System LSI Research Articles

Insights on the Optical and Infrared Nature of MAXI J0709-159: Implications for High-Mass X-ray Binaries

In our previous study (Bhattacharyya et al., 2022), HD 54786, the optical counterpart of the MAXI J0709-159 system, was identified to be an evolved star, departing from the main sequence, based on comparisons with non-X-ray binary systems. In this paper, using color-magnitude diagram (CMD) analysis for High-Mass X-ray Binaries (HMXBs) and statistical t-tests, we found evidence supporting HD 54786’s potential membership in both Be/X-ray binaries (BeXRBs) and supergiant X-ray binaries (SgXBs) populations of HMXBs. Hence, our study points towards dual optical characteristics of HD 54786, as an X-ray binary star and also belonging to a distinct evolutionary phase from BeXRB towards SgXB. Our further analysis suggests that MAXI J0709-159, associated with HD 54786, exhibits low-level activity during the current epoch and possesses a limited amount of circumstellar material. Although similarities with the previously studied BeXRB system LSI +61° 235 (Coe et al., 1994) are noted, continued monitoring and data collection are essential to fully comprehend the complexities of MAXI J0709-159 and its evolutionary trajectory within the realm of HMXBs.

Impact of FinFET with plural number of channel width using novel one step of trench formation process on pattern design time and works for system LSI

Impact of FinFET with plural number of channel width using novel one step of trench formation process on pattern design time and works for system LSI

Impact of FinFET with plural number of channel width using novel one step of trench formation process on fabrication cost for system LSI

Impact of FinFET with plural number of channel width using novel one step of trench formation process on fabrication cost for system LSI

The black hole candidate LS I +61°303

In recent years, fundamental relationships for the black hole X-ray binaries have been established between their X-ray luminosity $L_X$ and the photon index $\Gamma$ of their X-ray spectrum. For the moderate-luminosity regime, an anti-correlation between $\Gamma$ and $L_X$ has been observed. In this article, aimed to verify if the moderate luminous X-ray binary system LSI +61303 is a black hole, we analyse $Swift$ observations of LSI +61303. We compare the derived $L_X$ vs $\Gamma$ distribution, first with the statistical trend for black hole X-ray binaries, then with the trend of the pulsar PSR B1259-63, and finally with the individual trends of the black hole X-ray binaries Swift J1357.2-0933 and V404 Cygni. We find that the system PSR B1259-63 shows a positive correlation between $\Gamma$ and $L_X$, whereas in contrast LSI +61303 shows the same anti-correlation as for black hole X-ray binaries. Moreover, the trend of LSI +61303 in the $L_X$/$L_{Eddington} - \Gamma$ plane overlaps with that of the two black holes Swift J1357.2-0933 and V404 Cygni. All three systems, Swift J1357.2-0933, V404 Cygni and LSI +61303 well trace the last part of the evolution of accreting black holes at moderate-luminosity until their drop to quiescence.

A novel horizontal channel NAND structure for vertically stacked type system LSI

A novel horizontal channel NAND structure for vertically stacked type system LSI

The broad-band radio spectrum of LS I +61°303 in outburst

Aims: Our aim is to explore the broad-band radio continuum spectrum of LSI+61303 during its outbursts by employing the available set of secondary focus receivers of the Effelsberg 100 m telescope. Methods: The clear periodicity of the system LSI+61303 allowed observations to be scheduled covering the large radio outburst in March-April 2012. We observed LSI+61303 on 14 consecutive days at 2.6, 4.85, 8.35, 10.45, 14.3, 23, and 32 GHz with a cadence of about 12 hours followed by two additional observations several days later. Based on these observations we obtained a total of 24 quasi-simultaneous broad-band radio spectra. Results: During onset, the main flare shows an almost flat broad-band spectrum, most prominently seen on March 27, 2012, where - for the first time - a flat spectrum (alpha=0.00+/-0.07, S nu^alpha) is observed up to 32 GHz (9 mm wavelength). The flare decay phase shows superimposed 'sub-flares' with the spectral index oscillating between -0.4 and -0.1 in a quasi-regular fashion. Finally, the spectral index steepens during the decay phase, showing optically thin emission with values alpha $\sim$ -0.5 to -0.7. Conclusions: The radio characteristics of LSI+61303 compare well with those of the microquasars XTE J1752-223 and Cygnus X-3. In these systems the flaring phase is actually also composed of a sequence of outbursts with clearly different spectral characteristics: a first outburst with a flat/inverted spectrum followed by a bursting phase of optically thin emission.

Long-term OVRO monitoring of LS I +61°303: confirmation of the two close periodicities

Context: The gamma-ray binary LSI+61303 shows multiple periodicities. The timing analysis of 6.7 yr of GBI radio data and of 6 yr of Fermi-LAT GeV gamma-ray data both have found two close periodicities P1(GBI) = 26.49 \pm 0.07 d, P2(GBI)=26.92 \pm 0.07 d and P1(gamma)=26.48 \pm 0.08 d, P2(gamma) = 26.99 \pm 0.08 d. Aims: The system LSI+61303 is the object of several continuous monitoring programs at low and high energies. The frequency difference between f1 and f2 of only 0.0006 d(-1) requires long-term monitoring because the frequency resolution in timing analysis is related to the inverse of the overall time interval. The Owens Valley Radio Observatory (OVRO) 40 m telescope has been monitoring the source at 15 GHz for five years and overlaps with Fermi-LAT monitoring. The aim of this work is to establish whether the two frequencies are also resolved in the OVRO monitoring. Methods: We analysed OVRO data with the Lomb-Scargle method. We also updated the timing analysis of Fermi-LAT observations. Results: The periodograms of OVRO data confirm the two periodicities P1(OVRO) = 26.5 \pm 0.1 d and P2(OVRO) = 26.9 \pm 0.1 d. Conclusions: The three indipendent measurements of P1 and P2 with GBI, OVRO, and Fermi-LAT observations confirm that the periodicities are permanent features of the system LSI+61303. The similar behaviours of the emission at high (GeV) and low (radio) energy when the compact object in LSI+61303 is toward apastron suggest that the emission is caused by the same periodically (P1) ejected population of electrons in a precessing (P2) jet.

Analysis of pattern area reduction for logic circuit and system LSI with SGT

Analysis of pattern area reduction for logic circuit and system LSI with SGT

3102 三次元半導体の物理的・経済的評価を用いた適正設計(OS12 技術経営)

3102 三次元半導体の物理的・経済的評価を用いた適正設計(OS12 技術経営)

Design Technology of Stacked Type DTMOS

SUMMARYStacked type DTMOS, which makes it possible to realize both the high‐speed, low‐power characteristics of FinFET type DTMOS and small the pattern area of stacked transistors, has been newly proposed. The delay time of the substrate of stacked type DTMOS can be reduced to less than 10% of that for conventional FinFET type DTMOS by using the sidewall connection between the gate and substrate. By using a stacked structure of NMOS with a (110) substrate on PMOS with a (100) substrate, high‐speed performance with optimized mobility value can be realized without sacrificing the pattern area. Furthermore, the pattern area of the inverter/NAND circuit, LSI for communication, and the DRAM buffer circuit with stacked type DTMOS is compared with that of conventional FinFET type DTMOS. The newly proposed stacked type DTMOS is a promising candidate for realizing high‐performance system LSI such as GHz class microprocessors.

Intrinsic physical properties and Doppler boosting effects in LS I +61°303

Our aim is to show how variable Doppler boosting of an intrinsically variable jet can explain the long-term modulation of 1667 \pm 8 days observed in the radio emission of LSI+61303. The physical scenario is that of a conical, magnetized plasma jet having a periodical (P1) increase of relativistic particles, Nrel, at a specific orbital phase, as predicted by accretion in the eccentric orbit of LSI+61303. Jet precession (P2) changes the angle, eta, between jet axis and line of sight, thereby inducing variable Doppler boosting. The problem is defined in spherical geometry, and the optical depth through the precessing jet is calculated by taking into account that the plasma is stratified along the jet axis. The synchrotron emission of such a jet was calculated and we fitted the resulting flux density Smodel(t) to the observed flux density obtained during a 6.5-year monitoring of LSI+61303 by the Green Bank radio interferometer. Our physical model for the system LSI+61303 is not only able to reproduce the long-term modulation in the radio emission, but it also reproduces all the other observed characteristics of the radio source, the orbital modulation of the outbursts, their orbital phase shift, and their spectral index properties. Moreover, a correspondence seems to exist between variations in the ejection angle induced by precession and the rapid rotation in position angle observed in VLBA images. We conclude that the peak of the long-term modulation occurs when the jet electron density is around its maximum and the approaching jet is forming the smallest possible angle with the line of sight. This coincidence of maximum number of emitting particles and maximum Doppler boosting of their emission occurs every 1667 days and creates the long-term modulation observed in LSI+61303.

Long-term periodicity in LS I +61°303 as beat frequency between orbital and precessional rate

Context: In the binary system LSI+61303 the peak flux density of the radio outburst, which is related to the orbital period of 26.4960 +/- 0.0028d, exibits a modulation of 1667 +/- 8 d. The radio emission at high spatial resolution appears structured in a precessing jet with a precessional period of 27-28 d. Aims: How close is the precessional period of the radio jet to the orbital period? Any periodicity in the radio emission should be revealed by timing analysis. The aim of this work is to establish the accurate value of the precessional period. Methods: We analyzed 6.7 years of the Green Bank Interferometer database at 2.2 GHz and 8.3 GHz with the Lomb-Scargle and phase dispersion minimization (PDM) methods and performed simulations. Results: The periodograms show two periodicities, P1 = 26.49 +/- 0.07 d (\nu1=0.03775 d^{-1}) and P2 = 26.92 +/- 0.07 d (\nu2 = 0.03715 d^{-1}). Whereas radio outbursts have been known to have nearly orbital occurrence P1 with timing residuals exhibiting a puzzling sawtooth pattern, we probe in this paper that they are actually periodical outbursts and that their period is Paverage= (2/(\nu1 + \nu2)= 26.70 +/- 0.05 d. The period Paverage as well as the long-term modulation Pbeat=1/(\nu1 - \nu2)=1667 +/- 393 d result from the beat of the two close periods, the orbital P1 and the precessional P2 periods. Conclusions: The precessional period, indicated by the astrometry to be of 27--28 d, is P2=26.92 d. The system \lsi seems to be one more case in astronomy of beat, i.e., a phenomenon occurring when two physical processes create stable variations of nearly equal frequencies. The very small difference in frequency creates a long-term variation of period 1/(\nu1-\nu2). The long-term modulation of 1667 d results from the beat of the two close orbital and precessional rates.

VLBA images of the precessing jet of LS I +61°303

Context: In 2004, changes in the radio morphology of the Be/X-ray binary system LSI+61303 suggested that it is a precessing microquasar. In 2006, a set of VLBA observations performed throughout the entire orbit of the system were not used to study its precession because the changes in radio morphology could tentatively be explained by the alternative pulsar model. However, a recent radio spectral index data analysis has confirmed the predictions of the two-peak microquasar model, which therefore does apply in LSI+61303. Aims: We revisit the set of VLBA observations performed throughout the orbit to determine the precession period and improve our understanding of the physical mechanism behind the precession. Methods: By reanalyzing the VLBA data set, we improve the dynamic range of images by a factor of four, using self-calibration. Different fitting techniques are used and compared to determine the peak positions in phase-referenced maps. Results: The improved dynamic range shows that in addition to the images with a one-sided structure, there are several images with a double-sided structure. The astrometry indicates that the peak in consecutive images for the whole set of observations describes a well-defined ellipse, 6-7 times larger than the orbit, with a period of about 28 d. Conclusions: A double-sided structure is not expected to be formed from the expanding shocked wind predicted in the pulsar scenario. In contrast, a precessing microquasar model can explain the double- and one-sided structures in terms of variable Doppler boosting. The ellipse defined by the astrometry could be the cross-section of the precession cone, at the distance of the 8.4 GHz-core of the steady jet, and 28d the precession period.

A C-Based Variable Length and Vector Pipeline Architecture Design Methodology and Its Application

The size and performance of a System LSI depend heavily on the architecture which is chosen. As a result, the architecture design phase is one of the most important steps in the System LSI development process and is critical to the commercial success of a device. In this paper, we propose a C-based variable length and vector pipeline (VVP) architecture design methodology and apply it to the design of the output probability computation circuit for a speech recognition system. VVP processing accelerated by loop optimization, memory access methods, and application-specific cir- cuit design was implemented to calculate the Hidden Markov Model (HMM) output probability at high speed and its performance is evaluated. It is shown that designers can explore a wide range of design choices and generate complex circuits in a short time by using a C-based pipeline architecture design method.

Design Technology of Stacked Type DTMOS

Stacked type DTMOS which enables to realize both high-speed low-power characteristics of FinFET type DTMOS and small pattern area of stacked transistor has been newly proposed. The delay time of substrate of stacked type DTMOS can be reduced to less than 10% compared with that of conventional FinFET type DTMOS by using the sidewall connection between gate and substrate. By using stacked structure of NMOS with (110) substrate on PMOS with (100) substrate high speed performance with the optimized mobility value can be realized without sacrificing the pattern area. Furthermore, the pattern area of inverter/NAND circuit, LSI for communication and DRAM buffer circuit with stacked type DTMOS has been compared with that of conventional FinFET type DTMOS. Newly proposed stacked type DTMOS is a promising candidate for realizing high performance system LSI such as the microprocessor of GHz operation.

Reeducation for Design Engineers in Fukuoka System LSI College

Reeducation for Design Engineers in Fukuoka System LSI College

System LSI Design Education Program Promoted by STARC

System LSI Design Education Program Promoted by STARC

2213 システムデザインのためのモデリング手法に関する研究(OS5-1 製品設計開発のためのモデリング・方法論・マネジメントI,OS5 モデル駆動型の製品システム開発)

The system LSI has been improved its values by increasing its circuit scaling and technology scaling based on Moore's law. However, semiconductor devices are expected to face physical and economical miniaturization limits in the near future, and traditional technology scaling based on the Moore's law is going to fail. Therefore, 3D technology, like 3D-SiP (System-in-Package), has been realized rapidly as a key to break through these limits. However, by increasing circuit scaling and evaluation point such as heat caused by shift to 3D structure, design quality is reduced, because it becomes difficult to define and visualize whole system. In this paper, using SysML (System Modeling Language), which is generally used for defining systems, we visualize whole system and optimize 3D-SiP system.

1106 製品設計におけるシステムズアプローチの計算機支援に関する研究(OS1-2 製品設計開発のためのモデリング・方法論・マネジメントII,OS1 製品設計開発のためのモデリング・方法論・マネジメント)

A quality of a design result in the early stage of the product development is very important, because it has high impact on the basic and detailed design stage. However, especially in the early stage, the problem structure and kind is often not defined yet. This research focuses on the problem definition in the early design stage. Using product function and product structure, a system approach to declare the problem in product design is proposed in this paper. Two design example is examined by proto-type system; (1) an electric fan system and (2) large-scaled integrated circuit (system LSI). In conclusion, the possibility of deriving product constraints by grouping the dependencies defined inside the product model.

Inductorless 8.9 mW 25 Gb/s 1:4 DEMUX and 4 mW 13 Gb/s 4:1 MUX in 90 nm CMOS

A low-power inductorless 1:4 DEMUX and a 4:1 MUX for a 90 nm CMOS are presented. The DEMUX can be operated at a speed of 25 Gb/s with the power supply voltage of 1.05 V, and the power consumption is 8.9 ㎽. The area of the DEMUX core is 29 × 40 ㎛². The operation speed of the 4:1 MUX is 13 Gb/s at a power supply voltage of 1.2 V, and the power consumption is 4 ㎽. The area of the MUX core is 30 × 18 ㎛². The MUX/DEMUX mainly consists of differential pseudo-NMOS. In these MUX/DEMUX circuits, logic swing is nearly rail-torail, and a low Vdd. The component circuit is more scalable than a CML circuit, which is commonly used in a high-performance MUX/DEMUX. These MUX/DEMUX circuits are compatible with conventional CMOS logic circuit, and it can be directly connected to CMOS logic gates without logic level conversion. Furthermore, the circuits are useful for core-to-core interconnection in the system LSI or chip-to-chip communication within a multi-chip module, because of its low power, small footprint, and reasonable operation speed.