Hybrid Linear Closed‐Form Solution in Wireless Localization

In wireless localization, several linear closed‐form solution (LCS) methods have been investigated as a direct result of the drawbacks that plague the existing iterative methods, such as the local minimum problem and heavy computational burden. Among the known LCS methods, both the direct solution method and the difference of squared range measurements method are considered in this paper. These LCS methods do not have any of the aforementioned problems that occur in the existing iterative methods. However, each LCS method does have its own individual error property. In this paper, a hybrid LCS method is presented to reduce these errors. The hybrid LCS method integrates the two aforementioned LCS methods by using two check points that give important information on the probability of occurrence of each LCS's individual error. The results of several Monte Carlo simulations show that the proposed method has a good performance. The solutions provided by the proposed method are accurate and reliable. The solutions do not have serious errors such as those that occur in the conventional standalone LCS and iterative methods.     

Writing current reduction and total set resistance analysis in PRAM

We evaluated the limit of scaling bottom electrode contact (BEC) heater size and high resistivity heater to reduce writing current. It was found that the resistivity of heater should be increased for reducing writing current below the heater size of about 50 nm without any undesirable increase of resistance of the crystalline state (SET state, Rset). It was shown in the numerical simulations that the dissipated heat loss through BEC during melting GST was decreased in the increase of resistivity of heater. In addition, we analyzed the resistance components contributing to the total set resistance. It was observed that the undesired sharp increase of Rset as the BEC size decreases below 50 nm was attributed to the resistance component of GST–BEC interface. In the case of high resistivity heater, the contributions of both incomplete crystallization and heater itself were enhanced.     

Detection of repolarization alternans with an implantable cardioverter defibrillator lead in a porcine model

Mechanistic links have been suggested between repolarization alternans (RPA) and the onset of ventricular tachycardia (VT) and/or fibrillation. Endocardial detection of RPA may, therefore, be an important step in future device-based treatments of arrhythmias. Here, we investigate if RPA could be detected during acute ischemia using an implantable cardioverter defibrillator (ICD) lead (tip to distal coil) located in the right ventricular apex. In 18 pigs, the right coronary (n = 10) or left anterior descending coronary (n = 8) artery was occluded for 10 min using a balloon catheter, followed by reperfusion for 30 min, and re-occlusion for 30 min. RPA magnitude, computed using the modified moving average (MMA) method, showed a sharp increase in all 18 animals, from a mean baseline level of 1.9 +/- 1.3 mV to 3.0 +/- 1.3 mV during first occlusion (p < 0.001). RPA magnitude showed a prominent increase in 10 animals during re-occlusion, from a mean baseline level of 1.7 +/- 1.0 mV to 3.3 +/- 1.5 mV (p < 0.001). The protocol was terminated during the first two stages of occlusion and reperfusion for the remaining 8 animals due to the occurrence of ventricular fibrillation (VF). These results confirm that RPA increases under ischemic conditions and that it is possible to detect and track RPA dynamics with an ICD lead that is positioned in a clinically realistic location. Such an approach may be useful in formulating improved arrhythmia detection and control algorithms.     

A Multi‐Functional Highly Efficient Upconversion Luminescent Film with an Array of Dielectric Microbeads Decorated with Metal Nanoparticles

Upconversion nanoparticles (UCNPs) have been integrated with photonic platforms to overcome the intrinsically low quantum efficiency limit of upconversion luminescence (UCL). However, platforms based on thin films lack transferability and flexibility, which hinders their broader and more practical application. A plasmonic structure is developed that works as a multi‐functional platform for flexible, transparent, and washable near‐infrared (NIR)‐to‐visible UCL films with ultra‐strong UCL intensity. The platform consists of dielectric microbeads decorated with plasmonic metal nanoparticles on an insulator/metal substrate. Distinct improvements in NIR confinement, visible light extraction, and boosted plasmonic effects for upconversion are observed. With weak NIR excitation, the UCL intensity is higher by three orders of magnitude relative to the reference platform. When the microbeads are organized in a square lattice array, the functionality of the platform can be expanded to wearable and washable UCL films. The platform can be transferred to transparent, flexible, and foldable films and still emit strong UCL with a wide viewing angle.     

Making Large‐Area Titanium Disulfide Films at Reduced Temperature by Balancing the Kinetics of Sulfurization and Roughening

The synthesis of large‐area TiS₂ thin films is reported at temperatures as low as 500 °C using a scalable two‐step method of metal film deposition followed by sulfurization in an H₂S gas furnace. It is demonstrated that the lowest‐achievable sulfurization temperature depends strongly on the oxygen background during sulfurization. This dependence arises because Ti? O bonds present a substantial kinetic and thermodynamic barrier to TiS₂ formation. Lowering the sulfurization temperature is important to make smooth films, and to enable integration of TiS₂ and related transition metal dichalcogenides—including metastable phases and alloys—into device technology.     

Hydration-Induced Void-Containing Hydrogels for Encapsulation and Sustained Release of Small Hydrophilic Molecules

Efficient encapsulation and sustained release of small hydrophilic molecules from traditional hydrogel systems are challenging due to the large mesh size of 3D networks and high water content. Furthermore, the encapsulated molecules are prone to early release from the hydrogel prior to use, resulting in a short shelf life of the formulation. Here, a hydration-induced void-containing hydrogel (HVH) based on hyperbranched polyglycerol-poly(propylene oxide)-hyperbranched polyglycerol (HPG-PPG-HPG) as a robust and efficient delivery system is presented for small hydrophilic molecules. Specifically, after the HPG-PPG-HPG is incubated overnight at 4 °C in the drug solution, it is hydrated into a hydrogel containing micron-sized voids, which can encapsulate hydrophilic drugs and achieve 100% drug encapsulation efficiency. In addition, the voids are surrounded by a densely packed polymer matrix, which restricts drug transport to achieve sustained drug release. The hydrogel/drug formulation can be stored for several months without changing the drug encapsulation and release properties. HVH hydrogels are injectable due to shear thinning properties. In rats, a single injection of the HPG-PPG-HPG hydrogel containing 8 µg of tetrodotoxin (TTX) produces sciatic nerve block lasting up to 10 h without any TTX-related systemic toxicity nor local toxicity to nerves and muscles.     

T-Ray Sensing and Imaging

T-ray wavelengths are long enough to pass through dry, nonpolar objects opaque at visible wavelengths, but short enough to be manipulated by optical components to form an image. Sensing in this band potentially provides advantages in a number of areas of interest to security and defense such as screening of personnel for hidden objects and the retection of chemical and biological agents. Several private companies are developing smaller, reliable cheaper systems allowing for commercialization and this motivates us to review a number of promising applications within this paper. While there are a number of challenges to be overcome there is little doubt that T-ray technology will play a significant role in the near future for advancement of security, public health, and defense.     

Coil‐Capacitor Circuit Design of a Transcutaneous Energy Transmission System to Deliver Stable Electric Power

A new transcutaneous energy transmission (TET) system was developed for transmitting electrical power to an implanted device, such as an artificial heart in a patient's body. This new design can maintain a stable output voltage independent of the load resistance. The system includes a compensation capacitor to reduce energy loss and increase power transfer efficiency. Experimental results show that the output voltage of the receiving coil changes very little as the load resistance varies from 14.8 Ω to 15 kΩ, which corresponds to a change in output power from 0.1 to 97 W.     

Interfacial reaction between 42Sn-58Bi solder and electroless Ni-P/immersion Au under bump metallurgy during aging

The interfacial reaction between 42Sn-58Bi solder (in wt.% unless specified otherwise) and electroless Ni-P/immersion Au was investigated before and after thermal aging, with a focus on the formation and growth of an intermetallic compound layer, consumption of under bump metallurgy (UBM), and bump shear strength. The immersion Au layer with thicknesses of 0 μm (bare Ni), 0.1 μm, and 1 μm was plated on a 5-μm-thick layer of electroless Ni-P (with 14–15 at.% P). The 42Sn-58Bi solder balls were then fabricated on three different UBM structures by using screen printing and pre-reflow. A Ni₃Sn₄ layer formed at the joint interface after the pre-reflow for all three UBM structures. On aging at 125°C, a quaternary phase, identified as Sn₇₇Ni₁₅Bi₆Au₂, was observed above the Ni₃Sn₄ layer in the UBM structures that contain Au. The thick Sn₇₇Ni₁₅Bi₆Au₂ layer degraded the integrity of the solder joint, and the shear strength of the solder bump was about 40% less than the nonaged joints.