Earticle

Time-temperature integrators (TTIs) based on aqueous enzyme solutions produce transparent colors which lead to difficulty in distinguishing its color change by naked eye. In this present study, this issue has been solved by increasing the opacity of laccase-based TTI without changes in the kinetics (same zero-order reaction) and temperature dependency (similar Arrhenius activation energy values) of the color change. The opacity was increased by introducing TiO2, latex, BaSO4, or ZnO, in combination with a hydrocolloid (xanthan gum, acacia gum, pectin, and CMC) into the TTI system. The combination of TiO2 and xanthan gum was the best. This finding broadened the advantages of laccasebased TTI to more practical uses for consumer convenience.

A printable time temperature integrator (TTI) consisting of oxygen indicator and cover films with various oxygen permeability was developed. The printing ink contained methylene blue (oxygen indicator) which changed in color during storage. TiO2 and glycerol for UV-activation of TTI and zein and ethanol for printing performance were also contained in the printing ink. The cover film on the ink was employed to control the color change rate and temperature dependency (Arrhenius activation energy, Ea) by using the different films (PE, PET, OPP, and LLDPE). The film properties were varied by annealing. TTI was produced by silk screen printing. As a result, the color change rates were different for the cover films, being the highest in TTI with LLDPE, followed by OPP, PE, and PET. The rate decreased with increase in the cover film thickness. The Ea was the highest in TTI with LLDPE, followed by OPP, PE, and PET. The Ea did not change with the cover film thickness. The annealed PVC and PET film were lower in oxygen permeability than the unannealed ones, indicating the lower color change rate.

A novel printable time-temperature integrator (TTI) composed of a natural coloring matter, anthocyanidin, was developed. The anthocyanin was biochemically modified to change in color over week scale, compared to the original anthocyanin over month scale change. The anthocyanin extracted from strawberry was converted to its aglycone, anthocyanidin, by the treatment with β-glucosidase. The print paste was composed of the freeze-dried powder of anthocyanidin, pullulan, glycerol and distilled water, which was screen-printed. The TTI performance were examined in terms of kinetics and temperature dependency. The activation energy of anthocyanidin TTI was 86.92 kJ/mol. Compared with the activation energy of foods, the applicable food groups were found. Applicable food groups were chilled meat products and fish. The major benefits of the TTI were the printability to be practical in use and the eco-friendliness with the natural pigment.

TTI 상용제품인 Fresh-check을 명태의 냉장유통 중 품질 예측에 사용할 때 그 성능이 항상 최적화되어 있을 수 없 다는 가정하에서, TTI를 냉장유통의 어느 시점에서 부착하 는 것이 가장 바람직한지를 수학적으로 분석하였다. TTI 부 착시점으로 크게 ‘어획 후 선상에서, ‘부산국제수산물도매 시장에서’, ‘마트에서’의 세 경우로 나누었다. 먼저, 등온 실험을 통하여 TTI의 색 변화와 명태의 Pseudomonas spp. 에 관한 kinetic과Arrhenius 온도의존성 모델 식을 완성하였 다. 얻어진 모델식을 사용하여 냉장유통에 해당하는 dynamic 온도조건에 대하여 수리적으로 TTI의 색 변화와 명태의 품질변화를 계산하였다. 그 결과, 마트에서 부착했을 때 TTI 색 변화가 종료 점에 도달한 시간이 명태의 부패시간과 가장 일치하였다. 따라서 상용 TTI 제품 을 사용할 경우 부착시점의 선택이 중요함을 알 수 있었다.

It was mathematically analyzed at which steps to activate TTI in the cold chain for Alaska pollack, assuming that the performance of a commercial TTI product, and Fresh-check, could not always be optimized for the pollack. Three places were selected for the TTI activation, such as on fishing ship, Busan cooperative fish market, and mart. First, the kinetic and Arrhenius temperature dependent models were experimentally built under isothermal conditions. The color index of TTI and the level of Pseudomonas spp. of pollack were measured at time intervals. Second, the resultant models were used in the mathematical calculations for dynamic temperature conditions included in the cold chain. As a result, the TTI activated at the mart place showed the best agreement between the spoilage time of the pollack and the time for the TTI color to reach its end-point. It was therefore found that it is practically important to optimally select the TTI activation place or time when using a commercial TTI product.

모델 현장으로 야외 임시 생선 판매장을 설치하여 TTI가 부착된 고등어 및 명태의 판매 중 TTI의 색 변화와 생선 품질을 모니터링하였다. 생선은 스티로폼 박스 위에 얼음을 깔고 그 위에 진열되었고, 주기적으로 얼음을 채워서 신선 도를 유지시켰다. 일정 시간 간격마다 고등어, 명태, TTI를 채취하여 TTI의 색 변화와 냉장생선의 품질 정도를 측정하 였다. 품질 인자로 VBN과 Pseudomonas spp.를 고등어와 명태 각각에 대하여 적용하였다. 부패 시점은 VBN과 Pseudomonas spp.이 특정 수준에 도달했을 때로 간주하였다. 그 결과 온도가 높은 날에는 생선이 부패되기 시작하였고 그 시점에서 TTI 색이 종료점(제품 특성에 따름)에 도달하였 다. 따라서 생선의 부패 시점을 TTI의 색변화를 관찰함으로써 가능함을 알 수 있었다.

TTI was applied to monitor the quality changes of fish displayed at a mock store. Chilled fishes were displayed with TTI on a styrofoam box filled with crushed ice. The ice was periodically refilled to maintain the fish freshness. The color of TTI and the qualities of mackerel and Alaska pollack were measured during displaying. VBN and Pseudomonas spp. were used as the quality factors of mackerel and Pollack, respectively. The spoilage time was regarded as when the factors reached their critical levels. The fishes were spoiled when the color of TTI reached an end-point. It was therefore found out that it is possible to predict the fish spoilage by observing the TTI color change.

In this paper, modified architecture of CMOS capacitive fingerprint sensor readout circuit is presented for general type of a switched capacitive integrator scheme. The proposed architecture supports wide and flexible operation range without ADC. It also operates faster than a typical integrator scheme for one frame image capture. The circuit includes an analog comparator in each pixel and counters. The referenced analog voltage of each sensor cell is controlled by an external or internal bias.

In this paper, a cross-coupled gain-boosting current-mode integrator is proposed, which is better than typical current mirror integrator when compared in terms of increasing gain and frequency response. The results of small signal equivalent circuit analysis and HSPICE simulation of the proposed integrator show that gain and frequency response is improved at supply voltages of 1V band. An example application using the proposed integrator low- voltage current-mode filter is also presented. The simulated cutoff frequency of the designed filter is 200MHz at a supply voltage of 1.8V.

This paper proposes 128x100 array fingerprint sensor with the modified parasitic insensitive switched capacitor integrator. The modified parasitic insensitive switched capacitor integrator includes four switches to eliminate parasitic capacitance and transfer a generated charge. The proposed circuit also frees from the influence of skin resistivity, because the effect of the voltage drop through skin resistor is very small. The scheme of one pixel includes a pixel level charge transfer and also parasitic insensitive switched capacitor integrator with a differential amplifier. The proper operation is validated by HSPICE for one-pixel and RTL simulation including logic synthesis for a full chip design on condition of 0.35μm typical CMOS process and 3.3V power. The layout is performed by full custom flow for one-pixel and auto P&R for a full chip. The area of a full chip is 8721 μm x 6921 μm and the gate count is 1,140,553. The area of one-pixel is 58 x 58 μm2. Pitch is 60 μm and image resolution is 423dpi.

본 논문에서는 설계 요구가 높고, 전력 소모가 높은 opamp를 이용하는 기존의 능동형 적분기를, 수동형 적분기로 대체하여 고속의 저전력, 고해상도 특성을 갖는 incremental delta-sigma ADC를 소개한다. 능동형 적분기에서 수동형 적분기로의 변환을 위해, 기존의 능동형 적분기의 특성을 분석하였다. 이를 바탕으로 opamp의 설계 요구를 낮추고, 더 나아가 opamp를 사용하지 않는 저전력의 수동형 적분기를 제안하였다. 65nm 공정을 이용하여 수동형 적분기로 구성된 1차 single-bit incremental delta-sigma ADC를 설계하였다. Transistor-level 시뮬레이션 결과, 이는 supply 전압이 1.2V인 상황에서 modulator만 0.6uW, digital filter를 포함한 ADC 전체에서 6.25uW를 소모하며 BW 22KHz, SNDR 71dB, dynamic range 74.6dB을 달성하였다.

This paper presents a low power and high resolution incremental delta-sigma ADC that utilizes a passive integrator instead of an opamp-based active integrator. Opamp is a power-hungry block that involves tight design tradeoffs. To avoid the use of active integrator, the s-domain characteristic of an active integrator is first analyzed. Based on the analysis, an active integrator with low gain design is proposed as an alternative design method. To save power even more aggressively, a passive integrator with no static current is proposed. A 1st order single-bit incremental delta-sigma ADC using the proposed passive integrator is implemented in a 65nm CMOS process. Transistor-level simulation shows that the ADC consumes only 0.6uW under 1.2V supply while achieving SNDR of 71dB with 22kHz bandwidth. The estimated total power consumption including digital filter is 6.25uW, and resulting power efficiency is on a par with state-of-the-art A/D converters.

본 논문에서는 software defined radio(SDR) 등의 디지털 RF/IF(Intermediate Frequency)에 사용되는 CIC 필터의 처짐 현상을 위한 보상 필터를 제안한다. 제안된 보상 필터는 근사적 선형 위상 특성을 가지며, interpolator/decimator의 기저 대역에서 가장 낮은 레이트로 동작하는 2차의 필터이므로 저연산량을 요구하므로 비용 효율적이다. 또한 처짐 현상을 보상하면서도 저지대역에서는 성능 열화가 거의 발생하지 않는다 예제를 통한 설계 및 성능 분석 결과, 제안된 보상 방법을 적용한 통신 시스템에 있어서 성능 향상을 보였고, 기존의 보상 방법과 비교하여 성능 및 메모리 사용량, 연산량에서 우수함을 보였다.

In this paper, a filter is proposed to compensate droop of the CIC filter for SDR. The proposed compensation filter has almost linear-phase characteristic, requires low operational complexity, and is cost-effective due to its second-order characteristic and lowest operational rate in the baseband.. Especially, it compensates droop in the passband with little performance degradation in the stopband. It is shown, by a design example and its performance analysis, that the proposed compensation method gives performance enhancement in communication systems. It is also shown that the proposed method is superior to conventional ones in view of memory usage and computational load.

A multiple classification system based on a new boosting technique has been approached utilizing different biometric traits, that is, color face, iris and eye along with fingerprints of right and left hands, handwriting, palm-print, gait (silhouettes) and wrist-vein for person authentication. The images of different biometric traits were taken from different standard databases such as FEI, UTIRIS, CASIA, IAM and CIE. This system is comprised of three different super-classifiers to individually perform person identification. The individual classifiers corresponding to each super-classifier in their turn identify different biometric features and their conclusions are integrated together in their respective super-classifiers. The decisions from individual super-classifiers are integrated together through a mega-super-classifier to perform the final conclusion using programming based boosting. The mega-super-classifier system using different super-classifiers in a compact form is more reliable than single classifier or even single super-classifier system. The system has been evaluated with accuracy, precision, recall and F-score metrics through holdout method and confusion matrix for each of the single classifiers, super-classifiers and finally the mega-super-classifier. The different performance evaluations are appreciable. Also the learning and the recognition time is fairly reasonable. Thereby making the system is efficient and effective.

This paper presents an alternative frequency adaptive grid synchronization technique named HDN-FLL, which can accurately extract the fundamental positive- and negative-sequence components and interested harmonics in adverse three-phase grid voltage. The HDN-FLL is based on the harmonic decoupling network (HDN) consisting of multiple first order complex vector filters (FOCVF) with a frequency-locked loop (FLL), which makes the system frequency adaptive. The stability of the proposed FLL is strictly verified to be global asymptotically stable. In addition, the linearization and parameters tuning of the FLL is also discussed. The structure of the HDN has been widely used as a prefilter in grid synchronization techniques. However, the stability of the general HDN is seldom discussed. In this paper, the transfer function expression of the general HDN is deduced and its stability is verified by the root locus method. To show the advantages of the HDN-FLL, a simulation comparison with other gird synchronization methods is carried out. Experimental results verify the excellent performance of the proposed synchronization method.

An enzymatic time-temperature integrator (TTI) system based on the reaction between porcine esterase and tripropionin, which causes a pH change, was developed. A pH decline in the esterase-based TTI system changed the color of the pH indicator from blue to light green. After calculating the response rate constant by measuring color changes in the TTI under different temperature conditions, an Arrhenius plot was prepared, and activation energy was estimated. The activation energy of the TTI measured at isothermal conditions (5, 10, 15, 20, and $30^{\circ}C$) was 53.6-54.6 kJ/mol. In addition, the TTI endpoint could be adjusted by modifying the amount of esterase consumed to fit different shelf lives of food. The results showed that the new esterase-based TTI could be used to indicate the time-temperature history of food.

Time-temperature integrators (TTIs) are simple and cost-efficient tools which may be used to predict food quality. Enzymatic TTIs are devised to indicate food quality in the form of color alterations from green to red, based on the cumulative impacts of temperature and time period on the enzymatic reactions. In this study, the quality of ground beef patties was investigated for the parameters of pH levels, color, VBN, water holding capacity, and total microbial counts, depending on various storage temperatures (5, 15, and $25^{\circ}C$). TTIs were attached to the surface of the ground beef patties in order to evaluate the degree of correlating colorimetric changes with the determined quality parameters. Through the Arrhenius equation, activation energy and constant reaction rates of TTI, VBN, and total microbial counts were calculated as to observe the relationship between enzymatic reactions of the TTI and food spoilage reactions of the ground beef patties. VBN and total microbial counts were already increased to reach decomposition index (VBN: 20, total microbial count: 7-8 Log CFU/g) of meat at middle stage of storage period for each storage temperature. Although activation energy of TTI enzymatic reactions and food spoilage reactions of the ground beef patties were similar, the change of TTI color was not a coincidence for food spoilage at $5^{\circ}C$ and $15^{\circ}C$ of storage temperature. It was suggested that TTI should be designed individually for storage temperature, time, type of meat, or decomposition index of meat.

육류의 품질예측에 가장 적합한 TTI의 조건을 분석하기 위하여, 온도-시간 이력에 따른 TTI의 색 변화와 Pseudomonas spp.의 증식수준을 수학적으로 Simulation 하였다. 일련의 kinetics 및 온도의존성 관련 함수식의 연산에는 수치해석 기법인 Euler's method를 적용하였으며, MS Excel VBA기반 컴퓨터 프로그램을 작성하여 계산하였다. 쇠고기의 저장 유통에 대한 몇 가지 온도-시간 경로에 대하여, 저장 시간에 따른 TTI 색 함수 및 $T_{eff}$(해당 온도-시간 이력에 대한 일종의 대표적 온도 값)의 변화를 simulation 하였다. 온도의존성(활성화에너지)가 서로 다른 TTI에 대하여 Simulation한 결과, 먼저 Pseudomonas 증식의 활성화 에너지와 같은 활성화에너지를 갖는 TTI의 경우 같은 색에 대하여 온도-시간 이력에 상관없이 항상 같은 증식수준을 나타냈다. 반면에 활성화에너지가 서로 다른 경우 TTI가 같은 색에 대하여 온도-시간 이력에 따라 서로 다른 증식수준을 나타냈다. 결론적으로 육류의 특정 품질에 대한 적합한 TTI는 서로 온도의존성이 일치할 때 가장 정확한 예측 값을 얻을 수 있음을 알 수 있었다.

The temperature dependence of time temperature integrator (TTI) was investigated in terms of the Arrhenius activation energy (Ea) to determine TTI requirements to accurately predict meat quality during storage. Mathematical simulation was conducted using a numerical analysis. First, using Euler's method and MS Excel VBA, the TTI color change was kinetically modeled and numerically calculated under several storage conditions. From the TTI color variable profiles calculated from the storage time-temperature profiles, $T_{eff}$, which is a constant temperature representing the whole temperature profiles, was calculated. Upon predicting Pseudomonas spp. concentrations (one of the meat qualities) from $T_{eff}$, it was found that if $Ea_{microbial\;spoilage}=Ea_{TTI}$ be true, then Pseudomonas concentrations were calculated to be constant with the same TTI color values, regardless of time-temperature profiles, whereas if $Ea_{microbial\;spoilage}{\neq}Ea_{TTI}$ then Pseudomonas concentrations varied even with the same TTI color values. This indicates that each TTI color value represents its own fixed degree of meat quality, only if $Ea_{meat\;qualities}=Ea_{TTI}$.

A time-temperature integrator (TTI) is a device used to show a time-temperature dependent change that reflects the temperature history and quality status of the food to which it is attached. An enzymatic TTI system based on the reaction between Burkholderia cepacia lipase and tricaprylin, which causes a pH change, was developed. The temperature dependence of the response rate of this new lipase-type TTI was modeled using the Arrhenius equation, and the estimated activation energy was calculated as $70.61{\pm}11.10$ kJ/mol (${\pm}95%$ confidence interval). The TTI response was validated under dynamic storage conditions with independent variable temperature experiments, and a good agreement was obtained between the predicted and measured values.