Suppressor Devices Research Articles

Gunshot Residue Deposition With and Without Firearm Suppressors (Silencers).

Forensic pathologists recognize the importance of estimating the range of fire for gunshot entrance wounds. Classically described ranges of fire include contact, close range, medium (or intermediate) range, and indeterminate (or distant) range. The presence or absence of gunshot residue (smoke/soot and/or gunpowder) and the characteristics of the gunshot residue are evaluated in order to estimate the range of fire. It is well known that interposed targets can block or otherwise alter gunshot residue deposition. In this preliminary study, a comparison is made between gunshot defects produced on targets using firearms with and without an attached suppressor device (so-called "silencer"). Comparisons are made at various distances from the targets, using multiple weapon/ammunition calibers.

A Cost-Effective Structure for Secondary Discharge Control to Improve System-Level ESD Immunity of a Mobile Product

A structure embedded in a printed circuit board is proposed to control secondary discharge currents and improve the system-level electrostatic discharge (ESD) immunity for a mobile product with a metal frame. Noise voltages and discharge currents were measured and analyzed according to several secondary discharge paths, such as an air arc, a voltage suppressor device, and with the interlaced suppression device. ESD events that caused soft failures of a real commercial mobile product were tested while a high-definition video was playing. System-level ESD-induced noise and soft failures were cost effectively reduced by the interlaced suppression device.

Design and Optimization of High-Failure-Current Dual-Direction SCR for Industrial-Level ESD Protection

In an industrial-grade bus, transient voltage suppressor (TVS) devices that need to withstand inrush currents ensure electrostatic discharge (ESD) reliability of the core chip. This article designs four types of dual-direction silicon-controlled rectifier (DDSCR) device structures based on the 0.5-μm CMOS process. The ESD performance of the TVS device is predicted and verified based on the basic principles of the device, two-dimensional device simulation, and transmission line pulse test results. Four DDSCR structures are embedded with floating N+ to adjust the device's holding voltage window. The results show that the current release capacity of DDSCR_1 is 81.93 mA/μm. The current release capability of DDSCR_2, which has a double-dummy-gate structure, is 82.37 mA/μm. The current release capability of DDSCR_3 of the gate-controlled structure is 86.68 mA/μm. The current release capability of DDSCR_4 of the double-dummy-gate structure and the gate-controlled structure is 86.25 mA/μm. Furthermore, the effect of the size of these devices on the ESD characteristics was studied. The on-resistance of the device structure is calculated by the curve-fitting method. The influence of the dummy gate structure and the gate-controlled structure on the ESD characteristics is analyzed. Finally, the optimal device size to meet the window is found.

Mn-Zn Ferrite Round Cable EMI Suppressor With Deep Grooves and a Secondary Short Circuit for Different Frequency Ranges

A novel Mn-Zn ferrite round cable electromagnetic interference (EMI) suppressor with deep grooves and a secondary short circuit was constructed, realized and measured. Three steps were passed in novel suppressor development: from developing a suitable magnetic material, to constructing a suppressor device, to forming a new class of possible applications. Soft ferrite feedstock was formed from fine commercial Mn-Zn powder and a Solvent system binder based mainly on wax. Cylinder-shape cores with grooves were injected by powder injection molding (PIM) technology, chemically and thermally debinded and sintered at optimal conditions (1280°C/2 h). The samples were aimed to serve as cores for EMI suppressors on cables. Their impedance versus frequency was measured using the core length as a parameter. After that, copper wire was placed into the grooves on the outside surface of cores to form a secondary coil and different configurations were considered. The contribution of the short circuit coil inserted into the grooves to EMI suppression was measured and analyzed also. Maximal impedance values can be achieved with a secondary short circuited winding which passes through every groove. It was also shown that ferrite cores of the same length could be used for different frequency ranges by changing the configuration of secondary short circuited windings.

Development of Transient Voltage Suppressor Device with Abrupt Junctions Embedded by Epitaxial Growth Technology

A new Zener transient voltage suppressor (TVS) consisting of abrupt junctions of epitaxial layers has been developed. Differential resistance in the breakdown region is obtained as low as 5Ω, and the reverse leakage current is substantially suppressed by one to two orders of magnitude compared to a conventional Zener diode. The reliability of the TVS is confirmed based on its maximum allowed reverse current level and the robustness of its electrostatic discharge endurance against ±8 kV of the human body model (HBM) at a wide range of operating temperatures (30°C to 180°C). This significant improvement is primarily attributed to the abrupt junction profile formed by low-temperature processes, followed by epitaxial growth technology prohibiting redistribution of dopant elements.

Ion chromatographic system with a novel switching suppression device

Ion chromatography (IC) has been a powerful tool for measuring ionic species in environmental samples such as tap, river and drain waters. Suppressor modules (membrane and disposable column types) have been used for reducing the background of a baseline. A new type of suppressor device, which has a suppressor resin and switching valve was developed. Fresh ionic resin is introduced into a groove for each analysis to perform the suppression of the working eluent. The eluent composition for obtaining higher sensitivity and better resolutions among ionic species and carbonate ion was also investigated. Although carbonate buffers are used for ion separation in general, the separation of carbonate ion from other ions was not achieved. A borate eluent resulted in good resolutions and higher sensitivity. A new column was also developed for obtaining higher column efficiency and resolution. The optimization of anion separation using a new IC system (IC-2001) that consists of a new suppressor device, an anion-exchange column (TSKgel SuperIC-Anion, 150×4.6 mm), an autosampler, a conductivity cell and a pump in a compact module is described.

Ion-exchange-based eluent-free preconcentration of some anions

Preconcentration procedures based on ion-exchange methods are often used to enhance the sensitivities of analytical techniques where the eluent used for eluting the preconcentrated ions does not influence the subsequent analytical step. Until recently, only a limited use of ion-exchange-based sample preconcentration procedures has been found in those analytical techniques where the eluent components strongly influence the separation procedure [e.g., capillary electrophoresis (CE)]. In this paper, we present a preconcentration procedure based on (i) the preconcentration of anions on an ion-exchange resin, (ii) the subsequent elution of analytes, and (iii) on-line removal of eluent components by chemical suppression using an appropriate suppressor device (either packed-bed suppressor column or micromembrane suppressor). The adjustment of the system parameters, combined with a computer-controlled, sensing/switching system, resulted in a minimal additional dilution of the eluted preconcentrated anions. The efficiency of the proposed enrichment/matrix removal procedure was tested by using off-line CE analysis of collected preconcentrated samples, reaching a LOD of 1 μg/l for a selected anion.

Application and safety issues for transient voltage surge suppressors

This paper is intended as a guide to users and manufacturers of transient voltage surge suppressor devices based on metal-oxide varistor semiconductors. Many current designs and applications can result in safety problems, including short circuits, explosions, and energized panels and grounding conductors. If the recommendations contained in this paper are followed, then electrical system safety and reliability will be enhanced. The subjects of fusing, connections, grounding, and component compatibility are explored as they pertain to surge suppressor design and application.

Recent developments in surfactant analysis by ion chromatography

A simple and sensitive method for analysing surfactants by ion chromatography (IC) is described. The method uses ion-pair separation with gradient elution and suppressed conductivity detection. Two types of suppressor devices are used. The electrochemically regenerated ion suppressor (ERIS; patent pending) is ideal for continuous unattended operation. It uses an electrochemical process to self-regenerate the suppressor cells. No regenerant reagent or system is required and no chemical waste is generated. This suppressor is compatible with up to 30% organic solvents in the mobile phase. For mobile phases containing higher organic concentration, the solid-phase chemical suppressor (SPCS) was used. The SPCS uses disposable suppressor cartridges as the suppression device. No regeneration or maintenance is needed with this suppressor since the cartridges are disposable. The SPCS cartridges are compatible with up to 80% organic solvents. Separation of surfactants was based on ion-pair interaction on a reversed-phase column. Both anionic and cationic surfactants can be determined using this method. The detection limits for the surfactants are in the parts-per billion and low parts-per million ranges.

Digital time-domain investigation of transient behaviour of coupling capacitor voltage transformer

This paper reports a set of digital time-domain simulation studies conducted on TEHMP161A Coupling Capacitor Voltage Transformer (CCVT) of Haefely-Trench. The Electro-Magnetic Transients Program (EMTP) is used to develop the CCVT model and conduct the transient studies. The accuracy of the CCVT model is verified through comparison of the EMTP simulation results with those obtained from test results. The investigations demonstrate that the developed model can accurately predict CCVT transient response, e.g. the phenomenon of ferroresonance. The model is developed (1) to determine impact of transients on CCVT response, (2) to design, optimize and compare protective and ferroresonance suppressor devices of CCVT, and (3) to predict CCVT transient response on power system monitoring and protection schemes.

Studies on system performance and sensitivity in ion chromatography

Improvements in HPLC instrumentation, suppressor technology and ion-exchange columns have occurred over the past several years to the point where an ion chromatograph can now be configured for anion analysis using a considerable variety of hardware, suppressor and column combinations. A number of parameters, including hardware configuration, effect of temperature, column type and suppressor device, were studied with a view toward optimizing the performance of an ion chromatographic (IC) system. It was found that dual-piston, reciprocating pumps used with low-pressure pulse dampeners significantly reduced baseline noise for both suppressed and non-suppressed conductivity detector combinations, while column temperature control proved essential in order to achieve routine sub-ppb detectability in non-suppressed IC. In general, the use of suppressed IC resulted in lower detection limits than non-suppressed IC when using the same columns and hardware. Of the columns studied, the methacrylate-based HR column was found to give the best overall separation selectivity when using a carbonate-bicarbonate eluent and suppressed conductivity detection. The majority of column and suppressor combinations evaluated gave acceptable performance, although some gave less than satisfactory results. Also, some combinations resulted in lower than expected analytical results, particularly for chloride, when quantitated using single-point calibration. In addition to the use of commercially available suppressor devices, there is also a large number of high-capacity cation exchangers which can be used as suppressors and these columns, in some instances, may offer equivalent (or superior) performance compared to the commercial devices.

New membrane-based electrolytic suppressor device for suppressed conductivity detection in ion chromatography

This paper discusses the newest advancement in chemical suppression preceding conductivity detection. The new suppressor uses electrolysis of deionized water to generate the required acid or base for the suppression neutralization reaction and utilizes the electrical field to enhance, through electrodialysis, the suppressor's capacity for neutralization. The suppressor is able to accommodate eluents as high as 150 m M NaOH, without the need for a separate regenerant solution, by recycling the conductivity detector cell waste to the regenerant and electrolysing the water in the waste stream to the required acid or base. The device is able to use deionized water as regenerant and neutralize the eluent stream to deionized water without the expected increase in resistance by employing ion exchange material in intimate contact with the electrodes and the membranes. The current is carried with low resistance through the ion-exchange material via ion transport from one ion-exchange site to another.

Gradient elution of aliphatic carboxylic acids by ion chromatography in the ion-suppression mode

The gradient ion chromatography separation and detection of aliphatic carboxylic acids in the homologous series of butyric acid through stearic acid as well as some unsaturated fatty acids are presented. The separation mode requires the ion suppression of the weak acid analytes for a reversed-phase inteaction while detection by electrical conductivity requires analyte ionization through a cation-exchange micromembrane suppressor device.

Perspective of SST aircraft noise problem. II - Thrust losses and installation factors

The current state of research concerning noise suppression for SST jet engines is presented. Results of an extensive research program of both model and large scale levels which has investigated many different noise suppressor concepts are described. Test results covered in Part I (previously published in the Journal of Aircraft) show several fundamental means to reduce jet noise at different frequency regions. In Part II, means to reduce thrust losses associated with installed suppressor devices are shown. Installed noise suppressor designs are based on these charts. The factors which control noise levels for takeoff are examined. Substantial improvements in SST noise footprints are indicated as suppression development continues.

A Carrier-Operated Echo Suppressor and Control Device

Of the numerous distortions affecting high quality facsimile reception, noise and echo represent the most troublesome offenders. This paper describes a device which fills the critical need for suppression of noise and echo currents on two-way multipoint facsimile networks. Laboratory test data as well as operational performance results, gathered during field trials of two prototype units, are presented. Additional applications for the device, including TONLOC, disabling of compandors during picture transmission, and possible application to data transmission systems are discussed.