circ}C$</TEX>의 예열 온도를 필요로 하였다. 높은 <TEX>$C^*$</TEX> 효율을 얻기 위해서는 가압 압력이 높아져야 했으며, 이로 인해 촉매 상단의 분해 성능이 저하되면서 전체 추력기 성능 저하가 유발되었다. 이를 해결하기 위해 미세한 금속 메쉬를 인젝터 후단에 삽입하여 추진제의 분무 특성을 향상시켰으며, 실험 결과 촉매의 성능 저하 현상이 개선되었음을 확인하였다. The HAN which is an ionic liquid is a non-toxic monopropellant with high storability, and its specific impulse can be increased by blending methanol, thereby it can substitute the hydrazine. The HAN was synthesized by acid-base reaction of hydroxylamine and nitric acid, and the blending ratio of HAN and methanol is 8.2:1. The iridium catalyst was used to decompose the HAN, and 1 N class thruster with shower head type injector having one orifice was used to evaluate the HAN/Methanol propellant. The thermal stability of distributor was increased by using ceramic material to endure the high temperature of product gas. The preheating temperature of catalyst should be <TEX>$400^{\circ}C$</TEX> at least for the complete decomposition. The feeding pressure should be increased to increase the <TEX>$C^*$</TEX> efficiency, thereby the decomposition performance was decreased upstream catalyst, and the performance of thruster was decreased. The fine metal mesh was inserted after the injector to improve the atomization of propellant, thereby it can settle the performance decrease problem. The phenomenon of performance decrease was remarkably improved owing to the insertion of fine metal mesh.

Effects of gas depletion on dc plasma deposited, a-Si single junction p–i–n solar cells with i-layers deposited at 10 Å/s

The growth rate of a-Si increases with dc plasma current with a single slope at high flow rates but with a reduced slope above a certain power for lower flow rates when using a showerhead type gas delivery system. This is in contrast to saturation of the growth rate under gas depletion conditions previously reported. The change to a smaller slope for lower flow rates at higher powers can be understood in terms of a transition to reactive radical dominated growth. We show that a-Si single junction cell performance deteriorates under gas depletion conditions.

中空糸膜を用いた海洋二酸化炭素の測定

In order to measure the CO 2 mixing ratios in air equilibrated with seawater (xCO 2 S ), we tested a multi-layered composite hollow-fiber membrane (MHF) module aboard the TS Hokuto-maru in the North Pacific in January-February 1996 and July-August 1996. The MHF module is much smaller (300 cm 3 ) than the currently used shower-head type equilibrator (110 dm 3 installation volume). The mean difference in xCO 2 S (ΔxCO 2 S ) values between the two systems determined 14 minutes apart was 1.6 ppm with a standard deviation of 2.2 ppm (n = 73) for the southbound cruise in January, and -1.9 ppm with a standard deviation of 1.8 ppm (n = 103) for the northbound cruise in February, 1996. The difference in average ΔxCO 2 S between the two legs was mainly caused by the effect of water temperature difference between the shower-head type equilibrator and the MHF module. By taking into account the effect on xCO 2 S of water-temperature difference between the two equilibrators, the mean ΔxCO 2 S was as low as 0.1 ppm (n = 732) with a standard deviation of 3.7 ppm for the cruise in July-August 1996. These results indicate that no systematic difference exists between the two equilibrators. The MHF has potential for future use as an equilibrator that is compact and easy to install.

Characterization of High Rate Deposited PECVD Silicon Dioxide Films for MCM Applications

Silicon dioxide has recently received considerable attention as an interlayer dielectric for use in multichip modules (MCMs) because of its excellent properties. A high deposition rate at relatively low temperatures is desirable for process compatibility and high throughput. PECVD silicon dioxide films up to 7 μm thick were deposited at 1000 Å/min in a showerhead type system using , , and . Substrate temperature was varied from 250–350°C. The deposited films were annealed at various temperatures (up to 500°C). Uniformity, etch rate, film stress, refractive index, Si 2p and O 1s binding energies, and Si‐H and OH bonding configurations were studied. C‐V and I‐V characterizations of the films were performed to investigate their electrical quality. All the as‐deposited films exhibited moderate compressive stress. A considerable change in stress was observed after annealing the films in the above noted temperature range. OH content in the films was found to decrease and the hydrogen content in the films was found to increase with increasing deposition temperature. A good correlation between silanol (Si‐OH) and hydrogen content and silicon richness of the films with film stress was observed. The refractive index was found to decrease with increasing anneal temperature for all the films. Etching rates were lower for films deposited at higher temperatures. All films exhibited excellent breakdown characteristics.

A mathematical representation of a modified stagnation flow reactor for MOCVD applications

Computed results are presented describing the behavior of a modified stagnation point reactor for an MOCVD system, employing a showerhead type gas distributor. The principal findings of the work are the following: (a) By this arrangement, it is possible to obtain a very high spatial uniformity in the deposition rate, in cases better than 0.35% for a five inch diameter wafer. (b) Both the absolute values of the gas velocity and the standoff distance were found to play a critical role in affecting the uniformity of the deposition rate. Indeed a small standoff distance was found to be an essential ingredient in obtaining a good spatial uniformity of the deposit. (c) “An upside down” orientation was found to be helpful in minimizing thermal natural convection and a further refinement was found to be possible by imposing a desired radial distribution on the gas inlet velocity profile.

A Thermal Control System for Thermal Cycling

Abstract A microprocessor-based system has been developed to control varying temperature during material characterization tests. The system controls temperature independently over four zones. Four control zones are used in order to provide two-dimensional temperature control on a flat plate specimen. Specimen cooling is provided by forced air through shower head type nozzles.