Search

We analyzed thermal characteristics of power transistors based on the complementary InGaP/InGaAs/GaAs collector-up heterojunction bipolar transistors (HBTs), and especially for stable wireless applications under extreme operations. A newly developed structure, incorporating the graded InGaAs base and the nonuniform collector, without employing additional thermal-removal design is presented. Significantly, the multi-finger devices achieved compelling high speed and heat dissipation. Results show that the fairly matched high-frequency performance has been exhibited and over 30% improvement in the surface-temperature-rise ratio is achieved. As a consequence of the effective alleviation of unstable feedback phenomena by this novel arrangement, exploiting the advantageous characteristics of complementary collector-up HBTs for thermally reliable high-speed wireless applications is feasible.

Understanding the effect of fiber orientation on mechanical properties is a primary consideration for long fiber-reinforced thermoplastics in automotive applications. In injection-molded parts, the classical Folgar-Tucker model has been used to predict the shell-core structure of short fiber orientation patterns. However, this model results in a thinner core region for long fiber composites. Recently, the RSC (Reduced Strain Closure), ARD (Anisotropic Rotary Diffusion), and iARD-RPR (improved ARD and Retarding Principal Rate) models are potential models developed in relation to suspension rheology. In addition to improving the inaccurate predictions, a so-called inlet condition of fiber orientation set at the gate is examined in the RSC. In this approach, a significant requirement is to numerically investigate the nature of the shell-core structure, while validating a predictive difference between the orientation models via related experimental data. Dramatic changes in the orientation distribution at various filling times and mold temperatures are discussed herein.

Fiber composites are the pinnacle of lightweight materials in the automotive industry. The orientation of the reinforcing fibers strongly affects the mechanical performance of the finished part. However, fiber orientation prediction with high accuracy is difficult for a complex flow field in practical injection molding. Recently, an objective model, iARD-RPR (Improved Anisotropic Rotary Diffusion and Retarding Principal Rate), has been significant to provide anisotropic distribution of fiber orientation, such as the well-known skin-shell-core structure. Micro-computed tomography (micro-CT) scan is a state-of-the-art technique for measuring a very high 3D resolution of a specimen's fiber orientation data. According to the micro-CT experiments and injection molding simulations with the iARD-RPR computation, we investigate changes in fiber orientation distributions at different concentrations in a rectangle plate, while the alignment of fibers found in weld line is revealed for tensile bar. Comparisons of the fiber orientation predictions with the validated experimental data are also presented herein.

We present a novel thermal management design for InGaP/GaAs power amplifiers (PAs) by placing the graphene heat spreader (GHS) at the backside of GaAs/InGaAs/InGaP collector-up (C-up) heterojunction bipolar transistors (HBTs), including n-p-n and p-n-p types. The GHS was used to create extra escape channel for thermal spread, and a physics-based analysis was performed to justify heat-dissipation improvements. Temperature distribution in the GHS and the application of these spreaders to ameliorate thermal coupling effects on multifinger transistors were discussed. Compared to the n-p-n device, the p-n-p device exhibits greater thermal stability enhancement results, which are extraordinary and reproducible. Both numerical simulation and experimental measurement were achieved to scrutinize thermal performance of the GHS. This brief demonstrates the potential of the suggested structure in replacing the conventional thermal-removal configuration of GaAs-based HBTs used in high-efficiency cellular handset PAs.

In this paper, the characteristics of InGaP/GaAs collector-up (C-up) pnp and npn heterojunction bipolar transistors (HBTs) with the graded InGaAs base and the nonuniform doped collector are demonstrated, and the performances as well as the reliability of the novel HBTs have been compared with the conventional InGaP/GaAs HBTs with various collector structures and thermal schemes. Compared to conventional HBTs, the studied C-up HBTs exhibited better current-driving capability, higher RF efficiency, and improved long-term reliability. Note that the pnp device displayed greater thermal stability enhancements, which are distinct and reproducible, than the npn device. The favorable data of the pnp C-up HBT could be attributed to higher electron mobility, resulting in low base resistance and higher emitter resistance improving the thermal stability. The comparison results, based on pragmatic observations from the C-up HBTs without relatively large heat-dissipation configurations, should be very useful for the reliable and the cost-effective design as small-scale power amplifiers in the wideband CDMA system.

Long fiber-reinforced thermoplastic (LFRT) composites are a very important lightweight material for practical use by the automotive industry because their mechanical performance is superior to that of short fibers. Microstructures of LFRT products, including fiber orientation state and fiber length distribution, strongly affect their mechanical properties and testing. Prior numerical approaches were limited by their inability to analyze many complex flows. Currently, the 3D numerical technology is able to analyze a varying geometry flow. We therefore aim to derive accurate predictions of fiber microstructure in a reliable 3D flow simulation of an injection molded LFRT composite part, with the use of objective fiber orientation and fiber length models. In addition, the microstructure data imported to calculate appropriate mechanical properties effectively improves the prediction accuracy of structural performance for an LFRT part. In such an integrative simulation, the predictive results are compared to related experimental data for the purpose of evaluation.

This study monitors environmental radiation using a thermoluminescent dosimeter (TLD) in the treatment vault of Axesse (Elekta 2538) linear accelerator. The TLD system was optimized for initial temperature, heat rate, and maximum set temperature using the Taguchi method. The half value layer was determined. Minimum detectable dose using this optimized TLD method was also identified.

With the continuing advancement in light-emitting efficiency of high-power light-emitting diodes (LEDs), a nondestructive evaluation on thermal reliability, especially regarding the operating temperature and thermal resistance, which directly affect their lifetime and luminous characteristics, is needed. In this paper, we develop a methodology of using a 3-D numerical simulation for transient thermal-conduction analysis, which is combined with the electrical test method to evaluate the junction temperature of a variety of LEDs. As a result, the simulated temperature for LEDs was found to increase with time, whereas the slug temperature showed the same trend for the simulation and the experiment. The measured results indicate that the thermal resistance of AlGaInP-material-based red and amber LEDs reveals higher variability than that of InGaN-material-based white and green LEDs. Via the luminous flux experiment, we have found that the thermal resistance of the LEDs is not the major determination factor of their luminous flux decay. In contrast, the luminous flux decay of the LED is dependent on the chip material being used. Notably, the slug temperature, observed from the pulsed-driven experiment, of the LED appeared to be lower than that observed in the normal steady operation. It is demonstrated that the lifetime and reliability of high-power LEDs can be improved by decreasing the junction and slug temperatures of the devices. This is important as the slug temperature can be controlled by external cooling techniques. In practice, the developed methodology is not restricted to analyze particular LED packaging forms and can be used to investigate various kinds of multichip LED modules as well.

SUMMARY The effects of thermal-dissipation structure on the thermal performance of nanoscale InGaP/GaAs collector-up heterojunction bipolar transistors were investigated by using the advanced hybrid optimization technique, a combination of the three-dimensional finite-element method for temperature-distribution analysis and the technology computer-aided design tool for power-performance evaluation. Through adequately locating the thermal-dissipation structure at the rear side of the transistor and via effective thickness-thinning procedures, which reduce foundry cost, the thermal coupling between collector fingers has been greatly ameliorated and a power-added efficiency of 45% is achieved. Copyright © 2013 John Wiley & Sons, Ltd.

SUMMARY An effective device structure for thermal management of multifinger InGaP/GaAs collector-up heterojunction bipolar transistors (HBTs), compelling active components in high-efficiency handset power amplifiers, is presented for the first time. From the unique 3-D thickness-adjusting numerical analysis, based on a finite element model, the miniaturized device can lead to a greater than 40% reduction in the thickness of plated gold layer. Above all, this is quite different from previous attempts, in which the thermal resistance was reduced by increasing the thickness of plated gold layer. Compared with literature works, the thermally stable design with an innovative heat-spread configuration shows a 50% reduction in thermal resistance and demonstrates favorable power performance. Copyright © 2013 John Wiley & Sons, Ltd.

A number of intricate configurations have been proposed to enhance the thermal stability of state-of-the-art power heterojunction bipolar transistors (HBTs). Existing structures for alleviating temperature-interference effects within HBTs are nevertheless not efficient enough to realize miniaturized power amplifiers in next-generation cellular phones. Key thermal parameters, including the temperature-distribution profile, the thermal resistance, the out power, and the power-added efficiency (PAE), of a cost-effective heat-spreading structure have been optimized by the device-physics-based genetic algorithm, and a demonstration on multifinger InGaP/GaAs collector-up HBTs, which exhibit noticeable RF performance, is presented. Comparatively, the significant results, which guarantee the reliability, indicate that the thermal resistance can be substantially decreased by 50%, and a PAE of more than 55% is attained from this novel design.

In this paper, we have successfully developed an intellectual parameter-extraction methodology on the basis of a genetic algorithm (GA), involving the efficient search-space separation and local-minima-convergence prevention schemes. Via an evolutionary simulation tool complemented with appropriate analytic equations, the enhanced approach has been applied to determine the significant figures-of-merit (FoMs), including internal quantum efficiency (ηi) as well as transparency current density (Jtr) of semiconductor lasers, minimum noise figure (NFmin) as well as associated available gain (GA,assoc) of low-noise amplifiers (LNAs), and DC as well as AC characteristics of heterojunction bipolar transistors (HBTs). For the first time, demonstrated FoM-extraction results, which coincide well with the actually measured data, for state-of-the-art InGaAs quantum-well lasers, advanced SiGe LNAs, and abrupt ZnSe/Ge/GaAs HBTs are simultaneously presented to validate this multi-parameter analysis and robust optimization. Copyright © 2011 John Wiley & Sons, Ltd.

In this article, the design parameters of a cutting tool for manufacturing a rotary knife with multi-cutting angles have been studied. An objective function and constraints are defined, and optimized solutions are found by using two methods: global search and sequential quadratic programming. Hobbing and the concept of tooth undercutting were used to manufacture a rotary knife with multi-cutting angles. The proposed method not only improved the manufacturing efficiency over the traditional method (milling and grinding), but also significantly improved the strength of the rotary knife and the chip discharge ability, as shown by the finite-element analysis of the stress distribution and deformation of two different kinds of rotary knives.

This research focuses on the analysis of vibration and noise control of a fuselage. A closed cylindrical shell is chosen as the theoretical model of the fuselage of an aircraft. The noise resulted from propellers is the main source of excitation to the fuselage vibration. The vibration can further induce interior noise within the fuselage. For attenuating the vibration of the fuselage and its accompanying interior noise, several pairs of piezoelectric sheets are attached to the shell. Each piezoelectric pair connected to an appropriate electric circuit can serve as a dynamic absorber. For a better performance, feedback control algorithms are introduced to form active absorbers. The dynamic responses of the composite cylindrical shell and the corresponding interior sound fields are analytically formulated. Numerical results are presented. The active absorbers are proven to yield good effects on vibration and noise reductions. Some parameter studies are also given in this manuscript.

A feeding experiment was conducted to determine the dietary calcium (Ca) requirement for juvenile hybrid tilapia, Oreochromis niloticus × O. aureus reared in nature water. Purified diet supplemented with 0, 1, 2, 3, 4, 5, 7 and 10 g Ca kg−1 diet providing of 0.6, 1.6, 2.6, 3.7, 4.7, 5.5, 7.5 and 10.7 g Ca kg−1 diet, respectively, were fed to tilapia (mean initial weight: 0.52 ± 0.01 g, n = 3) for 8 weeks. Each diet was fed to three replicate groups of fish in a closed, recirculating fresh water rearing system. The rearing water contained 27.1–33.3 mg L−1 Ca. The tilapia fed the diets supplemented with ≥3.7 g Ca kg−1 had significantly (P

An improved methodology, based on the genetic algorithm, is developed to design thermal-via structures and circuit parameters of advanced InGaP and InGaAs collector-up heterojunction bipolar transistors (C-up HBTs), which are promising miniature high-power amplifiers (HPAs) in cellular communication systems. Excellent simulated and measured results demonstrate the usefulness of this technique.

Owing to the complex geometry of helical cutting tools, several manufacturing processes are required to produce the profile of the cutter and the cutting angles. If the traditional method of manufacture were used, the cost would be frustratingly expensive. In this paper, a novel straight-sided hob cutter design consisting of two curved cutting edges and three straight cutting edges with different pressure angles is proposed. By applying designed rake profile equations of a hob cutter, the principle of coordinate transformation, the theory of differential geometry, and the theory of gearing, a mathematical model of the helical cutting tool is derived. In addition, the cutting angles, the condition of full undercutting, and the width of the top land of the cutter are also studied. The novelty of the design is such that the multiangles of the helical cutting tool can be manufactured in one hobbing process, thereby simplifying the manufacturing process. The results and concepts proposed in the paper will be beneficial as design guidance for tool designers, will enhance the manufacturing processes of helical cutting tools, and will assist tool-related industries in upgrading their technology and competitiveness.

BackgroundSingapore is a small industrialized island state with a low accident rate and few hazardous chemical-related injuries reported. However, the use of chemicals continues to increase and pose hazards in the workplace.AimsTo study workplace chemical injuries and exposures to improve worksite safety.MethodsWork-related chemical exposure cases were identified from emergency department (ED) computerized records from 2007 to 2010.ResultsA total of 239 cases were identified. Most of the patients were male (92%) and young adults (73% aged between 21 and 40 years). Fifty per cent of the workers were foreign workers. Most of them were cleaners, labourers and technicians (53%) and worked mainly in the construction and manufacturing industries (47%). All the exposures were acute and presented within 4h of the exposure incident (52%). Most of the chemical exposures were to the eye (55%) and skin (32%). The chemicals involved included corrosives (41%), hydrocarbons (18%) and cleaning solutions (9%). Pre-hospital decontamination (eye and skin irrigation) was performed for 54% of the workers. Antidote treatment with calcium gluconate for hydrofluoric acid exposure was used for five patients in the ED. Only 11% of patients were admitted. Four patients had surgical procedures and five patients had long-term complications. Forty-five incidents were notified to the Ministry of Manpower. The under-reporting rate for cases with >3 days of medical leave was 66%.ConclusionsWork-related chemical exposures that present to the ED had low morbidity. Most of the workers did well with immediate decontamination and supportive treatment but antidotes were required for some exposures. Language: en

Electron capture cross sections in collisions of C3+ ions with atomic hydrogen have been studied using the close-coupling two-centre atomic orbital (AO) expansion method by treating the collision system in a quasi-two-electron model. Total electron capture cross sections to the dominant individual singlet and triplet excited states are calculated over the energy range 0.1-50 keV amu-1. The results are compared with existing experimental data and with theoretical calculations based on the molecular orbital (MO) expansion method. It is found that our AO results are in general agreement with the MO results of Errea et al (1991 J. Phys. B: At. Mol. Opt. Phys. 24 4061) and with experiments but that discrepancies still exist in the details.

We calculated the total electron-capture cross section for collisions of C{sup 4+} ions with atomic hydrogen in the energy range of 10{endash}2000 eV/nucleon using the close-coupling two-center atomic orbital expansion method. Various basis sets have been used to check the convergence of the calculation and the results are shown to be in general agreement with existing experimental data. However, we found no evidence of a dip in the total electron-capture cross sections near 500 eV/nucleon as reported by Bliek {ital et al.} [Phys. Rev. A {bold 56}, 526 (1997)]. {copyright} {ital 1998} {ital The American Physical Society}

In this paper we consider the second law of thermodynamics for a dissipative system and its symmetry property in terms of contact geometry. We first show that the inaccessibility condition of Caratheodory and the assumption of semipositive definite property of the dissipative energy are equivalent to Clausius’ inequality. The inaccessibility condition then gives rise to a generalized Gibbs relation (GGR). By means of the GGR a 1-form ω can be defined such that the zero of ω reproduces the GGR. Such 1-form ω has the property ω∧(dω)n≠0 and ω∧(dω)n+1=0. The integral surface of the GGR is an n-dimensional 1-graph space G (Legendre submanifold) of a 1-jet space J1(En,R), where En is the base space of J1(En,R) with thermodynamic variables as its coordinates. The (2n+1)-dimensional J1(En,R) equipped with the 1-form ω is also called a contact bundle K, where the intensive thermodynamic variables are considered as the contact elements to K at every x. Next we construct an isovector field Xf such that the inaccessi...

Pure Si2H6 and GeH4 are used to grow Si and Si1−xGex epilayers at 550 °C by ultrahigh vacuum-chemical molecular epitaxy. 0.1% B2H6 and 100 ppm PH3 diluted in H2 are used as the p- and n-type dopant gases in Si/Si1−xGex epitaxy. The Ge mole fraction x and the growth rate of Si1−xGex epilayers show very strong dependence on the total source gas flow rate ([GeH4]+[Si2H6]) and the source gas ratio ([GeH4]/[GeH4]+[Si2H6]). The results can be explained by the relationships of the source fluxes, relative incorporation efficiency at activated surface sites, and hydrogen desorption under different growth conditions. The boron concentration of Si1−xGex increases with increasing GeH4 flow rate by keeping Si2H6 and B2H6 flow rates constant. It may be due to the increase of the surface sites which is caused by the increase of the hydrogen desorption rate when a higher Ge mole fraction epilayer is grown. The phosphorus concentrations of Si and Si1−xGex show different behavior with PH3 flux at higher PH3 flow rates whil...

Background Tryptophan metabolites have been suggested to play a role in immune modulation, wherein those have recently been shown to be endogenous ligands of aryl hydrocarbon receptor (AhR; a unique cellular chemical sensor). However, the involvement of tryptophan metabolites and AhR in modulating mast cell function remains to be fully defined. We therefore investigated that the functional impacts of tryptophan metabolites on human and mouse mast cell responses in vitro and their functional importance in vivo. Methods Three tryptophan metabolites, kynurenine (KYN), kynurenic acid (KA) and quinolinic acid (QA), were examined in terms of their effect on IgE-mediated responses in mouse bone marrow-derived mast cells (BMMCs) and in human peripheral blood-derived cultured mast cells (HCMCs) and on in vivo anaphylactic responses. For evaluation of AhR involvement, we examined the responses of mast cells from AhR-null or AhR-wild-type mice with the use of a known AhR antagonist, CH223191. Results Kynurenine, but not KA and QA, enhanced IgE-mediated responses, including degranulation, LTC4 release, and IL-13 production in BMMCs through the activation of PLCγ1, Akt, MAPK p38, and the increase of intracellular calcium. KYN also enhanced cutaneous anaphylaxis in vivo. These enhancing effects of KYN were not observed in AhR-deficient BMMCs and could be inhibited by CH223191 in BMMCs. Further, KYN had similar enhancing effects on HCMCs, which were inhibited by CH223191. Conclusion The AhR-KYN axis is potentially important in modulating mast cell responses and represents an example of AhR's critical involvement in the regulation of allergic responses.

Deposition of a boron‐containing layer using B2H6 diluted with H2 on a Si(001) surface has been carried out in an ultrahigh‐vacuum chemical‐vapor‐deposition (UHV‐CVD) system. The deposited boron‐containing layers were characterized by atomic force microscope and Auger electron spectroscopy (AES), and the junction depth was determined by secondary‐ion‐mass spectroscopy. Effective doping is accomplished before perceivable nucleation is initiated. Islands are first formed on the substrate surface at a small dose of diborane, and the grains coalesce to form a rough film for higher doses. At growth temperature above 800 °C, the film is composed of possibly SiB6, according to AES depth profiles. Correlation between the junction depth and the sheet resistance of the UHV‐CVD‐deposited specimens prepared under various conditions is discussed. Postdeposition rapid thermal annealing was performed to study the effect of subsequent thermal cycles on the junction depth and sheet resistance.

The epitaxial silicon layer selectively grown on the reactive ion etched (RIE) silicon substrate using CF4, CHF3 and Ar etching gases has been studied. Defects and contaminants induced by the RIE process result in a rough epilayer, and degrade the current–voltage (I–V) characteristics. An interfacial carbide layer is present between the epilayer and the RIE treated substrate. Using an efficient and convenient after‐etching treatment with a CF4/O2 low‐energy plasma, we obtain a clean Si surface in the patterned oxide windows for selective epitaxial growth, and the electrical characteristics are significantly improved.

We explore the competitive concepts of neural network identification and fuzzy logic adaptive inference into the aircraft antilock brake system (ABS) design. The nonlinearities typically characterized by look-up tables are emulated with neural identifiers and subsequently integrated in the ABS design. The highly nonlinear aircraft dynamics coupled with varying operating conditions and uncertainties are handled well with the proposed rulebased fuzzy logic controller. The proposed methodology is shown to be robust under various runway ground conditions. The proposed aircraft ABS design with neural networks and fuzzy logic can persistently provide the maximum achievable traction force for deceleration purposes, as compared with other ABS and non-ABS schemes.

A polyamide (nylon-66, N66) was blended with a series of polyurethanes (PU) based on different polyols or chain extenders. The effects of PU structure and content on the mechanical properties of the blends were investigated. The morphology of the polyblends was examined by scanning electron microscopy. The Izod impact strength of the blends increased with increasing PU content and showed a maximum value at the composition of 15 wt % PU. The effects of moisture content on the mechanical properties of the blends were also investigated. It was found that the water-toughened N66 could be further toughened by the addition of PU. Polyester-type PU rather than polyether type PU was recommended for the toughening of N66 because the blends containing the former showed higher tensile strength and Izod impact strength except at very low moisture (0.3 wt %) content. Carboxyl groups was introduced into the molecular chains of PU by using dimethylol propionic acid as chain extender replacing part of 1,4-butanediol. The blends containing PU with carboxyl groups showed a lower Izod impact strength than those without carboxyl groups in the structure of PU.

The specific volume of polymer blends with different degree of compatibility has been measured at high pressure, up to 2000 kg/cm2, in the molten state by a dilatometer. The specific volume and thermal expansion coefficient of the molten homopolymers at zero pressure were satisfactorily fitted to a simplified Simha–Somcynsky equation. The specific volume of styrene–butadiene (SBR) random copolymer, which is considered to be a compatible system, at a constant styrene composition can be calculated by an semiempirical equation based on the Tait equation. The temperature dependence of excess specific volume of SBR with different styrene content at zero pressure was estimated by a combining rule in terms of self-and cross interactions. The concentration-dependent equation is derived to estimate the specific volume of SBR with various styrene contents. Both the thermal and dynamic mechanical analysis of the blend from the two polystyrene (PS) and polybutadiene (BR) homopolymers show a low degree of compatibility. The weight fractions of each domain consisting of PS blending with BR and those of the components in each domain can be calculated from the mass balance on the two domains and the rearranged Couchman equation. The specific volume of PS–BR composed of two phases obeys the principle of additivity from the weight fractions of the specific volume of the corresponding phases. © 1994 John Wiley & Sons, Inc.

A variety of complex configurations have been attempted to enhance the thermal stability of modern heterojunction bipolar transistors (HBTs). Existing structures for improving thermal management of power HBTs, nevertheless, are not small enough to realize miniaturized power amplifiers in high-efficiency cellular phones. A highly compact heat-spreading structure (HSS) simulated by the genetic algorithm (GA) is proposed, and the demonstration on multi-finger InGaP/GaAs collector-up HBTs, which show noticeable power performance, is presented. Comparatively, the improved results indicate that the thermal resistance can be substantially decreased by 50%, and a power-added efficiency (PAE) more than 55% is achieved from this novel design

Advanced collector-up (C-up) heterojunction bipolar transistors (HBTs) with the thermal-via configuration (TVC) have been analyzed using a genetic algorithm (GA). Novel packaging structures are presented and evaluated in detail. With careful optimization, the thermal performance can be maximized by improving the thermal resistance over 40%, and the conventional TVC can be further reduced by 35%. The proposed approach is demonstrated on the multifinger InGaP/GaAs C-up HBT, which is attractive as the active component in power amplifiers. A comparison of measured, finite-element-calculated, and GA-extracted results has been made. Consequently, it is shown that the remarkable thermal management can be achieved with a miniature heat-dissipation design, and the thermally stable InGaP/GaAs C-up HBT should be feasible for implementation in intelligent wireless communication systems.

The heat capacity and phase relation of polymer blends consisting of two homopolymers or a homopolymer with a block copolymer have been investigated by differential scanning calorimetry (DSC). Polystyrene (PS) and polybutadiene (BR) are the two homopolymers, while the styrene–butadiene–styrene (SBS) copolymer is employed as the block copolymer in this study. The heat capacity and specific volume of the PS and BR homopolymers increase with increasing temperature at a constant pressure. The heat capacity of styrenebutadiene (SBR) random copolymer, which is considered a miscible system, can be calculated by an additive rule from the addition of the styrene and butadiene segment number fractions in the random copolymer multiplied by the corresponding heat capacity of PS and BR homopolymers. However, the heat capacity of the immiscible system of the SBS triblock copolymer can be estimated by the addition of the two segment number fractions multiplied by the reciprocal of the corresponding heat capacity of the PS and BR homopolymers. The thermal and dynamic mechanical analysis data of the polyblend from the two PS and BR homopolymers both show a low degree of miscibility. A saturated solubility of the homopolymer dissolved in the SBS block copolymer is proposed and the purification of the styrene and butadiene phases in the SBS copolymer is observed as it blends with either PS or BR homopolymer. The heat capacity of polymer blends composed of two phases obey the principle of additivity from the weight fractions of the heat capacity of the corresponding individual phase. © 1993 John Wiley & Sons, Inc.

As proposed in a classical paper [1], an inverted transistor design with a smaller collector on top and a larger emitter at the bottom is defined as the collector-up hetero-junction bipolar transistor (C-up HBT). Compared to the traditional emitter-up (E-up) HBT, the C-up HBT exhibits reduced base-collector junction capacitance, which is nearly one-third that of the E-up HBT, hence the C-up HBT is expected to show better microwave performance that makes it possible to be used as the active component in the power amplifier (PA) [2]. In an advanced wireless communication system, small HBT-based PAs are demanded to promote the development of the system-on-chip (SOC) or system-in-package (SIP) technology. The miniaturization of PAs depends primarily on the thermal management of HBTs. Previous researches suggested the thermal-via configuration (TVC) made up of plated heat sink (PHS) and conductive epoxy underneath the C-up HBT fingers to dissipate heat [3]. The innovative configurations lead to low thermal resistances, and hence the temperature within transistor fingers is lowered. In the other respect, when circuit designers laying out the current-mode logic gate using E-up HBTs, each transistor has to be isolated from each other, and the emitters of the switching pair are connected through the metal layer [4]. Replaced E-up transistors by C-up transistors, the emitters of the switching pair are merged in the buried layer of the substrate. The transistors do not have to be fully isolated from each other, and metal interconnection is minimized.

Semiconductor market trends indicate the rapid development of new integrated systems containing both optoelectronic and wireless-communication functionalities [1]. For projection-display devices and high-density optical disks in new integrated systems, the green light can be generated from solid-state lasers, in combination with second-harmonic generation (SHG) crystal, owing to their distinct features such as low noise, high-frequency-modulation capability, compactness, and low-power consumption [2]. The 1060 nm InGaAs quantum-well (QW) laser diode is one of applicable active components for this application [3]. However, the internal loss (α j ), the internal quantum efficiency (η j , and the transparency current density (J th ), which are fig-ures-of-merit (FoMs) for the QW laser under high-power-laser operation, are needed to be further improved. In the other respect, the low-noise amplifier (LNA), for wireless-communication functionalities in new integrated systems, is exploited to overcome the noise produced in subsequent stages by amplifying incoming radio-frequency (RF) signals, while introducing minimum amount of noise [4]. Nowadays, the SiGe LNA employing HBTs has been a main contender among the Si-based IC industry due to their advantages of higher cutoff frequency, lower noise, and better power performance. In general, the performance of SiGe LNAs relies on the geometrical-scaling issue, e.g., the emitter-length scaling [5]. For the HBT-based LNA design, attention should be devoted to optimizing FoMs such as the minimum noise figure (NF mm ) and the associated available gain (G A, assoc ) [6].

A theoretical model for the electron-hole exchange interaction in three-dimensionally (3D) confining semiconductor nanostructures is presented to explain the observed decreasing tendency of the fine-structure splittings (FSSs) of small InGaAs/GaAs self-assembled quantum dots (QDs) with increasing the emission energies. The experimentally revealed FSS reduction is shown to be highly associated with the significant 3D spreading of electronic orbitals and reduced overlap of electron and hole wave functions in small and/or Ga-diffused QDs. The combination of quantum size and Ga-diffusion effects substantially reduces the averaged $e\text{\ensuremath{-}}h$ exchange interaction and leads to the reduced FSSs in the regime of high emission energy.

The specific volume of thermoplastic polymers and composites with glass fiber have been measured at high pressure, up to 2000 kg/cm2, in the molten state by a dilatometer. The specific volume and thermal expansion coefficient of the melts increase with increasing temperature at a constant pressure at a constant temperature. The data of specific volume of molten polymers were satisfactorily fitted to an empirical equation of state based on the Tait equation. Furthermore, it is found that the data of specific volume of molten composites were suitably fitted by an additive rule of Tait equation from the volume fractions of specific volume of polymers and the glass fiber in composites. The thermal expansion coefficients of molten polymers and composites are approach to the derivative values of the Tait equation, and the additive Tait equation, respectively.

In this paper, we made an in-depth study on the fabrication of low-pressure MOCVD-grown 1055-1064 nm multi-quantum-well and super-lattice laser diodes, which can be used for green-light generation combined with second-harmonic generation crystal. Due to the simplicity of the configuration and high reliability, large merits in terms of size, cost, and power consumption would arise. Furthermore, direct modulation is possible in the laser diodes, which would lead to a highly compact pulsed laser source.

We devise a finite-element model to analyze the thermal performance of collector-up (C-up) heterojunction bipolar transistors (HBTs) with a thermal-via configuration. A demonstration on the GaInP/GaAs C-up HBT is presented in this Brief, and the novelty of this work is that both 2D and 3D temperature-distribution analyses are performed. The 2D results indicate that the original thermal-via configuration can be reduced by 29%. Furthermore, the results show that the maximum temperature within the collector calculated from 3D analysis is lower than that from the 2D analysis. Based on the 3D analysis, it is revealed that the reported configuration can be reduced by 32%. Therefore, the C-up HBT with a compact thermal-via should be helpful for miniaturization of heat-dissipation packaging configurations within HBT-based high-power amplifiers.

The temperature distribution of heat-dissipation structures has been designed using the 3-D thermal FEM method. Results on multi-finger InGaP C-up HBTs demonstrate that the thickness of heat-dissipation packaging configurations can be further reduced by 40%, and the achieved heat-dissipation performance will not be deteriorated. From this efficient analysis, it is believed that miniaturization of C-up HBTs with compact heat-dissipation structures can be used in small-scale HPAs.

The InGaAs/GaAs multi-quantum-well as well as the AlGaAs/GaAs and the GaAsP/GaAs super-lattice laser diodes were successfully fabricated by low-pressure MOCVD system, and a number of novel structures were explored in this systematic investigation. The strain-relief effect and the composition of cladding layers were analyzed in detail. Via a series of growth experiments, we concluded that better lasing efficiency and the minimum threshold current could be obtained from the sample made up of the AlGaAs/GaAs structure combined with the 60% Aluminum content of the AlGaAs cladding layer.

A novel finite-element modeling approach is developed to design thermal-via packaging configurations of collector-up heterojunction bipolar transistors (C-up HBTs) in high-power amplifiers (HPAs). The thermal interaction between HBT fingers has been examined based on the temperature distribution phenomena in multifinger C-up HBTs. The results reveal that the overall compactness of thermal-via configuration can be further improved more than 33%.

To investigate how central and peripheral nerves affect lysozyme secretion from tracheal submucosal glands in ferrets we injected substance P (20 nmol/kg in 200 microliters) intracisternally or intravenously into anesthetized artificially ventilated ferrets. We collected 3-ml samples from a perfused (3 ml/5 min) segment of trachea in situ during 15 min before and 45 min after injection of substance P. Content of lysozyme, a specific marker of tracheal submucosal gland serous cell secretion in ferrets, was measured spectrophotometrically in each sample. Intracisternal substance P increased peak lysozyme output threefold compared with baseline. This increase was abolished completely by cutting both superior laryngeal nerves (SLN) and was partially inhibited by atropine, phentolamine, or propranolol. Intravenous substance P increased peak lysozyme output 10-fold compared with baseline. This increase was partly abolished by cutting both SLN. We concluded that intracisternal substance P stimulated the central nervous system (CNS) and activated cholinergic, adrenergic, and nonadrenergic noncholinergic secretomotor nerves to tracheal glands and that intravenous substance P increased lysozyme secretion both by acting directly on tracheal glands and indirectly on the CNS to activate secretomotor nerves.

The thermal conductivities of molten polypropylene and its glass fiber composites were measured by the compensating hot wire method. The testing apparatus empolyed was designed and tested in our laboratory. The measurements were carried out with temperatures ranging from 170 to 230°C and pressures from 1 to 2000 kg/cm2. The results show that the thermal conductivity increases with increasing pressure and glass fiber content, but is almost independent of temperature. The thermal conductivity data were fitted satisfactorily with a proposed empirical equation for polypropylene and Lewies-Nielsen equation for the composites, respectively.

A heat-dissipation packaging configuration of GaInP collector-up (C-up) heterojunction bipolar transistors (HBTs) has been designed and evaluated systematically. 2-D and 3-D finite-element modeling (FEM) approaches are built up to simulate the actual devices and to analyze the temperature distribution behavior. The results show that the reported configuration can be further reduced by 42%. Therefore, thinning the thermal-via structure constructed in GaInP collector-up HBTs should be useful for miniaturization of high-power amplifier (HPA) designs, and the developed FEM method can be very effective for optimizing HBT-based HPAs in future cellular phone systems.

To carry out the miniaturization design of backside-via packaging structures underneath collector-up HBTs, a 3-D finite-element model has been developed for analyzing temperature-distribution phenomena within the configurations. The results are demonstrated on the three-finger InGaP/GaAs collector-up HBT. Compared to previous reports, backside-via structures can be further reduced by 42% while maintaining the same heat-dissipation performance.