Transition Probability Test for an RO-Based Generator and the Relevance between the Randomness and the Number of ROs

A ring oscillator is a well-known circuit used for generating random numbers, and interested readers can find many research results concerning the evaluation of the randomness with a packaged test suit. However, the authors think there is room for evaluating the unpredictability of a sequence from another viewpoint. In this paper, the authors focus on Wold's RO-based generator and propose a statistical test to numerically evaluate the randomness of the RO-based generator. The test adopts the state transition probabilities in a Markov process and is designed to check the uniformity of the probabilities based on hypothesis testing. As a result, it is found that the RO-based generator yields a biased output from the viewpoint of the transition probability if the number of ROs is small. More precisely, the transitions 01 -> 01 and 11 -> 11 happen frequently when the number l of ROs is less than or equal to 10. In this sense, l > 10 is recommended for use in any application, though a packaged test suit is passed. Thus, the authors believe that the proposed test contributes to evaluating the unpredictability of a sequence when used together with available statistical test suits, such as NIST SP800-22

Consideration for Affects of an XOR in a Random Number Generator Using Ring Oscillators

A cloud service to offer entropy has been paid much attention to. As one of the entropy sources, a physical random number generator is used as a true random number generator, relying on its irreproducibility. This paper focuses on a physical random number generator using a field-programmable gate array as an entropy source by employing ring oscillator circuits as a representative true random number generator. This paper investigates the effects of an XOR gate in the oscillation circuit by observing the output signal period. It aims to reveal the relationship between inputs and the output through the XOR gate in the target generator. The authors conduct two experiments to consider the relevance. It is confirmed that combining two ring oscillators with an XOR gate increases the complexity of the output cycle. In addition, verification using state transitions showed that the probability of the state transitions was evenly distributed by increasing the number of ring oscillator circuits

A Room-Temperature High-Conductivity Metal Printing Paradigm with Visible-Light Projection Lithography

Fabricating electronic devices require integrating metallic conductors and polymeric insulators in complex structures. Current metal-patterning methods such as evaporation and laser sintering require vacuum, multistep processes, and high temperature during sintering or postannealing to achieve desirable electrical conductivity, which damages low-temperature polymer substrates. Here reports a facile ecofriendly room-temperature metal printing paradigm using visible-light projection lithography. With a particle-free reactive silver ink, photoinduced redox reaction occurs to form metallic silver within designed illuminated regions through a digital mask on substrate with insignificant temperature change (<4 °C). The patterns exhibit remarkably high conductivity achievable at room temperature (2.4 × 107 S m−1, ≈40% of bulk silver conductivity) after simple room-temperature chemical annealing for 1–2 s. The finest silver trace produced reaches 15 µm. Neither extra thermal energy input nor physical mask is required for the entire fabrication process. Metal patterns were printed on various substrates, including polyethylene terephthalate, polydimethylsiloxane, polyimide, Scotch tape, print paper, Si wafer, glass coverslip, and polystyrene. By changing inks, this paradigm can be extended to print various metals and metal–polymer hybrid structures. This method greatly simplifies the metal-patterning process and expands printability and substrate materials, showing huge potential in fabricating microelectronics with one system

Identification of 45 New Neutron-Rich Isotopes Produced by In-Flight Fission of a 238U Beam at 345 MeV/nucleon

A search for new isotopes using in-flight fission of a 345 MeV/nucleon 238U beam has been carried out at the RI Beam Factory at the RIKEN Nishina Center. Fission fragments were analyzed and identified by using the superconducting in-flight separator BigRIPS. We observed 45 new neutron-rich isotopes: 71Mn, 73,74Fe, 76Co, 79Ni, 81,82Cu, 84,85Zn, 87Ga, 90Ge, 95Se, 98Br, 101Kr, 103Rb, 106,107Sr, 108,109Y, 111,112Zr, 114,115Nb, 115,116,117Mo, 119,120Tc, 121,122,123,124Ru, 123,124,125,126Rh, 127,128Pd, 133Cd, 138Sn, 140Sb, 143Te, 145I, 148Xe, and 152Ba

Charging and Aggregation Behavior of Cellulose Nanofibers in Aqueous Solution

To understand the charging and aggregation of cellulose nanofibers (CNFs), we performed the following experimental and theoretical studies. The charging behavior of CNFs was characterized by potentiometric acid–base titration measuring the density of deprotonated carboxyl groups at different KCl concentrations. The charging behavior from the titration was quantitatively described by the 1-p<i>K</i> Poisson–Boltzmann (PB) model for a cylinder. The electrophoretic mobility of CNFs was measured as a function of pH by electrophoretic light scattering. The mobility was analyzed with the equation for an infinitely long cylinder considering the relaxation of the electric double layer. Good agreement between experimental mobilities and theoretical calculation was obtained by assuming a reasonable distance from the surface to the slipping plane. The result demonstrated that the negative charge of CNFs originates from the deprotonation of β­(1–4)-d-glucuronan on the surface. The aggregation behavior of CNFs was studied by measuring the hydrodynamic diameter of CNFs at different pH and KCl concentrations. Also, we calculated the capture efficiencies of aggregation, using interaction energies of perpendicularly and parallelly oriented cylinders. The interaction energies between cylinders in both orientations were obtained by the Derjaguin, Landau, Verwey, and Overbeek theory, where the electrostatic repulsion was calculated from the surface potential obtained by the 1-p<i>K</i> PB model. From comparison of the theoretical capture efficiency with the measured hydrodynamic diameter, we suggest that CNFs can be aggregated in perpendicular orientation at low pH and low salt concentration, and the fast aggregation regime of CNFs is realized by the reduction of electric repulsion for both perpendicularly and parallelly interacting CNFs. Meanwhile, the application of Smoluchowski’s equation to the mobility of CNFs results in the underestimation of the zeta potential

Fabrication of a Textile-Based Wearable Blood Leakage Sensor Using Screen-Offset Printing

We fabricate a wearable blood leakage sensor on a cotton textile by combining two newly developed techniques. First, we employ a screen-offset printing technique that avoids blurring, short circuiting between adjacent conductive patterns, and electrode fracturing to form an interdigitated electrode structure for the sensor on a textile. Furthermore, we develop a scheme to distinguish blood from other substances by utilizing the specific dielectric dispersion of blood observed in the sub-megahertz frequency range. The sensor can detect blood volumes as low as 15 μL, which is significantly lower than those of commercially available products (which can detect approximately 1 mL of blood) and comparable to a recently reported value of approximately 10 μL. In this study, we merge two technologies to develop a more practical skin-friendly sensor that can be applied for safe, stress-free blood leakage monitoring during hemodialysis