Possibility Of Further Enhancement Research Articles

Study on the fabrication of silicon nanoparticles in an amorphous silicon light absorbing layer for solar cell applications

Hydrogenated amorphous-silicon (a-Si:H) thin-film solar cells have advantages of relatively simple technology, less material consumption, higher absorption ratio compared to crystalline silicon, and low cost due to the use of cheaper substrates rather than silicon wafers. However, together with those advantages, amorphous-silicon thin-film solar cells face several issues such as a relatively lower efficiency, a relatively wider bandgap, and the Staebler-Wronski effect (SWE) compared to other competing materials (i.e., crystalline silicon, CdTe, Cu(InxGa(1−x))Se2 (CIGS), etc.). As a remedy for those drawbacks and a way to enhance the cell conversion efficiency at the same time, the employment of crystalline silicon nanoparticles (Si-NPs) in the a-Si matrix is proposed to organize the quantum-dot (QD) structure as the light-absorbing layer. This structure of the light absorbing layer consists of single-crystal Si-NPs in an a-Si:H thin-film matrix. The single-crystal Si-NPs are synthesized by using SiH4 gas decomposition with CO2 laser pyrolysis, and the sizes of Si-NPs are calibrated to control their bandgaps. The synthesized size-controlled Si-NPs are directly transferred to another chamber to form a QD structure by using co-deposition of the Si-NPs and the a-Si:H matrix. Transmission electron microscopy (TEM) analyses are employed to verify the sizes and the crystalline properties of the Si-NPs alone and of the Si-NPs in the a-Si:H matrix. The TEM results show successful co-deposition of size-controlled Si-NPs in the a-Si:H matrix, which is meaningful because it suggests the possibility of further enhancement of the a-Si:H solar-cell structure and of tandem structure applications by using a single element.

An Investigation into the Performance Enhancement and Salient Features of AMR-WB Speech Codec Used in GSM Communication

The 3rd Generation Partnership Project (3GPP) along with European Telecommunication Standard Institute (ETSI) recommended new speech coding scheme, called Adaptive Multi Rate (AMR) in 2000 and 2001. The proposed scheme has two variants: AMR-Narrowband (AMR-NB) and AMR-WB (AMR- Wideband). The speech quality of AMR-WB in GSM systems is remarkably high compared with that of AMR-NB speech codec because it encompasses wider bandwidth of the speech signal, 50-7000 Hz, instead of 200-3400 Hz in AMR-NB. But there are always possibilities for improvement. This paper investigates the salient features of AMR-WM codec and various possibilities for further enhancement in its speech quality. Two algorithms are recommended for incorporation into the standard AMR-WB to achieve this goal.

ARDesigner: A web-based system for allosteric RNA design

RNA molecules play vital informational, structural, and functional roles in molecular biology, making them ideal targets for synthetic biology. However, several challenges remain for engineering novel allosteric RNA molecules, and the development of efficient computational design techniques is vitally needed. Here we describe the development of Allosteric RNA Designer (ARDesigner), a user-friendly and freely available web-based system for allosteric RNA design that incorporates mutational robustness in the design process. The system output includes detailed design information in a graphical HTML format. We used ARDesigner to engineer a temperature-sensitive AR, and found that the resulting design satisfied the prescribed properties/input. ARDesigner provides a simple means for researchers to design allosteric RNAs with specific properties. With its versatile framework and possibilities for further enhancement, ARDesigner may serve as a useful tool for synthetic biologists and therapeutic design. ARDesigner and its executable version are freely available at http://biotech.bmi.ac.cn/ARDesigner.

Critical Temperature Enhancement by Biaxial Compressive Strain in FeSe0.5Te0.5 Thin Films

High-purity epitaxial FeSe0.5Te 0.5 thin films with different thicknesses were grown by pulsed laser ablation on different substrates. By varying the film thickness, T c values of up to 21 K were observed, significantly larger than the bulk value. Structural analyses indicated that the a axis changes significantly with the film thickness and is linearly related to T c. The latter result indicates the important role of the compressive strain in enhancing T c: the compressive strain derives from the Volmer–Weber growth of the films. The critical temperature is also related to both the Fe–(Se,Te) bond length and angle, suggesting the possibility of further enhancement.

T c = 21 K in epitaxial FeSe0.5Te0.5 thin films with biaxial compressive strain

Epitaxial FeSe0.5Te0.5 thin films with different thickness were grown by pulsed laser ablation deposition on different substrates. High purity phase and fully epitaxial growth were obtained. By varying the film thickness, superconducting transition temperatures up to 21 K were observed, significantly larger than the bulk value 16.2 K. Structural analyses indicated that the c-axis is smaller than the bulk value but it is almost independent of the film thickness and the a-axis changes significantly with the film thickness and is linearly related to the Tc. The latter result indicates the important role of the compressive strain in enhancing Tc. Tc is also related to both the Fe–(Se,Te) bond length and angle, suggesting the possibility of further enhancement.

Novel induction heating system for service cycle thermo-mechanical fatigue testing

The concept of an active/passive coil arrangement has been devised as part of the development of a flexible induction heating system to provide well controlled temperature distributions during complex service cycle thermo-mechanical fatigue tests involving low alloy bainitic and martensitic steels. Introducing a passive coil at the mid-specimen gauge length position is responsible for a significant reduction in axial temperature gradient during thermal transients. The effectiveness of this novel new arrangement is demonstrated and the possibilities for further enhancement are explored.

Near-Infrared Metal-Enhanced Fluorescence Using a Liquid–Liquid Droplet Micromixer in a Disposable Poly(Methyl Methacrylate) Microchip

Solution-based metal-enhanced fluorescence of near-infrared fluorophores in a poly(methyl methacrylate) microchip is studied. A liquid–liquid droplet micromixer is used for rapid mixing of fluorophores with silver nanoparticles while maintaining discrete packets of known analytes for reproducible quantitative analysis. Nanoparticle aggregation within the microchip is controlled by individually adjusting salt concentration, colloid concentration, and mixing efficiency. Results identify an optimal salt concentration for aggregate formation and enhanced fluorescence, while the impacts of colloid concentration and mixing efficiency increase linearly, suggesting the possibility of further enhancement. Fluorescence enhancements of 35-fold were achieved on a microfluidics device using metal-enhanced fluorescence in a discrete solution-based system with exposure times of only 50 ms.

이종의 통계정보를 이용한 품사 부착 기법

통계적 방식의 품사부착 문제는 보통 N-그램과 같을 단일 통계정보를 활용하지만 단순한 통계 정보라는 원천적인 한계가 있어 많은 오류가 발생한다. 따라서 다양한 정보를 활용하는 것이 정확도를 높일 가능성이 있다는 데는 이론의 여지가 없다. 그러나 다른 종류의 통계 자료는 배타적 자료가 아닌 한 상충되는 정보를 가질 수밖에 없으므로 이러한 정보들로부터 어떻게 종합적인 결론을 내는가가 문제이다. 본 논문에서는 이러한 상이한 통계정보를 통합하는 방법으로 언어 모델의 구성에서 활용된 바 있는 최대엔트로피 모델의 한국어 품사 부착에의 사용 가능성을 제시한다. 여기서는 이종의 통계정보로서 N그램과, 트리거 쌍을 사용하게 된다. 이러한 트리거 쌍 통계정보를 N그램과 함께 최대엔트로피 모델링을 했을 경우 퍼플렉시티가 어떻게 변화하는지에 대한 실험결과를 관찰하게 될 것이다. 트리거 쌍은 또한 다양하게 문맥사이즈를 변화할 수 있으며, N그램의 확률 모델도 다양하기 때문에 여러 종류의 실험을 통한 많은 향상을 예상 할 수 있다. 본 실험에서는 단일 모델 사용시 94.9 %의 정확도를 가진 3-그램 모델에 트리거 쌍을 최대 엔트로피 방식으로 추가한 견우 95.6% 의 정확도를 보여 0.7% 포인트의 정확도 향상을 기록하였다. 따라서 향후 다양한 정보원을 개발하여 최대엔트로피 방식으로 통합할 경우 지속적인 정확도 향상을 가져 올 수 있는 가능성을 보여준다고 할 수 있다. Statistical POS tagging is prone to error, because of the inherent limitations of statistical data, especially single source of data. Therefore it is widely agreed that the possibility of further enhancement lies in exploiting various knowledge sources. However these data sources are bound to be inconsistent to each other. This paper shows the possibility of using maximum entropy model to Korean language POS tagging. We use as the knowledge sources n-gram data and trigger pair data. We show how perplexity measure varies when two knowledge sources are combined using maximum entropy method. The experiment used a trigram model which produced 94.9% accuracy using Hidden Markov Model, and showed increase to 95.6% when combined with trigger pair data using Maximum Entropy method. This clearly shows possibility of further enhancement when various knowledge sources are developed and combined using ME method.

Ion irradiation dependence of the superconducting properties of (Cu,C)Ba 2Ca 3Cu 4O 10.5− δ

To further enhance the critical current density ( J c) and irreversibility field ( H irr) of (Cu,C)Ba 2Ca 3Cu 4O 10.5− δ (hereafter described as (Cu,C)-1234), pinning centers were introduced by heavy-ion irradiation. Polycrystalline samples were irradiated with Au 15+ ions (240 MeV energy) or Xe 14+ ions (200 MeV energy) at a fluence of 10 11 ions/cm 2. J c (77 K, 1 T) shows a remarkable increase from 3.9 × 10 4 to 4.1 × 10 6 A/cm 2 for Au 15+ ion irradiated sample and increase from 3.9 × 10 4 to 1.5 × 10 5 A/cm 2 for Xe 14+ ion irradiated sample. The value of H irr(77 K) is about 12.5 T for Au 15+ ion irradiated sample and for Xe 14+ ion irradiated sample, peak effect like behavior was observed at 77 K. Ion irradiation is much effective to introduce pinning centers in (Cu,C)-1234 and to control or optimize J c and H irr values of (Cu,C)-1234. These results indicate the possibility of further enhancement of J c and reaching a high H irr for (Cu,C)-1234.

Heavy-ion irradiation dependence of the superconducting properties of (Cu,C)Ba2Ca3Cu4O10.5−δ

To enhance or improve critical currents density (Jc) and irreversibility field (Hirr) of (Cu,C)Ba2Ca3Cu4O10.5−δ ((Cu,C)-1234), pinning centers were introduced by heavy-ion irradiation. The polycrystalline samples were irradiated with Au15+ ions (240 MeV energy) at various fluence of 1×1011, 2.5×1011 and 5×1011 ions/cm2. Jc and Hirr were determined for the irradiated samples as well as unirradiated samples. Jc (77 K, 1 T) increase from 3.9×104 A/cm2 to 4.1×106 A/cm2 for at fluence of 1×1011 ions/cm2 of heavy-ion irradiated sample and decreases with further increase of fluence. These results indicate the possibility of further enhancement of Jc and of achieving a very high Hirr of (Cu,C)-1234 below a fluence of 1×1011 ions/cm2.

Superconducting properties of the heavy-ions and neutron irradiated (Cu,C)Ba 2Ca n−1 Cu nO 2 n+4− δ ( n=3, 4 and 5)

For further enhancement of critical currents density J c and irreversibility field H irr of (Cu 1− x C x ) Ba 2Ca n−1 Cu n O 2 n+4− δ ((Cu,C)-( n−1) n, n=3, 4 and 5) family, pinning centers were introduced by ion and neutron irradiation in these compounds. The polycrystalline samples were irradiated with 3.6×10 17 neutrons/cm 2 or with Au 15+ ions (240 MeV energy) at a fluence of 1×10 11 ions/cm 2. J c and H irr were determined for the irradiated samples as well as unirradiated samples. The intragrain J c was evaluated from M– H curves using Bean's critical state model. In (Cu,C)-12( n−1) n, J c (77 K, 1 T) shows a remarkable increase from 3.9×10 4 to 9.1×10 5 A/cm 2 for neutron irradiated (Cu,C)-1234 and from 3.9×10 4 to 4.1×10 6 A/cm 2 for heavy-ion irradiated (Cu,C)-1234. These results indicate the possibility of further enhancement of J c and of achieving a very high H irr of (Cu,C)-1234 in (Cu,C)-12( n−1) n family.

Superconducting properties of internal-tin Nb/sub 3/Sn wire with enhanced current capacity

The possibilities for further enhancement of critical current density in internal tin Nb/sub 3/Sn strands have been investigated. An appropriate modified design of internal-tin composite wire has been developed and samples of the wire have been fabricated and analyzed. It was shown that non-copper critical current density J/sub c/ attained 2000 A/mm/sup 2/ (at 12 T, 4.2 K, 0.1 /spl mu/V/cm) and the hysteresis losses were equal to 770 mJ/cm/sup 3/ (for magnetic field varying in the range of /spl plusmn/3 T). The variations of the critical current density and hysteresis losses were investigated as a function of the wire diameter. The Nb/sub 3/Sn layer microstructure has been investigated and the relationships between the microstructure parameters and superconducting properties have been discussed. The measurements of critical current were carried out at the temperatures from 4.2 K up to T/sub c/ and the results obtained are given.

Scattering of surface polaritons by molecules near a metallic slab surface

The interaction of surface polaritons (SP's) with vibrating molecules in the vicinity of a metallic slab is considered in the framework of electromagnetic theory. Special attention is paid to processes in which, after absorption of surface polaritons, an excited molecule decays back to surface polaritons, i.e. scattering of surface polaritons. Emphasis is laid on the theoretical analysis of the dependence of the SP scattering cross section on the thickness of the slab. A recent conjecture on the possibility of further enhancement of signal in surface enhanced Raman scattering due to the excitation of long-range SP's guided by a very thin metallic slab is also discussed.

Flow Injection-Spectrophotometric Determination of Trace Amounts of Iron with 2-Pyridyl-3′-sulfophenylmethanone 2-Pyrimidylhydrazone and Possibility of Sensitization by Analogue-Derivative Spectrophotometric Monitoring

A selective flow injection analysis (FIA) system has been proposed for the spectrophotometric determination of trace amounts of iron based on the 1:2 (metal:ligand) complex formation between iron(II) and 2-pyridyl-3′-sulfophenylmethanone 2-pyrimidylhydrazone(PSPmH). The system permits high throughput of 70 solutions per hour. The lower limit of determination is 10ppb of iron. The procedure has been applied successfully to the determination of iron in water samples. Possibility of further enhancement in the sensitivity in FIA by introducing analogue-derivative spectrophotometric monitoring is also suggested.

Structural specificities in acylation of hemoglobin and sickle hemoglobin by diaspirins.

Double-headed aspirins with bridging groups of different length and molecular structure have been examined for their reactivity with hemoglobin A or S. The compounds constructed are bound in the beta-cleft and show a wide range of beta-beta cross-linking effectiveness. Oxygenation curves of the modified hemoglobins in the presence of inositol hexaphosphate are strikingly modified. Many of the diaspirins also produce substantial changes in the minimum gelling concentration of sickle hemoglobin. These reagents offer possibilities for further enhancement of specificity toward hemoglobin, particularly by taking advantage of stereoselectivities.