Excelitas Technologies (Singapore)

Infrared (IR) sensor module deploy for hazardous gas leakage detection is crucial to provide and maintain offshore Oil & Gas platform asset integrity and improve operational risk management by avoiding accidental disaster and mitigating risk associated with danger involve in oil production. These sensor modules must remain robust under harsh ambient environment. Hence, designing novel high temperature interconnects material bill of materials (BOM) with compatible barrier metallization [1-2] and robust hermetic sealing material further enhanced sensor reliability. By reducing BOM oxidation degradation at high ambient temperature [3-4], reliability of the sensor is maintained. For this study, the TV (test vehicle, Figure 1) consist of an Alumina (Al 2 O 3 ) substrate casing which houses all the active components and is hermetically sealed with a Silicon (Si) die that acts as an IR filter. Laser and seam welding are common method of performing hermetic sealing but they suffer from low throughput issues. An investigative benchmark of various hermetic sealing methods and materials will be discussed in great details, targeting Alumina (Al 2 O 3 ) to Silicon (Si) interfaces sealing. Both sealing surfaces have no metallization. Materials such as high temperature low outgassing adhesive, glass frit paste and ceramic paste will be applied on the TV via dispensing or screen printing method and their corresponding hermeticity performance of the sealing interface will be investigated. The silicon filter is 3.7 × 3.7 mm in size and will be mounted on a 3.8 × 3.8mm ceramic substrate casing. TV hermeticity degradation response (base on MIL-STD-883J Method 1014.14 which requires 10−9 cc/sec leak rate) is examined after reliability evaluation is conducted, which include Thermal Cycling (TC, −55°C to 250°C, 500 cycles) and High Temperature Storage (HTS, 250°C, 500 hours). The objective of this paper is to report the high temperature reliability performance of various benchmarked sealing materials and understand and document the degradation mechanism and hermeticity response (via MIL-STD leak test) after HTS and TC test at 250°C.

The versatility of mid-infrared metamaterial absorbers along with the ease of fabrication has been widely used in thermal imaging, molecule sensing, and many other applications. Controllable multispectral absorption is highly required for small footprint, multi-purpose, and real-time sensing applications. In this paper, we present the polarization control of interchangeable multispectral absorption based on the dual-band metamaterial absorber in split mode. Large modulation depth of absorption is obtained during multi-band transition through polarization control. We perform theoretical and numerical analysis to explain the results by formulating an equivalent circuit for the asymmetric cross resonator. Thermal controllability is also demonstrated to show the reversible and repeatable manipulation of absorption intensity at a given wavelength. Moreover, we characterized the limitation of this device under extreme high temperature. This work offers a design methodology for interchangeable multispectral metamaterial absorber from a new perspective by adopting polarization of incident light as a control mechanism, and this will open up possibilities for many valuable applications in the future.

An efficient way of utilizing the large amount of remote sensing data for target detection and classification has always been challenging. The idea of compressive sensing (CS) enables successful reconstruction and processing from a small set of measurements which, by conventional wisdom, is considered to be an incomplete set of data. An appropriate metric for measuring the quality of the reconstructed signal, for applications like mine hunting using sonar images, is the accuracy of target detection. In this work, we evaluate the performance of target detection on compressively sensed and reconstructed sonar images to measure the quality of reconstruction. It is observed that the detection performance on CS reconstructed images is superior to the detection on the original raw data.

In this paper, we explore the idea of improving the efficiency of factorial design for parameter tuning of metaheuristics. In a standard full factorial design, the number of runs increases exponentially as the number of parameters. To reduce the parameter search space, one option is to first partition parameters into disjoint categories. While this may be done manually based on user guidance, an automated approach proposed in this paper is to apply a fractional factorial design to partition parameters based on their main effects where each partition is then tuned independently. With a careful choice of fractional design, our approach yields a linear rather than exponential run time performance with respect to the number of parameters. We empirically evaluate our approach for tuning a simulated annealing algorithm that solves an industry spares inventory optimization problem. We show that our proposed methodology leads to improvements in terms of the quality of solutions when compared to a pure application of an automated parameter tuning configurator ParamILS.

Accurate Spectrum sensing is a vital task in military wideband receivers. The discrete Fourier transform filter bank (DFTFB) used in conventional energy detectors fails to detect the exact locations and edges of occupied frequency bands (channels). In this paper, an energy detector based on tree-structured DFTFB (TDFTFB) is proposed for detecting the edges of channels. Simulation results are presented to show the trade-off between accurate edge detection and the number of filter bank stages required. Simulation results show that the proposed method detects the edges of channels with an error less than 2% using a 2-stage, 8 point TDFTFB while the conventional DFTFBs cannot detect the edges of the channels. The receiver operating characteristics (ROC) plot for the proposed method shows better performance than the conventional DFTFBs.

The performance of a cognitive radio system depends on how well it can maximize the usage of a free frequency band without causing any interference to the primary user. Thus the abilities to detect a primary user as well as to avoid any false alarm are of paramount importance for such a system. For energy detector based spectrum sensing in cognitive radios, these abilities are influenced by the threshold set to distinguish signal from noise. Conventional energy detectors are based on a fixed threshold. This may not be optimum in low SNR conditions where the performance of fixed threshold based detector can vary from the targeted performance metrics substantially. In this paper, we propose a method to change the threshold based on the number of samples, to optimize the detection parameters, namely probability of detection and probability of false alarm. We also introduce a control parameter which is used to vary the set threshold and thereby obtain a response more suited to the operational requirements than that obtained by a fixed threshold based energy detector. Simulation results are presented to show a different perspective of the importance of the sensing time to the performance metrics of the energy detector.

The long-range goal of the Z-Pinch IFE program is to produce an economically-attractive power plant using high-yield z-pinch-driven targets (~3GJ) with low rep-rate per chamber (~0.1 Hz). The present mainline choice for a Z-Pinch IFE power plant uses an LTD (Linear Transformer Driver) repetitive pulsed power driver, a Recyclable Transmission Line (RTL), a dynamic hohlraum z-pinch-driven target, and a thick-liquid wall chamber. The RTL connects the pulsed power driver directly to the z-pinch-driven target, and is made from frozen coolant or a material that is easily separable from the coolant (such as carbon steel). The RTL is destroyed by the fusion explosion, but the RTL materials are recycled, and a new RTL is inserted on each shot.A development path for Z-Pinch IFE has been created that complements and leverages the NNSA DP ICF program. Funding by a U.S. Congressional initiative of $4M for FY04 through NNSA DP is supporting assessment and initial research on (1) RTLs, (2) repetitive pulsed power drivers, (3) shock mitigation [because of the high yield targets], (4) planning for a proof-of-principle full RTL cycle demonstration [with a 1 MA, 1 MV, 100 ns, 0.1 Hz driver], (5) IFE target studies for multi-GJ yield targets, and (6) z-pinch IFE power plant engineering and technology development. Initial results from all areas of this research are discussed.

A compact broadband stripline-fed slot antenna is presented. The stripline-fed slot is covered with polytetrafluoroethylene (PTFE)-filled rectangular slot. With the PTFE-filled slot acting as an impedance transformer, the 10 dB return loss bandwidth of this antenna can be extended to be over 20%. The size of the antenna is only 0.49/spl lambda//sub 0//spl times/0.29/spl lambda//sub 0/ at the center frequency of 6.1 GHz. The wide bandwidth and compact size make it very suitable to be used in C-band mobile satellite (MSAT) vehicle phased-array applications.

Services are by nature perishable. As such, managing a service firm’s capacity to match supply and demand has been touted as one of the key problems of services marketing and management practice. This paper advances an alternative perspective of unused service capacity. Based on a review of current literature and an exploratory study, this paper employs a theory‐in‐use methodology to map out a set of capacity strategy propositions. These propositions show a divergence between what literature suggests and what service firms actually practise with regard to reducing the occurrence of unused service capacity. The paper also demonstrates that capacity can be employed as a resource to achieve a series of strategic objectives that serve to improve the performance of the firm. Service firms should therefore approach capacity management not only from the standpoint of operations management, but also from that of marketing.