Ruthenium dye-sensitized SnO2/TiO2 coupled solar cells

The photoelectrochemical behaviors of RuL₂(NCS)₂ dye-sensitized SnO₂/TiO₂ coupled solar cell was studied and compared with TiO₂ single system. The coupled system shows higher incident photon-to-current conversion efficiency (IPCE) value than the single system. A maximum IPCE value in the coupled system with 3.5 μm-thick SnO₂ and 7 μm-thick TiO₂ attained 82.4% at 530 nm wavelength. The higher IPCE value in the coupled system is attributed to the charge separation by fast electron transfer process from the excited RuL₂(NCS)₂ dye to TiO₂ to SnO₂ in the system with different energy level.     

Color registration error reduction method compensating the influence of belt thickness variation in electrophotographic process

This paper proposes a new belt drive control method for reducing a belt velocity-fluctuation that is caused by a belt thickness-variation in the circumferential direction. A belt driving system performs feedback control with a rotary encoder-output mounted on a driven roller. This proposed method correct the reference value of the feedback control for the purpose of the belt velocity regulation. The correction includes two steps. The first step acquires the encoder-output of the driven roller and calculates the rotational angular velocity-fluctuation with one cycle of the belt rotation. The second step converts from the velocity-fluctuation to the correction value of the feedback reference. The correction value cancels a detection error of the driven roller caused by the belt thickness-variation. After these steps, the belt driving system controls the belt velocity as compensating the belt velocity-fluctuation. Experimental result showed the significant fluctuation reduction on a typical tandem-engine printer.     

Partial scan design and test sequence generation based on reduced scan shift method

This paper presents a partial scan algorithm, calledPARES (PartialscanAlgorithm based onREduced Scan shift), for designing partial scan circuits. PARES is based on the reduced scan shift that has been previously proposed for generating short test sequences for full scan circuits. In the reduced scan shift method, one determines proch FFs must be controlled and observed for each test vector. According to the results of similar analysis, PARES selects these FFs that must be controlled or observed for a large number of test vectors, as scanned FFs. Short test sequences are generated by reducing scan shift operations using a static test compaction method. To minimize the loss of fault coverage, the order of test vectors is so determined that the unscanned FFs are in the state required by the next test vector. If there are any faults undetected yet by a test sequence derived from the test vectors, then PARES uses a sequential circuit test generator to detect the faults. Experimental results for ISCAS'89 benchmark circuits are given to demonstrate the effectiveness of PARES.     

Schottky barrier heights of contact metals to p-type ZnSe

Schottky barrier heights (SBHs) of a variety of metals (In, Cd, Nb, Ti, W, Cu, Ag, Au, Ni, Pt, and Se) contacting to p-ZnSe grown by a molecular beam epitaxy method were determined by analyzing capacitance-voltage (C-V) and/or current density-voltage (J-V) curves. The SBH values of the Au and Ni contacts were determined from intersections of straight lines of the C⁻²-V curves to be 1.23 and 1.13 eV, respectively. The J-V calculations provided a large SBH value of 1.2 ± 0.1 eV for a variety of metals, indicating that the Fermi-level could be pinned at the contact interface. Reduction of the SBH values to a level lower than 0.4 eV and/or increase of doping concentrations to a level higher than 10²⁰ cm⁻³ are essential to obtain an ohmic contact with contact resistivity of around 10⁻³ Ω·cm².     

The effects of 18 alpha,beta-glycyrrhetinic acid on the hormonal induction of tyrosine aminotransferase in rat primary cultured hepatocytes

Complementary medicine (CM) is popular with patients but physicians do not feel at ease with this situation and some fear that the patient might be the loser. Their fear is based on the perception that some CM practitioners have dubious qualifications and competence and that too little is known about the efficacy and safety of many complementary therapies. It follows that, in the interest of the patient and all other parties involved, we urgently need more and better research to fill the void. Integration of complementary medicine into mainstream care requires a minimum of essential evidence. As in all areas of medicine, there can be no short cut to rigorous research.     

Electrical properties at p-ZnSe/metal interfaces

In order to prepare low resistance ohmic contacts to p-ZnSn by the “deposition and annealing (DA)” technique which has been extensively used for GaAs and Si-based devices, formation of a heavily doped layer by the p-ZnSe/metal reaction is required. For p-ZnSe/Ni contacts, Ni and Se reacted preferentially at the ZnSe/Ni interface upon annealing at temperatures higher than 250°C. However, capacitance-voltage measurements showed that the net acceptor concentration (N_A-N_D) close to the p-ZnSe/Ni interface was reduced upon the Ni/ZnSe reaction, resulting in high contact resistance. For p-ZnSe/Au contacts, neither Au/ZnSe reaction nor reduction of the acceptor concentration were observed after annealing at temperatures lower than 300°C. This indicates that although the metal/p-ZnSe reaction is mandatory to prepare a heavily doped layer, the reaction induced an increase in the compensation donors in the p-ZnSe substrate. In order to increase the acceptor concentration in the vicinity of the p-ZnSe/metal interface through diffusion from the contact materials, Li or O which was reported to play the role of an acceptor in ZnSe was deposited with a contact metal and annealed at elevated temperatures. Ni or Ag was selected as the contact metal, because these metals were expected to enhance Li or O doping by reacting with ZnSe. However, the current density-voltage characteristics of the Li(N)/Ni and Ag(O) contacts exhibited rectifying behavior, and the contact resistances increased with increasing annealing temperature. The present results indicated that, even though the acceptor concentration in the p-ZnSe substrate increased by diffusion of the dopants from the contact elements, an increment of the compensation donors was larger than that of the acceptors. The present experiments indicated that preparation of low resistance ohmic contacts by forming a heavily doped intermediate layer between p-ZnSe and metal is extremely difficult by the DA technique.     

An abnormally shortened fatigue life of steels caused by anelasticity

Some abnormal fatigue life shortenings dependent upon load frequency for several steels are discussed. A possible relation between anelasticity caused by interstitial atoms and the abnormal fatigue life drop is presented. Normally, interstitial atoms are in a position which minimizes the energy around a dislocation, the Snoek ordering sites. We consider the Snoek effect as a typical example of anelasticity, and the possibility on atoms moving from attractive sites to repulsive ones when repeated stresses are applied and discuss a theory to explain the reduction of the fatigue life using Snoek ordered atoms moving out by fatigue stress at the frequency of Snoek effect. Bending fatigue tests were conducted to obtain the relationship between fatigue life and load frequency at two different temperatures (298 K and 333 K) for an iron nitrided steel. A sharp fatigue life drop was observed at a load frequency corresponding to the resonant frequency of the Snoek effect for nitrogen atoms. The frequency was about 3 Hz and 298 K and shifted to a higher frequency — about 6 Hz — at 333 K. Results reveal that the possible explanation to those abnormal phenomena may be anelasticity.Work partially conducted at Laboratorio E and Departamento de Ciencias de Materiales, Universidad Simón Bolívar, Venezuela.     

Effect of Grain Boundaries on Thermal Conductivity of Silicon Carbide Ceramic at 5 to 1300 K

The thermal conductivity of a SiC ceramic was measured as 270 W·m⁻¹·K⁻¹ at room temperature. At low temperatures ( T < 25 K), the decrease in the conductivity was proportional to T ³ on a logarithmic scale, which indicated that the conductivity was controlled by boundaries. The calculated phonon mean free path in the ceramic increased with decreased temperature, but was limited to ∼4 μm, a length almost equal to the grain size, at temperatures below 30 K. We concluded that the thermal conductivity of the ceramic below 30 K was influenced significantly by grain boundaries and grain junctions.     

Proposed Phenomenological PTCR Model and Accompanying Phenomenological PTCR Chart

The positive temperature coefficient of resistivity (PTCR) behavior of semiconductive BaTiO₃ is well explained by the Heywang model, which predicts the resistivity behavior above the Curie point based on the acceptor state density at the grain boundaries, the charge carrier density, and the energy gap, E _s, between the conduction band and the acceptor levels. However, the relationship between these parameters and the production parameters (sintering time, composition, and cooling rate) is not well understood. Recently, the present authors have found that E _s can be increased by thorough oxidation. This increase is attributed to a change in the oxidation state of the acceptor. Based on this finding and results from the literature, a phenomenological PTCR model and an accompanying PTCR chart for acceptor–donor-codoped BaTiO₃ are proposed to clarify this relationship. The PTCR chart clarifies that acceptor dopant concentrations, oxidation time, and oxygen partial pressure during oxidation or cooling can be optimized simultaneously to obtain optical PTCR properties.