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Summary: The mechanism by which arcuate nucleus kisspeptin (ARNKISS) neurons co-expressing glutamate, neurokinin B, and dynorphin intermittently synchronize their activity to generate pulsatile hormone secretion remains unknown. An acute brain slice preparation maintaining synchronized ARNKISS neuron burst firing was used alongside in vivo GCaMP GRIN lens microendoscope and fiber photometry imaging coupled with intra-ARN microinfusion. Studies in intact and gonadectomized male mice revealed that ARNKISS neuron synchronizations result from near-random emergent network activity within the population and that this was critically dependent on local glutamate-AMPA signaling. Whereas neurokinin B operated to potentiate glutamate-generated synchronizations, dynorphin-kappa opioid tone within the network served as a gate for synchronization initiation. These observations force a departure from the existing “KNDy hypothesis” for ARNKISS neuron synchronization. A “glutamate two-transition” mechanism is proposed to underlie synchronizations in this key hypothalamic central pattern generator driving mammalian fertility.

This paper proposes a per-phase switching frequency control method to extend the lifespan of a three-phase voltage source inverter. The model predictive control that can intuitively deal with various control objectives is used in the proposed method. The cost function of the proposed technique consists of two terms. One is for current control, and another is for switching frequency control of each phase. Also, if necessary, a term for capacitor current RMS reduction can be added to the proposed cost function. The proposed technique reduces the switching loss of the most aged phase by reducing the number of switching operations. As a result, the reduced switching losses lower the junction temperature of the switching device. This extends the lifetime of the switching device. In addition, in the proposed technique, the capacitor current RMS, which can increase due to the per-phase switching frequency control, is effectively reduced by using the optional term for the capacitor current RMS reduction. The performances of the proposed method were verified through simulations and experiments.

Direct methanation in an integrated CO2 capture and utilization system has recently gained considerable attention as a promising approach owing to its simplified process and lower requirement of total thermal energy as compared to conventional CO2 capture and utilization techniques. This study formulated macroporous structured Ni/CaO catal-sorbents by controlling the Ni-to-CaO ratio. The influence of this ratio on the CO2 capture (capacity and kinetics) and direct methanation performances (productivity and kinetics) was evaluated at 500 °C. CO2 capture combined with direct methanation experiments revealed that 10Ni/CaO exhibited the best CO2 capture capacity, kinetics, and CH4 productivity with the thermal stability of Ni and CaO species.

In this study, a Ru-doped Ni pellet-type catalyst was prepared to produce hydrogen via steam methane reforming (SMR). A small amount of Ru addition on the Ni catalyst improved Ni dispersion, thus affording a higher catalytic activity than that of the Ni catalyst. During the daily startup and shutdown (DSS) operations, the CH4 conversion of Ni catalysts significantly decreased because of Ni metal oxidation to NiAl2O4, which is not reduced completely at 700 °C. Conversely, the oxidized Ni species in the Ru–Ni catalyst can be reduced under SMR conditions because of H2 spillover from the surface of Ru onto the surface of Ni. Consequently, the addition of a small quantity of Ru to the Ni catalyst can improve the catalytic activity and stability during the DSS operation.

This paper proposes a novel input power factor control method based on a concept of virtual capacitors to provide unity input power factor for three-phase matrix rectifiers. The proposed algorithm introduces, at the input terminal of the matrix rectifier, an imaginary input capacitor generated by modifying a reference vector of the space vector modulation method. The virtual input capacitor, which is fictitiously built in parallel with an input LC filter, successfully compensates for the leading power factor of the LC filter of the matrix rectifier. Thus, the proposed method yields a unity power factor operation despite the presence of the LC filter of the three-phase matrix rectifier. In addition, under a condition when the unity power factor operation cannot be realized, the proposed algorithm adjusts a virtual capacitance to obtain a maximum achievable power factor operation. Because the proposed technique yields the input power factor control by introducing the virtual capacitor and adjusting a reference space vector, the proposed algorithm can be easily incorporated with conventional space vector modulation algorithms for the three-phase matrix rectifiers. Thus, the proposed method can control input power factor without employing proportional-integral controllers used in conventional power factor control methods for the matrix rectifiers, leading to simple control structure and straightforward tuning process for power factor control.

This paper proposes a direct power control (DPC) method with a minimum reactive power reference for ac-to-dc matrix rectifiers using space vector modulation. Based on the calculated active and reactive power reference values, the developed DPC algorithm directly controls both the active and reactive power components of the source by operating the three-phase matrix rectifiers, thereby obtaining the sinusoidal input currents and output dc voltage/current of the rectifier. The proposed DPC method instantaneously determines a source reactive power reference command to achieve a unity input power factor or maximum achievable power factor on given input and output conditions, because ac-to-dc matrix rectifiers cannot always attain a unity power factor due to the existence of the input capacitors. In addition, the developed algorithm calculates the minimum reactive power reference without using any circuit parameters. Thus, the proposed algorithm is free from any inevitable parameter uncertainty, resulting in a more robust and accurate power factor control for the rectifier. Based on the minimum reactive power reference, the proposed algorithm enables matrix rectifiers to operate at an input power factor that can be maximally obtained at all times. The effectiveness of the proposed method was verified by the simulations and experiments.

In this study, the CO2 sorption mechanisms and regeneration properties of alumina-based sorbent using K2CO3 loading under high-pressure and moderate temperature conditions were examined. To investigate the mechanism of CO2 sorption, a zirconium-based sorbent was compared with an alumina-based sorbent. The CO2 capture capacities of the PAI10, 20, 30, and 40 were 32.3, 63.0, 95.4, and 124.5 mg CO2/g sorbent, respectively. To investigate the CO2 sorption mechanism of an alumina-based sorbent, we performed XRD, TG/DTG, and FTIR analyses after CO2 sorption in the presence of 10 vol% CO2 and H2O each at 200 °C and 20 atm. For PAI10–40 sorbents, KHCO3 and KAl(CO3)(OH)2 phases were observed by TG/DTG and FTIR analysis. For PAI-x sorbents, it was confirmed that the captured CO2 is desorbed completely at a temperature below 400 °C at 20 atm.

This paper proposes a model predictive virtual flux control (MPVFC) method that can mitigate the degradation of the total harmonic distortion of rectifier input currents experienced by active frontend (AFE) rectifiers when input voltages are distorted by harmonics. The proposed method utilizes a cost function based on virtual fluxes, which are robust to input voltage distortions, to control the rectifiers. For the calculation of the proposed cost function which consists of a predictive value of the rectifier virtual flux and a reference of the rectifier virtual flux, the dynamics of AFE rectifiers and the definition of the integration in the discrete time domain are used. Also, the phase of the reference current which is needed when calculating the reference of the rectifier virtual flux is obtained by the input virtual flux. The proposed MPVFC method shows better input current waveforms with lower total harmonic distortion than those obtained with the conventional model predictive control method under input voltage distortion conditions, which was proved via simulations and experiments.

A predictive direct power control (PDPC) technique to decrease switching loss by injecting offset voltage is proposed for three-phase voltage source converters. The active and reactive power elements of the converter are directly controlled by using three-phase future converter input voltages, which are modified for lowering switching losses by injecting a future offset voltage. Switching operations, generated by the developed PDPC algorithm with modified converter voltage, stop switching operation in one of the converter phases exposed to the highest input current. The non-switching period and the non-switching phase in the proposed technique is automatically adjusted by the reactive power reference, which leads to high efficiency, irrespective of varying input power factor angle condition. The proposed algorithm chooses one optimal voltage vector enabling future active and reactive power to approach closest to the future power references and prohibiting switching of one converter phase conducting the highest current at each step. Therefore, the developed technique can directly control power components and increase converter efficiency, which is proven by simulation and experimental verification.

Ru-based eggshell-type catalysts, in which Ru is located at the outer region of the pellet, were prepared by the impregnation method, using spherically shaped γ-Al2O3 pellets for steam-methane reforming (SMR). Ru was only supported on the external region of the pellet because of the strong interaction between its precursor and the alumina pellet. The Ru precursor penetrated the inside of the pellet by adding nitric acid to the impregnation solution. The distribution and thickness of the Ru layer in the catalyst can be controlled using the HNO3/Ru molar ratio and contact time at the impregnation step. Among the catalysts, the graded eggshell-type catalyst showed the highest activity and long-term stability in the SMR reaction. In addition, in the daily startup and shutdown (DSS) operation, similar to the hydrogen production environment for domestic polymer electrolyte membrane fuel cells (PEMFC), the graded eggshell-type catalyst showed high activity and stability after multiple cycles. Based on the experimental studies, it was confirmed that Ru-based catalysts are suitable for steam-methane reforming for PEMFC.

Fe-Ni and Co-Fe-Ni catalysts were prepared by the wet impregnation method for the production of high-calorific synthetic natural gas. The influence of Ni addition to Fe and Co-Fe catalyst structure and catalytic performance was investigated. The results show that the increasing of Ni amount in Fe-Ni and Co-Fe-Ni catalysts increased the formation of Ni-Fe alloy. In addition, the addition of nickel to the Fe and Co-Fe catalysts could promote the dispersion of metal and decrease the reduction temperature. Consequently, the Fe-Ni and Co-Fe-Ni catalysts exhibited higher CO conversion compared to Fe and Co-Fe catalysts. A higher Ni amount in the catalysts could increase C1–C4 hydrocarbon production and reduce the byproducts (C5+ and CO2). Among the catalysts, the 5Co-15Fe-5Ni/γ-Al2O3 catalyst affords a high light hydrocarbon yield (51.7% CH4 and 21.8% C2–C4) with a low byproduct yield (14.1% C5+ and 12.1% CO2).

In this study, the frequency characteristics of series DC arcs are analyzed according to the types of frequency fluctuations caused by inverters in photovoltaic (PV) systems. These frequency fluctuation types used in analysis include centralized frequency fluctuations by three-phase inverter, spread frequency fluctuations by three-phase inverter, and centralized frequency fluctuations by single-phase inverter. To collect arc current data, the frequency fluctuations are generated by inverters in the arc-generating circuit, designed by referring to UL1699B, and the arcs are generated by separating the arc rods of the arc generator. The frequency analysis of the arc current data, collected using an oscilloscope, is conducted using MATLAB. From the results of the frequency characteristics analysis, it is confirmed that the frequencies in the range from 5 to 40 kHz increase after arc generation regardless of the type of frequency fluctuation. In addition, the smaller the current, the greater the increase in frequencies between 5 and 40 kHz after arc generation. Further, in case of arc currents with centralized frequency fluctuations, for larger switching frequencies, the 5 to 40 kHz components increase to a greater extent after arcing.

Mega trends in the global automotive industry are environmentally friendly. As laws and regulations tighten at the government level, the automobile industry is striving to develop a drive system that can operate without using fossil fuels, instead of developing an internal combustion engine using fossil fuels. Environmentally-friendly energy is attracting attention as an alternative to solve the problems of air pollution and fossil fuel depletion. Electricity is attracting the most attention among environmentally-friendly alternative fuels. In addition, research on the development of a high-efficiency and high-reliability advanced electric automobile drive system are actively being carried out. In this study, a two-speed transmission for electric vehicles is developed using environmentally-friendly fuel. The 1st and the 2nd planetary gear modules were integrated, the ring gear and the carrier gear were shared, and the dual disc brake was used to design a mechanism for fixing each sun and shifting gear. Such a structure can improve shift energy efficiency compared to that of conventional transmissions. It was judged that the structure was suitable for an electric car using a limited power supply. Each gear was designed by calculating bending strength and surface durability.

Representing the probability and uncertainty of outcomes facilitates adaptive behavior by allowing organisms to prepare in advance and devote attention to relevant events. Probability and uncertainty are often studied only for valenced (appetitive or aversive) outcomes, raising the question of whether the identified neural machinery also processes the probability and uncertainty of motivationally neutral outcomes. Here, we aimed to dissociate valenced from valence-independent (i.e., generic) probability (p; maximum at p = 1) and uncertainty (maximum at p = 0.5) signals using human neuroimaging. In a Pavlovian task (n = 41; 19 females), different cues predicted appetitive, aversive, or neutral liquids with different probabilities (p= 0, p = 0.5, p = 1). Cue-elicited motor responses accelerated, and pupil sizes increased primarily for cues that predicted valenced liquids with higher probability. For neutral liquids, uncertainty rather than probability tended to accelerate cue-induced responding and decrease pupil size. At the neural level, generic uncertainty signals were limited to the occipital cortex, while generic probability also activated the anterior ventromedial prefrontal cortex. These generic probability and uncertainty signals contrasted with cue-induced responses that only encoded the probability and uncertainty of valenced liquids in medial prefrontal, insular, and occipital cortices. Our findings show a behavioral and neural dissociation of generic and valenced signals. Thus, some parts of the brain keep track of motivational charge while others do not, highlighting the need and usefulness of characterizing the exact nature of learned representations. [ABSTRACT FROM AUTHOR]

The properties of the unidirectional out-of-plane nematic liquid crystal tilt angle are investigated in view of van der Waals interaction between nematic liquid crystal molecules and anisotropic and isotropic polyimide layers. The results have shown that the relation between the anchoring energy and the thickness of the polyimide layer might be dependent on lower material.

In this paper properties of nematic liquid crystals aligned on polyimide surfaces exposed to a low-energy Ar ion beam are investigated. We studied how the pretilt angle of a liquid crystal cell is affected by ion-beam conditions, such as the energy of the incident ions, the angle of incidence, and the exposure time. X-ray photoelectron spectroscopy data indicate that ion-beam exposure changes the chemical bonding states of the polyimide surface, which may be one of the main causes of anisotropic liquid crystal alignment. We also found that twisted-nematic cells fabricated by the ion-beam alignment method have the voltage holding time enough for application to thin-film-transistor liquid crystal displays. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

A method is proposed for confirming the biaxial phase in thermotropic nematic liquid crystals for measuring the electro-optic characteristics. The results have confirmed the biaxial nature of the bent-core mesogen 4,4'-(1,3,4oxadiazole2,5diyl)dipheptylbenzoate (ODBP-Ph-[C.sub.7]).

A dual mode liquid crystal display (LCD) is proposed, which has realized dynamic and memory operating LCD modes in a display panel by using horizontal switching and bistable chiral splay nematic LCD modes. This dual mode LCD has shown a high contrast ratio of over 100:1 for both the dynamic and memory operations.

Combination of dark injection space-charge-limited current (DI-SCLC) and trap-free SCLC measurements is used to demonstrate a quasi-Ohmic contact formed by the indium tin oxide (ITO)/buckminsterfullerene ([C.sub.60]) electrode with N,N'-bis(naphthalen-1-yl)-N, N'-bis(phenyl) benzidine (NPB). The Ohmic contact formed allows to estimate the NPB hole mobility through the use of both DI-SCLC and trap-free SCLC analysis.

A vertical alignment (VA) liquid crystal cell is proposed that is controlled by double-side in-plane switching (DSIPS) with a positive dielectric anisotropy liquid crystal material. The studies have shown that the DSIPS cell has a large misalignment tolerance and wide viewing angle property with negative C film and the total response time of the DSIPS cell is as fast as that of the conventional VA-IPS cell.

Study is conducted which proposes that the abnormal reverse tilt domains observed during the splay-to-bend transition in a splay-aligned LC cell came from the locally asymmetric effect of pretilt angle by using the same alignment layer in the upper and low substrates. Results revealed that in splay-aligned liquid crystal (LC) cell rubbed with the same alignment layer the reverse tilt domains must be generated as the middle state during the transition from the splay to the bend states, and only a splay-aligned LC cell rubbed with the different alignment layer eliminates the abnormal reverse tilt domains.

Measuring the pretilt angle by using the crystal rotation method even when the pretilt angle is between 20 degree and 70 degree is proposed. The pretilt angle is found by measuring the rotation angles where transmittances become maximum and minimum in the periodic transmittance characteristics obtained with the variation of rotation angle.

To investigate the catalytic performance of diesel reforming catalysts for production of hydrogen gas, Ni-Al catalyst was prepared by the polymer-modified incipient method (NA10-PM). NA10-PM showed excellent catalytic performance and economic feasibility in the auto-thermal reforming reaction, compared to other commercially available catalysts. In particular, auto-reduced NA10-PM showed higher dodecane conversion and similar selectivity at 750 °C compared to H2-reduced NA10-PM. X-ray diffraction (XRD) studies showed that the fresh state of NA10-PM initially automatically reduced by product gases through thermal decomposition of dodecane, and then NiAl2O4 was completely reduced to metallic nickel by the CO and H2 gases produced during the reaction. Additionally, catalytic performance of auto-reduced NA10-PM were investigated at varying steam/carbon molar ratio (S/C) and oxygen/carbon molar ratio (O2/C) in order to determine the optimum conditions of the auto-thermal reforming reaction. The conversion of dodecane over auto-reduced NA10-PM catalyst was remarkable (93%) and increased during the reaction, under conditions of S/C = 1.23, O2/C = 0.25, and gas hourly space velocity of 12,000 h-1 at 750 °C. The results of this study demonstrated that the auto-reduced NA10-PM catalyst was applied successfully for auto-thermal reforming of dodecane. [ABSTRACT FROM AUTHOR]

The effects of the SnO2 pore size and metal oxide promoters on the sensing properties of SnO2-based thick film gas sensors were investigated to improve the detection of very low H2S concentrations (<1 ppm). SnO2 sensors and SnO2-based thick-film gas sensors promoted with NiO, ZnO, MoO3, CuO or Fe2O3 were prepared, and their sensing properties were examined in a flow system. The SnO2 materials were prepared by calcining SnO2 at 600, 800, 1,000 and 1,200 °C to give materials identified as SnO2(600), SnO2(800), SnO2(1000), and SnO2(1200), respectively. The Sn(12)Mo5Ni3 sensor, which was prepared by physically mixing 5 wt% MoO3 (Mo5), 3 wt% NiO (Ni3) and SnO2(1200) with a large pore size of 312 nm, exhibited a high sensor response of approximately 75% for the detection of 1 ppm H2S at 350 °C with excellent recovery properties. Unlike the SnO2 sensors, its response was maintained during multiple cycles without deactivation. This was attributed to the promoter effect of MoO3. In particular, the Sn(12)Mo5Ni3 sensor developed in this study showed twice the response of the Sn(6)Mo5Ni3 sensor, which was prepared by SnO2(600) with the smaller pore size than SnO2(1200). The excellent sensor response and recovery properties of Sn(12)Mo5Ni3 are believed to be due to the combined promoter effects of MoO3 and NiO and the diffusion effect of H2S as a result of the large pore size of SnO2. [ABSTRACT FROM AUTHOR]

The sensing behavior of SnO2-based thick film gas sensors in a flow system in the presence of a very low concentration (ppb level) of chemical agent simulants such as acetonitrile, dipropylene glycol methyl ether (DPGME), dimethyl methylphosphonate (DMMP), and dichloromethane (DCM) was investigated. Commercial SnO2 [SnO2(C)] and nano-SnO2 prepared by the precipitation method [SnO2(P)] were used to prepare the SnO2 sensor in this study. In the case of DCM and acetonitrile, the SnO2(P) sensor showed higher sensor response as compared with the SnO2(C) sensors. In the case of DMMP and DPGME, however, the SnO2(C) sensor showed higher responses than those of the SnO2(P) sensors. In particular, the response of the SnO2(P) sensor increased as the calcination temperature increased from 400 °C to 800 °C. These results can be explained by the fact that the response of the SnO2-based gas sensor depends on the textural properties of tin oxide and the molecular size of the chemical agent simulant in the detection of the simulant gases (0.1-0.5 ppm). [ABSTRACT FROM AUTHOR]

In the bistable chiral splay nematic mode, the splay and π twist states are used for the two stable states. The transition between two memory states is strongly dependent on the strength of electric fields. In this paper, we investigated the correlation between the in-plane electric fields strength and the bistable property by calculating bistable curve. We also demonstrated the gray scale of bistable chiral splay nematic liquid crystal display by varying strength of the in-plane electric fields created by an inter-digital electrode with varying electrode spacing. [ABSTRACT FROM AUTHOR]

We have investigated the domain growth of antiferroelectric liquid crystal display under the switching process by means of CCD camera pictures. Its dynamic behavior was simulated by our extended bilayer model. In this model, we supplement free energy of antiferroelectric liquid crystal display with the coupling coefficient between adjacent molecules in the same layer, because domain growth propagates parallel to the smectic layer. The mechanism of the domain growth in antiferroelectric liquid crystal display can be described by the extended bilayer model. [ABSTRACT FROM AUTHOR]

To remove hydrogen sulfide from hot coal gases at middle temperature, the various sorbents were prepared by precipitation or co-precipitation method. The cobalt and nickel-based sorbents promoted with alumina showed good regeneration properties during multiple cycles. The roles of each component in the sulfidation and regeneration were discussed with the results from XRD and TPD. [ABSTRACT FROM AUTHOR]

The CO2 absorption properties of potassium-based TiO2 sorbents prepared by calcining at various temperatures from 300 to 700 °C under N2 and air were investigated in a fixed bed reactor at 60 °C. The CO2 capture capacity of the sorbent was changed dramatically depending on the structure of the sorbent, which was affected by calcination atmosphere, as well as calcination temperature. [ABSTRACT FROM AUTHOR]

We propose an optical configuration to compensate dispersion characteristics in the dark state of a normally-black twisted-nematic (NB-TN) liquid crystal display (LCD). By optimization of parameters with a parameter space diagram (PSD), the high contrast-ratio (CR) over 500:1 could be obtained using two +A plates. Furthermore, excellent dispersion characteristics were also obtained in the bright state. We confirmed the performance of the proposed method and structure through both the numerical calculations and the experiments. [ABSTRACT FROM AUTHOR]

In the bistable chiral splay nematic (BCSN) mode, the splay and π twist states are used for the two stable states. The transition between the memory states accompanies the motion of the disclination line, due to the topologically inequivalent from each other. The switching time is consistently coupled with the propagation velocity of the disclination line, which strongly depends on the amplitude of the applied voltage. In this paper, we demonstrate the gray scale of BCSN liquid crystal display (LCD) by the control of the domain density of the splay and twist states during the transition process. [ABSTRACT FROM AUTHOR]

We propose a transflective dual mode liquid crystal display, which is composed of a transmissive part for dynamic mode and a reflective part for a memory mode in a pixel. The proposed configuration has single cell gap and single rubbing direction in both parts. In order to make the reflectance minimized and maximized for dark and bright states of memory part, the parameters of LC layer and retardation film are optimized by using the Jones matrix method. Moreover, the operating voltage of dynamic part is found to depend on the retardation values of compensation films. With this configuration, the dynamic and memory modes show high contrast ratio of 1100:1 and 20:1, respectively, by calculation, while 220:1 and 10:1, respectively, by experiment. [ABSTRACT FROM AUTHOR]

We study the properties of the vertical alignment of liquid crystal on amorphous SiON (a-SiON) thin film exposed by ion beam. a-SiON thin films are deposited on the indium-tin-oxide coated glass substrates by using radio-frequency magnetron sputtering system in the temperature range from 25 to 400°C. The transmittance and surface roughness of a-SiON thin films are enhanced with the increase in deposition temperature. After the substrates were deposited by sputtering system, we exposed them to ion beam and fabricated vertical alignment liquid crystal cells. As a result, the fabricated liquid crystal cells show uniform pretilt angle range from 88 to 89° and high thermal stability over 100°C for 20 hours. [ABSTRACT FROM AUTHOR]